Effects of SO2 exposure on allergic sensitization in the guinea pig

Lung Regeneration: Cells, Models, and Mechanisms

Lung epithelium, the lining that covers the inner surface of the respiratory tract, is directly exposed to the environment and thus susceptible to airborne toxins, irritants, and pathogen-induced damages. In adult mammalian lungs, epithelial cells are generally quiescent but can respond rapidly to repair of damaged tissues. Evidence from experimental injury models in rodents and human clinical samples has led to the identification of these regenerative cells, as well as pathological metaplastic states specifically associated with different forms of damages. Here, we provide a compendium of cells and cell states that exist during homeostasis in normal lungs and the lineage relationships between them. Additionally, we discuss various experimental injury models currently being used to probe the cellular sources-both resident and recruited-that contribute to repair, regeneration, and remodeling following acute and chronic injuries. Finally, we discuss certain maladaptive regeneration-associated cell states and their role in disease pathogenesis.

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.

Annual SO2 exposure, asthma, atopy, and lung function in Puerto Rican children

BACKGROUND

Long-term effects of sulfur dioxide (SO₂ ) exposure on children, a vulnerable population, are largely unknown. Further, how long-term SO₂ affects Puerto Rican children living in the island of Puerto Rico, a group with high asthma prevalence, is unclear. We evaluated the effects of annual average 1-hour daily maximum SO₂ average on asthma, atopy, total immunoglobulin E (IgE), and lung function in Puerto Rican children.

METHODS

A cohort of 678 children (351 with asthma, 327 without asthma) was recruited in Puerto Rico from 2009 to 2010. Annual average 1-hour daily maximum SO₂ exposure was interpolated utilizing publicly available monitoring data. Multivariable logistic and linear regression was used for the analysis of asthma, atopy (defined as an IgE ≥0.35 IU/mL to at least one of five common aero-allergens), total IgE, and lung function measures (forced vital capacity [FVC], forced expiratory volume in 1 second [FEV1], and FEV1/FVC ratio).

RESULTS

Annual SO₂ exposure (per 1 ppb) was significantly associated with asthma (odds ratio [OR] = 1.42; 95% confidence interval [CI] = 1.05-1.91) and atopy (OR = 1.35; 95% CI = 1.02-1.78). Such exposure was also significantly associated with lower FEV1/FVC in all children (β = -1.42; 95% CI = -2.78 to -0.08) and in children with asthma (β = -2.39; 95% CI= -4.31 to -0.46). Annual SO₂ exposure was not significantly associated with total IgE, FEV1, or FVC.

CONCLUSIONS

Among Puerto Rican children in Puerto Rico, long-term SO₂ exposure is linked to asthma and atopy. In these children, long-term SO₂ exposure is also associated with reduced FEV1/FVC, particularly in those with asthma.

Effects of air pollutants on occurrences of influenza-like illness and laboratory-confirmed influenza in Hefei, China

Accumulating evidence suggests that air pollution is a risk factor for adverse respiratory and cardiovascular health outcomes. However, the different impacts of exposure to air pollutants on influenza virus activity and influenza-like illness (ILI) have not been well documented in epidemiological studies. We examined the association between air pollutants of particular matters < 2.5 μm (PM_2.5), particular matters < 10 μm (PM₁₀), nitrogen dioxide (NO₂), sulfur dioxide (SO₂), and influenza occurrences in Hefei, China, from December 2013 to December 2015 by generalized Poisson additive regression models. The result suggested that PM_2.5 and PM₁₀ had similar effects on clinical ILI and influenza incidence. PM₁₀ was negatively associated with clinical ILI (relative risk (RR) 0.980, 95% confidence interval (CI) 0.974-0.987), while PM_2.5 were positively associated with clinical ILI (RR 1.040; 95% CI 1.032-1.049). RRs for the laboratory-confirmed cases of influenza were 0.813 (95% CI, 0.755-0.875) for PM₁₀ and 1.216 (95% CI, 1.134-1.304) for PM_2.5. Nevertheless, the impacts of SO₂ and NO₂ on ILI and influenza were distinct. SO₂ had significant influence on laboratory-confirmed influenza and had no significant linear relationship with ILI. NO₂ was negatively correlated with influenza but had no obvious effect on clinical ILI cases. The present study contributes novel evidence on understanding of the effects of various air pollutants on influenza activities, and these findings can be useful and important for the development of influenza surveillance and early warning systems.

Emission of sulfur dioxide from polyurethane foam and respiratory health effects

Recently, health damage to children exposed to synthetic polyurethane (PU) running tracks has aroused social panic in China. Some possible toxic volatiles may be responsible for these damages. However, the exact cause remains unclear. We have detected a low concentration of sulfur dioxide (SO₂; 1.80-3.30 mg/m³) on the surface of the PU running track. Surprisingly, we found that SO₂ was generated from the PU running track, and even such a low concentration of SO₂ could induce severe lung inflammation with hemorrhage, inflammatory cell infiltration, and inflammatory factor secretion in mice after 2-week exposure. Prolonged exposure (5 weeks) to the SO₂ caused chronic pulmonary inflammation and pulmonary fibrosis in the mice. Peripheral hemogram results showed that platelet concentration increased significantly in the SO₂ group compared to that in the control group, and the proportion of blood neutrophils and monocytes among total leukocytes was more imbalanced in the SO₂ group (16.6%) than in the control group (8.0%). Further histopathology results of sternal marrow demonstrated that hematopoietic hyperplasia was severely suppressed with increased reticular stroma and adipocytes under SO₂ exposure. These data indicate that a low concentration of SO₂ generated spontaneously from PU running track outdoors as a secondary product is still harmful to health, as it impairs the respiratory system, hematopoiesis, and immunologic function. This indicates that the low-concentration SO₂ could be a major cause of diseases induced by air pollution, such as chronic obstructive pulmonary disease.

