Background and purpose: The underlying mechanisms of nonalcoholic steatohepatitis (NASH) are poorly understood, and little is known about hepatocellular apoptosis in NASH. Cyclooxygenase (COX)-2, the key enzyme in eicosanoid metabolism, is highly expressed in NASH. COX-2 can also regulate the release of mediators of inflammation, such as tumor necrosis factor (TNF)-α and interleukin (IL)-6. The aim of our study was to evaluate the effects of COX-2 on hepatocellular apoptosis and the mechanism of the action in the pathogenesis of NASH in rats.
Methods: Sprague-Dawley rats were fed a high-fat diet (HFD) or standard diet for 8 and 12 weeks. COX-2 and cytokines expression in hepatic tissue and TNF-α and IL-6 levels in serum were measured at 8 and 12 weeks. Moreover, celecoxib (10 mg/kg body weight once a day) was administered to rats for 4 weeks to inhibit the expression of COX-2. Liver pathology was assessed by hematoxylin and eosin (H&E) stain and electron microscopy. Hepatocyte apoptosis was evaluated by TUNEL staining.
Results: COX-2 messenger RNA and protein were highly expressed in livers of HFD rats and were correlated with the severity of steatohepatitis (R = 0.82, p < 0.01). COX-2 upregulation was preceded by increases in TNF-α and IL-6. The level of hepatocellular apoptosis was significantly higher in HFD rats than in the control rats. The hepatocellular apoptosis was suppressed by the inhibition of COX-2.
Conclusions: COX-2 may promote hepatocellular apoptosis by interacting with TNF-α and IL-6 in NASH in rats.