Altered Airway Responsiveness Research Articles

Electronic smoking devices: a dangerous hobby for children and adolescents. A review

The bandwagon for electronic smoking devices among children and adolescents is currently epidemic-like. This is due to the misconception supported by manufacturers about the alleged safety of e-cigarettes and vapes compared to tobacco smoking. However, to date, it has been established that the use of electronic smoking devices, on the contrary, leads to an increase in nicotine dependence, increases the risk of smoking, and double consumption. The long-term health effects of inhaled aerosol from electronic smoking devices have not been thoroughly studied. However, studies showed its cytotoxic and immunosuppressive effects, the ability to drive inflammation and oxidative stress, impair mucociliary clearance, alter airway reactivity, cause DNA damage, and hamper its repair. The association between the use of electronic smoking devices and asthma has been shown. The potential adverse health effects of e-cigarettes need to be carefully studied, especially in children and adolescents.

Perioperative Care of the Pediatric Patient and an Algorithm for the Treatment of Intraoperative Bronchospasm.

Asthma remains a common comorbid condition in patients presenting for anesthetic care. As a chronic inflammatory disease of the airway, asthma is known to increase the risk of intraoperative bronchospasm. As the incidence and severity of asthma and other chronic respiratory conditions that alter airway reactivity is increasing, a greater number of patients at risk for perioperative bronchospasm are presenting for anesthetic care. As bronchospasm remains one of the more common intraoperative adverse events, recognizing and mitigating preoperative risk factors and having a pre-determined treatment algorithm for acute events are essential to ensuring effective resolution of this intraoperative emergency. The following article reviews the perioperative care of pediatric patients with asthma, discusses modifiable risk factors for intraoperative bronchospasm, and outlines the differential diagnosis of intraoperative wheezing. Additionally, a treatment algorithm for intraoperative bronchospasm is suggested.

Influence of the early-life gut microbiota on the immune responses to an inhaled allergen.

Antibiotics, among the most used medications in children, affect gut microbiome communities and metabolic functions. These changes in microbiota structure can impact host immunity. We hypothesized that early-life microbiome alterations would lead to increased susceptibility to allergy and asthma. To test this, mouse pups between postnatal days 5-9 were orally exposed to water (control) or to therapeutic doses of azithromycin or amoxicillin. Later in life, these mice were sensitized and challenged with a model allergen, house dust mite (HDM), or saline. Mice with early-life azithromycin exposure that were challenged with HDM had increased IgE and IL-13 production by CD4+ T cells compared to unexposed mice; early-life amoxicillin exposure led to fewer abnormalities. To test that the microbiota contained the immunological cues to alter IgE and cytokine production after HDM challenge, germ-free mice were gavaged with fecal samples of the antibiotic-perturbed microbiota. Gavage of adult germ-free mice did not result in altered HDM responses, however, their offspring, which acquired the antibiotic-perturbed microbiota at birth showed elevated IgE levels and CD4+ cytokines in response to HDM, and altered airway reactivity. These studies indicate that early-life microbiota composition can heighten allergen-driven Th2/Th17 immune pathways and airway responses in an age-dependent manner.

