Exercise-induced asthma and the generation of neutrophil chemotactic activity

Prevalence and mechanisms of development of asthma and airway hyperresponsiveness in athletes

A high prevalence of asthma and airway hyperresponsiveness (AHR) has been reported in the athlete population. Factors potentially predisposing athletes to these conditions have not been clearly identified. Although moderate exercise has been shown to be beneficial in patients with asthma, repeated high-intensity exercise could possibly contribute to the development of asthma and AHR. This report provides an overview of the prevalence and possible mechanisms of development of asthma and AHR in the athlete population. The prevalence of asthma and AHR are higher in athletes than in the general population, particularly in swimmers and athletes performing sports in cold air environments. Possible mechanisms involved in the development of asthma in athletes are still uncertain; however, the content and physical characteristics of the inhaled air seem to be important factors, while immune and neurohumoral influences could play a modulatory role. This report stresses the need for further studies to better define the aetiologic factors and mechanisms involved in the development of asthma and AHR in athletes, and proposes relevant preventive and therapeutic measures.

Effects of single-dose fluticasone on exercise-induced asthma in asthmatic children: a pilot study

A single high dose of inhaled corticosteroid (ICS) can increase airway caliber in children with asthma attacks and laryngitis subglottica. Presumably the effect is due to the vasoconstrictive and antiedematous properties of topical steroids. Enlarged vessels have been suggested to play a role in the pathophysiology of exercise-induced bronchial obstruction (EIB). To investigate this, we evaluated the effect of a single high dose of fluticasone propionate (FP) on EIB in asthmatic children. Nine children aged 8-16 years with mild to moderate asthma were included. All children had a history of EIB, which was confirmed by an exercise test. None was taking ICS maintenance therapy. The children inhaled either a single dose of 1 mg FP or placebo on 2 separate days within 7-14 days. After inhalation, airway caliber (FEV(1)) was assessed for 4 hr before exercise. Then an exercise challenge was performed on a treadmill to assess EIB (% fall FEV(1)). A significant increase in FEV(1) was observed 1 hr after inhalation of FP compared to placebo. Response to exercise was expressed as maximal % fall in FEV(1) from baseline (% fall) and as area under the curve (AUC) of the 30-min time/response curve. The % fall FEV(1) after exercise and the AUC were significantly reduced when FP was inhaled compared to placebo inhalation (% fall 9.7% vs. 19.2%, respectively, P = 0.038 and AUC 92.0%.min vs. 205.7%.min, respectively, P = 0.03). There was considerable individual variability in reduction of EIB, with 5 out of 9 children having a clinically significant response. We conclude that a single high dose of inhaled FP has an acute protective effect on the bronchial response to exercise in a substantial proportion of asthmatic children.

Human neutrophils express the high-affinity receptor for immunoglobulin E (Fc epsilon RI): role in asthma

Polymorphonuclear neutrophils (PMNs) are important effector cells in host defense and the inflammatory response to antigen. The involvement of PMNs in inflammation is mediated mainly by the Fc receptor family, including IgE receptors. Recently, PMNs were shown to express two IgE receptors (CD23/Fc epsilon RII and galectin-3). In allergic diseases, the dominant role of IgE has been mainly ascribed to its high-affinity receptor, Fc epsilon RI. We have examined the expression of Fc epsilon RI by PMNS: mRNA and cell surface expression of Fc epsilon RI alpha chain was identified on PMNs from asthmatic subjects. Furthermore, preincubation with human IgE Fc fragment blocks completely the binding of anti-Fc epsilon RI alpha chain (mAb15--1) to human PMNS: Conversely, preincubation of PMNs with mAb15--1 inhibits significantly the binding of IgE Fc fragment to PMNs, indicating that IgE bound to the cell surface of PMNs mainly via the Fc epsilon RI. Peripheral blood and bronchoalveolar lavage (BAL) PMNs from asthmatic subjects also express intracellular Fc epsilon RI alpha and beta chain immunoreactivity. Engagement of Fc epsilon RI induces the release of IL-8 by PMNS: Collectively, these observations provide new evidence that PMNs express the Fc epsilon RI and suggest that these cells may play a role in allergic inflammation through an IgE-dependent activation mechanism.

