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makes up the ADAPTIVE immune system
- consists of groups of cells, tissues, and organs that generate immune responses against their own transformed cells and foreign invaders
** lymphoid tissues are widely distributed bc pathogens can enter the body at any point
** lymphoid tissue is a CT characterized by a rich supply of lymphocytes
- consists of groups of cells, tissues, and organs that generate immune responses against their own transformed cells and foreign invaders
** lymphoid tissues are widely distributed bc pathogens can enter the body at any point
** lymphoid tissue is a CT characterized by a rich supply of lymphocytes
1. RBCS (erythrocytes):
5-6million per microliter of blood- work to transport oxygen (and CO2)
2. White blood cells (leukocytes):
5,000-10,000 per microliter of blood- work in defense and immunity
- Basophil
- Eosinophil
- Neutrophil
- Lymphocyte
- Monocyte
3. Platelets:
250,000-400,000 per microliter of blood- function in blood clotting
*** In the body, these formed elements are suspended in PLASMA, when taken outside of the body- blood will clot, leaving (the liquid) serum behind
5-6million per microliter of blood- work to transport oxygen (and CO2)
2. White blood cells (leukocytes):
5,000-10,000 per microliter of blood- work in defense and immunity
- Basophil
- Eosinophil
- Neutrophil
- Lymphocyte
- Monocyte
3. Platelets:
250,000-400,000 per microliter of blood- function in blood clotting
*** In the body, these formed elements are suspended in PLASMA, when taken outside of the body- blood will clot, leaving (the liquid) serum behind
Insoluble fibrin that has been converted from soluble fibrinogen is ablood clot
** a fibrin containing network trapping blood cells
* clotted blood breaks fibrinogen --> fibrinSteps in making a blood smear1. prick finger and collect a small amount of blood using a micropipette
2. place a drop of blood on a slide
3a. using second slide, pull the drop of blood across the first slides surface, leaving a thin layer of blood on the slide
3b. after blood dries, apply a stain briefly and rinse. Place a coverslip on top
4. When viewed under the microscope, blood smear reveals the components of the formed elementsBlood smears are commonly stained withWright Stain (methylene blue and eosin)
Methylene Blue:
-a basic dye: so stains acidic structures blue (like hematoxylin)
it will stain ""basophilic"- base loving structures:
- DNA in nucleus
- RNA in cytoplasm
- Specific granules of basophils
Eosin:
- an acidic dye (like H&E): so it stains basic structures pink/red
It will stain "acidophilic" or "eosinophilic" structures:
- Hemoglobin (which is not overall basic- but it does have regions of basic AA)
- Specific granules of eosinophils (contains the major basic protein)The lysosomes (primary granules) of all leukocytes stainAZUROPHILIC
** a reddish blue from binding to azures, substances formed when methylene blue is oxidized
** RBCs DONT have lysosomes so they DO NOT stain with thisT or F: RBCS have a HUGEEEE NucleusFALSE!
they have absolutely NO nucleus or organelles
** they had one in their development in the bone marrow but then they released it
NOTE:
RBC (aka erythrocytes) primary function is the transport of O2 and CO2
- RBCs are basically just bags of hemoglobin
- RBCS make up 99% of ALL blood cellsThe percentage by volume of packed red blood cells in a given sample of blood after centrifugation is referred to asHematocrit
In males= 40-50%
Females= 35-45%
** note that males have more erythrocytes per unit volume than females do
males= 4.7-6.1 x10^6/ mm^3
females= 4.2-5.4 x 10^6/mm^3
** Females have a lower hematocrit because they menstruate every month- women with heavier flows can at times become anemic- this is not much concern for a doctor- they will just prescribe/recommend that the women take iron. However, for a male this is much more alarming it may signify a problem such as colon cancer where a pt may be losing significant amounts of blood through their stoolWho has more erythrocytes per unit volume? People living at lower or higher altitudesMembers of both sexes who live at higher altitudes will have more erythrocytes!
** the number of RBCs in the circulation is regulated to meet O2 carrying needs and this is done via the hormone Erythropoietin (which is secreted mainly by kidneys in adults and by the liver in the fetus, it adjusts RBC production to match O2 demand)What are the main four things found in erythrocytes (RBCs)1. plasma membrane
2. cytoskeleton
3. hemoglobin (this makes up 95% of RBCs protein content, 30% weight of RBC and its gives them their red color)
4. Glycolysis enzymes: since during formation in the bone marrow (erythropoeisis), developing RBCs lose their nucleus and organelles (only keeping their cytoskeleton)- this means RBCs also do not have any mitochondria, soooo the mature RBCs actually make ATP exclusively through cytoplasmic glycolysis using glucose in the blood plasmaLife span of a RBCsis limited- 120 days
* the avg RBC will pass through the heart ~500,000 times
- their cell membrane will eventually rupture; or the aged cell is phagocytosed in the spleen, liver, and bone marrow
** 1 % of RBCs are replace daily and these new ones are called RETICULOCYTESDescribe the shape of RBCSbiconcave shape
* this shape maximizes their surface area/volume ration, therefore maximizes O2 and CO2 exchange
~~ normal it is about 8 microns wide (um)
- <6um= a MICROCYTE
- >9um= a MACROCYTEName for condition in which red cells are of unequals size.
- it is a feature of many anemias and other blood conditionsAnisocytosisWhat is the purpose of the "tight-fit" of a RBC moving through a capillaryIt maximizes membrane-membrane contact to facilitate gas exchange
** RBCs pass easily through the smallest blood vessels by folding on themselves and can thus pass through even the narrowest capillariesWhat type of fibers are found around many small blood vessels (along with nerves and muscles)Reticular fibers- Collagen Type IIIIn small blood vessels, RBCs often stack up in aggregates calledRouleauxWhat maintains the biconcave shape of a RBCa specialized cytoskeleton of actin-spectin (spectrin protein binding to actin)
** this provides the mechanical stability and flexibility necessary to withstand forces experienced during circulation
** NOTE: ankyrin binds spectrin to plasma membrnae and this can be defective in Hereditary SpherocytosisThe integral membrane proteins of RBCs are of what two major families1. Glycophorins 2) Band 3 proteins
- the carbohydrate groups on glycophorins and band 3 proteins (and on glycolipids) form the ABO blood group antigens (sugar transferases determine ABO blood group)
- sugar transferase A (type A blood), B (type B blood) , AB (type AB blood), or None (type O blood)A patients RBCs are found to be round and convex this could be do toHereditary Spherocytosis (HS)
- a somatic dominant trait
* defective spectrin or ankyrin, which binds spectrin to plasma membrane
** the RBCs do not form their normal biconcave shape but rather they are found to be round and convex --- this makes them abnormally fragile and prone to rapidly break down- they also transport less O2
** Morphology of HS: RBCs are more spherical, lack the central area of pallor on a stained blood filmWhat is more abundant in the blood: RBCs of WBCsRBCS!!!
(WBCs or lueukocytes are much less abundant ~600 times less abundant: their total number in peripheral blood is 6500-10,000ul)Where do WBCs function?Unlike RBCS they DO NOT function in the blood, rather they DO FUNCTION IN THE TISSUES!!
** WBCS are a normal component of CT
** they dont function in the blood but they do use blood to transport themselves from the bone marrow where they are made to their major sites of activity in tissues
* they leave the bloodstream by migrating between endothelial cells of the blood blood vessels- diapedesis (the crawling), extravasation (the whole process)Leukocytes are classified based onThe presence or absence of specific granules (granulocytes or agranulocytes)
1. Granulocytes
- Neutrophils (most abundant), eosinophils, basophils: all have specific granules (secondary granules) - and can be differentiated according to their color of staining with Wright stain
** each granulocyte has different set of enzymes/weapons- to fight diff. enemies
2. Agranulocytes
- Lymphocytes, monocytes- DONT have specific granules, however ALL WBCs possess small, nonspecific azurophilic granules (secondary granules- lysosomes)What is the purpose of a differential WBC count(this is the % of total counted WBC type- out of 100 of counted blood cells % that are neutrophils, eosinophils, etc.)
the differential counts the percentage of each type and will determine if:
- if the cells are present in normal proportion to one another
- if one cell type is increased or decreased
- if immature cells are presentIf there is a requirement for increased activity of any WBC type in the PERIPHERAL TISSUES, the number and proportion of that cell type rises markedly IN THE BLOOD. Can you give two examples of this?- In a bacterial infection: neutrophil count will go up
- In a parasitic infection: eosinophil count will go upWhich live longer: agranulocytes or granulocytesAgranulocytes live much longer!!! (lymphocytes and monocytes)
- Lymphocytes can live a few days to a number of years if they become memory lymphocytes
- Monocytes can live a few days in the blood, but several months to years in connective tissuesAre granulocytes dividing cellsNO! they are ALL NONDIVIDING terminal cells- with a life span of only a few days after they are released from bone marrow, if they dont "die in battle" first
** withdrawal of growth factors when granulocytes leave the bone marrow is what triggers their apoptosis in the CT after a few days
Lifespans:
- Neutrophils: live a few hours in blood, a few days in tissues
- Eosinophils and Basophils: only live a few daysWhat are the most numerous of the white blood cellsNeutrophils (aka Polymorphonuclear leukocytes)
- they constitute 60-70% of the total leukocyte population
Description:
* the lobes of their multilobed nucleus (3-5lobes) are connected to each other by slender chromatin threads
* neutrophils are motile cells: they leave the circulation and migrate to their site of action in the connective tissues (they are the best at diapedisis bc their lobes allow them to get really skinny- and slip through endothelial cells)
** neutrophils (and all WBCs) are INACTIVE and spherical while circulating in the blood stream but show an ACTIVE ameboid movement upon adhering to a solid substrate (like in the tissues)Main function of neutrophils is toact as the first line of host cellular defense against BACTERIAL infections
** they defend tissues outside the blood by killing their targets
* neutrophils are among the FIRST cells to appear in acute bacterial infections
*** dead neutrophils and bacteria are the main ingredients of pusThe key to identifying neutrophils is the shape of their nucleus which is3-5 lobed nuclei
- they also have azurophilic non-specific granules (lysosomes)
and neutral-staining specific granulesCan neutrophils survive in anaerobic environmentYES!
* neutrophils contain few mitochondria as they use mainly glycolysis to generate ATP
- the ability of neutrophils to survive in an anaerobic environment is highly advantageous, because they can kill bacteria and help clean up the debris in poorly oxygenated regions, ex: inflamed or necrotic tissue
** neutrophils contain a lot of glycogen (which is used as a fuel source for glycolysis)Neutrophils are active phagocytes of bacteria and other small particles- what are two reasons that they select bacteria/particles to be phagocytosed?1. They are coated with antibodies and/or complement (i.e. opsonized with "eat me" signals or,
2. bc they are emitting chemoattractors
** chemoattractors/chemotactically active factors are important mediators of a number of processes because they attract the needed cell types to the area where they are needed.
they function in:
1. immune responses
2. inflammation
3. wound healing
4. embryogenesisChemotaxiscrawling along a soluble concentration gradient towards its sourceCan you give two examples of chemotactically active factors1. N-formylated Oligopeptides of Bacterial Origin:
- mitochondria also make N-formylated proteins when they translate proteins inside mitochondria (just like bacteria),
- ruptured mitochondria release these proteins (13 proteins with N-formyl groups) - they are chemotactic for phagocytic cells because the body thinks it is being invaded
* one main reason that necrosis causes inflammation
* this is part of the INNATE immune system (neutrophils will recognize any bacterium, regardless of whether they have ever seen this particular strain before (if the bacteria is opsonized with antibodies, it is an even better target)
2. Chemokines: a subset of cytokines which can induce chemotaxis of a leukocyte (a cytokine is any number of substances, such as interferon, interleukin, and growth factors, which are secreted by certain cells of the immune system, and have an effect on other cells)4 classic symptoms of inflammation (swollen reddened state) produced in an area of the body as a reaction to injury or infection1. Swelling- caused by edema
2. Redness- caused by increased blood flow
3. Heat- caused by increased blood flow
4. Pain- caused by irritation of nerve ends
5. Inhibition of the affected area (seen sometimes)
** acute inflammation is a rapid host response that serves to deliver leukocytes and plasma proteins (such as antibodies) to sites of infection or tissue injury)Acute inflammation has 3 major components that occur in sequence- what are they1. alterations in vascular caliber that lead to an increase in blood flow
2. structural changes in the microvasculature that permit plasma proteins and leukocytes to leave the circulation ** loosening of capillary endothelial cell tight junctions
(Histamine increases the size of blood vessels)
3. MIGRATION of the leukocytes from the microcirculation (diapedesis), their ACCUMULATION in the focus of injury, and their ACTIVATION to eliminate the offending agentNeutrophil behavior in inflammationChemical messengers are released by basophils, mast cells, blood plasma, and damaged tissue. These inflammatory chemicals stimulate leukocyte margination (adhesion to the capillary wall), diapedesis (crawling through the capillary wall), chemotaxis (movement toward that source of the inflammatory chemicals), and phagocytosis (engulfing bacteria or other pathogens)Passage of blood cells (especially white blood cells) through intact capillary walls and into surrounding tissue is known asDiapedesisA patient comes to your office with extremely low blood pressure while dealing with Pneumonia.. What are you concerned of?* When sepsis is accompanied by low blood pressure, it is called SEPTIC SHOCK and carries the highest risk of death and complications
*** sepsis is a serious condition that occurs as a complication of a severe local infection when it spreads throughout the body
- it develops when the chemicals of immune system released into the bloodstream to fight and infection cause inflammation throughout the ENTIRE BODY instead of just locally
* cytokines released in a large scale inflammatory response result in
- massive vasodilation
- increased capillary permeability
- decreased systemic vascular resistance
***** low blood pressure, reduces tissue perfusion pressure, causing the tissue hypoxia that is characteristic of shockDo eosinophils and basophils contain different substances in their granulesYES!What are the 2 main type of granules that neutrophils contain- which contain hundreds of proteins, "weapons" used to kill bacteria1. Azurophilic granules (aka primary granules)
- These are the LYSOSOMES of the nuetrophil and contain myeloperoxidase, which helps to generate highly reactive bactericidal hypochlorite and chloramines (neutrophil oxidative burst)
2. Specific granules (aka secondary granules)
- "neutral"- colored in neutrophils
- the smallest granules which contain various enzymes and antimicrobial agents (ex. lysozyme, lactoferrin)Neutrophil Oxidative Burst1. During Phagocytosis, NADPH oxidase causes a burst of O2 consumption that leads to the formation of:
- superoxide (O2-) anions and
- hydrogen peroxide H2O2 (* both are destructive by themselves)
2. H2O2 used by myeloperoxidase (MPO) plus Cl- to form HOCL, which then produces the strongly antiseptic hypochlorite ion (OCl-), the active ingredient in bleach!
** this "bleach" denatures proteins and membranes of microorganisms and kills them
* it can also kill other cells of the body, "collateral damage" of fighting infectionA pt comes to your office complaining of recurrent life-threatening bacterial and fungal infections in either his skin, lungs, GI tract, lymph nodes, liver, and spleen. What could be the cause hmmmmmChronic Granulomatous Disease (CGD)
- an inherited disorder of phagocytic cells
- results from an inability of phagocytes to produce bactericidal superoxide anions O2- (caused by a defect in the NADPH oxidase enzyme of phagocytes)
** CGD can lead to these recurrent life-threatening bacterial and fungal infections that occur most commonly in those organs that serve as barriers against the entry of microorganisms from the environmentWhat are Neutrophil Extracellular Traps (NETs)- Extracellular strands of decondensed DNA in complex with histones and granule proteins, which were expelled from dying neutrophils to ensnare and kill microbes
** NETs provide for a high local concentration of antimicrobial components and bind, disarm, and kill microbes extracellularly independent of phagocytic uptake
** NETs may also serve as physical barrier that prevents further spread of the pathogens
** Neutrophils can shoot NETs as traps to catch pathogens- just like spider man!
**** This NET formation (NETosis) is one of the 3 ways that Neutrophils kills things- the other 2 ways are phagocytosis and degranulation (for "prey" too big to phagocytose)What kills more bacteria: NETs or by neutrophil phagocytosisNETs!!!
* these are both good and bad
On good side:
- delivering the granule proteins into NETS may keep potentially injurious proteins like proteases from diffusing away and inducing damage in tissue adjacent to the site of inflammation (i.e. prevent "collateral damage")
On the bad side:
- NETs may also later cause autoimmune disease by stimulating formation of antibodies against DNA. Exaggerated NETosis or diminished NET clearance likely increases risk of autoreactivity to NET componentsDescribe EosinophilsThey have a sausage-shaped, bilobed nucleus
- the two lobes are connected by a thin chromatin strand and nuclear envelope
- are round cells (in the blood),
- have large, salmon pink colored specific granules
*** MAJOR BASIC PROTEIN causes eosinophilic/acidophilic staining of specific granules
* eosinophils also contain azurophilic non-specific granules (lysosomes)Eosinophils function in- parasitic infections
- asthma and allergies (together with mast cells and basophils)An increase in the number of eosinophils in the blood is referred to asEosinophilia
* associated with parasitic infections and allergic reactionsParasitean organism that grows, feeds, and is sheltered on or in a differed organism while contributing nothing to the survival of its host
- parasites are of diff. types and range in size from tiny, single-celled, microscopic organisms (protozoa) to large, multi-cellular worms (helminths) that may be seen without a microscope
** Bacteria can also be parasites, BUT eosinophils generally fight MULTICELLULAR parasites like WORMS, which can be quite large (a tapeworm, for example, may be up to 20 ft long)The way that eosinophils attack their prey is based on two considerations1. their prey are (usually) eukaryotes like themselves
2. their prey are (usually) much bigger than they are, and too big to be phagocytosedEosinophil specific granules containMAJOR BASIC PROTEIN (50% of total granule protein)
- the highly basic nature of the protein contributes to its toxicity by causing it to "gum up" and denature proteins on the plasma membrane of other eukaryotes
** it causes eosinophilia (acidophilia) of specific granules- gives eosinophils their name!
NOTE: eosinophils contain diff "weapons" than neutrophils because they are hunting different "prey" (not bacteria)On EM which WBC can be recognized because of the dark stripe on its specific granulesEosinophils
** this line is the Major Basic ProteinSince parasites are often too large to be phagocytosed, how do eosinophils kill them?They attach to their surface and extrude the contents of their granules (both specific and non-specific) into the extracellular space
*** IMPORTANT: Eosinophils are often first attracted to surface of parasite by BOUND ANTIBODIES, they then release their granulesWhen eosinophils release the Major Basic Protein (and other substances) into tissue, in addition to killing the parasites it can also cause tosurrounding normal tissue (collateral damage)
ex. If this happens in the intestine, it can cause diarrhea and other irritationsA hallmark of allergic disease isinfiltration of the tissues with increased numbers of eosinophils (eosinophilia)
- result of co-ordinated action of cytokines causing selective trafficking of eosinophils into allergic tissue
Ex:
- Allergy, cow's milk intolerance, and gluten sensitivity cause increased numbers of eosinophils in the bowel mucosa
- Asthma causes increased numbers of eosinophils in the lung tissueIf a pt comes to you with bronchial asthma it is likely thatthey have an increased number of eosinophils in their lung tissueThe rarest leukocyte, less than 1% of the total leukocyte populationBasophils
- have numerous basophilic (blue) granules in the cytoplasm that usually make it difficult to see the nucleus clearly
- has an S-shaped nucleus, but you usually cant see it in light micrographs because of the granules
** the specific granules of basophils contain heparin and histamine (like mast cells)Basophil function is very similar to the function ofMast cells BUT they are different cell types!
On the good side of basophils:
- they leave the blood and accumulate at the site of infection or other inflammation- there they release a variety of mediators such as histamine, serotonin, prostaglandins and leukotrienes which increase the blood flow to the area and in other ways add to the inflammatory process
On the bad side of basophils:
- they have immunoglobulin E (IgE) receptors (like mast cells) and the mediators released by basophils play an important part in some allergic responses such as hay fever and in anaphylactic response to insect stingsSince Basophils closely resemble Mast cells of connective tissue and their basophilic granules look like those of mast cells; and their granules both also contain histamine and heparin. How are these two differentiated?By their location!
- If it is in blood- it is a basophil
- If it is in connective tissue- odds are it is a mast cell because basophils are very rare in CTThe largest of the circulating blood cells (range in size from 12-20 microns) areMonocytes - an Agranulocyte-
- they are ~2-3 times the diameter of RBCs
- constitute 3-8% of the leukocyte population
- have large, acentric, indented or kidney-shaped nucleus
- the chromatin network is coarse by not overly dense
- their cytoplasm is bluish gray and has numerous azurophilic ganules, (lysosomes) BUTTTTT it has NO SPECIFIC GRANULESFunctions of Monocytes1. Avid Phagocytes:
- in tissues they phagocytose and destroy dead and defunct cells as well as antigens and foreign particulate matter (such as bacteria)
2. Antigen Presenting Cells
- they play a major role in the immune response
* part of mononuclear phagocyte systemMononuclear Phagocytes Systemmembers of family play a major role all over the human body
- all develop as monocytes in bone marrow
- then enter the bloodstream
- then leave the blood and enter CT where they develop into macrophages
** the characteristics of the CT surrounding the newly formed macrophages determine their exact final differentiation
ex: if it is dermis they can further differentiate into Langerhan's cells (microglia in nervous system) and then the enter the epidermis; if it is bone, they can become osteoclasts (etc)Which Agranulocyte consititutes 20-25% of the total circulating leukocyte populationLymphocytes
- round cells, slightly indented
- dense (heterochromatic) round nucleus (apprx. 8 microns) that occupies most of the cell
- thin rim of cytoplasm stains light blue and contains a few azurophilic granules, BUT NO SPECIFIC GRANULES
- they vary in life span (some live only a few days and others survive in the circulating blood for many years)
** the 3 groups of lymphocytes (B, T, and NK cells) ALL look the same by histological stainingLymphocytes are 20-25% of the leukocytes in the blood but they are the main type of cell found in thelymph!
Hence the name: Lymphocyte!
* lymphocytes recirculate between blood, tissues, and lymph
- they do this as part of the immune system that monitors the tissues
** they are the only cells that is able to enter to tissue and go back into the blood (blood --> tissue --> lymph)B- lymphocytes can transform intoAntibody-secreting plasma cells (in tissue)
** have extensice rER and "clockface" nucleusT or F: Platelets are cells that are formed from other cellsFALSE!!!
Blood platelets (aka thrombocytes) are NOT cells, they are pieces of a cell
- derived in the bone marrow from a giant precursor cell: megakaryocyte
* platelets life spain is about 10 days
** their primary function is to prevent excessive internal or external bleeding after and injury by helping to form blood clots
NOTE: in a blood smear, platelets are often found as aggregatesDescribe plateletsThey are nonnucleated, disklike cell fragments 2-4 microns in diameter containing:
- lysosomes
- mitochondria
- some ER
- some Golgi
- three types of granules
- extensive cytoskeleton
In a cutaway diagream of a platelet you see:
1. Peripheral MT bundle (maintains the shape)
2. Actin and myosin (clost contraction)
3. Organelles facilitate clotting
- Mitochondria for ATP production
- Granules contain clotting factors
- Dense tubular system sequestering Ca2+ for signaling (similar to SR in skeletal muscle)
- Open Canalicular system facilitates signaling and secretionPlatelet granules containVon Willebrand Factor
- promotes adhesion of platelets to endothelial cells, also produced by endothelial cell
Platelet Factor IV
- stimulates blood coagulation
& other factorsPlatelets function inblood clotting and wound repairHow do platelets function in blood clottingTo seal wounded endothelium
- platelets help to temporarily seal off the site of a wound by sticking to the exposed, damaged edges of the blood vessels
* Platelets are activated upon exposure to collagen of basal lamina and CT underlying endothelial cells of blood vessels ** which is normally hidden except when endothelium is injured
WHEN PLATELETS BIND TO WOUNDED ENDOTHELIUM:
- they become activated, release their granules and these factors react with the clotting factors in the blood (like fibrinogen) to form blood clotSince the blood clot formed by platelets is only a temporary solution to stop bleeding, what is neededVessel repair!
The aggregated platelets help this process by secreting chemicals, primarily:
- Platelet-derived growth factor (PDGF) and
- Transforming Growth Factor beta (TGF beta)
** these substances promote invasion of fibroblasts from surrounding CT into the wounded area to form a scar and also repair of blood vessel endothelium
** local applications of these factors in increased concentrations through platelet-rich plasma (prp) has been used as an adjunct to wound healing for several decadesErythropoiesis requires proliferation of cells, heme synthesis, and DNA synthesis and therefore requires:- iron
- folate
- B12Causes of Anemia- blood loss
- decreased erythrocyte production (due to iron deficiency, folate or B12 deficiency, thalassemia, or cancers)
- hemolysisTwo types of anemia includeMicrocytic and Macrocytic
Microcytic:
- small or immature erythrocytes
- lack of: iron, heme, or hemoglobin
- can be do to lead poisoning
Macrocytic: (growth of RBC without division)
- Megaloblastic Anemia (folate)
** enlarged cells and nuclei- do to a failure to make sufficient number of normal erythrocytes because cells do not divide normally
- Pernicious Anemia (B12)Signs of severe Iron Insufficiency- Anemia- fainting
- chest pain
- angina
- heart attack
other main symptoms:
- fatigue
- weakness
- pallor
- palpitations
- headache
- cold hands and feet
- sore or inflamed, swollen tongue
- brittle nails
- restless leg syndrome
- hair lossIron insufficiency (causing Anemia) is more common inwomen (have higher dietary requirements)
- lack of iron impairs hemoglobin synthesis and causes MICROcytic hypochromic anemia: leads to pallor, weakness, lassitude
* lack of iron can also be caused by massive hemorrhage, chronic blood loss, menstruation, growth, or pregnancy2 important properties of iron1. electron carrier in redox reactions it can be converted from Fe3+ (Ferric form) and Fe2+ (Ferrous form)
*** it can switch between the ferrous and ferric states to facilitate reduction/oxidation and electron transfer
2. Reversible oxygen binding
Fe2+ + O2 --><--- Fe2+...O2
** only ferrous iron (Fe2+) binds O2, ferric iron (Fe3+) does notDoes Fe3+ function as an oxygen carrierNO!
only Fe2+ (ferrous iron) can bind to oxygenIn the body iron can be foundPresent in many proteins either bound to Cys side chains (FeS proteins) or as part of hemes:
- Hemoglobin: binds O2 in RBCs
- Myoglobin: binds O2 in muscle
- Respiratory cytochromes: electron carriers in respiratory chain
- Cytochrome P450: enzyme of drug metabolism and steroid synthesis
Iron-sulfur clusters: redox centers in electron transport; active sites of various proteins
- they are often cubic or rhomboid forms of iron and sulfur (Fe4S4 or Fe2S2)Heme is thetightly bound prosthetic group of Hemoglobin, myoglobin, the cytochrome P450, catalase, and many other proteins
* it comprises one ferrous ion (Fe2+) in the center and a protoporphyrin IX (a tetrapyrrole ring)
thus heme+globin protein= hemoglobinRecommended intake of iron per dayrecommended
- 8mg for males
- 18mg for females
** absorption and distribution is tightly regulated: about 1mg/day is absorbed
Sources of iron:
- liver, and lean meat: give heme iron (heme iron is absorbed with 30% efficiency)
- beans and spinach: non-heme iron (non-heme iron which is mostly in vegetables is absorbed with <10% efficiency through the DMT-1 intestinal transporter)
** Absorption of Non-heme iron is facilitated by gastric acid and Vitamin C (reducing agent to convert it to its ferrous form) and reduced by phytate, tannins, and antacids (found in other foods)Some alcoholics are at risk foriron overloadPeople with strict vegetarian diets may haveLow iron status
* because vegetable iron (NON-heme iron) is more poorly absorbedwhich is absorbed more efficiently: Heme or Non-heme ironHeme ironFree (unbound or unchelated) iron isFree iron (Fe3+ and Fe2+) is
dangerous due to catalyzing free radical formation
* Role of iron in Haber- Weiss reaction: Free iron can catalyze formation of hydroxyl radical, the hyper-reactive ROS species
NOTE: Fe3+ is safer- but almost all iron in the body is tightly bound to proteinsTransport of iron across the membranes requires it to be in theFerrous State (Fe2+)- divalent cation transporters
** redox enzymes called ferroxidases cooperate with membrane transporters to change the oxidation stateIron is stored as cells asFerric Iron (Fe3+) in ferritin and hemosiderin
** NOTE: iron is also transported in the blood as ferric iron bound to transferrinIn the body- the most mg of Iron can be found inHemoglobin
- with men having more than womenIron absorption and use is regulated byerythropoietinMajor sites of iron storage in the body are1. Liver (~1g): it is stored here as ferritin
2. Reticuloendothelial macrophages (~0.6g) - senescent RBCs are degraded in macrophagesIron is found in circulation or use in1. erythrocytes ~1.8g
2. bone marrow ~0.3mg (marrow uses ~20mg/day)
3. myoglobin- 0.3-0.5gDescribe the circulation of iron in the body1. <10%; ~1mg of dietary iron is taken up
2. similar small percentage is lost to excretion, loss of skin, etc
3. iron is transported using transferrin
4. iron is stored as ferritin (mostly)
5. only ~3mg of iron is in the circulation
6. iron from senscent RBCs is stored in the reticuloendothelial macrophages in a rapidly deliverable form
7. bone marrow takes up ~20mg/day for use in making RBCsDietary iron is generally liberated as the Fe3+ form (ferric), this is then converted intoFe2+ Form (ferrous) for transport through the dmt-1 divalent metal transporter
** it is stored in enterocytes in ferritin (Fe3+) and released as needed and converted to Fe2+ (this Fe2+ exits through ferroportin) - is converted back to Fe3+ by hephaestin or by ceruloplasmin and bound to transferrin (Tf)
** excess dietary iron in ferritin lost as enterocytes are sloughed off (~1mg/day)Iron uptake in the dudenum is facilitated by- Ascorbate
- Amino acids
- Citrate
- Iron deficiency
It is inhibited by:
- Phytates
- Tannins
- Soil
- Iron overload
- Antacids
Competed by:
- Lead
- Cobalt
- Strontium
- Manganese
- ZincDMT1 (divalent metal transporter) absorbs non-heme iron asFe2+Ferritin and Hemosiderin (a partially denatured form of ferritin, that is abundant when iron stores are high) storeFe3+ in the cell
** Ferritin is the major storage form or iron in cells, it is regulated to maintian iron levels appropriately and measured clinically for anemia and hemochromatosis
- Ferritin can oxidize iron to Fe3+ and stored it in a mineral form (ferric hydroxyphosphate FeO(OH) with some FeO(H2PO4)- this is enclosed by 24 subunits in a shell around the mineral core- makes a repeating unit of iron storage (many of thses are inside the shell)
- release of iron from ferritin occurs by transport of ferritin to lysosomes (along with DMT1 transporters), where it is degraded and the iron reduced and exported
Nml values:
- Men: 18-270 ng/mL
- Women: 18-160 ng/mL
- Children (6 months-15yrs): 7-140ng/mL
- Infants (1-5 months): 50-200ng/mL
- Neonates: 25-200 ng/mL
>1000ng/ml- indicates hemochromatosis
* ng/mL= nanograms per milliliter
* ng/mL- mcg/LFerroportin bringsFe2+ across basolateral membraneTransferrin (Tf) bindsFe3+ in the blood
* it carries 2 Fe3+
** it is the main iron carrier in circulation
- It is rarely occupied- normally around 30% of sites have iron (normal range is 20-55%)
Transferrin concentration is measured as Total Iron Binding Capacity (or TIBC): how much iron can be bound by transferrin
Serum Iron/Total Binding Capacity= Transferrin Saturation
** these numbers are useful in screening chronic iron overloas or deficiencyCells acquire iron byreceptor-mediated endocytosis
* not that heme and other iron-containg proteins are synthesized in individual cells, so all cells require that iron be delivered to them
Steps of this cellular absorption
1. Transferrin (Tf)- bound iron binds to receptors
2. Receptor-mediated transferrin endocytosis
3. Free iron is released, reduced, and transported to cytoplasm (DMT)
4. Re-oxidized iron can be stored in ferritin (as Fe3+)
5. Iron can be translocated to mitochondria for incorporation into:
- Heme
- Iron-sulfur clustersHow is iron regulated intracellularlyIn iron deficiency, cells make more transferrin receptor and less apoferritin
- this is done by Iron Regulatory Proteins (IRPs)- that bind to iron response elements in the mRNAs when iron is scarce- these are forms of TRANSLATIONAL regulation
* at same time a decrease in Ferritin means you will release more Fe from iron storeHepcidin acts toHepcidin is released when iron is high
It works to limit iron absorption by inhibiting the iron exporter ferroportin in:
- intestinal enterocytes
- macrophages (which phagocytose sensecent RBCs and release the iron from the cells to the circulation)
- liver stores
* its net effect is to LOWER circulating iron and dietary absorption
and it effectively acts as FEEDBACK INHIBITION
NOTE:
- iron increases hepcidin
- some pathological conditions (cancer or inflammation) also increase hepcidin
- hepcidin is regulated transcriptionally (increased hepcidin mRNA levels with higher iron levels)
** Iron can be rate-limiting for growth of bacteria in blood. Hepcidin restricts iron supply in infections and cancers and lead to Anemia of Chronic Disease because Iron is trapped in macrophagesMaintenance of Iron HomeostasisOn a dialy basis as much iron is lost as is absorbed (net intesting absorption and excretion is near zero in adults)
- ~1mg out of 10-20mg daily req. of iron is absorbed and a similar amt is lost to excretion along with excess dietary iron
** Iron from worn-out RBCs is recycled from macrophages in spleen, liver, and elsewhere to the bone marrow
- bone marrow uses ~20mg/day for making fresh erythrocytes- this is delivered via transferrin from liver and spleen macrophages
* A similar amt of iron (~20 mg total) is delivered to spleen and liver from senescent erythrocyte taken up by macrophagesWhat are some causes of Iron deficiency Anemia- Poor nutrition
- rapid growth
- menorrhagia (heavy periods)
- pregnancy
- acute blood loss
- blood-sucking parasites
- occult bleeding: colon cancer?Who is mostly affected by iron deficiency anemia20-25% of worlds babies have iron deficiency anemia
- Normal infants: Hematocrit of 50-60% at birth, 35-40% at 6 months
NOTE: breast milk has more bio-available iron in lactoferrin than cows milk
42% of women worldwide and 26% of men are "anemic" according to WHO
- daily allowance in US is 8mg/day for men and 18mg/day for menstruating women
** iron supplements are given routinely during pregnancy (you need about a 4g increase to compensate for blood loss at birth and other costs of preganancy that req iron- note that you do save some iron via not menstruating, and contraction of maternal RBC mass after birth)
In US, 9-11% of toddlers, adolescent girls and women of childbearing age or "iron deficient"Aplastic Anemiacaused by bone marrow failureHemolytic Anemiacaused by destruction of RBCsThalassemia:Inability to make hemoglobin alpha or beta chainsSideroblastic anemia:inability to use iron for heme synthesis, for example in deficiency of vitamin B6Megaloblastic (macrocytic) anemia:caused by impairment of DNA synthesisAnemia of renal diseasedue to lack of kidney hormone erythropoietin, which is needed to stimulate the bone marrowHemochromatosisGenetic Iron Overload
10-40g of iron (2.5g is typical in a male)
* more prevalent in older men from northern europe
*** exacerbated by mutations in HFE gene (homozygosity for the C282Y mutation) , which senses iron in the liver: this reduces hepcidin secretion, more iron absorption through ferroportin
- this affects the liver, heart, and endocrine glands, anterior pituitary malfunction, darkening of the skin
- it increases risk for liver cirrhosis, diabetes, cardiomyopathy, and arthritis
Treatment= repeated phlebotomy
** only 5% of homozygotes develop symptoms
- "Bantu hemosiderosis" in South Africa is caused by a mutation in ferroportin geneIs iron overload caused by anemia treated with phlebotomyNOO
Only Hemochromatosis- Genetic Iron Overload (due to homozygosity for the C282Y mutation in HFE gene) is treated by phlebotomyWhat are other reasons for iron overload, other than Hemochromatosis- Alchoholism: alcohol increases iron absorption, frequent iron excess in liver of patients with alcoholic liver disease
- Anemia: even if not caused by iron deficiency, it increases iron absorption
- Blood transfusions: iron introduced by blood transfusions ends up as storage ironTransferrin saturation is a good indicator ofiron deficiency or overload
Serum iron/TIBC (total iron binding capacity)= transferrin saturationHemtocrit, Hemoglobin, Transferrin saturation, Serum Ferritin are all ___ in iron deficiencydecreasedTransferrin saturation (normally 20-55%) and serum ferritin (normally 1.2-30mcg/dL) areIncreased in iron overload
- Hematocrit (41-49%) and hemoglobin (12-18%) remain normal
** Serum Ferriten is an indicator of tissue iron stores (it is used to confirm iron deficiency)
- it leaks out of dying cells in liver and elsewhere who release ferritin, and can be measured in with a radioimmunoassay (this value is much lower than serum iron- which is mostly on transferrin
In iron overload: the Serum Ferriten is >50-100mcg/dLWhat occurs once senescent erythrocytes are taken up by macrophagesIn these macrophages heme is converted to bilirubin which then travels on albumin to the liver
- the liver conjugates bilirubin and sends diglucuronide to bile and intestines
- bilirubin is deconjugated in intestine and converted to urobilinogen (whihc is mostly converted by bacteria to brown stercobilin and excreted- some is re-absorbed, oxidized in the kidney and excreted there as urobilin (yellow)
unconjugated= indirect bilirubin
conjugated= direct bilirubinHeme Degradation- erythrocytes last ~120 days
- most lost heme is from erythrocytes (85%) with the remainder from hepatic P450 and other cytochromes
- Heme is oxidized, iron released, and the macrocycle broken
- converted to bilirubin
- sent to liver for excretion in the bile as a diglucuronide adduct
- after transport to the liver: proprionic acids are modified, reacted with UDP-glucuronide
then secreted as Bilirubin diglucuronide into the bileHeme excretion- Secretion of bilirubin-diglucuronide into the bile
- removal by bacteria of glucuronic acid makes: Urobilinogen
- is mostly oxidized to stercobilin (brown)
- some reabsorbed to portal circulation and then converted to yello urobilin and excreted in the urine by the kidneysJaundice (AKA icterus)is not a disease, but a common symptom (due to disorder of heme degradation)
- Yellow discoloration of sclerae, nails, and skin
*reflects increased bilirubin levels in the blood and deposition (normal bilirubin= 2-17micromolar (1.0mgl/dL)- jaundice occurs with > 40 micromolar)
Causes of jaundice include:
- Hemolysis (prehepatic jaundice)
- Biliary obstruction
- Neonatal jaundice
- Congenital defects
** premature babies are unable to conjugate bilirubin and excrete- so it will cross over the BBB faster (they have less mechanisms to keep it from the CNS)- may lead to brain damage-- there is a type of phototherapy that helps to cure thisDecreased iron refers to ___ anemiaMicrocyticFolate (vitamin B9) and B12 deficiency refers to ____ anemiaMacrocyticSources of Vitamin B9 (Folate) and its deficiencySources: green leafy vegetables, yeast, liver, some fruits (heat labile)
- deficiency: pregnant women, alcoholics
* most common vitamin deficiency in the US
- mild or borderline deficiency is commin it can be caused by:
- loss (pregnancy)
- poor dietary habits
- poor absorption (alcoholism, intestinal pathology).
- or inhibition by methotrexate
Sxs: Megaloblastic Anemia
- megaloblasts= oversized RBC precursors in the bone marrow
- macrocytes= oversized RBCs in the blood
* these cells are formed when DNA replication cannot keep pace with cell growth, while RBC production slows down
* megaloblastic changes are also seen in other tissues with rapidly dividing cells, for ex; Intestinal epithelium
sxs:
- Loss of appetite
- weight loss
- weakness
- glossitis (sore tongue)*
- irritabilityWhat do Folate Supplements help to preventSpina Bifida (incomplete closure of the lumbar spine) and anencephaly(absence of the brain), two common neural tube defects
- current recommendation is that all women who might become pregnant should consume at least 400micrograms of folic acid/day
* Neural Tube defects are among the most serious birth defects (1:400 births)The principal role of folate is to act as a singlemethyl group donor
Folate (gets its nitrogens reduced along this path)--> Dihydryo-Folate (DHF) --> Tetrahydro-folate (THF) ** this is active part of folate that is used for chemistry** it can become either 5,10N-methylene-THF which becomes 5-methyl-THF or 10N-formyl-THF
- 5,10N-methylene-THF gives methylene for synthesis of pyrimidines
- 5N-methyl-THF give methyl for methylation of DNA, proteins, and lipids
- 10N-formyl-THF gives formyl for the synthesis of purinesIn folate chemistry for donating methylseither serine or glycine is used, not both at once
** serine and glycine can be broken down in the reaction of THF --> 5,10N-methylene-THF..they can also be used for the synthesis of glycine and serine; the reactions lie near equilibrium are are reversible by mass action
- FIGLU is formiminoglutamate.. it is formed from the breakdown of histidine. The N5-Formimino-THF can be converted to either 5,10 methylene THF or N10-formyl-THF
** then the reaction of 5,10-methylene-THF to 5-methyl-THF is biologically irreversible (HIGHLY EXERGONIC) **this is why the following methionine synthase reaction is so important. Without it, folate gets trapped as 5-methyl-folate and cannot be reconverted to THF
Methionine synthase (AKA homocysteine methyltransferase) then uses B12 as a cofactor
- it catalyzes synthesis of methionine from homocysteine- the added methyl group comes from 5-methyl-THF
**5 methyl-THF trap hypothesis is that B12 deficiency fails to regenerate THF from 5-methyl-THF (5-methyl-THF then accumulates and creates a folate insufficiency)
** thus signs and symptoms of B12 and folate deficiency are similar. Both result in MACROCYTIC anemia
sxs need to be investigated to see if the deficiency is due to folate or B12Folate requires action by the enzyme ____ to be turned into THFDihydrofolate reductase (DHFR)
** Methotrexate (aka Amethopterin) is a competitive inhibitor: used to treat lung cancer, breast cancer, leukemia, lymphoma, osteosarcome and also various autoimmune diseases
- Aminopterin is another folate analogue used as a chemotherapeutic and immune suppressant
Both methotrexate and aminopterin work by inhibiting dihydrofolate reductase (competitive inhibitor)- this prevents THF formation and prevents purine and pyrimidine biosynthesis.
*rapidly dividing cells req purines and pyrimidines for DNA replication- therefore these agents target dividing cells more than non-dividing cells in Go. - the severe side effects are because normal cells that undergo division are also targeted- this particularly affects the immune system and erythropoiesisSource of Vitamin B12- Synthesized ONLY in bacteria, NOT in plants- the rarest vitamins
- only available from animal products: liver, red meat, eggs, dairy, and enhanced cerealsDeficiency of Vitamin B12 (aka cobalamin)results in anemia
- malabsorption may be commin in older people
- often malabsorption due to loss of intrinsic factor (IF) resulting in pernicious anemia
- the anemia is partly because of B12's role in salvaging methyl-THF back to THF via the methionine synthase reaction
** later stages show neuropsychiatric symptoms (ex. Ataxia)
RDA= 2.4micrgrams but several (2-5) mg are typically stored, thus deficiency may not be apparent for a long timePernicious Anemiastrictly defined as the loss of Vitamin B12 due to loss of intrinsic factor (IF) and poor absorption
= Megaloblastic with low folate
** however it is often used to describe ALL cases of anemia from B12 deficiency
** loss of intrinsic factor can result from autoimmune disease attacking the parietal cells of the stomach or from surgical removal of part of the stomach, or a congenital deficiency
Sx's:
- tired and weak- fatigue
- parasthesia (skin tingling)
- glossitis (tongue soreness)
- other symptoms typically associated with anemia
can also include:
- depression
- low grade fever
- diarrhea
- dyspepsia
- weight loss
- neuropathy
- jaundice
- cheilitis
eventually: cognitive impairment (CNS effects may occur in absence of anemia- treatment IM injections of cyano cobalamin or high oral doses)Describe the structure of Vitamin B12 (aka Cobalamin) and the two specific reactions it carries out- it is a cobalt-containing, pyrrole ring system (similar to porphyrins, but not identical)
- comes in various forms (-CN, -CH3, -deoxy-adenosyl)
Required as an enzyme cofactor for only two known specific reactions:
- methylmalonyl-coA mutase- uses the deoxyadenosyl form (to get odd chain fatty acids into the TCA cycle)
- methionine synthase (aka 5-Methyl-THF-homocysteine methytransferases)- uses the methyl formMethyl malonyl CoA mutase (MCM)- in the mitochondria
- isomerizes methylmalonyl-CoA --> succinyl-CoA
* MCM is involved in metabolism of branched-chain AA isoleucine, valine as well as methionine, threonine, thymine, and odd-chain fatty acids
** it requires the deoxyadenosyl form of Vitamin B12Methionine Synthase (aka homocysteine methyltransferase)uses 5-methyl-THF as a substrate and ties together B12 and folate metabolismMeasurement of ___ is diagnostic for B12 deficiencymethylmalonate
* homocysteine is elevated in both folate deficiency and B12 deificiency but methylmalonic acid is elevated ONLY in B12 deficiencyAbsorption of Vitamin B12 (aka Cobalamin) in the intestine and transport in the blood requires specific factors such as:- B12 is initially bound to transcobalamin I (TC I)- secreted by salivary glands to protect it against stomach acid
- B12 then binds tightly to intrinsic factor, a protein secreted by the parietal cells of the stomach
* the B12/IF complex is absorbed in the ileum - which then goes to the blood
- in the blood, B12 is transported in complex with transcobalamin II (TC II) another protein, to be carried to the liver through the portal circulation
** B12 lost to excretion in the bile is recovered through re-absorption in the intestine (therefore: re-absorption in the intestine preserves B12)Schilling Testtests for absorption of vitamin B12, once normal B12 levels have been establishedVitamin B12 deficiency is very similar to folate deficiency but folate does not show theneurological symptomsMost proteins are synthesized in the liver with the exception ofimmunoglobulinsColloid Osmotic Pressure refers toAlbumin trying to pull H2O into the blood- this opposes hydrostatic pressure which is H2O trying to get out of the blood vessels
* on the arterial end: you have more hydrostatic pressue than the venous end
- but the oncotic pressure stays SAME on both sides- because amount of Albumin does not change
ex: An alcoholic patient with low albumin in blood will have a low oncotic pressure so he will be losing alot of H2O= edema
ex: Pt bleeding profusely, do they have less oncotic pressure? NO! bc the concentration of Albumin does not change- it is only the amount that is lessNo Coagulant the blood will beclotted --> yellow liquid up top= serum (supinatant from cogulated blood) ** has NO fibrinogenExamples of AnticoagulantsHeparin
Citrate
Oxalate
EDTA
Ex: Blood + Anticoagulant ( like Citrate/EDTA - binds to Ca++ and Mg ++ ) centrifuge gives you plasma as the supinatant (plasma is 60% albumin, as well as other plasma proteins- and it does have fibrinogen)In a serum electrophoresis on the extreme left you will havealbumin and on the extreme right you will have gamma globulin (predominantly immunoglobulins)Albumin functions to- determine oncotic pressure
- transport of fatty acids, bilirubin ( a break down product of heme) etc.
- drug transport (salicylates, barbiturates, sulfonamides, warfarin, penicillin)Hypoalbuminemiadecrease blood albumin
- causes H2O to leave from the blood vessel to the ECF- causing ECF to expand- leads to edema
Why would someone develop this?
- reduced synthesis of albumin maybe due to damage to the liver- (IL6/stress response)
- altered distribution (increased capillary permeability, decreased lymph clearance)
- increased catabolism (increased breakdown of albumin due to chronic infections/trauma)
- abnormal losses (burns, renal disease, GI bleeding/loss, hemorrhage
** all these above things could cause hypoalbuminemiaReasons for Hyperalbuminemia (increased albumin)- Dehydration: loss of water and concentration of substances in within the vascular system - same albumin in the blood, but since less H2O it is more concentrated
- Excessive stasis (slowing or stopping of normal flow) during venepuncture: increased hydrostatic pressure and lose H2Oalpha1-globulin (these are negative APRs)* this is seen in an electrophereis
- they are mostly transport proteins and protease inhibitors (limit inflammation and vascular damage)
Main one=
alpha1-antitrypsin: is synthesized by hepatocytes and inhibits trypsin and elastase ** especially in the lungs (neutrophils) and other proteases (so its main function is antiprotease activity in the lung: pulmonary emphysema- it inhibits elastase (a protective protein) in the lung.)
** alpha1- antitrypsin is measured by the trypsin inhibitory capacitydecreased levels of alpha1-antitrypsin could signifylung damagealpha2-globulin- includes protease inhibitors and transport proteins
Main one:
** alpha2-macroglobulin (transcuprein)- a protease inhibitor of plasmin (breaks down clots formed in blood), thrombin and kallikrein, carrier of cytokines and growth factors, zinc and copper transporter
also have
- Haptoglobin: binds free Hb, haptoglobin-hemoglobin complex targets hb for removal by spleen
- ceruloplasmin: transports iron and copper
- thyroxine-binding globulin: highest affinity T3 and T4 transporter
- alpha2-antiplasmin: inhibits plasmin and neutrophil elastase
- protein C (autothrombin IIa, factor XIV): activated protein C (APC) inhibits Factor Va and VIIIaBeta-globulinmay separate into Beta1 and Beta2 peaks
- Beta-2 microglobulin: binds MHC I related proteins, MHC I, QA and CD1- invovled in recognition of self vs non self, hemochromatosis protein (HEF protein)- regulates transferring binding to is receptor
- Plasminogen: zymogen of plasmin and angiostatin; plasmin activated clotting an fibrinolysis
- sex hormon binding globulin: androgen and estrogen binding protein
- transferrin: high affinity iron binding protein
(B2 peak and tail) also has immunoglobins IgA and IgM
- IgA: rare in plasma, mono or multimeric. Regulates Fc receptor mediated inflammatory responses; includes antibody dependent cell-mediated cytotoxicity (ADCC) and degranulation of granulocytes
- IgM: pentamerix, 10 antigen binding sites- regulates opsonizationGamma-globulinpredominanty immunoglobins (on right in electropheresis band)
- IgA
- IgM
- IgG: 75% of free immunoglobins in area, has 2 antigen binding site- functions include rols in agglutination, opsonization, pathogen recognition, type II and III hypersensitivity etc.In liver cirrhosisconcentration of albumin decreases
- while alpha 2 and gamma increaseAPRs ___ in the presence of inflammationincrease
- Albumin is a negative APR (acute phase response) so it decreases in the presence of inflammation
while other proteins will increaseIn nephrotic syndrome (seen in advanced diabetes)There is a decrease in Albumin as it is lost in the urine, and increase in alpha2 and a decreased in gamma
** BOTH Beta2-microglobulin (subunit of HLA) and alpha2-macroglobulin (a protease inhibitor) are used in the detection of nephrotic syndrome [ both of these are acute phase proteins ]Ceruloplasmin (an APR) is an enzyme that transportscopper
It is used in detection of Wilsons disease
- Copper deposition
- Kayser-Fleisher rings (rings in the eyes)
- Hepatic damge
- arthritic changesalpha-fetoprotein (an APR)is produced in the fetal liver
In pregancny it is is increased it indicated: neural tube defect. If it is decreased in down syndrome (Down is downs)
* if it is increased in elderly non pregnant it may indicate hepatocellular cancerFibrinogen is involved inClot formationThe first protein to rise in an acute infection or inflammation, or response to injuryC-reactive protein (CRP)
(the acute phase reactant binds extracts of pneumococal cell walls- CRP is usually increase in pneumococal infection/any inflammatory process)
ex. in major surgery- wont discharge till CRP back to normal levelsFree heme is carried byhemopexin (Hpx)What is the role of Haptoglobin (Hp)after intravascular hemolysis of RBCs the Hb must be bound to Haptoglobin because Hb is toxic on its own in the body
- Heme is then passed to hemopexin and taken into macrophages to be degradedIncreased albumin is due todehydrationDecreased albuminmalnutrition, chronic infections, burns, hemorrhage, impaired liver function, nephrotic syndrome, pregnancy, malnutrition
(only need 1 amino acid missing to get hypoalbumin)Decreased alpha-globulins can lead toAlpha1-antitrypsin deficiencyIncreased alpha2-globulins could lead toNephrotic syndromeDecreased alpha2-globulins could lead tosevere liver disease, wilsons disease, malnutrition2,3 BPG keeps Hb in theT state
- Hb offloads oxygenContents of a mature RBC- 35% Hb
- 60% water
* has 2 alpha and 2 beta chains with an iron (Fe2+) and a heme attached to both (so in Hb there is extensive interactions between unlike subunits )
** oxygenation to Hb causes a considerable structural conformational changePorphyrin- iron complex isHeme
- Fe2+ is added to the porphyrin in the bone marrow
- iron on transferrin is picked up from the blood by immature erythroblasts in the marrow
- Heme is assembled in the mitochondria of immautre erythroblastsTwo states of HbT state: "tense"- deoxygenated
R state: "relaxed"- oxygenated (just imagine yourself breathing in air)
** oxygenation rotaes the alpha1beta1 dimer in relation to alpha2beta2 dimber about 15 degrees
- each pair of alpha and beta subunits stay relatively in the same position to each other under both oxygenated and deoxygenated states
- deoxy: alpha and beta subunit pairs twist relative to other pair
- oxy: alpha and beta subunits twist back to reform salf bridgesWhat state does iron have to be in to bind oxygenFe2+ stateThe protein part of hemoglobin isGlobin
* fromed in cytoplasm and joined in the cytoplasm to the heme that was fromed in the mitochondria
- Hemoglobin- erythrocyte
- Myoglobin- muscle (if in blood indicated muscle damage- called rhabdomyolysis, or toxicity to the kidney: protoxin as myoglobin, ferrihemate is the toxin (it dissociates from myoglobin in acidic environment)
- Neuroglobin- nervous system (used as oxygen store during ischemia and hypoxia)Globin in erythrocytes is atetramer of 2 alpha (or alpha like subunits) and 2 beta (or beta like subunits)
Alpha and alpha-like subunits:
- alpha (found in HbF and HbA): embryonic period --> adulthood (location of stem cell changes: yolk sac --> liver --> gut --> bone marrow)
- zeta: embryonic period in stem cells of the yolk sac, important in alpha thalassemia
Beta and beta-like subunits:
- beta: liver stem cells --> gut --> bone marrow
- delta: made only after birth (mutations result in beta thalassemia)
- epsilon: embyronic period --> early years of life
- gamma: fetal --> early lifeThalassemiaunderproduction of one type of hemoglobin subunit
* most mutations are in regulatory gene
- alpha thalassemia: one of the 4 gene copies of a is not expressed
- beta thalassemiia (MICROCYTIC anemia): one copy is mutated or not expressed or incorrectly splicedDifference between sickle cell anemia and chronic hemolytic anemiaSickle cell anemia: point mutation in HbB --> HbS (Glu --> Val at amino acid 6)
Chronic hemolytic anemia: HbB point mutation --> Hb C or Hb E2,3-bisphosphoglycerate (2,3-BPG)made from 1,3 bisphosphoglycerate (glycolytic intermediate)
1:1 with hemoglobin (normal)
- it is an allosteric regulator of Hb: binds with highest affinity to deoxyhemoglobin in the respiring tissues (not lung)- it induces off loading of oxygen into tissues (so decreased affinity of Hb for oxygen)
* An increase in 2,3 BPG: hyperthroidism or chronic anemia- it is also seen to be very high in blood of smokers
* A decrease in 2,3 BPG: seen in high altitude pulmonary edema and dialysis due to loss into filtrateWhich globin is highest in the fetusgamma
- alpha and beta are highest in adults- this is seen at 24 weeks
* alpha is high most of lifeMyoglobin hasobly one subunit and one heme groupCarbon monoxide is different from CO2 in that itbinds to the same sight where O2 binds (when instead CO2 binds to AA in the globin chain)
Carbon monoxide binds to heme 200x higher affinity than oxygen
- it forms Carboxyhemoglobin (CO-Hb): note that smokers have a higher circulating level of CO-Hb
** this increases your risk of blood clots- you can treat this with Hyperbaric Therapy (3 Atm with oxygen)Methemoglobin, MetHbIron is in the Ferric state, Fe3+ : it cannot bind/transport oxygen- the color is deep bluish, chocolate brown (dark maroon)
** used as a treatment for cyanide poisoning
- it binds cyanide at a very high affinity; poorly reversible and prevents the cyanide binding to cytochrome c oxidase, have to induce formation of Methemoglobin
Note: nitrates induce methhemoglobenemia
* blood stains turning brown is a result of the spontaneous formation of methemoglobin when exposed to air (hemoglobin is converted to methemoglobin spontaneously: Methemoglobin reductase --> MetHb --> Hb)
** if you have greater than 70% metHb- could result in deathA human cell contains 28,602 different proteins, 2,709 of these areenzymes
- they are distributed in the cytosol, nucleus, rER and sER, golgi bodies, mitochondria, lysosomes, plasma and organellar membranes
** most enzymes are present in cells at much higher concentrations than in plasma (bc they are confined to the area in which they have to do their work)
- changes in plasma enzyme levels may help to detect and localize tissue cell damage or proliferation, or to monitor treatment and progress of disease
* in the absence of cell damage the rate of release of plasma enzymes depends on:
- the rate of cell proliferation (indicative of a tumor)
- the degree of induction of enzyme synthesisPlasma cholinesterase (BuChE) (AKA butinol cholinesterase is measured inorganic phosphate poisoning
* it breaks down esters like ACh
* it also degrades drugs such as scoline and cocaine
- it is found in plasma and synthesized in the liver
NOTE: acteylcholinesterase (AchE) (which is found predominantly in nervous tissue and erythrocytes) ONLY degrades ACh (plasma cholinesterase can degrade ACh and others)
** Organic phsophatases like nerve gases work to increase ACh- therefore they inhibit the activity of cholinesterases (they induce bronchiospasm, bradycardia, muscle paralysis- this is what you do with roach spray)The ratio of aspartate and alanine transaminases (AST/ALT) is commonly elevated inalcoholismWhat enzyme can be used to diagnose bone and bile duct disordersAlkaline phosphatase (ALP)Name of an enzyme that was previously used to diagnose prostate cancerAcid phosphatase (ACP)
* Alkaline and acid phosphatases are a group of enzymes that display maximum activity at pH 5 or 10
* they are attached to the cell membrane, suggesting an association between their activity and membrane transport
It is found in the cells of the:
- Prostate (prostate specific antigen- PSA: tumor marker)
- Liver
- Erythrocytes
- Platelets
- BoneLactate Dehydrogenase (LDH)is an enzyme found in glycolysis
* it has 5 subtypes/isoenzymes
- LDH 1 and 2 are elevated in acute myocardial infarction (MIs)
- LDH5 is elevated in hepatic disorders (Acute Hepatitis)Gamma-glutamyltransferase (GGT) is induced byalcohol
* GGT is found mainly in cell membranes of:
- Liver and bile duct****
- kidney
- pancrease
- several other organs
Causes of raised (enzyme induction) GGT:
- drugs and alcohol
ex: anticonvulsants
- also increased in cholestatic liver disease
- hepatocellular damageAmylase and lipase arepancreatic enzymes that are indicative of pancreatitis
* Amylase and lipase (intestinal) are produced by the pancreas for digestion of starch and fat
* Amylase is also found in the saliva
* Amylase AND lipase are increased in the plasma in acute pancreatitis and are necessary to differentiate between different causes of abdominal pain
* both enzymes are excreted in the urine and are elevated in plasma in renal failureWhy are enzymes measured?Bc the relase of enzymes from cells may indicate:
- necrosis or severe damage to cells
- increased concentration of enzymes in cells
- duct obstruction (ex. in bile duct)
- reduced urinary excretionwhat are the 3 isoenzymes of creatine kinase- CK-MM (increased in damaged skeletal muscle)
- CK-MB (cardiac muscle- increased in MI )
- CK-BB (increased in brain tumor)
*** Creatine phosphate is an energy store in skeletal muscle that provides a phsophate to make ATP and creatine with aid of creatine kinase (CK)Catalyses dohydrolytic cleavage of various esters of cholineDecreased levels of plasma cholinesterase (BuChE) could be indicative ofHepatic disease: decreased synthesis of the enzyme
or an
Inherited abnormal variant of plasma cholinesterase with low biological activity
- Ingestion of organophosphates (OP's) or absorption via skin interferes with the activity of both plasma and acetyl cholinesterases. OP's are irreversible inhibitors of acetylcholinesterase
** clinical symptoms of this arise from the buildup of ACh
Treatment: Atropine Sulfate (competitive antagonist of ACh receptors- it inhibits the action of ACh on all the muscarinic receptors)Increased levels of plasma cholinesterase (BuChE) could be indicative of- Nephrotic Syndrome (excretion in urine)
- Rapidly growing cells: liver recoveryA group of enzymes that catalyze the transfer of an amino group from AA's too alpha-ketoacidsTransaminases
** ALWAYS requires Vitamin B6
ex: Pyruvate takes a nitrogen from AA with help of B6 and makes Alanine
** note this is not in the plasma but will be seen with tissue damageAspartate Transaminase (AST) can be found in high concentrations in the cells of- CARDIAC and skeletal muscle
- LIVER
- kidney
- erythrocytes
High levels may indicate:
- Artefactual (hemolysis)
- Physiological in neonatal
VERY high levels seen in:
- viral hepatitis
- myocardial infarction
- circulatory failure
*** the two main condition with HIGH [AST]= Viral hepatitis and MIAlanine Transaminase (ALT) is present in high concentrations in cells of the- Liver
- Skeletal and cardiac muscle (lesser extent)
- Kidney (lesser extent)
Marked increases are seen in:
- circulatory failure
- ACUTE VIRAL HEPATITIS
Moderate increases are in:
- LIVER CIRRHOSIS
- CHOLESTATIC JAUNDICE
- post cardiac surgery
- skeletal muscle diseaseAn AST/ALT ratio of 2.0 or higher is indicative ofAlcoholic liver disease
* the normal AST/ALT ratio is approximately 0.8Alkaline phosphatase (ALP)Is used to detect bone disease (in an electropheresis you would see high levels in bone and liver)
Physiological changes in ALP levels seen in:
- normal pregnancy
- infancy and childhood
- high fat meals
- diseases that affect the bile duct *
- bone dieases *
------
there is also a leukocyte alkaline phosphatase (LAP) score
- if its high= leukemoid reaction
- if its low= chronic myelogenous leukemiaIncreased GGT (Gamma-Glutamyltransferase) is increased inHepatocellular damageWhich is elevated in bone disease GGT or ALPALP!!
