Lovekamp-Swan Tara, Jetten Anton M, Davis Barbara J
Laboratory of Women's Health, National Institute of Environmental Health Sciences, P.O. Box 12233, MD A2-01, Research Triangle Park, NC 27709, USA.
Mol Cell Endocrinol. 2003 Mar 28;201(1-2):133-41. doi: 10.1016/s0303-7207(02)00423-9.
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.
过氧化物酶体增殖物激活受体（PPARs）是脂质代谢和细胞分化的关键调节因子。增塑剂邻苯二甲酸二（2-乙基己基）酯是一种过氧化物酶体增殖剂，其活性代谢物单-（2-乙基己基）邻苯二甲酸酯（MEHP）在细胞反式激活试验中可激活PPARα和PPARγ。MEHP是一种雌性生殖毒物，可降低芳香化酶的活性、mRNA和蛋白质水平，芳香化酶是卵巢颗粒细胞中将睾酮转化为雌二醇的限速酶。为了验证MEHP通过PPAR途径抑制芳香化酶这一假说，将颗粒细胞与MEHP（50μM）或PPARγ或PPARα的选择性激活剂一起培养48小时，并通过实时RT-PCR分析基因表达。PPARα和PPARγ激活剂均像MEHP一样显著降低芳香化酶mRNA和雌二醇的产生。PPARγ选择性拮抗剂GR 259662部分阻断了MEHP对芳香化酶的抑制作用，表明MEHP通过PPARγ起作用，但并非唯一途径。MEHP和PPARα选择性激动剂GW 327647诱导了17β-羟基类固醇脱氢酶IV（一种已知的PPARα调节基因）的表达，并且在添加PPARγ选择性拮抗剂后诱导作用得以维持。PPARα选择性激活还诱导了颗粒细胞中芳烃受体（AhR）、CYP1B1和环氧化物水解酶的表达。这些数据支持了一个模型，即MEHP激活PPARα和PPARγ以抑制芳香化酶，并改变颗粒细胞中与代谢和分化相关的其他基因。
