Inhibition of hepatitis B virus gene expression and replication by helioxanthin and its derivative

Chronic hepatitis B virus (HBV) infection continues to be an important worldwide cause of morbidity and mortality. All the currently approved therapeutic drugs have their limitations: interferon-α (IFN-α) has limited efficacy and a high incidence of adverse effects; nucleoside analogues are very efficient HBV DNA inhibitors, but resistance occurs eventually. Therefore, it is important to develop new non-nucleoside/nucleotide agents with different modes of action that can be used for antiviral combination therapy. Here, we report on a novel class of compounds, helioxanthin and its derivative 5-4-2, which had potent anti-HBV activities in HepG2.2.15 cells, with the EC₅₀s of 1 and 0.08 μM, respectively. The lamivudine-resistant HBV, L526M/M550V double mutant strain, was also sensitive to helioxanthin and 5-4-2. This class of compounds not only inhibited HBV DNA, but also decreased HBV mRNA and HBV protein expression. The EC₅₀ of HBV DNA inhibition was consistent with the EC₅₀ of HBV 3.5 Kb transcript inhibition, which was 1 and 0.09 μM for helioxanthin and 5-4-2 respectively. Western blot analysis of cell lysate from HepG2.2.15 cells showed that the core protein expression decreased in a dose-dependent manner after drug treatment. In conclusion, helioxanthin and 5-4-2 are potentially unique new anti-HBV agents, which possess a different mechanism of action from existing therapeutic drugs. Both compounds inhibited HBV RNA and protein expression in addition to inhibiting HBV DNA.