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Molecules to Cells > ILA 11 Eicosanoid Metabolism > Flashcards

ILA 11 Eicosanoid Metabolism Flashcards

Describe the functions and clinical significance of the eicosanoids: prostaglandins, prostacyclins, thromboxanes, leukotrienes, 5-HETE, and lipoxins Interpret the abbreviation nomenclature for eicosanoids Explain the roles of the significant enzymes in the biosynthesis of the eicosanoids Explain the two roles of glutathione in eicosanoid synthesis Describe the impact of NSAIDs, acetaminophen, asthma drugs, and anti-inflammatory steroids on eicosanoid biosynthesis and function

1
Q

What is an eicosanoid?

A

considered to act as local hormones functioning through G-protein receptors

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2
Q

What are the two methods of arachidonic acid formation?

A
  1. From cell membrane phospholipids using Phospholipase A2
  2. Dietary Linoleic Acid

Slide 10

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3
Q

Prostaglandins are produced by which tissue types?

A

most tissues

Slide 11

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4
Q

PGE2 is known pharmaceutically as what?

A

Dinoprostone

Slide 11

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5
Q

What are the fuctions of PGE2?

A
  • Inflamatory mediator
  • Pyrogenic
  • Vasodilation (lowers BP)
  • Bronchodilation
  • Contraction of longtitudinal muscle in intestine
  • Used pharmaceutically to induce labor

Slide 11

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6
Q

What are the pharmaceutical names of PGF2α?

A

Dinoprost or Carboprost

Slide 11

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7
Q

What are the functions of PGF2α?

A
  • Vasoconstriction
  • Contraction of smooth muscle
  • Used pharmaceutically to induce labor

Slide 11

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8
Q

What 2 enzymatic activities occur in Prostaglandin Synthase?

A
  1. Cycloxygenase
  2. PG hydroperoxidase

Slide 13

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9
Q

What are the 2 isozymes of Prostaglandin Synthase (PGS) and thier functions?

A
  1. PGS-1(COX-1) - constitutively expressed (clotting)
  2. PGS-2 (COX-2) - produced in response to inflamatory signals (pain & inflammation)

Slide 13

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10
Q

What enzyme catalyzes the conversion of arachidonic acid to PGG2 (step 1 of PGS)?

A

Cyclooxygenase

as part of the Prostaglandin Synthase Complex

Slide 14

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11
Q

Prostaglandins have the characteristic shape of what?

A

Hairpins

Slide 12

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12
Q

What enzyme catalyzes the conversion of PGG2 to PGH2 (step 2 of PGS)?

A

(Hydro)Peroxidase

Slide 15

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13
Q

The peroxidase reaction in step 2 of PGS requires what cofactor?

A

Reduced Glutathione

Slide 15

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14
Q

Which prostaglandins are produced from PGH2?

A
  • PGD2
  • PGE2
  • PGF2α

Slide 16

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15
Q

What is Prostacyclin (PGI2)?

What is it a class of? Where is it primarily produced? Funcitons?

A
  • class of prostaglandins
  • endothelium of blood vessels
  • Vasodilation, inhibition of platelet aggregation, increased formation of cAMP

Slide 17

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16
Q

What prostaglandin is prostacyclin produced from?

A

PGH2

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17
Q

What are thromboxanes (TXs) a derivative of?

A

PGH2

Slide 19

18
Q

What primarily produces thromboxanes?

A

Platelets

Slide 19

19
Q

What are the functions of thromboxanes?

A
  • promotes platelet aggregation
  • decreases formation of cAMP
  • vasoconstriction
  • mobilizes intracellular calcium
  • smooth muscle contraction

Slide 19

20
Q

Thromboxanes are produced from what precursor molecule?

A

PGH2

Slide 20

21
Q

What enzyme catalyzes the synthesis of thromboxanes?

A

Thromboxane Synthase

Slide 20

22
Q

What do NSAIDs do?

Inhibition of what to prevent what?

A

inhibit cyclooxygenase to prevent synthesis of prostaglandins, thromboxanes, and prostacyclin

NSAIDs have anti-inflamatory, anti pyretic, & pain relieving effects

Slide 21

23
Q

How does Aspirin work?

