UNIVERSITY OF COPENH AGEN FACULTY OF HEALTH A ND MEDICAL SCIENCES Doctoral Dissertation Kirstine Callø The Transient Outward Potassium Current in Healthy and Diseased Hearts December 2017 The Faculty of Health and Medical Sciences at the University of Copenhagen has accepted this dissertation, which consists of the already published dissertations listed below, for public defence for the doctoral degree in Veterinary Science. Copenhagen, 24th of October 2018. Professor Ulla Wewer, Dean Public defence will be held in auditorium A1-05.01, Dyrlægevej 100, Frederiksberg Campus, University of Copenhagen, Friday 11th of January 2019 at 1 p.m. Kirstine Callø Section for Anatomy, Biochemistry and Physiology Department of Veterinary and Animals Sciences Faculty of Health and Medical Sciences University of Copenhagen [email protected] Copenhagen 30.12.2018 ISBN 978-87-971049-0-3 1 1 Contents 2 PUBLICATIONS..................................................................................................................... 3 3 PREFACE .............................................................................................................................. 4 3.1 Conflict of interests ........................................................................................................................................ 4 4 DANSK RESUMÉ................................................................................................................... 5 5 SUMMARY IN ENGLISH ........................................................................................................ 7 5.1 Abbreviations................................................................................................................................................. 9 5.2 Overview of cardiac currents and ion channel subunits ................................................................................10 5.3 Nomenclature ...............................................................................................................................................11 5.3.1 Currents ........................................................................................................................................................... 11 5.3.2 Ventricular layers ............................................................................................................................................ 11 6 INTRODUCTION - ELECTRICAL ACTIVITY OF THE HEART....................................................... 12 6.1 Aim and hypotheses......................................................................................................................................12 6.2 The electrocardiogram, ECG ..........................................................................................................................12 6.3 The cardiac conduction system .....................................................................................................................13 6.3.1 Purkinje networks ........................................................................................................................................... 14 6.4 The cardiac action potential and underlying ionic currents ...........................................................................16 6.4.1 Nodal action potentials ................................................................................................................................... 17 6.4.2 Atrial action potentials .................................................................................................................................... 18 6.4.3 Action potentials in the His-Purkinje system .................................................................................................. 19 6.4.4 Ventricular action potentials ........................................................................................................................... 20 6.5 Excitation-contraction ...................................................................................................................................21 6.6 Neurohumoral regulation .............................................................................................................................22 6.6.1 Sympathetic regulation of the heart ............................................................................................................... 23 6.6.2 Parasympathetic regulation of the heart ........................................................................................................ 24 7 REGIONAL HETEROGENEITY OF VENTRICULAR ACTION POTENTIAL MORPHOLOGY AND IMPLICATIONS FOR CARDIAC FUNCTION ................................................................................... 26 7.1 Transmural heterogeneity in early repolarization .........................................................................................26 7.2 The role of the transient outward potassium current in excitation-contraction coupling ..............................28 7.3 The transient outward potassium current, Ito ................................................................................................31 7.3.1 Molecular composition of Ito ........................................................................................................................... 31 7.3.2 Pharmacology of Ito,f ........................................................................................................................................ 32 7.3.3 The effect of Ito activators NS5806 and NS3623 on isolated canine ventricular cells ..................................... 33 7.4 Pathophysiological implications of Ito,f ..........................................................................................................37 7.4.1 Ito,f and cardiac arrhythmias ............................................................................................................................ 37 7.4.2 Ito,f in heart failure ........................................................................................................................................... 39 7.5 Is pharmaceutically increased Ito,f potentially beneficial in failing hearts? .....................................................42 8 CONCLUDING REMARKS AND FUTURE PERSPECTIVES ........................................................ 45 8.1 The physiological significance of the Purkinje fibre distribution ....................................................................45 8.2 Is pharmaceutically increased Ito,f potentially beneficial in heart failure? ......................................................46 8.3 Methological considerations .........................................................................................................................47 8.4 Conclusion ....................................................................................................................................................48 9 ACKNOWLEDGEMENTS ...................................................................................................... 48 10 REFERENCES ................................................................................................................... 49 2 2 PUBLICATIONS The dissertation is based on the following publications: A dual potassium channel activator improves repolarization reserve and normalizes ventricular action potentials. Calloe K, Di Diego JM, Hansen RS, Nagle S, Treat JA, Cordeiro JM. Biochem Pharmacol. 2016 May 15;108:36-46 Tissue-specific effects of acetylcholine in the canine heart. Calloe K, Goodrow R, Antzelevitch C, Olesen SP, Cordeiro JM. Am J Physiol Heart Circ Physiol. 2013 Jul 1;305(1):H66-75. Physiological consequences of transient outward K+ current activation during heart failure in canine left ventricle. Cordeiro JM*, Calloe K*, Moise NS, Kornreich B, Giannandrea D, Diego JDM, Olesen SP, Antzelevitch C. J *Contributed equally. J Mol Cell Cardiol. 2012 Jun;52(6):1291-8. Comparison of the effects of a transient outward potassium channel activator on currents recorded from atrial and ventricular cardiomyocytes. Calloe K, Nof E, Jespersen T, Chlus N, Di Diego JM, Olesen SP, Antzelevitch C, Cordeiro JM. J Cardiovasc Electrophysiol. 2011 Sep;22(9):1057-66. Effect of the Ito activator NS5806 on cloned Kv4 channels depends on the accessory protein KChIP2. Lundby A, Jespersen T, Schmitt N, Grunnet M, Olesen SP, Cordeiro JM, Calloe K. British J of Pharmacol. 2010; 160(8):2028-44. Differential effects of the transient outward K+ current activator NS5806 in the canine left ventricle. Calloe K, Soltysinska E, Jespersen T, Lundby A, Antzelevitch C, Olesen SP, Cordeiro JM. J Mol Cell Cardiol. 2010; 48:191-200. A transient outward potassium current activator recapitulates the electrocardiographic manifestations of Brugada syndrome. Calloe K*, Cordeiro JM*, Di Diego JM, Hansen RS, Grunnet M, Olesen SP, Antzelevitch C. *Contributed equally. Cardiovasc Res. 2009; 81(4):686-94. Editorial comment: in Cardiovasc. Res. 2009, 81:635-636. 3 3 PREFACE The present thesis is based on studies performed at the Department of Veterinary and Animal Sciences (IVH) and the Department of Biomedical Sciences (BMI) at the University of Copenhagen (UCPH) and the Masonic Medical Research Laboratory (MMRL), Utica, NY, USA from 2008 to 2016. I wish to express my gratitude to Professor Dan A. Klærke for his enthusiasm and encouragement. His way of approaching and exploring new scientific ideas is very inspiring and constantly reminds me that science is fun. Thank you for being a true mentor.