RT Journal Article
SR Electronic
T1 Use of a Reporter Gene Assay to Predict and Rank the Potency and Efficacy of CYP3A4 Inducers
JF Drug Metabolism and Disposition
JO Drug Metab Dispos
FD American Society for Pharmacology and Experimental Therapeutics
SP 1499
OP 1504
VO 29
IS 11
A1 El-Sankary, Wafaa
A1 Gibson, G. Gordon
A1 Ayrton, Andy
A1 Plant, Nick
YR 2001
UL http://dmd.aspetjournals.org/content/29/11/1499.abstract
AB Regulation of the CYP3A4 gene has been studied using an in vitro reporter gene assay. The effect of 17 xenobiotics on ∼1 kilobase of the CYP3A4 proximal promoter, upstream of a secretory placental alkaline phosphatase reporter gene was investigated following transfection into the HepG2 cell line. Transfections were carried out either in the basal system or with cotransfection of expression plasmids for the human pregnane X receptor (hPXR) and the human glucocorticoid receptor (hGR), two important receptors in the regulation of CYP3A4 gene expression. Compounds were tested at four concentrations, and the resulting data were used to calculate maximal induction (Imax) and EC50values. An “overall inductive ability” (IA) was derived by dividingImax by EC50. Of the compounds tested seven were established transcriptional inducers, all of which were positive in the in vitro assay. The remaining 10 compounds represented a group with preliminary evidence for CYP3A transcriptional activation. Nine of these compounds produced statistically significant inductions in vitro, with only pravastatin failing to activate the reporter gene. This is of potential interest in light of the high IA values observed with the other structurally and functionally similar statins tested. We conclude that a four-concentration-point, in vitro model is capable of identifying CYP3A4 transcriptional inducers and yields an IA value allowing the ranking of compounds for their overall ability to induce CYP3A4 transcription. In addition, the majority of the compounds tested showed increased IA values in the hPXR/hGR cotransfected system, underpinning the importance of these receptors in CYP3A4 gene transcriptional regulation. The American Society for Pharmacology and Experimental Therapeutics