PM2.5 induced pulmonary fibrosis in vivo and in vitro

Melatonin prevents pulmonary fibrosis caused by PM2.5 exposure by targeting epithelial-mesenchymal transition

Pulmonary fibrosis is a lung disorder characterized by the accumulation of abnormal extracellular matrix, scar tissue formation, and tissue stiffness. Type II alveolar epithelial cells (AEII) play a critical role in repairing lung tissue after injury, and repeated injury to these cells is a key factor in the development of pulmonary fibrosis. Chronic exposure to PM2.5, a type of air pollution, has been shown to increase the incidence and severity of pulmonary fibrosis by enhancing the activation of EMT in lung epithelial cells. Melatonin, a hormone with antioxidant properties, has been shown to prevent EMT and reduce fibrosis in previous studies. However, the mechanism through which melatonin targets EMT to prevent pulmonary fibrosis caused by PM2.5 exposure has not been extensively discussed before. In this current study, we found that melatonin effectively prevented pulmonary fibrosis caused by prolonged exposure to PM2.5 by targeting EMT. The study demonstrated changes in cellular morphology and expression of EMT markers. Furthermore, the cell migratory potential induced by prolonged exposure to PM2.5 was greatly reduced by melatonin treatment. Finally, in vivo animal studies showed reduced EMT markers and improved pulmonary function. These findings suggest that melatonin has potential clinical use for the prevention of pulmonary fibrosis.

Atmospheric fine particulate matter (PM2.5) induces pulmonary fibrosis by regulating different cell fates via autophagy

The presence of respiratory diseases demonstrates a positive correlation with atmospheric fine particulate matter (PM2.5) exposure. The respiratory system is the main target organ affected by PM2.5, and exposure to PM2.5 elevates the likelihood of developing pulmonary fibrosis (PF). In this study, lung epithelial cell (BEAS-2B) and fibroblast (NIH-3T3) were used as in vitro exposure models to explore the mechanisms of PF. PM2.5 exposure caused mitochondrial damage in BEAS-2B cells and increased a fibrotic phenotype in NIH-3T3 cells. Epithelial cells and fibroblasts have different fates after PM2.5 exposure due to their different sensitivities to trigger autophagy. Exposure to PM2.5 inhibits mitophagy in BEAS-2B cells, which hinders the removal of damaged mitochondria and triggers cell death. In this process, the nuclear retention of the mitophagy-related protein Parkin prevents it from being recruited to mitochondria, resulting in mitophagy inhibition. In contrast, fibroblasts exhibit increased levels of autophagy, which may isolate PM2.5 and cause abnormal fibroblast proliferation and migration. Fibrotic phenotypes such as collagen deposition and increased α-actin also appear in fibroblasts. Our results identify PM2.5 as a trigger of PF and delineate the molecular mechanism of autophagy in PM2.5 induced PF, which provides new insights into the pulmonary injury.

Biomass fuels related-PM2.5 promotes lung fibroblast-myofibroblast transition through PI3K/AKT/TRPC1 pathway

Emerging evidence has suggested that exposure to PM2.5 is a significant contributing factor to the development of chronic obstructive pulmonary disease (COPD). However, the underlying biological effects and mechanisms of PM2.5 in COPD pathology remain elusive. In this study, we aimed to investigate the implication and regulatory effect of biomass fuels related-PM2.5 (BRPM2.5) concerning the pathological process of fibroblast-to-myofibroblast transition (FMT) in the context of COPD. In vivo experimentation revealed that exposure to biofuel smoke was associated with airway inflammation in rats. After 4 weeks of exposure, there was inflammation in the small airways, but no significant structural changes in the airway walls. However, after 24 weeks, airway remodeling occurred due to increased collagen deposition, myofibroblast proliferation, and tracheal wall thickness. In vitro, cellular immunofluorescence results showed that with stimulation of BRPM2.5 for 72 h, the cell morphology of fibroblasts changed significantly, most of the cells changed from spindle-shaped to star-shaped irregular, α-SMA stress fibers appeared in the cytoplasm and the synthesis of type I collagen increased. The collagen gel contraction experiment showed that the contractility of fibroblasts was enhanced. The expression level of TRPC1 in fibroblasts was increased. Specific siRNA-TRPC1 blocked BRPM2.5-induced FMT and reduced cell contractility. Additionally, specific siRNA-TRPC1 resulted in a decrease in the augment of intracellular Ca2+ concentration ([Ca2+]i) induced by BRPM2.5. Notably, it was found that the PI3K inhibitor, LY294002, inhibited enhancement of AKT phosphorylation level, FMT occurrence, and elevation of TRPC1 protein expression induced by BRPM2.5. The findings indicated that BRPM2.5 is capable of inducing the FMT, with the possibility of mediation by PI3K/AKT/TRPC1. These results hold potential implications for the understanding of the molecular mechanisms involved in BRPM2.5-induced COPD and may aid in the development of novel therapeutic strategies for pathological conditions characterized by fibrosis.

Assessment of cellular senescence potential of PM2.5 using 3D human lung fibroblast spheroids in vitro model

Background

Epidemiological studies demonstrate that particulate matter 2.5 (PM2.5) exposure closely related to chronic respiratory diseases. Cellular senescence plays an important role in many diseases. However, it is not fully clear whether PM2.5 exposure could induce cellular senescence in the human lung. In this study, we generated a three-dimensional (3D) spheroid model using isolated primary human lung fibroblasts (HLFs) to investigate the effects of PM2.5 on cellular senescence at the 3D level.

Methods

3D spheroids were exposed to 25-100 μg/ml of PM2.5 in order to evaluate the impact on cellular senescence. SA-β-galactosidase activity, cell proliferation, and the expression of key genes and proteins were detected.

Results

Exposure of the HLF spheroids to PM2.5 yielded a more sensitive cytotoxicity than 2D HLF cell culture. Importantly, PM2.5 exposure induced the rapid progression of cellular senescence in 3D HLF spheroids, with a dramatically increased SA-β-Gal activity. In exploiting the mechanism underlying the effect of PM2.5 on senescence, we found a significant increase of DNA damage, upregulation of p21 protein levels, and suppression of cell proliferation in PM2.5-treated HLF spheroids. Moreover, PM2.5 exposure created a significant inflammatory response, which may be at least partially associated with the activation of TGF-β1/Smad3 axis and HMGB1 pathway.

Conclusions

Our results indicate that PM2.5 could induce DNA damage, inflammation, and cellular senescence in 3D HLF spheroids, which may provide a new evidence for PM2.5 toxicity based on a 3D model which has been shown to be more in vivo-like in their phenotype and physiology than 2D cultures.