GGT and ALP are BOTH increased in bile duct disease but GGT is NOT elevated in bone disease like ALP is
sooo..
- In diseases of the bile duct BOTH GGT and ALP are raised
- In diseases of the bone the GGT is NORMAL and the ALP is raisedWhat is the most specific marker of an MI (myocaridal infarction)Troponin 1
REMEMBER!!!!: Troponin I is a PROTEIN, NOT an enzyme!!!!
CK-MB IS an enzyme
soo if the question reads: what enzyme is most indicative of an MI the answer will be CK-MB
** Troponin is the most sensitive and specific for an MI
** CK-MB is relatively specific but NOT as specific as Troponin
- Lactate dehydrogenase is not as specific as troponin (High LDH1 and LDH2 indicates MI)
- Aspartate transaminase (AST) is NOT specific for heart damageHematopoiesis (AKA Hemopoiesis)The process of blood cell formation from established blood cell precursors
- mature blood cells have a relatively short life-spain, must be continuously replace by the progeny of stem cells
- after birth, production of new blood cells occurs in the BONE MARROW
- under normal conditions, the production of blood cells can adjust rapidly to the need of the body, increasing several-fold in a short time
- In a healthy adult person, apprx. 10^11- 10^12 (10^12= one trillion) new blood cells are produced daily in order to maintain steady state levels in the peripheral circulation
** increased altitude= increased RBC
** bacterial infection= increased neutrophil___ single type of hematopoeitic stem cell in the bone marrow gives rise to ALL the formed elements of the bloodONE! (Multipotential hematopoietic stem cell)
** differentiates into two lines
- Lymphoid Line: gives rise to ALL the lymphocytes (B cells, T cells which mature in the Thymus, and NK cells)
- Myeloid line "relating to bone marrow": gives rise to everything BUT lymphocytes (erythrocytes, platelets, neutrophils, eosinophils, basophils, monocytes; also mast cells)Of the two daughter cells produced when a stem cell divides:- one daughter remains a stem cell (will continue to have stem cells throughout life- keeps an available population of stem cells always )
- one daughter goes on to terminally differentiateA hematopoetic stem cell isMultipotent
** they give rise to "transient" cells of connective tissueTotipotentcan become both embryo and extra-embryonic cells/tissues
ex. ZygotePluripotent(blastocyst inner cell mass) can become all cell types of embryo, but CANNOT become extra-embryonic cells/tissuesThe gastrula can differentiateEndoderm (internal layer)
- Lung cell (alveolar cell)
- Thyroid cell
- Pancreatic cell
Mesoderm (middle layer)
- Cardiac muscle cells
- Skeletal muscle cells
- Tubule cell of the kidney
- RBCs & WBCs
- Smooth muscle (in Gut)
Ectoderm (External Layer):
- Skin cells of Epidermis
- Neuron of Brain
- Pigment Cell
Germ Cells:
- Sperm
- EggMesenchymal stem cell gives rise to"fixed" cells of connective tissue
- fibroblasts
- adipocyte
- chondrocytes
- osteocytes
- chondroblasts
- osteoblastsIn the 3rd-4th week of gestation blood precursor cells arise from theyolk sac mesodermIn the 5th week of gestation __ and __ are temporary hematopoietic tissuesLiver and spleen
** mostly liver
** remember 5 + 5At about the 5th month of gestation the ___ becomes increasingly important hematopoietic tissueBone marrow
** remember 5 + 5After birth blood cells derived from stem cells are found in thebone marrow (the bone marrow also produces (T cells) that migrate to the lymphoid organs where they become immunocompetentOne of the largest organs of the body, which is the main site of hematopoiesis in adultsBone Marrow !
it is considered a type of connective tissue
** it is found in spongy/trabecular/canvellous bone and in the medullary/bone marrow cavity of the diaphysis2 types of bone marrow that exsist areRed Bone Marrow
- color is produced by the presence of blood and blood-forming cells
Yellow Bone Marrow
- collor is produced by the presence of a great number of adipose cells
** In a new-born all marrow is red. As the child grows, most of the bone marrow changes gradually into the yellow variety
** 25 yr old: red marrow is confined to cancellous bone: the proximal quarters of the long bones (femora, humeri), skull bones, ribs, sternum, scapulae, clavicle, vertebrae, pelvis and upper half of sacrum
** BUTTT in response to severe blood loss, yellow bone marrow can become red bone marrow any time in life
Yellow bone marrow is "seeded" by blood-borne hematopoetic cells2 components of Red bone marrow are1. stroma: where the blood cells develop "land"
2. sinusoids: blood vessels where the mature blood cells enter the blood stream "SEA"
** in bone marrow both are inside the bony spiculesCollagen Type I is stained withH&ECollagen Type III is stained withsilver stainDescribe the Stroma "LAND" of the Red Bone Marrow- 3- dimensional meshwork of reticular cells (Type III collagen) AKA adventitial cells, but are basically fibroblasts & a delicate web of reticular fibers containing hematopoietic cells, macrophages, and a few adipocytes
Reticular cells:
- secrete reticular fibers composed of Type III collagen
- send cytoplasmic projections outward (away from basal lamina of endothelial cells)- these touch projections of other reticular cells; forms a 3-D network surrounding discrete hemapoietic cords (islands)
** remember that reticular fibers are agyrophilic (silver loving)
** remember that this reticular cell and fiber network is THE supporting mesh in soft tissues such as the: liver, bone marrow, and the tissues and organs of the lymphatic system (such as spleen, and lymph nodes)
The stroma also contains fibers and ground substance like other CT:
- collagen types I and III
- fibronectin
- laminin
- proteoglycans
Laminin and fibronectin and others interact with cell receptors (integrins) to bind developing cells to the reticular fibers in the stroma
- when the developing cells are mature and ready to enter bloodstream, they inactivate their integrins and release from meshworkThe sinusoids "SEA" from Red Bone Marrow are formed bysinusoidal capillaries (most soucres call these sinusoidal capillaries; a few sources call them venous sinuses)
- they are lined by endothelial cells sitting on a discontinuous basal lamina
** sinusoids are where RBCs, WBCs, and platelets enter the circulation after their production in the bone marrowCFU stands forColony Forming UnitGEMM stands forGranulocyte
Erythrocyte
Monocyte
Megakaryocyte
& Mast cellHematopoietic Stem Cell
((old) PPSC- pluripotential stem cell) splits intoLympoid Stem cell (CFU-L) and a Myeloid Stem Cell (CFU-GEMM)
Lymphoid Stem Cell (CFU-L):
- Some migrate to THYMUS where they become T Lymphocytes, then they migrate to populate specific regions of peripheral lymphoid organs
- Some differentiate into B lymphocytes within the Bone Marrow and then migrate to peripheral lymphoid organs
** actually, B cells do not completely develop until after they leave bone marrowCFU-E leads toErythropoiesis- development of erythrocytes
- cells get smaller
- nucleus condenses, eventually it is extruded
- gradually loses ribosomes, mRNA, and organelles
- gradually gains hemoglobin
Steps:
1. Hematopoietic Stem Cell
- CFU-GEMM and CFU-E are intermediates--
2. Proerythroblast (20hr)
3. Basophilic erythroblast (20hr)
4. Polychromatophilic erythroblast (25hr)
5. Orthochromatic erythroblast (30hr)
6. Reticulocyte (2-3days) - No nuecleus (nucleus condenses becomes pyknotic and eventually gets extruded)
7. Erythrocyte (120 days)
** from first recognizable (proerythroblast) to release into bloodstream takes 7 daysWhat is the first recognizable cell to know a cell is differentiating into an erythrocyteProerythroblast
** it is a large cell, basophilic cytoplasm, visible nucleoli (comes from CFU-E which is NOT morphologically distinguishable)
** basophilia is caused by the large number of polyribosomes invovled in synthesis of HbBasophilic erythroblaststrongly basophilic cytoplasm, no visible nucleoli
* basophilia caused by large number of polyribosomes involved in the synthesis of HbName the stage in erythropoiesis: polyribosomes decrease, and areas of cytoplasm begin to be filled with Hb which is acidophilic. Thus, this stage cell stains both colors (basophilic and acidophilic)Polychromatophilic ErythroblastName the stage in erythropoiesis: Nucleus continues to condense, lose evident basophilic (but not quite all polyribosomes) resulting in uniform acidophiliaOrthochromatophilic erythroblastAfter an orthochromatophilic erythroblast expels its nucleus it becomes aReticulocyte (an immature erythrocyte)
- still has a few polyribosomes that aggregate (when treated with dye cresyl blue) to form a stained "reticular" networkThe reticulocyte leaves the bone marrow and passes into the bloodstream becoming anerythrocyte
* the mature form, has lost all polyribosomes
- the reticulocyte will lose its mitochondria and ribosomes within a day or two to become a mature erythrocyteHow are all the nuclei that are released by erythroblast degradedErythrocyte clones develop in the bone marrow on the surface of a macrophage nurse cell, which phagocytoses and digests the nuclei discarded by the erythroblasts before their conversion to reticulocytesNearly ALL erythrocytes are released into the circulation asReticulocytes as soon as they are formed
* Reticulocytes are about 1-2% of RBCs in blood stream, % can increase after blood lossT or F: the bone marrow is the greatest storage site for erythrocytesFALSE!!!!!!
bone marrow is NOT a storage site for erythrocytesHematopoetic Growth Facotrs- ALL are secreted proteins that bind to receptors on their target cells
- they control rates of hematopoeisis of stem cell (can have other functions as well)
ex: Erytropoietin (EPO): synthethezied and secreted by cells in the KIDNEY in response to decreased blood oxygen concentration
* acts on recepetors on surface of CFU-ETwo examples of how EPO is used in real life- Renal failure patients on dialysis were universally anemic before the advent of commercial EPO and required transfusions
- EPO is also (illegaly) sometimes used as a blood doping agent in endurance sports such as bicycle racing, triathlons and marathon runningHow is EPO concentration regulated by oxygen levels?Hypoxia-inducible factors (HIFs) are constitutively synthesized transcription factors for EPO
** in the presence of HIGH levels of oxygen, HIFs are hydroxylated and proteosomally degraded, transcription of EPO fallsDo mast cells come from basophilsNO!
- Mast cells also come from CFU-GEMM, but by a different lineage than basophilsEach stage of cell differentiation is modulated by a combination ofcytokines and other growth factorsDescribe the life cycle of RBCs1. Low O2 levels in blood stimulate kidneys to produce EPO
2. EPO levels rise in the blood
3. EPO and necessary raw materials in blood promote erythropoiesis in red bone marrow
4. New erythrocytes enter bloodstream; function ~120days
5. Aged and damaged RBCs are engulfed by macrophages of LIVER, SPLEEN and BONE MARROW; the Hb is broken downGranulocytopoiesisdevelopment of granulocytes (neutrophils, basophils, and eosinophils)
** mitotic phase takes ~ 1 week; post-mitotic phase also takes ~1week
1. Myeloblast
- looks like lymphocytes but often has 3-5 prominent nucleoli
2. Promyelocyte
- Azurophilic (non-specific) granules
3. Myelocyte **(can tell cells apart at this stage)
- Oval or flat nucleus, specific granules appear; last stage at whcih cell division is possible
4. Metamyelocyte
- specific granules continue to accumulate, nucleus indented, C or V shape
5. Band/stab cell
- eosinophil and basophil stab cells exist but are rarely found, mainly band cells are immature neutrophils
6. Mature eosinophils, neutrophils, basophilsat what stage of granulocytopoiesis can the cells be told apartMyelocyte
** first stage in which specific granules appear"Shift to the left"- increased number of immature neutrophils in the blood
- large number of BAND CELLS appear in the blood
this is called a "shift to the left" and it is an indication of a bacterial infection
*** Unlike erythrocytes, mature and near-mature neutrophils are stored in bone marrow
- ratio of these neutrophils in bone marrow to bloodstream is ~5:1
- this reserve pool can be released abruptly into the circulation in response to inflammation, infection, or strenous exercise
This can be visualized by looking at a blood smear stained with Wright stain; doing a differential WBC count orr today most moder, urban medical labs have an automated hematology analyzer which count, measure, and analyze RBCs, WBCs, and platelets as well as measure the amount of hemoglobin in the blood and within each red blood cellMonocytopoiesis** Note that monocytes and neutrophils shar the same progenitor (CFU-GM)
Monoblast --> Promonocyte --> Monocyte --> Macrophages
Promonocyte: cytoplasm is bluish and houses numerous azurophilic (non-specific) granules (lysosome)
Monocyte: Every day, the avg adult forms more than 10 billion monocytes, most of which then enter the circulation- within a day or two, the newly formed monocytes enter the CT spaces of the body and transform into macrophagesBoth monocytes and neutrophils share ___ as their progenitorGFU-GMLeukemiasare malignant clones of leukocyte precursors
- they occur in lymphoid tissue (lymphocytic leukemias) and in bone marrow (myelogenous and monocytic leukemias)
- in these diseases, there is usually a release of large numbers of immature cells into the blood
- leads to lack of some cell types and excessive production of others (which are often abnormal in function)
- the patient is usually anemic and prone to infectionMegakaryocytopoiesisorigion of platelets (CFU-GEMM --> CFU-Meg)
- the nucleus become highly polyploid, it contains up to 30x as much DNA as a normal cell (chromosomes replicate but the cell doesnt divide
- giant cell, invaginations of plasma membrane form demarcation membranes with platelet granules inside of each
* These break off to form platelets- platelets do not contain nuclei, but they do contain granules that contain:
- Platelet-derives growth factor
- Fibroblast growth factor
- Von Willebrand factor (which promotes adhesion of platelets to endothelial cells)
- Platelet Factor IV (which stimulates blood coagulation)
IN ADULTS
- platelets originate in the Red Bone Marrow by fragmentation of the cytoplasm of mature megakaryocytes (megakaryocytes arise by differentiation of megakaryoblasts)- each megakaryocyte produces betwen 5,000-10,000 platelets
** Soo megakaryocytes form thin processes that cross the wall of the sinusoid and fragment at their tips, liberating the plateletsHow do RBCs enter blood stream from the marrow- Because erythrocytes (unlike leukocytes) do NOT have sufficient motility to cross the wall of the sinusoid, they are believed to enter the sinusoid by a pressure gradient that exists across its wall
* in red bone marrow, veins leaving are smaller than arteries entering, creates pressure "suction" that "sucks" mature RBCs from stroma into capillary
*** ON THE CONTRARY:
- WBCS (Leukocytes), after the action of releasing substances, cross the wall of the sinusoid by their own activity (diapedesis in reverse)Once in the blood stream do granulocytes divide againNO! they never divide again
In contrast,
- monocytes/macrophages and lymphocytes all have the potential for further divisionHemostasis is the process ofblood clotting
- occurs when small blood vessel (capillary) is damaged
- clot seals the blood vessel until it regenerates
* occurs in just 3-6 minutesWhat 3 major events occur in Hemostasis1. Vasoconstriction
2. Platelet plug formation
3. Coagulation of blood
- ALL beginning the moment the vessel is damaged-
* coagulation takes longer, and is completed after vasoconstriction and platelet plug formation occurActivated platelets secrete chemicals includingserotonin
ADP
Thromboxane
** platelets become activated and stick together after exposure to collagen fibers on an injured blood vesselsAfter injury to a blood vessel the damage to smooth muscles and blood vessel and stimulation of pain receptors can lead toblood vessel spasms and constriction
* vasoconstrictionAn injury to a blood vessel may result in thromboplastin release- what are the stops after its release that lead up to coagulationThromboplastin, platelet factor 3, and calcium ion interact to form prothrombin activator
- prothrombin activator convertes prothrombin --> thrombin
- thrombin converts fibrinogen (soluble proteins) into long, insoluble proteins called fibrin
* fibrin forms a mesh that traps erythrocytes and platelets, pulls the edges of the broken vessel together and forms a clotthrombus vs embolusThrombus- a blood clot that forms in an unbroken vessel (ex. sitting on a flight for a long time)- a large thrombus may block blood flow, causing tissue death
where as an
Embolus: is a blood clot that forms then breaks away and floats freely in the blood vessels. An embolus may then lodge in a capillary and block blood flowWhat are some causese of a Thrombus- injury to a blood vessel or build-up of fatty plaques (both create rough surfaces inside vessel, which may activate platelets
- poor blood circulation (cloothing factors accumulate)
** NOTE: immobility increases the risk of deep vein thrombus in the legsVon Willebrand factor carriesFactor 8 (VIII)
** it is NOT a clotting factor it just carriesHemophilia A is caused by lack ofFactor VIII (8)Hemophilia B is caused by lack ofFactor IX (9)Both Hemophilia A (lack of factor VIII) and B (lack of factor IX) arerecessive sex-linked trait (more common in men)
Sxs:
-prolonged bleeding even from minor injuries
-excessive bruising
-bruised and swollen joints
-excessive clumsiness and falling
Treatment:
- intravenous injection of clotting factors
- donated plasma
- synthetic clotting factorsWhat does it mean that endothelial cells (which line the vessels) are thromboresistant in natureThey express thrombomodulin and heparin sulfate to keep inappropriate thrombi from forming
- they also release tissue plasminogen activator and urokinase in the presence of thrombin shut off the coagulation cascade in the presence of IIa (thombin)What does it mean that the Subendothelium (beneath the endothelium) is thrombogenic in natureThey express Von Willebrand Factor (vWF), collagen, and tissue factor to kick off the coagulation cascadeDeficiency of Factor XII (12) DOES NOTresult in bleeding because you can still activate factor XI (11) with the thrombin created in the extrinsic/common pathwayBoth the intrinsic and Extrinsic pathway meet at theCommon pathway:
- activation of factor X (10) which convers prothrombin --> thrombin
thrombin then converts Fibrinogen --> fibrin
and activated XIII which then converts Fibrin --> cross-linked fibrin with the help of calcium
( a fibrin monomer closs-links into a fibrin fimer --> which forms a fibrin polymer to form a mesh)
*** this cross-linking occurs through Transglutaminase Reaction (from Glutamine ---> Lysine): makes a peptide bond to form the fibrin polymer
(remember this step needs Factor XIII to be converted to XIIIa by Thrombin in order for it to occur)TFPI (tissue factor pathway inhibitor) inhibitsextrinsic pathway
- it is activated by the presence of thrombinExtrinsic pathway is activated byTissue factor III (which is exposed by damage)Hemostasis: Coagulation and Clot Stabilization is triggered byexposure of blood to collagen
this pathway includes:
- prothrombin
- calcium
- fibrinogen
- fibrin
- polymerizationT or F: you only need the Extrinsic pathway to clot properlyFALSE!!! you need both the extrinsic and intrinsic pathways
- they are intertwined in such a way that if youre missing something on either the extrinsic or intrinsic side you will NOT be able to clot properly (form fibrin)
- you need factors VIII and IX to use the intrinsic pathwayIs tissue factor just floating around in the bodyNO!
- it appears when you need to form a clot
* tissue factor and VIIa (which does happen to be floating around in the blood) convert factor X --> Xa (which then convertes prothrombin --> thrombin, which converts fibrinogen --> fibrin)
** so clotting initially begins in the extrinsic pathway !!
- As soon as we make a little Xa, that Xa along with the tissue factor pathway inhibitor turns off the extrinsic pathway!
- NOTE: a little thrombin is formed before the pathway is shut off and that thrombin is actually what kicks off the intrinsic pathway! (with factors VIII and IX)
- Fibrin formation then proceeds along this pathway until it is no longer neededWhat would you use to measure the function of the EXTRINSIC PATHWAY and the COMMON PATHWAY. Extended by WarfarinPT (prothrombin time)What measures the function of the INTRINSIC pathway and the common pathway. In vitro extension by heparinaPTT (partial thromboplatin time)Vitamin-K dependent coagulation componentsFactors X, IX, VII, II proteins C, S
(mnemonic: 1972- [10,9,7,2]What inhibites the vitamin-K reductase and effective levels of vitamin-K dependent coagulation components- and will extend the PT (prothrombin time)Warfarin (Coumadin)What increases the activity of ATIII and aPTT in vitroHeparin (drug)
- is purifed from animalsSynthesis of Thromboxane A2 (TXA2) is initiated byactivated platelets
- TXA2 increases platelet activation and aggregation
- Its synthesis is inhibited by Aspirin- which is an irreversible inhibitor of the COX (cyclooxygenase enzyme) - would inhibit platelet aggregation: NOT an anticoagulant but it is an antiplatlet drug
Arachiodonic Acid (from the ends of phospholipids) is converted to Thromboxane A2 and Prostacyclin via the COX enzymeThrombin also activates Plasmin which leads toFibrinolysis
Fibrin polymer (with help of Plasmin that becomes activated by Thrombin) is lysed into Fibrin fragments
** this clot dissolution occurs as soon as the injury is healed - to restor the normal flow of blood
** Plasminogen is converted to the active form PLasmin by 2 distinct Plasminogen Activators (PAs):
- tissue plasminogen activator (t-PA) from injured endothelial cells
- urokinase from kidney endothelial cells and plasmaWhat are the two Plasminogen ActivatorsTissue Plasminogen activator (tPA) & Urokinase
- they convert plasminogen --> plasmin which aids in fibrin polymer becoming Fibrin degradation products
*** streptokinase can also be used as an activator
- these can be inhibited by plasminogen activator inhibitor 1 and 2what two things could inhibit plasminalpha2-antiplasmin
and
alpha2-macroglobulinWhat are some physiological inhibitors of Coagulation- Antithrombin III (activated by heparin) ** blocks mainly clotting factors in the Intrinsic Pathway
- Activated Thrombomodulin (activates Protein C which inturn inhibits Factors Va and VIIIa)
** NOTE thrombin promtoes coagulation but it is also an anti-coagulant because it has mechanisms to prevent over coagulationWhat are some NON-physiological inhibitors of coagulation- Vitamin K antagonists (in vivo) : ex. Warfarin
**** mainly related to extrinsic pathway: Vitamin K does carboxylation of glutamate residues in factors 2,7,9,10- so an antagonist would BLOCK this carboxylation
** Warfarin is also an antagonist that is similar to vitamin K- it blocks carboxylation of factors 2,7,9,10 so the extrinsic and common pathways are NOT activated
- Calcium chelators
- EDTA (ethylenediaminotetraacetic acid)
- Citrate
- OxalateAn increase in Plasma D-Dimers could indicate- Deep Vein Thrombosis
- Pulmonary Embolism
- Disseminated Intravascular Coagulation (DIC)
*** Plasma D-Dimers are cross-linked fragments containing D-Dimer epitopes
Q) If you have a patient with elevated plasma D-Dimer- this patient needs an anticoagulant. Which would you give?
- you should use Heparin! which has immediate effects. Warfarin takes apprx. 17hrs so takes too longA PT test could show abnormalities inExtrinsic and Common pathway & deficiency/inhibition of VII, X, V, II, I
** this is commonly caused by liver disease, warfarin therapy, and DICA PTT test would show abnormalities inINTRINSIC and Common pathway
deficieny/inhibition of XII, IX, VIII, X. V, II, I
** this is commone in heparin therapyThrombin time (TT) would showdeficiency/abnormal I, inhibition of II by heparin or FDPs
** common in heparin therapyFibrin degradation products would indicateaccelerated destruction of fibrinogen
** commonly due to DIC (disseminated intravascular coagulation)Bleeding time could help to indicate an abnormality inabnormal platelet function
** commonly caused by Aspirin, uremia, Von Willebrand diseaseWhat laboratory test or studies would be most appropriate to order on a patient with a suspected hematological disorder?- Complete blood count (CBC)
- Peripheral Blood Smear (PBS)
- Differential WBC count
- Corrected Reticulocyte Count (Corrected Retic #)
*** other lab tests that depend upon the results of the above tests:
- Hemoglobin Electropheresis
- Fe Panel, Serum B12, and folate levels etc
--
You can also do a Bone Marrow examination if indicatedWhat are the components of a Complete Blood Count (CBC)- Hemoglobin (Hb)
- Hematocrit (Hct) or packed cell volume (PCV)
- Red blood cell count
- RBC indices (MCV, MCH, MCHC): Mean Corpuscular Volume, Mean Corpuscular Hb, Mean Corpuscular Hb Concentration-- these are simply average quantities and may NOT detect abnormalities in blood with mixed cellular populations
- Red cell distribution width (RDW)
- White blood cell (WBC) count
- Platelet count
- Evaluation of peripheral blood smear (PBS)Best indicator of oxygen-carrying capacity of bloodHemoglobin (Hb)
* it is accurate and preferable to hematocrit for diagnosis of AnemiaHematocrit or Packed Cell Volume (PCV)Accurate, simple screening test for anemia
- volume of blood occupied with cells as opposed to serum-RBC count is decreased inAnemiaRBC count is increased in- Primary polycythemia (aka primary polycythemia vera)
- Secondary polycythemia
- Hemoconcentration (due to dehydration in an individual)Most important blood INDEX for classifying AnemiasMean Corpuscular Volume (MCV)
* it is the avg volume of RBCs
MCV= PCV (packed cell volume or hematocrit)/RBC count
[Nml= 80-100micrometers^3 or fl]
BASED ON MCV VALUE ERYTHROCYTES CAN BE CATEGORIZED AS:
- Microcytic (<80micrometers ^3): Low MCV
- Normocytic (80-100): Nml MCV
- Macrocytic (aka Megaloblastic) (>100): High MCV ** cells are paler than normal and largerAverage mass of Hb in an individual RBCMean Corpuscular Hemoglobin (MCH)
MCH= Hb/RBC count
[Nml= 25.4-34.6 pg]
* MCH increases or decreases in parallel with MCV- therefor once you have MCV, MCH does not provide much additional diagnostic informationAverage Hb concentration in a given volume of packed RBCsMean Corpuscular Hb Concentration: MCHC
MCHC= Hb/PCV
[Nml= 31-36 g/dL]
*** this is what give the color or chromia of RBCs**
- Hypochromic (decreased): can be due to Fe deficiency
- Normochomic RBC
- Hyperchromic (increased staining): can be due to hereditary spherocytosis, sicle cell disease, homozygous hemoglobin C
NOTE: hyperchromic is NOT a term used clinically to describe AnemiaAnisocytosisDifference in widths of RBCs
** RED CELL DISTRIBUTION WIDTH (RDW): reflects variation in size of RBCs in peripheral blood
Nml range: 11.6=14.8%
- Increased in many types of Anemia: Iron deficiency, Pernicious (due to lack of intrinsic factor, resulting in lack of VitB12 resulting in Megaloblastic Anemia), or Folate deficiency (caused Megaloblastic Macrocytic Anemia)
- Thalassemia
- Liver DiseaseWhat is the most important blood count following RBC indicesWhite blood cell count- tells you your Total leukocyte count (TLC) in a volume of blood
** can be done by manual methods or by automated cell counters
Nml: 4,500-11,000/mm^3
Not that a Child <2 weeks will have significantly wider range (~5.0-21.0 x 10^3/microL) it is displaced upwardsDifferential Leukocyte count (WBC diff)takes 100 WBC and subdivides leukocytes by percentage of each type
From Highest Percentage to Lowest:
1. Neutrophils
- Segmented (mature)= 54-62%
- Bands (immature)= 3-5%
2. Lymphocytes: 25-33%
3. Monocytes: 3-7%
4. Eosinophils: 1-3%
5. Basophils: 0.07%
Mnemonic: Never let monkeys eat bananasPlatelet (PLT) countPlatelets are anucleate masses derived from cytolpasmis budding of megakaryocytes
* normal: 150,000-400,000 mm^3
- counted on automated cell counters
- rough estimate on peripheral smear examination
Major Causes of Thrombocytopenia:
- Decreased platelet production
- Decreased platelet survival
- Sequestration (hypersplenism)
- Dilution (transfusions)- platelets have a short half life so they are lost in transfusionsWhat is looked at when doing a Peripheral Blood Smear (PBS)- Erythrocytes: size (related to MCV), abnormal shape, Hb concentration (gives RBCs its color- reflected by central pallor: related to MCH and MCHC) , RBC inclusion bodies?
- Leukocytes: Differential count, abnormal cellular morphology?
- Platelets: Presence/absence/size?
Also look for abnormal cells/structures:
- Immature cells (normoblast, myeloblast, lymphoblast)
- Atypical lymphocyte
- Medathrombocytes (very large platelets)
- Parasites (malaria; filaria)What would Nucleated RBCs indicated on a peripheral blood smear (PBS)This would be a reflection of erythropoietic response to massive hemorrhage or hemolysisWhat does the presence of reticulocytes in a peripheral blood smear indicate?Erythropoiesis
- reticulocytes are newly released RBCs from bone marrow
* they are identified with supra-vital stains
what is seen is thread-like RNA filaments in the cytoplasm
** in 24 hrs these develop into mature erythrocytesMarker of effective erythropoiesisReticulocyte Count
Nml: <3%
* this percent count is FALSELY increase in anemia so a correction is required
- the initial % must be correct for degree of anemia
Corrected reticulocyte count= Actual Hct/45(the avg nml hematocrit) x reticulocyte count
Ex: if you Hct=15% and Retic count= 18%
your corrected reticulocyte count is 6%
*** an addition correction is also required if RBC polychromasia is present: what you would do is divide intial corrected reticulocyte count (for degree of anemia) by 2If your RBCs appear larger with more than one color (bluish gray) this may indicatePolychromasia
- In a case like this one would see persistance of RNA and an increased number of reticulocytes
*** remember that is RBC polychromasia is present an addition correction is needed for the reticulocyte count: you must divide the corrected reticulocyte count by 2What type of iron studies could one do in a hematologic assessment- Serum iron
- Serum Ferritin
- Total iron binding capacity [TIBC]
- Iron saturation (%)What type of specific confirmatory tests could be done in a hematologic assessment- Sickling Test
- G-6-PD Assay
- Serum Vitamin B12/ Folate levels
- Antibodies to Intrinsic Factor (seen in perincious anemia)What would one expect to see in a hematological assessment of a pt with AnemiaIt depends on the type of Anemia
Blood Loss Anemia & Hemolytic Anemia:
- Decreased RBC, Hb, Hematocrit; but increased Reticulocytes
Inadequate production Anemia:
- Decreaased RBC, Hb, Hct AND DECREASED reticulocytesWhat would one expect to find in a hematological assessment of a patient with PolycythemiaIncreased Rbc, Hb, and Hct
can have
- Polycythemia Vera
- Secondary Polycythemia from high altitude, smoking, obesity, COPD etcReasons for a Microcytic Blood cell- Iron deficiency
- Thalassaemia
(microcytic: MCV <76fL)Normocytic (normal RBCs) can be seen in- acute blood loss
- anemia of chronic disease; ex: infections, malignancy, CT diseaseMacrocytic (MCV >96fL) wwould be found inMegaloblastic Marrow and it could occur with Vitamin B12 or folate deficiencyAnemias could be classified based on- Blood loss
- Increased destruction (hemolytic anemia)
- Intrisic (intracorpuscular) abnormalities: can be Hereditary like membrane abnormalitites, enzyme deficiencies, and disorders of Hb synthesis or Acquired like membrane defects
- Impaired RBC production
- Extrinsic (extracorpuscular) abnormalities: which can be antibody-mediated, from mechanical trauma to red cells, or from infections like malariaA Macro-ovalocyte of a RBC could be seen inHereditary SpherocytosisWhat are the types of classifications for the concentration of Hb in RBCS (reflected by central pallor (paleness) (related to MCH and MCHC)- Normochromic: normal Hb concentration
- Hypochromic: decreased Hb concentration and increased central pallor
- Hyperchromic: increased Hb concentration and loss of/decreased central pallor (seen in hereditary spherocytosis and some sickle cells)
- Polychromasia: RBCs with more than one color and loss of central pallorWhat are some abnormal shapes (poikilocytosis) that there can be of RBCsMicrospherocyte
- In hereditary spherocytosis and immune hemolytic anemia
Sickle cell
- homozygous sickle cell disease
Tear-drop cell
- Myelofibrosis and Marrow infiltration
** reflects marked fragmentation
Schistocyte
- Microangiopathic hemolytic anemiaWhat are some abormal RBC inclusion bodies that could be found in the cytoplasm- Basophilic stippling: from Pb (lead) poisioning- acutally caused by Fe granules
- Howell-Jolly bodies: seen in Asplenia (no spleen), Hyposplenia, and in sickle cell
- Cabots ring bodies: which are MT spindle remnants seen in megaloblastic anemias
- Heinzs bodies: due to denatured HbWhite blood cell disorders can be classified asReactive/inflammatory or Neoplastic
Reactive/Inflammatory ones could be either Quantitative or Qualitative
- Quantitative could mean leukocytosis or leukopenia
- Qualitative is about leukocyte defects (ex. Pelger-Huet and Chediak-Higashi)
Neoplasitc: are Leukemias and LymphomasWhat are some procedures that could be done in bone marrow examination- bone marrow aspiration (this gives better cytologic details- with the report available on the same day)
- bone marrow biopsy ( gives better architectual details but the report is available only after 5-7 days; more painful procedure- Helps with identification of hypocellular vs normocellular vs hypercellular marrow on biopsy image )
** these are mainly done in pelvis and axial skeleton in an adult- less commonly it is done in the sternum
When would you do this?
- Evaluation of unexplained CBC results
- Diagnosing Malignancy (cancer): primary bone marrow cancers (Leukemia and Myeloma) and secondary bone marrow malignancies or metastatic cancer
- Evaluation of iron stores: Myelodysplastic/Myeloproliferatic disorders
- Evaluation of disseminated infection (Tuberculosis, Fungal disease)
- Bone marrow donor harvesting (aspiration)Explain how you would do a bone marrow (BM) biopsySites: sternum, anterior iliac crest, posterior iliac crest** (safest, favored site)
Position: prone or on contralateral side to biopsy site
Surface anatomical landmark: Iliac crest identified by palpation. Biopsy sit marked with indelible ink
Preparation: Informed, written, signed, conset. Aspectic Technique and Local Anesthesia
*** BM could be
- Hypoplastic
- Normal
- Granuloma
- Hyperblastic with blastsAll Hb proteins (should) consist of2 alpha-like and 2 Beta-like subunits in one terameric protein
** if the production of Beta-Hb is reduced 10%, so will production of alpha-Hb
*** if production of one is reduced more then 50% then a surplus of the other type will be seen (the surplus of the othery type of Hb chain often is at the center of the molecular mechanism of disease)
** remember that Hb is found in RBC with normal lifespan of ~120 days --> constant life long production
- RBC lifespan is usually reduced in Hb diseasesOn any given day the majory of RBCs that are present wereproduced weeks to months earlierAfter birth you have a switch from the embryonic gamma in the liver and spleen to theBeta ~ 3 months after birth , you also begin to see delta later on in life
* NOTE that starting in the embryonic period and at full production at 2 months of life the alpha chain is present throughout a persons life span
-- these expression switches involve epigenetics (methylation) of genes no longer needed ((this is NOT changing the DNA sequence BUT it changes access to the DNA and therefore changes the expression pattern of proteins))What are the types of Hb that are present* HbF= alpha2-gamma2
* HbA = alpha2-beta2 (normal adult Hb)
* HbA2= alpha2-delta2 (minor adult Hb)
- HbGower(1)= zeta2-epsilon2
- HbGower (2)= alpha2-epsilon2
- HbPortland= zeta2-gamma2Describe Hb Gene ClustersAll alpha-like genes in one cluster, all Beta-like in another (on different chromosomes)
- the locus control region (LCR) upstream (5') of it all
- progression so that more downstream genes are more heavily expressed later in developmentDifference between Variants and Alleles in reference to HbVariants are Hb with changed AA content (usually from point mutation)
- More than 1000 variants are described, most neutral (OMIM lists 522 alleles of the Beta-Hb gene)
- Each variant is caused by a different allele at the DNA/gene level
Alleles include both those causing variants and those with reduced expression
** heterozygote frequency can be very high in some populations
** variants are at the protein level, alleles are at the DNA levelWhat is used in the routine identification of HbProtein electropheresis under two different conditions together identifies most common variants:
- Cellulose acetate at pH 8.6
- Citrate-agar at acidic pH
OR iso-electric foscuing can do the same in one gel
* more advanced problems are sent to specialty labs
** LOOK at document on protein electropheresis on canvas**HbSSickle Cell Anemia
- Due to a change in AA from Glu --> Val to give BetaS
** switch from charged to uncharged AA
- All carriers of this anemia have exactly the same mutation
* the mutation happenede independently at least twice
HbS: tetramer of alpha2Beta^S2
- HbSS is often used to designate a homozygot for Sickle Cell
Q) you have a switch from gamma --> beta Hb production happening just before birth, at what age should symptoms of sickle cell become noticeable?
- should be 3-6 month of age this is when you have BetaHb becomes predominant - still takes while after this to see the sx's of the disease so pt's usually not diagnosed till 6-12 months of age- some symptoms in previous quarter
** NOTE that at birth the predominant Hb is Alpha2-gamma2What drives the separation in electropheresis?Charge difference!
NOT size
** Ex: Electrophoretic separation between HbA and HbS is possible because the sickle cell mutation (Glu -> Val) removes a negative charge from the Beta chain
(remember that a cathode= negative charge entering)Most common hemoglobinopathy in Black African DescendantsSickle Cell Anemia
An autosomal recessive disorder due to a point mutation in codon 6 (single nucleotide change in a codon): glutamic acid is replaced by valine
- Heterozygotes [ Sickle cell trait, HbAS- (HbS-40% HbA- 60%)]
*** Note heterozygotes DO NOT develop red cell sickling because their HbA prevents HbS polymerization
- No anemia: 8-10% of Black Americans
- Homozygous (HbSS)- alpha2beta2- produces anemiaWhy do RBCs sickle?HbS molecules aggregate and polymerize in deoxygenated state into long needle-like fibers (RBCs assume a sickle/boat-like shapr)
* predominantly extravascular hemolysis of sickle cells
- cytoplasm is transformed into a rigid filamentous gel and leads to less deformable sickled red cells
NOTE:
HbS must be >60% in order for RBCs to sickle this is why you rarely see sickling in Sickle Cell Trait bc HbS is too low in HbAS to produce sickling in peripheral blood
** sickling may occur at high altitudes or increased atmospheric pressure (scuba diving)
Increased deoxyHb causes increase risk sickling
- Acidosis (causes O2 release from RBCs)
- Dehydration: increase deoxyHb in RBCs
- Hypoxemia: decrease O2 saturation of HbPathogenesis of Sickle Cell Anemia1. Initial sickling: reversible with administration of O2
2. Recurrent sickling: irreversible sickling due to membrane damage (from repeated cycles of deoxygenation)- increased adherence to endothelium
3. Irreversibly Sickled Cells: increased RBC adherence to endothelial cells in micro-circulation, increased RBC adhesion molecules- RBCs sticky in slugglish blood flow, gives inflammation (decreased NO), micro-vascular occlusions (vaso-occlusive crises)- ischemic damage
** changes in phospholipids of the membranes results in stronger adherence to endothelial cells, which further impairs blood flowClinical Manifestations of Sickle Cell Anemia- Icteric Sclera: jaundiced sclera
- Frontal blossing: marrow expansion, hemolysis compensation-- expanded medullary cavity: diploic space is markedly widened due to marrow hyperplasia. Trabeculae are oriented perpendicular to the inner table, giving a "CREW CUT APPEARANCE**"What occurs in a Vasocclusive Crisis in Sickle Cell Anemia- Sudden episodes of tissue hypoxia
- Ischemia leads to hypoxia which results in infarts (ex: splenic infarts- repeated infarts of spleen heals with fibrosis- left with scar tissue)- can lead to Howel Jolly Bodies (note these are not specific for sickle cell but their presence is indicative of diminished splenic fx.)
- Severe pain
- Location of pain depends upon the organ involvedAplastic Crisis in Sickle Cell AnemiaThe bone marrow becomes exhausted- Complete blood count (CBC) shows Pancytopenia (decrease in all RBCs, WBCs, and PLTSs)Sequestration Crisis in Sickle Cell Anemia"Acute Sequestration Crisis"
- Sickled cells become trapped in the spleen --> obstructing blood flow with pooling and enlargement of the spleen
* leads to shock and hypovolemia
- circulatory collapse and death can occur in less than 30 minutes
* leads to an enlarged spleenComplications of Sickle Cell Anemia- Retinopathy
- Crapiomegaly --> congestive heart failure
- Pulmonary infarcts --> Pneumonia
- Splenomegaly --> Splenic atrophy (autosplenectomy)
- Infarcts of extremities
- Aseptic bone necrosis--> osteomyelitis
- Ulcers
- Cerebral infarts (stroke)--> mental retardation
- Vaso-occlusion
- Bone Marrow hyperplasia
- Renal infarcts --> HematuriaLong term complications of Sickle Cell Anemia- Pigmented gall stones: from increased bilirubin turnover
- Susceptibility to infections: Pneumonia due to streptococcus pneumoniae or Hemophilus influenzae, Miningitis, Osteomyelitis due to staphylococcus aureus or salmonella
** recurrent infection with encapsulated bacteria
- Splenomegaly in children (increased spleen)
- Autosplenectomy in adults (due to repeated infarctions as a result of micro-vascular occlusions--scarring and atrophy)How to diagnose sickle cell anemia- Hb will be low (anemia by 6 months (Hb 6.0-10.0g/dL)
- High reticulocyte count
Peripheral Blood Smear will show Sickle cells (drepanocytes) and Howell Jolly (HJ) Bodies( which reflect functional asplenia)
* Infants are asymptomatic for the first 8-10 weeks of life, as they have high levels of HbF
- A moderate- severe normocytic normochromic anemia shows by 6 months of age and persists through life
- In adults with HbSS, the mean MCV is 90
- Blood smears show a variable number of sickled forms, target cells, cigar-shaped cells, and ovalocytes
- Featurs of accelerate erythropoiesis may include polychromatophilia, basophilic stippling and normoblastosis
- WBC count is consistently elevated due to an increase in # of mature granulocytes
- Platelets are generally increased reflecting reduced or absent splenic sequestrationWhat Laboratory tests could be done for sickle cell anemiaSickling Test
- done if you suspect sickle cell anemia or trait
- In vitro sickling after adding reducing agent (Na meta-bisulfit)
or
Hb electrophoresis
- HbS predominant (80-95%)
- HbF present
- HbA2 normal
** HbA is absentWhat are some tools to diagnose Sickle Cell TraitSymptoms:
- generally none
- rare renal problems
- high altitude splenic infarction
- possible hemolytic crisis
Lab:
- Normal PBS, CBC, and Reticulocyte #
Hb electrophoresis shows:
- HbA (alpha2-beta2) 60%
- HbS 40%
- Normal HbA2 (alpha2-delta2) and HbF (alpha2-gamma2)
** HbA prevents HbS polymerization. Normally RBCs do not sickle
** Under extreme conditions (flight at high altitude in unpressurized aircraft, deep sea diving), red cells may sickleWhere is there a high occurence of Sickle cells alleles (HbS)in historical malaria areas (heterozygote advantage)
- Plasmodium Falciparum Malaria-
HbAA (homozygot normal) has medium survival
HbAS(heterozygote) has a higher survival than HbAA
HbSS(homozygote for sickle cell alleles) has a lower survival
** high freq. of Thalassaemia in the mediterranean and east Asia probably have the same cause - as does some enzyme deficienciesSickle cell disease vs Sickle cell anemia"sickle cell anemia"= disease found in homozygote
"sickle cell disease": two usages:
1. Disease found in homozygote
2. Descriptor for everyone who has any sickled cells = homozygotes + heterozygotes
** heterozygotes most frequently described with "sickle cell trait"
** the two usages of sickle cell disease are in current use in different laboratoresWhat traits modify severity of HbSS- HbF (persistence of fetal Hb)
- alpha-thalassaemia trait or silent carrier (lower Hb concentration)
- HbC
** these are all expected to improve the clinical pictureMolecular Testing for HbS- Restriction enzyme difference (MstII) and allele specific oligonucleotide (ASO) hydridization
** this was presented by Dr. Lawson- review this**HbC- Glu6Lys (glutamic acid to lysine: negative charge to positive charge- notice the codon number if 6, same location as in HbS) Glu and Lys are opposing charges so there is repulsion in HbC so sickling less severe than HbS
* Mutation happened only once in western sub-saharan Africa (HbC crystals seen in blood analysis)
* HbAC and HbCC BOTH significantly lower risk of Malaria death (heterozygote advantage)- significantly less pathology than HbAS and HbSS, respectively
** HbSC gives a somewhat milder sickle cell disease compared to HbSS but WORSE than HbAS
--- HbSC is example of compound heterozygote--Disease with diminished expression of HbThalassemia
also written as Thalassaemia
(can be beta or alpha)Beta- Thalassaemia is due to- Single base substitutions including frameshifts
- Few large deletions or insertions
Estimates: about 60,000 ppl with symptomatic Beta-Thal born each year, less than 300,000 alive
** most ppl with this do not survive very long
** notice that the more common type of mutation is different in beta- vs alpha-thalassemiaWhat is the genetics behind Beta-Thalassemia- Beta-Hb production from the thalassemia allele can be none (Beta^0) or reduced (Beta+, sometimes milder versions are stated as beta++)
- Homozygous Beta0Beta0 or compound heterozygote Beta0Beta+ usually have Beta-Thalassemia Major (this is most significant clinically)
- Homozygous Beta+Beta+ usually have Beta-Thalassemia Intermida
- the different type of heterozygotes with one normal allele all have beta-thalassemia minor (carrier usually no symptoms)
** genotype-phenotype correlation is incomplete: notice the use of the word usually indicating variation among patientsWhat is the mechanism for Beta-Thalassemia- severely reduced production of beta-Hb chains
- alpha-Hb chains in surplus (cannot produce homo-tetramers, precipitation inside cells- centers for oxidative damage of membrane proteins and lipids)
- increased destruction of RBC precursors in bone marrow
- shortened RBC lifespan in circulation
**** for molecular mechanism of cell damage, focus on the chain that is in surplusAlpha thalaseemia alleles- Alpha thalassemia carriers: malaria areas of africa and asia (especially south-east asia), rare in Mediterranean
* Allele alpha-thalassemia 1: usually found in ppl of Asian descent only (both genes deleted)
* Allele alpha-thalaseemia 2: Africa and Asia (still one gene left)
- a normal chromosome would have two copies producing alpha-Hb, so in a person with two copies of the chromosome (expected) missone one copy lowers production by 25%
ex. 1/3 of ppl from Thailand are carriers of one of these two allelesDeletions on Chromosome 16, alpha-thalassemia- silent carrier: one deletion
- alpha-thalassemia trait (mild anemia): 2 copies left, 2 copies deleted- mild sx's
- Hemoglobin H disease, moderately severe anemia (3 copies deleted)
- Hemoglobin Barts Disease, hydrops fetalis (all four copies deleted)
** Hb H and Hb Barts disease is rare in people of African descent but more common in people from SE Asia bc of the distribution of the two types of allelesThalassemia is aAutosomal Recessive Disorder
- due to absent/decreased synthesis of alpha-beta globin chains
** quantitative Hb abnormalities
- Beta-thalassemia: failure of beta chain synthesis (common in black americans, greeks, italian, india and east asia)
- Alpha-thalassemia: failure of alpha chain synthesis (common in south-east asia and in black americans)
Fetal Hb: predominant in fetus, trace in adults (HbF- alph2gamma2)
Adult Hb: 95-97% adult blood (HbA- alpha2beta2)
Adult Hb2: 1-4% adult blood (HbA2- alpha2delta2)What are some associated clinical syndromes of Beta ThalassemiaBeta Thalassemia Major (Cooleys Anemia)
- Beta+/Beta+ or Beta0/Beta0 or Beta+/Beta0
- severe
- transfusion dependent
Beta Thalassemia Minor/Trait
- Beta+/Beta or Beta0/Beta
- Mild anemia
----------------------
**Beta: Normal Beta-globin chain synthesis
**Beta+: some beta-globin chain synthesis
**Beta0: No Beta-globin chain synthesis
---
Defective globin chains results in ineffective erythropoiesis due to precipitation of abnormal Hb's within newly formed RBCs and increased erythrocyte fragilityEtiology and Pathogenesis of Beta Thalassemia- Normal HbA Globin Chain Production
- Beta Thalassemia Absent (beta0) or Decreased (beta+): beta chain production of Hb --> Reduced Hb and Excess unpaired alpha- chains leads to insoluble RBC inslusions that lead to membrane damage and cause hemolysis of RBCs (premature destruction <120days)
** the excess unpaired alpha chains aggregate to cause hemolysis
- unstable tetramers of alpha chains formed that percipitate in the cytoplasm of developing erythroid precursorsComplications of Hemolytic AnemiaIncreased ineffective erythropoiesis
- destruction of RBC precursors
- erythroid hyperplasia in BM
- BM expansion results in bony deformities
Progressive Splenomegaly
- mature RBC hemolysis
Extra-medullary Hematopoiesis (causes hepatosplenomegaly and formation of soft tissue masses)
- Excess Fe absorption and progressive tissue deposition
** increased O2 affinity of HbF as well as the underlying anemia impair oxygen delivery and lead to increased EPO
- EPO excess causes marrow erythroid hyperplase - the marrow apace is expanded causing facial and cranial bone deformities
** excess erythropoiesis causes increased iron absorption; which along with repeated blood transfusions, creates iron overloadBeta Thalasemmia Clinical Presentation- Thalassemia Facies: prominent front and parietal bones and enlarged maxilla
** hair on end appearance/crew-cut appearance- erosion of cortex and new bone formationClinical Features of Beta-Thalassemia Major- Anemia > 6-9 months
- growth retardation
- delayed sexual maturation
- splenomegaly/hepatomegaly
- skeletal changes: osteopenic, expanded marrow cavity, thin cortex
- systemic iron overload (due to blood transfusions): cirrhosis, cardiomyopathy/arrhythmia- congestive heart failure (CHF), death (2nd- 3rd decade)
IN LABORATORY you will see:
- Low Hb (3-6gm%)
- PBS: Microcytic Hypochromic & target cells
- Reticulocyte count: increased
- BM exam: iron stores increased and erythroid hyperplasiaBeta-Thalassemia: Confirming diagnosis and TreatmentRx= Blood Tx and Fe chealtors: deferoxamine with Vitamin C
Hb Electrophoresis: HbF is markedly increased and HbA2 is normal/increased/decreased
- In Beta0, most of the Hb is HbF, increased HbA2 (5-8%) is also seen
- In Beta+, some HbA is also present
Treatment:
- Blood transfusions: Fe overload --> Fe deposits --> damages heart, liver & endocrine systemBeta Thalassemia Minor (Thalassemia Trait)- less severe: one mutated Beta-chain allele
- RBCs carry less oxygen than normal
- common in mediterranean, middle east, africa
- Asymptomatic/mild anemia
- selective survival advantage for falciparum malaria
Labs:
- CBC: decreased RBC, Hb, Hct, MCV, MCHC
- increased corrected reticulocyte count
- PBS: microcytic hypochromic RBCs and target cells
*HbA2 may also be increased and normal- slight increased in HbFAlpha Thalassemiadecreased or absent alpha chains
- excess unpaired beta, gamma, or delta chains
** there are 2 alpha globin genes on each chromosome 16
** clinically significant: alpha thalassemia results from 3-4 alpha gene deletions
*** production of alpha-globin is decreased due to a gene deletion or inactivation
-----------
- Deletion of a single alpha globin chain= silent carrier (asymptomatic)- hematological findings include slight microcytosis and decreased MCV
- Deletion of 2 alpha-globin chains= alpha-thal trait (asymptomatic or mild anemia (~Beta thal trait)- hematological findings include mild microcytic anemia and decreased MCV
- Deletion of 3 alpha-globin chains= HbH disease (beta4) common in asians- moderate microcytic anemia and HbH on electrophoresis
- Deletion of all 4 alpha globin chains (comon in south east asia)= Hydrops Fetalis (HF) and Hb Barts (gamma4)- this is lethal in utero without blood transfusions, severe pallor, generalized edema and massive splenomegaly (~HDN), lifelong transfusion dependence, hemachromatosis without Fe chelation, Rx= BM transplantation) - Hb Barts has increased affinity for oxygen
** ~HDN= similar to hemolytic disease of the newbornTrue or false: imbalance of Hb with Beta and gamma-Hb chains is not bound to alpha chainsTrue!
- Beta and gamma-Hb chains CAN form homo-tetramers (therefore less precipitation than in beta-thalassemia )
- shortened RBC lifespan and aborted production just like in Beta-thalassemiaWhat are the main differences in Severe alpha and beta ThalassemiaAlpha thalassemia: surplus beta chain (and gamma chain), forms homotetramers and has precipitation but less of the surplus
Beta thalassemia: surplus Alpha chain, does NOT form homotetramers, has precepition all surplusHbEA substitution GAG --> AAG in codon 26 leading to Glu26Lys
- this substitution leads to altered splicing (slow removal of intron 1, partial use of alternatic splice donor around codon 26--> some products are non-functional --> reduced concentration of Hb
** common in India and South east Asia, up to 30% allele frequency in some areas- most common Hb variant in california
- Heterozygotes HbAE some protection against P.falciparum malaria
*** this is a mixed occurence becuase HbE both changes an AA and reduces production
HbE/HbA heterozygotes: near normal MCV
HbE/HbE homozygotes: frequently benign (mild hypochromic microcytic anemia)- can be classified as mild Beta+ Thalassemia (Hb > 10g/dL)HbE/Beta-Thalassemia compound heterozygotes- Mild (15%): 9-12g/dL Hb- rarely need treatment except when infections hit
- Intermediate (most): 6-7g/dL Hb- similar to beta-thal intermedia
- Severe (rest- up to 1/2 in some reports): 4-5g/dL Hb (treat as Beta-thal major)
What causes the variation?
