Severe Airway Hyperresponsiveness Research Articles

Marijuana smoke induces severe pulmonary hyperresponsiveness, inflammation, and emphysema in a predictive mouse model not via CB1 receptor activation.

Sporadic clinical reports suggested that marijuana smoking induces spontaneous pneumothorax, but no animal models were available to validate these observations and to study the underlying mechanisms. Therefore, we performed a systematic study in CD1 mice as a predictive animal model and assessed the pathophysiological alterations in response to 4-mo-long whole body marijuana smoke with integrative methodologies in comparison with tobacco smoke. Bronchial responsiveness was measured with unrestrained whole body plethysmography, cell profile in the bronchoalveolar lavage fluid with flow cytometry, myeloperoxidase activity with spectrophotometry, inflammatory cytokines with ELISA, and histopathological alterations with light microscopy. Daily marijuana inhalation evoked severe bronchial hyperreactivity after a week. Characteristic perivascular/peribronchial edema, atelectasis, apical emphysema, and neutrophil and macrophage infiltration developed after 1 mo of marijuana smoking; lymphocyte accumulation after 2 mo; macrophage-like giant cells, irregular or destroyed bronchial mucosa, goblet cell hyperplasia after 3 mo; and severe atelectasis, emphysema, obstructed or damaged bronchioles, and endothelial proliferation at 4 mo. Myeloperoxidase activity, inflammatory cell, and cytokine profile correlated with these changes. Airway hyperresponsiveness and inflammation were not altered in mice lacking the CB1 cannabinoid receptor. In comparison, tobacco smoke induced hyperresponsiveness after 2 mo and significantly later caused inflammatory cell infiltration/activation with only mild emphysema. We provide the first systematic and comparative experimental evidence that marijuana causes severe airway hyperresponsiveness, inflammation, tissue destruction, and emphysema, which are not mediated by the CB1 receptor.

Clinical predictors of remission and persistence of adult-onset asthma

Adult-onset asthma is an important but relatively understudied asthma phenotype and little is known about its natural course and prognosis. The remission rate is believed to be low, and it is still obscure which factors predict remission or persistence of the disease. This study sought to determine the remission rate and identify predictors of persistence and remission of adult-onset asthma. Two hundred adult patients with recently diagnosed (<1year) asthma were recruited from secondary and tertiary pulmonary clinics and prospectively followed for 5years. Clinical, functional, and inflammatory parameters were assessed at baseline and at yearly visits. Asthma remission was defined as absence of asthma symptoms for ≥1year and no asthma medication use for ≥1year. Descriptive statistics and logistic regression analysis were performed. Five-year follow-up data of 170 patients (85%) was available. Of these, 27 patients (15.9%) experienced asthma remission. Patients with asthma persistence were older, had worse asthma control, required higher doses of inhaled corticosteroids, had more severe airway hyperresponsiveness, more often nasal polyps, and higher levels of blood neutrophils as compared to patients who experienced clinical remission. In a multivariable logistic regression analysis, only moderate to severe bronchial hyperresponsiveness and nasal polyps were independent predictors of asthma persistence. Patients with these 2 characteristics had <1% chance of asthma remission. One in 6 patients with adult-onset asthma experiences remission within the first 5years of the disease. Inpatients with moderate to severe bronchial hyperresponsiveness and nasal polyposis, the chance of remission is close to zero.

Phloretin Attenuates Allergic Airway Inflammation and Oxidative Stress in Asthmatic Mice.

Phloretin (PT), isolated from the apple tree, was previously demonstrated to have antioxidative and anti-inflammatory effects in macrophages and anti-adiposity effects in adipocytes. Inflammatory immune cells generate high levels of reactive oxygen species (ROS) for stimulated severe airway hyperresponsiveness (AHR) and airway inflammation. In this study, we investigated whether PT could reduce oxidative stress, airway inflammation, and eosinophil infiltration in asthmatic mice, and ameliorate oxidative and inflammatory responses in tracheal epithelial cells. BALB/c mice were sensitized with ovalbumin (OVA) to induce asthma symptoms. Mice were randomly assigned to the five experimental groups: normal controls; OVA-induced asthmatic mice; and OVA-induced mice injected intraperitoneally with one of the three PT doses (5, 10, or 20 mg/kg). In addition, we treated inflammatory human tracheal epithelial cells (BEAS-2B cells) with PT to assess oxidative responses and the levels of proinflammatory cytokines and chemokines. We found that PT significantly reduced goblet cell hyperplasia and eosinophil infiltration, which decreased AHR, inflammation, and oxidative responses in the lungs of OVA-sensitized mice. PT also decreased malondialdehyde levels in the lung and reduced Th2 cytokine production in bronchoalveolar lavage fluids. Furthermore, PT reduced ROS, proinflammatory cytokines, and eotaxin production in BEAS-2B cells. PT also suppressed monocyte cell adherence to inflammatory BEAS-2B cells. These findings suggested that PT alleviated pathological changes, inflammation, and oxidative stress by inhibiting Th2 cytokine production in asthmatic mice. PT showed therapeutic potential for ameliorating asthma symptoms in the future.

