The Role And Mechanism Of EV-miR-421 In PM_2.5 Exposure-induced Cardiac Dysfunction In Mice

Background:Air pollution,via ambient PM_2.5,is a big threat to public health since it associates with increased hospitalization,incidence rate and motility of cardiopulmonary injury.However,the potential mediators of pulmonary injury in PM_2.5-induced cardiovascular disorder are not fully understood.A recent study found that PM_2.5exposure promotes the secretion of extracellular vesicles（EV）,while the role and molecular mechanism of EV in PM_2.5-induced cardiac dysfunction have not been elucidated.Objective:To investigate the role and molecular mechanism of extracellular vesicles in the process of cardiac dysfunction and myocardial injury triggered by acute PM_2.5exposure.Methods:Firstly,we utilized echocardiography,TUNEL staining and western blotting to assess the cardiac function and cardiomyocyte apoptosis respectively.To verify the effect of small extracellular vesicles in PM_2.5-induced cardiac dysfunction and cardiomyocyte apoptosis,we performed the intraperitoneal injection of GW4869into mice.Secondly,size exclusion chromatography was used to isolate the EVs from mice serum.Primary neonatal rat cardiomyocytes were treated with EV and the supernatants of Beas-2B cells.For the characterization of EVs,TEM,western blotting（CD63,CD9,Alix,Tsg101）and nanoparticle tracking analysis were performed.Real-time PCR was used to assess the content of mi R-421 in cells and EV.We then figured out the downstream of mi R-421 through bioinformatic prediction and firefly luciferase reporter assay.Finally,we constructed AAV9-mi R421 sponge to specifically inhibit the cardiac expression of mi R-421 to investigate the role of mi R-421 in PM_2.5-induced cardiac function.Results:s EV in serum of PM_2.5-exposed mice caused cardiomyocyte apoptosis.GW4869 treatment could attenuate PM_2.5-induced cardiac dysfunction and cardiomyocyte apoptosis.In addition,we found that PM_2.5exposure promoted the s EV secretion in Beas-2B cells after PM_2.5exposure.Especially,the growing release of s EV was accompanied by the increased flux of EV-mi R421,which exacerbated cardiomyocyte apoptosis.Luciferase reporter gene experiment preliminarily showed that ACE2 was the target gene of EV-mi R421 in cardiomyocyte,whose downregulation mediated the toxicity of PM_2.5-induced cardiomyocyte apoptosis.Finally,specific inhibition of mi R-421 in heart can effectively alleviate PM_2.5-induced cardiac dysfunction.Conclusions:PM_2.5exposure promotes s EV-linked mi R421 release after lung injury and hereby contributes to PM_2.5-induced cardiac dysfunction via suppressing ACE2.