ENVIRONMENTAL TESTICULAR TOXICITY & GERM CELL APOPTOSIS

描述（改编自申请人摘要）：本研究的重点 该项目是关于启动睾丸生殖细胞的机制 在毒物诱导的支持细胞损伤后进行凋亡。最近 有证据表明，暴露于环境毒物（有机化学品， 金属和热量）是导致男性精液质量下降的原因。 过去50年然而，尽管毒物暴露和男性 不孕症，很少有人知道的机制，这些代理人引起的， 生殖细胞的丧失。 在本研究项目中，研究者将使用单-（2-乙基己基） 邻苯二甲酸酯（MEHP），一种广泛表征的支持细胞毒物，作为我们的主要 模型试剂，以研究启动生殖细胞进行凋亡的机制。 在上一个赠款供资期间，调查人员确定， （CD 95）信号通路参与睾丸生殖的启动 MEHP诱导的支持细胞损伤后的细胞凋亡。最近，他们做了两个 令人兴奋和关键的观察：1）Fas在生殖细胞中的重新分布 MEHP暴露后从胞浆定位到膜定位的变化，以及，2） 年轻的gld小鼠缺乏功能性形式的FasL，对 MEHP诱导的凋亡，而成年gld小鼠敏感。这些基本 观察结果导致了两个工作假设的发展。1)FAS 在MEHP诱导的生殖细胞凋亡的起始中起主导作用， p53激活导致生殖细胞膜Fas表达 并赋予其对凋亡的敏感性。第一个具体目标是 一种建议利用表达功能失调的Fas的突变小鼠（lpr小鼠） 或FasL（gld小鼠），以直接检查MEHP介导的生殖细胞的依赖性。 细胞凋亡对Fas表达的影响。在第二个目标中， p53参与介导Fas的膜分布， 在体外，使用表达温度敏感突变体的GC-2spd细胞， p53，或在体内，使用p53缺失小鼠。在最后两个目标中， 通过评估可溶性形式的重要性， FasL和其他Fas非依赖性信号机制的参与 MEHP诱导的生殖细胞凋亡增加的发病机制。这 研究MEHP刺激生殖细胞凋亡将提供基础 深入了解生殖细胞的敏感性调节机制， 化学诱导睾丸损伤后的细胞凋亡。

DESCRIPTION (Adapted from the applicant's abstract): The focus of this research project is on the mechanisms responsible for initiating testicular germ cells to undergo apoptosis after toxicant-induced Sertoli cell injury. Recent evidence suggests that exposure to environmental toxicants (organic chemicals, metals, and heat) is responsible for a decline in semen quality in men over the Last 50 years. However, despite this association of toxicant exposure and male infertility, Little is known of the mechanisms by which these agents cause a loss of germ cells. In this research project, the investigators will use mono-(2-ethyLhexyL) phthalate (MEHP), a widely characterized Sertoli cell toxicant, as our primary model agent to study the mechanisms initiating germ cells to undergo apoptosis. In the previous grant-funding period the investigators established that the Fas (CD95)- signaling pathway participates in the initiation of testicular germ cell apoptosis after MEHP-induced Sertoli cell injury. Recently, they made two exciting and critical observations: 1) The re-distribution of Fas in germ cell changes from a cytosolic to a membrane localization after MEHP exposure and, 2) young gld mice, that lack a functional form of FasL, are not sensitive to MEHP-induced apoptosis whereas adult gld mice are sensitive. These fundamental observations have led to the development of two working hypotheses. 1) Fas plays the dominant role in the initiation of MEHP- induced germ cell apoptosis, and, 2) p53 activation leads to the expression of Fas on the germ cell membrane and confers its sensitivity to apoptosis. The first specific aim of this proposal utilizes mutant mice that express either dysfunctional Fas (lpr mice) or FasL (gld mice) to directly examine the dependence of MEHP-mediated germ cell apoptosis on the cellular expression of Fas. In the second aim, the involvement of p53 in mediating the membrane distribution of Fas is tested both in vitro, using GC-2spd cells that express a temperature sensitive mutant of p53, or in vivo, using p53 null mice. In the Last two aims, the two hypotheses are further challenged by evaluating both the importance of the soluble form of FasL and the participation of alternative Fas-independent signaling mechanisms in the pathogenesis of MEHP-induced increases in germ cell apoptosis. This investigation of MEHP-stimulated germ cell apoptosis will provide fundamental insights into mechanisms regulating the sensitivity of germ cell to undergo apoptosis after chemical-induced testicular injury.