Bronchial hyperresponsiveness and airway inflammation in adolescents with asymptomatic childhood asthma

BACKGROUND: About 70% of childhood asthmatics become free of asthma-related symptoms during adolescence. Little is known about bronchial hyperresponsiveness (BHR) and airway inflammation in young adults with "outgrown" childhood asthma. METHODS: We studied 61 nonsmoking medical students (18 intermittent mild asthmatics, 23 students with outgrown childhood asthma but free of asthma-related symptoms for 10 years (asymptomatic asthmatics) and 20 healthy students). BHR and lung function were measured, and induced sputum samples analyzed for eosinophil count, eosinophilic cationic protein (ECP), granulocyte-macrophage colony stimulating factor (GM-CSF), and tumor necrosis factor-alpha (TNF-alpha). RESULTS: BHR was still present in most asymptomatic asthmatics, but it was milder compared with healthy students. Only three subjects with previous asthma had no BHR and no signs of airway inflammation. Percentages of eosinophil, and ECP, TNF-alpha and GM-CSF concentrations in induced sputum of mild asthmatics and asymptomatic asthma groups were higher than in the healthy group. In asymptomatic asthmatics group, the duration of asthma, sputum eosinophil percentage, and the level of TNF-alpha in sputum correlated significantly with BHR. CONCLUSIONS: Only a few subjects with longstanding asymptomatic asthma could be considered as cured; most asymptomatic asthmatics continued to exhibit BHR and signs of airway inflammation. The outcome of childhood asthma and BHR was associated with the degree of airway inflammation and the duration of childhood asthma.     

Effect of current exposure to Der p 1 on asthma symptoms, airway inflammation, and bronchial hyperresponsiveness in mite-allergic asthmatics

The existence of a dose-response relationship between indoor allergen exposure and sensitization has been widely described, but the effect of allergen exposure on asthma activity (symptoms, bronchial hyperresponsiveness [BHR], and inflammation) is not clear. Our aim was to determine the existence of an association among current exposure to mite allergens and symptoms, BHR, and airway inflammation assessed in blood and sputum from asthmatic patients sensitized to Dermatophagoides pteronyssinus. We selected 31 mild and recently diagnosed (12-24 months) asthma patients sensitized to D. pteronyssinus. Allergenic exposure (Der p 1, Der 2) was assessed by a commercial assay based on monoclonal antibodies (mAb), carried out on the dust samples collected from patients' beds in a standardized way. Patients completed an asthma symptom questionnaire and underwent skin tests, methacholine bronchial challenge, and sputum induction. Sputum cell profile was analyzed and eosinophil cationic protein (ECP), tryptase, albumin, and interleukin(IL)-5 levels were quantified in sputum supernatant. Total eosinophil numbers and ECP levels were measured in blood samples. Most patients were exposed to Der p 1 levels under 2 microg/g of dust. Der p 1 exposure was higher among the subjects with positive sputum tryptase detection (P = 0.020). Der p 1 levels showed a trend toward correlation with asthma symptoms (P = 0.066, r = 0.36) and correlated with sputum tryptase levels (P = 0.032, r = 0.42). No relationship between BHR, eosinophilic inflammation, and allergenic exposure was found. Our results suggest that asthma symptoms and lung mast-cell activation are at least partially dependent on current allergen exposure. The lack of correlation between mite exposure, eosinophilic inflammation, and BHR supports the role of other factors that enhance the immunologic response initiated by allergen, increasing the activity of asthma.     

