Chemical Characterization of Two Seasonal PM2.5 Samples in Nanjing and Its Toxicological Properties in Three Human Cell Lines

Understanding PFAS toxicity through cell culture metabolomics: Current applications and future perspectives

Per- and polyfluoroalkyl substances (PFAS), ubiquitous environmental contaminants, pose significant challenges to ecosystems and human health. While cell cultures have emerged as new approach methodologies (NAMs) in ecotoxicity research, metabolomics is an emerging technique used to characterize the small-molecule metabolites present in cells and to understand their role in various biological processes. Integration of metabolomics with cell cultures, known as cell culture metabolomics, provides a novel and robust tool to unravel the complex molecular responses induced by PFAS exposure. In vitro testing also reduces reliance on animal testing, aligning with ethical and regulatory imperatives. The current review summarizes key findings from recent studies utilizing cell culture metabolomics to investigate PFAS toxicity, highlighting alterations in metabolic pathways, biomarker identification, and the potential linkages between metabolic perturbations. Additionally, the paper discusses different types of cell cultures and metabolomics methods used for studies of environmental contaminants and particularly PFAS. Future perspectives on the combination of metabolomics with other advanced technologies, such as single-cell metabolomics (SCM), imaging mass spectrometry (IMS), extracellular flux analysis (EFA), and multi-omics are also explored, which offers a holistic understanding of environmental contaminants. The synthesis of current knowledge and identification of research gaps provide a foundation for future investigations that aim to elucidate the complexities of PFAS-induced cellular responses and contribute to the development of effective strategies for mitigating their adverse effects on human health.

Application of three-dimensional Raman imaging to determination of the relationship between cellular localization of diesel exhaust particles and the toxicity

A diesel exhaust particle (DEP) is a type of particulate matter that is easily produced from combustion in a diesel power engine. It has been reported that DEPs can cause short- and long-term health problems. This is because DEPs are complex mixtures that are highly inhalable through the airways due to their small particle size. However, the relationship between intracellular localization of DEPs after their deposition in the lungs and the subsequent biological responses remains to be clarified. This is due to difficulties in distinguishing particles that are inside the cells from those that are outside. In this study, A549 human lung epithelial cells were exposed to DEPs at concentrations of 0, 25, 75, or 200 µg/mL for different periods, after that particles in the A549 cells were analyzed by three-dimensional (3D) images obtained from a Raman microscope. The cytotoxic effects of DEPs on the A549 cells were investigated by measuring cell viability, the levels of intracellular reactive oxygen species (ROS) and cell death. The Raman microscopy revealed that the particles invaded the A549 cells, and at a concentration of 200 µg/mL, they markedly decreased cell viability, increased intracellular ROS production, triggered late apoptosis/necrosis and induced nuclear damage. These results suggest that intracellular DEPs exposed at a high concentration may be highly toxic and can impair the viability of A549 cells. Furthermore, the 3D images from the Raman microscopy can be used to evaluate intracellular particle dynamics.

Potential cytotoxicity of PM2.5-bound PAHs and toxic metals collected from areas with different traffic densities on human lung epithelial cells (A549)

Laboratory and epidemiological researches have indicated that ambient air particulate matter have a plays critical role in causing diseases. The current research evaluated the chemical attributes of PM2.5 in the ambient air of the cities of Karaj and Fardis and determined its toxicological effects on human lung epithelial cells (A549). In the study city, 16 points were selected from the two high-traffic and low-traffic points for sampling. A sampling of ambient air was carried out in spring, summer, autumn, and winter 2018-19. Air sampling was performed for 24 h according to the EPA-TO/13A guidelines. To analyze of toxic metals and polycyclic aromatic hydrocarbons (PAHs), ICP-OES and GC-MS were used, respectively, and for cell toxicity analysis, an ELISA reader was used. Then from SPSS, Excel and R software were used for statistical analysis. The results of the current study indicated that the concentration of PAHs carcinogenic in the autumn season in high-traffic stations was the highest and equal to 9.3 ng/m3, and in the spring season in the low-traffic stations, it was the lowest and equal to 5.82 ng/m3. In general, during the period of study, Heavy metals including Zn, Fe, Pb, Cu, and Al had the highest concentration compared to other metals. However, Hg, Cr, As, Pb, Cu, Cd, and Zn were higher concentration in the winter and autumn seasons than in the spring and summer seasons. Cell viability measurements by using MTT showed that low-traffic and high-traffic stations had the highest toxicity in autumn season compared to other seasons. (p < 0.05). In general, high-traffic stations had the highest toxicity than low-traffic stations. The general conclusion of the present study was that PM2.5-bound PAHs and toxic metals, due to their high concentration, were toxic pollutants in air for residents of Karaj and Fardis. Also, the high concentration of PM2.5 caused the mitochondrial activity of A549 cells to stop and this stop was more significant in cold seasons and high-traffic areas.

