Cytokine and chemokine expression in cigarette smoke-induced lung injury in guinea pigs.

The guinea pig model of cigarette smoke (CS)-induced lung injury is known to exhibit many pathophysiological similarities to chronic obstructive pulmonary disease (COPD), but the expression profiles of inflammatory mediators in the lung are poorly understood. Quantitative real-time RT-PCR was used in this study to investigate the pulmonary expression profiles of cytokine and chemokine mRNA in response to single or repeated CS exposure in guinea pigs. A single CS exposure did not induce obvious inflammatory cell infiltration into the lungs, but it led to significant increases in the mRNA expression of tumour necrosis factor-alpha, interleukin (IL)-1beta, IL-8, and monocyte chemoattractant protein (MCP)-1, and decreases in IL-5 and granulocyte-macrophage colony-stimulating factor. Repeated CS exposure induced many features of COPD, such as marked accumulation of macrophages and neutrophils, augmented protease activities, lung structural alterations and increased airway resistance, accompanied by significant increases in the mRNA expression of IL-1beta and MCP-1 and decreases in IL-2, IL-5, transforming growth factor-beta, and eotaxin. In conclusion, in guinea pigs, inflammatory mediator changes in the lungs following cigarette smoke exposure are largely similar to those reported for smokers and/or chronic obstructive pulmonary disease patients. This model will therefore be useful to further understand the pathogenesis of chronic obstructive pulmonary disease.     

Autophagy protein microtubule-associated protein 1 light chain-3B (LC3B) activates extrinsic apoptosis during cigarette smoke-induced emphysema

Chronic obstructive pulmonary disease (COPD) is a debilitating disease caused by chronic exposure to cigarette smoke (CS), which involves airway obstruction and alveolar loss (i.e., emphysema). The mechanisms of COPD pathogenesis remain unclear. Our previous studies demonstrated elevated autophagy in human COPD lung, and as a cellular and tissue response to CS exposure in an experimental model of emphysema in vivo. We identified the autophagic protein microtubule-associated protein 1 light chain-3B (LC3B) as a positive regulator of CS-induced lung epithelial cell death. We now extend these initial observations to explore the mechanism by which LC3B mediates CS-induced apoptosis and emphysema development in vivo. Here, we observed that LC3B(-/-) mice had significantly decreased levels of apoptosis in the lungs after CS exposure, and displayed resistance to CS-induced airspace enlargement, relative to WT littermate mice. We found that LC3B associated with the extrinsic apoptotic factor Fas in lipid rafts in an interaction mediated by caveolin-1 (Cav-1). The siRNA-dependent knockdown of Cav-1 sensitized epithelial cells to CS-induced apoptosis, as evidenced by enhanced death-inducing signaling complex formation and caspase activation. Furthermore, Cav-1(-/-) mice exhibited higher levels of autophagy and apoptosis in the lung in response to chronic CS exposure in vivo. In conclusion, we demonstrate a pivotal role for the autophagic protein LC3B in CS-induced apoptosis and emphysema, suggestive of novel therapeutic targets for COPD treatment. This study also introduces a mechanism by which LC3B, through interactions with Cav-1 and Fas, can regulate apoptosis.     

Exposing a deadly alliance: Novel insights into the biological links between COPD and lung cancer

Chronic obstructive pulmonary disease (COPD) affects more than 200 million people worldwide and is expected to become the third leading cause of death in 2020. COPD is characterized by progressive airflow limitation, due to a combination of chronic inflammation and remodeling of the small airways (bronchiolitis) and loss of elastic recoil caused by destruction of the alveolar walls (emphysema). Lung cancer is the most important cause of cancer-related death in the world. (Cigarette) smoking is the principal culprit causing both COPD and lung cancer; in addition, exposure to environmental tobacco smoke, biomass fuel smoke, coal smoke and outdoor air pollution have also been associated with an increased incidence of both diseases. Importantly, smokers with COPD – defined as either not fully reversible airflow limitation or emphysema – have a two- to four-fold increased risk to develop lung cancer. In this review, we highlight several of the genetic, epigenetic and inflammatory mechanisms, which link COPD and carcinogenesis in the lungs. Elucidating the biological pathways and networks, which underlie the increased susceptibility of lung cancer in patients with COPD, has important implications for screening, prevention, diagnosis and treatment of these two devastating pulmonary diseases.     

