Early and late asthmatic reaction after allergen challenge

The Effect of Seasonal Priming on Specific Inhalation Challenges With Birch and Grass Allergen Among Persons With Allergic Rhinitis

Objectives: Allergic diseases are prevalent in the working population, and work-related airborne pollen exposure might be substantial, especially among outdoor workers, resulting in work-exacerbated effects. Seasonal exposure to pollen may induce a priming effect on the allergic bronchial response resulting in exaggerated effects at the end of the natural pollen season. This was previously observed among people with asthma but may also be of importance for persons with allergic rhinitis. In this study, we examined the effect of seasonal priming on bronchial responsiveness among young adults with allergic rhinitis and no or mild asthma. In addition, we explored the association between the baseline characteristics of participants and the severity of bronchoconstriction. Finally, we evaluated the application of a novel non-linear regression model to the log-dose-response curves.

Material and methods: In a crossover design, 36 participants underwent specific inhalation challenges (SICs) with either grass or birch allergen outside and at the end of the pollen season. The differences in bronchial response were evaluated by comparing the dose-response profiles and PD₂₀ estimates derived by applying a non-linear regression model.

Results: The results showed that 12 of the 19 grass pollen-exposed participants had a lower PD₂₀ at the end of the season compared with the outside season. For birch, this was true for nine out of the 17 participants. However, no statistically significant effects of the seasonal pollen exposure were found on neither the shape nor the magnitude of the modeled dose-response curves for either birch allergen, p = 0.77, or grass allergen, p = 0.45. The model depicted a good fit for the data. Among the baseline characteristics, only the size of the skin prick test for grass allergen was associated with PD₂₀.

Conclusion: This study does not support a priming effect of pollen exposure on the bronchial response from the natural seasonal exposure levels of grass or birch allergens among young adults with allergic rhinitis.

Ultra-high-resolution computed tomography shows changes in the lungs related with airway hyperresponsiveness in a murine asthma model

In vivo presentation of airway hyper-responsiveness (AHR) at the different time points of the allergic reaction is not clearly understood. The purpose of this study was to investigate how AHR manifests in the airway and the lung parenchyma in vivo following exposure to different stimuli and in the early and late phases of asthma after allergen exposure. Ovalbumin (OVA)-induced allergic asthma model was established using 6-week female BALB/c mice. Enhanced pause was measured with a non-invasive method to assess AHR. The dynamic changes of the airway and lung parenchyma were evaluated with ultra-high-resolution computed tomography (128 multi-detector, 1024 × 1024 matrix) for 10 h. While the methacholine challenge showed no grossly visible changes in the proximal airway and lung parenchyma despite provoking AHR, the OVA challenge induced significant immediate changes manifesting as peribronchial ground glass opacities, consolidations, air-trapping, and paradoxical proximal airway dilatations. After resolution of immediate response, multiple episodes of AHRs occurred with paradoxical proximal airway dilatation and peripheral air-trapping in late phase over a prolonged time period in vivo. Understanding of airflow limitation based on the structural changes of asthmatic airway would be helpful to make an appropriate drug delivery strategy for the treatment of asthma.

PKCε stimulation of TRPV1 orchestrates carotid body responses to asthmakines

Key points

We have previously shown that carotid body stimulation by lysophosphatidic acid elicits a reflex stimulation of vagal efferent activity sufficient to cause bronchoconstriction in asthmatic rats.

Here, we show that pathophysiological concentrations of asthma‐associated prototypical Th2 cytokines also stimulate the carotid bodies.

Stimulation of the carotid bodies by these asthmakines involves a PKCε–transient receptor potential vanilloid 1 (TRPV1) signalling mechanism likely dependent on TRPV1 S502 and T704 phosphorylation sites.

As the carotid bodies’ oxygen sensitivity is independent of PKCε–TRPV1 signalling, systemic blockade of PKCε may provide a novel therapeutic target to reduce allergen‐induced asthmatic bronchoconstriction.

Consistent with the therapeutic potential of blocking the PKCε–TRPV1 pathway, systemic delivery of a PKCε‐blocking peptide suppresses asthmatic respiratory distress in response to allergen and reduces airway hyperresponsiveness to bradykinin.

Abstract

The autonomic nervous system orchestrates organ‐specific, systemic and behavioural responses to inflammation. Recently, we demonstrated a vital role for lysophosphatidic acid in stimulating the primary autonomic oxygen chemoreceptors, the carotid bodies, in parasympathetic‐mediated asthmatic airway hyperresponsiveness. However, the cacophony of stimulatory factors and cellular mechanisms of carotid body activation are unknown. Therefore, we set out to determine the intracellular signalling involved in carotid body‐mediated sensing of asthmatic blood‐borne inflammatory mediators. We employed a range of in vitro and rat in situ preparations, site‐directed mutagenesis, patch‐clamp, nerve recordings and pharmacological inhibition to assess cellular signalling. We show that the carotid bodies are also sensitive to asthma‐associated prototypical Th2 cytokines which elicit sensory nerve excitation. This provides additional asthmatic ligands contributing to the previously established reflex arc resulting in efferent vagal activity and asthmatic bronchoconstriction. This novel sensing role for the carotid body is mediated by a PKCε‐dependent stimulation of transient receptor potential vanilloid 1 (TRPV1), likely via TRPV1 phosphorylation at sites T704 and S502. Importantly, carotid body oxygen sensing was unaffected by blocking either PKCε or TRPV1. Further, we demonstrate that systemic PKCε blockade reduces asthmatic respiratory distress in response to allergen and airway hyperresponsiveness. These discoveries support an inflammation‐dependent, oxygen‐independent function for the carotid body and suggest that targeting PKCε provides a novel therapeutic option to abate allergic airway disease without altering life‐saving autonomic hypoxic reflexes.

