Measurement of Airway Hyperresponsiveness in Mice

Asthma has been the most prevalent chronic respiratory disease (Mensah et al. J Allergy Clin Immunol 142:744-748, 2018). To explore pathogenic mechanism or new treatments of asthma, mice have been utilized to model the disease. Eosinophilic airway inflammation, allergen specific-IgE, and airway hyperresponsiveness have been characteristic features of allergic asthma (Drake et al. Pulm Ther 5:103-115, 2019). In mouse models, airway hyperresponsiveness to inhaled broncho-constrictor agents such as methacholine chloride (MCh) has been a key disease marker (Alessandrini et al. Front Immunol 11:575936, 2020). A variety of systems to assess airway reactivity in mice are currently available. Here, three distinct systems are described as these have been used in many publications. In the first system, an invasive system in which mice are anesthetized and intubated followed by mechanical ventilation, lung resistance (R), dynamic compliance (C), and other respiratory parameters with MCh challenge are measured. In the second system, a noninvasive system equipped with a chamber in which mice can move freely and spontaneously breathe, changes in airways with MCh challenge are measured as enhanced pause (Penh) values. In the third system, in vitro airway smooth muscle (ASM) reactivity is monitored in an extracted mouse tracheal duct with a cholinergic agonist challenge or electrical stimulation. Each of these systems has unique features, benefits, or disadvantages.

Aerosol Generation and Mitigation During Methacholine Bronchoprovocation Testing: Infection Control Implications in the Era of COVID-19

BACKGROUND

Methacholine bronchoprovocation or challenge testing (MCT) is commonly performed to assess airway hyper-responsiveness in the setting of suspected asthma. Nebulization is an aerosol-generating procedure, but little is known about the risks of MCT in the context of the ongoing coronavirus disease 2019 (COVID-19) pandemic. We aimed to quantify and characterize aerosol generation during MCT by using different delivery methods and to assess the impact of adding a viral filter.

METHODS

Seven healthy subjects performed simulated MCT in a near particle-free laboratory space with 4 different nebulizers and with a dosimeter. Two devices continuously sampled the ambient air during the procedure, which detected ultrafine particles, from 0.02-1 μm, and particles of sizes 0.3, 0.5, 1.0, 2.0, 5.0, and 10 µm, respectively. Particle generation was compared among all the devices, with and without viral filter placement.

RESULTS

Ultrafine-particle generation during simulated MCT was significant across all the devices. Ultrafine-particle (0.02-1 μm) concentrations decreased 77%-91% with the addition of a viral filter and varied significantly between unfiltered (P < .001) and filtered devices (P < .001). Ultrafine-particle generation was lowest when using the dosimeter with filtered Hudson nebulizer (1,258 ± 1,644 particle/mL). Ultrafine-particle concentrations with the filtered nebulizer devices using a compressor were higher than particle concentrations detected when using the dosimeter: Monaghan (3,472 ± 1,794 particles/mL), PARI (4,403 ± 2,948), Hudson (6,320 ± 1,787) and AirLife (9,523 ± 5,098).

CONCLUSIONS

The high particle concentrations generated during MCT pose significant infection control concerns during the COVID-19 pandemic. Particle generation during MCT was significantly reduced by using breath-actuated delivery and a viral filter, which offers an effective mitigation strategy.

The Montelukast Therapy in Asthmatic Children with and without Food Allergy: Does It Make Any Difference?

INTRODUCTION

Children with food allergy are at increased risk for asthma and asthma morbidity. Since leukotrienes are implicated in the pathogenesis of both asthma and probably in food allergies, we hypothesized that asthmatic children with concomitant food allergy may have a favorable response to antileukotriene treatment.

METHODS

Asthmatic children aged 6-18 years with and without food allergy were treated with montelukast and placebo in a double-blind, placebo-controlled cross-over parallel-group study. The primary outcome of the study was improvement in FEV1%. Asthma control tests, spirometry and methacholine challenges were performed as well as Fractional Exhaled Nitric Oxide (FeNO) levels. PGD2, CystLT, and lipoxin levels were measured in exhaled breath condensate (EBC).

RESULTS

A total of 113 children were enrolled and 87 completed the study in accordance with the protocol. At baseline, children with food allergy and asthma (FAA) had higher levels of PGD2 and CysLT levels in the EBC than children with asthma alone (AA) (p < 0.001 for each). In the montelukast arm, although FEV1% was significantly higher in the FAA group compared to AA (p = 0.005), this effect was linked to the baseline difference of FEV1% between both arms. Montelukast treatment failed to improve FEV1% in both groups compared to the placebo. No effect of montelukast was observed in the remaining study parameters.

CONCLUSION

Although children with FAA do not show a more favorable response to montelukast treatment compared to AA, a significant difference between baseline PGD2 and CystLT levels between FAA and AA groups may point to a different endotype of childhood asthma.

Bronchial Provocation Testing for the Identification of Exercise-Induced Bronchoconstriction

Exercise-induced bronchoconstriction (EIB) occurs in patients with asthma, children, and otherwise healthy athletes. Poor diagnostic accuracy of respiratory symptoms during exercise requires objective assessment of EIB. The standardized tests currently available are based on the assumption that the provoking stimulus to EIB is dehydration of the airway surface fluid due to conditioning large volumes of inhaled air. "Indirect" bronchial provocation tests that use stimuli to cause endogenous release of bronchoconstricting mediators from airway inflammatory cells include dry air hyperpnea (eg, exercise and eucapnic voluntary hyperpnea) and osmotic aerosols (eg, inhaled mannitol). The airway response to different indirect tests is generally similar in patients with asthma and healthy athletes with EIB. Furthermore, the airway sensitivity to these tests is modified by the same pharmacotherapy used to treat asthma. In contrast, pharmacological agents such as methacholine, given by inhalation, act directly on smooth muscle to cause contraction. These "direct" tests have been used traditionally to identify airway hyperresponsiveness in clinical asthma but are less useful to diagnose EIB. The mechanistic differences between indirect and direct tests have helped to elucidate the events leading to airway narrowing in patients with asthma and elite athletes, while improving the clinical utility of these tests to diagnose and manage EIB.

