The role of glutamate transporter-1a in the induction of brain ischemic tolerance in rats

This study was undertaken to determine the role of glutamate transporter-1a (GLT-1a), one of the splice variants of glutamate transporter-1, in the induction of brain ischemic tolerance by cerebral ischemic preconditioning (CIP). We used a rat global cerebral ischemic model and assessed changes by neuropathological evaluation, Western blot analysis, immunohistochemistry, real-time PCR, in vivo brain microdialysis, and high performance liquid chromatography. We found that CIP induced a significant upregulation of GLT-1a expression in the CA1 hippocampus in a time course corresponding to that of neuroprotection of CIP against brain ischemia. Severe brain ischemia for 8 min induced delayed downregulation of GLT-1a, an obvious increase in glutamate concentration and delayed neuronal death of the pyramidal neurons in the CA1 hippocampus. When the animals were pretreated with CIP before the severe ischemia, the above changes normally induced by the severe ischemia were effectively prevented. Importantly, such a preventive effect of CIP on these changes was significantly inhibited by intracerebroventricular administration of GLT-1a antisense oligodeoxynucleotides, which have been proven to specifically inhibit the expression of GLT-1a protein and mRNA, and had no effect on the expression of GLT-1b. In addition, the concentration of aspartate was also elevated after severe brain ischemic insult. However, CIP had no effect on the elevated aspartate concentrations. These results indicate that GLT-1a participated in the brain ischemic tolerance induced by CIP in rats. (c) 2011 Wiley Periodicals, Inc.

本研究旨在确定谷氨酸转运体 - 1的剪接变体之一谷氨酸转运体 - 1a（GLT - 1a）在脑缺血预处理（CIP）诱导脑缺血耐受中的作用。我们采用大鼠全脑缺血模型，并通过神经病理学评估、蛋白质印迹分析、免疫组织化学、实时聚合酶链反应、体内脑微透析以及高效液相色谱法来评估变化。我们发现，CIP诱导海马CA1区GLT - 1a表达显著上调，其时间进程与CIP对脑缺血的神经保护作用时间进程一致。8分钟的严重脑缺血诱导GLT - 1a延迟下调，谷氨酸浓度明显升高以及海马CA1区锥体神经元延迟性死亡。当动物在严重缺血前接受CIP预处理时，严重缺血通常诱导的上述变化得到有效预防。重要的是，脑室内给予GLT - 1a反义寡脱氧核苷酸可显著抑制CIP对这些变化的预防作用，已证实该反义寡脱氧核苷酸可特异性抑制GLT - 1a蛋白和mRNA的表达，且对GLT - 1b的表达无影响。此外，严重脑缺血损伤后天冬氨酸浓度也升高。然而，CIP对升高的天冬氨酸浓度无影响。这些结果表明，GLT - 1a参与了大鼠CIP诱导的脑缺血耐受。（c）2011威利期刊公司