Cigarette Smoke Directly Promotes Pulmonary Arterial Remodeling and Kv7.4 Channel Dysfunction

Asthma and chronic obstructive pulmonary disease are characterized by chronic airway inflammation. Studies using bronchoalveolar lavage (BAL) have shown an increased proportion of eosinophils in the BAL fluid from asthmatics compared with that from normal subjects, whereas studies of chronic obstructive pulmonary disease (COPD) have shown increased numbers of neutrophils. Induced sputum allows sampling of respiratory tract secretions from patients and control subjects, providing a noninvasive method of studying airway secretions and allowing characterization of cells and measurement of soluble markers. We investigated whether induced sputum was a useful method of studying airway fluid from patients with moderate to severe COPD and whether it could be used to compare inflammation in this condition with that in asthma. An initial reproducibility study was undertaken. Sputum was induced twice in 13 patients with severe COPD at a 14-d interval. Total and differential cell counts were carried out and were found to be reproducible over this period. Sputum was then induced in 14 patients with COPD, 23 patients with asthma, 12 healthy cigarette smokers, and 16 normal nonsmoking control subjects. We found a significant increase in neutrophils and increased concentrations of tumor necrosis factor-alpha (TNF alpha) and interleukin-8 (IL-8) in the patients with COPD compared with the smoking and nonsmoking control subjects. Interleukin-8, but not TNF alpha, was significantly higher in the COPD group than in the asthmatic group. We conclude that the cytokines TNF alpha and IL-8 may be involved in the inflammation in COPD.

The prevalence of chronic obstructive pulmonary disease (COPD) is age-dependent, suggesting an intimate relationship between the pathogenesis of COPD and aging. In this study we investigated whether the senescence of alveolar epithelial and endothelial cells is accelerated in emphysematous lungs. Samples of lung tissue were obtained from patients with emphysema, asymptomatic smokers, and asymptomatic nonsmokers. Paraffin-embedded lung tissue sections were evaluated for cellular senescence by quantitative fluorescence in situ hybridization to assess telomere shortening, and by immunohistochemistry to assess the expression of senescence-associated cyclin-dependent kinase inhibitors. Tissue sections were also immunostained for proliferating cell nuclear antigen (PCNA), surfactant protein A, and CD31. The patients with emphysema had significantly higher percentages of type II cells positive for p16INK4a and p21CIP1/WAF1/Sdi1 than the asymptomatic smokers and nonsmokers. They had also significantly higher percentages of endothelial cells positive for p16INK4a than the asymptomatic smokers and nonsmokers, and higher percentages of endothelial cells positive for p21CIP1/WAF1/Sdi1 than the asymptomatic nonsmokers. Telomere length in alveolar type II cells and endothelial cells was significantly shorter in the patients with emphysema than in the asymptomatic nonsmokers. The level of p16INK4a expression was negatively correlated with the level of PCNA expression. The level of alveolar cell senescence was positively correlated with airflow limitation. These results suggest that the senescence of alveolar epithelial and endothelial cells is accelerated in patients with emphysema. Cellular senescence may explain the abnormal cell turnover that promotes the loss of alveolar cells in emphysematous lungs.

Chronic obstructive pulmonary disease (COPD) is one of the most common causes of death worldwide. We report in an emphysema model of mice chronically exposed to tobacco smoke that pulmonary vascular dysfunction, vascular remodeling, and pulmonary hypertension (PH) precede development of alveolar destruction. We provide evidence for a causative role of inducible nitric oxide synthase (iNOS) and peroxynitrite in this context. Mice lacking iNOS were protected against emphysema and PH. Treatment of wild-type mice with the iNOS inhibitor N(6)-(1-iminoethyl)-L-lysine (L-NIL) prevented structural and functional alterations of both the lung vasculature and alveoli and also reversed established disease. In chimeric mice lacking iNOS in bone marrow (BM)-derived cells, PH was dependent on iNOS from BM-derived cells, whereas emphysema development was dependent on iNOS from non-BM-derived cells. Similar regulatory and structural alterations as seen in mouse lungs were found in lung tissue from humans with end-stage COPD. Copyright © 2011 Elsevier Inc. All rights reserved.