Please use this identifier to cite or link to this item: http://hdl.handle.net/2440/62712
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Type: Journal article
Title: Regulation of CYP3A4 by pregnane X receptor: The role of nuclear receptors competing for response element binding
Author: Istrate, M.
Nussler, A.
Eichelbaum, M.
Burk, O.
Citation: Biochemical and Biophysical Research Communications, 2010; 393(4):688-693
Publisher: Academic Press Inc
Issue Date: 2010
ISSN: 0006-291X
0006-291X
Statement of
Responsibility: 
Monica A. Istrate, Andreas K. Nussler, Michel Eichelbaum, Oliver Burk
Abstract: Induction of the major drug metabolizing enzyme CYP3A4 by xenobiotics contributes to the pronounced interindividual variability of its expression and often results in clinically relevant drug-drug interactions. It is mainly mediated by PXR, which regulates CYP3A4 expression by binding to several specific elements in the 5' upstream regulatory region of the gene. Induction itself shows a marked interindividual variability, whose underlying determinants are only partly understood. In this study, we investigated the role of nuclear receptor binding to PXR response elements in CYP3A4, as a potential non-genetic mechanism contributing to interindividual variability of induction. By in vitro DNA binding experiments, we showed that several nuclear receptors bind efficiently to the proximal promoter ER6 and distal xenobiotic-responsive enhancer module DR3 motifs. TRalpha1, TRbeta1, COUP-TFI, and COUP-TFII further demonstrated dose-dependent repression of PXR-mediated CYP3A4 enhancer/promoter reporter activity in transient transfection in the presence and absence of the PXR inducer rifampin, while VDR showed this effect only in the absence of treatment. By combining functional in vitro characterization with hepatic expression analysis, we predict that TRalpha1, TRbeta1, COUP-TFI, and COUP-TFII show a strong potential for the repression of PXR-mediated activation of CYP3A4 in vivo. In summary, our results demonstrate that nuclear receptor binding to PXR response elements interferes with PXR-mediated expression and induction of CYP3A4 and thereby contributes to the interindividual variability of induction.
Keywords: Nuclear receptor; PXR; CYP3A4; Induction; Hepatocyte
Rights: Copyright © 2010 Elsevier Inc. All rights reserved.
RMID: 0020102514
DOI: 10.1016/j.bbrc.2010.02.058
Appears in Collections:Pharmacology publications

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