Cellular interactions in aspirin-exacerbated respiratory disease

PURPOSE OF REVIEW

The purpose of this review is to summarize the complex cellular interactions of aspirin-exacerbated respiratory disease (AERD) and how these interactions promote pathogenic mechanisms of AERD.

RECENT FINDINGS

In addition to characteristic changes in eicosanoid levels, recent studies have identified increases in alarmin cytokines (IL-33, thymic stromal lymphopoietin) as well as activated innate lymphoid and plasma cell populations in samples from AERD patients.

SUMMARY

Patients with AERD typically demonstrate high levels of proinflammatory eicosanoids including cysteinyl leukotrienes (CysLTs) and prostaglandin D2 (PGD2) and hyporesponsiveness to prostaglandin E2 (PGE2). CysLTs are released by mast cells, eosinophils, and adherent platelets and promote epithelial release of IL-33, which activates mast cells and group 2 innate lymphoid cells (ILC2s) in concert with CysLTs. TSLP induces PGD2 release from mast cells which activates and recruits eosinophils, basophils, Th2 cells, and ILC2s via CRTH2. In turn, ILC2s and other cell types produce Th2 cytokines IL-4, IL-5, and IL-13 that, along with CysLTs and PGD2, promote bronchoconstriction, eosinophilic tissue inflammation, and mucus production.

Cell-Specific DNA Methylation Signatures in Asthma

Asthma is a complex trait, often associated with atopy. The genetic contribution has been evidenced by familial occurrence. Genome-wide association studies allowed for associating numerous genes with asthma, as well as identifying new loci that have a minor contribution to its phenotype. Considering the role of environmental exposure on asthma development, an increasing amount of literature has been published on epigenetic modifications associated with this pathology and especially on DNA methylation, in an attempt to better understand its missing heritability. These studies have been conducted in different tissues, but mainly in blood or its peripheral mononuclear cells. However, there is growing evidence that epigenetic changes that occur in one cell type cannot be directly translated into another one. In this review, we compare alterations in DNA methylation from different cells of the immune system and of the respiratory tract. The cell types in which data are obtained influences the global status of alteration of DNA methylation in asthmatic individuals compared to control (an increased or a decreased DNA methylation). Given that several genes were cell-type-specific, there is a great need for comparative studies on DNA methylation from different cells, but from the same individuals in order to better understand the role of epigenetics in asthma pathophysiology.

Aspergillus fumigatus-Secreted Alkaline Protease 1 Mediates Airways Hyperresponsiveness in Severe Asthma

The hallmark features of allergic asthma are type 2 (eosinophilic) inflammation and airways hyperresponsiveness (AHR). Although these features often comanifest in mouse lungs in vivo, we demonstrate in this study that the serine protease Alp1 from the ubiquitous mold and allergen, Aspergillus fumigatus, can induce AHR in mice unable to generate eosinophilic inflammation. Strikingly, Alp1 induced AHR in mice devoid of protease-activated receptor 2/F2 trypsin-like receptor 1 (PAR2/F2RL1), a receptor expressed in lung epithelium that is critical for allergic responses to protease-containing allergens. Instead, using precision-cut lung slices and human airway smooth muscle cells, we demonstrate that Alp1 directly increased contractile force. Taken together, these findings suggest that Alp1 induces bronchoconstriction through mechanisms that are largely independent of allergic inflammation and point to a new target for direct intervention of fungal-associated asthma.

Protective Role of Eosinophils and TNFa after Ozone Inhalation

Introduction

Exposure to ozone induces deleterious responses in the airways that include shortness of breath, inflammation, and bronchoconstriction. People with asthma have increased airway sensitivity to ozone and other irritants. Dr. Allison Fryer and colleagues addressed how exposure to ozone affects the immune and physiological responses in guinea pigs. Guinea pigs are considered a useful animal model for studies of respiratory and physiological responses in humans; their response to airborne allergens is similar to that in humans and shares some features of allergic asthma. Fryer and colleagues had previously observed that within 24 hours of exposure, ozone not only induced bronchoconstriction but also stimulated the production of new cells in the bone marrow, where all white blood cells develop. As a result of ozone exposure, increased numbers of newly synthesized white blood cells, particularly eosinophils, moved into the blood and lungs. The central hypothesis of the current study was that newly synthesized eosinophils recruited to the lungs 3 days after ozone exposure were beneficial to the animals because they reduced ozoneinduced bronchoconstriction. The investigators also hypothesized that the beneficial effect seen in normal (nonsensitized) animals was lost in animals that had been injected with an allergen, ovalbumin (sensitized). They also planned to explore the effects of inhibitors of certain cytokines (cellsignaling molecules). Immune responses in sensitized animals are dominated by a Th2 pattern, which is characterized by the synthesis of cytokines (interleukin [IL]-4, IL-5, and IL-13) and the Th2 subset of CD4+ T lymphocytes and the cells they activate (predominantly eosinophils, and B lymphocytes that switch to making immunoglobulin E [IgE]). Thus, sensitized animals were used as a model of allergic humans, whose immune responses tend to be dominated by IgE.

Approach

Fryer and colleagues exposed normal and sensitized (allergic) guinea pigs to 2 ppm ozone or filtered air for 4 hours and measured changes in cell numbers and airway responses 1 or 3 days later. They counted the numbers of eosinophils and other white blood cells (macrophages, neutrophils, and lymphocytes) in bone marrow, blood, and bronchoalveolar lung lavage fluid. The investigators also measured important physiological responses, including bronchoconstriction. Some animals were pretreated with etanercept and monoclonal anti-IL-5, which block tumor necrosis factor-a (TNFa) and IL-5, respectively. TNFa and IL-5 blockers have been used to treat patients with asthma. A key feature of the study was a technique to distinguish which white blood cells were synthesized after exposure from those that already existed, by injecting animals with bromodeoxyuridine (BrdU). BrdU is a thymidine analogue that is incorporated into the DNA of dividing cells, serving as a marker of newly produced cells. Therefore, a snapshot can be obtained of the proportion of newly synthesized (BrdU-positive) versus pre-existing (BrdU-negative) cell types.

Key results

1. Allergic and normal animals differed in the time course of bronchoconstriction and changes in cell types after ozone exposure. In normal animals, bronchoconstriction increased substantially at day 1 but decreased by day 3 after ozone exposure. In contrast, in allergic animals bronchoconstriction remained high at day 3. Ozone also increased the percentage of newly formed, BrdU2 positive eosinophils in the bone marrow and lungs of normal but not allergic animals. 2. Pretreatment with the TNFa blocker etanercept had complex effects, which differed between normal and allergic animals. In normal animals, etanercept decreased ozone-induced new synthesis of eosinophils in the bone marrow and blocked eosinophil migration to the lung; it also increased bronchoconstriction at day 3 (relative to day 1 without etanercept). In allergic animals, etanercept had no effect on any cell type in the bone marrow or lung after exposure to ozone and did not change bronchoconstriction compared with allergic animals not treated with etanercept. Etanercept tended to increase the numbers of blood monocytes and lymphocytes in air- and ozone-exposed normal and allergic animals at day 3, but had no effect on eosinophils in blood at this time point. This was one of the few statistically significant findings in the blood of exposed animals in the study. 3. Anti-IL-5 reduced bronchoconstriction at day 3 after exposure of allergic animals to ozone. In contrast, bronchoconstriction was greatly increased in normal animals treated with anti-IL-5.

Conclusions

Fryer and colleagues explored the airway and cellular responses in guinea pigs exposed to ozone. The HEI Review Committee, which conducted an independent review of the study, agreed that the findings supported the authors’ hypothesis (1) that exposure to ozone stimulates production of eosinophils in bone marrow, (2) that these newly formed eosinophils migrate to the lungs, and (3) that those eosinophils play a delayed but potentially beneficial role in reducing ozone-induced inflammation in the airways of healthy normal animals, but not in allergen-sensitized animals. The Committee also agreed that guinea pigs were a good model for studying responses to an allergen, because a major subtype of asthma (the high Th2 or allergic type) is associated with high levels of eosinophils in the blood. A novel finding was that the TNFa blocker etanercept decreased ozone-induced formation of eosinophils in the bone marrow and blocked eosinophil migration to the lung in normal animals. However, because injecting etanercept had little effect on eosinophils and did not decrease bronchoconstriction in allergic guinea pigs, the potential for treating patients with allergic asthma with TNFa blockers is uncertain. This is consistent with the poor performance of TNFa blockers in clinical studies of asthma treatment. Blocking the cytokine IL-5 with an anti-IL-5 antibody substantially decreased bronchoconstriction in sensitized animals. This suggests that therapies targeting IL-5 and eosinophils would be promising in at least some types of asthma. The Committee expressed caution toward experiments with cytokine blockers, both in animal models and humans, because such blockers are often not specific to a particular cell type and may differ at different sites in the body. Without further detailed confirmation of the effects of the blockers, interpreting these experiments can be challenging. The Committee concluded that the study by Fryer and colleagues raises several intriguing directions for future research, including exploring ways in which newly formed eosinophils differ from pre-existing ones, and how such findings apply to humans with allergy or asthma.