We have previously shown that carotid body stimulation by lysophosphatidic acid elicits a reflex stimulation of vagal efferent activity sufficient to cause bronchoconstriction in asthmatic rats.

Here, we show that pathophysiological concentrations of asthma‐associated prototypical Th2 cytokines also stimulate the carotid bodies.

Stimulation of the carotid bodies by these asthmakines involves a PKCε–transient receptor potential vanilloid 1 (TRPV1) signalling mechanism likely dependent on TRPV1 S502 and T704 phosphorylation sites.

As the carotid bodies’ oxygen sensitivity is independent of PKCε–TRPV1 signalling, systemic blockade of PKCε may provide a novel therapeutic target to reduce allergen‐induced asthmatic bronchoconstriction.

Consistent with the therapeutic potential of blocking the PKCε–TRPV1 pathway, systemic delivery of a PKCε‐blocking peptide suppresses asthmatic respiratory distress in response to allergen and reduces airway hyperresponsiveness to bradykinin.

Effects of the Toll-like receptor 7 (TLR7) agonist, AZD8848, on allergen-induced responses in patients with mild asthma: a double-blind, randomised, parallel-group study

Background

Although allergic asthma is a complex area with many interacting factors involved, the ‘hygiene hypothesis’ proposes that a lack of exposure to infection during childhood may polarise the immune system towards allergen-reactive Th2-type responses in genetically susceptible individuals. Toll-like receptors (TLRs) play a key role within the innate immune system and TLR7 agonists have previously been shown to up-regulate Th1 responses and down-regulate Th2 responses to allergens in murine models of allergic or chronic asthma. This study aimed to examine the efficacy and safety of the novel TRL7 agonist AZD8848, which has been developed as an antedrug.

Methods

In this double-blind, randomised, parallel-group study, AZD8848 60 μg or placebo was administered intranasally once-weekly for 8 weeks in patients with mild-to-moderate allergic asthma (NCT00999466). Efficacy assessments were performed at 1 and 4 weeks after the last dose. The primary outcome was the late asthmatic response (LAR) fall in forced expiratory volume in 1 s (FEV₁) after allergen challenge at 1-week post-treatment.

Results

AZD8848 significantly reduced average LAR fall in FEV₁ by 27% vs. placebo at 1 week after treatment (p = 0.035). This effect was sustained at 4 weeks post-treatment; however, it did not reach clinical significance. AZD8848 reduced post-allergen challenge methacholine-induced airway hyper-responsiveness (AHR) vs. placebo at 1 week post-dosing (treatment ratio: 2.20, p = 0.024), with no effect at 4 weeks. There was no significant difference between the two groups in plasma cytokine, sputum Th2 cytokine or eosinophil responses post-allergen challenge at 1 week after treatment. The incidence of adverse events was similar in the two groups. AZD8848 was generally well tolerated.

Conclusions and clinical relevance

In patients with allergic asthma, TLR7 agonists could potentially reduce allergen responsiveness by stimulating Type 1 interferon responses to down-regulate the dominant Th2 responses.

Trial registration

clinicaltrials.gov identifier NCT00999466.

Cholinergic synapse pathway gene polymorphisms associated with allergen-induced late asthmatic responses

Allergen inhalation challenge triggers well-defined airway responses in mild, allergic asthmatics. Some individuals develop only an isolated early response (early responders (ERs)) characterised by acute airway smooth muscle constriction immediately following allergen inhalation. Others develop a late response (dual responders (DRs)) that begins 3–4 h later, resulting in prolonged reduction of airway function, associated with cellular infiltration, inflammation and hyperresponsiveness of the airways [1]. It is not well understood how certain individuals are protected from developing a late response. Our previous research identified novel RNA transcripts in peripheral blood that are predictive of asthmatics who could develop a late response. Our findings pointed towards the presence of inherent differences underlying molecular mechanisms that predispose asthmatic individuals to the late response [2].

Cholinergic synapse pathway gene polymorphisms may play a role in regulating a type of asthmatic airway response triggered upon allergen challengehttp://bit.ly/2lJx1VG

Enhance the dissolution rate and oral bioavailability of pranlukast by preparing nanosuspensions with high-pressure homogenizing method

PURPOSE

Pranlukast, one of the potential therapeutic tools in the treatment of asthma, has limited clinical applications due to its poor water solubility. The study is aimed to provide a platform for better utilizing pranlukast with enhancement of the dissolution rate and, thus, the oral bioavailability of pranluka'st by preparing nanosuspensions through high-pressure homogenization method.

METHOD

Poloxamer407 and PEG200 were chosen as stabilizer and surfactant. The formulation was investigated systematically with the dissolution tests as predominant method. Nanosuspensions were prepared by programmed high-pressure homogenization method. The product was characterized by particle size analysis, TEM and XRD are evaluated by in vitro dissolution tests and in vivo absorption examination. In addition, nanosuspensions with only pranlukast were prepared and compared with formulated nanosuspensions.

RESULTS

The optimal values of formulation were 0.5% (w/v) pranlukast with 0.375% (w/v) Poloxamer407, 0.375% (w/v) PEG200 and the screened programming homogenizing procedure parameters were 680 bar for the first 15 circles, 1048 bar for the next 9 circles and 1500 bar for the last 9 circles. Nanosuspensions of 318.2 ± 7.3 nm, -29.3 ± 0.8 mV were obtained. The XRD analysis indicated no change of crystalline occurred in the process of homogenization. The in vitro dissolution behavior of nanosuspensions exhibited complete release in 30 min with a remarkable fast dissolution rate. The in vivo bioavailability of formulated pranlukast nanosuspensions demonstrated its enhancement of fast onset of therapeutic drug effects with 4.38-fold improved compared to that of raw crystals.

CONCLUSION

The study provides a feasible, practical thinking of industry development in the clinical use of pranlukast.

