The NMDA and AMPA/KA receptors are involved in glutamate-induced alterations of occludin expression and phosphorylation in brain endothelial cells
The NMDA and AMPA/KA receptors are involved in glutamate-induced alterations of occludin expression and phosphorylation in brain endothelial cells
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DOI：
10.1038/sj.jcbfm.9600445
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发表时间：
2007-08-01
影响因子：
6.3
通讯作者：
Toborek, Michal
中科院分区：
文献类型：
--
作者：
Andras, Ibolya E.;Deli, Maria A.;Toborek, Michal
谷氨酸水平在脑缺血和中风时显著升高。这可能会导致血脑屏障(BBB)的开放，并导致进一步的脑损伤。由于内皮紧密连接是血脑屏障完整性的关键因素，本研究的目的是探讨谷氨酸诱导培养的脑微血管内皮细胞紧密连接蛋白occludin改变的机制。短暂的谷氨酸暴露导致细胞内闭塞蛋白的重新分布，随后该蛋白的总水平下降，BMECs的屏障功能减弱。抑制N-甲基-D-天冬氨酸(NMDA)或α-氨基-3-羟基-5-甲基异恶唑-4-丙酸/海人藻酸(AMPA/KA)受体可减弱谷氨酸引起的封闭蛋白再分布的改变，但对总蛋白水平无影响。谷氨酸处理也增加了阻滞素的酪氨酸磷酸化，降低了苏氨酸的磷酸化。MK-801抑制NMDA受体部分保护谷氨酸诱导的阻断素酪氨酸磷酸化升高。此外，MK-801预处理可减轻谷氨酸介导的内皮屏障功能的破坏。6，7-二硝基喹恶啉-2对AMPA/KA受体的阻断作用3-二酮(DNQX)对阻断素苏氨酸残基的低磷酸化有保护作用，但不影响内皮完整性的破坏。这些发现表明，NMDA和AMPA/KA受体对阻滞素磷酸化和BBB功能的破坏具有相反的作用。
Glutamate levels increase dramatically in cerebral ischemia and stroke. This may lead to opening of the blood-brain barrier (BBB) and induce further brain damage. Because endothelial tight junctions are critical elements of the BBB integrity, the aim of this study was to investigate the mechanisms of glutamate-induced alterations of the tight-junction protein occludin in cultured brain microvascular endothelial cells (BMECs). Transient exposure to glutamate resulted in cellular redistribution of occludin, followed by a decrease in the total level of this protein and diminished barrier function of BMECs. Inhibition of the N-methyl-D-aspartate (NMDA) or alpha-amino-3-hydroxy-5-methylisoxazole-4- propionate/kainate (AMPA/KA) receptors attenuated glutamate-induced changes in occludin redistribution but not in the total protein levels. Treatment with glutamate also increased tyrosine phosphorylation and decreased threonine phosphorylation of occludin. Inhibition of the NMDA receptors by MK-801 partially protected against glutamate-induced elevation of occludin tyrosine phosphorylation. In addition, pretreatment with MK-801-attenuated glutamate-mediated disruption of endothelial barrier function. Blocking of the AMPA/KA receptors by 6,7-dinitroquinoxaline-2. 3-dione (DNQX) protected against hypophosphorylation of threonine residues of occludin; however, it did not affect disruption of endothelial integrity. These findings indicate the opposite effects of the NMDA and AMPA/KA receptors on occludin phosphorylation and disruption of the BBB functions.