Cooperative action of glutamate transporters and cystine/glutamate antiporter system X_c^– protects from oxidative glutamate toxicity.

Lewerenz, Jan; Klein, Mathias; Methner, Axel

Oxidative glutamate toxicity in the neuronal cell line HT22 is a model for cell death by oxidative stress. In this paradigm, an excess of extracellular glutamate blocks the glutamate/cystine-antiporter system , depleting the cell of cysteine, a building block of the antioxidant glutathione. Loss of glutathione leads to the accumulation of reactive oxygen species and eventually cell death. We selected cells resistant to oxidative stress, which exhibit reduced glutamate-induced glutathione depletion mediated by an increase in the antiporter subunit xCT and system activity. Cystine uptake was less sensitive to inhibition by glutamate and we hypothesized that glutamate import via excitatory amino acid transporters and immediate re-export via system underlies this phenomenon. Inhibition of glutamate transporters by l- trans-pyrrolidine-2,4-dicarboxylic acid (PDC) and DL-threo-β-benzyloxyaspartic acid (TBOA) exacerbated glutamate-induced cell death. PDC decreased intracellular glutamate accumulation and exacerbated glutathione depletion in the presence of glutamate. Transient overexpression of xCT and the glutamate transporter EAAT3 cooperatively protected against glutamate. We conclude that EAATs support system to prevent glutathione depletion caused by high extracellular glutamate. This knowledge could be of use for the development of novel therapeutics aimed at diseases associated with depletion of glutathione like Parkinson's disease.

NEURONS; CELL lines; OXIDATIVE stress; GLUTATHIONE; REACTIVE oxygen species; AMINO acids; PARKINSON'S disease

Journal of Neurochemistry, 2006, Vol 98, Issue 3, p916

0022-3042

Academic Journal

10.1111/j.1471-4159.2006.03921.x