孕期多环芳烃暴露通过DNA去甲基化引起子代学习记忆损害的队列和机制研究

Prenatal PAH exposures lead neurodevelopmental retartation showing learning and memory deficiency dominantly.DNA methylation controlling neurodevelopment and cognitive function may play pivotal roles in neurodevelopmental retardation induced by Prenatal PAH exposure. So far, how PAH challenging DNA methylation is not clear in offspring neurodevelopmental retardation. Low global DNA methylation was found in cord blood and animal hippocampus under PAH exposure. It is reasonable to speculate that PAH exposures disrupt DNA demethlation considering that DNA repair participates DNA demethlation process and PAH metabolites result PAH-DNA adducts. 5-hydroxymethylcytosine(5hmc), a new found intermediates in TET catalyzed DNA demethylation, was abundant in brain regulating neurodevelopment and cognitive function. PAH perturbs DNA demethlation may result inappropriate 5hmc modification in global and learning and memory specific gene which contributes to offspring neurodevelopmental retardation. Blood global 5hmc was related to environmental particle matter exposure implying that it may be a early adverse biomarker in offspring neurodevelopmental retartation . In this study, relationship among PAH exposure , 5hmc in cord blood global and learning and memory specific gene and child neurodevelopment was studied in a birth cohort. And PAH DNA adducts perturb 5hmc modification in global and specific gene of learning and memory in LTP impairment which was explored in Prenatal PAH exposure animal model.These data may provide novel information for biomarker development and impairment mechanism in PAH neurodevelopmental toxicity.

孕期暴露多环芳烃可致子代智力发育迟缓，主要表现为学习记忆能力降低。DNA甲基化控制神经发育，调控学习记忆，可能在孕期多环芳烃暴露致子代智力迟缓中发挥关键作用，但多环芳烃暴露与外周血基因组DNA甲基化间没有得到一致的结果。现发现多环芳烃引起海马基因组DNA甲基化降低，可能是扰乱DNA去甲基化,引起基因组5-羟甲基胞嘧啶（5hmc）和学习关键基因5hmc修饰改变，抑制学习记忆关键基因表达，损害了学习记忆功能。最新发现环境颗粒物可明显增加外周血基因组5hmc水平，基因组5hmc可能是多环芳烃暴露所致神经发育迟缓的标志物，本研究通过出生队列研究多环芳烃孕期暴露与儿童神经发育间的关系，并评估基因组5hmc，学习记忆关键基因5hmc 作为标志物的可行性，通过孕期染毒动物实验分析多环芳烃引起BDNF、Arc、Reelin基因的5hmc修饰改变进而引发LTP损害的机理，为多环芳烃神经发育毒性预防提供资料。

以苯并[a]芘（Benzo[a]pyrene，B[a]P）为代表的多环芳烃类物质（Polycyclic Aromatic Hydrocarbons ,PAHs）是最主要的职业和环境污染物，主要来源于矿物性燃料的不完全燃烧,广泛分布于水体、空气以及土壤中,多环芳烃类物质不但具有致癌性，而且具有明显神经发育毒性，我国的能源结构少油多煤，燃煤引起的多环芳烃污染可能是一个长期面临的环境难题。且随着我国工业化的发展，能源消耗的增加，环境中多环芳烃类物质的污染引起的神经发育功能损伤是一个巨大的公共卫生问题，由于其关系着我国人口素质的提高，每个人一直处于多环芳烃的暴露中，胎源学说认为，胚胎发育期是外源物最为敏感的作用期，人体从胎儿期就已处于多环芳烃的毒性作用之中，神经发育关键期的神经功能任何轻微的改变可能意味着成年期神经功能不可逆的损伤或造成对一些损害因素的易感性增加，孕期多环芳烃暴露所致的神经发育毒性及其机制研究具有重要意义。本项目通过出生队列发现了孕期多环芳烃的暴露与新生儿、2岁以及4岁儿童儿童神经发育的关联，评估5hmc、BDNF基因5hmc、端粒长度、线粒体DNA拷贝数在孕期多环芳烃的暴露0-2岁儿童神经发育关系的中介效应，为评估孕期多环芳烃暴露的健康效应和早期标志提供依据。通过母鼠孕期苯并芘染毒，观察子鼠在不同时期神经行为变化，分析对于子代不同发育期神经行为的影响。观察不同时期学习关键分子BDNF、ARC等的mRNA和蛋白质变化以及DNA羟甲基化、甲基化和相应关键酶的变化以及BDNF等特定分子5hmc，发现DNA羟甲基化、甲基化是影响学习记忆关键分子转录的主要机制，为预防多环芳烃的神经发育毒性提供了潜在靶点，为进一步深入研究提供了资料。