Combined use of exhaled hydrogen peroxide and nitric oxide in monitoring asthma

Oxidative stress contributes to airway inflammation and exhaled hydrogen peroxide (H2O2) and nitric oxide (NO) are elevated in asthmatic patients. We determined the concentrations of expired H2O2 and NO in 116 asthmatic (72 stable steroid-naive, 30 stable steroid-treated, and 14 severe steroid-treated unstable patients) and in 35 healthy subjects, and studied the relation between exhaled H2O2, NO, FEV1, airway responsiveness, and eosinophils in induced sputum. Both exhaled H2O2 and NO levels were elevated in steroid-naive asthmatic patients compared with normal subjects (0.72 +/- 0.06 versus 0.27 +/- 0.04 microM and 29 +/- 1.9 versus 6.5 +/- 0. 32 ppb, respectively; p < 0.001) and were reduced in stable steroid-treated patients (0.43 +/- 0.08 microM, p < 0.05, and 9.9 +/- 0.97 ppb, p < 0.001). In unstable steroid-treated asthmatics, however, H2O2 levels were increased, but exhaled NO levels were low (0.78 +/- 0.16 microM and 6.7 +/- 1.0 ppb, respectively). There was a correlation between expired H2O2, sputum eosinophils and airway hyperresponsiveness (methacholine PC20). Exhaled NO also correlated with sputum eosinophils, but not with airway hyperresponsiveness. Our findings indicate that measurement of expired H2O2 and NO in asthmatic patients provides complementary data for monitoring of disease activity.     

Elevated levels of expired breath hydrogen peroxide in bronchiectasis

Airway inflammation is important in the development and progression of many lung diseases, including bronchiectasis. Activation of inflammatory cells such as neutrophils, eosinophils, and macrophages induces a respiratory burst resulting in the production of reactive oxygen species such as hydrogen peroxide (H2O2). We have measured exhaled H2O2 in patients with documented bronchiectasis and investigated whether the concentration of H2O2 is related to the disease severity, as defined by lung function. We also investigated whether the concentrations of expired H2O2 were different in bronchiectatic patients who received inhaled corticosteroids compared with steroid-na?ve patients. In 37 patients with bronchiectasis (mean age, 45 +/- 2.5 yr; FEV1, 59 +/- 3% pred), mean H2O2 concentration in exhaled breath condensate was significantly elevated as compared with the values in 25 age-matched (mean age, 42 +/- 2 yr) normal subjects (0.87 +/- 0.01 versus 0.26 +/- 0.04 microM, p < 0.001). There was a significant negative correlation between H2O2 and FEV1 (r = -0.76, p < 0.0001). Patients treated with inhaled corticosteroids had values of H2O2 similar to those of steroid-na?ve patients (0.8 +/- 0.1 versus 0.9 +/- 0.1, p > 0.05). We conclude that H2O2 is elevated in exhaled air condensate of patients with bronchiectasis and is correlated with disease severity. Measurement of H2O2 may be used as a simple noninvasive method to monitor airway inflammation and oxidative stress.     

Nitrite levels in breath condensate of patients with cystic fibrosis is elevated in contrast to exhaled nitric oxide

BACKGROUND: Nitric oxide (NO) is released by activated macrophages, neutrophils, and stimulated bronchial epithelial cells. Exhaled NO has been shown to be increased in patients with asthma and has been put forward as a marker of airways inflammation. However, we have found that exhaled NO is not raised in patients with cystic fibrosis, even during infective pulmonary exacerbation. One reason for this may be that excess airway secretions may prevent diffusion of gaseous NO into the airway lumen. We hypothesised that exhaled NO may not reflect total NO production in chronically suppurative airways and investigated nitrite as another marker of NO production. METHODS: Breath condensate nitrite concentration and exhaled NO levels were measured in 21 clinically stable patients with cystic fibrosis of mean age 26 years and mean FEV1 57% and 12 healthy normal volunteers of mean age 31 years. Breath condensate was collected with a validated method which excluded saliva and nasal air contamination and nitrite levels were measured using the Griess reaction. Exhaled NO was measured using a sensitive chemiluminescence analyser (LR2000) at an exhalation rate of 250 ml/s. Fourteen patients with cystic fibrosis had circulating plasma leucocyte levels and differential analysis performed on the day of breath collection. RESULTS: Nitrite levels were significantly higher in patients with cystic fibrosis than in normal subjects (median 1.93 microM compared with 0.33 microM). This correlated positively with circulating plasma leucocytes and neutrophils (r = 0.6). In contrast, exhaled NO values were not significantly different from the normal range (median 3.8 ppb vs 4.4 ppb). There was no correlation between breath condensate nitrite and lung function and between breath condensate nitrite and exhaled NO. CONCLUSIONS: Nitrite levels in breath condensate were raised in stable patients with cystic fibrosis in contrast to exhaled NO. This suggests that nitrite levels may be a more useful measure of NO production and possibly airways inflammation in suppurative airways and that exhaled NO may not reflect total NO production.     

