Changes in sputum composition during 15 min of sputum induction in healthy subjects and patients with asthma and chronic obstructive pulmonary disease

Exhaled Nitric Oxide and Sputum Eosinophils Are Complementary Tools for Diagnosing Occupational Asthma

BACKGROUND

Exposure-related changes in exhaled nitric oxide (FeNO) and sputum eosinophils have not been thoroughly compared in the investigation of occupational asthma.

OBJECTIVE

This study aimed at comparing the accuracies of the changes in FeNO concentrations and sputum eosinophil counts in identifying asthmatic reactions induced by occupational agents during specific inhalation challenges (SICs).

METHODS

This retrospective multicenter study included 321 subjects who completed an assessment of FeNO and sputum eosinophils before and 24 h after SICs with various occupational agents, of whom 156 showed a positive result.

RESULTS

Post-challenge changes in FeNO and sputum eosinophils showed similar accuracies, with areas under the receiver operating characteristics curve of 0.78 (95% confidence interval [95% CI], 0.72-0.83) and 0.81 (95% CI, 0.76-0.86), respectively. Increases in FeNO level ≥ 13 ppb and sputum eosinophils ≥ 1.25% were identified as the optimal threshold values for differentiating positive from negative SICs. Using these thresholds, the changes in FeNO and sputum eosinophils each achieved a ≥ 95% specificity but a low sensitivity (55% and 62%, respectively). FeNO and sputum eosinophils showed discordant increases in 38% of subjects with a positive SIC. Combining either a rise in FeNO ≥ 13 ppb or an increase in sputum eosinophils ≥ 1.25% increased the sensitivity to 77%.

CONCLUSIONS

Increases in FeNO concentration and/or sputum eosinophils after exposure to occupational agents strongly support a diagnosis of occupational asthma. The assessment of both markers of airway inflammation should be regarded as a reliable complementary tool to spirometry for identifying bronchial responses to occupational agents.

Progress in research on induced sputum in asthma: a narrative review

OBJECTIVE

To explore the clinical significance of induced sputum in asthma through a retrospective analysis of induced sputum in patients with asthma.

DATA SOURCES

The data and references cited in this article were obtained from PubMed, Sci-Hub, and Web of Science.

STUDY SELECTION

Observational studies with reliable data were selected.

CONCLUSIONS

The cytological count, -omics, and pathogen detection of induced sputum are helpful for the clinical diagnosis of asthma and in guiding medication choices.

Breath and Sputum Analyses in Asthmatic Patients: An Overview

Recent advancements in asthma management include non-invasive methodologies such as sputum analysis, exhaled breath condensate (EBC), and fractional exhaled nitric oxide (FeNO). These techniques offer a means to assess airway inflammation, a critical feature of asthma, without invasive procedures. Sputum analysis provides detailed insights into airway inflammation patterns and cellular composition, guiding personalized treatment strategies. EBC collection, reflecting bronchoalveolar lining fluid composition, provides a non-invasive window into airway physiology. FeNO emerges as a pivotal biomarker, offering insights into eosinophilic airway inflammation and aiding in asthma diagnosis, treatment monitoring, and the prediction of exacerbation risks. Despite inherent limitations, each method offers valuable tools for a more comprehensive assessment of asthma. Combining these techniques with traditional methods like spirometry may lead to more personalized treatment plans and improved patient outcomes. Future research is crucial to refine protocols, validate biomarkers, and establish comprehensive guidelines in order to enhance asthma management with tailored therapeutic strategies and improved patient outcomes.

