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Background: The etiology of Parkinson's disease (PD) remains unknown. To approach the issue of PD's risk factors from a new perspective, we hypothesized that coupling the geographic distribution of PD with spatial statistics may provide new insights into environmental epidemiology research. The aim of this case-control study was to examine the spatial dependence of PD prevalence in the Canton of Geneva, Switzerland (population = 474,211)., Methods: PD cases were identified through Geneva University Hospitals, private neurologists and nursing homes medical records (n = 1115). Controls derived from a population-based study (n = 12,614) and a comprehensive population census dataset (n = 237,771). All individuals were geographically localized based on their place of residence. Spatial Getis-Ord Gi* statistics were used to identify clusters of high versus low disease prevalence. Confounder-adjustment was performed for age, sex, nationality and income. Tukey's honestly significant difference was used to determine whether nitrogen dioxide and particulate matters PM 10 concentrations were different within PD hotspots, coldspots or neutral areas., Results: Confounder-adjustment greatly reduced greatly the spatial association. Characteristics of the geographic space influenced PD prevalence in 6% of patients. PD hotspots were concentrated in the urban centre. There was a significant difference in mean annual nitrogen dioxide and PM 10 levels (+3.6 μg/m3 [p < 0.001] and +0.63 μg/m3 [p < 0.001] respectively) between PD hotspots and coldspots., Conclusion: PD prevalence exhibited a spatial dependence for a small but significant proportion of patients. A positive association was detected between PD clusters and air pollution. Our data emphasize the multifactorial nature of PD and support a link between PD and air pollution., (Copyright © 2021 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Background: Ambient air pollution can contribute to the development and exacerbation of COPD. However, the influence of air pollution on objective COPD phenotypes, especially from imaging, is not well studied. We investigated the influence of long-term exposure to air pollution on lung function and quantitative imaging measurements in a Korean cohort of participants with and without COPD diagnosis., Methods: Study participants (N = 457 including 296 COPD cases) were obtained from the COPD in Dusty Areas (CODA) cohort. Annual average concentrations of particulate matter less than or equal to 10 μm in diameter (PM 10 ) and nitrogen dioxide (NO 2 ) were estimated at the participants' residential addresses using a spatial air pollution prediction model. All the participants underwent volumetric computerized tomography (CT) and spirometry measurements and completed survey questionnaires. We examined the associations of PM 10 and NO 2 with FVC, FEV 1 , emphysema index, and wall area percent, using linear regression models adjusting for age, gender, education, smoking, height, weight, and COPD medication., Results: The age of study participants averaged 71.7 years. An interquartile range difference in annual PM 10 exposure of 4.4 μg/m 3 was associated with 0.13 L lower FVC (95% confidence interval (CI), - 0.22- -0.05, p = 0.003). Emphysema index (mean = 6.36) was higher by 1.13 (95% CI, 0.25-2.02, p = 0.012) and wall area percent (mean = 68.8) was higher by 1.04 (95% CI, 0.27-1.80, p = 0.008). Associations with imaging phenotypes  were not observed with NO 2 ., Conclusions: Long-term exposure to PM 10 correlated with both lung function and COPD-relevant imaging phenotypes in a Korean cohort.

The effect of the tetrapeptide bronchogen on the structural and functional state of the bronchial epithelium and inflammatory activity in the lungs was studied in the chronic obstructive pulmonary disease (COPD) model, created in rats by a 60-day intermittent exposure to nitrogen dioxide. The cell composition and cytokine-enzyme profile of bronchoalveolar lavage fluid (BALF), the content of secretory immunoglobulin A and surfactant protein B in BALF were determined. Following the course of peptide treatment the decreased activity of neutrophilic inflammation with the normalization of cellular composition and profile of pro-inflammatory cytokines and enzymes in the bronchoalveolar space was observed. The structure of bronchial epithelium, disturbed during formation of COPD model, was restored and accompanied by restoration of its functional activity as evidenced by an increase of secretory immunoglobulin A (local immunity marker) and surfactant protein B, responsible for reducing the alveolar surface tension.

In model of chronic obstructive pulmonary disease induced in rats by 60-day intermittent exposure to nitrogen dioxide mast cells participation in the mechanism of bronchial smooth muscle contractile activity patterns was evaluated. Since the 31st day, one group of rats was inhaled with sodium cromoglycate every day before the nitrogen dioxide exposure to stabilize the mast cell membrane. The other group (control) hasn’t been treated. Isometric contraction of the bronchial isolated preparations in response to nerve or smooth muscle stimulation were determined. Inhibition of mast cell degranulation and the release of endogenous histamine by stabilizing cell membranes prevented the development of bronchial smooth muscle hyperactivity caused by prolonged inhalation of nitrogen dioxide. It is believed that a mechanism to increase the contractile activity of the bronchial wall smooth muscles is mediated by activation of the transmembrane adenosine receptor in resident mast cells, leading to their partial degranulation with release of histamine, acting on the histamine Hl-receptors with the launch of reflex pathways through intramural ganglion neurons.

Uremic pruritus (UP), also known as chronic kidney disease-associated pruritus, is a common and disabling symptom in patients undergoing maintenance hemodialysis (MHD). The pathogenesis of UP is multifactorial and poorly understood. Outdoor air pollution has well-known effects on the health of patients with allergic diseases through an inflammatory process. Air pollution-induced inflammation could occur in the skin and aggravate skin symptoms such as pruritus or impair epidermal barrier function. To assess the role of air pollutants, and other clinical variables on uremic pruritus (UP) in HD patients, we recruited 866 patients on maintenance HD. We analyzed the following variables for association with UP: average previous 12-month and 24-month background concentrations for nitrogen dioxide (NO2) and carbon monoxide (CO), and suspended particulate matter of <2.5 μm (PM2.5). In a multivariate logistic regression, hemodialysis duration, serum ferritin levels, low-density lipoprotein levels, and environmental NO2/CO levels were positively associated with UP, and serum albumin levels were negatively associated with UP. This cross-sectional study showed that air pollutants such as NO2 and CO might be associated with UP in patients with MHD.

Effect of mast cell degranulation blockade on the inflammatory response and character of the lung tissue structure-functional changes were evaluated in the chronic obstructive pulmonary disease model produced in rats by 60-day intermittent exposure to nitrogen dioxide. The membrane stabilizer sodium cromoglicate was used to blockade of mast cell degranulation. Lung tissue sections were stained with toluidine blue to identify mast cells. Bronchoalveolar lavage fluid (BALF) cytogram was determined. The levels of mast cell tryptase and chymase, proinflammatory cytokine TNF-α, surfactant protein B were measured in BALF. Suppression of mast cell degranulation prevented the release of proteases in the bronchoalveolar space and reduced activity of the inflammatory process. The influx of inflammatory cells and TNF-α concentration decreased. There was no interstitial inflammatory infiltration. Bronchoalveolar epithelium structure was recovered that is the basis of its functional usefulness. The results confirm the active involvement of mast cells in the development of the inflammatory process in obstructive pulmonary diseases and allow us to consider them as a possible therapeutic target.

