Acute exercise decreases airway inflammation, but not responsiveness, in an allergic asthma model

The relationships between Physical activity and asthma control and Body Mass Index (BMI) in patients with asthma

OBJECTIVE

Asthma is one of the most common chronic conditions in developed countries. We examined whether physical activity (PA) is related to asthma control and body mass index (BMI) in asthma patients.

METHODS

Cross-sectional data collected on PA (ActiGraph GT3X-BT), asthma control (the Asthma Control Questionnaire; ACQ), and BMI were examined in 206 adults (mean[sd] age 47.2[13.8] years; 49.5% had an obese BMI) with clinically diagnosed asthma. Relationships between PA and continuous BMI and asthma control were assessed using linear regression. Differences in PA across obesity (non-obese: <30 Kg/m2/obese: ≥30 Kg/m2) and asthma control categories (controlled: ≤0.75/uncontrolled: >0.75 ACQ score) were also examined.

RESULTS

Median (p25, p75) steps counts and peak cadence were 6035 (4248, 8461) steps/day and 123 (115, 133) steps in a minute, respectively. There were nearly 2000 fewer steps/day among those with uncontrolled asthma versus controlled and among those with obese BMI versus nonobese, respectively (both p < 0.05). In regression models adjusted for relevant covariates each 1-unit increase in ACQ score was associated with -686 [95%CI -997, -13] (p ≤ 0.05) average steps/day. The statistical significance of these findings was attenuated (p ≥ 0.05) when BMI was added to the model. However, the point estimate was not reduced (-766 [95%CI -1060, 34].

CONCLUSIONS

Overall step counts were low in this population despite peak cadence values suggesting that most participants could perform moderate intensity activity. Increasing step counts should be considered an important lifestyle intervention goal in obese and non-obese asthma patients with low PA levels.

The Microbiota and Equine Asthma: An Integrative View of the Gut-Lung Axis

Both microbe-microbe and host-microbe interactions can have effects beyond the local environment and influence immunological responses in remote organs such as the lungs. The crosstalk between the gut and the lungs, which is supported by complex connections and intricate pathways, is defined as the gut-lung axis. This review aimed to report on the potential role of the gut-lung gut-lung axis in the development and persistence of equine asthma. We summarized significant determinants in the development of asthma in horses and humans. The article discusses the gut-lung axis and proposes an integrative view of the relationship between gut microbiota and asthma. It also explores therapies for modulating the gut microbiota in horses with asthma. Improving our understanding of the horse gut-lung axis could lead to the development of techniques such as fecal microbiota transplants, probiotics, or prebiotics to manipulate the gut microbiota specifically for improving the management of asthma in horses.

Comparing the Effect of Acute Moderate and Vigorous Exercise on Inflammation in Adults with Asthma: A Randomized Controlled Trial

Rationale: Exercise is associated with improvements in asthma; however, the mechanisms responsible are not clear. Exercise induces changes in systemic inflammation, and it is possible that these inflammatory effects extend to the airways of people with asthma. Studies in healthy adults suggest inflammatory responses are dependent on exercise intensity: Although acute moderate exercise is antiinflammatory, acute vigorous exercise appears to be neutral or proinflammatory. The effect of exercise intensity on inflammation has not been investigated in people with asthma. Objectives: To compare acute changes in airway and systemic inflammation after a bout of moderate or vigorous exercise in physically inactive adults with asthma and to establish whether these effects differ according to asthma phenotype. Methods: Participants were randomized to either 1) control (no intervention), 2) 45 minutes of moderate exercise, or 3) 30 minutes of vigorous exercise. Induced sputum and blood samples were collected at baseline and 4 hours after intervention. Results: Fifty-six participants (75% female; mean age, 33.4 [9.9] yr) completed the trial. Moderate exercise induced a significant reduction in sputum eosinophil count (-173 [-337 to -10]; P = 0.032) and sputum percentage eosinophils (-2.2 [-4.9 to 0.5]; P = 0.049) relative to control. Vigorous exercise had no effect on airway inflammation. The antiinflammatory effects of moderate exercise were greatest in participants with eosinophilic asthma, with larger reductions in sputum eosinophils and larger increases in plasma interleukin (IL)-1ra than seen in participants with noneosinophilic asthma. Vigorous exercise induced a systemic proinflammatory response in participants with eosinophilic asthma, indicated by an increase in serum IL-5 and IL-1β; however, this had no effect on airway inflammation. Conclusions: Exercise intensity modifies the acute inflammatory response to exercise in adults with asthma. Although a bout of moderate exercise is associated with a reduction in eosinophilic airway inflammation, vigorous exercise has no effect on airway inflammation. Interestingly, the effects of moderate exercise vary by asthma phenotype, with greater antiinflammatory effects in participants with eosinophilic asthma. Future studies should examine the impact of exercise training at different intensities on inflammation and clinical asthma outcomes. Clinical trial registered with the Australian New Zealand Clinical Trials Registry (ACTRN 12615000294550).

Physical activity and childhood asthma control: Mediation and moderation role of body mass index

BACKGROUND

Physical activity (PA) may be associated with asthma management. Whether PA is associated with childhood asthma control is not well studied, and the role of body mass index (BMI) in this association remains unclarified. This study aimed to evaluate the association between PA and childhood asthma control and investigate the potential mediating and modifying role of BMI in the association.

METHODS

This cross-sectional study involved 303 asthmatic children aged 5-14 years. Information on PA was collected from children. Asthma control was assessed using a valid questionnaire by children and their parents. Height and weight were objectively measured and BMI was calculated and classified. Multiple linear regression, mediation, and moderation analyses were performed.

RESULTS

There was a positive association between PA and childhood asthma control with adjustment for variates (B = 0.144, p = .012). Mediation analysis indicated that BMI status negatively mediated the association (estimate = -0.656, 95% credit interval: -1.645, -0.006), and such indirect effect is lower than the direct effect (indirect effect/direct effect = 58.3%). No evidence of effect modification by BMI was observed (P_interaction = 0.516). Stratified analyses showed that the significant association was only observed in children with overweight/obesity (normal weight: B = 0.863, p = .189; overweight/obese: B = 1.494, p = .044).

CONCLUSIONS

Increased PA is associated with improved childhood asthma control, especially for children with higher BMI. BMI exhibited a negative effect but not effect modification in this association. PA should be encouraged to improve asthma control for asthmatic children. Besides, mechanisms other than weight loss may explain the association.

Defining a role for exercise training in the management of asthma

The prevalence of asthma remains high worldwide, with increasing awareness of the morbidity and mortality from asthma in low-income countries. In the UK, despite the development of biological treatments, many patients remain suboptimally controlled, and mortality rates have been static for decades. Therefore, new approaches are needed to treat asthma that are scalable at minimal cost. Exercise immunology is an expanding field, and there is growing evidence that exercise can modulate inflammatory and immune processes in asthma. Whilst exercise is encouraged in current treatment guidelines, there are no specific recommendations as to the intensity, frequency or duration of exercise exposure. Despite national and international guidance to increase exercise, patients with asthma are less likely to engage in physical activity. This review explores the disease modifying benefit of exercise in asthma. We also review the domains in which exercise exerts positive clinical effects in asthma, including the effects of exercise on symptom scores, quality of life, psychosocial health, and in the obese asthma phenotype. Finally, we review the barriers to exercise in asthma, given the benefits it confers. A better understanding of the mechanisms through which exercise exerts its positive effects in asthma may provide more accurate prescription of exercise training programmes as part of broader asthma management, with the potential of identification of new drug targets.

