Activation of different pathways of apoptosis by air pollution particulate matter (PM2.5) in human epithelial lung cells (L132) in culture

Protective Potential of a Botanical-Based Supplement Ingredient against the Impact of Environmental Pollution on Cutaneous and Cardiopulmonary Systems: Preclinical Study

Air pollution is a growing threat to human health. Airborne pollution effects on respiratory, cardiovascular and skin health are well-established. The main mechanisms of air-pollution-induced health effects involve oxidative stress and inflammation. The present study evaluates the potential of a polyphenol-enriched food supplement ingredient comprising Lippia citriodora, Olea europaea, Rosmarinus officinalis, and Sophora japonica extracts in mitigating the adverse effects of environmental pollution on skin and cardiopulmonary systems. Both in vitro and ex vivo studies were used to assess the blend's effects against pollution-induced damage. In these studies, the botanical blend was found to reduce lipid peroxidation, inflammation (by reducing IL-1α), and metabolic alterations (by regulating MT-1H, AhR, and Nrf2 expression) in human skin explants exposed to a mixture of pollutants. Similar results were also observed in keratinocytes exposed to urban dust. Moreover, the ingredient significantly reduced pollutant-induced ROS production in human endothelial cells and lung fibroblasts, while downregulating the expression of apoptotic genes (bcl-2 and bax) in lung fibroblasts. Additionally, the blend counteracted the effect of urban dust on the heart rate in zebrafish embryos. These results support the potential use of this supplement as an adjuvant method to reduce the impact of environmental pollution on the skin, lungs, and cardiovascular tissues.

Effect of altered human exposome on the skin and mucosal epithelial barrier integrity

Pollution in the world and exposure of humans and nature to toxic substances is continuously worsening at a rapid pace. In the last 60 years, human and domestic animal health has been challenged by continuous exposure to toxic substances and pollutants because of uncontrolled growth, modernization, and industrialization. More than 350,000 new chemicals have been introduced to our lives, mostly without any reasonable control of their health effects and toxicity. A plethora of studies show exposure to these harmful substances during this period with their implications on the skin and mucosal epithelial barrier and increasing prevalence of allergic and autoimmune diseases in the context of the "epithelial barrier hypothesis". Exposure to these substances causes an epithelial injury with peri-epithelial inflammation, microbial dysbiosis and bacterial translocation to sub-epithelial areas, and immune response to dysbiotic bacteria. Here, we provide scientific evidence on the altered human exposome and its impact on epithelial barriers.

Air pollution induces pyroptosis of human monocytes through activation of inflammasomes and Caspase-3-dependent pathways

According to the World Health Organization (WHO), air pollution is one of the most serious threats for our planet. Despite a growing public awareness of the harmful effects of air pollution on human health, the specific influence of particulate matter (PM) on human immune cells remains poorly understood. In this study, we investigated the effect of PM on peripheral blood monocytes in vitro. Monocytes from healthy donors (HD) were exposed to two types of PM: NIST (SRM 1648a, standard urban particulate matter from the US National Institute for Standards and Technology) and LAP (SRM 1648a with the organic fraction removed). The exposure to PM-induced mitochondrial ROS production followed by the decrease of mitochondrial membrane potential and activation of apoptotic protease activating factor 1 (Apaf-1), Caspase-9, and Caspase-3, leading to the cleavage of Gasdermin E (GSDME), and initiation of pyroptosis. Further analysis showed a simultaneous PM-dependent activation of inflammasomes, including NLRP3 (nucleotide-binding oligomerization domain-like receptor pyrin domain containing 3) and Caspase-1, followed by cleavage of Gasdermin D (GSDMD) and secretion of IL-1β. These observations suggest that PM-treated monocytes die by pyroptosis activated by two parallel signaling pathways, related to the inorganic and organic PM components. The release of IL-1β and expression of danger-associated molecular patterns (DAMPs) by pyroptotic cells further activated the remnant viable monocytes to produce inflammatory cytokines (TNF-α, IL-6, IL-8) and protected them from death induced by the second challenge with PM.In summary, our report shows that PM exposure significantly impacts monocyte function and induces their death by pyroptosis. Our observations indicate that the composition of PM plays a crucial role in this process-the inorganic fraction of PM is responsible for the induction of the Caspase-3-dependent pyroptotic pathway. At the same time, the canonical inflammasome path is activated by the organic components of PM, including LPS (Lipopolysaccharide/endotoxin). PM-induced pyroptosis of human monocytes. Particulate matter (PM) treatment affects monocytes viability already after 15 min of their exposure to NIST or LAP in vitro. The remnant viable monocytes in response to danger-associated molecular patterns (DAMPs) release pro-inflammatory cytokines and activate Th1 and Th17 cells. The mechanism of PM-induced cell death includes the increase of reactive oxygen species (ROS) production followed by collapse of mitochondrial membrane potential (ΔΨm), activation of Apaf-1, Caspase-9 and Caspase-3, leading to activation of Caspase-3-dependent pyroptotic pathway, where Caspase-3 cleaves Gasdermin E (GSDME) to produce a N-terminal fragment responsible for the switch from apoptosis to pyroptosis. At the same time, PM activates the canonical inflammasome pathway, where activated Caspase-1 cleaves the cytosolic Gasdermin D (GSDMD) to produce N-terminal domain allowing IL-1β secretion. As a result, PM-treated monocytes die by pyroptosis activated by two parallel pathways-Caspase-3-dependent pathway related to the inorganic fraction of PM and the canonical inflammasome pathway dependent on the organic components of PM.

Apoptotic volume decrease (AVD) in A549 cells exposed to water-soluble fraction of particulate matter (PM10)

Exposure to atmospheric particulate matter (PM) is recognized as a human health risk factor of great concern. The present work aimed to study the cellular mechanisms underlying cytotoxic effects of airborne particulate matter <10 µm in size (PM₁₀), sampled in an urban background site from January to May 2020, on A549 cells. In particular, the study addressed if PM₁₀ exposure can be a main factor in the induction of the Apoptotic Volume Decrease (AVD), which is one of the first events of apoptosis, and if the generation of intracellular oxidative stress can be involved in the PM₁₀ induction of apoptosis in A549 cells. The cytotoxicity of PM₁₀ samples was measured by MTT test on cells exposed for 24 h to the PM₁₀ aqueous extracts, cell volume changes were monitored by morphometric analysis of the cells, apoptosis appearance was detected by annexin V and the induction of intracellular oxidative stress was evaluated by the ROS sensitive CM-H₂DCFDA fluorescent probe. The results showed cytotoxic effects ascribable to apoptotic death in A549 cells exposed for 24 h to aqueous extracts of airborne winter PM₁₀ samples characterized by high PM₁₀ value and organic carbon content. The detected reduced cell viability in winter samples ranged from 55% to 100%. Normotonic cell volume reduction (ranging from about 60% to 30% cell volume decrease) after PM₁₀ exposure was already detectable after the first 30 min clearly indicating the ability of PM₁₀, mainly arising from biomass burning, to induce Apoptotic Volume Decrease (AVD) in A549 cells. AVD was prevented by the pre-treatment with 0.5 mM SITS indicating the activation of Cl^- efflux presumably through the activation of VRAC channels. The exposure of A549 cells to PM₁₀ aqueous extracts was able to induce intracellular oxidative stress detected by using the ROS-sensitive probe CM-H₂DCFDA. The PM₁₀-induced oxidative stress was statistically significantly correlated with cell viability inhibition and with apoptotic cell shrinkage. It was already evident after 15 min exposure representing one of the first cellular effects caused by PM exposure. This result suggests the role of oxidative stress in the PM₁₀ induction of AVD as one of the first steps in cytotoxicity.

Cell Death Pathways: The Variable Mechanisms Underlying Fine Particulate Matter-Induced Cytotoxicity

Recently, the advent of health risks due to the cytotoxicity of fine particulate matter (FPM) is concerning. Numerous studies have reported abundant data elucidating the FPM-induced cell death pathways. However, several challenges and knowledge gaps are still confronted nowadays. On one hand, the undefined components of FPM (such as heavy metals, polycyclic aromatic hydrocarbons, and pathogens) are all responsible for detrimental effects, thus rendering it difficult to delineate the specific roles of these copollutants. On the other hand, owing to the crosstalk and interplay among different cell death signaling pathways, precisely determining the threats and risks posed by FPM is difficult. Herein, we recapitulate the current knowledge gaps present in the recent studies regarding FPM-induced cell death, and propose future research directions for policy-making to prevent FPM-induced diseases and improve knowledge concerning the adverse outcome pathways and public health risks of FPM.