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.

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.

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.

Effects of distance from a heavily transited avenue on asthma and atopy in a periurban shantytown in Lima, Peru

BACKGROUND

Proximity to roadways increases the risk of asthma in developed countries; however, relatively little is known about this relationship in developing countries, where rapid and uncontrolled growth of cities has resulted in urban sprawl and heavy traffic volumes.

OBJECTIVE

We sought to determine the effect of distance from a heavily transited avenue on asthma symptoms and quantitative respiratory outcome measures in a periurban shantytown in Lima, Peru.

METHODS

We enrolled 725 adolescents aged 13 to 15 years who were administered a survey on asthma symptoms and measured spirometry, response to allergy skin testing, and exhaled nitric oxide (eNO). We calculated distances from the main avenue for all households and measured indoor particulate matter in 100 households. We used multivariable regression to model the risk of asthma symptoms, risk of atopy, eNO levels, and FEV(1)/forced vital capacity ratio as a function of distance.

RESULTS

Compared against 384 meters, the odds of current asthma symptoms in households living within 100 meters increased by a factor of 2 (P < .05). The odds of atopy increased by a factor of 1.07 for every 100-meter difference in the distance from the avenue (P = .03). We found an inverse relationship in prebronchodilator FEV(1)/forced vital capacity and distance to the avenue in female subjects (P = .01) but not in male subjects. We did not find an association between eNO or household particulate matter levels and distance.

CONCLUSION

Living in close proximity to a high-traffic-density avenue in a periurban community in Peru was associated with a greater risk of asthma symptoms and atopy. Regulation of mobile-source pollutants in periurban areas of developing countries might help reduce the burden of asthma symptoms and atopy.

Effects of climatic changes and urban air pollution on the rising trends of respiratory allergy and asthma

Over the past two decades there has been increasing interest in studies regarding effects on human health of climate changes and urban air pollution. Climate change induced by anthropogenic warming of the earth's atmosphere is a daunting problem and there are several observations about the role of urbanization, with its high levels of vehicle emissions and other pollutants, and westernized lifestyle with respect to the rising frequency of respiratory allergic diseases observed in most industrialized countries.There is also evidence that asthmatic subjects are at increased risk of developing exacerbations of bronchial obstruction with exposure to gaseous (ozone, nitrogen dioxide, sulfur dioxide) and particulate inhalable components of air pollution.A change in the genetic predisposition is an unlikely cause of the increasing frequency in allergic diseases because genetic changes in a population require several generations. Consequently, environmental factors such as climate change and indoor and outdoor air pollution may contribute to explain the increasing frequency of respiratory allergy and asthma. Since concentrations of airborne allergens and air pollutants are frequently increased contemporaneously, an enhanced IgE-mediated response to aeroallergens and enhanced airway inflammation could account for the increasing frequency of allergic respiratory diseases and bronchial asthma.Scientific societies such as the European Academy of Allergy and Clinical Immunology, European Respiratory Society and the World Allergy Organization have set up committees and task forces to produce documents to focalize attention on this topic, calling for prevention measures.

Sodium sulfite aggravated allergic sensitization and airway inflammation in mite allergen sensitized BALB/c mice

Sulfur dioxide is a typical air pollutant. Sulfite, which is formed at the bronchial mucosa from inhaled sulfur dioxide, might play a role in the exacerbation of asthma. In this study, we investigated the effects of sodium sulfite and its interaction with a house dust mite (Dermatophagoides pteronyssinus, Der p) on allergic sensitization and airway inflammation. BALB/c mice were divided into four groups: control (n = 10), mite intranasal (mIN, n = 12), sodium sulfite intranasal (sIN, n = 12) and mIN + sIN (n = 12). In non-control groups, the mice were sensitized on day 8 and day 15 with mite allergen subcutaneously. Mite allergen was then administrated intranasally from day 15 to day 22 in mIN and mIN+sIN groups. Sodium sulfite was administrated in sIN and mIN + sIN groups intranasally from day 1 to day 22. Plasma Der p-specific IgE, IgG2a, lung histopathology and cytokine levels (IL-5 and IFN-γ) were analyzed. In comparison between mIN (or sIN) and mIN + sIN group, Der p-specific IgE levels were significantly higher in mIN + sIN group (p < 0.01). Besides, Der p-specific IgG2a level was significantly lower in mIN + sIN group than mIN (or sIN) group (p < 0.01). The peribronchiolar, alveolar and total inflammatory scores were increased in the mIN + sIN group comparing with the control group (p < 0.05, p < 0.01, p < 0.01, respectively). Lung supernatant in mIN + sIN group has higher IL-5/IFN-γ ratio than control, mIN or sIN group (all p < 0.05). Our study concluded sodium sulfite may enhance allergic sensitization as well as airway inflammation in mite allergen sensitized BALB/c mice.

Irritant and adjuvant effects of gaseous formaldehyde on the ovalbumin-induced hyperresponsiveness and inflammation in a rat model

BACKGROUND

Formaldehyde (FA) is a common indoor air pollutant that can cause asthma in people experiencing long-term exposure. While FA and other man-made chemicals contribute to the stimulation of asthma in the general population, the underlying molecular pathogenesis of this relationship is not yet well understood.

