Synergistic Effects of Erythromycin and Budesonide on the Mitigation of Tracheal Stenosis through Transformation of the Macrophage Phenotype and Upregulation of HDAC2

Abstract Objective: We investigated the molecular mechanisms of the combination of erythromycin and budesonide for the treatment for tracheal stenosis (TS). Methods: The rabbit animal model of TS was established by scraping the inner wall of the trachea. and treated with erythromycin or budesonide afterwards. The treatment effects were evaluated by histological measurement. We quantify the mRNA expression of the M1 and M2 macrophage markers by quantitative PCR and the protein expression of histone deacetylase 2 (HDAC2) by western blotting. We used RAW264.7 cells simulated with lipopolysaccharide and interleukin 4 to determine if erythromycin and budesonide can promote the transformation of macrophages by using flow cytometry. M1/M2 macrophages and fibroblasts were co-cultured, and alpha smooth muscle actin (α-SMA) was detected by immunofluorescence. Results: The rabbit TS model showed the formation of stenosis in the tracheal tissue, and the thickness of the tracheal mucosa and submucosa was significantly increased. These histological changes were recovered in the treatment groups, with the most recovery occurring with combination treatment of erythromycin and budesonide. The mRNA expression of iNOS, CD206, CD163, and Arg1 and the protein expression of HDAC2 were increased in the treated groups. In vitro , erythromycin combined with budesonide transformed naïve macrophages to M2 macrophages, and the ratio of M1 and M2 macrophages tended to be 1.0. The expression level of α-SMA was decreased in the co-culture of M1 and M2 with fibroblasts. Conclusion: Erythromycin combined with budesonide can regulate the phenotype transformation of macrophages by upregulating HDAC2 and improving stenosis after tracheal injury.