Baseline spirometry parameters as predictors of airway hyperreactivity in adults with suspected asthma

BACKGROUND

Methacholine challenge tests (MCTs) are used to diagnose airway hyperresponsiveness (AHR) in patients with suspected asthma where previous diagnostic testing has been inconclusive. The test is time consuming and usually requires referral to specialized centers. Simple methods to predict AHR could help determine which patients should be referred to MCTs, thus avoiding unnecessary testing. Here we investigated the potential use of baseline spirometry variables as surrogate markers for AHR in adults with suspected asthma.

METHODS

Baseline spirometry and MCTs performed between 2013 and 2019 in a large tertiary center were retrospectively evaluated. Receiver-operating characteristic curves for the maximal expiratory flow-volume curve indices (angle β, FEV1, FVC, FEV1/FVC, FEF_50%, FEF_25-75%) were constructed to assess their overall accuracy in predicting AHR and optimal cutoff values were identified.

RESULTS

A total of 2983 tests were analyzed in adults aged 18-40 years. In total, 14% of all MCTs were positive (PC20 ≤ 16 mg/ml). All baseline spirometry parameters were significantly lower in the positive group (p < 0.001). FEF_50% showed the best overall accuracy (AUC = 0.688) and proved to be useful as a negative predictor when applying FEF_50% ≥ 110% as a cutoff level.

CONCLUSIONS

This study highlights the role of FEF_50% in predicting AHR in patients with suspected asthma. A value of ≥ 110% for baseline FEF_50% could be used to exclude AHR and would lead to a substantial decrease in MCT referrals.

Antioxidant MnTBAP does not protect adult mice from neonatal hyperoxic lung injury

BACKGROUND

Oxygen therapy and mechanical ventilation are important predisposing factors for the development of bronchopulmonary dysplasia (BPD), leading to increased morbidity and mortality in premature infants. Oxygen toxicity mediated by reactive oxygen species (ROS) may play an important part in the development of BPD. We studied the effects of MnTBAP, a catalytic antioxidant on airway responsiveness and alveolar simplification in adult mice following neonatal hyperoxia.

METHODS

Mice litters were randomized to 85 %O2 or room air (RA) on D3 for 12 days to receive either MnTBAP (10 mg/kg/d) or saline intraperitoneally. Methacholine challenge (MCC) performed at 8 and 12 weeks of age by whole-body plethysmography to assess airway reactivity. Alveolarization quantified on lung sections by radial alveolar count (RAC) and mean linear intercept (MLI). Cell counts assessed from bronchoalveolar lavage (BAL) performed at 15 weeks.

RESULTS

Mice exposed to hyperoxia and MnTBAP (OXMN) had significantly higher airway reactivity post-MCC at 8 weeks compared to RA and O2 groups. At 12 weeks, airway reactivity was higher post-MCC in both hyperoxia and OXMN groups. MnTBAP did not attenuate hyperoxia-induced airway reactivity in adult mice. Hyperoxia exposed mice demonstrated large and distended alveoli on histopathology at 2 and 15 weeks. MnTBAP did not ameliorate hyperoxia-induced lung injury as assessed by RAC/MLI. Absolute lymphocyte count was significantly higher in BAL in the hyperoxia and OXMN groups.

CONCLUSIONS

MnTBAP, a catalytic antioxidant, did not afford protection from hyperoxia-induced lung injury in adult mice.

Aerosolized hyaluronic acid decorated, ferulic acid loaded chitosan nanoparticle: A promising asthma control strategy

Vibrating mesh nebulizers are recognized as the most efficient actuation technique over conventional inhalers for drug deposition. This study explored hyaluronic acid (HA) decorated, ferulic acid (FA) loaded chitosan (CS) nanoparticle (FACHA) aerosolized using vibrating mesh nebulizer as strategic combination of drug, nanocarrier and delivery device for effective asthma control. FACHA exhibited spherical morphology with suitable size (164.2 ± 9.7 nm), zeta potential (24.0 ± 0.5 mV), entrapment efficiency (EE%) (65.0 ± 1.5), loading capacity (LC%) (18.5 ± 0.4) and mass median aerodynamic diameter (MMAD) of 1.81 ± 0.15 µm, ascertaining efficient drug deposition. In vivo inhalation toxicity assessment confirmed safety, while, FACHA prophylaxis mitigated inflammation, airway hypersensitivity and remodelling in ovalbumin (OVA) induced mice models. The results thus accentuated the role of pro-pulmonary surface chemistry conferred by HA functionalization that improved 1) thermal stability (thermogravimetric analysis - TGA) and 2) therapeutic efficacy of FA, by facilitating better interaction and transportation across mucus barrier, which otherwise suffers poor bioavailability and rapid metabolism.

The Effect of Bronchoconstriction by Methacholine Inhalation in a Murine Model of Asthma

INTRODUCTION

Bronchoconstriction was recently shown to cause airway remodeling and induce allergic airway inflammation in asthma. However, the mechanisms how mechanical stress via bronchoconstriction could induce airway inflammation and remodeling remain unclear.

OBJECTIVE

We investigated the effect of bronchoconstriction induced by methacholine inhalation in a murine model of asthma.

METHODS

BALB/c female mice were sensitized and challenged with ovalbumin (OVA), followed by treatment with methacholine by a nebulizer twice a day for 7 days. Twenty-four hours after the last methacholine treatment, the bronchoalveolar lavage fluid (BALF) and lung tissues were collected. The BALF was analyzed for total and differential cell counts and cytokine levels. The lung tissues were analyzed for goblet cell metaplasia, thickness of the smooth muscle, and lung fibrosis. The expression of cytokines in the lung was also examined.

RESULTS

OVA sensitization and challenge induced infiltration of total cells, macrophages, and eosinophils in the BALF along with goblet cell metaplasia and increased airway smooth muscle hypertrophy. Seven days after the last OVA challenge, untreated mice achieved reduction in airway inflammation, while methacholine maintained the number of BALF total cells, macrophages, and eosinophils. The percentage of goblet cells and the thickness of airway smooth muscle were also maintained by methacholine. Moreover, the treatment of methacholine induced the expression of transforming growth factor (TGF)-β in the lung. This result indicates that the production of TGF-β is involved in induction of airway remodeling caused by bronchoconstriction with methacholine.

CONCLUSIONS

Repeated bronchoconstriction caused by methacholine inhalation elicited allergic airway inflammation and airway remodeling.

