Evidence for Dual Effects of DNA-Reactive Bile Acid Derivatives (Bamets) on Hepatitis B Virus Life Cycle in an In Vitro Replicative System

A liver targeting strategy to direct antiviral drugs toward hepatitis B virus (HBV) was investigated. As model drugs we used cisplatin-bile acid derivatives (Bamets) to determine the production of virions by HBV-transfected hepatoblastoma cells (HepG2 2.2.15). Drug uptake was determined using flameless atomic absorption spectrometry to measure platinum cell contents. Cytotoxic effect was determined by formazan formation and neutral red uptake tests. The release of viral surface protein was evaluated by ELISA. The abundance of HBV-DNA in the medium was determined by quantitative real-time PCR and its structure by Southern blot analysis. The uptake of Bamets by HepG2 2.2.15 cells was higher than that of cisplatin. At concentrations lower than 10 μM, distinct Bamets have no toxic effect on host cells, whereas cisplatin dramatically reduced cell viability at concentrations higher than 1 μM. All the drugs tested inhibited the release of viral proteins to the medium, but induced a marked and progressive dose-dependent increase in the amount of viral DNA in the medium. This was mainly due to the release of short fragments of HBV-DNA in the case of cisplatin. On the contrary, Bamets induced an enhanced release of circular forms of HBV-DNA. These findings suggest the existence of a dual effect of Bamets on HBV life-cycle by enhancing the production of DNA replicative intermediates but reducing the secretion of complete virions. Altogether these characteristics recommend consideration of these compounds as a useful experimental tool in the investigation of novel liver targeted therapeutic agents based on bile acid derivatives for the treatment of HBV infections, or to carry out further studies on the HBV life cycle.