PT  - JOURNAL ARTICLE
AU  - Jessica Mwinyi
AU  - Isa Cavaco
AU  - Begum Yurdakok
AU  - Souren Mkrtchian
AU  - Magnus Ingelman-Sundberg
TI  - The ligands of the estrogen receptor α regulate cytochrome P4502C9 (CYP2C9) expression
AID  - 10.1124/jpet.110.175075
DP  - 2011 Jan 01
TA  - Journal of Pharmacology and Experimental Therapeutics
PG  - jpet.110.175075
4099  - http://jpet.aspetjournals.org/content/early/2011/04/14/jpet.110.175075.short
4100  - http://jpet.aspetjournals.org/content/early/2011/04/14/jpet.110.175075.full
AB  - Cytochrome P4502C9 (CYP2C9) is an important drug metabolizing enzyme responsible for the metabolism of about 16% of all clinically relevant drugs. It was previously shown 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 due to 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 ERE half site at the position (-149/-145). Its ERα binding activity was tested by the luciferase gene reporter assay. Promoter constructs bearing this site were co-transfected 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 upregulated 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 the chromatin immunoprecipitation data. Taken together these results indicate that ERα and its ligands play an important role in the regulation of CYP2C9 expression.