Background: Bradykinin (BK) mediates acute allergic asthma and airway remodelling. Nuclear factor-kappa B (NF-kB) is potentially involved in BK B2 receptor (B2R) regulation. Objective: In this observational cross-sectional study, B2R and NF-kB expression was evaluated in bronchial biopsies from mild asthmatics (after diluent/allergen challenge) and healthy controls, examining the role of NF-kB in B2R expression in primary human fibroblasts from normal and asthmatic subjects (HNBFb and HABFb). Methods: B2R and NF-kB (total and nuclear) expression was analysed by immunohistochemistry in biopsies from 10 mild intermittent asthmatics (48 h after diluent/allergen challenge) and 10 controls undergoing bronchoscopy. B2R co-localization in 5B5+ and αSMA+ mesenchymal cells was studied by immunofluorescence/confocal microscopy, and B2R expression in HABFb/HNBFb incubated with interleukin (IL)-4/IL-13 with/without BK, and after NF-kB inhibitor, by Western blotting. Results: Bronchial mucosa B2R and nuclear NF-kB expression was higher in asthmatics after diluent (B2R only) and allergen challenge than in controls (P <0.05), while B2R and NF-kB (total and nuclear) increased after allergen compared with after diluent (P <0.05). Allergen exposure increased B2R expression in 5B5+ and αSMA+ cells. Constitutive B2R protein expression was higher in HABFb than in HNBFb (P <0.05) and increased in both cell types after IL-13 or IL-4/IL-13 and BK treatment. This increase was suppressed by a NF-kB inhibitor (P <0.05). Conclusions & Clinical Relevance: Bronchial B2R expression is constitutively elevated in allergic asthma and is further increased after allergen exposure together with NF-kB expression. NF-kB inhibitor blocked IL-4/IL-13-induced increase in B2R expression in cultured fibroblasts, suggesting a role as potential anti-asthma drug.
- Asthmatic fibroblasts
- Bradykinin B2 receptor (B2R)
- Nuclear factor-kappa B (NF-kB)
ASJC Scopus subject areas
- Immunology and Allergy