Abstract
House dust mite allergens (HDM) cause bronchoconstriction in asthma patients and induce an inflammatory response in the lungs due to the release of cytokines, chemokines and additional mediators. The mechanism how HDM components achieve this is largely unknown. The objective of this study was to assess whether HDM components of Dermatophagoides pteronissinus with protease activity (Der p 1) and unknown enzymatic activity (Der p 2, Der p 5) induce biological responses in a human airway-derived epithelial cell line (A549), and if so, to elucidate the underlying mechanism(s) of action. A549 cells were incubated with HDM extract, Der p 1, recombinant Der p 2 and recombinant Der p 5. Cell desquamation was assessed by microscopy. The proinflammatory cytokines, IL-6 and IL-8, were measured by ELISA. Intracellular Ca2+ levels were assessed in A549 cells and in mouse fibroblasts expressing the human protease activated receptor (PAR)1, PAR2 or PAR4. HDM extract, Der p 1 and Der p 5 dose-dependently increased the production of IL-6 and IL-8. Added simultaneously, Der p 1 and Der p 5 further increased the production of IL-6 and IL-8. The action of Der p 1 was blocked by cysteine-protease inhibitors, while that of Der p 5 couldn't be blocked by either serine- or cysteine protease inhibitors. Der p 5 only induced cell shrinking, whereas HDM extract and Der p1 also induced cell desquamation. Der p 2 had no effect on A549 cells. Der p 1's protease activity causes desquamation and induced the release of IL6 and IL-8 by a mechanism independent of Ca2+ mobilisation and PAR activation. Der p 5 exerts a protease-independent activation of A549 that involves Ca2+ mobilisation and also leads to the production of these cytokines. Together, our data indicate that allergens present in HDM extracts can trigger protease-dependent and protease-independent signalling pathways in A549 cells.
Highlights
House dust mite (Dermatophagoides pteronissinus) extracts contain allergens with potent sensitising capacities in atopic subjects
House dust mite extract and Der p 1 induce morphological changes and cell desquamation in A549 cultures As summarized in table I, both house dust mites (HDM) extract and purified natural Der p 1 dose-dependently induced morphological changes. Low concentrations of these compounds were associated by cell shrinking, whereas higher concentrations lead to total cell desquamation of confluent A549 cell layers without affecting cell viability
PAR2 agonist (NH2-S-L-I-G-K-V-C) increased cytokine production in A549 cells Because epithelial cells express protease-activated receptors (PAR), we examined whether a protease activated receptor (PAR)-mediated mechanism is involved in HDM and Der p 1 induced cytokine production
Summary
House dust mite (Dermatophagoides pteronissinus) extracts contain allergens with potent sensitising capacities in atopic subjects. Airway-derived epithelial cells have been shown to increase the release of proinflammatory cytokines, such as interleukin (IL)-6 and IL-8, in response to proteases present in HDM-, pollen- and fungal extracts [4,5,6,7]. In addition to protease-mediated mechanisms, a protease-independent activation of epithelial cells has been observed in studies with HDM extracts [4]. The latter observation suggested a possible interaction of airway epithelial cells with non-protease compounds of HDM extracts
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
