title: Effects of taurine on glutamate uptake and degradation in Müller cells under diabetic conditions via antioxidant mechanism.
abstract: 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.
authors.affiliation: Department of Nutrition and Food Hygiene, School of Preventive Medicine, The Third Military Medical University, Shapingba District, Chongqing, PR China.
authors.forename: Kaihong
authors.initials: K
authors.lastname: Zeng
authors.forename: Hongxia
authors.initials: H
authors.lastname: Xu
authors.forename: Ka
authors.initials: K
authors.lastname: Chen
authors.forename: Jundong
authors.initials: J
authors.lastname: Zhu
authors.forename: Yong
authors.initials: Y
authors.lastname: Zhou
authors.forename: Qianyong
authors.initials: Q
authors.lastname: Zhang
authors.forename: Mi
authors.initials: M
authors.lastname: Mantian
mesh_terms: D027322:Amino Acid Transport System X-AG / Q000032:analysis / Q000378:metabolism*; D000818:Animals; D002374:Catalase / Q000032:analysis; D002478:Cells, Cultured; D003930:Diabetic Retinopathy / Q000378:metabolism; D005947:Glucose / Q000009:adverse effects / Q000378:metabolism; D005974:Glutamate-Ammonia Ligase / Q000378:metabolism; D018698:Glutamic Acid / Q000378:metabolism*; D005979:Glutathione Peroxidase / Q000032:analysis; D009569:Nitric Oxide / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000032:analysis; D012160:Retina / Q000187:drug effects* / Q000201:enzymology; D013482:Superoxide Dismutase / Q000032:analysis; D013654:Taurine / Q000494:pharmacology*
chemical_list: D027322:Amino Acid Transport System X-AG; D017382:Reactive Oxygen Species; D013654:Taurine; D009569:Nitric Oxide; D018698:Glutamic Acid; D002374:Catalase; D005979:Glutathione Peroxidase; D013482:Superoxide Dismutase; D005974:Glutamate-Ammonia Ligase; D005947:Glucose