Increase in markers of airway inflammation after ozone exposure can be observed also in stable treated asthmatics with minimal functional response to ozone

Effect of ozone on allergic airway inflammation

Background

Exposure to ozone (O₃) is associated with increased risk of exacerbations of asthma, but the underlying mechanisms are not well studied.

Objective

We sought to determine whether O₃ exposure would enhance airway inflammatory responses to allergen and the GSTM1-null genotype would modulate this enhancement.

Methods

In a crossover design, 10 asthmatic participants (5 with GSTM1-null genotype) who had specific sensitization to Dermatophagoides pteronyssinus (DP) were exposed to 160 ppb O₃ or filtered air (FA) control for 4 hours on 2 separate days at least 3 weeks apart. At 20 hours after exposure, endobronchial challenge with DP allergen, and sham normal saline (NS) instillation, were performed in separate bronchi. Six hours later, a second bronchoscopy was performed to collect bronchoalveolar lavage (BAL) from the DP- and NS-challenged segments for analyses of inflammatory biomarkers. Linear regression compared cell and cytokine responses across the 4 exposure groups (FA-NS, O₃-NS, FA-DP, O₃-DP). Effect modification by GSTM1 genotype was assessed in stratified regressions.

Results

BAL eosinophil counts were increased in segments challenged with DP compared to sham-challenged segments (P < .01). DP challenge compared to sham also caused a significant increase in BAL concentrations of the T_H2 cytokines IL-4, IL-5, IL-10, and IL-13 (P < .03 for all comparisons). O₃ exposure did not significantly affect BAL cells or cytokine after DP challenge. Compared to GSTM1-present participants, GSTM1-null participants had significantly lower eosinophil (P < .041) and IL-4 (P < .014) responses to DP challenge after O₃ exposure.

Conclusions

While O₃ did not cause a clear differential effect on airway inflammatory responses to allergen challenge, those responses did appear to be modulated by the antioxidant enzyme, GSTM1.

Exposure to ozone impacted Th1/Th2 imbalance of CD4+ T cells and apoptosis of ASMCs underlying asthmatic progression by activating lncRNA PVT1-miR-15a-5p/miR-29c-3p signaling

This investigation attempted to elucidate whether lncRNA PVT1-led miRNA axes participated in aggravating ozone-triggered asthma progression. One hundred and sixty-eight BALB/c mice were evenly divided into saline+air group, ovalbumin+air group, saline+ozone group and ovalbumin+ozone group. Correlations were evaluated between PVT1 expression and airway smooth muscle function/inflammatory cytokine release among the mice models. Furthermore, pcDNA3.1-PVT1 and si-PVT1 were, respectively, transfected into CD⁴⁺T cells and airway smooth muscle cells (ASMCs), and activities of the cells were observed. Ultimately, a cohort of asthma patients was recruited to estimate the diagnostic performance of PVT1. It was demonstrated that mice of ovalbumin+ozone group were associated with higher PVT1 expression, thicker trachea/airway smooth muscle and smaller ratio of Th1/Th2-like cytokines than mice of ovalbumin+air group and saline+ozone group (P<0.05). Moreover, pcDNA3.1-PVT1 significantly brought down Th1/Th2 ratio in CD⁴⁺ T cells by depressing miR-15a-5p expression and activating PI3K-Akt-mTOR signaling (P<0.05). The PVT1 also facilitated ASMC proliferation by sponging miR-29c-3p and motivating PI3K-Akt-mTOR signaling (P<0.05). Additionally, PVT1 seemed promising in diagnosis of asthma, with favorable sensitivity (i.e. 0.844) and specificity (i.e. 0.978). Conclusively, lncRNA PVT1-miR-15a-5p/miR-29c-3p-PI3K-Akt-mTOR axis was implicated in ozone-induced asthma development by promoting ASMC proliferation and Th1/Th2 imbalance.

