Iguratimod ameliorates bleomycin-induced pulmonary fibrosis by inhibiting the EMT process and NLRP3 inflammasome activation

Pulmonary fibrosis is the deadliest manifestation of connective tissue disease (CTD). Iguratimod (IGU) is a new drug that is used for controlling CTD. Clinical studies have found that IGU has certain advantages in improving lung function and shows great potential for pulmonary fibrosis therapy. However, the specific mechanism is not clear. This study was designed to observe and investigate the therapeutic effects of IGU on bleomycin-induced pulmonary fibrosis and further investigate its underlying mechanism. A mouse model of pulmonary fibrosis was induced by intratracheal injection of bleomycin (BLM). Model mice were randomly assigned to receive different concentrations of IGU. A TGF-β (T)-induced A549 epithelial-mesenchymal transition (EMT) cell model was utilized to investigate the effects of IGU on EMT in vitro. The NLRP3 inflammasome was activated by the costimulation of LPS+ATP (LA) to evaluate the effects of IGU in vitro. We found that IGU resulted in favourable therapeutic outcomes by affecting inflammatory infiltration and collagen deposition. Additionally, the markers of the BLM-mediated EMT phenotype and NLRP3-activated phenotype in the lung were also attenuated after IGU administration. In vitro experiments, the results confirmed its anti-EMT and anti-NLRP3 inflammasome activation effects.We then found that the anti-lung fibrosis effect of IGU was accompanied by a decrease in reactive oxygen species (ROS) production. IGU can inhibit the EMT process and NLRP3 inflammasome activation and reduce ROS production to ameliorate pulmonary fibrosis, which may provide new insights into the further application of IGU in interstitial pulmonary fibrosis.