May 12, 2018 - Shin-Huei Liu, MD, Wen-Han Cheng, Wei-Lun Lin, MS, Tzu- ...... Dong-Hyeok Kim, MD, Jong-Il Choi, MD, PHD, Suk-kyu Oh,. MD, Yun Gi Kim, ...
S590 POSTER B-PO06: Poster Session VI Saturday, May 12, 2018 9:30 AM - 12:00 PM
B-PO06-001 ISOPROTERENOL-INDUCED ACTION POTENTIAL SHORTENING MEDIATED BY SUR1-CONTAINING K ATP CHANNELS IN HUMAN IPS-DERIVED ATRIAL CARDIOMYOCYTES Joshua M. Lader, MD, Bin Lin, PhD, Huaqian Yang, PhD, William A. Coetzee, PhD, Lei Bu, PhD, Bruce D. Gelb, MD and Glenn I. Fishman, MD. New York University School of Medicine, New York, NY, Mount Sinai School of Medicine, New York, NY Background: KATP channels couple cellular metabolism and electrophysiology. Their molecular composition varies in different tissues and species. Rodent atrial KATP channels have the SUR1 regulatory subunit, are activated by diazoxide and have been implicated in arrhythmogenesis in hypertension and excess β-adrenergic tone. In contrast, human atrial KATP channels are insensitive to diazoxide and modulate APD only during extreme metabolic stress, where the SUR2A regulatory subunit is thought to be predominant. Objective: We hypothesized that changes in the human atrial action potential associated with β-agonism are mediated by recruitment of SUR1-containing KATP channels. Methods: We used human induced pluripotent stem cell (hiPSC)-derived atrial cardiomyocytes where expression of a fluorescent reporter is driven by the atrial-specific gene sarcolipin. Atrial specification was induced with retinoic acid. Di-4-ANBDQBS was used to perform optical action potential measurements on days 65-80 of differentiation. Excised patch clamping was used to evaluate KATP channel density. Heterozygous ABCC8 (SUR1+/-) cells were generated using CRISPR/CAS9. Results: Optical mapping data are for APD90 with stimulation at 1.25 Hz. The combination of isoproterenol (ISO, 10µM) and rolipram (ROL, 10µM) abbreviated APD compared to control (247.4±12.5ms, n=16 vs 344.2±22.9ms, n=22; p=0.002). This was ameliorated by 10µM glibenclamide (312.0±18.9ms, n=23 vs 247.4±12.5ms, n=16; p=0.01). More patches from cells exposed to ISO and ROL had functional KATP channels (4/22 vs 0/24, p=0.045). Diazoxide shortened APD (267.3±21.7ms, n=20 vs 344.2±22.9ms, n=22; p=0.02). This was potentiated by prior β-agonism (179.7±14.3ms, n=18 vs 267.3±21.7ms, n=20; p=0.002). Deletion of one ABCC8 allele ameliorated APD shortening with exposure to ISO, ROL, and diazoxide (240.9±18.2ms, n=14 vs 179.7±14.3ms, n=18; p=0.012). Functional KATP channel density after exposure to β-agonists was reduced in SUR1+/- cells (1/40 vs 4/22, p=0.049). Conclusion: SUR1-containing KATP channels partially mediate β-adrenergic APD shortening in human atrial cells and may represent a therapeutic target for atrial arrhythmia prevention.
