Nitric oxide metabolites in induced sputum: a marker of airway inflammation in asthmatic subjects

An update on the diagnostic biomarkers for asthma

Asthma is a respiratory disorder accounts for ~339 million cases per annum. The initial diagnosis of asthma relies on the symptomatic identification of characters, such as wheeze, shortness of breath, chest tightness, and cough. The presence of two or more of these symptoms may be considered as indicative of asthma. The asthma-diagnostic also involves spirometry test before and after inhaling a bronchodilator like albuterol. Because asthma pathophysiology involves participation of immune system, the cytokines play an important role. The review discusses various molecules that are or may be used as biomarkers for the asthma diagnosis.

Toward point-of-care management of chronic respiratory conditions: Electrochemical sensing of nitrite content in exhaled breath condensate using reduced graphene oxide

We present a portable non-invasive approach for measuring indicators of inflammation and oxidative stress in the respiratory tract by quantifying a biomarker in exhaled breath condensate (EBC). We discuss the fabrication and characterization of a miniaturized electrochemical sensor for detecting nitrite content in EBC using reduced graphene oxide. The nitrite content in EBC has been demonstrated to be a promising biomarker of inflammation in the respiratory tract, particularly in asthma. We utilized the unique properties of reduced graphene oxide (rGO); specifically, the material is resilient to corrosion while exhibiting rapid electron transfer with electrolytes, thus allowing for highly sensitive electrochemical detection with minimal fouling. Our rGO sensor was housed in an electrochemical cell fabricated from polydimethyl siloxane (PDMS), which was necessary to analyze small EBC sample volumes. The sensor is capable of detecting nitrite at a low over-potential of 0.7 V with respect to an Ag/AgCl reference electrode. We characterized the performance of the sensors using standard nitrite/buffer solutions, nitrite spiked into EBC, and clinical EBC samples. The sensor demonstrated a sensitivity of 0.21 μA μM^-1 cm^-2 in the range of 20-100 μM and of 0.1 μA μM^-1 cm^-2 in the range of 100-1000 μM nitrite concentration and exhibited a low detection limit of 830 nM in the EBC matrix. To benchmark our platform, we tested our sensors using seven pre-characterized clinical EBC samples with concentrations ranging between 0.14 and 6.5 μM. This enzyme-free and label-free method of detecting biomarkers in EBC can pave the way for the development of portable breath analyzers for diagnosing and managing changes in respiratory inflammation and disease.

Biomarkers in the Management of Difficult Asthma

Difficult asthma is a heterogeneous disease of the airways including various types of bronchial inflammation and various degrees of airway remodeling. Therapeutic response of severe asthmatics can be predicted by the use of biomarkers of Type2-high or Type2-low inflammation. Based on sputum cell analysis, four inflammatory phenotypes have been described. As induced sputum is time-consuming and expensive technique, surrogate biomarkers are useful in clinical practice.

Eosinophilic phenotype is likely to reflect ongoing adaptive immunity in response to allergen. Several biomarkers of eosinophilic asthma are easily available in clinical practice (blood eosinophils, serum IgE, exhaled nitric oxyde, serum periostin). Neutrophilic asthma is thought to reflect innate immune system activation in response to pollutants or infectious agents while paucigranulocytic asthma is thought to be not inflammatory and characterized by smooth muscle dysfunction. We currently lack of user-friendly biomarkers of neutrophilic asthma and airway remodeling.

In this review, we summarize the biomarkers available for the management of difficult asthma.

Induced Sputum Nitrite Levels Correlate with Clinical Asthma Parameters in Children Aged 7-18 Years with Mild to Moderate Persistent Asthma

PURPOSE

The objective of this study is to measure levels of nitrites in induced sputum in children with asthma and correlate it with clinical asthma parameters.

METHOD

This prospective observational study was done in PGIMER, Dr. Ram Manohar Lohia Hospital, New Delhi, on 91 children aged 7-18 years with mild and moderate persistent asthma. Patients were specifically evaluated for five clinical parameters of asthma (i.e. Days of acute exacerbations, use of salbutamol as rescue medication, emergency visits, nights with cough, days of school absence) and induced sputum nitrite levels was done at the time of enrollment and 3 months after treatment with inhaled budesonide.

