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American Journal of Physiology. Lung... Dec 2021Increased insulin is associated with obesity-related airway hyperreactivity and asthma. We tested whether the use of metformin, an antidiabetic drug used to reduce...
Increased insulin is associated with obesity-related airway hyperreactivity and asthma. We tested whether the use of metformin, an antidiabetic drug used to reduce insulin resistance, can reduce circulating insulin, thereby preventing airway hyperreactivity in rats with dietary obesity. Male and female rats were fed a high- or low-fat diet for 5 wk. Some male rats were simultaneously treated with metformin (100 mg/kg orally). In separate experiments, after 5 wk of a high-fat diet, some rats were switched to a low-fat diet, whereas others continued a high-fat diet for an additional 5 wk. Bronchoconstriction and bradycardia in response to bilateral electrical vagus nerve stimulation or to inhaled methacholine were measured in anesthetized and vagotomized rats. Body weight, body fat, caloric intake, fasting glucose, and insulin were measured. Vagally induced bronchoconstriction was potentiated only in male rats on a high-fat diet. Males gained more body weight, body fat, and had increased levels of fasting insulin compared with females. Metformin prevented development of vagally induced airway hyperreactivity in male rats on high-fat diet, in addition to inhibiting weight gain, fat gain, and increased insulin. In contrast, switching rats to a low-fat diet for 5 wk reduced body weight and body fat, but it did not reverse fasting glucose, fasting insulin, or potentiation of vagally induced airway hyperreactivity. These data suggest that medications that target insulin may be effective treatment for obesity-related asthma.
Topics: Animals; Asthma; Bronchial Hyperreactivity; Bronchoconstriction; Bronchoconstrictor Agents; Diet, High-Fat; Female; Glucose; Hyperinsulinism; Hypoglycemic Agents; Male; Metformin; Methacholine Chloride; Obesity; Rats; Rats, Sprague-Dawley; Vagus Nerve; Weight Gain
PubMed: 34668415
DOI: 10.1152/ajplung.00202.2021 -
Journal of Applied Physiology... Dec 2021Late-onset nonallergic (LONA) asthma in obesity is characterized by increased peripheral airway closure secondary to abnormally collapsible airways. We hypothesized that...
Late-onset nonallergic (LONA) asthma in obesity is characterized by increased peripheral airway closure secondary to abnormally collapsible airways. We hypothesized that positive expiratory pressure (PEP) would mitigate the tendency to airway closure during bronchoconstriction, potentially serving as rescue therapy for LONA asthma of obesity. The PC [provocative concentration of methacholine causing 20% drop in forced expiratory volume in 1 s (FEV1)] dose of methacholine was determined in 18 obese participants with LONA asthma. At each of four subsequent visits, we used oscillometry to measure input respiratory impedance (Z) over 8 min; participants received their PC concentration of methacholine aerosol during the first 4.5 min. PEP combinations of either 0 or 10 cmHO either during and/or after the methacholine delivery were applied, randomized between visits. Parameters characterizing respiratory system mechanics were extracted from the Z spectra. In 18 patients with LONA asthma [14 females, body mass index (BMI): 39.6 ± 3.4 kg/m], 10 cmHO PEP during methacholine reduced elevations in the central airway resistance, peripheral airway resistance, and elastance, and breathing frequency was also reduced. During the 3.5 min following methacholine delivery, PEP of 10 cmHO reduced A and peripheral elastance compared with no PEP. PEP mitigates the onset of airway narrowing brought on by methacholine challenge and airway closure once it is established. PEP thus might serve as a nonpharmacological therapy to manage acute airway narrowing for obese LONA asthma. Standard pharmacological treatments are not effective in people with obesity and asthma. We assessed the efficacy of positive expiratory pressure (PEP) as a therapy to mitigate airway hyperresponsiveness in the asthma of obesity. Our results indicate that PEP might serve as a nonpharmacological therapy to manage acute airway narrowing in obese individuals with late-onset nonallergic asthma.
Topics: Asthma; Bronchial Provocation Tests; Bronchoconstriction; Female; Forced Expiratory Volume; Humans; Methacholine Chloride; Obesity
PubMed: 34647827
DOI: 10.1152/japplphysiol.00399.2021 -
BioMed Research International 2021Exposure of the respiratory system to the L3 crude extract (AE) induces airway inflammation; however, the mechanism underlying this inflammatory response remains...
