低剂量苯暴露所致造血干细胞损伤的表观遗传机制

The risk assessment of low-dose benzene exposure has become a new challenge for the occupational and environmental health. Clarifying the target organ damage mechanism of low-dose benzene exposure is very important to protect the workers' health. Based on the preliminary data, this study aims to elaborate epigenetic regulation mechanisms and significance of low-dose benzene exposure injury by low-dose benzene exposure animal model, hematopoietic stem cells (HSCs) in vitro culture technique, and established occupational benzene exposure study cohort. First, the differential expression pattern of methylated gene and miRNA which link with benzene exposure and HSCs damage will be screened by high-throughput sequencing and bioinformatics analysis. Then, HSCs isolated from human umbilical cord blood will be used to explore the role and regulation mechanisms of epigenetic molecules in HSCs oxidative and genetic damage under low-dose benzene exposure. At last, the roles of these epigenetic molecules as biomarkers of benzene exposure or damage effects will be verified and the relationship among low-dose benzene exposure, genetic damage degree and epigenetic regulation will be determined. This study will further elucidate the mechanisms of benzene toxicity, provide specific and sensitive biomarkers for health surveillance of workers exposed to benzene and provide theoretical basis for risk assessment of low-dose benzene exposure.

低剂量苯暴露风险评估成为职业卫生和环境卫生面临的新挑战，明确低剂量苯暴露的靶器官损害机制对保护职业苯暴露工人健康具有重要的意义。本课题拟在前期研究基础上，采用低剂量苯中毒动物模型和体外造血干细胞(HSCs)培养技术，结合已建立的职业苯暴露工人研究队列，阐述低剂量苯暴露损伤的表观遗传调控机制和意义。首先，通过高通量测序和生物信息学分析，筛查出与苯暴露及HSCs损伤相链接的差异表达的甲基化基因和特异miRNAs表达模式；然后，利用人脐带血分离的HSCs，探讨这些表观遗传分子在低剂量苯暴露情况下对HSCs产生氧化损伤、遗传损伤的调控机制；最后，在职业苯暴露工人研究队列中验证这些表观遗传分子作为苯暴露或苯损伤效应生物标志的作用，明确低剂量苯暴露、遗传损伤程度和表观遗传调控三者之间的关系。本研究将进一步完善苯中毒机制，为苯暴露人群健康监护提供特异的生物标志，并为低剂量苯暴露风险评估提供理论依据。

有机溶剂苯的主要危害是血液毒性，因其抑制骨髓造血功能而导致再生障碍性贫血，甚至白血病。而低剂量苯暴露风险评估已成为职业卫生和环境卫生面临的新挑战，深入阐释低剂量苯暴露的靶器官损害机制，寻找苯中毒早期敏感生物标志，对保护苯暴露人群健康具有重要意义。我们利用健康孕产妇分娩后脐带血获得的CD34+细胞，经苯代谢物氢醌（HQ）处理后筛查获得差异表达的miRNAs，并在体外细胞模型中进行验证和作用机制研究。发现HQ可通过不同miR介导抑制CD34+细胞向不同细胞系分化。对其中与造血祖细胞髓系分化和红系细胞分化有关的miR-146a、miR-451a、miR-486-5p开展了体外细胞模型研究，发现HQ通过miR-146a介导的TRAF6//NF-κB通路抑制单核-巨噬分化。对于苯抑制红系细胞分化与miR-451a，miR-486-5p的关联性研究，我们首先利用Hemin诱导的K562细胞构建红细胞分化模型，验证了HQ可以通过下调miR-451a和miR-486-5p表达从而抑制红系细胞分化的关系。进而采用动物试验发现C57BL/6小鼠吸入1ppm苯28d后，即可发现外周血红细胞计数显著降低，且与miR-451a和miR-486-5p表达降低相关。苯中毒队列人群的分析，也观察到miR-451a和miR-486-5p与HQ抑制红系分化的密切联系。如果能够进一步开展大规模人群研究，有望确定其在低苯暴露人群健康监护中的意义。此外，我们对苯暴露人群开展了健康损害与特异性基因DNA甲基化和组蛋白修饰关系及其机制的探索，发现苯暴露对细胞遗传损伤（彗星尾部含量）及其在预测苯血液毒性中的应用价值；而这些苯所致遗传损伤可能受到MGMT基因甲基化或组蛋白H3第四位赖氨酸的三甲基化（H3K4me3）调控，为进一步开展各表观遗传分子间网络调控提供了线索。