Hepatitis C virus regulates transforming growth factor beta1 production through the generation of reactive oxygen species in a nuclear factor kappaB-dependent manner.

BACKGROUND & AIMS: The generation of oxidative stress and transforming growth factor beta1 (TGF-beta1) production play important roles in liver fibrogenesis. We have previously shown that hepatitis C virus (HCV) increases hepatocyte TGF-beta1 expression. However, the mechanisms by which this induction occurs have not been well studied. We explored the possibility that HCV infection regulates TGF-beta1 expression through the generation of reactive oxygen species (ROS), which act through > or =1 of the p38 mitogen-activated protein kinase (MAPK), extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and nuclear factor kappaB (NFkappaB) signaling pathways to induce TGF-beta1 expression. METHODS: We used small molecule inhibitors and short interfering RNAs to knock down these pathways to study the mechanism by which HCV regulates TGF-beta1 production in the infectious JFH1 model. RESULTS: We demonstrated that HCV induces ROS and TGF-beta1 expression. We further found that JFH1 induces the phosphorylation of p38MAPK, JNK, ERK, and NFkappaB. We also found that HCV-mediated TGF-beta1 enhancement occurs through a ROS-induced and p38 MAPK, JNK, ERK1/2, NFkappaB-dependent pathway. CONCLUSIONS: These findings provide further evidence to support the hypothesis that HCV enhances hepatic fibrosis progression through the generation of ROS and induction of TGF-beta1. Strategies to limit the viral induction of oxidative stress appear to be warranted to inhibit fibrogenesis.