Methodological Aspects of Induced Sputum

We aimed to conduct a state-of-the-art review of the current literature and offer further insights into the methodological aspects concerning induced sputum. The increasing popularity of sputum induction as a non-invasive and cost-effective method for obtaining lower airway secretions from patients who cannot produce sputum naturally has led to extensive research and applications in respiratory conditions like asthma and COPD. This technique allows for analysis of the cellular and biochemical components of the sputum to take place, providing insights into airway inflammation, immune cells, and help in predicting treatment response. Furthermore, induced sputum enables various analyses, including microRNA and gene expression studies and immunophenotyping. The procedure is generally safe and well tolerated, even in patients with airflow limitations; however, monitoring lung function is essential, especially in those with airway hyperresponsiveness. Optimal saline solution concentration and inhalation duration have been investigated, recommending a 15-20 min induction with hypertonic saline. Expectoration involves coughing at the end of each inhalation time. Careful handling during sputum processing is necessary for obtaining accurate results in cell cytology, immunocytochemistry, and in situ hybridization. Overall, induced sputum offers significant advantages as a preferred alternative for large-scale and repeated airway sampling, despite some technical demands and limitations.

Hypertonic Solution in Severe COVID-19 Patient: A Potential Adjuvant Therapy

Coronavirus disease 2019 (COVID-19) features hyper-inflammation, cytokine storm, neutrophil function changes, and sodium chloride (NaCl) homeostasis disruption, while the treatment with NaCl hypertonic solutions (HS) controls electrolytic body homeostasis and cell functions. HS treatment is a simple, popular, economic, and feasible therapy to regulate leukocyte function with a robust anti-inflammatory effect in many inflammatory diseases. The purpose of this narrative review is to highlight the knowledge on the use of HS approaches against viral infection over the past years and to describe the mechanisms involved in the release of neutrophil extracellular traps (NETs) and production of cytokine in severe lung diseases, such as COVID-19. We reported the consequences of hyponatremia in COVID-19 patients, and the immunomodulatory effects of HS, either in vitro or in vivo. We also described the relationship between electrolyte disturbances and COVID-19 infection. Although there is still a lack of clinical trials, hypertonic NaCl solutions have marked effects on neutrophil function and NETs formation, emerging as a promising adjuvant therapy in COVID-19.

Mepolizumab effectiveness in patients with severe eosinophilic asthma and co-presence of bronchiectasis: A real-world retrospective pilot study

BACKGROUND

The association of bronchiectasis (BE) in patients with severe eosinophilic asthma (SEA) is quite frequent. Mepolizumab is a well-recognized treatment for SEA; we aim to evaluate its effectiveness in SEA patients with and without BE in real-life.

METHODS

We performed a single-center retrospective pilot study, including patients with SEA treated with mepolizumab for one year. Asthma control test (ACT), lung function, annual exacerbations rate, oral corticosteroid dosage, FeNO, chronic mucous secretions, blood and sputum eosinophils were recorded at baseline and after 6 and 12 months.

RESULTS

we included 32 patients (mean age: 52.3 ± 10, 59% female). 50% showed co-presence of bronchiectasis, (SEA + BE). Significant improvements were found in ACT [(13.8 ± 4.6 to 20.7 ± 4.1, p = 0.0009) and (13 ± 4.8 to 20.7 ± 4.6, p = 0.0003)], annual exacerbations rate [from 7 (4-12) to 0 (0.00-0.75) and from 8 (4-12) to 0 (0-1), p < 0.0001], and blood eosinophils count [748 cells/μL (400-1250) vs. 84 cells/μL (52.5-100), and from 691 cells/μL (405-798) vs. 60 cells/μL (41-105), p < 0.0001] in SEA and SEA + BE group respectively, already after 6 months of treatment. A reduction in daily oral corticosteroids intake at 12 months was shown [from 15 mg (0-25) to 0 mg (0-0), p = 0.003 and from 8.8 mg (0-25) to 0 mg (0-0) (p = 0.01)] in both SEA and SEA + BE, respectively. Similar results were found, comparing SEA + BE patients based on the severity of bronchiectasis.

CONCLUSIONS

Mepolizumab effectively improves asthma symptoms control, reducing annual exacerbations and corticosteroid intake in all patients with SEA, even in the subgroup with coexisting bronchiectasis, independently of their severity.