OBJECTIVE

To explore FA as an irritant for the onset of asthma and as an adjuvant for the induction of allergy.

METHODS

In the present study, 40 Wistar rats in five experimental groups were exposed to: (i) saline; (ii) ovalbumin (OVA); (iii) OVA + FA at 417 ppb; (iv) OVA + FA at 2500 ppb; and (v) FA at 2500 ppb. Current and prior occupational exposure limits in China were established at 417 ppb and 2500 ppb, respectively. Gaseous FA was administrated to the animals for 6 h/day before and during OVA immunization or saline treatment. Measured outcomes included in situ lung function analysis, cytokine measurement, and histological changes in the rat lungs.

RESULTS

The airway reactivity, lung histological changes, pulmonary interleukin-4 secretion, and eosinophil infiltration in the OVA and FA exposed rats were significantly higher after gaseous FA exposures of 417 and 2500 ppb. While FA exposure alone did not induce significant structural changes to the airway, and the rate of inflammatory cell infiltration was the same as for the control group, pulmonary levels of interferon-gamma were significantly elevated in the exposed rats.

CONCLUSIONS

FA may be an irritant as well as serve as an adjuvant for the onset of asthma or asthma-like symptoms.

Air pollution as a potential contributor to the 'epidemic' of autoimmune disease

There has been remarkable progress over the past 20 years in pushing forward our understanding of many facets of autoimmune disease. Indeed, knowledge of the genetic basis of autoimmunity and the molecular and cellular pathways involved in its pathogenesis has reached an unprecedented level. Yet this knowledge has not served to prevent autoimmune disease nor to curtail the dramatic rise in its incidence over the same interval. Population-level genetic changes cannot explain this trend; thus, environmental factors are strongly implicated. Among the possible environmental contributors to autoimmune disease, air pollution exposure has received very little attention. Although there is only a small amount of published data directly examining a possible causal relationship between air pollution exposure and autoimmunity, data from related fields suggests that it could facilitate autoimmunity as well. If correct, this hypothesis could prove to have sizeable public health implications.

Asthma symptoms and airway narrowing in children growing up in an urban versus rural environment

The development of asthma and allergy appears to be the result of gene-environment interaction. Potential environmental risk factors such as outdoor and indoor air pollution, infections, allergen exposure, diet, and lifestyle patterns may trigger respiratory symptoms and compromise lung function in children. Specific features of urban and rural lifestyle may constitute distinct risk factors but may also coexist within certain socioeconomic levels. Children of rural environments are at lower risk for asthma and aeroallergen sensitization. The protective effect has been associated with close contact with large animals, but the genetic factor also plays a contributory role. Children with prolonged exposure to urban environment are at increased risk of reduced lung function and those that reside in polluted areas exhibit slower lung growth. It is possible that polluted urban environment per se facilitates subclinical small airway disease. Evidence to date supports a strong relation between residential area as a potential risk factor for childhood asthma symptoms and airway obstruction and a western type of socioeconomic development.

[Allergic respiratory diseases and outdoor air pollution]

INTRODUCTION

After having increased for some time, the prevalence of allergic diseases may have reached a plateau. During this increase, considerable concomitant changes in air pollution have occurred. Photo-oxidant air pollution, related to traffic, has become preponderant. The implication of air pollution in the epidemic of allergies is still debated.

BACKGROUND

Experimental studies have suggested that the effect of air pollutants, including particulates and ozone, on the worsening and even the induction of allergies is biologically plausible. In addition, epidemiological studies have shown a short term impact of the peaks of air pollution on exacerbations of asthma. On the other hand, the results of epidemiological studies dealing with the long-term effects of chronic exposure to air pollution on the prevalence of allergies are less consistent.

VIEWPOINTS

The implementation of new-born cohorts, the use of dispersion models to improve exposure assessment and the study of gene-environment correlations, should increase our knowledge of the role of traffic-related air pollutants in the development of allergies and identify subjects more sensitive to their effects.

CONCLUSIONS

Some traffic-related air pollutants may have played a more important role in the increase in the prevalence of allergies than was assumed from the first epidemiological studies.

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.

Increased sensitization in urban vs. rural environment--rural protection or an urban living effect?

In a population-based longitudinal cohort study, we tested the hypothesis that children growing up in a high-traffic polluted urban area (UA) in the Athens' basin have higher prevalence of allergies and sensitization when compared with those growing up in a Greek provincial rural area (RA). We recruited 478 and 342 children aged 8-10 living in the UA and the RA, respectively. Respiratory health was assessed by a parent-completed questionnaire in three phases: 1995-96 (phase 1), 1999-2000 (phase 2), 2003-04 (phase 3) and skin-prick testing to common indoor and outdoor aeroallergens was performed at phases 1 and 2. Reported asthma and eczema did not differ between the two areas, whereas reported hay fever was persistently more prevalent in the UA than in the RA (16.5%, 17.0%, 18.2% vs. 7.0%, 8.3%, 9.6%, respectively). Sensitization was more prevalent in the UA at both phases (19.0% vs. 12.1% in phase 1, 20.0% vs. 14.1% in phase 2). Residential area contributed independently to sensitization to >or=1 aeroallergens (OR: 0.29; 95% CI: 0.13-0.66; p = 0.003) and to polysensitization (OR: 0.28; 95% CI: 0.10-0.82; p = 0.020) in phase 1. These associations were independent of farming practices. No significant contributions were found in phase 2. Our results suggest that long-term exposure to urban environment is associated with a higher prevalence of hay fever but not of asthma or eczema. The negative association between rural living and the risk of atopy during childhood, which is independent of farming practices, implies that it is mainly driven by an urban living effect.

