Effect of cigarette smoke extract on Th17 inflammation and the anti-inflammatory effect of glucocorticoids in human airway smooth muscle cells

Abstract

<b>Background:</b> Asthmatic smokers do not respond to glucocorticoids as effectively as non-smokers. Th17 cytokines play a key role in neutrophilic airway inflammation, which associated with cigarette smoking, in asthma. This study explors the effect of cigarette smoke (CS) and Th17 cytokine (IL-17A) on production of neutrophilic chemokines and whether CS can reduce the inhibitory effect of glucocorticoids on neutrophilic airway inflammation. <b>Methods:</b> CS extract (CSE) was prepared from the smoke of two research cigarettes bubbled into 20 ml of cell culture medium. HASMCs were pre-treated with and without CSE (3.5%) for 24h. Cells were then treated with fluticasone (10-11-10-6 M) for 1 hour prior to incubation with CSE, IL-17A&nbsp;(10 ng/ml), or CSE + IL17A for 24h. Neutrophilic chemokines were measured in supernantes by ELISA. <b>Results:</b> CSE stimulated production of CXCL-8, but not CXCL-1 and IL-17A, in HASMCs. CSE-induced production of CXCL-8 was sensitive to inhibition by fluticasone (IC50=0.304 nM). IL-17A induced CXCL-8 and CXCL-1 production in HASMCs and the induction of CXCL-8, but not CXCL-1, was sensitive to inhibition by fluticasone (IC50=0.05123 nM). CSE pre-treatment and IL-17A increased CXCL-8 concentration by 5.4-fold compared with IL-17A alone. CSE reduced the inhibitory effect of fluticasone on IL-17A-induced CXCL-8 production (IC50=0.6725 nM and 0.05123 nM, respectively). <b>Conclusion:</b> CS may contribute to neutrophilic airway inflammation in asthma by inducing production of neutrophil chemokines. CS may also reduce the anti-inflammatory effect of glucocorticoids on neutrophilic airway inflammation.