Oxidative stress indices induced by industrial and urban PM2.5-bound metals in A549 cells

Review of in vitro studies evaluating respiratory toxicity of aerosols: impact of cell types, chemical composition, and atmospheric processing

In recent decades, several cell-based and acellular methods have been developed to evaluate ambient particulate matter (PM) toxicity. Although cell-based methods provide a more comprehensive assessment of PM toxicity, their results are difficult to comprehend due to the diversity in cellular endpoints, cell types, and assays and the interference of PM chemical components with some of the assays' techniques. In this review, we attempt to clarify some of these issues. We first discuss the morphological and immunological differences among various macrophage and epithelial cells, belonging to the respiratory systems of human and murine species, used in the in vitro studies evaluating PM toxicity. Then, we review the current state of knowledge on the role of different PM chemical components and the relevance of atmospheric processing and aging of aerosols in the respiratory toxicity of PM. Our review demonstrates the need to adopt more physiologically relevant cellular models such as epithelial (or endothelial) cells instead of macrophages for oxidative stress measurement. We suggest limiting macrophages for investigating other cellular responses (e.g., phagocytosis, inflammation, and DNA damage). Unlike monocultures (of macrophages and epithelial cells), which are generally used to study the direct effects of PM on a given cell type, the use of co-culture systems should be encouraged to investigate a more comprehensive effect of PM in the presence of other cells. Our review has identified two major groups of toxic PM chemical species from the existing literature, i.e., metals (Fe, Cu, Mn, Cr, Ni, and Zn) and organic compounds (PAHs, ketones, aliphatic and chlorinated hydrocarbons, and quinones). However, the relative toxicities of these species are still a matter of debate. Finally, the results of the existing studies investigating the effect of aging on PM toxicity are ambiguous, with varying results due to different cell types, different aging conditions, and the presence/absence of specific oxidants. More systematic studies are necessary to understand the role of different SOA precursors, interactions between different PM components, and aging conditions in the overall toxicity of PM. We anticipate that our review will guide future investigations by helping researchers choose appropriate cell models, resulting in a more meaningful interpretation of cell-based assays and thus ultimately leading to a better understanding of the health effects of PM exposure.

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.

Phosphocholine-induced energy source shift alleviates mitochondrial dysfunction in lung cells caused by geospecific PM2.5 components

Fine particulate matter (PM2.5) is globally recognized for its adverse implications on human health. Yet, remain limited the individual contribution of particular PM2.5 components to its toxicity, especially considering regional disparities. Moreover, prevention solutions for PM2.5-associated health effects are scarce. In the present study, we comprehensively characterized and compared the primary PM2.5 constituents and their altered metabolites from two locations: Taiyuan and Guangzhou. Analysis of year-long PM2.5 samples revealed 84 major components, encompassing organic carbon, elemental carbon, ions, metals, and organic chemicals. PM2.5 from Taiyuan exhibited higher contamination, associated health risks, dithiothreitol activity, and cytotoxicities than Guangzhou's counterpart. Applying metabolomics, BEAS-2B lung cells exposed to PM2.5 from both cities were screened for significant alterations. A correlation analysis revealed the metabolites altered by PM2.5 and the critical toxic PM2.5 components in both regions. Among the PM2.5-down-regulated metabolites, phosphocholine emerged as a promising intervention for PM2.5 cytotoxicities. Its supplementation effectively attenuated PM2.5-induced energy metabolism disorder and cell death via activating fatty acid oxidation and inhibiting Phospho1 expression. The highlighted toxic chemicals displayed combined toxicities, potentially counteracted by phosphocholine. Our study offered a promising functional metabolite to alleviate PM2.5-induced cellular disorder and provided insights into the geo-based variability in toxic PM2.5 components.