Long-term exposure to background air pollution related to respiratory and allergic health in schoolchildren

BACKGROUND

The impact of air pollution on asthma and allergies still remains a debate.

OBJECTIVE

Our cross-sectional study was intended to analyse the associations between long-term exposure to background air pollution and atopic and respiratory outcomes in a large population-based sample of schoolchildren.

METHODS

Six thousand six hundred and seventy-two children aged 9-11 years recruited from 108 randomly schools in six French cities underwent a clinical examination including a skin prick test (SPT) to common allergens, exercise-induced bronchial reactivity (EIB) and skin examination for flexural dermatitis. The prevalence of asthma, allergic rhinitis (AR) and atopic dermatitis was assessed by a standardized health questionnaire completed by the parents. Three-year-averaged concentrations of air pollutants (NO2, SO2, PM10 and O3) were calculated at children' schools using measurements of background monitoring stations.

RESULTS

After adjusting for confounders, EIB, lifetime asthma and lifetime AR were found to be positively related to an increase in the exposure to SO2, PM10 and O3. The adjusted odds ratios (aOR) per increase of 5 microg/m3 of SO2 was 1.39 (95% confidence interval (CI)=1.15-1.66) for EIB and 1.19 (1.00-1.41) for lifetime asthma. The aOR for lifetime AR per increase of 10 microg/m3 of PM10 was 1.32 (CI=1.04-1.68). Moreover, SPT positivity was associated with O3 (aOR=1.34; CI=1.24-1.46). Associations with past year symptoms were consistent, even if not always statistically significant. Results persisted in long-term resident (current address for at least 8 years) children. However, no consistent positive association was found with NO2.

CONCLUSIONS

A moderate increase in long-term exposure to background ambient air pollution was associated with an increased prevalence of respiratory and atopic indicators in children.

Environmental risk factors and allergic bronchial asthma

The prevalence of allergic respiratory diseases such as bronchial asthma has increased in recent years, especially in industrialized countries. A change in the genetic predisposition is an unlikely cause of the increase in allergic diseases because genetic changes in a population require several generations. Consequently, this increase may be explained by changes in environmental factors, including indoor and outdoor air pollution. Over the past two decades, there has been increasing interest in studies of air pollution and its effects on human health. Although the role played by outdoor pollutants in allergic sensitization of the airways has yet to be clarified, a body of evidence suggests that urbanization, with its high levels of vehicle emissions, and a westernized lifestyle are linked to the rising frequency of respiratory allergic diseases observed in most industrialized countries, and there is considerable evidence that asthmatic persons are at increased risk of developing asthma exacerbations with exposure to ozone, nitrogen dioxide, sulphur dioxide and inhalable particulate matter. However, it is not easy to evaluate the impact of air pollution on the timing of asthma exacerbations and on the prevalence of asthma in general. As concentrations of airborne allergens and air pollutants are frequently increased contemporaneously, an enhanced IgE-mediated response to aeroallergens and enhanced airway inflammation could account for the increasing frequency of allergic respiratory allergy and bronchial asthma. Pollinosis is frequently used to study the interrelationship between air pollution and respiratory allergy. Climatic factors (temperature, wind speed, humidity, thunderstorms, etc) can affect both components (biological and chemical) of this interaction. By attaching to the surface of pollen grains and of plant-derived particles of paucimicronic size, pollutants could modify not only the morphology of these antigen-carrying agents but also their allergenic potential. In addition, by inducing airway inflammation, which increases airway permeability, pollutants overcome the mucosal barrier and could be able to "prime" allergen-induced responses. There are also observations that a thunderstorm occurring during pollen season can induce severe asthma attacks in pollinosis patients. After rupture by thunderstorm, pollen grains may release part of their cytoplasmic content, including inhalable, allergen-carrying paucimicronic particles.

Increasing allergy potency of Zinnia pollen grains in polluted areas

There is much evidence that allergic symptoms represent a major health problem in polluted cities. The aim of this research is to elucidate some microscopic effects of air pollutants on pollen structure, proteins, and allergenicity. A scanning electron microscopy study of pollen grains indicated that in polluted areas, airborne particles accumulate on the surface of pollen grains and change the shape and tectum of pollen. Also, many vesicles are released from polluted pollen grains and the pollen material agglomerates on the surface of pollen grains. SDS-PAGE revealed that different proteins exist in mature and immature pollen grains. There were no significant differences between protein bands of polluted and nonpolluted pollen grains, but in polluted pollen, protein content decreases in response to air pollution, causing the release of pollen proteins. The results indicate that mature pollen have more allergenicity than immature pollen. According to the experiments polluted pollen grains are more effective than nonpolluted pollen grains in inducing allergic symptoms. Air pollutants can cause allergic symptoms, but when associated with allergen pollen grains, their allergenicity power is increased.

Environmental pollution and allergy

OBJECTIVES

Among the theories supporting the increase of allergic diseases in modern western countries during the last several decades is the concept that environmental pollutants may play a vital role. Reading this article will enable the reader to recognize the effect of different types of environmental pollution on the development, modulation, and persistence of allergic reactions.

