title: Effects of calmodulin-dependent protein kinase II inhibitor, KN-93, on electrophysiological features of rabbit hypertrophic cardiac myocytes.
abstract: Cardiac hypertrophy is an independent risk factor for sudden cardiac death in clinical settings and the incidence of sudden cardiac death and ventricular arrhythmias are closely related. The aim of this study was to determine the effects of the calmodulin-dependent protein kinase (CaMK) II inhibitor, KN-93, on L-type calcium current (I(Ca, L)) and early after-depolarizations (EADs) in hypertrophic cardiomyocytes. A rabbit model of myocardial hypertrophy was constructed through abdominal aortic coarctation (LVH group). The control group (sham group) received a sham operation, in which the abdominal aortic was dissected but not coarcted. Eight weeks later, the degree of left ventricular hypertrophy (LVH) was evaluated using echocardiography. Individual cardiomyocyte was isolated through collagenase digestion. Action potentials (APs) and I(Ca, L) were recorded using the perforated patch clamp technique. APs were recorded under current clamp conditions and I(Ca, L) was recorded under voltage clamp conditions. The incidence of EADs and I(ca, L) in the hypertrophic cardiomyocytes were observed under the conditions of low potassium (2 mmol/L), low magnesium (0.25 mmol/L) Tyrode's solution perfusion, and slow frequency (0.25-0.5 Hz) electrical stimulation. The incidence of EADs and I(ca, L) in the hypertrophic cardiomyocytes were also evaluated after treatment with different concentrations of KN-92 (KN-92 group) and KN-93 (KN-93 group). Eight weeks later, the model was successfully established. Under the conditions of low potassium, low magnesium Tyrode's solution perfusion, and slow frequency electrical stimulation, the incidence of EADs was 0/12, 11/12, 10/12, and 5/12 in sham group, LVH group, KN-92 group (0.5 μmol/L), and KN-93 group (0.5 μmol/L), respectively. When the drug concentration was increased to 1 μmol/L in KN-92 group and KN-93 group, the incidence of EADs was 10/12 and 2/12, respectively. At 0 mV, the current density was 6.7±1.0 and 6.3±0.7 PA·PF(-1) in LVH group and sham group, respectively (P>0.05, n=12). When the drug concentration was 0.5 μmol/L in KN-92 and KN-93 groups, the peak I(Ca, L) at 0 mV was decreased by (9.4±2.8)% and (10.5±3.0)% in the hypertrophic cardiomyocytes of the two groups, respectively (P>0.05, n=12). When the drug concentration was increased to 1 μmol/L, the peak I(Ca, L) values were lowered by (13.4±3.7)% and (40±4.9)%, respectively (P<0.01, n=12). KN-93, a specific inhibitor of CaMKII, can effectively inhibit the occurrence of EADs in hypertrophic cardiomyocytes partially by suppressing I(Ca, L), which may be the main action mechanism of KN-93 antagonizing the occurrence of ventricular arrhythmias in hypertrophic myocardium.
authors.affiliation: Department of Emergency, Fujian Provincial Hospital, Provincial College of Clinical Medicine, Fujian Medical University, Fuzhou, 350001, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Ke
authors.affiliation: Department of Emergency, Fujian Provincial Hospital, Provincial College of Clinical Medicine, Fujian Medical University, Fuzhou, 350001, China. cf9066@126.com.
authors.forename: Feng
authors.initials: F
authors.lastname: Chen
authors.affiliation: General Department, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China.
authors.forename: Cuntai
authors.initials: C
authors.lastname: Zhang
authors.affiliation: General Department, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China.
authors.forename: Xing
authors.initials: X
authors.lastname: Xiao
authors.affiliation: Department of Emergency, Fujian Provincial Hospital, Provincial College of Clinical Medicine, Fujian Medical University, Fuzhou, 350001, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Tu
authors.affiliation: Department of Emergency, Fujian Provincial Hospital, Provincial College of Clinical Medicine, Fujian Medical University, Fuzhou, 350001, China.
authors.forename: Musen
authors.initials: M
authors.lastname: Dai
authors.affiliation: Department of Emergency, Fujian Provincial Hospital, Provincial College of Clinical Medicine, Fujian Medical University, Fuzhou, 350001, China.
authors.forename: Xiaoping
authors.initials: X
authors.lastname: Wang
authors.affiliation: Department of Emergency, Fujian Provincial Hospital, Provincial College of Clinical Medicine, Fujian Medical University, Fuzhou, 350001, China.
authors.forename: Bing
authors.initials: B
authors.lastname: Chen
authors.affiliation: Department of Emergency, Fujian Provincial Hospital, Provincial College of Clinical Medicine, Fujian Medical University, Fuzhou, 350001, China.
authors.forename: Min
authors.initials: M
authors.lastname: Chen
mesh_terms: D000818:Animals; D001596:Benzylamines / Q000494:pharmacology*; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D006332:Cardiomegaly / Q000378:metabolism / Q000503:physiopathology*; D005260:Female; D032383:Myocytes, Cardiac / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology*; D011817:Rabbits; D013449:Sulfonamides / Q000494:pharmacology*; D000096926:Benzenesulfonamides
chemical_list: D001596:Benzylamines; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D013449:Sulfonamides; C072105:KN 93; D000096926:Benzenesulfonamides