The association between ambient particulate matter exposure and the telomere-mitochondrial axis of aging in newborns

BACKGROUND

Particulate matter (PM) is associated with aging markers at birth, including telomeres and mitochondria. It is unclear whether markers of the core-axis of aging, i.e. tumor suppressor p53 (p53) and peroxisome proliferator-activated receptor gamma co-activator 1 alpha (PGC-1α), are associated with prenatal air pollution and whether there are underlying mechanisms.

METHODS

556 mother-newborn pairs from the ENVIRONAGE birth cohort were recruited at the East Limburg Hospital in Genk (Belgium). In placenta and cord blood, telomere length (TL) and mitochondrial DNA content (mtDNAc) were measured using quantitative real-time polymerase chain reaction (qPCR). In cord plasma, p53 and PGC-1α protein levels were measured using ELISA. Daily ambient PM_2.5 concentrations during gestation were calculated using a spatial temporal interpolation model. Distributed lag models (DLMs) were applied to assess the association between prenatal PM_2.5 exposure and each molecular marker. Mediation analysis was performed to test for underlying mechanisms.

RESULTS

A 5 µg/m³ increment in PM_2.5 exposure was associated with -11.23 % (95 % CI: -17.36 % to -4.65 %, p = 0.0012) and -7.34 % (95 % CI: -11.56 % to -2.92 %, p = 0.0014) lower placental TL during the entire pregnancy and second trimester respectively, and with -12.96 % (95 % CI: -18.84 % to -6.64 %, p < 0.001) lower placental mtDNAc during the third trimester. Furthermore, PM_2.5 exposure was associated with a 12.42 % (95 % CI: -1.07 % to 27.74 %, p = 0.059) higher cord plasma p53 protein level and a -3.69 % (95 % CI: -6.97 % to -0.31 %, p = 0.033) lower cord plasma PGC-1α protein level during the third trimester. Placental TL mediated 65 % of the negative and 17 % of the positive association between PM_2.5 and placental mtDNAc and cord plasma p53 protein levels, respectively.

CONCLUSION

Ambient PM_2.5 exposure during pregnancy is associated with markers of the core-axis of aging, with TL as a mediating factor. This study strengthens the hypothesis of the air pollution induced core-axis of aging, and may unravel a possible underlying mediating mechanism in an early-life epidemiological context.

The cytotoxicity of PM2.5 and its effect on the secretome of normal human bronchial epithelial cells

Exposure to airborne fine particulate matter (PM_2.5) induced various adverse health effects, such as metabolic syndrome, systemic inflammation, and respiratory disease. Many works have studied the effects of PM_2.5 exposure on cells through intracellular proteomics analyses. However, changes of the extracellular proteome under PM_2.5 exposure and its correlation with PM_2.5-induced cytotoxicity still remain unclear. Herein, the cytotoxicity of PM_2.5 on normal human bronchial epithelia cells (BEAS-2B cells) was evaluated, and the secretome profile of BEAS-2B cells before and after PM_2.5 exposure was investigated. A total of 83 proteins (58 upregulated and 25 downregulated) were differentially expressed in extracellular space after PM_2.5 treatment. Notably, we found that PM_2.5 promoted the release of several pro-apoptotic factors and induced dysregulated secretion of extracellular matrix (ECM) constituents, showing that the abnormal extracellular environment attributed to PM_2.5-induced cell damage. This study provided a secretome data for the deep understanding of the molecular mechanism underlying PM_2.5-caused human bronchial epithelia cell damage.

Redox Regulatory Changes of Circadian Rhythm by the Environmental Risk Factors Traffic Noise and Air Pollution

Significance: Risk factors in the environment such as air pollution and traffic noise contribute to the development of chronic noncommunicable diseases. Recent Advances: Epidemiological data suggest that air pollution and traffic noise are associated with a higher risk for cardiovascular, metabolic, and mental disease, including hypertension, heart failure, myocardial infarction, diabetes, arrhythmia, stroke, neurodegeneration, depression, and anxiety disorders, mainly by activation of stress hormone signaling, inflammation, and oxidative stress. Critical Issues: We here provide an in-depth review on the impact of the environmental risk factors air pollution and traffic noise exposure (components of the external exposome) on cardiovascular health, with special emphasis on the role of environmentally triggered oxidative stress and dysregulation of the circadian clock. Also, a general introduction on the contribution of circadian rhythms to cardiovascular health and disease as well as a detailed mechanistic discussion of redox regulatory pathways of the circadian clock system is provided. Future Directions: Finally, we discuss the potential of preventive strategies or "chrono" therapy for cardioprotection. Antioxid. Redox Signal. 37, 679-703.

Effect of combustion particle morphology on biological responses in a Co-culture of human lung and macrophage cells

Atmospheric aging of combustion particles alters their chemical composition and morphology. Previous studies have reported differences in toxicological responses after exposure to fresh versus aged particles, with chemical composition being the prime suspect behind the differences. However, less is known about the contribution of morphological differences in atmospherically aged particles to toxicological responses, possibly due to the difficulty in resolving the two properties (composition and morphology) that change simultaneously. This study altered the shape of lab-generated combustion particles, without affecting the chemical composition, from fractal-like to a more compact spherical shape, using a water condensation-evaporation method. The two shapes were exposed to a co-culture of human airway epithelial (A549) and differentiated human monocyte (THP-1) cells at air-liquid interface (ALI) conditions. The particles with different shapes were deposited using an electrostatic field-based ALI chamber. For the same mass dose, both shapes were internalized by cells, induced a pro-inflammatory response (IL-8 and TNFα), and enhanced CYP1A1 gene expression compared to air controls. The more compact spherical particles (representative of atmospherically aged particles) induced more early apoptosis and release of TNFα compared to the more fractal-like particles. These results suggest a contribution of morphology to the increased toxicity of aged combustion-derived particles.

Pathogenic Mechanisms of Secondary Organic Aerosols

Air pollution represents a major health problem and an economic burden. In recent years, advances in air pollution research has allowed particle fractionation and identification of secondary organic aerosol (SOA). SOA is formed from either biogenic or anthropogenic emissions, through a mass transfer from the gaseous mass to the particulate phase in the atmosphere. They can have deleterious impact on health and the mortality of individuals with chronic inflammatory diseases. The pleiotropic effects of SOA could involve different and interconnected pathogenic mechanisms ranging from oxidative stress, inflammation, and immune system dysfunction. The purpose of this review is to present recent findings about SOA pathogenic roles and potential underlying mechanisms focusing on the lungs; the latter being the primary exposed organ to atmospheric pollutants.

The Impact of Air Pollution on the Course of Cystic Fibrosis: A Review

Cystic fibrosis (CF) is a lethal and widespread autosomal recessive disorder affecting over 80,000 people worldwide. It is caused by mutations of the CFTR gene, which encodes an epithelial anion channel. CF is characterized by a great phenotypic variability which is currently not fully understood. Although CF is genetically determined, the course of the disease might also depend on multiple other factors. Air pollution, whose effects on health and contribution to respiratory diseases are well established, is one environmental factor suspected to modulate the disease severity and influence the lung phenotype of CF patients. This is of particular interest as pulmonary failure is the primary cause of death in CF. The present review discusses current knowledge on the impact of air pollution on CF pathogenesis and aims to explore the underlying cellular and biological mechanisms involved in these effects.

A comparative study on the model of PM2.5 direct or indirect interaction with bronchial epithelial cells

The impact of PM_2.5 on epithelial cells is a pivotal process leading to many lung pathological changes and pulmonary diseases. In addition to PM_2.5 direct interaction with epithelia, macrophages that engulf PM_2.5 may also influence the function of epithelial cells. However, among the toxic researches of PM_2.5, there is a lack of evaluation of direct or indirect exposure model on human bronchial epithelial cell against PM_2.5. In this present research, PM_2.5-exposed human bronchial epithelial cell line (BEAS-2B) serves as the direct interaction model. By contrast, a PM_2.5-stimulated co-culture model of macrophages and epithelial cells based on the transwell system was adopted as indirect stimulation model. By comparing these two models of interaction, we examined the viability of BEAS-2B and mRNA/protein expression profile of oxidative stress and inflammatory response-related transcription factors Nrf2, NF-kB, and according inflammatory indicators such as IL-1, IL-6, and IL-8, with a view to evaluating the effects of different interaction models of PM_2.5 on epithelial cell damage in vitro. Our results indicated that under the same doses, the direct stimulation model of PM_2.5 could inhibit the viability of BEAS-2B. Furthermore, the indirect stimulation model strengthen inflammation response of epithelia under the higher concentration of PM_2.5 and induce epithelia to undergo EMT under the lower concentration of PM_2.5. Overall, we have found that macrophage involvement may protect epithelia from PM_2.5 cytotoxic effect, while it strengthens the inflammation response and induce epithelia to undergo EMT.