Targeting integrin α5β1 ameliorates severe airway hyperresponsiveness in experimental asthma.

Treatment options are limited for severe asthma, and the need for additional therapies remains great. Previously, we demonstrated that integrin αvβ6-deficient mice are protected from airway hyperresponsiveness, due in part to increased expression of the murine ortholog of human chymase. Here, we determined that chymase protects against cytokine-enhanced bronchoconstriction by cleaving fibronectin to impair tension transmission in airway smooth muscle (ASM). Additionally, we identified a pathway that can be therapeutically targeted to mitigate the effects of airway hyperresponsiveness. Administration of chymase to human bronchial rings abrogated IL-13-enhanced contraction, and this effect was not due to alterations in calcium homeostasis or myosin light chain phosphorylation. Rather, chymase cleaved fibronectin, inhibited ASM adhesion, and attenuated focal adhesion phosphorylation. Disruption of integrin ligation with an RGD-containing peptide abrogated IL-13-enhanced contraction, with no further effect from chymase. We identified α5β1 as the primary fibronectin-binding integrin in ASM, and α5β1-specific blockade inhibited focal adhesion phosphorylation and IL-13-enhanced contraction, with no additional effect from chymase. Delivery of an α5β1 inhibitor into murine airways abrogated the exaggerated bronchoconstriction induced by allergen sensitization and challenge. Finally, α5β1 blockade enhanced the effect of the bronchodilator isoproterenol on airway relaxation. Our data identify the α5β1 integrin as a potential therapeutic target to mitigate the severity of airway contraction in asthma.

Propranolol versus atenolol in the treatment of infantile hemangioma: a comparative study

Objective To evaluate the efficacy and safety of oral propranolol versus atenolol in the treatment of infantile hemangioma (IH). Methods A total of 75 infants with IH aged 5-24 weeks were randomly divided into two groups: propranolol group (n = 30) orally administrating propranolol 2 mg · kg-1·d-1 in 3 divided doses daily for 24 consecutive weeks, atenolol group (n = 45) orally administrating atenolol 1 mg·kg-1·d-1 once a day for 24 consecutive weeks. After 1-, 4-, 12-, 24-week treatment, the infants with IH were followed and adverse reactions were recorded. In addition, the activity of IH was assessed by hemangioma activity score (HAS) before and after 24-week treatment, and changes of HAS were compared between the propranolol group and atenolol group. Results There was no significant difference in the proportion of patients experiencing satisfactory regression of hemangioma between the propranolol group and atenolol group (70% [21/30] vs. 75.6% [34/45 ], P > 0.05). Treatment failure occurred in one patient in the propranolol group because of severe airway hyperreactivity, and in another patient in the atenolol group because of drug resistance. The incidence rates of gastrointestinal reactions, central nervous system adverse effects, chills on the extremities and bronchiolitis complicated by airway hyperreactivity were all significantly higher in the propranolol group than in the atenolol group (all P < 0.05). None of hypotension, hypoglycemia and bradycardia occurred in the two groups. Conclusion Compared with propranolol, atenolol shows similar efficacy but less adverse effects in the treatment of IH. Key words: Hemangioma; Child; Propranolol; Atenolol; Comparative effectiveness research

Longitudinally Stable, Clinically Defined Clusters of Patients with Asthma Independently Identified in the ADEPT and U-BIOPRED Asthma Studies.

