Characterization of allergenicity of Platanus pollen allergen a 3 (Pla a 3) after exposure to NO2 and O3

Direct detection of 3-nitrotyrosine reveals the nitration of proteins in laboratory exposure and ambient aerosols

Tyrosine residues in proteins can be nitrated to form 3-nitrotyrosine (3-NT) under the influence of ozone (O3) and nitrogen dioxide (NO2) in the air, which may introduce health impacts. A selective and sensitive enzyme-linked-immunoassay (ELISA) method was developed to determine 3-NT in modified model protein (bovine serum albumin, BSA) and ambient aerosol samples. The nitration degrees (NDs) of BSA in the exposure experiments with different durations were detected by both the ELISA and spectrophotometric methods (i.e., NDELISA and NDSEC-PDA), which show good coincidence. The kinetic investigation by both ΔNDELISA and ΔNDSEC-PDA in the exposure experiments shows that the rate coefficients (k) of the pseudo-first-order kinetic rate reactions of protein nitration were comparable. These results indicate that direct detection of 3-NT by the ELISA method can be applied for laboratory exposure samples analysis for kinetic studies. Based on the selective detection of 3-NT, NDELISA provides a promising measure for the assessment of ND in model proteins. 3-NT was also measured in PM2.5 samples in summer in Guangzhou, southern China, ranging from 10.1 to 404 pg/m3, providing clear evidence of protein nitration in ambient aerosols. We further proposed that 3-NT/protein can be used as a proxy to evaluate protein nitration in ambient aerosols. A significant correlation was observed between 3-NT/protein and O3, confirming the crucial role of O3 in protein nitration. Our results show that the direct detection of 3-NT by the ELISA method can be more widely applied in the laboratory and field-based studies for understanding the mechanisms of protein nitration.

Studies on adsorption and synergistic biological effects induced by microplastic particles and the Platanus pollen allergenic protein 3(Pla a3)

Microplastics (MPs) are pervasive as emerging pollutants in ambient particles and may pose a potential threat to human health through respiratory exposure. Especially, impact of climate change has led to an extended blooming period for many plants, resulting in elevated pollen levels in the air, and leading to a continuous increase in the number of individuals suffering from allergenic diseases. However, the interactions between the MPs and allergenic proteins, remain largely unexplored. In this study, we investigated cellular toxicity of the MPs and Platanus pollen allergenic protein (Pla a3) based on the characterization of two typical microplastics (polystyrene, PS and polyethylene, PE). Our results indicated that UV irradiation could make surface alterations of the MPs, including breakage, particle size reduction, and an increase in surface oxygen-containing functional groups. These changes significantly enhanced the adsorption of the Pla a 3 protein. The 'protein coronas' formed by the MPs and the Pla a3 caused more damage to the A549 cells than Pla a3 alone. Reactive oxygen species (ROS) generation and elevated superoxide dismutase (SOD) levels increased significantly after the A549 cells were exposure to the protein coronas. This excessive oxidative stress led to significant inflammation and cytokine production increase, with IL-1β, IL-4, IFN-γ, and TNF-α levels rising by 1.84 ± 0.01, 2.37 ± 0.04, 1.94 ± 0.09, and 2.19 ± 0.05-fold times respectively compared to that of the Pla a 3 exposure alone. This study provided a fundamental data for further research for the allergenicity induced by the pollen proteins.

Interactions among Cupressaceae pollen, air pollutants and meteorology in the urban and suburban areas of Beijing, China

