| OBJECTIVE:Cardiovascular disease is currently the most important cause of death in humans.In patients with myocardial infarction,the timely and effective treatment for reducing acute myocardial ischemia injury,limiting myocardial infarction area,maintaining left ventricular systolic function and preventing heart failure is myocardial blood reperfusion.However,the process of reperfusion itself can further aggravate myocardial damage,a phenomenon known as myocardial ischemia reperfusion(MI/R)injury.There are many known risk factors for cardiovascular diseases,such as hypertension,tobacco use,obesity,hyperlipidemia and diabetes.Patients with type 2 diabetes(T2DM)had increased myocardial infarction size,decreased myocardial blood reflow,increased incidence of congestive heart failure,and decreased survival after myocardial ischemia/reperfusion compare to non-T2DM patients.Adiponectin(APN)is an adipocytokine secreted by adipose tissue.In patients with obesity and T2DM,plasma APN level is significantly reduced,leading to increased sensitivity of myocardium to MI/R injury.MicroRNA(micro ribonucleic acid,miRNA)is a kind of endogenous single non-coding RNAs,length about 22 nucleotides.Change of microRNAs expression is strongly associated with various cardiovascular diseases,such as myocardial infarction(MI),ventricular remodeling,cardiomyopathy.Studys indicate that miRNA expression change in patients with diabetes contributes to the diagnosis,progression,prognosis of multiple diseases and treatment response.The mechanism of hypoadiponectinemia aggravating myocardial ischemia reperfusion injury in diabetes mellitus remain incompletely understood.METHODS:Adult male C57BL/6 and APN knockout(KO)mice were subjected to MI/R.MiRNAs from ventricular tissue were isolated for microarray analysis,to explore the changes of miRNA expression profile after MI/R and to screen out eligible target miRNA.Cardiac fuction,myocardial infarction size,plasma CK-MB level were measured after administration of miRNA inhibitor or mimic by invivo-jetPET system in MI/R model mice.Target miRNA function was predicted using Gene ontology(GO)analysis;downstream mRNA was screened out by Profiler PCR Array and confirmed by Luciferase reporter assay.To address downstream pathway mediated by miRNA,neonatal cardiomyocytes were exposed in simulated ischemia reperfusion(SI/R)condition after high glucose high lipid(HGHL)treatment.High fat diet(HFD)induced diabetic mice subjected to MI/R with or without treatment of APN were utilized to verify the function of target miRNA and downstream gene.RESULTS:microRNA-449b were the most significantly upregulated(3.98-fold)microRNA of 23 identified by a discovery-driven microRNA profile screening of wild type(WT)and APN KO mice subjected to MI/R.The endogenous antioxidant NFE2L1(nuclear factor erythroid 2-related factor 1,Nrf-1)was inhibited by increased microRNA-449b after MI/R in APN KO and HFD mice.Administration of anti-miR449b effectively reduced myocardial infarction size and apoptosis in APNKO and HFD mice subjected to MI/R.A miR449b mimic augmented cardiac infarct size and apoptosis in WT mice after MI/R.Go analysis predicted antioxidant activity to be most affected by the miRNA-449.Oxidative species generation analysis(DHE staining and lucigenin detection)demonstrated anti-miR449b effectively decreased oxidative stress in HFD and APNKO mice after MI/R.As miRNA-449b binds the Nrf-1 3’-UTR region,reducing luciferase activity,Nrf-1 is the downstream target of miRNA-449b.APN treatment significantly reduced miR449b formation,increased Nrf-1 protein levels,and attenuated superoxide generation in HFD and APNKO mice after MI/R.Furthermore,Nrf-1 overexpression suppressed SI/R-induced superoxide production and apoptosis.Finally,neonatal cardiomyocytes were subjected to miR449b,resulting in upregulated Nrf-1 and reduced superoxide generation.Such effects were abrogated in the presence of a miR449b mimic in neonatal cardiomyocytes subjected to high-glucose high-lipid treatment.CONCLUSION:We demonstrate for the first time that Nrf-1 is a new revealed endogenous antioxidant,regulated by APN via miR449b modulation,protecting against anti-oxidative stress during diabetic I/R injury. |
