Imatinib mesylate inhibits the profibrogenic activity of TGF-β and prevents bleomycin-mediated lung fibrosis
Craig E. Daniels, … , Andrew H. Limper, Edward B. Leof
Craig E. Daniels, … , Andrew H. Limper, Edward B. Leof
Published November 1, 2004
Citation Information: J Clin Invest. 2004;114(9):1308-1316. https://doi.org/10.1172/JCI19603.
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Article Nephrology

Imatinib mesylate inhibits the profibrogenic activity of TGF-β and prevents bleomycin-mediated lung fibrosis

Abstract

Idiopathic pulmonary fibrosis is a progressive and fatal fibrotic disease of the lungs with unclear etiology. Prior efforts to treat idiopathic pulmonary fibrosis that focused on anti-inflammatory therapy have not proven to be effective. Recent insight suggests that the pathogenesis is mediated through foci of dysregulated fibroblasts driven by profibrotic cytokine signaling. TGF-β and PDGF are 2 of the most potent of these cytokines. In the current study, we investigated the role of TGF-β–induced fibrosis mediated by activation of the Abelson (Abl) tyrosine kinase. Our data indicate that fibroblasts respond to TGF-β by stimulating c-Abl kinase activity independently of Smad2/3 phosphorylation or PDGFR activation. Moreover, inhibition of c-Abl by imatinib prevented TGF-β–induced ECM gene expression, morphologic transformation, and cell proliferation independently of any effect on Smad signaling. Further, using a mouse model of bleomycin-induced pulmonary fibrosis, we found a significant inhibition of lung fibrosis by imatinib. Thus, Abl family members represent common targets for the modulation of profibrotic cytokine signaling.

Authors

Craig E. Daniels, Mark C. Wilkes, Maryanne Edens, Ted J. Kottom, Stephen J. Murphy, Andrew H. Limper, Edward B. Leof

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TGF-β stimulates c-Abl–dependent signaling. (A) IMR90 cells were treated...
TGF-β stimulates c-Abl–dependent signaling. (A) IMR90 cells were treated with DMEM alone (–) or containing 10 ng/ml TGF-β2 (+). Following 30-minute stimulation, c-Abl kinase activity or Smad2 (p-Smad2) and Smad3 (p-Smad3) phosphorylation was determined. Total c-Abl, Smad2, and Smad3 protein is shown below the corresponding activity. (B) Top blots: IMR90 cells, Abl–/–Arg–/– MEFs, Abl–/–Arg–/– fibroblasts stably expressing (+) WT-c-Abl or dominant negative c-Abl, or PDGF-α and -β receptor–null F cells (PDGFR–/–) were left untreated (–) or treated (+) for 24 hours with TGF-β2 (10 ng/ml) and/or imatinib (10 μg/ml). Imatinib was added 20 minutes before TGF-β2, and fibronectin mRNA accumulation was determined. Bottom blots: Ethidium bromide staining for 28S and 18S ribosomal RNA subunits prior to Northern analysis. Top left graph: The fold fibronectin mRNA stimulation by TGF-β2 is indicated for the various cell types. Results represent the mean ± SE of 2 separate experiments. Bottom left graph: Cell lines as described above were transfected with a fibronectin luciferase construct. The fold induction of 10 ng/ml TGF-β2 with or without 5 μg/ml imatinib was determined as described in Methods and by Penheiter et al. (51). Right graphs: Collagen I (top) and collagen III (bottom) luciferase activity was determined as described for the bottom left graph. Results for all luciferase assays represent the mean ± SE of 2 separate experiments, each done in triplicate.