Arachidonic Acid and Cyclooxygenase Pathway

Study Notes

Arachidonic Acid and Inflammation

Arachidonic acid is a 20-carbon fatty acid with 4 double bonds.
It is involved in the cycloxygenase pathway and enzymatic pathways.
Enzymatic pathways include COX-1 and COX-2, which produce prostaglandins.

COX-1 and COX-2

COX-1 is always expressed and protects the gastric mucosa.
COX-2 is induced by injury and is involved in inflammation.
NSAIDS (non-steroidal anti-inflammatory drugs) block both COX-1 and COX-2, but can cause gastric problems.
Blocking COX-2 reduces inflammation and is beneficial for patients with high levels of PGE2.

Prostaglandins

Prostaglandins are products of arachidonic acid and have various functions, including:
- Vasodilation and inhibition of platelet aggregation (PGI2).
- Pro-inflammatory effects (PGE2).
- Abortion (PGE2).
- Receptors for prostaglandins act on different targets, such as thrombosis and vasodilation.

Omega-3 Fatty Acids

Omega-3 fatty acids reduce the formation of prostaglandins and leukotrienes.
They give rise to 3-series prostaglandins, which are less potent than the 2-series.

Leukotrienes

Leukotrienes are formed from arachidonic acid through the 5-lipoxygenase pathway.
They have pro-inflammatory effects, including:
- Vasoconstriction.
- Increased permeability.
- Chemotaxis.
Zileuton inhibits 5-lipoxygenase, reducing the formation of leukotrienes.

Inhibition of Inflammation

Inhibiting the release of arachidonic acid from phospholipids can reduce inflammation.
Blocking the action of phospholipase A2 can prevent the formation of prostaglandins and leukotrienes.

Description

This quiz covers the role of arachidonic acid in the cyclooxygenase pathway, including its conversion to prostaglandins and the regulation of COX-1 and COX-2 enzymes. It also touches on the importance of these pathways in inflammation and the menstrual cycle.