Background: Cardiovascular disease is a leading cause of death worldwide. Arrhythmias are associated with significant morbidity and mortality related to cardiovascular disease. Recent work illustrates that many cardiac arrhythmias are initiated by a pathologic imbalance between kinase and phosphatase activities in excitable cardiomyocytes.
Objective: To test the relationship between myocyte kinase/phosphatase imbalance and cellular and whole animal arrhythmia phenotypes associated with ankyrin-B cardiac syndrome.
Methods: By using a combination of biochemical, electrophysiological, and in vivo approaches, we tested the ability of calcium/calmodulin-dependent kinase (CaMKII) inhibition to rescue imbalance in kinase/phosphatase pathways associated with human ankyrin-B-associated cardiac arrhythmia.
Results: The cardiac ryanodine receptor (RyR(2)), a validated target of kinase/phosphatase regulation in myocytes, displays abnormal CaMKII-dependent phosphorylation (pS2814 hyperphosphorylation) in ankyrin-B(+/-) heart. Notably, RyR(2) dysregulation is rescued in myocytes from ankyrin-B(+/-) mice overexpressing a potent CaMKII-inhibitory peptide (AC3I), and aberrant RyR(2) open probability observed in ankyrin-B(+/-) hearts is normalized by treatment with the CaMKII inhibitor KN-93. CaMKII inhibition is sufficient to rescue abnormalities in ankyrin-B(+/-) myocyte electrical dysfunction including cellular afterdepolarizations, and significantly blunts whole animal cardiac arrhythmias and sudden death in response to elevated sympathetic tone.
Conclusions: These findings illustrate the complexity of the molecular components involved in human arrhythmia and define regulatory elements of the ankyrin-B pathway in pathophysiology. Furthermore, the findings illustrate the potential impact of CaMKII inhibition in the treatment of a congenital form of human cardiac arrhythmia.
Copyright © 2012 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.