Acute exposure to hair bleach causes airway hyperresponsiveness in a rabbit model

Ammonium persulphate (APS) and hydrogen peroxide (H2O2) are used as oxidants in many industrial processes and are the main constituents of standard hair bleaching products. In a previous study, it was demonstrated that aerosols of APS induce alterations in airway responsiveness. The present study examined whether exposure for 4 h to a hair bleach composition (containing APS, potassium persulphate and H2O2) or H2O2 could induce airway hyperresponsiveness and/or an obstructive ventilation pattern in a rabbit model. Exposure to the aerosols altered neither baseline airway resistance, dynamic elastance, slope of inspiratory pressure generation nor arterial blood pressure and blood gas measurements. Similarly to APS, hair bleach aerosols containing > or =10.9 mg x m(-3) persulphate (ammonium and potassium salt) in air and > or =1.36 mg x m(-3) H2O2 in air caused airway hyperresponsiveness to acetylcholine after 4 h of exposure. Aerosolized H2O2 (> or =37 mg x m(-3) in air) did not influence airway responsiveness to acetylcholine. The results demonstrate that hair bleaching products containing persulphates dissolved in H2O2 cause airway hyperresponsiveness to acetylcholine in rabbits.     

Cold jet: a method to obtain pure Schwann cell cultures without the need for cytotoxic, apoptosis-inducing drug treatment

Trace gases in exhaled air have been used as a simple means of assessing metabolic reactions. The investigations of trace gases derived from bacteria in human exhalation are usually hydrogen (H2) or methane (CH4). On the other hand, nitrous oxide (N2O) is also derived from microorganisms, especially denitrifying bacteria. Although many kinds of denitrifying bacteria have been isolated on and in the human body, there has been few concerning N2O. We studied 222 healthy people from the age of 5 to 85 years. The analysis of N2O in exhaled air was carried out by a infrared-photoacoustic (IR-PAS) analyzer. It was found that N2O ranged from 0 to 1670 ppbv in exhaled air and that 59% (131) of the subjects were producers of N2O. A highly significant relationship was observed between age and concentrations of N2O (r = 0.40, P < 0.01). The rate of production in young children and in the aged was significantly higher than that in adults aged 20-39 years (P < 0.01), and less than 30% were producers during puberty. The change of normal microflora on and in human body with aging may have caused the significant relationship between age and emissions of N2O.     

The effect of alcohol ingestion on exhaled nitric oxide

The concentration of nitric oxide (NO) is increased in the exhaled air of patients with inflammatory lung diseases, including asthma, possibly reflecting cytokine-mediated chronic airway inflammation. Endogenous NO is generated from L-arginine by the action of several types of NO synthase (NOS). NOS have structural similarities with cytochrome P450 reductases. Alcohol decreases exhaled NO in animals, but this has not previously been investigated in man. We studied the effect of alcohol ingestion in nine asthmatic and 12 normal subjects, measuring the peak concentration of exhaled NO using a modified chemiluminescence analyser. A significant decrement in NO occurred in asthmatic patients (mean +/- SEM before ethanol 204 +/- 58 to 158 +/- 59 parts per billion (ppb) after ethanol; p < 0.02), without significant change in the normal subjects (122 +/- 14 to 114 +/- 15 ppb). Thus, in our study, alcohol decreased exhaled nitric oxide in asthmatic subjects but not in normal individuals. This may reflect preferential action on inducible nitric oxide synthase which is expressed in asthmatic airways. An inhibitory effect of ethanol on inducible nitric oxide synthase may contribute towards the effect of alcohol in asthma.     