Exercise, methacholine, and adenosine 5'-monophosphate challenges in children with asthma: relation to severity of the disease

Bronchial hyperreactivity is a characteristic feature of asthma and can be evaluated by different challenges. The aim of this study was to compare exercise, methacholine (MCH), and adenosine 5'-monophosphate (AMP) challenges in 135 children and young adults (mean age +/- SD, 12.4+/-3.9 years) with asthma, and to examine the utility of the different challenges in predicting those children with asthma likely to require prophylactic antiinflammatory treatment. The sensitivity of MCH challenge in detecting bronchial hyperreactivity (at or below 8 mg/mL) was 98%, that of AMP challenge (at or below 200 mg/mL) 95.5%, and that of exercise (more than 8.2% fall in FEV(1)) was 65%. There was a significant difference between mild asthmatic children (85 patients, intermittent asthma, step 1 of NIH guidelines) and moderate asthmatics (50 patients, steps 2 and 3 of guidelines) in relation to the logarithmic mean provocation concentration to elicit a 20% fall in FEV(1) (PC(20)) to MCH (0.49 mg/mL vs. 0.15 mg/mL, P<0.00001), that to AMP (7.67 mg/mL vs. 3.60 mg/mL, P = 0.001), and in relation to the mean percent fall in FEV(1) after exercise (13.9% vs. 22.0%, P = 0.001). Sensitivity and specificity curves between the two severity groups of asthma were constructed, and the intersection point of the two curves for each type of challenge was determined. When mild asthmatics were compared to moderate asthmatics, the intersection points for MCH, AMP, and exercise were 66%, 63%, and 61%, respectively. Logistic regression analysis and receiver operating characteristic (ROC) curves of the three challenges for the two severity groups of asthma showed that methacholine was a better discriminating challenge between the severity groups than the other two challenges. We conclude that the sensitivities of AMP and MCH challenges in the detection of bronchial hyperreactivity in children and young adults with asthma are very similar and higher than that of exercise. There is a significant difference between mild and moderate asthmatics within the three bronchial challenges, with MCH discriminating better than AMP or exercise between groups.

Immunosuppressive and cytotoxic effects of furosemide on human peripheral blood mononuclear cells

BACKGROUND

We have previously shown that children with mild asthma have a modest improvement in their pulmonary function tests after aerosolized furosemide. The mechanism of action is not known. The observation that furosemide possesses a similar profile of protection as sodium cromoglycate and nedocromil sodium suggests that furosemide may inhibit mediator production and release.

OBJECTIVE

We studied the in vitro effects of furosemide on cytokine release from normal human peripheral blood mononuclear cells (PBMC) induced by E. coli lipopolysaccharide (LPS).

METHODS

Peripheral blood mononuclear cells were isolated by density gradient centrifugation, stimulated with LPS and incubated at 37 degrees C with varying concentrations of furosemide, hydrocortisone, sodium cromoglycate, and nedocromil sodium for 24 hours. Supernatants were extracted and study for levels of tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), and interleukin-8 (IL-8). Intracellular IL-6 and TNF-alpha concentrations were also measured by cell cytometry. Cell viability was examined using XTT cell proliferation test and-measuring the release of lactate dehydrogenase (LDH).

RESULTS

There was a significant reduction in levels of TNF-alpha and IL-6 at a furosemide concentration of 0.5 x 10(-2) M and a reduction in IL-8 levels at 10(-2) M. This inhibition was comparable to that found with equivalent molar concentrations of hydrocortisone. These findings were also confirmed with measurements of intracellular IL-6 and TNF-alpha by cell cytometry. High concentration of furosemide at 10(-2) M caused significant cellular cytotoxicity.

CONCLUSION

These data suggest that furosemide may exhibit an anti-inflammatory effect. Specifically, the addition of furosemide resulted in decreased production of cytokines. This effect may be due to an immunosuppressive activity on monocytes as well as a direct cytotoxic effect at high furosemide concentrations.

