What is Pathology - What are the main inflammatory mediators generated from arachidonic acid?
Cell membrane phospholipids produce arachidonic acid, a lipid-derived eicosanoid. Arachidonic acid is metabolised in two ways after it is produced inside the cell:
Prostaglandins (PG) of the PGD, PGE, and PGF families, prostacyclin (also known as PGI2), and thromboxane are all produced through the cycloxygenase pathway. Prostacyclin, which prevents platelet aggregation and works as a powerful vasodilator, is produced primarily by endothelial cells. Platelets, on the other hand, create thromboxane preferentially, which promotes platelet aggregation and vasoconstriction. Smooth muscle cell contraction is stimulated by PGE2.
Lipoxygenase Pathway: This pathway produces leukotrienes (LTC4, LTD4, and LTE4), which act on smooth muscle cells in the bronchi and blood arteries. They cause bronchoconstriction, vasoconstriction, and increased vascular permeability in asthmatics, earning them the moniker "slow-reacting anaphylactic drugs" (SRS-A). LTB4 is a highly effective chemotactic factor. Vasodilation is caused by lipoxins.
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