The effects on bronchial epithelial mucociliary cultures of coarse, fine, and ultrafine particulate matter from an underground railway station

Are metals in exhaled breath condensate and urine associated with oxidative/nitrosative stress and metabolism-related biomarkers? Results from 303 randomly selected Parisian subway workers

BACKGROUND

Subway particles can cause oxidative stress, with metals being a key factor. Only few epidemiological studies have examined the role of metal mixtures in this effect for subway workers.

OBJECTIVES

This cross-sectional study examined the relationship between metal concentrations in exhaled breath condensate (EBC) and urine, and biomarkers of oxidative/nitrosative stress and metabolism in subway workers.

METHODS

The study involved 303 randomly selected Parisian metro workers exposed to various levels of subway particles. Metals in EBC and urine were measured using ICP-MS, and biomarkers were analyzed through liquid chromatography-mass spectrometry. Factor analysis as dimension reduction strategy and cluster analysis to account for metal mixtures and multiple multi-media effect biomarkers was used along with multivariable linear regression analysis on factor variables adjusted for potential confounders.

RESULTS

Significant positive associations were observed between urinary metals and oxidative stress biomarkers, despite similar metal levels in workers and the general population. Metals in EBC were linked to nitrosative stress and other metabolites in EBC. Worker occupation correlated with small chain fatty acids in EBC and urinary levels of barium and titanium. Smoking was associated with effect biomarkers but not with exposure biomarkers.

CONCLUSIONS

Elevated metal levels in EBC and urine are associated with altered bronchopulmonary metabolites and increased systemic oxidative stress. While Ba and Ti may originate from brake wear, other metals identified in EBC and urine are not clearly related with subway particles and may be from non-occupational sources. Smoking showed a stronger relationship with the workers' oxidative stress status than occupation.

Ferruginous components of particulate matters in subway environments, α-Fe2O3 or Fe3O4, exacerbates allergies

The respiratory effects of particulate matter (PM) in subway station platforms or tunnels have attracted considerable research attention. However, no studies have characterized the effects of subway PM on allergic immune responses. In this study, iron oxide (α-Fe2O3 and Fe3O4) particles-the main components of subway PM-were intratracheally administered to BALB/c mice where ovalbumin (OVA) induced allergic pulmonary inflammation. Iron oxide particles enhanced OVA-induced eosinophil recruitment around the bronchi and mucus production from airway epithelium. The concentrations of type 2 cytokines, namely, interleukin (IL)-5 and IL-13, in bronchial alveolar lavage fluids were increased by iron oxide particles. Iron oxide particles also increased the number of type 2 innate lymphoid cells and CD86+ cells in the lung. Moreover, phagocytosis of particles in lung cells was confirmed by Raman spectroscopy. In a subsequent in vitro study, bone marrow-derived antigen-presenting cells (APCs) isolated from NC/Nga mice were exposed to iron oxide particles and OVA. They were also exposed to outdoor ambient PM: Vehicle Exhaust Particulates (VEP) and Urban Aerosols (UA) as references. Iron oxide particles promoted the release of lactate dehydrogenase, C-X-C motif chemokine ligand 1 and IL-1α from APCs, which tended to be stronger than those of VEP. These results suggest that iron oxide particles enhance antigen presentation in the lungs, promoting allergic immune response in mice; iron oxide particles-induced death and inflammatory response of APCs can contribute to allergy exacerbation. Although iron oxide particles do not contain various compounds like VEP, iron oxide alone may have sufficient influence.

Metal and oxidative potential exposure through particle inhalation and oxidative stress biomarkers: a 2-week pilot prospective study among Parisian subway workers

OBJECTIVE

In this pilot study on subway workers, we explored the relationships between particle exposure and oxidative stress biomarkers in exhaled breath condensate (EBC) and urine to identify the most relevant biomarkers for a large-scale study in this field.

METHODS

We constructed a comprehensive occupational exposure assessment among subway workers in three distinct jobs over 10 working days, measuring daily concentrations of particulate matter (PM), their metal content and oxidative potential (OP). Individual pre- and post-shift EBC and urine samples were collected daily. Three oxidative stress biomarkers were measured in these matrices: malondialdehyde (MDA), 8-hydroxy-2'deoxyguanosine (8-OHdG) and 8-isoprostane. The association between each effect biomarker and exposure variables was estimated by multivariable multilevel mixed-effect models with and without lag times.

RESULTS

The OP was positively associated with Fe and Mn, but not associated with any effect biomarkers. Concentration changes of effect biomarkers in EBC and urine were associated with transition metals in PM (Cu and Zn) and furthermore with specific metals in EBC (Ba, Co, Cr and Mn) and in urine (Ba, Cu, Co, Mo, Ni, Ti and Zn). The direction of these associations was both metal- and time-dependent. Associations between Cu or Zn and MDAEBC generally reached statistical significance after a delayed time of 12 or 24 h after exposure. Changes in metal concentrations in EBC and urine were associated with MDA and 8-OHdG concentrations the same day.

CONCLUSION

Associations between MDA in both EBC and urine gave opposite response for subway particles containing Zn versus Cu. This diverting Zn and Cu pattern was also observed for 8-OHdG and urinary concentrations of these two metals. Overall, MDA and 8-OHdG responses were sensitive for same-day metal exposures in both matrices. We recommend MDA and 8-OHdG in large field studies to account for oxidative stress originating from metals in inhaled particulate matter.

Cardiolipin Membranes Promote Cytochrome c Transformation of Polycyclic Aromatic Hydrocarbons and Their In Vivo Metabolites

The catalytic properties of cytochrome c (Cc) have captured great interest in respect to mitochondrial physiology and apoptosis, and hold potential for novel enzymatic bioremediation systems. Nevertheless, its contribution to the metabolism of environmental toxicants remains unstudied. Human exposure to polycyclic aromatic hydrocarbons (PAHs) has been associated with impactful diseases, and animal models have unveiled concerning signs of PAHs' toxicity to mitochondria. In this work, a series of eight PAHs with ionization potentials between 7.2 and 8.1 eV were used to challenge the catalytic ability of Cc and to evaluate the effect of vesicles containing cardiolipin mimicking mitochondrial membranes activating the peroxidase activity of Cc. With moderate levels of H2O2 and at pH 7.0, Cc catalyzed the oxidation of toxic PAHs, such as benzo[a]pyrene, anthracene, and benzo[a]anthracene, and the cardiolipin-containing membranes clearly increased the PAH conversions. Our results also demonstrate for the first time that Cc and Cc-cardiolipin complexes efficiently transformed the PAH metabolites 2-hydroxynaphthalene and 1-hydroxypyrene. In comparison to horseradish peroxidase, Cc was shown to reach more potent oxidizing states and react with PAHs with ionization potentials up to 7.70 eV, including pyrene and acenaphthene. Spectral assays indicated that anthracene binds to Cc, and docking simulations proposed possible binding sites positioning anthracene for oxidation. The results give support to the participation of Cc in the metabolism of PAHs, especially in mitochondria, and encourage further investigation of the molecular interaction between PAHs and Cc.

Redox and inflammatory mechanisms linking air pollution particulate matter with cardiometabolic derangements

Air pollution is the largest environmental risk factor for disease and premature death. Among the different components that are present in polluted air, fine particulate matter below 2.5 μm in diameter (PM2.5) has been identified as the main hazardous constituent. PM2.5 mainly arises from fossil fuel combustion during power generation, industrial processes, and transportation. Exposure to PM2.5 correlates with enhanced mortality risk from cardiovascular diseases (CVD), such as myocardial infarction and stroke. Over the last decade, it has been increasingly suggested that PM2.5 affects CVD already at the stage of risk factor development. Among the multiple biological mechanisms that have been described, the interplay between oxidative stress and inflammation has been consistently highlighted as one of the main drivers of pulmonary, systemic, and cardiovascular effects of PM2.5 exposure. In this context, PM2.5 uptake by tissue-resident immune cells in the lung promotes oxidative and inflammatory mediators release that alter tissue homeostasis at remote locations. This pathway is central for PM2.5 pathogenesis and might account for the accelerated development of risk factors for CVD, including obesity and diabetes. However, transmission and end-organ mechanisms that explain PM2.5-induced impaired function in metabolic active organs are not completely understood. In this review, the main features of PM2.5 physicochemical characteristics related to PM2.5 ability to induce oxidative stress and inflammation will be presented. Hallmark and recent epidemiological and interventional studies will be summarized and discussed in the context of current air quality guidelines and legislation, knowledge gaps, and inequities. Lastly, mechanistic studies at the intersection between redox metabolism, inflammation, and function will be discussed, with focus on heart and adipose tissue alterations. By offering an integrated analysis of PM2.5-induced effects on cardiometabolic derangements, this review aims to contribute to a better understanding of the pathogenesis and potential interventions of air pollution-related CVD.

