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Direct Thrombin Inhibition Reduces Lung Collagen, Accumulation, and Connective Tissue Growth Factor mRNA Levels in Bleomycin-Induced Pulmonary Fibrosis

https://doi.org/10.1016/S0002-9440(10)62525-4Get rights and content

Dramatic activation of the coagulation cascade has been extensively documented for pulmonary fibrosis associated with acute and chronic lung injury. In addition to its role in hemostasis, thrombin exerts profibrotic effects via activation of the major thrombin receptor, protease-activated receptor-1. In this study, we examined the effect of the direct thrombin inhibitor, UK-156406 on fibroblast responses in vitro and on bleomycin-induced pulmonary fibrosis in rats. UK-156406 significantly inhibited thrombin-induced fibroblast proliferation, procollagen production, and connective tissue growth factor (CTGF) mRNA levels when used at equimolar concentration to the protease. Thrombin levels in bronchoalveolar lavage fluid and expression of thrombin and protease-activated receptor-1 in lung tissue were increased after intratracheal instillation of bleomycin. The characteristic doubling in lung collagen in bleomycin-treated animals (38.4 ± 2.0 mg versus 17.1 ± 1.4 mg, P < 0.01) was preceded by significant elevations in α1(I) procollagen and CTGF mRNA levels (3.0 ± 0.4-fold and 6.3 ± 0.4-fold respectively, (P < 0.01), and total inflammatory cell number. UK-156406, administered at an anticoagulant dose, attenuated lung collagen accumulation in response to bleomycin by 35 ± 12% (P < 0.05), inhibited α1(I) procollagen and CTGF mRNA levels by 50% and 35%, respectively (P < 0.05), but had no effect on inflammatory cell recruitment. This is the first report showing that direct thrombin inhibition abrogates lung collagen accumulation in bleomycin-induced pulmonary fibrosis.

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Supported by the Medical Research Council, U.K (Clinical Training Fellowship to D.C.J.H), The Wellcome Trust (program grant 051154), and The Middlesex Hospital Special Trustees.

D. C. J. H. and N. R. G. contributed equally to this work.

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