New Considerations About Measuring Airway Hyperresponsiveness

Measuring airway responsiveness to inhaled bronchoconstrictor stimuli, such as methacholine or histamine, has become an important tool in the diagnosis of asthma. This is measured by patients inhaling increasing closes or concentrations of the bronchoconstrictor stimulus until a given level of bronchoconstriction is achieved. Inhaled allergens initiate processes that increase airway inflammation and enhance airway hyperresponsiveness in asthmatic subjects. Studies using inhaled allergen challenges have provided insight into how changes in airway hyperresponsiveness are regulated by induced inflammatory processes. These changes in airway hyperresponsiveness (1-2 doubling doses) have been shown to be of much smaller magnitude than those demonstrated when asthmatics with stable airway hyperresponsiveness are compared to normals (4-8 doubling doses). These allergen-induced changes would be of little relevance in subjects with normal airway responsiveness, because they would not increase the degree of airway responsiveness into the asthmatic range. They are, however, important in asthmatics who already have airway hyperrespon-siveness because they are similar to changes associated with worsening asthma control. It is likely that the mechanisms responsible for the changes in airway hyperresponsiveness following experimental allergen exposure are similar to those producing transient worsening of control in asthmatics. Nevertheless, it is unlikely that the mechanisms of the transient allergen-induced airway hyperresponsiveness will explain the underlying mechanisms of the persistent airway hyperresponsiveness in asthmatic patients when compared with normal individuals.     

Airway autonomic nervous system dysfunction and asthma]

Airways are richly innervated by 4 nervous systems, namely adrenergic, cholinergic, inhibitory nonadrenergic noncholinergic (i-NANC), and excitatory NANC (e-NANC) nervous systems. Dysfunction or hyperfunction of these systems may be involved in the inflammation or airway hyperresponsiveness observed in asthmatic patients. The cholinergic nervous system is the predominant neural bronchoconstrictor pathway in humans. Airway inflammation shows exaggerated acetylcholine release from cholinergic nerves via dysfunction of the autoreceptor, muscarinic M2, which is possibly caused by major basic protein or IgE. Vasoactive intestinal peptide (VIP) and nitric oxide (NO) released from i-NANC nerves act as an airway smooth muscle dilator. The effects of VIP and NO are diminished after allergic reaction by inflammatory cell-mediated tryptase and reactive oxygen species. Thus, in asthmatic airways, the inflammatory change-mediated neural imbalance may result in airway hyperresponsiveness. Tachykinins derived from e-NANC nerves have a variety of actions including airway smooth muscle contraction, mucus secretion, vascular leakage, and neutrophil attachment, and may be involved in the pathogenesis of asthma. Since tachykinin receptor antagonists are effective for bradykinin- and exercise-induced bronchoconstriction in asthmatic patients, these drugs may be useful for asthma therapy.     

Absence of late airway response despite increased airway responsiveness and eosinophilia in a murine model of asthma

In asthmatics an immediate asthmatic response occurs after antigen provocation. Furthermore, asthmatic patients display airway hyperresponsiveness, accompanied by airway eosinophilia. In some patients late asthmatic responses can be detected. Many controversies still exist about the relations between the different airway responses and inflammatory cell infiltration, we therefore used a murine model to investigate associations between these phenomena. In this study we show the presence of antigen-induced early bronchoconstrictive responses, accompanied by increased serum mucosal mast cell protease-1 (MMCP-1) levels. However, we were unable to demonstrate late bronchoconstrictive responses either at the time when eosinophils start to infiltrate the lungs or when both airway hyperresponsiveness and eosinophilia are established. With sequential exposures to antigen, an association exists between development of airway hyperresponsiveness and eosinophilia. In contrast, resolution of this hyperreactivity appears to be dissociated from eosinophilia after stopping the antigen challenges. Based on these data, we conclude that mast cell degranulation is a plausible cause of early bronchoconstrictive responses. Furthermore, late bronchoconstrictive responses are not related to the infiltration of eosinophils or development of airway hyperresponsiveness in this murine model. Finally, we conclude that airway hyperresponsiveness and eosinophilia are only associated with each other during the induction phase and not after the final antigen challenge.     

