The effect of an inhaled leukotriene antagonist, L-648,051, on early and late asthmatic reactions and subsequent increase in airway responsiveness in man

Methacholine-Induced Cough in the Absence of Asthma: Insights From Impulse Oscillometry

Introduction

The pathophysiologic differences between methacholine-induced cough but normal airway sensitivity (COUGH) and healthy individuals (CONTROL) are incompletely understood and may be due to differences in the bronchodilating effect of deep inspirations (DIs). The purpose of this study is to compare the bronchodilating effect of DIs in individuals with classic asthma (CA), cough variant asthma (CVA), and COUGH with CONTROL and to assess impulse oscillometry (IOS) measures as predictors of the bronchodilating effect of DIs.

Methods

A total of 43 adults [18 female; 44.8 ± 12.3 years (mean ± SD); n = 11 CA, n = 10 CVA, n = 7 COUGH, n = 15 CONTROL] underwent modified high-dose methacholine challenge, with IOS and partial/maximal expiratory flow volume (PEFV/MEFV) maneuvers (used to calculate DI Index) to a maximum change (Δ) in FEV₁ of 50% from baseline (MAX). Cough count and dyspnea were measured at each dose. The relation between IOS parameters and DI Index was assessed at baseline and MAX using multivariable linear regression analysis.

Results

Cough frequency, dyspnea intensity, and baseline peripheral resistance (R5-R20) were significantly greater in COUGH compared with CONTROL (p = 0.006, p = 0.029, and p = 0.035, respectively). At MAX, the DI Index was significantly lower in COUGH (0.01 ± 0.36) compared with CA (0.67 ± 0.97, p = 0.008), CVA (0.51 ± 0.73, p = 0.012), and CONTROL (0.68 ± 0.45, p = 0.005). Fres and R5-R20 were independent IOS predictors of the DI Index.

Conclusion

The bronchodilating effect is impaired in COUGH and preserved in mild CA, CVA, and CONTROL. Increased peripheral airway resistance and decreased resonant frequency are associated with a decreased DI Index. COUGH is a clinical phenotype distinct from healthy normals and asthma.

Bronchodilating effect of deep inspirations in asthma and chronic cough

The pathophysiologic processes distinguishing classic asthma (CA), cough-variant asthma (CVA), and methacholine (MCh)-induced cough but normal airway sensitivity (COUGH) are inadequately understood and may be a result of differences in the ability to bronchodilate following a deep inspiration (DI). The purpose of this study was to compare the bronchodilating effect of DIs in individuals with CA, CVA, and COUGH using high-dose MCh. Individuals aged 18-65 yr with CA or suspected CVA completed high-dose MCh testing to a maximum change in forced expiratory volume in 1 s (FEV1) of 50% from baseline (MAX). Impulse oscillometry (IOS) measurements and partial and maximal-flow volume curves (used to calculate a DI index) were recorded at baseline and at each dose of MCh. Body plethysmography was performed at baseline and MAX. Twenty-eight subjects [25 women, 39.8 ± 11.9 yr (means ± SD)] were studied (n = 11 CA, n = 10 CVA, and n = 7 COUGH). At MAX, the percent change in FEV1 was greater in subjects with CA compared with those with CVA (P < 0.001) and COUGH (P < 0.001), and the percent change in forced vital capacity was greater in those with CA than with COUGH (P = 0.017). Subjects with CA and CVA developed dynamic hyperinflation and gas trapping. In subjects with CA and CVA, all IOS parameters were significantly increased from baseline to MAX, except for central respiratory resistance (R20). In individuals with COUGH, total respiratory resistance, R20, and resonant frequency were significantly increased from baseline. At MAX, the DI index was positive in all groups, suggesting preserved bronchodilation (CA, 0.67 ± 0.97; CVA, 0.51 ± 0.73; COUGH, 0.01 ± 0.36; P = 0.211). We conclude that the bronchodilating effect of DIs is preserved in individuals with CA, CVA, and borderline with COUGH; however, hyperinflation and gas trapping are avoided in subjects with COUGH alone.

