Induction and regulation of matrix metalloproteinase-12 in human airway smooth muscle cells.
BACKGROUND
The 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.


METHODS
Laser 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.


RESULTS
We 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)-1beta, 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-1beta on MMP-12, indicating a role for these kinases in IL-1beta-induced induction and release of MMP-12. IL-1beta-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)-alpha through enhancing activator protein-1 activation by IL-1beta. Transforming growth factor-beta had no significant effect on MMP-12 induction.


CONCLUSIONS
Our findings indicate that human airway smooth muscle cells express and secrete MMP-12 that is up-regulated by IL-1beta and TNF-alpha. 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.
Xie
Shaoping
S
Experimental Studies, National Heart and Lung Institute, Imperial College, London, UK. s.xie@imperial.ac.uk
Issa
Razao
R
Sukkar
Maria B
MB
Oltmanns
Ute
U
Bhavsar
Pankaj K
PK
Papi
Alberto
A
Caramori
Gaetano
G
Adcock
Ian
I
Chung
K Fan
KF
D001980:Bronchi / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects / Q000502:physiology; D006801:Humans; D007375:Interleukin-1 / Q000008:administration & dosage*; D053508:Matrix Metalloproteinase 12; D008666:Metalloendopeptidases / Q000378:metabolism*; D009130:Muscle, Smooth / Q000187:drug effects / Q000378:metabolism*; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000008:administration & dosage*
D007375:Interleukin-1; D014409:Tumor Necrosis Factor-alpha; D008666:Metalloendopeptidases; C507122:MMP12 protein, human; D053508:Matrix Metalloproteinase 12