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Experimental Lung Research 2023Force adaptation is a process whereby the contractile capacity of the airway smooth muscle increases during a sustained contraction (aka tone). Tone also increases the...
Force adaptation is a process whereby the contractile capacity of the airway smooth muscle increases during a sustained contraction (aka tone). Tone also increases the response to a nebulized challenge with methacholine , presumably through force adaptation. Yet, due to its patchy pattern of deposition, nebulized methacholine often spurs small airway narrowing heterogeneity and closure, two important enhancers of the methacholine response. This raises the possibility that the potentiating effect of tone on the methacholine response is not due to force adaptation but by furthering heterogeneity and closure. Herein, methacholine was delivered homogenously through the intravenous (i.v.) route. Female and male BALB/c mice were subjected to one of two i.v. methacholine challenges, each of the same cumulative dose but starting by a 20-min period either with or without tone induced by serial i.v. boluses. Changes in respiratory mechanics were monitored throughout by oscillometry, and the response after the final dose was compared between the two challenges to assess the effect of tone. For the elastance of the respiratory system (E), tone potentiated the methacholine response by 64 and 405% in females (37.4 ± 10.7 61.5 ± 15.1 cmHO/mL; = 0.01) and males (33.0 ± 14.3 166.7 ± 60.6 cmHO/mL; = 0.0004), respectively. For the resistance of the respiratory system (R), tone potentiated the methacholine response by 129 and 225% in females (9.7 ± 3.5 22.2 ± 4.3 cmHO·s/mL; = 0.0003) and males (10.7 ± 3.1 34.7 ± 7.9 cmHO·s/mL; < 0.0001), respectively. As previously reported with nebulized challenges, tone increases the response to i.v. methacholine in both sexes; albeit sexual dimorphisms were obvious regarding the relative resistive elastic nature of this potentiation. This represents further support that tone increases the lung response to methacholine through force adaptation.
Topics: Male; Female; Animals; Mice; Methacholine Chloride; Lung; Respiratory Mechanics; Bronchial Provocation Tests; Airway Resistance
PubMed: 37477352
DOI: 10.1080/01902148.2023.2237127 -
The Journal of Allergy and Clinical... Nov 2023The emerging role of sphingosine-1-phosphate (S1P) in regulating smooth muscle functions has led to the exploration of the possibility that this sphingolipid could...
BACKGROUND
The emerging role of sphingosine-1-phosphate (S1P) in regulating smooth muscle functions has led to the exploration of the possibility that this sphingolipid could represent a potential therapeutic target in asthma and other lung diseases. Several studies in animal surrogates have suggested a role for S1P-mediated signaling in the regulation of airway smooth muscle (ASM) contraction, airway hyperresponsiveness, and airway remodeling, but evidence from human studies is lacking.
OBJECTIVE
We sought to compare the responsiveness of the airways to S1P in healthy and asthmatic individuals in vivo, in isolated human airways ex vivo, and in murine airways dissected from healthy and house dust mite (HDM)-sensitized animals.
METHODS
Airway responsiveness was measured by spirometry during inhalation challenges and by wire myography in airways isolated from human and mouse lungs. Thymidine incorporation and calcium mobilization assays were used to study human ASM cell responses.
RESULTS
S1P did not induce contraction of airways isolated from healthy and HDM-exposed mice, nor in human airways. Similarly, there was no airway constriction observed in healthy and asthmatic subjects in response to increasing concentrations of inhaled S1P. However, a 30-minute exposure to S1P induced a significant concentration-dependent enhancement of airway reactivity to methacholine and to histamine in murine and human airways, respectively. HDM-sensitized mice demonstrated a significant increase in methacholine responsiveness, which was not further enhanced by S1P treatment. S1P also concentration-dependently enhanced proliferation of human ASM cells, an effect mediated through S1P receptor type 2, as shown by selective antagonism and S1P receptor type 2 small-interfering RNA knockdown.
CONCLUSIONS
Our data suggest that S1P released locally into the airways may be involved in the regulation of ASM hyperresponsiveness and hyperplasia, defining a novel target for future therapies.
