POS0413 IGURATIMOD AMELIORATES BLEOMYCIN-INDUCED PULMONARY FIBROSIS VIA INHIBITINGEMT PROCESS AND NLRP3 INFLAMMASOME ACTIVATION

Abstract

BackgroundInterstitial pulmonary fibrosis is the deadliest manifestation of rheumatoid arthritis (RA), and its pathogenesis is complicated. As a new drug for controlling RA, clinical studies have found that iguratimod (IGU) has certain advantages in improving lung function and shows great potential for pulmonary fibrosis therapy[1]. However, the specific mechanism of IGU in treating pulmonary fibrosis is not clear.ObjectivesThis study was designed to observe and investigate the therapeutic effects of IGU on bleomycin-induced pulmonary fibrosis in mice and further investigate its underlying mechanism, aiming to provide a further theoretical basis for clinical rational drug use.MethodsA mouse model of pulmonary fibrosis was induced by intratracheal injection of bleomycin (BLM)[2]. Model mice were randomly assigned to receive Sodium carboxymethyl cellulose (CMC) or different concentrations of IGU. HE staining and immunohistochemical staining were performed to observe the therapeutic effects of IGU on mouse fibrosis. TGF-β induced A549 EMT cell model was utilized to investigate the effects of IGU on EMT in vitro[3]. NLRP3 inflammasome was activated by the co-stimulation of TGF-β+LPS+ATP (TLA) to evaluate the effects of IGU in vitro[4].ResultsWe found that IGU resulted in favorable therapeutic outcomes by affecting the inflammation infiltration (Figure 1A) and collagen deposition (Figure 1B). Immunohistochemical results showed that IGU downregulated the levels of α-SM and NLRP3. Additionally, the markers of BLM-mediated EMT (Figure 1C) phenotype and NLRP3-activated (Figure 1D) phenotype in the lung were also attenuated after IGU administration. In vitro experiments, the results confirmed its anti-EMT effects of reducing the expression of interstitial proteins Vimentin and α-SMA and restoring the content of epithelial protein E-cadherin. Besides, IGU could inhibit NLRP3 activation by downregulating NLRP3 related marker proteins, reducing the secretion of IL-1β, and attenuating caspase-1 activity. We then found that IGU anti-EMT and anti-NLRP3 effect was accompanied by decreased ROS production.Figure 1.IGU ameliorates BLM-induced pulmonary inflammation and pulmonary fibrosis. (A) Representative lung micrographs of lung tissues stained with HE. Magnification, × 200. (B) Representative photographs of lung tissues stained with Masson’s trichrome staining. Magnification, × 200. (C) Representative results of western blot for E-cadherin, Vimentin, α-SMA expression in lung tissues. GAPDH was used as the endogenous control. (D) Representative results of western blot for NLRP3, caspase-1, cleaved-caspase-1 p20, IL-1β expression in lung tissues. GAPDH was used as the endogenous control.ConclusionIGU can inhibit the EMT process and NLRP3 inflammasome activation, reduce ROS production to ameliorate pulmonary fibrosis, which may provide new insights into the further application of IGU in Interstitial pulmonary fibrosis.