The lipid mediators prostaglandins and leukotrienes are produced from arachidonic acid present in membrane phospholipids and stimulate vascular and cellular reactions in acute inflammation.
Arachidonic acid is a 20 carbon polyunsaturated fatty acid that is derived from dietary sources or by conversion from the essential fatty acid linoleic acid.
Arachidonic acid derived mediators are synthesized by two major classes of enzymes
Arachidonic acid is a 20 carbon polyunsaturated fatty acid that is derived from dietary sources or by conversion from the essential fatty acid linoleic acid.
Arachidonic acid derived mediators are synthesized by two major classes of enzymes
- Cyclooxygenases
- Lipooxygenases
Cyclooxygenase pathway:
Arachidonic acid - Prostaglandin G2 - Prostaglandin H2 - Prostacyclin PGI2, Thrombaxane A2 - PGD2 - PGE2.
Lipooxygenase pathway:
5HPETE - Leukotriene A4 - Leukotriene C4 - Leukotriene D4, Leukotriene E4 and Lipoxin A4 and Lipoxin B4
Principal actions of arachidonic acid metabolites in inflammation:
- Vasodilation - PGI2, PGE1, PGE2, PGD2
- Vasoconstriction - Thromboxane A2, Leukotrienes C4, D4, E4
- Increased vascular permeability - Leukotrienes C4, D4, E4
- Chemotaxis, leukocyte adhesion - Leukotrienes B4
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