Peripheral blood manifestations of T(H)2 lymphocyte activation in stable atopic asthma and during exercise-induced bronchospasm

BACKGROUND

Recently, TH2 lymphocyte activation has been shown to play a key role in initiating and propagating the inflammatory response in asthmatic airways. This is manifest through increased numbers of "activated" CD25-(IL-2R)-bearing T-helper cells and can be seen through the IL-5 driven recruitment of eosinophils and IL-4-mediated B-cell expression of CD23 (low affinity IgE receptor) and ultimately IgE production.

OBJECTIVE

To gain a better understanding of the role of immune cells in asthma by describing the peripheral blood immune cell phenotypes in mild atopic asthma.

METHODS

We enrolled 13 patients with mild atopic asthma and a group of seven nonatopic, nonasthmatic controls. Objective measures of lung function were obtained. The peripheral blood was analyzed by flow cytometry for specific cellular markers at rest and during the development of exercise induced bronchospasm.

RESULTS

At rest the number of CD23-bearing B cells (169/mL versus 117/mL; P = .05) and the number of CD25-bearing T cells (355/mL versus 237/mL; P = .03) were increased in the asthma group. There was a linear relationship between these two lymphocyte subsets and the maximum voluntary ventilation at rest (r = 0.56, P = .01 and r = 0.57, P = .01). With the development of exercise-induced bronchospasm there was a significantly greater increase in CD23-positive B cells (96.7/mL versus 59.7/mL; P = .05) and CD25-positive T cells (111.8/mL versus 45.1; P = .01) in the asthma group.

CONCLUSIONS

These data indicate that TH2 lymphocyte activation is manifested by increased numbers of CD23-bearing B cells and CD25-bearing T cells in the peripheral blood of patients with stable mild atopic asthma. Further, these immune cell subsets correlate with markers of resting lung function and increase in the peripheral blood early after the development of exercise-induced bronchospasm.

Enhanced neutrophil chemotactic activity after bronchial challenge in subjects with grain dust-induced asthma

BACKGROUND

There have been few reports suggesting involvement of neutrophils in induction of bronchoconstriction after inhalation of grain dust.

OBJECTIVES

To understand the role of neutrophils in pathogenesis of grain dust-induced asthma.

MATERIALS AND METHODS

We observed serum neutrophil chemotactic activity during grain dust-bronchoprovocation tests in six asthmatic subjects with positive bronchial challenges (group I). They were compared with those of six symptomatic subjects from the same workplace with negative bronchial challenges (group II).

RESULTS

After grain dust inhalation, serum neutrophil chemotactic activity significantly increased at 30 minutes (P = .028), and then decreased to baseline level at 240 minutes (P = .028) in five subjects of group I having isolated early asthmatic responses. Enhanced neutrophil chemotactic activity was persistent for up to 240 minutes in one asthmatic subject having both early and late asthmatic responses. There was, however, no significant change in serum neutrophil chemotactic activity during bronchial challenges in subjects of group II. Pre-incubation of sera with anti-interleukin-8 (IL-8) antibody did not affect the neutrophil chemotactic activity results of group I subjects.

CONCLUSION

These results suggest that enhanced neutrophil chemotactic activity distinct from IL-8 may contribute to significant bronchoconstriction induced by grain dust.

BAL neutrophilia in asthmatic patients. A by-product of eosinophil recruitment?

Although neutrophil number may be increased in the airways of patients with asthma, its pathogenetic role in this disorder remains unclear. We evaluated BAL of 8 normal control subjects, 30 +/- 2 years of age, and 24 patients with mild asthma: 17 patients with allergic asthma, 24 +/- 1 years of age, and 7 patients with nonallergic asthma, 30 +/- 1 years of age. The BAL of asthmatic patients showed increased numbers of neutrophils (p < 0.01), eosinophils (p < 0.01), and ciliated epithelial cells (p < 0.05) and increased concentrations of myeloperoxidase (MPO) (p < 0.01) compared with control subjects. Positive correlations were observed between the number of BAL neutrophils and eosinophils (Rs = 0.780, p < 0.0001) and between BAL neutrophil numbers and BAL MPO levels (Rs = 0.40, p < 0.05). No correlations were found between the following: (1) BAL eosinophils or neutrophils and BAL epithelial cells (p > 0.05, each comparison); (2) BAL neutrophils or eosinophils and log Pd15 methacholine (MCh) (p > 0.05, each comparison); or (3) BAL epithelial cells or log Pd15 MCh and BAL MPO (p > 0.05, each comparison). Dividing the patient population into two groups, allergic asthmatics and nonallergic asthmatics, similar BAL neutrophil, eosinophil, and epithelial cell numbers and similar MPO levels were found (p > 0.05, each comparison). In addition, the correlations between BAL neutrophils and eosinophils showed similar significance in the two patient subgroups (p > 0.05, each comparison). These results suggest that, both in allergic and nonallergic asthma, airway recruitment and activation of neutrophils occur as does parallel eosinophil migration. However, airway neutrophils do not seem to contribute significantly to epithelial cell injury or to airway hyperresponsiveness in the steady state.

