Glutamatergic plumes – a novel mechanism of excitability in the brain after TBI.

谷氨酸羽流——TBI 后大脑兴奋性的一种新机制。

• 批准号: 10575578
• 负责人: PUNAM MADHUKAR SAWANT-POKAM
• 金额: $ 42.22万
• 依托单位: UNIVERSITY OF UTAH
• 依托单位国家: 美国
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-09-21 至 2024-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10575578
• 关键词: Acute; Affect; Anatomy; Animal Model; Animals; Apical; Astrocytes; Automobile Driving; Brain; Brain Injuries; Calcium; Caring; Cause of Death; Cells; Chronic; Clinical; Data; Dendrites; Drug Targeting; Electrophysiology (science); Environment; Event; Failure; Familial Hemiplegic Migraine; Female; Frequencies; Functional disorder; GLAST Protein; Genetic; Glutamate Transporter; Glutamates; Goals; Hour; Human; Image; Impairment; Incidence; Injury; Intervention; Lead; Literature; Long-Term Potentiation; Mediator of activation protein; Medical; Membrane; Military Personnel; Modeling; Mus; N-Methyl-D-Aspartate Receptors; Neurologic Dysfunctions; Neurons; Neuropil; Outcome; Pharmacology; Population; Prevalence; Publishing; Reporting; Resolution; Risk; Source; Stimulus; Survivors; Synapses; Synaptic plasticity; Testing; Tissues; Traumatic Brain Injury; Whole-Cell Recordings; Work; awake; base; calcium indicator; controlled cortical impact; experience; experimental study; extracellular; genetic manipulation; glutamatergic signaling; hippocampal pyramidal neuron; human model; in vivo; insight; male; mild traumatic brain injury; mortality; nervous system disorder; neuronal excitability; novel; postsynaptic; relating to nervous system; response; reuptake; sensory cortex; tool; treatment strategy; two photon microscopy; two-photon; uptake; virus genetics

Project Summary/Abstract Traumatic brain injury (TBI) is a major cause of mortality in both military and civilian populations. Meanwhile, TBI survivors are at greater risk for long-term increases in brain network hyper-excitability. Despite the global burden of TBI, there have been very few animal studies focused on mechanisms of excitability at synaptic and network levels. Our goal is to dissect the potential mechanisms underlying TBI-associated excitability after mild and severe brain injury. Recently, we observed an increased incidence of noncanonical glutamate release events, known as glutamatergic plumes, 48 hours after TBI. Increased frequency of plumes can facilitate spreading depolarization (SD) initiation. SD is an excitable phenomenon detected after TBI and is correlated with increased tissue damage and poor outcome. Thus, the prevalence of plumes suggests that the network is dysfunctional after TBI. We will examine this novel form of aberrant glutamate signaling in the brain, including the consequences of plumes on post-TBI excitability. We will employ simultaneous in vivo whole-cell recording and two-photon microscopy, alongside genetic tools to manipulate mechanisms of plumes. We will examine both male and female mice as females experience worse excitability-related complications post-TBI. In Aim 1, we will determine the source of plumes in controlled cortical impact (CCI) and mild TBI models, and how those mechanisms are altered in female mice. Based on our recent data, glutamate reuptake failure by astrocytes facilitates plumes. Thus, we hypothesize that astrocytic clearance mechanisms are responsible for glutamate plumes after TBI. To test this hypothesis, we will genetically ablate/enhance key astrocyte mediators of glutamate clearance in vivo. These experiments will establish a precise mechanism of glutamate dysfunction (plumes) in the post-TBI environment. In Aim 2, we will determine whether plumes can influence synaptic plasticity and network dynamics after TBI. Our pilot data shows calcium loading is enhanced during spontaneous neuronal activity after TBI. Based on current literature, glutamate dysfunction, such as increases in extracellular glutamate, can drive calcium influx in the naïve brain. Since elevation in intracellular calcium is an important feature of long-term potentiation (LTP) induction, we hypothesize that plumes in TBI drive brief but strong postsynaptic calcium elevations contributing to LTP and thus to an increase in network excitability. This is important since aberrant changes in synaptic plasticity are implicated in many neurological disorders. Notably, we will ask if and how plumes induce plasticity in dendrites by performing two-photon imaging of dendritic calcium transients after TBI. Furthermore, we will examine the mechanistic connection between plumes (and astrocytic mechanisms) and SD-associated calcium load after TBI. We hypothesize that plumes provide the stimulus necessary for the activation of NMDA receptors, thereby causing calcium to surge during SD after TBI. Thus, plumes may enhance the damage caused by both SD and neuronal calcium elevation after TBI. Our findings will result in novel and targeted mechanisms of post-traumatic excitability, including potential drug targets.

项目总结/摘要 创伤性脑损伤（TBI）是军人和平民死亡的主要原因。同时， TBI幸存者的大脑网络过度兴奋性长期增加的风险更大。尽管全球 由于TBI的负担，很少有动物研究集中在突触和突触后的兴奋性机制， 网络层次。我们的目标是剖析TBI相关兴奋性的潜在机制， 和严重的脑损伤最近，我们观察到非典型谷氨酸释放事件的发生率增加， 也就是脑外伤后48小时出现的放射性羽状物羽流频率的增加可以促进传播 去极化（SD）起始。SD是TBI后检测到的可兴奋现象，并且与TBI后的增加相关。 组织损伤和不良结局。因此，羽状物的普遍存在表明，在 创伤性脑损伤我们将研究这种大脑中异常谷氨酸信号的新形式，包括其后果。 对创伤后兴奋性的影响我们将采用同时在体内全细胞记录和双光子 显微镜，以及遗传工具来操纵羽流的机制。我们将检查男性和女性 雌性小鼠在TBI后经历更差的兴奋性相关并发症。在目标1中，我们将确定 可控皮质撞击（CCI）和轻度TBI模型中羽流的来源，以及这些机制如何改变 在雌性小鼠中。根据我们最近的数据，谷氨酸再摄取失败的星形胶质细胞促进羽毛。因此我们 假设星形胶质细胞清除机制负责TBI后谷氨酸羽流。为了验证这一 假设，我们将在体内基因消融/增强谷氨酸清除的关键星形胶质细胞介质。这些 这些实验将建立TBI后环境中谷氨酸功能障碍（羽状物）的精确机制。 在目标2中，我们将确定TBI后羽流是否会影响突触可塑性和网络动力学。 我们的初步数据显示，钙负荷增强TBI后自发神经元活动。基于 目前的文献中，谷氨酸功能障碍，如细胞外谷氨酸的增加，可以驱动钙内流， 在天真的大脑中。由于细胞内钙离子的升高是长时程增强（LTP）的一个重要特征， 我们假设TBI中的羽状物驱动短暂但强烈的突触后钙离子升高 有助于LTP，从而增加网络的兴奋性。这一点很重要，因为 突触可塑性与许多神经障碍有关。值得注意的是，我们将询问羽流是否以及如何诱导 通过对TBI后树突钙瞬变进行双光子成像，研究树突的可塑性。此外，委员会认为， 我们将研究羽状物（和星形胶质细胞机制）和SD相关的 TBI后钙负荷。我们假设羽流为NMDA的激活提供了必要的刺激 受体，从而导致钙激增期间SD TBI后。因此，羽流可能会增加损害 这是由TBI后SD和神经元钙升高引起的。我们的发现将导致新的和有针对性的 创伤后兴奋机制，包括潜在的药物靶点。