Atmospheric pollutants alter the physicochemical properties of pollen allergens, and raise a high risk of co-exposure to more aeroallergens in the allergic population. It is necessary to reveal the relationships between them and the impacts of meteorology on them both. Herein, synchronous data of aerobiology, pollution and meteorology at the same location are used to investigate the correlation between Cupressaceae pollen (major allergen in Norther China) and atmospheric pollutants, and their association with meteorological factors at different timescales in the urban and suburban areas of Beijing, China. In this research, the correlation between allergenic pollen, air pollutants and meteorological factors may display distinct patterns at daily and hourly timescales. Daily concentration of Cupressaceae pollen was positively correlated with PM2.5 and O3. Hourly pollen concentration exhibited positive correlation with NOx and PM2.5 during high-pollen episodes. Increasing temperature and decreasing relative humidity after sunrise facilitate pollination, causing hourly pollen peak. Temperature exhibited a strong positive correlation with daily and hourly O3 concentrations. Highly humid conditions largely decreased allergenic pollen and O3 concentrations but increased NOx and PM2.5 concentrations. In the urban area, local winds considerably impacting on hourly pollen peaks were associated with high levels of NOx and PM2.5. Concentration weighted trajectory (CWT) results indicated that allergenic pollen and O3 may have some common potential source areas. This research will help us to get a better understanding of the linkage between allergenic pollen and air pollutants, and their dynamics under varying meteorological conditions, and provide effective support on addressing respiratory allergies on the risk of co-exposure for allergenic pollen and air pollutants in the urban and suburban areas of Beijing city.

The impact of ecosystem nitrogen enrichment on pollen allergy: a cross-sectional paired comparison study

BACKGROUND

The prevalence of allergy to aeroallergens is rising, driven by both environmental and lifestyle changes. However, the role of ubiquitous nitrogen enrichment in exacerbating pollen allergy remains unclear. This study aimed to investigate the impact of nitrogen on pollen allergenicity by connecting the resulting ecological changes with allergic outcomes.

METHODS

We conducted a cross-sectional paired comparison study, examining differences between nitrogen-enriched (fertilised) and non-enriched common semi-natural grasslands in Belgium. Pollen from paired grasslands (n=50, enriched [n=25] vs non-enriched [n=25]) based on their common geography, were sampled following a standardised protocol. We analysed grassland pollen abundance, quantified pollen species composition via DNA sequencing, and assessed pollen allergenicity using basophil activation testing and specific IgE measurements in a cross-sectional sample of adults who were allergic to grass pollen (n=20). Basophil activation test outcome measures included area under the dose-response curve, maximal reactivity (CD63max), and effective concentration eliciting 50% basophil activation.

FINDINGS

Nitrogen-enriched grasslands produced significantly more pollen, with a 6·2-fold increase compared with their unfertilised counterparts (3·6 mg/m2vs 0·6 mg/m2). When normalised to protein content, pollen from these enriched grasslands showed increased allergenic potential, with 5·1 times higher basophil activation test sensitivity and a 1·3-fold increase in specific IgE titres compared with their unfertilised counterparts (geometric mean fertilised 3·63 kUA/L vs unfertilised 2·81 kUA/L).

INTERPRETATION

Nitrogen enrichment substantially increased pollen abundance and allergenicity, indicating a heightened allergy burden in nitrogen-rich environments. These findings underscore the need for policies addressing nitrogen pollution to mitigate its public health impacts.

FUNDING

Belgian Science Policy Office.

Novel Approach Methodologies in Modeling Complex Bioaerosol Exposure in Asthma and Allergic Rhinitis Under Climate Change

The undeniable impact of climate change and air pollution on respiratory health has led to increasing cases of asthma, allergic rhinitis and other chronic non-communicable immune-mediated upper and lower airway diseases. Natural bioaerosols, such as pollen and fungi, are essential atmospheric components undergoing significant structural and functional changes due to industrial pollution and atmospheric warming. Pollutants like particulate matter(PMx), polycyclic aromatic hydrocarbons(PAHs), nitrogen dioxide(NO2), sulfur dioxide(SO2) and carbon monoxide(CO) modify the surface and biological properties of atmospheric bioaerosols such as pollen and fungi, enhancing their allergenic potentials. As a result, sensitized individuals face heightened risks of asthma exacerbation, and these alterations likely contribute to the rise in frequency and severity of allergic diseases. NAMs, such as precision-cut lung slices(PCLS), air-liquid interface(ALI) cultures and lung-on-a-chip models, along with the integration of data from these innovative models with computational models, provide better insights into how environmental factors influence asthma and allergic diseases compared to traditional models. These systems simulate the interaction between pollutants and the respiratory system with higher precision, helping to better understand the health implications of bioaerosol exposure. Additionally, NAMs improve preclinical study outcomes by offering higher throughput, reduced costs and greater reproducibility, enhancing the translation of data into clinical applications. This review critically evaluates the potential of NAMs in researching airway diseases, with a focus on allergy and asthma. It highlights their advantages in studying the increasingly complex structures of bioaerosols under conditions of environmental pollution and climate change, while also addressing the existing gaps, challenges and limitations of these models.

