ENVIRONMENTAL TESTICULAR TOXICITY & GERM CELL APOPTOSIS

在这个研究项目中， 生殖细胞中的转导过程被认为是最后的共同点。 毒物诱导的睾丸生殖细胞死亡途径 睾丸支持细胞损伤 为了验证这个想法，支持细胞 有毒物质，单-（2-乙基己基）邻苯二甲酸酯（MEHP），将用于 刺激年轻（28日龄）大鼠睾丸生殖细胞凋亡。 大鼠睾丸生殖细胞凋亡是一种常见的 限制生殖细胞克隆扩增的生理机制 在睾丸里 在初步的实验中， MEHP导致生殖细胞的非预期初始（3 h）抑制 随后刺激生殖细胞凋亡（12 h）。 这些发现表明，MEHP暴露改变了 睾丸生殖细胞凋亡的调控。 此外该 Fas介导途径的三种组分在 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 细胞凋亡信号转导系统，其中Fas 作为一种受体蛋白来触发内在的自杀程序， 牢房 这些基本的观察导致了 以下工作假设的发展：MEHP破坏 支持细胞-生殖细胞相互作用，导致刺激 Fas介导的这些细胞之间的信号转导过程 改变支持细胞导向生殖细胞的生理机制 凋亡 这一假设将通过设计的具体目标进行检验。 1)表征MEHP诱导的表达变化 Fas介导的途径在睾丸中的组成部分，并确定 Fas相关蛋白组分的细胞特异性定位 2）阐明Fas介导的细胞凋亡在MEHP中的作用。 诱导生殖细胞损失通过抑制FasL的表达， 体外和体内。 最近的证据表明，环境 接触有毒物质在男性不育症中起一定作用。 然而，在这方面， 尽管接触环境因子和 不孕症，很少有人知道的机制，这些代理 导致精子数量减少。 邻苯二甲酸酯，模型毒物 在本项目中使用的，被发现在环境中广泛， 它们在食品包装和生物医学装置中作为增塑剂的用途。 邻苯二甲酸酯致大鼠睾丸损伤的实验研究 将提供线索，既生理机制， 毒素诱导的睾丸生殖细胞死亡，并提供深入了解 环境毒物致不孕机理 暴露。

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.