Polycyclic aromatic hydrocarbons from diesel emissions exert proallergic effects in birch pollen allergic individuals through enhanced mediator release from basophils

Children's exposure to polycyclic aromatic hydrocarbon (PAHs): a review on urinary 1-hydroxypyrene and associated health effects

This article reviewed the published studies on the environmental exposure to polycyclic aromatic hydrocarbons (PAHs) among children and assessed the urinary 1-hydroxypyrene (1-OHP) level as a biomarker of exposure to PAHs. The current knowledge of the potential health effects of increased 1-OHP in children was reviewed. Additionally, the influence of genetic polymorphism on the urinary 1-OHP level was discussed in this review. The assembled data showed that children who are attending schools or living close to industrial and polluted urban areas might have greater exposure to higher concentrations of PAHs with a higher level of urinary 1-OHP when compared to those children living in rural areas. Urinary 1-OHP may be a reliable biomarker for determining the genotoxic effects, oxidative stress and inflammation caused by exposure to PAHs. Strong research evidence indicated that the total body burden of PAHs should be evaluated by biomonitoring of 1-OHP in line with other urinary PAHs metabolites (with 2-3 rings) to evaluate recent total exposure to PAHs. Overall, the study suggests implementing a mitigation plan to combat air pollution to provide a cleaner environment for children.

EAACI Molecular Allergology User's Guide 2.0

Since the discovery of immunoglobulin E (IgE) as a mediator of allergic diseases in 1967, our knowledge about the immunological mechanisms of IgE-mediated allergies has remarkably increased. In addition to understanding the immune response and clinical symptoms, allergy diagnosis and management depend strongly on the precise identification of the elicitors of the IgE-mediated allergic reaction. In the past four decades, innovations in bioscience and technology have facilitated the identification and production of well-defined, highly pure molecules for component-resolved diagnosis (CRD), allowing a personalized diagnosis and management of the allergic disease for individual patients. The first edition of the "EAACI Molecular Allergology User's Guide" (MAUG) in 2016 rapidly became a key reference for clinicians, scientists, and interested readers with a background in allergology, immunology, biology, and medicine. Nevertheless, the field of molecular allergology is moving fast, and after 6 years, a new EAACI Taskforce was established to provide an updated document. The Molecular Allergology User's Guide 2.0 summarizes state-of-the-art information on allergen molecules, their clinical relevance, and their application in diagnostic algorithms for clinical practice. It is designed for both, clinicians and scientists, guiding health care professionals through the overwhelming list of different allergen molecules available for testing. Further, it provides diagnostic algorithms on the clinical relevance of allergenic molecules and gives an overview of their biology, the basic mechanisms of test formats, and the application of tests to measure allergen exposure.

Air Pollution and Allergic Rhinitis: Role in Symptom Exacerbation and Strategies for Management

This article reviews the current understanding of the role of air pollution in both the symptom exacerbation and rising prevalence of allergic rhinitis (AR) for the development of future AR therapeutics and management strategies. We discuss the epidemiological evidence for this relationship through birth cohort studies, the economic impact of AR, and the influence of air pollution through the lens of the exposome framework of allergic disease development. This is followed by a discussion on the influence of diesel exhaust and diesel exhaust particles (DEP) from motor vehicle emissions and their implication in the rising prevalence of allergic disease and allergic sensitization through triggering inflammatory signalling pathways that exacerbate AR symptoms. Finally, a summary is provided of clinical trials assessing the influence of air pollution on AR with a depiction of currently available therapies and management strategies. Future directions in the development of AR modalities given the air pollution-mediated symptom exacerbation are challenged with unfolding the complex gene–environment interaction product of heterogenous AR presentation.

