谷氨酸和D-丝氨酸代谢异常在发育期双酚A暴露所致学习记忆损伤中作用机制研究

Developmental bisphenol A (BPA) exposure can affect the neurobehavioral and mental development of children. Glutamate (Glu) and D-serine (D-ser) play important roles in both learning and memory ability and neurodevelopment. Our previous results showed that BPA can up-regulate Glu level, down-regulate D-ser level and inhibit SIRT4 expression in hippocampus. However, the molecular mechanism of Glu and D-ser metabolic abnormalities induced by BPA are still not clear. This project intended to explore the alternations of both expression and function of Glu and D-ser synthesis enzyme, catabolism enzyme, and transporters in animal model and cell culture. Results will help to reveal the exact molecular mechanism of Glu and D-ser metabolic abnormalities induced by BPA exposure. By interfering with the expression of SIRT4 in vitro, we further examined the effect of BPA exposure on the Glu and D-ser metabolism, to clarify the regulatory role of SIRT4 in BPA induced Glu and D-ser metabolic abnormalities. Results will elucidate the molecular mechanism that BPA exposure can inhibit the SIRT4 expression and subsequently affect Glu and D-ser metabolism, thus cause learning and memory impairment. In summary, this project can provide new ideas for revealing the mechanism of learning and memory impairment induced by BPA, and provide new basis for the prevention and treatment of children's behavioral and mental retardation caused by BPA.

发育期双酚A（BPA）暴露可导致儿童神经行为异常和智力发育障碍。谷氨酸（Glu）和D-丝氨酸（D-ser）在学习记忆及神经发育过程中具有重要作用。申请者发现，BPA能够上调海马中Glu含量，下调D-ser含量，抑制其代谢调控因子SIRT4表达，而BPA所致Glu和D-ser代谢异常的分子机制尚未阐明。本项目拟在动物和细胞两个层面，从Glu和D-ser的合成酶、分解酶及转运体的表达与功能角度，揭示BPA所致Glu和D-ser代谢异常的关键环节；通过体外干扰SIRT4表达，进一步检测BPA暴露对Glu和D-ser代谢的影响，解析SIRT4在BPA所致Glu和D-ser代谢异常中的调控机制。阐明BPA暴露通过抑制SIRT4表达干扰Glu和D-ser的正常代谢从而引起学习记忆损伤的分子机制。本项目可为揭示BPA所致学习记忆损伤机制提供新思路，为BPA所致儿童行为异常和智力发育障碍的防治提供新依据。

双酚A（BPA）是常见的环境内分泌干扰物，可导致儿童神经行为异常和智力发育障碍，但机制不清。谷氨酸（Glu）和D-丝氨酸（D-ser）为中枢神经系统内重要的神经递质，是NMDAR活化不可或缺的激动剂及共激动剂，其含量的稳定在学习记忆过程中具有重要作用。本项目成功建立了体内、体外BPA暴露模型，明确了母体孕期BPA暴露对子代大鼠学习记忆能力的损伤作用，及对发育各阶段子代大鼠海马中Glu及D-ser代谢的影响及可能作用位点；基于原代培养的星形胶质细胞（AS）BPA暴露模型，初步揭示了AS在BPA所致Glu和D-ser代谢异常中的作用。主要研究发现如下：（1）母体孕期BPA暴露可使BPA透过胎盘屏障及血脑屏障，进入子代大鼠脑组织并贮存；（2）母体孕期BPA暴露可诱导子代大鼠学习记忆能力损伤、海马突触超微结构异常；（3）母体孕期BPA暴露可通过抑制子代大鼠海马中的GS、GLS1及GDH的表达、促进GLAST及GLT-1的表达，最终上调海马中Glu含量；（4）母体孕期BPA暴露可通过抑制子代大鼠海马中SR、asc-1及ASCT-2的表达、促进ASCT-1的表达、胚胎期促进而断乳后抑制DAAO表达，最终导致海马中D-ser含量呈现胚胎期上调而断乳后下调的趋势；（5）母体孕期BPA暴露可影响子代大鼠海马中NMDAR/PSD-95/nNOS-NO-cGMP信号通路的信息传递；（6）BPA暴露可促进原代培养的AS内GS、ASCT-2表达，抑制GLS1、GDH、SR及DAAO表达，从而影响AS内Glu及D-ser代谢；（7）体内体外研究均显示，BPA暴露可促进SIRT4表达。上述研究结果可推测，BPA暴露可通过干扰Glu和D-ser代谢过程中关键酶、转运体的正常表达，扰乱Glu和D-ser代谢过程，导致NMDAR/PSD-95/nNOS-NO-cGMP信号通路的信息传递异常，而该过程参与了BPA所致的学习记忆功能障碍，项目研究成果可为BPA暴露所致的儿童智力发育障碍的防治工作提供科学参考依据。