Maternal urban particulate matter (SRM 1648a) exposure disrupted the cellular immune homeostasis during early life: The potential attribution of altered placental transcriptome profile

Ambient fine particular matter (PM2.5) exposure has been associated with numerous adverse effects including triggering functional disorders of the placenta and inducing immune imbalance in offspring. However, how maternal PM2.5 exposure impacts immune development during early life is not fully understood. In the current study, we exposed mice with low-, middle-, and high-dose PM2.5 during pregnancy to investigate the potential link between the transcriptional changes in the placenta and immune imbalance in mice offspring induced by PM2.5 exposures. Using flow cytometry, we found that the proportions of B cells, CD3+CD4+ T cells, CD3+CD8+ T cells, and macrophage (Mφ) cells were altered in the blood of PM2.5-exposed mice pups but not dendritic cells (DCs) and natural killer cells (NKs). Using bulk RNA sequencing, we found that PM2.5 exposure altered the transcriptional profile which indicated an inhibition of the complement and coagulation cascades in the placenta. Weighted gene co-expression network analysis (WGCNA) revealed the potential crosstalk between the perturbation of placental gene expression and the changes of immune cell subsets in pups on postnatal day 10 (PND10). Specifically, WGCNA identified a cluster of genes including Defb15, Defb20, Defb25, Cst8, Cst12, and Adam7 that might regulate the core immune cell types in PND10 pups. Although the underlying mechanisms of how maternal PM2.5 exposure induces peripheral lymphocyte disturbance in offspring still remain much unknown, our findings here shed light on the potential role of placental dysfunction in these adverse effects.

Urban aerosol particulate matter promotes mitochondrial oxidative stress-induced cellular senescence in human retinal pigment epithelial ARPE-19 cells

Environmental exposure to urban particulate matter (UPM) is a serious health concern worldwide. Although several studies have linked UPM to ocular diseases, no study has reported effects of UPM exposure on senescence in retinal cells. Therefore, this study aimed to investigate the effects of UPM on senescence and regulatory signaling in human retinal pigment epithelial ARPE-19 cells. Our study demonstrated that UPM significantly promoted senescence, with increased senescence-associated β-galactosidase activity. Moreover, both mRNA and protein levels of senescence markers (p16 and p21) and the senescence-associated secretory phenotype, including IL-1β, matrix metalloproteinase-1, and -3 were upregulated. Notably, UPM increased mitochondrial reactive oxygen species-dependent nuclear factor-kappa B (NF-κB) activation during senescence. In contrast, use of NF-κB inhibitor Bay 11-7082 reduced the level of senescence markers. Taken together, our results provide the first in vitro preliminary evidence that UPM induces senescence by promoting mitochondrial oxidative stress-mediated NF-κB activation in ARPE-19 cells.

Effects of urban particulate matter on the quality of erythrocytes

With the acceleration of industrialisation and urbanisation, air pollution has become a serious global concern as a hazard to human health, with urban particulate matter (UPM) accounting for the largest share. UPM can rapidly pass into and persist within systemic circulation. However, few studies exist on whether UPM may have any impact on blood components. In this study, UPM standards (SRM1648a) were used to assess the influence of UPM on erythrocyte quality in terms of oxidative and metabolic damage as well as phagocytosis by macrophages in vitro and clearance in vivo. Our results showed that UPM had weak haemolytic properties. It can oxidise haemoglobin and influence the oxygen-carrying function, redox balance, and metabolism of erythrocytes. UPM increases the content of reactive oxygen species (ROS) and decreases antioxidant function according to the data of malonaldehyde (MDA), glutathione (GSH), and glucose 6 phosphate dehydrogenase (G6PDH). UPM can adhere to or be internalised by erythrocytes at higher concentrations, which can alter their morphology. Superoxide radicals produced in the co-incubation system further disrupted the structure of red blood cell membranes, thereby lowering the resistance to the hypotonic solution, as reflected by the osmotic fragility test. Moreover, UPM leads to an increase in phosphatidylserine exposure in erythrocytes and subsequent clearance by the mononuclear phagocytic system in vivo. Altogether, this study suggests that the primary function of erythrocytes may be affected by UPM, providing a warning for erythrocyte quality in severely polluted areas. For critically ill patients, transfusion of erythrocytes with lesions in morphology and function will have serious clinical consequences, suggesting that potential risks should be considered during blood donation screening. The current work expands the scope of blood safety studies.

