Dexmedetomidine exhibits antiarrhythmic effects on human-induced pluripotent stem cell-derived cardiomyocytes through a Na/Ca channel-mediated mechanism

Background: Ventricular-like human-induced pluripotent stem cell-derived cardiomyocytes (hiPSCCMs) exhibit the electrophysiological characteristics of spontaneous beating. Previous studies demonstrated that dexmedetomidine (DMED), a highly selective and widely used alpha(2)-adrenoceptor agonist for sedation, analgesia, and stress management, may induce antiarrhythmic effects, especially ventricular tachycardia. However, the underlying mechanisms of the DMED-mediated antiarrhythmic effects remain to be fully elucidated. Methods: A conventional patch-clamp recording method was used to investigate the direct effects of DMED on spontaneous action potentials, pacemaker currents (I-f), potassium (K+) channel currents (I-K1 and I-Kr), sodium (Na+) channel currents (I-Na), and calcium (Ca2+) channel currents (I-Ca) in ventricular-like hiPSC-CMs. Results: DMED dose-dependently altered the frequency of ventricular-like spontaneous action potentials with a half-maximal inhibitory concentration (IC50) of 27.9 mu M (n=6) and significantly prolonged the action potential duration at 90% repolarization (APD(90)). DMED also inhibited the amplitudes of the INa and ICa without affecting the activation and inactivation curves of these channels. DMED decreased the time constant of the Na+ and Ca2+ channel activation at potential -40 to -20 mv, and -20 mv. DMED increased the time constant of inactivation of the Na+ and Ca2+ channels. However, DMED did not affect the I-K1, I-Kr, I-f, and their current-voltage relationship. The ability of DMED to decrease the spontaneous action potential frequency and the Na+ and Ca2+ channel amplitudes, were not blocked by yohimbine, idazoxan, or phentolamine. Conclusions: DMED could inhibit the frequency of spontaneous action potentials and decrease the I-Na and I-Ca of hiPSC-CMs via mechanisms that were independent of the alpha(2)-adrenoceptor, the imidazoline receptor, and the alpha(1)-adrenoceptor. These inhibitory effects on hiPSC-CMs may contribute to the antiarrhythmic effects of DMED.