eicosanoids

Eicosanoids are characterized by

Containing 20 carbon atoms

Eicosanoids are synthesized from

C20 polyunsaturated fatty acids

Parent fatty acids of eicosanoids

Linoleic and linolenic acids

Dietary contribution to eicosanoids

They can be synthesized directly from dietary eicosanoic acids

Source of arachidonic acid for eicosanoid synthesis

The 2-position of membrane phospholipids

Enzyme releasing arachidonic acid from phospholipids

Phospholipase A2

Tissue distribution of eicosanoids

Produced in almost all tissues

Main classes of eicosanoids

Prostanoids and leukotrienes

Prostanoids are synthesized via

Cyclooxygenase (cyclic) pathway

Types of prostanoids

Prostaglandins, prostacyclins, and thromboxanes

Leukotrienes are synthesized via

Lipoxygenase (linear) pathway

Prostaglandins are best described as

Potent local hormones

Very low concentrations of prostaglandins cause

Smooth muscle contraction

Types of prostaglandins

PGD, PGE, and PGF

Effect of PGE₂

Vasodilatation

Effect of PGF₂

Vasoconstriction and uterine contraction

Clinical use of PGF₂

Induction of labor

Effect of prostaglandins on gastric secretion

Inhibition of gastric secretion

Clinical use of prostaglandins in the stomach

Treatment of peptic ulcer

Role of prostaglandins in inflammation

Increase inflammatory response

Mechanism of action of anti-inflammatory drugs

Inhibition of prostaglandin synthesis

Prostacyclin (PGI) is synthesized by

Vascular endothelium

Functions of prostacyclin

Vasodilation and inhibition of platelet aggregation

Thromboxane (TX) is mainly found in

Platelets, lung, and macrophages

Functions of thromboxane

Vasoconstriction and platelet aggregation

Leukotrienes are involved in

Chemotaxis, inflammation, and allergic reactions

Types of leukotrienes

LTB4, LTA4, LTC4, LTD4, and LTE4

Clinical significance of leukotrienes

Bronchial asthma

Drugs used in asthma targeting leukotrienes

LT synthesis inhibitors and LT receptor antagonists