Expression of CysLT2 receptors in asthma lung, and their possible role in bronchoconstriction

BACKGROUND

The expression and functional role of CysLT2 receptors in asthma have not been clarified. In this study, we evaluated CysLT2 receptors expression, and effects of CysLT2-and CysLT1/2-receptor antagonists on antigen-induced bronchoconstriction using isolated lung tissues from both asthma and non-asthma subjects.

METHODS

CysLT1 and CysLT2 receptors expression in asthma and non-asthma lung tissue preparations was examined in immunohistochemistry experiments, and their functional roles in antigen-induced bronchoconstriction were assessed using ONO-6950, a dual CysLT1/2-receptor antagonist, montelukast, a CysLT1 receptor antagonist, and BayCysLT2RA, a CysLT2 receptor-specific antagonist.

RESULTS

CysLT1 receptors were expressed on the bronchial smooth muscle and epithelium, and on alveolar leukocytes in 5 in 5 non-asthma subjects and 2 in 2 asthma subjects. On the other hand, although degrees of CysLT2 receptors expression were variable among the 5 non-asthma subjects, the expression in the asthma lung was detected on bronchial smooth muscle, epithelium and alveolar leukocytes in 2 in 2 asthma subjects. In the non-asthma specimens, antagonism of CysLT2 receptors did not affect antigen-induced bronchial contractions, even after pretreatment with the CysLT1-receptor specific antagonist, montelukast. However, in the bronchus isolated from one of the 2 asthma subjects, antagonism of CysLT2 receptors suppressed contractions, and dual antagonism of CysLT1 and CysLT2 receptors resulted in additive inhibitory effect on anaphylactic contractions.

CONCLUSIONS

CysLT2 receptors were expressed in lung specimens isolated from asthma subjects. Activation of CysLT2 receptors may contribute to antigen-induced bronchoconstriction in certain asthma population.

Modulation of allergen-induced bronchoconstriction by fluticasone furoate and vilanterol alone or in combination

BACKGROUND

This placebo-controlled study assessed the effects of the once-daily inhaled corticosteroid (ICS) fluticasone furoate (FF) and long-acting beta(2) -agonist (LABA) vilanterol (VI) on early and late asthmatic responses (EAR/LAR) and airway hyper-responsiveness (AHR).

METHODS

Patients (n = 27) were randomized to FF (100 μg), VI (25 μg), FF/VI (100/25 μg), and placebo for 21 days (four periods). Allergen challenge was performed 1 h post-dose on day 21. AHR was assessed on day 22 using methacholine.

RESULTS

Allergen challenge caused an early change (0-2 h) in minimum forced expiratory volume in 1 s (FEV(1)) of -1.091 l (95% CI: -1.344; -0.837) following placebo therapy; changes were -0.955 l (-1.209; -0.702), -0.826 l (-1.070; -0.581), and -0.614 l (-0.858; -0.370) following VI, FF, or FF/VI therapy, respectively. Treatment differences were significant for all comparisons between therapies. Mean changes in 0-2 h %FEV(1) were as follows: -28.05 (placebo), -23.10 (VI), -22.33 (FF), and -16.10 (FF/VI). Following placebo, the late change (4-10 h) in weighted mean FEV(1) was -0.466 l (-0.589; -0.343) and -0.298 l (-0.415; -0.181) after VI, and was +0.018 l with both FF/VI (-0.089; 0.124) and FF (-0.089; 0.125). Treatment differences were significant for all comparisons between therapies except FF/VI vs FF. Mean changes in 4-10 h %FEV(1) were as follows: -21.08 (placebo), -14.30 (VI), -5.02 (FF), and -5.83 (FF/VI). AHR 24 h after allergen challenge was significantly reduced with FF/VI and FF vs placebo, and FF/VI was superior to either component.

CONCLUSION

Combined treatment with FF/VI provides additive protection from the EAR relative to its components, significant protection over VI alone from the LAR, and confers sustained protection from hyper-responsiveness 24 h post-dose.

Asthmatic airway neutrophilia after allergen challenge is associated with the glutathione S-transferase M1 genotype

RATIONALE

Asthma is a heterogeneous lung disorder characterized by airway inflammation and airway dysfunction, manifesting as hyperresponsiveness and obstruction. Glutathione S-transferase M1 (GSTM1) is a multifunctional phase II enzyme and regulator of stress-activated cellular signaling relevant to asthma pathobiology. A common homozygous deletion polymorphism of the GSTM1 gene eliminates enzyme activity.

OBJECTIVES

To determine the effect of GSTM1 on airway inflammation and reactivity in adults with established atopic asthma in vivo.

METHODS

Nineteen GSTM1 wild-type and eighteen GSTM1-null individuals with mild atopic asthma underwent methacholine and inhaled allergen challenges, and endobronchial allergen provocations through a bronchoscope.

MEASUREMENTS AND MAIN RESULTS

The influx of inflammatory cells, panels of cytokines and chemokines linked to asthmatic inflammation, F(2)-isoprostanes (markers of oxidative stress), and IgE were measured in bronchoalveolar lavage fluid at baseline and 24 hours after allergen instillation. Individuals with asthma with the GSTM1 wild-type genotype had greater baseline and allergen-provoked airway neutrophilia and concentrations of myeloperoxidase than GSTM1-null patients. In contrast, the eosinophilic inflammation was unaffected by GSTM1. The allergen-stimulated generation of acute-stress and proneutrophilic mediators, tumor necrosis factor-α, CXCL-8, IL-1β, and IL-6, was also greater in the GSTM1 wild-type patients. Moreover, post-allergen airway concentrations of IgE and neutrophil-generated mediators, matrix metalloproteinase-9, B-cell activating factor, transforming growth factor-β1, and elastase were higher in GSTM1 wild-type individuals with asthma. Total airway IgE correlated with B-cell activating factor concentrations. In contrast, levels of F(2)-isoprostane were comparable in both groups. Finally, GSTM1 wild-type individuals with asthma required lower threshold concentrations of allergen to produce bronchoconstriction.

CONCLUSIONS

The functional GSTM1 genotype promotes neutrophilic airway inflammation in humans with atopic asthma in vivo.

Increased mast cell density and airway responses to allergic and non-allergic stimuli in a sheep model of chronic asthma

Background

Increased mast cell (MC) density and changes in their distribution in airway tissues is thought to contribute significantly to the pathophysiology of asthma. However, the time sequence for these changes and how they impact small airway function in asthma is not fully understood. The aim of the current study was to characterise temporal changes in airway MC density and correlate these changes with functional airway responses in sheep chronically challenged with house dust mite (HDM) allergen.

Methodology/Principal Findings

MC density was examined on lung tissue from four spatially separate lung segments of allergic sheep which received weekly challenges with HDM allergen for 0, 8, 16 or 24 weeks. Lung tissue was collected from each segment 7 days following the final challenge. The density of tryptase-positive and chymase-positive MCs (MC_T and MC_TC respectively) was assessed by morphometric analysis of airway sections immunohistochemically stained with antibodies against MC tryptase and chymase.

MC_T and MC_TC density was increased in small bronchi following 24 weeks of HDM challenges compared with controls (P<0.05). The MC_TC/MC_T ratio was significantly increased in HDM challenged sheep compared to controls (P<0.05). MC_T and MC_TC density was inversely correlated with allergen-induced increases in peripheral airway resistance after 24 weeks of allergen exposure (P<0.05). MC_T density was also negatively correlated with airway responsiveness after 24 challenges (P<0.01).

Conclusions

MC_T and MC_TC density in the small airways correlates with better lung function in this sheep model of chronic asthma. Whether this finding indicates that under some conditions mast cells have protective activities in asthma, or that other explanations are to be considered requires further investigation.

Transgenic expression of human S100A12 induces structural airway abnormalities and limited lung inflammation in a mouse model of allergic inflammation

BACKGROUND

The calcium-binding protein S100A12 is highly up-regulated in the serum and sputum of patients with allergic asthma and is suggested to be a biomarker and pathologic mediator of asthma.

OBJECTIVE

To test the role of S100A12 in mediating airway inflammation in a mouse model of allergic lung inflammation.

METHODS

Transgenic (TG) mice that express human S100A12 and wild-type (WT) littermates were sensitized and challenged with ovalbumin (OVA) and assessed for inflammation, lung structure, and function.

