nitrogen-dioxide and Emphysema

Cigarette smoke is the most important cause for the development of chronic obstructive pulmonary disease (COPD). Since only a minority of smokers and some nonsmokers develop COPD, other factors must be involved as well. NO2 is an important air pollutant associated with respiratory symptoms in humans and emphysema development in animal models. We hypothesized that combined exposure to NO2 and cigarette smoke will enhance pulmonary inflammation and emphysema development. Mice were exposed to 20 ppm NO2 for 17 h/day, to 24 puffs of cigarette smoke 2 times per day, to their combination, or to control air for 5 days/wk during 4 wk. Following the last NO2 exposure and within 24 h after the last smoke exposure the mice were sacrificed. Lungs were removed and analyzed for several inflammatory parameters and emphysema. Cigarette smoke exposure increased eosinophil numbers and levels of tumor necrosis factor (TNF)-alpha, KC, monocyte chemoattractant protein (MCP)-1, and interleukin (IL)-6. NO2 exposure increased goblet cells, eosinophils, and the levels of IL-6, while it decreased the levels of IL-10. Four weeks of NO2, cigarette smoke, or their combination was not sufficient to induce significant emphysema, nor did it lead to increased numbers of lymphocytes, neutrophils, or macrophages in lung tissue. Instead, NO2 exposure attenuated the smoke-induced increases in levels of TNF-alpha, KC, and MCP-1. These dampening effects of NO2 may be due to modulating effects of NO2 on cytokine production by macrophages and epithelial cells, which have been reported earlier. The next step is to translate these findings of combined, controlled exposure in animals to the human situation.

Topics: Administration, Inhalation; Animals; Cell Count; Cytokines; Disease Models, Animal; Drug Antagonism; Drug Therapy, Combination; Emphysema; Eosinophils; Female; Inhalation Exposure; Lung; Mice; Mice, Inbred Strains; Nicotiana; Nitrogen Dioxide; Pneumonia; Smoke; Smoking

The major features of chronic obstructive pulmonary disease (COPD) comprise a not fully reversible airflow limitation associated with an abnormal inflammatory response, increased mucus production and development of emphysema-like lesions. Animal models that closely mimic these alterations represent an important issue for the investigation of pathophysiological mechanisms. Since most animal models in this area have focused on specific aspects of the disease, we aimed to investigate whether exposure of C57BL/6 mice to nitrogen dioxide (NO2) may cause a more complex phenotype covering several of the characteristics of the human disease. Therefore, mice were exposed to NO2 for 14h each day for up to 25 days. Initial dose response experiments revealed the induction of a significant inflammatory response at a dose of 20 ppm NO2. Mice developed progressive airway inflammation together with a focal inflammation of the lung parenchyma characterized by a predominant influx of neutrophils and macrophages. In addition, goblet cell hyperplasia was detected in the central airways and increased collagen deposition was found in the lung parenchyma. NO2-exposed mice developed emphysema-like lesions as indicated by a significantly increased mean linear intercept as compared to control mice. Finally, the assessment of lung functional parameters revealed the development of progressive airway obstruction over time. In conclusion, our data provide evidence that the inflammatory response to NO2 exposure is associated with increased mucus production, development of airspace enlargement and progressive airway obstruction. Thus, NO2-exposed mice may serve as a model to investigate pathophysiological mechanisms that contribute to the development of human COPD.

Topics: Animals; Bronchitis, Chronic; Bronchoalveolar Lavage Fluid; Disease Models, Animal; Dose-Response Relationship, Drug; Emphysema; Leukocyte Count; Lung; Macrophages, Alveolar; Mice; Mice, Inbred C57BL; Neutrophils; Nitrogen Dioxide; Oxidants, Photochemical; Pulmonary Disease, Chronic Obstructive; Pulmonary Ventilation; Specific Pathogen-Free Organisms

