Difficult asthma in children: an analysis of airway inflammation

BACKGROUND: Difficult asthma in children displays distinct clinical patterns, and its physiopathology remains poorly understood. OBJECTIVE: To determine the characteristics of the bronchial inflammatory profile in children with difficult asthma. METHODS: We performed endobronchial biopsy and bronchoalveolar lavage in 28 children with persistent bronchial obstruction despite high doses of inhaled corticosteroids and regular treatment with long-acting beta(2)-agonists: 13 had persistent symptoms and 15 had few or no symptoms. RESULTS: The number of eosinophils (P =.03) and neutrophils (P =.04) in the epithelium was significantly higher in symptomatic children than in children with few symptoms. Reticular basement membrane thicknening was similar in both groups. IFNgamma levels (P =.03) and IFNgamma/IL-4 ratio (P =.01) were significantly higher in children with few symptoms. CONCLUSIONS: In symptomatic children, T(H)2-type inflammation was associated with the presence of activated eosinophils in the epithelium, whereas asthma in children with few symptoms was associated with an increase in T(H)1 cytokine levels. The high levels of IFNgamma suggest that this T(H)1 cytokine may modulate the local inflammatory response.     

Noninvasive methods for the detection of upper and lower airway inflammation in atopic children

BACKGROUND: Exhaled nitric oxide (FE(NO)) and exhaled breath condensate (EBC) are noninvasive methods to assess inflammation. OBJECTIVE: To investigate the role of the FE(NO) and of the EBC pH and IL-5 levels in atopic children. METHODS: We evaluated oral and nasal FE(NO) and the pH and IL-5 of oral and nasal EBC in children with atopic dermatitis (AD; n = 18), allergic rhinitis (AR; n = 18), intermittent asthma (n = 21), moderate persistent asthma (n = 18), and healthy controls (HCs; n = 16). RESULTS: Oral FE(NO) was significantly increased in asthma, whereas the nasal values were increased in AR and asthma in comparison with HCs. The pH of oral EBC was lower in AD and asthma than in AR and HCs, whereas the nasal levels were lower in AD, AR, and asthma than in HCs. The oral IL-5 was higher in AD, AR, and asthma in comparison with HCs, whereas the nasal IL-5 concentrations were higher in asthma and AR than in HCs. In AR, the nasal FE(NO) correlated with the IL-5 values and with the disease duration. In intermittent asthma, oral and nasal pH inversely correlated with the exacerbations, whereas in moderate asthma, the nasal IL-5 positively correlated with exacerbations. In AD, the oral and nasal IL-5 positively correlated with the serum IgE. CONCLUSION: These markers of nasal and bronchial inflammation, accessible with noninvasive techniques, might be useful to identify patients with uncontrolled diseases and to verify the usefulness of new therapeutic approaches. CLINICAL IMPLICATIONS: These markers are useful tools to monitor the upper and lower airway inflammation in atopic children.     

Adiposity, asthma, and airway inflammation

BACKGROUND: Several studies have found obesity to be associated with an increased prevalence of asthma. For reasons that remain unclear, this association has often been reported to be stronger in women than in men. One possible explanation might be that these studies have used body mass index to identify adiposity, which might be a less reliable measure of body fat in men than in women. OBJECTIVE: We sought to explore the association between body fat percentage measured by means of bioelectrical impedance analysis and asthma, airflow obstruction, and airway inflammation in men and women. METHODS: Respiratory questionnaires, spirometry, bronchodilator response, exhaled nitric oxide level, and percentage of body fat were measured in a population-based cohort of approximately 1000 individuals at age 32 years. RESULTS: There was a significant association between the percentage of body fat and asthma in women (P = .043) but not in men (P = .75). Airflow obstruction was associated with percentage of body fat in women (P = .046), but there was an inverse association in men (P = .010). Bronchodilator responsiveness was also associated with lower body fat in men (P = .004). Airway inflammation, measured by means of exhaled nitric oxide, was not associated with body fat in either women (P = .17) or men (P = .25). CONCLUSION: Adiposity is associated with asthma and airflow obstruction in women. This does not appear to be mediated by airway inflammation. In men airflow obstruction and bronchodilator responsiveness are associated with a lower percentage of body fat. CLINICAL IMPLICATIONS: In women, but not in men, obesity is associated with asthma and airflow obstruction, but there was no association with airway inflammation.     

