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

Particulate matter-induced oxidative stress - Mechanistic insights and antioxidant approaches reported in in vitro studies

Inhaled particulate matter (PM) is a key factor in millions of yearly air pollution-related deaths worldwide. The oxidative potential of PM indicates its ability to promote an oxidative environment. Excessive reactive oxygen species (ROS) can cause cell damage via oxidative stress, leading to inflammation, endoplasmic reticulum stress, airway remodeling, and various cell death modes (apoptosis, ferroptosis, pyroptosis). ROS can also interact with macromolecules, inducing DNA damage and epigenetic modifications, disrupting homeostasis. These effects have been studied extensively in vitro and confirmed in vivo. This review explores the oxidative potential of airborne particles and PM-induced ROS-mediated cellular damage observed in vitro, highlighting the link between oxidative stress, inflammation, and cell death modes described in the latest literature. The review also analyzes the effects of ROS on DNA damage, repair, carcinogenicity, and epigenetics. Additionally, the latest developments on the potential of antioxidants to prevent ROS's harmful effects are described, providing future perspectives on the topic.

Difference in the cellular response following THP-1 derived phagocytic monocyte cells exposure to commercial aluminum-based adjuvants and aluminum-containing vaccines

BACKGROUND

Aluminum-based adjuvants (ABAs) enhance the immune response following vaccine injection. Their mechanisms of action are not fully understood, and their bio-persistency have been described associated with long-term adverse effects.

METHODS

We evaluated and compared the cellular effects of the two main ABAs and whole vaccines on ATP production, ROS generation and cytokines production (IL-6 and IL-10), using THP-1 cells.

RESULTS

ABAs altered the cell energy metabolism by increasing ROS production after 24 h and reducing ATP production after 48 h. In addition, both ABAs and whole vaccines induced different kinetics of IL-6 production, whereas only ABAs induced IL-10 secretion.

CONCLUSION

This study showed clearly, for a first time, a difference in cellular response to the ABAs and whole vaccines which should be taken into consideration in future studies focusing on the effect of ABA in vaccines. Future studies on ABAs should also pay attention to mitochondrial function alterations following exposure to ABA-containing vaccines.

Fabrication of Poly(Lactic Acid)@TiO2 Electrospun Membrane Decorated with Metal-Organic Frameworks for Efficient Air Filtration and Bacteriostasis

The development of high-performance filtration materials is essential for the effective removal of airborne particles, and metal-organic frameworks (MOFs) anchored to organic polymer matrices are considered to be one of the most promising porous adsorbents for air pollutants. Nowadays, most air filters are generally based on synthetic fiber polymers derived from petroleum residues and have limited functionality, so the use of MOFs in combination with nanofiber air filters has received a lot of attention. Here, a conjugated electrostatic spinning method is demonstrated for the one-step preparation of poly(lactic acid) (PLA) nanofibrous membranes with a bimodal diameter distribution and the anchoring of Zeolitic Imidazolate Framework-8 (ZIF-8) by the introduction of TiO2 and in situ generation to construct favorable multiscale fibers and rough structures. The prepared PLA/TZ maintained a good PM2.5 capture efficiency of 99.97%, a filtration efficiency of 96.43% for PM0.3, and a pressure drop of 96.0 Pa, with the highest quality factor being 0.08449 Pa-1. Additionally, ZIF-8 was uniformly generated on the surface of PLA and TiO2 nanofibers, obtaining a roughened structure and a larger specific surface area. An enhanced filtration retention effect and electrostatic interactions, as well as active free radicals, can be generated for the deep inactivation of bacteria. Compared with the unmodified membrane, PLA/TZ prepared antibacterial characteristics induced by photocatalysis and Zn2+ release, with excellent bactericidal effects against S. aureus and E. coli. Overall, this work may provide a promising approach for the development of efficient biomass-based filtration materials with antimicrobial properties.