Pyrroloquinoline quinone ameliorates PM2.5-induced pulmonary fibrosis through targeting epithelial-mesenchymal transition

Pulmonary fibrosis is a lung disorder affecting the lungs that involves the overexpressed extracellular matrix, scarring and stiffening of tissue. The repair of lung tissue after injury relies heavily on Type II alveolar epithelial cells (AEII), and repeated damage to these cells is a crucial factor in the development of pulmonary fibrosis. Studies have demonstrated that chronic exposure to PM2.5, a form of air pollution, leads to an increase in the incidence and severity of pulmonary fibrosis by stimulation of epithelial-mesenchymal transition (EMT) in lung epithelial cells. Pyrroloquinoline quinone (PQQ) is a bioactive compound found naturally that exhibits potent anti-inflammatory and anti-oxidative properties. The mechanism by which PQQ prevents pulmonary fibrosis caused by exposure to PM2.5 through EMT has not been thoroughly discussed until now. In the current study, we discovered that PQQ successfully prevented PM2.5-induced pulmonary fibrosis by targeting EMT. The results indicated that PQQ was able to inhibit the expression of type I collagen, a well-known fibrosis marker, in AEII cells subjected to long-term PM2.5 exposure. We also found the alterations of cellular structure and EMT marker expression in AEII cells with PM2.5 incubation, which were reduced by PQQ treatment. Furthermore, prolonged exposure to PM2.5 considerably reduced cell migratory ability, but PQQ treatment helped in reducing it. In vivo animal experiments indicated that PQQ could reduce EMT markers and enhance pulmonary function. Overall, these results imply that PQQ might be useful in clinical settings to prevent pulmonary fibrosis.

Fine particulate matter PM2.5 and its constituent, hexavalent chromium induce acute cytotoxicity in human airway epithelial cells via inflammasome-mediated pyroptosis

PM2.5-induced airway injury contributes to an increased rate of respiratory morbidity. However, the relationship between PM2.5 toxicants and acute cytotoxic effects remains poorly understood. This study aimed to investigate the mechanisms of PM2.5- and its constituent-induced cytotoxicity in human airway epithelial cells. Exposure to PM2.5 resulted in dose-dependent cytotoxicity within 24 h. Among the PM2.5 constituents examined, Cr(VI) at the dose found in PM2.5 exhibited cytotoxic effects. Both PM2.5 and Cr(VI) cause necrosis while also upregulating the expression of proinflammatory cytokine transcripts. Interestingly, exposure to the conditioned PM, obtained from adsorption in the Cr(VI)-reducing agents, FeSO4 and EDTA, showed a decrease in cytotoxicity. Furthermore, PM2.5 mechanistically enhances programmed pyroptosis through the activation of NLRP3/caspase-1/Gasdermin D pathway and increase of IL-1β. These pyroptosis markers were reduced when exposure to conditioned PM. These findings provide a deeper understanding of mechanisms underlying PM2.5 and Cr(VI) in acute airway toxicity.

Effects of indoor air pollution on clinical outcomes in patients with interstitial lung disease: protocol of a multicentre prospective observational study

BACKGROUND

Idiopathic pulmonary fibrosis (IPF) is a chronic progressive fibrosing interstitial lung disease with a poor prognosis. While there is evidence suggesting that outdoor air pollution affects the clinical course of IPF, the impact of indoor air pollution on patients with IPF has not been extensively studied. Therefore, this prospective multicentre observational study aims to investigate the association between indoor air pollution and clinical outcomes in patients with IPF.

METHODS AND ANALYSIS

This study enrolled 140 patients with IPF from 12 medical institutes in the Seoul and Metropolitan areas of the Republic of Korea. Over the course of 1 year, participants visited the institutes every 3 months, during which their clinical data and blood samples were collected. Additionally, indoor exposure to particulate matter ≤2.5 µm (PM2.5) was measured using MicroPEM (RTI International, Research Triangle Park, North Carolina, USA) in each participant's house for 5 days every 3 months. Lung function was assessed using both site spirometry at each institution and portable spirometry at each participant's house every 3 months. The study will analyse the impact of indoor PM2.5 on clinical outcomes, including mortality, acute exacerbation, changes in lung function and health-related quality of life, in the participants. This study represents the first attempt to evaluate the influence of indoor air pollution on the prognosis of patients with IPF.

ETHICS AND DISSEMINATION

This study has received approval from the institutional review board of all participating institutions, including Asan Medical Center, Seoul, Republic of Korea (2021-0072).

TRIAL REGISTRATION NUMBER

KCT0006217.

Epigenetic mechanisms of particulate matter exposure: air pollution and hazards on human health

Environmental pollution nowadays has not only a direct correlation with human health changes but a direct social impact. Epidemiological studies have evidenced the increased damage to human health on a daily basis because of damage to the ecological niche. Rapid urban growth and industrialized societies importantly compromise air quality, which can be assessed by a notable accumulation of air pollutants in both the gas and the particle phases. Of them, particulate matter (PM) represents a highly complex mixture of organic and inorganic compounds of the most variable size, composition, and origin. PM being one of the most complex environmental pollutants, its accumulation also varies in a temporal and spatial manner, which challenges current analytical techniques used to investigate PM interactions. Nevertheless, the characterization of the chemical composition of PM is a reliable indicator of the composition of the atmosphere, the quality of breathed air in urbanized societies, industrial zones and consequently gives support for pertinent measures to avoid serious health damage. Epigenomic damage is one of the most promising biological mechanisms of air pollution-derived carcinogenesis. Therefore, this review aims to highlight the implication of PM exposure in diverse molecular mechanisms driving human diseases by altered epigenetic regulation. The presented findings in the context of pan-organic cancer, fibrosis, neurodegeneration and metabolic diseases may provide valuable insights into the toxicity effects of PM components at the epigenomic level and may serve as biomarkers of early detection for novel targeted therapies.

