Hepatic expression of inducible nitric oxide synthase transcripts in chronic hepatitis C virus infection: relation to hepatic viral load and liver injury.

Hepatitis C virus (HCV) causes acute and often also chronic liver disease. Hepatocellular injury might result from both a host response directed to inhibit viral spread and from processes initiated by the virus itself. To study mechanisms involved in hepatocellular injury, liver tissue from chronically HCV-infected patients was analyzed for the expression of the inducible isoform of nitric oxide synthase (iNOS) and for interferon gamma (IFN-gamma) by a quantitative, competitive reverse-transcription-polymerase chain reaction (RT-PCR) technique. Moreover, hepatic viral load was determined by two independent techniques, and liver tissue was evaluated histopathologically in detail. Liver tissue from HCV-infected patients was shown to express elevated levels of iNOS transcripts compared with non-HCV-infected patients. Increased iNOS transcript expression, however, was not accompanied by significantly elevated serum nitrite plus nitrate (NOx) concentration, although some of the chronic HCV-infected patients reached markedly higher serum NOx levels than the control group or healthy individuals, respectively. Hepatic iNOS expression was found to be positively correlated to hepatic HCV-RNA content on the one hand, and weakly to hepatic IFN-gamma expression, previously shown to be solely associated with hepatic necro-inflammatory activity among the histopathological parameters studied, on the other hand. In contrast to IFN-gamma transcript expression, neither hepatic iNOS expression nor hepatic HCV-RNA content were related to hepatic inflammatory activity. The presented data are compatible with the assumption that HCV might be able to stimulate iNOS expression both directly and indirectly via its capacity to induce IFN-gamma.