Heterogeneous Oxidation Products of Fine Particulate Isoprene Epoxydiol-Derived Methyltetrol Sulfates Increase Oxidative Stress and Inflammatory Gene Responses in Human Lung Cells

Hydroxyl radical (·OH)-initiated oxidation of isoprene, the most abundant nonmethane hydrocarbon in the atmosphere, is responsible for substantial amounts of secondary organic aerosol (SOA) within ambient fine particles. Fine particulate 2-methyltetrol sulfate diastereoisomers (2-MTSs) are abundant SOA products formed via acid-catalyzed multiphase chemistry of isoprene-derived epoxydiols with inorganic sulfate aerosols under low-nitric oxide conditions. We recently demonstrated that heterogeneous ·OH oxidation of particulate 2-MTSs leads to the particle-phase formation of multifunctional organosulfates (OSs). However, it remains uncertain if atmospheric chemical aging of particulate 2-MTSs induces toxic effects within human lung cells. We show that inhibitory concentration-50 (IC50) values decreased from exposure to fine particulate 2-MTSs that were heterogeneously aged for 0 to 22 days by ·OH, indicating increased particulate toxicity in BEAS-2B lung cells. Lung cells further exhibited concentration-dependent modulation of oxidative stress- and inflammatory-related gene expression. Principal component analysis was carried out on the chemical mixtures and revealed positive correlations between exposure to aged multifunctional OSs and altered expression of targeted genes. Exposure to particulate 2-MTSs alone was associated with an altered expression of antireactive oxygen species (ROS)-related genes (NQO-1, SOD-2, and CAT) indicative of a response to ROS in the cells. Increased aging of particulate 2-MTSs by ·OH exposure was associated with an increased expression of glutathione pathway-related genes (GCLM and GCLC) and an anti-inflammatory gene (IL-10).

Oxidative stress and inflammation induced by air pollution-derived PM2.5 persist in the lungs of mice after cessation of their sub-chronic exposure

More than 7 million early deaths/year are attributable to air pollution. Current health concerns are especially focused on air pollution-derived particulate matter (PM). Although oxidative stress-induced airway inflammation is one of the main adverse outcome pathways triggered by air pollution-derived PM, the persistence of both these underlying mechanisms, even after exposure cessation, remained poorly studied. In this study, A/JOlaHsd mice were also exposed acutely (24 h) or sub-chronically (4 weeks), with or without a recovery period (12 weeks), to two urban PM2.5 samples collected during contrasting seasons (i.e., autumn/winter, AW or spring/summer, SS). The distinct intrinsic oxidative potentials (OPs) of AW and SS PM2.5, as evaluated in acellular conditions, were closely related to their respective physicochemical characteristics and their respective ability to really generate ROS over-production in the mouse lungs. Despite the early activation of the nuclear factor erythroid 2-related factor 2 (Nrf2) cell signaling pathway by AW and, in a lesser degree, SS PM2.5, in the murine lungs after acute and sub-chronic exposures, the critical redox homeostasis was not restored, even after the exposure cessation. Accordingly, an inflammatory response was reported through the activation of the nuclear factor-kappa B (NF-κB) cell signaling pathway activation, the secretion of cytokines, and the recruitment of inflammatory cells, in the murine lungs after the acute and sub-chronic exposures to AW and, in a lesser extent, to SS PM2.5, which persisted after the recovery period. Taken together, these original results provided, for the first time, new relevant insights that air pollution-derived PM2.5, with relatively high intrinsic OPs, induced oxidative stress and inflammation, which persisted admittedly at a lower level in the lungs after the exposure cessation, thereby contributing to the occurrence of molecular and cellular adverse events leading to the development and/or exacerbation of future chronic inflammatory lung diseases and even cancers.

Guidelines for measuring and reporting particle removal efficiency in fibrous media

Adopting standardized and reliable methodologies to accurately measure particle removal efficiency when developing fibrous materials for controlling airborne contamination is crucial. Here, the authors recommend best practices for experimental assessments and reporting to ensure a reliable evaluation of new airborne particle filtration media and technologies.