Protein lysine acetylation played an important role in NH3-induced AEC2 damage and pulmonary fibrosis in piglets

Gaseous ammonia (NH3), as a main air pollutant in pig farms and surrounding areas, directly affects animal and human health. The lung, as an important organ for gas exchange in the respiratory system, is damaged after NH3 exposure, but the underlying mechanism needs to be further explored. In this study, seven weeks old piglets were exposed to 50 ppm NH3 for 30 days, and displayed pulmonary fibrosis. Then, the toxicological mechanism of NH3-induced pulmonary fibrosis was explored from the aspects of whole genome wide protein expression and post-translational modification. Totally, 404 differentially expressed proteins (DEPs) and 136 differentially lysine acetylated proteins (DAPs) were identified. The expression or lysine acetylation levels of proteins involved in mitochondrial energy metabolism including fatty acid oxidation (CPT1A, ACADVL, ACADS, HADHA, and HADHB), TCA cycle (IDH2 and MDH2), and oxidative phosphorylation (NDUFB7, NDUFV1, ATP5PB, ATP5F1A, COX5A, and COX5B) were significantly changed after NH3 exposure, which suggested that NH3 disrupted mitochondrial energy metabolism in the lung of piglets. Next, we found that type 2 alveolar epithelial cells (AEC2) damaged after NH3 exposure in vivo and in vitro. Integrin-linked kinase (ILK) was enriched in focal adhesion pathway, and showed significantly up-regulated acetylation levels at K191 (FC = 2.99) and K209 sites (FC = 1.52) after NH3 exposure. We illustrated that ILK-K191 hyper-acetylation inhibited AEC2 proliferation and induced AEC2 apoptosis by down-regulating pAKT-S473 in vitro. In conclusion, for the first time, our study revealed that protein acetylation played an important role in the process of NH3-induced pulmonary fibrosis in piglets. Our findings provided valuable insights into toxicological harm of NH3 to human health.

Particulate matter-mediated oxidative stress induces airway inflammation and pulmonary dysfunction through TXNIP/NF-κB and modulation of the SIRT1-mediated p53 and TGF-β/Smad3 pathways in mice

Exposure to particulate matter is currently recognized as a serious aggravating factor of respiratory diseases. In this study, we investigated the effects of particulate matter (PM) on the respiratory system in BALB/c mice and NCI-H292 cells. PM (0, 2.5, 5 and 20 mg/kg) was administered to mice by intra-tracheal instillation for 7 days. After a 7 day-repeated treatment of PM, we evaluated inflammatory cytokines/cell counts in bronchoalveolar lavage fluid (BALF) and conducted pulmonary histology and functional test. We also investigated the role of TXNIP/NF-κB and SIRT1-mediated p53 and TGF-β/Smad3 pathways in PM-induced airway inflammation and pulmonary dysfunction. PM caused a significant increase in pro-inflammatory cytokines, inflammatory cell counts in bronchoalveolar lavage fluid. PM-mediated oxidative stress down-regulated thioredoxin-1 and up-regulated thioredoxin-interacting protein and activation of nuclear factor-kappa B in the lung tissue and PM-treated NCI-H292 cells. PM suppressed sirtuin1 protein levels and increased p53 acetylation in PM-exposed mice and PM-treated NCI-H292 cells. In addition, PM caused inflammatory cell infiltration and the thickening of alveolar walls by exacerbating the inflammatory response in the lung tissue. PM increased levels of transforming growth factor-β, phosphorylation of Smad3 and activation of α-smooth muscle actin, and collagen type1A2 in PM-exposed mice and PM-treated NCI-H292 cells. In pulmonary function tests, PM exposure impaired pulmonary function resembling pulmonary fibrosis, characterized by increased resistance and elastance of the respiratory system, and resistance, elastance, and damping of lung tissues, whereas decreased compliance of the respiratory system, forced expired volume and forced vital capacity. Overall, PM-mediated oxidative stress caused airway inflammation and pulmonary dysfunction with pulmonary fibrosis via TXNIP pathway/NF-κB activation and modulation of the SIRT1-mediated TGF-β/Smad3 pathways. The results of this study can provide fundamental data on the potential adverse effects and underlying mechanism of pulmonary fibrosis caused by PM exposure as a public health concern. Due to the potential toxicity of PM, people with respiratory disease must be careful with PM exposure.

Promotion of myofibroblast differentiation through repeated treatment of fibroblasts to low concentrations of PM2.5

Exposure to particulate matter ≤ 2.5 µm (PM2.5) is a risk factor for many lung diseases. Although the toxicologic effects of PM2.5 on airway epithelium are well-described, the effects of PM2.5 on fibroblasts in the lung are less studied. Here, we sought to examine the effects of PM2.5 on the differentiation of fibroblasts into myofibroblasts. Although a single treatment of fibroblasts did not result in a change in collagen or the myofibroblast marker α-SMA, exposing fibroblasts to sequential treatments with PM2.5 at low concentrations caused a robust increase in these proteins. Treatment of fibroblasts with IMD0354, an inhibitor to nuclear factor κB, but not with an antagonist to aryl hydrocarbon receptor, abolished the ability of PM2.5 to induce myofibroblast differentiation. These data demonstrate that potential impact of PM2.5 to fibroblast activation and fibrosis and support the importance of utilizing low concentrations and varying exposure protocols to toxicologic studies.

TGF-β Regulates m6A RNA Methylation after PM2.5 Exposure

PM2.5 exposure leads to a variety of respiratory diseases, including pulmonary fibrosis, metastatic lung cancer, etc. Exposure to PM2.5 results in the alteration of epigenetic modification. M6A RNA methylation is an essential epigenetic modification that regulates gene expression at the post-transcriptional level. Our previous study found that PM2.5 exposure up-regulated m6A RNA methylation and TGF-β expression level in the lung, but the mechanisms and pathways of PM2.5 regulation of m6A RNA methylation are still unclear. Moreover, a previous study reported that the TGF-β signal pathway could regulate m6A RNA methylation. Based on this evidence, we investigate the role of the TGF-β signaling pathway in PM2.5-induced m6A RNA methylation with the A549 cell line. Our results showed that PM2.5 could induce upregulation of m6A RNA methylation, accompanied by increased expression of TGF-β, Smad3, methyltransferase-like 3 (METTL3), methyltransferase-like 14 (METTL14). Furthermore, these alterations induced by PM2.5 exposure could be reversed by treatment with TGF-β inhibitor. Therefore, we speculated that the TGF-β signal pathway plays an indispensable role in regulating m6A RNA methylation after PM2.5 exposure. Our study demonstrates that PM2.5 exposure influences m6A RNA methylation by inducing the alteration of the TGF-β signal pathway, which could be an essential mechanism for lung-related diseases induced by PM2.5 exposure.

