Permeabilization of the inner mitochondrial membrane by Ca2+ ions is stimulated by t-butyl hydroperoxide and mediated by reactive oxygen species generated by mitochondria.
The extent of swelling undergone by deenergized mitochondria incubated in KCl/sucrose medium in the presence of Ca2+ alone or Ca2+ and t-butyl hydroperoxide decreases by decreasing molecular oxygen concentration in the reaction medium; under anaerobiosis no swelling occurs. This swelling is also inhibited by the presence of exogenous catalase or by the Fe2+ chelator o-phenanthroline in a time-dependent manner. The production of protein thiol cross-linking that leads to the formation of protein aggregates induced by Ca2+ and t-butyl hydroperoxide does not occur when mitochondria are incubated in anaerobic medium or in the presence of o-phenanthroline. In addition, it is also shown that the yield of stable methyl radical adducts, obtained from rat liver mitochondria treated with t-butyl hydroperoxide and the spin trap DMPO, is reduced by addition of EGTA and increases by addition of Ca2+ ions. These data support the hypothesis that Ca2+ ions stimulate electron leakage from the respiratory chain, increasing the mitochondrial production of reactive oxygen species.
Castilho
R F
RF
Departamento de Bioquímica, Universidade Estadual de Campinas, Brazil.
Kowaltowski
A J
AJ
Meinicke
A R
AR
Bechara
E J
EJ
Vercesi
A E
AE
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000693:Anaerobiosis; D000818:Animals; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D002374:Catalase / Q000494:pharmacology; D003432:Cross-Linking Reagents / Q000494:pharmacology; D005609:Free Radicals / Q000378:metabolism; D066298:In Vitro Techniques; D007425:Intracellular Membranes / Q000187:drug effects / Q000378:metabolism; D008565:Membrane Proteins / Q000302:isolation & purification / Q000378:metabolism; D008930:Mitochondria, Liver / Q000187:drug effects / Q000378:metabolism*; D008933:Mitochondrial Swelling / Q000187:drug effects / Q000502:physiology; D008954:Models, Biological; D018384:Oxidative Stress; D010100:Oxygen / Q000378:metabolism; D010539:Permeability / Q000187:drug effects; D010545:Peroxides / Q000494:pharmacology; D010618:Phenanthrolines / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D017382:Reactive Oxygen Species / Q000378:metabolism; D020122:tert-Butylhydroperoxide
D003432:Cross-Linking Reagents; D005609:Free Radicals; D008565:Membrane Proteins; D010545:Peroxides; D010618:Phenanthrolines; D017382:Reactive Oxygen Species; D020122:tert-Butylhydroperoxide; D002374:Catalase; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D010100:Oxygen; D002118:Calcium; C025205:1,10-phenanthroline