Differential Effects of Superoxide Dismutase Isoform Expression on Hydroperoxide-induced Apoptosis in PC-12 Cells

• Published in: The Journal of biological chemistry 2003-04, Vol.278 (15), p.13294-13301
• Main Authors: Pias, Erin K, Ekshyyan, Oleksandr Y, Rhoads, Carol A, Fuseler, John, Harrison, Lynn, Aw, Tak Yee
• Format: Article
• Language: English
• Subjects: Animals; Apoptosis - drug effects; Apoptosis - physiology; Caspase 3; Caspases - metabolism; Enzyme Activation - drug effects; Glutathione - metabolism; Glutathione Disulfide - metabolism; Humans; Isoenzymes - genetics; Isoenzymes - metabolism; PC12 Cells; Rats; Reactive Oxygen Species - metabolism; Superoxide Dismutase - genetics; Superoxide Dismutase - metabolism; tert-Butylhydroperoxide - pharmacology; Transfection
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M208670200

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 .