In guinea pigs, we have previously demonstrated that the contribution of Rho-kinase to airway responsiveness in vivo and ex vivo is enhanced after active sensitization with ovalbumin (OA). Using conscious, unrestrained OA-sensitized guina pigs, we now investigated the role of Rho-kinase in the development of airway hyperresponsiveness (AHR) after the allergen-induced early (EAR) and late asthmatic reaction (LAR) in vivo.
Histamine and PGF2α PC100-values (provocation concentrations causing 100% increase in pleural pressure) were assessed before OA-challenge (basal airway responsiveness) and after the OA-induced EAR (5 h after challenge) and LAR (23 h after challenge). Thirty minutes later, saline or the specific Rho-kinase inhibitor Y-27632 (5 mM, nebulizer concentration) were nebulized, after which PC100-values were reassessed.
In contrast to saline, Y-27632 inhalation significantly decreased the basal responsiveness toward histamine and PGF2α before OA-challenge, as indicated by increased PC100 -values. Both after the allergen-induced EAR and LAR, AHR to histamine and PGF2α was present, which was reversed by Y-27632 inhalation. Moreover, there was an increased effectiveness of Y-27632 to reduce airway responsiveness to histamine and PGF2α after the EAR and LAR as compared to pre-challenge conditions. Saline inhalations did not affect histamine or PGF2α PC100-values at all. Interestingly, under all conditions Y-27632 was significantly more effective in reducing airway responsiveness to PGF2α as compared to histamine. Also, there was a clear tendency (P = 0.08) to a more pronounced degree of AHR after the EAR for PGF2α than for histamine.
The results indicate that inhalation of the Rho-kinase inhibitor Y-27632 causes a considerable bronchoprotection to both histamine and PGF2α. Moreover, the results are indicative of a differential involvement of Rho-kinase in the agonist-induced airway obstruction in vivo. Increased Rho-kinase activity contributes to the allergen-induced AHR to histamine and PGF2α after both the EAR and the LAR, which is effectively reversed by inhalation of Y-27632. Therefore, Rho-kinase can be considered as a potential pharmacotherapeutical target in allergic asthma.
Although airway inflammation and airway hyperreactivity are observed after allergen inhalation both in allergic humans and animals, little is known about the mechanisms by which inflammatory cells can contribute to allergen-induced airway hyperreactivity. To understand how inflammatory cell infiltration can contribute to airway hyperreactivity, the location of these cells within the airways may be crucial Using a guinea pig model of acute allergic asthma, we investigated the inflammatory cell infiltration in different airway compartments at 6 and 24 h (i.e. after the early and the late asthmatic reaction, respectively) after allergen or saline challenge in relation to changes in airway reactivity (AR) to histamine. At 6 h after allergen challenge, a threefold (p < 0.01) increase in the AR to histamine was observed. At 24 h after challenge, the AR to histamine was lower, but still significantly enhanced (1.6-fold, p < 0.05). Adventitial eosinophil and neutrophil numbers in both bronchi and bronchioli were significantly increased at 6 h post-allergen provocation as compared with saline (p < 0.01 for all), while there was a strong tendency to enhanced eosinophils in the bronchial submucosa at this time point (p = 0.08). At 24h after allergen challenge, the eosinophilic and neutrophilic cell infiltration was reduced. CD3+ T lymphocytes were increased in the adventitial compartment of the large airways (p < 0.05) and in the parenchyma (p < 0.05) at 24h post-allergen, while numbers of CD8+ cells did not differ from saline treatment at any time point post-provocation. The results indicate that, after allergen provocation, inflammatory cell numbers in the airways are mainly elevated in the adventitial compartment. The adventitial inflammation could be important for the development of allergen-induced airway hyperreactivity.
