Targeting glutamate carboxypeptidase in perinatal brain injury

项目概要/摘要 尽管在新生儿护理和治疗性低温的实施方面取得了重大进展， 新生儿脑病的早产儿存活者发展认知和学习缺陷的风险很高 即使在没有功能性运动缺陷的情况下。最近的研究表明小脑功能障碍与 长期学习障碍。浦肯野细胞发育受损与 小脑联合学习障碍。小胶质细胞已被证明在神经系统疾病中发挥重要作用。 小脑皮质的主要输出神经元浦肯野细胞的发育。子宫内炎症 导致小胶质细胞活化，导致浦肯野细胞发育不良和小脑学习 赤字小脑中活化的小胶质细胞过度表达谷氨酸羧肽酶II（GCPII）， 其水解丰富的神经肽N-乙酰基谷氨酸盐（NAAG，一种特异性激动剂， 代谢型谷氨酸受体，mGluR3）与N-乙酰基-天冬氨酸和谷氨酸的结合。NAAG水平降低， 与认知受损有关。这项研究提出了特异性靶向小胶质细胞GCPII酶， 与纳摩尔有效但脑穿透性差的GCPII抑制剂2PMPA（2- （膦酰基甲基）戊烷-1，5-二酸）（D-2PMPA）。核心假设是正常的小胶质细胞 功能和动力学在小脑发育中起着关键作用， 用D-2PMPA激活的小胶质细胞将导致小脑中NAAG增加， 小剂量内毒素对幼兔小脑发育及学习记忆的影响 在子宫里这将通过（1）评价低剂量宫内内毒素暴露对 浦肯野细胞发育、小脑小胶质细胞反应和小脑学习（经典眨眼测试 条件反射）。(2)评价D- 2PMPA介导的小胶质细胞GCPII抑制对6 - 8周浦肯野细胞发育和小脑学习的影响 （3）确定小脑的机制， NAAG介导的D-2PMPA的神经保护作用诱导mGluR3的激活。这项研究将提供一个 更好地了解围产期低度母胎炎症如何导致 小脑长期学习障碍。这项工作是创新的，因为它使用了一种新颖而有效的D- 2PMPA与靶向小胶质细胞GCPII缀合，用于解决认知和学习缺陷并使正常 围产期脑损伤兔模型中小脑的发育。这一多PI提案将带来 围产期/新生儿脑损伤，神经药理学/GCP2和纳米医学的协同专业知识，以及 临床翻译来实现这些目标。这项工作可以导致新疗法的发展， 解决新生儿脑损伤常见的学习缺陷。

Project summary/abstract Despite significant advances in neonatal care and implementation of therapeutic hypothermia, term and preterm survivors of neonatal encephalopathy are at high risk for developing cognitive and learning deficits even in the absence of functional motor deficits. Recent studies have implicated cerebellar dysfunction with the long-term learning disorders seen in these children. Impaired Purkinje cell development has been linked to impairment in cerebellar associative learning. Microglia have been shown to play a major role in the development of Purkinje cells, the primary output neurons of the cerebellar cortex. Intrauterine inflammation leads to microglial activation that results in maldevelopment of the Purkinje cells and cerebellar learning deficits. Activated microglia in the cerebellum overexpress the enzyme glutamate carboxypeptidase II (GCPII), which hydrolyzes the abundant neuropeptide N-acetylaspartylglutamate (NAAG, a specific agonist of the metabotropic glutamate receptor, mGluR3) to N-acetyl-aspartate and glutamate. Reduced NAAG levels have been linked to impaired cognition. This study proposes to specifically target microglial GCPII enzyme using dendrimer conjugated to the nanomolar potent but poorly brain penetrating GCPII inhibitor 2PMPA (2- (phosphonomethyl) pentane-1,5-dioic acid) (D-2PMPA). The central hypothesis is that normal microglial function and dynamics play a critical role in cerebellar development, and inhibiting upregulated GCPII in activated microglia with D-2PMPA will lead to increased NAAG in the cerebellum enabling normal Purkinje cell development and improving cerebellar learning and memory in juvenile rabbits exposed to low dose endotoxin in utero. This will be tested by (1) Evaluating the effects of low dose intrauterine endotoxin exposure on Purkinje cell development, cerebellar microglial response and cerebellar learning (tested by classical eyeblink conditioning reflex) in a rabbit model of maternal inflammation induced brain injury. (2) Evaluate efficacy of D- 2PMPA mediated microglial GCPII inhibition on Purkinje cell development and cerebellar learning at 6-8 weeks of age in rabbits exposed to intrauterine inflammation and (3) Determine mechanisms of cerebellar neuroprotection by D-2PMPA mediated by NAAG induced activation of mGluR3. This study will provide a better understanding of how low-grade maternal-fetal inflammation in the perinatal period can lead to cerebellar learning deficits long term. The proposed work is innovative because it uses a novel and potent D- 2PMPA conjugate to target microglial GCPII for addressing cognitive and learning deficits and enable normal development of the cerebellum in a rabbit model of perinatal brain injury. This Multi-PI proposal will bring synergistic expertise in perinatal/neonatal brain injury, neuropharmacology/GCP2 and nanomedicine, and clinical translation to accomplish these aims. This work can lead to the development of novel therapies to address learning deficits commonly seen with neonatal brain injury.