Circulating catecholamines in exercise and hyperventilation induced asthma

Allosteric modulator potentiates β2AR agonist-promoted bronchoprotection in asthma models

Asthma is a chronic inflammatory disease associated with episodic airway narrowing. Inhaled β2-adrenergic receptor (β2AR) agonists (β2-agonists) promote - with limited efficacy - bronchodilation in asthma. All β2-agonists are canonical orthosteric ligands that bind the same site as endogenous epinephrine. We recently isolated a β2AR-selective positive allosteric modulator (PAM), compound-6 (Cmpd-6), which binds outside of the orthosteric site and modulates orthosteric ligand functions. With the emerging therapeutic potential of G-protein coupled receptor allosteric ligands, we investigated the impact of Cmpd-6 on β2AR-mediated bronchoprotection. Consistent with our findings using human β2ARs, Cmpd-6 allosterically potentiated β2-agonist binding to guinea pig β2ARs and downstream signaling of β2ARs. In contrast, Cmpd-6 had no such effect on murine β2ARs, which lack a crucial amino acid in the Cmpd-6 allosteric binding site. Importantly, Cmpd-6 enhanced β2 agonist-mediated bronchoprotection against methacholine-induced bronchoconstriction in guinea pig lung slices, but - in line with the binding studies - not in mice. Moreover, Cmpd-6 robustly potentiated β2 agonist-mediated bronchoprotection against allergen-induced airway constriction in lung slices obtained from a guinea pig model of allergic asthma. Cmpd-6 similarly enhanced β2 agonist-mediated bronchoprotection against methacholine-induced bronchoconstriction in human lung slices. Our results highlight the potential of β2AR-selective PAMs in the treatment of airway narrowing in asthma and other obstructive respiratory diseases.

Physical training in adults with asthma: An integrative approach on strategies, mechanisms, and benefits

Asthma is a chronic airway disease characterized by airflow limitation and respiratory symptoms associated with chronic airway and systemic inflammation, bronchial hyperreactivity (BHR), and exercise-induced bronchoconstriction (EIB). Asthma is a heterogeneous disease classified according to distinct airway and systemic inflammation. Patients commonly present with several comorbidities, including anxiety, depression, poor sleep quality, and reduced physical activity levels. Individuals with moderate to severe asthma often have more symptoms and difficulty achieving adequate clinical control, which is associated with poor quality of life, despite proper pharmacological treatment. Physical training has been proposed as an adjunctive therapy for asthma. Initially, it was suggested that the effect of physical training might be attributed to the improved oxidative capacity and reduced production of exercise metabolites. However, in the last decade, there has been evidence that aerobic physical training promotes anti-inflammatory effects in asthma patients. Physical training improves BHR and EIB, asthma symptoms, clinical control, anxiety, and depression levels, sleep quality, lung function, exercise capacity, and dyspnea perception. Furthermore, physical training reduces medication consumption. The most commonly used exercise strategies are moderate aerobic and breathing exercises; however, other techniques, such as high-intensity interval training, have shown promising effects. In the present study, we reviewed the strategies and beneficial effects of exercise on clinical and pathophysiological asthma outcomes.

Heart rate recovery in adult individuals with asthma

Slow heart rate recovery (HRR) after exercise is a predictor of overall mortality in individuals with and without cardiovascular or respiratory disorders. No data on adults with asthma are available. The purpose of the study is to evaluate the prevalence of slow HRR in these individuals as compared with those with chronic obstructive pulmonary disease (COPD). We performed a retrospective analysis of baseline characteristics and physiological response to the six-minute walking distance test of stable individuals with asthma or COPD. Slow HRR was defined as HRpeak - HR at 1 minute after end exercise <12 bpm. Individuals with asthma walked significantly longer (median (IQR): 455 (385-512) vs 427 (345-485) meters; p=0.005) with a lower prevalence of slow HRR (30.3% vs 49.0%, respectively: p<0.001) than those with COPD. Individuals with asthma and slow HRR were older and walked less than those with normal HRR, without any difference in airway obstruction or in disease severity. Multivariate analysis showed that only the difference HRpeak - baseline HR (∆HR), was a predictor of slow HRR in both groups. More than 30% of adult individuals with asthma may show slow HRR. Only exercise ∆HR but no baseline characteristic seems to predict the occurrence of slow HRR.

Exercise-induced bronchoconstriction in elite or endurance athletes:: Pathogenesis and diagnostic considerations

OBJECTIVE

To review the pathogenesis and evaluation of exercise-induced bronchoconstriction pertaining to the elite or endurance athlete, as well as propose a diagnostic algorithm based on the current literature.

DATA SOURCES

Studies were identified using Ovid MEDLINE and reference lists of key articles.

STUDY SELECTIONS

Randomized controlled trials were selected when available. Systematic reviews and meta-analyses of peer-reviewed literature were included, as were retrospective studies and observational studies of clinical interest.

RESULTS

Exercise-induced bronchoconstriction (EIB) is the physiologic entity in which exercise induces acute narrowing of the airways and occurs in patients both with and without asthma. It may present with or without respiratory symptoms, and the underlying cause is likely attributable to environment stressors to the airway encountered during exercise. These include the osmotic effects of inhaled dry air, temperature variations, autonomic nervous system dysregulation, sensory nerve reactivity, and airway epithelial injury. Deposition of allergens, particulate matter, and gaseous pollutants into the airway also contribute. Elite and endurance athletes are exposed to these stressors more frequently and in greater duration than the general population.

CONCLUSION

A greater awareness of EIB among elite and endurance athletes is needed, and a thorough evaluation should be performed if EIB is suspected in this population. We propose an algorithm to aid in this evaluation. Symptoms should not be solely relied on for diagnosis but should be taken into the context of bronchoprovocative challenges, which should replicate the competitive environment as closely as possible. Further research is needed to validate these tests' predictive values.

Epistasis between phenylethanolamine N-methyltransferase and β2-adrenergic receptor influences extracellular epinephrine level and associates with the susceptibility to allergic asthma

BACKGROUND

Reduced extracellular epinephrine level often associates with asthma-related symptoms; however, the correlation between asthma and genetic variants in genes participating in the epinephrine signalling pathway remains unclear.

OBJECTIVE

To characterize the functions of single nucleotide polymorphisms (SNPs) in phenylethanolamine N-methyltransferase (PNMT) and β2-adrenergic receptor (ADRB2), and to study the effects, including both direct and epistatic, of these SNPs on serum epinephrine level and asthma susceptibility.

METHODS

Single nucleotide polymorphisms functions were characterized through in vitro luciferase assay. ADRB2 gene expression level in peripheral blood mononuclear cell (PBMC) was measured by transcriptome sequencing and expression microarray on two separate Asian cohorts (NUS-UTAR, n = 278 and NUS-TA, n = 58). Serum epinephrine level was assessed on a Singapore Chinese cohort (NUS-SH, n = 314) with 155 asthmatic and 159 non-asthmatic subjects. A separate Singapore Chinese cohort (NUS-G, n = 3009) was genotyped to show disease association (direct and epistatic effect) of functional SNPs in PNMT and ADRB2.

RESULTS

Reduced serum epinephrine level was associated with increased asthma risk in Singapore Chinese. The minor allele of rs876493 was shown to increase PNMT promoter activity and reduce asthma risk. Multiple SNPs in ADRB2 forms a haplotype that was associated with the differential promoter activity of this gene. In this haplotype, rs11168070 was associated directly with ADRB2 expression in PBMCs. Both minor alleles from rs876493 and rs11168070 contribute synergistically to reduce asthma risk and increase serum epinephrine level.

