Background: Matrix metalloproteinases (MMPs) digest extracellular matrix components and might be important mediators of tissue remodeling. Proteinase activated receptor-2 (PAR-2) is expressed in a variety of cell types including epithelial cells. PAR-2 receptors are activated by serine proteases such as trypsin and mast cell tryptase and have been implicated in inflammation.
Objective: To study the effects of PAR-2-mediated airway epithelial cell activation on the production of MMP-9.
Methods: A specific PAR-2-activating peptide and trypsin were used to activate the human airway epithelial cell line A549 as well as primary cultures of small airway epithelial cells (SAEC). MMP-2 and MMP-9 messenger RNA and enzymatic activity were evaluated by RT-PCR and gelatin zymography, respectively.
Results: PAR-2-activating peptides upregulated MMP-9 mRNA expression and release of MMP-9 enzymatic activity from airway epithelial cells but had no effect on MMP-2 production. Dexamethasone and budesonide (10(-6) to 10(-10) mmol) inhibited PAR-2-mediated MMP-9 release. Pretreatment with indomethacin indicated that MMP-9 release was not prostaglandin dependent. Inhibitors of the MAP kinase MEK- 1, and NFkappaB showed that both pathways are important for PAR-2-mediated MMP-9 release. Trypsin, a physiologic PAR-2 activator, upregulated MMP-9 but also MMP-2 release from airway epithelial cells.
Conclusion: PAR-2 receptors appear to play an important role in the regulation of MMP-9 release from airway epithelial cells. As such, these receptors may be critical elements in tissue remodeling in asthma and other inflammatory conditions in the airways.