Preconditioning with cortical spreading depression decreases intraischemic cerebral glutamate levels and down-regulates excitatory amino acid transporters EAAT1 and EAAT2 from rat cerebral cortex plasma membranes
Preconditioning with cortical spreading depression decreases intraischemic cerebral glutamate levels and down-regulates excitatory amino acid transporters EAAT1 and EAAT2 from rat cerebral cortex plasma membranes
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DOI：
10.1046/j.1471-4159.2000.0750812.x
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发表时间：
2000-08-01
影响因子：
4.7
通讯作者：
Hakim, A
中科院分区：
文献类型：
--
作者：
Douen, AG;Akiyama, K;Hakim, A
我们之前报道过，在 3 天前接受皮质扩散抑制 (CSD) 预处理的大鼠中，短暂性局灶性脑缺血后，皮质梗塞体积减少了 50%。先前 CSD 的保护作用机制仍不清楚。最近的研究表明，兴奋性氨基酸转运蛋白（EAAT）的逆转是脑缺血期间细胞外谷氨酸水平升高的主要原因。本研究测量了 CSD 预处理对 (a) 缺血内谷氨酸水平和 (b) 大鼠缺血皮质内谷氨酸转运蛋白调节的影响。 CSD 或假预处理三天后，使大鼠遭受 200 分钟的局灶性脑缺血，并通过体内微透析测量细胞外谷氨酸浓度。皮质谷氨酸暴露量从假处理组 (n = 8) 的 1,772.4 +/- 1,469.2 mu M-min 下降到 CSD 处理组 (n = 13) 的 569.0 +/- 707.8 mu M-min (p < 0.05)，减少了 70%。通过蛋白质印迹分析评估 CSD 预处理对大鼠大脑皮层质膜 (PM) 中谷氨酸转运蛋白水平的影响。在 CSD 后第 1、3 和 7 天观察到 PM 部分的神经胶质谷氨酸转运蛋白亚型 EAAT2 和 EAAT1 下调，但在 0 或 21 天则没有观察到。半定量泳道分析显示，CSD 后 3 天，EAAT2 最大下降 90%，EAAT1 最大下降 50%。神经元亚型 EAAT3 不受 CSD 影响。这一下调时期与报道的诱导缺血耐受的时间范围一致。这些数据与谷氨酸转运蛋白功能的逆转一致，导致缺血期间谷氨酸释放，并表明这些转运蛋白的下调可能有助于 CSD 诱导的缺血耐受。
We previously reported a 50% reduction in cortical infarct volume following transient focal cerebral ischemia in rats preconditioned 3 days earlier with cortical spreading depression (CSD). The mechanism of the protective effect of prior CSD remains unknown. Recent studies demonstrate reversal of excitatory amino acid transporters (EAATs) to be a principal cause for elevated extracellular glutamate levels during cerebral ischemia. The present study measured the effect of CSD preconditioning on (a) intraischemic glutamate levels and (b) regulation of glutamate transporters within the ischemic cortex of the rat. Three days following either CSD or sham preconditioning, rats were subjected to 200 min of focal cerebral ischemia, and extracellular glutamate concentration was measured by in vivo microdialysis. Cortical glutamate exposure decreased 70% from 1,772.4 +/- 1,469.2 mu M-min in sham-treated (n = 8) to 569.0 +/- 707.8 mu M-min in CSD-treated (n = 13) rats (p < 0.05). The effect of CSD preconditioning on glutamate transporter levels in plasma membranes (PMs) prepared from rat cerebral cortex was assessed by western blot analysis. Down-regulation of the glial glutamate transporter isoforms EAAT2 and EAAT1 from the PM fraction was observed at 1, 3, and 7 days but not at 0 or 21 days after CSD. Semiquantitative lane analysis showed a maximal decrease of 90% for EAAT2 and 50% for EAAT1 at 3 days post-CSD. The neuronal isoform EAAT3 was unaffected by CSD. This period of down-regulation coincides with the time frame reported for induced ischemic tolerance. These data are consistent with reversal of glutamate transporter function contributing to glutamate release during ischemia and suggest that down-regulation of these transporters may contribute to ischemic tolerance induced by CSD.