title: Transforming growth factor beta1-mediated activation of the smooth muscle alpha-actin gene in human pulmonary myofibroblasts is inhibited by tumor necrosis factor-alpha via mitogen-activated protein kinase kinase 1-dependent induction of the Egr-1 transcriptional repressor.
abstract: Transforming growth factor (TGF) beta1 is a mediator of myofibroblast differentiation in healing wounds in which it activates transcription of the smooth muscle alpha-actin (SMalphaA) gene via dynamic interplay of nuclear activators and repressors. Targeting components of TGFbeta1 signaling may be an effective strategy for controlling myofibroblasts in chronic fibrotic diseases. We examined the ability of proinflammatory tumor necrosis factor (TNF)-alpha to antagonize TGFbeta1-mediated human pulmonary myofibroblast differentiation. TNF-alpha abrogated TGFbeta1-induced SMalphaA gene expression at the level of transcription without disrupting phosphorylation of regulatory Smads. Intact mitogen-activated protein kinase kinase (Mek)-extracellular signal-regulated kinase (Erk) kinase signaling was required for myofibroblast repression by TNF-alpha via induction of the early growth response factor-1 (Egr-1) DNA-binding protein. Egr-1 bound to the GC-rich SPUR activation element in the SMalphaA promoter and potently suppressed Smad3- and TGFbeta1-mediated transcription. Reduction in Smad binding to the SMalphaA promoter in TNF-alpha-treated myofibroblasts was accompanied by an increase in Egr-1 and YB-1 repressor binding, suggesting that the molecular mechanism underlying repression may involve competitive interplay between Egr-1, YB-1, and Smads. The ability of TNF-alpha to attenuate myofibroblast differentiation via modulation of a Mek1/Erk/Egr-1 regulatory axis may be useful in designing new therapeutic targets to offset destructive tissue remodeling in chronic fibrotic disease.
authors.affiliation: Department of Physiology and Cell Biology and the Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University, Columbus, 43210, USA.
authors.forename: Xiaoying
authors.initials: X
authors.lastname: Liu
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Kelm
authors.forename: Arthur R
authors.initials: AR
authors.lastname: Strauch
mesh_terms: D000199:Actins / Q000235:genetics*; D051766:Early Growth Response Protein 1 / Q000378:metabolism*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005347:Fibroblasts / Q000187:drug effects / Q000201:enzymology*; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D008168:Lung / Q000166:cytology; D048369:MAP Kinase Kinase 1 / Q000378:metabolism*; D008957:Models, Genetic; D009130:Muscle, Smooth / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding / Q000187:drug effects; D012097:Repressor Proteins / Q000378:metabolism; D051899:Smad2 Protein / Q000378:metabolism; D051906:Smad7 Protein / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects; D053773:Transforming Growth Factor beta1 / Q000494:pharmacology*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D051840:Y-Box-Binding Protein 1 / Q000378:metabolism
chemical_list: D000199:Actins; C497325:EGR1 protein, human; D051766:Early Growth Response Protein 1; D012097:Repressor Proteins; C497782:SMAD2 protein, human; C497806:SMAD7 protein, human; D051899:Smad2 Protein; D051906:Smad7 Protein; D053773:Transforming Growth Factor beta1; D014409:Tumor Necrosis Factor-alpha; D051840:Y-Box-Binding Protein 1; D048049:Extracellular Signal-Regulated MAP Kinases; D048369:MAP Kinase Kinase 1