In order to quantify parenchymal, vascular and epithelial changes occurring in the exudative and organizing phase of diffuse alveolar damage (DAD) induced by inhaled NO2 groups of 7 rats were continuously exposed to 5, 10 or 20 ppm NO2 for 3 and 25 days alternatively. AgNOR analysis revealed the highest proliferative activity in the epithelium of the respiratory bronchioles. In this region already after 3d exposure to 5 ppm the maximum AgNOR number was reached. In contrast to long-term exposure after 3d exposure to 5 and 10 ppm NO2 the AgNOR number in the respiratory bronchioles was significantly higher than in central airway epithelia. After long-term exposure to 5 and 10 ppm AgNOR number decreased to normal values or showed no further significant increase, long-term exposure to 20 ppm resulted in a further increase of the AgNOR number. A significant increase of the alveolar circumference and decrease of alveolar surface density was found after an exposure to 20 ppm for 3d and long-term exposure to 10 and 20 ppm NO2, whereas the 5 ppm exposure groups disclosed no significant change of these values. Medial hypertrophy was detected after exposure to 10 and 20 ppm NO2 for 25 days, after the exposure to 5 ppm for 3d and 25d medial thickness was significantly decreased due to vasodilation induced by NO, one of the major reaction products of NO2.

Topics: Animals; Dose-Response Relationship, Drug; Emphysema; Male; Nitrogen Dioxide; Nucleolus Organizer Region; Pulmonary Alveoli; Rats; Rats, Sprague-Dawley; Reference Values; Silver; Staining and Labeling; Time Factors

In order to clarify the role of nitrogen dioxide (NO2) in the development of lung injury, male Wistar rats were exposed continuously to 0.3 or 5.0 ppm NO2 for 10, 20, 30, 60 and 90 days, and alveolar macrophages and lavage fluid obtained by bronchoalveolar lavage were examined. The results were as follows: 1) The number of alveolar macrophages increased significantly in response to NO2 exposure. Throughout the whole test period, the largest number was obtained in the group exposed to 5.0 ppm, followed by the group exposed to 0.3 ppm, and then by the control group. 2) The plasminogen activator (PA) released from alveolar macrophages was increased dose-dependently by NO2 exposure. The activities were significantly high in the groups exposed for 10 to 20 days at each concentration, and then slightly decreased at 30 days. Thereafter, activity showed a tendency to increase, reaching the maximum level on the 60th day of exposure. 3) Similarly, the fibrinolytic activity in the lavage fluid was increased dose-dependently by NO2 exposure. The maximum activity was noted on the 10th day of exposure, followed by a rapid decrease up to the 30th day, and a slight rise again between the 60th and 90th day. 4) In the group exposed to 5.0 ppm NO2, total protein in the lavage fluid increased, and the elastase inhibitory capacity (EIC) per milligram of protein decreased. In the group exposed to 0.3 ppm NO2, however, no difference from the control group was noted. These results revealed that the alveolar macrophages were affected and increased PA activity as a result of exposure to as little as 0.3 ppm NO2. This was shown to result in an increase of the fibrinolytic activity in the alveoli, leading to damage to the lung tissue. This evidence may explain the morphological findings of the appearance of emphysematous change in the lungs of rats exposed to low levels of NO2. For the detection of the effect of NO2 on the lung tissue, PA appears to be a more sensitive indicator than EIC.

Topics: Animals; Emphysema; Fibrinolysis; Macrophages; Male; Nitrogen Dioxide; Plasminogen Activators; Pulmonary Alveoli; Rats; Rats, Inbred Strains

Topics: Air; Asthma; Emphysema; Humans; Mediastinal Emphysema; Nitrogen Dioxide; Subcutaneous Emphysema; Tokyo

Exposure of rats to 150 ppm NO2 for 2 hours causes death from pulmonary oedema. Continuous exposure to 25 ppm for 150 days causes gross enlargement with loss of elastic recoil and proliferative and metaplastic epithelial changes in the vicinity of the terminal bronchioles. Continuous exposure to 2 ppm results in an initial loss of cilia and focal hyperplasia of the terminal bronchiolar epithelium, but these changes, for the most part, quickly subside. Chronic daily exposure of rats to tobacco smoke results in proliferative and metaplastic epithelial changes in the vicinity of the terminal and respiratory bronchioles. Also, both at this site and elsewhere, aggregates of golden-brown pigment-laden macrophages accumulate in the lungs. The proliferative/metaplastic changes are similar to those seen in response to NO2, asbestos and other irritant gases and particles. The aggregates of golden-brown macrophages are seemingly a special feature of the response to tobacco smoke. Some rats exposed for over two years to tobacco smoke, develop foci of squamous metaplasia, firstly in the region of terminal bronchioles, but later at points scattered throughout the lung parenchyma. Comparable changes have not been reported in rats exposed to NO2. Although no strictly comparable data for NO2 and tobacco smoke exposure are available, it is reasonable to conclude that, whereas the NO2 in tobacco smoke may contribute to the production of cuboidal/columnar metaplasia in the vicinity of terminal bronchioles, it otherwise plays little part in the aetiology of lesions in the lungs of smoke-exposed rats.

