Glutamine synthetase becomes nitrated and its activity is reduced during repetitive seizure activity in the pentylentetrazole model of epilepsy
Glutamine synthetase becomes nitrated and its activity is reduced during repetitive seizure activity in the pentylentetrazole model of epilepsy
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DOI：
10.1111/j.1528-1167.2008.01642.x
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发表时间：
2008-10-01
期刊：
影响因子：
5.6
通讯作者：
Zilles, Karl
中科院分区：
文献类型：
--
作者：
Bidmon, Hans-J;Goerg, Boris;Zilles, Karl
目的：星形胶质细胞特异性谷氨酰胺合成酶（GS）在谷氨酸循环和γ -氨基丁酸（GABA）代谢中起关键作用。GS蛋白表达或活性的改变被认为与癫痫发生有关。GS可能导致癫痫的机制、方式和地点仍在讨论中。在这里，我们提出了一个问题，即显示星形细胞应激反应的大脑区域是否与GS的改变有关。方法：采用与局灶性热休克反应（HSR）相关的GS免疫反应性（GSIR）的地形量化方法，研究戊四唑诱发大鼠重复性癫痫发作（PIRS）后GS、HSP-27和GFAP的生化和组织学改变。盐水处理的大鼠作为对照，gs -抑制剂l -蛋氨酸-亚砜胺（MSO）处理的大鼠作为阳性对照。结果：在PIRS过程中，GSIR和gs蛋白的含量没有变化。通过组织化学（原位）和mso处理大鼠的天然（未加热）蛋白质提取物观察到GSIR的显著降低。在受PIRS影响的大鼠中，gs -活性显示出与酶的硝化相关的显著的区域特异性降低。讨论：这些结果表明，PIRS和GS抑制都没有减少GS蛋白的数量，但MSO干扰抗体与天然GS的结合。PIRS导致了星形细胞应激反应的局域性增加，而MSO引起了广泛的、均匀的星形细胞HSR，与GS含量的定量变化无关。在PIRS大鼠中，显示出强胶质HSR的区域，gs -活性和gs -硝化反应降低，这些都是亚硝化应激反应的明确指标。
Purpose: The astrocyte-specific glutamine synthetase (GS) plays a key role in glutamate recycling and Gamma-aminobutyric acid (GABA) metabolism. Changes in the expression or activity of GS have been proposed to contribute to epileptogenesis. The mechanisms or how and where GS may contribute to epilepsy is still a matter of discussion. Here we asked the question whether brain regions, which show an astrocytic stress response respond with alterations of GS.Methods: Biochemical and histological alterations of GS, HSP-27, and GFAP were studied after pentylenetetrazole-incluced repetitive epileptic seizures (PIRS) in rats using a topographical quantification of the GS-immunoreactivity (GSIR) in relation to the focal heat shock response (HSR). Saline-treated rats served as controls and rats treated by the GS-inhibitor, L-methionine-sulfoximine (MSO) served as a positive control.Results: No changes in the amount of GSIR and GS-protein occurred during PIRS. A significant reduction of GSIR was observed by histochemistry (in situ) and in native (nonheated) protein extracts of MSO-treated rats. In rats affected by PIRS, GS-activity showed a significant, region-specific reduction in association with a nitration of the enzyme.Discussion: These results show that neither PIRS nor GS-inhibition reduced the amount of GS protein, but that MSO interferes with antibody binding to native GS. PIRS resulted in a focal increase of astrocytic stress response, whereas MSO caused a widespread, homogeneous astrocytic HSR independent from quantitative changes of GS content. In rats with PIRS the regions showing a strong glial HSR, respond with reduced GS-activity and GS-nitration, which all together are clear indicators of a nitrosative stress response.