ENVIRONMENTAL TESTICULAR TOXICITY & GERM CELL APOPTOSIS

描述(改编自申请人的摘要)：本研究的重点 该项目是关于启动睾丸生殖细胞的机制。 毒物诱导的支持细胞损伤后发生细胞凋亡。近期 有证据表明，接触环境毒物(有机化学品、 金属和高温)是导致男性精液质量下降的原因。 过去的50年里。然而，尽管这种毒物接触和男性 不孕症，人们对这些病原体引起不孕症的机制知之甚少 生殖细胞的丧失。 在这个研究项目中，研究人员将使用单(2-乙基己基) 邻苯二甲酸盐(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，研究启动生殖细胞发生凋亡的机制。 在之前的赠款资助期内，调查人员确定，联邦储备委员会 (CD95)-信号通路参与睾丸生殖细胞的启动 MEHP诱导Sertoli细胞损伤后的细胞凋亡最近，他们做了两个 激动人心的关键观察：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，2) 缺乏FasL功能形式的年轻GLD小鼠对 MEHP可诱导细胞凋亡，而成年GLD小鼠则敏感。这些基本原则 观察结果导致了两个工作假说的发展。1)Fas 在MEHP诱导的生殖细胞凋亡中起主导作用， P53的激活导致生殖细胞膜上Fas的表达 并赋予其对细胞凋亡的敏感性。这样做的第一个具体目标是 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)直接检测MEHP介导的细菌的依赖性 细胞凋亡对细胞Fas表达的影响。在第二个目标中， 检测P53在Fas膜分布中的作用 在体外，使用表达温度敏感突变体的GC-2spd细胞 P53，或体内，使用P53基因缺失的小鼠。在《最后两个目的》中，两个假设 通过评估可溶形式的 FasL与Fas非依赖性信号转导机制的参与 在MEHP的发病机制中，生殖细胞凋亡率增加。这 MEHP刺激的生殖细胞凋亡的研究将提供基础 对生殖细胞敏感性调节机制的洞察 化学性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.