RESULTS

The mean age of subjects was 10.79 ± 2.563yrs. Six (6.59%) patients were not able to perform induced sputum, eighty five (93.41%) patients were suitable for data analysis. There was significant reduction in sputum nitrite levels from 33.42 ± 22.04nmol/ml at enrollment to 11.72 ± 5.61 nmol/ml (P < 0.0005) after 3 months of inhaled budesonide therapy. Significant positive correlation was found between reduction in sputum nitrite level and control of asthma symptoms: Days of acute exacerbations(r value = 0.548, P value = 0.0001), Days of salbutamol use as rescue medication (r value = 0.431, P value =< 0.0001), Number of emergency visits(r value = 0.414, P value = 0.0001), Nights with cough (r value = 0.259, P value = 0.0169), Days of school absence(r value = 0.411, P value = 0.0001). Sputum nitrite levels were significantly higher in moderate persistent asthmatics as compared to mild at the time of enrollment (P < 0.0005), which shows that induced sputum nitrite levels correlate with asthma severity.

CONCLUSIONS

This study confirms that nitrites in induced sputum correlate well with clinical asthma parameters and asthma severity in children and is a simple, non invasive, and cheap method which can be used as a parameter for monitoring of asthma.

Correlation between nitrites in induced sputum and asthma symptoms in asthmatic schoolchildren

OBJECTIVE

To determine if nitrites (nitric oxide metabolites) measured in induced sputum decrease and correlate with improvement of clinical asthma symptoms after treatment, we performed a prospective longitudinal study in a tertiary care hospital in Arequipa, Peru.

METHODS

In 95 schoolchildren with mild and moderate persistent asthma we determined nitrites in induced sputum samples (measured using the Griess assay). Clinical parameters and exercise bronchial challenge (EBC) test were performed twice, at baseline and after 3 months of beclomethasone-dipropionate treatment (median doses: 300 mcg/day, IQR: 300-450).

RESULTS

Sixty out of 95 children completed the study (median age of 9-year [IQR: 7-13]). A significant change in sputum nitrites levels between admission and the end of the study was observed (34.4 nmol/ml [IQR:18.2-58.4] and 11.2 nmol/ml [6-20.1], respectively, P = < 0.0001). Also a significant correlation between decrease of sputum nitrites levels and improvement of clinical parameters (acute exacerbations [r = 0.361, P = 0.005]; use of salbutamol [r = 0.322, P = 0.013]; emergency visits [r = 0.275, P = 0.033]; and school absence [r = 0.41, P = 0.001]) from admission to the end of the study was found. However, sputum nitrites levels did not correlated with peripherical blood eosinophils or serum IgE levels or with EBC test at any point of the study. The decrease of sputum nitrites levels after the treatment was significant in each asthma group (mild and moderate), but not between groups.

CONCLUSION

This study showed that measured nitrite in induced sputum (a simple and cheap non-invasive method) is a good alternative for monitoring asthmatic treatment in schoolchildren.

Evaluation of biomarkers in bronchoalveolar lavage fluid for discrimination between asthma and chronic bronchitis in cats

OBJECTIVE

To compare concentrations of interleukin (IL)-4, interferon (IFN)-gamma, tumor necrosis factor (TNF)-alpha and total nitric oxide (NO) metabolites in bronchoalveolar lavage fluid (BALF) for discrimination between asthma and chronic bronchitis in cats.

ANIMALS

97 cats.

PROCEDURES

Cats screened with cytologic examination of BALF included 13 client-owned cats with naturally developing asthma, 8 client-owned cats with chronic bronchitis, 23 research cats with experimentally induced asthma, 33 research cats with experimentally induced nonseptic suppurative inflammation of the airways, and 20 healthy control cats. Banked unconcentrated BALF supernatant samples were assayed for concentrations of IL-4, IFN-gamma, TNF-alpha, and total NO metabolites.

RESULTS

Concentrations of IL-4 and IFN-gamma in BALF were less than the limits of detection for most cats, precluding statistical analysis. No significant differences were detected among groups for TNF-alpha concentrations. Concentrations of total NO metabolites were significantly higher in cats with clinical chronic bronchitis, compared with research cats with nonseptic suppurative inflammation or research cats with asthma.

