Regulation of Two Members of the Steroid-Inducible Cytochrome P450 Subfamily (3A) in Rats

Cooper, Kathryn; Reik, Linda M.; Jayyosi, Zaid; Bandiera, Stelvio M.; Kelley, Michael J.; Ryan, Dene E.; Daniel, R.; McCluskey, Stuart A.; Levin, Wayne; Thomas, Paul E.

doi:10.1006/abbi.1993.1154

Cited by 96 publications

(49 citation statements)

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“…The signal in male liver was slightly higher than in female liver, consistent with a previous study that used the same antibody (Johnson et al, 2000). However, the strong signal observed in female liver does not agree with the fact that the CYP3A2 is male-specific in adult rats (Cooper et al, 1993). Since this CYP3A2 polyclonal antibody has not been rigorously tested for cross-reactivity with other rat CYP3A forms, it is clear that this antibody is not measuring specifically the CYP3A2 levels.…”

Section: Fold Induction Of the Cyp3a4-luc Reporter In Male (M) And Fesupporting

confidence: 71%

Differential Regulation of the Human Cyp3a4 Promoter in Transgenic Mice and Rats

Zhang¹,

Purchio²,

Coffee³

et al. 2004

Drug Metab Dispos

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This article is available online at http://dmd.aspetjournals.org ABSTRACT:Previously we described a transgenic mouse model [FVB/NTg(CYP3A4-luc)Xen] using a reporter construct consisting of 13 kilobases of the human CYP3A4 promoter driving the firefly luciferase gene in the inbred FVB/N mouse strain. Here we report regulation of the same CYP3A4-luc reporter gene in a transgenic outbred mouse strain (CD-1) and in a transgenic rat (SpragueDawley). Basal reporter expression and responses to several xenobiotics in the transgenic CD-1 mice [CD-1/Crl-Tg(CYP3A4-luc)Xen] were similar to those in the transgenic FVB/N mice. In both mouse backgrounds, the basal levels of the reporter were higher in male compared with female, and in the FVB/N strain there was greater induction for all drugs in male compared with female; however, in the CD-1 background this gender difference for induction was not obvious. In contrast with transgenic mice, transgenic rats [SD/Tac-Tg(CYP3A4-luc)Xen] expressed the luciferase reporter at higher basal levels in female compared with male rats. Responses to some compounds were much greater in rats than in mice, and the kinetics of induction was different with peak induction occurring later in the rat compared with the mouse. Our results suggest that the human CYP3A4 promoter is regulated differently in transgenic mice and rats in some aspects.

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Section: Fold Induction Of the Cyp3a4-luc Reporter In Male (M) And Fesupporting

confidence: 71%

Differential Regulation of the Human Cyp3a4 Promoter in Transgenic Mice and Rats

Zhang¹,

Purchio²,

Coffee³

et al. 2004

Drug Metab Dispos

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“…Studies aimed at elucidating the precise mechanism of CYP3A activation by glucocorticoids have predominantly focused on the rat isoforms, particularly the major glucocorticoid-inducible form, CYP3A23 Gonzalez et al, 1985;Simmons et al, 1987;Ribeiro and Lechner, 1992;Cooper et al, 1993;Komori and Oda, 1994;Sidhu and Omiencinski, 1995). Insights gained from studying rat genes have led directly to a greater understanding of the regulation of CYP3A isoforms from various species (Wrighton et al, 1985;Barwick et al, 1996;Lehmann et al, 1998).…”

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confidence: 99%

Two-Stage Glucocorticoid Induction ofCYP3A23through Both the Glucocorticoid and Pregnane X Receptors

Huss

Kasper

2000

Mol Pharmacol

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Glucocorticoid inducibility of the CYP3A23 gene is conferred by a multisite unit comprising binding sites for several members of the nuclear receptor superfamily of transcription factors, including the chicken ovalbumin upstream promoter-transcription factor COUP-TF, pregnane X receptor (PXR), and hepatocyte nuclear factor 4 (HNF-4). The presence of three binding sites, each of which interacts with more than one factor, contributes to the complexity of the CYP3A23 glucocorticoid-responsive region. Despite the glucocorticoid sensitivity of this gene, direct binding of ligand-activated glucocorticoid receptor (GR) to the CYP3A23 dexamethasone-responsive region (DexRE) is not required for induction. This study demonstrates that DexRE-2 is the key element within the CYP3A23 proximal promoter, conferring ligand sensitivity via its interaction with the PXR/RXR␣ heterodimer. The DexRE-1 and HNF-4 sites are not ligand-responsive, but are essential accessory elements required for full promoter inducibility. In addition to ligandmediated activation of PXR, the overall induction response involves a GR-mediated stimulation of PXR and RXR␣ expression. Hence, the induction pathway can be divided into two stages. In stage one, maximal induction requires a GR-dependent increase in PXR and RXR␣ expression, and stage two is characterized by direct transcriptional activation of CYP3A23, which is dependent on ligand-activated PXR as well as accessory factors bound at the DexRE-1 and HNF-4 sites. Because multiple proteins bind at each element within the glucocorticoid-responsive region, factors not contributing to ligand responsiveness, such as chicken ovalbumin upstream promotertranscription factor, may modulate the response through competitive interactions.