Chemical Composition and Transgenerational Effects on Caenorhabditis elegans of Seasonal Fine Particulate Matter

While numerous studies have demonstrated the adverse effects of fine particulate matter (PM) on human health, little attention has been paid to its impact on offspring health. The multigenerational toxic effects on Caenorhabditis elegans (C. elegans) were investigated by acute exposure. PM_2.5 and PM₁ samples were collected and analysed for their chemical composition (inorganic ions, metals, OM, PAHs) in different seasons from April 2019 to January 2020 in Lin'an, China. A higher proportion of organic carbon components (34.3%, 35.9%) and PAHs (0.0144%, 0.0200%) occupied the PM_2.5 and PM₁ samples in winter, respectively. PM₁ in summer was enriched with some metal elements (2.7%). Exposure to fine PM caused developmental slowing and increased germ cell apoptosis, as well as inducing intestinal autofluorescence and reactive oxygen species (ROS) production. PM₁ caused stronger toxic effects than PM_2.5. The correlation between PM component and F0 generation toxicity index was analysed. Body length, germ cell apoptosis and intestinal autofluorescence were all highly correlated with Cu, As, Pb, OC and PAHs, most strongly with PAHs. The highest correlation coefficients between ROS and each component are SO₄^2- (R = 0.743), Cd (R = 0.816) and OC (R = 0.716). The results imply that OC, PAHs and some transition metals play an important role in the toxicity of fine PM to C. elegans, where the organic fraction may be the key toxicogenic component. The multigenerational studies show that PM toxicity can be passed from parent to offspring, and gradually returns to control levels in the F3-F4 generation with germ cell apoptosis being restored in the F4 generation. Therefore, the adverse effects of PM on reproductive damage are more profound.

Biochemical evidence of PM2.5 critical components for inducing myocardial fibrosis in vivo and in vitro

PM_2.5 constituents are tightly linked to the initiation of many cardiovascular diseases (CVDs). Little is known, however, about the events which critical components of PM_2.5 can induce the initiating events in CVDs. C57BL/6 female mice were exposed to PM_2.5 (3 mg/kg b.w.) from four different cities (Taiyuan, Beijing, Hangzhou, and Guangzhou) by oropharyngeal aspiration every other day. PM_2.5 from Taiyuan increased the diastolic function of the hearts and induced myocardial fibrosis with increased areas of interstitial fibrosis through the NOX4/TGF-β1/Smad 3/Col1a1 pathways. Pb, Cr, Mn, Zn, and most of the polycyclic aromatic hydrocarbons (PAHs) were positively associated with the related indicators of cardiac diastolic function and myocardial fibrosis by using Pearson correlation (R² = 0.9085-0.9897). To determine the critical components in PM_2.5 that can induce the occurrence of myocardial fibrosis, BEAS-2b cells were treated with one or more of five candidate components with/without Guangzhou PM_2.5, and then the conditioned medium of BEAS-2b was used to culture AC16 cells. The results showed that Zn + Pb + Mn + BaP with PM_2.5 from Guangzhou exposure significantly increased reactive oxygen species production of BEAS-2b cells and induced a dramatic increase of myocardial fiber-related gene expression (Col1a1 and TGF-β) in AC16 cells. It indicated that the different mass concentrations of Zn, Pb, Mn, and ΣPAHs in PM_2.5 might be the critical factors that modulated myocardial fibrosis induction by targeted. Our study provided a novel avenue for further elucidation of molecular mechanisms of PM_2.5 components-induced myocardial fibrosis.

Oxidative stress response in pulmonary cells exposed to different fractions of PM2.5-0.3 from urban, traffic and industrial sites

The aim of this work was to study the relationship between oxidative stress damages and particulate matter (PM) chemical composition, sources, and PM fractions. PM_2.5-0.3 (PM with equivalent aerodynamic diameter between 2.5 and 0.3 μm) were collected at urban, road traffic and industrial sites in the North of France, and were characterized for major and minor chemical species. Four different fractions (whole PM_2.5-0.3, organic, water-soluble and non-extractable matter) were considered for each of the PM_2.5-0.3 samples from the three sites. After exposure of BEAS-2B cells to the four different fractions, oxidative stress was studied in cells by quantifying reactive oxygen species (ROS) accumulation, oxidative damage to proteins (carbonylated proteins), membrane alteration (8-isoprostane) and DNA damages (8-OHdG). Whole PM_2.5-0.3 was capable of inducing ROS overproduction and caused damage to proteins at higher levels than other fractions. Stronger cell membrane and DNA damages were found associated with PM and organic fractions from the urban site. ROS overproduction was correlated with level of expression of carbonylated proteins, DNA damages and membrane alteration markers. The PM_2.5-0.3 collected under industrial influence appears to be the less linked to cell damages and ROS production in comparison with the other influences.