Melatonin reduces airway inflammation in ovalbumin-induced asthma

Asthma is a common chronic inflammatory airway disease that is recognized as a major public health problem. In this study, we evaluated the effects of melatonin on allergic asthma using a murine model of ovalbumin (OVA)-induced allergic asthma and BEAS-2B cells. To induce allergic asthma, the mice were sensitized and airway-challenged with OVA. Melatonin was administered by intraperitoneal injection once per day at doses of 10 and 15 mg/kg from days 21 to 23 after the initial OVA sensitization. We investigated the effects of melatonin on proinflammatory cytokines and matrix metalloproteinase-9 (MMP-9) activity and expression in tumor necrosis factor (TNF)-α-stimulated BEAS-2B cells. The administration of melatonin significantly decreased the number of inflammatory cells, airway hyperresponsiveness, and immunoglobulin (Ig) E with reductions in interleukin (IL)-4, IL-5, and IL-13. Melatonin attenuated the airway inflammation and the mucus production in lung tissue and significantly suppressed elevated MMP-9 expression and activity induced by an OVA challenge. In TNF-α-stimulated BEAS-2B cells, treatment with melatonin significantly reduced the levels of proinflammatory cytokines and lowered the expression and activity of MMP-9. These results indicate that melatonin effectively suppressed allergic asthma induced by an OVA challenge. The results suggest a potential role for melatonin in treating asthma.     

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 rush immunotherapy on airway inflammation and airway hyperresponsiveness after bronchoprovocation with allergen in asthma

Background: Rush immunotherapy (RIT) has been shown to be effective in allergic asthma. Objective: We investigated the mechanisms of RIT on the basis of cytokine production by T-cell lines and airway inflammation and responsiveness. Methods: Subjects were 8 patients with house dust mite–allergic asthma treated with dust mite extract RIT for 6 months and 6 RIT-untreated control patients. IL-5 production by Dermatophagoides farinae –specific T-cell lines, eosinophil percentages, and eosinophil cationic protein (ECP) in induced sputum and airway responsiveness to allergen and histamine were evaluated before and after treatment. Changes in eosinophil percentages and ECP in induced sputum and responsiveness to histamine 24 hours after allergen inhalation were also studied. Results: After 6 months of RIT, percentages of total eosinophils (43.0% ± 6.90% to 16.8% ± 2.48%; P < .01), percentages of EG2⁺ eosinophils (32.6% ± 6.39% to 19.7% ± 4.68%; P < .01) and ECP (362.7 ± 125.3 ng/mL to 26.2 ± 5.15 ng/mL; P < .05) decreased in induced sputum, and IL-5 production by T-cell lines decreased (617 ± 93.2 pg/mL to 200.0 ± 34.1 pg/mL; P < .01). RIT decreased both early- and late-phase bronchoconstriction (early phase: 33.2% ± 3.46% to 25.4% ± 1.42%; P < .03; late phase: 16.2% ± 3.52% to 6.2% ± 1.96%; P < .03) and suppressed increases in the percentages of total (61.8% ± 4.89% to 42.0% ± 4.67%; P < .01) and EG2-positive eosinophils (55.54% ± 7.21% to 36.5% ± 6.43%; P < .01) and ECP (685.6 ± 217.0 ng/mL to 85.4 ± 23.4 ng/mL; P < .05) in induced sputum after allergen inhalation. RIT also decreased airway responsiveness to dust mite (1:303.7 ± 123.7 wt/vol to 1:65.0 ± 13.2 wt/vol; P < .03) and to histamine before (397.1 ± 206.9 μg/mL to 1391.3 ± 283.3 μg/mL; P < .03) and after allergen inhalation (139.2 ± 36.5 μg/mL to 629.1 ± 196.3 μg/mL; P < .03). Conclusion: RIT decreases airway inflammation and airway hyperresponsiveness before and after bronchial provocation with allergen, possibly by inhibiting both allergen-specific T-cell– and mast cell-dependent pathways. RIT is an effective antiinflammatory treatment in allergic asthma. (J Allergy Clin Immunol 1998;102:927-34.)     

let-7在小鼠哮喘模型气道炎性反应中的作用及机制

目的 观察let-7家族微RNA抑制剂(anti-let-7)对支气管哮喘(简称哮喘)小鼠气道炎性反应的影响,并探讨let-7参与哮喘形成的机制.方法 32只小鼠按随机数字法分为4组(n=8),即正常对照组(A组)、哮喘组(B组)、干预对照组(C组)和干预组(D组).其中B、C和D组用鸡卵蛋白(OVA)免疫,建立哮喘模型,A组以生理盐水替代OVA处理.D组小鼠激发前注射anti-let-7以抑制内源性let-7表达,C组小鼠注射乱序siRNA对照.比较各组小鼠支气管肺泡灌洗液(BALF)的细胞计数,肺组织中let-7e以及BALF中白细胞介素-10(IL-10)含量;体外用anti-let-7转染肺癌细胞A549,并检测细胞中let-7e表达和细胞培养上清中IL-10的含量;荧光素酶报告法检测let-7e是否直接靶向IL-10.结果 与A组相比,B组和C组小鼠BALF中细胞总数和嗜酸粒细胞数显著增加[(20.32±5.33)×109/L和(24.74±6.69)×109/L比(7.12± 1.88)×109/L,(6.45±2.5)×109/L和(7.12±2.66)×109/L比(0.04±0.01)×109/L,均P＜0.01];肺组织中let-7e水平明显升高(分别为3.83倍和3.27倍,均P＜0.01).与C组比较,D组BALF中细胞总数和嗜酸粒细胞数明显减少[(13.85±3.74)× 109/L比(24.74±6.69)×109/L,(2.15±1.13)×109/L比(7.12±2.66)×109/L,均P＜0.05];肺组织中let-7e显著降低[(0.45±0.22)比(3.28±0.45),P＜0.01],同时BALF中IL-10水平明显升高[(4.68±0.85)比(1.70±0.29),P＜0.01].此外,在肺癌细胞A549 中转染anti-let-7,let-7e表达显著下降[(0.22±0.03)比(1.00±0.11),P＜0.01],同时培养上清中IL-10明显上升[(2.58±0.35)比(1.00±0.15),P＜0.01].体外let-7e过表达显著降低IL-10报告载体的荧光素酶活性[(0.59±0.06)比(1.00±0.03),P＜0.01],而对突变的IL-10报告载体没有抑制作用.结论 anti-let-7对哮喘小鼠气道炎性反应具有明显的抑制作用,其作用机制可能与let-7直接靶向并抑制IL-10有关.     