Seasonal dynamics of cold airway hyperresponsiveness in patients with asthma

Introduction. Cold air-induced bronchoconstriction in patients with asthma, leading to a breakdown in disease control, is one of the most serious problems in the northern countries of the world.Aim. To assess the seasonal dynamics of the airway response (ΔFEV1CA) to cold bronchoprovocation in asthma patients with cold airway hyperresponsiveness (CAHR).Materials and methods. Out of 513 asthma patients who underwent primary bronchoprovocation testing, 273 patients (140 women; 133 men) with diagnosed CAHR took part in the retrospective analysis. The design objectification of clinical data using the Asthma Control Test questionnaire (ACT, Quality Metric Inc., 2002), a screening questionnaire for identifying clinical symptoms of response to low ambient temperature in everyday life; assessment of the lung function; bronchoprovocation test of 3-minute isocapnic hyperventilation with cold (-20ºC) air (IHCA).Results. At the time of testing, the average age of patients was 34.8±0.87 years, FEV1 88.5±1.3% of predicted, FEV1/VC 70.9±0.7%; ACT 16 (12; 19) points. On average in the group, ΔFEV1CA was -19.2±0.6%. The frequency of CAHR detection in the winter was 22%, spring – 34%, summer – 22%, autumn – 24% (p>0.05). The minimum changes in FEV1 in response to IHCA were recorded in May-June (mean value ΔFEV1CA -16.2±1.3 and -14.5±1.6%, respectively) and were significantly less in comparison with February (-21.9±2.3%, p˂0.05) and April (-23.0±2.36%, p˂0.01). A correlation has been found between the monthly mean values of meteorological parameters and CAHR, as well as the value of ACT in points and ΔFEV1 (r=0.16; p=0.018).Conclusion. Seasonal changes in the strength of the action of meteorological factors produce a change in the response of the airways to cold bronchoprovocation, and contribute to the loss of asthma control. The maximum values of CAHR fall on February-April, August, November. The data obtained reflect the presence of a complex interaction of physical environmental factors in the induction of seasonal fluctuations of CAHR, which requires a search for specific mechanisms for the formation of altered airway reactivity associated with the characteristics of molecular reception of low temperatures and humidity in the human airways.

Intrauterine Growth Restriction Promotes Postnatal Airway Hyperresponsiveness Independent of Allergic Disease

Introduction: Intrauterine growth restriction (IUGR) is associated with asthma. Murine models of IUGR have altered airway responsiveness in the absence of any inflammatory exposure. Given that a primary feature of asthma is airway inflammation, IUGR-affected individuals may develop more substantial respiratory impairment if subsequently exposed to an allergen. This study used a maternal hypoxia-induced mouse model of IUGR to determine the combined effects of IUGR and allergy on airway responsiveness.Methods: Pregnant BALB/c mice were housed under hypoxic conditions (10.5% O2) from gestational day (GD) 11-GD 17.5 (IUGR group; term = GD 21). Following hypoxic exposure, mice were returned to a normoxic environment (21% O2). A second group of pregnant mice were housed under normoxic conditions throughout pregnancy (Control). All offspring were sensitized to ovalbumin (OVA) and assigned to one of four treatment groups: Control – normoxic and saline challenge; IUGR – hypoxic and saline challenge; Allergy – normoxic and OVA challenge; and IUGR + Allergy – hypoxic and OVA challenge. At 8 weeks of age, and 24 h post-aerosol challenge, mice were tracheostomised for methacholine challenge and assessment of lung mechanics by the forced oscillation technique, and lungs subsequently fixed for morphometry.Results: IUGR offspring were lighter than Control at birth and in adulthood. Both Allergy and IUGR independently increased airway resistance after methacholine challenge. The IUGR group also exhibited an exaggerated increase in tissue damping and elastance after methacholine challenge compared with Control. However, there was no incremental effect on airway responsiveness in the combined IUGR + Allergy group. There was no impact of IUGR or Allergy on airway structure and no effect of sex on any outcome.Conclusion: IUGR and aeroallergen independently increased bronchoconstrictor response, but when combined the pathophysiology was not worsened. Findings suggest that an association between IUGR and asthma is mediated by baseline airway responsiveness rather than susceptibility to allergen.

Prenatal Maternal Lipopolysaccharide and Mild Newborn Hyperoxia Increase Intrapulmonary Airway but Not Vessel Reactivity in a Mouse Model.

