Icariin Attenuates Isoproterenol-induced Myocardial Fibrosis In Mice Via Regulating The PPARγ/NF-κB Signaling Pathway

Objective: To observe the effect of icariin(ICA)on myocardial fibrosis induced by isoproterenol(ISO)in mice and to research the mechanism based on PPARγ/NF-κB signaling pathway.Methods: Sixty male C57BL/6 mice of 7 weeks old were randomly divided into control group(Control),ISO group(ISO),low-dose(15 mg/kg,ICA-L),middle-dose(30 mg/kg,ICA-M)and high-dose(60 mg/kg,ICA-H)of ICA-treated group and losartan-treated group(9 mg/kg,LOS)after adaptive feeding for a week.The Control group was subcutaneously injected with normal saline,and the other groups were subcutaneously injected with ISO(5 mg/kg,qd)for 14 days to established the myocardial fibrosis model.The ICA-treated groups and the LOS group were administrated with ICA or losartan(ig,qd),respectively.The other groups were received the same amount of double distilled water(ig,qd).After 14 days administration,left ventricular ejection fraction(LVEF),left ventricular fraction shortening rate(LVFS),left ventricular end-systolic volume(LVESV),left ventricular end-diastolic volume(LVEDV),left ventricular internal diameter at end-systole(LVIDs),left ventricular internal diameter at end-diastole(LVIDd),left ventricular systolic anterior wall thickness(LVAWs),and left ventricular systolic posterior wall thickness(LVPWs)were evaluated by small animal ultrasound.The heart was obtained and the left ventricle was separated.The heart mass index(HMI)and the left ventricular mass index(LVMI)were calculated.The morphologic changes of the left ventricle were observed by H&E staining and transverse diameter of myocardial cell(TDM)was calculated.Left ventricular fibrosis was observed by Masson staining and collagen volume fraction(CVF)was calculated.The protein expression of ANP,c TnⅠ,PPARγ,NF-κB(p65),TNF-α,IL-6,IL-1β,α-SMA,MMP-2,MMP-9 and TIMP-1 in the left ventricular tissue were detected by western blotting.Results: Compared with the control group,LVEF,LVFS,LVAWs and LVPWs were decreased significantly(P<0.05);LVESV,LVEDV,LVIDs and LVIDd were increased significantly(P<0.05);HMI and LVMI were increased significantly(P<0.05);it was observed that myocardial cells were arranged in disorder and infiltrated with inflammatory cells in the left ventricle and TDM was increased significantly(P<0.05);the deposition of collagen in the left ventricle was increased and CVF was increased significantly(P<0.05);the protein expression of ANP,c TnⅠ,NF-κB(p65),TNF-α,IL-6,IL-1β,α-SMA and MMP-9 were up-regulated(P<0.05);the protein expression of PPARγ,MMP-2 and TIMP-1 were down-regulated(P<0.05)in the ISO group.Compared with the ISO group,LVEF,LVFS,LVAWs and LVPWs were increased obviously(P<0.05);LVESV,LVEDV,LVIDs and LVIDd were decreased obviously(P<0.05);HMI and LVMI were decreased obviously(P<0.05);myocardial cells were relatively neat and infiltrated with inflammatory cells were improved in the left ventricle and TDM decreased obviously(P<0.05);the deposition of collagen in the left ventricle was decreased and CVF decreased obviously(P<0.05);the protein expression of ANP,c TnⅠ,NF-κB(p65),TNF-α,IL-6,IL-1β,α-SMA and MMP-9 were down-regulated(P<0.05);the protein expression of PPARγ,MMP-2 and TIMP-1were up-regulated(P<0.05)in the ICA-M,ICA-H and LOS groups.Conclusion:(1)ICA improves myocardial fibrosis and left ventricular dysfunction induced by ISO in mice.(2)The underlying mechanism may be at least related to:(1)reduce the protein expression of TNF-α,IL-6 and IL-1β,to repress the inflammatory reaction through regulating PPARγ/NF-κB;(2)reduce the protein expression ofα-SMA and MMP-9 and increase the protein expression of MMP-2 and TIMP-1,to regulate the synthesis and degradation of the extracellular matrix by regulating PPARγ/NF-κB.