Processing Nomex Nanofibers by Ionic Solution Blow-Spinning for Efficient High-Temperature Exhausts Treatment

Hard-to-dissolve polymers provide next-generation alternatives for high-performance filter materials owing to their intrinsically high chemical stability, superior mechanical performance, and excellent high-temperature resistance. However, the mass production of hard-to-dissolve nanofibers still remains a critical challenge. A simple, scalable, and low-cost ionic solution blow-spinning method has herein been provided for the large-scale preparation of hard-to-dissolve Nomex polymeric nanofibers with an average diameter of nearly 100 nm. After rapidly dissolving Nomex microfibers in the lithium chloride/dimethylacetamide (LiCl/DMAc) solution system, the conductive solution can be stably and conductivity-independently processed into nanofibers. The method optimizes electrospinning and avoids spinnability degradation and potential safety hazards caused by high electrical conductivity. Owing to nanofibrous structure and high dipole moment, Nomex nanofibrous filters show a stable high filtration efficiency of 99.92% for PM_0.3 with a low areal density of 4.6 g m^-2, as well as a low-pressure drop of 189.47 Pa. Moreover, the flame-retardant filter can work at 250 °C and 280 °C for a long and short time without shrinking or burning, respectively, exhibiting a high filtration efficiency of 99.50% for PM_0.3-10.0. The outstanding properties and low cost enable the efficient capture of PM from various high-temperature exhausts, making Nomex nanofibrous membrane an even more ideal industrial-grade air filter than polypropylene, polytetrafluoroethylene, polyimide, and ceramic nanofibrous filters.

GRAPHICAL ABSTRACT

Hard-to-dissolve nanofibers provide alternatives for high-efficiency and low-resistant air filtration but are limited by the universality and economics of fabrication methods. A scalable and efficient ionic solution blow-spinning strategy has herein been proposed in preparing hard-to-dissolve nanofibrous filters.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s42765-022-00231-x.

Polluting characteristics, sources, cancer risk, and cellular toxicity of PAHs bound in atmospheric particulates sampled from an economic transformation demonstration area of Dongguan in the Pearl River Delta, China

The Songshan Lake Science and Technology Industrial Park is a national economic transition demonstration area, which centers at a traditional industrial region, in Dongguan, China. We were interested in the involved atmospheric particulates-bound PAHs regarding their sources, cancer risk, and related cellular toxicity for those in other areas under comparable conditions. In this study, the daily concentrations of TSP, PM₁₀, and PM_2.5 were averaged 127.95, 95.91, and 67.62 μg/m³, and the bound PAHs were averaged 1.31, 1.22, and 0.77 ng/m³ in summer and 12.72, 20.51 and 40.27 ng/m³ in winter, respectively. The dominant PAHs were those with 5-6 rings, and 4-6 rings in summer and winter, respectively. The incremental lifetime cancer risk (ILCR) (90th percentile probability) of total PAHs was above 1.00E-06 in each age group, particularly high in adolescents. Sensitivity analysis indicated that slope factor and body weight had greater impact than exposure duration and inhalation rate on the ILCR. Moreover, treatment of human bronchial epithelial BEAS-2B cells with mixed five indicative PAHs increased the formation of ROS, DNA damage (elevation in γ-H2AX), and protein levels of CAR, PXR, CYP1A1, 1A2, 1B1, while reduced the AhR protein, with the winter mixture more potent than summer. For the sources of PAHs, the stable carbon isotope ratio analysis and diagnostic ratios consistently pointed to petroleum and fossil fuel combustion as major sources. In conclusion, our findings suggest that particulates-bound PAHs deserve serious concerns for a cancer risk in such environment, and the development of new power sources for reducing fossil fuel combustion is highly encouraged.

