Increased urinary excretion of LTE4 after exercise and attenuation of exercise-induced bronchospasm by montelukast, a cysteinyl leukotriene receptor antagonist

BACKGROUND

A study was undertaken to determine whether montelukast, a new potent cysteinyl leukotriene receptor antagonist, attenuates exercise-induced bronchoconstriction. The relationship between the urinary excretion of LTE4 and exercise-induced bronchoconstriction was also investigated.

METHODS

Nineteen non-smoking asthmatic patients with a forced expiratory volume in one second (FEV1) of > or = 65% of the predicted value and a reproducible fall in FEV1 after exercise of at least 20% were enrolled. Subjects received placebo and montelukast 100 mg once daily in the evening or 50 mg twice daily, each for two days, in a three-period, randomised, double blind, crossover design. In the evening, approximately 20-24 hours after the once daily dose or 12 hours after the twice daily dose, a standardised exercise challenge was performed. Data from 14 patients were available for complete analysis.

RESULTS

The mean (SD) maximal percentage decrease in FEV1 after exercise was 29.6 (16.0), 17.1 (8.2), and 14.0 (9.4) for placebo, once daily, and twice daily regimens, respectively. The mean (95% CI) percentage protection was 37 (15 to 59) for the group who received 50 mg twice daily and 50 (31 to 69) for those who received 100 mg once daily. Active treatments were not different from each other. The mean (SD) plasma concentrations of montelukast were higher after the twice daily regimen (1.27 (0.81) microgram/ml) than after the once daily regimen (0.12 (0.09) microgram/ml); there was no correlation between the percentage protection against exercise-induced bronchoconstriction and plasma concentrations. After exercise urinary excretion of LTE4 increased significantly during placebo treatment (from 34.3 to 73.7 pg/mg creatinine; p < 0.05) but did not correlate with the extent of exercise-induced bronchoconstriction.

CONCLUSIONS

Montelukast protects similarly against exercise-induced bronchoconstriction between plasma concentrations of 0.12 and 1.27 micrograms/ml. The increase in the urinary excretion of LTE4 after exercise and the protection from exercise-induced bronchoconstriction with a cysteinyl leukotriene receptor antagonist provide further evidence of the role of leukotrienes in the pathogenesis of exercise-induced bronchoconstriction.

Identification and partial characterization of an exercise-induced neutrophil chemotactic factor in bronchial asthma

A heat-stable neutrophil chemotactic factor (NCF) has been identified in the serum of 13 atopic asthmatic subjects after treadmill exercise. Peak activity was detected at 10 min and returned to prechallenge values by 1 h. No NCF activity was detected in the sera of three nonasthmatic atopic or four normal nonatopic individuals performing the same task. NCF produced by exercise (NCFEX) had a similar time-course of release to NCF provoked by specific antigen (NCFAG). The appearance of circulating NCFEX and NCFAG closely paralleled the fall in peak expiratory flow rate/forced expiratory volume in 1 s (PEFR/FEV1). Histamine challenge in atopic asthmatics at concentrations giving a comparable change in PEFR/FEV1 to that evoked by exercise or inhaled antigen was not associated with the appearance of circulating NCF. In seven subjects NCFEX release was inhibited by prior administration of disodium cromoglycate. NCFEX and NCFAG eluted as single peaks of activity when applied separately to columns of Sephadex G-200, and both were an estimated 750,000 daltons. NCFEX and NCFAG also eluted as single peaks of activity, at between 0.15 and 0.30 M NaCl, following anion exchange chromatography on DEAE-Sephacel (pH 7.8). The isoelectric points of NCFEX and NCFAG were virtually identical (between pH 6.0 and 6.5) as determined by chromatofocusing on Polybuffer Exchanger 94. The activities of NCFEX and NCFAG were substantially reduced, in both a time- and dose-dependent fashion, after incubation with trypsin and chymotrypsin. Partially purified NCFEX and NCFAG promoted both stimulated random migration (chemokinesis) as well as directional migration (chemotaxis). These experiments indicate that NCFEX and NCFAG might be identical substances and raise the possibility that mediators by hypersensitivity are released during exercise-induced asthma in atopic subjects.