Treadmill exercise restores memory and hippocampal synaptic plasticity impairments in ovalbumin-sensitized juvenile rats: Involvement of brain-derived neurotrophic factor (BDNF)

Studies demonstrate that asthma, especially during childhood, affects the functions of the brain including learning and memory. Exercise is well known for its neuroprotective functions and for its beneficial effects on asthma. We aimed to assess the effects of exercise on cognitive function, synaptic plasticity, and hippocampal brain-derived neurotrophic factor (BDNF) levels in ovalbumin (OVA) sensitized juvenile rats. Rats were sensitized by intraperitoneal administration and inhaled OVA. Animals were subjected to treadmill running exercise during the OVA-challenged period. T-helper type 2 (Th2) cytokine [interleukin (IL)-4], Th1 cytokine (INF-γ) levels, and INF-γ/IL-4 (Th1/Th2) ratio in bronchoalveolar lavage fluid (BALF), and tracheal response to methacholine and OVA were measured. Further, memory behaviors and BDNF levels were measured in the hippocampus as well as long-term potentiation (LTP) was assessed by recording field excitatory postsynaptic potentials (fEPSPs) in the hippocampus. The levels of IL-4 and TGF-β were decreased but INF-γ level and INF-γ/IL-4 ratio increased in the BALF due to exercise in the OVA-sensitized animals. In addition, exercise improved OVA-sensitization induced cognitive impairments, increased BDNF levels, and enhanced hippocampal LTP in OVA-sensitized rats. Exercise is not only effective in the alleviation of airway inflammation by restoring Th1/Th2 cytokines balance, but also is a candidate for improvement of memory and synaptic plasticity deficits partially through increasing the levels of hippocampal BDNF in OVA-sensitized rats.

Optimizing lifestyle interventions in adult patients with comorbid asthma and obesity

The prevalence of obesity and asthma are both increasing at alarming rates. The link between obesity and asthma suggests that obesity contributes to both risk of new onset asthma and increased asthma severity. The emerging evidence demonstrating the role of obesity and other lifestyle factors, such as diet and physical activity, on asthma outcomes warrants lifestyle interventions that can address these components of asthma care. This review examines the current literature on the pathophysiology of obesity's role in asthma, as well as the role of diet and physical activity in weight loss and in asthma outcomes. We discuss recent studies that employ lifestyle interventions to target improved asthma outcomes. Finally, we discuss the future direction of research in this area. The reviews of this paper are available via the supplemental material section.

Contemporary management techniques of asthma in obese patients

Introduction: Obesity-associated asthma represents a heterogeneous group of clinical phenotypes, including an adult-onset phenotype. These patients often have difficult to control symptoms and often are less likely to respond to conventional asthma therapies.Areas covered: This review covers the effects of lifestyle interventions, including diet and weight loss, effect asthma outcomes and how obesity-associated asthma responds to conventional approaches to asthma management.Expert opinion: Management of obesity-associated asthma should include lifestyle modifications aimed at weight reduction, management of other co-morbidities, and limiting systemic steroids. As many of these patients have non-Th2 asthma, long-acting muscarinic antagonists and macrolides may be potentially helpful. Medications to treat metabolic syndrome.

Anti-oxidant and Anti-inflammatory Effects of Aquatic Exercise in Allergic Airway Inflammation in Mice

Oxidative stress and inflammation are key pathways responsible for the pathogenesis of asthma. Aquatic exercise (AE) has been proven to elicit a variety of biological activities such as anti-oxidant and anti-inflammatory effects. However, although proper forms of AE provide beneficial health effects, incorrect forms and types of AE are potentially injurious to health. Several studies have investigated AE, but the relationship between types of AE and asthma has not been fully elucidated. This study evaluated the effects of two types of AE according to resistance on ovalbumin (OVA)-induced allergic airway inflammation in mice. BALB/c mice were subjected to OVA sensitization and challenge, and then to different types of AE including, walking and swimming, in a pool filled with water to a height of 2.5 and 13 cm for 30 min, respectively. AE reduced OVA-induced eosinophilic inflammation, airway hyperresponsiveness, and serum immunoglobulin E level. AE significantly inhibited increases in interleukin (IL)-4, IL-5, IL-13, histamine, leukotriene D4, and tryptase levels in bronchoalveolar lavage fluid (BALF). AE also effectively suppressed mucus formation, lung fibrosis, and hypertrophy of airway smooth muscle within the lung tissues. This exercise markedly reduced the levels of malondialdehyde while increased glutathione and superoxide dismutase (SOD) activity in lung tissues. Furthermore, AE significantly decreased tumor necrosis factor-α, IL-6 levels, and prostaglandin E2 production in BALF. The inhibitory effects of swimming on the levels of biomarkers related to oxidative stress and inflammation were greater than that of walking. These effects may have occurred through upregulation of NF-E2-related factor 2/heme oxygenase-1 signaling and suppression of mitogen-activated protein kinase/nuclear factor-κB pathway. Cumulative results from this study suggest that AE might be beneficial in mitigating the levels of biomarkers related to oxidative stress and inflammation. Thus, this therapy represents a crucial non-pharmacological intervention for treatments of allergic airway inflammation.

Impact of Lifestyle Interventions Targeting Healthy Diet, Physical Activity, and Weight Loss on Asthma in Adults: What Is the Evidence?

Unhealthy lifestyle factors such as poor diet quality, sedentary lifestyle, and obesity are associated with negative health consequences in asthma including poor asthma control, impaired quality of life, and greater health care utilization. Lifestyle modification is the cornerstone of behavioral treatments and has been effective in chronic diseases such as atherothrombotic vascular disease and diabetes. There is a critical need for lifestyle interventions in asthma care that address obesity and its intimately linked risk behaviors in terms of poor diet and physical inactivity. We present in this commentary the promising lifestyle interventions emerging in asthma care that target poor diet, physical inactivity and weight loss, the proposed mechanisms of these lifestyle interventions, and the critical need for guideline-concordant lifestyle interventions in asthma care.

Aerobic Exercise Attenuated Bleomycin-Induced Lung Fibrosis in Th2-Dominant Mice

INTRODUCTION

The aim of this study was to investigate the effect of aerobic exercise (AE) in reducing bleomycin-induced fibrosis in mice of a Th2-dominant immune background (BALB/c).

METHODS

BALB/c mice were distributed into: sedentary, control (CON), Exercise-only (EX), sedentary, bleomycin-treated (BLEO) and bleomycin-treated+exercised (BLEO+EX); (n = 8/group). Following treadmill adaptation, 15 days following a single, oro-tracheal administration of bleomycin (1.5U/kg), AE was performed 5 days/week, 60min/day for 4 weeks at moderate intensity (60% of maximum velocity reached during a physical test) and assessed for pulmonary inflammation and remodeling, and cytokine levels in bronchoalveolar lavage (BAL).