Inhalation of PM2.5 from diesel exhaust promote impairment of mitochondrial bioenergetics and dysregulate mitochondrial quality in rat heart: implications in isoproterenol-induced myocardial infarction model

Aim: Ambient exposure of PM_2.5 from diesel exhaust (termed as diesel particulate matter [DPM]) can induce cardiotoxicity that can be manifested into myocardial ischemia/infarction, where the survival depends on mitochondrial function. The mechanism for DPM-induced mitochondrial dysfunction is yet to be elucidated and the consequential impact of impaired mitochondria on the severity of myocardial infarction (MI) has not been established.Materials and methods: Female Wistar rats were exposed to DPM (0.5 mg/ml) for 3 h daily (to achieve a PM_2.5 concentration of 250 µg/m³) for 21 d trailed by an induction of MI using isoproterenol (ISO).Conclusion: DPM exposure altered the basal ECG pattern and increased heart weight (HW) to body weight (BW) ratio from control. Loss of mitochondrial quality in the cardiac tissue was observed in DPM exposed animals, measured via declined ETC enzyme activity, reduced ATP levels, high oxidative stress, low mitochondrial copy number, and low expression of the mitochondrial genes involved in mitophagy (PINK and PARKIN) and mitochondrial fusion (MFN-1). Subsequent induction of MI in DPM exposed animals (DPM + ISO) further deteriorated the normal sinus rhythm, accompanied by elevated plasma CK and LDH level, increased myocardial caspase activity, downregulation of Peroxisome proliferator-activated receptor-gamma coactivator (PGC1-α), transcription factor A (TFAM), DNA polymerase subunit gamma (POLG), and other mitochondrial quality control genes. Based on these results, we conclude that DPM alters the electrophysiology and ultrastructure of the heart that aggravates the MI-induced cardiotoxicity, where the diminished mitochondrial quality can be the potential contributor.

Citrus junos Tanaka Peel Extract and Its Bioactive Naringin Reduce Fine Dust-Induced Respiratory Injury Markers in BALB/c Male Mice

Particulate matter (PM) 10 refers to fine dust with a diameter of less than 10 µm and induces apoptosis and inflammatory responses through oxidative stress. Citrus junos Tanaka is a citrus fruit and contains bioactive flavonoids including naringin. In the present study, we aimed to identify the preventive effect of Citrus junos Tanaka peel extract (CPE) against PM10-induced lung injury. As a proof of concept, NCI-H460 cells were treated with CPE (800 μg/mL, 12 h) in conjunction with PM10 to examine intracellular antioxidative capacity in the pulmonary system. In an in vivo model, male BALB/c mice (n = 8/group) were randomly assigned into five groups: NEG (saline-treated), POS (PM10 only), NAR (PM10 + naringin, 100 mg/kg), CPL (PM10 + CPE low, 100 mg/kg), and CPH (PM10 + CPE high, 400 mg/kg). Intervention groups received dietary supplementations for 7 days followed by PM10 exposure (100 mg/kg, intranasal instillation). Compared to the NEG, the CPE decreased to 22% of the ROS generation and significantly increased cell viability in vitro. The histological assessments confirmed that pulmonary damages were alleviated in the PM10 + CPL group compared to the POS. Pro-inflammatory cytokines and NF-κB/apoptosis signaling-related markers were decreased in the PM10 + CPL group compared to the POS. These results indicated that CPE showed promising efficacy in preventing pulmonary injuries in vivo. Such protection can be explained by the anti-oxidative capacity of CPE, likely due to its bioactives, including naringin (7.74 mg/g CPE). Follow-up human intervention, as well as population-level studies, will further shed light on the preventive efficacy of CPE against pulmonary damage in humans.

Lipid peroxidation index of particulate matter: Novel metric for quantifying intrinsic oxidative potential and predicting toxic responses

Using particulate matter (PM) mass as exposure metric does not reveal the intrinsic PM chemical characteristics or toxic potential, which is crucial for monitoring the sources of emission causing adverse health effects and developing risk mitigating strategies. Oxidative stress and ensuing lipid peroxidation (LPO) in the lung are crucial underlying mechanisms of action by which PM drives cardiorespiratory disease. In the current study, we have postulated and demonstrated that the intrinsic potential of PM to elicit LPO, defined as "LPO index" as a novel approach for characterizing oxidative potential of PM (PMOP) and predicting biological toxicity. First, we exposed unsaturated phosphatidylcholine (PC), an abundant phospholipid in the cell membrane, pulmonary surfactant, and lipoproteins to PM and analyzed the total burden of LPO byproducts generated as a measure of LPO index using a LPO reporter dye, BODIPY-C11. PM exposure resulted in a concentration-dependent increase in LPO. Second, we developed a novel method to expose the captured serum apoB100 lipoprotein particles to PM or its constituents and assessed the levels of specific oxidized-phospholipid on apoB100 particles by immunoassay using E06 monoclonal antibody (mab) that recognizes only PC containing oxidized-phospholipids (Ox-PCs). The immunoassay was highly sensitive to evaluate the PM LPO index and was modifiable by metal quenchers and exogenous antioxidant and radical quenchers. Third, to prove the pathophysiological relevance of Ox-PCs, we found that PM exposure generates Ox-PCs in mice lungs, pulmonary surfactant and lung cells. Fourth, we observed that treatment of macrophages with BAL fluid from PM exposed mice or PM-exposed pulmonary surfactant stimulated IL-6 production, which was abrogated by neutralization of Ox-PCs by mab E06 suggesting that Ox-PCs in lungs are proinflammatory. Overall, our study suggests that Ox-PCs as a probe of PM LPO index is a biologically relevant pathogenic biomarker and has a high value for evaluating PMOP.

In vitro impact preliminary assessment of airborne particulate from metalworking and woodworking industries

Inhalation is the main route of exposure to airborne pollutants. To evaluate the safety and assess the risks of occupational hazards different testing approaches are used. 3D airway epithelial tissues allow to mimic exposure conditions in vitro, generates human-relevant toxicology data, allows to elucidate the mode of action of pollutants. Gillian3500 pumps were used to collect the airborne particulate from woodworking and metalworking environments. EpiAirway tissues were used to model half working day (4 h), full working day (8 h), and 3 working day exposures to occupational pollutants. Tissue viability was assessed using an MTT assay. For preliminary assessment, RT-qPCR analyses were performed to analyze the expression of gelsolin, caspase-3, and IL-6. Tissue morphology was assessed by hematoxylin/eosin staining. An effect on the proliferation of lung epithelial cell line A549 was assessed. Acute exposure to workspace pollutants slightly affected tissue viability and did not change the morphology. No inhibiting effect was observed on the proliferation of A549 cells. Preliminary analysis showed that both types of particles suppressed the expression of gelsolin, with the effect of metalworking samples being more pronounced. A slight reduction in caspase-3 expression was observed. Particles from metalworking suppressed IL-6 expression.

Organ-on-a-chip platforms for evaluation of environmental nanoparticle toxicity

Despite showing a great promise in the field of nanomedicine, nanoparticles have gained a significant attention from regulatory agencies regarding their possible adverse health effects upon environmental exposure. Whether those nanoparticles are generated through intentional or unintentional means, the constant exposure to nanomaterials can inevitably lead to unintended consequences based on epidemiological data, yet the current understanding of nanotoxicity is insufficient relative to the rate of their emission in the environment and the lack of predictive platforms that mimic the human physiology. This calls for a development of more physiologically relevant models, which permit the comprehensive and systematic examination of toxic properties of nanoparticles. With the advancement in microfabrication techniques, scientists have shifted their focus on the development of an engineered system that acts as an intermediate between a well-plate system and animal models, known as organ-on-a-chips. The ability of organ-on-a-chip models to recapitulate in vivo like microenvironment and responses offers a new avenue for nanotoxicological research. In this review, we aim to provide overview of assessing potential risks of nanoparticle exposure using organ-on-a-chip systems and their potential to delineate biological mechanisms of epidemiological findings.

Effect of water-soluble PM10 on the production of TNF-α by human monocytes and induction of apoptosis in A549 human lung epithelial cells

Long-term exposure to airborne particles of 10 µm and less in size (PM₁₀) in dust can lead to increased risk of diseases such as respiratory, cardiovascular, lung cancer and atherosclerosis. The aim of the study was to evaluate the effects of water-soluble PM₁₀ particles in the Middle East Dust (MED) storm in Ahvaz, Iran, on the production of TNF-α by human monocytes. In addition, we assessed the level of induction of apoptosis in isolated A549 human pulmonary epithelial cells. For this purpose, isolated human blood monocytes (250,000 to 300,000 cell/ ml) as well as isolated human pulmonary A549 epithelial cells (100,0000 cell/ ml) were exposed to various concentrations (62.5, 125, 250, 500 µg/ml) of water-soluble PM₁₀ particles for different incubation periods (12, 24, 48 h). The results showed that exposure to PM₁₀ particles increased the production of TNF-α in human monocytes and promoted apoptosis induction in A549 cells, in both concentration and incubation of period-dependent manner. In conclusion, airborne dust particles in Ahvaz city contain active compounds capable of increasing production of the pro-inflammatory cytokine, TNF-α, and inducing apoptosis of lung epithelial cells.

