Investigating the effect of pretreatment with azithromycin on inflammatory mediators in bronchial epithelial cells exposed to cigarette smoke

Abstract

Purpose of the study: Macrolide therapy is effective in reducing chronic obstructive pulmonary disease (COPD) exacerbations. Our recent study has shown the effectiveness of taking azithromycin in COPD patients, not only ex-smokers but also current smokers. Beyond their anti-microbial effects, macrolides have anti-inflammatory and immunomodulatory properties. The aim of this study was to determine if pretreatment with azithromycin modulates cigarette smoke-induced inflammation in airway epithelial cells. We hypothesized that pretreatment with azithromycin decreases exacerbation frequency by modulating inflammation in human airway epithelial cells exposed to cigarette smoke. Materials and methods: BEAS-2B bronchial epithelial cells were incubated with 5% cigarette smoke extract (CSE) for 3 h, 6 h, and 24 h. Then, airway epithelial cells were pretreated with azithromycin and exposed to 5% CSE. In each stage, the expression and release of IL-6 and IL-8 mRNA were analyzed by quantitative real-time PCR (qRT-PCR) and enzyme-linked immunosorbent assay (ELISA), respectively. Results: There was a significant increase of IL-6 and IL-8 mRNA, as well as an increase in extracellular IL-8 protein following exposure to 5% CSE. When cells were pretreated with azithromycin and exposed to 5% CSE for 3 h, there was a significant dose-dependent decrease in the expression of IL-6 mRNA. A final concentration of 9 µg/mL of azithromycin was sufficient to decrease IL-6, IL-8 mRNA, and extracellular IL-8 levels. Conclusion: Pretreatment with azithromycin decreased the expression of IL-6 and IL-8 mRNA and the release of IL-8 in bronchial epithelial cells exposed to cigarette smoke. These results demonstrate the direct effect of azithromycin on inflammatory mediators in bronchial epithelial cells exposed to cigarette smoke.