RESULTS

Following OVA sensitization and challenge, S100A12 TG mice showed reduced peribronchial and perivascular inflammation, mucus production, and eosinophilia as well as attenuated airway responsiveness to contractile agonist compared with WT sensitized and challenged animals. This is explained, at least in part, by remodelled airways in S100A12 TG mice with thinning of the airway smooth muscle. S100A12 exposure induced Fas expression and activation of caspase 3 in cultured airway smooth muscle cells, suggesting that airway smooth muscle abnormalities observed in S100A12 TG mice may be mediated through myocyte apoptosis.

CONCLUSION AND CLINICAL RELEVANCE

S100A12 is one of the most abundant proteins found in the airways of human asthmatics, and it was postulated that S100A12 could mediate the inflammatory process. Our study shows for the first time that TG expression of S100A12 in the lung of mice does not exacerbate lung inflammation in a model of OVA-induced allergic inflammation. We speculate that the high levels of S100/calgranulins found in bronchoalveolar lavage fluid of asthmatics and of OVA-treated TG S100A12 mice do not significantly mediate pulmonary inflammation.

Swimming pool-induced asthma

A 13-year-old elite swimmer presented with wheezing after indoor swimming training. On the basis of her clinical history and the tests performed, exercise-induced asthma and mold-induced asthma were ruled out and a diagnosis of chlorine-induced asthma was made.

Nociceptin modulates bronchoconstriction induced by sensory nerve activation in mouse lung

Nociceptin/orphanin FQ (N/OFQ), the endogenous ligand for the N/OFQ peptide receptor (NOP), inhibits tachykinin release in the airway of several animal models. The aim of this study was to investigate the role of the N/OFQ-NOP receptor system in bronchoconstriction induced by sensory nerve activation in the isolated mouse lung. We used C57BL/6J NOP(+/+), NOP(-/-), and Balb/C mice sensitized (or not) to ovalbumin. Bronchopulmonary function coupled with measurements of endogenous N/OFQ levels before and after capsaicin-induced bronchoconstriction in the presence or absence of NOP-selective agonists/antagonists are presented. N/OFQ significantly inhibited capsaicin-induced bronchoconstriction in both naive and sensitized mice, these latter animals displaying airway hyperresponsiveness to capsaicin. The inhibitory effect of N/OFQ were not observed in NOP(-/-) mice, and were mimicked/abolished by the selective NOP agonist/antagonist University of Ferrara Peptide (UFP)-112/UFP-101 in NOP(+/+) mice. UFP-101 alone potentiated the effect of capsaicin in naive mice, but not in sensitized mice. Endogenous N/OFQ levels significantly decreased in sensitized mice relative to naive mice. We have demonstrated that a reduction in endogenous N/OFQ, or the lack of its receptor, causes an increase in capsaicin-induced bronchoconstriction, implying a role for the N/OFQ-NOP receptor system in the modulation of capsaicin effects. Moreover, for the first time, we document differential airway responsiveness to capsaicin between naive and sensitized mice due, at least in part, to decreased endogenous N/OFQ levels in sensitized mice.

Retinoic acid prevents virus-induced airway hyperreactivity and M2 receptor dysfunction via anti-inflammatory and antiviral effects

Inhibitory M(2) muscarinic receptors on airway parasympathetic nerves normally limit acetylcholine release. Viral infections decrease M(2) receptor function, increasing vagally mediated bronchoconstriction. Since retinoic acid deficiency causes M(2) receptor dysfunction, we tested whether retinoic acid would prevent virus-induced airway hyperreactivity and prevent M(2) receptor dysfunction. Guinea pigs infected with parainfluenza virus were hyperreactive to electrical stimulation of the vagus nerves, but not to intravenous acetylcholine, indicating that hyperreactivity was due to increased release of acetylcholine from parasympathetic nerves. The muscarinic agonist pilocarpine, which inhibits vagally mediated bronchoconstriction in control animals, no longer inhibited vagally induced bronchoconstriction, demonstrating M(2) receptor dysfunction. Treatment with all-trans retinoic acid (1 mg/kg) prevented virus-induced hyperreactivity and M(2) receptor dysfunction. However, retinoic acid also significantly reduced viral titers in the lungs and attenuated virus-induced lung inflammation. In vitro, retinoic acid decreased M(2) receptor mRNA expression in both human neuroblastoma cells and primary cultures of airway parasympathetic neurons. Thus, the protective effects of retinoic acid on airway function during viral infection appear to be due to anti-inflammatory and antiviral mechanisms, rather than to direct effects on M(2) receptor gene expression.

Radioresistant cells expressing TLR5 control the respiratory epithelium's innate immune responses to flagellin

Bacterial products (such as endotoxins and flagellin) trigger innate immune responses through TLRs. Flagellin-induced signalling involves TLR5 and MyD88 and, according to some reports, TLR4. Whereas epithelial and dendritic cells are stimulated by flagellin in vitro, the cell contribution to the in vivo response is still unclear. Here, we studied the respective roles of radioresistant and radiosensitive cells in flagellin-induced airway inflammation in mice. We found that i.n. delivery of flagellin elicits a transient change in respiratory function and an acute, pro-inflammatory response in the lungs, characterized by TLR5- and MyD88-dependent chemokine secretion and neutrophil recruitment. In contrast, TLR4, CD14 and TRIF were not essential for flagellin-mediated responses, indicating that TLR4 does not cooperate with TLR5 in the lungs. Respiratory function, chemokine secretion and airway infiltration by neutrophils were dependent on radioresistant, TLR5-expressing cells. Furthermore, lung haematopoietic cells also responded to flagellin by activating TNF-alpha production. We suggest that the radioresistant lung epithelial cells are essential for initiating early, TLR5-dependent signalling in response to flagellin and thus triggering the lung's innate immune responses.

Stress and airway reactivity in a murine model of allergic airway inflammation

Airway reactivity is a phenomenon with vast clinical implications in children. The regulation of airway reactivity is influenced by local and central mechanisms. In airway diseases like bronchial asthma, the pathological regulation of the airway caliber causes symptoms like cough and dyspnea. Stress has long been considered a powerful manipulator in the physiological regulation of the airways. To explore potential mechanisms linking stress to the exacerbation of asthma, we developed an animal model that combines allergic airway inflammation and exposure to stress. This review summarizes the experimental data obtained in our and similar mouse models. First, we describe the innervation and neuromediators in the airways, next we analyze the occurrence of airway hyperresponsiveness, and then we explore the phenomenon of stress to finally connect all of the topics in a synopsis.

[Fifty percent of pollinosis patients sensitive to birch pollen demonstrate bronchoconstriction during bronchial provocation test with the allergen]

Birch pollens are known as seasonal asthma precipitants. Our earlier studies evidenced a very high frequency of positive results bronchial allergen challenges in pollinosis patients sensitive to grass pollen. The aim of the study was to evaluate how often the bronchial challenge with birch pollen allergen causes bronchoconstriction.

MATERIAL AND METHODS

Studies were performed outside of pollen season on 30 patients sensitive to birch pollen allergen. Before the allergen challenges bronchial provocation tests with methacholine were performed in all subjects.

RESULTS

About 13% of examined group had bronchial hyperreactivity (PC20FEV1Mch < 8 mg/ml) and 50% demonstrated bronchoconstriction after birch pollen allergen inhalation.

CONCLUSIONS

About 13 percent of patients sensitive to birch pollen demonstrated nonspecific hyperrectivity out of pollen season. Bronchial birch allergen challenge tests are positive in about half of birch sensitive patients with pollinosis.

Effects of selective and non-selective COX inhibitors on antigen-induced release of prostanoid mediators and bronchoconstriction in the isolated perfused and ventilated guinea pig lung

The contribution of cycloxygenase (COX)-1 and COX-2 in antigen-induced release of mediators and ensuing bronchoconstriction was investigated in the isolated perfused guinea pig lung (IPL). Antigen challenge with ovalbumin (OVA) of lungs from actively sensitised animals induced release of thromboxane (TX)A(2), prostaglandin (PG)D(2), PGF(2)(alpha), PGI(2) and PGE(2), measured in the lung effluent as immunoreactive TXB(2), PGD(2)-MOX, PGF(2)(alpha), 6-keto PGF(1)(alpha) and PGE(2), respectively. This release was abolished by the non-selective COX inhibitor flurbiprofen (10 microM). In contrast, neither the selective COX-1 inhibitor FR122047 nor the selective COX-2 inhibitor celecoxib (10 microM each) significantly inhibited the OVA-induced bronchoconstriction or release of COX products, except for PGD(2). Another non-selective COX inhibitor, diclofenac (10 microM) also significantly inhibited antigen-induced bronchoconstriction. The data suggest that both COX isoenzymes, COX-1 and COX-2 contribute to the immediate antigen-induced generation of prostanoids in IPL and that the COX-1 and COX-2 activities are not associated with different profiles of prostanoid end products.