Gut microbiota from androgen-altered donors alter pulmonary responses to ozone in female mice

In mice, both androgens and the gut microbiota modify pulmonary responses to ozone. We hypothesized that androgens affect gut microbiota and thereby impact pulmonary responses to ozone. To address this hypothesis, we transferred cecal microbiota from male castrated or sham castrated C57BL/6J mice into female germ-free recipient C57BL/6J mice. Four weeks later mice were exposed to ozone (2 ppm) or room air for 3 hr. The gut microbiomes of castrated versus sham castrated donors differed, as did those of recipients of microbiota from castrated versus sham castrated donors. In recipients, ozone-induced airway hyperresponsiveness was not affected by donor castration status. However, compared to mice receiving microbiota from sham castrated donors, mice receiving microbiota from castrated donors had elevated numbers of bronchoalveolar lavage (BAL) neutrophils despite evidence of reduced lung injury as measured by BAL protein. Serum concentrations of IL-17A and G-CSF were significantly greater in recipients of castrated versus sham castrated microbiota. Furthermore, BAL neutrophils correlated with both serum IL-17A and serum G-CSF. Our data indicate that androgen-mediated effects on the gut microbiota modulate pulmonary inflammatory responses to ozone and suggest a role for circulating IL-17A and G-CSF in these events.

Transcriptional Effects of Ozone and Impact on Airway Inflammation

Epidemiological and challenge studies in healthy subjects and in individuals with asthma highlight the health impact of environmental ozone even at levels considered safe. Acute ozone exposure in man results in sputum neutrophilia in 30% of subjects particularly young children, females, and those with ongoing cardiopulmonary disease. This may be associated with systemic inflammation although not in all cases. Chronic exposure amplifies these effects and can result in the formation of asthma-like symptoms and immunopathology. Asthmatic patients who respond to ozone (responders) induce a greater number of genes in bronchoalveolar (BAL) macrophages than healthy responders with up-regulation of inflammatory and immune pathways under the control of cytokines and chemokines and the enhanced expression of remodeling and repair programmes including those associated with protease imbalances and cell-cell adhesion. These pathways are under the control of several key transcription regulatory factors including nuclear factor (NF)-κB, anti-oxidant factors such as nuclear factor (erythroid-derived 2)-like 2 NRF2, the p38 mitogen activated protein kinase (MAPK), and priming of the immune system by up-regulating toll-like receptor (TLR) expression. Murine and cellular models of acute and chronic ozone exposure recapitulate the inflammatory effects seen in humans and enable the elucidation of key transcriptional pathways. These studies emphasize the importance of distinct transcriptional networks in driving the detrimental effects of ozone. Studies indicate the critical role of mediators including IL-1, IL-17, and IL-33 in driving ozone effects on airway inflammation, remodeling and hyperresponsiveness. Transcription analysis and proof of mechanisms studies will enable the development of drugs to ameliorate the effects of ozone exposure in susceptible individuals.

Impact of Internal and External Factors on EBC-pH and FeNO Changes in Humans Following Challenge with Ethyl Acrylate

Acute effects of ethyl acrylate exposure at 5 ppm for 4 h include changes of pH in exhaled breath condensate (EBC-pH) and exhaled nitric oxide (FeNO). So far, few data have been reported for atopic persons or the impact of the exposure conditions on biomarkers, e.g., constant versus variable application of irritants. Nine atopic and eighteen healthy volunteers without bronchial hyperresponsiveness were exposed for 4 h to ethyl acrylate concentrations of 0.05 ppm (sham), 5 ppm (constant concentration), and 0-10 ppm (variable, mean concentration of 5 ppm) in an exposure laboratory. A positive atopic status was defined according to specific IgE concentrations to common inhalant allergens (sx1 ≥ 0.35 kU/L). Biomarker levels were assessed before and after challenge and adjusted for levels after sham exposure (net response). Ethyl acrylate at constant, but not at variable concentrations induced a significant change in the net responses of EBC-pH and FeNO. Concerning FeNO, this could be observed only for atopic persons. The changes of biomarker levels were related to their baseline values. Biomarker responses to challenge with ethyl acrylate may be influenced by the patterns of application as well as baseline airway inflammation and atopic status of the volunteers.

