Background: Beneficial effects of azithromycin in cystic fibrosis (CF) have been reported, however, its mechanism of action remains unclear. The present study aimed at investigating the effect of azithromycin oil CF airway epithelial cells. Methods: Primary cultures of purified tracheal epithelial cells from F508del and normal homozygous Mice were established. Responses to lipopolysaccharide from Pseudomonas aeruginosa (LPS, 0.1 mu g/ml) oil mRNA expression of reutrophil-related chemokines, pro- and anti-inflammatory cytokines were investigated in the presence or the absence of azithromycin (1 mu g/ml). Results: CF airway epithelial cells showed upregulation of MIP-2 and KC responses to LPS, and azithromycin failed to downregulate these responses. In contrast, in CF cells, azithromycin increased KC and TNF-alpha expression under non-stimulated and LPS-stimulated conditions, respectively. In non-CF cells, the macrolide potentiated the LPS response oil MIP-2 and on IL-10. Conclusions: Airway epithelial cells contribute to the dysregulated immune processes in CF. Azithromycin rather stimulates cytokine expression in CF airway epithelial cells. (C) 2009 European Cystic Fibrosis Society. published by Elsevier B.V All rights reserved.