COX Inhibitors and Thromboregulation

Prostacyclin inhibits platelets and dilates blood vessels, whereas thromboxane A2 activates platelets and constricts vessels. In mice lacking receptors for prostacyclin, intimal injury provokes a severe reaction within the artery, whereas in mice lacking thromboxane A2 receptors the response is subdued. These findings are relevant to clinical concerns that cyclooxygenase-2 inhibitors, which specifically impair the formation of prostacyclin, may increase susceptibility to cardiovascular events. Aspirin, which inhibits both prostacyclin and thromboxane A2, protects against arterial thrombosis.