The Role of Airways 17β-Estradiol as a Biomarker of Severity in Postmenopausal Asthma: A Pilot Study

Background: Asthma severity differs according to gender; in adult women, there is higher prevalence and severity of asthma than in men, and it coincides with changes in sex hormones. Recently, a new phonotype of asthma has been identified that appears after menopause, and it may be associated with decreased estrogen levels. Our goal was to study the 17β-estradiol (E2) concentrations in the blood and airways of women affected by asthma onset after menopause, evaluating its possible role in the severity of the disease. Methods: We enrolled 33 consecutive women with a diagnosis of postmenopausal asthma, recruited from the outpatient pulmonary clinic: 18 with severe (SA) and 15 with mild-to-moderate (MMA) asthma. We also included 30 age-matched healthy menopausal women as controls (HS). All subjects enrolled underwent blood and sputum collection (IS), and E2 concentrations were determined in plasma and sputum supernatant samples using an enzyme-linked immunosorbent assay (ELISA) kit. Results: Significantly higher serum concentrations of E2 were found in postmenopausal SA compared to MMA and HS, respectively (33 ± 5.5 vs. 24 ± 6.63 vs. 7.79 ± 1.54 pg/mL, p < 0.05). Similar results were found in the IS: significantly higher levels of E2 were detected in patients with postmenopausal SA compared with MMA and HS, respectively (0.34 ± 0.17 vs. 0.26 ± 0.13 vs. 0.07 ± 0.06 pg/mL, p < 0.05). We found positive correlations between IS E2 concentrations and sputum neutrophil levels in SA group (ρ = 0.52, p < 0.05). Conclusions: Our findings showed the possibility to measure E2 in the airways, and it has increased in postmenopausal asthmatic patients, especially in those with SA. Airways E2 levels may serve as a suitable biomarker of postmenopausal SA to help to phenotype SA patients with neutrophil inflammation.

Spontaneous sputum discriminates inflammatory phenotypes in patients with asthma

BACKGROUND

Eosinophils in induced sputum are not only a useful biomarker for diagnosing asthma but are also associated with severe asthma. However, little is known about the association between eosinophils in spontaneous sputum and asthma severity.

OBJECTIVE

To investigate whether spontaneous sputum eosinophils are related to severe asthma in adult patients with asthma.

METHODS

We conducted a retrospective cross-sectional study on 86 people with asthma whose spontaneous sputa were successfully collected. Patients were classified into 4 phenotypes according to the eosinophil and neutrophil levels in spontaneous sputum. We determined the association between inflammatory phenotypes and severe asthma. Moreover, we also compared asthma severity among the phenotypes classified according to blood eosinophils and spontaneous sputum eosinophils.

RESULTS

Asthma phenotypes were as follows: paucigranulocytic, 30.2%; neutrophilic, 18.6%; eosinophilic, 32.6%; and mixed, 18.6%. People with eosinophilic asthma had the highest blood eosinophils, total immunoglobulin E (IgE), and fractional exhaled nitric oxide among the 4 phenotypes. Significant differences were observed in asthma severity between the phenotypes (P = .019). In particular, 57.2% and 56.2% of patients had severe eosinophilic asthma and mixed asthma, respectively. The logistic regression analysis revealed that spontaneous sputum eosinophilia represented the strongest association with severe asthma among the inflammatory variables. Finally, more patients with severe asthma were included in the phenotype with spontaneous sputum eosinophils greater than 3% and blood eosinophils less than or equal to 300/μL and in the phenotype with spontaneous sputum eosinophils greater than 3% and blood eosinophils greater than 300/μL.

CONCLUSION

Spontaneous sputum can provide helpful information on airway inflammatory phenotyping in patients with asthma.