- Beta0 vs Beta+
- persistence of HbF to varying degrees: in many E/Beta0 with no HbA, 40-60% of Hb is HbE, the rest HbF (and a little HbA2)
** the genotype does not directly predict severity of phenotypeHbS/Beta-Thalassemia compound heterozygotesSymptoms will be Sickle Cell disease, not Beta-thalassemia
- sickle cell anemia for SBeta0 (or slightly milder due to lower concentrations of Hb)
- milder for SBeta+Persistent HbF- Fetal Hb is <1% in most adults
- some ppl synthesize high amounts of HbF - no significant clinical problem (the high amts of HbF in ppl with inherited persistent HbF will happen even if they have no hemoglobinopathy alleles)
* genetic variation at position- 158 of the G gamma globin gene
- In ppl with HbSS, HbF constitute 2-20%
- Hydroxyuria is used experimentally to increase HbF production in Beta-Thalassemia (it is hypothesized that this occurs as a selective destruction of the fastest dividing RBC precursers- it so happens that HbF producing cells (F-cells) are dividing at a slower paceTissues and organs of the lymphatic system includediffuse lymphatic tissues, lymphatic nodules, lymph nodes, spleen, bone marrow, thymusLymphocytes can be found in theblood and in the thymus
There are 3 types of lymphocytes:
- T cells
- B cells
- NK cells
** these three can be told apart by immunocytochemistry (because diff lymphocytes express different surface markers) BUT you CANNT tell them apart on H&E stained sections
** Lymphocytes are the most abundant (by far) cell type of lymphoid tissuePrimary (central) Lymphoid organs- Site of development and maturation of lymphocytes into mature, BUT NAIVE (have yet to see an antigen) immunocompetent cells
Includes:
- Thymus: CFU-L cells leave the bone marrow after "birth" and mature to T cells in the thymus (becomes immunocompetent but niave)
- Red Bone Marrow: Where both Tcells and B cells are "born' and where B-cells mature (become immunocompetent, but niave). NOTE: B cells also mature further after leaving the bone marrowSecondary (peripheral) lymphoid organs- Where immunocompetent cells can interact with antigen and with each other to mount a response against invading antigens or pathogens
Includes:
- Spleen
- Lymph Nodes
- Tonsils and Adenoids, Bronchus, Mesenteric, Peyers Patch..The ability of a lymphocyte to produce a normal immune response following exposure to an antigen is referred to asimmunocompetenceLymphocytes are able to respond to an antigen when they see one (unlike stem cells) BUT what are they called if they have YET to be exposed to an antigenNaiveBilateral organ located in the mediastinumThymus
- A primary lymphoid organ-
* CFU-L cells from the bond marrow develop here into immunocompetent T cells
- The thymus possesses a thin Dense Irregular CT capsule from which trabeculae (each of a series or group of partitions formed by bands or columns of CT) extend into the parenchyma (functional tissue of an organ as distinguished from CT and supporting tissue) of the organ that divides it into incomplete lobules
** each lobule has a peripheral darkly stained zone known as the cortex and a central light zone known as the medulla
The capsule and trabeculae contain:
- blood vessels
- EFFERENT (but not afferent) lymphatic vessels
- nervesProduction of T cells in the thymus1. CFU-L cells from BM in newborn to adult (immuno-INcompetent) (CD4- and CD8-) begin their "education" in the cortex of thymus where they divide by mitosis
2. Thymocyte undergo POSITIVE SELECTION in cortex: must be able to recognize certain MHC molecules and be immunocompetent
** apoptosis if they DONT recogenize these, those that survive migrate to medulla (corpses removed by machrophage phagocytosis)
3. In medulla, they undergo NEGATIVE selection: any thymocyte that recognizes a self-antigen undergoes apoptosis
4. Thus, the thymocytes undergo both positive and negative selection
** over 95% die by apoptosis
** this is why the medulla of the thymus is lighter-staining than the cortex, it contains fewer cellsMain cell types found in the thymus include:1. Thymocytes (developing T lymphocytes)
2. Epithelial reticular cells (ERCs)
- Which are stellate cells (arranged in a radiating pattern like that of a star), have light staining oval nuclei, prominent nucleoli, eosinophilic cytoplasm, contain KERATIN intermediate filaments in their cytoplasm (like epithelial cells)
* 6 different types- that performs many diff. function in thymus
1. Forming Framework of thymus
2. Forms blood thymus barrier
3. Forms Hassal's (thymic) corpusclesHow do epithelial reticular cells (ERCs) form the framework of the thymus- the ERCs are usually joined to each other by desmosomes, forming a 3-D cytoreticulum that provides structural support for the developing thymocytesVimentin is found infibroblasts/reticular cellsHow do epithelial reticular cells aid in forming the blood-thymus barrierBlood- thymus barrier (formed by 3 structures):
1. Capillary endothelial cells linked by tight junctions
2. Dual basal laminae produced by ERC and endothelial cells
3. ERCs joined by desmosomes
- also macrophages hover nearby to "gobble up" any antigens that manage to pass through this barrier
** the blood-thymus barrier regulates exchange of substances between the circulatory system and thymus, providing a sequestered environment for immature T cells to develop
- the barrier prevents immature T cells from contacting foreign (non-self) antigens coming from the blood, because contact with "random" antigens at this stage will cause the T cells to die by apoptosisHassals or Thymic Corpuscles (corpuscle= a rounded globular mass of cells)* Formed by the epithelial reticular cells
- they are found ONLY in the thymic medulla
** diagnostic for the medulla**
- the central area consists of degenerating or necrotic cells
Function: secrete factors that aid in thymocyte developmentthe medulla is lighter than the cortex becauseit has a fewer number of cellsA rare congenital disorder involving failure of the thymus to develop properlyDiGeorge Syndrome (AKA Thymic Aplasia)
Cause:
- Faulty development of 3rd and 4th pharyngeal pouches in early development (caused by a defect on chromosome 22 due to a recombination error during meiosis)
* Pt's with this may have poor T-cell production because of a smaller thymus and, as a result, have an increased susceptibility to viral, fungal and bacterial infectionsDescribe Thymic Involution- The thymus is fully formed and functional at birth and very active through early childhood
- it persists as a alrge organ until about puberty
- then T-cell differentiation and proliferation are reduced and most of the lymphatic tissue is replaced by adipose tissue
** this shrinking of the thymus with age is known as thymic involutionIn adults, naive T cells are hypothesized to be primarily maintained bycell division of existing naive T cellsAll other lymphoid organs except the ___ originate EXCLUSIVELY from mesenchyme (mesoderm)Thymus
** thymus has DUAL embryonic origin
1. Its lymphocytes are from bone marrow (mesenchymal/mesoderm origin)
2. BUT is Epithelial Reticular Cells (ERCs) are from the endoderm (like some other epithelial cells)Primary lymphatic organs are wherelymphocytes are formed and become immunocompetent (but naive)
1. Thymus 2. Red Bone MarrowA secondary lymphatic tissue/organ is where a naive lymphocyte first comes in contact with an antigen and an immune response is generated. What are some examples of secondary lymphatic tissues- Spleen
- Lymph Nodes
- Tonsils
- Diffuse Lymphatic tissue (Peyers patches, Appendix etc..)What two forms of secondary lymphoid tissue are possibleEncapsulated and Not Encapsulated
1. Encapsulated: i.e. Surrounded by CT capsule
Forms Lymphoid organs:
- lymph nodes
- spleen
- tonsils (partially encapsulated)
2. Not encapsulated: diffuse within lamina propria CT below epithelium
- Mucosal-associated lymphoid tissue (MALT)- has multiple locationsWhat is the Immunological sequence that occurs in Bacterial Infections in the Adaptic Immune system?1. Bacteria (or other antigen) invade the body
2. Antigen presenting cells APCs (macrophages, dendritic cells others) phagocytose bacteria and then present antigen to NAIVE T cells, which acitvates these T cells
3. Activated T cells turn on naive B cells
4. B cells can transform into plasma cells- secrete antibodies specific to invading bacteria
5. Antibodies opsinize invading bacteria; bacteria are then destroyed by adaptive immune system- (also make memory B cells)What are the major cell types (in addition to lymphocytes) in secondary Lymphatic tissueDendritic Cells, Macrophages, Plasma Cells
1. Dendritic Cells
- the BEST antigen presenting cell in the body
- main fx: to process antigen material and present it on the cell surface to the T cells of the immune system
** these are dericed from monocytes (are a type of macrophage)
2. Macrophages
- are phagocytis AND APCs
- less efficient APC than dendritic cells
- they are excellent "garbage collectors" but not nearly as good antigen-presenting cells as dendritic cells
- they do the bulk of filtering lymph in lymph nodes and blood in spleen by phagocytosis
* derived from monocytes
3. Plasma cell
- a fully differentiated B-lymphocyte that produces a single type of antibody
- has an asymmetric "clock-face" nucleus
- more cytoplasm than lymphocyte
4. Follicular Dendritic CellsLymph is fluid that leaks out of capillaries and becomesinterstitial fluid then enters lymphatic vessels- it is then filtered through lymph nodes and rejoins blood circulation
** 90% of leaked fluid re-enters capillaries
** 10% becomes interstitial fluid/lymphEvery bit of lymph is filtered through at least ____ (~100-200 in the body) before the fluid is dumped back in the blood circulationat least one lymph node
** this is the way that the immune system constantly monitors drainage from tissues for pathogenic invaders
*** lymph nodes are a SECONDARY lymphatic organ- this means an antigenis respons is initiated and antibodies are produced against any "non-self" antigens present (in lymph in this case)Describe the structure of a lymph nodeNodes are covered by a capsule (dense irregular CT) and have capsular extensions, the trabeculae, which provide support for blood vessels entering into the nodes
* the concave surface contains the hilum: where arteries, veins, and EFFERENT lymph vessels enter and exit the node
3 main regions of a lymph node include:
1. Cortex: mostly B cells- contains lymphatic follicles/nodules
2. Paracortex: mostly T cells
3. Medulla: mostly plasma cells- made of medullary cords and sinusesDescribe how lymph flows through a lymph node1. Lymph enters the lymph node through AFFERENT lymphatics
2. The lymph is filtered through a reticular fiber network and the "filtered bits" are exposed to APCs (mainly dendritic cells), T and B cells, and other cells of the immune system
*** begins an antigenic response**
3. The now filtered lymph exits the lymph node through EFFERENT lymphatics
-----------
Lymph containing micro-organisms, soluble antigens, APCs, and a few B cells, enters the lymph node via AFFERENT lymphatic vessels which enter endothelial lined:
1. Subscapsular sinuses and
2. Peritrabecular sinuses, which lead to a meshwork of
3. Medullary sinuses in the medulla. These medullary sinuses become larger channels that combine to form the
4. Efferent lymphatic vessels that exit at the hilumWhat forms the framework that holds the lymphocytes in place in ALL lymphoid tissue/organs EXCEPT thymus (bc in thymus the ERCs form the framework)Reticular CT
* cells crawl in and out of this fixed framework
- Made of reticular fibers (type III collagen) secreted by reticular cells (specialized fibroblasts)
- the fibers are argyrophilic ("silver-loving")
** reticular fibers can be found in the subcapsular sinue where they "churn up" the lymph as it moves through, and any "bits" can get phagocytosed by macrophages and dendritic cells (APCs) lining the walls of the sinuses.
** this is the reticular framework found inside lymph sinuses, but NOT blood sinusesWhat can be found in large quantities lining the walls of the subcapsular sinus and what is its functionMany macrophages and dendritic cells line the walls of the subcapsular sinus to phagocytose any antigen, and then present it to naive T cells to begin an immune responseA very important structure found in ALL secondary lymphatic tissue when it is mounting an antigenic responseSecondary lymphatic follicle/nodule
- this is a follicle containing lymphocytes that have been ACTIVATED by antigen
- ring of B cells that surround lighter-staining GERMINAL CENTER that contains proliferating B cells, plasma cells, and T helper cells
- The germinal center develops when a lymphocyte that has recognized an antigen returns to a primary nodule and undergoes proliferaton
*** NOTE:
in secondary lymphoid nodules the light region is light because the lymphocytes are ACTIVATED and have larger light staining cytoplasm and more euchromatin in nucleus, NOT fewer cells
where as in the
Thymus, the light regions in medulla are light because there are FEWER lymphocytes present in this regionprimary follicle/noduleUNactivated lymphoid follicle
- contains small, inactive B cells (edges are hard to spot)
- no light staining germinal centerWhat can be found in a secondary follicle that is required for the creation of more specific antibodiesFollicular Dendritic Cells (FDCs)
- found in the germinal center of secondary follicles
- have Fc receptors; can bind antigen antibody complexes
- have many cytoplasmic processes that can TRAP antigen;
FDCs are NOT APCs, they dont phagocytose and process antigen
** they are require for creation of more specific antibodies
- B lymphocytes that can make more specific antibodies bind tighter to antigen coating FDC
- Soak up growth factors produced by FDC and stay alive
- the lower affinity ab-producing cells die by apoptosis because they DONT get growth factorsAnywhere there is a secondary follicle (F)- with a light staining germinal center- is seen in secondary lymphoid tissue this signifies the presence ofactivated B cells
** their presence means your immune system has encountered a foreign antigen and is generating antibody secreting plasma cells and memory B cells
** this is why you get swollen lymph nodes when fighting infectionLymphocytes enter secondary lymphatic tissue by diapedesis through specialized blood vessels calledHigh Endothelial Venules (HEVs)
- the endothelial cells lining there are cuboidal/coulmnar (rather than squamous like other blood vessels)
* they are located in the paracortex of the lymph nodeL-selectins on lymphocytes bind ______ on HEV endothelial cells so they will leave bloodstream (*Lymphocyte Homing)Addressins
** these are what attracts lymph out of blood4 types of cell adhesion molecules1. Integrins (Heterophilic- bind cell to ECM)
2. Cadherins (Homophilic- bind cell to identical cell)
3. Ig-superfamily (IgSF) (mostly Homophilic): although exploited extensively for functional roles in immue recognition, such as for antibodies and T-cell receptors, the immunoglobin fold is also found in a wide variety of structures employed in cell-cell interaction (ALL members contain a domain known as an immunoglobulin domain or fold **)
4. Selectins (Heterophilic): binds cell to CARBOHYDRATE on another cell (there is L, P and E selectins)L-selectinTransmembrane protein on lymphocytes
- binds CARBOHYDRATE ligand expressed on endothelial cells in high endothelial venules (HEVs)
** used to attract lymphocytes to secondary lymphatic organs in high endothelial venules (LYMPHOCYTE HOMING)P, E SelectinsSelectin is on endothelial cells, Carbohydrate ligand is on leukocytes
** used to attract leukocytes like neutrophils to sites of inflammation
** remember- "athletic" process= PE (bc Neutrophils move with diapedesis)What are the steps following after an antigen with or without APCs enters with afferent lymphafter entering in with afferent lymph it moves in the subcapsular sinus and the APCs phagocytose antigen
- The naive T and B cells enter the lymph node from blood through high endothelial venules in paracortex, migrate to cortex
- In the cortex, APC present antigen to naive T cell ACTIVATES it and the activated T cell ACTIVATES naive B cell, forms a secondary follicle, some B cells transform into plasma cells
- Antibody-secreting plasma cells migrate to medulla; effector T cells exit node in the lymphIn the medulla of a lymph node, what is the difference between the medullary cords and the medullary sinusesMedullary cords: are sites of high antibody production containing
- plasma cells
- macrophages
- B cells
Medullary Sinuses (or sinusoids): are vessel-like spaces separating the medullary cords
* lymph flows into the medullary sinuses from cortical sinuses and then into the EFFERENT lymphatic vesselsWhat are two main reasons for swollen lymph nodes1. After exposure to antigen such as a disease-causing organism, lymph nodes make MORE and LARGER secondary follicles (* this makes the lymph node LARGER)- after plasma cells and memory B cells leave the new follicles, the lymph node can shrink back down
2. Cancer cells can be released from a tumor in one site in the body, get carried in lymph to lymph node, get trapped in lymph node, keep dividing (* swollen lymph node can be the first sign of a tumor located somewhere in the body)
- the condition of the lymph nodes is very important in cancer staging: it decides the treatment to be used, and determines the prognosisT or F: the spleen filters lymphFALSE!!!!!
the spleen ONLY filters BLOOD!!!
---lymph nodes filter lymph--The largest secondary immune organ in the body- The spleen- it is about the size of a clenched fist
* it is enclosed by a dense CT capsule from which trabeculae extend into the parenchyma of the organ
- the Hilum carries nerves and arteries into the splenic pulp and veins and efferent lymphatic out of it
** like the thymus, the spleen possesses EFFERENT, but NOT afferent lymph vessels
**** NOTE: any antigens come from filtereing blood, not lymphWhat are two main functions of the spleen?1. Filters blood: mounts an immune response to antigens, particularly bacteria, circulating in the blood
2. Removes aged and damaged erythrocytes from the blood circulationwhat is the difference between Red and White Pulp of the spleenRed Pulp:
- Where blood is filtered (~75% of the spleen)
- Consists of: sinusoids and splenic cords (of Bilroth)
White Pulp:
- production site of lymphocytes that react against the antigen/any foreign antigens that are filtered from the blood in the red pulp and makes antibodies against them
** when stained with H&E, "white" pulp appears blue/purple because of lymphocytesBlood flow through the red pulp1. Some penicillar arteries in spleen are open-ended, dumping blood into the splenic cords (of Bilroth) "open circulation"
2. Plasma and formed elements of blood must pass between stave cells lining sinusoid to reenter blood circulation inside sinusoids "closed circulation"
** NOTE: the spleen is the only human organ where blood passes through spaces NOT lined by endothelia or other barrier-forming cellsDescribe the 2 components of Red Pulp1. Sinusoids (sinusoidal capillaries)
- the blood vessels, (the "sea"
- NO reticular fibers/cells in blood sinuses (unlike lymph sinuses)
2. Splenic Cords (of Bilroth)
- made of Reticular Fibers (Type III collagen), (the "land")- alot of resident macrophages and dendritic cells
** in the splenic red pulp, all the blood is dumped here and then has to reenter the sinusoids through slits in walls of sinusoids to re-enter the bloodstreamIn the Red Pulp of Spleen what is the name for the unusually elongated endothelial cells that are oriented in parallel with the sinusoids blood flowStave Cells
- these are sparsely wrapped in Reticular Fibers (type III collagen)- much like the hoops surrounding a wooden keg
*they have incomplete basal lamina (so cells can cross)
- When RBCs reach the end of their lifespan, they are no longer flexible enough to fit through the slits- many macrophages sit here and wait to phagocytose the RBCs that cannot make it
- also, at the end of lifespan, SCRAMBLASE is activated that flips phosphatidylsering to outside of RBC membrane, "Eat me" signal for macrophages
** after splenectomy- RBCs are phagocytosed by macrophages in other parts of the body (liver, bone marrow; dont have slits) because of this "eat me" signalCollagen type 3 fibers (reticular fibers) areagyrophilic- "silver loving"
NOTE: the regularly spaced, circumferential ribs encircling the sinus endothelium are readily distinguished from the random distributed reticular fibers of the surrounding splenic cordsThe splenic cords containRBCs, Neutrophils, Macrophages, and blood platelets
** A reticular cell framework supports the cord. The sinus is bounded by the epithelial cells that form the basket-like structure of the sinusBlood flow in the white pulp of spleenblood enters splenic artery --> trabecular artery --> central arteries/arterioles (which are surrounding by T cells of the white pulp called "periarterial" or "periarteriolar" lymphoid sheath (PALS)
- B cells in these sheaths can form nodules - and around these nodules are located the marginal zone sinuses
** emerging from the white pulp, the central arteriole branches as the penicillar arterioles, which lead to sheathed capillaries. From these the blood flows into either a closed circulation passing directly into splenic sinuses or an open circulation, being dumped from the vasculature into the lymphoid tissue of the red pulps splenic cords
* from there viable blood cells reenter the vasculature through the walls of the sinusesT or F: the white pulp of the spleen contains both B and T cellsTRUE!
But mostly T cells surround central artery- forms PALS (periarterial lymphoid sheaths)
- if reacting against antigen- also see a secondary follicle or nodule that is mostly B cells
*** In a histological slide of White Pulp
- the sinuses can be seen at the periphery between white and red pulp
- The marginal zone on the outside of the germinal center is an important area for the interaction of APCs carrying antigens from the red pulp with lymphocytes of the white pulp
** When a large nodule with a germinal center forms in the PALS (periarterolar lymphatic sheath), the central arteriole is deplaced to the nodules peripheryWith Massons Trichome StainYou visualize the following:
- Red keratin and muscle fibers
- Blue or green Collagen (*Collagen Type I is bid in blood vessels) and bone
- Light red or pink cytoplasm
- Dark brown to black cell nucleiWhy would you get a spleenectomyA ruptured spleen can lead to life-threatening internal bleeding
- because of open circulation in red pulp; if the splenic capsule is puncuted, the blood will flow directly out of the spleen
- common inury-related causes of a ruptured spleen include MVA and severe blows to the abd during contact sports, such as football or hockey
AFTER a spleenectomy:
- aged RBCs are removed by macrophages in the sinusoids of the liver and bone marrow (RBCs still express PS eat my signal at end of lifespan)
- diminished responsiveness to some vaccines
- increased susceptibility to infection by bacteria and protozoaIn Common sites of invasion by pathogens because the lumens of these tracts are open to the external environment (digestive, respiratory, genitourinary)- you can find alot ofDiffuse lymphoid tissue "guarding" these mucosal surfaces,
called Diffuse Lymphatic Tissue or MUCOSA-ASSOCIATED LYMPHATIC TISSUE (MALT)
* this is NOT surrounded by a connective tissue cpasule (except for tonsils which are partially encapsulated)
- consists of lots of lymphocytes clustered together in (usually) lamina propria of certain tissues, can form nodules or follicles
MALT is populated by:
- T and B lymphocytes
- Plasma cells
- Macrophages
- Dendritic cells
- Follicular Dendritic cells
** each of which is well situated to encounter antigens passing through the mucosal epitheliumName a component of MALT (GALT: gut-associated lymphoid tissue)Peyer's Patches
- aggregates of lymphoid nodules found in the ileum ~30 in humans
- involved in the development of immunity to antigens present there
** they are diffuse lymphatic tissues with secondary nodules
** Peyers patches are located in the Lamina PropriaWhat Special cell is located in the gut-associated lymphoid tissue (GALT/MALT) of the Peyers patches and other parts of the GI tractMicrofold (M) cells
- these transfer antigens from the lumen (by phagocytosis and pinocytosis) and present them to dendritic cells and macrophages & helper T and B cells lying in deep invaginations of their basal cell surfaces
- then the appropraite immune response is generated in the underlying lamina propria
** the antigen is transported by the M cell to the organized lymphoid follicle containing B cells. The activated B cells mature into plasma cells, which produce secretory IgA and release it into the lumen where it reacts with antigen that caused its productionBlind pouch off the cecum of the large intestineAppendix
- lamina propria and submucosa are generally FILLED with lymphocytes and lymphoid follicles
- has high endothelial venules (HEVs) to bring in naive T and B cells from the blood
*** the appendix is a significant part of MALT
** has a muscularis externa
NOTE: peyers patches in the ileum had a muscularis mucosaAggregations of nodular and internodular tissue in the walls of the pharynxTonsils
- these tissues are the immune systems FIRST line of defense against ingested or inhaled foreign pathogens
3 types:
1. Palatine*: in the lateral walls of the oral pharynx (near the palate)
2. Lingual: at the base of the tongue
3. Pharyngeal (adenoids): at the rood of the nasopharynx
** tonsils most commonly refer to palatine tonsils- which are masses of lymphatic material situated at either side of the back of the human throat
Tonsilitis= inflammation of the tonsils- gives those white thins on your tonsils bc the characteristic morphology of the tonsils"Ring of Waldheyer"masses of lymphoid tissue form a ring of defense against everything entering through the mouthPalatine TonsilsOn the L and R area of the oral cavity
- dense lymphoid tissue that forms a band of lymphatic nodules that lie just below a non-keratinized, stratified squamous epithelium lining the oral cavity in this region
- Overlying epithelium forms invaginations called crypts that penetrate into the band of nodules
- the cryptes are labyrinth tubules that are entered by things such as bacteria and other small particles in the mouth
- movement of particles down the crypts allows contact with the tonsil immune system cells
- there is an incomplete CT capsule surrounding the tonsil
- there are EFFERENT lymphatic vessels coming out of the tonsils, but NO afferent ones
** any antigen comes in from the mouth cavityTonsils (like ALL secondary lymphoid tissue) have1. HEVs to bring in naive T and B cells from the blood (** remember there were no HEVs in the spleen, why was this?bc whole components of blood get dumped there and they can just find where they need to go they dont need a special thing to bring them in)
2. secondary follicles/nodules, follicular dendritic cells in germinal centers (also primary follicles)
3. reticular cells/fibers to make the frameworkWhat are the 3 things the immune system can distinguish between?1. Self vs. nonself
2. Micro vs. Macroscopic invaders
- micro: bacteria, viruses, protazoans, fungi (small enough to be phagocytosed)
- macro: (metazoans) ex. worms (not big enough to be phagocytosed
2. Intra vs. Extracellular invaders (immune system needs different paths for each
-----these distinguishing elements dictate the type of immune response----
- Extracellular Microscopic Organisms: Unicellular- can be physically flagged by molecules present in body fluids and destroyed by lysis or phagocytosis
- Intracellular Microscopic Organisms: (these are found hidden inside of cells- shielded from molecules of the immune system meant to flag them for destruction)- destroyed by killing the cells harboring them
- Large extracellular organisms (multicellular- too large to be phagocytosed or lysed) these are destroyed by hordes of cells releasing corroding molecules on themCharacteristic Flow of an Immune Response to an Extracellular Bacterial InfectionUpon first contact with the body the bacterium must first pass through physico-chemical barriers (ex: skin and fatty acids)
- once it passes this is activates complement system which can lead to lysis, phagocytosis (macrophages & neutrophils) or inflammation
- inflammation increases the recruitment of neutrophila and monocytes/macrophages and makes more complement which again can increase lysis and phagocytosis
- this is all from the innate immune system---
- Dendritic cells which are also part of the innate immunity also increase phagocytosis which leads to the adaptive immune response
- Antigen presentation/activation of T lymphocyts which can lead to increased production of neutrophils and monocytes in the bone marrow or activation of B lymphocytes which make antibodiesThe essential feature of the adaptive immune response is its reliance onT lymphocytes2 phases of an immune response include1. Innate phase: triggered upon antigen exposure and remains active until antigen is eliminated
2. Adaptive phase: takes hrs to days to fully develop after antigen exposure (this is triggered by cells of the innate immune system like dendritic cells and macrophages)
& many cells acting during the innate phase are also called upon to act during the adaptive phase (ex. Neutrophila, macrophages, NK cells)An added advantage of adaptive immunity is the development ofmemory- which prevent re-infectionImmune System- effort to combat potentially hazardous materials
- restoration of normal structure and function
Role of the immune system is:
- defense against infections or against tumors
- can injure cells and induce pathologic inflammation
- recognizes and responds to tissue grafts and newly introduced proteins
NOTE: the immue system can do both protection AND destruction2 central principles upon which the immune system is predicatedRecognition and Self-Discrimination
Recognition
- The body must have the capacity to "recognize" the invading material and this is achieved through cell surface receptors that bind ligands on invaders
Self-discrimination
- An immune response must implicitly be directed at a "foreign' substance to defend self from harm
- the generation of nonself immune cells occurs by the process of elimination of self-reactive precursorsMediators of Humoral ImmunityB lymphocytes
** these respond to extracellular microbes by secreted antibody which blocks infections and eliminates extracellular microbesMediators of Cell-mediated immunityT lymphocytes
(can have Helper T or Cytotoxic T lymphocytes)
- Helper T lymphocytes respond to phagocytosed microbes that can live within macrophages through activation of a macrophage- this leads to elimination of phagocytosed microbed
- Cytotoxic T lymphocytes respond to intracellular microbes (ex. viruses) replicating within infected cell by killing the infected cell and eliminated reservoirs of infectionList some Antigen Presenting cells ( Capture of antigens for display to lymphocytes)- Dendritic cells: initiation of T cell responses
- Macrophages: effector phase of cell mediated immunity
- Follicular Dendritic Cells: display of antigens to B lymphocytes in humoral immune responsesEffector Cells (elimination of antigens)- T lymphocytes: activation of phagocytes, killing infected cells
- Macrophages: phagocytosis and killing of microbes
- Granulocytes: killing microbes
** induction site is where immune cells meet antigen, get activated, and move to effector sites to perform their functionsDescribe Lymphocyte recirculationLymphocytes circulate twise
1. they circulate to find antigen and become activated (inductive site)
2. they re-circulate to find and destroy pathogens (effector site)Role of the immune systemDefense against infections:
- Primary Immunodeficiencies: deficient immunity results in increased susceptibility to infections; ex. AIDS
- Vaccination boosts immune defenses and protects against infections (prevention of disease through vaccination)
Defense against tumors:
- Potential for immunotherapy of cancer (ex. B cell acut lymphoblastic leukemia (ALL)- CAR therapy
The immune system can injure cells and induce pathologic inflammation
- immune responses are the caused of allergic, autoimmune, and other inflammatory diseases (ex. TNF-alpha mAb for treatment of rheumatoid arthritis)
The immune system recognizes and responds to tissue grafts and newly introduced proteins:
- immune responses are barriers to transplantation and gene therapyCharacteristics of Innate Immune response* born with it
It is Group specific:
- multiple, relatively specific antigen receptors per cell
- recognize antigen based on common structural motifs
- recognize antigen marked by complement
Always present/immediate response
Short-lived- NO MEMORYCharacteristics of Adaptive Immune responsesAntigen-Specific
- Cells express a unique antigen receptor
Called upon only when necessary
Slow response
Long-lived:
- Second response against pathogen is better, faster, and stronger than first
- "Immunological Memory"What Cells are part of the innate immune response- Natural Barriers
- Pagocytes: dendritic cells, neutrophils, macrophages
- Mast cells, Eosinophils, Basophils
- Complement (**this one also has an adaptive component)What cells are part of Adaptive ImmunityB cells and T cells
- along with their productsWhat are the phases of immunological action1. Cognitive phase: must be able to see and find pathogen- does this with receptors on cells that bind to microbial molecules
this causes
2. Activation phases: activation of a previously silent immune cell which can no move on to
3. Effector phase: kills target
NOTE: immune system is expected to NOT be self reactive (Tolerance Induction- this is where we select for cells that are NOT self reactive)The cognitive (recognition) phase of innate immunity is mediated byreceptors on innate immune cells named Pattern Recognition Receptors (PRR's), these are
- limited in number (dozens) ** think bc you are already born with them so they must be limited
- specificity is predetermined and fairly broad (generally respond to groups of organisms)
- SAME for all cells
- Little of NO expansion upon stimulationType I PRRs in Innate Immunity areSecreted PRRs:
- circulate in blood and lymph
- MANNAN BINDING LECTIN (MBL), a collecting- binds to CHO on bacteria to initiate complement activation (this MBL is a protein produced by the liver in serum--> activates complement when bound- this is called the Lectin Pathway)
NOTE: formation of MBL is Induced by IL-6
* other C-type lectin receptors and C-reactive proteins function similarlyType 2 PRRs in Innate immunity arePhagocytosis PRRs/ Scavenger Receptors
* when these bind the result is phagocytosis
- High affinity for mannos residues
- bind to bacteria and facilitate phagocytosis
- pathogen-derived proteins are presented to T cells (antigen processing and presentation)Type 3 PRRs in Innate Immunity areSignaling Receptors
** binding of these results in signaling with up-regulation of genes in the nucleus
Type include:
TLRs (Toll-like receptors):
- homologous to toll receptors
- on macrophages, dendritic cells, and epithelial cells (cell membrane and on endosomes)
- binding to pathogens results in activation of signal transduction and expression of cytokine genes
NLRs (Nod-like receptors):
- Nucleotide oligomerization domain-like receptors (cytosolic)
RLRs (RIG-like receptors):
- Retinoic acid-inducible gene-like receptors (cytoplasmic)Microbial Ligands recognized by PRRs includeUnique Microbial structures
- Pathogen- associated Molecular Patterns: PAMPs
- Damage-associated Molecular Patterns: DAMPs (damage to tissues products released that can also induce activity)
- also have MAMPs and BAMPsPAMPsPathogen- Associated Molecular Patterns that bind with PRRs
these are:
- not shared with the host
- common to many pathogens
- invariant (preferably, ex: flu is variable always changing- not good for us)
** A Type 3 PRR: TLRs (toll-like recptors)- can be found on the plasma membrane and they recognize extracellular material
ex.
- TLR-2: binds Bacterial peptidoglycan (a component of the bacterial cell wall)
- TLR-4: Most frequently seen* binds to lipopolysaccharide on gram negative bacteria
- TLR-5: binds to flagella
** Some TLRs can also be found on the inside of the cell in an endosome and these are known to bind to viruses- specifically the nucleic acids of ingested microbesIn Adaptive Immunity- cognitive functions are mediated byunique cell surface receptors:
- specific to each cell (each B cell and T cell express receptors of only ONE specificity)
- receptor is generated by recombination of genes encoding the receptor (germline gene rearrangement)
- rearrangements are random, and are antigen independent
- allows for high degree of diversity in antigen receptors (many lymphocytes of only ONE specificity)
- expanded upon stimulation
basically....
- specificity is guaranteed by having each cell ONLY carry receptors specific for ONE antigen
- diversity is ensured by the staggering number of lymphocytes, each possesing specificity for only one antigenDifference between BCRs and TCRs in the Cognitive Phase of Adaptive Immune RecognitionB cell recptor (BCR, immunoglobin, antibody)- bind antigen DIRECTLY (NO MHC needed, & it recognizes many different kinds of antigen)
- Used by B cells to recognize antigens
- in response to antigen they secrete antibodies
T cell receptor (TCR)- MHC RESTRICTED- recognizes ONLY peptides on MHC
- used by T cells to recognize antigen
- in response to antigen they help other cells become cytotoxic (with cytokines and cell-surface interactions)
- kill infected cells
** BOTH BCR and TCR belong to the IgSuperFamily - when you have an issue with BCR this can affect the TCRDifferences between receptors of the Innate Immunity vs Adaptive ImmunityInnate Immunity
- Specificity inherited in the genome
- Expressed by all cells of a particular type (ex. macrophages)
- triggers immediate response
- recognizes broad classes of pathogens
- interacts with a range of molecular structures of a given type
Adaptive Immunity
- encoded in multiple gene segments
- requires gene rearrangement
- clonal distribution
- able to discriminate between even closely related molecular structuresProperties of the Adaptive Immune Response Include- specificity
- diversity
- clonal expansion
- anamnestic reaction (secondary response and booster response)
- memorythe process of the body returning back to normal after an immune response is referred to asContraction (homeostasis)
* your cytokines can start a response and also end itAquired/ Adaptic Immunity can be further subdivided into what two types of responsesActive and Passive Response (both can be natural or artificial)
Active (make own antibodies)
- Natural: exposure to infectiour agent (ex. cold/infection)
- Artificial: immunization (ex. vaccine)
Ex: all residents of a nursing home inoculated with an H3N2 influenza-A preparation. What type of immunity is stimulated by this procedure= artificial active
**** this gives memory
Passive (recieve ready made anitbodies- serum (antibodies) from an immune individual)
- Natural: maternal antibodies (ex. breast feeding)
- Artificial: antibodies from other sources (ex. recieving anti-tetanus shot after cutting yourself with something rusty)
** passive DOES NOT have memory
BOTH ACTIVE AND PASSIVE HAVE SPECIFICITYOverview of innate recognition- lymph drains antigen and innate cells to secondary lymphoid tissue leads to
- activation of B cells and T cells
- T cells become effector T cells, B cells secrete antibodies
- the effector T cells and antibodies traffic to site of infection and the Killer T cells can kill infected cells and the antibodies & cytokines can go on and trigger additional functionsComplement participates in both theinnate and adaptive immune responsesTerm used to describe two or more cytokines that have the same effect on the cells that they bondRedundancyWhich cytokine stimulates hepatocytes to produce actue phase proteins that function as early indicators of inflammationIL-6Where would an antigen entering the body in subcutaneous injection most likely activate its specific lymphocytesDraining lymph nodesThe greatest concentration of T lymphocytes is found in which part of the lymph nodeIn the paracortical zoneCytokines and chemokines always achieve their effects throughsignaling, and the first step in cytokine signaling is cytokine-receptor bindingName receptors that are part of the Cytokine Receptor Family- Type I cytokine (hemopoietin) receptors
- Type II cytokine receptors
- TNF receptor family
- IL-1 receptor family (*** key on in inflammation)
- Seven transmembran GPCRS (their ligands are chemokines)Name some subunit compositions of cytkine receptorsComming Gamma Chain Family
- this is mainly for proliferation cytokineswhich signaling pathway is at the root of the initiation of inflammatory responseNF-KBeta Signaling Pathway
"canonical pathway"
- can be activated with TNF family receptor, TLR, or Antigen receptor
which ever it is they all lead to activation of NEMO which phosphorylates IKBetaalpha leading to protesomal degradation of it --> this realeases and translocates NF-kBeta transcription factor to the nucleus where it bind NF-kBeta responsive elements (ex. cytokine gene as cytokine receptor gene promoters among others)Type I and Type II cytokine receptors only differ slightly in structure, but they respond similarly and generally activate aJaK/STAT signaling pathways
1. Cytokine receptor sitting on plasma membrane with JAK attached
2. Attachment of cytokine leads to cytokine-mediated receptor dimerization; JAK-mediated phosphorylation of receptor chains
3. Recruitment of STATs to cytokine receptor
4. JAK-mediated phosphorylation and dimerization of STATs
5. Translocation of STATs to nucleus
5. transcriptionInflammasomea multiprotein complex in the cytosol of many cells (especially monocyte-derived phagocytic cells like monocytes, macrophages, and dendritic cells) that proteolitically activates the inactive precursor of IL-1beta or IL-18
It is composed of
1. A detection component, usually a NOD-like receptor (NLR)
2. An effector component which is caspase-1 (this cleaves the inactive form pro-IL1beta)
3. An adaptor component linking the other two components
** once a signal is detected by the NLR, caspase-1 is activated and precursor IL-1Beta (or IL-18) is cleaved into its active form and is ready for secretion - which can lead to acute inflammation
*** secretion of IL-1Beta (or IL-18) requires TWO signals: one activating the NF-Kbeta pathway and one activating the inflammasome- both are triggered by microbial products (ex. reactive oxygen species, K+ efflux, crystals, etc.)Stimulation by IL-1Beta triggers the synthesis and secretion ofmany inflammatory mediators
- IL-1Beta signals through the NF-KBeta pathway, as well as the stress-activated protein kinase (SAPK) pathway p38 and JNK, members of the mitogen-activate protein kinase (MAPK) pathways ((cross talk with MAP kinase pathway))
** leads to transcription of IL-1Beta responsive genes:
- IL-1Beta
- IL-6
- TNF-alpha
** these are the most important for inflammationMany available drugs aimed at reducing inflammation act onIL-1Beta signaling or the gene products it activatesNonSteroidal Anti-inflammatory drugs (NSAIDS) such as acetylsalicylic acid, ibuprofen, and acetaminophen are over the counterCOX-1 and COX-2 inhibitors that are used for treating many minor (fever and pain) and major conditions (gout, arthritis, etc.)
**** COX-2 is a prostaglandin (it is an IL-1Beta responsive gene turns on in inflammation)IL-1Beta, the gene products it activates, as well as complement fragments ALL coordinate to induceendothelial activation and transendothelil migration in post-capillary venules, which are responsible for the cardinal signs of inflammation: heat, redness, swelling, and painComplement usesC3a and C5aMacrophage-released IL-12 following microbe internalization stimulatesNK cells to secrete IFN-gama
- IFN-gamma secretion by NK cells in turn enhances macrophage microbicidal activity
- this increases the macrophages killing capacity
(M1= classically-activated macrophage)
*** this release of IL-12 from the macrophage is targeted to treat Psoriasis, Chrons disease, and ulcerative colitis with UstekinumadStimuli and signaling events that result in IL-12 secretion by macrophages, as well as cytokines and signaling pathways that activate macrophages to become M1 macrophages include- PAMPs and DAMPs activating the canonical pathway leading to IL-12 secretion
- TNF-alpha signaling leads to increase in IL-12 secretion
- IFN-gamma signaling leads to an increase in the killing response of macrophagesCytokines that are involved in inflammation- IL-1Beta
- IL-6
- TNF-alpha
** IL-1, IL-6, TNF-alpha, CXCL8- all induce local inflammaitonCytokines involved in TH1IL-12 (released from macrophages- stimulates the secretion of IFN-gamma by NK cells, which in turn activates macrophages to increase their microbicidal activity)
IFN-gamma
TNF-alpha
** these target macrophages and activates them so that they can protect against intracellular pathogensCytokines involved in TH2IL-4
IL-5
IL-13
IL-10
** these activate eosinophils and mast cells; and alternative macrophage activation against HelminthsCytokines involved in ChemotaxisCXCL8 (IL-8)Cytokines involved in ApoptosisCD95L/CD95 (FasL/Fas)
TNF-alpha/TNFR-1Cytokines involved in proliferationIL-1Beta
IL-2
IL-6
IL-7
IL-21
M-CSF
G-CSF
GM-CSFCytokines involved in TregTGF-Beta
IL-10Cytokines involved in TH17IL-6
TGF-Beta
IL-17
IL-22Cytokines involved in hematopoiesis/ developmentIL-3
IL-5
IL-6
IL-7
M- CSF
G- CSF
GM- CSFCytokines inolved in antiviral activityIFN-gamma
TNF- alphaChemokines exert their action through concentration gradients and ligand-receptor interactions. Can you name two structural families of chemokines?CC-chemokines
- signal through CCR (cystiene-cysteine)
- includes: MCP-1, MIP-1, RANTES, eotaxin
CXC- chemokines
- signal through CXCR
- includes CXCL8 (aka IL-8)**Paracrine functions of proinflammatory cytokines includeendothelium activation and macrophage activationTNF, IL-1, and IL-6 can act on the brain to inducefeverIL-1 and IL-6 when acting on the liver produceAcute phase proteins which further assist the immune responseTNF, IL-1, IL-6 act on the bone marrow to increaseleukocyte productionTH17secretes the cytokines IL-17 and IL-22
- these do neutrophil recruitment and activation against extracellular bacteria and fungiTfh (T follicular helper cell)is defined by the cytokines IL-21 (and IFN-gamma or IL-4)
- these target B cells to produce anitbodies against extracellular pathogensTrue or F: cytokines are involved in isotype switchTRUE!
* they can help in determining which isotype an antibody will be: IgM, IgG, IgE, IgADifferent cytokines can activate a macrophage to be classically activated or alternatively activated. What is the difference?Classically activated macrophages (M1): inflammatory
vs.
Alternatively activated macrophages (M2): can be anti-inflammatory or involved in tissue repairDescribe the aberrant response that occurs in Leishmaniasis- Response with Th2 rather than Th1 leads to a disseminated infection
* an abberant immune response by some individuals contributes to a severe form of the infection or disease, in the disseminated form of this diseases (multiple lesions over while body) as opposed to control of the infection (cutaneous leishmaniasis or oriental sore; a few localized legions)
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** same thing occurs in Leprosy (Th2 is produced instead of Th1 - leading to the lepromatous form of hte diseases - as opposed to the controlled form (tuberculoid form) the pt would have gotten if they expressed the controlled form of the infection mediated by Th1)
** leprosy is better controlled by the TH1 response
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Some in HIV pts with a Th1 response have a slower progression to AIDS in the absence of therapy- whereas those with an aberrant TH2 response have a faster progresssion to AIDSfirst line of defenseinnate immunity
- this is pre-formed (constitutive, natural, native)
- rapid response
- NON-specific: its receptors are encoded in the germ line, has identical receptors, not clonally distributed
- NO memory
- triggers the adaptive responseBarriers to infection arephysical, chemical, biological
- physical: skin
- chemical: killing of microbes by locally produced antibiotics (ex. epithelial cells secrete peptides)
- biological: killing of microbes and infected cells by intraepithelial lymphocytesMain physical barrier of the innate immune systemSkin
- it is oily with antimicrobial secretions (fatty acids, defensins in sweat; sebaceous gland secretions)
- chemotactic secretions: TNF-alpha, IL-8, etc.
- antigen presentation by dendritic cells
- TIGHT junctions at ALL locations
*** if these tight junctions break- there is NO defense, these MUST be maintainedHow does innate immunity function in the Respiratory tract- mucus
- ciliated epithelium: cough-sneeze reflex (part of immune defense)
- surfactants (collectins): secreted by Type II pneumocytes, lubrication of the alveoli, and binds pathogens for phagocytosis
- alveolar macrophagesHow does innate immunity function in the gastrointestinal tract- stomach aciditiy (not that many bacteria in the stomach because of this)
- resident bacteria
- epithelium
- PANETH cells: secrete- alpha-defensins, lysozyme and phospholipase-AHow does the innate immunity function in the genitourinary tract- flushing action of urine (flushes out toxins)
- urine acidity (antimicrobial)
- vaginal secretions, lysozyme
- Tamm-Horsfall protein (THP; antimicrobial-immunomodulation)-this helps to prevent UTIsSjogrens syndromeinability of the immune system to make tears or salivaList the Cells of innate immunity1. epithelial cells
2. phagocytes
- macrophages
- neutrophils
- dendritic cells
3. NK cells, intraepithelial lymphocytes
*** Note that generally lymphocytes are part of the Adaptive immune system but these are special lymphocytes that are innateWhat are some proteins found in innate immunity (humoral function)1. IFN-alpha, beta, gamma, and lambda
- these do inhibition of viral replication and activation of NK cells (these do not prevent viral infection BUT they do prevent viral replication)
** Type I IFNs: IFN-alpha and IFN-Beta
Type II IFNs: IFN-gamma
Type III IFNs: IFN- lambda
- Type I and III have very similar functions and are primarily involved in antiviral defense
- IFN-gamma is also involved in defenses against intracellular pathogens, BUT it is associated more with cellular immunity
2. Complement: proteins in serum that augment the immune system
3. Acute phase proteins
- C-reactive protein (CRP)
- Mannan binding lectin ( a type I PRR)
*** NOTE: there is always a rise in acute phase proteins just before inflammation is about to occur
4. DefensinsFirst response to infection or traumaInflammation
- chang in vascular permeability: Mast cells aid in this: note that the immune cells are inside of the blood vessel and they have to get out to reach the site of infectionDe-
Cardinal Signs:
- Redness (rubor): increased blood flow-erythema
- Warmth (calor): increased blood flow- pyrogens
- Swelling (tumor): leakage of plasma- local edema
- Pain (dolor): pressure on nerve ending, bradykinin, histamine
- loss of function
** long before any of this occurs the CRP (C-reactive protein) increases (which is an acute phase protein)- this is an indicator of inflammationDescribe the proscess of leukocyte migration in inflammatory response1. there are signals that are sent to alert phagocytes when there is an infection (recieves inflammatory stimulus)
2. WBC moves to the margin this is called Margination- the WBC is "Rolling" along bc it is in a low-affinity state with integrins
2. Expression of adhesion molecules such as the integrine and selections by chemokines
3. Pavementing: WBC sticks to the endothelium - now there is a higher affinity state for the integrin - WBC stops at a junction and does diapedesis (exits from the blood vessel into the extracellular space)
*** the margination and pavementing are due to high expression of selectins and integrin, leukocyte adhesion, and CD18/ICAM-1 ( a patient could have Luekocyte Adhesion deficiency due to lack of CD18)
** NOTE: there are some diseases where the WBC is UNABLE to squeeze through the endothelium and these individuals are more prone to infection
4. Once in the extracellular space Chemokines (ex. IL-8) drive chemotaxis of the phagocyte in a directional motion (the phagocyte moves in a straight line) to the microbe (other chemokines include: C5a, TNF-alpha, PG-E2, IL-1)Leukocyte Adhesion Deficiencyphagocytes lack (CR3) CD18 so they are unable to interact with ICAM-1- the patient is prone to infection because they are unable to do the margination and pavementing step of phagocyte mobilisation in the inflammation response
** like a police being left at the station with a call to attend to but he has no vehicle to get thereInnate Effector Functions includeHumoral Response
- acute phase proteins (ex. CRP)
- complement
Cellular Response
- phagocytes
- intra epithelial lymphocytes
- natural killer cells
** cellular responses use receptors such as Toll-like receptor, cytokine receptor, and complement receptor- which can release cytokines, phagocyte oxidase, nitric oxide, and enhace phagocytosis respectively- leading to inflammation (enhanced adaptive immunity), or the killing of the microbeComplement can be bothInnate and Adaptive
It can be activated in 3 ways:
1. Alternative Pathway
2. Clasical Pathway
3. Lectin Pathway
**** classical pathway is the only one that is adpative because it involves antibodies, the other two are innate
Some key players of Complement:
- C3a: inflammation
- C3b: opsonization and phagocytosis
- C5a: inflammation
- C6-9: lysis of microbe
*** note ALL pathways end in lysisResting Phagocytes get their energy from glycolysis- they can not kill and they can not make powerful radicals- in order to do so they have to go through induction. What are 3 enzymes that allow this to occur?1. G-6P dehydrogenase (shifts metabolism to Pentose phosphate pathway)
2. NADPH oxidase (this is critical for the phagocyte to kill)
*** clinically a NBT (nitro blue tetrazolium) test can be used to measure a phagocytes killing capacity by ROS
- an increased NBT= phagocyte can kill (strong blue)
- decreased NBT= phagocyte CANT kill (faint blue)
3. Myeloperoxidase: generates HOCL ion- clinically this is not necessary so once you have NADPH oxidase you are already a 90% affective macrophageAn absence of NADPH oxidase could lead toChronic granulomatous diseaseIntraepithelial lymphocytes (IELs) act asinnate lymphocytes
- they are mostly CD8 cells (which are cytotoxic T cells)
- they can kill infected epithelial cells spontaneouslyNatural Killer Cells (a cell of the innaate immune system) areSpecial type of T cell- CD2+/ CD3 negative
** CD2+ is on all of these cells it is an adhesion molecule
- it is 5-10% PBL; large Granular lymphocyte
** this is abnormal bc lymphocytes are usually always agranular but this one is granular
- they express CD56, but NOT TCR
- The express: KAR (killer activation receptor) which enabled NK cell to kill and KIR (killer inhibition recepto) which blocks killing of normal cells with MHC1
NK cells are activated by:
- IL-12, IFN-alpha, TNF-alpha, IL-15 etc.