Bronchial responsiveness to inhaled histamine was measured two, seven, and 30 hours after allergen inhalation challenge in 19 atopic subjects. The provocative histamine concentrations causing a 20% fall in FEV1 (PC20) at these three times were compared with the baseline value, with values obtained two and seven hours after diluent inhalation, and with those obtained five to seven days after allergen challenge in the 12 late responders. Seven subjects had allergen induced isolated early asthmatic responses (delta FEV1 22.6% (SD 6.6%)) with less than a 5% late fall in FEV1. There was no change in the six histamine PC20 values measured in these seven subjects; the geometric mean PC20 was 1.0-1.3 mg/ml on all six occasions. Twelve subjects had an allergen induced early asthmatic response (delta FEV1 26.3% (9.8%)) followed by a definite (greater than 15% delta FEV1, n = 7) or equivocal (5-15% delta FEV1, n = 5) late asthmatic response. The geometric mean histamine PC20 was not significantly different two hours after allergen inhalation either from baseline (0.67 v 0.78 mg/ml) or from that seen two hours after diluent (0.67 v 0.95). It was significantly reduced at seven (0.24 mg/ml) and at 30 hours (0.44 mg/ml) but had returned to baseline when repeated five to seven days later (0.74 mg/ml). In 10 subjects with a dual response who had a repeat antigen challenge the mean early and late response and delta PC20 at seven and 30 hours were similar. These data show that bronchial responsiveness to a non-allergic stimulus has not increased two hours after allergen inhalation following spontaneous recovery of the early asthmatic response but before the start of the late asthmatic response.
Subjects with allergic asthma develop isolated late asthmatic reactions after inhalation of allergen‐derived T cell peptides. Animal experiments have shown that airway hyperresponsiveness (AHR) is CD4+ cell‐dependent. It is hypothesised that peptide inhalation produces increases in non‐specific AHR and a T cell‐dominant bronchial mucosal inflammatory response.
Bronchoscopy, with bronchial biopsies and bronchoalveolar lavage (BAL), was performed in 24 subjects with cat allergy 6 h after aerosol inhalation of short overlapping peptides derived from Fel d 1, the major cat allergen. Biopsy specimens and BAL fluid were studied using immunohistochemistry and ELISA.
Twelve of the 24 subjects developed an isolated late asthmatic reaction without a preceding early (mast cell/histamine‐dependent) reaction characteristic of whole allergen inhalation. These responders had significant between‐group differences (responders vs non‐responders) in the changes (peptide vs diluent) in AHR (p = 0.007) and bronchial mucosal CD3+ (p = 0.005), CD4+ (p = 0.006) and thymus‐ and activation‐regulated chemokine (TARC)+ (p = 0.003) but not CD8+ or CD25+ cells or eosinophils, basophils, mast cells and macrophages. The between‐group difference for neutrophils was p = 0.05 but with a non‐significant within‐group value (peptide vs diluent, responders, p = 0.11). In BAL fluid there was a significant between‐group difference in TARC (p = 0.02) but not in histamine, tryptase, basogranulin, C3a or C5a, leukotrienes C4/D4/E4, prostaglandins D2 or F2α.
Direct activation of allergen‐specific airway T cells by peptide inhalation in patients with atopic asthma leads to increased AHR with local increases in CD3+ and CD4+ cells and TARC but no significant changes in eosinophils or basophil/mast cell products. These findings support previous animal experiments which showed a CD4+ dependence for AHR.
Early-phase reactions (EPRs) and late-phase reactions (LPRs) are characteristic features of bronchial asthma, although the pathogenetic mechanisms responsible for each of the responses are not fully defined. A murine model of EPRs and LPRs was developed to investigate the role of IL-5 and eosinophils in development of both responses. After initial intraperitoneal sensitization and airway challenge to ovalbumin (OVA), mice were provoked by additional exposure to OVA. An EPR, characterized by a transient increase in airway responsiveness, was observed 5–30 minutes after antigen provocation. This response was followed by an LPR that reached its maximum at 6 hours after challenge and was characterized by increased airway responsiveness and significant lung eosinophilia. The EPR was blocked by cromoglycate and albuterol, whereas the LPR was abolished by cromoglycate and hydrocortisone. Before provocation with allergen, administration of anti–IL-5 antibody prevented the influx of eosinophils into the lung tissue and abolished the LPR but not EPR. These results suggest that IL-5 and eosinophils are essential for development of the LPR, but not EPR, in this model.