Value of bronchial reversibility to salbutamol, exhaled nitric oxide and responsiveness to methacholine to corroborate the diagnosis of asthma in children

INTRODUCTION AND OBJECTIVES

Functional and inflammatory measures have been recommended to corroborate asthma diagnosis in schoolchildren, but the evidence in this regard is conflicting. We aimed to determine, in real-life clinical situation, the value of spirometry, spirometric bronchial reversibility to salbutamol (BDR), bronchial responsiveness to methacholine (MCT) and fractional exhaled nitric oxide (FENO), to corroborate the diagnosis of asthma in children on regular inhaled corticosteroids (ICS) referred from primary care.

METHODS

One hundred and seventy-seven schoolchildren with mild-moderate persistent asthma, on treatment with regular ICS, participated in the study. Abnormal tests were defined as FENO ≥ 27 ppb, BDR (FEV1 ≥ 12%) and methacholine PC20 ≤ 4 mg/mL.

RESULTS

The proportions of positive BDR, FENO and MCT, were 16.4%, 33.3%, and 87.0%, respectively. MCT was associated with FENO (p < 0.03) and BDR (p = 0.001); FENO was associated with BDR (p = 0.045), family history of asthma (p = 0.003) and use of asthma medication in the first two years of life (p = 0.004). BDR was significantly related with passive tobacco exposure (p = 0.003).

CONCLUSIONS

Spirometry, BDR and BDR had a poor performance for corroborating diagnosis in our asthmatic children on ICS treatment; on the contrary, MCT was positive in most of them, which agrees with previous reports. Although asthma tests are useful to corroborate asthma when positive, clinical diagnosis remains the best current approach for asthma diagnosis, at least while better objective and feasible measurements at the daily practice are available. At present, these tests may have a better role for assessing the management and progression of the condition.

Direct bronchoprovocation test methods: history 1945-2018

INTRODUCTION

Bronchoprovocation inhalation challenge tests with direct acting stimuli (e.g. methacholine) are widely used clinically to aid in the diagnosis of asthma. Areas covered: The history of direct challenges with histamine and muscarinic agonists is reviewed. This began with parenteral administration of stimuli with responses monitored clinically and by VC, progressing to inhalation dose-response challenges monitored by FEV₁ and FEV₁/VC ratio, both (the challenge method and the technology to measure FEV₁) developed by Robert Tiffeneau in the mid-1940s. Careful standardization of methods has become appreciated albeit after-the-fact. Recent guidelines recommend standardizing the methacholine PD₂₀ at 400 μg above which a methacholine challenge is considered negative.

CONCLUSIONS

The methacholine inhalation test is highly sensitive for a diagnosis of current asthma when symptoms under evaluation are clinically current and when methacholine is inhaled without deep inhalations. Under these circumstances, a methacholine PD₂₀ > 400 μg excludes current asthma with reasonable certainty. PD₂₀ values >25 μg and ≤400 μg will have a variable specificity and positive predictive value for asthma which increases the lower the PD₂₀ and the higher the pre-test probability for a diagnosis of asthma. A PD₂₀ ≤25 μg has high specificity and low sensitivity for asthma.

Bacterial respiratory tract inflammation in neonatal rat model is attenuated by benzofuran through inhibition of GATA3

The current study was aimed to investigate the effect of benzofuran on asthma neonatal rat model. Twenty-five neonatal rats were assigned into five groups; Normal control, untreated, 1 mg/kg, 8 mg/kg and 10 mg/kg treatment groups. Methacholine was administered orally to the rats of untreated and treatment groups. Animals in the normal control group were given PBS as a vehicle. FlexiVent system employing a computer-controlled mouse ventilator along with respiratory mechanics was used for the analysis of airway resistance in the rats. Cytokine level and IFN-γ in the rat serum samples was performed by ELISA in accordance with the instructions of manufacturer. Methacholine administration into the rats caused a marked increase in lung airway resistance. However, treatment with 8 and 10 mg/kg doses of benzofuran led to marked decrease in the airway resistance. Benzofuran treatment prevented accumulation of macrophages and inflammatory cells in the lung airways. Inhibition of inflammation in methacholine administered rats by benzofuran was also confirmed by hematoxylin & eosin-staining. Examination of the rat serum showed significantly higher level of Th2 cytokines (IL-4, -5 and -13) in the untreated rats. However, treatment of methacholine administered rats with benzofuran significantly inhibited Th2 cytokine expression. The level of IFN-γ was increased by benzofuran treatment in methacholine administered rats. In methacholine administered rats the level of IgE was markedly higher however treatment of asthma rats with benzofuran inhibited up-regulation of IgE significantly. The expression of T-bet is decreased and that of GATA-3 is increased by methacholine administration in the rat lungs. Benzofuran treatment of methacholine administered rats prevented reduction in T-bet and up-regulation of GATA-3 expression in the rat lungs. The effect of benzofuran was significant at the doses of 8 and 10 mg/kg and non-significant at 1 mg/kg. These finding suggest that benzofuran inhibits expression of dominant T-helper 2 cytokines through targeting GATA-binding protein 3 transcription factor. Thus benzofuran can be of therapeutic importance for the treatment of asthma.

[Guidelines for methacholine provocation testing]

Bronchial challenge with the direct bronchoconstrictor agent methacholine is commonly used for the diagnosis of asthma. The "Lung Function" thematic group of the French Pulmonology Society (SPLF) elaborated a series of guidelines for the performance and the interpretation of methacholine challenge testing, based on French clinical guideline methodology. Specifically, guidelines are provided with regard to the choice of judgment criteria, the management of deep inspirations, and the role of methacholine bronchial challenge in the care of asthma, exercise-induced asthma, and professional asthma.

Methacholine induces extracellular matrix production by human airway smooth muscle cells through β-catenin signaling

Altered extracellular matrix (ECM) production by airway smooth muscle cells (ASMCs) is an important feature of airway remodeling. Muscarinic receptor agonists contribute to ECM production in vivo, but the mechanisms involved remain unclear. This study attempted to investigate the role of methacholine in promoting ECM production by human ASMCs (HASMCs) and the underlying mechanism. We found that methacholine induced the expression of collagen I protein and multiple ECM genes. β-catenin signaling was activated in this process upon GSK3β phosphorylation, leading to upregulation of total and active β-catenin. Silencing β-catenin by specific small interfering RNA (siRNA) or with the β-catenin inhibitor, PKF115-584, decreased collagen I expression. Conversely, overexpression of active β-catenin by adenoviruses carrying the S33Y-β-catenin mutant increased the methacholine-induced collagen I expression. Furthermore, methacholine induced TGF-β expression in HASMCs, while pan-TGF-β-neutralizing antibody only partially decreased collagen I expression. These findings suggest that methacholine induced ECM production through β-catenin signaling and partially through TGF-β.

