title: TGF-beta and Smad3 signaling link inflammation to chronic fibrogenesis.
abstract: Transient adenovirus-mediated gene transfer of IL-1beta (AdIL-1beta), a proinflammatory cytokine, induces marked inflammation and severe and progressive fibrosis in rat lungs. This is associated with an increase in TGF-beta1 concentration in bronchoalveolar lavage (BAL) fluid. TGF-beta1 is a key cytokine in the process of fibrogenesis, using intracellular signaling pathways involving Smad2 and Smad3. In this study we investigate whether inflammation induced by IL-1beta is able to independently induce lung fibrosis in mice deficient in the Smad3 gene. Seven days after AdIL-1beta administration, similar levels of IL-1beta transgene are seen in BAL in both wild-type (WT) and knockout (KO) mice, and BAL cell profiles demonstrated a similar marked neutrophilic inflammation. Phospho-Smad2 staining was positive in areas of inflammation in both WT and KO mice at day 7. By day 35 after transient IL-1beta expression, WT mice showed marked fibrosis in peribronchial areas, quantified by picrosirius red staining and morphometry. However, there was no evidence of fibrosis or collagen accumulation in IL-1beta-treated KO mice, and peribronchial areas were not different from KO mice treated with the control adenovector. TGF-beta1 and phospho-Smad2 were strongly positive at day 35 in fibrotic areas observed in WT mice, but no such staining was detectable in KO mice. The IL-1beta-induced chronic fibrotic response in mouse lungs is dependent on Smad3. KO and WT animals demonstrated a similar inflammatory response to overexpression of IL-1beta indicating that inflammation must link to the Smad3 pathway, likely through TGF-beta, to induce progressive fibrosis.
authors.affiliation: Department of Pathology and Molecular Medicine, Center for Gene Therapeutics, McMaster University, Hamilton, Ontario, Canada.
authors.forename: Philippe
authors.initials: P
authors.lastname: Bonniaud
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Margetts
authors.forename: Kjetil
authors.initials: K
authors.lastname: Ask
authors.forename: Kathy
authors.initials: K
authors.lastname: Flanders
authors.forename: Jack
authors.initials: J
authors.lastname: Gauldie
authors.forename: Martin
authors.initials: M
authors.lastname: Kolb
mesh_terms: D030201:Activin Receptors, Type I / Q000378:metabolism; D000818:Animals; D001992:Bronchoalveolar Lavage Fluid; D002908:Chronic Disease; D004195:Disease Models, Animal; D018450:Disease Progression; D006801:Humans; D007249:Inflammation / Q000276:immunology / Q000378:metabolism; D007375:Interleukin-1 / Q000502:physiology; D008168:Lung / Q000276:immunology / Q000378:metabolism* / Q000473:pathology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D017346:Protein Serine-Threonine Kinases; D011658:Pulmonary Fibrosis / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D051381:Rats; D000077293:Receptor, Transforming Growth Factor-beta Type I; D018125:Receptors, Transforming Growth Factor beta / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics / Q000276:immunology*; D051900:Smad3 Protein / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D016212:Transforming Growth Factor beta / Q000502:physiology*; D015854:Up-Regulation / Q000276:immunology
chemical_list: D007375:Interleukin-1; D018125:Receptors, Transforming Growth Factor beta; D051900:Smad3 Protein; C497791:Smad3 protein, mouse; D016212:Transforming Growth Factor beta; D017346:Protein Serine-Threonine Kinases; D030201:Activin Receptors, Type I; D000077293:Receptor, Transforming Growth Factor-beta Type I; C000625843:Tgfbr1 protein, rat