Zhang Shun, Niu Qiang, Gao Hui, Ma Rulin, Lei Rongrong, Zhang Cheng, Xia Tao, Li Pei, Xu Chunyan, Wang Chao, Chen Jingwen, Dong Lixing, Zhao Qian, Wang Aiguo
Department of Environmental Health and MOE Key Lab of Environment and Health, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, 13 Hangkong Road, Wuhan 430030, Hubei, PR China.
Department of Environmental Health and MOE Key Lab of Environment and Health, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, 13 Hangkong Road, Wuhan 430030, Hubei, PR China.
Environ Pollut. 2016 May;212:97-104. doi: 10.1016/j.envpol.2016.01.059. Epub 2016 Feb 1.
Fluoride, a ubiquitous environmental contaminant, is known to impair testicular functions and fertility; however the underlying mechanisms remain obscure. In this study, we used a rat model to mimic human exposure and sought to investigate the roles of apoptosis and autophagy in testicular toxicity of fluoride. Sprague-Dawley rats were developmentally exposed to 25, 50, or 100 mg/L sodium fluoride (NaF) via drinking water from pre-pregnancy to post-puberty, and then the testes of offspring were excised on postnatal day 56. Our results demonstrated that developmental NaF exposure induced an enhanced testicular apoptosis, as manifested by a series of hallmarks such as caspase-3 activation, chromatin condensation and DNA fragmentation. Further study revealed that fluoride exposure elicited significant elevations in the levels of cell surface death receptor Fas with a parallel increase in cytoplasmic cytochrome c, indicating the involvement of both extrinsic and intrinsic apoptotic pathways. Intriguingly, fluoride treatment also simultaneously increased the number of autophagosomes and the levels of autophagy marker LC3-II but not Beclin1. Unexpectedly, the expression of p62, a substrate that is degraded by autophagy, was also significantly elevated, suggesting that the accumulated autophagosomes resulted from impaired autophagy degradation rather than increased formation. Importantly, these were associated with marked histopathological lesions including spermatogenic failure and germ cell loss, along with severe ultrastructural abnormalities in testes. Taken together, our findings provide deeper insights into roles of excessive apoptosis and defective autophagy in the aggravation of testicular damage, which could contribute to a better understanding of fluoride-induced male reproductive toxicity.
氟化物是一种普遍存在的环境污染物，已知会损害睾丸功能和生育能力；然而，其潜在机制仍不清楚。在本研究中，我们使用大鼠模型模拟人类暴露情况，试图研究凋亡和自噬在氟化物睾丸毒性中的作用。将Sprague-Dawley大鼠从孕前到青春期通过饮用水发育性暴露于25、50或100mg/L的氟化钠（NaF）中，然后在出生后第56天切除后代的睾丸。我们的结果表明，发育性NaF暴露诱导睾丸凋亡增强，表现为一系列特征，如半胱天冬酶-3激活、染色质浓缩和DNA片段化。进一步研究表明，氟化物暴露导致细胞表面死亡受体Fas水平显著升高，同时细胞质细胞色素c平行增加，表明外源性和内源性凋亡途径均参与其中。有趣的是，氟化物处理还同时增加了自噬体的数量和自噬标记物LC3-II的水平，但未增加Beclin1的水平。出乎意料的是，自噬降解的底物p62的表达也显著升高，这表明自噬体的积累是由于自噬降解受损而非形成增加所致。重要的是，这些与明显的组织病理学损伤有关，包括生精失败和生殖细胞丢失，以及睾丸严重的超微结构异常。综上所述，我们的研究结果为过度凋亡和自噬缺陷在睾丸损伤加重中的作用提供了更深入的见解，这有助于更好地理解氟化物诱导的男性生殖毒性。
