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Quantitative Profiling of the Effects of Vanoxerine on Human Cardiac Ion Channels and its Application to Cardiac Risk.

Obejero-Paz CA, Bruening-Wright A, Kramer J, Hawryluk P, Tatalovic M, Dittrich HC, Brown AM - Sci Rep (2015)

Bottom Line: At clinically relevant concentrations, verapamil blocked hCav1.2 and hERG, as did vanoxerine and bepridil both of which also blocked hNav1.5.In acute experiments and simulations, dofetilide produced early after depolarizations (EADs) and arrhythmias, whereas verapamil, vanoxerine and bepridil produced no proarrhythmia markers.Additionally we propose that trafficking inhibition of hERG be added to CiPA.

View Article: PubMed Central - PubMed

Affiliation: ChanTest Corporation, a Charles River Company, Discovery Services, 14656 Neo Parkway, Cleveland, OH 44128, USA.

ABSTRACT
Vanoxerine has been in clinical trials for Parkinsonism, depression and cocaine addiction but lacked efficacy. Although a potent blocker of hERG, it produced no serious adverse events. We attributed the unexpected result to offsetting Multiple Ion Channel Effects (MICE). Vanoxerine's effects were strongly frequency-dependent and we repositioned it for treatment of atrial fibrillation and flutter. Vanoxerine terminated AF/AFL in an animal model and a dose-ranging clinical trial. Reversion to normal rhythm was associated with QT prolongation yet absent proarrhythmia markers for Torsade de Pointes (TdP). To understand the QT/TdP discordance, we used quantitative profiling and compared vanoxerine with dofetilide, a selective hERG-blocking torsadogen used for intractable AF, verapamil, a non-torsadogenic MICE comparator and bepridil, a torsadogenic MICE comparator. At clinically relevant concentrations, verapamil blocked hCav1.2 and hERG, as did vanoxerine and bepridil both of which also blocked hNav1.5. In acute experiments and simulations, dofetilide produced early after depolarizations (EADs) and arrhythmias, whereas verapamil, vanoxerine and bepridil produced no proarrhythmia markers. Of the MICE drugs only bepridil inhibited hERG trafficking following overnight exposure. The results are consistent with the emphasis on MICE of the CiPA assay. Additionally we propose that trafficking inhibition of hERG be added to CiPA.

No MeSH data available.


Related in: MedlinePlus

(a) Top: Step-ramp voltage protocol applied at 1 Hz used to measure block of hERG channel currents produced by vanoxerine (channels expressed in HEK293 cells at room temperature RT, ~22 °C). Bottom: superimposed currents recorded in control, 3 and 30 nM vanoxerine and 1 μM E-4031. (b) Top: protocol at 1 Hz used to measure block of hCav1.2 channel currents (CHO cells, RT ~ 22 °C). The initial step in the step-ramp protocol is to zero mV where the leak current is minimal and the peak current is measured. Bottom: experiment showing block produced by 30 nM vanoxerine and 25 nM nifedipine +30 μM Cd2+. Currents were recorded using perforated patch clamp with amphotericin B. (c) Top: voltage protocol at 1 Hz used to evaluate block of peak hNav 1.5 channel currents (HEK 293 cells, RT ~ 22 °C). The initial step in the step-ramp protocol is to −15 mV where open probability is approximately maximal and the driving force for Na+ is reduced providing better voltage control. Inset: blocking effects of 30 nM vanoxerine and 2 mM lidocaine on an expanded time scale. (d) Top: voltage protocol at 1 Hz used to measure block of ATX II- activated late hNav1.5 channel currents (ATX at 30 nM). Late currents were measured at their maxima during the ramp. Inset: block by vanoxerine at 100 and 1000 nM and lidocaine at 2 mM on an expanded current scale.
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f1: (a) Top: Step-ramp voltage protocol applied at 1 Hz used to measure block of hERG channel currents produced by vanoxerine (channels expressed in HEK293 cells at room temperature RT, ~22 °C). Bottom: superimposed currents recorded in control, 3 and 30 nM vanoxerine and 1 μM E-4031. (b) Top: protocol at 1 Hz used to measure block of hCav1.2 channel currents (CHO cells, RT ~ 22 °C). The initial step in the step-ramp protocol is to zero mV where the leak current is minimal and the peak current is measured. Bottom: experiment showing block produced by 30 nM vanoxerine and 25 nM nifedipine +30 μM Cd2+. Currents were recorded using perforated patch clamp with amphotericin B. (c) Top: voltage protocol at 1 Hz used to evaluate block of peak hNav 1.5 channel currents (HEK 293 cells, RT ~ 22 °C). The initial step in the step-ramp protocol is to −15 mV where open probability is approximately maximal and the driving force for Na+ is reduced providing better voltage control. Inset: blocking effects of 30 nM vanoxerine and 2 mM lidocaine on an expanded time scale. (d) Top: voltage protocol at 1 Hz used to measure block of ATX II- activated late hNav1.5 channel currents (ATX at 30 nM). Late currents were measured at their maxima during the ramp. Inset: block by vanoxerine at 100 and 1000 nM and lidocaine at 2 mM on an expanded current scale.

Mentions: The present in vitro experiments used similar cardiac action potential-like step-ramps delivered at 1 Hz from holding potentials of −80 mV for all three heterologously expressed channel currents. Drug effects were corrected for rundown as described in Methods. Figure 1 shows examples of the four currents studied using the step-ramp voltage protocol. The time courses and CRs of these experiments are shown in Supplementary Figures 1 and 2 respectively.


