Role of reactive oxygen species in transforming growth factor-β1- inuduced fibronectin secretion and α-smooth muscle actin expression in human lung fibroblasts

Background : The transforming growth () plays a key role in lung fibrosis. However, the molecular mechanisms involved in -induced lung fibrosis are unclear. is the key inducer of myofibroblast transdifferentiation via de novo synthesis of muscle actin (). Since signals through reactive oxygen species (ROS) and ROS have been shown to induce accumulation of extracellular matrix (ECM) in various tissues, this study examined if ROS play a role in -induced fibronectin secretion and expression in human lung fibroblasts, MRC-5 cells. Methods : Growth arrested and synchronized MRC-5 cells were stimulated with (0.2-10 ng/ml) in the presence or absence of N-acetylcysteine (NAC) or diphenyleneiodonium (DPI) for up to 96 hours. Dichlorofluorescein (DCF)-sensitive cellular ROS were measured by FACScan and secreted fibronectin and cellular by Western blot analysis. Results : increased the level of fibronectin secretion and expression in MRC-5 cells in a dosedependent manner. Both NAC (20 and 30 mM) and DPI (1 and ) significantly inhibited -induced fibronectin and upregulation. The -induced cellular ROS level was also significantly reduced by NAC and DPI. Conclusions : The results suggest that NADPH oxidase-dependent ROS play an important role in -induced fibronectin secretion and expression in MRC-5 cells, which leads to myofibroblast transdifferentiation and progressive lung fibrosis.