Antifibrotic effects of Lck inhibition on bleomycin-induced pulmonary fibrosis in mice

Abstract

Rationale: Nintedanib is one of two drugs approved for the treatment of idiopathic pulmonary fibrosis. It targets fibroblast growth factor receptors, platelet-derived growth factor receptors and vascular endothelial growth factor receptors shown to be involved in the lung fibrosis pathology, but also Src family kinases including lymphocyte-specific protein tyrosine kinase (Lck) with a low IC50 value. Nevertheless, the significance of Lck inhibition in lung fibrosis is not fully elucidated yet. Aim: To explore the effect of Lck inhibition on experimental lung fibrosis in mice with focus on lymphocytes. Methods: Murine lymphocytes were isolated from spleen by CD4+ T Cell Isolation Kit (Miltenyi Biotec). The inhibitory effect of the Lck inhibitor A-770041 on the phosphorylation of Lck in murine lymphocytes was examined using immunoblot. Lung fibrosis was induced in mice by intratracheal administration of bleomycin. A-770041 was administrated daily by gavage. Bronchoalveolar lavage (BAL) was performed on day 7. Lung tissues were analyzed on day 21 using the Ashcroft score and hydroxyproline assay. Results: A-770041 inhibited the phosphorylation of Lck in murine lymphocytes in a concentration-dependent manner. In the mouse model, A-770041 significantly mitigated lung fibrosis induced by bleomycin. The treatment with A-770041 significantly decreased the total cell number in the BAL fluid, suggesting that the inflammation leading to fibrosis was alleviated by A-770041. Conclusions: These results support the role of lymphocytes in the early stage of lung fibrosis, and suggest that A-770041 might be useful to ameliorate lung inflammation induced by fibrotic injury and subsequent fibrogenesis.