Receptor-activated Smad localisation in Bleomycin-induced pulmonary fibrosis

Abstract

Background:Recent advances in fibrosis biology have identified transforming growth factor (TGF)-β type I receptor-mediated activation of Smads as playing a central part in the development of fibrosis. However, to date, there have been few studies that examined the localisation and distribution of receptor-activated Smads protein (R-Smads: Smad2 and 3) during the fibrosis progression.Aims:To histopathologically assess the time-course change of the localisation and distribution of the Smads protein in pulmonary fibrosis.Methods:Pulmonary fibrosis was induced by intranasal injection of bleomycin (0.3 U/mouse). Lungs were isolated 2, 5, 7, 9 and 14 days after bleomycin treatment. Histological changes in the lungs were evaluated by haematoxylin-eosin stain or Masson’s trichrome stain, and scored. TGF-β1, Smad3 and phosphorylated Smad2 localisations in lung tissues were determined by immunohistochemistry.Results:The bleomycin treatment led to considerable pulmonary fibrotic changes accompanied by marked increase in TGF-β1 expression in infiltrating macrophages. With the progression in fibrosis (day 7–14), marked increases in Smad3-positive and pSmad2-positive cells were observed. There were intense Smad3-positive and pSmad2-positive signals localised to the nuclei of the infiltrating macrophages and to type II epithelial cells, and less intense signals in fibroblasts and hyperplastic alveolar/bronchiolar epithelial cells.Conclusions:The time-course data of TGF-β1 and R-Smads indicate that progressive enhancement of TGF-β1 signalling via R-Smad is activated in the process of fibrosis progression.

Latent Transforming Growth Factor-β-Binding Protein-4 Regulates Transforming Growth Factor-β1 Bioavailability for Activation by Fibrogenic Lung Fibroblasts in Response to Bleomycin

“…40,41 Bronchoalveolar fluid and lung tissues were collected at day 8 and day 14 when fibroblast activation in bleomycin-induced lung fibrosis model occurs. 42 Consistent with the previous observation of increased TGF-␤ in the lungs of bleomycin-stimulated Thy-1 knockout mice, we also observed increased TGF-␤ signaling in lungs from bleomycin-treated Thy-1 knockout mice. Immunohistochemical staining showed that both knockout and wild-type mice have increased nuclear accumulation of phosphorylated Smad3 in the lungs with bleomycin treatment.…”

LY2109761 Attenuates Radiation-Induced Pulmonary Murine Fibrosis via Reversal of TGF-β and BMP-Associated Proinflammatory and Proangiogenic Signals

“…Our data suggest that LY2109761 attenuates profibrotic signaling directly, but also balances the complex TGFb/BMP signaling: LY2109761 dramatically reduced radiation-induced upregulation of Gremlin (Grem2) and also upregulated BMP2 expression. Moreover, LY2109761 reduced radiation-induced downstream signaling genes of TGF-b including Smads 6, 7, and 9 but also MDM2 in accordance with lung histology showing reduced p-Smad2, with increased p-Smad2 levels being associated with lung fibrosis (29). While radiation slightly increased and LY2109761 clearly decreased Smad1 phosphorylation, Smad2 or Smad3 phosphorylation was hardly affected in fibroblasts.…”

TGFβ signaling in lung epithelium regulates bleomycin-induced alveolar injury and fibroblast recruitment

“…We isolated type II AECs from SPC.Cre.TGF␤R2 fl/fl .Rosa. Stop.lacZ mice and littermate controls at 2 wk after bleomycin administration, at which time lung TGF␤ levels are elevated (18). After AEC isolation, we performed a targeted TGF␤/ BMP-specific 96-well array (SABiosciences) to evaluate expression of TGF␤/BMP-dependent genes.…”