Laboratory of Molecular Pharmacology, Division of Pharmaceutical Sciences, Kanazawa University Graduate School of Natural Science and Technology, Kanazawa, Ishikawa, Japan.
J Neurosci Res. 2010 Aug 1;88(10):2177-87. doi: 10.1002/jnr.22388.
We have previously shown differential vulnerabilities to glutamate (Glu) excitotoxicity mediated by the N-methyl-D-aspartate (NMDA) receptor (NMDAR) between rat cortical and rat hippocampal neurons in culture. In this study, we evaluated the possible induced tolerance to NMDA neurotoxicity in cultured rat striatal neurons with prior sustained activation of NMDAR. Brief exposure to Glu or NMDA for 1 hr led to a significant decrease in cellular vitality determined 24 hr later in cultured rat striatal neurons, whereas no marked loss was seen in cellular survival after exposure to Glu or NMDA in striatal neurons previously cultured with Glu or NMDA. Sustained culture with Glu or NMDA invariably led to a significant decrease in protein levels of NR2, but not NR1, subunits without affecting their mRNA levels. Similar induced tolerance was seen to the excitotoxicity of NMDA in hippocampal neurons in a manner sensitive to an NMDAR antagonist. Prior culture with NMDA induced less effective alterations in both intracellular free Ca(2+) levels and mitochondrial membrane potentials after the addition of NMDA in striatal neurons. However, calpain inhibitor-I significantly prevented the decreased NR2B and NR2C protein levels in striatal neurons cultured with NMDA. These results suggest that prior tonic activation of NMDAR would induce tolerance to the excitotoxicity mediated by NMDAR through a mechanism related to calpain-induced down-regulation of particular NR2 subunits in rat striatal neurons.
我们之前已经证明，在培养的大鼠皮质和海马神经元中，N-甲基-D-天冬氨酸（NMDA）受体（NMDAR）介导的谷氨酸（Glu）兴奋性毒性存在差异。在这项研究中，我们评估了在培养的大鼠纹状体神经元中，通过 NMDAR 的持续激活，对 NMDA 神经毒性可能产生的诱导耐受。短暂暴露于 Glu 或 NMDA 1 小时会导致培养的大鼠纹状体神经元在 24 小时后细胞活力明显下降，而在先前用 Glu 或 NMDA 培养的神经元中暴露于 Glu 或 NMDA 后，细胞存活没有明显损失。持续培养 Glu 或 NMDA 总是导致 NR2 亚基而不是 NR1 亚基的蛋白水平显著下降，但不影响其 mRNA 水平。在海马神经元中，NMDA 兴奋性毒性也存在类似的诱导耐受，这对 NMDAR 拮抗剂敏感。在纹状体神经元中，NMDA 加药后，NMDA 预先培养会导致细胞内游离 Ca(2+)水平和线粒体膜电位的改变不那么有效。然而，钙蛋白酶抑制剂-I 显著防止了 NMDA 培养的纹状体神经元中 NR2B 和 NR2C 蛋白水平的降低。这些结果表明，NMDAR 的持续紧张激活会通过与钙蛋白酶诱导的特定 NR2 亚基下调相关的机制诱导对 NMDAR 介导的兴奋性毒性的耐受。
