title: Differential effects of superoxide dismutase isoform expression on hydroperoxide-induced apoptosis in PC-12 cells.
abstract: The current study examines the contribution of mitochondria-derived reactive oxygen species (ROS) in tert-butyl-hydroperoxide (TBH)-induced apoptotic signaling using clones of undifferentiated pheochromocytoma (PC-12) cells that stably overexpress the human mitochondrial or cytoplasmic forms of superoxide dismutase (SOD) (viz. Mn-SOD or CuZn-SOD, respectively). Exposure of wild type cells to TBH caused an early generation of ROS (30 min) that resulted in cell apoptosis at 24 h. These responses were attenuated with N-acetylcysteine pretreatment; however, N-acetylcysteine was ineffective in cytoprotection when added after TBH-induced ROS formation. Stable overexpression of SOD isoforms caused a 2- and 3.5-fold elevation in CuZn-SOD and Mn-SOD activities in the cytoplasm and mitochondria, respectively, and 3-fold increases in cellular GSH content. Accordingly, the stable overexpression of Mn-SOD attenuated TBH-induced mitochondrial ROS generation and cell apoptosis. Whereas transient Mn-SOD expression similarly prevented PC-12 apoptosis, this was associated with increases in SOD activity but not GSH, indicating that cytoprotection by Mn-SOD overexpression is related to mitochondrial ROS elimination and not due to increases in cellular GSH content per se. Stable or transient CuZn-SOD overexpression exacerbated cell apoptosis in conjunction with accelerated caspase-3 activation, regardless of cell GSH levels. Collectively, our results support a role for mitochondrial ROS in TBH-induced PC-12 apoptosis that is attenuated by Mn-SOD overexpression and is independent of cellular GSH levels per se.
authors.affiliation: Department of Molecular and Cellular Physiology, Louisiana State University Health Sciences Center, Shreveport, Louisiana 71130-3932, USA.
authors.forename: Erin K
authors.initials: EK
authors.lastname: Pias
authors.forename: Oleksandr Y
authors.initials: OY
authors.lastname: Ekshyyan
authors.forename: Carol A
authors.initials: CA
authors.lastname: Rhoads
authors.forename: John
authors.initials: J
authors.lastname: Fuseler
authors.forename: Lynn
authors.initials: L
authors.lastname: Harrison
authors.forename: Tak Yee
authors.initials: TY
authors.lastname: Aw
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D005978:Glutathione / Q000378:metabolism; D019803:Glutathione Disulfide / Q000378:metabolism; D006801:Humans; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D016716:PC12 Cells; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism; D013482:Superoxide Dismutase / Q000235:genetics / Q000378:metabolism*; D014162:Transfection; D020122:tert-Butylhydroperoxide / Q000494:pharmacology*
chemical_list: D007527:Isoenzymes; D017382:Reactive Oxygen Species; D020122:tert-Butylhydroperoxide; D013482:Superoxide Dismutase; C505407:CASP3 protein, human; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases; D005978:Glutathione; D019803:Glutathione Disulfide