The dynamic face of respiratory research: understanding the effect of airway disease on a lung in constant motion

The lungs are in a constant state of motion. The dynamic nature of tidal breathing, whereby cycles of pressure changes across the lungs cause the chest wall, lung tissue and airways to repeatedly expand and contract, ventilates the lung tissue and allows respiration to occur. However, these regular cycles of tidal inspirations and expirations are punctuated by breaths of differing volumes, most particularly periodic deep inspirations. In normal, healthy subjects, these deep inspirations have a dual effect in reducing airway responsiveness. Firstly, deep inspirations taken under baseline conditions protect the airways against subsequent bronchoconstriction, termed DI bronchoprotection. Secondly, deep inspirations are able to dramatically reverse bronchoconstriction. The ability for deep inspirations to reverse bronchoconstriction appears to be due to both the ability to dilate the airways with a full inspiration to total lung capacity (TLC) and the rate at which the airways re-narrow once tidal breathing is resumed. Deep inspiration reversal is reduced in subjects with asthma and is due both to a reduced ability to dilate the airways as well as an increase in the rate of re-narrowing. On the other hand, DI bronchoprotection is completely absent in asthma. Although the mechanisms behind these abnormalities remain unclear, the inability for deep inspirations to both protect against and fully reverse bronchoconstriction in patients with asthma appears critical in the development of airway hyperresponsiveness. As such, determining the pathophysiology responsible for the malfunction of deep inspirations in asthma remains critical to understanding the disease and is likely to pave the way for novel therapeutic targets.

In vitro effects of flunisolide on MMP-9, TIMP-1, fibronectin, TGF-beta1 release and apoptosis in sputum cells freshly isolated from mild to moderate asthmatics

BACKGROUND

Corticosteroids play an important role in inflammation and remodelling of airways and are considered an important therapeutic target in asthma. Inflammation in asthma is characterized by a dysregulation of eosinophil apoptosis and of markers of airways remodelling. We evaluated the ability of flunisolide to inhibit in vitro the release of metalloproteinases-9 (MMP-9), tissue inhibitor metalloproteinases-1 (TIMP-1), transforming growth factor (TGF-beta) and fibronectin by sputum cells (SC) as well as to induce sputum eosinophil apoptosis.

METHODS

The SC, isolated from induced sputum samples of 12 mild-to-moderate asthmatics, were cultured for 24 h in the presence or absence of flunisolide (1, 10 and 100 microM). The release of mediators was assessed by enzyme-linked immunosorbent assay (ELISA) whereas apoptosis was studied by TUNEL technique.

RESULTS

Flunisolide (10 microM) significantly reduced MMP-9 and TIMP-1 (P = 0.0011 and P < 0.0001 respectively) and increased MMP-9/TIMP-1 molar ratio (P = 0.004). In addition, flunisolide decreased TGF-beta and fibronectin release by SC (P = 0.006; and P < 0.0001 respectively) and increased eosinophil apoptosis (P < 0.001).

CONCLUSIONS

These results demonstrate that flunisolide may play an important role in the inhibition of airway inflammation and remodelling, by promoting the resolution of eosinophilic inflammation and by inhibiting the release of MMP-9, TIMP-1, TGF-beta and fibronectin.

Absence of deep inspiration-induced bronchoprotection against inhaled allergen

Deep inspiration-induced bronchoprotection appears to be a major mechanism through which airway obstruction by spasmogens is avoided. Loss of bronchoprotection is associated with airway hyper-responsiveness. Individuals with allergic rhinitis and no airway hyperresponsiveness develop obstruction after allergen inhalation. To test the hypothesis that deep inspiration-induced bronchoprotection is not active against allergic reactions, we performed four single-dose bronchial challenges, two with methacholine and two with allergen, on 10 subjects with allergic rhinitis. Without deep inspirations, the methacholine-induced reduction in FEV1 from baseline was 36.9 +/- 3.6% (mean +/- SEM); this was attenuated to 15.0 +/- 2.0 when five deep inspirations preceded methacholine inhalation (p = 0.0001). When allergen was inhaled, the reduction in FEV1 was 24.7 +/- 2.9% and 28.8 +/- 6.4% without and with deep inspirations, respectively. We conclude that bronchoprotection by deep inspirations is absent against allergic reactions. Understanding the cause of this phenomenon may shed light into the pathogenesis of airway hyperresponsiveness in allergic asthma.

