Effect of azelastine, montelukast, and their combination on allergen-induced bronchoconstriction in asthma

OBJECTIVES: Histamine and cysteinyl leukotrienes play an important role in early (EAR) and late (LAR) allergen reactions. Although protection by anti-histamines and anti-leukotrienes has been studied extensively, little is known about the effect of their combination. We, therefore, assessed the effect of clinically recommended doses of azelastine and montelukast alone and in combination on EAR and LAR. METHODS: Seventeen patients (mean age 31 years, 14 m/3 f) with asthma and proven EAR and LAR received an oral dose of 4 mg azelastine twice daily, or 10mg montelukast once daily, or both for 1 week, in a double-blind, double-dummy, cross-over fashion. FEV(1) was measured after single-dose allergen challenges during EAR (0-2h) and LAR (2-9h). RESULTS: Azelastine, montelukast and their combination protected against both EAR and LAR (p<0.004, each) by 46% and 43%, 76% and 59%, and 89% and 78%, respectively. Azelastine was not as effective during EAR but equally effective to montelukast during LAR. The combination was superior to each drug alone during both EAR and LAR (p<0.05, each). CONCLUSION: The combination of azelastine and montelukast in clinically recommended doses has a greater effect in suppressing early and late allergen reactions than each drug alone.     

Effect of 15-(s)-hydroxyeicosatetraenoic acid on allergen-induced asthmatic responses

15-(s)-hydroxyeicosatetraenoic acid (15-HETE), a major oxidative metabolite of arachidonic acid in human lungs, has complex actions on the 5-lipoxygenase pathway in different cell systems. We have examined the effect of inhaled 15-HETE on the early and late asthmatic responses (EAR and LAR) and the associated change in nonspecific bronchial responsiveness to inhaled allergen in 10 subjects with atopic asthma. On 2 separate days 3 wk apart, subjects inhaled either 70 nmol 15-HETE or the diluent (sodium phosphate buffer) in a randomized and double-blind fashion, followed by a dose of allergen that had previously been shown to produce a 25% fall in baseline FEV1. Analysis of the area under the FEV1 response time course curves (AUC) in the first hour revealed that preinhalation with 15-HETE increased the EAR by 39% from that achieved after the diluent (p less than 0.05). In the seven subjects who were classified as dual responders by developing a LAR previously (greater than 15% fall in baseline FEV1 3 to 8 h after allergen challenge), 15-HETE did not cause any significant change in the magnitude of the LAR when compared with that observed after placebo. The values of the provocation concentration of histamine causing a 20% fall in FEV1 (Pc20) at 8 h postchallenge were significantly reduced on both study days when compared with the corresponding preallergen challenge values, whether analyzed for the whole group or for the seven dual responders (p less than 0.05). 15-HETE had no effect on this allergen-acquired airway hyperresponsiveness to histamine when compared with the diluent.(ABSTRACT TRUNCATED AT 250 WORDS)     

Inhaled synthetic surfactant abolishes the early allergen-induced response in asthma.

Allergen-induced inhibition of pulmonary surfactant in asthma may promote airway oedema and consequently potentiate the severity of the asthmatic response. A randomised, single-blind, cross-over study of an inhaled synthetic phospholipid dry-powder surfactant (Pumactant) was conducted in atopic, asthmatic subjects with previously documented early and late asthmatic responses (EAR and LAR) to an inhaled allergen. This was conducted to evaluate the role of exogenous surfactant administration on EAR and LAR. A total of seven subjects had complete evaluable data and received the full dose of Pumactant. Asthmatic subjects inhaled two separate doses of 400 mg Pumactant prior to an allergen exposure. The first dose was administered 8 h in advance and the second dose 30 min in advance. The dosage occurred through a purpose-built administration device. This was followed by a standard bronchial-provocation test, and forced expiratory volume in one second (FEV1) was measured at regular intervals over a 10-h period. Pumactant was well tolerated and, surprisingly, abolished the EAR but not the LAR in all seven subjects. The mean area under the curve between 0-2 h (EAR) following bronchial provocation test was 0.08 for the Pumactant treatment group (PT) and 13.29 for the no treatment (NT) group. The maximum drop in FEV1 for EAR was 4.19% and 23.98% in the PT and the NT group, respectively. The demonstration of inhibition of the early asthmatic response by exogenous surfactant, provides the first evidence that pulmonary surfactant dysfunction may also contribute to the very early asthmatic response to allergen. Exogenous surfactant administration could serve as a useful adjunct in controlling the early allergen-induced symptoms in patients with allergic asthma.     