BACKGROUND: The cysteinyl leukotrienes (LTC4, LTD4 and LTE4) have been implicated in the pathogenesis of allergen-induced airway responses. The effects of pretreatment with BAYx 1005, an inhibitor of leukotriene biosynthesis via antagonism of 5-lipoxygenase activating protein, on allergen-induced early and late asthmatic responses has been evaluated. METHODS: Eight atopic subjects with mild asthma participated in a two period, double blind, placebo controlled, cross-over trial. Subjects were selected on the basis of a forced expiratory volume in one second (FEV1) of > 70% predicted, a methacholine provocative concentration causing a 20% fall in FEV1 (PC20) of < 32 mg/ ml, a documented allergen- induced early response (EAR, > 15% fall in FEV1 0-1 hour after allergen inhalation) and late response (LAR, > 15% fall in FEV1 3-7 hours after allergen inhalation), and allergen-induced airway hyperresponsiveness (at least a doubling dose reduction in the methacholine PC20 30 hours after allergen inhalation). During the treatment periods subjects received BAYx 1005 (500 mg twice daily) or placebo for 3.5 days; treatment periods were separated by at least two weeks. On the third day of treatment, two hours after administration of medication, subjects performed an allergen inhalation challenge and FEV1 was measured for seven hours. RESULTS: Treatment with BAYx 1005 attenuated the magnitude of both the allergen-induced early and late asthmatic responses. The mean (SE) maximal fall in FEV1 during the EAR was 26.6 (3.3)% during placebo treatment and 11.4 (3.3)% during treatment with BAYx 1005 (mean difference 15.2 (95% confidence interval (CI) 9.4 to 21.00) with a mean protection afforded by BAYx 1005 of 57.1%. The mean (SE) maximal fall in FEV1 during the LAR was 19.8 (5.7)% during placebo treatment and 10.7 (4.4)% during BAYx 1005 treatment (mean difference 9.2 (95% CI 1.4 to 17.0) with a mean protection afforded by BAYx 1005 of 46.0%. The area under the time response curve (AUC0-3) was also reduced after treatment with BAYx 1005 compared with placebo by 86.5%.h (mean difference 26.3 (95% CI 17.1 to 38.5)) and the AUC3-7 by 59.6%.h (mean difference 26.9 (95% CI-3.8 to 57.6)). CONCLUSIONS: These results show that antagonism of 5-lipoxygenase activating protein can attenuate allergen-induced bronchoconstrictor responses and support an important role for the cysteinyl leukotrienes in mediating these asthmatic responses.
Bronchial hyperresponsiveness (BHR) is an important pathophysiological feature of asthma. In addition to the diagnostic significance, BHR is associated with the severity of airway inflammation and BHR- based treatment approaches has been shown to be effective. Nevertheless, challenge tests are time consuming, inconvenient to patients, and are not accessible in every primary care physicians. We aimed to develop a questionnaire for the assessment of BHR in Korean subjects.
From the 24 University-affiliated hospitals, we recruited 149 adults between age 20 and 40 years with more than one asthmatic symptom (cough, sputum or dyspnea) and who had bronchial provocation test. A list of 33 symptoms, past history of allergy or smoking and 10 provoking stimuli were selected for the BHR questionnaire. After a methacholine challenge test patients were asked to complete each questionnaire. For each item of questionnaire, diagnostic odds ratios for the presence of BHR were calculated and multiple logistic regression analysis was performed to select final questionnaire items. Receiver operating characteristic (ROC) curve analysis was used to evaluate the sensitivity and specificity of the selected questionnaire items.
Methacholine challenge test was positive in 36 patients (24.2%). Eleven symptoms and 2 provoking stimuli items were statistically significant by the results of diagnostic odds ratio. According to the result of multiple logistic regression analysis, 4 items were finally selected for the significant BHR questionnaire: the presence of wheezing episode, past history of physician-diagnosed asthma, family history of asthma. The psychiatric stress was negatively associated provoking stimuli item for the presence of BHR. The area under the ROC curve was 0.80 (95% CI, 0.72-0.86). Sensitivity was 84.9% (95% CI, 68.1-94.9) and specificity was 65.5% (95% CI, 55.8-74.3).
Four BHR questionnaire items including wheezing episode, past history of physician-diagnosed asthma, family history of asthma and psyachiatric stress stimuli were able to assess the presence of BHR in Korean adults.
Allergen inhalation challenge has been useful for examining the mechanisms of allergen-induced airway inflammation and the associated physiological changes and for documenting the efficacy of drugs to treat asthma. Allergen inhalation by a sensitized subject results in acute bronchoconstriction, beginning within 15-30 min and lasting 1-3 hr, which can be followed by the development of a late asthmatic response. Individuals who develop both an early and late response after allergen have more marked increases in airway hyperresponsiveness, and greater increases in allergen-induced airway inflammation, particularly in airway eosinophils and basophils. All of the currently available and effective treatments for asthma modify some aspects of allergen-induced responses. These medications include short-acting and long-acting inhaled β2-agonists, inhaled corticosteroids, cromones, methylxanthines, leukotriene inhibitors, and anti-IgE monoclonal antibody. In addition, allergen inhalation challenge has become a useful method which can, in a very limited number of patients, provide key information on the therapeutic potential of new drugs being developed to treat asthma.
