Repeated exposure to low levels of sulfur dioxide (SO2) enhances the development of ovalbumin-induced asthmatic reactions in guinea pigs

Identification of exhaled volatile organic compounds that characterize asthma phenotypes: A J-VOCSA study

BACKGROUND

Asthma is characterized by phenotypes of different clinical, demographic, and pathological characteristics. Identifying the profile of exhaled volatile organic compounds (VOCs) in asthma phenotypes may facilitate establishing biomarkers and understanding asthma background pathogenesis. This study aimed to identify exhaled VOCs that characterize severe asthma phenotypes among patients with asthma.

METHODS

This was a multicenter cross-sectional study of patients with severe asthma in Japan. Clinical data were obtained from medical records, and questionnaires were collected. Exhaled breath was sampled and subjected to thermal desorption gas chromatography-mass spectrometry (GC/MS).

RESULTS

Using the decision tree established in the previous nationwide asthma cohort study, 245 patients with asthma were divided into five phenotypes and subjected to exhaled VOC analysis with 50 healthy controls (HCs). GC/MS detected 243 VOCs in exhaled breath samples, and 142 frequently detected VOCs (50% of all samples) were used for statistical analyses. Cluster analysis assigning the groups with similar VOC profile patterns showed the highest similarities between phenotypes 3 and 4 (early-onset asthma phenotypes), followed by the similarities between phenotypes 1 and 2 (late-onset asthma phenotypes). Comparisons between phenotypes 1-5 and HC revealed 19 VOCs, in which only methanesulfonic anhydride showed p < 0.05 adjusted by false discovery rate (FDR). Comparison of these phenotypes yielded several VOCs showing different trends (p < 0.05); however, no VOCs showed p < 0.05 adjusted by FDR.

CONCLUSIONS

Exhaled VOC profiles may be useful for distinguishing asthma and asthma phenotypes; however, these findings need to be validated, and their pathological roles should be clarified.

Asthma: The Use of Animal Models and Their Translational Utility

Asthma is characterized by chronic lower airway inflammation that results in airway remodeling, which can lead to a permanent decrease in lung function. The pathophysiology driving the development of asthma is complex and heterogenous. Animal models have been and continue to be essential for the discovery of molecular pathways driving the pathophysiology of asthma and novel therapeutic approaches. Animal models of asthma may be induced or naturally occurring. Species used to study asthma include mouse, rat, guinea pig, cat, dog, sheep, horse, and nonhuman primate. Some of the aspects to consider when evaluating any of these asthma models are cost, labor, reagent availability, regulatory burden, relevance to natural disease in humans, type of lower airway inflammation, biological samples available for testing, and ultimately whether the model can answer the research question(s). This review aims to discuss the animal models most available for asthma investigation, with an emphasis on describing the inciting antigen/allergen, inflammatory response induced, and its translation to human asthma.

Back to the future: re-establishing guinea pig in vivo asthma models

Research using animal models of asthma is currently dominated by mouse models. This has been driven by the comprehensive knowledge on inflammatory and immune reactions in mice, as well as tools to produce genetically modified mice. Many of the identified therapeutic targets influencing airway hyper-responsiveness and inflammation in mouse models, have however been disappointing when tested clinically in asthma. It is therefore a great need for new animal models that more closely resemble human asthma. The guinea pig has for decades been used in asthma research and a comprehensive table of different protocols for asthma models is presented. The studies have primarily been focused on the pharmacological aspects of the disease, where the guinea pig undoubtedly is superior to mice. Further reasons are the anatomical and physiological similarities between human and guinea pig airways compared with that of the mouse, especially with respect to airway branching, neurophysiology, pulmonary circulation and smooth muscle distribution, as well as mast cell localization and mediator secretion. Lack of reagents and specific molecular tools to study inflammatory and immunological reactions in the guinea pig has however greatly diminished its use in asthma research. The aim in this position paper is to review and summarize what we know about different aspects of the use of guinea pig in vivo models for asthma research. The associated aim is to highlight the unmet needs that have to be addressed in the future.

