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 rapidlymetabolized
drugs on CYP expression by inhibiting their metabolism; however, ABT’s own
effects on expression of CYP enzymes have been unknown. In this study, we show that ABT upregulates
expression of CYP2B6 and CYP3A4 by activating CAR. In freshly isolated human
hepatocytes, ABT increased mRNA expression levels 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 rapidlymetabolized
drugs is limited and requires precaution especially in studies examining regulation of
CYP expression at the transcriptional level.