Mechanisms of tissue inhibitor of metalloproteinase 1 augmentation by IL-13 on TGF-beta 1-stimulated primary human fibroblasts.
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.
Zhou
Xiuxia
X
University of Pittsburgh Medical Center, Pittsburgh, PA 15213, USA.
Hu
Haizhen
H
Huynh
Mai-Lan N
ML
Kotaru
Chakradhar
C
Balzar
Silvana
S
Trudeau
John B
JB
Wenzel
Sally E
SE
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
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