Physiology, Thromboxane A2

Excerpt

Thromboxane A2 (TxA2) is in the family of lipids known as eicosanoids, which are metabolites of arachidonic acid generated by the sequential action of 3 enzymes—phospholipase A2, COX-1/COX-2 and TxA2 Synthase (TXAS). TxA2 was originally described as being released from platelets and is now known to be released by various other cells, including macrophages, neutrophils, and endothelial cells. Named after its role in thrombosis, TxA2 has prothrombotic properties, as it stimulates the activation of platelets and platelet aggregation. TxA2 is also a known vasoconstrictor and gets activated during times of tissue injury and inflammation. While prostaglandin counterbalances its thrombotic and vasoconstrictor properties, prostacyclin (PGI2) has various physiological and pathological situations where this balance becomes dysregulated. Increased activity of TxA2 may play a role in the pathogenesis of myocardial infarction, stroke, atherosclerosis, and bronchial asthma. Increased action of TxA2 also has implications in pulmonary hypertension, kidney injury, hepatic injury, allergies, angiogenesis, and metastasis of cancer cells.