| Background:Myocardial infarction(MI)causes serious damage to cardiac function and threatens life safety.After MI,it causes ischemia and hypoxia in the heart,triggering inflammation and myocardial cell apoptosis in the infarcted area,leads to the rational remodeling of heart disease and the decline of cardiac function,and ultimately leads to heart failure.It is of great significance to find scientific and effective methods to prevent and improve ischemic heart disease and myocardial cell apoptosis.Moderate exercise after myocardial infarction can effectively reduce myocardial cell apoptosis and inflammation and improve cardiac function.Fibroblast growth factor 21(FGF21)belongs to the subgroup of fibroblast growth factor 19.Fibroblast growth factor receptor 1(FGFR1)is a heart-specific receptor of FGF21.Inhibiting the expression of FGFR1 significantly decreased the phosphorylation of ErK downstream.Myocardial cells can autocrine FGF21,which plays an important role in inhibiting apoptosis and inflammation.Does exercise improve myocardial function relate to the up-regulation of FGF21 expression in myocardial infarction by aerobic exercise?Does it activate the FGF21/FGFR1-ErK/PGC-1a/NF-kappa B signaling pathway?At present,there is no direct literature report.The purpose of this study was to investigate the inhibitory effect of aerobic exercise on the expression of endogenous fibroblast growth factor 21(FGF21)on myocardial cell apoptosis in myocardial infarction(MI)and its mechanism,so as to provide theoretical and experimental basis for the effective means of exercise to prevent ischemic heart disease.Methods:Animal Surgery,Grouping and Intervention:50 male Sprague-Dawley rats(purchased from the Laboratory Animal Management Center of Xi'an Jiaotong University,animal quality certificate number:SCXK 2017-003,weighing 180-220g,were fed in cages with 8 rats in each cage,fed freely,at room temperature of 22-28?.The model of myocardial infarction was established by permanent ligation of anterior descending branch of left coronary artery after one week of adaptation feeding.The sham-operated group only modeled without ligation.48 rats were successfully.The model was randomly divided into six groups:sham operation group(S),quiet myocardial infarction group(MI)and myocardial infarction+aerobic exercise group(ME),myocardial infarction+receptor inhibitor PD 166866 group(MD),myocardial infarction+PBS control group(MP),myocardial infarction+aerobic exercise+receptor inhibitor PD 166866 group(MDE),with 8 rats in each group.After operation,adaptive training was performed in ME group and MDE group at a speed of 15 m/min,30 min/d and 5 d×1 wk.After that,formal training was performed at 16 m/min(50%-60%VO2 max),60 min/d and 5 d/wk ×4 wk.Drug injection and exercise were carried out simultaneously.After the end of the exercise,abdominal anesthesia was carried out the next day.Blood was taken and heart and skeletal muscle were taken for use.Cardiac function evaluation and morphological experiment in rats:Cardiac function was assessed by hemodynamic parameters.Collagen volume fraction(CVF%)was observed and analyzed by Masson staining on routine paraffin sections,and cross section(CSA%)of skeletal muscle cells was observed and analyzed by HE staining on routine paraffin sections,and apoptosis was observed by TUNEL staining.Cell group and intervention:H9C2 rat cardiomyocytes were treated with 400?mol/L H2O2 for 4 hours to construct apoptotic model.Literature shows that AMPK signals are activated after different ways of exercise.Therefore,AICAR,an AMPK agonist,is used to intervene in H9C2 rat cardiomyocytes to simulate exercise effects.Cells were divided into normal control group(C),FGF21 recombinant protein intervention group(CF),fibroblast growth factor 1 receptor inhibitor group(CP),AMPK agonist AICAR intervention group(CA),FGF21 recombinant protein and ACAR co-intervention group(CFA),fibroblast growth factor 1 receptor inhibitor and ACAR co-intervention group(CPA).AICAR interfered with H9C2 rat cardiomyocyte concentration of 1 mM;the concentration gradient experiment was conducted in the FGF21 recombinant protein intervention