They posses Fc receptors, FcgammaRIII (CD16; ADCC)
- they have inducible expression of FasL (cell cytotoxicity)
- Release perforin (makes a whole in the target)/ granzyme (cell cytotoxicity- goes in and destroys target)- these use KAR
- also it releases IFN-gamma in response to IL-12 stimulationWhat is the marker for NK cellCD56
* it is NOT found on any other cell but a NK cellA NK cell will NOT kill a cell ifa cell expresses MHC class 1 and KIR (killer inhibition receptor) are engagedA NK cell WILL kill a cell ifMHC class 1 is downregulated/lacking
- KAR (Killer Activation Receptor) is bound - leads to release of perforin and granzymes to kill the cellHow do NK cells do Adaptive Killingthrough Antibody Dependent Cellular Cytotoxicity (ADCC)
1. Virus antigen is presented on the infected cell
2. An antibody (like IgG) binds its Fab portion to the antigen
3. The antibodys Fc region binds to the FcgammaRIII (CD16) portion of the NK cell
4. This leads to NK activation-> NK expresses FasL --> release of granules (perforin/granzyme)
5. Caspase becomes activated
6. Fas and the target are destroyed
*** FasL (Fas ligand) delivers the death signal to the Fas death receptor
Apoptosis is an important part of immunity:
- kill infected cells by inducing apoptosis
- eliminate self-reactive lymphocytes during development
- get rid of effector T cells after infection is terminated
Apoptosis can be triggered through Fas
- Fas and FasL are induced during an immune response
- Binding of FasL to Fas induces apoptosis of Fas-expressing cellBinding of ___ to ___ induces cell death in fas-expressing cellsFasL to Fas
- the cell that kills expresses FasL
- the cell that is to be killed expresses Fas
ex. NK cell expresses FasL
** binding of FasL and Fas turns on the death domain which will turn on caspase-8 and lead to apoptosisIf the transcription factor NF-KBeta is inacctive what is most likely responsible for the lack of activation of this factorDysfunction of Toll-like receptorIn complement C3 and C4 are responsible forclearance of immune complexesWhat ligand do KAR (killer activating receptors) on natural killer cells recognizePAMP on microorganismsWhat ligand do KIRs (killer inhibitory receptors) on natural killer cells recognizaeMHC class I moleculesSomatically generated receptors found on B and T lymphocytes arerandomly generated during developmentFunction of the Immune Sytem- Detect potentially hazardous materials then
- eliminate or inactivate them
To preform that function, it must:
- be able to recognize these material, and distinguish them from "self"Define an antigenIn the past: An antigen is a substance that induces the formation of antibodies because it is recognized by the immune system as foreign to the body
Presently it is defined as:
- a molecule that is recognized by the immune system
- a substance that can induce an immune response, usually foreign
* NOTE: the immune response is not limited to antibody production; may be humoral or cellular, innate or adpative
* when an antigen actually produces a response it is referred to as an immunogen (sometimes an antigen is unable to produce a response)What are some properties that make a good antigen?1. Size- at least 6,000-10,000 daltons (6-10kd): anything smaller than this is a Hapten (non-antigen)
2. Complex:
- Proteins are the BEST antigens because of their complex nature
- Polysaccharides also make good antigens
- Nucleic acids and phospholipids are weak antigens
- small molecules (hormones, lipids, simple sugars) usually must be conjugated to a larger macromulecule to be antigenic
3. Foreignness: if it does not look foreign, it is not a good antigen (you want the immune system to bind non-self)
4. Solubility:
- molecules that are easily solubilized are better antigens
- insoluble molecules tend to pass through body unrecognizedAntigens that provoke an immune response are termedImmunogens
- ALL immunogens are antigens
- but, NOT all antigens are immunogens
** sooo not all antigens are able to provoke an immune responseFactors influencing immunogenicity (what factors make antigen immunogenic)?1. Dose
- very small quantities may get rapidly cleared
- very large quantities may inhibit response
** so size must be just right
2. Route:
** best route= blood stream
- entry of host for most pathogens by crossing mucosal surface (ex. GI: most are rapidly degraded and do not get much chance to interact with immune cells)
- those that enter the blood stream can remain intact and have more potential to drive immune response
** imagine if all the food you at was immunogenic? that would be really bad- this is way any antigen taken orally is usually non-immunogenic
3. Adjuvants:
- chemical substances that enhace the immune response to an antigen (augment immunogenicity)
they are thought to: (bc were not sure how they work)
- prolong the persistence of the antigen
- stimulate or modulate immune cells
- enhancing macrophage functionHaptens- small molecules that, on their own, are NOT immunogenic
- but they CAN bind antibody
- they generally only have ONE epitope
** to make a hapten immunogenic, it MUST be bound to a protein carrier molecule to form a conjugateEpitopes (AKA antigenic determinants)Portion of antigen that binds the antigen recognition molecule
* number of epitopes= valence of the antigen
** this is the part of the antigen recognized by antibody
- peptide recognized by the T cell receptorAn antigen with 4 epitopes, has a valency of4
** so 4 antibodies can bind specific for an epitopeWhat are the phases of Antigen Elimination1. inject the antigen (this is when the amount of circulating antigen is at its highest)
2. Equilibrium phase: distribution of antigen between vascular and extravascular compartments
3. Catabolic Decay phase: elimination of antigen by innate cells; processing and presentation of antigen to T cell
4. Immune Elimination phase: the formation of antigen-antibody immune complex and removal of complex ( T cells activated- no free antibody, it is bound by remaining antigen- forms immune complex)
** after this there is NO more antigen- and any antibody produced will be noticed
5. The apperance of free antibody in serum ( Detectable antigen specific antibody)
*** NOTE: antibody production starts at the end of phase 2 but there is NO free antibody during formation of immune complex in phase 3B cells jobmake antibodies
(Antibody= Immunoglobin= B cell receptor (when surface bound))
1. Resting B cell (membrane bound Ig)
2. Encounter with antigen (bacterium)
3. Stimulated B cell gives rise to antibody-secreting plasma cells which secrete antibodiesBasic structure of an antibody4 chains: 2 heavy, 2 light
Fab portion= amino terminal: increased variability to generate specific combos and it binds antigen
** Fab portion is made of both the heavy and light chains
Fc portion= constant domain
Hinge region: allows flexibilityFunctions of Antibody secretion by plasma cells1. Neutralization: antibody preventa bacterial adherence by binding the pathogen
2. Opsonization: antibody promotes phagocytosis by binding pathogen
3. Complement activation: antibody activates complement, which enhances opsonization and lyses some bacteria via the classical pathwayFc receptors allow recognition of theFc portion of antibodies
ex: the Fcgamma receptor (CD16) on NK cell binds to the Fc portion of an antibody
** this is what can result in ADCCWhat allows antibodies to bind to different epitopes?Combinatorial Diversity
- their genes exsist in segments (V, D, J segments) that give them their variety
Light chains: V and J recombinations
** you can have two types of light chains: gamma and K - any given antibody will either have K or gamma- NOT both
Heavy chains: have V, D, J recombinations
- your heavy chain will posses a Cm of C something at the end (ex. Cm= IgM- this determines the type of heavy chain)
*** Gene rearrangement is mediated by RAG-1 and RAG-2 (without these there would be no rearrangement- so cant make antibodies)
NOTE: if a heavy chain has two C's at the end (ex. Cm and Cd in the constant region- you pick the C that is closest to the variabl V D J portion - so in this case you would have IgM)
NOTE: TCR part of immunoglobin family- they also depend on RAG1 and RAG2 for its constructionCombinatorial Diversity in Antibodies is mediated byRAG1 and RAG2Junctional Diversity is mediated byTdT
- the formation of the junction between gene segments involves DNA cleavage and the addition or deletion of nucleotides to create a joint (this further enhances diversity of antibody by point mutation that can be induced)
* this random addition by the enzyme terminal deoxynuceotidyl transferase TdT, or random deletion by exonuclease, results in a further level of variability or junctional diversityDiverse specificity of antibodies is reflected in the degree of amino acid variability inthe hypervariable, HV regions (AKA the complementarity determinant region, CDR) and the framework regions, FR, within the variable-region
*** FR= framework it is variable but NOT as variable as the HV regions
** CDR determines how specific binding will be AKA hot spots
** these determine specificityProteolytic enzyme products tell us about the structure of the antibody molecule- Papain: IgG --> 2 Fab + Fc
- Pepsin: IgG --> (Fab')2 + Fc'
*** Significance of enzymatic cleavage of IgG:
- ability to cross the placenta
- Fabgamma CANNOT cross
- Fcgamma CAN cross - because the Fcgamma receptor on placental cell- allow for active crossing of IgG
- Fabm cannot cross
- Fcm cannot crossName some characteristics of the constant region of immunoglobulin (Fc)- constant sequence
- crystalizable
- carboxyl terminal
- cell binding
- complement binding
- complement activatingWhat is an isotypic difference in antibodiesThis denotes the antibody calsses (IgM, IgD, IgG, IgE, IgA)
* determined by the heavy chain
** this defines the functioon (how the antibody contributes to the immune response)What is an Idiotype difference in and antibodyHas to do with the Fab region (antigen binding site)
* determined by the variability of the domains of the heavy and light chains
*** sooo has to do with variations in variable region, particularly the hypervariable region
** this defines the specificity (which antigen it will bind)
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Different from isotype*** which deremined the class of IgIgM- FIRST antibody secreted in immune response
- Found on surface on naive B cells (IgM is also part of BCR or cell bound)
- Secreted as a pentamer (5 identical units, bound by joining "J" chain, 10 antigen binding sites)
- readily activates classical complement (more powerful in activating complement than IgG)
** if you only see IgM present= a new and current infectionIgG- SECOND "late" antibody to be secreted
- secreted in large amounts
- MOST ABUNDANT isotype in blood and lymph
- secreted as a monomer
Function:
- activate classical complement
- opsonization of pathogens (triggering phagocytosis and triggering antibody-dependent cell cytotoxicity- ADCC)
- neutralization
*** if you only note the presence of IgG- this signifies a NON-current infection, but rather an OLD infectionIgA- Mucosal Immunity-
- secreted as a monomer and as a dimer
- dimeric form contains J chain and secretory component: secretory component facilitates transport across epithelium into secretions of the mucosal system
- Most predomiant isotype produced in the GUT
Main function:
- neutralizationA secretory component is ONLY found inIgAIgE- Secreted as monomer
- binds with high affinity to Fcepsilon receptors on mast cells, eosinophils, and basophils
- efficiently triggers degranulation
- important in allergy and response to helminths (parasites)
**IgE has low levels in serumIgDexpressed on surface of naive B cells
- secreted form has NO known functionWhich two isotypes are expressed on the surface of naive B cellsIgD and IgMDescribe the Antibody Isotype tissue distribution- IgM is only in blood
- IgG is in blood, tissues, and can cross placenta
- IgA is found in the lumen of the guy, in secretions (saliva, tears, milk), on mucous membranes (respiratory and GI/GU)
- IgE is found bound in FCepsilon receptors on mast cells in tissuesThe immunoglobin isotype is determined by theH chain constant regionWhat process takes place during the lag period between antigen contact and detection of adaptive immunityInnate immune effectors are eliminating antigenIf V(D)J recombo events cannot take place due to the absence of RAG1 and RAG2 genes...B cells and T cells will be affectedAntibody-dependent cell-mediated cytotoxicity (ADCC) is a process in which antibody-coated cells are killed bycells with Fc receptors for IgEWhen do lymphocytes acquire their antigen specificitybefore they encounter antigenComplement has both innate and adaptive functions. What are theyMain function of complement is lysis of extracellular organisms
- adaptive functions are activated by antibodies
* the term complement was coined following initial observations that these serum proteins assisted, or complemented, microbial lysis mediated by antibodies
- complement is a set of serum and cell surface proteins that interact with one another and with other molecules of the immune system to generate important effectors of innate and adaptive immune responsesWhich two complement pathways are exactly identical except for their starting pointClassical and Lectin Pathway
Classical: activated by antigen-antibody complexes
Lectin: activated by plasma lectings binding to microbes
** there is also the alternative pathway (which is the first to kick in) it is activated by microbial surfaces
*** ALL 3 pathways of complement activation lead to the formation of a common terminal cell lytic complex that is inserted in cell membranes
- Alternative and lectin pathways are innate
- Classical pathway is acquired/adaptiveComplement activation (AKA complement fixation) consists of acascade of proteolytic enzymes that generate inflammatory mediators and opsonins (sequential proteolysis of complement proteins which in turn generate complexes that also posses proteolytic activity (similar to the coagulation and kinin systems)- some components of the complement system can mediate several proteolytic reactions thus ensuring a rapid amplification of the response
- some biologically active cleavage products resulting from complement activation covalently bind to microbe surfaces, antibodies bound to microbes and other antigens, as well as apoptotic bodies (macrophages must clear these dead cells)
- by products of complement activation stimulate inflammation (cytokine and complement response trigger inflammation)
- complement is inhibited by host regulatory proteins NOT normally present on microbes (this is what allows complement to act on everything but our bodies- because we have inhibitors that inhibit its function on our cells)COmplement proteins- are normal serum proteins (about 10% of serum proteins)
- there are over 30 known components (most soluble, some membrane bound)
- soluble components of complement live as zymogens (an inactive prescursor enzyme that is altered to become an active protease that celaves and thereby induces the proteolytic activity of the next complement protein in the cascade)
- they are also heat labile (sensitive to heat): can be inactivated by heat (56 degrees celsius for 30 minutes)- some diagnostic tests rely on inactivating complement to not interferes with measurementsComplement is activated bymicrobes and by antibodies bound to microbes and other antigensComplement cascades can result in- microbe lysis
- microbe and apoptotic body opsonization ("tagging") resulting in microbe or apoptotic body phagocytosis by neutrophils and macrophages
- soluble byproducts that trigger and further stimulate inflammationComplement proteins are primarily synthesized byliver (hepatocytes) [** especially when liver is stimulated by proinflammatory cytokines (especially IL-6)] BUT some complement proteins are synthesized by
- monocytes
- macrophages
- epithelial cells
- fibroblastsOpsonin vs. OpsonizationOpsonin:
- molecule that becomes attached to surface of microbe and can be recognized by surface receptors of neutrophils and macrophages and that increases the efficiency of phagocytosis of the microbe
- opsonins include: IgG antibodies, which are recognized by the Fcgamma receptor on phagocytes, and fragments of complement proteins, which are recognized by CR1 (CD35) and by leukocyte integrin Mac-1 (CD11b/CD18)
- these are basically molecule that binds a cellular surface to trigger phagocytosis
ex. antibodies, or complement components
Opsonization: process of attaching opsonins, such as IgG or complement fragments, to microbial surfaces to target the microbes for phagocytosis (so this is the process of molecule binding to a cellular surface for the purpose of triggering phagocytosis)5 functions of complement1. Opsonization
- tagging of targe so immune system knows what to kill (C3b is main one that triggers for phagocytosis)
2. Inflammation
- C3a and C5a bind mast cells and trigger release of inflammation
3. Microbial lysis:
- form a pore in the membrane- the insides leak out (bacteria swells leading to lysis)
4. B lymphocyte activation
- complement serves as a signal for B cells to make specific antibody (specificity provided by BCR)- * note BCR has CR2
5. Clearance of immune complexes
- increase accumulation of antigen from microbe. Antibodies will bind the antigenWhat is part of the B cell receptor (BCR) complex that is necessary for B cell activation?CR2 (CD21)What is present on the surface of erythrocytes, coupled with complement fragments bound to IgG, that are paramount for clearing immune complexes?Complement Receptor Type I (CR1)
* inefficient immune complex clearance (i.e. defficiency in some complement components) can lead to serious, sometimes fatal, disease manifestations:
- Systemic lupus erythematosus
- Polyarteritis nodosa
- Poststreptococcal glomerulonephritis
- Serum sickness (clinical and experimental)
- Arthus reaction (experimental)Describe the process of clearance of immune complexes as a function of complement1. Immune complexes activate complement (leads to deposition of many molecules of C3b on the immune complex)
2. These immune complexes can be bound to erythrocytes through C3b/CR1 interaction
3. In the spleen, splenic macrophages uncouple erythrocytes from immune complexes; immune complexes are phagocytosed and destroyed by splenic macrophages, and erythrocytes are recycledWhat are the 4 types of Complement ReceptorsType 1 complement receptor (CR1, CD35):
- Found on: mononuclear phagocytes, neutrophils, B and T cells, and erythrocytes
- Function in phagocytosis and clearance of immune complexes
Type 2 complement receptor (CR2, CD21):
*** involved in B cells activation
- so it is found on B lymphocytes and acts as a coreceptor for B cell activation
Type 3 complement receptor (CR3, Mac-1, CD11bCD18):
- Found in mononuclear phagocytes, neutrophils, NK cells
- Functions in phagocytosis and leukocyte adhesion to endothelium (via ICAM-1)
Type 4 complement receptor (CR4, p150, 95, CD11cCD18):
- Found on Mononuclear phagocytes, neutrophils, NK cells
- Function in phagocytes and though to function in cell adhesion
**** Types 1,3,4 are complement receptors that sit on phagocytic cells that enable cells to grab microbes with added tagging called complementC3 convertase termed as C4bC2a is the same thing asC4bC2b
- note that C3a is soluble and C3b is found on surface of pathogen
BUT
- C2a is on the surface of the microbe, and C2b is the soluble fragment (so for this exam just remember that C3 convertase whether it be C4bC2a or C4bC2b are BOTH virtually the same thing )All 3 complement pathways (Classical, Lectin, and Alternative) all converge atC3 cleavage into C3a and C3b - which lead to the activation of late stages of complement (TERMINAL PHASE OF COMPLEMENT ACTIVATION (C5-C9) which form the membrane attack complex (MAC)- culminates with a pore in the membrane that lyses the target cell
** soo all 3 pathways lead to C3 convertases and C5 convertases, with the terminal phase (membrane attack complex or MAC) being identical for all 3 pathwaysWhat is the first complement cascade to be activatedAlternative Pathway
1. C3 spontaneously cleaves "tick over"- if this takes place close to the membrane then C3b binds the membrane and Factor B comes in and binds C3b
2. Factor D (a plasma serine protease) comes in and cleaves Factor B- stabilization is done by properdin - this cleavage yields C3 convertase
*** C3 convertase is the first amplifying stage of complement- it takes more C3 and deposits more C3b and releases more C3a
- C3b: increases opsonization and increases opsonin on the surface of target
- C3a: drives more inflammation
3. C3b covalently binds to cell surface and binds to C3bBb to form C5 convertase
*** C5 convertase is the 2nd ampliflying step- increases that amount of C5 being cleaved to C5b and C5a
- C5b goes to the late stage and triggers formation of the pore that is meant to lyse the bacteria
NOTE:
- These alternative pathway amplification stages (C3 convertase and C5 convertase, also yield a great amount of soluble C3a and C5a respectively, thereby stimulating further inflammation)
- C5b initiates the terminal phase of complement activation resulting in membrane attack complex (MAC) and the creation of pores in surface that trigger cellular lysisWhich is theoretically the second complement pathway to be activated?Lectin Pathway
* this is because the lectins (Ex: Mannose-binding lectin (MBL)) that trigger this pathway are part of the so-called Acute-Phase proteins which are generated as a result of inflammation (IL-6 action in the liver)
1. MBL associates with the mannose-associated seriene proteases 1 to 3 (MASP1, MASP2, and MASP3) these are AKA mannan-binding lectin serine proteases
2. MASPs cleave plasma C4 into C4b and C4a, resulting in the deposition of C4b on cell surface and release of C4a in the fluid phase
- then plasma C2 is cleaved by MASPs to yield C2a cell surface deposition and release of C2b in fluid phase in fluid phase
3. Surface bound C4bC2a= the C3 convertase which catalyzes cleavage of C3 into C3b and C3a to yield 1) microrganism opsonization and release of inflammatory soluble C3a (in analogy to the alternative pathway, this is an amplification step of the lectin pathway) and 2) C3b binding to C4bC2a to yield C5 convertase (C4bC2aC3b)
4. C5 convertase catalizes cleavage of numerous C5 molecules into C5b and C5a
** the actions of the lectin pathway C3 convertase and C5 convertase result in the same effects as those described for the alternative pathway, namely stimulation of inflammation, opsonization for phagocytosis, and pore formation as a result of MHCThe lectin and classical pathways of complement activation are identical except for the opsonins that trigger their activation- what are the differencesLectins and folicins of the lectin pathway are like C1q (the first complement component of the classical pathway of complement activation)
- also MASPs from lectin pathway are homologous to the serine proteases C1r and C1s of the classical pathway of complement activation
* C1q is a hexamer of 6 collagen-like arms that each posses a globular head, the head being the part that binds the Fc portion of antibodiesIn the case of IgG, how many antibodies do you need to activate the classicy pathway of complement activation?Need atleast 2 Antibodies to activate in case of IgG becuase you must crosslink the Two Fc portions in order for it to work
*** on the contrary the IgM antibody and 5 Fc portions so there is only one antibody needed in the case of IgM
*** this is why IgM is much better at initiating complement than IgGWhich is the last complement pathway to be activatedThe Classical Pathway
- because antibody (immunoglobulin) production usually takes atleast a couple of days (on avg 1-2 weeks)
1. C1q cross-linking of Fc portions of antibodies bound to multivalent Ag triggers the cleavage of C1s by C1r
2. Activated C1s then cleaves C4 into C4b and C4a
- C4b covalently binds the pathogens surface
- C4a is released in the fluid phase where it mediates the inflammatory process
2. Then plasma C2 is cleaved by C1s to yield C2a cell surface deposition and association with C4b and release of C2b in fluid phase
3. Resulting C4bC2a complex = C3 convertase (like in the lectin pathway)
- catalizes cleavage of C3 into C3b and C3a to yield 1) microorganism opsinization and release of inflammatory soluble C3a (like alternative and lectin pathways- this is an amplifications tep) 2) C3b binding to C4bC2a to yield C5 convertase (C4bC2aC3b)
5. C5 convertase catalizes cleavage of numerous C5 into C5b and C5a
*** the actions of the classical pathway C3 convertase and C5 convertase result in the same effects as those described for the alternative and lectin pathways, namely stimulation of inflammation, opsonization for phagocytosis, and pore formation as result of MAC
** NOTE: C1 (C1qr2s2) is a large multimeric protein complex composed of C1q, C1r, and C1s subunites; C1q is a hexamer that binds the Fc portion of immunoglobin molecules, C1r (dimer) is a serine protease which cleaves C1s to activate it, and C1s (dimer) is the actual serine protease that cleaves C4 and C2The terminal phase of complement activation, which is common to ALL 3 activation pathways it theElaboration of the membrane attack complex or MAC
1. C5 convertase (C3bBb3b of alternative pathway or C4b2a3b of lecting and classical pathwa) results in cleavage of serum C5 into C5b and C5a
- C5a is released into fluid-phase where it mediates further inflammatory reactions
- C5b binds serum C6 to induce conformation change in C6 that allows the C5b/C6 complex to bind the membrane surface
2. Serum C7 then binds C5b to form a C5bC6C7 complex
- membrane-bound C7 is amphiphilic and penetrate the membrane
3. Serum C8 then binds C5b of the C5bC6C7 complex and stably penetrates the membrane to form an unstable pore (0.4-3.0nm in diameter)
- large numbers of C5bC6C7C8 unstable pored can result in cellular lysis, BUT the recruitment and polymerization of serum C9 creaters larger stable pores (1.0-11.0nm in internal diameter) that act as channels through which water and ions move freely
- the resulting osmotic swelling culminates in cellular rupture of lysis
4. Serum C9 molecules bound to the curface C5bC6C7C8 complex therefore polymerize to create a large stable pore in the plasma membrane to yield an active membrane attack complex (MAC)
NOTE: C9 is structurally homologous to the perforin secreted by NK cells and cytotoxic T lymphocytes, and that the pores formed by C9 are similar to the pores that result from the polymerization of perforinLeft unchecked, complement activation candamage normal host cells and unnecessarily prolong inflammation hence the complement system is normally tightly regulatedWhat is the function of C1 INHC1 INH is a serine protease inhibitor (serpin) that prevents C1r2s2 from becoming proteolytically active by binding to and inactivating the active site of serine proteases (this process also results in the dissociation of the C1r2s2 tetramer from the C1q hexamer
** NOTE that normally C1q binds to antigen-complexed antibodies, resulting in activation of C1r2s2
** C1 INH is an inhibitor of both the lectin and classical pathways of complementWhat is the function of Factor I?AKA C3b/C4b inactivator
- it is a trypsin-like serine protease that accelerates the decay of C3b and C4b; it acts by cleaving C3b to yield iC3b and C3f (membrane-bound and fluid phase), as well as C4b to yield C4c and C4dWhat is the function of Factor H?It decays Bb from C3b and is a cofactor for degradation of C3b to iC3b by the serine protease FI (it works in conjunction with Factor I)
* this dismantles the C3 convertase
** it is more for the alternative pathwayC4BP prevents the formation and accelerates the decay of the C3 convertase of what two pathwaysLectin and Classical pathways of complement activation
- it does so by cleaving C4b into C4c and C4d
** also remember that C4BP is also a cofactor for Factor I that leads to C3b and C4b inactivation (inhibits C3 convertase)What does decay acelerating factor (DAF or CD55) do?prevents the assembly of the C3 convertase of all 3 complement fixation pathways (lectin, classical, and alternative) by dissociating C4b from C2a as weel as C3b with BbWhat does protectin (CD59) do?prevents the incorporation of C9 by interfering with C8 into the membrane attack complex (MAC) thereby preventing stable pore formation of the late stage of complement fixationGenetic deficiencies in classical pathway components can includeDeficiencies in the following from the lectin and classical pathway: C1q, C1r, C4, C2
or
Deficiencies in C3 (which would affect all the pathways)
** C2 deficiency is the most common: individuals can be asymptomatic to increased susceptibility to infections
* C3 deficiency is frequent in pyogenic infections, and it is sometimes fatalDeficiencies in alternative pathway components can include:Deficiences in Factor B, D, properdin, MBL, or MASP-2
- these can lead to increased susceptibility to meningococcal (Neisseria Meningitidis) infections (more frequent, or recurrent, disease; greater dissemination, or spread in the body, leading to different type of disease)
- thin-walled organisms which tend to be more affected by complement lysis
- some Neisseria spp. strains posses polysaccharide capsules that do not activate the innate pathways of complement activation wellA deficiency in the alternative pathway component Properdin may result inincreased susceptibility to BACTERIAL infections (especially thin-walled bacteria)Hereditary Angiodema (HAE) could be caused by a deficiency inC1 INH deficiency
- increase in edema fluid
- edema in the skin and mucosa causing abdominal pain, vomiting, diarrhea, and obstruction of airways (potentially life-threatening)
** the contribution of C1 INH deficiency in HAE is really exerted through its effect on the contact system (kinin/kallikrein system); its contribution on the complement system is minor.
- the vascular leakage in HAE is mainly due to lack of plasma kallikrein and factor XII inhibition, which leads to increased bradykinin (ex. C1 INH is also an inhibitor of plasma kallikrein and factor XII; its dysfucntion (either through low serum concentration of normal C1 INH (HAE type 1) or normal concentration of defective C1 INH (HAE type II) leads to increased bradykinin, the main vasoactive effector in HAE and, therefore edemaFactor I deficiency can lead toincrease in fluid-phase C3 convertase C3bBb
- leads to serum C3 depletion
- which leads to increased susceptibility to pyogenic infections mainly, but atypical haemolitic syndrome (aHUS) is sometimes seen (secondary to lack of Factor H binding..)
* this increases infection by thin walled organisms
* this is mostly in the alternative pathway
* fluid-phase C3 convertase refers to an active C3 convertase that has NOT yet been stabilized by properdinFactor H deficiency can lead toExcess activation of the alternative pathway which leads to excessive consumption of C3
- can lead to glomerulonephritis and atypical haemolytic uremic syndrome resulting from reduced clearance of immune complexesGenetic deficiences in terminal components of complement (C5, C6, C7, C8, C9) can lead toincreased susceptibility to disseminiated meningococcal (Neisseria meningitidis) infections and Neisseria gonorrhoear infections
** again, thin-walled organisms which tend to be more affected by complement lysisParoxysmal Nocturnal Hemoglobinuria (PNH) could be due to deficiency inDAF (CD55) or Protectin (CD59) due to phosphatidylinositol glycan class A (PIGA) mutation
- this can lead to pore formation in erythrocytes
- causes fatigue, smooth muscle dystonias, venous thrombosis, abd pain, intravascular hemolysis, and hemoglobinuria
*** lack of phosphatidylinositol glycan class A (PIGA) results in lack of blood cell glycosylphosphatidylinositol-linked CD55 and CD59 proteins that protect them from the attack by the complement systemDeficiency in complement receptors could lead toLeukocyte adhesion deficiency
- deficiency in CR3 or CR4 (mutation in beta chain of CR3 and CR4; the beta chain (CD18) of CR3 & CR4 is shared by the CD11/CD18 family of integrins)
- leads to defects in leukocyte adhesion and therefore, recruitment of neutrophils (leukocyte adhesion deficiency)
- leads to recurrent pyogenic infectionsInnocent Bystander effect- Deposition and fixing of terminal components of complement (C5bC6C7C8, which can also create pores in lipid membranes..) on normal host cells can lead to the destruction of these cells-- can lead to systemic lupus erythematous, atypical hemolytic uremic syndrome, complocentric membranoglomerulopathies
* this innocent bystander effect is limited by the action of CD59, and another host complement regulator, the S proteinImmune complex-mediated disease includesSystemic vasculitis and glomerulonephritis
- deposition of immune complexes in the walls of blood vessels and the kidney glomeruli
- acute microinflammation resulting in destruction of blood vessel walls and glomeruli leading to thrombosis, ischemia, and scarringEvasion of complement by microbes is possible by- Thick cell walls preventing the function of the MAC
- Recruitment of host complement regulatory factors by microbes to avoid complement activation (factor H, DAF, and CD59)
- Production of microbial factors that mimic host complement regulatory factors (C1q-binding protein (E.coli), staphylococcal complement inhibitor, gpC-1 (herpesviruses), gp160 (T. cruzi) and others
- Microbial production of inflammation inhibitors, such as the chemokine inhibitory protein of staphylococci (CHIPS)Anything that is a product of T lymphocytes is part of theAdaptive Immune SystemWhen T cells develop in the thymus- they have to be educated and selected for. What does this?Antigen Presentation does this
- it gets rid of self reactive T-lymphocytesCD8 T lymphocytes respond to antigen presented onMHC-ICD4 T lymphocytes respond to antigen presented onMHC-IIThe process of MHC-I restricted antigen presentation selecting and activating CD8 lymphocytes and MHC-II restricted antigen presentation selecting and activating CD4 lymphocytes allows the adaptive immune system (in this case T cells) to distinguish betweenself and non-self (as well as tumor cells)
** this occurs as part of T lymphocyte development, T cell activation, as weel as effector cell activation (such as B lymphocytes and macrophages)MHC-I is found onmost somatic nucleated cells (APCs)
ex: all cells of the body, except for RBC, sperm and ovaMHC-II are found onProfessional Ag Presenting Cells (pAPCs) like:
- Dendritic Cells (**best one)
- Macrophages
- B lymphocytes (present antigens to CD4 T cells when they need help)
- Thymic stromal cells
** NOTE: pAPCs express BOTH MHC-I and MHC-II (leukocytes are indeed somatic nucleated cells)
** also antigen presentation is required during T lymphocyte development and therefore thymic stromal epithelial cells are also pAPCs, but ONLY during the process of T cell developmentSomatic nucleated cells (including pAPCs) present antigen toCD8 T lymphocytes
- leading to the elimination of INFECTED or TUMOR CELLS-
** MHC-I presentation: it exists for purpose of killing infected or transformed cellsProfessional Ag presenting cells present Ag toCD4 T lymphocytes
*This leads to REGULATION of the imune system with:
- Th cells: inflammatory
- Tfh cells: have germinal center and activating B cells
- Treg cells: make sure there is NOT too much inflammation- brings back immune system to normal
** MHC-II presentation: exists for purpose of regulating immune responseClass I MHC bind to8-10 AA long Antigenic peptides
Class I MHC has 3 domains on alpha chain (AKA heavy chain):
alpha1 & alpha 2 which make the peptide binding cleft (where the antigenic peptide binds to present TCR) and alpha 3
** the whole molecule has 4 domains- the 4th domain contributed by Beta2m
It is a heterodimer: 2 polypeptide chains: one alpha chain (variable ~6 diff. kinds- this gives specificiy)- it is associated with Beta2m (and this is same for every MHC-I)Class II MHC consist of 2 polypeptide chains which areAlpha and Beta chain (both polymorphic)
- both chains are also membrane-spanning polypeptide chains and both contain two domains: alpha1 and alpha2, as well as the Beta1 and Beta2 domains
- Once again, the complete class II MHC is a heterodimer
- Peptide binding domains are the alpha1 and beta1 domains
- Class II MHC bind short peptides of at least 13 AA and up to 21 AA in length (hence there is a greater variation in the lengths of peptides presented by MHC-II, as compared to those presented on MHC-ICD3 is a marker forT lymphocytes
* it is used to count the number of T lymphocytesDescribe the structure of TCR- Two polypeptide chains (alpha and beta) of roughly equal length
- Both chains have variable (V) and constant (C) regions
Genes:
- the alpha chains has V and J gene segments
- beta chain has V,D, J gene segments
-----
The TCR is a heterodimer composed of 2 glycosylated polypeptide chains belonging to the immunoglobulin superfamily, and there are 2 types of TCRS: alpha-beta TCRs and gamma-delta TCRS
- the alpha-beta TCR is composed of one alpha chain and one Beta chain
- whereas the gamma-delta TCR is made up of one gamma chain and one delta chain
*** the alpha-beta TCR is the type found on the majority of T lymphocytes, and it binds MHC/antigen peptide complexes (MHC-I or MHC-II)The sole function of a TCR isengaging and antigen
- but it must have a signal to have this engagment- but CANT signal because cytoplasmic tail- soo it is associated to other peptide chains (these 6 chains: 2 epsilon, 1 delta, 1 gamma, 2 zeta- make up CD3 which is a marker for T lymphocytes) so that it can do this signal transduction to the nucleus
- allow the nucleus to know that is has engaged an antigenBCRs bind antigenALONE
* they do not have MHC restricted presentation like TCRsA single MHC-I allele can only bind peptides withrelated anchor residues (ex. aromatic aa such as Tyr, Phe, and Trp are related; other examples would be Val, Leu, Ile, and Met which are all hydrophobic or Lys and Arg which are hydrophilic)
- this explains why a limited number of MHC-I molecules (max of 6 in case of humans) can present extremely high numbers of different peptieds: as long as the anchor residues are present for any given MHC allele, there can be variation in the parts separating the anchor residues
- the main known source of these peptides is the proteasome (or immunoproteasome under inflammatory conditions)There is greater variation int he length of peptides presented byMHC-II, as compared to those presented by MHC-I
- As for MHC-I, diff class II MHC alleles bind peptides with different anchor residue preferences (but these anchor residues are located more centrally as compared to MHC-I anchor residues), but a single MHC-II allele can also bind peptides with anchor residues that are related.
- this agian explains the variability of peptides that can be presented by only a limited set of MHC-II molecules
* the source of these peptides is mainly endosomal (phagocytic/endocytic vacuoles)T cells recognize antigens as peptides presented inMHC (i.e. are MHC-restricted)
* B cells directly interact with free antigen
* MHC restriction means that the TCR must interact favorably with BOTH the antigenic peptide AND the MHC molecule (i.e. the antigenic pepitide AND the alpha1 and alpha2 domains of the MHC-I molecule, or the antigenic peptide AND the alpha1 and Beta1 domains of the MHC-II molecules
** SO recognition ONLY occurs when BOTH the antigenic peptide AND the MHC molecule are a good fitExogenous Pathway of antigen presentationMHC-II-restricted Ag presentation
- these are produced in acidified endocytic vesicles like endosomes and phagolysosomes
steps include
1. Uptake of extracellular protesin intor vesicular compartments of APC (like a dendritic cell)
2. Processing of internalized proteins in endosomal/lyososomal vesicles
--
- in the mean time on the membrane of the ER there is an unstable alpha beta chain of the class II MHC- it is so unstable that it may fall apart so it is involved iwth an invariant chain (this is a place holder for the peptide- this structure goes to the golgi where it acquires sugar moieties bc it is glycoprotein
3. Is this above biosynthesis of class II MHC molecules and their transport into endosomes
- at this location there are HLA-DM proteins which allow for replacement of the place holder CLIP peptide with the antigenic peptides (this is the association of processed peptides with class II MHC molecules in vesicles)
4. then at last you have expression of peptide-MHC II complexes on the cell surface which can engage a CD4+ Helper T cellThe endogenouc MHC isMHC-I restricted Antigen Presentation (allows for detection of injuries within the cell- like viruses)
Steps include:
1. Production of proteins in the cytosol
- antigenic peptides loaded onto MHC class I molecules are mostly generated by the proteasome(proteolitc degradation of proteins), peptides produced in te cytosol must first be transported into the lumen of the ER via the transporters associated with antigen presentation TAP1 and TAP2
2. newly synthesized MHC class I molecules remain inside the ER until they are loaded with antigenic peptides- this is achieved via accessory and chaperon proteins
- Calnexin: keeps MHC class I alpha chain inactive and partially folded inside the ER
- ERp57: does proper folding of MHC class I alpha chain through isomerization of disulfide bons present on the heavy chain
- Tapasin functions like the invarient chain and/or HLA-DM chain in MHC-II (Tapaisn brides TAP1 with the MHC-II molecule) ** this occurs after the binding of Beta2-m
3. The loaded MHC class I molecule can then be transported to the cell surface, via the golgi complex and secretory vesicles, where antigen presentation occurs following the fusion of the secretory vesicles with the plasma membrane
** it can now bind with a CD8+ cytotoxic T lymphocyteDescribe the proccess of cross-presentation in MHC-I restricted Ag presentationin some cases material taken up through endocytosis "leaks" into cytosol
** this leaked material can be processed by proteasomes and enter the MHC-I-restricted Ag presentation pathway
*** so MHC-I is supposed to work on things that are intracellular- so this cross-presentation is referring to extracellular material that ends up being presented by MHC-I molecules on a cells surface, usually a pAPC
** this is one of the reasons behind graft rejection - the major rejection process is done by CD8 lymphocytesAntigen Presentation for T cell Activation requires3 signals
1. Activaton (Antigen Presentation): engagement of TCR with MHC molecule
2. Survival (Co-stimulation): via CD28 engagement with CD80/CD86 (AKA B.7.1 and B7.2)
3. Differentiation: from cytokines (which will determine which effector T lymphocyte you develop into depending on which microorgnism you are dealing with. Ex: TH1, TH2, TH17, Tfh, Treg)
NOTE: CD8 T cells require MORE co-stimulation than CD4 cells hence the CD4 help CD8 activation comes from CD4 TH1 cell help
- CD40L present on the surfacre of activated CD4 cells *TH1 engage CD40 on the surface of the pAPC and, with cytokines such as IL-2 and IFN-gamma, leads to high enough pAPC CD80/CD86 expression to activate CD8 cells into becoming CTLsDescribe what occurs in Signal 1 of the TCR1. APC presents through MHC I and MHC II (whichever it is the TCR function is exactly the same)
2. CD4/CD8 and CD3 come closer together and are phosphorylated by kinase (LCK)
3. This allows docking of ZAP-70 which also gets phosphorylated by LCK also and carries the signal down stream
4. ZAP-70 is involved in activating phospholipase C gamma 1 and PI3-kinase , and the MAP kinase pathway
** this process leads to the activation of transcription factors NFAT, NF-KBeta, and AP-1
** their main action is to bind the promoter region of IL-2 and its receptors
** NOTE: signal 1 does NOT generate enough NFAT and NFkBeta to really do much and that is why it needs signal 2 (co-stimulatory signal)
which uses CD28 to activate PIP3 which gives NFAT and NFkB (this reinforces signal 1 to ensure you get enough transcription factor on IL-2 and its receptorSignal 3 of Antigen Presentation for T cell ActivationDepends on the particular pathogen (i.e. the cytokines provided by the innate system during Ag presentation)
Th1 cells: in presence of IL-12 and IFN-gamma
Th2 cells: in presence of IL-4
Th17 cells: in presence of IL-6, IL-23, and TGF-Beta
Treg cells: in presence of IL-10, TGF-Beta or both
*** NOTE: cytokine signaling is primarily achieved through the Jak/STAT signaling pathwayWhen T cells are first out of the thymue they havelow-affinity IL-2R
** it needs both signals 1 and 2 to increase the expression of IL-2 (clonal expansion of the adaptive immune system)
- this increase in IL-2 allows for expression of IL-2Ralpha chain which forms a high-affinity IL-2R
** NOTE: you also need signals 1 and 2 to be responsice to the cytokines from signal 3Antigen presentaion of naive T cells in presence of IL-12 (from dendritic cell) and IFN-gamma (from NK cell) leads to production ofTH1 cell
- good at dealing with intracellular microorganisms
** targets macrophages to deal with intracellular microorganisms- this plays a role in autoimmunity; chronic inflammationIn order to deal with a large extracellular pathogen (worms), what cytokines will be producedIL-4, IL-5, (IL-10) and (IL-13)
** mast cells and eosinophils release this IL-4
- these will produce a TH2 cell
NOTE: aberrant TH2 activation is involved also in asthma and allergies (TH2 signals eosinophila to attack parasites (helminth) - can play a role in allergy)In order to deal with extracellular microorganisms, what cytokines will be producedIL-6 and TGF-beta (secreted by dendritic cells)
these make an inflammatory Th17 cells - which goes on to secrete IL-17 and 22
** Some types of TH17 responses are also involved in the development of autoimmune disease hence TH17 are divided into inflammatory (i.e protective) and pathologic (i.e. autoimmune) - these TH17 work via neutrophils to attack extracellular pathogens- and they may play a role in autoimmunityPeripheral tolerance and termination is dealt withTreg cells
- these are made in the presence of anti-inflammatory cytokines like TGF-beta and/or IL-10
** NOTE: TGF-beta is seen as anti-inflammatory here, BUT in other areas it can be seen as inflammatory- so which form is dictated by what cytokines it is associated withwhat type of T cell is the specialized life-long companion of the B cellTFH (follicular helper T lymphocytes) - they go into the primary follicle and build the secondary follicle or germinal center
NOTE: generation of high-affinity antibodies is done in the germinal center
** also the likelihood of the B and T cell interaction is increased by the convergence of helper T lymphocyte and B lymphocytes to the edge of the primary follicleIn peripheral tissue, such as an infection site, TH1 cells are presentedAg by macrophges (MHC-II restricted) and in return, TH1 cells provide CD40L, IFN-gamma, and TNF-alpha among others to the requesting macrophage to help it increase its microbicidal capacithy
** CD4 T lymphcyte helper (TH1) cells also help to activate CD8 cells via stimulating APCs with their CD40L to increase B7If you have an autoimmune disease due to activation of T cells. What are you going to want to target?B7
- sequestering this will turn off the T cell if you do not need itIn the case of Tumor cells what may be turned offCD8 T lymphocytes- which should normally act in their removal
** treatment would be aimed at overturning this turning off of CD8 cells to keep them on to kill tumor cellsOnce activated, the life-span of an effector T lymphocyte (ex. TH cell) isdramatically shortened (this is normal to avoid tissue damage and chronic inflammation)
UNLESS
if the cell iscontinuously being re-stimulated by antigen (antigen persists)- T cells are given survival signals and continue performing their functions, such as cytokine production ( a great clinical correlation of this is strep throat)
As long as there is Antigen there is inflammation
and as long as there is inflammation there is CD80/CD86 (B7) expression
----but if you were to start getting rid of antigen, then these co-stimulatory molecules will go down and you will go back to homeostasis---Affinity vs AvidityAffinity: how tight a molecule binds another molecule (how tight is the interaction)
vs
Avidity: how much binding there is.. (thought of in terms of valence)
- this is "How many things are grabbing" (ex: grabbing something with 5 fingers will ensure that you can lift it)What are 2 ways of shutting off a T cell if it is NOT going to die on its own?A. Cell intrinsic inhibitory signal
- Once T cell activated by APC it expresses CD28 which responds to B7, but once activated it also starts to express CTLA-4
- CTLA-4 uses the same ligand as CD28 so there is a competition between the two
- If the affinity for CTLA-4 for B7 (AKA CD80/CD86) is much greater than that of CD28- this switched off the T cell activation (signal is blocked)
* CD28 usually provides T cell activation
* if you increase the avidity of CD28 that would maintain the T cell active
* As long has you have increased inflammation, you have increased B7 this increases the chance that CD28 will bind rather than CTLA-4
* decreased inflammation, decreased B7 switch back to CTLA-4 being more likely to bind and you turn off the CD8 or CD4 cell
---
B. Blocking and removing B7 on APC
- increased CTLA-4 captures B7 becfore the activated T cell gets its CD28 engaged (this is a treatment used in many autoimmune diseases and tumors) - this reduces B7 costimulation
ex. Activated T lymphocytes also express other types of inhibitory receptors, PD-1 and PD-2, whose ligands are PD-L1 and PD-L2 respectively; PD-1/PD-L1 is particullary important in therapeutics
- engagement of PD-1 by PD-L1 leads to termination of T cell activation in a manner that is similar as that seen for CTLA-4When naive T cell binds to peptide: MHC on a cell that does not express CD80/86, the cell becomesnon-responsive to antigen (anergic) and cannot subsequently become activated; these usually eventually dies from apoptosis or become Treg cells (depending on context) - Peripheral Tolerance-
** Self reacted T cells being killed in the thymus= Central tolerance
- if they escape to the periphery and act against self antigen in absence of co-stimulation- the cell will be partially reactive or die (irregular T cell)= Peripheral Tolerance
NOTE: some T cells are let in with the ability to become autoreactive because some microorganisms express antigen that closely resembles self antigenNatural killer cells (NK) cells respond toMHC-I-like proteins or foreign proteins expressed at the surface of a cell to be eliminated
These MHC-I-like molecules (or altered-self) ligands are:
- MICA
- MICB
- (HLA-E)
** these can be induced by cellular stress to signal cytotoxiv cells that stressed cells need to be eliminated (provided that stressed cells express little or no MHC-I)
NOTE:
NK cells can also be activated with Pathogen-derived ligands:
- viral proteins (in plasma membrane)
- heparan sulfate
- proteoglycans
NOTE:
- if the NK cells inhibitory receptor is engaged- NK cell is NOT activated; no cell killing
- if the NK cells inhibitory receptor is NOT engaged- NK cell is activated; killing of infected cellWhat are 2 special cases of antigen presentation- Natural Killer Cells
- Intraepithelial T lymphocytes (IEL)Intraepithelial T lymphocytes (IEL) mostly expressCD8 on gamma:delta T cells
- these kill off infection in epithelial cells via perforin/granzyme and Fas-dependent pathways
* these are recognized via MHC-I but IEL DONT require activation by APC but they also have an activating receptor found in NK cells (IELs are like hybrid of CTLs and NK cells)- they recognize and kill altered cells in the same way
- these are activated in MALTs and the skin
- they undergo negative selection in thymus, so few self-reactive IELs leave the thymus
Type b IEL are the ones that are gamma:deltaTCRs- these DO NOT bind conventional peptide: MHC-I ligands; instead, they bind non-classical MHC-I molecules and other ligands (ex. PAMPs) --- because of this there is little potential for autoimmunityNatural Killer T lymphocytes (NKT cells)T cell receptors of these cells interact with CD1 (an MHC-I like molecule)
- CD1 is important in glycolipid antigen presentation (which are present in fungi and microbes) to NKT cells
- CD1 reacts by releasing cytokines (ex. IL-4 or IFN-gamma) or being cytotoxic
* these are important in innate control of some infections and help direct adaptive immune responses; ex: recognition of mycobacteria
NKT cells are:
- different from NK cells and T lymphocytes
- generally considered innateSuperantigen activationcross-links TCRs with MHC-II molecule in such a way that CD4+ T lymphocytes are activated independent of the presence or absence of peptide int he peptide-binding groove (Antigen)
- it does so by recruiting B7 and CD28 (which provide the signal independt of the antigen)
- results in: non-specific activation of CD4 T lymphocytes which leads to excess secretion of proinflammatory cytokines that affect vascular permeability
- sometimes up to 25% of lymphocytes are activated and this increases inflammatory cytokines like TNF-alpha which are what increase vascular leakage and can lead to shock and death
- BUT if you survive this shock or death you are left with depletion of CD4 T lymphocyte popylation leading to immunosuppression
** Typical examples of superAg are the staphylococcal and streptococcal toxic shock syndrome toxins and staphylococcal enterotoxins (SEs) but other organisms such as virsuses and fungi can produce superAg
NOTE: some superAg can also cross-link class I MHC and the TCR of CD8 T lymphocytes, with similar consequencesMHC-I restricted activation of naive CD8 T lymphocytes by pAPCs occurs insecondary lymphoid tissue
1. activated CD8 T lymphocytes become armed with CD95L (FasL) on their surface, and synthesize perforin, granzyme, and granulysin among others which accumulate in granules and are delivered to target cells (infected cells or tumor cells) to kill them by apoptosis (activated CD8 cells are referred to as cytotoxic T lymophcytes of CTLs)
2. CD8 T cells are activated in secondary lymphoid tissue but exert most of their function in the periphery where infected cells or tumor cells are present; CTLs can exert their function in secondary lymphoid tissue as well when the infected cells are found in these tissues (ex. HIV infections or lymphomas)MHC-II restricted activation of naive CD4 T lymphocytes by pAPCs occurs insecondary lymphoid tissues (just like MHC I activation of CD8)
- activated CD4 T lymphocyte can the provide help in the form of CD40L and secretion of cytokines to other leukocytes either in the secondary lymphoid tissuse (ex. 1) help pAPCs activate CD8 lymphocytes and 2) help activate B lymphocytes to induce germinal centers and antibody production
or in the periphery (ex. 3. macrophage activation for the killing of intracellular microorganisms, either phagocytosed or through macrophage infection)The Three MHC-I genes (alpha-chain) areHLA-A, HLA-B, HLA-C
* HLA stands for Human Leukocyte Antigen
** these are on ALL somatic, nucleated cells (hence erythrocytes and gametes do not normally express HLAs)The Thre MHC-II genes (one for the alpha-chain and one for the beta-chain)- HLA-DP (has an alpha and beta chain)
- HLA- DQ (has alpha and beta chain)
- HLA- DR (has alpha and beta chain)- this one encodes an extra beta chain
** these are usually restricted to pAPCs
Nomenclature examples:
- HLA-DQ*0025 stands for allele number 25 for the alpha-chain of HLA-DQ
- Similarly, HLA-DQB*0003 stands for allele number 3 for the beta-chain of HLA-DQMHC ispolygenic
* meaning it has many different MHC genes for MHC-I and MHC-II- there are many different versions or alleles (sometimes numbered in hundreds) of the same gene withint the population- (this leads to an increase of Ag peptides that can be displayed by an individual, as compared to a single MHC molecule)
- Human MHC genes are called human leukocyte Ag (HLA)- they are on every cell, but named this way bc found first on leukocytes
NOTE: MHC is located on chromosome 6MHC expression isCo-Dominant
- you inherit 3 alleles of MHC I from both paernts
- also inherit 3 alleles for MHCII each alpha and beta from both parents
* and each are equally expressed (co-dominant)
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if you inherit 3 alleles from MHCI from 1 parent and 3 diff. alleles from another parent- you will express 6 diff. MHC I molecules
If you inherit same alelles from both parents for only ONE of the genes you will express 5
**** review this****
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Number of expressed MHC types on cells:
MHC-I: minimum of 3 and maximum of 6, avg 6 given high polymorphism
MHC-II: minimum of 3 and maximum of 12 (bc 2 chains to consider- so in theory it is 12)
** use theoretical values (but note that the real avg is about 8- this is lower than expected bc 1. even though ppl are heterozygous at most loci, some people may be homozygous, and 2. some alpha:beta pairings are unstable and never get expressed on the cell surface
* combined MHC-I and MHC-II: minimum of 6 and maximum of 18 (again, in theory), avg of 14
** use theoretical values when calculating**What are the two classes of TCR1. alpha:beta TCR on alpha:beta T cells** (will mostly be looking at these)
- T cells that express alpha:beta TCRs recognize antigen in the form of peptides
- peptides MUST be presented in the context of MHC (MHC-restricted)
2. gamma:delta TCR on gamma:delta T cells
- gamma:delta T cells recognize peptide and non-peptide antigens
- recognize antigen WITHOUT MHC
- ex: IELsList the steps in Thymocyte Development1. T lymphocyte progenitor is found in the bone marrow
- this migrates to the thymus (specifically the corticomedullary junction of the thymus) where it becomes a...
2. Thymocyte
- this migrates towars the cortex and once here goes through...
3. Thymocyte proliferation
- this occurs from thymic stromal cells cytokine secretion of IL-7 and Notch 1, 1 week later there is acquisition of the adhesion molecule CD2 making the cell a...
4. Double Negative (DN) Thymocyte: meaning it expresses CD2 but niether CD4 or CD8
- this cell then migrates towars the subcapsular region in the thymus where it goes through
5. DN Thymocyte TCR gene rearrangement (rearrangement of its genes)- this is RAG-1/RAG-2 and TdT-dependent
- Successful TCR beta-chain rearrangmenet occurs as well as association with pre-T-alpha-chain and CD3, then in the subcapsular region you have..
6. DN Thymocyte pre-TCR proliferation (and at this point the expression of CD4 and CD8 begins, alone with successful TCR-alpha-chain rearrangement) the cell now becomes a
7. Double Positive (DP) Thymocyte (meaning it expresses CD4 and CD8) in the cortex
- At this point you have positive selection (ensure TCR can interact with self-MHC), Ag presentation by thymic cortical epithelial cells, and CD4/CD8 lineage commitment- MHC class preference this leads to
8. Single Positive (SP) CD4+ of CD8+ Thymocyte (in the cortex)
- At this point these move through to the medulla where they undergo Negative selection(ensure that the TCR does not respond to self antigen), Ag presentation by BM-derived DCs and macrophages, and Central Tolerance- which finally yields a
9. Mature, naive, and resting CD4+ or CD8+ T lymphocyte leave the thymus from its medulla and go on to move to the periphery
** NOTE: this cells migration in development is cortex to subcapsular zone to cortex to medullaPositive selectionA test of TCRs to ensure it can interact with self-MHC
* this occurs deep in the thymic cortex
* & the cells involved in this process are thymic cortical epithelial cells
This process leads to
- maturation of cells that can sufficiently react with the persons MHC allotypes and
- also determines if a double-positive cell becomes a CD4+ cell or CD8+ cell
- if TCR preferentially interacts with class I MHC molecule: cell commits to CD8+ lineage
- if TCR preferentially interacts with class II MHC: cells comits to CD4+ lingeage
** if the TCR fails to interact with either MHC-I or MHC-II the cell diesNegative selectionA test of TCRs to ensure that they do NOT respond to self-antigen
** mostly occurs in the medulla
** once key factor in this process is the ability of the cells to provide co-stimulation (CD80/86); thymocytes specific for self-MHC: self-peptide complexes that receive co-stimulation in the thymic medulla are signaled to die, thereby eliminating those positively selected thymocytes that are self-specific and could potentially lead to autoimmune disease
** Negative selection is the main driving force behind the development of central tolerance, i.e. the process by which one's immune system tolerates one antigens by eliminating most self-reactive T lymphocytes in the thymusPeripheral toleranceeliminating or rendering T lymphocytes unresponsive to "ubiquitous" antigen once they have left the thymus and reached the peripheryT or F: Mature, naive, resting T lymphocytes are longer-lived than B cells and, in the absence of antigen stimulation, may live for yearsTRUE!
NOTE: in the presence of antigen, they may become activated and release cytokines that mediate effector functions (these cells have a dramatically shorten lifespan-- days to weeks), or become memory cells responsible for long-term immunity (with a lifespan of months to years)Once leaving the periphery, CD4 T cells differentiate from a TH0 cell (mature, naive, resting T lymphocyte intoEffector cells (after re-circulation between secondary lymphoid tissues and if colicited by antigen presentation, activation, proliferation, and differentiation.... they can become:)
- Th1 (if exposed to IL-12 and IFN-gamma)
- Th2 (if exposed to IL-4, with or without combos of IL-13, IL-5, and IL-10)
- Th17 (if exposed to IL-6, IL-23, and TGF-Beta)
- Tfh (if exposed to IL-21, IL-12, IL-23, and TGF-beta)
- Treg (if exposed to TGF-beta and/or IL-10)
** these can then now in the secondary lymphoid tissue and in the site of infection either carry out their
- effector functions in which case they will be short-lived and die quickly after performing their function
or
- become memory cells (long-lived) which become reactiveate upon Ag presentation
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On other hand antigen presenation to a CD8 cell in secondary lymphoid tissue leads to CTL differention- these can also become memory cells (long-lived) which are reactivated upon Ag presentationWhat proteins are needed by CD4 T cells to preform their functions- Cytokines (ex. IFN-gamma, IL-4, IL-17, IL-21 etc.)
and surface molecules like:
- CD40 ligan and CD40L and Fas ligand or FasLWhat proteins are needed by CD8 T cells to preform their functions- Cytokines (ex. IFN-gamma)
- Cytotoxins (ex. perforin, granulysin, granzyme etc.)
- Surface molecules (ex. CD95L or FasL)Antigen presentation for the purpose of T lymphocyte development (Positive and Negative selection) occurs in theThymus (a primary lymphoid organ)Antigen presentation for the purpose of T lymphocyte acitvation (response to infection) occurs in theLymph nodes, spleen (secondary lymphoid organs)
** this requires co-stimulatory signals (CD80/CD86)Antigen presentation for the purpose of effector responses (B lymphocyte help, macrophage activation, etc.) as well as Antigen presentation for the purpose of reactivation of memory T lymphocytes occurs at theSite of infection and Seconday follicles (in the affected tissue)In the absence of MHC-IIthere is no possible selection for CD4 cellsIn the absence of CD3there is no signal or signaling cluster on the TCR (there will be a lack in the number of lymphocytes including BOTH CD4 and CD8)In the absence of RAG1/RAG2 (recombinationg-activating genes 1 & 2) there will be a lack ofTotal number of lymphocytes both CD4 and CD8
as well as B lymphocytes, Monocytes, and NK cells
** without this cells are unable to undergo rearrangementEffector T cellschange gene expression profiles and thereby gain the capacity to express proteins they will need to perform their effector functions
- CD4 T cells (T helper cells (inflammation) or T regulatory cells (shut down inflammation) these secrete cytokines (IL-4 & IFN-gamma) and express surface molecules (ex. CD40L)
- CD8 T cells (Cytotoxic T lymphocytes): secrete cytokines (IFN-gamma), express surface molecules (FasL) and release cytotoxins- proteins that are used to kille infected cells (pore formation by perforin)Th1 cells are presented Ag by macrophages (MHC-II restricted), and in return these Th1 cells provideCD40L, IFN-gamma, and TNF-alpha among other things to the requesting macrophage to help it increase it microbicidal capcity ( aids in killing intracellular pathogens)
** remember that a macrophage can secrete IL-12 which affects NK cell to release IFN-gamma which can increase the killing capacity of a macrophage
Macrophage increases its killing capacity by:
- production of ROS, NO, and increased lysosomal enzymes: leads to killing of microbes in phagolysosomes (effector function of macrophages)
- secretion of cytokines (TNF, IL-1, IL-12) and chemokines: TNF, IL-1 do leukocyte recruitment (inflammation) and IL-12 does TH1 differentiationa and IFN-gamma production
- increased expression of B7 costimulations, MHC molecules- increased T cell activation (amplification of T cell responseTarget cells of cytotoxic T cells include- infected cells
- tumor cellsTh2 migrate to the tissues where they can- induce eosinophil production (bone marrow) and activation in the affected tissues-- this is IL-5 dependent
- mucus-production by intesetinal goblet cells and intestinal smooth muscle contraction (peristalsis) to expell dying or dead worms--- IL4 and IL-13 dependent
some Th2 cells can also
- remain in secondary lymphoid tissue to further specialize into Tfh cells after migrating towards C cell-rich areas; once back in the primary follicl, Tfh cells induce germinal center (secondary follicle) formation and maintenance, and trigger IgE isotype-switching (mainly) and affinity maturation in B lymphocytes for the purpose of eosinophil and mast cell sensitization (binding of IgE to mast cell and eosinophil FcepsilonR)-- having more than one FcepsilonR stimulated at once which is possible for large Ag such as a worm- triggers degranulation on the part of the eosinophil to release molecules (ex. Major basic protein) that damages the worms surface
- Th2 in some circumstances can also trigger alternative macrophage activation; which serves to repair damaged tissues through release of polyamines and proline, which induce proliferation and collagen production, respectivelyTh17 cells migrate to the tissues where they releaseIL-17 and IL-22 (to get rid of extracellular bacteria and fungi)
- In the BM: IL-17 triggers BM cells to secrete IL-6, G-CSF, and GM-CSF to increase monocyte and neutrophil (especially) production- this explains the neutrophilia associated in bacterial infections
- In epithelia: IL-17 and IL-22 stimulate the production of more proinflammatory cytokines (IL-1, IL-6, and TNF-alpha) as well as chemokine (CXCL8 and CXCL2) to recruit newly produced neutrophils to the infection site, and the production of antimicrobial peptides such as defensins; IL-22 also contributes to greater barrier integrite of epitheliaTreg cells expressanti-inflammatory cytokines (IL-10 and TGF-beta) to promote tolerance and prevent inflammation, as well as CTLA-4 to inactive Th cells and terminate adaptive immune responses
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NOTE: Treg cells originate from two locations
- in the thymus: some self-reactive thymocytes that escapre negative selection, but become Treg cells prior to exiting the thymus
- or in the periphery: Ag presentation (MHC-II-restricted) in the presence of TGF-beta
*** note that Treg cells express CD25 and CTLA-4 on their surfaceWhat are the functions of Treg cells- promote self-tolerance
- tolerance to innocuous Ag
- prevent T cell responses
- terminate T cell responses
- inhibit other leukocyte functions
Tools used to do this include:
- TGF-beta
- IL-10
- CTLA-4
- PD-1
- CD25Engagement of PD-L1 by PD-L1+ cells inducesT cells apoptosis, anergy, functional exhaustion, or IL-10 production
** some drugs target this as well as the expression of CTLA-4
- used to treat metastatic melanoma and lung cancerMemory T lymphocytes is produced bylong-lived memory B cells and memory T cells
- these are generated during the primary immune response against the pathogen from a subset of effector cells
- after primary adaptive immune response, pathogen-specific memory cells outnumber their naive counterparts by several orders of magnitude
- memory cells have capacity to respond to specific antigen faster and better than naive cells
*** memory CD8 T lymphocyte development relies on CD4 T lymphocyte help and IL-2 stimulation since CD8 T lympphocyts that DO NOT express CD40 cannot become memory T cells where as those that express CD40 canImmunosenescenceThis has to do with thymic involution (thymus is fully developed before birth then begins to degenerate steadily throughout life one year after birth and is replaced by fat)
** this reduced production of new T lymphocytes DOES NOT impair T cell immunity (neither does a thymectomy in adults) - this is because by adulthood, individuals posses memory T lymphocytes to the most common potentially life-threatening pathogens
- soo as one ages theire Memory T cells increase where has their Naive T cells decrease in number
** note memory T cells also decrease wayyyyy later in age- and immunity wanes with time (this is not of importance in this course rlly)Adaptive immune reactions for most tissues occurs in thelymph nodes
- for blood infections, primary site of adaptive immune response is the spleen
- for mucosal infections, MALTS are where adaptic immune reactions are primarily heldB cells play a critical role in adaptive immune response. What are the main features that allow it to do this?1. They recognize and respond to antigen
2. Secrete antibodies
3. Present antigen to T cellsBCR is classified as an immunoglobulin. What two immunoglobulins can it beIgM and IgD
** remember as the B cell develops it must engage RAG1/ RAG2 to mediate gene rearrangements (this allows for adpative diversity)Omenn Syndromemutations of RAG1 and/or RAG2 result in severe combined immune deficiency
- this results in a complete lack of circulating T and B cells due to an early block in lymphoid development
- as well as a lack in antibodiesDescribe the process of B cell development1. Stem cell in the bone marrow
- B-cell rearrangments of the heavy chain (VDJ rearrangement in the next 2 steps-
2. Early pro-b cell
3. Late pro-b cells
-B-cell rearrangement of light chain V-J in next two steps--
4. Large pre-B cell
5. Small pre-B cell
-- At theend of pre-B cell you have heavy and light chain- you have IgM--
6. Immature B cells
7. Mature B cell ( also has IgD along with IgM so- whole process must be repeated again for IgD)
** NOTE: a cell will be B cell when it begins to express certain markers along with the BCR these markers include
- CD19 (one of the early markers on a B cell)
- CD21
- CD20In the stage of pro-B cell to pre-B cell- if a functional heavy chain is expressed after Pro-B cell stage
- it will complex with surrogate light chain to form a (pre-B receptor)
- the surrogate light chain has VpreB and gamma5
** surrogate light chain is needed bc the light chain is NOT yet arranged- this is present before IgM is expressed
** if function, then you have progression to pre- B cellB cell development goes through certain checkpoints to ensure that the cell meets certain criteria. Can you recall some of these?1. Are heavy chains rearranged after pro-B cell stage? if no then apoptosis, if yes go on to pre-B-cell receptor
2. Are light chains rearranged properly? if yes ges on to become BCR, if not then apoptosis
3. Is IgM being expressed?The elimination of self-reactive clones (Tolerance Induction) of B cells involvesThis is the process of Negative Selection (Tolerance Induction):
- heavy and light chain rearrangements are random this means you may have some self-reactive BCRs are often generated
- These self-reactive BCRs (recognize ubiquitous self-antigen) are deleted or functionally inactivated
NOTE:
Unlike T cells who die right away if they are self-reactive, B cells have the ability to undergo "Receptor Editing":
- Immature B cells with self-reactive BCRs can attempt to rearrange light chain
- Some B cells exhaust their attempts to make a BCR that is NOT self-reactive (i.e. they are still self-reactive) and get signaled to die by apoptosis (clonal deletion)
- if the new receptor is no longer, self-reactive, the immature B cell migrates to the periphery and maturesWhat is the second set of induction tolerance that B cells undergo upon exiting the bone marrowwhen self-reactive B cell recognized self-antigen in periphery
- cell dies by apoptosis or the cell becomes anergic (incapable of future activation)
NOTE: not all self-antigens are expressed in the bone marrowDo immature B cells exite the bone marrow?yes! they receive signals for further maturation outside of the bone marrow
- they circulate between the blood, secondary lymphoid tissues and lymph
- in secondary lymphoid tissue, immature B cells receive singals (in form of cytokines) to survive and mature
- exit secondary lymphoid tissue (via efferent lymph) and circulate again
- exit secondary tissue as a mature B cellWhat does a mature B cell expressA mature B cell expresses both IgM and IgD
- they are considered "naive" or a "virgin" until it encounters its specific antigen
And these Naive, mature B cells recognize antigen through BCR (surface IgM or IgD)
- binding to antigen causes clustering, or cross-linking of BCR
- this cross-linking results in generation of signals sent through BCR complex
- the signals lead to changes of gene expressionWhat molcules are required in B cell signalingIgalpha and IgBeta are required for the signaling of a BCR
** remember CD3 was required for the signaling of a TCRWhat makes up the B cell receptor complex- BCR (antibody molecule) that is surface bound
It complexes with:
- Igalpha and IgBeta which mediate intracellular signaling
- CD19: is the signaling chain of the complex (along with Igalpha and Igbeta)
- CD20
- CD21 (AKA CR2- Complement Receptor 2) which recognizes C3d fragments deposited on pathogens- this recognition augments B cell activation
- CD81: forms signaling complex with CD19, as well as with other surface molecules
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NOTE:
- CD21 was an important binding site for the Epstein Barr virus
- CR1 was found on RBCs and other cells- necessary for immune complex clearance from circulationActivated B cells undergo differentiation intoeither Plasma cells which make antibodies or Memory cells that are prepared for later exposure
Plasma Cells:
- terminally differentiated antibody synthesizing and secreting machines
- IgM is NO longer surface-bound but secreted
No longer can respond to antigen
- lose surface IgM (BCR)
- Stop MHC class II expression
- express CD27
Memory Cells:
- survive for long periods
- allow for more rapid and robust secondary antibody response
- express CD27first antibodyIgM (low affinity and short half life- this is why it needs to switch from IgM to IgD= Somatic Hypermutation)Late antibodyIgD (higher affinity than IgM)What occurs post- activation of the B cellsActivated B cells undergo proliferation and clonal expansion (make lots of copies of themselves)
and
Activated B cells undergo specialized method of improving antibody molecules such as:
- somatic hypermutation (IgM --> IgD) - driven by AID
- affinity maturation (IgD has higher affinity)- increasing the number of hot spots available making the antibody molecule more AVID, also increasing the number of CDRs (After 2 weeks after primary immunization you have IgM/IgG- IgG has high affinity and high half life)
- isotype (class) switch: this process involves looping out fragments in order to switch isotype class (remember you go with the C that is closest to VDJ when deciding isotype)- in this process the Fab region stays the same- you are just switching class.The process of somatic hypermutation and isotype switching are mediated by what enzymeActivation-induced cytidine deaminase (AID)
- the synthesis of this enzyme is controlled by IL-4 and CD-40 activation signals
** remember CD40 and CD40L are what interact
** these above conditions are needed for hypermutation to occur
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AID functions in activation induced deamination of cytosine to uracil which leads to hypermutation- these mutations result in changes of the affinity of the antibody
I.e.