Background: Traffic-related air pollution may contribute to cardiovascular morbidity. In urban areas, exposures during physical activity are of interest owing to increased breathing rates and close proximity to vehicle emissions., Methods: We conducted a cross-over study among 53 healthy non-smoking women in Montreal, Canada during the summer of 2013. Women were exposed to traffic pollutants for 2-hours on three separate occasions during cycling on high and low-traffic routes as well as indoors. Personal air pollution exposures (PM(2.5), ultrafine particles (UFP), black carbon, NO₂, and O₃) were evaluated along each route and linear mixed-effects models with random subject intercepts were used to estimate the impact of air pollutants on acute changes in blood pressure, heart rate variability, and micro-vascular function in the hours immediately following exposure. Single and multi-pollutant models were examined and potential effect modification by mean regional air pollution concentrations (PM(2.5), NO₂, and O₃) was explored for the 24-hour and 5-day periods preceding exposure., Results: In total, 143 exposure routes were completed. Each interquartile increase (10,850/cm³) in UFP exposure was associated with a 4.91% (95% CI: -9.31, -0.512) decrease in reactive hyperemia index (a measure of micro-vascular function) and each 24 ppb increase in O₃ exposure corresponded to a 2.49% (95% CI: 0.141, 4.84) increase in systolic blood pressure and a 3.26% (95% CI: 0.0117, 6.51) increase in diastolic blood pressure 3-hours after exposure. Personal exposure to PM(2.5) was associated with decreases in HRV measures reflecting parasympathetic modulation of the heart and regional PM(2.5) concentrations modified these relationships (p < 0.05). In particular, stronger inverse associations were observed when regional PM(2.5) was higher on the days prior to the study period. Regional PM(2.5) also modified the impact of personal O₃ on the standard deviation of normal to normal intervals (SDNN) (p < 0.05): a significant inverse relationship was observed when regional PM(2.5) was low prior to study periods and a significant positive relationship was observed when regional PM(2.5) was high., Conclusion: Exposure to traffic pollution may contribute to acute changes in blood pressure, autonomic and micro-vascular function in women. Regional air pollution concentrations may modify the impact of these exposures on autonomic function.

In vitro models are promising approaches to investigate the adverse effects and the mode of action of air pollutants on the respiratory tract. We designed a dynamic system that allows the single or repeated exposure of cultured cells to two major indoor air gaseous pollutants, formaldehyde (HCHO) and nitrogen dioxide (NO2), alone or as a mixture. In this system, the Calu-3 human bronchial epithelial cell line was exposed at the air-liquid interface (ALI) or submerged by culture medium to synthetic air or to target concentrations of HCHO and/or NO2 once or on 4 consecutive days before assessment of cell viability and necrosis, IL-6 and IL-8 release and trans-epithelial electrical resistance. Our data showed that whereas the ALI method can be used for single short-term exposures only, the submerged method provides the possibility to expose Calu-3 cells in a repeated manner. As well, we found that repeated exposures of the cells to HCHO and NO2 at concentrations that can be found indoors triggered a significant decrease in cell metabolism and an increase in IL-8 release that were not evoked by a single exposure. Thus, our work highlights the fact that the development of systems and methods that allow repeated exposures of cultured cells to gaseous compounds in mixtures is of major interest to evaluate the impact of air pollution on the respiratory tract., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

A method for experimental reproduction of stages of chronic obstructive pulmonary disease formation (from acute inflammation to bronchopulmonary tissue restructuring characteristic of this disease) is presented. Lung injury and inflammation were induced by nitrogen dioxide. Hyperplasia and hypersecretion of goblet cells, squamous cell metaplasia of the ciliary epithelium, emphysema, and focal fibrosis served as the morphological substrate for the formation of bronchial obstruction. The adequacy of the model is confirmed by signs characteristic of chronic obstructive pulmonary disease: hyperexpression of CD3 lymphocytes in the bronchial wall and parenchyma, manifold increased production of TNFα and TGFβ, high concentrations of circulating pathogenic immune complexes. Persistence of the structural and functional shifts throughout 6 months after exposure to nitrogen dioxide indicated a chronic course of the resultant pathological process.

Development of chronic obstructive pulmonary disease (COPD) involves not only the bronchial and respiratory areas of the lungs, but also the system of pulmonary circulation, which begins with the defeat of capillary blood flow. One of radiological methods of studying lung microcirculatory functions is perfusion scintigraphy. We designed the technique of radiological examination and identified its abilities in determination of the role of vascular dysfunctions in experimental model of development of COPD. We assessed the results of pharmacological agents that affect the microcirculatory bed of the lungs and smooth muscles of pulmonary arteries in rats. Studies have shown the promise of the possibility of using the drug sulodexide for studying impaired endothelial function in clinical practice.

Smoke from forest fires contains significant amounts of gaseous and particulate pollutants. Firefighters exposed to wildland fire smoke can suffer from several acute and chronic adverse health effects. Consequently, exposure data are of vital importance for the establishment of cause/effect relationships between exposure to smoke and firefighter health effects. The aims of this study were to (1) characterize the relationship between wildland smoke exposure and medical parameters and (2) identify health effects pertinent to wildland forest fire smoke exposure. In this study, firefighter exposure levels of carbon monoxide (CO), nitrogen dioxide (NO₂), and volatile organic compounds (VOC) were measured in wildfires during three fire seasons in Portugal. Personal monitoring devices were used to measure exposure. Firefighters were also tested for exhaled nitric oxide (eNO) and CO before and after their firefighting activities. Data indicated that exposure levels during firefighting activities were beyond limits recommended by the Occupational Exposure Standard (OES) values. Medical tests conducted on the firefighters also indicated a considerable effect on measured medical parameters, with a significant increase in CO and decrease in NO in exhaled air of majority of the firefighters.

Numerous studies have focused on the effects of exposure to air pollution on health; however, certain subsets of the population tend to be more exposed to such pollutants depending on their social or demographic characteristics. In addition, exposure to toxicants during pregnancy may play a deleterious role in fetal development as fetuses are especially vulnerable to external insults. The present study was carried out within the framework of the INMA (Infancia y Medio Ambiente or Childhood and the Environment) multicenter cohort study with the objective of identifying the social, demographic, and life-style factors associated with nitrogen dioxide (NO(2)) exposure in the subjects in the cohort. The study comprised 785 pregnant women who formed part of the INMA cohort in Valencia, Spain. Outdoor levels of NO(2) were measured at 93 sampling sites spread over the study area during four different sampling periods lasting 7 days each. Multiple regression models were used for mapping outdoor NO(2) throughout the area. Individual exposure was assigned as: 1) the estimated outdoor NO(2) levels at home, and 2) the average of estimated outdoor NO(2) levels at home and work, weighted according to the time spent in each environment. The subjects' socio-demographic and life-style information was obtained through a questionnaire. In the multiple linear analyses, the outdoor NO(2) levels assigned to each home were taken to be the dependent variable. Other variables included in the model were: age, country of origin, smoking during pregnancy, parity, season of the year, and social class. These same variables remained in the model when the dependent variable was changed to the NO(2) levels adjusted for the subjects' time-activity patterns. We found that younger women, those coming from Latin American countries, and those belonging to the lower social strata were exposed to higher NO(2) levels, both as measured outside their homes as well as when time-activity patterns were taken into account. These subgroups also have a higher probability of being exposed to NO(2) levels over 40 μg/m(3), which is the annual limit for maximum safe exposure, as established by European Directive 2008/50/EC., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Objective: To establish the rats model of acute pulmonary edema induced by inhalation of high concentrations of nitrogen dioxide (NO2)., Methods: 38 SD rats were divided into the experimental group (n = 30) and the control group (n = 8). 30 rats in the experimental group were exposed to (6747.47 ± 25.24) mg/m(3) NO2 in the exposure system. At the time point of 6, 12, 18, 24 h, chest X-ray examination was taken for the experimental group. And at each time point, 6 rats were sacrificed after taking blood samples. After sacrificing, the lung of rats was taken for pathological examination and calculated lung wet/dry weight ratio. Erythrocyte superoxide dismutase (SOD) activity and plasma atrial natriuretic peptide (ANP) concentration of blood samples were detected., Results: Acute pulmonary edema was successfully induced by exposure to NO2 in 30 rats within 24 hours. There were some cloudy shadows without clear edge on the chest X-ray. To the time point of 12 hours, shadows combined with each other, and to the time point of 18 hours, the whole lung became "white" on the X-ray. The situation stabilized but not improved at the time point of 24 hours. HE staining of the lung tissue showed that to the time point of 6 hours, the alveolar gap increased and small amount of eosinophilic liquid leaked into alveolar. To the time point of 12 hours, alveolar combined with each other and eosinophilic liquid increased in amount. To the time point of 18 hours, the whole alveolar was filled with eosinophilic liquid and the situation stabilized till the time point of 24 hours. Wet/dry weight ratio of the experimental group at each time point were 5.6 ± 0.20, 6.89 ± 0.25, 8.03 ± 0.47, 7.81 ± 0.45. There was significant difference compared with the control group which was 4.72 ± 0.06 (P < 0.01). There was statistical difference between 12, 18, 24 h and 6 h time points (P < 0.01). Moreover, statistical difference was observed between 18, 24 h and 12 h time points for wet/dry weight ratio (P < 0.01). The erythrocyte SOD activity reduced significantly. Compared with the control group, there was a statistical difference (P < 0.01) at each time point. After exposure of 18 and 24 hours, plasma ANP concentration (136.66 ± 35.37) and (134.10 ± 60.41) ng/ml respectively, which were higher than (31.31 ± 13.06) ng/ml of control group and (34.71 ± 13.42) ng/ml of 6 hours time point and (47.98 ± 7.86) ng/ml. The differences were significant (P < 0.01)., Conclusion: High concentrations of NO2 can induce acute pulmonary edema model successfully in SD rats.