Circulating catecholamines in exercise and hyperventilation induced asthma

Plasma noradrenaline, adrenaline, and cyclic 3'5' AMP (cAMP) were measured in seven asthmatic patients with known exercise-induced bronchospasm and six matched non-atopic control subjects during a standard treadmill exercise test and then during matched isocapnic hyperventilation. Normal subjects showed a 5.5 fold rise in noradrenaline and a 3.2 fold rise in adrenaline during exercise compared with a 2.1 fold rise in noradrenaline and no significant rise in adrenaline in asthmatics who all developed bronchoconstriction after exercise (mean fall in peak flow rate 28.4 +/- 5.8%). Plasma cAMP rose 1.4 fold in controls but showed no significant rise in asthmatics. This reduced sympatho-adrenal response to exercise in asthmatics is difficult to explain. The failure of circulating catecholamines to rise and stimulate beta adrenoceptors on the mast cell may facilitate the release of bronchoconstrictor mediators. Matched hyperventilation produced bronchospasm in asthmatics (mean fall in peak flow rate 29.0 +/- 4.4%) but no change in catecholamines in either group suggesting that circulating catecholamines have no direct role in exercise-induced bronchospasm but may play a permissive role via the mast cell.

The new phosphodiesterase 4 inhibitor roflumilast is efficacious in exercise-induced asthma and leads to suppression of LPS-stimulated TNF-alpha ex vivo

Roflumilast is a new phosphodiesterase 4 (PDE4) inhibitor developed by Byk Gulden Pharmaceuticals for the treatment of chronic obstructive pulmonary disease and asthma. A placebo-controlled, randomized, double-blind, two-period crossover study was performed to investigate the safety and efficacy of roflumilast in 16 patients with exercise-induced asthma. The patients received placebo or roflumilast (500 microg/day) for 28 days, each according to the randomly determined treatment sequences roflumilast/placebo and placebo/roflumilast. In both study periods, exercise challenge was performed 1 hour after dosing on days 1, 14, and 28. FEV1 was measured before exercise challenge, immediately after the end of exercise challenge, and then at 1, 3, 5, 7, 9, and 12 minutes after the end of challenge. Blood samples for the determination of lipopolysaccharide (LPS)-stimulated tumor necrosis factor alpha (TNF-alpha) in whole blood ex vivo as a surrogate marker for the inhibition of inflammatory cell activation were taken predose on days 1 and 28. Serial safety measurements were performed during both study periods. Analysis of variance for the crossover design showed a significant superiority of roflumilast over placebo on day 28. The mean percentage fall of FEV1 after exercise was reduced by 41% as compared to placebo (p = 0.021). An improvement of lung function during roflumilast treatment was also observed on days 1 and 14. The median TNF-alpha level decreased by 21% (p = 0.009) during roflumilast treatment but remained essentially constant under placebo. It is concluded that roflumilast is effective in the treatment of exercise-induced asthma. This result was accompanied by a significant reduction of TNF-alpha levels ex vivo. Treatment with roflumilast was safe and well tolerated.

Venous plasma histamine in exercise- and hyperventilation-induced asthma in man

1. Venous plasma histamine was measured by a specific and sensitive radioenzymatic assay in seven male extrinsic asthmatic and six age-matched non-atopic non-asthmatic male subjects during exercise and voluntary isocapnic hyperventilation. 2. There was no change in peak expiratory flow in normal subjects with exercise or hyperventilation, but asthmatic subjects showed a 29.4 +/- SEM 5.8% fall after exercise and a 29.0 +/- 5.4% fall after matched hyperventilation. 3. Plasma histamine was significantly higher (P less than 0.05) in asthmatic (6.2 +/- 0.95 nmol/l) than that in normal subjects (3.4 +/- 0.61 mol/l) and showed a significant (P less than 0.01) rise (to 14.4 +/- 1.83 nmol/l) during exercise in asthmatic, but not in normal subjects. This suggests that discharge of mast-cell mediators may occur during exercise in asthmatic subjects who develop exercise-induced asthma. 4. With hyperventilation there was no change in plasma histamine in either asthmatic or normal subjects, but this does not exclude the possibility that mediators may be released locally in the airways.