[Occurrence of delayed symptoms after a challenge test with methacholine]

There are few prospective studies available on the development of delayed symptoms following challenge tests with methacholine (MCT) at the currently recommended doses. The objective of this study was to describe the nature and frequency of respiratory symptoms suggestive of bronchospasm developing within 24hours after a MCT. The study was offered to adult patients who underwent MCT seen consecutively between June and October 2015. Following the test, a questionnaire adapted from the GINA asthma control questionnaire bearing on diurnal and nocturnal symptoms (cough, dyspnoea, wheeze and tightness), was delivered to the patient and the replies collected by telephone 24hours later. Of the 101 patients included (initial FEV1 2.82±0.79L), 46 (46 %) were MCT+ and 55 (54 %) MCT-. Among the MCT-, 4 (7 %) presented with immediate symptoms (S+) and 4 (7 %) with delayed symptoms. Among the MCT+ patients, 36 (78 %) presented with immediate symptoms (P<0.001 compared with the MCT- patients), and 39 (85 %) with delayed symptoms (P<0.001 compared with the MCT- patients). Delayed symptoms developed with a mean of 5h30 after the provocation test. Immediate and delayed symptoms were more frequent in subjects having significant non-specific bronchial hyper-reactivity. Informing patients of the risk of developing delayed symptoms seems useful and allows optimization of their management after a MCT.

Bronchial hyper-responsiveness after preterm birth

Being born preterm often adversely affects later lung function. Airway obstruction and bronchial hyperresponsiveness (BHR) are common findings. Respiratory symptoms in asthma and in lung disease after preterm birth might appear similar, but clinical experience and studies indicate that symptoms secondary to preterm birth reflect a separate disease entity. BHR is a defining feature of asthma, but can also be found in other lung disorders and in subjects without respiratory symptoms. We review different methods to assess BHR, and findings reported from studies that have investigated BHR after preterm birth. The area appeared understudied with relatively few and heterogeneous articles identified, and lack of a pervasive understanding. BHR seemed related to low gestational age at delivery and a neonatal history of bronchopulmonary dysplasia. No studies reported associations between BHR after preterm birth and the markers of eosinophilic inflammatory airway responses typically found in asthma. This should be borne in mind when treating preterm born individuals with BHR and airway symptoms.

Objective confirmation of asthma diagnosis improves medication adherence

OBJECTIVE

The impact of diagnostic work-up in asthma management on medication redemption and probably also drug adherence is largely unknown, but we hypothesized that a confirmed diagnosis of asthma in a hospital-based out-patient clinic increases the willingness to subsequent medication redemption in a real life setting.

METHODS

In a retrospective register-based study, 300 medical records of patients referred with possible asthma during one year were examined, of whom 171 had asthma (57%). One-year data on dispensed medicine was collected using the Danish Registry of Medicinal Product Statistics. Patients who had a positive asthma (e.g. bronchial challenge) were classified as verified asthma, whereas unverified asthma refers to doctor's diagnosis of asthma with negative or no diagnostic tests performed.

RESULTS

111 (65%) had a verified diagnosis and patients with verified asthma were more frequently prescribed new therapy compared to those with unverified asthma (88.9% vs. 65.0%, respectively, p < 0.001). No difference was found in first time redemption of prescriptions (72% vs. 64%, respectively, p = 0.3), whereas the second (52% vs. 27%, p = 0.001) and third or more asthma redeemed prescriptions (37% vs. 17%, p = 0.006) showed increased redemption of prescription and probably adherence in the verified compared with the unverified patients with asthma. Furthermore, the use of inhaled corticosteroid (ICS) was calculated as Percent Days Covered (PDC), which was higher in the verified group compared with the non-verified asthma group (88% vs. 30%, p = 0.004).

CONCLUSION

Objective verification of a diagnosis of asthma using asthma tests was associated with an improved redemption of prescription.

Spirometry or Body Plethysmography for the Assessment of Bronchial Hyperresponsiveness?

Methacholine testing is one of the standard tools for the diagnosis of mild asthma, but there is little information about optimal outcome measures. In this study a total of 395 college students were tested by the ATS dosimeter protocol for methacholine testing, with minor modification. Body plethysmography and spirometry were measured after each inhalation step. The end-of-test-criteria were (i) decrease in forced expiratory volume in 1 s (FEV1) of ≥ 20 % and (ii) doubling of specific airway resistance and its increase to ≥ 2.0 kPa∙s. The results were expressed by receiver operating characteristic (ROC) plots using questionnaire answers as a reference. The areas under the ROC curves were iteratively calculated for a wide range of thresholds for both measures. We found that ROC plots showed maximal sensitivities of about 0.5-0.6 for FEV1 and about 0.7 for specific airway conductance (sGt), with similar specificities of about 0.7-0.8 taking questions with the known high specificity as references. Accordingly, larger maximal areas under the ROC curve were observed for body plethysmography, but the differences were small. A decrease in FEV1 of about 15 % and a decrease of sGt of about 60 % showed the largest areas under the ROC curves. In conclusion, body plethysmography yielded better sensitivity than spirometry, with similar specificity. However, replacing the common spirometric criterium for a positive test (20 % decrease in FEV1 from baseline) by the optimal body plethysmographic criterium would result in an increase of false positive tests from about 4 to 8 % in healthy young adults.