Effect of allergen inhalation on the maximal response plateau of the dose-response curve to methacholine.

Methacholine dose response curves (DRC) in asthmatic subjects are characterized by a leftward shift and increased maximal response. Allergen inhalation in atopic subjects shifts the DRC to the left, but the effect on the shape is unknown. This study was designed to investigate the effect of allergen inhalation on the maximal response plateau of the methacholine DRC in 16 atopic subjects; nine had mild asthma and seven had rhinitis. They were challenged with allergen and with control solutions in a single-blind design. Methacholine challenges (up to 199 mumol) were performed at baseline and 24 h after the control and allergen challenges. A plateau of the DRC was defined as a difference of less than 5% in FEV1 between the last two or more doses. The maximal response was obtained by averaging the values on the plateau and was reached by all except one subject. Allergen inhalation induced an early asthmatic response (EAR) in all subjects and an additional late asthmatic response (LAR) in 6 subjects. In subjects with an EAR alone the maximal response to methacholine 24 h after allergen challenge was not different from control (mean difference, 2.9% fall in FEV1; p greater than 0.05). In subjects with LAR, the mean value for the maximal response increased from 28.5% after control to 36.5% after allergen (mean difference, 8.0%; p less than 0.05). Of six subjects who developed LAR two lost the plateau on the DRC after allergen challenge. We conclude that allergen inhalation increases the maximal response to methacholine in those subjects who have a LAR.     

Thromboxane A2 Production in Allergen-Induced Immediate and Late Asthmatic Responses: Its Possible Role in Inducing the Late Response

To determine whether thromboxane A₂ (TXA₂) participates in allergen-induced asthmatic responses, we measured plasma TXB₂ levels during allergen-induced immediate and late asthmatic responses (IAR and LAR) in atopic asthmatics. We also examined the effect of a TXA₂ synthetase inhibitor, OKY-046, on the responses.

Plasma TXB₂ levels increased in both IAR and LAR, being 2.2 times higher in LAR than in IAR. Plasma TXB₂ levels in LAR reached the peak 4 hours after allergen challenge when FEV₁ had just begun to decrease in LAR. OKY-046 inhibited both IAR and LAR with decreased plasma TXB₂ levels.

We conclude that TXA₂ is produced in allergen-induced asthmatic responses and participates in the responses, especially in inducing LAR.     

Discrepant nasal and bronchial nitric oxide kinetics during early and late phase allergic reactions

Late allergic reactions (LAR) following allergen challenge occur in different compartments. We studied the kinetics of nasal and bronchial nitric oxide (NO) in mild asthmatics after allergen challenge. Twelve males with intermittent asthma (28 yr, FEV1 97% of predicted, PC20methacholine <8 mg/ml) and known LAR after bronchial allergen challenge underwent nasal and bronchial allergen provocation using the same allergen separated by a washout of 3 weeks. Nasal and bronchial NO were measured before challenge, during early (EAR) and late phase reactions, and 24 h after allergen. The mean (sem) maximum fall of FEV1 at EAR was 31.9+/-3.2% (P=0.001), and 17.6+/-2.2% (P=0.004) during LAR. All patients developed nasal EAR (max. fall in nasal rhinomanometric flow 64.8+/-7.6% of baseline) after nasal challenge, and 10 patients demonstrated nasal LAR with a fall in nasal flow of 65.9+/-6.6% (both P=0.002, respectively). During EAR, there was stronger reduction of nasal (-19.2+/-6.2%,P=0.039) than bronchial NO (-6.9+/-5.2% of baseline, P=ns). In contrast, bronchial NO also tended to decrease during bronchial LAR (-8.8+/-6.8%,P=ns), while nasal NO slightly increased non-significantly (+17+/-10.8%, P=ns). After 24 h, bronchial NO was significantly elevated (+78.1+/-40.1%, P=0.039), whereas nasal NO was unchanged (+6.1+/-15.1%, P=ns). The intraindividual difference between bronchial and nasal changes of NO during LAR, but not EAR or after 24 h, was significant (lung vs. nose: -35.6+/-14.1% relative difference, P=0.039). Despite similar functional responses in nose and bronchi, nasal NO kinetics following allergen challenge differ from bronchial NO. The concise mechanisms accounting for this discrepancy warrant further investigations.     

