在甘氨酸裂解多酶系统活性发生基因改变的小鼠中，缺血性损伤与细胞外甘氨酸浓度之间的直接相关性。

Direct correlation between ischemic injury and extracellular glycine concentration in mice with genetically altered activities of the glycine cleavage multienzyme system.

作者信息

Oda Masaya, Kure Shigeo, Sugawara Taku, Yamaguchi Suguru, Kojima Kanako, Shinka Toshikatsu, Sato Kenichi, Narisawa Ayumi, Aoki Yoko, Matsubara Yoichi, Omae Tomoya, Mizoi Kazuo, Kinouchi Hiroyuki

机构信息

Department of Medical Genetics, Tohoku University School of Medicine, Seiryomachi, Aobaku, Japan.

出版信息

Stroke. 2007 Jul;38(7):2157-64. doi: 10.1161/STROKEAHA.106.477026. Epub 2007 May 17.

DOI:10.1161/STROKEAHA.106.477026

PMID:17510459

Abstract

BACKGROUND AND PURPOSE

Ischemia elicits the rapid release of various amino acid neurotransmitters. A glutamate surge activates N-methyl-d-aspartate (NMDA) glutamate receptors, triggering deleterious processes in 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 multienzyme system (GCS), which plays a fundamental role in maintaining extracellular glycine concentration.

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 neuronal injury after transient occlusion of the middle cerebral artery in these mice by measuring extracellular amino acid concentrations in microdialysates.

RESULTS

High-GCS and low-GCS mice had significantly lower and higher basal concentrations of extracellular glycine than did controls, respectively. In low-GCS mice, the extracellular glycine concentration reached 2-fold of control levels during ischemia, and infarct volume was significantly increased by 69% with respect to controls. In contrast, high-GCS mice had a significantly smaller infarct 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 infarct size, suggesting that glycine operated via the NMDA receptor.

CONCLUSIONS

There is a direct correlation between ischemic injury and extracellular glycine concentration maintained by the GCS.

摘要

背景与目的

缺血会引发多种氨基酸神经递质的快速释放。谷氨酸激增会激活N-甲基-D-天冬氨酸（NMDA）谷氨酸受体，从而引发神经元中的有害过程。尽管甘氨酸是NMDA受体的协同激动剂，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，我们研究了甘氨酸裂解多酶系统（GCS）活性发生基因改变的小鼠的缺血性损伤，该系统在维持细胞外甘氨酸浓度方面起着重要作用。

方法

通过转基因表达甘氨酸脱羧酶（一种关键的GCS成分），培育出GCS活性增加的小鼠品系（为C57BL/6对照小鼠的340%）（高GCS小鼠）。通过转基因表达甘氨酸脱羧酶的显性负性突变体，建立了另一种GCS活性降低的小鼠品系（为对照的29%）（低GCS小鼠）。我们通过测量微透析液中的细胞外氨基酸浓度，研究了这些小鼠大脑中动脉短暂闭塞后的神经元损伤。

结果

高GCS和低GCS小鼠的细胞外甘氨酸基础浓度分别显著低于和高于对照组。在低GCS小鼠中，缺血期间细胞外甘氨酸浓度达到对照水平的2倍，梗死体积相对于对照组显著增加了69%。相比之下，高GCS小鼠的梗死体积显著减小（减小了21%）。在整个实验过程中，细胞外谷氨酸浓度未观察到显著差异。NMDA甘氨酸位点拮抗剂SM-31900可减小梗死面积，表明甘氨酸通过NMDA受体发挥作用。