L-Type Calcium Channel Inhibition Contributes to the Proarrhythmic Effects of Aconitine in Human Cardiomyocytes

Abstract

Aconitine (ACO) is well-known for causing lethal ventricular tachyarrhythmias. While cardiac Na+ channel opening during repolarization has long been documented in animal cardiac myocytes, the cellular effects and mechanism of ACO in human remain unexplored. This study aimed to assess the proarrhythmic effects of ACO in human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). ACO concentration-dependently (0.3 ~ 3.0 μM) shortened the action potentials (AP) durations (APD) in ventricular-like hiPSC-CMs by > 40% and induced delayed after-depolarization. Laser-scanning confocal calcium imaging analysis showed that ACO decreased the duration and amplitude of [Ca2+]i transients and increased in the beating frequencies by over 60%. Moreover, ACO was found to markedly reduce the L-type calcium channel (LTCC) currents (ICa,L) in hiPSC-CMs associated with a positive-shift of activation and a negative shift of inactivation. ACO failed to alter the peak and late Na+ currents (INa) in hiPSC-CMs while it drastically increased the late INa in Guinea-pig ventricular myocytes associated with enhanced activation/delayed inactivation of INa at -55 mV~ -85 mV. Further, the effects of ACO on ICa,L, INa and the rapid delayed rectifier potassium current (Ikr) were validated in heterologous expression systems by automated voltage-clamping assays and a moderate suppression of Ikr was observed in addition to concentration-dependent ICa,L inhibition. Lastly, increased beating frequency, decreased Ca2+ wave and shortened field potential duration were recorded from hiPSC-CMs by microelectrode arrays assay. In summary, our data demonstrated that LTCC inhibition could play a main role in the proarrhythmic action of ACO in human cardiomyocytes.

Aconitine‑induced cardiac arrhythmia in human induced pluripotent stem cell‑derived cardiomyocytes

“…Furthermore, the results suggested that ACO-induced cardiomyocyte death is mediated, at least in part, by inducing apoptosis. Overall, these results are in agreement with those of previous studies from cellular and human biopsy studies demonstrating ACO-induced cardiotoxicity ( 7 , 9 , 22 ).…”

“…Studies have reported that ACO is capable of inducing VT and VF by opening the Na + channels of isolated cardiac myocytes from mice, rats, guinea pigs and rabbits ( 21 ). In addition, ACO-induced LTCC inhibition has been reported ( 5 , 22 ). In the present study, the RTCA Cardio system was applied, which is able to monitor the contractility of cardiomyocyte in real-time, to evaluate the arrhythmogenic effects of ACO in hiPSC-CMs.…”

Bradycardia and Hypotension from Improper Use of Aconite Root: A Case Report and Brief Review

“…The increase in intracellular Na + favors an increase in intracellular Ca 2+ through the activation of the Ca 2+ /Na + bidirectional exchanger and the release of intracellular Ca 2+ stored in the sarcoplasmic reticulum [18,25,26]. Aconitine has also been shown to block the potassium channels responsible for rapid and ultra-rapid delayed rectifier currents, which can result in further prolongation of the action potential [15,25,27]. The effects on calcium and potassium develop delayed afterdepolarization during the refractory period.…”

“…Higher concentrations of aconitine suppress action potential transmission by continuous opening of the Na + channel, which reduces the release of acetylcholine at the axonal end terminus and the vagotonic effects at the myocardium [18,25]. The bradycardia and hypotensive manifestations can be explained by activation of the ventromedial nucleus of the hypothalamus associated with depression of the circulatory system and inhibition of L-type calcium channel currents that serve as a major driver of pacemaker monocytes [18,21,25,26,27]. These complex electrophysiological mechanisms generate self-excitatory abnormal microcircuits within the cardiac and nervous systems, which can trigger cardiovascular features such as arrhythmia, conduction blocks, bradycardia and asystole [18,25].…”

Research progress of aconitine toxicity and forensic analysis of aconitine poisoning

“…More importantly, aconitine could also shorten action potential duration, reduce L-type calcium currents, thereby contributing to the proarrhythmic effects in human-induced pluripotent stem cellderived cardiomyocytes. The effects of aconitinecaused arrhythmia and underlying mechanisms were further studied in human cardiomyocytes model [67]. In addition, it is noteworthy that the Na þ -Ca 2þ exchange (NCX) system plays a vital role in regulating cardiac contractility and electrical activity in different animal modes.…”