Effects of in vitro exposure to nitrogen dioxide on human alveolar macrophage release of neutrophil chemotactic factor and interleukin-1

To evaluate the potential toxic and immunologic effects of nitrogen dioxide (NO2) exposure on cells from the lower respiratory tract, normal human alveolar macrophages obtained by bronchoalveolar lavage were exposed to increasing concentrations of NO2 using an in vitro exposure system. Alveolar macrophages exposed to 5, 10, or 15 ppm NO2 for 3 hr showed no difference in cell viability when compared to air-exposed macrophages. In addition, the spontaneous release of neutrophil chemotactic factor (NCF) was not changed by NO2 exposure, nor was there any effect on the ability of alveolar macrophages to release increased amounts of NCF following stimulation with activated zymosan. Furthermore, alveolar macrophages did not spontaneously release interleukin-1 (IL-1) following air or NO2 exposure. When stimulated with influenza virus both air- and NO2-exposed cells released increased amount of IL-1, but was no significant difference in the amount of IL-1 released by air- and NO2-exposed alveolar macrophages. Thus, although NO2 exposure is known to incite an inflammatory response in the lower respiratory tract, using the in vitro exposure system described in this study we were unable to demonstrate a direct toxic effect of NO2 on viability or any NO2-induced change in the release of the immunoregulatory molecules NCF and IL-1.     

Effects of 0.60 PPM nitrogen dioxide on circulating and bronchoalveolar lavage lymphocyte phenotypes in healthy subjects

Nitrogen dioxide (NO2) is a common oxidant air pollutant. Animal studies have suggested that NO2 exposure causes a decrease in the numbers of some splenic lymphocyte subtypes and impairs lymphocyte-dependent immune responses. To investigate whether ambient levels of NO2 alter circulating and bronchoalveolar lavage fluid (BALF) human lymphocytes, we studied five healthy nonsmoking adult volunteers. In each subject, blood and bronchoalveolar lavage fluid was obtained and then, more than 2 weeks later, volunteers were exposured to 0.60 ppm NO2 for 2 hr with intermittent light to moderate exercise on 4 separate days within a 6-day period. We measured standard tests of pulmonary function (airway resistance, thoracic gas volume, maximal expiratory flow) and had the subjects rate the severity of respiratory symptoms before and after each NO2 exposure. Circulating and BALF lymphocytes were labeled with fluorochrome-conjugated monoclonal antibodies to human lymphocyte antigens and a flow cytometer was used to count lymphocyte subtypes. Neither any single day's exposure nor all four exposures caused a change in symptoms or in the results of tests of pulmonary function. The total number of circulating lymphocytes obtained after NO2 exposure was slightly greater than at baseline (1792 +/- 544 vs 1598 +/- 549 cells/mm3 at baseline; P = not significant) but the proportions of lymphocyte subtypes did not differ. In the BALF obtained after NO2 exposure and in the baseline state, the total number of lymphocytes and the percentages of T cells (CD 3), B cells (CD 20), T cytotoxic-suppressor cells (CD 8), T helper-inducer cells (CD 4), and large granular lymphocytes (CD 57) also did not differ after NO2 exposure. A slightly but significantly greater proportion of natural killer cells (CD 16) was found in the BALF obtained after NO2 exposure (7.2 +/- 3.1 vs 4.2 +/- 2.4% of total lymphocytes). We conclude that repeated exposures of healthy nonsmoking adults to 0.60 ppm NO2 are not associated with clinically significant symptoms, changes in airway caliber, or alterations in circulating and BALF lymphocyte subtypes. We suggest that brief, daily exposures to NO2 at levels higher than those achieved in urban atmosphere are unlikely to provoke acute respiratory impairment in healthy, nonsmoking adults.     

Effect of nitrogen dioxide on respiratory viral infection in airway epithelial cells.