ADEPT (Airways Disease Endotyping for Personalized Therapeutics) and U-BIOPRED (Unbiased Biomarkers for the Prediction of Respiratory Disease Outcome Consortium) are independent asthma biomarker studies that aim to enable personalization of therapies. Patients in both studies were identified by similar criteria, and similar clinical parameters and biomarkers were assessed in blood, sputum, and airway samples. Fuzzy partition-around-medoid clustering was performed on the ADEPT dataset (n = 154) and independently on the U-BIOPRED asthma dataset (n = 82), filtered to match ADEPT inclusion criteria. For both studies, the same eight easily measurable clinical variables were used, and ADEPT also included methacholine airway hyperresponsiveness. Models for cluster classification probabilities were derived and applied to the 12-month longitudinal ADEPT data and the full U-BIOPRED adult asthma dataset (n = 397) as independent external validation. Four clusters were identified in the ADEPT-asthma study population with distinct clinical and biomarker profiles. In general, Cluster 1 consists of patients with mild asthma not treated with steroids and well controlled with preserved lung function and a low-inflammatory phenotype; Cluster 2 is partially controlled, with mild airflow obstruction but severe airway hyperresponsiveness and a Th2 phenotype (brittle phenotype); Cluster 3 is partially controlled with mild airflow obstruction but reduced vital capacity, less bronchodilator reversibility, and a non-Th2 phenotype with neutrophilic inflammation (chronic obstructive pulmonary disease-like); and Cluster 4 is poorly controlled, with marked airflow obstruction, marked bronchodilator reversibility, and a mixed inflammatory phenotype. Overall, the ADEPT clusters were stable over 12 months and reproduced by identifying four analogous clusters in the U-BIOPRED asthma dataset, with distributions for most clustering and nonclustering variables similar to ADEPT. We report four clinical clusters in ADEPT and confirmed these by external validation in U-BIOPRED. The ADEPT clusters have distinct clinical and molecular characteristics, are stable over 12 months, and present opportunities for the development of tailored therapeutics for asthma.

Hyaluronan mediates airway hyperresponsiveness in oxidative lung injury.

Chlorine (Cl2) inhalation induces severe oxidative lung injury and airway hyperresponsiveness (AHR) that lead to asthmalike symptoms. When inhaled, Cl2 reacts with epithelial lining fluid, forming by-products that damage hyaluronan, a constituent of the extracellular matrix, causing the release of low-molecular-weight fragments (L-HA, <300 kDa), which initiate a series of proinflammatory events. Cl2 (400 ppm, 30 min) exposure to mice caused an increase of L-HA and its binding partner, inter-α-trypsin-inhibitor (IαI), in the bronchoalveolar lavage fluid. Airway resistance following methacholine challenge was increased 24 h post-Cl2 exposure. Intratracheal administration of high-molecular-weight hyaluronan (H-HA) or an antibody against IαI post-Cl2 exposure decreased AHR. Exposure of human airway smooth muscle (HASM) cells to Cl2 (100 ppm, 10 min) or incubation with Cl2-exposed H-HA (which fragments it to L-HA) increased membrane potential depolarization, intracellular Ca(2+), and RhoA activation. Inhibition of RhoA, chelation of intracellular Ca(2+), blockade of cation channels, as well as postexposure addition of H-HA, reversed membrane depolarization in HASM cells. We propose a paradigm in which oxidative lung injury generates reactive species and L-HA that activates RhoA and Ca(2+) channels of airway smooth muscle cells, increasing their contractility and thus causing AHR.

Low-intensity aerobic exercise training attenuates airway inflammation and remodeling in a rat model of steroid-resistant asthma