RESULTS

At 45 days post injury, compared to BLEO, BLEO+EX demonstrated reduced collagen deposition in the airways (p<0.001) and also in the lung parenchyma (p<0.001). In BAL, a decreased number of total leukocytes (p<0.01), eosinophils (p<0.001), lymphocytes (p<0.01), macrophages (p<0.01), and neutrophils (p<0.01), as well as reduced pro-inflammatory cytokines (CXCL-1; p<0.01), (IL-1β; p<0.001), (IL-5; p<0.01), (IL-6; p<0.001), (IL-13; p<0.01) and pro-fibrotic growth factor IGF-1 (p<0.001) were observed. Anti-inflammatory cytokine IL-10 was increased (p<0.001).

CONCLUSION

AE attenuated bleomycin-induced collagen deposition, inflammation and cytokines accumulation in the lungs of mice with a predominately Th2-background suggesting that therapeutic AE (15-44 days post injury) attenuates the pro-inflammatory, Th2 immune response and fibrosis in the bleomycin model.

Aerobic Exercise Reduces Asthma Phenotype by Modulation of the Leukotriene Pathway

Introduction

Leukotrienes (LTs) play a central role in asthma. Low- to moderate-intensity aerobic exercise (AE) reduces asthmatic inflammation in clinical studies and in experimental models. This study investigated whether AE attenuates LT pathway activation in an ovalbumin (OVA) model of asthma.

Methods

Sixty-four male, BALB/c mice were distributed into Control, Exercise (Exe), OVA, and OVA + Exe groups. Treadmill training was performed at moderate intensity, 5×/week, 1 h/session for 4 weeks. Quantification of bronchoalveolar lavage (BAL) cellularity, leukocytes, airway remodeling, interleukin (IL)-5, IL-13, cysteinyl leukotriene (CysLT), and leukotriene B4 (LTB4) in BAL was performed. In addition, quantitative analyses on peribronchial leukocytes and airway epithelium for LT pathway agents: 5-lypoxygenase (5-LO), LTA4 hydrolase (LTA4H), CysLT₁ receptor, CysLT₂ receptor, LTC4 synthase, and LTB4 receptor 2 (BLT2) were performed. Airway hyperresponsiveness (AHR) to methacholine (MCh) was assessed via whole body plethysmography.

Results

AE decreased eosinophils (p < 0.001), neutrophils (p > 0.001), lymphocytes (p < 0.001), and macrophages (p < 0.01) in BAL, as well as eosinophils (p < 0.01), lymphocytes (p < 0.001), and macrophages (p > 0.001) in airway walls. Collagen (p < 0.01), elastic fibers (p < 0.01), mucus production (p < 0.01), and smooth muscle thickness (p < 0.01), as well as IL-5 (p < 0.01), IL-13 (p < 0.01), CysLT (p < 0.01), and LTB4 (p < 0.01) in BAL were reduced. 5-LO (p < 0.05), LTA4H (p < 0.05), CysLT₁ receptor (p < 0.001), CysLT₂ receptor (p < 0.001), LTC4 synthase (p < 0.001), and BLT2 (p < 0.01) expression by peribronchial leukocytes and airway epithelium were reduced. Lastly, AHR to MCh 25 mg/mL (p < 0.05) and 50 mg/mL (p < 0.01) was reduced.

Conclusion

Moderate-intensity AE attenuated asthma phenotype and LT production in both pulmonary leukocytes and airway epithelium of OVA-treated mice.

Heme Attenuation Ameliorates Irritant Gas Inhalation-Induced Acute Lung Injury

AIMS

Exposure to irritant gases, such as bromine (Br2), poses an environmental and occupational hazard that results in severe lung and systemic injury. However, the mechanism(s) of Br2 toxicity and the therapeutic responses required to mitigate lung damage are not known. Previously, it was demonstrated that Br2 upregulates the heme degrading enzyme, heme oxygenase-1 (HO-1). Since heme is a major inducer of HO-1, we determined whether an increase in heme and heme-dependent oxidative injury underlies the pathogenesis of Br2 toxicity.

RESULTS

C57BL/6 mice were exposed to Br2 gas (600 ppm, 30 min) and returned to room air. Thirty minutes postexposure, mice were injected intraperitoneally with a single dose of the heme scavenging protein, hemopexin (Hx) (3 μg/gm body weight), or saline. Twenty-four hours postexposure, saline-treated mice had elevated total heme in bronchoalveolar lavage fluid (BALF) and plasma and acute lung injury (ALI) culminating in 80% mortality after 10 days. Hx treatment significantly lowered heme, decreased evidence of ALI (lower protein and inflammatory cells in BALF, lower lung wet-to-dry weight ratios, and decreased airway hyperreactivity to methacholine), and reduced mortality. In addition, Br2 caused more severe ALI and mortality in mice with HO-1 gene deletion (HO-1-/-) compared to wild-type controls, while transgenic mice overexpressing the human HO-1 gene (hHO-1) showed significant protection.

INNOVATION

This is the first study delineating the role of heme in ALI caused by Br2.

CONCLUSION

The data suggest that attenuating heme may prove to be a useful adjuvant therapy to treat patients with ALI.

Therapeutic potential of an orally effective small molecule inhibitor of plasminogen activator inhibitor for asthma

Asthma is one of the most common respiratory diseases. Although progress has been made in our understanding of airway pathology and many drugs are available to relieve asthma symptoms, there is no cure for chronic asthma. Plasminogen activator inhibitor 1 (PAI-1), a primary inhibitor of tissue-type and urokinase-type plasminogen activators, has pleiotropic functions besides suppression of fibrinolysis. In this study, we show that administration of TM5275, an orally effective small-molecule PAI-1 inhibitor, 25 days after ovalbumin (OVA) sensitization-challenge, significantly ameliorated airway hyperresponsiveness in an OVA-induced chronic asthma model. Furthermore, we show that TM5275 administration significantly attenuated OVA-induced infiltration of inflammatory cells (neutrophils, eosinophils, and monocytes), the increase in the levels of OVA-specific IgE and Th2 cytokines (IL-4 and IL-5), the production of mucin in the airways, and airway subepithelial fibrosis. Together, the results suggest that the PAI-1 inhibitor TM5275 may have therapeutic potential for asthma through suppressing eosinophilic allergic response and ameliorating airway remodeling.

Exercise and asthma: an overview

The terms 'exercise-induced asthma' (EIA) and 'exercise-induced bronchoconstriction' (EIB) are often used interchangeably to describe symptoms of asthma such as cough, wheeze, or dyspnoea provoked by vigorous physical activity. In this review, we refer to EIB as the bronchoconstrictive response and to EIA when bronchoconstriction is associated with asthma symptoms. EIB is a common occurrence for most of the asthmatic patients, but it also affects more than 10% of otherwise healthy individuals as shown by epidemiological studies. EIA and EIB have a high prevalence also in elite athletes, especially within endurance type of sports, and an athlete's asthma phenotype has been described. However, the occurrence in elite athletes shows that EIA/EIB, if correctly managed, may not impair physical activity and top sports performance. The pathogenic mechanisms of EIA/EIB classically involve both osmolar and vascular changes in the airways in addition to cooling of the airways with parasympathetic stimulation. Airways inflammation plays a fundamental role in EIA/EIB. Diagnosis and pharmacological management must be carefully performed, with particular consideration of current anti-doping regulations, when caring for athletes. Based on the demonstration that the inhaled asthma drugs do not improve performance in healthy athletes, the doping regulations are presently much less strict than previously. Some sports are at a higher asthma risk than others, probably due to a high environmental exposure while performing the sport, with swimming and chlorine exposure during swimming as one example. It is considered very important for the asthmatic child and adolescent to master EIA/EIB to be able to participate in physical activity on an equal level with their peers, and a precise early diagnosis with optimal treatment follow-up is vital in this aspect. In addition, surprising recent preliminary evidences offer new perspectives for moderate exercise as a potential therapeutic tool for asthmatics.

