IRE1信号通路在热诱导睾丸生殖细胞凋亡中的作用

The role of IRE1 signal pathway in scrotal hyperthermia-evoked germ cell apoptosis in testes

目的探讨内质网应激IRE1信号通路在急性热应激诱导睾丸生殖细胞凋亡中的作用。方法 24只成年ICR雄性小鼠,随机分为4组。将热处理组小鼠身体的下1/3部分(包括阴囊、后腿和尾巴)浸于43℃恒温水浴中15 min,于热处理后0.5、2和6 h取睾丸组织。将对照组小鼠下腹部浸入22℃水浴15 min,6 h后取睾丸组。采用TUNEL法检测睾丸组织生殖细胞凋亡;用半定量RT-PCR技术检测u XBP-1/s XBP-1 mRNA表达;用Western blot检测睾丸总蛋白p-JNK表达。结果单次热应激能够明显诱导小鼠睾丸生殖细胞凋亡。与对照组相比,热处理能够明显降低睾丸组织u XBP-1/s XBP-1 mRNA的比值,以热处理后0.5和2 h最为显著,而随着时间的延长,又逐渐恢复正常。热应激明显诱导睾丸JNK(另一个IRE1的下游分子)磷酸化水平。结论单次热处理能激活睾丸组织内质网应激IRE1通路,在早期可能激活IRE1-XBP-1通路保护睾丸组织对抗热应激,而后期可能通过激活IRE1-JNK通路诱导睾丸生殖细胞凋亡。

Objective To investigate the role of IRE1 pathway in scrotal hyperthermia-evoked germ cell apoptosis in testes. Methods Twenty-four adult male ICR mice were randomly divided into four groups. Mice in heat stress groups were theramally pretreated under a third part of the body （ including the scrotum, hind legs and tail） and soaked in 43℃ for 15 min and killed at 0.5,2, and 6 h after heat exposure for testicular tissue. The control mice were immersed in a water bath maintained at 22℃ and killed at 6 h after heat exposure. Using the testicular tissue to do histologic examination. Using the semi-quantitative RT-PCR to inspect uXBP-1/sXBP-1 mRNA expression. Using the Western blot to detect the p-JNK expression. Results A single, acute scrotal hyperthermia significantly increased testicular germ cell apoptosis, as determined by terminal dUTP nick-end labelling （TUNEL）. Additional experiment showed that spliced form of XBP-1, the target of the IRE1 pathway, was significantly increased in testes of mice at 0. 5 and 2 h after heat stress. However, the level of pbosphorylated JNK, another downstream target of the IRE1 pathway and a component of the ER stress-mediated apoptotic pathway, were markedly increased in the testes of mice treated with heat. Conclusion A single, acute scrotal hyperthermia significantly activates IRE1 signal pathway of endoplasmic reticulum stress in testes, IRE1-XBP-1 pathway protects germ cells from heat stress in the early stage and IRE1-JNK pathway triggers testicular germ ceils apoptosis in the later phase.