CaMKII inhibition rescues proarrhythmic phenotypes in the model of human ankyrin-B syndrome

BACKGROUNDCardiovascular 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.OBJECTIVETo test the relationship between myocyte kinase/phosphatase imbalance and cellular and whole animal arrhythmia phenotypes associated with ankyrin-B cardiac syndrome.METHODSBy 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.RESULTSThe cardiac ryanodine receptor (RyR2), a validated target of kinase/phosphatase regulation in myocytes, displays abnormal CaMKII-dependent phosphorylation (pS2814 hyperphosphorylation) in ankyrin-B+/− heart. Notably, RyR2 dysregulation is rescued in myocytes from ankyrin-B+/− mice overexpressing a potent CaMKII-inhibitory peptide (AC3I), and aberrant RyR2 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.CONCLUSIONSThese 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.