Effect of PM2.5 exposure on adhesion molecules and systemic nitric oxide in healthy adults: The role of metals, PAHs, and oxidative potential

Since there is limited evidence on the impact of PM2.5 content on cardiovascular biomarkers, we conducted a cross-sectional study on 89 healthy adults from October 12 to November 21, 2021. We measured daily PM2.5 in two distinct regions during different time windows: a high-traffic urban area and an industrial suburb. The concentrations of metals, PAHs, and oxidative potential (OP) were determined using ICP-MS, GC-MS, and dithiothreitol (DTT), respectively. Systemic biomarkers, including NO, sICAM-1, sVCAM-1, MDA, and CRP, were quantified in each subject simultaneously. A generalized linear model was used to examine the association between PM2.5 toxicity and each health endpoint. Our findings indicated that daily PM2.5 concentrations exceeded the WHO-recommended level by approximately sevenfold. We found that PM2.5 exposure was associated with adverse cardiovascular outcomes. Moreover, exposure to PM2.5 mass, total PAHs, and certain trace metals (Ni, Fe, V, As, and Pb) resulted in a decline in serum NO levels. At lag 3, exposure to PM2.5 mass resulted in a significant decrease in NO levels [1.32% (95% CI: -2.27, -0.12)] and total PAHs [2.05% (95% CI: -3.93, -0.12)]. In contrast, OP exhibited a mild correlation with NO level increases. Positive associations were observed between PM2.5 and its chemical constituents (PAHs, As, Cu, OP) and adhesion molecules at different lag times. An increase of 0.16 ppb in PAH concentrations at an interquartile range was associated with a 4.74% decline (95% CI, -7.80, -0.55) in the sVCAM-1 level. However, our study did not reveal any significant trend between pollutants and other biomarkers (sICAM-1, MDA, and CRP). Consequently, our findings suggest that different PM2.5 chemical compositions exhibit diverse behavior in biological responses.

Characterization of risks and pathogenesis of respiratory diseases caused by rural atmospheric PM2.5

Forty-six percent of the world's population resides in rural areas, the majority of whom belong to vulnerable groups. They mainly use cheap solid fuels for cooking and heating, which release a large amount of PM2.5 and cause adverse effects to human health. PM2.5 exhibits urban-rural differences in its health risk to the respiratory system. However, the majority of research on this issue has focused on respiratory diseases induced by atmospheric PM2.5 in urban areas, while rural areas have been ignored for a long time, especially the pathogenesis of respiratory diseases. This is not helpful for promoting environmental equity to aid vulnerable groups under PM2.5 pollution. Thus, this study focuses on rural atmospheric PM2.5 in terms of its chemical components, toxicological effects, respiratory disease types, and pathogenesis, represented by PM2.5 from rural areas in the Sichuan Basin, China (Rural SC-PM2.5). In this study, organic carbon is the most significant component of Rural SC-PM2.5. Rural SC-PM2.5 significantly induces cytotoxicity, oxidative stress, and inflammatory response. Based on multiomics, bioinformatics, and molecular biology, Rural SC-PM2.5 inhibits ribonucleotide reductase regulatory subunit M2 (RRM2) to disrupt the cell cycle, impede DNA replication, and ultimately inhibit lung cell proliferation. Furthermore, this study supplements and supports the epidemic investigation. Through an analysis of the transcriptome and human disease database, it is found that Rural SC-PM2.5 may mainly involve pulmonary hypertension, sarcoidosis, and interstitial lung diseases; in particular, congenital diseases may be ignored by epidemiological surveys in rural areas, including tracheoesophageal fistula, submucous cleft of the hard palate, and congenital hypoplasia of the lung. This study contributes to a greater scientific understanding of the health risks posed by rural PM2.5, elucidates the pathogenesis of respiratory diseases, clarifies the types of respiratory diseases, and promotes environmental equity.

Contribution of water-soluble extracts to the oxidative and inflammatory effects of atmospheric aerosols: A critical review

Exposure to atmospheric particulate matter (PM) has been associated with heightened risks of lung cancer, cardiovascular and respiratory diseases. PM exposure also affects the immune system, leading to an increased susceptibility to infections, exacerbating pre-existent inflammatory and allergic lung diseases. Atmospheric PM can primarily impact human health through the generation of reactive oxygen species (ROS) that subsequently induce or exacerbate inflammation. These cytotoxic effects have been related with PM concentration, and its chemical constituents, including metals, solvent extractable organics (e.g., polycyclic aromatic hydrocarbons), and water-soluble ions. Although not receiving much attention, the fine aerosol water-soluble organic matter (WSOM) can account for a substantial portion of the overall fine PM mass and has been shown to present strong oxidative and immunomodulatory effects. Thus, the objective of this review is to provide a comprehensive analysis of the role of the water-soluble fraction of PM, with a specific focus on the contribution of the WSOM component to the cytotoxic properties of atmospheric PM. The chemical properties of the water-soluble PM fraction are briefly discussed, while emphasis is put on how PM size, composition, and temporal variations (e.g., seasonality) can impact the pro-oxidative activity, the modulation of inflammatory response, and the cytotoxicity of the water-soluble PM extracts.