Exercise-Induced Bronchoconstriction and the Air We Breathe

An association between airway dysfunction and airborne pollutant inhalation exists. Volatilized airborne fluorocarbons in ski wax rooms, particulate matter, and trichloromines in indoor environments are suspect to high prevalence of exercise-induced bronchoconstriction and new-onset asthma in athletes competing in cross-country skiing, ice rink sports, and swimming. Ozone is implicated in acute decreases in lung function and the development of new-onset asthma from exposure during exercise. Mechanisms and genetic links are proposed for pollution-related new-onset asthma. Oxidative stress from airborne pollutant inhalation is a common thread to progression of airway damage. Key pollutants and mechanisms for each are discussed.

Involvements of p38 MAPK and oxidative stress in the ozone-induced enhancement of AHR and pulmonary inflammation in an allergic asthma model

Background

Exposure to ambient ozone (O₃) increases the susceptivity to allergens and triggers exacerbations in patients with asthma. However, the detailed mechanisms of action for O₃ to trigger asthma exacerbations are still unclear.

Methods

An ovalbumin (OVA)-established asthmatic mouse model was selected to expose to filtered air (OVA-model) or 1.0 ppm O₃ (OVA-O₃ model) during the process of OVA challenge. Next, the possible involvements of p38 MAPK and oxidative stress in the ozone actions on the asthma exacerbations were investigated on the mice of OVA-O₃ model by treating them with SB239063 (a p38 MAPK inhibitor), and/or the α-tocopherol (antioxidant). Biological measurements were conducted including airway hyperresponsiveness (AHR), airway resistance (Raw), lung compliance (CL), inflammation in the airway lumen and lung parenchyma, the phosphorylation of p38 MAPK and heat shock protein (HSP) 27 in the tracheal tissues, and the malondialdehyde (MDA) content and the glutathione peroxidase (GSH-Px) activity in lung tissues.

Results

In OVA-allergic mice, O3 exposure deteriorated airway hyperresponsiveness (AHR), airway resistance (Raw), lung compliance (CL) and pulmonary inflammation, accompanied by the increased oxidative stress in lung tissues and promoted p38 MAPK and HSP27 phosphorylation in tracheal tissues. Administration of SB239063 (a p38 MAPK inhibitor) on OVA-O3 model exclusively mitigated the Raw, the CL, and the BAL IL-13 content, while α-tocopherol (antioxidant) differentially reduced the BAL number of eosinophils and macrophages, the content of BAL hyaluronan, the peribronchial inflammation, as well as the mRNA expression of TNF-α and IL-5 in the lung tissues of OVA-O3 model. Administration of these two chemical inhibitors similarly inhibited the AHR, the BAL IFN-γ and IL-6 production, the perivascular lung inflammation and the lung IL-17 mRNA expression of OVA-O3 model. Interestingly, the combined treatment of both compounds together synergistically inhibited neutrophil counts in the BALF and CXCL-1 gene expression in the lung.

Conclusions

O₃ exposure during the OVA challenge process promoted exacerbation in asthma. Both p38 MAPK and oxidative stress were found to play a critical role in this process and simultaneous inhibition of these two pathways significantly reduced the O₃-elicited detrimental effects on the asthma exacerbation.

Ozone-induced eosinophil recruitment to airways is altered by antigen sensitization and tumor necrosis factor-α blockade