Comparison of incremental and bolus dose inhaled allergen challenge in asthmatic patients

BACKGROUND

Attenuation of airway responses to inhaled allergen is increasingly used to evaluate anti-asthma drugs. Many studies use different allergen challenge methods and the presence of the late asthmatic response can be identified by a screening challenge with inhalation of incremental doses of allergen. Once defined, subsequent challenges are often administered as a constant dose based on the dose from the screening challenge. Previously, constant dose challenges have been employed but never validated.

OBJECTIVE

A comparative study of two methods of delivering inhaled allergen by evaluating the responses of an incremental dose allergen challenge and the same cumulative dose administered as a bolus over a single inhalation.

METHODS

Thirty-five male patients with mild allergic asthma underwent incremental dose challenge followed 3-6 weeks later by a bolus dose challenge. Bronchoconstrictor responses were expressed as the maximum percentage fall in FEV1 from baseline during the early (0-2 h) and late (4-10 h) asthmatic responses and area under the percentage change in FEV1-time curve (AUC).

RESULTS

There were no significant differences between the challenges. The mean +/- SEM fall in FEV1 following incremental and bolus dose challenge was 33.1 +/- 1.8% and 29.9 +/- 2.2% during the early response, and 36.9 +/- 2.4% and 34.0 +/- 3.1% during the late response, respectively. The mean +/- SEM AUC following incremental and bolus dose challenge was 35 +/- 3 and 33 +/- 3 Delta%FEV1/h for the AUC0-2 h, 147 +/- 12 and 139 +/- 16 Delta%FEV1/h for the AUC4-10 h, and 204 +/- 14 and 190 +/- 19 Delta%FEV1/h for the AUC0-10 h, respectively.

CONCLUSION

Bolus dose allergen challenge is a safe method to administer inhaled allergen in clinical trials with a valid response when compared with incremental dose allergen challenge.

The effect of Cys LT1 receptor blockade on airway responses to allergen

STUDY OBJECTIVE

To evaluate the effect of a potent experimental leukotriene receptor antagonist, MK-571, on airway responses to inhaled allergen.

DESIGN

Randomized, double-blind, placebo-controlled, crossover trial.

SETTING

Clinical research center.

SUBJECTS

Eight male volunteers with allergic asthma.

INTERVENTIONS

An intravenous loading dose was followed by an 8-hour infusion of MK-571 or placebo, with a 7- to 14-day washout between treatments. Allergen challenge was performed after the loading dose and a histamine challenge was performed before and 24 hours after allergen.

MEASUREMENTS AND MAIN RESULTS

Forced expiratory volume in 1 second was measured serially. MK-571 provided about 50% protection during maximum early and late responses compared with placebo (p=0.005), but airway obstruction persisted 8-24 hours after allergen on both treatment days. Airway responsiveness to histamine was not significantly attenuated at 24 hours.

CONCLUSION

Blocking Cys LT1 receptors for 8 hours attenuated the early and late responses but did not interrupt the cascade of events leading to subsequent allergen-induced airway obstruction and hyperreactivity.

How do we monitor asthma control?

The present consensus on asthma management includes avoidance of triggers, education, regular follow-up, and an action plan that relies on symptoms and lung function measurements for the monitoring of disease severity. Inclusion of objective measurements for monitoring seems to be important because patients and physicians may not always recognize asthma symptoms or their severity. However, the additional value of monitoring peak flow and symptoms in guiding asthma therapy has not been well established. Furthermore, it can be questioned whether a treatment strategy which is solely based on optimizing symptoms and lung function leads to optimal control of asthma in each individual patient, since airway hyperresponsiveness (AHR) and airways inflammation may persist. The chronicity of such abnormalities may lead to airways remodelling, thereby worsening the long-term outcome of asthma. It has been shown that AHR provides prognostic information on asthma control, because it can serve as a valuable noninvasive surrogate marker of airways inflammation when added to the guides of asthma therapy. A limited increase in dose of inhaled steroids, instead of applying an increased dose indiscriminately, can be successfully tailored to the needs of the individual patient based on the degree of AHR. Such a strategy leads to both a better clinical outcome and a better histologic outcome. The present worldwide effort is to find alternative markers of airways inflammation in asthma that can be easily implemented in routine practice. In the near future, longitudinal studies will determine which parameter is potentially most useful in guiding asthma management.

