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Interaction of mite allergens Der p3 and Der p9 with protease-activated receptor-2 expressed by lung epithelial cells
1AVAIL Biomedical Research Institute, Avail GmbH, Spalentorweg 18, CH-4051 Basel, Switzerland.
Abstract:
The respiratory epithelium represents the first barrier encountered by airborne Ags. Two major dust mite Ags, Der p3 and Der p9, are serine proteases that may activate lung epithelial cells by interaction with the protease-activated receptor 2 (PAR-2). In this study both Der p3 and Der p9 cleaved the peptide corresponding to the N terminus of PAR-2 at the activation site. Both Ags sequentially stimulated phosphoinositide hydrolysis, transient cytosolic Ca(2+) mobilization, and release of GM-CSF and eotaxin in human pulmonary epithelial cells. These responses were similar to those observed with trypsin and a specific PAR-2 agonist and were related to the serine protease activity of Der p3 and Der p9. Cell exposure to the Ags resulted in a refractory period, indicating that a PAR had been cleaved. Partial desensitization to Der p3 and Der p9 by the PAR-2 agonist suggested that PAR-2 was one target of the Ags. However, PAR-2 was not the only target, because the PAR-2 agonist caused less desensitization to Der p3 and Der p9 than did trypsin. A phospholipase C inhibitor prevented the cytokine-releasing effect of the PAR-2 agonist and abolished or reduced (>70%) the cytokine-releasing effects of Der p3 and Der p9. Our results suggest that Der p 3 and Der p9 may induce a nonallergic inflammatory response in the airways through the release of proinflammatory cytokines from the bronchial epithelium and that this effect is at least in part mediated by PAR-2.
Insights
Dust mite allergens Der p3 and Der p9 activate airway epithelial cells via protease-activated receptor 2 (PAR-2), triggering inflammation. This suggests a non-allergic pathway for airway irritation by these common allergens.
Area of Science:
- Immunology
- Cell Biology
- Respiratory Medicine
Background:
- The respiratory epithelium acts as a primary defense against airborne antigens (Ags).
- Dust mite allergens, Der p3 and Der p9, are serine proteases potentially activating lung epithelial cells through protease-activated receptor 2 (PAR-2).
Purpose of the Study:
- To investigate the interaction of Der p3 and Der p9 with human pulmonary epithelial cells.
- To determine the role of protease-activated receptor 2 (PAR-2) in mediating cellular responses to these dust mite allergens.
Main Methods:
- Assessed the cleavage of a PAR-2 activating peptide by Der p3 and Der p9.
- Measured phosphoinositide hydrolysis, calcium (Ca2+) mobilization, and cytokine release (GM-CSF, eotaxin) in response to allergens and PAR-2 agonists.
- Utilized a phospholipase C inhibitor to evaluate its effect on allergen-induced responses.
- Investigated desensitization patterns using PAR-2 agonist and trypsin.
Main Results:
- Der p3 and Der p9 directly cleaved the PAR-2 activation site peptide.
- Both allergens induced phosphoinositide hydrolysis, Ca2+ mobilization, and release of GM-CSF and eotaxin, mimicking trypsin and a PAR-2 agonist.
- Evidence suggested PAR-2 is a target, but not the sole target, of Der p3 and Der p9.
- A phospholipase C inhibitor significantly reduced or abolished allergen-induced cytokine release.
Conclusions:
- Der p3 and Der p9 can induce non-allergic inflammation in airways.
- Proinflammatory cytokine release from bronchial epithelium, at least partially mediated by PAR-2, is a key mechanism.
- These findings highlight a potential pathway for airway irritation independent of allergic sensitization.