MCP-1/CCR2信号通路介导的星形胶质细胞对小胶质细胞的调控在POCD发生发展中的作用

Postoperative cognitive dysfunction (POCD) is correlated with the peripheral operation-triggered central inflammation. Previous discovery: In POCD mice, the levels of peripheral and central inflammatory factors were promoted, the astrocytes were activated, while the activated microglial cells in the hippocampus and the expression of CCR2 increased significantly. Therefore, we speculate that the peripheral operation can activate the central astrocytes, releasing a great amount of monocyte chemotactic factor 1 (MCP-1), which can not only induce the entering of the monocytes in the peripheral blood into the center, but also promote the activation to the M1 direction of two kinds of central microglia, amplifying the central inflammatory response, and finally exacerbate POCD. This study will use CCR2-/- mice and cross bone marrow transplantation technology, to observe the change of cognitive function after surgery, hippocampal MCP-1 level, number and direction of activated microglia; in the whole and the cell model, to observe the effect of expression of astrocytic MCP-1 on the direction of microglia activation and the peripheral blood monocyte chemotaxis, so as to explore the role of MCP-1/CCR2 signaling pathway in enlarging the central inflammation to promote POCD, and provide a new target for the prevention and treatment of POCD.

术后认知功能障碍(POCD)与外周手术促发的中枢炎症相关。前期发现：POCD小鼠外周和中枢炎症因子水平升高，星形胶质细胞活化，同时海马中活化小胶质细胞增多以及CCR2的表达明显升高。因此，我们推测外周手术可活化中枢的星形胶质细胞，释放大量的单核细胞趋化因子1（MCP-1）,不仅能够趋化外周血液中的单核细胞进入中枢，而且会促进中枢的两种小胶质细胞向M1方向活化，放大中枢炎症反应，最终加剧POCD。本研究拟应用CCR2-/-小鼠，通过骨髓交叉移植技术，观察术后认知功能的改变、海马MCP-1的水平、小胶质细胞的活化数目和方向；在整体和细胞模型上，观察星形胶质细胞表达的MCP-1对小胶质细胞活化方向的影响及其对外周血单核细胞的趋化作用，从而探讨MCP-1/CCR2信号通路在放大中枢炎症促发POCD中的作用，为防治POCD提供新的靶标。

开展离体实验，在原代培养星形胶质细胞和小胶质细胞的基础上，发现TNF-α可刺激星形胶质细胞释放CCL2，即使洗去上清中的TNF-α，星形胶质细胞也可继续分泌CCL2。TNF-α刺激过的星形胶质细胞上清可刺激小胶质细胞活化，而预先给予CCL2-siRNA，小胶质细胞的活化受到抑制，迁移能力下降，说明星形胶质细胞可通过其释放的CCL2促进小胶质细胞细胞活化。而在星形胶质细胞上清孵育小胶质细胞之前，预先给予CCR2拮抗剂，小胶质细胞的活化也受到明显抑制，说明CCL2是通过小胶质细胞上的CCR2发挥作用。建立胫骨骨折内固定手术的POCD模型，免疫荧光双标发现，CCL2主要表达于星形胶质细胞上，而CCR2表达于小胶质细胞上，手术可增加CCL2和CCR2的表达，而侧脑室预先给予CCR2拮抗剂，CCR2表达下降，小胶质细胞的活化也受到抑制，并且发现大鼠的认知行为学得到明显改善，海马区炎症因子的表达均受到明显抑制，神经元的功能得到保护，说明星形胶质细胞和小胶质细胞之间的CCL2/CCR2信号通路在POCD 的发生发展中发挥重要作用。基于以上结果，目前已发表相关SCI论文2篇，其中一篇影响因子大于5，另一篇大于3，并协助培养2名研究生。