Gliotoxic action of glutamate on cultured astrocytes.
Because of the well-documented importance of glutamate clearance by astrocytes in protecting neurons against excitotoxicity, it was interesting to examine whether L-glutamate exerts a toxic action on cultured astrocytes. Cell damage was evaluated by measuring activity of lactate dehydrogenase (LDH) released into the culture medium. Exposure of astrocyte cultures of the neonatal rat cerebral cortex to L-glutamate resulted in a concentration- and time-dependent increase in the release of LDH. L-Glutamate-induced gliotoxicity appeared to be mediated predominantly by the increase of oxidative stress because the reduced glutathione content and its effects were almost completely blocked by vitamin E and pyrrolidinedithiocarbamate. To support this notion further, the supplementation or depletion of intracellular reduced glutathione content attenuated or worsened L-glutamate toxicity, respectively. Activation of the glutamate transporter mimicked the action of L-glutamate on astrocytes. In addition, degrees of cell damage were not directly correlated to the levels of glutamate uptake. Moreover, the mechanism of this toxicity required energy and macromolecular synthesis. Taken together, brief exposure to L-glutamate resulted in glutamate uptake and cell swelling, whereas sustained exposure injured astrocytes via oxidative stress instead of the excitatory mechanism.
Chen
C J
CJ
Department of Education and Research, Taichung Veterans General Hospital, Taichung, Taiwan, Republic of China. cjchen@vghtc.vghtc.gov.tw
Liao
S L
SL
Kuo
J S
JS
D018528:ATP-Binding Cassette Transporters / Q000037:antagonists & inhibitors / Q000378:metabolism; D027322:Amino Acid Transport System X-AG; D000596:Amino Acids / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D001253:Astrocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects; D015687:Cell Hypoxia; D002478:Cells, Cultured; D018920:Coculture Techniques; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005947:Glucose / Q000378:metabolism / Q000494:pharmacology; D018698:Glutamic Acid / Q000378:metabolism* / Q000493:pharmacokinetics / Q000633:toxicity*; D005978:Glutathione / Q000378:metabolism; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D009457:Neuroglia / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism; D017470:Receptors, Glutamate / Q000378:metabolism
D018528:ATP-Binding Cassette Transporters; D027322:Amino Acid Transport System X-AG; D000596:Amino Acids; D004791:Enzyme Inhibitors; D018691:Excitatory Amino Acid Antagonists; D019384:Nucleic Acid Synthesis Inhibitors; D011500:Protein Synthesis Inhibitors; D017382:Reactive Oxygen Species; D017470:Receptors, Glutamate; D018698:Glutamic Acid; D007770:L-Lactate Dehydrogenase; D005978:Glutathione; D005947:Glucose