Topics: Humans; Mice; Animals; Sphingosine-1-Phosphate Receptors; Methacholine Chloride; Asthma; Muscle, Smooth; Cell Proliferation
PubMed: 37474025
DOI: 10.1016/j.jaci.2023.05.028 -
Respiratory Research Jul 2023Accumulating clinical evidence links Obstructive Sleep Apnea (OSA) with worse outcomes of asthma, but impact on airway function remains sparsely studied. We tested...
INTRODUCTION
Accumulating clinical evidence links Obstructive Sleep Apnea (OSA) with worse outcomes of asthma, but impact on airway function remains sparsely studied. We tested effects of Chronic Intermittent Hypoxia (CIH) - a hallmark of OSA - on airway hyperresponsiveness (AHR), in a rat model of chronic allergen-induced inflammation.
METHODS
Brown Norway rats were exposed to six weeks of CIH or normoxia (NORM) concurrent with weekly house dust mites (HDM) or saline (SAL) challenges. At endpoint, we assessed responses to seven Methacholine (Mch) doses (0, 4, 8, 16, 32, 64, 128 mg/mL) on a FlexiVent system (Scireq). Maximal (or plateau) responses (reactivity) for total respiratory system Resistance (R) and Elastance (E), Newtonian airway resistance (R a measure of central airways function) and tissue damping (G, a measure of distal airways function) were plotted.
RESULTS
HDM/CIH-treated animals demonstrated the highest reactivity to Mch in R and E compared to all other groups (HDM/NORM, SAL/CIH and SAL/NORM p < 0.05 for all comparisons, for doses 5-7 for R, and for doses 4-7 for E). The enhanced R response was due to an increase in G (doses 4-7, p < 0.05 for comparisons to all other groups), whereas R was not affected by CIH.
CONCLUSIONS
In rats chronically challenged with HDM, concurrent CIH exposure induces AHR primarily in the distal airways, which affects the respiratory system frequency-dependent elastic properties.
Topics: Rats; Animals; Pyroglyphidae; Allergens; Respiratory Hypersensitivity; Lung; Hypoxia; Methacholine Chloride; Inflammation; Sleep Apnea, Obstructive; Disease Models, Animal
PubMed: 37468919
DOI: 10.1186/s12931-023-02493-4 -
PloS One 2023People experiencing asthma exacerbations are at increased risk of cardiovascular events. To better understand the relationship between asthma exacerbations and... (Randomized Controlled Trial)
Randomized Controlled Trial
BACKGROUND
People experiencing asthma exacerbations are at increased risk of cardiovascular events. To better understand the relationship between asthma exacerbations and cardiovascular risk, this randomized case-control, cross-over controlled trial assessed the immediate systemic inflammatory and vascular responses to acutely induced pulmonary inflammation and bronchoconstriction in people with asthma and controls.
METHODS
Twenty-six people with asthma and 25 controls underwent three airway challenges (placebo, mannitol, and methacholine) in random order. Markers of cardiovascular risk, including serum C-reactive protein, interleukin-6, and tumor necrosis factor, endothelial function (flow-mediated dilation), microvascular function (blood-flow following reactive hyperemia), and arterial stiffness (pulse wave velocity) were evaluated at baseline and within one hour following each challenge. The systemic responses in a) asthma/control and b) positive airway challenges were analyzed. (ClinicalTrials.gov reg# NCT02630511).
RESULTS
Both the mannitol and methacholine challenges resulted in clinically significant reductions in forced expiratory volume in 1 second (FEV1) in asthma (-7.6% and -17.9%, respectively). Following positive challenges, reduction in FEV1 was -27.6% for methacholine and -14.2% for mannitol. No meaningful differences in predictors of cardiovascular risk were observed between airway challenges regardless of bronchoconstrictor response.
CONCLUSION
Neither acutely induced bronchoconstriction nor pulmonary inflammation and bronchoconstriction resulted in meaningful changes in systemic inflammatory or vascular function. These findings question whether the increased cardiovascular risk associated with asthma exacerbations is secondary to acute bronchoconstriction or inflammation, and suggest that other factors need to be further evaluated such as the cardiovascular impacts of short-acting inhaled beta-agonists.
