Concentrations of exhaled nitric oxide in asthmatics and subjects with allergic rhinitis sensitized to the same pollen allergen

The Pattern of Sensitization Influences Exhaled and Nasal Nitric Oxide Levels in Young Adults

Nitric oxide (NO) from upper (nasal NO, nNO) or lower airways (fractional exhaled NO, FeNO) is considered a surrogate marker for Th2-type inflammation, which is influenced by atopy. The aim of this study was to analyze nNO and FeNO in regard to qualitative and quantitative aspects of sensitization. We evaluated 244 non-smoking young adults. All of them were first-year students recruited for a longitudinal study. An inhalation allergy screening tool was used for atopy definition (specific immunoglobulin E (sIgE) to sx1 ≥ 0.35 kU/L), and also sIgE response to three inhalant perennial allergens, house dust mite (HDM, d1), cat (e1), and dog (e5), was determined in the non-pollen season. With respect to sx1, 100 subjects could be classified as atopic. Sensitization to one, two, or three perennial allergens could be demonstrated in 46, 10, and 16 students, respectively. The subjects with positive IgE response to sx1, but not sensitized to HDM, cat, and/or dog, had FeNO levels comparable to those of non-atopic subjects (13.5 vs. 13.0 ppb, respectively; p = 0.485). These levels were significantly lower compared to atopic subjects being sensitized to any perennial allergen (19.0 ppb; p = 0.0003). After grouping the atopic subjects for perennial sensitization patterns, significantly higher FeNO could be detected in subjects with poly-sensitization (n = 26; 26.0 ppb) compared to the mono-sensitized ones (n = 46; 18.0 ppb; p = 0.023). Regarding nNO, no differences could be observed. Applying a two-way ANOVA, we could reveal a significant correlation of specific HDM-IgE CAP-class with FeNO (p < 0.0001) and nNO levels (p = 0.007). Finally, a significant relationship was found between nNO and FeNO for the whole cohort (p < 0.0001). In summary, our findings support the argument that atopy and perennial sensitization should be considered for the interpretation of NO.

The association between daily outpatient visits for allergic rhinitis and pollen levels in Beijing

To investigate the effects of aerosol pollen on human health, we carried out a time-series analysis of daily general practitioner consultations for allergic rhinitis (AR) in Beijing. The objective of this study was to assess the possible effects of pollen on clinic visits for allergic rhinitis in Beijing during the pollen season. We found a strong association between the concentration of pollen in ambient air and the number of consultations for allergic rhinitis. Females had significantly more outpatient visits than males when the levels of pollen increased. Young people (20-60 years old) had had significantly more outpatient visits than older people (over 60 years old) when the levels of pollen increased. After adjusting for air pollutants, the relative risks of pollen on daily number of outpatient for AR were increased.

Effects of allergen exposure on methacholine and AMP-induced air trapping in pollen-sensitive subjects

BACKGROUND

The effect of pro-inflammatory stimuli on bronchoconstrictor-induced air trapping has not been studied.

OBJECTIVE

To determine the effect of natural allergen exposure, a pro-inflammatory stimulus, on methacholine- and adenosine 5'-monophospate (AMP)-induced air trapping.

METHODS

Airway responsiveness to methacholine and AMP before and during the pollen season was obtained in 25 subjects with pollen allergy and in 10 healthy controls. The response was expressed by the sensitivity (PC20 value) and by the slope and intercept of the FVC values recorded at each step of the challenge against the corresponding FEV1 values.

RESULTS

The slope and intercept FVC versus FEV1 values for both methacholine and AMP were significantly higher in subjects with pollen allergy than in healthy controls. In the group with pollen allergy, both methacholine and AMP PC20 values decreased significantly during the pollen season. However, the mean (95% CI) slope FVC versus FEV1 values for methacholine were 1.00 (0.84-1.16) before the pollen season and 0.99 (0.86-1.12, P = 0.90) during the pollen season. Similar results were obtained with AMP.

CONCLUSIONS

Although the air trapping induced by both methacholine and AMP is significantly greater in subjects with pollen allergy than in healthy controls, natural allergen exposure is associated with a selective increase in airway sensitivity without concomitant changes in bronchoconstrictor-induced air trapping. These findings suggest that the information provided by the bronchoconstrictor-induced change in FEV1 and FVC is not equivalent and may be complementary.

Exhaled nitric oxide measurement is not useful for predicting the response to inhaled corticosteroids in subjects with chronic cough

BACKGROUND

Increased concentrations of exhaled nitric oxide (ENO) are identified predominantly in subjects with chronic cough due to conditions that habitually respond well to therapy with inhaled corticosteroids (ICSs). The aim of this study was to assess the usefulness of ENO in predicting the response to ICS therapy in subjects with chronic cough and to determine the relationship between either methacholine or adenosine 5'-monophosphate (AMP) responsiveness and the response to ICS therapy.