Exhaled nitric oxide is higher both at day and night in subjects with nocturnal asthma

Nitric oxide in exhaled air is thought to reflect airway inflammation. No data have been reported so far on circadian changes in NO in subjects with nocturnal asthma. To determine whether exhaled NO shows a circadian rhythm inverse to the circadian rhythm in airway obstruction in subjects with nocturnal asthma, we conducted a study involving six healthy controls, eight individuals without nocturnal asthma (4-h to 16-h variation in peak expiratory flow [PEF] <= 15%), and six individuals with nocturnal asthma (4-h to 16-h PEF variation > 15%). Smoking, use of corticosteroids, and recent respiratory infections were excluded. NO concentrations were measured at 12, 16, 20, and 24 h, and at 4, 8, and 12 h of the next day, using the single-breath method. At the same times, FEV1 and PEF were also measured. Mean NO concentrations were significantly higher in subjects with nocturnal asthma than in subjects without nocturnal asthma, and higher in both groups than in healthy controls at all time points. Mean exhaled NO levels over 24 h correlated with the 4-h to 16-h variation in PEF (r = 0.61, p < 0.01). Exhaled NO did not show a significant circadian variation in any of the three groups as assessed with cosinor analysis, in contrast to the FEV1 in both asthma groups (p < 0.05). At 4 h, mean +/- SD NO levels were higher than at 16 h in subjects with nocturnal asthma; at 50 +/- 20 ppb versus 42 +/- 15 ppb (p < 0.05); other measurements at all time points were similar. Differences in NO and FEV1 from 4 h to 16 h did not correlate with one another. We conclude that subjects with nocturnal asthma exhale NO at higher levels both at night and during the day, which may reflect more severe diurnal airway-wall inflammation. A circadian rhythm in exhaled NO was not observed. NO levels did not correspond to the circadian rhythm in airway obstruction. The small increase in NO at 4 h may indicate an aspect of inflammation, but it is not associated with increased nocturnal airway obstruction.     

Increased nitric oxide in exhaled air of asthmatic patients

Nitric oxide (NO) gas is produced by various cells within the lower respiratory tract, including inflammatory and epithelial cells, and is detectable in the exhaled air of normal human subjects. We have measured exhaled NO in patients with asthma, since several cell types that are activated in asthma can produce NO after induction. NO was measured reproducibly by a slow vital capacity manoeuvre and an adapted chemiluminescence analyser. NO was detectable in exhaled air of 67 control subjects (mean peak concentration 80.2 [SE 4.1] ppb) and was significantly reduced by inhalation of the specific NO synthase inhibitor NG-monomethyl-L-arginine. 61 non-steroid-treated asthmatic subjects had significantly higher peak expired NO concentrations than controls (283 [16] ppb, p < 0.001) but 52 asthmatic patients receiving inhaled corticosteroids had levels similar to controls (101 [7] ppb). High exhaled NO concentrations in asthmatic patients may reflect induction of NO synthase, which is known to be inhibited by steroids. Measurement of exhaled NO concentrations may be clinically useful in detection and management of cytokine-mediated inflammatory lung disorders.     

Exhaled nitric oxide is not elevated in the inflammatory airways diseases of cystic fibrosis and bronchiectasis

Airways inflammation has been associated with increased nitric oxide (NO) in the exhaled breath. It was, therefore, questioned whether exhaled NO could act as an indicator of the severity of airways inflammation in the chronic suppurative lung diseases cystic fibrosis (CF) and bronchiectasis. NO levels in a single exhalation were measured using a chemiluminescence analyser. Thirty-six patients with CF and 16 with bronchiectasis were studied and compared with 22 normal subjects and 35 asthmatic patients. All subjects were nonsmokers and all measurements were made when patients were clinically stable. In addition, exhaled NO was measured in 10 CF patients at the time of onset of an acute infective exacerbation and followed for 7 days during the treatment of the exacerbation in eight of the 10 patients. No significant differences were found in NO levels in patients with CF or bronchiectasis compared with normals (median 4.0, 5.5 and 4.4 parts per billion (ppb), respectively), but all were lower than in asthma patients (10.4 ppb). The NO levels in the CF patients at time of exacerbation were not increased and did not change during treatment. These data show that nitric oxide levels in the exhaled breath of patients with chronic suppurative lung diseases, in contrast to asthma, are not elevated, despite the presence of substantial airways inflammation. Possible explanations include poor diffusion of nitric oxide across increased and viscous airway secretions, removal of nitric oxide by reaction with reactive oxygen species in the inflamed environment and failure of upregulation of epithelial inducible nitric oxide synthase in chronic suppurative conditions.     