Particulates induced lung inflammation and its consequences in the development of restrictive and obstructive lung diseases: a systematic review

Particulate matters (PMs) are significant components of air pollution in the urban environment. PMs with aerodynamic diameter less than 2.5 μm (PM_2.5) can penetrate to the alveolar area and introduce numerous compounds to the pneumocystis that can initiate inflammatory response. There are several questions about this exposure as follows: does PM_2.5-induced inflammation lead to a specific disease? If yes, what is the form of the progressed disease? This systematic review was designed and conducted to respond to these questions. Four databases, including Web of Science, Scopus, PubMed, and Embase, were reviewed systematically to find the related articles. According to the included articles, the only available data on the inflammatory effects of PM_2.5 comes from either in vitro or animal studies. Both types of studies have shown that the induced inflammation is type I and includes secretion of proinflammatory cytokines. The exposure duration of longer than 28 weeks was not observed in any of the reviewed studies. However, as there is not a specific antigenic component in the urban particulate matters and based on the available evidence, the antigen-presenting is not a common process in the inflammatory responses to PM_2.5. Therefore, neither signaling to repair cells such as fibroblasts nor over-secretion of extracellular matrix (ECM) proteins can occur following PM_2.5-induced inflammation. These pieces of evidence weaken the probability of the development of fibrotic diseases. On the other hand, permanent inflammation induces the destruction of ECM and alveolar walls by over-secretion of protease enzymes and therefore results in progressive obstructive effects.

Pollutant-sex specific differences in respiratory hospitalization and mortality risk attributable to short-term exposure to ambient air pollution

BACKGROUND

Many studies have reported associations of individual pollutants with respiratory hospitalization and mortality based on different populations, which makes it difficult to directly compare adverse health effects among multiple air pollutants.

OBJECTIVES

The study goal is to compare acute respiratory-related hospitalization and mortality associated with short-term exposure to three ambient air pollutants and analyze differences in health risks by season, age and sex.

METHODS

Hourly measurements of air pollutants (ozone, NO₂, PM_2.5) and temperature were collected from ground-monitors for 24 cities along with daily hospitalization (1996-2012) and mortality (1984-2012) data. National associations between air pollutant and health outcome were estimated for season (warm, cold vs. year-round), age (base ≥ 1, seniors > 65), and sex (females ≥ 1 and males ≥ 1) using Bayesian hierarchical models.

RESULTS

Overall, the three air pollutants were significantly associated with acute respiratory health outcomes at different lag-days. For respiratory hospitalization, the increased risks in percent changes with 95% posterior intervals for a 10-unit increase in each pollutant were: ozone (lag1, 0.7% (0.4, 0.9)), NO₂ (lag0, 0.7% (0.1, 1.4)), and PM_2.5 (lag1, 1.3% (0.7, 1.9)). For respiratory mortality: ozone (lag2, 1.2% (0.4, 1.9)), NO₂ (lag1, 2.1% (0.6, 3.5)), and PM_2.5 (lag1, 0.6% (-1.0, 2.2)). While some differences in risk were observed by season and age group, sex-specific differences were more pronounced. Compared with males, females had a higher respiratory mortality risk (1.8% (0.6, 2.9) vs 0.5% (-0.3, 1.3)) from ozone, a higher respiratory hospitalization risk (0.9% (0.0, 1.8) vs 0.6% (-0.3, 1.4)) but lower mortality risk (1.4% (-1.0, 3.7) vs 2.2% (0.4, 4.0)) from NO₂, and a lower hospitalization risk (0.7% (-0.2, 1.7) vs 1.8% (1.0, 2.6)) from PM_2.5.

CONCLUSION

This study reports significant health effects of short-term exposure to three ambient air pollutants on respiratory hospitalization (ozone≈NO₂ < PM_2.5 per-10 unit; ozone>NO₂ ≈ PM_2.5 per-IQR) and mortality (ozone≈NO₂ > PM_2.5) in Canada. Pollutant-sex-specific differences were found, but inconclusive due to limited biological and physiological explanations. Further studies are warranted to understand the pollutant-sex specific differences.

PM2.5-related cell death patterns

With the increasingly serious problem of environmental pollution, the health problems caused by PM2.5 are gradually coming into our line of sight. Previous researches have indicated that air pollution is nearly related to various diseases, but few studies have focused on the exact function mediated by particulate matter less than 2.5 (PM2.5) in these diseases. PM2.5 is known to induce multiple ways of cell death, including autophagy, necrosis, apoptosis, pyroptosis and ferroptosis. Therefore, it is of much importance to understand the different ways of cell death caused by PM2.5 in the pathogenesis and treatment of PM2.5-related diseases. This present review is an insight of multiple ways of PM2.5‑induced cell death in different diseases.

PM2.5 induces autophagy-mediated cell apoptosis via PI3K/AKT/mTOR signaling pathway in mice bronchial epithelium cells

Air pollution can highly impact the respiratory system in healthy individuals. Studies have indicated that particles with an aerodynamic diameter of ≤2.5 µm (PM2.5) can be considered to be harmful for lung alveoli and bronchial epithelium cells. PM2.5 can be directly inhaled and can deeply penetrate into the lung alveoli, causing lung dysfunction. However, the toxicological mechanism mediated by PM2.5 for respiratory disease has still not been clearly determined. The purpose of the current study was to investigate the effects of PM2.5 on mouse bronchial epithelium cells (MBECs) and explored the possible mechanism mediated by PM2.5 in MBECs. The results of the current study indicated that PM2.5 markedly decreased lung function, including total lung capacity, residual volume, vital capacity and airway resistance in experimental mice. The results demonstrated that PM2.5 markedly induced inflammatory responses, oxidative injury and MBEC apoptosis. PM2.5 increased interleukin (IL)-1β and IL-6 expression, and reactive oxygen species production in MBECs. Furthermore, PM2.5 specifically induced PI3K, AKT and mTOR expression in MBECs. Disruption of PI3K/AKT/mTOR signaling was also indicated to effectively inhibit apoptosis of MBECs. In conclusion, the results of the current study systematically demonstrated the role of apoptosis-mediated MBEC apoptosis in PM2.5-treated mice, and provides a potential strategy for preclinical intervention in patients with PM2.5-induced lung diseases.

Differential expression of nuclear genes encoding mitochondrial proteins from urban and rural populations in Morocco

Urbanization in low-income countries represents an important inflection point in the epidemiology of disease, with rural populations experiencing high rates of chronic and recurrent infections and urban populations displaying a profile of noncommunicable diseases. To investigate if urbanization alters the expression of genes encoding mitochondrial proteins, we queried gene microarray data from rural and urban populations living in Morocco (GSE17065). The R Bioconductor packages edgeR and limma were used to identify genes with different expression. The experimental design was modeled upon location and sex. Nuclear genes encoding mitochondrial proteins were identified from the MitoCarta2.0 database. Of the 1158 genes listed in the MitoCarta2.0 database, 847 genes (73%) were available for analysis in the Moroccan dataset. The urban-rural comparison with the greatest environmental differences showed that 76.5% of the MitoCarta2.0 genes were differentially expressed, with 97% of the genes having an increased expression in the urban area. Enrichment analysis revealed 367 significantly enriched pathways (adjusted p value < 0.05), with oxidative phosphorylation, insulin secretion and glucose regulations (adj.p values = 6.93E-16) being the top three. Four significantly perturbed KEGG disease pathways were associated with urbanization-three degenerative neurological diseases (Huntington's, Alzheimer's, and Parkinson's diseases) and herpes simplex infection (false discover rate corrected p value (PGFdr) < 0.2). Mitochondrial RNA metabolic processing and translational elongation were the biological processes that had the greatest enrichment (enrichment ratios 14.0 and 14.8, respectively, FDR < 0.5). Our study links urbanization in Morocco with changes in the expression of the nuclear genes encoding mitochondrial proteins.