Arterial plasma histamine levels at rest, and during and after exercise in patients with asthma: effects of terbutaline aerosol

Eight asthmatic patients and two normal subjects performed two identical exercise tests 140 minutes apart (first test preceded by inhalation of saline and the second by terbutaline sulphate). A ninth asthmatic patient exercised twice after placebo 40 minutes apart. Arterial plasma levels of histamine and cyclic AMP, expiratory flow rates and volumes were measured at rest and during and after exercise. After the first test the mean +/- SEM fall in PEFR was 45.2 +/- 2.6%. In five asthmatics there was an increase in plasma histamine (mean +/- SEM 14.8 +/- 3.3 pmol ml-1) coinciding with exercise-induced asthma (EIA). Histamine levels returned to pre-exercise values within 30 minutes. After terbutaline these five patients had histamine levels greater than those observed before, during, or after the first test. This effect may have been the result of changes in pulmonary microcirculation. After the second test the levels decreased indicating no further release of histamine in response to exercise. No EIA occurred in these patients after terbutaline. The other patients and the two normal subjects had little or no change in histamine throughout the study. The one patient in whom exercise was repeated after placebo demonstrated less histamine release and less EIA after the second test.

Reduction of exercise-induced asthma oxidative stress by lycopene, a natural antioxidant

BACKGROUND

Lycopene has previously been shown to have high antioxidative activity. In view of the controversy regarding the beneficial effect of antioxidants on asthma, the acute effects of lycopene (LYC-O-MATO) on airway hyperreactivity were assessed in patients with exercise-induced asthma (EIA).

METHODS

Twenty patients with EIA participated in our study to verify the antioxidative effects. The test was based on the following sequence: measurement of baseline pulmonary function, 7-min exercise session on a motorized treadmill, 8-min rest and again measurement of pulmonary function, 1-week, oral, randomly administered, double-blind supplementation of placebo or 30 mg/day of lycopene (LYC-O-MATO), measurement of pulmonary function at rest, 7-min exercise session, and 8-min rest and again measurement of pulmonary function. A 4-week washout interval was allowed between each protocol.

RESULTS

All patients given placebo showed significant postexercise reduction of more than 15% in their forced expiratory volume in 1 s (FEV1). After receiving a daily dose of 30 mg of lycopene for 1 week, 11 (55%) patients were significantly protected against EIA. Serum analyses of the patients by high-pressure liquid chromatography detected in the lycopene-supplemented patients an elevated level of lycopene compared to the placebo group, with no change in retinol, tocopherols, or in the other carotenoids.

CONCLUSIONS

Our results indicate that a daily dose of lycopene exerts a protective effect against EIA in some patients, most probably through an in vivo antioxidative effect.

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.

Adenosine level in exhaled breath increases during exercise-induced bronchoconstriction

In asthmatic patients, airway obstruction provoked by exercise challenge is accompanied by an increase in plasma adenosine level. In this study, the current authors investigated if exercise-induced bronchoconstriction was associated with local changes of adenosine concentration in the airways. Oral exhaled breath condensate (EBC) collection (5-min duration) and forced expiratory volume in one second (FEV1) measurements were performed at rest (baseline) and 4-8 times after treadmill exercise challenge in healthy and asthmatic subjects. Adenosine concentration in EBC was determined by HPLC. Observations indicated that physical exercise results in bronchoconstriction together with a significant increase of adenosine level in EBC in asthmatic patients (mean+/-sd maximal fall in FEV1 27+/-13%; associated increase in adenosine 110+/-76% as compared to baseline), but not in healthy control subjects. Exercise-induced changes in adenosine concentration correlated significantly with the fall in FEV1 values in asthmatic patients. In conclusion, the observed increase in adenosine concentration of oral exhaled breath condensate most probably reflects changes in the airways during exercise-induced bronchoconstriction. Due to its known bronchoconstrictor property in asthma, adenosine may contribute to the development of bronchospasm.

Prolonged protection against exercise-induced bronchoconstriction by the leukotriene D4-receptor antagonist cinalukast

OBJECTIVES

The degree and duration of protection against exercise-induced bronchoconstriction afforded by three doses of a specific leukotriene D4 receptor antagonist, cinalukast, were assessed after an initial dosing and after 1 week of therapy.

METHODS

A placebo-controlled crossover study was performed in eight male patients who had mild, stable asthma and exercise-induced bronchoconstriction. Treatment consisted of four 7-day periods of placebo and three dose levels of the drug (10, 50, and 200 mg administered orally). Exercise challenge was performed at 2 hours and 8 hours after treatment on the first and seventh treatment days. The response was measured as the area under the FEV1-time effect curve (AUEC).

