Interaction of Wnt/β-catenin and Nrf2 pathways in cigarette smoke-induced inflammation and emphysema

OBJECTIVE The present study aimed to investigate the relationship between Wnt/β-catenin and Nrf2 signaling pathways,and understanding the mechanisms underlying the process of inflammatory in chronic obstructive pulmonary disease(COPD),which was a serious disease of respiratory system.METHODS We duplicate the emphysema model with porcine pancreatic elastase(PPE)in Nrf2-/-and WT mouse for 21d,and intraperitoneal injection of Li Cl,the activator of Wnt/β-catenin signaling pathway from 14 d to the end.Hematoxylin and eosin(H&E)staining was performed to assess the histopathologic level,and immunohistochemistry(IHC)for Mac-3(the marker of macrophagocyte)and Ly6G(the marker of neutrophil)was used to observe the inflammatory infiltrate,while the levels of Wnt/β-catenin and Nrf2 signaling pathways related proteins heme oxygenase-1(HO-1),NAD(P)H:quinone oxidoreductase 1(NQO1),and the expression of inflammatory cytokine interleukin-6(IL-6)were detected by Western blotting of lung tissues.In vitro,cigarette smoke extract(CSE)-treated normal human bronchial epithelial(NHBE)cells,cell viability was examined by MTT assay,and then we treated recombinant human Wnt3a,si Nrf2 and si Wnt3a to measure the expression of Wnt3a,β-catenin,Nrf2,HO-1,NQO-1,and IL-6.Cellular immunofluorescence staining was employed to identify the nuclear translocation of Nrf2.RESULTS We found that the Li Cl-treated group has markedly decreased the damage of alveolar structure and inflammatory signs than the model group of WT mice rather than Nrf2-/-group.It also seen that Li Cl not only increasedβ-catenin,but it also led to a comparable increase in Nrf2,HO-1,NQO1,and decrease of IL-6 compared with WT model groups but except to Nrf2-/-group in vivo.And it showed that Wnt3atreatment has significantly increased the nuclear translocation of Nrf2 and the expression of HO-1 and NQO1,reduced the IL-6 release,while there has no significance when Nrf2 was blocked in CSE-induced NHBE cells.CONCLUSION Our results demonstrated that Wnt3a/β-catenin significantly balanced oxidative stress and attenuated inflammation reaction by promoting Nrf2 nuclear translocation and activity.