Seasonal Variation in the Chemical Composition and Oxidative Potential of PM2.5

Exposure to fine particulate matter (PM2.5) has well-established systemic human health effects due in part to the chemical components associated with these exposures. Oxidative stress is a hypothesized mechanism for the health effects associated with PM2.5 exposures. The oxidative potential of PM2.5 has recently been suggested as a metric that is more indicative of human health effects than the routinely measured PM2.5 concentration. The purpose of this study was to analyze and compare the oxidative potential and elemental composition of PM2.5 collected at two locations during different seasons. PM2.5 was collected onto PTFE-coated filters (n = 16) along two highways in central Oregon, USA in the Winter (January) and Summer (July/August). PM2.5 was extracted from each filter via sonication in methanol. An aliquot of the extraction solution was used to measure oxidative potential using the dithiothreitol (DTT) assay. An additional aliquot underwent analysis via inductively coupled plasma—mass spectrometry (ICP-MS) to quantify elements (n = 20). Differences in PM2.5 elemental composition were observed between locations and seasons as well as between days in the same season. Overall, concentrations were highest in the winter samples but the contribution to total PM2.5 mass was higher for elements in the summer. Notably, the oxidative potential (nM DTT consumed/µg PM2.5/min) differed between seasons with summer samples having nearly a two-fold increase when compared to the winter. Significant negative correlations that were observed between DTT consumption and several elements as well as with PM2.5 mass but these findings were dependent on if the data was normalized by PM2.5 mass. This research adds to the growing evidence and justification for investigating the oxidative potential and composition of PM2.5 while also highlighting the seasonal variability of these factors.

Outdoor air pollution and cancer: An overview of the current evidence and public health recommendations

Outdoor air pollution is a major contributor to the burden of disease worldwide. Most of the global population resides in places where air pollution levels, because of emissions from industry, power generation, transportation, and domestic burning, considerably exceed the World Health Organization's health-based air-quality guidelines. Outdoor air pollution poses an urgent worldwide public health challenge because it is ubiquitous and has numerous serious adverse human health effects, including cancer. Currently, there is substantial evidence from studies of humans and experimental animals as well as mechanistic evidence to support a causal link between outdoor (ambient) air pollution, and especially particulate matter (PM) in outdoor air, with lung cancer incidence and mortality. It is estimated that hundreds of thousands of lung cancer deaths annually worldwide are attributable to PM air pollution. Epidemiological evidence on outdoor air pollution and the risk of other types of cancer, such as bladder cancer or breast cancer, is more limited. Outdoor air pollution may also be associated with poorer cancer survival, although further research is needed. This report presents an overview of outdoor air pollutants, sources, and global levels, as well as a description of epidemiological evidence linking outdoor air pollution with cancer incidence and mortality. Biological mechanisms of air pollution-derived carcinogenesis are also described. This report concludes by summarizing public health/policy recommendations, including multilevel interventions aimed at individual, community, and regional scales. Specific roles for medical and health care communities with regard to prevention and advocacy and recommendations for further research are also described.

Long-term PM2.5 exposure increases the risk of non-small cell lung cancer (NSCLC) progression by enhancing interleukin-17a (IL-17a)-regulated proliferation and metastasis

PM_2.5 is a class of airborne particles and droplets with sustained high levels in many developing countries. Epidemiological studies have indicated that PM_2.5 is closely associated with the increased morbidity and mortality of lung cancer in the world. Unfortunately, the effects of PM_2.5 on lung cancer are largely unknown. In the present study, we attempted to explore the role of PM_2.5 in the etiology of NSCLC. Here, we found that long-term PM_2.5 exposure led to significant pulmonary injury. Epithelial-mesenchymal transition (EMT) and cancer stem cells (CSC) properties were highly induced by PM_2.5 exposure. EMT was evidenced by the significant up-regulation of MMP2, MMP9, TGF-β1, α-SMA, Fibronectin and Vimentin. Lung cancer progression was associated with the increased expression of Kras, c-Myc, breast cancer resistance protein BCRP (ABCG2), OCT4, SOX2 and Aldh1a1, but the decreased expression of p53 and PTEN. Importantly, mice with IL-17a knockout (IL-17a^-/-) showed significantly alleviated lung injury and CSC properties following PM_2.5 exposure. Also, IL-17a^-/--attenuated tumor growth was recovered in PM_2.5-exposed mice injected with recombinant mouse IL-17a, accompanied with significantly restored lung metastasis. Taken together, these data revealed that PM_2.5 could promote the progression of lung cancer by enhancing the proliferation and metastasis through IL-17a signaling.

Air pollutants disrupt iron homeostasis to impact oxidant generation, biological effects, and tissue injury

Air pollutants cause changes in iron homeostasis through: 1) a capacity of the pollutant, or a metabolite(s), to complex/chelate iron from pivotal sites in the cell or 2) an ability of the pollutant to displace iron from pivotal sites in the cell. Through either pathway of disruption in iron homeostasis, metal previously employed in essential cell processes is sequestered after air pollutant exposure. An absolute or functional cell iron deficiency results. If enough iron is lost or is otherwise not available within the cell, cell death ensues. However, prior to death, exposed cells will attempt to reverse the loss of requisite metal. This response of the cell includes increased expression of metal importers (e.g. divalent metal transporter 1). Oxidant generation after exposure to air pollutants includes superoxide production which functions in ferrireduction necessary for cell iron import. Activation of kinases and phosphatases and transcription factors and increased release of pro-inflammatory mediators also result from a cell iron deficiency, absolute or functional, after exposure to air pollutants. Finally, air pollutant exposure culminates in the development of inflammation and fibrosis which is a tissue response to the iron deficiency challenging cell survival. Following the response of increased expression of importers and ferrireduction, activation of kinases and phosphatases and transcription factors, release of pro-inflammatory mediators, and inflammation and fibrosis, cell iron is altered, and a new metal homeostasis is established. This new metal homeostasis includes increased total iron concentrations in cells with metal now at levels sufficient to meet requirements for continued function.

Assessment of Air Pollutant PM2.5 Pulmonary Exposure Using a 3D Lung-on-Chip Model

Airborne particulate matters have posed significant risk to human health worldwide. Fine particulate matters (PM2.5, aerodynamic diameter <2.5 μm) are associated with increased morbidity and mortality attributed to pulmonary diseases. An advanced in vitro model would benefit the assessment of PM2.5 induced pulmonary injuries and drug development. In this work, we present a PM2.5 exposure model to evaluate the pulmonary risk of fine particulate matter exposure in an organotypic manner with the help of 3D human lung-on-a-chip. By compartmentalized co-culturing of human endothelial cells, epithelial cells, and extra cellular matrix, our lung-on-a-chip recapitulated the structural features of the alveolar-blood barrier, which is pivotal for exogenous hazard toxicity evaluation. PM2.5 was applied to the channel lined with lung epithelial cells to model the pulmonary exposure of fine particulate matter. The results indicated acute high dose PM2.5 exposure would lead to various malfunctions of the alveolar-capillary barrier, including adheren junction disruption, increased ROS generation, apoptosis, inflammatory biofactor expression in epithelial cells and endothelial cells, elevated permeability, and monocyte attachments. Collectively, our lung-on-a-chip model provides a simple platform to investigate the complex responses after PM2.5 exposure in a physiologically relevant level, which could be of great potential in environmental risk assessment and therapeutic treatment development.

Oxidative stress induced by ultrafine carbon black particles can elicit apoptosis in vivo and vitro

Although carbon black (CB) particles have potential hazards to human health, the toxicological studies on CB are still limited. The purpose of this study was to investigate the effect of oxidative stress induced by ultrafine CB particles on apoptosis in vivo and vitro. Male C57BL/6 mice were inhalation exposed to CB for 28 days, and 16HBE cells were treated by CB particles and also added antioxidant (NAC). Antioxidant enzymes activities (CAT, SOD, GSH-Px) and ROS in the lungs and cells were evaluated. Apoptosis-related proteins (Bcl-2, Bax, Cleaved Caspase-3, pro-Caspase-3, Caspase-7, Caspase-8, Caspase-9, PARP-1) were tested by Western blot (WB), immunohistochemistry (IHC), and real-time PCR. The reduction of antioxidant enzymes activities and the addition of ROS in CB exposure groups were observed, and the gene and apoptosis-related proteins levels were increased in CB exposure mice. The results of CB-treated 16HBE cells were consistent with those of mice, and apoptosis rate was increased in CB-treated 16HBE cells. When the cells were treated with NAC, ROS induced by CB decreased, SOD and CAT activities of CB-treated 16HBE cells were increased. Apoptosis rate of 16HBE cells treated with NAC and CB was significantly decreased, and the expression of C-Caspase-3 was also decreased. Therefore, oxidative stress induced by ultrafine CB particles can elicit apoptosis in vivo and vitro. Antioxidants can significantly reduce oxidative damage and apoptosis induced by CB.

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.

