Amyloid-beta-PirB 相互作用介导小胶质细胞表型和功能变化参与AD进展的机制研究

Amyloid-beta (Aβ) deposition leading to the formation of senile plaques is one of the main pathological features of AD. There are activated microglial cells aggregated around senile plaques, but the activity of microglial uptake of Aβ is inhibited conspicuously, and neuron degenerates persistently. The detailed mechanisms are unclear. Recent study has identified PirB as an Aβ receptor. Interestingly, PirB mediates memory deficits and the loss of synaptic plasticity in AD transgenic mice model. Our preliminary experimental results show that the expression of PirB receptor increases remarkably in microglia in APP/PS1 transgenic mice; unexpectedly, the down-regulation of PirB can increase microglial uptake of Aβ obviously. It suggests that Aβ binding the receptor of PirB may induce microglia phenotype and functional changes, and then promote AD-like lesions, but the mechanism is unclear. Based on this information, we will clarify whether Aβ-PirB receptor interaction will promote the change of microglia phenotype, and inhibit microglial uptake of Aβ, and release proinflammatory cytokines by using the BV2 microglial cell lines, primary microglial cell cultures, and crossed APP/PS1 transgenic (Tg) mice with PirB-/- mice to generate APP/PS1 littermates with (PirB+/- Tg) or without (PirB-/- Tg) PirB. Then it attenuates AD-like pathological and/or functional injury in PirB-/- Tg mice. This project displays theoretical and practical significance in facilitating understanding of the function of microglia in the progress of AD, and it provides a new idea for discovering new target molecules for treatment of AD.

Aβ沉积形成老年斑是AD主要病理特征之一。老年斑周围有大量活化小胶质细胞聚集，但此时小胶质细胞吞噬功能显著降低，神经元却持续退化，机制不清。最新研究发现PirB为Aβ受体，参与了AD模型鼠记忆缺失和突触可塑性下降。前期实验结果显示AD鼠小胶质细胞中PirB表达显著增加；下调PirB能明显增加小胶质细胞吞噬Aβ能力，揭示Aβ-PirB相互作用可能介导了小胶质细胞表型和功能改变，进而促进AD样病变，其机制急待阐明。基于此，本课题拟从细胞（BV2细胞系和原代细胞培养）和整体（APP/PS1转基因鼠和PirB-/- 敲除鼠）水平，阐明Aβ-PirB相互作用对小胶质细胞表型、吞噬功能、促炎或抗炎因子释放效能的影响和分子机制；探讨特异性调节小胶质细胞中PirB水平或干预信号通路中关键分子能否缓解AD样病变和脑功能损伤。该研究将初步阐明小胶质细胞在AD进展中的作用机制，为发现AD药物新靶点提供新思路。

β淀粉样蛋白（Aβ）沉积形成老年斑是AD主要病理特征之一。老年斑周围有大量活化小胶质细胞聚集，但此时小胶质细胞吞噬功能显著降低，神经元却持续退化。研究发现配对免疫球蛋白样受体B（Paired immunoglobulin-like receptor B，PirB）为Aβ受体，参与了AD模型鼠记忆缺失和突触可塑性下降，提示Aβ-PirB相互作用可能介导了小胶质细胞功能改变，进而促进AD样病变，机制不清。本课题拟从BV2小胶质细胞系和转基因APP/PSn小鼠水平，采用细胞与分子生物学技术、免疫学与形态学方法及行为学检测等，探讨Aβ-PirB相互作用对小胶质细胞功能及小鼠行为学的影响和分子机制。研究结果显示：①APP/PSn转基因鼠脑中PirB显著增加并且与小胶质细胞、老年斑之间存在共定位；②PirB通过PP2A-AMPK轴调节小胶质细胞对Aβ的吞噬与炎症因子释放；③转基因鼠APP/PSn海马中下调PirB蛋白促进了小胶质细胞向M2型转换，增加了对Aβ斑块的吞噬与抗炎因子释放，改善了行为学缺陷。总之，Aβ-PirB相互作用介导了小胶质细胞表型及功能改变，进而促进AD进展，为发现AD药物新靶点提供新思路。