Distribution and levels of alpha-1-antitrypsin in the lung and plasma in smokers and chronic obstructive pulmonary disease.

Our recent non-biased proteomic screening study revealed elevated SerpinA1 i.e. alpha-1-antitrypsin (AAT) levels in induced sputum of smokers with Chronic obstructive pulmonary disease (COPD). This study was designed to further investigate the role of AAT in smokers and subjects with COPD. The expression/distribution of AAT was studied by immunohistochemistry/digital image morphometry in the lung, by Western blot in the lung and sputum, and by ELISA in the plasma at baseline (n = 349) and after a 2-year follow-up (n = 58). AAT was localized mainly in airway and alveolar epithelium and endothelium, especially in smokers and in those with COPD. AAT was elevated in smokers and in subjects with COPD in the lung endothelial cells. Total lung AAT immunoreactivity was elevated in subjects with moderate COPD compared with smokers and with non-smokers. AAT showed elevated tendency in sputum of smokers with COPD compared with 'healthy' smokers. Plasma AAT levels were elevated in smokers with/without COPD compared with non-smokers. In the follow-up, plasma AAT concentrations decreased significantly after quitting smoking. Chronic smoking/COPD leads to AAT elevation especially in the endothelium of the lung periphery; these changes reflect only modestly to the AAT in sputum, while plasma AAT significantly reflects smoking-related systemic manifestations, and decreases after smoking cessation.

Sputum proteomics identifies elevated PIGR levels in smokers and mild-to-moderate COPD.

Chronic obstructive pulmonary disease (COPD) is one of the leading causes of morbidity and mortality around the world. However, the exact mechanisms leading to COPD and its progression are still poorly understood. In this study, induced sputum was analyzed by cysteine-specific two-dimensional difference gel electrophoresis (2D-DIGE) coupled with mass spectrometry to identify proteins involved in COPD pathogenesis. The comparison of nonsmokers, smokers, and smokers with moderate COPD revealed 15 changed proteins with the majority, including polymeric immunoglobulin receptor (PIGR), being elevated in smokers and subjects with COPD. PIGR, which is involved in specific immune defense and inflammation, was further studied in sputum, lung tissue, and plasma by Western blot, immunohistochemistry/image analysis, and/or ELISA. Sputum PIGR was characterized as glycosylated secretory component (SC). Lung PIGR was significantly elevated in the bronchial and alveolar epithelium of smokers and further increased in the alveolar area in mild to moderate COPD. Plasma PIGR was elevated in smokers and smokers with COPD compared to nonsmokers with significant correlation to obstruction. In conclusion, new proteins in smoking-related chronic inflammation and COPD could be identified, with SC/PIGR being one of the most prominent not only in the lung but also in circulating blood.