title: Proliferation of pulmonary interstitial fibroblasts is mediated by transforming growth factor-beta1-induced release of extracellular fibroblast growth factor-2 and phosphorylation of p38 MAPK and JNK.
abstract: Idiopathic pulmonary fibrosis (IPF; a progressive lung disease) is characterized by parenchymal remodeling with enlarged air spaces called honeycomb cysts and palisades of fibroblasts called fibroblast foci. In IPF, lung epithelial cells covering honeycomb cysts and fibroblast foci aberrantly express the active conformation of the potent fibrogenic cytokine transforming growth factor-beta1 (TGF-beta1). Using explanted rat lung slices, we transfected alveolar epithelial cells with the retrovirus pMX containing a site-directed mutation in which Cys223 and Cys225 were substituted with serines, resulting in release of biologically active TGF-beta1 and fibroblast proliferation and remodeling that resembled IPF. Fibroblasts obtained from transfected explants and in culture for 6 weeks incorporated 6.59 +/- 1.55-fold more [3H]thymidine compared with control fibroblasts without transfection or fibroblasts obtained from transfected explants cultured with antibody to fibroblast growth factor-2 (FGF-2). Primary lung fibroblasts obtained from normal rat lungs cultured with TGF-beta1 expressed increased levels of phosphorylated p38 MAPK and JNK, but not ERK1/2. The presence of TGF-beta1 caused an immediate release of extracellular FGF-2 from primary pulmonary fibroblasts; and in the presence of anti-FGF-2 antibody, phosphorylated p38 MAPK and JNK were abrogated. TGF-beta inhibits cell proliferation by suppression of c-Myc and induction of p15INK46, p21CIP1, or p27KIP. Fibroblasts cultured with TGF-beta1 showed no regulation of c-Myc or induction of p15INK46, p21CIP1,or p27KIP. These findings suggest that pulmonary fibroblasts may not respond to the anti-proliferative effects of TGF-beta1, but proliferate in response to TGF-beta1 indirectly by the release of FGF-2, which induces phosphorylation of p38 MAPK and JNK.
authors.affiliation: Respiratory Division, Department of Medicine, University of British Columbia. nkhalil@interchange.ubc.ca
authors.forename: Nasreen
authors.initials: N
authors.lastname: Khalil
authors.forename: Ying Dong
authors.initials: YD
authors.lastname: Xu
authors.forename: Robert
authors.initials: R
authors.lastname: O'Connor
authors.forename: Vincent
authors.initials: V
authors.lastname: Duronio
mesh_terms: D000818:Animals; D015153:Blotting, Western; D049109:Cell Proliferation; D002478:Cells, Cultured; D016895:Culture Media, Serum-Free / Q000494:pharmacology; D050762:Cyclin-Dependent Kinase Inhibitor p15 / Q000378:metabolism; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D016222:Fibroblast Growth Factor 2 / Q000378:metabolism*; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism*; D005822:Genetic Vectors; D006133:Growth Substances; D008168:Lung / Q000378:metabolism / Q000473:pathology; D048670:MAP Kinase Kinase 4 / Q000378:metabolism*; D020935:MAP Kinase Signaling System; D051379:Mice; D008809:Mice, Inbred C3H; D041681:NIH 3T3 Cells; D010641:Phenotype; D010766:Phosphorylation; D011650:Pulmonary Alveoli / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012190:Retroviridae / Q000235:genetics / Q000378:metabolism; D013936:Thymidine / Q000737:chemistry / Q000378:metabolism; D013997:Time Factors; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000378:metabolism*; D053773:Transforming Growth Factor beta1; D014746:Vimentin / Q000737:chemistry; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
chemical_list: C493958:Cdkn1a protein, rat; C493962:Cdkn1b protein, rat; D016895:Culture Media, Serum-Free; D050762:Cyclin-Dependent Kinase Inhibitor p15; D050759:Cyclin-Dependent Kinase Inhibitor p21; D006133:Growth Substances; C508961:Tgfb1 protein, mouse; C508962:Tgfb1 protein, rat; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D014746:Vimentin; D016222:Fibroblast Growth Factor 2; D050760:Cyclin-Dependent Kinase Inhibitor p27; D048051:p38 Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D013936:Thymidine