Oxidation 1-methyl naphthalene based on the synergy of environmentally persistent free radicals (EPFRs) and PAHs in particulate matter (PM) surface

Studies of the environmental fate through the interactions of particle-associated polycyclic aromatic hydrocarbons (PAHs) with environmentally persistent free radicals (EPFRs) are presented. The formation of PAHs and EPFRs typically occurs side by side during combustion-processes. The laboratory simulation studies of the model PAH molecule 1-Methylnaphthalene (1-MN) interaction with model EPFRs indicate a transformational synergy between these two pollutants due to mutual and matrix interactions. EPFRs, thorough its redox cycle result in the oxidation of PAHs into oxy-/hydroxy-PAHs. EPFRs have been shown before to produce OH radical during its redox cycle in aqueous media and this study has shown that produced OH radical can transform other PM constituents resulting in alteration of PM chemistry. In model PM, EPFRs driven oxidation process of 1-MN produced 1,4-naphthoquinone, 1-naphthaldehyde, 4-hydroxy-4-methylnaphthalen-1-one, and various isomers of (hydroxymethyl) naphthalene. Differences were observed in oxidation product yields, depending on whether EPFRs and PAHs were cohabiting the same PM or present on separate PM. This effect is attributed to the OH radical concentration gradient as a factor in the oxidation process, further strengthening the hypothesis of EPFRs' role in the PAH oxidation process. This finding is revealing new environmental role of EPFRs in a natural degradation process of PAHs. Additionally, it points to implications of such PM surface chemistry in the changing mobility of PAHs into an aqueous medium, thus increasing their bioavailability.

PM2.5 induced liver lipid metabolic disorders in C57BL/6J mice

PM2.5 can cause adverse health effects via several pathways, such as inducing pulmonary and systemic inflammation, penetration into circulation, and activation of the autonomic nervous system. In particular, the impact of PM2.5 exposure on the liver, which plays an important role in metabolism and detoxification to maintain internal environment homeostasis, is getting more attention in recent years. In the present study, C57BL/6J mice were randomly assigned and treated with PM2.5 suspension and PBS solution for 8 weeks. Then, hepatic tissue was prepared and identified by metabolomics analysis and transcriptomics analysis. PM2.5 exposure can cause extensive metabolic disturbances, particularly in lipid and amino acids metabolic dysregulation.128 differential expression metabolites (DEMs) and 502 differently expressed genes (DEGs) between the PM2.5 exposure group and control group were detected. The Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses showed that DEGs were significantly enriched in two disease pathways, non-alcoholic fatty liver disease (NAFLD) and type II diabetes mellitus (T2DM), and three signaling pathways, which are TGF-beta signaling, AMPK signaling, and mTOR signaling. Besides, further detection of acylcarnitine levels revealed accumulation in liver tissue, which caused restricted lipid consumption. Furthermore, lipid droplet accumulation in the liver was confirmed by Oil Red O staining, suggesting hepatic steatosis. Moreover, the aberrant expression of three key transcription factors revealed the potential regulatory effects in lipid metabolic disorders, the peroxisomal proliferative agent-activated receptors (PPARs) including PPARα and PPARγ is inhibited, and the activated sterol regulator-binding protein 1 (SREBP1) is overexpressed. Our results provide a novel molecular and genetic basis for a better understanding of the mechanisms of PM2.5 exposure-induced hepatic metabolic diseases, especially in lipid metabolism.

Toxicological Effects of Fine Particulate Matter (PM2.5): Health Risks and Associated Systemic Injuries-Systematic Review

Previous studies focused on investigating particulate matter with aerodynamic diameter ≤ 2.5 µm (PM2.5) have shown the risk of disease development, and association with increased morbidity and mortality rates. The current review investigate epidemiological and experimental findings from 2016 to 2021, which enabled the systemic overview of PM2.5's toxic impacts on human health. The Web of Science database search used descriptive terms to investigate the interaction among PM2.5 exposure, systemic effects, and COVID-19 disease. Analyzed studies have indicated that cardiovascular and respiratory systems have been extensively investigated and indicated as the main air pollution targets. Nevertheless, PM2.5 reaches other organic systems and harms the renal, neurological, gastrointestinal, and reproductive systems. Pathologies onset and/or get worse due to toxicological effects associated with the exposure to this particle type, since it can trigger several reactions, such as inflammatory responses, oxidative stress generation and genotoxicity. These cellular dysfunctions lead to organ malfunctions, as shown in the current review. In addition, the correlation between COVID-19/Sars-CoV-2 and PM2.5 exposure was also assessed to help better understand the role of atmospheric pollution in the pathophysiology of this disease. Despite the significant number of studies about PM2.5's effects on organic functions, available in the literature, there are still gaps in knowledge about how this particulate matter can hinder human health. The current review aimed to approach the main findings about the effect of PM2.5 exposure on different systems, and demonstrate the likely interaction of COVID-19/Sars-CoV-2 and PM2.5.

PM2.5 promotes pulmonary fibrosis by mitochondrial dysfunction

Pulmonary fibrosis is known as an incurable lung disorder with irreversible progression of chronic injury, myofibroblast proliferation, extracellular matrix (ECM) accumulation, and tissue scarring. Atmospheric particulate matter 2.5 (PM_2.5 ) is implicated as a risk factor of several diseases, especially lung diseases such as pulmonary fibrosis. The molecular mechanism which participates PM_2.5 -induced pulmonary fibrosis in type II alveolar cells (AEII) has yet to be determined. Our results proved that short- and long-term exposure to PM_2.5 significantly stimulated epithelial-mesenchymal transition (EMT) activity in AEII cells, according to, changes in gene signature analyzed by RNA-seq and cell morphology. Furthermore, Gene Ontology (GO) enrichment analysis also suggested that mitochondrial dysfunction was related to progression of pulmonary fibrosis in AEII after PM_2.5 exposure. We observed a marked decline in mitochondria membrane potential (MMP), as well as fragmented mitochondria, in AEII cells exposed to PM_2.5 , which suggests that energy metabolism is suppressed after PM_2.5 exposure. We also confirmed that PM_2.5 exposure could influence the expression levels of Mfn1, Mfn2, and Drp1 in AEII. Pretreatment of mitochondrial fusion promoter M1 was able to reverse mitochondrial dysfunction as well as EMT in AEII. These data suggested the key role of mitochondrial fragmentation in AEII, which was induced by PM_2.5 exposure, and participated pathogenesis of pulmonary fibrosis. Finally, we investigated the response of lung tissue exposed to PM_2.5 in vivo. The data indicated that the lung tissue exposed to PM_2.5 obviously induced collagen accumulation. Moreover, IHC results revealed that PM_2.5 enhanced Drp1 expression but suppressed Mfn1 and Mfn2 expression in lung tissue. The current study provides novel insight of pulmonary fibrosis caused by PM_2.5 exposure.