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“…CYP3A2 is the form expressed in uninduced animals; however, its expression displays a gender and developmental stage-dependent pattern (8, 20 -22). Despite its high homology (89%) to 3A23, CYP3A2 is only weakly induced by glucocorticoids (23,24). CYP3A23 is expressed at low levels in untreated animals but is highly inducible by glucocorticoids, such as dexamethasone, and by PCN, a synthetic steroid with no hormonal activity (16,25).…”

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confidence: 99%

Nuclear Receptor Involvement in the Regulation of Rat Cytochrome P450 3A23 Expression

Huss¹,

Kasper

1998

Journal of Biological Chemistry

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Many genes of the cytochrome P450 3A (CYP3A) subfamily, including several human and rat isoforms, are inducible by glucocorticoids. In the rat CYP3A23 gene, a 110-base pair segment of the proximal 5-flanking region mediates dexamethasone activation. Three binding sites (DexRE-1, DexRE-2, and Site A), identified by DNase I footprinting analysis, were characterized for their relative contribution to both basal activity and dexamethasone inducibility. Site-directed mutagenesis of DexRE-1 (؊144 to ؊169) and DexRE-2 (؊118 to ؊136) demonstrated that each contained a core imperfect AGGTCA direct repeat, which comprised a consensus nuclear receptor binding site, and was essential for dexamethasone responsiveness but was not required for basal activity. Competition gel shift and supershift analyses revealed that both sites can bind the orphan nuclear receptor chicken ovalbumin upstream promoter-transcription factor.Site A (؊85 to ؊110) was shown to be important for both basal activity and dexamethasone responsiveness. Point mutants displayed a reduced (2-3-fold) induction response, compared with 15-fold for wild-type, which was accompanied by a 40 -60% drop in basal activity. Site A was shown to bind the liver-enriched nuclear receptor hepatocyte nuclear factor 4. Our studies demonstrate that the mechanism mediating glucocorticoidinducible transcriptional activity of CYP3A23 involves multiple binding sites for members of the nuclear receptor superfamily.The cytochrome P450s (CYPs) 1 make up a superfamily of heme-containing monooxygenases that are found most abundantly in liver endoplasmic reticulum and catalyze the oxidation or reduction of both endogenous and foreign substrates, often as an essential step in their elimination (1). CYP expression is modulated by endogenous and exogenous compounds, which may reflect a homeostatic mechanism whereby normal "endogenous ligand" concentrations are maintained. In early studies, steroids were shown to regulate expression of a cytochrome P450 family that was distinct from the 3-methylcholanthrene or phenobarbital inducible P450s (2-5). Pregnenolone 16␣-carbonitrile (PCN) was characterized as the prototypical inducer of the CYP3A family; however, many glucocorticoids have been shown to be more potent than PCN, whereas certain non-glucocorticoids, such as phenobarbital and macrolide antibiotics, also induce the same protein (6 -8). CYP3A proteins have been identified in several species, including rat, rabbit, mouse, and human (9 -14). The major glucocorticoid-responsive CYP3A gene in rat is 3A23, whereas 3A4 and 3A5 are inducible forms in human (15, 16). CYP3A enzymes metabolize over 60% of therapeutically relevant compounds and are involved in 6␤-hydroxylation of the endogenous steroids testosterone, progesterone, and cortisol (17-19).Regulation of rat 3A genes CYP3A23 and 3A2 has been the most extensively characterized. CYP3A2 is the form expressed in uninduced animals; however, its expression displays a gender and developmental stage-dependent pattern (8, 20 -22). Despite its hi...

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Regulation of Two Members of the Steroid-Inducible Cytochrome P450 Subfamily (3A) in Rats

Cited by 96 publications

References 0 publications

Differential Regulation of the Human Cyp3a4 Promoter in Transgenic Mice and Rats

Differential Regulation of the Human Cyp3a4 Promoter in Transgenic Mice and Rats

Two-Stage Glucocorticoid Induction ofCYP3A23through Both the Glucocorticoid and Pregnane X Receptors

Nuclear Receptor Involvement in the Regulation of Rat Cytochrome P450 3A23 Expression

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