Chronic and Evolving Inflammation after Traumatic Brain Injury: Microglial Priming and Neuropsychiatric Complications

项目摘要/摘要： 创伤性脑损伤可导致严重的神经精神问题和神经退行性病变。 在受伤后随着时间的推移而发展。这些问题可能通过神经炎性过程传播， 在最初的受伤之后，继续进行得很好。Pt.3我们已经报道了小鼠弥漫性脑损伤导致“小胶质细胞启动” 在皮质和海马区，小胶质细胞仍处于致敏状态，并高度 损伤后30天(30dpi)免疫挑战后的炎症。在此应用程序中，我们显示了一个截然不同的 从急性(8-24小时)到亚急性(7天)再到慢性(30天)皮质炎症/小胶质细胞的阶段转变 颅脑损伤后引流。急性颅脑损伤后出现炎症反应，发展为亚急性期7。 以干扰素I型信号为主的DPI。干扰素反应由细胞窘迫和 损伤以促进免疫反应，从而启动包括小胶质细胞在内的先天免疫细胞。我们提供 皮质神经元损伤的证据7dpi和相应的小胶质细胞激活。Pts.3和6单细胞RNA 皮质7 dpi的序列(ScRNAseq)显示与创伤相关的独特的小胶质细胞簇，受影响。 由IFN提供。这些小胶质细胞参与了树突状细胞的重塑和神经元稳态的抑制。在30岁时 DPI，有认知障碍(与HPC和CTX相关)，网络连接减少， 启动的小胶质细胞的免疫反应性。小胶质细胞在这些过程中是关键的，因为小胶质细胞的消除 (CSF1R拮抗剂)可预防脑损伤引起的神经炎症和干扰素信号转导，减轻树突状细胞萎缩， 和改进的网络连接性。因此，我们假设干扰素信号的增加在 促进小胶质细胞启动和慢性神经炎、树突状细胞重塑和认知功能下降。至 为了解决这个问题，我们提出了三个目标，利用小鼠的中线液体撞击损伤。在AIM-1中，我们将淘汰 小胶质细胞为确定小胶质细胞对大脑皮质和海马区其他中枢神经系统细胞的影响，亚 急性的和慢性的在脑损伤后。ScRNAseq将用于确定小胶质细胞的转录组特征 随着时间的推移，与星形胶质细胞、少突胶质细胞和神经元在脑损伤后3个关键时间平行。这个 重点将是确定哪些细胞表达干扰素和干扰素受体，以及它们对增加的干扰素有何反应 用TBI发信号。在AIM-2中，我们将确定干扰素信号在慢性神经炎、病理、 脑损伤后认知功能减退和小胶质细胞启动。在这里，我们将在干扰素-a/b的水平上减弱干扰素信号。 受体激活(干扰素αrko，mgl-干扰素αrko)和干扰素产生(Stingko)，以确定在多大程度上 这些干预措施改善了神经炎症、病理和小胶质细胞的启动。在AIM-3中，我们将确定 如果颅脑损伤诱导的小胶质细胞启动、慢性神经炎和认知功能下降30dpi被强迫逆转 小胶质细胞周转率。当干扰素应答最高为7dpi时，我们将移除小胶质细胞(CSF1R拮抗剂)，并且 允许小胶质细胞重新聚集到30dpi。这些目标的完成将为干扰素途径提供新的见解 这似乎在脑外伤后由小胶质细胞介导的急性炎症向慢性炎症的转变过程中至关重要。

PROJECT SUMMARY/ABSTRACT: Traumatic brain injury (TBI) can lead to significant neuropsychiatric problems and neurodegenerative pathologies that develop with time after injury. These issues may be propagated by neuroinflammatory processes that continue well after the initial injury. Pt.3 We have reported that diffuse TBI in mice leads to “microglial priming” within cortical and hippocampal regions, in which the microglia remain in a sensitized state and are highly inflammatory following an immune challenge 30 days post injury (30 dpi). In this application, we show a distinct phase transition from acute (8-24 h) to sub-acute (7 d) and then to chronic (30 d) cortical-inflammation/microglia priming after TBI. Acutely, there was an inflammatory response after TBI that evolved into a subacute phase 7 dpi that was dominated by interferon (IFN) type I signaling. IFN responses are activated by cell distress and damage to promote an immune response that can prime innate immune cells, including microglia. We provide evidence of cortical neuronal damage 7 dpi with corresponding microglial activation. Pts.3&6 Single cell RNA seq (scRNAseq) of the cortex 7 dpi shows unique clusters of microglia, trauma-associated, that are influenced by IFNs. These microglia are involved in dendritic remodeling and suppression of neuronal homeostasis. At 30 dpi, there was cognitive impairment (associated with HPC & CTX), reduced network connectivity, and increased immune reactivity of primed microglia. Microglia are critical in these processes because microglial elimination (CSF1R antagonist) prevented TBI-induced neuroinflammation and IFN signaling, attenuated dendritic atrophy, and improved network connectivity. Thus, we hypothesize that increased interferon signaling is critical in promoting microglial priming and chronic neuroinflammation, dendritic remodeling, and cognitive decline. To address this, three aims are proposed using a midline fluid percussion injury in mice. In Aim-1, we will eliminate microglia to determine the influence of microglia on other CNS cells in the cortex and hippocampus acutely, sub- acutely, and chronically after TBI. ScRNAseq will be used to determine the transcriptome signature of microglia over time and in parallel with astrocytes, oligodendrocytes, and neurons at 3 these critical times after TBI. The focus will be determining which cells express IFNs and IFN receptors, and how they respond to increased IFN signaling with TBI. In Aim-2, we will determine if IFN signaling is critical in chronic neuroinflammation, pathology, cognitive decline, and microglial priming after TBI. Here, we will attenuate IFN signaling at the levels of IFN-a/b receptor activation (IFNαRKO, Mgl-IFNαRKO) and IFN production (STINGKO) to determine the extent to which these interventions ameliorate neuroinflammation, pathology, and microglial priming. In Aim-3, we will determine if TBI-induced microglial priming, chronic neuroinflammation, and cognitive decline 30 dpi are reversed by forced microglia turnover. We will remove microglia (CSF1R antagonist) when IFN responses are highest 7 dpi, and allow for microglial repopulation to 30 dpi. Completion of these aims will provide new insight on the IFN pathway that appears to be critical in the transition from acute to chronic inflammation mediated by microglia after TBI.