Human bronchial epithelial cells express an active and inducible biosynthetic pathway for leukotrienes B4 and C4

BACKGROUND

Human bronchial epithelial cells synthesize cyclooxygenase and 15-lipoxygenase products, but the 5-lipoxygenase (5-LO) pathway that generates the leukotriene (LT) family of bronchoconstrictor and pro-inflammatory mediators is thought to be restricted to leucocytes.

OBJECTIVE

We hypothesized that human bronchial epithelial cells (HBECs) express a complete and active 5-LO pathway for the synthesis of LTB4 and LTC4, either constitutively or after stimulation.

METHODS

Flow cytometry, RT-PCR, Western blotting, enzyme immunoassays and reverse-phase high-performance liquid chromatography were used to investigate constitutive and stimulated expression of 5-LO pathway enzymes and the synthesis of LTs B4 and C4 in primary HBECs and in the 16-HBE 14o- cell line.

RESULTS

Constitutive mRNA and protein expression for 5-LO, 5-LO-activating protein (FLAP), LTA4 hydrolase and LTC4 synthase were demonstrated in primary HBECs and in the 16-HBE 14o- cell line. In 16-HBE 14o- cells, treatment with calcium ionophore A23187, bradykinin or LPS up-regulated the expression of these enzymes. The up-regulation of 5-LO was blocked by the anti-inflammatory glucocorticoid dexamethasone. Human bronchial epithelial cells were shown to generate bioactive LTs, with primary HBECs generating 11-fold more LTC4 and five-fold more LTB4 than 16-HBE 14o- cells. LT production was enhanced by ionophore treatment and blocked by the FLAP inhibitor MK-886.

CONCLUSIONS

Expression of an active and inducible 5-LO pathway in HBEC suggests that damaged or inflamed bronchial epithelium may synthesize LTs that contribute directly to bronchoconstriction and leucocytosis in airway inflammation.

The allergen bronchoprovocation model: an important tool for the investigation of new asthma anti-inflammatory therapies

Allergen bronchoprovocation tests have been used for more than two decades in the investigation of respiratory allergic diseases such as asthma and rhinitis. These bronchial challenges are now well standardized and can offer key information on the therapeutic potential of new agents and on their anti-inflammatory effects on the airways. Both standard and low-dose allergen provocations are safe when performed by experienced investigators and do not lead to persistent worsening of asthma or change in airway function. The evaluation of new therapeutic agents by these methods can also provide important information on the mechanisms of development and persistence of airway diseases.

Influence of total IgE levels on the severity of sting reactions in Hymenoptera venom allergy

BACKGROUND

Detection of specific IgE for Hymenoptera venoms and skin tests are well established diagnostic tools for the diagnosis of insect venom hypersensitivity. The aim of our study was to analyze the effect of total IgE levels on the outcome of generalized anaphylactic reactions after a Hymenoptera sting.

METHODS

Two hundred and twenty patients allergic to bee, wasp, or European hornet venom were included in the study. Their specific and total IgE levels, serum tryptase levels, skin tests, and sting history were analyzed.

RESULTS

In patients with mild reactions (grade I, generalized skin symptoms) we observed higher total IgE levels (248.0 kU/l) compared to patients with moderate reactions (grade II, moderate pulmonary, cardiovascular, or gastrointestinal symptoms; 75.2 kU/l) and severe reactions (grade III, bronchoconstriction, emesis, anaphylactic shock, or loss of consciousness; 56.5 kU/l; P < 0.001). Accordingly, 25% of the patients with low levels of total IgE (<50 kU/l), but no individual with total IgE levels >250 kU/l, developed loss of consciousness (P = 0.001). Additionally, specific IgE levels were related to total IgE levels: Specific IgE levels increased from 1.6 to 7.1 kU/l in patients with low (<50 kU/l) and high (>250 kU/l) total IgE levels, respectively (P < 0.001). Specific IgE levels correlated inversely to the clinical reaction grades, however, this trend was not statistically significant (P = 0.083).

CONCLUSION

Patients with Hymenoptera venom allergy and high levels (>250 kU/l) of total IgE, predominantly develop grade I and grade II reactions and appear to be protected from grade III reactions. However, this hypothesis should be confirmed by extended studies with sting challenges.

Dose-dependent recruitment of CD25+ and CD26+ T cells in a novel F344 rat model of asthma

The ovalbumin (OVA)-induced airway inflammation in rats is a commonly used model to explore the pathobiology of asthma. However, its susceptibility varies greatly between rat strains, and presently Brown Norway (BN) rats are preferentially used. Since recruitment of T cells to the lungs depends on the CD26 (dipeptidyl peptidase IV, DPPIV) expression, Fischer 344 strain (F344) rats are a highly relevant rat strain, in particular because CD26-deficient substrains are available. To establish a F344 rat model of asthma, we challenged F344 rats using different doses of aerosolized antigen (0%, 1%, 2.5%, 5%, and 7.5% OVA) and compared these effects with intratracheal instillation of OVA (1.5 mg/0.3 ml). Asthmoid responsiveness was determined by analysis of early airway responsiveness (EAR), antigen-specific IgE levels, as well as airway inflammation including the composition of T cell subpopulations in the bronchoalveolar lavage (BAL) and lung tissue with special respect to the T cell activation markers CD25 and CD26. Even low allergen doses caused allergen-specific EAR and increases of antigen-specific IgE levels. However, EAR and IgE levels did not increase dose dependently. Higher concentrations of OVA led to a dose-dependent increase of several immunological markers of allergic asthma including an influx of eosinophils, T cells, and dendritic cells. Interestingly, a dose-dependent increase of CD4(+)/CD25(+)/CD26(+) T cells was found in the lungs. Summarizing, we established a novel F344 rat model of aerosolized OVA-induced asthma. Thereby, we found a dose-dependent recruitment of cellular markers of allergic asthma including the activated CD4(+)/CD25(+)/CD26(+) T cell subpopulation, which has not been described in asthma yet.

Efficacy of IL-13 neutralization in a sheep model of experimental asthma

IL-13 contributes to airway hyperresponsiveness, mucus secretion, inflammation, and fibrosis, suggesting that it plays a central role in asthma pathogenesis. Neutralization of IL-13 with sIL-13Ralpha2-Fc (sIL-13R) reduces allergen-induced airway responses in rodent models of respiratory disease, but its efficacy in a large animal model has not been previously reported. In this study, we determined whether two different strategies for IL-13 neutralization modified experimental asthma in sheep. Sheep with natural airway hypersensitivity to Ascaris suum antigen were treated intravenously either with sIL-13R, a strong antagonist of sheep IL-13 bioactivity in vitro, or with IMA-638 (IgG1, kappa), a humanized antibody to human IL-13. Higher doses of IMA-638 were used because, although it is a potent antagonist of human IL-13, this antibody has 20 to 30 times lower binding and neutralization activity against sheep IL-13. Control animals received human IgG of irrelevant specificity. Sheep were treated 24 h before inhalation challenge with nebulized A. suum. The effects on antigen-induced early and late bronchial responses, and antigen-induced hyperresponsiveness, were assessed. Both sIL-13R and IMA-638 provided dose-dependent inhibition of the antigen-induced late responses and airway hyperresponsiveness. The highest dose of IMA-638 also reduced the early phase response. These findings suggest that IL-13 contributes to allergen-induced airway responses in this sheep model of asthma, and that neutralization of IL-13 is an effective strategy for blocking these A. suum-induced effects.

Bronchodilatory effects of the aqueous extract of Gynostemma pentaphyllum and gypenosides III and VIII in anaesthetized guinea-pigs

The bronchodilatory activity of the aqueous extract of Gynostemma pentaphyllum Makino leaves was investigated in anaesthetized guinea-pigs and compared with two of its isolated gypenosides (III and VIII). The results showed that the intravenous administration of the decoction of G. pentaphyllum (2.5, 5 or 10 mg kg(-1)) decreased bronchial resistance in basal conditions and significantly (P < 0.01) reduced (68% inhibition) the bronchoconstrictor action of histamine. Furthermore, the extract antagonized (80% inhibition) the bronchoconstrictor response induced by the antigen in sensitized guinea-pigs. Gypenosides III (0.7 mg kg(-1), i.v.) and VIII (0.3 mg kg(-1), i.v.) caused a similar protective effect in both experimental models used; however, the duration and the intensity of the action was less than that of the extract containing corresponding quantities of gypenosides III and VIII. This study confirmed the validity of the traditional use of this plant in the treatment of asthma and other respiratory disorders.