Subway station dust-induced pulmonary inflammation may be due to the dysfunction of alveolar macrophages: Possible contribution of bound elements

With its increasing value as a means of public transportation, the health effects of the air in subway stations have attracted public concern. In the current study, we investigated the pulmonary toxicity of dust collected from an air purifier installed on the platform of the busiest subway station in Seoul. We found that the dust contained various elements which are attributable to the facilities and equipment used to operate the subway system. Particularly, iron (Fe), chromium (Cr), zirconium (Zr), barium (Ba), and molybdenum (Mo) levels were more notable in comparison with those in dust collected from the ventilation chamber of a subway station. To explore the health effects of inhaled dust, we first instilled via the trachea in ICR mice for 13 weeks. The total number of pulmonary macrophages increased significantly with the dose, accompanying hematological changes. Dust-laden alveolar macrophages and inflammatory cells accumulated in the perivascular regions in the lungs of the treated mice, and pulmonary levels of CXCL-1, TNF-α, and TGF-β increased clearly compared with the control. The CCR5 and CD54 level expressed on BAL cell membranes was also enhanced following exposure to dust, whereas the CXCR2 level tended to decrease in the same samples. In addition, we treated the dust to alveolar macrophages (known as dust cells), lysosomal and mitochondrial function decreased, accompanied by cell death, and NO production was rapidly elevated with concentration. Moreover, the expression of autophagy- (p62) and anti-oxidant (SOD-2)-related proteins increased, and the expression of inflammation-related genes was dramatically up-regulated in the dust-treated cells. Therefore, we suggest that dysfunction of alveolar macrophages may importantly contribute to dust-induced inflammatory responses and that the exposure concentrations of Cr, Fe, Mo, Zr, and Ba should be considered carefully when assessing the health risks associated with subway dust. We also hypothesize that the bound elements may contribute to dust-induced macrophage dysfunction by inhibiting viability.

Toxicity and health effects of ultrafine particles: Towards an understanding of the relative impacts of different transport modes

Exposure to particulate matter (PM) has been associated with a wide range of adverse health effects, but it is still unclear how particles from various transport modes differ in terms of toxicity and associations with different human health outcomes. This literature review aims to summarize toxicological and epidemiological studies of the effect of ultrafine particles (UFPs), also called nanoparticles (NPs, <100 nm), from different transport modes with a focus on vehicle exhaust (particularly comparing diesel and biodiesel) and non-exhaust as well as particles from shipping (harbor), aviation (airport) and rail (mainly subway/underground). The review includes both particles collected in laboratory tests and the field (intense traffic environments or collected close to harbor, airport, and in subway). In addition, epidemiological studies on UFPs are reviewed with special attention to studies aimed at distinguishing the effects of different transport modes. Results from toxicological studies indicate that both fossil and biodiesel NPs show toxic effects. Several in vivo studies show that inhalation of NPs collected in traffic environments not only impacts the lung, but also triggers cardiovascular effects as well as negative impacts on the brain, although few studies compared NPs from different sources. Few studies were found on aviation (airport) NPs, but the available results suggest similar toxic effects as traffic-related particles. There is still little data related to the toxic effects linked to several sources (shipping, road and tire wear, subway NPs), but in vitro results highlighted the role of metals in the toxicity of subway and brake wear particles. Finally, the epidemiological studies emphasized the current limited knowledge of the health impacts of source-specific UFPs related to different transport modes. This review discusses the necessity of future research for a better understanding of the relative potencies of NPs from different transport modes and their use in health risk assessment.

An investigation of the PM2.5 concentrations and cumulative inhaled dose during subway commutes in Changchun, China

Air quality in subway systems is crucial as it affects the health of passengers and staff. Although most tests of PM2.5 concentrations in subway stations have taken place in public areas, PM2.5 is less understood in workplaces. Few studies have estimated the cumulative inhaled dose of passengers based on real-time changes in PM2.5 concentrations as they commute. To clarify the above issues, this study first measured PM2.5 concentrations in four subway stations in Changchun, China, where measuring points included five workrooms. Then, passengers' exposure to PM2.5 during the whole subway commute (20-30 min) was measured and segmented inhalation was calculated. The results showed that PM2.5 concentration in public places ranged from 50 to 180 μg/m3, and was strongly correlated with outdoors. While the PM2.5 average concentration in workplaces was 60 µg/m3, and it was less affected by outdoor PM2.5 concentration. Passenger's cumulative inhalations in single commuting were about 42 μg and 100 μg when the outdoor PM2.5 concentrations were 20-30 μg/m3 and 120-180 μg/m3, respectively. The PM2.5 inhalation in carriages accounted for the largest proportion of the entire commuting, about 25-40%, because of the longer exposure time and higher PM2.5 concentrations. It is recommended to improve the tightness of the carriage and filter the fresh air to improve the air quality inside. The average daily PM2.5 inhaled by staff was 513.53 μg, which was 5-12 times higher than that of passengers. Installing air purification devices in workplaces and reminding staff to take personal protection can positively protect their health.

Review of the British Thoracic Society Winter Meeting 23 November 2022 23-25 November 2022

The British Thoracic Society Winter Meeting at the QEII Centre in London provided the first opportunity for the respiratory community to meet and disseminate research findings face to face since the start of the COVID-19 pandemic. World-leading researchers from the UK and abroad presented their latest findings across a range of respiratory diseases. This article aims to represent the range of the conference and as such is written from the perspective of a basic scientist, a physiotherapist and two doctors. The authors reviewed showcase sessions plus a selection of symposia based on their personal highlights. Content ranged from exciting new developments in basic science to new and unpublished results from clinical trials, delivered by leading scientists from their fields including former deputy chief medical officer Professor Sir Jonathan Van-Tam and former WHO chief scientist Dr Soumya Swaminathan.

Effect Of Atmospheric Particulate Matter On The Functional State Of Mitochondria

The health risks associated with outdoor air pollution are of global concern. Atmospheric air pollution negatively affects a number of key aspects of human health, including the functioning of the respiratory, cardiovascular and central nervous systems, but many issues remain unresolved about the relationship between atmospheric air pollution and the development and course of pathologies. The review analyzes data from Russian and foreign sources on the effect of atmospheric particulate matter on the functional state of mitochondria. The effect of air pollution on structural changes in mitochondria, ATP synthesis, production of reactive oxygen species, damage to mitochondrial DNA, and mitochondrial membrane potential has been shown. The data presented in the review indicate the need for further studies of the functional state of mitochondria under the impact of solid particles in atmospheric air.

Magnetic and microscopic investigation of airborne iron oxide nanoparticles in the London Underground

Particulate matter (PM) concentration levels in the London Underground (LU) are higher than London background levels and beyond World Health Organization (WHO) defined limits. Wheel, track, and brake abrasion are the primary sources of particulate matter, producing predominantly Fe-rich particles that make the LU microenvironment particularly well suited to study using environmental magnetism. Here we combine magnetic properties, high-resolution electron microscopy, and electron tomography to characterize the structure, chemistry, and morphometric properties of LU particles in three dimensions with nanoscale resolution. Our findings show that LU PM is dominated by 5-500 nm particles of maghemite, occurring as 0.1-2 μm aggregated clusters, skewing the size-fractioned concentration of PM artificially to larger sizes when measured with traditional monitors. Magnetic properties are largely independent of the PM filter size (PM₁₀, PM₄, and PM_2.5), and demonstrate the presence of superparamagnetic (< 30 nm), single-domain (30-70 nm), and vortex/pseudo-single domain (70-700 nm) signals only (i.e., no multi-domain particles > 1 µm). The oxidized nature of the particles suggests that PM exposure in the LU is dominated by resuspension of aged dust particles relative to freshly abraded, metallic particles from the wheel/track/brake system, suggesting that periodic removal of accumulated dust from underground tunnels might provide a cost-effective strategy for reducing exposure. The abundance of ultrafine particles identified here could have particularly adverse health impacts as their smaller size makes it possible to pass from lungs to the blood stream. Magnetic methods are shown to provide an accurate assessment of ultrafine PM characteristics, providing a robust route to monitoring, and potentially mitigating this hazard.

