Na+-dependent SR Ca2+ overload induces arrhythmogenic events in mouse cardiomyocytes with a human CPVT mutation

Simon Sedej, Frank R. Heinzel, Stefanie Walther, Nataliya Dybkova, Paulina Wakula, Jan Groborz, Phillip Gronau, Lars S. Maier, Marc A. Vos, F. Anthony Lai, Carlo Napolitano, Silvia G. Priori, Jens Kockskämper, Burkert Pieske

Research output: Contribution to journalArticlepeer-review

Abstract

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.

Original languageEnglish
Pages (from-to)50-59
Number of pages10
JournalCardiovascular Research
Volume87
Issue number1
DOIs
Publication statusPublished - Jul 1 2010

Keywords

  • Delayed afterdepolarization
  • JTV-519
  • Ouabain
  • Ryanodine receptor
  • Sodium

ASJC Scopus subject areas

  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)
  • Physiology
  • Medicine(all)

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