The dynamic balance between neuronal volume and chloride handling in network excitability after traumatic brain injury

创伤性脑损伤后网络兴奋性中神经元体积和氯处理之间的动态平衡

• 批准号: 10661080
• 负责人: PUNAM MADHUKAR SAWANT-POKAM
• 金额: $ 38.5万
• 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: 2022-07-15 至 2027-06-30
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10661080
• 关键词: Affect; Alcian Blue; Anions; Astrocytes; Biophysics; Blood Vessels; Brain Injuries; Cations; Cause of Death; Cells; Cerebral Edema; Chlorides; Clinical; Complex; Data; Development; Down-Regulation; Drug Targeting; Edema; Electric Capacitance; Elements; Equilibrium; Event; Extracellular Matrix; Failure; Female; GABA Receptor; Gel; Gelatinase B; Genetic; Glutamates; Goals; Histological Techniques; Homeostasis; Hour; Image; Impairment; Injury; Intervention; Label; Link; Matrix Metalloproteinases; Mediating; Mediator; Membrane; Membrane Potentials; Monitor; Morbidity - disease rate; Movement; Mus; Neurons; Outcome; Pattern; Population; Potassium; Predisposition; Process; Publishing; Receptor Activation; Recovery; Regulation; Resistance; Resolution; Role; Seizures; Sex Differences; Shapes; Stains; Swelling; Testing; Therapeutic Intervention; Time; Traumatic Brain Injury; Up-Regulation; Water; Water Movements; Whole-Cell Recordings; Work; cell type; chloride-cotransporter potassium; controlled cortical impact; extracellular; genetic manipulation; in vivo; in vivo two-photon imaging; insight; male; mild traumatic brain injury; mortality; neuronal excitability; novel; protective effect; response; reuptake; severe injury; success; synaptic inhibition; therapeutic target; tool; transmission process; two photon microscopy; two-photon

Project Summary/Abstract Cerebral edema is the most significant cause of morbidity and mortality following traumatic brain injury (TBI). Though a major target for intervention, current treatments have limited success, perhaps due to the incomplete understanding of edema mechanisms. The task of this proposal is to dissect potential mechanisms underlying TBI-associated neuronal edema, with a particular focus on how edema affects neuronal and network excitability after mild and severe injury. We recently found that neuronal swelling is associated with reduced expression of the cation chloride transporter KCC2 48 hours after controlled cortical impact (CCI) TBI. To our initial surprise, we discovered that neuronal swelling coincided with reduced cellular and network excitability 48 hours post- CCI. And furthermore, when we treated neuronal swelling we observed increased excitability - suggesting that neuronal volume and excitability changes are intimately linked. These results were unexpected, as we predicted that lower levels of KCC2 expression would increase intraneuronal chloride and reduce the efficacy of inhibition – an effect that would increase excitability. However, the excitability of neurons is also affected by their shape: an edematous neuron is less excitable, which may overpower effects of KCC2 on chloride homeostasis. Moreover, despite continued reductions in KCC2 expression, neuronal volume is normalized by one-week post-CCI. This implies that mechanisms beyond KCC2 expression are involved in neuronal volume regulation. This proposal focuses on mechanisms of neuronal edema and its resolution after TBI. In addition, these studies will examine the contributions of neuronal and astrocytic mechanisms on excitability following injury and during recovery. We will test our hypotheses using genetic manipulations, simultaneous in vivo whole cell recording and two- photon microscopy, and histological techniques. In Aim 1, we examine the mechanisms of neuronal edema at 48 hours and at 1 week after CCI and mild TBI, time points when edema is maximal and resolved, respectively. We hypothesize that extracellular impermeant anions are the missing element in the edema response. In Aims 2 & 3, we examine how neuronal volume (and associated chloride shifts) affect excitability at 48 hours and one week after TBI. In Aim 2, we examine to what extent: 1. GABAergic activity is rendered excitatory after TBI, and 2. neuronal volume impacts mechanisms of chloride and water movement across neuronal membranes to influence inhibition. In Aim 3, we assess the effects of neurons (i.e., neuronal volume and chloride transport) and astrocytes (potassium and glutamate clearance) on excitability. In particular, we will examine susceptibility to seizures and spreading depolarizations, which are two key consequences of the hyperexcitable network after TBI. We hypothesize that failure to reuptake potassium and glutamate by astrocytes may contribute - in conjunction with neuronal effects - to enhanced excitability. Our findings will result in a mechanistic understanding of neuronal edema and excitability, including potential drug targets, which in turn could prompt a reassessment of how and why we treat edema clinically.

项目摘要/摘要 脑水肿是创伤性脑损伤（TBI）后发病和死亡率的最重要原因。 尽管干预的主要目标，但当前治疗的成功有限，也许是由于不完整的 了解水肿机制。该提案的任务是剖析潜在机制 TBI相关的神经元水肿，特别关注水肿如何影响神经元和网络令人兴奋 轻度和重伤后。我们最近发现，神经元肿胀与降低的表达有关 受控皮质冲击（CCI）TBI后48小时，阳离子氯化物转运蛋白KCC2。令我们最初的惊喜， 我们发现，神经元肿胀与降低的细胞和网络刺激性相吻合，48小时 CCI。此外，当我们治疗神经元肿胀时，我们观察到兴奋的增加 - 表明 神经元音量和令人兴奋的变化密切相关。这些结果是出乎意料的，正如我们预测的那样 较低水平的KCC2表达将增加氯化神经元的氯化物并降低抑制效率 - 会增加兴奋的效果。但是，神经元的兴奋也受到其形状的影响： 水肿的神经元不那么令人兴奋，这可能会压倒KCC2对氯化物稳态的影响。而且， 尽管KCC2表达持续降低，但通过一周后CCI将神经元体积归一化。这 意味着超出KCC2表达的机制与神经元体积调节有关。这个建议 重点关注神经元水肿的机制及其在TBI后的分辨率。此外，这些研究将检查 神经元和星形胶质细胞机制对受伤后和恢复期间令人兴奋的贡献。 我们将使用遗传操作，简单的体内整体记录和两种方法来检验我们的假设 光子显微镜和组织学技术。在AIM 1中，我们检查了48个神经元水肿的机制 小时和在CCI和轻度TBI之后的1周，水肿分别是最大和解决的时间点。我们 假设细胞外不受欢迎的阴离子是水肿反应中缺失的元素。在目标2＆ 3，我们检查神经元体积（以及相关的氯化物移位）如何在48小时零一个星期影响兴奋性 在TBI之后。在AIM 2中，我们检查了何种程度：1。GABA能活性在TBI之后引起兴奋性和2。 神经元体积影响氯化物的机制和跨神经元机制的水运动以影响 在AIM 3中，我们评估了神经元（即神经元和氯化物转运）的影响 星形胶质细胞（钾和谷氨酸清除）兴奋性。特别是，我们将研究对 癫痫发作和散布去极化，这是TBI后过度可见网络的两个关键后果。 我们假设未能通过星形胶质细胞重新摄取钾和谷氨酸 - 可能会造成 具有神经元效应 - 增强了令人兴奋的效果。我们的发现将导致对 神经元水肿和令人兴奋的人，包括潜在的药物靶标，这又可能会重新评估 我们如何以及为什么在临床上治疗水肿。