German Cockroach Extract Induces Activation of Human Eosinophils to Release Cytotoxic Inflammatory Mediators

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Abstract
Background: Eosinophils play an important role in the pathogenesis of allergic diseases. Sensitization and exposure to cockroach allergen have been demonstrated to be one of the major risk factors for the development of bronchial asthma. However, little is known regarding the functional capacity of cockroach extract antigen to activate human eosinophils. Objective: We investigated whether German cockroach extract can activate human eosinophils to release cytotoxic inflammatory mediators. Methods: Purified eosinophils from the peripheral blood were incubated with various concentrations (0–200 µg/ml) of German cockroach extract antigen. Effector functions of eosinophils were checked by degranulation and superoxide anion production. In addition, we examined surface expression of CD11b and CD69, and intracellular activation of p38 mitogen-activated protein kinase (p38 MAP kinase) in cockroach-stimulated eosinophils. Results: German cockroach extract induced degranulation and superoxide production from human eosinophils. In addition, incubation of eosinophils for 3 h with the cockroach extract resulted in an increased level of the surface expression of CD11b and CD69. Furthermore, cockroach-induced superoxide production from eosinophils was significantly inhibited by the pretreatment of cells with a p38 MAP kinase inhibitor SB202190. Indeed, a large amount of phosphorylated forms of p38 MAP kinase was detected in cockroach-stimulated eosinophils. Conclusions: Our results suggest that German cockroach extract induces activation of human eosinophils to release cytotoxic inflammatory mediators such as superoxide and granular proteins.