Background Aerobic exercise can improve symptoms, reduce airway inflammation, and even ameliorate airway remodeling in asthmatic animals and patients. However, previous studies have focused mainly on the effect of aerobic exercise on steroid-sensitive asthma (SSA). The goals of this study were to determine the effect of low-intensity aerobic exercise training on airway hyperresponsiveness, inflammation, and remodeling in a rat model of steroid-resistant asthma (SRA) and to identify the potential mechanisms underlying these effects. Methods Endotoxin-free ovalbumin with or without lipopolysaccharide were applied to establish rat models of SRA and SSA, respectively. Airway hyperresponsiveness, inflammation, remodeling, expression of interleukin (IL)-25, IL-33, thymic stromal lymphopoietin (TSLP), high mobility group box-1 (HMGB1), and IL-17 in bronchoalveolar lavage fluid (BALF), and the role of dexamethasone (DXM) were compared between these two asthmatic rat models. The effect of low-intensity aerobic exercise training and anti-HMGB1 treatment on airway hyperresponsiveness, inflammation, and remodeling in SRA rats also was evaluated. Results SRA rats developed neutrophil-dominated airway inflammation ((29.5±4.1)% of the total cell numbers in BALF), whereas SSA rats developed eosinophil-dominated airway inflammation ((24.0±6.1)% of the total cell numbers in BALF). Compared with SSA rats, SRA rats had more severe airway hyperresponsiveness, lower levels of IL-25 ((33.6±10.3) vs. (104.8±24.9) pg/ml), IL-33 ((87.5±25.0) vs. (226.6±40.7) pg/ml), and TSLP ((1 933.2±899.5) vs. (7 224.0±992.1) pg/ml), and higher levels of HMGB1 ((21.2±4.5) vs. (5.4±1.6) ng/ml) and IL-17 ((780.5±261.7) vs. (291.4±76.4) pg/ml) in BALF (all P &lt;0.05). However, there was no significant difference in goblet cell hyperplasia, subepithelial collagen thickness, and airway smooth muscle remodeling between the two groups. Compared with control SSA rats, airway hyperresponsiveness, inflammation, and remodeling in SRA rats were less sensitive to DXM treatment. Anti-HMGB1 treatment attenuated airway hyperresponsiveness, inflammation, and remodeling in SRA rats to a certain extent and was accompanied by lower levels of IL-17 ((369.2±126.7) vs. (780.5±261.7) pg/ml in control SRA rats) in BALF (P &lt;0.05). Low-intensity aerobic exercise training decreased the expression of both HMGB1 ((14.1±2.9) vs. (21.2±4.5) ng/ml in control SRA rats) and IL-17 ((545.3±148.6) vs. (780.5±261.7) pg/ml in control SRA rats) in BALF (all P &lt;0.05) and was accompanied by improved airway hyperresponsiveness, inflammation, and remodeling in SRA rats (all P &lt;0.05). Conclusions Low-intensity aerobic exercise training attenuated airway hyperresponsiveness, inflammation, and remodeling in a rat model of SRA. Decreased HMGB1 and IL-17 levels in BALF by aerobic exercise training at least partly contributed to the improvements of SRA.

Small airway impairment and bronchial hyperresponsiveness in asthma onset.

PurposeOur study tried to find a relationship between baseline FEF25-75% and airway hyperresponsiveness (AHR) and whether a greater FEF25-75% impairment may be a marker of a more severe hyperresponsiveness in subjects with normal FEV1 and FEV1/FVC and suggestive asthma symptoms. Besides, we tried to asses a FEF25-75% cut-off value to identify hyper-reactive subjects.Methods4,172 subjects (2,042 M; mean age: 38.3±14.9; mean FEV1 % predicted: 100.5±12.7 and FEV1/FVC: 85.4±6.8) were examined after performing a methacholine (Mch) test. All subjects reported a symptom onset within 3 years before the test. Subjects with PD20<400 or >400 µg were arbitrarily considered affected by moderate/severe and borderline AHR, respectively.ResultsPD20 values were 213 (IQR:86-557), 340 (IQR:157-872) and 433 (IQR:196-1032) µg in subjects with baseline FEF25-75≤50%, FEF25-75 between 50 and 70% and FEF25-75>70% respectively (P<0.0001). Only in moderate/severe hyper-reactive subjects (excluded borderlines), PD20 was lower in the FEF25-75≤50% subgroup than in the 1 with FEF25-75>70%. The hyperreactive subjects percentage, was higher in those with FEF25-75≤50% and lower in those with FEF25-75>70% (P<0.0001). FEF25-75<50% (compared to FEF25-75>70%) was a higher AHR risk factor, especially in subjects with moderate/severe AHR (OR: 2.18 [IQR:1.41-3.37]; P<0.0001). Thresholds yielding the highest combined sensitivity/specificity for FEF25-75% were 75.19 (area under curve [AUC]: 0.653) and 74.95 (AUC:0.688) in subjects with PD20<2,400 and <400 µg respectively. FEV1, FVC, and FEV1/FVC measured in subjects with different FEF25-75≤50%, FEF25-75>50 and ≤70% or FEF25-75>70% levels were similar both in normoreactive and hyperreactive subjects.ConclusionsAt asthma onset, reduced baseline FEF25-75 values with normal FEV1 and FEV1/FVC may predict AHR. Detectable predictive cut-off values do not exist because even normoreactive subjects can show lower FEF25-75 values. Furthermore, a greater FEF25-75 reduction may be associated to a more severe AHR, suggesting a possible FEF25-75 role in the management of asthma when FEV1 and FEV1/FVC are normal.