Self-reported mental distress under the shifting daylight in the high north

Our knowledge of airways reactivity to inflammatory agonists is derived predominantly from tests dominated by large airway responsiveness. To determine directly, the histamine responsiveness of the smallest airways, eight normal and 11 asymptomatic asthmatic subjects were studied utilizing a wedged bronchoscope technique. A fiberoptic bronchoscope was wedged in the anterior segment of the right upper lobe and a double-lumen catheter was advanced through the working channel to its tip. With a constant flow of gas (5% CO2 in air) through one lumen of the catheter, pressure at the tip of the bronchoscope was measured with the subject breath-holding at FRC. Peripheral airways resistance (Rp) was measured at baseline and after saline, histamine (10, 50, 100 mg/ml) and isoproterenol (2 mg/ml) challenge through the bronchoscope. Baseline Rp of asthmatics (0.041 +/- 0.015 cm H2O/ml/min; mean +/- SE) was significantly greater than normal subjects (0.011 +/- 0.003 cm H2O/ml/min; p = 0.019). The log of the concentration of histamine that caused a 100% increase in peripheral airways response was greater in the normal subjects than in the asthmatic subjects (p = 0.0114) and correlated with whole lung responsiveness to histamine in asthmatics (r = 0.847, p < 0.05). Isoproterenol reversed completely the increase in Rp in normal subjects but not asthmatic subjects. The results of this study demonstrate that the resistance of the smallest peripheral airways, when measured directly, increased when challenged locally with histamine in both normal subjects and asthmatic subjects. However, the peripheral airways responsiveness was significantly enhanced in asthmatic subjects relative to normal controls.     

Exhaled nitric oxide (NO) is reduced shortly after bronchoconstriction to direct and indirect stimuli in asthma

Exhaled NO is increased in patients with asthma and may reflect disease severity. We examined whether the level of exhaled NO is related to the degree of airway obstruction induced by direct and indirect stimuli in asthma. Therefore, we measured exhaled NO levels before and during recovery from histamine and hypertonic saline (HS) challenge (Protocol 1) or histamine, adenosine 5'-monophosphate (AMP), and isotonic saline (IS) challenge (Protocol 2) in 11 and in nine patients with mild to moderate asthma, respectively. The challenges were randomized with a 2-d interval. Exhaled NO and FEV1 were measured before and at 4, 10, 20, and 30 min after each challenge. NO was measured during a slow VC maneuver with a constant expiratory flow of (0.05 x FVC)/s against a resistance of 1 to 2 cm H2O. Baseline exhaled NO levels were not significantly different between study days in Protocol 1 (mean +/- SD: 4.8 +/- 1.8 ppb [histamine] versus 5.4 +/- 2.1 ppb [HS], p = 0.4) or in Protocol 2 (7.9 +/- 4.7 ppb [histamine], 8.3 +/- 5.2 ppb [AMP], and 7.2 +/- 3.7 ppb [IS], p = 0.7). A significant reduction in exhaled NO was observed directly after HS (mean +/- SEM: 39.2 +/- 3.9 %fall) and AMP challenge (32.3 +/- 7.3 %fall) (MANOVA, p < 0.001), respectively, whereas exhaled NO levels tended to decrease after histamine challenge. Isotonic saline challenge did not induce changes in exhaled NO (p = 0.7). There was a positive correlation between %fall in FEV1 and the %fall in exhaled NO after histamine, HS, and AMP challenge as indicated by the mean slope of the within-subject regression lines (p <= 0.04). We conclude that acute bronchoconstriction, as induced by direct and indirect stimuli, is associated with a reduction in exhaled NO levels in asthmatic subjects. This suggests that airway caliber should be taken into account when monitoring exhaled NO in asthma.     