CONCLUSION AND CLINICAL RELEVANCE

Epistatic interaction between genetic variants from PNMT (rs876493) and ADRB2 (rs11168070) is associated with serum epinephrine level and the susceptibility of asthma. Our findings improved the current understanding of the genetic basis of this disease, while genotypic states of these SNPs may serve as potential biomarkers to predict susceptibility to the disease.

GLCCI1 rs37973 is associated with the response of adrenal hormone to inhaled corticosteroids in asthma

Background

Previous studies have demonstrated that glucocorticoid-induced transcript 1 gene (GLCCI1) rs37973 mutant genotype is associated with poor inhaled corticosteroid (ICS) response in asthmatics. As human airway relaxation is regulated by circulation epinephrine, which can be enhanced by corticosteroid. It is unknown whether or not GLCCI1 rs37973 is associated with circulation epinephrine and cortisol concentrations in asthma. The aim of this study is to evaluate these relationships.

Methods

A total of 182 asthmatics and 180 healthy controls were recruited for the study. 30 mild-to-moderate asthmatics received fluticasone propionate (125 μg, bid) treatment for 12 weeks. GLCCI1 rs37973 genotyping was performed with the iPlex MassARRAY genotyping platform. The plasma concentrations of cortisol and epinephrine of each participant were detected by enzyme linked immunosorbent assay (ELISA) kits.

Results

GLCCI1 rs37973 homozygotes mutant genotype GG had a higher plasma epinephrine concentration (median concentration 27.032 pg/ml, n_GG = 36; median concentration 23.149 pg/ml, n_AA+AG = 146; P = 0.015) and cortisol concentration (median concentration 1.141 ng/ml, n_GG = 36; median concentration 0.921 ng/ml, n_AA+AG = 146; P = 0.013). Both epinephrine concentration and cortisol concentration in plasma were positively correlated with FEV₁ (r = 0.889 and r = 0.821, respectively. n_asthma = 182). For asthmatics treated with ICS, rs37973 was associated with change in plasma epinephrine and cortisol concentration in a recessive model (AA + AG vs GG), with GG had less improvement in epinephrine concentration [ΔEPI_AA+AG = 6.843 (9.26) pg/ml, n_AA+AG = 26; ΔEPI_GG = −1.666 (6.52) pg/ml, n_GG = 4; P = 0.018] and cortisol concentration [ΔCOR_AA+AG = 0.3040 (0.21) ng/ml, n_AA+AG = 26; ΔCOR_GG = −0.066 (0.24) ng/ml, n_GG = 4; P = 0.009].

Conclusions

Our study suggested that the poor ICS response in GLCCI1 rs37973 mutant genotype might be related to the less increased amplitudes of plasma epinephrine and cortisol in asthmatic patients.

Trial registration

ChiCTR-RCC-13003634 www.chictr.org.cn. Active since September 27, 2013.

Heating-induced contraction in airways smooth muscle: A possible causative factor of exercise-induced bronchoconstriction

Asthmatic patients often suffer from bronchoconstriction or asthma following breathing hot air or exposure to exercise due to raises the core body temperature. However, the direct effect of heating airways has not been studied yet. The aim of this study is to investigate the effect of heating on tracheal and bronchiolar smooth muscles. Isolated ovine tracheal strips and bronchiolar segments preparations were suspended in organ baths containing Krebs' solution for isometric tension recording. Tissues responses were examined during decreasing and elevating baths temperature (20 °C, 40 °C-45 °C and 50 °C). Cooling or heating induced rapid and reproducible contractions proportional with decreasing or increasing temperature respectively in tracheal and bronchiolar preparations. On reset to 37 °C the tone returned rapidly to basal level. Changing the bath's temperature from 37 °C to 20 °C or to 40 °C and 45 °C for tracheal strips or to 45 °C and 50 °C for bronchiolar segments induced contractions in both preparations. Changing the temperature below or above the normal body temperature (37 °C), leads to airways contractions. Heating induced contractions in tracheal and bronchiolar smooth muscle proportional to the heating temperature. Therefore, breathing hot air or elevation of body core temperature due to exercise can be considered possible causative factor of heating- or exercise-induced bronchoconstriction.

Thoracoabdominal Asynchrony Contributes to Exercise Limitation in Mild Asthmatic Subjects

This study aimed to better understand how subjects with stable asthma and without exercise-induced bronchoconstriction respond to mild exercise. Breathing pattern, chest wall compartmental and operational volumes, and thoracoabdominal asynchrony were assessed in 11 stable asthmatic subjects and 10 healthy subjects at rest and during exercise in a cycle-ergometer through optoelectronic plethysmography. Dyspnea and sensation of leg effort were assessed through Borg scale. During exercise, with similar minute ventilation, a significant lower chest wall tidal volume (p = 0.003) as well as a higher respiratory rate (p < 0.05) and rapid shallow breathing (p < 0.05) were observed in asthmatic when compared to healthy subjects. Asthmatic subjects exhibited a significantly lower inspiratory (p < 0.05) and expiratory times (p < 0.05). Intergroup analysis found a significant higher end-expiratory chest wall volume in asthmatic subjects, mainly due to a significant increase in volume of the pulmonary ribcage (RCp; 170 ml, p = 0.002), indicating dynamic hyperinflation (DH). Dyspnea and sensation of leg effort were both significantly greater (p < 0.0001) in asthmatic when compared to healthy subjects. In addition to a higher thoracoabdominal asynchrony found between RCp and abdominal (AB) (p < 0.005) compartments in asthmatic subjects, post-inspiratory action of the inspiratory ribcage and diaphragm muscles were observed through the higher expiratory paradox time of both RCp (p < 0.0001) and AB (p = 0.0002), respectively. Our data suggest that a different breathing pattern is adopted by asthmatic subjects without exercise-induced bronchoconstriction during mild exercise and that this feature, associated with DH and thoracoabdominal asynchrony, contributes significantly to exercise limitation.

Redistribution of adrenomedullary nicotinic acetylcholine receptor subunits and the effect on circulating epinephrine levels in a murine model of acute asthma

The lack of circulating epinephrine (EPI) in the pathogenesis of asthma has long been attributed to the lack of adrenergic nerves in human airways. However, in this study we considered that EPI levels are regulated by EPI release in addition to synthesis. Nicotinic acetylcholine receptors (nAChRs) have been shown to control EPI release, and we hypothesized that redistribution of nAChR subunits modulates EPI release and circulating EPI levels. Using a mouse model of asthma, circulating EPI levels were measured by enzyme-linked immunosorbent assays. Changes in the expression of nAChR subunits in the adrenal medulla were observed by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blot analysis. Expression of phenylethanolamine N-methyltransferase, tyrosine hydroxylase and galanin was detected by RT-qPCR. Lung pathology, airway resistance (RL) and EPI levels were also assessed after treatment with an α7 nAChR agonist or antagonist. α7 nAChR mRNA expression in the adrenal medulla was increased by more than 2-fold (P<0.05), and circulating EPI levels increased rapidly after treatment with the α7 nAChR agonist. These results indicated that increased EPI release, which was caused by the overexpression of α7 nAChR, was responsible for elevated circulating EPI levels. After treatment with an agonist of α7 nAChR, RL was significantly decreased. Serum corticosterone levels in individual mice were measured to rule out glucocorticoid as the main mediator of changes in EPI levels. On the whole, redistribution of nAChR subunits, primarily α7 nAChR, occurs in the adrenal medulla in asthmatic mice. Increased α7 nAChR expression can rapidly increase serum EPI levels and decrease airway responsiveness.

