Transcriptional Regulation of CYP2C9 Gene

Abstract

Although cytochrome P450 2C9 (CYP2C9) is a major CYP expressed in the adult human liver, its mechanism of regulation is poorly known. In previous work, we have shown that CYP2C9is inducible in primary human hepatocytes by xenobiotics including dexamethasone, rifampicin, and phenobarbital. The aim of this work was to investigate the molecular mechanism(s) controlling the inducible expression of CYP2C9. Deletional analysis ofCYP2C9 regulatory region (+21 to −2088) in the presence of various hormone nuclear receptors suggested the presence of two functional response elements, a glucocorticoid receptor-responsive element (−1648/−1684) and a constitutive androstane receptor-responsive element (CAR, −1783/−1856). Each of these were characterized by co-transfection experiments, directed mutagenesis, gel shift assays, and response to specific antagonists RU486 and androstanol. By these experiments we located a glucocorticoid-responsive element imperfect palindrome at −1662/−1676, and a DR4 motif at −1803/−1818 recognized and transactivated by human glucocorticoid receptor and by hCAR and pregnane X receptor, respectively. Identification of these functional elements provides rational mechanistic basis for CYP2C9induction by dexamethasone (submicromolar concentrations), and by phenobarbital and rifampicin, respectively. CYP2C9 appears therefore to be a primary glucocorticoid-responsive gene, which in addition, may be induced by xenobiotics through CAR/pregnane X receptor activation. Although cytochrome P450 2C9 (CYP2C9) is a major CYP expressed in the adult human liver, its mechanism of regulation is poorly known. In previous work, we have shown that CYP2C9is inducible in primary human hepatocytes by xenobiotics including dexamethasone, rifampicin, and phenobarbital. The aim of this work was to investigate the molecular mechanism(s) controlling the inducible expression of CYP2C9. Deletional analysis ofCYP2C9 regulatory region (+21 to −2088) in the presence of various hormone nuclear receptors suggested the presence of two functional response elements, a glucocorticoid receptor-responsive element (−1648/−1684) and a constitutive androstane receptor-responsive element (CAR, −1783/−1856). Each of these were characterized by co-transfection experiments, directed mutagenesis, gel shift assays, and response to specific antagonists RU486 and androstanol. By these experiments we located a glucocorticoid-responsive element imperfect palindrome at −1662/−1676, and a DR4 motif at −1803/−1818 recognized and transactivated by human glucocorticoid receptor and by hCAR and pregnane X receptor, respectively. Identification of these functional elements provides rational mechanistic basis for CYP2C9induction by dexamethasone (submicromolar concentrations), and by phenobarbital and rifampicin, respectively. CYP2C9 appears therefore to be a primary glucocorticoid-responsive gene, which in addition, may be induced by xenobiotics through CAR/pregnane X receptor activation. cytochrome P-450 pregnane X receptor glucocorticoid receptor glucocorticoid-responsive element constitutive androstane receptor retinoid X receptor xenobiotic responsive enhancer module Dulbecco's modified Eagle's medium pregnenolone 16α-carbonitrile 1,4-bis[2-(3,5-dichloropyridyloxy)]-benzene constitutive androstane receptor-responsive element dithiothreitol electrophoretic mobility shift assay tyrosine aminotransferase Cytochrome P-450 (CYP)1is the generic name of a superfamily of heme-thiolate proteins that play a critical role in the oxidative metabolism of xenobiotics, including drugs, environmental pollutants and contaminants, and biological signaling molecules such as steroid hormones and biliary salts. CYP2C9 is a member of the CYP2C subfamily, which in man includes at least three other members, i.e. CYP2C8, CYP2C18, and CYP2C19 (1Goldstein J.A. de Morais S. Pharmacogenetics. 