Site of airflow obstruction during early and late phase asthmatic responses to allergen bronchoprovocation

Chronic asthma and late asthmatic responses (LAR) are associated with local inflammation which might be expected to produce airflow obstruction in small airways and to increase nonspecific airway reactivity. In contrast, early asthmatic responses (EAR) are primarily bronchospastic and probably involve more central airways. We challenged 17 nonsmoking, mildly asthmatic atopic subjects with allergen bronchoprovocation and measured changes in spirometry (FEV1) over the next 24 hours. Each subject also performed a helium-oxygen (He-O2) flow-volume loop before challenge (baseline), during the EAR, and six hours and 24 hours after challenge to measure the effect of gas density on flow rates at midvital capacity. Twelve subjects had both an EAR and a LAR; five subjects had only a LAR. Of these 17 subjects, 15 were initially density dependent, while only two were density independent. During the EAR, 13 percent of the density dependent population had significant decreases in delta Vmax 50 percent; 47 percent had significant decreases during LAR. The He-O2 flow data analyzed at specified time points after challenge revealed significant decreases in the mean delta Vmax 50 percent at six hours in those who had only a LAR (p less than 0.01). In those who had a dual airway response, density dependence increased during the EAR, but decreased at six and significantly at 24 hours (p less than 0.05) postchallenge. There was a strong trend for the severity of the LAR (measured by changes in FEV1) to be directly related to the total decrease in delta Vmax 50 percent during the LAR. We conclude that late asthmatic responses occur frequently after a single antigenic bronchial challenge and can be associated with persistent symptoms. The LAR were often associated with a decrease in density dependence of maximal expiratory airflow, and therefore, may involve small airways.     

The effects of Mycobacterium vaccae on allergen-induced airway responses in atopic asthma.

T-helper (Th)2 cytokines play a central role in asthma. Therefore, a double-blind randomised study was conducted to investigate whether heat-killed Mycobacterium vaccae (SRL172), a potent downregulator of Th2 cytokines, can reduce allergen-induced airway responses in patients with atopic asthma. A total 24 male asthmatics participated in this study. A bronchial allergen challenge was performed along with early (EAR) and late asthmatic responses (LAR) 2 weeks before and 3 weeks after a single intradermal injection of SRL172 or placebo. Before and after treatment, serum immunoglobulin (Ig)E levels and in vitro production of interleukin (IL)-5 by peripheral blood lymphocytes were studied. Neither treatment affected the EAR. SRL172 caused a mean 34% reduction of the area under the curve of the forced expiratory volume in one second (FEV1) changes during the LAR, which failed to reach conventional statistical significance when compared with placebo. SRL172 also caused a mean 25% decrease in the maximum fall in FEV1 during LAR, but this was not significantly different from placebo. SRL172 caused a reduction in serum IgE and IL-5 synthesis in vitro 3 weeks post-treatment (p = 0.07). This study shows a trend toward significance for the effects of heat-killed Mycobacterium vaccae (SRL172) on allergen-induced airway responses. Further clinical trials, involving multiple dosing, are needed.     

