The SIRT1 inhibitor, nicotinamide, inhibits hepatitis B virus replication in vitro and in vivo.

We previously reported that SIRT1, an NAD(+)-dependent deacetylase belonging to the class III histone deacetylases, enhances hepatitis virus B (HBV) replication by targeting the transcription factor AP-1. However, the potential antiviral effects of nicotinamide, a SIRT1 inhibitor, have not yet been explored. In this study, we show that nicotinamide exhibits potent anti-HBV activity with little cytotoxicity. Nicotinamide suppressed both HBV DNA replicative intermediates and 3.5-kb mRNA expression. Moreover, nicotinamide treatment also suppressed core protein expression and the secretion of the hepatitis B surface antigen (HBsAg) and the hepatitis B e antigen (HBeAg) in HBV-expressing cell models. Importantly, nicotinamide treatment suppressed serum HBV DNA, HBsAg and HBeAg levels and liver HBV DNA in HBV-transgenic mice. Furthermore, using a dual-luciferase reporter assay, it was found that nicotinamide exhibited a marked inhibitory effect on the HBV core, SpI, SpII and X promoters, accompanied by decreased expression of the transcription factors AP-1, C/EBPα and PPARα. Therefore, nicotinamide suppresses HBV replication in vitro and in vivo by diminishing HBV promoter activity. This study highlights the potential application of nicotinamide in HBV therapy.