DATA SOURCES

Data sources include references to relevant articles and texts. To characterize the influence of environmental pollutants on allergic reactions (allergotoxicology), epidemiologic, clinical, and experimental data are considered.

RESULTS

The investigations show that air pollution patterns differ with respect to their effect upon allergies. Classical air pollution (type I) with high sulfur dioxide and dust particles seems not to be associated with allergic disease in humans. However, type II pollution characterized by elevation of oxides of nitrogen (NOx), ozone (O3), tobacco smoke, fine and ultrafine particulate matter, and diesel exhaust particles seems to enhance allergic disease.

CONCLUSIONS

The data suggest that environmental pollution can act at different levels and by complex interactions both outside and inside the individual and influence allergic diseases.

Childhood risk factors for atopy and the importance of early intervention

The increasing prevalence of atopic diseases, particularly atopy-associated asthma, has become a major challenge for allergists and public health authorities in many countries. The understanding of the natural history of the atopic march, including the determinants that are modifiable and might become candidates for preventive intervention, is still very limited. Information provided by cross-sectional studies can only generate hypotheses, which need to be supported by prospective, longitudinal, cohort studies. Ultimately, it will depend on the results of well-controlled intervention studies to identify which nutritional, environmental, or lifestyle-related factors should be considered for early intervention and might be useful to reverse the epidemiologic trend.

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

BACKGROUND

Sulfur dioxide (SO2) is one of the major air pollutants. It is known to aggravate asthma symptoms in human beings, but few studies have focused on the effects of SO2 upon the development of bronchial asthma in animal models.

OBJECTIVE

This study was undertaken to evaluate the role of SO2 upon the development of ovalbumin (OA)-induced asthmatic reactions in guinea pigs.

METHODS

Guinea pigs were divided into four groups: (1) OA- and SO2-exposed group (n = 12), (2) SO2-exposed group (n = 12), (3) OA-exposed group (n = 11), and (4) saline-exposed group (n = 7). Guinea pigs of the first and second groups were exposed to 0.1 ppm SO2 for 5 hours a day on 5 consecutive days. Guinea pigs in the first and third groups inhaled 0.1% OA aerosols for 45 minutes a day on days 3, 4, and 5. One week after the sensitization procedure, all the guinea pigs underwent bronchial challenge with 1.0% OA aerosols, using unrestricted whole-body plethysmography. Bronchoalveolar lavage and histopathologic examination were performed 24 hours after the bronchial challenge.

RESULTS

Increases in enhanced pause (Penh), as an index of airway obstruction, after the bronchial challenge was significantly higher in OA- and SO2-exposed group (group 1) than the other groups (P < .05, respectively). Eosinophil counts in bronchoalveolar lavage fluids were also significantly higher in group 1 than in the other groups (P < .05, respectively). Histopathologic findings of bronchial and lung tissue in the group 1 showed an infiltration of inflammatory cells, bronchiolar epithelial damage, and mucus and cell plug in the lumen, but no significant abnormalities were observed in the other groups.

CONCLUSIONS

These results indicate that repeated exposure to low levels of sulfur dioxide may enhance the development of ovalbumin-induced asthmatic reactions in guinea pigs.

Animal models of asthma: potential usefulness for studying health effects of inhaled particles

Asthma is now recognized to be a chronic inflammatory disease that affects the whole lung. Incidence appears to be increasing despite improved treatment regimens. There is substantial epidemiological evidence suggesting a relationship between the incidence and severity of asthma (e.g., hospitalizations) and exposure to increased levels of air pollution, especially fine and ultrafine particulate material, in susceptible individuals. There have been a few studies in animal models that support this concept, but additional animal studies to test this hypothesis are needed. However, such studies must be performed with awareness of the strengths and weaknesses of the currently available animal models. For studies in mice, the most commonly used animal, a broad spectrum of molecular and immunological tools is available, particularly to study the balance between Th1 and Th2 responses, and inbred strains may be useful for genetic dissection of susceptibility to the disease. However, the mouse is a poor model for bronchoconstriction or localized immune responses that characterize the human disease. In contrast, allergic lung diseases in dogs and cats may more accurately model the human condition, but fewer tools are available for characterization of the mechanisms. Finally, economic issues as well as reagent availability limit the utility of horses, sheep, and primates.

Exposure to diesel exhaust aggravates nasal allergic reaction in guinea pigs

Diesel exhaust particulates (DEP) () and exposure to diesel exhaust (DE) induce nasal mucosal hyperresponsiveness to histamine. Therefore, in the present study, we investigated whether or not exposing guinea pigs to DE aggravates the nasal allergic reaction induced by repeated nasal administration of ovalbumin (OVA). Guinea pigs were exposed to filtered air or to DE (DE containing 0.3 or 1.0 mg/m(3) of DEP) for 5 wk. During exposure to filtered air or to DE, guinea pigs were administered 1% of OVA in saline into the nasal cavities once a week. Sneezes were counted and nasal secretions were measured as indices of sneezing responses and rhinorrhea for 20 min after OVA administration. Titers of specific anti-OVA-IgG and anti-OVA-IgE and the number of eosinophils infiltrated into both nasal epithelium and subepithelium were measured at the end of the exposure to DE. Exposure to DE enhanced the number of sneezes and the amount of nasal secretions induced by OVA. Titers of specific anti-OVA-IgG and anti-OVA-IgE also significantly increased in DE-exposed animals. Exposure to DE also augmented the number of eosinophils that infiltrated both the nasal epithelium and the subepithelium induced by OVA. These results suggest that exposure to DE enhances the nasal allergic reaction induced by repeated antigen administration in guinea pigs.