Sulfur dioxide exposure enhances Th2 inflammatory responses via activating STAT6 pathway in asthmatic mice

Sulfur dioxide (SO₂) is one of potential risk factors for induction and/or exacerbation of asthma, but the underlying mechanisms are not well understood. In this study, we investigate the role of SO₂ in asthma using a classical asthmatic model with allergic airway inflammation by treating C57BL/6 mice with ovalbumin (OVA) and/or 10 mg/m³ SO₂. Our results showed that SO₂ exposure alone induced slight pathological changes but did not significantly increase inflammatory cell counts, pro-inflammatory cytokine expression, and mucus production in the airway of mice, whereas SO₂ exposure in OVA-induced asthmatic mice caused marked pulmonary pathological changes and significantly increased the counts of eosinophil-rich leukocytes compared with OVA alone asthmatic mice. The expression of MUC5AC, TNF-α, Th2 cytokines (IL-4, IL-5, and IL-13) and STAT6 was further up-regulated in OVA plus SO₂ treated mice compared with OVA alone treated mice. In addition, exposure to SO₂ alone markedly elevated STAT6 mRNA levels and hydrogen peroxide (H₂O₂) content in the lung. These findings suggest that SO₂ amplifies Th2 inflammatory responses in OVA-induced asthmatic mice by activating STAT6, which can further induce Th2 cytokine expression. Induction of STAT6 expression might be an important mechanism underlying the increased risk for asthma after environmental exposure.

Relación de los mecanismos inmunológicos del asma y la contaminación ambiental

Introducción. Se calcula que más de 300 millones de personas alrededor del mundo padecen asma y se estima que para el año 2025 esta cifra se incremente a 400 millones debido a los contaminantes criterio. Sin embargo, dadas sus limitaciones, los estudios epidemiológicos son controversiales sobre la contaminación y el desarrollo de asma.Objetivos. Describir las diferencias y similitudes de la respuesta inmunológica de pacientes asmáticos y los modelos animales de asma alérgica después de la exposición a contaminantes criterio y elementos biológicos, para así identificar los factores inmunológicos relacionados con el desarrollo de asma.Materiales y método. Se realizó una búsqueda sistemática en las bases de datos sobre asma y los diferentes contaminantes criterio.Resultados. La respuesta Th2 es activada por la inhalación de ozono, dióxido de nitrógeno, azufre y la exposición aguda a material particulado, mientras que el contacto con ciertos tipos de pólenes y glucanos y la exposición crónica de partículas incrementa la respuesta Th1, la cual inhibe a la respuesta Th2 produciendo un “efecto protector”.Conclusiones. La respuesta Th1 podría causar baja o nula asociación entre la exposición a contaminación y el desarrollo de asma en las diferentes ciudades, adicionando de esta manera otra limitación a los estudios epidemiológicos.

Mechanisms of Heightened Airway Sensitivity and Responses to Inhaled SO2 in Asthmatics

Sulfur dioxide (SO2) is a problematic inhalable air pollutant in areas of widespread industrialization, not only in the United States but also in countries undergoing rapid industrialization, such as China, and it can be a potential trigger factor for asthma exacerbations. It is known that asthmatics are sensitive to the effects of SO2; however, the basis of this enhanced sensitivity remains incompletely understood. A PubMed search was performed over the course of 2014, encompassing the following terms: asthma, airway inflammation, sulfur dioxide, IL-10, mouse studies, and human studies. This search indicated that biomarkers of SO2 exposure, SO2 effects on airway epithelial cell function, and animal model data are useful in our understanding of the body's response to SO2, as are SO2-associated amplification of allergic inflammation, and potential promotion of neurogenic inflammation due to chemical irritant properties. While definitive answers are still being sought, these areas comprise important foci of consideration regarding asthmatic responses to inhaled SO2. Furthermore, IL-10 deficiency associated with asthma may be another important factor associated with an inability to resolve inflammation and mitigate oxidative stress resulting from SO2 inhalation, supporting the idea that asthmatics are predisposed to SO2 sensitivity, leading to asthma exacerbations and airway dysfunction.

Effect of sulfur dioxide on inflammatory and immune regulation in asthmatic rats

BACKGROUND

Exposure to sulfur dioxide (SO2) increases asthma risk. Inflammatory and immune responses are typical in asthma disease. The exact effect of SO2 on modulation of the inflammatory and immune responses in asthmatic rats remains unclear.

OBJECTIVES

Here we sought to investigate the molecular mechanisms underlying the NF-κB inflammatory pathway and the Th1/Th2 imbalance in asthmatic rats exposed to SO2.