C5a receptor signalling in dendritic cells controls the development of maladaptive Th2 and Th17 immunity in experimental allergic asthma.

The pathways underlying dendritic cell (DC) activation in allergic asthma are incompletely understood. Here we demonstrate that adoptive transfer of ovalbumin-pulsed wild-type (wt) but not of C5a receptor-deficient (C5aR⁻/⁻) bone marrow (BM)-derived DCs (BMDCs) induced mixed T helper type 2 (Th2)/Th17 maladaptive immunity, associated with severe airway hyperresponsiveness, mucus production, and mixed eosinophilic/neutrophilic inflammation. Mechanistically, antigen uptake, processing, and CD11b expression were reduced in C5aR⁻/⁻ BMDCs. Further, interleukin (IL)-1β, -6, and -23 production were impaired resulting in reduced Th17 cell differentiation, associated with accelerated activated T-cell death in vitro and in vivo. Surprisingly, we found an increased frequency of CD11b(hi)CD11c(int)Gr1⁺F4/80⁺ cells, expressing arginase and nitric oxide synthase in C5aR⁻/⁻ BM preparations. Intratracheal administration of ovalbumin-pulsed wt DCs and sorted CD11b(hi)CD11c(int)Gr1⁺F4/80⁺ C5aR⁻/⁻ cells reduced Th2 immune responses in vivo. Together, we uncover novel roles for C5aR in Th17 differentiation, T-cell survival, and differentiation of a DC-suppressor population controlling Th2 immunity in experimental allergic asthma.

BMI can influence adult males’ and females’ airway hyperresponsiveness differently

Background: Epidemiological data indicate that obesity is a risk factor for asthma, but scientific literature is still debating the association between changes in body mass index (BMI) and airway hyperresponsiveness (AHR). Methods: This study aimed at evaluating the influence of BMI on AHR, in outpatients with symptoms suggestive of asthma. 4,217 consecutive adult subjects (2,439 M; mean age: 38.2±14.9 yrs; median FEV1 % predicted: 100 [IQR:91.88-107.97] and FEV1/FVC % predicted: 85.77% [IQR:81.1-90.05]), performed a methacholine challenge test for suspected asthma. Subjects with PD20 &lt; 200 or 200 &lt; PD20 &lt; 800 or PD20 &gt; 800 were considered affected by severe, moderate or mild AHR, respectively. Results: A total of 2,520 subjects (60% of all cases) had a PD20 &lt; 3,200 μg, with a median PD20 of 366 μg [IQR:168–1010.5]; 759, 997 and 764 patients were affected by mild, moderate and severe AHR, respectively. BMI was not associated with increasing AHR in males. On the contrary, obese females were at risk for AHR only when those with moderate AHR were considered (OR: 1.772 [1.250-2.512], p = 0.001). A significant reduction of FEV1/FVC for unit of BMI increase was found in moderate AHR, both in males (β = −0.255; p =0.023) and in females (β = −0.451; p =0.017). Conclusions: Our findings indicate that obesity influences AHR only in females with a moderate AHR level. This influence may be mediated by obesity-associated changes in baseline lung function.

BMI can influence adult males’ and females’ airway hyperresponsiveness differently