Chronic obstructive pulmonary disease and lung cancer: new molecular insights

Both chronic obstructive pulmonary disease (COPD) and lung cancer are major causes of death worldwide. In most cases this reflects cigarette smoke exposure which is able to induce an inflammatory response in the airways of smokers. Indeed, COPD is characterized by lower airway inflammation, and importantly, the presence of COPD is by far the greatest risk factor for lung cancer amongst smokers. Cigarette smoke induces the release of many inflammatory mediators and growth factors including TGF-β, EGFR, IL-1, IL-8 and G-CSF through oxidative stress pathways and this inflammation may persist for decades after smoking cessation. Mucus production is also increased by these inflammatory mediators, further linking airway inflammation to an important mechanism of lung cancer. A greater understanding of the molecular and cellular pathobiology that distinguishes smokers with lung cancer from smokers with and without COPD is needed to unravel the complex molecular interactions between COPD and lung cancer. By understanding the common signalling pathways involved in COPD and lung cancer the hope is that treatments will be developed that not only treat the underlying disease process in COPD, but also reduce the currently high risk of developing lung cancer in these patients.     

Pathogenesis of COPD. Part III. Inflammation in COPD.

Chronic obstructive pulmonary disease (COPD) is mostly caused by cigarette smoking and affects up to 25% of smokers. Air pollution and occupational exposure to dust and fumes can also induce COPD. COPD is characterised by airflow limitation that is not fully reversible and chronic inflammation of the lung. Most patients with COPD also have evidence of tissue remodelling in the smaller airways. How the different pathological features are linked remains unknown. The inflammation of the COPD lung is initially caused by cigarette smoke and the increased infiltration of immune cells into the lung, but it is not clear why the inflammation persists after smoking cessation, while other pathologies partly reverse. Furthermore, anti-inflammatory treatments are not very successful and only control the symptoms but do not cure the disease. Animal models suggest that the imbalance of proteases and antiproteases is central to the major pathologies in the COPD lung. However, this hypothesis was never fully confirmed in humans and may only explain the degenerative stage of the disease, emphysema. The role of tissue-forming cells in the pathogenesis of COPD has not been adequately studied and indicates a deregulated synthesis of growth factors and cytokines in COPD. Finally, recent studies indicate that alpha-1-antitrypsin activity plays a role in all forms of COPD.     

New concepts in the pathobiology of chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is characterized by an abnormal persistent inflammatory response to cigarette smoke. This noxious insult leads to emphysema and airway remodeling, manifested by squamous and mucous metaplasia of the epithelium, smooth muscle hypertrophy, and airway wall fibrosis. These pathologic abnormalities interact synergistically to cause progressive airflow obstruction. Although it has been accepted that the spectrum of COPD is vast, the reasons for the development of different phenotypes from the same exposure to cigarette smoke have not been determined. Furthermore, it is becoming increasingly clear that airways disease and emphysema often coexist in many patients, even with a clear clinical phenotype of either emphysema or chronic bronchitis. Recent studies have focused on the nature of the inflammatory response to cigarette smoke, the inflammatory cell lines responsible for COPD pathogenesis, and new biomarkers for disease activity and progression. New cytokines are being discovered, and the complex interactions among them are being unraveled. The inflammatory biomarker that has received the most attention is C-reactive protein, but new ones that have caught our attention are interleukin (IL)-6, tumor necrosis factor-alpha, IL-8, and IL-10. Further research should focus on how these new concepts in lung inflammation interact to cause the various aspects of COPD pathology.     

Mast cells and COPD

The pathogenesis of chronic obstructive pulmonary disease (COPD) is based on the innate and adaptive inflammatory immune response to the inhalation of toxic particles and gases. Although tobacco smoking is the primary cause of this inhalation injury, many other environmental and occupational exposures contribute to the pathology of COPD. The immune inflammatory changes associated with COPD are linked to a tissue-repair and -remodeling process that increases mucus production and causes emphysematous destruction of the gas-exchanging surface of the lung. The common form of emphysema observed in smokers begins in the respiratory bronchioles near the thickened and narrowed small bronchioles that become the major site of obstruction in COPD. The inflamed airways of COPD patients contain several inflammatory cells including neutrophils, macrophages, T lymphocytes, and dendritic cells. The relative contribution of mast cells to airway injury and remodeling is not well documented. In this review, an overview is given on the possible role of mast cells and their mediators in the pathogenesis of COPD. Activation of mast cells and mast cell signaling in response to exposure to cigarette smoke is further discussed.     

