RESUMEN
Mitochondria-targeted cationic plastoquinone derivative SkQ1 (10-(6'-plastoquinonyl) decyltriphenylphosphonium) has been investigated as a potential tool for treating a number of ROS-related ocular diseases. In OXYS rats suffering from a ROS-induced progeria, very small amounts of SkQ1 (50 nmol/kg per day) added to food were found to prevent development of age-induced cataract and retinopathies of the eye, lipid peroxidation and protein carbonylation in skeletal muscles, as well as a decrease in bone mineralization. Instillation of drops of 250 nM SkQ1 reversed cataract and retinopathies in 3-12-month-old (but not in 24-month-old) OXYS rats. In rabbits, experimental uveitis and glaucoma were induced by immunization with arrestin and injections of hydroxypropyl methyl cellulose to the eye anterior sector, respectively. Uveitis was found to be prevented or reversed by instillation of 250 nM SkQ1 drops (four drops per day). Development of glaucoma was retarded by drops of 5 microM SkQ1 (one drop daily). SkQ1 was tested in veterinarian practice. A totally of 271 animals (dogs, cats, and horses) suffering from retinopathies, uveitis, conjunctivitis, and cornea diseases were treated with drops of 250 nM SkQ1. In 242 cases, positive therapeutic effect was obvious. Among animals suffering from retinopathies, 89 were blind. In 67 cases, vision returned after SkQ1 treatment. In ex vivo studies of cultivated posterior retina sector, it was found that 20 nM SkQ1 strongly decreased macrophagal transformation of the retinal pigmented epithelial cells, an effect which might explain some of the above SkQ1 activities. It is concluded that low concentrations of SkQ1 are promising in treating retinopathies, cataract, uveitis, glaucoma, and some other ocular diseases.
Asunto(s)
Envejecimiento , Oftalmopatías/veterinaria , Mitocondrias/metabolismo , Plastoquinona/análogos & derivados , Animales , Transporte Biológico , Ceguera/tratamiento farmacológico , Ceguera/fisiopatología , Ceguera/veterinaria , Gatos , Perros , Oftalmopatías/tratamiento farmacológico , Oftalmopatías/fisiopatología , Oftalmopatías/prevención & control , Femenino , Caballos , Técnicas In Vitro , Masculino , Mitocondrias/química , Mitocondrias/efectos de los fármacos , Plastoquinona/metabolismo , Plastoquinona/farmacología , Progeria/inducido químicamente , Progeria/fisiopatología , Progeria/veterinaria , Conejos , Ratas , Especies Reactivas de Oxígeno/metabolismo , Retina/efectos de los fármacos , Retina/metabolismo , Retina/fisiopatologíaRESUMEN
Low (C(1/2) = 1.5 x 10(-7) M) concentrations of horse cytochrome c strongly inhibit H(2)O(2) production by rat heart mitochondria under conditions of reverse electron transfer from succinate to NAD(+). The effect is abolished by binding of cytochrome c with liposomes and is not prevented by SOD. Yeast cytochrome c is much less effective than the horse protein whereas acetylated horse cytochrome c is without effect. H(2)O(2) formation stimulated by antimycin A is resistant to added cytochrome c. In inside-out submitochondrial vesicles, H(2)O(2) production is suppressed by all three cytochrome c samples tested, but at higher concentrations (C(1/2) is about 5 x 10(-7) M). In vesicles, SOD abolishes the cytochrome c inhibition. We conclude that extramitochondrial cytochrome c is competent in down-regulation of the Complex I H(2)O(2) production linked to the reverse electron transfer. Such an effect is absent in the inside-out submitochondrial vesicles where another antioxidant cytochrome c function can be observed, i.e. the oxidation of O(2-*) to O(2). A possible role of cytochrome c in the antioxidant defence is discussed.
