防己茯苓汤通过AMPK/PGC-1α/MFN2-PKM2信号通路调控线粒体功能治疗心肌纤维化OA

Objective:To investigate the effects and mechanisms of Fangji Fulingtang(FFD)on mitochondrial function in the mouse model of myocardial fibrosis(MF).Methods:Sixty SPF-grade male C57BL/6J mice were randomly allocated into six groups(n=10 per group):control,model,low-dose,medium-dose,and high-dose(3.315,6.63,and 13.26 g·kg-1,respectively)FFD,and captopril(20 mg·kg-1).MF was induced by subcutaneous injection of isoproterenol(10 mg·kg-1·d-1)in other groups except the control group for 14 consecutive days,with simultaneous gavage of corresponding drugs.Left ventricular ejection fraction(LVEF)and left ventricular fractional shortening(LVFS)were measured by echocardiography.Serum levels of creatine kinase-MB(CK-MB),cardiac troponin I(cTnI),N-terminal pro-brain natriuretic peptide(NT-pro BNP),tumor necrosis factor-α(TNF-α),interleukin-1β(IL-1β),and interleukin-6(IL-6)were determined by enzyme-linked immunosorbent assay(ELISA).Malondialdehyde(MDA),superoxide dismutase(SOD),and glutathione(GSH)levels were measured by biochemical assays.Reactive oxygen species(ROS)were detected by dihydroethidium(DHE)fluorescence staining.Hematoxylin-eosin(HE),Masson's trichrome,and wheat germ agglutinin(WGA)staining were performed to evaluate myocardial structure and fibrosis.Mitochondrial ultrastructure and function were assessed by transmission electron microscopy,adenosine triphosphate(ATP)colorimetric assay,and JC-1 fluorescence staining.The protein levels of phosphorylated adenosine monophosphate-activated protein kinase α subunit(p-AMPKα),AMPKα,peroxisome proliferator-activated receptor gamma coactivator-1α(PGC-1α),mitofusin 2(MFN2),pyruvate kinase M2 isoform(PKM2),lactate dehydrogenase A(LDHA),and hypoxia-inducible factor 1 alpha(HIF-1α)were analyzed by Western blot.Results:Compared with the control group,the model group exhibited decreased LVEF and LVFS,increased heart weight index and heart weight-to-tibia length ratio(P<0.01),elevated levels of myocardial injury markers(CK-MB,cTnI,and NT-pro BNP),inflammatory cytokines(TNF-α,IL-1β,and IL-6),and MDA,along with reduced SOD and GSH levels(P<0.01).Enhanced interstitial collagen deposition and cardiomyocyte hypertrophy were observed in the model group(P<0.01).Transmission electron microscopy and JC-1 staining revealed mitochondrial swelling,crista disruption,decreased ATP content,and reduced red/green fluorescence ratio in the model group(P<0.01).Western blot analysis demonstrated downregulation of p-AMPKα,PGC-1α,and MFN2 and upregulation of PKM2,LDHA,and HIF-1α in the model group(P<0.01).Compared with the model group,treatment with FFD or captopril improved LVEF and LVFS,reduced heart weight index and heart weight-to-tibia length ratio(P<0.05,P<0.01),lowered the serum levels of CK-MB,cTnI,NT-pro BNP,TNF-α,IL-1β,IL-6,and MDA,increased the SOD and GSH levels(P<0.05,P<0.01),attenuated the myocardial fibrosis and cardiomyocyte hypertrophy(P<0.01),and restored the mitochondrial ultrastructure.The medium and high-dose FFD groups as well as the captopril group showed increased ATP production and red/green fluorescence ratio(P<0.05,P<0.01).Furthermore,FFD upregulated the expression of p-AMPKα and PGC-1α while downregulating the expression of LDHA and HIF-1α(P<0.05,P<0.01).Conclusion:FFD activates the AMPK/PGC-1α/MFN2 signaling pathway and inhibits the PKM2/LDHA/HIF-1α axis to restore mitochondrial function and energy metabolic homeostasis,thereby attenuating isoproterenol-induced myocardial fibrosis.