1994; 4: 285-299Crossref PubMed Scopus (519) Google Scholar). Accumulating evidence indicates that CYPC9 ranks second, after CYP3A4, among the most expressed drug-metabolizing enzymes in human liver (2Miners J.O. Birkett D.J. Br. J. Clin. Pharmacol. 1998; 45: 525-538Crossref PubMed Scopus (761) Google Scholar). CYP2C9 is involved in the metabolism of numerous substrates including phenytoin, tolbutamide, torsemide, S-warfarin, and numerous nonsteroidal anti-inflammatory drugs (reviewed in Refs. 1Goldstein J.A. de Morais S. Pharmacogenetics. 1994; 4: 285-299Crossref PubMed Scopus (519) Google Scholar and 2Miners J.O. Birkett D.J. Br. J. Clin. Pharmacol. 1998; 45: 525-538Crossref PubMed Scopus (761) Google Scholar). In contrast to the large amount of data on the biochemistry, enzymology, pharmacology, and genetic polymorphism of CYP2C9, little is known on the inducibility of this gene in response to xenobiotics in humans. We recently demonstrated that CYP2C9 is inducible at the mRNA and protein levels in human hepatocytes in primary cultures in response to xenobiotics shown previously to beCYP3A4 and CYP2B6 inducers such as dexamethasone, rifampicin, and phenobarbital (3Gerbal-Chaloin S. Pascussi J.M. Pichard-Garcia L. Daujat M. Waechter F. Fabre J.M. Carrere N. Maurel P. Drug Metab. Dispos. 2001; 29: 242-251PubMed Google Scholar). The concentration and time dependence of CYP2C9 mRNA expression in response to these three inducers, compared with those of CYP3A4 and CYP2B6 mRNAs, were consistent with the possible implication of at least three receptors in the inducible expression of CYP2C9: the glucocorticoid receptor (GR), the pregnane X receptor (PXR, also named steroid and xenobiotic receptor and pregnane-activated receptor), and the constitutive androstane receptor (CAR), respectively (3Gerbal-Chaloin S. Pascussi J.M. Pichard-Garcia L. Daujat M. Waechter F. Fabre J.M. Carrere N. Maurel P. Drug Metab. Dispos. 2001; 29: 242-251PubMed Google Scholar, 4Kliewer S.A. Moore J.T. Wade L. Staudinger J.L. Watson M.A. Jones S.A. McKee D.D. Oliver B.B. Willson T.M. Zetterstrom R.H. Perlmann T. Lehmann J.M. Cell. 1998; 92: 73-82Abstract Full Text Full Text PDF PubMed Scopus (1344) Google Scholar, 5Sueyoshi T. Kawamoto T. Zelko I. Honkakoski P. Negishi M. J. Biol. Chem. 1999; 274: 6043-6046Abstract Full Text Full Text PDF PubMed Scopus (627) Google Scholar). Recent reports on PXR and CAR, two new members of the steroid receptor superfamily, have considerably clarified our understanding of the inducible regulation of CYP genes from families 2 and 3, in response to xenobiotics in rodents and in man (4Kliewer S.A. Moore J.T. Wade L. Staudinger J.L. Watson M.A. Jones S.A. McKee D.D. Oliver B.B. Willson T.M. Zetterstrom R.H. Perlmann T. Lehmann J.M. Cell. 1998; 92: 73-82Abstract Full Text Full Text PDF PubMed Scopus (1344) Google Scholar, 5Sueyoshi T. Kawamoto T. Zelko I. Honkakoski P. Negishi M. J. Biol. Chem. 1999; 274: 6043-6046Abstract Full Text Full Text PDF PubMed Scopus (627) Google Scholar, 6Bertilsson G. Heidrich J. Svensson K. Asman M. Jendeberg L. Sydow B.M. Ohlsson R. Postlind H. Blomquist P. Berkenstam A. Proc. Natl. Acad. Sci. U. S. A. 1998; 95: 12208-12213Crossref PubMed Scopus (796) Google Scholar, 7Blumberg B. Sabbagh W.J. Juguilon H. Bolado J.J. van, M. C. Ong E.S. Evans R.M. Genes Dev. 1998; 12: 3195-3205Crossref PubMed Scopus (820) Google Scholar, 8Lehmann J.M. McKee D.D. Watson M.A. Willson T.M. Moore J.T. Kliewer S.A. J. Clin. Invest. 1998; 102: 1016-1023Crossref PubMed Scopus (1389) Google Scholar, 9Honkakoski P. Negishi M. J. Biol. Chem. 1997; Full Text Full Text PDF PubMed Scopus Google Scholar, J. B. J. Biol. Chem. 1997; Full Text Full Text PDF PubMed Scopus Google Scholar). PXR a with and this shown to through to element at in the J.M. McKee D.D. Watson M.A. Willson T.M. Moore J.T. Kliewer S.A. J. Clin. Invest. 