Methods: Eosinophils were isolated from the blood of healthy volunteers or allergic subjects, and their adhesion to recombinant human periostin was measured using eosinophil peroxidase assays. Eosinophil O2−generation was examined based on the superoxide dismutase-inhibitable reduction of cytochrome C. Eosinophil-derived neurotoxin (EDN) concentrations in cell media were measured by ELISA as a marker of degranulation, and concentrations of cytokine/chemokines were also measured.
Results: Periostin directly induces eosinophil adhesion, which was enhanced by IL-5. Periostin also activated other functions of eosinophils such as O2− generation and EDN release. Anti-αM or anti-β2 integrin monoclonal antibody suppressed the eosinophil adhesion, O2−generation, and EDN release induced by periostin. Finally, periostin increased the production of transforming growth factor (TGF-β)1, TGF-β2 and cysteinyl leukotrienes (cysLTs) from eosinophils.
Conclusions: These findings suggested that periostin up-regulates eosinophil functions through αMβ2 integrin. These effects may be involved in the activation of eosinophils and in the development of remodeling in the airway of Th2-dominant asthma, and could possibly aggravate the disease.