Acute exposure to seasonal PM2.5 induces toxicological responses in A549 cells cultured at the air-liquid interface mediated by oxidative stress and endoplasmic reticulum stress.

Atmospheric fine particulate matter (PM2.5) enters the human body through respiration and poses a threat to human health. This is not only dependent on its mass concentration in the atmosphere, but also related to seasonal variations in its chemical components, which makes it important to study the cytotoxicity of PM2.5 in different seasons. Traditional immersion exposure cannot simulate the living environment of human epithelial cells in the human body, making this method unsuitable for evaluating the inhalation toxicity of PM2.5. In this study, a novel air-liquid interface (ALI) particulate matter exposure device (VITROCELL Cloud 12 system) was used to evaluate the toxic effects and potential mechanisms of human lung epithelial cells (A549) after exposure to seasonal PM2.5. PM2.5 samples from four seasons were collected and analyzed for chemical components. After 6 h of exposure to seasonal PM2.5, winter PM2.5 exhibited the highest cytotoxicity among most toxicity indicators, especially apoptosis rate, reactive oxygen species (ROS), inflammatory responses and DNA damage (γ-H2AX). The effect of autumn PM2.5 on apoptosis rate was significantly higher than that in spring, and there was no significant difference in other toxicity indicators between spring and autumn. The cytotoxicity of summer PM2.5 was the lowest among the four seasons. It should be noted that even exposure to low doses of summer PM2.5 leads to significant DNA damage in A459 cells. Correlation analysis results showed that water-soluble ions, metallic elements, and polycyclic aromatic hydrocarbons (PAHs) were associated with most toxicological endpoints. Inhibitors of oxidative stress and endoplasmic reticulum (ER) stress significantly inhibited cellular damage, indicating that PM2.5-induced cytotoxicity may be related to the generation of ROS and ER stress. In addition, PM2.5 can induce ER stress through oxidative stress, which ultimately leads to apoptosis.

Chemical Characteristics and Cytotoxicity to GC-2spd(ts) Cells of PM2.5 in Nanjing Jiangbei New Area from 2015 to 2019.

PM2.5 is an air pollutant with complex components. After entering the body through respiration, PM2.5 can not only cause respiratory diseases, but also break through the blood-testis barrier and influence the reproductive system. PM2.5 with different components may result in different toxic effects. In the first five years of Nanjing Jiangbei New Area, industrial transformation would change the concentration and chemical fraction of PM2.5 in the local environment to a certain extent. In this study, PM2.5 collected in Nanjing Jiangbei New Area every autumn and winter from 2015 to 2019 was analyzed. PM2.5 concentration generally decreased year by year. The large proportion of secondary inorganic ions indicated the presence of secondary pollution at the sampling site. PM2.5 was mainly emitted from fossil fuel combustion and vehicle exhaust. The cytotoxicity of PM2.5 samples was evaluated by PM2.5 exposure to mouse spermatocytes (GC-2spd(ts) cells). Cell viability was relatively low in 2016 and 2018, and relatively high in 2017 and 2019. Reactive oxygen species levels and DNA damage levels followed similar trends, with an overall annual decrease. The cytotoxicity of PM2.5 on GC-2spd(ts) cells was significantly correlated with water-soluble ions, water-soluble organic carbon, heavy metals and polycyclic aromatic hydrocarbons (p < 0.01). According to principal component analysis and multiple linear regression, fossil fuel combustion, secondary transformation of pollutants and construction dust were identified as the major contributors to cytotoxic effects, contributing more than 50%.

Ecotoxicity induced by total, water soluble and insoluble components of atmospheric fine particulate matter exposure in Caenorhabditis elegans.

Although PM2.5 could cause toxicity in environmental organisms, the toxicity difference of PM2.5 under different solubilities is still poorly understood. To acquire a better knowledge of the ecotoxicity of PM2.5 under different solubilities, the model animal Caenorhabditis elegans (C. elegans) was exposed to Total-PM2.5, water insoluble components of PM2.5 (WIS-PM2.5) and water soluble components of PM2.5 (WS-PM2.5). The physiological (growth, locomotion behavior, and reproduction), biochemical (germline apoptosis, and reactive oxygen species (ROS) production) indices, and the related gene expression were examined. According to the findings, acute exposure to these three components caused adverse physiological effects on growth and locomotion behavior, and significantly induced germline apoptosis or ROS production. In contrast, prolonged exposure showed stronger adverse effects than acute exposure. Additionally, the results of multiple toxicological endpoints showed that the toxicity effects of WIS-PM2.5 are more intense than WS-PM2.5, which means that insoluble components contributed more to the toxicity of PM2.5. Prolonged exposure to 1000 mg/L WS-PM2.5, WIS-PM2.5, and Total-PM2.5 dramatically altered the expression of stress-related genes, which further indicated that apoptosis, DNA damage and oxidative stress play a crucial part in toxicity induced by PM2.5.

