Resolvin E1 dampens airway inflammation and hyperresponsiveness in a murine model of asthma

Resolvin E1 (RvE1; 5S, 12R, 18R-trihydroxyeicosapentaenoic acid) is an anti-inflammatory lipid mediator derived from the omega-3 fatty acid eicosapentaenoic acid (EPA). It has been recently shown that RvE1 is involved in the resolution of inflammation. However, it is not known whether RvE1 is involved in the resolution of asthmatic inflammation. To investigate the anti-inflammatory effect of RvE1 in asthma, a murine model of asthma was studied. After RvE1 was administered to mice intraperitoneally, there were decreases in: airway eosinophil and lymphocyte recruitment, specific Th2 cytokine, IL-13, ovalbumin-specific IgE, and airway hyperresponsiveness (AHR) to inhaled methacholine. Moreover, RvE1-treated mice had significantly lower mucus scores compared to vehicle-treated mice based on the number of goblet cells stained with periodic acid-schiff (PAS). These findings provide evidence that RvE1 is a pivotal counterregulatory signal in allergic inflammation and offer novel multi-pronged therapeutic approaches for human asthma.     

Fat-1 transgenic mice with elevated omega-3 fatty acids are protected from allergic airway responses

Omega-3 polyunsaturated fatty acids (n-3 PUFA) have been implicated in the alleviation of asthma. Recent studies have demonstrated that the n-3 PUFA derived lipid mediators, protectin D1 and resolvin E1, may act as potent resolution agonists in airway inflammation. The effects of the n-3 PUFA tissue status itself on asthma pathogenesis remains to be further investigated. In this study allergic airway inflammation induced by allergen sensitization and aerosol challenge in Fat-1 and wild-type mice was investigated. Fat-1 transgenic mice displayed increased endogenous lung n-3 PUFA. When allergen-sensitized and aerosol-challenged, these animals had decreased airway inflammation with decreased leukocyte accumulation in bronchoalveolar lavage fluid and lung parenchyma. The Fat-1 mice had a shift to the right in the dose-response relationship for methacholine induced bronchoconstriction with a significant increase in the log ED200. The Fat-1 mice had lower BALF concentrations of the pro-inflammatory cytokines IL-1α, IL-2, IL-5, IL-9, IL-13, G-CSF, KC and RANTES. Furthermore, increased lung tissue amounts of the counter-regulatory mediators protectin D1 and resolvin E1 were found in Fat-1 mice after bronchoprovocative challenge. These results therefore demonstrate a direct protective role for lung n-3 PUFA in allergic airway responses and an increased generation of protectin D1 and resolvin E1 in this context.     

NK cells are effectors for resolvin E1 in the timely resolution of allergic airway inflammation

Immune responses are pathologically sustained in several common diseases, including asthma. To determine endogenous proresolving mechanisms for adaptive immune responses, we used a murine model of self-limited allergic airway inflammation. After cessation of allergen exposure, eosinophils and T cells were cleared concomitant with the appearance of increased numbers of NK cells in the lung and mediastinal lymph nodes. The mediastinal lymph node NK cells were activated, expressing CD27, CD11b, CD69, CD107a, and IFN-γ. NK cell depletion disrupted the endogenous resolution program, leading to delayed clearance of airway eosinophils and Ag-specific CD4(+) T cells. NK cell trafficking to inflamed tissues for resolution was dependent upon CXCR3 and CD62L. During resolution, eosinophils and Ag-specific CD4(+) T cells expressed NKG2D ligands, and a blocking Ab for the NKG2D receptor delayed clearance of these leukocytes. Of interest, NK cells expressed CMKLR1, a receptor for the proresolving mediator resolvin E1, and depletion of NK cells decreased resolvin E1-mediated resolution of allergic inflammation. Resolvin E1 regulated NK cell migration in vivo and NK cell cytotoxicity in vitro. Together, these findings indicate new functions in catabasis for NK cells that can also serve as targets for proresolving mediators in the resolution of adaptive immunity.     

Local nitric oxide levels reflect the degree of allergic airway inflammation after segmental allergen challenge in asthmatics.

