Azithromycin reduces exaggerated cytokine production by M1 alveolar macrophages in cystic fibrosis

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 F508del mutation and their wild-type controls. Classical (M1) and alternative (M2) macrophage polarization and responses to lipopolysaccharide from Pseudomonas aeruginosa (LPS) were investigated and the effect of azithromycin was examined in both cell populations. We showed that alveolar macrophage counts were 1.7-fold higher in CF as compared to wild-type mice. The macrophage-related chemokine, 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 to controls. LPS-stimulated expression of pro-inflammatory mediators, such as nitric oxide synthase-(NOS)-2, IL-1beta and CCL-2, was increased while anti-inflammatory IL-10 expression was decreased in CF macrophages. Azithromycin, added to cell cultures at 1 mg/l, significantly reduced pro-inflammatory cytokine expression (IL-1beta, CCL-2, tumor necrosis factor-(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