Physicochemical characterization and oxidative potential of size fractionated Particulate Matter: Uptake, genotoxicity and mutagenicity in V-79 cells

For many years, the impact of Particulate Matter (PM) in the ambient air has been one of the major concerns for the environment and human health. The consideration of the heterogeneity and complexity of different size fractions is notably important for the assessment of PM toxicological effects. The aim of the study was to present a comprehensive size-composition-morphology characterization and to assess the oxidative potential, genotoxicity, and mutagenicity of the atmospheric PM fractions, collected by using MOUDI near a busy roadside in Lucknow, India. Physicochemical characterization of ambient coarse particles (1.8-10 µm), fine particles (0.32-1.8 µm), quasi-ultrafine (0.1-0.32 µm) and ultrafine particles (≤0.1 µm) along with SRM 1649b was done using TEM, SEM, DLS, NTA, ICP-MS, and IC in parallel with the estimation of exogenous Reactive Oxygen Species (ROS) by acellular assays. In this study, two different acellular assays, dithiothreitol (DTT) and the CM-H₂DCFDA assay, indicated stronger mass-normalized bioactivity for different size ranges. Enrichment factor analysis indicated that the different size fractions were highly enriched with elements of anthropogenic origin as compared to elements of crustal origin. The endotoxin concentration in different size fractions was also estimated. Cellular studies demonstrated significant uptake, cytotoxicity, ultrastructural changes, cellular ROS generation, and changes in the different phases of the cell cycle (Sub G1, G1, S, G2/M) exposed to different size fractions. The Comet assay and the Micronucleus assay were used to estimate genotoxicity. Mutagenic potential was revealed by the HGPRT gene forward mutation assay in V-97 cells. Conclusively, our results clearly indicate that the genotoxic and mutagenic potential of the coarse PM was greater than the other fractions, and interestingly, the ultrafine PM has higher bioactivity as compared to quasi-ultrafine PM.

Adverse effects of air pollution-derived fine particulate matter on cardiovascular homeostasis and disease

Air pollution is a rapidly growing major health concern around the world. Atmospheric particulate matter that has a diameter of less than 2.5 µm (PM2.5) refers to an air pollutant composed of particles and chemical compounds that originate from various sources. While epidemiological studies have established the association between PM2.5 exposure and cardiovascular diseases, the precise cellular and molecular mechanisms by which PM2.5 promotes cardiovascular complications are yet to be fully elucidated. In this review, we summarize the various sources of PM2.5, its components, and the concentrations of ambient PM2.5 in various settings. We discuss the experimental findings to date that evaluate the potential adverse effects of PM2.5 on cardiovascular homeostasis and function, and the possible therapeutic options that may alleviate PM2.5-driven cardiovascular damage.

RNA-Seq Analysis of UPM-Exposed Epithelium Co-Cultivated with Macrophages and Dendritic Cells in Obstructive Lung Diseases

Background. Elevated concentrations of airborne pollutants are correlated with an enlarged rate of obstructive lung disease morbidity as well as acute disease exacerbations. This study aimed to analyze the epithelium mRNA profile in response to airborne particulate matter in the control, asthma, and COPD groups. Results. A triple co-culture of nasal epithelium, monocyte-derived macrophages, and monocyte-derived dendritic cells obtained from the controls, asthma, and COPD were exposed to urban particulate matter (UPM) for 24 h. RNA-Seq analysis found differences in seven (CYP1B1, CYP1B1-AS1, NCF1, ME1, LINC02029, BPIFA2, EEF1A2), five (CYP1B1, ARC, ENPEP, RASD1, CYP1B1-AS1), and six (CYP1B1, CYP1B1-AS1, IRF4, ATP1B2, TIPARP, CCL22) differentially expressed genes between UPM exposed and unexposed triple co-cultured epithelium in the control, asthma, and COPD groups, respectively. PCR analysis showed that mRNA expression of BPIFA2 and ENPEP was upregulated in both asthma and COPD, while the expression of CYP1B1-AS1 and TIPARP was increased in the epithelium from COPD patients only. Biological processes changed in UPM exposed triple co-cultured epithelium were associated with epidermis development and epidermal cell differentiation in asthma and with response to toxic substances in COPD. Conclusions. The biochemical processes associated with pathophysiology of asthma and COPD impairs the airway epithelial response to UPM.

Role of air pollutants in airway epithelial barrier dysfunction in asthma and COPD

Chronic exposure to environmental pollutants is a major contributor to the development and progression of obstructive airway diseases, including asthma and COPD. Understanding the mechanisms underlying the development of obstructive lung diseases upon exposure to inhaled pollutants will lead to novel insights into the pathogenesis, prevention and treatment of these diseases. The respiratory epithelial lining forms a robust physicochemical barrier protecting the body from inhaled toxic particles and pathogens. Inhalation of airborne particles and gases may impair airway epithelial barrier function and subsequently lead to exaggerated inflammatory responses and airway remodelling, which are key features of asthma and COPD. In addition, air pollutant-induced airway epithelial barrier dysfunction may increase susceptibility to respiratory infections, thereby increasing the risk of exacerbations and thus triggering further inflammation. In this review, we discuss the molecular and immunological mechanisms involved in physical barrier disruption induced by major airborne pollutants and outline their implications in the pathogenesis of asthma and COPD. We further discuss the link between these pollutants and changes in the lung microbiome as a potential factor for aggravating airway diseases. Understanding these mechanisms may lead to identification of novel targets for therapeutic intervention to restore airway epithelial integrity in asthma and COPD.

Exposure to air pollution induces airway epithelial barrier dysfunction through several mechanisms including increased oxidative stress, exaggerated cytokine responses and impaired host defence, which contributes to development of asthma and COPD. https://bit.ly/3DHL1CA

The health effects of traffic-related air pollution: A review focused the health effects of going green

Traffic-related air pollution (TRAP) is global concern due to both the ecological damage of TRAP and the adverse health effects in Humans. Several strategies to reduce TRAP have been implemented, including the use of sustainable fuels, after-treatment technologies, and new energy vehicles. Such approaches can reduce the exhaust of particulate matter, adsorbed chemicals and a range of gases, but from a health perspective these approaches are not always successful. This review aims to discuss the approaches taken, and to then describe the likely health effects of these changes.

Forgotten but not gone: Particulate matter as contaminations of mucosal systems

A decade ago, environmental issues, such as air pollution and the contamination of the oceans with microplastic, were prominently communicated in the media. However, these days, political topics, as well as the ongoing COVID-19 pandemic, have clearly taken over. In spite of this shift in focus regarding media representation, researchers have made progress in evaluating the possible health risks associated with particulate contaminations present in water and air. In this review article, we summarize recent efforts that establish a clear link between the increasing occurrence of certain pathological conditions and the exposure of humans (or animals) to airborne or waterborne particulate matter. First, we give an overview of the physiological functions mucus has to fulfill in humans and animals, and we discuss different sources of particulate matter. We then highlight parameters that govern particle toxicity and summarize our current knowledge of how an exposure to particulate matter can be related to dysfunctions of mucosal systems. Last, we outline how biophysical tools and methods can help researchers to obtain a better understanding of how particulate matter may affect human health. As we discuss here, recent research has made it quite clear that the structure and functions of those mucosal systems are sensitive toward particulate contaminations. Yet, our mechanistic understanding of how (and which) nano- and microparticles can compromise human health via interacting with mucosal barriers is far from complete.

Interactions of nasal epithelium with macrophages and dendritic cells variously alter urban PM-induced inflammation in healthy, asthma and COPD

Urban particulate matter (UPM) is an important trigger of airway inflammation. The cross-talk between the external and internal matrix in the respiratory tract occurs due to the transepithelial network of macrophages/dendritic cells. This study characterized the immune processes induced by the epithelium after UPM exposure in special regard to interactions with monocyte-derived dendritic cells (moDCs) and monocyte-derived macrophages (moMφs) in obstructive lung diseases. A triple-cell co-culture model (8 controls, 10 asthma, and 8 patients with COPD) utilized nasal epithelial cells, along with moMφs, and moDCs was exposed to UPM for 24 h. The inflammatory response of nasal epithelial cells to UPM stimulation is affected differently by cell-cell interactions in healthy people, asthma or COPD patients of which the interactions with DCs had the strongest impact on the inflammatory reaction of epithelial cells after UPM exposure. The epithelial remodeling and DCs dysfunction might accelerate the inflammation after air pollution exposure in asthma and COPD.

Recent progress in research on PM2.5 in subways

Nowadays, PM2.5 concentrations greatly influence indoor air quality in subways and threaten passenger and staff health because PM2.5 not only contains heavy metal elements, but can also carry toxic and harmful substances due to its small size and large specific surface area. Exploring the physicochemical and distribution characteristics of PM2.5 in subways is necessary to limit its concentration and remove it. At present, there are numerous studies on PM2.5 in subways around the world, yet, there is no comprehensive and well-organized review available on this topic. This paper reviews the nearly twenty years of research and over 130 published studies on PM2.5 in subway stations, including aspects such as concentration levels and their influencing factors, physicochemical properties, sources, impacts on health, and mitigation measures. Although many determinants of station PM2.5 concentration have been reported in current studies, e.g., the season, outdoor environment, and station depth, their relative influence is uncertain. The sources of subway PM2.5 include those from the exterior (e.g., road traffic and fuel oil) and the interior (e.g., steel wheels and rails and metallic brake pads), but the proportion of these sources is also unknown. Control strategies of PM mainly include adequate ventilation and filtration, but these measures are often inefficient in removing PM2.5. The impacts of PM2.5 from subways on human health are still poorly understood. Further research should focus on long-term data collection, influencing factors, the mechanism of health impacts, and PM2.5 standards or regulations.