CONCLUSIONS AND CLINICAL RELEVANCE

There were no significant differences in tested biomarkers between cats with asthma and healthy control cats. None of the measured cytokines or NO metabolites were useful for discriminating between cats with naturally developing asthma and those with chronic bronchitis.

Prostaglandin E2 and cysteinyl leukotriene concentrations in sputum: association with asthma severity and eosinophilic inflammation

BACKGROUND

Inflammation of the airways in asthma is associated with the production of cysteinyl leukotrienes (cysLT), prostaglandin (PG)E(2), 8-isoprostane, nitric oxide and other mediators. However, the relationship between asthma severity or eosinophilic inflammation and the concentrations of mediators in sputum is unclear.

OBJECTIVE

To assess sputum PGE(2), cysLT, 8-isoprostane and nitrate concentrations, as well as urinary leukotriene (LT)E(4) and 9alpha,11beta-prostaglandin (PG)F(2) concentrations, in patients with differing severities of asthma and eosinophilic or non-eosinophilic airway inflammation.

METHODS

Inflammatory cells in sputum were assessed in 12 patients with mild, 14 with moderate and 12 with severe persistent asthma, as well as in 13 control subjects. Asthmatic patients were categorized into those with eosinophilic or non-eosinophilic airway inflammation. Sputum PGE(2), cysLT and 8-isoprostane, and urinary LTE(4) were extracted on immunoaffinity sorbents, and the concentrations of all mediators were measured using enzyme immunoassays. Sputum nitrate concentrations were measured on a chemiluminescence analyzer.

RESULTS

Sputum PGE(2) concentrations were higher in both moderate (1710 pg/mL) and severe asthmatic (1590 pg/mL) compared with control subjects (827 pg/mL) (P<0.05). CysLT concentrations were higher in moderate asthmatic compared with control or severe asthmatic subjects (P<0.05). Sputum PGE(2) concentrations were lower in patients with eosinophilic (1180 pg/mL) compared with non-eosinophilic airway inflammation (2520 pg/mL) (P=0.02). In contrast, sputum cysLT and urinary LTE(4) concentrations were higher in those with eosinophilic airway inflammation (P<0.05). Forced expiratory volume in 1 s was inversely correlated with sputum eosinophils in all asthmatic patients (r(s)=-0.5, P=0.002). There were no significant differences in sputum 8-isoprostane or nitrate concentrations.

CONCLUSIONS

Increased airway concentrations of PGE(2) are consistent with the hypothesis that PGE(2) has a bronchoprotective and anti-inflammatory role in patients with more severe asthma. A reduced PGE(2) to cysLT ratio in the airways may adversely affect lung function and contribute to persistence of symptoms and airway remodelling in patients with eosinophilic airway inflammation.

Impact of age on pH, 8-isoprostane, and nitrogen oxides in exhaled breath condensate

BACKGROUND

Few studies have addressed the effects of aging on levels of inflammatory markers in exhaled breath condensate (EBC). The aim of this study was to determine whether there are significant age-associated differences in pH, 8-isoprostane, and nitrogen oxide values in EBC from a population of healthy adults.

MATERIAL AND METHODS

EBC samples were obtained from 75 healthy volunteers aged 18 to 80 years and stratified into five groups according to age (n = 15): 18 to 29, 30 to 39 years, 40 to 49 years, 50 to 59 years, and 60 to 80 years. The following were measured in the samples collected: pH before and after deaeration, nitrite, nitrate, and 8-isoprostane. Differences between the groups were assessed by the Kruskal-Wallis test.

RESULTS

Significant differences in deaerated pH (p < 0.0001) were found in the group of individuals 60 to 80 years of age as compared to the remaining groups. Significant differences were also found in 8-isoprostane levels between the younger and older groups (18 to 29 years and 30 to 39 years of age; p = 0.006 and p = 0.034, respectively). There were no significant differences in nitrite or nitrate values between younger and older individuals.

CONCLUSION

The results of this study indicate that pH and 8-isoprostane levels in EBC show a relationship with age. Thus, values obtained in studies with control groups may require adjustment for these factors.

