HBV induces liver fibrosis through the generation of reactive oxygen species in a pyruvate-dependent manner.

BACKGROUND AND AIMS: Chronic hepatitis B (CHB) is a major etiology of liver cirrhosis. We previously found that pyruvate, a key intermediate in many metabolic pathways, increases HBV replication. However, the mechanism by which pyruvate mediates HBV-induced liver fibrosis is not well characterized. We hypothesize that HBV induces liver fibrosis through a pyruvate-peroxisome proliferator-activated receptor α (PPARα)-reactive oxygen species (ROS) pathway.

APPROACH AND

RESULTS

We evaluated HBV-induced fibrogenesis in HepAD38, HBV-infected NTCP-HepG2, primary human hepatocytes (PHHs), and HSC lines (LX2) in mono-culture and co-culture models and in patient sera. We also evaluated the effects of PPARα agonist/antagonist and ROS inhibition on HBV-induced liver fibrosis in cell culture, HBV carrier mouse, HBV-Transgenic mouse (HBV-Tg), humanized liver mouse, and human precision-cut liver slice (PCLS) models. We found that HBV increased pyruvate levels and fibrosis-related gene expression in both HBV-infected hepatocytes and patient sera. Supernatants from HBV-infected cells (HBVsup) and pyruvate supplementation independently and additively increased expression of profibrotic genes (TGF-β1, TIMP-1, COL1A1, and α-SMA), activated ROS production, and inhibited PPARα expression. Notably, PPARα inhibition and siRNA knockdown increased ROS production and profibrogenic gene expression, while activation of PPARα blocked HBVsup-induced and pyruvate-induced ROS generation and fibrogenesis. ROS was confirmed to be downstream of PPARα-related fibrogenesis, as ROS inhibition abrogated HBVsup-induced, pyruvate supplementation-induced, or PPARα inhibition-induced liver fibrosis.

CONCLUSIONS

HBV infection induces pyruvate production and decreases PPARα expression, leading to increased ROS generation and liver fibrosis. Pyruvate and PPARα represent novel targets for antifibrotic therapeutic development in CHB.