A comprehensive understanding of ambient particulate matter and its components on the adverse health effects based from epidemiological and laboratory evidence

The impacts of air pollution on public health have become a great concern worldwide. Ambient particulate matter (PM) is a major air pollution that comprises a heterogeneous mixture of different particle sizes and chemical components. The chemical composition and physicochemical properties of PM change with space and time, which may cause different impairments. However, the mechanisms of the adverse effects of PM on various systems have not been fully elucidated and systematically integrated. The Adverse Outcome Pathway (AOP) framework was used to comprehensively illustrate the molecular mechanism of adverse effects of PM and its components, so as to clarify the causal mechanistic relationships of PM-triggered toxicity on various systems. The main conclusions and new insights of the correlation between public health and PM were discussed, especially at low concentrations, which points out the direction for further research in the future. With the deepening of the study on its toxicity mechanism, it was found that PM can still induce adverse health effects with low-dose exposure. And the recommended Air Quality Guideline level of PM_2.5 was adjusted to 5 μg/m³ by World Health Organization, which meant that deeper and more complex mechanisms needed to be explored. Traditionally, oxidative stress, inflammation, autophagy and apoptosis were considered the main mechanisms of harmful effects of PM. However, recent studies have identified several emerging mechanisms involved in the toxicity of PM, including pyroptosis, ferroptosis and epigenetic modifications. This review summarized the comprehensive evidence on the health effects of PM and the chemical components of it, as well as the combined toxicity of PM with other air pollutants. Based on the AOP Wiki and the mechanisms of PM-induced toxicity at different levels, we first constructed the PM-related AOP frameworks on various systems.

Physico-chemical properties of aluminum adjuvants in vaccines: Implications for toxicological evaluation

Aluminum salts have been used as adjuvants in human vaccines since 1932. The most used adjuvants are Al oxyhydroxide (AlOOH) and Al hydroxyphosphate (AlOHPO₄). Al adjuvants have different physico-chemical properties. The differences in these properties are not well documented and not considered by the Food and Drug Administration (FDA), though they can largely influence biological effects of the adjuvants which are particulate components. In this study, different physico-chemical properties including the shape, size and charge of particles have been evaluated under different conditions in three Al adjuvants containing-vaccines and two corresponding commercial adjuvants suspensions. The results showed that the two Al adjuvants have different shapes, sizes and charges but both form aggregates. In addition, a clear effect of dilution on the size of the aggregates was observed. Moreover, different sizes of Al particles were measured for both Al oxyhydroxide adjuvant alone or in the vaccine, at identical concentrations, displaying the impact of adsorbed proteins on the size of aggregates in the case of the vaccine. Taken together, this paper suggests the importance to evaluate, before any biological and especially toxicological impact study, the whole physico-chemical properties of Al particle without restricting to the sole evaluation of the injected concentration. Furthermore, any modification of these mentioned parameters during manipulation, before animal or cell exposure, should be considered. In a more global way, the fixed "safe dose" of Al adjuvants should be specific for each type of Al adjuvant independently or for a mix of the two compounds, due to their different properties.

Cytotoxicity and oxidative stress induced by atmospheric mono-nitrophenols in human lung cells

Nitrophenols (NPs) are hazardous pollutants found in various environmental matrices, including ambient fine particulate matter (PM_2.5), agricultural residues, rainwater, wildfires, and industrial wastes. This study showed for the first time the effect of three pure nitrophenols and their mixture on human lung cells to provide basic understanding of the NP influence on cell elements and processes. We identified NPs in ambient PM_2.5 and secondary organic aerosol (SOA) particles generated from the photooxidation of monocyclic aromatic hydrocarbons in the U.S. EPA smog chamber. We assessed the toxicity of identified NPs and their equimolar mixture in normal bronchial epithelial (BEAS-2B) and alveolar epithelial cancer (A549) lung cell lines. The inhibitory concentration-50 (IC₅₀) values were highest and lowest in BEAS-2B cells treated with 2-nitrophenol (2NP) and 4-nitrophenol (4NP), respectively, at 24 h of exposure. The lactate dehydrogenase (LDH) assay showed that 4NP, the most abundant NP we identified in PM_2.5, was the most cytotoxic NP examined in both cell lines. The annexin-V/fluorescein isothiocyanate (FITC) analysis showed that the populations of late apoptotic/necrotic BEAS-2B and A549 cells exposed to 3NP, 4NP, and NP equimolar mixture increased between 24 and 48 h. Cellular reactive oxygen species (ROS) buildup led to cellular death post exposure to 3NP, 4NP and the NP mixtures, while 2NP induced the lowest ROS buildup. An increased mitochondrial ROS signal following NP exposure occurred only in BEAS-2B cells. The tetramethylrhodamine, methyl ester, perchlorate (TMRM) assay showed that exposed cells exhibited collapse of the mitochondrial membrane potential. TMRM signals decreased significantly only in BEAS-2B cells, and most strongly with 4NP exposures. Our results suggest that acute atmospheric exposures to NPs may be toxic at high concentrations, but not at ambient PM_2.5 concentrations. Further chronic studies with NP and NP-containing PM_2.5 are warranted to assess their contribution to lung pathologies.