Influence of smoking on airway inflammation and remodelling in asthma

Background Although exposure to tobacco smoke has been associated with increased morbidity and mortality, cigarette smoking is still common in the asthmatic population. Induced sputum neutrophilia has been observed in asthmatic smokers, but the effects of regular smoking on their bronchial mucosa morphology remain to be defined. This study documents the inflammatory and remodelling features in bronchial biopsies of smoking compared with non‐smoking asthmatics. Methods We analysed bronchial biopsies from 24 steroid‐naïve young subjects with mild asthma: 12 non‐smoking and 12 currently smoking subjects. In addition to airway morphology assessment, inflammation and remodelling were analysed by immunohistochemistry using antibodies against CD3, CD68, major basic protein, neutrophil elastase, and tryptase. Expression of the cytokines IL‐4, IL‐5, IL‐8, IFN‐γ, transforming growth factor‐β, and TNF was determined by in situ hybridization. Results Compared with non‐smoking asthmatic subjects, smoking asthmatics' bronchial mucosa showed squamous cell metaplasia, in addition to increased expression of subepithelial neutrophil elastase, IFN‐γ, and intraepithelial IL‐8. Conclusions Smoking status modifies morphological and inflammatory processes in young subjects with mild asthma. The changes may possibly affect asthma treatment responses and clinical outcomes.     

Eosinophilic airway inflammation and the prognosis of childhood asthma

BACKGROUND: Eosinophilic airway inflammation is a key pathophysiological feature of asthma that can predict treatment response. However, the prognostic value of sputum eosinophilia is not established. OBJECTIVE: The aim of this study was to determine the influence of induced sputum eosinophilia on the prognosis of childhood asthma. METHODS: A cohort of children with asthma was evaluated by induced sputum analysis at inception and classified as having either eosinophilic asthma (EA) (sputum eosinophils >2.5%) or non-eosinophilic asthma (NEA). After a mean follow-up period of 5 years, eligible subjects (n=83) were contacted and 69 subjects (33 EA, 36 NEA) evaluated. The children had a mean age of 15.9 years, and 61% were male. RESULTS: Children with EA reported more wheeze during the follow-up period (27% vs. 6% wheezed most years; P<0.0001), increased night waking during the past 12 months (28% vs. 3% reported weekly waking; P=0.01), and greater impairment of quality of life due to asthma (P=0.04). Subsequent beta2-agonist use was increased in children with EA (P=0.02), although there was no difference in corticosteroid use. In EA, subsequent forced expiratory volume in 1 s/forced vital capacity was lower (79% vs. 86%; P=0.01) and grass pollen allergy was more prevalent (77% vs. 27%; P=0.006). CONCLUSION: In children, eosinophilic airway inflammation is associated with deteriorating asthma over time. This is consistent with the hypothesis that airway inflammation has an adverse impact on the prognosis of childhood asthma, and suggests a role for monitoring inflammation in asthma management.     

Persistent peripheral airway obstruction in children with severe asthma

We reviewed pulmonary function data on 447 children with the diagnosis of asthma, who were studied in our laboratory over a 6-year interval. We found 19 with evidence of consistent airway obstruction. Two patients who had obvious causes for persistent obstruction were excluded. Seven of the remaining 17 patients consented to further studies. In six of the seven patients studied, flow rates at low lung volumes were severely depressed and remained unchanged after 2 weeks of vigorous "inpatient" therapy. No clinical benefit was apparent. One patient had relentlessly worse disease and died of his asthma. The autopsy revealed changes characteristic of asthma. We conclude that some children with severe asthma have persistent and severe peripheral airway obstruction. These findings challenge the current paradigm that asthma in children is a completely "reversible" illness. Long-term follow-up of children with persistent chronic obstruction may clarify the question of childhood origin of adult lung disease.