Proteomic and phosphoproteomic remodeling in a rabbit model of electrical storm

Abstract

Abstract Background Electrical storm (ES), characterized by repetitive ventricular tachycardia/fibrillation (VT/VF) over a short time-interval, is a major problem with substantial mortality in patients with implantable cardioverter-defibrillators (ICDs) and structural heart diseases, but therapeutic strategy in the survivors has not been established, likely due to incomplete understanding of the pathophysiology. Objective To explore molecular mechanisms of ICD-shocked VT/VF-related death in experimental ES. Methods The model was created by inducing chronic complete atrioventricular-block in ICD-implanted rabbits, causing cardiac hypertrophy, QT-prolongation, and VT/VF-episodes. Relative protein/phosphoprotein abundances in hearts from 5 rabbits with ES (defined as ≥3 VF-episodes/24-hr period) experiencing 81±28 VF-episodes and 5 controls (CTL) were assessed by iTRAQ LC-MS/MS and key regulatory pathways were examined by Ingenuity-Pathway-Analysis. Results Proteomic analysis identified 1938 proteins, 302 of which were differentially expressed between ES and CTL (P<0.05). ES was profoundly associated with mitochondrial dysfunction and oxidative phosphorylation inactivation along with decreased measurement and predicted inhibition of electron transport chain-proteins. Reductions in mitochondrial matrix-enzymes inferred downregulation of fatty acid β-oxidation and TCA-cycle. Transcriptional factors including nuclear respiratory factor 1 and peroxisome proliferative activated receptor, gamma, coactivator 1 alpha involved in mitochondrial biogenesis were predicted downregulated and TP53 linked to mitochondrial depolarization upregulated. Phosphoproteome detected 641 phosphorylated proteins, 168 of which have changes in phosphorylation state in ES versus CTL (P<0.05). Aberrant phosphorylation-patterns occurred in Z-disc proteins of sarcomeres and Ca2+-handling proteins. Protein-kinase A and G, calcium, Ca2+/calmodulin protein-kinase, AMP-activated protein-kinase, and extracellular signal-regulated kinases/mitogen-activated protein-kinase signalings were activated, all coupling to nuclear integrators and mitochondrial transcription, which showed prediction opposite to proteomic data. Conclusions ES may cause mitochondrial damage, which can explain mechanical dysfunction and associated mortality. Direct effects of ICD-shocked VT/VF merit further investigations.