Glutamate Receptors in Hypoxic-ischemic Injury to Developing Oligodendrocytes

描述（由申请人提供）：发育中的大脑缺氧缺血性损伤导致毁灭性的神经系统后果。引人注目的是，缺氧缺血性脑损伤的模式高度依赖于年龄。在足月婴儿中，缺氧缺血主要影响大脑皮层，并伴有特征性的神经元损失。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，这种疾病称为脑室周围白质软化症（PVL）。正在发育的OL（预髓鞘OL，称为“preOL”）极易受到缺氧缺血性损伤，是PVL的主要细胞底物。我们发现，在体内和体外，谷氨酸受体（GluR）的表达受ol的发育调控，嗜离子型GluRs （iGluRs）介导ol的缺氧缺血性损伤，而代谢型GluRs （mGluRs）可以调节ol的缺氧缺血性损伤。然而，特异性iGluRs和mGluRs在缺氧缺血性ol前损伤中的作用及其信号机制仍不清楚。该提案的中心假设是Ca2+渗透性iGluRs介导缺氧缺血性ol前损伤，并且1组mGluRs可以调节这种损伤，涉及iGluRs和mGluRs之间的分子相互作用以及不同受体后信号传导事件的整合。我们将着重于确定在ol前损伤中iGluRs和mGluRs之间的串扰机制。该项目的目的是为缺氧缺血性ol前损伤的年龄特异性机制提供新的见解，并确定治疗脑白质紊乱的ol前损伤的潜在年龄特异性治疗策略。本提案的目的1是确定ol前兴奋性毒性中iGluR功能和信号的改变序列，目的是确定特定的治疗可达靶点。Aim 2将扩展我们的初步结果，并进一步研究mGluRs在ol前损伤中发生脑白质损伤的新作用。目的3将确定iGluRs和mGluRs之间相互作用的分子机制。我们将研究mGluR调节是否会导致iGluR亚基表达、磷酸化状态和内化的变化，并研究细胞内Ca2+和氧化应激，以及Akt（蛋白激酶B）、CaMKII （Ca2+/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mGluRs调节iGluR介导的preOL损伤中的具体作用。该项目的完成将有助于阐明缺氧缺血性前ol损伤的新机制，并为开发控制脑白质疾病（如PVL）的前ol损伤的治疗策略确定新的靶点，目前尚无特异性治疗方法。

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.