Maternal high-fat diet increases airway sensory innervation and reflex bronchoconstriction in adult offspring

Children born to obese mothers are prone to develop asthma and airway hyperresponsiveness, but the mechanisms behind this are unclear. Here we developed a mouse model of maternal diet-induced obesity that recapitulates metabolic abnormalities seen in humans born to obese mothers. Offspring of dams fed a high-fat diet (HFD) showed increased adiposity, hyperinsulinemia, and insulin resistance at 16 wk of age despite being fed only a regular diet (RD). Bronchoconstriction induced by inhaled 5-hydroxytriptamine was also significantly increased in offspring of HFD-fed versus RD-fed dams. Increased bronchoconstriction was blocked by vagotomy, indicating this reflex was mediated by airway nerves. Three-dimensional (3-D) confocal imaging of tracheas collected from 16-wk-old offspring showed that both epithelial sensory innervation and substance P expression were increased in the offspring of HFD-fed dams compared with offspring of RD-fed dams. For the first time, we show that maternal high-fat diet increases airway sensory innervation in offspring, leading to reflex airway hyperresponsiveness.NEW & NOTEWORTHY Our study reveals a novel potential mechanism, by which maternal high-fat diet increases the risk and severity of asthma in offspring. We found that exposure to maternal high-fat diet in mice leads to hyperinnervation of airway sensory nerves and increased reflex bronchoconstriction in offspring fed a regular diet only. These findings have important clinical implications and provide new insights into the pathophysiology of asthma, highlighting the need for preventive strategies in this patient population.

The cumulative effect of methacholine on large and small airways when deep inspirations are avoided

BACKGROUND AND OBJECTIVE

The effect of serial incremental concentrations of methacholine is only slightly cumulative when assessed by spirometry. This limited cumulative effect may be attributed to the bronchodilator effect of deep inspirations that are required between concentrations to measure lung function. Using oscillometry, the response to methacholine can be measured without deep inspirations. Conveniently, oscillometry can also dissociate the contribution of large versus small airways. Herein, oscillometry was used to assess the cumulative effect of methacholine in the absence of deep inspirations on large and small airways.

METHODS

Healthy and asthmatic volunteers underwent a multiple-concentration methacholine challenge on visit 1 and a single-concentration challenge on visit 2 using the highest concentration of visit 1. The maximal response was compared between visits to assess the cumulative effect of methacholine. The lung volume was also measured after the final concentration to assess hyperinflation.

RESULTS

In both healthy and asthmatic subjects, increases in resistance at 19 Hz (R_rs19 ), reflecting large airway narrowing, did not differ between the multiple- and the single-concentration challenge. However, increases in resistance at 5 Hz (R_rs5 ) minus R_rs19 , reflecting small airway narrowing, were 117 and 270% greater in the multiple- than the single-concentration challenge in healthy (p = 0.006) and asthmatic (p < 0.0001) subjects, respectively. Hyperinflation occurred with both challenges and was greater in the multiple- than the single-concentration challenge in both groups.

CONCLUSION

Without deep inspirations, the effect of methacholine is cumulative on small airways but not on large airways. Lung hyperinflation and derecruitment may partially explain these different responses.

Effects of airway smooth muscle contraction and inflammation on lung tissue compliance

There are renewed interests in using the parameter K of Salazar-Knowles' equation to assess lung tissue compliance. K either decreases or increases when the lung's parenchyma stiffens or loosens, respectively. However, whether K is affected by other common features of respiratory diseases, such as inflammation and airway smooth muscle (ASM) contraction, is unknown. Herein, male C57BL/6 mice were treated intranasally with either saline or lipopolysaccharide (LPS) at 1 mg/Kg to induce pulmonary inflammation. They were then subjected to either a multiple or a single-dose challenge with methacholine to activate ASM to different degrees. A quasi-static pressure-driven partial pressure-volume maneuver was performed before and after methacholine. The Salazar-Knowles' equation was then fitted to the deflation limb of the P-V loop to obtain K, as well as the parameter A, an estimate of lung volume (inspiratory capacity). The fitted curve was also used to derive the quasi-static elastance (E_st) at 5 cmH₂O. The results demonstrate that LPS and both methacholine challenges increased E_st. LPS also decreased A, but did not affect K. In contradistinction, methacholine decreased both A and K in the multiple-dose challenge, while it decreased K but not A in the single-dose challenge. These results suggest that LPS increases E_st by reducing the open lung volume (A) and without affecting tissue compliance (K), while methacholine increases E_st by decreasing tissue compliance with or without affecting lung volume. We conclude that lung tissue compliance, assessed using the parameter K of Salazar-Knowles' equation, is insensitive to inflammation but sensitive to ASM contraction.

Clinical implications of concentration of alveolar nitric oxide in asthmatic and non-asthmatic subacute cough

Asthma is an important cause of subacute cough. The concentration of alveolar nitric oxide (CANO) is a sensitive inflammatory indicator in peripheral airways, and it has received much less attention than the fraction of exhaled nitric oxide (FeNO₅₀). The main objective of this study was to explore the correlation between CANO and clinical parameters in asthmatic and non-asthmatic subacute cough, which might promote understanding of the clinical utility of CANO in these special patient populations. 155 patients with subacute cough were included consecutively, of which 25 were diagnosed as asthmatic. Data for demographic characteristics, FeNO₅₀, CANO, baseline spirometry, bronchial provocation test (or bronchodilation test) and response dose ratio (RDR) were collected. Differences between the asthmatic and non-asthmatic groups were analyzed. Spearman's correlation coefficient (ρ) was used to evaluate the correlation between FeNO₅₀, CANO and other clinical parameters. In patients with subacute cough, baseline CANO values did not differ between asthmatic and non-asthmatic patients (4.4(1.3, 11.4) versus 4.0(2.1, 6.8) ppb,P> 0.05). Besides, CANO exhibited a stronger association with pulmonary function parameters when compared with FeNO₅₀. For asthmatic subacute cough, CANO was inversely correlated with FEV₁/FVC (ρ= -0.69,P< 0.01) and small airway parameters including MEF25 (ρ= -0.47,P< 0.05) and MMEF (ρ= -0.45,P< 0.05). For non-asthmatic subacute cough, CANO was inversely correlated with MEF25 (ρ= -0.19,P< 0.05) and RDR (ρ= -0.21,P< 0.05). In subacute cough, asthmatic and non-asthmatic patients had similar values of baseline CANO. In both asthmatic and non-asthmatic subacute cough, CANO exhibited a stronger association with pulmonary function parameters when compared with FeNO₅₀. A low CANO value in non-asthmatic subacute cough corresponded to a higher value of RDR, which implied a stronger tendency towards airway responsiveness.