METHODS

Male Wistar rats were challenged by ovalbumin (OVA) or SO2 alone or together, and then mRNA and protein levels of some inflammatory and immune genes were measured. NF-κB nuclear translocation was analyzed. Bronchoalveolar lavage (BAL), inflammatory cell counts and histopathologic examination were performed.

RESULTS

(1) OVA plus SO2 induced abnormal pathological changes and inflammatory responses in lung relative to exposure to OVA alone; (2) showing NF-κB nuclear translocation and activation through up-regulating IKKβ mRNA and protein expression and down-regulating IκBα expression in the presence of OVA or OVA plus SO2; (3) OVA plus SO2 significantly raised TNF-α and IL-6 levels in BALF compared with the OVA group; (4) SO2 markedly elevated IL-4 levels and decreased IFN-γ levels in BALF in the asthmatic rats, stimulating IgE generation which was closely related to inhibiting the expression of Foxp3, a specific marker of regulatory T cells.

CONCLUSIONS

SO2 affects the airway inflammatory and immune responses of the asthmatic rats and enhances the susceptibility to OVA by aggravating inflammatory responses in lungs, up-regulating pro-inflammatory cytokine expression, and causing the Th1/Th2 imbalance, which might contribute to the increased risk of asthma disease.

Role of prostaglandin D2 /CRTH2 pathway on asthma exacerbation induced by Aspergillus fumigatus

Aspergillus fumigatus is often associated in asthmatic patients with the exacerbation of asthma symptoms. The pathomechanism of this phenomenon has not been fully understood. Here, we evaluated the immunological mechanisms and the role of the prostaglandin D2 / Chemoattractant Receptor-Homologous Molecule Expressed on Th2 Cells (CRTH2) pathway in the development of Aspergillus-associated asthma exacerbation. We studied the effects of A. fumigatus on airway inflammation and bronchial hyper-responsiveness in a rat model of chronic asthma. Inhalation delivery of A. fumigatus conidia increased the airway eosinophilia and bronchial hyper-responsiveness in ovalbumin-sensitized, challenged rats. These changes were associated with prostaglandin D2 synthesis and CRTH2 expression in the lungs. Direct inflammation occurred in ovalbumin-sensitized, challenged animals, whereas pre-treatment with an antagonist against CRTH2 nearly completely eliminated the A. fumigatus-induced worsening of airway eosinophilia and bronchial hyper-responsiveness. Our data demonstrate that production of prostaglandin D2 followed by eosinophil recruitment into the airways via a CRTH2 receptor are the major pathogenic factors responsible for the A. fumigatus-induced enhancement of airway inflammation and responsiveness.

Bisulfite and sulfite as derivatives of sulfur dioxide alters biomechanical behaviors of airway smooth muscle cells in culture

Sulfur dioxide (SO2) is a common air pollutant that triggers asthmatic symptoms, but its toxicological mechanisms are not fully understood. Specifically, it is unclear how SO2 in vivo affects airway smooth muscle (ASM) cells of which the mechanics is known to ultimately mediate airway hyperresponsiveness (AHR) - a hallmark feature of asthma. To this end, we investigated the effects of bisulfite/sulfite (1:3 M/M in neutral fluid to simulate the in vivo derivatives of inhaled SO2 in the airways), on the viability, migration, stiffness and contractility of ASM cells cultured in vitro. The results showed that bisulfite/sulfite consistently increased viability, migration, F-actin intensity and stiffness of ASM cells in similar fashion as concentration increasing from 10(-4) to 10(-1) mmol/L. However, bisulfite/sulfite increased the ASM cell contractility induced by KCl only at the concentration between 10(-4) and 10(-3) mmol/L (p < 0.05), while having no consistent effect on that induced by histamine. At the concentration of 10(0) mmol/L, bisulfite/sulfite became acutely toxic to the ASM cells. Taken together, the data suggest that SO2 derivatives at low levels in vivo may directly increase the mass, stiffness and contractility of ASM cells, which may help understand the mechanism in which specific air pollutants contribute in vivo to the pathogenesis of asthma.

