Ozone exposure enhances mast-cell inflammation in asthmatic airways despite inhaled corticosteroid therapy

Climate change, air pollution and chronic respiratory diseases: understanding risk factors and the need for adaptive strategies

Under the background of climate change, the escalating air pollution and extreme weather events have been identified as risk factors for chronic respiratory diseases (CRD), causing serious public health burden worldwide. This review aims to summarize the effects of changed atmospheric environment caused by climate change on CRD. Results indicated an increased risk of CRD (mainly COPD, asthma) associated with environmental factors, such as air pollutants, adverse meteorological conditions, extreme temperatures, sandstorms, wildfire, and atmospheric allergens. Furthermore, this association can be modified by factors such as socioeconomic status, adaptability, individual behavior, medical services. Potential pathophysiological mechanisms linking climate change and increased risk of CRD involved pulmonary inflammation, immune disorders, oxidative stress. Notably, the elderly, children, impoverished groups and people in regions with limited adaptability are more sensitive to respiratory health risks caused by climate change. This review provides a reference for understanding risk factors of CRD in the context of climate change, and calls for the necessity of adaptive strategies. Further interdisciplinary research and global collaboration are needed in the future to enhance adaptability and address climate health inequality.

Identification of an ATP/P2X7/mast cell pathway mediating ozone-induced bronchial hyperresponsiveness

Ozone is a highly reactive environmental pollutant with well-recognized adverse effects on lung health. Bronchial hyperresponsiveness (BHR) is one consequence of ozone exposure, particularly for individuals with underlying lung disease. Our data demonstrated that ozone induced substantial ATP release from human airway epithelia in vitro and into the airways of mice in vivo and that ATP served as a potent inducer of mast cell degranulation and BHR, acting through P2X7 receptors on mast cells. Both mast cell-deficient and P2X7 receptor-deficient (P2X7-/-) mice demonstrated markedly attenuated BHR to ozone. Reconstitution of mast cell-deficient mice with WT mast cells and P2X7-/- mast cells restored ozone-induced BHR. Despite equal numbers of mast cells in reconstituted mouse lungs, mice reconstituted with P2X7-/- mast cells demonstrated significantly less robust BHR than mice reconstituted with WT mast cells. These results support a model where P2X7 on mast cells and other cell types contribute to ozone-induced BHR.

Scientometric analysis: identification of research trends for ozone as an air pollutant for 2011-2019

Ground level ozone is a major air pollutant with known toxic effects on humans. The research field is well established with many scientists from developed and developing countries contributing original research articles. Strict regulations for ozone air pollution are being implemented worldwide based on supporting scientific literature. In this scientometric analysis, we have analyzed the research trends in the field of ozone air pollution during 2011-2019. The collected SCOPUS data was analyzed using common scientometric analysis methods for known indicators to identify top ten rankings and scientific collaborations important for the field. Our result demonstrates that the USA is leading the field as USEPA and American regulatory authorities have funded most of the research. Two scientists, Russell A.G. and Schwartz J., working in American institutions, are leading with the most publications. Our assessment of ozone and PM together shows a significant impact on research direction in the last years to accommodate the study of both air pollutants together. In addition, we have analyzed the possible disease trends in the field for the last 3 years and identified that cardiovascular system, nervous system, and diabetes are upcoming disease areas that would be studied in the coming future.

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.

The effects of neutralizing anti-murine interleukin-17A monoclonal antibody on ozone-induced inflammation and glucocorticoids insensitivity in a murine model of asthma

BACKGROUND AND OBJECTIVE

Exposure to ozone contributed to the worsening of inflammation and glucocorticoids insensitivity in OVA-challenged asthma. Interleukin-17A participates centrally in stages of the inflammatory response and glucocorticoids insensitivity. In this study, the effect of neutralizing anti-murine interleukin-17A monoclonal antibody (IL-17A mAb) on inflammation and glucocorticoids insensitivity in ozone-exposed and ovalbumin (OVA)-challenged mice was investigated.

METHODS

Mice were sensitized and challenged with OVA and then exposed to ozone. Dexamethasone (Dex) and IL-17A mAb were administrated in corresponding periods.