Smooth Muscle Hypocontractility and Airway Normoresponsiveness in a Mouse Model of Pulmonary Allergic Inflammation

The contractility of airway smooth muscle (ASM) is labile. Although this feature can greatly modulate the degree of airway responsiveness in vivo, the extent by which ASM's contractility is affected by pulmonary allergic inflammation has never been compared between strains of mice exhibiting a different susceptibility to develop airway hyperresponsiveness (AHR). Herein, female C57BL/6 and BALB/c mice were treated intranasally with either saline or house dust mite (HDM) once daily for 10 consecutive days to induce pulmonary allergic inflammation. The doses of HDM were twice greater in the less susceptible C57BL/6 strain. All outcomes, including ASM contractility, were measured 24 h after the last HDM exposure. As expected, while BALB/c mice exposed to HDM became hyperresponsive to a nebulized challenge with methacholine in vivo, C57BL/6 mice remained normoresponsive. The lack of AHR in C57BL/6 mice occurred despite exhibiting more than twice as much inflammation than BALB/c mice in bronchoalveolar lavages, as well as similar degrees of inflammatory cell infiltrates within the lung tissue, goblet cell hyperplasia and thickening of the epithelium. There was no enlargement of ASM caused by HDM exposure in either strain. Unexpectedly, however, excised tracheas derived from C57BL/6 mice exposed to HDM demonstrated a decreased contractility in response to both methacholine and potassium chloride, while tracheas from BALB/c mice remained normocontractile following HDM exposure. These results suggest that the lack of AHR in C57BL/6 mice, at least in an acute model of HDM-induced pulmonary allergic inflammation, is due to an acquired ASM hypocontractility.

A nurse-led hierarchical management model for the out-of-hospital management of children with bronchial asthma: a prospective randomized controlled study

OBJECTIVE

To explore the effects of a nurse-led hierarchical management model for managing the out-of-hospital asthma control and quality of life in children with bronchial asthma.

METHODS

A prospective randomized controlled study was designed. Children with bronchial asthma treated in our hospital were recruited as the study cohort and randomly divided into a test group (n=60) and a control group (n=60). After their discharge from the hospital, the children with bronchial asthma in both groups underwent out-of-hospital management led by nurses. In addition to this management, the test group underwent hierarchical management according to the results of their social living ability and temperament type evaluations. The levels of control of the asthma within 6 months after discharge were compared between the two groups. The changes in the asthma control test (ACT) scores, the daily variation rates in the peak expiratory flows (PEF), the pulmonary functions, the changes in the airway inflammation indicators, and the two groups' quality of life were compared. In addition, univariate and multivariate logistic regressions were used to analyze the factors influencing the acute asthma attacks in children.

RESULTS

Compared with the control group, the number of acute asthma attacks, the emergency medical treatment and hospitalization rates in children with acute asthma attacks within 6 months were significantly decreased in the test group (P<;0.05). After 3 and 6 months of the nursing, the test group had better ACT scores, better daily PEF variation rates, better pulmonary function, better serum inflammatory factors, better Medication Adherence Report Scale for Asthma (MARS-A) scores, and better pediatric asthma quality of life questionnaire (PAQLQ) scores than the control group (all P<;0.05). A multivariate logistic regression analysis showed that acute asthma attacks in childhood asthma were associated with the age of the first attack ≤f years (OR=3.635), a family history of rhinitis/asthma (OR=1.425), poor medication adherence (OR=1.855), the baseline IgE level (OR=1.305), and the hierarchical nursing management (OR=0.593).

CONCLUSIONS

A nurse-led hierarchical management model can effectively improve the level of out-of-hospital asthma control in children with bronchial asthma and can improve their pulmonary function and quality of life as well.

Effects of (a Combination of) the Beta2-Adrenoceptor Agonist Indacaterol and the Muscarinic Receptor Antagonist Glycopyrrolate on Intrapulmonary Airway Constriction

Expression of bronchodilatory β₂-adrenoceptors and bronchoconstrictive muscarinic M₃-receptors alter with airway size. In COPD, (a combination of) β₂-agonists and muscarinic M₃-antagonists (anticholinergics) are used as bronchodilators. We studied whether differential receptor expression in large and small airways affects the response to β₂-agonists and anticholinergics in COPD. Bronchoprotection by indacaterol (β₂-agonist) and glycopyrrolate (anticholinergic) against methacholine- and EFS-induced constrictions of large and small airways was measured in guinea pig and human lung slices using video-assisted microscopy. In guinea pig lung slices, glycopyrrolate (1, 3 and 10 nM) concentration-dependently protected against methacholine- and EFS-induced constrictions, with no differences between large and small intrapulmonary airways. Indacaterol (0.01, 0.1, 1 and 10 μM) also provided concentration-dependent protection, which was greater in large airways against methacholine and in small airways against EFS. Indacaterol (10 μM) and glycopyrrolate (10 nM) normalized small airway hyperresponsiveness in COPD lung slices. Synergy of low indacaterol (10 nM) and glycopyrrolate (1 nM) concentrations was greater in LPS-challenged guinea pigs (COPD model) compared to saline-challenged controls. In conclusion, glycopyrrolate similarly protects large and small airways, whereas the protective effect of indacaterol in the small, but not the large, airways depends on the contractile stimulus used. Moreover, findings in a guinea pig model indicate that the synergistic bronchoprotective effect of indacaterol and glycopyrrolate is enhanced in COPD.

Biseugenol Exhibited Anti-Inflammatory and Anti-Asthmatic Effects in an Asthma Mouse Model of Mixed-Granulocytic Asthma

In the present work, the anti-inflammatory and antiasthmatic potential of biseugenol, isolated as the main component from n-hexane extract from leaves of Nectandra leucantha and chemically prepared using oxidative coupling from eugenol, was evaluated in an experimental model of mixed-granulocytic asthma. Initially, in silico studies of biseugenol showed good predictions for drug-likeness, with adherence to Lipinski’s rules of five (RO5), good Absorption, Distribution, Metabolism and Excretion (ADME) properties and no alerts for Pan-Assay Interference Compounds (PAINS), indicating adequate adherence to perform in vivo assays. Biseugenol (20 mg·kg⁻¹) was thus administered intraperitoneally (four days of treatment) and resulted in a significant reduction in both eosinophils and neutrophils of bronchoalveolar lavage fluid in ovalbumin-sensitized mice with no statistical difference from dexamethasone (5 mg·kg⁻¹). As for lung function parameters, biseugenol (20 mg·kg⁻¹) significantly reduced airway and tissue damping in comparison to ovalbumin group, with similar efficacy to positive control dexamethasone. Airway hyperresponsiveness to intravenous methacholine was reduced with biseugenol but was inferior to dexamethasone in higher doses. In conclusion, biseugenol displayed antiasthmatic effects, as observed through the reduction of inflammation and airway hyperresponsiveness, with similar effects to dexamethasone, on mixed-granulocytic ovalbumin-sensitized mice.

DM-induced Hypermethylation of IR and IGF1R attenuates mast cell activation and airway responsiveness in rats

Diabetes has been reported to modulate the airway smooth muscle reactivity and lead to attenuation of allergic inflammatory response in the lungs. In this study, we aimed to study the effect of insulin on cell activation and airway responsiveness in patients with diabetes mellitus (DM). The airway contraction in rat model groups including a non‐DM group, a non‐DM+INDUCTION group, a DM+INDUCTION group and a DM+INDUCTION+INSULIN group was measured to observe the effect of insulin on airway responsiveness. Radioenzymatic assay was conducted to measure the levels of histamine, and ELISA assay was conducted to measure bronchial levels of interleukin (IL)‐1b, tumour necrosis factor (TNF)‐a, cytokine‐induced neutrophil chemoattractant (CINC)‐1, P‐selectin and β‐hexosaminidase. The tension in the main and intrapulmonary bronchi of DM+INDUCTION rats was lower than that of the non‐DM+INDUCTION rats, whereas the treatment of insulin partly restored the normal airway responsiveness to OA in DM rats. The release of histamine was remarkably suppressed in DM+INDUCTION rats but was recovered by the insulin treatment. Also, OA significantly increased the levels of IL‐1b, TNF‐a, CINC‐1 and P‐selectin in non‐DM rats, whereas insulin treatment in DM+INDUCTION rats partly restored the normal levels of IL‐1b, TNF‐a, CINC‐1 and P‐selectin in DM rats. Moreover, the expression of IR and IGF1R was evidently suppressed in DM rats, with the methylation of both IR and IGF1R promoters was aggravated in DM rats. Therefore, we demonstrated that DM‐induced hypermethylation inhibited mast cell activation and airway responsiveness, which could be reversed by insulin treatment.

