Calcium/Calmodulin-Dependent Protein Kinase II Activity Persists During Chronic β-Adrenoceptor Blockade in Experimental and Human Heart Failure

Abstract

Background Considerable evidence suggests that CaMKII overactivity plays a crucial role in the pathophysiology of heart failure (HF), a condition characterized by excessive β-adrenoceptor (β-AR) stimulation. Recent studies indicate a significant crosstalk between β-AR signaling and CaMKII activation presenting CaMKII as a possible downstream mediator of detrimental β-AR signaling in HF. In this study we investigated the effect of chronic β-AR blocker treatment on CaMKII activity in human and experimental HF. Methods and Results Immunoblot analysis of myocardium from end stage HF patients (n=12) and non-HF subjects undergoing cardiac surgery (n=12) treated with β-AR blockers revealed no difference in CaMKII activity when compared to non-β-AR-blocker-treated patients. CaMKII activity was judged by analysis of CaMKII expression, autophosphorylation and oxidation and by investigating the phosphorylation status of CaMKII downstream targets. To further evaluate these findings, CaMKIIδC transgenic mice were treated with the β1-AR blocker metoprolol (270 mg/kg*d). Metoprolol significantly reduced transgene-associated mortality (n≥29, p<0.001), attenuated the development of cardiac hypertrophy (−14±6% heart weight/tibia length, p<0.05) and strongly reduced ventricular arrhythmias (−70±22% PVCs, p<0.05). On a molecular level, metoprolol expectedly decreased PKA dependent phospholamban (PLN) and ryanodine receptor 2 (RyR2) phosphorylation (−42±9% for P-PLN-S16 and −22±7% for P-RyR2-S2808, p<0.05). However, this was neither paralleled by a reduction in CaMKII autophosphorylation, oxidation and substrate binding nor a change in the phosphorylation of CaMKII downstream target proteins (n≥11). The lack of CaMKII modulation by β-AR blocker treatment was confirmed in healthy wildtype mice receiving metoprolol. Conclusions Chronic β-AR blocker therapy in patients and in a mouse model of CaMKII-induced HF is not associated with a change in CaMKII activity. Thus, our data suggests that the molecular effects of β-AR blockers are not based on a modulation of CaMKII. Directly targeting CaMKII may therefore further improve HF therapy in addition to β-AR blockade.

ADAMTS13 Deficiency Shortens the Life Span of Mice With Experimental Diabetes

“…However, we cannot rule out the possibility that other as yet unrecognized b-ADR-mediated mechanisms may contribute to the arrhythmogenic phenotype elicited in diabetic Adamts13 2/2 mice. Our observation is in line with that in a recent study of experimental and human heart failure that demonstrated that the rise of CaMKII activity in an oxidative microenvironment did not depend on b-ADR stimulation (57), suggesting that other factors may be involved. Evidence exists that TSP1 expression is upregulated in the myocardium of diabetic animals (20,21), and through immunohistochemistry experiments we found that TSP1 staining localizes in perivascular and interstitial areas, but not in cardiomyocytes, in diabetic mice.…”

Arrhythmogenic Mechanisms in Heart Failure: Linking β-Adrenergic Stimulation, Stretch, and Calcium

“…Perhaps one of the most investigated of these is the CaMKII pathway, perhaps due to the multimodal action of this kinase, and the fact that targeting this molecule may lead to selective modulation of proarrhythmic RyRs ( Dries et al, 2018a ). Interestingly it was recently shown that CaMKII activity persists even during chronic β-adrenergic blockade in HF, indicating that these two pathways could be targeted independently ( Dewenter et al, 2017 ). To date, however, there are no clinically available CaMKII inhibitors, likely due to the lack of selective, bioavailable compounds.…”

Nitro-fatty acids suppress ischemic ventricular arrhythmias by preserving calcium homeostasis

“…RyR2 activity and dysfunction, we next investigated the effect of NO 2 -OA treatment on CaMKII activity by performing a substrate binding assay using GST-HDAC4 419-670, which contains a CaMKII activity-dependent binding site 31 . CaMKII activity of Iso stimulated isolated cardiomyocytes was significantly reduced after NO 2 -OA treatment (Fig.…”