Glutamate Receptors in Hypoxic-ischemic Injury to Developing Oligodendrocytes

描述(由申请人提供)：对发育中的大脑的缺氧缺血损伤会导致毁灭性的神经后果。值得注意的是，缺氧缺血性脑损伤的模式高度依赖于年龄。在足月儿中，缺氧缺血主要影响大脑皮层，具有特征性的神经元丢失。然而，在早产儿中，缺氧缺血选择性地影响脑白质，并对发育中的少突胶质细胞(OL)造成显著损伤，这种疾病被称为脑室周围白质软化症(PVL)。发育中的OL(Pre-PMinating OL，简称“Preol”)对缺氧缺血损伤非常敏感，是PVL的主要细胞底物。在体内和体外，谷氨酸受体(GluR)的表达受到发育的调节，离子型GluRs(IGluRs)介导前OLS的缺氧缺血损伤，而代谢性GluRs(MGluRs)可以调节这种损伤。然而，特异性的iGluRs和mGluRs在缺氧缺血型Preol损伤中的作用和信号机制仍很不清楚。该方案的中心假设是，钙离子通透性的iGluRs介导缺氧缺血型Preol损伤，而第1组mGluRs可以调节这种损伤，导致iGluRs和mGluRs之间的分子相互作用和不同的受体后信号事件的整合。我们将重点探讨iGluRs和mGluRs之间的串扰在Preol损伤中的机制。本项目的目标是为缺氧缺血型Preol损伤的年龄特异性机制提供新的见解，并确定潜在的年龄特异性治疗策略，以治疗导致脑白质疾病的Preol损伤。这项建议的目的1是确定在Preol兴奋毒性中iGluR功能和信号的变化顺序，目的是确定特定的治疗靶点。目的2将扩展我们的初步结果，并进一步研究mGluRs在Preol损伤中在体内发生脑白质损伤中的新作用。目的3将确定iGluRs和mGluRs相互作用的分子机制。我们将研究mGluR调节是否导致iGluR亚单位表达、磷酸化状态和内在化的变化，以及细胞内钙离子和氧化应激，以及Akt(蛋白激酶B)、CaMKII(钙/钙调蛋白激酶II)、CaN(钙调神经磷酸酶)和PKC(蛋白激酶C)等信号分子在mGluR介导的Preol损伤的调节中的具体作用。该项目的完成将有助于阐明缺氧缺血型Preol损伤的新机制，并为开发治疗策略确定新的靶点，以控制导致脑白质障碍的Preol损伤，例如PVL，目前还没有针对这种疾病的特定治疗方法。 公共卫生相关性：脑室周围白质软化(PVL)是早产儿脑损伤的主要形式，也是脑性瘫痪的最常见原因。在美国每年出生的56000名早产儿中，PVL影响高达50%，但目前还没有针对这种严重的人类疾病的治疗方法。本项目旨在确定离子型和代谢型谷氨酸受体在PVL细胞底物--发育中的少突胶质细胞缺氧缺血损伤中的分子相互作用机制。通过该项目获得的科学知识可能有助于PVL预防策略的制定和脑性瘫痪儿童的护理。

DESCRIPTION (provided by applicant): Hypoxic-ischemic injury to the developing brain leads to devastating neurological consequences. Strikingly, the pattern of hypoxic-ischemic brain injury is highly age-dependent. In term infants, hypoxia-ischemia predominantly affects cerebral cortex with characteristic neuronal loss. However, in premature infants, hypoxia- ischemia selectively affects cerebral white matter with prominent injury to the developing oligodendrocyte (OL), a disorder termed periventricular leukomalacia (PVL). The developing OL (pre-myelinating OL, termed "preOL") is highly vulnerable to hypoxic-ischemic injury and is the major cellular substrate of PVL. We have shown that glutamate receptor (GluR) expression is developmentally regulated on OLs in vivo and in vitro, and that ionotropic GluRs (iGluRs) mediate hypoxic-ischemic injury to preOLs, but metabotropic GluRs (mGluRs) can modulate this injury. However, the role of specific iGluRs and mGluRs in hypoxic-ischemic preOL injury and the signaling mechanisms remain largely unknown. The central hypothesis of the proposal is that Ca2+-permeable iGluRs mediate hypoxic-ischemic preOL injury and that group 1 mGluRs can modulate this injury, entailing the molecular interplay between iGluRs and mGluRs and the integration of distinct post-receptor signaling events. We will focus on determining the mechanisms of the crosstalk between iGluRs and mGluRs in preOL injury. The goal of this project is to provide new insights into the age-specific mechanisms of hypoxic-ischemic preOL injury, and to determine potential age-specific therapeutic strategies for treating preOL injury that underlies cerebral white matter disorders. Aim 1 of this proposal is to determine the sequence of alterations of iGluR function and signaling in preOL excitotoxicity, with the aim to identify specific therapeutically accessible targets. Aim 2 will expand upon our preliminary results and further investigate the novel role of mGluRs in preOL injury in developing cerebral white matter injury in vivo. Aim 3 will determine the molecular mechanisms of the interplay between iGluRs and mGluRs. We will examine whether mGluR modulation leads to changes in iGluR subunit expression, phosphorylation state, and internalization, and also investigate intracellular Ca2+ and oxidative stress, and the specific roles of signaling molecules such as Akt (protein kinase B), CaMKII (Ca2+/calmodulin kinase II), CaN (calcineurin), and PKC (protein kinase C) in the modulation of iGluR-mediated preOL injury by mGluRs. Completion of this project will help to elucidate novel mechanisms of hypoxic-ischemic preOL injury and to identify new targets for the development of therapeutic strategies to control preOL injury that underlies cerebral white matter disorders, such as PVL, for which no specific therapy currently exists. PUBLIC HEALTH RELEVANCE: Periventricular leukomalacia (PVL) is the predominant form of brain injury in the premature infant, and the most common cause of cerebral palsy. PVL affects up to 50% of the 56,000 premature infants born in the U. S. every year, yet currently no therapy exists for this serious human disorder. This project seeks to determine the mechanisms of the molecular interplay between ionotropic and metabotropic glutamate receptors in hypoxic- ischemic injury to the developing oligodendrocyte - the cellular substrate of PVL. The scientific knowledge to be acquired through this project is of likely benefit to the development of preventive strategies for PVL and the care of children with cerebral palsy.