In Vitro Analysis of Azithromycin's Effect on J774 Murine Macrophages Challenged with Aspergillus fumigatus: Azithromycin Improves Macrophage Response to Aspergillus fumigatus.

Background: Patients with chronic lung diseases often suffer from pulmonary aspergillosis, caused by Aspergillus fumigatus (AF). Alveolar macrophages play a key role in the initial immune response to AF. Azithromycin (AZM), commonly known for its immunomodulatory properties in reducing exacerbations and improving lung function, has mixed effects on the development of aspergillosis. While some studies suggest AZM aids AF-colonized patients, others indicate increased rates of AF colonization.

Objective: Given AZM's positive impact on host response to other pathogens, we hypothesized that it would improve immune responses to AF by modulating macrophage function. We investigated the in vitro effect of AZM on J774 murine macrophage response to Aspergillus fumigatus.

Method: The murine macrophage cell line J774 was polarized into distinct phenotypes: (1) classical M1 macrophages, generated using interferon-gamma (IFN-γ) and lipopolysaccharide (LPS); (2) azithromycin-treated M1 macrophages (hereafter referred to as M1A macrophages), generated by treating M1 cells with azithromycin in addition to IFN-γ and LPS; and (3) alternatively activated M2 macrophages, generated using interleukin-4 (IL-4), interleukin-13 (IL-13), and LPS. These polarized macrophages were then analyzed for cytokine production, fungal killing capacity, and reactive oxygen species (ROS) generation.

Results: We observed a shift in macrophage phenotype toward an anti-inflammatory-like profile in the AZM-treated group, characterized by an increased fungal killing compared to both M1- and M2-polarized groups. This was accompanied by a reduction in interleukin-6 (IL-6) cytokine production, an increase in arginase activity, without any significant change in ROS generation. Further assays confirmed that the observed increase in fungal clearance was attributable to AZM's impact on macrophages rather than any direct antifungal activity against Aspergillus fumigatus.

Conclusion: These findings suggest AZM enhances macrophage function, boosting anti-inflammatory responses and improving fungal clearance.