Physiological assessment of inflammation in the peripheral lung of asthmatic patients

Even the asymptomatic asthmatic person with normal lung function may have peripheral airway obstruction and inflammation along with hyperresponsiveness to nonspecific challenges. The airway caliber change induced immediately following a deep inhalation (DI) appears to relate to the mechanism (inflammation vs. smooth muscle constriction) and site (peripheral vs. more central) of obstruction and the degree of hyperresponsiveness. Data are presented and reviewed that support the notion that relative hysteresis of parenchyma (including peripheral airways and alveolar ducts) and airways (more centrally located, conducting airways) can explain the magnitude and sign of airway caliber change that follow a DI in asthmatic subjects.     

Physiological assessment of inflammation in the peripheral lung of asthmatic patients

Even the asymptomatic asthmatic person with normal lung function may have peripheral airway obstruction and inflammation along with hyperresponsiveness to nonspecific challenges. The airway caliber change induced immediately following a deep inhalation (DI) appears to relate to the mechanism (inflammation vs. smooth muscle constriction) and site (peripheral vs. more central) of obstruction and the degree of hyperresponsiveness. Data are presented and reviewed that support the notion that relative hysteresis of parenchyma (including peripheral airways and alveolar ducts) and airways (more centrally located, conducting airways) can explain the magnitude and sign of airway caliber change that follow a DI in asthmatic subjects.     

Pharmacology of airway inflammation in asthma

Chronic desquamative eosinophilic bronchitis is a characteristic pathologic feature of asthma which may even antedate the onset of symptoms. The pharmacology of asthmatic inflammation has been relatively poorly studied and most of the current data available have been inferred indirectly from studies of bronchial hyperresponsiveness and late-phase responses. Apart from mast cells, the effects of drugs used in the treatment of asthma on other airway inflammatory cells such as eosinophils, alveolar macrophages, etc. have not been extensively studied. The pharmacology of asthmatic inflammation should comprise the study of various aspects of this inflammatory response such as airway microvascular leakage, mediator release, and cell chemotaxis. Ultimately the pharmacologic modulation of the pathologic features of the asthmatic airway by the chronic use of antiasthma drugs, coupled with clinical responses, need to be investigated using bronchial biopsies and broncholveolar lavage in asthmatic patients.     

Mechanisms of airway hyperresponsiveness in asthma

Abstract:   Airway hyperresponsiveness (AHR) is a fundamental abnormality in asthma. There are many potential factors contributing to the excessive airway response demonstrable on airway challenge. These range from abnormalities of airway smooth muscle, airway remodelling and airway inflammation to abnormalities in the neural control of airway calibre. None of these by themselves fully explains the abnormalities seen on the dose response curves of the asthmatic. In this review, the main mechanisms are described, together with recent evidence providing a pathway by which a number of these mechanisms may interact to cause AHR through abnormality in ventilation distribution and airway closure. There is now evidence for a close relationship between ventilation heterogeneity and AHR which could be exploited clinically.     

卡介菌多糖核酸对支气管哮喘小鼠气道反应性及气道炎症的影响

目的 探讨卡介菌多糖核酸对哮喘小鼠气道反应性及气道炎症的影响.方法 选择Balb/c小鼠,以卵白蛋白致敏激发建立小鼠哮喘模型,设立卡介菌多糖核酸组、正常组、哮喘组.卡介菌多糖核酸按剂量具体分为1 μg,10 μg,100 μg亚组,均在第一次抗原致敏前7 d腹腔注射给药.末次激发后48 h采用美国Buxco公司小鼠整体体积扫描记法测定气道反应性,以乙酰甲胆碱各浓度激发时增强的呼吸间歇(Enhanced Pause,Penh)表示.以PC100[气道反应性升高为生理盐水(NS)值2倍时的Mch激发浓度]及Penh/NS%max综合评价气道反应性.收集支气管肺泡灌洗液,涂片后苏木素-伊红染色计数嗜酸粒细胞比例,肺组织病理检测.结果 1μg肛组PC100(13.2±6.9)g/L、10/μg组(11.8±5.58)g/L与哮喘组(5.97±1.73)g/L相比,P<0.01表示差异有统计学意义;1 μg、10 μg组Penh/NS%max分别为(623.22±252.39)%,(519.71±200.41)%,显著低于哮喘组(1 306.83±540.46)%,P<0.01.10 μg组BALF嗜酸粒细胞百分比为(42.75±7.44)%显著低于哮喘组(57.25±13.2)%,P<0.01,1 μg组、100 μg组BALF嗜酸粒细胞百分比与哮喘组相比,差异无统计学意义.结论 卡介菌多糖核酸可以显著抑制哮喘小鼠的气道高反应性及气道炎症.     