Exposure of the respiratory system to the L3 crude extract (AE) induces airway inflammation; however, the mechanism underlying this inflammatory response remains unknown. AE contains allergens that promote allergic inflammation; exposure to AE may potentially lead to asthma. In this study, we aimed to establish a murine model to assess the effects of AE on characteristic features of chronic asthma, including airway hypersensitivity (AHR), airway inflammation, and airway remodeling. Mice were sensitized for five consecutive days each week for 4 weeks. AHR, lung inflammation, and airway remodeling were evaluated 24 h after the last exposure. Lung inflammation and airway remodeling were assessed from the bronchoalveolar lavage fluid (BALF). To confirm the immune response in the lungs, changes in gene expression in the lung tissue were assessed with reverse transcription-quantitative PCR. The levels of IgE, IgG1, and IgG2a in blood and cytokine levels in the BALF, splenocyte, and lung lymph node (LLN) culture supernatant were measured with ELISA. An increase in AHR was prominently observed in AE-exposed mice. Epithelial proliferation and infiltration of inflammatory cells were observed in the BALF and lung tissue sections. Collagen deposition was detected in lung tissues. AE exposure increased , , and expression in the lung, as well as the levels of antibodies specific to AE. IL-4, IL-5, and IL-13 were upregulated only in LLN. These findings indicate that an increase in IL-4 CD4 T cells in the LLN and splenocyte resulted in increased Th2 response to AE exposure. Exposure of the respiratory system to AE resulted in an increased allergen-induced Th2 inflammatory response and AHR through accumulation of inflammatory and IL-4 CD4 T cells and collagen deposition. It was confirmed that plays an essential role in causing asthma in mouse models and has the potential to cause similar effects in humans.
Topics: Airway Remodeling; Animals; Anisakis; Antibody Specificity; Biomarkers; Bronchial Hyperreactivity; Cytokines; Disease Models, Animal; Inflammation Mediators; Lung; Methacholine Chloride; Mice, Inbred BALB C; Pneumonia; Th2 Cells; Mice
PubMed: 34580637
DOI: 10.1155/2021/2522305 -
Investigative Ophthalmology & Visual... Sep 2021The functional characteristics of receptors that regulate lacrimal gland myoepithelial cells are still somewhat unclear. To date, mainly muscarinic receptors have been...
PURPOSE
The functional characteristics of receptors that regulate lacrimal gland myoepithelial cells are still somewhat unclear. To date, mainly muscarinic receptors have been of interest; however, further knowledge is needed regarding their expression and functional roles. For this purpose, primary cultures of rat lacrimal gland myoepithelial cells were established and examined functionally.
METHODS
Rat lacrimal glands were excised, minced, and further digested, yielding mixtures of cells that were seeded in culturing flasks. After 4-6 weeks, primary monocultures of myoepithelial cells were established, verified by immunocytochemistry. The cells were stained for all muscarinic receptor subtypes (M1-M5) and examined functionally regarding intracellular [Ca2+] responses upon activation of muscarinic receptors. For methodological verification, purinergic functional responses were also studied.
RESULTS
Expression of muscarinic receptor subtypes M2-M5 was detected, whereas expression of muscarinic M1 receptors could not be shown. Activation of muscarinic receptors by the non-selective muscarinic agonist methacholine (3 × 10-11-10-3 M) did not cause a significant increase in intracellular [Ca2+]. However, activation of purinergic receptors by the non-selective purinergic agonist ATP (10-8-10-3 M) caused a concentration-dependent increase in intracellular [Ca2+] that could be blocked by the P2 antagonists PPADS and suramin.
CONCLUSIONS
Primary cultures of rat lacrimal gland myoepithelial cells were established that displayed a heterogeneous expression of muscarinic receptors. Purinergic functional responses demonstrated a viable cell population. Upon treatment with methacholine, no significant increase in intracellular [Ca2+] could be detected, indicating that cholinergic activation of myoepithelial cells occurs via other intracellular messengers or is dependent on interaction with other cell types.
Topics: Adenosine Triphosphate; Animals; Calcium; Cells, Cultured; Dose-Response Relationship, Drug; Epithelial Cells; Immunohistochemistry; Lacrimal Apparatus; Male; Methacholine Chloride; Muscarinic Agonists; Rats; Rats, Sprague-Dawley; Receptors, Muscarinic; Receptors, Purinergic
PubMed: 34546325
DOI: 10.1167/iovs.62.12.19 -
International Journal of Molecular... Aug 2021In this study we assessed the effects of antigen exposure in mice pre-sensitized with allergen following viral infection on changes in lung function, cellular responses...