Biological effect of PM10 on airway epithelium-focus on obstructive lung diseases

Recently, a continuous increase in environmental pollution has been observed. Despite wide-scale efforts to reduce air pollutant emissions, the problem is still relevant. Exposure to elevated levels of airborne particles increased the incidence of respiratory diseases. PM₁₀ constitute the largest fraction of air pollutants, containing particles with a diameter of less than 10 μm, metals, pollens, mineral dust and remnant material from anthropogenic activity. The natural airway defensive mechanisms against inhaled material, such as mucus layer, ciliary clearance and macrophage phagocytic activity, may be insufficient for proper respiratory function. The epithelium layer can be disrupted by ongoing oxidative stress and inflammatory processes induced by exposure to large amounts of inhaled particles as well as promote the development and exacerbation of obstructive lung diseases. This review draws attention to the current state of knowledge about the physical features of PM₁₀ and its impact on airway epithelial cells, and obstructive pulmonary diseases.

Application of green tea catechins, polysaccharides, and flavonol prevent fine dust induced bronchial damage by modulating inflammation and airway cilia

Airborne fine dust particles (FDPs) have been identified as major toxins in air pollution that threaten human respiratory health. While searching for an anti-FDP reagent, we found that green tea extract (GTE) and fractions rich in flavonol glycosides (FLGs) and crude tea polysaccharides (CTPs) had protective effects against FDP-stimulated cellular damage in the BEAS-2B airway epithelial cell line. The GTE, FLGs, and CTPs significantly increased viability and lowered oxidative stress levels in FDP-treated cells. Combined treatment with GTE, FLGs, and CTPs also exerted synergistic protective effects on cells and attenuated FDP-induced elevations in inflammatory gene expression. Moreover, the green tea components increased the proportion of ciliated cells and upregulated ciliogenesis in the airway in FDP-stimulated BEAS-2B cells. Our findings provide insights into how natural phytochemicals protect the airway and suggest that green tea could be used to reduce FDP-induced airway damage as an ingredient in pharmaceutical, nutraceutical, and also cosmeceutical products.

PM2.5 organic extract mediates inflammation through the ERβ pathway to contribute to lung carcinogenesis in vitro and vivo

An increasing number of researches have shown that fine particulate matter (PM2.5) is closely related to increased respiratory inflammation and can even lead to lung cancer. Estrogen receptor β (ERβ) has been demonstrated to be involved in several cancers. However, the exact role of ERβ in PM2.5 organic extract (Po)-promoted inflammation and lung cancer remains unknown. The purpose of this study was to investigate whether ERβ is involved in Po induced inflammation and lung cancer. In vitro, our results showed that interleukin-6 (IL-6) and ERβ were simultaneously increased in lung bronchial epithelial cells exposed to Po; additionally, inhibition of ERβ decreased IL-6 expression and secretion through inactivating ERK and AKT and further promoted cells malignant transformation. Moreover, we performed an animal model of inhalation exposure to Po using female C57BL/6 mice. Although we were unable to find tumor tissue in mice exposed to Po, we detected evidence of lung inflammation, epithelial-to-mesenchymal transition (EMT) phenotype and severe pulmonary injury; in addition, intraperitoneal injection of PHTPP (an ERβ inhibitor) showed that the above phenomena have been improved, which demonstrate that Po stimulates IL-6 expression to promote inflammation, EMT phenotype and lung injury through the ERβ pathway. In conclusion, our results confirmed the potential toxic effect of PM2.5, and increased our understanding of PM2.5 carcinogenic potential by exploring the mechanism of ERβ regulating inflammation.

Effect of concentration and duration of particulate matter exposure on the transcriptome and DNA methylome of bronchial epithelial cells

Exposure to particulate matter (PM) from ambient air pollution is a well-known risk factor for many lung diseases, but the mechanism(s) for this is not completely understood. Bronchial epithelial cells, which line the airway of the respiratory tract, undergo genome-wide level changes in gene expression and DNA methylation particularly when exposed to fine (<2.5 µm) PM (PM_2.5). Although some of these changes have been reported in other studies, a comparison of how different concentrations and duration of exposure affect both the gene transcriptome and DNA methylome has not been done. Here, we exposed BEAS-2B, a bronchial epithelial cell line, to different concentrations of PM_2.5, and compared how single or repeated doses of PM_2.5 affect both the transcriptome and methylome of cells. Widespread changes in gene expression occurred after cells were exposed to a single treatment of high-concentration (30 µg/cm²) PM_2.5 for 24 h. These genes were enriched in pathways regulating cytokine-cytokine interactions, Mitogen-Activated Protein Kinase (MAPK) signaling, PI3K-Akt signaling, IL6, and P53. DNA methylomic analysis showed that nearly half of the differentially expressed genes were found to also have DNA methylation changes, with just a slightly greater trend toward overall hypomethylation across the genome. Cells exposed to a lower concentration (1 µg/cm²) of PM_2.5 demonstrated a comparable, but more attenuated change in gene expression compared to cells exposed to higher concentrations. There were also many genes affected by lower concentrations of PM_2.5, but not higher concentrations. Additionally, repeated exposure to PM_2.5 (1 µg/cm²) for seven days resulted in transcriptomic and DNA methylomic changes that were distinct from cells treated with PM_2.5 for only one day. Compared to single exposure, repeated exposure to PM_2.5 caused a more notable degree of hypomethylation across the genome, though certain genes and regions demonstrated increased DNA methylation. The overall increase in hypomethylation, especially with repeated exposure to PM_2.5, was associated with an increase in expression of ten-eleven translocation enzymes. These data demonstrate how variations in concentration and duration of PM_2.5 exposure induce distinct differences in the transcriptomic and DNA methylomic profile of bronchial epithelial cells, which may have important implications in the development of both acute and chronic lung disease.

Effects of air pollution particles (ultrafine and fine particulate matter) on mitochondrial function and oxidative stress - Implications for cardiovascular and neurodegenerative diseases

Environmental pollution is a major cause of global mortality and burden of disease. All chemical pollution forms together may be responsible for up to 12 million annual excess deaths as estimated by the Lancet Commission on pollution and health as well as the World Health Organization. Ambient air pollution by particulate matter (PM) and ozone was found to be associated with an all-cause mortality rate of up to 9 million in the year 2015, with the majority being of cerebro- and cardiovascular nature (e.g. stroke and ischemic heart disease). Recent evidence suggests that exposure to airborne particles and gases contributes to and accelerates neurodegenerative diseases. Especially, airborne toxic particles contribute to these adverse health effects. Whereas it is well established that air pollution in the form of PM may lead to dysregulation of neurohormonal stress pathways and may trigger inflammation as well as oxidative stress, leading to secondary damage of cardiovascular structures, the mechanistic impact of PM-induced mitochondrial damage and dysfunction is not well established. With the present review we will discuss similarities between mitochondrial damage and dysfunction observed in the development and progression of cardiovascular disease and neurodegeneration as well as those adverse mitochondrial pathomechanisms induced by airborne PM.

Oxidative Stress From Exposure to the Underground Space Environment

There are a growing number of people entering underground spaces. However, underground spaces have unique environmental characteristics, and little is known about their effects on human health. It is crucial to elucidate the effects of the underground space environment on the health of humans and other organisms. This paper reviews the effects of hypoxia, toxic atmospheric particles, and low background radiation in the underground space environment on living organisms from the perspective of oxidative stress. Most studies have revealed that living organisms maintained in underground space environments exhibit obvious oxidative stress, which manifests as changes in oxidants, antioxidant enzyme activity, genetic damage, and even disease status. However, there are few relevant studies, and the pathophysiological mechanisms have not been fully elucidated. There remains an urgent need to focus on the biological effects of other underground environmental factors on humans and other organisms as well as the underlying mechanisms. In addition, based on biological research, exploring means to protect humans and living organisms in underground environments is also essential.

Toxicity of iron nanoparticles towards primary cultures of human bronchial epithelial cells

Air pollution is a public health issue and the toxicity of ambient particulate matter (PM) is well-recognized. Although it does not mostly contribute to the total mass of PM, increasing evidence indicates that the ultrafine fraction has generally a greater toxicity than the others do. A better knowledge of the underlying mechanisms involved in the pathological disorders related to nanoparticles (NPs) remains essential. Hence, the goal of this study was to determine better whether the exposure to a relatively low dose of well-characterized iron-rich NPs (Fe-NPs) might alter some critical toxicological endpoints in a relevant primary culture model of human bronchial epithelial cells (HBECs). We sought to use Fe-NPs representative of those frequently found in the industrial smokes of metallurgical industries. After having noticed the effective internalization of Fe-NPs, oxidative, inflammatory, DNA repair, and apoptotic endpoints were investigated within HBECs, mainly through transcriptional screening. Taken together, these results revealed that, despite it only produced relatively low levels of reactive oxygen species without any significant oxidative damage, low-dose Fe-NPs quickly significantly deregulated the transcription of some target genes closely involved in the proinflammatory response. Although this inflammatory process seemed to stay under control over time in case of this acute scenario of exposure, the future study of its evolution after a scenario of repeated exposure could be very interesting to evaluate the toxicity of Fe-NPs better.

