The Effects Of Macrophages On Post Myocardial Infarction Ventricular Arrhythmias Via Gap Junction And KCa3.1

Background Post-myocardial infarction(MI)ventricular arrhythmias are the main causes of sudden cardiac deaths in MI patients.The morbidity is high and the prognosis is poor.The underlying electrophysiological mechanisms of post-MI arrhythmias remain to be elucidated.Macrophages are important innate immune cells involved in post-MI inflammatory responses,but their roles in post-MI arrhythmias remain unclear.Objective We aimed to investigate the direct effects of macrophages on cardiac electrophysiology and post-MI ventricular arrhythmias and the mechanisms.Methods Mononuclear cell subset levels in MI patients and healthy controls were analyzed by flow cytometry.Gap junction formation was determined by immunofluorescence staining in hearts from MI patient and MI mice.Differentially expressed genes post-MI were identified by RNA sequencing.Macrophages and cardiomyocytes were cocultured in vitro,and the effects on electrophysiological properties were assessed by patch clamping.The underlying electrophysiological mechanisms were investigated by inhibition of gap junction,KCa3.1 and store-operated calcium entry.The effects of KCa3.1inhibition on cardiac electrophysiology and post-MI arrhythmias were assessed by ambulatory electrocardiogram telemetry and intracardiac programmed stimulation in vivo.Results Levels of pro-inflammatory monocytes were significantly elevated in patients with post-MI arrhythmias(p<0.001).Macrophages formed gap junction with cardiomyocytes in MI border zones of MI patient and mice,and pro-inflammatory macrophages were significantly increased 3 days post-MI(p<0.001).RNA sequencing identified Kcnn4,which encodes KCa3.1,as the most differentially expressed gene encoding ion channel,and the upregulation of KCa3.1 is mainly attributed to macrophages.In vitro coculture experiments demonstrated that connection with M0 macrophages via gap junction did not significantly affect the action potential durations(APDs)of cardiomyocytes.However,the APDs of cardiomyocytes connected with M1 macrophages were significantly prolonged(APD50,p<0.001;APD90,p<0.001),which were effectively attenuated by gap junction inhibitor GAP26,KCa3.1 inhibitor TRAM34,KCa3.1 silencing or store-operated calcium entry inhibitor SKF96365.In vivo results demonstrated that application of TRAM34 significantly decreased the durations of intracardiac stimulation-induced ventricular arrhythmia in MI mice(p=0.031).Conclusions After MI,macrophages affect the electrophysiological properties of cardiomyocytes and arrhythmias via gap junction and KCa3.1.Macrophages and KCa3.1 are novel mechanisms and potential therapeutic targets of post-MI ventricular arrhythmias.