Allergen sensitization and allergic airway disease are likely to come about through the inhalation of Ag with immunostimulatory molecules. However, environmental pollutants, including nitrogen dioxide (NO2), may promote adaptive immune responses to innocuous Ags that are not by themselves immunostimulatory. We tested in C57BL/6 mice whether exposure to NO2, followed by inhalation of the innocuous protein Ag, OVA, would result in allergen sensitization and the subsequent development of allergic airway disease. Following challenge with aerosolized OVA alone, mice previously exposed via inhalation to NO2 and OVA developed eosinophilic inflammation and mucus cell metaplasia in the lungs, as well as OVA-specific IgE and IgG1, and Th2-type cytokine responses. One hour of exposure to 10 parts per million NO2 increased bronchoalveolar lavage fluid levels of total protein, lactate dehydrogenase activity, and heat shock protein 70; promoted the activation of NF-kappaB by airway epithelial cells; and stimulated the subsequent allergic response to Ag challenge. Furthermore, features of allergic airway disease were not induced in allergen-challenged TLR2-/- and MyD88-/- mice exposed to NO2 and aerosolized OVA during sensitization. These findings offer a mechanism whereby allergen sensitization and asthma may result under conditions of high ambient or endogenous NO2 levels.

Chest radiographic and high-resolution computed tomography findings of 3 patients with inhalational lung injury due to nitrogen dioxide were reported. Chest radiographs showed ill-defined round opacities which tended to coalesce in both lung with inner lung predominance. High-resolution computed tomography showed ground-glass attenuation and ill-defined centrilobular nodules distributed predominantly in the inner and middle lung zones. One patient showed progression of opacities, which corresponded to the findings of acute respiratory distress syndrome.

A nitric oxide inhaling equipment cooperated with the ventilator synchronously, is introduced in this paper. This equipment monitors the inspiratory flow of the ventilator by a gas flow meter, and works out the flow value of NO on the therapeutic condition using the formula of gas dilution. Then its mass flow controller controls the flow of NO and delivers it to the respiratory circuit. At the same time, the concentrations of NO and NO2 are detected by the electrochemical NO/NO2 sensors before the therapeutic gas enters into the patient. The experimental result shows that this equipment can work with the ventilator in-phase periodically, the volume of E/(I+E) NO be saved, and the output of NO2 < or = 0.7 x 10(-6). Thus the equipment not only has realized the intellectual monitoring and gas-dispensing, but also has improved the precision of inhaled NO concentration with a better reliability and security during the therapy.

In addition to being an air pollutant, NO2 is a potent inflammatory oxidant generated endogenously by myeloperoxidase and eosinophil peroxidase. In these studies, we sought to determine the effects of NO2 exposure on mice with ongoing allergic airway disease pathology. Mice were sensitized and challenged with the antigen ovalbumin (OVA) to generate airway inflammation and subsequently exposed to 5 or 25 ppm NO2 for 3 days or 5 days followed by a 20-day recovery period. Whereas 5 ppm NO2 elicited no pathological changes, inhalation of 25 ppm NO2 alone induced acute lung injury, which peaked after 3 days and was characterized by increases in protein, LDH, and neutrophils recovered by BAL, as well as lesions within terminal bronchioles. Importantly, 25 ppm NO2 was also sufficient to cause AHR in mice, a cardinal feature of asthma. The inflammatory changes were ameliorated after 5 days of inhalation and completely resolved after 20 days of recovery after the 5-day inhalation. In contrast, in mice immunized and challenged with OVA, inhalation of 25 ppm NO2 caused a marked augmentation of eosinophilic inflammation and terminal bronchiolar lesions, which extended significantly into the alveoli. Moreover, 20 days postcessation of the 5-day 25 ppm NO2 inhalation regimen, eosinophilic and neutrophilic inflammation, pulmonary lesions, and AHR were still present in mice immunized and challenged with OVA. Collectively, these observations suggest an important role for NO2 in airway pathologies associated with asthma, both in modulation of degree and duration of inflammatory response, as well as in induction of AHR.

Background: Several recent studies have reported significant health effects of air pollution even at low levels of air pollutants, but in most of these studies linear non-threshold relations were assumed., Aims: To investigate the NO2 mortality dose-response association in nine cities participating in the APHEA-2 project using two different methods: the meta-smooth and the cubic spline method., Methods: The meta-smooth method developed by Schwartz and Zanobetti is based on combining individual city non-parametric smooth curves; the cubic spline method developed within the APHEA-2 project combines individual city estimates of cubic spline shaped dose-response relations. The meta-smooth method is easier and faster to implement, but the cubic spline method is more flexible for further investigation of possible heterogeneity in the dose-response curves among cities., Results: In the range of the pollutant common to all cities the two methods gave similar and comparable curves. Using the cubic spline method it was found that smoking prevalence acts as an effect modifier with larger NO2 effects on mortality at lower smoking prevalence., Conclusions: The NO2-mortality association in the cities included in the present analysis, could be adequately estimated using the linear model. However, investigation of the city specific dose-response curves should precede the application of linear models.

Inflammatory mechanisms are thought to play an important role in the pathogenesis of acute and chronic obstructive pulmonary diseases. In a rat inhalation model using continuous exposure to 10 ppm nitrogen dioxide for 1, 3, and 20 d, we investigated the inflammatory response with particular focus on the activation state of alveolar macrophages. Whereas the number of inflammatory cells and total protein concentration were increased in the bronchoalveolar lavage (BAL), the amount of the proinflammatory cytokine tumor necrosis factor-alpha was markedly reduced with increasing exposure time. In contrast, interleukin (IL)-10 and IL-6 were found at elevated levels and intracellular amounts of suppressor of cytokine signaling-3 protein increased in BAL cells. Upon in vitro lipopolysaccharide stimulation, BAL cells revealed reduced capability to produce the proinflammatory mediators tumor necrosis factor-alpha, IL-1 beta, and nitric oxide, but showed markedly increased transcription and protein release for IL-10. In addition, elevated levels of IL-6, scavenger receptor B, and suppressor of cytokine signaling-3 mRNA were detected in BAL cells from exposed animals. Analyses of highly purified alveolar macrophages indicated that changes in the activation state of these cells were responsible for the observed effects. In conclusion, a priming toward development of the alternatively activated macrophage phenotype occurred in the lungs of rats following nitrogen dioxide inhalation.