METHODS

A total of 43 patients with chronic cough were studied. During the baseline period, ENO measurement, spirometry, and concentration-response studies with both methacholine and AMP were performed. For the next 4 weeks, the patients were treated with inhaled fluticasone propionate, 100 microg twice daily. At baseline (1 week) and during the 4-week treatment period, patients twice daily completed entries in a diary, in which they recorded daytime and nighttime cough symptom scores.

RESULTS

Nineteen patients (44%) responded well to fluticasone therapy. The receiver operating characteristic curve analysis showed that the accuracy of identifying the response to ICS therapy for ENO at baseline was poor. The sensitivity and specificity of ENO for predicting the response to ICS therapy, using 20 parts per billion as the ENO cutoff point, were 53% and 63%, respectively. Differences in both prevalence and degree of airway responsiveness to either methacholine or AMP between fluticasone-responsive subjects and nonresponsive subjects were also not significant.

CONCLUSIONS

Although a significant proportion of subjects with chronic cough respond well to ICS therapy, these patients cannot be identified by ENO levels or AMP responsiveness at baseline.

Maximal response plateau to adenosine 5'-monophosphate in asthma. Relationship with the response to methacholine, exhaled nitric oxide, and exhaled breath condensate pH

BACKGROUND

No information is available on the plateau in response to adenosine 5'-monophosphate(AMP). The aims of the present study were (1) to determine whether plateau can be detected with AMP and the relation with the plateau in response to methacholine, and (2) to identify the relation between the plateau and indirect markers of airway inflammation, such as exhaled nitric oxide (ENO) and exhaled breath condensate (EBC) pH.

METHODS

Airway responsiveness to high concentrations of methacholine and AMP, ENO levels, and EBC pH values were obtained in 31 subjects with well-controlled asthma. Concentration-response curves were characterized by their concentration of agonist that produces a decrease in FEV(1) of 20% and, if possible, by the level of plateau.

RESULTS

Although the prevalence of plateau with methacholine (48%) and AMP (58%) was similar, the two challenges did not identify plateau in exactly the same individuals. In 14 subjects who showed plateau with both bronchoconstrictor agents, the mean plateau level for methacholine was 26.0% (95% confidence interval [CI], 21.3 to 30.8), compared with 16.5% (95% CI, 12.2 to 20.8; p < 0.0001) for AMP. Both ENO and EBC pH values were similar in subjects with plateau and in those without plateau.

CONCLUSIONS

In well-controlled asthmatics, the plateau in response to AMP can be identified at a milder degree of obstruction than the plateau in response to methacholine, but the two agonists are not identifying the same airway abnormalities. Furthermore, if ENO and EBC pH are markers of inflammation, the determination of the presence or level of plateau is not a reliable method to identify airway inflammation in asthma.

The clinical significance of exhaled nitric oxide in asthma

Asthma is an inflammatory disease of the airways, for which many therapeutic options are available. Guidelines for the management of asthma suggest a stepwise approach to pharmacotherapy based on assessment of asthma severity and control. However, the assessment of asthma control presently relies on surrogate measures, such as the frequency of symptoms or the frequency of use of short-acting beta2-adrenergic agonists. There is no simple, noninvasive technique for the assessment of severity of actual airway inflammation in asthma. The collection and analysis of nitric oxide (NO) levels in exhaled breath has recently become feasible in humans. Based on increased exhaled NO (eNO) levels in patients with asthma, eNO analysis has been proposed as a novel, noninvasive approach to the assessment and monitoring of airway inflammation, and as a basis for adjustments in asthma therapy. In the present paper, the relationship of elevated eNO levels in asthma with inflammatory, physiological and clinical markers of asthma in adults was reviewed. Use of eNO is a promising tool for diagnosing asthma, for monitoring asthma control and for guiding optimal anti-inflammatory asthma therapy. However, because of many unresolved questions, eNO cannot be recommended at present for routine clinical management of adults with asthma.

Bronchial responsiveness to methacholine and adenosine 5'-monophosphate in young children with asthma: their relationship with blood eosinophils and serum eosinophil cationic protein

BACKGROUND

Bronchial hyperresponsiveness is a characteristic feature of asthma, and is usually measured by bronchial challenges using direct or indirect stimuli. Blood eosinophil numbers and serum levels of eosinophil cationic protein (ECP) are considered as indirect measures of airway inflammation in asthma. The aim of this study was to investigate whether bronchial responsiveness to adenosine 5'-monophosphate (AMP) is more closely associated with blood eosinophil markers, compared with that to methacholine, in young children with asthma.