Adenosine receptor subtypes in airways responses of sensitized guinea-pigs to inhaled ovalbumin

Endogenous adenosine is released in asthmatic patients’ lungs by inhaled allergen, however, its exact role in asthmatic responses or the receptors mediating these responses has not been determined. Our hypothesis was that adenosine released during allergen challenge contributes to the airways responses to inhaled allergen. The effects of selective antagonists of the four adenosine receptor subtypes were investigated on the airways responses of sensitized guinea-pigs to inhaled ovalbumin to ascertain the role of adenosine in these allergen responses, and compared with a corticosteroid, dexamethasone.Early (EAR) and late asthmatic responses (LAR) to inhaled ovalbumin (10 μg/ml) of sensitized, conscious guinea-pigs were recorded by whole body plethysmography following administration of selective adenosine receptor antagonists. Airway reactivity to inhaled histamine (1 mM) and inflammatory cell influx in bronchoalveolar lavage fluid were also determined 24 h after ovalbumin challenge.ZM241385 (A_2A receptor antagonist) did not affect these responses, whereas DPCPX (A₁ receptor antagonist) exerted a small inhibition only of the LAR. MRS1706 (A_2B receptor antagonist) inhibited the airways hyperreactivity and cellular influx and enhanced the EAR. MRS1220 (A₃ receptor antagonist) inhibited the airways hyperreactivity and cellular influx without affecting EAR and LAR. Dexamethasone inhibited the ovalbumin-induced late asthmatic responses, airways hyperreactivity and cellular influx.The blockade of airway hyperreactivity and inflammatory cell influx by A_2B and A₃ receptor antagonists suggests that endogenous adenosine is released by inhaled allergen and these responses are mediated via A_2B and A₃ receptors in guinea-pigs. The adenosine released by allergen inhalation does not, however, appear to be involved in the EAR, but it may contribute to the LAR via A₁ receptors.     

The inhibitory effect of nebulized albuterol on the early and late asthmatic reactions and increase in airway responsiveness provoked by inhaled allergen in asthma

It is widely held that inhaled beta 2-adrenoceptor agonists inhibit the early asthmatic response (EAR) but not the late response (LAR) or attendant increase in bronchial responsiveness. In this study of 10 atopic asthmatic subjects, we have investigated the effects of a high dose of nebulized albuterol (2.5 mg) on the allergen-provoked EAR, LAR, and increase in histamine responsiveness. In a randomized blinded fashion, study subjects inhaled the following combinations: albuterol followed 10 min later by allergen, placebo followed by allergen, albuterol followed by saline (albuterol, placebo, and control study periods, respectively). Airway caliber was measured as FEV1 and followed at regular intervals for 7.5 h postallergen. Bronchial responsiveness to histamine was measured and recorded as the PC20 value before and at 1.5, 3.5, 5.5, and 7.5 h after allergen or control challenge. During the placebo study period, allergen challenge caused mean 29.6 +/- 6.4 and 24.4 +/- 6.4% falls in FEV1 at 20 min and 7.5 h, respectively (both p less than 0.05), and a progressive decrease in PC20 amounting to a geometric mean of 1.9 doubling dilutions at 7.5 h (p less than 0.05). Albuterol followed by allergen resulted in a 13.1 +/- 2.2% increase in FEV1 prior to allergen followed by abolition of the EAR and inhibition of the LAR with only a 9.2 +/- 3.5% fall in FEV1 at 7.5 h, significantly different from that of placebo at 7.5 h (p = 0.048). Similarly, PC20 histamine fell by only 0.64 doubling dilutions at 7.5 h, not significantly different from baseline values but different from placebo values (p = 0.03).(ABSTRACT TRUNCATED AT 250 WORDS)     

Natural exposure to pollen reduces the threshold but does not change the pattern of response to the allergen in allergic subjects

It is known that exposure to seasonal allergen in sensitized asthmatics increases non-specific bronchial responsiveness, but it is controversial if exposure to seasonal allergen influences the presence and the severity of the late asthmatic response (LAR) to allergen. Fifteen asthmatic subjects sensitized to grass pollen performed a specific bronchial provocative test (sBPT) with Phleum pratensis extract before and during the pollen season. Changes of methacholine were also assessed. Allergen PD20FEV1 significantly decreased during the pollen season with respect to outside (allergen PD20FEV1, geometric mean: 0.10 vs. 0.23 biological units; P < 0.05), but the pattern of specific airway response did not change. Particularly, a consistent LAR was observed in three subjects outside the pollen season and in two subjects during the pollen season. Seven subjects with isolated early asthmatic response (EAR) outside the season did not show LAR after allergen inhalation during the pollen season. However, four of five subjects with slight LAR outside the pollen season (deltaFEV1% between 15 and 20%) lost LAR during season. Methacholine sensitivity increased slightly but significantly from outside to during the pollen season. This increase was greater in subjects with LAR outside the pollen season. The natural exposure to pollen induces an increase in bronchial sensitivity to allergen in sensitized subjects, but it does not induce LAR in subjects without LAR outside the pollen season.     