Toxicological appraisal of the chemical fractions of ambient fine (PM2.5-0.3) and quasi-ultrafine (PM0.3) particles in human bronchial epithelial BEAS-2B cells

New toxicological research is still urgently needed to improve the current knowledge about the induction of some underlying mechanisms of toxicity by the different chemical fractions of ambient particulate matter (PM). This in vitro study sought also to better evaluate and compare the respective toxicities of fine particles (PM_2.5-0.3) and their inorganic and organic chemical fractions, and the respective toxicities of the organic chemical fractions of PM_2.5-0.3 and quasi-ultrafine particles (PM_0.3). Human bronchial epithelial BEAS-2B cells were also exposed for 6-48 h to relatively low doses of PM_2.5-0.3 and their organic extractable (OEM_2.5-0.3) and non-extractable (NEM_2.5-0.3) fractions, and the organic extractable fraction (OEM_0.3) of PM_0.3. We reported that not only PM_2.5-0.3, but also, to a lesser extent, its inorganic chemical fraction, NEM_2.5-0.3, and organic chemical fraction, OEM_2.5-0.3, were able to significantly induce ROS overproduction and oxidative damage notwithstanding the early activation of NRF2 signaling pathway. Moreover, for any exposure, inflammatory and apoptotic events were noticed. Similar results were observed in BEAS-2B cells exposed to OEM_0.3, rich of polycyclic aromatic hydrocarbons and their nitrated and oxygenated derivatives. In BEAS-2B cells exposed for 24 and 48 h to OEM_2.5-0.3 and OEM_0.3, to a higher extent, there was an alteration of the levels of some critical proteins even though crucial for the autophagy rather than a real reduction of autophagy. It is noteworthy that the toxicological effects were equal or mostly higher in BEAS-2B cells exposed for 6 and/or 24 h to PM_2.5-0.3 from those exposed to NEM_2.5-0.3 or OEM_2.5-0.3, and in BEAS-2B cells exposed for 6 and/or mostly 24 h to OEM_0.3 from those exposed to OEM_2.5-0.3. Taken together, these results revealed the higher potentials for toxicity, closely linked to their respective physical and chemical characteristics, of PM_2.5-0.3 vs NEM_2.5-0.3 and/or OEM_2.5-0.3, and OEM_0.3 vs OEM_2.5-0.3.

Upregulation of epithelial metallothioneins by metal-rich ultrafine particulate matter from an underground railway

Airborne particulate matter (PM) is a leading cause of mortality and morbidity. However, understanding of the range and mechanisms of effects of PM components is poor. PM generated in underground railways is rich in metals, especially iron. In the ultrafine (UFPM; <0.1 μm diameter) fraction, the combination of small size and metal enrichment poses an unknown health risk. This study aimed to analyse transcriptomic responses to underground UFPM in primary bronchial epithelial cells (PBECs), a key site of PM deposition. The oxidation state of iron in UFPM from an underground station was determined by X-ray absorption near edge structure (XANES) spectroscopy. Antioxidant response was assayed using a reporter cell line transfected with an antioxidant response element (ARE)-luciferase construct. Differentiated PBECs were exposed to UFPM for 6 h or 24 h for RNA-Seq and RT-qPCR analysis. XANES showed predominance of redox-active Fe3O4, with ROS generation confirmed by induction of ARE-luciferase expression. 6 h exposure of PBECs to UFPM identified 52 differentially expressed genes (DEGs), especially associated with epithelial maintenance, whereas 24 h exposure yielded 23 DEGs, particularly involved with redox homeostasis and metal binding. At both timepoints, there was upregulation of members of the metallothionein family, low molecular weight proteins with antioxidant activity whose main function is binding and homeostasis of zinc and copper ions, but not iron ions. This upregulation was partially inhibited by metal chelation or ROS scavenging. These data suggest differential regulation of responses to metal-rich UFPM depending on exposure period, and highlight novel pathways and markers of PM exposure, with the role of metallothioneins warranting further investigation.

Endogenous doesn't always mean innocuous: a scoping review of iron toxicity by inhalation

Ambient air pollution is a leading risk factor for the global burden of disease. One possible pathway of particulate matter (PM)-induced toxicity is through iron (Fe), the most abundant metal in the atmosphere. The aim of the review was to consider the complexity of Fe-mediated toxicity following inhalation exposure focusing on the chemical and surface reactivity of Fe as a transition metal and possible pathways of toxicity via reactive oxygen species (ROS) generation as well as considerations of size, morphology, and source of PM. A broad term search of 4 databases identified 2189 journal articles and reports examining exposure to Fe via inhalation in the past 10 years. These were sequentially analyzed by title, abstract and full-text to identify 87 articles publishing results on the toxicity of Fe-containing PM by inhalation or instillation to the respiratory system. The remaining 87 papers were examined to summarize research dealing with in vitro, in vivo and epidemiological studies involving PM containing Fe or iron oxide following inhalation or instillation. The major findings from these investigations are summarized and tabulated. Epidemiological studies showed that exposure to Fe oxide is correlated with an increased incidence of cancer, cardiovascular diseases, and several respiratory diseases. Iron PM was found to induce inflammatory effects in vitro and in vivo and to translocate to remote locations including the brain following inhalation. A potential pathway for the PM-containing Fe-mediated toxicity by inhalation is via the generation of ROS which leads to lipid peroxidation and DNA and protein oxidation. Our recommendations include an expansion of epidemiological, in vivo and in vitro studies, integrating research improvements outlined in this review, such as the method of particle preparation, cell line type, and animal model, to enhance our understanding of the complex biological interactions of these particles.

Toxicity of fine and quasi-ultrafine particles: Focus on the effects of organic extractable and non-extractable matter fractions

To date no study has been able to clearly attribute the observed toxicological effects of atmospheric particles (PM) to a specific class of components. The toxicity of both the organic extractable matter (OEM_2.5-0.3) and non-extractable matter (NEM_2.5-0.3) of fine particles (PM_2.5-0.3) was compared to that of PM_2.5-0.3 in its entirety on normal human epithelial bronchial BEAS-2B cells in culture. The specific effect of the quasi-ultrafine fraction (PM_0.3) was assessed, by comparing the responses of cells exposed to the PM_2.5-0.3 and PM_0.3 organic extractable matter, OEM_2.5-0.3 and OEM_0.3 respectively. Chemically, PAH, O-PAH, and N-PAH were respectively 43, 17, and 4 times more concentrated in PM_0.3 than in PM_2.5-0.3, suggesting thereby a predominant influence of anthropogenic activities and combustion sources. BEAS-2B cells exposed to PM_2.5-0.3, NEM_2.5-0.3, EOM_2.5-0.3 and OEM_0.3 lead to different profiles of expression of selected genes and proteins involved in the metabolic activation of PAH, O-PAH, and N-PAH, and in the genotoxicity pathways. Specifically, OEM_0.3 was the most inducer for phase I and phase II enzymes implicated in the metabolic activation of PAH (AHR, AHRR, ARNT, CYP1A1, CYP1B1, EPHX-1, GSTA-4) thereby producing the highest DNA damage, felt by ATR and, thereafter, a cascade of protein phosphorylation (CHK1/CHK2/MDM2) closely related to the cell cycle arrest (P21 and P53 induction). This study underlined the crucial role played by the organic chemicals present in PM_0.3. These results should be considered in any future study looking for the main chemical determinants responsible for the toxicity of ambient fine PM.

Molecular mechanisms linking environmental toxicants to cancer development: Significance for protective interventions with polyphenols

Human exposure to environmental toxicants with diverse mechanisms of action is a growing concern. In addition to well-recognized carcinogens, various chemicals in environmental and occupational settings have been suggested to impact health, increasing susceptibility to cancer by inducing genetic and epigenetic changes. Accordingly, in this review, we have discussed recent insights into the pathological mechanisms of these chemicals, namely their effects on cell redox and calcium homeostasis, mitochondria and inflammatory signaling, with a focus on the possible implications for multi-stage carcinogenesis and its reversal by polyphenols. Plant-derived polyphenols, such as epigallocatechin-gallate, resveratrol, curcumin and anthocyanins reduce the incidence of cancer and can be useful nutraceuticals for alleviating the detrimental outcomes of harmful pollutants. However, development of therapies based on polyphenol administration requires further studies to validate the biological efficacy, identifying effective doses, mode of action and new delivery forms. Innovative microphysiological testing models are presented and specific proposals for future trials are given. Merging the current knowledge of multifactorial actions of specific polyphenols and chief environmental toxicants, this work aims to potentiate the delivery of phytochemical-based protective treatments to individuals at high-risk due to environmental exposure.

