The role of chemokines in exercise-induced bronchoconstriction in asthma

Background: The pathogenesis of exercise-induced bronchoconstriction in asthma is incompletely understood, and the role of chemokines has not been investigated. Objective: To investigate the involvement of the CC chemokines eotaxin, regulated upon activation normal T-cell expressed and secreted (RANTES), thymus and activation-regulated chemokine (TARC), and the CXC chemokine interferon-gamma-inducible protein 10 (IP-10) in exercise-induced bronchoconstriction. Methods: Four groups were enrolled: asthmatic children with positive (n = 15) and negative (n = 15) responses to exercise, children with cystic fibrosis (n = 14), and healthy children (n = 11). Levels of eotaxin, RANTES, TARC, and IP-10 were determined in plasma before, immediately after, and 6 and 24 hours after exercise challenge using enzyme-linked immunosorbent assay. Transcriptional activity was measured using reverse transcriptase-polymerase chain reaction. Results: Exercise did not induce any significant changes in systemic chemokine levels. A significant difference was observed only in the preexercise IP-10 levels among groups (P =.045). There was a significant difference in peripheral blood eosinophil counts among groups (P =.003). In asthmatic children with a positive response to exercise, there was an inverse correlation between eosinophil counts and eotaxin levels (r = -0.616; P = .01) and between forced expiratory volume in 1 second and TARC levels (r = -0.865; P = .001). Reverse transcriptase-polymerase chain reaction studies did not show any difference in the transcription of the chemokines. Conclusions: Exercise does not cause any changes in the systemic expression of eosinophilic chemokines. Peripheral blood eosinophils may be a determinant of the exercise response, and eotaxin and TARC may be associated with eosinophil counts and forced expiratory volume in 1 second in children with a bronchoconstrictor response to exercise.