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BACKGROUND:Exercise is an effective strategy to prevent and treat various cardiovascular diseases and protect the heart from ischemia-reperfusion injury.Its mechanism of action needs to be studied in depth. OBJECTIVE:To observe the effect of aerobic exercise preconditioning on myocardial ischemia-reperfusion injury and to explore the effect of endothelial nitric oxide synthase(eNOS)activation(including coupling and phosphorylation). METHODS:Eighty adult Wistar rats were randomly divided into sedentary(n=40)and exercise(n=40)groups.The rats in the exercise group were subjected to aerobic exercise for 8 weeks while those in the sedentary group were quietly fed and caged.After 8 weeks of intervention,three experiments were performed.(1)Experiment 1:After the last training,cardiac function,cardiac nitric oxide metabolite content and cardiac eNOS,phosphorylated eNOS-S1177,eNOS dimer and eNOS monomer protein expression levels were detected.(2)Experiment 2:Rats were divided into sedentary control group,exercise control group,sedentary+eNOS inhibitor group,exercise+eNOS inhibitor group,all of which were subjected to an in vitro myocardial ischemia-reperfusion injury experiment.eNOS inhibitor was continuously infused into the sedentary+eNOS inhibitor group and exercise+eNOS inhibitor group 10 minutes before reperfusion,and cardiac function and myocardial infarction area were detected 3 hours after reperfusion.(3)Experiment 3:Rats were divided into sedentary control group,exercise control group,sedentary+eNOS coupler group and exercise+eNOS coupler group,all of which were subjected to an in vitro myocardial ischemia-reperfusion injury experiment.The rats in the sedentary+eNOS coupler group and exercise+eNOS coupler group were treated with eNOS coupler.Myocardial infarct area,cardiac nitric oxide metabolite content,cardiac protein expression of eNOS,phosphorylated eNOS-S1177,eNOS dimer,eNOS monomer and 3-nitrotyrosine were detected 3 hours after reperfusion.The phosphorylated eNOS-S1177/eNOS ratio reflected the phosphorylated/dephosphorylated level of eNOS and eNOS dimer/monomer ratio reflected eNOS coupling/uncoupling level. RESULTS AND CONCLUSION:Experiment 1:Compared with the sedentary group,the exercise group had increased cardiac output and left ventricular ejection fraction(P<0.05),increased nitrite and S-nitrosothiol contents(P<0.05),upregulated phosphorylated eNOS-S1177,eNOS protein expression and phosphorylated eNOS-S1177/eNOS ratio(P<0.05),eNOS dimer protein expression and eNOS dimer/monomer ratios were elevated(P<0.05).Experiment 2:Compared with the sedentary control group,left ventricular development pressure increased(P<0.05)and myocardial infarct area decreased(P<0.05)in the exercise control group.Compared with the exercise control group,left ventricular development pressure decreased(P<0.05)and myocardial infarct area increased(P<0.05)in the exercise+eNOS inhibitor group.Experiment 3:Compared with the sedentary control group,the exercise control group had increased left ventricular developmental pressure(P<0.05),decreased myocardial infarct area(P<0.05),decreased phosphorylated eNOS-S1177/eNOS ratio(P<0.05),decreased eNOS dimer/monomer ratio(P<0.05),increased S-nitrosothiol content(P<0.05),and decreased 3-nitrotyrosine protein expression(P<0.05).Compared with the exercise control group,the exercise+eNOS coupler group had decreased left ventricular developmental pressure(P<0.05),increased myocardial infarct area(P<0.05),increased phosphorylated eNOS-S1177/eNOS ratio(P<0.05),increased eNOS dimer/monomer ratio(P<0.05),and elevated 3-nitro tyrosine protein expression(P<0.05).To conclude,aerobic exercise preconditioning could induce cardioprotection,which is related to uncoupling and dephosphorylation of eNOS during cardiac ischemia-reperfusion,thereby inhibiting the excessive production of nitric oxide and reducing nitro-oxidative stress.
