Abstract 438: Downregulation of Ca 2+ /calmodulin-dependent Protein Kinase Type II Delta in the Heart by Antisense Oligonucleotides Mitigates Development of Post-infarct Ventricular Arrhythmias

Abstract

Pathological activation of Ca2+/calmodulin-dependent protein kinase type II delta (CaMK2d) has been implicated in the development of heart failure (HF) and arrhythmia. In preclinical models, inhibition or deletion of cardiac CaMK2d has shown a benefit to prevent HF progression or arrhythmia occurrence. We hypothesized that reduction of CaMK2d in the heart by antisense oligonucleotides (ASO) can mitigate the inducibility of MI-associated ventricular arrhythmias. Eight-week-old female C57BL6/N mice, which received permanent ligation of the left anterior descending coronary artery, were randomized to receive PBS, control ASO or two different mouse CaMK2d ASOs five days after the surgery. The ASOs were administered subcutaneously at 50 mg/kg weekly for four weeks. At the end of study, programmed electrical stimulation (PES) was performed to evaluate ventricular effective refractory period (VERP) and inducibility of ventricular arrhythmias (VA). PCR results showed 70% reduction of cardiac CaMK2d in the CaMK2d ASO groups and no changes of other CaMK2 isoforms. There is no significant change of VERP (VERP expressed as mean±SEM, PBS: 35.2±3.0 ms, control ASO: 36.2±3.8 ms, CaMK2d ASO1: 35.7±2.3 ms and CaMK2d ASO2: 33.8±1.4 ms) while the inducible arrhythmias by PES are declined after CaMK2d ASO treatment (VA inducibility index expressed as mean±SEM, PBS: 1.21±0.27, control ASO: 1.21±0.52, CaMK2d ASO1: 0.54±0.22, CaMK2d ASO2: 0.47±0.22). Echocardiography and invasive hemodynamic studies were unable to demonstrate significant functional improvements in the CaMK2d ASO treated groups, suggesting that the anti-arrhythmia effects of CaMK2d ASO treatment were not secondary to improved cardiac mechanics. In conclusion, ASO-mediated reduction of cardiac CaMK2d in a murine MI model ameliorates MI-associated ventricular arrhythmias, providing in vivo proof-of-concept support of the pathological role of CaMK2d activity in MI-related arrhythmia.