MICROGLIAL ACTIVATION IN TRAUMATIC BRAIN INJURY

描述（改编自申请人摘要）：创伤性脑损伤（TBI） 诱导激活小胶质细胞，大脑的免疫效应细胞。的 小胶质细胞在TBI中的作用是一把双刃剑， 神经保护和神经变性作用。因此，治疗目标 最大限度地减少负面的，神经毒性的小胶质细胞行为，同时最大限度地 神经保护小胶质细胞与其他脑细胞相互作用的解剖 参与小胶质细胞的生化途径的类型和鉴定 TBI后的激活难以在体内完成。目前的许多 体外小胶质细胞损伤模型不能再现 创伤性脑损伤是指组织拉伤或拉伸。本提案的目的是 检查负责TBI诱导的小胶质细胞的信号转导途径 激活并确定激活对神经元损伤的后果， 使用一个良好表征的体外拉伸损伤模型。我们最近的研究 表明小胶质细胞并不直接被拉伸损伤激活， 被拉伸损伤的星形胶质细胞释放的可溶性因子激活。 活化的小胶质细胞形态学改变，花生四烯酸增加， 释放，并增强细胞内钙信号传导， 巨噬细胞活化这是我们第一次发现， 谷氨酸介导的钙信号通路在活化的小胶质细胞，这可能 在小胶质细胞和受损的星形胶质细胞之间构成信号网络， 神经元我们还发现，拉伸损伤的星形胶质细胞和严重的 受损的神经元将ATP释放到细胞外空间。我们假设 创伤损伤的星形胶质细胞和神经元释放的谷氨酸和ATP 启动小胶质细胞趋化性激活。在本建议中，我们将 继续剖析牵张诱导的细胞凋亡中的信号通路， 通过检查花生四烯酸释放，谷氨酸介导的小胶质细胞活化 钙信号，形态学变化，增殖，主要 组织相容性抗原表达、吞噬作用和趋化性。我们将 还确定了牵张激活的小胶质细胞改变 神经元钙信号传导或发挥神经毒性作用。使用抑制剂， 花生四烯酸级联，钙信号，嘌呤能和谷氨酸能 受体，我们将试图抵消小胶质细胞神经毒性。体外 神经保护和神经毒性机制的剖析 创伤后小胶质细胞的增加可以使开发更有效的 旨在减少TBI后继发性损伤的策略， 小胶质细胞从神经毒性到神经保护作用的平衡。

DESCRIPTION (adapted from applicant's abstract): Traumatic brain injury (TBI) induces activation of microglia, the immune effector cells of the brain. The role of microglia in TBI is one of double-edged sword, having both neuroprotective and neurodegenerative effects. Therefore, a treatment goal would be to minimize negative, neurotoxic microglial actions while maximizing neuroprotection. Dissection of microglial interactions with other brain cell types and identification of biochemical pathways involved in microglial activation after TBI is difficult to accomplish in vivo. Many of the current models of in vitro microglial injury do not reproduce the major component of TBI, that being tissue strain or stretch. The goal of this proposal is to examine the signal transduction pathways responsible for TBI-induced microglial activation and determine the consequences of activation on neuronal injury, using a well-characterized in vitro stretch-injury model. Our recent studies demonstrate that microglia are not directly activated by stretch injury, but are activated by soluble factors released from stretch-injured astrocytes. Activated microglia had morphological alterations, increased arachidonic acid release, and enhanced intracellular calcium signaling consistent with macrophage activation. For the first time, we have identified upregulation of a glutamate-mediated calcium-signaling pathway in activated microglia, which may constitute a signaling network between microglia and injured astrocytes and neurons. We have also found that stretch-injured astrocytes and severely injured neurons release ATP into the extracellular space. We hypothesize that glutamate and ATP released by traumatically injured astrocytes and neurons initiates microglial chemotaxis activation. In the present proposal, we will continue to dissect the signaling pathways involved in stretch-induced microglial activation by examining arachidonic acid release, glutamate-mediated calcium signaling, morphological changes, proliferation, major histocompatibility antigen expression, phagocytosis, and chemotaxis. We will also determine the mechanisms through which stretch-activated microglia alter neuronal calcium signaling or exert neurotoxic effects. Using inhibitors of the arachidonic acid cascade, calcium signaling, purinergic and glutamatergic receptors, we will attempt to counteract microglial neurotoxicity. In vitro dissection of the mechanisms involved in the neuroprotection and neurotoxicity of microglia after trauma could permit the development of more effective strategies aimed at reduction of secondary injury after TBI by shifting the balance of microglial effects from neurotoxic to neuroprotective.