Peroxisome proliferator activated receptor alpha (PPARα) ameliorates ethanol induced hepatic steatohepatitis. However, its role in alcoholic liver fibrosis has not been fully clarified. The aim of this study was to elucidate the effect and the molecular basis of PPARα in ethanol induced liver fibrosis in mice. C57BL/6J mice were fed with 4% ethanol-containing Lieber-DeCarli liquid diet for eight weeks, and intraperitoneal injected with 5% carbon tetrachloride (CCl₄) for the last four weeks to induce alcoholic liver fibrosis. PPARα agonist WY14643 was administered to mice during the last couple of weeks. The effects of PPARα induction on liver histology, activation of hepatic stellate cells (HSCs), as well as hepatic expression of inflammatory and fibrogenic factors were assessed. The ethanol plus CCl₄ treated mice exhibited progressive liver injury including piecemeal necrosis of hepatocytes, severe inflammatory cells infiltration and bridging fibrosis. This was accompanied by down-regulated hepatic expression of PPARα and the protective cytokines adiponectin, heme oxygenase-1 and interleukin-10. Additionally, up-regulation of the proinflammatory cytokine tumor necrosis factor-alpha, as well as the profibrogenic genes osteopontin, transforming growth factor-beta 1, visfatin, phosphatidylinositol 3-kinase, matrix metalloproteinase-2 (MMP-2) and MMP-9 was observed. WY14643 treatment restored expression of cytokines altered by ethanol plus CCl₄ treatment and concomitantly ameliorated the liver injury. The present study provides evidence for the protective role of PPARα induction in ameliorating ethanol mediated fibrosis through mediation of inflammatory and fibrogenic factors.

Background and Aim. Heme oxygenase‐1 (HO‐1) has been verified to play an important role in nonalcoholic steatohepatitis (NASH), but the mechanism remains unclear. In this study, we aimed to clarify whether induction of HO‐1 reverses steatofibrosis via suppression of the Wnt signaling pathway and to explore the potential mechanism of HO‐1 on NASH‐related liver fibrosis. Methods. Mice were fed with a methionine‐choline‐deficient (MCD) diet for 8 weeks to induce steatohepatitis‐related liver fibrosis and were treated with HO‐1 inducer Hemin and inhibitor ZnPP. Mouse sera were collected for the biochemical analysis, and livers were obtained for further histological observation and gene expression analysis. HSC‐T6 cells were cultured for the in vitro study and were administrated with Hemin and si‐HO‐1 to induce or inhibit the expression of HO‐1. qPCR and Western blot were used to assess the mRNA and protein levels of genes. Results. MCD‐fed mice developed marked macrovesicular steatosis, focal necrosis, and inflammatory infiltration and pericellular fibrosis in liver sections. Administration of Hemin could significantly ameliorate the severity of steatosis, inflammation, and fibrosis and also could decrease the serum ALT and AST. We demonstrated that HO‐1 induction was able to downregulate the key regulator of the canonical Wnt pathway Wnt1 and the noncanonical Wnt pathway Wnt5a. The downstream factors of the Wnt pathway β‐catenin and NFAT5 were inhibited by Hemin, but GSK‐3β was upregulated compared to the MCD group, which were consistent with the in vitro study. Hemin markedly inhibited the TGF‐β1/Smad signaling pathway in both in vivo and in vitro studies. Conclusion. Our study demonstrated that HO‐1 inhibited the activation of canonical and noncanonical Wnt signaling pathways in NASH‐related liver fibrosis. Thus, these results may suggest a new therapeutic strategy for NASH‐related liver fibrosis.