Diesel Exhaust Particles Exposure Research Articles

Diesel exhaust particles alter gut microbiome and gene expression in the bumblebee Bombus terrestris.

Insect decline is a major threat to ecosystems around the world as they provide many important functions, such as pollination or pest control. Pollution is one of the main reasons for the decline, alongside changes in land use, global warming, and invasive species. While negative impacts of pesticides are well-studied, there is still a lack of knowledge about the effects of other anthropogenic pollutants, such as airborne particulate matter, on insects. To address this, we exposed workers of the bumblebee Bombus terrestris to sublethal doses of diesel exhaust particles (DEPs) and brake dust, orally or via air. After 7 days, we looked at the composition of the gut microbiome and tracked changes in gene expression. While there were no changes in the other treatments, oral DEP exposure significantly altered the structure of the gut microbiome. In particular, the core bacterium Snodgrassella had a decreased abundance in the DEP treatment. Similarly, transcriptome analysis revealed changes in gene expression after oral DEP exposure, but not in the other treatments. The changes are related to metabolism and signal transduction, which indicates a general stress response. Taken together, our results suggest potential health effects of DEP exposure on insects, here shown in bumblebees, as gut dysbiosis may increase the susceptibility of bumblebees to pathogens, while a general stress response may lower available energy resources. Those effects may exacerbate under natural conditions where insects face a multiple-stressor environment.

Diesel exhaust particles alter adipose mitochondria bioenergetics

Diesel exhaust particles (DEP) constitute a significant quantity of air pollution that infiltrate the bloodstream to drive systemic pathologies. While some pathologies are obvious, such as COPD and heart failure, others are less apparent, such as insulin resistance, diabetes, and even obesity. In every case, a role for the receptor of advanced glycation end-products (RAGE) has been implicated. RAGE are cell surface receptors that are implicated in pathological processes, such as inflammation and diabetic complications. Despite the known connection between DEP and metabolic disorders, the effects of DEP exposure on adipose tissue mitochondrial function is unknown. To understand the potential role of RAGE signaling in the context of adipose tissue DEP exposure, mice were nasally exposed to either room air, nebulized diesel exhaust particles, or nebulized diesel exhaust particles + semi-synthetic glycosaminoglycan ethers (SAGEs, RAGE signaling inhibitors) every weekday for three weeks. Inguinal adipose tissue samples were obtained following exposure, and mitochondrial respiration rates were measured. In mice exposed to DEP or DEP + SAGE, mitochondrial respiration of inguinal adipose tissue was not significantly different compared to the room air control mice with the addition of glutamate and malate or ADP. However, respiration was significantly increased with the addition of succinate and FCCP in the inguinal adipose tissue from mice exposed to DEP. The results of this work indicate that DEP exposure elicits a negative effect on adipose mitochondrial respiration. This work was supported in part by funding from Levels Health (BTB) and the National Institutes of Health (NIH 1R15-HL152257, PRR and BTB). This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Trajectory of neutrophilic responses in a mouse model of pollutant-aggravated allergic asthma

Experimental studies suggest that neutrophils could contribute to allergic asthma pathogenesis, that is mainly driven by type 2 immunity. Inhalation of diesel exhaust particles (DEP) is implicated in both exacerbation and development of asthma. Since exposure to DEP is associated with a neutrophilic component, we aimed to investigate how exposure to the combination of allergens and DEP modulates neutrophilic responses. Human bronchial epithelial cells (HBEC) were exposed to house dust mite (HDM), DEP or HDM + DEP in vitro to determine the expression of neutrophil-recruiting chemokines. Female (C57BL/6 J) mice were intranasally instilled with saline, DEP, HDM or combined HDM + DEP for 3 weeks (subacute) or 6 weeks (chronic). The neutrophilic responses were determined in lung tissue and bronchoalveolar lavage fluid (BALF). Simultaneous exposure to HDM + DEP resulted in increased CXCL1 and CXCL8 mRNA expression by HBEC in vitro. In mice, subacute exposure to HDM + DEP induced a strong mixed eosinophilic/neutrophilic inflammation in BALF and lung and was associated with higher expression of neutrophil-attracting chemokines and NET formation compared to the sole exposures. After chronic HDM + DEP exposure, a similar neutrophilic response was observed, however the NET formation was less pronounced. Interestingly, the increase of BALF eosinophils was also significantly attenuated after chronic HDM + DEP exposure compared to the subacute exposure. Subacute and chronic HDM + DEP exposure induced goblet cell hyperplasia and airway hyperresponsiveness. Our data suggest a role for neutrophils and NETs in pollutant-aggravated eosinophilic allergic asthma. Moreover, subacute exposure to HDM + DEP induces a mixed eosinophilic/neutrophilic response whereas upon chronic HDM + DEP exposure there is a shift in inflammatory response with a more prominent neutrophilic component.