Mechanisms of Particles in Sensitization, Effector Function and Therapy of Allergic Disease

Humans have always been in contact with natural airborne particles from many sources including biologic particulate matter (PM) which can exhibit allergenic properties. With industrialization, anthropogenic and combustion-derived particles have become a major fraction. Currently, an ever-growing number of diverse and innovative materials containing engineered nanoparticles (NPs) are being developed with great expectations in technology and medicine. Nanomaterials have entered everyday products including cosmetics, textiles, electronics, sports equipment, as well as food, and food packaging. As part of natural evolution humans have adapted to the exposure to particulate matter, aiming to protect the individual's integrity and health. At the respiratory barrier, complications can arise, when allergic sensitization and pulmonary diseases occur in response to particle exposure. Particulate matter in the form of plant pollen, dust mites feces, animal dander, but also aerosols arising from industrial processes in occupational settings including diverse mixtures thereof can exert such effects. This review article gives an overview of the allergic immune response and addresses specifically the mechanisms of particulates in the context of allergic sensitization, effector function and therapy. In regard of the first theme (i), an overview on exposure to particulates and the functionalities of the relevant immune cells involved in allergic sensitization as well as their interactions in innate and adaptive responses are described. As relevant for human disease, we aim to outline (ii) the potential effector mechanisms that lead to the aggravation of an ongoing immune deviation (such as asthma, chronic obstructive pulmonary disease, etc.) by inhaled particulates, including NPs. Even though adverse effects can be exerted by (nano)particles, leading to allergic sensitization, and the exacerbation of allergic symptoms, promising potential has been shown for their use in (iii) therapeutic approaches of allergic disease, for example as adjuvants. Hence, allergen-specific immunotherapy (AIT) is introduced and the role of adjuvants such as alum as well as the current understanding of their mechanisms of action is reviewed. Finally, future prospects of nanomedicines in allergy treatment are described, which involve modern platform technologies combining immunomodulatory effects at several (immuno-)functional levels.

Interactions between polycyclic aromatic hydrocarbons and epoxide hydrolase 1 play roles in asthma

Asthma, as one of the most common chronic diseases in children and adults, is a consequence of complex gene-environment interactions. Polycyclic aromatic hydrocarbons (PAHs), as a group of widespread environmental organic pollutants, are involved in the development, triggering and pathologic changes of asthma. Various previous studies reported the critical roles of PAHs in immune changes, oxidative stress and environment-gene interactions of asthma. EPHX1 (the gene of epoxide hydrolase 1, an enzyme mediating human PAH metabolism) had a possible association with asthma by influencing PAH metabolism. This review summarized that (1) the roles of PAHs in asthma-work as risk factors; (2) the possible mechanisms involved in PAH-related asthma-through immunologic and oxidative stress changes; (3) the interactions between PAHs and EPHX1 involved in asthma-enzymatic activity of epoxide hydrolase 1, which affected by EPHX1 genotypes/SNPs/diplotypes, could influence human PAH metabolism and people's vulnerability to PAH exposure. This review provided a better understanding of the above interactions and underlying mechanisms for asthma which help to raise public's concern on PAH control and develop strategies for individual asthma primary prevention.

Bronchial epithelial innate and adaptive immunity signals are induced by polycyclic aromatic hydrocarbons

Polycyclic aromatic hydrocarbons including Benzo[a]pyrene have been recognised as important pollutant chemicals with the potential to influence the respiratory system in disease. Airway epithelial cells are an integral component of how immune responses are directed as a consequence of exposure to inhaled material. It was aim of this study to examine how such cells respond to PAH exposure and to characterise the immune response. Human primary bronchial epithelial cells (HPBECs) were exposed to Benzo[a]pyrene, Benzo[e]pyrene, Fluoranthene and Benzo[b]fluoranthene for 24 h and a repeat exposure up to 7 days, and examined for global gene expression using RNA-Seq. In addition to increased expression of CYP1A1 and other AHR dependent changes, we identified significant increases in innate and adaptive immune signals including, IL-1A, IL-19, SERPINB2, STAT6, HLA-DMB and HLA-DRA. We also observed increased expression of HMOX1 and NQO1, genes involved in the response to oxidative stress. Immune system related gene expression was differentially induced by each compound with Benzo[a]pyrene and Benzo[b]fluoranthene demonstrating the most potent responses. Differential induction paralleled the level to which AHR dependent gene expression and oxidative stress markers were induced. We also observed similar levels of gene expression when cells were exposed to organic extracts from diesel exhaust particles. In conclusion, hazard characterisation of responses to PAH exposure in HPBECs highlights specific responses of both innate and adaptive immunity.

