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.

项目摘要/摘要 创伤性脑损伤（TBI）是军事和平民死亡率的主要原因。同时， TBI冲浪者在大脑网络高兴趣性中长期增加的风险更大。尽管有全球 TBI负担，很少有动物研究重点是突触和 网络级别。我们的目标是剖析中期之后TBI相关的潜在机制 和严重的脑损伤。最近，我们观察到了非规范谷氨酸释放事件的增加， TBI后48小时被称为谷氨酸能羽。羽流的频率增加可以促进扩散 去极化（SD）倡议。 SD是TBI后检测到的令人兴奋的现象，与增加相关 组织损伤和不良预后。这就是羽流的患病率表明该网络在 TBI。我们将检查这种新颖的形式的大脑中异常谷氨酸信号传导，包括后果 TBI后令人兴奋的李子。我们将采用简单的体内全细胞记录和两光子 显微镜，以及遗传工具，以操纵羽毛机制。我们将检查男性和女性 TBI后，作为雌性的小鼠作为女性的激动人心的并发症。在AIM 1中，我们将确定 受控皮质冲击（CCI）和轻度TBI模型的羽流源，以及如何改变这些机制 在雌鼠中。根据我们最近的数据，星形胶质细胞收藏夹的谷氨酸再摄取失败。那，我们 假设星形胶质细胞清除机制是TBI后负责谷氨酸羽状的。测试这个 假设，我们将通常在体内烧蚀/增强谷氨酸清除的关键星形胶质细胞介质。这些 实验将在TBI后环境中建立谷氨酸功能障碍（羽）的精确机制。 在AIM 2中，我们将确定李子是否可以影响TBI后的突触可塑性和网络动力学。 我们的试点数据显示，在TBI后发起神经元活性期间，钙负荷得到了增强。基于 当前的文献，谷氨酸功能障碍，例如细胞外谷氨酸的增加，可以驱动钙影响力 在天真的大脑中。由于细胞内钙的升高是长期增强的重要特征（LTP） 诱导，我们假设TBI驱动器中的羽毛短暂，但突触后钙升高很强 有助于LTP，从而增加网络兴奋性。这很重要，因为异常变化 在许多神经系统疾病中隐含突触可塑性。值得注意的是，我们将询问羽毛是否以及如何影响 TBI后，通过对树突状钙瞬变进行两光子成像，在树突中的可塑性。此外， 我们将检查羽毛（和星形细胞机制）与SD相关的机械连接 TBI后的钙负载。我们假设羽流提供了激活NMDA所需的刺激 受体，从而导致TBI后SD期间钙涌动。那就可以增强损坏 TBI后由SD和神经元钙抬高引起。我们的发现将导致新颖和针对性 创伤后兴奋的机制，包括潜在的药物靶标。