A Distinctive Alveolar Macrophage Activation State Induced by Cigarette Smoking

Abstract

Rationale: Macrophages are believed to play a central role in emphysema based largely on data from mouse models. However, the relevance of these models to smoking-related lung disease in humans is uncertain. Objectives: We sought to comprehensively characterize the effects of smoking on gene expression in human alveolar macrophages and to compare these with effects seen in transgenic mouse models of emphysema. Methods: We used DNA microarrays with genomewide coverage to analyze alveolar macrophages from 15 smokers, 15 nonsmokers, and 15 subjects with asthma (disease control). Selected gene expression changes were validated by polymerase chain reaction and ELISA. Expression changes were compared with those identified by microarray analysis of interleukin-13-overexpressing and integrin-␤6-deficient mice, which both develop emphysema. Measurements and Main Results: All 15 smokers shared a common pattern of macrophage gene expression that distinguished them from nonsmokers, a finding not observed in subjects with asthma. We identified 110 genes as differentially expressed in smokers despite using conservative statistical methods. Matrix metalloproteinase 12, a proteinase that plays a critical role in mouse models, was the third most highly induced gene in smokers (ninefold, p Ͻ 0.0001). However, most changes in smokers were not reflected in mouse models. One such finding was increased osteopontin expression in smokers (fourfold, p ϭ 0.006), which was confirmed at the protein level and correlated with the degree of airway obstruction. Conclusions: Smoking induces a remarkably consistent and distinctive pattern of alveolar macrophage activation. These studies identify aspects of mouse models that are directly relevant to human smokers and also reveal novel potential mediators of smokingrelated diseases.Keywords: gene expression profiling; matrix metalloproteinases; osteopontin; pulmonary emphysemaThere are an estimated 1.3 billion habitual cigarette smokers worldwide (1) and 46 million adult smokers in the United States (2). Smoking-related lung diseases include chronic obstructive pulmonary disease (COPD), which comprises emphysema, chronic bronchitis, and small airway disease (3), as well as several interstitial lung diseases (4). Cigarette smoke induces inflammation, oxidative stress, and tissue injury in the respiratory tract (5). Among the inflammatory changes observed in smokers are changes in the number (6) and function (7, 8) of alveolar macrophages.How human alveolar macrophages may contribute to the development of emphysema in habitual smokers is a topic of ongoing investigation. The expression and/or function of several proteinases, including matrix metalloproteinase 1 (MMP-1), MMP-2, MMP-9, and MMP-14 (9-15) and cathepsins L and C (16-18), have been found to be increased in studies of smokers and subjects with COPD, and polymorphisms in the MMP1 and MMP12 genes have been associated with decline in lung function in smokers (19). These data suggest that macrophages may contribute to emphysema through product...

Essential Role of Osteopontin in Smoking-Related Interstitial Lung Diseases

“…OPN concentrations in BALF reflected the find- However, OPN levels in BALF were just above the detection limit of the ELISA system, and therefore have to be interpreted cautiously. Microarray studies already suggested increased OPN expression in smokers, 13,21 but this is the first study showing a clear link between OPN and smoking-related interstitial lung disease.…”

“…13,21 Smoking-related interstitial lung diseases are characterized by macrophage accumulation and fibrotic remodeling of the lung. [1][2][3] There is a clear link between cigarette smoke and induction of these diseases, however the responsible substances in cigarette smoke need to be identified.…”

“…Total RNA was reversetranscribed with StrataScript RT (Stratagene, CA) using oligo (dT) [12][13][14][15][16][17][18] …”

“…9 -11 It was shown that concentrations of granulocyte-macrophage colony stimulating factor (GMCSF) in patients with PLCH are increased, 12 but the mechanisms that lead to the expansion of the pulmonary macrophage pool and fibrosis in smokers are poorly understood. [1][2][3] Based on the findings of a microarray study, Woodruff et al 13 have recently proposed that alveolar macrophages from smokers exhibit a distinctive macrophage activation state that is accompanied by increased OPN expression. Osteopontin is a glycoprotein found in the extracellular matrix of bone.…”

Osteopontin: Role in immune regulation and stress responses

“…OPN has been identified as a biomarker for various types of cancers and inflammatory diseases (Rangaswami et al, 2006;Ramaiah and Rittling, 2007). Excessive or dysregulated OPN expression has been linked to the pathogenesis of both autoimmune disorders such as multiple sclerosis (Steinman et al, 2002), systemic lupus erythematosus (Zandman-Goddard and Shoenfeld, 2003), rheumatoid arthritis (Xu et al, 2005), atherosclerosis (Ohsuzu, 2004) and other inflammatory diseases including cardiovascular disease , chronic obstructive pulmonary disease (Woodruff et al, 2005), inflammatory bowl disease (Gassler et al, 2002), and asthma (Xanthou et al, 2007).…”