BackgroundEpidemiological data indicate that obesity is a risk factor for asthma, but scientific literature is still debating the association between changes in body mass index (BMI) and airway hyperresponsiveness (AHR).MethodsThis study aimed at evaluating the influence of BMI on AHR, in outpatients with symptoms suggestive of asthma.4,217 consecutive adult subjects (2,439 M; mean age: 38.2±14.9 yrs; median FEV1 % predicted: 100 [IQR:91.88-107.97] and FEV1/FVC % predicted: 85.77% [IQR:81.1-90.05]), performed a methacholine challenge test for suspected asthma. Subjects with PD20 < 200 or 200 < PD20 < 800 or PD20 > 800 were considered affected by severe, moderate or mild AHR, respectively.ResultsA total of 2,520 subjects (60% of all cases) had a PD20 < 3,200 μg, with a median PD20 of 366 μg [IQR:168–1010.5]; 759, 997 and 764 patients were affected by mild, moderate and severe AHR, respectively. BMI was not associated with increasing AHR in males. On the contrary, obese females were at risk for AHR only when those with moderate AHR were considered (OR: 1.772 [1.250-2.512], p = 0.001). A significant reduction of FEV1/FVC for unit of BMI increase was found in moderate AHR, both in males (β = −0.255; p =0.023) and in females (β = −0.451; p =0.017).ConclusionsOur findings indicate that obesity influences AHR only in females with a moderate AHR level. This influence may be mediated by obesity-associated changes in baseline lung function.

Constitutive production of IL-13 promotes early-life Chlamydia respiratory infection and allergic airway disease.

Deleterious responses to pathogens during infancy may contribute to infection and associated asthma. Chlamydia respiratory infections in early life are common causes of pneumonia and lead to reduced lung function and asthma. We investigated the role of interleukin-13 (IL-13) in promoting early-life Chlamydia respiratory infection, infection-induced airway hyperresponsiveness (AHR), and severe allergic airway disease (AAD). Infected infant Il13(-/-) mice had reduced infection, inflammation, and mucus-secreting cell hyperplasia. Surprisingly, infection of wild-type (WT) mice did not increase IL-13 production but reduced IL-13Rα2 decoy receptor levels compared with sham-inoculated controls. Infection of WT but not Il13(-/-) mice induced persistent AHR. Infection and associated pathology were restored in infected Il13(-/-) mice by reconstitution with IL-13. Stat6(-/-) mice were also largely protected. Neutralization of IL-13 during infection prevented subsequent infection-induced severe AAD. Thus, early-life Chlamydia respiratory infection reduces IL-13Rα2 production, which may enhance the effects of constitutive IL-13 and promote more severe infection, persistent AHR, and AAD.

Obesity in asthma: more neutrophilic inflammation as a possible explanation for a reduced treatment response

The incidence of asthma and obesity is increasing worldwide, and reports suggest that obese patients have more severe asthma. We investigated whether obese asthma patients have more severe airway obstruction and airway hyper-responsiveness and a different type of airway inflammation than lean asthmatics. Furthermore, we assessed the effect of obesity on corticosteroid treatment response. Patient data from four well-documented asthma cohorts were pooled (n = 423). We evaluated FEV(1) , bronchial hyper-responsiveness (PC(20) ) to either methacholine/histamine or adenosine 5'-monophosphate (AMP) (differential) cell counts in induced sputum and blood and corticosteroid treatment response in 118 patients. At baseline, FEV(1) , PC(20) methacholine or histamine, and PC(20) AMP values were comparable in 63 obese (BMI ≥ 30 kg/m(2) ) and 213 lean patients (BMI <25 kg/m(2) ). Obese patients had significantly higher blood neutrophils. These higher blood neutrophils were only seen in obese women and not in obese men. After a two-week treatment with corticosteroids, we observed less corticosteroid-induced improvement in FEV(1) %predicted in obese patients than in lean patients (median 1.7% vs 6.3% respectively, P = 0.04). The percentage of sputum eosinophils improved significantly less with higher BMI (P = 0.03), and the number of blood neutrophils increased less in obese than in lean patients (0.32 x10(3) /μl vs 0.57 x10(3) /μl, P = 0.046). We found no differences in asthma severity between obese and nonobese asthmatics. Interestingly, obese patients demonstrated more neutrophils in sputum and blood than nonobese patients. The smaller improvement in FEV(1) and sputum eosinophils suggests a worse corticosteroid treatment response in obese asthmatics.