Improvement of respiratory resistance by hot water immersing exercise in adult asthmatic patients

Acute effect of hot water immersing exercise on respiratory resistance (RR) was investigated in 12 adult asthmatics and six healthy males. They underwent mild exercise with comparable heart rates (HR = 120) in a hot water pool (water temp. 38°C) for 10 minutes. RRs were measured before and until 40 minutes after the exercise. Mean RRs of the patients before exercise (0.36 Kpa/l/s) reduced to less than 0.32 during 15 to 30 minutes after exercise (p<0.05). RRs of healthy subjects (0.19 Kpa/l/s) did not decrease significantly. Analysis of humoral factors relating to exercise metabolism and autonomic nervous system function of the patients suggested that the influence of sympathetic nervous activation persisted until 20 minutes after exercise. This physiotherapy had a specific feasibility for adult asthmatics in preventing exercise-induced wheezing.

Hyperventilation during electroencephalography: safety and efficacy

PURPOSE

To determine safety and efficacy of hyperventilation (HV) during electroencephalography (EEG).

METHODS

We report the findings of a prospective multicentre National Service Evaluation of the occurrence of adverse events, seizures and interictal epileptiform discharges seen in association with HV during EEG, in a relatively unselected, largely out patient population of 3475 being investigated predominantly for possible epileptic seizures.

RESULTS

Adverse events occurred rarely, and there were no reported significant cerebrovascular, cardiovascular or respiratory events. Of the 3170 patients suspected of 'epilepsy or possible epilepsy' 69 patients (2.2%) had seizures provoked by HV, but only one (0.03%) had a generalised tonic clonic seizure. The elicitation or increase of interictal epileptiform discharges (IEDs) was seen in 387 (12.2%) of the total 3170 patients with suspected epilepsy who hyperventilated. Furthermore 31 patients (0.9%) had psychogenic non-epileptic seizures.

CONCLUSION

HV is rarely associated with adverse events, but contributes to the diagnosis and classification of seizure disorders in an appreciable proportion of patients with epilepsy and non-epileptic attacks. These findings confirm that HV in selected patients is a valid activation technique in diagnostic EEG, where the potential benefits out weigh the risks, and also provide information that may assist the informed consent process.

High-intensity training induces EIB in rats through neuron transdifferentiation of adrenal medulla chromaffin cells

A high prevalence of exercise-induced bronchoconstriction (EIB) can be found in elite athletes, but the underlying mechanisms remain elusive. Airway responsiveness, NGF and epinephrine (EPI) levels, and chromaffin cell structure in high- (HiTr) and moderate-intensity training (MoTr) rats with or without ovalbumin (OVA) sensitization were measured in a total of 120 male Sprague-Dawley rats. The expression of NGF-associated genes in rat adrenal medulla was tested. Both HiTr and OVA intervention significantly increased airway resistance to aerosolized methacholine measured by whole body plethysmography. HiTr significantly increased inflammatory reaction in the lung with a major increase in peribronchial lymphocyte infiltration, whereas OVA significantly increased the infiltration of various inflammatory cells with an over 10-fold increase in eosinophil level in bronchoalveolar lavage. Both HiTr and OVA intervention upregulated circulating NGF level and peripherin level in adrenal medulla, but downregulated phenylethanolamine N-methyl transferase level in adrenal medulla and circulating EPI level. HiTr + OVA and HiTr + ExhEx (exhaustive exercise) interventions significantly enhanced most of the HiTr effects. The elevated NGF level was significantly associated with neuronal conversion of adrenal medulla chromaffin cells (AMCC). The levels of p-Erk1/2, JMJD3, and Mash1 were significantly increased, but the levels of p-p38 and p-JNK were significantly decreased in adrenal medulla in HiTr and OVA rats. Injection of NGF antiserum and moderate-intensity training reversed these changes observed in HiTr and/or OVA rats. Our study suggests that NGF may play a vital role in the pathogenesis of EIB by inducing neuron transdifferentiation of AMCC via MAPK pathways and subsequently decreasing circulating EPI.

Transformation of adrenal medullary chromaffin cells increases asthmatic susceptibility in pups from allergen-sensitized rats

Background

Studies have shown that epinephrine release is impaired in patients with asthma. The pregnancy of female rats (dams) with asthma promotes in their pups the differentiation of adrenal medulla chromaffin cells (AMCCs) into sympathetic neurons, mediated by nerve growth factor, which leads to a reduction in epinephrine secretion. However, the relatedness between the alteration of AMCCs and increased asthma susceptibility in such offspring has not been established.

Methods

In this study, we observed the effects of allergization via ovalbumin on rat pups born of asthmatic dams.

Results

Compared to the offspring of untreated controls, bronchial hyperreactivity and airway inflammation were more severe in the pups from sensitized (asthmatic) dams. In pups exposed to nerve growth factor (NGF) in utero these effects were aggravated further, but the effects were blocked in pups whose dams had been treated with anti-NGF. Furthermore, alterations in AMCC phenotype corresponded to the degree of bronchial hyperreactivity and lung lesions of the different treatment groups. Such AMCC alterations included degranulation of chromaffin granules, reduction of epinephrine and phenylethanolamine-n-methyl transferase, and elevation of NGF and peripherin levels.

Conclusions

Our results present evidence that asthma during the pregnancy of rat dams promotes asthma susceptibility in their offspring, and that the transformation of AMCCs to neurons induced by NGF plays an important role in this process.

The effect of unilateral adrenalectomy on transformation of adrenal medullary chromaffin cells in vivo: a potential mechanism of asthma pathogenesis

BACKGROUND

Decreased epinephrine (EPI) is an important underlying factor of bronchoconstriction in asthma. Exogenous β(2)-adrenergic receptor agonist is one of the preferred options to treat asthma. We previously showed that this phenomenon involved adrenal medullary chromaffin cell (AMCC) transformation to a neuron phenotype. However, the underlying molecular mechanism is not fully understood. To further explore this, an asthmatic model with unilateral adrenalectomy was established in this study.

METHODOLOGY/PRINCIPAL FINDINGS

Thirty-two rats were randomly into four groups (n = 8 each) control rats (controls), unilateral adrenalectomy rats (surgery-control, s-control), asthmatic rats (asthma), unilateral adrenalectomy asthmatic rats (surgery-induced asthma, s-asthma). Asthmatic rats and s-asthmatic rats were sensitized and challenged with ovalbumin (OVA). The pathological changes in adrenal medulla tissues were observed under microscopy. EPI and its rate-limiting enzyme, phenylethanolamine N-methyl transferase (PNMT), were measured. Peripherin, a type III intermediate filament protein, was also detected in each group. The asthmatic rats presented with decreased chromaffin granules and swollen mitochondria in AMCCs, and the s-asthmatic rats presented more serious pathological changes than those in asthmatic rats and s-control rats. The expressions of EPI and PNMT in asthmatic rats were significantly decreased, as compared with levels in controls (P<0.05), and a further decline was observed in s-asthmatic rats (P<0.05). The expression of peripherin was higher in the asthmatic rats than in the controls, and the highest level was found in the s-asthmatic rats (P<0.05).

CONCLUSION/SIGNIFICANCE

Compared with asthmatic rats and s-control rats, the transformation tendency of AMCCs to neurons is more obvious in the s-asthmatic rats. Moreover, this phenotype alteration in the asthmatic rats is accompanied by reduced EPI and PNMT, and increased peripherin expression. This result provides further evidence to support the notion that phenotype alteration of AMCCs contributes to asthma pathogenesis.