The early asthmatic response is associated with glycolysis, calcium binding and mitochondria activity as revealed by proteomic analysis in rats

Background

The inhalation of allergens by allergic asthmatics results in the early asthmatic response (EAR), which is characterized by acute airway obstruction beginning within a few minutes. The EAR is the earliest indicator of the pathological progression of allergic asthma. Because the molecular mechanism underlying the EAR is not fully defined, this study will contribute to a better understanding of asthma.

Methods

In order to gain insight into the molecular basis of the EAR, we examined changes in protein expression patterns in the lung tissue of asthmatic rats during the EAR using 2-DE/MS-based proteomic techniques. Bioinformatic analysis of the proteomic data was then performed using PPI Spider and KEGG Spider to investigate the underlying molecular mechanism.

Results

In total, 44 differentially expressed protein spots were detected in the 2-DE gels. Of these 44 protein spots, 42 corresponded to 36 unique proteins successfully identified using mass spectrometry. During subsequent bioinformatic analysis, the gene ontology classification, the protein-protein interaction networking and the biological pathway exploration demonstrated that the identified proteins were mainly involved in glycolysis, calcium binding and mitochondrial activity. Using western blot and semi-quantitative RT-PCR, we confirmed the changes in expression of five selected proteins, which further supports our proteomic and bioinformatic analyses.

Conclusions

Our results reveal that the allergen-induced EAR in asthmatic rats is associated with glycolysis, calcium binding and mitochondrial activity, which could establish a functional network in which calcium binding may play a central role in promoting the progression of asthma.

Establishing the phenotype in novel acute and chronic murine models of allergic asthma

Allergic asthma is a chronic disease of the airways, with superimposed acute inflammatory episodes which correspond to exacerbations of asthma. Two novel models of allergic asthma have been developed in mice receiving the same allergen sensitisation, but with acute or chronic allergen exposures, the latter to mimic the human situation more closely. Ovalbumin-sensitised mice were challenged by ovalbumin inhalation twice on the same day for the acute model, and 18 times over a period of 6 weeks for the chronic model. Lung function was monitored in conscious, unrestrained mice immediately after the last challenge for up to 12 h. Airway responsiveness to inhaled methacholine and serum antibody levels were determined 24 h after challenge. Bronchoalveolar inflammatory cell recruitment was determined at 2 or 24 h. Acute and chronically treated mice had similar early and late asthmatic responses peaking at 2 h and 7-8 h, respectively. IgE and IgG antibody levels, compared with naïve mice, and eosinophil infiltration, compared with naïve and saline challenge, were elevated. Airway hyperresponsiveness to methacholine was observed 24 h after challenge in both models. The acute model had higher levels of eosinophilia, whereas the chronic model showed hyperresponsiveness to lower doses of methacholine and had higher levels of total IgE and ovalbumin-specific IgG antibodies. Both novel murine models of allergic asthma bear a close resemblance to human asthma, each offering particular advantages for studying the mechanisms underlying asthma and for evaluating existing and novel therapeutic agents.

Validated safety predictions of airway responses to house dust mite in asthma

BACKGROUND

House dust mite (HDM) is the most common aeroallergen causing sensitization in many Western countries and is often used in allergen inhalation challenges. The concentration of inhaled allergen causing an early asthmatic reaction [provocative concentration of inhaled allergen causing a 20% fall of forced expiratory volume in 1 s (FEV(1))(PC(20) allergen)] needs to be predicted for safety reasons to estimate accurately the severity of allergen-induced airway responsiveness. This can be accomplished by using the degree of non-specific airway responsiveness and skin sensitivity to allergen.

OBJECTIVE

We derived prediction equations for HDM challenges using PC(20) histamine or PC(20) methacholine and skin sensitivity data obtained from patients with mild to moderate persistent asthma and validated these equations in an independent asthma population.

METHODS

PC(20) histamine or PC(20) methacholine, skin sensitivity, and PC(20) allergen were collected retrospectively from 159 asthmatic patients participating in allergen challenge trials. Both the histamine and methacholine groups (n=75 and n=84, respectively), were divided randomly into a reference group to derive new equations to predict PC(20) allergen, and a validation group to test the new equations.

RESULTS

Multiple linear regression analysis revealed that PC(20) allergen could be predicted either from PC(20) methacholine only ((10)log PC(20) allergen=-0.902+0.741.(10)log PC(20) methacholine) or from PC(20) histamine and skin sensitivity (SS) ((10)log PC(20) allergen=-0.494+0.231.(10)log SS+0.546.(10)log PC(20) histamine). In the validation study, these new equations accurately predicted PC(20) allergen following inhalation of HDM allergen allowing a safe starting concentration of allergen of three doubling concentrations below predicted PC(20) allergen in all cases.

CONCLUSION

The early asthmatic response to inhaled HDM extract is predominantly determined by non-specific airway responsiveness to methacholine or histamine, whereas the influence of the cutaneous sensitivity to HDM appears to be rather limited. Our new equations accurately predict PC(20) allergen and hence are suitable for implementation in HDM inhalation studies.

Expression of activated Fc gamma RII discriminates between multiple granulocyte-priming phenotypes in peripheral blood of allergic asthmatic subjects

BACKGROUND

Allergic asthma is associated with chronic airway and systemic immune responses. Systemic responses include priming of peripheral blood eosinophils, which is enhanced after allergen challenge. In a subpopulation of asthmatic subjects, neutrophils are associated with bronchial inflammation.

OBJECTIVE

We sought to monitor systemic granulocyte priming in allergic asthmatic subjects as a consequence of chronic and acute inflammatory signals initiated by allergen challenge.

METHODS

Blood was taken at baseline and 6 to 24 hours after allergen challenge in asthmatic subjects with and without late asthmatic responses. Systemic granulocyte priming was studied by using expression of cellular markers, such as alpha-chain of Mac-1 (alpha m)/CD11b, L-selectin/CD62L, and an activation epitope present on Fc gamma RII/CD32 recognized by monoclonal phage antibody A17.

