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A subset of patients with asthma have persistently elevated exhaled nitric oxide despite directly observed high-dose inhaled corticosteroid (ICS) therapy. In these patients there is no reduction in induced sputum eosinophil counts and no clinical response to ICS suggesting that epithelial responsiveness to ICS is critical to their efficacy. In order to investigate epithelial cell responses to corticosteroids we modelled in vitro a potentially relevant mechanism: type 2 cytokine induced eotaxin production. We present here an initial characterisation of the release of CCL26 (eotaxin-3) by epithelial cells after stimulation with IL-4, IL-13 or both. When epithelial cell lines A549, high passage BEAS2B and 16HBE were treated with IL-4, IL-13 or in combination only A549 cells were able to secrete CCL26. A549 cells treated with 100 ng/mL IL-4 and IL-13 secreted 1680+/-130 (mean+/-SD) pg CCL26 per million cells. Secretion was time dependent. High passage BEAS2B and 16HBE cells treated similarly secreted undetectable CCL26 <23pg CCL26/106 cells. Low passage BEAS2B secreted CCL26 in one preliminary experiment. Further titration of IL-4 and IL-13 yielded an optimum dose of IL-4 / 13 which in A549 cells showed little evidence of synergy when the two cytokines were added together. IL4/13 induced secretion of CCL26 was inhibited by fluticasone in a dose dependent manner with 2nM reducing CCL26 production from 6670+/-1740 to 3440+/-370 pg per million cells. This pathway may be relevant to eosinophil recruitment in the airway in asthma and is a potentially useful in vitro model system to study ICS resistance in severe asthma.


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