Maternal infection is a risk for preterm delivery. Preterm newborns often require supplemental oxygen to treat neonatal respiratory distress. Newborn hyperoxia exposure is associated with airway and vascular hyperreactivity, while the complications of maternal infection are variable. In a mouse model of prenatal maternal intraperitoneal lipopolysaccharide (LPS, embryonic day 18) with subsequent newborn hyperoxia (40% oxygen × 7 days) precision-cut living lung slices were used to measure intrapulmonary airway and vascular reactivity at 21 days of age. Hyperoxia increased airway reactivity to methacholine compared to room air controls. Prenatal maternal LPS did not alter airway reactivity in room air. Combined maternal LPS and hyperoxia exposures increased airway reactivity vs. controls, although maximal responses were diminished compared to hyperoxia alone. Vessel reactivity to serotonin did not significantly differ in hyperoxia or room air; however, prenatal maternal LPS appeared to attenuate vessel reactivity in room air. Following room air recovery, LPS with hyperoxia lungs displayed upregulated inflammatory and fibrosis genes compared to room air saline controls (TNFαR1, iNOS, and TGFβ). In this model, mild newborn hyperoxia increases airway but not vessel reactivity. Prenatal maternal LPS did not further increase hyperoxic airway reactivity. However, inflammatory genes remain upregulated weeks after recovery from maternal LPS and newborn hyperoxia exposures.

In Vitro Consequences of Electronic-Cigarette Flavoring Exposure on the Immature Lung

Background: The developing lung is uniquely susceptible and may be at increased risk of injury with exposure to e-cigarette constituents. We hypothesize that cellular toxicity and airway and vascular responses with exposure to flavored refill solutions may be altered in the immature lung. Methods: Fetal, neonatal, and adult ovine pulmonary artery smooth muscle cells (PASMC) were exposed to popular flavored nicotine-free e-cigarette refill solutions (menthol, strawberry, tobacco, and vanilla) and unflavored solvents: propylene glycol (PG) or vegetable glycerin (VG). Viability was assessed by lactate dehydrogenase assay. Brochodilation and vasoreactivity were determined on isolated ovine bronchial rings (BR) and pulmonary arteries (PA). Results: Neither PG or VG impacted viability of immature or adult cells; however, exposure to menthol and strawberry flavored solutions increased cell death. Neonatal cells were uniquely susceptible to menthol flavoring-induced toxicity, and all four flavorings demonstrated lower lethal doses (LD50) in immature PASMC. Exposure to flavored solutions induced bronchodilation of neonatal BR, while only menthol induced airway relaxation in adults. In contrast, PG/VG and flavored solutions did not impact vasoreactivity with the exception of menthol-induced relaxation of adult PAs. Conclusion: The immature lung is uniquely susceptible to cellular toxicity and altered airway responses with exposure to common flavored e-cigarette solutions.

Reversing Cholinergic Bronchoconstriction by Common Inotropic Agents: A Randomized Experimental Trial on Isolated Perfused Rat Lungs.

The ability of inotropic agents to alter airway reactivity and lung tissue mechanics has not been compared in a well-controlled experimental model. Therefore, we compared the potential to alter lung tissue viscoelasticity and bronchodilator effects of commonly used inotropic agents in an isolated perfused rat lung model. After achieving steady state lung perfusion, sustained bronchoconstriction was induced by acetylcholine (ACh). Isolated rat lungs were then randomly allocated to 6 groups treated with either saline vehicle (n = 8) or incremental concentrations of inotropes (adrenaline, n = 8; dopamine, n = 7; dobutamine, n = 7; milrinone, n = 8; or levosimendan, n = 6) added to the whole-blood perfusate. Airway resistance (Raw), lung tissue damping (G), and elastance were measured under baseline conditions, during steady-state ACh-induced constriction and for each inotrope dose. No change in Raw was observed after addition of the saline vehicle. Raw was significantly lower after addition of dopamine (maximum difference [95% CI] of 29 [12-46]% relative to the saline control, P = .004), levosimendan (58 [39-77]%, P < .001), and adrenaline (37 [21-53]%, P < .001), whereas no significant differences were observed at any dose of milrinone (5 [-12 to 22]%) and dobutamine (4 [-13 to 21]%). Lung tissue damping (G) was lower in animals receiving the highest doses of adrenaline (difference: 22 [7-37]%, P = .015), dobutamine (20 [5-35]%, P = .024), milrinone (20 [6-34]%, P = .026), and levosimendan (36 [19-53]%, P < .001) than in controls. Although dobutamine and milrinone did not reduce cholinergic bronchoconstriction, they reversed the ACh-induced elevations in lung tissue resistance. In contrast, adrenaline, dopamine, and levosimendan exhibited both potent bronchodilatory action against ACh and diminished lung tissue damping. Further work is needed to determine whether these effects are clinically relevant in humans.