group.The concentration gradient was o ng/mL,25 ng/mL,50 ng/mL,75 ng/mL and 100 ng/mL,respectively.The intervening time of both groups was 15h.The treatment concentration of FGFR1 inhibitor was 100 ng/mL and the intervention time was 24 hours.Detection of biochemical and molecular biological indicators:serum FGF21 expression was detected by ELISA,myocardial and skeletal muscle cell apoptosis was detected by Caspase-3 kit,and protein expression of FGF21/FGFR1,Bax,Bcl-2,p53,TNF-?,IL-10,collagen-?,collagen-? and ErK/PGC-1a/NF-kappa B pathway were detected by Western blotting.The expression of FGF21 and FGFR1 was detected by RT-qPCR.Results:(1)The results of TUNEL multicolor immunofluorescence staining,Western blotting and Caspease-3 show that apoptosis was further deteriorated after the intervention of cardiac specific receptor inhibitor of fibroblast growth factor 21;aerobic exercise could significantly inhibit myocardial apoptosis in myocardial infarction.It is suggested that fibroblast growth factor 21 plays an important role in inhibiting apoptosis of myocardial cells in myocardial infarction.(2)Western blotting results show that aerobic exercise could significantly inhibit the inflammatory response of myocardial infarction,and the inhibitor of cardiac specific receptor of fibroblast growth factor 21 interfered with the deterioration of myocardial inflammatory response in myocardial infarction rats.It is suggested that fibroblast growth factor 21 plays an important role in inhibiting the inflammatory response of the heart in rats with myocardial infarction.(3)Masson staining and Western blotting show that aerobic exercise could significantly inhibit the expression of Collagen-? and Collagen-?,and reduce the excessive proliferation of collagen fibers in myocardial infarction.Fibroblast growth factor 21 receptor FGFR1 inhibitor(PD 166866)further aggravated the degree of collagen fibrosis after intervention.It is suggested that fibroblast growth factor 21 plays an important role in improving collagen fibrosis in myocardial infarction.(4)Hemodynamic tests showed that cardiac function was further deteriorated after the intervention of cardiac specific receptor of fibroblast growth factor 21.Aerobic exercise could significantly improve myocardial infarction function.It is suggested that fibroblast growth factor 21 plays an important role in improving myocardial function of myocardial infarction by exercise,and the correlation analysis shows that exercise improves myocardial function of myocardial infarction is closely related to exercise up-regulation of fibroblast growth factor 21 of myocardial infarction.(5)Western blotting results show that aerobic exercise significantly increased the expression of FGFRI gene and fibroblast growth factor 21/fibroblast growth factor 1 protein in myocardium of rats with nyocardial infarction,activated ErK/PGC-1a/NF-kappa B signal in myocardium of rats with myocardial infarction,but the expression of FGF21 gene is not significant after aerobic exercise intervention.It is suggested that aerobic exercise can activate ErK/PGC-1a/NF-kappa B signaling pathway in myocardium of rats with myocardial infarction and is positively correlated with up-regulation of the expression of fibroblast growth factor 21 in myocardium of rats with myocardial infarction by exercise.However,cardiac fibroblast growth factor 21 protein expression stimulated by aerobic exercise may mainly come from other organs.(6)Aerobic exercise inhibits apoptosis and loss of skeletal muscle caused by myocardial infarction.Aerobic exercise significantly reduce the expression of Bax/Bcl-2,p53 and Caspease-3 in skeletal muscle through FGF21,increase the cross-sectional area of skeletal muscle cells in rats with myocardial infarction,and inhibit apoptosis of skeletal muscle cells and loss of skeletal muscle caused by myocardial infarction.The correlation analysis shows that there is a positive correlation between exercise and up-regulation of fibroblast growth factor 21 in myocardial infarction skeletal muscle.