The Underlying Mechanisms Of Angiotensin Receptor-neprilysin Inhibitor Improve Heart Failure With Preserved Ejection Fracion Via IL-1?/mitochondrial Oxidative Stress

Background:Heart Failure?HF?is defined as the inability of the heart to provide sufficient forward output to meet the perfusion and oxygenation requirements of the tissues.Two major cardiac mechanisms were involved in it which include systolic dysfunction and diastolic dysfunction.Hypertension is the most common co-morbidity in HFpEF patients.It has been investigated that HFrEF conversed from HFpEF is uncommon.Previous studies have suggested that patients with HFpEF do not have a specific genetic form,most patients have both hypertension and diabetes.Hypertension is a major risk factor for the development of HFpEF.However,there is no direct clinical evidence for the drug treatment for HFpEF.Mitochondria dysfunction is considered an important therapeutic target for directly improving cardiac function.Although the benefits of SAC/VAL might be related to the inhibition of neutral endonucleases,the exact mechanism is undetermined.We hypothesis SAC/VAL protective effects through regulation of mitochondrial fission/fusion,IL-1?,and MCP-1 reduction in hypertension-induced HFpEF mice.It might provide a new target for the clinical treatment of HFpEF.Aim:?1?To verify the effects of SAC/VAL on cardiac function in different HFpEF mice model.?2?To investigate whether the above effects of Sac/Val through mitochondrial fission/fusion.?3?To investigate the effects of SAC/VAL on mitochondrial oxidative stress,mPTP,and ATP synthesis.Methods:Thirty DOCA-salt hypertension mice were divided into three groups randomly: DOCA group,DOCA+ SAC/VAL group,and control group.SAC/VAL?60mg/kg.day?was administrated at9:00 am for 12 weeks.The tail arterial pressure was measured every two weeks.Echocardiogram was performed to screen the HFpEF model.?1?To determine the effects of Sac/Val on cardiac function of HFpEF,echocardiography was performed to evaluate the left ventricular diastolic function.The HF scores and lung weight was measured at all groups.?2?To evaluate the effect ofSAC/VAL on oxidative stress in myocardial mitochondria,the NOX4 expression in both cardiac tissue and cardiomyocyte mitochondria were separately detected.The mitochondrial oxidative stress in cardiomyocytes was performed by the mitochondrial superoxide indicator MitoSOX Red under confocal.?3?To clarify whether the above effects of SAC/VAL through mitochondrial fission/fusion modulation.The mitofusin protein 1?MFN1?,mitofusin protein 2?MFN2?,and the mitochondrial fusion inhibitor protein dynamin-related protein 1?Drp-1?,mitochondrial fission protein 1?Fis1?,optical atrophy 1?OPA1?,peroxisome proliferator-activated receptor-activated receptor ? co-activator 1??PGC-1??,nuclear factor E2-related factor?NRF-1?,mitochondrial transcription factor A?Tfam?expression were confirmed by western blot.Statistical analysis was analyzed by SPSS 22.0.Results:After 12 weeks of intragastric administration,compared with the control group,the SBP and DBP were significantly reduced in SAC/VAL.There was no difference between DOCA mice and control mice in left ventricular ejection fraction?53.61% ± 2.17% vs.68.00% ± 6.62 % control group,P<0.05?.Echocardiography showed that E'/A' was decreased in DOCA mice and enhanced after treated with SAC/VAL?DOCA vs.SAC/VAL: 0.762 ±0.05 vs.1.352±0.12,P<0.05?,E/E'?DOCA vs.SAC/VAL: 22.04±1.49 vs.19.27±1.72,P<0.05?,the heart score was significantly increased in DOCA mice compared with control mice?3.1 vs.0,P<0.05?,the above indicators proved the success of HFpEF model.SAC/VAL significantly reduced the expression of NOX4 in both cardiac tissue and cardiomyocytes mitochondrial?P<0.01?.MitoSOX Red was performed to evaluate the oxidative stress levels in ventricular cardiomyocytes.The expression of MFN1,MFN2,and OPA1 was significantly reduced in DOCA mice?P<0.05?.SAC/VAL up-regulated this protein.Drp-1,as an important role in mitochondrial fission,was up-regulated in DOCA mice?P<0.05?.This can be suppressed by SAC/VAL.The expression of mitochondrial fission protein Fis1 in the DOCA group was significantly higher compared with control group?P<0.05?.Although SAC/VALreduced its expression,there was no significant difference between those two groups.However,there was no significant difference in the expression of NRF1 between the control and DOCA group?P>0.05?.Conclusion: In our study,the improvement of SAC/VAL on cardiac function is achieved by regulating myocardial mitochondrial fusion/fission and improving myocardial mitochondrial oxidative stress.Our study found that in the HFpEF model caused by hypertension,myocardium and mitochondrial NOX4 might be the key point related to this process.Background: Epidemiological studies have shown that the prevalence of heart failure with preserved