Induction of CYP2B6 and CYP3A4 expression by 1-aminobenzotriazole (ABT) in human hepatocytes.

1-Aminobenzotriazole (ABT) has been widely used in drug development process as an irreversible inhibitor of CYP enzymes. One potential use of ABT is to potentiate pharmacological effects of rapidly-metabolized drugs on CYP expression by inhibiting their metabolism; however, ABT's own effects on CYP expression have been unknown. In this study, we show that ABT up-regulates expression of CYP2B6 and CYP3A4 potentially by activating nuclear receptor CAR. In freshly isolated human hepatocytes, ABT increased mRNA expression of CYP2B6 and CYP3A4 in a concentration-dependent manner. ABT also modulated CYP-inducing actions of CITCO and rifampin, the known inducers of CYP2B6 and CYP3A4. Results from luciferase reporter assays confirmed that ABT increases CYP2B6 promoter activity in CAR-expressing HepG2 cells. These results suggest that the use of ABT as a potentiator of pharmacological effects of rapidly-metabolized drugs is limited due to its own pharmacological actions on CYP expression as a CAR activator.