Correlation of α/γ-Fe2O3 nanoparticles with the toxicity of particulate matter originating from subway tunnels in Seoul stations, Korea

According to the increasing concern about particulate matter (PM) pollution at subway systems, particularly its potentially severe effects on human health, this study investigated the constituents, characteristics, and toxicity of PM collected at underground subway stations in Seoul, Korea. It was found that α/γ-Fe₂O₃ NPs, which are considered as thermal products derived from the brake-wheel-rail interface, were the main components of PM (57.6% and 48% of PM₁₀ and PM_2.5, respectively). In addition, hydrothermally synthesized α/γ-Fe₂O₃ NPs, proposing to possess similar properties to those of Fe₂O₃ contained in PM, were used to investigate the correlation of these oxides with PM toxicity. In particular, the synthesized γ-Fe₂O₃ NPs induced a negligibly toxic, while the synthesized α-Fe₂O₃ NPs and PM showed remarkably toxic effects on HeLa cells and zebrafish embryos, specifically in reducing cell proliferation to 85% and 72% survival, causing high apoptosis of 29.8% and 29.3%, and inhibiting the development of embryos up to 60% and 8% after prolonged exposure, respectively. It is considered that α-Fe₂O₃ NPs were primarily responsible for the harmful effects of PM, resulting in significant damage to DNA due to their capacity of producing high reactive oxygen species (ROS) and, thus, deleterious effects on the human body.

Co-expression of Hsp70 Protein and Autophagy Marker Protein LC3 in A549 Cells and THP1 Cells Exposed to Nanoparticles of Air Pollution

The ability of air particulate matter (PM) to cause reactive oxygen species-driven protein damage is associated with both COPD and lung cancer, but the mechanisms are unsettled. In this study, we investigated the co-expression of Hsp70 and the autophagy marker protein LC3 in A549 cells (alveolar epithelial cell line) and THP-1 cells (monocyte/macrophage cells) grown in media supplemented with 100 μg/mL of four types of PM: carbon black (CB), urban dust (UD), nanoparticulate CB (NPCB), and nanoparticulate CB coated with benzo(a)pyrene (NPCB-BaP). Fluorescent monoclonal antibodies and flow cytometry were used to assess the expression and co-expression of HSP70 and LC3 proteins. Hsp70 expression was significantly increased by all PM, while LC3 was decreased by CB in A549 cells, unchanged by CB and UD in THP-1 cells and increased by NPCB and NPCB-BaP in both cell types. All PMs increased the Hsp70/LC3 ratio in binary scatterplots; the relationship was positive and linear, which may reflect chaperone-dependent autophagy. The UD was the only PM type that affected the slopes of the spatial trend lines and altered binary patterns of Hsp70/LC3 distribution in THP1 cells. These findings provide an insight into the molecular mechanisms regulating proteostasis in PM-exposed cells through the chaperone-autophagy system in the cytoplasm.

Particulate matter exposure shapes DNA methylation through the lifespan

Exposure to airborne particulate matter (PM) has been associated with detrimental health effects. DNA methylation represents the most well-studied epigenetic factor among the possible mechanisms underlying this association. Interestingly, changes of DNA methylation in response to environmental stimuli are being considered for their role in the pathogenic mechanism, but also as mediators of the body adaptation to air pollutants.Several studies have evaluated both global and gene-specific methylation in relation to PM exposure in different clinical conditions and life stages. The purpose of the present literature review is to evaluate the most relevant and recent studies in the field in order to analyze the available evidences on long- and short-term PM exposure and DNA methylation changes, with a particular focus on the different life stages when the alteration occurs. PM exposure modulates DNA methylation affecting several biological mechanisms with marked effects on health, especially during susceptible life stages such as pregnancy, childhood, and the older age.Although many cross-sectional investigations have been conducted so far, only a limited number of prospective studies have explored the potential role of DNA methylation. Future studies are needed in order to evaluate whether these changes might be reverted.

Cellular Responses to Exposure to Outdoor Air from the Chinese Spring Festival at the Air-Liquid Interface

The Spring Festival is the most important holiday in China. During this time, the levels of particulate matter (PM) as well as gaseous copollutants significantly increase because of the widespread enjoyment of fireworks. The expression patterns of microRNAs may serve as valuable signatures of exposure to environmental constituents. We exposed macrophages to the whole stream of outdoor air at the air-liquid interface aiming at closely approximating the physiological conditions and the inhalation situation in the lung. 58 miRNAs were up-regulated, and 68 miRNAs were down-regulated in the night of the New Year's Eve (exposure group E2N1) compared to filtered-air exposed control cells. The target genes of the up-regulated miRNAs were enriched in immunity- and inflammation-linked pathways, such as the TLR-NF-κB pathway. Compared to the E2N1 group, 29 miRNAs were up-regulated, and 23 miRNAs were down-regulated in the cells exposed to air from the daytime of the Chinese New Year with higher concentrations of particles, SO₂, and nitrogen oxide. The target genes of the up-regulated miRNAs were mostly enriched in apoptosis, adhesion, and junction-related pathways. These results preliminarily unravel part of the toxic mechanisms of air constituents and provide clues for discovering the main drivers of air pollution-induced disorders.

Effect of collection methods on combustion particle physicochemical properties and their biological response in a human macrophage-like cell line

In vitro studies are a first step toward understanding the biological effects of combustion-derived particulate matter (cdPM). A vast majority of studies expose cells to cdPM suspensions, which requires a method to collect cdPM and suspend it in an aqueous media. The consequences of different particle collection methods on particle physiochemical properties and resulting biological responses are not fully understood. This study investigated the effect of two common approaches (collection on a filter and a cold plate) and one relatively new (direct bubbling in DI water) approach to particle collection. The three approaches yielded cdPM with differences in particle size distribution, surface area, composition, and oxidative potential. The directly bubbled sample retained the smallest sized particles and the bimodal distribution observed in the gas-phase. The bubbled sample contained ∼50% of its mass as dissolved species and lower molecular weight compounds, not found in the other two samples. These differences in the cdPM properties affected the biological responses in THP-1 cells. The bubbled sample showed greater oxidative potential and cellular reactive oxygen species. The scraped sample induced the greatest TNFα secretion. These findings have implications for in vitro studies of air pollution and for efforts to better understand the underlying mechanisms.

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.

Omics approach reveals metabolic disorders associated with the cytotoxicity of airborne particulate matter in human lung carcinoma cells

Exposure to airborne particulate matter (PM) _2.5 induced various adverse health effects, such as metabolic syndrome, systemic inflammation and respiratory infection. However, a global influence of PM_2.5-induced metabolic and proteomic disorders remains confusing, and the underlying mechanism is still under-explored. Herein, LC-MS/MS-based metabolomics, lipidomics and isobaric tags for relative and absolute quantification (iTRAQ)-based proteomics were applied to analyze the toxicological characteristics of PM_2.5 from Taiyuan City in China (Taiyuan-PM_2.5) on human lung carcinoma cells (A549) after the 24-h treatment. Metabolites, lipids and proteins that have distinctive differences were screened by SIEVE, LipidSearch and Proteome Discoverer, respectively. The abundance of 56 metabolites (40 increased and 16 decreased), 22 lipids (19 increased and 3 decreased) and 81 proteins (55 up-regulated and 26 down-regulated) were significantly changed upon the PM_2.5 treatment. Among the proteomics analysis, 16 proteins were specifically related to RNA splicing, mainly including up-regulated serine/arginine-rich splicing factor 1 (SRSF1), SRSF2, small nuclear ribonucleoprotein 70 kDa (snRNP70), small nuclear ribonucleoprotein polypeptide B (SNRPB), SNRPC, SNRPE and down-regulated heterogeneous nuclear ribonucleoprotein U-like 2 (hnRNP UL2). At the metabolic level, PM_2.5 exposure significantly altered the sphingolipid metabolism, including ceramide, serine, sphingosine and sphingomyelin. It was proposed that excessive accumulation of ceramide and expression of key enzymes (ceramide synthases, phingomyelinase, sphingosine kinase types 2 and protein phosphatase-1) induced the secretion of pro-inflammatory cytokines, generation of lipotoxicity and alterations of RNA splicing in PM_2.5-treated A549  cells. In general, our results demonstrated that ceramide accumulation and altered RNA splicing could becritical contributors to PM_2.5-induced cytotoxicity at metabolic and proteomic level, which might be considered as potential markers for toxicological evaluation of PM_2.5 samples.

A magnetic covalent organic framework as an adsorbent and a new matrix for enrichment and rapid determination of PAHs and their derivatives in PM2.5 by surface-assisted laser desorption/ionization-time of flight-mass spectrometry

Fe₃O₄@COFs served as an adsorbent and new matrix for SALDI-TOF-MS analysis of PAHs and their derivatives in PM_2.5 with clear background, good reproducibility and sensitivity.

