Effects Of Barbaloin And Sodium Houttuyfonate On Myocardial Electrophysiology And Their Antiarrhythmic Effects

There is an increasing incidence of cardiovascular diseases with the aging of the population,and thus posing a serious threat to human health.Arrhythmia is an important group of diseases of cardiovascular system.Arrhythmias can occur alone or with other cardiovascular diseases.Although great progress has been made in the medical treatments of arrhythmias in recent years,most antiarrhythmic drugs have severe arrhythmogenic effects,leading to the high mortality rate of patients with arrhythmias.Relevant data showed that among the heart diseases,80%of sudden cardiac death is caused by arrhythmias.Therefore,the exploration of novel,effective anti-arrhythmic drugs with low toxicity and side effects has become one of the most important aspects in the current researches about treatment of heart diseases.Currently,Traditional Chinese medicine preparations have been gradually used in clinical treatment of cardiovascular diseases.Because Chinese herbal medicine has been used for thousands of years and has been continuously improved,it has the advantages of low cost and high safety.However,due to the complicated composition of traditional Chinese medicine,the biological activities among various components are mostly unclear,which makes it difficult to improve the quality standards and conform to international standards of traditional Chinese medicine preparations.The Chinese herbal extracts monomer not only retains the advantages of low cost,low toxicity and side effects of traditional Chinese medicine,but also has a clear chemical composition,which facilitates the analysis and application of drugs.Thus,it is of great theoretical and practical significances to explore novel anti-arrhythmic drugs with high efficacy,low costs and toxic side effects based on the Chinese herbal extracts.In the present study,we selected barbaloin and sodium houttuyfonate from a variety of herbal extracts which are cardioprotective such as baicalin,barbaloin,notoginsenoside R1,ginkgolide,apigenin,and sodium houttuyfonate through experiments to explore their anti-arrhythmic effects.We conducted expreiments to investigate the effects of barbaloin and sodium houttuyfonate on various transmembrane ion channel currents,contractility of rabbit ventricular myocytes and Langendorff-perfused heart.This study is divided into the following three parts to discuss.Part 1.Screening for herbal monomers affecting sodium currents,potassium currents or calcium currents in rabbit ventricular myocytesBaicalin,barbaloin,notoginsenoside R1,ginkgolide B,apigenin,ginsenoside Rg1,ginsenoside Rg2 and sodium houttuyfonate are cardioprotective herbal extracts,so we screened for potential,developmentally valuable antiarrhythmic drugs by examing their effects on the peak sodium current(I_Na.P),inward rectifier potassium current(I_K1)and L-type calcium current(I_Ca.L)in rabbit ventricular myocytes.The results showed that baicalin,notoginsenoside R1,ginkgolide B,apigenin,ginsenoside Rg1,and ginsenoside Rg2 didn’t affect I_Na.P,I_K1 or I_Ca.L,while barbaloin and sodium houttuyfonate exerted significant effects on both I_Na.P and I_Ca.L.Therefore,we will explore the potential antiarrhythmic effects of barbaloin and sodium houttuyfonate by further experimental studies at the cellular and organ levels.Part 2.Barbaloin inhibits ventricular arrhythmias by modulating voltage-gated ion channels in rabbitsPurpose:Investigate the effects of barbaloin on action potential（AP）and various transmembrane ion channels of rabbit ventricular myocytes as well as Langendorff-perfused heart,accordingly laying the electrophysiological foundation for the development of new antiarrhythmic drugs.Methods:The rabbit ventricular myocytes were isolated by enzymatic digestion.The whole-cell patch-clamp technique was applied to record AP and the main transmembrane ion channel currents of the isolated ventricular myocytes.Anemonia sulcata toxin II-（ATX II）and elevation of calcium level ventricular myocytes were employedtoinduceearlyafterdepolarizations（EADs）anddelayed afterdepolarizations（DADs）in ventricular myocytes,respectively,and aconitine was used to induce Langendorff-perfusion cardiac arrhythmias.Then we observed and analyzed the alterations in AP,EADs,DADs,various ion channel currents and Langendorff-perfused cardiac arrhythmias before and after intervention with barbaloin.Results:Barbaloin（100 and 200μmol/L）significantly shortened the action potential duration（APD）and attenuated the maximum depolarization velocity（Vmax）and APD reverse-rate dependence in rabbit ventricular myocytes.Additionally,barbaloin（100 and 200μmol/L）effectively eliminated EADs and DADs in ventricular myocytes.Moreover,barbaloin（10,50,100 and 200μmol/L）inhibited I_Ca.L and I_Na.P in a concentration-dependent manner,with half maximal inhibitory concentration(IC₅₀)values of 137.06μmol/L and 559.80μmol/L,respectively,and barbaloin at 100 and 200μmol/L significantly inhibited the ATX II-enhanced late sodium current(I_Na.L)by 36.6%±3.3%and 71.8%±6.5%,respectively.However,barbaloin（100 and 800μmol/L）exerted no effects on the I_K1 or the rapidly activated delayed rectifier potassium current(I_Kr)in ventricular myocytes.Furthermore,barbaloin（200μmol/L）inhibited aconitine-induced ventricular arrhythmias in Langendorff-perfused rabbit hearts.Conclusion:Barbaloin eliminated EADs and DADs and blocked I_Ca.L,I_Na.P and ATX II-enhanced I_Na.L in ventricular myocytes.Barbaloin also inhibited aconitine-induced ventricular arrhythmias in Langendorff-perfused rabbit hearts.Thus,barbaloin has potential as a low-cost and safe antiarrhythmic drug.Part 3.Sodium houttuyfonate exerts its cardioprotective effects by modulating the voltage-gated ion channels and contractility in rabbit ventricular myocytesPurpose: Investigate the effects of sodium houttuyfonate on the main transmembrane ion channels and contractility in rabbit ventricular myocytes to explore its underlying anti-arrhythmic effects.Methods: After isolating the rabbit ventricular myocytes through enzymatic digestion,the whole-cell patch-clamp technique was applied to record INa.P、INa.L and ICa.L and visual motion edge detection system was used to detect the contractility of the ventricular myocytes.Then we observed and analyzed the alterations in ion channel currents and contractility of the ventricular myocytes before and after administration of sodium houttuyfonate to explore its potential of being an effective anti-arrhythmic drug.Results: sodium houttuyfonate inhibited INa.P in a concentration-dependent manner with an IC50 value of 137.06 μmol/L,and the inhibition ratio of 50μmol/L and 100μmol/L sodium houttuyfonate on ATX II-increased INa.L were 30.1% and 57.1%,respectively.In addition,sodium houttuyfonate increased ICa.L with an half maximal effective concentration（EC50）value of 37.10 μmol/L,and it also slowed down the steady-state inactivation and accelerated the inactivation-reactivation process of ICa.L.Furthermore,sodium houttuyfonate was effective to enhance the contractility of ventricular myocytes.Conclusion: sodium houttuyfonate has class I anti-arrhythmic drug properties,and sodium houttuyfonate can increase ICa.L and enhance cardiomyocyte contractility so that it has a unique advantage in the treatment of patients with heart failure complicated by arrhythmias.Thus,sodium houttuyfonate is a promising widely-used anti-arrhythmic drug candidate.