ABSTRACT
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 on 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 microg/ml) on mRNA expression of neutrophil-related chemokines, pro- and anti-inflammatory cytokines were investigated in the presence or the absence of azithromycin (1 microg/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 on 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.
Subject(s)
Anti-Bacterial Agents/administration & dosage , Azithromycin/administration & dosage , Cystic Fibrosis/drug therapy , Cytokines/drug effects , Cytokines/metabolism , Animals , Cell Culture Techniques , Cells, Cultured/drug effects , Cells, Cultured/immunology , Cystic Fibrosis/immunology , Cystic Fibrosis/metabolism , Disease Models, Animal , Epithelial Cells/drug effects , Epithelial Cells/immunology , Mice , Mice, Inbred Strains , Neutrophils/drug effects , Neutrophils/metabolism , RNA, Messenger/drug effects , RNA, Messenger/metabolism , Trachea/cytology , Trachea/drug effects , Trachea/immunologyABSTRACT
Macrophages phagocyte pathogenic microorganisms and orchestrate immune responses by producing a variety of inflammatory mediators. The cystic fibrosis (CF) transmembrane conductance regulator chloride channel has been reported to be of pivotal importance for macrophage functions. The exact phenotype and role of macrophages in CF is still unknown. Alveolar and peritoneal macrophages were monitored in CF mice homozygous for the F508 del mutation and in wild-type control animals. Classical (M1) and alternative (M2) macrophage polarization and responses to LPS from Pseudomonas aeruginosa were investigated, and the effect of azithromycin was examined in both cell populations. We show that alveolar macrophage counts were 1.7-fold higher in CF as compared with wild-type mice. The macrophage-related chemokine, chemokine C-C motif ligand (CCL)-2, was found to be at least 10-fold more abundant in the alveolar space of mutant mice. Cell count and CCL-2 protein levels were also increased in the peritoneal cavity of CF mice. Both M1 and M2 macrophage polarization were significantly enhanced in alveolar and peritoneal cells from F508del-CF mice as compared with control animals. LPS-stimulated expression of proinflammatory mediators, such as nitric oxide synthase-2, IL-1beta, and CCL-2, was increased, whereas anti-inflammatory IL-10 expression was decreased in CF macrophages. Azithromycin, added to cell cultures at 1 mg/liter, significantly reduced proinflammatory cytokine expression (IL-1beta, CCL-2, TNF-alpha) in M1-induced CF and wild-type alveolar macrophages. Our findings indicate that CF macrophages are ubiquitously accumulated, and that these cells are polarized toward classical and alternative activation status. Azithromycin down-regulates inflammatory cytokine production by M1-polarized CF alveolar macrophages.
