Digestive and liver disease : official journal of the Italian Society of Gastroenterology and the Italian Association for the Study of the Liver
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Cyclo-oxygenase (prostaglandin endoperoxide synthase) is the enzyme which metabolizes the conversion of arachidonic acid to prostaglandin. It exists in at least two isoforms: the constitutive (cyclo-oxygenase-1) and the inducible (cyclo-oxygenase-2) which is controlled by a number of factors, including cytokines and intracellular messengers. These enzymes are the therapeutic targets of non-steroidal anti-inflammatory drugs such as aspirin and ibuprofen. ⋯ Although cyclo-oxygenase-1 seems to be expressed in physiological conditions and cyclo-oxygenase-2 in inflammatory conditions, it is not yet possible to identify all their different roles. Cyclo-oxygenase-2 may be expressed constitutively, whereas the generation of prostaglandin by cyclo-oxygenase-2 may replace that by cyclo-oxygenase-1 in some situations (or vice-versa). Both cyclo-oxygenase isoenzymes contribute to mucosal defence and the inhibition of the two isoforms contributes to the pathogenesis of non-steroidal anti-inflammatory drug-induced gastric damage.