Severe uncontrolled asthma with bronchiectasis: a pilot study of an emerging phenotype that responds to mepolizumab

Background

Asthma and bronchiectasis are different conditions that frequently coexist. The prevalence of bronchiectasis rises considerably in subjects with severe asthma (25%–51%).

Objective

We evaluated the clinical and biological efficacy of mepolizumab on our pilot population of severe uncontrolled asthmatics with bronchiectasis not related to other pathologies.

Patients and methods

Four patients with severe uncontrolled asthma and diagnosed as bronchiectasis were recruited and started biological treatment with mepolizumab. Standard investigations were performed in all four patients at baseline (T0), after 3 months (T1) and after 1 year (T2) of treatment.

Results

After 1 year (T2) of therapy with mepolizumab, patients showed a significant increment of asthma control test value (12±1.1 vs 24.5±0.3, P<0.01), a reduction of the number of exacerbations/year (5±0.7 vs 0.75±0.75, P<0.01), an increase of pre-bronchodilator FEV₁ (1,680±500 vs 1,860±550 mL, P<0.01) and a reduction of eosinophils in blood (0.75±0.14 vs 0.12±0.02 cells/µL, P<0.01), in the sputum (9.6%±2.1% vs 5.6%±2.7%, P<0.05) and in nasal cytology (++ vs +).

Conclusion

The efficacy of mepolizumab in terms of reduction of inflammation and increase of control that we observed in our patients might suggest that targeting the IL-5 in severe eosinophilic asthma with bronchiectasis may be a good therapeutic strategy.

Looking for Airways Periostin in Severe Asthma: Could It Be Useful for Clustering Type 2 Endotype?

BACKGROUND

Severe asthma is heterogeneous clinically and biologically and is often difficult to control. In particular, the type 2 (T2) immunity endotype of severe asthma is gaining increasing interest because it is susceptible to newly developed biologic treatments that can transform the quality of life of these patients. The aim of this study was to analyze periostin concentrations in the airways of patients with severe asthma, evaluating its role in clustering the T2 endotype.

METHODS

We enrolled 40 consecutive patients with severe asthma (T2 endotype: n = 25; non-T2 endotype: n = 15), 21 patients with mild to moderate asthma, and 15 healthy control subjects. All subjects enrolled underwent exhaled breath condensate (EBC) and sputum collection, eosinophil count in blood, fractional exhaled nitric oxide, and IgE measurement. Periostin was assessed by an enzyme-linked immunosorbent assay kit on EBC and induced sputum (IS) supernatant.

RESULTS

We were able to detect higher periostin levels in the EBC (0.75 ± 0.46 vs 0.70 ± 0.19 vs 0.11 ± 0.05 ng/mL, P < .05 and P < .01) and in IS (0.55 ± 0.23 vs 0.31 ± 0.13 vs 0.16 ± 0.120 ng/mL, P < .05 and P < .01) of patients with severe asthma compared with patients with mild to moderate asthma and healthy control subjects, respectively. We further found an increase of periostin levels in both samples in T2 endotype compared with non-T2 endotype (EBC: 0.88 ± 0.46 vs 0.52 ± 0.46 ng/mL; IS: 0.69 ± 0.19 vs 0.39 ± 0.16 ng/mL; P < .05) and a correlation between periostin levels in EBC and sputum.

CONCLUSIONS

We found that periostin is measurable in the airways and increased in patients with severe asthma, especially in those from the T2 endotype. Unlike serum periostin, which may be derived from several sources outside the lung, airways periostin is a useful marker of severe eosinophilic asthma and may help to phenotype patients that will respond to the biologic agents.