The effect of exposure to irritant air pollutants on the development of allergic airway disease is poorly understood. This study examines the effects of the lower respiratory tract irritant, NO(2), on the outcome of ovalbumin (OVA)-induced allergic airway disease. Male and female C57Bl/6 mice were sensitized by weekly intraperitoneal (ip) OVA injections for 3 wk followed by daily 1-h OVA aerosol inhalation challenge for 3 or 10 d. Initially, mice were exposed daily for 3 d to air or 0.7 or 5 ppm NO(2) for 2 h following each OVA aerosol challenge. OVA exposure resulted in pronounced lower airway inflammation, as evidenced by a significant increase in bronchoalveolar lavage (BAL) total cellularity and eosinophil levels. BAL eosinophil levels were significantly lower in OVA-NO(2) compared to OVA-air animals. The reduction was similar at both NO(2) exposure concentrations. In a subsequent study, sensitized animals were exposed for 3 or 10 d to aerosolized OVA followed by air or 0.7 ppm NO(2). BAL eosinophils were again reduced at 3 d by OVA-NO(2) exposure compared to OVA-air mice. At 10 d the eosinophilia was virtually abolished. This reduction in OVA-induced cellular inflammation by NO(2) was confirmed by histopathological analysis. Contrary to expectations, exposure to NO(2) during the aerosol challenge to OVA dramatically diminished the outcome of allergic disease in lungs as measured by airway cellular inflammation.

Brief, high-level nitrogen dioxide (NO(2)) exposures are major hazards during fires and heat-generating explosions. To characterize the lung response to a brief high-level NO(2) exposure, we exposed two groups (n = 5) of 325-375 g, male, Sprague-Dawley rats to either 200 +/- 5 ppm (376 +/- 9 mg/m(3)) NO(2) or room air for 15 min. The rats were nose-only exposed in a multiport exposure chamber fitted with pressure transducers to monitor their respiration during exposure. One hour after exposure, we euthanized the rats, collected blood samples, lavaged the lungs with warm saline, and then excised them. One lung lobe was cooled to -196 degrees C and used for low-temperature electron paramagentic resonance (EPR) analysis. The remainder was homogenized and used for biochemical analyses. Inspired minute ventilation (V(i)) during exposure decreased 59% (p < 0.05). Calculated total inspired dose was 0.880 mg NO(2). In lung lavage, both total and alveolar macrophage cell counts declined (approximately 75%, p < 0.05), but epithelial cell count increased 8.5-fold. Lung weight increased 40% (p < 0.05) after exposure. In the blood, potassium and methemoglobin increased 45 and 18% (p < 0.05), respectively; glucose, lactate, and total hemoglobin were not altered significantly. EPR analysis of lung tissue revealed hemoglobin oxidation and carbon-centered radical formation. Vitamins E and C and uric acid were depleted, and lipid peroxidation measured by three different methods (TBARS, conjugated dienes, and fluorescent peroxidation end products) was elevated, but total protein, DNA, and lipid contents were unchanged. These observations combined demonstrate that a brief (15 min) high-level (200 ppm) NO(2) exposure of rats was sufficient to cause significant damage. However, comparison of the exposure dose normalized to rat body weight with previously reported sheep and estimated human values revealed significant differences. This raises a question about interspecies dosimetry and species-specific responses when animal data are extrapolated to humans and used for safety standard setting, particularly with high-level brief exposures.

This study examined the effects of nitrogen dioxide (NO(2)) exposure on airway inflammation, blood cells, and antiviral respiratory defense. Twenty-one healthy volunteers were exposed on separate occasions to air and 0.6 and 1.5 ppm NO(2) for 3 h with intermittent moderate exercise. Phlebotomy and bronchoscopy were performed 3.5 h after each exposure, and recovered cells were challenged with respiratory viruses in vitro. Blood studies revealed a 4.1% NO(2) dose-related decrease in hematocrit (P = 0.003). Circulating total lymphocytes (P = 0.024) and T lymphocytes (P = 0.049) decreased with NO(2) exposure. Exposure to NO(2) increased the blood lymphocyte CD4(+)-to-CD8(+) ratio from 1.74 +/- 0.11 to 1.85 +/- 0.12 in males but decreased it from 1.88 +/- 0.19 to 1.78 +/- 0.19 in females (P < 0.001 for gender difference). Polymorphonuclear leukocytes in bronchial lavage increased with NO(2) exposure (P = 0.003). Bronchial epithelial cells obtained after exposure to 1.5 ppm NO(2) released 40% more lactate dehydrogenase after challenge with respiratory syncytial virus than with air exposure (P = 0.024). In healthy subjects, exposures to NO(2) at levels found indoors cause mild airway inflammation, effects on blood cells, and increased susceptibility of airway epithelial cells to injury from respiratory viruses.

The effect of long-term supplementation of food reductones, 2,5-dimethyl-4-hydroxy-3(2H)-furanone (DMHF) (2%, w/w), detected in many foodstuffs including soy sauce, and hydroxyhydroquinone (1,2,4-benzenetriol) (HHQ) (1.2%, w/w), detected in coffee, on mouse lipid peroxidation and type IV and I allergy responses was investigated. The effect of supplementation of these reductones combined with NO(2) inhalation (5-6 ppm) was also investigated. Levels of thiobarbituric acid-reactive substances in lung were remarkably increased, and those in kidney and liver were slightly decreased by supplementation of DMHF or HHQ. The degree of 2,4-dinitrochlorobenzene (DNCB)-sensitized lymph node cell proliferation as assessed by lymph node assay was remarkably enhanced by supplementation of DMHF or HHQ. Both the DNCB-sensitized and the trimellitic anhydride-sensitized increases in IgE levels of mice were enhanced to greater extent by supplementation of DMHF or HHQ. In no cases were additive effects of NO(2) inhalation observable. Allergen-sensitized type IV and I allergy responses of mice may be enhanced by supplementation of food reductones, DMHF or HHQ.

The toxic effects of nitrogen dioxide (NO2) and ozone (O3) are mediated through the formation of free radicals, which can cause DNA strand breaks. The present study demonstrates that exposure to NO2 and O3 causes a stimulation of poly(ADP-ribose) (polyADPR) synthetase in alveolar macrophages of rats. Three-month-old male Sprague-Dawley rats, specific pathogen free, were exposed to either 1.2 ppm NO2 or 0.3 ppm O3 alone or a combination of these 2 oxidants continuously for 3 days. The control group was exposed to filtered room air. To evaluate whether exposure to these two oxidants (NO2 and O3) caused DNA damage to lung cells, the activity of polyADPR synthetase was measured. Cellular DNA repair is dependent upon the formation of poly(ADP-ribose) polymerase, which is catalyzed by polyADPR synthetase. PolyADPR synthetase is known to be activated in response of DNA damage. The results showed that the enzyme activity was stimulated after exposure to O3 or exposure to NO2 + O3. Ozone exposure caused a 25% increase in the enzyme activity as compared to the control. Combined exposure to NO2 + O3 showed a 53% increase in the enzyme activity. These results were statistically significant as compared to the control and NO(2) exposure groups. Other parameters such as total cell count, cell viability, and differential cell count were also determined. The stimulation of polyADPR synthetase activity after O3 exposure or NO2 + O3 exposure reflects a response to lung cellular DNA repair, which may be used as an indicator for assessing DNA damage caused by oxidant injury.

Cells of Nitrosomonas eutropha grown under anoxic conditions with hydrogen as electron donor and nitrite as electron acceptor were initially unable to oxidize ammonia (ammonium) and hydroxylamine when transferred to oxic conditions. Recovery of ammonia and hydroxylamine oxidation activity was dependent on the presence of NO2. Under oxic conditions, without addition of NO2, ammonia consumption started after 8 - 9 days, and small amounts of NO and NO2 were detectable in the gas atmosphere. Removing these nitrogen oxides by intensive aeration, ammonia oxidation activity decreased and broke off after 15 days. Addition of gaseous NO2 (25 ppm1) led to a fast recovery of ammonia oxidation (3 days). Simultaneously, the arrangement of intracytoplasmic membranes (ICM) changed from circular to flattened vesicles, the protein pattern revealed an increase in the concentration of a 27 and a 30 kDa polypeptide, and the cytochrome c content increased significantly.