Nitric oxide (NO) levels are increased in the exhaled air of asthmatics. As NO levels correlate with allergic airway inflammation, NO measurement has been suggested for disease monitoring. In patients with asthma, we previously demonstrated that intrabronchial treatment with a natural porcine surfactant enhanced airway inflammation after segmental allergen provocation. We studied whether local levels of NO reflect the degree of allergic airway inflammation following segmental allergen challenge with or without surfactant pretreatment. Segmental NO, as well as nitrite and nitrate in bronchoalveolar lavage (BAL) fluid, was measured before and after segmental challenge with either saline, saline plus allergen, or surfactant plus allergen in 16 patients with asthma and five healthy subjects. The data were compared with inflammatory BAL cells. Segmental NO levels were increased after instillation of saline (p < 0.05), or surfactant plus allergen in asthmatics (p < 0.05), and values were higher after surfactant plus allergen compared to saline challenge. Nitrate BAL levels were not altered after saline challenge but increased after allergen challenge (p < 0.05) and further raised by surfactant (p < 0.05), whereas nitrite levels were not altered by any treatment. Segmental NO and nitrate levels correlated with the degree of eosinophilic airway inflammation, and nitrate levels also correlated with neutrophil and lymphocyte numbers in BAL. In healthy subjects, NO, nitrite, and nitrate were unaffected. Thus, segmental NO and nitrate levels reflect the degree of allergic airway inflammation in patients with asthma. Measurement of both markers can be useful in studies using segmental allergen provocation, to assess local effects of potential immunomodulators.     

Biomarkers of some pulmonary diseases in exhaled breath

Analysis of various biomarkers in exhaled breath allows completely non-invasive monitoring of inflammation and oxidative stress in the respiratory tract in inflammatory lung diseases, including asthma, chronic obstructive pulmonary disease (COPD), cystic fibrosis (CF), bronchiectasis and interstitial lung diseases. The technique is simple to perform, may be repeated frequently, and can be applied to children, including neonates, and patients with severe disease in whom more invasive procedures are not possible. Several volatile chemicals can be measured in the breath (nitric oxide, carbon monoxide, ammonia), and many non-volatile molecules (mediators, oxidation and nitration products, proteins) may be measured in exhaled breath condensate. Exhaled breath analysis may be used to quantify inflammation and oxidative stress in the respiratory tract, in differential diagnosis of airway disease and in the monitoring of therapy. Most progress has been made with exhaled nitric oxide (NO), which is increased in atopic asthma, is correlated with other inflammatory indices and is reduced by treatment with corticosteroids and antileukotrienes, but not (β₂-agonists. In contrast, exhaled NO is normal in COPD, reduced in CF and diagnostically low in primary ciliary dyskinesia. Exhaled carbon monoxide (CO) is increased in asthma, COPD and CF. Increased concentrations of 8-isoprostane, hydrogen peroxide, nitrite and 3-nitrotyrosine are found in exhaled breath condensate in inflammatory lung diseases. Furthermore, increased levels of lipid mediators are found in these diseases, with a differential pattern depending on the nature of the disease process. In the future it is likely that smaller and more sensitive analysers will extend the discriminatory value of exhaled breath analysis and that these techniques may be available to diagnose and monitor respiratory diseases in the general practice and home setting.     

Resolvin d1 and aspirin-triggered resolvin d1 promote resolution of allergic airways responses

Asthma is a disease of airway inflammation that in most cases fails to resolve. The resolution of inflammation is an active process governed by specific chemical mediators, including D-series resolvins. In this study, we determined the impact of resolvin D1 (RvD1) and aspirin-triggered RvD1 (AT-RvD1) on the development of allergic airway responses and their resolution. Mice were allergen sensitized, and RvD1, AT-RvD1 (1, 10, or 100 ng), or vehicle was administered at select intervals before or after aerosol allergen challenge. RvD1 markedly decreased airway eosinophilia and mucus metaplasia, in part by decreasing IL-5 and IκBα degradation. For the resolution of established allergic airway responses, AT-RvD1 was even more efficacious than RvD1, leading to a marked decrease in the resolution interval for lung eosinophilia, decrements in select inflammatory peptide and lipid mediators, and more rapid resolution of airway hyperreactivity to methacholine. Relative to RvD1, AT-RvD1 resisted metabolic inactivation by macrophages, and AT-RvD1 significantly enhanced macrophage phagocytosis of IgG-OVA-coated beads in vitro and in vivo, a new proresolving mechanism for the clearance of allergen from the airways. In conclusion, RvD1 and AT-RvD1 can serve as important modulators of allergic airway responses by decreasing eosinophils and proinflammatory mediators and promoting macrophage clearance of allergen. Together, these findings identify D-series resolvins as potential proresolving therapeutic agents for allergic responses.     

