表观遗传调控在PFCs干扰雄性生殖内分泌中的作用机制

Perfluorinated compounds (PFCs) are persistent organic pollutants widespread in environment. At present, PFCs exposure and its effects on human health, especially on male reproduction have increasingly raised public concerns. Testicular steroidogenesis is one of the most important components of male reproductive endocrine. Previous studies have demonstrated that PFCs exposure can disturb steroid hormones biosynthesis by affecting the expression of key genes involved in testicular steroidogenesis. However, the underlying molecular mechanisms are still far from being completely understood. Based on the evidence that DNA methylation and histone methylation/acetylation play a pivotal role in steroidogenesis, and that PFCs exposure can change the status of epigenetic modifications in cells, using the male rat model, this proposal plans to analyze the effects of PFOS/PFOA exposure on global DNA methylation and histone methylation/acetylation levels, epigenetic modifications of steroidogenic gene promoter, as well as on steroidogenic gene expression and steroid hormone contents in rat testis. We will also investigate the transgenerational effects of male reproductive endocrine toxicity induced by PFOS/PFOA. In addition, by analyzing PFOS/PFOA and steroid hormone levels in serum of reproductive-aged male population, as well as DNA methylation and histone methylation/acetylation status in human sperms based on animal experimental results, we will explore the relationships of PFOS/PFOA exposure-DNA methylatiion/histone modification-steroid hormone-sperm quality by statistics in combination with the clinical epidemiologic data. Through doing these, we hope to validate our toxicological hypothesis that PFOS/PFOA affects testicular steroidogenesis by altering the status of epigenetic modifications and subsequent steroidogenic gene expression, so as to reveal the roles of epigenetic modifications in PFCs-mediated male reproductive endocrine disruption.

全氟化合物（PFCs）是环境中广泛存在的一类持久性有机污染物，其人群暴露对男性生殖健康的影响已越来越为人们所关注。睾丸类固醇激素合成是雄性生殖内分泌的重要方面。研究表明，PFCs暴露可影响睾丸类固醇激素合成通路中关键基因的表达，从而干扰激素合成，然而其内在分子机制尚不清楚。基于DNA甲基化和组蛋白修饰在睾丸类固醇激素合成过程中的重要作用，以及PFCs可改变细胞表观遗传修饰的研究证据，本项目拟以PFOS/PFOA为研究对象，分析PFOS/PFOA暴露对大鼠睾丸DNA甲基化、组蛋白甲基化/乙酰化及类固醇激素合成的影响，并探讨该毒性的传代效应；基于动物实验结果，在人群水平上分析PFOS/PFOA暴露-表观遗传修饰-激素水平-精子质量的相关性。希望验证PFOS/PFOA通过改变表观遗传修饰影响睾丸类固醇激素合成相关基因表达，从而干扰激素合成的假设，部分揭示PFCs诱导雄性生殖内分泌毒性的分子机制。

全氟化合物（PFCs）是环境中广泛存在的一类持久性有机污染物，其人群暴露对男性生殖健康具有显著的不良影响。然而，PFCs暴露干扰雄性生殖内分泌的分子机制目前仍不清楚。因此，本项目基于体内外实验模型，主要研究了组蛋白修饰在PFOS/PFOA暴露影响睾丸类固醇激素合成中的作用机制，并联合利用蛋白质组学和代谢组学技术进一步研究了PFOS/PFOA诱导雄性生殖毒性的分子机制。通过本研究，取得如下创新成果：.1. PFOS暴露分别通过提高组蛋白H3K9和H3K18的乙酰化（H3K9/K18ac）水平而激活大鼠睾丸类固醇激素合成限速基因CYP11A1、StAR的表达，并因此促进孕酮和睾酮的合成。该现象可能反映了PFOS的“毒物兴奋效应”，即在低剂量暴露时PFOS反而激活类固醇激素合成通路。.2. PFOA暴露可通过降低组蛋白H3K9的一/三甲基化（H3K9me1/3）水平，激活睾丸类固醇激素合成限速基因StAR的表达，从而提高大鼠睾丸中孕酮、睾酮和雌二醇的合成水平。此外，体外实验结果显示PFOA和H3K9me1/3去甲基化酶抑制剂（quercetin）共暴露后睾丸间质细胞（MLTC-1）中H3K9me1/3水平部分恢复，并抑制了PFOA诱导的 StAR表达上调，从而验证了上述动物实验结果。.3. 联合蛋白质组学和代谢组学研究发现，PFOS和PFOA暴露均可显著改变大鼠睾丸中与雄性生殖密切相关的蛋白质和代谢物水平，从而促进大鼠睾丸类固醇激素合成，并且这种促进作用与睾丸中的脂肪酸代谢改变有关。此研究结果也从另一角度印证了前面发现的低剂量PFOS和PFOA通过表观遗传（组蛋白修饰）机制促进睾丸类固醇激素合成的结论。.本项目研究结果不仅可为揭示表观遗传调控在PFOS/PFOA干扰睾丸类固醇激素合成中的作用机制提供参考，还有望筛选有效的蛋白/代谢标志物用于环境PFCs暴露的男性生殖健康风险评估，并提出可能的干预措施。