Autophagy Inhibitors Suppress Environmental Particulate Matter-induced Airway Inflammation

Background:Particulate matter(PM),a complicated mixture of a number of components,including acids,organic chemicals,metals,and soil or dust particles,can cause worsened respiratory symptoms,more frequent medication use,decreased lung function,airway injury,and increased mortality.However,drugs that can protect against PM-induced airway injury remain insufficient.We have recently demonstrated a pivotal role of autophagy in mediating PM-induced airway injury.Autophagy was required for PM-induced expression of inflammatory cytokines and mucus hypersecretion via activation of NF-?B and AP-1 pathways.Thus,we proposed that autophagy inhibitors(spautin-1 and 3-Methyladenine,3-MA)might be effective treatments for PM-induced airway injury,which may provide novel preventive and/or protective approaches for PM-related airway injury.Objective:To investigate wether autophagy inhibitor(spautin-1 or 3-MA)can suppress environmental particulate matter-induced airway inflammation and explore the underlying mechanisms.Methods:Autophagy inhibitors(Spautin-1 or 3-MA)were added to PM-treated HBE cells and then the levels of autophagy and NF-?B related proteins were detected by western blot.Moreover,we examined the expression of inflammatory cytokines after intervention of autophagy inhibitors(Spautin-1 and 3-MA)and PM by Q-PCR.In vivo,male C57BL/6 mice(6-8w)were respectively randomly divided into 4 groups:NS group,PM group(100 ?g/d/mice),Spautin-1(0.5 mg/d/mice)or 3-MA group(200 ?g/d/mice)and PM plus Spautin-1 or 3-MA group(PM+Spautin-lor PM+3-MA).Mice were sacrificed 24 hours after the final PM treatment,and total number of inflammatory cells,the neutrophil proportion,neutrophils in BALF were measured.Lung tissue was processed for HE staining to observe the inflammatory cell infiltration around the airway.The lung homogenate was analysed to detect the expression of inflammatory cytokines such as CXCL-1,CXCL-2 by Q-PCR and ELISA.Results:1.In Spautin-1 or 3-MA treated HBE cells,the PM-induced mRNA transcripts and secreted protein levels of IL-6 and IL-8 were significantly attenuated.Morover,the PM-induced expressions of p65 and.p-p65 were notably decreased by autophagy inhibitors(Spautin-1 or 3-MA)in HBE cells.2.In vivo,Compared with controls,PM-instilled mice showed increased total inflammatory cells and neutrophils in the BALF.Moreover,mice treated with Spautin-1 or 3-MA before instillation of PM showed a significant decrease in lung inflammation(total inflammatory cells,the neutrophil proportion,and neutrophils)versus mice only exposure to PM.PM-induced inflammatory cytokines such as CXCL-1,CXCL-2 were also significantly reduced in mice treated with Spautin-1 or 3-MA.Histological analysis further confirmed that the PM-induced airway inflammation was significantly ameliorated by autophagy inhibitors.Conclusion:Our study indicates that autophagy inhibitors effectively decrease the PM-induced airway inflammation via suppressing the NF-?B pathway,which may provide novel preventive and/or protective approaches for PM-related airway injury.