Danshensu alleviates bleomycin-induced pulmonary fibrosis by inhibiting lung fibroblast-to-myofibroblast transition via the MEK/ERK signaling pathway

Pulmonary fibrosis (PF) is a chronic pulmonary interstitial disease, and its pathological process is closely related to fibroblast–myofibroblast differentiation. Danshensu (DSS) has been reported to exert an anti-fibrotic effect in heart and liver. However, it is unknown whether DSS has an equally anti-fibrotic effect on lungs. To evaluate the effect of DSS on PF and demonstrate its possible molecular mechanisms, we established an in vitro model on TGF-β1 (5 ng/mL)-stimulated NIH3T3 cells and in vivo model on bleomycin (BLM) (5 mg/kg)-induced PF mice. In vitro, our results revealed that 50 μM DSS effectively inhibited the fibroblast proliferation, migration and differentiation into myofibroblast. In vivo, our results showed that DSS (28 and 56 mg/kg) reduced damaged lung structures, infiltrated inflammatory cells and accumulated areas of collagen deposition. Moreover, we showed that DSS decreased the fibroblast-specific protein 1 (FSP-1) – and α-SMA-positive areas. Meanwhile, we indicated that DSS reduced the expression of TGF-β1, α-SMA and COL-I in the lung tissues of mice. To further explore the mechanism of DSS on alleviating PF, we detected the MEK/ERK signaling pathway. Our results showed that DSS reduced the phosphorylation of MEK1/2 and ERK1/2, indicating that DSS might inhibit the MEK/ERK signaling pathway. Taken together, these results demonstrated that DSS could suppress lung fibroblast proliferation, migration and differentiation to myofibroblasts, possibly through suppressing the MEK/ERK signaling pathway, which suggested that DSS might be a potential therapeutic drug for PF treatment.