Exercise and asthma: an overview

The terms 'exercise-induced asthma' (EIA) and 'exercise-induced bronchoconstriction' (EIB) are often used interchangeably to describe symptoms of asthma such as cough, wheeze, or dyspnoea provoked by vigorous physical activity. In this review, we refer to EIB as the bronchoconstrictive response and to EIA when bronchoconstriction is associated with asthma symptoms. EIB is a common occurrence for most of the asthmatic patients, but it also affects more than 10% of otherwise healthy individuals as shown by epidemiological studies. EIA and EIB have a high prevalence also in elite athletes, especially within endurance type of sports, and an athlete's asthma phenotype has been described. However, the occurrence in elite athletes shows that EIA/EIB, if correctly managed, may not impair physical activity and top sports performance. The pathogenic mechanisms of EIA/EIB classically involve both osmolar and vascular changes in the airways in addition to cooling of the airways with parasympathetic stimulation. Airways inflammation plays a fundamental role in EIA/EIB. Diagnosis and pharmacological management must be carefully performed, with particular consideration of current anti-doping regulations, when caring for athletes. Based on the demonstration that the inhaled asthma drugs do not improve performance in healthy athletes, the doping regulations are presently much less strict than previously. Some sports are at a higher asthma risk than others, probably due to a high environmental exposure while performing the sport, with swimming and chlorine exposure during swimming as one example. It is considered very important for the asthmatic child and adolescent to master EIA/EIB to be able to participate in physical activity on an equal level with their peers, and a precise early diagnosis with optimal treatment follow-up is vital in this aspect. In addition, surprising recent preliminary evidences offer new perspectives for moderate exercise as a potential therapeutic tool for asthmatics.

Heme oxygenase-1-mediated autophagy protects against pulmonary endothelial cell death and development of emphysema in cadmium-treated mice

Pulmonary exposure to cadmium, a major component of cigarette smoke, has a dramatic impact on lung function and the development of emphysema. Cigarette smoke exposure induces heme oxygenase-1 (HO-1), a cytoprotective enzyme. In this study, we employed a truncated mouse model of emphysema by intratracheal instillation of cadmium (CdCl2) solution (0.025% per 1 mg/kg body wt) in HO-1(+/+), HO-1(-/-), and overexpressing humanized HO-1 bacterial artificial chromosome (hHO-1BAC) mice. We evaluated the role of HO-1 in cadmium-induced emphysema in mice by analyzing histopathology, micro-computed tomography scans, and lung function tests. CdCl2-exposed HO-1(-/-) mice exhibited more severe emphysema compared with HO-1(+/+) or hHO-1BAC mice. Loss of pulmonary endothelial cells (PECs) from the alveolar capillary membrane is recognized to be a target in emphysema. PECs from HO-1(+/+), HO-1(-/-), and hHO-1BAC were employed to define the underlying molecular mechanism for the protection from emphysema by HO-1. Electron microscopy, expression of autophagic markers (microtubule-associated protein 1B-light chain 3 II, autophagy protein 5, and Beclin1) and apoptotic marker (cleaved caspase 3) suggested induction of autophagy and apoptosis in PECs after CdCl2 treatment. CdCl2-treated HO-1(-/-) PECs exhibited downregulation of autophagic markers and significantly increased cleaved caspase 3 expression and activity (∼4-fold higher). Moreover, hHO-1BAC PECs demonstrated upregulated autophagy and absence of cleaved caspase 3 expression or activity. Pretreatment of HO-1(+/+) PECs with rapamycin induced autophagy and resulted in reduced cell death upon cadmium treatment. Induction of autophagy following CdCl2 treatment was found to be protective from apoptotic cell death. HO-1 induced protective autophagy in PECs and mitigated cadmium-induced emphysema.

Acute exercise is associated with reduced exhaled nitric oxide in physically inactive adults with asthma

BACKGROUND

Although exercise has multiple health benefits, relatively little attention has been paid to its potential therapeutic effects in those with asthma.

OBJECTIVE

To examine the effects of acute exercise on inflammation in physically inactive and active adults with asthma.

METHODS

Fourteen adults with asthma (n = 6 physically inactive, n = 8 physically active) completed (1) 30 minutes of moderate-intensity exercise on a treadmill and (2) 30 minutes of rest in random order, with 4 weeks between sessions. Exhaled nitric oxide (eNO) was measured before and after the intervention (0, 0.5, 1, 2, 4, and 24 hours). Blood inflammatory mediators were measured before and after the intervention (0, 2, and 24 hours).

RESULTS

Physically inactive participants had a significant decrease in eNO 4 hours after exercise (-4.8 ppb, -6.4 to -0.5 ppb, P = .028), which was not observed in physically active participants (P = .362). Interluekin-1 receptor antagonist increased in the physically inactive group 2 hours after exercise, with this increase strongly correlated with the decrease in eNO at 4 hours (R = -0.685, P = .007) and 24 hours (R = -0.659, P = .014) after exercise. Interleukin-6 was increased significantly 2 hours after exercise in physically inactive participants. Blood neutrophils and nuclear factor erythroid 2-like 2 gene expression were increased 2 hours after exercise in the overall cohort.

CONCLUSION

This study demonstrates that acute moderate-intensity exercise is associated with decreased eNO in physically inactive adults with asthma and suggests that interluekin-1 receptor antagonist could have a role in mediating this effect. The attenuated response in physically active participants might be due to the sustained anti-inflammatory effects of exercise training. Future studies should investigate the impact of exercise intensity and exercise training on airway inflammation in those with asthma.

TRIAL REGISTRATION

Australian New Zealand Clinical Trials Registry (http://www.anzctr.org.au), registration number ACTRN12613001014741.

Hyaluronan mediates airway hyperresponsiveness in oxidative lung injury

Chlorine (Cl2) inhalation induces severe oxidative lung injury and airway hyperresponsiveness (AHR) that lead to asthmalike symptoms. When inhaled, Cl2 reacts with epithelial lining fluid, forming by-products that damage hyaluronan, a constituent of the extracellular matrix, causing the release of low-molecular-weight fragments (L-HA, <300 kDa), which initiate a series of proinflammatory events. Cl2 (400 ppm, 30 min) exposure to mice caused an increase of L-HA and its binding partner, inter-α-trypsin-inhibitor (IαI), in the bronchoalveolar lavage fluid. Airway resistance following methacholine challenge was increased 24 h post-Cl2 exposure. Intratracheal administration of high-molecular-weight hyaluronan (H-HA) or an antibody against IαI post-Cl2 exposure decreased AHR. Exposure of human airway smooth muscle (HASM) cells to Cl2 (100 ppm, 10 min) or incubation with Cl2-exposed H-HA (which fragments it to L-HA) increased membrane potential depolarization, intracellular Ca(2+), and RhoA activation. Inhibition of RhoA, chelation of intracellular Ca(2+), blockade of cation channels, as well as postexposure addition of H-HA, reversed membrane depolarization in HASM cells. We propose a paradigm in which oxidative lung injury generates reactive species and L-HA that activates RhoA and Ca(2+) channels of airway smooth muscle cells, increasing their contractility and thus causing AHR.

