Thy-1 expression regulates the ability of rat lung fibroblasts to activate transforming growth factor-beta in response to fibrogenic stimuli.
Distinct subpopulations of fibroblasts contribute to lung fibrosis, although the mechanisms underlying fibrogenesis in these subpopulations are not clear. Differential expression of the glycophosphatidylinositol-linked protein Thy-1 affects proliferation and myofibroblast differentiation. Lung fibroblast populations selected on the basis of Thy-1 expression by cell sorting were examined for responses to fibrogenic stimuli. Thy-1 (-) and Thy-1 (+) fibroblast populations were treated with platelet-derived growth factor-BB, interleukin-1beta, interleukin-4, or bleomycin and assessed for activation of transforming growth factor (TGF)-beta, Smad3 phosphorylation, and alpha-smooth muscle actin and fibronectin expression. Thy-1 (-) fibroblasts responded to these stimuli with increased TGF-beta activity, Smad3 phosphorylation, and expression of alpha-smooth muscle actin and fibronectin, whereas Thy-1 (+) fibroblasts resisted stimulation. The unresponsiveness of Thy-1 (+) cells is not because of defective TGF-beta signaling because both subsets respond to exogenous active TGF-beta. Rather, Thy-1 (-) fibroblasts activate latent TGF-beta in response to fibrogenic stimuli, whereas Thy-1 (+) cells fail to do so. Defective activation is common to multiple mechanisms of TGF-beta activation, including thrombospondin 1, matrix metalloproteinase, or plasmin. Thy-1 (-) lung fibroblasts transfected with Thy-1 also become resistant to fibrogenic stimulation, indicating that Thy-1 is a critical biological response modifier that protects against fibrotic progression by controlling TGF-beta activation. These studies provide a molecular basis for understanding the differential roles of fibroblast subpopulations in fibrotic lung disease through control of latent TGF-beta activation.
Department of Pathology, University of Alabama at Birmingham, Volker Hall 668, 1670 University Blvd., Birmingham, AL 35294-0019, USA.
Yong
Y
Zhou
James S
JS
Hagood
Joanne E
JE
Murphy-Ullrich
D000199:Actins / Q000378:metabolism; D000818:Animals; D000925:Anticoagulants / Q000494:pharmacology; D000970:Antineoplastic Agents / Q000494:pharmacology; D000077214:Becaplermin; D001761:Bleomycin / Q000494:pharmacology; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000378:metabolism; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism*; D005353:Fibronectins / Q000378:metabolism; D005786:Gene Expression Regulation; D007375:Interleukin-1 / Q000494:pharmacology; D015847:Interleukin-4 / Q000494:pharmacology; D008168:Lung / Q000187:drug effects / Q000378:metabolism*; D009130:Muscle, Smooth / Q000187:drug effects / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D020574:Proto-Oncogene Proteins c-sis; D011658:Pulmonary Fibrosis / Q000378:metabolism* / Q000473:pathology; D051381:Rats; D011917:Rats, Inbred Lew; D011994:Recombinant Proteins / Q000494:pharmacology; D015398:Signal Transduction; D051900:Smad3 Protein; D018800:Thy-1 Antigens / Q000378:metabolism*; D015534:Trans-Activators / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000378:metabolism*
D000199:Actins; D000925:Anticoagulants; D000970:Antineoplastic Agents; D004268:DNA-Binding Proteins; D005353:Fibronectins; D007375:Interleukin-1; D010982:Platelet-Derived Growth Factor; D020574:Proto-Oncogene Proteins c-sis; D011994:Recombinant Proteins; D051900:Smad3 Protein; C497787:Smad3 protein, rat; D018800:Thy-1 Antigens; D015534:Trans-Activators; D016212:Transforming Growth Factor beta; D001761:Bleomycin; D000077214:Becaplermin; D015847:Interleukin-4