A Review of the Effects of Major Atmospheric Pollutants on Pollen Grains, Pollen Content, and Allergenicity

This review summarizes the available data related to the effects of air pollution on pollen grains from different plant species. Several studies carried out either on in situ harvested pollen or on pollen exposed in different places more or less polluted are presented and discussed. The different experimental procedures used to monitor the impact of pollution on pollen grains and on various produced external or internal subparticles are listed. Physicochemical and biological effects of artificial pollution (gaseous and particulate) on pollen from different plants, in different laboratory conditions, are considered. The effects of polluted pollen grains, subparticles, and derived aeroallergens in animal models, in in vitro cell culture, on healthy human and allergic patients are described. Combined effects of atmospheric pollutants and pollen grains-derived biological material on allergic population are specifically discussed. Within the notion of "polluen," some methodological biases are underlined and research tracks in this field are proposed.

Mechanistic impact of outdoor air pollution on asthma and allergic diseases

Over the past decades, asthma and allergic diseases, such as allergic rhinitis and eczema, have become increasingly common, but the reason for this increased prevalence is still unclear. It has become apparent that genetic variation alone is not sufficient to account for the observed changes; rather, the changing environment, together with alterations in lifestyle and eating habits, are likely to have driven the increase in prevalence, and in some cases, severity of disease. This is particularly highlighted by recent awareness of, and concern about, the exposure to ubiquitous environmental pollutants, including chemicals with oxidant-generating capacities, and their impact on the human respiratory and immune systems. Indeed, several epidemiological studies have identified a variety of risk factors, including ambient pollutant gases and airborne particles, for the prevalence and the exacerbation of allergic diseases. However, the responsible pollutants remain unclear and the causal relationship has not been established. Recent studies of cellular and animal models have suggested several plausible mechanisms, with the most consistent observation being the direct effects of particle components on the generation of reactive oxygen species (ROS) and the resultant oxidative stress and inflammatory responses. This review attempts to highlight the experimental findings, with particular emphasis on several major mechanistic events initiated by exposure to particulate matters (PMs) in the exposure-disease relationship.

Polycyclic aromatic hydrocarbons and childhood asthma

Asthma is the most common chronic illness in children living in developed countries and the leading cause of childhood hospitalization and school absenteeism. Prevalence rates of asthma are increasing and show disparities across gender, geographic regions, and ethnic/racial groups. Common risk factors for developing childhood asthma include exposure to tobacco smoke, previous allergic reactions, a family history of asthma, allergic rhinitis or eczema, living in an urban environment, obesity and lack of physical exercise, severe lower respiratory tract infections, and male gender. Asthma exacerbation in children can be triggered by a variety of factors, including allergens (e.g., pollen, dust mites, and animal dander), viral and bacterial infections, exercise, and exposure to airway irritants. Recent studies have shown that exposure to polycyclic aromatic hydrocarbons (PAHs), a major component of fine particulate matter from combustion sources, is also associated with onset of asthma, and increasing asthmatic symptoms. In this paper, we review sources of childhood PAH exposure and the association between airborne PAH exposure and childhood asthma prevalence and exacerbation.

Differential Transcriptional Changes in Mice Exposed to Chemically Distinct Diesel Samples

Epidemiological studies have linked exposure to ambient particulate matter (PM) with increased asthmatic symptoms. Diesel exhaust particles (DEP) are a predominant source of vehicle derived ambient PM, and experimental studies have demonstrated that they may have adjuvant potential when given with an antigen. We previously compared 3 DEP samples: N-DEP, A-DEP, and C-DEP in a murine ovalbumin (OVA) mucosal sensitization model and reported the adjuvant activity to be: C-DEP ≈ A-DEP > N-DEP. The present study analyzed gene expression changes from the lungs of these mice. Transcription profiling demonstrated that all the DEP samples altered cytokine and toll-like receptor pathways regardless of type, with or without antigen sensitization. Further analysis of DEP exposure with OVA showed that all DEP treatments altered networks involved in immune and inflammatory responses. The A- and C-DEP/OVA treatments induced differential expression of apoptosis pathways in association with stronger adjuvant responses, while expression of cell cycle control and DNA damage pathways were also altered in the C-DEP/OVA treatment. This comprehensive approach using gene expression analysis to examine changes at a pathway level provides detailed information on events occurring in the lung after DEP exposure, and confirms that the most bioactive sample induced many more individual genes and changes in immunoregulatory and homeostatic pathways.