Topics: Animals; Disease Models, Animal; Emphysema; Epithelial Cells; Epithelium; Lung; Mice; Nitrogen Dioxide; Pulmonary Alveoli; Rats; Tobacco Smoke Pollution

Topics: alpha 1-Antitrypsin; Animals; Bronchi; Cricetinae; Elastin; Emphysema; Epithelium; Humans; Lung; Microscopy, Electron; Nitrogen Dioxide; Pancreatic Elastase

Topics: Coal Mining; Emphysema; Humans; Nitrogen Dioxide; Occupational Diseases

Beagle dogs (104) comprising one control and seven treatment groups were exposed 16 hours daily for 68 months to filtered air, raw or photochemically reacted auto exhaust, oxides of sulfur or nitrogen, or their combinations. After a further 32 to 36 months in clean air, morphologic examination of lungs by light microscopy, scanning electron microscopy, and transmission electron microscopy revealed two important exposure-related lesions. They were enlargement of air spaces in proximal acinar regions, with and without increases in the number and size of interalveolar pores, and hyperplasia of nonciliated bronchiolar cells. Proximal enlargment of air spaces was most severe, both subjectively and morphometrically, in those dogs exposed to oxides of nitrogen, oxides of sulfur, or oxides of sulfur with photochemically reacted auto exhause. In contrast, hyperplasia of nonciliated bronchiolar cells was most severe in dogs exposed to raw auto exhaust alone or with oxides of sulfur. The air space enlargement and hyperplasia of bronchiolar epithelium correlated with functional impairment reported as occurring in these dogs. Foci of ciliary loss with and without squamous metaplasia were occasionally observed in trachea and bronchi. The observations indicate that enlargement of proximal acinar air spaces with some loss of interalveolar septa can develop in the absence of alveolar fenestrations. The persistnt nature of bronchiolar cell proliferations in such circumstances was also demonstrated. Two major toxicologic implications are (1) the production of permanent lung damage by much lower concentrations of pollutants than previously reported and (2) the apparent lack of additive or synergistic effects between oxidant gases and sulfur oxides.

Topics: Air Pollutants; Animals; Atmosphere Exposure Chambers; Bronchi; Dogs; Emphysema; Hyperplasia; Lung; Male; Metaplasia; Nitric Oxide; Nitrogen Dioxide; Organ Size; Pulmonary Alveoli; Sulfur Oxides; Total Lung Capacity; Trachea; Vehicle Emissions

Normal lung architecture of the rat, mouse, hamster, horse, and human was compared to that of emphysematous lungs from the same species by utilizing a light microscope and a scanning electron microscope (SEM). The results obtained by SEM examination of normal and emphysematous lungs corresponded to those obtained with the light microscope. However, the SEM provided a view of alveoli and airway morphology not obtainable with the light microscope. Because of the variability in pore size and number of pores per alveolus, a pore-to-alveolus ratio was determined with the SEM on the normal lungs of the above species plus the rabbit, dog, guinea pig, and rhesus monkey. Depending on the extent of other pathways for collateral ventilation, differences in number of pores per alveolus may affect a species' susceptibility to a given mechanism in the genesis of spontaneous or induced emphysema. The small number of pores per alveolus in the rat, mouse, rabbit, and hamster suggests that they would not be responsible for emphysematous changes. Pores do appear to be involved in human and horse emphysema.

Topics: Aged; Animals; Cricetinae; Dogs; Emphysema; Guinea Pigs; Haplorhini; Horses; Humans; Lung; Male; Mice; Microscopy, Electron, Scanning; Nitrogen Dioxide; Pulmonary Alveoli; Rabbits; Rats; Species Specificity

Topics: Animals; Edema; Emphysema; Histological Techniques; Lung; Lung Diseases; Nitrogen Dioxide; Organ Size; Pulmonary Alveoli; Rats; Smoking

Topics: Animals; Emphysema; Nitrogen Dioxide; Rats; Respiratory Function Tests

Topics: Emphysema; Nitrogen; Nitrogen Dioxide; Pulmonary Emphysema; Rats; Research; Toxicology

Topics: Animals; Autoantibodies; Emphysema; Guinea Pigs; Nitrogen; Nitrogen Dioxide; Pulmonary Emphysema; Research; Toxicology