1998; 102: 1016-1023Crossref PubMed Scopus (1389) Google Scholar). B. C. Pharmacol. 1999; PubMed Scopus Google the presence of a element xenobiotic responsive enhancer module a and located at and demonstrated that this element with the to PXR is by numerous known to such as rifampicin, and dexamethasone D.J. Jones S.A. B. C. Willson T.M. J.L. Kliewer S.A. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). The of these for the human PXR in the In contrast to is in the and the in response to phenobarbital P. Negishi M. J. 1998; PubMed Scopus Google through of T. T. Zelko I. Moore R. K. Negishi M. Cell. Biol. 1999; PubMed Scopus Google Scholar). a with have a element module in genes H. B. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google A. C. A. PubMed Scopus Google which was characterized by Honkakoski P. Negishi M. J. Biol. Chem. 1997; Full Text Full Text PDF PubMed Scopus Google Scholar). The element is located at in CYP2B6 and a DR4 motif T. Kawamoto T. Zelko I. Honkakoski P. Negishi M. J. Biol. Chem. 1999; 274: 6043-6046Abstract Full Text Full Text PDF PubMed Scopus (627) Google Scholar). a molecules among CYP inducers were shown to to human at concentrations), and the and to be of of appears as a a that shown to through mechanism P. Negishi M. J. 1998; PubMed Scopus Google and other known as CYP inducers and of D.J. Jones S.A. B. C. Willson T.M. J.L. Kliewer S.A. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). The aim of the work was to investigate the molecular mechanism(s) of of CYP2C9 by dexamethasone, rifampicin, and phenobarbital. this the region of this gene was and by including analysis of co-transfection with nuclear receptor expression directed mutagenesis, and gel shift the of two functional responsive elements in the regulatory region imperfect glucocorticoid-responsive element at and a element at medium was from rifampicin, pregnenolone 16α-carbonitrile and were from was from P. was from ofCYP2C9 region was in after by human as a and and was with and was by were was by a in and were by as a and and and were with to and were with The and two of the of a and a gene was by L. The expression was by J. C. The expression was by of of and and by The hCAR expression were by as a by M. and and and The and N. S. P. 1994; PubMed Scopus Google The expression was by M. cultures of human hepatocytes were and as (3Gerbal-Chaloin S. Pascussi J.M. Pichard-Garcia L. Daujat M. Waechter F. Fabre J.M. Carrere N. Maurel P. Drug Metab. Dispos. 2001; 29: 242-251PubMed Google Scholar). The and were from the and and were in with to the were with of of and of of hCAR expression in medium and were in in in with medium for the medium was by and were for with dexamethasone, rifampicin, and were to the of the was a to the of the and a in a in a in and a in was of were for at in of in the presence of of proteins from with a and to the of proteins to were with including and a assays, were with of were on a gel and to at in The gel was a and was T. Kawamoto T. Zelko I. Honkakoski P. Negishi M. J. Biol. Chem. 1999; 274: 6043-6046Abstract Full Text Full Text PDF PubMed Scopus (627) Google were for at in of and in the presence of of proteins from with were with including and which were assays, were with of hCAR by M. were on a gel and to at in The gel was a and was J.M. McKee D.D. Watson M.A. Willson T.M. Moore J.T. Kliewer S.A. J. Clin. Invest. 1998; 102: 1016-1023Crossref PubMed Scopus (1389) Google were for at in of of and of in the presence of 2 of PXR proteins expressed in and were of including and B. C. Pharmacol. 1999; PubMed Scopus Google Scholar). were on a gel and to at in The gel was a and was from hepatocytes to the of were by a M. aminotransferase mRNA was by a specific by T. J. and CYP2C9 mRNA was by assay as (3Gerbal-Chaloin S. Pascussi J.M. Pichard-Garcia L. Daujat M. Waechter F. Fabre J.M. Carrere N. Maurel P. Drug Metab. Dispos. 