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-1β], tumor necrosis factor alpha [TNF-α], interferon gamma [IFN-γ], IL-6, IFN-α/β, and hepatocyte growth factor [HGF]) presumably involved in hepatitis, on primary cultured murine hepatocytes. Among these cytokines, only IFN-γ induced LDH release from hepatocytes in both time- and dose-dependent fashions. The cytotoxic effect was inhibited by antiserum-containing anti-mouse IFN-γ monoclonal antibodies (R4–6A2). Moreover, intriguingly, IFN-γ induced 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-γ on hepatocytes was caused by inductive apoptosis. The LDH release and DNA fragmentation induced by IFN-γ were inhibited by HGF in a dose-dependent manner, whereas they seemed to be accelerated by TNF-α. Flow cytometry analysis of the nuclei of treated hepatocytes confirmed the interactions in DNA degradation. The DNA synthesis of cultured hepatocytes was also reduced by IFN-γ but recovered by hepatocyte growth factor. Taken together, IFN-γ is presumed to be a critical cytokine in hepatic damage, and the network composed of IFN-γ, TNF-α, and HGF may play an important role in the regulation of liver injury.