Action of an endocrine disruptor on the Leydig cell

说明(申请人提供)：邻苯二甲酸酯，邻苯二甲酸二乙基己酯(DEHP)，是许多塑料的组成化学物质，赋予它们灵活性。塑料在美国和大多数工业化国家无处不在，DEHP在化学上不与塑料基质结合，随着时间的推移会渗出：因此，人类接触DEHP的情况很普遍。接触DEHP与男性性发育中断和生育力下降有关。Earl Gray和他的同事的研究表明，DEHP是抗雄激素的，其男性生殖毒性的机制不是通过在雄激素受体水平上的直接干扰来实现的。P.I.和其他研究人员已经表明，在体内暴露于DEHP后，大鼠间质细胞的雄激素分泌受到影响。这导致了为本应用提供总体主题的假设，即DEHP的内分泌干扰特性是由于对间质细胞发育的不利影响，从而导致雄激素分泌减少。与这一假说一致的是，中国人民解放军S实验室的最新数据表明，幼年动物的间质细胞类固醇合成受损存在一个关键的敏感性窗口。在这次更新应用的实验中，我们将分析DEHP暴露的可能性：i.抑制类固醇生成因子-I的表达水平，这是一种关键的核转录因子，调节间质细胞和垂体促性腺激素的分化，并减少米勒抑制物质的作用，米勒抑制物质是一种受SF-1调控的生长因子，限制了间质细胞的分裂；ii.抑制祖细胞间质细胞的增殖；以及III.推迟类固醇生成酶基因的表达和类固醇生成能力的获得。出生后长期暴露于DEHP导致脑下垂体促性腺激素分泌水平增加，血清睾酮和雌二醇水平升高，这与间质细胞增生有关，间质细胞是肿瘤发生的先兆。DEHP处理的大鼠常可观察到间质细胞瘤的形成。我们将描述DEHP诱导的间质细胞增殖的时间过程，并分析黄体生成素、睾酮和雌二醇在肿瘤发生发展中的作用。这些研究将首次确定间质细胞参与DEHP的内分泌干扰效应。我们的数据将有助于识别暴露在环境污染物中的生物标志物，并为监管机构制定消费品中DEHP和邻苯二甲酸盐的使用限制提供信息。

DESCRIPTION (provided by applicant): The phthalate ester, diethylhexylphthalate (DEHP), is a constituent chemical of many plastics, conferring their flexibility. Plastics are used ubiquitously in the United States and most industrialized countries and DEHP, which is not chemically bound to the plastic matrix, leaches out over time: human exposure is therefore widespread. Exposure to DEHP is associated with disruption of male sexual development and decreased fertility. Studies by Earl Gray and colleagues have shown that DEHP is anti-androgenic, and that its mechanism of male reproductive toxicity is not through direct interference at the level of the androgen receptor. The P.I. and others have shown that androgen secretion by rat Leydig cells is compromised after in vivo exposures to DEHP. This leads to the hypothesis providing the overall theme to the present application, that the endocrine disrupting properties of DEHP result from adverse effects on Leydig cell development with consequent decreases in androgen secretion. Consistent with this hypothesis, recent data from the P.l.'s lab demonstrate the existence of a critical window of sensitivity for impairment of Leydig cell steroidogenesis in younger animals. In the experiments described for this renewal application, we will analyze the potential for DEHP exposures: I. to suppress expression levels of steroidogenic factor-I, a key nuclear transcription factor that regulates differentiation of Leydig cells and pituitary gonadotropes, and decrease the action of Mullerian inhibiting substance, an SF-1 regulated growth factor that limits Leydig cell division; II. to inhibit proliferation of progenitor Leydig cells; and III. to delay acquisition of steroidogenic enzyme gene expression and steroidogenic capacity. Chronic postnatal exposures to DEHP induced increased levels of gonadotropic secretion by the pituitary and elevated serum testosterone and estradiol levels, which were associated with Leydig cell hyperplasia, a precursor to tumorigenesis. Formation of Leydig cell tumors is commonly observed in DEHP-treated rats. We will describe the time course of DEHP induced Leydig cell hyperplasia and analyze the role of LH, testosterone, and estradiol in the development of tumorigenesis. These studies will be the first to define the involvement of Leydig cells in the endocrine disrupting effects of DEHP. Our data will facilitate identification of biomarkers of exposure to environmental pollutants, and provide information to regulatory agencies in setting limits for the use of DEHP and phthalates in consumer products