Anthelmintic nitazoxanide protects against experimental pulmonary fibrosis

Abstract Background and Purpose Nitazoxanide is a therapeutic anthelmintic drug. Our previous studies found that nitazoxanide and its metabolite tizoxanide activated adenosine 5′‐monophosphate‐activated protein kinase (AMPK) and inhibited signal transducer and activator of transcription 3 (STAT3) signals. As AMPK activation and/or STAT3 inhibition are targets for treating pulmonary fibrosis, we hypothesized that nitazoxanide would be effective in experimental pulmonary fibrosis. Experimental Approach The mitochondrial oxygen consumption rate of cells was measured by using the high‐resolution respirometry system Oxygraph‐2K. The mitochondrial membrane potential of cells was evaluated by tetramethyl rhodamine methyl ester (TMRM) staining. The target protein levels were measured by using western blotting. The mice pulmonary fibrosis model was established through intratracheal instillation of bleomycin. The examination of the lung tissues changes were carried out using haematoxylin and eosin (H&E), and Masson staining. Key Results Nitazoxanide and tizoxanide activated AMPK and inhibited STAT3 signalling in human lung fibroblast cells (MRC‐5 cells). Nitazoxanide and tizoxanide inhibited transforming growth factor‐β1 (TGF‐β1)‐induced proliferation and migration of MRC‐5 cells, collagen‐I and α‐smooth muscle cell actin (α‐SMA) expression, and collagen‐I secretion from MRC‐5 cells. Nitazoxanide and tizoxanide inhibited epithelial–mesenchymal transition (EMT) and inhibited TGF‐β1‐induced Smad2/3 activation in mouse lung epithelial cells (MLE‐12 cells). Oral administration of nitazoxanide reduced the bleomycin‐induced mice pulmonary fibrosis and, in the established bleomycin‐induced mice, pulmonary fibrosis. Delayed nitazoxanide treatment attenuated the fibrosis progression. Conclusions and Implications Nitazoxanide improves the bleomycin‐induced pulmonary fibrosis in mice, suggesting a potential application of nitazoxanide for pulmonary fibrosis treatment in the clinic.