Nitrogen dioxide (NO(2)) is a common air pollutant outdoors and indoors in homes with unvented combustion sources. It is also a constituent of tobacco smoke. Epidemiological studies suggest that children exposed to NO(2), or living with smoking parents, have an increased incidence of respiratory viral infections. The most common virus causing severe respiratory symptoms in infants and young children is respiratory syncytial virus (RSV). In the present study we investigated whether NO(2) exposure affects RSV infection in airway epithelial cells, the host cells for viral replication and virus-induced cytokine production. Cultures of the bronchial epithelial cell line BEAS-2B exposed to 0.5, 1.0, and 1.5 ppm NO(2) for 60 min were infected with RSV. Viral replication, as well as RSV-induced interleukin (IL)-6 and IL-8, was assessed at various times postinfection. The NO(2) doses used were not toxic to the BEAS-2B cells as measured by release of lactic dehydrogenase (LDH). The internalization of RSV was increased by exposure to 0.5 ppm NO(2) and decreased by exposure to 1.5 ppm NO(2). On the other hand, the release of infectious virus 48 h postexposure was not affected by the two lower doses of NO(2), but was significantly reduced in cells exposed to 1.5 ppm NO(2). Virus-induced cytokine production was also significantly reduced in cells exposed to 1.5 ppm NO(2), and not affected by 0.5 and 1.0 ppm. It is likely that the decrease in cytokine production is related to the decrease in viral burden. These data suggest that possible increases in viral clinical symptoms associated with NO(2) may not be caused by increased susceptibility of the epithelial cells to infection but may result from effects of NO(2) on host defenses that prevent the spread of virus.     

Pulmonary function, airway responsiveness, and respiratory symptoms in asthmatics following exercise in NO2

Two experiments were conducted to determine respiratory responses of persons with asthma performing intermittent moderate exercise while exposed to low concentrations of NO2. In the first, preliminary experiment, 13 male subjects, aged 19-35, with mild asthma were exposed on separate days in a chamber (natural breathing, 20 degrees C, 40% RH) to 0.30 ppm NO2 and to a control or "clean air" exposure (0.0 ppm NO2). Exposure included three 10-min periods of moderate treadmill exercise (VE = 44.5 liter/min), each followed by symptom measurement and pulmonary function testing. The average decrease in FEV1 following the initial 10 min exercise in 0.30 ppm was 11% which was significantly greater (p less than 0.05) than that observed in clean air (7%). Differences in FVC and SRaw were not significantly different at this time. Slight cough and dry mouth and throat were apparent only after the first exercise in NO2. After the second and third exercises, decreases in FEV1 and FVC and increases in SRaw were significantly greater in 0.30 than in 0.0 ppm NO2. Individual subject responses were variable. These results suggested that some asthmatics who perform moderate exercise while exposed to 0.30 ppm NO2 may experience bronchoconstriction and reduction in spirometric performance. Because of these preliminary findings, a more comprehensive, concentration-response experiment was conducted. Twenty-one male volunteers with mild asthma were exposed for 75 min with natural breathing to 0.0, 0.15, 0.30, and 0.60 ppm NO2. Exposure included three 10-min periods of moderate treadmill exercise (VE = 43 liter/min), each exercise followed by symptoms measurement and pulmonary function testing. In addition, airway responsiveness was measured two hr after each exposure by methacholine bronchial challenge testing. In the control exposures (0.0 ppm NO2), the exercise alone caused substantial decrements in pulmonary function. These decrements (as measured by decreases in FEV1 and FVC, and increases in SRaw) were not increased relative to the control exposure after any exercise session in any concentration of NO2. Furthermore, there was no overall group-averaged indication of a concentration-related effect of the NO2 on pulmonary function. Likewise, symptoms reported after NO2 exposure were not significantly different from those reported in clean air. Group-averaged airway responsiveness after exercise in NO2 was also not different from responsiveness after exercise in clean air. For only two subjects was there any indication of a concentration-related increase in airway responsiveness due to exposure to NO2.(ABSTRACT TRUNCATED AT 400 WORDS)     

