Secondary Calcium Responses and Excitotoxicity

继发性钙反应和兴奋性毒性

基本信息

批准号：
6466441
负责人：
Claude W Shuttleworth
金额：
$ 24.49万
依托单位：
UNIVERSITY OF NEW MEXICO
依托单位国家：
美国
项目类别：
财政年份：
2002
资助国家：
美国
起止时间：
2002-04-01 至 2006-03-31
项目状态：
已结题

项目摘要

DESCRIPTION (provided by applicant): Nerve cell death resulting from stroke, head injury and a range of degenerative disorders is a major cause of mortality and also has devastating effects on the lives of survivors. Understanding the mechanisms of this cell death is an important goal, since development of successful treatments could greatly minimize the subsequent social cost of these conditions. A common triggering event in neurodegeneration is widely held to be the excessive release of the excitatory transmitter glutamate, and subsequent massive Ca2+ influx. This process has been termed "excitotoxicity." We have investigated excitotoxic mechanisms in restricted regions of nerve dendrites, and shown that glutamate receptor agonists initiate sustained Ca2+ elevations at these sites, and that these "secondary Ca2+ responses" then spread very slowly throughout neurons and lead to cell death. Our hypothesis is that fine dendrites, being richly endowed with Ca2+ -permeable glutamate receptors and channels, act as initiation sites of excitotoxic Ca2+ signals, and that procedures to prevent the initiation and/or spread of secondary Ca2+ responses will provide important new approaches to limiting cell death. We have exploited differences in excitotoxic vulnerability between inbred murine strains (C57B1/6 and C57B1/10) to clearly demonstrate the involvement of these responses in excitotoxic cell death in intact slice preparations. As well as implicating secondary responses as key determinants of excitotoxic vulnerability, this work has resulted in novel preparations that permit the first rigorous investigations of 1) mechanisms underlying secondary response initiation, 2) mechanisms by which secondary responses spread through dendritic processes and 3) how secondary responses trigger cellular damage. Acute murine hippocampal slices will be studied using combined electrophysiological and single-cell Ca2+ imaging approaches. Secondary responses will be initiated using glutamate receptor agonists, and pharmacological approaches used to identify the routes of Ca2+ entry involved in triggering, and progression of these events. Studies to determine the basis for murine strain differences in secondary response generation will be complemented by immunohistochemical approaches. A further set of mechanistic studies will test the hypothesis that mitochondrial Ca2+ loading is a key event linking secondary responses to cellular damage, using imaging methods to assess mitochondrial function, Ca2+ loading and production of reactive oxygen species. In the long term, results from these studies should provide a basis for novel interventions designed at preventing cell death following excitotoxic stimulation at sites remote from neuronal somata. such as might occur in a very wide range of neurological disorders.

描述（由申请人提供）：中风导致的神经细胞死亡，头部受伤和一系列退行性疾病是死亡的主要原因并对幸存者的生活造成毁灭性影响。了解这种细胞死亡的机制是一个重要的目标，因为成功的治疗可以大大减少随后的社会成本这些条件。神经退行性疾病中常见的触发事件被广泛认为兴奋性递质谷氨酸的过度释放，以及随后大量 Ca2+ 流入。这个过程被称为“兴奋性毒性”。我们研究了神经受限区域的兴奋性毒性机制树突，并表明谷氨酸受体激动剂启动持续的 Ca2+ 这些地点的海拔，然后这些“次级 Ca2+ 反应” 在整个神经元中传播非常缓慢并导致细胞死亡。我们的假设是细小的树突，富含Ca2+可渗透的谷氨酸受体和通道，作为兴奋性毒性 Ca2+ 信号的起始位点，以及防止二次 Ca2+ 的引发和/或扩散的程序反应将为限制细胞死亡提供重要的新方法。我们有利用近交系小鼠之间兴奋性毒性脆弱性的差异菌株（C57B1/6 和 C57B1/10）以清楚地证明这些菌株的参与完整切片制剂中兴奋性毒性细胞死亡的反应。也表明次级反应是兴奋性毒性的关键决定因素脆弱性，这项工作产生了新颖的准备工作，使首次严格调查 1) 二次反应的机制启动，2）次级反应通过树突传播的机制过程以及 3) 次级反应如何触发细胞损伤。急性鼠类海马切片将结合电生理学和单细胞 Ca2+ 成像方法。将启动二次响应使用谷氨酸受体激动剂和药理学方法确定参与触发和进展的 Ca2+ 进入途径这些事件。确定小鼠品系差异基础的研究免疫组织化学将补充二次反应的产生接近。进一步的一组机制研究将检验以下假设：线粒体 Ca2+ 负荷是将次级反应与细胞损伤，使用成像方法评估线粒体功能，Ca2+ 活性氧的负载和产生。从长远来看，结果这些研究应该为设计新颖的干预措施提供基础防止远离远离的部位的兴奋性毒性刺激后的细胞死亡神经元体体。例如可能发生在非常广泛的神经系统疾病中失调。