Effect of heterogeneous ventilation and nitric oxide production on exhaled nitric oxide profiles.

Elevated exhaled nitric oxide (NO) in the breath of asthmatic subjects is thought to be a noninvasive marker of lung inflammation. Asthma is also characterized by heterogeneous bronchoconstriction and inflammation, which impact the spatial distribution of ventilation in the lungs. Since exhaled NO arises from both airway and alveolar regions, and its level in exhaled breath depends strongly on flow, spatial heterogeneity in flow patterns and NO production may significantly affect the exhaled NO signal. To investigate the effect of these factors on exhaled NO profiles, we developed a multicompartment mathematical model of NO exchange using a trumpet-shaped central airway segment that bifurcates into two similarly shaped peripheral airway segments, each of which empties into an alveolar compartment. Heterogeneity in flow alone has only a minimal impact on the exhaled NO profile. In contrast, placing 70% of the total airway NO production in the central compartment or the distal poorly ventilated compartment can significantly increase (35%) or decrease (-10%) the plateau concentration, respectively. Reduced ventilation of the peripheral and acinar regions of the lungs with concomitant elevated NO production delays the rise of NO during exhalation, resulting in a positive phase III slope and reduced plateau concentration (-11%). These features compare favorably with experimentally observed profiles in exercise-induced asthma and cannot be simulated with single-path models. We conclude that variability in ventilation and NO production in asthmatic subjects impacts the shape of the exhaled NO profile and thus impacts the physiological interpretation.     

Protective effect of resolvin E1 on the development of asthmatic airway inflammation

Resolvin E1 (RvE1) is an anti-inflammatory lipid mediator derived from the omega-3 fatty acid eicosapentaenoic acid (EPA), and strongly acts in the resolution of inflammation. We previously reported that RvE1 dampens airway inflammation and hyperresponsiveness in a murine model of asthma. In the present study, to elucidate the effects of RvE1 on the development of asthmatic airway inflammation, we investigated whether RvE1 acts on different phases of an OVA-sensitized and -challenged mouse model of asthma. RvE1 treatments at the time of either OVA sensitization or at the time of OVA challenge were investigated and compared with RvE1 treatments at the time of both OVA sensitization and challenge. After RvE1 was administered to mice intraperitoneally at the time of both OVA sensitization and challenge, there were decreases in airway eosinophil and lymphocyte recruitment, as well as a reduction in Th2 cytokine and airway hyperresponsiveness. RvE1 treatment at the time of either OVA sensitization or challenge also improved AHR and airway inflammation. Our results suggest that RvE1 acts on several phases of asthmatic inflammation and may have anti-inflammatory effects on various cell types.     

Exhaled nitric oxide and nasal tryptase are associated with wheeze,rhinitis and nasal allergy in primary school children

Abstract

Rhinitis and asthma are the most common respiratory diseases in children. We assessed whether airway inflammation markers were associated with nasal allergies and self-reported symptoms of wheeze and rhinitis in 130 children 6–12 year old in an epidemiological context. Independent of sex and age, the fraction of exhaled nitric oxide (FeNO) and nasal mast cell (MC) activation (tryptase ≥?5?ng/mL) were positively associated with wheeze, rhinitis and with nasal allergy. Nasal eosinophil cationic protein (ECP) and exhaled breath condensate (EBC) markers (pH, 8-isoprostane, interleukin-1β) were not associated with symptoms or with nasal allergy. In conclusion, FeNO and nasal tryptase reflect allergic inflammation in the respiratory system.     