Role of prostaglandin E2 in bronchoconstriction-triggered cough response in guinea pigs

A feature of cough variant asthma is a heightened cough response to bronchoconstriction. The mediators of this response are unknown. This study was designed to elucidate the role of lipid mediators in bronchoconstriction-triggered cough response in an experimental animal model. We examined the influence of bronchoconstriction on cell components and mediators including prostaglandin E₂ (PGE₂) in bronchoalveolar lavage fluid (BALF). We studied the cough response to bronchoconstriction (CRB) by measuring the correlation between the increase in enhanced pause (Penh), an index of bronchoconstriction, and cough counts induced by methacholine (Mch) inhalation in conscious guinea pigs. We then examined the effects of intraperitoneal pretreatment with 16, 16-dimethyl-prostaglandin E₂ (dm-PGE₂) on CRB and cough counts. The total number of cells and cell components in the BALF were not influenced by bronchoconstriction. While levels of PGE₂, prostaglandin I₂, and cysteinyl leukotrienes were significantly increased, levels of prostaglandin D₂, thromboxane B₂, and substance P in the BALF were not. Dm-PGE₂ significantly decreased the Mch-induced increase in Penh. Following bronchoconstriction by additional Mch inhalation, dm-PGE₂ produced an increase in CRB and cough counts in a dose-dependent manner. Additionally, the heightened CRB following dm-PGE₂ treatment was suppressed by pretreatment with PGE₂ receptor (E-prostanoid EP) -1 and EP-3 antagonists in a dose-dependent manner, but not by EP-2 and EP-4 antagonists. The EP-1 antagonist also decreased cough counts. These results suggest that PGE₂ acts as an exacerbating factor for bronchoconstriction-triggered cough. EP1 and EP3 may provide new therapeutic targets for cough variant asthma.

Bronchoprotective effect of deep inspirations in cough variant asthma: A distinguishing feature in the spectrum of airway disease?

PURPOSE

To assess the effect of deep inspirations (DIs) on airway behaviour in individuals with classic asthma (CA), cough variant asthma (CVA), and methacholine (MCh)-induced cough but normal airway sensitivity (COUGH) during bronchoprovocation.

METHODS

Twenty-five adults (18 female; 44.8 ± 12.3 years (Mean ± SD); n = 9 CA, n = 9 CVA, and n = 7 COUGH) completed two single-dose MCh challenges, with and without DIs. Bronchoprotection was assessed by comparing changes in bronchoconstriction (FEV₁, FVC, FEV₁/FVC, FEF₅₀, FEF_25-75), gas trapping (RV, RV/TLC) and impulse oscillometry (IOS) measurements.

RESULTS

The% changes in FEV₁ with and without DIs were not significantly different within any group. Decreases in FEF₅₀ and FEF_25-75 were greater in CA (p = 0.041 and p = 0.029), decreases in FVC (% predicted) and FEV₁/FVC(%) were less in CVA (p = 0.048 and p = 0.010), and increases in RV (L) and RV/TLC (% predicted) were less in COUGH (p = 0.007 and p = 0.028), respectively. No differences in IOS measurements were noted.

CONCLUSIONS

DIs triggered bronchoconstriction in CA, bronchoprotection in CVA, and prevented gas trapping in COUGH.

Peri-adolescent asthma symptoms cause adult anxiety-related behavior and neurobiological processes in mice

Human and animal studies have shown that physical challenges and stressors during adolescence can have significant influences on behavioral and neurobiological development associated with internalizing disorders such as anxiety and depression. Given the prevalence of asthma during adolescence and increased rates of internalizing disorders in humans with asthma, we used a mouse model to test if and which symptoms of adolescent allergic asthma (airway inflammation or labored breathing) cause adult anxiety- and depression-related behavior and brain function. To mimic symptoms of allergic asthma in young BALB/cJ mice (postnatal days [P] 7-57; N=98), we induced lung inflammation with repeated intranasal administration of house dust mite extract (most common aeroallergen for humans) and bronchoconstriction with aerosolized methacholine (non-selective muscarinic receptor agonist). Three experimental groups, in addition to a control group, included: (1) "Airway inflammation only", allergen exposure 3 times/week, (2) "Labored breathing only", methacholine exposure once/week, and (3) "Airway inflammation+Labored breathing", allergen and methacholine exposure. Compared to controls, mice that experienced methacholine-induced labored breathing during adolescence displayed a ∼20% decrease in time on open arms of the elevated plus maze in early adulthood (P60), a ∼30% decrease in brainstem serotonin transporter (SERT) mRNA expression and a ∼50% increase in hippocampal serotonin receptor 1a (5Htr1a) and corticotropin releasing hormone receptor 1 (Crhr1) expression in adulthood (P75). This is the first evidence that experimentally-induced clinical symptoms of adolescent asthma alter adult anxiety-related behavior and brain function several weeks after completion of asthma manipulations.

Specific inhalation challenge: the relationship between response, clinical variables and lung function

INTRODUCTION

The specific inhalation challenge (SIC) is considered the gold standard for the diagnosis of occupational asthma (OA). However, its use is not standardised, and the intensity of exposure is regulated empirically. The aim of this study was to identify clinical variables and/or pulmonary function variables able to predict the scale of patients' response to SIC.

MATERIAL AND METHODS

All patients who underwent SIC at our centre between 2005 and 2013 were studied. Anthropometric characteristics, atopic status, type of causal agent, latency times, pulmonary function tests and SIC results were analysed.

RESULTS

Two hundred and one patients (51% men) were assessed, of whom 86 (43%) had positive SIC. In the patients with positive results, 29 (34%) were exposed to high molecular weight (HMW) agents and 57 (64%) to low molecular weight (LMW) agents. Patients with a positive SIC exposed to HMW agents had a higher fall in FEV₁ after SIC compared with those exposed to LMW agents (p=0.036). The type of asthmatic reaction after SIC also differed between the groups (p=0.020). The logistic regression analysis showed that patients with a higher PC₂₀ before SIC were less likely to have severe decreases in FEV1 after SIC after adjusting for potential confounders (OR=0.771, 95% CI 0.618 to 0.961, p=0.021).

CONCLUSIONS

The scale of the response to SIC is influenced mainly by the degree of bronchial hyper-responsiveness, regardless of whether the causative agent is HMW or LMW, or whether the response is early or late.