Roflumilast inhibition of pulmonary leukotriene production and bronchoconstriction in ovalbumin-sensitized and -challenged Guinea pigs

This study investigated the effects of roflumilast, a PDE4 inhibitor, on slow-reacting substance of anaphylaxis (SRS-A)-mediated bronchoconstriction and pulmonary leukotriene (LT) release in ovalbumin (OVA)-sensitized and -challenged guinea pigs. Animals were treated with roflumilast orally (0.04, 0.12, 0.4, or 4 mg/kg) or placebo 1 hour before OVA challenge. Bronchoconstriction was quantified by measuring airway conductance (Gaw) and dynamic lung compliance (Cdyn). Roflumilast significantly attenuated the decrease in Gaw (50% inhibitory dose [ID50] = 0.33 mg/kg) and Cdyn (ID50 = 0.25 mg/kg) in a dose-dependent manner and significantly inhibited Cys-LT (ID50 = 0.06 mg/kg) and LTB4 (ID50 = 0.05 mg/kg) release versus placebo-treated animals. Roflumilast did not affect LTD4-induced bronchoconstriction. These findings support the role of roflumilast as an anti-inflammatory treatment for asthma.

Effects of various anti-asthmatic agents on mite allergen-pulsed murine bone marrow-derived dendritic cells

BACKGROUND

Dendritic cells (DCs) play an important role in the immune response and are critically involved in asthma. beta2-agonists could potentially exacerbate type 2 T helper (Th2) cell-mediated immune response.

OBJECTIVES

To determine the effects of various anti-asthmatic agents on DCs function both in vitro and in vivo.

METHODS

Murine bone marrow-derived DCs were pulsed with mite allergen in the presence of pranlukast, salbutamol, salmeterol or fluticasone. These DCs were then inoculated intranasally into naïve mice to induce allergic airway inflammation in vivo.

RESULTS

Pranlukast reduced IL-10 and increased IL-12, while fluticasone reduced both IL-10 and IL-12 production by mite allergen-pulsed DCs. Allergic airway inflammation in pranlukast- and fluticasone-treated and mite allergen pulsed DCs-harbouring mice was attenuated and such response was associated with inhibition of Th2 response in the airway. Salbutamol did not alter cytokine production, while salmeterol reduced IL-12 production by mite allergen-pulsed DCs. Lung pathology in beta2-agonist-harbouring mice was comparable with those of mite allergen-pulsed DCs-harbouring mice.

CONCLUSIONS

Our results indicate that leukotriene receptor antagonists and corticosteroids inhibit DCs-induced Th2 skewed immune response, and that short- and long-acting beta2-agonists do not modify DCs-induced allergic airway inflammation.

Comparison of early and late responses to antigen of sensitized guinea pig parenchymal lung strips

The peripheral lung parenchyma has been studied as a component of the asthmatic inflammatory response. During induced constriction, tissue resistance increases in different asthma models. Approximately 60% of the asthmatic patients show early and late responses. The late response is characterized by more severe airway obstruction. In the present study, we evaluated lung parenchymal strips mechanics in ovalbumin-sensitized guinea pigs, trying to reproduce both early and late inflammatory responses. Oscillatory mechanics of lung strips were performed in a control group (C), in an early response group (ER), and in two late response groups: 17 h (L1) and 72 h (L2) after the last ovalbumin challenge. Measurements of resistance and elastance were obtained before and after ovalbumin challenge in C and ER groups and before and after acetylcholine challenge in all groups. Using morphometry, we assessed the density of eosinophils and smooth muscle cells, as well as collagen and elastin content in lung strips. The baseline and postagonist values of resistance and elastance were increased in ER, L1, and L2 groups compared with C (P < or = 0.001). The morphometric analysis showed an increase in alveolar eosinophil density in ER and L2 groups compared with C (P < 0.05). There was a significant correlation between eosinophil density in parenchymal strips of C, L1, and L2 groups and values of resistance and elastance postacetylcholine (r = 0.71, P = 0.001 and r = 0.74, P < 0.001, respectively). The results show that the lung parenchyma is involved in the late response, and the constriction response in this phase is related to the eosinophilic inflammation.

Effect of omalizumab on adenosine 5'-monophosphate responsiveness in subjects with allergic asthma

BACKGROUND

The objective of this study was to evaluate the effects of omalizumab on bronchoconstriction induced by methacholine and adenosine 5'-monophosphate (AMP).

METHODS

Thirty-four subjects with mild to moderate allergic asthma were randomized to receive placebo (n = 16) or omalizumab (n = 18) subcutaneously during 12 weeks. Airway responsiveness to AMP was measured at baseline and after 4 and 12 weeks of treatment, whereas the response to methacholine was measured at baseline and after 12 weeks of treatment.

RESULTS

After 4 weeks of treatment, the increase in AMP PC(20) (provocative concentration required to produce a 20% fall in FEV(1)) was significantly greater in the omalizumab group than in the placebo group, the mean difference in the change between the groups being 1.52 doubling concentrations (95% CI, 0.25-2.79, p = 0.02). Compared with baseline, the mean AMP PC(20) values at 12 weeks were increased by 1.91 doubling concentrations with omalizumab (p < 0.001) and 1.01 doubling concentrations with placebo (p = 0.16), but changes were not significantly different between the treatment groups. Changes in methacholine PC(20) values were not significantly different between the omalizumab and placebo groups.

CONCLUSIONS

In subjects with allergic asthma, omalizumab reduces the response to AMP without decreasing the response to methacholine. These findings are consistent with the conclusion that the contribution of IgE to the development of AMP bronchoconstriction is more important than their role in the induction of methacholine hyperresponsiveness.

Early- and late-phase bronchoconstriction, airway hyper-reactivity and cell influx into the lungs, after 5'-adenosine monophosphate inhalation: comparison with ovalbumin

BACKGROUND

Antigen inhalation in atopic asthmatic patients results in an early asthmatic response (EAR), accompanied by a late asthmatic response (LAR) in 60% of patients. Inhaled 5'-adenosine monophosphate (5'-AMP) causes immediate bronchoconstriction in asthmatics but not in normal subjects.

OBJECTIVES

The aims of this study were to investigate whether 5'-AMP can produce a LAR, airway hyper-reactivity (AHR) and cell influx to the lungs, in a sensitized guinea-pig model of asthma, and to compare with the profile of activity after ovalbumin (OVA) inhalation.

METHODS

Airway responses to inhaled OVA (10 microg/mL) and 5'-AMP (3 and 300 mm) of actively sensitized, conscious guinea-pigs were determined by whole body plethysmography as the change in specific airway conductance (sGaw). Inhaled histamine (1 mm) was used to investigate AHR, and cell influx was determined by bronchoalveolar lavage (BAL).

RESULTS

Exposure to OVA revealed an EAR, and LAR at 6 h post-challenge. AHR to histamine occurred 24 h after challenge together with a significant increase in total and differential (eosinophils and macrophages) cell counts. Low dose 5'-AMP (3 mm) produced an EAR, LAR at 6 h after challenge, and AHR to histamine 12 h post-challenge. No AHR occurred 24 h after inhalation. Total and macrophage cell counts were increased significantly 6, 12 and 24 h after exposure. Bronchodilatation followed high dose 5'-AMP (300 mm), followed by a LAR at 6 h. AHR to histamine occurred 12 h after challenge, but not at 24 h. A significant increase in total and differential (eosinophils and macrophages) cell counts occurred 6, 12 and 24 h post-exposure. No changes were observed in non-sensitized guinea-pigs.

CONCLUSION

OVA challenge revealed an EAR, LAR, cell influx and AHR in a guinea-pig model of asthma. This study demonstrated for the first time that a LAR and AHR to histamine can be revealed following 5'-AMP inhalation, in sensitized but not unsensitized guinea-pigs. Cell influx at 6, 12 and 24 h post-challenge suggests that it may be associated with the LAR and AHR.

Effects of Ding-Chuan-Tang on bronchoconstriction and airway leucocyte infiltration in sensitized guinea pigs

Ding-Chuan-Tang (DCT), a traditional Chinese medicine, has been used in treatment of the bronchial asthma for several centuries. However, the therapeutic mechanism of these Chinese medicine are still far from clear. To understand the mechanism of antiasthmatic property of DCT. A guinea pig model of allergic asthma was used to investigate the effects of DCT on ovalbumin-induced early and late asthmatic responses and airway inflammation, particularly the extent of eosinophil infiltration, and examine it direct beta2-adrenoceptor agonist activity in guinea-pig isolated trachea. We had used three different protocals in ovalbumin sensitized guinea pigs by administrating 10 g/kg of DCT extracts to sensitized guinea pigs 30 min before antigen challenge (group I), 5 hr after antigen challenge (group II) and 2.5 g/kg once daily from the day of sensitization to the day of challenge. Our result showed that administration of DCT singificantly inhibited the antigen induced immediate asthmatic responses (IAR) in group I and inhibited both IRA and late asthmatic responses (LAR) in actively sensitized guinea pig in group III. DCT caused concentration-dependent relaxations in strips of guinea pig trachea contracted with carbachol, however ICI-118551, a selective beta2-adrenoceptor antagonist, didn't significantly competitively inhibit the relaxations caused by DCT. Furthermore, examination of bronchoalveolar lavage fluid (BALF) revealed that DCT significantly inhibited the increase in percent of eosinophils in the airway after antigen challenge in three group. Histopathologic examination showed DCT suppressed the eosinophil infiltration into lung tissue. These results suggest that the antiasthmatic effect of DCT is mainly due to its bronchodilatation effect and its ability to inhibit the eosinophil into the airway and there is prophylactic effect of DCT on allergen-induced airway inflammation.