Inhibitory effect of pulmonary surfactant proteins A and D on allergen-induced lymphocyte proliferation and histamine release in children with asthma

The role of pulmonary surfactant proteins in the pathogenesis of airway inflammation and the impact on asthma has not been elucidated. This study was designed to examine the effect of surfactant proteins A (SP-A) and D (SP-D) on phytohemagglutinin- (PHA) and mite allergen Dermatophagoides pteronyssinus (Der p)-induced histamine release and the proliferation of peripheral blood mononuclear cells (PBMC) in children with asthma in stable condition (n = 21), asthmatic children during acute attacks (n = 9), and age-matched control subjects (n = 7). The results show that SP-A and SP-D were able to reduce the incorporation of [3H]thymidine into PBMC in a dose-dependent manner. In addition to the intact, native SP-A and SP-D proteins, a recombinant peptide composed of the neck and carbohydrate recognition domain (CRD) of SP-D [SP-D(N/CRD)] was also found to have the same suppressive effect on lymphocyte proliferation. This effect was abolished by the presence of 100 mM mannose (for SP-A) or maltose (for SP-D) in the culture medium, which suggested that the CRD regions of SP-A and SP-D may interact with the carbohydrate structures on the surface molecules of lymphocytes. The inhibitory effects of surfactant proteins on PHA- and Der p-stimulated lymphocyte responses were observed in stable asthmatic children and age-matched control subjects, while only a mild suppression (< 25%) was seen in activated lymphocytes derived from asthmatic children with acute attacks. SP-A and SP-D were also found to inhibit allergen-induced histamine release, in a dose-dependent manner, in the diluted whole blood of asthmatic children. We conclude that both SP-A and SP-D can inhibit histamine release in the early phase of allergen provocation and suppress lymphocyte proliferation in the late phase of bronchial inflammation, the two essential steps in the development of asthmatic symptoms. It appears that SP-A and SP-D may be protective against the pathogenesis of asthma.     

Non-invasive monitoring of bronchial inflammation in asthma

The present consensus on the diagnosis and treatment of asthma relies on symptoms and lung function measurements for the monitoring of disease severity. Even though this probably remains the cornerstone of asthma management, the rapidly increasing insight into the pathogenesis and pathophysiology of the disease is presently leading to the development of more direct measurements of airway inflammation, which may provide potentially relevant information on its clinical course and prognosis. However, at present none of these has sufficiently been validated for current use in monitoring patients with asthma. First, there are new ways of looking at symptoms and lung function. Careful measurements of symptoms by visual analogue scale (VAS) are suggesting that inflammatory activity within the airways can be subjectively perceived, a sensitivity which may be blunted in patients with brittle asthma. In addition, modern physiological parameters, such as the degree of bronchodilatation following a deep breath (M/P-ratio), are strongly associated with airway inflammation. Second, there are multiple cellular and/or soluble markers of inflammation in peripheral blood (using PCR, in situ hybridization, flow cytometry, or circulating mediators and cytokines) and in urine (LTE4, EPX). Recently this has been extended by similar measurements in hypertonic saline-induced sputum (cell differentials and specific stainings on cytospins, flow cytometry, and levels of e.g. ECP, IL-5, IL-8). Finally, mediators and cytokines in the condensate of exhaled air (H2O2, leukotrienes, IL-5?) as well as exhaled NO are currently under evaluation. Adding such markers of airway inflammation as guides in asthma therapy is potentially useful. As a first step towards such a new approach we have recently shown that adding the reduction of airway hyperresponsiveness to the aims of asthma therapy leads to a better clinical as well as histological outcome after two years of treatment. In conclusion, there are new and exciting perspectives in the monitoring of disease severity in asthma in the future. Longitudinal studies presently ongoing will elucidate which parameter is potentially most useful in guiding asthma management.     

The use of noninvasive biological means in assessing lipids in children

Gas chromatographic analysis of the lipid fatty acid spectrum of blood (serum and plasma), sweat, and exhaled air condensate in children with acute pneumonia and dermatitis caused by alimentary allergies showed good correlation of the results. Therefore, biological objects obtained by noninvasive methods can be used for studies of lipid metabolism in children.     

Cytokine profiles of stimulated blood lymphocytes in asthmatic and healthy adolescents across the school year

T cell cytokines play an important role in mediating airway inflammation in asthma. The predominance of a Th2 cytokine profile, particularly interleukin (IL)-4 and IL-5, is associated with the pathogenesis and course of asthma. The aim of this study was to test the hypothesis that a stressful life event alters the pattern of cytokine release in asthmatic individuals. Thirteen healthy controls and 21 asthmatic adolescents gave blood samples three times over a semester: midsemester, during the week of final examinations, and 2-3 weeks after examinations. Interferon-gamma (IFN-gamma), IL-2, IL-4, and IL-5 were measured from supernatants of cells stimulated with PHA/PMA for 24 h. Cells from asthmatic subjects released significantly more IL-5 during the examination and postexamination periods, whereas cells from healthy controls released significantly more IL-2 during the midsemester and examination periods, thereby indicating a bias for a Th2-like pattern in asthmatics and a Th1-like pattern in healthy controls. IL-4 and IL-5 production showed a marked decrease during and after examinations in healthy controls, whereas this decline was absent in asthmatics. The ratios of IFN-gamma:IL-4 and IFN-gamma:IL-5 also revealed significant changes in the profile of cytokine release across the semester. These results indicate differential cytokine responses in asthmatics that may become pronounced during periods of cellular activation.     