Exercise training, lymphocyte subsets and their cytokines production: experience of an Italian professional football team and their impact on allergy

BACKGROUND

In recent years, numerous articles have attempted to shed light on our understanding of the pathophysiological mechanisms of exercise-induced immunologic changes and their impact on allergy and asthma. It is known that lymphocyte subclasses, cytokines, and chemokines show modifications after exercise, but outcomes can be affected by the type of exercise as well as by its intensity and duration. Interesting data have been presented in many recent studies on mouse models, but few studies on humans have been performed to check the long-term effects of exercise over a whole championship season.

METHODS

This study evaluated lymphocyte subsets and their intracellular IL-2, IL-4, TNF-α, and IFN-γ production in professional football (soccer) players, at three stages of the season, to evaluate if alterations occur, particularly in relation to their allergic status.

RESULTS AND CONCLUSION

Despite significant mid-season alterations, no significant lymphocyte subclasses count modifications, except for NKs that were significantly higher, were observed at the end. IL-2 and IL-4 producing cells showed a significant decrease (P = 0.018 and P = 0.001, but in a steady fashion for IL-4), confirming the murine data about the potential beneficial effects of aerobic exercise for allergic asthma.

Exercise training, lymphocyte subsets and their cytokines production: experience of an Italian professional football team and their impact on allergy

BACKGROUND

In recent years, numerous articles have attempted to shed light on our understanding of the pathophysiological mechanisms of exercise-induced immunologic changes and their impact on allergy and asthma. It is known that lymphocyte subclasses, cytokines, and chemokines show modifications after exercise, but outcomes can be affected by the type of exercise as well as by its intensity and duration. Interesting data have been presented in many recent studies on mouse models, but few studies on humans have been performed to check the long-term effects of exercise over a whole championship season.

METHODS

This study evaluated lymphocyte subsets and their intracellular IL-2, IL-4, TNF-α, and IFN-γ production in professional football (soccer) players, at three stages of the season, to evaluate if alterations occur, particularly in relation to their allergic status.

RESULTS AND CONCLUSION

Despite significant mid-season alterations, no significant lymphocyte subclasses count modifications, except for NKs that were significantly higher, were observed at the end. IL-2 and IL-4 producing cells showed a significant decrease (P = 0.018 and P = 0.001, but in a steady fashion for IL-4), confirming the murine data about the potential beneficial effects of aerobic exercise for allergic asthma.

Obesity in asthma: approaches to treatment

There is mounting evidence that obesity is associated with asthma, both of which are seeing a dramatic increase in prevalence. Not only is obesity a risk factor for the development of asthma but it is also associated with poor asthma control. Asthma phenotypes associated with obesity include early-onset allergic asthma and late-onset non-allergic asthma. The pathogenesis of the linkage is complex; obesity causes a variety of mechanical, metabolic, and immunological changes that can affect the airways. The treatment of asthma in obesity can be challenging, as obesity is associated with poor response to standard controller medications. A tailored approach that involves combining pharmacologic and non-pharmacologic therapies including weight loss, dietary interventions, and exercise, along with identification and treatment of obstructive sleep apnea, should therefore be considered in this population.

Evaluation of immune response after moderate and overtraining exercise in wistar rat

OBJECTIVE(S)

The effect of prolonged overtraining on cytokine kinetics was compared with moderate exercise in the present study.

MATERIALS AND METHODS

Male Wistar rats were randomly divided into control sedentary (C), moderate trained (MT), (V=20 m/min, 30 min/day for 6 days a week, 8 weeks), overtrained (OT) (V=25 m/min, 60min/day for 6 days a week, 11 weeks) and recovered overtrained (OR) (OT plus 2 weeks recovery) groups, (n=6 for each group). Immediately, 24 hr and 2 weeks (in OR) after last bout of exercise blood samples were obtained. The plasma concentrations of TNFα, IL-6, IL-10, IL-4 and IFN were measured by ELISA method.

RESULTS

Immediately after last bout of exercise the following findings were observed; IL-6, IL-10 and TNFα concentrations increased in OT and OR groups compared with control (P<0.05-P<0.001). Serum level of IL-4 decreased (P<0.01) but IFN increased (P<0.05) in MT group vs. control. In addition, circulatory levels of TNFα, IL-6, IL-10 and IL-4 were higher but the IFN concentrations were lower in OT and OR groups than MT group (P<0.05-P<0.01). The IFN-γ/IL4 ratio was significantly increased in MT (P<0.01) while it decreased in OT group. There were not statistical differences in TNFα, IL-6, and IFN levels between different time intervals after exercise in MT, OT and OR groups.

CONCLUSION

These data confirm a positive effect of moderate exercise on immune function and a decrease in susceptibility to viral infection by inducing Th1 cytokine profile shift. However, prolonged and overtraining exercise causes numerous changes in immunity that possibly reflects physiological stress and immune suppression.

Deletion of airway cilia results in noninflammatory bronchiectasis and hyperreactive airways

The mechanisms for the development of bronchiectasis and airway hyperreactivity have not been fully elucidated. Although genetic, acquired diseases and environmental influences may play a role, it is also possible that motile cilia can influence this disease process. We hypothesized that deletion of a key intraflagellar transport molecule, IFT88, in mature mice causes loss of cilia, resulting in airway remodeling. Airway cilia were deleted by knockout of IFT88, and airway remodeling and pulmonary function were evaluated. In IFT88(-) mice there was a substantial loss of airway cilia on respiratory epithelium. Three months after the deletion of cilia, there was clear evidence for bronchial remodeling that was not associated with inflammation or apparent defects in mucus clearance. There was evidence for airway epithelial cell hypertrophy and hyperplasia. IFT88(-) mice exhibited increased airway reactivity to a methacholine challenge and decreased ciliary beat frequency in the few remaining cells that possessed cilia. With deletion of respiratory cilia there was a marked increase in the number of club cells as seen by scanning electron microscopy. We suggest that airway remodeling may be exacerbated by the presence of club cells, since these cells are involved in airway repair. Club cells may be prevented from differentiating into respiratory epithelial cells because of a lack of IFT88 protein that is necessary to form a single nonmotile cilium. This monocilium is a prerequisite for these progenitor cells to transition into respiratory epithelial cells. In conclusion, motile cilia may play an important role in controlling airway structure and function.