A Rodent Model of Human-Dose-Equivalent 5-Fluorouracil: Toxicity in the Liver, Kidneys, and Lungs

5-Fluorouracil (5-FU) is a chemotherapy drug widely used to treat a range of cancer types, despite the recurrence of adverse reactions. Therefore, information on its side effects when administered at a clinically recommended dose is relevant. On this basis, we examined the effects of the 5-FU clinical treatment on the integrity of the liver, kidneys, and lungs of rats. For this purpose, 14 male Wistar rats were divided into treated and control groups and 5-FU was administered at 15 mg/kg (4 consecutive days), 6 mg/kg (4 alternate days), and 15 mg/kg on the 14th day. On the 15th day, blood, liver, kidney, and lung samples were collected for histological, oxidative stress, and inflammatory evaluations. We observed a reduction in the antioxidant markers and an increase in lipid hydroperoxides (LOOH) in the liver of treated animals. We also detected elevated levels of inflammatory markers, histological lesions, apoptotic cells, and aspartate aminotransferase. Clinical treatment with 5-FU did not promote inflammatory or oxidative alterations in the kidney samples; however, histological and biochemical changes were observed, including increased serum urea and uric acid. 5-FU reduces endogenous antioxidant defenses and increases LOOH levels in the lungs, suggesting oxidative stress. Inflammation and histopathological alterations were also detected. The clinical protocol of 5-FU promotes toxicity in the liver, kidneys, and lungs of healthy rats, resulting in different levels of histological and biochemical alterations. These results will be useful in the search for new adjuvants to attenuate the adverse effects of 5-FU in such organs.

MitoQ ameliorates PM2.5-induced pulmonary fibrosis through regulating the mitochondria DNA homeostasis

Pulmonary fibrosis is a severe pulmonary disease, and may related to PM_2.5 exposure. Our study aims to explore the pathogenesis of PM_2.5-induced pulmonary fibrosis, and MitoQ protective effect in this process. Our results find that inflammatory cells aggregation and pulmonary fibrosis in mice lung after PM_2.5 exposure. Moreover, Collagen I/III overproduction, EMT and TGF-β1/Smad2 pathway activation in mice lung and BEAS-2B after PM_2.5 exposure. Fortunately, these changes were partially ameliorated after MitoQ treatment. Meanwhile, severe oxidative stress, mitochondrial homeostasis imbalance, overproduction of 8-oxoG (7,8-dihydro-8-oxoguanine), as well as the inhibition of SIRT3/OGG1 pathway have founded in mice lung or BEAS-2B after PM_2.5 exposure, which were alleviated by MitoQ treatment. Collectively, our study found that oxidative stress, especially mitochondrial oxidative stress participates in the PM_2.5-induced pulmonary fibrosis, and MitoQ intervention had a protective effect on this progress. Moreover, mitochondrial DNA homeostasis might participate in the pulmonary fibrosis caused by PM_2.5 exposure. Our study provides a novel pathogenesis of PM_2.5-caused pulmonary fibrosis and a possible targeted therapy for the pulmonary diseases triggered by PM_2.5.

Calcium oxalate crystal-induced secretome derived from proximal tubular cells, not that from distal tubular cells, induces renal fibroblast activation

BACKGROUND

Kidney stone disease (KSD) is commonly accompanied with renal fibrosis, characterized by accumulation and reorganization of extracellular matrix (ECM). During fibrogenesis, resident renal fibroblasts are activated to become myofibroblasts that actively produce ECM. However, such fibroblast-myofibroblast differentiation in KSD remained unclear. Our present study thus examined effects of secreted products (secretome) derived from proximal (HK-2) vs. distal (MDCK) renal tubular cells exposed to calcium oxalate monohydrate (COM) crystals on activation of renal fibroblasts (BHK-21).

METHODS

HK-2 and MDCK cells were treated with 100 µg/ml COM crystals under serum-free condition for 16 h. In parallel, the cells maintained in serum-free medium without COM treatment served as the control. Secretome derived from culture supernatant of each sample was mixed (1:1) with fresh serum-free medium and then used for BHK-21 culture for another 24 h.

RESULTS

Analyses revealed that COM-treated-HK-2 secretome significantly induced proliferation, caused morphological changes, increased spindle index, and upregulated fibroblast-activation markers (F-actin, α-SMA and fibronectin) in BHK-21 cells. However, COM-treated-MDCK secretome had no significant effects on these BHK-21 parameters. Moreover, level of transforming growth factor-β1 (TGF-β1), a profibrotic factor, significantly increased in the COM-treated-HK-2 secretome but not in the COM-treated-MDCK secretome.

CONCLUSIONS

These data indicate, for the first time, that proximal and distal tubular epithelial cells exposed to COM crystals send different messages to resident renal fibroblasts. Only the secretome derived from proximal tubular cells, not that from the distal cells, induces renal fibroblast activation after their exposure to COM crystals. Such differential effects are partly due to TGF-β1 secretion, which is induced by COM crystals only in proximal tubular cells.

NAT10 accelerates pulmonary fibrosis through N4-acetylated TGFB1-initiated epithelial-to-mesenchymal transition upon ambient fine particulate matter exposure

Exposure to ambient fine particulate matter (PM_2.5) has been linked to a higher pulmonary fibrosis risk. Dysregulation of the epitranscriptome results in abnormal expression of mRNAs during fibrosis development. N4-acetylcytidine (ac4C) is one of the most frequent RNA epigenetic alterations, however, its function in PM_2.5-triggered fibrosis is yet unknown. In this study, lung epithelial and murine models were established and exposed to PM_2.5 to analyze the function of ac4C alteration in pulmonary fibrosis and underlying mechanisms. Meanwhile, the expression levels of only known ac4C "writer" protein, N-acetyltransferase 10 (NAT10), were significantly induced in pulmonary epithelia, relative to the control. Subsequently, NAT10 enhanced the stability of transforming growth factor beta 1 (TGFB1) mRNA as well as protein levels. As an up-stream driver, TGFB1 accelerated EMT and fibrosis process. Inhibition of NAT10 significantly protected against pulmonary EMT and fibrosis driven by PM_2.5 exposure, whereas TGFB1 overexpression reversed the protective effects of NAT10 inhibition. Thus, NAT10 accelerated PM_2.5-triggered pulmonary fibrosis via increasing TGFB1 mRNA stability in an ac4C-dependent manner. Our results reveal a pivotal role of NAT10-regulated mRNA ac4C acetylation in PM_2.5-triggered pulmonary fibrosis and uncover the potential epitranscriptional mechanism.