Airway Hyperresponsiveness in Asthma: Measurement and Clinical Relevance

Airway hyperresponsiveness is a characteristic feature of asthma, and its measurement is an important tool in its diagnosis. With a few caveats, methacholine bronchial provocation by a 2-minute tidal breathing method is highly sensitive; a negative test result (PC₂₀ > 16 mg/mL, PD₂₀ > 400 μg) rules out current asthma with reasonable certainty. A PC₂₀ value of less than 1 mg/mL/PD₂₀ value of less than 25 μg is highly specific (ie, diagnostic) but quite insensitive for asthma. For accurate interpretation of the test results, it is important to control and standardize technical factors that have an impact on nebulizer performance. In addition to its utility to relate symptoms such as cough, wheeze, and shortness of breath to variable airflow obstruction (ie, to diagnose current asthma), the test is useful to make a number of other clinical assessments. These include (1) evaluation of patients with occupational asthma, (2) evaluation of patients with exercise-induced respiratory symptoms, (3) evaluation of novel asthma medications, (4) evaluation of relative potency of inhaled bronchodilators, (5) as a biomarker to adjust anti-inflammatory therapy to improve clinical outcomes, and (6) in the evaluation of patients with severe asthma to rule out masqueraders such as laryngeal dysfunction. The actual mechanism of altered smooth muscle behavior in asthma that is assessed by direct (eg, methacholine) or indirect (eg, allergen) bronchial provocation remains one of the most fundamental questions related to asthma that needs to be determined. The test is underutilized in clinical practice.

Bronchial hyperresponsiveness in childhood: A narrative review

Bronchial hyperresponsiveness (BHR) is an important but not asthma-specific characteristic and can be assessed by direct and indirect methods, based on the stimulus causing airway obstruction. BHR has been proposed as a prognostic marker of asthma severity and persistence, and may also be used to control pharmacological management of asthma. The most recent data on the prevalence and development of BHR in childhood and its predictive value for subsequent asthma development in late adolescence and adulthood is discussed in this review. According to the BHR-related scientific articles written in the English language and indexed in the publicly searchable PubMed database, the prevalence of BHR varies based upon the methods used to assess it and the population examined. In general, however, BHR prevalence is reduced as children grow older, in both healthy and asthmatic populations. While asthma can be predicted by BHR, the predictive value is limited. Reduced lung function, allergic sensitization, female sex, and early respiratory illness have been identified as risk factors for BHR. The collective studies further indicate that BHR is a dynamic feature related to asthma, but asymptomatic BHR is also common. Ultimately, the prevalence of BHR varies depending on the population, the environment, and the evaluation methods used. While both the methacholine challenge and the exercise test may predict asthma in adolescence or early adulthood, the predictive value is higher for the methacholine challenge compared to the exercise test. The collective data presented in the present study demonstrate how BHR develops through childhood and its relation to bronchial asthma.

[Mechanisms of non-specific airway hyperresponsiveness: Methacholine-induced alterations in airway architecture]

Multiple mechanisms drive non-specific airway hyperresponsiveness in asthma. At the organ level, methacholine inhalation induces a complex bronchomotor response involving both bronchoconstriction and, to some extent, paradoxical bronchodilatation. This response is heterogeneous both serially, along a single bronchial axis, and in parallel, among lung regions. The bronchomotor response to methacholine induces contraction of distal airways as well as focal airway closure in select lung territories, leading to anatomically defined ventilation defects and decreased vital capacity. In addition, loss of the bronchoprotector and bronchodilator effects of deep inspirations is a key contributor to airway hyperresponsiveness in asthma.

A positive methacholine challenge based on specific airway conductance: A case report

A 30-year-old Caucasian man presented to the pulmonary function laboratory for a methacholine challenge test. Following inhalation of the final dose of methacholine, the forced expiratory volume in 1 s (FEV1) was 8% below baseline. However, the patient complained of chest tightness and dyspnea, similar to the symptoms he experienced after running. Repeat specific airway conductance was found to be 73% below baseline, indicating marked airway hyper-responsiveness. Because the reduction in specific airway conductance was accompanied by familiar symptoms, the post-test probability of asthma increases, even in the absence of a 20% reduction in FEV1.

Effects of methacholine infusion on desflurane pharmacokinetics in piglets

The data of a corresponding animal experiment demonstrates that nebulized methacholine (MCh) induced severe bronchoconstriction and significant inhomogeneous ventilation and pulmonary perfusion (V̇_A/Q̇) distribution in pigs, which is similar to findings in human asthma. The inhalation of MCh induced bronchoconstriction and delayed both uptake and elimination of desflurane (Kretzschmar et al., 2015) [1].

The objective of the present data is to determine V̇_A/Q̇ matching by Multiple Inert Gas Elimination Technique (MIGET) in piglets before and during methacholine- (MCh-) induced bronchoconstriction, induced by MCh infusion, and to assess the blood concentration profiles for desflurane (DES) by Micropore Membrane Inlet Mass Spectrometry (MMIMS).

Healthy piglets (n=4) under general anesthesia were instrumented with arterial, central venous, and pulmonary artery lines. The airway was secured via median tracheostomy with an endotracheal tube, and animals were mechanically ventilated with intermittent positive pressure ventilation (IPPV) with a FiO₂ of 0.4, tidal volume (V_T)=10 ml/kg and PEEP of 5cmH₂O using an open system. The determination of V._A/Q. was done by MIGET: before desflurane application and at plateau in both healthy state and during MCh infusion. Arterial blood was sampled at 0, 1, 2, 5, 10, 20, and 30 min during wash-in and washout, respectively.

Bronchoconstriction was established by MCH infusion aiming at doubling the peak airway pressure, after which wash-in and washout of the anesthetic gas was repeated. Anesthesia gas concentrations were measured by MMIMS. Data were analyzed by ANOVA, paired t-test, and by nonparametric Friedman׳s test and Wilcoxon׳s matched pairs test.

We measured airway pressures, pulmonary resistance, and mean paO₂ as well as hemodynamic variables in all pigs before desflurane application and at plateau in both healthy state and during methacholine administration by infusion. By MIGET, fractional alveolar ventilation and pulmonary perfusion in relation to the V.A/Q. compartments, data of logSDQ̇ and logSDV̇ (the second moments describing global dispersion, i.e. heterogeneity of distribution) were estimated prior to and after MCh infusion. The uptake and elimination of desflurane was determined by MMIMS.

Methacholine challenge test by wheezing and oxygen saturation in preschool children with asthma

Methacholine challenge test (MCT) performed with spirometry is a commonly used test to evaluate bronchial hyperreactivity (BHR) in children. However, preschoolers do not usually collaborate.

OBJECTIVES

To assess the usefulness of MCT through clinical evaluation (wheezing auscultation and decreased pulse arterial oxygen saturation [SpO2]) in recurrent wheezing preschoolers with asthma, in comparison to healthy controls.

