Spreading Depolarizations and Post-Ischemic Injury

描述（由申请人提供）：目前缺血性卒中的临床治疗选择非常有限，非常需要能够在卒中发作后数小时内安全给药并最大限度减少神经元损失的干预措施。人们早就知道，在动物中风模型中会出现重复性扩散去极化（SD）波（类似于皮层扩散性抑制），但直到最近才令人信服地表明，SD在人类缺血性脑损伤后非常普遍。SD在神经元和神经胶质中产生大量的离子再分布，需要消耗代谢能量来恢复稳态。缺血后的重复SD对脑组织产生了严重的额外代谢需求，而脑组织已经受到局部血流减少的影响。因此，预防这些缺血后SD事件的发作和进展，或甚至限制其有害后果的方法可能在临床医学中具有实质性的积极结果。我们已经发现，Zn ~（2+）可以在SD的启动中发挥重要作用，并且在每个SD事件之后，从突触释放Zn ~（2+）是实质性的。Zn 2+以前已被证明是有毒的神经元和神经胶质细胞，我们的总体假设是，Zn 2+增加与SD作出了重大贡献，缺血后的损伤。我们认为这是由于神经元和星形胶质细胞中的Zn 2+积累，这反过来1）降低了SD事件的起始阈值，2）作为Ca 2+兴奋性毒性的上游触发因素。目的1中的研究利用来自小鼠的海马切片制备物来评估单个神经元和星形胶质细胞群体中Zn 2+释放和积累的机制。目的2探讨锌离子促进海马脑片SD的机制，包括抑制星形胶质细胞摄取功能和上调神经元NMDA受体功能。目的3测试Zn 2+是SD后Ca 2+失调的上游的假设，并测试破坏目的1&2中鉴定的过程的干预是否在脑切片和体内提供神经元活力的显著改善。突触结构和功能的切片研究将通过小鼠局灶性缺血的体内研究来补充。每个目标都应该独立地为该领域提供重要的新信息，当结合在一起时，这些机制研究应该提出新的方法来限制缺血性脑损伤的巩固和扩散。 公共卫生相关性：该项目旨在确定新的方法来限制中风的有害后果。中风后，大脑激活的异常波有助于损伤的扩散。该项目旨在确定新的方法来限制这些激活扩散波的发作或后果，从而改善功能恢复。

DESCRIPTION (provided by applicant): Current options for clinical treatment of ischemic strokes are currently very limited and there is a great need for interventions that can be safely administered during a period of several hours following the onset of a stroke and minimize neuronal loss. It has long been known that repetitive waves of spreading depolarizations (SD) (analogous to cortical spreading depression) occur in animal stroke models, but only recently has it been convincingly shown that SDs are very prevalent following human ischemic brain injuries. SDs produce massive ionic redistributions in neurons and glia, requiring the expenditure of metabolic energy to restore homeostasis. The repetitive SDs following ischemia place a severe additional metabolic demand on brain tissue that is already compromised by reductions in local blood flow. Thus approaches to prevent the onset and progression of these post-ischemic SD events, or even to limit their deleterious consequences, are likely to have substantial positive outcomes in clinical medicine. We have discovered that Zn2+ can play an important role in initiation of SD, and that Zn2+ release from synapses is substantial following each SD event. Zn2+ has previously been demonstrated to be toxic to both neurons and glia, and our overall hypothesis is that Zn2+ increases associated with SD make a significant contribution to injury following ischemia. We propose that this is due to Zn2+ accumulation in both neurons and astrocytes, which in turn 1) lowers the threshold for initiation of SD events and 2) serves as an upstream trigger for Ca2+ excitotoxicity. Studies in Aim 1 utilize hippocampal slice preparations from mice to evaluate the mechanisms of Zn2+ release and accumulation in single neurons and populations of astrocytes. Aim 2 examines mechanisms by which Zn2+ can facilitate the onset of SD in hippocampal slices, including inhibition of astrocyte uptake function and up-regulation of neuronal NMDA receptor function. Aim 3 tests the hypothesis that Zn2+ is upstream of Ca2+ deregulation following SD, and tests whether interventions that disrupt the processes identified in Aims 1&2 provide significant improvements in neuronal viability in brain slice and in vivo. Slice studies of synaptic structure and function will be complemented by in vivo studies of focal ischemia in mice. Each aim should independently provide significant new information for the field, and when taken together, these mechanistic studies should suggest novel approaches to limit the consolidation and spread of ischemic brain injury. PUBLIC HEALTH RELEVANCE: This project is designed to identify new approaches to limit the deleterious consequences of a stroke. Following a stroke, aberrant waves of brain activation contribute to the spread of injury. This project is designed to identify new approaches to limit the onset, or consequences, of these spreading waves of activation and thereby improve functional recovery.