Coal dust nanoparticles induced pulmonary fibrosis by promoting inflammation and epithelial-mesenchymal transition via the NF-κB/NLRP3 pathway driven by IGF1/ROS-mediated AKT/GSK3β signals

Pneumoconiosis is the most common and serious disease among coal miners. In earlier work on this subject, we documented that coal dust (CD) nanoparticles (CD-NPs) induced pulmonary fibrosis (PF) more profoundly than did CD micron particles (CD-MPs), but the mechanism has not been thoroughly studied. Based on the GEO database, jveen, STRING, and Cytoscape tools were used to screen hub genes regulating PF. Particle size distribution of CD were analyzed with Malvern nanoparticle size potentiometer. Combining 8 computational methods, we found that IGF1, POSTN, MMP7, ASPN, and CXCL14 may act as hub genes regulating PF. Based on the high score of IGF1 and its important regulatory role in various tissue fibrosis, we selected it as the target gene in this study. Activation of the IGF1/IGF1R axis promoted CD-NPs-induced PF, and inhibition of the axis activation had the opposite effect in vitro and in vivo. Furthermore, activation of the IGF1/IGF1R axis induced generation of reactive oxygen species (ROS) to promote epithelial-mesenchymal transition (EMT) in alveolar epithelial cells (AECs) to accelerate PF. High-throughput gene sequencing based on lung tissue suggested that cytokine-cytokine receptor interaction and the NF-kB signaling pathway play a key role in PF. Also, ROS induced inflammation and EMT by the activation of the NF-kB/NLRP3 axis to accelerate PF. ROS can induce the activation of AKT/GSK3β signaling, and inhibition of it can inhibit ROS-induced inflammation and EMT by the NF-kB/NLRP3 axis, thereby inhibiting PF. CD-NPs induced PF by promoting inflammation and EMT via the NF-κB/NLRP3 pathway driven by IGF1/ROS-mediated AKT/GSK3β signals. This study provides a valuable experimental basis for the prevention and treatment of coal workers' pneumoconiosis. Illustration of the overall research idea of this study: IGF1 stimulates coal dust nanoparticles induced pulmonary fibrosis by promoting inflammation and EMT via the NF-κB/NLRP3 pathway driven by ROS-mediated AKT/GSK3β signals.

Different exposure modes of PM2.5 induces bronchial asthma and fibrosis in male rats through macrophage activation and immune imbalance induced by TIPE2 methylation

Exposure to PM_2.5 can aggravate the occurrence and development of bronchial asthma and fibrosis. Here, we investigated the differences in bronchial injury caused by different exposure modes of PM_2.5 (high concentration intermittent exposure and low concentration continuous exposure), and the mechanism of macrophage activation and respiratory immune imbalance induced by PM_2.5, leading to bronchial asthma and airway fibrosis using animal and cell models. A "PM_2.5 real-time online concentrated animal whole-body exposure system" was used to conduct PM_2.5 respiratory exposure of Wistar rats for 12 weeks, which can enhance oxidative stress in rat bronchus, activate epithelial cells and macrophages, release chemokines, recruit inflammatory cells, release inflammatory factors and extracellular matrix, promote bronchial mucus hypersecretion, inhibit the expression of epithelial cytoskeletal proteins, destroy airway barrier, and induce asthma. Furthermore, PM_2.5 induced M2 polarization in lung bronchial macrophages through JAK/STAT and PI3K/Akt signaling pathways, and compared with low concentration continuous exposure, high concentration intermittent exposure of PM_2.5 could regulate significantly higher expression of TIPE2 protein through promoter methylation of TIPE2 DNA, thereby activating PI3K/Akt signaling pathway and more effectively inducing M2 polarization of macrophages. Additionally, activated macrophages release IL-23, and activated epithelial cells and macrophages released TGF-β1, which promoted the differentiation of Th17 cells, triggered the Th17 dominant immune response, and activated the TGF-β1/Smad2 signaling pathway, finally causing bronchial fibrosis. Moreover, when the total amount of PM_2.5 exposure was equal, high concentration-intermittent exposure was more serious than low concentration-continuous exposure. In vitro experiments, the co-culture models of PM_2.5 with BEAS-2B, WL-38 and rat primary alveolar macrophages further confirmed that PM_2.5 could induce the macrophage activation through oxidative stress and TIPE2 DNA methylation, and activate the TGF-β1/Smad2 signaling pathway, leading to the occurrence of bronchial fibrosis.

Long-term exposure to PM2.5 aggravates pulmonary fibrosis and acute lung injury by disrupting Nrf2-mediated antioxidant function

Epidemiological studies have indicated that exposure to ambient air-borne fine particulate matter (PM2.5) is associated with many cardiopulmonary diseases; however, the underlying pathological mechanisms of PM2.5-induced lung injury remain unknown. In this study, we aimed to assess the impact of acute or prolonged exposure to water-insoluble fractions of PM2.5 (PM2.5 particulate) on lung injury and its molecular mechanisms. Balb/c mice were randomly exposed to PM2.5 once (acute exposure) or once every three days for a total of 6 times (prolonged exposure). Lung, BALF and blood samples were collected, and pulmonary pathophysiological alterations were analyzed. Nrf2 knockout mice were adapted to assess the involvement of Nrf2 in lung injury, and transcriptomic analysis was performed to delineate the mechanisms. Through transcriptomic analysis and validation of Nrf2 knockout mice, we found that acute exposure to PM2.5 insoluble particulates induced neutrophil infiltration-mediated airway inflammation, whereas prolonged exposure to PM2.5 insoluble particulate triggered lung fibrosis by decreasing the transcriptional activity of Nrf2, which resulted in the downregulated expression of antioxidant-related genes. In response to secondary LPS exposure, prolonged PM2.5 exposure induced more severe lung injury, indicating that prolonged PM2.5 exposure induced Nrf2 inhibition weakened its antioxidative defense capacity against oxidative stress injury, leading to the formation of pulmonary fibrosis and increasing its susceptibility to secondary bacterial infection.