The pulmonary effects of ozone and nitrogen dioxide alone and combined in healthy and asthmatic adolescent subjects

Separate exposures to 0.12 ppm ozone (O3) or 0.18 ppm nitrogen dioxide (NO2) have not demonstrated consistent changes in pulmonary function in adolescent subjects. However, in polluted urban air, O3 and NO2 occur in combination. Therefore, this project was designed to investigate the pulmonary effects of combined O3 and NO2 exposures during intermittent exercise in adolescent subjects. Twelve healthy and twelve well-characterized asthmatic adolescent subjects were exposed randomly to clean air or 0.12 ppm O3 and 0.30 ppm NO2 alone or in combination during 60 minutes of intermittent moderate exercise (32.5 1/min). The inhalation exposures were carried out while the subjects breathed on a rubber mouthpiece with nose clips in place. The following pulmonary functional values were measured before and after exposure: peak flow, total respiratory resistance, maximal flow at 50 and 75 percent of expired vital capacity, forced expiratory volume in one second and forced vital capacity (FVC). Statistical significance of pulmonary function changes was tested by analysis of covariance for repeated measures. After exposure to 0.12 ppm O3 a significant decrease was seen in maximal flow at 50% of FVC in asthmatic subjects. After exposure to 0.30 ppm NO2 a significant decrease was seen in FVC also in the asthmatic subjects. One possible explanation for these changes is the multiple comparison effect. No significant changes in any parameters were seen in the asthmatic subjects after the combined O3-NO2 exposure or in the healthy subjects after any of the exposures.     

Pulmonary function responses of older men and women to NO2

The pulmonary function of eight men and eight women (51 to 76 years of age), all non-smokers, was measured before and after 2-hr exposures to filtered air (FA) and 0.60 ppm nitrogen dioxide (NO2). The subjects alternated 20-min periods of rest and 20-min periods of cycle ergometer exercise at a work load predetermined to elicit a ventilatory minute volume (VE) of approximately 25 liter/min. Functional residual capacity was determined pre- and postexposure. Forced vital capacity was determined preexposure and 5 min after each exercise period. VE was measured during the last 2 min of each exercise period, and heart rate was monitored throughout each exposure. The pulmonary function data were evaluated as the percentage change from pre- to postexposure to partially remove the effect of differences between men and women in absolute lung volume. There were no statistically significant (P greater than 0.05) differences between the responses of men and women to FA or NO2 exposure. There were no significant (P greater than 0.05) changes in any variable consequent to FA or NO2 exposure. Our older subjects had responses to NO2 exposure similar to those of young adults, suggesting that, at least for healthy people, exposure to 0.60 ppm NO2 has little effect.     

Experimental PVC material challenge in subjects with occupational PVC exposure

BACKGROUND: Polyvinyl chloride (PVC) materials have been linked to asthma in several epidemiologic studies, but the possible causal factors remain unknown. PARTICIPANTS: We challenged 10 subjects experimentally to degraded PVC products under controlled conditions. All of the subjects had previously experienced respiratory symptoms suspected to be caused by this kind of exposure in their work place. Five subjects had doctor-diagnosed asthma. METHODS: The subjects were exposed to degraded PVC material in an exposure chamber ; a challenge with ceramic tile was used as the control test. We followed exhaled nitric oxide, nasal NO, lung functions, cytokines [tumor necrosis factor-alpha (TNF-alpha) , interleukin-4 (IL-4) , IL-6, and IL-12] and NO in nasal lavage fluid (NAL) during and after the exposures. We also measured 2-ethylhexanol in exhaled breath samples and NAL. RESULTS: On the morning after the PVC exposure, subjects reported respiratory tract symptoms significantly more often than they did after the control test (50% vs. 0%, respectively ; p = 0.029 ; n = 10) . We did not detect any changes in lung functions or levels of exhaled NO, nasal NO, or NO in NAL after PVC challenge compared with the control test. Cytokine levels increased after both exposures, with no statistically significant difference between situations. All of the exhaled breath samples collected during the PVC exposure contained 2-ethylhexanol. CONCLUSIONS: PVC flooring challenge can evoke respiratory tract symptoms in exposed subjects. Our results do not support the hypothesis that PVC materials themselves evoke immediate asthmatic reactions. The chamber test used is well suited to this type of exposure study.     

