Notch信号调控小胶质细胞极化在Alzheimer病中的作用及机制研究

Microglia, specialized macrophages residing in the central nervous system, play two opposite roles in the pathogenesis of Alzheimer's disease (AD): promoting inflammation by secreting pro-inflammatory cytikines, and attenuating the disease progression by clearing amyloid β(Aβ), which are corresponding to the M1 and M2 polarization phenotypes of macrophages. It would be benificial for the treatment of AD if we could specifically regulate the balance of M1/M2 polarization of microglia. However, the mechanism of microglia M1/M2 polarization is not clear yet. Notch signaling has been proved to play a key role in the regulation of macrophage polarization.Our previous data showed that Notch signaling promoted the M1 polarization and inhibited the M2 polarization of macrophages,and promoted the M1 polarization of microglia cell line. In the present proposal, we are planning to analyze the polarization of microglia after the deletion/activation of Notch signaling by ultilizing gene-modified mice model. The Notch deletion mice will be further crossed with AD mouse model, and the AD pathology and polarization of microglia after the deletion of Notch signaling will be analyzed. The interaction between Notch signaling pathway and miR124 will be studied in detail to elucidate the mechanism of the effect of Notch on microglia polarization. We hope to reveal a new role of Notch signaling in the pathogenesis of AD, and to provide new idea for the treatment of AD.

小胶质细胞是定居于中枢神经系统的巨噬细胞，在Alzheimer病(AD)中具有分泌促炎因子促进疾病进展和清除β淀粉样蛋白缓解病情的双重作用，分别对应于巨噬细胞的M1和M2极化状态，如能有针对性地调节小胶质细胞M1/M2极化的平衡，将有助于缓解AD进展。然而，关于小胶质细胞M1/M2极化的调控机制尚知之甚少。Notch是调控细胞双向分化的关键信号途径，我们前期工作发现Notch信号促进巨噬细胞M1极化、抑制M2极化，促进小胶质细胞系M1极化。本项目拟利用基因修饰小鼠深入分析Notch信号缺失后小胶质细胞的极化特点，并与AD模型小鼠结合，分析小胶质细胞缺失Notch信号后AD小鼠病理改变及小胶质细胞极化特点，研究Notch信号途径与miR124的相互作用，探讨Notch发挥作用的机制。本研究预期将阐明Notch信号调控小胶质细胞极化在AD发病中的作用及机制，为选择性治疗AD提供新思路。

阿尔茨海默病（Alzheimer’s diease，AD）是老年人最常见的以进行性认知障碍和记忆力减退为主要临床表现的神经变性疾病，β淀粉样蛋白(amyloid β, Aβ)沉积及其引发的炎症是AD发病的关键机制。小胶质细胞是定居于中枢神经系统的巨噬细胞，在AD中具有分泌促炎因子促进疾病进展和清除β淀粉样蛋白缓解病情的双重作用，分别对应于巨噬细胞的M1和M2极化状态，如能有针对性地调节小胶质细胞M1/M2极化的平衡，将有助于缓解AD进展。然而，关于小胶质细胞M1/M2极化的调控机制尚知之甚少。Notch是调控细胞双向分化的关键信号途径，我们前期工作发现Notch信号促进巨噬细胞M1极化、抑制M2极化。本项目利用Notch途径关键转录因子RBP-J在单核-巨噬细胞敲除的小鼠，深入分析Notch信号途径对脑内小胶质细胞极化的调控，并将AD模型小鼠与Notch信号缺失小鼠结合，在体分析小胶质细胞Notch信号缺失后AD小鼠的学习记忆能力及大脑内Aβ沉积等AD病理改变，探讨Notch发挥作用的机制。我们将单核-巨噬细胞特异性表达Cre的Lyz2-Cre小鼠与RBP-Jf/f小鼠交配，获得了在巨噬细胞敲除RBP-J基因的Lyz2-Cre/RBP-Jf/f小鼠，Southern blot鉴定确认了RBP-J在小胶质细胞具有较高的剔除效率；利用上述小鼠分析小胶质细胞的体内和体外极化特性，发现Notch信号缺失后，小胶质细胞向M1方向的极化减弱，向M2方向的极化增强，说明Notch信号促进小胶质细胞的M1极化，明确了Notch信号途径在小胶质细胞极化中的作用。进一步将Lyz2-Cre/RBP-Jf/f小鼠与AD模型小鼠APP/PS1转基因小鼠交配，最终获得了基因型为Lyz2-Cre/RBP-Jf/f/APP/PS1小鼠及相关对照小鼠；利用上述小鼠进行迷宫实验、被动回避实验等行为学研究，发现Lyz2-Cre/RBP-Jf/f小鼠的学习记忆能力显著弱于对照AD模型小鼠；进一步分析了小鼠脑内Aβ沉积等AD病理改变，发现Lyz2-Cre/RBP-Jf/f小鼠脑内AD炎症显著弱于对照模型小鼠。本研究进一步证实了Notch信号途径在小胶质细胞极化中的作用，明确了Notch信号通过促进小胶质细胞M1极化参与AD发病，为下一步有针对性地调控小胶质细胞极化并用于AD治疗提供了积极的思路。