| Objective The purpose of this study was to discuss the mechanism of butyrate,a metabolite of intestinal flora,regulating mouse alveolar macrophage autophagy and promoting the clearance of Klebsiella pneumoniae(K.pneumoniae)through SQSTM1-LC3 signal pathway.Methods To construct the intestinal flora depleted mice and p62/Sqstm1 gene knockout alveolar macrophages.The mice were infected with hypervirulent Klebsiella pneumoniae GN 181689 by nasal drops,and the lung pathology,bacterial load and survival rate were observed.Autophagy related proteins were observed by cellular immunofluorescence.Western blotting detected the expression of autophagy receptor protein P62 and LC3.The scavenging ability of MH-S cells was observed by gentamicin sterilization experiment.The expressions of autophagy related genes Atg5,Atg7,Beclin1,p62,Nbr1,Tax1bp1 and pro-inflammatory factors Tnfα、Il1β and Il6 were detected by real-time quantitative PCR.Results Butyrate can reduce the pulmonary bacterial load in the lungs of K.pneumoniae infected mice,reduce the injury of lung tissue and improve the survival rate of mice.Butyrate can improve the pathological damage of lung tissue,reduce the bacterial load of lung tissue and prolong the survival time of mice.Butyrate promoted clearance of K.pneumoniae by MH-S cells,and autophagy was enhanced after infection of K.pneumoniae by MH-S cells.Butyrate promoted the expression of LC3 and P62 protein and autophagy-related genes Tax1bp1,p62 and Nbr1 in MH-S cells.After p62 gene knockout,the ability of MH-S cells to scavenge K.pneumoniae decreased and the protective effect of butyrate decreased.After butyrate treatment,the expression of inflammatory cytokines Tnfα,Il1β and Il6 in MH-S cells decreased.Conclusions 1.Butyrate,a metabolite of intestinal flora,plays a protective role in K.pneumoniae pneumonia.2.After K.pneumoniae infection,the autophagy level of MH-S cells increased,and butyrate could participate in the autophagy process by regulating the expression of autophagy related protein P62,and promote the clearance of bacteria in MH-S cells.3.Butyrate inhibited the expression of Tnfα,Il1β and Il6 in MH-S cells infected by K.pneumoniae. |
