Spreading Depolarizations and Post-Ischemic Injury

描述(由申请人提供)：目前缺血性中风的临床治疗选择非常有限，非常需要能够在中风发作后几个小时内安全实施的干预措施，并将神经元损失降至最低。我们早就知道在动物卒中模型中会出现重复的扩散性去极化(SD)波(类似于皮质扩散性抑制)，但直到最近才有令人信服的证据表明，在人类缺血性脑损伤后，重复扩散性去极化(SD)非常普遍。十二烷基硫酸钠在神经元和神经胶质细胞中产生大量的离子重新分布，需要消耗代谢能量来恢复动态平衡。脑缺血后重复性的十二烷基硫酸钠给脑组织带来了严重的额外代谢需求，而这种需求已经受到局部血流量减少的影响。因此，预防这些缺血后SD事件的发生和发展，甚至限制其有害后果的方法，可能会在临床医学上产生实质性的积极结果。我们发现，锌在SD的启动过程中起着重要的作用，并且在每次SD事件后，突触释放大量的锌。锌对神经元和神经胶质细胞都有毒性作用，我们的总体假设是锌离子的增加与SD相关，对脑缺血后的损伤有重要作用。我们认为这是由于锌在神经元和星形胶质细胞中的积累，从而1)降低了启动SD事件的阈值，2)作为钙兴奋毒性的上游触发因素。目的1的研究利用小鼠的海马片标本来评估锌在单个神经元和星形胶质细胞群体中释放和积聚的机制。目的2研究锌促进海马脑片SD发病的机制，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。AIM 3测试了以下假设，即在SD后，锌是钙离子释放的上游，并测试了干扰AIMS 1和2中确定的过程的干预措施是否显著改善了脑片和活体中的神经元活性。对突触结构和功能的切片研究将得到小鼠局灶性缺血的体内研究的补充。每个目标都应该独立地为该领域提供重要的新信息，当这些机制研究结合在一起时，应该提出新的方法来限制缺血性脑损伤的巩固和扩散。 与公共卫生相关：该项目旨在确定限制中风有害后果的新方法。中风后，大脑激活的异常波会导致损伤的扩散。该项目旨在确定新的方法，以限制这些不断蔓延的激活波的开始或后果，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.