Bisphenol A alters human CYP3A4 enzyme expression and activity

Abstract

Bisphenol A (BPA) is an endocrine-disrupting chemical largely used in consumer products and has been reported to interact with the pregnane X receptor (PXR). Human CYP3A4 enzyme has an essential role in hydroxylation of steroid hormones and is regulated at the molecular level by PXR. The purpose of our study is to describe the effect of BPA on CYP3A4 transcriptional expression and enzyme activity in the human hepatoma cell line, DPX2. Laboratory-based study. The human hepatoma cell line DPX2, engineered to stably harbor human PXR was exposed to BPA at increasing relevant concentrations followed by total RNA isolation. CYP3A4 mRNA levels were subsequently determined by reverse transcription, and quantitative real-time polymerase chain reaction (RT-PCR). Results were expressed as the mean fold induction.DMSO served as control. CYP3A4 enzyme activity assays were conducted directly in DPX2 cells cultured in 96-well plates. The cells were treated with various concentrations of BPA for 24 hours and CYP3A4 activity was measured with a luminescent CYP3A4 substrate (P450-Glo CYP3A4 Assay with with luciferin IPA). Treatment of human DPX2 cells with BPA induced a significant increase in CYP3A4 mRNA expression at 5,10, and 50μM compared to control (P<0.05). BPA also induced CYP3A4 enzyme activity at concentrations relevant to human exposure, but at higher concentrations, a decrease in enzyme activity occurs.Tabled 1BPA effects on CYP3A4 mRNA expression and enzyme activity, respectively.TreatmentMean fold induction in CYP3A4 mRNA expressionP value mRNA expressionMean fold induction in CYP3A4 enzyme activityP value enzyme activityDMSO11BPA 1μM3.10.611.4P>0.05BPA 5μM8.2P<0.0012P<0.05BPA 10μM11.4P<0.0013.7P<0.05BPA 50μM10P<0.0013.7P<0.05BPA 100μM3.30.371.7P<0.05 Open table in a new tab BPA, in relevant exposure ranges, demonstrates induction of CYP3A4 mRNA expression and activity in human hepatoma cells in vitro which in vivo may affect endocrine function by altering steroid hormone metabolism/action.