Airway inflammation in severe chronic obstructive pulmonary disease: relationship with lung function and radiologic emphysema

The lung pathology of severe chronic obstructive pulmonary disease (COPD) has been poorly investigated. We examined surgical specimens obtained from patients with severe (forced expiratory volume in 1 second [FEV(1)] = 29 +/- 3% predicted, n = 9) or mild/no airflow limitation (FEV(1) = 86 +/- 5% predicted, n = 9) and similar smoking history. With histochemical and immunohistochemical methods we quantified the structural changes and the inflammatory cells in small airways and in muscular pulmonary arteries. As compared with smokers with mild/no COPD, smokers with severe COPD had an increased number of leukocytes in the small airways, which showed a positive correlation with the radiologic score of emphysema and with the value of residual volume, and a negative correlation with the values of FEV(1) and carbon monoxide diffusing capacity. The inflammatory process was characterized by an increase in CD8(+) and CD4(+) T-lymphocytes in the airway wall and by an increase in macrophages in the airway epithelium. When all smokers were considered together, the smoking history was correlated with both the airway wall and smooth muscle thickness, suggesting that smoking itself may play a role in the development of structural changes. No structural and cellular differences were observed in pulmonary arteries between smokers with severe COPD and smokers with mild/no COPD. In conclusion, in the small airways of smokers with severe COPD, there is an increased number of leukocytes, which is correlated with reduced expiratory flow, lung hyperinflation, carbon monoxide diffusion impairment, and radiologic emphysema, suggesting a role for this inflammatory response in the clinical progression of the disease.     

Mineral particles in the human bronchial mucosa and lung parenchyma. II. Cigarette smokers without emphysema.

The effects of cigarette smoke on the microanatomic deposition and retention pattern of exogenous mineral particles is unknown. To determine how cigarette smoke affects long-term particle retention in those with minimal smoke-related disease, we selected autopsy lungs from ten smokers without evidence of emphysema at autopsy, and used analytical electron microscopy to examine exogenous mineral particle concentration in the mucosa of seven different bronchi of varying sizes and four parenchymal sites fed by those bronchi. These data were compared with values from twelve lifetime nonsmokers. Overall, total mean particle burden in the parenchyma in the smokers and nonsmokers was similar, but there was a markedly decreased particle load retained in the smokers' airways. The consistent increase in particle burden seen in nonsmokers as airways became narrower and more distant from the carina was lost in many, but not all, of the smokers, especially for particles larger than 1 micron, and this effect did not appear to depend on amount of smoking. Rare polonium particles were found but were too sparse to use as a smoke distribution marker. However, calcium-containing particles, previously suggested by us to represent calcium carbonate actually derived from the smoke, were present in greatest concentration in the larger airways and distal parenchyma. These observations indicate the following in smokers without parenchymal smoke-induced structural damage: (1) Overall, cigarette smoking disrupts the normal retention (? deposition) pattern of particles in the airways. (2) Cigarette smoking leads to markedly decreased long-term retention of exogenous mineral particles in the airways without significantly affecting overall tissue particle retention. (3) The distribution of calcium particles in the airways and parenchyma in smokers is similar to that predicted in a recently published model of smoke particle deposition, and further supports the idea that calcium-containing particles can be used as a direct tracer of smoke particle deposition. In the present study this distribution indicates that the large airways and parenchyma receive the greatest smoke deposition. (4) Within the group of smokers, some people appear resistant to the disruptive effects of smoke on particle retention patterns, whereas other people smoking comparable amounts show markedly abnormal retention patterns. The latter may have unusual sensitivity to cigarette smoke and perhaps susceptibility to smoke-induced diseases.     