Estrogen Replacement Therapy Prevents Airway Dysfunction in a Murine Model of Allergen-Induced Asthma

We previously reported that 17β-estradiol (E₂) prevents hyperresponsiveness to carbachol of murine asthmatic tracheal rings in vitro. We now investigated whether E₂ is similarly effective in reducing airway hyperreactivity in a murine model of allergic asthma in vivo. Female ovariectomized BALB/c mice were rendered asthmatic by a 25-day protocol of sensitization to ovalbumin. Under positive-pressure ventilation, anesthetized asthmatic mice exhibited a dramatic increase in airway responsiveness to increasing doses of inhaled methacholine compared to PBS-sensitized controls, as reflected in decreased dynamic compliance of the respiratory system and increased tissue damping, tissue elastance, and airway resistance. Furthermore, asthmatic mice exhibited hypercellularity and increased protein concentration in the bronchoalveolar lavage, strong signs of peribronchial cuffing with inflammatory cells and increased goblet cell activity. To test the effects of estrogen, three additional groups of mice were implanted subcutaneously with different amounts of slow-release E₂ pellets at the time of ovariectomy and rendered asthmatic as before. E₂ dose-dependently inhibited airway hyperresponsiveness to methacholine, reduced bronchoalveolar lavage hypercellularity, and virtually eliminated histologic signs of inflammation and goblet cell hyperactivity. The inflammation and airway hyperactivity in asthmatic mice was associated with an increase in bronchoalveolar lavage levels of TGFβ1, which was completely abolished in E₂-treated asthmatic mice. We conclude that estrogen replacement therapy effectively ameliorates the pathologic profile of murine allergic asthma.     

卡介菌多糖核酸对支气管哮喘小鼠气道反应性及气道炎症的影响

目的探讨卡介菌多糖核酸对哮喘小鼠气道反应性及气道炎症的影响。方法选择Balb／c小鼠,以卵白蛋白致敏激发建立小鼠哮喘模型,设立卡介菌多糖核酸组、正常组、哮喘组。卡介菌多糖核酸按剂量具体分为1μg,10μg,100μg亚组,均在第一次抗原致敏前7d腹腔注射给药。末次激发后48h采用美国Buxco公司小鼠整体体积扫描记法测定气道反应性,以乙酰甲胆碱各浓度激发时增强的呼吸间歇（Enhanced Pause,Penh）表示。以PC100[气道反应性升高为生理盐水（NS）值2倍时的Mch激发浓度]及Penh／NS％max综合评价气道反应性。收集支气管肺泡灌洗液,涂片后苏木素-伊红染色计数嗜酸粒细胞比例,肺组织病理检测。结果1μg组PC100（13．2±6．9）g／L、10μg组（11．8±5．58）g／L与哮喘组（5．97±1．73）g／L相比,P〈0．01表示差异有统计学意义;1μg、10μg组Penh／NS％max分别为（623．22±252．39）％、（519．71±200．41）％,显著低于哮喘组（1306．83±540．46）％,P〈0．01。10μg组BALF嗜酸粒细胞百分比为（42．75±7．44）％显著低于哮喘组（57．25±13．2）％,P〈0．01,1μg组、100μg组BALF嗜酸粒细胞百分比与哮喘组相比,差异无统计学意义。结论卡介菌多糖核酸可以显著抑制哮喘小鼠的气道高反应性及气道炎症。     

Unimodal distribution of bronchial hyperresponsiveness to methacholine in asthmatic patients.

