Aims Mutations in the cardiac ryanodine receptor Ca2+ release channel, RyR2, underlie catecholaminergic polymorphic ventricular tachycardia (CPVT), an inherited life-threatening arrhythmia. CPVT is triggered by spontaneous RyR2-mediated sarcoplasmic reticulum (SR) Ca2+ release in response to SR Ca2+ overload during-adrenergic stimulation. However, whether elevated SR Ca2+ content-in the absence of protein kinase A activation-affects RyR2 function and arrhythmogenesis in CPVT remains elusive. Methods and resultsIsolated murine ventricular myocytes harbouring a human RyR2 mutation (RyR2R4496C+/-) associated with CPVT were investigated in the absence and presence of 1 mol/L JTV-519 (RyR2 stabilizer) followed by 100 mol/L ouabain intervention to increase cytosolic [Na+] and SR Ca 2+ load. Changes in membrane potential and intracellular [Ca 2+] were monitored with whole-cell patch-clamping and confocal Ca2+ imaging, respectively. At baseline, action potentials (APs), Ca2+ transients, fractional SR Ca2+ release, and SR Ca2+ load were comparable in wild-type (WT) and RyR2 R4496C+/- myocytes. Ouabain evoked significant increases in diastolic [Ca2+], peak systolic [Ca2+], fractional SR Ca 2+ release, and SR Ca2+ content that were quantitatively similar in WT and RyR2R4496C+/- myocytes. Ouabain also induced arrhythmogenic events, i.e. spontaneous Ca2+ waves, delayed afterdepolarizations and spontaneous APs, in both groups. However, the ouabain-induced increase in the frequency of arrhythmogenic events was dramatically larger in RyR2R4496C+/- when compared with WT myocytes. JTV-519 greatly reduced the frequency of ouabain-induced arrhythmogenic events. Conclusion The elevation of SR Ca2+ load-in the absence of-adrenergic stimulation-is sufficient to increase the propensity for triggered arrhythmias in RyR2R4496C+/- cardiomyocytes. Stabilization of RyR2 by JTV-519 effectively reduces these triggered arrhythmias.
- Delayed afterdepolarization
- Ryanodine receptor
ASJC Scopus subject areas
- Cardiology and Cardiovascular Medicine
- Physiology (medical)