Ozone-induced changes in the serum metabolome: Role of the microbiome.

Ozone is an asthma trigger. In mice, the gut microbiome contributes to ozone-induced airway hyperresponsiveness, a defining feature of asthma, but the mechanistic basis for the role of the gut microbiome has not been established. Gut bacteria can affect the function of distal organs by generating metabolites that enter the blood and circulate systemically. We hypothesized that global metabolomic profiling of serum collected from ozone exposed mice could be used to identify metabolites contributing to the role of the microbiome in ozone-induced airway hyperresponsiveness. Mice were treated for two weeks with a cocktail of antibiotics (ampicillin, neomycin, metronidazole, and vancomycin) in the drinking water or with control water and then exposed to air or ozone (2 ppm for 3 hours). Twenty four hours later, blood was harvested and serum analyzed via liquid-chromatography or gas-chromatography coupled to mass spectrometry. Antibiotic treatment significantly affected 228 of the 562 biochemicals identified, including reductions in the known bacterially-derived metabolites, equol, indole propionate, 3-indoxyl sulfate, and 3-(4-hydroxyphenyl)propionate, confirming the efficacy of the antibiotic treatment. Ozone exposure caused significant changes in 334 metabolites. Importantly, ozone-induced changes in many of these metabolites were different in control and antibiotic-treated mice. For example, most medium and long chain fatty acids declined by 20–50% with ozone exposure in antibiotic-treated but not control mice. Most taurine-conjugated bile acids increased with ozone exposure in antibiotic-treated but not control mice. Ozone also caused marked (9-fold and 5-fold) increases in the polyamines, spermine and spermidine, respectively, in control but not antibiotic-treated mice. Each of these metabolites has the capacity to alter airway responsiveness and may account for the role of the microbiome in pulmonary responses to ozone.

Activation of angiotensin-converting enzyme 2 (ACE2) attenuates allergic airway inflammation in rat asthma model

Angiotensin-I converting enzyme (ACE) is positively correlated to asthma, chronic obstructive pulmonary disease (COPD), acute respiratory distress syndrome (ARDS) and is highly expressed in lungs. ACE2, the counteracting enzyme of ACE, was proven to be protective in pulmonary, cardiovascular diseases. In the present study we checked the effect of ACE2 activation in animal model of asthma. Asthma was induced in male wistar rats by sensitization and challenge with ovalbumin and then treated with ACE2 activator, diminazene aceturate (DIZE) for 2weeks. 48h after last allergen challenge, animals were anesthetized, blood, BALF, femoral bone marrow lavage were collected for leucocyte count; trachea for measuring airway responsiveness to carbachol; lungs and heart were isolated for histological studies and western blotting. In our animal model, the characteristic features of asthma such as altered airway responsiveness to carbachol, eosinophilia and neutrophilia were observed. Western blotting revealed the increased pulmonary expression of ACE1, IL-1β, IL-4, NF-κB, BCL2, p-AKT, p-p38 and decreased expression of ACE2 and IκB. DIZE treatment prevented these alterations. Intraalveolar interstitial thickening, inflammatory cell infiltration, interstitial fibrosis, oxidative stress and right ventricular hypertrophy in asthma control animals were also reversed by DIZE treatment. Activation of ACE2 by DIZE conferred protection against asthma as evident from biochemical, functional, histological and molecular parameters. To the best of our knowledge, we report for the first time that activation of ACE2 by DIZE prevents asthma progression by altering AKT, p38, NF-κB and other inflammatory markers.

Lipopolysaccharide does not alter small airway reactivity in mouse lung slices.