Low voltage vagal nerve stimulation reduces bronchoconstriction in guinea pigs through catecholamine release

OBJECTIVE

  Electrical stimulation of the vagus nerve at relatively high voltages (e.g., >10 V) can induce bronchoconstriction. However, low voltage (≤2 V) vagus nerve stimulation (VNS) can attenuate histamine-invoked bronchoconstriction. Here, we identify the mechanism for this inhibition.

METHODS

  In urethanea-nesthetized guinea pigs, bipolar electrodes were attached to both vagus nerves and changes in pulmonary inflation pressure were recorded in response to i.v. histamine and during VNS. The attenuation of the histamine response by low-voltage VNS was then examined in the presence of pharmacologic inhibitors or nerve ligation.

RESULTS

  Low-voltage VNS attenuated histamine-induced bronchoconstriction (4.4 ± 0.3 vs. 3.2 ± 0.2 cm H(2) O, p < 0.01) and remained effective following administration of a nitric oxide synthase inhibitor, NG-nitro-L-arginine methyl ester, and after sympathetic nerve depletion with guanethidine, but not after the β-adrenoceptor antagonist propranolol. Nerve ligation caudal to the electrodes did not block the inhibition but cephalic nerve ligation did. Low-voltage VNS increased circulating epinephrine and norepinephrine without but not with cephalic nerve ligation.

CONCLUSION

  These results indicate that low-voltage VNS attenuates histamine-induced bronchoconstriction via activation of afferent nerves, resulting in a systemic increase in catecholamines likely arising from the adrenal medulla.

Kidney-tonifying recipe can repair alterations in adrenal medullary chromaffin cells in asthmatic rats

Traditional Chinese medicine suggests that renal deficiency is a causative factor of asthma, and tonifying kidney drugs are believed to be an appropriate and beneficial treatment. The adrenal medullary chromaffin cells (AMCC) transition to the neuronal phenotype is known to occur in asthma, as evidenced by degranulation of chromaffin granules, decline of epinephrine (EPI) and phenylethanolamine-n-methyl transferase (PNMT), and obvious alterations in cellular architecture. In this study, rats were sensitized and challenged with ovalbumin, then treated with Kidney-Tonifying Recipe (KTR) to evaluate the therapeutic effect. Tissues were evaluated for changes in pathology and EPI, PNMT, and peripherin expression. Degranulation of chromaffin granules and appearance of neurite-like process were found in AMCC from asthmatic rats, and these changes were corrected by KTR treatment. EPI and PNMT expressions were decreased in asthmatic rats and increased by KTR treatment. Peripherin expression was increased in asthmatic rats and decreased in the KTR-treated group. Morphological changes and decreases in EPI were observed when cultured AMCC were exposed to sera from asthmatic rats in vitro, and these changes were attenuated with the addition of sera from KRT-treated rats. These results suggest that the Kidney-Tonifying Recipe is capable of repairing asthma-associated alterations in endocrine function and the ultrastructure of AMCC.

Effects of exercise training on airway responsiveness and airway cells in healthy subjects

Airway responsiveness to methacholine (Mch) in the absence of deep inspirations (DIs) is lower in athletes compared with sedentary individuals. In this prospective study, we tested the hypothesis that a training exercise program reduces the bronchoconstrictive effect of Mch. Ten healthy sedentary subjects (M/F: 3/7; mean + or - SD age: 22 + or - 3 yr) entered a 10-wk indoor rowing exercise program on rowing ergometer and underwent Mch bronchoprovocation in the absence of DIs at baseline, at weeks 5 and 10, as well as 4-6 wk after the training program was completed. Exercise-induced changes on airway cells and markers of airway inflammation were also assessed by sputum induction and venous blood samples. Mean power output during the 1,000 m test was 169 + or - 49 W/stroke at baseline, 174 + or - 49 W/stroke at 5 wk, and 200 + or - 60 W/stroke at 10 wk of training (P < 0.05). The median Mch dose used at baseline was 50 mg/ml (range 25-75 mg/ml) and remained constant per study design. At the pretraining evaluation, the percent reduction in the primary outcome, the inspiratory vital capacity (IVC) after inhalation of Mch in the absence of DIs was 31 +/- 13%; at week 5, the Mch-induced reduction in IVC was 22 + or - 19%, P = 0.01, and it further decreased to 15 + or - 11% at week 10 (P = 0.0008). The percent fall in IVC 4-6 wk after the end of training was 15 + or - 11% (P = 0.87 vs. end of training). Changes in airway cells were not associated with changes in airway responsiveness. Our data show that a course of exercise training can attenuate airway responsiveness against Mch inhaled in the absence of DIs in healthy subjects and suggest that a sedentary lifestyle may favor development of airways hyperresponsiveness.

Bronchodilator effects of exercise hyperpnea and albuterol in mild-to-moderate asthma

In asthmatic patients, either bronchodilatation or bronchoconstriction may develop during exercise. In 18 patients with mild-to-moderate asthma, we conducted two studies with the aims to 1) quantify the bronchodilator effect of hyperpnea induced by incremental-load maximum exercise compared with effects of inhaled albuterol (study 1, n=10) and 2) determine the time course of changes in airway caliber during prolonged constant-load exercise (study 2, n=8). In both studies, it was also investigated whether the bronchodilator effects of exercise hyperpnea and albuterol are additive. Changes in airway caliber were measured by changes in partial forced expiratory flow. In study 1, incremental-load exercise was associated with a bronchodilatation that was approximately 60% of the maximal bronchodilatation obtainable with 1,500 microg of albuterol. In study 2, constant-load exercise was associated with an initial moderate bronchodilatation and a late airway renarrowing. In both studies, premedication with inhaled albuterol (400 microg) promoted sustained bronchodilatation during exercise, which was additive to that caused by exercise hyperpnea. In conclusion, in mild-to-moderate asthmatic individuals, hyperpnea at peak exercise was associated with a potent yet not complete bronchodilatation. During constant-load exercise, a transient bronchodilatation was followed by airway renarrowing, suggesting prevalence of constrictor over dilator effects of hyperpnea. Finally, the bronchodilator effect of hyperpnea was additive to that of albuterol.

Exercise-induced asthma, respiratory and allergic disorders in elite athletes: epidemiology, mechanisms and diagnosis: part I of the report from the Joint Task Force of the European Respiratory Society (ERS) and the European Academy of Allergy and Clinical Immunology (EAACI) in cooperation with GA2LEN

AIMS

To analyze the changes in the prevalence of asthma, bronchial hyperresponsiveness (BHR) and allergies in elite athletes over the past years, to review the specific pathogenetic features of these conditions and to make recommendations for their diagnosis.

METHODS

The Task Force reviewed present literature by searching Medline up to November 2006 for relevant papers by the search words: asthma, bronchial responsiveness, EIB, athletes and sports. Sign criteria were used to assess level of evidence and grades of recommendation.

RESULTS

The problems of sports-related asthma and allergy are outlined. Epidemiological evidence for an increased prevalence of asthma and BHR among competitive athletes, especially in endurance sports, is provided. The mechanisms for development of asthma and bronchial hyperresponsiveness in athletes are outlined. Criteria are given for the diagnosis of asthma and exercise induced asthma in the athlete.

CONCLUSIONS

The prevalence of asthma and bronchial hyperresponsiveness is markedly increased in athletes, especially within endurance sports. Environmental factors often contribute. Recommendations for the diagnosis of asthma in athletes are outlined.

