Direct correlation between ischemic injury and extracellular glycine concentration in mice with genetically altered activities of the glycine cleavage multienzyme system
Direct correlation between ischemic injury and extracellular glycine concentration in mice with genetically altered activities of the glycine cleavage multienzyme system
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DOI：
10.1161/strokeaha.106.477026
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发表时间：
2007-07-01
期刊：
影响因子：
8.3
通讯作者：
Kinouchi, Hiroyuki
中科院分区：
文献类型：
--
作者：
Oda, Masaya;Kure, Shigeo;Kinouchi, Hiroyuki
背景和目的-缺血引起各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，引发神经元中的有害过程。尽管甘氨酸是 NMDA 受体的共激动剂，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，我们检查了甘氨酸裂解多酶系统 (GCS) 活性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发挥着重要作用。方法 - 通过甘氨酸脱羧酶的转基因表达产生了 GCS 活性增加的小鼠系（C57BL/6 对照小鼠的 340%），甘氨酸脱羧酶是关键的酶。 GCS 成分（高 GCS 小鼠）。另一种 GCS 活性降低的小鼠系（对照的 29%）是通过甘氨酸脱羧酶显性失活突变体的转基因表达（低 GCS 小鼠）建立的。我们通过测量微透析液中的细胞外氨基酸浓度来检查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着低于和高于对照组。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，并且梗死体积相对于对照显着增加69%。相比之下，高 GCS 小鼠的梗塞体积明显较小（减少了 21%）。在整个实验中，细胞外谷氨酸浓度没有观察到显着差异。 NMDA 甘氨酸位点的拮抗剂 SM-31900 可减轻梗塞面积，表明甘氨酸通过 NMDA 受体发挥作用。结论 - 缺血性损伤与 GCS 维持的细胞外甘氨酸浓度之间存在直接相关性。
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.