Cigarette smoke extract (CSE) reduces the anti-inflammatory effect of Fluticasone in human airway smooth muscle cells (HASMCs)

Background: Asthma is a chronic inflammatory lung disorder. Clinical studies suggest asthmatic smokers do not respond to the anti-inflammatory drug glucocorticoids as well as non-smokers, but whether cigarette smoke can reduce steroid sensitive in vitro is unclear. This study aims to explore whether CSE reduces the anti-inflammatory effect of fluticasone in HASMCs Methods: CSE was prepared from the smoke of two cigarettes bubbled into 20ml of cell culture medium. Confluent and growth-arrested HASMCs were pre-treated with or without CSE for 24 or 48 h, and then with Fluticasone (10-11-10-6M) for 1 h prior to incubation with TNFα (1ng/ml), CSE (3.5%), or both for 24 h. Cytokines and chemokines in the medium were measured by ELISA. IC50 of Fluticasone was calculated using GraphPad Prism Results: TNFa and CSE both induced CXCL8 and IL-6 production in HASMCs. TNFα- and CSE-induced CXCL8 was similarly inhibited by Fluticasone in a concentration-dependent manner (IC50 0.2135nM vs 0.5253nM). CSE-induced IL-6 was more sensitively inhibited by Fluticasone than TNFα-induced IL-6 (p<0.0001 by two-way ANOVA, IC50 0.0209nM vs 0.5646nM). TNFα and CSE co-treatment and 24 and 48 h CSE pre-treatment prior to TNFα treatment significantly reduced the inhibitory effect of Fluticasone on CXCL8 production compared with TNFα-induced CXCL8 production alone (p<0.0001, IC50 2.914nM vs 0.2135nM, p<0.0001, IC50 3.438nM vs 0.2135nM and p<0.0001, IC50 2.956nM vs 0.2135nM, respectively), but had no effect on TNFα-induced IL-6 production Conclusion: CSE selectively reduce the anti-inflammatory effect of fluticasone on TNFα-induced production of the neutrophil chemoattractant CXCL8 in HASMCs