Ozone is an atmospheric pollutant that causes lung inflammation and airway hyperresponsiveness. Ozone's effects occur in two distinct phases that are mediated by different populations of eosinophils. In the acute phase 1 day after exposure, mature airway-resident eosinophils alter parasympathetic nerve function that results in airway hyperresponsiveness. At this time point, the severity of hyperresponsiveness correlates with the number of eosinophils in close proximity to airway nerves, but not with eosinophils in bronchoalveolar lavage. Three days later, newly divided eosinophils are recruited to airways by a tumor necrosis factor-α-dependent mechanism. These new eosinophils paradoxically attenuate ozone-induced airway hyperresponsiveness. Ozone's effects on airway tissue eosinophils and nerve-associated eosinophils 3 days after exposure are unknown. Thus, we tested ozone's effects on eosinophils in airway subepithelium and around airway nerves 1 and 3 days after ozone in nonsensitized and ovalbumin-sensitized guinea pigs with or without the tumor necrosis factor-α antagonist, etanercept, and compared changes in eosinophils with ozone-induced airway hyperresponsiveness. More eosinophils were present in small, noncartilaginous airways and along small airway nerves compared to large cartilaginous airways in all treatment groups. The number of airway and nerve-associated eosinophils were unaffected 1 day after ozone exposure, whereas significantly fewer airway eosinophils were present 3 days later. Airway and nerve-associated eosinophils were also decreased in small airways 3 days after ozone in sensitized animals. These changes were blocked by etanercept. Airway eosinophils, but not nerve-associated or bronchoalveolar lavage eosinophils correlated with airway hyperresponsiveness 3 days after ozone. Our findings indicate ozone causes persistent alterations in airway eosinophils and reinforce the importance of characterizing eosinophils' effects within distinct airway compartments.

Neutrophilic Bronchial Inflammation Correlates with Clinical and Functional Findings in Patients with Noncystic Fibrosis Bronchiectasis

Background. Neutrophilic bronchial inflammation is a main feature of bronchiectasis, but not much is known about its relationship with other disease features. Aim. To compare airway inflammatory markers with clinical and functional findings in subjects with stable noncystic fibrosis bronchiectasis (NCFB). Methods. 152 NFCB patients (62.6 years; females: 57.2%) underwent clinical and functional cross-sectional evaluation, including microbiologic and inflammatory cell profile in sputum, and exhaled breath condensate malondialdehyde (EBC-MDA). NFCB severity was assessed using BSI and FACED criteria. Results. Sputum neutrophil percentages inversely correlated with FEV1 (P < 0.0001; rho = -0.428), weakly with Leicester Cough Questionnaire score (P = 0.068; rho = -0.58), and directly with duration of the disease (P = 0.004; rho = 0.3) and BSI severity score (P = 0.005; rho = 0.37), but not with FACED. Sputum neutrophilia was higher in colonized subjects, P. aeruginosa colonized subjects showing greater sputum neutrophilia and lower FEV1. Patients with ≥3 exacerbations in the last year showed a significantly greater EBC-MDA than the remaining patients. Conclusions. Sputum neutrophilic inflammation and biomarkers of oxidative stress in EBC can be considered good biomarkers of disease severity in NCFB patients, as confirmed by pulmonary function, disease duration, bacterial colonization, BSI score, and exacerbation rate.

Ozone Ameliorates Doxorubicine-Induced Skin Necrosis - results from an animal model

Doxorubicin (DXR) extravasation result with serious morbidity like skin ulceration and necrosis. The purpose of this study is to determine the protective effects of ozone, olive oil, dimethyl sulfoxide (DMSO), and coenzyme Q10 in the treatment of DXR-induced skin ulcers on rats. After an intradermal injection of DXR on a basis of an animal extravasation model, the materials were topically applied. The ulcer sizes were measured, and a punch biopsy was taken from the extravasation site in which the skin ulcers formed at the end of the experiment. The samples were analyzed for tumor necrosis factor alpha (TNF-α), interleukin 1-beta (IL1β), malondialdehyde (MDA), superoxide dismutase (SOD), and glutathione peroxidase (GSH-Px) enzymes, and examined histopathologically. The ulcer sizes clearly decreased in the study groups, including DMSO, olive oil, ozone plus coenzyme Q10, and ozone plus olive oil groups in comparison with the control group with the exception of the coenzyme Q10 group. The malondialdehyde levels were lower in the DMSO, olive oil, ozone plus olive oil, and ozone plus coenzyme Q10 groups than they were in the control group, but they were not significantly different. The TNF-α level was lower in the DMSO, ozone plus olive oil, coenzyme Q10, and ozone plus coenzyme Q10 groups in comparison with the control group. There was no significant change in the SOD, GSH-Px, and IL1β levels in the study groups in comparison with the control and the sham groups. The ozone plus olive oil group could be considered to be an alternate therapy for skin ulcers due to DXR extravasation.

