Downregulation of Glutamine Synthetase via GLAST Suppression Induces Retinal Axonal Swelling in a Rat Ex Vivo Hydrostatic Pressure Model
Downregulation of Glutamine Synthetase via GLAST Suppression Induces Retinal Axonal Swelling in a Rat Ex Vivo Hydrostatic Pressure Model
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DOI：
10.1167/iovs.11-7375
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发表时间：
2011-08-01
影响因子：
4.4
通讯作者：
Izumi, Yukitoshi
中科院分区：
文献类型：
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作者：
Ishikawa, Makoto;Yoshitomi, Takeshi;Izumi, Yukitoshi
目的.高水平的谷氨酸盐对视网膜GC是有毒的。因此，细胞外谷氨酸的有效缓冲对于保护视网膜结构和功能是重要的。GLAST（视网膜中的主要谷氨酸转运蛋白）和谷氨酰胺合成酶（GS）调节细胞外谷氨酸积累并防止兴奋性毒性。本研究是在离体大鼠视网膜暴露于环境压力急性增加的功能和表达的GLAST和GS的变化的检查。将离体大鼠视网膜暴露于升高的流体静压24小时。采用免疫组化和实时荧光定量PCR检测GLAST和GS的表达。还检查了（2S，3S）-3-[3-[4-（三氟甲基）苯甲酰氨基]苄氧基]天冬氨酸（TFBTBOA）（一种谷氨酸转运蛋白抑制剂）和L-甲硫氨酸-S-磺酰亚胺（MSO）（一种GS. MTS抑制剂）的作用。在这个急性模型中，Western印迹和实时RTPCR分析显示，基本上（75毫米汞柱），但不是中度（35毫米汞柱），升高的压力抑制GLAST表达，降低GS活性，并诱导轴突肿胀之间的GC层和内界膜。然而，在适度升高的压力（35 mm Hg）下，TFB-TBOA或MSO的给药也诱导轴突肿胀和兴奋性毒性神经元损伤。MSO不抑制GLAST的表达，但TFB-TBOA显著抑制GS的表达，提示压力负荷时GS的下调可能是GLAST表达受损所致。在急性眼内压升高期间，由于GLAST表达降低导致GS活性下调，视网膜处于危险之中。（Invest Ophthalmol维斯科学。2011; 52：6604-6616）DOI：10.1167/iovs.11-7375
PURPOSE. High levels of glutamate can be toxic to retinal GCs. Thus, effective buffering of extracellular glutamate is important in preserving retinal structure and function. GLAST, a major glutamate transporter in the retina, and glutamine synthetase (GS) regulate extracellular glutamate accumulation and prevent excitotoxicity. This study was an examination of changes in function and expression of GLAST and GS in ex vivo rat retinas exposed to acute increases in ambient pressure.METHODS. Ex vivo rat retinas were exposed to elevated hydrostatic pressure for 24 hours. The expression of GLAST and GS were examined using immunochemistry and real-time PCR analysis. Also examined were the effects of (2S, 3S)-3-[3-[4-(trifluoromethyl) benzoylamino] benzyloxy] aspartate (TFBTBOA), an inhibitor of glutamate transporters, and L-methionine-S-sulfoximine (MSO), an inhibitor of GS.RESULTS. In this acute model, Western blot and real-time RTPCR analyses revealed that substantially (75 mm Hg), but not moderately (35 mm Hg), elevated pressure depressed GLAST expression, diminished GS activity, and induced axonal swelling between the GC layer and the inner limiting membrane. However, at the moderately elevated pressure (35 mm Hg), administration of either TFB-TBOA or MSO also induced axonal swelling and excitotoxic neuronal damage. MSO did not depress GLAST expression but TFB-TBOA significantly suppressed GS, suggesting that downregulation of GS during pressure loading may result from impaired GLAST expression.CONCLUSIONS. The retina is at risk during acute intraocular pressure elevation due to downregulation of GS activity resulting from depressed GLAST expression. (Invest Ophthalmol Vis Sci. 2011; 52: 6604-6616) DOI: 10.1167/iovs.11-7375