Abstract
Cytochrome P4502C19 (CYP2C19) is an important drug-metabolizing enzyme involved in the biotransformation of, for example, proton pump inhibitors and antidepressants. Several in vivo studies have shown that the CYP2C19 activity is inhibited by oral contraceptives, which can cause important drug interactions. The underlying molecular mechanism has been suggested to be competitive inhibition. However, the results presented here indicate that estradiol derivatives down-regulate CYP2C19 expression via estrogen receptor (ER) α, which interacts with the newly identified ER-binding half site [estrogen response element (ERE)] at the position −151/−147 in the CYP2C19 promoter. In gene reporter experiments in Huh-7 hepatoma cells, the activity of the luciferase construct carrying a 1.6-kb long CYP2C19 promoter fragment cotransfected with ERα was down-regulated upon treatment with 17β-estradiol (EE) or 17α-ethinylestradiol (ETE) at half-maximum concentrations of 10−7 and 10−8 M, respectively. Mutations introduced into the ERE half site −151/−147 significantly inhibited these ligand-dependent effects. Electrophoretic mobility shift assays and quantitative chromatin immunoprecipitation experiments revealed that estrogen receptor α binds to this element. A significant suppression of CYP2C19 transcription by female sex steroids was confirmed by reverse transcription polymerase chain reaction after hormonal treatment of human hepatocytes. Inhibition experiments using a stable human embryonic kidney 293 CYP2C19 cell line revealed competitive inhibition at much higher concentrations of EE and ETE compared with those required for transcriptional inhibition. These results indicate that both EE and ETE inhibit CYP2C19 expression via an ERα-dependent regulatory pathway, thus providing a new insight into the molecular mechanism behind the inhibitory effect of oral contraceptives on CYP2C19 activity.
Footnotes
This work was supported by Hjärnfonden, Torsten och Ragnar Söderbergs Stiftelser [Grant MT22/08]; the Swedish Research Council [Grant K2008-66X-05949-28-3]; the Danish Agency of Science, Technology and Innovation; the Lundbeck Foundation; and the Portuguese Foundation for Science and Technology [Grant SFRH/BPD/34152/2006; IBB-Institute for Biotechnology and Bioengineering/CBME-Centro di Biomedicina Molecular E Estrutural, LA, Fondo Europeo de Desarrollo Regional/POCI 2010].
Article, publication date, and citation information can be found at http://molpharm.aspetjournals.org.
doi:10.1124/mol.110.065540.
-
ABBREVIATIONS:
- OC
- oral contraceptive
- ETE
- 17α-ethinylestradiol
- EE
- estradiol
- ER
- estrogen receptor
- ERE
- estrogen responsive element
- 4-OHT
- 4-hydroxytamoxifen
- R
- raloxifene
- EMSA
- electrophoretic mobility shift assay
- kb
- kilobase(s)
- NE
- nuclear extract
- ChIP
- chromatin immunoprecipitation
- PCR
- polymerase chain reaction
- bp
- base pair(s)
- RT
- reverse transcription.
- Received April 10, 2010.
- Accepted July 30, 2010.
- Copyright © 2010 The American Society for Pharmacology and Experimental Therapeutics
MolPharm articles become freely available 12 months after publication, and remain freely available for 5 years.Non-open access articles that fall outside this five year window are available only to institutional subscribers and current ASPET members, or through the article purchase feature at the bottom of the page.
|