Influence of the Polymorphism C-509T in the TGFB1 Gene Promoter on the Response to Montelukast

Transforming growth factor beta 1 (TGFB1) is a multifunctional cytokine with a key role in asthma airway inflammation and remodeling. Since elevated levels of this cytokine in airways might be associated with response to asthma therapy, the aim of this study was to investigate whether the presence of the polymorphism C-509T in the promoter of the TGFB1 gene is associated with response to montelukast. A group of 102 asthmatic patients was genotyped for the presence of the C-509T polymorphism by DNA sequencing and subjected to induced sputum sampling. Cells from sputum samples and BEAS 2B cells were treated with montelukast and endogenous TGFB1 expression was measured by quantitative real-time polymerase chain reaction. The promoter activity was analyzed by luciferase assays in BEAS 2B cells transfected with constructs carrying variants -509C and -509T of the TGFB1 gene promoter. After treatment with montelukast, the decrease in TGFB1 gene expression was greater for the -509TT genotype (58.9%) than for the -509CC and -509CT genotypes (49.6% and 31.8%, respectively) (P = 0.071). In BEAS 2B cells, expression of endogenous TGFB1 was reduced by about 27% after montelukast treatment, while luciferase activity of both promoter variants was increased after montelukast treatment (-509C allele: 48.3%, P = 0.060; and -509T allele: 100.5%, P = 0.062). A more intensive response was registered in the promoter containing the -509T allele, which had 135% higher activity than the -509C variant (P = 0.035). This study showed that the presence of the -509T allele in the TGFB1 promoter might modulate effects of montelukast on TGFB1 gene expression, but future studies are necessary, taking into consideration other genetic and nongenetic factors. It is of potential importance for clinical management of asthma to clarify the influence of the C-509T polymorphism on the response to treatment with montelukast.

Effect of aging on sputum inflammation and asthma control

BACKGROUND

Aged asthmatic patients experience increased morbidity and mortality. Knowledge of the aging effect on airway inflammation and asthma control is limited.

OBJECTIVE

We sought to compare airway inflammation and its relationship to asthma control in aged versus younger patients and determine whether differences are asthma specific or caused by "inflamm-aging."

METHODS

We performed a prospective study of aged (>60 years) and younger (21-40 years) inner-city patients with asthma. After a run-in period to control for inhaled corticosteroid use, induced sputum was collected. Age-matched nonasthmatic control subjects were included to measure age-related inflammatory changes.

RESULTS

Aged (mean age, 67.9 ± 5.1 years; n = 35) compared with younger (mean age, 30.8 ± 5.9 years; n = 37) asthmatic patients had significantly worse asthma control and lower FEV₁. Aged asthmatic patients had higher sputum neutrophil (30.5 × 10⁴/mL and 23.1%) and eosinophil (7.0 × 10⁴/mL and 3.8%) numbers and percentages compared with younger patients (neutrophils, 13.0 × 10⁴/mL [P < .01] and 6.9% [P < .01]; eosinophils, 2.0 × 10⁴/mL [P < .01] and 1.2% [P < .01]). Aged asthmatic patients had higher sputum IL-6 (P < .01) and IL-8 (P = .01) levels. No significant inflammatory differences between aged and younger control subjects were observed. In aged asthmatic patients increased sputum IL-6 and macrophage inflammatory protein 3α/CCL20 levels were significantly associated with decreased asthma control and increased sputum neutrophil numbers and IL-1β, IL-6, and macrophage inflammatory protein 3α/CCL20 levels were associated with hospitalization.

CONCLUSIONS

The inflammatory patterns of aged versus younger asthmatic patients are associated with increased sputum neutrophil and eosinophil values and cytokine levels related to neutrophil recruitment. Differences in airway inflammation can contribute to diminished asthma control in the aged. Further understanding of asthma pathophysiology in aged patients is needed to improve management of this vulnerable population.

Airway inflammation in Japanese COPD patients compared with smoking and nonsmoking controls

PURPOSE

To assess the importance of inflammation in chronic obstructive pulmonary disease (COPD) by measuring airway and systemic inflammatory biomarkers in Japanese patients with the disease and relevant control groups.