asthma; allergen; inflammation; drug development
The inhibition of immediate allergen or histamine induced airflow obstruction by inhaled ketotifen, clemastine, sodium cromoglycate, and placebo was studied in two groups of asthmatic subjects. Single doses of ketotifen (0.5 mg), clemastine (0.5 mg), sodium cromoglycate (20 mg), or placebo were administered by inhalation 45 minutes before bronchial provocation testing at weekly intervals, double blind and in random order. Inhalation of ketotifen and clemastine, but not sodium cromoglycate, caused an increase in the amount of histamine which had to be administered to cause a 20% fall in FEV1 from control levels (PD20-FEV1) compared with placebo. The PD20-FEV1 for allergen increased significantly after inhalation of clemastine and sodium cromoglycate. Clemastine, primarily an H1 receptor antagonist, inhibited airflow obstruction after inhalation of both histamine and allergen. Its inhibitory effect on allergen induced asthma did not differ significantly from that of sodium cromoglycate. Ketotifen, when inhaled in a single dose of 0.5 mg before bronchial provocation testing, showed potent antihistamine activity, but there was no evidence of any additional "antianaphylactic" activity.
Twenty seven aspirin sensitive asthmatic patients were studied to determine the relationship between non-specific bronchial responsiveness to inhaled histamine and the degree of sensitivity to aspirin (aspirin threshold dose). No correlation was found between provocative concentration of histamine (PC20H) and aspirin threshold dose. In 11 patients the influence of aspirin desensitisation on bronchial reactivity to inhaled histamine was examined. Mean PC20H measured the day after the patients were desensitised to 600 mg of aspirin did not change significantly from the values before desensitisation. These observations suggest that sensitivity to aspirin and non-specific bronchial hyperreactivity in asthmatic patients are independent phenomena.
Background: Bronchial hyperresponsiveness (BHR) is characteristic of asthmatic airways, is induced by airway inflammation, and is reduced by inhaled corticosteroids (ICS). The time course for the onset and cessation of the effect of ICS on BHR is unclear. The effect of inhaled fluticasone propionate (FP) on BHR in patients with mild persistent asthma was assessed using time intervals of hours, days and weeks.
Methods: Twenty six asthmatic patients aged 21–59 years were selected for this randomised, double blind, parallel group study. The effect of 250 µg inhaled FP (MDI) administered twice daily was compared with that of placebo on BHR assessed using a dosimetric histamine challenge method. The dose of histamine inducing a decrease in forced expiratory volume in 1 second (FEV1) by 15% (PD15FEV1) was measured before and 6, 12, 24 and 72 hours, and 2, 4 and 6 weeks after starting treatment, and 48 hours, 1 week and 2 weeks after cessation of treatment. Doubling doses of changes in PD15FEV1 were calculated and area under the curve (AUC) statistics were used to summarise the information from individual response curves.
Results: The increase in PD15FEV1 from baseline was greater in the FP group than in the placebo group; the difference achieved significance within 72 hours and remained significant until the end of treatment. In the FP group PD15FEV1 was 1.85–2.07 doubling doses above baseline between 72 hours and 6 weeks after starting treatment. BHR increased significantly within 2 weeks after cessation of FP treatment.
Conclusions: A sustained reduction in BHR to histamine in patients with mild asthma was achieved within 3 days of starting treatment with FP at a daily dose of 500 µg. The effect tapered within 2 weeks of cessation of treatment.
Allergen induced early phase airway response and airway plasma exudation are predominantly mediated by inflammatory mast cell mediators including histamine, cysteinyl leukotrienes (cysLTs) and thromboxane A2 (TXA2). The aim of the present study was to evaluate whether repeated allergen exposure affects early phase airway response to allergen challenge.
A trimellitic anhydride (TMA) sensitized guinea pig model was used to investigate the effects of low dose repeated allergen exposure on cholinergic airway responsiveness, early phase airway response and plasma exudation, as well as local airway production of mast cell derived cysteinyl leukotrienes and thromboxane B2 (TXB2) after allergen challenge.