Altered long non-coding RNAs expression in normal and diseased primary human airway epithelial cells exposed to diesel exhaust particles

Background Exposure to diesel exhaust particles (DEP) has been linked to a variety of adverse health effects, including increased morbidity and mortality from cardiovascular diseases, chronic obstructive pulmonary disease (COPD), metabolic syndrome, and lung cancer. The epigenetic changes caused by air pollution have been associated with increased health risks. However, the exact molecular mechanisms underlying the lncRNA-mediated pathogenesis induced by DEP exposure have not been revealed. Methods Through RNA-sequencing and integrative analysis of both mRNA and lncRNA profiles, this study investigated the role of lncRNAs in altered gene expression in healthy and diseased human primary epithelial cells (NHBE and DHBE-COPD) exposed to DEP at a dose of 30 μg/cm2. Results We identified 503 and 563 differentially expressed (DE) mRNAs and a total of 10 and 14 DE lncRNAs in NHBE and DHBE-COPD cells exposed to DEP, respectively. In both NHBE and DHBE-COPD cells, enriched cancer-related pathways were identified at mRNA level, and 3 common lncRNAs OLMALINC, AC069234.2, and LINC00665 were found to be associated with cancer initiation and progression. In addition, we identified two cis-acting (TMEM51-AS1 and TTN-AS1) and several trans-acting lncRNAs (e.g. LINC01278, SNHG29, AC006064.4, TMEM51-AS1) only differentially expressed in COPD cells, which could potentially play a role in carcinogenesis and determine their susceptibility to DEP exposure. Conclusions Overall, our work highlights the potential importance of lncRNAs in regulating DEP-induced gene expression changes associated with carcinogenesis, and individuals suffering from COPD are likely to be more vulnerable to these environmental triggers.

Evaluating the effect of acute diesel exhaust particle exposure on P-glycoprotein efflux transporter in the blood–brain barrier co-cultured with microglia

A growing public health concern, chronic Diesel Exhaust Particle (DEP) exposure is a heavy risk factor for the development of neurodegenerative diseases like Alzheimer’s (AD). Considered the brain’s first line of defense, the Blood–Brain Barrier (BBB) and perivascular microglia work in tandem to protect the brain from circulating neurotoxic molecules like DEP. Importantly, there is a strong association between AD and BBB dysfunction, particularly in the Aβ transporter and multidrug resistant pump, P-glycoprotein (P-gp). However, the response of this efflux transporter is not well understood in the context of environmental exposures, such as to DEP. Moreover, microglia are seldom included in in vitro BBB models, despite their significance in neurovascular health and disease. Therefore, the goal of this study was to evaluate the effect of acute (24 hr.) DEP exposure (2000 μg/ml) on P-gp expression and function, paracellular permeability, and inflammation profiles of the human in vitro BBB model (hCMEC/D3) with and without microglia (hMC3). Our results suggested that DEP exposure can decrease both the expression and function of P-gp in the BBB, and corroborated that DEP exposure impairs BBB integrity (i.e. increased permeability), a response that was significantly worsened by the influence of microglia in co-culture. Interestingly, DEP exposure seemed to produce atypical inflammation profiles and an unexpected general downregulation in inflammatory markers in both the monoculture and co-culture, which differentially expressed IL-1β and GM-CSF. Interestingly, the microglia in co-culture did not appear to influence the response of the BBB, save in the permeability assay, where it worsened the BBB’s response. Overall, our study is important because it is the first (to our knowledge) to investigate the effect of acute DEP exposure on P-gp in the in vitro human BBB, while also investigating the influence of microglia on the BBB’s responses to this environmental chemical.

Citrus peel extract protects against diesel exhaust particle-induced chronic obstructive pulmonary disease-like lung lesions and oxidative stress.