Leukotrienes, leukotriene receptor antagonists and leukotriene synthesis inhibitors in asthma: an update. Part II: clinical studies with leukotriene receptor antagonists and leukotriene synthesis inhibitors in asthma

The demonstration that leukotrienes, mainly cysteinyl leukotrienes, have biological properties relevant to the pathogenesis of asthma has stimulated the development of many therapeutic compounds to block these deleterious effects. Two main classes of leukotriene modulators have been developed: CysLT1 receptor antagonists and leukotriene synthesis inhibitors. This article reviews the pharmacodynamics, the effects on baseline airway function, the protective effects in airway challenges as well as the results in chronic asthma of the different leukotriene modulators. In addition, the complementary anti-inflammatory effect of leukotriene modulators to that of corticosteroids and H1-histamine receptor antagonists is reviewed. Finally, a concise overview of the clinical responsiveness to this new class of drug, the safety and the drug interactions as well as the place in the strategies of treatment for asthmatic patients of the leukotriene modulators is also provided.

Comparative effects of a glucocorticosteroid, theophylline and the peptido-leukotriene-antagonist CGP 45715A on antigen-induced early and late phase airway response and inflammatory cell influx in sensitised guinea pigs

A novel model of allergic early and late-phase reaction in the airways of conscious guinea pigs was developed and the effect of established and novel antiasthmatic drugs on peak of immediate response, late phase response and associated inflammatory cell influx investigated. Guinea pigs were sensitised twice in adjuvant (50 mg/kg silica + 0.1 ml/kg Bordetella pertussis). Under cover of 10 mg/kg i.p. mepyramine guinea pigs exhibited still a pronounced immediate reaction. During a screening phase about 75% of guinea pigs demonstrated a late phase reaction of decrease of tidal volume between 4-10 h after ovalbumin inhalation. In a cross over study theophylline at 50 mg/kg p.o. (-1 h before ovalbumin) tended to attenuate not only the peak of the immediate reaction by about 69% (P>0.05, n = 12), but inhibited the airway late phase response significantly (P<0.05, 5-10 h, n = 12). Methylprednisolone (40 mg/kg p.o. 1 h before ovalbumin) did not inhibit the immediate response, but the late phase response. In contrast the cysteinyl-leukotriene antagonist CGP 45715A (Iralukast; 30 mg/kg p.o. 2 h before ovalbumin) neither interfered with the peak of the immediate, nor with the late phase response. When bronchoalveolar lavage by orotracheal route was performed 24 h after ovalbumin inhalation, total cell count, eosinophils, neutrophils, macrophages and lymphocytes were significantly increased in ovalbumin-controls compared to sham (n = 5; P<0.05). Methylprednisolone reduced significantly the antigen-induced increase of total cell count and eosinophil number. Neither theophylline nor the cysteinyl-leukotriene receptor antagonist attenuated the antigen-associated cell influx. The results do not provide evidence for a major role of cysteinyl-leukotrienes in the late phase response and inflammatory cell influx in this model.