Adrenal influences on the inhibitory effects of procaterol, a selective Beta-two-adrenoceptor agonist, on antigen-induced airway microvascular leakage and bronchoconstriction in Guinea pigs

While the guinea pig has been the preferred choice for use as a model of allergic bronchial asthma in the evaluation of anti-asthmatic drugs, it has been shown that antigen-induced bronchoconstriction in guinea pigs is attenuated by epinephrine released from the adrenal gland. In order to investigate the possible influence of the adrenal gland on the effects of antiexudative and bronchodilative drugs on antigen-induced airway responses, we examined the inhibitory effects of procaterol, a selective beta(2)-adrenoceptor agonist, on antigen-induced airway microvascular leakage and bronchoconstriction in adrenalectomized guinea pigs and compared them with the drug's effects in sham-operated animals. Guinea pigs sensitized passively with anti-ovalbumin (OA) guinea-pig serum were adrenalectomized or sham-operated under urethane anesthesia and examined 30 min after surgery in the following experiments. (1) Animals were intravenously administered Evans blue dye to quantify airway plasma exudation, and then OA was inhaled for 10 min while measuring pulmonary inflation pressure, a parameter of bronchoconstriction. Procaterol (1, 3, 10, or 30 microg/kg) or saline (control) was administered into the airways 10 min prior to OA inhalation. The amount of extravasated Evans blue dye in the airways was calculated. (2) Venous blood samples were collected during OA or saline inhalation and plasma catecholamine levels were compared. In control animals, OA-induced increases in both the amount of Evans blue dye and in pulmonary inflation pressure were markedly greater in adrenalectomized animals than in sham-operated animals. Procaterol dose-dependently inhibited OA-induced airway microvascular leakage and bronchoconstriction, and its effects were more potent in adrenalectomized animals (significant at 1 microg/kg and higher) than in sham-operated animals (significant at 10 microg/kg and higher). Although the plasma concentration of epinephrine during OA inhalation was approximately 3 times higher than that during saline inhalation in sham-operated animals, no difference was seen in adrenalectomized animals. In conclusion, while procaterol essentially possesses pronounced inhibitory effects on antigen-induced airway microvascular leakage and bronchoconstriction in guinea pigs, the effects are considerably masked by epinephrine released from the adrenal gland.

Mast cell mediator release in nonasthmatic subjects after endobronchial adenosine challenge

BACKGROUND

Adenosine 5'-monophosphate (AMP) has been shown to cause bronchoconstriction in atopic subjects but to have no effect on nonatopic nonasthmatic subjects. Endobronchial AMP challenge has previously been shown to cause mast cell mediator release in asthmatic subjects, but it is unknown whether a similar response occurs in atopic nonasthmatic and nonatopic nonasthmatic control subjects who have no response to inhalation AMP challenge.

OBJECTIVE

This study examined the change in mast cell-derived products after endobronchial saline challenge and AMP challenge in subjects with and without a positive inhalation response to AMP.

METHODS

Inhalation challenge with AMP challenge was performed in normal, atopic nonasthmatic, and atopic asthmatic subjects. Levels of mast cell mediators were measured after endobronchial adenosine challenge and after placebo endobronchial saline challenge.

RESULTS

There were significant increases in histamine, tryptase, protein, and prostaglandin D2 levels (P=.02, P=.02, P=.01, and P=.01, respectively) after AMP challenge compared with after saline challenge in nonatopic nonasthmatic subjects. There was no significant increase in any mediator in either of the other 2 groups.

CONCLUSION

This study suggests dissociation between mediator release and bronchoconstriction in response to AMP.

Airway eosinophil accumulation on sensory neuropeptide release in a guinea pig model of distilled-water-induced bronchoconstriction

BACKGROUND

Increased numbers of eosinophils in the airways is characteristic of asthma. However, it remains unclear whether airway eosinophils enhance or reduce the release of neuropeptides in the airways in vivo. This study was conducted to elucidate the influence of airway eosinophil accumulation on the ultrasonically nebulized distilled water (UNDW)-induced bronchoconstriction in our newly developed animal model, which is mediated by sensory neuropeptides.

METHODS

Guinea pigs were transnasally treated with 100 mg/kg of platelet activating factor (PAF), or vehicle, twice a week for 3 weeks. We then conducted three experiments. In the first, UNDW was inhaled 20 min after aerosolized antigen challenge, and bronchoalveolar lavage (BAL) was performed in PAF-treated and passively sensitized animals. In the second, PAF-treated animals were exposed for 20 s to ascending doses of methacholine at intervals of 5 min In the third, passively sensitized animals were administered selective NK1 antagonist, SR 140333, selective NK2 antagonist, SR 48968, or vehicle, intravenously 5 min before UNDW-induced bronchoconstriction.

RESULTS

The proportion of eosinophils in BAL fluid was significantly increased in guinea pigs treated with PAF, compared with the vehicle. The PAF treatment did not affect antigen-induced immediate asthmatic response, UNDW-induced bronchoconstriction, or bronchial responsiveness to inhaled methacholine. SR 140333, but not SR 48968, inhibited the UNDW-induced bronchoconstriction.

CONCLUSION

We conclude that eosinophils accumulated in the airways, caused by repeated intranasal administration of PAF, does not affect the release of substance P induced by UNDW inhalation, or the action of released substance P in vivo.

Neurokinin-1 receptor mediates stress-exacerbated allergic airway inflammation and airway hyperresponsiveness in mice

BACKGROUND

A wealth of clinical observation has suggested that stress and asthma morbidity are associated. We have previously established a mouse model of stress-exacerbated allergic airway inflammation, which reflects major clinical findings.

OBJECTIVE

The aim of the current study was to investigate the role of the neurokinin- (NK-)1 receptor in the mediation of stress effects in allergic airway inflammation.

METHODS

BALB/c mice were systemically sensitized with ovalbumin (OVA) on assay days 1, 14, and 21 and repeatedly challenged with OVA aerosol on days 26 and 27. Sound stress was applied to the animals for 24 hours, starting with the first airway challenge. Additionally, one group of stressed and one group of nonstressed mice received the highly specific NK-1 receptor antagonist RP 67580. Bronchoalveolar lavage fluid was obtained, and cell numbers and differentiation were determined. Airway hyperreactivity was measured in vitro by electrical field stimulation of tracheal smooth-muscle elements.

RESULTS

Application of stress in sensitized and challenged animals resulted in a significant increase in leukocyte number in the bronchoalveolar lavage fluid. Furthermore, stressed animals showed enhanced airway reactivity. The increase of inflammatory cells and airway reactivity was blocked by treatment of animals with the NK-1 receptor antagonist.

CONCLUSION

These data indicate that the NK-1 receptor plays an important role in mediating stress effects in allergen-induced airway inflammation.

Role of macrophages in virus-induced airway hyperresponsiveness and neuronal M2 muscarinic receptor dysfunction

Viral infections exacerbate asthma. One of the pathways by which viruses trigger bronchoconstriction and hyperresponsiveness is by causing dysfunction of inhibitory M(2) muscarinic receptors on the airway parasympathetic nerves. These receptors normally limit acetylcholine (ACh) release from the parasympathetic nerves. Loss of M(2) receptor function increases ACh release, thereby increasing vagally mediated bronchoconstriction. Because viral infection causes an influx of macrophages into the lungs, we tested the role of macrophages in virus-induced airway hyperresponsiveness and M(2) receptor dysfunction. Guinea pigs infected with parainfluenza virus were hyperresponsive to electrical stimulation of the vagus nerves but not to intravenous ACh, indicating that hyperresponsiveness was due to increased release of ACh from the nerves. In addition, the muscarinic agonist pilocarpine no longer inhibited vagally induced bronchoconstriction, indicating M(2) receptor dysfunction. Treating animals with liposome-encapsulated dichloromethylene-diphosphonate depleted macrophages as assessed histologically. In these animals, viral infection did not cause airway hyperresponsiveness or M(2) receptor dysfunction. These data suggest that macrophages mediate virus-induced M(2) receptor dysfunction and airway hyperresponsiveness.

The lung as a privileged site for the beneficial actions of PGE2

Prostaglandin E2 (PGE2) is commonly considered a potent proinflammatory mediator and is involved in several inflammatory diseases. In the lung, as opposed to many other parts of the body, PGE2 has a role in limiting the immune-inflammatory response as well as tissue repair processes. Understanding the full implications of the regulatory role of PGE2 and how beneficial processes, such as inflammation and tissue repair, become dysregulated to the point of causing disease, might disclose new perspectives in the treatment of pulmonary diseases.

