Effect of inhaled glucocorticoids on IL-1β and IL-1 receptor antagonist (IL- 1ra) expression in asthmatic bronchial epithelium

Abstract

Background - Accumulating evidence suggests that the cytokine network is central to the immunopathology of bronchial asthma and the existence of naturally occurring cytokine antagonists has added to this complexity. Upregulation of both interleukin 1β (IL-1β) and its naturally occurring receptor antagonists interleukiu 1 receptor antagonist (IL-1ra), has previously been observed on asthmatic bronchial epithelium compared with normal airways. Methods - The effect of inhaled beclomethasone dipropionate (BDP) on asthmatic bronchial epithelial expression of IL-1β and IL-1ra was studied. Frozen bronchial biopsy specimens from nine asthmatic subjects receiving 1000 μg BDP daily for eight weeks and from six asthmatic subjects receiving matching placebo were stained with anti-IL-1β and anti-IL-1ra antibodies. Hue-saturation-intensity (HSI) colour image analysis was used to quantify the brown immunoperoxidase reaction colour present on the bronchial epithelium. Results - There was a significant twofold decrease in the epithelial expression of IL1β after treatment with BDP but no significant change was seen in IL-1ra (p= 0.175). Conclusion - The selective inhibition of IL-1β, without effect on IL-1ra, provides a novel mechanism for the anti- inflammatory action of glucocorticosteroids.