Nitrites in induced sputum as a simple and cheap non-invasive marker of airway inflammation for asthmatic schoolchildren

To determine if there are differences in the nitric oxide metabolites (nitrites) in sputum of patients with persistent asthma and healthy schoolchildren, we performed a case-control study in a tertiary care hospital in Arequipa, Perú. Nitrites in induced sputum samples were measured using the Griess assay in 30 persistent asthmatics (mean age of 10.1 yr) and 30 controls (mean age of 11.9 yr). The mean +/- s.d. of nitrites among asthmatics was significantly higher than the controls (16.30 +/- 8.6 vs. 10.25 +/- 4.68 nmol/ml, respectively, p = 0.001). Moreover, the nitrite level in the sputum in children with severe persistent asthma was higher than in the level found in the moderate and mild asthmatics (32.83 +/- 9.48 vs. 18.10 +/- 1.96 vs. 11.84 +/- 4.73 nmol/ml, respectively, p < 0.01 for linear trend). This study showed for the first time in children that asthmatics have significantly higher levels of nitrites in induced sputum than healthy controls and that the level of nitrite correlates with the severity of the asthma. Nitrite levels in sputum, a simple and cheap, non-invasive method, may be a good alternative to measure the severity of inflammation in asthmatic children.

Ym1 and Ym2 expression in a mouse model exposed to diesel exhaust particles

BACKGROUND

Chitinase may play a role in regulating allergic diseases.

OBJECTIVE

We studied the role of chitinase in a mouse model exposed to diesel exhaust particles (DEP). Mice were exposed to intranasal DEP (0.6 mg/mL) for 5 days and challenged with aerosolized DEP (6 mg/m(3)) on days 6-8. Enhanced pause (Penh), as an airway obstruction marker, was measured on day 9, and bronchoalveolar lavage (BAL) fluid and lung tissues were collected on day 10. The expression of Ym1 and Ym2 mRNA was assessed in lung tissue extracts by reverse transcription-polymerase chain reaction.

RESULTS

DEP induced significant increases in methacholine-induced Penh and IL-4 levels in BAL fluid relative to the control group. Peribronchial and perivascular inflammatory cell infiltrates were prominent in the DEP group. DEP induced Ym1 and Ym2 mRNA expression in lung tissue extracts relative to the control group.

CONCLUSION

These results demonstrate that DEP induced airway hyperresponsiveness and Ym mRNA expression via a Th2 cell-biased response, suggesting that chitinase may play an important role in airway inflammation and responsiveness upon exposure to DEP in a mouse model, and may therefore be involved in regulating allergic diseases.

Breath condensate nitrite correlates with hyperinflation in chronic obstructive pulmonary disease

Estimating the degree of pulmonary hyperinflation in chronic obstructive pulmonary disease (COPD) is not always straight forward. Standard pulmonary function tests provide only a crude estimate of this important aspect of COPD. In addition, good patient cooperation cannot always be achieved and therefore adds to the uncertainties with regard to the extent of hyperinflation of the lung. The aim of this investigation was to characterize exhaled breath condensate nitrite in volunteers, healthy smokers, and stable COPD (GOLD-stages 0-4) and to compare this parameter with inflammatory markers in exhaled breath condensate and with lung function in order to test the hypothesis that elevated exhaled breath condensate nitrite reflects hyperinflation in COPD. We found a logarithmic correlation of exhaled breath condensate nitrite to residual volume (r=0.75, p<0.0001), total lung capacity (r=0.51, p<0.0001), and thoracic gas volume (r=0.71, p<0.0001) but no correlation of exhaled breath condensate nitrite concentrations with levels of inflammatory cytokines in exhaled breath condensate (interleukin (IL)-8, IL-1beta, IL-6, IL-10, IL-12, and tumor necrosis factor-alpha). Analysis of COPD subgroups revealed a logarithmic correlation of EBC nitrite to residual volume, total lung capacity, and intrathoracic gas volume exclusively for patients characterized by GOLD classes 2, and higher. Our results confirm a relation of exhaled breath condensate nitrite levels and hyperinflation measured by conventional pulmonary function tests. Investigations using isolated lung models and cells stretched in culture also provide insight into this relation. Exhaled breath condensate nitrite may be a biochemical indicator of pulmonary overdistension.

Eosinophilic inflammation, remodeling of lower airway, bronchial responsiveness and cough reflex sensitivity in non-asthmatic subjects with nasal allergy

BACKGROUND

It has been reported that nasal allergy influences the lower airway inflammation and functions. We elucidated whether nasal allergy would contribute to lower airway inflammation and functions.