Repeated low dose allergen exposure increased cholinergic airway responsiveness. In contrast, early phase airway response and plasma exudation in response to a high-dose allergen challenge were strongly attenuated after repeated low dose allergen exposure. Inhibition of the airway response was unspecific to exposed allergen and independent of histamine receptor blocking. Furthermore, a significant reduction of cysteinyl leukotrienes and TXB2 was found in the airways of animals repeatedly exposed to a low dose allergen. However, in vitro stimulation of airway tissue from animals repeatedly exposed to a low dose allergen with arachidonic acid and calcium ionophore (A23187) induced production of cysteinyl leukotrienes and TXB2, suggesting enhanced activity of 5-lipoxygenase and cyclooxygenase pathways.
The inhibition of the early phase airway response, cysteinyl leukotriene and TXB2 production after repeated allergen exposure may result from unresponsive effector cells.
Guinea pig; Allergen exposure; Cholinergic responsiveness; Early phase airway response; Plasma exudation; 5-lipoxygenase; Cyclooxygenase
Bronchial provocation studies on 15 workers occupationally exposed to formaldehyde are described. The results show that formaldehyde exposure can cause asthmatic reactions, and suggest that these are sometimes due to hypersensitivity and sometimes to a direct irritant effect. Three workers had classical occupational asthma caused by formaldehyde fumes, which was likely to be due to hypersensitivity, with late asthmatic reactions following formaldehyde exposure. Six workers developed immediate asthmatic reactions, which were likely to be due to a direct irritant effect as the reactions were shorter in duration than those seen after soluble allergen exposure and were closely related to histamine reactivity. The breathing zone concentrations of formaldehyde required to elicit these irritant reactions (mean 4.8 mg/m3) were higher than those encountered in buildings recently insulated with urea formaldehyde foam, but within levels sometimes found in industry.
Immediate asthmatic responses have been regarded as the characteristic type of asthmatic response to follow exposure to inhaled allergens in patients with extrinsic asthma. They begin within minutes, clear within one to three hours and are inhibited by disodium cromoglycate but not by corticosteroids. They involve the reaction of antigen with antibodies usually of the IgE class. In recent years allergen inhalation tests have demonstrated the frequent occurrence of late asthmatic responses, either following immediate responses (dual responses) or occurring in isolation. The late asthmatic responses begin two to six hours after the allergen challenge, are prolonged and often severe, and are inhibited by both disodium cromoglycate and corticosteroids. The mechanisms involved in their provocation are not clearly understood but from the allergic viewpoint they may involve the participation of IgG ± IgM antibodies and/or IgE antibodies. Late asthmatic responses explain the frequent occurrence of allergen-induced prolonged asthma. Their features suggest that they are more important than immediate responses in the pathophysiology of asthma.
Both standard and low-dose allergen provocations are an established tool in asthma research to improve our understanding of the pathophysiological mechanism of allergic asthma. However, clinical symptoms are less likely to be induced. Therefore, we designed a protocol for repetitive high-dose bronchial allergen challenges to generate clinical symptoms and airway inflammation.
A total of 27 patients aged 18 to 40 years with positive skin-prick tests and mild asthma underwent repetitive high-dose allergen challenges with household dust mites for four consecutive days. Pulmonary function and exhaled NO were measured at every visit. Induced sputum was analysed before and after the allergen challenges for cell counts, ECP, IL-5, INF-γ, IL-8, and the transcription factor Foxp3.
We found a significant decrease in pulmonary function, an increased use of salbutamol and the development of a late asthmatic response and bronchial hyperresponsiveness, as well as a significant induction of eNO, eosinophils, and Th-2 cytokines. Repeated provocation was feasible in the majority of patients. Two subjects had severe adverse events requiring prednisolone to cope with nocturnal asthma symptoms.
Repeated high-dose bronchial allergen challenges resulted in severe asthma symptoms and marked Th-2-mediated allergic airway inflammation. The high-dose challenge model is suitable only in an attenuated form in diseased volunteers for proof-of-concept studies and in clinical settings to reduce the risk of severe asthma exacerbations.
Bronchial allergen challenge; Bronchial hyperresponsiveness; Exhaled NO; Eosinophils; IL-5; IL-8; IFN-γ; Foxp3
Both ventilation (V) and perfusion (Q) of the lungs are altered in asthma, but their relationships with allergen-induced airway responses and gas exchange are not well described.
The effects of aerosolized allergen provocation of V/Q abnormalities in nonsmoking, male atopic asthmatics (six dual responders and two isolated early responders) were compared with measurements of airflow limitation (forced expiratory volume in 1 s [FEV1]), gas exchange (arterial oxygen saturation, arterial oxygen partial pressure and alveolar-arterial oxygen gradient) and airway reactivity (provocative concentration of histamine causing a decrease of 20% in FEV1). V and Q lung scans at 30 min and 6 h following allergen challenge and changes in all variables were compared with prechallenge data. Digital image data were registered to baseline scans, and quantitative comparisons of changes made were supported by qualitative assessments of the images.
