miR-320/DUSP8/JNK轴通过影响tau病变参与AD发病的机制研究

Tau pathology is one of the main pathologies of AD and closely correlated with the cognitive deficit in AD patients. MiR-320 expression is significantly increased in AD brain, but its role remains unclear. We previously found: miR-320 overexpression resulted in dramatic increases in tau phosphorylation and somatodendritic missorting, accompanied by enhanced activity of JNK; upregulation of its target gene DUSP8 significantly blocked these changes; DUSP8 levels were significantly decreased in AD transgenic mouse brain; knockdown of DUSP8 led to a significant increase in tau phosphorylation in N2a cell. Therefore, we speculate that: miR-320 may contribute to AD pathogenesis by promoting tau pathology via miR-320/DUSP8/JNK signaling axis. This project intends to use RNAi, biochemical, electrophysiological and confocal imaging methods to explore the role of miR-320/DUSP8/JNK signaling axis in tau pathology and the potential beneficial effect of miR-320 knockdown on learning and memory impairments in AD. This study will provide more insights into the pathogenesis of AD and identify novel drug targets for AD treatment.

Tau病变是AD的核心病变之一，与患者认知障碍密切相关。miR-320表达水平在AD脑内显著升高，但作用未知。申请人前期发现：过表达miR-320能显著增加tau的磷酸化修饰和tau往树突胞体的异位，同时提高tau相关蛋白激酶JNK的活性；上调miR-320的靶基因DUSP8能显著逆转上述改变；DUSP8含量在AD转基因小鼠脑内显著降低；在N2a细胞中下调DUSP8，tau磷酸化显著增加。因此，申请人推测：miR-320可能通过miR-320/DUSP8/JNK信号轴促进tau病变，从而参与AD发病。本项目拟运用RNA干扰、生物化学、电生理、激光共聚焦扫描成像等技术，从细胞和整体水平研究miR-320/DUSP8/JNK轴在tau病变中的作用和机制，同时探索下调miR-320对AD学习记忆障碍的改善作用。该研究将为AD的病理机制提供新的补充，为AD的药物治疗提供潜在的靶点。

Tau病变是AD的核心病变之一，与患者认知障碍密切相关。miR-320是在脑内富集的一种microRNA，研究显示其在AD患者脑内表达水平显著升高。通过实验，我们发现与对照组相比，miR-320的表达水平在两种AD转基因小鼠模型（htau小鼠和APP/PS1小鼠）的大脑海马内呈现年龄依赖性的增高。在2月龄APP/PS1小鼠海马内，发现过表达miR-320能导致tau蛋白磷酸化水平显著增加、可溶/不可溶比例发生变化、JNK活性增加、相关突触蛋白表达水平降低。此外，过表达miR-320还会显著导致2月龄APP/PS1小鼠的海马依赖的空间学习记忆能力出现障碍。而上调miR-320的靶基因DUSP8能明显逆转上述改变。除此之外，在实验中还观察到了一个有意思的现象，小鼠在过表达miR-320后产生了抑郁样的行为表现。已经有不少研究指出抑郁等情绪行为与相关组织细胞的免疫改变息息相关，我们接下来会在这个方向做进一步的相关研究。综上，我们的结果较好的阐释了miR-320在AD的tau病变中的相关作用机制，为AD的防治提供了潜在的可能靶点。