Spider web biomonitoring: A cost-effective source apportionment approach for urban particulate matter

Elevated levels of particulate matter (PM) in urban atmospheres are one of the major environmental challenges of the Anthropocene. To effectively lower those levels, identification and quantification of sources of PM is required. Biomonitoring methods are helpful tools to tackle this problem but have not been fully established yet. An example is the sampling and subsequent analysis of spider webs to whose adhesive surface dust particles can attach. For a methodical inspection, webs of orb-weaving spiders were sampled repeatedly from 2016 to 2018 at 22 locations in the city of Jena, Germany. Contents of Ag, Al, As, B, Ba, Ca, Cd, Co, Cr, Cs, Cu, Fe, K, La, Li, Mg, Mn, Mo, Na, Ni, P, Pb, Rb, S, Sb, Si, Sn, Sr, Th, Ti, V, Y, Zn and Zr were determined in the samples using inductively coupled plasma-mass spectrometry (ICP-MS) and inductively coupled plasma-optical emission spectroscopy (ICP-OES) after aqua regia digestion. Multivariate statistical methods were applied for a detailed evaluation. A combination of cluster analysis and principal component analysis allows for the clear identification of three main sources in the study area: brake wear from car traffic, abrasion of tram/train tracks and particles of geogenic origin. Quantitative source contributions reveal that high amounts of most of the metals are derived from a combination of brake wear and geogenic particles, the latter of which are likely resuspended by moving vehicles. This emphasizes the importance of non-exhaust particles connected to road traffic. Once a source identification has been performed for an area of interest, classification models can be applied to assess air quality for further samples from within the whole study area, offering a tool for air quality assessment. The general validity of this approach is demonstrated using samples from other locations.

Atmospheric particulate matter impedes autophagic flux by impairing lysosomal milieu and integrity in human umbilical vein endothelial cells (HUVECs)

Autophagy is a dynamic process for waste disposal and cell equilibrium. Previous studies have demonstrated that atmospheric particulate matter (APM) induces autophagy and enhances LC3II expression in human vascular endothelial cells. However, the underlying mechanism of autophagosome accumulation in human vascular endothelial cells under the exposure to APM has not been understood. In principle, the upregulation of LC3II or autophagosomes accumulation is presumably caused by the enhancement of autophagic ability, or alternatively, by the abnormal autophagic degradation. Therefore, in the current study, autophagic ability and autophagic flux are systemically studied to decipher the exact cause of autophagosomes accumulation in human umbilical vein endothelial cells (HUVECs) in response to a standard urban particulate matter, PM SRM1648a. As a result, it was observed that after 24 h of exposure, PM SRM1648a significantly increases LC3II expression with apparent autophagosomes accumulation in HUVECs. Compared with the control group, there is a time-dependent increase in p62, a protein of autophagic substrate that can be preliminarily used to evaluate the autophagic degradation, in the PM SRM1648a-exposed HUVECs, which suggested that normal function of autophagic degradation was probably impaired. Additionally, mRFP-GFP-LC3 assay and LAMP-2/LC3B co-localization suggested that autolysosomes (fusion between autophagosomes and lysosomes) were partially inhibited in PM SRM1648a-treated HUVECs. Furthermore, LC3II turn-over assay hinted that after 24 h, LC3II upregulation is attributed to the blockage of autophagic flux instead of the enhancement of autophagic induction. Mechanistically, the blockade of autophagic flux can be explained by the detrimental effects of PM SRM1648a on lysosomal function, including lysosomal destabilization, lysosomal alkalization and hydrolase inactivation, which are involved in the blockade of fusion between autophagosomes and lysosomes, further disrupting autophagic degradation and waste disposal. These observations provide evidence that PM SRM1648a destroys the equilibrium of lysosomal stability and thus results in the dysfunction of autophagic flux, eventually contributing to endothelial cell damage.

Antioxidant potential of Sargassum horneri extract against urban particulate matter-induced oxidation

Particulate matter is a major contribution of air pollution and detrimental to human health. The in vitro antioxidant activities of a brown seaweed, Sargassum horneri ethanol extract (SHE) against particulate matter-induced oxidative stress were investigated by measuring 1,1-diphenyl-2-picrylhydrazyl (DPPH) free-radical scavenging activity, hydrogen peroxide (H₂O₂) scavenging activity, superoxide anion (O₂ ^·-) inhibition, hydroxyl radical ( ^· OH) scavenging activity, reducing power, and the metal ion-chelating effect. All in vitro antioxidant activities were increased as the concentration of SHE increased (0-1000 μg/mL). When treated with particulate matter at 0-1000 μg/mL, the DPPH free radical, and H₂O₂ scavenging activities, reducing power, and metal ion-chelating abilities of SHE were significantly decreased (p < 0.05). These results indicate that Sargassum horneri, which is a rich source of bioactive compounds, can be used as a natural source of antioxidants in the food industries.