Variations in Nocturnal Residual Layer Height and Its Effects on Surface PM2.5 over Wuhan, China

Large amounts of aerosols remain in the residual layer (RL) after sunset, which may be the source of the next day’s pollutants. However, the characteristics of the nocturnal residual layer height (RLH) and its effect on urban environment pollution are unknown. In this study, the characteristics of the RLH and its effect on fine particles with diameters <2.5 μm (PM2.5) were investigated using lidar data from January 2017 to December 2019. The results show that the RLH is highest in summer (1.55 ± 0.55 km), followed by spring (1.40 ± 0.58 km) and autumn (1.26 ± 0.47 km), and is lowest in winter (1.11 ± 0.44 km). The effect of surface meteorological factors on the RLH were also studied. The correlation coefficients (R) between the RLH and the temperature, relative humidity, wind speed, and pressure were 0.38, −0.18, 0.15, and −0.36, respectively. The results indicate that the surface meteorological parameters exhibit a slight correlation with the RLH, but the high relative humidity was accompanied by a low RLH and high PM2.5 concentrations. Finally, the influence of the RLH on PM2.5 was discussed under different aerosol-loading periods. The aerosol optical depth (AOD) was employed to represent the total amount of pollutants. The results show that the RLH has an effect on PM2.5 when the AOD is small but has almost no effect on PM2.5 when the AOD is high. In addition, the R between the nighttime mean RLH and the following daytime PM2.5 at low AOD is −0.49, suggesting that the RLH may affect the following daytime surface PM2.5. The results of this study have a guiding significance for understanding the interaction between aerosols and the boundary layer.

Potential cytotoxicity of trace elements and polycyclic aromatic hydrocarbons bounded to particulate matter: a review on in vitro studies on human lung epithelial cells

A large number of studies have been conducted for clarifying toxicological mechanisms of particulate matter (PM) aimed to investigate the physicochemical properties of PM and providing biological endpoints such as inflammation, perturbation of cell cycle, oxidative stress, or DNA damage. However, although several studies have presented some effects, there is still no consensus on the determinants of biological responses. This review attempts to summarize all past research conducted in recent years on the physicochemical properties of environmental PM in different places and the relationship between different PM components and PM potential cytotoxicity on the human lung epithelial cells. Among 447 papers with our initial principles, a total of 50 articles were selected from 1986 to April 2020 based on the chosen criteria for review. According to the results of selected studies, it is obvious that cytotoxicity in human lung epithelial cells is created both directly or indirectly by transition metals (such as Cu, Cr, Fe, Zn), polycyclic aromatic hydrocarbons (PAH), and ions that formed on the surface of particles. In the selected studies, the findings of the correlation analysis indicate that there is a significant relationship between cell viability reduction and secretion of inflammatory mediators. As a result, it seems that the observed biological responses are related to the composition and the physicochemical properties of the PMs. Therefore, the physicochemical properties of PM should be considered when explaining PM cytotoxicity, and long-term research data will lead to improved strategies to reduce air pollution.