The effect of anti-integrin monoclonal antibodies on antigen-induced pulmonary inflammation in allergic rabbits

The integrin adhesion molecules are involved in the recruitment and activation of inflammatory cells at sites of inflammation in a variety of diseases. In the present study, we have investigated the effects of blocking monoclonal antibodies (mAbs) directed against CD49d (alpha(4) integrin), CD18 (beta(2) integrin) and the alpha sub-units of beta(2) integrin CD11a (LFA-1 integrin) and CD11b (Mac-1 integrin), on antigen (Ag)-induced acute bronchoconstriction and cellular recruitment in allergic rabbits in vivo. Inhaled Ag (Alternaria tenuis) challenge of neonatally sensitised rabbits caused an acute bronchoconstriction demonstrated by an increase in lung resistance (R(L)) and decrease in dynamic compliance (C(dyn)) and pulmonary inflammation characterised by an increase in bronchoalveolar lavage (BAL) inflammatory cells, particularly eosinophils, 24 h after challenge. Pre-treatment with the anti-CD49d mAb (Max-68P), significantly inhibited the Ag-induced acute bronchoconstriction in terms of R(L) and (C(dyn)). Treatment with the other anti-integrin mAbs had no effect on the acute bronchoconstriction after inhaled Ag challenge.Pre-treatment with the anti-integrin mAbs had differential effects in blocking the recruitment of inflammatory cells 24 h after inhaled Ag in the allergic rabbits. The data show that in the allergic rabbit model of asthma, VLA-4 (CD49d/CD29) only, is involved in the acute bronchoconstriction, suggesting an involvement of mast cell degranulation. Furthermore, eosinophil recruitment and activation appears to be mediated by a combination of VLA-4 (CD49d/CD29) and LFA-1 (CD18/CD11a). However in contrast, lymphocyte recruitment appears to be mediated by a combination of LFA-1 (CD18/CD11a) and Mac-1 (CD18/CD11b).

The early allergic response in small airways of human precision-cut lung slices

To study the role of small airways in the early allergic response (EAR), the method of human precision-cut lung slices (PCLS) was developed and used to examine the bronchoconstriction elicited by passive sensitisation and allergen provocation. Viable human PCLS of 250-microm thickness containing airways <1.5 mm in outer diameter were prepared from lung lobes obtained from lung resection and taken into culture. According to the low release of lactate dehydrogenase and the constant ciliary beat frequency, human PCLS were viable for at least 3 days. Following overnight passive sensitisation with serum from allergic individuals, administration of grass-pollen extract or activating immunoglobulin E antibody resulted in immediate airway contraction that was quantified by videomicroscopy. The extent of the EAR increased with decreasing airway size (outer airway diameter), with the strongest response occurring in the terminal bronchioles. Histamine receptor antagonism was ineffective, and leukotriene or thromboxane receptor antagonism attenuated the early allergic response only in some cases. However, simultaneous blockade of leukotriene and thromboxane receptors almost completely prevented the early allergic response in the precision-cut lung slices from all individuals, suggesting such a dual treatment as a potential future asthma therapy.

Accentuated T helper type 2 airway response after allergen challenge in cyclooxygenase-1-/- but not cyclooxygenase-2-/- mice

Acute pharmacologic inhibition of cyclooxygenase (COX)-1 or -2 during allergen sensitization and exposure leads to enhanced T helper type 2 (Th2) airway responses. COX-1 and -2 play functionally distinct roles in lymphocyte development, and consequently, genetic deficiency of either enzyme, as opposed to acute pharmacologic inhibition, may modulate Th2-mediated allergic airway disease differently. An ovalbumin-induced mouse model of allergic airway disease was used. The immunophenotype of bronchoalveolar lavage lymphocytes was assessed by flow cytometry, bronchoalveolar lavage cytokines, and chemokines were measured by enzyme-linked immunosorbent assay, adhesion molecule expression was assessed by immunoblotting in combination with immunohistochemistry, and bronchoconstriction was assessed by whole body plethysmography. The airways of COX-1-/- mice contained increased numbers of CD4+ and CD8+ T cells, exaggerated levels of the Th2 cytokines interleukin-4, -5, and -13, and increased levels of eotaxin and thymus- and activation-regulated chemokine. Allergen-induced bronchoconstriction was also increased in COX-1-/- mice. Vascular cell adhesion molecule-1 and intercellular adhesion molecule-1 levels were increased in lungs of both COX-1-/- and COX-2-/- mice relative to wild type. These data suggest that genetic deficiency of COX-1 but not COX-2 modulates T cell recruitment, Th2 cytokine secretion, and lung function in the allergic airway.

Implication of the bradykinin receptors in antigen-induced pulmonary inflammation in mice

1. The involvement of bradykinin (BK) receptors in the allergic inflammation associated with airway hyper-reactivity (AHR) was evaluated by means of the selective bradykinin B(1) receptor (BKB(1)-R) antagonists R-715 (Ac-Lys-[D-betaNal(7), Ile(8)]desArg(9)-BK) and R-954 (Ac-Orn[Oic(2), alpha-MePhe(5), D-betaNal(7), Ile(8)]desArg(9)-BK) or the selective bradykinin B(2) receptor (BKB(2)-R) antagonist HOE-140 (D-Arg(0)-Hyp(3)-Thi(5)-D-Tic(7)-Oic(8)-BK). Cellular migration and AHR were examined 24 h after the second ovalbumin (OA) challenge. 2. R-715 (10-500 microg kg(-1)) and R-954 (1-100 microg kg(-1)) injected intravenously (i.v.), 5 min prior to aerosol OA challenges, decreased by approximately 50% the induced lung eosinophilia in OA-sensitized mice but did not reduce AHR. 3. HOE-140 (1 microg kg(-1)) administered in the same manner, decreased mononuclear cell and eosinophil infiltration in the bronchoalveolar lavage fluid (BALF) of OA-sensitized mice. Moreover, treatment of OA-sensitized mice with HOE-140 (100 microg kg(-1)) completely abolished the AHR to carbachol. 4. The BKB(1)-R agonist desArg(9)-BK (DBK; 10-1000 microg kg(-1)) administered intratrachealy to normal mice had no effect on the basal cell counts recovered in BALF nor on the plasma extravasation, while the BKB(2)-R selective agonist BK (20 microg kg(-1)) stimulated mononuclear cell migration, neutrophilia and plasma extravasation in normal mouse lungs. Such effects were inhibited by HOE-140 (10 microg kg(-1)). 5. Our results suggest that the airway inflammatory response induced by antigen challenge in mice is mediated by stimulation of both BKB(1)-R and BKB(2)-R.

[Bronchoconstriction in administration of ACE inhibitors]

The aim of the study was assessment of bronchial capacity in the treatment with ACE inhibitors. 92 patients with essential hypertension stage I-II (mean age 52 years), ischemic heart disease and bronchial asthma (a mild, moderate and severe course) in a relative remission were treated for arterial hypertension with ACE inhibitors enalapril and diroton. Enalapril improved cough indices by 38.3%, diroton--by 13.3%. This was accompanied by a rise in the level of natural antibodies to bradikinin.

Repeated allergen inhalation induces phenotypic modulation of smooth muscle in bronchioles of sensitized rats

Repeated ovalbumin (OA) or saline exposure of sensitized Brown Norway rats was examined on agonist reactivity, airway smooth muscle (ASM) content, and contractile protein expression in small bronchioles at 24 h, 7 days, and 35 days after challenge. OA increased ASM content (P < 0.05 vs. saline) at 24 h, which resolved by 7 days. Maximum developed tension (T(max)) to carbachol, KCl, and 4-beta-phorbol 12,13-dibutyrate was increased (P < 0.05) by OA in bronchioles at 24 h but was abrogated after correction for ASM. Differences in T(max) were not present at 7 days. In contrast, at 35 days, T(max) was increased (P < 0.05) after correction for ASM. Smooth muscle (sm)-alpha-actin, sm-myosin heavy chain (MHC) isoform 1, calponin, smoothelin-A, and sm-myosin light chain kinase expression were reduced (P < 0.05) by OA at 24 h in bronchioles but not in trachealis. Consistent with contraction findings, no difference in expression of these proteins was detected at 7 days. At 35 days, however, with the exception of sm-alpha-actin, their abundance was again reduced (P < 0.05) by OA. Nonmuscle MHC and beta-actin were unchanged throughout by OA. These findings indicate persistent changes in contractile protein content, consistent with ASM phenotypic modulation in vivo, which occur in response to repeated OA inhalation. Thus, OA exposure induces structural changes in bronchiole ASM content and in agonist responsiveness ex vivo that resemble remodeling in asthma.

