PROTECTIVE EFFECT OF HEPATOCYTE GROWTH-FACTOR ON INTERFERON-GAMMA-INDUCED CYTOTOXICITY IN MOUSE HEPATOCYTES

We examined the interactive effect of several cytokines (interleukin-1 beta [IL-1 beta], tumor necrosis factor alpha [TNF-alpha], interferon gamma [INF-gamma], IL-6, IFN-alpha/beta, and hepatocyte growth factor [HGF]) presumably involved in hepatitis, on primary cultured murine h epatocytes. Among these cytokines, only IFN-gamma induced LDH release from hepatocytes in both time- and dose-dependent fashions, The cytoto xic effect was inhibited by antiserum-containing anti-mouse IFN-gamma monoclonal antibodies (R4-6A2). Moreover, intriguingly, IFN-gamma indu ced DNA fragmentation in the hepatocytes in a time- and dose-dependent fashion according to the gel electrophoresis of genomic DNA and flow cytometry analysis. These results suggest that the cytotoxic effect of IFN-gamma on hepatocytes was caused by inductive apoptosis. The LDH r elease and DNA fragmentation induced by IFN-gamma were inhibited by HG F in a dose-dependent manner, whereas they seemed to be accelerated by TNF-alpha. Flow cytometry analysis of the nuclei of treated hepatocyt es confirmed the interactions in DNA degradation. The DNA synthesis of cultured hepatocytes was also reduced by IFN-gamma but recovered by h epatocyte growth factor. Taken together, IFN-gamma is presumed to be a critical cytokine in hepatic damage, and the network composed of IFN- gamma, TNF-alpha, and HGF may play an important role in the regulation of liver injury.