title: Stimulation by pro-apoptotic valinomycin of cytosolic NADH/cytochrome c electron transport pathway-Effect of SH reagents.
abstract: Intrinsic and extrinsic apoptosis are both characterised by the presence of cytochrome c (cyto-c) in the cytosol. We present data on the extra-mitochondrial NADH oxidation catalysed by exogenous (cytosolic) cyto-c, as a possible answer to the paradox of apoptosis being an energy-dependent program but characterized by the impairment of the respiratory chain. The reduction of molecular oxygen induced by the cytosolic NADH/cyto-c pathway is coupled to the generation of an electrochemical proton gradient available for ATP synthesis. Original findings show that SH reagents inhibit the NADH/cyto-c system with a conformational change mechanism. The mitochondrial integrity-test of sulfite oxidase unequivocally demonstrates that this enzyme (120kDa) can be released outside but exogenous cyto-c (12.5kDa) does not permeate into mitochondria. Valinomycin at 2nM stimulates both the energy-dependent reversible mitochondrial swelling and the NADH/cyto-c oxidation pathway. The pro-apoptotic activity of valinomycin, as well as to the dissipation of membrane potential, can be also ascribed to the increased activity of the NADH/cyto-c oxidation pathway useful as an additional source of energy for apoptosis. It can be speculated that the activation of the NADH/cyto-c system coupled to valinomycin-induced mitochondrial osmotic swelling may represent a strategy to activate apoptosis in confined solid tumours.
authors.affiliation: Department of Biological and Environmental Sciences and Technologies, Section of Human Anatomy, University of Salento, Lecce, Italy.
authors.forename: Dario Domenico
authors.initials: DD
authors.lastname: Lofrumento
authors.affiliation: Department of Biosciences, Biotechnology and Biopharmaceutics, University of Bari, Bari, Italy.
authors.forename: Gianluigi
authors.initials: G
authors.lastname: La Piana
authors.affiliation: Department of Biosciences, Biotechnology and Biopharmaceutics, University of Bari, Bari, Italy.
authors.forename: Valeria
authors.initials: V
authors.lastname: Palmitessa
authors.affiliation: Department of Biosciences, Biotechnology and Biopharmaceutics, University of Bari, Bari, Italy.
authors.forename: Daniela Isabel
authors.initials: DI
authors.lastname: Abbrescia
authors.affiliation: Department of Biosciences, Biotechnology and Biopharmaceutics, University of Bari, Bari, Italy. Electronic address: nicolaelio.lofrumento@uniba.it.
authors.forename: Nicola Elio
authors.initials: NE
authors.lastname: Lofrumento
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D045304:Cytochromes c / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D045222:Electron Transport Chain Complex Proteins / Q000378:metabolism*; D004734:Energy Metabolism / Q000187:drug effects; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D008930:Mitochondria, Liver / Q000378:metabolism*; D009243:NAD / Q000378:metabolism*; D051381:Rats; D014634:Valinomycin / Q000494:pharmacology*
chemical_list: D045222:Electron Transport Chain Complex Proteins; D009243:NAD; D014634:Valinomycin; D045304:Cytochromes c
keywords: Apoptosis; Cytochrome c; Cytosolic NADH oxidation; Mitochondrial contact sites; SH inhibitors; Valinomycin