Examination of Glucocorticoid receptor alpha-mediated transcriptional regulation of P-glycoprotein, CYP3A4, and CYP2C9 genes in placental trophoblast cell lines.
The placental trophoblast at different stages of pregnancy contains some drug transporters and xenobiotic-metabolising enzymes, as well as ligand-activated nuclear receptors, which control their inducible transcriptional regulation. Glucocorticoid receptor alpha (GRalpha) is expressed in both placental syncytiotrophoblast and cytotrophoblast. GRalpha was shown to control inducible expression of several enzymes of the cytochrome P-450 family (CYP) and the drug transporter P-glycoprotein in the liver. However, GRalpha-mediated transcriptional regulation of drug transporters and CYPs has not been studied in the placental trophoblast. In this study, we examined the expression and activity of GRalpha in the transcriptional regulation of P-glycoprotein, CYP3A4, and CYP2C9 in placental trophoblast cell lines. Employing RT-PCR, Western blotting, and luciferase gene reporter assay, we detected the expression and activity of GRalpha in JEG3 and BeWo cell lines. However, we observed that only MDR1 mRNA was up-regulated after treatment of placental cells with dexamethasone. Accordingly, only the promoter of the MDR1 gene was activated by dexamethasone in gene reporter assays in placental cells and the activation was abolished by RU486, an antagonist of GRalpha. CYP3A4 and CYP2C9 promoters were activated in placental cells only after co-transfection with hepatocyte nuclear factor 4alpha (HNF4alpha), which indicates the hepatocyte-specific character of GRalpha-mediated regulation of the genes. On the other hand, coexpression of HNF4alpha had no effect on the activation of the MDR1 gene promoter, suggesting HNF4alpha-independent regulation via GRalpha. We conclude that GRalpha may be involved in the transcriptional regulation of P-glycoprotein in the placental trophoblast. We also indicate that the CYP3A4 and CYP2C9 genes are not inducible through GRalpha in placental cell lines, due to the lack of HNF4alpha expression and possibly some additional hepatocyte-specific transcriptional factors.
Pavek
P
P
Department of Pharmacology and Toxicology, Faculty of Pharmacy, Charles University, Heyrovskoho 1203, Hradec Kralove 500 05, Czech Republic. petr.pavek@faf.cuni.cz
Cerveny
L
L
Svecova
L
L
Brysch
M
M
Libra
A
A
Vrzal
R
R
Nachtigal
P
P
Staud
F
F
Ulrichova
J
J
Fendrich
Z
Z
Dvorak
Z
Z
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000096:biosynthesis*; D001189:Aryl Hydrocarbon Hydroxylases / Q000096:biosynthesis*; D002460:Cell Line; D045744:Cell Line, Tumor; D065729:Cytochrome P-450 CYP2C9; D051544:Cytochrome P-450 CYP3A; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis*; D003907:Dexamethasone / Q000494:pharmacology; D005260:Female; D051557:Hepatocyte Nuclear Factor 4 / Q000502:physiology; D006801:Humans; D011247:Pregnancy; D011401:Promoter Regions, Genetic / Q000502:physiology; D012333:RNA, Messenger / Q000378:metabolism; D011965:Receptors, Glucocorticoid / Q000502:physiology*; D015533:Transcriptional Activation / Q000502:physiology; D014327:Trophoblasts / Q000378:metabolism*
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; C496592:HNF4A protein, human; D051557:Hepatocyte Nuclear Factor 4; D012333:RNA, Messenger; D011965:Receptors, Glucocorticoid; C411470:glucocorticoid receptor alpha; D003907:Dexamethasone; D003577:Cytochrome P-450 Enzyme System; C450260:CYP2C9 protein, human; D065729:Cytochrome P-450 CYP2C9; D001189:Aryl Hydrocarbon Hydroxylases; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human