DNA甲基化在生命早期暴露双酚A致Th免疫应答异常中的调控机制及其与儿童过敏性疾病关联的研究

Bisphenol A (BPA) is a kind of environmental endocrine disruptors with multiple organ toxicity. Recently, there are more concerns on the immunotoxicity of BPA, however, supporting human studies are limited. The potential health effects and mechanism underlying BPA in relation to immunotoxicity remain unclear. There are some evidences that the mechanism of BPA altering gene expression was by epigenetic regulation in non-lymphoid cells. Therefore, we will determine maternal urinary concentration of BPA in middle trimester pregnancy and the model of Th immune response in newborn cord blood and levels of DNA methylation, and their infant allergic diseases by paired tracking survey. At the same time, BPA at different doses will be administrated orally in the drinking water to establish animal model of early life BPA exposed. The effect of maternal BPA exposure on gene methylation related with controlling the development and differentiation of T lymphocyte, as well as the model of Th immune response, IgE and inflammatory factor under allergen stimulation in different development period of offspring will be analyzed. While, we will separate and culture monocyte of cord blood from healthy delivery woman to study further the regulatory mechanism of DNA methylation about BPA immunotoxicity by using inhibitor of DNA methyltransferases. Results of this study may contribution to the understanding of the molecular mechanism underlying BPA exposure during early life increasing the risk of children allergic diseases by the effect of DNA methylation modification on the balance of Th1/Th2 and Treg/Th17.

双酚A（BPA）是一种多器官毒性的环境内分泌干扰物。近年来BPA免疫毒性已引起关注，但相关人群研究较少，其潜在危害效应及相关机制尚不清楚。BPA可通过表观遗传修饰改变基因表达的机制研究在非免疫细胞已得到证实。据此，我们检测孕中期妇女BPA暴露水平及新生儿脐带血Th免疫应答模式和基因甲基化水平，并配对跟踪调查婴幼儿过敏性疾病发生情况。建立生命早期不同剂量BPA暴露动物模型，研究母体BPA暴露对子代T淋巴细胞发育和分化过程相关调控基因甲基化修饰的影响，检测不同发育阶段仔鼠在过敏源刺激下的Th免疫应答模式及IgE和炎症因子水平。分离健康产妇脐带血单核细胞进行体外培养，使用DNA甲基转移酶抑制剂，进一步探讨DNA甲基化在BPA免疫毒性效应中的调控机制。以阐明生命早期BPA暴露可通过甲基化修饰影响Th1/Th2和Treg/Th17平衡，进而增加儿童过敏性疾病发生风险的分子机制。

目前儿童过敏性疾病高发原因及机制尚不明确。有研究发现双酚A (BPA) 暴露可能与儿童哮喘发病风险增高有关，但相关人群研究很少，其潜在危害效应及机制尚不清楚。因此，本项目将通过儿童现况和母子队列研究，阐明儿童过敏性疾病发生现况及影响因素，BPA暴露水平与儿童湿疹发生的关联；母孕期BPA暴露对新生儿湿疹发生的影响及可能机制。结合动物实验及细胞培养，研究和验证BPA暴露对Th细胞分化影响的关键窗口期及相关机制。. 本项目结果显示：儿童过敏性疾病高发，以湿疹发病率最高；BPA暴露可增加儿童过敏性疾病发生风险，其机制与BPA激活mTOR信号通路，抑制FoxP3基因或蛋白表达、同时激活炎症、引起自噬异常进而影响Th细胞分化有关；另外，BPA可上调FoxP3基因甲基化水平，也可通过表观遗传机制对Th分化产生影响。. 6-11岁儿童常见过敏性疾病报告率：湿疹37.4%，过敏性鼻炎13.2%，食物过敏14.5%，哮喘2.9%。湿疹儿童尿中BPA水平明显高于对照组。母子队列中6月龄新生儿湿疹报告率为55.3%；湿疹患儿的母亲在孕中晚期尿中BPA暴露水平明显增高；脐带血单核细胞RORrt和FOXP3基因表达增高；胎盘组织FOXP3基因甲基化增高，FOXP3蛋白表达降低；胎盘组织RORrt和NF-КB蛋白表达水平明显增高。动物实验和细胞培养：孕期和哺乳期BPA暴露可导致Treg/Th17失衡，其机制与BPA激活mTOR通路而抑制Foxp3表达、激活RORγt蛋白表达有关。 低剂量BPA暴露可加重哮喘小鼠肺部炎症反应，其机制与BPA激活自噬有关；另外，BPA可激活脾脏TLR4/NF-κB和mTOR信号通路，抑制Foxp3表达、激活RORγt和GATA3表达、使血清IgE升高；同时，BPA可上调脾Foxp3基因甲基化水平。因此，BPA可通过激活mTOR信号通路和表观遗传机制影响Th细胞分化，加重哮喘小鼠肺和全身免疫功能异常。. 胚胎期和婴幼儿时期是预防儿童湿疹等过敏性疾病的关键窗口期，BPA暴露可增加儿童过敏性疾病发生风险。本研究为探寻儿童过敏性疾病高发原因及相关机制提供了新思路；也为筛查和发现儿童过敏性疾病的易感人群提供了早期筛查指标；同时为今后过敏性疾病的早期预防和靶向治疗提供一定的理论基础。