Combined action potential- and dynamic-clamp for accurate computational modelling of the cardiac IKr current.

In the present work Action-Potential clamp (APC) and Dynamic clamp (DC) were used in combination in order to optimize the Luo-Rudy (LRd) mathematical formulation of the guinea-pig rapid delayed rectifier K(+) current (IKr), and to validate the optimized model. To this end, IKr model parameters were adjusted to fit the experimental E4031-sensitive current (IE4031) recorded under APC in guinea-pig myocytes. Currents generated by LRd model (ILRd) and the optimized one (IOpt) were then compared by testing their suitability to replace IE4031 under DC. Under APC, ILRd was significantly larger than IE4031 (mean current densities 0.51±0.01 vs 0.21±0.05pA/pF; p<0.001), mainly because of different rectification. IOpt mean density (0.17±0.01pA/pF) was similar to the IE4031 one (NS); moreover, IOpt accurately reproduced IE4031 distribution along the different AP phases. Models were then compared under DC by blocking native IKr (5μM E4031) and replacing it with ILRd or IOpt. Whereas injection of ILRd overshortened AP duration (APD90) (by 25% of its pre-block value), IOpt injection restored AP morphology and duration to overlap pre-block values. This study highlights the power of APC and DC for the identification of reliable formulations of ionic current models. An optimized model of IKr has been obtained which fully reversed E4031 effects on the AP. The model strongly diverged from the widely used Luo-Rudy formulation; this can be particularly relevant to the in silico analysis of AP prolongation caused by IKr blocking or alterations.

[1]  Derick R. Peterson,et al.  Increased Risk of Arrhythmic Events in Long-QT Syndrome With Mutations in the Pore Region of the Human Ether-a-go-go–Related Gene Potassium Channel , 2002, Circulation.

[2]  T J Campbell,et al.  Inhibition of the human ether‐a‐go‐go‐related gene (HERG) potassium channel by cisapride: affinity for open and inactivated states , 1999, British journal of pharmacology.

[3]  S. Bryant,et al.  Regional differences in the delayed rectifier current (IKr and IKs) contribute to the differences in action potential duration in basal left ventricular myocytes in guinea-pig. , 1998, Cardiovascular research.

[4]  Hui-zhen Wang,et al.  Inactivation gating determines nicotine blockade of human HERG channels. , 1999, American journal of physiology. Heart and circulatory physiology.

[5]  E. Carmeliet.  Voltage- and time-dependent block of the delayed K+ current in cardiac myocytes by dofetilide. , 1992, The Journal of pharmacology and experimental therapeutics.

[6]  P. C. Viswanathan,et al.  Novel characteristics of a misprocessed mutant HERG channel linked to hereditary long QT syndrome. , 2000, American journal of physiology. Heart and circulatory physiology.

[7]  M. Sanguinetti,et al.  A mutation in the pore region of HERG K+ channels expressed in Xenopus oocytes reduces rectification by shifting the voltage dependence of inactivation , 1998, The Journal of physiology.

[8]  M. Sanguinetti,et al.  A mechanistic link between an inherited and an acquird cardiac arrthytmia: HERG encodes the IKr potassium channel , 1995, Cell.

[9]  Antonio Zaza,et al.  Control of the cardiac action potential: The role of repolarization dynamics. , 2010, Journal of molecular and cellular cardiology.

[10]  Mirei Nagai,et al.  Dissociation of E-4031 from the HERG channel caused by mutations of an amino acid results in greater block at high stimulation frequency. , 2003, Cardiovascular research.

[11]  M. Rocchetti,et al.  Rate dependency of β‐adrenergic modulation of repolarizing currents in the guinea‐pig ventricle , 2006, The Journal of physiology.

[12]  Y Rudy,et al.  Two components of the delayed rectifier K+ current in ventricular myocytes of the guinea pig type. Theoretical formulation and their role in repolarization. , 1995, Circulation research.

[13]  Yoram Rudy,et al.  Subunit Interaction Determines IKs Participation in Cardiac Repolarization and Repolarization Reserve , 2005, Circulation.

