Exercise training prevents ventricular tachycardia in CPVT1 due to reduced CaMKII-dependent arrhythmogenic Ca2+ release

Aims

Catecholaminergic polymorphic ventricular tachycardia type 1 (CPVT1) is caused by mutations in the cardiac ryanodine receptor (RyR2) that lead to disrupted Ca²⁺ handling in cardiomyocytes and ventricular tachycardia. The aim of this study was to test whether exercise training could reduce the propensity for arrhythmias in mice with the CPVT1-causative missense mutation Ryr2-R2474S by restoring normal Ca²⁺ handling.

Methods and results

Ryr2-R2474S mice (RyR-RS) performed a 2 week interval treadmill exercise training protocol. Each exercise session comprised five 8 min intervals at 80–90% of the running speed at maximal oxygen uptake (VO_2max) and 2 min active rest periods at 60%. VO_2max increased by 10 ± 2% in exercise trained RyR-RS (ET), while no changes were found in sedentary controls (SED). RyR-RS ET showed fewer episodes of ventricular tachycardia compared with RyR-RS SED, coinciding with fewer Ca²⁺ sparks and waves, less diastolic Ca²⁺ leak from the sarcoplasmic reticulum, and lower phosphorylation levels at RyR2 sites associated with Ca²⁺–calmodulin-dependent kinase type II (CaMKII) compared with RyR-RS SED. The CaMKII inhibitor autocamtide-2-related inhibitory peptide and also the antioxidant N-acetyl-l-cysteine reduced Ca²⁺ wave frequency in RyR-RS equally to exercise training. Protein analysis as well as functional data indicated a mechanism depending on reduced levels of oxidized CaMKII after exercise training. Two weeks of detraining reversed the beneficial effects of the interval treadmill exercise training protocol in RyR-RS ET.

Conclusion

Long-term effects of interval treadmill exercise training reduce ventricular tachycardia episodes in mice with a CPVT1-causative Ryr2 mutation through lower CaMKII-dependent phosphorylation of RyR2.

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