Noninvasive effects measurements for air pollution human studies: methods, analysis, and implications

Human exposure studies, compared with cell and animal models, are heavily relied upon to study the associations between health effects in humans and air pollutant inhalation. Human studies vary in exposure methodology, with some work conducted in controlled settings, whereas other studies are conducted in ambient environments. Human studies can also vary in the health metrics explored, as there exists a myriad of health effect end points commonly measured. In this review, we compiled mini reviews of the most commonly used noninvasive health effect end points that are suitable for panel studies of air pollution, broken into cardiovascular end points, respiratory end points, and biomarkers of effect from biological specimens. Pertinent information regarding each health end point and the suggested methods for mobile collection in the field are assessed. In addition, the clinical implications for each health end point are summarized, along with the factors identified that can modify each measurement. Finally, the important research findings regarding each health end point and air pollutant exposures were reviewed. It appeared that most of the adverse health effects end points explored were found to positively correlate with pollutant levels, although differences in study design, pollutants measured, and study population were found to influence the magnitude of these effects. Thus, this review is intended to act as a guide for researchers interested in conducting human exposure studies of air pollutants while in the field, although there can be a wider application for using these end points in many epidemiological study designs.

Inhibitory effect of hydrogen sulfide on ozone-induced airway inflammation, oxidative stress, and bronchial hyperresponsiveness

Exposure to ozone has been associated with airway inflammation, oxidative stress, and bronchial hyperresponsiveness. The goal of this study was to examine whether these adverse effects of ozone could be prevented or reversed by hydrogen sulfide (H2S) as a reducing agent. The H2S donor sodium (NaHS) (2 mg/kg) or vehicle (PBS) was intraperitoneally injected into mice 1 hour before and after 3-hour ozone (2.5 ppm) or air exposure, and the mice were studied 24 hours later. Preventive and therapeutic treatment with NaHS reduced the ozone-induced increases in the total cells, including neutrophils and macrophages; this treatment also reduced levels of cytokines, including TNF-α, chemokine (C-X-C motif) ligand 1, IL-6, and IL-1β levels in bronchial alveolar lavage fluid; inhibited bronchial hyperresponsiveness; and attenuated ozone-induced increases in total malondialdehyde in bronchoalveolar lavage fluid and decreases in the ratio of reduced glutathione/oxidized glutathione in the lung. Ozone exposure led to decreases in the H2S production rate and in mRNA and protein levels of cystathionine-β-synthetase and cystathionine-γ-lyase in the lung. These effects were prevented and reversed by NaHS treatment. Furthermore, NaHS prevented and reversed the phosphorylation of p38 mitogen-activated protein kinase and heat shock protein 27. H2S may have preventive and therapeutic value in the treatment of airway diseases that have an oxidative stress basis.

Evaluating potential response-modifying factors for associations between ozone and health outcomes: a weight-of-evidence approach

BACKGROUND

Epidemiologic and experimental studies have reported a variety of health effects in response to ozone (O3) exposure, and some have indicated that certain populations may be at increased or decreased risk of O3-related health effects.

OBJECTIVES

We sought to identify potential response-modifying factors to determine whether specific groups of the population or life stages are at increased or decreased risk of O3-related health effects using a weight-of-evidence approach.

METHODS

Epidemiologic, experimental, and exposure science studies of potential factors that may modify the relationship between O3 and health effects were identified in U.S. Environmental Protection Agency's 2013 Integrated Science Assessment for Ozone and Related Photochemical Oxidants. Scientific evidence from studies that examined factors that may influence risk were integrated across disciplines to evaluate consistency, coherence, and biological plausibility of effects. The factors identified were then classified using a weight-of-evidence approach to conclude whether a specific factor modified the response of a population or life stage, resulting in an increased or decreased risk of O3-related health effects.

DISCUSSION

We found "adequate" evidence that populations with certain genotypes, preexisting asthma, or reduced intake of certain nutrients, as well as different life stages or outdoor workers, are at increased risk of O3-related health effects. In addition, we identified other factors (i.e., sex, socioeconomic status, and obesity) for which there was "suggestive" evidence that they may increase the risk of O3-related health effects.