Characterization of nitrated aromatic compounds in fine particles from Nanjing, China: Optical properties, source allocation, and secondary processes.

Recently, nitrated aromatic compounds (NACs) have received much attention due to their role as key chromophores of brown carbon (BrC) and their impact on human health and the climate. In this study, a method for detection of 12 NACs in the atmosphere was developed and applied to the detection of 191 atmospheric samples in the northern suburbs of Nanjing in 2017. The average concentration of total NACs in Nanjing was 26.48 ng m-3, which was lower than that in North China. The total NACs also showed obvious seasonal variation, with the highest concentration in winter (51.99 ng m-3) and the lowest concentration in summer (11.26 ng m-3). Moreover, the contribution of subcomponents of NACs also changed with the seasons. Nitrophenols (NPs) and nitrocatechols (NCs) were most abundant in winter, while nitrosalicylic acids (NSAs) were more abundant in summer, accounting for 30%, 27%, and 85%, respectively. The reason for this result may be due to the different sources of dominance of NACs in different seasons. The light absorption of NACs to water-soluble BrC was mainly concentrated in the 300-400 nm range, and its contribution reached the maximum at 310 nm. NPs and NCs had the highest contribution to BrC among all NACs in winter, with a range of 25-54% and 3-59%, respectively. The Positive Matrix Factorization (PMF) was used to analyze the main sources of NACs in different seasons. Secondary generation was the largest source in summer, accounting for 43.5%, and biomass combustion contributed the most in autumn, accounting for 36.7%. NACs are affected by temperature, especially in summer, and the subcomponents vary in temperature dependence. The secondary generation process of NACs is affected by NO2 and O3, especially when NO2 is greater than 40 µg m-3 and O3 is less than 220 µg m-3.

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.

Identification and semi-quantification of nitrooxy organosulfates in aerosol particles by HPLC-MS/MS.

Organosulfates (OSs) derived from the oxidation of biogenic volatile organic compounds (BVOCs) in the presence of anthropogenic sulfate aerosols are the important tracers of secondary organic aerosols (SOAs). In order to better understand the concentration of pinene-nitrooxy organosulfates (pNOSs) in Nanjing, a sensitive high-performance liquid chromatography-electron spray ionization spectrum/mass spectrum (HPLC-ESI-MS/MS) to determine pNOSs in PM2.5 has been developed and validated in this study. Firstly, Hypersil Gold C18 (Thermo Scientific, San Jose, USA) was selected to separate pinene-derived nitrooxy organosulfates (pNOSs) based on their polarity. Three kinds of pNOSs were detected in the full scan mode (MS) with an ESI source under the negative mode. Secondly, three isomers of pNOSs with fragment ions m/z 220, 151, and 142 were identified based on the MS/MS maps. At least two pairs of transfer ions should be selected as identification and quantification ions according to the optimization results of target compounds. For example, to determine pNOSs, these transfer ions of m/z 294 → 247, m/z 294 → 231, m/z 294 → 220, m/z 294 → 142, m/z 294 → 151, m/z 294 → 96, m/z 294 → 80 were selected as quantification and identification ions. Finally, the influence of scan mode on pNOS detection was evaluated, and the results showed that pNOSs were most sensitive in the SRM (selected reaction monitor) scan mode. Therefore, the SRM scan mode was chosen to detect pNOSs. We applied this method to analyze year-round PM2.5 (PM2.5 is fine particulate matter, which refers to particulate matter in ambient air with an aerodynamic equivalent diameter of less than or equal to 2.5 microns) samples in Nanjing. The average concentration of all the three kinds of pNOSs was 69.95 ng m-3. The results showed that the average concentration of pNOSs was high in spring (92.94 ng m-3) and summer (90.57 ng m-3), and lowest in winter (30.03 ng m-3).

Seasonal variation, source contribution, and impact factors of biogenic organic aerosols in PM2.5 in Nanjing, China.