A matrix-assisted laser desorption ionization-time-of-flight-time-of-flight-mass spectrometry-based toxicoproteomic screening method to assess in vitro particle potencies

Knowledge of biological reactivity and underlying toxicity mechanisms of airborne particulate matter (PM) is central to the characterization of the risk associated with these pollutants. An integrated screening platform consisting of protein profiling of cellular responses and cytotoxic analysis was developed in this study for the estimation of PM potencies. Mouse macrophage (J774A.1) and human lung epithelial cells (A549) were exposed in vitro to Ottawa urban particles (EHC6802) and two reference mineral particles (TiO₂ and SiO₂). Samples from the in vitro exposure experiment were tested following an integrated classical cytotoxicity/toxicoproteomic assessment approach for cellular viability (CellTiter Blue®, lactate dehydrogenase) and proteomic analyses. Cellular proteins were pre‐fractionated by molecular weight cut‐off filtration, digested enzymatically and were analyzed by matrix‐assisted laser desorption ionization–time‐of‐flight–time‐of‐flight–mass spectrometry for protein profiling and identification. Optimization of detergent removal, pre‐fractionation strategies and enzymatic digestion procedures led to increased tryptic peptide (m/z) signals with reduced sample processing times, for small total protein contents. Proteomic analyses using this optimized procedure identified statistically significant (P < 0.05) PM dose‐dependent changes at the molecular level. Ranking of PM potencies based on toxicoproteomic analysis were in line with classical cytotoxicity potency‐based ranking. The high content toxicoproteomic approach exhibited the potential to add value to risk characterization of environmental PM exposures by complementing and validating existing cytotoxicity testing strategies.

To estimate in vitro potencies of ambient air particles we developed an integrated screening platform that enabled protein profiling of cellular responses and cytotoxic analyses. Extensive optimization of the toxicoproteomic analysis was carried out. Cellular proteomic changes were consistent with cytotoxicity findings. The integration of proteomic and cytotoxicity analyses results provided insight into particulate matter cytotoxic reactivity‐related mechanistic information at the molecular level.

PM2.5 Exposure Elicits Oxidative Stress Responses and Mitochondrial Apoptosis Pathway Activation in HaCaT Keratinocytes

Background:

PM_2.5 (aerodynamic diameter ≤ 2.5 μm) is a dominant and ubiquitous air pollutant that has become a global concern as PM_2.5 exposure has been linked to many adverse health effects including cardiovascular and pulmonary diseases. Emerging evidence supports a correlation between increased air PM_2.5 levels and skin disorders although reports on the underlying pathophysiological mechanisms are limited. Oxidative stress is the most common mechanism of PM_2.5-induced adverse health effects. This study aimed to investigate PM_2.5-induced oxidative damage and apoptosis in immortalized human keratinocyte (HaCaT) cells.

Methods:

HaCaT cells were exposed to 0, 25, 50, 100, or 200 μg/ml PM_2.5 for 24 h. Reactive oxygen species (ROS) generation, lipid peroxidation products, antioxidant activity, DNA damage, apoptotic protein expression, and cell apoptosis were measured.

Results:

PM_2.5 exposure (0-200 μg/ml) for 24 h resulted in increased ROS levels (arbitrary unit: 201.00 ± 19.28, 264.50 ± 17.91, 305.05 ± 19.57, 427.95 ± 18.32, and 436.70 ± 17.77) and malondialdehyde production (0.54 ± 0.05 nmol/mg prot, 0.61 ± 0.06 nmol/mg prot, 0.68 ± 0.05 nmol/mg prot, 0.70 ± 0.05 nmol/mg prot, and 0.76 ± 0.05 nmol/mg prot), diminished superoxide dismutase activity (6.47 ± 0.28 NU/mg prot, 5.97 ± 0.30 NU/mg prot, 5.15 ± 0.42 NU/mg prot, 4.08 ± 0.20 NU/mg prot, and 3.76 ± 0.37 NU/mg prot), and increased DNA damage and apoptosis in a dose-dependent manner in HaCaT cells. Moreover, cytochrome-c, caspase-3, and caspase-9 expression also increased proportionately with PM_2.5 dosing.

Conclusion:

PM_2.5 might elicit oxidative stress and mitochondria-dependent apoptosis that likely manifests as skin irritation and damage.

Placental promoter methylation of DNA repair genes and prenatal exposure to particulate air pollution: an ENVIRONAGE cohort study

BACKGROUND

Exposure to particulate air pollution has been linked with risk of carcinogenesis. Damage to repair pathways might have long-term adverse health effects. We aimed to investigate the association of prenatal exposure to air pollution with placental mutation rate and the DNA methylation of key placental DNA repair genes.

METHODS

This cohort study used data from the ongoing ENVironmental Influence ON early AGEing (ENVIRONAGE) birth cohort, which enrols pairs of mothers and neonates (singleton births only) at the East-Limburg Hospital (Genk, Belgium). Placental DNA samples were collected after birth. We used bisulfite-PCR-pyrosequencing to investigate the mutation rate of Alu (a marker for overall DNA mutation) and DNA methylation in the promoter genes of key DNA repair and tumour suppressor genes (APEX1, OGG1, PARP1, ERCC1, ERCC4, p53, and DAPK1). We used a high-resolution air pollution model to estimate exposure to particulate matter with a diameter less than 2·5 μm (PM_2·5), black carbon, and NO₂ over the entire pregnancy on the basis of maternal address. Alu mutation was analysed with a linear regression model, and methylation values of the selected genes were analysed in mixed-effects models. Effect estimates are presented as the relative percentage change in methylation for an ambient air pollution increment of one IQR (ie, the difference between the first and third quartiles of exposure in the entire cohort).

FINDINGS

500 biobanked placental DNA samples were randomly selected from 814 pairs of mothers and neonates who were recruited to the cohort between Feb 1, 2010, and Dec 31, 2014, of which 463 samples met the pyrosequencing quality control criteria. IQR exposure increments were 3·84 μg/m³ for PM_2·5, 0·36 μg/m³ for black carbon, and 5·34 μg/m³ for NO₂. Among these samples, increased Alu mutation rate was associated with greater exposure to PM_2·5 (r=0·26, p<0·0001) and black carbon (r=0·33, p<0·0001), but not NO₂. Promoter methylation was positively associated with PM_2·5 in APEX1 (7·34%, 95% CI 0·52 to 14·16, p=0·009), OGG1 (13·06, 3·88 to 22·24, p=0·005), ERCC4 (16·31%, 5·43 to 27·18, p=0·01), and p53 (10·60%, 4·46 to 16·74, p=0·01), whereas promoter methylation of DAPK1 (-12·92%, -22·35 to -3·49, p=0·007) was inversely associated with PM_2·5 exposure. Black carbon exposure was associated with elevated promoter methylation in APEX1 (9·16%, 4·06 to 14·25, p=0·01) and ERCC4 (27·56%, 17·58 to 37·55, p<0·0001). Promoter methylation was not associated with pollutant exposure in PARP1 and ERCC1, and NO₂ exposure was not associated with methylation in any of the genes studied.

INTERPRETATION

Transplacental in-utero exposure to particulate matter is associated with an increased overall placental mutation rate (as measured with Alu), which occurred in concert with epigenetic alterations in key DNA repair and tumour suppressor genes. Our results suggest that exposure to air pollution can induce changes to fetal and neonatal DNA repair capacity. Future studies will be essential to elucidate whether these changes persist and have a role in carcinogenic insults later in life.

FUNDING

European Research Council and the Flemish Scientific Fund.

Function of PM2.5 in the pathogenesis of lung cancer and chronic airway inflammatory diseases

Previous research has identified that air pollution is associated with various respiratory diseases, but few studies have investigated the function served by particulate matter 2.5 (PM2.5) in these diseases. PM2.5 is known to cause epigenetic and microenvironmental alterations in lung cancer, including tumor-associated signaling pathway activation mediated by microRNA dysregulation, DNA methylation, and increased levels of cytokines and inflammatory cells. Autophagy and apoptosis of tumor cells may also be detected in lung cancer associated with PM2.5 exposure. A number of mechanisms are involved in triggering and aggravating asthma and COPD, including PM2.5-induced cytokine release and oxidative stress. The present review is an overview of the underlying molecular mechanisms of PM2.5-induced pathogenesis in lung cancer and chronic airway inflammatory diseases.

