title: Calmodulin/CaMKII inhibition improves intercellular communication and impulse propagation in the heart and is antiarrhythmic under conditions when fibrosis is absent.
abstract: In healthy hearts, ventricular gap junctions are mainly composed by connexin43 (Cx43) and localize in the intercalated disc, enabling appropriate electrical coupling. In diseased hearts, Cx43 is heterogeneously down-regulated, whereas activity of calmodulin/calcium-calmodulin protein kinase II (CaM/CaMKII) signalling increases. It is unclear if CaM/CaMKII affects Cx43 expression/localization or impulse propagation. We analysed different models to assess this.
  
  
  
  AC3-I mice with CaMKII genetically inhibited were subjected to pressure overload (16 weeks, TAC vs. sham). Optical and epicardial mapping was performed on Langendorff-perfused rabbit and AC3-I hearts, respectively. Cx43 subcellular distribution from rabbit/mouse ventricles was evaluated by immunoblot after Triton X-100-based fractionation. In mice with constitutively reduced CaMKII activity (AC3-I), conduction velocity (CV) was augmented (n = 11, P < 0.01 vs. WT); in AC3-I, CV was preserved after TAC, in contrast to a reduction seen in TAC-WT mice (-20%). Cx43 expression was preserved after TAC in AC3-I mice, though arrhythmias and fibrosis were still present. In rabbits, W7 (CaM inhibitor, 10 µM) increased CV (6-13%, n= 6, P< 0.05), while susceptibility to arrhythmias decreased. Immunoconfocal microscopy revealed enlarged Cx43 cluster sizes at intercalated discs of those hearts. Total Cx43 did not change by W7 (n= 4), whereas Triton X-100 insoluble Cx43 increased (+21%, n= 4, P< 0.01). Similar findings were obtained in AC3-I mouse hearts when compared with control, and in cultured dog cardiomyocytes. Functional implication was shown through increased intercellular coupling in cultured neonatal rat cardiomyocytes.
  
  
  
  Both acute and chronic CaM/CaMKII inhibition improves conduction characteristics and enhances localization of Cx43 in the intercalated disc. In the absence of fibrosis, this reduced the susceptibility for arrhythmias.
authors.affiliation: Department of Medical Physiology, Division of Heart & Lungs, University Medical Center Utrecht, Utrecht, The Netherlands Department of Cardiovascular Research, Research Institute of Environmental Medicine, Nagoya University, Nagoya, Japan Department of Pathophysiology, Oita University School of Medicine, Yufu, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Takanari
authors.affiliation: Department of Medical Physiology, Division of Heart & Lungs, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Vincent J A
authors.initials: VJ
authors.lastname: Bourgonje
authors.affiliation: Department of Medical Physiology, Division of Heart & Lungs, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Magda S C
authors.initials: MS
authors.lastname: Fontes
authors.affiliation: Department of Medical Physiology, Division of Heart & Lungs, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Antonia J A
authors.initials: AJ
authors.lastname: Raaijmakers
authors.affiliation: Department of Medical Physiology, Division of Heart & Lungs, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Helen
authors.initials: H
authors.lastname: Driessen
authors.affiliation: Department of Medical Physiology, Division of Heart & Lungs, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: John A
authors.initials: JA
authors.lastname: Jansen
authors.affiliation: Department of Medical Physiology, Division of Heart & Lungs, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Roel
authors.initials: R
authors.lastname: van der Nagel
authors.affiliation: Department of Medical Physiology, Division of Heart & Lungs, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Bart
authors.initials: B
authors.lastname: Kok
authors.affiliation: Department of Medical Physiology, Division of Heart & Lungs, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Leonie
authors.initials: L
authors.lastname: van Stuijvenberg
authors.affiliation: Department of Medical Physiology, Division of Heart & Lungs, University Medical Center Utrecht, Utrecht, The Netherlands Department of Cardiology, Radboud University Medical Center, Nijmegen, The Netherlands.
authors.forename: Mohamed
authors.initials: M
authors.lastname: Boulaksil
authors.affiliation: Department of Cardiovascular Research, Research Institute of Environmental Medicine, Nagoya University, Nagoya, Japan.
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Takemoto
authors.affiliation: Department of Cardiovascular Research, Research Institute of Environmental Medicine, Nagoya University, Nagoya, Japan.
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Yamazaki
authors.affiliation: Department of Cardiovascular Research, Research Institute of Environmental Medicine, Nagoya University, Nagoya, Japan.
authors.forename: Yukiomi
authors.initials: Y
authors.lastname: Tsuji
authors.affiliation: Department of Cardiovascular Research, Research Institute of Environmental Medicine, Nagoya University, Nagoya, Japan.
authors.forename: Haruo
authors.initials: H
authors.lastname: Honjo
authors.affiliation: Department of Cardiovascular Research, Research Institute of Environmental Medicine, Nagoya University, Nagoya, Japan.
authors.forename: Kaichiro
authors.initials: K
authors.lastname: Kamiya
authors.affiliation: Nagoya University, Nagoya, Japan.
authors.forename: Itsuo
authors.initials: I
authors.lastname: Kodama
authors.affiliation: Division of Cardiology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MA, USA.
authors.forename: Mark E
authors.initials: ME
authors.lastname: Anderson
authors.affiliation: Department of Medical Physiology, Division of Heart & Lungs, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Marcel A G
authors.initials: MA
authors.lastname: van der Heyden
authors.affiliation: Department of Medical Physiology, Division of Heart & Lungs, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Harold V M
authors.initials: HV
authors.lastname: van Rijen
authors.affiliation: Department of Medical Physiology, Division of Heart & Lungs, University Medical Center Utrecht, Utrecht, The Netherlands a.a.b.vanveen@umcutrecht.nl.
authors.forename: Toon A B
authors.initials: TA
authors.lastname: van Veen
authors.affiliation: Department of Medical Physiology, Division of Heart & Lungs, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Marc A
authors.initials: MA
authors.lastname: Vos
mesh_terms: D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000378:metabolism / Q000494:pharmacology*; D001145:Arrhythmias, Cardiac / Q000378:metabolism*; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2 / Q000378:metabolism*; D002147:Calmodulin / Q000378:metabolism*; D002450:Cell Communication / Q000187:drug effects*; D018031:Connexin 43 / Q000378:metabolism; D004285:Dogs; D017629:Gap Junctions / Q000378:metabolism; D006321:Heart / Q000503:physiopathology*; D006329:Heart Conduction System / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D023421:Models, Animal; D009206:Myocardium / Q000378:metabolism*; D011817:Rabbits; D051381:Rats
chemical_list: D000889:Anti-Arrhythmia Agents; D002147:Calmodulin; D018031:Connexin 43; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2
keywords: Arrhythmogenicity; CaMKII; Calmodulin; Conduction velocity; Connexin43