Calcium/calmodulin-dependent protein kinase II (CaMKII) inhibition ameliorates arrhythmias elicited by junctin ablation under stress conditions

Abstract

Background Aberrant calcium signaling is considered as one of the key mechanisms contributing to arrhythmias, especially in the context of heart failure. In human heart failure, there is significant down-regulation of the sarcoplasmic reticulum protein junctin and junctin deficiency in mice is associated with stress-induced arrhythmias. Objective This study was designed to determine whether the increased SR Ca2+ leak and arrhythmias, associated with junctin ablation, may be associated with increased CaMKII activity and phosphorylation of the cardiac ryanodine receptor (RyR2) and whether pharmacological inhibition of CaMKII activity may prevent these arrhythmias. Methods Using a combination of biochemical, cellular and in vivo approaches, we tested the ability of KN-93 to reverse aberrant CaMKII phosphorylation of RyR2. Specifically, we performed protein phosphorylation analysis, in vitro cardiomyocyte contractility and Ca2+ kinetics, and in vivo ECG analysis in the junctin deficient mice. Results In the absence of junctin, RyR2 channels displayed CaMKII-dependent hyperphosphorylation. Notably, CaMKII inhibition by KN-93 reduced the in vivo incidence of stress-induced ventricular tachycardia by 65% in junctin null mice. At the cardiomyocyte level, KN-93 reduced the percentage of junctin null cells exhibiting spontaneous Ca2+ aftertransients and aftercontractions under stress conditions, by 35% and 37% respectively. At the molecular level, KN-93 blunted the CaMKII mediated hypephosphorylation of RyR2 and PLN under stress conditions. Conclusion Our data suggest that CaMKII inhibition is effective in preventing arrhythmogenesis in the setting of junctin ablation, through modulation of both SR Ca2+ release and uptake. Thus, it merits further investigation as promising molecular therapy.

Loss of myeloid differentiation protein 1 promotes atrial fibrillation in heart failure with preserved ejection fraction

“…In our study, chronic aldosterone infusion decreased SERCA2a protein expression and the phosphorylation of PLB at Thr17 and increased NCX1 protein expression and the phosphorylation of RyR2 but did not alter RyR2 or PLB protein expression. Phosphorylation of PLB at Thr17 site is a specific target of CaMKII, and activated CaMKII is associated with increased phosphorylation of PLB at Thr17 site . However, in our study, the level of phosphorylation of PLB at Thr17 is markedly decreased in the aldosterone‐induced heart, where activated CaMKII was observed, although no apparent change in total PLB abundance.…”

CaMKII Activation Promotes Cardiac Electrical Remodeling and Increases the Susceptibility to Arrhythmia Induction in High-fat Diet–Fed Mice With Hyperlipidemia Conditions

“…Phosphorylation of PLB at T17 site is a specific target of CaMKII and activated CaMKII is generally associated with increased phosphorylation of PLB at T17 site. 39 However, we found that p-PLB (at T17 site) is significantly decreased in the HFD-induced heart, where activated CaMKII was observed, although no apparent change was in total PLB abundance (Fig. 5 ).…”

Proarrhythmic Remodeling of Calcium Homeostasis in Cardiac Disease; Implications for Diabetes and Obesity

“…Stabilization of RyR2-mediated Ca release can be achieved indirectly by targeting CaMKII, given chronic activity in cardiac disease has been linked to RyR2 channel dysfunction ( Ai et al, 2005 ; Uchinoumi et al, 2016 ; Zhang, 2017 ). It has been demonstrated that blockade of CaMKII and inhibition of RyR2 phosphorylation in cardiac disease improves intracellular Ca 2+ homeostasis and attenuates arrhythmogenesis ( Ather et al, 2013 ; Tzimas et al, 2015 ; Uchinoumi et al, 2016 ), including in a rat model of type 2 diabetes ( Sommese et al, 2016 ), but this is also not a universal finding ( Chakraborty et al, 2014 ). Alternatively, stabilization could be achieved by a reduction of RyR2 oxidation.…”