Mast cell mediators cause early allergic bronchoconstriction in guinea-pigs in vivo: a model of relevance to asthma

One feature of allergic asthma, the EAR (early allergic reaction), is not present in the commonly used mouse models. We therefore investigated the mediators involved in EAR in a guinea-pig in vivo model of allergic airway inflammation. Animals were sensitized using a single OVA (ovalbumin)/alum injection and challenged with aerosolized OVA on day 14. On day 15, airway resistance was assessed after challenge with OVA or MCh (methacholine) using the forced oscillation technique, and lung tissue was prepared for histology. The contribution of mast cell mediators was investigated using inhibitors of the main mast cell mediators [histamine (pyrilamine) and CysLTs (cysteinyl-leukotrienes) (montelukast) and prostanoids (indomethacin)]. OVA-sensitized and challenged animals demonstrated AHR (airway hyper-responsiveness) to MCh, and lung tissue eosinophilic inflammation. Antigen challenge induced a strong EAR in the sensitized animals. Treatment with a single compound, or indomethacin together with pyrilamine or montelukast, did not reduce the antigen-induced airway resistance. In contrast, dual treatment with pyrilamine together with montelukast, or triple inhibitor treatment, attenuated approximately 70% of the EAR. We conclude that, as in humans, the guinea-pig allergic inflammation model exhibits both EAR and AHR, supporting its suitability for in vivo identification of mast cell mediators that contribute to the development of asthma. Moreover, the known mast cell mediators histamine and leukotrienes were major contributors of the EAR. The data also lend further support to the concept that combination therapy with selective inhibitors of key mediators could improve asthma management.

Allergic diseases and air pollution

The prevalence of allergic diseases has been increasing rapidly, especially in developing countries. Various adverse health outcomes such as allergic disease can be attributed to rapidly increasing air pollution levels. Rapid urbanization and increased energy consumption worldwide have exposed the human body to not only increased quantities of ambient air pollution, but also a greater variety of pollutants. Many studies clearly demonstrate that air pollutants potently trigger asthma exacerbation. Evidence that transportation-related pollutants contribute to the development of allergies is also emerging. Moreover, exposure to particulate matter, ozone, and nitrogen dioxide contributes to the increased susceptibility to respiratory infections. This article focuses on the current understanding of the detrimental effects of air pollutants on allergic disease including exacerbation to the development of asthma, allergic rhinitis, and eczema as well as epigenetic regulation.

Chronic exposure to sulfur dioxide enhances airway hyperresponsiveness only in ovalbumin-sensitized rats

Sulfur dioxide (SO(2)) is a common air pollutant that triggers asthmatic symptoms, but its toxicological mechanisms are not fully understood. Specifically, it is unclear how airborne SO(2) affects airway hyperresponsiveness (AHR) - a hallmark feature of asthma. To this end, we investigated the effects of chronic exposure to SO(2) on AHR, airway inflammation, tissue remodeling, cell stiffness (G') and contractility of the airway smooth muscle cell (ASMC). Newborn Sprague-Dawley (SD) rats sensitized to ovalbumin (OVA) was used as the model to mimic asthmatic symptoms. The experimental results show that exposure to SO(2): (1) significantly increased Penh (an indicator of AHR) in the OVA-sensitized rats (p<0.01) but not in the normal rats (p>0.05), which correlated with the increase of airway smooth muscle mass; (2) increased IL-4 production in BALF of both the normal (p<0.05) and OVA-sensitized rats (p<0.001), but decreased IFN-γ in BALF of only the normal rats, and in serum only increased IL-4 production of the OVA-sensitized rats (p<0.001); (3) increased ASMC stiffness (G') and contractility only in the OVA-sensitized rats (p<0.001, p<0.05, respectively). Taken together, these results demonstrate that SO(2) may be a universal airway inflammatory factor, but more importantly, specific to exacerbating AHR in asthmatics only. These findings uncover a potential mechanism of SO(2)-induced health effects and may provide a basis for therapeutic targets.

Effects of simulated downwind coal combustion emissions on pre-existing allergic airway responses in mice

CONTEXT

Coal-fired power plant emissions can contribute a significant portion of the ambient air pollution in many parts of the world.

OBJECTIVE

We hypothesized that exposure to simulated downwind coal combustion emissions (SDCCE) may exacerbate pre-existing allergic airway responses.

METHODS

Mice were sensitized and challenged with ovalbumin (OVA). Parallel groups were sham-sensitized with saline. Mice were exposed 6 h/day for 3 days to air (control, C) or SDCCE containing particulate matter (PM) at low (L; 100 μg/m³), medium (M; 300 μg/m³), or high (H; 1000 μg/m³) concentrations, or to the H level with PM removed by filtration (high-filtered, HF). Immediately after SDCCE exposure, mice received another OVA challenge (pre-OVA protocol). In a second (post-OVA) protocol, mice were similarly sensitized but only challenged to OVA before air/SDCCE. Measurement of airway hyperresponsiveness (AHR), bronchoalveolar lavage (BAL), and blood collection were performed ~24 h after the last exposure.