Sex Differences in the Impact of Dietary Fiber on Pulmonary Responses to Ozone

Ozone causes airway hyperresponsiveness, a defining feature of asthma. We have reported that the gut microbiome contributes to sex differences in ozone-induced airway hyperresponsiveness. Altering dietary fiber affects the gut microbiome. The purpose of this study was to determine the effects of dietary fiber on pulmonary responses to ozone and whether these effects differ by sex. We fed male and female mice fiber-free diets or diets enriched in one of two types of dietary fiber, cellulose and pectin, for 3 days before ozone exposure. Compared with control diets or pectin-enriched diets, cellulose-enriched diets attenuated ozone-induced airway hyperresponsiveness in male but not female mice. In contrast, fiber-free diets augmented responses to ozone in female but not male mice. Analysis of 16S rRNA sequencing of fecal DNA also indicated sex differences in the impact of dietary fiber on the gut microbiome and identified bacterial taxa that were associated with ozone-induced airway hyperresponsiveness. Our data suggest that microbiome-based therapies such as prebiotics may provide an alternative therapeutic strategy for air pollution-triggered asthma, but they indicate that such therapeutics may need to be tailored differently for males and females.

Early life microbiome perturbation alters pulmonary responses to ozone in male mice

Early life changes in the microbiome contribute to the development of allergic asthma, but little is known about the importance of the microbiome for other forms of asthma. Ozone is a nonatopic asthma trigger that causes airway hyperresponsiveness and neutrophil recruitment to the lungs. The purpose of this study was to test the hypothesis that early life perturbations in the gut microbiome influence subsequent responses to ozone. To that end, we placed weanling mouse pups from The Jackson Laboratories or from Taconic Farms in sex-specific cages either with other mice from the same vendor (same-housed) or with mice from the opposite vendor (cohoused). Mice were maintained with these cagemates until use. The gut microbial community differs in mice from Jackson Labs and Taconic Farms, and cohousing mice transfers fecal microbiota from one mouse to another. Indeed, 16S rRNA sequencing of fecal DNA indicated that differences in the gut microbiomes of Jackson and Taconic same-housed mice were largely abolished when the mice were cohoused. At 10-12 weeks of age, mice were exposed to room air or ozone (2 ppm for 3 hr). Compared to same-housed mice, cohoused male but not female mice had reduced ozone-induced airway hyperresponsiveness and reduced ozone-induced increases in bronchoalveolar lavage neutrophils. Ozone-induced airway hyperresponsiveness was greater in male than in female mice and the sex difference was largely abolished in cohoused mice. The data indicate a role for early life microbial perturbations in pulmonary responses to a nonallergic asthma trigger.

Response to bronchodilator and clinical, pathophysiological features in patients with nonasthmatic eosinophilic bronchitis

INTRODUCTION

Whether nonasthmatic eosinophilic bronchitis (NAEB) shows response to bronchodilator (RB) remains unclear.

OBJECTIVES

To investigate the RB and its relationship with clinical and pathophysiological features in NAEB.

METHODS

Fifty-one patients with NAEB were assigned in a 2:1 ratio to receive oral bambuterol hydrochloride (n = 34, 10 mg, once daily, for 3 days) or matched placebo (n = 17) randomly, of whom 48 patients (32 with bronchodilator and 16 with placebo) completed the study. Sputum induction, spirometry and cough reflex sensitivity were measured. RB was considered when cough Visual analogue scale (VAS) score decreased 30% or more after treatment. Cough reflex sensitivity was defined as the lowest concentration of capsaicin inducing five coughings or more (C5), and presented as Log C5.

RESULTS

The responsive rate of patients with bronchodilator was significantly higher than that with placebo (34.4% vs 6.3%, P < 0.05). The VAS score decreased significantly in patients with bronchodilator (median: 6.0-3.0, P < 0.01). There was a significantly higher median Log C5 (2.7 vs 1.3, P < 0.05), and a higher trend of decline in FEV₁ % predicted and MMEF% predicted after bronchial provocation in patients with RB as compared with patients without RB. No significant differences in baseline percentages of sputum eosinophil were found between patients with RB and that without RB.

CONCLUSIONS

One third of patients with NAEB respond well to bronchodilator treatment, which are related with lower cough reflex sensitivity and increased airway responsiveness. The relationship between NAEB and asthma needs to be investigated further.

Microbiota Contribute to Obesity-related Increases in the Pulmonary Response to Ozone

Obesity is a risk factor for asthma, especially nonatopic asthma, and attenuates the efficacy of standard asthma therapeutics. Obesity also augments pulmonary responses to ozone, a nonatopic asthma trigger. The purpose of this study was to determine whether obesity-related alterations in gut microbiota contribute to these augmented responses to ozone. Ozone-induced increases in airway responsiveness, a canonical feature of asthma, were greater in obese db/db mice than in lean wild-type control mice. Depletion of gut microbiota with a cocktail of antibiotics attenuated obesity-related increases in the response to ozone, indicating a role for microbiota. Moreover, ozone-induced airway hyperresponsiveness was greater in germ-free mice that had been reconstituted with colonic contents of db/db than in wild-type mice. In addition, compared with dietary supplementation with the nonfermentable fiber cellulose, dietary supplementation with the fermentable fiber pectin attenuated obesity-related increases in the pulmonary response to ozone, likely by reducing ozone-induced release of IL-17A. Our data indicate a role for microbiota in obesity-related increases in the response to an asthma trigger and suggest that microbiome-based therapies such as prebiotics may provide an alternative therapeutic strategy for obese patients with asthma.

The Inhibition of Caspase-1- Does Not Revert Particulate Matter (PM)-Induced Lung Immunesuppression in Mice

Background: Air pollution is becoming a threatening issue for human health. Many epidemiological studies relate air pollution index to adverse effects in terms of disease incidence and/or disease exacerbation. In our previous studies, we found air pollutants can induce the release of pro-inflammatory cytokines from human peripheral blood cells. To better understand, the effects of air pollution in the lung, we took advantage of an animal model. Experimental Approach: Mice were intratracheally and daily exposed to urban collected particulate matter (PM, PM10, and PM1) and to the sub-micrometric carbonaceous component, Soot. Results: We found that PM10, PM1, and Soot promoted lung inflammation associated to higher bronchial responsiveness and lower dilation together with an immunosuppressive lung environment, characterized by tolerogenic dendritic cells (DCs), macrophages and myeloid -derived suppressor cells (MDSCs), the latter two Arginase I positive. In support, higher recruitment of Treg associated to higher levels of IL-10 were detected in the lung of PM10, PM1, and Soot treated mice. This effect was not abolished by the administration of a caspase-1 inhibitor, Ac-Y-VAD, implying that the canonical inflammasome complex was not associated to PMx-induced lung immunosuppression in mice. Conclusion: Our study proves that PM exposure leads to an immunosuppressive lung environment in a caspase-1-independent manner, paving the way to understand the molecular and cellular mechanism/s underlying the establishment of some respiratory disorders according to the exposure to air pollution.

