Cyclooxygenases: Proliferation and differentiation

Abstract

Prostaglandins are formed from arachidonic acid by the action of cyclooxygenase and subsequent downstream synthetases. Mainly two cyclooxygenase isoforms have been identified which are now known as cyclooxygenase-1 and cyclooxygenase-2. Both iso-enzymes transform arachidonic acid to prostaglandins, but differ in their distribution and their physiological roles. The two isoenzymes are similar in protein structure but are produced by divergent genes and have different biological functions. Cyclooxygenase-1 is a constitutively expressed enzyme in most mammalian tissues and maintains normal cellular physiological functions, such as platelet aggregation and gastric cytoprotection; while cyclooxygenase-2 is normally expressed at a very low level in most tissues and is highly inducible by growth factors, cytokines, and tumour promoters. In several studies, the effect of cyclooxygenases on different cell types has been investigated. This review focuses on cyclooxygenases function, cell proliferation and differentiation.

Key words: Cyclooxygenases, proliferation, differentiation, prostaglandins, tumor.