Statin inhibits large hepatitis delta antigen-Smad3 -twist-mediated epithelial-to-mesenchymal transition and hepatitis D virus secretion

Abstract

Background: Hepatitis D virus (HDV) infection may induce fulminant hepatitis in chronic hepatitis B patients (CHB) or rapid progression of CHB to cirrhosis or hepatocellular carcinoma. There is no effective treatment for HDV infection. HDV encodes small delta antigens (S-HDAg) and large delta antigens (L-HDAg). S-HDAg is essential for HDV replication. Prenylated L-HDAg plays a key role in HDV assembly. Previous studies indicate that L-HDAg transactivates transforming growth factor beta (TGF-β) and induces epithelial-mesenchymal transition (EMT), possibly leading to liver fibrosis. However, the mechanism is unclear. Methods: The mechanisms of the activation of Twist promoter by L-HDAg were investigated by luciferase reporter assay, chromatin immunoprecipitation, and co-immunoprecipitation analysis. ELISA and Western blotting were used to analyze L-HDAg prenylation, TGF-β secretion, expression of EMT markers, and to evaluate efficacy of statins for HDV treatment. Results: We found that L-HDAg activated Twist expression, TGF-β expression and consequently induced EMT, based on its interaction with Smad3 on Twist promoter. The treatment of statin, a prenylation inhibitor, resulted in reduction of Twist promoter activity, TGF-β expression, and EMT, and reduces the release of HDV virions into the culture medium. Conclusions: We demonstrate that L-HDAg activates EMT via Twist and TGF-β activation. Treatment with statins suppressed Twist expression, and TGF-β secretion, leading to downregulation of EMT. Our findings clarify the mechanism of HDV-induced EMT, and provide a basis for possible novel therapeutic strategies against HDV infection.

Signaling Induced by Chronic Viral Hepatitis: Dependence and Consequences

“…HBV infection is also restricted by TGF-β [ 171 ], while HDV seems to stimulate TGF-β in luciferase reporter gene assays [ 172 ]. This is consistent with a reported activation of TGF-β expression by HDV via an L-HDAg-mediated activation of the Twist promoter through binding to SMAD3 on Smad-binding elements (SBEs) [ 173 ]. This is an interesting finding that may help to understand the aggravation of HBV liver disease and the rapid fibrosis progression in HDV/HBV-infected patients [ 174 ].…”

Development of a Bioassay for Continuous Monitoring of TWIST1 Activity

“…in various tissues) and cell type-dependent manner. Multiple attempts to quantitatively measure the expression and activity of TWIST1 have been tested, for example by using TWIST1 promoter sequences followed by diverse reporter genes [62,63] , [64]. Additionally, reporters containing TWIST1 3'UTR have been used for investigation of microRNAs affecting TWIST1 expression [65,66].…”

Hepatitis D: advances and challenges

“…[ 48 ] Furthermore, it has been indicated that HDV may cause liver fibrosis through the modulation of transforming beta-growth factor-induced signaling and the activation of epithelial-mesenchymal transition, whereas the exact underlying mechanisms of HDV pathogenesis remain largely elusive and require further investigation. [ 71 , 72 ]…”

“…Interestingly, HDV isolates from different genotypes exhibited remarkable differences in their replication efficiency and envelopment preferences in experimental models in vitro. [48] Furthermore, it has been indicated that HDV may cause liver fibrosis through the modulation of transforming beta-growth factor-induced signaling and the activation of epithelial-mesenchymal transition, whereas the exact underlying mechanisms of HDV pathogenesis remain largely elusive and require further investigation [71,72] …”

“…[48] Furthermore, it has been indicated that HDV may cause liver fibrosis through the modulation of transforming beta-growth factor-induced signaling and the activation of epithelial-mesenchymal transition, whereas the exact underlying mechanisms of HDV pathogenesis remain largely elusive and require further investigation. [71,72] Therapeutic development For decades, pegylated interferon (IFN) alpha is the only treatment regimen currently recommended by the international guidelines. [73] However, a long-term sustained virological response can only be achieved in minority patients, [2,31,62,73] although patients with HDV genotype 5 seem to have a better response to IFN treatment.…”