Induction of Antioxidant and Detoxifying Enzymes via the Nrf2-ARE Pathway by Oriental Bezoar

Objectives Oriental bezoar, a gallstone formed in the gall sac of Bos taurus Linné var. domesticus Gmelin ( Bovidae ), has been used as a crude drug in oriental medicine for stroke, convulsion, epilepsy, swelling and pain in the throat, and high fever. Despite reports on the antioxidative effect of oriental bezoar-containing drugs, in vitro -cultured calculus bovis (a substitute for oriental bezoar), and its components (namely, bilirubin and biliverdin), the intracellular mechanism of the antioxidative action of oriental bezoar remains unclear. Therefore, we studied the effect of oriental bezoar on the nuclear factor erythroid 2-related factor 2 (Nrf2)-antioxidant response element (ARE) pathway, which transcriptionally regulates genes encoding antioxidant and detoxifying enzymes, such as heme oxygenase-1 ( HO-1 ), glutathione-S-transferase alpha 1 ( GSTA1 ), and quinone oxidoreductase 1 ( NQO1 ), to elucidate its antioxidative effect. Methods ARE promoter activity and mRNA expression ( HO-1, GSTA1 , and NQO1 ) in HepG2 cells supplemented with test drugs were examined in vitro by luciferase reporter assay and real-time PCR, respectively. Results Oriental bezoar induced ARE promoter activity and increased the mRNA expression level of HO-1, GSTA1 , and NQO1 . Its components, namely, bilirubin and biliverdin, also increased the ARE promoter activity. Conclusion These results suggest that oriental bezoar can induce antioxidative and detoxification effects via the Nrf2-ARE pathway.