Study On The Protective Mechanism Of ?-arrestin2 In Chronic Heart Failure Against Ventricular Arrhythmia

Background:Ventricular arrhythmias are a common cause of sudden cardiac death among patients with chronic heart failure(CHF).Abnormal repolarization process of the cardiac action potential(AP)is thought to contribute significantly to ventricular arrhythmogenesis.The rapid component of the delayed rectifier potassium current(IKr),which is encoded by the human ether-a-go-go-related gene(hERG),is most responsible for phase 3 repolarization and is vitally important to repolarize the cell membrane orderly at the end of AP.Data from several studies suggest that the hERG/IKr currents are attenuated during CHF,thus providing a mechanism for the pathophysiology behind the increased incidence of arrhythmias under stress.Carvedilol,a nonsubtype-selective ?-AR antagonist,has proven particularly effective in the treatment of heart failure.Its unique mode of action that stimulating ?-arrestinmediated signaling may be responsible for the advantage.Recent work has revealed an interesting insight that ?-arrestin may play a cardioprotective role during CHF.Recently,a ?-arrestin signaling-mediated increase in IKr has been reported in HEK cells.This study was designed to investigate the role of ?-arrestin in hERG/IKr regulation and ventricular arrhythmias during CHF and to provide a new perspective for its prevention and treatment.Methods:1.We applied a well-established CHF guinea pig model and the cardiac function was evaluated by echocardiography at 12 weeks after TAC surgery.The guinea pigs were subjected to electrocardiogram to measure the heart rate and corrected QT interval.HE and Masson staining were used to observe the extent of myocardial hypertrophy and fibrosis.Effective refractoriness period(ERP)was tested in Langendorff perfused hearts by programmed electrical stimulation(PES).APs and IKr currents were recorded in left ventricular myocytes from adult guinea pigs using whole-cell patch-clamp technique.The mRNA and protein levels of ?arrestins in left ventricle tissues were detected by real-time quantative PCR and Western Blot.2.In vitro study,Adv-?-arrestin2 and Adv-?-arrestin2 siRNA were contructed and transfected to primary cardiomyocytes separated from adult guinea pigs.Then pathological hypertrophy model was induced with phenylephrine(PE).The ANP,myh7 and mRNA ?-arrestin2 levels in myocytes were detected by qRT-PCR.The whole-cell patch-clamp technique was used to record the IKr currents and APs.3.In vivo study,guinea pigs were injected with AAV9 to interfere or overexpression the level of ?-arrestin2 in myocardium at 1 week after TAC surgery.Electrocardiogram was performed to assess cardiac function.HE and Masson staining were used to observe the extent of myocardial hypertrophy and fibrosis.The electrocardiographic measurement parameters were evaluated,and the incidence of arrhythmias was recorded.PES were performed to evaluate the effects of ?-arrestin2 on ERP.IKr currents were measured by whole-cell patchclamp recording.Results:1.CHF guinea pigs had higher heart rates and longer QT intervals.Prolonged ERP and APs and decreased IKr were also observed during CHF.Notably,the ventricular ?-arrestin2 levels were decreased in the guinea pigs with CHF compared with their control group.2.Sustained PE stimulation reduced the density of the IKr current.?-arrestin2 expression measured in myocytes cultured with PE using qRT-PCR was downregulated.?-arrestin2 overexpression significantly attenuated the PE-induced decrease in the IKr current.Moreover,?-arrestin2 was capable of ameliorating the AP prolongation following PE exposure.3.AAV9-?-arr2 injections did not alleviate pathological cardiac remolding or improve cardiac fibrosis,indicating that the alterations in vitro might not caused by improvement in cardiac function.The heart rates were lower and the QTc intervals were shorter in the CHF+AAV9-?-arr2 group than in the CHF+NC group.AAV9-?-arr2 transfection into guinea pigs with CHF significantly suppressed the incidence of norepinephrine-induced arrhythmias.Hearts were less susceptible to malignant arrhythmia after ?-arrestin2 enhancement.Also,?-arrestin2 overexpression markedly attenuated the decrease of IKr density during CHF.Conclusions:?-arrestin2 levels were decreased in the heart of guinea pigs with CHF.The role of ?-arrestin2 in myocardial hypertrophy can regulate IKr and AP.Enhanced ?arrestin2 may contribute to impair dysregulation of the hERG/IKr current and prevent ventricular arrhythmias during CHF.Thus,?-arrestin2 may be an effective antiarrhythmic strategy for patients with CHF.