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Respiratory Research

, 6:148

First Online: 16 December 2005Received: 01 April 2005Accepted: 16 December 2005


BackgroundThe elastolytic enzyme matrix metalloproteinase MMP-12 has been implicated in the development of airway inflammation and remodeling. We investigated whether human airway smooth muscle cells could express and secrete MMP-12, thereby participating in the pathogenesis of airway inflammatory diseases.

MethodsLaser capture microdissection was used to collect smooth muscle cells from human bronchial biopsy sections. MMP-12 mRNA expression was analysed by quantitative real-time RT-PCR. MMP-12 protein expression and secretion from cultured primary airway smooth muscle cells was further analysed by Western blot. MMP-12 protein localization in bronchial tissue sections was detected by immunohistochemistry. MMP-12 activity was determined by zymography. The TransAM AP-1 family kit was used to measure c-Jun activation and nuclear binding. Analysis of variance was used to determine statistical significance.

ResultsWe provide evidence that MMP-12 mRNA and protein are expressed by in-situ human airway smooth muscle cells obtained from bronchial biopsies of normal volunteers, and of patients with asthma, COPD and chronic cough. The pro-inflammatory cytokine, interleukin IL-1β, induced a >100-fold increase in MMP-12 gene expression and a >10-fold enhancement in MMP-12 activity of primary airway smooth muscle cell cultures. Selective inhibitors of extracellular signal-regulated kinase, c-Jun N-terminal kinase and phosphatidylinositol 3-kinase reduced the activity of IL-1β on MMP-12, indicating a role for these kinases in IL-1β-induced induction and release of MMP-12. IL-1β-induced MMP-12 activity and gene expression was down-regulated by the corticosteroid dexamethasone but up-regulated by the inflammatory cytokine tumour necrosis factor TNF-α through enhancing activator protein-1 activation by IL-1β. Transforming growth factor-β had no significant effect on MMP-12 induction.

ConclusionOur findings indicate that human airway smooth muscle cells express and secrete MMP-12 that is up-regulated by IL-1β and TNF-α. Bronchial smooth muscle cells may be an important source of elastolytic activity, thereby participating in remodeling in airway diseases such as COPD and chronic asthma.

AbbreviationsAP-1activator protein-1

ASMCairway smooth muscle cells

COPDchronic obstructive pulmonary disease

ECMextracellular matrix

ERKextracellular signal-regulated kinases

GAPDHglyceraldehyde-3-phosphate dehydrogenase

JNKc-Jun N-terminal kinases

LCMlaser capture microdissection


MAPKmitogen-activated protein kinase

MMPmatrix metalloproteinase

PCRpolymerase chain reaction

p-c-Junphosphorylated c-Jun

PI3-Kphosphatidylinositol 3-kinase

RTreverse transcription

SMsmooth muscle

TGFtransforming growth factor

Th2T helper lymphocyte 2-derived

TNFtumour necrosis factor

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Autor: Shaoping Xie - Razao Issa - Maria B Sukkar - Ute Oltmanns - Pankaj K Bhavsar - Alberto Papi - Gaetano Caramori - Ian Adc


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