Hepatocyte steatosis in HCV patients promotes fibrosis by enhancing TGF-beta liver expression

Genetic dominance of transforming growth factor-β1 polymorphisms in chronic liver disease

Chronic liver disease (CLD) is an extremely common clinical condition accompanied by sustained inflammatory response leading to tissue damage. Transforming growth factor-β1 (TGF-β1) is known as a master immune regulator in CLDs, but the association between TGF-β1 polymorphisms and CLD risk is controversial and inconclusive, and the genetic dominance of CLDs remains unknown. In this study, the relationship between TGF-β1 polymorphisms and CLD susceptibility is systematically analyzed based on 35 eligible studies. Individuals with the TGF-β1-509 allele (TT or CT) or codon 10 allele (Pro/Pro) show an increased risk of CLDs. Subgroup analyses indicate TGF-β1-509C/T has a significant correlation with cirrhosis and chronic hepatitis C, codon 10 is associated with chronic hepatitis B occurrence, and codon 25 exhibits a relationship with autoimmune hepatitis risk. Missense mutations in G29E, A105S, D191N, and F321L of TGF-β1 are the genetic factors of HCC susceptibility. Furthermore, the TGF-β1 gene expression is significantly elevated in CLD patients, and the TGF-β1 codon 263 is located close to the region where the TGF-β1 dimerization interacts, indicating the TGF-β1 codon 263 variant may affect the secretion of TGF-β1 by altering its dimerization. Together, our findings provide new insights into the immune regulator gene TGF-β1 polymorphisms as susceptibility factors for CLD occurrence and regulators for TGF-β1 expression, which have implications for the regulation of immune factors during CLD development.

Astragalus and Paeoniae radix rubra extract inhibits liver fibrosis by modulating the transforming growth factor‑β/Smad pathway in rats

It has been previously demonstrated that Astragalus and Paeoniae radix rubra extract (APE) had a protective effect against liver fibrosis in mice. The present study aimed to investigate the hepatoprotective effect of APE on CCl₄-induced hepatic fibrosis in rats. Liver fibrosis was induced in male Sprague-Dawley rats by intraperitoneal injection of 50% CCl₄ twice a week for eight weeks. Organ coefficients, serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), hexadecenoic acid (HA), laminin (LN), procollagen type III (PCIII), hydroxyproline (Hyp), glutathione (GSH-Px), malondialdehyde (MDA), superoxide dismutase (SOD) and transforming growth factor β1 (TGF-β1) levels were measured in rats with hepatic fibrosis. Histopathological changes in affected livers were studied using hematoxylin-eosin and Masson’s trichrome staining. The expression of transforming growth factor-β/Smad pathway proteins, α-smooth muscle actin (α-SMA), collagen I and collagen III was observed in fibrotic livers using western blot analysis. The present study observed significant reductions in serum levels of AST, ALT, HA, LN, PCIII and Hyp in APE-treated (2.6 and 5.2 g/kg) rats, indicating the significant hepatoprotective effects of APE. Furthermore, the depletion of GSH-Px and SOD, in addition to the accumulation of MDA in liver tissue was suppressed by APE (2.6 and 5.2 g/kg). Pathological assessment of CCl₄-induced fibrotic livers revealed a significant reduction of liver injury and development of hepatic fibrosis in rats treated with APE (2.6 and 5.2 g/kg). Moreover, APE (2.6 and 5.2 g/kg) decreased the elevation of TGF-β1, α-SMA, collagen I and collagen III expression, inhibited Smad2/3 phosphorylation as well as elevated the expression of the TGF-β1 inhibitor Smad7. These results suggested that APE may protect against liver damage and inhibit the progression of CCl₄-induced hepatic fibrosis. The mechanism of action of APE is hypothesized to proceed via scavenging free radicals, decreasing TGF-β1 levels and blocking of the TGF-β/Smad signaling pathway.

Hepatitis C virus (HCV) proteins induce NADPH oxidase 4 expression in a transforming growth factor beta-dependent manner: a new contributor to HCV-induced oxidative stress

Viral hepatitis-induced oxidative stress accompanied by increased levels of transforming growth factor beta (TGF-beta) and hepatic fibrosis are hallmarks of hepatitis C virus (HCV) infection. The mechanisms of redox regulation in the pathogenesis of HCV-induced liver disease are not clearly understood. The results of our current studies suggest that reactive oxygen species (ROS) derived from Nox4, a member of the NADPH oxidase (Nox) family, could play a role in HCV-induced liver disease. We found that the expression of HCV (genotype 1a) cDNA constructs (full-length and subgenomic), core protein alone, viral RNA, or replicating HCV (JFH-AM2) induced Nox4 mRNA expression and ROS generation in human hepatocyte cell lines (Huh-7, Huh-7.5, HepG2, and CHL). Conversely, hepatocytes expressing Nox4 short hairpin RNA (shRNA) or an inactive dominant negative form of Nox4 showed decreased ROS production when cells were transfected with HCV. The promoters of both human and murine Nox4 were used to demonstrate transcriptional regulation of Nox4 mRNA by HCV, and a luciferase reporter tied to an approximately 2-kb promoter region of Nox4 identified HCV-responsive regulatory regions modulating the expression of Nox4. Furthermore, the human Nox4 promoter was responsive to TGF-beta1, and the HCV core-dependent induction of Nox4 was blocked by antibody against TGF-beta or the expression of dominant negative TGF-beta receptor type II. These findings identified HCV as a regulator of Nox4 gene expression and subsequent ROS production through an autocrine TGF-beta-dependent mechanism. Collectively, these data provide evidence that HCV-induced Nox4 contributes to ROS production and may be related to HCV-induced liver disease.