In this study we assessed the effects of antigen exposure in mice pre-sensitized with allergen following viral infection on changes in lung function, cellular responses and tight junction expression. Female BALB/c mice were sensitized to ovalbumin and infected with influenza A before receiving a second ovalbumin sensitization and challenge with saline, ovalbumin (OVA) or house dust mite (HDM). Fifteen days post-infection, bronchoalveolar inflammation, serum antibodies, responsiveness to methacholine and barrier integrity were assessed. There was no effect of infection alone on bronchoalveolar lavage cellular inflammation 15 days post-infection; however, OVA or HDM challenge resulted in increased bronchoalveolar inflammation dominated by eosinophils/neutrophils or neutrophils, respectively. Previously infected mice had higher serum OVA-specific IgE compared with uninfected mice. Mice previously infected, sensitized and challenged with OVA were most responsive to methacholine with respect to airway resistance, while HDM challenge caused significant increases in both tissue damping and tissue elastance regardless of previous infection status. Previous influenza infection was associated with decreased claudin-1 expression in all groups and decreased occludin expression in OVA or HDM-challenged mice. This study demonstrates the importance of the respiratory epithelium in pre-sensitized individuals, where influenza-infection-induced barrier disruption resulted in increased systemic OVA sensitization and downstream effects on lung function.
Topics: Airway Resistance; Animals; Bronchial Hyperreactivity; Claudin-1; Down-Regulation; Female; Influenza A virus; Methacholine Chloride; Mice; Mice, Inbred BALB C; Orthomyxoviridae Infections; Ovalbumin; Pyroglyphidae; Treatment Outcome
PubMed: 34445491
DOI: 10.3390/ijms22168790 -
Frontiers in Physiology 2021The contractility of airway smooth muscle (ASM) is labile. Although this feature can greatly modulate the degree of airway responsiveness , the extent by which ASM's...
The contractility of airway smooth muscle (ASM) is labile. Although this feature can greatly modulate the degree of airway responsiveness , 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 , 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.
PubMed: 34267677
DOI: 10.3389/fphys.2021.698019 -
Respiratory Medicine Sep 2021Bronchial hyperresponsiveness (BHR) is a key pathophysiological feature of asthma. Methacholine challenge test (MCT) is a common bronchoprovocation test useful for...
BACKGROUND
Bronchial hyperresponsiveness (BHR) is a key pathophysiological feature of asthma. Methacholine challenge test (MCT) is a common bronchoprovocation test useful for confirming a diagnosis of asthma. Studies of BHR in the general population of Asian countries are rare.
AIM
To estimate prevalence and determinants of BHR in Hanoi, Vietnam, and to study the association between BHR and symptoms common in asthma and previously diagnosed asthma.
METHODS
1500 out of 5872 randomly selected adults in urban and rural Hanoi, who had participated in a questionnaire survey (83% participated), were randomly selected and invited to clinical examinations. Totally 684 subjects (46%) participated. MCT was performed in 366 subjects. BHR was defined as a FEV-decrease of ≥20% from baseline following methacholine inhalations (PC). Cut offs used in the analyses were PC ≤ 1 mg/ml, ≤2 mg/ml and ≤8 mg/ml.
RESULTS
The prevalence of BHR was 16.4% at doses ≤8 mg/ml, while 9.6% reacted on doses ≤2 mg/ml. PC ≤ 2 mg/ml was associated with FEV <80% of predicted. PC ≤ 2 mg/ml, but not PC ≤ 8 mg/ml, was associated with multi-sensitization to airborne allergens. BHR defined as PC ≤ 8 mg/ml was associated with age >45y. The combination of asthmatic wheeze (wheezing with breathlessness apart from colds) and BHR, irrespectively of magnitude of BHR, was more common than the combination of BHR with previously diagnosed asthma.
CONCLUSIONS
The results indicate BHR to be more common in Hanoi than previously found in south-east Asia. Although the prevalence of physician diagnosed asthma has increased in Vietnam, our results indicate that asthma still may be underdiagnosed in Vietnam.
Topics: Adult; Asthma; Bronchial Hyperreactivity; Bronchial Provocation Tests; Female; Forced Expiratory Volume; Humans; Male; Methacholine Chloride; Middle Aged; Prevalence; Surveys and Questionnaires; Vietnam
PubMed: 34246130
DOI: 10.1016/j.rmed.2021.106513 -
Biosensors & Bioelectronics Oct 2021The methacholine challenge test is considered to be the gold standard bronchoprovocation test used to diagnose asthma, and this test is always performed in pulmonary...