All subjects showed evidence of impaired gas exchange, as reflected by lowered arterial oxygen tension and widened alveolar arterial oxygen gradients. Baseline V/Q scans were abnormal, and there were allergen-induced changes in V and Q at 30 min, with scans at 6 h showing additional changes in Q, particularly in dual responders. Allergen-induced gas trapping was evident at 30 min and was sustained at 6 h.
Regional patterns of V and Q derived from lung scintigraphy showed a wider range of disturbances than were indicated by the magnitude of airflow limitation and arterial hypoxemia following allergen provocation, and they remained abnormal despite normalization of FEV1. Imaging of regional abnormalities of gas exchange may be relevant in the evaluation of patients with asthma.
Airway responses; Allergen inhalation; Asthma; Gas exchange; Lung scintigraphy
Airway mycoplasma infection may be associated with asthma pathophysiology. However, the direct effects of mycoplasma infection on asthma remain unknown. Using a murine allergic-asthma model, we evaluated the effects of different timing of airway Mycoplasma pneumoniae infection on bronchial hyperresponsiveness (BHR), lung inflammation, and the protein levels of Th1 (gamma interferon [IFN-γ]) and Th2 (interleukin 4 [IL-4]) cytokines in bronchoalveolar lavage fluid. When mycoplasma infection occurred 3 days before allergen (ovalbumin) sensitization and challenge, the infection reduced the BHR and inflammatory-cell influx into the lung. This was accompanied by a significant induction of Th1 responses (increased IFN-γ and decreased IL-4 production). Conversely, when mycoplasma infection occurred 2 days after allergen sensitization and challenge, the infection initially caused a temporary reduction of BHR and then increased BHR, lung inflammation, and IL-4 levels. Our data suggest that mycoplasma infection could modulate both physiological and immunological responses in the murine asthma model. Our animal models may also provide a new means to understand the role of infection in asthma pathogenesis and give evidence for the asthma hygiene hypothesis.
Both atopy and bronchial hyperresponsiveness (BHR) are characteristic features of asthma. They are also found among non-asthmatic subjects, including allergic rhinitis patients and the general population. Atopy and BHR in asthma are closely related. Atopy induces airway inflammation as an IgE response to a specific allergen, which causes or amplifies BHR. Moreover, significant evidence of the close relationship between atopy and BHR has been found in non-asthmatic subjects. In this article, we discuss the relationship between atopy and BHR in the general population, asthmatic subjects, and those with allergic rhinitis. This should widen our understanding of the pathophysiology of atopy and BHR.
Allergic rhinitis; asthma; atopy; bronchial hyperresponsiveness; patients; population
BACKGROUND--It has recently been reported that acetaldehyde induces bronchoconstriction indirectly via histamine release. However, no study has been performed to assess whether acetaldehyde worsens bronchial responsiveness in asthmatic subjects so this hypothesis was tested. METHODS--Methacholine provocation was performed on three occasions: (1) after pretreatment with oral placebo and inhaled saline (P-S day), (2) after placebo and inhaled acetaldehyde (P-A day), and (3) after a potent histamine H1 receptor antagonist terfenadine and acetaldehyde (T-A day) in a double blind, randomised, crossover fashion. Nine asthmatic subjects inhaled 0.8 mg/ml acetaldehyde or saline for four minutes. After each inhalation a methacholine provocation test was performed. RESULTS--Methacholine concentrations producing a 20% fall in FEV1 (PC20-MCh) on the P-A day (0.48 mg/ml, 95% CI 0.21 to 1.08) and T-A day (0.41 mg/ml, 95% CI 0.22 to 0.77) were lower than those on the P-S day (0.85 mg/ml, 95% CI 0.47 to 1.54). There was no change in the PC20-MCh between the P-A and T-A days. A correlation was observed between the logarithmic values of PC20-MCh (log PC20-MCh) on the P-S day and the potentiating effect of acetaldehyde on the methacholine responsiveness [(log PC20-MCh on P-A day)-(log PC20-MCh on P-S day)] (rho = 0.82). CONCLUSIONS--Acetaldehyde induces bronchial hyperresponsiveness in patients with asthma by mechanisms other than histamine release.