RESULTS

Eosinophils of asthmatic subjects have a primed phenotype identified by cell-surface markers. Neutrophils of these patients were subtly primed, which was only identified after activation with N-formyl-methionyl-leucyl-phenylalanine. After allergen challenge, an acute increase in eosinophil priming characterized by enhanced expression of activated Fc gamma RII was found in patients experiencing a late asthmatic response and not in patients with a single early asthmatic response. In contrast, expression of alpha m/CD11b and L-selectin on granulocytes was not different between control and asthmatic subjects and was not affected by allergen challenge. Interestingly, expression of both adhesion molecules was positively correlated, and alpha m expression on eosinophils and neutrophils correlated positively with bronchial hyperresponsiveness.

CONCLUSION

Different phases, phenotypes, or both of allergic asthma are associated with distinct priming profiles of inflammatory cells in peripheral blood.

CLINICAL IMPLICATIONS

Insight in differences of systemic innate responses will lead to better definition of asthma subtypes and to better designs of new therapeutic options.

A critical appraisal of methods used in early clinical development of novel drugs for the treatment of asthma

Asthma is a heterogeneous disorder characterized by chronic airway inflammation, hyperresponsiveness and remodeling. Being the hallmark of asthma, airway inflammation has become the most important target for therapeutic agents. Consequently, during the past decade various semi-and non-invasive methods have been explored to sample the airway inflammation in asthma. In this review, we provide a practical overview of the current status of various sampling techniques including sputum induction, exhaled breath analysis, and bronchoprovocation tests (BPTs). We focus on their applicability for monitoring in clinical practice and in intervention trials in asthma.

Effects of allergen inhalation and oral glucocorticoid on concentrations of serum-soluble CD86 in allergic asthmatics

The aim of the present study was to investigate effects of allergen inhalation and oral glucocorticoid on concentration of serum soluble CD86 in patients with allergic asthma. Our results showed that the serum soluble CD86 concentrations in the dual responder group increased from 491.8 +/- 15.4 IU/ml before allergen inhalation to 603.8 +/- 19.3 IU/ml 24 h after allergen inhalation. In the isolated early responders, there was no significant increase in serum soluble CD86 concentrations after allergen inhalation compared with baseline levels. There was a significant decrease in serum soluble CD86 concentrations after 2 weeks of glucocorticoid therapy (448.3 +/- 15.1 IU/ml) compared with baseline values (532.7 +/- 12.3 IU/ml), whereas there was no significant difference in the placebo group. This study has demonstrated that serum soluble CD86 concentrations increased after allergen inhalation in sensitized asthmatic subjects, and that serum sCD86 concentrations were downregulated by prednisolone therapy.

Effects of allergen inhalation and oral glucocorticoid on serum soluble CTLA-4 in allergic asthmatics

BACKGROUND

The serum soluble cytotoxic T lymphocyte associated antigen-4 (sCTLA-4) concentration is significantly elevated in patients with asthma, and sCTLA-4 concentration correlate with the severity of asthma. The aim of the present study was to investigate effects of allergen inhalation and oral glucocorticoid on concentration of serum sCTLA-4 in patients with allergic asthma.

METHODS

Allergen inhalation challenge was conducted in allergic asthmatics with isolated early asthma response and those with dual asthma response. In a randomized, double-blind, placebo-controlled, parallel group fashion, prednisolone or placebo was give orally once a day for 2 weeks. Venous blood samples were collected before and after allergen inhalation or prednisolone administration for obtaining sera. The serum sCTLA-4 concentrations were determined using enzyme-linked immunosorbent assay.

RESULTS

The serum sCTLA-4 concentrations in the dual responder group increased from 29.0 (14.5-43.7) microg/l [median (25-75 percentiles)] before allergen inhalation to 44.0 (24.3-61.3) microg/l 24 h after allergen inhalation. In the isolated early responders, there were no significant increase in serum sCTLA-4 concentrations after allergen inhalation compared with baseline levels. There was a significant decrease in serum sCTLA-4 concentrations after 2 weeks of glucocorticoid therapy [22.0 (15.5-31.0) microg/l] compared with baseline values [37.0 (19.5-53.0) microg/l], whereas there was no significant difference in the placebo group.

CONCLUSION

This study has demonstrated that serum sCTLA-4 concentrations increased after allergen inhalation in sensitized asthmatic subjects, and that serum sCTLA-4 concentrations were downregulated by prednisolone therapy.

Long-acting beta2-agonists: comparative pharmacology and clinical outcomes

Salmeterol and formoterol are both long-acting beta(2)-adrenoceptor agonists (beta(2)-agonists). They both provide excellent bronchodilating and bronchoprotective effects in patients with asthma but their are some differences between these two long-acting beta(2)-agonists in vitro and in vivo. Formoterol has a greater potency and intrinsic activity than salmeterol, which can become especially apparent at higher doses than that clinically recommended, and in contracted bronchi. Long-term use of long-acting beta(2)-agonists can induce tolerance, which can be partially reversed with corticosteroids. Long-acting beta(2)-agonists have some anti-inflammatory effects in vitro, but data in vivo are less convincing. Compared with doubling the dose of inhaled corticosteroids, the addition of inhaled long-acting beta(2)-agonists to inhaled corticosteroids improves symptom control in patients with asthma and reduces both the exacerbation rate of asthma and hospital admission rate. No enhanced airway responsiveness or loss of perception of dyspnea has been observed with the use of inhaled long-acting beta(2)-agonists. Monotherapy with long-acting beta(2)-agonists is not recommended.