2001; 29: 242-251PubMed Google Scholar). In work, we that of CYP2C9 mRNA by dexamethasone that of a gene known to be by M. B. G. J. PubMed Scopus Google in of time and concentration dependence in primary human hepatocytes (3Gerbal-Chaloin S. Pascussi J.M. Pichard-Garcia L. Daujat M. Waechter F. Fabre J.M. Carrere N. Maurel P. Drug Metab. Dispos. 2001; 29: 242-251PubMed Google Scholar). to for a functional glucocorticoid-responsive element in gene CYP2C9. this the region of CYP2C9 from to was of a gene by a in and of this region were The various CYP2C9 were which expression is with of a were for in the presence of dexamethasone, and was from was as shown in and response to of dexamethasone at and of these suggested the presence of a located on the region of CYP2C9, a analysis of of CYP2C9 was The in of the gene was in of the including the In these were with the expression a was in response to dexamethasone for and a major in was with and including and the of a and of a functional in of to of CYP2C9 by the CYP2C9 were in with and with for was by of with dexamethasone for were for which was to is expressed as the of in the presence of to this in the of the of to the region to was in three in the to shown in this was transactivated by in the presence of that this was were with in the presence of Although RU486 a of this the of the The 2C9 to dexamethasone in hepatocytes the In experiments with were was also in primary human hepatocytes and was transactivated by dexamethasone as shown in RU486 analysis of region demonstrated the presence of two by three the role of these two were by directed as a in the of and in the of were in in the presence of expression and of shown in the of was to of the The CYP2C9 region is to as with a gel shift analysis was In a we that the the was and this was by as with and the was a for this and the in of was experiments with shown in The of to is by a this was by in with this that to with a for is expressed in our cultures J.M. L. Fabre J.M. Maurel P. Pharmacol. PubMed Scopus Google Scholar, J.M. S. Fabre J.M. Maurel P. Pharmacol. PubMed Scopus Google Scholar). We therefore of CYP2C9 mRNA by dexamethasone is by protein be for this this human hepatocytes were in a medium for and to dexamethasone for in the presence of a of protein experiments that protein is by in these of CYP2C9 mRNA expression by assay is in CYP2C9 mRNA by In of CYP2C9 mRNA by and phenobarbital was by and by in in the presence of of CYP3A4 mRNA by was by in In our previous (3Gerbal-Chaloin S. Pascussi J.M. Pichard-Garcia L. Daujat M. Waechter F. Fabre J.M. Carrere N. Maurel P. Drug Metab. Dispos. 2001; 29: 242-251PubMed Google the data on and the of of on mRNA that CYP2C9 is a primary gene, in human We have previously that of CYP2C9 mRNA in response to phenobarbital in primary human hepatocytes that of CYP2B6 mRNA in of time and concentration dependence (3Gerbal-Chaloin S. Pascussi J.M. Pichard-Garcia L. Daujat M. Waechter F. Fabre J.M. Carrere N. Maurel P. Drug Metab. Dispos. 2001; 29: 242-251PubMed Google Scholar). was therefore that for the of CYP2C9. We for possible in regulatory region by analysis of The the were with of a the human were for and the three of the element from CYP2B6 gene T. Kawamoto T. Zelko I. Honkakoski P. Negishi M. J. Biol. Chem. 1999; 274: 6043-6046Abstract Full Text Full Text PDF PubMed Scopus (627) Google was as shown in and were transactivated to a by and hCAR hCAR transactivated data In and were transactivated the implication of in the of these was with of and in the presence of of and of The shown in the of to a the of this as from previous D.J. Jones S.A. B. C. Willson T.M. J.L. Kliewer S.A. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). was to the of by this on hCAR I. P. Moore D.D. Cell. Biol. PubMed Scopus Google Scholar). In these that a element is located in the region of directed to on of CYP2C9 by hCAR of on the motif and and were by as and were in with expression and with for were for which was to were with expression and was as of the is by the of in the presence of to this in the of the of of this the was two a from to and a from to The of these to with hCAR and with was by gel shift We a and that this hCAR as previously T. Kawamoto T. Zelko I. Honkakoski P. Negishi M. J. Biol. Chem. 1999; 274: 6043-6046Abstract Full Text Full Text PDF PubMed Scopus (627) Google Scholar, 9Honkakoski P. Negishi M. J. Biol. Chem. 1997; Full Text Full Text PDF PubMed Scopus Google Scholar). was by and in the presence of of with the for hCAR and The and of were in the with and the of the of the the presence of imperfect DR4 motif and motif is to as this DR4 with for hCAR of DR4 and DR4 its as a for DR4 The experiments were a with hCAR The the was by and the was by of with experiments that a DR4 motif by hCAR is located in the region and the of was by this DR4 and DR4 were to the by directed and were in with hCAR expression shown in the of a and of was in of a gene by a in was with and in and was experiments were for were transactivated by and to a by hCAR as shown in In these experiments that the DR4 motif located in the region and is recognized and transactivated by hCAR and for of this gene by phenobarbital. We have shown previously that CYP2C9 is inducible by rifampicin, a of CYP3A4 and of (3Gerbal-Chaloin S. Pascussi J.M. Pichard-Garcia L. Daujat M. Waechter F. Fabre J.M. Carrere N. Maurel P. Drug Metab. Dispos. 2001; 29: 242-251PubMed Google Scholar). CYP3A4 by shown to be on PXR J.M. McKee D.D. Watson M.A. Willson T.M. Moore J.T. Kliewer S.A. J. Clin. Invest. 1998; 102: 1016-1023Crossref PubMed Scopus (1389) Google we that this receptor be involved in the of CYP2C9 as this CYP2C9 and the were in with a expression In experiments were a three of the CYP3A4 8Lehmann J.M. McKee D.D. Watson M.A. Willson T.M. Moore J.T. Kliewer S.A. J. Clin. Invest. 1998; 102: 1016-1023Crossref PubMed Scopus (1389) Google Scholar). Although was transactivated of PXR by rifampicin, as of the was transactivated by PXR in response to its T. Kawamoto T. Zelko I. Honkakoski P. Negishi M. J. Biol. Chem. 1999; 274: 6043-6046Abstract Full Text Full Text PDF PubMed Scopus (627) Google demonstrated that PXR and to and including We therefore for the of PXR to to and the motif this were as a in the presence of PXR by in and this a with the and the this was by in with the for the and experiments as a shown in a with and the this was by in and with the for the and PXR is to the and were in with expression The were for with i.e. rifampicin, and was In experiments, the expression and the were as The data from of experiments in I. of and by was of that in response to of by was in of this by was is in with by that of is this element is to the a motif B. C. Pharmacol. 1999; PubMed Scopus Google Scholar). of by was by for was and by in response to in the of In these data that PXR is to to and element in response to analysis of and by of in with of in with of in with of in with and were in with expression The were for in the presence of and was and with to the of in to in in of In experiments, the expression and the were as of in with of in with of in with of in with in a new and were in with expression The were for in the presence of and was and with to the of in to in in of In experiments, the expression and the were as we on the presence of two functional responsive elements in the regulatory region of gene CYP2C9, a palindrome at and a motif at The presence of these two elements provides the mechanistic basis for the of CYP2C9 by dexamethasone and in primary human In addition, the that PXR may to and the the that is a known of this gene in and in S. Pascussi J.M. Pichard-Garcia L. Daujat M. Waechter F. Fabre J.M. Carrere N. Maurel P. Drug Metab. Dispos. 