Increased levels of exhaled nitric oxide during nasal and oral breathing in subjects with seasonal rhinitis

BACKGROUND: Allergic rhinitis is associated with nasal mucosal inflammation. Exhaled nitric oxide may be a useful marker of inflammation and has recently been shown to be increased in patients with asthma. OBJECTIVE: The purpose of this study was to determine whether exhaled levels of nitric oxide are increased with nasal breathing in patients with seasonal allergic rhinitis compared with nonatopic individuals and whether there is an increase with oral breathing consistent with lower respiratory inflammation in the absence of clinical asthma. METHODS: Nitric oxide levels in exhaled air were measured by chemiluminescence in 18 nonatopic volunteers and 32 patients with seasonal rhinitis. Measurements were made with both nasal and oral exhalation and orally after 10 seconds and 60 seconds of breath-holding. The detection limit was 1 part per billion (ppb). RESULTS: In control subjects nasal levels of nitric oxide in exhaled air (mean +/- SD, 24.7 +/- 9.2 ppb) were higher than those after oral exhalation (11.1 +/- 2.5 ppb, p less than 0.0001). Breath-holding significantly increased levels of nitric oxide in exhaled air in a time-dependent manner. Levels of exhaled nitric oxide were significantly higher for all measurements in patients with seasonal rhinitis, with levels without breath-holding of 35.4 +/- 11.3 ppb (p less than 0.001) in nasally exhaled air and 16.3 +/- 5.9 ppb (p less than 0.001) in orally exhaled air. Nasal levels were significantly higher than oral levels in subjects with rhinitis (p less than 0.0001). CONCLUSIONS: The results indicate that exhaled nitric oxide may be a useful marker for nasal inflammation in patients with seasonal rhinitis and suggest that generalized airway inflammation may be present, even without clinical asthma, in such patients.     

Effect of short- and long-acting inhaled beta2-agonists on exhaled nitric oxide in asthmatic patients

Increased concentrations of exhaled nitric oxide (NO) occur in patients with asthma, and exhaled NO may be useful for assessing the effect of drug therapy on airway inflammation. Beta2-agonists have been proposed to have both proinflammatory and anti-inflammatory effects. We therefore assessed exhaled NO after beta2-agonists in asthmatic patients. Two randomized, double-blind, placebo-controlled studies were conducted. Firstly, exhaled NO was measured in 18 asthmatics (9 taking inhaled glucocorticosteroids (GCS)) before and after nebulized salbutamol (5 mg), or identical placebo (0.9% saline). Exhaled NO and forced expiratory volume in one second (FEV1) were measured at 15 min intervals for 1 h (Study 1). Secondly, the effect of 1 week of treatment with the long-acting beta2-agonist, salmeterol (50 microg b.i.d.), added to either budesonide (800 microg b.i.d.) or placebo, was studied in eight mild asthmatic subjects (Study 2). Exhaled NO was measured by a chemiluminescence analyser, adapted for on-line recording. In Study 1, exhaled NO showed no significant change at any time-point in patients not taking inhaled GCS. In asthmatics on inhaled GCS, exhaled NO increased compared to placebo at 15 and 30 min, but this did not reach statistical significance. In Study 2, treatment with salmeterol increased FEV1, but exhaled NO levels were not significantly changed, either after budesonide treatment (143+/-35 to 179+/-67 ppb), or after placebo (201+/-68 to 211+/-65 ppb). Our results confirm that single high dose salbutamol does not increase exhaled nitric oxide in asthmatics not taking inhaled glucocorticosteroids. Salbutamol may increase exhaled nitric oxide in asthmatics taking inhaled glucocorticosteroids. However, regular use of salmeterol resulted in no change in exhaled nitric oxide, either used alone or in combination with inhaled glucocorticosteroids.     