RESULTS

On the first day of treatment, the mean (+/- SEM) AUEC at 2 hours was 24.2 +/- 3.3 L.min after placebo and was 5.5 +/- 2.2 L.min, 6.3 +/- 2.7 L.min, 3.3 +/- 3.8 L.min after 10 mg, 50 mg, and 200 mg, respectively (p < 0.05 for all values compared with placebo). The AUEC at 8 hours on the first day was 25.1 +/- 4.4 L.min after placebo and was 6.8 +/- 4.1 L.min, 11.2 +/- 2.5 L.min, and 5.0 +/- 2.8 L.min after 10 mg, 50 mg, and 200 mg, respectively (p < 0.05 for all values compared with placebo). The protection afforded by 10 mg of cinaluicast was lost after 7 days of treatment but persisted with 50 mg and 200 mg doses.

CONCLUSION

Orally administered cinalukast provides at least 8 hours of protection against exercise-induced bronchoconstriction. This protection is lost with regular treatment for 1 week for the lowest dose studied.

Effect of physical training on exercise-induced bronchoconstriction

A 6-week period of physical training of 28 asthmatic children reduced the exercise-induced percentage fall in peak expiratory flow (from baseline) from 44 +/- 4% (mean +/- SE) to 30 +/- 4%. Resting pulmonary function was unchanged. Resting and maximum heart rate (submaximal treadmill running) and postexercise plasma lactate were all lowered by training. The individual values for exercise-induced bronchoconstriction and postexercise plasma lactate correlated positively before and after training. Furthermore, the training-induced reduction in these parameters correlated. In 14 asthmatic children, who served as controls, exercise-induced bronchoconstriction and physical fitness remained unchanged during a comparable period. The study demonstrates a beneficial effect of endurance training on exercise-induced bronchoconstriction and working capacity.

Plasma adenosine concentration increases during exercise: a possible contributing factor in exercise-induced bronchoconstriction in asthma

We investigated whether the level of plasma adenosine (ADO) changed during exercise and whether this could be related to exercise-induced bronchoconstriction. Baseline levels of ADO did not differ, but exercise resulted in higher ADO in patients with asthma than in healthy subjects (86 +/- 35 vs 59 +/- 16 nmol/L; P <.001). In patients with asthma, the increase in ADO was related to decreases in FEV(1) (r (2) = 0.475; P <.05) and SaO(2) (r (2) = 0.693; P <.05). These data suggest that adenosine might be involved in the development of exercise-induced bronchoconstriction.

Blood eosinophil counts for the prediction of the severity of exercise-induced bronchospasm in asthma

It has been suggested that airway eosinophilic inflammation is associated with the severity of exercise-induced bronchospasm (EIB). Blood eosinophils are known to be an indirect marker of airway inflammation in asthma. The aim of this study is to investigate that a simple and easy blood test for blood eosinphil counts may predict the severity of EIB in asthma. Seventy-seven men with perennial asthma (age range 18-23 years) were included. Lung function test, skin prick test, and blood tests for eosinophils counts and total IgE levels were performed. Methacholine bronchial provocation test and, 24 h later, free running test were carried out. EIB was defined as a 15% reduction or more in post-exercise FEV1 compared with pre-exercise FEV1 value. Atopy score was defined as a sum of mean wheal diameters to allergens. EIB was observed in 60 (78%) of 77 subjects. Asthmatics with EIB showed significantly increased percentages of eosinophils (P<0.01), log eosinophil counts (P<0.001), and atopy scores (P<0.05) and decreased log PC20 values (P < 0.05) compared with asthmatics without EIB. Asthmatics with eosinophils of > 700 microl(-1) (36.9 +/- 12.7%) had significantly greater maximal % fall in FEV1 after exercise than asthmatics with eosinophils of < 350 microl(-1) (24.7 +/- 16.6%, P <0.05). Blood eosinophil counts > 350 microl(-1) yielded the specificity of 88% and positive predictive value of 93% for the presence of EIB. When a multiple regression analysis of maximal % fall in FEV1 according to log eosinophil counts, log PC20, log IgE and atopy score was performed, only blood eosinophil counts were significant factor contributing to the maximal % fall in FEV1 after exercise. These findings not only suggest that a simple blood test for eosinophils may be useful in the prediction of the severity of EIB, but also reinforce the view that airway eosinophilic inflammation may play a major role in EIB in asthma.