Moderate aerobic exercise alters migration patterns of antigen specific T helper cells within an asthmatic lung

Studies have indicated increased incidence and severity of allergic asthma due to western lifestyle and increased sedentary activity. Investigations also indicate that exercise reduces the severity of asthma; however, a mechanism of action has not been elucidated. Additional work implicates re-distribution of T helper (Th) cells in mediating alterations of the immune system as a result of moderate aerobic exercise in vivo. We have previously reported that exercise decreases T helper 2 (Th2) responses within the lungs of an ovalbumin (OVA)-sensitized murine allergic asthma model. Therefore, we hypothesized that exercise alters the migration of OVA-specific Th cells in an OVA-challenged lung. To test this hypothesis, wildtype mice received OVA-specific Th cells expressing a luciferase-reporter construct and were OVA-sensitized and exercised. OVA-specific Th cell migration was decreased in OVA-challenged lungs of exercised mice when compared to their sedentary controls. Surface expression levels of lung-homing chemokine receptors, CCR4 and CCR8, on Th cells and their cognate lung-homing chemokine gradients revealed no difference between exercised and sedentary OVA-sensitized mice. However, transwell migration experiments demonstrated that lung-derived Th cells from exercised OVA-sensitized mice exhibited decreased migratory function versus controls. These data suggest that Th cells from exercised mice are less responsive to lung-homing chemokine. Together, these studies demonstrate that moderate aerobic exercise training can reduce the accumulation of antigen-specific Th cell migration into an asthmatic lung by decreasing chemokine receptor function.

Neuroimmune semaphorin 4D is necessary for optimal lung allergic inflammation

Neuroimmune semaphorin 4D (Sema4D) was found to be expressed and function in the nervous and immune systems. In the immune system, Sema4D is constitutively expressed on T cells and regulates T cell priming. In addition, it displays a stimulatory function on macrophages, DC, NK cells, and neutrophils. As all these cells are deeply involved in asthma pathology, we hypothesized that Sema4D plays a critical non-redundant regulatory role in allergic airway response. To test our hypothesis, we exposed Sema4D(-/-) and WT mice to OVA injections and challenges in the well-defined mouse model of OVA-induced experimental asthma. We observed a significant decrease in eosinophilic airway infiltration in allergen-treated Sema4D(-/-) mice relative to WT mice. This reduced allergic inflammatory response was associated with decreased BAL IL-5, IL-13, TGFβ1, IL-6, and IL-17A levels. In addition, T cell proliferation in OVA₃₂₃₋₃₃₉-restimulated Sema4D(-/-) cell cultures was downregulated. We also found increased Treg numbers in spleens of Sema4D(-/-) mice. However, airway hyperreactivity (AHR) to methacholine challenges was not affected by Sema4D deficiency in either acute or chronic experimental disease setting. Surprisingly, lung DC number and activation were not affected by Sema4D deficiency. These data provide a new insight into Sema4D biology and define Sema4D as an important regulator of Th2-driven lung pathophysiology and as a potential target for a combinatory disease immunotherapy.

Dietary restriction and exercise improve airway inflammation and clinical outcomes in overweight and obese asthma: a randomized trial

BACKGROUND

Obesity and asthma are associated conditions; however, the mechanisms linking the two remain unclear. Few studies have examined the effects of weight loss on inflammation and clinical outcomes in obese-asthma.

OBJECTIVE

To compare the effects of weight loss achieved by dietary restriction, exercise or combined dietary restriction and exercise on airway inflammation and clinical outcomes in overweight and obese adults with asthma.

METHODS

Participants (n = 46; 54.3% female, body mass index (mean ± SD) 33.7 ± 3.5 kg/m(2) ) were randomized to complete a 10-week dietary, exercise or combined dietary and exercise intervention. Dual-energy x-ray absorptiometry was performed, the Juniper Asthma Control Questionnaire and Juniper Asthma Quality of Life Questionnaire completed and inflammatory markers, dietary intake and physical activity measured. The trial was registered with the Australian Clinical Trials Registry: ACTRN12611000235909.

RESULTS

Retention was 82.6%. Mean ± SD weight loss was 8.5 ± 4.2%, 1.8 ± 2.6% and 8.3 ± 4.9% after the dietary, exercise and combined interventions respectively. Asthma control improved after the dietary (mean ± SD; -0.6 ± 0.5, P ≤ 0.001) and combined interventions (-0.5 ± 0.7, P = 0.040), whereas quality of life improved after the dietary [median (IQR); 0.9 (0.4, 1.3), P = 0.002], exercise [0.49 (0.03, 0.78), P = 0.037] and combined [0.5 (0.1, 1.0), P = 0.007] interventions. A 5-10% weight loss resulted in clinically important improvements to asthma control in 58%, and quality of life in 83%, of subjects. Gynoid adipose tissue reduction was associated with reduced neutrophilic airway inflammation in women [β-coefficient (95% CI); 1.75 (0.02, 3.48), P = 0.047], whereas a reduction in dietary saturated fat was associated with reduced neutrophilic airway inflammation in males (r = 0.775, P = 0.041). The exercise intervention resulted in a significant reduction to sputum eosinophils [median (IQR); -1.3 (-2.0, -1.0)%, P = 0.028].

CONCLUSION AND CLINICAL RELEVANCE

This study suggests a weight-loss goal of 5-10% be recommended to assist in the clinical management of overweight and obese adults with asthma. The obese-asthma phenotype may involve both innate and allergic inflammatory pathways.

Geniposide inhibits airway inflammation and hyperresponsiveness in a mouse model of asthma

Our group recently reported the strong anti-inflammatory effects of geniposide (Gen), a bioactive iridoid glucoside derived from gardenia jasminoides, in a mouse acute lung injury model. Herein, we hypothesized that Gen might also have potential therapeutic benefits in treatment of asthma, which was tested in a mouse model of ovalbumin (Ova)-induced allergic airway inflammation. Ova-sensitized and -challenged BALB/c mice, as compared with control animals, displayed airway hyperresponsiveness (AHR), bronchoalveolar lavage eosinophilia, mucus hypersecretion, and increased T help 2 (Th2)-associated cytokine and chemokine amounts, as well as serum Ova-specific immunoglobulin E (IgE) level. Being compared with the Ova-induced hallmarks of asthma, intraperitoneal Gen treatment prevented eosinophilic pulmonary infiltration, attenuated the increases in interleukin (IL)-4, IL-5, and IL-13, and reduced eotaxin and vascular cell adhesion molecule 1 (VCAM-1) expression. Also, Gen significantly ameliorated the Ova-driven airway hyperresponsiveness, mucus hypersecretion, and allergen-specific IgE level, which are the cardinal pathophysiological symptoms in allergic airway diseases. In addition, the efficacy of Gen was comparable to that of dexamethasone (Dex), a currently available anti-asthmatic drug. Collectively, our findings reveal that the development of immunoregulatory strategies based on Gen may be considered as an effective adjuvant therapy for allergic asthma.