Rationale: In humans, immune responses to inhaled aeroallergens develop in the lung and draining lymph nodes. Many animal models of asthma bypass this route and instead use intraperitoneal injections of allergen using aluminum hydroxide as an adjuvant.
Objectives: We investigated whether allergic sensitization through the airway elicits immune responses qualitatively different than those arising in the peritoneum.
Methods: Mice were sensitized to allergen through the airway using low-dose LPS as an adjuvant, or through the peritoneum using aluminum hydroxide as an adjuvant. After a single allergen challenge, ELISA and flow cytometry were used to measure cytokines and leukocyte subsets. Invasive measurements of airway resistance were used to measure allergen-induced airway hyperreactivity (AHR).
Measurements and Main Results: Sensitization through the peritoneum primed strong Th2 responses and eosinophilia, but not AHR, after a single allergen challenge. By contrast, allergic sensitization through the airway primed only modest Th2 responses, but strong Th17 responses. Th17 cells homed to the lung and released IL-17 into the airway on subsequent encounter with inhaled allergen. As a result, these mice developed IL-17–dependent airway neutrophilia and AHR. This AHR was neutrophil-dependent because it was abrogated in CXCR2-deficient mice and also in wild-type mice receiving a neutrophil-depleting antibody. Individually, neither IL-17 nor ongoing Th2 responses were sufficient to confer AHR, but together they acted synergistically to promote neutrophil recruitment, eosinophil recruitment and AHR.
Conclusions: Allergic sensitization through the airway primes modest Th2 responses but strong Th17 responses that promote airway neutrophilia and acute AHR. These findings support a causal role for neutrophils in severe asthma.
asthma; lung; immunity
The definition of "clinical asthma remission" is based on absence of symptoms and use of medication. However, in the majority of these subjects airway inflammation is still present when measured. In the present study we investigated whether "complete asthma remission", additionally defined by the absence of bronchial hyperresponsiveness (BHR) and the presence of a normal lung function, is associated with the absence of airway inflammation.
Patients with a former diagnosis of asthma and a positive histamine provocation test were re-examined to identify subjects with complete asthma remission (no asthma symptoms or medication, PC20 histamine > 32 mg/ml, FEV1 > 90% predicted). Patients with PC20 histamine ≤ 32 mg/ml were defined as current asthmatics and were divided in two groups, i.e. asthmatics with and without BHR to adenosine 5'monophoshate (AMP). Sputum induction was performed 1 week before and 1 hour after AMP provocation. Sputum induction and AMP provocation were previously shown to be sensitive markers of airway inflammation.
Seven patients met criteria for complete asthma remission. Twenty-three were current asthmatics, including twelve without hyperresponsiveness to AMP. Subjects with complete asthma remission showed no AMP-induced sputum eosinophilia (median (range) 0.2 (0 - 4.6)% at baseline and 0.2 (0 - 2.6)% after AMP). After AMP, current asthmatics had a significant increase in sputum eosinophils (0.5 (0 - 26.0)% at baseline and 2.6 (0 - 32.0) % after AMP), as had the subgroup of current asthmatics without hyperresponsiveness to AMP (0.2 (0 - 1.8)% at baseline and 1.3 (0 - 6.3)% after AMP).
Subjects with complete asthma remission, in contrast to subjects with current asthma, do not respond with eosinophilic inflammation in sputum after AMP provocations. These data lend support to the usefulness of the definition of complete asthma remission.
The objective of this study is to investigate whether BCG infection before, during or after sensitization suppresses allergen-induced airway hyperresponsiveness and eosinophilic inflammation in allergic asthma rats, and to determine the required dose of BCG to induce such an inhibition. Eighty-seven Sprague-Dawley (SD) rats were sensitized and provoked with ovalbumin (OA). A pretreatment of 6 x 10(4) or 6 x 10(5) colony forming units (CFUs) of BCG or saline was done at four different times: 3 days before sensitization, at sensitization, 3 days before provocation, or at provocation. The assessment of tracheal smooth muscle (TSM) responsiveness to electrical field stimulation or acetylcholine (ACh) and bronchoalveolar lavage (BAL) were performed 1 day after OA provocation. Doses of 6 x 10(4) CFUs inhibited TSM sensitivity of rats infected 3 days before sensitization or at sensitization, but not 3 days before provocation or at provocation. However, doses of 6 x 10(5) CFUs significantly inhibited not only the airway eosinophilia of rats infected 3 days before sensitization or at sensitization, but also the TSM sensitivity of rats infected 3 days before provocation or at provocation. In conclusion, BCG infection suppresses the development of sensitivity of airway smooth muscle and airway eosinophilic inflammation in allergic asthma rats. Furthermore, a relatively high dose of BCG infection inhibits airway sensitivity, even after allergen sensitization.