Comparison of indoor and outdoor oxidative potential of PM2.5: pollution levels, temporal patterns, and key constituents

Oxidative potential (OP) of PM_2.5 is an emerging health indicator representing its ability to induce oxidative stress and cause adverse health effects. We examined pollution levels, temporal variations, and key constituents of PM_2.5 OP by DTT assay in both indoor and outdoor environments in Nanjing, China, for over one year. Outdoor OP_M (mass-normalized OP characterizes toxicity) and OP_V (volume-based OP characterizes overall oxidative burden) in Nanjing were at a medium level compared to results reported for twenty-seven cities. Although PM_2.5 mass concentration consistently decreased during outdoor-to-indoor transport, OP_M varied by a factor of up to 2 in either direction, indicating a change of PM_2.5's ability to disrupt oxidative-reductive balance. Temporally, both outdoor and indoor OP_M exhibited a significant seasonality pattern (P < 0.01) as autumn > summer > spring > winter. Outdoor and indoor daytime-nighttime OP_V and OP_M are fluctuating within two-fold range. In addition, the change in water-soluble Fe had the highest correlation coefficient (P < 0.05) with ΔOP_M (ΔOP_M = OP_{M, in}-OP_{M, out}) among constituents measured here. Our results suggest that development of mitigation strategies take indoor PM_2.5's OP into account, instead of outdoors only, since they differ.

Chemical Characterization of Seasonal PM2.5 Samples and Their Cytotoxicity in Human Lung Epithelial Cells (A549)

In order to study the toxicity of fine particulate matter (PM_2.5) sourced from different seasons on human health, we collected PM_2.5 samples quarterly from March 2016 to February 2017 in Nanjing, China. The component analysis results showed that high proportions of water-soluble organic carbon (WSOC), SO₄²⁻, Ca²⁺ and Mg²⁺ were found in the summer samples, while high proportions of NO₃⁻, NH₄⁺ and heavy metals were observed in the spring and winter samples. Then human lung epithelial cells (A549) were exposed to the PM_2.5 samples. The toxicological results indicated that reactive oxygen species (ROS) production in the spring and winter samples was higher than that in the summer and fall samples, which was related to the contribution of some heavy metals and inorganic ions (e.g., Pb and NO₃⁻). However, the apoptosis rates of the cells showed the opposite seasonal changes as what the ROS did, which might be caused by the higher WSOC content in the summer. In addition, regression analysis also showed the importance of the PM_2.5 components in ROS production and apoptosis. Particularly, Zn had the strongest correlation with ROS production (R = 0.863) and cell apoptosis (R = 0.675); thus, the specific toxicity of Zn in PM_2.5 deserves further investigation. Our results could be beneficial for assessing the health risks and controlling the toxic components of PM_2.5 in Nanjing.

The neuro-immune interaction in airway inflammation through TRPA1 expression in CD4+ T cells of asthmatic mice

Asthma is an inflammatory disorder of the airways dominated by a Th2-type pattern. Recently, an emerging interest arises whether transient receptor potential ankyrin 1 (TRPA1) plays a potential role in the adaptive immune response. In this study, the role of TRPA1 in the development and exacerbation of asthma was explored. The classic OVA-induced asthma and OVA plus PM2.5-induced exacerbated asthma model were used. The CD4+ T cells were sorted from spleen in asthmatic and exacerbated asthmatic mice. In the BALB/c mice treated with OVA, the increased phenotype of asthma was obtained, accompanied by the high expression of TRPA1 in lung tissue and levels of IL-4, IL-13, NGF, PGD₂ in BAL. In contrast, genetic deletion or pharmacological inhibition of TRPA1 alleviated the phenotype of asthma. Similarly, in wild type (WT) C57BL/6 mice treated with OVA, the high expression of TRPA1 in lung tissues was obtained, and the levels of IL-4, IL-13, NGF, PGD₂ in BAL remarkably increased when compared with those in the TRPA1 deleted mice. Furthermore, high expression of TRPA1 was detected in CD4+ T cells of OVA-treated WT C57BL/6 mice. Additional detection in the asthmatic mice exacerbated by OVA plus PM2.5 also showed high TRPA1 expression in lung tissue and CD4+ T cells. All evidence confirmed that TRPA1 is essential for the development and exacerbation of asthma. More importantly, the expression of TRPA1 in CD4+ T cells of different asthmatic mice suggested that it might be involved in neuro-immune interactions in airway inflammation of asthmatic mice.