Balanced, polyvalent antiglutamatergic action as a novel approach to efficacious

描述(申请人提供)：N-甲基-D-天冬氨酸(N-甲基-D-天冬氨酸)和(RS)-amino-3-hydroxy-5-methyl-4-isoxazolepropioinic酸/海人藻酸亚型的过度激活的离子型谷氨酸受体会引发许多事件，导致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，在正常的大脑生理中发挥着关键作用。因此，许多以前的高选择性和强大的谷氨酸受体拮抗剂，通常是针对NMDAR的，临床试验失败也就不足为奇了，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由于：1)NMDA拮抗剂损害NMDAR的基本生理功能；2)AMPA/海人藻酸受体介导的完整兴奋性毒性；3)NMDA拮抗剂引起的谷氨酸释放增加。目前的研究测试了这一新概念，即在突触前和突触后具有多价作用且效力适中的抗谷氨酸能药物具有克服这些限制的潜力，因为它可以产生有效的神经保护，仍然能够使大脑生理功能所需的谷氨酸受体活性达到平衡水平，从而避免显著的副作用。3，5-二溴-D-酪氨酸(3，5-DBR-D-Tyr)通过抑制NMDA和AMPA/海人藻酸受体和谷氨酸释放，结合其抗氧化特性，可能是此类药物的代表。我们将利用膜片钳技术、高效液相色谱/串联质谱仪和谷氨酸摄取技术研究3，5-DBR-D-Tyr在神经元培养中作用的细胞机制。3，5-DBR-D-Tyr将利用短暂性大脑中动脉闭塞(MCAO)引起的中风大鼠模型在体内研究其神经保护特性。3，5-DBR-D-Tyr的抗谷氨酸和抗氧化作用将被用毛细管电泳微渗析和激光诱导荧光检测来阐明。为了获得3，5-DBR-D-Tyr的安全性，将对治疗动物的心血管参数、感觉运动信息的处理、肾功能和组织病理学变化进行评估。目的#1：研究3，5-DBR-D-Tyr在脑内作用的细胞机制。目的#2：观察3，5-DBR-D-Tyr对大鼠短暂性脑梗塞模型的神经保护作用，并探讨其作用机制。与公共卫生相关：谷氨酸受体是潜在药物的明显靶点，旨在改善一系列中枢神经系统疾病的症状。以前许多高选择性和强效的谷氨酸受体拮抗剂未能通过临床试验，主要是因为它们产生了副作用。这项研究测试了这一新概念，即具有多价作用和中等效力的抗谷氨酸能药物有可能克服这些限制，产生有效的神经保护，并仍然能够使生理大脑功能所需的谷氨酸受体活性达到平衡水平，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.