Effect of omega-3 fatty acid supplementation on resolvin (RvE1)-mediated suppression of inflammation in a mouse model of asthma

Objective: ResolvinE1 (RvE1), an endogenous lipid mediator derived from omega 3 fatty acids contributes to resolution of allergic inflammatory responses. We investigated effects of RvE1 (R) and omega 3 fatty acids (O) on airway reactivity and inflammation using allergic mice. Methods: Mice were divided into control (nonasthmatic; CON) and allergen sensitized-challenged (asthmatic; SEN) groups, and were sensitized i.p. on days 1, 6 with 0.2 μg ovalbumin (OVA) followed by 5% OVA aerosol challenges on days 11-13. RvE1 was administered i.p. postallergen challenge, while omega 3 fatty acids (fish oil) were administered via oral gavage once daily (days 1-13). Whole body plethysmography and bronchoalveolar lavage (BAL) studies were performed on day 14. Results: RvE1 attenuated airway responsiveness to methacholine (48 mg/ml) in treated asthmatic mice vs. nontreated (150 ± 27.88% in SEN vs. 54 ± 7.52% in SEN + R, p < .05). No difference was observed with omega-3 supplementation (115 ± 19.28% in SEN + O) or treatment with both RvE1 and omega 3 fatty acids (39 ± 12.37% in SEN + R + O vs. 54 ± 7.52% in SEN + R). Differential BAL cell analysis showed that RvE1 decreased eosinophils and neutrophils in SEN mice (p < .005) while no difference was observed with omega-3 fatty acids. SEN + R + O group had similar results as RvE1 treated mice, suggesting that only RvE1 attenuated inflammation. Conclusions: RvE1 attenuated airway responsiveness and inflammation in asthmatic mice. Omega-3 fatty acids, although a precursor for RvE1 formation, had no additive effects on RvE1 decreases in airway inflammation and airway reactivity. Our data suggests that omega-3 supplementation has little effect on airway inflammation and reactivity in our model of asthma.

Sex Differences in Pulmonary Responses to Ozone in Mice. Role of the Microbiome

We have previously reported that the mouse gut microbiome contributes to pulmonary responses to ozone, a common asthma trigger, and that short-chain fatty acids, end products of bacterial fermentation, likely contribute to this role of the microbiome. A growing body of evidence indicates that there are sex-related differences in gut microbiota and these differences can have important functional consequences. The purpose of this study was to determine whether there are sex-related differences in the impact of the gut microbiota on pulmonary responses to ozone. After acute exposure to ozone, male mice developed greater airway hyperresponsiveness than female mice. This difference was abolished after antibiotic ablation of the gut microbiome. Moreover, weanling female pups housed in cages conditioned by adult male mice developed greater ozone-induced airway hyperresponsiveness than weanling female pups raised in cages conditioned by adult females. Finally, ad libitum oral administration via drinking water of the short-chain fatty acid propionate resulted in augmented ozone-induced airway hyperresponsiveness in male, but not female, mice. Overall, these data are consistent with the hypothesis that the microbiome contributes to sex differences in ozone-induced airway hyperresponsiveness, likely as a result of sex differences in the response to short-chain fatty acids.

The Microbiome Regulates Pulmonary Responses to Ozone in Mice

Previous reports demonstrate that the microbiome impacts allergic airway responses, including airway hyperresponsiveness, a characteristic feature of asthma. Here we examined the role of the microbiome in pulmonary responses to a nonallergic asthma trigger, ozone. We depleted the microbiota of conventional mice with either a single antibiotic (ampicillin, metronidazole, neomycin, or vancomycin) or a cocktail of all four antibiotics given via the drinking water. Mice were then exposed to room air or ozone. In air-exposed mice, airway responsiveness did not differ between antibiotic- and control water-treated mice. Ozone caused airway hyperresponsiveness, the magnitude of which was decreased in antibiotic cocktail-treated mice versus water-treated mice. Except for neomycin, single antibiotics had effects similar to those observed with the cocktail. Compared with conventional mice, germ-free mice also had attenuated airway responsiveness after ozone. 16S ribosomal RNA gene sequencing of fecal DNA to characterize the gut microbiome indicated that bacterial genera that were decreased in mice with reduced ozone-induced airway hyperresponsiveness after antibiotic treatment were short-chain fatty acid producers. Serum analysis indicated reduced concentrations of the short-chain fatty acid propionate in cocktail-treated mice but not in neomycin-treated mice. Dietary enrichment with pectin, which increased serum short-chain fatty acids, also augmented ozone-induced airway hyperresponsiveness. Furthermore, propionate supplementation of the drinking water augmented ozone-induced airway hyperresponsiveness in conventional mice. Our data indicate that the microbiome contributes to ozone-induced airway hyperresponsiveness, likely via its ability to produce short-chain fatty acids.

Foetal growth restriction in mice modifies postnatal airway responsiveness in an age and sex-dependent manner

Epidemiological studies demonstrate an association between intrauterine growth restriction (IUGR) and asthma; however the underlying mechanism is unknown. We investigated the impact of maternal hypoxia-induced IUGR on airway responsiveness in male and female mice during juvenility and adulthood. Pregnant BALB/c mice were housed under hypoxic conditions for gestational days 11-17.5 and then returned to normoxic conditions for the remainder of pregnancy. A control group was housed under normoxic conditions throughout pregnancy. Offspring were studied at 2 weeks (juveniles) and 8 weeks (adults), where lung volume was assessed by plethysmography, airway responsiveness to methacholine determined by the forced oscillation technique and lungs fixed for morphometry. IUGR offspring were lighter at birth, exhibited "catch-up growth" by 2 weeks, but were again lighter in adulthood. IUGR males were "hyper-responsive" at 2 weeks and "hypo-responsive" as adults, in contrast with IUGR females who were hyper-responsive in adulthood. IUGR males had increased inner and total wall thickness at 2 weeks which resolved by adulthood, while airways in IUGR females were structurally normal throughout life. There were no differences in lung volume between Control and IUGR offspring at any age. Our data demonstrate changes in airway responsiveness as a result of IUGR that could influence susceptibility to asthma development and contribute to sexual dimorphism in asthma prevalence which switches from a male dominated disease in early life to a female dominated disease in adulthood.

Spleen tyrosine kinase inhibition blocks airway constriction and protects from Th2-induced airway inflammation and remodeling

BACKGROUND

Spleen tyrosine kinase (Syk) is an intracellular nonreceptor tyrosine kinase, which has been implicated as central immune modulator promoting allergic airway inflammation. Syk inhibition has been proposed as a new therapeutic approach in asthma. However, the direct effects of Syk inhibition on airway constriction independent of allergen sensitization remain elusive.