The bacterial endotoxin, lipopolysaccharide (LPS) has been associated with occupational airway diseases with asthma-like symptoms and in acute exacerbations of COPD. The direct and indirect effects of LPS on small airway reactivity have not been fully elucidated. We tested the hypothesis that both in vitro and in vivo LPS treatment would increase contraction and impair relaxation of mouse small airways. Lung slices were prepared from naïve Balb/C mice and cultured in the absence or presence of LPS (10 μg/ml) for up to 48 h for measurement of TNFα levels in conditioned media. Alternatively, mice were challenged with PBS or LPS in vivo once a day for 4 days for preparation of lung slices or for harvest of lungs for Q-PCR analysis of gene expression of pro-inflammatory cytokines and receptors involved in airway contraction. Reactivity of small airways to contractile agonists, methacholine and serotonin, and bronchodilator agents, salbutamol, isoprenaline and rosiglitazone, were assessed using phase-contrast microscopy. In vitro LPS treatment of slices increased TNFα release 6-fold but did not alter contraction or relaxation to any agonists tested. In vivo LPS treatment increased lung gene expression of TNFα, IL-1β and ryanodine receptor isoform 2 more than 5-fold. However there were no changes in reactivity in lung slices from these mice, even when also incubated with LPS ex vivo. Despite evidence of LPS-induced inflammation, neither airway hyperresponsiveness or impaired dilator reactivity were evident. The increase in ryanodine receptor isoform 2, known to regulate calcium signaling in vascular smooth muscle, warrants investigation. Since LPS failed to elicit changes in small airway reactivity in mouse lung slices following in vitro or in vivo treatment, alternative approaches are required to define the potential contribution of this endotoxin to altered small airway reactivity in human lung diseases.

Alteration of Airway Reactivity and Reduction of Ryanodine Receptor Expression by Cigarette Smoke in Mice.

Small airways are a major site of airflow limitation in chronic obstructive pulmonary disease (COPD). Despite the detrimental effects of long-term smoking in COPD, the effects of acute cigarette smoke (CS) exposure on small airway reactivity have not been fully elucidated. Balb/C mice were exposed to room air (sham) or CS for 4 days to cause airway inflammation. Changes in small airway lumen area in response to contractile agents were measured in lung slices in situ using phase-contrast microscopy. Separate slices were pharmacologically maintained at constant intracellular Ca(2+) using caffeine/ryanodine before contractile measurements. Gene and protein analysis of contractile signaling pathways were performed on separate lungs. Monophasic contraction to serotonin became biphasic after CS exposure, whereas contraction to methacholine was unaltered. This altered pattern of contraction was normalized by caffeine/ryanodine. Expression of contractile agonist-specific receptors was unaltered; however, all isoforms of the ryanodine receptor were down-regulated. This is the first study to show that acute CS exposure selectively alters small airway contraction to serotonin and down-regulates ryanodine receptors involved in maintaining Ca(2+) oscillations in airway smooth muscle. Understanding the contribution of ryanodine receptors to altered airway reactivity may inform the development of novel treatment strategies for COPD.

Anaesthesia management of patients with airway susceptibilities

Anaesthesia management of patients with airway susceptibility remains a challenge in daily clinical practice due to the increased risk of perioperative bronchospasm. Therefore, understanding the mechanisms participating in the interaction between anaesthetic drugs and the lungs is essential in providing the optimal care for patients with chronic lung diseases. Experimental studies performed on various animal models mimicking airway susceptibility have played a key role in understanding the pathogenesis of lung diseases and have characterised the different pathways involved in the altered airway and lung tissue responses to anaesthetic agents. This narrative review highlights the progress that has been achieved by investigations in animal models and discusses the potential translation of these experimental findings to the clinical setting. The application of animal models with normal and allergically sensitised airways demonstrated that volatile and intravenous anaesthetic agents, muscle relaxants, analgesics and local anaesthetics exert their pulmonary effects via different neurosensorial pathways and through activating various receptors in the lungs. Attention is drawn to the significant differences in the pulmonary effects of anaesthetic agents between lungs with normal and those with susceptible airways. Extrapolating clear-cut conclusions from animal research to clinical practices should be made with caution, particularly for muscle relaxants, opioids and local anaesthetics wherein complex pathophysiological mechanisms are responsible for the potential respiratory effects of these agents. Animal models are of great importance in evaluating the potential interaction between anaesthetic drugs and the lungs, in identifying the pathways involved and in targeting preventive or treatment strategies to the lung compartment primarily involved.

