title: Mechanisms of tissue inhibitor of metalloproteinase 1 augmentation by IL-13 on TGF-beta 1-stimulated primary human fibroblasts.
abstract: BACKGROUND
  TGF-beta induces expression of tissue inhibitor of metalloproteinase 1 (TIMP-1), a potent inhibitor of matrix metalloproteinases that controls extracellular matrix metabolism and deposition. IL-13 alone does not induce TIMP-1, but in combination with TGF-beta it augments TIMP-1 expression. Although these interactions have implications for remodeling in asthma, little is understood regarding the mechanisms controlling TIMP-1 product.
  
  
  OBJECTIVE
  To explore the role of Smads and mitogen-activated protein kinase kinase (MEK)-extracellular signal-regulated kinase (ERK) in the TIMP-1 augmentation by IL-13+TGF-beta1 in primary human airway fibroblasts.
  
  
  METHODS
  Real-time PCR, Western blot, ELISA, and transient transfection were used to evaluate the mechanisms of TIMP-1 augmentation.
  
  
  RESULTS
  IL-13 enhanced TGF-beta1-induced Smad-2 and Smad-3 phosphorylation, transient transfection with dominant-negative Smad-2 or Smad-3 decreased TIMP-1 mRNA expression in the presence of TGF-beta1 and IL-13+TGF-beta1 through inhibition of Smad-2 or Smad-3 phosphorylation. ERK phosphorylation was increased by IL-13 and IL-13+TGF-beta1. MEK-ERK inhibition decreased TIMP-1 mRNA/protein to a greater degree after IL-13+TGF-beta1 stimulation versus TGF-beta1 alone. MEK-ERK inhibition also significantly increased Akt phosphorylation under all conditions and decreased Smad-3 phosphorylation in the presence of IL-13+TGF-beta1. In contrast, phosphoinositide-3 kinase-Akt inhibition increased phosphorylation of ERK and Smads, leading to increased TIMP-1.
  
  
  CONCLUSIONS
  These results indicate that IL-13 augments TGF-beta1-induced TIMP-1 expression through increased Smad phosphorylation. These increases occur as TGF-beta1 downregulates IL-13-induced phosphoinositide-3 kinase activation while leaving the positive effect of IL-13-induced ERK on Smad signaling.
  
  
  CONCLUSIONS
  This augmentation of TGF-beta1-induced TIMP-1 by IL-13 could contribute to the fibrosis and airway remodeling seen in the presence of T(H)2 inflammation in asthma.
authors.affiliation: University of Pittsburgh Medical Center, Pittsburgh, PA 15213, USA.
authors.forename: Xiuxia
authors.initials: X
authors.lastname: Zhou
authors.forename: Haizhen
authors.initials: H
authors.lastname: Hu
authors.forename: Mai-Lan N
authors.initials: ML
authors.lastname: Huynh
authors.forename: Chakradhar
authors.initials: C
authors.lastname: Kotaru
authors.forename: Silvana
authors.initials: S
authors.lastname: Balzar
authors.forename: John B
authors.initials: JB
authors.lastname: Trudeau
authors.forename: Sally E
authors.initials: SE
authors.lastname: Wenzel
mesh_terms: D000276:Adjuvants, Immunologic / Q000502:physiology*; D000328:Adult; D001249:Asthma / Q000201:enzymology / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D001980:Bronchi / Q000201:enzymology / Q000276:immunology / Q000473:pathology; D002478:Cells, Cultured; D015536:Down-Regulation / Q000276:immunology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000502:physiology; D005260:Female; D005347:Fibroblasts / Q000201:enzymology* / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D005355:Fibrosis; D006801:Humans; D018793:Interleukin-13 / Q000502:physiology*; D020935:MAP Kinase Signaling System / Q000276:immunology; D008297:Male; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology; D010766:Phosphorylation; D051785:Smad Proteins / Q000378:metabolism / Q000502:physiology; D018418:Th2 Cells / Q000276:immunology / Q000378:metabolism; D019715:Tissue Inhibitor of Metalloproteinase-1 / Q000096:biosynthesis / Q000502:physiology*; D053773:Transforming Growth Factor beta1 / Q000502:physiology*; D015854:Up-Regulation / Q000276:immunology
chemical_list: D000276:Adjuvants, Immunologic; D018793:Interleukin-13; D051785:Smad Proteins; D019715:Tissue Inhibitor of Metalloproteinase-1; D053773:Transforming Growth Factor beta1; D019869:Phosphatidylinositol 3-Kinases; D048049:Extracellular Signal-Regulated MAP Kinases