Menzies Research Institute, University of Tasmania, Hobart, Tasmania 7000, Australia.
Neurochem Int. 2013 Apr;62(5):719-30. doi: 10.1016/j.neuint.2012.12.015. Epub 2013 Jan 3.
Excitotoxicity, induced by the aberrant rise in cytosolic Ca(2+) level, is a major neuropathological process in numerous neurodegenerative disorders. It is triggered when extracellular glutamate (Glu) concentration reaches neuropathological levels resulting in dysregulation and hyper-activation of ionotropic glutamate receptor subtype (iGluRs). Even though all three members of the iGluRs, namely N-methyl-d-aspartate (NMDAR), α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPAR) and kainate (KAR) receptors are implicated in excitotoxicity, their individual contributions to downstream signaling transduction have not been explored. In this study, we report a comprehensive description of the recruitment of cellular processes in neurons upon iGluR activation during excitotoxicity through temporal (5h, 15h, and 24h) global gene profiling of AMPA, KA, NMDA, and Glu excitotoxic models. DNA microarray analyses of mouse primary cortical neurons treated with these four pharmacological agonists are further validated via real-time PCR. Bi-model analyses against Glu model demonstrate that NMDARs and KARs play a more pivotal role in Glu-mediated excitotoxicity, with a higher degree of global gene profiling overlaps, as compared to that of AMPARs. Comparison of global transcriptomic profiles reveals aberrant calcium ion binding and homeostasis, organellar (lysosomal and endoplasmic reticulum) stress, oxidative stress, cell cycle re-entry and activation of cell death processes as the main pathways that are significantly modulated across all excitotoxicity models. Singular profile analyses demonstrate substantial transcriptional regulation of numerous cell cycle proteins. For the first time, we show that iGluR activation forms the basis of cell cycle re-activation, and together with oxidative stress fulfill the "two-hit" hypothesis that accelerates neurodegeneration.
兴奋性毒性是许多神经退行性疾病中的主要神经病理过程，是由细胞溶质 Ca(2+)水平异常升高引起的。当细胞外谷氨酸 (Glu) 浓度达到神经病理水平时，会触发兴奋性毒性，导致离子型谷氨酸受体亚型 (iGluRs) 的失调和过度激活。尽管 iGluRs 的三个成员，即 N-甲基-D-天冬氨酸 (NMDAR)、α-氨基-3-羟基-5-甲基-4-异恶唑丙酸 (AMPA) 和 kainate (KAR) 受体都与兴奋性毒性有关，但它们对下游信号转导的个体贡献尚未得到探索。在这项研究中，我们通过对 AMPA、KA、NMDA 和 Glu 兴奋毒性模型的瞬时（5h、15h 和 24h）全基因谱分析，全面描述了 iGluR 激活在兴奋毒性过程中对神经元细胞过程的募集。通过对用这四种药理学激动剂处理的小鼠原代皮质神经元进行 DNA 微阵列分析，并通过实时 PCR 进一步验证。针对 Glu 模型的双模型分析表明，与 AMPAR 相比，NMDAR 和 KAR 在 Glu 介导的兴奋性毒性中发挥更关键的作用，具有更高程度的全局基因谱重叠。对全转录组谱的比较揭示了异常的钙离子结合和动态平衡、细胞器（溶酶体和内质网）应激、氧化应激、细胞周期重新进入和细胞死亡过程的激活是所有兴奋毒性模型中显著调节的主要途径。单一谱分析表明，许多细胞周期蛋白的转录调控显著。我们首次表明，iGluR 激活是细胞周期重新激活的基础，与氧化应激一起满足加速神经退行性变的“双打击”假说。
