CaMKII inhibition has dual effects on spontaneous Ca 2+ release and Ca 2+ alternans in ventricular cardiomyocytes from mice with a gain-of-function RyR2 mutation

Am J Physiol Heart Circ Physiol. 2021 Aug 1;321(2):H446-H460. doi: 10.1152/ajpheart.00011.2021. Epub 2021 Jul 16.

Abstract

In conditions with abnormally increased activity of the cardiac ryanodine receptor (RyR2), Ca2+/calmodulin-dependent protein kinase II (CaMKII) can contribute to a further destabilization of RyR2 that results in triggered arrhythmias. Therefore, inhibition of CaMKII in such conditions has been suggested as a strategy to suppress RyR2 activity and arrhythmias. However, suppression of RyR2 activity can lead to the development of arrhythmogenic Ca2+ alternans. The aim of this study was to test whether the suppression of RyR2 activity caused by inhibition of CaMKII increases propensity for Ca2+ alternans. We studied spontaneous Ca2+ release events and Ca2+ alternans in isolated left ventricular cardiomyocytes from mice carrying the gain-of-function RyR2 mutation RyR2-R2474S and from wild-type mice. CaMKII inhibition by KN-93 effectively decreased the frequency of spontaneous Ca2+ release events in RyR2-R2474S cardiomyocytes exposed to the β-adrenoceptor agonist isoprenaline. However, KN-93-treated RyR2-R2474S cardiomyocytes also showed increased propensity for Ca2+ alternans and increased Ca2+ alternans ratio compared with both an inactive analog of KN-93 and with vehicle-treated controls. This increased propensity for Ca2+ alternans was explained by prolongation of Ca2+ release refractoriness. Importantly, the increased propensity for Ca2+ alternans in KN-93-treated RyR2-R2474S cardiomyocytes did not surpass that of wild type. In conclusion, inhibition of CaMKII efficiently reduces spontaneous Ca2+ release but promotes Ca2+ alternans in RyR2-R2474S cardiomyocytes with a gain-of-function RyR2 mutation. The dominant effect in RyR2-R2474S is to reduce spontaneous Ca2+ release, which supports this intervention as a therapeutic strategy in this specific condition. However, future studies on CaMKII inhibition in conditions with increased propensity for Ca2+ alternans should include investigation of both phenomena.NEW & NOTEWORTHY Genetically increased RyR2 activity promotes arrhythmogenic Ca2+ release. Inhibition of CaMKII suppresses RyR2 activity and arrhythmogenic Ca2+ release. Suppression of RyR2 activity prolongs refractoriness of Ca2+ release. Prolonged refractoriness of Ca2+ release leads to arrhythmogenic Ca2+ alternans. CaMKII inhibition promotes Ca2+ alternans by prolonging Ca2+ release refractoriness.

Keywords: CPVT1; Ca2+ alternans; CaMKII; RyR2; arrhythmias.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / pharmacology
  • Adrenergic beta-Agonists / pharmacology
  • Animals
  • Arrhythmias, Cardiac / metabolism
  • Benzylamines / pharmacology
  • Calcium / metabolism*
  • Calcium Channel Agonists / pharmacology
  • Calcium-Calmodulin-Dependent Protein Kinase Type 2 / antagonists & inhibitors*
  • Calcium-Calmodulin-Dependent Protein Kinase Type 2 / metabolism
  • Gain of Function Mutation
  • Heart Ventricles / cytology
  • Isoproterenol / pharmacology
  • Mice
  • Myocytes, Cardiac / drug effects*
  • Myocytes, Cardiac / metabolism
  • Protein Kinase Inhibitors / pharmacology*
  • Ryanodine Receptor Calcium Release Channel / genetics*
  • Ryanodine Receptor Calcium Release Channel / metabolism
  • Sarcoplasmic Reticulum / drug effects*
  • Sarcoplasmic Reticulum / metabolism
  • Sulfonamides / pharmacology
  • Tachycardia, Ventricular / genetics*
  • Tachycardia, Ventricular / metabolism

Substances

  • Adrenergic beta-Agonists
  • Benzylamines
  • Calcium Channel Agonists
  • Protein Kinase Inhibitors
  • Ryanodine Receptor Calcium Release Channel
  • Sulfonamides
  • ryanodine receptor 2. mouse
  • KN 93
  • 3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester
  • Calcium-Calmodulin-Dependent Protein Kinase Type 2
  • Isoproterenol
  • Calcium

Supplementary concepts

  • Polymorphic catecholergic ventricular tachycardia