Cigarette smoke-induced acute airway impairment]

Cigarette smoking has been implicated in many pulmonary disorders, including chronic bronchitis and chronic obstructive lung disease. Cigarette smoking is associated with increased airway responsiveness. Acute exposure to cigarette smoke increases airway responsiveness in a dose-dependent manner. A superoxide is involved in airway hyper-responsiveness induced by cigarette smoke, perhaps by direct toxic action. Cigarette smokers have increased numbers of neutrophils present in their lower respiratory tract. Acute exposure to cigarette smoke initiates a superoxide-dependent mechanism that, through NF-kappa B activation and IL-8 expression, induces infiltration of neutrophils into the airways in vivo. The alveolar macrophage is one potential source of NF-kappa B activation and IL-8 production after acute exposure to cigarette smoke. Manipulation of NF-kappa B by antioxidants in vivo may be useful in limiting biologic processes such as pro-inflammatory cytokine production, which may lead to neutrophil accumulation in the lung.     

慢性烟雾暴露引起小鼠肺气肿伴淋巴滤泡形成

目的 研究不同时间慢性香烟烟雾暴露对小鼠肺气肿和淋巴滤泡形成的影响.方法 6～8周龄SPF级近交系C57BL/6雌性小鼠24只,随机分组:12周暴露组、12周对照组、24周暴露组、24周对照组,观察12周和24周不同暴露时间小鼠肺气肿和肺淋巴滤泡新生情况,分析淋巴滤泡的细胞和分子构成.结果 24周烟雾暴露小鼠的肺泡破坏指数(48.28±2.01)％高于12周烟雾暴露小鼠(33.85±0.84)％,肺气肿程度加重;12周的烟雾暴露不能使肺组织形成结构成熟的淋巴滤泡,但是经24周暴露后,小鼠肺组织形成典型的淋巴滤泡.淋巴滤泡主要由大量的B细胞、CD3+T细胞、CD4+T细胞、CD8+T细胞构成,少量基质细胞和CXCL13+细胞也参与了淋巴滤泡的形成.结论 24周慢性烟雾暴露刺激可以导致小鼠肺组织结构破坏并伴淋巴滤泡形成.     

Effect of long-term cigarette smoke exposure on pulmonary vascular structure and function in the guinea pig.

To investigate the effect of chronic exposure to cigarette smoke on the structure and function of the pulmonary vasculature, we used a guinea pig model of cigarette smoke-induced emphysema, in which groups of guinea pigs were exposed to smoke for periods of 1, 3, 6, and 12 months. We found that the mean pulmonary artery pressure in smokers was increased at one month, a time at which there was no evidence of emphysema. Although the vascular pressures remained elevated, they did not progressively increase, even though there was progressive lung destruction. Pulmonary hypertension was associated with muscularization of the arterioles, seen as an increase in the percentage of small pulmonary vessels with double elastic lamina. We conclude that chronic exposure to cigarette smoke will produce pulmonary hypertension in the guinea pig, and that the hemodynamic changes are accompanied by alteration of the structure of the small pulmonary arterioles and arteries. The apparent dissociation of pulmonary hypertension and emphysema suggests that the pulmonary hypertension is not due to destruction of the lung capillary bed. The etiology of this process may be smoke-induced inflammation with release of vasoactive substances as well as proteolytic enzymes.     

Prostacyclin prevents pulmonary endothelial cell apoptosis induced by cigarette smoke

RATIONALE: Impaired endothelial cell-dependent vasodilation, inflammation, apoptosis, and proliferation are manifestations of endothelial dysfunction in chronic obstructive pulmonary disease (COPD). Prostacyclin (PGI(2)) is a major product of the cyclooxygenase pathway with potent vasodilatory and antimitogenic properties and may be relevant to endothelial dysfunction in COPD. OBJECTIVES: To determine if PGI(2) expression is altered in smoking-related lung disease and if it may be protective in COPD-associated endothelial dysfunction. METHODS: We evaluated, by immunohistochemistry, Western blotting, and polymerase chain reaction, human emphysema tissue compared with normal tissue for expression of prostacyclin synthase (PGI(2)S). We examined the effects of cigarette smoke extract (CSE) and aldehyde components on eicosanoid expression in primary human pulmonary microvascular endothelial cells. Finally, we used a murine model of lung-specific PGI(2)S overexpression and in vitro studies to determine if PGI(2) expression has protective effects on cigarette smoke-induced endothelial apoptosis. MEASUREMENTS AND MAIN RESULTS: Human emphysema lung tissue exhibited lower PGI(2)S expression within the pulmonary endothelium than in normal lung. In vitro studies demonstrated that CSE, and in particular the alpha,beta unsaturated aldehyde acrolein, suppressed PGI(2)S gene expression, whereas CSE significantly induced the upstream mediators COX-2 and cytosolic phospholipase A2 in human pulmonary microvascular endothelial cells. Mice with lung-specific PGI(2)S overexpression exhibited less endothelial apoptosis after chronic smoke exposure. In vitro, iloprost exhibited protective effects on CSE-induced apoptosis. CONCLUSIONS: PGI(2) has protective effects in the pulmonary vasculature after acute and chronic cigarette smoke exposure. An imbalance in eicosanoid expression may be important to COPD-associated endothelial dysfunction.     

