title: Ventricular arrhythmias, increased cardiac calmodulin kinase II expression, and altered repolarization kinetics in ANP receptor deficient mice.
abstract: Cardiac hypertrophy is associated with ventricular arrhythmias and sudden death. The molecular mechanisms that predispose the hypertrophied heart to arrhythmias are not well understood. In mice, deletion of the gene coding for the atrial natriuretic peptide receptor, guanylyl cyclase A (GC-A-/-), causes arterial hypertension, cardiac hypertrophy and sudden death. We used this mouse model to study molecular mechanisms of arrhythmias in the hypertrophied heart. Right and left ventricular monophasic action potential durations (APD) were recorded in isolated, Langendorff-perfused hearts during pacing from the right atrium and ventricle. The atrioventricular (AV) node was ablated to provoke bradycardia. Intracellular Ca(2+) transients were measured in isolated INDO-1 loaded ventricular myocytes. Cardiac expression of Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) was analyzed by western blotting. Polymorphic ventricular arrhythmias (pVT) occurred spontaneously after mechanical AV block in 20/45 hearts from 12-month-old GC-A-/- mice (P < 0.05), but neither in age-matched GC-A+/+ hearts nor in hearts from 3-month-old mice of either genotype. Triggered activity preceded pVT. APD were prolonged and systolic Ca(i)(2+) levels were increased in GC-A-/- hearts independently of age. In 12-month-old GC-A-/- hearts only, dispersion of APD and expression levels of CaMKII were increased. CaMKII expression was particularly increased in hearts with pVT. Direct inhibition of CaMKII activation by KN93 (0.5 or 2 microM) or inhibition of Ca(2+)/calmodulin-dependent activation of CaMKII by W-7 (25 microM) suppressed pVT in GC-A-/- hearts (P < 0.05) while prolonging APD. The combination of increased CaMKII activity and altered action potential characteristics facilitates ventricular arrhythmias in hypertrophic GC-A-/- hearts.
authors.affiliation: Department of Cardiology and Angiology, Hospital of the University of Münster, and Institute for Arteriosclerosis Research at the University of Münster, Münster 48129, Germany. kirchhp@uni-muenster.de
authors.forename: Paulus
authors.initials: P
authors.lastname: Kirchhof
authors.forename: Larissa
authors.initials: L
authors.lastname: Fabritz
authors.forename: Ana
authors.initials: A
authors.lastname: Kilić
authors.forename: Frank
authors.initials: F
authors.lastname: Begrow
authors.forename: Günter
authors.initials: G
authors.lastname: Breithardt
authors.forename: Michaela
authors.initials: M
authors.lastname: Kuhn
mesh_terms: D000200:Action Potentials; D000375:Aging / Q000502:physiology; D000818:Animals; D001145:Arrhythmias, Cardiac / Q000473:pathology / Q000503:physiopathology*; D009320:Atrial Natriuretic Factor / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004594:Electrophysiology; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic; D006162:Guanylate Cyclase / Q000172:deficiency* / Q000235:genetics; D006352:Heart Ventricles / Q000187:drug effects / Q000473:pathology / Q000503:physiopathology*; D007700:Kinetics; D051379:Mice; D018345:Mice, Knockout; D017461:Receptors, Atrial Natriuretic Factor / Q000172:deficiency* / Q000235:genetics; D013997:Time Factors
chemical_list: D004791:Enzyme Inhibitors; D009320:Atrial Natriuretic Factor; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D006162:Guanylate Cyclase; D017461:Receptors, Atrial Natriuretic Factor; C091715:atrial natriuretic factor receptor A; D002118:Calcium