Genome screen for asthma and bronchial hyperresponsiveness: interactions with passive smoke exposure

BACKGROUND: Asthma is a common respiratory disease caused by the interaction of genetic susceptibility and exposure to various environmental factors. Passive smoke exposure, characterized by parental smoking, has been shown to be a risk factor for the development of atopy and asthma. OBJECTIVE: We sought to perform a genome-wide linkage screen for asthma and bronchial hyperresponsiveness (BHR) and to determine the influence of passive tobacco smoke exposure during childhood on the results of genetic linkage studies to investigate gene-environment interactions. METHODS: A genome-wide linkage screen for asthma and BHR was performed in 200 families ascertained through a parent with asthma. Analyses were performed separately for the entire sample and for the smoking-exposed and nonexposed families. RESULTS: For asthma and BHR, the strongest evidence for linkage was observed for chromosomes 3p and 5q. The families in which the children were exposed to passive smoking accounted for the evidence for linkage of BHR to 5q ( P < .001), but evidence for linkage to 3p was found in both sets of families. Similar results were observed for asthma. However, there was no observed difference in the frequency of asthma or BHR in the offspring from the smoke-exposed compared with the nonexposed families. CONCLUSION: The results from this study demonstrate that the influence of susceptibility genes for a common disease such as asthma might not be apparent unless there is the appropriate exposure to environmental stimuli, such as passive exposure to cigarette smoke. This approach should be useful for identification of asthma susceptibility genes.     

Comparison of the effects on bronchial hyperresponsiveness of antiallergic agents and beclomethasone dipropionate in long-term bronchial asthma

The effect of antiallergic agents (DSCG (disodium cromoglycate), ketotifen, and ibudilast) and beclomethasone dipropionate inhaler (BDI) on bronchial hyperresponsiveness to histamine inhalation was retrospectively assessed in 72 asthmatic patients with more than a year's duration of the disease. Decrease in bronchial hyperresponsiveness to histamine was observed in 10 out of the 33 (30%) antiallergic-agents-treated patients (group A, mean duration = 7.8 months), in 12 of 19 (63.2%) BDI-treated patients (group B, 6.2 months), but only 2 of the 20 (10%) control patients (group C, 7.8 months). Improvement of histamine PC₂₀ was from 310 to 597 μg/ml ( P <0.01) in group A, from 308 to 1622 μg/ml ( P <0.0005) in group B, and from 575 to 525 μg/ml (NS) in group C. A significant decrease in the peripheral eosinophil count was observed only in group B. The improvement in bronchial hyperresponsiveness was parallel with that of asthmatic symptoms; the percentage of patients becoming symptom-free rose from 12 to 42%, 5 to 89%, and 5 to 20% in groups A, B, and C, respectively. Out of 11 unimproved patients in group A, 7 showed a significant improvement in their histamine PC₂₀ by BDI treatment (mean PC₂₀: 311 → 1828 μg/ml). These results suggest that BDI might be more effective than antiallergic agents in the treatment of patients with long-standing bronchial asthma.     

Natural killer T cells are dispensable in the development of allergen-induced airway hyperresponsiveness, inflammation and remodelling in a mouse model of chronic asthma

Natural killer T (NK T) cells have been shown to play an essential role in the development of allergen-induced airway hyperresponsiveness (AHR) and/or airway inflammation in mouse models of acute asthma. Recently, NK T cells have been reported to be required for the development of AHR in a virus induced chronic asthma model. We investigated whether NK T cells were required for the development of allergen-induced AHR, airway inflammation and airway remodelling in a mouse model of chronic asthma. CD1d^−/− mice that lack NK T cells were used for the experiments. In the chronic model, AHR, eosinophilic inflammation, remodelling characteristics including mucus metaplasia, subepithelial fibrosis and increased mass of the airway smooth muscle, T helper type 2 (Th2) immune response and immunoglobulin (Ig)E production were equally increased in both CD1d^−/− mice and wild-type mice. However, in the acute model, AHR, eosinophilic inflammation, Th2 immune response and IgE production were significantly decreased in the CD1d^−/− mice compared to wild-type. CD1d-dependent NK T cells may not be required for the development of allergen-induced AHR, eosinophilic airway inflammation and airway remodelling in chronic asthma model, although they play a role in the development of AHR and eosinophilic inflammation in acute asthma model.     