METHODS

266 subjects aged 21-39 years were interviewed with special emphasis on history of asthma and nasal allergies (perennial allergic rhinitis (PAR) and seasonal allergic rhinitis (Japanese cedar pollinosis; PO)). Symptomatic subject was defined when nasal symptoms were present during a 3-week study period. Pulmonary function, provocative concentration of methacholine causing a 20% fall in forced expiratory volume in 1 s (PC20), capsaicin cough threshold defined as capsaicin concentration eliciting 5 or more coughs (C5) and eosinophil percentage in hypertonic saline-induced sputum were measured.

RESULTS

Based on the interview, 232 subjects without asthma were divided into symptomatic (n = 25) and asymptomatic (n = 22) PAR, PO on-season (n = 15) and off-season (n = 36), and non-nasal allergy subjects (control) (n = 134). Sputum eosinophils were significantly greater in symptomatic PAR than another four groups (p < 0.01). FEV1/FVC ratio was significantly lower in PAR than control (p < 0.05). Maximum mean expiratory flow was lower in PAR than control (asymptomatic: p < 0.05, symptomatic: p = 0.06). C5 was not different among groups. PAR tended to have a lower PC20 compared to control (symptomatic: p = 0.078; asymptomatic: p = 0.086).

CONCLUSIONS

These results suggest that eosinophilic inflammation occurred in symptomatic period of PAR may contribute to development of lower airway remodeling and bronchial hyperresponsiveness. Reversely, PO may not be associated with lower airway eosinophilic inflammation or abnormal bronchial functions. Nasal allergy dose not influence the cough reflex sensitivity.

Oxidative stress in the pathogenesis of asthma

Asthma affects 5% to 10% of the population of the United States. In asthmatics, oxidative stress occurs not only as a result of inflammation but also from environmental exposure to air pollution. The specific localization of antioxidants in the lung and the adaptive changes during asthma underscore the importance of oxidative stress, and therapeutic interventions that decrease exposure to environmental reactive oxygen species or augment endogenous antioxidant defenses might be beneficial as adjunctive therapies in asthmatic patients.

Changes in the expression of NO synthase isoforms after ozone: the effects of allergen exposure

Background

The functional role of nitric oxide (NO) and various nitric oxide synthase (NOS) isoforms in asthma remains unclear.

Objective

This study investigated the effects of ozone and ovalbumin (OVA) exposure on NOS isoforms.

Methods

The expression of inducible NOS (iNOS), neuronal NOS (nNOS), and endothelial NOS (eNOS) in lung tissue was measured. Enhanced pause (P_enh) was measured as a marker of airway obstruction. Nitrate and nitrite in bronchoalveolar lavage (BAL) fluid were measured using a modified Griess reaction.

Results

The nitrate concentration in BAL fluid from the OVA-sensitized/ozone-exposed/OVA-challenged group was greater than that of the OVA-sensitized/saline-challenged group. Methacholine-induced P_enh was increased in the OVA-sensitized/ozone-exposed/OVA-challenged group, with a shift in the dose-response curve to the left, compared with the OVA-sensitized/saline-challenged group. The levels of nNOS and eNOS were increased significantly in the OVA-sensitized/ozone-exposed/OVA-challenged group and the iNOS levels were reduced compared with the OVA-sensitized/saline-challenged group.

Conclusion

In mice, ozone is associated with increases in lung eNOS and nNOS, and decreases in iNOS. None of these enzymes are further affected by allergens, suggesting that the NOS isoforms play different roles in airway inflammation after ozone exposure.

Exhaled breath condensate nitrite and its relation to tidal volume in acute lung injury

STUDY OBJECTIVE

Mechanical ventilation may damage the lung. Low tidal volume (VT) is protective, but VT is scaled to body weight (BW) and may be high in functionally small ARDS lungs. We hypothesized that exhaled breath condensate (EBC) nitrite (NO(2)(-)) concentration may increase with lung distension.

DESIGN

Prospective, noncontrolled study.

SETTING

University hospital and medical ICU.