Topics: Humans; Methacholine Chloride; Cardiovascular Diseases; Pulse Wave Analysis; Risk Factors; Asthma; Bronchoconstriction; Bronchial Provocation Tests; Forced Expiratory Volume
PubMed: 37459335
DOI: 10.1371/journal.pone.0288623 -
The Journal of Clinical Investigation Sep 2023Asthma is a chronic inflammatory disease associated with episodic airway narrowing. Inhaled β2-adrenergic receptor (β2AR) agonists (β2-agonists) promote - with...
Asthma is a chronic inflammatory disease associated with episodic airway narrowing. Inhaled β2-adrenergic receptor (β2AR) agonists (β2-agonists) promote - with limited efficacy - bronchodilation in asthma. All β2-agonists are canonical orthosteric ligands that bind the same site as endogenous epinephrine. We recently isolated a β2AR-selective positive allosteric modulator (PAM), compound-6 (Cmpd-6), which binds outside of the orthosteric site and modulates orthosteric ligand functions. With the emerging therapeutic potential of G-protein coupled receptor allosteric ligands, we investigated the impact of Cmpd-6 on β2AR-mediated bronchoprotection. Consistent with our findings using human β2ARs, Cmpd-6 allosterically potentiated β2-agonist binding to guinea pig β2ARs and downstream signaling of β2ARs. In contrast, Cmpd-6 had no such effect on murine β2ARs, which lack a crucial amino acid in the Cmpd-6 allosteric binding site. Importantly, Cmpd-6 enhanced β2 agonist-mediated bronchoprotection against methacholine-induced bronchoconstriction in guinea pig lung slices, but - in line with the binding studies - not in mice. Moreover, Cmpd-6 robustly potentiated β2 agonist-mediated bronchoprotection against allergen-induced airway constriction in lung slices obtained from a guinea pig model of allergic asthma. Cmpd-6 similarly enhanced β2 agonist-mediated bronchoprotection against methacholine-induced bronchoconstriction in human lung slices. Our results highlight the potential of β2AR-selective PAMs in the treatment of airway narrowing in asthma and other obstructive respiratory diseases.
Topics: Humans; Mice; Animals; Guinea Pigs; Methacholine Chloride; Ligands; Asthma; Lung; Binding Sites; Receptors, Adrenergic, beta-2
PubMed: 37432742
DOI: 10.1172/JCI167337 -
The Journal of Allergy and Clinical... Nov 2023Exposure to certain agents in the workplace can trigger occupational asthma or work-exacerbated asthma, both of which come under the heading of work-related asthma...
BACKGROUND
Exposure to certain agents in the workplace can trigger occupational asthma or work-exacerbated asthma, both of which come under the heading of work-related asthma (WRA). Understanding the burden that WRA represents can help in the management of these patients.
OBJECTIVE
To assess the influence of occupation on asthma in real life and analyze the characteristics of patients with WRA included in an asthma cohort.
METHODS
This was a prospective multicenter study of a cohort of consecutive patients with asthma. A standardized clinical history was completed. Patients were classified as having WRA or non-WRA. All patients underwent respiratory function tests, FeNO test, and methacholine challenge (methacholine concentration that causes a 20% drop in FEV) at the beginning of the study. They were classified into two groups, depending on their employment status: employed (group 1) or unemployed (group 2).
RESULTS
Of the 480 patients included in the cohort, 82 (17%) received the diagnosis of WRA. Fifty-seven patients (70%) were still working. Mean age (SD) was 46 (10.69) years in group 1 and 57 (9.91) years in group 2 (P < .0001). Significant differences were observed in adherence to treatment (64.9% in group 1 vs 88% in group 2; P = .0354) and in severe asthma exacerbations (35.7% in group 1 vs 0% in group 2; P = .0172). No significant differences were observed in the rest of the variables analyzed.
CONCLUSIONS
The burden of WRA in specialized asthma units is not negligible. The absence of differences in the severity of asthma, the treatment administered, alterations in lung function, and the number of exacerbations in those working versus not working may support the idea that advice regarding changing jobs should be customized for individual patients.
