Pradillo J M, Hurtado O, Romera C, Cárdenas A, Fernández-Tomé P, Alonso-Escolano D, Lorenzo P, Moro M A, Lizasoain I
Departamento de Farmacología, Facultad de Medicina, Universidad Complutense de Madrid, 28040 Madrid, Spain.
Neuroscience. 2006;138(4):1171-8. doi: 10.1016/j.neuroscience.2005.12.010. Epub 2006 Jan 25.
A short ischemic event (ischemic preconditioning) can result in subsequent resistance to severe ischemic injury (ischemic tolerance). Glutamate is released after ischemia and produces cell death. It has been described that after ischemic preconditioning, the release of glutamate is reduced. We have shown that an in vitro model of ischemic preconditioning produces upregulation of glutamate transporters which mediates brain tolerance. We have now decided to investigate whether ischemic preconditioning-induced glutamate transporter upregulation takes also place in vivo, its cellular localization and the mechanisms by which this upregulation is controlled. A period of 10 min of temporary middle cerebral artery occlusion was used as a model of ischemic preconditioning in rat. EAAT1, EAAT2 and EAAT3 glutamate transporters were found in brain from control animals. Ischemic preconditioning produced an up-regulation of EAAT2 and EAAT3 but not of EAAT1 expression. Ischemic preconditioning-induced increase in EAAT3 expression was reduced by the TNF-alpha converting enzyme inhibitor BB1101. Intracerebral administration of either anti-TNF-alpha antibody or of a TNFR1 antisense oligodeoxynucleotide also inhibited ischemic preconditioning-induced EAAT3 up-regulation. Immunohistochemical studies suggest that, whereas the expression of EAAT3 is located in both neuronal cytoplasm and plasma membrane, ischemic preconditioning-induced up-regulation of EAAT3 is mainly localized at the plasma membrane level. In summary, these results demonstrate that in vivo ischemic preconditioning increases the expression of EAAT2 and EAAT3 glutamate transporters the upregulation of the latter being at least partly mediated by TNF-alpha converting enzyme/TNF-alpha/TNFR1 pathway.
短暂的缺血事件（缺血预处理）可导致随后对严重缺血损伤产生抵抗（缺血耐受）。缺血后谷氨酸会释放并导致细胞死亡。据描述，缺血预处理后谷氨酸的释放会减少。我们已经表明，缺血预处理的体外模型会使介导脑耐受的谷氨酸转运体上调。我们现在决定研究缺血预处理诱导的谷氨酸转运体上调是否也发生在体内、其细胞定位以及这种上调的调控机制。以大鼠大脑中动脉短暂闭塞10分钟作为缺血预处理模型。在对照动物的脑中发现了EAAT1、EAAT2和EAAT3谷氨酸转运体。缺血预处理使EAAT2和EAAT3上调，但未使EAAT1表达上调。TNF-α转换酶抑制剂BB1101可降低缺血预处理诱导的EAAT3表达增加。脑内注射抗TNF-α抗体或TNFR1反义寡脱氧核苷酸也可抑制缺血预处理诱导的EAAT3上调。免疫组织化学研究表明，虽然EAAT3的表达位于神经元细胞质和质膜中，但缺血预处理诱导的EAAT3上调主要定位于质膜水平。总之，这些结果表明，体内缺血预处理会增加EAAT2和EAAT3谷氨酸转运体的表达，后者的上调至少部分由TNF-α转换酶/TNF-α/TNFR1途径介导。