The methacholine challenge test is considered to be the gold standard bronchoprovocation test used to diagnose asthma, and this test is always performed in pulmonary function labs or doctors' offices. Methacholine (MCH) acts by inducing airway tightening/bronchoconstriction, and more importantly, MCH is hydrolyzed by cholinesterase enzyme (ChE). Recently, the American Thoracic Society raised concerns about pulmonary function testing during the COVID-19 pandemic due to recently reported correlation between cholinesterase and COVID-19 pneumonia severity/mortality, and it was shown that cholinesterase levels are reduced in the acute phase of severe COVID-19 pneumonia. This work describes the microfabrication of potentiometric sensors using copper as the substrate and chemically polymerized graphene nanocomposites as the transducing layer for tracking the kinetics of MCH enzymatic degradation in real blood samples. The in-vitro estimation of the characteristic parameters of the MCH metabolism [Michaelis-Menten constant (K) and reaction velocity (V)] were found to be 241.041 μM and 56.8 μM/min, respectively. The proposed sensor is designed to be used as a companion diagnostic device that can (i) answer questions about patient eligibility to perform methacholine challenge tests, (ii) individualize/personalize medical dosing of methacholine, (iii) provide portable and inexpensive devices allowing automated readouts without the need for operator intervention (iv) recommend therapeutic interventions including intensive care during early stages and reflecting the disease state of COVID-19 pneumonia. We hope that this methacholine electrochemical sensor will help in assaying ChE activity in a "timely" manner and predict the severity and prognosis of COVID-19 to improve treatment outcomes and decrease mortality.
Topics: Biosensing Techniques; Bronchoconstrictor Agents; COVID-19; Humans; Methacholine Chloride; Pandemics; SARS-CoV-2
PubMed: 34166943
DOI: 10.1016/j.bios.2021.113439 -
Investigative Ophthalmology & Visual... Jun 2021Patients that medicate with antidepressants commonly report dryness of eyes. The cause is often attributed to the anticholinergic properties of the drugs. However,...
PURPOSE
Patients that medicate with antidepressants commonly report dryness of eyes. The cause is often attributed to the anticholinergic properties of the drugs. However, regulation of tear production includes a substantial reflex-evoked component and is regulated via distinct centers in the brain. Further, the anticholinergic component varies greatly among antidepressants with different mechanisms of action. In the current study it was wondered if acute administration of antidepressants can disturb production of tears by affecting the afferent and/or central pathway.
METHODS
Tear production was examined in vivo in anesthetized rats in the presence or absence of the tricyclic antidepressant (TCA) clomipramine or the selective serotonin reuptake inhibitor (SSRI) escitalopram. The reflex-evoked production of tears was measured by challenging the surface of the eye with menthol (0.1 mM) and cholinergic regulation was examined by intravenous injection with the nonselective muscarinic agonist methacholine (1-5 µg/kg).
RESULTS
Acute administration of clomipramine significantly attenuated both reflex-evoked and methacholine-induced tear production. However, escitalopram only attenuated reflex-evoked tear production, while methacholine-induced production of tears remained unaffected.
CONCLUSIONS
This study shows that antidepressants with different mechanisms of action can impair tear production by attenuating reflex-evoked signaling. Further, antimuscarinic actions are verified as a likely cause of lacrimal gland hyposecretion in regard to clomipramine but not escitalopram. Future studies on antidepressants with different selectivity profiles and mechanisms of action are required to further elucidate the mechanisms by which antidepressants affect tear production.
Topics: Animals; Antidepressive Agents; Cholinergic Antagonists; Citalopram; Clomipramine; Dry Eye Syndromes; Evoked Potentials, Visual; Lacrimal Apparatus; Methacholine Chloride; Miotics; Rats; Tears
PubMed: 34096973
DOI: 10.1167/iovs.62.7.8 -
Respiratory Physiology & Neurobiology Oct 2021Balb/c mice respiratory mechanics was studied in two intravenous methacholine (MCh) protocols: bolus and continuous infusion. The Constant Phase Model (CPM) was used in...
Balb/c mice respiratory mechanics was studied in two intravenous methacholine (MCh) protocols: bolus and continuous infusion. The Constant Phase Model (CPM) was used in this study. The harmonic distortion index (k) was used to assess the respiratory system nonlinearity. The analysis of variance showed difference between groups (OVA vs control) and among doses for both protocols. Bolus protocol posttest: there was a difference between OVA and control at 0.3 and 1 mg/kg doses (p<0.0001 and p<0.001) for R. Infusion: there was a difference between OVA and control at 192 μg.kg.min dose for R, G and H, (p<0.01; p<0.001; p<0.001). An increment was found in k values near to the observed peak values in bolus protocol. The bolus protocol could better differentiate inflamed and non-inflamed airway resistance, whereas the differences between OVA and control in continuous infusion protocol were associated to airway- and, mainly, parenchyma-related parameters. Moreover, the bolus protocol presented a higher nonlinear degree compared to the infusion protocol.
Topics: Animals; Asthma; Bronchoconstrictor Agents; Disease Models, Animal; Male; Methacholine Chloride; Mice; Mice, Inbred BALB C; Models, Theoretical; Respiratory Mechanics
PubMed: 34062282
DOI: 10.1016/j.resp.2021.103705