[Respiratory allergy and environmental pollution in pediatrics]

Allergic disease and pollution effects on children are a subject of worldwide concern. Outdoor pollution is the sum of acid particle (SO2, NO2, PM) and photochemical (ozone) pollution. Experimental studies demonstrated correlation between animals and humans concerning inhalation of pollutants and inflammatory and functional effects. Several studies among children confirmed with variable odds ratios the interaction between air pollution and respiratory health, but other studies showed no clear effect. Physicians should inform parents with children experiencing respiratory disease.

Allergic diseases in farmers' children

Several studies have reported lower rates of allergic sensitization and allergies in children living in rural as compared to urban communities. This has been attributed to the lower levels of air pollution in rural areas. The question arises whether other factors in the rural environment could explain the lower prevalence rates of allergic sensitization and hay fever. A first report from rural South Bavaria in Germany demonstrated that children living in a home where coal and wood were used for heating had a significantly lower risk of suffering from hay fever (odds ratio 0.57 (0.34-0.98)), of being sensitized to common allergens (OR 0.67 (0.49-0.93)) and of having bronchial hyperresponsiveness (OR 0.55 (0.34-0.90)) than their peers living in homes with other heating systems. Subsequently, the Swiss Study on Childhood Allergy and Respiratory Symptoms with Respect to Air Pollution (SCARPOL) tested the hypothesis that farming as parental occupation was associated with a lower risk of hay fever and atopy. A total of 1620 (86.0%) 6-15-year-old schoolchildren living in three rural communities of Switzerland were examined using a standardized questionnaire completed by the parents and IgE antibodies against six common aeroallergens in serum samples of 404 (69.3.0%) of the 13-15-year-olds. Farming as parental occupation was significantly associated with lower rates of reported hay fever symptoms and allergic sensitization. Comparing children from farming with those from non-farming environments, the adjusted OR was 0.34 (95% CI: 0.12-0.89) for sneezing attacks during the pollen season, and 0.31 (95% CI: 0.13-0.73) for a sensitization to allergens. These results have recently been confirmed in a new and much larger survey in rural South Bavaria. Several alternative explanations have to be considered when interpreting these findings, namely, selection bias, the development of tolerance, increased microbial stimulation and a more traditional lifestyle (diet and housing conditions). Based on present knowledge, the underlying environmental factor explaining the protective effect of the farming environment has not yet been identified.

Mechanisms of allergy and chemical sensitivity

Allergy and chemical sensitivity are closely related disorders in which environmental exposures produce inflammatory reactions. For allergy, environmental proteins bind to IgE antibody on mast cells leading to the release of inflammatory mediators. In chemical sensitivity, low molecular weight chemicals bind to chemoreceptors on sensory nerve C-fibers leading to the release of inflammatory mediators. Clinical manifestations are similar in the two conditions. The overlap between the two conditions has a basis in mechanism, so the similarity of clinical manifestations and high percentage of individuals with both conditions may have a biological basis. Chronic exposures can lead to adaptation phenomena. Depression has been associated with both allergy and chemical sensitivity. Both the allergic and chemical irritant responses may be subjected to conditioning so that the response is triggered by other stimuli. Evidence for conditioning is strongest for allergy. Both allergy and chemical sensitivity can be acquired in association with irritant exposures.

Association of ambient air-pollution levels with acute asthma exacerbation among children in Singapore

BACKGROUND

Air-pollution levels have been shown to be associated with increased morbidity of respiratory diseases.

METHODS

Data for ambient air-pollutant levels, meteorologic factors, and hospitalization or emergency room (ER) visits for acute asthma in Singapore children over a 5-year period (1990-4) were obtained and analyzed for associations by time-series methods.

RESULTS

Throughout this period, the annual mean and 24-h mean levels for sulfur dioxide (SO2), nitrogen dioxide (NO2), and total suspended particles (TSP) and maximum 1-h daily average for ozone were generally within the air-quality guidelines established by the World Health Organization (WHO). However, positive correlation between levels of each of these pollutants and daily ER visits for asthma was observed in children aged 3-12 years, but not among adolescents and young adults (13-21 years old). The association with SO2 and TSP persisted after standardization for meteorologic and temporal variables. An adjusted increase in 2.9 ER visits for every 20 microg/m3 increase in atmospheric SO2 levels, lagged by 1 day, was observed on days when levels were above 68 microg/m3. With TSP, an adjusted increase of 5.80 ER visits for every 20 microg/m3 increase in its daily atmospheric levels, lagged by 1 day, was observed on days with levels above 73 microg/m3. Similar results were also obtained after controlling for autocorrelation by time-series analysis.

CONCLUSIONS

These associations were observed even though the overall levels of all pollutants were generally within the air-quality guidelines established by the WHO. These findings suggest that asthmatic children are susceptible to increased levels of air pollutants, particularly SO2 and TSP, although the ambient levels are generally within "acceptable" ranges.

Prevalence of hay fever and allergic sensitization in farmer's children and their peers living in the same rural community. SCARPOL team. Swiss Study on Childhood Allergy and Respiratory Symptoms with Respect to Air Pollution

INTRODUCTION

Lower prevalence rates of allergic diseases in rural as compared with urban populations have been interpreted as indicating an effect of air pollution. However, little is known about other factors of the rural environment which may determine the development of atopic sensitization and related diseases.

