Eicosanoids Flashcards

1
Q

Eicosanoids are important bio-active agents synthesized form what?

A

PUFAs - 20 carbons long

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2
Q

Prostanoids are synthesized by the ___ pathway

A

cyclooxygenase (COX)

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3
Q

The leukotrienes and lipoxins are synthesized by the ____ pathway

A

lipoxygenase

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4
Q

Both the COX pathway and the lipoxygenase pathway start with a 20 carbon PUFA, usually ____ acid

A

arachidonic

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5
Q

The arachidonic acid is derived from membrane ____. It is released by the action of ____ ___

A

phospholipid; phospholipase A2

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6
Q

What is the rate-limiting step in prostaglandin synthesis?

A

hydrolysis of arachidonic acid

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7
Q

Agents which stimulate the production of prostaglandins do so by stimulating the activity of what?

A

phospholipase A2

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8
Q

The other C20 PUFAs may serve as precursors. EPA (C20:5) is obtained from what? It is a w-__ acid

A

diet; 3

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9
Q

PGH2 is the first prostaglandin product and is the common intermediate of what?

A
  1. the other important prostaglandins

2. the thromboxanes

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10
Q

Prostaglandin synthase (PGS) has two components: cylclooxygenase (COX) and PG hydroperoxidase. What do these two components catalyze?

A
  1. COX: catalyzes synthesis of PGG2

2. PG hydroperoxidase catalyzes the formation of PGH2 from PGG2

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11
Q

PG hydroperoxidase requires what?

A

GSH

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12
Q

The number of double bonds in the side chains depends on the PUFA precursor. IF the precursor is eicosatrienoic acid, the product would be ____. If the precursor is eicosapentaenoic acid, the product would be ___.

A

PGH1; PGH3

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13
Q

There are two forms of COX. COX1 is a ____ enzyme found where?

A

constitutive; found in gastric mucosa, platelets, vascular endothelium and kidney

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14
Q

There are two forms of COX. COX2 is a ___ enzyme found where?

A

inducible; found in activated macrophages and monocytes which have been stimulated by PAF, IL-1, or LPS; also found in smooth muscle cells, epithelial cells and neurons

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15
Q

COX2 induction is inhibited by ____

A

glucocorticoids

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16
Q

The ____ inhibit COX.

ex: aspirin, ibuprofen etc.

17
Q

Aspirin inhibits COX__ more than COX__

18
Q

Aspirin’s mechanism of action involves ___ of the COX enzyme

A

acetylation

19
Q

Steroid anti-inflammatory drugs (hydrocortisone, prednisone) act by inhibiting this enzyme’s activity.

A

phospholipase A2

20
Q

PGE2 and PGF2 are major prostaglandins produced where?

A

kidney and spleen

21
Q

PGE2 is produced by what?

A

macrophages, mast cells, and B cells

22
Q

PGD2 is produced by ___ cells

23
Q

PGI2 and PGF2 are major prostaglandins produced by ___ ___

A

blood vessels

note: PGI2 is an important inhibitor of platelet aggregation

24
Q

Thromboxane A2 (TXA2) is a major prostaglandin produced by ____

A

platelets

note: stimulates platelet aggregation

25
The half-life of TXA2 is very long. True or false?
False; very short - it is rapidly converted to the inactive TXB2
26
In what 3 ways do prostaglandins mediate inflammation?
1. induce redness and heat 2. increase capillary permeability 3. pyrogens activate synthesis of prostaglandins
27
Prostaglandins stimulate ____ contraction and inhibit ____ acid secretion
uterine; gastric
28
HPETEs are highly reactive intermediates that are rapidly converted to their analogous _____ acids or to ____
HETEs; leukotrienes
29
The most important products of lipoxygenases in humans is ____-____ since these are converted into the leukotrienes
5-HPETE
30
Leukotrienes are important secretory products of ____ and each one contains a conjugated ___ group
leukocytes; trienoic note: the subscript number refers to the total number of double bonds
31
Leukotrienes mediate ____ disorders
inflammatory
32
SRS-A is a mixture of LTC4, LTD4, and LTE4 and is a potent stimulator of the ___ ___ musculature
bronchial airway
33
LTB4, LTC4, LTD4, and LTE4 increase ___ ___
vascular permeability
34
inhibition of angiogenesis, clearance of pulmonary edema, and protection of reperfusion injury are all actions of what?
lipoxins
35
Current drugs for ___ include 5-LOX inhibitors, and LT-receptor antagonists
asthma
36
Eicosanoids act via a __ trans-membrane __ ___ coupled receptor
7; G protein