Department of Cardiology, Medical University Hospital Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany.
Naunyn Schmiedebergs Arch Pharmacol. 2010 May;381(5):385-400. doi: 10.1007/s00210-010-0496-7. Epub 2010 Mar 13.
The antidepressant amoxapine has been linked to cases of QT prolongation, acute heart failure, and sudden death. Inhibition of cardiac hERG (Kv11.1) potassium channels causes prolonged repolarization and is implicated in apoptosis. Apoptosis in association with amoxapine has not yet been reported. This study was designed to investigate amoxapine effects on hERG currents, hERG protein trafficking, and hERG-associated apoptosis in order to elucidate molecular mechanisms underlying cardiac side effects of the drug. hERG channels were expressed in Xenopus laevis oocytes and HEK 293 cells, and potassium currents were recorded using patch clamp and two-electrode voltage clamp electrophysiology. Protein trafficking was evaluated in HEK 293 cells by Western blot analysis, and cell viability was assessed in HEK cells by immunocytochemistry and colorimetric MTT assay. Amoxapine caused acute hERG blockade in oocytes (IC(50) = 21.6 microM) and in HEK 293 cells (IC(50) = 5.1 microM). Mutation of residues Y652 and F656 attenuated hERG blockade, suggesting drug binding to a receptor inside the channel pore. Channels were mainly blocked in open and inactivated states, and voltage dependence was observed with reduced inhibition at positive potentials. Amoxapine block was reverse frequency-dependent and caused accelerated and leftward-shifted inactivation. Furthermore, amoxapine application resulted in chronic reduction of hERG trafficking into the cell surface membrane (IC(50) = 15.3 microM). Finally, the antidepressant drug triggered apoptosis in cells expressing hERG channels. We provide evidence for triple mechanisms of hERG liability associated with amoxapine: (1) direct hERG current inhibition, (2) disruption of hERG protein trafficking, and (3) induction of apoptosis. Further experiments are required to validate a specific pro-apoptotic effect mediated through blockade of hERG channels.
抗抑郁药阿莫沙平与 QT 间期延长、急性心力衰竭和猝死有关。心脏 hERG（Kv11.1）钾通道的抑制导致复极化延长，并与细胞凋亡有关。阿莫沙平引起的凋亡尚未报道。本研究旨在研究阿莫沙平对 hERG 电流、hERG 蛋白运输和 hERG 相关凋亡的影响，以阐明该药物心脏副作用的分子机制。hERG 通道在非洲爪蟾卵母细胞和 HEK 293 细胞中表达，使用膜片钳和双电极电压钳电生理学记录钾电流。Western blot 分析评估 HEK 293 细胞中的蛋白运输，免疫细胞化学和比色 MTT 测定评估 HEK 细胞中的细胞活力。阿莫沙平在卵母细胞（IC50=21.6μM）和 HEK 293 细胞（IC50=5.1μM）中引起急性 hERG 阻断。Y652 和 F656 残基的突变减弱了 hERG 阻断，表明药物结合在通道孔内的受体上。通道主要在开放和失活状态下被阻断，并且观察到电压依赖性，在正电位下抑制减少。阿莫沙平阻断呈反向频率依赖性，并导致失活加速和向左移位。此外，阿莫沙平的应用导致 hERG 向细胞表面膜的运输慢性减少（IC50=15.3μM）。最后，抗抑郁药药物在表达 hERG 通道的细胞中引发凋亡。我们提供了与阿莫沙平相关的 hERG 易感性的三重机制的证据：（1）直接 hERG 电流抑制，（2）hERG 蛋白运输中断，和（3）诱导凋亡。需要进一步的实验来验证通过阻断 hERG 通道介导的特定促凋亡作用。