B-PO06-002 IN SILICO AND IN VITRO PREDICTION OF STATEDEPENDENT DRUG BINDING TO KV11.1 William Lee, MBBS, FRACP, Monique J. Windley, PhD, Jamie I. Vandenberg, MBBS, PhD and Adam P. Hill, PhD. Victor Chang Cardiac Research Institute, Sydney, Australia, Victor Chang Cardiac Research Inst., Molecular Cardiology and Biophysics, Sydney, NSW, Australia Background: In the past 20 years several structurally unrelated
Heart Rhythm, Vol. 15, No. 5, May Supplement 2018 drugs have been withdrawn from the market due to off target blockade of the Kv11.1 potassium channel resulting in delayed cardiac repolarization and sudden cardiac death. Key to understanding the dynamic nature of Kv11.1-drug binding is elucidating a drug’s binding preference to different voltage gating-states of the channel. A better understanding of this relationship is required to develop more accurate arrhythmia risk prediction assays. Objective: To develop a simplified method for determining the state dependence of Kv11.1-drug interactions. Methods: A mathematical model of Kv11.1 gating was used to simulate the effects of a wide range (n=6561) of theoretical drugs under multiple voltage protocols. Due to the dynamic nature of drug binding, different apparent IC50 values were obtained for each voltage protocol. Machine learning was used to compare differences in IC50 values for each drug and generate a classification algorithm to accurately predict each drug’s preference for binding to the open and/or inactivated state of Kv11.1. This algorithm was then tested for accuracy using a separate verification panel of 2000 theoretical drugs. Using in vitro manual voltage clamp, the IC50 values of a panel of 4 drugs was tested using in silico optimized voltage protocols. The in vitro measured IC50 values were then used to assess the accuracy of the in silico model. Results: IC50 values from 3 voltage protocols were required to give accurate state preference predictions. Receiver operator curves were made to evaluate the accuracy of prediction for each state preference; with an area under the curve for open state: 1.00, inactivated state: 0.96 and no state preference: 0.93, and an overall prediction accuracy of 97%. The state-preference of all 4 drugs in vitro was accurately predicted by the in silico classification algorithm. Conclusion: State-dependent drug binding to Kv11.1 is important in arrhythmia risk assessment. In vitro measures of potency are dependent on a drug’s Kv11.1 state-binding preference. In silico modelling has demonstrated that state dependence can be determined accurately with simple measures of drug potency.
B-PO06-003 PLASTICITY IN INTRACARDIAC GANGLIONATED PLEXI NEURONS IN SPONTANEOUSLY HYPERTENSIVE RATS (SHRS) Jesse L. Ashton, PhD, Bruce H. Smaill, PhD and Johanna M. Montgomery, BS, PhD. University of Auckland, Auckland, New Zealand, Department of Physiology, Auckland, New Zealand Background: Autonomic neurons located in ganglionated plexi (GP) on the heart transmit neural activity to the myocardium and can trigger arrhythmias. Little is known about the properties of the synapses formed on and by GP neurons and how these change (i.e. undergo plasticity) with hypertension and atrial arrhythmias. The inaccessibility of GP neurons for whole cell recordings has been a major contributing factor to this lack of knowledge. Objective: To perform pioneering whole cell recordings from intact GP to determine how hypertension alters GP neuron physiology and synaptic activity. Methods: Evoked action potentials and spontaneous postsynaptic currents were recorded from GP neurons in isolated atrial preparations from 14 to 16 month SHRs and Wistar-Kyoto controls using whole cell patch clamp. Results: GP neurons in SHRs showed decreased excitability, as evidenced by decreased action potential amplitude, and increased duration of the action potential and afterhyperpolarisation (Table 1). GP neurons in SHRs also showed elevated spontaneous synaptic activity, including a higher
S591
Poster Session VI
proportion of large amplitude currents, and a higher proportion of short intervals between synaptic events indicating a higher frequency of synaptic activity. Conclusion: The successful development of whole cell recordings from GP neurons has enabled us to detect functional remodelling of GP neuron excitability and synaptic activity. Our data reveal that chronic hypertension enhances synaptic communication in the GP, which may contribute to the increased arrhythmia burden in this condition.