Role of exhaled nitric oxide in asthma

Nitric oxide (NO), an evanescent atmospheric gas, has recently been discovered to be an important biological mediator in animals and humans. Nitric oxide plays a key role within the lung in the modulation of a wide variety of functions including pulmonary vascular tone, nonadrenergic non-cholinergic (NANC) transmission and modification of the inflammatory response. Asthma is characterized by chronic airway inflammation and increased synthesis of NO and other highly reactive and toxic substances (reactive oxygen species). Pro- inflammatory cytokines such as TNFalpha and IL-1beta are secreted in asthma and result in inflammatory cell recruitment, but also induce calcium- and calmodulin-independent nitric oxide synthases (iNOS) and perpetuate the inflammatory response within the airways. Nitric oxide is released by several pulmonary cells including epithelial cells, eosinophils and macrophages, and NO has been shown to be increased in conditions associated with airway inflammation, such as asthma and viral infections. Nitric oxide can be measured in the expired air of several species, and exhaled NO can now be rapidly and easily measured by the use of chemiluminescence analysers in humans. Exhaled NO is increased in steroid-naive asthmatic subjects and during an asthma exacerbation, although it returns to baseline levels with appropriate anti-inflammatory treatment, and such measurements have been proposed as a simple non-invasive method of measuring airway inflammation in asthma. Here the chemical and biological properties of NO are briefly discussed, followed by a summary of the methodological considerations relevant to the measurement of exhaled NO and its role in lung diseases including asthma. The origin of exhaled NO is considered, and brief mention made of other potential markers of airway inflammation or oxidant stress in exhaled breath.     

Lipopolysaccharide binding protein potentiates airway reactivity in a murine model of allergic asthma

The development of allergic asthma is influenced by both genetic and environmental factors. Epidemiologic data often show no clear relationship between the levels of allergen and clinical symptoms. Recent data suggest that bacterial LPS may be a risk factor related to asthma severity. Airborne LPS is typically present at levels that are insufficient to activate alveolar macrophages in the absence of the accessory molecule LPS binding protein (LBP). LBP levels are markedly elevated in bronchoalveolar lavage fluids obtained from asthmatic subjects compared with those in normal controls. We hypothesized that LBP present in the lung could augment the pulmonary inflammation and airway reactivity associated with allergic asthma by sensitizing alveolar macrophages to LPS or other bacterial products and triggering them to release proinflammatory mediators. We compared wild-type (WT) and LBP-deficient mice using a defined Ag immunization and aerosol challenge model of allergic asthma. Immunized LBP-deficient mice did not develop substantial Ag-induced airway reactivity, whereas WT mice developed marked bronchoconstriction following aerosol Ag sensitization and challenge with methacholine. Similarly, production of NO synthase 2 protein and the NO catabolite peroxynitrite was dramatically higher in the lungs of WT mice following challenge compared with that in LBP-deficient mice. Thus, NO production appears to correlate with airway reactivity. In contrast, both mice developed similar pulmonary inflammatory cell infiltrates and elevated mucin production. Thus, LBP appears to participate in the development of Ag-induced airway reactivity and peroxynitrite production, but does not seem to be required for the development of pulmonary inflammation.     

A comparison between intratracheal and inhalation delivery of Aspergillus fumigatus conidia in the development of fungal allergic asthma in C57BL/6 mice

Allergic asthma is a debilitating disease of the airways characterized by airway hyperresponsiveness, eosinophilic inflammation, goblet cell metaplasia with associated mucus hypersecretion,?and airway wall remodelling events, particularly subepithelial fibrosis and smooth muscle cell hyperplasia. Animal models that accurately mimic these hallmarks of allergic airways disease are critical for studying mechanisms associated with the cellular and structural changes that lead to disease pathogenesis. Aspergillus fumigatus, is a common aeroallergen of human asthmatics. The intratracheal (IT) delivery of A. fumigatus conidia into the airways of sensitized mice has been described as a model of allergic disease. Here, we compared the IT model with a newly developed inhalation (IH) challenge model. The IH model allowed multiple fungal exposures, which resulted in an exacerbation to the allergic asthma phenotype. Increased recruitment of eosinophils and lymphocytes, the hallmark leukocytes of asthma, was noted with the IH model as compared to the IT model in which macrophages and neutrophils were more prominent. Immunoglobulin E (IgE) production was significantly greater after IH challenge, while that of IgG(2a) was higher after IT challenge. Airway wall remodelling was pronounced in IH-treated mice, particularly after multiple allergen challenges. Although the IT model may be appropriate for the examination of the played by innate cells in the acute response to fungus, it fails to consistently reproduce the chronic remodelling hallmarks of allergic asthma. The ability of the IH challenge to mimic these characteristics recommends it as a model suited to study these important events.     

