EXCITOTOXICITY IN CIRCULATORY ARREST--BRAIN INJURY

描述（逐字从申请人的摘要）：该项目的目标是 明确低温致兴奋性神经元损伤的机制 循环停止（HCA），并制定预防方法。在我们的犬 HCA生存模型，复制心脏病期间的临床经验 手术，狗在18 ℃下停止循环2小时 持续神经功能缺损和选择性 神经元死亡我们最初发现， 受体拮抗剂在HCA诱导的损伤之前和之后减少神经元 坏死我们现在已经表明，神经元死亡可以通过凋亡或 坏死机制我们发现HCA后谷氨酸的释放导致 一氧化氮（NO）的积累，其介导神经元死亡， 神经元型一氧化氮合酶（NOS）的抑制减少了NO的产生， 防止细胞凋亡 我们假设线粒体功能障碍决定了 HCA后通过凋亡或坏死引起的迟发性兴奋毒性神经元损伤， 缺血预处理（IPC）可以防止神经元凋亡， 通过打开内表面ATP依赖性钾通道， 线粒体膜我们进一步假设NO可能作为一种中介物 IPC对神经元的损伤和保护作用。初步 我们的实验表明，二氮嗪，一种ATP依赖性钾通道， 开松剂能产生药理作用的IPC， 作用于线粒体内膜的心肌细胞凋亡。在我们 在犬模型中，二氮嗪显示出几乎完全消除神经功能缺损 HCA后，在选择的神经元群体中细胞凋亡减少。我们 缺氧可激活HIF-1，诱导iNOS的表达， 产生NO，这是IPC晚期形式的推定分子途径。 我们建议：（1）测量线粒体功能障碍的代谢指标， 在我们的犬模型中使用HCA后的'H'和'P MRSI的特定脑区 和（2）将这些与神经元存活、凋亡和坏死相关联;（3） 检查二氮嗪作为神经保护手段的药理学IPC和（4） 确定如何打开钾离子通道改变其 （5）确定NO是如何作为介导IPC的 保护和保护大脑。这项研究将加快临床 在兴奋性毒性级联反应中使用抑制剂并促进IPC的开发 通过药理学手段提供脑保护， 心血管手术中HCA后的患者结局。

DESCRIPTION (Verbatim from Applicant's Abstract): The goal of the project is to define the mechanisms of excitotoxic neuronal injury caused by hypothermic circulatory arrest (HCA) and to develop the means to prevent it. In our canine survival model of HCA, replicating clinical experience during cardiac operations, dogs subjected to 2 hours of circulatory arrest at 18degreesC sustain a consistent neurologic deficit and histologic pattern of selective neuronal death. We originally showed that administration of selective glutamate receptor antagonists before and after HCA-induced injury reduced the neuronal necrosis. We have now shown that neuronal death can occur by apoptotic or necrotic mechanisms. We showed that glutamate release after HCA results in accumulation of nitric oxide (NO), which mediates neuronal death and that inhibition of neuronal nitric oxide synthase (NOS) reduces production of NO in the brain and prevents apoptosis. We hypothesize that mitochondrial dysfunction determines the mechanism of delayed excitotoxic neuronal injury after HCA by apoptosis or necrosis and that neuronal apoptosis can be prevented by ischemic preconditioning (IPC), achieved pharmacologically by opening ATP-dependent potassium channels on the inner mitochondrial membrane. We further hypothesize that NO may act as a mediator both of neuronal injury and neuronal protection by IPC. In preliminary experiments we have shown that diazoxide, an ATP-dependent potassium channel opener can produce pharmacologic IPC and that that this agent can prevent apoptosis in cardiomyocytes acting on the inner mitochondrial membrane. In our canine model, diazoxide has shown near total elimination of neurologic deficit following HCA, with reduction in apoptosis in select neuronal populations. We also showed that hypoxia can activate HIF-1 with induction of iNOS and production of NO, a putative molecular pathway of the late form of IPC. We propose to: (1) measure metabolic indicators of mitchondrial dysfunction in specific brain regions using 'H and 'P MRSI following HCA in our canine model and (2) correlate these with neuronal survival, apoptosis and necrosis; (3) to examine pharmacologic IPC with diazoxide as means of neuroprotection and (4) determine how opening the potassium channels in the mitochondrion alters its function to effect IPC; (5) to establish how NO can act as mediator of both injury and protection in the brain. This research will expedite the clinical use of inhibitors in the excitotoxic cascade and facilitate exploitation of IPC by pharmacologic means to provide cerebral protection resulting in better patient outcomes after HCA in cardiovascular operations.