title: Mitochondrial damage due to SOD1 deficiency in SH-SY5Y neuroblastoma cells: a rationale for the redundancy of SOD1.
abstract: Superoxide dismutases (SODs) represent the first line of defense against oxidative stress, which is considered an essential factor in several neurodegenerative diseases and aging. We investigated the role of the copper,zinc superoxide dismutase (SOD1) in the maintenance of intracellular redox homeostasis by analyzing the early effects of SOD1 down-regulation in SH-SY5Y neuroblastoma cells. Through the use of small interference RNA, SOD1 was efficiently down-regulated at 48 h after transfection without any significant effect on cell viability. The steady-state concentration of superoxide was significantly increased after 12 h, when SOD1 was only slightly decreased, and progressively returned to values close to those observed in control cells. The superoxide increase was buffered by the enhanced levels of antioxidant glutathione (GSH); however, GSH increase was not sufficient to avoid damage to proteins in terms of carbonyls. GSH-depleting agents, such as BSO or diamide, further increased protein damage and committed SOD1 deficient cells to death, confirming the pivotal role played by this antioxidant. Although SOD1 declined mostly in the cytosolic compartment, mitochondria were significantly affected with impairment of the mitochondrial transmembrane potential and a decrease in ATP production. Together with these effects carbonylation of mitochondrial proteins was detected and in particular a consistent carbonylation and decrease of the antiapoptotic protein Bcl-2. These conditions induced a high susceptibility of SOD1-depleted cells to treatment with the mitochondrial reactive oxygen species producing agent rotenone. Overall, the results demonstrate that loss of SOD1 leads to severe damage of mitochondria, suggesting an important biological role for this enzyme in the preservation of mitochondrial homeostasis.
authors.affiliation: Department of Biology, University of Rome Tor Vergata, Via della Ricerca Scientifica, 1, Rome, 00133, Italy.
authors.forename: Katia
authors.initials: K
authors.lastname: Aquilano
authors.forename: Paola
authors.initials: P
authors.lastname: Vigilanza
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Rotilio
authors.forename: Maria Rosa
authors.initials: MR
authors.lastname: Ciriolo
mesh_terms: D045744:Cell Line, Tumor; D006706:Homeostasis; D006801:Humans; D008928:Mitochondria / Q000473:pathology*; D028361:Mitochondrial Diseases / Q000209:etiology* / Q000473:pathology; D024101:Mitochondrial Proteins / Q000378:metabolism; D009447:Neuroblastoma / Q000201:enzymology / Q000473:pathology* / Q000648:ultrastructure; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000032:analysis; D012402:Rotenone / Q000494:pharmacology; D013482:Superoxide Dismutase / Q000172:deficiency*; D000072105:Superoxide Dismutase-1
chemical_list: D024101:Mitochondrial Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; C000606290:SOD1 protein, human; D012402:Rotenone; D013482:Superoxide Dismutase; D000072105:Superoxide Dismutase-1