METHODS

Methacholine and AMP bronchial challenges were performed in 4- to 6-year-old children with asthma (n = 77) and in healthy controls (n = 32), using a modified auscultation method. The end-point was defined as the appearance of wheezing and/or oxygen desaturation. The peripheral blood eosinophil counts and serum ECP concentrations were determined in each subject.

RESULTS

A positive response to methacholine (end-point concentration < or =8mg/ml) and to AMP (end-point concentration < or =200 mg/ml) was observed in 74 (96.1%) and 66 asthmatic children (85.7%), respectively. A majority of controls was unresponsive to both challenges. In the asthma group, there was no significant correlation between methacholine end-point concentration and the eosinophil counts (r = -0.111, P = 0.337) or serum ECP levels (r = -0.126, P = 0.274). In contrast, AMP end-point concentration correlated significantly with the eosinophil counts (r = -0.372, P = 0.001) and with serum ECP levels (r = -0.371, P = 0.001).

CONCLUSIONS

Our results suggest that bronchial responsiveness to AMP is more closely related to airway inflammation, compared with that to methacholine, and support the potential usefulness of AMP challenges in detecting inflammatory changes in young children with asthma.

The connection between allergic rhinitis and bronchial asthma

PURPOSE OF REVIEW

The relationship between allergic rhinitis and asthma has intrigued practicing physicians since the turn of the century. Investigations during the past two decades have led to an increased understanding of this relationship.

RECENT FINDINGS

A growing body of evidence clearly demonstrates that patients with allergic rhinitis, in the absence of asthma, have distinct abnormalities of lower airway function, including alterations in physiology, histology and biochemistry. In addition, epidemiologic surveys have consistently shown allergic rhinitis as an independent risk factor for developing asthma, and that preexisting abnormalities in lung function may predispose to lower airway disease development. Clinical trials show that specific allergen immunotherapy for children and adults with seasonal allergic rhinitis reduces the risk of developing asthma. In patients with established asthma and concomitant allergic rhinitis, several medications have significant effects upon the upper and lower airways, including intranasal corticosteroids, oral antihistamines, and leukotriene receptor antagonists.

SUMMARY

Our understanding of the natural history of allergic rhinitis could lead to improvements in early intervention, potentially preventing the progression of allergic rhinitis to asthma. Aggressive treatment of rhinitis in patients with concomitant asthma may enhance asthma outcomes and quality of life for all patients with these chronic diseases.

Effect of montelukast on symptoms and exhaled nitric oxide levels in 7- to 14-year-old children with seasonal allergic rhinitis

BACKGROUND

Cysteinyl leukotrienes have been found to exert potent inflammatory effects in the upper airways and play a fundamental role in the pathogenesis of allergic rhinitis. Previous studies have reported increased levels of exhaled nitric oxide (eNO) in patients with allergic rhinitis without asthma symptoms.

OBJECTIVE

To investigate the role of treatment with montelukast on symptoms, eNO levels, and peripheral eosinophil counts of children with seasonal allergic rhinitis during pollen season.

METHODS

A randomized, double-blind, parallel-group study performed between April and June 2005 in 57 children aged 7 to 14 years with seasonal allergic rhinitis was performed. The study comprised a 1-week screening period, a 1-week run-in period, and a 2-week treatment period with once daily montelukast, 5 mg, or matching placebo.

RESULTS

No significant difference at baseline was found in symptom scores, eNO levels, and blood eosinophil counts between the treatment and placebo groups. After 2 weeks of montelukast treatment, improvements from the baseline in the daytime nasal, composite, and daytime eye symptoms scores were significantly greater in the montelukast group compared with the placebo group (P < .001, P < .001, and P < .01, respectively). A significant decrease was also found in eosinophil counts (P < .001) in the montelukast group compared with the placebo group after treatment. Montelukast treatment did not produce a significant effect on eNO levels compared with placebo (P = .96).

CONCLUSION

Montelukast treatment provided significant improvement in symptoms and peripheral eosinophil counts of school-age children with seasonal allergic rhinitis; however, it did not show a significant effect on eNO levels.

