title: The ligands of estrogen receptor α regulate cytochrome P4502C9 (CYP2C9) expression.
abstract: Cytochrome P4502C9 (CYP2C9) is an important drug-metabolizing enzyme responsible for the metabolism of approximately 16% of all clinically relevant drugs. It was shown previously that the activity of CYP2C9 in vivo is inhibited by oral contraceptives. The mechanisms of this effect have not been elucidated. We hypothesize that this may occur because of the sex steroid-dependent activation of estrogen receptor α (ERα) with further transactivation of the CYP2C9 gene. Here, we show that the CYP2C9 promoter indeed contains a functionally relevant estrogen responsive element (ERE) half-site at position -149/-145. Its ERα binding activity was tested by the luciferase gene reporter assay. Promoter constructs bearing this site were cotransfected with ERα into Huh7 hepatoma cells and treated with various ERα ligands including 4-hydroxytamoxifen (4-OHT), raloxifene (R), 17β-estradiol (EE), and 17α-ethinylestradiol (ETE). The luciferase activity driven by the wild-type CYP2C9 promoter construct was up-regulated by 4-OHT and R and significantly or marginally suppressed by ETE and EE, respectively. An identical effect was observed in primary hepatocytes treated with these compounds. Mutations introduced into the ERE half-site abolished the observed effects in the Huh7 cells. Electrophoretic mobility-shift assay revealed sequence-specific binding of a nuclear protein to the oligonucleotide containing the ERE half-site, which was identified as ERα by antibody supershift analysis. In addition, the association of ERα with CYP2C9 promoter was strongly supported by chromatin immunoprecipitation data. Taken together, these results indicate that ERα and its ligands play an important role in the regulation of CYP2C9 expression.
authors.affiliation: Department of Physiology and Pharmacology, Section of Pharmacogenetics, Karolinska Institutet, Stockholm, Sweden. jessica.mwinyi@ki.se
authors.forename: Jessica
authors.initials: J
authors.lastname: Mwinyi
authors.forename: Isa
authors.initials: I
authors.lastname: Cavaco
authors.forename: Begum
authors.initials: B
authors.lastname: Yurdakok
authors.forename: Souren
authors.initials: S
authors.lastname: Mkrtchian
authors.forename: Magnus
authors.initials: M
authors.lastname: Ingelman-Sundberg
mesh_terms: D001189:Aryl Hydrocarbon Hydroxylases / Q000096:biosynthesis* / Q000235:genetics / Q000502:physiology; D001665:Binding Sites / Q000502:physiology; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D065729:Cytochrome P-450 CYP2C9; D004958:Estradiol / Q000378:metabolism; D047628:Estrogen Receptor alpha / Q000235:genetics / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic; D022781:Hepatocytes / Q000201:enzymology; D006801:Humans; D006915:Hydroxytestosterones / Q000378:metabolism; D008024:Ligands
chemical_list: C506487:ESR1 protein, human; D047628:Estrogen Receptor alpha; D006915:Hydroxytestosterones; D008024:Ligands; C032278:4,17 beta-dihydroxy-4-androstene-3-one; D004958:Estradiol; C450260:CYP2C9 protein, human; D065729:Cytochrome P-450 CYP2C9; D001189:Aryl Hydrocarbon Hydroxylases