Pulmonary function responses of young and older adults to mixtures of O3, NO2 and PAN

The pulmonary function of 32 nonsmokers (eight men and eight women, 18-26 years of age; eight men and eight women, 51-76 years of age) was measured before and after two-hour exposures to (1) filtered air (FA), (2) 0.45 ppm ozone (O3), (3) 0.13 ppm peroxyacetyl nitrate + 0.45 ppm O3 (PAN/O3), (4) 0.60 ppm nitrogen dioxide + 0.45 ppm O3 (NO2/O3), and (5) 0.13 ppm PAN + 0.60 ppm NO2 + 0.45 ppm O3 (PAN/NO2/O3). Subjects alternated 20-minute periods of rest and exercise (ventilation = 25 L/min). Forced vital capacity (FVC) was measured pre-exposure and five-minutes after each exercise period. Forced expiratory volume in one sec (FEV1.0) and forced expiratory flow between 25 and 75 percent of FVC (FEF25-75%) were calculated from the FVC tests. Data were analyzed by 4-factor analysis of variance (sex, age, time period, exposure). The responses of men and women were similar. FA exposure induced no effects. The young subjects' decrements in FVC, FEV1.0 and FEF25-75% became significant (P less than 0.01) after the second exercise period of the O3, NO2/O3 and PAN/NO2/O3 exposures, while the PAN/O3 decrements were significant (P less than 0.01) after the first exercise period. Although PAN/O3 induced significant decrements earlier than the other conditions including O3, the mean pre- to post-exposure decrements for the four conditions including O3 were similar. In contrast, the older subjects had smaller and fewer significant decrements in pulmonary functions. They had significant mean decrements in FVC following the third exercise period of the NO2/O3 and PAN/NO2/O3 exposures, in FEV1.0 after the third exercise period of the PAN/O3 and NO2/O3 exposures, and in FEF 25-75% beginning after the second exercise period of the NO2/O3 exposure. The results suggest that older men and women are less responsive to O3 and mixtures of O3, NO2 and PAN than young men and women, and that O3 is responsible for the decrements observed in pulmonary function.     

Airway responses to 2.0 ppm nitrogen dioxide in normal subjects

Nitrogen dioxide (NO2) is a common indoor air pollutant. To characterize the acute respiratory responses to this gas, 18 nonsmoking normal subjects (mean age +/- standard deviation [SD] = 25 +/- 4 yr) were exposed to filtered air or 2 ppm NO2 gas for 1 hr in a 30-m3 environmental chamber on different days, typically 1 wk apart, in a double-blind randomized fashion. Lung function tests included forced vital capacity, forced expiratory volume in one second, partial expiratory flow at 40% of vital capacity (Vp40), functional residual capacity, and specific airway conductance, and were measured before and after exposure. Airway reactivity to methacholine inhalation was determined within 45 min of each exposure. The dose of methacholine in mg/ml to cause a 40% decrease in specific airway conductance (PD40) was measured. Airway reactivity to methacholine aerosol increased significantly after NO2, which is shown by a decrease in the concentration of methacholine; PD40 (AIR) = 101 +/- 44, PD40 (NO2) = 81 +/- 45 mg/ml, p = .003. No significant changes were noted in the lung function tests after NO2 exposure. These findings indicate that normal nonsmokers exposed to 2.0 ppm NO2 for 1 hr develop an increase in airway reactivity to methacholine aerosol, which is not associated with changes in lung volumes, flow rates, or respiratory symptoms.     

