Multiple effects of honokiol on the life cycle of hepatitis C virus

Abstract

Background Honokiol, a small active molecular compound extracted from magnolia, has recently been shown to inhibit hepatitis C virus (HCV) infection in vitro. Aims This study further characterized aspects of the HCV lifecycle affected by the antiviral functions of honokiol. Methods The influence of honokiol on HCV infection, entry, translation and replication was assessed in Huh-7.5.1 cells using cell culture-derived HCV (HCVcc), HCV pseudo-type (HCVpp) and sub-genomic replicons. Results Honokiol had strong antiviral effect against HCVcc infection at non-toxic concentrations. Combined with interferon-α, its inhibitory effect on HCVcc was more profound than that of ribavirin. Honokiol inhibited the cell entry of lentiviral particles pseudo-typed with glycoproteins from HCV genotypes 1a, 1b, and 2a, but not of the vesicular stomatitis virus. It had inefficient activity on HCV internal ribosome entry site (IRES)-translation at concentrations with significant anti-HCVcc effects. The expression levels of components of replication complex, NS3, NS5A and NS5B, were down-regulated by honokiol in a dose-dependent manner. It also inhibited HCV replication dose dependently in both genotypes 1b and 2a sub-genomic replicons. Conclusions Honokiol inhibits HCV infection by targeting cell entry and replication and, only at a concentration >30 μM, IRES-mediated translation of HCV life cycle. Based on its high therapeutic index (LD₅₀/EC₉₀ = 5.4), honokiol may be a promising drug for the treatment of HCV infection.