title: Antioxidant defences in cybrids harboring mtDNA mutations associated with Leber's hereditary optic neuropathy.
abstract: Oxidative stress and imbalance between free radical generation and detoxification may play a pivotal role in the pathogenesis of Leber's hereditary optic neuropathy (LHON). Mitochondria, carrying the homoplasmic 11778/ND4, 3460/ND1 and 14484/ND6 mtDNA point mutations associated with LHON, were used to generate osteosarcoma-derived cybrids. Enhanced mitochondrial production of reactive oxygen species has recently been demonstrated in these cybrids [Beretta S, Mattavelli L, Sala G, Tremolizzo L, Schapira AHV, Martinuzzi A, Carelli V & Ferrarese C (2004) Brain 127, 2183-2192]. The aim of this study was to characterize the antioxidant defences of these LHON-affected cells. The activities of glutathione peroxidase (GPx), glutathione reductase (GR), superoxide dismutases (SOD) and catalase, and the amounts of glutathione (GSH) and oxidized glutathione (GSSG) were measured in cybrids cultured both in glucose-rich medium and galactose-rich medium. The latter is known to cause oxidative stress and to trigger apoptotic death in these cells. In spite of reduced SOD activities in all LHON cybrids, and of low GPx and GR activities in cells with the most severe 3460/ND1 and 11778/ND4 mutations, GSH and GSSG content were not significantly modified in LHON cybrids cultured in glucose medium. In contrast, in galactose, GSSG concentrations increased significantly in all cells, indicating severe oxidative stress, whereas GR and MnSOD activities further decreased in all LHON cybrids. These data suggest that, in cells carrying LHON mutations, there is a decrease in antioxidant defences, which is especially evident in cells with mutations associated with the most severe clinical phenotype. This is magnified by stressful conditions such as exposure to galactose.
authors.affiliation: Department of Pharmacology and Anesthesiology, Pharmacology Section, University of Padova, Italy.
authors.forename: Maura
authors.initials: M
authors.lastname: Floreani
authors.forename: Eleonora
authors.initials: E
authors.lastname: Napoli
authors.forename: Andrea
authors.initials: A
authors.lastname: Martinuzzi
authors.forename: Giorgia
authors.initials: G
authors.lastname: Pantano
authors.forename: Valentina
authors.initials: V
authors.lastname: De Riva
authors.forename: Roberta
authors.initials: R
authors.lastname: Trevisan
authors.forename: Elena
authors.initials: E
authors.lastname: Bisetto
authors.forename: Lucia
authors.initials: L
authors.lastname: Valente
authors.forename: Valerio
authors.initials: V
authors.lastname: Carelli
authors.forename: Federica
authors.initials: F
authors.lastname: Dabbeni-Sala
mesh_terms: D000975:Antioxidants / Q000378:metabolism*; D016022:Case-Control Studies; D002374:Catalase / Q000378:metabolism; D002478:Cells, Cultured; D004252:DNA Mutational Analysis; D004272:DNA, Mitochondrial / Q000235:genetics*; D005347:Fibroblasts / Q000378:metabolism; D005690:Galactose / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism; D005979:Glutathione Peroxidase / Q000378:metabolism; D005980:Glutathione Reductase / Q000378:metabolism; D006801:Humans; D006822:Hybrid Cells / Q000378:metabolism* / Q000473:pathology; D008928:Mitochondria / Q000378:metabolism; D009154:Mutation / Q000235:genetics*; D029242:Optic Atrophy, Hereditary, Leber / Q000235:genetics*; D010100:Oxygen / Q000378:metabolism*; D012867:Skin / Q000378:metabolism; D013482:Superoxide Dismutase / Q000378:metabolism
chemical_list: D000975:Antioxidants; D004272:DNA, Mitochondrial; D002374:Catalase; D005979:Glutathione Peroxidase; D013482:Superoxide Dismutase; D005980:Glutathione Reductase; D005978:Glutathione; D005947:Glucose; D010100:Oxygen; D005690:Galactose