title: Cooperative interaction between ascorbate and glutathione during mitochondrial impairment in mesencephalic cultures.
abstract: A decrease in total glutathione, and aberrant mitochondrial bioenergetics have been implicated in the pathogenesis of Parkinson's disease. Our previous work exemplified the importance of glutathione (GSH) in the protection of mesencephalic neurons exposed to malonate, a reversible inhibitor of mitochondrial succinate dehydrogenase/complex II. Additionally, reactive oxygen species (ROS) generation was an early, contributing event in malonate toxicity. Protection by ascorbate was found to correlate with a stimulated increase in protein-glutathione mixed disulfide (Pr-SSG) levels. The present study further examined ascorbate-glutathione interactions during mitochondrial impairment. Depletion of GSH in mesencephalic cells with buthionine sulfoximine potentiated both the malonate-induced toxicity and generation of ROS as monitored by dichlorofluorescein diacetate (DCF) fluorescence. Ascorbate completely ameliorated the increase in DCF fluorescence and toxicity in normal and GSH-depleted cultures, suggesting that protection by ascorbate was due in part to upstream removal of free radicals. Ascorbate stimulated Pr-SSG formation during mitochondrial impairment in normal and GSH-depleted cultures to a similar extent when expressed as a proportion of total GSH incorporated into mixed disulfides. Malonate increased the efflux of GSH and GSSG over time in cultures treated for 4, 6 or 8 h. The addition of ascorbate to malonate-treated cells prevented the efflux of GSH, attenuated the efflux of GSSG and regulated the intracellular GSSG/GSH ratio. Maintenance of GSSG/GSH with ascorbate plus malonate was accompanied by a stimulation of Pr-SSG formation. These findings indicate that ascorbate contributes to the maintenance of GSSG/GSH status during oxidative stress through scavenging of radical species, attenuation of GSH efflux and redistribution of GSSG to the formation of mixed disulfides. It is speculated that these events are linked by glutaredoxin, an enzyme shown to contain both dehydroascorbate reductase as well as glutathione thioltransferase activities.
authors.affiliation: Department of Neurology, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, Piscataway, New Jersey, USA.
authors.forename: Julie
authors.initials: J
authors.lastname: Ehrhart
authors.forename: Gail D
authors.initials: GD
authors.lastname: Zeevalk
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D001205:Ascorbic Acid / Q000378:metabolism*; D019328:Buthionine Sulfoximine / Q000494:pharmacology; D002839:Chromans / Q000494:pharmacology; D004220:Disulfides / Q000378:metabolism; D005456:Fluorescent Dyes; D005978:Glutathione / Q000378:metabolism*; D019803:Glutathione Disulfide / Q000378:metabolism; D008314:Malonates / Q000633:toxicity; D008636:Mesencephalon / Q000166:cytology / Q000187:drug effects / Q000196:embryology / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism*; D018384:Oxidative Stress / Q000187:drug effects; D010300:Parkinson Disease / Q000209:etiology / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D000975:Antioxidants; D002839:Chromans; D004220:Disulfides; D005456:Fluorescent Dyes; D008314:Malonates; D019328:Buthionine Sulfoximine; C030290:malonic acid; D005978:Glutathione; D001205:Ascorbic Acid; C010643:6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid; D019803:Glutathione Disulfide