Adenosine, methacholine, and exercise challenges in children with asthma or paediatric chronic obstructive pulmonary disease

BACKGROUND

Bronchial hyperreactivity to methacholine is present in children with asthma and other types of paediatric chronic obstructive pulmonary disease (COPD), while hyperreactivity to exercise is more specific for asthma. Adenosine 5'-monophosphate (AMP) is a potent bronchoconstrictor and, like exercise, may provoke asthma by activating mast cells. This study investigated the suitability of AMP as a specific challenge for asthma in children.

METHODS

Bronchial provocation challenges with methacholine and AMP were performed in a double blind fashion using tidal breathing in 51 children with asthma, 21 with paediatric COPD of various types, and in 19 control children. Each subject also underwent a standardised exercise challenge after inhalation challenges were completed. Sensitivity and specificity curves were constructed and the intersection point of sensitivity and specificity for each type of challenge was determined.

RESULTS

When the asthmatic patients were compared with the children with COPD, the intersection points for AMP, exercise and methacholine were 90%, 85%, and 50%, respectively. When compared with the controls the same intersection points were 98%, 84%, and 92%, and when children with paediatric COPD were compared with controls they were 55%, 50%, and 82%.

CONCLUSIONS

Methacholine distinguishes both asthma and paediatric COPD from controls with a sensitivity of 82-92%, but does not distinguish between asthma and paediatric COPD; exercise and AMP distinguish asthma from controls with a sensitivity and specificity of 84-98% but they also distinguish asthma from paediatric COPD with a sensitivity and specificity of 85-90%. AMP inhalation is a practical aid for diagnosing asthma and distinguishing it from COPD in children of all ages.

Exercise testing revisited. The response to exercise in normal and atopic children

BACKGROUND

Wide differing criteria are used to define the normal airway response to exercise, and as a consequence the estimated incidence of exercise-induced bronchospasm (EIB) in atopic children is wide. The purpose of this study was to establish normal range for changes in spirometry after exercise in children and then to use these normal values to assess the incidence of EIB in atopic children.

METHODS

Pulmonary function was assessed before, and 2, 5, and 10 min after 6 min of free running exercise in a group of 48 normal and 96 atopic children (70 asthmatics, 17 with allergic rhinitis, and 9 with atopic dermatitis/food hypersensitivity).

RESULTS

The EIB (defined as the normal group mean value -2 SD) occurred with a > 10 percent fall in FEV1, > 17.5 percent fall in peak expiratory flow rate (PEFR), > 26 percent fall in mean forced expiratory flow during the middle half of the forced vital capacity (FEF25-75), and > 40 percent fall in FEF25. Sixty-three of 70 asthmatic patients had EIB by at least one of these definitions, most marked at 5 min postexercise. The combination of FEV1 and FEF25-75 criteria enabled detection of all subjects with EIB. By FEV1 and FEF25-75 criteria, none of the subjects with allergic rhinitis or dermatitis had EIB. The fall in FEV1 after exercise in children with allergic rhinitis was within the range of normal, but with a significantly lower mean value than control subjects.

CONCLUSIONS

EIB should be defined by using more than one maximum expiratory flow-volume curve parameter (ie, FEV1 and FEF25-75). The EIB (defined as a fall in FEV1 and FEF25-75) was only seen in asthmatic children and not in other atopic groups.

