Taurine buffers glutamate homeostasis in retinal cells in vitro under hypoxic conditions.
OBJECTIVE
We investigated whether taurine indirectly protects neurons under hypoxia by affecting retinal Müller cells, which are known to play important roles in the regulation of retinal glutamate content.


METHODS
Retinal cells isolated from rats were exposed to hypoxia for 24 h. We evaluated the retinal neuron survival, glutamate content in cultures with and without taurine under hypoxic conditions. The glutamate clearance function correlated with the expression of glutamine synthetase (GS) mRNA and L-glutamate/L-aspartate transporter (GLAST) mRNA. Immunohistochemical staining of glial fibrillary acidic protein (GFAP), vimentin and S-100 protein was performed to examine cytoskeletal changes in retinal Müller cells.


RESULTS
Retinal neurons treated with taurine exhibited significantly higher survival rates than those without taurine under hypoxia. Taurine inhibited the upregulation of GFAP and vimentin, and inhibited the downregulation of GLAST, GS and the nuclear-cytoplasmic ratio of S-100 under hypoxia. In addition, taurine inhibited the upregulation of the glutamate content in neurons and retinal Müller cells upon hypoxic exposure.


CONCLUSIONS
These data suggest that hypoxic damage to cultured retinal cells is decreased by taurine. The neuroprotection by taurine may relate to buffering glutamate homeostasis via modulation of the glutamate clearance by retinal Müller cells.
Chen
Fang
F
Department of Nutrition and Food Hygiene, Chongqing Key Laboratory of Nutrition and Food Safety, Third Military Medical University, Chongqing, China.
Mi
Mantian
M
Zhang
Qianyong
Q
Wei
Na
N
Chen
Ka
K
Xu
Hongxia
H
Yuan
Jialin
J
Zhou
Yong
Y
Lang
Haibin
H
Yu
Xiaoping
X
Wang
Bin
B
Wang
Jian
J
Tang
Yong
Y
Chang
Hui
H
D027322:Amino Acid Transport System X-AG / Q000235:genetics; D000818:Animals; D002021:Buffers; D002470:Cell Survival; D002478:Cells, Cultured; D019084:Fluorescent Antibody Technique, Indirect; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D005974:Glutamate-Ammonia Ligase / Q000235:genetics; D018698:Glutamic Acid / Q000378:metabolism*; D006706:Homeostasis / Q000502:physiology*; D000860:Hypoxia / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D055351:Retinal Neurons / Q000187:drug effects* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D009418:S100 Proteins / Q000378:metabolism; D013654:Taurine / Q000494:pharmacology*; D014746:Vimentin / Q000378:metabolism
D027322:Amino Acid Transport System X-AG; D002021:Buffers; D005904:Glial Fibrillary Acidic Protein; D012333:RNA, Messenger; D009418:S100 Proteins; D014746:Vimentin; D013654:Taurine; D018698:Glutamic Acid; D005974:Glutamate-Ammonia Ligase