Combatting the antigenicity of common ragweed pollen and its primary allergen Amb a 1 with cold atmospheric pressure air plasma

Airborne allergens, especially those originating from various types of pollen, significantly compromise the health and well-being of individuals on a global scale. Here, cold atmospheric pressure plasma (CAP) created in ambient air was used to treat highly allergenic and invasive Ambrosia artemisiifolia pollen. Immunoassays were used to evaluate the impact of CAP on the principal A. artemisiifolia allergen Amb a 1, demonstrating that > 90 % reduction in antigenicity could be achieved. Chemical analyses using Fourier Transform infrared revealed that CAP induced significant alterations to proteins on the surface of pollen grains, resulting in a 43 % increase in the amide I peak area and a 57 % increase in the amide II peak area. These findings were corroborated by Raman and X-ray photoelectron spectroscopy, which indicated that the protein modifications induced by CAP were due to carbonylation and nitration/nitrosylation processes. Beyond protein transformations, CAP also induced notable oxidation and modification of lipid-like compounds, polysaccharides and sporopollenin. Evident transformations at the chemical level translated into morphological changes at the grain surface, manifesting as increased roughness via significant outer-layer etching. These findings underscore the potential of CAP technology as a viable approach for mitigating against the allergenicity of pollen, providing a deeper understanding into the underlying chemical mechanisms.

Evaluation of laboratory and environmental exposure systems for protein modification upon gas pollutants and environmental factors

Chemical modifications of proteins induced by ambient ozone (O3) and nitrogen oxides (NOx) are of public health concerns due to their potential to trigger respiratory diseases. The laboratory and environmental exposure systems have been widely used to investigate their relevant mechanism in the atmosphere. Using bovine serum albumin (BSA) as a model protein, we evaluated the two systems and aimed to reduce the uncertainties of both the reactants and products in the corresponding kinetic study. In the laboratory simulation system, the generated gaseous pollutants showed negligible losses. Ten layers of BSA were coated on the flow tube with protein extraction recovery of 87.4%. For environmental exposure experiment, quartz fiber filter was selected as the upper filter with low gaseous O3 (8.0%) and NO2 (1.7%) losses, and cellulose acetate filter was appropriate for the lower filter with protein extraction efficiency of 95.2%. The protein degradation process was observed without the exposure to atmospheric oxidants and contributed to the loss of protein monomer mass fractions, while environmental factors (e.g., molecular oxygen and ultraviolet) may cause greater protein monomer losses. Based on the evaluation, the study exemplarily applied the two systems to protein modification and both showed that O3 promotes the protein oligomerization and nitration, while increased temperature can accelerate the oligomerization and increased relative humidity can inhibit the nitration in the environmental exposure samples. The developed laboratory and environmental systems are suitable for studying protein modifications formed under different atmospheric conditions. A combination of the two will further reveal the actual mechanism of protein modifications.

Alteration of the health effects of bioaerosols by chemical modification in the atmosphere: A review

Bioaerosols are a subset of important airborne particulates that present a substantial human health hazard due to their allergenicity and infectivity. Chemical reactions in atmospheric processes can significantly influence the health hazard presented by bioaerosols; however, few studies have summarized such alterations to bioaerosols and the mechanisms involved. In this paper, we systematically review the chemical modifications of bioaerosols and the impact on their health effects, mainly focusing on the exacerbation of allergic diseases such as asthma, rhinitis, and bronchitis. Oxidation, nitration, and oligomerization induced by hydroxyl radicals, ozone, and nitrogen dioxide are the major chemical modifications affecting bioaerosols, all of which can aggravate allergenicity mainly through immunoglobulin E pathways. Such processes can even interact with climate change including the greenhouse effect, suggesting the importance of bioaerosols in the future implementation of carbon neutralization strategies. In summary, the chemical modification of bioaerosols and the subsequent impact on health hazards indicate that the combined management of both chemical and biological components is required to mitigate the health hazards of particulate air pollution.

