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Elucidation of the Mechanisms for Glutamate Release in Ischemic Neuronal Injury

阐明缺血性神经元损伤中谷氨酸释放的机制

基本信息

批准号：
11470283
负责人：
KIRINO Takaaki
金额：
$ 9.47万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B).
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2000
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-11470283/
关键词：
cerebral ischemia glutamate transporter knockout mice gerbil delayed neuronal death GLT-1

项目摘要

Elucidation of the Mechanisms for Glutamate Release in Ischemic Neuronal InjuryThere have been an accumulating evidence that extracellular glutamate is contineously taken up and regulated in concentration by glutamate transporters. Especially, GLT-1 is specifically and widely distributed in forebrain area. Recently, GLT-1 has reported to release intracellular glutamate toward extracellular space in a condition such as ischemia.To test this hypothesis and make sure the function of GLT-1 during ischemia, we determined extracellular glutamate concentration in gerbils with naive and ischemic condition by inhibition of glutamate transporter. In addition, we produced a focal cerebral ischemia by cauterization of the middle cerebral artery in mice with GLT-1 gene deleted and its wild type.Results :(1) We infused tPDC, an inhibitor of a glutamate transporter and collected extracellular fluid of gerbil brain by a microdialysis method. We confirmed that extracellular glutamate increased during an inhibition of a glutamate transporter. This result indicates that a glutamate transporter plays an important role in regulating extracellular glutamate concentration. As the next step, we induced a transient global ischemia to gerbils which were pre-infused with tPDC.We could not confirm the significant protective effect against neurons in CA1 sector of the hippocampus of the animals.(2) We used GLT-1 gene knockout mice to examine whether ischemic neuronal death is accelerated and an infarct size is augmented. By producing a permanent focal cerebral ischemia, there was no differences in infarct volumes (homozygotes : 12.6±10.3, wild type : 12.6±6.8, Mean±SD mm^3). Since there is a possibility that the severity of an initial ischemic insult but not glutamate toxicity affected the neuronal cell death, we are ongoing to measure the infarct volumes by adopting ischemia-reperfusion models which are less severe than permanent ischemia.

缺血性神经元损伤中谷氨酸释放机制的研究越来越多的证据表明，细胞外谷氨酸被谷氨酸转运体持续摄取并调节其浓度。尤其是GLT-1在前脑区特异而广泛的分布。近年来，GLT-1在缺血等条件下向细胞外释放谷氨酸，为了验证这一假设并确定GLT-1在缺血过程中的功能，我们通过抑制谷氨酸转运体的方法测定了沙土鼠在初始和缺血条件下细胞外谷氨酸的浓度。结果：（1）灌胃谷氨酸转运体抑制剂tPDC，用微透析法收集沙土鼠脑细胞外液。我们证实，细胞外谷氨酸增加谷氨酸转运蛋白抑制期间。这一结果表明谷氨酸转运蛋白在调节细胞外谷氨酸浓度方面发挥着重要作用。下一步，我们诱导沙土鼠短暂性全脑缺血，预先注入tPDC，我们不能证实对动物海马CA 1区的神经元有明显的保护作用。(2)我们使用GLT-1基因敲除小鼠来检查缺血性神经元死亡是否加速和梗死面积是否增加。通过产生永久性局灶性脑缺血，梗死体积没有差异（纯合子：12.6±10.3，野生型：12.6±6.8，平均值±标准差mm^3）。由于存在初始缺血损伤的严重性而非谷氨酸毒性影响神经元细胞死亡的可能性，因此我们正在通过采用比永久性缺血更轻的缺血-再灌注模型来测量梗死体积。