Role of lipoperoxidation and sulfhydryl oxidation on sensitization of mitochondrial complex III to oxidative damage by Fe2+

Abstract

Mitochondrial fatty acids (FA) are key oxidative stress (OE) targets. FA peroxidation propensity augments as its unsaturation degree (UD) increase. Thus, augment on UD of FA from mitochondrial membranes may exacerbate mitochondrial damage during OE. This aspect has physiological importance because increasing fashion in population to ingest polyunsaturated FA. To investigate the influence of UD over the damage to electron transport chain (ETC) by OE, as well localization and chemical nature of damage, we used S. cerevisiae mitochondria as model because its membrane FA content can be manipulated. In mitochondria with monounsaturated FA, lipoperoxidation levels were unaffected by 50 μM Fe2+, while only complex III activity was inhibited by 50%. Damage on complex III was attributed mainly to OH• attack because mannitol partially protected against activity impairment. In contrast, in mitochondria with linolenic acid (C18:3, 80% of total FA), Fe2+ increased ten‐fold lipoperoxidation levels and fully inhibits complex III, which was prevented in 75% and 23% by the anti‐lipoperoxidative agent BHT and β‐mercaptoethanol, respectively, indicating a dual damage on –SH groups and lipids. These results show that lipoperoxidation sensitize ETC towards oxidative damage, being complex III the most labile enzyme affected by –SH and lipid oxidation. Supported by Fondos Mixtos CONACYT‐ Gob. Edo. de Michoacán (64277, 64308), COECYT and CIC‐UMSNH (2.16) grants.