诱导M2型小胶质细胞极化在脑出血后的神经保护作用及机制研究

Microglia are the most important inflammatory cells in brain, which participates in the inflammatory response after brain injury. There are two phenotypes of microglia polarization, M1 and M2. M1 is the classical-activated microglia, which is a pro-inflammation type. M2 is the selective-activated microglia, which is an anti-inflammatory type. In animal models of cerebral infarction and brain trauma, the microglia appear a short polarization to M2 and trend to M1 polarization after brain injury, while induction of microglial cells to M2, the inflammatory response was obviously inhibited after brain injury. However, the role of M2 after intracerebral hemorrhage has not been reported. In this study, firstly, we will detected the time course and regions in brain of M1/M2 by the method of the USPIO enhanced MRI, Western blot, RT-PCR, ELISA and immunofluorescence. And then, administration of exogenous M2 to evaluate the effect of M2 on hematoma absorption, and inhibition of inflammation, apoptosis of neurons, brain edema and axonal injury and other neuroprotective effect after ICH. Finally, with the treatment of bexarotene, to make sure whether bexarotene is able to promote microglia to M2 polarization through activation RXR-PPAR gamma dimer, and thus play a neuroprotective role after ICH.

小胶质细胞是脑组织中最主要的炎症细胞，参与脑损伤后炎症反应。小胶质细胞可以极化为M1及M2两种不同表型，M1为经典活化型，为促炎型，M2为选择活化型，为抗炎型。在脑梗死、脑创伤等模型中均发现，在脑损伤后小胶质细胞出现短暂的向M2型极化，而后向M1型极化的趋势，诱导小胶质细胞向M2型极化，可以明显的抑制脑损伤后神经炎症反应。然而在脑出血后M2的作用尚无研究报道。本课题首先应用USPIO增强MRI、Western blot、RT-PCR、ELISA、免疫荧光等方法分别检测ICH后不同时间点脑组织不同区域中M1、M2型小胶质细胞极化情况。而后给予外源性M2，评价M2在ICH后对血肿吸收、抑制神经炎症反应、抑制神经元凋亡、抑制脑水肿及减轻轴突损伤等方面的神经保护作用，最后给予贝沙罗汀治疗，明确贝沙罗汀在ICH后能否通过激活RXR-PPARγ二聚体促进小胶质细胞向M2型极化，从而发挥神经保护作用。

炎症反应是脑出血后重要的继发性损伤的重要组成部分。尤其是小胶质细胞活化及极化在脑出血后炎症反应中发挥了重要作用。本研究发现在BV-2细胞炎症模型中，miR-199a-5p可以靶向结合SIRT1，并抑制SIRT1表达，从而激活NLRP3炎症小体，进一步加重了LPS诱导BV-2细胞的炎性损伤。IL-4 可以通过介导 JAK1/STAT6 通路促进小鼠脑出血后 M2 型小胶质细胞极化而发挥神经保护作用。本课题是对脑出血后炎症反应损伤机制的补充，对为寻找治疗脑出血后靶向药物提供临床前期依据。