Involvement of superoxide and nitric oxide on airway inflammation and hyperresponsiveness induced by diesel exhaust particles in mice

We previously demonstrated that chronic intratracheal instillation of diesel exhaust particles (DEP) induces airway inflammation and hyperresponsiveness in the mouse, and that these effects were partially reversed by the administration of superoxide dismutase (SOD). In the present study, we have investigated the involvement of superoxide in DEP-induced airway response by analyzing the localization and activity of two enzymes: (1) a superoxide producer, NADPH cytochrome P-450 reductase (P-450 reductase), and (2) a superoxide scavenger, SOD, in the lungs of the exposed mice and controls. P-450 reductase was detected mainly in ciliated cells and clara cells: its activity was increased by the repeated intratracheal instillation of DEP. While CuZn-SOD and Mn-SOD were also present in the airway epithelium, their activity was significantly decreased following DEP instillation. Exposure to DEP doubled the level of nitric oxide (NO) in the exhaled air. DEP exposure also increased the level of constitutive NO synthase (cNOS) in the airway epithelium and inducible NO synthase (iNOS) in the macrophages. Pretreatment with N-G-monomethyl L-arginine, a nonspecific inhibitor of NO synthase, significantly reduced the airway hyperresponsiveness induced by DEP. These results indicate that superoxide and NO may each contribute to the airway inflammation and hyperresponsiveness induced by the repeated intratracheal instillation of DEP in mice.     

Hydrogen peroxide activates mitogen-activated protein kinases and Na+-H+ exchange in neonatal rat cardiac myocytes

Reperfusion of cardiac tissue after an ischemic episode is associated with metabolic and contractile dysfunction, including reduced tension development and activation of the Na+-H+ exchanger (NHE). Oxygen-derived free radicals are key mediators of reperfusion abnormalities, although the cellular mechanisms involved have not been fully defined. In the present study, the effects of free radicals on mitogen-activated protein (MAP) kinase function were investigated using cultured neonatal rat ventricular myocytes. Acute exposure of spontaneously beating myocytes to 50 micromol/L hydrogen peroxide (H2O2) caused a sustained decrease in contraction amplitude (80% of control). MAP kinase activity was measured by in-gel kinase assays and Western blot analysis. Acute exposure to H2O2 (100 micromol/L, 5 minutes) resulted in sustained MAP kinase activation that persisted for 60 minutes. Catalase, but not superoxide dismutase, completely inhibited MAP kinase activation by H2O2. Pretreatment with chelerythrine (10 micromol/L, 45 minutes), a protein kinase C inhibitor, or genistein (75 micromol/L, 45 minutes) or herbimycin A (3 micromol/L, 45 minutes), tyrosine kinase inhibitors, caused significant inhibition of H2O2-stimulated MAP kinase activity (51%, 78%, and 45%, respectively, at 20 minutes). Brief exposure to H2O2 also stimulated NHE activity. This effect was completely abolished by pretreatment with the MAP kinase kinase inhibitor PD 98059 (30 micromol/L, 60 minutes). These results suggest that low doses of H2O2 induce MAP kinase-dependent pathways that regulate NHE activity during reperfusion injury.     

Exhaled NO during graded changes in inhaled oxygen in man

BACKGROUND: Nitric oxide (NO) is present in the exhaled air of animals and humans. In isolated animal lungs the amount of exhaled NO is decreased during hypoxia. A study was undertaken to determine whether changes in arterial oxygen tension affect levels of exhaled NO in humans. METHODS: Sixteen healthy subjects were randomised to inhale different gas mixtures of oxygen and nitrogen in a double blind crossover study. Eight gas mixtures of oxygen and nitrogen (fractional inspired oxygen concentration (FiO2) 0.1 to 1.0) were administered. Exhaled NO was measured with a chemiluminescence detector from end expiratory single breath exhalation. RESULTS: A dose-dependent change in exhaled NO during graded oxygen breathing was observed (p = 0.0012). The mean (SE) exhaled NO concentration was 31 (3) ppb at baseline, 39 (4) ppb at an FiO2 of 1.0, and 26 (3) ppb at an FiO2 of 0.1. CONCLUSIONS: The NO concentration in exhaled air in healthy humans is dependent on oxygen tension. Hyperoxia increases the level of exhaled NO, which indicates increased NO production. The mechanism behind this phenomenon remains to be elucidated.