Molecular insights into microbial transformation of bioaerosol-derived dissolved organic matter discharged from wastewater treatment plant

Wastewater treatment plants (WWTP) are important sources of aerosol-derived dissolved organic matter (ADOM) which may threaten human health via the respiratory system. In this study, aerosols were sampled from a typical WWTP to explore the chemical molecular diversity, molecular ecological network, and potential toxicities of the ADOM in the aerosols. The high fluorescence index (>1.9) and biological index (0.66-1.17) indicated the strong autogenous microbial source characteristics of the ADOM in the WWTP. DOM and microbes in the wastewater were aerosolized due to strong agitation and bubbling in the treatment processes, and contributed to 74 % and 75 %, respectively, of the ADOM and microbes in the aerosols. The ADOM was mainly composed of CHO and CHOS accounting for 35 % and 29 % of the total number of molecules, respectively, with lignin-like (69 %) as the major constituent. 49 % of the ADOM transformations were thermodynamically limited, and intragroup transformations were easier than intergroup transformations. Bacteria in the aerosols involved in ADOM transformations exhibited both cooperative and divergent behaviors and tended to transform carbohydrate-like and amino sugar/protein-like into recalcitrant lignin-like. The microbial compositions were affected by atmosphere temperature and humidity indirectly by modulating the properties of ADOM. Tannin-like, lignin-like, and unsaturated hydrocarbon-like molecules in the ADOM were primary toxicity contributors, facilitating the expression of inflammatory factors IL-β (2.2-5.4 folds), TNF-α (3.5-7.0 folds), and IL-6 (3.5-11.2 folds), respectively.

The Cytotoxic Effects of Fine Particulate Matter (PM2.5) from Different Sources at the Air-Liquid Interface Exposure on A549 Cells

The health of humans has been negatively impacted by PM2.5 exposure, but the chemical composition and toxicity of PM2.5 might vary depending on its source. To investigate the toxic effects of particulate matter from different sources on lung epithelial cells (A549), PM2.5 samples were collected from residential, industrial, and transportation areas in Nanjing, China. The chemical composition of PM2.5 was analyzed, and toxicological experiments were conducted. The A549 cells were exposed using an air-liquid interface (ALI) exposure system, and the cytotoxic indicators of the cells were detected. The research results indicated that acute exposure to different sources of particulate matter at the air-liquid interface caused damage to the cells, induced the production of ROS, caused apoptosis, inflammatory damage, and DNA damage, with a dose-effect relationship. The content of heavy metals and PAHs in PM2.5 from the traffic source was relatively high, and the toxic effect of the traffic-source samples on the cells was higher than that of the industrial- and residential-source samples. The cytotoxicity of particulate matter was mostly associated with water-soluble ions, carbon components, heavy metals, PAHs, and endotoxin, based on the analysis of the Pearson correlation. Oxidative stress played an important role in PM2.5-induced biological toxicity.

Oxidative stress and activation of H2A.X in lung alveolar epithelial cells (A549) by nanoparticulate carbon black

Fine airborne particulate matter enter the respiratory system, induce oxidative stress and initiate DNA damage. The aim of our study was the estimation of cell viability, oxidative stress, DNA damage, cell cycle alterations and activation of histone H2A.X. Experiments were done on lung alveolar epithelial (A549) cells grown for 24 h with 200 µg mL-1 coarse carbon black (CB), or nanoparticulate CB (NPCB). Neither CB nor glutathione depletion altered cell viability, growth rates, and H2A.X expression while NPCB decreased cell viability, increased oxidative stress and DNA damage. The cell cycle was blocked at G0/G1. NPCB but not CB increased expression and activation of H2A.X at mRNA and protein levels. Co-expression data point to γH2A.X as a major NPCB target, and show the interdependence of γH2A.X and oxidative stress. We conclude, that NPCB increases γ-H2A.X expression in A549 cells at mRNA and protein levels and stimulates H2A.X (Ser139), phosphorylation, associated with oxidative stress, the DNA damage response and G1 cell cycle arrest.