OBJECTIVE

The authors tested the hypothesis that children growing up on a farm were less likely to be sensitized to common aerollergens and to suffer from allergic diseases than children living in the same villages but in nonfarming families.

MATERIALS AND METHODS

Three age groups of schoolchildren (6-7 years, 9-11 years, 13-15 years) living in three rural communities were included in the analyses. An exhaustive questionnaire was filled in by 1620 (86.0%) parents. A blood sample was provided by 404 (69.3%) of the 13-15 year olds to determine specific IgE antibodies against six common aeroallergens.

RESULTS

Farming as parental occupation was reported for 307 children (19.0%). After adjustment for potential covariates such as family history of asthma and allergies, parental education, number of siblings, maternal smoking, pet ownership, indoor humidity and heating fuels, farming as parental occupation was significantly associated with lower rates of sneezing attacks during pollen season (adjusted OR 0.34, 95% CI 0.12-0.89) and atopic sensitization (adjusted OR 0.31, 95% CI 0.13-0.73) whereas the association with wheeze (adjusted OR 0.77 95% CI 0.38-1.58) and itchy skin rash (adjusted OR 0.86, 95% CI 0.49-1.50) was not statistically significant. The risk of atopic sensitization was lower in children from full-time farmers (adjusted OR 0.24, 95% CI 0.09-0.66) than from part-time farmers (adjusted OR 0.54, 95% CI 0.15-1.96).

CONCLUSION

Factors directly or indirectly related to farming as parental occupation decrease the risk of children becoming atopic and developing symptoms of allergic rhinitis.

Maternal smoking during pregnancy and lactation increases the risk for atopic eczema in the offspring

BACKGROUND

Maternal smoking during pregnancy has been shown to lead to immunologic changes in the offspring. However, little is known about the influence of this exposure on atopic manifestations.

OBJECTIVE

Our purpose was to investigate the influence of air pollutants on manifestations of atopy in preschool children.

METHODS

Unselected cohorts of a total of 678 5- to 6-year-old preschool children (350 boys, 328 girls) were investigated in areas with different degrees of air pollution in Bavaria. Data on the history of atopic diseases and other relevant factors were obtained by questionnaire. A skin-prick test was performed with common aeroallergens. Manifestation of atopy was defined as personal history of atopic disease or positive prick test to either grass pollen, house dust mite, or cat and analyzed multivariately.

RESULTS

Of all children, 38.9% exhibited at least one manifestation of atopy. Atopic eczema was reported in 7.9% to 15.5%, hayfever in 4.1% to 25.6%, and asthma in 3.0% to 8.1%. Of the mothers, 12.6% smoked during pregnancy or lactation or both. Analysis of the manifestation of atopy including sex, location, nitrogen oxide and sulfur dioxide exposure and maternal smoking as covariates revealed an influence of the maternal smoking during pregnancy/lactation. Of children whose mothers had smoked during pregnancy/lactation, 52.2% exhibited manifestations of atopy in contrast to 35.7% of children of nonsmoking mothers (p < 0.044). A history of atopic eczema was the only component of the variable "manifestation of atopy" that was significantly associated with maternal smoking during pregnancy and lactation. A causal interpretation of this finding, however, was not supported by a follow-up study.

CONCLUSION

Maternal smoking during pregnancy or lactation or both might play a role in the development of atopic eczema and should be avoided.

Epidemiology of allergic diseases

The escalation of allergic diseases (hay fever, asthma, atopic eczema) over recent decades has been linked to an increase in environmental pollutants. The prevalence of hay fever is associated with genetic predisposition, and some reports show an association with urban areas, socioeconomic status, and combined high allergen and automobile exhaust exposure. In asthma, there is also some evidence for geographical variations in prevalence; exercise challenge tests prove positive more often in urban areas than in rural areas. Although genetic predisposition is the strongest single risk factor for atopic eczema, air pollutants may aggravate the condition by acting as unspecific irritants and immunomodulators, leading to increased immunoglobulin E expression. In a study of 678 pre-school children, the influence of maternal smoking habits on individual measures of atopy revealed a positive association between smoking during pregnancy/lactation, and a positive history of atopic eczema. An East-West German comparative study examining different types and levels of air pollution, i.e. sulphurous (industrial; East) and oxidising (urban; West), showed that the prevalence of atopic eczema was greatest in East Germany. When various direct and indirect parameters of air pollution exposure were measured, the greatest association with atopic eczema was found with NOx exposure (indoor use of gas without a cooker hood), and close proximity to roads with heavy traffic. The increased prevalence of atopic eczema cannot be explained by changes in study methodology over time, or conventional risk factors alone; environmental risk factors may be an important contributing factor.

