星形胶质细胞α7nAChR调控脑缺血后炎症反应的作用和机制研究

Ischemic stroke causes high morbidity and mortality. Severe neuroinflammation is the key target for prevention and treatment of secondary injury following brain ischemia. Astrocyte plays important roles in this process. Our previous studies showed that the cholinergic anti-inflammation pathway regulated neuroinflammation. For one thing, expression of nicotinic acetylcholine receptor alpha 7 subunit (α7nAChR) decreased in ischemic penumbra. For another, activation of α7nAChR in astrocyte could inhibit the production of pro-inflammatory cytokines. We also found that NDRG2, an astrocyte-specific protein for regulation of inflammation, was up-regulated, and its nuclear translocation led to phosphorylation of STAT3 after ischemic brain injury. Meanwhile, α7nAChR agonist inhibited up-regulation of NDRG2, indicating α7nAChR might regulate inflammatory cytokines release via NDRG2/STAT3 pathway. On the basis of previous studies, established brain ischemia model in vitro and in vivo, and astrocyte-specific NDRG2-/- mice, we aim to clarify the role of astrocytic α7nAChR in mediation of neuroinflammation and brain injury and investigate the regulatory effects of NDRG2/STAT3 pathway in this process. It is expected to elucidate the mechanism underlying astrocytic regulation of neuroinflammation through cholinergic anti-inflammation pathway following brain ischemia, and provide a novel target for prevention and treatment of ischemic stroke.

缺血性脑卒中致残、致死率极高。暴发性炎症反应是缺血后继发性脑损伤防治的关键，星形胶质细胞在此过程中发挥重要调控作用。我们前期研究发现胆碱能抗炎通路介导神经炎症调控：缺血脑区α7nAChR表达和活性降低，激活星形胶质细胞α7nAChR可抑制炎症因子释放。另外，缺血损伤时，星形胶质细胞特异性炎症调控蛋白NDRG2表达上调、核转位并调控STAT3磷酸化。同时，α7nAChR激动剂可抑制NDRG2表达，提示α7nAChR可能通过NDRG2/STAT3通路调控缺血后星形胶质细胞炎症因子释放。本项目拟在前期研究基础上，基于在体、离体缺血损伤模型和星形胶质细胞特异性NDRG2-/-小鼠，进一步明确星形胶质细胞α7nAChR介导脑缺血炎症反应和神经损伤的作用，探讨NDRG2/STAT3通路在此过程中的调控作用，为阐明星形胶质细胞胆碱能抗炎通路参与脑缺血炎症反应提供理论依据，并为脑缺血防治提供新靶点。

缺血性脑卒中致残、致死率极高。暴发性炎症反应是缺血后继发性脑损伤防治的关键，星形胶质细胞在此过程中发挥重要调控作用。申请人课题组的前期研究发现胆碱能抗炎通路介导脑缺血后的神经炎症调控，而胆碱能受体α7nAChR在脑缺血后具有重要的神经保护作用。本项目在此基础上，证实激活α7nAChR可通过抑制星形胶质细胞活化，减少促炎症因子IL-1、IL-6、TNF-α、HMGB1释放，促进抗炎因子IL-10、TGF-β生成；并利用星形胶质细胞/神经元共培养和小鼠动物模型，证实激活星形胶质细胞α7nAChR减轻脑缺血后的神经元损伤和神经功能损害。NDRG2是星形胶质细胞上特异性的炎症调控蛋白，申请人课题组的前期研究发现抑制NDRG2可发挥脑保护效应，其具体作用机制与调控STAT3信号途径有关。因此，课题组在本项目中进一步研究星形胶质细胞α7nAChR对NDRG2/STAT3信号途径的调控效应。研究结果显示，激活星形胶质细胞α7nAChR可抑制NDRG2在星形胶质细胞上的表达和核转位，并减少STAT3磷酸化。基于这一结果，课题组利用NDRG2慢病毒转染和星形胶质细胞特异性NDRG2-/-小鼠（GFAP-NDRG2-KO）调控NDRG2的表达，证实脑缺血后激活星形胶质细胞α7nAChR通过NDRG2影响神经元转归。此外，课题组的研究还证实，星形胶质细胞α7nAChR可通过抑制NDRG2减少STAT3磷酸化，进而减少STAT3激活导致的炎症因子释放，表明星形胶质细胞α7nAChR抑制NDRG2/STAT3通路调控缺血后星形胶质细胞炎症因子释放是其发挥脑保护效应的关键分子机制。本项目的研究成果进一步阐明了星形胶质细胞信号途径参与胆碱能抗炎通路的调控机理，为探索更有效的缺血性脑损伤防治措施提供新的干预靶点。