The Role and Potential Pathogenic Mechanism of Particulate Matter in Childhood Asthma: A Review and Perspective

Asthma, the most common chronic respiratory disease in children, affects numerous people worldwide. Accumulating evidence suggests that exposure to high levels of particulate matter (PM), either acutely or chronically, is associated with the exacerbation and incidence of pediatric asthma. However, the detailed pathogenic mechanisms by which PM contributes to the incidence of asthma remain largely unknown. In this short review, we summarize studies of relationships between PM and pediatric asthma and recent advances on the fundamental mechanisms of PM-related asthma, with emphases on cell death regulation and immune system responses. We further discuss the inadequacy of current studies and give a perspective on the prevention strategies for pediatric asthma.

PM2.5 on the London Underground

INTRODUCTION

Despite the London Underground (LU) handling on average 2.8 million passenger journeys per day, the characteristics and potential health effects of the elevated concentrations of metal-rich PM2.5 found in this subway system are not well understood.

METHODS

Spatial monitoring campaigns were carried out to characterise the health-relevant chemical and physical properties of PM2.5 across the LU network, including diurnal and day-to-day variability and spatial distribution (above ground, depth below ground and subway line). Population-weighted station PM2.5 rankings were produced to understand the relative importance of concentrations at different stations and on different lines.

RESULTS

The PM2.5 mass in the LU (mean 88 μg m-3, median 28 μg m-3) was greater than at ambient background locations (mean 19 μg m-3, median 14 μg m-3) and roadside environments in central London (mean 22 μg m-3, median 14 μg m-3). Concentrations varied between lines and locations, with the deepest and shallowest submerged lines being the District (median 4 μg m-3) and Victoria (median 361 μg m-3 but up to 885 μg m-3). Broadly in agreement with other subway systems around the world, sampled LU PM2.5 comprised 47% iron oxide, 7% elemental carbon, 11% organic carbon, and 14% metallic and mineral oxides. Although a relationship between line depth and air quality inside the tube trains was evident, there were clear influences relating to the distance from cleaner outside air and the exchange with cabin air when the doors open. The passenger population-weighted exposure analysis demonstrated a method to identify stations that should be prioritised for remediation to improve air quality.

CONCLUSION

PM2.5 concentrations in the LU are many times higher than in other London transport Environments. Failure to include this environment in epidemiological studies of the relationship between PM2.5 and health in London is therefore likely to lead to a large exposure misclassification error. Given the significant contribution of underground PM2.5 to daily exposure, and the differences in composition compared to urban PM2.5, there is a clear need for well-designed studies to better understand the health effects of underground exposure.

Impacts of Organomodified Nanoclays and Their Incinerated Byproducts on Bronchial Cell Monolayer Integrity

Incorporation of engineered nanomaterials (ENMs) into nanocomposites using advanced manufacturing strategies is set to revolutionize diverse technologies. Of these, organomodified nanoclays (ONCs; i.e., smectite clays with different organic coatings) act as nanofillers in applications ranging from automotive to aerospace and biomedical systems. Recent toxicological evaluations increased awareness that exposure to ONC can occur along their entire life cycle, namely, during synthesis, handling, use, manipulation, and disposal. Compared to other ENMs, however, little information exists describing which physicochemical properties contribute to induced health risk. This study conducted high content screening on bronchial epithelial cell monolayers for coupled high-throughput in vitro assessment strategies aimed to evaluate acute toxicity of a library of ONCs (all of prevalent use) prior to and after simulated disposal by incineration. Coating-, incineration status-, and time-dependent effects were considered to determine changes in the pulmonary monolayer integrity, cell transepithelial resistance, apoptosis, and cell metabolism. Results showed that after exposure to each ONC at its half-maximal inhibitory concentration (IC₅₀) there is a material-induced toxicity effect with pristine nanoclay, for instance, displaying acute loss of monolayer coverage, resistance, and metabolism, coupled with increased number of apoptotic cells. Conversely, the other three ONCs tested displayed little loss of monolayer integrity; however, they exhibited differential coating-dependent increased apoptosis and up to 40-45% initial reduction in cell metabolism. Moreover, incinerated byproducts of ONCs exhibited significant loss of monolayer coverage and integrity, increased necrosis, with little evidence of monolayer re-establishment. These findings indicate that characteristics of organic coating type largely determine the mechanism of cytotoxicity and the ability of the monolayer to recover. Use of high content screening coupled with traditional in vitro assays proves to serve as a rapid pulmonary toxicity assessment tool to help define prevention by targeted physicochemical material properties design strategies.

Seasonal Variation in the Biological Effects of PM2.5 from Greater Cairo

Greater Cairo (Egypt) is a megalopolis where the studies of the air pollution events are of extremely high relevance, for the geographical-climatological aspects, the anthropogenic emissions and the health impact. While preliminary studies on the particulate matter (PM) chemical composition in Greater Cairo have been performed, no data are yet available on the PM’s toxicity. In this work, the in vitro toxicity of the fine PM (PM_2.5) sampled in an urban area of Greater Cairo during 2017–2018 was studied. The PM_2.5 samples collected during spring, summer, autumn and winter were preliminary characterized to determine the concentrations of ionic species, elements and organic PM (Polycyclic Aromatic Hydrocarbons, PAHs). After particle extraction from filters, the cytotoxic and pro-inflammatory effects were evaluated in human lung A549 cells. The results showed that particles collected during the colder seasons mainly induced the xenobiotic metabolizing system and the consequent antioxidant and pro-inflammatory cytokine release responses. Biological events positively correlated to PAHs and metals representative of a combustion-derived pollution. PM_2.5 from the warmer seasons displayed a direct effect on cell cycle progression, suggesting possible genotoxic effects. In conclusion, a correlation between the biological effects and PM_2.5 physico-chemical properties in the area of study might be useful for planning future strategies aiming to improve air quality and lower health hazards.

Particulate matter and the airway epithelium: the special case of the underground?

Airborne particulate matter (PM) is a leading driver of premature mortality and cardiopulmonary morbidity, associated with exacerbations of asthma and chronic obstructive pulmonary disease, idiopathic pulmonary fibrosis, and lung cancer. The airway epithelium, as the principal site of PM deposition, is critical to the effects of, and initial response to, PM. A key mechanism by which PM exerts its effects is the generation of reactive oxygen species (ROS), inducing antioxidant and inflammatory responses in exposed epithelial cells. However, much of what is known about the effects of PM is based on research using particulates from urban air. PM from underground railways is compositionally highly distinct from urban PM, being rich in metals associated with wheel, rail and brake wear and electrical arcing and component wear, which endows underground PM with potent ROS-generating capacity. In addition, underground PM appears to be more inflammogenic than urban PM in epithelial cells, but there is a lack of research into effects on exposed individuals, especially those with underlying health conditions. This review summarises current knowledge about the effects of PM on the airway epithelium, how the effects of underground PM may be different to urban PM and the potential health consequences and mitigation strategies for commuters and workers in underground railways.

Airborne particulate matter in underground railways is much more concentrated and metal-rich than that found above ground. The evidence surrounding what this might mean for effects on the airways of exposed commuters and staff is limited and inconsistent.http://bit.ly/2KtcorT

Mixture Effects of Diesel Exhaust and Metal Oxide Nanoparticles in Human Lung A549 Cells

Airborne ultrafine particles (UFP) mainly derive from combustion sources (e.g., diesel exhaust particles—DEP), abrasion sources (non-exhaust particles) or from the unintentional release of engineered nanoparticles (e.g., metal oxide nanoparticles—NPs), determining human exposure to UFP mixtures. The aim of the present study was to analyse the combined in vitro effects of DEP and metal oxide NPs (ZnO, CuO) on human lung A549 cells. The mixtures and the relative single NPs (DEP, ZnO, CuO) were characterized by transmission electron microscopy (TEM), dynamic light scattering (DLS) and inductively coupled plasma-optic emission spectroscopy (ICP-OES). Cells were exposed for different times (3–72 h) to mixtures of standard DEP at a subcytotoxic concentration and ZnO and CuO at increasing concentrations. At the end of the exposure, the cytotoxicity was assessed by 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide (MTT) and clonogenic tests, the pro-inflammatory potential was evaluated by interleukin-8 (IL-8) release and the cell morphology was investigated by fluorescence and transmission electron microscopy. The obtained results suggest that the presence of DEP may introduce new physico-chemical interactions able to increase the cytotoxicity of ZnO and to reduce that of CuO NPs.

