A COMPARATIVE STUDY OF IRON- AND COPPER-INDUCED OXIDATIVE STRESS IN RAT LIVER ISOLATED MITOCHONDRIA.

MUSACCO SEBIO, R; BAJICOFF, S; BOVERIS, A; ACOSTA, JM; REYNOSO, S; SAPORITO MAGRIÑÁ, C.; PAREDES FLEITAS, P; REPETTO, M

Buenos Aires

Congreso; III International Congress of Translational Medicine; 2016

Maestría Internacional en Ciencias Biomédicas, Facultad de Farmacia y Bioquímica y Facultad de Medicina, UBA

Introduction: The transition metals copper (Cu) and iron (Cu) are micronutrients necessary at low concentration for different vital functions whereas at higher concentrations they become toxic. Wilson?s disease and Haemochromatosis are the most known examples for Cu and Fe toxicity. Here, the pathophysiology proposed in both cases involves the ability of the metals to catalyse the formation of the highly reactive hydroxyl radical (OH?) through the Fenton/Haber-Weiss reaction. Hypothesis: Cu and Fe are able to produce oxidative damage by OH? formation as well as by the direct action of the metals on biomolecules. Methodology: Rat liver isolated mitochondria were exposed to Cu(II) and Fe(III) overloads in the respiration medium. Mitochondrial function (oxygen consumption assessed in a Clark-type electrode), phospholipid peroxidation (assessed as malondialdehyde content) and total thiol content (reaction with DTNB) were determined. Results: Both metals were able to decrease the mitochondrial function. However, much lower concentrations were needed for Cu to become toxic, compared to Fe. The decrease of the oxygen consumption and respiratory control was considerably more pronounced when mitochondria were exposed to conditions of high H2O2/O2- production (incubation in inactive metabolic state or state 4), showing the participation of these species in metal toxicity. Both metals induced phospholipid peroxidation in a concentration-dependent manner but, interestingly, only when substrates for oxygen consumption were available indicating that the mere presence of the metals is not enough to produce oxidative damage to these biomolecules. Regarding Cu, the antioxidant glutathione (GSH) was the most efficient in preventing mitochondrial dysfunction and phospholipid oxidation. Nevertheless, in the case of Fe, these protective effects were only observed upon butylated hydroxytoluene (BHT) supplementation. This differential response to the antioxidant supplementation is indicating that differences in the mechanism of toxicity of the metals do exist. Finally, we found that Cu, but not Fe, is able to react in a direct and stoichiometric manner with the mitochondrial thiol groups. Conclusion: Cu and Fe toxicity present at some point a common toxic mechanism of OH? generation through Fenton/Haber-Weiss reaction. However, Cu may also participate in intracellular oxidative mechanism by direct reaction with protein thiol groups and, specially, GSH.