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/或母婴感染的早产儿，这两种情况都可能涉及兴奋性少突胶质细胞(Preol)的损伤。本项目的一个中心假设是，PVL的一个主要因素是诱导白质(WM)固有的细胞中谷氨酸受体(GluR)介导的兴奋毒性。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敏感性。我们的体外和体内兴奋性毒性损伤模型表明，早髓鞘OLs(PreOLS)选择性地易受兴奋性毒性和 缺氧性/缺血性损伤至少部分是由于钙(Ca~(2+))-渗透性α-氨基-3-羟基-5-甲基-4-异丙唑丙酸酯(AMPA)和海人藻酸(KA)离子亲性GluR的发育过度所致。我们已经证明，在PVL易感性的发育期(23-36周)，这些GluR在发育中的人类WM的OL上也有类似的过度表达。我们的体内和体外药理研究表明，钙离子通透性AMPA/KA受体拮抗剂可以减轻Preol的兴奋性毒性。我们最近扩展了我们的研究，以探讨GluRs在反复发生缺氧/缺血的临床相关环境中对前OL的作用，并表明亚阈值、亚致死性兴奋毒性损伤使前OL对损伤敏感，并且这种现象是AMPA/KA受体依赖的。在本提案中，我们将深入研究GluRs在正常人WM中的发育表达，并确定PVL后GluRs的表达是否发生变化(目标1)。我们将在体外测定致死性和亚致死性OGD后前OOL中Glur功能、表达和信号的变化(目标2)。同时，我们将确定体内致死性缺氧/缺血损伤和亚致死性缺氧后Glur功能和表达的变化(目标3)。最后，我们的目标是表征在缺氧/缺血白质损伤的易感性窗口期间白质中其他类型细胞上GluR的表达，并评估体内致死性缺氧/缺血或亚致死性缺氧后这些细胞中GluR的变化(Aim4)。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有效性。该项目的总体目标是更好地了解GluRs在PVL中的作用，以便设计新的针对年龄的治疗方法。

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.