METHODS

Spectral confocal microscopy of human and murine lung tissue was performed to localize Syk expression. The effects of prophylactic or therapeutic Syk inhibition on allergic airway inflammation, hyperresponsiveness, and airway remodeling were analyzed in allergen-sensitized and airway-challenged mice. The effects of Syk inhibitors BAY 61-3606 or BI 1002494 on airway function were investigated in isolated lungs of wild-type, PKCα-deficient, mast cell-deficient, or eNOS-deficient mice.

RESULTS

Spleen tyrosine kinase expression was found in human and murine airway smooth muscle cells. Syk inhibition reduced allergic airway inflammation, airway hyperresponsiveness, and pulmonary collagen deposition. In naïve mice, Syk inhibition diminished airway responsiveness independently of mast cells, or PKCα or eNOS expression and rapidly reversed established bronchoconstriction independently of NO. Simultaneous inhibition of Syk and PKC revealed additive dilatory effects, whereas combined inhibition of Syk and rho kinase or Syk and p38 MAPK did not cause additive bronchodilation.

CONCLUSIONS

Spleen tyrosine kinase inhibition directly attenuates airway smooth muscle cell contraction independent of its protective immunomodulatory effects on allergic airway inflammation, hyperresponsiveness, and airway remodeling. Syk mediates bronchoconstriction in a NO-independent manner, presumably via rho kinase and p38 MAPK, and Syk inhibition might present a promising therapeutic approach in chronic asthma as well as acute asthma attacks.

The Natural Course of Atopic Dermatitis and the Association with Asthma

In this paper, we aimed to explore the potential mechanism underlying atopic dermatitis (AD) and its association with asthma. The BALB/c mice were randomly assigned to three groups, including the vehicle control (VD) group, the AD group, and the treatment (TR) group. The AD mice model was successfully constructed in the AD and TR group. The dermatitis severity scores and skin lesions were significantly increased in AD mice after DNCB application. Airway responsiveness in the AD group was significantly higher than in the TR group. The number of inflammatory cells was increased in skin lesions and bronchoalveolar lavage fluid (BALF) of AD mice. The levels of IL-4, IL-5, IFN-γ, and OVA-IgE in BALF supernatants of mice in the AD group were higher than those in the VC group. All the changes in AD mice were decreased by tacrolimus. These results indicate that AD may be a significant risk factor for atopic asthma development.

High levels of physical activity are associated with poorer asthma control in young females but not in males

BACKGROUND AND OBJECTIVE

Earlier studies on the levels of physical activity in asthma patients compared with controls have yielded varying results. We have previously reported that high versus moderate levels of physical activity were associated with higher prevalence of wheezing, especially in females. Here we studied the levels of physical activity in young patients with asthma and healthy subjects and their effect on asthma control.

METHODS

Four hundred eight physician-diagnosed patients with asthma and 118 controls (10-34 years) answered questions concerning frequency and/or duration of physical activity and undertook the Asthma Control Test (ACT), spirometry, methacholine challenges and exhaled nitric oxide measurements.

RESULTS

Asthma patients were more frequently physically active (P = 0.01) and for longer durations (P = 0.002) than controls. Highly versus moderately physically active patients with asthma had a higher prevalence of not well-controlled asthma (ACT < 20) when physical activity was assessed by frequency (40.6% vs 24.1%, P = 0.001) or duration (39.0% vs 21.7%, P < 0.001). This was only seen in females who had reduced ACT items (P < 0.05). Frequently versus moderately active females had an odds ratio of 4.81 (2.43, 9.51) to have ACT < 20, while no such effect was found in males (OR 1.18 (0.61, 2.30)) and this interaction was statistically significantly associated with gender (P = 0.003). No differences in fraction of exhaled nitric oxide or methacholine reactivity were found between moderately and highly physically active females with asthma.

CONCLUSION

Young asthma patients were more active than controls. High levels of physical activity were associated with poor asthma control as judged by the ACT in females, but not in males, and this appears unrelated to airway inflammation or responsiveness.

Resistin deficiency in mice has no effect on pulmonary responses induced by acute ozone exposure

Acute exposure to ozone (O3), an air pollutant, causes pulmonary inflammation, airway epithelial desquamation, and airway hyperresponsiveness (AHR). Pro-inflammatory cytokines-including IL-6 and ligands of chemokine (C-X-C motif) receptor 2 [keratinocyte chemoattractant (KC) and macrophage inflammatory protein (MIP)-2], TNF receptor 1 and 2 (TNF), and type I IL-1 receptor (IL-1α and IL-1β)-promote these sequelae. Human resistin, a pleiotropic hormone and cytokine, induces expression of IL-1α, IL-1β, IL-6, IL-8 (the human ortholog of murine KC and MIP-2), and TNF. Functional differences exist between human and murine resistin; yet given the aforementioned observations, we hypothesized that murine resistin promotes O3-induced lung pathology by inducing expression of the same inflammatory cytokines as human resistin. Consequently, we examined indexes of O3-induced lung pathology in wild-type and resistin-deficient mice following acute exposure to either filtered room air or O3. In wild-type mice, O3 increased bronchoalveolar lavage fluid (BALF) resistin. Furthermore, O3 increased lung tissue or BALF IL-1α, IL-6, KC, TNF, macrophages, neutrophils, and epithelial cells in wild-type and resistin-deficient mice. With the exception of KC, which was significantly greater in resistin-deficient compared with wild-type mice, no genotype-related differences in the other indexes existed following O3 exposure. O3 caused AHR to acetyl-β-methylcholine chloride (methacholine) in wild-type and resistin-deficient mice. However, genotype-related differences in airway responsiveness to methacholine were nonexistent subsequent to O3 exposure. Taken together, these data demonstrate that murine resistin is increased in the lungs of wild-type mice following acute O3 exposure but does not promote O3-induced lung pathology.

Regulation of allergic lung inflammation by endothelial cell transglutaminase 2

Tissue transglutaminase 2 (TG2) is an enzyme with multiple functions, including catalysis of serotonin conjugation to proteins (serotonylation). Previous research indicates that TG2 expression is upregulated in human asthma and in the lung endothelium of ovalbumin (OVA)-challenged mice. It is not known whether endothelial cell TG2 is required for allergic inflammation. Therefore, to determine whether endothelial cell TG2 regulates allergic inflammation, mice with an endothelial cell-specific deletion of TG2 were generated, and these mice were sensitized and challenged in the airways with OVA. Deletion of TG2 in endothelial cells blocked OVA-induced serotonylation in lung endothelial cells, but not lung epithelial cells. Interestingly, deletion of endothelial TG2 reduced allergen-induced increases in respiratory system resistance, number of eosinophils in the bronchoalveolar lavage, and number of eosinophils in the lung tissue. Endothelial cell deletion of TG2 did not alter expression of adhesion molecules, cytokines, or chemokines that regulate leukocyte recruitment, consistent with other studies, demonstrating that deletion of endothelial cell signals does not alter lung cytokines and chemokines during allergic inflammation. Taken together, the data indicate that endothelial cell TG2 is required for allergic inflammation by regulating the recruitment of eosinophils into OVA-challenged lungs. In summary, TG2 functions as a critical signal for allergic lung responses. These data identify potential novel targets for intervention in allergy/asthma.