Chronic obstructive pulmonary disease (COPD) is the third leading cause of death worldwide and characterized by emphysema, small airway remodeling and mucus hypersecretion. Citrus peels have been widely used as food spices and in traditional Chinese medicine for chronic lung disease. Given that citrus peels are known for containing antioxidants and anti-inflammatory compounds, we hypothesize that citrus peel intake can suppress oxidative stress and inflammatory response to air pollution exposure, thereby alleviating COPD-like pathologies. This study aimed to investigate the efficacy of citrus peel extract, namely Guang Chenpi (GC), in preventing the development of COPD induced by diesel exhaust particles (DEPs) and its potential mechanism. DEP-induced COPD-like lung pathologies, inflammatory responses and oxidative stress with or without GC treatment were examined in vivo and in vitro. Our in vivo study showed that GC was effective in decreasing inflammatory cell counts and inflammatory mediator (IL-17A and TNF-α) concentrations in bronchoalveolar lavage fluid (BALF). Pretreatment with GC extract also significantly decreased oxidative stress in the serum and lung tissue of DEP-induced COPD rats. Furthermore, GC pretreatment effectively reduced goblet cell hyperplasia (PAS positive cells) and fibrosis of the small airways, decreased macrophage infiltration as well as carbon loading in the peripheral lungs, and facilitated the resolution of emphysema and small airway remodeling in DEP-induced COPD rats. An in vitro free radical scavenging assay revealed robust antioxidant potential of GC in scavenging DPPH free radicals. Moreover, GC demonstrated potent capacities in reducing ROS production and enhancing SOD activity in BEAS-2B cells stimulated by DEPs. GC treatment significantly attenuated the increased level of IL-8 and MUC5AC from DEP-treated BEAS-2B cells. Mechanistically, GC treatment upregulated the protein level of Nrf-2 and could function via MAPK/NF-κB signaling pathways by suppressing the phosphorylation of p38, JNK and p65. Citrus peel extract is effective in decreasing oxidative stress and inflammatory responses of the peripheral lungs to DEP exposure. These protective effects further contributed to the resolution of COPD-like pathologies.

Neuro‐Glia‐Vascular‐on‐a‐Chip System to Assess Aggravated Neurodegeneration via Brain Endothelial Cells upon Exposure to Diesel Exhaust Particles

AbstractAir pollution induces neurodegeneration, including cognitive deficits, neuroinflammation, and disruption of the blood–brain barrier. The mechanisms underlying air pollution‐mediated neurodegeneration have not yet been fully elucidated given the limited knowledge on intercellular interactions. A brain‐on‐a‐chip platform is presented comprising neurons, glia, and brain endothelial cells (bECs; neuro‐glia‐vascular, NGV) and diesel exhaust particle (DEP)‐induced neurodegeneration is evaluated with a particular focus on the intercellular interactions. DEP exposure in the NGV model yields Alzheimer's disease‐like signatures, including amyloid beta accumulation, tau phosphorylation, hydrogen peroxide (H2O2)/reactive oxygen species (ROS) production, and neuronal cell death. bEC‐secreted granulocyte‐macrophage colony‐stimulating factor (GM‐CSF) stimulates microglial activation and the overproduction of H2O2/ROS in microglia, suggesting that the bEC‐microglia‐neuron is a neurodegeneration cascade. Pharmacological inhibition at each step of the cascade, including GM‐CSF neutralization, microglial activation suppression, and ROS scavenging, prohibits neurodegeneration in the NGV model. Therefore, intercellular interactions should be further studied of air pollution‐induced neurodegeneration.

