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The Glutamate Aspartate Transporter (GLAST) Mediates L: -Glutamate-Stimulated Ascorbate-Release Via Swelling-Activated Anion Channels in Cultured Neonatal Rodent Astrocytes.
MedLine Citation:
PMID:  22886112     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
Vitamin C (ascorbate) plays important neuroprotective and neuromodulatory roles in the mammalian brain. Astrocytes are crucially involved in brain ascorbate homeostasis and may assist in regenerating extracellular ascorbate from its oxidised forms. Ascorbate accumulated by astrocytes can be released rapidly by a process that is stimulated by the excitatory amino acid, L: -glutamate. This process is thought to be neuroprotective against excitotoxicity. Although of potential clinical interest, the mechanism of this stimulated ascorbate-release remains unknown. Here, we report that primary cultures of mouse and rat astrocytes release ascorbate following initial uptake of dehydroascorbate and accumulation of intracellular ascorbate. Ascorbate-release was not due to cellular lysis, as assessed by cellular release of the cytosolic enzyme lactate dehydrogenase, and was stimulated by L: -glutamate and L: -aspartate, but not the non-excitatory amino acid L: -glutamine. This stimulation was due to glutamate-induced cellular swelling, as it was both attenuated by hypertonic and emulated by hypotonic media. Glutamate-stimulated ascorbate-release was also sensitive to inhibitors of volume-sensitive anion channels, suggesting that the latter may provide the conduit for ascorbate efflux. Glutamate-stimulated ascorbate-release was not recapitulated by selective agonists of either ionotropic or group I metabotropic glutamate receptors, but was completely blocked by either of two compounds, TFB-TBOA and UCPH-101, which non-selectively and selectively inhibit the glial Na(+)-dependent excitatory amino acid transporter, GLAST, respectively. These results suggest that an impairment of astrocytic ascorbate-release may exacerbate neuronal dysfunction in neurodegenerative disorders and acute brain injury in which excitotoxicity and/or GLAST deregulation have been implicated.
Authors:
Darius J R Lane; Alfons Lawen
Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-8-12
Journal Detail:
Title:  Cell biochemistry and biophysics     Volume:  -     ISSN:  1559-0283     ISO Abbreviation:  Cell Biochem. Biophys.     Publication Date:  2012 Aug 
Date Detail:
Created Date:  2012-8-13     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9701934     Medline TA:  Cell Biochem Biophys     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Affiliation:
Department of Biochemistry and Molecular Biology, School of Biomedical Sciences, Monash University, Melbourne, VIC, 3800, Australia, darius.lane@sydney.edu.au.
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