Objective To investigate the antifibrotic effect of combined treatment with sodium arsenite (SA, biotransformation product of arsenic trioxide) and N-acetylcysteine (NAC) on pulmonary fibrosis. Methods L929 fibroblasts were treated with SA or NAC for 24 h before measuring cell viability. The combination drug ratio was determined by examining the effects of different ratios of SA and NAC on viability of L929 cells, and the cell migration ability was detected using scratch assay and Transwell assay. Immunofluorescence assay was used to detect the effects of combined administration of SA and NAC on the expressions of α-smooth muscle actin (α-SMA), collagen type I α1 (COL1A1), and reactive oxygen species (ROS) level in transforming growth factor-β1 (TGF-β1)-induced L929 cells. A mouse model of idiopathic pulmonary fibrosis was established induced by bleomycin, after intervention with SA or NAC for 28 d, the survival and body weight changes of mice were observed. Hematoxylin-eosin (HE) and Masson staining were used to observe pathological changes in lung tissue. The total protein content, TGF-β1 level in bronchoalveolar lavage fluid (BALF), and hydroxyproline (Hyp) level in lung tissue were detected. Immunofluorescence assay was used to detect the expressions of α-SMA, COL1A1, CD86 and CD206 in lung tissue. Results The synergistic effect of SA and NAC combination therapy was related to their ratio. When SA∶NAC = 2∶1, the combination could significantly inhibit viability and migration of L929 cells (P < 0.001), and was superior to the monotherapy group (P < 0.01, 0.001). The combined administration of SA and NAC (2∶1) significantly down-regulated the expressions of α-SMA and COL1A1 in L929 cells induced by TGF-β1 (P < 0.001), and reduced ROS level (P < 0.01). The in vivo experimental results showed that compared with model group, the combined administration of SA and NAC (2∶1) could prolong the survival cycle of mice, increase body weight, reduce lung tissue damage and collagen deposition, decrease the total protein content, TGF-β1 level in BALF and Hyp level in liver tissue (P < 0.01, 0.001), reduce the expression of α-SMA and COL1A1 in lung tissue (P < 0.001), inhibit M2 polarization of lung tissue macrophages (P < 0.001), and had no significant toxic effects on major organs. Conclusion The combination of SA and NAC has a synergistic anti-pulmonary fibrosis effect, providing experimental evidence for the treatment of idiopathic pulmonary fibrosis with arsenic agents combined with thiol donors.

idiopathic pulmonary fibrosis  /  arsenic trioxide  /  sodium arsenite  /  N-acetylcysteine  /  TGF-β1  /  M2 macrophage polarization  /  oxidative stress