RESULTS

Compared with OVA-challenged mice, combination administration of ozone exposure and OVA challenge increased the recruitment of inflammatory cells in bronchoalveolar lavage fluid, enhanced the inflammation scores and levels of inflammatory cytokines and IL-17A mRNA, and caused the activation of p38 MAPK together with down regulation of glucocorticoids recepters (GR) in lung tissue. Monotherapy of IL-17A mAb partially attenuated lung inflammation in OVA-challenged and ozone-exposed mice, while the combination treatment of Dex and IL-17A mAb effectively reduced lung inflammation, inactivated p38 MAPK and up regulated GR in lung tissue.

CONCLUSIONS

Ozone exposure worsened OVA-challenged airway inflammation, activation of p38 MAPK and down regulation of GR in OVA-sensitized and -challenged mice, which was effectively counteracted by IL-17A mAb, and combination treatment of IL-17A mAb and Dex shows profound efficacy in inhibiting airway inflammation and improving glucocorticoids insensitivity synergistically.

Mast cells in asthma--state of the art

Mast cells (MCs) play a central role in tissue homoeostasis, sensing the local environment through numerous innate cell surface receptors. This enables them to respond rapidly to perceived tissue insults with a view to initiating a co-ordinated programme of inflammation and repair. However, when the tissue insult is chronic, the ongoing release of multiple pro-inflammatory mediators, proteases, cytokines and chemokines leads to tissue damage and remodelling. In asthma, there is strong evidence of ongoing MC activation, and their mediators and cell-cell signals are capable of regulating many facets of asthma pathophysiology. This article reviews the evidence behind this.

Acute exposure to wood smoke from incomplete combustion--indications of cytotoxicity

Background

Smoke from combustion of biomass fuels is a major risk factor for respiratory disease, but the underlying mechanisms are poorly understood. The aim of this study was to determine whether exposure to wood smoke from incomplete combustion would elicit airway inflammation in humans.

Methods

Fourteen healthy subjects underwent controlled exposures on two separate occasions to filtered air and wood smoke from incomplete combustion with PM₁ concentration at 314 μg/m³ for 3 h in a chamber. Bronchoscopy with bronchial wash (BW), bronchoalveolar lavage (BAL) and endobronchial mucosal biopsies was performed after 24 h. Differential cell counts and soluble components were analyzed, with biopsies stained for inflammatory markers using immunohistochemistry. In parallel experiments, the toxicity of the particulate matter (PM) generated during the chamber exposures was investigated in vitro using the RAW264.7 macrophage cell line.

Results

Significant reductions in macrophage, neutrophil and lymphocyte numbers were observed in BW (p < 0.01, <0.05, <0.05, respectively) following the wood smoke exposure, with a reduction in lymphocytes numbers in BAL fluid (<0.01. This unexpected cellular response was accompanied by decreased levels of sICAM-1, MPO and MMP-9 (p < 0.05, <0.05 and <0.01). In contrast, significant increases in submucosal and epithelial CD3+ cells, epithelial CD8+ cells and submucosal mast cells (p < 0.01, <0.05, <0.05 and <0.05, respectively), were observed after wood smoke exposure. The in vitro data demonstrated that wood smoke particles generated under these incomplete combustion conditions induced cell death and DNA damage, with only minor inflammatory responses.

Conclusions

Short-term exposure to sooty PAH rich wood smoke did not induce an acute neutrophilic inflammation, a classic hallmark of air pollution exposure in humans. While minor proinflammatory lymphocytic and mast cells effects were observed in the bronchial biopsies, significant reductions in BW and BAL cells and soluble components were noted. This unexpected observation, combined with the in vitro data, suggests that wood smoke particles from incomplete combustion could be potentially cytotoxic. Additional research is required to establish the mechanism of this dramatic reduction in airway leukocytes and to clarify how this acute response contributes to the adverse health effects attributed to wood smoke exposure.

Trial registration

NCT01488500

Electronic supplementary material

The online version of this article (doi:10.1186/s12989-015-0111-7) contains supplementary material, which is available to authorized users.

Impact of ozone exposure on the response to glucocorticoid in a mouse model of asthma: involvements of p38 MAPK and MKP-1

Background

Molecular mechanisms involved in the oxidative stress induced glucocorticoids insensitivity remain elusive. The mitogen-activated protein kinase phosphatase (MKP) 1 mediates a part of glucocorticoids action and can be modified by exogenous oxidants. Whether oxidant ozone (O₃) can affect the function of MKP-1 and hence blunt the response to corticotherapy is not clear.

Methods

Here we employed a murine model of asthma established with ovalbumin (OVA) sensitization and challenge to evaluate the influence of O₃ on the inhibitory effect of dexamethasone on AHR and airway inflammation, and by administration of SB239063, a selective p38 MAPK inhibitor, to explore the underlying involvements of the activation of p38 MAPK and the expression of MKP-1.