The effect of cromolyn sodium and albuterol on early and late phase bronchoconstriction and airway leukocyte infiltration after allergen challenge of nonanesthetized guinea pigs

We describe the effects of the antiallergic drug cromolyn sodium and the beta 2-selective adrenoceptor agonist albuterol against early and late phase changes in specific airways conductance (sGaw) and leukocyte infiltration into the airways after allergen challenge of nonanesthetized guinea pigs. Inhalation of ovalbumin by sensitized guinea pigs induced three phases of airways obstruction: an early asthmatic response (EAR) peaking at 2 h, a late response (LAR) peaking at 17 h, and a further late response (LLAR) being observed at 72 h. The LAR was accompanied by a 13-fold rise in neutrophils and a four-fold rise in eosinophils recovered by bronchoalveolar lavage (BAL) at 17 h. By 72 h, the BAL content of neutrophils had returned to near normal, whereas eosinophil numbers had risen to 6.7-fold above baseline. Inhalation of an aerosolized solution of cromolyn, 10 mg/ml, 15 min before challenge inhibited both the EAR and LAR and the influx of neutrophils into the airways at 17 h but had no effect on eosinophil accumulation. Inhalation of cromolyn at 6 h, i.e., after the completion of the EAR, inhibited the LAR, the LLAR, and the rise in eosinophils at 72 h but did not reduce the influx of neutrophils at 17 h. Administration of cromolyn at both 15 min before and 6 h after challenge inhibited all changes in sGaw and reduced the accumulation of neutrophils at 17 h and the influx of eosinophils at 72 h. In contrast, inhalation of albuterol, 0.1 mg/ml, 15 min before allergen provocation blocked the EAR and the rise in BAL neutrophils at 17 h but did not inhibit the LAR. Inhalation of albuterol at 6 h partially reversed the LAR but had no effect on either the LLAR or cellular changes. Given at both times, albuterol inhibited the EAR and neutrophil accumulation at 17 h and partially reversed the LAR but produced no other effects.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effect of an increase in inhaled allergen dose after rimiterol hydrobromide on the occurrence and magnitude of the late asthmatic response and the associated change in nonspecific bronchial responsiveness

We have used a short-acting beta 2-adrenoceptor agonist, rimiterol hydrobromide, to allow a larger dose of allergen to be administered to previous single "early allergen responders" to investigate if an increased dose of allergen could induce a late asthmatic response (LAR) and whether this would influence the subsequent level of allergen-acquired nonspecific bronchial hyperresponsiveness. Pretreatment with inhaled rimiterol hydrobromide 400 microgram enabled an increase in allergen dose inhaled by a geometric mean of 8.9-fold (range, 2 to 29.1) in eight atopic subjects with mild asthma who initially were classified as single early responders with a maximal fall in FEV 3 to 8 h after allergen challenge (Lmax) of less than 15% from baseline value. The magnitude of the early asthmatic response was similar to that obtained on the control day when allergen challenge was performed in the absence of rimiterol hydrobromide. Five subjects were converted to dual allergen responders with Lmax of greater than 15% from premedication baseline value. For the whole group, there was a significant increase in the magnitude of LAR whether calculated as Lmax (p less than 0.05) or as area under the FEV1 time response curve between 3 and 8 h postchallenge (p less than 0.01). The provocation concentrations of methacholine causing a 20% fall in FEV1 (PC20) at 8 h postchallenge were significantly reduced on both days when compared with the corresponding prechallenge values (p less than 0.05 on control day, p less than 0.01 on rimiterol day). However, despite the increase in the magnitude of LAR on the rimiterol day, the reduction in postchallenge PC20 did not differ significantly from that occurring on the control day.(ABSTRACT TRUNCATED AT 250 WORDS)     

