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Endocrine Physiology > Eicosanoids > Flashcards

Eicosanoids Flashcards

1
Q

What are the two classes of eicosanoids?

A

PG and Thromboxanes or Leukotrienes

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2
Q

How do eicosanoids differ from normal hormones?

A

formed locally de novo synthesis from membrane lipids, not stored by cells, paracrine action, biosynthesis from cellular precursors triggered in response to various stimuli including hormones

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3
Q

What is a key function of eicosanoids?

A

inflammatory; both pro and anti

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4
Q

Where are they produced?

A

platelets, eosinophils, basophils, mast cells, macrophages, endothelial cells, brain, heart, and smooth muscle cells

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5
Q

What body functions are they essential for?

A

maintainence of gastric mucosa, induction of labor, pro and anti-thrombotic

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6
Q

What are the signs of inflammation?

A

Pain (dolor), heat (calor), redness (rubor), swelling (tumor) and loss of function

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7
Q

What causes the redness in inflammation? What else does this cause?

A

enlarged capillaries due to vasodilation; also temperature increase

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8
Q

What causes edema in inflammation?

A

increased capillary permeability allows for influx of fluid and cells

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9
Q

What causes pus formation in inflammatory response?

A

phagocytic cells attracted to ite relase lytic enzymes, damaging healthy cells, accumulation of cells and fluid forms pus

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10
Q

What is responsible for the pain associate with inflammation?

A

mediators released by phagocytic cells

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11
Q

What are the three stages of catabolism/biosynthesis of PG?

A

release of arichdonis acid from membrane phospholipids (deacetylation, RATE LIMITING), oxygenation of arachidonic acid to yield PGH2 (PG endoperoxide= precursor via PG synthase), Conversion of PGH2 to other PG or to TXA2 in cell type specific manner

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12
Q

Where is PGHsynthase most abundant? What kind of enzyme?

A

ER, cyclooxygenase or COX, shuttle back and forth btwn ER and nuclear membrane in reponse to stimuli

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13
Q

What is the difference in Cox 1 and Cox 2 expression?

A

COX 1 constitutive, COX2 inducible

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14
Q

What are the characteristics of COX1?

A

homodimer bound to surface of lipid bilayer by hydrophobic membrane binding helices

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15
Q

What are the steps of biosynthesis of leukotrienes?

A

arachidonic acid to 5-HPETE by 5-lipoxygenase, to Leukotriene A4 by 5-lipoxygenase, to Leukotriene B4 by hydrolase to Leukotriene C4 by adding glutathione, to Leukotriene D4 losing glutamic acid, lose glycerin o get Leukotriene E4

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16
Q

how are eicosanoids transported out of the cell after synthesis?

A

facilitated transport through PG transporter (PGT) to exert paracrine action on family of PGR

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17
Q

What are the three types of receptor forms?

A

all GPCR; “relaxant”, “contractile”, and “inhibitory”

18
Q

What are the relaxant receptors? signal pathway used?

A

IP, DP1, EP2 and EP4 form one cluster; Gs mediated increase in intracellular cAMP

19
Q

What are the contractile receptors? signal pathway used?

A

EP1, FP, and TP; Gq mediated increase in cAMP

20
Q

What are the inhibitory receptors? signal pathway used?

A

EP3 that couples; Gi decreasing cAMP formation

21
Q

What is the biological action of TPbeta?

A

vasoconstriction on VSMC

22
Q

What is the biological action of IP on VSMC?

A

vasodilation

23
Q

What is the biological action of TPalpha?

A

platelet aggregation

24
Q

What is the biological action of IP on platelet?

A

platelet declumping

25
Q

What is the biological action of FP?

A

uterine smooth muscle contraction, parturition

26
Q

What is the biological action of DP2?

A

Th2 lymphocyte, chemotaxis

27
Q

What is the biological action of DP1?

A

allergic asthma, lung epithelium

28
Q

What is the biological action of EP4?

A

bone resorption through osteoclast activity

29
Q

What is the biological action of EP3?

A

fever generation Neurons of OVLT in POA

30
Q

What is the biological action of EP2?

A

maturation for ovulation and fertilization in ovarian CO cells

31
Q

What is the biological action of EP1?

A

pain response in spinal neurons

32
Q

Where does NSIADs work in this pathway?

A

AA to PGH2

33
Q

What is the biological action of LTB4?

A

high affinity for B-LT1 receptors on Neutrophils causing chemotaxis; low affinity for B-LT2 receptor on How do hydrocortisone and dexamethasone work?most tissues unknown response

34
Q

What is the biological action of LTC4?

A

modification to LTD4 -> CysLT1 receptor on airway smooth muscle and post capillary venule causing bronchoconstriction and edema; both LTC4 and LTD4 to CysLT2 receptor heart, adrenal, brain and spleen-> unknown response

35
Q

Where in this pathway do the asthma drugs montelukast (singulair) and zafirlukast (Accolate) act? What type of drug are they?

A

block binding of LTD4 to airway smooth muscle receptor; CysLT1 receptor antagonist

36
Q

What enzyme is specifically blocked by NSAIDS?

A

PGsynthase (COX1 and COX2)

37
Q

how does aspirin work?

A

inactivates both COX1 and COX2 by covalently acetylating serine residue; suicide inhibitor, blocks proper substrate access and orientation in receptor site; inactivates enzyme irreversibly both in platelets and endothelial cells; Endothelial cells can recover activity by synthesis of enzyme, platelets cant

38
Q

What are some selective COX2 inhibitors? When are they used clinically?

A

Coxibs, Celebrex (celecoxib), and rofecoxib (Vioxx), arthritis and pain symptom management; 2nd gen valdecoxib and etoricoxib under clinical development

39
Q

How do leukotriene modifiers or antileukotrienes work?

A

5-lipoexygenase inhibitors- Zyflo

40
Q

How do hydrocortisone and dexamethasone work?

A

decrease production of leukotrienes and PG by inhibiting phospholipase A as well as COX

41
Q

How and why does a fish oil diet effect the eicosanoids?

A

high eicosapentanoic acid (EPA) and ararchidonic acid relative (omega 3); high EPA in membrane when ecosanoid synthesis is initiated they will produce PGI3 and TXA3 instead of PGI2 and TXA2; PGI# same platelet activity as PGI2 but TXA3 much weaker platelet aggregating than TXA2 (decreasing MI risk)

Endocrine Physiology (9 decks)

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