Results

Ozone exposure not only aggravated the pulmonary inflammation and AHR, but also decreased the inhibitory effects of dexamethasone, accompanied by the elevated oxidative stress, airway neutrophilia, enhanced phosphorylation of p38 MAPK, and upregulated expression of IL-17. Administration of SB239063 caused significant inhibition of the p38 MAPK phosphorylation, alleviation of the airway neutrophilia, and decrement of the ozone-induced IL-17 expression, and partly restored the ozone-impaired effects of dexamethasone. Ozone exposure not only decreased the protein expression of MKP-1, but also diminished the dexamethasone-mediated induction process of MKP-1 mRNA and protein expression.

Conclusions

The glucocorticoids insensitivity elicited by ozone exposure on current asthma model may involve the enhanced phosphorylation of p38 MAPK and disturbed expression of MKP-1.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-014-0126-x) contains supplementary material, which is available to authorized users.

Airway inflammatory responses to diesel exhaust in allergic rhinitics

CONTEXT

Proximity to traffic, particularly to diesel-powered vehicles, has been associated with inducing and enhancing allergies. To investigate the basis for this association, we performed controlled exposures of allergic rhinitics to diesel exhaust (DE) at a dose known to be pro-inflammatory in healthy individuals.

OBJECTIVE

We hypothesized that diesel-exhaust exposure would augment lower airway inflammation in allergic rhinitics.

MATERIALS AND METHODS

Fourteen allergic rhinitics were exposed in a double-blinded, randomized trial to DE (100 μg/m³ PM₁₀) and filtered air for 2 h on separate occasions. Bronchoscopy with endobronchial mucosal biopsies and airway lavage was performed 18 h post-exposure, and inflammatory markers were assessed.

RESULTS

No evidence of neutrophilic airway inflammation was observed post-diesel, however, a small increase in myeloperoxidase was found in bronchoalveolar lavage (p = 0.032). We found no increases in allergic inflammatory cells. Reduced mast cell immunoreactivity for tryptase was observed in the epithelium (p = 0.013) parallel to a small decrease in bronchial wash stem cell factor (p = 0.033).

DISCUSSION AND CONCLUSION

DE, at a dose previously shown to cause neutrophilic inflammation in healthy individuals, induced no neutrophilic inflammation in the lower airways of allergic rhinitics, consistent with previous reports in asthmatics. Although there was no increase in allergic inflammatory cell numbers, the reduction in tryptase in the epithelium may indicate mast cell degranulation. However, this occurred in the absence of allergic symptoms. These data do not provide a simplistic explanation of the sensitivity in rhinitics to traffic-related air pollution. The role of mast cells requires further investigation.

Application of metabolomics approaches to the study of respiratory diseases

Metabolomics is the global unbiased analysis of all the small-molecule metabolites within a biological system, under a given set of conditions. These methods offer the potential for a holistic approach to clinical medicine, as well as improving disease diagnosis and understanding of pathological mechanisms. Respiratory diseases including asthma and chronic obstructive pulmonary disorder are increasing globally, with the latter predicted to become the third leading cause of global mortality by 2020. The root causes for disease onset remain poorly understood and no cures are available. This review presents an overview of metabolomics followed by in-depth discussion of its application to the study of respiratory diseases, including the design of metabolomics experiments, choice of clinical material collected and potentially confounding experimental factors. Particular challenges in the field are presented and placed within the context of the future of the applications of metabolomics approaches to the study of respiratory diseases.

Ambient ozone and pulmonary innate immunity

Ambient ozone is a criteria air pollutant that impacts both human morbidity and mortality. The effect of ozone inhalation includes both toxicity to lung tissue and alteration of the host immunologic response. The innate immune system facilitates immediate recognition of both foreign pathogens and tissue damage. Emerging evidence supports that ozone can modify the host innate immune response and that this response to inhaled ozone is dependent on genes of innate immunity. Improved understanding of the complex interaction between environmental ozone and host innate immunity will provide fundamental insight into the pathogenesis of inflammatory airways disease. We review the current evidence supporting that environmental ozone inhalation: (1) modifies cell types required for intact innate immunity, (2) is partially dependent on genes of innate immunity, (3) primes pulmonary innate immune responses to LPS, and (4) contributes to innate-adaptive immune system cross-talk.