Adenosine receptors: promising targets for the development of novel therapeutics and diagnostics for asthma

Interest in the role of adenosine in asthma has escalated considerably since the early observation of its powerful bronchoconstrictor effects in asthmatic but not normal airways. A growing body of evidence has emerged in support of a proinflammatory and immunomodulatory role for the purine nucleoside adenosine in the pathogenic mechanisms of chronic inflammatory disorders of the airways such as asthma. The fact that adenosine enhances mast cell allergen-dependent activation, that elevated levels of adenosine are present in chronically inflamed airways, and that adenosine given by inhalation cause dose-dependent bronchoconstriction in subjects with asthma emphasizes the importance of adenosine in the initiation, persistence and progression of these common inflammatory disorders of the airways. These distinctive features of adenosine have been recently exploited in the clinical and research setting to identify innovative diagnostic applications for asthma. In addition, because adenosine exerts its multiple biological activities by interacting with four adenosine receptor subtypes, selective activation or blockade of these receptors may lead to the development of novel therapies for asthma.

Exhaled nitric oxide, total serum IgE and allergic sensitization in childhood asthma and allergic rhinitis

Exhaled nitric oxide (eNO) levels are correlated with several markers of atopy and inflammatory activity in the airways, but the relationship between eNO and total serum IgE has not been fully elucidated in the context of allergic sensitization. The aim of this study was to investigate the relationship between eNO, total serum IgE and allergic sensitization in childhood asthma and allergic rhinitis. eNO levels, lung function, skin prick tests and total serum IgE were determined in 109 children (mean age, 10.4 yr) with mild intermittent asthma and in 41 children (mean age, 10.1 yr) with allergic rhinitis; 25 healthy non-atopic children were recruited as controls. eNO levels (median) were significantly higher in patients with asthma (22.7 p.p.b.) and in those with allergic rhinitis (15.3 p.p.b.) than in healthy controls (5.9 p.p.b.). Children with allergic asthma had higher eNO levels than children with allergic rhinitis. A significant positive correlation was found between eNO and total serum IgE (asthma, r = 0.42, p < 0.0001; allergic rhinitis, r = 0.31, p < 0.01), and between eNO and the number of positive skin prick tests (asthma, r = 0.31, p < 0.0001; allergic rhinitis, r = 0.39, p < 0.01). eNO levels were better correlated with total IgE than with the number of positive skin prick tests. This correlation was independent of allergic sensitization. High total serum IgE represents a specific and predictive marker of eNO increase in children with asthma or allergic rhinitis. This finding adds further support to the hypothesis that increased serum IgE could be a marker itself of airway inflammation in patients with allergic disease.

Phenol-containing saline solution as a diluent for adenosine 5'-monophosphate in bronchial challenge testing

OBJECTIVES

To investigate the effect of dissolving adenosine 5'-monophosphate (AMP) with phenol-containing saline solution on the stability and the bronchoconstrictive properties of this indirect agonist.

METHODS

Eleven subjects with asthma well controlled with short-acting inhaled beta2-agonists as required or with inhaled corticosteroids were studied. Bronchial challenge tests with AMP dissolved with either normal saline solution or saline solution containing 0.4% phenol were performed on separate days. Furthermore, to assess the potential influence of the phenol-containing saline solution on the stability of the bronchoconstrictor agent, AMP solutions in concentrations of 40 microg/mL and 400 microg/mL were prepared in saline solution and phenol-containing saline solution and, after 30 min, the AMP levels were determined by high-performance liquid chromatography (HPLC) assay.

RESULTS

The geometric mean AMP provocative concentration causing a 20% fall in FEV1 (PC20) was 13.49 mg/mL (95% confidence interval [CI], 6.76 to 26.91) for the saline solution method, and AMP PC20 for the saline solution with phenol method was 8.91 mg/mL (95% CI, 3.39 to 23.44) [p = 0.18]. No significant differences were found between the concentrations of AMP made in saline solution compared to those made in phenol-containing saline solution measured by HPLC.

CONCLUSION

These observations indicate that normal saline solution with or without phenol can be used as the diluent for AMP. However, since a potential risk with AMP of industrial sources is the bacterial contamination, adding a preservative such as phenol to a saline solution diluent might be recommended.

Research applications and implications of adenosine in diseased airways

Adenosine, when given by inhalation, initiates the narrowing of airways in subjects with asthma or chronic obstructive pulmonary disease (COPD). The underlying mechanism of this narrowing appears to involve the stimulation of specific mast cell surface adenosine receptors with the subsequent release of mediators and contraction of airway smooth muscle. Although methacholine and histamine have become gold standards as bronchial provocants used to quantify bronchial hyperresponsiveness, the airways response to the indirect stimulus adenosine more closely reflects bronchial inflammation. This distinctive feature of adenosine could be exploited to enable superior diagnostic discrimination between asthma and COPD, allow better monitoring of disease activity and progression, and improve the individual adjustment of long-term asthma management with topical glucocorticosteroids. In this article, we review recent developments in this area of rapidly evolving clinical research, focusing on the putative role of adenosine as a mediator of airway inflammation and as a useful bronchoprovocant in several clinical and research applications.