IFN-gamma inhibits the proliferation of allergen-activated T lymphocytes from atopic, asthmatic patients by inducing Fas/FasL-mediated apoptosis

The defect in interferon-gamma (IFN-gamma) production that results in a T helper cell type 2-dominated response may be responsible for a decrease in the apoptosis of allergen-activated T cells in asthma. We investigated the effect of recombinant IFN-gamma on proliferation, Fas/Fas ligand (FasL) expression, and apoptosis in allergen-stimulated peripheral blood mononuclear cells obtained from atopic, asthmatic patients and nonatopic, control subjects. The addition of IFN-gamma at the start of cultures markedly inhibited the proliferative response to a specific allergen in cells from all asthmatic patients, whereas no change was observed in cells from nonatopic, control subjects. IFN-gamma induced an increase in the expression of Fas and FasL by allergen-stimulated CD4+ T cells from asthmatic patients and caused the apoptosis of these cells. A Fas-blocking monoclonal antibody prevented the inhibitory effect of IFN-gamma on allergen-induced proliferation. These results suggest that IFN-gamma inhibits the proliferation of allergen-stimulated CD4+ T cells from atopic, asthmatic patients by inducing the surface expression of Fas and FasL, which in turn triggers their apoptotic program. The defect in IFN-gamma production involved in the allergic, immune response may therefore be responsible for a decrease in apoptosis of allergen-activated T lymphocytes in the airways of atopic, asthmatic patients.

Kinetics of bone marrow eosinophilopoiesis and associated cytokines after allergen inhalation

Allergen inhalation is associated with increased eosinophil/basophil progenitors in bone marrow 24 hours after allergen inhalation. This study examined the kinetics of eosinophilopoiesis in dual (n = 14), compared with isolated early, responders (n = 12). Dual responders, in contrast to isolated early responders, develop significant sputum and blood eosinophilia and prolonged airway hyperresponsiveness. Bone marrow aspirates were taken before and 5, 12, 24, and 48 hours after allergen inhalation. In dual responders, increases in interleukin (IL)-3-responsive progenitors were detected as early as 5 hours after allergen inhalation, and IL-5-responsive progenitors were detected at 12 and 24 hours. No changes were detected in isolated early responders. Bone marrow IL-5 protein levels increased at 12 and 24 hours in dual responders only and these increases correlated with increases in IL-5-responsive progenitors. In addition, bone marrow IFN-gamma levels increased in dual responders at 48 hours. These data demonstrate that, in dual responders, there is allergen-induced activation of an eosinophilopoietic process that is rapid and sustained, and a relationship between increased bone marrow IL-5 levels and increased eosinophil production. We propose that after allergen inhalation, time-dependent changes in cytokine levels in the bone marrow control differentiation of eosinophil/basophil progenitors.

Effect of bradykinin on allergen induced increase in exhaled nitric oxide in asthma

BACKGROUND

Exposure of patients with atopic asthma to allergens produces a long term increase in exhaled nitric oxide (FENO), probably reflecting inducible NO synthase (NOS) expression. In contrast, bradykinin (BK) rapidly reduces FENO. It is unknown whether BK suppresses increased FENO production after allergen exposure in asthma, and whether it modulates FENO via NOS inhibition.

METHODS

Levels of FENO in response to aerosolised BK were studied before (day 3) and 48 hours after (day 10) randomised diluent (diluent/placebo/BK (Dil/P/BK)), allergen (allergen/placebo/BK (All/P/BK), and allergen/L-NMMA/BK (All/L/BK)) challenges (day 8) in 10 atopic, steroid naïve, mild asthmatic patients with dual responses to inhaled house dust mite extract. To determine whether BK modulates FENO via NOS inhibition, subjects performed pre- and post-allergen BK challenges after pretreatment with the NOS inhibitor L-NMMA in the All/L/BK period.

RESULTS

Allergen induced a fall in FENO during the early asthmatic reaction (EAR) expressed as AUC(0-1) (ANOVA, p=0.04), which was followed by a rise in FENO during the late asthmatic reaction (LAR) expressed as AUC(1-48) (ANOVA, p=0.008). In the Dil/P/BK period, FENO levels after BK on pre- and post-diluent days were lower than FENO levels after placebo (difference 23.5 ppb (95% CI 6.2 to 40.9) and 22.5 ppb (95% CI 7.3 to 37.7), respectively; p<0.05). Despite the long lasting increase in FENO following allergen challenge in the LAR, BK suppressed FENO levels at 48 hours after allergen challenge in the All/P/BK period, lowering the increased FENO (difference from placebo 54.3 ppb (95% CI 23.8 to 84.8); p=0.003) to the baseline level on the pre-allergen day (p=0.51). FENO levels were lower after L-NMMA than after placebo on pre-allergen (difference 10.85 ppb (95% CI 1.3 to 20.4); p=0.03) and post-allergen (difference 36.2 ppb (95% CI 5.5 to 66.9); p=0.03) days in the All/L/BK and All/P/BK periods, respectively. L-NMMA did not significantly potentiate the pre- and post-allergen reduction in BK induced FENO.

CONCLUSIONS

Bradykinin suppresses the allergen induced increase in exhaled NO in asthma; this is not potentiated by L-NMMA. Bradykinin and L-NMMA may follow a common pathway in reducing increased NO production before and after experimental allergen exposure. Reinforcement of this endogenous protective mechanism should be considered as a therapeutic target in asthma.

