Combined treatment of tacrolimus and pirfenidone effectively improves BLM-induced pulmonary fibrosis in mice by inhibiting the TGFβ1/Smad2/3 signaling

Background: Interstitial lung disease manifests as a pulmonary complication of connective tissue diseases, significantly affecting patients' mortality and morbidity. This study aimed to investigate the roles of tacrolimus (TAC) and/or pirfenidone (PFD) in interstitial lung disease.

Methods: A mouse model of bleomycin (BLM)-induced lung fibrosis was established. Subsequently, the Animals were orally administered 32 mg/kg TAC and/or 100 mg/kg PFD dissolved in distilled water. The survival rate, body weight changes, and wet-to-dry lung weight ratio were monitored. To assess lung inflammation and fibrosis, Hematoxylin-eosin staining and Masson's trichrome staining were performed. RT-qPCR and western blotting were conducted to measure expression levels of fibrotic genes. Additionally, the effects of TAC and/or PFD on the protein levels of factors involved in the TGFβ1/SMAD2/3 signaling pathway were evaluated using western blotting.

Results: Compared with TAC or PFD treatment alone, the combination of TAC and PFD markedly improved BLM-induced changes in survival rate, body weight, and wet-to-dry lung weight ratio. Pathological analysis revealed that BLM induced inflammation and fibrosis, as evidenced by inflammatory cell infiltration, tissue edema, destruction of alveolar structure, and Collagen deposition. These pathological changes were effectively attenuated by TAC and PFD treatment. The protein and mRNA expression levels of pro-fibrotic genes were elevated by BLM, and the trend was reversed by TAC and PFD. Moreover, TAC and PFD inhibited the activity of TGFβ1/SMAD2/3 signaling in mouse lung tissues.

Conclusion: Combined treatment of TAC and PFD effectively improves BLM-induced inflammatory response and pulmonary fibrosis in mice through inhibition of the TGFβ1/SMAD2/3 signaling.

Bleomycin; Interstitial lung disease; Lung fibrosis; Pirfenidone; Tacrolimus.