Characterization of the role of glutathione in repin-induced mitochondrial dysfunction, oxidative stress and dopaminergic neurotoxicity in rat pheochromocytoma (PC12) cells.
Repin, a major constituent in extracts of the plant Centaurea repens is thought to be the active principal responsible for the development of equine nigropallidal encephalomalacia (ENE), a fatal Parkinson-like neurodegenerative disorder in horses. Although the exact mechanism by which ingestion of this weed causes ENE is uncertain, a limited body of experimental evidence suggests a critical role for the glutathione redox system. In the present study, the mechanism of repin neurotoxicity was examined in PC12 cells with a focus on determining the role of glutathione (GSH) in repin-induced mitochondrial dysfunction, oxidative stress and dopaminergic toxicity. The results demonstrate that repin reduced both cellular GSH levels and mitochondrial function in a manner that was time- and concentration-dependent. The repin-induced changes in GSH levels were found to precede the changes in mitochondrial function. Depletion of GSH with a potent GSH depletor (ethacrynic acid (EA)) and a GSH synthesis inhibitor (buthionine sulfoximine (BSO)) prior to repin treatment enhanced the repin-induced mitochondrial change. In addition, repin caused a concentration-dependent decrease in cellular dopamine levels in NGF-differentiated PC12 cells. Increases in intracellular GSH levels induced by pre-treatment with reducing agents (N-acetyl-L-cysteine or reduced glutathione) completely protected the cells from repin-induced mitochondrial and dopaminergic toxicity. Antioxidants, coenzyme-Q and ascorbic acid completely blocked repin-induced dopaminergic toxicity. These data suggest that GSH plays a critical role in repin-induced neurotoxicity and that the maintenance of neuronal redox status may prove to be a useful strategy for the prevention and/or treatment of ENE. The results support the view that GSH depletion, leading to oxidative damage and subsequent mitochondrial dysfunction, may serve as a trigger for neuronal cell death.
Tukov
Francis F
FF
Department of Pharmacology and National Center for Natural Products Research, Research Institute of Pharmaceutical Sciences, School of Pharmacy, University of Mississippi, 317 Faser Hall, Mississippi, MS 38677, USA.
Rimoldi
John M
JM
Matthews
John C
JC
D000818:Animals; D004298:Dopamine / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D005978:Glutathione / Q000502:physiology*; D008928:Mitochondria / Q000187:drug effects* / Q000378:metabolism; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects* / Q000502:physiology; D016716:PC12 Cells; D051381:Rats; D012717:Sesquiterpenes / Q000633:toxicity*
D012717:Sesquiterpenes; C064339:repin; D005978:Glutathione; D004298:Dopamine