Regulation of TGF-β1-driven Differentiation of Human Lung Fibroblasts: EMERGING ROLES OF CATHEPSIN B AND CYSTATIN C* |
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Authors: | Mariana Kasabova Alix Joulin-Giet Fabien Lecaille Brendan F Gilmore Sylvain Marchand-Adam Ahlame Saidi Gilles Lalmanach |
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Institution: | From the ‡INSERM U1100, Pathologies Pulmonaires: Protéolyse et Aérosolthérapie, Equipe 2: Mécanismes Protéolytiques dans l''Inflammation, Centre d''Etude des Pathologies Respiratoires, Université François Rabelais, Faculté de Médecine, F-37032 Tours, France and ;the §Queen''s University Belfast, School of Pharmacy, McClay Research Centre, Belfast, BT9 7BL, United Kingdom |
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Abstract: | Lung matrix homeostasis partly depends on the fine regulation of proteolytic activities. We examined the expression of human cysteine cathepsins (Cats) and their relative contribution to TGF-β1-induced fibroblast differentiation into myofibroblasts. Assays were conducted using both primary fibroblasts obtained from patients with idiopathic pulmonary fibrosis and human lung CCD-19Lu fibroblasts. Pharmacological inhibition and genetic silencing of Cat B diminished α-smooth muscle actin expression, delayed fibroblast differentiation, and led to an accumulation of intracellular 50-kDa TGF-β1. Moreover, the addition of Cat B generated a 25-kDa mature form of TGF-β1 in Cat B siRNA-pretreated lysates. Inhibition of Cat B decreased Smad 2/3 phosphorylation but had no effect on p38 MAPK and JNK phosphorylation, indicating that Cat B mostly disturbs TGF-β1-driven canonical Smad signaling pathway. Although mRNA expression of cystatin C was stable, its secretion, which was inhibited by brefeldin A, increased during TGF-β1-induced differentiation of idiopathic pulmonary fibrosis and CCD-19Lu fibroblasts. In addition, cystatin C participated in the control of extracellular Cats, because its gene silencing restored their proteolytic activities. These data support the notion that Cat B participates in lung myofibrogenesis as suggested for stellate cells during liver fibrosis. Moreover, we propose that TGF-β1 promotes fibrosis by driving the effective cystatin C-dependent inhibition of extracellular matrix-degrading Cats. |
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Keywords: | Collagen Cysteine Protease Protease Protease Inhibitor Pulmonary Fibrosis Smad Pathway |
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