Characterization of the dystrophin-glycoprotein complex in airway smooth muscle: role of δ-sarcoglycan in airway responsiveness

The dystrophin-glycoprotein complex (DGC) is an integral part of caveolae microdomains, and its interaction with caveolin-1 is essential for the phenotype and functional properties of airway smooth muscle (ASM). The sarcoglycan complex provides stability to the dystroglycan complex, but its role in ASM contraction and lung physiology in not understood. We tested whether δ-sarcoglycan (δ-SG), through its interaction with the DGC, is a determinant of ASM contraction ex vivo and airway mechanics in vivo. We measured methacholine (MCh)-induced isometric contraction and airway mechanics in δ-SG KO and wild-type mice. Last, we performed immunoblotting and transmission electron microscopy to assess DGC protein expression and the ultrastructural features of tracheal smooth muscle. Our results reveal an age-dependent reduction in the MCh-induced tracheal isometric force and significant reduction in airway resistance at high concentrations of MCh (50.0 mg/mL) in δ-SG KO mice. The changes in contraction and lung function correlated with decreased caveolin-1 and β-dystroglycan abundance, as well as an age-dependent loss of caveolae in the cell membrane of tracheal smooth muscle in δ-SG KO mice. Collectively, these results confirm and extend understanding of a functional role for the DGC in the contractile properties of ASM and demonstrate that this results in altered lung function in vivo.

Anti-oxidant N-acetylcysteine diminishes diesel exhaust-induced increased airway responsiveness in person with airway hyper-reactivity

BACKGROUND

Inhalation of diesel exhaust (DE) at moderate concentrations causes increased airway responsiveness in asthmatics and increased airway resistance in both healthy and asthmatic subjects, but the effect of baseline airway responsiveness and anti-oxidant supplementation on this dynamic is unknown.

OBJECTIVES

We aimed to determine if changes in airway responsiveness due to DE are attenuated by thiol anti-oxidant supplementation, particularly in those with underlying airway hyper-responsiveness.

METHODS

Participants took N-acetylcysteine (600 mg) or placebo capsules three times daily for 6 days. On the last of these 6 days, participants were exposed for 2 h to either filtered air (FA) or DE (300 μg/m(3) of particulate matter smaller than 2.5 microns). Twenty-six non-smokers were studied under each of three experimental conditions (filtered air with placebo, diesel exhaust with placebo, and diesel exhaust with N-acetylcysteine) using a randomized, double-blind, crossover design, with a 2-week washout between conditions. Methacholine challenge was performed pre-exposure (baseline airway responsiveness) and post-exposure (effect of exposure).

RESULTS

Anti-oxidant supplementation reduced baseline airway responsiveness in hyper-responsive individuals by 20% (p = 0.001). In hyper-responsive individuals, airway responsiveness increased 42% following DE compared with FA (p = 0.03) and this increase was abrogated with anti-oxidant supplementation (diesel exhaust with N-acetylcysteine vs. filtered air with placebo, p = 0.85).

CONCLUSIONS

Anti-oxidant (N-acetylcysteine) supplementation protects against increased airway responsiveness associated with DE inhalation and reduces need for supplement bronchodilators in those with baseline airway hyper-responsiveness. Individuals with variants in genes of oxidative stress metabolism when exposed to DE are protected from increases in airway responsiveness if taking anti-oxidant supplementation.

Nitrogen dioxide exposure and airway responsiveness in individuals with asthma

Controlled human exposure studies evaluating the effect of inhaled nitrogen dioxide (NO2) on the inherent responsiveness of the airways to challenge by broncho-constricting agents have had mixed results. In general, existing meta-analyses show statistically significant effects of NO2 on the airway responsiveness of individuals with asthma. However, no meta-analysis has provided a comprehensive assessment of the clinical relevance of changes in airway responsiveness, the potential for methodological biases in the original papers, and the distribution of responses. This paper provides analyses showing that a statistically significant fraction (i.e. 70% of individuals with asthma exposed to NO2 at rest) experience increases in airway responsiveness following 30-min exposures to NO2 in the range of 200 to 300 ppb and following 60-min exposures to 100 ppb. The distribution of changes in airway responsiveness is log-normally distributed with a median change of 0.75 (provocative dose following NO2 divided by provocative dose following filtered air exposure) and geometric standard deviation of 1.88. About a quarter of the exposed individuals experience a clinically relevant reduction in their provocative dose due to NO2 relative to air exposure. The fraction experiencing an increase in responsiveness was statistically significant and robust to exclusion of individual studies. Results showed minimal change in airway responsiveness for individuals exposed to NO2 during exercise.

Hyperinsulinemia potentiates airway responsiveness to parasympathetic nerve stimulation in obese rats

Obesity is a substantial risk factor for developing asthma, but the molecular mechanisms underlying this relationship are unclear. We tested the role of insulin in airway responsiveness to nerve stimulation using rats genetically prone or resistant to diet-induced obesity. Airway response to vagus nerve stimulation and airway M2 and M3 muscarinic receptor function were measured in obese-prone and -resistant rats with high or low circulating insulin. The effects of insulin on nerve-mediated human airway smooth muscle contraction and human M2 muscarinic receptor function were tested in vitro. Our data show that increased vagally mediated bronchoconstriction in obesity is associated with hyperinsulinemia and loss of inhibitory M2 muscarinic receptor function on parasympathetic nerves. Obesity did not induce airway inflammation or increase airway wall thickness. Smooth muscle contraction to acetylcholine was not increased, indicating that hyperresponsiveness is mediated at the level of airway nerves. Reducing serum insulin with streptozotocin protected neuronal M2 receptor function and prevented airway hyperresponsiveness to vagus nerve stimulation in obese rats. Replacing insulin restored dysfunction of neuronal M2 receptors and airway hyperresponsiveness to vagus nerve stimulation in streptozotocin-treated obese rats. Treatment with insulin caused loss of M2 receptor function, resulting in airway hyperresponsiveness to vagus nerve stimulation in obese-resistant rats, and inhibited human neuronal M2 receptor function in vitro. This study shows that it is not obesity per se but hyperinsulinemia accompanying obesity that potentiates vagally induced bronchoconstriction by inhibiting neuronal M2 muscarinic receptors and increasing acetylcholine release from airway parasympathetic nerves.

Role of prostaglandin D2 /CRTH2 pathway on asthma exacerbation induced by Aspergillus fumigatus

Aspergillus fumigatus is often associated in asthmatic patients with the exacerbation of asthma symptoms. The pathomechanism of this phenomenon has not been fully understood. Here, we evaluated the immunological mechanisms and the role of the prostaglandin D2 / Chemoattractant Receptor-Homologous Molecule Expressed on Th2 Cells (CRTH2) pathway in the development of Aspergillus-associated asthma exacerbation. We studied the effects of A. fumigatus on airway inflammation and bronchial hyper-responsiveness in a rat model of chronic asthma. Inhalation delivery of A. fumigatus conidia increased the airway eosinophilia and bronchial hyper-responsiveness in ovalbumin-sensitized, challenged rats. These changes were associated with prostaglandin D2 synthesis and CRTH2 expression in the lungs. Direct inflammation occurred in ovalbumin-sensitized, challenged animals, whereas pre-treatment with an antagonist against CRTH2 nearly completely eliminated the A. fumigatus-induced worsening of airway eosinophilia and bronchial hyper-responsiveness. Our data demonstrate that production of prostaglandin D2 followed by eosinophil recruitment into the airways via a CRTH2 receptor are the major pathogenic factors responsible for the A. fumigatus-induced enhancement of airway inflammation and responsiveness.

