Azithromycin Polarizes Macrophages to an M2 Phenotype via Inhibition of the STAT1 and NF-κB Signaling Pathways

Abstract

Azithromycin is effective at controlling exaggerated inflammation and slowing the long-term decline of lung function in patients with cystic fibrosis. We previously demonstrated that the drug shifts macrophage polarization toward an alternative, antiinflammatory phenotype. In this study we investigated the immunomodulatory mechanism of azithromycin through its alteration of signaling via the NF-kB and STAT1 pathways. J774 murine macrophages were plated, polarized (with IFN-g, IL-4/-13, or with azithromycin plus IFN-g) and stimulated with LPS. The effect of azithromycin on NF-kB and STAT1 signaling mediators was assessed by Western blot, homogeneous time-resolved fluorescence assay, nuclear translocation assay, and immunofluorescence. The drug's effect on gene and protein expression of arginase was evaluated as a marker of alternative macrophage activation. Azithromycin blocked NF-kB activation by decreasing p65 nuclear translocation, although blunting the degradation of IkBa was due, at least in part, to a decrease in IKKb kinase activity. A direct correlation was observed between increasing azithromycin concentrations and increased IKKb protein expression. Moreover, incubation with the IKKb inhibitor IKK16 decreased arginase expression and activity in azithromycin-treated cells but not in cells treated with IL-4 and IL-13. Importantly, azithromycin treatment also decreased STAT1 phosphorylation in a concentration-dependent manner, an effect that was reversed with IKK16 treatment. We conclude that azithromycin anti-inflammatory mechanisms involve inhibition of the STAT1 and NF-kB signaling pathways through the drug's effect on p65 nuclear translocation and IKKb.

Increased phagocytosis in the presence of enhanced M2-like macrophage responses correlates with increased primary and latent HSV-1 infection

“…Our results underscore the importance of a tightly controlled balance of M1/M2 macrophages. Although M2 macrophages are thought to be more protective and play a major role in tissue repair as is demonstrated in a cystic fibrosis model of lung injury [49]. Our study clearly shows that macrophage balance is critical to control HSV-1 primary and latent infections.…”

COVID-19: Immunology and treatment options

“…In addition to its antimicrobial properties, azithromycin is sometimes used for its immunomodulatory properties, especially in patients with chronic pulmonary disorders. Azithromycin polarizes macrophages towards an anti-inflammatory M2 phenotype, and inhibits pro-inflammatory STAT1 and NFκB signaling pathways [139,140]. In the context of anti-inflammatory effects, it is of particular interest that azithromycin is used in patients requiring intensive care for non-COVID-19 related ARDS and is associated with a significant reduction in mortality and shorter time to extubation [141][142][143].…”

Management of patients with neuromuscular disorders at the time of the SARS-CoV-2 pandemic

“…clini caltr ials.gov). Azithromycin is a macrolide antibiotic that may be able to suppress inflammation [78] and be effective as adjunctive therapy in ARDS [79]. It is now being studied as an adjunctive treatment for patients with COVID-19, with apparently positive results, but validation in randomized trials is needed [60,61].…”