In this study, a liquid chromatography-mass spectrometry (HPLC-ESI-MS/MS) was used to develop a rapid method to detect carbohydrates (one anhydrosugar, five sugars, and four sugar alcohols) and monoterpene secondary organic aerosol (SOAM) tracers in the atmosphere, successfully applied to 139 atmospheric aerosol samples in Nanjing in 2019. Anhydrosugar (levoglucosan) is the most abundant carbohydrate in the atmospheric environment, with an annual mean concentration of 103.96 ng m-3. The measured compounds exhibited distinct seasonal variation, with a higher concentration in spring and summer and a lower concentration in autumn and winter. The distinct seasonal variation in these Bioorganic aerosol (BOA) tracers may be caused by the different dominant sources in different seasons. Their seasonal trends are also similar to other worldwide observations. In Nanjing, the yield of SOAM tracers is affected by meteorological conditions and anthropogenic pollutants (e.g., NO2 and O3). Furthermore, five source factors (secondary formation, biomass burning, soil resuspension, plant debris, and fungal spores) of BOA and their geographic origin were obtained using the Positive Matrix Factor (PMF) and Potential Source Contribution Factor (PSCF) models. The contribution of these factors to BOA also varies, with biomass burning (77.4 %) contributing the most, followed by fungal spores (12.2 %) and soil suspension (2.1 %).

Seasonal variations and potential sources of biomass burning tracers in particulate matter in Nanjing aerosols during 2017-2018.

Biomass burning (BB) is an important source of atmospheric particulate matter and can adversely affect air quality, visibility, human health, and climate change. To study the characteristics and potential source regions of BB tracers in PM2.5, a liquid chromatography-mass spectrometry instrument (HPLC-MS/MS) is applied in this study to develop and validate a method to determine organic tracers of BB in 397 aerosol samples. The total mean concentrations of 17 tracers measured in 2017 and 2018 were 333.32 ng m-3 and 243.45 ng m-3, respectively. Among them, the concentration of levoglucosan was the highest among all the tracers, with 325.63 ng m-3 in 2017 and 237.47 ng m-3 in 2018. The BB tracers showed obvious seasonal variations characteristics, most of which were abundant in winter. However, the concentrations of 3,4-dimethoxyacetic acid and sinapinic acid were higher in summer and spring than that in the other seasons. There were obvious differences in the Potential Source Contribution Factor (PSCF) model results of the BB's potential source area annually and in different seasons. The results of the potential source analysis showed that Beijing-Tianjin-Hebei had a great impact on the Nanjing air quality in 2017. Finally, five source factors for BB were identified based on the Positive Matrix Factor (PMF) model, and these were cellulose, hardwood, softwood, grass, and secondary formed. During the 2 years, cellulose was the largest contributor to biomass burning. Owing to the different fire conditions each year, the contribution of the five factors to the BB tracers was also different. For example, the contribution of softwood to the BB tracers was greater in 2018 (8.4%) than in 2017 (5.2%), while the contributions of hardwood and cellulose did not change significantly.

68Ga-NOTA PET imaging for gastric emptying assessment in mice.

BACKGROUND: Positron emission tomography (PET) has the potential for visualization and quantification of gastric emptying (GE). The traditional Chinese medicine (TCM) has been recognized promising for constipation. This study aimed to establish a PET imaging method for noninvasive GE measurement and to evaluate the efficacy of a TCM on delayed GE caused by constipation using PET imaging. METHODS: [68Ga]Ga-NOTA was synthesized as the tracer and sesame paste with different viscosity were selected as test meals. The dynamic PET scans were performed after [68Ga]Ga-NOTA mixed with test meals were administered to normal mice. Two methods were utilized for the quantification of PET imaging. A constipation mouse model was treated with maren chengqi decoction (MCD), and the established PET imaging scans were performed after the treatment. RESULTS: [68Ga]Ga-NOTA was synthesized within 20 min, and its radiochemical purity was > 95%. PET images showed the dynamic process of GE. %ID/g, volume, and total activity correlated well with each other. Among which, the half of GE time derived from %ID/g for 4 test meals were 3.92 ± 0.87 min, 13.1 ± 1.25 min, 17.8 ± 1.31 min, and 59.7 ± 3.11 min, respectively. Constipation mice treated with MCD showed improved body weight and fecal conditions as well as ameliorated GE measured by [68Ga]Ga-NOTA PET. CONCLUSIONS: A PET imaging method for noninvasive GE measurement was established with stable radiotracer, high image quality, and reliable quantification methods. The efficacy of MCD on delayed GE was demonstrated using PET.