Background: Chronic rhinosinusitis with nasal polyps is characterized by TH2-biased eosinophilic inflammation. Eosinophils have been shown to generate so-called extracellular eosinophilic traps (EETs) under similar pathologic conditions.
Objective: Our aim was to investigate a possible link between EET formation and the presence of Staphylococcus aureus, an organism frequently colonizing the upper airways, at the human mucosal site of the disease.
Methods: Tissue slides were investigated for the presence of EETs and S aureus by using immunofluorescent staining and the PNA-Fish assay, respectively. An ex vivo human mucosal disease tissue model was used for artificial infection with S aureus. Cell markers were analyzed by using immunohistochemistry, the Luminex Multiplex assay, ELISA, PCR, and immunoblotting and linked to the presence of EETs.
Results: About 8.8% ± 4.8% of the infiltrating eosinophils exhibited EETs in patients' nasal polyp tissues. Formation of EETs was associated with increased IL-5 (P < .05) and periostin (P < .05) tissue levels and colonization with S aureus (P < .05). By using an ex vivo human mucosal disease tissue model, EET formation was induced (4.2 ± 0.9-fold) on exposure to S aureus but not Staphylococcus epidermidis. Eosinophils were shown to migrate (P < .01) toward S aureus and entrap the bacteria both inside and outside the mucosal tissue. Blocking NAPDH oxidase activity led to a complete inhibition (P < .05) of EET formation by S aureus.
Conclusion: Eosinophils are likely to be specifically recruited to S aureus and possibly other microorganisms and form EETs at sites of airway epithelial damage to protect the host from infections in patients with chronic rhinosinusitis with nasal polyps.
Keywords: Chronic rhinosinusitis; Staphylococcus aureus; eosinophils; epithelial barrier; extracellular eosinophilic traps; polyps.
Copyright © 2017 American Academy of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.