Airway epithelial cells release eosinophil survival-promoting factors (GM-CSF) after stimulation of proteinase-activated receptor 2

Background: Epithelium is considered an active participant in allergic infl ammation. Proteinase-activated receptor (PAR) 2 is expressed in a variety o f cell types, including epithelial cells, and has been implicated in inflam mation. Objective: PAR-2-mediated activation of airway epithelial cells induces the release of mediators that could promote eosinophil survival and mediate eo sinophil recruitment. Methods: PAR-2-activating peptides were used to activate the human airway e pithelial cell line A549. as well as primary cultures of small airway epith elial cells (SAECs), Human peripheral blood eosinophils were cultured in th e presence or absence of epithelial cell supernatants. Survival was assesse d by using an Annexin V apoptosis detection kit. GM-CSF and eotaxin were me asured by using ELISA. Results: Eosinophils undergo apoptosis in the absence of growth factors. Su pernatants from PAR-2-activated A549 epithelial cells increased eosinophil survival. Supernatants from resting SAECs also increased eosinophil surviva l, but supernatants From PAR-2-activated SAECs showed a greater effect. The effect of PAR-2-activated epithelial cell supernatants on eosinophil survi val was completely inhibited by a neutralizing anti-GM-CSF antibody but not an anti-IL-5 antibody. Resting A549 cells did not release any detectable G MCSF, whereas PAR-2-activated cells released 35 pg/10(6) cells. Resting SAE Cs released 754.3 pg/10(6) cells of GM-CSF, which was further increased to 1360.5 pg/106 cells after PAR-2-mediated activation. Budesonide inhibited t his PAR-2 effect. PAR-2-activated epithelial cells also released eotaxin. Conclusion: PAR-2-mediated activation of airway epithelial cells induced re lease of GM-CSF, which promoted eosinophil survival and activation. It also induced release of eotaxin, which could mediate eosinophil recruitment to the airways.