Effect of obesity on bronchial hyperreactivity among Latino children

The association between obesity and bronchial hyperreactivity (BHR) in children has not been fully demonstrated in cross-sectional or longitudinal studies, and no study has specifically addressed Latino children. A cross-sectional study of 450 children (10-18 years) from public schools was conducted in Mexico city. Among this group, 260 met the study criteria (no chronic respiratory illnesses, including asthma and rhinitis; no acute respiratory infections; and no tobacco-exposure or endocrine or body dysmorphic disorders), and 229 performed reproducible pulmonary function and methacholine challenge tests and were fully analyzed. According to BMI percentiles, 40 were normal weight, 116 were obese, and 73 morbidly obese. Children in the morbidly obese group had significantly higher % FVC than those in the normal-weight group, and obese children had higher % PEF those in the morbidly obese and normal-weight groups. In the BHR methacholine challenge test, baseline FEV1 values among obese children were significantly lower than in the morbidly obese group. Using adjusted percentages for FEV1 , values were significantly lower among obese compared to morbidly obese children at metacholine concentrations of 0.25, 1, and 4 mg/ml. The proportion of positive BHR (PC20 ≤ 16 mg/ml) was higher in these two groups compared to normal-weight children (28.4%, 17.8%, and 12.5%, respectively), although differences were not significant. Our findings show that obesity by itself is not a sufficient condition to alter airway responsiveness to methacholine in a group of adolescents.

Natural‐source d‐α‐tocopheryl acetate inhibits oxidant stress and modulates atopic asthma in humans in vivo

Asthma is associated with oxidant stress and diminished antioxidant defenses. Yet, the mechanistic role of oxidant stress and antioxidant supplementation in human asthmatics remains uncertain. We determined the effect of high doses of the antioxidant natural-source d-α-tocopheryl acetate for 16 weeks on allergen-induced airway oxidant stress, inflammation, and bronchial responsiveness to methacholine and allergen in atopic asthmatics in vivo. Thirty-three mild atopic asthmatics underwent bronchoscopy with baseline bronchoalveolar lavage and segmental allergen challenge. The allergen-challenged airway was lavaged 24 h later. At least 3 weeks later, patients underwent inhaled challenges with methacholine and specific allergen. Volunteers took 1500 IU of natural-source d-α-tocopheryl acetate daily for at least 16 weeks. At the end of the treatment, the two bronchoscopies and inhaled methacholine and allergen challenges were repeated. F(2)-isoprostanes, specific markers of oxidant stress, and selected Th1 and Th2 cytokines were analyzed in the lavage fluid. Following supplementation of natural-source d-α-tocopheryl acetate, plasma concentrations of α-tocopherol increased and γ-tocopherol decreased. Both baseline and allergen-induced F(2)-isoprostanes significantly decreased, providing biochemical evidence for an antioxidant effect. Natural-source d-α-tocopheryl acetate reduced allergen-provoked concentrations of interleukin 3 and interleukin 4 and augmented levels of interleukin 12 in bronchoalveolar lavage fluid. Natural-source d-α-tocopheryl acetate improved airway responsiveness to methacholine but did not alter airway reactivity to specific allergen. Inhibition of oxidant stress by natural-source d-α-tocopheryl acetate modulates allergic inflammation and airway hyperresponsiveness in human atopic asthmatics in vivo. These results need to be confirmed by a randomized placebo-controlled trial.