SHORT-TERM DIESEL EXHAUST PARTICLE NEUROTOXICITY MEDIATED BY TLR4 ACROSS AGE AND SEX

Abstract Experimental animal exposures show neurotoxic effects of diesel in young mice even after short-term exposures. We hypothesize that neuroinflammatory effects of diesel exhaust particles (DEP) are mediated by toll-like receptor 4 (TLR4) activation in brain microglia. We studied both sexes of young (2 months) and middle-aged (18 months) TLR4 flx/flx (CX3CR1CreER +/-) mice, in which macrophage-specific TLR4 deletion is induced by tamoxifen. DEP from National Institute of Science and Technology (NIST 2975) was suspended in pure water and re-aerosolized for 5 hr exposure at 100 µg/m3 concentration. Experimental groups were Filtered Air+Corn Oil, DEP+Corn Oil, Filtered Air+Tamoxifen, DEP+Tamoxifen. We studied markers of inflammation, oxidative stress, and microglia activation in the white matter of corpus callosum. At baseline, middle-aged mice showed higher levels of microglia activation (Iba-1), complement activation (C5, C5a), and oxidative stress (8-OHdG, 4HNE). DEP significantly increased microglial activation, inflammation, and oxidative stress. TLR4 knockdown showed a rescue effect in DEP group for Iba-1 and 8-OHdG in young but not in middle-aged mice. Both C5a and 4HNE were rescued by TLR4 knockdown in young and middle-aged mice, possibly with less robust effects in older mice. No significant sex effects were observed. Middle-aged mice have higher levels of baseline white matter inflammation and oxidative stress. DEP exposure caused robust neuroinflammatory and oxidative responses in white matter across ages. TLR4 knockdown attenuated DEP caused neuroinflammatory and oxidative responses, suggesting that microglia play an important role in DEP neurotoxicity.

The effect of hypoxia on diesel exhaust particle toxicity in lung epithelial cells

ABSTRACT Hypoxia is characterised by tissue oxygen concentrations below 2% and occurs in several pathologies including neurodegenerative and chronic lung diseases. Air pollution and its major component, particulate matter, are also a public health concern and are directly implicated in the onset of chronic lung disease. Therefore, an understanding of the effects of hypoxia on the susceptibility of lung tissues to air pollutants is crucial. In this study we investigate the effects of hypoxia on the toxicity of diesel exhaust particles (DEP) in two lung epithelial cells: human and rat type II alveolar cells. The goal is to discern whether hypoxia exacerbates the toxic response to DEP exposure in both 24-hour and 48-hour exposures. We subjected both cell lines to increasing concentrations of DEP for 24 and 48 hours in both normoxic and hypoxic (2% oxygen) incubation conditions and measured the rate of cell death, proliferation, and pro-inflammatory cytokine and chemokine production. The results indicate that hypoxia increases DEP cytotoxicity in RLE6TN but not A549 cells, and that hypoxia decreases the production of pro-inflammatory markers induced by exposure to DEP. These results suggest an increased susceptibility to particulate matter toxicity when prolonged or chronic hypoxia is present.

PM2.5 exposure exacerbates mice thoracic aortic aneurysm and dissection by inducing smooth muscle cell apoptosis via the MAPK pathway

Air pollution is a major public health concern worldwide. Exposure to fine particulate matter (PM2.5) is closely associated with cardiovascular diseases. However, the effect of PM2.5 exposure on thoracic aortic aneurysm and dissection (TAAD) has not been fully elucidated. Diesel exhaust particulate (DEP) is an important component of PM2.5, which causes health effects and is closely related to the incidence of cardiovascular disease. In the current study, we found that DEP exposure increased the incidence of aortic dissection (AD) in β-aminopropionitrile (BAPN)-induced thoracic aortic aneurysm (TAA). In addition, exposure to PM2.5 increased the diameter of the thoracic aorta in mice models. The number of apoptotic cells increased in the aortic wall of PM2.5-treated mice, as did the protein expression level of BAX/Bcl2 and cleaved caspase3/caspase3. Using a rhythmically stretching aortic mechanical simulation model, fluorescent staining indicated that PM2.5 administration could induce mitochondrial dysfunction and increase reactive oxygen species (ROS) levels in human aortic smooth muscle cells (HASMCs). Furthermore, ERK1/2 mitogen-activated protein kinase (MAPK) signaling pathways participated in the apoptosis of HASMCs after PM2.5 exposure. Therefore, we concluded that PM2.5 exposure could exacerbate the progression of TAAD, which could be induced by the increased apoptosis in HASMCs through the ERK1/2 MAPK signaling pathway.

