Metabolic-induced cytotoxicity of diosbulbin B in CYP3A4-expressing cells.

As a candidate antitumor agent, diosbulbin B (DB) can induce serious liver toxicity and other adverse reactions. DB is mainly metabolized by CYP3A4 in vitro and in vivo, but the cytotoxicity and anti-tumor mechanisms of DB have yet to be clarified. This study aimed to determine whether the cytotoxicity and anti-tumor effects of DB are related to the metabolism-induced activation of CYP3A4 in various cell models, including CYP-free NIH3T3 cells, primary rat hepatocytes, HepG2 and L02 cells of high CYP3A4 expression and wild-type. Results showed that DB did not markedly decrease the viability of NIH3T3 cells. DB metabolites, obtained from the metabolism by mouse liver microsomes, did not elicit cytotoxicity on NIH3T3 cells either. By contrast, DB could induce significant cytotoxicity on primary rat hepatocytes. The DB induced cytotoxicity on HepG2 or L02 cells with high CYP3A4 expression were stronger than those on wild-type cells. As a metabolic biomarker, the metabolite conjugate (M31) of DB with GSH was detected in the incubation system. A higher amount of M31 was generated in the transfected HepG2 and L02 cells than in the wild-type cells at different time points. Ketoconazole, however, could restrain DB induced cytotoxicity on primary rat hepatocytes and in CYP3A4 transfected HepG2 and L02 cells. Therefore, the cytotoxicity of DB was closely related to CYP3A4-metabolized reactive DB metabolites.