上调小胶质细胞靶向吞噬功能改善放射性脑损伤的机制研究

In radiation induced brain injury, impairment of microglial phagocytosis leads to deficiency of remyelination and axon regeneration.Yet how radiation induces impairment of microglial phagocytosis is not elucidative. Whether improvement of microglial phagocytosis could promote remyelination as well as axon regeneration hence to benefit the recovery of radiation induced brain injury merits further investigation. Preliminary data and literatures indicate that TREM2 plays a pivot role in microglial phagocytosis. Upreguation of TREM2 might improve phagocytosis while lacking of speficity of recognition of apoptotic cells. MFG-E8, as bridge protein secreted by microglia, could recognize apoptotic cells by binding to PtdSer on apoptotic cells, and to integrin receptor on microglia. This study aims to investigate the effect of improvement of phagocytosis by upregulation of TREM2. TREM2 -/- cell line would be used in vitro while TREM2 knock out mice in vivo experiment. Signal transduction pathways involved in the mechanism of how radiation induces impairment of phagocytosis would be examined. Recombinant-MFG-E8 is used to enhance the recognition of apoptotic cells. Remyelination and axon regeneration would be examined to evaluate the effect of modulation of phagocytosis in the radiation induced brain injury. The study would provide evidence of targeting microglial phagocytosis for the further treatment strategy of radiation induced brain injury.

放射性脑损伤中，小胶质细胞（MG）吞噬功能下降使损伤性物质蓄积,引起髓鞘及轴突再生障碍加重放射损伤。但是放射通过何种机制抑制MG吞噬尚不明确，能否上调MG吞噬功能促进髓鞘及轴突再生改善脑损伤值得进一步研究。我们前期实验及文献提示TREM2可能介导MG吞噬功能，但不能靶向识别受损细胞因而可能误吞正常神经元；而MG分泌的MFG-E8可靶向识别受损细胞，但病理状态时分泌量低。本课题拟采用受体激动剂结合TREM2 -/-细胞及TREM2敲除动物模型，离体通过荧光微球吞噬实验，在体以双光子显微技术动态观察活体细胞吞噬能力，探讨放射后MG吞噬模式改变及TREM2在MG吞噬中的作用与上游信号机制；上调TREM2提高MG吞噬能力并联用MFG-E8提高吞噬靶向性，离体通过共培养髓鞘形成模型，在体行轴突和髓鞘染色及神经元损伤病理检查，明确上调MG靶向吞噬改善脑损伤的机制，为放射性脑损伤的治疗提供新的突破口。

放射性脑损伤中，小胶质细胞（Microglial , MG）吞噬功能下降使损伤性物质蓄积，引起髓鞘及轴突再生障碍而加重放射损伤。放射影响MG 吞噬的机制尚不明确，上调MG 吞噬功能能否促进髓鞘及轴突再生改善脑损伤值得研究。本课题原拟采用受体激动剂结合TREM2 -/-细胞及TREM2 敲除动物模型，探讨放射后MG 吞噬模式改变及TREM2在MG 吞噬中的作用与上游信号机制。我们发现放射后TREM2在皮层和海马区表达下调，完成TREM2敲除动物表型鉴定，同时开展P2受体介导吞噬功能的研究，发现放射后P2Y6受体表达增加，提示P2Y6受体参与介导MG吞噬功能；利用高选择性P2Y6拮抗剂MRS拮抗P2Y6受体，探讨P2Y6受体介导MG吞噬功能与炎症级联损伤、脱髓鞘以及凋亡的关系，明确上调MG 靶向吞噬改善脑损伤的机制，为放射性脑损伤治疗提供新突破口。