Roles of cyclooxygenase-2 in tissue injury during hemorrhagic shock

Prostaglandins (PGs), which play a pivotal role in the cytokine network, have been implicated in the pathophysiology of circulatory shock, but the precise role of cyclooxygenase-2 (COX-2) in circulatory shock is still not known. This study investigated whether or not COX-2 affects liver and bowel injury during hemorrhagic shock (HS). Male Sprague-Dawley rats were subjected to decompensated HS followed by resuscitation. Besides the time course of tissue injury and mRNA expression of COX-2 in the liver and bowel during HS, we investigated the effect of N-(2-cyclohexyloxy-4-nitrophenyl)methane sulfonamide (NS398), a specific inhibitor of COX-2, on injury to these organs. The liver injury, evaluated by plasma aminotransferase levels and histology, was evident at the end of the shock period (Shock-0h) and had significantly increased 1 h after the start of resuscitation (Shock-1h) (P < 0.01). The bowel injury, assessed by histological findings in the terminal ileum, was scarcely detectable at Shock-0h but became noticeable at Shock-1h (P < 0.01). COX-2 mRNA expression was up-regulated in the liver during HS whereas it did not change in the bowel. NS398 treatment significantly exacerbated both liver and bowel injury. These lines of evidence suggest that COX-2-derived PGs provide protection against HS-induced liver and bowel injury.