Quantitative Profiling of the Effects of Vanoxerine on Human Cardiac Ion Channels and its Application to Cardiac Risk.

Obejero-Paz CA, Bruening-Wright A, Kramer J, Hawryluk P, Tatalovic M, Dittrich HC, Brown AM - Sci Rep (2015)

(a) Top: Step-ramp voltage protocol applied at 1 Hz used to measure block of hERG channel currents produced by vanoxerine (channels expressed in HEK293 cells at room temperature RT, ~22 °C). Bottom: superimposed currents recorded in control, 3 and 30 nM vanoxerine and 1 μM E-4031. (b) Top: protocol at 1 Hz used to measure block of hCav1.2 channel currents (CHO cells, RT ~ 22 °C). The initial step in the step-ramp protocol is to zero mV where the leak current is minimal and the peak current is measured. Bottom: experiment showing block produced by 30 nM vanoxerine and 25 nM nifedipine +30 μM Cd2+. Currents were recorded using perforated patch clamp with amphotericin B. (c) Top: voltage protocol at 1 Hz used to evaluate block of peak hNav 1.5 channel currents (HEK 293 cells, RT ~ 22 °C). The initial step in the step-ramp protocol is to −15 mV where open probability is approximately maximal and the driving force for Na+ is reduced providing better voltage control. Inset: blocking effects of 30 nM vanoxerine and 2 mM lidocaine on an expanded time scale. (d) Top: voltage protocol at 1 Hz used to measure block of ATX II- activated late hNav1.5 channel currents (ATX at 30 nM). Late currents were measured at their maxima during the ramp. Inset: block by vanoxerine at 100 and 1000 nM and lidocaine at 2 mM on an expanded current scale.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4663487&req=5

f1: (a) Top: Step-ramp voltage protocol applied at 1 Hz used to measure block of hERG channel currents produced by vanoxerine (channels expressed in HEK293 cells at room temperature RT, ~22 °C). Bottom: superimposed currents recorded in control, 3 and 30 nM vanoxerine and 1 μM E-4031. (b) Top: protocol at 1 Hz used to measure block of hCav1.2 channel currents (CHO cells, RT ~ 22 °C). The initial step in the step-ramp protocol is to zero mV where the leak current is minimal and the peak current is measured. Bottom: experiment showing block produced by 30 nM vanoxerine and 25 nM nifedipine +30 μM Cd2+. Currents were recorded using perforated patch clamp with amphotericin B. (c) Top: voltage protocol at 1 Hz used to evaluate block of peak hNav 1.5 channel currents (HEK 293 cells, RT ~ 22 °C). The initial step in the step-ramp protocol is to −15 mV where open probability is approximately maximal and the driving force for Na+ is reduced providing better voltage control. Inset: blocking effects of 30 nM vanoxerine and 2 mM lidocaine on an expanded time scale. (d) Top: voltage protocol at 1 Hz used to measure block of ATX II- activated late hNav1.5 channel currents (ATX at 30 nM). Late currents were measured at their maxima during the ramp. Inset: block by vanoxerine at 100 and 1000 nM and lidocaine at 2 mM on an expanded current scale.
Mentions: The present in vitro experiments used similar cardiac action potential-like step-ramps delivered at 1 Hz from holding potentials of −80 mV for all three heterologously expressed channel currents. Drug effects were corrected for rundown as described in Methods. Figure 1 shows examples of the four currents studied using the step-ramp voltage protocol. The time courses and CRs of these experiments are shown in Supplementary Figures 1 and 2 respectively.

Bottom Line: At clinically relevant concentrations, verapamil blocked hCav1.2 and hERG, as did vanoxerine and bepridil both of which also blocked hNav1.5.In acute experiments and simulations, dofetilide produced early after depolarizations (EADs) and arrhythmias, whereas verapamil, vanoxerine and bepridil produced no proarrhythmia markers.Additionally we propose that trafficking inhibition of hERG be added to CiPA.

View Article: PubMed Central - PubMed

Affiliation: ChanTest Corporation, a Charles River Company, Discovery Services, 14656 Neo Parkway, Cleveland, OH 44128, USA.

ABSTRACT
Vanoxerine has been in clinical trials for Parkinsonism, depression and cocaine addiction but lacked efficacy. Although a potent blocker of hERG, it produced no serious adverse events. We attributed the unexpected result to offsetting Multiple Ion Channel Effects (MICE). Vanoxerine's effects were strongly frequency-dependent and we repositioned it for treatment of atrial fibrillation and flutter. Vanoxerine terminated AF/AFL in an animal model and a dose-ranging clinical trial. Reversion to normal rhythm was associated with QT prolongation yet absent proarrhythmia markers for Torsade de Pointes (TdP). To understand the QT/TdP discordance, we used quantitative profiling and compared vanoxerine with dofetilide, a selective hERG-blocking torsadogen used for intractable AF, verapamil, a non-torsadogenic MICE comparator and bepridil, a torsadogenic MICE comparator. At clinically relevant concentrations, verapamil blocked hCav1.2 and hERG, as did vanoxerine and bepridil both of which also blocked hNav1.5. In acute experiments and simulations, dofetilide produced early after depolarizations (EADs) and arrhythmias, whereas verapamil, vanoxerine and bepridil produced no proarrhythmia markers. Of the MICE drugs only bepridil inhibited hERG trafficking following overnight exposure. The results are consistent with the emphasis on MICE of the CiPA assay. Additionally we propose that trafficking inhibition of hERG be added to CiPA.

No MeSH data available.


Related in: MedlinePlus