- These base changes lead to altered binding affinities
- those B cells with improved affinity will be clonally selected and will proliferate
** if affinity had become lower the cells would be deleted
** if the affinity has increased you could make a high affinity antibodyActivated B cells need help. What forms of help do they need?1. B cells require T cells for them to make that switch (soo T cells help B cells to make antibody)
2. B cell activation also requires 3 signals:
- B cell presents peptide to T cell
- CD40-CD40L
- Cytokines binding to cytokine receptors
** T cells also had 3 signals with APCs-The expression of IgM is inhibited byIL-4, IFN-gamma, and TGF-betaThe expression of IgG3 is induced byIFN-gamma
and Inhibited by: IL-4 and TGF-BetaIgG1 expression is induced byIL-4
inhibited by IFN-gammaExpression of IgG2b is induced byIgG2bExpresssion of IgG2a is induced byIFN-gamma
Inhibited by IL-4IgE expression is induced byIL-4 and inhibited by IFN-gammaIL-5 augments the production ofIgA
- TGF-beta induces the production of IgAThymus-independent (TI) antigensare some bacterial antigens that can stimulate naive B cells in the absence of T cell help
ex: polysaccharides and lipopolysaccharides
Signal #2 comes from antigen itself
- without T cell help, antibody repertoire agianst TI antigen is limited: there is NO class switching and NO affinity maturation
NOTE: signal #2 (CD40-CD40L) is necessary for B cell activation by both T-dependent and T-independent antigensWhat is involved in the humoral immune response to T- INDEPENDENT antigenIgM productionB cells with the longest life span are thememory cellsWhy is B cell isotype switching important for an effective immune responseTo produce antibodies that can perform different functionsWhich immunoglobulin region/domain determines the affinity, specificity and idiotype of the moleculethe light and heavy chain hypervariable domainsWhat property is exhibited by the fact that each B cell productively rearranges a single H and L chain alleleAllelic exclusionThe difference between what we should be doing and what we are presently doingQuality Gap
- it is often defined by "best practices" based on clinical guidelines that are "evidence based"; that is, based upon aggregated research that has been systematically reviewed for quality and reliabilityIf a patient is looking up their own treatment online without the help of a physician this is referred to as aSelf-care system
- not involving a physician or alternative care provider or any structured system of health care provision
The patient plus whatever resources he or she uses that are not part of the health care system like:
- advice from family and friends
- patients own research
- prior experience
- assumptions, beliefs (also religious) etc.If a large academic center involves many divisions, specialties, and support services, linking microsystems and mesosystems to care for patients in a large geographic community it is referred to as aMacrosystemA small group ambulatory care clinic with multiple services such as local small lab and xray would be referred to as aMicrosystem
- a small group of people who work together on a regular basis to provide care to a discrete subpopulation of patients (ex. private physician office)
includes:
- small group of doctors, nurses, others
- some administrative support
- some information technology
- a small population of patients
** interdependent for a common aim, purposeIf only the patient and the physician are invovled in a medical care scenario it is referred to as aPatient-provider system
- individual caregiver and patietn system-A cardiac care program which consists of multiple services aimed at the treatment of patients with cardiac issues is reffered to as aMesosystem
- multiple microsystems linked together to care for patients with a specific type of problem
- linked microsystems working together for management of specific type of problem/problems
ex: cardiac care organization
- CCU and cardiac step-down units (inpatient): nursing, clerical, cardiologist
- cardiac catheterization lab
- cardiac rehabilitation (outpatient)
ex. Emergency department
- nursing, medical staff, laboratory & radiology, clerical, social services
ex. Neonatal ICU care (family, physicians, nurses, respiratory therapy, biomedical technology, admissions, discharge planners, laboratory)A focused aim statement should include achange, a direction and quantitiy of change, a time frame for the project, and some indication of relevance or importance of the projectName some steps in improvement process- creating a focused aim statement
- process modeling
- brainstorming a list of possible changes
- identifying mesures
- performing PDSA cyclesQuality improvementinvolves everyone and affects everyoneHow do both culture and context influence health care systemsculture= patterns of learned group-related perception
& contextDescribe a model for improvementAim: What are we trying to accomplish?
Measures: How will we know that a change is an improvement?
Change: What change can we make that will result in improvement?In process modeling you are looking forcontributing factors and root causesIn brainstorming a list of possible changes?- brings people together to get diverse viewpoints
- everything is up for discussion- no ones ideas are maligned
- uses a discovery method to establish ideas for change
- creates a list of possible changes after possible problems are identified with process modelingWhat does PDSA stand forP: background and aim
D: intervene/do
S: measure/study
A: change and next steps/act
** the PDSA cycle is a model for improvement similar to a treatment plan for a patient- simple to complex with as many iterations as warrantedThe science of how chemicals interact with living systemsPharmacologyA chemical compound used to achieve some type of clinical goalA drug- it can be:
- inorganic compounds (ex. metals)
- small or large organic molecules (comprised of C,H,O with minor additions of other elements)
- bio-macromolecules (recombinant proteins; antibodies; polysaccharids; nucleic acids; etc.- also mostly organic molecules; some very largeWe will be tested on drugs by theirgeneric name
- offical name of a drug given to it after approval by the Food and Drug Administration (FDA)
ex. IbuprofenPharmokinetics (PK)What the body does to the drug
- addresses the way the body interacts with a drug from absorption through excretion-
primary 4 components are: absorption, distribution, metabolism, excretion
** knowledge of this is essential for creating a drug delivery regimen that will maintain the drug at the active site at concentrations within the therapeutic rangePharmacodynamics (PD)what the drug does to the body
- studies the effects, actions, and mechanisms of drugs in the body
- drugs can either target self or non-selfToxicologyscience of adverse effects of chemicals on the body
- the intent is to adminster drugs to achieve a therapeutic effect with the least possible toxicity
* all drugs have some level of adverse side effects - these can variety between patients and situations in terms of their frequency of occurence and/or in their severity
- just beacuse a drug has the potential to cause a particular adverse effect does not mean that it will cause that effect in all patients utilizing that particular agentPharmacogenomicshow genetic differences may affect the absorption, metabolism or response to drugs
- gene variants can play a huge role in efficacy and safety of drug administration to individuals
ex. cyp2D6 (cytochrome P450 2D6) has many different noraml variants in individuals- thus a sig. number of patients may either metabolize these drugs more slowly or much more quickly than expected. The result would be either an accumulation of a toxic amount of the drug, or failure to achieve a therapeutically-useful blood levelThe route of administration is known to affect absorption of the drug. Describe two modes of administrationSystemic: drug is transported throughout body by general circulation, thus reaching all (or most) body compartments
- enteral administration (oral)- via GI
- parenteral administration (subcutaneous, intramuscular, intravenous, transdermal)- avoiding the GI (includes buccal and sublingual)
NOTE: difference between "transdermal" and "topical": when drugs are formulated to be administered to the skin for systemic effects, its referred to as "transdermal"
- there are factors affecting absorption from various routes including polarity (water vs lipid solubility), molecular size, site of metabolism, and other parametes
- the rate at which drugs will be absorbed from these various routs is directly proportional to blood flow at site of absorption
Local: deliver drug primarily to therapeautic target site (but some drug will almost always end up in the circulation)
- topical on skiin, eye, nose
- rectal or vaginal (which can also be a route for systemic circulation)The fraction of administered drug that reaches the general circulation in biologically-active formBioavailability
- will be unique to each route of administration
** the IV bioavailability of ALL drugs is 100%paitent compliance when taking drugs is usually much better fororal medicineFirst-pass effectabsorbed drug goes immediately to the liver where it may be metabolized before reaching the rest of the body and its target
- this refers to the fact that ALL orally administered drugs have to pass through some aspect of the GI tract AND the liver (any or all of these locations may inactivate some fraction of the administered dose before it has a chance to reach the target location)
** this greatly affects the drug bioavailability of orally administered drugsBody compartments where the drug becomes located and/or concentrated as it moves through systemic circulationDrug distribution
(ex. a drug concentrated in adipose tissue)Apparent volume of fluid required to contain the total amount of drug in the body at the concentration measured in the plasmaVolume of distribution
- more lipophilic drugs tend to have a higher apparent volume of distribution at steady-state (because they become accumulated in various organs)
- more ionized or serum-protein bound drugs have a lower apparent volume of distribution (because protein binding and ionization both tend to keep drugs from crossing cell membranes to get out of the blood)Metabolism may- involve biotransformation (conversion to a different chemical substance- a "metabolite")
- result in conjugation of the drug with other molecules changing their chemical properties
with the result of
- inactivating the drug (which is most common)Major enzymes of drug metabolism areCytochrome P450 (cyp) enzymes (referred to as a "microsomal enzyme" )
and UDP-glucuronosyltransferaseMost important route for drug eliminationRenal excretion
- drugs or their metabolites are passed out of the body in the urine
** in renal failure the excretion of many drugs is greatly reduced and this must be taken into consideration for prescribing and/or dosing decisionsClearancethe RATE of removal of the drug from the body relative to concentration of drug in the blood (it is NOT the total amount of drug removed per time, because clearnace is dependent upon concentration)
- is expressed as the volume of blood from which the durg is removed per unit of time (ex. ml/min)
types:
- hepatic clearance
- renal clearance
- total clearance- sum of both the above ratest1/2Half-life: the time required for half of the drug in the body to be removed
- after 1 half-life: 50% of the original amount of drug in blood remains
- 2 half-lifes: 25% of the original amount
- 3 half-lives: 12.5%
- 4 half-lives: 6.25%Mechanism of actionthe action of the drug at its molecular target while pharmacological effect refers to the observable consequences of the actions of the drug
- so mechanism of action is basically the biochem behind what drug is doing in body
ex. enhaces sodium-channel inactivation or binds cell wall AAs inhibiting peptidoglycan syntehsis
- pharamcological effects would be the actual outcome a patient can see with taking the medication (ex. recuded seizures, killing off of the bacterial infection)when a drug interacts with a biological receptor and activates that receptor to carry out its biological activity it is reffere to as anagonistA drug which, when bound to its receptor (or target) fails completely to produce any activation of that receptor AND blocks the effect of an agonistAntagonist
- Competitive: compete with agonist for the agonist binding site, increased agonist concentration can overcome competitive antagonists
- Non-competive: either bind to site on the receptor that is separate from agonist binding site and allosterically reduce the effect of the agonists or they bind irreversibly and reduce the effect of agonist; when these bind the agonist concentration does NOT alter the effect of this type of antagonistHow tightly a drug binds to its receptorAffinity
- potency of a drug is directly related to its affinity for the receptor producing the pharmacological effectAbility to discriminate between different types of receptorsSelectivity
- related to the affinity in that the drug will be relatively selective for receptors for which it has the highest affinity
* you may be able to selectively block physiological actions by: receptor selectivity (specificity) and dose (affinity)-- note that these are not completely independentThe amount of drug required to produce a specified effectPotency
- this is directly related to affinity
- the higher the affinity, the greater the potencythe largest effect that can be achieved with a particular drug, regardless of doseEfficacyTherapeutic effectDesired pharmacological outcome
- could be cure: like in the case of antibiotics or cancer chemotherapy
or
- could be alteration of physiological functions and/or alleviation of symptoms: like most other durgsContraindicationcondition or situation that makes the use of a particular drug inadvisable
- Absolute: use in certain patients is absolutely inadvisable
- Relative: inadvisable but not completely ruled out if risks are outweighed by the benefitsPrecautionuse of a particular drug in specific patients should be done with great care in certain situations
ex. Truck driver should be aware that a drug may make him sleepyhighest medical warning from FDAblack box warning
- serious or life-threatening risksPregnancy Category Xmeans it is absolutely contraindicated in pregnant females
- fetal abnormalities or human fetal risk
- risks in pregnant women clearly outweigh the potential benefits
(includes drugs like warfarin, metotrexate, and statins)
NOTE:
- Pregnancy category A is the most safe then you have B, C, D and X which is the worsePrototype drugmember of a drug class (drugs of the same general chemical category and same general mechanism of action) that most others are compared to
- usually but not always it is the first drug developed in a class or the one first used clinically
- it is the drug for which there is a lot of clinical experience
- often no longer the best or most commonly used (but features of new drug are compared to prototype to show their advantages)Antihistamine drugs areH1 receptor antagonistsFirst generation H1 blockers includeDiphenhydramineSecond generation H1 blockers include- Cetirizine
- Fexofenadine
- LoratadineThere is a wide distribution of H1 and H2 receptors in the periphery and the CNS; what are the different functions of histamine in these- histamine can exert local or widespread effects depending on where it is released and how much is released
- histamine contracts many smooth muscles (ex. bronchi and gut)
- histamine relaxes some smooth muscles (ex. those in small blood vessels)
- bronchoconstriction and contraction of the gut are mediated by H1 receptors. In the CNS, H1 activation inhibits appetite and increases wakefulnessOne may be able to selectively block physiological actions by- receptor selectivity (specificity)
- dose (affinity)
** note that these are not completely independentIn allergic reactions, Histamine H1 receptors are DIRECTLY involved in- pruritis (itching)
- mucosal edema ("stuffiness")
- sneezing
** in addition, H1 receptors cause release of ACH that interacts with muscarinic receptors to cause mucus secretion (so, histamine H1 receptors INDIRECTLY cause mucus secretion)
in the skin: urticaria (rashes) exhibit vasodilation, vascular permeability (swelling) and pruritis, all of which are mediated by H1 receptors
- in the airways H1 receptor activation causes bronchospasm and edema, which are components of asthma
NOTE: elevated plasma and tissue levels are found in allergic responses in the nose, skin, and airwaysThe prototype drug for the first generation H1 antagonistsDiphenhydramine
Mechanism of action: competitive antagonist at histamine H1 receptors
- it is also a competitive antagonist at muscarinic cholinergic receptors (this means it is not completely selective for H1 receptors)
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Diphenhydramine
- can be administered via multiple routes: oral, IM, IV, topical
- widely distributed in the body, including the CNS (except when used topically)
- nearly 100% is metabolized in the liver by cyps: more rapidly in children than adults
- potential for clinically-relevant drug interactions and/or effects of decreased liver function (appears to inhibit CYP2D6)Diphenhydramine- reduce symptoms of nasal and dermatological allergies caused by histamine release
- sedation (drowsiness) via antagonism of CNS muscarinic receptors
- inhibition of nausea, vomiting, and vertigo via antagonism of histaminergic and cholinergic signals from vestibular system
- anti-parkinsonism effects due to via antagonism of CNA muscarinic receptors
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Systemic administration allows for treatment of: allergic reactions, insomnia (short-term therapy only) and motion sickness
Topical administration allows for treatment of: relied of pain and itching associated with bites, poison ivy, poison oak, and posion sumac and other topical allergens
*** Found in benadryl, tylenol, dramamineAdverse side effects of DiphenhydramineSystemic adminisitration
- sedation (additive with alcohol)
- thickening of bronchial secretions
- less freq. dry mouth (xerostomia), blurred vision, hypotension, tachycardia, urinary retention
Topical administration:
- uncommon: photosensitiviy, rash, hives (urticaria)
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Precautions when taking this drug (no real contraindications)
Systemic:
- In people with asthma due to thickening of bronchiole secretions
-due to possible muscarinic effects
- not recommended for daytime use in children
- pregnancy (crosses placenta)
- lactation (enters breast milk)
Topical administration:
- neonates, premature infants, breast-feeding, young childrenCompared to prototype H1 antagonists (Diphenhydramine), the second generation antagonists (Cetirizine, Fexofenadine, Loratidine) arenotably less sedative and have greatly reduced "off-target" effects
- they do not effectively enter the CNS (thus less sedative)
- more selective for H1 receptors (thus, less other off-target effects; ex: little or no muscarinic effects)
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Pharmacological effects: reduction in symptoms of nasal allergies and allergic dermatosis caused by histamine release
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Pharmacokinetic properties of the group
- oral administration ONLY
- widespread distribution EXCEPT for CNS (in contrast to first generation H1 antagonists)What are the specific pharmacokinetics to each Second Generation H1 antagonist?Cetirizine:
- High bioavailability (~70%)
- No p450 metabolism; minor hepatic glucuronidation and oxidation
- 70-85% excreted in urine, remainder in feces
Fexofenadine:
- shouldnt be taken with fruit juices which may inhibit absorption
- is a CYP3A4 substrate, but only ~5% is metabolized
- most is excreted unchanged in feces; about 5% in urine
Loratadine:
- extensively metabolized via CYP2D6 and 3A4 to an active metabolite
- excreted about equallly in urine and feces
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All 3 of these Second Generation H1 Antagonists are
therapeutically used for:
- relief of allergic symptoms due to seasonal allergies
- pervention and relief of urticaria (hives)- but oral administration, not topical
Possible adverse effects:
- nausea and GI symptoms
- drowsiness
Precautions:
- cross the placenta; fexofenadine has been shown to be teratogenic in animals (category C)
- cetirizine and loratadine are category BThe only antihistamine on the drug list that is administered topicallyDiphenhydramineWhat are the phenotypes and genotypes of the ABO blood groupsPhenotypes: A, B, AB, O
Genotypes: AA/AO (for Type A), BB/BO (for Type B), AB (for Type AB), and OO (for Type O)
- alleles A and B are codominant (presence of both alleles at the same time)
- allele O is recessive
Definitions: antibody is produced by the immune system; antigen is whatever the antibody will bind
therefore A and B are antigensAntigens (mostly) are found on thesurface of cells, while antibodies are in solution
* antigen is therefore associated with RBC (and WBC) fraction while antibodies are in plasma/serum fractions
NOTE: antigens are present on ALL cells, not just limited to RBC (ABO blood type therefore needs to be checked before any transplantation)Describe the schematic of ABO production1. The cell with a precursor with alot of carbohydrate receives a fucose via fucose transferase
- this gives substance H with an L-fucose attached (this is also an antign) -
2. Next Glycosyl Transferase can place the following terminal sugars (the A/B/O antigens are N-linked and O-linked oligosaccharides in either glycoproteins or sphingolipids found on the plasma membrane):
- N-acetylgalactosamine: to yield A
- D-galactose: to yield B
- or Glycosyl transferase is inactivated to yield O- the terminal sugar is missing (due to a framshift mutation at delta G258)- the inactive fucose transferase is NOT allelic even though the phenotype looks like an "O" (locus heterogeneity)
* NOTE: this is on ANY cell not just RBCs & that these sugar structures attached to the cell membrane differ at the terminal membrane because the allelic Glycosyl transferases producing A or B blood type differ in 4 amino acids (the two alleles differ in substrate specificity)
*** If fucose transferase is absent- you will NOT get A, B, O but you will get the blood type Oh (Bombay phenotype)- higher incidence in people from India subcontinent- this is still part of the O blood type
** most other blood groups have antigens that are proteinsthe O blood type is defined as the absence ofA and the absence of BEpistasis/ Modifier geneInteraction between non-allelic gene (interaction between one gene and a diff. one, not allowing the other gene to express itself- so basically one gene is a modifier gene of the other gene)
ex. An hh person has blood type O (subtype Oh) even if she has genotype AB in the ABO system- because she has a mutation in glucose transferase
** Epistasis might be the underlying reason for reduced penetrance in some diseases
** Modifier genes is another term for epistatis interactionsMost genetic traits and allelic frequencies differe in their indcidence btweenpopulationsA Whole Blood Donation is seperated intoRed blood cells
- used to increase the amount of RBCs after trauma or surgery or to treat severe anemia (can be stored 42 days in fridge and 10yrs in freezer)- can be used in cases of Beta-thalassemia, car accident, or surgery.
Fresh Frozen Plasma
- to correct a deficiency in coagulation factors or to treat shock due to plasma loss from burns or massive bleeding (can be stored 1 yr in the freezer)
Concentrate of Platelets
- to treat or revent bleeding due to lowplatelet levels. To correct functional platelet problems (can be stored 5 days at room temp)
Cyroprecipitate
- to treat fibrinogen deficiences (can be kept 1 yr in the freezer)
***** Whole blood is never used in a transfusion- it is separated into different blood components which are usedIt should appear valid that any blood recipient would be able to receive any blood once (this is true for most blood type including Rhesus) BUT this is NOT true becauseAny of us carries antibodies against those A, B, or H antigens that we do not encode ourselves and this is probably due to cross reactions with bacterial antigens
*** it is very important to note that we also have ABO antigens on other cells- and this is important to note in transplantationType O blood- NO A or B antigens on the RBCs
- both Anti- A and Anti- B in serum
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Could receive RBCs from Type O blood only (note that compatability for RBCs is determine by the antigens on the cells in the donor- you DO NOT give blood to a recipient that has antibodies that would react with those antigens)
Could receive plasma from: Type O, A, B, and AB (for this note that the same antibodies are present in the plasma as in the serum and you CANNOT give antibodies that would attack the cells of the recipient)Type A blood- A antigen on RBC
- Anti-B in serum
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Receives
RBCS from Type A and Type O
and
Plasma from A and ABType B blood- B antigen on RBC
- Anti-A in serum
-----
Receives
RBCs from Type B and Type O
and
Plasma from B and ABType AB blood- A and B antigens
- No antibodies in serum
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Receives
RBCs from Type AB, A, B, O
and
Plasma from ABT or F: whole blood is always used for blood transfusionsFALSE! this happens next to never!
- butt if it did you would have to have a donor and a recipient with the same blood typeAcute Hemolytic Transfusion Reactioncaused by mismatch in the blood types: because of preformed antibodies against RBC
- mechanism: FAST destruction of blood cells by preexisting antibodies
consists of: fever, chills, nause, CP, back pain, pain at transfusion site, hypotension, dyspnea, oligurea, dark urine
- mortality rate is high (40%)
Could be caused by:
- ABO mismatch OR
- mistmatch in any other blood group if there has been prior exposure (ex. Thalassemia- repeat recipient)
***** this is the ONLY transfusion reaction that can be caused by ABO mismatch
** fever can also be an early sign of acute hemolytic transfusion reaction- as such, a patient with fever starting during transfusion should be monitored extre carefully for other signsDelayed Hemolytic Reaction- Caused by mismatch in blood types: NO preformed antibodies against RBC
- Mechanism: slow destruction of blood cells as the antibodies are formed and light inflammation
- slight fever, malaise, weakness, light anemia, sometimes hyperbilirubinemia
- timeframe is one to two weeks (dont get symptoms right away)
- normally not severe
- this reaction is seen with other blood groups
- CANNOT be caused by ABO mismatchFebrile Nonhemolytic Transfusion Reaction- Chills and rigors with fever of greater than 1 degree celsius
- fewer is caused by destruction of the transfusion leucocytes, which causes release of cytokines
- generally mild; this is the most frequent problem associated with transfusions*
- timeline: during or up to 2 hrs after transfusion
- often caused by preformed antibodies against antigens on leukocytes (HLA/MHC)In the blood bank, blood is separated into its components. If RBC are used for transfusion, they are most often insaline solution, not in serum
because the amount of serum injected normally is too small to matter in transfusions:
- people with blood of type O are universal donors
- people with type AB are universal recipients
* normally, transfusions are carefully matches, except maybe in extreme emergencies- when they will just use type ORhesus Blood Group- differs in presence (Rh+) or absence (Rh-, autosomal recessive) or the rhesus antigen (protein)
- determined by presence or absence of polypeptide D (different AA varients in the polypeptide explain subgroups of Rh+)
- 15% of North americans are Rh- (variation between populations)
- No antibodies against Rh+ in Rh- people (different from the situation in ABO blood group system)
*** the antigen here is a protein
** also Rhesus, Rh, and D are used interchangeblyHemolytic Disease of the newborn- Anti-Rh+ antibodies (IgG) will cross the placenta and attack RBC of next Rh+ baby (mainly late in pregnancy) (anti-Rh sometimes called Anti-D)
- Anemia, immature RBC in circulation; in severe cases: edema in utero (hyrops fetalis or erythroblastosis fetalis) and fetal death affects 0.125% of births
- After birth, continued breakdown of RBC, lead to hyperbilirubinemia, and jaundice
- Untreated, bilirubin build-up in brain leads to cerebral damage (kernicterus) and sometimes/usually death (blood-bran barrier not fully developed)
*** treat with exchange transfusions (use blood of type O, Rh-)
Occurs when a Rh- mother have previously been immunized with Rh+ antigen (so it is in her 2nd or later pregnancy)
4 reasons this can occur:
- at birth of a Rh+ baby
- at abortion of Rh+ fetus
- by transfusion
- by aminocentesis/chorion villi samplingHow do you prevent Hemolytic Disease of the New born (Rh)- Make sure the mother NEVER develops antibodies
- Rh- mothers: injection of anti-RH+ antibodies (RhoGam) max. 72h after birth prevents production of anti-Rh+ antibodies by the mother (current recommendation is to also inject at week 28 (or weeks 28+34) - this is safe because RhoGam contains IgG
- should not be necesary if mother and 1st child are ABO incompatible, as anti-A or anti-B antibodies destroys the fetal RBC before damage is done
* treat in current pregnancy to avoid problems in later pregnanciesHemolytic Disease of the New Born (ABO) *****not same as Rh- A mild version occurs with ABO incompatibility: O mother and A, B, or AB father
- most often the anti-A and anti-B antibodies are IgM, that CANNOT cross the placenta
- when they happen to be of the IgG type that CAN cross, then problems may occur
- relatively common cause of mild neonatal jaundice, rarely more severe
- can happen with the first child (Rh incompatibility almost always cause problems in later parties)
*** in rare cases this can lead to hemolytic disease just as severe as the one caused by RhesusHow many blood groups are thereThere are about 20 other systems other than the ABO and Rh
- transfusion could happen with most of them at least once because: there are no pre-forms antibodies OR preformed antibodies are only reactive at low temperaturs and using blood preheated to 37 degrees celsius alleviates the problem
- standard practic is to lab test for compatability between the actual recipient and the expected donor
** most of these (but not all) have protein as their antigensExamples of other blood groups other than ABO and Rh- Lewis (Le): most common reason for lack of compatibility between materials matched for ABO and Rh. The antigen in this system are also carbohydrate structures, just like ABO and contra most other blood groups
- People with anti-U are problematic: so rare that is difficult to find donor
- Autoanti-P (Donath Landsteiner) antibodies in hemolysis
- the genes encoding blood groups C and E is physically close to the gene encoding the Rhesus blood group (which is sometimes called D), but is really acting independent of this
- Kell antigen: large protein with antigenic regions. If abesnt, patient present with acanthocytosis, shortened RBC survival, and muscular dystrophy including the heart muscle
- Duffy: has two alleles (Fya, Fyb) that are both binding sites for P.vivax. More than 70% of people in malaria regions lack these antigens
- A delayed hemolytic transfusion reaction that occurs with blood tested compatible are often caused by delayed appearance of anti-Jka (one of the antigens in the Kidd blood group)Which donors would be compatible with a 24 year old women with blood type A, Rh-A, Rh-
O, Rh-
*** Type A blood means it excludes anything with a B
*** Rh- means it CANNOT recieve Rh+Neoplastic WBC disorders includeLeukemia
LymphomaNon-neoplastic (reactive/inflammatory WBC disorders) can be seperated intoQuantitative WBC disorders and Qualitative WBC disorders
- Quantitative is further divided into Leukopenia and LeukocytosisWhich cells are responsible for the major changes in WBC countNeutrophils and lymphocytesAn increase in the total number of white cells per liter of blood exceeds the higher limit of normal in peripheral blood due to any causeLeukocytosis> 11,000/cmm
* normal range of white cell count: 5,000-11,000cmm
Causes:
Physiological
- newborn, pregnancy
Pathological
- early reaction to many diseases
- type of WBC affected varies with cause
- neoplastic/non-neoplastic conditions
Ex:
can be a combination of any of the following:
- neutrophilia
- lymphocytosis
- monocytosis
- eosinophilia
- basophiliaMechanisms and causes of leukocytosisIncreased production in the marrow
- chronic infection or inflammation (growth-factor-dependent), paraneoplastic (ex. Hodgkin Lymphoma; growth factor-dependent), myeloproliferative disorders (ex. chronic myeloid leukemia; growth factor-independent)
Increased release from Marrow store (like in thalassemia:
- Endotoxemia
- Infection
- Hypoxia
Decreased Margination:
- Excercise
- Catecholamines
Decreased Extravasation into tissues:
- GlucocorticoidsNeutrophilic Leukocytosis can be due toAcute bacterial infections, especially those caused by pyogenic organisms; sterile inflammation caused by for exampl, tissue necrosis (myocardial infarction, burns)Eosinophilic leukocytosis (eosinophilia) can be due toAllergic disorders such as asthma, hay fever, parasitic infestations; drug reactions, certain malignancies (ex. Hodgkin and some non-hodgkin lymphomas); autoimmune disorders (ex. pemphigus, dematitis herpetiformis) and some vasculitides; atheroembolic disease (transient)Basophilic leukocytosis (basophilia)rare, often indicative of a myeloperoliferative disease (ex. chronic myelogenous leukemia)
* usually poor prognosisMonocytosis is due toChronic infections (ex. tuberculosis), bacterial endocarditis, rickettsiosis, and malaria; autoimmune disorders (ex. systemic lupus erythematosus); inflammatory bowel diseases (ex. ulcerative colitis)Lymphocytosis can accompanymonocytosis in many disorders associated with chronic immunologic stimulation (ex. tuberculosis, brucellosis); viral infections (ex. hepatitis A, cytomegalovirus, epstein-barr virus), bordetella pertussis infectionWhere are blood cells taken out of when you take out bloodCirculating Pool
* excercise moves cells from marginating to circulatingGranulocyte production and storage occurs in thebone marrowPathogenesis of leukocytosis- Increased production in BM (like in myeloproliferative disorders- ex. chornic myeloid leukemia, chronic inflammation (growth factor dependent)
- Increased release from BM stroes (infection, endotoxemia, hypoxia)
- Decreased margination (excercise, catecholamines)
- Decreased extravasation into tissues (glucocorticoids)Causes of neutrophilia/neutrophilic leukocytosis- Infections (acute bacterial infections ex. Acute Appendicitis, abscess)
- Sterile inflammation (myocardial infarction, burns)
- Drugs (decrease neutrophil adhesion and release from marrow stores- corticosteroids)
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** this is an incres in neutrophila (absolute count >7000cel/microliter
** shift to the left (immature neutrophil precursors in PB (>10% band neutrophil or any neutrophil younger than a band))Morphological cahnges in neutrophila in sepsis or severe inflammatory disorders- Toxic granules: coarser and darker than normal neutrophil granules, represent abnormal azurophilic (primary granules)
- Dohle bodies: dull gray inclusions representing patches of dilated rER
- Cytoplasmic vacuoles: phagolysosomes, indicating presence of phagocytosisLeukemoid reactionExaggerated benign leukocyt response
- high leukocyte count >30,000 (often >50,000/microliter) with immature myeloid granulocytes in blood stimulating leukemia (chronic myeloid leukemia)
- composed largely of mature neutrophils with low portion of bans and myelocytes
Causes:
- severe infections: sepsis, perforated acute appendicitis, whooping cough, infectious mono; severe hemorrhage
*** present with fever and shift to the leftHow can you tell apart the leukemoid reaction vs leukemiaLeukemoid reaction has high LAP score
Chronic myelogenous leukemia has low LAP score
** soo LAP score is increased when it is just reaction, not cancer
LAP= leukocyte alkaline phosphatase (LAP)Pathogenesis of Eosinophilia (increased eosinophils in the peripheral blood)- release of eosinophil chemotactic factor from mast cells/basophils in type I IgE mediated hypersensitivity reactions
- growth factor IL-5
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Causes:
- Allergic disorders: asthma, hay fever, drug reaction to penicillin
- Parasitic infections
- Skin diseases (pemphigus, dermatitis herpetiformis
- Certain malignancies (hodgkins lymphoma)
- Collagen vascular diseasesCauses of Basophilia (increase in basophils)Rare
- >5% basophils: indicative of myelo-proliferative disease (ex. chronic myeloid leukemia)Marker of chonic inflammationMonocytosis
found in
- Chronic infections: tuberculosis, bacterial endocarditis
- Chronic inflammation in ulcerative colitis, collagen vascular diseases (SLE- systemic lupus erythematous)Causes of lymphocytosis (increase in lymphocytes)Infections
- viral: infectious mono, CMV, mumps, measles
- bacteral: whooping cough, TB, brucellosis
- parasitic: toxoplasmosis
Autoimmune disease- SLE
Endocrine- grave's disease
Malignancy: chronic lymphoid leukemiaInfectious Mononucleosis (IM)Cause:
- EBV (herpes virus)- most common cause
- CMV: less common: heterophila-ve IM
Clinical feature
- in adolescents or young adults
- aka "kissing disease"
- classic triad: fever, pharyngitis (sore throat with gray-white membrane on tonsils), lymphadenopathy (posterior auricular), and sometiems hepato-splenomegaly
-------
Peripheral blood smear will show >10% atypical lymphocytes
- Downey cell cytoplasm ~ "ballerina skirt" appearance
- resemble monocytes (thus called mononucleosis)
----
Pathogenesis:
- EBV invades B-lymphocytes via CD21 receptors
- CD8 T-lymphocytes respond against B cells to form atypical lymphocytes
**** abnormal looking cells are T cells even though the virus is invading the B cells***
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Lab diagnosis:
Mono-spot test:
- Rapid slide test based on Paul-Bunnel reaction
- Heterophile antibodies (non-specific IgM)
- react with other species i.e. RBCs of sheep, beef and horses
- few patients may be negative in 1st week- repeat may be necessary
Specific tests
- IgM antibodies against EBV viral antigen: most helpful in acute disease
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Potential complication: splenic rupture, this is why patient should avoid contact sports for 6 weeks
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Course:
- self-limited
- resolves within 4-6 weeksIn the cortex of the lymph node this is whereFollicles with B cells are found
- in paracortex T cells are foundLymphadenopathy-local/generalize enlargement?
- tender/non-tender?
Reactive hyperplasia: acute lymphadenitis and chronic lymphadenitis
OR
Neoplastic conditions with lymph node infiltration: primary tumor like lymphoma/leukemia or secondary tumor like metastatic tumorAcute lymphadenitiesCaused by
- Bacterial infection: focal involvement- cervical lymphnode draining infected teeth, tonsils, axillary/inguinal lymph node draining infections in extremities
- systemic viral infection: generalized lymph node involvement
C/F:
- enlarged, painful lymphnode with red overlying skin
- can form draining sinsues; heal by scarring
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Lymph node morphology
- gross: swollen, gray-red congested
- microscopy: prominent reactive germinal centers or necrosis, neutrophils, macrophades with ingested debrisChronic LymphadenitisNon-tender lymph node enlargement
Types
- Follicular hyperplasea
- Para-cortical lymphoid hyperplasia
- Sinus (reticular) hyperplasia
- Necrotizing lymphadenitis
- Granulomatous lymphadenitisFollicular hyperplasia- lymph node architecture is well presereves: secondary follicles (large, oblong) with prominent germinal centers and many mitotic figures
"benign- not follicular lymphoma"
found in
- rheumatoid arthritic
- toxoplasmosis
- HIV- early stagesPara-cortical hyperplasia (where T cells are)- Activated lymphoyctes in T-cell regions of the cortex (inter-follicular regions (paracortex) show activated T cells)
- Found in viral infection ex. Infectious mononucleosisSinus hyperplasia- Lymphatic sinusoids (distended and prominent, contain many histiocytes)
found in
- lymph nodes draining a cancer (breast carcinoma)
- sinus histiocytosis with massive lymphadenopathy
- langerhan cell hisiocytosisGranulomatous lymphadenitisChronic lymphadenitis with granulomatous inflammation with or without caseation necrosis
- granuloma: focal accumulation of activated macrophages
- caseation necrosis- cheesy appearance of dead tissue occuring within a granulom
ex. tuberculosis, fungal infectionsNecrotizing lymphadenitis"Catscratch disease"
- mixed B and T cell hyperplasia
- self-limited lymphadenitis seen in children
- stellate, necrotizing granuloma in regional lymph nodes (ex. axillary, cervical)
- due to bacterial infection (Bartonella Henselae)Leukopenia (low WBC dount)- decrease in neutrophils (neutropenia or granulocytopenia, and agranulocytosis)
- decrease in lymphocytes (lymphopenia)Pathogenesis of NeutropeniaInadequate/ ineffecitive production:
- aplastic anemia (bone marrow failure)
- space-occupying lesions
- solid cancers
- granuloma
- hematologic malignancies that suppress granulopoiesis
DNA problems
- megaloblastic anemia
- cancer chemotherapy, radiation sickness
Increased destruction/splenic sequestration
- immune mediated injury- idipathic, SLE, drugs
- splenomegaly
Increased peripheral utilization:
- overwhelming bacterial, fungal, rickettsial infections
Drugs
- anti-cancer drugs-alkylating agents/anti-metabolits
- idosyncratic reaction: aminopyrine, cholramphenicol, suldonamides, chlorpromazine, thiouracil, phenylbutazoneAgranulocytosisClinically significant reduction in neutrophils (<100 neutrophils/microL0
- serious consequence of making individuals susceptible to bacterial and fungal infections
Causes:
Drug toxicity (most common cause)
- alkylating agents, anti-metabolites
- predicatble dose related
Idiosyncratic reaction to drugs
- antibody mediated destruction of mature neutrophils
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Clinical Features of neutropenia
Neutropenia
- malaise, chills, fever
- marked weakness and fatigability
- ulcers and enlarged regional lymph node
Agranulocytosis
- mouth ulcers with pseudo-membranes laden with infective bacteria and/or fungi
- death within a few daysBone marrow in neutropenic pateintsHypercellular:
- compensatory increase with peripheral neutrophil destruction
- ineffective production (megaloblastic anemia, MDS)
Hypocellualr:
- agents that suppress or destroy granulocytic precursors
- aplastic anemiaLymphopeniaDecreased circulating lymphocytes
Causes:
Durgs: corticosteroids, cyclophosphamide
Autoimmune destruction: SLE
Immuno-deficiency syndrome: DiGeorge syndrome (T cell deficiency), AIDS, Severe combine immunodeficiency
Endocrine: Cushings SyndromeAntianemia DrugsIron preparations:
Oral:
- Ferrous sulfate
- Ferrous gluconate
Parenteral:
- Iron dextran
- Ferric gluconate
Iron Antidotes:
- Deferoxamine
- Deferasirox
Vitamin B12 Preparations
- Cyanocobalamin
Folic Acid Preparations
- Folic Acid
- LeucovorinHematopoietic Growth Factors (Erythropoiesis Stimulating Agents)- Epoetin alfa
- Darbepoetin alfaRenal failure is usually due to aerythropoietin deficiencyMicrocytic Anemia secondary toIron Deficiency
(low Hb, low Hct, low MCV)Oral Iron preparations are withFe2+
- Ferrous Sulfate
- Ferrous Gluconate
(these work to increase iron, replace iron found in Hb, myoglobin, and enzymes)
(works for prevention and treatment of iron-deficiency anemia- hypochromic, microcytic anemia)
** oral and Fe2+ (ferrous) iron are perferably used
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Adverse effect:
- acute iron toxicity (overdose): GI bleeding, vomiting, abd pain and bloody diarrhea- seen most commonly in young children who accidentally ingest iron tabletsParenteral Iron is usuallyFe3+
- Iron Dextran (given intramuscularly and IV)
- Ferric Gluconate (given via IV)
MOA:
- increase iron, replaces iron found in Hb, myoglobin and enzymes
Used to treat:
- iron-deficiency in pts with chronic anemia who cannot be maintained with oral iron (ex. chronic kidney disease undergoing hemodialysis in conjunction with supplemental erythropoietin therapy)
- treatment of iron-deficiency in pts who are unable to tolerate or absord oral iron
Adverse effects
- not so bad: injection site reactions, headache, light-headedness, muscle cramps, nausea and diarrheaDifference between acute (overdose) and chronic (hemochromatosis) iron toxicityAcute (overdose):
- most common in young children who accidently ingest iron tablets (as few as 10 can be lethal)
- children experience necrotizing gastroenteritis with vomiting, abd pain and bloody diarrhea. In some cases severe metabolic acidosis, coma, and death may occur
- whole bowel irrigation should be used to remove unabsorbed pills and Deferoxamine can be given to bind iron
- activated charcoal binds to most toxins but does NOT bind iron
Chronic (hemochromatosis):
- excess iron is deposited in heart, liver, pancreas and other organs (can cause damage to these)
- most commonly seen in pts. with inherited hemochromatosis and pts who receive many red cell transfusions over a long period of time (ex. individuals with beta-thalassemia)
- Chronic iron overload can be treated with oral Dferasirox or parenteral Deferoxamine
- Chronic iron overload in the absence of anemia is most efficiently treated with intermittent phlebotomy. One unit of blood can be removed every week until the excess iron is removedDescribe the clinical uses of Deferasirox and Deferoxamine (**these are iron chelators)Deferasirox
- Given orally only (only chronic)
- used in treatment of chonic iron overload
- Adverse effects: acute renal failure, hepatic failure, and GI hemorrhage, which may be fatal
Deferoxamine
- Given IV, IM, and SubQ
- used in treatment of acute iron overload and chronic iron overload
- Adverese effect: infusion reaction (skin, flushing, urticaria and shock)
*** Both of these MOA= binds to Fe3+ (ferric) ions to form a complex which is then excreted in urine (deferoxamine) or feces and bile (deferasirox)Macrocytic Anemia can be secondary due toVitamin B12 or Folate DeficiencyCyanocobalaminSynthetic form of VitB12
Route of administration:
- IM and SubQ (IV is not recommended)
- Oral: not recommeded due to poor absorption. May be used if parenteral therapy is refused or poorly tolerated
MOA:
- supplement VitB12 (cobalamin); coenzyme for various enzymatic reactions necessary for the synthesis of nucleic acids and proteins
Clinically used for:
Treatment of vitB12 deficiency due to:
- pernicious anemia (due to decreased intrinsic factor)
- deficiency due to dietary deficiency or malabsorption, inadequate secretion of intrinsic factor and inadequate utilization of vitB12 during neoplastic (cancer) treatment
- increased requirement due to pregnancy, hemorrhage, thyrotoxicosis, malignancy and liver or kidney disease
Adverse effects:
- patients with Leber disease who recieve vitB12 treatment may suffer from optic atrophy (severe rapid)
- VitB12 deficiency masks polycythemia vera (a blood cancer- cant grow bc doesnt have vitB12 to grow). Resolution of VitB12 deficiency may unmask polychythemia veraDifferences between the Folic Acid Preparations: Folic acid and Leucovorin (folinic acid)Folic Acid
- given oral (preferred), IM, IV, and SubQ
- MOA: supplementation of folic acid required for enzymatic reactions necessary for nucleic acid synthesis
- used as supplementaton to prevent neural tube defects in developing fetus
Leucovorin
- oral, IM and IV
- MOA: is a reduced form of folic acid- provides folic acid required for nucleic acid synthesis. Bypasses the dihydrofolate reductase catalyzed reaction that synthesizes tetrahydrofolate, which is blocked by the chemotherapy drug methotrexate
- used as rescue agent after high dose methotrexate (cancer chemotherapy drug) treatment
- cancer chemotherapy; increase the toxicity of the cancer chemotherapy drug 5-fluorouracil
** BOTH used in treatment of megaloblastic anemia due to folate deficiencyHematopoiesis- all blood cells, including the cells of the immune system are derived from pluripotent hematopoietic stem cells
- the type of mature cell that develops is determined by exposure of progenitor cells to specific growth factors
- a recombinant form of the growth factor erythropoietin (EPO) is used to treat some types of anemiaDescribe the difference between Erythropoietin Drugs: Epoetin alfa and Darbepoetin AlfaEpoetin alpha
- a recombinant human EPO
Darbepoetin alpha
- a modified form of EPO with a greater half-life
*** both given IV and SubQ
*** both MOA= induction of erythropoiesis by interacting with EPO receptors on RBC progenitors and stimulating differentiation and proliferation. Induces the release of reticulocytes from the bone marrow to the bloodstream. This results in an increase in hematocrit and hemoglobin levels
Both are clinically used in:
Anemia
- due to chronic kidney disease (EPO is made in the kidney)
- due to chemotherapy in patients with cancer
- due to zidovudine in HIV-infected patients
also in
Patients scheduled to undergo elective, noncardiac, nonvascular surgery- reduces the need for allogenic RBC transfusion
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Adverse effects:
BLACK BOX WARNING: erythropoeisis- stimulating agents (ESAs) increased the risk of serious cardiovascular events, MI, stroke, venous thromboembolism, vascular access thrombosis, and mortality in clinical studes when administered to target hemoglobin levels >11g/dL
- contraindication in patients who are mildly anemic or nonanemic
- hypertensionPrimary Endocrine Glands (purpose is the production and release of chemical messengers that travel throughout the body)Pituitary gland
Thyroid gland
Parathyroid glands
Thymus gland
Adrenal gland
Pancreas
Ovaries
TestesSecondary Endocrine Glands (have priamry functions associated with other organs)Hypothalamus
Pineal gland
Heart (right atrium) - atrial natriuretic peptide (ANP)
Liver
Stomach
Kidney
Adipose tissue - Leptin
Small intestineTransient Endocrine gland or Endocrine structure (present for only a short duration)Placenta
Corpus Luteum3 major classes of "hormones" based on structureAmines: derived from one or two modified AA's, usually tyrosine (or tryptophan). Can be hydrophilic or hydrophobic (ex. Epinephrine)
Peptides: derived from 3 or more linked AA. Usually hydrophilic (ex. Oxytocin)
Steroids: derived from cholesterol, includes Vitamin D3. Hydrophobic (ex. Cortisol)
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Plus 2 "hormone-like" classes:
- Prostanoids: derived from fatty acid (arachidonic acid), most are cytokines
- Gases: ex. Nitric Oxide (NO), hydrogen sulfide (H2S)3 patterns of hormone secretionEpisodic Release
- A specific stimulus arrives and the hormone is released. If only paracrine/autocrine substance are released, this can be called a "localized burst"
- Insulin is an ex. of hormone released when glucose levels rise in the bloodstream
Pulsatile Release ***most common***
- hormone is released in a series of regularly timed short bursts, typically with time between the bursts devoted to hormone action and metabolism
- Growth hormone is an ex. of hormone released in short bursts when stimulated to do so by hypothalamic hormones
Circadian and other larger-timed rhythms:
- A modulation of pulsatile release. Significantly more hormone is released at certain times of the day (circadian), month or yr than at other points in the respective time cycle
- ex. MelatoninDescribe Episodic Release of hormones- Baseline stays low until some condition occurs that stimulates hormone release
- Acute release of hormone often starts with exocytosis of stored material (ex. preformed insulin)
- Further release (second stage) of newly synthesized hormone occurs indefinitely
- release ends only when the condition for stimulus ends
*** this can be seen in water-soluble hormones (like insulin) and in lipid-soluble hormones as wellDescribe Pulsatile Release of Hormones- Characterized by relatively stable time periods between releases (producing "peaks" of high concentrations of hormone)
- Baselines are typical of time periods of very little secretion (allows target receptors and cells time to "reset", to better respond to the presence of the next "peak"
- both the timing between peaks and quantity of hormone secreted can be modulated (Ex. 1 GnRH peak/hr promoted LH secretion but 1 GnRH peak/3 hrs promotes more FSH secretion insteadWhat are 3 types of Hormone Control1. Homeostatic feedback, almost always negative
- physiological response-drive vs. endocrine axis-driven
Ex. of Physiological response driven feedback-- If plasma glucose rises too high (hyperglycemia), insulin is secreted to reduce it. If it drops too low (hypoglycemia), glucagon and/or catecholamines (epinephrine) are secreted to increase it- each activates a series of generally oppossing biochemical processes to produce its change in blood glucose
2. Neural control:
- includes adrenergic (epi/norepi), cholinergic (ACh), serotoninergic
- can serve homestatic feedback
- Nervous system directly commands hormone release- often involves neurons or related neural tissue cells as secretagogues
Ex: the cells in the adrenal medulla that secrete catecholamines are derived from neural crest cells
3. Chronotropic control (modulation)
- includes pulsatile (such that chronotropic modulation influences the quantity of hormone released at each time), diurnal, mentrual, seasonal and developmental rhythms
- involved neuronal signals
- can modulate homeostatic feedback
Ex: Circadian cycle of cortisol secretion: cortisol is the primary human glucocorticoid- its secretion peaks at 9-10am and is minimal at midnight
- note that Growth hormone on the other hand which supports cortisol catabolism actually peaks at midnight (kids growth at night)Target cell vs Target tissueTarget cell: any cell that can change its activity in some way, due to its reaction to the presence of a given hormone
- target cells contain hormone receptors which may be on the cell surface (if hormone cant cross membrane because it is too big or polar) or intracellular: when a hormone binds the hormone-receptor complex initiates some activity change
Target tissue: a group of cells that collectively respond to the presence of a given hormone at each individual cell
* for most hormones, mass release of hormone molecules allow target tissues to be affected, often within a single organReceptors can be divided into two basic classes based on their structure and mechanism of action. What are these?Plasma Membrane Receptors (Ion channels, GPCR, or catalytic)
and
Nuclear Receptors (which bine to regulatory sequences in DNA and increase or decrease gene transcription)
** review Dr. Pederson Cell Signaling LectureCell Surface hormone receptors requireSecond messengers
- Membrane-bound receptors are highly variable and hormone specific
- Biomolecules binding to membrane-bound receptors INDIRECTLY regulate transcription through second messenger signaling pathwaysThe advantage of lipid-soluble hormones is thatif you can get them into the cell, the cell machinery for gene transcirption and translation will always be there- so these hormones can exert their effects. The cells receptors are intracellular, either in the cytoplasm or in the nucleus
Ex.
Steroids, thyroid hormone, retinoic acid (active Vit A) and calcitriol (the active form of Vit D) either diffuse across or are transported across the cell membrane
- some receptors start in cytoplams, others in the nucleus
- they DIRECTLY regulate gene transcription
*** disadvantage of these routes is slow speed (slower to start and slower to stop than water soluble hormones who use a second messenger)Name some signaling biomolecules that are lipophilic- Steroids
- Iodothyronines (Thyroid Hormone)
- Calcitriol (Vitamin D)
- Eicodanoids)
* these have transport proteins to move them through the body- ex albumin and thyroid hromone- binding globulin (TBG)
* their plasma half-life is usually long (hours to days) and their receptor is usually always intracellular
* MOA: receptor-hormone complexes bind to response elements and act in the nucleusName some signaling biomolecules that are hydrophilic- Polypeptides
- Proteins
- Glycoproteins
- Catecholamines (ex. epinephrine)
*** these usually have NO transport proteins, their plasma half-life is short (minutes), their receptor is usually in the plasma membrane
** certain exceptions (ex. growth hromone and Insulin-like growth factor I (IGF-1)) also bind to transport proteins - so these take longer to disappear from the blood unlike most water-soluble hormones)
MOA: second messengers (cAMP, cGMP, Ca2+, DAG, phosphokinases, etc.)Hormone action is dependent on the concentration and the receptor density at the site ofACTION, not in the plasma
- Systemic (plasma) concentrations of "locally-acting" biomolecules likely do not represent the true level acting at the target site beacuse the biomolecules binds rapidly with receptors upregulated at the site of release, thereby keeping "escape" into the systemic concentration at a minimum
** systemic concentrations of endocrine (hemocrine) "hormones" represent the level of hormone acting on most tissues distributed throughout the body
*** For most water-soluble hormones that ARE classic endocrine hormones, the amount in the plasma should be proportional to that in the fluid surrounding the target cellsUpregulation vs. DownregulationThe goal is an appropriate response when the hormone is present
- Up-regulation: increases receptor number, leaving cells able to respond to even low levels of hormone
- Down-regulation: prevents overstimulation in excess of hormone (adaptation or desensitization)For water soluble hormone the receptors are on thecell surfaceFor lipid soluble hormones the receptors areintracellularThe more tightly hormones bind to transport molecules,the longer are their half-livesT or F: removal of hormone is as important as secretion of hormoneTrue!
Metabolic clearance rate (MCR)= volume of plasma cleared of a hormone per unit of time (inversely related to the half-life- the faster the clearance rate, the shorter the half-life of hormone in plasma)
- Water-soluble hormone have greater MCRs than lipid-soluble hormones
- hormone need to be temporary so their effects can occur and can disappear when no longer needed
*** Kidney and Liver are MAJOR sites for hormone extraction and degradation- breakdown products appear in the urine or the bile.
- target tissues also can degrade many hormonesIf you have two hormones and one is metabolized faster than the other,its clearance will be greater than the other
(higher MCR)
first hormone will have shorter half-lifeGeneral Rules involving hormonal half-lives1. Locally-acting biomolecules are often metabolized by locally-produced degrading enzyme and therefore exhibit a short half-life (ex. vasoconstrictors degraded by endopeptidases)
2. Small peptides typically act locally and exhibit the shortest half-lives
3. Hypothalamic hormones exhibit relatives short half-lives
4. Hydrophilic biomolecules have shorter half-lives than hydrophobid biomolecules (hydrophobic hormones typically bind to serum proteins which extends half-life)
5. Pro-hormones and break-down metabolites exhibit a longer half-life than the most active biomolecule/hormone (ex. T3 (the more bioactive thyroid hormone) has a shorter half-life than T4 (the hormone found in higher quantities)What is the avergae half-life for predominantly locally-acting biomolecules, with some water-soluble endocrine hromones~2 min
These include:
Angiotensin II
Endothelin-1
Epinephrine
ProstaglandinsWhat is the half-life for a biomolecule that is involed in episodic release~3-5min
This is InsulinWhat are the half-lives for predominantly lipid-soluble endocrine hormones. Transported in circulation bound to binding proteins- Growth Hormone (18-24 min)
- Aldosterone (~30 min)
- Cortisol (~60-90 min)
- Porgesterone (12-16 hrs)
- Triiodothyronine (T3) (16-24 hrs)
- Thyroxine (T4) (~7days)The endocrine system sends messages to control and regulate metabolic activity of the body using hormones that are- released by endocrine secretory cells and
- carried by the blood circulatory system (endocrine organs have rich blood supply)Endocrine system includes1. Glands: pituitary, thyroid, parathyroids, adrenals, pineal (also testes and ovaries but not worrying about that much now)
2. Clusters of endocrine cells within an organ (ex. islets of langerhans (pancreas)
3. Isolated endocrine cells in tissues (ex. mucosa of GI)"the leader of the endocrine orchestra"Pituitary Gland
- controls secretions of other endocrine glands
- found sitting in the sella turcica of the sphenoid bone
- has a connection with the base of the brain by a stalk (aka infundibulum)Describe the Dual embryological origin of the pituitary gland1. Neurohypophysis
- from nervous tissue that migrates inferiorly from the floor of the diencephalon
- subdivided into PARS NERVOSA (posterior lobe) and INFUNDIBULUM/STALK (stem and median eminence)
2. Adenohypophysis
- from oral ectoderm
- subdivided into PARS DISTALIS (anterior lobe), PARS TUBERALIS (surround stalk), and PARS INTERMEDIADescribe the blood supply of the pituitary glandArterial Supply
-Superior hypophyseal artery (from internal carotid) supplies pars tuberalis and infundibulum. Also forms the primary capillary plexus in the median eminence
- Inferior hypophyseal artery primarily supplies posterior lobe; with a few branches to the anterior lobe
* Note: capillaries are fenestrated so they have many small channels with high vascular permeability which allows a rapid exchange of substances between the hypothalamus and the pituitary
Venous Drainage
- Hypophyseal portal veins drain primary capillary plexus (formed by superior hypophyseal artery) which delivers its blood into the second capillary plexusPosterior lobe of Pituitary GlandPars Nervosa (neurohypophysis)
- smaller than anterior lobe-Anterior lobe of Pituitary GlandPars Distalis (adenohypophysis)
- much larger than posterior lobe-What cell types can be found in the Anterior Lobe of the Pituitary Gland (adenohypophysis or pars distalis)Chromophil Cells: they have the affinity for ACID and BASIC dyes (these cells are arranged in irregular CLUSTERS or CORDS):
Acidophil Cells (alpha cells): pink with H&E dye
- Somatotropes: secrete growth hormone
- Mammotropes: secrete prolaction
Basophil cells (beta cells): blue with H&E dye
- Gonadotropes (FSH and LH), Thyrotropes (TSH), and Corticotropes (ACTH)
*** these different hormone producing cells in the anterior lobe (pars distalis) of the pituitary gland are detected with Immunohistochemistry (IHC)
Chromophobe cells: low or no affinity to any dyesPars Intermedia- Rudimentary region
- Found between pars distalis and pars nervosa
- Contains weakly basophilic cuboidal follicular cells that contain secretory granules- (it is not known for sure what they secrete but they are thought to secrete melanocyte stimulating hormone (MSH)
- Colloid filled cysts known as Rathke's cysts present (remnants of Rathkes pouch)Pars Nervosa (posterior lobe)- Irregularly organized
- Contains PITUICYTES- which are neuralgia in nature: these may provide a supporting function for the unmyelinated axons within the pars nervosa
- these axons whose cell bodies are located in the supraoptic and paraventricular nuclei of the hypothalamus enter the pars nervosa via the hypothalamo-hypophyseal tract
* Axons have expanded axon terminals called HERRING BODIES within the pars nervosa
- These Herring Bodies contain oxytocin and antidiuretic hormone (ADH/Vasopressin)- they STORE these hormones which are MANUFACTURED IN THE HYPOTHALAMUSThyroid Gland- A deep structure of the neck
- Consists of left and right lobes connected by the isthmus, which normally lies at the level of the 2nd-4th tracheal rings
- A pyramidal lobe may also be present in some individuals; being a remnant of the thyroglossal duct and found extending superiorly from the isthmus
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Thyroid gland is supplied by the R and L superior and inferior thyroid arteries and sometimes the thyroid ima (from the brachiocephalic trunk but this is NOT present in all individuals
Drains via the superior, inferior, and middle thyroid veins to the internal jugular vein and via inferior thyroid to brachiocephalic veinThe thyroid gland is covered byLoose CT capsule that sends septa into substance of the gland (parenchyma) forming a supporting framework
- The parenchyma is composed of thyroid follicles that consist of a simple epithelium that surrounds colloid
* Note also the presence of parafollicular cells that manufacture the hormone calcitoninThyroid Folliclefunctional unit producing T3 and T4. Consists of follicular lumen surrounded by a single-layered cuboidal epithelium (columnar when stimulated)
- Lumen filled with "colloid" consisting of the glycoprotein thyroglobulin
- Low turnover of follicular cells: one mitosis/8 yearsParathyroid Glands-pea-sized, round structures usually found embedded in the POSTERIOR surface of the thyroid gland
-a thick CT capsule separates the glands from the thyroid tissue
* Most people have 4 parathyroid glands (two superior and two inferior), but occasionally there are more in tissues of the neck or chest
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Its blood supply is essentially the same as the thyroid gland
- Supplied by superior and inferior thyroid arteries and sometimes the thyroid ima (from brachiocephalic trunk but NOT present in all individuals)
- Drains via the superior and middle thyroid veins to internal jugular vein and via inferior thyroid to brachiocephalic veinDescribe the structure and composition of the Parathyroid GlandA connective tissue capsule sends septa/trabeculae (T) into substance of gland; within which are located blood vessels
2 main types of cells within the gland
1. Chief cells (AKA principal cells)
- more numerous and smaller than oxyphil cells
- darker staining cytoplasm
2. Oxyphil cells
-stain lighter, usually larger than chief cells
-cell membranes clearly visible
** With increasing age- secretory cells are replaced by adipocytes
- chief cells on EM examination contain secretory granules containing parathyroid hormone
- the fx. of oxyphil cells is unknownSuprarenal (AKA Adrenal) Glands- Retroperitoneal organs
- Lies on superiormedial aspect of the kidney
- Surrounded by CT capsule and renal fascia
- Has an outer cortex and an inner medulla that have different embryological origins
Cortex can be further subdivided into 3 layers:
1. Zona glomerulosa
2. Zona fasciculata ** Occupies the bulk of the gland*
3. Zona reticularis
* the medulla has no such subdivisions: is secretes catecholamines (mostly epinephrine and norepinephrine)
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Arterial Supply
1. Suprarenal artery from inferior phrenic
2. Middle suprarenal from abdominal aorta
3. Inferior suprarenal from renal artery
Drains via suprarenal vein which drains into inferior vena cava (IVC) on the RIGHT and the renal vein on the LEFTThe zona glomerulosa (ZG) of the adrenal (suprarenal) gland secretesmineralcorticoids (ex. aldosterone)
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- it is made of closely packed columnar or pyramidal-shaped cells; some contain vacuoles
- arranged in CLUSTERS surrounding capillariesThe zona fasciculata (ZF) of the adrenal (suprarenal) gland secretesglucocorticoids (ex. cortisol)
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- ZF is arranged in straight CORDS, one or two cells thick
- polyhedral
- cells in more superficial portion of layer are mainly SPONGIOCYTES (any of the cells of the adrenal cortex that have a spongy appearance due to lipid vacuoles)
- deeper cells appear more denserThe zona reticularis (ZR) of the adrenal (suprarenal) gland secretessex steroids- (androgens, mainly dehydroepiandrosterone (DHEA)
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- ZR is made of irregularly shaped cords of cells
- Cells slightly smaller than in the other layers
- Often difficulat to demarcate junction between zona fasciculata and reticularisWhat cells are found in the adrenal medullaChromaffin cells (ChC)
- polyhedral cells
- large with pale-staining cytoplasm
- have an extensive vascular networkPineal Gland- Cone-shaped (5-8mm length; 3-5mm width), midline projection form the roof of the diencephalon (it is attached to the diencephalon (part of the brain between cerebrum and brainstem) via a stalk
- Covered by pia mater
- CT septa (containing blood vessels) originate in the pia mater and penetrate the pineal gland
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Arterial supply is profuse. The posterior choroidal arteries are the main supply; they are a set of 10 branches that arise from the posterior cerebral artery
Venous drainage: via the internal cerebral veinsDescribe the structure of the pineal glandIt is covered by pia mater, which sends CT septa into the organ, dividing it into lobules
Two cell types:
1. Pinealocytes (95% of the cells)
- large, round cells with pale nuclei organized into cord-like clusters
- they are secretory cells and produce SEROTONIN and MELATONIN
- sympathetic nerve fibers form synapses on the pinealocytes (stimulate melatonin secretion during darkness)
2. Interstitial cells (less common)
- Modified astrocytes
- elongated cells with elongated nuclei
- supportive in functionWhere can Corpora Aranaceum (AKA brain sand) be foundPineal Gland!