2001; 29: 242-251PubMed Google Scholar, D.D. J. Clin. Pharmacol. PubMed Scopus Google Scholar). The role of in the of CYP gene expression the of and J. Biol. Chem. Full Text PDF PubMed Google Scholar, G. C. K. T. L. K. Drug Metab. Dispos. Google Scholar). Although among the inducers in data evidence in of a major implication of this receptor in and other data the of in CYP gene In have that in primary cultures of hepatocytes and genes in response to xenobiotics was by of dexamethasone of by were inducers K. T. J. N. 1999; PubMed Scopus Google Scholar, H. M. L. M. P. Pharmacol. 1997; PubMed Scopus Google Scholar, Pharmacogenetics. PubMed Scopus Google Scholar, D.J. J.J. S. J. PubMed Scopus Google Scholar, M. Pharmacol. Google Scholar). We recently a for these J.M. L. Fabre J.M. Maurel P. Pharmacol. PubMed Scopus Google Scholar, J.M. S. Fabre J.M. Maurel P. Pharmacol. PubMed Scopus Google Scholar). primary cultures of human we that expression of CAR, and is by dexamethasone and to the that the expression of CAR, and to the inducible expression which the of these nuclear receptors for and for this analysis of the of CYP2C9 region the presence of numerous most of which Morais S. H. J. J.A. PubMed Scopus Google Scholar). The element characterized a with two by with to the two in the and in the for the for of compared with as suggested by of this in in its to and by In work, we that of CYP2C9 mRNA in response to dexamethasone that of in of time and concentration dependence in primary human hepatocytes (3Gerbal-Chaloin S. Pascussi J.M. Pichard-Garcia L. Daujat M. Waechter F. Fabre J.M. Carrere N. Maurel P. Drug Metab. Dispos. 2001; 29: 242-251PubMed Google Scholar). the of CYP2C9 mRNA was at In of CYP3A4 mRNA in the at least dexamethasone, CYP2B6 mRNA was inducible by dexamethasone consistent with the that dexamethasone PXR at J.M. McKee D.D. Watson M.A. Willson T.M. Moore J.T. Kliewer S.A. J. Clin. Invest. 1998; 102: 1016-1023Crossref PubMed Scopus (1389) Google and is a hCAR D.J. Jones S.A. B. C. Willson T.M. J.L. Kliewer S.A. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). In addition, we that of CYP2C9 and by dexamethasone is to in of CYP2C9 by phenobarbital is by this the data in the and previous work (3Gerbal-Chaloin S. Pascussi J.M. Pichard-Garcia L. Daujat M. Waechter F. Fabre J.M. Carrere N. Maurel P. Drug Metab. Dispos. 2001; 29: 242-251PubMed Google that CYP2C9 is a primary glucocorticoid-responsive this is the a functional in CYP S. Pharmacol. Google demonstrated the presence of a functional glucocorticoid-responsive element in the human gene at of the by that this element was of two by T.M. D.J. J.A. Biol. 1998; PubMed Scopus Google functional at in the regulatory region of receptor elements of two with to the in the as by a of from to D.J. Evans R.M. Cell. Full Text PDF PubMed Scopus Google Scholar). The is located at of the CYP2C9 and in a of two by of the element in in its to and by DR4 were previously in the of J. B. J. Biol. Chem. 1997; Full Text Full Text PDF PubMed Scopus Google P. Negishi M. J. Biol. Chem. 1997; Full Text Full Text PDF PubMed Scopus Google T. Kawamoto T. Zelko I. Honkakoski P. Negishi M. J. Biol. Chem. 1999; 274: 6043-6046Abstract Full Text Full Text PDF PubMed Scopus (627) Google as as in human CYP3A4 T. Kawamoto T. Zelko I. Honkakoski P. Negishi M. J. Biol. Chem. 1999; 274: 6043-6046Abstract Full Text Full Text PDF PubMed Scopus (627) Google Scholar, I. Negishi M. PubMed Scopus Google Scholar). The element a for hCAR as compared with the as by experiments in gel shift The presence of such element is in with the that CYP2C9 mRNA is inducible by phenobarbital in with CYP2B6 mRNA in of time and concentration dependence in primary cultures of human hepatocytes (3Gerbal-Chaloin S. Pascussi J.M. Pichard-Garcia L. Daujat M. Waechter F. Fabre J.M. Carrere N. Maurel P. Drug Metab. Dispos. 