Background: Oxidant stress delivered by nitrogen dioxide (NO2) inhalation impairs the function of extracellular surfactant as well as surfactant phospholipid metabolism in type II pneumocytes. Because protection against oxidant stress is important to normal lung function, the lung contains a variety of antioxidants, including vitamin E. Whether administration of this antioxidant during NO2 inhalation attenuates NO2-induced alterations in phospholipid metabolism in type II pneumocytes has not been studied., Methods: We exposed rats to identical NO2 body doses (720 p.p.m. x h) using continuous, intermittent, or repetitive protocols. During exposure periods, the animals received daily intramuscular injections of vitamin E (25 mg kg-1). We isolated type II pneumocytes from NO2-exposed rats and evaluated them for cell yield and viability, as well as for synthesis and secretion of phosphatidylcholine (PC) as measures of surfactant metabolism., Results: The yield of type II pneumocytes was significantly elevated from animals that had been exposed continuously to NO2 whereas in intermittently and repeatedly exposed rats, cell yield was similar to yield from control animals. Viability of the isolated cells was similar in controls and all NO2 exposure protocols. Vitamin E treatment of the NO2-exposed rats neither changed cell yield nor cell viability. Phospholipid de novo synthesis, as estimated by choline incorporation into PC, was increased most after continuous NO2 inhalation whereas in the other conditions there was only a slight increase. Vitamin E administration further increased phospholipid synthesis; this difference reached statistical significance only in the case of intermittent NO2 exposure. Secretion of phosphatidylcholine from type II cells was only reduced after continuous NO2 inhalation and administration of the antioxidant reduced the impairment., Conclusion: Because vitamin E appears to preserve the ability of type II pneumocytes isolated from NO2-exposed rats to synthesize and secrete surfactant lipid, we conclude that administration of vitamin E may mitigate NO2-induced lung injury.

To improve patients' quality of life and decrease pollution risks to medical personnel, we tested the usefulness of a nitric oxide (NO) inhalation system consisting of a nasal cannula and a demand valve in an open circuit system. To estimate the content of NO entering the lung with the open system, concentrations of NO and nitrogen dioxide (NO2) were measured in a mechanical lung model, and then nitrocylhaemoglobin (NO-Hb), methaemoglobin (Met-Hb), and nitrite (NO2-) + nitrate (NO3-) concentrations in venous blood were measured in eight healthy subjects. Exhaust NO and NO2 in the open system were also observed in 14 healthy subjects. In the lung model, NO concentration delivered with the open system was approximately 1/11 of that in the gas tank. Increases in Met-Hb and NO2- + NO3- with the open system showed that the concentration of delivered NO was approximately 1/9 of that in the gas tank. The open system reduced exhaust NO to 1/10 in human subjects. These data suggest that this NO inhalation system delivers sufficient NO to spontaneously breathing patients. In addition, these findings indicate that there is little environmental toxicity associated with the open circuit system.

Tumor necrosis factor a (TNFalpha) and manganese superoxide dismutase (MnSOD) are thought to play critical roles in the process of lung injury, repair, and disease. The induction of TNFalpha and MnSOD were examined in a model of progressive pulmonary fibrosis along the length of the alveolar duct in rats exposed for 1, 5, and 8 weeks to a combination of 0.8 ppm ozone and 14.4 ppm nitrogen dioxide. This oxidant injury model results in a triphasic response with an initial inflammatory stage during weeks 1-3, followed by a partial resolution at weeks 4-5, and a final stage of rapidly progressive fibrosis during weeks 6-8. Changes in TNFalpha and MnSOD labeling for the proximal and distal alveolar ducts of the lungs were quantified using immunohistochemistry and morphometric techniques at 1, 5, and 8 weeks of exposure. A significant elevation in MnSOD was noted in alveolar macrophages and interstitial cells of the proximal and distal portions of the alveolar duct following 8 weeks of exposure. Labeling for TNFalpha only in the proximal region of the alveolar duct, was significantly increased in alveolar macrophages after 1 and 8 weeks of exposure, while a significant increase in TNFalpha labeling of interstitial cells in proximal regions was noted at all time points. We conclude that MnSOD is elevated in areas of focal injury as well as the more distal protected areas of the lungs, while TNFalpha correlates strongly with both the temporal and spatial aspects of greatest cellular injury in the lungs.

Ozone (O(3)) and nitrogen dioxide (NO(2)) are highly reactive and toxic oxidant pollutants. The objective of this study is to compare chemokine, cytokine, and antioxidant changes elicited by acute exposures of O(3) and NO(2) in a genetically sensitive mouse. Eight-week-old C57Bl/6J mice were exposed to 1 or 2.5 ppm ozone or 15 or 30 ppm NO(2) for 4 or 24 h. Changes in mRNA abundance in lung were assayed by slot blot and ribonuclease protection assay (RPA). Messages encoding metallothionein (Mt), heme oxygenase I (HO-I), and inducible nitric oxide synthase (iNOS) demonstrated increased message abundance after 4 and 24 h of exposure to either O(3) or NO(2). Furthermore, increases in message abundance were of a similar magnitude for O(3) and NO(2). Messages encoding eotaxin, macrophage inflammatory protein (MIP)-1alpha, and MIP-2 were elevated after 4 and 24 h of exposure to 1 ppm ozone. Interleukin-6 was elevated after 4 h of exposure to ozone. After 4 h of 2.5 ppm ozone exposure, increased mRNAs of eotaxin, MIP-1alpha, MIP-2, Mt, HO-I, and iNOS were elevated to a higher magnitude than were detected after 1 ppm ozone. Monocyte chemoattractant protein (MCP-1) was elevated following 15 ppm NO(2) exposure. After 4 h of 30 ppm NO(2) exposure, messages encoding eotaxin, MIP-1alpha, MIP-2, and MCP-1 were elevated to levels similar to those detected after ozone exposure. Our results demonstrate a similar antioxidant and chemokine response during both O(3) and NO(2) exposure. Induction of these messages is associated with the duration and concentration of exposure. These studies suggest that these gases exert toxic action through a similar mechanism.

Oxidative stress is implicated in the pathology of numerous diseases of the lung. These include cystic fibrosis, chronic obstructive airway disease and asthma. All these conditions are characterised by an imbalance between the amounts of reactive oxygen species (ROS) and available antioxidant defences. In the lung, ROS arise from endogenous sources, such as the influx of inflammatory cells or exogenous sources, such as from air pollution and cigarette smoke. When ROS production increases the redox balance of the airways alters, and this can lead to bronchial hyperactivity and further inflammation. The lung, like many other tissues, has a range of antioxidant defences which help to maintain a balanced redox status. These antioxidants are present in the intracellular, the vascular and extracellular respiratory tract lining fluid (RTLF) compartments. The reduced glutathione (GSH) content of RTLF is particularly high and new findings are beginning to reveal the role that the RTLF GSH pool plays in defending the lung.

We examined the possibility that predilution of a concentrated nitric oxide (NO) source with nitrogen, before contact with oxygen, can reduce the inspired nitrogen dioxide (NO2) concentration during administration of nitric oxide. A Manley Blease and a Siemens Servo 900 C ventilator delivered 10, 20, 40, 60 and 80 parts per million (ppm) NO using an NO source of 1000, 400 and 200 ppm. With the Manley Blease system, predilution from 1000 to 200 ppm NO reduced the inhaled NO2 concentration from 0.14 to 0.05 ppm (p < 0.01) at 10 ppm inhaled NO, and from 1.20 to 1.00 ppm (p < 0.01) at 40 ppm inhaled NO. With the Siemens Servo 900 C ventilator, inspiratory NO2 concentrations decreased from 0.21 to 0.11 ppm (p < 0.01) at 10 ppm inhaled NO, and from 1.49 to 1.16 ppm (p < 0.01) at 40 ppm NO. Predilution from 1000 to 400 ppm NO reduced the inspired NO2 concentrations by < 3% using either ventilator when the inspirated NO concentration was 80 ppm. Predilution of NO with nitrogen significantly reduced the inspired NO2 concentrations for nitric oxide concentrations between 10 and 40 ppm, but offered no clinically relevant advantage at higher NO concentrations.