- These are extracellular mineral deposits (calcium and magnesium salts)
- These calcareous concretions begin to form in childhood and increase with age
- Function unknown and the "brain sand" does NOT have an effect on pineal gland functionPancreas- Retroperitoneal organ
- Found within the epigastric, and left hypochondria regions (possibly umbilical)
- It traverses diagonally from the descending (second) duodenum all the way over to the spleen
Has 4 anatomical parts:
Head: lies against the second and third parts of the duodenum. Lower portion extending inferiorly from the head is the uncinate process
Neck: directly anterior to superior mesenteric artery and veins, and the portal vein
Body:
Tail: the tail of the pancreas extends into the splenorenal ligament which is associated with the spleenBlood supply of the pancreasArterial: branches from the splenic, superior and inferior pancreaticoduodenal arteries
Venous: from the body and tail join the splenic vein, and the pancreaticoduodenal veins drain into the superior mesenteric vein or portal veinThe pancreas is an accessory gland of the digestive system with both exocrine and endocrine function can you describe bothExocrine: production of digestive enzymes that are carried via the pancreatic duct to the duodenum
Endocrine: release of hormones that regulate carbohydrate metabolism, the endocrine portion is referred to as the islets of langerhans (l), and are scattered among the exocrine portion (secretory acini)
* its flimsy connective tissue capsule forms septa, which subdivide the gland into lobulesEndocrine Pancreas- Most islets of langerhands that comprise endocrine pancreas are too small to be seen by gross examination
- they vary greatly in size ~70% are in size range of 50-250 micrometers in diameter. Smaller islets are dispersed throughout the acinar lobules and most larger islets lie along the main and interlobular ducts of the pancreas
- Most islets are spherical or ellipsoid, but they can be irregular in shape
- In adult humans the number of islets is calculated to be 500,000-1 million. Islets comprise 1-2% of the pancreas
**** is a Serial section of one of these islets the following can be stained:
- Alpha cells: glucagon
- Beta cells: insulin (these are most present)
- Delta cells: somatostatin (these are fewest)Hypothalamus (a secondary endocrine gland)- part of the forebrain
- involved in many drives (ex. hunger and sex drives)
- important relay point between the "higher-brain" cortex and brainstem
- important in autonomic nervous system function
- has many nuclei with many specialized functionsThe true "master gland" of the body- for endocrine purposesHypothalamus
- it is a site of production of many "releasing" and "inhibiting" hormones that affect anterior pituitary gland function
- site of production of oxytocin and vasopressin/ADH, which will eventually be secreted in posterior pituitary
- controlled through feedback systems with modulation from neural and hormonal factorsName the Hypothalamic nuclei involved in endocrine function (produce hormones)- Paraventricular and supraoptic nuclei
- Preoptic area
- Arcuate nucleus
- Ventromedial nucleusWhat are the functions/ hormones produced from the Paraventricular and Supraoptic Nuceli of the Hypothalamus- Regulate water balance
- produce ADH and oxytocin
- destruction causes diabetes insipidus
- paraventricular nucleus projects to autonomic nuclei of brain stem and spinal cord
** Paraventricular: fluid balance (ADH), milk let-down (OXY), parturition, integration of autonomic and control of anterior pituitary
*** Supraoptic: fluid balance, milk let-down, parturition- mostly gives ADH and OXY.
Hormones produced:
- CRH
- TRH
- ADH
- OXY (major)What are the functions/ hormones released from the Preoptic area of the hypothalamus- Contains sexual dimorphic nucleus
- regulates release of gonadotropic hormones
** controls ovulation (LH and FSH) and sexual behavious (SDN) and some parental behavior in some organisms
Hormones:
- GnRH
- ADH
- OXY (minor)What are the functions/hormons released from the Arcuate Nucleus of the hypothalamus- produces hypothalamic releasing factors
- contains DOPA-ergic neurons that inhibit prolactin release
*** control of anterior pituitar- production of hypothalamic releasing and inhibiting factors
Hormones:
- GHRH
- GHIH (aka somatostatin)
- GnRH
- DA (dopamine)What are the functions/hormones released from the Ventromedial nucleus of the hypothalamus- Satiety center
- destruction results in obesity and savage behavior
** stimulation- decreased eating, lesion-obesity
Hormones:
- GHIH (aka somatostatin)The hypothalamus has 2 morphological and functional classes of neurons (I and II) that fall into 3 functional categoriesI. Magnocellular (big neurons)
1. These neurons (functional category) contain VASOPRESSIN and OXY. they project axons into the posterior pituitary (neural lobe) for hormone release
II. Parvicellular (small neurons)
2. A subset of neuron, the neuroendocrine-related functional group- they project into the median eminence (ME)- they secrete RELEASING and INHIBITING hormones into the hypohphyseal portal blood stream (long portal vessels) for control of anterior pituitary hormone secretion
3. A subset of parvicellular neurons of the PVN. They are involved in central autonomic control and are thus outside the normal scope of this moduleThe two classes of neurons of the hypothalamus that most DIRECTLY affect the endocrine system areParvicellular (paraventricular and medial basal) and Magnicellular (paraventricular and supraoptic) hypothalamic neurosecretory cells
Parvicellular:
- deliver their endocrine products to capillaries that drain into a portal system, one that runs specifically from hypothalamis capillary beds to anterior pituitary capillary beds
- then the pituitary cells respond to those hormones by secreting THEIR hormones into those capillaries which then go out through venous drainage to the rest of the body
Magnicellular:
- cell bodies are located within the hypothalamus but they DONT deliver their products to hypothalamic capillaries. Instead their axons proceed to the posterior pituitary where a different capillary bed is located. Into that different capillary bed the axon terminals of these secretory neurons will deliver their products, again to go out to the rest of the body
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Parvicelluar: paraventricular n. , preoptic n., arcuate n.
Magnicellular: paraventricular n. and supraoptic n.Which hormones are produced in the Pars Distalis (Denohypophysis or Anterior pituitary)- larger part of the pituitary gland1. growth hormone (GH)
2. prolactin (PRL)
3. luteinizing hormone (LH)
4. follicle stimulating hormone (FSH)
5. thyroid stimulating hormone (TSH)
6. adrenocorticotrophic hormone (ACTH)Which hormones are produced by the pars nervosa (neurohypophysis, or posterior pituitary)- smaller part of pituitary gland- Oxytocin and Vasopression (AVP or VP, aka ADH)Where is Melanocyte-stimulating hormone (MSH) thought the be released fromPars intermedia of the pituitary glandWhy is being referred to by ADH vs VasopressinEXACTLY the same hormone!
- ADH- typically talking about its renal effects
- Vasopression or arginine vasopression- cardiovascular effects for its vessel-squezzing effects
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1. Osmoreceptors detect increased osmotic pressure and Baroreceptors (in the aortic arch, carotid sinus) detect decresed blood pressure)
2. These circumstances stimulate the release of ADH from the posterior pituitary- this ADH can either act to
- vasoconstrict blood vessels (vasopressin)
- increase reabsorption of water in the kidneys (ADH)
3. either way both these lead to increased blood volume and increased blood pressureV1 vs V2 (vasopressin receptors)V1:
- smooth muscle contraction
- phospholipase C (PLC) stimualtes calcium mobilization
- associated with vasoconstriction, thus "vasopressin"
V2:
- water balance
- stimulates adenylyl cyclase and cAMP
- associated with water retention, thus "ADH"
** more sensitive to slightly elevated ADH levels than V1 is
- BOTH work to increase blood pressureMechanism of action of ADH- Acts at the distal tubules and collecting ducts of nephrons in the kidneys
- it increases the formation of cAMP via Gs proteins, adenyly cyclase
- increased cAMP in turn increases the aquaporin protein channels in the collecting duct of the nephron
- reabsoprtion of water through aquaporin channels (aquaporins needed due to the low permeability of water in the membranes) decreases urine volume and increase blood volume (ADH brinds water into the ECF but not sodium or chloride)
** on the side facing the waste products (the lumen), the number of aquaporin water channels that are located in the membrane is dependent on how much ADH is present in the blood, to bind to receptors in those cells. The more ADH there is, the more water is reabsorbed and the more blood volume goes up and urine volume goes down
** this is controlled by V2 receptors on basolateral membranes of these epithelial cellsDiabetes Insipidus- inability of the body to produce or release ADH
- inability of the kidney to respond to ADH
** either results in polyuria (excess production of urine)
- this urine is very hypotonic and typically contains no glucose
- if not countered with increased water intake, dehydration will occur
2 types:
Central: inability of body to produce or release ADH from the posterior pituitary
- Tumors
- Trauma
- Surgery
Nephrogenic: inability of the kidneys to respond to ADH (treatment is to correct the underlying renal disorder)
- Renal diseases
- ADH-unresponsive kidney
- Drugs (lithium)Syndrome of Inappropriate ADH secretion (SIADH)excess ADH from the posterior pituitary gland or from another source ex: Carcinoma mostly in the lungs (Small cell carcinoma) results in excess water retention by the kidneys
-- Initial immediate improvement: requires sharp restriction of daily water intakeAre tumor cells capable of secreting hormonesYES!
ex. Small cell carcinoma can lead to secretion of excess ADH leading to Syndrome of Inappropriate ADH secretion (SIADH)Oxytocinproduced in PVN (paraventricular nucleus)
- Target tissues: smooth muscle of uterus and mammary glands
- its receptors are GPCR-linked, utilizing PLC and calcium
- it stimulates MLCK and smooth muscle contraction
** mostly associated with partuition and labor, and milk letdown and secretion in nursing
- for lactation- suckling triggers afferent impulses (OXY binds to OTR to cause milk ejection "letdown")- milk is actively ejected through a neuroendocrine reflex
- labor and parturition in the utereus- dilation triggers afferent impulses (also a neuroendocrine reflex) (OXY binds to OTR to cause myometrial contractions)
** OTR= oxtytocin receptorsADH and oxytocin are released from theposterior pituitaryT or F: oxtytocin causes the breast to make milkFALSE!
prolactin doesThe junction between nervous and endocrine systemsAnterior Pituitary
1. Nervous tissue in the hypothalamus releases specific releasing and inhibiting hormones into a hypophyseal portal system
2. Specific cells in the anterior pituitary respond by secreting hormones that are often both tropic and trophic
- Tropic: any hormone whose target tissue is another gland. All of the hypothalamic releasing and inhibiting hormones and most of the anterior pituitary hormones are tropic hormones
- Trophic: any hormone which stimulates growth and differentiation of its target tissues. In clinical situations where the trophic hormone is not present, the target tissue will often experience apoptosis of its preexisting cells and that tissue will atrophy as those cells are not replaced
*** some hormones can be both (ex: TSH has another gland as its target (thyroid, so tropic) and can cause follicular tissue there to grow and differentiate (trophic)
** most of hypothalamic releasing hormones are tropic. Most are also trophic, such that without them most secretory cells in the anterior pituitary DO NOT function
3. Pituitary hromones then affect target organs throughout the body
4. Some of these target organs are glands, too
5. Ultimately body functions are controlledDominant pattern of secretion for hypothalamic and pituitary regions isPulsatile secretion
- a hormone with a short half-life is secreted, delivered, and metabolized on a time and quantity regulated fashion
ex. GnRH stimulates LH and FSH secretion which in turn stimulates gonadal sterioid secretion and gametogenesis
*** can be modified by an addition circadian release pattern for some of these hormones (ex. Cortisol secretion is pulsatile but maximum peak size is usually in the morning)
- modulation of existing pulsatile patterns make peaks "bigger" or "smaller" that are reflected in stronger or weaker effects at target cells
- in special circumstances, episodic release of hormones can also occur (ex. CRH secretion with severe acute stress)
* clearance of water-soluble hormones is typically quick (within a few minutes) and is accomplished by the hormones target cellsGnRH from hypothalamus stimulates release ofFSH and LH from the anterior pituitary
- Works on gonads to cause ovulation, estrogen, progesterone
- In males does spermatogenesis and testosterone
** trophic effectsGHRH from the hypothalamus stimulates the release ofGH (aka somatotropin) from the anterior pituitary which works on the
- liver and other cells to secrete IGFs (aka somatomedins)
- and other organs and tissues to increase protein synthesis metabolism of carbohydrates and lipids
*** GHIH (aka somatostatin, SST, SS, SRIH) from the hypothalamus has an inhibitory effect of GH in the anterior pitutary and inhibits these functionsTRH from the hypothalamus causes release ofTSH (aka thyrotropin) from the anterior pituitary
- works on the thyroid to secrete thyroxine (T4) and triiodothyroxine (T3)
** trophic effectCRH from the hypothalamus causes release ofACTH (aka corticotropin) from the anterior pituitary
- works on the adrenal cortex to release cortisol and androgenDopamine (DA) from the hypothalamus works on theAnterior pituitary to INHIBIT release of prolactin which usually causes growth and milk production, immune and osmo-regulation
** dopamine inhibits an otherwise constitutive release of prolactin by activation of the dopamine-2 receptor (this release is usually controlled by combination of small stimuli from many hormones)Growth Hormone and Prolactin areAcidophils
(body and breast are pink)FSH, LH, TSH, and ACTH areBasophilsCorticotroperegulation with CRH in the hypothalamus, secretes the tropic hormone ACTH acts on an MC2R (GPCR)
- target endocrine gland= zona fasciculata and zona reticularis of the adrenal cortex
** cortisol is the peripheral hormone involved in negative feedbackThyrotroperegulation with TRH in hypothalamus, secretes the tropic hormone TSH acts on the TSH receptor (GPCR)
- target endocrine gland= thyroid epithelium
** Triiodothyronine involved in negative feedbackGonadotroperegulation with GnRH, secretes FSH and LH acts on the FSH and LH receptors
- target endocrine gland (ovary- theca and granulosa, testes- leydig and sertoli cells)
** estrogen, progesterone, testosterone, and inhibin are involved in its negative feedbackSomatotroperegulation with GHRH (stimulatory) and Somatostatin (inhibitory) which secrete GH acts on GH receptor (JAK/STAT linked cytokine receptor)
- target endocrine gland (liver
- Negative feedback with IGF-I and GH (short loop)Lactotroperegulation with Dopamine (inhibitory) and PRL-releasing factor (Stimulatory) which secrete prolactin acts on prolactin receptor (JAK/STAT-linked cytokine receptor)
- NO endoncrine target organ- not part of an endorcine axis
- no negative feedback hormoneThe terms short loop and long loop are used fornegative (and occasional positive) feedback control of the hypothalamo-pituitary-peripheral gland axes
** reference point at which control conditions are measured it the part of the brain called the hypothalamus
ALL hypothalamo-pituitary-peripheral gland feedbak loops have their origin point hereultra-short feedback loopshypothalamic-released substances directly reduce further hypothalamic release of substances
- no known physiological ultra-short loopsshort feedback loops- anterior pituitary hormones provide negative feedback on the axis
- under physiological conditions only GH and Prolactin provide short-loop feedback
** others can do so under pathological condtions (ex. ACTH) - ACTH can provide this in Addisons Disease aka primary adrenal insufficiency
*** the hormone from the pituitary gland goes back and does negatice feedback on the hypothalamusMost common feeback loops in the H-P axis arelong-loop
- the output of peripheral gland provies negative (and on one occasion positive) feedback on the hypothalamus and/or pituitary gland.
- Estradial, testosterone, progesterone, IGF-1, cortisol, T3 and T4 provide this feedback
** hormone produced in peripheral gland goes back to hypothalamus so the regulated variable is the peripheral hormoneGive an example of pituitary hormones regulating the release of the hypothalamic releasing hormoneThis is Short loop negative feedback
ex. High levels of GH feeback on the hypothalamus to reduce the secretion of GHRHHypothalamo-pituitary adrenal axisLong loop negative feedback
- Cortisol from the peripheral gland (adrenal cortex) dominates the feedback process (stops its own production)
- in the gonads, it would primarily be testosterone and estrogen, the sex steroids, that would feed back upon their own production
** similarly the thyroid gland would secrete thyroid hormone, which would feed back upon the hypothalamus' action in a long loopHypothalamo-pituitary-ovarian axisPositive Feedback loop variant
* designed to drive a particular event- it is very RARE in physiology
ex. The positive feedback loop with estradiol that drives ovulation at one point in the womans ovarian cycle- some consequences of this process will eventually restore a more typical negative feedback
- rapidly increasing LH and FSH and estrogen levels - until some target cells in ovary begin to secrete progesterone, which separately restores negative feedback to this axis
* four of the 8 hypothalamo-pituitray gland loops involve the gonads- first three involve the ovaries, fourth involves the testes (no one human has all 4 of these axes present- no one human has both ovaries and testes)The Hypothalamo-pituitary ovarian axis, negative feedback variants:- ovary with the corpus luteum (yellow body) secretes progesterone, which exerts negative feedback late in the ovarian cycle, just as estradiol does for the early part of the ovarian cycle
* their negative feedback inhibits both GnRH and LH, FSH productionThe Hypothalamo-Pituitary-Testis Axis- looks like the two negative-feedback driven ovarian axes, because it operates the same way
* testosterone is the regulated hormone in the plasma of males
high amounts of testosterone will lead to a decrease in GnRH and LH & FSH
* gonadally produced testosterone always exerts long-loop negative feedbackThe hypothalamo-pituitary-thyroid axis- long-loop feedback
* two significant peripheral gland hormones that provide this feedback, the two variants of thyroid hormone (T4 and T3)
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Hypothalamus produces thyrotropin-releasing-hormone (TRH)
- anterior pituitary produces thyrotropin, aka TSH
- thyroid gland produces two varieties of Thyroid hormone (TH): thyroxine (T4) and triiodothyronine (T3)
*** the long-loop negative feedback is by TH (especially T3) on the hypothalamus and pituitary glandParvicellular hypothalamic-anterior pituitary systemDopamine (DA) producing neurons in the arcuate nucleus of the hypothalamus- regulation of pituitary prolactin (PRL) secretion from the anterior lobeProlactin (PRL)a protein hromone (~198 AA very large!) of the anterior pituitary gland that was originally names for its ability to promote lactation in response to the suckling stimulus of hungry young mammals
- it is not only synthesized in pituitary gland, but also in the CNS, immune system, the uterus, and even the mammary gland
- moreover, its biological actions are not limited solely to reproduction because it has been shown to control a variety of behaviors and even play a role in the homeostasis and immunregulation (immunostimulation)Prolactin (PRL) is under tonic _______ control of dopamine (DA)inhibitory
Dopamine goes up, PRL goes down
DA goes down, PRL goes up
** Tonic: state of continuous unremitting action
- this is not a muscle contraction, but it is a state of continuous, unremitting action of stopping the anterior pituitary from secreting too much prolactin
- in absence of DA frm hypothalamus, prolactin levels would rise to abnormally high values in plasma and produce pathological effects
*NOTE: many interacting hormons (TRH, OXY, VIP) have consititutive effects that stimulate the anterior pituitary to release PRL (Normal PRL is <20ng/mL)Unlike all other anterior pituitary hormones, prolactin typically hasconstitutive secretion (contant secretion unless inhibited) - Hypothalamo-Pituitary-Mammary axis-
- when PRL is high- short loop feedback happens
- dopamine secretion then goes up and then it reduces prolactin
* pathologically high levels of TRH have been shown to dramatically increase PRL secretion
* PRL also inhibits the gonads, to temporarily reduce fertility during breastfeeding
NOTE: prolactin only feeds back on the hypothalamus- it does not feed back directly on the pituitary lactotropesParvicellular hypothalamic-anterior pituitary system2 diff hormones produced in the hypothalamus:
- Growth hormone releasing hormone (GHRH): producing neurons in the arcuate nucleus of the hypothalamus- regulation of pituitary growth hormone (GH) secretion from the anterior lobe
- Somatostatin (GHIH, SST) is mainly produced by neuroendocrine neurons of both the arcuate and periventricular nuclei of the hypothalamus- inhibition of pituitary growth hormone (GH) secretion from the anterior loveGrowth Hormone (GH)- a protein hormone, very large (191 AA)
- produced and secreted by anterior pituitary Somatotrophs
- a major participant in control of several complex physiologic processes, including growth and metabolism
*** secretion peaks during puberty and then slowly declines during adulthood
GH and IGF1 increas in parallel during puberty, after puberty the levels begin to fall throughout adulthood and then decline somewhat rapidly after apprx age 60
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During adulthood, GH and IGF regulate and maintain body mass, and facilitate compensatory growth (ex. removal of kidney, increased cell division in the remaining kidney lets it grow until its total mass comes to apprx. the former mass of the two kidneys combined)
- thus for most of a persons life, growth hormones ability to help stimulate growth of long bones is secondary to its other effects promoting maintenance of what has already been producedThe secretion of GH changedthroughout the day (Pulsatile Secretion throughout the day)
- this pattern is modified by sudden need for energy as in strenuous exercise (episodic secretion) and is also highest near midnight and into the early monring (chronotropic control with circadian rhythm)
* in children, most of the actual growth takes place during sleep
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Stimulated by:
- hypoglycemia
- protein deficiency
- exercise
- trauma
- peaks during sleep
Normal levels of GH in adults: (in plasma) 1.6 to 3ng/ml
Child or adolescent: 6ng/ml
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So GH increases metabolism (glucose metabolism- it prevents there from being too little glucose) and increases growthHypothalamo-pituitary-liver axis for GH and IGFGH: exerts short-loop feedback being a pituitary hromone
IGF-1: exerts long loop feedback being a peripheral gland hormone
* both are negative feedback bc end result is restriction of GH secretion from the pituitary somatotropes
- by restricting hypothalamic GHRH you limit GH secretion
- by stimulating hypothalmic release of the inhibitory somatostatin you also inhibit GH secretion from pituitary gland
- if you directly inhibit somatotropes you limit GH secretion too
- hypothalmic NYP-secreting neuron also increases somatostatin secretion and is an access point for other forms of modulationFactors stimulating GH secretion- hypoglycemia
- decreased blood free fatty acids
- high levels of AA (used as substrates for protein productiona nd eventual growth)
- starvation, especially with severe protein deficiency
- stress, trauma, and/or excitement
- exercise
- testosterone, estrogen
- ghrelin (secreted when stomach is empty)
- deep sleep
- GHRHFactors inhibiting GH secretion- hyperglycemia (this stimulates insulin, a noraml person with transient hyperglycemia will be accompanied by a higher insulin that has been secreted to deal with the excess glucose and a reduction in GH that would otherwise help to keep blood glucose too high.
- increased blood free fatty acids
- aging
- obesity
- GH (exogenous)
- GHIH (somatostatin)
- somatomedins (IGFs)GH signal transduction occurson cell surface, not intracellular
- membrane-bound dimer
- it requires binding of GH at two sites
- receptor then dimerizes and activates cytoplasmic Janus kinases
- second messenger cascade from there involving ERK1/2 and STAT, increasing transcription of target genes
**JAK/STAT pathway
- translation results in production of many proteins assocaited with growth and metabolismGrowth hormone has important direct effects on protein, lipid, and carbohydrate metabolismFor carbs and lipids:
- generally works in the OPPOSITE direction as insulin, it causese INCREASES in plasma glucose and TAGs
For AA and overall growth
- it acts in the same direction as insulin, uptake of AA, increased protein synthesis and growth, and decreased protein catabolism
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so Insulin and GH workin in opp directions (insluin gets glucose out of the blood, GH gets it into blood) BUT once in the tissues they work similarly- both work to increase protein synthesisIn adipose tissue GHstimulates: lipolysis
Inhibits: glucose uptakeIn the liver GHstimulates
- protein synthesis
- gluconeogenesis
- IGF production, secretion
** unlike almost all other protein hormones, IGF is NOT stored in the liver
NOTE: IGF-1 and GH rise and fall almost at the same time in plasmaIn the muscle GHStimulates
- protein synthesis
- AA uptake
Inhibits:
- glucose uptake3 direct tissue-specific effects of GH1. decreases fat mass- puts it to work
2. increases glucose production and release at liver
3. increases protein synthesis in muscleGHs indirect effects are mediated primarily byInsulin like growth factor- I (IGF-I)
- it is secreted from the liver in response to GH
- a majority of growth promoting effects of GH are actually due to IGF-1
** like GH, IGF-1 has a dedicated transport protein (IGFBP-3) that extends its half-life to match that of GH
----
so IGFs also
Increase:
- Synthesis of protein, RNA, DNA, and cell size and number and organ size and organ function in the kidneys, prancreas, intestine, islets, parathyroids, skin, CT, bone, heart, lung
and also
Increase:
- AA uptake, protein, RNA, and DNA synthesis, collagen, chondroitin sulfate, cell size and number, and linear growth in chondrocytes
** unlike most other peptide hormones, almost all of the effects of IGF-1 are due to its ability to induce gene transcripiton and translation of gene products into working molecules in target cells, much as steroid would do
- many of the effects of IGF-1 tend to be "long-range" such as incresed cell size and number, increased collagen mass, etcIGF-1 has receptors that are much likeInsulins receptors
- many of its growth promoting effects also resemble insulin
BUT
- unlike insulin, IGF-1 does NOT significantly promote glucose uptake by muslce, adipose cells- at physiological levels
* another form of IGF, IGF-2 has less physiological activity in adults than does IGF-1 (but it appears to be more important than IGF-1 in fetal life)
* IGF-1 can bind to the insulin receptor but at 100 times less affinity than insulin, so it is functionally inactive through that receptors
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IGF Type 1 receptor:
- ACTIVE second messenger signaling
- receptor signaling: TYRK (tyrosine-kinase) phosphorylation, multiple pathways:
- SH2 (Src) pathway
- PI3K/PIP2 pathway
- SH2 pathwayIGF-1 effects in chondrocytesStimulates:
- AA uptake
- protein synthesis
- RNA synthesis
- DNA synthesis
- Collagen production
- Chondroitin sulfate
- Hyperplasia (increase cells)
- Hypertrophy (increase size)IGF-1 effects on the liverit has none!IGF-1 effects on muscleStimulates
- protein synthesis
- AA uptakeGH acts first on the liver, muscle, and adipose- then theIGFs bind to receptors on its target tissues throughout the body to regulate growth and maintenance
** IGF1 is apprx only 1/10th to 1/12th effective as insulin in lowering serum glucose, so most of actual glucose uptake required for skeletal muscle growth is probably being mediated by insulin directly, not IGF-1In a circumstance with high protein intake and high carbohydrate intakethe priority is growth enhancement
- GH, Insulin elevates, so are IGFs
- less energy to store
- protein synthesis and growth increasedIn a circumstance with high carbohydrate (CHO) intake and low protein:the priority is energy storage
- insulin is elevated, GH reduced
- more energy is stored
- little net effect on protein synthesis, growthIn a circumstance of fastingthe priority is energy mobilization
- insulin reduced (bc hypoglycemia), GH elevated, IGF reduced; modulation at level of liver
- protein synthesis and new growth is reducedLow CHO/High protein involvesglucagon for gluconeogenesisIn the absence of insulin,peripheral tissue glucose use decreases, thereby conserving glucose for essential tissues, such as the brainPrimary Hyperthyroidism- thyroid gland is overactive and does not respond approriately to TSH presence or absence
- T3 and/or T4 levels are too high
* one would expect undetectable levels of TSH in the plasma because feedback from the excess TH would reduce its secretion
ex. Graves disease, TSH receptors bound by an antibody that stimulates TH secretionSecondary Hyperthyroidism- the thyroid gland responds appropriately to an excessive quantity of TSH, again leading to too much TH
* one would expect high levels of BOTH TSH and TH in the plasma
ex. Anterior Pituitary TumorPrimary Hypothyroidism- thyroid gland is underactive, and does not respond appropriately to TSH presence or absence. TH levels are too low as a result
* one would expect high levels of TSH in the plasma because feedback from TH would be minimal
ex. reaction of thyroid following radioactive iodine therapy or resection
ex. chronic iodine deficiency in dietSecondary hypothyroidism- the thyroid gland is normal but there is little to no TSH coming from the pituitary, therefore TH levels are too low
ex. reaction of thyroid following pituitary resectionName 3 classes of hormonesAmino acid derived hormones
- catecholamines (ex. epinephrine, norepinephrine)
- serotonin
- thyroxine and triiodothyronine
Protein/peptide hormones
- insulin
- growth hormone
- vasopressin
Steroid and lipid derived hormones
- androgens (testosterone and DHEA)- (steroid derived)
- prostaglandins and leukotrienes (lipid derived)Hormones that are bound to binding proteins/carriers in the blood have- reduced activity
- increased half-life
(ex. Albumin- note when it is bound it is NOT active, only free fraction exerts an action)Unbound hormone aka Free Hormone is theactive form
- binds receptors as free
- cross into interstitium from vessels or into cells
- reduced half-lifeWhat values can be looked at when measuring blood concentration?- Total concentrations
- Bound concentrations
- Free concentrations
(ex. free levels of thyroid hormone T3 and T4 are found in much lower concentrations in the blood as compared to the bound forms)T or F: many hormones must be carried through the bloodTrue!Transthyretin transportsthyroxine in bloodGH binding protein (GHBP) transportsgrowth hormoneEx. of transport globulins that bind a hormone class for blood transport- Steroid hormones are transported on albumin or specific globulin transport proteins
- Transcortin binds progestins and glucocorticoids in bloodWhat do carrier proteins for plasma transport provide- protection from destruction in blood
- solubility in the blood
- limit release into tissues (increases half life in blood)
- increase hormone pool and evens out spikes in secretion
(ex. Transthyretin, GH binding protein (GHBP), albumin or specific globulin transport proteins, transcortin)What two amino acids allow for the production of hormonesTyrosine and Tryptophan
Tyrosine with help of BH4 becomes --> L-DOPA --> Dopamine (DA)--> Norepinephrine (NE) --> Epinephrine (EPI)
*** all these products have inhibitory effect on BH4
Tryptophan with help of BH4 becomes Serotonin (5-HT)--> Melatonin (MT)
** serotonin has inhibitory effect on BH4
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Deficiency in BH4 may be misdiagnosed as Phenylketonuria
- loss of any of the 3 enzymes that recylce BH4
- decreased levels of catecholamines and serotonin
- elevated levels of phenylalanine
- Suadi Arabia, Taiwan, China, and Turkey the major cause of elevated Phenylalanine is the BH4 deficiencySerotonin and Melatonin come from which AATryptophanSteroid hormones are usually derived fromCholesterol
using several enzymes (3beta-HSD, CYP450 and others) it can make:
- Progesterone which can become Aldosterone, Cortisol, and Testosterone
- Testosterone then goes on to become Estradiol (E2)
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Congenital Adrenal Hyperplasias (CAH)
- deficiency in cytochrome P450 enzymes or
- deficiency in 3beta-HSD (does not need cytochrome P450)Lipid derived/ Arachiodonic Acid derived hormones include theEicosanoids
- Phospholipids combined with DAG make--> Arachiodonic Acid or eicosatrienoic acid or eicosapentaenoic acid this can either directly become a Leukotriene (LTs) or Prostaglandin H
- Prostaglandin H then can become either Prostacylcin, Prostaglandin, ThromboxaneDescribe the maturation of insulinPre-proinsulin goes to the Endoplasmic reticulum where its peptide portion is cleaved to yield --> Proinsulin which then goes to the golgi where it is further cleaved into Insulin and the C-peptide
** C-peptide can be used as a marker for insulin levels
** NOTE: if you give a Type I Diabetic insulin- you will not see C-peptide, this is because these individuals are five insulin by itselfOxytocin is mature when the ___ removed leaving the amino groupGlycine
---Prepro-oxytocin has the amino portion cutt off, removal of the glycine from this portion yields oxytocin- The other portion of prepro-oxytocin that was left behind gave Neurophysin I, also the COOH portion yields Hid
- Neurophysin I is the transport protein for oxytocin (it is a monomer and carries 1 oxytocin)Vasopressin/ADH is mature when the ___ is removed leaving the amino groupglycine
-- Preprovasopressin has the amino portion cutt off, removal of glycine from this portion yields vasopressin- the other portion of the prevasopressin yields Neurophysin II, also the COOH portion yields glycoprotein which makes copeptin
- Neurophysin II is the transport protein for vasopressin/ADH
*** NOTE: it is different from the monomeric Neurophysin I which carries only one oxytocin. Neurophysin II dimerizes and it is able to carry 2 vasopressinACTH, MSH, and Beta-endorphin are all made fromProopiomelanocortin (POMC)
* ACTH can be split into alpha-MSH and CLIP
** an increase in ACTH, MSH, Beta-endorphin means there is an increase in propiomelanocortinAngiotensinogen is conveted to Angiotensin I viaRenin (from the kidney)Angiotensin I is converted to angiotensin II viaAngiotensin converting enzyme (from the lung)
** Angiotensin II does vasocontriction, increases blood pressue, remodeling of the heart especially in heart failureTherapeutic uses of pharmacology in endocrinology1. Hormone replacement therapy
2. Controlling inappropriate hormone secretion
3. Evoking or blocking the action of a hormone in order to achieve some desired metabolic effectFrom the endocrine system replacement therapies of peptides and protein hormones are- degraded in the GI tract (require parenteral administration
- rapidly metabolic (short half-life)
- primarily fast-acting via membrane receptorsFrom the endocrine system replacement therapies of steroids are- efficiently absorbed by any epithelial surface
- circulate bound to binding proteins
- longer half-life than peptides and proteins
- primarily regulate gene transcription via intracellular receptorsWhich drugs have agonist activity on growth hormone- Somatropin
- MecaserminWhich drugs have antagonist activity on growth hormone- Octreotide
- PegvisomantWhich drug acts on Prolactin- Bromocriptine (D2 dopamin agonist)Which drugs act on the posterior pitutary- Oxytocin
Vasopressin (AKA ADH):
- Desmopressin (agonist)
- Conivaptan (antagonist)Growth hormone (AKA Somatotropin) has 2 distinct effects which areDirect effects
(binding its receptor on target cells)
- fat cells (adipocytes) growth hormone receptors
- growth hormone stimulated them to break down TAG and supresses their ability to take up and accumulate circulating lipids
or
Indirect effects
(mediated primarily by a insulin-like growth factor I (IGF-I))
- secreted from the liver and other tissues in response to GH. A majority of the growth promoting effects of growth hormone is actually due to IGF-I acting on its target cellsTreatment for Growth hormone deficiency- Replacement therapy
- Historically, GH for therapeutic use was purified from human cadaver pituitaries (the drawbacks were limited quantities and it was linked to Creutzfeldt-Jakob disease)
- currently GH is produced by recombinant DNA technology
* Somatropin
- referes to multiple brand name GH preparations that match native GH
- net effect of somatropin is to increase linear growth (if epiphyses are open) and lean body mass
- therapu is continued until adequate height is attained, epiphyses close, or response stopsSomatropin- administered subcutaneously once daily (since it is a protein)
- ~70% bioavailable
- circulating half-life 20 minutes; biological half-life much longer
Indications for treatment/use:
- GH deficiency in children or adults
- genetic conditions associated with short stature (turner syndrome, noonan syndrome, prader-willi syndrome)
- chronic renal insufficiency
- children born small for gestational age
- children with idiopathic short stature
- AIDS associated wasting
- malabsorption associated with short bowel syndrome
* also used in anti-aging programs/athletic performance enhancement (this is band in most sports)
Contraindications:
- acute critical illness
- evidence of active malignancy
- proliferative or severe nonproliferative retinopathy
- unsupervised Prader-Willi Syndrome
Adverse Effects:
- Children: generally well tolerate. Rare side effects (intracranial hypertension, papilledema, visual changes, headache, nausea, vomiting, type 2 diabetes, slipped epiphysis, scoliosis)
- Adults: occur more frequently (peripheral edema, carpal tunnel syndrome, arthralgias, myalgias)
Drug Interactions (that may cause reduced effects)
- Estrogen
- GlucocorticoidsMecasermin- Recombinant human IGF-1
- 2nd product available in combination with its binding protein IGFBP-3 (prolongs half life)
Therapeutic uses:
- Used in Laron syndrome in which there is a lack of responsiveness to GH due to either a mutated GH receptor or development of antibodies to the GH receptor
- short stature is caused by IGF-1 deficiency despite high GH
- other- severe insulin resistance, muscular dystrophy, HIV releated adipose redistribution syndrome
Pharmacokinetics:
- subcutaneous injection
- nearly 100% bioavailable
- metabolized in kidney and liver
- bound to circulating proteins
- half life ~ 6 hours
Contraindications:
- close epiphysis
- active or suspected neoplasia (similar to GH)
Adverse effects:
- hypoglycemia (give with a snack)
- Lipohypertrophy
- others similar to GH
** pt's with severe hyperglycemia this can be a treatment for themTreatment of hypersecretion of growth hormonemay call for
- surgery or radiation (usually caused by pituitary tumor)
- drugs that inhibit GH secretion (Octreotide and Lanreotide)
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You cant somatostatin bc its half life is 1-3min (would need a continuous infusion) so you use
- Octreotide: short acting subcutanous, long acting intramuscular
- Lanreotide: long acting deep subcutaneousSomatostatin AnalogsSomatostatin was named for its effect of inhibiting secretion of GH from the pituitary gland
- 5 stomatostatin receptors have been identified and characterized. Each of the receptors activates distinct signaling mechanisms within cells
- In addition to the hypothalamus, somatostatin is also produced by D cells of the pancreatic islets, the GI mucosa, and the C cells of the thyroid
- In addition to its potent inhibitory effect on GH secretion, somatostatin also has important inhibitory influences on many other hormones, including:
- insulin
- glucagon
- gastrin
- secretin
- VIP
- TSH
- Pro- and adverse- effects may occur via interaction with somatostatin receptors at these sites
Therapeutic Uses:
- GH over-activity
- Symptomatic treatment of metastatic carcinoid tumors
- Adenomas secreting vasoactive intestinal peptide (VIP)
- Thyrotrope adenomas that over secrete TSH
- bleeding esophageal varices (exact mechanism is unclear)
- perioperative prophylaxis in pancreatic surgery
- modified forms radiolabeled for diagnostic uses or targeted destruction of tumors
Adverse Effects
- GI (50%), Gallstones (25%)
- Bradycardia, QT prolongation
- Hypothyroid, Hypoglycemia, HyperglcyemiaPegvisomant (GH antagonist)- Binds to GH receptors, but DOES NOT activate JAK-STAT signaling or stimulate IGF-1 secretion
- Approved for the treatment of acromegaly when Octreotide and other Somatostatin analogs are not able to fully control the disease***
- Do NOT use if unexplained elevation hepatic transaminases
- Side effects similar to somatostatin analogs and lipohypertrophy
- Concern for GH secreting adenomas- monitor pituitary MRIDopamine is an agonist at its receptorsD1 and D2
- in the pituitary, activation of D2 receptors by dopamine agonists DECREASES prolactin releaseA DA (dopamina) antagonist willblock the effect of DA thus may increase prolactin secretion
- Hyperprolactinemia consequences include: gynecomastia, inappropriate lactation, infertility in both males and females
** Hyperprolactinemia can be treated with the prototype dopamine agonist-- BROMOCRIPTINE (a semi-synthetic ergot alkaloid whose selectivity for D2 is > than D1) and also Cabergoline (which is preferred)
** remember D2 receptors when activated by a DA agonists decrease prolactin release
Bromocriptine is:
- well-absorbed
- extensive 1st pass metabolism through the liver (7% reaches circulation)
- half life 2-8 hrs
- it normalizes prolactin in 70-80%; decreases tumor size in 50%
Adverse effects of the drug: nause, vomiting, headache, postural hypotension, nasal congestion, CNS effects
- start low and tirate- this leads to tolerance over time
Other uses:
- Parkinsons disease, uncontrolled Type 2 diabetesPreferred drug treatment for hyperprolactinemiaCabergoline (dopamine receptor agonist)
- higher affinity and greater selectivity for D2 receptor (just like Bromocriptine)
- has greater efficacy and fewer side effects
- it is well absorbed with extensive 1st pass metabolism through liver
- half life 63-69 hrs (once a day dosing is sufficient)
- normalizes prolactin in 80%, decreases tumor size in significant number
Adverse effects:
- nausea, vomiting, headache, postural hypotension, dizziness
- start low and titrate- tolerance over time
Other uses:
- use in Parkinsons Disease (like Bromocriptine)
*** NOTE: Bromocriptine was in addition used to treat uncontrolled Type 2 diabetes, Cabergoline is NOTDrug-induced hyperprolactinemiaAn adverse effect of a variety of drugs that are D2 antagonists
- Antipsychotics (ex. Haloperidol)
- Metoclopramide (D2 antagonist targeted at CTZ and gastric emptying)
* Primary clinical symptom of this adverse effect is gynecomastia and/or galactorrheaOxytocin and Vasopressin (ADH) from the posterior pituitary areCyclic nonapeptides that differe by 2 amino acids at the 3 and 8 position (Ile-->Phe and Leu--> Arg)
- they need to be parenterally administered for indications requiring careful dosing
- can be administered intranasally for less critical conditionsSites of action of OxytocinUterus (stimulates frequency and force of contractions)
- highly dependent on estrogen
- 8 fold increase in sensitivity to oxytocin in last half of pregnancy
- 30 fold increase in receptor sites
- antagonized by progesterone
Breast (role in milk ejection)
- secretion stimulated by suckling or mechanical stimulation
- contraction of myoepithelium pushing milk from alveolar channels to collecting sinuses
Brain (animal studies implicate role in trust, social bonding)
- being investigated for social phobies and autism
- "cuddle" or "love" hormoneTherapeutic uses of Oxytocin- Induction of labor
- Augmentation of labor
- Prevent postpartum hemorrhage
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it is IV administered or IM administered
- half life is 1-15 minutes (needs continuous infusion)
- urine excretion
Adverse effects:
- uterine hyperstimulation, hypotension, reflex tachycardia, uterine rupture, compormised fetal oxygenation, trauma to mother or fetus (passage through incomplete dilated cervix)Difference between the two main Vasopressin (ADH) receptorsV1 (on arteriolar smooth muscles)
- mediate the pressor effect of vasopressin through IP3/DAG- calcium as a second messenger system
V2 (on basolateral membrane of cells in the distal and collecting duct)
- antidiuretic effects are mediated by increase in cAMP
* extrarenal V2 receptors mediate the release of coagulation factors- VIIIc and Von Willebrand FactorPrimary hormone regulating body fluid osmolalityVasopressin: antidiuretic hormone (ADH)
- its release from the posterior pituitary is stimulated by: increased plasma osmolality and hypovolemia or hypotension
Actions:
- In the renal collecting duct, it increases the permeability of the cell membrane to water
- it is a potent vasopressor/vasconstrictor
- As a neurotransmitter it plays a role in secretion of ACTH, CV (cardiovascular) system regulation, body temperature, other visceral functions
- Promotes release of coagulation factors
- increases platelet aggregation
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Therapeutic Uses (V1 receptor mediated)
- post-operative ileus
- bleeding esophageal varicies
- vasodilatory shock
- post cardiac arrest
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Pharmocokinetics:
- not absorbed orally
- IV onset: within 15 minutes (needs continous infusion)
- half-life: 10-20 minutes
- metabolism: hepatic and renal (minor)
Adverse effects:
- facial pallor, nausea, belching, cramps, arrhythmia, reduced CO, peripheral ischemia
- water intoxication
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Therapeutic uses (V2 receptor mediated):
- central Diabetes Insipidus
- bleeding disorders
- primary nocturnal enuresis
- post lumbar puncture headache
this one can be
onset: oral (1hr), nasal (15-30min), SL (30min)
half-life: 2-4hrs (duration of action 6-14 hrs)
elimination: renal
Adverse effects:
- water intoxication, hyponatremiaSynthetic analog of VasopressinDesmopressin (DDAVP
- change at AAs 1 and 8
- 3000x antidiuretic/vasopressor ratio compared to vasopressin
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- can be given orally (<1% bioavailability)
- intranasally (3-4% bioavailability)
- parenterallyCentral vs Nephrogenic Diabetes InsipidusCentral: inadequate vasopressin secretion
Causes:
- injury, surgery, trauma to head in regio of pituitary or hypothalamus
- tumor
- cerebral aneurysms
- CNS ischemia
- brain infection (i.e encephalitis)
- familial (autosomal dominant)
- idiopathic
Treatment:
- Desmopression (variety of dosing options, the dose is individualised to response)
- fluid restriction
Nephrogenic: insufficient renal response to vasopressin (we wont be tested on details of this at the moment)
** to distinguish these from eachother give the pt. Desmopressin (if desmopressin works pt ahas central)
Both:
- impaired renal water conservation
- excrete large volumes (>30ml/kg/day) of dilute (<200mOsm/kg) urine: polydipsia
** you can distinguish Diabetes Insipidus from Primary polydipsia through measuring the plasma osmolalityVasopressin AntagonistsConivaptan and Tolvaptan
Conivaptan
- nonselective V1a/V2 antagonist
- intravenous
- half-life 5-12h, metabolized in liver, eliminated in kidney
Tolvaptan:
- selective V2 antagonist
- oral
- half life 3-12 hrs, 1% excreted by kidney
Adverse effects seen in both:
- osmotic demyelination syndrom
- polyuria, dehydration, hypotension, thirst, dry mouth, GI
- In tolvaptan use an adverse effect could be liver damage
Therapeutic effects
- SIADH (syndrome of inappropriate ADH)
- Congestive heart failure
- Cirrhosis
- Nephrosis
- Low or normal arterial blood volume with concomitant hyponatremia (euvolemic hyponatremia and hypovolemic hyponatriemia)Requirements of the body in terms of maintenance of blood glucose- sufficient circulating glucose
- resting glucose: near 4-5mM (less than 100mmg/dl)
- after eating: ~10mM (less than 200mg/dl)
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Hypoglycemia (serious condition) the body will consider this as a stress response
normal fasting glucose: 70-99mg/dL or 3.9-5.5mM
normal glucose 2 hr postprandial: <140mg/dL 7.8mM
* this leads to increased production of both GH and cortisol
A major role of cortisol= stimulation of gluconeogenesis to supply blood glucose from production in the liver
- breakdown of protein for gluconeogenic precursors
- stimulation of synthesis of gluconeogenic enzymes
* reduced insulin and increasing Glucagon, NE, and E are normal responses to fasting
* Hypoglycemia produces more acute rises in cortisol and epinephrineIn presence of low blood glucose, cortisol stimulatesgluconeogenesisIn presence of low blood glucose, both NE, E, and Glucagon induceglycogenolysis
- BUT glucagon ALSO does gluconeogenesisthe body requires a continuous supply of glucose because of thebrain and RBCsUpon depletion of dietary glucosemobilization of liver glycogen occurs (you only have a 24hr supply of this liver glycogen (will be depleted after 1 day)- Glycogen breakdown supplies glucose initially- peaks delivery around 4hrs into fasting, then declines slowly- the cross overpoint for source of glucose switching from mostly glycogen to mostly gluconeogenesis is about 16hrs)
- lipolysis is activated (free fatty acids become the major energy source for skeletal m., liver, adipose tissue, cardiac muscle, as well as other tissues- increase steadily as glucose drops)-
- Gluconeogenesis increases slowly after the absorptive period (peaks after a day, then decreases in starvation)
- Protein degradation contributes to gluconeogenis and ketogenic precursors
- then Ketogeneiss sets in after several days
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Similar thing listed in stesp:
1. After postprandial glucose is absorbed, liver glycogen stores supply glucose to the baseline level (4-5mM)
2. Gluconeogenesis begins to contribute but increases slowly in its contribution
3. At about 16 hrs after a meal, gluconeogenesis becomes more important than liver glycogen stores
4. At 24 hrs, liver glycogen stores are exhausted and body becomes reliat on gluconeogenesis for all glucose
5. After a day of fasting (starvation), ketone bodies begin to rise in circulation. These increase and level off after 3 days
6. Ketone bodies a produced in the liver from fat beta-oxidation and the Ac-CoA being produced
7. Ketone bodies reduce the reliance of the brain on glucose (the brain can utilize ketone bodies). This effect slows protein breakdown (protein sparing phenomenon)Insulin responds toincrease glucose after a meal (its is secreted from the beta cells of the pancreas)
its effects:
- promotes glucose use, particulary in skeletal muscle and adipose tissue
- upregulates GLUT4 in skeletal muscle and adipose
- promotes general anabolism
- activates LPL in adipose tissue
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In fasting state: both insulin and BG levels decline, and glucagon increasesCarbohydrate metabolism- Fed State- High circulating glucose, signals high insulin
- Insulin promotes general glucose utilization, glycogen synthesis, and general anabolism
- Excess energy can aslo be stored as fat in adipose tissue
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Increased glucose from digestion is delivered from the intestinces through the portal circulation to the liver (the liver buffers the amount of glucose going into the circulation
- excess glucose in liver: stored as glycogen or converted to fat an exported as VLDL to adipose tissue
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High circulating glucose enters pancreatic beta-cells and signals insulin secretion (insulin is secreted in response to high glucose)
* insulin signals liver, skeletal m., adipose tissue and other organs to
- use glucose as the principal energy source (increase uptake of glucose, turn on glycolysis)
- store fat in adipose tissue
- store glucose as glycogen in muscle
- general anabolic signaling
* circulating glucose in the blood is stored as glycogen in muscle and converted to fatty acids and stored as TAG in adipose and liverStandard metabolic pathway for energy production in the fed state- Glycolysis: transformation of glucose --> pyruvate; generates small amoutn of energy quickly (includes galactose and fructoes catabolism)
- TCA cycle: breakdown of acetyl to CO2 with production of reducing equivalents (NADH and CoQH2
- Oxidative phosphorylation: electron transport. Converts high energy electrons (reducing power) to ATP and makes water from oxygen
** Also in the Fed states Carbohydrate can be used in:
1. Glycogenesis (major stores: liver and muscle. Many other cells store glycogen to a small extent)
2. Fat synthesis (in the liver, principally). A bit is stored locally, but most is sent to VLDL, which is secreted to circulation and delivers fat to peripheral tissues. In fed state, this is delivered mostly to adipose tissueIn Carbohydrate metabolism during the fasted state- there are low glucose signals which cause insulin to drop and glucagon to increase (also epi/norepi increase)
- liver glycogenolysis is promoted to provide circulating glucose for blood and brain
More slowly: there is also fatty acid release from adipose and gluconeogenesis
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In fasting
Glycolysis becomes down regulated and fatty acids become the main source of energy (exceptions= brain and RBC which req. glucose)
- The liver supplies glucose to glucose-requiring organs (brain and RBCs)- there are 2 sources of glucose:
1. Glycogenolysis: glycogen breakdown to form glucose
2. Gluconeogenesis
- early in the fast, liver begins to break down its glycogen stored to keep blood glucose sufficiently high to support brain and erythrocyte function
* since muscle lacks the enzyme glucose-6-phosphatase, muscle glycogen stores cant be used to supply glucose to any other organGlycogen mobilization in the liver vs muscleMuscle: glycogen for internal use only (exercise)
** remember muscle lacks the enzyme glucose-6-phosphatase so it can not supply any other organ
Liver: glycogen is converted to circulating glucose
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In initial fasting: liver will break down glycogen to supply circulating glucose
Signaling for the breakdown of glycogen:
- Liver: glucagon in the liver; epinephrine can also signal- BOTH go through cAMP/PKA
- Muscle: Epinephrine signals glycogen breakdown. Also exercise via calcium or low ATP will signal glycogen breakdown
* glucose is NOT sent to circulation in muscls, but used directly by muscleCarbohydrate Metabolism during extended fast (early starvation 4-24hr) - increased glucagon/ epi/norepi- glycogenolysis- slows as liver glycogen stores are depleted
- gluconeogenesis (glucose during fasting is made in the liver and the kidney)- precursors are alanine and glutamine from protein breakdown, lactate from anaerobic metabolism, and glycerol from trigyceride lipolysis (glycerol, alanine, glutamine, and lactate are precursors)
- FA oxidation
- Proteolysis (occurs to support gluconeogenesis)
* Fat feeds the body during fasting- the action of epi/norepi on adipose releases free fatty acids. Many tissues use fat as the main energy source, including skeletal muscle. Some FFA are converted to VLDLGluconeogenesisIn the fasting state
Purpose: to maintain circulating glucose conc. and prevent hypoglycemia during extended fasting (>4hr)
occurs in: liver and kidney
- synthesizes glucose for export to the circulation
- hormone status: insulin is low, glucagon is high. Cortisol, epinephrine, and norepinephrine may also be high
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During extended fasting (early starvation), insulin drops to low levels and glucagon continues to increase. Glucagon stimulated glycogen breakdown to supply circulating glucose, and with extended fasting, will then also induce gluconeogenesis- the synthesis of glucose from precursors
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Pyruvate is considered start point in this process, it cant be directly revered to PEP so it goes through 2 other reactions:
- conversion to oxaloacetate --> phosphoenolpyruvate
(OAA is a TCA cycle intermediate and allows TCA cycle to feed into gluconeogenesis)
- from PEP glycolysis is revered till Fructose 1,6-bisphosphatem where a separate enzyme is required to convert it to F6P
- the reversal results in G-6P. Another gluconeogenic enzyme, glucose phosphatase is req. to convert G6-phosphate to glucoseT or F: fatty acid degradation supports gluconeogenesisFALSE
it does not , niether does Acetyl-CoA
* neither fatty acids nor acetyl-CoA acts as a gluconeogenic precursor
* this is a major principle of metabolism and dictates much of the metabolic logic in starvation and diabetesDuring carbohydrate metabolism, glucose enters the cell viaspecific transporters
- Hexokinase or Glucokinase catalyzes phosphorylation of Glucose --> G6P (this phosphorylation traps it into the cell)
* to increase the uptake of glucose and its storage as glycogen and fat, muscle and adipose tissue express an insulin-responsive glucose transporter (GLUT4) in addition to GLUT1, which dramatically increases glucose uptake in the presence of insuliin
* in these tissues, glucose transport is typically the rate limiting step in glucose entry
* Beta-cells of the pancrease release insulin to signal the presence of glucose in the blood
- in skeletal and cardiac muscle and adipose tisse: insulin induces the transport of GLUT4 from the endosome to the plasma membrane- this increases the uptake of glucose, and GLUT1 provides basal uptake
NOTE: When insulin levels decrease, glucose transporters move from cell membrane to the intracellular storade pool, where they can be recycled
- vesicles fuse to form an organelle called the endosomeDescribe insulin receptor action1. insulin binds insulin receptor
2. this recruits insulin receptor substrate 1 (IRS-1)
3. IRS-1 activates PI3-kinase, which then phosphorylates PIP2 to PIP3
4. PIP3 binds PKB aand phosphoinositide-dependent kinase 1 (PDK1) resulting in phosphorylation of PKB, and its activation
5. PKB phosphorylates TBC1D4, permitting rab activation on vesicles, and vesicle fusion with the plasma membraneThe different GLUT transporters and their KmsGLUT1 is the default transporter in most tissues, including skeletal muscle (it is NOT in the liver, kidney, intestines or beta-cells) - has medium Km
GLUT2 has a HIGH Km wrt the physiological blood glucose concentration- the higher the glucose the faster it enters into cells, good for organs that need glucose to import to increase upon feeding (liver, kidney, intestine). Thus, transport is responsive to changes in glucose concentration - in these tissues, the glucose entry is NOT rate limiting, rather glucokinase activity is the rate limiting step in committing glucose to the cell
GLUT3 has a LOW Km - higher or lower glucose will NOT have a large effect on how much glucose enters the cells. The brain which relies on glucose, then maintains a reasonable supply even at lower randes of blood because the GLUT3 transporter is low Km
GLUT4 transport has a medium Km (like GLUT1)- this is the INSULIN SENSITIVE transporter, works in adipose tissue and muscle - this is the principal means of hormone regulated glucose utilization
** in tissues with GLUT1/GLUT4, typically glucose entry is the rate limiting step in glucose metabolismGlucokinase vs. HexokinaseGlucokinase- in liver, pancreas (high Km- simialar to Km of GLUT2 )
Its regulation:
- induced by insulin (higher expression levels)
- cooperative response to glucose (sharper transition point with changes in concentration)
- mobilized from nuclear sequestration by glucose (sequestered in nucleus during fasting state)
Hexokinase- in muscle and most other tissues (low Km)
* regulated step- strongly favorable
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Hexokinase commits glucose to the cell in many tissues, however:
1. In liver, G6P can be reversed to glucose by glucose-6-phosphatase to export glucose, or G6P can be diverted to glycogen storage
2. In skeletal muscle, G6P can be diverted to glycogen storage, for entry into glycolysis at a later time
3. Most other tissues neither export glucose, nor store much glycogen (most store a little), so hexokinase largely determines entry into glycolysisGlycogenesisGlycogen storage that occurs in
- Mostly liver and muscle
- smaller amounts in other tissues (like RBCs)
Liver glycogen: for maintaining circulating glucose
Muscle glycogen: for energy during exercise
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Main points:
1. Protein called Glycogenin (which is part of glycogen)
- it carries out the initial two glucose additions
2. Glycogen synthase does elongation of the glucose chain with alpha 1,4-linkages
3. Branching enzyme adds branch points as needed using alpha 1,6 linkages
Steps:
- G6P converted to G1P by phosphoglucomutase
- G1P converted to Uridine-Diphosphate-Glucose (UDP-glucose)
- Glycogenin catalyzes addition of 2 glucoses to itself on a tyrosine, using UDP-glucose as the substrate
- Glycogen synthase catalyzes chain lengthening of alpha (1-4) glycosidic linkages using UDP-glucose as a substrate
- Branching enzyme moves a chain to make alpha (1-6) glycosidic linkages and generates a branch pointDeficiency in Glycogen Synthase leads toGlycogen Storage Disorder 0
- characterized by fasting hypoglycemia and postprandial hyperglycemia and gluoseuriaDeficiencies in glycogen branching enzyme that generates the alpha (1-6) glycosidic bonds can lead toAndersen DiseaseDeficiency in the liver enzyme (in glycogen metabolism) leads tohepatosplenomegaly, eventual cirrhosis and cardiac problems
- found in infancy, very rareGlycogenolysisIn fasting state: (insulin dropping, glucagon rising)
- maintains circulating glucose concentrations and prevents hypoglycemia during short to intermedia-term fasting (2-4hr plus)
- it releases glucose for export to the circulation
- insulin is low, glucagon is high. Cortisol, epinephrine and norepinephrine may also be high
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Glycogen phosphorylase: cleaves the 1,4-glycosidic bond of the linear portions of the glycogen chain from the non-reducing ends yielding glucose-1-phosphate
Glycogen debranching enzyme: processes the branch points through a seires of transfers of glycosidic bonds between shortened branches- the branch point itself (1-6) is hydrolyzed to glucose rather than glucose-1-phosphate by the debranching enzymeMcArdle SyndromeDeficiency in glycogen phosphorylase (affects glycogenolysis)
- these pts have temporary weakness after exercise and accumulation of glycogen in muscle. It is chronic and relatively benign.Pompe Diseaseabsence of lysosomal enzyme that hydrolyzes the glycosidic bonds to glucose (not G1P) called alpha (1-4) glucosidase. When this enzyme is defective, glycogen accumulates in vacuoles in the lysosome - associated with massive cardiomegaly and often leads to early death from heart failure
* this is a defect in glycogenolysisCori disease (aka Glycogen storage disease III)due to a defect in the debranching enzyme in glycogenolysis
- this can include the 4:4 transferase activity, or the glucosidase activity, or both. It can affect liver or muscle- the liver type can result in fasting hypoglycemia and glycogen with abnormal structure
* leads to fasting hypoglycemiaAfter glycogen phosphorylase adds the phosphate to the 1-position of glucose (where cleavage occurs)- this phosphate has to be moved to the 6-position to continue glycolysis. What enzyme carries out this reactionPhosphoglucose Mutase
* we recover a high energy phosphate bond that was lost during glycogen synthesis- this is why addition of glucose only costs 1 ATP equivalent
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Phosphoglucomutase converts G1P to G6P- G6P is hydrolyzed to glucose Glc in liver by glucose-6-phosphatase (not in muscle, only gluconeogenic organs have G6Pase- liver and kidney )
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Glucose 6-phosphatase is located in the ER (it is transported to the ER and glucose is transported back out)- it is principally reg. by its Km for G6P (higher than the typical G6P conc. in the fed state
- during gluconeogenesis and glycogenolysis, G6P conc. rise and then enzyme can function on the higher conc. of substrate
- expression is increase moderately by cAMP and also by cortisol
- starvation increases expressionVon Gierke Disease (aka Glycogen storage disease I)Deficiency in glucose-6-phosphatase
- results in severe fastin hypoglycemia
- there are two types resulting from deficiencies in the phosphatase (Type Ia) or in the translocase T1 (Type Ib)Regulation of glycogen metabolism in muscleGlycogen phosphorylase is
- Inhibited by G6P and ATP
- Activated by Ca2+ and AMP (important in muscles bc there may be more immediate needs for glycogen reserves during muscle contraction)
*Particularly important for muscle: AMP allosteric activator and Ca2+ through effects on calmodulin-dependent phosphorylase kinase- via neuronal stimulation of muscle activity
Glycogen synthase is activated by G6PRegulation of glycogen metabolism in the liverNO AMP regulation unlike in muscle
Glycogen phosphorylase:
- inhibited by G6P, ATP and glucose
- activated by Ca2+
** liver phosphorylase is also Ca2+ activated for "fight or flight" by epinephrine/ alpha-adrenergic mediated Ca2+ release by activating phosphorylase kinase
Glycogen synthase:
- activated by G6PRegulation of glycogenolysis by phosphorylation- Glucagon in the liver and epinephrine in the muscle and liver activate glycogenolysis by phosphorylating and activating phosphorylase through cAMP-dependent signaling pathway
- this strongly activates glycogeneolyiss and the production of Glucose-1-P
** in fed state, insulin activates protein phosphatase 1, which dephosphorylates and inactivates there enzymes
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- Ca2+ can also bind to calmodulin subunitof phosphorylase kinase, activating it without phosphorylation- can then activate glycogen phosphorylase, causing glycogen degradation
- Under extreme conditions of anoxia and depletion of ATP, AMP activates glycogen phosphorylase B without it being phosphorylatedGlycogen synthase should only be active withsurplus glucose and generally anabolic conditions
it is activated by Insulin
1. insulin activation of protein phosphatase 1, leading to dephosphorylation of glycogen synthase
2. insulin activates PKB (Akt) which then phosphorylates glycogen synthase kinase rendering it inactive - inactive GSK prevents phosphorylation of glycogen synthase by GSK, leaving glycogen synthase active
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inhibited by glucagon in the liver- via cAMP/PKA cascade to phosphorylate and inactivate glycogen synthase
inhibited by epinephrine via beta-adrenergic receptors-via cAMP/PKA cascade in liver and in muscleGlycogen Synthase KinasePhosphorylates glycogen synthase and inactivates it to glycogen synthase b
- GSK is inactivated by insulin via Akt (Protein Kinase B)- thus, insulin prevents glycogen synthase phosphorylation by GSK and renders glycogen synthase activeRegulation of glycogenesis by hormonesInsulin activates Phosphatase-1 (reverses phosphorylation by glucagon/cAMP/PKA pathway)
- reversal/dephosphorylation of these pathways leads to:
- inactivation of phosphorylase kinase and glycogen phosphorylase
- ACTIVATION of glycogen synthase (is activated via dephosphorylation)
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Insulin counteracts glucagon or epinephrine beta-adrenergic signaling by increasing cAMP degradation -therby blocking PKA and the following effects
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Glucagon phosphorylates via cAMP/PKA
- this activates phosphorylase kinase
- inactivates glycogen synthase
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Epinephrine aslo phosphorylates via beta-adrenergic/cAMP/PKA effects
- can induce Ca2+ release in the liver which also activates phosphorylase kinaseZona glomerulosa (ZG) of the Adrenal (suprarenal) gland secretesMineralcorticoids- aldosteroneZone fasciculata (ZF) of the adrenal (suprarenal) gland secretesGlucocorticoids- cortisolZona reticularis (ZR) of the adrenal (suprarenal) gland secretessex steroids- androgens, mainly dehydroepiandrosterone (DHEA)Medulla of the Adrenal (suprarenal) gland secretescatecholamines (mostly epinephrine (epi), some norepinephrine (NE))List and describe the three groups of adrenal steroids1. Mineralcorticoids
- Prototype: aldosterone
- produced in Zona Glomerulosa
- Needs 21-Hydroxylase (ZG/ZF) and aldosterone synthase (ZG only)
- Function: increase salt and water retention, mostly through renal action
2. Glucocorticoids
- Prototype: Cortisol (aka Hydrocortisone)
- produced in Zona Fasciculata (minor production from ZG)
- Needs 21-Hydroxylase (ZG/ZF) and 17 alpha hydroxylase (ZF/ZR)
- Function: many ex. Increase energy mobilization from all sources including proteins, and anti-inflammatory effects
3. Adrenal Androgens
- Prototypes: DHEA, Androstenedione
- Produced in Zona Reticularis
- Needs 17-alpha hydroxylase (ZF/ZR) and 17,20 lyase, (ZR only)
- Weak androgenic effects, precursor to gonadal androgens and estrogensWhich has a longer half-life cortisol or aldosteroneCortisols half-life is greater than that of aldosterone
* cortisol remains in the plasma for a longer time than aldosterone
- on avg, cortisol is produced at a secretion rate 100x greater than that of aldosterone and its concentration in the plasma is 2000x greater than that of aldosterone
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cortisol is a glucocorticoid from ZF
aldosterone is a mineralcorticoid from ZG
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Aldosterone lacks a specific binding protein of its own to transport it through the blood, so generally speaking as it is secreted it is bound loosely to albumin, is delivered to its target tissue, and is rapidly metabolized thereafter. In contrast, cortisol binds tightly to a cortisol-binding globulin, so it takes longer for any of its molecules to be released. If one stores a higher number of molecules (ex. Higher concentration), then even the small fraction released at any time is enough for the bodys needs. So the binding protein is what makes the differenceThe adrenal androgen DHEA, whose direct effect is weak, is mostly foundsulfated in the plasma as DHEA-S, at concentrations over ten times greater than cortisol
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DHEA is an adrenal androgen from ZR (has highest secretion of all)
Cortisol is a glucocorticoid from ZF
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DHEA does not have a specific binding protein but unlike aldosterone it also has very few target tissues, and it serves as a source of precursors to the synthesis of more potent androgens and estrogens by the gonadsMineralcorticoids includeAldosterone (from ZG)Glucocorticoids includeCorticosterone (from ZG)
Cortisol (from ZF)Adrenal androgens includeDehydroepiandrosterone
Androstenedione
Dehydroepiandrosterone Sulfate (DHEA-S)
ALL made from the ZRT or F: In the ZG and the ZF, the same enzyme converts a precursor into a glucocorticoidTrue!