Minimal tolerance to the bronchoprotective effect of inhaled salmeterol/fluticasone combination on allergene challenge

In order to assess whether the administration of salmeterol/fluticasone propionate combination (50/250 mcg by Diskus) for 1 week induces tolerance to the bronchoprotective effect of salmeterol on allergen challenge, a single-blind, cross-over study was carried out. We studied nine subjects (eight men and one woman; mean age+/-SD: 31.3+/-11.0 yr) with mild intermittent allergic asthma, never treated with regular beta2-agonists or inhaled corticosteroids. In a previous allergen challenge all subjects had shown a positive early airway response (EAR) to allergen. They underwent allergen challenge after 1-week treatment with placebo and a single dose of placebo immediately before allergen challenge (T1), or 1-week treatment with placebo and a single dose of salmeterol/fluticasone immediately before allergen challenge (T2), or 1-week treatment with salmeterol/fluticasone combination bid and a single dose of salmeterol/fluticasone immediately before allergen challenge (T3). EAR was evaluated both as maximum decrease in FEV1 (MaxDeltaFEV1 %) after allergen challenge and as area under FEV1 -time curve. MaxDeltaFEV1 % during allergen challenge protected by placebo (T1) was significantly greater than MaxDeltaFEV1 % during allergen challenges protected by single dose of salmeterol/fluticasone (T2) and by salmeterol/fluticasone 1-week treatment (T3). No difference was found in MaxDeltaFEV1 % between T2 and T3. The same results were observed also after computing the area under the curve for each challenge. When individually considered, all subjects were protected against EAR (protection index > or = 80%) at T2, while at 3 seven out of nine subjects were still protected against EAR. In conclusion, the simultaneous administration of salmeterol and fluticasone in the same device prevents in almost 80% of examined subjects the development of tolerance to the protective effect of salmeterol on allergen challenge. This observation may contribute to explain the positive interaction between inhaled beta2-agonists and corticosteroids in the long-term treatment of asthma.     

Effect of whole-body x-irradiation on antigen-induced airway response in sensitized guinea pigs.

The objectives of this study were to test the hypothesis that x-irradiation inhibits the late asthmatic response (LAR) without influencing the early asthmatic response (EAR) and to examine the mechanism of the inhibitory effect. Twenty sensitized guinea pigs were irradiated at a dose of 8 Gy. The next day, one-half of the animals were injected intravenously with spleen cells (2 x 10(8)) collected from unirradiated sensitized guinea pigs, whilst the other half were injected with vehicle only. Ten additional unirradiated sensitized guinea pigs also received vehicle only. Antigen inhalation challenge took place two days later. Pulmonary resistance was measured for 6 h after antigen exposure, and bronchoalveolar lavage and lung fixation were then undertaken. The area under the percentage pulmonary resistance curve 2-6 h after allergen inhalation was used for analysis of the LAR, while the maximal percentage change in pulmonary resistance was used for analysis of the EAR. Irradiation abolished the LAR (364.4+/-49.4 versus 62.8+/-10.4) without inhibiting the EAR (229.3+/-27.2 versus 278.7+/-40.2) and significantly inhibited the accumulation of eosinophils and lymphocytes in the airways. Transfer of spleen cells restored the LAR (334.4+/-66.8) and the recruitment of cells to the levels seen in unirradiated sensitized guinea pigs. In addition, transfer of only CD4+ T-lymphocytes separated from the spleen cells restored the LAR (439.4+/-62.1) and the cell infiltration into the airways. These inhibitory effects of x-irradiation were due to decreases in numbers of CD4+ T-lymphocytes.     

The relationship between airway responsiveness measured before and after the allergen-induced late asthmatic response.