REDUCTION OF PM2.5 TOXICITY ON HUMAN ALVEOLAR EPITHELIAL CELLS A549 BY TEA POLYPHENOLS

Tea-derived polyphenols have anticancer and antioxidant properties, and they can regulate oxidative stress. This study was designed to quantify both the toxic effects of fine particulate matter with aerodynamic diameter less than 2.5 μm (PM2.5) and determine whether tea polyphenols could provide a protective effect against PM2.5 toxicity on human alveolar epithelial A549 cells in vitro. Cytotoxic effects of the PM2.5 on A549 cells were measured by means of cell viability, the expression of caspase-3, bax/bcl-2 and C/EBP-homologous protein (CHOP), and the generation of intracellular reactive oxygen species, malondialdehyde and superoxide dismutase. The results showed that tea polyphenols ameliorated some of the adverse effects of PM2.5 on A549 cell viability and superoxide dismutase levels. In addition, tea polyphenols decreased the production of reactive oxygen species, malondialdehyde generation, and apoptosis in response to PM2.5 exposure. Therefore, our results support a role for tea polyphenols in reducing the toxicity of PM2.5, particularly with regard to targeting oxidative stress and apoptosis.

Cell death pathways of particulate matter toxicity

Humans are exposed to various complex mixtures of particulate matter (PM) from different sources. Long-term exposure to high levels of these particulates has been linked to a diverse range of respiratory and cardiovascular diseases that have resulted in hospital admission. The evaluation of the effects of PM exposure on the mechanisms related to cell death has been a challenge for many researchers. Therefore, in this review, we have discussed the effects of airborne PM exposure on mechanisms related to cell death. For this purpose, we have compiled literature data on PM sources, the effects of exposure, and the assays and models used for evaluation, in order to establish comparisons between various studies. The analysis of this collected data suggested divergent responses to PM exposure that resulted in different cell death types (apoptosis, autophagy, and necrosis). In addition, PM induced oxidative stress within cells, which appeared to be an important factor in the determination of cell fate. When the levels of reactive oxygen species were overpowering, the cellular fate was directed toward cell death. This may be the underlying mechanism of the development or exacerbation of respiratory diseases, such as emphysema and chronic obstructive pulmonary diseases. In addition, PM was shown to cause DNA damage and the resulting mutations increased the risk of cancer. Furthermore, several conditions should be considered in the assessment of cell death in PM-exposed models, including the cell culture line, PM composition, and the interaction of the different cells types in in vivo models.

Genetic and epigenetic alterations in normal and sensitive COPD-diseased human bronchial epithelial cells repeatedly exposed to air pollution-derived PM2.5

Even though clinical, epidemiological and toxicological studies have progressively provided a better knowledge of the underlying mechanisms by which air pollution-derived particulate matter (PM) exerts its harmful health effects, further in vitro studies on relevant cell systems are still needed. Hence, aiming of getting closer to the human in vivo conditions, primary human bronchial epithelial cells derived from normal subjects (NHBE) or sensitive chronic obstructive pulmonary disease (COPD)-diseased patients (DHBE) were differentiated at the air-liquid interface. Thereafter, they were repeatedly exposed to air pollution-derived PM_2.5 to study the occurrence of some relevant genetic and/or epigenetic endpoints. Concentration-, exposure- and season-dependent increases of OH-B[a]P metabolites in NHBE, and to a lesser extent, COPD-DHBE cells were reported; however, there were more tetra-OH-B[a]P and 8-OHdG DNA adducts in COPD-DHBE cells. No increase in primary DNA strand break nor chromosomal aberration was observed in repeatedly exposed cells. Telomere length and telomerase activity were modified in a concentration- and exposure-dependent manner in NHBE and particularly COPD-DHBE cells. There were a global DNA hypomethylation, a P16 gene promoter hypermethylation, and a decreasing DNA methyltransferase activity in NHBE and notably COPD-DHBE cells repeatedly exposed. Changes in site-specific methylation, acetylation, and phosphorylation of histone H3 (i.e., H3K4me3, H3K9ac, H3K27ac, and H3S10ph) and related enzyme activities occurred in a concentration- and exposure-dependent manner in all the repeatedly exposed cells. Collectively, these results highlighted the key role played by genetic and even epigenetic events in NHBE and particularly sensitive COPD-DHBE cells repeatedly exposed to air pollution-derived PM_2.5 and their different responsiveness. While these specific epigenetic changes have been already described in COPD and even lung cancer phenotypes, our findings supported that, together with genetic events, these epigenetic events could dramatically contribute to the shift from healthy to diseased phenotypes following repeated exposure to relatively low doses of air pollution-derived PM_2.5.

Air Quality Effects on Human Health and Approaches for Its Assessment through Microfluidic Chips

Air quality depends on the various gases and particles present in it. Both natural phenomena and human activities affect the cleanliness of air. In the last decade, many countries experienced an unprecedented industrial growth, resulting in changing air quality values, and correspondingly, affecting our life quality. Air quality can be accessed by employing microchips that qualitatively and quantitatively determine the present gases and dust particles. The so-called particular matter 2.5 (PM2.5) values are of high importance, as such small particles can penetrate the human lung barrier and enter the blood system. There are cancer cases related to many air pollutants, and especially to PM2.5, contributing to exploding costs within the healthcare system. We focus on various current and potential future air pollutants, and propose solutions on how to protect our health against such dangerous substances. Recent developments in the Organ-on-Chip (OoC) technology can be used to study air pollution as well. OoC allows determination of pollutant toxicity and speeds up the development of novel pharmaceutical drugs.

PM2.5 obtained from urban areas in Beijing induces apoptosis by activating nuclear factor-kappa B

BACKGROUND

Particulate matter (PM), which has adverse effects on citizen health, is a major air pollutant in Beijing city. PM_2.5 is an indicator of PM in urban areas and can cause serious damage to human health. Many epidemiological studies have shown that nuclear factor-kappa B (NF-κB) is involved in PM_2.5-induced cell injury, but the exact mechanisms are not well understood.

METHODS

The cytotoxic effects of PM_2.5 at 25-1600 μg/ml for 24 h were determined by MTT assay in Chinese hamster ovary cells (CHO) cells. Flow cytometry was used to determine the apoptosis rate induced by PM_2.5. The destabilized enhanced green fluorescent protein (d2EGFP) green fluorescent protein reporter system was used to determine the NF-κB activity induced by PM_2.5. The expression of pro-apoptotic Bcl-2-associated death promoter (BAD) proteins induced by PM_2.5 was determined by western blotting to explore the relationship between PM_2.5 and the NF-κB signaling pathway and to determine the toxicological mechanisms of PM_2.5.

RESULTS

PM_2.5 collected in Beijing urban districts induces cytotoxic effects in CHO cells according to MTT assay with 72.28% cell viability rates even at 200 μg/ml PM_2.5 and flow cytometry assays with 26.97% apoptosis rates at 200 μg/ml PM_2.5. PM_2.5 increases the activation levels of NF-κB, which have maintained for 24 h. 200 μg/ml PM_2.5 cause activation of NF-κB after exposure for 4 h, the activation peak appears after 13.5 h with a peak value of 25.41%. The average percentage of NF-κB activation in whole 24 h is up to 12.9% by 200 μg/ml PM_2.5. In addition, PM_2.5 decreases the expression level of the pro-apoptotic protein BAD in a concentration-dependent manner.

CONCLUSIONS

PM_2.5 induces NF-κB activation, which persists for 24 h. The expression of pro-apoptotic protein BAD decreased with increased concentrations of PM_2.5. These findings suggest that PM_2.5 plays a major role in apoptosis by activating the NF-κB signaling pathway and reducing BAD protein expression.

Transcriptome-wide analyses indicate mitochondrial responses to particulate air pollution exposure

BACKGROUND

Due to their lack of repair capacity mitochondria are critical targets for environmental toxicants. We studied genes and pathways reflecting mitochondrial responses to short- and medium-term PM₁₀ exposure.

METHODS

Whole genome gene expression was measured in peripheral blood of 98 adults (49% women). We performed linear regression analyses stratified by sex and adjusted for individual and temporal characteristics to investigate alterations in gene expression induced by short-term (week before blood sampling) and medium-term (month before blood sampling) PM₁₀ exposure. Overrepresentation analyses (ConsensusPathDB) were performed to identify enriched mitochondrial associated pathways and gene ontology sets. Thirteen Human MitoCarta genes were measured by means of quantitative real-time polymerase chain reaction (qPCR) along with mitochondrial DNA (mtDNA) content in an independent validation cohort (n = 169, 55.6% women).

RESULTS

Overrepresentation analyses revealed significant pathways (p-value <0.05) related to mitochondrial genome maintenance and apoptosis for short-term exposure and to the electron transport chain (ETC) for medium-term exposure in women. For men, medium-term PM₁₀ exposure was associated with the Tri Carbonic Acid cycle. In an independent study population, we validated several ETC genes, including UQCRH and COX7C (q-value <0.05), and some genes crucial for the maintenance of the mitochondrial genome, including LONP1 (q-value: 0.07) and POLG (q-value: 0.04) in women.

CONCLUSIONS

In this exploratory study, we identified mitochondrial genes and pathways associated with particulate air pollution indicating upregulation of energy producing pathways as a potential mechanism to compensate for PM-induced mitochondrial damage.