Résumé
Objective To clarify the role of FLT3 signaling-dependent pulmonary conventional dendritic cells (cDCs) in the pathogenesis of lipopolysaccharide (LPS)-induced acute lung injury (ALI),and as well as the modulation effects of cDCs in vivo on the inflammatory responses to acute lung injury.Methods Thirty C57BL/6 male mice were divided into normal control group,LPS group,FLT3L pretreatment group,lestaurtinib,(a high efficient and specific blocker in FLT3 signal pathway) pretreatment group and vehicle (DMSD) control group.FLT3L and lestaurtinib were administrated subcutaneously for 5 days.Murine model of ALI was subsequently established by intra-tracheal application of LPS and lung specimens were harvested 6 h or 24 h later.The accumulation and maturation of pulmonary cDCs were assessed by flow cytometry.IL-6 and TNF-α were quantified to evaluate lung inflammation.Lung injury was estimated by lung wet weight/body weight ratio (LWW/BW) and histopathological assessment.Lung myeloperoxidase (MPO) activity was measured to evaluate neutrophil infiltration.Transcription factors Tbet/GATA-3 mRNA ratio was determined to estimate balance of Th1/Th2 response.IFN-γ and IL-4 were quantified to evaluate Th1-specific and Th2-specific cytokine production respectively.Results The accumulation and maturation of pulmonary cDCs peaked at 6h after LPS challenge.FLT3L pretreatment significantly stimulated the accumulation and maturation of pulmonary cDCs (P ＜ 0.05),leading to markedly deterioration of LWW/BW and lung histopathological changes.Meanwhile lung MPO activity and T-bet/GATA-3 mRNA ratio were elevated (P ＜ 0.05).Furthermore,the production of IL-6,TNF-α and IFN-γwas markedly increased by FLT3L pretreatment (P ＜ 0.05).In contrast,lestaurtinib pretreatment markedly inhibited the accumulation and maturation of pulmonary cDCs (P ＜ 0.05),leading to significant improvement of LWW/BW and lung histopathological changes.Meanwhile lung MPO activity and T-bet/ GATA-3 mRNA ratio were decreased (P ＜ 0.05).Furthermore lestaurtinib efficiently suppressed the production of IL-6,TNF-α and IFN-γ (P ＜ 0.05).Conclusion This study thus demonstrated that FLT3 signaling-dependent pulmonary cDCs could control the initiation of acute lung inflammation response to LPS-induced ALI through the regulation of neutrophil infiltration and balance of Thl/Th2 response.
Résumé
Objective To investigate the accumulation and maturation status of pulmonary conventional dendritic cells (cDCs) in the early phase of acute lung injury (ALI),and to explore the way of the inflammatory responses and lung injury modulated by cDCs in vivo.MethodsMale C57BL/6 mice were randomly ( random number) divided into the normal control group,6 h-ALI group and 24 h-ALI group.Murine model of ALI was made by intra-tracheal administration of lipopolysaccharide (LPS) and lung specimens were taken 6 h or 24 h later.The accumulation and maturation status of pulmonary cDCs were assessed by flow cytometry.IL-6 and TNF-α were quantified to evaluate the lung inflammation.Transcription factors T-bet/GATA-3 mRNA ratio was determined to estimate the balance between Th1/Th2 responses.IFN-γand IL-4 were quantified to evaluate Thl-specific and Th2-specific cytokine production respectively.Lung injury was estimated by lung wet weight/body weight ratio (LWW/BW) and histopathological assessment.Comparison between groups was performed using one -way ANOVA.ResultsCompared with normal control group,LPS challenge resulted in higher level of IL-6 and TNF-α,increased LWW/BW ratio and significant histopathological changes (P ＜0.01 ).The accumulation and maturation of pulmonary cDCs in 6 h-ALI group were significantly increased after LPS challenge (P ＜0.01 ),while the accumulation and maturation of pulmonary cDCs in 24 h-ALI group were significantly lower than that in 6 h-ALI group ( P ＜0.01 ).Compared with normal control group,the expression of T-bet mRNA in 24 h-ALI group was markedly enhanced ( P ＜ 0.01 ) and the production of IFN-γ was increased as well ( P ＜ 0.01 ).ConclusionsThe accumulation and maturation of pulmonary cDCs peaked within 24 h after LPS challenge,pulmonary cDCs may initiate and amplify acute lung inflammation of ALI by enhancing the Th1 immune response and ensuing cytokine production.