(7)FGF21 plays an important role in inhibiting skeletal muscle inflammation in rats with myocardial infarction.Inflammatory response is triggered by myocardial infarction,which is aggravated by the intervention of FGF21 receptor inhibitor(PD 166866).Aerobic exercise,aerobic exercise and receptor inhibitor inhibit the inflammatory response.(8)The expression of FGF21 in skeletal muscle increased significantly after myocardial infarction,while the expression of FGF21 decreased significantly,which may be related to the synthesis and rapid release of FGF21 in skeletal muscle.Aerobic exercise increase the level of FGF21 in skeletal muscle and circulation,and the level of FGF21 in skeletal muscle and myocardium is positively correlated with the level of serum FGF21.(9)AICAR significantly inhibited the inflammation and apoptosis of H9C2 cardiomyocytes induced by hydrogen peroxide,significantly increased the expression of FGF21/FGFR1 in H9C2 cardiomyocytes induced by hydrogen peroxide,and significantly activated ErK/PGC1?/NF-kappa B signaling pathway in H9C2 cardiomyocytes after different concentrations of fibroblast growth factor 21 recombinant protein or AICAR intervention.(10)AICAR or FGF21 recombinant protein intervention significantly reduce the number of TUNEL positive particles,Bax/Bcl-2 ratio and p53 protein expression.FGF21 receptor inhibitor(PD 166866)significantly increased the number of TUNEL positive particles and Bax/Bcl-2 ratio in H9C2 myocardial cells.The results show that exercise or FGF21 significantly inhibited the apoptosis of H9C2 cardiomyocytes induced by hydrogen peroxide.(11)AICAR or FGF21 recombinant protein intervention significantly reduce the ratio of TNF-a/IL-10.FGF21 receptor inhibitors significantly increase the TNF-a/IL-10 ratio of H9C2 cells.The results show that exercise or FGF21 significantly inhibited the inflammatory response of H9C2 myocardial cells.(12)AICAR or FGF21 recombinant protein intervention significantly increase ErK1/2 and PGC-1? expression,and significantly decreased pNF-kappa B/NF-kappa B ratio.FGFR1 inhibitor(PD 166866)significantly inhibited ErK/PGC1?/NF-kappa B signaling pathway in H9C2 cardiomyocytes.These results suggest that exercise activates ErK/PGC-la/NF-kappa B signaling pathway in H9C2 cardiomyocytes through FGF21.Conclusion:(1)Aerobic exercise significantly promoted the expression of FGF21/FGFR1 in myocardium of rats with myocardial infarction,inhibited the expression of inflammatory factors in myocardium of rats with myocardial infarction,overproliferation of collagen and apoptosis of myocardial cells of rats with myocardial infarction,and improved cardiac function.There is a positive correlation between the improvement of myocardial infarction function by aerobic exercise and the increase of myocardial fibroblast growth factor 21 expression.Aerobic exercise significantly activates ErK1/2-PGC-1a/NF-kappa B signaling pathway and is associated with up-regulation of myocardial FGF21.(2)Aerobic exercise significantly promoted the expression of FGF21 in skeletal muscle and serum of rats with myocardial infarction.Aerobic exercise increase the cross-sectional area of skeletal muscle,inhibit the expression of inflammatory factors and apoptosis of skeletal muscle cells induced by myocardial infarction in rats,and is related to the increased expression of FGF21 in skeletal muscle promoted by exercise.(3)Exogenous AICAR or FGF21 recombinant protein intervention significantly reduced the apoptosis and inflammation of H9C2 myocardial cells induced by hydrogen peroxide,and activated ErK1/2-PGC-1a/NF-kappa B signaling pathways.These results suggest that exercise can activate ErK/PGC-1a/NF-kappa B signaling pathway in cardiomyocytes through FGF21,and reduce apoptosis and inflammation of cardiomyocytes.In conclusion,exercise improves myocardial function by stimulating the expression and release of fibroblast growth factor 21 in skeletal muscle,increasing circulatory and myocardial fibroblast growth factor 21 levels,and activating the ErK1/2-PGC-1a-NF-KB signaling pathway in myocardial infarction,thereby reducing the inflammatory response of the heart and inhibiting myocardial cell apoptosis and fibrosis in myocardial infarction. |
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