RESULTS

SDCCE significantly increased BAL macrophages and eosinophils in OVA-sensitized mice from the post-OVA protocol. However, there was no effect of SDCCE on BAL macrophages or eosinophils in OVA-sensitized mice from the pre-OVA protocol. BAL neutrophils were elevated following SDCCE in both protocols in nonsensitized mice. These changes were not altered by filtering out the PM. In the post-OVA protocol, SDCCE decreased OVA-specific IgG₁ in OVA-sensitized mice but increased levels of total IgE, OVA-specific IgE and OVA-specific IgG₁ and IgG(2a) in non-sensitized animals. In the pre-OVA protocol, SDCCE increased OVA-specific IgE in both sensitized and non-sensitized animals. Additionally, BAL IL-4, IL-13, and IFN-γ levels were elevated in sensitized mice.

CONCLUSION

These results suggest that acute exposure to either the particulate or gaseous phase of SDCCE can exacerbate various features of allergic airway responses depending on the timing of exposure in relation to allergen challenge.

Association between tree pollen counts and asthma ED visits in a high-density urban center

BACKGROUND

Asthma exacerbation patterns are cyclic in nature and often correlate with air particle concentrations.

OBJECTIVE

To examine the relationship between asthma-related emergency department (ED) visits and outdoor air quality for pediatric and adult patients in a high asthma prevalence area, the New York City borough of the Bronx.

METHODS

Numbers of daily asthma-related adult and pediatric ED visits during one complete year (1999) were obtained from the seven major Bronx hospitals. Daily values of nitrogen oxides (NO(x)), ozone (O(3)), sulfur dioxide (SO(2)), and pollen counts were acquired.

RESULTS

Asthma-related ED visit numbers were highest in December-January and lowest in July. There were three distinct peaks of increased asthma ED visits: winter (December-January), spring (late April-May), and fall (October). The spring peak was the most striking and coincided with high tree pollen counts (tree pollen: r = 0.90, p = .03). We observed a positive correlation between asthma ED visits in the winter and SO(2) and NO(x) levels. Winter peaks of SO(2) and NO(x) in early December appeared to precede the winter asthma peak.

CONCLUSIONS

The spring asthma peak is closely associated with increased tree pollen counts, and the asthma increase at this time is likely due to allergic reactions to pollen. No significant associations could be established with the fall peak. The winter peak correlates with elevated SO(2) and NO(x) levels.

Past, present, and future of allergy in Korea

Korean allergology has made great progress in keeping pace with global scientific advances in spite of a short history. Outstanding academic and scientific researches have been performed in a variety of allergy fields in Korea. Epidemiologic studies revealed increasing prevalence of asthma and allergic diseases and considerable morbidity and mortality in Korea. Novel inhalant allergens such as citrus red mite and two-spotted spider mite as causes of asthma and allergic rhinitis have been discovered and reported in Korea. Bidirectional translational researches have been performed and are underway to elucidate the pathogenesis of asthma and allergy, mechanisms of airway inflammation and remodeling, and new therapeutic modalities for asthma and allergic diseases. Experimental asthma models of different phenotypes according to exposed levels of lipopolysaccharide or double-stranded RNA suggested the crucial role of the innate immunity in the development of allergic airway inflammation and a new insight for asthma pathogenesis, in which both Th1 and Th2 inflammation are involved. In the field of genetic researches, numerous genetic associations with asthma and asthma-related phenotypes, such as atopy, IgE production, and airway hyperresponsiveness, have been demonstrated in Korean population. The Easy Asthma Management (EAM) program, a computer-assisted asthma management program, is anticipated to facilitate the achievement of more successful clinical outcomes by filling the gaps between guidelines and actual practices. The Integration of these multi-disciplinary allergy research resources and translation of scientific achievements to the bedside and society will lead to better allergy and asthma control in Korea.

