Nintedanib alleviates pulmonary fibrosis in vitro and in vivo by inhibiting the FAK/ERK/S100A4 signalling pathway

Nintedanib is an effective treatment for pulmonary fibrosis (PF), but the exact mechanism by which this agent works to delay the progression of PF remains unclear. In this study, we explored whether nintedanib alleviates PF at least partially by inhibiting the focal adhesion kinase (FAK)/ERK/S100A4 signalling pathway. Bleomycin (BLM) was used to induce PF in a mouse model, and human fetal lung fibroblast 1 (HFL-1) cells were exposed to transforming growth factor-β 1 (TGF-β1) to create an in vitro model of PF. In both models, nintedanib was administered either alone or in conjunction with a FAK vector. In mouse lung tissues, histopathology, inflammatory factor levels, and collagen content were assessed; in HFL-1 cells, HFL-1 activity was assessed, along with collagen I, collagen III, and α-SMA levels. Both mouse tissue and HFL-1 cells were examined for levels of indices associated with extracellular matrix and the FAK/ERK/S100A4 signalling pathway. In mice exposed to BLM, lung inflammation and extracellular matrix deposition were significantly increased. These factors were alleviated by nintedanib treatment but were aggravated by overexpression of FAK. In HFL-1 cells, nintedanib inhibited HFL-1 activity and collagen I, collagen III, and α-SMA levels, whereas overexpression of FAK produced the opposite effect. In both tissues and cells, the FAK/ERK/S100A4 signalling pathway was activated, but nintedanib was able to suppress this pathway. These results suggest that nintedanib alleviates PF by inhibiting the FAK/ERK/S100A4 signalling pathway both in vivo and in vitro.