Particulate matter promotes the epithelial to mesenchymal transition in human lung epithelial cells via the ROS pathway

Objects: Epidemiologic studies have linked exposure to airborne pollutant particulate matter (PM) with increased rates of chronic cardiopulmonary diseases, including asthma and idiopathic pulmonary fibrosis (IPF). Several investigations have suggested that the epithelial-to-mesenchymal transition (EMT) may contribute to the complex pathobiology of environmental exposure-mediated pulmonary fibrosis. The present study was designed to characterize the mechanisms of PM-mediated EMT in human lung epithelial cells (HBECs). Methods and results: PM induced significant dose (0-100 mu g/ml) and time (0-72 h)-dependent increases in transforming growth factor beta (TGF beta) and fibronectin (FN) protein levels in HBECs lysates. PM-activated TGF beta and FN protein production in HBECs was prevented by the antioxidant N-acetyl-cysteine (NAC, 5 mM). Furthermore, the NF-KB inhibitor BAY11-7082 (5 mu M) abolished PM-induced FN production in HBECs. Biomarkers of EMT (ACTA2, SNAIL1 and SNAIL2) in PM-treated HBECs were significantly increased at the mRNA level compared to control cells. Conclusions: These results demonstrate that PM increases protein levels of TGF beta and FN via reactive oxygen species (ROS)-dependent pathways. In addition, PM exposure induces EMT in human lung epithelial cells, supporting a novel mechanism for PM-induced pulmonary fibrosis.