Effects of Different Concentrations of Oil Mist Particulate Matter on Pulmonary Fibrosis In Vivo and In Vitro

Oil-mist particulate matter (OMPM) refers to oily particles with a small aerodynamic equivalent diameter in ambient air. Since the pathogenesis of pulmonary fibrosis (PF) has not been fully elucidated, this study aims to explore the potential molecular mechanisms of the adverse effects of exposure to OMPM at different concentrations in vivo and in vitro on PF. In this study, rats and cell lines were treated with different concentrations of OMPM in vivo and in vitro. Sirius Red staining analysis shows that OMPM exposure could cause pulmonary lesions and fibrosis symptoms. The expression of TGF-β1, α-SMA, and collagen I was increased in the lung tissue of rats. The activities of MMP2 and TIMP1 were unbalanced, and increased N-Cadherin and decreased E-Cadherin upon OMPM exposure in a dose-dependent manner. In addition, OMPM exposure could activate the TGF-β1/Smad3 and TGF-β1/MAPK p38 signaling pathways, and the differentiation of human lung fibroblast HFL-1 cells. Therefore, OMPM exposure could induce PF by targeting the lung epithelium and fibroblasts, and activating the TGF-β1/Smad3 and TGF-β1/MAPK p38 signaling pathways.

Dimethylarginine dimethylaminohydrolase 1 protects PM2.5 exposure-induced lung injury in mice by repressing inflammation and oxidative stress

BACKGROUND

Airborne fine particulate matter with aerodynamic diameter ≤ 2.5 μm (PM_2.5) pollution is associated with the prevalence of respiratory diseases, including asthma, bronchitis and chronic obstructive pulmonary disease. In patients with those diseases, circulating asymmetric dimethylarginine (ADMA) levels are increased, which contributes to airway nitric oxide deficiency, oxidative stress and inflammation. Overexpression of dimethylarginine dimethylaminohydrolase 1 (DDAH1), an enzyme degrading ADMA, exerts protective effects in animal models. However, the impact of DDAH1/ADMA on PM_2.5-induced lung injury has not been investigated.

METHODS

Ddah1^-/- and DDAH1-transgenic mice, as well as their respective wild-type (WT) littermates, were exposed to either filtered air or airborne PM_2.5 (mean daily concentration ~ 50 µg/m³) for 6 months through a whole-body exposure system. Mice were also acutely exposed to 10 mg/kg PM_2.5 and/or exogenous ADMA (2 mg/kg) via intratracheal instillation every other day for 2 weeks. Inflammatory response, oxidative stress and related gene expressions in the lungs were examined. In addition, RAW264.7 cells were exposed to PM_2.5 and/or ADMA and the changes in intracellular oxidative stress and inflammatory response were determined.

RESULTS

Ddah1^-/- mice developed more severe lung injury than WT mice after long-term PM_2.5 exposure, which was associated with greater induction of pulmonary oxidative stress and inflammation. In the lungs of PM_2.5-exposed mice, Ddah1 deficiency increased protein expression of p-p65, iNOS and Bax, and decreased protein expression of Bcl-2, SOD1 and peroxiredoxin 4. Conversely, DDAH1 overexpression significantly alleviated lung injury, attenuated pulmonary oxidative stress and inflammation, and exerted opposite effects on those proteins in PM_2.5-exposed mice. In addition, exogenous ADMA administration could mimic the effect of Ddah1 deficiency on PM_2.5-induced lung injury, oxidative stress and inflammation. In PM_2.5-exposed macrophages, ADMA aggravated the inflammatory response and oxidative stress in an iNOS-dependent manner.

CONCLUSION

Our data revealed that DDAH1 has a marked protective effect on long-term PM_2.5 exposure-induced lung injury.

Metabolic profiling disturbance of PM2.5 revealed by Raman spectroscopy and mass spectrometry-based nontargeted metabolomics

Fine particulate matter (PM_2.5) is an important risk factor affecting human health. Therefore, a quick method for finding metabolic targets in situ in ambient fine particulate matter is crucial. In this study, the impact of PM_2.5 on human lung epithelial cells (A549) was investigated by Raman spectroscopy and mass spectrometry (MS)-based nontargeted metabolomics analysis. Raman detection indicated that exposure to PM_2.5 reduced the levels of phenylalanine, tyrosine, and nucleotides. Metabolomics results not only demonstrated a significant decrease of the aforementioned metabolites but also added some important metabolite information that could not be detected by Raman spectroscopy. Our study demonstrated that Raman spectroscopy was an in situ, real-time, and rapid detection method for detecting metabolites, especially suitable for the assignment of phenylalanine/tyrosine and nucleotides, which play important roles in cellular growth. Moreover, the metabolic profiling changes observed upon PM_2.5 treatment mainly involved phenylalanine, tyrosine metabolism, purine and pyrimidine metabolism, and energy metabolism, clearly demonstrating that PM_2.5 can inhibit the synthesis of protein and DNA/RNA and reduce cellular energy supplies, further influencing cellular proliferation and other activities.

Effects of air pollution on human health - Mechanistic evidence suggested by in vitro and in vivo modelling

Airborne particulate matter (PM) comprises both solid and liquid particles, including carbon, sulphates, nitrate, and toxic heavy metals, which can induce oxidative stress and inflammation after inhalation. These changes occur both in the lung and systemically, due to the ability of the small-sized PM (i.e. diameters ≤2.5 μm, PM_2.5) to enter and circulate in the bloodstream. As such, in 2016, airborne PM caused ∼4.2 million premature deaths worldwide. Acute exposure to high levels of airborne PM (eg. during wildfires) can exacerbate pre-existing illnesses leading to hospitalisation, such as in those with asthma and coronary heart disease. Prolonged exposure to PM can increase the risk of non-communicable chronic diseases affecting the brain, lung, heart, liver, and kidney, although the latter is less well studied. Given the breadth of potential disease, it is critical to understand the mechanisms underlying airborne PM exposure-induced disorders. Establishing aetiology in humans is difficult, therefore, in-vitro and in-vivo studies can provide mechanistic insights. We describe acute health effects (e.g. exacerbations of asthma) and long term health effects such as the induction of chronic inflammatory lung disease, and effects outside the lung (e.g. liver and renal change). We will focus on oxidative stress and inflammation as this is the common mechanism of PM-induced disease, which may be used to develop effective treatments to mitigate the adverse health effect of PM exposure.

