肠道微生物调控脑缺血后小胶质细胞激活及极化的机制

The microbial-gut-brain axis is one of the hotspots for neuroscience studies. Recent research shows microbiota in the gut are essential to the regulation of microglial maturation and activation. However, microglial activation and polarization may play a critical role in the pathophysiology of stroke. So we speculate that microbial-gut-brain axis also play an important role in the pathophysiology of stroke. We also observed that stroke patients can lead to gut microbial disorders and poor prognosis. Whether the intestinal microflora disorders could secondary induce to the microglial activation, maturation and polarization? And whether could it aggravate the brain damage after ischemia? Could the brain damage be reduced by the regulation of intestinal microbes? So we try to investigate the changes of the gut microbiota and the effects of the gut microbiota on the microglia activation and polarization after focal cerebral ischemia introduced by permanent middle cerebral artery occlusion(pMCAO) in mice on the basis of our previous work, and explore the changes of the neuropathology and neurobehavior, and evaluate the changes of the related genes and proteins in the microglia activation and polarization using the immunohistochemistry, RT-PCR and Western Blot, Flow cytometry and high throughput 16rRNA sequencing technique.At the same time the gut microbiota were improved or damaged by short chain fatty acids or antibiotics, and to investigate whether it has protective effect on the brain . The molecular mechanisms of activation and polarization of microglia on the regulation of the gut microbiota will be explored emphatically after cerebral ischemia and will provide new strategies and targets for the treatment of cerebral ischemia.

“微生物-肠-脑轴”为神经科学研究的热点之一。研究显示肠道微生物可调控小胶质细胞成熟和激活；而小胶质细胞激活、极化及其炎症反应在脑卒中病理生理中具有重要作用。因此，我们推测“微生物-肠-脑轴”在脑卒中的病理生理中亦发挥重要作用。我们亦观察到脑卒中可导致患者肠微生物失调及预后不良；然而，肠道微生物失调能否继发影响小胶质细胞激活、成熟及极化？能否继发加重脑损害？通过调节肠道微生物能否减轻脑损害？为此，我们在前期工作基础上，试图利用小鼠持久性大脑中动脉闭塞模型，结合神经病理和神经行为学，利用免疫组化、RT-PCR、蛋白质印迹、流式细胞术和高通量16rRNA 测序技术，观察脑缺血后肠道微生物变化，以及对小胶质细胞激活及极化的继发影响；同时通过短链脂肪酸或抗生素改善或破坏肠微生物，探讨其是否具有脑保护作用，并重点研究肠道微生物调控缺血后小胶质细胞激活及极化的分子机制，为治疗脑缺血提供新的策略和靶点。

探讨缺血性脑损伤及修复的机制，寻找脑卒中潜在的治疗干预靶点，是目前的热点及难点。脑缺血后最初免疫激活为快速的先天免疫反应，并导致炎症；募集炎症细胞，导致适应性免疫反应激活。小胶质细胞激活及极化在炎症免疫反应中具有重要作用。研究表明宿主肠道微生物通过调节小胶质细胞激活和内稳态来影响CNS的免疫系统，肠道微生物持续地控制CNS小胶质细胞的成熟和功能。“微生物-肠道-脑轴”已成为神经科学研究的热点之一。本课题利用小鼠脑缺血模型，通过16SrRNA高通量测序分析观察到小鼠卒中后肠道菌群的的动态变化；缺血性卒中后出血炎症和小胶质细胞激活。通过药物调整脑梗死小鼠模型的肠道菌群，可以改善缺血小鼠神经功能，减轻脑梗死体积，对脑缺血具有一定的保护作用。更昔洛韦可能通过调节炎症相关基因，改善小鼠脑缺血，促进神经功能恢复。丁苯酞（NBP）可减少小血管死亡，促进神经元和血管再生。同时，在临床工作中，观察到急性脑梗死患者出现便秘的发生率较高，可达31.15%，且便秘组患者具有更高的炎症，以及神经功能缺失更明显。提示急性脑缺血后可出现肠道功能障碍，并且与炎症和神经功能缺失严重程度有关。该研究为脑缺血提供新的治疗策略和靶点