铅暴露对大鼠海马神经环路形成的影响及突触稳态调控机制

Lead is an important environmental-neurotoxin, which is known to impair the cognition in children. The seriousness of the situation was emphasized in a 2012 report from the CDC Advisory Committee on Childhood Lead Poisoning Prevention stating that "no level of Pb appears to be safe" for children. Based on our previous work, we propose that the dysfunction of hippocampal neuro-circuitry is the keynote of chronic lead exposure leading to the impairments of cognition. To test our hypothesis, we will follow the following clues: how lead exposure affecting the synaptic transmission and synaptic scaling, taking effects in synapse formation, leading to the dysfunction of hippocampal neuro-circuitry, then causes the impairments of learning and memory. We will propose to employ a combined two-photon microscope, viral tracing, electrophysiological, neuroimage and genetic approach in this study. And the three main scientific questions will be explored: 1) How about the morphological alteration of neurons in hippocampal neuro-circuitry during the synapse formation after chronic lead exposure. What about the excitory and inhibitory neurotransmission, Wnt signaling pathways contruibute in this process?. 2) With viral tracing approch, how about the connection of hippocampus-prefrontal cortex altered by lead exposure? We will further explore the dysfunction of neuro-circuitry connection and mechanisms using micro-electrode array recording in rats chronically exposed to lead.3) Calcium plays important roles in synaptic scaling. We asked whether lead impairs the homoestatic synaptic plasticity through competitive binding to the calcium sites This study may help understanding the neuro-circuitry mechanisms of impairments induced by lead exposure.

铅是一种重要的环境神经毒，且无安全剂量，主要损伤儿童智力发育。基于申请者前期工作基础，本项目提出如下假说：铅暴露引起海马相关神经环路结构和功能的损伤可能是铅致认知损伤的关键环节。思路是：铅暴露影响海马神经环路形成→环路连接异常→突触稳态紊乱→认知功能损伤。我们将综合应用双光子显微成像、跨突触病毒神经示踪、神经电生理及细胞分子生物学等前沿技术，研究：1)铅暴露对发育期海马神经环路树突棘大小、形状，树突密度等突触形成的影响，探讨兴奋性和抑制性神经递质、Wnt信号转导通路等在其中的贡献；2)应用病毒跨突触神经示踪，研究铅引起海马-前额叶等神经环路连接异常，并结合多通道微电极阵列技术研究铅对大鼠神经环路功能的影响；3)铅是否通过竞争性的占据钙的位点，损伤稳态突触可塑性，损伤突触形成及神经环路重塑。本项目将深入系统地研究铅暴露致脑发育损伤的神经环路机理，探寻有效防治策略，具有重要科学和现实意义。

铅是一种重要的环境神经毒，且无安全剂量，主要损伤儿童智力发育。该项目的研究思路是：铅暴露影响海马神经环路形成→环路连接异常→突触稳态紊乱→认知功能损伤。我们综合应用了跨突触病毒神经示踪、神经电生理及细胞分子生物学等前沿技术，取得了一系列进展：1) 完成铅暴露对突触结构可塑性损伤的影响及机理，发现了铅能够导致海马神经元及树突棘的损伤，WNT通路相关蛋白在上述损伤中发挥介导作用，并利用分子生物学方法研究了铅对Wnt, mTOR及突触前蛋白的影响；2)应用病毒跨突触神经示踪，研究铅引起海马—前额叶等神经环路连接异常。利用伪狂犬病毒PRV以及狂犬病毒RV-△G的体内注射和荧光检测，研究了铅暴露对海马CA1区神经元与其他脑区投射、尤其是一级投射的改变，并对受损神经元环路的类型进行了定位分析，深入探讨了铅暴露对神经环路的损伤形态研究；3)铅损伤了稳态突触可塑性的诱导，并会引起突触后膜上异型GluA1 and GluA2 AMPA 受体的合成和膜插入，并且全反式维甲酸不参与该突触稳态诱导。通过该项目的实施，共发表SCI论文11篇，其中关于铅对突触稳态的研究成果2018年以封面论文发表在美国毒理学会刊Toxicological Sciences上。培养了博士后 2 名，博士研究生 3 名，硕士研究生9名。其中，肖桂然博士 2016 年获博士后创新人才支持计划（人社部，人才类荣誉，合作导师是汪惠丽教授）。汪惠丽教授2017年荣获合肥工业大学“师德先进个人”，2018年荣获科技部科技创新领军人才。本项目系统地研究铅暴露致脑发育损伤的神经环路机理，探寻有效防治策略，具有重要科学和现实意义。