mGluR5 inhibits microglial activation and neuronal cell death after TBI

描述（由申请方提供）：创伤性脑损伤（TBI）导致神经元细胞死亡，并伴有与小胶质细胞活化相关的星形胶质细胞增殖和炎症，这导致不可逆的组织损伤。这种继发性损伤在损伤后数秒至数分钟内开始，并可能持续数天、数周甚至数月至数年。我们实验室的最新证据显示，损伤后CNS中的慢性炎症至少持续6个月。炎症可能导致创伤后慢性神经变性以及阿尔茨海默病（AD）或帕金森综合征等疾病。在我们实验室的初步研究表明，炎症可能会受到抑制的小胶质细胞中的mGluR5受体的激活。此外，我们的数据表明，mGluR5的影响可能是通过对NADPH氧化酶的作用介导的，NADPH氧化酶的作用是通过小胶质细胞产生活性氧（ROS），并可能在损伤后小胶质细胞的持续激活中发挥重要作用。提出的研究旨在解决以下假设：（1）NADPH氧化酶抑制减少TBI后小胶质细胞活化、促炎因子的产生和相关的神经功能障碍;（2）mGluR5刺激减弱小胶质细胞活化和继发性神经元细胞死亡，并改善TBI后的功能结果;（3）mGluR5而不是mGluR1部分地通过抑制NADPH氧化酶来调节原代小胶质细胞培养物、小胶质细胞系和小胶质细胞/神经元共培养物中的小胶质细胞活化和神经毒性;（4）G1q蛋白信号转导途径是mGluR5信号转导事件的关键组成部分，导致抑制小胶质细胞NADPH氧化酶和抑制小胶质细胞活化。具体目的是证明：（1）NADPH氧化酶在TBI后慢性神经元细胞丢失和相关神经功能障碍中小胶质细胞活化和相关促炎因子产生中的重要性;（2）mGluR5刺激减弱小胶质细胞活化，与mGluR5整体敲除动物相比，在TBI后减少神经元细胞死亡并改善功能结果，mGluR5整体敲除动物显示更大的小胶质细胞活化，神经元细胞死亡我们还将使用条件性/诱导性敲除小鼠区分小胶质细胞与神经元mGluR5的相对作用;（3）在小胶质细胞刺激的多细胞培养模型中，mGluR5而不是mGluR1调节小胶质细胞活化和神经毒性;（4）G1q-蛋白质信号转导途径由mGluR5刺激启动，并且通过防止小胶质细胞的激活而对小胶质细胞活性的减弱至关重要。NADPH氧化酶复合物，使用体外小胶质细胞模型。公共卫生相关性全国每年有100万例创伤性脑损伤（TBI）。TBI患者表现出损伤后至少持续3周的长时间小胶质细胞活化的证据。拟议的工作中，我们将调查小胶质细胞和神经元mGluR5的神经保护作用，将提供初步调查的一种新的治疗方法TBI。

DESCRIPTION (provided by applicant): Traumatic brain injury (TBI) causes neuronal cell death, combined with astroglial proliferation and inflammation associated with the activation of microglia, which contributes to irreversible tissue damage. Such secondary injury begins within seconds to minutes after the insult and may continue for days, weeks and potentially even months to years. Recent evidence from our laboratory shows chronic inflammation in the CNS lasting at least 6 months after injury. Inflammation may contribute to chronic neurodegeneration after trauma as well as to disorders such as Alzheimer's disease (AD) or Parkinson's syndrome. Pilot studies in our laboratory have indicated that inflammation may be inhibited by activation of mGluR5 receptors in microglia. Furthermore, our data suggest that mGluR5 effects may be mediated by actions on the NADPH oxidase enzyme, which functions to produce reactive oxygen species (ROS) by microglia and may play a significant role in persistent activation of microglia following injury. The proposed studies are intended to address the following hypotheses: (1) NADPH oxidase inhibition reduces microglial activation, production of pro-inflammatory factors and associated neurological dysfunction after TBI; (2) mGluR5 stimulation attenuates microglia activation and secondary neuronal cell death, and improves functional outcomes after TBI; (3) mGluR5, but not mGluR1, modulates microglial activation and neurotoxicity in primary microglia cultures, a microglial cell line, and microglia/neuronal co-cultures, in part through inhibition of NADPH oxidase; and (4) the G1q-protein signal transduction pathway is the critical component of the mGluR5 signal transduction events leading to inhibition of microglial NADPH oxidase and suppression of microglial activation. Specific aims are to demonstrate: (1) the importance of NADPH oxidase in microglial activation and correlated production of pro-inflammatory factors in the chronic neuronal cell loss and associated neurological dysfunction after TBI; (2) that mGluR5 stimulation attenuates microglial activation, decreases neuronal cell death and improves functional outcomes after TBI in contrast to mGluR5 global knockout animals that show greater microglial activation and neuronal cell death. We will also distinguish the relative roles of microglial versus neuronal mGluR5 using conditional/inducible knockout mice; (3) that mGluR5, but not mGluR1, modulates microglial activation and neurotoxicity in multiple cell culture models of microglial stimulation; and (4) that the G1q-protein signal transduction pathway is initiated by mGluR5 stimulation and is critical for attenuation of microglial activity by preventing activation of the NADPH oxidase enzyme complex, using in vitro microglial cell models. PUBLIC HEALTH RELEVANCE There are 1 million incidences of traumatic brain injury (TBI) per year nationally. Patients with TBI demonstrate evidence of prolonged microglial activation that lasts at least 3 weeks post-injury. The proposed work, in which we will investigate the neuroprotective effects of microglial and neuronal mGluR5, will provide initial investigation to a novel therapeutic approach for TBI.