Distribution of bronchial hyperresponsiveness to methacholine was assessed in 791 consecutive patients who were referred to the outpatient clinic of the pulmonary department due to asthmatic or persistent lower airway symptoms. Bronchial asthma was diagnosed in 319 patients. Clinical sensitivity of methacholine challenge for the disease was 89 percent and specificity, 76 percent. The degree of bronchial hyperresponsiveness in the entire group of asthmatic patients was unimodally log normal distributed. Of the 82 patients with allergic rhinitis without concurrent asthma, 27 percent had bronchial hyperresponsiveness, but of a markedly lesser degree than in the hyperresponsive asthmatic patients. In 49 patients with chronic bronchitis, 22 percent had hyperresponsiveness. The present data indicate that the degree of bronchial hyperresponsiveness in asthmatic patients is unimodally distributed, supporting the view that both genetic and environmental factors have an impact upon its development. Although the degree of bronchial hyperresponsiveness in asthma is more pronounced than in allergic rhinitis or in chronic bronchitis, a marked overlap exists.     

抗IL-5抗体联合抗IL-13抗体对支气管哮喘小鼠气道炎症及气道高反应性的影响

目的 观察抗IL-5抗体（Anti-IL-5 Ab）联合抗IL-13抗体（Anti-IL-13 Ab）对支气管哮喘（简称哮喘）小鼠气道炎症及气道高反应性的影响,为临床应用奠定基础.方法 50只雌性Balb/c小鼠随机分成正常组、哮喘组、Anti-IL-5 Ab治疗组、Anti-IL-13 Ab治疗组和Anti-IL-5 Ab联合Anti-IL-13Ab治疗组.以清洁级Balb/c小鼠构建哮喘模型,采用腹腔注射卵蛋白和氢氧化铝混悬液处理动物.采用瑞氏染色对哮喘小鼠进行支气管肺泡灌洗液中的细胞分类及计数,应用小鼠肺功能仪检测气道阻力的变化.结果 ①Anti-IL-5 Ab联合Anti-IL-13 Ab 治疗组小鼠症状较哮喘组及其他治疗组明显减轻;②Anti-IL-5 Ab联合Anti-IL-13 Ab 治疗组可有效降低哮喘小鼠支气管肺泡灌洗液中嗜酸粒细胞、中性粒细胞、淋巴细胞等炎症细胞水平,与Anti-IL-5 Ab治疗组及Anti-IL-13 Ab治疗组比较差异有统计学意义（P〈0.05）;③Anti-IL-5 Ab联合Anti-IL-13 Ab治疗组可有效降低哮喘小鼠气道高反应性,与Anti-IL-5 Ab治疗组及Anti-IL-13 Ab治疗组比较差异有统计学意义（P〈0.05）.结论 Anti-IL-5 Ab 联合Anti-IL-13 Ab治疗组不但可抑制哮喘小鼠肺部嗜酸粒细胞、中性粒细胞、淋巴细胞等炎症细胞浸润,还可以抑制哮喘迟发反应,降低气道高反应性,改善肺功能,为治疗哮喘提供新的解决办法.     

Relationship of complete respiratory dysfunction: one linked airway. A selective clinical discussion.

There is increasing clinical, immunologic, and pathophysiological consensus that allergic rhinitis (AR) and asthma are different manifestations of a single condition: inflammation of the upper and lower airways characterized by nasal and bronchial hyperresponsiveness. Most patients with asthma have AR and asthma is present in a large percentage of patients with AR. Rhinitis is a major riskfactor for asthma. Treating rhinitis in patients with AR and asthma improves not only the rhinitis but also the asthma. It is becoming clinically evident and studies have confirmed that improving the upper airway also helps the lower airway. There appears to be a connection between upper and lower airway dysfunction, suggesting one linked airway. There also seems to be a relationship between AR and asthma, suggesting that the two conditions are manifestations of one syndrome of complete respiratory dysfunction. The evidence is compelling but it is not completely established.     

Bronchial hyperresponsiveness and airway inflammation markers in nonasthmatics with allergic rhinitis.

