Increased Levels of Interleukin-33 and Thymic Stromal Lymphopoietin in Exhaled Breath Condensate in Chronic Bronchial Asthma

Abstract

Background: Epithelium-derived cytokines such as thymic stromal lymphopoietin (TSLP), interleukin (IL)-25, and IL-33 are important contributors to inflammation in asthma. Exhaled breath condensate (EBC) is a noninvasive method used to assess the inflammation of airways. Our aim was to assess the levels of TSLP, IL-25, IL-33, and its receptor ST2l/IL-1 R4 in EBC in patients with asthma and to correlate these with serum levels and asthma control. Methods: EBC and serum levels of TSLP, IL-25, IL-33, and ST2l/IL-1 R4 were measured in 44 patients with chronic bronchial asthma (14 in the uncontrolled phase) and 19 healthy control participants. Results: EBC levels of IL-33 and TSLP and serum levels of IL-33 were statistically higher in patients with asthma than in controls. IL-25 and ST2l/IL-1 R4 were present in EBC at barely detectable levels and were not analyzed. The EBC and serum levels of all studied mediators did not differ between controlled and uncontrolled asthma patients, except for the serum level of ST2l/IL-1 R4, which was higher in uncontrolled asthma. There were no correlations between serum and EBC levels of TSLP and IL-33 or between either serum and EBC levels and the forced expiratory volume in 1 s or the total IgE level. Conclusions: Higher levels of IL-33 and TSLP in EBC provide evidence supporting a role for these mediators in asthma. Their levels do not discriminate between controlled and uncontrolled asthma. The local reaction within the epithelium is independent of the systemic reaction.