Functionally Conserved Xenobiotic Responsive Enhancer in Cytochrome P450 3A7

doi:10.1006/bbrc.2000.4066

Biochemical and Biophysical Research Communications

Volume 280, Issue 1, 12 January 2001, Pages 139-144

https://doi.org/10.1006/bbrc.2000.4066 Get rights and content

Abstract

Nuclear receptors CAR and PXR play a key role in cytochrome P450 gene induction by xenobiotics. Human cytochrome P450 3A7 (CYP3A7) is expressed from early in gestation until the perinatal period, when there is a switch in expression to CYP3A4. Here we demonstrate that a PXR and CAR responsive enhancer is located approximately 8 kb upstream of the proximal CYP3A7 promoter. This distal xenobiotic responsive enhancer module (XREM) is conserved with the XREM of CYP3A4. Interestingly, not only the XREM, but also the entire promoters exhibit 90% sequence identity up to −8.8 kb, indicating a close evolutionary distance. We propose that the promoters have coevolved to functionally conserve P450 gene induction in response to xenobiotics through CAR and PXR. Thus, nuclear receptors for xenobiotics may not only play a role to provide a survival advantage during adulthood, but also to protect the embryo against endogenous and exogenous toxins.

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Neonatal cytochrome P450 CYP3A7: A comprehensive review of its role in development, disease, and xenobiotic metabolism
2019, Archives of Biochemistry and Biophysics
Citation Excerpt :
The regulation of CYP3A7 has turned out to be quite complex and involves a number of genetic control elements. Indeed, Sp1, Sp3, HNF-3β, USF1, XREM, and NFκB have all been implicated in regulation of the CYP3A7 gene [149,150]. Several variant alleles of the CYP3A7 gene have been identified, including 2 coding region and 4 noncoding region variants (Table 6).
The human cytochrome P450 CYP3A7, once thought to be an enzyme exclusive to fetal livers, has more recently been identified in neonates and developing infants as old as 24 months post-gestational age. CYP3A7 has been demonstrated to metabolize two endogenous compounds that are known to be important in the growth and development of the fetus and neonate, namely dehydroepiandrosterone sulfate (DHEA-S) and all-trans retinoic acid (atRA). In addition, it is also known to metabolize a variety of drugs and xenobiotics, albeit generally to a lesser extent relative to CYP3A4/5. CYP3A7 is an important component in the development and protection of the fetal liver and additionally plays a role in certain disease states, such as cancer and adrenal hyperplasia. Ultimately, a full understanding of the expression, regulation, and metabolic properties of CYP3A7 is needed to provide neonates with appropriate individualized pharmacotherapy. This article summarizes the current state of knowledge of CYP3A7, including its discovery, distribution, alleles, RNA splicing, expression and regulation, metabolic properties, substrates, and inhibitors.
Genomewide comparison of the inducible transcriptomes of nuclear receptors CAR, PXR and PPARα in primary human hepatocytes
2016, Biochimica et Biophysica Acta - Gene Regulatory Mechanisms
The ligand-activated nuclear receptor pregnane X receptor (PXR, NR1I2) and the constitutive androstane receptor (CAR, NR1I3) are two master transcriptional regulators of many important drug metabolizing enzymes and transporter genes (DMET) in response to xenobiotics including many drugs. The peroxisome proliferator-activated receptor alpha (PPARα, NR1C1), the target of lipid lowering fibrate drugs, primarily regulates fatty acid catabolism and energy-homeostasis. Recent research has shown that there are substantial overlaps in the regulated genes of these receptors. For example, both CAR and PXR also modulate the transcription of key enzymes involved in lipid and glucose metabolism and PPARα also functions as a direct transcriptional regulator of important DMET genes including cytochrome P450s CYP3A4 and CYP2C8. Despite their important and widespread influence on liver metabolism, comparative data are scarce, particularly at a global level and in humans. The major objective of this study was