- Corticosterone (in ZG)
** in ZG it takes one more enzyme to go beyond the glucocorticoid step into the mineralcorticoid aldosterone
- Cortisol (in ZF)T or F: so many glucocorticoids and mineracorticoids are produced in the ZRFALSE!
synthesis of these are gone in the ZR
- in its place are enzyme to move the products from cholesterol into one of the 3 adrenal androgens: dehydroepiandrosterone (DHEA), androstenedione, and DHEA-sulfate (DHEA-S)The primary mineralcorticoidAldosterone
- exclusively synthesized in Zona Glomerulosa
- essential for life
- promotes sodium retention and potassium excretion by the kidney, in the collecting duct
- it also increases H+ excretion there
- other tissues affected: GI tract, sweat glands, and salivary glands epithelil cells, to enhance absorption in the former and modify exocrine secretions in the latter
- expands ECF volume (thus increase blood volume & blood pressure)
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NOTE: both cortisol and corticosterone have significantly less potent mineralcorticoid effects but they too can slighlty affect sodium and water retention under physiological conditions (about 10% of the total mineralcorticoid activity), and to a greater degree in certain pathologies (ex. Cushings syndrome)Control of Aldosterone SecretionPrimary control
- a low sodium level, either directly or indirectly secondary to low plasma volume
- low sodium level detected by the kidneys juxtaglomerular cells
- they secrete Renin which activates angiotensin I
- angiotensin II is then made in the lungs - it then signal the ZG to synthesize and secrete aldosterone
Secondary control: is form excess potassium, which directly signals aldosterone secretion
Other modulators include ACTH, which is controlled by cortisol feedback but which also increases aldosterone secretionAngiotensin II ________ change ACTH levelsDOES NOT
- cortisol does change ACTH levels
** on the contrary Angotensin IIs primary effect on increasing aldosterone is DIRECT, not indirect
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- Angiotensin II can modulate cortisols main negative feedback control over CRH and ACTH secretion
- It can also stimulate thirst to increase water ingestion and eventual plasma volume
- It stimulates postereior pituitary ADH (AVP) secretion to further increase water retention, but these too are minor functions of Angiotensin II compared to its directly stimulating aldosterone secretionAldosterone Mechanism of Action- intracellular receptor in nephrons distal tubule and collecting tubules/ducts- in renal principal cells
- mRNA production there
Aldosteronr have to work on 3 proteins to get its effects:
- increased # of Electrogenic Sodium Channels (apical)- Na+ in
- increased Na/K pumps (basal)- sodium out of cell, K+ into cells
* more ability to reabsorb Na+, water follows Na+
- increased apical potassium channels- K+ leaks into cell
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There are target tisssues of aldosterone other than renal principal cells, such as cells in the salivary ducts and others in the colon, but the most important of aldosterones effects take place in the kidney
* the mechanism in these other tissues are functionally the same as described above, increased sodium transport capacityGlucocorticoidsCorticosterone from the ZG and Cortisol (aka hydrocortisone) from the ZF are the two priamry glucocorticoids
* cortisol is more prominent and more potent
A general circadian rhythm is associated with cortisol secretion and concentraion in the plasma (circadian rhythm plus pulsatile secretion)Control of Cortisol Secretion (feedback loops)- Hypothalamo-pituitary-adrenal-axis exerts primary control (long loop feedback from cortisol levels in the blood)
- Many modulators: circadian signals, stress signals affect CRH secretion
- ACTH is required to grow and differentiate cells of the adrenal cortex (ZG cells are the most immature and ZR cells next to the medulla undergo apoptosis)
* ACTH is a basophil
- ACTH signals the zona fasciculata to secrete cortisol
- As cortisol works in the body, many of the stressors are relieved
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Cortisols negative feedback- is the most important feedback chemicalACTH isa peptide hormone that operates through cAMP and PKA in the adrenal cortex
-ACTH stimulates production of the ACTH receptor and of key proteins in steroid synthesis
* other factors affecting expressing of the ACTH receptor are ACTH, glucocorticoids, and angiotensin IICortisol has a direct long-loop negative feedback onboth ACTH from pituitary and CRH (CRF) from hypothalamus
- angiotensin II is modulator of CRH (CRF) secrtion- it is related to stress response- by relieving stress, one reduced the excitatory action of these stressors
*** cortisols actions relieve stressors that also drive secretion
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when active- cortisol causes:
- supressed function of the immune system
- gluconeogenesis in the liver
- protein catabolism in muscle
- lipolysis in adipose tissue (fat mobilization)
- stabilizes lysosomes
** all of these actions relieve stressCortisol is a steroid hormoneJust like any other steroid, the specific proteins produced vary by target tissue
- like aldosterone, cortisol acts by entering cells, binding to a receptor in the cytoplasm, and the hormone-receptor complex acts in the nucleus to alter transcription for the mRNAs of many protein that will carry out the cellular function for those target cells
* UNLIKE aldosterone, cortisol has MANY target cells with MANY different functions
* NOTE: these effects do not go away till the proteins are degradedPermissive hormonesaugment or inhibit the action of other hormonesPermissive effectsa second hormone (the permissive hormone) acts on a cell to (typically) enhance or (rarely) inhibit the responsiveness of the cell to a primary (and different) homrone)
- either way, the permissive hormone helps the primary hormone maintain homeostasis
- abnormal levels of the permissive hormone often result in abnormal function of the primary hormone
Ex's:
1. Thyroid hormones increase the number of adrenergic receptors in the cardiomyocytes, allowing the catecholamines to regulate tone
2. Glucocorticoids enhance the effects of GH (during hypoglycemic states) on skeletal muscle myocytes to regulate glucose metabolism. One way to do this is to increase responsiveness of the myocytes by producing more receptors to GH
3. Glucocorticoids decrease GLUT-4 expression, weakening insulin effects in several tissues. This too is a permissive effect albeit in the opposite direction
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* whether you are altering the receptor number for some hormone or the number of enzymes within the cell, you are setting the stage as it were for a stronger or a weaker response to some other signal molecule that could bind to those receptors
- when the signal does arrive, only if ALL the intracellular machines of the target cell are already present and primed and ready to go, will the signal molecule be able to induce a sig. effect within the cell (that hormone or neurotransmitter that is the signal molecule gets the credit for the action, BUT the permissive hromone (ex. thyroid hormone) made it possiblePermissive effects of cortisol- Inhibits expression of genes for several pituitary hromones (ex. prolactin, POMC (pre-ACTH) and ADH)
*** ex. Increased cortisol, decreased GnRH production (may cause a women to miss a cycle)
- permissive effects on glucagon and epinephrine
- regulates levels of insulin-sensitive GLUT-4 proteins, which then alters abilitiy to respond to insulin in skeletal muscle and adipose tissueDirect effect of cortisolmany are "anti-anabolic"
- converts protein to glucose
- accelerates protein mobilization and degradation (exception: liver)
- converts AAs into glucose precursors
- inhibits protein synthesis
- inhibits glucose uptake and decreases glucose utilization during hypoglycemia
- enhaces glucoagon release
- tendency to raise blood glucose
** cortisol is main hormone responsible in "muscle wasting" because of its strong effects on body-wide protein breakdown and AA conversion into energy sources (liver is the exception to this rule- it still builds proteins under cortisol stimulation)
- skeletal muscle breakdown (esp. in excess) and liver, blood protein buildup; effect on CT too
- cortisol has a double effect on adipose tissue, both increasing lipolysis directly and through increased glucagon secretion and its effects on blood glucose, indirectly- (lipolysis and a net shift in cellular metabolism from a mostly-carb usage to a more lipid-metabolizing mode (esp. in starvation)
- glucocorticoids decrease insulin sensitivity, indirectly reducing insulins ability to decrease blood glucose and promote glucose entry into tissues
- in skeletal muscle cortisol helps to increase gluconeogenesis and other means to increase blood glucose (driect and indirect)T or F: Cortisol generally requires at least 2 hrs and more typically several hrs for its effects to be observedTrue!Other effects of glucocorticoids (cortisol)- Water retention (minor *effect over baseline action) and increased blood proteins (direct) and hematocrit
(via increased EPO), so possibility for increased blood volume overall
** licorice can turn "minor" into "dangerously major" resulting in hypertension
- mixed effect on water balance, direct mineralcorticoid effect but inhibited ADH effect. Hypokalemia possible
- immune depression by many mechanims including decreased prostaglandin production
- increased GI growth and function, increased gastric acid secretion
- decreased collagen formation, decreased osteoblast activity, increased bone resroption, decreased intestinal calcium absorption, and decreased renal calcium reabsorption- net effect is lowered plasma calcium and likely increase in PTH, calcitriol to compensate
- inhibition of many hypothalamo-pituitary-peripheral gland axes
- effects on mood and cognition, both positive and negativeOne of the functions of Glucocortiocoids anti-inflammatory effects is theSynthesis and Function of Annexin 1- which supressed phospholipase A2 (blocks eicosanoid production)
- inhibits main products of inflammation, prostaglandins, and leukotrienes
* they inhibit prostaglandin synthesis at level of phospholipase A2 as well as at the level of cycloocygenase/PGE isomerase (like COX-2), the latter effect being much like that of NSAIDs, potentiating the anti-inflammatory effect
** inhibition of arachidonic acid becoming prostaglandin which is then released into cytosol or from cell to cause inflammation
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glucocorticoids can also reduce lymphocyte counts acutely redistributing lymphocytes from the intravascular compartment to the spleen, lymph nodes, and BM
also can inhibit monocyte differentiation into macrophages, and macrophage phagocytosis and cytotoxic activityAdrenal Medulla is amodified sympathetic ganglion
- Catecholamins are class of water-soluble amine hormones that are derived from tyrosine: includes NE and E (the two that are major secretory products of the adrenal medulla)
* since 4 epinephrine are secreted for every 1 norepinephrine, it is common to only mention epinephrine as being secreted
- these stimulate sympathetic response from cells and tissues that are relatively poorly innervated but relatively well perfused and also stimulate secretion of neurotransmitters from other sympathetic motor neurons throughout the body to generate a response
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* in most cases, epinephrine binds preferentially to beta receptors and norepinephrine to alpha receptors but both can bind to either
- the sensitivity of these receptors can vary, which can fundamentally produce distinct effects depending on whether the high sensitivity receptors are bound (lower concentrations in plasma) or both sets of receptors are bound (higher concentrations in plasma)Sympathetic system deals with"Fight or flight or freeze"Sympathetic autonomic ganglia are dervied from thethoracolumbar roots
- ability of the hormones of the adrenal medulla to travel even to those target tissues which are beyond the direct reach of sympathetic motor neurons, thuse completing the "whole-body activation" aspect of sympathetic control of involuntary body processes
These hormones (adrenal catecholamines) are
- secreted at the same time as the rest of the sympthathetic NS is active
- water soluble
- have very short half-livesEpinehrine has a higher affinity forbeta receptors (beta 1 and beta 2, but it can also bind alpha 1 and alpha 2 receptors)
* NE with alpha receptors (alpha 1 and alpha 2, but can bind to beta 1 receptors)
* meaning that these two hormones, depending on their relative concentrations at the taget tissue, can mediate different effects through different receptors and second messenger systemsSympathetic Autonomic Pathways are bothneural and endocrineFunctions of Catecholamines- stimulates "fight or flight or freeze" reaction
- increases plasma glucose levels
- increased cardiovascular function
- increased metabolic function
- decreased gastrointestinal and genitourinary functionOne of the major function of epinephrine is to affectglucose metbaolism and supply in the plasma
*NOTE: that levels of glucagon, insulin, and cortisol among others will also impact glucose metabolism
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Adrenal catecholamines stimulate fatty acid and glycerol backbone release from adipose tissue
- the carbs are then converted into new glucose via gluconeogenesis (BUT the major hepatic conversion of adipose stores is of fatty acids into ketoacids)
- both newly made glucose and ketoacids can then be used as fuel sources elsewhere in the body
- via beta 2 receptors, epinephrine stimulates glucaon secretion
- via alpha 2 receptors, epinephrine inhibits insulin secretion
- epinephrine also stimulates both muscle and liver to break down glycogen for additional glucose supply in plasma
- any skeletal muscl that is actively working during this release might have its local needs supersede this general schematic so think of this as a function of all the nonworking muscles during the energy mobilization phase of response to catecholamines
*** this effect is acute
- further secretion of more epinephrine and norepinephrine will be required for these effects to be maintained for a longer time period, at which point glucocorticoids might become more importantAdrenal Hypofunctiontwo types primary and secondary- both manifest with inability to retain sufficient water and sodiumAddisons diseaseAKA primary adreal insufficiency (primary adrenal hypofunction)
Adrenal tissue does NOT respond to ACTH
- low production of aldosterone and cortisol
- little to no feedback of ACTH secretion
- ACTH levels in plasma are far above normalSecondary adrenal insufficiency- Little production of ACTH
- Without ACTH, adrenal gland produces little aldosterone and cortisol
- ACTH levels will be low but it measureable in the lab, CRH levels would be highAdrenal HyperfunctionCan be primary or secondary just as in other tissues with hypothalmopituitary control
- usually presented as hypersecretion of cortisol (CUSHING SYNDROME), so if primary cortisol is up and ACTH is down, and if secondary both cortisol and ACTH are elevatedCatecholamines help to ensure that the oxygen and nutrients are available for a person to meet the challeneges of an acute stressor such as those associated with exercise, because if not compensated it can lead to- hypoglycemia (from rapid glucose intake by muscle)
- hypoxia (from inadequate ventilation)
- potentially shock (by large-scale production of vasodilators)
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Fixed by sympathetics
1. Brochodilation mediated by beta-2-receptors: ensures adequate oxygen in the blood
2. Inhibition of smooth muscles (i.e. gastric smooth muscles) that are not necessary for this response (redirects oxygen and nutrients to those tissues which do require more oxygen and nutrients)
3. Catecholamines help to mobilize energy resources in the blood to accompany increased oxygen to working tissues (direct)
4. Catecholamins indirectly increase blood glucose by altering secretion of other hormones
5. Sympathetic stimulation including adrenal catecholamines increase 3 different aspects of heart function
- increase strength (contractility) this is called (inotropy) by which it contract by altering ca2+ release and uptake in cardiac myocytes
- increase in heart rate (chronotropy)
- decrease length of time during which the heart actively contracts (lusotropy)
6. Vasculature is affected by sympathetic stimulation and adrenal catecholamines
- alpha-receptor mediated constriction of veins and lymphatic vessels hels to maintain venous return (req. for adequate cardiac output)
- constriction of many of bodys arterioles through alpha receptors help to maintain blood pressure so that blood flow is maintained and with it delivery of nutrients to working musclesAll sympathetic effects ultimately work toincrease nutrient supply to muscle and adequate supply of oxygen and glucose to the brainDescribe the integration of the Adrenal Medulla and the Adrenal cortex in the stress response (stress response is mediated both acutely and chronically by adrenal gland hormones)Adrenal Medulla (*acute- first to respond in sympathetic response)- short term flight or fight or alarm stage with use of epinephrine and norepinephrine
- changes end immediately when stressor ends
Adrenal cortex- long term adjustment or resistance stage (CRH from hypothalamus --> ACTH from pituitary --> Cortisol released from adrenal cortex)
- AA turned to as primary food source for cells
- muscle wasting and weakness
- inhibition of functions that are not essential to the body like reproduction (via inhibiting the hypothalamus' release of hormones)
** NOTE: processes induced by glucocorticoid are long-term because once the proteins causing these functions are made, theyll kepp working until they break down themselves or are recycled- which can take a while
** best to think the EPI, NE, and cortisol all work together to respond to stressIntegrated response to an acute stressor include- Changes in cortisol, catecholamines, and insulin/glucagon
- enhanced cortisol= extra nutrient availability with which to deal with the acute stressor
- increased catecholamines help with overall sympathetic nervous system activation- which includes nutrient mobilization
- insulin/glucagon ration drops (means increased glucagon present to further ensure that adequate glucose is available in the blood to deal with any acute threat)Integrated response to chronically elevated cortisol could result inCushings Syndrome
- cortisol effects combine with those of excess insulin to promote excess food intake and nutrient stoage, resulting in obesity and other pathological aspects of cushings syndromeSteroids are "classical" hormones that are produced byendocrine glands and transported by the blood
- made in the adrenal cortex, gonads, and placenta
- derived from cholesterol (makes them lipid-soluble= therefore no vesicular storage)
- transported by plasma proteins: transcortin (glucocorticoids), sex-hormone binding globulin (estrogens, androgens)
- act on transcription factors (on nuclear receptors)
- have oxidative side chain cleavages
- hydroxylations (P450-dependent)
* inactivation mainlt in the liverClasses of steroid hormones1. Progestins
- Formed during menstrual cycle (by the corpus luteum) and pregnancy (by the placenta)
- Most important: PROGESTERONE
2. Glucocorticoids
- "Stress Hormone" from the adrenal cortex that regulates major metabolic pathways
- CORTISOL
3. Minceralcorticoids
- Regulators of renal sodium and potassium excretion, from adrenal cortex
- ALDOSTERONE
4. Androgens
- The virilizing hormones from the testis, also formed in the adrenal cortex
- TESTOSTERONE
5. Estrognes
- Regulators of female reproductive function, from ovary and placenta
- ESTRADIOLSources of cholesterol include- LDL and HDL from blood (low density and high density lipoproteins)
- Endogenous synthesis
- Stored cholesterol estersIn the testis cholesterol can be converted toProgestrine and androgens
** in the ovaries you have this plus estrogens
** and then in the adrenal cortex you can have cholesterol --> progestins which splits into androgens, glucocorticoids, or mineralcorticoidsThe mineralcorticoid aldosterone is found in theZona glomerulosaGlucocorticoids- Corticosterone in ZG
- Cortisol in ZFProgestins- Prognenlone
- Progesterone
* in ZGAdrenal androgensDehydroepiandrosterone --> DHEA-S
and
Androstenedione
* in ZRSynthesis of ProgesteroneCholesterol is fed to the enzyme desmolase by the StAR (steriodogenic acute regulator) protein (this feeding step is regulatory). Desmolase then convertes the cholesterol to pregnenolone which becomes progesteroneWith the help of several hydroxylases progesterone can become bothcortisol or aldosteroneTestosterone becomes estradiol with the help ofAromataseSteroid hydrozylations areMonooxygenase reactions
- molecular oxygen is a substrate, and only one oxygen atom from the oxygen molecule enters the steroid
- cytochrome P-450 is a heme-containing subunit of the enzyme - it activates O2 for the reaction
** this requires NADPHWhich is more potent: testosterone or dihydrotestosteroneDihydrotestosterone
- it is made mainly in the target tissues
Testosterone (from the testes, not the adrenal gland) and either become
- (6-8%) Dihydrotestosterone via 5-alpha reductase
- (0.3%) Estradiol with help of aromatase
- inactive productsLong Loop negative feedback is from aPeripheral gland hormone
Ex: The hypothalamo-pituitary-adrenal axis
* Cortisol released from adrenal cortex provides negative long-loop feedback (inhibits release of ACTH from pituitary and inhibits CRH release from hypothalamus)ACTH activates what enzymes that is responsible for increasing glucocorticoidsACTH from the pituitary activates desmolase
Cholesterol is converted to progestins via desmolase
- progestins than can become Androgens or glucocoritcoids
** all in the adrenal gland
***** glucocorticoid then have feedback inhibition in the pituitary to decrease the amount of ACTH that is secretedDisorders of Glucocorticoids1. Addison Disease: lack of corticosteroids. Most often caused by autoimmune destruction of adrenal cortex
2. Cushing Syndrome: Excess glucocorticoids. Can be caused by an ACTH-secreting pituitary tumor (Cushing Disease)
3. Licorice-induce hypertension: A component of licorice root prevents the oxidation of cortisol to cortisoneA syndrome of glucocorticoid excessCushing Syndrome
- Many cases are iatrogenic (caused by a doctor overprescribing/pateint taking to much anti-inflammatory steroids)
Leads to:
- truncal obesity, but fat is lost from extremities
- weak connective tissue, striae
- insulin-antagonistic effects (from glucocorticoids), can cause secondary diabetes mellitus
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Different from Cushing Disease:
- ACTH-secreting tumor in anterior pituitary gland. Causes 70% of non-iatrogenic cushing syndrome. Pigmentary changes in addition to Cushing Syndrome (remember alpha-MSH stimulater hyperpigmentation if the person has increased ACTH)ACTH-secreting tumor in the pituitary gland can lead toCushing diseaseCortisol is a glucocorticoid, but has also mineralcorticoid activity. What is its inactive productCortisone is cortisols inactive product
Cortisol --> Cortisone (via 11-hydoxysteroid dehydrogenase)
** licorice inhibits this reaction in the kidneys
- causes an increase in cortisol which can lead to an increase in hypertension because it is a mineralcorticoid
** this is why pateints with hypertension should not eat licoriceDisorders of Sex steroids1. Congenital Adrenal Hyperplasia (adrenogenital syndrome)
- deficiency of 21-hydroxylase or 11-hydroxylase (or both!)
- reduced corticosteroids
- elevated ACTH
- overproduction of adrenal androgens (since the path from progestins to glucocorticoids is inhibited- pushes towards androgen production)
2. 5alpha reductase deficiency
(testosterone is not converted into dihydrotestosterone but rather estradiol--> this is what explains the ambiguous genitalia)
- ambiguous external genitalia
- virilization at pubertyWith decrease in 21-hydroxylase and 11-hydroxylase, progesterone cannot becomeCortisol nor aldosterone
- so instead progesterone is pushed toward the production of testosterone
Testosterone using aromatase can become estradiol21-Hydroxylase deficiency would result inoverproduction of androgens but deficiency in glucocorticoid and mineralcorticoid production
can lead to:
- hyperkalemia (kidneys begin taking up K+ because losing Na+)
- salt craving (no mineralcorticoids- loss of salt leads to salt craving)
- virilization (from increased androgens)11-Hydroxylase deficiencyAdrenal androgens are overproduced
Accumulating deoxycorticosterone acts as a mineralcorticoid
- virilization
- hypokalemia (opposite of the hyperkalemia that was caused by 21-hydroxylase deficiency)
- edema, hypertension (because the accumulating deoxycorticosterone retains sodium and water)Treatment for Adrenogenital Syndrome (aka congenital adrenal hyperplasia)Administration of cortisol
- causes the feebadk inhibition on the pituitary needed to drop ACTH levels
** remember this syndrome was caused by an inhibition of glucocorticoid production (which would usually feedback inhibit pituitary to stop ACTH buildup- butt in this syndrome ACTH is accumulating along with increased production of androgens)Diagnosis of Congenital Adrenal Hyperplasia- intersex phenotype of genotypic females
- precocious puberty in males (testosterone --> estradiol)
- adrenal glands enlarged at birth
- elevated 17-OH-progesterone and 17-ketosteroids
- elevated ACTH
- electrolyte abnormalities
- salt craving in 21-hydroxylase deficiency
Treatment:
- cortisol, even prenatally after prenatal diagnosisImportance of Dihydrotestosterone (DHT)It is a more potent androgen than testosterone itself. In utero it helps males develop normal external genitalia
** remember that 5-alpha reductase is needed to convert testosteron into dihydrotestosterone
* a deficiency in 5-alpha reductase inhibits this process- testosterone is therefor pushed to make estradiol instead with the help of aromatase (this increase of estradiol is what accounts for the ambiguous genitalia seen in 5alpha-reductase deficiency)
** remember testosterone can also become inactive products- along with dihydrotestosterone and estradiolDisorders of the Adrenal CortexCongenital Adrenal hyperplasia (CAH)
Disorders with increased function (hyperadrenalism)
- Hypercortisolism (Cushing Syndrome)
- Primary Hyperaldosteronism (increased mineralcorticoids)
Disorders with decreased function (hypoadrenalism)
- Chronic adrenal insufficiency (Addison disease)
- Acute adrenocortical insufficiency (Adrenal crisis): Waterhouse-Friderichsen SyndromeDisorders (neoplasma) of the adrenal medulla- Pheochromocytoma: secrete epinephrine and norepinephrine in adults with severe hypertension, wont metastasize
- Neuroblastoma: affects children (mainly malignant)A decrease in 21 hydroxylase could mean a deficiency inmineralcorticoids (aldosterone, corticosterone) and
glucocorticoids (cortisol)
but and increase in ACTH and testosterone
***this is commonly tested in USMLE
** can lead to Congenital Adrenal Hyperplasia (CAH)
- leads to virilization (condition where females develop features associated with male hormones (androgens) as one of the things)A decrease in 11 hydroxylase can cause deficiency inaldosterone (mineralcorticoids)A decrease in 17 hydroxylase can mean a decrease inglucocorticoids (cortisol)
and
Sex steroids (testosterone)Cortisol has feedback inhibition onACTH from the anterior pituitary and CRH from the hypothalamusCongenital Adrenal Hyperplasia (CAH) is a deficiency of an enzyme involved in the synthesis of gluco- and mineralcorticoids, which is the most common type21-hydroxylase deficiency is the most common
MOA: cortisol deficiency --> leads to increased serum ACTH --> bilateral adrenocortical hyperplasia (hypersecretion of androgens)
Presents as
- female neonates with ambiguous genitalia
- boys with precocious puberty (large penis, deeper voice etc)
- possibilitity of life-threatening salt wasting, hyponatremia and hyperkalemia (since decreases aldosterone- sodium not being absorbed, but there is increase in K+ --> this is life-threatening!)Main signs of Hypercortisolism (Cushing Syndrome)- Moon-like face (lower voice, large amt of hair, acne)
- Buffalo humps on back
- Abdominal striae
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Common Causes of Cushing Syndrome:
- exogenous glucocorticoids (most common)
- ACTH-producing pituitary adenoma, carcinoma, hyperplasia--> high ACTH --> bilateral adrenal hyperplasia ( CUSHING DISEASE)
- Adenoma or carcinoma of the adrenal cortex (ACTH-independent, with low serum ACTH)
- Paraneoplastic syndromes (common in lung cancers): disorders associated with production of biologically active substances (ex. hormones) by cancer cells (ACTH will stimulate the adrenal gland it doesnt mattere where it is produced)In Exogenous Hypercortisolismthe adrenal gland undergoes atrophy (becomes smaller)In Endogenous Hypercortisolismthe adrenal gland undergoes hyperplasia (increases in size)Major clinical manisfestation of Primary HyperaldosteronismHypertension (retention of Na+)
- hypokalemia in severe cases --> muscle weakness and cardiac arrhythmias
Classification by cause:
- Bilateral idiopathic hyperaldosteronism due to bilateral nodular adrenocortical hyperplasia (in 66% of cases- most common cause*)
- Solitary aldosterone-producing adrenocortical adenoma (Conn syndrome -33% of cases)
Rare causes:
- Adrenocortical carcinoma
- Glucocorticoid- remediable due to mutations in zona glomerulosa cells make them responsive to ACTHT or F: One is unable to differentiate the zone in whihc an Adrenal Cortical Adenoma is growing by viewing it grosslyTrue!
3 zones of the Adrenal Cortex all with lipids and steroid hormone synthesis
- an adenoma in these 3 locations will look the same- they are indistinguishable- so cannot distinguish if the adenoma would be producing androgens, glucocorticoids, or aldosteroneDrugs that act as glucocorticoids- Hydrocortisone (cortisol)
- Prednisone (intermediate acting)- a corticosteroid agonist
- Dexamethasone (long acting)Drugs that inhibit ACTH secretionPasireotideDrugs that inhibit SteroidogenesisKetoconazole ( a corticoisteroid synthesis inhibitor)Glucocorticoid Receptor Antagonist drugMifepristone (RU486)Mineralcorticoid drugsFludrocortisone (a corticosteroid agonist)Mineralcorticoid Antagonist drugSpironolactone
Eplerenone3 modes of physiologic regulation of ACTH secretion in HPA axis- Diurnal rhythm (peak in morning, decline at end of day)
- Negative feedback by corticosteroids
- Increase steroidogenesis in response to stress
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Usually ACTH itself is not uses therapeuticlly bc it is limited due to its side effects, inconvenience, and unpredicatable)
it also has:
- rapid absorption (parenteral)
- 15 min half life; rapid hydrolysis
- adverse effects due to corticosteroid secretion
* Cosyntropin (synthetic)- diagnostic testing HPA axisAdrenal development and function requires ACTH. Glucocorticoids suppress ACTH secretion via negative feedback. If the axis has been suppressed due to chonic administration of exogenous drugs thenabrupt drug withdrawl can be fatal (corticosteroid therapy less than 7 days is unlikely to cause axis suppression)
NOTE:
- glucocorticoid hormone receptors (GRs) are widely distributed across tissues, where their actions vary considerably.
- adrenal cortical hormones are steroids and act by regulating protein synthesis (some effects of adrenal steroids or analogs used as drugs may take some time to be effective- effects may last varying amounts of time after the drug is withdrawn, depending upon the half-life of regulated proteins
- for disease, optimal dose is detemine by trial, error, and re-evaluation; goal is to find lowest effective dose for management of condition. Use adjunctive therapies or steroid sparing therapies when possiblePermissive effects of cortisol- Inhibit expression of genes for several pituitary hormones (ex. prolactin, POMC (preACTH), and ADH)Cortisol regulates levels of insulin sensitive GLUT-4 proteins, which thenalters ability to respond to insulin in skeletal muscle and adipose- this leads to hyperglycemia"anti-anabolic" effects of cortisol- converts protein to glucose
- accelerate protein mobilization and degradation (except in the liver)
- converts AAs into glucose precursors
- inhibits protein synthesis
- inhibits glucose uptake and decreases glucose utilization during hypoglycemia
- enhances glucagon release
- tendency to raise blood glucoseGlucocorticoid Drugs- Hydrocortisone (equal anti-inflammatory and Na+-retaining potency)
- Prednisone (more anti-inflammatory)
- Dexamethasone (purely anti-inflammatory)
Mineralcorticoid:
- Fludrocortisone (mostly Na+ retaining) - a very potent mineralcotioid with high glucocorticoid activity
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These are given: oral, IV, IM, local site (synovial space, occular, skin, respiratory tract) -- ALL can do and achieve the same effects
* Most are highly protein bound, if they are unbound they are active
Metabolism:
- All but two (Hydrocortisone and Prednisone) need enzymatic activation
- Their mineralcorticoid effects of glucocorticoids are insufficient to replace aldosteroneDescribe some toxicities associated with GlucocorticoidsWithdrawal of Therapy:
- Flar up of treated disease
- Acute adrenal insufficiency (mild- fever, myalgia, arthralgia, malaise; severe (can lead to coma), taper over weeks, months, sometimes as much to a year)
- Pseudotumor cerebri
Continued use of supra-physiological dose:
- Fluid and electrolyte handling: Hypokalemic alkalosis and hypertension
- Metabolic: hyperglycemia, glycosuria
Long term toxicity of glucocorticoids:
- Increase susceptibility to infection
- Peptic ulcer disease (cocomitant NSAID or aspirin)
- Myopathy
- Behavioral changes (nervousness, insomnia, changes in mood, overt psychosis)
- Cataracts
- Osteoperosis/Osteonecrosis (calcium and vitD)
- Effects on growth and developmentFludrocortisoneVery potent mineralcorticoid with high glucocorticoid activity; used primarily for its mineralcorticoid effects
- promotes increased reabsorption of sodium and loss of potassium from renal distal tubules
It is given:
- orally
- eliminated by the liver
- half-life ~3.5hrs (biologic half life 18-36hrs)
Adverse effects:
- Same as those seen with glucocorticoids
- obviouslt skewed towards mineracorticoid featuresAdrenal insufficiency can be bothacute and chronicAcute adrenal insufficiencyLife threatening
Sxs: Nausea, vomiting, abd pain, dehydration, hypnatremia, hyperkalemia, weakness, lethargy, hypotension
Causes:
- Adrenal gland disorder
- Structural/functional lesions of anterior pituitary or hypothalamus
- Abrupt withdrawal of glucocorticoid therapy
Treatment
- IV Hydrocortisone or Dexamethasone
- IV fluids
- Therapy for any precipitating cause (treat underlying cause)Chronic Adrenal InsufficiencyAddisions Disease
- hair loss
- blurry vision
- abd pain
- decreased appetite
- darkening of skin (hyperpigmentation)
- shaking or tremors
- anxiety
Congenital Adrenal Hyperplasia
** similar symptoms as acute but with lesser severity than acute adrenal insufficiency
Require chronic
- Glucocorticoid: increase dose in times of illness, stress, or surgery
- Mineralcorticoid: increase does in times of intense exercise, sweating, or diarrhea
- Liberal salt intake dietCorticosteroids can also be used in Non-endocrine diseases such as- Rheumatic disorders
- Nephrotic syndrome
- Allergic diseases
- Infectious disease (pneumocystis, H. influenze meningitis)
- Asthma/COPDChronic therapy for cushing disease (or syndrome) cannot be stopped abruptly because one could end up withAddisionian Crisis (so must taper off the dose)
* Treatment for Cushing Syndrome or Disease include:
- Surgical options to remove primary cause of tumor (must give steroid post surgery)
- Slow tapering of pharmacologic glucocorticoid
- Inhibitor of ACTH secretion
- Inhibitory of adrenal steroidogenesisDexamethasone Suppression Test- measures the response of adrenal glands to ACTH
Low Dose Overnight test
- pt given dexamethasone at 11PM, cortisol measured at 8AM following morning- suppression of cortisol to less than 1.8micrograms/dL suggests strongly that patient DOES NOT have Cushing Syndrome
High Dose Overnight test
- Measure cortisol on the morning of the test- then patient given dexamethason at 11pm- draw blood next morning at 8am for a cortisol measurment (normal result= greater than 50% reduction in plasma cortisol)Drug that is an inhibitor of ACTH secretionPasireotide:
A Somatostatin Analog that inhibits growth hormone secretion, ACTH secretion and reduces cortisol levels
- subcutaneous dosing
- highly protein bound, half life ~12 hrs, renal and hepatic elimination
Side effects:
- Bradycardia, QT prolongation, peripheral edema, hyperglycemia, GI distress, headache, fatigue, hepatic enzyme elevationDrug that is an inhibitor of SteroidogenesisKetoconazole
Antifungal agent
- Dose related inhibition of CYP17 and CYP11A1 involved in steroid biosynthesis
- In addition to glucocorticoid synthesis, it also inhibits androgen synthesis; can cause gynecomastia as a side-effect in male patients
- typical dose 2-4x dose as antifungal
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-Bioavailability decreases as gastric pH increases (why it is recommended patients take on empty stomach)
-Hepatic metabolism: half life ~8 hrs
Drawbacks
- hepatic dysfunction, possible severe injury, death
- has MANY drug interactionsMifepristoneA glucocorticoid receptor antagonist
- Progesterone receptor antagonist: pregnancy terminantion
- At high doses: inhibits glucocorticoid receptor, NO effect on mineralcorticoid activity
Use:
- treatment of elevated blood sugar in patients with Cushing's Syndrome and type II Diabetes who failed or are not candidates for surgical treatment
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- this is well absorbed orally. Has a long half life 18-21 hrs. Hepatic metabolism to active metabolites. Fecal and renal elimination
Side effects:
- Nausea, loss of appetite, muscle and joint pain, fatigue, hypokalemia, irregular menstrual bleeding
DO NOT USE in women who are or have any interest in acheiving pregnancySpironolactone and Eplerenone are bothMineralocorticoid (aldosterone receptor) Antagonists
- Potassium sparing diuretic used in CHF, liver disease used in the treatment of primary hyperaldosteronism
- Spironolactone is sometimes used as an antiandrogen
- Relatively slow onset of action (several days to become fully effective) and long duration of action. Hepatic metabolism
Side effects:
- Hyperkalemia, Hypertriglyceridemia, Dizziness, fatigue, gynecomastia (from spironolactone)
- Caution: K level >/= 5.5mEq/L at initiation, CrCl </= 30ml/min, concurrent use of strong CYP 3A4 inhibitorsThe purpose of insulin is to regulate blood glucose (sugar) in the normal range, it is secreted in response toHigh blood glucose
Action: stimulates many cells of the body to absorb and use glucose thereby decresing blood sugar levels
* C-peptide (connecting peptide) from the original proinsulin molecule is co-secreted with insulin
- its secretion is inhibited by low blood glucose-
** An example of product-mediated negative feedback (different, than say, levels of GH in the blood)
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Insulin is a peptide hormone so it requires
- hnRNA transcription
- mRNA processing
- translation
- post-translational processing
- its secretion is via exocytosis, like every other peptide hormoneInsulin is secreted by beta cells- the arterial and venous blood are on opposite sides of the beta cells- what are in each of these that aid insulin in its secretion?Receptors are concentrated on the arterial-facing membrane: sense how much glucose there is present
Insulin is secreted into the venous blood, enroute to the liver (to portal circulation- directly or indirectly)
*technically each cell operates relatively independently, but they combine for a powerful collective effect on secretion
*arterial-facing membranes are better for determine the state of glucose levels and hormone levels in the general circulation than are venous-facing membranesSecretion of insulin is anEpisodic secretion
- When blood glucose levels rise, insulin is secreted until blood glucose levels fall again to a normal range
*NOTE: there is a transport maximumDescribe the main pathway fro insulin secretion1. Glucose entry via GLUT-2, other nutrients too
- Other energy sources such as fatty acids or amino acids such as leucine or arginie also increase ATP levels in the cell, turning on the intracellular signal-
2,3. Metabolize glucose or other nutrients
4,5. ATP, NADH levels are up
- the levels of ATP produced within the cell cause it to become and intracrine messenger- ATP acts inside the cell as a messenger via closing potassium channels which then produce the membrane potential changes and subsequent exocytosis of insulin-
6. K+ channel closes (depolarizes cell and opens the voltage-gated calcium channels) and Ca2+ channels open (depolarizes cell more)
7. This Ca2+ along with other calcium from intracellular stores then binds to motor (exocytosis) proteins that "drag" vesicles containing insulin to the basolateral membrane resulting in exocytosis of insulin molecules
8. Exocytosis of insulin
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So the extracellular conc. of glucose alters concentration of ATP and that proportionally increases intracellular calcium. If ECF glucose is up, then ATP is up, calcium is up, and insulin secretion is upModulation pathways for insulin secretion* With the right modulation, a given increase in BG could result in as much as 3x more insulin being secreted than with no modulation at all
* the main pathway MUST have occured for any modulation to occur
What gets modulated?
1. The amount of additional calcium in the cytoplasm whose source are intracellular calcium depots (ex. endoplasmis reticulum)
- 2 most common stimulators are parasympathetic neurotransmitters (ACh) acting through muscarinic receptors, and free fatty acids (FFAs) acting through GPR40 receptor --> both act through Gq --> PLC --> IP3 increases intracellular calcium --> more motor protein binding and more exocytosis
2. The responsiveness and/or activity of the motor proteins involved in actual exocytosis: adenyly cyclase second messenger pathway is uses
- Stimulated by incretins binding to GLP-1 receptors --> Gs --> adenylyl cyclase --> cAMP --> PKA potentiates motor protein action
- Inhibited by sympathetics via Gi acting on alpha-2 adrenergic receptors
**** both of these work together to increase insulin secretion- via increased intracellular calcium and increased responsiveness/activity to that calicum (3x main path insulin secretion rate)****
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It is possible to provide parenteral nutrition (via IV) but oral food intake is always preferred because the incretins associated with oral nutrition yield a better insulin secretion and better blood glucose controlFactors stimulating insulin secretionIncreased
- blood glucose
- blood FFAs
- blood AA's
- GI hormones (gastrin, CCK, secreting, glucose-dependent insulinotropic peptide)
- GH
- Parasympathetic stimulation: ACh
- Insulin resistance; obesity
- Certain drugs
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**** glucose-dependent insulinotropic peptide (gastric inhibitory peptise) and ACh, increase intracellular Ca2+ through other signaling pathways and enhance the effect on glucose- but do NOT have major effects on insulin secretion in the absence of glucoseFactors inhibiting insulin secretion- Decreased BG
- Fasting
- Somatostatin (aka GHIH)
- Alpha-adrenergic activity
- Leptin (secreted by high fat)
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Somatostatin and NE (by activating alpha-adrenergic receptors) inhibit exocytosis of insulin
* somatostatin used to modulate beta cells in pancreatic islet is almost always paracrine, from delta cells in the same islet- here it is not endocrine hormone as it would be said if it were secreted from the hypothalamus and affecting the anterior pituitary somatotrophsThe rise in insulin after parenteral administration of a given dose of glucose is 2-3 times LOWER than that for the same quantity of glucose from the oral route. The difference is attributed toIncretins (a class of GI-secreted hormones, among whose targets are beta cells- they modulate the sensititvity of insulin secretion)
- Primarily glucose-dependent insulinotropic poylpeptise (aka gastric inhibitory peptide [GIP]) and - Glucagon-like peptide 1 [GLP-1]
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The fact that GI-secreted hormone can boost insulin secretion supports a feed-forward effect in which presence of glucose in the tract causes the hormones to prime the beta cells for glucoses arrival following absorption
* incretins do their function by binding to receptors on pancreatic beta cells, and increasing cAMP within the cell- the more cAMP- the more secretory proteins in the ready state- so that when the Ca2+ does arrive from somewhere else (ex: ECF secondary to high plasma glucose)- motor proteins are as charged up as possibleBiphasic secretion of Insulin- When glucose rises, at first insulin secretion goes up dramatically then it drops (0-6min) then it rises slowly to the level at which it was first secreted (expansion/replenishment of the RRP- 6-30min)
- Generally this is attributed to an initial release of stored insulin in secretory vesicles (RRP= readily releasable pool for insulin secretion within the beta cell), followed by production of new insulin after a few minutes
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When insulins effects have successfully reduced BG, the glucose signal for further insulin secretion ends and the metabolism and clearance of the already-secreted insulin rapidly follows.
- During this "downtime", the beta cells store a new set of insulin proteins and store them in vesicles, functionally replacing the readily releasable pool of insulin that has been depleted by the end of the first phasePrimary target tissues for insulin- liver hepatocytes
- skeletal muscle cells (+cardiac)
- adipocytesAre neurons and erythrocytes target tissues for insulin?NO!