Autonomic nervous system control of the cardiovascular and respiratory systems in asthma

Patients with asthma have exaggerated bronchoconstriction of their airways in response to certain indirect (e.g. cold air, allergens, dust, exercise) or direct (e.g. inhaled methacholine) stimuli. This 'hyper-reactivity' usually co-exists with airway inflammation, although the pathophysiological mechanisms underlying these changes are not fully understood. It is likely that this hyper-reactivity is associated with abnormal autonomic nervous system (ANS) control. In particular, the parasympathetic (vagal) component of the ANS appears to be implicated in the pathogenesis of asthma. In addition, several studies have suggested the existence of differential alteration in ANS function following exercise in asthmatics compared with non-asthmatic individuals. Several early studies suggested that the altered autonomic control of airway calibre in asthma might be reflected by a parallel change in heart rate. Cardiac vagal reactivity does indeed appear to be increased in asthma, as demonstrated by the cardiac response to various autonomic functions tests. However, other studies have reported a lack of association between bronchial and cardiac vagal tone, and this is in accord with the concept of system-independent ANS control. This review provides a discussion of cardiovascular-autonomic changes associated with either the pathophysiology of asthma per se or with asthma pharmacotherapy treatment. Previous investigations are summarised suggesting an apparent association between altered autonomic-cardiovascular control and bronchial asthma. The full extent of autonomic dysfunction, and its clinical implications, has yet to be fully determined and should be the subject of future investigation.

Role of airway endogenous nitric oxide on lung function during and after exercise in mild asthma

We hypothesized that nitric oxide (NO), a known mild bronchodilator that can be released by several cell types within pulmonary airways, might protect airways during exercise in asthmatic subjects. We studied 17 individuals with documented exercise-induced asthma (screening exercise evaluation) on 2 study days: after treatment with inhaled NO synthase inhibitor N(G)-monomethyl-l-arginine (l-NMMA; 2 ml of 25 mg/ml mist) and after treatment with saline vehicle. Pulmonary resistance (Rl, esophageal manometry) rose and forced expiratory volume in 1 s fell more after l-NMMA compared with saline treatment, suggesting a bronchoprotective role for NO at baseline. The rise in Rl seen after l-NMMA treatment was nearly completely reversed early in exercise, suggesting a non-NO-mediated bronchodilation. A slow rise in Rl during constant-load exercise and dramatic increase in Rl after exercise were the same on the 2 treatment days, indicating little role for NO in regulating airway function during and after exercise. We conclude that endogenous NO plays little role in regulating airway function during and after exercise in subjects with mild asthma.

Exercise-induced bronchodilation in natural and induced asthma: effects on ventilatory response and performance

We studied whether bronchodilatation occurs with exercise during the late asthmatic reaction (LAR) to allergen (group 1, n = 13) or natural asthma (NA; group 2, n = 8) and whether this is sufficient to preserve maximum ventilation (VE(max)), oxygen consumption (VO(2 max)), and exercise performance (W(max)). In group 1, partial forced expiratory flow at 30% of resting forced vital capacity increased during exercise, both at control and LAR. W(max) was slightly reduced at LAR, whereas VE(max), tidal volume, breathing frequency, and VO(2 max) were preserved. Functional residual capacity and end-inspiratory lung volume were significantly larger at LAR than at control. In group 2, partial forced expiratory flow at 30% of resting forced vital capacity increased greatly with exercise during NA but did not attain control values after appropriate therapy. Compared with control, W(max) was slightly less during NA, whereas VO(2 max) and VE(max) were similar. Functional residual capacity, but not end-inspiratory lung volume at maximum load, was significantly greater than at control, whereas tidal volume decreased and breathing frequency increased. In conclusion, remarkable exercise bronchodilation occurs during either LAR or NA and allows VE(max) and VO(2 max) to be preserved with small changes in breathing pattern and a slight reduction in W(max).

Neuroendocrine and leukocyte responses and pulmonary function to acute stressors

Although stress is linked to asthma exacerbation, underlying mechanisms are unclear. Given the shared relevance to stress and asthma, select neuroendocrine and immune responses to acute stressors and their impact on pulmonary function were examined, comparing responses between students with (n = 20) and without childhood asthma (n = 16). Students were challenged with speech and math tasks. Blood samples were collected five times: before tasks, immediately after first and second tasks, and 15 and 60 minutes posttasks. Pulmonary function was measured four times, excluding midtask point. Stress reactivity patterns did not differ between two groups. However, all measures showed significant changes across the challenge. Plasma epinephrine and norepinephrine rose during tasks and declined after tasks, p < .001. Cortisol mainly declined after tasks, p = .03. Leukocyte count increased during tasks with increased lymphocyte percentage that declined after tasks, while neutrophil percentage changed opposite to lymphocytes, p < .001 each. Changes in pulmonary function were significant, p < .05, but were not predicted by the magnitude of neuroendocrine and immune changes. Instead, neuroendocrine and immune levels explained 33%-51% of variance on concurrent pulmonary function. Findings indicate that acute stress induces significant neuroendocrine and immune changes that can affect pulmonary function. However, stress reactivity needs further investigation with larger samples and people with a more severe form of asthma.

Catecholamines in hyperpnoea-induced airway constriction of guinea pigs

1. We found previously that propranolol augments hyperpnoea-induced bronchoconstriction (HIB). This study was performed to investigate the underlying mechanism of this aug- menting action of propranolol. 2. In the first series, 45 young Hartley guinea-pigs were divided into five groups: control; propranolol; adrenalectomy; metoprolol and reserpine. Each animal underwent three periods: baseline, hyperpnoea, and recovery. For each animal 1 ml of arterial blood was sampled during the baseline and recovery periods. 3. Treatments of propranolol, metoprolol, and reserpine caused significant decreases in both dynamic respiratory compliance (Crs) and forced expiratory volume in 0.1 s (FEV0.1) during the baseline period. Hyperpnoea caused slight but not significant decreases in Crs, FEV0.1, and maximal expiratory flow at 50% total lung capacity (TLC) (V(max50)) during the recovery period in the control group. Propranolol, but not other treatments, significantly augmented these decreases (indicating HIB). Plasma noradrenaline and adrenaline levels in the reserpine group were not detectable. The above treatments or hyperpnoea did not induce any significant effect on the plasma noradrenaline level. Plasma adrenaline level of the control group was higher than that of either adrenalectomy or reserpine group during the baseline and the recovery periods. 4. In the second series, we avoided repeated blood samplings. Forty-eight animals were evenly divided into two groups: control and propranolol. Each group was again evenly divided into three subgroups: baseline; hyperpnoea, and recovery. Five minutes into the recovery period, we demonstrated HIB in the control group. In terms of V(max50), this HIB was significantly augmented by propranolol. Plasma noradrenaline and adrenaline levels, however, were not significantly altered by either hyperpnoea or propranolol. 5. Taken together, these data suggest that propranolol-augmented HIB has no direct relationship with decreased catecholamine activity.

Airway function after cyclooxygenase inhibition during hyperpnea-induced bronchoconstriction in guinea pigs

Airway function deteriorates significantly on cessation of exercise or isocapnic hyperventilation challenges but is largely preserved during the challenge in humans and guinea pigs. PGE(2), an endogenous bronchodilator, might be responsible for the preservation of lung function during hyperventilation (HV). We hypothesized that PGE(2) might have a protective effect during HV, partially explaining the minimal changes in respiratory system resistance (Rrs) usually seen during HV in humans and guinea pigs. Therefore, changes in Rrs were measured during and after HV in anesthetized, mechanically ventilated guinea pigs treated with flurbiprofen (FBN) or placebo. With HV, there was an initial bronchodilation that was unaffected by FBN. Rrs then increased with time during HV, an effect that was blocked by FBN. After HV, Rrs increased further in all groups, but the increase in Rrs was less in the FBN-treated groups. FBN treatment reduced the PGE(2) concentration slightly in lung lavage fluid compared with placebo. We found no enhancement or refractoriness of the Rrs response to repeat bouts of HV and no effect of FBN treatment on the response of Rrs to repeat HV. These results suggest that a constrictor PG is released during and possibly after HV and that the post-HV increase in Rrs is the sum of effects of the PG released during HV and a second constrictor mechanism operating after HV. We found no evidence for bronchodilator PG during or after HV in the guinea pig.

