Sinha Hikim Amiya P, Lue Yanhe, Diaz-Romero Maruja, Yen Pauline H, Wang Christina, Swerdloff Ronald S
Division of Endocrinology, Department of Medicine, Harbor-UCLA Medical Center and Research and Education Institute, Box 446, 1000W Carson Street, Torrance, CA 90509, USA.
J Steroid Biochem Mol Biol. 2003 Jun;85(2-5):175-82. doi: 10.1016/s0960-0760(03)00193-6.
A growing body of evidence demonstrates that germ cell death both spontaneous (during normal spermatogenesis) and that induced by suppression of hormonal support or increased scrotal temperature occurs via apoptosis. The mechanisms by which these proapoptotic stimuli activate germ cell apoptosis are not well understood. In order to provide some insight, here we report the key molecular components of the effector pathways leading to caspase activation and increased germ cells apoptosis triggered by mildly increased scrotal temperature. Short-term exposure (43 degrees C for 15 min) of the testis to mild heat results, within 6h, in stage- and cell-specific activation of germ cell apoptosis in rats. Initiation of apoptosis was preceded by a redistribution of Bax from a cytoplasmic to paranuclear localization in heat-susceptible germ cells. Such relocation of Bax is further accompanied by sequestration of mitochondria and endoplasmic reticulum (ER) into paranuclear areas, cytosolic translocation of cytochrome c and is associated with activation of the initiator caspase 9 and the executioner caspases 3, 6, and 7, and cleavage of PARP. Furthermore, Bax is co-localized with ER in the susceptible germ cells as assessed by combined two-photon and confocal microscopy and Western blot analyses of fractionated testicular lysates. In additional studies, using gld and lpr(cg) mice, which harbor loss-of-function mutations in Fas-ligand (FasL) and Fas, respectively, we demonstrated that heat-induced germ cell apoptosis is not blocked, thus providing further evidence that the Fas signaling system is dispensable for heat-induced germ cell apoptosis in the testis. Taken together, these results demonstrate that the mitochondria- and possibly also ER-dependent pathways are the key apoptotic pathways for heat induced germ cell death in the testis.
越来越多的证据表明，生殖细胞死亡，无论是自发的（在正常精子发生过程中），还是由激素支持的抑制或阴囊温度升高所诱导的，都是通过凋亡发生的。这些促凋亡刺激激活生殖细胞凋亡的机制尚未完全了解。为了提供一些见解，我们在此报告了导致半胱天冬酶激活和阴囊温度轻度升高引发的生殖细胞凋亡增加的效应器途径的关键分子成分。将睾丸短期暴露于温和的热环境（43摄氏度，15分钟），在6小时内会导致大鼠生殖细胞凋亡的阶段特异性和细胞特异性激活。在热敏感的生殖细胞中，凋亡的启动之前是Bax从细胞质重新分布到核旁定位。Bax的这种重新定位还伴随着线粒体和内质网（ER）被隔离到核旁区域，细胞色素c的胞质易位，并与起始半胱天冬酶9和执行半胱天冬酶3、6和7的激活以及PARP的裂解有关。此外，通过双光子和共聚焦显微镜联合分析以及分级睾丸裂解物的蛋白质印迹分析评估，Bax在敏感生殖细胞中与内质网共定位。在进一步的研究中，我们使用分别在Fas配体（FasL）和Fas中具有功能丧失突变的gld和lpr（cg）小鼠，证明热诱导的生殖细胞凋亡并未被阻断，从而提供了进一步的证据，即Fas信号系统对于睾丸中热诱导的生殖细胞凋亡是可有可无的。综上所述，这些结果表明线粒体和可能还有内质网依赖性途径是睾丸中热诱导生殖细胞死亡的关键凋亡途径。