Arterial plasma histamine after exercise in normal individuals an in patients with exercise-induced asthma

1. Arterial plasma histamine concentrations, forced expiratory volume in 1.0 s (FEV1.0) and peak expiratory flow rate were determined in nine patients with exercise-induced asthma and in five control subjects before and after 8 min of cycle-ergometer exercise. 2. In the controls neither FEV1.0 nor peak expiratory flow rate fell by more than 5% in any individual during the 30 min postexercise period. The asthmatic patients all experienced a fall in FEV1.0 or peak expiratory flow rate, or both, of 15% or more in the period 5-20 min after completion of the exercise. 3. There was no difference between the control subjects and the asthmatic patients in the plasma histamine response to exercise. In both groups there was an insignificant rise of about 40% during exercise, although the initial levels were higher in the asthmatic patients. 4. The mean plasma histamine peak of the asthmatic patients preceded the mean maximal fall of FEV1.0 and peak expiratory flow rate by approximately 15 min. However, no positive correlation was found between rise in, or peak, plasma histamine levels and decrease in lung function. 5. Three non-atopic asthmatic patients had a significantly higher mean plasma histamine concentration during exercise than had the atopic subjects. 6. A strong positive correlation in asthmatic patients, and asthmatic and control subjects together was found between age and mean postexercise plasma histamine concentrations. 7. The results do not support a direct role for histamine in the production of exercise-induced asthma.

Effects of a PAF-antagonist (BN 52063) on bronchoconstriction and platelet activation during exercise induced asthma

1. The effects of a specific PAF acether antagonist (BN 52063) on the response to isocapnic hyperventilation with dry cold air (ISH study) and exercise (EIA study) were assessed in a single dose and short term treatment study in 10 patients with exercise induced asthma. 2. ISH challenge was performed twice within 1 h after administration of either placebo, 240 mg BN 52063 p.o. or inhalation of 2.4 mg BN 52063. Hyperventilation increased Raw from 0.30 +/- 0.02 to 0.89 kPa s l-1 (P less than 0.001) after the first challenge and from 0.28 +/- 0.04 to 0.84 +/- 0.06 kPa s l-1 (P less than 0.001) after the second challenge. Oral pretreatment with BN 52063 did not result in a reduction of bronchoconstriction during both challenges. A significant increase of Raw was noted immediately after inhalation of BN 52063. An inhibition of PAF induced platelet aggregation (by a factor of 2) occurred after oral administration of BN 52063 after both ISH challenges (P less than 0.05). No significant inhibition of PAF induced platelet aggregation was seen after inhalation of BN 52063. At concentrations up to 30 microM in vitro, BN 52063 inhibited PAF induced platelet aggregation in a dose dependent manner. The IC50 of BN 52063 against the aggregating effect of 1 microM PAF was 7.0 +/- 2.1 microM. 3. In the EIA study the patients were challenged on the third day of treatment with either placebo or 240 mg BN 52063 p.o. or 5 mg BN 52063 by inhalation. Peak expiratory flow rates (PEFR) fell by 155 +/- 37 1 min-1 after exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

Exercise and isocapnic hyperventilation-induced bronchoconstriction in asthma: relevance of circulating basophils to measurements of plasma histamine

The relationship of airway cooling during exercise to changes in airway caliber, plasma histamine levels, and circulating basophils was investigated in eight allergic asthmatic and eight normal subjects. In asthma matched RHE during exercise and ICH produced almost identical bronchoconstriction with maximum falls in SGaw of 61.0 +/- 4.5% and 57.9 +/- 5.2%, respectively. A similar RHE in normal subjects was associated with a 7.9 +/- 3.3% fall in SGaw. The resting plasma-histamine levels were higher in the asthmatic (0.52 +/- 0.06 ng/ml) than in the normal (0.31 +/- 0.07 ng/ml, p less than 0.05) subjects. No significant change in plasma histamine occurred after exercise in either group nor in the asthmatic subjects with ICH. In contrast, exercise but not ICH stimulated an increase in leukocytes, basophils, and total blood histamine in parallel with the airway response that reached a maximum at 2 to 5 min in both normal and asthmatic subjects. There was a positive correlation between basal plasma and total blood-histamine levels (r = 0.67, p less than 0.01) in normal and asthmatic subjects suggesting that basophils contribute significantly to plasma histamine. The spontaneous basophil release of histamine was greater in asthmatic (13.4 +/- 2%) than in normal subjects (6.46 +/- 7%, p less than 0.005), which is consistent with the higher resting plasma-histamine levels in the asthmatic subjects. These findings suggest that plasma-histamine changes with exercise in asthma but not ICH may be related to the associated basophilia and sample handling rather than intrapulmonary mast cell degranulation.

