title: Dopamine toxicity in neuroblastoma cells: role of glutathione depletion by L-BSO and apoptosis.
abstract: Dopamine (DA), while an essential neurotransmitter, is also a known neurotoxin that potentially plays an etiologic role in several neurodegenerative diseases. DA metabolism and oxidation readily produce reactive oxygen species (ROS) and DA can also be oxidized to a reactive quinone via spontaneous, enzyme-catalyzed or metal-enhanced reactions. A number of these reactions are cytotoxic, yet the precise mechanisms by which DA leads to cell death remain unknown. In this study, the neuroblastoma cell line, SK-N-SH, was utilized to examine DA toxicity under varying oxidant states. Cells pretreated with the glutathione (GSH)-depleting compound, L-buthionine sulfoximine (L-BSO), exhibited enhanced sensitivity to DA compared to controls (non-GSH-depleted cells). Furthermore, in cells pretreated with L-BSO, the addition of ascorbate (250 microM) afforded significant protection against DA-induced toxicity, while pyruvate (500 microM) had no protective effect. To further characterize the possibility that DA is associated with oxidative stress, additional studies were carried out with manganese (30 microM) as a pro-oxidant. Manganese and DA (200 microM), although not cytotoxic when individually administered to SK-N-SH cells, had a synergistic action on cytotoxicity. Finally, morphological and molecular markers of programmed cell death (apoptosis) were observed in cells treated with DA and L-BSO. These markers included membrane blebbing and internucleosomal DNA fragmentation. These results suggest that DA toxicity is tightly linked to intracellular oxidant/antioxidant levels, and that environmental factors, such as excessive Mn exposure, may modulate cellular sensitivity to DA.
authors.affiliation: Department of Physiology and Pharmacology, Wake Forest University School of Medicine, Wake Forest University, Winston-Salem, NC 27157-1083, USA.
authors.forename: A H
authors.initials: AH
authors.lastname: Stokes
authors.forename: D Y
authors.initials: DY
authors.lastname: Lewis
authors.forename: L H
authors.initials: LH
authors.lastname: Lash
authors.forename: W G
authors.initials: WG
authors.lastname: Jerome
authors.forename: K W
authors.initials: KW
authors.lastname: Grant
authors.forename: M
authors.initials: M
authors.lastname: Aschner
authors.forename: K E
authors.initials: KE
authors.lastname: Vrana
mesh_terms: D017209:Apoptosis; D001205:Ascorbic Acid / Q000494:pharmacology; D001681:Biological Assay; D019328:Buthionine Sulfoximine / Q000494:pharmacology*; D002462:Cell Membrane / Q000187:drug effects / Q000648:ultrastructure; D002851:Chromatography, High Pressure Liquid; D053938:DNA Fragmentation; D004298:Dopamine / Q000378:metabolism / Q000633:toxicity*; D004357:Drug Synergism; D005978:Glutathione / Q000378:metabolism*; D006801:Humans; D008345:Manganese / Q000494:pharmacology; D008855:Microscopy, Electron, Scanning; D009447:Neuroblastoma / Q000378:metabolism* / Q000473:pathology / Q000648:ultrastructure; D018384:Oxidative Stress / Q000187:drug effects; D019289:Pyruvic Acid / Q000494:pharmacology; D014407:Tumor Cells, Cultured
chemical_list: D008345:Manganese; D019328:Buthionine Sulfoximine; D019289:Pyruvic Acid; D005978:Glutathione; D001205:Ascorbic Acid; D004298:Dopamine