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A direct correlation between ischemic injury and extracellular glycine concentration in mice with genetically altered activities of the glycine cleavage multi-enzyme system

甘氨酸裂解多酶系统活性基因改变的小鼠缺血性损伤与细胞外甘氨酸浓度之间的直接相关性

基本信息

批准号：
17591497
负责人：
KINOUCHI Hiroyuki
金额：
$ 2.24万
依托单位：
University of Yamanashi
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2005
资助国家：
日本
起止时间：
2005 至 2006
项目状态：
已结题

项目摘要

[Background and Purpose] Ischemia elicits rapid release of various amino acid neurotransmitters. Glutamate surge activates N-methyl-D-aspartate (NMDA) glutamate receptors, triggering deleterious process of neurons. Although glycine is a coagonist of the NMDA receptor, the effect of extracellular glycine concentration on ischemic injury remains controversial. To approach this issue we examined ischemic injury in mice with genetically altered activities of the glycine cleavage multi-enzyme system (GCS), which plays a fundamental role in maintaining extracellular glycine concentration. [Materials and Methods] A mouse line with increased GCS activity (340% of C57BL/6 control mice) was generated by transgenic expression of glycine decarboxylase, a key GCS component (high-GCS mice). Another mouse line with reduced GCS activity (29% of controls) was established by transgenic expression of a dominant negative mutant of glycine decarboxylase (low-GCS mice). We examined the neuronal injury after transient occlusion of middle cerebral artery in these mice, measuring extracellular aminoacid concentrations by microdialysis method. [Results] The high-GCS and low-GCS mice had significantly lower and higher basal concentrations of extracellular glycine than controls, respectively. In low-GCS mice, extracellular glycine reached to 2-hold control level during ischemia and the infarction volume was significantly increased by 69% of controls. In contrast, high-GCS mice had significantly smaller infarction volume by 21%. No significant difference was observed in extracellular glutamate concentrations throughout the experiments. An antagonist for the NMDA glycine site, SM-31900, attenuated infarction size, suggesting that glycine operated via NMDA receptor. [Conclusions] There is a direct correlation between ischemic injury and extracellular glycine concentration maintained by the GCS.

【背景与目的】缺血引起多种氨基酸神经递质快速释放。谷氨酸激增激活n -甲基- d -天冬氨酸（NMDA）谷氨酸受体，引发神经元的有害过程。虽然甘氨酸是NMDA受体的促凝剂，但细胞外甘氨酸浓度对缺血性损伤的影响仍存在争议。为了解决这个问题，我们研究了甘氨酸切割多酶系统（GCS）基因改变的小鼠缺血性损伤，该系统在维持细胞外甘氨酸浓度中起着重要作用。【材料与方法】通过转基因表达GCS关键成分甘氨酸脱羧酶（glycine decarboxylase），获得GCS活性提高的小鼠系（GCS高值小鼠）（C57BL/6对照小鼠的340%）。通过转基因表达甘氨酸脱羧酶显性阴性突变体（低GCS小鼠），建立了GCS活性降低的另一小鼠品系（占对照组的29%）。我们用微透析法测定细胞外氨基酸浓度，观察小鼠短暂性大脑中动脉闭塞后的神经元损伤情况。[结果]与对照组相比，高gcs组和低gcs组的细胞外甘氨酸基础浓度分别显著降低和升高。低gcs小鼠缺血时细胞外甘氨酸达到2 hold控制水平，梗死体积显著增加69%。相比之下，高gcs小鼠的梗死体积明显减少21%。在整个实验过程中，细胞外谷氨酸浓度无显著差异。一种NMDA甘氨酸位点的拮抗剂SM-31900可以减小梗死的大小，表明甘氨酸通过NMDA受体起作用。[结论]缺血损伤与GCS维持的细胞外甘氨酸浓度有直接关系。