title: Cystine/glutamate exchange modulates glutathione supply for neuroprotection from oxidative stress and cell proliferation.
abstract: The cystine/glutamate exchanger (xCT) provides intracellular cyst(e)ine for production of glutathione, a major cellular antioxidant. Using xCT overexpression and underexpression, we present evidence that xCT-dependent glutathione production modulates both neuroprotection from oxidative stress and cell proliferation. In embryonic and adult rat brain, xCT protein was enriched at the CSF-brain barrier (i.e., meninges) and also expressed in the cortex, hippocampus, striatum, and cerebellum. To examine the neuroprotective role of xCT, various non-neuronal cell types (astrocytes, meningeal cells, and peripheral fibroblasts) were cocultured with immature cortical neurons and exposed to oxidative glutamate toxicity, a model involving glutathione depletion. Cultured meningeal cells, which naturally maintain high xCT expression, were more neuroprotective than astrocytes. Selective xCT overexpression in astrocytes was sufficient to enhance glutathione synthesis/release and confer potent glutathione-dependent neuroprotection from oxidative stress. Moreover, normally nonprotective fibroblasts could be re-engineered to be neuroprotective with ectopic xCT overexpression indicating that xCT is a key step in the pathway to glutathione synthesis. Conversely, astrocytes and meningeal cells derived from sut/sut mice (xCT loss-of-function mutants) showed greatly reduced proliferation in culture attributable to increased oxidative stress and thiol deficiency, because growth could be rescued by the thiol-donor beta-mercaptoethanol. Strikingly, sut/sut mice developed brain atrophy by early adulthood, exhibiting ventricular enlargement, thinning of the cortex, and shrinkage of the striatum. Our results indicate that xCT can provide neuroprotection by enhancing glutathione export from non-neuronal cells such as astrocytes and meningeal cells. Furthermore, xCT is critical for cell proliferation during development in vitro and possibly in vivo.
authors.affiliation: Kinsmen Laboratory of Neurological Research and Brain Research Center, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z3.
authors.forename: Andy Y
authors.initials: AY
authors.lastname: Shih
authors.forename: Heidi
authors.initials: H
authors.lastname: Erb
authors.forename: Xiaojian
authors.initials: X
authors.lastname: Sun
authors.forename: Shigenobu
authors.initials: S
authors.lastname: Toda
authors.forename: Peter W
authors.initials: PW
authors.lastname: Kalivas
authors.forename: Timothy H
authors.initials: TH
authors.lastname: Murphy
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D002460:Cell Line; D049109:Cell Proliferation; D002478:Cells, Cultured; D003553:Cystine / Q000235:genetics / Q000378:metabolism*; D018698:Glutamic Acid / Q000235:genetics / Q000378:metabolism*; D005978:Glutathione / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D051379:Mice; D008809:Mice, Inbred C3H; D008822:Mice, Transgenic; D009474:Neurons / Q000166:cytology / Q000378:metabolism; D018696:Neuroprotective Agents / Q000378:metabolism*; D018384:Oxidative Stress / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar
chemical_list: D018696:Neuroprotective Agents; D018698:Glutamic Acid; D003553:Cystine; D005978:Glutathione