Diesel exhaust particulate emissions and in vitro toxicity from Euro 3 and Euro 6 vehicles

Incomplete combustion processes in diesel engines produce particulate matter (PM) that significantly contributes to air pollution. Currently, there remains a knowledge gap in relation to the physical and chemical characteristics and also the biological reactivity of the PM emitted from old- and new-generation diesel vehicles. In this study, the emissions from a Euro 3 diesel vehicle were compared to those from a Euro 6 car during the regeneration of a diesel particulate filter (DPF). Different driving cycles were used to collect two types of diesel exhaust particles (DEPs). The particle size distribution was monitored using an engine exhaust particle sizer spectrometer and an electrical low-pressure impactor. Although the Euro 6 vehicle emitted particulates only during DPF regeneration that primarily occurs for a few minutes at high speeds, such emissions are characterized by a higher number of ultrafine particles (<0.1 μm) compared to those from the Euro 3 diesel vehicle. The emitted particles possess different characteristics. For example, Euro 6 DEPs exhibit a lower PAH content than do Euro 3 samples; however, they are enriched in metals that were poorly detected or undetected in Euro 3 emissions. The biological effects of the two DEPs were investigated in human bronchial BEAS-2B cells exposed to 50 μg/mL of PM (corresponding to 5.2 μg/cm²), and the results revealed that Euro 3 DEPs activated the typical inflammatory and pro-carcinogenic pathways induced by combustion-derived particles, while Euro 6 DEPs were less effective in regard to activating such biological responses. Although further investigations are required, it is evident that the different in vitro effects elicited by Euro 3 and Euro 6 DEPs can be correlated with the variable chemical compositions (metals and PAHs) of the emitted particles that play a pivotal role in the inflammatory and carcinogenic potential of airborne PM.

Toxicity mechanism of acrolein on DNA damage and apoptosis in BEAS-2B cells: Insights from cell biology and molecular docking analyses

Acrolein is a hazardous air pollutant for humans and is responsible for many pulmonary diseases, but the underlying mechanisms have not been completely elucidated. This work is focused on the genotoxicity effects of human bronchial epithelial (BEAS-2B) cells induced by acrolein (20, 40, 80 μM). The molecular mechanism was investigated base on DNA damage and mitochondrial apoptosis pathways. The results showed that after exposure to acrolein, the cell viability, glutathione (GSH) of BEAS-2B cells were reduced. Reactive oxygen species (ROS) level significantly increased, accompanied by increased levels of DNA damage-related indicators 8-hydroxy-2 deoxyguanosine (8-OHdG), DNA content of comet tail (Tail DNA%), olive tail moment (OTM), and nucleus morphology. Cell arrested at the G2/M phase. Then, the DNA damage response (DDR) signaling pathway (Ataxia-telangiectasia-mutated (ATM) and Rad-3-related (ATR)/Chk1 and ATM/Chk2) and the consequent cell cycle checkpoints were activated. The expression of γ-H2AX was significantly increased, indicating that acrolein induced DNA double-strand breaks. Molecular docking assay showed that acrolein bound to DNA in a spontaneous process. Moreover, mitochondrial apoptosis pathway involved in apoptosis, mitochondrial membrane potential (MMP) and adenosine triphosphate (ATP) content of BEAS-2B cells were significantly reduced, and the apoptosis rate was significantly increased. The protein expression of Bax/Bcl-2 and Cleaved Caspase-3 were increased, and JNK signaling pathway was activated. All the results indicated that acrolein induced DNA damage, activated DDR and mitochondrial apoptosis pathways, which might be the pivotal factors to mediate cytotoxicity in BEAS-2B cells.