Autonomic regulation after exercise evidenced by spectral analysis of heart rate variability in asthmatic children

BACKGROUND

Bronchial asthma is associated with abnormal autonomic nervous function in childhood. Exercise is one of the most common precipitating factors of acute asthmatic crises although the exact mechanism of autonomic regulation in asthmatic children after exercise is unclear.

OBJECTIVE

The aim of this study was to investigate the features of autonomic regulation after exercise in asthmatic and control children.

METHODS

Pulmonary function tests and heart rate variability spectral analysis were performed in 15 asthmatic children and 7 control children (age 6 to 15 years) during and after an exercise challenge.

RESULTS

The maximum % fall of forced expiratory volume in 1 second (FEV1) was significantly greater (P < .01) in asthmatic subjects (9.1 +/- 5.1%) than in normal control subjects (1.0 +/- 2.5%). The high frequency band (HF) amplitude, an index of cardiac vagal tone, 5 minutes after exercise was significantly higher (P < .05) in the asthmatic subjects (14.4 +/- 7.9 msec) than in control subjects (5.9 +/- 2.6 msec). Furthermore, the difference in the HF amplitude between the control group and the exercise-induced asthma group was significant both 5 minutes (P < .01) and 10 minutes (P < .05) after challenge. There was a significant correlation (P = .565, P = .0165) between HF amplitude 5 minutes after exercise and the magnitude of the decrease in FEV1. On the other hand, no significant difference was observed in the low frequency band amplitude between the controls and the asthmatic subjects. The ratio of low frequency to high frequency power, which is suggested to correlate with cardiac sympathetic activity, did not differ between the two groups.

CONCLUSION

These findings suggest that autonomic nervous activities, particularly vagal response after exercise, in asthmatic children is different from that in control children.

Airway obstruction during exercise and isocapnic hyperventilation in asthmatic subjects

We compared pulmonary mechanics measured during long-term exercise (LTX = 20 min) with long-term isocapnic hyperventilation (LTIH = 20 min) in the same asthmatic individuals (n = 6). Peak expiratory flow (PEF) and forced expiratory volume in 1 s (FEV(1)) decreased during LTX (-19.7 and -22.0%, respectively) and during LTIH (-6.66 and 10. 9%, respectively). In contrast, inspiratory pulmonary resistance (RL(I)) was elevated during LTX (57.6%) but not during LTIH (9.62%). As expected, airway function deteriorated post-LTX and post-LTIH (FEV(1) = -30.2 and -21.2%; RL(I) = 111.8 and 86.5%, respectively). We conclude that the degree of airway obstruction observed during LTX is of a greater magnitude than that observed during LTIH. Both modes of hyperpnea induced similar levels of airway obstruction in the posthyperpnea period. However, the greater airway obstruction during LTX suggests that a different process may be responsible for the changes in airway function during and after the two modes of hyperpnea. This finding raises questions about the equivalency of LTIH and LTX in the study of airway function during exercise-induced asthma.

Physical activity and asthma

The relationship between asthma and exercise and the resultant disability (ie, the impact on activities of daily living, including physical activity) shows wide interpatient and intrapatient variability, being influenced not only by the disease but additional psychosocial variables. There are a variety of helpful pharmacologic and nonpharmacologic measures in dealing with simple exercise-induced asthma, and new therapeutic options are being developed. The cardiorespiratory performance characteristics of asthmatic patients are very frequently suboptimal, either because of symptom-limited exercise tolerance or secondary deconditioning consequent upon inactivity. Medically supervised physical training can produce significant beneficial change. Recommendations for rehabilitation of asthmatic patients would include individualized exercise prescription and advice based on objective criteria of exercise capability, with flexibility in the programs offered, in order to cater to the broadest spectrum of patient disability.

Effects of inhibition of the L-arginine/nitric oxide pathway on vasodilation caused by beta-adrenergic agonists in human forearm

BACKGROUND

We examined whether vasodilator responses to beta-agonists in human forearm vasculature are mediated in part through the nitric oxide pathway.

METHODS AND RESULTS

We measured forearm blood flow responses to brachial artery infusions of beta-adrenergic agonists in healthy men. Salbutamol was more than 100 times as potent as dobutamine. Cumulative doses of salbutamol (0.3 to 3.5 nmol.min-1) did not cause tachyphylaxis to an identical repeated infusion after a 24-minute recovery period. Vasodilators were infused with this sequence during coinfusion of saline and NG-monomethyl-L-arginine (L-NMMA, 4 mumol.min-1), an inhibitor of nitric oxide synthase. L-NMMA coinfusion inhibited responses (area under the dose-response curve) to isoproterenol (0.01 to 0.1 nmol.min-1) by 59 +/- 7% (n = 5) and inhibited those to salbutamol (0.3 to 3.5 nmol.min-1) by 52 +/- 6% (n = 8). L-NMMA had no significant effect on vasodilator responses to nitroprusside (2.7 to 11.0 nmol.min-1, n = 8), verapamil (20 to 80 nmol.min-1, n = 8), or prostacyclin (0.08 to 0.24 nmol.min-1, n = 8).

CONCLUSIONS

These results suggest that beta-adrenergic vasodilator responses in human forearm vasculature are mediated predominantly through beta 2-adrenergic receptors and are dependent on nitric oxide synthesis.

Wingate test performance in children with asthma: aerobic or anaerobic limitation?

To investigate the anaerobic capacity in children with bronchial asthma, eight male children with atopic asthma (age: 12 +/- 1.7 yr) and seven healthy control subjects (age: 12 +/- 1 yr) performed a 30-s all-out exercise test: the Wingate anaerobic test (WanT). Post-exercise plasma epinephrine (E), norepinephrine (NE), venous blood lactate (La), and blood pH levels were determined. Peak power (Ppeak), mean power (Pm), and total energy expenditure (Wtot) during the WanT were assessed. The relative importance of aerobic (WO2) and anaerobic (Wana) energy release during the WanT was also evaluated. In comparison with control subjects, the children with asthma exhibited lower Ppeak (W.kg-1): 6 +/- 1.14 vs 7.3 +/- 0.5, P < 0.05; lower Pm (W.kg-1): 4.7 +/- 0.8 vs 5.9 +/- 0.5, P < 0.05; and lower Wtot (Jg-1): 140.3 +/- 25 vs 176.9 +/- 19, P < 0.05. The relative contribution of WO2 (26%) and Wana (74%) to the Wtot was identical in both groups. Blood lactate and pH kinetics revealed significantly lower La values and less acidosis in the asthmatic group (P < 0.001). Lastly, E (pg.ml-1) concentrations were lower in the asthmatic group: 274.96 +/- 84.58 vs 901.28 +/- 604.76, P < 0.05. These results suggest a reduced anaerobic capacity in children with asthma. A diminished adrenergic response to exhausting exercise, leading to a decreased anaerobic glycolysis, could partly account for this phenomenon.