Diesel exhaust particles inhibit lung branching morphogenesis via the YAP/TAZ pathway

Prenatal exposure to air pollution may associated with inhibition of lung development in the child, however the possible mechanism is unclear. We investigated the effects of traffic-related diesel exhaust particle (DEP) exposure on fetal lung branching morphogenesis and elucidate the possible mechanism. Ex vivo fetal lungs collected from ICR mice at an age of 11.5 embryonic (E) days were exposed to DEPs at 0 (control), 10, and 50 μg/mL and branching morphogenesis was measured for 3 days. Normal IMR-90 human fetal lung fibroblast cells were exposed to DEPs at 0 (control), 10, and 50 μg/mL for 24 h. We observed that DEP exposure significantly inhibited lung branching morphogenesis with reduced lung branching ratios and surface areas on day 3. RNA sequencing (RNA-Seq) showed that DEP increased the inflammatory response and impaired lung development-related gene expressions. DEPs significantly decreased Yes-associated protein (YAP), phosphorylated (p)-YAP, transcriptional coactivator with a PDZ-binding motif (TAZ), and p-TAZ in IMR-90 cells at 10 and 50 μg/mL. Treatment of fetal lungs with the YAP inhibitor, PFI-2, also demonstrated restricted lung branching development similar to that of DEP exposure, with a significantly decreased lung branching ratio on day 3. DEP exposure significantly decreased the lung branching modulators fibroblast growth factor receptor 2 (FGFR2), sex-determining region Y-box 2 (SOX2), and SOX9 in IMR-90 cells at 10 and 50 μg/mL. Fetal lung immunofluorescence staining showed that DEP decreased SOX2 expression in fibronectin+ fibroblasts. DEP exposure decreased the cellular senescence regulator, p-sirtuin 1 (SIRT1)/SIRT1 in IMR-90 cells, with RNA-Seq showing impaired telomere maintenance. DEP exposure impaired fetal lung growth during the pseudoglandular stage through dysregulating the Hippo signaling pathway, causing fibroblast lung branching restriction and early senescence. Prenatal exposure to traffic-related air pollution has adverse effects on fetal lung development.

Diesel exhaust particle exposure accelerates oxidative DNA damage and cytotoxicity in normal human bronchial epithelial cells through PD-L1

Diesel exhaust particles (DEPs) are a major cause of cancer progression as well as a variety of acute and chronic diseases. It is well-known that programmed death-ligand 1 (PD-L1) is an immune checkpoint molecule that can induce immune escape in tumor cells. However, the function of PD-L1 in bronchial epithelial cells or how PD-L1 relates to cellular oxidation under DEPs-mediated oxidative stress is not well known. In this study, we investigated how PD-L1 affected DEPs-induced oxidative stress and cytotoxicity in human bronchial epithelial (HBE) cells, Beas-2B. DEPs not only induced intracellular reactive oxygen species (ROS) production, but also increased PD-L1 expression in HBE cells. Beas-2B cells overexpressing PD-L1 showed higher levels of ROS production, DNA damage, and apoptosis after DEPs treatment compared to control cells. In particular, the expression of an antioxidant enzyme heme-oxygenase-1 (HO-1) and nuclear translocation and transcriptional activity of Nrf2, a major regulator of HO-1, were lower in Beas-2B overexpressing PD-L1 cells than in control cells. DEPs-induced ROS generation, DNA damage and apoptosis in Beas-2B cells overexpressing PD-L1 were significantly restored by overexpressing HO-1. Collectively, our results suggest that DEPs can increase the expression of PD-L1 in HBE cells and that overexpressing PD-L1 might eventually promote DEPs-induced oxidative DNA damage and apoptosis.

Neurotoxicity of Diesel Exhaust Particles.

Air pollution particulate matter (PM) is strongly associated with risks of accelerated cognitive decline, dementia and Alzheimer's disease. Ambient PM batches have variable neurotoxicity by collection site and season, which limits replicability of findings within and between research groups for analysis of mechanisms and interventions. Diesel exhaust particles (DEP) offer a replicable model that we define in further detail. Define dose- and time course neurotoxic responses of mice to DEP from the National Institute of Science and Technology (NIST) for neurotoxic responses shared by DEP and ambient PM. For dose-response, adult C57BL/6 male mice were exposed to 0, 25, 50, and 100μg/m3 of re-aerosolized DEP (NIST SRM 2975) for 5 h. Then, mice were exposed to 100μg/m3 DEP for 5, 100, and 200 h and assayed for amyloid-β peptides, inflammation, oxidative damage, and microglial activity and morphology. DEP exposure at 100μg/m3 for 5 h, but not lower doses, caused oxidative damage, complement and microglia activation in cerebral cortex and corpus callosum. Longer DEP exposure for 8 weeks/200 h caused further oxidative damage, increased soluble Aβ, white matter injury, and microglial soma enlargement that differed by cortical layer. Exposure to 100μg/m3 DEP NIST SRM 2975 caused robust neurotoxic responses that are shared with prior studies using DEP or ambient PM0.2. DEP provides a replicable model to study neurotoxic mechanisms of ambient PM and interventions relevant to cognitive decline and dementia.