ABSTRACT
BACKGROUND:Postmenopausal osteoporosis significantly increases the risk of fracture,which seriously affects the quality of life of patients.Exercise therapy is an important non-drug means and prevention and treatment strategy for patients with osteoporosis,in which strength training is the best mode,but its specific biological mechanism has not been determined. OBJECTIVE:To investigate the effects of strength training on bone morphology,materials and biomechanics in ovariectomized rats and to explore the mechanism of extracellular matrix remodeling. METHODS:Forty-eight female Sprague-Dawley rats were divided into sham operation group,sham operation exercise group,ovariectomized group and ovariectomized exercise group according to the random number table method.The menopausal animal model was established by bilateral ovariectomy in the ovariectomized group and ovariectomized exercise group,while sham operation was performed in the sham operation group and sham operation exercise group.Four weeks after operation,the sham operation exercise group and the ovariectomized exercise group underwent 12-week tail weight-bearing ladder training,and the sham operation group and the ovariectomized group were raised quietly in the cage.The bilateral femur and tibia were separated after training.The right tibia was used for dual-energy X-ray densitometry and biomechanical,biophysical and biochemical analyses,the left tibia was detected using micro-computed tomography for bone microstructural examination,the right femur was subjected to hematoxylin-eosin staining for histological observation,and the left femur was used for western blot and gelatin zymography detection of protein expression and enzyme activity of extracellular matrix metabolism-related factors,respectively. RESULTS AND CONCLUSION:Compared with the sham operation group,the maximal load and stiffness decreased(P＜0.05),bone density,bone mineral density,bone inorganic matter content,bone calcium content decreased(P＜0.05),bone water content increased(P＜0.05),trabecular bone volume fraction,trabecular connectivity density,and trabecular number decreased(P＜0.05),trabecular separation,structural model index increased(P＜0.05),bone adipocyte number and cross-sectional area increased(P＜0.05),matrix metalloproteinase-2 activity decreased(P＜0.05),and protein expression of tissue inhibitor of metalloproteinase-1 and osteoprotegerin increased(P＜0.05)in the ovariectomized group.Compared with the ovariectomized group,the maximal load,stiffness,fracture load and resilience increased(P＜0.05),bone mineral density,bone mineral content,bone mineral density,bone inorganic matter content,and bone calcium content increased(P＜0.05),bone water content decreased(P＜0.05),trabecular separation and bone marrow area decreased(P＜0.05),trabecular bone thickness,cortical bone volume fraction,cortical bone area fraction,cortical bone thickness,and cortical bone porosity increased(P＜0.05),bone adipocyte number and cross-sectional area reduced(P＜0.05),matrix metalloproteinase-2 activity increased(P＜0.05),and protein expression of tissue inhibitor of metalloproteinase-1,Runt-related transcription factor 2 and osteoprotegerin decreased(P＜0.05)in the ovariectomized exercise group.To conclude,strength training can protect against bone injury caused by estrogen deficiency,which is characterized by improvement of bone biomechanical properties,bone tissue composition and bone microstructure,and its mechanism is related to the regulation of extracellular matrix remodeling.
ABSTRACT
BACKGROUND:Stem cell therapy is an alternative treatment strategy for restoring damaged myocardial tissue after acute myocardial infarction.Exercise preconditioning can induce endogenous cardioprotective effects in the body.However,the efficacy and mechanism of the combined application are still unclear. OBJECTIVE:To explore the effect and possible mechanism of exercise preconditioning combined with bone marrow mesenchymal stem cells on the therapeutic effect in rats with acute myocardial infarction. METHODS:Seventy male SD rats were randomly divided into sham operation group,model group,stem cell therapy group,exercise preconditioning group,and combined intervention group.Rats in the exercise preconditioning group and combined intervention group underwent 8-week aerobic exercise on the treadmill before modeling.The animal model of acute myocardial infarction was made by ligating the anterior descending coronary artery.The stem cell therapy group and the combined intervention group were injected with bone marrow mesenchymal stem cells(1×109 L-1,1 mL)through the tail vein the next day after modeling.After 4 weeks of treatment,the exercise performance was evaluated by a graded treadmill exercise test.The cardiac structure and function were detected by echocardiography.The left ventricle was isolated.2,3,5-Triphenyltetrazolium chloride staining was used to evaluate myocardial infarct size.Masson staining was used to obtain collagen volume fraction.CD31 immunohistochemical staining was used to detect myocardial capillary density.TUNEL staining was used to detect myocardial cell apoptosis.Immunoblotting was used to detect protein expression levels of stromal cell-derived factor 1,CXC chemokine receptor protein 4,tumor necrosis factor-α,interleukin-10,and vascular endothelial growth factor. RESULTS AND CONCLUSION:(1)Intervention efficacy:Compared with the sham operation group,exercise performance,left ventricular ejection fraction,left ventricular fractional shortening,and CD31 positive cell rate decreased(P<0.05);myocardial infarct size,collagen volume fraction,and myocardial