Pharmacological actions of the selective and non-selective beta-adrenoceptor antagonists celiprolol, bisoprolol and propranolol on human bronchi

1. The pharmacological actions of the beta-adrenoceptor antagonists, celiprolol, bisoprolol and propranolol were investigated in human lung tissue by radioligand binding experiments as well as in human isolated bronchi by functional experiments in organ baths. 2. Data from lung tissue were compared to those obtained from myocardial membranes. 3. Lung tissue was obtained from 10 patients having undergone lung resection for bronchial carcinoma and myocardial tissue from a patient who had received a heart transplantation. 4. In radioligand binding experiments, celiprolol exhibited a high affinity binding to beta 1-adrenoceptors in heart and a low affinity binding to beta 2-adrenoceptors in lung tissue. The selectivity obtained for the beta 1-adrenoceptor was calculated to a factor of eleven. 5. Compared to bisoprolol and propranolol, celiprolol elicited the lowest affinity for the beta-adrenoceptor, as judged from the K1-values. 6. In the absence and presence of the guanine nucleotide Gpp(NH)p celiprolol did not affect receptor binding. 7. In functional experiments on intact bronchi, celiprolol, bisoprolol and propranolol failed to produce relaxation (+/- forskolin) or a significant difference in efficacy in antagonizing the relaxant effects of isoprenaline. However, a rank order of potencies was revealed (propranolol:bisoprolol:celiprolol = 46:12:1). 8. Plasma concentrations for celiprolol and bisoprolol usually achieved in vivo were below the IC50 value obtained in vitro. In contrast, for propranolol, plasma concentrations were nearly identical with the IC50 value. 9. It is concluded that celiprolol is a selective beta 1-adrenoceptor antagonist on human heart and has no agonistic properties on intact human bronchi. Compounds such as celiprolol and bisoprolol may in comparison to propranolol, possess reasonable therapeutic advantages in the treatment of patients with obstructive lung disease due to their low affinity for beta 2-adrenoceptors.

Effects of inspired air conditions on catecholamine response to exercise in asthma

The influence of different inspired air conditions on exercise-induced bronchoconstriction (EIB) is well appreciated. However, the mechanism by which this influence is exerted is uncertain. To determine if varied inspired air conditions during exercise could affect the catecholamine response to physical exercise, we had 13 asthmatic and 6 healthy children (aged 10-18 years) undergo two bouts of cycle ergometry tests under different air conditions. One test was done while breathing cold dry (CD) air (temperature, -20.2 degrees C; relative humidity, 0%) and the other while breathing warm humid (WH) air (temperature, 34.3 degrees C; relative humidity, 100%). Forced expiratory volume in 1 second (FEV1) and plasma catecholamine concentrations were recorded before and after exercise. Marked EIB (48 +/- 5% SEM fall in FEV1 from baseline) developed in all asthmatics after the CD exercise, but no EIB was noted after the WH exercise. Normal controls had no EIB under either test conditions. Plasma levels of catecholamines at rest, and the changes that occurred during and after exercise, were comparable within as well as between the groups in both tests. Catecholamines did not rise in asthmatics following development of EIB. These data demonstrate that inspired air conditions do not influence the sympathoadrenal response to exercise, at least as reflected in plasma catecholamine levels. In fact, this response did not differ between asthmatics and normals, irrespective of the development of EIB. These results are consistent with previous reports about impaired catecholamine response of asthmatics to bronchoconstriction.

Effect of psychic stimulation on plasma catecholamine concentrations and nasal patency in patients with nasal allergy

To compare the degree of sympathoadrenal and nasal vascular response to psychic stimulation between patients with nasal allergy and normal controls, we measured the changes in plasma norepinephrine and epinephrine concentrations and nasal patency elicited by cannulation into the forearm vein and mental arithmetic in 28 patients with nasal allergy and age- and sex-matched normal controls. Ten of the 28 allergy patients had markedly swollen, pale, edematous nasal mucosa and served as a subgroup of nasal allergy patients. Plasma catecholamine levels increased significantly, with a synchronous increase of nasal patency, during stimulation. Among the three groups, no statistical differences were observed in plasma catecholamine levels either at rest or during stimulation. There was no significant difference in extent of increase of nasal patency induced by stimulation in the total group of subjects with nasal allergy compared with normal controls. However, it was significantly smaller in a subgroup of nasal allergy patients having markedly pale, edematous swelling of the nasal mucosa.

Changes in serum catecholamine levels during acute bronchospasm

STUDY OBJECTIVES

Previous studies reported that norepinephrine levels increased during acute asthma, while epinephrine levels have remained at normal levels. The purpose of this study was to determine whether the lack of rise in epinephrine levels is due to an inherent defect in catecholamine secretion in asthmatics or is a result of an insufficient stimulus for epinephrine release.

DESIGN

County-owned, university-affiliated emergency department.

SETTING

Prospective study.

TYPE OF PARTICIPANTS

Patients more than 18 years old presenting to the ED with an acute exacerbation of asthma or chronic obstructive pulmonary disease (COPD).

INTERVENTIONS

Initial phlebotomy and spirometry were followed by treatment with either albuterol or albuterol and glycopyrrolate. Asthmatic patients received steroids. Phlebotomy and spirometry were performed again after treatment.

MEASUREMENTS AND MAIN RESULTS

There was no difference in epinephrine levels between patients with asthma and those with COPD either before or after treatment. Norepinephrine levels were higher in patients with COPD, both before and after treatment. There was only a weak correlation between epinephrine levels and pretreatment FEV1 for asthma but not for COPD.

CONCLUSION

Moderate bronchospasm is not a major stimulus for epinephrine release in either acute asthma or COPD.

Roles of eosinophils and catecholamines in pathophysiology of exercise-induced asthma

To study the roles of eosinophils and catecholamines in the pathophysiology of exercise-induced asthma (EIA), an exercise challenge test was performed in 22 asthmatic children, using a bicycle ergometer, and the changes in lung function, plasma norepinephrine (NE), epinephrine (E) and eosinophil cationic protein (ECP) levels with exercise were evaluated. Subjects were classified into three groups from the results of lung function test, respectively: EIA-negative group. EIA-positive groups with good recovery and poor recovery. Eosinophil counts before exercise in the EIA-positive groups were significantly higher than those in the EIA-negative group. The ECP levels rose with exercise in all groups. Five minutes after exercise, ECP values fell to the pre-exercise level in the EIA-negative group, but rose to higher levels in EIA-positive groups. Plasma E levels rose with exercise and showed 4-fold increase in the EIA-negative group, whereas only 1.5-fold increase of plasma E levels was observed in the EIA-positive group with poor recovery. From these findings, a possible contribution of sympathoadrenal hypofunction and a probable involvement of eosinophils in the pathophysiology of EIA have been suggested.

Adrenergic response in children with asthma on exogenous stimuli

In asthmatic children it was investigated whether the degree of impairment of the adrenergic response on exogenous stimuli is related to the magnitude of the 24-hour amplitude in airflow obstructions. Urinary-adrenaline and noradrenaline excretion after house dust mite (HDM) inhalation and after exercise was measured. Nine children with (group I), and nine without increased airflow obstruction overnight (group II) and nine age matched healthy children (group C) were included in the study. All patients showed an early obstructive reaction (EOR) after HDM challenge. Six children in group I and five in group II developed an EOR on exercise. A significant increase in urinary adrenaline excretion was observed after exercise in the control group (P < 0.05, values on the control and challenge day being 5.4 +/- 0.9 and 10.0 +/- 1.6 mumol/mol creat.). The same occurred for noradrenaline (P < 0.01, values being 28.2 +/- 2.5 and 49.0 +/- 5.7 mumol/mol creat.). Adrenergic response after both stimuli was impaired in the asthmatic groups, in group I more pronounced than in group II. Values from group I for adrenaline on the control day, HDM and exercise challenge were 6.0 +/- 0.8, 4.7 +/- 0.6, 6.0 +/- 1.0 and for noradrenaline 36.1 +/- 2.7, 27.2 +/- 2.3, 38.4 +/- 4.9 mumol/mol creat., respectively. Values from group II for adrenaline on these days were 5.6 42- 1.0, 3.7 42- 0.6 and 9.0 +/- 1.3 and for noradrenaline 28.3 +/- 3.2, 22.4 +/- 2.5, 41.3 +/- 5.9 mumol/mol creat., respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of exercise-induced bronchoconstriction on refractoriness

