Reversible redox-dependent modulation of mitochondrial aconitase and proteolytic activity during in vivo cardiac ischemia/reperfusion

Abstract

Prooxidents can induce reversible inhibition or irreversible inactivation and degradation of the mitochondrial enzyme aconitase. Cardiac ischemia͞reperfusion is associated with an increase in mitochondrial free radical production. In the current study, the effects of reperfusion-induced production of prooxidants on mitochondrial aconitase and proteolytic activity were determined to assess whether alterations represented a regulated response to changes in redox status or oxidative damage. Evidence is provided that ATP-dependent proteolytic activity increased during early reperfusion followed by a time-dependent reduction in activity to control levels. These alterations in proteolytic activity paralleled an increase and subsequent decrease in the level of oxidatively modified protein. In vitro data supports a role for prooxidants in the activation of ATP-dependent proteolytic activity. Despite inhibition during early periods of reperfusion, aconitase was not degraded under the conditions of these experiments. Aconitase activity exhibited a decline in activity followed by reactivation during cardiac reperfusion. Loss and regain in activity involved reversible sulfhydryl modification. Aconitase was found to associate with the iron binding protein frataxin exclusively during reperfusion. In vitro, frataxin has been shown to protect aconitase from [4Fe-4S] 2؉ cluster disassembly, irreversible inactivation, and, potentially, degradation. Thus, the response of mitochondrial aconitase and ATP-dependent proteolytic activity to reperfusioninduced prooxidant production appears to be a regulated event that would be expected to reduce irreparable damage to the mitochondria.H ighly reactive oxygen derived free radicals, such as superoxide anion (O 2•Ϫ ) and the prooxidant hydrogen peroxide (H 2 O 2 ), can interact with a variety of cellular components, altering both structure and function (1). Although evidence for these reactions has long been sought as indication of free radical involvement in degenerative disorders, recent evidence indicates that these processes also participate in the regulation of cellular function (1, 2). This finding is exemplified by the discovery of enzymatic systems, such as thioredoxin reductase͞thioredoxin (3), glutaredoxin (4), methione sulfoxide reductase (5), and sulfiredoxin (6), which catalyze reversal of oxidative modifications to protein and restoration of protein function. Additionally, receptor-and enzyme-mediated systems exist that catalyze the production of free radicals in response to changes in extracellular and intracellular factors (1, 2). It is therefore important that free radicals produced during physiological and pathophysiological conditions be investigated not simply for their potential to carry out damaging processes but also to induce appropriate alterations in response to changes in cellular homeostasis.Reduction and͞or cessation of blood f low to myocardial tissue, termed ischemia, occurs primarily as a result of formation of atherosclerotic lesions in the coronary arteries...

Hydrogen peroxide scavenging rescues frataxin deficiency in a Drosophila model of Friedreich's ataxia

“…17 could be at least partially caused by H 2 O 2 -mediated oxidative damage to iron cofactors. The exquisite sensitivity of the mACON Fe-S cluster to frataxin deficiency has been well established (17,23,32,46). Thus, the increased activity of ACON by H 2 O 2 scavenging may foreshadow discovery of proa b Fig.…”

“…Yeast, Drosophila, mouse, and cell culture models of frataxin deficiency have revealed important roles for frataxin and its homologs in mitochondrial iron storage (7)(8)(9)(10)(11)(12)(13)(14)(15), regulation of intracellular iron trafficking (7,8,10,16,17), iron-sulfur (Fe-S) cluster (16)(17)(18)(19)(20)(21) and heme biogenesis (14,22), and reactivation of the labile Fe-S cluster of mitochondrial aconitase (mACON) (22,23). A role for frataxin in preventing formation of deleterious reactive oxygen species (ROS) has been well established (12,15,24), invoking a paradigm of FRDA pathology in which ROS toxicity leads to mitochondrial dysfunction with subsequent cell death (for review, see refs.…”

The Krebs Cycle and Mitochondrial Mass Are Early Victims of Endothelial Dysfunction

“…The structural predilection of iron-sulfur center in aconitase-2 to reactive oxygen species and peroxynitrite 21 may in part explain its selective vulnerability. Prolonged exposure of mitochondria to oxidants results in disassembly of the [4Fe-4S] 2ϩ cubane cluster, carbonylation, and degradation of the enzyme, 22 potentially establishing the link between oxidant stress and enzyme inactivation, as detected during cardiac ischemia/ reperfusion 23 and eventual reduction in aconitase-2 abundance. Aconitase-2 has been previously found to be specifically targeted by oxidative damage during aging.…”

Critical Pathways in Heart Function: Bis(2-chloroethoxy)methane-Induced Heart Gene Transcript Change in F344 Rats

“…Thus, the response to CEM exposure involved changes that take place at the cell membrane (e.g., response to extracellular signals, ion transport, cell adhesion). DISCUSSION Cardiac disease leads to impairment of energy supply through mitochondria damage (Ballinger, 2005;Ballinger et al, 2002;Bulteau et al, 2005;Kang and Hamasaki, 2005;Rosenberg, 2004). Thus, in the CEM rat model of heart toxicity, where mitochondria damage occurs, we explored changes in heart transcripts associated with energy supply and demand, and how changes in heart transcripts may help to maintain heart function.…”