Respiratory syncytial virus-induced airway hyperresponsiveness is independent of IL-13 compared with that induced by allergen

BACKGROUND: IL-13 is a central mediator of allergen-induced airway hyperresponsiveness (AHR), but its role in respiratory syncytial virus (RSV)-induced AHR is not defined. The combination of allergen exposure and RSV infection is known to increase AHR and lung inflammation, but whether IL-13 regulates this increase is similarly not known. OBJECTIVE: Our objective was to determine the role of RSV infection and IL-13 on airway responsiveness and lung inflammation on sensitized and challenged mice. METHODS: Using a murine model of RSV infection and allergen exposure, we examined the role of IL-13 in the development of AHR and lung inflammation in IL-13 knockout mice, as well as using a potent IL-13 inhibitor (IL-13i). Mice were sensitized and challenged to allergen, and 6 days after the last challenge, they were infected with RSV. IL-13 was inhibited using an IL-13 receptor alpha(2)-human IgG fusion protein. AHR to inhaled methacholine was measured 6 days after infection, as was bronchoalveolar lavage fluid and lung inflammatory and cytokine responses. RESULTS: RSV-induced AHR was unaffected by the IL-13i, despite prevention of goblet cell hyperplasia. Similar results were seen in IL-13-deficient mice. In sensitized and challenged mice, RSV infection significantly increased AHR, and after IL-13i treatment, AHR was significantly reduced, but to the levels seen in RSV-infected mice alone. CONCLUSIONS: These results indicate that despite some similarities, the mechanisms leading to AHR induced by RSV are different from those that follow allergen sensitization and challenge. Because IL-13 inhibition is effective in preventing the increases in AHR and mucus production in sensitized and challenged mice infected with RSV, IL-13i could play an important role in preventing the consequences of viral infection in patients with allergic asthma.     

Methacholine vs adenosine on intra and extrathoracic airway hyperresponsiveness in patients with cough variant asthma

Background: Airway hyperresponsiveness (AHR) can be studied by bronchoprovocation test (BPT) using direct (methacholine – MCh) or indirect (adenosine 5′‐monophosphate – AMP) stimuli. These two substances have not been compared in cough variant asthma (CVA). Objective: We designed a randomized, single‐blind, cross‐over study to compare AMP and MCh in the detection of CVA. Additionally, we examined whether assessment of extrathoracic airway hyperresponsiveness (EAHR) during MCh and AMP helped in the evaluation of CVA. Methods: Patients with CVA with previous positive MCh BPT performed challenges with AMP and MCh. The variables were: (i) a provocative dose producing a 20% fall in forced expiratory volume in 1 s (FEV₁) value (PD₂₀MCh); (ii) a provocative dose producing a 25% fall in the maximal mid‐inspiratory flow (FIF₅₀) from baseline (PD₂₅MCh) for MCh; (iii) a provocative concentration producing a 20% fall in FEV₁ value (PC₂₀AMP) and (iv) a provocative concentration producing a 25% fall in the FIF₅₀ from baseline (PC₂₅AMP) for AMP. Results: All 113 patients with CVA responded to PD₂₀MCh and 96% and 69% responded to PC₂₀AMP, if we used PC₂₀ ≤ 200 mg/ml or PC₂₀ ≤ 100 mg/ml, respectively, with an excellent correlation between these two tests (r = 0.87 and 0.76, respectively). Extrathoracic AHR associated with AHR was found in 10% in MCh challenge and in 11% with AMP challenge and no patients had EAHR alone. Conclusion: Adenosine challenges correlate well with MCh in patients with CVA. A minority (c. 10%) of CVA patients have EAHR as measured by these tests, while most had AHR as assessed with each of the challenge agents.     