CONCLUSIONS

Using a weight-of-evidence approach, we identified a diverse group of factors that should be considered when characterizing the overall risk of health effects associated with exposures to ambient O3.

Disease models of chronic inflammatory airway disease: applications and requirements for clinical trials

PURPOSE OF REVIEW

This review will discuss methodologies and applicability of key inflammatory models of respiratory disease in proof of concept or proof of efficacy clinical studies. In close relationship with these models, induced sputum and inflammatory cell counts will be addressed for phenotype-directed drug development. Additionally, important regulatory aspects regarding noninvestigational medicinal products used in bronchial challenges or clinical inflammatory models of respiratory disease will be highlighted.

RECENT FINDINGS

The recognition of an ever increasing number of phenotypes and endotypes within conditions such as asthma and chronic obstructive pulmonary disease urges phenotyping of study populations already in early clinical phases of drug development. Apart from the choice of a relevant disease model, recent studies show that especially targeted therapies need to be tested in well defined disease subsets for adequate efficacy assessment. Noninvasive biomarkers, especially sputum inflammatory cell counts, aid phenotyping and are useful outcome measures for novel, targeted therapies.

SUMMARY

Disease phenotyping becomes increasingly important for efficient and cost-effective drug development and subsequent disease management. Inflammatory models of respiratory disease combined with sputum biomarkers are important tools in this approach.

Induced sputum, exhaled NO, and breath condensate in occupational medicine

OBJECTIVE

Studies of fractional exhaled NO (FeNO) or induced sputum are now well standardized and the exponential increase in publications about exhaled breath condensate reflects growing interest in a noninvasive diagnosis of pulmonary diseases in occupational medicine.

METHODS

This review describes current techniques (FeNO, induced sputum, and exhaled breath condensate) for the study of inflammation and oxidative stress biomarkers.

RESULTS

These biomarkers are FeNO, cytokines, H2O2, 8-isoprostane, malondialdehyde, and nitrogen oxides. These techniques also include the study of markers of the toxic burden in the lungs (heavy metals and mineral compounds) that are important in occupational health exposure assessment.

CONCLUSIONS

In occupational medicine, the study of both volatile and nonvolatile respiratory biomarkers can be useful in medical surveillance of exposed workers, the early identification of respiratory diseases, or the monitoring of their development.

Role of GSTM1 in resistance to lung inflammation

Lung inflammation resulting from oxidant/antioxidant imbalance is a common feature of many lung diseases. In particular, the role of enzymes regulated by the NF-E2-related factor 2 transcription factor has recently received increased attention. Among these antioxidant genes, glutathione S-transferase Mu 1 (GSTM1) has been most extensively characterized because it has a null polymorphism that is highly prevalent in the population and associated with increased risk of inflammatory lung diseases. Present evidence suggests that GSTM1 acts through interactions with other genes and environmental factors, especially air pollutants. Here, we review GSTM1 gene expression and regulation and summarize the findings from epidemiological, clinical, animal, and in vitro studies on the role played by GSTM1 in lung inflammation. We discuss limitations in the existing knowledge base and future perspectives and evaluate the potential of pharmacologic and genetic manipulation of the GSTM1 gene to modulate pulmonary inflammatory responses.

Anti-malarial drug artesunate ameliorates oxidative lung damage in experimental allergic asthma