Effects of ozone and neutrophils on function and morphology of the isolated rat lung

Since whole-animal studies suggest that neutrophils play a role in ozone-induced impairment of pulmonary function and increases in airway reactivity, this study was designed to study more precisely the interaction of neutrophils and ozone using the isolated perfused rat lung. Sprague-Dawley rat lungs (n = 60) were ventilated for 3 h with 95% air and 5% CO2 alone or mixed with 1 ppm ozone and perfused with buffer alone or with neutrophils (8 x 10(7)). RL, Cdyn, Ppa, airway reactivity to methacholine, lung/body weight, bronchoalveolar lavage fluid (BALF) protein concentration, and airway lesions were analyzed using a two-way GLM or Kruskal-Wallis test (p < or = 0.05 significant). Both ozone and neutrophils increased RL and decreased Cdyn. Ozone but not neutrophils increased airway reactivity to methacholine. Neutrophils but not ozone increased lung weight/body weight and BALF protein concentration. Ozone damaged airway epithelium. In distal bronchioles, neutrophils enhanced this damage. We conclude that (1) ozone impaired pulmonary function, increased airway reactivity, and damaged airway epithelium without causing measurable microvascular leak; (2) neutrophils impaired pulmonary function, probably a result of microvascular leak, but did not change airway reactivity or damage airway epithelium; and (3) neutrophils had no effect on ozone-induced airway reactivity but had an additive effect on ozone-induced pulmonary function impairment and a synergistic effect on ozone-induced airway epithelial injury.

Airway inflammation, bronchial reactivity and asthma

Asthma is a common disease of children the basis of which is a state of chronic immunological inflammation which causes bronchial hyperreactivity and renders the patient liable to develop widespread airways obstruction in response to a variety of stimuli. In many instances it is likely that the immunological inflammation results from ongoing antigenic stimuli with the release of chemical mediators responsible for short term bronchospasm and cytokines responsible for the ongoing inflammatory process. Other insults can apparently result in very similar immunological events in asthmatics, particularly viral infections and a similar process can be initiated in children without asthma, including those with chronic bacterial infections of the lungs. There are differences in the bronchial hyperreactivity of asthma and other diseases which suggest that in the asthmatic the mast cell is either different structurally or functionally and this renders the patient susceptible to exercise induced asthma in addition to the bronchial hyperreactivity to chemical mediators common to a number of diseases with hyperreactivity. There is good evidence of direct genetic control of atopy and the large majority of children with asthma are atopic but there is no direct genetic link between atopy and asthma and twin studies strongly suggest the existence of a 'permissive' asthma gene which will allow the disease to develop if there is an appropriate external trigger. The only drugs which have been shown to significantly reduce bronchial reactivity are the corticosteroids with a lesser effect noted for sodium cromoglycate and nedocromil. Inhaled corticosteroids can reverse the immunologic inflammatory process and reduce bronchial reactivity, sometimes to normal levels, but on stopping treatment the patient reverts back to the asthmatic state. At the present time it appears that controlled longterm inhaled corticosteroid therapy is the most rational treatment for significant perennial childhood asthma.

Eosinophils in exercise-induced asthma

The variations in serum levels of eosinophil cationic protein (ECP) have been measured after exercise challenge of 13 patients with asthma with exercise-induced asthma (EIA) and nine patients with asthma without EIA. The patients were treated before exercise in a randomized and blinded fashion with inhalation of one dose of either disodium chromoglycate, terbutaline, or budesonide and in an open study with 4 weeks of inhaled budesonide. In the group with EIA, there was, in some patients, an initial increase in serum levels of ECP after exercise, but 60 minutes after exercise, the levels were significantly reduced (p less than 0.001). Disodium chromoglycate and 4 weeks of budesonide treatment inhibited this reduction. Histamine challenge of the group with EIA produced a similar fall in serum ECP levels (p less than 0.001). The group without EIA had initially lower levels of ECP than the group with EIA (p less than 0.05 to p less than 0.01), and ECP stayed unaltered after exercise. The preexercise serum ECP levels correlated significantly to the maximal fall in peak expiratory flow in the untreated group (r = 0.91; p less than 0.001) and in the group receiving one dose of budesonide (r = 0.62; p less than 0.05). The blood eosinophil counts were unchanged after challenge and not related to lung function. The results suggest that the ECP content in serum reflects the degree of allergic inflammation in the lungs and thereby the degree of bronchial hyperreactivity.