Astragaloside IV Improves Pressure Overload-induced Myocardial Remodelling By Inhibiting The Activation Of NLRP3 Inflammasome

ObjiectiveThe aim of this study was to study the protective effect of astragaloside IV(ASIV)on myocardial fibrosis and inflammation induced by pressure overload in rats and to explore the potential mechanism.MethodsMale healthy SD rats established a pressure overload model by abdominal aortic constriction(AAC),and the model was successfully determined by ultrasound indicators.After abdominal aortic stenosis,rats were given intraperitoneal injection of gentamicin(0.01 mmol / kg / d)for 1 week,followed by intragastric administration of As-IV(40 and 80 mg / kg)for 10 weeks.Forty rats were randomly divided into 5 groups: sham operation group,model group(AAC group),low-dose group(AAC + ASIV,40 mg / kg / d),and high-dose group(AAC + ASIV,80 mg / kg)/ d)and inhibitor group(AAC + MCC950,10 mg / kg /d).Measurement of cardiac function indicators: cardiac index(HMI,mg / g),left ventricular index(LVMI,(mg / g),left ventricular posterior wall thickness(LVPWs,mm),Left ventricular end-diastolic posterior wall thickness(LVPWd,mm),end-diastolic ventricular septal thickness(IVSd,mm),systolic ventricular septal thickness(IVSs,mm)and left ventricular ejection fraction(LVEF,%).HE staining was used to observe myocardial morphological changes in rats;Changes in rat myocardial fibrosis;ELISA kits detect the levels of type I collagenpro-carboxyl terminal pro-peptide(PICP)and its inhibitor type-I collagen cross-linked carboxy-terminal peptide(ICTP)in blood.Oxidative stress kits were used to assay the levels of malondialdehyde(MDA)and superoxide dismutase(SOD);The reactive oxygen speciese(ROS)production in AAC heart tissues was determined by dihydroethidium(DHE)staining;Immunohistochemistry was used to assess transforming growth factor(TGF-β1)and inflammasome(NLRP3);and Western blotting was used to measure the protein expression of transforming growth(TGF-β1),mothers against DPP homologue(Smad2),NLRP3,cysteine aspartate-specific proteinase(caspase-1),pro-caspase-1,apoptosis-associated speck-like protein(ASC),interleukin-18(IL-18)and Interleukin-1β(IL-1β).ResultsCompared with the sham operation group,after abdominal aorta narrowing and modeling,(1)rats LVPWd,IVSd,LVPWs,IVSs,HMI and LVMI increased(p<0.05),while LVEF% decreased(p<0.05);(2)HE staining showed that myocardial tissue was disorderly arranged,part of myocardial cells were edema and inflammatory cell infiltration between myocardial tissues;(3)Masson staining showed an increase in the area of fibrosis between myocardial tissues;(4)ELISA showed an increase in the expression of MDA,PCP,and ICTP(p<0.01)in serum and a decrease in SOD(p<0.01);(5)DHE staining showed an increase in ROS expression in myocardial tissue;(6)Immunohistochemistry showed increased expression of NLRP3 and TGF-β1 protein in myocardial tissue;(7)Western blot showed that IL-1β,IL-18,ASC,Caspase-1,Pro-caspase-1,NLRP3,Smad2 and TGF-β1 protein expression levels were increased in myocardial tissue(p<0.01).Compared with the model group,after astragaloside IV treatment,(1)rats LVPWd,LVPWs,IVSs,IVSd,HMI and LVMI decreased(p<0.05),while LVEF%increased(p<0.05);(2)HE staining showed pressure overload The myocardial pathological damage caused was improved,edema myocardial cells and decreased,inflammatory cell infiltration reduced;(3)Masson staining showed adecrease in the area of myocardial fibrosis;(4)ELISA showed that the expression of PICP,ICTP and MDA,(p<0.01)in serum decreased,SOD(p<0.01)Increased expression;(5)DHE staining showed decreased ROS expression in myocardial tissue;(6)Immunohistochemistry showed reduced expression of NLRP3 and TGF-β1 protein in myocardial tissue;(7)Western blot showed ASC,Caspase-1,Pro-caspase-1,NLRP3,IL-1β,IL-18 Smad2 and TGF-β1 protein expression levelsin myocardial tissue were reduced(p <0.01).Compared with the model group,(1)LVRPWd,LVPWs,IVSs,IVSd,HMI and LVMI were reduced in rats(p<0.05),and LVEF% was increased(p <0.05)after administration of NLRP3 inflammatory body inhibitors(MCC950).(2)HE staining showed that myocardial pathological damage caused by pressure overload was improved,edema of cardiomyocytes and inflammatory cells were reduced;(3)Masson staining showed a decrease in the area of fibrosis between myocardial tissues;(4)ELISA showed serum MDA,PICP and ICTP(p<0.01)Reduced expression,increased expression of SOD(p<0.01);(5)DHE staining showed reduced ROS expression in myocardial tissue;(6)Immunohistochemistry showed reduced expression of NLRP3 and TGF-β1 proteins in myocardial tissue;(7)Western blot showed ASC,Caspase-1,Pro-caspase-1,NLRP3,IL-1β,IL-18,Smad2 and TGF-β1 protein expression levels were reduced(p <0.01).ConclusionsASIV has protective effects on myocardial fibrosis and inflammation induced by AAC in rats.The protective mechanism of ASIV on myocardial fibrosis may be partly achieved by inhibiting the activation of the NLRP3 inflammasome and regulating oxidative stress.