Pranlukast: a review of its use in the management of asthma

Pranlukast (Onon, Azlaire), is an orally administered, selective, competitive antagonist of the cysteinyl leukotrienes (LT) C(4), LTD(4) and LTE(4). It is indicated for the prophylactic treatment of chronic bronchial asthma in paediatric and adult patients. The efficacy of pranlukast 225mg twice daily in adults with mild to moderate asthma was demonstrated in double-blind, placebo- or azelastine-controlled studies of 4 or 8 weeks' duration. The drug at this dosage was superior to both comparators in improving mean attack scores and morning and/or evening peak expiratory flow rates, and decreasing the use of rescue bronchodilators (p < 0.05). In limited clinical studies, pranlukast 225mg twice daily appeared to be as effective as montelukast 10mg once daily and zafirlukast 40mg twice daily in adults with mild to moderate asthma. Tachyphylaxis was absent when the drug was administered for up to 4 years. In patients requiring high-dose inhaled corticosteroid therapy, pranlukast 225 mg twice daily plus a halved dosage of inhaled corticosteroid was as effective as the original dosage of inhaled corticosteroid. Pranlukast was also effective in patients with mild to severe asthma in a clinical practice setting. In a double-blind trial, greater improvements in most outcome measures were observed with pranlukast than with oxatomide in children and adolescents with asthma. In clinical trials, pranlukast was well tolerated in adult and paediatric patients with asthma, with an adverse event profile similar to that of placebo. Gastrointestinal events and hepatic function abnormalities were the most commonly reported adverse events. No clinically significant differences in adverse event profiles between pranlukast, zafirlukast or montelukast were shown in limited comparisons. Although Churg-Strauss syndrome has been noted in pranlukast recipients, a direct causal relationship is unlikely.

CONCLUSIONS

Pranlukast is a well tolerated and effective preventative treatment in adult and paediatric patients with persistent asthma of all severities. In some patients, pranlukast may be beneficial when added to low-dose inhaled corticosteroids; it may also be a viable alternative to increasing inhaled corticosteroid dosages. The efficacy of pranlukast relative to placebo has been confirmed; its efficacy relative to other therapy awaits further investigation. Nonetheless, pranlukast is a useful therapeutic option (with as-required short-acting beta(2)-agonists), either as preventative monotherapy for the treatment of mild persistent asthma or in conjunction with inhaled corticosteroids in the management of moderate or severe persistent asthma.

Exposure to diesel exhaust exacerbates allergen-induced airway responses in guinea pigs

Diesel exhaust (DE) is a major air pollutant in urban areas. To clarify the effects of DE on the exacerbation of asthma, guinea pigs were exposed 12 h daily to 3 mg/m(3) DE or air for 8 wk with or without sensitization to ovalbumin (OVA). In the DE-exposed sensitized animals, both immediate (IAR) and late (LAR) airway responses were enhanced after the inhalation challenge by OVA, compared with the DE-unexposed sensitized animals. Mucus was greatly accumulated in the airways of DE-exposed sensitized animals during IAR. The number of eosinophils and level of sialic acid concentration in bronchial lavage fluids were also significantly higher in the DE-exposed sensitized animals than in the DE-unexposed control animals. During LAR, intercellular spaces of the bronchial epithelium became enlarged in the DE-exposed sensitized animals, showing infiltration by numerous eosinophils. Albumin concentration was significantly higher in the bronchial lavage fluids from the DE-exposed sensitized animals than in those from the DE-unexposed control animals. These results suggest that exposure to DE enhances mucus hypersecretion and eosinophilic inflammation during IAR. DE exposure also increases airway permeability and airway inflammation during LAR. Thus, DE exposure exacerbates allergen-induced airway responses in guinea pigs.

Montelukast: a review of its therapeutic potential in persistent asthma

Montelukast is a cysteinyl leukotriene receptor antagonist used to treat persistent asthma in patients aged > or = 6 years. The drug has a rapid onset of action. Improvements in lung function and reductions in as-needed beta2-agonist usage are apparent within 1 day of initiating montelukast treatment in adults and adolescents (aged > or = 15 years treated with 10 mg/day) or children (aged 6 to 14 years treated with 5 mg/day) with persistent asthma as shown in clinical trials. In two 12-week, multicentre, randomised, double-blind studies in adults and adolescents aged > or = 15 years with persistent asthma [forced expiratory volume in 1 second (FEV1) = 50 to 85% predicted] there was significantly (p < 0.05) greater improvement in FEV1, symptom scores, peak expiratory flow (PEF), as-needed beta2-agonist use, peripheral eosinophil counts and health-related quality of life (QOL) in patients treated with montelukast 10 mg/day than in recipients of placebo. Improvements were significantly greater in patients treated with inhaled beclomethasone 400 microg/day than in recipients of montelukast 10 mg/day in 1 of these studies. Nonetheless, 42% of montelukast recipients experienced > or = 11% improvement in FEV1, the median improvement in this parameter in beclomethasone-treated patients. In an 8-week multicentre, randomised, double-blind, study in children aged 6 to 14 years with persistent asthma (FEV1 50 to 85% predicted), montelukast 5 mg/day produced significantly greater improvements in FEV1, clinic PEF, as-needed beta2-agonist use, peripheral eosinophil counts, asthma exacerbations and QOL scores than placebo. The combination of montelukast 10 mg/day plus inhaled beclomethasone 200 microg twice daily provided significantly better asthma control than inhaled beclomethasone 200 microg twice daily in adults with poorly controlled asthma (mean FEV1 = 72% predicted) despite 4 weeks treatment with inhaled beclomethasone. Patients receiving the combination experienced significant improvements in FEV1 and morning PEF, significant reductions in daytime symptom scores, as-needed beta2 agonist usage and night-time awakenings with asthma, and had significantly lower peripheral blood eosinophil counts after 16 weeks in this multicentre, randomised, double-blind, placebo-controlled study. Among adults (FEV1 > or = 70%) treated with montelukast 10 mg/day for 12 weeks, inhaled corticosteroid dosages were titrated downward by 47% (vs 30% in placebo recipients), 40% of patients were tapered off of inhaled corticosteroids (vs 29%), and significantly fewer patients (16 vs 30%) experienced failed corticosteroid rescues in a multicentre, randomised, double-blind study. During clinical studies, the frequency of adverse events in montelukast-treated adults, adolescents and children was similar to that in placebo recipients. In conclusion, montelukast is well tolerated and effective in adults and children aged > or = 6 years with persistent asthma including those with exercise-induced bronchoconstriction and/or aspirin sensitivity. Furthermore, montelukast has glucocorticoid sparing properties. Hence, montelukast, as monotherapy in patients with mild persistent asthma, or as an adjunct to inhaled corticosteroids is useful across a broad spectrum of patients with persistent asthma.