Single blind allergen (Ag) and saline solution bronchial challenges were performed on two successive study days in ten asthmatic subjects. Histamine challenges were performed before, at approximately 2 h (or after resolution of the immediate bronchial response [IR]), and 24 h after saline solution or Ag inhalation. Specific airway conductance (SGaw) was measured after delivery of challenge agents until a 50 percent fall in SGaw was observed. The SGaw was monitored over 8 h for immediate and late asthmatic responses (LAR). Results were expressed as provocative concentrations eliciting a 50 percent decrease in SGaw (SGawPC50HIS). No significant changes from baseline SGaw or SGawPC50HIS were demonstrated after saline solution. Eight subjects (dual reactors) exhibited both an IR and LAR after Ag and two had isolated IRs. Of the eight dual reactors, five had greater than 50 percent decreases in SGawPC50HIS immediately after resolution of the IR and six exhibited such decrements 24 h after Ag provocation. Mean baseline SGawPC50HIS (N = 10) on the Ag challenge day was 3.2 +/- 4.59 mg/ml and decreased to 0.92 +/- 4.56 mg/ml at 102 to 187 minutes after Ag (p = 0.0009) and was significantly decreased from baseline at 1.47 +/- 3.8 mg/ml 24 h after Ag (p = 0.0004). One of the two patients with isolated IR also showed an early onset increase in airway responsiveness (EOR). There was a significant correlation between the percentage of fall from baseline in SGawPC50HIS immediately after the IR and that at 24 h after Ag (r = 0.811, p = 0.005). There was no significant correlation between the decrease in SGawPC50HIS after the IR and the magnitude of the LAR. These data suggest that (1) the early events occurring prior to the LAR may determine changes in airway responsiveness observed at 24 h after Ag challenge, and (2) the EAR to histamine is not exclusively associated with the LAR.     

The effects of multiple dosing with zileuton on antigen-induced responses in sheep

In a previous study, a single dose of zileuton (10 mg/kg, po) given 2 h before antigen challenge, had a minimal effect on the antigen-induced early airway response (EAR), although it was effective in blocking the late airway response (LAR). Because our previous data indicated that 5-lipoxygenase (5-LO) products contribute to the severity of the antigen-induced EAR in these animals, we hypothesized that the lack of effect of zileuton on the EAR may have had to do with inadequate tissue levels. Therefore, in this study, we determined if multiple dosing with zileuton, which theoretically could improve tissue levels, would provide protection against the antigen-induced EAR as well as the LAR. Each sheep was used in each of the three trials (> or = 15 days apart), the order of which was randomized. For trial 1, the sheep were treated with zileuton (10 mg/kg in 0.1% methylcellulose, p.o.) once a day for 4 days; for trials 2, the sheep were treated with zileuton (10 mg/kg, p.o.) for 2 days; and, for trial 3, the animals were treated with vehicle (0.1% methylcellulose) for 4 days as in trial 1. In all trials, antigen challenge followed 1 h after the last treatment. In the placebo trial, antigen challenge resulted in characteristic EAR (407 +/- 102%, increase over baseline) and LAR (335 +/- 75%, increase over baseline). The antigen-induced effects were completely blocked by the 4-day treatment (EAR = 24 +/- 3%; LAR = 17 +/- 3%, P < 0.05 vs. placebo). In the 2-day trial, the immediate increase in R1, after antigen challenge was only partially blocked (EAR = 163 +/- 16%, P < 0.10 vs. placebo and P < 0.05 vs. 4-day trial), but the late response was completely blocked (24 +/- 3%). The protection against the EAR obtained with the 4-day treatment was significantly better (P < 0.05) than that obtained with the 2-day treatment. The results of this study show that multiple dosing with the 5-LO inhibitor, zileuton, provides protection against the antigen-induced EAR as well as LAR. The effect on the EAR is dependent on the treatment time, with dosing 4 days before antigen challenge providing a more significant effect than either dosing 2 days before challenge (this study) or on the same day as antigen challenge as was seen by us previously. This effect may be related to increased tissue levels of the drug.     

