The effects of dexamethasone on cigarette smoke induced gene expression changes in COPD macrophages

Chronic obstructive pulmonary disease (COPD) is a smoking related inflammatory airway disease in which macrophages play a key role. Previously we have shown that cigarette smoke extract (CSE) causes suppression of macrophage inflammatory mediators, with the exception of IL-8. We now investigate the effects of dexamethasone on these gene expression changes. Monocyte derived macrophages (MDMs) were cultured with CSE and dexamethasone. Microarray analysis was used to assess inflammatory mediator regulation, with qPCR and ELISA also performed for selected cytokines. The major effect of CSE was down-regulation of inflammatory genes (11 probe sets). For CSE regulated genes (n = 13), the median fold change with CSE alone was − 2.84 and with dexamethasone alone was − 2.97. Both treatments combined caused the greatest suppression of gene expression; − 4.47. qPCR also showed that IL-1β, GM-CSF and IL-6 mRNA levels were significantly reduced by CSE and further suppressed by dexamethasone. qPCR and ELISA showed that IL-8 levels were increased by CSE, with suppression by dexamethasone. We show that CSE suppressed the expression of some inflammatory genes whilst up-regulating IL-8. Dexamethasone further suppressed gene expression when combined with CSE. The combined effect of GC and CSE causes suppression of the macrophage innate immune response.