The effects of air pollutants exposure on the transmission and severity of invasive infection caused by an opportunistic pathogen Streptococcus pyogenes

Currently, urbanization is associated with an increase in air pollutants that contribute to invasive pathogen infections by altering the host's innate immunity and antimicrobial resistance capability. Streptococcus pyogenes, also known as Group A Streptococcus (GAS), is a gram-positive opportunistic pathogen that causes a wide range of diseases, especially in children and immunosuppressed individuals. Diesel exhaust particle (DEP), a significant constituent of particulate matter (PM), are considered a prominent risk factor for respiratory illness and circulatory diseases worldwide. Several clinical and epidemiological studies have identified a close association between PM and the prevalence of viral and bacterial infections. This study investigated the role of DEP exposure in increasing pulmonary and blood bacterial counts and mortality during GAS M1 strain infection in mice. Thus, we characterized the upregulation of reactive oxygen species production and disruption of tight junctions in the A549 lung epithelial cell line due to DEP exposure, leading to the upregulation of GAS adhesion and invasion. Furthermore, DEP exposure altered the leukocyte components of infiltrated cells in bronchoalveolar lavage fluid, as determined by Diff-Quik staining. The results highlighted the DEP-related macrophage dysfunction, neutrophil impairment, and imbalance in pro-inflammatory cytokine production via the toll-like receptor 4/mitogen-activated protein kinase signaling axis. Notably, the tolerance of the GAS biofilms toward potent antibiotics and bacterial resistance against environmental stresses was also significantly enhanced by DEP. This study aimed to provide a better understanding of the physiological and molecular interactions between exposure to invasive air pollutants and susceptibility to invasive GAS infections.

Repeated exposure of bronchial epithelial cells to particular matter increases allergen-induced cytokine release and permeability.

Long term particulate matter (PM) exposure has been associated with an increased incidence of respiratory diseases. Here, an in vitro model was developed to study how long term diesel exhaust particle (DEP) exposure might predispose to the development of allergic reactions. Airway epithelial (16HBE) cells were exposed to low concentrations of diesel exhaust particle (DEP) for 4days after which they were challenged with house dust mite (HDM) extract (24h). Compared to acute exposure (24h), 4days DEP exposure to 16HBE cells further reduced the transepithelial electrical resistance (TEER) and increased CXCL-8 release. DEP pre-exposure aggravated HDM-induced loss of TEER, increased tracer flux across the barrier and reduced CLDN-3 expression in these 16HBE cells. HDM-induced cytokine (IL-6, CCL-22, IL-10 and CXCL-8) release was significantly increased after DEP pre-exposure. In the current study an in vitro model with long term PM exposure was presented, which might be helpful for further understanding the interplay between long term PM exposure and allergic responses.

Ultrafine Diesel Exhaust Particles Induce Apoptosis of Oligodendrocytes by Increasing Intracellular Reactive Oxygen Species through NADPH Oxidase Activation.