Airborne, Vehicle-Derived Fe-Bearing Nanoparticles in the Urban Environment: A Review

Airborne particulate matter poses a serious threat to human health. Exposure to nanosized (<0.1 μm), vehicle-derived particulates may be hazardous due to their bioreactivity, their ability to penetrate every organ, including the brain, and their abundance in the urban atmosphere. Fe-bearing nanoparticles (<0.1 μm) in urban environments may be especially important because of their pathogenicity and possible association with neurodegenerative diseases, such as Alzheimer's and Parkinson's diseases. This review examines current knowledge regarding the sources of vehicle-derived Fe-bearing nanoparticles, their chemical and mineralogical compositions, grain size distribution and potential hazard to human health. We focus on data reported for the following sources of Fe-bearing nanoparticles: exhaust emissions (both diesel and gasoline), brake wear, tire and road surface wear, resuspension of roadside dust, underground, train and tram emissions, and aircraft and shipping emissions. We identify limitations and gaps in existing knowledge as well as future challenges and perspectives for studies of airborne Fe-bearing nanoparticles.

Toxicological effects of ambient fine (PM2.5-0.18) and ultrafine (PM0.18) particles in healthy and diseased 3D organo-typic mucocilary-phenotype models

The knowledge of the underlying mechanisms by which particulate matter (PM) exerts its health effects is still incomplete since it may trigger various symptoms as some persons may be more susceptible than others. Detailed studies realized in more relevant in vitro models are highly needed. Healthy normal human bronchial epithelial (NHBE), asthma-diseased human bronchial epithelial (DHBE), and COPD-DHBE cells, differentiated at the air-liquid interface, were acutely or repeatedly exposed to fine (i.e., PM_2.5-0.18, also called FP) and quasi-ultrafine (i.e., PM_0.18, also called UFP) particles. Immunofluorescence labelling of pan-cytokeratin, MUC5AC, and ZO-1 confirmed their specific cell-types. Baselines of the inflammatory mediators secreted by all the cells were quite similar. Slight changes of TNFα, IL-1β, IL-6, IL-8, GM-CSF, MCP-1, and/or TGFα, and of H3K9 histone acetylation supported a higher inflammatory response of asthma- and especially COPD-DHBE cells, after exposure to FP and especially UFP. At baseline, 35 differentially expressed genes (DEG) in asthma-DHBE, and 23 DEG in COPD-DHBE, compared to NHBE cells, were reported. They were involved in biological processes implicated in the development of asthma and COPD diseases, such as cellular process (e.g., PLA2G4C, NLRP1, S100A5, MUC1), biological regulation (e.g., CCNE1), developmental process (e.g., WNT10B), and cell component organization and synthesis (e.g., KRT34, COL6A1, COL6A2). In all the FP or UFP-exposed cell models, DEG were also functionally annotated to the chemical metabolic process (e.g., CYP1A1, CYP1B1, CYP1A2) and inflammatory response (e.g., EREG). Another DEG, FGF-1, was only down-regulated in asthma and specially COPD-DHBE cells repeatedly exposed. While RAB37 could help to counteract the down-regulation of FGF-1 in asthma-DHBE cells, the deregulation of FGR, WNT7B, VIPR1, and PPARGC1A could dramatically contribute to make it worse in COPD-DHBE cells. Taken together, these data contributed to support the highest effects of UFP versus FP and highest sensitivity of asthma- and notably COPD-DHBE versus NHBE cells.

Exposure of normal and chronic bronchitis-like mucosa models to aerosolized carbon nanoparticles: comparison of pro-inflammatory oxidative stress and tissue injury/repair responses

Carbon nanoparticles (CNP) are generated by incomplete combustion of diesel engines. Several epidemiological studies associated higher susceptibility to particulate matter related adverse respiratory outcomes with preexisting conditions like chronic bronchitis (CB). Therefore, we compared the effect of CNP exposure on primary bronchial epithelial cells (PBEC) developed in air-liquid interface (ALI) models of normal versus CB-like-mucosa.PBEC cultured at ALI represented normal mucosa (PBEC-ALI). To develop CB-like-mucosa (PBEC-ALI/CB), 1 ng/ml interleukin-13 was added to the basal media of PBEC-ALI culturing. PBEC-ALI and PBEC-ALI/CB were exposed to sham or to aerosolized CNP using XposeALI^® system. Protein levels of CXCL-8 and MMP-9 were measured in the basal media using ELISA. Transcript expression of pro-inflammatory (CXCL8, IL6, TNF, NFKB), oxidative stress (HMOX1, SOD3, GSTA1, GPx), tissue injury/repair (MMP9/TIMP1) and bronchial cell type markers (MUC5AC, CC10) were assessed using qRT-PCR.Increased secretion of CXCL-8 and MMP-9 markers was detected 24 h post-exposure in both PBEC-ALI and PBEC-ALI/CB with more pronounced effect in the later. Pro-inflammatory and tissue injury markers were increased at both 6 h and 24 h post-exposure in PBEC-ALI/CB. Oxidative stress markers exhibited similar responses at 6 h and 24 h post-exposure in PBEC-ALI/CB. The club cell specific marker CC10 was increased by 300 fold in PBEC-ALI/CB and 20 fold in PBEC-ALI following CNP exposure.Our data indicates an earlier and stronger reaction of pro-inflammatory, oxidative stress and tissue injury markers in PBEC-ALI/CB models compared to PBEC-ALI models following CNP exposure. The findings may provide insight into the plausible mechanisms of higher susceptibility among predisposed individuals to nanoparticle exposure.

Effects of Different Components of PM2.5 on the Expression Levels of NF-κB Family Gene mRNA and Inflammatory Molecules in Human Macrophage

Background: Studies have found that exposure to fine particulate matter with sizes below 2.5 µm (PM2.5) might cause inflammation response via the NF-κB pathway. To date, only a few studies have focused on the toxicity of different components of PM2.5. We aimed to explore the effects of PM2.5 with different components on the expression levels of NF-κB family gene mRNA and inflammatory molecules in human macrophages. Methods: Human monocytic cell line THP-1-derived macrophages were exposed to water-soluble (W-PM2.5), fat-soluble (F-PM2.5), and insoluble (I-PM2.5) PM2.5. The cell survival rate was measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The levels of inflammatory molecules were determined by enzyme-linked immunosorbent assay (ELISA), and the relative mRNA levels of the NF-κB family gene were determined by real time PCR. Results: PM2.5 could decrease the cell viability. After exposure to W-PM2.5, the levels of interleukins (IL)-1β and IL-12 p70 significantly increased. After exposure to F-PM2.5, the levels of IL-12 p70 significantly increased. The levels of IL-12 p70 and TNF-α after exposure to I-PM2.5 were significantly higher than that in W- and F-PM2.5 treatment groups. The levels of IL-8, C reactive protein (CRP), and cyclooxygenase (COX)-2 increased only after exposure to I-PM2.5. F-PM2.5 increased the mRNA levels of NF-κB genes, especially NF-κB1 and RelA. Conclusions: PM2.5 can decrease the cell survival rate and up-regulate the expression of NF-κB family gene mRNA and inflammatory molecules. The main toxic components of PM2.5 related to inflammatory response in macrophages were the I-PM2.5.

In vitro evaluation of organic extractable matter from ambient PM2.5 using human bronchial epithelial BEAS-2B cells: Cytotoxicity, oxidative stress, pro-inflammatory response, genotoxicity, and cell cycle deregulation

A particular attention has been devoted to the type of toxicological responses induced by particulate matter (PM), since their knowledge is greatly complicated by the fact that it is a heterogeneous and often poorly described pollutant. However, despite intensive research effort, there is still a lack of knowledge about the specific chemical fraction of PM, which could be mainly responsible of its adverse health effects. We sought also to better investigate the toxicological effects of organic extractable matter (OEM) in normal human bronchial epithelial lung BEAS-2B cells. The wide variety of chemicals, including PAH and other related-chemicals, found in OEM, has been rather associated with early oxidative events, as supported by the early activation of the sensible NRF-2 signaling pathway. For the most harmful conditions, the activation of this signaling pathway could not totally counteract the ROS overproduction, thereby leading to critical oxidative damage to macromolecules (lipid peroxidation, oxidative DNA adducts). While NRF-2 is an anti-inflammatory, OEM exposure did not trigger any significant change in the secretion of inflammatory cytokines (i.e., TNFα, IL-1β, IL-6, IL-8, MCP-1, and IFNγ). According to the high concentrations of PAH and other related organic chemicals found in this OEM, CYP1A1 and 1B1 genes exhibited high transcription levels in BEAS-2B cells, thereby supporting both the activation of the critical AhR signaling pathway and the formation of highly reactive ultimate metabolites. As a consequence, genotoxic events occurred in BEAS-2B cells exposed to this OEM together with cell survival events, with possible harmful cell cycle deregulation. However, more studies are required to implement these observations and to contribute to better decipher the critical role of the organic fraction of air pollution-derived PM_2.5 in the activation of some sensitive signaling pathways closely associated with G1/S and intra-S checkpoint blockage, on the one hand, and cell survival, on the other hand.