Transient decrease of exhaled nitric oxide after acute exposure to passive smoke in healthy subjects

Nitric oxide (NO) is produced and detected in the exhalate from the respiratory tract where it plays important regulatory functions. Exhaled nitric oxide (eNO) concentrations are reduced in active cigarette smokers between cigarettes and in nonsmoking subjects during short-term exposure to environmental tobacco smoke. In this study, the authors evaluated eNO before and after an acute exposure to environmental tobacco smoke in healthy, nonsmoking subjects (n = 12). Baseline eNO levels were measured by chemiluminescence at baseline (1 hr before exposure), shortly after the end of exposure, and 10 and 30 min after the end of exposure. Mean room air NO concentration increased from 3 ppb to 4 ppm (range, 560 ppb-8.5 ppm) during the exposure period. Carboxyhemoglobin levels were assessed before and after the exposure with spectrophotometry. All subjects had decreased eNO with exposure to environmental tobacco smoke (mean +/- standard error of the mean: 16.65 +/- 1.35 ppb to 13.86 +/- 1.33 ppb; p < .001). These concentrations remained significantly decreased at 10 min and recovered within 30 min. No modifications in airway resistance or increase in carboxyhemoglobin levels were observed. Exposure to environmental tobacco smoke transiently--but consistently--decreased eNO concentration in healthy, nonsmoking subjects, suggesting that second-hand smoke can directly affect NO in the airway environment.     

The effect of formaldehyde exposure on cytokine production in murine alveolar macrophages

The vapor of formaldehyde has been reported to represent a potential health hazard, resulting in respiratory dysfunction. To determine the potential role of alterations in the alveolar macrophages induced by inhalation of formaldehyde, we studied the cytokine production of murine alveolar macrophages. Mice were exposed at 0, 2.5, 5, 10 ppm of formaldehyde for 16 hrs daily, respectively. Durations of inhalation were 7, 14, 21 and 28 days. Immediately after the formaldehyde exposure, murine alveolar macrophages were harvested from the mice. 18 hrs after LPS stimulation, the cytokines (IL-4, IL-10, IFN-gamma, TNF-alpha) were measured in the supernatant of cultured murine alveolar macrophages using the ELISA method. No levels of formaldehyde exposure changed these cytokine productions. Either our dose or duration of formaldehyde exposure might not have been enough to produce significant changes of cytokine production of murine alveolar macrophages. Further experiments with low but longer formaldehyde exposure may be needed to understand the effect of formaldehyde on cytokine production.     

Transient Decrease of Exhaled Nitric Oxide after Acute Exposure to Passive Smoke in Healthy Subjects

Nitric oxide (NO) is produced and detected in the exhalate from the respiratory tract where it plays important regulatory functions. Exhaled nitric oxide (eNO) concentrations are reduced in active cigarette smokers between cigarettes and in nonsmoking subjects during short-term exposure to environmental tobacco smoke. In this study, the authors evaluated eNO before and after an acute exposure to environmental tobacco smoke in healthy, nonsmoking subjects (n = 12). Baseline eNO levels were measured by chemiluminescence at baseline (1 hr before exposure), shortly after the end of exposure, and 10 and 30 min after the end of exposure. Mean room air NO concentration increased from 3 ppb to 4 ppm (range, 560 ppb-8.5 ppm) during the exposure period. Carboxyhemoglobin levels were assessed before and after the exposure with spectrophotometry. All subjects had decreased eNO with exposure to environmental tobacco smoke (mean ± standard error of the mean: 16.65 ± 1.35 ppb to 13.86 ± 1.33 ppb; p < .001). These concentrations remained significantly decreased at 10 min and recovered within 30 min. No modifications in airway resistance or increase in carboxyhemoglobin levels were observed. Exposure to environmental tobacco smoke transiently–but consistently–decreased eNO concentration in healthy, nonsmoking subjects, suggesting that second-hand smoke can directly affect NO in the airway environment.     