apoptotic rate increased(P<0.05)in the model group.Compared with the model group,exercise performance was not statistically significant(P>0.05)in the stem cell therapy group,and the exercise performance improved(P<0.05)in the exercise preconditioning and combined intervention groups;left ventricular ejection fraction,left ventricular fractional shortening,and CD31 positive cell rate increased(P<0.05),and the myocardial infarct size,collagen volume fraction,and cardiomyocyte apoptosis rate decreased(P<0.05)in the stem cell therapy,exercise preconditioning,and combined intervention groups.Compared with the stem cell therapy group,exercise performance,left ventricular ejection fraction,left ventricular shortening fraction,and CD31 positive cell rate increased(P<0.05),myocardial infarct size,collagen volume fraction,and myocardial cell apoptosis rate decreased(P<0.05)in the combined intervention group.(2)Protein expression:Compared with the sham operation group,the expression of tumor necrosis factor-α increased(P<0.05),while interleukin-10 and vascular endothelial growth factor expression decreased(P<0.05)in the model group.Compared with the model group,the expression of CXC chemokine receptor protein 4 increased(P<0.05)in the stem cell therapy group and combined intervention group,and the expression of tumor necrosis factor-α decreased(P<0.05)while interleukin-10 and vascular endothelial growth factor increased(P<0.05)in the stem cell therapy group,exercise preconditioning group,and combined intervention group.Compared with the stem cell therapy group,the expression of tumor necrosis factor-α decreased(P<0.05),while CXC chemokine receptor protein 4,interleukin-10,and vascular endothelial growth factor increased(P<0.05)in the combined intervention group.To conclude,exercise preconditioning can enhance the therapeutic effect of bone marrow mesenchymal stem cells in rats with acute myocardial infarction,which can inhibit cardiac remodeling,improve cardiac function,and delay the progress of heart failure.Its mechanism is related to the promotion of stem cell homing,inhibition of inflammatory response,and promotion of angiogenesis.
ABSTRACT
BACKGROUND:Exercise training is an important non-drug rehabilitation method for many heart diseases,and it can also enhance the heart's tolerance to adverse stressors(such as myocardial ischemia),that is,exercise preconditioning.Granulocyte colony-stimulating factor can effectively mobilize stem cell homing and differentiation and promote the repair of damaged myocardium.However,the effect of the combination of the two treatments is not yet clear. OBJECTIVE:To explore the effect of granulocyte colony-stimulating factor supplementation combined with high-intensity intermittent exercise preconditioning on cardiac remodeling in rats with acute myocardial infarction and investigate its possible mechanism. METHODS:Totally 58 male Wistar rats were divided into sham group(n=10),model group(n=12),model drug group(n=12),model exercise group(n=12)and model combined treatment group(n=12).The myocardial infarction rat model was made by coronary artery ligation.The model exercise group and the model combined treatment group were pretreated with 8 weeks of high-intensity intermittent exercise on an electric treadmill before modeling.The model drug group and the model combined treatment group were subcutaneously injected with human recombinant granulocyte colony-stimulating factor 3 hours after modeling for 5 days(10 μg/kg per day).At 8 weeks after administration,echocardiography was used to detect heart structure and function;heart was stained with 2,3,5-triphenyltetrazolium chloride and Masson staining to obtain myocardial infarct area and collagen volume fraction,respectively.Vessel density and cell apoptosis rate were detected by immunofluorescence.Real-time fluorescent quantitative PCR was utilized to detect the mRNA expression of embryonic genes(brain natriuretic peptide,β-myosin heavy chain)and myocardial contraction regulatory factors(α-myosin heavy chain,sarcoplasmic reticulum Ca2+-ATPase).Western blot assay was used to detect the protein expression of cardiac stromal cell-derived factor 1,CXC chemokine receptor protein 4,Janus kinase 2(JAK2),signal transducer and activator of transcription 3(STAT3),Bcl2,Bax,and cleaved caspase-3. RESULTS AND CONCLUSION:(1)Compared with sham group,myocardial infarct size,collagen volume fraction,and apoptosis rate increased(P<0.05);vessel density,left ventricular fractional shortening,and left ventricular ejection fraction decreased(P<0.05);brain natriuretic peptide and β-myosin heavy chain mRNA increased(P<0.05),α-myosin heavy chain and sarcoplasmic reticulum Ca2+-ATPase mRNA and α-myosin heavy chain/β-myosin heavy chain ratio decreased(P<0.05);stromal cell-derived factor 1,CXC chemokine receptor protein 4,Bax,cleaved caspase-3 protein expression increased(P<0.05);p-JAK2,p-STAT3,and Bcl-2 protein expression decreased(P<0.05)in the model group.(2)Compared with the model group,the above indexes in the model drug and model exercise groups were significantly improved(P<0.05).Compared with the model drug and model exercise groups,the above parameters were further ameliorated(P<0.05)in the model combined treatment group.(3)The results showed that supplementation of granulocyte colony-stimulating factor or high-intensity intermittent exercise preconditioning alone can improve cardiac remodeling in rats with acute myocardial infarction,and the combined therapy has a better effect,which may be related to the induction of stem cell homing and the activation of JAK2/STAT3 signaling pathway to inhibit cardiomyocyte apoptosis.