Effects of an eosinophil chemotaxis inhibitor, TAK-661, on antigen-induced asthmatic responses in allergic sheep

Eosinophils have been shown to play a role in allergen-induced airway responses. The aim in this study was to examine the effects of TAK-661, a newly developed product as a specific inhibitory agent of eosinophil chemotaxis, on antigen-induced asthmatic responses in allergic sheep model. Seven Ascaris-sensitive, "dual-respondent" allergic sheep were provocated by an Ascaris suum antigen or phosphate-buffered saline 2 hrs after intra-stomach administration of TAK-661 or a placebo. Pulmonary resistances were measured throughout the experiment, and airway responsiveness to methacholine, bronchoalveolar lavage (BAL), and histological examination were performed 8 hrs after the antigen challenge. Antigen provocation induced dual-phase bronchoconstriction, eosinophilia in BAL and eosinophil infiltration into the airway wall, and an increase in airway responsiveness in placebo-treated sheep. The administration of TAK-661 significantly reduced the bronchoconstriction during the late phase, along with the inhibition of eosinophilia in BAL and the eosinophil infiltration into the airway wall. TAK-661 had a tendency to reduce early-phase bronchoconstriction and airway hyperresponsiveness, but there were no significant differences. These findings suggest that the eosinophil accumulation into the airway induced by antigen provocation may contribute to the development of late-phase bronchoconstriction, however, the development of airway hyperresponsiveness during late asthmatic response may not always be due to only eosinophilic inflammation in the airway.

Mediators of adenosine- and ovalbumen-induced bronchoconstriction of sensitized guinea-pig isolated airways

The mediators of bronchoconstriction of isolated lungs and trachea from ovalbumen sensitized guinea-pigs to adenosine and ovalbumen were examined using relevant antagonists. Changes in perfusion pressure and tension of paired lung halves and tracheal spiral strips, respectively, were recorded in response to adenosine (1 mM lung, 300 microM trachea), histamine (10 microM), methacholine (10 microM) and ovalbumen (10 microg). One half was perfused with antagonist while the other received vehicle. Tracheal strips were superfused throughout with the P(1) receptor antagonist 8-phenyltheophylline, to examine 8-phenyltheophylline-resistant responses. The histamine H(1) receptor antagonist, mepyramine (1.5 mM), the cyclooxygenase inhibitors, indomethacin (5 mM) and diclofenac (5 mM), the leukotriene receptor antagonist, zafirlukast (1 mM), and the lipoxygenase inhibitor, zileuton (20 mM), alone failed to inhibit bronchoconstriction by adenosine and ovalbumen of the lung and trachea. When two antagonists were combined, only mepyramine and zafirlukast significantly reduced the lung responses to adenosine and ovalbumen. The tracheal adenosine response was substantially reduced, although not significantly, while ovalbumen was significantly reduced. When mepyramine, indomethacin and zafirlukast were combined, the lung constriction by adenosine and ovalbumen were virtually abolished. Similarly, the combination of mepyramine, diclofenac and zafirlukast significantly attenuated the lung responses to adenosine and ovalbumen. Thus, histamine, cyclooxygenase products and leukotrienes alone are not responsible for the bronchoconstriction of isolated sensitized lung tissues to adenosine or ovalbumen, which appears to be due to the release of all three mediators.

Key role for mast cells in nonatopic asthma

The mechanisms involved in nonatopic asthma are poorly defined. In particular, the importance of mast cells in the development of nonatopic asthma is not clear. In the mouse, pulmonary hypersensitivity reactions induced by skin sensitization with the low-m.w. compound dinitrofluorobenzene (DNFB) followed by an intra-airway application of the hapten have been featured as a model for nonatopic asthma. In present study, we used this model to examine the role of mast cells in the pathogenesis of nonatopic asthma. First, the effect of DNFB sensitization and intra-airway challenge with dinitrobenzene sulfonic acid (DNS) on mast cell activation was monitored during the early phase of the response in BALB/c mice. Second, mast cell-deficient W/W(v) and Sl/Sl(d) mice and their respective normal (+/+) littermate mice and mast cell-reconstituted W/W(v) mice (bone marrow-derived mast cells-->W/W(v)) were used. Early phase mast cell activation was found, which was maximal 30 min after DNS challenge in DNFB-sensitized BALB/c, +/+ mice but not in mast cell-deficient mice. An acute bronchoconstriction and increase in vascular permeability accompanied the early phase mast cell activation. BALB/c, +/+ and bone marrow-derived mast cell-->W/W(v) mice sensitized with DNFB and DNS-challenged exhibited tracheal hyperreactivity 24 and 48 h after the challenge when compared with vehicle-treated mice. Mucosal exudation and infiltration of neutrophils in bronchoalveolar lavage fluid associated the late phase response. Both mast cell-deficient strains failed to show any features of this hypersensitivity response. Our findings show that mast cells play a key role in the regulation of pulmonary hypersensitivity responses in this murine model for nonatopic asthma.

Studying human airway pharmacology in microsections: application of videomicrometry

The influence of endogenously-released mediators and activated eosinophils on the airway lumen and the effect of passive sensitization on anti-immunoglobulin (Ig)-E-induced contractile responses was investigated by videomicrometry. Human bronchial sections of 2-3 mm internal diameter, placed in 250 microL Hank's balanced salt solution on microtitre plates, were monitored and recorded by digitized image analysis. Airway preparations exhibited a spontaneous narrowing (mean+/-SEM -33+/-5% of the luminal area). Removal of the bronchial epithelium almost completely prevented the development of spontaneuous narrowing (-6+/-3%; p<0.001). The addition of platelet-activating factor stimulated human eosinophils to the bronchial sections led to significant narrowing of the airway lumen (-39+/-9%; p<0.05). Passive sensitization induced hyperresponsiveness to polyclonal anti-IgE (-35+/-8%; p<0.01). It is concluded that videomicrometry is suitable for studying interactions between human airways and inflammatory cells, as well as the effect of passive sensitization on smooth muscle reactivity in vitro, without the imposition of preload. Under these conditions, human airways exhibited a spontaneous decrease of the airway lumen over time suggesting a role for epithelium-derived mediators because the development of spontaneous tone was epithelium dependent.

Piceatannol, a Syk-selective tyrosine kinase inhibitor, attenuated antigen challenge of guinea pig airways in vitro

Activation of nontransmembrane protein tyrosine kinases, such as Lyn and Syk, has been shown to be the earliest detectable signaling response to Fc receptor (Fc epsilon RI) cross-linking on mast cells leading to mast cell degranulation. The present study examined the effects of piceatannol (3,4,3',5'-tetrahydroxy-trans-stilbene, 10-100 microM), a Syk-selective tyrosine kinase inhibitor, on ovalbumin-induced anaphylactic contraction of isolated guinea pig bronchi and release of histamine and peptidoleukotrienes from chopped lung preparations. Pretreatment with piceatannol slightly suppressed ovalbumin-induced peak anaphylactic bronchial contraction but markedly (P<0.05) facilitated relaxation of the anaphylactically contracted bronchi. Piceatannol did not inhibit direct histamine-, leukotriene D(4)- or KCl-induced bronchial contraction, nor revert an existing anaphylactic bronchial contraction. Piceatannol, at 30 microM and above, significantly (P<0.05) prevented ovalbumin-induced release of both histamine and peptidoleukotrienes from lung fragments. Piceatannol did not inhibit exogenous arachidonic acid-induced release of peptidoleukotrienes from lung fragments. Our data show for the first time that inhibition of Syk tyrosine kinase can attenuate anaphylactic bronchial contraction in vitro, probably via inhibition of mast cell degranulation.

Early phase bronchoconstriction in the mouse requires allergen-specific IgG

Allergen provocation of allergic asthma patients is often characterized by an initial period of bronchoconstriction, or early phase reaction (EPR), that leads to maximal airway narrowing within 15-30 min, followed by a recovery period returning airway function to baseline within 1-2 h. In this study, we used a defined OVA provocation model and mice deficient for specific leukocyte populations to investigate the cellular/molecular origins of the EPR. OVA-sensitized/challenged wild-type (C57BL/6J) mice displayed an EPR following OVA provocation. However, this response was absent in gene knockout animals deficient of either B or T cells. Moreover, transfer of OVA-specific IgG, but not IgE, before the OVA provocation, was capable of inducing the EPR in both strains of lymphocyte-deficient mice. Interestingly, an EPR was also observed in sensitized/challenged mast cell-deficient mice following an OVA provocation. These data show that the EPR in the mouse is an immunologically based pathophysiological response that requires allergen-specific IgG but occurs independent of mast cell activities. Thus, in the mouse the initial period of bronchoconstriction following allergen exposure may involve neither mast cells nor IgE-mediated events.