Background: The HepaRG cells have key drug metabolism functionalities comparable to
those of primary human hepatocytes. Many studies have reported that this cell line can be used as a reliable
in vitro model for human drug metabolism studies, including the assessment of cytochrome P450
Objectives: The objective of this study is to determine whether CYP mRNA level measurement is superior
to the CYP enzyme activity measurement as a convenient high-throughput method for evaluating
CYP induction potential using HepaRG cells.
Methods: QuantiGene Plex 2.0 Assay and LC/MS/MS. mRNA expression levels and enzyme activities
of CYP1A2, CYP2B6, and CYP3A in HepaRG cells treated with prototypical inducers of each CYP
isoform [omeprazole (OME) for CYP1A2, phenobarbital (PB) for CYP2B6, and rifampicin (RIF) for
CYP3A] were evaluated.
Results: Although the activities of CYP2B6 and CYP3A were induced by treatment with PB and RIF,
we found that the activity of phenacetin O-deethylase (PHOD), which is known as a marker of the activity
of CYP1A2, was also enhanced by treatment with these non-CYP1A2 inducers in HepaRG cells.
Based on previously published reports, we hypothesized that the expression ratio of CYP3A to
CYP1A2 is much higher in HepaRG cells than in human hepatocytes; this may result in a nonnegligible
contribution of CYP3A to the PHOD reaction in HepaRG cells. Studies using CYP3A inhibitor and
pregnane X receptor-knockout HepaRG cells supported this hypothesis.
Conclusion: The measurement of mRNA serves as a higher reliable indicator for the evaluation of
CYP induction potential when using HepaRG cells.