Toll-Like Receptor Ligands LPS and Poly (I:C) Exacerbate Airway Hyperresponsiveness in a Model of Airway Allergy in Mice,Independently of Inflammation

It is well-established that bacterial and viral infections have an exacerbating effect on allergic asthma, particularly aggravating respiratory symptoms, such as airway hyperresponsiveness (AHR). The mechanism by which these infections alter AHR is unclear, but some studies suggest that Toll-like receptors (TLRs) play a role. In this study, we investigated the impact of TLR3 and TLR4 ligands on AHR and airway inflammation in a model of pre-established allergic inflammation. Female BALB/c mice were sensitised and challenged intranasally (i.n.) with either PBS or ovalbumin (OVA) and subsequently i.n. challenged with poly (I:C) (TLR3) or LPS (TLR4) for four consecutive days. The response to methacholine was measured in vivo; cellular and inflammatory mediators were measured in blood, lung tissue and broncheoalveolar lavage fluid (BALF). OVA challenge resulted in an increase in AHR to methacholine, as well as increased airway eosinophilia and TH2 cytokine production. Subsequent challenge with TLR agonists resulted in a significant increase in AHR, but decreased TLR-specific cellular inflammation and production of immune mediators. Particularly evident was a decline in LPS-induced neutrophilia and neutrophil-associated cytokines following LPS and poly (I:C) treatment. The present data indicates that TLRs may play a pivotal role in AHR in response to microbial infection in allergic lung inflammation. These data also demonstrate that aggravated AHR occurs in the absence of an exacerbation in airway inflammation and that allergic inflammation impedes a subsequent inflammatory response to TLRs. These results may parallel clinical signs of microbial asthma exacerbation, including an extended duration of illness and increased respiratory symptoms.     

IFN-gamma-inducible protein 10 (CXCL10) contributes to airway hyperreactivity and airway inflammation in a mouse model of asthma

Allergic asthma is an inflammatory disease of the airways characterized by eosinophilic inflammation and airway hyper-reactivity. Cytokines and chemokines specific for Th2-type inflammation predominate in asthma and in animal models of this disease. The role of Th1-type inflammatory mediators in asthma remains controversial. IFN-gamma-inducible protein 10 (IP-10; CXCL10) is an IFN-gamma-inducible chemokine that preferentially attracts activated Th1 lymphocytes. IP-10 is up-regulated in the airways of asthmatics, but its function in asthma is unclear. To investigate the role of IP-10 in allergic airway disease, we examined the expression of IP-10 in a murine model of asthma and the effects of overexpression and deletion of IP-10 in this model using IP-10-transgenic and IP-10-deficient mice. Our experiments demonstrate that IP-10 is up-regulated in the lung after allergen challenge. Mice that overexpress IP-10 in the lung exhibited significantly increased airway hyperreactivity, eosinophilia, IL-4 levels, and CD8(+) lymphocyte recruitment compared with wild-type controls. In addition, there was an increase in the percentage of IL-4-secreting T lymphocytes in the lungs of IP-10-transgenic mice. In contrast, mice deficient in IP-10 demonstrated the opposite results compared with wild-type controls, with a significant reduction in these measures of Th2-type allergic airway inflammation. Our results demonstrate that IP-10, a Th1-type chemokine, is up-regulated in allergic pulmonary inflammation and that this contributes to the airway hyperreactivity and Th2-type inflammation seen in this model of asthma.     