This study determined if the degree of exercise-induced refractoriness is determined by the degree of exercise-induced bronchoconstriction. In 12 patients with exercise-induced asthma (mean [SEM] age 27 [3] years) we performed 2 pairs of exercise challenges 45 min apart at different work loads on 2 days. Mean (SEM) total respiratory heat loss during low and high work loads was 3.4 (0.2) and 5.1 (0.4) kcal, respectively. After the first and second exercise challenge at low work loads, mean (SEM) SRaw increased by 107 (15) and 73 (16)% (n.s.), as compared to 361 (40) and 98 (25)% at high work loads (p less than 0.005). We found a correlation between the initial airways response and refractoriness (r = 0.58, p less than 0.005) and conclude that the degree of refractoriness after exercise-induced bronchoconstriction is in part dependent on the severity of exercise-induced bronchoconstriction.

Comparison of refractoriness after exercise- and hyperventilation-induced asthma

To study the relationship of bronchoconstriction and refractoriness we performed pairs of exercise and hyperventilation tests in 15 patients (mean [SEM] age 28.5 [2.8] years) with a history of exercise-induced asthma. Mean (SEM) maximum specific airway resistance (SRaw) increased during the first exercise test to 33.9 (4.5) and during the second exercise test to 29.8 (5.2) cmH2O x s (n.s.). Mean (SEM) maximum specific airway resistance (SRaw) increased during the first hyperventilation test to 44.0 (5.9) and during the second hyperventilation test to 27.4 (3.3) cmH2O x s (p less than 0.01). Mean maximum bronchoconstriction after corresponding exercise and hyperventilation tests did not differ statistically. There was a significantly larger inter-individual variability in the airway response to hyperventilation (p less than 0.001). From these data we suggest that similar refractoriness can be observed after both exercise and hyperventilation.

Circulating plasma concentrations of atrial natriuretic peptide and catecholamines in response to maximal exercise in normal and asthmatic subjects

BACKGROUND

Intravenous infusion of atrial natriuretic peptide has been shown to cause bronchodilatation in patients with asthma and endogenous atrial natriuretic peptide is known to rise with exercise. Whether an aberration in release of atrial natriuretic peptide is concerned in the pathogenesis of exercise induced bronchoconstriction has not been studied.

METHODS

The atrial natriuretic peptide response to exercise was studied in eight men with exercise induced asthma and eight age matched non-asthmatic men. Subjects exercised to exhaustion on a treadmill, using the Bruce protocol. Atrial natriuretic peptide and catecholamines were measured at the end of each stage of exercise and oxygen consumption and heart rate were monitored throughout.

RESULTS

Both groups showed a 3.5 fold increase in plasma atrial natriuretic peptide during exercise (mean (SE): normal subjects 25 (4) pmol/l; asthmatic subjects 24 (5) pmol/l), with no difference between the two groups. There was a close correlation between plasma atrial natriuretic peptide concentrations and oxygen uptake, catecholamine release, and heart rate in both groups. The catecholamine response was similar in the asthmatic and normal subjects, both groups showing a four fold rise in plasma adrenaline and a 4-5 fold rise in plasma noradrenaline.

CONCLUSION

A defect in the release of circulating atrial natriuretic peptide does not account for exercise induced asthma; the concentrations of the circulating peptide that were achieved may effect a small reduction in airway reactivity. Our data do not support the idea that asthmatic patients have abnormal sympathoadrenal activity.

Reversible T-wave abnormality in severe acute asthma: an electrocardiographic sign of severity

Reversible electrocardiographic (ECG) abnormalities are well recognized in severe acute asthma. Inferior lead T-wave abnormalities have only rarely been reported, and their frequency and significance have not been well documented. We studied 70 consecutive patients with severe acute asthma on admission to hospital and during recovery, in order to examine the frequency and natural history of such changes and to document their relationship to the severity of the attack. Twenty-two patients (34%) had inferior lead T-wave inversion on ECGs performed within 1 h of admission (group 1), whereas the rest did not (group 2). Apart from sinus tachycardia this was the most common ECG abnormality. Patients with inferior T-wave inversion were found to have more severe asthma in terms of degree of pulsus paradoxus, peak expiratory flow rate, forced expiratory volume in 1 s and arterial blood oxygen tension. Ten group 1 and ten group 2 patients underwent two-dimensional echocardiography during the acute phase of their illness and during recovery. Six (60%) group 1 patients showed echocardiographic evidence of right ventricular pressure overload compared with only one (10%) patient in group 2 (P less than 0.02). Following recovery, voluntary hyperventilation and exercise testing in ten group 1 patients failed to reproduce the ECG changes seen on admission. Reversible inferior lead T-wave abnormalities may occur in the severe acute asthma and appear to be related to the severity of the attack.

A bronchial response comparison of exercise and methacholine in asthmatic subjects

The authors compared the inhaled methacholine and exercise responses in 22 stable unmedicated asthmatic patients. The exercise and methacholine challenges were performed at one to three week intervals. Bronchial responsiveness to methacholine was measured in relation to the concentration of methacholine (PC20M). The response to exercise was expressed as the percentage of fall in FEV1 from the pre-exercise FEV1. The findings showed that 21 of 22 subjects demonstrated a fall in FEV1 of more than 20% after methacholine challenge, while only 9/22 subjects experienced a similar decrease in FEV1. All 9 of these positive response exercise cases completed three consecutive exercise challenges prior to the methacholine challenge. Of these cases, five were refractory to the repeated exercise challenge, and the PD20M at the nonexercise stage was significantly lower than the postexercise state. In fact, the methacholine challenge sensitivity actually decreased (PD20 increased) after repeated exercise. The authors concluded that methacholine seems to be a more sensitive bronchial provocation test than exercise. Second, only 55.6% of the exercise test-positive subjects were refractory to the second exercise challenge. Therefore, other factors besides the release of mediators should be considered in exercise-induced asthma. Third, methacholine sensitivity actually decreased (PD20 increases) after repeat exercise challenge.

Responses of asthmatic and non-asthmatic athletes to prolonged treadmill running

Metabolic and cardio-respiratory responses of four asthmatic and four non-asthmatic athletes to two hours of treadmill running at 70 percent of maximal oxygen uptake are compared. The asthmatic group had pre-exercise airflow obstruction, as indicated by the lower forced expiratory volume in one second (FEV1) even after medication (2.90 +/- 0.661) compared to the non-asthmatic group (4.09 +/- 1.331). Changes in blood lactate, glucose and catecholamine concentrations as a result of the two hour run were similar for the two groups. However, the pattern of breathing was different. The asthmatics had a slower breathing frequency but a similar tidal volume to the non-asthmatics. Both groups had an increase in the ventilation rate over the two hour run. For the non-asthmatic group, this increase in ventilation was achieved by an increase in the breathing frequency (p less than 0.01), whereas tidal volume was reduced (p less than 0.05). The increase in the ventilation rate over the two hour run for the asthmatic group was brought about by a small increase in breathing frequency (p less than 0.05), whereas tidal volume was not changed. This maintenance of the tidal volume by the asthmatic athletes during endurance running may compensate for the airflow obstruction, and so allow successful participation in endurance running.