Asunto(s)
Antioxidantes/metabolismo , Grupo Citocromo c/metabolismo , Especies Reactivas de Oxígeno/metabolismo , Animales , Antibacterianos/farmacología , Antimicina A/farmacología , Bovinos , Peróxido de Hidrógeno/metabolismo , Técnicas In Vitro , Liposomas , Mitocondrias Cardíacas/efectos de los fármacos , Mitocondrias Cardíacas/metabolismo , RatasRESUMEN
Both natural (laurate) and artificial (m-chlorocarbonylcyanide phenylhydrazone; CCCP) uncouplers strongly inhibit O2.- and H2O2 formation by rat heart mitochondria oxidizing succinate. Carboxyatractylate, an ATP/ADP antiporter inhibitor, abolishes the laurate inhibition, the CCCP inhibition being unaffected. Atractylate partially releases the inhibition by laurate and decelerates the releasing effect of carboxyatractylate. GDP is much less effective than carboxyatractylate in releasing the laurate inhibition of reactive oxygen species (ROS) formation. Micromolar laurate concentrations arresting the ROS formation cause strong inhibition of reverse electron transfer from succinate to NAD+, whereas State 4 respiration and the transmembrane electric potential difference (delta psi) level are affected only slightly. It is suggested that (i) free fatty acids operate as natural 'mild uncouplers' preventing the transmembrane electrochemical H+ potential difference (delta muH+) from being above a threshold critical for ROS formation by complex I and, to a lesser degree, by complex III of the respiratory chain, and (ii) it is the ATP/ADP-antiporter, rather than uncoupling protein 2, that is mainly involved in this antioxidant mechanism of heart muscle mitochondria.
Asunto(s)
Transporte de Electrón/efectos de los fármacos , Ácidos Grasos/farmacología , Peróxido de Hidrógeno/antagonistas & inhibidores , Mitocondrias Cardíacas/metabolismo , Especies Reactivas de Oxígeno/metabolismo , Animales , Ácidos Grasos/metabolismo , Peróxido de Hidrógeno/metabolismo , Translocasas Mitocondriales de ADP y ATP/metabolismo , RatasRESUMEN
Formation of H2O2 has been studied in rat heart mitochondria, pretreated with H2O2 and aminotriazole to lower their antioxidant capacity. It is shown that the rate of H2O2 formation by mitochondria oxidizing 6 mM succinate is inhibited by a protonophorous uncoupler, ADP and phosphate, malonate, rotenone and myxothiazol, and is stimulated by antimycin A. The effect of ADP is abolished by carboxyatractylate and oligomycin. Addition of uncoupler after rotenone induces further inhibition of H2O2 production. Inhibition of H2O2 formation by uncoupler, malonate and ADP+Pi is shown to be proportional to the delta psi decrease by these compounds. A threshold delta psi value is found, above which a very strong increase in H2O2 production takes place. This threshold slightly exceeds the state 3 delta psi level. The data obtained are in line with the concept [Skulachev, V.P., Q. Rev. Biophys. 29 (1996), 169-2021 that a high proton motive force in state 4 is potentially dangerous for the cell due to an increase in the probability of superoxide formation.
Asunto(s)
Peróxido de Hidrógeno/metabolismo , Potenciales de la Membrana , Mitocondrias Cardíacas/fisiología , Adenosina Difosfato/farmacología , Animales , Malonatos/farmacología , Mitocondrias Cardíacas/efectos de los fármacos , Mitocondrias Cardíacas/metabolismo , Nitrilos/farmacología , Fosfatos/farmacología , Protones , Ratas , Rotenona/farmacologíaRESUMEN
Preparations of coupled mitochondria were labeled with fluorescein isothiocyanate (FITC). Comparison of characteristics of FITC bound to mitochondria versus azolectin liposomes indicates that a significant part of the probe is bound to mitochondrial proteins including proteins of the matrix side of the inner membrane. The experiments with the probe indicate that mitochondrial proteins resemble typical polyelectrolytes with constant of dissociation close to 10(-7).H+ and K+ compete for binding to mitochondrial proteins at neutral pH. The slow deprotonation of matrix proteins is observed during equilibration of matrix protons with medium protons. This process is not restricted to the transmembrane proton transfer. The data are explained by the theory of immobilized buffer. Under certain conditions the extent of dissociation of the matrix immobilized buffer correlates with the rate of mitochondrial respiration in state 3P according to chance.