Identification of urban particulate matter-induced disruption of human respiratory mucosa integrity using whole transcriptome analysis and organ-on-a chip

Background

Exposure to air particulate matter (PM) is associated with various diseases in the human respiratory system. To date, most in vitro studies showing cellular responses to PM have been performed in cell culture using a single cell type. There are few studies considering how multicellular networks communicate in a tissue microenvironment when responding to the presence of PM. Here, an in vitro three-dimensional (3D) respiratory mucosa-on-a-chip, composed of human nasal epithelial cells, fibroblasts, and endothelial cells, is used to recapitulate and better understand the effects of urban particulate matter (UPM) on human respiratory mucosa.

Results

We hypothesized that the first cells to contact with UPM, the nasal epithelial cells, would respond similar to the tissue microenvironment, and the 3D respiratory mucosa model would be a suitable platform to capture these events. First, whole transcriptome analysis revealed that UPM induced gene expression alterations in inflammatory and adhesion-related genes in human nasal epithelial cells. Next, we developed an in vitro 3D respiratory mucosa model composed of human nasal epithelial cells, fibroblasts, and endothelial cells and demonstrated that the model is structurally and functionally compatible with the respiratory mucosa. Finally, we used our model to expose human nasal epithelial cells to UPM, which led to a disruption in the integrity of the respiratory mucosa by decreasing the expression of zonula occludens-1 in both the epithelium and endothelium, while also reducing vascular endothelial cadherin expression in the endothelium.

Conclusions

We demonstrate the potential of the 3D respiratory mucosa model as a valuable tool for the simultaneous evaluation of multicellular responses caused by external stimuli in the human respiratory mucosa. We believe that the evaluation strategy proposed in the study will move us toward a better understanding of the detailed molecular mechanisms associated with pathological changes in the human respiratory system.

Urban particulate matter (PM) suppresses airway antibacterial defence

Background

Epidemiological studies have shown that urban particulate matter (PM) increases the risk of respiratory infection. However, the underlying mechanisms are poorly understood. PM has been postulated to suppress the activation of airway epithelial innate defence in response to infection.

Methods

The effects of PM on antibacterial defence were studied using an in vitro infection model. The levels of antimicrobial peptides were measured using RT-PCR and ELISA. In addition to performing colony-forming unit counts and flow cytometry, confocal microscopy was performed to directly observe bacterial invasion upon PM exposure.

Results

We found that PM PM increased bacterial invasion by impairing the induction of β-defensin-2 (hBD-2), but not the other antimicrobial peptides (APMs) secreted by airway epithelium. PM further increases bacteria-induced ROS production, which is accompanied by an accelerated cell senescence and a decrease in bacteria-induced hBD-2 production, and the antioxidant NAC treatment attenuates these effects. The PM exposure further upregulated the expression of IL-8 but downregulated the expression of IL-13 upon infection.

Conclusions

PM promotes bacterial invasion of airway epithelial cells by attenuating the induction of hBD-2 via an oxidative burst. These findings associate PM with an increased susceptibility to infection. These findings provide insight into the underlying mechanisms regarding the pathogenesis of particulate matter.

Protective effects of chebulic acid on alveolar epithelial damage induced by urban particulate matter

BACKGROUND

Chebulic acid (CA) isolated from T. chebula, which has been reported for treating asthma, as a potent anti-oxidant resources. Exposure to ambient urban particulate matter (UPM) considered as a risk for cardiopulmonary vascular dysfunction. To investigate the protective effect of CA against UPM-mediated collapse of the pulmonary alveolar epithelial (PAE) cell (NCI-H441), barrier integrity parameters, and their elements were evaluated in PAE.

METHODS

CA was acquired from the laboratory previous reports. UPM was obtained from the National Institutes of Standards and Technology, and these were collected in St. Louis, MO, over a 24-month period and used as a standard reference. To confirm the protection of PAE barrier integrity, paracellular permeability and the junctional molecules were estimated with determination of transepithelial electrical resistance, Western Blotting, RT-PCR, and fluorescent staining.

RESULTS

UPM aggravated the generation of reactive oxygen species (ROS) in PAE and also decreased mRNA and protein levels of junction molecules and barrier integrity in NCI-H441. However, CA repressed the ROS in PAE, also improved barrier integrity by protecting the junctional parameters in NCI-H411.

CONCLUSIONS

These data showed that CA resulted in decreased UPM-induced ROS formation, and the protected the integrity of the tight junctions against UPM exposure to PAE barrier.