PATIENTS AND METHODS

This was the first study of its type in Japanese COPD patients. It was a non-treatment study in which 100 participants were enrolled into one of three groups: nonsmoking controls, current or ex-smoking controls, and COPD patients. All participants underwent standard lung function assessments and provided sputum and blood samples from which the numbers of inflammatory cells and concentrations of biomarkers were measured, using standard procedures.

RESULTS

The overall trends observed in levels of inflammatory cells and biomarkers in sputum and blood in COPD were consistent with previous reports in Western studies. Increasing levels of neutrophils, interleukin 8 (IL-8), surfactant protein D (SP-D), and Krebs von den Lungen 6 (KL-6) in sputum and clara cell 16 (CC-16), high-sensitivity C-reactive protein (hs-CRP), and KL-6 in serum and plasma fibrinogen were seen in the Japanese COPD patients compared with the non-COPD control participants. In sputum, significant correlations were seen between total cell count and matrix metalloproteinase 9 (MMP-9; P<0.001), neutrophils and MMP-9 (P<0.001), macrophages and KL-6 (P<0.01), total cell count and IL-8 (P<0.05), neutrophils and IL-8 (P<0.05), and macrophages and MMP-9 (P<0.05). Significant correlations were also observed between some inflammatory cells in sputum and biomarkers in serum, with the most significant between serum CC-16 and both total cell count (P<0.005) and neutrophils (P<0.005) in sputum.

CONCLUSION

These results provide evidence for the first time that COPD in Japanese patients is a multicomponent disease, involving both airway and systemic inflammation, in addition to airway obstruction. Therefore, intervention with anti-inflammatory therapy may provide additional benefit in disease management of COPD in Japan.

Hypertonic saline in treatment of pulmonary disease in cystic fibrosis

The pathogenesis of lung disease in cystic fibrosis is characterised by decreased airway surface liquid volume and subsequent failure of normal mucociliary clearance. Mucus within the cystic fibrosis airways is enriched in negatively charged matrices composed of DNA released from colonizing bacteria or inflammatory cells, as well as F-actin and elevated concentrations of anionic glycosaminoglycans. Therapies acting against airway mucus in cystic fibrosis include aerosolized hypertonic saline. It has been shown that hypertonic saline possesses mucolytic properties and aids mucociliary clearance by restoring the liquid layer lining the airways. However, recent clinical and bench-top studies are beginning to broaden our view on the beneficial effects of hypertonic saline, which now extend to include anti-infective as well as anti-inflammatory properties. This review aims to discuss the described therapeutic benefits of hypertonic saline and specifically to identify novel models of hypertonic saline action independent of airway hydration.

What's new in asthma pathophysiology and immunopathology?

Research on asthma pathophysiology over the past decade has expanded the complex repertoire involved in the pathophysiology of asthma to include inflammatory, immune and structural cells, as well as a wide range of mediators. Studies have identified a role for connective and other mesenchymal tissues involved in airway remodeling. Recent findings have implicated the innate immune response in asthma and have revealed interesting patterns of interaction between the innate and adaptive immune response and the associated complex chronic inflammatory reaction. New immune cell populations have also been added to this repertoire, including Tregs, natural killer T cells and Th17 cells. The role of the eosinophil, a prominent pathological feature in most asthma phenotypes, has also been expanding to include roles such as tissue modifiers and immune regulators via a number of fascinating and hitherto unexplored mechanistic pathways. In addition, new and significant roles have been proposed for airway smooth muscle cells, fibroblasts, epithelial and endothelial cells. Tissue remodeling is now considered an integral element of asthma pathophysiology. Finally, an intricate network of mediators, released from both immune and inflammatory cells, including thymus stromal lymphopoietin and matrix metalloproteinases, have added to the complex milieu of asthma immunity and inflammation. These findings have implications for therapy and the search for novel strategies towards better disease management. Sadly, and perhaps due to the complex nature of asthma, advances in therapeutic discoveries and developments have been limited. Thus, understanding the precise roles played by the numerous dramatis personae in this odyssey, both individually and collectively within the context of asthma pathophysiology, continues to pose new challenges. It is clear that the next stage in this saga is to embark on studies that transcend reductionist approaches to involve system analysis of the complex and multiple variables involved in asthma, including the need to narrow down the phenotypes of this condition based on careful analysis of the organs (lung and airways), cells, mediators and other factors involved in bronchial asthma.