METHODS

We performed the MCT (modified Cockroft method) on healthy and on asthmatic preschoolers. The end point was determined by the presence of wheezing in the chest and/or tracheal auscultation (PCw) and/or a decrease in SpO2 of ≥5 from the baseline value (PCSpO2). Maximal methacholine concentration was 8 mg/ml.

RESULTS

The study population comprised 65 children: 32 healthy and 33 asthmatic children. There were no differences in demographic characteristics between the groups. The median methacholine doses for PCw and for PCSpO2 were significantly lower among asthmatic than healthy children: 0.5 mg/ml (0.25-0.5 mg/ml) vs. 2 mg/ml (1-4 mg/ml), respectively, p<0.001; and 0.25 mg/ml (0.25-0.5 mg/ml) and 2 mg/ml (0.5-4 mg/ml), respectively, p<0.001. The best cut-off point of PCw was observed at a methacholine concentration of 0.5 mg/ml (AUC=0.72 [95% CI=0.66-0.77]), its sensitivity was 91%, specificity 43%, PPV 16% and NPV 98%. For PCSpO2 the best cut-off point was a methacholine concentration of 1 mg/ml (AUC=0.85 [95% CI 0.81-0.89]), with sensitivity of 80%, specificity 74%, PPV 49%, and NPV 92%. There were no adverse reactions.

CONCLUSION

MCT using clinical parameters such as wheezing auscultation and SpO2 measurement could be a useful and safe test to confirm BHR among preschoolers.

Reprint of "Non-invasive measure of respiratory mechanics and conventional respiratory parameters in conscious large animals by high frequency Airwave Oscillometry"

INTRODUCTION

A number of drugs in clinical trials are discontinued due to potentially life-threatening airway obstruction. As some drugs may not cause changes in core battery parameters such as tidal volume (Vt), respiratory rate (RR) or minute ventilation (MV), including measurements of respiratory mechanics in safety pharmacology studies represents an opportunity for design refinement. The present study aimed to test a novel non-invasive methodology to concomitantly measure respiratory system resistance (Rrs) and conventional respiratory parameters (Vt, RR, MV) in conscious Beagle dogs and cynomolgus monkeys.

METHODS

An Airwave Oscillometry system (tremoFlo; THORASYS Inc., Montreal, Canada) was used to concomitantly assess Rrs and conventional respiratory parameters before and after intravenous treatment with a bronchoactive agent. Respiratory mechanics measurements were performed by applying a short (i.e. 16s) single high frequency (19Hz) waveform at the subject's airway opening via a face mask. During measurements, pressure and flow signals were recorded. After collection of baseline measurements, methacholine was administered intravenously to Beagle dogs (n=6) and cynomolgus monkeys (n=4) at 8 and 68μg/kg, respectively.

RESULTS

In dogs, methacholine induced significant increases in Vt, RR and MV while in monkeys, it only augmented RR. A significant increase in Rrs was observed after methacholine administration in both species with mean percentage peak increases from baseline of 88 (53)% for dogs and 28 (16)% for cynomolgus monkeys.

CONCLUSION

Airwave Oscillometry appears to be a promising non-invasive methodology to enable respiratory mechanics measurements in conscious large animals, a valuable refinement in respiratory safety pharmacology.

Low levels of fractional exhaled nitric oxide and deep inhalation bronchoprotection are associated with mannitol non-responsiveness in asthma

BACKGROUND

Airway hyperresponsiveness (AHR) to indirect agents like mannitol is thought to be dependent on concurrent airway inflammation as these stimuli exert their effects via the release of bronchoconstricting mediators from inflammatory cells. Airway inflammation correlates negatively with deep inhalation bronchoprotection against direct stimuli like methacholine. We hypothesised that deep inhalation bronchoprotection to methacholine would be absent and airway inflammation would be present in individuals with AHR to inhaled mannitol.

METHODS

Twenty asthmatic, otherwise healthy individuals, either gender, aged 18-65 years, with a Visit 1 (screening) methacholine two-minute tidal breathing PC20 of 16 mg/mL or less completed the study. Visits 2 and 3 consisted of either mannitol or deep inhalation methacholine challenge in random order, at least 24 h apart. All visits were completed within a period of two weeks.

RESULTS

Eleven of the twenty participants had AHR to mannitol (PD15 ≤ 635 mg, the "responders") and nine did not (the "non-responders"). Responders did not bronchoprotect to methacholine via deep inhalation (doubling dose shift = 0.7; p = 0.13) and had high levels of exhaled nitric oxide (geometric mean 49 ppb; range 16-109 ppb). Conversely, significant deep inhalation bronchoprotection to methacholine occurred in the non-responder group (doubling dose shift = 1.6; p = 0.013). This group also had significantly lower levels of exhaled nitric oxide (geometric mean 23 ppb (range 16-45 ppb; p = 0.015).

CONCLUSIONS

Deep inhalation bronchoprotection to methacholine and low levels of exhaled nitric oxide coincide with mannitol non-responsiveness in an asthmatic population. Clinical Trials Registration #NCT01642745 (clinicaltrials.gov).

The activating protein 1 transcription factor basic leucine zipper transcription factor, ATF-like (BATF), regulates lymphocyte- and mast cell-driven immune responses in the setting of allergic asthma

BACKGROUND

Mice without the basic leucine zipper transcription factor, ATF-like (BATF) gene (Batf(-/-)) lack TH17 and follicular helper T cells, which demonstrates that Batf is a transcription factor important for T- and B-cell differentiation.

OBJECTIVE

In this study we examined whether BATF expression would influence allergic asthma.

METHODS

In a cohort of preschool control children and children with asthma, we analyzed BATF mRNA expression using real-time PCR in PBMCs. In a murine model of allergic asthma, we analyzed differences in this allergic disease between wild-type, Batf transgenic, and Batf(-/-) mice.

RESULTS

In the absence of corticosteroid treatment, children with recurrent asthma have a significant increase in BATF mRNA expression in their PBMCs. Batf(-/-) mice display a significant reduction in the pathophysiologic responses seen in asthmatic wild-type littermates. Moreover, we discovered a decrease in IL-3 production and IL-3-dependent mast cell development in Batf(-/-) mice. By contrast, IFN-γ was induced in lung CD4(+) and CD8(+) T cells. Intranasal delivery of anti-IFN-γ antibodies induced airway hyperresponsiveness and inflammation in wild-type but not in Batf(-/-) mice. Transgenic overexpression of Batf under the control of the CD2 promoter/enhancer augmented lung inflammation and IgE levels in the setting of experimental asthma.

