Effects of antiarrhythmic drugs on apoptotic pathways in H9c2 cardiac cells

Antiarrhythmic drugs may induce cellular apoptosis in the heart. By using representatives of 5 different categories of antiarrhythmic drugs, that is, pilsicainide, propranolol, nifekalant, verapamil, and amiodarone, we investigated whether these ion channel blockers or beta-antagonists affect cardiac apoptosis in cell cultures. Cultured H9c2 cells were treated with the drugs at varying concentrations. To determine the degree of apoptosis, the percentage of hypodiploid cells, mitochondrial transmembrane potential (DeltaPsi(m)), and activities of caspases were measured quantitatively. At 24 h after administration, only amiodarone induced apoptosis in the H9c2 cells. Amiodarone at a concentration of 14.8 microM or higher decreased DeltaPsi(m) and activated caspase-2 within 3 h of administration, and it caused the appearance of hypodiploid cells and activation of caspases-3 and -9 at 6 h or later. Thus, amiodarone, but none of the other antiarrhythmic drugs tested, possesses a pro-apoptotic effect, mainly via the mitochondrial pathway, suggesting that this effect is distinct from the blocking action of Na+, K+, and Ca2+ channels or the beta-adrenergic receptor. Furthermore, induction of apoptosis in a dose-dependent manner by amiodarone indicates the importance of monitoring the serum concentration in order to avoid its adverse effects.