Background: Rhinoviruses are associated with the majority of asthma exacerbations. To date, the pathogenesis of virus-induced asthma exacerbations is still unclear, and no safe effective therapy is available. Intercellular adhesion molecule-1 (ICAM-1) has a central role in inflammatory cell recruitment to the airways in asthma and is the receptor for 90% of rhinoviruses. We have previously shown that rhinovirus infection of lower airway epithelium induces ICAM-1 expression by a transcriptional mechanism that is critically nuclear factor-kappaB-dependent.
Objective: The purpose of this study was to investigate the effect of systemic (hydrocortisone [HC], dexamethasone [DM]) and topical (mometasone furoate [MF]) corticosteroids on rhinovirus-induced ICAM-1 up-regulation.
Methods: Cultured primary bronchial or transformed (A549) respiratory epithelial cells were pretreated with corticosteroids for 16 hours and infected with rhinovirus type 16 for 8 hours. ICAM-1 surface expression was evaluated by flow cytometry. In A549 cells ICAM-1 messenger RNA was evaluated by specific reverse transcription-PCR and promoter activation by chloramphenicol acetyltransferase assay.
Results: We observed inhibition of rhinovirus-induced ICAM-1 up-regulation with corticosteroid pretreatment in both primary bronchial epithelial and A549 cells. In A549 cells systemic and topical corticosteroids demonstrated a dose-dependent inhibition with similar efficacy (inhibitory concentration 50% 10(-10) mol/L, 10(-11) mol/L, and 10(-11) mol/L for HC, DM, and MF respectively). MF also inhibited ICAM-1 messenger RNA induction by rhinovirus infection in a dose-dependent manner. MF completely inhibited rhinovirus-induced ICAM-1 promoter activation. HC, DM, and MF had no direct effect on rhinovirus infectivity and replication in cultured cells.
Conclusion: Corticosteroids decrease rhinovirus-induced ICAM-1 up-regulation in respiratory epithelial cells and modulate pretranscriptional mechanisms. This effect may be important for the therapeutic control of virus-induced asthma exacerbations.