Health effects of particulate matter air pollution in underground railway systems - a critical review of the evidence

BACKGROUND

Exposure to ambient airborne particulate matter is a major risk factor for mortality and morbidity, associated with asthma, lung cancer, heart disease, myocardial infarction, and stroke, and more recently type 2 diabetes, dementia and loss of cognitive function. Less is understood about differential effects of particulate matter from different sources. Underground railways are used by millions of people on a daily basis in many cities. Poor air exchange with the outside environment means that underground railways often have an unusually high concentration of airborne particulate matter, while a high degree of railway-associated mechanical activity produces particulate matter which is physicochemically highly distinct from ambient particulate matter. The implications of this for the health of exposed commuters and employees is unclear.

MAIN BODY

A literature search found 27 publications directly assessing the potential health effects of underground particulate matter, including in vivo exposure studies, in vitro toxicology studies, and studies of particulate matter which might be similar to that found in underground railways. The methodology, findings, and conclusions of these studies were reviewed in depth, along with further publications directly relevant to the initial search results. In vitro studies suggest that underground particulate matter may be more toxic than exposure to ambient/urban particulate matter, especially in terms of endpoints related to reactive oxygen species generation and oxidative stress. This appears to be predominantly a result of the metal-rich nature of underground particulate matter, which is suggestive of increased health risks. However, while there are measureable effects on a variety of endpoints following exposure in vivo, there is a lack of evidence for these effects being clinically significant as may be implied by the in vitro evidence.

CONCLUSION

There is little direct evidence that underground railway particulate matter exposure is more harmful than ambient particulate matter exposure. This may be due to disparities between in vivo exposures and in vitro models, and differences in exposure doses, as well as statistical under powering of in vivo studies of chronic exposure. Future research should focus on outcomes of chronic in vivo exposure, as well as further work to understand mechanisms and potential biomarkers of exposure.

In vitro lung toxicity of indoor PM10 from a stove fueled with different biomasses

Biomass combustion significantly contributes to indoor and outdoor air pollution and to the adverse health effects observed in the exposed populations. Besides, the contribution to toxicity of the particles derived from combustion of different biomass sources (pellet, wood, charcoal), as well as their biological mode of action, are still poorly understood. In the present study, we investigate the toxicological properties of PM10 particles emitted indoor from a stove fueled with different biomasses. PM10 was sampled by gravimetric methods and particles were chemically analyzed for Polycyclic Aromatic Hydrocarbons (PAHs) and elemental content. Human lung A549 cells were exposed for 24 h to 1-10 μg/cm² PM and different biological endpoints were evaluated to comparatively estimate the cytotoxic, genotoxic and pro-inflammatory effects of the different PMs. Pellet PM decreased cell viability, inducing necrosis, while charcoal and wood ones mainly induced apoptosis. Oxidative stress-related response and cytochrome P450 enzymes activation were observed after exposure to all the biomasses tested. Furthermore, after pellet exposure, DNA lesions and cell cycle arrest were also observed. The severe genotoxic and pro-necrotic effects observed after pellet exposure were likely the consequence of the high metal content. By administering the chelating agent TPEN, the genotoxic effects were indeed rescued. The higher content in PAHs measured in wood and charcoal PMs was likely the reason of the enhanced expression of metabolizing and oxidative stress-related enzymes, like CYP1B1 and HO-1, and the consequent increase in apoptotic cell death. These data suggest that combustion particles from different biomass sources may impact on lung cells according to different pathways, finally producing different toxicities. This is strictly related to the PM chemical composition, which reflects the quality of the combustion and the fuel in particular. Further studies are needed to clarify the role of particle dimension and the molecular mechanisms behind the harmful effects observed.

Air pollution-derived PM2.5 impairs mitochondrial function in healthy and chronic obstructive pulmonary diseased human bronchial epithelial cells

In order to clarify whether the mitochondrial dysfunction is closely related to the cell homeostasis maintenance after particulate matter (PM_2.5) exposure, oxidative, inflammatory, apoptotic and mitochondrial endpoints were carefully studied in human bronchial epithelial BEAS-2B, normal human bronchial epithelial (NHBE) and chronic obstructive pulmonary disease (COPD)-diseased human bronchial epithelial (DHBE) cells acutely or repeatedly exposed to air pollution-derived PM_2.5. Some modifications of the mitochondrial morphology were observed within all these cell models repeatedly exposed to the highest dose of PM_2.5. Dose- and exposure-dependent oxidative damages were reported in BEAS-2B, NHBE and particularly COPD-DHBE cells acutely or repeatedly exposed to PM_2.5. Nuclear factor erythroid 2-p45 related factor 2 (NRF2) gene expression and binding activity, together with the mRNA levels of some NRF2 target genes, were directly related to the number of exposures for the lowest PM_2.5 dose (i.e., 2 μg/cm²), but, surprisingly, inversely related to the number of exposures for the highest dose (i.e., 10 μg/cm²). There were dose- and exposure-dependent increases of both nuclear factor kappa-B (NF-κB) binding activity and NF-κB target cytokine secretion in BEAS-2B, NHBE and particularly COPD-DHBE cells exposed to PM_2.5. Mitochondrial ROS production, membrane potential depolarization, oxidative phosphorylation, and ATP production were significantly altered in all the cell models repeatedly exposed to the highest dose of PM_2.5. Collectively, our results indicate a cytosolic ROS overproduction, inducing oxidative damage and activating oxygen sensitive NRF2 and NF-_kB signaling pathways for all the cell models acutely or repeatedly exposed to PM_2.5. However, one of the important highlight of our findings is that the prolonged and repeated exposure in BEAS-2B, NHBE and in particular sensible COPD-DHBE cells further caused an oxidative boost able to partially inactivate the NRF2 signaling pathway and to critically impair mitochondrial redox homeostasis, thereby producing a persistent mitochondrial dysfunction and a lowering cell energy supply.

Pro-inflammatory effects of extracted urban fine particulate matter on human bronchial epithelial cells BEAS-2B

Atmospheric particulate matter (PM) constitutes the major part of urban air pollution and is a heterogeneous mixture of solid and liquid particles of different origin, size, and chemistry. Human exposure to PM in urban areas poses considerable and significant adverse effects on the respiratory system and human health in general. Major contributors to PM content are combustion-related sources such as diesel vehicles, household, and industrial heating. PM is composed of thousands of different high molecular weight organic compounds, including poly-aromatic hydrocarbons (PAHs). The aim of this study was to clarify the cytotoxic effects of the extract of actual urban PM1 with high benzo[a]pyrene (BaP) content collected in Eastern European mid-sized city during winter heating season on human bronchial epithelial cells (BEAS-2B). Decreased cell viability, alteration of cell layer integrity, increased apoptosis, and oxidative stress were observed during the 3-day exposure to the PM extract. In addition, following PM exposure pro-inflammatory cytokine expression was upregulated at gene and protein levels. Morphology and motility changes, i.e., decreased cells' ability to cover scratch area, were also documented. We report here that the extract of urban PM1 may induce bronchial epithelium changes and render it pro-inflammatory and compromised within 3 days.

In Vitro and In Vivo Experimental Studies of PM2.5 on Disease Progression

Air pollution is a very critical issue worldwide, particularly in developing countries. Particulate matter (PM) is a type of air pollution that comprises a heterogeneous mixture of different particle sizes and chemical compositions. There are various sources of fine PM (PM2.5), and the components may also have different effects on people. The pathogenesis of PM2.5 in several diseases remains to be clarified. There is a long history of epidemiological research on PM2.5 in several diseases. Numerous studies show that PM2.5 can induce a variety of chronic diseases, such as respiratory system damage, cardiovascular dysfunction, and diabetes mellitus. However, the epidemiological evidence associated with potential mechanisms in the progression of diseases need to be proved precisely through in vitro and in vivo investigations. Suggested mechanisms of PM2.5 that lead to adverse effects and chronic diseases include increasing oxidative stress, inflammatory responses, and genotoxicity. The aim of this review is to provide a brief overview of in vitro and in vivo experimental studies of PM2.5 in the progression of various diseases from the last decade. The summarized research results could provide clear information about the mechanisms and progression of PM2.5-induced disease.

Insights in particulate matter-induced allergic airway inflammation: Focus on the epithelium

Outdoor air pollution is a major environmental health problem throughout the world. In particular, exposure to particulate matter (PM) has been associated with the development and exacerbation of several respiratory diseases, including asthma. Although the adverse health effects of PM have been demonstrated for many years, the underlying mechanisms have not been fully identified. In this review, we focus on the role of the lung epithelium and specifically highlight multiple cytokines in PM-induced respiratory responses. We describe the available literature on the topic including in vitro studies, findings in humans (ie observations in human cohorts, human controlled exposure and ex vivo studies) and in vivo animal studies. In brief, it has been shown that exposure to PM modulates the airway epithelium and promotes the production of several cytokines, including IL-1, IL-6, IL-8, IL-25, IL-33, TNF-α, TSLP and GM-CSF. Further, we propose that PM-induced type 2-promoting cytokines are important mediators in the acute and aggravating effects of PM on airway inflammation. Targeting these cytokines could therefore be a new approach in the treatment of asthma.