Multi-pronged inhibition of airway hyper-responsiveness and inflammation by lipoxin A(4)

The prevalence of asthma continues to increase and its optimal treatment remains a challenge. Here, we investigated the actions of lipoxin A(4) (LXA(4)) and its leukocyte receptor in pulmonary inflammation using a murine model of asthma. Allergen challenge initiated airway biosynthesis of LXA(4) and increased expression of its receptor. Administration of a stable analog of LXA(4) blocked both airway hyper-responsiveness and pulmonary inflammation, as shown by decreased leukocytes and mediators, including interleukin-5, interleukin-13, eotaxin, prostanoids and cysteinyl leukotrienes. Moreover, transgenic expression of human LXA(4) receptors in murine leukocytes led to significant inhibition of pulmonary inflammation and eicosanoid-initiated eosinophil tissue infiltration. Inhibition of airway hyper-responsiveness and allergic airway inflammation with a stable LXA(4) analog highlights a unique counter-regulatory profile for the LXA(4) system and its leukocyte receptor in airway responses. Moreover, our findings suggest that lipoxin and related pathways offer novel multi-pronged therapeutic approaches for human asthma.     

Airway reactivity to methacholine in nonatopic asymptomatic adults

We studied 50 nonsmoking volunteers, ages 18-35 yr, with no past or present history or physical examination findings of asthma, rhinitis, allergic disease, or recent respiratory infections, to evaluate the usefulness of the methacholine bronchoprovocation challenge (MBPC) as a screening test for asthma. All were skin-test-negative to 29 aeroallergens and had base-line pulmonary function values greater than 80% predicted. Fourteen (28%) subjects had a drop in forced expiratory volume in 1 s (FEV1) of 20% or greater at a provocative dose (PD20FEV1) less than or equal to 225 breath units. Moreover, when these subjects were compared with 21 asymptomatic allergic asthmatics, there was significant overlap between the two groups in concentration of methacholine causing this decline in FEV1. A positive MBPC at methacholine concentrations less than or equal to 5 mg/ml was not diagnostic of asthma, and a negative MBPC at methacholine concentrations greater than or equal to 10 mg/ml did not rule out asthma. These data strongly suggest that MBPC should not be used as the sole factor for the diagnosis of clinically significant asthma. A positive MBPC is one indication of the presence of airway hyperresponsiveness and thus is only one of many factors that must be considered in the diagnosis of asthma.     

Divergent immune responses to house dust mite lead to distinct structural-functional phenotypes

Asthma is a chronic airway inflammatory disease that encompasses three cardinal processes: T helper (Th) cell type 2 (Th2)-polarized inflammation, bronchial hyperreactivity, and airway wall remodeling. However, the link between the immune-inflammatory phenotype and the structural-functional phenotype remains to be fully defined. The objective of these studies was to evaluate the relationship between the immunologic nature of chronic airway inflammation and the development of abnormal airway structure and function in a mouse model of chronic asthma. Using IL-4-competent and IL-4-deficient mice, we created divergent immune-inflammatory responses to chronic aeroallergen challenge. Immune-inflammatory, structural, and physiological parameters of chronic allergic airway disease were evaluated in both strains of mice. Although both strains developed airway inflammation, the profiles of the immune-inflammatory responses were markedly different: IL-4-competent mice elicited a Th2-polarized response and IL-4-deficient mice developed a Th1-polarized response. Importantly, this chronic Th1-polarized immune response was not associated with airway remodeling or bronchial hyperresponsiveness. Transient reconstitution of IL-4 in IL-4-deficient mice via an airway gene transfer approach led to partial Th2 repolarization and increased bronchial hyperresponsiveness, along with full reconstitution of airway remodeling. These data show that distinct structural-functional phenotypes associated with chronic airway inflammation are strictly dependent on the nature of the immune-inflammatory response.     

Eotaxin-1 in exhaled breath condensate of stable and unstable asthma patients.

Background

Airway eosinophilia is considered a central event in the pathogenesis of asthma. Eotaxin plays a key role in selective eosinophil accumulation in the airways and, subsequently, their activation and degranulation. The study was undertaken to evaluate eotaxin-1 levels in the exhaled breath condensate (EBC) of asthmatics with different degrees of asthma severity and to establish the possible correlation of these measurements with other recognized parameters of airway inflammation.

Methods

EBC was collected from 46 patients with allergic asthma (14 with steroid-naïve asthma, 16 with ICS-treated, stable asthma, 16 with ICS-treated unstable asthma) and 12 healthy volunteers. Concentrations of eotaxin-1 were measured by ELISA.