Repeated allergen challenge as a new research model for studying allergic reactions

Repeated allergen challenge might be a more relevant model for studying symptomatic disease, because it gives more information on the patient's handling of chronic allergen exposure. Thus, this experimental model has more resemblance to the situation of natural allergen exposure, and the allergen load can be standardized. However, the response to repeated allergen challenge in individual patients can show a large variation, that is from a strongly enhanced response to complete diminution of the response. Successful allergen immunotherapy can change the response pattern of repeated allergen challenge in the skin into down-regulation of the late reaction. Chronic or repeated allergen exposure may result in an enhanced allergen-specific allergic response, involving allergen-specific T-cell activation. Different subsets of T cells can exert either activating or suppressive effects on inflammatory cells involved in subsequent allergic reactions. CD8+ T cells might exert suppressive effects, because they seem to be associated with a subsequent down-regulation of the late skin reaction after repeated allergen challenge (Fig. 4). Further studies are needed to compare the responses to repeated allergen challenge with the response to natural seasonal allergen exposure in the same patients and to explore possible underlying mechanisms using, for example, nasal biopsies.

Pharmacological inhibition of leukotriene actions

Leukotrienes represent a group of lipid mediators that play a very important role in a wide variety of pathological conditions. The presence of leukotrienes in inflammatory sites has been extensively documented, and accordingly research efforts have been directed towards the development of drugs that interfere with the formation or effects of leukotrienes. Although clinical application of such drugs has been disappointing in the past, recent discoveries of more potent and selective drugs seem to be promising. This review attempts to highlight some of these exciting developments.

Allergen-induced changes in airway responsiveness are related to baseline airway responsiveness

In the literature, bronchial allergen challenge is usually reported to result in an increase in histamine-induced airway responsiveness (AR). The present study investigated the relation between baseline AR and allergen-induced changes in AR. The effect of allergen challenge on AR was investigated in 21 atopic asthmatic patients. Allergen challenge resulted in a significant decrease in PC20 histamine after 24 h. When the group was divided into three subgroups according to baseline PC20 histamine, a significant decrease in PC20 histamine was found only in patients with relatively high baseline PC20 histamine (groups 1 and 2). A significant inverse correlation was found between baseline PC20 and allergen-induced PC20 histamine. The effect of repeated allergen challenge on AR was studied in eight patients. The first allergen challenge resulted in a significant decrease in PC20 histamine; no further decrease in mean PC20 histamine was seen after the second allergen challenge. These results suggest that allergen-induced changes in AR occur mainly in patients with relatively high baseline PC20 values. Once an increase in AR is induced, further allergen challenge does not always result in further increase in AR.

Eicosanoids and asthma: an update

There have been significant advances in our understanding of the role of eicosanoids as mediators in inflammation since their discovery over 50 years ago. Our more recent understanding of asthma as an inflammatory disease has led to the appreciation of eicosanoids potentially being pivotal mediators in promoting some of the changes in asthma. Of particular importance are the cysteinyl LTs in producing bronchospasm and bronchial hyperresponsivenss, and PGE2 in modulating the bronchospastic and inflammatory response. Evidence from clinical studies suggests that other eicosanoids may also contribute, but their importance is secondary and their relative contributions vary between individuals. The development of new drugs based on our partial understanding of the role that eicosanoid mediators may play in asthma promises new approaches to the treatment of this common chronic inflammatory condition.

Stereoselective metabolism of the 5-lipoxygenase inhibitor A-78773

Based on the knowledge that glucuronidation was a major route of metabolism of the N-hydroxyurea class of 5-lipoxygenase inhibitors, a simple in vitro glucuronidation assay was established using liver microsomes from various species, including man. Compounds that were potent inhibitors of 5-LO and showed a reduced metabolic liability in vitro were then characterized more extensively in experimental animals. This prudent usage of in vitro glucuronidation proved to be highly efficient and was indispensable in the identification of A-78773, a potent new long-acting 5-LO inhibitor. Further studies with liver microsomes revealed that glucuronidation of A-78773 was stereoselective and that the R(+) enantiomer was considerably more resistant to conjugation than the S(-) stereoisomer. Pharmacokinetic studies in experimental animals and humans confirmed the greater metabolic stability of the R(+) enantiomer. A single 400-mg oral dose of A-78773 inhibited ex vivo leukotriene biosynthesis for more than 24 hours. Since 78% of the drug plasma AUC following A-78773 administration was accounted for by the R(+) enantiomer, it is reasonable to assume that the majority of the leukotriene inhibition caused by the racemate is attributable to the R(+) enantiomer, A-79175, particularly at the later times. The equivalent 5-lipoxygenase inhibitory potency coupled with the superior pharmacokinetic profile of the R(+) enantiomer, A79175, compared to the S(-) enantiomer, A-79176, indicate that the development of this compound may be preferable to the racemate A-78773.

