Balanced, polyvalent antiglutamatergic action as a novel approach to efficacious

描述（由申请人提供）：n -甲基- d -天冬氨酸（NMDA）和(RS)-氨基-3-羟基-5-甲基-4-异唑丙酸(AMPA)/kainate亚型的嗜离子性谷氨酸受体过度激活可引发多种病理生理状态下的神经元损伤，包括急性缺氧缺血性脑损伤、癫痫和许多慢性神经退行性疾病。此外，谷氨酸是一种主要的兴奋性神经递质，在正常的脑生理中起着关键作用。因此，许多先前的高选择性和强效谷氨酸受体拮抗剂（通常针对NMDARs）在临床试验中失败并不奇怪，主要是因为它们产生了副作用。这些不良反应的发生可能是因为：1)NMDA拮抗剂损害了NMDARs的基本生理功能；2) AMPA/kainate受体介导的完整兴奋毒性；3) NMDA拮抗剂引起谷氨酸释放增加。目前的研究验证了一个新概念，即在突触前和突触后具有多价作用和中等效力的抗谷氨酸能药物有可能通过产生有效的神经保护来克服这些局限性，同时使生理脑功能所需的谷氨酸受体活性保持平衡水平，从而避免显著的副作用。3,5-二溴-二酪氨酸（3,5- dbr -d - tyr）通过抑制NMDA和AMPA/kainate受体和谷氨酸释放，结合其抗氧化性能，可能代表这些药物。我们将使用膜片钳、液相色谱/串联质谱和谷氨酸摄取测量来研究神经元培养中3,5 - dbr - d - tyr作用的细胞机制。3,5 - dbr - d - tyr的神经保护作用将在体内通过大脑中动脉闭塞（MCAO）引起的脑卒中大鼠模型进行研究。利用毛细管电泳微透析和激光诱导荧光检测技术研究3,5 - dbr - d - tyr的抗谷氨酸和抗氧化性能。为了获得3,5 - dbr - d - tyr的安全性，将评估治疗动物的心血管参数、感觉运动信息加工、肾功能和大脑组织病理学变化。目的1：表征大脑中3,5 - dbr - d - tyr作用的细胞机制。目的2：确定3,5 - dbr - d - tyr在脑卒中瞬时MCAO模型大鼠体内神经保护作用的有效性和安全性，并阐明其潜在机制。公共卫生相关性：谷氨酸受体是潜在药物的明显靶标，旨在改善各种中枢神经系统疾病的症状。许多先前的高选择性和强效谷氨酸受体拮抗剂在临床试验中失败，主要是因为它们产生的副作用。这项研究验证了一个新概念，即具有多价作用和中等效力的抗谷氨酸能药物有潜力克服这些局限性，通过产生有效的神经保护，仍然能够维持生理脑功能所需的平衡水平的谷氨酸受体活性，从而避免显著的副作用。

DESCRIPTION (provided by applicant): Excessively activated ionotropic glutamate receptors of both the N-methyl-D-aspartate (NMDA) and (RS)-amino-3-hydroxy-5-methyl-4-isoxazolepropioinic acid (AMPA)/kainate subtypes initiate numerous events leading to neuronal damage in a wide range of pathophysiological states, including acute hypoxic-ischemic brain injury, epilepsy and many chronic neurodegenerative diseases. Also, glutamate is a major excitatory neurotransmitter that plays a critical role in normal brain physiology. Therefore it is not surprising that many previous highly selective and potent glutamate receptor antagonists, usually specific to NMDARs, failed clinical trials, primarily because of side effects they produced. These adverse effects may occur because of: 1) impairment of essential physiological function of NMDARs by NMDA antagonists; 2) intact excitotoxicity mediated by AMPA/kainate receptors; 3) increase in glutamate release caused by NMDA antagonists. Current study tests the novel concept that antiglutamatergic agents with polyvalent actions at pre and postsynaptic sites and moderate potency have the potential to overcome these limitations by producing efficacious neuroprotection still enabling a level of balanced glutamate receptor activity required for physiological brain functions and thus avoiding significant side effects. 3, 5-dibromo-Dtyrosine (3,5-DBr-D-Tyr), by depressing NMDA and AMPA/kainate receptors and glutamate release in combination with its antioxidant properties, may represent such agents. We will investigate the cellular mechanisms of 3, 5-DBr-D-Tyr action in neuronal cultures using patch-clamp, liquid chromatography/tandem mass spectrometry and glutamate uptake measurements. The neuroprotective properties of 3, 5-DBr-D-Tyr will be studied in vivo using a rat model of stroke caused by transient middle cerebral artery occlusion (MCAO). Microdialysis with capillary electrophoresis and laser-induced fluorescence detection will be used to elucidate the antiglutamatergic and antioxidant properties of 3, 5-DBr-D-Tyr. In order to access safety of 3, 5-DBr-D-Tyr, cardiovascular parameters, processing of sensorimotor information, renal function and histopathological changes in the brain of treated animals will be evaluated. Aim #1: To characterize the cellular mechanisms of 3, 5-DBr-D-Tyr action in the brain. Aim #2: To determine efficacy and safety of the neuroprotective action of 3, 5-DBr-D-Tyr in vivo in the rat transient MCAO model of stroke and to elucidate underlying mechanisms. PUBLIC HEALTH RELEVANCE: Glutamate receptors represent an obvious target for potential pharmaceutical agents aiming at ameliorating symptoms of a wide range of CNS disorders. Many previous highly selective and potent glutamate receptor antagonists failed clinical trials, primarily because of side effects they produced. This study tests the novel concept that antiglutamatergic agents with polyvalent actions and moderate potency have the potential to overcome these limitations by producing efficacious neuroprotection and still enabling a level of balanced glutamate receptor activity required for physiological brain functions and thus avoiding significant side effects.