气道上皮IL-25促进哮喘气道重塑

目的:通过检测白细胞介素-25(IL-25)在嗜酸细胞性哮喘(EA)及非嗜酸细胞性哮喘(NEA)患者的血清、诱导痰及气道上皮中的表达,探讨其在支气管哮喘气道重塑中的作用。方法:选取初诊的哮喘患者55例,健康对照组27例,所有受试者均进行肺通气功能检查,然后采集空腹静脉血及诱导痰。据诱导痰中嗜酸性粒细胞(EOS)的比例将哮喘患者分为EA组和NEA组。采用ELISA检测血清及诱导痰中IL-25的水平,同时对其中的10例EA组患者、10例NEA组患者及10例健康对照者行电子支气管镜气道黏膜活检,免疫组织化学技术分析IL-25在气道上皮的表达,HE染色测量气道重塑的重要指标-基底膜厚度,并行血清及诱导痰中IL-25的水平与基底膜平均厚度的相关性分析。结果:与正常对照组相比,EA和NEA组哮喘患者的肺功能轻度受损。ELISA结果显示哮喘患者血清及诱导痰中IL-25的水平明显高于对照组(P<0.05),而EA和NEA组哮喘患者间差异无统计学意义(P>0.05)。免疫组织化学结果显示哮喘患者气道上皮IL-25的表达明显高于对照组,HE染色显示气道黏膜下的基底膜厚度明显增加(P<0.05)。相关性分析显示哮喘患者血清及诱导痰中IL-25水平与气道黏膜下基底膜平均厚度成正相关。结论:IL-25可能有促进哮喘气道重塑的作用,嗜酸性粒细胞与基底膜厚度无明显相关性,其在哮喘气道重塑中的作用可能是有限的。     

Attenuated production of intracellular IL-10 and IL-12 in monocytes from patients with severe asthma

Interleukin (IL)-10 and IL-12 production is decreased in peripheral blood mononuclear cells of patients with mild asthma. Using whole blood culture and flow cytometry we examined whether monocyte heterogeneity influenced IL-10 and IL-12 production in subjects with severe asthma. We demonstrated that IL-10 release in LPS-stimulated whole blood culture was decreased in patients with severe persistent asthma compared to those with mild asthma and controls (P = 0.04 and P < 0.001, respectively). In asthmatic patients, the percentage of CD14(+)CD16(+) cells was higher than that from normal subjects (P = 0.04). Severe asthmatics showed significantly less positive staining for IL-10 and IL-12 (P < 0.001 and P = 0.02, respectively) after stimulation in monocytes, compared to mild asthmatics and controls in both CD14(+)CD16(+) and CD14(+)CD16(minus sign) cells. These results suggest that IL-10 synthesis is attenuated in severe persistent asthma compared to mild asthma and that this cannot be explained by the increase in the CD14(+)CD16(+) monocytes in asthma.     

Combined effect of tumour necrosis factor-α and interleukin-13 polymorphisms on bronchial hyperresponsiveness in Korean children with asthma

Background TNF‐α and IL‐13, two pivotal pro‐inflammatory cytokines, are increased in asthmatic airways and may be linked to asthma susceptibility and/or bronchial hyperresponsiveness (BHR). Objective We investigated the association between the TNF‐α?308G/A polymorphism and asthma susceptibility or asthma‐related phenotypes in Korean children with asthma, and tested for a combined effect with IL‐13 polymorphisms. Methods Asthmatic children (n=719) and non‐atopic healthy control children (n=243) were evaluated for asthma phenotypes including total serum IgE and BHR to methacholine. Genotypes were determined by PCR‐restriction fragment length polymorphism analysis. Results The allele frequency of TNF‐α?308A in asthmatics (14.1%) was higher than that in control children [8.7%, odds ratio (OR) 1.72, 95% confidence interval (CI) 1.05–2.82]. Significantly lower PC₂₀ values were found in asthmatic children carrying one or two copies of the TNF‐α risk allele (?308A) vs. those homozygous for the common allele (P=0.026). Combined analysis revealed that atopic asthmatic children co‐inherited the risk alleles of TNF‐α?308G/A and IL‐13 +2044G/A more frequently than control children (aOR 1.91, 95% CI 1.00–3.65), and asthmatic children co‐inheriting both risk alleles had significantly lower PC₂₀ values vs. asthmatic children homozygous for the common alleles (P=0.024). Conclusion The TNF‐α promoter polymorphism (?308G/A) may be associated with asthma susceptibility and BHR in Korean children with asthma. In addition, there appears to be a synergistic effect between the TNF‐α promoter polymorphism and an IL‐13 coding region polymorphism in terms of asthma susceptibility and BHR in this population.     