Toxicological impact of organic ultrafine particles (UFPs) in human bronchial epithelial BEAS-2B cells at air-liquid interface

Air pollution has significant health effects worldwide, and airborne particles play a significant role in these effects. Ultrafine particles (UFPs) have an aerodynamic diameter of 0.1 μm or less, can penetrate deep into the respiratory tree, and are more toxic due to their large specific surface area, which should adsorb organic compounds. The aim of this study is to show the toxicological effects of UFPs with high organic content at low dose on BEAS-2B cells through at air-liquid interface (ALI) exposure using a Vitrocell® technology and a miniCAST (Combustion Aerosol Standard) generator. In conjunction with this approach, chemical analysis of particles and gas phase was performed to evaluate the presence of polycyclic aromatic hydrocarbons (PAHs). Chemical analyses confirmed the presence of PAHs in UFPs. With this experimental setup, exposure of the BEAS-2B cells induced neither cytotoxicity nor mitochondrial dysfunction. However, an increase of oxidative stress was observed, as assessed through Nrf2, NQO1, HO-1, CuZnSOD, MnSOD, and Catalase gene expression, together with significant induction of genes related to xenobiotic metabolism CYP1A1 and CYP1B1. Negative regulation of inflammatory genes expression (IL-6 and IL-8) was present three hours after the exposition to the UFPs. Taken together, this experimental approach, using repeatable conditions, should help to clarify the mechanisms by which organic UFPs induce toxicological effects.

Metal enriched quasi-ultrafine particles from stainless steel gas metal arc welding induced genetic and epigenetic alterations in BEAS-2B cells

Recent evidence has supported welding fume (WF)-derived ultrafine particles (UFP) could be the driving force of their adverse health effects. However, UFP have not yet been extensively studied and are currently not included in present air quality standards/guidelines. Here, attention was focused on the underlying genetic and epigenetic mechanisms by which the quasi-UFP (Q-UFP, i.e., ≤ 0.25 μm) of the WF emitted by gas metal arc welding-stainless steel (GMAW-SS) exert their toxicity in human bronchial epithelial BEAS-2B cells. The Q-UFP under study showed a monomodal size distribution in number centered on 104.4 ± 52.3 nm and a zeta potential of -13.8 ± 0.3 mV. They were enriched in Fe > Cr > Mn > Si, and displayed a relatively high intrinsic oxidative potential. Dose-dependent activation of nuclear factor erythroid 2-related factor 2 and nuclear factor-kappa B signaling pathway, glutathione alteration, and DNA, protein and lipid oxidative damage were reported in BEAS-2B cells acutely (1.5 and 9 μg/cm², 24 h) or repeatedly (0.25 and 1.5 μg/cm², 3 × 24 h) exposed to Q-UFP (p < 0.05). Alterations of the Histone H3 acetylation were reported for any exposure (p < 0.05). Differentially regulated miRNA and mRNA indicated the activation of some critical cell signaling pathways related to oxidative stress, inflammation, and cell cycle deregulation towards apoptosis. Taken together, these results highlighted the urgent need to better evaluate the respective toxicity of the different metals and to include the Q-UFP fraction of WF in current air quality standards/guidelines relevant to the occupational settings.