氧化应激在慢性阻塞性肺疾病发生中的作用及防治策略

COPD 特征是慢性气道炎症、细小支气管重塑及肺实质破坏。研究表明,香烟烟雾等有害气体所引起的氧化应激在 COPD 发展过程起到了至关重要的作用。吸烟增强氧化应激,使氧化/抗氧化比例失衡,直接损伤肺组织,加重气道炎症反应,引起自身免疫反应,最终导致气流受限。因此,对抗氧化应激、提高宿主抗氧化能力,是 COPD 防治的最新着重点。     

Extracellular superoxide dismutase protects against pulmonary emphysema by attenuating oxidative fragmentation of ECM

Extracellular superoxide dismutase (ECSOD or SOD3) is highly expressed in lungs and functions as a scavenger of O₂^{• ─}. ECM fragmentation, which can be triggered by oxidative stress, participates in the pathogenesis of chronic obstructive pulmonary disease (COPD) through attracting inflammatory cells into the lungs. The level of SOD3 is significantly decreased in lungs of patients with COPD. However, the role of endogenous SOD3 in the development/progression of emphysema is unknown. We hypothesized that SOD3 protects against emphysema by attenuating oxidative fragmentation of ECM in mice. To test this hypothesis, SOD3-deficient, SOD3-transgenic, and WT C57BL/6J mice were exposed to cigarette smoke (CS) for 3 d (300 mg total particulate matter/m³) to 6 mo (100 mg/m³ total particulate matter) or by intratracheal elastase injection. Airspace enlargement, lung inflammation, lung mechanical properties, and exercise tolerance were determined at different time points during CS exposure or after elastase administration. CS exposure and elastase administration caused airspace enlargement as well as impaired lung function and exercise capacity in SOD3-null mice, which were improved in mice overexpressing SOD3 and by pharmacological SOD mimetic. These phenomena were associated with SOD3-mediated protection against oxidative fragmentation of ECM, such as heparin sulfate and elastin, thereby attenuating lung inflammatory response. In conclusion, SOD3 attenuates emphysema and reduces oxidative fragmentation of ECM in mouse lung. Thus, pharmacological augmentation of SOD3 in the lung may have a therapeutic potential in the intervention of COPD/emphysema.     

Cigarette smoke impairs elastin resynthesis in lungs of hamsters with elastase-induced emphysema

The severity of pulmonary emphysema can be affected by exposure to cigarette smoke in several ways. Inactivation of alpha-1-antitrypsin and recruitment of leukocytes to lung airways shifts the protease-antiprotease balance towards increased elastolytic activity. The present study demonstrates an additional effect of cigarette smoke inhalation and retardation of the repair process and of the neosynthesis of cross-linked elastin. Hamsters with elastase-induced emphysema, exposed to cigarette smoke for 1 wk immediately after elastase administration, showed a 40% reduction of 14C-lysine incorporation into the elastin-specific cross-links, desmosine, and isodesmosine. Concomitantly, there was a decrease in the level of lung lysyl oxidase to that observed in uninjured control animals, in sharp contrast to the sevenfold increase in lysyl oxidase activity in hamsters with elastase-induced emphysema recovering under atmospheric conditions. These findings suggest that impairment of the production of lysyl oxidase and the resynthesis of cross-linked elastin by smoke inhalation exacerbates alveolar destruction.     