Inhaled ICI 204,219 blocks antigen-induced bronchoconstriction in subjects with bronchial asthma

Three inhalation formulations of ICI 204,219 were compared for antagonism of antigen-induced bronchoconstriction in 16 subjects with asthma who demonstrated reproducible hypersensitivity to allergen during screening challenges. Each subject received a single 0.2-mg dose of each formulation and was challenged with ragweed 30 min after administration of ICI 204,219 until the forced expiratory volume in 1 s (FEV1) decreased by 20 percent or the maximum allergen concentration (100 micrograms/ml) was reached. The majority of subjects tolerated 100 micrograms/ml of allergen without a 20 percent decrease in FEV1. Inhalation formulations of ICI 204,219 successfully inhibited bronchoconstriction in subjects with reproducible sensitivity to ragweed challenges.

Leukotriene-receptor antagonists and 5-lipoxygenase inhibitors in asthma

OBJECTIVE

To familiarize readers with a potentially new class of compounds for treating asthma. Background information on leukotrienes is provided in addition to an in-depth review of pertinent clinical trials.

DATA SOURCES

Information was obtained from controlled clinical trials, abstracts, and review articles identified through a MEDLINE search of English-language articles.

STUDY SELECTION

Emphasis was placed on early clinical trials that showed some benefit with these compounds as well as more recent studies using newer agents that produced more promising results.

DATA EXTRACTION

Information regarding leukotriene biochemistry was extracted from basic science research and data from human studies were evaluated by the authors according to patient selection, study design, methodology, and therapeutic response.

DATA SYNTHESIS

Leukotrienes have a pathophysiologic role in asthma. Two distinct but pharmacologically similar classes of leukotriene inhibitors are currently being clinically evaluated. These are leukotriene receptor antagonists and 5-lipoxygenase inhibitors. Early clinical trials with these agents yielded unfavorable results primarily because of lack of drug potency and selectivity, poor patient tolerance, and possibly the route of administration. Subsequent studies with more potent and selective agents have further implicated leukotrienes as biochemical mediators in asthma and, consequently, have shown promising clinical outcomes with respect to pulmonary function testing and patient tolerance.

CONCLUSIONS

Advancements in the pathogenesis of asthma are beginning to define a role for the leukotrienes. Although more studies are needed to assess the efficacy of leukotriene inhibitors, recent clinical trials using leukotriene-receptor antagonists and 5-lipoxygenase inhibitors indicate a potential for the expansion of therapeutic regimens currently used in the treatment of asthma.

Oral leukotriene inhibitor (MK-886) blocks allergen-induced airway responses

To elucidate the role of leukotrienes (LT) in allergic asthma in humans the effect of MK-886, an LT biosynthesis inhibitor, was evaluated on antigen-induced early (EAR) and late (LAR) asthmatic reactions and bronchial responsiveness to histamine. Eight atopic men participated in a two-part, double-blind, placebo-controlled, crossover trial. MK-886 was administered in two oral doses of 500 mg and 250 mg, 1 h before and 2 h after allergen inhalation, respectively. Biochemical effects of MK-886 were evaluated by the inhibition of urinary LTE4 excretion and calcium ionophore-stimulated LTB4 biosynthesis in whole blood ex vivo. MK-886 significantly inhibited the EAR by 58.4% (AUC0-3 h) and the LAR by 43.6% (AUC3-7 h) when compared with placebo (p < 0.01). There was no difference in PC20 histamine 30 h post allergen challenge between MK-886 and placebo (0.33 and 0.27 doubling doses, p > 0.1). MK-886 inhibited calcium ionophore-stimulated LTB4 production in whole blood (54.2 +/- 25.6%) for up to 6 h post allergen challenge. LTE4 excretion in urine was inhibited by 51.5% during the EAR by as much as 80% during the LAR. This indicates that LT play a role in allergen-induced asthmatic reactions in humans in vivo and that LT synthesis inhibitors such as MK-886 should be further explored for the treatment of asthma.

