Metformin enhanced the effect of pirfenidone on pulmonary fibrosis in mice

Background: The aim of the study is to observe the anti-inflammatory and antioxidative stress effects of metformin on bleomycin (BLM)-induced pulmonary fibrosis in mice.Methods: Mice with BLM-induced pulmonary fibrosis were treated with pirfenidone, metformin, pirfenidone plus metformin and the NADPH oxidase 4 (NOX4) inhibitor diphenyleneiodonium chloride (DPI). Pathological changes and hydroxyproline (HPO) levels were examined in the lung tissue of mice with pulmonary fibrosis. Superoxide dismutase (SOD) activity and malonaldehyde (MDA) levels in lung tissue were determined.Results: Compared with pirfenidone, pirfenidone plus metformin could reduce alveolar damage and collagen fibre deposition and alleviate BLM-induced pulmonary fibrosis. Lung HPO levels were significantly lower in the PFD + MET group than in the BLM group (p < 0.05). SOD levels in the lungs of mice were increased in the PFD + MET group than in the BLM group (p < 0.05). Metformin and pirfenidone plus metformin can reduce MDA levels (p < 0.05). Pirfenidone plus metformin could reduce HPO levels, increase SOD levels, and reduce MDA levels in the lungs of mice. There was a significant correlation between the HPO level and the Ashcroft score (r = 0.520, p < 0.001).Conclusion: Metformin enhanced the antifibrotic effects of pirfenidone on BLM-treated mice. Moreover, these findings provide an experimental basis for examining whether metformin can improve the antifibrotic effects of pirfenidone on patients with idiopathic pulmonary fibrosis (IPF). It has broad therapeutic prospects for patients with IPF.