miRNA-124靶向调控星形胶质细胞GLT-1介导阿尔茨海默病的神经兴奋毒性机制研究

One of the most important mechanism of AD is neuronal hyperexcitability. The process of AD can be delayed but not be reversed by inhibiting NMDA receptors. Our previous results confirmed that soluble Aβ-induced excitatory amino acid transporter（EAAT）dysfunction could affect glutamate accumulation, which leads to neuronal hyperexcitability. During this process, the GLT-1 in astrocytes, the subtype of EAATs, are responsible for the removal of glutamate to inhibit neuronal excitability. Upregulation of miRNA-124 can effectively rescue the impairment of Aβon synaptic plasticity. But the mechanism whether miRNA-124 is involved in the neuronal hyperexcitability of AD remains unclear. So we conclude that miRNA-124 that mainly expressed in neurons might regulates neuronal excitability through mediating the expression of GLT-1 in astrocytes of AD. Based on the above study, further studies would be carried out to identify the change of miRNA-124 distribution on neurons, astrocytes and exosome, whether miRNA-124 regulates GLT-1 gene expression in astrocytes in vivo and in vitro, and observe it’s effects in AD models and hippocampal neurons. Furthermore, we will investigate it’s effects on neuronal excitability in AD and the underlying mechanism. Our studies may provide a novel therapeutic targets for AD patients.

神经兴奋毒性是阿尔茨海默病（AD）重要的发病机制之一，miRNA作为重要的调控因子参与了神经兴奋性的调控。我们的前期研究证明：可溶性淀粉样蛋白（Aβ）损害星形胶质细胞上谷氨酸受体亚型GLT-1的功能，导致神经兴奋毒性。而上调miRNA-124可阻止Aβ对突触可塑性的损害。但主要表达于神经元上的miRNA-124是否介导AD中的神经兴奋毒性机制尚不明确。我们推测：可溶性Aβ通过降低神经元释放至外泌体中miRNA-124的含量，实现对星形胶质细胞上GLT-1的靶向调控，影响神经兴奋毒性。本研究拟采用神经元与星形胶质细胞共培养、神经电生理、外泌体提取等方法，分析Aβ对神经元、星形胶质细胞、外泌体中miRNA-124水平的影响，了解神经元是否通过miRNA-124以外泌体分泌方式靶向调控星形胶质细胞上GLT-1的证据，探讨其在Aβ所致的神经兴奋毒性中起的作用及分子机制，为AD的治疗提供新的思路。

谷氨酸能/γ-GABA能功能失调介导的神经兴奋毒性是阿尔茨海默病（AD）公认的关键致病机制。我们前期的研究发现可溶性Aβ可下调miRNA-124水平，致谷氨酸转运体（EAAT）功能异常、致突触可塑性损伤，同时我们发现神经干细胞源性（NSC）的外泌体可拮抗Aβ所致的神经凋亡，但具体机制尚未阐明。而近期的研究提示：NSC源性的外泌体可能通过调控非编码RNA水平，上调GLT-1功能改善神经兴奋毒性。故我们推测：可溶性Aβ可能通过下调miRNA-124水平，选择性抑制星形胶质细胞上EAAT亚型GLT-1，致神经兴奋毒性。而NSC源性的外泌体可通过非编码RNA吸附miRNA-124，上调GLT-1水平，改善突触可塑性。本研究拟采用转染APP/PS1转染的AD细胞和动物模型，通过神经电生理研究、Western Blot及PCR实验阐明可溶性Aβ是否通过下调miRNA-124水平，选择性抑制星形胶质细胞上GLT-1功能。通过对NSC源性的外泌体测序分析，明确目标circRNA；并通过蛋白质体外结合实验、circRNA下拉实验、免疫沉淀等实验明确和目标circRNA互相作用的miRNA，进一步阐明NSC源性的外泌体是否通过circRNA—miRNA-124—GLT-1通路，增强GLT-1的功能，减少突触间隙内谷氨酸的蓄积，降低神经兴奋毒性及改善突触可塑性.为抑制可溶性Aβ所致的毒性提供新的治疗靶点，为AD的防治提供新的策略。