Airway responsiveness depends on the diffusion rate of methacholine across the airway wall

During methacholine challenge tests of airway responsiveness, it is invariably assumed that the administered dose of agonist is accurately reflected in the dose that eventually reaches the airway smooth muscle (ASM). However, agonist must traverse a variety of tissue obstacles to reach the ASM, during which the agonist is subjected to both enzymatic breakdown and removal by the bronchial and pulmonary circulations. This raises the possibility that a significant fraction of the deposited agonist may never actually make it to the ASM. To understand the nature of this effect, we measured the time course of changes in airway resistance elicited by various durations of methacholine aerosol in mice. We fit to these data a computational model of a dynamically contracting airway responding to agonist that diffuses through an airway compartment, thereby obtaining rate constants that reflect the diffusive barrier to methacholine. We found that these barriers can contribute significantly to the time course of airway narrowing, raising the important possibility that alterations in the diffusive barrier presented by the airway wall may play a role in pathologically altered airway responsiveness.

Zinc supplementation alters airway inflammation and airway hyperresponsiveness to a common allergen

BackgroundZinc supplementation can modulate immunity through inhibition of NF-κB, a transcription factor that controls many immune response genes. Thus, we sought to examine the mechanism by which zinc supplementation tempers the response to a common allergen and determine its effect on allergic airway inflammation.MethodsMice were injected with zinc gluconate prior to German cockroach (GC) feces (frass) exposure and airway inflammation was assessed. Primary bone marrow-derived neutrophils and DMSO-differentiated HL-60 cells were used to assess the role of zinc gluconate on tumor necrosis factor (TNF)α expression. NF-κB:DNA binding and IKK activity were assessed by EMSA and in vitro kinase assay. Protein levels of A20, RIP1 and TRAF6 were assessed by Western blot analysis. Establishment of allergic airway inflammation with GC frass was followed by administration of zinc gluconate. Airway hyperresponsiveness, serum IgE levels, eosinophilia and Th2 cytokine production were assessed.ResultsAdministration of zinc gluconate prior to allergen exposure resulted in significantly decreased neutrophil infiltration and TNFα cytokine release into the airways. This correlated with decreased NF-κB activity in the whole lung. Treatment with zinc gluconate significantly decreased GC frass-mediated TNFα production from bone-marrow derived neutrophils and HL-60 cells. We confirmed zinc-mediated decreases in NF-κB:DNA binding and IKK activity in HL-60 cells. A20, a natural inhibitor of NF-κB and a zinc-fingered protein, is a potential target of zinc. Zinc treatment did not alter A20 levels in the short term, but resulted in the degradation of RIP1, an important upstream activator of IKK. TRAF6 protein levels were unaffected. To determine the application for zinc as a therapeutic for asthma, we administered zinc following the establishment of allergic airway inflammation in a murine model. Zinc supplementation decreased airway hyperresponsiveness and serum IgE levels, but had no effect on Th2 cytokine expression.ConclusionsThis report suggests that the mechanism by which zinc supplementation alters NF-κB activity is via the alteration of A20 activity. In addition, this study provides evidence that supplementation of zinc to asthmatics may alter airway reactivity and serum IgE levels, suggesting zinc supplementation as a potential treatment for asthmatics.