A pure culture of the obligately lithoautotrophic ammonia-oxidizer Nitrosomonas eutropha was grown in a laboratory-scale bioreactor with complete biomass retention. The air supply was supplemented with nitrogen dioxide (NO2; 25 or 50 ppm) or nitric oxide (NO; 25 or 50 ppm). Compared to cultures grown without these nitrogenous oxides, the addition of NO2 or NO to the culture resulted in a significant increase of the nitrification rate, specific activity of ammonia oxidation, growth rate, and maximum cell densities. In contrast, the growth yield slightly decreased in the presence of NO or NO2. Maximum cell densities of about 2 x 10(10) cells ml-1 and a maximum nitrification rate of about 221 mmol NH4+ l-1 day-1 were obtained after 3 weeks in the presence of 50 ppm NO2. Furthermore, in the stationary phase about 50% of the nitrite produced was aerobically denitrified to dinitrogen (N2) and traces of nitrous oxide (N2O). When cells were supplemented with NO, a high rate of aerobic denitrification occurred only during the first days of the exponential growth phase.

Nitrogen dioxide is formed during delivery of inhaled nitric oxide for the treatment of patients with pulmonary hypertension. Soda lime has been shown to absorb nitrogen dioxide. We tested three different commercially available soda lime preparations (Sodasorb, Drägersorb 800 and Sofnolime) for their efficacy in absorbing nitrogen dioxide and nitric oxide during simulated nitric oxide inhalation. All soda lime preparation absorbed nitrogen dioxide (15%, 24% and 34%, respectively). To test if this difference could be attributed to the potassium hydroxide (KOH) content of the different preparations, two other preparations with a higher (3.0% and 7.3% w/w, respectively) KOH content were tested and we found an increase in nitrogen dioxide removal up to 47% and 46%, respectively. We conclude that soda lime absorbed nitrogen dioxide during nitric oxide inhalation. This effect seemed to be moderate under simulated clinical conditions, but increased using soda lime with a higher KOH content. Nevertheless, we recommend continuous monitoring of inspired nitrogen dioxide concentration during clinical inhalation of nitric oxide.

Exposure to nitrogen dioxide (NO2) has been shown to activate glutathione metabolism in lung and lung lavage. Since GGT is a key enzyme in glutathione metabolism and we have previously characterized GGT expression in distal lung epithelium and in lung surfactant, we examined the NO2 exposed lung for induction of gamma-glutamyl transferase (GGT) mRNA, protein, and enzyme activity. We found that the GGT gene product is induced in lung by NO2. The GGT mRNA level in lung increases 2-fold within 6 hr and 3-fold after 24 hr of exposure to this oxidant gas, and this 3-fold elevation persists even after 14 days of exposure. The pattern of GGT mRNA expression switches from the single GGT mRNA III transcript in the normal lung to the dual expression of GGT mRNA I and mRNA III. Enzyme activity in whole lung increases 1.6- to 2.5-fold while extracellular surfactant-associated GGT activity accumulates 5.5-fold and GGT protein accumulates in lung surfactant. Induction of GGT mRNA and protein is evident in cells of the bronchioles by in situ hybridization and immunolocalization, respectively. In contrast, alveolar type 2 cells lack an in situ hybridization signal and exhibit a reduction in the intensity of immunostaining with prolonged exposure. Our studies show that NO2 induces GGT mRNA expression, including GGT mRNA1, in lung and GGT protein and enzyme activity in lung and lung lavage in response to the oxidative stress of NO2 inhalation.

We investigated whether exposure to a low level (490 micrograms/m3) of nitrogen dioxide (NO2) affects bronchial responsiveness to allergen and enhances allergen-induced increase in airway responsiveness to histamine. Eighteen subjects with asthma and allergy to pollen were exposed at rest to either purified air or NO2 for 30 min followed 4 h later by an allergen inhalation challenge. Responsiveness to histamine was measured the day after. Lung function during NO2 exposure and allergen challenge was measured by plethysmography and after exposure by a portable spirometer hourly. The order of exposure to NO2 and air was randomized and separated by at least 2 wk. The asthmatic reaction during the late phase was enhanced by NO2, and peak expiratory flow after allergen challenge was on average 6.6% lower (p = 0.02) after NO2 than after air exposure. The number of subjects having a late asthmatic reaction (fall in FEV1 > 15%) was seven after air and 10 after NO2 (NS). Peripheral blood samples were analyzed for differential cell counts before and after NO2/allergen and serum levels of eosinophil cationic protein (ECP). NO2 effect on lung function was neither associated with an increase in eosinophil numbers nor with ECP levels. NO2 did not affect lung function before allergen challenge, early asthmatic reaction, and allergen-induced increase in responsiveness to histamine. These results indicate that short exposure to an ambient level of NO2 followed several hours later by allergen inhalation enhances allergen-induced late asthmatic reaction.

The authors designed a low-deadspace system to deliver inhaled nitric oxide from a high-concentration (10%) source. Nitric oxide, nitrogen dioxide, and O2 concentrations were compared under simulated inhaled nitric oxide therapy (in vitro) from low (0.08%, 800 ppm) and high (10%, 100,000 ppm) sources of nitric oxide in nitrogen. O2 concentrations remained above 99% and nitrogen dioxide below 3 ppm for nitric oxide delivered at dosages up to 180 ppm from the 10% source. An acute toxicity trial (in vivo) was also performed in nine rabbits mechanically ventilated with 100% O2 for four hours. Six rabbits received 80 ppm nitric oxide from a 10% source and three control rabbits received only O2. Nitric oxide, nitrogen dioxide, and O2 concentrations were monitored in the ventilator circuit. Methemoglobin, arterial blood gases, arterial blood pressure, and heart rate were sampled every hour. At the 80-ppm nitric oxide dose, an average of 1.1 +/- 0.2 ppm of nitrogen dioxide was produced within the ventilator circuit. Arterial methemoglobin in rabbits that received nitric oxide rose by 0.5% from baseline, compared with a 0.2% rise for controls (p = 0.001). The authors conclude that inhaled nitric oxide therapy can be provided from a high-concentration source. Because this system does not reduce inspired O2 fraction, it may be more appropriate than low-source-concentration nitric oxide delivery systems for testing the efficacy of inhaled nitric oxide as an adjunct to optimal conventional medical therapy.

We investigated the effect of intratracheal injections of an extract of suspended particulate matter (SPM) obtained from the urban ambient air of Tokyo, upon the development of proliferative lesions of pulmonary endocrine cells (PECs) in the rat. We also examined the modification effects of nitrogen dioxide, sulfur dioxide, or both of them on the PEC lesions. Male F344 rats were divided into six experimental groups of 5 animals each. Twenty animals were treated with intratracheal instillations of SPM admixed with carbon once a week for 4 weeks with or without additional gaseous exposure (6 ppm nitrogen dioxide or 4 ppm sulfur dioxide) 16 hrs a day for 11 months. Five animals were given intratracheal injections of carbon suspended in saline and the other five were untreated. The subcardiac lobes of the right lung were fixed with 4% paraformaldehyde, and embedded in paraffin. PEC hyperplasias and papillomas were counted in 200 serial sections, 4 microns thick. The average incidences of PEC hyperplasia in the untreated animals and in those treated with carbon were 194 and 200/cm3, respectively. The average incidences of PEC hyperplasia in the animals exposed to SPM tar only, SPM tar plus nitrogen dioxide and sulfur dioxide, SPM tar with nitrogen dioxide and SPM tar with sulfur dioxide were 376, 378, 372 and 349/cm3, respectively. These were significantly higher than the levels of the control animals, and additional gaseous stimuli had no effect on the incidence of PEC hyperplasia. Besides PEC hyperplasia, a few PEC papillomas were found in the animals treated with SPM tar, regardless of gaseous exposure, but in the control animals no papilloma was evident. Thus, compounds in airborne particulates are considered to be responsible for the development of PEC hyperplasias and papillomas.

