The non-antibiotic macrolide EM900 attenuates HDM and poly(I:C)-induced airway inflammation with inhibition of macrophages in a mouse model

Objective Macrolides have been reported to reduce the exacerbation of severe asthma. The aim of this study was to clarify the effects and mechanisms of EM900, a non-antibiotic macrolide, on allergic airway inflammation. Methods Mice were sensitized and challenged by house dust mite (HDM), then exposed to polyinosinic-polycytidylic acid (poly(I:C)) as a model of asthma complicated with viral infection. Mice were administered with EM900. Airway inflammation was assessed from inflammatory cells in bronchoalveolar lavage fluid (BALF) and cytokines in lung tissues. Lung interstitial macrophages were counted by flow cytometry. Cytokine production, phosphorylation of NF-kappa B, and p38 in macrophages were examined by ELISA and western blotting. Results Counts of cells in BALF and concentrations of IL-13, IL-5, RANTES, IL-17A, and MIP-2 were significantly decreased by EM900 compared to those without EM900. Percentages of lung interstitial macrophages were significantly decreased with EM900. Concentrations of IL-6, RANTES, and MIP-2 induced by HDM and poly(I:C) were significantly suppressed by EM900 through the suppression of NF-kappa B and p38 phosphorylation in macrophages. Conclusions HDM and poly(I:C)-induced airway inflammation is attenuated by EM900 with the inhibition of lung interstitial macrophages. Clinical use of EM900 is expected, because EM900 has inhibitory effects against airway inflammation without inducing bacterial drug resistance.