The Iron Chelator Pyridoxal Isonicotinoyl Hydrazone Inhibits Mitochondrial Lipid Peroxidation Induced By Fe(ii)-citrate

Pyridoxal isonicotinoyl hydrazone (PIH) is able to prevent iron-mediated hydroxyl radical formation by means of iron chelation and inhibition of redox cycling of the metal. In this study, we investigated the effect of PIH on Fe(II)-citrate-mediated lipid peroxidation and damage to isolated rat liver mitochondria. Lipid peroxidation was quantified by the production of thiobarbituric acid-reactive substances (TBARS) and by antimycin A-insensitive oxygen consumption. PIH at 300 μM induced full protection against 50 μM Fe(II)-citrate-induced loss of mitochondrial transmembrane potential (Δψ) and mitochondrial swelling. In addition, PIH prevented the Fe(II)-citrate-dependent formation of TBARS and antimycin A-insensitive oxygen consumption. The antioxidant effectiveness of 100 μM PIH (on TBARS formation and mitochondrial swelling) was greater in the presence of 20 or 50 μM Fe(II)-citrate than in the presence of 100 μM Fe(II)-citrate, suggesting that the mechanism of PIH antioxidant action is linked with its Fe(II) chelating property. Finally, PIH increased the rate of Fe(II) autoxidation by sequestering iron from the Fe(II)-citrate complex, forming a Fe(III)-PIH 2 complex that does not participate in Fenton-type reactions and lipid peroxidation. These results are of pharmacological relevance since PIH is a potential candidate for chelation therapy in diseases related to abnormal intracellular iron distribution and/or iron overload. © 2001 Elsevier Science B.V. All rights reserved.42813744Bhattacharya, M., Ponka, P., Hardy, P., Hanna, N., Varma, D.R., Lachapelle, P., Chemtob, S., Prevention of postasphyxia electroretinal dysfunction with a pyridoxal hydrazone (1997) Free Radical Biol. 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Biochem., 145, pp. 53-60Hermes-Lima, M., Nagy, E., Ponka, P., Schulman, H.M., The iron chelator pyridoxal isonicotinoyl hydrazone (PIH) protects plasmid pUC-18 DNA against •OH-mediated strand breaks (1998) Free Radical Biol. Med., 25, pp. 875-880Hermes-Lima, M., Santos, N.C.F., Yan, J., Andrews, M., Schulman, H.M., Ponka, P., EPR spin trapping and 2-deoxyribose degradation studies of the effect of pyridoxal isonicotinoyl hydrazone (PIH) on •OH formation by the Fenton reaction (1999) Biochim. Biophys. Acta, 1426, pp. 475-482Hermes-Lima, M., Ponka, P., Schulman, H.M., The iron chelator pyridoxal isonicotinoyl hydrazone (PIH) and its analogues prevent damage to 2-deoxyribose mediated by ferric iron plus ascorbate (2000) Biochim. Biophys. Acta, 1523, pp. 154-160Hershko, C., Iron chelators (1994) Iron Metabolism in Health and Disease, pp. 391-426. , Brock, J.H., Halliday, J.W., Pippard, M.J., Powell, L.W. (Eds.). W.B. 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Characteristics Of Fe(ii)atp Complex-induced Damage To The Rat Liver Mitochondrial Membrane

It is well established that several iron complexes can induce oxidative damage in hepatic mitochondrial membranes by catalyzing the formation of · OH radicals and/or by promoting lipid peroxidation. This is a relevant process for the molecular basis of iron overload diseases. The present work demonstrates that Fe(II)ATP complexes (5-50 μM) promote an oxygen consumption burst in a suspension of isolated rat liver mitochondria (either in the absence or presence of Antimycin A), caused mainly by lipid peroxidation. Fe(II)ATP alone induced small levels of oxygen uptake but no burst. The time course of Fe(II)ATP oxidation to Fe(III)ATP in the extramitochondrial media also reveals a simultaneous 'burst phase'. The iron chelator Desferal (DFO) or the chain-break antioxidant butylated hydroxytoluene (BHT) fully prevented both lipid peroxidation (quantified as oxygen uptake burst) and mitochondrial swelling. DFO and BHT were capable of stopping the ongoing process of peroxidation at any point of their addition to the mitochondrial suspension. Conversely, DFO and BHT only halted the Fe(II)ATP-induced mitochondrial swelling at the onset of the process. Fe(II)ATP could also cause the collapse of mitochondrial potential, which was protected by BHT if added at the onset of the damaging process. These results, as well as correlation studies between peroxidation and mitochondrial swelling, suggest that a two phase process is occurring during Fe(II)ATP-induced mitochondrial damage: one dependent and another independent of lipid peroxidation. The involvement of lipid peroxidation in the overall process of mitochondrial membrane injury is discussed.1451536

The Role Of Reactive Oxygen Species In Mitochondrial Permeability Transition

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Effect Of Membrane Surface Charge And Salt On Ionophore Partitioning And Antiperoxidative Activity

We have previously shown that the ionophores lasalocid LAS), nigericin and monensin act as radical scavengers, inhibiting lipid peroxidation in mitochondria and in egg phosphatidylcholine (PC) liposomes containing negatively charged lipids and KCL as osmotic support. When tile osmotic support is sucrose, all ionophores failed to inhibit peroxidation. Here we analyse the kinetics of LAS membrane incorporation, a fundamental step for protection against lipid peroxidation. Despite the electrostatic repulsion, in the presence of KCI. the incorporation of tile anionic form (capable of complexing cations) is higher in negatively charged than in PC liposomes. Longer incubation times of LAS with PC liposomes increased ionophore incorporation, as attested by: i ) values of order parameter obtained from EPR spectra of lipid spin labels, ii) protection against lipid peroxidation (monitored by TBARS and conjugated diene), iii) LAS fluorescence and CD spectra. Sucrose prevents ionophore incorporation in both membrane systems. We conclude that the incorporation is characterized by a strong dependence on lipid charge, ionic compounds in the medium, and incubation time. Negatively charged membranes enhance the incorporation of LAS by increasing cation concentration at the interface, facilitating complexation, the limiting step of the process.11

Thapsigargin Causes Ca2+ Release And Collapse Of The Membrane Potential Of Trypanosoma Brucei Mitochondria In Situ And Of Isolated Rat Liver Mitochondria

Thapsigargin, previously reported to release Ca2+ from non-mitochondrial stores of different cell types, as well as nigericin, were found, when used at high concentrations, to release Ca2+ and collapse the membrane potential of Trypanosoma brucei bloodstream and procyclic trypomastigotes mitochondria in situ. At similarly high concentrations (>10 μM), thapsigargin was also found to release Ca2+ and collapse the membrane potential of isolated rat liver mitochondria. These results indicate that care should be taken when attributing the effects of thapsigargin in intact cells to the specific inhibition of the sarcoplasmic and endoplasmic reticulum Ca2+-ATPase family of calcium pumps. In addition, we have found no evidence for an increase in intracellular Ca2+ by release of the ion from intracellular stores by nigericin, measuring changes in cytosolic Ca2+ by dual wavelength spectrofluorometry in fura-2-loaded T. brucei bloodstream trypomastigotes or measuring Ca2+ transport in digitonin-permeabilized cells.268128564856