Abstract
Epithelial mesenchymal transition (EMT) is a key progression that promotes pulmonary fibrosis (PF). Numb, a phosphotyrosine-binding domain (PTB) protein, is implicated with EMT. Nuclear factor erythroid 2-related factor2 (Nrf2) and its downstream proteins heme oxygenase-1 (HO-1) and NAD(P)H: quinone oxidoreductase 1 (NQO1) constitute an important pathway of antioxidant defense signal for protecting against PF. It remains elusive whether Nrf2 antioxidant pathway and Numb have a potential relationship in EMT-mediated PF. Here, we observed the effects of Nrf2 pathway and Numb on bleomycin(BLM)-induced PF in Nrf2-knockout (Nrf2−/−) and wild-type (WT) mice. Meanwhile, rat type II alveolar epithelial cells line (RLE-6TN) and human epithelial cells line (A549) were both treated with an Nrf2 activator sulforaphane (SFN), or transfected siRNAs of Nrf2 and Numb to unravel roles of Nrf2 pathway, Numb and the link between them on transforming growth factor β1 (TGF-β1)-induced EMT. We found BLM-induced lung fibrosis were more severe in Nrf2−/− mice compared to WT mice with reduced expressions of HO-1 and NQO1. Numb was enhanced with down-regulated expressions of Nrf2 in BLM groups and further increased in Nrf2−/− groups. In vitro, given exogenous TGF-β1 on RLE-6TN and A549 up-regulated Numb expressions, accompanied with down-regulations of Nrf2 and its target proteins HO-1 and NQO1. Transfected with Nrf2 and Numb siRNAs further aggravated and relieved the progression of EMT, respectively. Inversely, activating Nrf2 pathway by SFN reduced the expression of Numb and EMT-related protein. Moreover, Numb deficiency by siRNA relieved the protection of activating Nrf2 against EMT. In conclusion, activating Nrf2 antioxidant pathway suppresses EMT during PF via inhibiting the abnormal expression of Numb. These findings provide insight into PF pathogenesis and a basis for novel treatment approaches.
Highlights
Pulmonary fibrosis (PF) is a chronic interstitial lung disease typically characterized by excessive production and deposition of extracellular matrix (ECM) and remodeling of abnormal lung tissue structure[1]
In this study we further explore whether heme oxygenase-1 (HO-1) and NAD(P)H: quinone oxidoreductase 1 (NQO1) are involved in Epithelial–mesenchymal transition (EMT)-induced PF when Nrf[2] is activated
We evaluated the expressions of Numb, Nrf[2], and its downstream effectors HO-1 and NQO1 in mouse lung tissue by western blotting (Fig. 2)
Summary
Pulmonary fibrosis (PF) is a chronic interstitial lung disease typically characterized by excessive production and deposition of extracellular matrix (ECM) and remodeling of abnormal lung tissue structure[1]. Epithelial–mesenchymal transition (EMT) serves as one of the most important avenues for the production of mesenchymal cells and excessive secretion of ECM, which promotes the development of PF3. It is a process performed by the loss of epithelial adhesion protein Ecadherin (E-cad) and the acquisition of interstitial cell marker α-smooth muscle actin (α-SMA). Myofibroblasts derived from epithelial cells by EMT exhibit abnormal proliferation and ECM overproduction, leading to the development of PF4. There is still lack of Official journal of the Cell Death Differentiation Association
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