CD8+ve cells in the lungs of smokers with chronic obstructive pulmonary disease.

Previous studies have shown an increased number of inflammatory cells and, in particular, CD8+ve cells in the airways of smokers with chronic obstructive pulmonary disease (COPD). In this study we investigated whether a similar inflammatory process is also present in the lungs, and particularly in lung parenchyma and pulmonary arteries. We examined surgical specimens from three groups of subjects undergoing lung resection for localized pulmonary lesions: nonsmokers (n = 8), asymptomatic smokers with normal lung function (n = 6), and smokers with COPD (n = 10). Alveolar walls and pulmonary arteries were examined with immunohistochemical methods to identify neutrophils, eosinophils, mast cells, macrophages, and CD4+ve and CD8+ve cells. Smokers with COPD had an increased number of CD8+ve cells in both lung parenchyma (p < 0.05) and pulmonary arteries (p < 0.001) as compared with nonsmokers. CD8+ve cells were also increased in pulmonary arteries of smokers with COPD as compared with smokers with normal lung function (p < 0.01). Other inflammatory cells were no different among the three groups. The number of CD8+ve cells in both lung parenchyma and pulmonary arteries was significantly correlated with the degree of airflow limitation in smokers. These results show that an inflammatory process similar to that present in the conducting airways is also present in lung parenchyma and pulmonary arteries of smokers with COPD.     

Time course of cigarette smoke-induced pulmonary inflammation in mice.

Inflammation of the airways and lung parenchyma plays a major role in the pathogenesis of chronic obstructive pulmonary disease. In the present study a murine model of tobacco smoke-induced emphysema was used to investigate the time course of airway and pulmonary inflammatory response, with a special emphasis on pulmonary dendritic cell (DC) populations. Groups of mice were exposed to either cigarette smoke or to control air for up to 24 weeks. In response to cigarette smoke, inflammatory cells (i.e. neutrophils, macrophages and lymphocytes) progressively accumulated both in the airways and lung parenchyma of mice. Furthermore, a clear infiltration of DCs was observed in airways (10-fold increase) and lung parenchyma (1.5-fold increase) of cigarette-exposed mice at 24 weeks. Flow cytometric analysis of bronchoalveolar lavage (BAL) DCs of smoke-exposed mice showed upregulation of major histocompatability complex II molecules and costimulatory molecules CD40 and CD86, compared with BAL DCs of air-exposed mice. Morphometric analysis of lung histology demonstrated a significant increase in mean linear intercept and alveolar wall destruction after 24 weeks of smoke exposure. In conclusion, the time course of the changes in inflammatory and dendritic cells in both bronchoalveolar lavage and the pulmonary compartment of cigarette smoke-exposed mice was carefully characterised.     

Functional significance of apoptosis in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a highly prevalent airway disease characterized by an abnormal inflammatory response of the lungs to noxious particles and gases. Cigarette smoking remains a major risk factor in COPD development. Accumulating evidence suggests that apoptosis, a regulated form of cell death, may play an important role in COPD pathogenesis. Increased numbers of apoptotic cells can be detected in lung tissue and airways of human subjects with COPD, relative to normal lungs or those from smokers without COPD. Alveolar wall destruction associated with emphysema development, may involve increased apoptosis of alveolar structural cells. Several intervention-induced apoptotic models (e.g., cigarette smoke, vascular-endothelial growth factor inhibition, and interferon-gamma) cause emphysematous changes in vitro and in vivo. Increased apoptosis in COPD can also imply defects in the normal physiological clearance of apoptotic cells. Additional factors that relate to perpetuation of the pathogenesis of COPD, including protease/antiprotease imbalance, inflammation and oxidative stress, may mutually promote apoptosis or contribute to impaired clearance of apoptotic cells. Given that cigarette smoking is the most common cause of COPD, identification of the pathways of cigarette smoke-induced apoptosis may further the understanding of COPD pathogenesis. However, apoptosis rate is not diminished after cessation of cigarette smoking, indicating that other mechanisms perpetuate apoptosis in COPD. Therefore, understanding functional relationships between apoptosis and protease/antiprotease imbalance, inflammation, oxidative stress and other factors potentially involved in COPD pathogenesis may uncover crucial therapeutic targets.