The aim of this study was to assess the effects of short-term exposure to low levels of nitrogen dioxide (NO2) on airway inflammation. We studied seven normal, eight mild asthmatic and seven chronic obstructive pulmonary disease (COPD) subjects. All subjects were exposed to air or to 0.3 parts per million (ppm) NO2 for 1 h, with moderate intermittent exercise, on different days and in random order. Before and 2 h after exposure, symptom score and results of pulmonary function tests (PFTs) were assessed. All subjects performed nasal lavage and hypertonic saline (HS) inhalation to collect sputum 2 h after both exposures. Asthmatic subjects had a higher percentage of eosinophils than normal and COPD subjects in HS-induced sputum after air (asthmatics: median 13 (range 0.4-37)%; normals: 0 (range 0-2)%; COPD 1.8 (range 0.1-19)%), whilst COPD patients showed a higher percentage of neutrophils than the two others groups. No significant differences in PFT values or percentages of inflammatory cells were observed in nasal lavage and in HS-induced sputum in normal, asthmatic and COPD subjects after NO2 exposure compared to air exposure, except for a mild decrease in forced expiratory volume in one second (FEV1) 2 h after NO2 exposure in COPD patients. Symptom score showed a mild increase after NO2 exposure both in normal subjects and in COPD patients. We conclude that short-term exposure to 0.3 ppm nitrogen dioxide does not induce an early detectable acute inflammation in proximal airways of normal subjects or of patients with asthma or chronic obstructive pulmonary disease.

The mammalian respiratory tract is densely innervated by sensory and autonomic fibres. Subsets of the nerves contain bioactive regulatory peptides, such as substance P, calcitonin gene-related peptide (CGRP), and neurokinins. The sensory nervous system responds to inhaled irritants, resulting in a release of neuropeptides and, thus, a decrease in the peptide immunoreactivity of the fibres. We examined the effects of inhaled nitrogen dioxide (NO2), a well-known indoor and outdoor air pollutant, on pulmonary sensory neuropeptides. Guinea-pigs were exposed for 4 h to 18 parts per million (ppm) NO2 or to air (n = 5 each). At the end of the exposure, they were killed with urethane and their lungs were fixed in 1% paraformaldehyde in phosphate-buffered saline. Cryostat sections were stained with antisera to an anatomical nerve marker, protein gene product (PGP) 9.5, and to CGRP and tachykinins, utilizing the avidin-biotinylated peroxidase method. In the noncartilaginous airways (diameter < 250 microns) of NO2-exposed animals, less tachykinin- and CGRP-immunoreactive nerve fibres were found compared with controls. No change was seen in the total nerve fibre distribution (PGP 9.5). It is concluded that the peptidergic nerves of guinea-pig peripheral airways are a sensitive indicator of exposure to nitrogen dioxide.

The use of inhaled nitric oxide (NO) in research and clinical applications requires the monitoring of NO and its autooxidation product nitrogen dioxide (NO2) in inspired gas and in the ambient environment. We describe an inexpensive electrochemical NO and NO2 analyzer that uses a critical orifice constant-flow controller and a microprocessor crossover correction for the measurement of NO and NO2 in the concentration range relevant to the use of inhaled NO. The analyzer proved to have good accuracy and precision for NO and NO2 in the range of concentrations relevant to studies of inhaled NO. In this range, the performance was similar to that of a chemiluminescence analyzer, and the response characteristics were not affected by varying the O2 concentration of the mixtures analyzed.

Immune hypersensitivity to house dust mite antigen (HDM) is a frequent cause of respiratory allergy. The objective of this study was to determine whether exposure to NO2, a common indoor air pollutant, modulates immune responses to HDM and influences immune-mediated lung disease. Brown Norway rats were immunized ip with 100 micrograms semipurified antigen and Bordetella pertussis adjuvant and challenged 2 weeks later with an intratracheal injection of 50 micrograms of a crude antigen preparation. Exposure to 5 ppm NO2 for 3 hr after both immunization and challenge procedures resulted in significantly higher levels of antigen-specific serum IgE, local IgA, IgG, and IgE antibody than air controls, and increased numbers of inflammatory cells in the lungs. Lymphocyte responsiveness to antigen in the spleen and MLN was also significantly higher in NO2-exposed animals. These data show that exposure to a common air pollutant can upregulate specific immune responses and subsequent immune-mediated pulmonary inflammation.

Nitrogen dioxide (NO2) is one of a number of nitrogen compounds that are by-products of combustion and occur in domestic environments following the use of gas or other fuels for heating and cooking. In this study, we examined the effect of two levels of NO2 on symptoms, lung function and airway hyperresponsiveness (AHR) in asthmatic adults and children. In addition, in the same subjects, we examined the effects of the same levels of NO2 mixed with combustion by-products from a gas space heater. The subjects were nine adults, aged 19-65 yrs, and 11 children, aged 7-15 yrs, with diagnosed asthma which was severe enough to require daily medication. All subjects had demonstrable AHR to histamine. Exposures were for 1 h on five separate occasions, 1 week apart, to: 1) ambient air, drawn from outside the building; 2) 0.3 parts per million (ppm) NO2 in ambient air; 3) 0.6 ppm NO2 in ambient air; 4) ambient air+combustion by-products+NO2 to give a total of 0.3 ppm; and 5) ambient air+combustion by-products+NO2 to give a total of 0.6 ppm. Effects were measured as changes in lung function and symptoms during and 1 h after exposure, in AHR 1 h and 1 week after exposure, and in lung function and symptoms during the week following exposure. Exposure to NO2 either in ambient air or mixed with combustion by-products from a gas heater, had no significant effect on symptoms or lung function in adults or in children. There was a small, but statistically significant, increase in AHR after exposure to 0.6 ppm NO2 in ambient air. However, there was no effect of 0.6 ppm NO2 on AHR when the combustion by-products were included in the test atmosphere nor of 0.3 ppm NO2 under either exposure condition. We conclude that a 1 h exposure to 0.3 or 0.6 ppm NO2 has no clinically important effect on the airways of asthmatic adults or children, but that 0.6 ppm may cause a slight increase in airway hyperresponsiveness.

The time-kinetics of NO2 induced effects on bronchial responsiveness are poorly known as most observations have been made shortly after exposure. The aim of this study was to measure nonspecific bronchial responsiveness, lung function and inflammatory markers at different times after NO2 exposure in asthmatics. Nineteen subjects with mild asthma were exposed to either purified air or 488 micrograms.m-3 (0.26 ppm) NO2 for 30 min during intermittent exercise. Airway responsiveness to histamine, specific airway resistance (sRaw) and thoracic gas volume (TGV) were measured 30 min, 5 h, 27 h and 7 days after exposure. Peripheral blood inflammatory mediators and the expression of an adhesion molecule, (Mac1) on granulocytes, were analysed 30 min and 27 h after exposure. Bronchial responsiveness to histamine was significantly increased 5 h after NO2 exposure when compared to air (median provocative dose of histamine required to cause 100% increase of sRaw ((PDsRaw,100%) 110 micrograms after NO2 exposure vs 203 micrograms on air). There was a tendency for an increase after 30 min, which was nonsignificant (median PDsRaw,100% 100 vs 153 micrograms). NO2 exposure did not affect sRaw, but TGV was significantly reduced after exposure. We found an increased expression of Mac-1 on granulocytes 30 min after NO2 exposure when compared to pre-exposure values. No effect was seen on tryptase, eosinophil cationic protein (ECP), or myeloperoxidase (MPO). These results suggest that exposure to an ambient level of NO2 causes a delayed effect on bronchial responsiveness in asthmatics. The increased expression of an adhesion molecule in peripheral blood may indicate a NO2-induced priming of human granulocytes.