Reproducibility of early and late asthmatic responses to allergen challenge in a large group of asthmatics

The specific bronchial provocative test (sBPT) coupled with allergen is used to investigate asthma. Very few studies have examined the reproducibility of responses to allergen challenge. The aim of this study was to measure the reproducibility of PD20FEV1 allergen and late asthmatic response (LAR) in 53 asthmatics and to relate the reproducibility to the time interval between two allergen challenges. Fifty-three atopic asthmatics performed two allergen challenges not less than 2 and not more than 26 weeks apart. Randomly, 19 subjects were assigned to a short-interval group (14-35 days between the two tests) and 34 to a long-interval group (40-180 days). In each challenge, the PD20FEV1 was sought for and the maximum % fall in FEV1 from 3 to 7 h after the allergen challenge was evaluated as a measurement of magnitude of the LAR. High intraclass correlation coefficients (R(I)) were found for both PD20FEV1 (R(I) = 0.78) and LAR (R(I) = 0.77) in all subjects. PD20FEV1 allergen showed a high R(I) in the long-interval group (R(I) = 0.80), but a low R(I) in the short-interval group (R(I) = 0.63). In contrast LAR showed a lower R(I) in the long-interval group (R(I) = 0.68) than in the short-interval group (R(I) = 0.77). Moreover, the R(I) for PD20FEV1 was particularly low in subjects with a dual pattern to the allergen challenge and a short interval between the two allergen challenges. Our study confirmed that asthmatic responses induced by allergen challenge have a good reproducibility. Moreover, we have demonstrated that the interval between two allergen challenges can determine a change in reproducibility in asthmatic responses induced by allergen challenge.     

Montelukast as add-on therapy to beta-agonists and late airway response.

The present study investigated whether single-dose oral leukotriene receptor antagonists as add-on therapy to short-acting beta-agonists, immediately after allergen challenge, block the late-phase airway response. In total, 35 mild asthmatics (mean age 24 yrs, 19 males) sensitised for house dust mites underwent two courses of bronchial allergen challenge. After the early allergic response (EAR), subjects received salbutamol once and were randomly assigned to either 10 mg of montelukast or placebo (double-blind crossover). To identify a late allergic response, forced expiratory volume in one second (FEV(1)) was monitored over the following 8 h. Baseline exhaled nitric oxide (NO) was determined ahead of each allergen challenge. Baseline NO levels differed significantly depending on the reaction to allergen challenge. In total, 12 subjects showed no significant response, 11 only showed an EAR, and 12 had a dual response and underwent further analysis. The area under the FEV(1) time-response curve 3-8 h after bronchial allergen challenge was -0.77+/-1.68 from the pre-challenge values on montelukast compared with -2.47+/-1.32 on placebo. The baseline exhaled NO fraction of subjects without an EAR was significantly lower than of those presenting a dual response. The results of the present study demonstrate that single-dose leukotriene receptor antagonists given orally right after the early allergic response can significantly inhibit the late allergic response after bronchial allergen challenge.     

Tolerance to the protective effect of salmeterol in mild untreated asthmatics

The aim of this study was to assess the distribution of the occurrence of tolerance to the protective effect of salmeterol on allergen challenge in a large sample of asthmatic subjects. We investigated 53 subjects (45 male and eight female), mean age 24+/-8.2 years, with mild intermittent asthma, in stable phase of the disease, never previously treated with regular beta2-agonists. All subjects with a previous positive early airway response (EAR) to a screening allergen challenge underwent, in double blind randomized, cross-over manner, three further allergen challenges: after placebo (T0), after a single dose (50 microg) of inhaled salmeterol (T1), and after regular treatment with inhaled salmeterol (50 microg bid) for 1 week (T2). All subjects showed an EAR after placebo treatment (T0), and were completely protected against EAR by the single dose of salmeterol (T1). After 1-week regular treatment with salmeterol (T2). 24 out of 53 subjects (45%) were still protected, whereas 29 subjects (55%) showed a significant EAR. The distribution of the response to allergen challenge, which was quite homogeneous at T0 and T1, showed considerable heterogeneity at T2. Tolerance to the protective effect of salmeterol on allergen challenge can be observed in a large group of previously untreated mild asthmatic subjects. This phenomenon is heterogeneously distributed, with some subjects still showing a complete protection similar to that obtained after a single dose of salmeterol and others showing a response similar to that obtained after placebo. The reason of this heterogeneity needs to be elucidated.