Proximity to Major Roadways is a Risk Factor for Airway Hyper-Responsiveness in Adults

Proximity to major roads is reported to be associated with asthma and airway hyper-responsiveness in children. Similar studies using objective measurements in adults are not available in Canada. To test the hypothesis that adult asthmatic patients who live close to major roads and highways in an urban environment are at a risk of moderate to severe airway hyper-responsiveness. Airway responsiveness was determined using methacholine bronchial provocation (PC(20)) tests in a cohort of 2625 patients who attended an outpatient clinic in Hamilton, Ontario. Patient addresses were geocoded in a geographic information system to determine proximity to major roads and highways. Multivariate linear and multinomial regression analyses were used to assess whether proximity to roads was a risk factor for airway hyper-responsiveness as measured by PC(20) methacholine. Patients who lived within 200 m of a major road had increased odds (OR 1.38 [95% CI 1.04 to 1.85]) of having moderate airway hyperresponsiveness (0.25 mg⁄mL <PC(20) <2.0 mg/mL) compared with having a normal response (PC(20) >16 mg/mL). Spatial analysis also revealed that the majority of patients with severe airway hyper-responsiveness lived within the urban core of the city while those with moderate to mild hyper-responsiveness were also dispersed in rural areas. In an adult population of patients attending an outpatient respiratory clinic in Hamilton, living close to major roadways was associated with an increased risk of moderate airway hyper-responsiveness. This correlation suggests that exposure to traffic emissions may provoke the pathology of airway hyper-responsiveness leading to variable airflow obstruction.

Maternal diesel inhalation increases airway hyperreactivity in ozone-exposed offspring.

Air pollutant exposure is linked with childhood asthma incidence and exacerbations, and maternal exposure to airborne pollutants during pregnancy increases airway hyperreactivity (AHR) in offspring. To determine if exposure to diesel exhaust (DE) during pregnancy worsened postnatal ozone-induced AHR, timed pregnant C57BL/6 mice were exposed to DE (0.5 or 2.0 mg/m(3)) 4 hours daily from Gestation Day 9-17, or received twice-weekly oropharyngeal aspirations of the collected DE particles (DEPs). Placentas and fetal lungs were harvested on Gestation Day 18 for cytokine analysis. In other litters, pups born to dams exposed to air or DE, or to dams treated with aspirated diesel particles, were exposed to filtered air or 1 ppm ozone beginning the day after birth, for 3 hours per day, 3 days per week for 4 weeks. Additional pups were monitored after a 4-week recovery period. Diesel inhalation or aspiration during pregnancy increased levels of placental and fetal lung cytokines. There were no significant effects on airway leukocytes, but prenatal diesel augmented ozone-induced elevations of bronchoalveolar lavage cytokines at 4 weeks. Mice born to the high-concentration diesel-exposed dams had worse ozone-induced AHR, which persisted in the 4-week recovery animals. Prenatal diesel exposure combined with postnatal ozone exposure also worsened secondary alveolar crest development. We conclude that maternal inhalation of DE in pregnancy provokes a fetal inflammatory response that, combined with postnatal ozone exposure, impairs alveolar development, and causes a more severe and long-lasting AHR to ozone exposure.

Rapamycin decreases airway remodeling and hyperreactivity in a transgenic model of noninflammatory lung disease

Airway hyperreactivity (AHR) and remodeling are cardinal features of asthma and chronic obstructive pulmonary disease. New therapeutic targets are needed as some patients are refractory to current therapies and develop progressive airway remodeling and worsening AHR. The mammalian target of rapamycin (mTOR) is a key regulator of cellular proliferation and survival. Treatment with the mTOR inhibitor rapamycin inhibits inflammation and AHR in allergic asthma models, but it is unclear if rapamycin can directly inhibit airway remodeling and AHR, or whether its therapeutic effects are entirely mediated through immunosuppression. To address this question, we utilized transforming growth factor-α (TGF-α) transgenic mice null for the transcription factor early growth response-1 (Egr-1) (TGF-α Tg/Egr-1(ko/ko) mice). These mice develop airway smooth muscle thickening and AHR in the absence of altered lung inflammation, as previously reported. In this study, TGF-α Tg/Egr-1(ko/ko) mice lost body weight and developed severe AHR after 3 wk of lung-specific TGF-α induction. Rapamycin treatment prevented body weight loss, airway wall thickening, abnormal lung mechanics, and increases in airway resistance to methacholine after 3 wk of TGF-α induction. Increases in tissue damping and airway elastance were also attenuated in transgenic mice treated with rapamycin. TGF-α/Egr-1(ko/ko) mice on doxycycline for 8 wk developed severe airway remodeling. Immunostaining for α-smooth muscle actin and morphometric analysis showed that rapamycin treatment prevented airway smooth muscle thickening around small airways. Pentachrome staining, assessments of lung collagen and fibronectin mRNA levels, indicated that rapamycin also attenuated fibrotic pathways induced by TGF-α expression for 8 wk. Thus rapamycin reduced airway remodeling and AHR, demonstrating an important role for mTOR signaling in TGF-α-induced/EGF receptor-mediated reactive airway disease.

