ENVIRONMENTAL TESTICULAR TOXICITY & GERM CELL APOPTOSIS

在这个研究项目中，激活一个凋亡信号 生殖细胞中的转导过程被认为是最终的共同之处。 毒物致睾丸生殖细胞死亡的途径 睾丸支持细胞损伤。为了测试这一想法，支持细胞 有毒物质邻苯二甲酸单(2-乙基己基)(MEHP)将用于 刺激幼龄(28日龄)大鼠睾丸生殖细胞凋亡。 大鼠睾丸生殖细胞的凋亡通常作为一种 限制生殖细胞克隆性增殖的生理机制 在睾丸里。在初步实验中，幼鼠暴露于 MEHP导致对生殖细胞的意外初始(3小时)抑制 先进行细胞凋亡，然后再刺激生殖细胞凋亡(12 h)。这些发现表明，接触MEHP会改变 睾丸生殖细胞凋亡的调控。此外， Fas介导的三种途径在人卵巢癌组织中的表达 睾丸：Fas受体(Fas)、Fas配体(FasL)和FAP-1。 在MEHP暴露后诱导。Fas介导的途径是一种 特征明确的凋亡信号转导系统，其中Fas 作为一种受体蛋白，在体内触发固有的自杀程序 牢房。这些基本的观察结果导致了 以下工作假说的发展：MEHP破坏 支持细胞-生殖细胞的相互作用导致刺激 Fas介导的细胞间信号转导过程 改变支持细胞定向生殖细胞的生理机制 细胞凋亡。这一假设将通过设计的特定目标进行检验。 1)研究MEHP诱导的血管内皮生长因子表达的变化。 睾丸中Fas介导的途径的组成并确定 Fas相关蛋白组分的细胞特异性定位 2)探讨Fas介导的细胞凋亡在MEHP中的作用。 抑制FasL的表达诱导生殖细胞丢失 体外和体内。最近的证据表明，环境 接触毒物在男性不育中起到了一定作用。然而， 尽管暴露于环境制剂和 不孕症，人们对这些药物的作用机制知之甚少 导致精子数量减少。邻苯二甲酸酯--模型毒物 在这个项目中使用，发现在环境中广泛存在，因为 它们在食品包装和生物医学设备中用作增塑剂。 邻苯二甲酸酯致大鼠睾丸损伤的实验研究 将提供有关生理和心理机制的线索 毒物诱导的睾丸生殖细胞死亡和对 环境毒物致不孕症的机制 曝光。

In this research project, activation of an apoptotic signal transduction process in germ cell is proposed as a ~final common pathway~ of germ cell death in the testis after toxicant-induced testicular Sertoli cell injury. To test this idea, the Sertoli cell toxicant, mono- (2-ethylhexyl) phthalate (MEHP), will be used to stimulate germ cell apoptosis in young (28 day old) rat testis. Apoptosis of germ cells in the testis occurs in rats routinely as a physiologic mechanism to limit the clonal expansion of germ cells in the testis. In preliminary experiments, exposure of young rats to MEHP resulted in an unexpected initial (3 h) inhibition of germ cell apoptosis followed later by a stimulation of germ cell apoptosis (12 h). These findings indicate that MEHP exposure alters the regulation of germ cell apoptosis in the testis. In addition, the expression of three components of the Fas-mediated pathway in testis: Fas receptor (Fas), Fas ligand (FasL) and FAP-1, was induced after MEHP exposure. The Fas-mediated pathway is a well characterized apoptotic signal transduction system where Fas acts as a receptor protein to trigger an intrinsic suicide program in the cell. These fundamental observations have led to the development of the following working hypothesis: MEHP disrupts Sertoli cell-germ cell interactions resulting in a stimulation of the Fas-mediated signal transduction process between these cells altering the physiologic mechanism of Sertoli cell-directed germ cell apoptosis. This hypothesis will be tested by specific aims designed 1) to characterize MEHP-induced alterations in the expression of components of the Fas-mediated pathway in testis and determine the cell-specific localization of the Fas-associated protein components and, 2) to delineate the role of Fas-mediated apoptosis in MEHP- induced germ cell loss by inhibiting the expression of FasL both in vitro and in vivo. Recent evidence suggests that environmental exposures to toxicants play a role in male infertility. However, despite the association of exposure to environmental agents and infertility, little is known of the mechanisms by which these agents cause decreased numbers of sperm. Phthalates, the model toxicants used in this project, are found widespread in the environment due to their use as plasticizers in food packaging and biomedical devices. The investigation of phthalate-induced testicular injury in the rat will provide clues into the mechanisms of both physiologic and toxicant-induced germ cell death in the testis and give insight into mechanisms of infertility resulting from environmental toxicant exposures.