Aeroallergen and food IgE sensitization and local and systemic inflammation in asthma

BACKGROUND

We recently reported an independent association between IgE sensitization to food allergens and increased airway inflammation, assessed by fraction of exhaled nitric oxide (FeNO), in a population-based study (J Allergy Clin Immunol, 130, 2012, 397). Similar studies have not been performed in populations with asthma. The aim of the present study was to investigate the allergic sensitization profile in asthmatics and examine FeNO, airway responsiveness and blood eosinophilia in relation to type and degree of IgE sensitization.

METHOD

FeNO, airway responsiveness, blood eosinophil count (B-Eos) and IgE sensitization to food allergens and aeroallergens were determined in 408 subjects with asthma, aged 10-34 years.

RESULTS

Asthmatics had higher prevalence of IgE sensitization against all allergens than controls (P < 0.001). Mite, pollen, furry animal, mould and food sensitizations were each associated with increased FeNO, airway responsiveness and B-Eos in asthmatics. IgE sensitization to mould, furry animals and food allergens was independently related to FeNO (all P < 0.05) after adjustment for age, sex, height, smoking history and medication. IgE sensitization to mould (P < 0.001) and furry animals (P = 0.02) was related to airway responsiveness in a similar model. Finally, IgE sensitization to mould (P = 0.001), furry animals (P < 0.001) and food allergens (P < 0.001) was independently related to B-Eos.

CONCLUSION

Independent effects of IgE sensitization to aeroallergens (furry animals and mould) and food allergens were found on both local and systemic markers of inflammation in asthma. The finding regarding food IgE sensitization is novel, and a clinical implication might be that even food sensitization must be assessed to fully understand inflammation patterns in asthma.

Beta-blockers: friend or foe in asthma?

BACKGROUND AND AIM

Recently, β-blockers have been suggested as a potential maintenance treatment option for asthma. The aim of this review is to provide an overview of the current knowledge of the potential benefits and risks of β-blocker therapy for asthma.

METHOD

Systematic literature review.

RESULTS

No significant increase in the number of patients requiring rescue oral corticosteroid for an exacerbation of asthma has been observed after initiation of β-blocker treatment. Patients with mild to moderate reactive airway disease, probably both asthma and chronic obstructive pulmonary disease, may have a limited fall in forced expiratory volume in 1 second (FEV1) following single-dose administration of β-blocker, whereas no change in FEV1 has been reported following long-term administration. In a murine model of asthma, long-term administration of β-blockers resulted in a decrease in airway hyperresponsiveness, suggesting an anti-inflammatory effect. In keeping with this, long-term administration of a nonselective β-blocker to steroid-naïve asthma patients has shown a dose-dependent improvement in airway hyperresponsiveness, and either an asymptomatic fall in FEV1 or no significant change in FEV1. Furthermore, available studies show that bronchoconstriction induced by inhaled methacholine is reversed by salbutamol in patients on regular therapy with a β-blocker. On the other hand, a recent placebo-controlled trial of propranolol and tiotropium bromide added to inhaled corticosteroids revealed no effect on airway hyperresponsiveness and a small, not statistically significant, fall in FEV1 in patients classified as having mild to moderate asthma.

CONCLUSION

The available, although limited, evidence suggests that a dose-escalating model of β-blocker therapy to patients with asthma is well tolerated, does not induce acute bronchoconstriction, and, not least, may have beneficial effects on airway inflammation and airway hyperresponsiveness in some patients with asthma. Further studies addressing the potential role of β-blocker therapy for asthma are clearly needed, but careful selection of the target population is warranted.

Augmented pulmonary responses to acute ozone exposure in obese mice: roles of TNFR2 and IL-13

BACKGROUND

Acute ozone (O(3)) exposure results in greater inflammation and airway hyperresponsiveness (AHR) in obese versus lean mice.

OBJECTIVES

We examined the hypothesis that these augmented responses to O(3) are the result of greater signaling through tumor necrosis factor receptor 2 (TNFR2) and/or interleukin (IL)-13.

METHODS

We exposed lean wild-type (WT) and TNFR2-deficient (TNFR2(-/-)) mice, and obese Cpe(fat) and TNFR2-deficient Cpe(fat) mice (Cpe(fat)/TNFR2(-/-)), to O(3) (2 ppm for 3 hr) either with or without treatment with anti-IL-13 or left them unexposed.

RESULTS

O(3)-induced increases in baseline pulmonary mechanics, airway responsiveness, and cellular inflammation were greater in Cpe(fat) than in WT mice. In lean mice, TNFR2 deficiency ablated O(3)-induced AHR without affecting pulmonary inflammation; whereas in obese mice, TNFR2 deficiency augmented O(3)-induced AHR but reduced inflammatory cell recruitment. O(3) increased pulmonary expression of IL-13 in Cpe(fat) but not WT mice. Flow cytometry analysis of lung cells indicated greater IL-13-expressing CD(4+) cells in Cpe(fat) versus WT mice after O(3) exposure. In Cpe(fat) mice, anti-IL-13 treatment attenuated O(3)-induced increases in pulmonary mechanics and inflammatory cell recruitment, but did not affect AHR. These effects of anti-IL-13 treatment were not observed in Cpe(fat)/TNFR2(-/-) mice. There was no effect of anti-IL-13 treatment in WT mice.

CONCLUSIONS

Pulmonary responses to O(3) are not just greater, but qualitatively different, in obese versus lean mice. In particular, in obese mice, O(3) induces IL-13 and IL-13 synergizes with TNF via TNFR2 to exacerbate O(3)-induced changes in pulmonary mechanics and inflammatory cell recruitment but not AHR.

Impaired response to deep inspiration in obesity

Deep inspirations modulate airway caliber and airway closure and their effects are impaired in asthma. The association between asthma and obesity raises the question whether the deep inspiration (DI) effect is also impaired in the latter condition. We assessed the DI effects in obese and nonobese nonasthmatics. Thirty-six subjects (17 obese, 19 nonobese) underwent routine methacholine (Mch) challenge and 30 of them also had a modified bronchoprovocation in the absence of DIs. Lung function was monitored with spirometry and forced oscillation (FO) [resistance (R) at 5 Hz (R5), at 20 Hz (R20), R5-R20 and the integrated area of low-frequency reactance (AX)]. The response to Mch, assessed with area under the dose-response curves (AUC), was consistently greater in the routine challenge in the obese (mean ± SE, obese vs. nonobese AUC: R5: 15.7 ± 2.3 vs. 2.4 ± 2.0, P < 0.0005; R20: 5.6 ± 1.4 vs. 1.4 ± 1.2, P = 0.027; R5-R20: 10.2 ± 1.6 vs. 0.9 ± 0.1.4, P < 0.0005; AX: 115.6 ± 22.0 vs. 1.5 ± 18.9, P < 0.0005), but differences between groups in the modified challenge were smaller, indicating reduced DI effects in obesity. Given that DI has bronchodilatory and bronchoprotective effects, we further assessed these components separately. In the obese subjects, DI prior to Mch enhanced Mch-induced bronchoconstriction, but DI after Mch resulted in bronchodilation that was of similar magnitude as in the nonobese. We conclude that obesity is characterized by increased Mch responsiveness, predominantly of the small airways, due to a DI effect that renders the airways more sensitive to the stimulus.

