title: Bcl-2 family proteins regulate mitochondrial reactive oxygen production and protect against oxidative stress.
abstract: Bcl-2 family proteins protect against a variety of forms of cell death, including acute oxidative stress. Previous studies have shown that overexpression of the antiapoptotic protein Bcl-2 increases cellular redox capacity. Here we report that cell lines transfected with Bcl-2 paradoxically exhibit increased rates of mitochondrial H(2)O(2) generation. Using isolated mitochondria, we determined that increased H(2)O(2) release results from the oxidation of reduced nicotinamide adenine dinucleotide-linked substrates. Antiapoptotic Bcl-2 family proteins Bcl-xL and Mcl-1 also increase mitochondrial H(2)O(2) release when overexpressed. Chronic exposure of cells to low levels of the mitochondrial uncoupler carbonyl cyanide 4-(triflouromethoxy)phenylhydrazone reduced the rate of H(2)O(2) production by Bcl-xL overexpressing cells, resulting in a decreased ability to remove exogenous H(2)O(2) and enhanced cell death under conditions of acute oxidative stress. Our results indicate that chronic and mild elevations in H(2)O(2) release from Bcl-2, Bcl-xL, and Mcl-1 overexpressing mitochondria lead to enhanced cellular antioxidant defense and protection against death caused by acute oxidative stress.
authors.affiliation: Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, Brazil.
authors.forename: Alicia J
authors.initials: AJ
authors.lastname: Kowaltowski
authors.forename: Robert G
authors.initials: RG
authors.lastname: Fenton
authors.forename: Gary
authors.initials: G
authors.lastname: Fiskum
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000502:physiology*; D017209:Apoptosis; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000031:analogs & derivatives* / Q000494:pharmacology; D002478:Cells, Cultured; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism*; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009243:NAD / Q000378:metabolism; D009363:Neoplasm Proteins / Q000235:genetics / Q000502:physiology; D010084:Oxidation-Reduction; D018384:Oxidative Stress / Q000235:genetics / Q000502:physiology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000502:physiology*; D051381:Rats; D051020:bcl-X Protein
chemical_list: D000975:Antioxidants; C494811:BCL2L1 protein, human; C494813:Bcl2l1 protein, rat; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D051020:bcl-X Protein; C108897:carbonylcyanide 4-trifluoromethoxyphenylhydrazone; D009243:NAD; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D006861:Hydrogen Peroxide