Inhibition of nitric oxide in LPS-stimulated macrophages of young and senescent mice by δ-tocotrienol and quercetin

Background

Changes in immune function believed to contribute to a variety of age-related diseases have been associated with increased production of nitric oxide (NO). We have recently reported that proteasome inhibitors (dexamethasone, mevinolin, quercetin, δ-tocotrienol, and riboflavin) can inhibit lipopolysaccharide (LPS)-induced NO production in vitro by RAW 264.7 cells and by thioglycolate-elicited peritoneal macrophages derived from four strains of mice (C57BL/6, BALB/c, LMP7/MECL-1^-/- and PPAR-α^-/- knockout mice). The present study was carried out in order to further explore the potential effects of diet supplementation with naturally-occurring inhibitors (δ-tocotrienol and quercetin) on LPS-stimulated production of NO, TNF-α, and other pro-inflammatory cytokines involved in the ageing process. Young (4-week-old) and senescent mice (42-week old) were fed control diet with or without quercetin (100 ppm), δ-tocotrienol (100 ppm), or dexamethasone (10 ppm; included as positive control for suppression of inflammation) for 4 weeks. At the end of feeding period, thioglycolate-elicited peritoneal macrophages were collected, stimulated with LPS, LPS plus interferon-β (IFN-β), or LPS plus interferon-γ (IFN-γ), and inflammatory responses assessed as measured by production of NO and TNF-α, mRNA reduction for TNF-α, and iNOS genes, and microarray analysis.

Results

Thioglycolate-elicited peritoneal macrophages prepared after four weeks of feeding, and then challenged with LPS (10 ng or 100 ng) resulted in increases of 55% and 73%, respectively in the production of NO of 46-week-old compared to 8-week-old mice fed control diet alone (respective control groups), without affecting the secretion of TNF-α among these two groups. However, macrophages obtained after feeding with quercetin, δ-tocotrienol, and dexamethasone significantly inhibited (30% to 60%; P < 0.02) the LPS-stimulated NO production, compared to respective control groups. There was a 2-fold increase in the production of NO, when LPS-stimulated macrophages of quercetin, δ-tocotrienol, or dexamethasone were also treated with IFN-β or IFN-γ compared to respective control groups. We also demonstrated that NO levels and iNOS mRNA expression levels were significantly higher in LPS-stimulated macrophages from senescent (0.69 vs 0.41; P < 0.05), compared to young mice. In contrast, age did not appear to impact levels of TNF-α protein or mRNA expression levels (0.38 vs 0.35) in LPS-stimulated macrophages. The histological analyses of livers of control groups showed lesions of peliosis and microvesicular steatosis, and treated groups showed Councilman body, and small or large lymphoplasmacytic clusters.

Conclusions

The present results demonstrated that quercetin and δ-tocotrienols inhibit the LPS-induced NO production in vivo. The microarray DNA analyses, followed by pathway analyses indicated that quercetin or δ-tocotrienol inhibit several LPS-induced expression of several ageing and pro-inflammatory genes (IL-1β, IL-1α, IL-6, TNF-α, IL-12, iNOS, VCAM1, ICAM1, COX2, IL-1RA, TRAF1 and CD40). The NF-κB pathway regulates the production of NO and inhibits the pro-inflammatory cytokines involved in normal and ageing process. These ex vivo results confirmed the earlier in vitro findings. The present findings of inhibition of NO production by quercetin and δ-tocotrienol may be of clinical significance treating several inflammatory diseases, including ageing process.     

