Exhaled RANTES and interleukin 4 levels after exercise challenge in children with asthma

Abstract

BackgroundDespite the universality and clinical significance of exercise-induced bronchospasm (EIB), the mechanisms responsible for it are incompletely understood. ObjectiveTo investigate the role of exhaled RANTES (regulated on activation, normal T-cell expressed and secreted) and interleukin (IL) 4 in EIB in children with asthma. MethodsFifty-six children with asthma were evaluated with exercise challenge and exhaled RANTES and IL-4 levels. Exhaled breath condensate was collected before and 30 minutes after exercise challenge. RANTES and IL-4 concentrations were determined using a specific immunoassay kit. ResultsA significant increase was found in RANTES levels after exercise challenge in the asthmatic children (P<.001). A statistically significant increase in RANTES levels was noted after exercise challenge in both the asthmatic children with EIB (n=25, P=.007) and in the non-EIB asthmatic group (n=31, P=.005). Our study revealed that exhaled RANTES level correlates significantly well with percentage of forced expiratory volume in 1 second (FEV1), exacerbation frequency, serum IgE, and body mass index. No statistically significant increase was found in IL-4 levels after exercise challenge. The maximal postexercise decrease in FEV1 strongly correlated with total eosinophil count (P<.001, r=−0.61) and baseline ratio of FEV1 to forced vital capacity (FVC) (P=.002, r=0.40). Results from multivariate regression analysis adjusted for age, sex, and atopy as covariates showed that eosinophil count and FEV1/FVC ratio were significantly associated with EIB. ConclusionWe found that exercise challenge, leading to hyperosmolar stimulus, may increase exhaled RANTES levels in children with asthma. In addition, exhaled RANTES levels correlate well with serum IgE, severity of asthma, FEV1/FVC ratio, and body mass index. RANTES and IL-4 may not be independent predictors for EIB. Furthermore, eosinophil count and FEV1/FVC ratio may predict the presence and severity of EIB in asthmatic children.