Department of Nutrition and Food Hygiene, School of Preventive Medicine, The Third Military Medical University, Shapingba District, Chongqing, PR China.
Mol Cell Neurosci. 2010 Oct;45(2):192-9. doi: 10.1016/j.mcn.2010.06.010. Epub 2010 Jun 25.
Glutamate is the excitatory neurotransmitter in the retina, but it is neurotoxic in excessive amounts. A decrease in the ability of Müller cells to remove glutamate from the extracellular space may play a crucial role in the disruption of glutamate homeostasis that occurs in the diabetic retina. Previously we have shown that taurine has protective effects against diabetes-induced glutamate dysmetabolism in retinal Müller cells. The aim of this study is to examine the effects and underlying mechanism of taurine on high glucose-induced alterations of Müller cells glutamate uptake and degradation. Müller cells cultures were prepared from 5- to 7-day-old Sprague-Dawley rats. Glutamate uptake was measured as (3)H-glutamate content of the lysates. Glutamine synthetase (GS) activity was assessed by a spectrophotometric assay. The expressions of glutamate transporters (GLAST) and GS were examined by RT-PCR and western-blot. In 25 mmol/l high glucose-treated cultures, Müller cells glutamate uptake, GS activity and GLAST, GS expressions were decreased significantly compared with 5 mmol/l normal glucose cultures (p<0.05). Taurine (1 and 10 mmol/l) significantly inhibited the high glucose-induced decreases in glutamate uptake, GS activity and GLAST, GS expressions (p<0.05). The generation of TBARS, ROS and NO in Müller cells increased significantly after treatment with high glucose compared with normal glucose. However, treatment of 1 and 10 mmol/l taurine resulted in a significant decrease in TBARS, ROS and NO levels (p<0.05). The high glucose treatment decreased antioxidant enzyme (catalase, SOD and GSH-px) activities compared with normal glucose. Taurine treatment increased the catalase, SOD and GSH-px activity in a dose-dependent manner. These findings suggest that taurine may regulate Müller cells' glutamate uptake and degradation under diabetic conditions via its antioxidant mechanism.
谷氨酸是视网膜中的兴奋性神经递质，但在过量时具有神经毒性。Müller 细胞从细胞外空间去除谷氨酸的能力下降，可能在糖尿病视网膜中发生的谷氨酸稳态破坏中发挥关键作用。先前我们已经表明，牛磺酸对视网膜 Müller 细胞中糖尿病诱导的谷氨酸代谢紊乱具有保护作用。本研究旨在研究牛磺酸对高葡萄糖诱导的 Müller 细胞谷氨酸摄取和降解改变的作用及其潜在机制。Müller 细胞培养物从 5-7 天大的 Sprague-Dawley 大鼠中制备。通过（3）H-谷氨酸的溶胞产物含量来测量谷氨酸摄取。通过分光光度法测定谷氨酰胺合成酶（GS）活性。通过 RT-PCR 和 Western blot 检测谷氨酸转运体（GLAST）和 GS 的表达。在 25mmol/l 高葡萄糖处理的培养物中，与 5mmol/l 正常葡萄糖培养物相比，Müller 细胞谷氨酸摄取、GS 活性和 GLAST、GS 表达明显降低（p<0.05）。牛磺酸（1 和 10mmol/l）显著抑制了高葡萄糖诱导的谷氨酸摄取、GS 活性和 GLAST、GS 表达降低（p<0.05）。与正常葡萄糖相比，高葡萄糖处理后 Müller 细胞中 TBARS、ROS 和 NO 的生成明显增加。然而，用 1 和 10mmol/l 牛磺酸处理可导致 TBARS、ROS 和 NO 水平显著降低（p<0.05）。高葡萄糖处理使抗氧化酶（过氧化氢酶、SOD 和 GSH-px）活性与正常葡萄糖相比降低。牛磺酸处理以剂量依赖的方式增加过氧化氢酶、SOD 和 GSH-px 活性。这些发现表明，牛磺酸可能通过其抗氧化机制调节糖尿病条件下 Müller 细胞的谷氨酸摄取和降解。
