Cellular effects of PM2.5 from Suzhou, China: relationship to chemical composition and endotoxin content

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.

Diversity and negative effect of PM0.3-10.0 adsorbed by needles of urban trees in Irkutsk, Russia

The study was performed in natural forests preserved within the Boreal zone city, Irkutsk, Russia. Test sites were selected in the forests in different districts of the city, where samples of Scots pine (Pinus sylvestris L.) and Siberian larch (Larix sibirica Ledeb.) needles were taken to study the adsorption on their surface of aerosol particles of different sizes, in microns: PM0.3, PM0.5, PM1, PM2.5, PM5, PM10. Scanning electron microscopy was used to obtain high-resolution photographs (magnification 800- × 2000, × 16,000) and aerosol particles (particulate matter-PM) were shown to be intensively adsorbed by the surface of needles, with both size and shape of the particles characterized by a wide variety. Pine needles can be covered with particles of solid aerosol by 50-75%, stomata are often completely blocked. Larch needles often show areas, which are completely covered with aerosol particles, there are often found stomata deformed by the penetration of PMx. X-ray spectral microanalysis showed differences in the chemical composition of adsorbed PMx, the particles can be metallic if metals predominate in their composition, carbonaceous-in case of carbon predominance-or polyelemental if the composition is complex and includes significant quantities of other elements besides metals and carbon (calcium, magnesium, potassium, sodium, sulfur, chlorine, fluorine). Since the particles contain a large proportion of technogenic pollutants, accumulation by the needles of some widespread pollutants was investigated. A direct correlation of a highly significant level between the concentration of PMx in the air and the accumulation of many heavy metals in pine and larch needles, as well as sulfur, fluorine, and chlorine, has been revealed, which indicates a high cleaning capacity of urban forests. At the same time, the negative impact of PMx particles on the vital status of trees is great, which shows in intense disturbance of the parameters of photosynthesis and transpiration, leading to a significant decrease in the growth characteristics of trees and reduction in the photosynthetic volume of the crowns. We consider that the results obtained are instrumental in developing an approach to improvement of urban forests status and creating a comfortable urban environment for the population.

Research progress on the effects of gut microbiome on lung damage induced by particulate matter exposure

Air pollution is one of the top five causes of death in the world and has become a research hotspot. In the past, the health effects of particulate matter (PM), the main component of air pollutants, were mainly focused on the respiratory and cardiovascular systems. However, in recent years, the intestinal damage caused by PM and its relationship with gut microbiome (GM) homeostasis, thereby affecting the composition and function of GM and bringing disease burden to the host lung through different mechanisms, have attracted more and more attention. Therefore, this paper reviews the latest research progress in the effect of PM on GM-induced lung damage and its possible interaction pathways and explores the potential immune inflammatory mechanism with the gut-lung axis as the hub in order to understand the current research situation and existing problems, and to provide new ideas for further research on the relationship between PM pollution, GM, and lung damage.

Gene Expression Changes Induced by Exposure of RAW 264.7 Macrophages to Particulate Matter of Air Pollution: The Role of Endotoxins

Despite the variable chemical and physical characteristics of particulate air pollutants, inflammation and oxidative stress have been identified as common mechanisms for cell damage and negative health influences. These effects are produced by organic components, especially by endotoxins. This study analyzed the gene expression profile after exposure of RAW 264.7 cells to the standard particulate matter (PM) material, NIST1648a, and PM with a reduced organic matter content, LAp120, in comparison to the effects of lipopolysaccharide (LPS). The selected parameters of cell viability, cell cycle progression, and metabolic and inflammatory activity were also investigated. Both forms of PM negatively influenced the parameters of cell activity. These results were generally reflected in the gene expression profile. Only NIST1648a, excluding LAp120, contained endotoxins and showed small but statistically significant pro-inflammatory activity. However, the gene expression profiling revealed strong pro-inflammatory cell activation induced by NIST1648a that was close to the effects of LPS. Changes in gene expression triggered by LAp120 were relatively small. The observed differences in the effects of NIST1648a and LAp120 were related to the content of organic matter in which bacterial endotoxins play an important role. However, other organic compounds and their interactions with other PM components also appear to be of significant importance.

Mechanistic toxicity assessment of fine particulate matter emitted from fuel combustion via pathway-based approaches in human cells

Fuel exhaust particulate matter (FEPM) is an important source of air pollution worldwide. However, the comparative and mechanistic toxicity of FEPMs emitted from combustion of different fuels is still not fully understood. This study employed pathway-based approaches via human cells to evaluate mechanistic toxicity of FEPMs. The results showed that FEPMs caused concentration-dependent (0.1-200 μg/mL) cytotoxicity and oxidative stress. FEPMs at low concentration (10 μg/mL) induced cell cycle arrest in S and G2 phases, while high level of FEPMs (200 μg/mL) caused cell cycle arrest in G1 phase. Different FEPMs induced distinct expression profiles of toxicity-related genes, illustrating different toxic mechanisms. Furthermore, FEPMs inhibited the phosphorylation of protein kinase A (PKA), which related with reproductive toxicity. Spearman rank correlations among the chemicals carried by FEPMs and the toxic effects revealed that PAHs and metals promoted cell cycle arrest in the G1 phase and suppressed PKA activity. Furthermore, PAHs (Nap and Acy) and metals (Al and Pb) in FEPMs were highly and positively correlated with the expression of genes involved in apoptosis, ER stress, metal stress and inflammation. Our findings offered more mechanistic information of FEPMs at the level of subcellular toxicity and help to better understand their potential health effects.

PM2.5 induces inflammatory responses via oxidative stress-mediated mitophagy in human bronchial epithelial cells

BACKGROUND

Fine particulate matter (PM_2.5) is a ubiquitous air pollutant, and it has been reported to be closely associated with lung inflammatory injury. In this study, the potential molecular mechanisms underlying PM_2.5-induced cellular inflammation in human bronchial epithelial (BEAS-2B) cells were investigated.

MATERIALS AND METHODS

Ambient PM_2.5 particulates from Suzhou, China, were collected and re-suspended in ultrapure water. Cellular damages, characterized by oxidative stress, mitochondrial injury, and inflammatory cytokine production, were determined in 24 h PM_2.5-treated BEAS-2B cells with or without 3-methyladenine (3-MA; autophagy inhibitor) pretreatment. Biomarkers related to oxidative damage, inflammatory injury and autophagy signaling pathways were also measured.

RESULTS

Uptake of PM_2.5 in BEAS-2B cells induced cellular oxidative damage, mitochondrial injury, and inflammatory responses as indicated by a significant decrease in GSH/GSSG ratio, increased MDA content, dilated mitochondria with loss and rupture of crista, and production of inflammatory cytokines. Activation of Nrf-2/TXNIP-mediated NF-κB and Bnip3L/NIX-dependent mitophagy signaling pathways, as well as accumulation of autophagosomes and autolysosomes, were also observed. A 6 h pretreatment of 3-MA increased PM_2.5-induced oxidative damage and cellular inflammation as indicated by increasing protein levels of HO-1, TXNIP, Bnip3L/NIX and IL-8 gene expression.

CONCLUSIONS

PM_2.5 induced cellular inflammatory injury by oxidative stress, mitochondrial dysfunction, and mitophagy initiation. Although induction of Bnip3L/NIX-mediated mitophagy in BEAS-2B cells appeared to confer protection in response to PM_2.5, dysfunction of autophagic flux may be a critical contributor to defective mitophagy and cellular inflammatory response.