Inhaled 'NO2 is absorbed by a free radical-dependent reaction mechanism that localizes the initial oxidative events to the extracellular space of the pulmonary surface lining layer (SLL). Because 'NO2 per se is eliminated upon absorption, most likely the SLL-derived reaction products are critical to the genesis of 'NO2-induced lung injury. We utilized analysis of the rate of 'NO2 disappearance from the gas phase to determine the preferential absorption substrates within rat SLL. SLL was obtained via bronchoalveolar lavage and was used either as the cell-free composite or after constituent manipulation [(i) dialysis, treatment with (ii) N-ethylmaleimide, (iii) ascorbate oxidase, (iv) uricase, or (v) combined ii + iii]. Specific SLL constituents were studied in pure chemical systems. Exposures were conducted under conditions where 'NO2 is the limiting reagent and disappears with first-order kinetics ([NO2]0 < or = 10 ppm). Reduced glutathione and ascorbate were the principle rat SLL absorption substrates. Nonsulfhydryl amino acids and dipalmitoyl phosphatidylcholine exhibited negligible absorption activity. Whereas uric acid and vitamins A and E displayed rapid absorption kinetics, their low SLL concentrations preclude appreciable direct interaction. Unsaturated fatty acids may account for < or = 20% of absorption. The results suggest that water soluble, low molecular weight antioxidants are the preferential substrates driving 'NO2 absorption. Consequently, their free radicals, produced as a consequence of 'NO2 exposure, may participate in initiating the 'NO2-induced cascade, which results in epithelial injury.

Background: Recent studies have suggested that exposure to air pollutants may enhance the airway responsiveness of susceptible individuals to inhaled allergen., Methods: To investigate the effect of exposure to nitrogen dioxide (NO2) on nasal airways resistance (NAR) and inflammatory mediators in nasal lavage fluid, eight subjects with a history of seasonal allergic rhinitis, who were tested out of season, were exposed in a randomized single-blind, crossover study to either air or 400 ppb NO2 for 6 hours. The changes in NAR and eosinophil cationic protein (ECP), mast cell tryptase (MCT), neutrophil myeloperoxidase (MPO), and interleukin-8 (IL-8) in nasal lavage fluid before and after exposure were evaluated. Another group of eight subjects with a history of seasonal allergic rhinitis were also randomized to exposure to air or 400 ppb NO2 for 6 hours and then challenged with allergen, before evaluation for changes in NAR and changes in ECP, MCT, MPO, and IL-8 in nasal lavage fluid., Results: Exposure to air or NO2 did not alter either NAR or the levels of ECP, MCT, MPO, or IL-8 in nasal lavage fluid. Allergen challenge after exposure to both air and NO2 significantly (p < 0.05) increased levels of MCT, but not MPO and IL-8 in the nasal lavage fluid. In addition, allergen challenge after exposure to NO2 but not air, significantly increased levels of only ECP in nasal lavage fluid (p < 0.05)., Conclusions: These results suggest that acute exposure to NO2 at concentrations found at the curbside in heavy traffic during episodes of pollution, may "prime" eosinophils for subsequent activation by allergen in individuals with a history of seasonal allergic rhinitis.

Nitrogen dioxide (NO2), the oxidation product of nitric oxide (NO), is a reactive free radical forming gas, the inhalation of which has been reported to induce severe damage to distal airways. In order to quantify dose and time course of parenchymal and vascular damage, rats were exposed to 5, 10 and 20 ppm NO2 for 3 and 25 days, followed by quantitative histology and morphometry of the lung. Histological investigations of the short-term exposed animals showed structural alterations extending from slight interstitial oedema after exposure to 5 ppm, to epithelial necrosis and interstitial inflammatory infiltration after exposure to 10 ppm, and an additional intra-alveolar oedema after 20 ppm. The pulmonary arteries disclosed no qualitative changes, such as muscularization of intra-acinar vessels. Long-term exposure to 10 ppm and 20 ppm NO2 resulted in emphysema and slight centrilobular interstitial fibrosis. Morphometric analysis revealed the alveolar surface density to be significantly diminished after short-term exposure to 20 ppm NO2 and long-term exposure to 10 and 20 ppm NO2. The medial thickness of pulmonary arteries was significantly increased after short- and long-term exposure to 20 ppm NO2 and long-term exposure to 10 ppm NO2. In the 5 ppm short- and long-term exposure groups the pulmonary arterial medial thickness was significantly decreased compared to controls. Correlation analysis revealed a negative correlation between average medial thickness and alveolar surface density (coefficient of correlation: -0.56). We conclude that the extent of NO2-induced pulmonary parenchymal and vascular alterations are closely related and concentration- and time-dependent.

Generally, the uptake of reactive gases by the respiratory tract is simulated assuming that all paths from the trachea to the most distal airspaces are equivalent. As this is not the case, especially for nonhumans, the adequacy of this approach to predict doses that can be useful in the fields of toxicology and risk assessment is subject to question. To explore this issue, a dosimetry model is developed which combines the use of one-dimensional convection-dispersion equations in conjunction with multiple path anatomic models so that the dosimetry model simultaneously simulates transport and uptake in all the airways and airspaces of the anatomic model. For this work, the anatomic model of the tracheobronchial (TB) region is patterned on cast data which describe the dimensions and branching network of the 4807 airways of the TB region of a rat. Distal to each of the 2404 terminal bronchioles of the anatomical model, the air space is modeled as a single path. The results presented are preliminary; they focus on the predictions themselves to obtain an understanding of what the model has to say about uptake in a complex set of branching airways. Results include the following predictions: (1) Regardless of path there is a similarity along different paths in the shape of concentration profiles as well as a similarity in the shape of dose profiles. (2) Along a path in the TB or pulmonary region, dose decreases distally. (3) Generally, proximal alveolar region (PAR, a region of major morphological damage due to O3 and NO2) dose decreases the more distal the PAR. (4) There is considerable variation in the doses of the different airways or alveolar surfaces in the same generation. (5) The maximum and minimum PAR doses do not correspond to paths with, respectively, the smallest and largest number of generations from the trachea to the PAR. (6) The ratio of the maximum to minimum PAR dose is very sensitive to tidal volume. These results give a more realistic understanding of respiratory tract gas transport and uptake. The model also predicts aspects that equivalent path models cannot, such as the dose distribution of different but morphologically equivalent sites.

Monitoring of nitric oxide (NO) and nitrogen dioxide (NO2) is a prerequisite for the clinical use of NO. Chemiluminescence, the reference method, cannot be used as a routine in clinical practice in view of its cost and other restraints. This study was performed to evaluate a device using an electrochemical method (Polytrons NO and NO2, Dräger). Forty-nine simultaneous measurements of NO and various oxides of nitrogen (NOx) concentrations by the two apparatus were performed. NO measurements by means of these two methods are very well correlated (r = 0.96; p < 10(-5)). The mean difference according to the method of Bland and Altman was 2.8 +/- 1.7 ppm, with the limits of agreement at -0.6 and +6.2 ppm (confidence interval of 95%). There was also a good correlation between measurements of NO2 obtained via Polytrons and NOx via chemiluminescence (r = 0.84; p < 10(-5)). However, NO2 measurements obtained via Polytrons may be insufficient to exclude potential toxicity of NO2 due to the inability to detect measurements in the ppb-range. This study demonstrates that devices designed for industrial purposes (Polytrons NO and NO2, Dräger) can be used for clinical purposes.