Formaldehyde exposure enhances inhalative allergic sensitization in the guinea pig

Formaldehyde (FA), a common indoor air pollutant, has been associated with increased prevalence rates of asthmatic symptoms among exposed individuals in epidemiologic surveys. We studied the influence of FA exposure on inhalative allergic sensitization in the guinea pig. Three groups of guinea pigs (n = 12 each) were exposed to clean air or two different FA concentrations (0.13 and 0.25 ppm) over 5 consecutive days. Exposure was followed by inhalation of 0.5% ovalbumin (OA) as sensitizing allergen. Three weeks later, specific bronchial provocation with OA was performed with body plethysmographic measurement of compressed air (CA). Furthermore, specific anti-OA-IgGl (reaginic) antibodies were determined in serum. In a further six animals, the respiratory tract was examined histologically for signs of inflammation directly after the end of FA or clean air exposure. In the group exposed to 0.25 ppm FA, 10/12 animals were found to be sensitized to OA (positive reaction on specific provocation) vs. 3/12 animals in the control group (P < 0.01). Furthermore, CA measurements of specific bronchial provocation and serum anti-OA-antibodies were significantly higher in the 0.25 ppm FA group than in controls (CA 0.35 vs. 0.09 ml median, P < 0.01; anti-OA-IgGl 13 vs. < 10 EU median, P < 0.05), indicating enhanced sensitization. In the group exposed to 0.13 ppm FA, no significant difference was found compared to the control group. There was no sign of inflammation of the lower airways in FA-exposed guinea pigs other than mucosal edema, which was discovered by morphometry. We conclude that short-term exposure to a low concentration of FA (0.25 ppm) can significantly enhance sensitization to inhaled allergens in the guinea pig.

Progression of allergy and asthma through childhood to adolescence

The reduction in asthma symptoms and bronchial hyperresponsiveness in adolescence is not well understood. Nor can the differences in asthma prevalence and severity between the sexes, which reverse at puberty, be explained. It has been suggested that the improvement in asthma during adolescence may result from diminished clinical and immunological responsiveness directly related to hormonal changes and that the effect of age on the prevalence of asthma in each sex may relate to differences in hormonal status, potentially influencing airway size, inflammation, and smooth muscle and vascular functions. However, few comprehensive studies are available. In summary, all wheezing is not asthma. Non-asthmatic wheezing illnesses may in part be attributable to anatomical abnormalities of the lung (transient early wheezing, premature birth). Little is known about the genetic and environmental determinants of childhood asthma, and factors related to the development of atopic sensitisation, such as exposure to allergens, infectious diseases, or tobacco smoke early in life, and dietary habits may be important, whereas the relevance of air pollution remains to be established. Unfortunately, we still do not know how to prevent the manifestation of childhood asthma.

Effects of sub-chronic exposure to SO2 on lipid and carbohydrate metabolism in rats

Sulfur dioxide (SO2) is a ubiquitous air pollutant, present in low concentrations in the urban air, and in higher concentrations in the working environment. While toxicological reports on SO2 have extensively dealt with the pulmonary system, essentially no data are available on the effects of chronic exposure to this pollutant on intermediary metabolism, although some biochemical changes in lipid metabolism have been detected. The present investigation was aimed at evaluating the effects of sub-chronic exposure to SO2 on concentrations of serum lipids/lipoproteins and on glucose metabolism, in animal models of hypercholesterolemia and diabetes. A specially designed control-inert atmosphere chamber was used, where male Sprague-Dawley rats fed on either standard or cholesterol enriched (HC) diets, as well as streptozotocin diabetics, were exposed to SO2 at 5 and 10 ppm, 24 h per day for 14 days. In rats, both on a standard diet and on a HC regimen, SO2 exposure determined a significant dose-dependent increase in plasma triglycerides, up to +363% in the 10 ppm HC exposed animals. This same gas concentration significantly reduced HDL cholesterol levels. In contrast, exposure of diabetic animals to 10 ppm SO2 resulted in a fall (-41%) of plasma and liver triglycerides and in a concomitant increase (+62%) of plasma HDL cholesterol. This discrepancy could apparently be related to diverging effects of SO2 exposure on plasma insulin levels in the different animal groups. Kinetic analyses of triglyceride synthesis carried out in rats on a standard diet revealed, in exposed animals, a significant reduction in the secretory rate, in spite of the concomitant hypertriglyceridemia. These findings suggest that SO2 exposure can markedly modify major lipid and glycemic indices, also indicating a differential response in normo/hyperlipidemic versus diabetic animals.

Interaction of air pollutants and pulmonary allergic responses in experimental animals

Asthma, which is primarily an allergic type of respiratory disease, has increased in the U.S. and Europe by 30% over the last decade. Air pollution may play a role in this rise, since during episodes of smog, hospital admissions due to asthma increase. Ambient air quality has generally improved since the Clean Air Act was implemented in 1971 however, and has led some investigators to suggest that the increased risk of asthma is associated with a deterioration of indoor air quality through the introduction of closed ventilation systems and constant climate control. Thus, although the direct health effects of acute and chronic air pollutant exposure are not in dispute, emphasis on the sources and location of exposure is changing from outdoors to the home environment and workplace. The few experimental studies which have investigated the interaction of air pollutants with allergic disease have shown that exposure to O3 or NO2 can increase levels of allergen-specific antibody and may augment allergic symptoms. These experiments are reviewed along with a study conducted in our laboratory which demonstrated the enhancing effect of NO2 exposure on immune responses and pulmonary inflammation following sensitization and pulmonary challenge with house dust mite allergen (HDM). In this study, rats exposed to 5 ppm NO2 for 3 h after each immunization had significantly higher levels of serum IgE and local IgA, IgG and IgE antibody than air controls. Lymphocyte activity in the spleen and local lymph nodes, and pulmonary inflammatory cells were also increased in NO2-exposed rats. The results show that exposure to NO2 enhances immune responsiveness and the severity of pulmonary inflammation following antigen challenge. Since allergic individuals and most asthmatics also have increased immunity to these proteins, the possibility that air pollutant exposure enhances immune responses to allergens and thus exacerbates immune-mediated lung disease exists.