Therapeutic effects of the rhSOD2-Hirudin fusion protein on bleomycin-induced pulmonary fibrosis in mice.

Idiopathic pulmonary fibrosis (IPF) is a disease with a poor prognosis and high mortality, posing a major threat to human health. Increased levels of inflammatory cytokines, reactive oxygen species and coagulation cascade have been extensively reported in IPF. We previously fused Hirudin and human manganese superoxide dismutase (hSOD2) to generate a dual-feature fusion protein, denoted as rhSOD2-Hirudin fusion protein. In this study, 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) and Hydroxyproline (HYP) assays were used to investigate the effects of rhSOD2-Hirudin protein on thrombin-induced fibroblast proliferation and collagen accumulation in vitro. Subsequently, the mice model of pulmonary fibrosis induced by bleomycin was used for evaluating the anti-inflammatory and anti-fibrotic effects of rhSOD2-Hirudin protein in vivo. Results showed that rhSOD2-Hirudin protein could inhibit the proliferation of fibroblasts and reduce the HYP production in vitro by inhibiting the activity of thrombin. In vivo experiments showed that lung inflammation and fibrosis were significantly decreased in rhSOD2-Hirudin protein-treated mice. Furthermore, rhSOD2-Hirudin protein treatment reduced profibrotic protein and gene expression while reducing the number of inflammatory cells in the lung. In conclusion, rhSOD2-Hirudin protein can effectively attenuate pulmonary fibrosis in vitro and in vivo, mainly by inhibiting the activity of thrombin meanwhile increasing SOD2 levels prevent cells from being damaged by reactive oxygen species, thereby mitigating IPF progression. This study provided important information on the feasibility and efficacy of rhSOD2-Hirudin protein as a novel therapeutic agent for IPF.