[14]  G. Hart,et al.  Regional differences in action potential characteristics and membrane currents of guinea‐pig left ventricular myocytes , 1998, Experimental physiology.

[15]  M. Sanguinetti,et al.  Class III antiarrhythmic drugs block HERG, a human cardiac delayed rectifier K+ channel. Open-channel block by methanesulfonanilides. , 1996, Circulation research.

[16]  M. Sanguinetti,et al.  Two components of cardiac delayed rectifier K+ current. Differential sensitivity to block by class III antiarrhythmic agents , 1990, The Journal of general physiology.

[17]  Stefano Severi,et al.  Computational cardiac electrophysiology is ready for prime time. , 2014, Europace.

[18]  B. Kerem,et al.  Variable Expression of Long QT Syndrome Among Gene Carriers from Families with Five Different HERG Mutations , 2001, Annals of noninvasive electrocardiology : the official journal of the International Society for Holter and Noninvasive Electrocardiology, Inc.

[19]  S. Heinemann,et al.  Inhibition of hEAG1 and hERG1 potassium channels by clofilium and its tertiary analogue LY97241 , 2003, British journal of pharmacology.

[20]  Ronald Wilders,et al.  Dynamic clamp: a powerful tool in cardiac electrophysiology , 2006, The Journal of physiology.

[21]  Martyn P Mahaut-Smith,et al.  Temperature dependence of human ether-a-go-go-related gene K+ currents. , 2006, American journal of physiology. Cell physiology.

[22]  C. Clancy,et al.  Computational approaches to understand cardiac electrophysiology and arrhythmias. , 2012, American journal of physiology. Heart and circulatory physiology.

[23]  L. Izu,et al.  Beta-adrenergic stimulation reverses the IKr–IKs dominant pattern during cardiac action potential , 2014, Pflügers Archiv - European Journal of Physiology.

[24]  Zhong Jian,et al.  Sequential dissection of multiple ionic currents in single cardiac myocytes under action potential-clamp. , 2011, Journal of molecular and cellular cardiology.

[25]  A. Hodgkin,et al.  A quantitative description of membrane current and its application to conduction and excitation in nerve , 1952, The Journal of physiology.

[26]  Gary Gintant,et al.  Rechanneling the cardiac proarrhythmia safety paradigm: a meeting report from the Cardiac Safety Research Consortium. , 2014, American heart journal.

[27]  D. Terrar,et al.  Protein kinase C enhances the rapidly activating delayed rectifier potassium current, IKr, through a reduction in C‐type inactivation in guinea‐pig ventricular myocytes , 2000, The Journal of physiology.

[28]  Antonio Zaza,et al.  Ionic currents during sustained pacemaker activity in rabbit sino‐atrial myocytes , 1997, The Journal of physiology.

[29]  Harry J. Witchel,et al.  Time course and voltage dependence of expressed HERG current compared with native ”rapid” delayed rectifier K current during the cardiac ventricular action potential , 1998, Pflügers Archiv.

[30]  T. Shibasaki,et al.  Conductance and kinetics of delayed rectifier potassium channels in nodal cells of the rabbit heart. , 1987, The Journal of physiology.

[31]  E Wanke,et al.  A toxin to nervous, cardiac, and endocrine ERG K+ channels isolated from Centruroides noxius scorpion venom , 1999, FASEB journal : official publication of the Federation of American Societies for Experimental Biology.

[32]  Antonio Zaza,et al.  Reverse rate dependency is an intrinsic property of canine cardiac preparations. , 2009, Cardiovascular research.

[33]  Ronald Wilders,et al.  UvA-DARE ( Digital Academic Repository ) HERG channel ( dys ) function revealed by dynamic action potential clamp technique , 2004 .

[34]  M. Sanguinetti,et al.  Single HERG delayed rectifier K+ channels expressed in Xenopus oocytes. , 1997, The American journal of physiology.

[35]  Antonio Zaza,et al.  Rate dependency of delayed rectifier currents during the guinea‐pig ventricular action potential , 2001, The Journal of physiology.

[36]  H. Strauss,et al.  A quantitative analysis of the activation and inactivation kinetics of HERG expressed in Xenopus oocytes , 1997, The Journal of physiology.