CONCLUSION

BATF is increased in non-steroid-treated asthmatic children. Targeting BATF expression resulted in amelioration of the pathophysiologic responses seen in children with allergic asthma, and BATF has emerged as a novel target for antiasthma interventions.

Frequency dependence of capnography in anesthetized rabbits

Aspirative capnography may be of help to diagnose early childhood asthma, but clinical usefulness in young children is limited by the relatively high respiratory rate. This study aimed to characterize the [Formula: see text] time course during airway constriction in 8 anesthetized rabbits, artificially ventilated at 30, 60 and 80breaths/min. Methacholine was inhaled to double the respiratory resistance measured at 8Hz by the forced oscillation technique. The capnogram shape changed in response to both methacholine and ventilatory frequency. Slope of phase II, the peak of first-order time derivative and trough of the second-order time derivative of the [Formula: see text] signal, were significantly attenuated after methacholine compared with baseline at all breathing rates (p<0.02). Moreover, significant correlations between respiratory reactance and resistance were observed with the phase III slope and the angle described by phase II and phase III (p<0.01). It is concluded that capnography may be useful to identify acute airway changes related to bronchoconstriction, even at high breathing frequencies.

Comparison of direct and indirect bronchoprovocation testing using ventilator-acquired pulmonary mechanics in healthy cats and cats with experimental allergic asthma

Airway hyperresponsiveness (AHR) is a key feature of asthma and can be measured using bronchoprovocation. Direct (methacholine, MCh) or indirect (adenosine-5-monophosphate, AMP; or mannitol) bronchoprovocants are used in human patients, the latter inducing AHR only with pre-existing airway inflammation. The present study compared the responses to direct (MCh) and indirect (mannitol, AMP) bronchoprovocation in healthy and asthmatic cats (n=6/group). The order of bronchoprovocant was randomized using a published table of random numbers and there was a 1-month washout before crossover to the next treatment. Pulmonary mechanics were measured in anesthetized and mechanically ventilated cats using a critical care ventilator. Saline at baseline and increasing doses of each bronchoprovocant were aerosolized for 30 s, followed by 4 min of data collection between doses. The endpoint for each bronchoprovocant was reached when airway resistance exceeded 200% of baseline values (EC200Raw). There was a significant difference (P<0.001) in the airway response of asthmatic vs. healthy cats over the range of MCh concentrations, despite there being no significant difference in the EC200Raw between the groups. Response to MCh was significantly greater (P<0.05) in asthmatic than in healthy cats at MCh concentrations as low as 0.0625 mg/mL. For AMP, a small subset of asthmatics (n=2/6) responded at low concentrations; four asthmatic cats and all healthy cats failed to respond even to the highest concentrations of AMP. One asthmatic cat but no healthy cats responded to mannitol. In conclusion, MCh discriminated asthmatic from healthy cats but neither AMP nor mannitol was an effective bronchoprovocant in this model.

Methacoline Challenge test as an Evaluator of Response to Statins in Bronchial Hyperresponsiveness

3-hydroxy-3-methylglutaryl-CoA reductase inhibitors (statins), are effective serum cholesterol-lowering agents which also have anti-inflammatory properties. The objective of this study was to evaluate the effect of atorvastatin on bronchial hyperresponsiveness. Adult patients (age 14 to 65 years) with bronchial hyperresponsiveness (BHR) diagnosis based on the spirometry with methacholine challenge test were entered into the study. The study was conducted in the National Research Institute of Tuberculosis and Lung Disease. Patients were randomized to receive either atorvastatin 20 mg/day or placebo for 4 weeks. Spirometric parameters were determined at baseline and at completion of the study. Twenty two patients with the age of 32.95±10.30 years completed the trial. Changes in airway responsiveness categories (moderate to severe, mild, borderline, normal) after the intervention were not significant in atorvastatin group as in placebo group (p-value= 0.131 for atorvastatin group and p-value = 0.305 for placebo group). Also, changes in methacholine solution number (different concentrations of methacholine) which caused at least 20% decrease in FEV1 were not significant between groups (p-value = 0.089). Although we could not find a significant difference, the patients' fall in FEV1 in atorvastatin group was observed in higher concentrations of methacholine. Median before treatment versus after treatment in atorvastatin group was 1 versus 4 mg/mL, while those were 2 versus 1 mg/mL in placebo group. This study showed a better but not significant hyperresponsiveness control in the treatment group. The result might be presented more pronounced, if we could increase the sample size.

Airway responsiveness to inhaled aspirin is influenced by airway hyperresponsiveness in asthmatic patients

BACKGROUND/AIMS

Many patients with aspirin-induced asthma have severe methacholine airway hyperresponsiveness (AHR), suggesting a relationship between aspirin and methacholine in airway response. This study was performed to determine whether methacholine AHR affects the response of asthmatics to inhaled aspirin.

METHODS

The clinical records of 207 asthmatic patients who underwent inhalation challenges with both aspirin and methacholine were reviewed retrospectively. An oral aspirin challenge was performed in patients with a negative inhalation response. The bronchial reactivity index (BRindex) was calculated from the percent decrease in lung function divided by the last dose of the stimulus.

RESULTS

Forty-one (20.9%) and 14 (7.1%) patients showed a positive response to aspirin following an inhalation and oral challenge, respectively. Only 24.3 and 14.3% of the responders had a history of aspirin intolerance, respectively. The methacholine BRindex was significantly higher in the inhalation responders (1.46 ± 0.02) than in the oral responders (1.36 ± 0.03, p < 0.01) and in non-responders (n = 141, 1.37 ± 0.01, p < 0.001). The aspirin BRindex was significantly correlated with the methacholine BRindex (r = 0.270, p < 0.001). Three of four patients who received the oral challenge, despite a positive inhalation test, showed negative responses to the oral challenge. Two of these patients had severe AHR.

CONCLUSIONS

A considerable number of asthmatic patients with no history of aspirin intolerance responded to the inhalation aspirin challenge. The airway response to aspirin was significantly correlated with methacholine-AHR, and a false-positive response to aspirin inhalation test seemed to occur primarily in patients with severe AHR.