Results

In the three groups of asthmatics, eotaxin-1 concentrations in EBC were significantly higher compared with healthy volunteers (steroid-naïve asthma: 9.70 pg/ml ± 1.70, stable ICS-treated asthma: 10.45 ± 2.00, unstable ICS-treated asthma: 17.97 ± 3.60, healthy volunteers: 6.24 ± 0.70). Eotaxin-1 levels were significantly higher in patients with unstable asthma than in the two groups with stable disease. We observed statistically significant correlations between the concentrations of eotaxin-1 in EBC and exhaled nitric oxide (F_ENO) or serum eosinophil cationic protein (ECP) in the three studied groups of asthmatics. We also discovered a significantly positive correlation between eotaxin-1 in EBC and blood eosinophil count in the groups of patients with unstable asthma and steroid-naïve asthma.

Conclusions

Measurements of eotaxin-1 in the EBC of asthma patients may provide another useful diagnostic tool for detecting and monitoring airway inflammation and disease severity.     

Requirements for allergen-induced airway hyperreactivity in T and B cell-deficient mice.

BACKGROUND: The pathogenesis of asthma is believed to reflect antigen-induced airway inflammation leading to the recruitment of eosinophils and activation of mast cells through cell-associated IgE. Controversies persist however, regarding the relative importance of different pathogenic cells and effector molecules. MATERIALS AND METHODS: A variety of gene-targeted mice were examined for the induction of cholinergic airway hyperresponsiveness (AH), allergic airway inflammation, mucus production, and serum IgE reactivity following intratracheal challenge with a potent allergen. AH was determined using whole-body plethysmography following acetylcholine challenge. Where possible, results were confirmed using neutralizing antibodies and cell-specific reconstitution of immune deficient mice. RESULTS: T and B cell-deficient, recombinase-activating-gene-deficient mice (RAG -/-) failed to develop significant allergic inflammation and AH following allergen challenge. Reconstitution of RAG -/- mice with CD4+ T cells alone was sufficient to restore allergen-induced AH, allergic inflammation, and goblet cell hyperplasia, but not IgE reactivity. Sensitized B cell-deficient mice also developed airway hyperreactivity and lung inflammation comparable to that of wild-type animals, confirming that antibodies were dispensable. Treatment with neutralizing anti-IL-4 antibody or sensitization of IL-4-deficient mice resulted in loss of airway hyperreactivity, whereas treatment with anti-IL-5 antibody or sensitization of IL-5-deficient mice had no effect. CONCLUSIONS: In mice, CD4+ T cells are alone sufficient to mediate many of the pathognomonic changes that occur in human asthma by a mechanism dependent upon IL-4, but independent of IL-5, IgE, or both. Clarification of the role played by CD4+ T cells is likely to stimulate important therapeutic advances in treatment of asthma.     

Oxidant stress modulates murine allergic airway responses

The allergic inflammation occurring in asthma is believed to be accompanied by the production of free radicals. To investigate the role of free radicals and the cells affected we turned to a murine model of allergic inflammation produced by sensitization to ovalbumin with subsequent aerosol challenge. We examined oxidant stress by measuring and localizing the sensitive and specific marker of lipid peroxidation, the F2-isoprostanes. F2-isoprostanes in whole lung increased from 0.30 +/- 0.08 ng/lung at baseline to a peak of 0.061 +/- 0.09 ng/lung on the ninth day of daily aerosol allergen challenge. Increased immunoreactivity to 15-F2t-IsoP (8-iso-PGF2alpha) or to isoketal protein adducts was found in epithelial cells 24 h after the first aerosol challenge and at 5 days in macrophages. Collagen surrounding airways and blood vessels, and airway and vascular smooth muscle, also exhibited increased immunoreactivity after ovalbumin challenge. Dietary vitamin E restriction in conjunction with allergic inflammation led to increased whole lung F2-isoprostanes while supplemental vitamin E suppressed their formation. Similar changes in immunoreactivity to F2-isoprostanes were seen. Airway responsiveness to methacholine was also increased by vitamin E depletion and decreased slightly by supplementation with the antioxidant. Our findings indicate that allergic airway inflammation in mice is associated with an increase in oxidant stress, which is most striking in airway epithelial cells and macrophages. Oxidant stress plays a role in the production of airway responsiveness.