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

Abstract

Background: Airway inflammation is a hallmark of asthma disease, and cytokines play a major role in the inflammation process. Human airway smooth muscle cells (HASMCs) are considered as an important source of inflammatory cytokines and chemokines in Asthma. Inhaled corticosteroids (ICS) are used with asthmatic patients as anti-inflammatory therapy to control the severity of the disease and maintain lung function. Clinical studies suggest asthmatic smokers do not respond to steroid as well as non-smokers, but whether cigarette smoke can reduce steroid sensitive in vitro is unclear. We hypothesise that cigarette smoke extract (CSE) reduces the anti-inflammatory effect of fluticasone in HASMCs. Methods: CSE was prepared from the smoke of two cigarettes bubbled into 20 ml of cell culture medium. Confluent and growth-arrested HASMCs were pre-treated with and without CSE (3.5%) for 24 or 48 hours and then were treated with fluticasone (10-11-10-6 M) for 1 hour prior to incubation with TNFa (1 ng/ml), CSE (3.5%), or TNFa + CSE for 24 hours. Cytokines and chemokines were measured in the collected medium by ELISA. MTT assay was used to assess the cell viability. IC50 of fluticasone was calculated using GraphPad Prism. Results: We found that TNFa induced CXCL8 and IL-6 production, but not IL-5, IL-13 and VEGF production, in HASMCs. CSE also induced CXCL8 and IL-6 production. TNFa- and CSE-induced CXCL8 was similarly inhibited by fluticasone in a concentration-dependent manner (IC50 0.2135nM vs 0.5253nM). Co-treatment of TNFa and CSE reduced the inhibitory effect of fluticasone significantly on CXCL8 production compared with TNFa alone (p<0.0001 by two-way ANOVA, IC50 2.914nM vs 0.2135nM). CSE pre-treatment for 24 and 48 hours prior to TNFa treatment significantly reduced the inhibition of CXCL8 production by fluticasone compared with TNFa alone (p<0.0001, IC50 3.438nM vs 0.2135nM and p<0.0001, IC50 2.956nM vs 0.2135nM, respectively). CSE-induced IL-6 was more sensitive to inhibition by fluticasone than TNFa-induced IL-6 (p<0.0001, IC50 0.0209nM vs 0.5646nM). But co-treatment of TNFa and CSE and CSE pre-treatment for 24 and 48 hours prior to TNFa treatment had no significant effect on the inhibition of IL-6 production compared with TNFa alone (IC50 2.719nM, 0.7341nM, 0.7758nM and 0.5646nM, respectively). Conclusion: Cigarette smoke selectively reduces the anti-inflammatory effect of fluticasone on TNF-induced production of the neutrophil chemoattractant CXCL8 in HASMCs.