Effects of CatK expression on TGF-β1 tissue content and secretion. Representative image and band analyses (A) of immunoblots from 2 months old WT and Ctsk-/- mice lung homogenates show upregulation of TGF-β1 expression in Ctsk-/- mice lung. (B) ELISA results show TGF-β1 secretion is increased in the Ctsk-/- - mice lung. (C) Relative amount of TGF-β1 in lung homogenate in the presence or absence of recombinant human CatK (1.15 nM). (D) shows TGF-β1 expression in the absence or presence of the cathepsin inhibitor LHVS. Image analysis was performed using Openlab software and Chemigenius system, respectively. All immunoblot experiments were performed in triplicates. The relative protein expression relates to the expression of β-actin.