小胶质细胞活化参与脑缺血预适应神经保护的作用及机制研究

Cerebral ischemic preconditioning (CIP) is an innate neuroprotective mechanism. However, the function of microglia has not been well-studied in this area. Past studies have shown that neuronal TLR-2 and -4 play a direct pivotal role in ischemic brain injury and functional deficits, at least at early time points. Furthermore, subsequent activation of microglia likely contributes to the delayed inflammatory processes that occur within the infarct region. However, our recent results, combined with growing evidence, suggest that CIP could reprogram the activation of microglia in ischemic stroke. Another finding of interest is a significant relationship between the area of the activation of microglia and the neuroprotection in CIP. Based on these findings, we hypothesized that CIP could reprogram the activation of microglia in ischemic cortex, leading to the induction of cytokines and other inflammatory mediators, which were involved in this neuroprotection. Here, we used a set of experiments in vivo and in vitro to elucidate the feature of this activation, the differentiation of distinct microglia, i.e., "classically activated" proinflammatory (M1) or "alternatively activated" anti-inflammatory (M2) cells, the mechanism of neuroprotection, and the role of the activation of microglia in the neuroprotection of CIP. Our work may confer a new therapeutic target of ischemic stroke.

脑缺血预适应是体内重要的内源性神经保护机制,小胶质细胞在此过程中作用尚不清楚。现已证实小胶质细胞在脑缺血过程中活化滞后，主要在继发性脑损伤中发挥作用。我们的前期工作及相关研究发现脑缺血预适应可使小胶质细胞活化过程提前，且其活化部位与脑缺血预适应的神经保护区域显著相关。据此我们提出"脑缺血预适应调控小胶质细胞活化发挥神经保护作用"的假设。本课题拟建立大鼠局灶脑缺血预适应模型及神经元+小胶质细胞氧糖剥离预适应共培养模型，并在小胶质细胞活化这个关键环节上进行干预，旨在：①研究脑缺血预适应调控的小胶质细胞活化特点及其与神经保护作用的关系；②从小胶质细胞免疫分型M1/M2角度探讨缺血预适应和致死性缺血引起小胶质细胞活化保护和损伤作用的机制，阐明两种病理状态下游信号的差异，明确小胶质细胞活化双刃剑作用的分界线；③探讨小胶质细胞活化诱导剂能否用于预防性治疗缺血性脑卒中，为脑缺血治疗提供新思路。

基本按计划执行，追踪国内外最新研究进展，围绕脑缺血预适应后小胶质细胞免疫表型变化，主要研究①脑缺血预适应调控的小胶质细胞活化特点及其与神经保护作用的关系；②从小胶质细胞免疫分型M1/M2 角度探讨缺血预适应和致死性缺血引起小胶质细胞活化保护和损伤作用的机制；③探讨小胶质细胞活化诱导剂能否用于预防性治疗缺血性脑卒中。研究结论及科学意义：①证实CIP可调控MCAO诱导的局灶性脑缺血皮层小胶质细胞数量增多，活化过程提前，参与CIP神经保护作用；②小胶质细胞免疫功能调控发挥保护作用，其作用机制可能与调控缺血性脑卒中早期小胶质细胞的M1/M2极化状态，抑制TLR2/4炎症信号通路过度活化，促使脑内IκB-α早期升高，并始终维持TNF-α表达在较低水平有关；③证实II 型大麻素受体激动剂（JWH133）能促进小胶质细胞由细胞毒表型（M1）向保护性表型（M2 型）转换，米诺环素联合JWH133显著减轻继发炎症脑损伤。我们的研究提示，小胶质细胞表型转换方向可能是减轻缺血性脑卒中所致的急性缺血缺氧性损伤的新的重要策略。