Microglia Dysregulation and Altered Responses to Stress after Traumatic Brain Injury

项目总结 在美国，超过530万人患有与创伤性脑损伤(TBI)相关的残疾。 越来越多的临床和实验证据表明，颅脑损伤常见的并存部位是下丘脑-垂体- 肾上腺(HPA)轴功能障碍，导致人类应激激素-皮质醇或 相当于啮齿类动物的皮质酮(CORT)。皮质醇抑制与神经元反应异常相关 并可加重脑创伤后的损伤，包括认知和行为缺陷。沉睡 碎片化是压力的一种常见后果，因此我们预测受伤后的睡眠碎片化 一种脆弱的生物途径，通过调节神经炎症来显著影响结果。为 例如，越来越多的数据表明，小胶质细胞通过永久化介导脑损伤诱导的慢性恢复 适应性不良的炎症、细胞毒性以及改变神经元的活性和可塑性。重要的是，这种小胶质细胞 创伤后应激源可能会使反应恶化。例如，小胶质细胞高表达糖皮质激素受体。 (GR)，它与皮质醇结合，诱导强大的抗炎信号。我们假设脑外伤引起的 抑制皮质醇可能损害GR在小胶质细胞中的抗炎作用，从而产生皮质醇。 对创伤性脑损伤后应激源的反应是确保炎症控制的关键。由于压力和压力的相互作用 对于免疫轴，必须更好地了解慢性应激对脑外伤预后的影响。这项建议旨在 确定脑损伤后睡眠碎片对神经元激活和应激回路的影响， 小胶质细胞糖皮质激素受体如何影响脑外伤后睡眠的炎症、神经元激活和认知 碎片化。目标1将确定小胶质细胞如何影响应激回路和海马神经元功能 有脑外伤后的睡眠碎片。要做到这一点，PT。3我们将通过CSF1R拮抗迅速耗尽小胶质细胞 并将具有和不具有小胶质细胞的动物暴露于脑损伤后睡眠碎裂，以确定细胞的特定作用 小胶质细胞在应激通路中对神经元激活的影响。我们将进一步确定海马体的RNA图谱 颅脑损伤后小胶质细胞耗竭后睡眠碎裂并进行电生理学检查以区分 海马区活动的差异是由于神经元功能和存活率的变化还是由于小胶质细胞的变化 发信号。Aim 2将测试小胶质细胞GR激活是否介导炎症、神经元激活和行为 在脑外伤后睡眠碎片化之后。为此，我们将使用pT。3小胶质细胞中可诱导的GR基因敲除 并确定RNA测序图谱、免疫组织化学和海马区依赖的差异 颅脑损伤后有睡眠碎片的行为任务。我们假设反应性小胶质细胞介导神经元 通过抑制GR抗炎作用对脑损伤后睡眠碎片作出反应的缺陷。最终， 这项拟议的研究将阐明脑外伤后的应激免疫功能障碍，并更好地了解如何改善 颅脑损伤幸存者的长期生活质量和预后。

PROJECT SUMMARY More than 5.3 million individuals suffer from a traumatic brain injury (TBI) related disability in the United States. Mounting clinical and experimental evidence shows a common co-morbidity of TBI is hypothalamic-pituitary- adrenal (HPA) axis dysfunction that results in the suppression of the stress hormone - cortisol in humans or the equivalent corticosterone (CORT) in rodents. Suppressed CORT is associated with aberrant neuronal responses in stress circuitry and can exacerbate post-TBI impairments, including cognitive and behavioral deficits. Sleep fragmentation is a frequent consequence of stress, thus we predict that post-injury sleep fragmentation engages a vulnerable biological pathway that substantially influences outcome by modulating neuroinflammation. For example, increasing data demonstrates that microglia mediate chronic TBI-induced recovery by perpetuating maladaptive inflammation, cytotoxicity, and altering neuronal viability and plasticity. Importantly, this microglial response may be worsened by post-TBI stressors. For example, microglia highly express glucocorticoid receptor (GR), which binds CORT to induce potent anti-inflammatory signaling. We hypothesize that TBI-induced suppression of CORT may compromise the anti-inflammatory action of GR in microglia, thus CORT production in response to stressors after TBI is vital to ensure control of inflammation. Due to the interplay of the stress and immune axes, the effect of chronic stress on TBI outcome must be better understood. This proposal aims to determine how neuronal activation and stress circuitry is altered in response to post-TBI sleep fragmentation, and how microglial GR may influence inflammation, neuronal activation, and cognition with post-TBI sleep fragmentation. Aim 1 will determine how microglia influence stress circuitry and hippocampal neuronal function with post-TBI sleep fragmentation. To do this, Pt. 3 we will rapidly deplete microglia through CSF1R antagonism and expose animals with and without microglia to post-TBI sleep fragmentation to define the cell specific role of microglia on neuronal activation in stress circuitry. We will further determine the RNA profile of the hippocampus following microglia depletion with post-TBI sleep fragmentation and perform electrophysiology to distinguish whether differences in hippocampal activity are due to changes in neuronal function and viability or microglial signaling. Aim 2 will test if microglial GR activation mediates inflammation, neuronal activation, and behavior following post-TBI sleep fragmentation. To do this, we will use Pt. 3 an inducible knockout of GR in microglia and determine differences in RNA sequencing profile, immunohistochemistry, and hippocampal-dependent behavioral tasks with sleep fragmentation after TBI. We hypothesize that reactive microglia mediate neuronal deficits in response to post-TBI sleep fragmentation through suppressed GR anti-inflammatory action. Ultimately, this proposed study will shed light on stress-immune dysfunction after TBI and better understand how to improve long-term quality of life and outcome for TBI survivors.