Idiopathic pulmonary fibrosis (IPF) is characterized by myofibroblast foci in lung parenchyma.Myofibroblasts are thought to originate from epithelial-to-mesenchymal transition (EMT).Wnt1 and lithium chloride (LiCl) induce EMT in alveolar epithelial cells (AECs),but the mechanisms are unclear.AECs were treated with Wnt1 and LiCl,respectively;morphological change and molecular changes of EMT,including E-cadherin,fibronectin,and vimentin,were observed.SB203580 was administrated to test the role of p38 MAPK signaling in EMT.Then AECs were treated with siRNAs targeting p38 MAPK to further test the effects of p38 MAPK,and the role was further confirmed by re-expression of p38 MAPK.At last β-catenin siRNA was used to test the role of β-catenin in the EMT process and relationship of β-catenin and p38 MAPK was concluded.Exposure of AECs to Wnt1 and LiCl resulted in upregulation of vimentin and fibronectin with subsequent downregulation of E-cadherin.Wnt1 and LiCl stimulated the p38 MAPK signaling pathways.Perturbing the p38 MAPK pathway either by SB203580 or through p38 MAPK siRNA blocked EMT and inhibited fibronetin synthesis,which were reversed by transfection of p38 MAPK expression plasmid.β-catenin siRNA attenuated the EMT process and decreased p38 MAPK phosphorylation,indicating that β-catenin is involved in the EMT-related changes through regulation of p38 MAPK phosphorylation.These findings suggest that p38 MAPK participates in the pathogenesis of EMT through Wnt pathway and that p38 MAPK may be a novel target for IPF therapy.