Most neurons are NOT target tissues, nor are erythrocytes
- Though they use glucose, their glucose transporters (GLUT-1 or GLUT-3), are INSULIN-INDEPENDENT (neither glial cells, neurons, nor RBCs are insulin-dependent)
* Regulation of plasma glucose levels are therefore necessary to prevent neurons from losing their proper level of activity. Too much can be as bad as too little, but there's a wider rand into "too much" than into "too little"
- A severe hypoglycemia will cause neurons to run out of ATP, since their ability to produce ATP anaerobically is minimal. This will also produce neuronal damage and could lead to death (neurons have a relatively higher metabolic rate than RBCs, so imbalances in BG more likely to affect them- disorientation, coma, etc.Which GLUT receptor is insulin dependentONLY GLUT-4
- it is found in the tissues that make up much of the gross mass of the body (skeletal muscle + fat) and cardiac muscle, too
- it is NOT found in hepatocytes (these only have GLUT-2)Insulin promotesgrowth
- works on many cell types to lower BG, FAs and AAs and promote their storge
- when these molecules enter blood during the absorptive state, insulin directs their cellular uptake and conversion into glycogen triglycerides (fat) and proteinThe insulin receptor is aTyrosine Kinase Receptor
It is composed of 2 alpha subunits and 2 beta subunits linked by disulfide bonds
- Alpha chains are entirely extracellular and bind to insulin
- Beta chains penetrate through the plasma membrane and transduce the signalGLUT-1,2,3,4 are theClass I Glucose Transporters
- GLUT-4 is the only one thats insulin-dependent (high affinity for glucose)
- GLUT-2: important in metabolism on behalf of the beta cell itself- it is co-directional unlike the others- allos release of or absorption of glucose into cells such as hepatocytes (transports galactose and fructose)
- GLUT-1 and GLUT-3: are dependent on the conc. of glucose and are mainly expressed in brain and erythrocytes, with some GLUT-3 in other tissues (these also transport galactose, not fructose)
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GLUT-1: in brain, RBC, endothelial cells, fetal tissues
GLUT-2: liver, pancreatic beta cell, SI, kidney
GLUT-3: brain, placenta, testes
GLUT-4: skeletal and cardiac muscle, adipocytesGLUT-5 is aClass II FRUCTOSE transported
- important in digestion and absorption of carbohydrates, but also in maintainence of sperm motility, in locations where fructose will not otherwise be used as a food source (spermatozoa, in the uterus and uterine tubes)
** expressed in small intestine and spermSodium-Glucose Transporter (SGLUT-1) is- important in absorption of glucose in the SI and of reabsorption of glucose in the PCT, but it is NOT intended to support metabolism directly
- it doesnt seem to fall directly into either class I or II because of its cotransporter function
** expressed in intestinal mucosa, kidney tubulesThe mobilization of GLUT-4 transportes for a direct increas in glucose uptake is ONLY applicable to those tissues-- includingcadiac muscle, skeletal muscle, and adipose tissue, but NOT hepatocytes- which express GLUT-4 transporters
* In tissues that DO have insulin receptors but DO NOT have GLUT-4 transporters (ex. hepatocytes) insulins promotion of enzymatic effects that increase anabolism and otherwise utilize glucose indirectly increase the conc. gradient for glucose
** this change in gradient causes increased glucose uptake by facilitated diffusion through whatever glucose transporters thse cells do have (GLUT-2 transporters in hepatocytes)
Bottom line: with or without GLUT-4, if there are enough GLUT-2, glucose transport into the target cell increases and glucose utilization does tooGeneral mechanism of action of insulin- Tyrosine Kinase receptor activity; activates several classes of intracellular messengers
- GLUT-4 transporters to cell membrane of select tissues, increases glucose uptake
- Increased activity of enzyme that store and/or process glucose
- Induction of transcription, increase in protein synthesis
- Increased glucose utilization occurs even in target cells with no GLUT4s (remember hepatocytes with GLUT-2s)Insulin drives metabolism by driving changes in enzyme activity towards higher acitivty in those enzymes involved in storing and processing in coming energy such as- Glucokinase
- 6-Phosphofructo-1-kinase
- Pyruvate kinase
* decrease plasma glucose via glycolysis to pyruvate and further glucose oxidation past pyruvate, and decreases gluconeogenesisGlucagon drive acitivty of those enzymes that are involved with the breakdown of molecules that will aid in increasing plasma glucose, these enzymes are- Glucose-6-phosphatase
- Fructose- 1,6- bisphosphatase
- Phophoenolpyruvate carboxykinase
** in contrast to insulin, glucagon inhibits glycolysis and promotes gluconeogenesis and eventual glucose export in the plasmaThe gene expression-production of more enzymes so that eventually there will be greater chages in the response of the cell to a given hormone is an example of aPermissive effect
- so is stoppage of production so that as existing proteins wear out eventually there will be smaller changes in cellular responsiveness to that hormoneActions of Insulin on Carbs1. Insulin promotes glucose transport into most cells in the body (using GLUT-4 and facilitated fissusion- needs a carrier protein)
2. Stimulates glycogenesis, the production of storage polysaccharide, glycogen from glucose in skeletal muscle and the liver
3. Insulin inhibits glycogenolysis- decreases glucose output by the liver and promotes storage of glucose as glycogen
4. Insulin inhibits gluconeogenesis- conversion of AAs or FAs into glucose by the liver
Overall:
- Glucose is stored, not produced. Combined with increased glucose uptake and cellular respiration, this has the net effect of reducing plasma glucoseActions of Insulin on Fats (lipids)1. Increases transport and conversion of glucose into fat
2. Promotes transport of fatty acids from the blood into adipose tissue
3. Inhibits lipolysis. Instead promotes TAG formation in adipocytes
4. At adipocytes, this decreases FA (and thus glucose) output and promotes storage of both ingested and de novo TAGs (one of many reasons why someone on high carb diet, nearly-no-fat diet with excess caloric intake can become obese)Actions of Insulin on Proteins1. Promotes transport and incorporation of AAs from the blood into muscles and other tissues
- this decreases blood AAs levels and prommotes protein synthesis in target cells
2. Insulin inhibits protein degradation
3. Net anabolic effect in the body (since neither GH nor IGF-1 significantly increase glucose uptake into muscle, this ability of insulin is necessary for protein synthesis to take place in high enough quantities to produce a net anabolic effect body-wide)
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** this is the opposite effect of cortisol- stimulates release of muscle-based AAs and their hepatic conversion into other fuel sources, promotes catabolism more than anabolismWhen growth hormone levels are elevated, one of its effects isincreased plasma glucose
- which then increases insulin (which then helps get the AAs into the cell and promotes production of the ATP that will go into peptide bonds)Insulins overall effects on the whole-body areassociated with the absorptive state
- overall decrease in glucose and ketoacids (fuels_
- decrease in plasma fats
- nurtients used to promote overall energy storage and anabolismHormones that can increase blood glucose in the presence of hypoglycemia includeFor the postabsorptive state: the most important is glucagon, but others (ex. cortisol, EPI, GH, and thyroid hormone) also play major roles
***In contrast, ONLY INSULIN is available to directly deal with a hyperglycemic state (most typical is the transient period known as the absorptive state) and bring it back towards normal blood glucose level
- Insulin has no back up hormone in case it failsGlucagon is apeptide hormone secreted by the alpha cells in the islets of langerhans in the pancreas into the hepatic portal circulation
- effects many of the same metabolic processes as insulin, but most of glucagons actions are opposite those of insulin
- major site of action for glucagon is the liver, with a lesser role at other tissues (ex. adipose tissue)Glucagon release from alpha cells in the pancreas is regulated byNegative feedback in response to the level of blood sugar
Inhibited by: elevated blood glucose
Activated by: a fall in blood glucose below normal, AAs (substrates for gluconeogenesis)Factors stimulating glucagon secretion- Decreased BG
- Increased AA's
- Exercise
- Circulating Catecholamines (beta2)Factors inhibiting glucagon secretion- Increased BG
- Somatostatin (SST, from delta cells)Actions of Glucagon on Carbs1. increase in glucose production by the liver and thus raises BG level
2. decreases glycogen synthesis
3. stimulates glycogenolysis
4. stimulates gluconeogenesis (mostly in liver)- the conversion of AA's into glucose, glycerol from TAG breakdown can also enter into gluconeogenesis
** many metabolic functions performed by the liver, that cells in the kidney have some reserve capacity to perform the same functions (this typically only manifests in sig. way only in extreme circumstandes (ex. some degree of renal gluconeogenesis during extended fasting) or in certain pathologiesAction of Glucagon on Fats (lipids)** less effect in adipose tissue than in the liver- only a few glucagon receptors in adipose tissue, so it only exerts a minor effect there
1. Stimulates lipolysis (as does epinephrine)
2. Inhibits TAG synthesis, especially in liver
3. Promotes conversion of the TAG glycerol component into glucose, in the liver
4. Promotes conversion of free FAs into ketoacids as an alternate fuel source for muscle, particularly when glucose is more chronically low, in liver also
*** epinephrine is a MUCH more important hormone in adipose tissue than is glucagon
- EPIs effects in adipose and in muscle, where there are NO glucagon receptors, dominate the energy-mobilizing aspects of these two tissues, to help provide the resources that glucagon-stimulated hepatocytes can use to convert to glucose or create ketone bodies for cellular metabolism
** since one of the singals for Epi secretion is low blood glucose, glucagon and epi act togetherActions of Glucagon on proteins- Inhibits protein synthesis in the liver
- Stimulates protein breakdown in the liver
- DOES NOT normally affect protein in skeletal muscle (bc there arent supposed to be glucagon receptors there- it doesnt have the enzyme that dephosphorylates glucose-6-phosphate into glucose)
- stimulates pathways that raise blood levels of glucose and fatty acids, a characteristic of the post-absorptive state
* increased glucagon release during times of fasting (the post-absorptive state)Cortisol, which helps to facilitate protein breakdown in skeletal mucles, actuallyINCREASES protein synthesis in the liver
- Same with GH
* glucagon, cortisol, GH all promote gluconeogenesisEffect of fuel flow in the body- Associated with postabsorptive state
- Results in increased glucose and ketoacid release (use of free fatty acids in ketoacid production)
* both glucose and ketoacids are fuels, the latter is especially important in prolonged fast (starvation)The most ypical hyperglycemic state is the transient period known as theabsorptive stateSomatostatin (SS, SST, SRIF, GHIH) is aPeptide hormone secreted by pancreatic delta cells and the GI tract, and the hypothalamus
- stimulus for pancreatic delta cell release is increase blood glucose (lower than that needed to stimulate insulin secretion)
- delta cells SST inhibits both insulin secretion and glucagon secretion
* It can alter PLC/PKC, reduce cAMP, and alter Ca2+ flux to counter other hormones stimulatory effects on target tissue
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In pancreatic islets, somatostatin is a paracrine agent, secreted from cells in the endocrine pancreas' delta cells to prevent oversecretion of both glucagon and insulin
- therefore prevents "burnout" of either alpha cells or beta cells in the pancreatic isletTrue or False:
Glucagon and Insulin are normally kept in balance such that blood glucose stays within the normal range by negative feedback on both hormones' productionTRUE!Difference between catecholamines (e.g. epinephrine) and glucagonCatecholamines have strong effects on both adipose tissue and muscle, while glucagon effects are marginal in adipose tissue, and, for lack of receptors, nonexistent in muscle
- so catecholamines can work in adipose tissue and muscle whereas glucagon can barely in adipose, and can not at all in muscleAbsorptive (fed) stateBodys endocrine/metabolic status at the time when
- energy levels in the gut and blood are very high, absorption occurring
- typically lasts 2-4hrs after a meal (post-prandial period) - 5-6hrs for a very big meal
- insulin promotes anabolism of target tissues
- fuels are absorbed into cells and used and/or stored therePost-absorptive stateBodys endocrine/metabolis status at the time when
- absorption is long over but energy reserves are still high
- typically begins by about 4 hrs after a meal (big heavy meals may be about 6hrs)
- glucagon is the primary hormone of the post-absorptive state (it may promote catabolism)
- fuel is mobilized from storage sites for body-wide usage
- eventually transitions into a starvation state over several daysFasting vs StarvingFasting: VOLUNTARY abstention from eating, while hunger cues last (24-48hrs since the persons last meal)
Starving: INVOLUNTARY lack of food consumpton despite hunger cues
* body's response, to maintain energy availability to brain and other fuel-sensitive tissues, will be the same, though more means may be employed than during a normal post-absorptive state
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The fasting state (chronic starvation) is a "survival mode" variant of a typical (early) post-absorptive state
- cortisol is typically a hormone of the fasting state, but not of the early post-absorptive state
- epinephrine and GH also support glucagons continued maintenance of blood glucose
* by a few days after ones last meal, this fasting state for metabolic purposes should be fully establishedAdjustments to chronic fasting- No cortisol component at first
- As body transitions to chronic starvation, ketone body production increases (cortisol secretion promotes skeletal muscle protein wasting as a source of emergency energy)
- Muscle begins to use fatty acids and ketone bodies as a major fuel source and stops using glucose
* after 3 days, glucose is reserved mostly for brain and erythrocytes
* prolonged chronic starvation results in muscle breakdown, autophagy and eventual organ failureHypoglycemiaBlood glucose <60mg/dL
- when extreme is fatal quickly
Causes: too little food, too much insulin or diabetes medicine, or extra activity
Sxs
- Shaking, fast HR, sweating, dizziness, anxious, hunger, impaired vision, weakness/fatigue, headache, irritable.
[Euglycemia (normal glucose 70-110mg/dL) is always preferred]HyperglycemiaFasting blood glucose levels >125mg/dL
Causes: too much food, too little insulin or diabetes pills, or stress
- often starts slow, may lead to medical emergency if not treated
Sxs:
- Extreme thirst, need to urinate often, dry skin, hungry, blurry vision, drowsy, slow-healing wounds
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Hyperglycemia is
- normal after a large meal- that is why insulin is secreted..but when hyperglycemia persists, there can be problems
- this leads to a large number of possible sxs, both acute and chronic- if chronic and sustained, diagnosed as Diabetes Mellitus
- If hyperglycemia is extreme, it can lead to ketoacidosis, coma, and deathClinical presentation of Diabetes Mellitus (DM)- Polyuria (peeing a lot), polydipsia (drinking a lot), and polyphagia ( eating a lot)
- Fasting blood sugar (FBS) > 126mg/dL
- Random blood sugar (RBS) > 200mg/dL
- HbA1c >6.5% (this is long-term glycosylation- helps you to check if a pt has been noncompliant with their Diabetes medication)
* if they are symptomatic: 1 abnormal value
* asymptomatic: 2 abnormal values
[symptom is something reported by a patient, a sign must be observerd or measured- it is possible for a patient to have signs of DM but not have noticed them]
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DM Type 1 (5-10%)
- Autoimmune: injury and/or inflammation (insulinitis) of islets of Langerhans
- Morphology: lymphocyte infiltration and beta-cell destrcution
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DM Type 2 (90-95%)
- Peripheral insulin resistance or impaired insulin secretion (could be do to consuming so much sugar the the receptors became downregulated)
Morphology:
- Amyloid accumulation
- Beta-cell atrophy (transition from Type 2 into Type 1)Pharmacological challenges of Type I DM vs Type 2 DMType I DM (hypoinsulinemia due to pancreatic Beta-cell destruction)
- requires replacement therapy
- trying to maintain a balance between "tight-control" of blood glucose and excessive risk of hypoglycemia
- is a significant challenge to titrate the replacement dose and coordinat with dietary intake and metabolic needs
Type II DM (primarily loss of target tissue responsiveness to insulin but really multifactorial)
- enhancing target tissue responsiveness to insulin and/or increase insulin release
- taking other steps to prevent hyperglycemia
- most patients will require combination therapy
- refer to current ADA standards for guidance
** Goal: is to minimize episodes of hypoglycemia in both typesDiabetes Mellitus Drugs (short-acting and long-acting insulins)Short-acting insulins: (very rapid v. regular)
- Insulin lispro
- Insulin regular
Long-acting insulins: (longer duration v. NPH)
- insulin NPH
- insulin glargine
NOTE: all insulin preparations are either native insulin or very similar analogs that have nearly identical actions at insulin receptorsType II Diabetes Mellitus Drugs (have 9 different classes):Biguanides
- Metformin
Sulfonylureas
- Glimepiride
- Glyburide
Thiazolidinediones
- Rosiglitazone
Alpha-glucosidase inhibitors
- Acarbose
Incretin Mimetics
- Exenatide
- Liraglutide
Gliflozine (SGLT2 inhibitors)
- Canagliflozin
Meglitinides
- Repaglinide
Dipeptidyl Peptidase-4 (DPP-4) Inhibitors):
- Sitagliptin
- Lingalipitin
Dopamine-2 Agonist
- BromocriptineEndogenous Insulin vs. Therapeutic Insulin therapyEndogenous: circulates unbound, short half-life (~6 minutes)
Therapeutic insulin therapy: altered to extend half life
- parenteral use (SQ, IV, IM).. pluse inhaled product
Insulin is prepared as
- an aqueous solution
- dosing and concentrations expressed as "units"
- standard= 100 units/ml
- also preparations that are 200,300, or 500 units/ml
Formulations:
Alterations to pharmacokinetics
- slow absorption from administration site
- alter AA sequence or structure to accelerate or prolong absorption (short acting/long acting-insulin)Short-Acting InsulinsRegular Insulin:
- molecules associate as hexamers in solution at neutral pH (slow absorption, take 30-45 min before meals) -
- can be administeres SQ, IV, or IM
Products
- Standard= 100unit/ml
- 500unit/ml: altered PK, acts closer to NPH
**** Inhaled insulin= preparation of regular insulin attached to a crystallized carrier- single use device - slightly more rapid than the injected lispro- cough is the main adverse side effect, contraindicated in smokers and patients with chronic lung disease, asthma, etc
Insulin analog (lispro) ** works fastest
- absorbed more rapidly than regular (0-15min before meals)
- administered SQ
Products
- 100 unitl/ml
- 3 types available: lispro, aspart, glulisine
- this has better outcomes than regular insulin (lower HbA1c, fewer hypoglycemia)
- higher costLong-acting insulin preparationsThese decrease rate of release from SQ depots, permitting a single injection to supply longer-lasting "background coverage" (basal insulin)
NPH insulin:
- combo of crystalline zinc insulin and protamine
- after SQ injection, protamine is enzymatically digested to release insulin that is then absorbed in the circulation
Insulin glargine: * has the longest duration of action
- Soluble at pH4 (as its packaged) due to sequence modifications - and then its aggregated when injected at neutral pH - thus leading to slow release into the circualtion
- provides a depndably sustained release from depot injectionsInsulin administartion types and factors that affect its absorptionCan be injected with
- pre-filled pen
- with a synringe
- insulin pump
Factors that affects its absorption:
- Site of injection
- Type of insulin
- Subcutaneous blood flow
- Smoking
- Muscle activity at site of injection
- Volume and concentration of insulin
- Depth of the injectionDiabetes control and complications trial (DCCT)Study measuring intensive vs standard blood sugar control in Type I Diabetics with insulin
- Showed that ppl with intensive treatment lowered their risk of diabetic eye, kidney, and nerve disease
* was not shown to lower risk of heart disease, since only a few had heart disease in the study
- participant with intensive treatment had an avg A1C of 7%, while those with conventional treatment- A1C of 9%
Risk: HypoglycemiaTreatment goal in DMMaintain appropriate glucose levels as continuously as possible
1. use long-acting insulin to maintain baseline insulin to support ongoing metabolic needs
2. administer short-acting insulin prior to meals to guard against postprandial hyperglycemia
3. Balance the above to prevent hypoglycemic episodes between meals and overnightMetforminA Biguanide
MOA: reduced hepatic glucose production by limiting gluconeogenesis, stimulating hepatic fatty acid oxidation and reducing lipogenesis
- also decreases intestinal glucose absorption and improves peripheral glucose uptake and utilization
Pharmokinetics:
- Oral bioavailbility= 70-80%, NOT protein bound, half-life 4-5hrs (taken twice a day), renal elimination
NOTE:
- Not likely to cause weight gain or hypoglycemia
- Delayed progression to DM in those with IGT (impaired glucose intolerance)
- Polycystic ovarian syndrome- infertility treatmentFirst line of therapy for type II DiabetesMetformine (a Biguanide)
- Monotherapy or combination
* UKPDS trial showed that the use of Metformine was associated with lower microvascular complications AND lower macrovascular complications
Side effects:
-GI (if you start low does and titrate- tolerance develops); B12 deficiency, peripheral neuropathy
- Most concerning: Lactic acidosis
** whats recommended to not get lactic acidosis:
- baseline renal function and periodic monitoring
- renal dose adjustments and contraindication points
- suspend therapy for real or possible renal insultsSulfonylurea (includes Glimepiride and Glyburide)MOA: bind to and inactivate the SUR1 (sulfonylurea receptor) subunit of the ATP-sensitive K+ channel on beta cells, analogous to response in the fed state, leading to release of insulin
- will increase insulin release regardless of glucose levels
- risk of hypolycemia
Pharmakokinetics:
- orally absorbed, best on empty stomach
- highly protein bound
- half life 2-4 hrs but effects 12-24 hrs
- hepatic metabolism and renal elimination
NOTES:
- 50-80% initially respond. Many will cease to respond with prolonged course
Conrtaindications: Type 1 pregnancy, lactations, severe renal or liver dysfunction
**** SPECIAL WARNING ON INCREASED RISK OF CARDIOVASCULAR MORTALITY
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Complications of hyperinsulinemia
In Type 2 Diabetes
- elevated serum insulin levels in most patients
- giving medications that further increase may reduce blood sugar by may potentiate worsening in other body systems
*** wont increase heart disease in combination with other products, so you should get diabetics on
- low dose aspirin
- lipid lowering with "statin"
- ACE inhibitors (when indicated)Thiazolidinediones (includes Rosiglitazone)MOA: selective agonist of PPARy
- activation of insulin-responsive genes that reg. carb and lipid metabolism
- primary site of action is fat, but also muscle and liver
- increases glucose utilization and decreases glucose production
Pharmacokinetics:
- oral absorption
- hepatic metabolism
- slow onset: 1-3 months for full therapeutic effect
NOTES:
- Monotherapy or combination therapy (req. endogenous or exogenous insulin)
- weight gain and edmea
- osteoperosisAlpha-glucosidase inhibitors (include acarbose)MOA: inhibits breakdonwn of starch and oligosaccharides to monosaccharides by inhibiting alpha-glucosidase
- slows absorption of carbs
- blunts postprandial rise in plasma glucose
Pharmacokinatics
- minimal absorption (local effects)
- renal elimination
NOTES:
- dose prior to meals and snaks
- GI side effects: intensity related to food choices
- May affect absorption of other medications
- Used in combo therapy- not monotherapyIncretin Mimetics (includes exenatide and liraglutide)MOA: activation of GLP-1 receptor resulting in increased biosynthesis of excretion of insulin in a glucose dependent manner
- CNS GLP-1 activation affects appetite and gastric emptying
Pharmacokinetics
- administration by SQ injection
- products vary in half life, metabolic and elimination pathways
- dose frequency varies from twice daily to weekly administration
NOTES:
- primary side effects: nausea, vomiting, delayed gastric emptying
- pancreatitis
- low risk of hypoglycemia when used alone
- CVD benefit: liraglutid, semaglutide, dulaglutide
**** Thyroid C Cell tumore- BLACK BOX WARNING ***Gliflozine (SGLT-2 inhibitors) - includes CanagliflozinCanagliflozin
MOA: reduce rate of glucose reclamation in the proximal tubule and lower blood glucose by promoting urinary loss
Pharmacokinetics
- orally absorbed independent of food
- 90% protein bound
- Half life ~12 hrs (OK for once daily dosing)
NOTES:
- risk of bacterial and fungal UTI
- Osteoperosis
- risk of amputation and reduce CVD (cardiovascular event)
- hypoglycemia rare alone; increased when combined with other drugsMedlitinides (includes Repaglinide)MOA: similar to sulfonylureads, bind to KATP channels in pancreatic beta cells to stimulate insulin release
Pharmacokinetics
- oral absorption
- short halfe life (~1hr)
- high protein binding
- hepatic metabolism
NOTES:
- not for monotherapy
- control of postprandial blood sugars
- risk of hypoglycemia
- drug interactions via protein binding or hepatic mechanismesDPP-4 Inhibitors (include Sitagliptin and Linagliptin)MOA: lower the activity of DPP-4 by >90% causing a two fold increase in concentrations of GLP-1 and GIP leading to increased insulin secretion and reduced glucagon levels
Pharmacokinetics: all available drugs in class are orally absorbed; most given once daily, are NOT bound to plasma proteins and have renal excretions
NOTES:
- No consistent adverse effects noted
- Possible severe joint painBromocriptine (a dopamine-2 receptor agonist)Exact mechanism in DM is unknown but improves insulin resistance and reduces glucose production
- oral absorption
* Used in Parkinson's disease and hyperprolactinemia (a pituitary disorder)
Side effects: nausea, dizziness, headacheStrategies for Type II DM pharmacotherapy include1. Act on the liver, muscle and/or adipose tissue to decrease glucose levels (biguanides (metformin); thiazolidinediones (rosiglitazone))
2. Act via the suldonylurea receptor to increase insulin secretion (sulfonylureas- glimepiride and glyburide)
3. Act via incretin receptors to increase insulin secretion (Incretin mimetics: exenatide, liraglutide)
4. Slow intestinal carb absorption (Alpha-glucosidase inhibitor- acarbose)
5. Inhibit renal glucose reabsorption (gliflozins)HypoglycemiaA serious and potentially fatal situation
3 clinical scenarios:
- Insulinoma and nonislet tumor
- treatment of diabetes mellitus
- use or ingestion of a glucose lowering agent by a nondiabetic
Treatment:
Mild to moderate symptoms: oral glucose and 15-20g of carbohydrate
Severe: IV glucose (dextrose) or glucagon injection
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Glucagon
- produced by rDNA technology
- interacts with glucagon receptor of cells (hepatocyte and other)
- IM or IV injection for hypoglycemia by patient, family, friends
- need adequate glycogen stores in liver
- after parenteral dose, give glucose or food
- side effects: nausea, vomitingBiggest risk of "tight control" of Type I Diabetes isHypoglycemiaThe metabolic pathway which produces 5-carbon monosaccharides is thePentose Phosphate Pathway
- the rate-limiting enzyme and comitted step for this is the Glucose-6-Phosphate dehydrogenase enzyme
- this enzyme is product inhibited by NADPH, the other sig. product of the pathway
** 5 carbon sugars could still be produced by bypassing this enzyme using the glycoclytic intermediates as start pointsGlycogen metabolism is regulated byintracellular free glucose
- glucose conc. inside cells directly reflect plasma glucose conc. because the GLUT2 transporters act by facilitated diffusion transport across cell plasma membranesPhosphoglucose isomerase isnot regulated and maintains equilibrium based on "mass action" of substrate concentrationsFructose 1,6-bisphosphate is regulated byFructose-2,6-bis-phosphate concentrationPyruvate carboxylase is regulated allosterically byacetyl-coA and ATP (activations)
- this works in the liver to activate gluconeogenesis
- presence of acetyl-CoA in the liver indicates that sufficient energetic reserves for glucose biosynthesis are being manufactures
* gluconeogenesis cannot operate without a ready supply of energy- typically the source for this is free fatty acidsGlucose-6-phosphatase is inhibited byfree glucose at high intracellular concentrations (~100mM) BUT this is way too high to be physiologically relevant
** remember glycogen phosphorylase in liver cells is allosterically inhibited by high intracellular free glucose conc.A key liver enzyme that responds to high extracellular insulin isGlycogen Synthase Kinase (GSK)
- Insulin acts on Akt protein (protein kinase B) which in turn modifies and inhibits basal acitivity of GSK. Therefore, when insulin is present the net effect is less conversion of glycogen synthase "a" into glycogen synthase "b', and more of the available glucose is stored as glycogenThe role of PEP carboxykinase in gluconeogenesisit converts oxaloacetate to phosphoenolpyruvateATP is required as an energy source, and thus is a substrate for somegluconeogenic enzymes
- BUT this is not really a substrate for the process; rather it is providing energy for the processFructose-1-phosphatecan feed into glycolytic intermediates and could, in principle, be a gluconeogenic precursor, BUT this rarely happens in practice as fructuse is typically present in the fed state and glycoclysis activeT or F: both Acetyl-coA and palmitate CANNOT be used as gluconeogenic precursorsTrue!
Acetyl-coA cannot be a gluconeogenic precursor as it is effectively degraded early in the TCA cycle, and there is NO enzymatic mechanism to convert it to another gluconeogenic precursor
- Pamitate is a fatty acid that would be converted to acetyl CoA and therefore also cannot be converted to a gluconeogenic precursorPyruvate is one of theprincipal gluconeogenic precursorsWhich step of glycolysis is bypassed by fructose-1-phosphatePFK-1The pathway that converts glucose --> sorbitol --> fructose is referred to as thePolyol PathwayGlycogen synthase is activated viadephosphorylationVon Gierke Glycogen storage disorder is due to deficiency ofGlucose-6-phosphataseWhat small molecule inhibits fructose 1,6-bisphosphatase (one of the 3 unique enzymes in gluconeogenesis)Fructose 2,6-bisphosphate
- this small reg. molecule directly inhibits fructose 1,6 bisphosphatase, competitively
- this is part of the insulin/glucagon regulation of the PFK-1/F16BPase regulatory bubbleGalactose-phosphate uridyl transferase makesUDP-galactose as part of the pathway that converts the galactose to glucoseRate-limiting step for glucose entry in muscle- Hexokinase is lower Km, below the circulating concentration, so it could be limiting if it was saturated constantly
- However, the rate of glucose entry is limited by the Glut1 transporters and can be increased by recruitment of the Glut4 transporters - these essentially determine the rate of uptake into muscle. Most glucose entering becomes immediately trapped by hexokinase mediated phosphorylation
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Whereas in the liver,
both glucokinase and Glut2 transporters are high Km to reflect increased activity in high glucose concentrations. In addition, glucokinase itself is regulated by glucose, F6P, F1P, and AMP. This is the key regulated step for glucose entry into cellular metabolismDeficiency in Galactose-1-Phosphate uridyltransferase leads toaccumulation of galactose in the blood
- in the eye this leads to formation of galactitol with an accompanying osmotic imbalance across the lens, and the formation of cateracts
- the high galactose levels block phosphoglucomutase in the liver, and leads to insufficient glycogen degradation
- this can be distinguished from the non-classical galactosemia which is a defect in galactokinase (this has the issues with cataract formation but no accompanying feeding and liver problems)Hereditary fructose intolerance leads toan accumulation of Fructose-1-phosphate (F1P), which effectively traps the phosphate pool so it is unavailable for ATP synthesis and unavailable for glycogen phospharylase as a substrate
- there is little glycogen degradation- results in fasting hypoglycemia
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Case: infant switched from breast feeding to formula and fruit juices begins to vomit and have severe hypoglycemia after eating- hereditary fructose intolerance is a congenital defect in metabolism that the infant may haveGlucagon is NOT activatedrapidly during exercise (it can be slowly), and it does NOT act on muscle, only on the liverIn severe exercise, ___ will rise rapidlycalcium
- Calcium will bind to calmodulin which then will activate phosphorylase kinase, and in turn activates glycogen phosphorylase by its phosphorylation
- Epinephrine will augment this effect when it reaches muscle via the cAMP/PKA phosphorylation of phosphorylase kinaseA priority of muscle is to replenishglycogen stores after exercise
- strenuous excercise for several hours will substantially deplete muscle glycogen
- so any food eaten after strenuous exercise will be stored as glycogen in the muscleMcCardles syndromeCharacterized by temporary muscle weakness and cramping with exercise (recovers from exercise then gets exhausted quickly again)
- due to a congenital deficiency in Glycogen PhosphorylaseGlucose-6-phosphate is synthesized in theEndoplasmic reticulum
- it allosterically regulated both glycogen synthase and glycogen phosphorylaseCalcium release in the liver is triggered byalpha-adrenergic stimulation by epinephrine
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In muscle, it is due to increased calcium triggering muscle contractionsT or F: glycogen phosphorylase kinase phosphorylation of glycogen phosphorylase is not catalytic in naturetrue!T or F: glycogen is NOT a gluconeogenic precursortrue!
- Lactate, Glutamine, Alanine, and Glycerol are though-T or F: glyceraldehyde 3-phosphate dehydrogenase is NOT common to the glycolytic and gluconeogenic pathwaysTrue!Conversion of acetyl CoA to malonyl CoA is the rate limiting step in fatty acid synthesis. Which enzyme catalyzes this reactionAcetyl CoA carboxylaseLipoprotein Lipase mediates uptake of fat in the fed state principally inAdipose tissue
** lipoprotein lipase is located in the capillary lumen of the target tissue
- there is can interact with lipoprotein particles and execute its enzymatic activity on the TAGs in the core of the lipoprotein particles. It is tethered by binding to heparan sulfate glycoproteins or binding to a specific binding proteinGlycerol-3-phosphate is required for the synthesis oftriacylglycerols from fatty acidsThe conversion of propinoyl CoA to succinyl CoA requires two enzymes which arePropionyl CoA Carboxylase (w/ Biotin) and Methymalonyl CoA mutase (w/ Vitamin B12)Beta-oxidation of long-chain fatty acids takes place in themitochondria
- very long chain beta-oxidation takes place in peroxisomes
** peroxisomal oxidation is for >C22, or branched-chain FA, by oxidation using oxygen (O2) as a substrateInhibition of COX-1 and COX-2 will increase production ofLeukotrienes
- can lead to asthmatic symptomsHormone sensitive lipase is activated in the fasted state to carry outrelease of free fatty acids from adipose tissueBreakdown of TAGs in skeletal muscle during exercise occurs in respons tohormonal or contraction signals, NOT because of fasting (you can exercise in either fed or fasted state)In fatty acid synthesis, acetyl CoA is carboxylated using CO2 to form malonyl CoA, the carbon that is added islost in the next stepZellwegers syndromeA general peroxisomal disorder
- failure of peroxisomes to oxidize very long chain fatty acids
Can lead to:
- failure to thrive in infants
- hepatomegaly
- high levels of iron and copper in the blood
- vision problemsInsulin activates protein phosphatase, which dephosphorylates acetyl CoA carboxylase (ACC). This activatesACC and generates malonyl CoA, the substrate for fatty acid synthesis.
- The malonyl CoA also will inhibit Carbitine Palmitoyl transferase I (CPT1)Malonyl CoA inhibitsCarnitine Palmitoyl Transferase I (CPT I) to block movement of fatty acids to the mitochondrial matrixRoles of chylomicronsDelivers:
- dietary fat to adipose tissue
- dietary cholesterol to the liver
- fatty acids to muscle
Activates lipoprotein lipaseDo chylomicrons activate hormone sensitive lipase?NO!Main role of the citrate/pyruvate shuttle is tomove acetyl CoA from the mitochondria to the cytosol
- while citrate is transported it is just an intermediaryMethylmalonyl CoA is an intermediate in thebreakdown of odd-chain fatty acids and branched chain amino acids and a few othersRegulators of acetyl CoA carboxylaseactivated by: Citrate and insulin
inhibited by: Palmitoyl CoA, Glucagon, AMPBeta-oxidation, the breakdown of fatty acids to acetyl-CoA takes place in thematrix of the mitocondriaAre red bloods cells fed by fatty acids in the fasted state?NO!
- RBCs do not have a mitochondria so they cannot utilize fatty acids as an energy sourceWhich vitamin is covalently coupled to the acyl carrier protein?B5 (pantothenic acid) is a constituent of CoA and of the acyl carrier protein- BOTH are required in fatty acid synthasis, BUT the B5 is coupled covalently to the acyl carrier proteinGlycerol kinase can only be found in theliver
- The liver can utilize glycerol released from adipose tissue or by the action of lipoprotein lipase for TAG synthesis, as as a gluconeogenic precursore
- BUT the liver has priority as other organs do not have glycerol kinase and cannot use it- this is presumably beacuse of the importance of glycerol as a gluconeogenic precursor during fasting, ensuring that the liver will get full use of itThe presence of dicarboxylic acids is a characteristic ofa deficiency in acyl-CoA dehydrogenase
* looking at length one can differentiate if it is a deficiency in medium chain length acyl-CoA dehydrogenase (MCAD)
- the fatty acids that accumulate undergo omega oxidation to get more energy
- the inability to completely degrade the fatty acids results in a low energy state of the liver
- It therefore has insufficient energy to sustain gluconeogenesis - this results in hypoglycemia (bc there would be insufficient energy for gluconeogenesis)Concentration of calcium inside the cytosol is10000 times lower than the outside
- makes a powerful electrochemical gradient
- to remove calcium from the cell against such a large concentration gradient, either primary or secondary transport (Na+/Ca2+ exchanger, Ca/Mg ATPase transporter)Calcium and phosphate together are key components to production of the major crystalline salt of bone,hydroxylapatiteThe ratio of freely dissolved to bound Ca2+ is even less in tissues like bone, in which almost ALL of the calcium is found insalts
* Calcium-Phosphate salts
- ectopic calcification occurs when solubility product (SP) exceeds the critical solubility product
* Hydroxyapatitie aka Hydroxylapatite= primary form of bodily calcium and phosphateA normal calcium intake usually exceedsnormal calcium absorption into the body
* normally feces and urine are the routes by which calcium exits the body- in pregnant and/or lactating females there are two other exit routs for calicum: from mother to fetus across the placenta and from mother to neonate from milk
* remember Ca2+ can function as a stool softnerIntestinal Calcium Absorption occurs via1. Paracellular transport (rare): pass through tight junctions from the lumen into the ECF from there into the blood
2. Apical and basolateral membranes
- Apical: Ca2+ channels (TRPV6)
- Basolateral: Sodium/Ca2+ exchanger and Primary active calcium transportIntracellular phosphate concentration is 100xhigher than extracellular
- mostly found in bone
- Of all its concentration throughout the body 90% is free, 10% is boundWhich hormones are involved in Calcium and Phosphate balance (6)* Parathyroid Hormone (PTH)
- Parathyroid Hormone-Related peptide (PTHrP): only in pathology as marker for some cancers
* Calcitrol (aka 1,25- (OH)2 cholecalciferol, or 1,25-(OH)2D3) - NONE are VitD but are called this by patients
- Calcitonin: corrects significantly high Ca2+ levels
* Fibroblast Growth Factor 23 (FGF-23)
***= the main 3Parathyroid hormoner (PTH)A peptide hormone
Low extracellular Ca2+: increases PTH
- This also regulated secretion of PTH indirectly by increasing calcitriol production
- High levels of calcitrol inhibit PTH secretion indirectly (by increasing plasma Ca2+)- So (high calcitrol; low PTH)
* the higher the calcium ion conc. outside the parathyroid cells, the lower the cAMP and the higher the Ca2+ inside the cell
- Gi inhibits adenylyl cyclase
- Gq activates release of calcium
* these brind down PTH concentration
High extracellular Ca2+: decreases PTH
- When calcium is low, there is high cAMP and low Ca2+, which stimulated PTH secretion
- Gs activates adenyly cyclase: high cAMP
- Gq is inhibited; low Ca2+
*** usually this hormone is in a tight range with calcium concentration
cAMP= Ca2+ (normal PTH levels)- this is the "just-right" pointExamples of feedback loops that are constitutivels secrete-until-stopped feedbacks- prolactin regulation
- calcium feedbackParathyroid cells are detectors and secretors all in oneWhen extracellular calcium is HIGH
More calcium sensors mobilize intracellular Ca2+ and decrease PTH compared to baseline
- modulated via Gq and Gi, leading to decreased PTH mRNA transcription and PTH production
- Gq: increases PLC which results in more calcium inside the cell
- Gi: reduces aenylyl cyclase activity, which results in less cAMP
- levels vary with ECF Ca2+
Calcitrol (the active form of VitD) also inhibits PTH gene expression and PTH production and secretion- while activating the transcription of more calcium sensors (CaSR)
* unlike regular sensors these inhibit secretion, the more of them you have at the cell surface, the more the process of PTH secretion will be inhibitedActions of Parathyroid hormoneWorks to Increase concentration of calcium in the blood by:
- Getting calcium out of bone (note the PTH mobilizes calcium salts out of bone- NOT collagen like cortisol does)
- Decreases loss of calcium in urine
- Indirect effect= increase prodcution of VitD (Calcitriol) which enhances absorption of calcium from intestine
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The price: PTH inhibits renal phosphate reabsorption, so decreased concentratin of phosphate in the bloodPTH increases the activity ofosteoclasts (to stimulate bone resorption- reduces mineralization of bone and have overall calcium release)
- PTH and calcitriol stimulated production of RANKL in osteoblasts (PTH normally, calcitrol only in emergency)
- RANKL binds to RANK osteoclast precursors
- leads to recruitment of mature osteoclasts from precursor cells
- Net increase in osteoclast activity leads to Ca2+ and posphate release into ECFPTH effects on phosphate (in a low plasma concentration state)- decreased renal tubular reabsorption of phosphate
- increased urinary exretion of phosphate
- decreased plasma phosphate concentration
* PTH increases plasma Ca++
and decreases plasma phosphateDirect vs indirect affects of increases paraythroid hormone secretion and plasma concentration as a result of trying to correct low plasma calcium concentrationPTH DIRECTLY
- increases bone resorption to increase release of calcium into plasma
- increases renal tubular reabsorption of calcium and decreases urinary excretion of calcium
- increases Calcitriol production by the kidneys, increases its plasma concentration
PTH INDIRECTLY
- increases intestinal absorption of calcium VIA VITD production!
- Calcitrol can also decreases urinary excretion of calcium
**** All these thins restore plasma clacium concentration toward normal ***PTHrP; Parathyroid Hormone Related Protein can be used totest for a possible hormone-secreting tumor
- at such unregulated high levels, it can produce exaggerated effects similar to those of hyperparathyroidism including hypercalcemia
* may play a role in development of hypercalcemia in malignancy
- some lung cancers are associated with hypercalcemia
- other cancers can be associated with hypercalcemiaCalcitonin is thought of as the"emergency brake"- a hormone that prevents pathology rather than ensure normality
Calcitonin works to
- Decrease clacium
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Calcitonin is
- secreted from parafollicular C cells of the thyroid- stimualted by gastrin or elevated plasma calcium
- inhibits osteoclast mediated bone resorption (decreasing serum calcium)
* NOT essential for human survival
- poential treatment for hypercalcemia (path)
- stimulates cAMP production in bone and kidneyCalcitrol (aka 1,25 (OH)2cholecalciferol- 1,25(OH)2D3)* the two forms of VitD are precursors to calcitriol, the active steriod hormone in calcium and phosphate balance
Calcitrol functions as a steroid hormone
- req. transport proteins and intracellular hormone receptors
- alters gene transcription for a number of proteins in target tissues
- effects are slow to start but also slow to stop, has a long half life
*** its 3 OH's come from
1. part of precursor steroid
2. Liver
3. Kidney
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VitD comes from 3 sources: solar radition of Pre-VitD3 into Vit D3, or ingested Vitmains D2 or D3The hormone FGF-23 reduces activation ofcalcidiol (inactive metabolite) to calcitriol
** PTH on the other hand stimulates calcitriol production
- Hypocalcemia and hypophosphatemia also promote its production
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NOTE: calcidiol is the form of VitD that is assayed in blood testsPrimary affect of calcitriolIncrease intestinal absorption of calcium and phosphate ions (increases calcium levels)
MOA: increase in production of proteins in intestinal epithelial cells that facilitate the absorption process
- this occurs when calcitriol binds to Vitamin D receptor and increases the transcription of these proteins
* this assumes adequate Ca2+ is being taken in in the diet
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Secondary effect
- increases calcium and phosphate reabsorption
Tertiary effect (only in emergencies)
- until calcium and phosphate levels are restores
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Calcitriol
DIRECTLY: inhibits PTH mRNA transcription
INDIRECTLY: decreases PTH secretion- by increasing plasma Ca++The intracellular receptor that binds to calcitriol is theVDR (Vitamin D Receptor)If calcitonin is only evoked in extreme hypercalcemia, how does the body lower a mild (nonpathological) hypercalcemia?- Passively just stop secreting PTH
- if it was extreme then you need to hit the calcitonin breakWhat hormone is responsible for reducing plasma phosphate aloneFibroblast Growth Factor 23 (FGF23)
- secreted by osteocytes and to a lesser extent, osteoblasts
- primary stimulus for secretion is increased serum phosphate or increase phosphorus
- other stimuli= PTH and calcitriol
- it is a peptide hormone, water soluble, short half life
Direct effects
1. impairs sodium-dependent phosphate transport in both intestinal and renal brush border membrane vesicles
2. inhibits production of calcitriol and stimulates breakdown of calcitriol
3. inhibits production/secretion of parathyroid hromone
* it DOES NOT directly interact with calciumBoth PTH and Calcitriol increase production ofFGF23
- which in turn decreases the production of both PTH and VitDPTH increases the production ofVitD while VitD decreases the production of PTH
* calcitriols indirect effect on PTH comes from increasing plasma clacium, which through Gi and Gq inhibits PTHCalcium dietary needs increase throughout the life cycle- after menopause, stable body calcium is dramatically reduced each yr in healthy women
- vitD production is reduced in the elderly as renal 1-alpha-hydroxylase enzyme function decreases
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bone density peaks in early adulthood in both males and females
- males have higher peak bone density
- with aging, bone density decreases
- women reach the "fracture threshold decades earlier then men on average"
* reason for mens stronger bones= estrogen vs testosteroneRecommended daily allowance of calcium for adultsUpper limit is 2.5-3.0 g/day
- amount absorbed into the body is depenedent upon plasma calcitriol
- BUT this allowance ensure there will be adequate calcium to absorb, should body need it- left over serves as stoool softenerLight-colored skin has fewer melanocytes andcan produce VitD faster than dark-colored skin
* if sunlight production of VitD everyday is adequate, dietary VitD not necessaryVitamin D deficiencySeconary to chronic renal failure, or:
- lack of sunlight plus lack of dietary supplementation
- Genetic diseases (pseudovitamin D deficiency)
* effects: lack of calcium absorption capacity, and sever hypocalcemia, rickets in children, and osteomalacia in adultsPrimary Hyperparathyroidism"bones, stones, groans (brain fog) "
Abnormall high calcium levels, leads to:
- stealing calcium from bones, leading to weakening
- excreting excess calcium can lead to kidney stones
- calcium imbalance can cause changes in muscle, nervous functions, and several conditions in the digestive system including painSecondary HyperparathyroidismSecondary because results from either chronic kidney disease (CKD) or dietary VitD deficiency combined with low UV exposure
- nephrons that are nonfunctional do not secrete calcitriol
- without dietary VitD, it must be produced with req. UV light (w/o adequate light- VitD3 (cholecalciferol) cant be produced de novo so kidneys lack precursors for calcitriol production
When this hormone is no longer made nor ingested
- calcitriols direct inhibition of PTH production disappears
- without this, plasma clacium leveles decreases
- PTH levels then rise to deal with low calcium levels, uninhibited by calcitriolPhysiological functions of calcium- Maintenance of skeletal structure
- Intracellular messenger activity
- Stabilizes DNA and RNA molecules* Remember if calcium plasma is at 16.0mg/dL and it is going along with the noraml ratio of free to complex/bound calcium-these values are 50-50%
Ex. in this case 8.0mg/dL will be found as free calciumUnder normal circumstances, how much calcium and phosphate is contained in bone1.5kgFoods that contain both phosphate and clacium- cheese
- wheat
- cod filet
- nonfat milkHow much of the total calcium in the body is contained within cellsbetween 1-2 percentWater-soluble hormones with half-lives measured in minutes not hours- Calcitonin
- Fibroblast growth factor-23
- Parathyroid hormone
- Paraythroid hormone-related peptideSynthesis pathway for VitDCholecalciferol from the sun --> Calcidiol in the liver --> Calcitriol in the kidney
* in the kidney a precursor molecule can be modified two ways- one is the active form of Vit D and other is inactive
- what is this precursor molecule? Clacidiol, and the carbon hydroxylation that is specifically stimulated by PTH and inhibited by FGF-23 is on carbon 1Primary effect of calcitriol in humansincrease absorption of calcium and phosphate from the GI tract lumenVitamine D receptor is foundinside the cell, bound by calcitriolRisk factors associated with Vit D Deficiency- indoor environemnt with little to no sun exposure
- vegan diet lacking supplements
- darker skin color
- living in polar regions, either north or south of the equatorParathyroid hormone, Calcitonin, and Vitamin D- related drugs are used in1. Prevention and treatment of osteomalacia/rickets
2. Regulation of parathyroid hormone secretion in hyperparathyroid clinical situations Ex. Renal failure, primar hyperparathyroidism
3. Treatment of Hypercalcemia, osteoporosis and other diseases of high bone turnoverCalcitriol- facilitates calcium and phosphate absorption in small intestine
- interacts with PTH to enhance mobilization from bone
- decreases renal excretion of calcium and phosphate
* Actions are mediated via Vit D receptor (VDR)
- cytosolic VDR binding
- translocates to nucleus
- interacts with DNA to modify gene transcription
Other effects:
- Affects mauration and differentiation of mononuclear cells; influencing cytokine production and immune function
- inhibits epidermal proliferation and promotes differentiation (skin related therapies)
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- Oral absorption is rapid
- highly protein bound (99.9%)
Adverse effects:
- hypercalcemia with or without hyperphophatemia
- hypervitminosis D
- Use caution in renal patients with rapidly progressive disease or hyperphosphatemiaVitamin D supplementsCholecalciferol= Vitamin D3 (animal form, potency higher)
Ergocalciferol= Vitamin D2 (plant form, used for food fortification, and in US for high dose VitD injection)
** lab values do not discriminate between these two
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- orally absorbed
- sequestered in fat (fat-soluble); obestiy may lead to functional VitD deficiency
- very long hald life
- hepatic metabolism then renal metabolism
Adverse effects:
- Vit D toxicity
- Hyperphophatemia
Drug interactions:
- sunscreen may prevent adequate vitD formation
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Primary use
- replacemnet therapy to prevent/treat osteomalacia and rickets (undermineralized bone)
- hypoparathyroidism
- osteoperosis
Other uses:
- Psoriasis
- Some cancers
- Supports innate immunity
* for all these uses it is 1,25 (OH)2D (calcitriol) that is the active form of the drugVitamin D itself can be considred a"prodrug"
- WONT be effective in regulation of Ca homeostasis during established renal failureVitamin D receptor activatorsParicalcitol and Doxercalciferol
Paricalcitol
- Synthetic calcitriol derivative with vitD2 (not D3) side chain
- reduces PTH without causing hypercalcemia or altering phosphate
- administered oral or IV
- treat secondary hyperparathyroid in patients with CKD (chronic kidney disease)
Doxercalciferol
- Prodrug that is metabolized to active form of VitD2 in liver (DOES NOT need kidney for activation
- Precaution: hypercalemia, hyperphosphatemi, over suppresion of PTH
- Oral or IV administration
- Treat secondary hypeparathyroid in patients with CKDMajor risk/adverse effect of calcitriol ishypercalcemia
- bc endogenous feedback regulation of calcitriol formation has been bypassedCaSR (calcium-sensing receptor) is aGPCR that functions to adjust rate of secretion of PTH in response to the level of circulating calcium
* calcitriol may affect PTH production and secretion in hyperparathyroid secreting states by altering the synthesis of both the CaSR and PTHCinacalet*Parathyroid Related*
- Ca-sensing receptor (CaSR) activator
- allosteric modulation of the Ca receptor enhances response to calcium
- reduces PTH release
USES:
1. secondary hyperparathyroidism in renal disease
2. primary hyperparathyroidism
3. sometimes parathyroid carcinoma
** in all these situations this drug "sensitizes" the CaSR to serum calcium, changing the set point between level of calcium and the rate of secretion of PTH such that PTH secretion is suppressed by lower amounts of calcium than normal
Adverse effects:
- primary problem to watch for is hypocalcemia
- concerns about cardiac and renal effects and other potential problems in systems that are sensitive to calcium, but not yet well describedTeriparatide handlesmoderate dose "spikes" of PTH - net bone formation
- MOA: same as PTH
USE:
- severe osteoperosis at high risk of fracture
- initial therapy for osteoperosis?
- administered by SQ injection
- enzymative breakdown in the liver followed by renal excretion
- short half life
Adverse effects: hypercalcemia, kidney stones, elevated uric acid, orthostatic hypotension
BLACK BOX WARNING: osteosarcoma = limit use to no more than 2 yrs and DONT use in those with increased risk for thisCalcitoninA hypocalcemic (and hypophosphate) hormone whose actions oppose PTH
- released by thyroid parafollicular C cells
- most potent peptide inhibitor of osteoclast mediated bone resorption
- secretion mediated by serum calcium levels (level high= calcitonin increase, level low= calcitonin decrease)
USES:
- hypercalcemia
- Paget's disease
- Osteoperosis
GIven via injection of nasal spray
effective duration= 6 hrs
- tolerance develops after a few days (for hypercalcemia)
side effects: nauses, cramping, swelling, hypersensitivity reactions
Added benefit to therapy: analgesis properties
** calcitonin inhibits osteoclastic activity via direct suppression of osteoclastic activityWhen lab values are obtained for "vitamin D", what compound is being measuredCalcidiol ( 25 (OH)D )The only drug currently available that stimulates new bone formation?Teriparatide
- stimulates osteoblasts to increase new bone formation
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Calcitonin works to prevent bone resorption- directly inhibits osteoclast activityThe high affinity ligand for VitD receptor activation iscalcitriol
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calcidiol can bind the VDR with very low affinity (this only results in biological response when the levels of calcidiol are excedingly (nonphysiologically) highMost appropriate use for VitD supplementation in a normal, healthy personVitamin D itself (cholecalciferol and ergocalciferol) which has no known biological activityMost high risk adverse effect of calcitriol administrationHypercalcemia
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Calcitriol is most likely required in the treatment of renal failure
- calcitriol can help to promote intestinal calcium absorptionCinacalcet is anallosteric modulator of the calcium-sensing receptor
- it does NOT bind to the same site in the receptor as Ca does
- it gives the receptor an enhanced effect to decrease PTH relative to the effect of the same level of serum Ca in the absence of Cincalet
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Most likely to treat
Secondary hyperparathyroidsim in renal failure, can also be helpful in primary hyperparathyroidism
- cinacalcet reduces PTH secretion.Primary target of calcitonin in the treatment of osteoperosisOsteoclast
- calcitonin inhibits osteoclast activity- decreases bone resorption in the short term
- it is NOT an effective overall monotherapy for osteoporosiswhich bone cell is the primary target of teriparatide in treatment of osteoperosisOsteoblast
- Teriparatide mimics PTH which works to stimulate osteoblastic bone formation
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exposure to higher levels of PTH can begin to recruit osteoclasts into bone resorption- changing net balance of bone turnover to net resorptionPGE3is made from ecosapentaenoic acid which is found in fish and algal oil
- seeds, nuts, and red meat have very little ecospentaenoic acidCortisol is a natural inhibitor of anover active immune system by inhibiting the synthesis of prostaglandins and leukotrienes that usually stimulate the immune system
- cortisol inhibits phospholipase A2 thereby inhibiting the production of arachiodonic acid (synthesis of all prostaglandind and leukotrienes requires arachidonic acid as a precursor)
- glucocorticoids, like cortisol, DO NOT have the same effect as androgrens which are the steroids that body builders take to become bulkyPGE2used to soften the cervix which allows for cevical dilation and thereby induces or accelerates labor. It also strengthens contractionsPGF2, Prostamide F2athis is Bimatoprost
- found in some eye lash enhancing makeup and used to lengthen and darken the eyelashes and eye brows
- also used in treatment of open angle gluacoma
- it alters the fluid maintenance of the eye and can cause red itchy eyes as well as the darkening and lengthening of eyelashes and eye browsAspirin inhibits COX1 and COX2 but does NOT inhibitlipoxygenase- which produces leukotrienes which cause smooth muscle constriction
- Leukotrienes are implicated in asthma symptoms and cause smooth muscle constriction and thus bronchoconstrictionPGI2Epoprostenol (chemically same as native PGI2)MisoprostolPGE1 analog used with mifepristone for termination of early pregnancyIloprostWhen administered for pulmonary arterial hypertension, this prostaglandin analog may cause caugh and bronchoconstriction
** it is administered by nebulizer- direct airway exposurePGF2alpha drugsLatanprost
Bimatoprost- additionally used to increase eyelash growth
Tafluprost
Travoprost
*** these above are used in eye to treat open angle gluacoma
Carboprost- effects on uterusDinoprostonePGE2 used for cervical ripening in induced laborAlprostadilPGE1 drug used to maintian patency of the ductus arteriosusT or F: prostaglandins and their analogs are highly specificFALSE!
- they lack selectivity and this explains their many adverse effects and why a drug may target very diverse actionsErection thats lasted for >5hrs accompanied by penile pain and tenderness could be caused byAlprostadil
- given intraurethrallyT or F: synthetic prostaglandins are NOT effective after oral administrationTRUE
they have a very short half-life- so they are unsuitable for oral administration
* some have been created that have a longer biological half life- these are administered orallyGluconeogenesis enables the liver tomaintain blood glucose levels during starvationStress response includes increases inCortisol, Growth hormone, and Epinephrine
- Cortisol: promotes fatty acid release from adipose tissue and synergistically enhances the effects of epinephrine and glucagon
- Epinephrine prepasres cells for increased glycogen breakdown and glycolysis and also promotes release of free fatty acidsStress results in the rapid mobilization of which circulating energy carriersFatty acids and glucose
**** involved in both stress and exerciseSkeletal muscles of well-trained individuals utliize more ___ than untrained during moderate to severe excercisePlasma fatty acids
- exercise promotes release of free fatty acids and this is the preferred substrateKetone bodies are produced in theliverThe metabolism of ethanol by the liverincreases NADH/NAD+ ratio reducing its ability to perform gluconeogeneis (increases drunkness, this works via alcohol dehydrogenase)Cori cyclelactate is taken up by the liver for synthesis of glucoseT or F: fatty acids can be used as carbon source for gluconeogenesisFALSE!
- Fatty acids are NOT gluconeogenic precursors
- Lactate and glycerol are howeverUrea is aproxy for nitrogen- whose principal source is protein degradation
- if a person eats carbs for a day then undergoes prolonged fasting their urea will be increased followed by a slow decline over many days (protein sparring phenomenon)Ketone bodies are synthesized in what cellular localeMitochondriaIf a marathon runner hits a "wall"- his muscle glycogen stores will becompletely depleted
- if this occurs upon finishing the race his main fuel source will be free fatty acids
- as time progresses muscle glycogen and TAG stores become depleted and contribute less while free fatty acid release increases and circulating glucose is used more
- this glucose is derived from gluconeogeneis and from liver glycogen stores
- to improve a runners ability to carb load and his use of fatty acids they could improve their aerobic conditions- leading to faster mobilization and utilization (helps to preserve glycogen stores during the race- wont hit the wall as fast)Which hormones are produced by the thyroid gland- Tri-iodothyronine (T3)
- Thyroxine (T4)
- CalcitoninBlood supply to the thyroid glandSuperior thyroid aa from the external carotid
and
Inferior thyroid aa from the subclavianWhen stimulated the thyroid follicle changes from cuboidal toSimple columnar epithelium surrounding a single follicular lumenPurpose of the follicular lumen in thyroid follicle is tostore thyroglobulin for use in thyroid hormone synthesisT or F: T3 is the most biologically active in tissuestrue ! (missing the top iodine, if it was bottom one would be RT3)In person consuming a normal diet containing iodine, apprx what percent of this persons iodine is stored in the thyroid gland2/3 or 67%In synthesis of thyroid hormone, what state and through what cellular mechanisms does iodine from the plasma enter the follicular cellEnters as iodide via facilitated diffusion vis a sodium symporter
- it exits the follicular lumen still as iodide via facilitated diffusion via a uniport called Pendrin
-----
In secretion of thyroid hormone, iodine from the colliod enters as iodine into the follicular cells via endocytosis of iodine-containing proteinsIn what compartment does the acutal production step of T3 and T4 synthesis take placeIn the lumen of the thyroid follicleMost secreted thyroid hormone is transported in the plasma asThyroxine (T4), bound to thyroid binding globulinThrough what mechanims does thyroid hormone alter the activity of its target cellsConversion of T4 --> T3 in the cytoplasm, then T3 binding to a nuclear receptor, then stimulation of transcriptionLeptin has a ___ on secretion of thyroid hormoneDirect effect on arcuate and paraventricular neurons, increasing TRH secretionPrimary function of thyroid hormoneincreases metabolic rate and increases growth and maturationFasting for a porlonged period and becoming critically ill can result in theadaptive respone of reduced T3 formationThyroid has permissive action on ___, increasing it in cardiac muscle - bc its proteins were result of thyroid hormone actionEpinephrineWhat affects of thyroid hormone increase heat production in the body- increased uncoupling protein-1 (UCP-1) in brown adipost tissue
- increases sodium-potassium pumpsThyroid hormones increased production of sex-hormone-binding-globulin isNOT directly related to metabolismEffects of thyroid hormone in white adipos tissue includestimulation of adipose cell differentiationEffects of thyroid hormoneincreased cardiac output, brain maturation, fertility in adults of reproductive ageWould deficiency of TBG in plasma cause any symptomsNO!What conditions can cause Thyrotoxicosis, a condition characterized by heat intolerancePrimary Hyperthyroidism and Secondary hyperthyroidismIn a patient with medullay carnimoa what hormones would be elevated in plasmaThyrotropin
and
CalcitoninIodine Deficiencycause of endemic goiter. Used to be common in many mountainous and inland regions: Alps, Himalaya, Great lakes region, congo basin
- low T3 and T4, high TSH
- goiter is caused by chronic overstimulation of the thyroid gland by TSH
- Now rare in europe and america, but still common in exotic placesPrimary hypothyroidismthyroid gland is underactive and does NOT respond appropriately to TSH presence or absence. TH levels are too low as a result
- would expect high levels of TSH in the plasma bc feedback from TH would be minimal
Ex. reaction of thyroid following radioactive iodine therapy or resection
ex. Chronic iodine deficiency in the dietMost common cause of HyperthyroidismGraves DiseaseWhat form of thyroid dysfuction is characteristic of Hashimoto diseasePrimary hypothyroidismWhat conditions is supplementation with iodine (found in salt from stores) intended to preventCretinism and Primary hypothyroidism
- cretinism: a condition characterized by physical deformity and learning disabilities that is caused by congenital thyroid deficiency.Most appropriate single agent to perscribe to pt with hypothyroidLevothyroxine (T4)- primary drug used for thyroid hromone replacement therapy
- while liothyronine may sometimes be indicated as a second drug- it is rarely indicated for single useMost potent activator of thyroid hormone receptor isTriiodothyronine (T3)
- thyroxine (T4) was the most abundant form of circulating thyroid hormone - it is delivered to target cells via the circulation- in target tissues, it is converted to T3 (triiodothyronine), which is the most potent activator of the thyroid hromone receptor
* liothyronine= generic drug name for T3Pregnant women on thyroid replacement therapy usually need anincrease in dose while they are pregnant
- though to be due to increased circulating levels of TBG (thyroid binding globulin)
- the adequacy of thyroxine dose is monitored by measuring TSH during pregnancy, just as at other times
- if the T4 does is NOT adequate as pregnancy proceeds, TSH will go up, signaling the need to increase the dosePharmacotherapy for hyperthyroidism that results in decreased thyroid hormone secretion within a short time (days or less)Potassium Iodide
- PTU (Propylthiouracil) requires much longer to make an effective changes - bc it has little or no effect on release of preformed thyroid hormonePropranolola beta adrenoreceptor antagonist
- can effectively help control the cardiac symptoms of hyperthyroidism without directly altering the thyroid status
- it does not treat hyperthyroidism itself, but it does help prevent some of the unpleasant and possibly dangerous effects, such as tachycardiaPropylthiouracil is an effective therapy for hyperthyroidism by regulating thecoupling of diiodotyrosyl residues (or di- and monoiodotyrosyl residues) to form thyroxine (or triiodothyronine)
* Thioamide drugs, including PTU, inhibit thyroid peroxidase which is important for two key steps in thyroid hormone synthesis: the oxidation of iodide to its active form, and the coupling of iodotyrosines
- both of these reactions occur in the extracellular colloid space surrounded by follicular cellsWhat should be administered to patients with severe hypothyroidism (myxedema crisis)Both liothyronine and levothyroxine
- bc the patients illness may suppress the abilitiy of target tissues to produce adequate liothyronine from levothyroxine alone
- in addition, liothyronine can initiate more rapid responses than waiting for levothyroxine to be convertedDrugs that can be used to treat hyperthyroidismPropanolol , propylthiouracil
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