P28 Nrf2 antioxidant pathway suppresses epithelial-mesenchymal transition through up-regulating Numb during pulmonary fibrosis

Abstract

Epithelial mesenchymal transition(EMT) is a key process in the development of pulmonary fibrosis (PF). Our previous studies have shown that nuclear factor erythroid 2 related factor 2 (Nrf2), an important regulator of antioxidant defence, alleviates the EMT in BLM-induced mouse models of PF. In recent work, Numb, a cell fate determinant, has been shown to appear even more frequently in PF or emphysema, but the relationship between Nrf2 and Numb is still unknown. To further explore the role of Numb in PF, bleomycin (BLM) was intratracheally injected into both Nrf2-knockout (Nrf2 −/− ) and wild-type mice to enable the assessment of the relationship between the Nrf2 antioxidant pathway, Numb and EMT. Rat type II alveolar epithelial cells (RLE-6TN) and human epithelial cells (A549) were treated with the Nrf2 activator sulforaphane, or transfected with Nrf2 and Numb siRNAs to determine the level of influence of Numb on EMT induced by TGF-β1. This study revealed that BLM-induced EMT and lung fibrosis were more severe in Nrf2 −/− mice compared to wild-type mice and interestingly Numb expression was upregulated at day 7 in the fibrosis model with also a protective increase in the level of Nrf2. In vitro , sulforaphane treatment attenuated TGF-β1-induced EMT accompanied by the further up-regulation of Numb. However, when Numb was silenced, the therapeutic effect of sulforaphane on the progression of EMT in RLE-6TN and A549 cells was attenuated in vitro . These findings suggest that the Nrf2 antioxidant pathway suppresses epithelial-mesenchymal transition through regulating Numb during pulmonary fibrosis.