Receptor-activated Smad localisation in bleomycin-induced pulmonary fibrosis.
BACKGROUND
Recent advances in fibrosis biology have identified transforming growth factor (TGF)-beta 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.


OBJECTIVE
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-beta1, 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-beta1 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-beta1 and R-Smads indicate that progressive enhancement of TGF-beta1 signalling via R-Smad is activated in the process of fibrosis progression.
Higashiyama
Hiroyuki
H
Department of Pharmacology, Tsukuba Research Laboratories, GlaxoSmithKline, Tsukuba, Ibaraki, Japan.
Yoshimoto
Daisuke
D
Okamoto
Yuji
Y
Kikkawa
Hideo
H
Asano
Satoshi
S
Kinoshita
Mine
M
D000818:Animals; D000903:Antibiotics, Antineoplastic; D001761:Bleomycin; D004195:Disease Models, Animal; D018450:Disease Progression; D007124:Immunoenzyme Techniques; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D011658:Pulmonary Fibrosis / Q000139:chemically induced / Q000378:metabolism* / Q000473:pathology; D015398:Signal Transduction; D051896:Smad Proteins, Receptor-Regulated / Q000378:metabolism*; D051899:Smad2 Protein / Q000378:metabolism; D051900:Smad3 Protein / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000378:metabolism
D000903:Antibiotics, Antineoplastic; D051896:Smad Proteins, Receptor-Regulated; D051899:Smad2 Protein; C497783:Smad2 protein, mouse; D051900:Smad3 Protein; C497791:Smad3 protein, mouse; D016212:Transforming Growth Factor beta; D001761:Bleomycin