Diesel exhaust particles (DEPs) are a main contributor to air pollution. Ultrafine DEPs can cause neurodegenerative diseases by increasing intracellular reactive oxygen species (ROS). Compared with other cells in the brain, oligodendrocytes responsible for myelination are more susceptible to oxidative stress. However, the mechanisms underlying ROS generation in oligodendrocytes and the susceptibility of oligodendrocytes to ROS by ultrafine DEPs remain unclear. Herein, we examined the effects of excessive ROS generated by NOX2, an isoform of the NADPH oxidase family, after exposure to ultrafine DEPs (200 μg/mL) on the survival of two types of oligodendrocytes—oligodendrocyte precursor cells (OPCs) and mature oligodendrocytes (mOLs)––isolated from the brain of neonatal rats. In addition, mice were exposed to ultrafine DEP suspension (20 μL, 0.4 mg/mL) via the nasal route for 1 week, after which the expression of NOX2 and cleaved caspase-3 was examined in the white matter of the cerebellum. Exposure to DEPs significantly increased NOX2 expression and ROS generation in OPCs and mOLs. OPCs and mOLs clearly exhibited viability reduction, and a significant change in p53, Bax, Bcl-2, and cleaved caspase-3 expression, after DEP exposure. In contrast, treatment with berberine (BBR), an NOX2 inhibitor, significantly mitigated these effects. In mice exposed to DEP, the presence of NOX2-positive and cleaved caspase-3-positive oligodendrocytes was demonstrated in the cerebellar white matter; NOX2 and cleaved caspase-3 expression in the cerebellum lysates was significantly increased. BBR treatment returned expression of these proteins to control levels. These results demonstrate that the susceptibility of OPCs and mOLs to ultrafine DEPs is, at least in part, caused by excessive ROS produced by NOX2 and the sequential changes in the expression of p53, Bax, Bcl-2, and cleaved caspase-3. Overall, NOX2 inhibitor enhances the survival of two types of oligodendrocytes.

Diesel exhaust particles alter cAMP dynamics in human bronchial epithelial cells

Diesel exhaust particles (DEP) are one of the main causes of air pollution and are associated with lung disorders. DEP exposure may promote several pathological processes, including epithelial‐to‐mesenchymal transition (EMT), inflammation and oxidative stress, which contribute to a decline in lung function. Cyclic AMP (cAMP) has been reported to alleviate lung dysfunction. The impact of DEP on cAMP signaling is largely unknown. Human bronchial epithelial (BEAS‐2B) cells were exposed to different concentrations (≤ 300 µg/ml) for up to 72 h. Markers of oxidative stress, inflammation, EMT, components of mitochondrial bioenergetics and cAMP signaling were evaluated. DEP increased gene expression of Nrf1, thioredoxin, HO‐1 and SOD‐2 (oxidative stress markers), and interleukin (IL)‐6 and IL‐8 (inflammatory markers), as well as the EMT marker transforming growth factor‐β1 (both mRNA and protein). Epithelial cell markers (E‐cadherin, ZO‐1) were reduced by DEP, whereas mesenchymal markers (β‐catenin, collagen‐1) were increased. DEP reduced both basal and ATP‐linked respiration as well as the glycolytic capacity of mitochondria. Concomitantly, DEP profoundly altered mitochondrial morphology and increased the gene expression of A‐kinase anchoring protein (AKAP) 1 (a known mitochondrial scaffold protein). Furthermore, DEP significantly affected Epac1 mRNA levels and appeared to increase Epac1 protein, but did not alter the expression of phospho‐PKA substrates. Interestingly, DEP increased gene expression levels of several AC family members (AC3, AC6 and AC7), the β2‐adrenoceptor (β2‐AR) and prostanoid E receptor subtype 4 (EP4). Importantly, real‐time measurements of cAMP demonstrated that DEP strongly reduced cAMP induced by forskolin (AC activator), fenoterol (β2‐AR agonist) and a stable EP4 agonist, implicating that DEP might limit the therapeutic effects of β2‐AR agonists used to treat lung disorders. Our findings suggest that DEP promotes oxidative stress, inflammation, and EMT. These profound alterations in cellular behavior were accompanied by changes in mitochondrial dysfunction and real‐time cAMP dynamics, which may contribute to lung dysfunction induced by air pollution exposure.

Probiotics Function as Immunomodulators in the Intestine in C57Bl/6 Male Mice Exposed to Inhaled Diesel Exhaust Particles on a High-Fat Diet.

