Abstract
Pulmonary fibrosis, a severe condition that can progress to respiratory failure and death, is characterized by aberrant activation/proliferation of fibroblasts and excessive extracellular matrix (ECM) deposition and has limited therapeutic options. Identifying novel mediators of pulmonary fibrosis is currently needed to facilitate the development of more effective therapeutic strategies targeting pulmonary fibrosis. The present study was designed to investigate whether transforming growth factor-β (TGF-β) induced protein (TGFBI), an extracellular matrix protein, regulates pulmonary fibrosis in vitro and in vivo and the possible mechanism of actions. It was found that protein expressions of TGFBI were significantly upregulated and G-protein signaling modulator 2 (GPSM2) expression downregulated in fibrotic lung tissues from bleomycin (BLM)-induced rats and TGF-β1-stimulated human lung IMR-90 fibroblasts. Either silencing TGFBI with specific siRNA or treatment with the TGF-β signaling inhibitor SB431542 significantly inhibited TGF-β1-induced fibrotic effects and dysregulation of GPSM2 and Snail expressions in IMR-90 fibroblasts. Moreover, GPSM2 overexpression also inhibited TGF-β1-induced fibrotic effects and Snail upregulation in IMR-90 fibroblasts. Silencing Snail with specific siRNA attenuated TGF-β1-induced fibrotic effects. Therefore, our findings suggest that the extracellular matrix protein TGFBI mediates pulmonary fibrosis through regulation of the GPSM2/Snail axis, which identifies TGFBI as a novel mediator of pulmonary fibrosis and may be a potential therapeutic target for the treatment of pulmonary fibrosis.