Tumor necrosis factor alpha alters the cytotoxic effect of hydrogen peroxide in cultured hepatocytes

We examined whether tumor necrosis factor-alpha (TNF) affects the cytotoxic capacity of reactive oxygen species on rat hepatocytes in culture. Both TNF and reactive oxygen species are involved in many inflammatory events including hepatic ischemia/reperfusion injury and endotoxic shock. Synchronous treatment of hepatocytes with both TNF and H2O2 demonstrated that TNF (2000 ng/ml) enhanced the cytotoxic effect of H2O2 (500 microM). By contrast, pretreatment with TNF (2000 ng/ml) for 24 h followed by exposure to H2O2 (1000 microM) reduced the reactive oxygen-induced cytotoxicity. We conclude that TNF increases the effects of reactive oxygen-induced cytotoxicity when exposed synchronously, whereas TNF pretreatment induces a cytoprotective effect to reactive oxygen species, presumably by up-regulation of the reduced form of glutathione levels in hepatocytes.