小胶质细胞Toll样受体选择性调控对外伤后神经血管单元功能损伤和重塑的影响研究

Nerve injury and repair after traumatic brain injury (TBI) has long been a hot topic in neuroscience. Microglial activation is considered to be one of the initiation factors of the cascade effect produced in the brain after injury. In our previous studies we had demonstrated that the inhibition of this activation could effectively reduce the second damage caused by inflammatory and immune response. On the other hand, it also participates in the removal of necrotic tissue and the nerve repair. Simply inhibiting its function may not result in good prognosis. Therefore, a whole and systemic research on the microglia funciton post TBI is the key to get a complete and correct assessment. Recent years, the Neurovascular Unit (NVU) which is comprised of neurons, glia cells and vascular is highly valued by more and more researchers, they take it as the basis to form a systemic research direction. It was proved that, the family of Toll-Like receptors (TLRs) played an important role in the activation of microglial cells, and could realize a selective control of this activation. In present experiment, we will take the neurovascular unit as the basis, drug and gene regulation as intervention means on the TBI models, and selectively regulate the activity of the TLRs signal pathway to control the microglia activation, in order to observe its effect on every component of "the Neurovascular Unit". We will investigate the mechanism of microglial cells in the nerve injury and repair and provide more reference for better regulation of the double-edged sword microglia.

外伤后的神经损伤和修复一直是神经科学领域的热点问题。小胶质细胞活化被认为是脑损伤瀑布效应的启动因素之一。我们前期研究证实抑制其活化可有效缓解炎症反应导致的继发性损害。但另一方面小胶质细胞也参与坏死组织的清除和损伤修复，单纯抑制其功能未必能获得良好的预后。因此全时程、整体化研究脑外伤后小胶质细胞的生物学效应是获得全面正确评估的关键。近年来神经元-胶质细胞-微血管组成的神经血管单元为人们所重视，形成以此为基础的整化研究方向。此外Toll样受体家族(TLRs)被证实在小胶质细胞活化中扮演重要角色，成为实现选择性调控其活化的手段。本实验在TBI模型上,以神经血管单元为基础，以药物干预和基因调控为工具，多时点的选择性干预TLRs信号通路活性，调控小胶质细胞的功能，观察其对"神经血管单元"各组分的影响，明确其在神经损伤和修复全程中的作用机制。为今后更好调控小胶质细胞这把双刃剑提供参考。

小胶质细胞是中枢神经系统（CNS）主要的免疫细胞，在创伤性脑损伤（TBI）病理过程中的炎症损伤和神经网路修复过程中均发挥了重要作用。但是扮演的双刃剑作用的具体机制并不明确。本课题在小胶质细胞两种表型（M1和M2）理论基础上，探讨了Toll样受体4（TLR4）及其下游信号通路在其活化和表型转换中的作用，以及对小胶质细胞如何参与TBI后神经血管单元的损伤和修复的作用与机制进行了初步研究。通过离体皮质损伤刺激模型和活体自由落体损伤模型，我们研究了TBI后不同时间点神经血管单元（包括小胶质细胞、星形胶质细胞、神经元和血管内皮细胞）的活化和损伤情况；证实了伤灶区域TLR4/MyD88/NF-kB信号通路激活。通过基因抑制和药物干预TLR4及其下游信号通路，证实了其对TBI后小鼠神经血管单元和神经功能的保护作用。这一保护作用部分是通过抑制小胶质细胞M1表型的活化，促进其向M2表型转化实现的。进一步检测发现TLR4 信号系统可以调控下游的炎症小体信号系统功能，对炎症小体的组装和活化中发挥重要作用。该活化作用可以被IL4/ PPARγ信号通路显著抑制。综上所述，我们研究证实了TLR4信号系统参与调控外伤后小胶质细胞的表型转换和功能作用，其下游机制在于TLR4/MyD88/NF-kB信号系统和炎症小体系统的激活，进而参与TBI后神经血管单元的损伤和修复。以上研究成果为今后治疗创伤性脑损伤提供了新的思路。