Effects Of Naringin On The Electrophysiology Of Mouse Ventricular Myocytes And Its Anti-arrhythmic Effect

Background:Currently,the treatment of cardiac arrhythmias is usually based on pharmacological therapy,and the use of Chinese herbal medicine for the treatment of cardiac arrhythmias has a promising future in China.Therefore,it is of greater significance to use the compounds extracted from herbal medicines as research subjects for anti-arrhythmic drugs.Naringin is a flavonoid extracted from the peel and pulp of grapefruit,orange,and tangerine,which has various biological activities such as anti-inflammatory,anti-cancer,antioxidant,and thrombosis reduction,and can be used to prevent cardiovascular diseases and has a protective effect on the heart.Studies have shown that the consumption of flavonoid-rich foods such as grapefruit,oranges,and tangerines can reduce the incidence of cardiac arrhythmias.However,the effect of naringin on ion channels in cardiomyocytes and on this aspect of cardiac electrophysiology has not been reported.Objective:This study aimed to investigate naringin’s effect on cardiomyocyte electrophysiology and its mechanism.Methods:At the cellular level,mouse ventricular myocytes were acutely isolated using a Langendorff-perfusion device.Action potentials and ionic currents were recorded from cardiac myocytes using a membrane clamp amplifier EPC 10.After sequestering the cells in whole-cell mode to break the membrane,two modes of experimentation were performed.The first uses current-clamp mode（C-clamp）for cardiomyocyte AP recordings;the second uses whole-cell mode（Whole-cell）for cardiomyocyte channel currents recordings.Three separate sets of experiments were performed in the current-clamp mode.The first group recorded the effect of naringin intervention on the action potential（AP）of normal cardiomyocytes.In the second set of recordings,early afterdepolarizations（EADs）were established in a cellular state arrhythmia model using the sodium channel-specific opener ATX II.The effect of naringin intervention on EADs was recorded.In the third group,after recording normal action potentials,a cellular state arrhythmia model of delayed afterdepolarization（DADs）was established using 3.6 mmol/L Ca Cl₂,and the effect of naringin intervention on DADs was recorded after the recordings were stabilized using naringin.Various ionic currents in cardiomyocytes were recorded in voltage clamp mode,and after the recordings were stabilized,naringin was used for intervention to record the effect of naringin intervention on ionic currents in cardiomyocytes.2.At the organ level,mouse hearts were rapidly removed and the hearts were perfused using a Langendorff-perfusion device,while a BL-420F biosignal acquisition and analysis system was used to record the isolated mouse heart electrocardiogram.The organ experiments were divided into a control group,ATX II intervention group,and ATX II+naringin intervention group,and all experiments were performed after ten minutes of normal tabletop fluid perfusion to investigate the effect of naringin on ATX II-induced arrhythmias at the organ level by observing the changes in ECG.Result:1.Naringin had a shortening effect on the action potential time course of mouse ventricular myocytes,shortening APD₅₀from 7.8±1.3 ms to 6.7±1.4 ms（n=9,P<0.001,compared with control）and APD₉₀from 34±4 ms to 29±3 ms（n=9,P<0.001,compared with control）.2.Naringin could concentration-dependently inhibit late sodium current(I_Na.L)and L-type calcium current(I_Ca.L)with IC₅₀of 311.6μmol/L（n=10）and 508.5μmol/L（n=9）,respectively.3.Naringin could concentration-dependently inhibit peak sodium current(I_Na.P)（n=12）,delayed rectifier potassium current（I_K）（n=9）,and transient outward potassium current(I_to)（n=9）.4.Naringin significantly shortened the action potential time course（APD）prolonged by anemone toxin II（ATX II）and significantly inhibited ATX II-induced early afterdepolarization（EAD）（n=12）and high calcium-induced delayed afterdepolarization（DAD）（n=11）at the cellular level.5.Naringin reduced ventricular tachycardia and ventricular fibrillation induced by ATX II at the organ level in isolated hearts（n=10）and prolonged their onset.Conclusion:Naringin inhibits arrhythmias EAD and DAD at the cellular level,has concentration-dependent inhibition of ventricular myocyte channel currents I_Na.L,I_Ca.L,I_Na.P,I_K,and I_to,and also exhibits antiarrhythmic effects at the organ level.The present study is the first to show that naringin may be a multichannel blocker with antiarrhythmic effects by electrophysiological methods.