Differential gene expression analysis in human monocyte-derived macrophages: impact of cigarette smoke on host defence.

Alveolar macrophages have been implicated in the pathophysiology of chronic obstructive pulmonary disease (COPD). In this setting they are routinely exposed to cigarette smoke and a range of pathogens including bacteria and viruses. The gene expression changes that result from these challenges may contribute to the initiation and progression of the disease. Understanding such changes is therefore of great interest and could aid the discovery of novel therapeutics. To study this, we stimulated monocyte-derived macrophages (MDM) from smokers and non-smokers with either cigarette smoke extract (CSE) or bacterially derived lipopolysaccharide (LPS) and profiled global transcriptional changes using Affymetrix arrays. LPS and CSE stimulation elicited markedly different transcriptome profiles with the former agent producing a larger number of significant changes. The CSE evoked changes showed some overlap with those observed when comparing habitual smokers with non-smokers, although the latter changes were generally of a more subtle nature. Detailed pathway analyses indicated that a number of genes involved in host defence were regulated following CSE stimulation and in MDM from smokers. In particular the interferon gamma (IFNgamma)-signalling pathway was significantly down-regulated following CSE stimulation, a finding that was confirmed by RT-PCR analysis. Furthermore, these changes were associated with suppressed release of the IFNgamma-induced chemokines, CXCL10 and CXCL9 from CSE treated MDM. In summary, our data provides evidence that smoking alters key mechanisms of host defence in macrophages. Such changes may explain the increased susceptibility of COPD patients to the lung infections that are associated with exacerbations of this disease.

Primary human alveolar type II epithelial cell chemokine release: effects of cigarette smoke and neutrophil elastase.

An early response to cigarette smoke is an influx of leukocytes into the lung. Alveolar epithelial type II (ATII) cells may contribute by releasing chemokines in response to cigarette smoke and neutrophil elastase (NE). Human ATII cells were purified from normal regions of lungs resected for carcinoma (n = 14). In vitro, these cells exhibited ATII cell characteristics: lamellar bodies, apical microvilli, tight junctions, and expressed surfactant apoprotein C. Basal ATII cell release of five chemokines ranked as follows: monocyte chemotactic protein (MCP)-1 > interleukin (IL)-8 > growth-related oncogene (GRO)-alpha > macrophage inflammatory protein (MIP)-1alpha > regulated on activation, normal T cell expressed and secreted (RANTES). MIP-1alpha and RANTES were often not detectable. After stimulation with a mixture of lipopolysaccharide/endotoxin (LPS), tumor necrosis factor-alpha, IL-1beta, and IFN-gamma, MCP-1 and IL-8 secretion rose 4-6-fold, whereas GRO-alpha rose 25-fold. NE stimulated IL-8 mRNA expression, and 10nM NE stimulated IL-8 secretion; however, 100 nM NE caused a decrease in extracellular IL-8, MCP-1, and GRO-alpha, attributed to proteolysis. Cigarette smoke extract (CSE) inhibited IL-8 mRNA expression and release of all chemokines. Glutathione protected against the effects of CSE, suggesting oxidative mechanisms. GRO-alpha, important in growth and repair, was sensitive to both stimulation, by LPS:cytokines, and inhibition, by CSE. Thus, contrary to the original hypothesis, high concentrations of NE and CSE resulted in reduced extracellular chemokine levels. We hypothesize that reduced ATII cell-derived chemokine levels compromise alveolar repair, contributing to cigarette smoke-induced alveolar damage and emphysema.