Bronchial hyperresponsiveness (BHR) is a characteristic feature of asthma which is often associated with airways inflammation. However, some patients with allergic rhinitis and no clinical evidence of asthma also exhibit BHR. This study therefore investigated whether inflammatory cell infiltrate is present in the induced sputum of nonasthmatic subjects with allergic rhinitis during the pollen season and examined its relationship with airway hyperresponsiveness to inhaled methacholine and adenosine 5'-monophosphate (AMP). Twenty subjects (12 allergic rhinitis, eight nonallergic controls) underwent methacholine and AMP challenge and sputum induction with hypertonic saline on separate days. Cell differentials were calculated from whole sputum samples. A significantly greater number of eosinophils was found in the sputum of nonasthmatic subjects with allergic rhinitis compared to that of nonallergic controls, their median (range) percentages being 17.5 (4-47) and 1.5 (0-5) (p<0.001) respectively. Although sputum eosinophilia failed to be significantly associated with methacholine responsiveness (r(s)=-0.50; p=0.095), the provocative concentration of AMP causing a 20% fall in forced expiratory volume in one second correlated strongly and significantly with the absolute number of eosinophils (r(s)= -0.73; p=0.007). Eosinophil cationic protein levels in the sputum of rhinitic subjects were significantly elevated compared to controls and correlated with eosinophil number (r(s)=0.67; p=0.017). These findings support the view that bronchial eosinophilia alone is insufficient to cause asthmatic symptoms. Diverse agonists for assessing bronchial hyperresponsiveness are selectively associated with airway inflammation in allergic rhinitis.     

Exhaled nitric oxide in pediatric asthma

Exhaled nitric oxide can now be measured in a clinical setting as a noninvasive, reproducible, facile, point-of-service test to measure airway inflammation, a central component of asthma that had not been assessed previously. An excellent surrogate marker of steroid-responsive eosinophilic airway inflammation, it serves to identify steroid-sensitive asthmatic patients and enables clinical monitoring of the response to steroid therapy and titration of the dose. Standardization of methodology and technological advances, such as the recent availability of handheld analyzers, individualized patient cards to store serial test measurements, and the assignment of coding procedural terminology, make this a necessary adjunct to clinical and functional assessment of airway obstruction and hyperresponsiveness in ambulatory pediatric and adult asthma practices.     

Asymptomatic airway hyperresponsiveness: relationships with airway inflammation and remodelling.

To study the physiopathology and significance of asymptomatic airway hyperresponsiveness (AHR), the clinical and bronchial immunohistological parameters were evaluated in subjects with asymptomatic and symptomatic AHR. Asymptomatic subjects with AHR (eight females/two males, no respiratory symptoms, provocative concentration of methacholine causing a 20% fall in forced expiratory volume in one second (PC20) <8 mg x mL(-1) and no treatment) were compared with asthmatic subjects paired for age, sex and PC20, and with nonatopic, nonasthmatic controls paired for age and sex. All three groups were evaluated once at baseline, whilst the asymptomatic AHR subjects were re-evaluated after 1 and 2 yrs. Measurements included spirometry, methacholine challenge, serum immunoglobulin (Ig)E, blood eosinophils, and bronchoscopy (at baseline and after 2 yrs only). At first evaluation, the mean blood eosinophil count, total serum IgE level, atopic index, baseline forced expiratory volume in one second (FEV1) and the degree of bronchial epithelial desquamation of the asymptomatic AHR subjects were similar to those of asthmatic subjects. However, they presented focal rather than the continuous bronchial subepithelial fibrosis observed in asthmatics. Their mucosal CD3, CD4, CD25, EG1 and EG2-positive cell counts were intermediate between those of the control subjects and asthmatics. At the end of the 2-yr follow-up, four of them had developed asthma symptoms. At this time, bronchial biopsies revealed an increase in the extent of subepithelial fibrosis and in the number of CD25 and CD4-positive cells, and a decrease in the number of CD8+ cells, particularly in subjects who developed asthma symptoms. These data suggest that asymptomatic airway hyperresponsiveness is associated with airway inflammation and remodelling, and that the appearance of asthma symptoms is associated with an increase in these features, particularly the CD4/CD8 ratio and airway fibrosis. Consequently, this study proposes an association between asymptomatic airway hyperresponsiveness and airway inflammation, structural changes and asthma although these relationships remain to be further evaluated.     

Fas/FasL与支气管哮喘

Fas受体和Fas配体(FasL)在免疫细胞上的表达相对较高,其介导的细胞凋亡、增殖与免疫细胞的凋亡、增殖及功能发挥密切相关,在哮喘免疫耐受及调控异常、Th1/Th2失衡、气道炎症、黏液产生、气道高反应及气道重塑中发挥了重要作用,有望成为哮喘治疗的突破口。但是,在Fas/FasL信号转导过程中,各种因素构成了一个复杂的调控网络,深入研究Fas/FasL信号转导途径及其相关的调控机制才能为哮喘治疗开创新途径。     

Reduced intracellular magnesium concentrations in asthmatic patients.