Prospective study of respiratory effects of formaldehyde among healthy and asthmatic medical students

We conducted a prospective evaluation of pulmonary function and respiratory symptoms among 103 medical students exposed to formaldehyde over a 7-month period to determine the incidence of bronchoconstriction and respiratory symptoms in response to exposure. Time-weighted average formaldehyde exposures were generally less than 1 part per million (ppm) and peak exposures were less than 5 ppm. Acute symptoms of eye and upper respiratory irritation were significantly associated with exposure. There was no pattern of bronchoconstriction in response to exposure after either 2 weeks or 7 months. Twelve subjects had a history of asthma; they were no more likely to have symptoms of respiratory irritation or changes in pulmonary function than those without such a history. These findings are consistent with previous case reports that indicate exposure to formaldehyde vapor at levels that are commonly encountered in occupational and residential settings do not commonly cause significant bronchoconstriction, even among subjects with preexisting asthma.     

Dose-response study of asthmatic volunteers exposed to nitrogen dioxide during intermittent exercise

Twenty-one mildly asthmatic volunteers were exposed to 0, 0.3, 1.0, and 3.0 ppm nitrogen dioxide (NO2) in purified background air in an environmental control chamber. Exposures were separated by 1-wk periods and occurred in random order. Each lasted 1 hr and included three 10-min bouts of moderately heavy exercise (mean ventilation rate 41 L/min). Exposure temperature was near 22 degrees C and relative humidity near 50%. Specific airway resistance and maximal forced expiratory performance were measured preexposure, after the initial exercise, and near the end of exposure. Bronchial reactivity was assessed immediately following exposure, by normocapnic hyperventilation with subfreezing air. Symptoms were recorded on questionnaires before, during, and for 1-wk after each exposure. Exercise induced significant bronchoconstriction regardless of NO2 level. No statistically significant untoward response to NO2 was observed at any exposure concentration. This negative finding agrees with our previous results, but contrasts with findings elsewhere of respiratory dysfunction after exposure to 0.3 ppm. The discrepancy is presently unexplained, but it may relate to different severity of asthma in different subject groups.     

Laboratory study of asthmatic volunteers exposed to nitrogen dioxide and to ambient air pollution

Adult volunteers with moderate to severe asthma (N = 59) underwent dose-response studies to assess their reactivity to nitrogen dioxide (NO2) in otherwise clean air. Exposure concentrations were 0.0 (control), 0.3 and 0.6 ppm. A subgroup (N = 36) also underwent exposures to Los Angeles area ambient air at times when NO2 pollution was expected. Concentrations of NO2 during ambient exposures were 0.086 +/- 0.024 ppm (mean +/- s.d.). All exposures took place in a movable chamber/laboratory facility. Each study lasted 2 hr, with alternating 10 min periods of exercise (mean ventilation rate 40 L/min) and rest. Lung function was measured prior to exposure and after 10 min, 1 hr and 2 hr of exposure. Symptoms were recorded prior to exposure, during exposure and for 1 week afterward. In some subjects bronchial reactivity to cold air was measured 1 hr after the end of exposure and again 24 hr later. Different exposure conditions were presented in randomized order, 1 week apart. No pollutant exposure produced statistically significant changes in lung function, symptoms, or bronchial reactivity, relative to clean air. Ambient air exposures produced the largest (still nonsignificant) mean changes in some lung function tests. Given the physiological and atmospheric variability, negative statistical results do not rule out a small unfavorable effect of ambient pollution on lung function. If any such effect occurred, it was not likely caused by NO2. Statistical results remained negative when the analysis was restricted to the 20 subjects with most severe lung dysfunction. In conclusion at least in the Los Angeles area, sensitivity to ambient concentrations of NO2 is not common, even among adult asthmatics with moderate to severe disease.     

Pulmonary NO2 toxicity in neonate and adult guinea pigs and rats

The pulmonary effects of NO2 were investigated in two animal species. Rats and guinea pigs aged from 5 to 60 days or more were exposed for 3 days either to 2 ppm or to 10 ppm NO2. Lung histology or superoxide dismutase (SOD) determination in alveolar macrophages was assessed in air and NO2-exposed animals. Results demonstrated that the lung histological alterations are different for both NO2-exposed species. Rats were more tolerant than guinea pigs, but rat and guinea pig newborns were less affected than adults. The enzyme response to NO2 exposure was similar in both species and a decrease in SOD activity was noted in animals of all ages. These observations support the conclusion that NO2 exposure leads to increased lung damage during the life span, but on the contrary, exposure to oxygen does not involve SOD induction. This suggests that the defense mechanisms against NO2 are different from those of O2.     