Platelet activation during exercise induced asthma: effect of prophylaxis with cromoglycate and salbutamol

Peak expiratory flow (PEF) and plasma concentrations of platelet factor 4 and beta thromboglobulin were measured before and after exercise in nine asthmatic patients and 12 non-asthmatic volunteers. Exercise was preceded by administration in random order of either placebo, salbutamol 200 micrograms, or sodium cromoglycate 2 mg from a pressurised inhaler. In control subjects there were minimal changes in PEF and plasma concentrations of platelet factor 4 and beta thromboglobulin. In the asthmatic patients the typical changes in PEF were seen on exercise; plasma concentrations of platelet factor 4 and beta thromboglobulin rose significantly in parallel, the rise preceding the fall in PEF. The changes in peak flow and platelet activation induced by exercise were attenuated by prior administration of salbutamol or cromoglycate. These results indicate that exercise induced asthma is associated with a rise in platelet release products similar to that observed in antigen induced asthma.

Circulating adrenaline and noradrenaline concentrations during exercise in patients with exercise induced asthma and normal subjects

A failure of the usual increase in plasma adrenaline and noradrenaline concentrations during submaximal exercise has been suggested as a contributory cause of exercise induced asthma. Six normal subjects and six asthmatic patients underwent a standard graded maximal exercise test. Measurements of oxygen consumption, minute ventilation, exercise time, blood lactate concentration, and heart rate indicated that the two groups achieved similarly high work loads during exercise. Mean FEV1 fell by 20% in asthmatic patients after exercise. Basal plasma adrenaline concentrations (nmol/l) increased in normal subjects from 0.05 to 2.7 and in asthmatic patients from 0.12 to 1.6 at peak exercise. Noradrenaline concentrations (nmol/l) increased in normal subjects from 2.0 to 14.3 and in asthmatic patients from 1.9 to 13.7 at peak exercise. The increases in adrenaline and noradrenaline in the asthmatic patients did not differ significantly from the increases in normal subjects. Thus a reduced sympathoadrenal response to exercise seems unlikely to be an important mechanism in the pathogenesis of exercise induced asthma.

Circulating concentrations of histamine, neutrophil chemotactic activity, and catecholamines during the refractory period in exercise-induced asthma

Circulating mediators and catecholamine concentrations have been measured in eight subjects with asthma who were subjected to two bouts of cycle ergometer exercise separated by 1 hour. The maximum falls in FEV1 were 21.9 +/- 2.3% (mean +/- SEM; n = 8) and 5.5 +/- 1.3% (mean +/- SEM; n = 8) after the first and second exercises, respectively. Serum neutrophil chemotactic activity (NCA) and plasma histamine and catecholamine levels in venous blood were measured with a microchemotaxis and two radioenzymatic techniques, respectively. There was a significant increase in NCA and plasma histamine concentrations after both exercise challenges, and there was no significant difference in the release of these mediators between the two exercise tests. Gel filtration chromatography demonstrated that the NCA detected after the first and second exercise tests had molecular sizes of approximately 600,000 daltons. There was no significant time-dependent increase in plasma norepinephrine and epinephrine concentrations after either exercise task, even though the patients were refractory to exercise-induced asthma after the second exercise. These results suggest that the refractory period in exercise-induced asthma is not caused by mediator depletion, as indicated by NCA and histamine measurements, or by protection of the airways through catecholamine release.