Respiratory syncytial virus reverses airway hyperresponsiveness to methacholine in ovalbumin-sensitized mice

Each year, approximately 20% of asthmatics in the United States experience acute symptom exacerbations, which commonly result from pulmonary viral infections. The majority of asthma exacerbations in very young children follow infection with respiratory syncytial virus (RSV). However, pathogenic mechanisms underlying induction of asthma exacerbations by RSV are not well understood. We therefore investigated the effect of post-sensitization RSV infection on lung function in ovalbumin (OVA)-sensitized BALB/c mice as a model of RSV asthma exacerbations. OVA sensitization of uninfected female BALB/c mice increased bronchoalveolar lavage fluid (BALF) eosinophil levels and induced airway hyperresponsiveness to the muscarinic agonist methacholine, as measured by the forced-oscillation technique. In contrast, intranasal infection with replication-competent RSV strain A2 for 2–8 days reduced BALF eosinophil counts and reversed airway hyperresponsiveness in a pertussis toxin-sensitive manner. BALF levels of the chemokine keratinocyte cytokine (KC; a murine homolog of interleukin-8) were elevated in OVA-sensitized, RSV-infected mice and reversal of methacholine hyperresponsiveness in these animals was rapidly inhibited by KC neutralization. Hyporesponsiveness could be induced in OVA-sensitized, uninfected mice by recombinant KC or the Gαi agonist melittin. These data suggest that respiratory syncytial virus induces KC-mediated activation of Gαi, resulting in cross-inhibition of Gαq-mediated M₃-muscarinic receptor signaling and reversal of airway hyperresponsiveness. As in unsensitized mice, KC therefore appears to play a significant role in induction of airway dysfunction by respiratory syncytial virus. Hence, interleukin-8 may be a promising therapeutic target to normalize lung function in both asthmatics and non-asthmatics with bronchiolitis. However, the OVA-sensitized, RSV-infected mouse may not be an appropriate model for investigating the pathogenesis of viral asthma exacerbations.

Effects of exercise training on airway closure in asthmatics

We previously reported that responsiveness to methacholine (Mch) in the absence of deep inspiration (DI) decreased in healthy subjects after a short course of exercise training. We assessed whether a similar beneficial effect of exercise on airway responsiveness could occur in asthmatics. Nine patients (male/female: 3/6; mean age ± SD: 24 ± 2 yr) with mild untreated asthma [forced expiratory volume in 1 s (FEV(1)): 100 ± 7.4% pred; FEV(1)/vital capacity (VC): 90 ± 6.5%] underwent a series of single-dose Mch bronchoprovocations in the absence of DI in the course of a 10-wk training rowing program (6 h/wk of submaximal and maximal exercise), at baseline (week 0), and at week 5 and 10. The single-dose Mch was established as the dose able to induce ≥ 15% reduction in inspiratory vital capacity (IVC) and was administered to each subject at every challenge occasion. Five asthmatics (male/female: 1/4; mean age ± SD: 26 ± 3 yr) with similar baseline lung function (FEV(1): 102 ± 7.0% predicted; FEV(1)/VC: 83 ± 6.0%; P = 0.57 and P = 0.06, respectively) not participating in the exercise training program served as controls. In the trained group, the Mch-induced reduction in IVC from baseline was 22 ± 10% at week 0, 13 ± 11% at week 5 (P = 0.03), and 11 ± 8% at week 10 (P = 0.028). The Mch-induced reduction in FEV(1) did not change with exercise (P = 0.69). The reduction in responsiveness induced by exercise was of the same magnitude of that previously obtained in healthy subjects (50% with respect to pretraining). Conversely, Mch-induced reduction in IVC in controls remained unchanged after 10 wk (%reduction IVC at baseline: 21 ± 20%; after 10 wk: 29 ± 14%; P = 0.28). This study indicates that a short course of physical training is capable of reducing airway responsiveness in mild asthmatics.

Rapid morphological characterization of isolated mitochondria using Brownian motion

Mitochondrial morphology has been associated with numerous pathologies including cancer, diabetes, obesity and heart disease. However, the connection is poorly understood-in part due to the difficulty of characterizing the morphology. This impedes the use of morphology as a tool for disease detection/monitoring. Here, we use the Brownian motion of isolated mitochondria to characterize their size and shape in a high throughput fashion. By using treadmill exercise training, mitochondria from heart and gastrocnemius of Balb/c mice were modulated in size and used to investigate the protocol. Consistent with previous reports, the heart mitochondria of untrained mice increased 5% in diameter immediately after a single bout of moderate exercise (1.091 ± 0.004 μm) as compared to completely sedentary controls (1.040 ± 0.022 μm). In addition, no change was observed in the size of gastrocnemius mitochondria (1.025 ± 0.018 μm), which was also in agreement with previous studies. The method was also successfully applied to smaller Saccharomyces cerevisiae mitochondria.

Allergy and sports in children

Physical activity is beneficial for children with positive outcomes for mental and physical well-being. Allergic conditions unique to the sporting arena may serve as an impediment to participation in physical activity for allergic children. A common example is exercise-induced asthma; less common activity-related allergic conditions include food-dependent exercise-induced anaphylaxis, exercise-induced anaphylaxis, and exercise-induced urticaria. Allergic children may also be at risk of allergic reactions when exposed to allergens that are more commonly found in the sports environment, e.g., latex, sports drinks, and medications such as NSAIDs. Recent advances in our understanding of the patho-physiological and immunologic mechanisms that may account for these conditions have facilitated more effective and safer management strategies. There are also important immunologic lessons to be learnt with respect to specific physical factors that may result in diminished allergen tolerance; indeed, these lessons may facilitate safer allergen desensitisation regimens. The role of the immune system in exercise-induced immunoallergic syndromes, clinical aspects, and diagnostic and therapeutic approaches are discussed in this review.

S100A12 and the Airway Smooth Muscle: Beyond Inflammation and Constriction

Airway inflammation, lung remodeling, and Airway Hyperresponsiveness (AHR) are major features of asthma and Chronic Obstructive Pulmonary Disease (COPD). The inflammatory response to allergens, air pollutants, and other insults is likely to play a key role in promoting structural changes in the lung including the overabundance of Airway Smooth Muscle (ASM) seen in asthmatics. These alterations or remodeling could, in turn, impact the immunmodulatory actions of the ASM, the ASM's contractile properties, and the development of AHR. New evidences suggest that airway inflammation and AHR are not tightly related to each other and that the structural component of the airway, mainly the ASM, is a chief driver of AHR. Members of the S100/calgranulins family have been implicated in the regulation of inflammation and cell apoptosis in various systems. S100A12 is highly expressed in neutrophils and is one of the most abundant proteins in the lungs of patients with asthma or COPD. Studies with genetic engineered mice with smooth muscle cell-targeted expression of human S100A12 revealed that S100A12 reduces airway smooth muscle amounts and dampens airway inflammation and airway hyperreactivity in a model of allergic lung inflammation. Thus, targeting airway smooth muscle for instance through delivery of pro-apoptotic S100A12 could represent an attractive means to promote ASM apoptosis and to reduce ASM abundance in asthmatics.

Airway epithelium mediates the anti-inflammatory effects of exercise on asthma

Airway epithelium plays an important role in the asthma physiopathology. Aerobic exercise decreases Th2 response in murine models of allergic asthma, but its effects on the structure and activation of airway epithelium in asthma are unknown. BALB/c mice were divided into control, aerobic exercise, ovalbumin-sensitized and ovalbumin-sensitized plus aerobic exercise groups. Ovalbumin sensitization occurred on days 0, 14, 28, 42, and aerosol challenge from day 21 to day 50. Aerobic exercise started on day 22 and ended on day 50. Total cells and eosinophils were reduced in ovalbumin-sensitized group submitted to aerobic exercise. Aerobic exercise also reduced the oxidative and nitrosative stress and the epithelial expression of Th2 cytokines, chemokines, adhesion molecules, growth factors and NF-kB and P2X7 receptor. Additionally, aerobic exercise increased the epithelial expression of IL-10 in non-sensitized and sensitized animals. These findings contribute to the understanding of the beneficial effects of aerobic exercise for chronic allergic airway inflammation, suggesting an immune-regulatory role of exercise on airway epithelium.

