Eicosanoids

Question 1

Three major classes of eicosanoids:

Answer 1

1. Prostaglandins (PGs)
2. Thromboxanes (TXs)
3. Leukotrienes (LTs)

Question 2

…… cleaves PIP2 to generate arachidonic acid and Lyso-PIP2

Answer 2

Phospholipase A2

Question 3

Functions of Eicosanoids:

Answer 3

• Produce a wide range of biological effects of the inflammatory response
– Intensity and duration of pain and fever
– Reproductive function (including the induction of labor)

Question 4

The following are characteristic of …….
– Inhibiting gastric acid secretion
– Regulating blood pressure through vasodilation or constriction
– Inhibiting, or, activating platelet aggregation and hence regulation of thrombosis

Answer 4

Eicosanoids

Question 5

What inhibits the synthesis of arachidonic acid?

Answer 5

Corticosteriods

Question 6

What inhibits Cycloxygenase 1 and 2 (COX 1)?

Answer 6

Aspirin and Other NSAIDS

Question 7

Eicosanoids function by using specific receptor-mediated G-protein linked signaling pathways that result in the …………

Answer 7

Increase in either c-AMP levels or an increase in intracellular calcium

Question 8

If present in a phospholipid, arachidonic acid will be at the …… position

Answer 8

C-2 position

Question 9

Phospholipase A2 acts on phosphatidyl-inositol and releases …….

Answer 9

Arachidonic Acid

Question 10

The immediate dietary precursor of arachidonate is ………..

Answer 10

Linoleic Acid

Question 11

What is the result of inhibiting both COX 1 and Cox 2?

Answer 11

Reduced production of both prostaglandins and thromboxanes

Question 12

Prostacyclin (PGI2) produced by …………… and Thromboxane A2 (TXA2), produced by ……………., play opposing key roles in regulating platelet aggregation and vasodilation

Answer 12

Endothelial Cells

Platelets

Question 13

The following functions are characteristic of.........
Platelet Aggregation
Vasoconstriction
Mobilizes intracellular calcium
Contraction of smooth muscle

Answer 13

Thromboxane A2 (TXA2)

Question 14

The following functions are characteristic of………
Vasodilation
Inhibits platelet Aggregation

Answer 14

Prostacyclin (PGI2)

Question 15

How does aspirin inhibit COX1 and COX2?

Answer 15

Aspirin inhibits COX-1 and COX-2 irreversibly by acetylation of a serine amino acid side chain in the active site of these enzymes

The result is to decrease synthesis of eicosanoids

Question 16

Aspirin’s inhibition of COX1 and COX2 results in……

Answer 16

-A decrease in platelets aggregation due to the reduced synthesis of TXA2 by platelets

Question 17

Two different types of PUFA’s:

Answer 17

2- Series (linoleic acid)

3-Series (linolenic acid)

Question 18

2-Series (linoleic acid) is derived from…… and produces ……

Answer 18

Arachidonic Acid

PGI2 and TXA2

Question 19

3-Series (linolenic acid) is derived from…… and produces ……

Answer 19

Eicosapentaenoic Acid

PGI3 and TXA3

Question 20

Either ……….. or ………….can be released by activation of PLA2 and used for eicosanoid synthesis.

Answer 20

EPA or arachidonic acid

Question 21

TXA3 (from EPA) is ………… potent than TXA2 (from arachidonic acid) in platelet aggregation

Answer 21

Less

Question 22

Arachidonic Acid is converted to 5-Hyroperoxyeicosatetrainoic acid (HPETE) by …………
5-HPETE is then converted into Leukotriene A4 (LTA4)

Answer 22

5-Lipoxygenase

Question 23

LTC, LTD, LTE and LTF contain either a peptide or cysteine in their structure and are therefore called

Answer 23

Cysteinyl-leukotrienes

Question 24

The ……………..are released during anaphylaxis and they are components of the slow-reacting substance of anaphylaxis (SRS-A). They are much more potent than histamine.

Answer 24

Cysteinyl-leukotrienes

Question 25

The following are characteristic of ……
• Airflow obstruction
• Increased secretion of mucus
• Bronchoconstriction
• Infiltration of inflammatory cells in the airway wall

Answer 25

Asthma

Question 26

Asthma treatment can include ……..of leukotriene synthesis or receptors.

Answer 26

Inhibition

Question 27

How do drugs inhibit leukotriene action?

Answer 27

1) Inhibit the release of arachidonic acid (cortisol), this also leads to less PG and TX synthesis
2) Inhibit of 5-lipoxygenase activity (results in reduced leukotriene synthesis)
3) Act as Cysteinyl-leukotriene receptor antagonists

Question 28

Prostaglandin E2 (PGE2) is mainly synthesized in the…..

Answer 28

Most Tissues, especially kidney

Question 29

Functions of Prostaglandin E2:

Answer 29

Mediator of inflammation;
Vasodilation;
Relaxes smooth muscle;
Used to induce labor