What does it inhibit?

A

inhibits both COX-1 & COX-2, but inhibits COX-1 more effectively than COX-2

Slide 21

24
Q

In terms of function, Acetaminophen has similar effects as NSAIDs, but lacks what effect?

A

Anti-inflamatory effect

Acetaminophen has pain-relieving & anti-pyretic effects like NSAIDs.

Slide 22

25
Q

What do we know about Acetaminophen?

Mechanism?

A
  • mechanism not fully understood
  • indirectly blocks cyclooxygenase
  • studies suggests it blocks COX-3 (isozyme of cyclooxygenase abundant in cerebral cortex & heart

Slide 22

26
Q

Where are Leukotrienes (LT) produced?

A
  • leukocytes
  • platelets
  • mast cells
  • heart & lung vascular tissue

Slide 23

27
Q

What are the functions of LTC4, LTD4, & LTE4?

A
  • contraction of smooth muscle
  • promote bronchoconstriction (important in asthma)
  • vasoconstriction
  • increased vascular permeability
  • anaphylaxis

Slide 23

28
Q

What are the functions of LTB4 & 5-HETE?

A
  • increased chemotaxis of polymorphonuclear (PMN) leukocytes
  • release of lysosomal enzymes from PMN leukocytes
  • adhesion to leukocytes

Slide 23

29
Q

What ezyme produces 5-HPETE from Arachidonic acid?

A

5-lipoxygenase

Slide 25

30
Q

LTA4 is the common precursor for which leukotrienes?

A

LTB4 & LTC4

Slide 26

31
Q

What compound is required for the synthesis of LTC4?

What happens to the compound?

A

Reduced Glutathione

It becomes part of the structure

Slide 26

32
Q

How are LTD4 & LTE4 produced from LTC4?

A

by removing glutamate and then glycine both from glutathione in LTC4

Slide 27

33
Q

Differentiate between glutathione function in:

leukotriene synthesis vs prostglandin synthesis

This a more complex question but was noted on the slide

A

In Leukotriene: the reduced glutathione is incorporated into LTC4 and then loses a glutamate & a glycine to form LTD4 & LTE4, respectively.

In Prostaglandin: the reduced glutathione is used in the reaction of PGG2 to form PGH2 using Peroxidase

Slides 15 (Prostaglandin) & 27 (Leukotriene)

34
Q

What are inhibitors of leukotriene synthesis and function used to treat?

A

Asthma

Slide 28

35
Q

How does the drug Zileuton (Zyflo) work?

What does it inhibit and prevent the synthesis of?

A

Inhibits 5-lipoxygenase preventing the synthesis of 5-HPETE & all leukotrienes derived from 5-HPETE

Slide 28

36
Q

How do LTC4, LTD4, & LTE4 antagonists (Montelukast, Zafirlukast) work?

A

They block the binding of these leukotrienes to their receptors

Slide 28

37
Q

Where are Lipoxins (LX) produced?

A

Leukocytes

Slide 30

38
Q

What are the functions of LXA4 & LXB4?

A
  • Inhibit angiogenesis
  • Promote clearance of pulmonary edema

Slide 30

39
Q

What are the two ways that lipoxins can be synthesized from arachidonic acid?

A
  1. Arachidonic Acid –(5-Lipoxygenase)–>5-HPETE —->LTA4–(15-Lipoxygenase)–>Lipoxins
  2. Arachidonic Acid –(15-Lipoxygenase)–>15-HPETE–(5-Lipoxygenase)–>Lipoxins

Slide 31

40
Q

How do anti-inflamatory steroids (Prednisone) work?

What do they inhibit? Prevent synthesis of?

A

Inhibit Phospholipase A2 preventing synthesis of most eicosanoids

converts phospholipids to arachidonic acid

Slide 32

41
Q

How do NSAIDs work?

A

inhibit cyclooxygenase preventing synthesis of most prostaglandins, thromboxanes, and prostacyclin

Slide 32

Molecules to Cells (20 decks)

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