Dual activation of PPARalpha and PPARgamma by mono-(2-ethylhexyl) phthalate in rat ovarian granulosa cells.
Peroxisome proliferator-activated receptors (PPARs) are key regulators of lipid metabolism and cell differentiation. The plasticizer di-(2-ethylhexyl) phthalate is a peroxisome proliferator, and its active metabolite mono-(2-ethylhexyl) phthalate (MEHP) activates PPARalpha and PPARgamma in cell transactivation assays. MEHP is a female reproductive toxicant and decreases activity, mRNA, and protein levels of aromatase, the rate-limiting enzyme that converts testosterone to estradiol in ovarian granulosa cells. To test the hypothesis that MEHP suppresses aromatase through PPAR pathways, granulosa cells were cultured with MEHP (50 microM) or selective activators of PPARgamma or PPARalpha for 48 h and gene expression was analyzed by real time RT-PCR. Both PPARalpha and PPARgamma activators significantly decreased aromatase mRNA and estradiol production like MEHP. The PPARgamma-selective antagonist GR 259662 partially blocked the suppression of aromatase by MEHP, suggesting that MEHP acts through PPARgamma, but not exclusively. MEHP and the PPARalpha-selective agonist GW 327647 induced expression of 17beta-hydroxysteroid dehydrogenase IV, a known PPARalpha-regulated gene, and induction was maintained with addition of the PPARgamma-selective antagonist. PPARalpha-selective activation also induced expression of aryl hydrocarbon receptor (AhR), CYP1B1, and epoxide hydrolase in the granulosa cell. These data support a model in which MEHP activates both PPARalpha and PPARgamma to suppress aromatase and alter other genes related to metabolism and differentiation in the granulosa cell.
Lovekamp-Swan
Tara
T
Laboratory of Women's Health, National Institute of Environmental Health Sciences, P.O. Box 12233, MD A2-01, Research Triangle Park, NC 27709, USA.
Jetten
Anton M
AM
Davis
Barbara J
BJ
D015067:17-Hydroxysteroid Dehydrogenases / Q000378:metabolism; D000818:Animals; D001141:Aromatase / Q000235:genetics; D047072:Aromatase Inhibitors; D001189:Aryl Hydrocarbon Hydroxylases / Q000378:metabolism; D015153:Blotting, Western; D002478:Cells, Cultured; D065633:Cytochrome P-450 CYP1B1; D004268:DNA-Binding Proteins / Q000378:metabolism; D004051:Diethylhexyl Phthalate / Q000031:analogs & derivatives* / Q000494:pharmacology*; D004746:Enoyl-CoA Hydratase; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004958:Estradiol / Q000378:metabolism; D005260:Female; D006107:Granulosa Cells / Q000187:drug effects* / Q000378:metabolism; D009097:Multienzyme Complexes; D064029:Peroxisomal Multifunctional Protein-2; D020025:Peroxisome Proliferators / Q000494:pharmacology; D012333:RNA, Messenger / Q000032:analysis*; D011863:Radioimmunoassay; D051381:Rats; D011916:Rats, Inbred F344; D018336:Receptors, Aryl Hydrocarbon / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism*; D018168:Receptors, Retinoic Acid / Q000378:metabolism; D047488:Retinoid X Receptors; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014157:Transcription Factors / Q000378:metabolism*; D015854:Up-Regulation
D047072:Aromatase Inhibitors; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D009097:Multienzyme Complexes; D020025:Peroxisome Proliferators; D012333:RNA, Messenger; D018336:Receptors, Aryl Hydrocarbon; D018160:Receptors, Cytoplasmic and Nuclear; D018168:Receptors, Retinoic Acid; D047488:Retinoid X Receptors; D014157:Transcription Factors; D004958:Estradiol; D004051:Diethylhexyl Phthalate; D015067:17-Hydroxysteroid Dehydrogenases; C491286:Hsd17b4 protein, rat; D001141:Aromatase; D001189:Aryl Hydrocarbon Hydroxylases; C585499:Cyp1b1 protein, rat; D065633:Cytochrome P-450 CYP1B1; D064029:Peroxisomal Multifunctional Protein-2; D004746:Enoyl-CoA Hydratase; C016599:mono-(2-ethylhexyl)phthalate