Amelioration of bleomycin-induced pulmonary fibrosis in a mouse model by a combination therapy of bosentan and imatinib.

INTRODUCTION

Idiopathic pulmonary fibrosis (IPF) is characterized by alveolitis, progressing into fibrosis. Due to the involvement of both endothelin and platelet-derived growth factor signaling in IPF, combination effects of a bosentan and imatinib were studied in mouse model of bleomycin-induced pulmonary fibrosis.

METHODS

Mice subjected to bleomycin instillation (0.05 U) and were administered with either bosentan (100 mg/kg) and/or imatinib (50 mg/kg). Inflammatory cell count, total protein estimation in bronchoalveolar lavage fluid, lung edema, superoxide dismutase, catalase, myeloperoxidase activities, and Hematoxylin & Eosin staining were performed on day 7. Hydroxyproline content, α-smooth muscle actin (SMA), collagens I and III gene expression analysis, immunohistochemistry, matrix metalloproteinases-9 and -2 activities, trichrome and sirius red staining were performed on day 21.

RESULTS

Combination treatment with bosentan and imatinib prevented bleomycin-induced mortality and loss of body weight more than the individual agents. On day 7, the combination therapy attenuated bleomycin-induced increase of total and differential inflammatory cell counts, total proteins, lung wet/dry weight ratio, myeloperoxidase activity, lung inflammatory cell infiltration more than individual agents alone. Bosentan but not imatinib ameliorated superoxide dismutase and catalase activities, which were lowered following bleomycin instillation. On day 21, combination therapy ameliorated bleomycin-induced increase of fibrosis score, collagen deposition, protein and gene expression of SMA, mRNA levels of collagens-I and -III, matrix metalloproteinase-9 and -2 activities more than monotherapy.

CONCLUSION

Combination of bosentan and imatinib exerted more enhanced protection against bleomycin-induced inflammation and fibrosis than either of the agents alone.