The Action of a Novel Fluoroquinolone Antibiotic Agent Antofloxacin Hydrochloride on Human‐Ether‐à‐go‐go‐Related Gene Potassium Channel

Abstract

The administration of certain fluoroquinolone antibacterials has recently been linked to QT interval prolongation, raising the clinical concerns over the cardiotoxicity of these agents. In this study, the effects of a novel fluoroquinolone, antofloxacin hydrochloride (AX) on human-ether-à-go-go-related gene (HERG) encoding potassium channels and the biophysical mechanisms of drug action were performed with whole-cell patch-clamp technique in transiently transfected HEK293 cells. The administration of AX caused voltage-and time-dependent inhibition of HERG K + current (I HERG ⁄ MiRP1 ) in a concentration-dependent manner but did not markedly modify the properties of channel kinetics, including activation, inactivation, deactivation and recovery from inactivation as well. In comparison with sparfloxacin (SPX), levofloxacin lactate (LVFX), the potency of AX to inhibit HERG tail currents was the least one, with an IC 50 value of 460.37 lM. By contrast, SPX was the most potent compound, displaying an IC 50 value of 2.69 lM whereas LVFX showed modest potency, with an IC 50 value of 43.86 lM, respectively. Taken together, our data suggest that AX only causes a minor reduction of I HERG ⁄ MiRP1 at the estimated free plasma level.The human-ether-à-go-go-related gene (HERG) encodes the pore-forming a-unit of the K + channel that resembles the rapid component of the delayed rectifier current I Kr in cardiac myocytes and non-cardiac cells [1]. It is well established that the inhibition of cardiac I Kr is associated with druginduced QT prolongation torsades de pointes arrhythmias (TdP) and sudden cardiac death. Indeed, it is now known that structurally diverse drugs associated with LQT syndromes (LQTS), including class III anti-arrhythmics, antimicrobials, prokinetic drugs, antihistamines, antidepressants and antipsychotic agents as well, share a common ability of blockage on HERG K + channels, resulting in a delay of cardiac repolarisation [2]. The fluoroquinolone class of antibacterials is widely prescribed for the treatment of infections due to their broad-spectrum antibiotic activity. However, the administrations of certain fluoroquinolone antibacterials have recently been linked to QT interval prolongation, raising the clinical concerns over the cardiotoxicity of these agents. For instance, sparfloxacin (SPX) and grepafloxacin (GPX) have been shown to prolong QT interval on electrocardiogram (ECG) at clinical doses [3][4][5]. In addition, they can induce TdP, a life-threatening ventricular arrhythmia [6,7], resulting in their withdrawn from the market in most countries. Antofloxacin hydrochloride (AX) is a newly developed fluoroquinolone antibiotic in China ( fig. 1). Compared with other available fluoroquinolones in clinical use, AX was well tolerated and demonstrated rapid absorption, highserum concentration, broad tissue distribution, and a long elimination half-life in both animal and human beings from a pharmacokinetic point of view [8,9]. This study aimed to examine the effects of AX on HERG currents het...

The protease inhibitor atazanavir blocks hERG K+ channels expressed in HEK293 cells and obstructs hERG protein transport to cell membrane

“…The current and kinetic characteristics of the hERG channel were recorded as previously described [15,17] , using an EPC-10 (HEKA electronic, Lambrecht-Pfalz, Germany) patch-clamp amplifier with Pulse 8.67 software (HEKA electronic, Lambrecht-Pfalz, Germany). Voltage commands and data acquisition were controlled by Pulsefit (v10.0) software (HEKA electronic, Lambrecht-Pfalz, Germany).…”

“…Western blot analysis of hERG protein was performed as described previously [15,17] . Briefly, ATV was diluted in serumand antibiotic-free DMEM and added to transfected HEK293 cells for 36-48 h. The cells were then scraped into ice-cold phosphate-buffered saline (PBS) and lysed in radioimmunoprecipitation assay (RIPA) buffer (50 mmol/L Tris-HCl at pH 7.5, 150 mmol/L NaCl, 5 mmol/L EDTA, 1% Nonidet P-40 buffer, and 10% glycerol) containing a protease inhibitor cocktail (Roche, Mannheim, Germany).…”

Blockage of hERG current and the disruption of trafficking as induced by roxithromycin

“…These values served as baseline controls. In the presence of roxithromycin added to the external solutions, a steady-state response was achieved before a subsequent concentration was applied (Guo et al 2010).…”

Identification and functional characterization of the human ether-a-go-go-related gene Q738X mutant associated with hereditary long QT syndrome type 2

“…Electrophysiological recordings. hERG currents were recorded by the whole-cell patch clamp technique at room temperature (18-23˚C) as previously described (8). GFP-positive cells were visually selected using an epifluorescence system (Olympus, Tokyo, Japan).…”

“…A giga-ohm (GΩ) seal resistance was achieved in all experiments. The kinetic characteristics of the hERG channel were recorded as previously described (8,9).…”