Farnesol-Loaded Liposomes Protect the Epidermis and Dermis from PM2.5-Induced Cutaneous Injury

Particulate matter with aerodynamic diameter ≤2.5 μm (PM2.5) increases oxidative stress through free radical generation and incomplete volatilization. In addition to affecting the respiratory system, PM2.5 causes aging- and inflammation-related damage to skin. Farnesol (Farn), a natural benzyl semiterpene, possesses anti-inflammatory, antioxidative, and antibacterial properties. However, because of its poor water solubility and cytotoxicity at high concentrations, the biomedical applications of Farn have been limited. This study examined the deleterious effects of PM2.5 on the epidermis and dermis. In addition, Farn-encapsulated liposomes (Lipo-Farn) and gelatin/HA/xanthan gel containing Lipo-Farn were prepared and applied in vivo to repair and alleviate PM2.5-induced damage and inflammation in skin. The prepared Lipo-Farn was 342 ± 90 nm in diameter with an encapsulation rate of 69%; the encapsulation significantly reduced the cytotoxicity of Farn. Lipo-Farn exhibited a slow-release rate of 35% after 192 h of incubation. The half-maximal inhibitory concentration of PM2.5 was approximately 850 μg/mL, and ≥400 μg/mL PM2.5 significantly increased IL-6 production in skin fibroblasts. Severe impairment in the epidermis and hair follicles and moderate impairment in the dermis were found in the groups treated with post-PM2.5 and continuous subcutaneous injection of PM2.5. Acute and chronic inflammation was observed in the skin in both experimental categories in vivo. Treatment with 4 mM Lipo-Farn largely repaired PM2.5-induced injury in the epidermis and dermis, restored injured hair follicles, and alleviated acute and chronic inflammation induced by PM2.5 in rat skin. In addition, treatment with 4 mM pure Farn and 2 mM Lipo-Farn exerted moderate reparative and anti-inflammatory effects on impaired skin. The findings of the current study indicate the therapeutic and protective effects of Lipo-Farn against various injuries caused by PM2.5 in the pilosebaceous units, epidermis, and dermis of skin.

Relationship between Cytotoxicity and Surface Oxidation of Artificial Black Carbon

The lacking of laboratory black carbon (BC) samples have long challenged the corresponding toxicological research; furthermore, the toxicity tests of engineered carbon nanoparticles were unable to reflect atmospheric BC. As a simplified approach, we have synthesized artificial BC (aBC) for the purpose of representing atmospheric BC. Surface chemical properties of aBC were controlled by thermal treatment, without transforming its physical characteristics; thus, we were able to examine the toxicological effects on A549 human lung cells arising from aBC with varying oxidation surface properties. X-ray photoelectron spectroscopy, as well as Raman and Fourier transform infrared spectroscopy, verified the presence of increased amounts of oxygenated functional groups on the surface of thermally-treated aBC, indicating aBC oxidization at elevated temperatures; aBC with increased oxygen functional group content displayed increased toxicity to A549 cells, specifically by decreasing cell viability to 45% and elevating reactive oxygen species levels up to 294% for samples treated at 800 °C.

Assessment of the PM2.5 oxidative potential in a coastal industrial city in Northern France: Relationships with chemical composition, local emissions and long range sources

The objective of this work was to relate PM_2.5 Oxidative Potential (OP) data to PM composition and PM local and distant source contributions. PM_2.5 collected in Dunkerque, a coastal industrial city in North of France, was extensively characterized for major and minor chemical species. PM_2.5 filters were extracted using a synthetic pulmonary fluid to achieve OP estimation based on Ascorbic Acid (AA) and dithiothreitol (DTT) depletion assays. In order to evidence relationships between OP values, chemical composition and local and distant source contributions, correlation coefficient, Principal Component Analysis (PCA), concentration roses, polar plots and concentration weighted trajectories were used. Heterogeneous conclusions were drawn using the three first methods as the bivariate polar plots lead to dismiss some of the correlations evidenced using correlation coefficient and PCA. Both AA and DTT tests appeared complementary as they were not sensitive to the same species/source contribution. The bivariate polar plot representation of OP values versus wind direction and wind speed revealed that PM_2.5 concentration and combustion sources were linked to OP-AA, whereas emissions from integrated steelworks, electric steelworks, heavy fuel oil combustion and traffic non-exhaust significantly contribute to OP-DTT. Sea-salts, aged sea-salts, crustal, secondary sulfates and secondary nitrates sources were not found to contribute to OP values. Constant weighted trajectories evidenced several source regions responsible for high OP values with Belgium, Germany, Netherlands and France at the leader position. Contribution of inland regions appeared possibly related to the biomass and traffic related combustion while heavy fuel oil combustion could also be involved in the contribution of marine and coastal areas.