The redox state of endogenous pyridine nucleotides can determine both the degree of mitochondrial oxidative stress and the solute selectivity of the permeability transition pore.
Acetoacetate, an NADH oxidant, stimulated the ruthenium red-insensitive rat liver mitochondrial Ca(2+) efflux without significant release of state-4 respiration, disruption of membrane potential (Deltapsi) or mitochondrial swelling. This process is compatible with the opening of the currently designated low conductance state of the permeability transition pore (PTP) and, under our experimental conditions, was associated with a partial oxidation of the mitochondrial pyridine nucleotides. In contrast, diamide, a thiol oxidant, induced a fast mitochondrial Ca(2+) efflux associated with a release of state-4 respiration, a disruption of Deltapsi and a large amplitude mitochondrial swelling. This is compatible with the opening of the high conductance state of the PTP and was associated with extensive oxidation of pyridine nucleotides. Interestingly, the addition of carbonyl cyanide p-(trifluoromethoxy)phenylhydrazone to the acetoacetate experiment promoted a fast shift from the low to the high conductance state of the PTP. Both acetoacetate and diamide-induced mitochondrial permeabilization were inhibited by exogenous catalase. We propose that the shift from a low to a high conductance state of the PTP can be promoted by the oxidation of NADPH. This impairs the antioxidant function of the glutathione reductase/peroxidase system, strongly strengthening the state of mitochondrial oxidative stress.
Departamento de Patologia Clínica, Faculdade de Ciências Médicas, Universidade Estadual de Campinas, 13083-970, SP, Campinas, Brazil.
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D000090:Acetoacetates / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / Q000494:pharmacology; D019069:Cell Respiration / Q000187:drug effects; D003958:Diamide / Q000494:pharmacology; D004553:Electric Conductivity; D005260:Female; D007425:Intracellular Membranes / Q000187:drug effects / Q000378:metabolism; D007473:Ion Channels; D008564:Membrane Potentials / Q000187:drug effects; D008565:Membrane Proteins / Q000378:metabolism*; D008930:Mitochondria, Liver / Q000187:drug effects / Q000378:metabolism*; D033681:Mitochondrial Membrane Transport Proteins; D000083162:Mitochondrial Permeability Transition Pore; D008933:Mitochondrial Swelling / Q000187:drug effects; D009243:NAD / Q000378:metabolism*; D009249:NADP / Q000378:metabolism*; D016877:Oxidants / Q000494:pharmacology; D010084:Oxidation-Reduction / Q000187:drug effects; D018384:Oxidative Stress / Q000187:drug effects; D010539:Permeability / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D017382:Reactive Oxygen Species / Q000378:metabolism; D013379:Substrate Specificity; D013439:Sulfhydryl Reagents / Q000494:pharmacology; D014475:Uncoupling Agents / Q000494:pharmacology
D000090:Acetoacetates; D007473:Ion Channels; D008565:Membrane Proteins; D033681:Mitochondrial Membrane Transport Proteins; D000083162:Mitochondrial Permeability Transition Pore; D016877:Oxidants; D017382:Reactive Oxygen Species; D013439:Sulfhydryl Reagents; D014475:Uncoupling Agents; D009243:NAD; D003958:Diamide; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; C016635:acetoacetic acid; D009249:NADP; D002118:Calcium