Paraquat induces pulmonary fibrosis through Wnt/β-catenin signaling pathway and myofibroblast differentiation

Paraquat (PQ) poisoning-induced pulmonary fibrosis always results in fatal harm to patients. Our study aimed to investigate the functions of the Wnt/beta-catenin pathway in PQ-induced pulmonary fibrosis. By comparing the proteomic profiles of rat lung tissues using protein array in the absence or presence of PQ, the Wnt/beta-catenin signaling, as a fibrosis-related pathway, was discovered to be profoundly activated by PQ. The protein levels of Wnt/beta-catenin signaling components including MMP-2, beta-catenin, Wnt3a, Wnt10b, Cyclin D1, and WISP1 were increased in PQ-treated rat lung tissues. Surprisingly, PQ was found to be able to promote lung epithelial cells and fibroblasts differentiating into myofibroblasts by activating Wnt/beta-catenin signaling pathway. Dickkopf-1 (DKK1), an antagonist of Wnt/beta-catenin signaling pathway, could inhibit the myofibroblast differentiation and attenuate PQ-induced pulmonary fibrogenesis in vitro and in vivo. The expression levels of fibroblasts markers Vimentin, alpha-smooth muscle actin (alpha-SMA) and Collagen I was detected and found to be increased when PQ treated and restored with additional DKK1 treatment. In summary, these assays indicated that Wnt/beta-catenin signaling pathway played a regulatory role in the differentiation of lung epithelial cells and fibroblasts, and the pathogenesis of pulmonary fibrosis related to PQ. Inhibition of the Wnt/beta-catenin signaling pathway may be investigated further as a potential fibrosis suppressor for pulmonary fibrosis therapy.