Lipopolysaccharide Induced The Abnormal Proliferation Of Mouse Lung Fibroblasts By FoxO3a/p27 Signaling Pathway

Backgrounds and Purpose: Lipopolysaccharide(LPS)in the cell walls of gram-negative bacilli is the main component of endotoxin,and is also an important pathogenic factor of sepsis-associated pulmonary fibrosis.Aberrant aggregation and activation of lung fibroblasts is a key process in pulmonary fibrosis,but the underlying mechanism remains enigmatic.In this study,we use LPS-stimulated lung fibroblasts as a sepsis-associated pulmonary fibrosis model,investigate the relationship between LPS and lung fibroblast proliferation and clarify the role of FoxO3 a / p27 signaling pathway in this process,in order to further enrich the specific mechanism of pulmonary fibrosis induced by LPS and to lay the foundation for the the prevention and treatment of sepsisassociated pulmonary fibrosis.Methods: The primary lung fibroblasts were cultured in vitro and the proliferation of lung fibroblasts stimulated by LPS was detected by CCK8 assay.The expression of p27 protein in mouse lung fibroblasts stimulated by different concentrations of LPS was detected by Western blot and immunofluorescence.The expression of nuclear FoxO3 a and cytoplasmic phosphorylated FoxO3a(p-FoxO3a)were measured by Western blot.To investigate the role of FoxO3 a on LPS-induced lung fibroblast proliferation,we transfected FoxO3a-OE lentivirus into cultured mouse lung fibroblasts to overexpress FoxO3 a or pretreated mouse lung fibroblasts with gefitinib to enhance FoxO3 a activity.The proliferation of lung fibroblasts was evaluated by CCK8 assay and the activation of FoxO3a/p27 pathway were confirmed by Western blot.Results: LPS could phosphorylate the nucleus FoxO3 a to reduce its activity and downregulate the expression of p27 protein,which eventually lead to the abnormal proliferation of lung fibroblasts.The overexpression of FoxO3 a significantly increased the expression of p27 and suppressed LPS-induced lung fibroblast proliferation.Upon treating fibroblasts with gefitinib,the phosphorylation of FoxO3 a was reduced and FoxO3 a translocated into the nucleus,the expression of p27 was significantly increased and the proliferation of lung fibroblasts mediated by LPS could also be inhibited effectively.Conclusion:The data from the current study demonstrate that inactivation of FoxO3a/p27 signaling pathway mediates LPS-induced abnormal proliferation of lung fibroblasts.Gefitinib can inhibit LPS-induced abnormal proliferation of lung fibroblasts through activation of FoxO3 a,which may play a protective role in sepsisassociated pulmonary fibrosis.