Effect of heparin on antigen-induced airway responses and pulmonary leukocyte accumulation in neonatally immunized rabbits

The effect of single administrations of aerosolized heparin, low molecular weight heparin (LMWH) and the linear polyanionic molecule, polyglutamic acid (PGA) were examined on antigen-induced airway hyperresponsiveness and leukocyte accumulation in neonatally immunized rabbits. Adult litter-matched NZW rabbits immunized within 24 h of birth with Alternaria tenuis antigen were treated with heparin, LMWH or PGA prior to or following antigen challenge (Alternaria tenuis). For each drug-treated group, a parallel group of rabbits were treated with the appropriate vehicle. In all groups, airway responsiveness to inhaled histamine and bronchoalveolar lavage (BAL) was performed 24 h prior to and following antigen challenge. Basal lung function in terms of resistance (R(L)) and dynamic compliance (C(dyn)) and acute bronchoconstriction was unaltered by pre-treatment with heparin, LMWH or PGA compared to their respective vehicles 24 h prior to or following antigen challenge. In vehicle-treated animals, airway hyperresponsiveness to inhaled histamine was indicated by an increase in the maximal responses of the cumulative concentration-effect curves to histamine and reductions in R(L)PC(50) and C(dyn)PC(35) values 24 h following antigen challenge. Heparin and LMWH given prior to antigen challenge significantly inhibited the development of airway hyperresponsiveness, whereas PGA did not. When given following antigen challenge, all three drugs failed to inhibit the development of airway hyperresponsiveness. Eosinophil and neutrophil cell numbers in BAL fluid increased significantly 24 h following antigen challenge. Heparin, LMWH and PGA failed to inhibit the increase in cell numbers following antigen challenge whether given prior to or following antigen challenge.

The effect of montelukast (MK-0476), a cysteinyl leukotriene receptor antagonist, on allergen-induced airway responses and sputum cell counts in asthma

BACKGROUND

Cysteinyl leukotrienes are capable of inducing chemotaxis of eosinophils in vitro and within the airways of animals and humans in vivo.

OBJECTIVE

We hypothesized that montelukast (MK-0476), a potent cysLT1 receptor antagonist, would protect against allergen-induced early (EAR) and late (LAR) asthmatic responses by virtue of anti-inflammatory properties. Hence, we studied the effect of pretreatment with oral montelukast on allergen-induced airway responses. As an exploratory endpoint, changes in inflammatory cell differentials and eosinophil cationic protein (ECP) were evaluated in hypertonic saline-induced sputum.

METHODS

Twelve asthmatic men (20-34 years, FEV1 79-109% predicted, histamine PC20FEV1 <4 mg/mL) with dual responses to inhaled house dust mite extract participated in a two-period, double-blind, placebo-controlled, crossover study. Three oral doses of montelukast (10 mg) or matching placebo were administered 36 and 12 h before, and 12 h post-allergen. The airway response to allergen was measured by FEV1, and the EAR and LAR were expressed as the corresponding areas under the time-response curves (AUC0-3 h and AUC3-8h, respectively). During each study period, sputum was induced with 4.5% NaCl 24 h before and 24 h after a standardized allergen challenge. Processed whole sputum cytospins were stained with Giemsa, and cell counts expressed as percentage nonsquamous cells. ECP was measured by FEIA in sputum supernatants.

RESULTS

All subjects completed the study. The changes in baseline FEV1 were not significantly different between the two pretreatments (P = 0.183). Montelukast significantly inhibited the EAR and LAR, reducing the AUC0-3h by 75.4% (P<0.001) and the AUC3-8h by 56.9% (P = 0.003) as compared with placebo. Sputa of nine subjects could be included in the analysis (<80% squamous cells). Allergen challenge significantly increased sputum eosinophils after placebo (mean change +/- SD: 4.8 +/- 5.8%, P = 0.038), with a similar trend after montelukast (mean change +/- SD: 4.1 +/- 5.4%; P = 0.056). The allergen-induced changes in sputum eosinophils and ECP, however, were not significantly different between the two pretreatments (P = 0.652 and P = 0.506, respectively).

CONCLUSION

We conclude that oral montelukast protects against allergen-induced early and late airway responses in asthma. However, using the present dosing and sample size, this protection was not accompanied with changes in sputum eosinophil percentage or activity, which may require more prolonged pretreatment with cysLT1 receptor antagonists.

Inflammation in asthma: the cornerstone of the disease and target of therapy

Asthma is a chronic disease associated with variable levels of airflow obstruction. Considerable evidence has been obtained to show that airway inflammation is a major factor in the pathogenesis of asthma in associated bronchial hyperresponsiveness, and in the level of disease severity. The inflammatory pattern in asthma is multicellular in nature, with mast cells, neutrophils, eosinophils, T lymphocytes, and epithelial cells participating in the response. Furthermore, it is known that mediators, cytokines, and chemokines from these cells contribute to the orchestration of the inflammatory process. Because airway inflammation appears to be a critical etiologic feature of asthma, it has become the target of therapy. In this review the features of airway inflammation will be examined, and the effect of therapeutic agents on markers of airway injury will be discussed. Establishing, understanding, and finally controlling the features of airway inflammation have given insight to disease pathogenesis and the effectiveness of various treatments. The integral role of inhaled corticosteroids in modifying the complex inflammatory component of asthma will be explored, with special focus on the high degree of efficacy associated with this treatment--vis-á-vis other therapeutic agents--in preventing or blocking specific proinflammatory markers.