Inhaled corticosteroids decrease vascularity of the bronchial mucosa in patients with asthma

BACKGROUND: Increased vascularity in airway mucosa is a distinctive feature of airway remodelling in asthma. While corticosteroids have proved most effective in modifying airway inflammation, the effect of inhaled corticosteroids on increased airway mucosal vascularity in asthmatics has been little studied. OBJECTIVE: We examined the effect of inhaled corticosteroid on airway vascularity in bronchial biopsy specimens taken from asthmatic patients. SUBJECTS AND METHODS: We studied bronchial biopsies from 28 asthmatic patients before and after treatment with inhaled beclomethasone dipropionate (BDP) 800 microg/daily, or placebo, for 6 months in a double-blind manner. Biopsy specimens were evaluated for number of vessels and percentage of area occupied by vessels, using computerized image analysis after staining for type IV collagen in vessel walls. Specimens were also examined for extent of collagen III in the subepithelial basement membrane. In addition, we compared asthmatic specimens with biopsy specimens taken from non-asthmatic control subjects. RESULTS: There was a significant increase in number of vessels (P < 0.01) and percent vascularity (P < 0.001) in the submucosa of asthmatic patients compared with control subjects. After 6 months of treatment, we observed significant improvements in forced expiratory volume in 1 s (FEV1), FEV1% and airway responsiveness (P < 0.05, each) in the BDP treatment group compared with the placebo group. This was accompanied by significant decreases in both vessel number and percent vascularity in the airways of BDP-treated patients (P < 0.05, each). We also observed a significant correlation between change in percent vascularity and change in collagen III thickness in the BDP-treated patients (rs = 0.90, P < 0.001). Furthermore, the change in percent vascularity was inversely correlated with both FEV1 (rs = -0.49, P < 0.05) and airway responsiveness (rs = -0.36, P < 0.05). CONCLUSION: These findings suggest that inhaled corticosteroid treatment of asthma reduced airway wall vascularity during airway remodelling.     

Inhaled vs subcutaneous effects of a dual IL-4/IL-13 antagonist in a monkey model of asthma

Background:  Pitrakinra is a recombinant protein derived from human interleukin-4 (IL-4) that binds to IL-4Rα and acts as a competitive antagonist of IL-4 and IL-13. The studies reported here compare the dose-ranging effects of pitrakinra on allergen-induced airway hyperresponsiveness (AHR) and airway eosinophilia when administered subcutaneously (s.c.) or by inhalation to the Ascaris suum -sensitive cynomolgus monkey for the purpose of elucidating the primary site of pitrakinra's anti-asthmatic action.
Methods:  Airway responsiveness to inhaled methacholine and bronchoalveolar lavage cell composition was determined before and after three allergen exposures with a 1-week course of twice-daily (b.i.d.) s.c. or inhaled pitrakinra or placebo treatment.
Results:  Treatment with s.c. pitrakinra significantly reduced allergen-induced AHR, with a maximum effect of a 2.8- to 3.8-fold increase in methacholine PC₁₀₀ relative to control ( P  < 0.05) observed at b.i.d. s.c. doses of 0.05–0.5 mg/kg. Inhaled pitrakinra also significantly reduced AHR with a similar maximum effect of a 2.8- to 3.2-fold increase in methacholine PC₁₀₀ relative to control ( P  < 0.05) at nominal b.i.d. doses of 3–100 mg. The maximal effect on AHR following inhalation was observed at a plasma concentration which exhibited no efficacy via the subcutaneous route. The effect of pitrakinra on lung eosinophilia was not statistically significant following either route of administration, although lung eosinophil count was reduced in all studies relative to control.
Conclusion:  Local administration of pitrakinra to the lung is sufficient to inhibit AHR, one of the cardinal features of asthma, indicating the therapeutic potential of inhaled pitrakinra in the treatment of atopic asthma.     