Effects of sulfur dioxide on expressions of p53, bax and bcl-2 in lungs of asthmatic rats

Inhibition of cell apoptosis is an increasingly important factor in modulating airway inflammation in asthma, which is related to environmental pollutants. To investigate the effects of sulfur dioxide (SO(2)) on the mRNA and protein expressions of apoptosis-related genes in lungs from asthmatic rats, male Wistar rats were challenged by ovalbumin (OVA) or SO(2) (2 ppm) inhalation alone or together. Examinations were performed 24 h after the last treatment. The mRNA and protein levels of p53, bax, and bcl-2 were analyzed in lungs using real-time reverse transcription-polymerase chain reaction (RT-PCR) assay and Western blot analysis, respectively. The results indicated that increases of bcl-2 or decreases of p53 and bax mRNA and protein levels were not significant in lungs of rats exposed to SO(2) alone, compared with controls, but elevated or reduced levels of these genes appeared in lungs of asthmatic rats exposed to SO(2) plus OVA, compared with controls, suggesting that SO(2) exposure could result in OVA-induced increases or decreases of transcription and translation levels of these apoptosis-related genes in rat lungs, and may have relations to airway inflammation in asthma. The regulation mechanism of apoptosis in asthma disease exposure to SO(2) needs further study.

Preexposure to amorphous silica particles attenuates but also enhances allergic reactions in trimellitic anhydride-sensitized brown Norway rats

Irritant-induced inflammation of the airways may aggravate respiratory allergy induced by chemical respiratory allergens. Therefore, the effect of airway irritation by synthetic amorphous silica (SAS) on respiratory allergy to trimellitic anhydride (TMA) was studied. Brown Norway (BN) rats were topically sensitized on day 0 and on day 7, subsequently exposed for 6 h/day for 6 days to 27 mg/m(3) SAS, and challenged by inhalation to a minimally irritating concentration of 12 mg/m(3) TMA, 24 h after the last SAS exposure. An additional group was exposed to SAS before a second challenge to TMA. Control groups were treated with vehicle, and/or did not receive SAS exposure. Breathing parameters, cellular and biochemical changes in bronchoalveolar lavage (BAL) fluid, and histopathological airway changes 24 h after challenge were the main parameters studied. Exposure to SAS alone resulted in transient changes in breathing parameters during exposure, and in nasal and alveolar inflammation with neutrophils and macrophages. Exposure to SAS before a single TMA challenge resulted in a slightly irregular breathing pattern during TMA challenge. SAS also diminished the effect of TMA on tidal volume, laryngeal ulceration, laryngeal inflammation, and the number of BAL (lung) eosinophils in most animals, but aggravated laryngeal squamous metaplasia and inflammation in a single animal. The pulmonary eosinophilic infiltrate and edema induced by a second TMA challenge was diminished by the preceding SAS exposure, but the number of lymphocytes in BAL was increased. Thus, a respiratory particulate irritant like SAS can reduce as well as aggravate certain aspects of TMA-induced respiratory allergy.

Prior SO2 exposure promotes airway inflammation and subepithelial fibrosis following repeated ovalbumin challenge

BACKGROUND

Exposure to allergens or air pollutants often leads to asthma exacerbations associated with aggravation of airway inflammation. Although, repeated allergen challenge often induces chronic allergic airway inflammation (CAAI) and airway remodelling, yet, the effects of brief exposure to air pollutants such as SO(2) on development of CAAI and airway remodelling remain to be clarified.

OBJECTIVE

The aim of the experiment was to investigate the effects of acute neutrophilic airway inflammation induced by brief exposure to SO(2) on development of CAAI and subepithelial fibrosis (SEF) in a murine model of asthma.

METHODS

Acute airway inflammation was induced by brief exposure to 50 p.p.m. SO(2) (1 h/d, 3 days). CAAI and SEF in BALB/c mice were induced by repeated challenge with ovalbumin (OVA) for 5 or 9 weeks with or without prior exposure to SO(2). Bronchoalveolar lavage fluid (BALF) eosinophilia as index of CAAI, BALF endothelin-1 (ET-1) and TGF-beta1 levels, morphometric evaluation of fibrotic area beneath subbasement membrane and lung hydroxyproline content (Hyp) as indexes of SEF were monitored.