to directly compare the genome-wide transcriptional changes elucidated by the activation of these three nuclear receptors in primary human hepatocytes. Cultures from six individual donors were treated with the prototypical ligands for CAR (CITCO), PXR (rifampicin) and PPARα (WY14,643) or DMSO as vehicle control. Genomewide mRNA profiles determined with Affymetrix microarrays were analyzed for differentially expressed genes and metabolic functions. The results confirmed known prototype target genes and revealed strongly overlapping sets of coregulated but also distinctly regulated and novel responsive genes and pathways. The results further specify the role of PPARα as a regulator of drug metabolism and the role of the xenosensors PXR and CAR in lipid metabolism and energy homeostasis. This article is part of a Special Issue entitled: Xenobiotic nuclear receptors: New Tricks for An Old Dog, edited by Dr. Wen Xie.
Genetically Modified Caco-2 Cells with Improved Cytochrome P450 Metabolic Capacity
2016, Journal of Pharmaceutical Sciences
The human intestinal Caco-2 cell line has been extensively used as a model of small intestinal absorption but it lacks expression and function of cytochrome P450 enzymes, particularly CYP3A4 and CYP2C9, which are normally expressed in the intestinal epithelium. In order to increase the expression and activity of CYP isozymes in these cells, we created 2 novel Caco-2 sublines expressing chimeric constitutive androstane or pregnane X receptors and characterized these cells for their metabolic and absorption properties. In spite of elevated mRNA expression of transporters and differentiation markers, the permeation properties of the modified cell lines did not significantly differ from those of the wild-type cells. In contrast, the metabolic activity was increased beyond the currently used models. Specifically, CYP3A4 activity was increased up to 20-fold as compared to vitamin D treated wild-type Caco-2 cells.
Regulation of CYP3A4 and CYP3A5 expression and modulation of " intracrine" metabolism of androgens in prostate cells by liganded vitamin D receptor
2012, Molecular and Cellular Endocrinology
We investigated the capacity for vitamin D receptor (VDR) to modulate the expression of CYP3A4 and other genes that may facilitate the oxidative inactivation of androgens such as testosterone and androstanediol within prostate cells. We report that exposure to the active hormonal form of vitamin D markedly increased gene expression of CYP3A4 and CYP3A5 and ultimately achieved levels of intracellular CYP3A enzyme activity within LNCaP prostate cancer cells that were comparable to that observed for Caco2 cells, an established model of CYP3A induction, and resulted in the increased turnover of testosterone to its inactive 6β-OH metabolite. We demonstrate that VDR directs CYP3A4 and CYP3A5 expression through binding to distinct regulatory motifs located within the 5′ promoter regions of both genes. The current data highlight the potential application of VDR-based treatment regimes as a means to limit the bioavailability of growth-promoting androgens within the tumor microenvironment.
PIAS4 represses vitamin D receptor-mediated signaling and acts as an E3-SUMO ligase towards vitamin D receptor
2012, Journal of Steroid Biochemistry and Molecular Biology
Citation Excerpt :
All generated vectors were subjected to DNA sequencing to confirm identity and correct reading frame of each gene insert. Firefly luciferase-based reporter constructs used in this study that incorporated upstream promoter regions from human CYP genes were: pGL3-CYP3A4 (−10,466 to +53 bps), previously described by Bertilson et al. [18] and a generous gift of Dr Patrik Blomquist, Karolinska Institute, and pGL3-CYP24A1 (−500 bp to +100 bp) kindly donated by Prof J. Wesley Pike, University of Wisconsin. Cultured cells were seeded unto a 24-well plate at 100,000 cells/well (for HEK293) or 75,000 cells/well (for MCF7) and maintained for a period of 24 h before transfection with the appropriate combination of plasmids via calcium phosphate precipitation.
