Effect of Azelastine on Cardiac Repolarization of Guinea-Pig Cardiomyocytes, hERG K<SUP>+</SUP> Channel, and Human L-type and T-type Ca<SUP>2+</SUP> Channel

초록

Azelastine is a second generation histamine HI receptor antagonist used as an anti-asthmatic and anti-allergic drug that can induce QT prolongation and torsades de pointes. We investigated the acute effects of azelastine on human ether-a-go-go-related gene (hERG) channels, action potential duration (APD), and L-type (I-Ca,I-L) and T-type Ca2+ current (I-Ca,I-T) to determine the electrophysiological basis for its proarrhythmic potential. Azelastine increased the APD at 90% of repolarization concentration dependently, with an IC50 of 1.08 nM in guinea-pig ventricular myocytes. We examined the effects of azelastine on the hERG channels expressed in Xenopus oocytes and HEK293 cells using two-microelectrode voltage-clamp and patch-clamp techniques. Azelastine induced a concentration-dependent decrease of the hERG current amplitude at the end of the voltage steps and tail currents. The IC50 for the azelastine-induced block of the hERG currents expressed in HEK293 cells was 11.43 nM, while the drug inhibited I-Ca,I-L and I-Ca,I-T with IC50 values of 7.60 and 26.21 mu M, respectively. The S6 domain mutations, Y652A partially attenuated and F656A abolished hERG current block. These results suggest that azelastine is a potent blocker of hERG channels rather than I-Ca,I-L or I-Ca,I-T, providing molecular mechanisms for the arrhythmogenic side effects during the clinical administration of azelastine.

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