RESULTS

Exposure to SO(2) led to acute neutrophilic inflammation and epithelial sloughing with profound elevation of BALF ET-1. Repeated OVA challenge resulted in CAAI and SEF along with elevation of Hyp, increase of fibrotic area beneath subbasement membrane and elevation of BALF TGF-beta1. Preceding SO(2) exposure exaggerated BALF eosinophilia, facilitated and enhanced SEF with more significant elevation of BALF ET-1 and TGF-beta1 levels compared with OVA-challenged mice without prior exposure to SO(2). The increase of Hyp was positively correlated with elevation of BALF TGF-beta1 during CAAI (r=0.842, P<0.01).

CONCLUSION

This data demonstrated that SEF developed in parallel with severity and time course of CAAI following repeated OVA challenge. SO(2)-induced acute epithelial injury and neutrophilic inflammation could enhance CAAI and promote SEF, probably through overexpression of ET-1 and TGF-beta1.

Diesel exhaust particles and allergenicity of pollen grains of Lilium martagon

Diesel exhaust particles are considered as the most important parts of air pollutants. Diesel exhaust particles have been shown to express both adjuvant activity for sensitization against common allergens and enhancing effects on allergic symptoms in sensitized individuals. In this research, pollen grains of Lilium martagon that are known as a non-allergic substance were collected and exposed to DEP 5 and 10 days. The allergy potency of different pollen extracts were compared by means of skin test, as well as analyses blood eosinophil numbers and IgE levels in the treated animals. Normal and DEP-exposed pollen grains were examined by scanning electron microscopy. Pollen extracts were also studied by SDS-PAGE for DEP-induced changes in protein profiles. Allergic bands were also studied and checked by using immunoblotting method. The results of the investigated allergy tests showed that DEP-exposed pollen grains are effective in inducing allergic symptoms. According to our microscopic observations, organic substances that exist in the DEP, mediate agglomeration of particles on the pollen surface. In appropriate conditions, water-soluble components of DEP may induce changes that affect the release of pollen proteins. SDS-PAGE showed protein profiles of pollen grains were changed and some new bands appeared in DEP-exposed pollen grains. Immunoblotting studies showed a new band in DEP-exposed pollen grains that react strongly with anti-IgE, but there is no allergenic band in normal pollen grains. On the other hand, diesel exhaust particles can carry pollen allergen molecules, induce new proteins (allergens), and also act as adjuvant for allergens.

Effects of sulfur dioxide on the expressions of MUC5AC and ICAM-1 in airway of asthmatic rats

Asthma is a chronic inflammatory disease characterized by infiltration and activation of various inflammatory cells and mucus secretion. To investigate the effects of SO(2) on the expressions of asthma related-genes, male Wistar rats were challenged by ovalbumin (OVA) or SO(2) (2 ppm) inhalation alone or together. Bronchoalveolar lavage and histopathologic examination were performed 24h after the last treatment. The mRNA and protein levels of MUC5AC and ICAM-1 were analyzed in lungs and tracheas using real-time reverse transcription-polymerase chain reaction (real-time RT-PCR) assay, immunohistochemistry method and Western blot analysis, respectively. Exposure to OVA or to OVA plus inhaled SO(2) significantly caused increases of the mRNA and protein levels of MUC5AC and ICAM-1 in lungs and tracheas of rats compared with the control (P <0.05 or P <0.01), but the increases of mRNA and protein levels after SO(2) inhalation were not statistically significant. Exposure to OVA plus inhaled SO(2) significantly not only induced the mRNA and protein expressions of these genes, but also induced the infiltration of inflammatory cells in lungs and tracheas and the increase of the numbers of inflammatory cells in bronchoalveolar lavage fluids (BALF), versus exposure to OVA alone. Meanwhile, a synergistic effect on the pathological changes between SO(2) and OVA was observed in lungs after SO(2) and OVA exposure. These results suggested that SO(2) could increase the expressions of MUC5AC and ICAM-1 on the transcription and translation levels in the lungs and tracheas from asthmatic rats, which might be one of the possible mechanisms that SO(2) pollution aggravates asthma disease.