Changes in bone marrow inflammatory cell progenitors after inhaled allergen in asthmatic subjects

Increases in inflammatory cell progenitors, particularly eosinophil/basophil colony-forming cells (Eo/B-CFU), occur in peripheral blood after allergen provocation. The role of bone marrow (BM) in these reactions is unclear. We examined the effect of allergen challenge on human bone marrow progenitor cell growth. Fifteen asthmatic subjects, eight dual responders (DR) and seven isolated early responders (IER), were challenged with inhaled allergen. BM aspirates were taken before and 24 h after challenge and progenitors were enumerated by a colony-forming assay. Eo/B-CFU numbers increased in both groups after allergen challenge (p < 0.0001). For DR, the increases were significant for BM incubated with optimal GMCSF and IL-5, but not with IL-3. For IER, the increases were significant for all three cytokines tested. At a suboptimal concentration of IL-5, there was a significant increase in the number of Eo/B-CFU after allergen in the DR, from 5.25 +/- 1.2 to 9.68 +/- 2.1 per 2.5 x 10(5) cells plated (p < 0.01), which was not demonstrated in the IER (p = 0.94). The responses at this concentration of IL-5 were different between groups (p < 0.05). These results demonstrate that inhaled allergen increases BM Eo/B-CFU, and that the bone marrow of dual responders is more responsive to IL-5 after allergen.

The effect of R 15.7/HO, an anti-CD18 antibody, on the late airway response and airway hyperresponsiveness in an allergic rabbit model

1. The effects of a mouse (IgG1 fraction) anti-CD 18 neutralizing antibody (R15.7) on allergen-induced late airway response (LAR), airway hyperresponsiveness (AHR) and cellular recruitment were investigated in an allergic rabbit model. 2. Litter-matched NZW rabbits immunized within 24 h of birth with Alternaria tenuis (i.p.) and subsequently exposed to the allergen (i.p.) for the first 3 months of life were challenged with inhaled allergen as adult rabbits. Lung function in terms of dynamic compliance (Cdyn; ml cmH2O-1) and total lung resistance (RL; cmH2O-1 s-1) was monitored for 6 h following the allergen challenge. On day 16, separate groups of rabbits were pretreated with either control antibody (a non-binding mouse IgG1, 1 mg kg-1, i.v.) or R15.7 (1 mg kg-1, i.v.) and 1 h later all were challenged with Alternaria tenuis and lung function monitored thereafter. Airway responsiveness to inhaled histamine was assessed by measuring RL and Cdyn 24 h before and after allergen challenge and bronchoalveolar lavage (BAL) was also performed 24 h before and after allergen challenge. 3. Pretreatment of rabbits with the control antibody had no effect on the LAR as measured by AUC (Cdyn, 0-6 h). However, the magnitude of the LAR following treatment with R15.7 was significantly reduced when compared to LAR demonstrated on 1st challenge (P < 0.001) or to that of the control group on both challenges (P < 0.01). 4. In control antibody pretreated rabbits allergen induced a significant 3.4 fold reduction in the PC50 response to inhaled histamine in terms of RL changes (P < 0.05) and a significant 2.1 fold reduction in PC35 response to inhaled histamine in terms of Cdyn changes (P < 0.05). However, in anti-CD 18 antibody pretreated rabbits there was no significant change in responsiveness to histamine 24 h following allergen, as assessed by either RL PC50 or Cdyn PC35. 5. Allergen challenge induced a significant increase in eosinophil and neutrophil numbers (P < 0.05) in rabbits pre-treated with control antibody, whereas treatment with R15.7 significantly inhibited this increase in the numbers of both cell types. 6. This study demonstrates that the neutralization of CD-18 molecules reduces allergen-induced infiltration of both eosinophils and neutrophils into the airways and abolishes the accompanying LAR and AHR. These results provide evidence to support a role for CD-18 adhesion molecules in the transmigration of inflammatory cells into airways.

Challenge tests in nose and bronchi: pharmacological modulation of rhinitis and asthma

In order to study the pathophysiology of allergic airway disease and its response to pharmacotherapy, allergic and non-allergic provocation challenge techniques can be employed. Lower airway challenge has been used widely, but the use of nasal challenge is becoming more widespread as its advantages are realized. New measurement techniques are also being used (e.g. acoustic rhinometry), along with more classical methods such as spirometry, peak airflow rate and symptom scores, to determine the response to challenge. In the lungs, allergen challenge produces a biphasic response, which is less clearly defined in the nose. Topical histamine challenge closely resembles the effects of an allergic reaction and acts by stimulating sensory nerve endings. Methacholine is also often used for nasal challenge (often in addition to histamine), due to its effects on glandular sensitivity. Exercise induces bronchoconstriction in asthmatics and can be imitated by inhalation of cold, dry air. Cold air induces glandular hypersecretion and nasal discharge in normal subjects, which is increased in severity in rhinitic patients. Drug effect investigations using antihistamines have shown that histamine is important in producing the symptom of sneezing, whereas nasal blockage is due to vasodilatation rather than plasma exudation and oedema. Beta 2-agonists reduce allergen-induced symptoms by stabilizing mast cells, whereas cholinoceptor antagonists reduce watery nasal secretion. Increased responsiveness of sensory nerves and nasal glands is a characteristic clinical feature of asthma and rhinitis, which is responsible for the symptomatology. These effects can be reduced by topical corticosteroids.

Therapeutic uses of heparin beyond its traditional role as an anticoagulant

A number of physiological effects have been ascribed to heparin since its discovery almost 80 years ago, many of which are independent from its first-described and best- characterized activity as an anticoagulant. Heparin and heparan sulphate are believed to possess many biological activities that include the ability to modulate embryonic development, neurite outgrowth, tissue homeostasis, wound healing, metastasis, cell differentation, cell proliferation and inflammation. In this review, David Tyrell, Stephen Kilfeather and Clive Page examine some of the activities of heparin (and heparin derivatives) beyond its effects as an anticoagulant, and discuss the therapeutic potential of this old, but certainly not antiquated, drug.