SV2A配体调控阿尔茨海默病关键神经免疫细胞功能的作用及其机制研究

Overactive neuroinflammation constitutes an important factor in the pathogenesis of Alzheimer’s disease (AD), and it is known that brain resident microglia (MI) and T lymphocytes from peripheral immune system play the critical role in AD neuroinflammation. Many studies, including our own preliminary study, have identified that, SV2A ligand Levetiracetam improves AD cognitive functions of both mouse model and some AD patients, but the mechanism is unclear, which hampers the progress of clinical studies. Our recent studies have identified that, SV2A is expressed in immune cells including MI and T lymphocytes; furthermore, SV2A expression levels are upregulated in MI from AD mouse model; and Levetiracetam treatment suppresses T lymphocyte immune functions. So, the scientific hypothesis for this project is that SV2A ligand probably suppress AD neuroinflamation. Based on this, the proposed research aims to: 1) investigate the effects of SV2A ligand on immune regulation and β-amyloid clearance mediated by microglia, through in vitro primary MI culture and in vivo AD mouse model; 2) investigate whether SV2A ligand can regulate immune cell infiltration in AD mouse brain and inhibit T lymphocyte functions; 3) develop iPSC derived human MI cultures to confirm the effects of SV2A ligand on human MI and T cell mediated neuroinflammation; and 4) further explore the mechanism of SV2A ligand in immune regulation of neuronal injury and synaptic loss. These studies will contribute to the exploration of novel therapeutic strategies for AD.

过度神经炎症反应是阿尔茨海默病（AD）重要致病因素，脑内常驻小胶质细胞（MI）和血源性T淋巴细胞发挥关键作用。已有多项研究显示，突触囊泡蛋白2A（SV2A）配体左乙拉西坦可改善AD小鼠模型、甚至部分AD患者的认知功能，但机制不明。我们前期研究发现：SV2A在MI和T淋巴细胞中表达，且表达量在AD来源的MI中显著上调，而左乙拉西坦可抑制T淋巴细胞免疫功能。故提出本项目科研假设：SV2A配体有可能抑制AD神经免疫炎症。为此，拟开展以下研究进行验证：①通过细胞模型和动物模型研究SV2A配体对小鼠MI免疫调控和β淀粉样蛋白清除效应；②验证SV2A配体能否调控AD小鼠脑皮质免疫细胞的渗入及抑制T淋巴细胞功能；③利用人类诱导多能干细胞衍生的人源MI证实SV2A配体抑制MI和T淋巴细胞介导的神经炎症反应；④探讨SV2A配体对神经元损伤与突触丧失的免疫调控机制。上述研究结论将有助于探索AD治疗新策略。

阿尔茨海默病（AD）是一种发生在早老期和老年期的神经退行性疾病。大脑海马区的神经发生形成新生神经元在学习、记忆形成等认知功能中都起到重要作用。.海马区神经发生障碍在AD早期就已出现，且与认知功能障碍密切相关，已成为探究AD发病机制的新热点。在此，我们通过人源性iPSCs诱导的iNSCs作为体外细胞模型，结合APP/PS1的AD模型小鼠为体内疾病模型，详细探究了突触囊泡蛋白2A（SV2A）在AD海马区神经发生障碍中的作用。通过研究，我们发现，.SV2A在NSCs中高表达，并且SV2A在AD疾病的动物及细胞模型中都显著地下降。进一步采用shRNA慢病毒，在iNSCs中敲除SV2A，我们发现SV2A缺失显著抑制NSCs的增殖。通过RNAseq对转录组学分析，发现SV2A缺失会上调p53通路促进iNSCs的死亡，采用p53通路抑制剂可以部分缓解SV2A缺失造成的增殖抑制。在体补充SV2A的促表达剂LEV可以改善AD小鼠的认知功能。因此，AD疾病中，Aβ导致SV2A下降后，通过上调p53信号通路促进凋亡参与到了AD神经发生障碍的机制中。本项目的完成可以更深入的阐述AD的发病机制，为AD的早期干预和治疗开拓新的思路和方向。