Plasma histamine in asthmatic and control subjects following exercise: influence of circulating basophils and different assay techniques

Arterial plasma histamine concentrations were measured after exercise in 10 subjects with extrinsic atopic asthma, 10 who were non-atopic and non-asthmatic and seven who were atopic but non-asthmatic, by a single isotope radioenzymatic assay. Significantly higher plasma histamine concentrations were found in the asthmatic subjects before exercise than in the non-atopic controls (p less than 0.05). The mean histamine concentration rose after exercise in all groups but the increased levels were not significantly different from pre-exercise values. Similarly, mean circulating basophil counts increased in all groups after exercise, and a highly significant correlation was found between basophil counts and whole blood histamine concentrations (p less than 0.001). In vitro studies showed that there was a significant correlation between the number of basophils added to plasma samples and the concentrations of histamine subsequently detected. Although the mean concentrations of plasma histamine and whole blood histamine and number of basophils in the atopic control group were intermediate between those found in the atopic asthmatic and non-atopic controls, none of the differences was significant. Venous plasma histamine concentrations after exercise were measured in a further five subjects with extrinsic atopic asthma and five non-atopic, non-asthmatic subjects before and after exercise with the more sensitive and specific double isotope radioenzymatic assay. Concentrations of plasma histamine measured by this assay were about one tenth of those measured by the single isotope radioenzymatic assay. Although a small rise in mean plasma histamine concentration occurred in both groups after exercise there was no significant difference in these levels either between or within the groups. We find no evidence from these studies on measurement of peripheral blood histamine to support the hypothesis that mast cell mediator release is implicated in the pathogenesis of exercise induced asthma.

Caffeine consumption decreases the response to bronchoprovocation challenge with dry gas hyperventilation

OBJECTIVE

To determine whether caffeine consumption affects bronchoprovocation challenge (BPC).

DESIGN

A prospective, double-blind, placebo-controlled, randomized, crossover trial.

PATIENTS

Eleven nonsmoking men, aged 18 to 42 years, with normal baseline spirometry and evidence of exercise-induced bronchospasm.

INTERVENTION

On three separate test days, each individual received, in random order, either placebo, 5 mg/kg caffeine, or 10 mg/kg caffeine, and then underwent BPC with eucapnic voluntary hyperventilation (EVH).

RESULTS

Caffeine (10 mg/kg) significantly reduced bronchoconstriction compared to placebo (p = 0.02). The reduction in bronchoconstriction correlated with the serum level of caffeine (p = 0.014).

CONCLUSIONS

Caffeine decreases bronchoconstriction due to EVH. Caffeine should be eliminated from diet prior to BPC.

Sympathoadrenal reactivity in exercise-induced asthma

The possibility that sympathoadrenal activity is altered in asthma was examined in eight patients with a history of exercise-induced asthma (EIA), eight matched patients with nonexercise induced asthma (NEIA), and eight matched healthy control subjects. No medication was allowed for at least one week before examination. In a pretrial exercise test diagnosis of EIA was confirmed and each individual's work capacity (Vo2 max) was determined. The trial consisted of an orthostatic test and a standardized exercise test at 80 to 90 percent of VO2 max on a treadmill. The trial exercise test caused a decrease in FEV1 in EIA patients only, whereas measurements of Sgaw revealed a significant but less pronounced postexercise bronchoconstriction in NEIA-patients as well. Basal plasma catecholamine levels were similar in all groups. Noradrenaline and adrenaline levels were approximately doubled by the orthostatic test and increased approximately ten-fold following exercise, with no differences between the groups. Plasma cAMP levels were approximately doubled by the exercise test. In the EIA patients there was an inverse correlation between increases in plasma cAMP and decreases in Sgaw. Our study does not support earlier claims that exaggerated catecholamine response to exercise causes postexercise bronchoconstriction by alpha-adrenoceptor stimulation in EIA. Differences in study results appear to have methodologic explanations.

The correlation between increased reactivity of the bronchi and of mediator releasing cells in asthma

The hypothesis that increased reactivity in asthma is not always limited to the bronchi but also exists in the mediator releasing system was investigated in forty-five asthmatic children, approximately half of whom had exercise-induced bronchoconstriction (EIB). The bronchial threshold to histamine was measured as an indicator of the reactivity of the bronchi and the histamine release from leucocytes without adding allergen (spontaneous histamine release) was considered as an indicator of the reactivity of the basophil leucocytes. There was a significant correlation between the histamine threshold and spontaneous histamine release and between these and EIB. These findings support the hypothesis.