Outdoor airborne allergens: Characterization, behavior and monitoring in Europe

Aeroallergens or inhalant allergens, are proteins dispersed through the air and have the potential to induce allergic conditions such as rhinitis, conjunctivitis, and asthma. Outdoor aeroallergens are found predominantly in pollen grains and fungal spores, which are allergen carriers. Aeroallergens from pollen and fungi have seasonal emission patterns that correlate with plant pollination and fungal sporulation and are strongly associated with atmospheric weather conditions. They are released when allergen carriers come in contact with the respiratory system, e.g. the nasal mucosa. In addition, due to the rupture of allergen carriers, airborne allergen molecules may be released directly into the air in the form of micronic and submicronic particles (cytoplasmic debris, cell wall fragments, droplets etc.) or adhered onto other airborne particulate matter. Therefore, aeroallergen detection strategies must consider, in addition to the allergen carriers, the allergen molecules themselves. This review article aims to present the current knowledge on inhalant allergens in the outdoor environment, their structure, localization, and factors affecting their production, transformation, release or degradation. In addition, methods for collecting and quantifying aeroallergens are listed and thoroughly discussed. Finally, the knowledge gaps, challenges and implications associated with aeroallergen analysis are described.

Impact of environmental nitrogen pollution on pollen allergy: A scoping review

The current rise in the prevalence of allergies to aeroallergens is incompletely understood and attributed to interactions with environmental changes and lifestyle changes. Environmental nitrogen pollution might be a potential driver of this increasing prevalence. While the ecological impact of excessive nitrogen pollution has been widely studied and is relatively well understood, its indirect effect on human allergies is not well documented. Nitrogen pollution can affect the environment in various ways, including air, soil, and water. We aim to provide a literature overview of the nitrogen-driven impact on plant communities, plant productivity, and pollen properties and how they lead to changes in allergy burden. We included original articles investigating the associations between nitrogen pollution, pollen, and allergy, published in international peer-reviewed journals between 2001 and 2022. Our scoping review found that the majority of studies focus on atmospheric nitrogen pollution and its impact on pollen and pollen allergens, causing allergy symptoms. These studies often examine the impact of multiple atmospheric pollutants and not just nitrogen, making it difficult to determine the specific impact of nitrogen pollution. There is some evidence that atmospheric nitrogen pollution affects pollen allergy by increasing atmospheric pollen levels, altering pollen structure, altering allergen structure and release, and causing increased allergenic reactivity. Limited research has been conducted on the impact of soil and aqueous nitrogen pollution on pollen allergenic reactivity. Further research is needed to fill the current knowledge gap about the impact of nitrogen pollution on pollen and their related allergic disease burden.

Impact of meteorological parameters and air pollutants on airborne concentration of Betula pollen and Bet v 1 allergen

The intensity of birch pollen season is expressed by seasonal pollen integral (SPIn, the sum of the mean daily pollen concentration during the birch pollination period) and the amount of Bet v 1 allergen released per birch pollen grain expressed by pollen allergen potency (PAP). Betula pollen and Bet v 1 allergen were simultaneously measured in the air of Bratislava from 2019 to 2022 by using two Burkard traps (Hirst-type and cyclone) in order to evaluate the causes of the seasonal variation in the SPIn and PAP levels. The highest SPIn (19,975 pollen/m3) was observed in 2022 and the lowest one (1484 pollen/m3) in 2021. The average daily PAP level (4.0 pg Bet v 1/pollen) was highest in 2019 and lowest (2.5 pg Bet v 1/pollen) in 2020. We found that seasonal variation in SPIn was associated mainly with the changes in environmental conditions during the pre-season period, whereas the year-to-year variation in PAP levels was attributed to environmental conditions during both pre- and in-season periods. Our results indicate that rainy weather in June 2020 and cold overcast weather in January‒February 2021 resulted in low SPIn in 2021. On the other hand, dry weather in June 2021 and warm weather in January‒February 2022 resulted in high SPIn in 2022. The low average daily PAP level in 2020 was associated with (1) low levels of gaseous air pollutants in March, when the ripening of pollen takes place; (2) an earlier start of the birch main pollen season (MPS); and (3) dry weather during the MPS. On the other hand, high PAP level in 2019 was associated with higher levels of air pollutants in March and during the MPS.