ejection fraction?HFp EF?is increasing.Most patients with HFp EF display older,diabetes mellitus?DM?and hypertension are each associated with morbidity and mortality and often occur with associated greater risk of adverse outcomes.The presence of DM can enhance the hospitalization of HFp EF to 70-80%.Among these patients,sudden cardiac death?SCD?is the main cause of death,accounting for 25% of the total mortality.In the first part of the study,we found that SAC/VAL can improve cardiac mitochondrial function by reducing myocardial inflammation in HFp EF.It has been reported that diabetic mellitus?DM?is associated with a prolonged QT interval and a high-risk of SCD.A recent publication shows that cardiac macrophage-derived interleukin-1??IL-1??causes QT prolongation and increases arrhythmic risk in DM.Nevertheless,how IL-1? signals arrhythmic risk is unclear.Methods: Thirty C57BL/6J mice aged 24-week were fed with a 60% kcal high-fat diet?HFD?for 20 weeks to induced DM model.The control mice were fed with 10% kcal HFD.SAC/VAL was given to the mice subsequently.?1?Echocardiography to compare mouse myopathy models will be performed as in previous studies.The Vevo 2100?Visual Sonics,Toronto,Canada?ultrasound unit will be used.M-mode images in the parasternal long-axis and the left ventricle short-axis views at the mid-papillary level will be used for the measurements.?2?Mice will be implanted subcutaneously with ETA-F10 telemetry monitors?Data Sciences International,St.Paul,Minnesota?.Mice will be anesthetized using vaporized isoflurane?Harvard Apparatus?.A midline neck incision will be made to expose the right jugular veins.A 1.1F Millar electrophysiology catheter?Millar Instruments,Houston,TX?will be advanced through the right jugular vein into the right ventricle.A STG2004 constant-current stimulator?ADInstruments,Colorado Spring,CO?will be used along with MCStimulus software to burst pace the heart.?3?The Leica SP2 laser confocal scanning system was used to monitor the intracellular Ca²⁺ circulation to detect Ca²⁺ activation activity.A 60×1.4NA oil immersion objective equipped with a confocal microscope and a Ca²⁺ sensitive indicator Fluo-3AM probe was used for liner scanning mode.All data were analyzed by SPSS 22.0.Results: In comparison to the control mice fed with low-fat diet,QT interval were substantially longer?50.6±1.8ms vs.41.5± 0.8ms,P<0.05?,and the inducibility of ventricular arrhythmia was significantly higher?P<0.05?.Underlying these electrophysiological changes were prolonged action potential duration?APD?of cardiomyocytes?411±15ms vs.61±5ms,P<0.05?and increased incidence of early afterdepolarizations?EADs?.Cardiac IL-1? was elevated accompanied by upregulated NADPH oxidase 2?NOX2?and increased mitochondrial reactive oxygen species?mito ROS?.Inhibiting IL-1? or mito ROS by treating HFD mice with an IL-1receptor antagonist?IL-1RA?or mito TEMPO?P<0.05?respectively,shortened QT interval and APD,reduced the inducibility of ventricular arrhythmia?P<0.05?,demonstrating that these electrophysiological changes were mediated by IL-1? and mito ROS.Moreover,IL-1RA ameliorated mito ROS elevation in DM,and mito TEMPO treatment abolished IL-1? induced EADs?P<0.05?.IL-1RA and mito TEMPO treatment reversed Ry R oxidation.Inhibiting Ca²⁺ leak by stabilizing oxidized Ry R ameliorated QT prolongation and arrhythmia inducibility.Conclusion: Our results suggested that increased mitochondrial ROS by IL-1? signaling causes Ry R oxidation thereby arrhythmic Ca²⁺ release is the underlying mechanism of DM associated arrhythmia.Cardiac IL-1? mediated the diabetes-associated electrophysiological changes and arrhythmic risk.Mito ROS provide a mechanistic link between IL-1? and DM-induced HFp EF associated arrhythmia.The clinical importance of heart failure with preserved ejection fraction?HFp EF?has recently become important.HFp EF refers to heart failure?HF?symptoms with normal or near-normal cardiac function on echocardiography.Common clinical characteristics of HFp EF include diastolic dysfunction,reduced compliance,and ventricular arrhythmia.HFp EF differs from the better-known HF with reduced ejection fraction?HFr EF?.Despite having a preserved ejection fraction,patients with HFp EF have symptoms such as shortness of breath,excessive tiredness,and limited exercise capability.Furthermore,the mortality rate and cumulative survival rate are as severe in HFp EF as they are in HFr EF.While beta-blockers and renin-angiotensin-aldosterone system modulators can improve the survival rate in HFr EF,no known therapeutic agents show similar effectiveness in HFp EF.Researchers have examined molecular events in the development of HFp EF using small and middle-sized animal models.This review discusses HFp EF with regard to etiology and clinical features and introduces the use of mouse and other animal models of human HFp EF.