Cyclic GMP-dependent protein kinase regulation of airway smooth muscle in asthma

The mechanisms regulating altered airway smooth muscle (ASM) cell tone and airway reactivity in asthma remain incompletely understood. For vascular smooth muscle (VSM), the most important endogenous relaxation pathway is the nitric oxide (NO)-guanylate cyclase-cyclic GMP-dependent protein kinase type I (PKGI) pathway in which endogenous NO from NO synthases or from exogenous nitrovasodilators activate guanylate cyclase, increasing cGMP levels, and activating PKGI. PKGI in turn targets specific VSM molecules that mediate smooth muscle relaxation. Recent evidence supports that in ASM, like in VSM, activators of guanylyl cyclases have significant cGMP-mediated relaxant and antiproliferative effects. PKGI is therefore a prime but unexplored candidate molecule to mediate ASM relaxation. Recently, we have used mice harbouring a mutation in the leucine zipper N-terminal interaction domain (LZM mice [1]) to test the hypothesis that PKGIα is a critical mediator of ASM relaxation that normally protects against airway hyperresponsivity via interactions with specific molecular targets, including ASM myosin phosphate and Rho/Rho-kinase, and that this regulatory system is perturbed in the setting of asthma. Using this knock-in mouse harboring a discrete mutation in the protein-protein interaction domain of PKGI, which disrupts NO-PKG-mediated smooth muscle relaxation by disrupting the PKGI-myosin phosphatase complex we have begun to explore the mechanism of PKGI-mediated ASM relaxation and the role of PKGI in models of asthma. Several asthma studies in LZM mice and WT littermates have now been performed and analyzed using both the acute and the chronic House Dust Mite (HDM) asthma model in WT and LZM mice. Endpoints examined include airway responsiveness to methacholine; quantification of inflammatory cell populations from Bronchoalveolar lavage (BAL); and studies of airway smooth muscle in the mice. In the LZM mice, there is a significant increase in bronchospasm noted in the airways of mutant mice in both acute and chronic asthma models. No differences between WT and LZM mice in the extent of increase in either total cells or in eosinophilia in BALF samples following HDM was noted in the either the acute or chronic models. The extent and volume of Airway SMC a-actin was also measured in the WT and LZM mice following HDM-induced asthma in the acute model. SMC labeling in the airways was quantified using immunohistochemistry and computerized morphometrics and for each measure, a significant increase in SMC number and total volume was noted in the LZM mice. Studies of PKG expression level and of SMC proliferation in the asthma models are underway. These experiments will provide better understanding of ASM relaxation at the molecular level and have the potential to identify novel gene targets for the development of new therapeutic approaches to bronchoconstriction in asthma.

Repeated exposure to organic material alters inflammatory and physiological airway responses

Farmers and smokers are repeatedly exposed to airborne organic material. We hypothesised that farmers and smokers show altered airway responses to inhaled organic, pro-inflammatory agents. A total of 11 farmers, 12 smokers and 12 controls underwent lipopolysaccharide (LPS) bronchial challenge and spent 3 h in a pig barn. Lung function, exhaled nitric oxide and bronchial responsiveness were assessed and nasal lavage fluid and induced sputum were also collected. Symptoms and body temperature were recorded before and after exposures. Following exposure to the pig barn, bronchial responsiveness, exhaled nitric oxide, sputum interleukin (IL)-6, nasal lavage cell count and IL-8 were increased to a greater extent in controls compared to farmers. The sputum IL-6 response was also attenuated in farmers after LPS challenge. The response shown by smokers following exposure to the pig barn was similar to that of controls regarding measurements of exhaled nitric oxide, IL-8 in nasal lavage and IL-6 in sputum, but more similar to farmers concerning bronchial responsiveness and the cell numbers present in nasal lavage. Sputum IL-8 showed a greater increase in smokers than in the other groups following LPS challenge. We conclude that individuals who are repeatedly exposed to organic material develop an adaptation to the effects of acute exposure to inhaled organic material.

Alcohol feeding blocks methacholine-induced airway responsiveness in mice

Historical accounts of alcohol administration to patients with breathing problems suggest that alcohol may have bronchodilating properties. We hypothesized that acute alcohol exposure will alter airway responsiveness (AR) in mice. To test this hypothesis, C57BL/6 mice were fed either 20% alcohol in drinking water (fed) or received a single intraperitoneal (ip) injection of alcohol (3 g/kg). Control groups received regular drinking water or ip saline. AR was assessed by means of ventilation or barometric plethysmography and reported as either total lung resistance or enhanced pause for each group of mice. To confirm alcohol exposure, elevated blood alcohol levels were documented. Alcohol feeding significantly blocked methacholine-triggered AR compared with water-fed controls. Comparable blunting of AR was also accomplished through a single ip injection of alcohol when compared with saline-injected controls. The alcohol response was slowly reversible in both routes of administration after withdrawal of alcohol: AR attenuation by alcohol persisted 12-20 h (ip) or up to 2 wk (fed) after blood alcohol cleared consistent with a sustained bronchodilator effect. These data demonstrate that brief alcohol exposure blunts AR in this murine model of alcohol exposure suggesting a role for alcohol in the modulation of bronchial motor tone.