Topics: Humans; Middle Aged; Asthma, Occupational; Bronchial Provocation Tests; Methacholine Chloride; Occupational Diseases; Occupational Exposure; Prospective Studies; Adult
PubMed: 37391017
DOI: 10.1016/j.jaip.2023.06.040 -
Experimental Physiology Aug 2023What is the central question of this study? The lung response to inhaled methacholine is reputed to be greater in male than in female mice. The underpinnings of this sex...
NEW FINDINGS
What is the central question of this study? The lung response to inhaled methacholine is reputed to be greater in male than in female mice. The underpinnings of this sex disparity are ill defined. What is the main finding and its importance? We demonstrated that male airways exhibit a greater content of airway smooth muscle than female airways. We also found that, although a more muscular airway tree in males might contribute to their greater responsiveness to inhaled methacholine than females, it might also curb the heterogeneity in small airway narrowing.
ABSTRACT
Mouse models are helpful in unveiling the mechanisms underlying sex disparities in asthma. In comparison to their female counterparts, male mice are hyperresponsive to inhaled methacholine, a cardinal feature of asthma that contributes to its symptoms. The physiological details and the structural underpinnings of this hyperresponsiveness in males are currently unknown. Herein, BALB/c mice were exposed intranasally to either saline or house dust mite once daily for 10 consecutive days to induce experimental asthma. Twenty-four hours after the last exposure, respiratory mechanics were measured at baseline and after a single dose of inhaled methacholine that was adjusted to trigger the same degree of bronchoconstriction in both sexes (it was twice as high in females). Bronchoalveolar lavages were then collected, and the lungs were processed for histology. House dust mite increased the number of inflammatory cells in bronchoalveolar lavages to the same extent in both sexes (asthma, P = 0.0005; sex, P = 0.96). The methacholine response was also markedly increased by asthma in both sexes (e.g., P = 0.0002 for asthma on the methacholine-induced bronchoconstriction). However, for a well-matched bronchoconstriction between sexes, the increase in hysteresivity, an indicator of airway narrowing heterogeneity, was attenuated in males for both control and asthmatic mice (sex, P = 0.002). The content of airway smooth muscle was not affected by asthma but was greater in males (asthma, P = 0.31; sex, P < 0.0001). These results provide further insights regarding an important sex disparity in mouse models of asthma. The increased amount of airway smooth muscle in males might contribute functionally to their greater methacholine response and, possibly, to their decreased propensity for airway narrowing heterogeneity.
Topics: Male; Female; Animals; Mice; Methacholine Chloride; Asthma; Lung; Bronchoconstriction; Muscle, Smooth
PubMed: 37341687
DOI: 10.1113/EP091236 -
The Journal of Asthma : Official... Dec 2023Remission of childhood asthma has not been widely studied. Patients in clinical remission continue to have some degree of bronchial hyperresponsiveness (BHR). The aim of...
OBJECTIVE
Remission of childhood asthma has not been widely studied. Patients in clinical remission continue to have some degree of bronchial hyperresponsiveness (BHR). The aim of this study was to investigate whether clinical parameters and lung function test are good parameters for discontinuation of inhaled corticosteroids (ICS) in asthmatic children, including patients with persistent BHR, as measured by the methacholine challenge test (MCT).
METHODS
One year after discontinuation of inhaled corticosteroids (ICS), MCT was performed in a group of 40 asthmatic children to confirm or exclude BHR. In all patients, ICS treatment was discontinued based on the same parameters: symptoms, spirometry, daily PEF, and negative bronchodilator test. After achieving complete asthma control for at least 6 to 12 months, ICS treatment was stepped down and discontinued. Clinical course and spirometry were followed up after ICS discontinuation.
RESULTS
Positive MCT was found in 50% of the patients. There was no statistically significant difference between the positive and negative MCT groups in age at initiation and discontinuation of ICS therapy, duration of ICS therapy, duration of stepping down period, FEV1, and PEF at the time of withdrawal of ICS and one year later. ICS treatment had to be restarted in two patients from the positive MCT group, due to recurrence of asthma symptoms.
