A Traditional Chinese Medicine, Maoto, Suppresses Hepatitis B Virus Production

概要

〔目的(Purpose)〕
Worldwide, millions of people suffer from hepatitis B virus (HBV) infection, putting them at a high risk of death from liver cirrhosis and cancer. Although effective anti-HBV drugs have been developed, current drugs have some limitations, as most of them have a risk of significant side effects. Therefore, the discovery of safe and effective anti-HBV drugs is still needed. Natural compounds are considered sources of novel, safe and effective therapeutics. In these regards, we screened a library of Kampos, traditional herbal medicines, for suppression of HBV production.

〔方法ならびに成績(Methods/Results)〕
The 1ibrary consisted of 41 Kampo extracts, provided by the University of Toyama. HepAD38.1 cells, a tetracycline-controlled HBV producing cell line, was incubated for 9 days with or without Kampo extracts in the tetracycline-negative (tet-off； virus production mode) condition. Cell viability was determined by an MTT assay. Anti-HBV activities were evaluated by qPCR of HBV DNA and an HBeAg ELISA in the soup. Results were further confirmed by additional cell lines such as HepG2-NTCP producing cel1 and Primary human hepatocytes(PHH).

We found that maoto reduced extracellular HBV DNA but not extracellular HBsAg during HBV infection, suggesting that it suppressed HBV production by interfering with HBV nucleocapsid incorporation into viral particles. We suggested the potential of maoto for increasing the efficacy of current anti-HBV drugs (i. e. Lainivudine；LV) when used in combination. Since the safety of maoto has been already confirmed, inaoto can be considered a candidate ant i-HBV agent if the effect is confirmed in vivo. Finally, we investigated the molecular mechanisms of how maoto suppressed extracellular HBV production by RNA-seq analysis of maoto-treated and untreated cells. We detected several up-regulated and down regulated genes however, we revealed that maoto reduced the expression of a host gene, Tropomyosin β chain (TPM2), whose downregulation also suppressed HBV production, similarly to maoto. The results suggested TPM2 as a novel molecular target for the development of anti-HBV agents.

〔総括(Conclusion)〕
Overall, maoto seems to be a unique candidate that targets a process different from those targeted by existing drugs and can enhance the anti-HBV activity of current drugs when used in combination.