Effects of ketotifen on symptoms and on bronchial mucosa in patients with atopic asthma

Ketotifen is marketed throughout the world as an antiallergy drug, but whether it affects infiltration of inflammatory cells into airway mucosa is not known. We studied the effects of ketotifen on symptoms, pulmonary function, and airway inflammation in 25 patients with atopic asthma. Patients took ketotifen (1 mg twice daily) or a matching placebo for 8 weeks in a double-blind, parallel-group study. Data recorded on diary cards were used for 2 weeks before treatment began, and they were used for the last 2 weeks of treatment to study asthma symptoms, use of β2–agonists, and peak expiratory flow (PEF). Pulmonary function tests, bronchial responsiveness to methacholine, and fiberoptic bronchoscopy were performed before and after treatment. Biopsy specimens were obtained by bronchoscopy. Specimens were stained immunohistochemically with monoclonal antibodies against stored eosinophil cationic protein (EG1), the secreted form of eosinophil cationic protein (EG2), mast-cell tryptase (AA1), neutrophil elastase (NP57), CD3, CD4, CD8, and CD25. The numbers of positively stained cells in the lamina propria were counted. Compared with the placebo, the ketotifen-treated group exhibited significant improvement of asthma symptoms ( P <0.05) and bronchial responsiveness (P<0.05). This was accompanied by a reduction of EG2+ eosinophils ( P <0.05), CD3+ T cells ( P <0.001), CD4+ T cells (P<0.01), and CD25+ activated T cells ( P <0.01) in the bronchial mucosa. These results suggested that the beneficial effects of ketotifen in bronchial asthma may result from consequent inhibition of activated eosinophils and T-cell recruitment into the airway. Moreover, ketotifen may relieve allergic inflammation in bronchial asthma.     

Sputum eosinophil count in a large population of patients with mild to moderate steroid-naive asthma: distribution and relationship with methacholine bronchial hyperresponsiveness

BACKGROUND: Although airway eosinophilia is seen as a cardinal feature of asthma, data eosinophilia are still lacking on the proportion of the asthma group exhibiting raised airway eosinophilia. This study aimed to assess the distribution of sputum eosinophil count and its relationship with methacholine bronchial hyperresponsiveness in mild to moderate steroid-naive asthmatic people. METHODS: Sputum was induced by inhalation of hypertonic saline (NaCl 4.5%) in 118 mild to moderate steroid-naive asthmatic people consecutively recruited from our outpatient clinic, and in 44 healthy people. The asthma group was selected on the basis of an forced expiratory volume in 1 s (FEV(1)) of > or = 70% predicted, and a provocative methacholine concentration causing a fall of 20% in FEV(1) (PC20 methacholine; PC(20)M) < or = 16 mg/ml. RESULTS: In the asthma group, the median (range) of the percentage and the absolute values of sputum eosinophils were 4.8% (0-75) and 38 10(3)/g (0-14,191), respectively, vs 0% (0-2.3) (P < 0.001) and 0 10(3)/g (0-53) (P < 0.001) in healthy participants. Based on the 95% percentile for normal values calculated from our healthy group, 69% of the asthma group had significantly raised sputum eosinophil count (that is > 2%). In the asthma group, multiple regression analysis followed by a stepwise procedure revealed that sputum eosinophil count was significantly and inversely associated with PC(20)M accounting for 16% of its total variance (P < 0.001) while neutrophil counts positively related to PC(20)M accounting for 4% of total variance (P < 0.05). By contrast, no significant relationship was found between either eosinophil or neutrophil counts and the slope of forced vital capacity (FVC) vs FEV(1) from the methacholine challenge. CONCLUSIONS: We conclude that two-thirds of people in the mild to moderate asthma group had increased sputum eosinophilia, which plays a limited role in determining the degree of methacholine airway hyperresponsiveness.