Abstract 20727: β-agonism Induces Recruitment of Diazoxide-Sensitive Katp Channels Via 14-3-3 in Human Atrial-Like Cardiomyocytes
Introduction: KATP channels couple cellular metabolism and electrophysiology. Their molecular composition and sensitivity to potassium channel openers vary in different tissues and species. Rodent atrial KATP channels are activated by diazoxide and have been implicated in arrhythmogenesis in models of hypertension and excess β-adrenergic tone. In contrast, human atrial KATP channels are activated by pinacidil (insensitive to diazoxide) and modulate APD only during extreme metabolic stress.
Hypothesis: Changes in the human atrial action potential associated with β-agonism are mediated by recruitment of diazoxide-sensitive 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.
Results: All data are for APD90 with programmed stimulation at 1.25 Hz, although similar results were seen at APD50 and APD70 and other pacing frequencies. Isoproterenol (10μM) and rolipram (10μM) resulted in reduction of APD90 (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). While exposure of cells to diazoxide resulted in APD shortening (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). Recruitment of diazoxide-sensitive current was blunted by prior incubation with R18, a 14-3-3 scavenger (248.8 ± 23.9ms, n=15 vs 179.7 ± 14.3ms, n=18; p=0.02). Conversely, pinacidil-induced APD shortening was blunted with prior β-agonism (159.3 ± 17.6ms, n=12 vs 115.2 ± 8.7ms, n=15; p=0.02).
Conclusions: KATP channels mediate β-adrenergic APD shortening in human atrial cells, a process associated with recruitment of diazoxide-sensitive current. This is dependent on 14-3-3 and associated with reduced pinacidil-sensitive current. KATP channels may represent a therapeutic target in the prevention of atrial arrhythmias associated with heightened β-adrenergic tone.
Author Disclosures: J. Lader: None. L. Bu: None. B. Gelb: None. G. Fishman: None.
- © 2016 by American Heart Association, Inc.