PATIENTS

Thirty-five ICU patients requiring mechanical ventilation (severe pneumonia, n = 31; exacerbated COPD, n = 4). Patients were scored according to American and European Consensus Conference on ARDS criteria (AECC) [no lung injury, n = 7; acute lung injury, n = 13; ARDS, n = 15], as well as the Murray lung injury severity score (LISS) [score 0, n = 3; score 0.1 to 2.5, n = 19; score > 2.5, n = 13].

INTERVENTIONS

EBC was collected and analyzed for NO(2)(-), interleukin (IL)-6, and IL-8. Serum was analyzed for IL-6, IL-8, and procalcitonin.

RESULTS

and measurements: EBC NO(2)(-) correlated well with VT (milliliters per kilogram of BW; r = 0.79, p < 0.0001) and expiratory minute volume (r = 0.60, p < 0.0001) but not with other ventilatory parameters or parameters of pulmonary (EBC IL-6, EBC IL-8) or systemic (serum IL-6, IL-8, and procalcitonin) inflammation. The ratio of EBC NO(2)(-) and the size of the VT correlated directly with lung injury (AECC, r = 0.66, p < 0.0001; LISS, r = 0.84, p < 0.0001).

CONCLUSION

EBC NO(2)(-) increased linearly with VT. The ratio of EBC NO(2)(-) to VT is assumed to reflect NO(2)(-) release at a given VT. An increase in this ratio indicates an inappropriate increase of NO(2)(-) production most likely due to mechanical stress of the remaining open lung units in injured lungs. We conclude that the EBC NO(2)(-)/VT ratio may help to identify situations of critical mechanical stress.

Nitric oxide in respiratory diseases

The formation and modulation of nitric oxide (NO) in the lungs is reviewed. Its beneficial and deleterious roles in airways diseases, including asthma, chronic obstructive pulmonary disease, and cystic fibrosis, and in animal models is discussed. The pharmacological effects of agents that modulate NO production or act as NO donors are described. The clinical pharmacology of these agents is described and the therapeutic potential for their use in airways disease is considered.

Optimization of sputum-processing methods for the measurement of interleukin-5: effects of protease inhibition

BACKGROUND

Interleukin (IL)-5 measurement in sputum samples has produced variable results that appear to be due to methodological problems. The aim of the present study was to investigate the effects of dithiothreitol (DTT), sputum protease inhibition and sample storage on IL-5 recovery in order to develop a method to accurately measure IL-5 in dispersed sputum supernatant.

METHODOLOGY

Measurement of IL-5 in sputum was performed in 22 subjects with airway disease. Interleukin-5 recovery was measured in samples spiked with recombinant human IL-5 using a commercial ELISA. A mix of four protease inhibitors (PI) was added to sputum processed using the selection method with dispersion using DTT and stored with and without inhibitors.

RESULTS

The addition of PI to sputum resulted in a 24% increase in IL-5 recovery. Recovery was not further increased with the addition of a blocking protein. Storage of IL-5-spiked sputum gave significantly less recovery. The addition of PI to sputum processed with DTT had no effect on total cell count, viability or cell differential.

CONCLUSION

Interleukin-5 recovery is increased by the addition of PI to samples processed using the selected portion method with DTT dispersion. A protease inhibitor cocktail should be added to sputum for IL-5 assay.

The effect of cigarette smoking on the levels of nitric oxide metabolites in the sputum of patients with acute asthma

Cigarette smoking may reduce the production of endogenous nitric oxide (NO), which plays an important role in inflammation of the asthmatic airway. NO metabolites in sputum were measured in 11 cigarette smokers and five nonsmokers, all with acute asthma. NO metabolite levels reflected the severity of asthmatic exacerbation, as they were significantly higher in patients with "severe," or "respiratory arrest imminent" asthma than in patients with "mild" to "moderate" asthma. There were no significant differences in sputum NO metabolite levels between smokers and nonsmokers with asthma, nor were any differences observed in NO metabolite levels for relative cigarette pack-years in smokers. These findings suggest that severe airway inflammation outweighs the effect of smoking on NO in the sputum of patients with asthma.