Actual Control State of Intermittent Asthma Classified on the Basis of Subjective Symptoms

Many primary care physicians begin treatment of asthma patients on the basis of their subjective symptoms. We hypothesized that patients diagnosed as having intermittent asthma on the basis of subjective symptoms by a primary care physician may have their asthma severity underestimated. We investigated 293 patients who were in their 20s and diagnosed as having asthma. Two hundred and fifteen patients with intermittent asthma diagnosed on the basis of subjective symptoms were chosen. We evaluated their asthma severity using FEV(1) (% predicted), airway hyperresponsiveness to histamine dihydrochloride, and exhaled nitric oxide level as factors that determine asthma severity. Among these patients, 27.8% were determined to have moderate or severe asthma by the pulmonary function test. History of childhood asthma was the only significant risk factor for a low pulmonary function. Among the patients, 60.9% showed moderate or severe airway hyperresponsiveness. History of childhood asthma was the only significant risk factor for the increase in airway hyperresponsiveness. Moreover, 53.8% showed a high exhaled nitric oxide level. History of childhood asthma was associated with an increased risk of a high eNO level as determined by univariate analysis, but no significant difference was observed in the comparison by multiple logistic regression analysis. The percentage of subjects classified into the mild group by all of the results of the three tests was only 20.6%. We showed that asthma severity classified on the basis of only subjective symptoms may be underestimated in young adults. We showed that the diagnosis of mild intermittent asthma needs to be determined carefully.

Complement-mediated regulation of the IL-17A axis is a central genetic determinant of the severity of experimental allergic asthma

Severe asthma is associated with interleukin 17A (IL-17A) production. The exact role of IL-17A in severe asthma and the factors driving its production are unknown. Here we have demonstrated that IL-17A mediated severe airway hyperresponsiveness (AHR) in susceptible strains of mice by enhancing IL-13-driven responses. Mechanistically, we have demonstrated that IL-17A and AHR were regulated by allergen-driven production of anaphylatoxins, as complement factor 5 (C5) and C5aR-deficient strains mounted robust IL-17A responses, while C3aR-deficient mice had reduced TH17 cells and AHR following allergen challenge. The opposing effects of C3a and C5a were mediated through their reciprocal regulation of IL-23 production. These data demonstrate a critical role for complement-mediated regulation of the IL-23–TH17 axis in severe asthma.

Arginase 1 and arginase 2 variations associate with asthma, asthma severity and β2 agonist and steroid response

Arginase probably plays an important role in asthma development, severity and progression. Polymorphisms in arginase 1 and arginase 2 genes have been associated with childhood asthma and FEV1 reversibility to beta2 agonists. We investigated the association between arginase 1 and arginase 2 polymorphisms and adult asthma, asthma severity and treatment response in a longitudinal cohort of 200 asthma patients. Patients were studied during 1962-1975 and reexamined during 1990-1999, together with their families. Longitudinal data on lung function and treatment were extracted from medical records. Associations between haplotype-tagging polymorphisms in arginase 1 (n=3) and arginase 2 (n=8) and asthma, asthma severity, acute response to bronchodilators and chronic response to inhaled corticosteroids were analyzed. Two polymorphisms in arginase 2 (rs17249437 and rs3742879) were associated with asthma and with more severe airway obstruction. Increased airway hyperresponsiveness and lower beta2 agonist reversibility, but not anticholinergic reversibility, were associated with both arginase 1 and arginase 2. Inhaled corticosteroids slowed down the annual FEV1 decline, which was significantly less effective in homozygote carriers of the C-allele of the arginase 1 polymorphism, rs2781667. We show that previously reported associations between arginase polymorphisms and childhood asthma are also present in adult asthma and the previously found associations with lower reversibility are specific for beta2 agonists. Furthermore, we identified associations of arginase 1 and arginase 2 genes with asthma severity, as reflected by a lower lung function, more severe airway hyperresponsiveness, and less long-term response to inhaled corticosteroids. Studies on the functionality of the polymorphisms are warranted to further unravel the complex mechanisms underlying these observations.