Zheng Chen, Qiao Zhi H, Hou Meng Z, Liu Nan N, Fu Bin, Ding Ran, Li Yuan Y, Wei Liang P, Liu Ai L, Shen Hui
Laboratory of Neurobiology in Medicine, School of Biomedical Engineering, Tianjin Medical UniversityTianjin, China.
Front Aging Neurosci. 2017 Jun 9;9:186. doi: 10.3389/fnagi.2017.00186. eCollection 2017.
Excessive activation of NMDA receptors (NMDARs) is implicated in pathological synaptic plasticity also known as post-ischemic long-term potentiation (i-LTP) which was produced by glutamate mediated excitotoxicity after stroke. In the past decades, many NMDARs inhibitors failed in clinical investigations due to severe psychotomimetic side effects. GLYX-13 is a NMDAR modulator with glycine site partial agonist properties and has potential protective effects on ischemic neuronal death. However, the underlying molecular mechanism of GLYX-13 attenuating the ischemic neuronal damage remains elusive. Our study was conducted to examine the molecular, cellular and behavioral actions of GLYX-13 in stroke, and further characterize the mechanism underlying the neuroprotective actions via modulation of the NMDAR subunit composition. In present study we found that oxygen-glucose deprivation (OGD) stroke model, GLYX-13 blocked i-LTP and restored the ratio of NR2A/NR2B subunit composition. The glycine site of NMDARs full coagonist D-serine completely blocked the effects of GLYX-13 on i-LTP. Besides, middle cerebral artery occlusion (MCAO) model, GLYX-13 decreased the cerebral infarct volume and reduced injury of hippocampus. Western analysis showed that GLYX-13 down-regulated the expression of phosphorylated NR2B (Tyr1472) and up-regulated phosphorylated NR2A (Tyr1325). Furthermore, GLYX-13 treatment along with NR2B specific antagonist (Ro256981) failed to exhibit any additional neuro-protective effects, whereas the application of NR2A antagonist (NVP-AAM007) abolished the neuroprotective effects of GLYX-13, which suggested that the protective action of GLYX-13 should be by its regulation of NMDAR subunit components. Our study provides important insights on the potential protective mechanism of GLYX-13 in ischemia and proposes the glycine site of NMDARs as a novel target for developing therapeutic strategies to store synaptic function in stroke.
N-甲基-D-天冬氨酸受体（NMDARs）的过度激活与病理性突触可塑性有关，这种可塑性也被称为缺血后长期增强（i-LTP），它是由中风后谷氨酸介导的兴奋性毒性产生的。在过去几十年中，许多NMDARs抑制剂由于严重的拟精神病副作用在临床研究中失败。GLYX-13是一种具有甘氨酸位点部分激动剂特性的NMDAR调节剂，对缺血性神经元死亡具有潜在的保护作用。然而，GLYX-13减轻缺血性神经元损伤的潜在分子机制仍然不清楚。我们进行这项研究是为了研究GLYX-13在中风中的分子、细胞和行为作用，并通过调节NMDAR亚基组成进一步阐明其神经保护作用的潜在机制。在本研究中，我们发现在氧糖剥夺（OGD）中风模型中，GLYX-13阻断了i-LTP并恢复了NR2A/NR2B亚基组成的比例。NMDARs完全共激动剂D-丝氨酸的甘氨酸位点完全阻断了GLYX-13对i-LTP的作用。此外，在大脑中动脉闭塞（MCAO）模型中，GLYX-13减小了脑梗死体积并减轻了海马损伤。蛋白质免疫印迹分析表明，GLYX-13下调了磷酸化NR2B（Tyr1472）的表达并上调了磷酸化NR2A（Tyr1325）的表达。此外，GLYX-13与NR2B特异性拮抗剂（Ro256981）联合处理未表现出任何额外的神经保护作用，而应用NR2A拮抗剂（NVP-AAM007）则消除了GLYX-13的神经保护作用，这表明GLYX-13的保护作用应该是通过其对NMDAR亚基组成的调节。我们的研究为GLYX-13在缺血中的潜在保护机制提供了重要见解，并提出将NMDARs的甘氨酸位点作为开发恢复中风中突触功能治疗策略的新靶点。