Effects of exposure to 4 ppm nitrogen dioxide in healthy and asthmatic volunteers

Healthy and asthmatic volunteer subjects (N = 25 and N = 23, respectively) were exposed twice each to purified air (control) and to 4 ppm nitrogen dioxide (NO2) in a controlled-environment chamber. Exposures lasted 75 min, and included 15 min each of light exercise (ventilation rate near 25 L/min) and heavy exercise (near 50 L/min). Compared to control, NO2 exposure produced no statistically significant untoward effects on airway resistance, symptoms, heart rate, skin conductance, or self-reported emotional state in normal or asthmatic subjects. Exercise was associated with significantly (P less than .001) increased airway resistance in both subject groups, although the increase in normals was small. In both groups, systolic blood pressure showed small but significant (P less than .01) decreases with NO2 exposure, compared to control. This effect, if real, may relate to formation of a vasodilating nitrite or nitrate from inhaled NO2. The lack of respiratory response contrasts with previous findings elsewhere; at present, this inconsistency is unexplained.     

Dietary Antioxidants and Ozone-Induced Bronchial Hyperresponsiveness in Adults with Asthma

Ozone exposure aggravates asthma, as has been demonstrated in both controlled exposures and epidemiologic studies. In the current double-blind crossover study, the authors evaluated the effects of dietary antioxidants (i.e., 400 IU vitamin E/500 mg vitamin C) on ozone-induced bronchial hyperresponsiveness in adult subjects with asthma. Seventeen subjects were exposed to 0.12 ppm of ozone or to air for 45 min during intermittent moderate exercise. Bronchial hyperresponsiveness was assessed with 10-min sulfur dioxide (i.e., 0.10 ppm and 0.25 ppm) inhalation challenges. Subjects who were given dietary antioxidants responded less severely to sulfur dioxide challenge than subjects given a placebo (i.e., forced expiratory volume in the 1st sec: -1.2% vs. 4.4%, respectively; peak flow: +2.2% vs. -3.0%, respectively; and mid-forced expiratory flow: +2.0% vs. -4.3%, respectively). Effects were more pronounced when subjects were grouped by response to sulfur dioxide at the screening visit. The results suggest that dietary supplementation with vitamins E and C benefits asthmatic adults who are exposed to air pollutants.     

Dietary antioxidants and ozone-induced bronchial hyperresponsiveness in adults with asthma

Ozone exposure aggravates asthma, as has been demonstrated in both controlled exposures and epidemiologic studies. In the current double-blind crossover study, the authors evaluated the effects of dietary antioxidants (i.e., 400 IU vitamin E/500 mg vitamin C) on ozone-induced bronchial hyperresponsiveness in adult subjects with asthma. Seventeen subjects were exposed to 0.12 ppm of ozone or to air for 45 min during intermittent moderate exercise. Bronchial hyperresponsiveness was assessed with 10-min sulfur dioxide (i.e., 0.10 ppm and 0.25 ppm) inhalation challenges. Subjects who were given dietary antioxidants responded less severely to sulfur dioxide challenge than subjects given a placebo (i.e., forced expiratory volume in the 1st sec: -1.2% vs. 4.4%, respectively; peak flow: +2.2% vs. -3.0%, respectively; and mid-forced expiratory flow: +2.0% vs. -4.3%, respectively). Effects were more pronounced when subjects were grouped by response to sulfur dioxide at the screening visit. The results suggest that dietary supplementation with vitamins E and C benefits asthmatic adults who are exposed to air pollutants.