CXCL9 Regulates TGF-β1-Induced Epithelial to Mesenchymal Transition in Human Alveolar Epithelial Cells.
Epithelial to mesenchymal cell transition (EMT), whereby fully differentiated epithelial cells transition to a mesenchymal phenotype, has been implicated in the pathogenesis of idiopathic pulmonary fibrosis (IPF). CXCR3 and its ligands are recognized to play a protective role in pulmonary fibrosis. In this study, we investigated the presence and extent of EMT and CXCR3 expression in human IPF surgical lung biopsies and assessed whether CXCR3 and its ligand CXCL9 modulate EMT in alveolar epithelial cells. Coexpression of the epithelial marker thyroid transcription factor-1 and the mesenchymal marker α-smooth muscle actin and CXCR3 expression was examined by immunohistochemical staining of IPF surgical lung biopsies. Epithelial and mesenchymal marker expression was examined by quantitative real-time PCR, Western blotting, and immunofluorescence in human alveolar epithelial (A549) cells treated with TGF-β1 and CXCL9, with Smad2, Smad3, and Smad7 expression and cellular localization examined by Western blotting. We found that significantly more cells were undergoing EMT in fibrotic versus normal areas of lung in IPF surgical lung biopsy samples. CXCR3 was expressed by type II pneumocytes and fibroblasts in fibrotic areas in close proximity to cells undergoing EMT. In vitro, CXCL9 abrogated TGF-β1-induced EMT. A decrease in TGF-β1-induced phosphorylation of Smad2 and Smad3 occurred with CXCL9 treatment. This was associated with increased shuttling of Smad7 from the nucleus to the cytoplasm where it inhibits Smad phosphorylation. This suggests a role for EMT in the pathogenesis of IPF and provides a novel mechanism for the inhibitory effects of CXCL9 on TGF-β1-induced EMT.
St. Vincent's University Hospital and School of Medicine and Medical Science, University College Dublin, Dublin 4, Ireland; UCD Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Dublin 4, Ireland;
Sarah L
SL
O'Beirne
St. Vincent's University Hospital and School of Medicine and Medical Science, University College Dublin, Dublin 4, Ireland; UCD Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Dublin 4, Ireland;
Sinead M
SM
Walsh
St. Vincent's University Hospital and School of Medicine and Medical Science, University College Dublin, Dublin 4, Ireland;
Aurélie
A
Fabre
UCD Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Dublin 4, Ireland;
Carlota
C
Reviriego
UCD Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Dublin 4, Ireland;
Julie C
JC
Worrell
St. Vincent's University Hospital and School of Medicine and Medical Science, University College Dublin, Dublin 4, Ireland; UCD Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Dublin 4, Ireland;
Ian P
IP
Counihan
UCD Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Dublin 4, Ireland;
Robert V
RV
Lumsden
UCD Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Dublin 4, Ireland;
Jennifer
J
Cramton-Barnes
Division of Pulmonary and Critical Care Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095; and.
John A
JA
Belperio
St. Vincent's University Hospital and School of Medicine and Medical Science, University College Dublin, Dublin 4, Ireland; UCD Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Dublin 4, Ireland;
Seamas C
SC
Donnelly
UCD Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Dublin 4, Ireland;
Denise
D
Boylan
INSERM Unité Mixte de Recherche 700, Physiopathologie et Epidémiologie de l'Insuffisance Respiratoire, Universite Denis Diderot, Paris 7, Unité de Formation et de Recherche de Médecine, 75018 Paris, France.
Joëlle
J
Marchal-Sommé
UCD Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Dublin 4, Ireland;
Rosemary
R
Kane
St. Vincent's University Hospital and School of Medicine and Medical Science, University College Dublin, Dublin 4, Ireland; UCD Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Dublin 4, Ireland; michael.p.keane@ucd.ie.
Michael P
MP
Keane
D000199:Actins / Q000096:biosynthesis; D015415:Biomarkers / Q000378:metabolism; D002460:Cell Line; D054370:Chemokine CXCL9 / Q000378:metabolism* / Q000494:pharmacology; D004847:Epithelial Cells / Q000378:metabolism; D058750:Epithelial-Mesenchymal Transition / Q000502:physiology*; D006801:Humans; D054990:Idiopathic Pulmonary Fibrosis / Q000473:pathology*; D009687:Nuclear Proteins / Q000096:biosynthesis; D010766:Phosphorylation; D011650:Pulmonary Alveoli / Q000166:cytology / Q000378:metabolism; D054367:Receptors, CXCR3 / Q000096:biosynthesis / Q000378:metabolism; D020545:Respiratory Mucosa / Q000166:cytology / Q000378:metabolism*; D051899:Smad2 Protein / Q000096:biosynthesis; D051900:Smad3 Protein / Q000096:biosynthesis; D051906:Smad7 Protein / Q000096:biosynthesis; D000074482:Thyroid Nuclear Factor 1; D014157:Transcription Factors / Q000096:biosynthesis; D053773:Transforming Growth Factor beta1 / Q000378:metabolism* / Q000494:pharmacology
C541116:ACTA2 protein, human; D000199:Actins; D015415:Biomarkers; C080810:CXCL9 protein, human; C515187:CXCR3 protein, human; D054370:Chemokine CXCL9; C000614412:NKX2-1 protein, human; D009687:Nuclear Proteins; D054367:Receptors, CXCR3; C497782:SMAD2 protein, human; C497790:SMAD3 protein, human; C497806:SMAD7 protein, human; D051899:Smad2 Protein; D051900:Smad3 Protein; D051906:Smad7 Protein; D000074482:Thyroid Nuclear Factor 1; D014157:Transcription Factors; D053773:Transforming Growth Factor beta1