The present study investigated the potential for members of the protein inhibitors of activated STAT (PIAS) family to function as co-regulators of the vitamin D signal pathway. Among the PIAS proteins evaluated, we establish PIAS4 as a potent inhibitor of the transcriptional responses of the CYP3A4 and CYP24A1 target genes to the active hormonal form of vitamin D, a repression that was observed to be dependent upon an intact SUMO-ligase function of PIAS4. We report that PIAS4 represents a direct binding partner for vitamin D receptor (VDR) and also facilitates its modification with SUMO2, a process that preferentially occurs on the apo-form of VDR and which is reversed upon binding of ligand. Our results implicate PIAS4 and the process of SUMOylation as important modulators of VDR-mediated signaling which may both represent flexible mechanistic components as to how vitamin D achieves its pleiotropic effects.
The effect of interferon-α on the expression of cytochrome P450 3A4 in human hepatoma cells
2011, Toxicology and Applied Pharmacology
Citation Excerpt :
Following IFNα exposure, a decrease in CYP3A4 mRNA was detectable at 1.5 h, and at 9 h had reached a nadir of 64% untreated levels (Fig. 2A). To test if the reduction in CYP3A4 mRNA was a reflection of decreased CYP3A4 promoter activity, a DNA fragment corresponding to the CYP3A4 promoter (encompassing base pairs − 10,466 to + 53) (Bertilsson et al., 2001) was fused to a luciferase gene and the resultant luciferase reporter construct (pCYP3A4-Luc) was transfected into HepG2 cells. As shown in Fig. 2B, the luciferase activity of the pCYP3A4-Luc reporter, like the endogenous CYP3A4 mRNA level, decreased to 60% untreated levels, in a concentration-dependent manner (Fig. 3A).
Interferon α (IFNα) is used to treat malignancies and chronic viral infections. It has been found to decrease the rate of drug metabolism by acting on cytochrome P450 enzymes, but no studies have investigated the consequences of IFNα treatment on the CYP3A4 isoform, responsible for the metabolism of a majority of drugs. In this study, we have examined the effect of IFNα on CYP3A4 catalytic activity and expression in human hepatoma cells. We found that IFNα inhibits CYP3A4 activity and rapidly down-regulates the expression of CYP3A4, independent of de novo protein synthesis. Pharmacologic inhibitors and a dominant-negative mutant expression plasmid were used to dissect the molecular pathway required for CYP3A4 suppression, revealing roles for Jak1 and Stat1 and eliminating the involvement of the p38 mitogen-activated and extracellular regulated kinases. Treatment of hepatoma cells with IFNα did not affect the nuclear localization or relative abundance of Sp1 and Sp3 transcription factors, suggesting that the suppression of CYP3A4 by IFNα does not result from inhibitory Sp3 out-competing Sp1. To our knowledge, this is the first report that IFNα down-regulates CYP3A4 expression largely through the JAK-STAT pathway. Since IFNα suppresses CYP3A4 expression, caution is warranted when IFNα is administered in combination with CYP3A4 substrates to avoid the occurrence of adverse drug interactions.

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^☆: The sequence for the CYP3A7 promoter has been deposited in GenBank under Accession No. AF329900.

¹: To whom correspondence should be addressed. Fax: +46 8 6954086. E-mail: [email protected].

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Regular ArticleFunctionally Conserved Xenobiotic Responsive Enhancer in Cytochrome P450 3A7☆

Abstract

Biochem. Pharmacol.

Biochem. Biophys. Res. Commun.

Biochem. Biophys. Res. Commun.

Cell

J. Biol. Chem.

J. Biol. Chem.

Life Sci.

Cytochrome P450 3A: Ontogeny and drug disposition

Clin. Pharmacokinet.

Catalysis of the 4-hydroxylation of retinoic acids by cyp3a7 in human fetal hepatic tissues

Drug Metab. Dispos.

Update: Clinically significant cytochrome P-450 drug interactions

Pharmacotherapy

Expression of CYP3A4, CYP3A5 and CYP3A7 in human duodenal tissue

Br. J. Clin. Pharmacol.

CYP3A gene expression in human gut epithelium

Pharmacogenetics

Regular Article
Functionally Conserved Xenobiotic Responsive Enhancer in Cytochrome P450 3A7☆