Mechanisms of Excitotoxic Injury to Oligodendrocytes

脑室周围白质软化症（PVL）发生在患有脑缺氧/缺血和/或先前暴露于母胎感染的早产儿中，这两种情况都可能涉及兴奋性毒性前少突胶质细胞（preOL）损伤。本项目的一个中心假设是PVL的一个主要因素是诱导白色物质（WM）内在细胞中谷氨酸受体（GluR）介导的兴奋性毒性。我们进一步假设，GluRs的发育状态增加了WM对兴奋性毒性损伤的易感性。我们的兴奋性毒性损伤的体外和体内模型表明，髓鞘形成前的OL（preOL）选择性地易受兴奋性毒性的影响， 缺氧/缺血性损伤至少部分是由于钙（Ca 2+）-可渗透的α-氨基-3-羟基-5-甲基-4-异恶唑丙酸酯（AMPA）和红藻氨酸（KA）离子型GluRs的发育过表达。我们已经表明，这些GluR在PVL易感性的发育窗口（23-36孕周）期间在发育中的人WM中的OL上类似地过表达。我们在体内和体外的药理学研究表明，前OL兴奋毒性可以减弱钙渗透AMPA/KA受体拮抗剂。我们最近扩展了我们的研究，以解决临床相关的缺氧/缺血反复发作的情况下，GluRs对前OL的作用，并表明，亚阈值，亚致死兴奋性毒性损伤致敏前OL损伤，这种现象是AMPA/KA受体依赖性。在本提案中，我们将深入研究正常人WM中GluRs的发育表达，并确定PVL（目的1）后表达是否改变。我们将确定体外前OL中致死OGD和亚致死OGD后GluR功能、表达和信号传导的变化（目的2）。与此同时，我们将确定体内致死性缺氧/缺血性损伤和亚致死性缺氧后GluR功能和表达的变化（目的3）。最后，我们的目标是表征在缺氧/缺血性白色物质损伤的脆弱性窗口期间，在白色物质中的其他细胞类型上的GluR的表达，并评估在体内致死性缺氧/缺血或亚致死性缺氧后这些细胞中的GluR改变（Aim 4）。在整个提案中，我们研究了针对GluRs的治疗策略的作用机制和疗效。该项目的总体目标是更好地了解GluRs在PVL中的作用，以设计新的年龄特异性疗法。

Periventricular leukomalacia (PVL) occurs in preterm infants suffering cerebral hypoxia/ischemia and/or prior exposure to maternal-fetal infection, both of which can involve excitotoxic preoligodendrocyte (preOL) injury. A central hypothesis in this Project is that a major factor in PVL is the induction of glutamate receptor (GluR)-mediated excitotoxicity in cells intrinsic to white matter (WM). We further hypothesize that the developmental status of GluRs increases susceptibility of the WM to excitotoxic injury. Our in vitro and in vivo models of excitotoxic injury demonstrated that premyelinating OLs (preOLs) are selectively vulnerable to excitotoxicity and hypoxic/ischemic injury at least in part due to a developmental overexpression of calcium (Ca2+)-permeable alpha amino-3-hydroxy-5-methyl-4-isox-azole propionate (AMPA) and kainate (KA) ionotropic GluRs. We have shown that these GluRs are similarly overexpressed on OLs in developing human WM during the developmental window of vulnerability to PVL (23-36 gestational weeks). Our pharmacologic studies in vivo and in vitro demonstrate that preOL excitotoxicity can be attenuated by Ca2+-permeable AMPA/KA receptor antagonists. We have recently extended our studies to address the role of GluRs on preOLs in the clinically relevant setting of recurrent episodes of hypoxia/ischemia, and show that subthreshold, sublethal excitotoxic injury sensitizes preOLs to injury, and that this phenomenon is AMPA/KA receptor-dependent. In the present proposal, we will characterize in-depth the developmental expression of GluRs in normal human WM and determine whether expression is altered following PVL (Aim 1). We will determine alterations in GluR function, expression and signaling following lethal OGD and sublethal OGD in preOLs in vitro (Aim 2). In parallel, we will determine alterations in GluR function and expression following lethal hypoxic/ischemic injury and sublethal hypoxia in vivo (Aim 3). Finally, we aim to characterize expression of GluRs on other cell types in white matter during the window of vulnerability to hypoxic/ischemic white matter injury, and to evaluate GluR alterations in these cells following lethal hypoxia/ischemia or sublethal hypoxia in vivo (Aim4). Throughout the proposal, we examine mechanism of action and efficacy of therapeutic strategies targeting GluRs. The overall goal of this project is to gain improved understanding of the role of GluRs in PVL in order to design new age-specific therapies.