Department of Pharmacology, School of Medicine, Universidad Complutense, Madrid 28040, Spain.
Department of Pharmacology, School of Medicine, Universidad Complutense, Madrid 28040, Spain Instituto de Investigación Sanitaria Gregorio Marañón, School of Medicine, Universidad Complutense, Madrid 28040, Spain
Cardiovasc Res. 2014 Nov 1;104(2):337-46. doi: 10.1093/cvr/cvu203. Epub 2014 Sep 9.
We hypothesize that some drugs, besides flecainide, increase the inward rectifier current (IK1) generated by Kir2.1 homotetramers (IKir2.1) and thus, exhibit pro- and/or antiarrhythmic effects particularly at the ventricular level. To test this hypothesis, we analysed the effects of propafenone, atenolol, dronedarone, and timolol on Kir2.x channels.
Currents were recorded with the patch-clamp technique using whole-cell, inside-out, and cell-attached configurations. Propafenone (0.1 nM-1 µM) did not modify either IK1 recorded in human right atrial myocytes or the current generated by homo- or heterotetramers of Kir2.2 and 2.3 channels recorded in transiently transfected Chinese hamster ovary cells. On the other hand, propafenone increased IKir2.1 (EC50 = 12.0 ± 3.0 nM) as a consequence of its interaction with Cys311, an effect which decreased inward rectification of the current. Propafenone significantly increased mean open time and opening frequency at all the voltages tested, resulting in a significant increase of the mean open probability of the channel. Timolol, which interacted with Cys311, was also able to increase IKir2.1. On the contrary, neither atenolol nor dronedarone modified IKir2.1. Molecular modelling of the Kir2.1-drugs interaction allowed identification of the pharmacophore of drugs that increase IKir2.1.
Kir2.1 channels exhibit a binding site determined by Cys311 that is responsible for drug-induced IKir2.1 increase. Drug binding decreases channel affinity for polyamines and current rectification, and can be a mechanism of drug-induced pro- and antiarrhythmic effects not considered until now.
我们假设某些药物（除氟卡尼外）可增加由 Kir2.1 同源四聚体产生的内向整流电流（IK1），从而在心室水平表现出致心律失常和/或抗心律失常作用。为了验证这一假说，我们分析了普罗帕酮、阿替洛尔、决奈达隆和噻吗洛尔对 Kir2.x 通道的作用。
使用膜片钳全细胞、内面向外和细胞贴附式记录技术记录电流。普罗帕酮（0.1 nM-1 μM）既不改变人右心房心肌细胞记录的 IK1，也不改变 Kir2.2 和 2.3 同源四聚体在瞬时转染的中国仓鼠卵巢细胞中产生的电流。另一方面，普罗帕酮通过与 Cys311 相互作用增加了 IKir2.1（EC50=12.0±3.0 nM），这一作用降低了电流的内向整流。普罗帕酮显著增加了所有测试电压下的平均开放时间和开放频率，导致通道的平均开放概率显著增加。与 Cys311 相互作用的噻吗洛尔也能增加 IKir2.1。相反，阿替洛尔和决奈达隆均未改变 IKir2.1。Kir2.1-药物相互作用的分子建模允许确定增加 IKir2.1 的药物的药效基团。
Kir2.1 通道具有由 Cys311 决定的结合位点，该结合位点负责药物诱导的 IKir2.1 增加。药物结合降低了通道对多胺和电流整流的亲和力，可能是药物致心律失常和抗心律失常作用的一种机制，直到现在还没有被考虑到。