Detection of allergen-induced airway hyperresponsiveness in isolated mouse lungs

Airway hyperresponsiveness (AHR) is a hallmark of bronchial asthma. Important features of this exaggerated response to bronchoconstrictive stimuli have mostly been investigated in vivo in intact animals or in vitro in isolated tracheal or bronchial tissues. Both approaches have important advantages but also certain limitations. Therefore, the aim of our study was to develop an ex vivo model of isolated lungs from sensitized mice for the investigation of airway responsiveness (AR). BALB/c mice were sensitized by intraperitoneal ovalbumin (Ova) and subsequently challenged by Ova inhalation. In vivo AR was measured in unrestrained animals by whole body plethysmography after stimulation with aerosolized methacholine (MCh) with determination of enhanced pause (P(enh)). Twenty-four hours after each P(enh) measurement, airway resistance was continuously registered in isolated, perfused, and ventilated lungs on stimulation with inhaled or intravascular MCh or nebulized Ova. In a subset of experiments, in vivo AR was additionally measured in orotracheally intubated, spontaneously breathing mice 24 h after P(enh) measurement, and lungs were isolated further 24 h later. Isolated lungs of allergen-sensitized and -challenged mice showed increased AR after MCh inhalation or infusion as well as after specific provocation with aerosolized allergen. AR was increased on days 2 and 5 after Ova challenge and had returned to baseline on day 9. AHR in isolated lungs after aerosolized or intravascular MCh strongly correlated with in vivo AR. Pretreatment of isolated lungs with the beta(2)-agonist fenoterol diminished AR. In conclusion, this model provides new opportunities to investigate mechanisms of AHR as well as pharmacological interventions on an intact organ level.

Measuring lung function in mice: the phenotyping uncertainty principle

Measuring lung function in mice is essential for establishing the relevance of murine models to human lung disease. However, making such measurements presents particular technical challenges due to the small size of the animal, particularly with regard to the measurement of respiratory flows. In this review, we examine the various methods currently available for assessment of lung function in mice and contrast them in terms of a concept we call the phenotyping uncertainty principle; each method can be considered to lie somewhere along a continuum on which noninvasiveness must be traded off against experimental control and measurement precision. Unrestrained plethysmography in conscious mice represents the extreme of noninvasiveness and is highly convenient but provides respiratory measures that are so tenuously linked to respiratory mechanics that they cannot be considered as meaningful indicators of lung function. At the other extreme, the measurement of input impedance in anesthetized, paralyzed, tracheostomized mice is precise and specific but requires that an animal be studied under conditions far from natural. In between these two extremes lie methods that sacrifice some precision for a reduction in the level of invasiveness, a promising example being the measurement of transfer impedance in conscious, restrained mice. No method is optimal in all regards; therefore, the appropriate technique to use depends on the application.

A reevaluation of the validity of unrestrained plethysmography in mice

Presently, unrestrained plethysmography is widely used to assess bronchial responsiveness in mice. An empirical quantity known as enhanced pause is derived from the plethysmographic box pressure [P(b)(t), where t is time] and assumed to be an index of bronchoconstriction. We show that P(b)(t) is determined largely by gas conditioning when normal mice breathe spontaneously inside a closed chamber in which the air is at ambient conditions. When the air in the chamber is heated and humidified to body conditions, the changes in P(b)(t) are reduced by about two-thirds. The remaining changes are thus due to gas compression and expansion within the lung and are amplified when the animals breathe through increased resistances. We show that the time integral of P(b)(t) over inspiration is accurately predicted by a term containing airway resistance, functional residual capacity, and tidal volume. We conclude that unrestrained plethysmography can be used to accurately characterize changes in airway resistance only if functional residual capacity and tidal volume are measured independently and the chamber gas is preconditioned to body temperature and humidity.

The increase in allergic respiratory diseases: survival of the fittest?

The prevalence of allergic respiratory diseases, asthma and allergic rhinoconjunctivitis, has increased since the advent of industrialization. The inverse relationship between the number of infections early in life and atopy has been interpreted as the "hygiene hypothesis." That is, many infections early in life promote the development of T helper type 1 cytokines, while fewer infections early in life favor the development of T helper type 2 (Th2) cytokines and atopy. An alternate interpretation of the same data, that atopy is protective against infections early in life, is rarely considered. With epidemiologic, historical, and immunologic data, I suggest that human evolution has favored individuals with an atopic predisposition. Th2 immune responses promote parity, and ensure successful pregnancy and term birth; provide the infant protection against infections and the inflammation induced by common pathogens in the first years of life until the immune system matures; and protect young adults exposed to viral respiratory pathogens. These traits are of particular value with the advent of industrialization, especially so in the era prior to the development of antibiotics. This theory contradicts the assumption that there is no biological or evolutionary advantage for allergic disease to exist in humans and has significant implications for our current and future treatments of allergic diseases.