Mechanisms of climate change and related air pollution on the immune system leading to allergic disease and asthma

Climate change is considered the greatest threat to global health. Greenhouse gases as well as global surface temperatures have increased causing more frequent and intense heat and cold waves, wildfires, floods, drought, altered rainfall patterns, hurricanes, thunderstorms, air pollution, and windstorms. These extreme weather events have direct and indirect effects on the immune system, leading to allergic disease due to exposure to pollen, molds, and other environmental pollutants. In this review, we will focus on immune mechanisms associated with allergy and asthma-related health risks induced by climate change events. We will review current understanding of the molecular and cellular mechanisms by which the changing environment mediates these effects.

The phenomenon of thunderstorm asthma in Bavaria, Southern Germany: a statistical approach

Higher incidences of asthma during thunderstorms can pose a serious health risk. In this study, we estimate the thunderstorm asthma risk using statistical methods, with special focus on Bavaria, Southern Germany. In this approach, a dataset of asthma-related emergency cases for the study region is combined with meteorological variables and aeroallergen data to identify statistical relationships between the occurrence of asthma (predictand) and different environmental parameters (set of predictors). On the one hand, the results provide evidence for a weak but significant relationship between atmospheric stability indices and asthma emergencies in the region, but also show that currently thunderstorm asthma is not a major concern in Bavaria due to overall low incidences. As thunderstorm asthma can have severe consequences for allergic patients, the presented approach can be important for the development of emergency strategies in regions affected by thunderstorm asthma and under present and future climate change conditions.

Lipid Ligands and Allergenic LTPs: Redefining the Paradigm of the Protein-Centered Vision in Allergy

Lipid Transfer Proteins (LTPs) have been described as one of the most prevalent and cross-reactive allergen families in the general population. They are widely distributed among the plant kingdom, as well as in different plant organs ranging from pollen to fruits. Thus, they can initiate allergic reactions with very different outcomes, such as asthma and food allergy. Several mouse models have been developed to unravel the mechanisms that lead LTPs to promote such strong sensitization patterns. Interestingly, the union of certain ligands can strengthen the allergenic capacity of LTPs, suggesting that not only is the protein relevant in the sensitization process, but also the ligands that LTPs carry in their cavity. In fact, different LTPs with pro-allergenic capacity have been shown to transport similar ligands, thus positioning lipids in a central role during the first stages of the allergic response. Here, we offer the latest advances in the use of experimental animals to study the topic, remarking differences among them and providing future researchers a tool to choose the most suitable model to achieve their goals. Also, recent results derived from metabolomic studies in humans are included, highlighting how allergic diseases alter the lipidic metabolism toward a pathogenic state in the individual. Altogether, this review offers a comprehensive body of work that sums up the background evidence supporting the role of lipids as modulators of allergic diseases. Studying the role of lipids during allergic sensitization might broaden our understanding of the molecular events leading to tolerance breakdown in the epithelium, thus helping us to understand how allergy is initiated and established in the individuals.

Comparison of the characterization of allergenic protein 3 (Pla a3) released from Platanus pollen grains collected in Shanghai during the spring of 2019 and 2020

Due to the COVID-19 pandemic in early 2020, large-scale industrial production has been stagnant and reduced, the urban air quality has been greatly improved. It provided an excellent opportunity to explore the effects of air pollutants on the sensitization of pollen allergen proteins in the environment. Platanus pollen grains sampled in the spring of 2019 and 2020 were used for detailed characterization and analysis. Scanning electron microscopy, Fourier transform infrared, X-ray spectroscopy (XPS), trypan blue staining, and western blot analysis were employed to characterize Platanus pollen protein released from pollen grains. Our data showed that the viability of the pollen grains in 2019 was lower compared that in 2020, and the pollen grains collected in 2019 had a higher absorption peak of protein functional groups. The XPS spectra assay result demonstrated that the binding energy of the high-resolution components had not variation on the surface of pollen grains, but relative content of nitrogen and peptide chain in the pollen grains sampled in 2019 were higher than in 2020. These results suggested that more protein in the pollen grains was released onto the surface of pollen grains. In addition, western blot assay showed that the expression of Pla a3 protein in pollen grains sampled in 2019 was significantly higher than that in 2020, revealing that air pollutants could enhance the expression of Pla a3 proteins in Platanus pollen.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s10453-021-09731-6.