Calcium-calmodulin dependent protein kinase mediates the intracellular signaling pathways of cardiac apoptosis in mice with impaired glucose tolerance

FEDERICO M; PORTIANSKY EL; SOMMESE L; ALVARADO FJ; BLANCO PB; ZANUZZI CN; DEDMAN J; KAETZEL M; WEHRENS XHT; MATTIAZZI A; PALOMEQUE J

THE JOURNAL OF PHYSIOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2017 vol. 595 p. 4089 - 4108

0022-3751

Background: The impact of cardiac apoptosis in pre-diabetic stages of diabetic cardiomyopathy is unknown. We previously described that myocytes from fructose-rich diet (FRD) animals exhibit arrhythmias produced by exacerbated Ca2+/calmodulin-dependent protein kinase (CaMKII) activity, ryanodine receptors (RyR2) phosphorylation and sarcoplasmic reticulum (SR) Ca2+ leak. The present experiments tested the hypothesis that this mechanism also underlies cardiac apoptosis in pre-diabetes. Methods and Results: We generated a pre-diabetic model in mice fed with FRD. FRD-mice showed an increase in oxidative stress, hypertrophy and systolic dysfunction. Moreover, FRD myocytes exhibited enhanced SR Ca2+ spontaneous events in the absence of SR Ca2+ load alterations vs. control-diet (CD) myocytes. In HEK293 cells, hyperglycemia significantly enhanced [3H]Ryanodine binding and CaMKII phosphorylation of RyR2-S2814 residue vs. normoglycemia. CaMKII-inhibition prevented hyperglycemia-induced alterations. FRD also evoked cardiac apoptosis in WT mice vs. CD-WT mice. Co-treatment with the ROS scavenger Tempol prevented FRD-induced apoptosis in WT-mice. In contrast, FRD enhanced oxidative stress but not apoptosis in FRD-SR-AIP mice, in which a CaMKII inhibitor is targeted to the SR. FRD produced mitochondrial membrane depolarization in WT mice but not in S2814A mice, in which the CaMKII phosphorylation site on RyR2 was ablated. Furthermore, FRD decreased mitochondrial area, mean Feret diameter and mean SR-mitochondrial distance vs. CD-WT hearts. This remodeling was prevented in AC3I mice, with cardiac targeted CaMKII inhibition. Conclusions: CaMKII phosphorylation of RyR2, SR Ca2+ leak and mitochondrial membrane depolarization are critically involved in the apoptotic pathway of pre-diabetic heart. The FRD-induced decrease in SR-mitochondrial distance is likely to additionally favor Ca2+ transit between both organelles.