2001; 29: 242-251PubMed Google Scholar). genes from the and the work CYP2C9 as a new for in be that CYP2C9 by phenobarbital be by PXR as phenobarbital is a PXR the of phenobarbital for is D.J. Jones S.A. B. C. Willson T.M. J.L. Kliewer S.A. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). We have shown J.M. S. Fabre J.M. Maurel P. Pharmacol. PubMed Scopus Google that phenobarbital the nuclear of in human hepatocytes at In addition, this is to CYP2C9 mRNA in these cultures at in the of (3Gerbal-Chaloin S. Pascussi J.M. Pichard-Garcia L. Daujat M. Waechter F. Fabre J.M. Carrere N. Maurel P. Drug Metab. Dispos. 2001; 29: 242-251PubMed Google Scholar). is therefore suggested at concentration phenobarbital the implication of PXR at concentration be CYP2C9 is inducible by in (3Gerbal-Chaloin S. Pascussi J.M. Pichard-Garcia L. Daujat M. Waechter F. Fabre J.M. Carrere N. Maurel P. Drug Metab. Dispos. 2001; 29: 242-251PubMed Google Scholar, D.D. J. Clin. Pharmacol. PubMed Scopus Google responsive to PXR was in the region that PXR to the is the that nuclear receptors to with to a of including and C. J. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). in response to rifampicin, a on and of the of the that CYP2C9 mRNA is induced by this in primary human hepatocytes and in be in the of experiments, we that of of by in response to was of The of by most the of of by this receptor and a of this motif by in the in of these is that element is of the region of for this for CYP3A4 B. C. Pharmacol. 1999; PubMed Scopus Google Scholar). In this gene, the motif at shown to with a element nuclear receptor including and located at to of CYP3A4 by that PXR the of on in the presence of rifampicin, in co-transfection experiments is in of this that the of hCAR for is that of the presence of the of in the of the CYP2C9 The presence of the two functional elements and a regulation of CYP2C9 in response to and the presence of the functional that CYP2C9 expression be constitutive the is in CYP2C9 is of the major expressed in (2Miners J.O. Birkett D.J. Br. J. Clin. Pharmacol. 1998; 45: 525-538Crossref PubMed Scopus (761) Google and this gene is expressed in our (3Gerbal-Chaloin S. Pascussi J.M. Pichard-Garcia L. Daujat M. Waechter F. Fabre J.M. Carrere N. Maurel P. Drug Metab. Dispos. 2001; 29: 242-251PubMed Google in which we have shown that is expressed and is functional J.M. L. Fabre J.M. Maurel P. Pharmacol. PubMed Scopus Google Scholar, J.M. S. Fabre J.M. Maurel P. Pharmacol. PubMed Scopus Google Scholar). In for CYP3A4 and CYP2B6 in these cultures to in the of a xenobiotic The that CYP2C9 mRNA is at in our cultures in the of dexamethasone that other expressed in these for nuclear also involved in the of this the implication of demonstrated in the regulation of CYP2C9 J.A. PubMed Scopus Google Scholar). the presence of a among the of genes by xenobiotics such as phenobarbital In addition, by and by be this is we in our primary cultures (3Gerbal-Chaloin S. Pascussi J.M. Pichard-Garcia L. Daujat M. Waechter F. Fabre J.M. Carrere N. Maurel P. Drug Metab. Dispos. 2001; 29: 242-251PubMed Google Scholar, J.M. L. Fabre J.M. Maurel P. Pharmacol. PubMed Scopus Google Scholar, J.M. S. Fabre J.M. Maurel P. Pharmacol. PubMed Scopus Google and in co-transfection experiments including and hCAR the of CYP2C9 mRNA in response to phenobarbital is that of CYP3A4 CYP2B6 in response to the the of CYP2C9 is (3Gerbal-Chaloin S. Pascussi J.M. Pichard-Garcia L. Daujat M. Waechter F. Fabre J.M. Carrere N. Maurel P. Drug Metab. Dispos. 2001; 29: 242-251PubMed Google Scholar, J.M. S. Pichard-Garcia L. Daujat M. Fabre J.M. Maurel P. 274: PubMed Scopus Google Scholar). In we have demonstrated in this work that CYP2C9is member of the of primary glucocorticoid-responsive and We S. M. L. and J. C. for various and F. for the and C. for of the