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1: Am J Respir Cell Mol Biol. 2005 Oct;33(4):387-93. Epub 2005 Jun 30.
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Transforming growth factor-beta1 drives airway remodeling in cigarette smoke-exposed tracheal explants.

Wang RD, Wright JL, Churg A.

Department of Pathology, University of British Columbia, Vancouver, BC, V6T 2B5 Canada.

Small airway remodeling (SAR) is an important cause of airflow obstruction in cigarette smokers, but whether SAR represents a response to smoke-evoked inflammation or is directly mediated by smoke-induced growth factor production is disputed. To examine this process, we exposed rat tracheal explants, a model free of exogenous inflammatory cells, to cigarette smoke in vitro. Cigarette smoke caused release of active transforming growth factor (TGF)-beta1, and this was prevented by the oxidant scavenger tetramethythiourea. Nuclear immunostaining for phospho-Smad2, a TGF-beta downstream signaling molecule, was present in epithelial and interstitial cells within 1 h after exposure. Smoke caused upregulation of gene expression of connective tissue growth factor (CTGF), a mediator of TGF-beta fibrogenic effects, within 2 h, and upregulation of procollagen gene expression at 24 h; both changes could be prevented by the TGF-beta antagonist fetuin (alpha2-HS-glycoprotein). In a cell-free system, recombinant human TGF-beta latency-associated peptide was oxidized by cigarette smoke, and smoke released active TGF-beta1 from recombinant latent TGF-beta1 via an oxidant mechanism. These experiments suggest that SAR in cigarette smokers may be caused by direct, smoke-mediated, oxidant-driven induction of growth factor signaling in the airway wall, and that SAR does not necessarily require exogenous inflammatory cells.

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PMID: 15994428 [PubMed - indexed for MEDLINE]