环境多溴联苯醚对小鼠精子发生过程的影响及其机制研究

The environmental pollution caused by chemicals is becoming more and more serious. Polybrominated diphenyl ethers (PBDEs) are of widespread existence in the environment. It can accumulate and decrease the number and quality of sperm after being introduced into organism, while its impact on spermatogenesis and its mechanism are still unclear. Our study showed that decabromodiphenyl ether (BDE-209) is the highest content of polybrominated diphenyl ether in the environment and organism. So we choose mice and spermatogenic cell lines as models, based on the developmental cycle of mouse sperm, to research the impact on the structures and quantitis of spermatogenic cells, as well as the quantitis and quality of sperm cells in different developmental stages after BDE-209 exposure, so as to determine the effect of BDE-209 on spermatogenesis in mice; to further investigate the effect of BDE-209 exposure on DNA damage, DNA damage repair pathways, RIPK1-mediated apoptosis and survival signal pathways, telomerase activity and telomere length in spermatogenic cells, confirming their relationships with spermatogenesis. We also study furtherly the relationships between changes of genomic DNA methylation in spermatogenic cells and the signal pathways mentioned above, and to confirm the regulating effect in the process of spermatogenesis, explaining the toxicity mechanism of BDE-209 exposure on spermatogenesis. Then we can provide basic data for elucidating the impact of environmental changes on the physiological functions of animals and its mechanisms, and provide a scientific evidence for the causes of biodiversity reduction and the etiology of male reproductive capacity decline.

化学物引起的环境污染日益严重，多溴联苯醚是广泛存在的环境污染物，进入机体后能蓄积并引起精子数量和质量下降，但其对精子发生过程的影响及其机制尚不清楚。本课题组研究表明，十溴联苯醚是环境和动物体内含量最高的多溴联苯醚。本研究拟根据小鼠精子发育时程，采用小鼠和生精细胞株为模型，研究十溴联苯醚暴露后小鼠不同发育阶段生精细胞数量、结构以及精子数量和质量的变化，确定十溴联苯醚对小鼠精子发生过程的影响；深入研究十溴联苯醚对生精细胞DNA损伤及其损伤修复反应路径、RIPK1介导的细胞凋亡/存活信号通路、端粒酶活性和端粒长度的影响，确定其与精子发生的关系；进一步探讨生精细胞DNA甲基化改变与上述信号通路之间关系，确定DNA甲基化改变对精子发生过程的调控作用，揭示十溴联苯醚对精子发生过程的作用机制。为阐明环境改变对动物生理机能的影响及其机制提供基础数据，为生物多样性下降和男性生殖能力下降的病因学提供科学依据。

十溴联苯醚是环境中广泛存在的环境污染物，对生态环境、生物和人类健康构成了潜在危胁。本研究发现，十溴联苯醚暴露可导致小鼠睾丸组织结构损伤和生精细胞凋亡，引起精子发生障碍；十溴联苯醚可通过诱发小鼠生精细胞氧化应激导致DNA损伤及其损伤修复反应通路，启动DNA损伤修复反应并导致生精细胞周期阻滞；但可能由于DNA损伤过于严重，导致损伤的DNA无法修复，从而诱导生精细胞凋亡；十溴联苯醚可能通过激活睾丸糖脂代谢相关通路（PPARγ/RXRα/SCAP/SREBP-1）导致糖脂代谢紊乱，进而引起睾丸生精细胞线粒体凋亡信号通路，诱导生精细胞凋亡；通过抑制组蛋白甲基化引起减数分裂启动受阻，同时上调DNA损伤修复相关的MRN复合体和p21的表达，引起细胞周期阻滞和增殖抑制，从而影响减数分裂进程。进一步研究发现，十溴联苯醚可导致小鼠精母细胞基因组DNA甲基化异常，引起DNA损伤修复、细胞增殖和精子发生相关基因的甲基化异常和表达异常。这些结果表明，十溴联苯醚可能通过引起生精细胞DNA甲基化异常，影响了DNA损伤修复反应和精子发生相关基因表达，引起生精细胞周期阻滞和凋亡，从而影响了精子发生。十溴联苯醚停止暴露后，其诱发的雄性生殖系统的毒性损伤并未得到改善，说明十溴联苯醚诱导的雄性生殖毒性在体内可长期存在。此外，本研究首次进行了十溴联苯醚和十溴二苯乙烷生殖毒性的比较性研究，发现二者诱发的雄性生殖毒性及其作用机制类似，二者均能通过氧化应激诱发生精细胞端粒酶活性降低和端粒长度缩短，进而引起端粒功能障碍，导致细胞增殖能力降低，激活生精细胞衰老和凋亡信号通路，导致生精细胞衰老和凋亡，引起精子数量和质量下降；只是十溴联苯醚诱发的毒性作用更强。本研究主要阐明了十溴联苯醚的雄性生殖毒性及其相关作用机制，为环境溴系阻燃剂暴露对动物和男性生殖生殖能力下降的病因学和防治提供了科学依据。