Relationship between the perception of dyspnoea and airway inflammatory markers

Poor dyspnoea perception in asthmatic patients seems to be associated with increased risk of asthma exacerbation. We have studied the relationship between basel ne dyspnoea perception and inflammatory markers in sputum in eight patients with mild asthma and in 13 patients with moderate to severe asthma. The perception of dyspnoea was scored on the Borg scale. Eosinophilic cationic protein (ECP) was measured by fluoroimmunoassay and by an interleukin (IL)-5 sandwich ELISA. The baseline Borg score was significantly higher in patients with severe asthma than in patients with mild to moderate asthma (4.1 +/- 0.29 vs. 2.28 +/- 0.28, P<0.05). The proportion of eosinophil and ECP levels in the sputum were significantly higher in patients with moderate to severe asthma. IL-5 in sputum was significantly increased in moderate to severe asthmatic patients compared to mild asthmatic patients. A significant relationship was found between the baseline perception score and FEV1/FVC (r = -0.53, P<0.01), sputum eosinophils (r = 0.70, P<0.01) and sputum ECP (r = 0.62, P<0.01). These findings suggest that the baseline perception score is related to inflammatory markers in sputum, and that the perception of dyspnoea as well as airway inflammatory markers may be considered to evaluate asthma severity.

Capillary electrophoresis analysis of nitrite and nitrate in sub-microliter quantities of airway surface liquid

We developed a simple capillary electrophoresis (CE) method to measure nitrite and nitrate concentrations in submicroliter samples of rat airway surface liquid (ASL), a thin (10-30 microm) layer of liquid covering the epithelial cells lining the airways of the lung. The composition of ASL has been poorly defined, in large part because of the small sample volume (approximately 1-3 microl per cm2 of epithelium) and difficulty of harvesting ASL. We have used capillary tubes for ASL sample collection, with microanalysis by CE using a 50 mM phosphate buffer (pH 3), with 0.5 mM spermine as a dynamic flow modifier, and direct UV detection at 214 nm. The limit of detections (LODs), under conditions used, for ASL analysis were 10 microM for nitrate and 30 microM for nitrite (SIN= 3). Nitrate and nitrite were also measured in rat plasma. The concentration of nitrate was 102+/-12 microM in rat ASL and 70+/-1.0 microM in rat plasma, whereas nitrite was 83+/-28 microM in rat ASL and below the LOD in rat plasma. After instilling lipopolysaccharide intratracheally to induce increased NO production, the nitrate concentration in ASL increased to 387+/-16 microM, and to 377+/-88 microM in plasma. The concentration of nitrite increased to 103+/-7.0 microM for ASL and 138+/-17 microM for plasma.

Nitric oxide metabolites in patients with asthma: induced sputum versus blood

Nitric oxide (NO) plays an important role in physiological regulation of the airways. The monitoring of airway inflammation has being observed in bronchial asthma directly, by sputum examination, and indirectly, by measurements in peripheral blood. To investigate the diagnostic value of these two methods, we compared NO metabolites in induced sputum and serum obtained in patients with asthma and control subjects. Hypertonic saline induced sputum and serum were obtained in 13 patients with asthma and 10 control subjects. NO metabolite level was assayed by using modified Griess reaction. Eosinophil cationic protein (ECP) was measured by fluoroimmunoassay, and detected interleukin (IL)-5 by a sandwich ELISA. The accuracy of the tests was measured by plotting the data in receiver operating characteristic (ROC) curves and comparing the area under the curve for NO metabolites. Asthmatic patients, compared with control subjects, had significantly higher NO metabolites in induced sputum (1252.5+/-203.3 mol l(-1) vs. 557.2+/-101.5 mol l(-1), P<0.01) but not in serum. IL-5 in induced sputum was detected more frequently in patients with asthma than in control subjects [11/13 (84.6%) vs. 1/10 (10%), P<0.01]. Asthmatic patients, compared with control subjects, had significantly higher ECP concentration in induced sputum (1270.0+/-197.9 g l vs. 154.6+/-47.4 g l(-1), P<0.01). There were significant positive correlations between NO metabolites in induced sputum and eosinophils, ECP in induced sputum (r=0.58 P<0.05; r=0.64, P<0.01) in patients with asthma but not in serum. The area under the ROC curve showed that NO metabolites in induced sputum (0.78) are more accurate marker than NO metabolites in serum (0.53) (P<0.05). These findings suggest that NO metabolites in induced sputum is a more valuable indicator to monitor asthmatic airway inflammation than those in serum.