fluorescent dyes. Results: IB shortened the action potential duration (APD) of atrial CMs in a dose dependent fashion (0.1 μM: ΔAPD= 8±3 ms, p=0.26; 0.5 μM ΔAPD= 31±7 ms, p=0.03; 1 μM: ΔAPD= 39±9 ms, p=0.007) without a demonstrable effect on ventricular CMs (p=0.70). IB prolonged the CaT in atrial (0.1 μM: ΔCaT= 8±4 ms, p=0.4; 0.5 μM: ΔCaT= 27±8 ms, p=0.02; 1 μM: ΔCaT= 31±8 ms, p=0.01) but did not have a significant effect on ventricular CMs (p=0.6). Two TKIs known to cause QT prolongation clinically demonstrated APD and CaT prolongation on ventricular (Nilotinib: ΔAPD= 28±4 ms, p=0.01; ΔCaT= 38±7 ms, p=0.008; Vandetanib: ΔAPD= 28±4 ms, p=0.02; ΔCaT= 31±6 ms, p=0.01), but not atrial CMs. Chronic exposure with IB led to the development of electrical alternans, a precursor of AF. Conclusion: Using hESC-derived CMs and cell-specific directed differentiation, we were able to demonstrate atrial specific effect of IB on the APD and CaT that would be expected to be pro-arrhythmic and increase the risk of AF. These effects were not seen on ventricular tissue. Other TKIs that have not been associated with AF clinically did not demonstrate atrial specific effects. Those agents identified as having an increased risk of QT prolongation were correctly identified using this pre-clinical screening tool.
B-PO06-005 SUBSTANTIAL PROARRHYTHMIC EFFECTS OF DIGITALIS IN FLECAINIDE- AND RANOLAZINE-PRETREATED HEARTS Christian Ellermann, MD, Julian Wolfes, Dirk Puckhaber, Lars Eckardt, MD and Gerrit Frommeyer, MD. Division of Electrophysiology, Department of Cardiovascular Medicine, University of Muenster, Muenster, Germany
B-PO06-004 MODELING TYROSINE KINASE INHIBITOR-INDUCED CARDIOTOXICITY IN HUMAN EMBRYONIC STEM CELLDERIVED ATRIAL AND VENTRICULAR CARDIOMYOCYTES Sanam Shafaattalab, PhD, Eric Lin, PhD, Effimia Christidi, PhD, Yulia Nartiss, MSc, Jee Hoon Lee, PhD, Stephanie Protze, PhD, Gordon Keller, PhD, Liam Brunham, MD, PhD, Glen F. Tibbits, PhD and Zachary Laksman, MD, MS. Simon Fraser University, Burnaby, BC, Canada, University of British Columbia, Vancouver, BC, Canada, University Health Network, Toronto, ON, Canada, University Health Network, Toronto, ON, Canada, University of British Columbia, BC, Canada, Simon Fraser University, Biomedical Physiology, Burnaby, BC, Canada, Cardiac Electrophysiology, Vancouver, BC, Canada Background: Ibrutinib (IB) is a novel tyrosine kinase inhibitor (TKI) used for the treatment of B cell cancers. Although IB is significantly more effective compared to previous agents, it increased the risk of developing atrial fibrillation (AF) nearly 10fold in randomized clinical trial patients. Objective: The purpose of this study was to understand the effect of IB and 6 other TKIs on atrial and ventricular cardiomyocytes (CMs). Methods: We have generated pure populations of atrial and ventricular CMs from human embryonic stem cells (hESCs) using previously published protocols based on BMP4 and Activin A. Atrial CMs were generated using retinoic acid. Optical mapping was employed to determine the effects of IB and other TKIs (Acalabrutinib, AVL-292, CNX-774, ONO-4059, Nilotinib, and Vandetanib). Voltage and calcium transients (CaT) of atrial and ventricular CMs were simultaneously quantified using
Background: A post-hoc analysis of the PALLAS trial suggested life-threatening interplay of dronedarone and digitalis. Thus, there is growing concern about possible interaction between digitalis glycosides and other antiarrhythmic drugs. Objective: To investigate the interplay between digitalis and the sodium channel blockers flecainide and ranolazine Methods: In 25 isolated rabbit hearts, flecainide (2µM, 12 hearts) or ranolazine (10µM, 13 hearts) were infused after generating baseline data. A volume-conducted ECG was recorded and eight catheters were placed endo- and epicardially to obtain cycle-length dependent action potential duration (APD90). Ventricular vulnerability was tested by a predefined pacing protocol employing premature extra stimuli (S2 and S3) and burst stimulation. Results: After flecainide treatment, no significant change of APD90 (+3ms, p=0.07) and a significant prolongation of QT interval (+38ms, p
