受体酪氨酸激酶Mer对创伤性脑损伤后小胶质细胞极化的调控作用及机制研究

Traumatic brain injury (TBI)is a devastating disease without effective therapies. Accumulating evidence suggests that inflammatory mechanisms are involved in the progression of TBI-induced brain injury. Microglia exert both protective and pathogenic roles in the brain and simply inhibition of microglia-mediated inflammation will not result in a favorable therapeutic outcome. Notably, recent research evidences suggest that dynamic equilibrium of microglial M1/M2 polarization is closely related to brain injury and functional recovery following TBI. Clarifing the regulatory mechanism of microglial M1/M2 polarization in TBI would be beneficial for treating this disease. Receptor tyrosine kinase Mer has been demonstrated to be an important regulator of inflammation. In the preliminary experiment, we found the expression of Mer protein is significantly increased after TBI. Mer is mainly expressed in the microglia. Inhibition of Mer by siRNA can significantly promoting M1 polarization, but lowing M2 polarization, suggesting that Mer may play a vital role in neuroinflammation in the pathophysiology of TBI. Based on our previous work, we plan to further elucidation of the roles and mechanisms of Mer in regulation of microglial polarization during the pathophysiological processes of TBI, which will contribute to develop novel therapeutic approaches for TBI.

创伤性脑损伤(TBI)发病率高，预后差，是临床急需解决的重要问题。炎症在TBI继发损伤及修复中起至关重要的作用，然而单纯抑制炎症的疗效非常有限。最新研究认为，小胶质细胞M1/M2型极化的稳态平衡与TBI组织损伤及修复密切相关，深入研究其极化调控机制将为TBI治疗提供新思路。受体酪氨酸激酶Mer是重要的炎症调控蛋白。我们预实验显示，在动物模型中，TBI小鼠脑组织中Mer蛋白表达明显升高，Mer蛋白表达于小胶质细胞上；在细胞模型中，通过siRNA抑制原代小胶质细胞Mer表达可显著促进小胶质细胞向M1型极化而抑制其向M2型极化，提示Mer可能是调控TBI后小胶质细胞M1/M2型极化及炎症反应的关键分子。本项目拟在前期工作的基础上，运用RNA干扰等技术手段，进一步解析Mer调控小胶质细胞M1/M2型极化的分子机制，进而明确TBI继发炎症损伤及修复的调控机制，为TBI治疗提供新策略。

创伤性脑损伤(TBI)是临床常见病，预后差，是临床急需解决的重要问题。小胶质细胞/巨噬细胞活化和神经炎症在TBI继发损伤及修复中起至关重要的作用，然而其调控机制尚未完全阐明。最新研究认为，小胶质细胞/巨噬细胞 M1/M2样活化的稳态平衡与TBI组织损伤及修复密切相关，深入研究其活化调控机制将为TBI治疗提供新思路。作为TAM家族重要成员之一，受体酪氨酸激酶Mer是重要的炎症调控蛋白，能够调控小胶质细胞/巨噬细胞的多种生理功能。然而，其在调控TBI后固有免疫反应及小胶质细胞/巨噬细胞激活中的功能及作用尚未有研究。因此，本研究拟探讨Mer在调控TBI后小胶质细胞/巨噬细胞活化及神经炎症反应中的作用及机制。在构建小鼠控制性皮质损伤模型后，予以脑室内注射Mer siRNA或尾静脉注射重组蛋白Protein S以干预，采用神经功能学评价、RT-PCR、Western blot、免疫磁珠细胞分选、免疫化学染色及激光共聚焦成像、Nissl染色和Fluoro-Jade B染色、脑组织含水量及脑组织体积缺损测定等实验技术手段，以评估分析Mer在TBI后的表达及活性改变，以及其对神经炎症及继发性脑损伤的影响。结果发现：Mer在TBI后急性期皮层脑组织中表达明显升高，且参与了小胶质细胞/巨噬细胞的M1/M2样活化及损伤后的神经炎症反应。具体地，Mer能激活STAT1/SOCSs信号通路，以调控TBI后小胶质细胞/巨噬细胞活化及神经炎症反应。抑制Mer能显著降低小胶质细胞/巨噬细胞M2样活化而增加M1样活化，由此加重TBI后继发性脑损伤及神经功能损害。相较而言，重组蛋白Protein S能通过激活Mer而在TBI中发挥神经保护作用。本研究结果提示Mer对创伤性脑损伤后小胶质细胞/巨噬细胞活化具有重要的调控作用，值得继续深入研究。