title: Posttranslational modifications and dysfunction of mitochondrial enzymes in human heart failure.
abstract: Deficiency of energy supply is a major complication contributing to the syndrome of heart failure (HF). Because the concurrent activity profile of mitochondrial bioenergetic enzymes has not been studied collectively in human HF, our aim was to examine the mitochondrial enzyme defects in left ventricular myocardium obtained from explanted end-stage failing hearts. Compared with nonfailing donor hearts, activity rates of complexes I and IV and the Krebs cycle enzymes isocitrate dehydrogenase, malate dehydrogenase, and aconitase were lower in HF, as determined spectrophotometrically. However, activity rates of complexes II and III and citrate synthase did not differ significantly between the two groups. Protein expression, determined by Western blotting, did not differ between the groups, implying posttranslational perturbation. In the face of diminished total glutathione and coenzyme Q10 levels, oxidative modification was explored as an underlying cause of enzyme dysfunction. Of the three oxidative modifications measured, protein carbonylation was increased significantly by 31% in HF (P < 0.01; n = 18), whereas levels of 4-hydroxynonenal and protein nitration, although elevated, did not differ. Isolation of complexes I and IV and F1FoATP synthase by immunocapture revealed that proteins containing iron-sulphur or heme redox centers were targets of oxidative modification. Energy deficiency in end-stage failing human left ventricle involves impaired activity of key electron transport chain and Krebs cycle enzymes without altered expression of protein levels. Augmented oxidative modification of crucial enzyme subunit structures implicates dysfunction due to diminished capacity for management of mitochondrial reactive oxygen species, thus contributing further to reduced bioenergetics in human HF.
authors.affiliation: Heart Research, Clinical Sciences, Murdoch Children's Research Institute, and Department of Paediatrics, University of Melbourne, Royal Children's Hospital, Melbourne, Australia; and Department of Surgery at Alfred Hospital, Monash University, Melbourne, Australia.
authors.forename: Freya L
authors.initials: FL
authors.lastname: Sheeran
authors.affiliation: Heart Research, Clinical Sciences, Murdoch Children's Research Institute, and Department of Paediatrics, University of Melbourne, Royal Children's Hospital, Melbourne, Australia; and Department of Surgery at Alfred Hospital, Monash University, Melbourne, Australia Salvatore.Pepe@mcri.edu.au.
authors.forename: Salvatore
authors.initials: S
authors.lastname: Pepe
mesh_terms: D000154:Aconitate Hydratase / Q000378:metabolism; D000447:Aldehydes / Q000378:metabolism; D015153:Blotting, Western; D002950:Citrate (si)-Synthase / Q000378:metabolism; D002952:Citric Acid Cycle; D045222:Electron Transport Chain Complex Proteins / Q000378:metabolism*; D042967:Electron Transport Complex I / Q000378:metabolism; D003576:Electron Transport Complex IV / Q000378:metabolism; D005260:Female; D005978:Glutathione / Q000378:metabolism; D006333:Heart Failure / Q000201:enzymology* / Q000378:metabolism; D006352:Heart Ventricles / Q000201:enzymology* / Q000378:metabolism; D006801:Humans; D007521:Isocitrate Dehydrogenase / Q000378:metabolism; D007655:Ketoglutarate Dehydrogenase Complex / Q000378:metabolism; D008291:Malate Dehydrogenase / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D008929:Mitochondria, Heart / Q000201:enzymology* / Q000378:metabolism; D025261:Mitochondrial Proton-Translocating ATPases / Q000378:metabolism; D009206:Myocardium / Q000201:enzymology / Q000378:metabolism; D010085:Oxidative Phosphorylation; D050050:Protein Carbonylation; D011499:Protein Processing, Post-Translational; D017382:Reactive Oxygen Species / Q000378:metabolism; D014451:Ubiquinone / Q000031:analogs & derivatives / Q000378:metabolism
chemical_list: D000447:Aldehydes; D045222:Electron Transport Chain Complex Proteins; D017382:Reactive Oxygen Species; D014451:Ubiquinone; D008291:Malate Dehydrogenase; D007521:Isocitrate Dehydrogenase; D007655:Ketoglutarate Dehydrogenase Complex; D003576:Electron Transport Complex IV; D002950:Citrate (si)-Synthase; C474451:F1F0-ATP synthase; D025261:Mitochondrial Proton-Translocating ATPases; D000154:Aconitate Hydratase; D042967:Electron Transport Complex I; C024989:coenzyme Q10; D005978:Glutathione; C027576:4-hydroxy-2-nonenal
keywords: human heart failure; mitochondria; oxidative stress; respiration