Hypertonic saline increases lung epithelial lining fluid glutathione and thiocyanate: two protective CFTR-dependent thiols against oxidative injury

Background

Cystic fibrosis is a debilitating lung disease due to mutations in the cystic fibrosis transmembrane conductance regulator protein (CFTR) and is associated with chronic infections resulting in elevated myeloperoxidase activity and generation of hypochlorous acid (HOCl). CFTR mutations lead to decreased levels of glutathione (GSH) and thiocyanate (SCN) in the epithelial lining fluid (ELF). Hypertonic saline is used to improve lung function however the mechanism is uncertain.

Methods

In the present study, the effect of GSH and SCN on HOCl-mediated cell injury and their changes in the ELF after hypertonic saline nebulization in wild type (WT) and CFTR KO mice was examined. CFTR sufficient and deficient lung cells were assessed for GSH, SCN and corresponding sensitivity towards HOCl-mediated injury, in vitro.

Results

CFTR (-) cells had lower extracellular levels of both GSH and SCN and were more sensitive to HOCl-mediated injury. In vivo, hypertonic saline increased ELF GSH in the WT and to a lesser extent in the CFTR KO mice but only SCN in the WT ELF. Finally, potential protective effects of GSH and SCN at concentrations found in the ELF against HOCl toxicity were examined in vitro.

Conclusions

While the concentrations of GSH and SCN associated with the WT ELF protect against HOCl toxicity, those found in the CFTR KO mice were less sufficient to inhibit cell injury. These data suggests that CFTR has important roles in exporting GSH and SCN which are protective against oxidants and that hypertonic saline treatment may have beneficial effects by increasing their levels in the lung.

Allergen inhalation decreases adenosine receptor expression in sputum and blood of asthma patients

BACKGROUND

Adenosine is a signalling nucleoside that has been proposed to contribute to the pathogenesis of asthma. Adenosine is produced in inflammatory environments and acts via adenosine receptors (A(1)R, A(2A)R, A(2B)R, and A(3)R) expressed by a wide variety of cells, resulting in pro- and anti-inflammatory effects.

OBJECTIVE

To compare AR expression in asthma patients and healthy subjects, and to assess the effect of allergen challenge on AR expression of inflammatory cells and on cytokines in peripheral blood and sputum in asthma.

METHODS

Asthma patients underwent an allergen challenge, and blood and induced sputum samples were taken before and 24 h after allergen challenge to study inflammatory cells numbers, AR expression and cytokine production. Blood and sputum were investigated at one time point in healthy subjects. AR expression was measured by flow cytometry (blood) or on cytospins using immunocytochemistry (sputum). Cytokines (luminex, ELISA) and adenosine (HPLC) were measured in sputum supernatant.

RESULTS

The percentage of A(2B)R expressing neutrophils in sputum was lower in asthma patients than in healthy subjects (P = 0.016). Allergen challenge decreased A(1)R and A(2A)R expression on neutrophils and A(1)R expression on T cells in peripheral blood (all P < 0.05). Allergen challenge increased IL-8 levels and eosinophil numbers (P < 0.05), whereas it decreased thymic stromal lymphopoietin levels and the percentage of A(1)R expressing macrophages in induced sputum (P < 0.05).

CONCLUSIONS

Allergen challenge has a down-regulatory effect on AR expression in asthma, suggesting a contribution of adenosine-related effector mechanisms in the pathophysiology.