A rat model of exercise-induced asthma: a nonspecific response to a specific immunogen

Exercise-induced bronchoconstriction (EIB) is common; however, key aspects of its pathogenesis are still unclear. We investigated the feasibility of adapting an established animal model of asthma to investigate the earliest stages of EIB. The hypothesis was that a single exposure to a normally innocuous, and brief, exercise challenge could trigger EIB symptoms in rats previously sensitized to ovalbumin (OVA) but otherwise unchallenged. Brown-Norway rats were sensitized by intraperitoneal injection of OVA at 0 and 2 wk. At week 3, animals were exposed to either aerosolized OVA (SS) or exercise (EXS). A trained, blinded, clinical observer graded EIB by respiratory sounds. Plasma and lung cytokine levels were analyzed. No control rats with or without exercise (EX, CON) showed evidence of EIB. Eighty percent of the SS group demonstrated abnormal breath sounds upon exposure to aerosolized OVA. Approximately 30% of EXS rats sensitized to OVA but exposed only to exercise had abnormal breath sounds. Lung tissue levels of TNF-α, IL-1α, growth-related oncogene/keratinocyte/chemoattractant, and IFN-γ were significantly higher (P < 0.001) in the SS group, relative to all other groups. Changes in most of these cytokines were not notable in the EXS rats, suggesting a different mechanism of EIB. Remarkably, IFN-γ, but not the other cytokines measured, was significantly elevated following brief exercise in both sensitized and unsensitized rats. Exercise led to detectable breathing sound abnormalities in sensitized rats, but less severe than those observed following classical OVA challenge. Precisely how this immune crossover occurs is not known, but this model may be useful in elucidating essential mechanisms of EIB.

Repeated bouts of aerobic exercise enhance regulatory T cell responses in a murine asthma model

We have reported previously that moderate intensity aerobic exercise training attenuates airway inflammation in a murine asthma model. Recent studies implicate regulatory T (Treg) cells in decreasing asthma-related airway inflammation; as such, the current study examined the effect of exercise on Treg cell function in a murine asthma model. Mice were sensitized with ovalbumin (OVA) prior to the start of exercise training at a moderate intensity 3x/week for 4weeks; exercise was performed as treadmill running (13.5m/min, 0% grade). Mice were OVA challenged repeatedly throughout the exercise protocol. At protocol completion, mice were analyzed for changes in the number and suppressive function of CD4(+)CD25(+)Foxp3(+) cells isolated from lungs, mediastinal lymph nodes, and spleens. Results show that exercise increased significantly the number of Foxp3(+) cells within the lungs and mediastinal lymph nodes, but not the spleens, of OVA-treated mice as compared with sedentary controls. Exercise also enhanced the suppression function of CD4(+)CD25(+)Foxp3(+) Treg cells derived from OVA-treated mice as compared with sedentary controls. Specifically, Treg cells from exercised, OVA-treated mice more effectively suppressed CD4(+)CD25(-) cell proliferation and Th2 cytokine production in vitro. Enhanced suppression was associated with increased protein levels of TGF-beta and lesser amounts of IL-10 and IL-17; however, blocking TGF-beta had no effect on suppressive functions. These data demonstrate that exercise-mediated increases in Treg cell function may play a role in the attenuation of airway inflammation. Further, these results indicate that moderate intensity aerobic exercise training may alter the Treg cell function within the asthmatic airway.

Respiratory syncytial virus induces airway insensitivity to beta-agonists in BALB/c mice

beta-Adrenergic agonists (beta-agonists) are commonly used to treat respiratory syncytial virus (RSV) bronchiolitis but are generally ineffective for unknown reasons. We have previously shown that RSV strain A2 inhibits bronchoalveolar epithelial responses to beta-agonists in a BALB/c mouse model by inducing heterologous keratinocyte cytokine (KC)/CXCR2-mediated desensitization of epithelial beta(2)-adrenergic receptors. The aim of the current study was to determine whether RSV also induces airway insensitivity to beta-agonists. Total lung resistance (R) was measured in anesthetized female BALB/c mice undergoing mechanical ventilation on a flexiVent computer-controlled piston ventilator. Data were analyzed using the single-compartment model. Infection with RSV A2 did not induce airway hyperresponsiveness to increasing doses of the nebulized cholinergic agonist methacholine (MCh) at any time point after RSV infection. Prenebulization with the beta-agonist terbutaline (100 muM) significantly attenuated bronchoconstrictive responses to 20 and 50 mg/ml MCh in uninfected mice and in mice infected with RSV 4-8 days postinfection (d.p.i.). However, in mice infected with replication-competent, but not UV-inactivated, RSV for 2 days, significant terbutaline insensitivity was found. Terbutaline insensitivity at 2 d.p.i. could be reversed by systemic preinfection treatment with neutralizing anti-CXCR2 antibodies, which reduced bronchoalveolar lavage (BAL) neutrophil counts but did not alter viral replication, BAL KC levels, or lung edema. Terbutaline insensitivity was also reversed by postinfection nebulization with neutralizing anti-KC or anti-CXCR2 antibodies and could be replicated in normal, uninfected mice by nebulization with recombinant KC. These data suggest that KC/CXCR2-mediated airway insensitivity to beta-agonists may underlie the modest utility of these drugs as bronchodilators in therapy for acute RSV bronchiolitis.

Repeated bouts of moderate-intensity aerobic exercise reduce airway reactivity in a murine asthma model

We have reported that moderate-intensity aerobic exercise training attenuates airway inflammation in mice sensitized/challenged with ovalbumin (OVA). The current study determined the effects of repeated bouts of aerobic exercise at a moderate intensity on airway hyperresponsiveness (AHR) in these mice. Mice were sensitized/challenged with OVA or saline and exercised at a moderate intensity 3 times/week for 4 weeks. At protocol completion, mice were analyzed for changes in AHR via mechanical ventilation. Results show that exercise decreased total lung resistance 60% in OVA-treated mice as compared with controls; exercise also decreased airway smooth muscle (ASM) thickness. In contrast, exercise increased circulating epinephrine levels 3-fold in saline- and OVA-treated mice. Because epinephrine binds beta(2)-adrenergic receptors (AR), which facilitate bronchodilatation, the role of beta(2)-AR in exercise-mediated improvements in AHR was examined. Application of the beta(2)-AR antagonist butoxamine HCl blocked the effects of exercise on lung resistance in OVA-treated mice. In parallel, ASM cells were examined for changes in the protein expression of beta(2)-AR and G-protein receptor kinase-2 (GRK-2); GRK-2 promotes beta(2)-AR desensitization. Exercise had no effect on beta(2)-AR expression in ASM cells of OVA-treated mice; however, exercise decreased GRK-2 expression by 50% as compared with controls. Exercise also decreased prostaglandin E(2) (PGE(2)) production 5-fold, but had no effect on E prostanoid-1 (EP1) receptor expression within the lungs of OVA-treated mice; both PGE(2) and the EP1 receptor have been implicated in beta(2)-AR desensitization. Together, these data indicate that moderate-intensity aerobic exercise training attenuates AHR via a mechanism that involves beta(2)-AR.