Individual canine airway response variability to a deep inspiration

In healthy individuals, a DI can reverse (bronchodilation) or prevent (bronchoprotection) induced airway constriction. For individuals with asthma or COPD, these effects may be attenuated or absent. Previous work showed that the size and duration of a DI affected the subsequent response of the airways. Also, increased airway tone lead to increased airway size variability. The present study examined how a DI affected the temporal variability in individual airway baseline size and after methacholine challenge in dogs using High-Resolution Computed Tomography. Dogs were anesthetized and ventilated, and on 4 separate days, HRCT scans were acquired before and after a DI at baseline and during a continuous intravenous infusion of methacholine (Mch) at 3 dose rates (17, 67, and 200 μg/min). The Coefficient of Variation was used as an index of temporal variability in airway size.We found that at baseline and the lowest dose of Mch, variability decreased immediately and 5 minutes after the DI (P < 0.0001). In contrast, with higher doses of Mch, the DI caused a variable response. At a rate of 67 μg/min of Mch, the temporal variability increased after 5 minutes, while at a rate of 200 μg/min of Mch, the temporal variability increased immediately after the DI. Increased airway temporal variability has been shown to be associated with asthma. Although the mechanisms underlying this temporal variability are poorly understood, the beneficial effects of a DI to decrease airway temporal variability was eliminated when airway tone was increased. If this effect is absent in asthmatics, this may suggest a possible mechanism for the loss of bronchoprotective and bronchodilatory effects after a DI in asthma.

Allergic airway responses in obese mice

RATIONALE

Epidemiologic data indicate an increased incidence of asthma in the obese.

OBJECTIVES

To determine whether obese mice exhibit augmented pulmonary responses after allergen sensitization and challenge.

METHODS

Lean, wild-type (C57BL/6), obese ob/ob, and obese db/db mice were sensitized to ovalbumin (OVA), and then challenged with aerosolized OVA or phosphate-buffered saline (PBS). Changes in total pulmonary resistance (Rl) induced by intravenous methacholine were measured by forced oscillation. Blood was collected, bronchoalveolar lavage (BAL) was performed, and lungs were harvested for measurement of cytokine expression by real-time reverse transcription-polymerase chain reaction.

MEASUREMENTS AND MAIN RESULTS

OVA challenge increased baseline Rl in ob/ob, but not wild-type, mice, and airway responsiveness was greater in ob/ob than wild-type mice, regardless of the challenge. Compared with PBS, OVA challenge caused an increase in the number of BAL fluid (BALF) cells, an increase in lung Th2 cytokine expression, and an increase in serum IgE. Significantly fewer BALF cells were recovered from OVA-challenged ob/ob versus wild-type mice, whereas serum IgE levels were elevated significantly more in ob/ob versus wild-type mice. BALF and lung Th2 cytokine expression was not different in ob/ob versus wild-type mice. Airway responsiveness was greater in db/db versus wild-type mice, regardless of the challenge, and OVA caused airway hyperresponsiveness in db/db but not wild-type mice, despite reduced BALF cells in OVA-challenged db/db versus wild-type mice.

CONCLUSIONS

These results demonstrate that obesity enhances OVA-induced changes in pulmonary resistance and serum IgE and that these changes are not the result of increased Th2 type airway inflammation.

Adverse effects of a single dose of (+)-sotalol in patients with mild stable asthma

AIMS

To investigate the effect of (+)-sotalol, which is not thought to possess clinically significant beta-adrenoceptor blocking activity, on airway responsiveness in subjects with mild asthma.

METHODS

A placebo controlled, double-blind, single dose, cross over study, evaluating the effects of oral (+)-sotalol 300 mg and oral (+/-)-sotalol 240 mg, on airway responsiveness, FEV1, and heart rate in 18 asthmatic volunteers with quantifiable levels of airway responsiveness.

RESULTS

Compared with placebo, (+)-sotalol induced a significant increase in airway responsiveness, and a significant decrease in FEV1, but there was no significant change in heart rate. Following (+/-)-sotalol there was no significant effect on airway responsiveness, but there were significant decreases in FEV1 and heart rate. In one subject both (+)-sotalol and (+/-)-sotalol provoked a 49% decrement in FEV1, and in another there were decrements of 20% and 18%, respectively.

CONCLUSIONS

Despite theoretical considerations, it cannot be assumed that (+)-sotalol is safe in patients with asthma.

Increased function of inhibitory neuronal M2 muscarinic receptors in diabetic rat lungs

1. The function of inhibitory neuronal M2 muscarinic receptors in diabetic rat lungs was investigated. 2. Neuronal M2 muscarinic receptors inhibit acetylcholine release from parasympathetic nerves. Thus, stimulation of neuronal M2 muscarinic receptors with muscarinic agonists, such as pilocarpine, inhibits acetylcholine release and vagally induced bronchoconstriction. In contrast, blockade of neuronal M2 muscarinic receptors with selective M2 muscarinic antagonists, such as AF-DX 116, potentiates acetylcholine release and vagally induced bronchoconstriction. 3. Rats were made diabetic by streptozotocin (65 mg kg (-1), i.v.). After 7 14 days the rats were anaesthetized with urethane (1.5 g kg (-1), i.p.), tracheostomized, vagotomized, ventilated and paralysed with suxamethonium (30 mg kg (-1), i.v.). Some 7 day diabetic rats were treated with low doses of long acting (NPH) insulin (2 units day (-1), s.c.) for 7 days before experimentation. This dose of insulin was not sufficient to restore normoglycaemia in diabetic rats. Thus, insulin-treated diabetic rats remained hyperglycaemic. 4. Distal electrical stimulation (5 70 Hz, 6 s, 40 V, 0.4 ms) of the vagi caused bronchoconstriction, measured as an increase in inflation pressure and bradycardia. In diabetic rats, vagally induced bronchoconstriction was significantly depressed vs controls. In contrast, bronchoconstriction caused by i.v. acetylcholine was similar in diabetic and control animals. 5. The function of neuronal M2 muscarinic receptors was tested with the muscarinic agonist pilocarpine (0.001-100.0 microg kg (-1), i.v.) and the antagonist AF-DX 116 (0.01-3.0 mg kg (-1), i.v.). Pilocarpine inhibited vagally-induced bronchoconstriction (30 Hz, 20-40 V, 0.4 ms at 6 s) and AF-DX 116 potentiated vagally-induced bronchoconstriction (20 Hz, 20-40 V, 0.4 ms at 6 s) to a significantly greater degree in diabetic rats compared to controls. 6. Both frequency-dependent vagally-induced bronchoconstriction and M2 muscarinic receptor function could be restored to nearly control values in diabetic rats treated with low doses of insulin. 7. Displacement of [3H]QNB (1 nM) with the agonist carbachol (10.0 nM-10.0 mM) from diabetic cardiac M2 muscarinic receptors revealed a half log increase in agonist binding affinity at both the high and low affinity binding sites vs controls. In contrast, M2 receptors from insulin-treated diabetic rat hearts showed no significant difference in binding affinity vs controls. 8. These data show that neuronal M2 muscarinic receptors in the lungs have increased function in diabetic rats, suggesting that insulin modulates M2 muscarinic receptor function.