mTOR通路在细菌性睾丸炎致血-睾屏障破坏的作用及机制研究

Inflammation in the testis following bacterial infection may chronify silently and the impairment of spermatogenesis remains unrecoverable even after the invading pathogen is eliminated by the antibiotic administration or host immune system within the testis. Therefore, infections and inflammation in the testis, including the acute and chronic forms, is widely accepted as an important etiological factor of male infertility. However, the mechanism of testicular immune homeostasis disturbance resulted from infection remains unclear. The blood-testis barrier (BTB) plays a critical role in maintaining immune privilege statue of the testis. Our preliminary study shows that BTB is very likely compromised during bacterial infection in an orchitis model induced by uropathogenic E. coli (UPEC). Structural or functional abnormal of BTB certainly contributes to testis dysfunction following infection. However, it is still largely unknown about underlying mechanism of BTB impairment caused by bacterial infection. Very recently, it is found that mTOR (mammalian target of rapamycin) signaling pathway plays an essential role in regulating the BTB timely "opening" and "closing" in the cycle of seminiferous epithelium. Whether mTOR pathway is also involved in BTB dysfunction following bacterial infection is yet to be elucidated. Based on what we learned from our UPEC infection model, in this proposal, we firstly plan to look at the correlation between BTB impairment and compromised immune privilege statue in the testis. Secondly, abnormal activation of mTOR signaling pathway following UPEC infection will also be investigated on in vitro and in vivo models. The effect of BTB dysfunction induced by mTOR pathway abnormal activation will be confirmed using specific pathway inhibitor rapamycin and RNAi technology. Furthermore, the virulence factors or inflammatory cytokines as well as molecular mechanism regulating mTOR abnormal activation will be explored. Together, this project will provide us a clearer picture about the connection of mTOR signaling pathway abnormal activation and BTB impairment in bacterial orchitis. More importantly, our study will allow us to gain deeper insight into the obscure mechanism of testicular dysfunction and immune homeostasis disturbance resulted from bacterial infection.

睾丸细菌感染引起的炎症反应和免疫稳态破坏可以在病原体清除后持续存在，造成睾丸功能损伤和不育。细菌感染导致睾丸免疫微环境失衡的分子机制尚未完全明确，血-睾屏障（BTB）结构或功能异常很可能是重要环节之一，但具体机制有待探索。我们前期研究证实尿源性致病型大肠杆菌（UPEC）感染睾丸能够引起炎症反应以及BTB破坏。最新研究证实mTOR信号通路是调控BTB正常开-闭的重要机制之一。本项目拟在大鼠及支持细胞UPEC感染模型上，首先分析BTB破坏与睾丸免疫豁免环境及功能失调的相关性，进而研究UPEC感染造成mTOR信号通路异常活化对BTB完整性的影响，最终确认UPEC感染导致mTOR通路异常的分子机制。这一研究有望明确mTOR信号通路对BTB的影响及其分子机制，并能深入了解睾丸感染对BTB的改变及调控，为进一步研究及防止睾丸感染后持续免疫稳态失衡和生精功能损伤提供新的认识。

细菌感染可以引起附睾-睾丸炎的炎症反应，对睾丸组织造成的破坏可以在病原体清除后持续存在，最终造成睾丸功能损伤和不育。前期研究提示血-睾屏障（BTB）结构或功能异常很可能是细菌性睾丸炎损伤睾丸功能的重要环节之一，但具体机制尚未清楚。本项目通过对睾丸炎动物模型及支持细胞体外感染模型的研究，证实尿源性致病性大肠杆菌（UPEC）感染可以激发支持细胞应激反应，下调支持细胞中细胞连接蛋白的表达水平，破坏睾丸支持细胞间连接，造成血睾屏障（BTB）结果及功能损坏；UPEC感染通过分泌可溶性毒力因子，打破睾丸支持细胞中mTORc1-mTORc2拮抗平衡，激活mTORc1及下游信号通路是造成BTB损伤的重要机制；应用特异性mTORc抑制剂可一定程度上阻断UPEC感染对BTB的损伤。本研究初次探索了细菌性睾丸炎中mTORc异常活化导致BTB破坏的机制，为进一步通过药物干预阻断感染造成的睾丸BTB破坏初步奠定基础，具有一定临床应用价值和社会意义。