Magnesium is important in the regulation of bronchomotor tone, and low dietary intake of magnesium has been associated with airway hyperresponsiveness in epidemiological studies. The concentration of magnesium in serum, erythrocytes and urine in 49 patients with asthma (29 males, aged 15-65 yrs) and in 25 normal subjects (15 males, aged 17-36 yrs) was studied by atomic absorption. Magnesium concentrations were significantly lower in erythrocytes and urine in both atopic (n = 26) and nonatopic (n = 23) asthmatic patients as compared with the control group, whereas serum concentrations did not differ. The concentration of magnesium in erythrocytes was not related to the degree of airway obstruction as measured by forced expiratory volume in one second (FEV1) but was significantly correlated with airway hyperresponsiveness measured as the provocative concentration causing a 20% fall in FEV1 to inhaled acetylcholine (r = 0.64; p<0.05). In addition, a magnesium tolerance test showed increased retention of magnesium (58.9% of administered dose in asthmatic patients compared with 8.9% in normal subjects, p<0.05). In conclusion, the low cellular concentration of magnesium may be associated with airway hyperresponsiveness in asthmatic patients.     

Different roles of interleukin-10 in onset and resolution of asthmatic responses in allergen-challenged mice

OBJECTIVE: Although interleukin (IL)-10 is an immunoregulatory cytokine produced by various cells including T cells, its precise role in asthma remains uncertain. The aim of this study was to investigate the role of IL-10 in experimental asthma using ovalbumin (OVA)-sensitized mice. METHODOLOGY: Mice were challenged with OVA aerosol, and airway responsiveness and inflammation were measured. OVA-specific IL-10-producing CD4+ T cells were counted from lung cells collected by enzymatic digestion and stimulated ex vivo with OVA. The effects of an anti-IL-10 antibody on airway responsiveness and inflammation were also evaluated. RESULTS: The OVA challenge caused airway hyperresponsiveness and eosinophilic inflammation. A significant increase in IL-10-producing CD4+ T cells was observed, mainly in the CD45RB(low) subset, for several days after the OVA challenge. Anti-IL-10 antibody treatment before the OVA challenge did not affect eosinophilic inflammation but significantly inhibited airway hyperresponsiveness 24 h after the OVA challenge. However, anti-IL-10 antibody treatment just before the last OVA challenge significantly attenuated the resolution of eosinophilic inflammation without affecting airway responsiveness 2 weeks after the OVA challenge. CONCLUSIONS: Intrinsic IL-10 may have a distinct role in the early and late phases of asthmatic responses. In the early phase, IL-10 induces airway hyperresponsiveness, while in the late phase IL-10 contributes to the resolution of eosinophilic inflammation.     

Effects of an eosinophil chemotaxis inhibitor,TAK-661, on antigen-induced asthmatic responses in allergic sheep

Eosinophils have been shown to play a role in allergen-induced airway responses. The aim in this study was to examine the effects of TAK-661, a newly developed product as a specific inhibitory agent of eosinophil chemotaxis, on antigen-induced asthmatic responses in allergic sheep model. Seven Ascaris-sensitive, "dual-respondent" allergic sheep were provocated by an Ascaris suum antigen or phosphate-buffered saline 2 hrs after intra-stomach administration of TAK-661 or a placebo. Pulmonary resistances were measured throughout the experiment, and airway responsiveness to methacholine, bronchoalveolar lavage (BAL), and histological examination were performed 8 hrs after the antigen challenge. Antigen provocation induced dual-phase bronchoconstriction, eosinophilia in BAL and eosinophil infiltration into the airway wall, and an increase in airway responsiveness in placebo-treated sheep. The administration of TAK-661 significantly reduced the bronchoconstriction during the late phase, along with the inhibition of eosinophilia in BAL and the eosinophil infiltration into the airway wall. TAK-661 had a tendency to reduce early-phase bronchoconstriction and airway hyperresponsiveness, but there were no significant differences. These findings suggest that the eosinophil accumulation into the airway induced by antigen provocation may contribute to the development of late-phase bronchoconstriction, however, the development of airway hyperresponsiveness during late asthmatic response may not always be due to only eosinophilic inflammation in the airway.