Epidemiological studies reveal a correlation between air pollution exposure and gastrointestinal (GI) diseases, yet few studies have investigated the role of inhaled particulate matter on intestinal integrity in conjunction with a high-fat (HF) diet. Additionally, there is currently limited information on probiotics in mitigating air-pollutant responses in the intestines. Thus, we investigated the hypothesis that exposure to inhaled diesel exhaust particles (DEP) and a HF diet can alter intestinal integrity and inflammation, which can be attenuated with probiotics. 4–6-w-old male C57Bl/6 mice on a HF diet (45% kcal fat) were randomly assigned to be exposed via oropharyngeal aspiration to 35 µg of DEP suspended in 35 µL of 0.9% sterile saline or sterile saline (CON) only twice a week for 4 w. A subset of mice was treated with 0.3 g/day of Winclove Ecologic® barrier probiotics (PRO) in drinking water throughout the duration of the study. Our results show that DEP exposure ± probiotics resulted in increased goblet cells and mucin (MUC)-2 expression, as determined by AB/PAS staining. Immunofluorescent quantification and/or RT-qPCR showed that DEP exposure increases claudin-3, occludin, zona occludens (ZO)-1, matrix metalloproteinase (MMP)-9, and toll-like receptor (TLR)-4, and decreases tumor necrosis factor (TNF)-α and interleukin (IL)-10 expression compared to CON. DEP exposure + probiotics increases expression of claudin-3, occludin, ZO-1, TNF-α, and IL-10 and decreases MMP-9 and TLR-4 compared to CON + PRO in the small intestine. Collectively, these results show that DEP exposure alters intestinal integrity and inflammation in conjunction with a HF diet. Probiotics proved fundamental in understanding the role of the microbiome in protecting and altering inflammatory responses in the intestines following exposure to inhaled DEP.

Diesel exhaust particles distort lung epithelial progenitors and their fibroblast niche

Chronic obstructive pulmonary disease (COPD) is a progressive lung disease characterized by inflammation and impaired tissue regeneration, and is reported as the fourth leading cause of death worldwide by the Centers for Disease Control and Prevention (CDC). Environmental pollution and specifically motor vehicle emissions are known to play a role in the pathogenesis of COPD, but little is still known about the molecular mechanisms that are altered following diesel exhaust particles (DEP) exposure. Here we used lung organoids derived from co-culture of alveolar epithelial progenitors and fibroblasts to investigate the effect of DEP on the epithelial-mesenchymal signaling niche in the distal lung, which is essential for tissue repair. We found that DEP treatment impaired the number as well as the average diameter of both airway and alveolar type of lung organoids. Bulk RNA-sequencing of re-sorted epithelial cells and fibroblasts following organoid co-culture shows that the Nrf2 pathway, which regulates antioxidants' activity, was upregulated in both cell populations in response to DEP; and WNT/β-catenin signaling, which is essential to promote epithelial repair, was downregulated in DEP-exposed epithelial cells. We show that pharmacological treatment with anti-oxidant agents such as N-acetyl cysteine (NAC) or Mitoquinone mesylate (MitoQ) reversed the effect of DEP on organoids growth. Additionally, a WNT/β-catenin activator (CHIR99021) successfully restored WNT signaling and promoted organoid growth upon DEP exposure. We propose that targeting oxidative stress and specific signaling pathways affected by DEP in the distal lung may represent a strategy to restore tissue repair in COPD.

LSEA Evaluation of Lipid Mediators of Inflammation in Lung and Cortex of Mice Exposed to Diesel Air Pollution.

Airborne ultrafine particle (UFP) exposure is a great concern as they have been correlated to increased cardiovascular mortality, neurodegenerative diseases and morbidity in occupational and environmental settings. The ultrafine components of diesel exhaust particles (DEPs) represent about 25% of the emission mass; these particles have a great surface area and consequently high capacity to adsorb toxic molecules, then transported throughout the body. Previous in-vivo studies indicated that DEP exposure increases pro- and antioxidant protein levels and activates inflammatory response both in respiratory and cardiovascular systems. In cells, DEPs can cause additional reactive oxygen species (ROS) production, which attacks surrounding molecules, such as lipids. The cell membrane provides lipid mediators (LMs) that modulate cell-cell communication, inflammation, and resolution processes, suggesting the importance of understanding lipid modifications induced by DEPs. In this study, with a lipidomic approach, we evaluated in the mouse lung and cortex how DEP acute and subacute treatments impact polyunsaturated fatty acid-derived LMs. To analyze the data, we designed an ad hoc bioinformatic pipeline to evaluate the functional enrichment of lipid sets belonging to the specific biological processes (Lipid Set Enrichment Analysis-LSEA). Moreover, the data obtained correlate tissue LMs and proteins associated with inflammatory process (COX-2, MPO), oxidative stress (HO-1, iNOS, and Hsp70), involved in the activation of many xenobiotics as well as PAH metabolism (Cyp1B1), suggesting a crucial role of lipids in the process of DEP-induced tissue damage.