Mechanisms underlying regulating expression of mitochondrial gene to determine death and survival in neurons

线粒体RNA转录本和蛋白质合成的下降以及线粒体DNA的损伤被认为是导致线粒体损伤导致神经元死亡的原因。为了评价线粒体功能障碍在谷氨酸诱导的神经元死亡中的作用，本研究观察了谷氨酸暴露对原代培养的小鼠皮质神经元线粒体RNA水平的影响。取15日龄胎鼠大脑皮层，取神经细胞。培养的大脑皮层神经元(12DIV)暴露于100μM的谷氨酸15min后，细胞死亡前，谷氨酸处理导致NADH-泛醌氧化还原酶亚基ND1和ND6mRNA的表达显著下降。由于线粒体RNA水平至少部分受核糖核酸酶-L降解的调节，我们接下来研究了谷氨酸暴露对核糖核酸酶-L表达的影响。逆转录-聚合酶链式反应分析显示谷氨酸能有效地提高核糖核酸酶-L基因的表达水平。N-甲基-D-天冬氨酸受体拮抗剂MK801可抑制核糖核酸酶-L的表达。以上结果提示，谷氨酸激活NMDA型受体可能通过增强核糖核酸酶-L的表达而降低原代培养的皮层神经元线粒体的核糖核酸水平。

A decline in the mitochondrial RNA transcripts and protein synthesis, as well as mitochondrial DNA damage, is considered to induce mitochondrial injury to cause neuronal death. To evaluate involvement of mitochondrial dysfunction in glutamate-induced neuronal death, in this study, we examined the effects of glutamate exposure on mitochondrial RNA level in primary cultured cortical neurons of mice. Cerebral cortex was dissected in 15 days-old fetal mouse to obtain neural cells. Cultured cortical neurons (12 DIV) obtained were exposed to glutamate for 15 min at 100 μM. Glutamate treatment led to a significant decrease in mRNA of ND1 and ND6, which are subunits of NADH-ubiquinone oxidoreductase, before cell death. As mitochondrial RNAs level is regulated at least in part by RNA degradation by RNase-L, we next examined the effect of glutamate exposure on expression of RNase-L. RT-PCR analysis revealed that glutamate was effective in increasing the level of RNase-L mRNA at least 2-12 h after treatment. The increase in expression of RNase-L was abolished by the NMDA receptor antagonist MK801. There results suggest that activation of NMDA receptor by glutamate reduces mitochondrial RNA level through enhanced expression of RNase-L in primary cultured cortical neurons.