Leukotrienes in bile during the early and the late airway responses after allergen challenge of sensitized rats

The Brown Norway rat produces high levels of IgE in response to active immunization and develops both early and late airway constrictor responses after subsequent allergen challenge. We have used this model of allergic asthma to investigate the temporal relationship between the in vivo synthesis of peptidoleukotrienes (peptido-LTs) and the late response. Brown Norway rats that had been sensitized by injection of ovalbumin 2 to 3 wk prior to the commencement of the experiment were subjected to bile duct cannulation and tracheal intubation. The rats were challenged 2 h later by intratracheal instillation of ovalbumin. Lung resistance was measured before and at frequent intervals after antigen challenge. Biliary peptido-LTs (LTC4, LTD4, LTE4, and N-acetyl-LTE4) were measured by a combination of high pressure liquid chromatography and radioimmunoassay in bile samples collected for a period of 1 h before instillation of ovalbumin, and between zero and 1 h, 1 and 4 h, 4 and 6 h, and 6 and 8 h, subsequently. All of the 10 rats subjected to antigen challenge developed early responses. Of these, six also developed late responses, whereas two died about 1 h after challenge. The levels of peptido-LTs excreted in bile between 4 and 8 h after antigen challenge (corresponding in time to the late responses) were about four times higher in the ovalbumin-instilled rats that developed late responses (n = 6) than in the ovalbumin-sensitized control rats that had been subjected to instillation of saline (n = 6; p < 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)

Reduced nonspecific bronchial reactivity and decreased airway response to antigen challenge in atopic asthmatic patients treated with the inhaled leukotriene D4 antagonist, L-648,051

We studied the effect of the inhaled leukotriene D4 antagonist, L-648,051, on antigen-induced bronchoconstriction and nonspecific bronchial reactivity. Ten males with mild atopic asthma completed a double-blind, randomized, two-period, placebo-controlled cross-over study. For a 7-day period patients inhaled either placebo or 6 mg of L-648,051 four times daily. Bronchial reactivity to methacholine was measured at base line (day 1) and after 6 days, treatment (day 7). On day 8, after inhaling 6 mg of the antagonist (or placebo), the patients were challenged by inhaled antigen; they received an additional 6 mg of the antagonist (or placebo) 3 h later. Pulmonary function (forced expiratory volume in 1 s, FEV1) was measured serially through an 8-h post-antigen challenge. Nonspecific airway reactivity was again measured on day 9. Compared to placebo, L-648,051 treatment diminished the methacholine reactivity, on both day 7 (NS) and on day 9 (P < 0.05). In addition, the immediate and late bronchial responses to antigen challenge on day 8 were attenuated in the patients when treated with L-648,051. In the immediate phase (0-3 h postchallenge), the airway response was significantly reduced at all recordings between 20 min and 1 h postchallenge. In the late phase (3-8 h postchallenge), the pulmonary response was also reduced. However, the reduction was statistically significant only at the 5-h recording. The results suggest that sulfidopeptide leukotrienes are of importance for nonspecific airway reactivity, and that leukotriene D4 is a significant mediator in the immediate asthmatic reaction.

Pharmacotherapy of childhood asthma. An inflammatory disease

The recognition that asthma constitutes 2 kinds of physiopathological reactions, namely bronchospasms (immediate reactions) and inflammatory responses (late reactions), suggests that the treatment should be focused against these events. Furthermore, the allergen provocation model, showing the existence of immediate and late asthmatic reactions, can be used to study the effects of different antiasthmatic drugs. Recently, the importance of inflammation in the pathogenesis of asthma in adults has led to the development of therapeutic regimens in which anti-inflammatory treatments are used frequently as a first-line step in the management of asthma. Although at the moment the hard data showing inflammation in childhood asthma are scarce, it is assumed that childhood asthma constitutes the same kind of chronic inflammatory processes as in adult asthma and that its treatment should also include anti-inflammatory drugs.