Porcine pancreatic extracts (PPE), which are widely used as a digestive drug in Korea, are composed of α-amylase and lipase. Such enzymes are commonly described as occupational allergens. This is the first report of occupational rhinitis caused by PPE developing into occupational asthma in a hospital nurse. She showed strong positive response in the skin prick test (SPT) (5+, wheal ratio of allergen to histamine) and had a high serum-specific IgE level to PPE, but showed a negative response in the methacholine bronchial challenge test (MBT). She had been exposed to PPE intermittently with intermittent medications for rhinitis. Two years later, she presented with rhinitis and additional asthmatic symptoms. In contrast to her first visit, she showed a positive response in the MBT, and developed bronchoconstriction in the PPE-bronchial provocation test (BPT). These findings suggest that inhalation of PPE powder can induce IgE-mediated occupational rhinitis in a hospital setting, which will develop into occupational asthma if avoidance is not complete.
Pancreatic Extracts; Occupational Rhinitis; Occupational Asthma, Specific IgE
Environmental exposures to cockroach allergen and endotoxin are recognized epidemiological risk factors for the early development of allergies and asthma in children. Because of this, it is important to examine the role of early life concurrent inhalation exposures to cockroach allergen and endotoxin in the pathogenesis of allergic airways disease.
We examined the effects of repeated concomitant endotoxin and cockroach allergen inhalation on the pulmonary and systemic immune responses of newborn and juvenile mice.
C3H/HeBFeJ mice were exposed to inhaled endotoxin and cockroach allergen via intranasal instillation from day 2 to 21 after birth, and systemic and pulmonary responses were examined in serum, bronchoalveolar lavage fluid, and lung tissue.
Cockroach allergen exposures induced pulmonary eosinophilic inflammation, total and allergen specific IgE, IgG1, and IgG2a production, and alveolar remodeling. Co-exposures with endotoxin and cockroach allergen significantly increased serum IgE and IgG1, lung inflammation, and alveolar wall thickness, and decreased airspace volume density. Importantly, compared to exposures with individual substances, the responses to co-exposures were more than additive.
Repeated inhalation exposures of neonatal and juvenile mice to endotoxin and cockroach allergen increased the pulmonary inflammatory and systemic immune responses in a synergistic manner and enhanced alveolar remodeling in the developing lung. These data underscore the importance of evaluating the effect of multiple, concurrent environmental exposures, and of using an experimental model that incorporates clinically relevant timing and route of exposures.
endotoxin; cockroach allergen; lung inflammation; allergy; enzyme hypothesis; synergistic effect
Existing asthma models develop tolerance when chronically exposed to the same allergen.
To establish a chronic model that sustains features of asthma long after discontinuation of allergen exposure.
We immunized and exposed mice to a combination of single, double or triple allergens (dust-mite, ragweed, and Aspergillus) intranasally for 8 weeks. Airway hyperreactivity and morphological features of asthma were studied 3 weeks after the allergen exposure. Signaling effects of the allergens were studied on dendritic cells.
Sensitization and repeated exposure to a single allergen induced tolerance. Sensitization to double, and especially triple allergens broke through tolerance and established AHR, eosinophilic inflammation, mast cell and smooth muscle hyperplasia, mucus production and airway remodeling that persisted at least 3 weeks after allergen exposure. Mucosal exposure to triple allergens in the absence of an adjuvant was sufficient to induce chronic airway inflammation. Anti-IL5 and -IL13 antibodies inhibited inflammation and AHR in the acute asthma model but not in the chronic triple allergen model. Multiple allergens produce a synergy in p38 MAPK signaling and maturation of dendritic cells, which provides a heightened T cell co-stimulation at a level that cannot be achieved with a single allergen.
Sensitivity to multiple allergens leads to chronic asthma in mice. Multiple allergens synergize in dendritic cell signaling and T cell stimulation that allows escape from the single allergen-associated tolerance development.
We have developed a model of chronic asthma that allows for the study and treatment of long-lasting features of asthma obviating the need for acute de novo allergen challenges.
chronic asthma; mouse; inflammation; airway hyperreactivity; tolerance; dendritic cells