Oxidative stress is a critical pathophysiological factor in the development of allergic airway inflammation, resulting in oxidative damage to lipids, proteins, and DNA. Our recent report revealed potent anti-inflammatory effects of the antimalarial drug artesunate in experimental allergic asthma. The present study investigated potential antioxidative effects of artesunate in a murine model of allergic asthma in comparison with dexamethasone, a potent corticosteroid. Mice were sensitized and challenged with ovalbumin and developed airway inflammation and oxidative lung damage. Artesunate markedly suppressed ovalbumin-induced increases in total cell, eosinophil, and neutrophil counts. In contrast, dexamethasone failed to inhibit neutrophil recruitment. Levels of the oxidative damage markers 8-isoprostane, 8-hydroxy-2-deoxyguanosine, and 3-nitrotyrosine were potently repressed by artesunate. However, dexamethasone showed weaker inhibitory effects on 3-nitrotyrosine production. Ovalbumin-induced increases in the expression of the pro-oxidants iNOS and NADPH oxidase (NOX1, 2, 3, and 4) were significantly abated by artesunate. Gene expression of regulatory subunits of NOX, p22phox and p67phox, was also reduced by artesunate. The expression and activities of the antioxidants superoxide dismutase and catalase were substantially reversed with artesunate in ovalbumin-challenged mice. Artesunate significantly enhanced nuclear levels of nuclear factor erythroid-2-related factor 2 (Nrf2) in lung tissues from ovalbumin-challenged mice and in TNF-α-stimulated human bronchial epithelial cells. Our findings implicate a potential therapeutic value for artesunate in the treatment of asthma via the amelioration of oxidative damage in allergic airways, and it may act by suppressing pro-oxidants and restoring the activities and expression of antioxidants via activation of Nrf2. Artesunate may be a potential novel anti-asthma drug capable of controlling both inflammation and oxidative damage in chronic severe asthma.

The effect of environmental oxidative stress on airway inflammation

PURPOSE OF REVIEW

Asthma is an inflammatory respiratory condition with significantly associated morbidity and mortality that is increasing in prevalence. Air pollution is an important factor in both the development of asthma and in asthma exacerbations. Oxidative stress as a result of exposure to air pollution and underlying genetic polymorphisms that may play a role in susceptibility to this oxidative stress are the subject of current investigation. This article reviews the data regarding the effects of air pollution on the innate immune response and potential clinical and treatment implications of how genetic polymorphisms affect this response.

RECENT FINDINGS

Recent investigation reveals how pollutant-induced oxidative stress impacts airway inflammatory responses. Work by our study group demonstrates that asthmatic patients have an exaggerated inflammatory response to air pollution-induced oxidative stress. New trials investigating antioxidants as potential therapeutic interventions may target this specific issue.

SUMMARY

Air pollution plays a critical role in asthma and may affect certain patients more than others. Further investigation into the genetic polymorphisms that affect inflammatory responses may help target patient populations at greatest risk for air pollution-induced asthma and may provide new therapeutic options for these patient populations.

Ozone induces inflammation in bronchial epithelial cells

AIM

Ozone is a main component of secondary pollutants of vehicle exhausts, and ozone exposure to children in urban areas may be associated with the development of asthma. However, little is known about the mechanism(s) by which ozone affects human airway epithelium and subsequent airway inflammation.

METHODS

Human bronchial epithelial cells were exposed to ozone at 0.16 mg/m(3) for varying periods. The concentrations of IL-1 and IL-6 secreted by the cells were measured by enzyme-linked immunosorbent assay (ELISA) and the contents of intracellular malondialdehyde (MDA) were determined. Furthermore, the conditional medium from the ozone-exposed cells was examined for stimulating human peripheral T lymphocytes from asthmatic patients and healthy subjects, and the production of cytokines was characterized by ELISA and quantitative real-time polymerase chain reaction (RT-PCR).

RESULTS

Ozone stimulated the IL-1 and IL-6 production by BEAS-2B cells and its stimulatory effects were time dependent. Furthermore, ozone exposure significantly increased the levels of MDA in BEAS-2B cells, as compared with that of the cells without ozone exposure, in a time-dependent manner. In addition, the conditional medium from the cells exposed to ozone, but not control condition medium, significantly increased the relative levels of IL-1 mRNA transcripts in human peripheral T lymphocytes from asthmatic patients, but not healthy subjects. However, the conditional medium did not induce significantly increased levels of IL-2 production by peripheral T cells.

CONCLUSIONS

Our data indicated that exposure to low levels of ozone for a short period induced increases in the pro-inflammatory markers and oxidative stress in epithelial cells, which might contribute to airway inflammation particularly in asthmatic children.