CONCLUSION
Clinical parameters, normal spirometry, daily PEF values, and a negative bronchodilator test are good parameters for discontinuing ICS treatment in asthmatic children, even in patients with persistent BHR. Children should continue to be monitored, as symptoms may recur.
Topics: Humans; Child; Asthma; Bronchodilator Agents; Adrenal Cortex Hormones; Bronchial Hyperreactivity; Methacholine Chloride; Bronchial Provocation Tests; Administration, Inhalation
PubMed: 37262011
DOI: 10.1080/02770903.2023.2220795 -
American Journal of Respiratory Cell... Aug 2023Asthma is a heterogeneous chronic airway disease with an unmet need for improved therapeutics in uncontrolled severe disease. The calcium-sensing receptor (CaSR) is a G...
Asthma is a heterogeneous chronic airway disease with an unmet need for improved therapeutics in uncontrolled severe disease. The calcium-sensing receptor (CaSR) is a G protein-coupled receptor upregulated in asthma. The CaSR agonist, spermine, is also increased in asthmatic airways and contributes to bronchoconstriction. CaSR negative allosteric modulators (NAMs) oppose chronic airway inflammation, remodeling, and hyperresponsiveness in murine and guinea pig asthma models, but whether CaSR NAMs are effective acute bronchodilators compared with standard of care has not yet been established. Furthermore, the ability of different classes of NAMs to inhibit spermine-induced CaSR signaling or methacholine (MCh)-induced airway contraction has not been quantified. Here, we show CaSR NAMs differentially inhibit spermine-induced intracellular calcium mobilization and inositol monophosphate accumulation in HEK293 cells stably expressing the CaSR. NAMs reverse MCh-mediated airway contraction in mouse precision-cut lung slices with similar maximal relaxation compared with the standard treatment, salbutamol. Of note, the bronchodilator effects of CaSR NAMs are maintained under conditions of β-adrenergic receptor desensitization when salbutamol efficacy is abolished. Furthermore, overnight treatment with some, but not all, CaSR NAMs prevents MCh-mediated bronchoconstriction. These findings further support the CaSR as a putative drug target and NAMs as alternative or adjunct bronchodilators in asthma.
Topics: Mice; Humans; Animals; Guinea Pigs; Bronchodilator Agents; Receptors, Calcium-Sensing; HEK293 Cells; Spermine; Asthma; Albuterol; Methacholine Chloride
PubMed: 37098022
DOI: 10.1165/rcmb.2021-0544OC -
Automated, high temporal resolution mechanics measurements during incubation of contractile tissues.Journal of Biomechanics May 2023Muscle tissue mechanics and contractility measurements have a great advantage over cultured cell level experiments as their mechanical and contractile properties are...
Muscle tissue mechanics and contractility measurements have a great advantage over cultured cell level experiments as their mechanical and contractile properties are much closer to in vivo tissue properties. However, tissue level experiments cannot be combined with incubation with the same time resolution and consistency as cell culture studies. Here we present a system in which contractile tissues can be incubated for days while intermittently being tested for their mechanical and contractile properties. A two-chamber system was developed with control of temperature in the outer chamber and CO and humidity control in the inner, sterile chamber. Incubation medium, to which biologically active components may be added, is reused after each mechanics test to preserve both added and released components. Mechanics and contractility are measured in a different medium to which, through a high accuracy syringe pump, up to 6 different agonists in a 100-fold dose range can be added. The whole system can be operated through fully automated protocols from a personal computer. Testing data shows accurate maintenance of temperature, CO and relative humidity at pre-set levels. Equine trachealis smooth muscle tissues tested in the system showed no signs of infection after 72 h with incubation medium replacement every 24 h. Methacholine dosing and electrical field stimulation every 4 h showed consistent responses. In conclusion, the developed system is a great improvement on the manual incubation techniques being used thus far, improving on time resolution, repeatability and robustness, while reducing contamination risk and tissue damage from repeated handling.
Topics: Animals; Horses; Carbon Dioxide; Muscle, Smooth; Muscle Contraction; Methacholine Chloride; Cells, Cultured
PubMed: 37058766
DOI: 10.1016/j.jbiomech.2023.111577