Paradoxical eosinophilic and cytokine responses to oral corticosteroid treatment in patients with asthma exacerbations

Background Thymic stromal lymphopoietin (TSLP) orchestrates eosinophilic inflammation, which may increase in asthma exacerbations. On the contrary, miR-1 inhibits TSLP-mediated eosinophil trafficking in lung endothelium. Whether the balance of TSLP and miR-1 levels determines the response to oral corticosteroids during the treatment of asthma exacerbations remains unknown. Objective To investigate the involvement of TSLP/miR-1 axis in inflammatory response to OCS treatment for asthma exacerbations. Methods We measured the concentrations of TSLP and other inflammatory cytokines and miR-1 expression during acute asthmatic exacerbations treated with standard oral corticosteroids (OCS) in a real-life setting. Twenty eight consecutive patients with acute asthma exacerbations treated with OCS for 1 week at the Emergency Department (ED) were studied prospectively. Steroid responders (SR) were identified by a significant reduction in blood eosinophils, whereas paradoxical responders (PR) showed no markedly decreased or even increased absolute blood eosinophil counts after OCS treatment. Differential white blood cell counts, blood cytokine levels and miR-1 expression within and between groups were compared before and after OCS treatment. The baseline cytokine concentrations in both groups were compared with those of stable asthmatics (SA). Results OCS treatment significantly reduced TSLP levels in steroid responders whereas this effect did not occur in paradoxical responders (P = 0.006 and P = 0.742, respectively). In contrast, miR-1 expression was unchanged in steroid responders in response to OCS, whereas it was markedly reduced in the paradoxical responders, despite higher expression at baseline compared with stable asthmatics, which may account for slower resolution of the exacerbation. Conclusions In some asthmatic patients with acute exacerbations who do not suppress eosinophils after a course of OCS, there is a paradoxical decrease in plasma miR-1 and increase in TSLP compared with steroid responders, which may result in slower clinical recovery.