Characterization of persistent materials of deposited PM2.5 in the human lung

Clearance of deposited urban air particulates (PMs) from the lung is vital for the protection of the lung tissue. Several studies have investigated the behavior of immune cells against these particulates in vitro and in vivo. However, the fate of particulates in the lung is yet unclear. Here, we report the results of our investigations on the clearance of particulates from the lung. Twelve normal lung tissue samples were taken from nonsmoking and non-occupationally exposed patients who needed lung lobectomy or segmentectomy. The remaining particulates were isolated from the alveolar area and extracellular matrix (ECM), separately, and their chemical composition was determined using the FE-SEM EDAX and GC-MS. Moreover, urban air PM_2.5 was collected in two forms dry and washed. These were characterized too. Our results showed that none of the metals in the deposited particulates structure is fully water-soluble. After contact with mucosal liquid, the alveolar particulates included Fe, Al, Si, Ti, and Ni. These elements were absent in the PMs isolated from ECM. The organics of alveolar and ECM particulates were the same and included tetra-decane, hexadecane, and octa-decane. None of the organics present in the urban air PM_2.5, such as PAHs, were available in isolated particulates from the lung tissue. This study shows that the full clearance of inhaled particulates does not happen in the lung. The immune system's primary function is detoxification by removing all components identifiable by immune cells. After that, the remained PMs will be relocated and deposited into the ECM.

Lung microbiome and transcriptome reveal mechanisms underlying PM2.5 induced pulmonary fibrosis

Airborne fine particulate matter (PM_2.5) is considered to be a risk factor for lung fibrosis, and therefore, it has attracted public attention due to its various physicochemical features and its adverse effects on health. However, little remains to be known regarding the mechanism of PM_2.5-induced pulmonary fibrosis. The lung microbiota may be a potential factor involved in the adverse outcomes of pulmonary fibrosis. Meanwhile, miRNAs are thought to be key regulators that participate in the complex interplay between the host and the microbiota. Hence, to investigate the potential mechanisms of pulmonary fibrosis, and to explore the impact of PM_2.5-induced alterations in miRNAs and the lung microbiota and possible interaction patterns in mice models, we took advantage of 16S rDNA gene sequencing, miRNAs sequencing (miRNAs-Seq), and mining of public databases profiling. The results of 16S rDNA analysis showed that PM_2.5 interfered with the microbial community composition, resulting in Proteobacteria becoming an additional dominant phylum. In addition, differentially expressed miRNAs were enriched in HIF-1 signaling, the IL-17 signaling, as well as Th17 cell differentiation pathways, which are closely related to microbial functional pathways. Significantly, a target miRNA, miR-149-5p, may be a key factor triggering the MAPK signal pathway related to pulmonary fibrosis and disturbing the homeostasis of lung bacterial flora. These results indicate that PM_2.5 may lead to interaction between lung microbiota dysbiosis and an imbalance of miRNA levels to form a vicious cycle that promotes lung fibrogenesis. The current study provides new insights into the progression of pulmonary fibrosis.

Lung toxicity of particulates and gaseous pollutants using ex-vivo airway epithelial cell culture systems

Air pollution consists of a multi-faceted mix of gases and ambient particulate matter (PM) with diverse organic and non-organic chemical components that contribute to increasing morbidity and mortality worldwide. In particular, epidemiological and clinical studies indicate that respiratory health is adversely affected by exposure to air pollution by both causing and worsening (exacerbating) diseases such as chronic obstructive pulmonary disease (COPD), asthma, interstitial pulmonary fibrosis and lung cancer. The molecular mechanisms of air pollution-induced pulmonary toxicity have been evaluated with regards to different types of PM of various sizes and concentrations with single and multiple exposures over different time periods. These data provide a plausible interrelationship between cellular toxicity and the activation of multiple biological processes including proinflammatory responses, oxidative stress, mitochondrial oxidative damage, autophagy, apoptosis, cell genotoxicity, cellular senescence and epithelial-mesenchymal transition. However, these molecular changes have been studied predominantly in cell lines rather than in primary bronchial or nasal cells from healthy subjects or those isolated from patients with airways disease. In addition, they have been conducted under different cell culture conditions and generally in submerged culture rather than the more relevant air-liquid interface culture and with a variety of air pollutant exposure protocols. Cell types may respond differentially to pollution delivered as an aerosol rather than being bathed in media containing agglomerations of particles. As a result, the actual pathophysiological pathways activated by different PMs in primary cells from the airways of healthy and asthmatic subjects remains unclear. This review summarises the literature on the different methodologies utilised in studying the impact of submicron-sized pollutants on cells derived from the respiratory tract with an emphasis on data obtained from primary human cell. We highlight the critical underlying molecular mechanisms that may be important in driving disease processes in response to air pollution in vivo.

The Physiological Effects of Air Pollution: Particulate Matter, Physiology and Disease

Nine out of 10 people breathe air that does not meet World Health Organization pollution limits. Air pollutants include gasses and particulate matter and collectively are responsible for ~8 million annual deaths. Particulate matter is the most dangerous form of air pollution, causing inflammatory and oxidative tissue damage. A deeper understanding of the physiological effects of particulate matter is needed for effective disease prevention and treatment. This review will summarize the impact of particulate matter on physiological systems, and where possible will refer to apposite epidemiological and toxicological studies. By discussing a broad cross-section of available data, we hope this review appeals to a wide readership and provides some insight on the impacts of particulate matter on human health.

Pathogenic Mechanisms of Secondary Organic Aerosols

Air pollution represents a major health problem and an economic burden. In recent years, advances in air pollution research has allowed particle fractionation and identification of secondary organic aerosol (SOA). SOA is formed from either biogenic or anthropogenic emissions, through a mass transfer from the gaseous mass to the particulate phase in the atmosphere. They can have deleterious impact on health and the mortality of individuals with chronic inflammatory diseases. The pleiotropic effects of SOA could involve different and interconnected pathogenic mechanisms ranging from oxidative stress, inflammation, and immune system dysfunction. The purpose of this review is to present recent findings about SOA pathogenic roles and potential underlying mechanisms focusing on the lungs; the latter being the primary exposed organ to atmospheric pollutants.

Inhaled tire-wear microplastic particles induced pulmonary fibrotic injury via epithelial cytoskeleton rearrangement

Tire wear microplastic particles (TWMPs) are emerging microplastic pollutants that have gained increasing attention lately. However, the health effect of inhaled airborne TWMPs has never been explored before and may already be included in particulate matter morbidity and mortality. Here, we endeavored to address the preliminary study of TWMP inhalation-induced pulmonary toxic effects and its epigenetic mechanisms in C57BL/6 mice. As a result, restricted ventilatory dysfunction and fibrotic pathological changes were observed in TWMP-treaded mice. Further research found that attenuation of miR-1a-3p plays an important role in TWMP-induced lung injury. Results from in vitro study confirmed that cytoskeleton regulatory gene twinfilin-1 was one of the target genes of miR-1a-3p, and involved in cytoskeleton rearrangement caused by TWMP exposure. Mechanistically, miR-1a-3p inhibited the F-actin formation by targeting cytoskeletal regulatory proteins twinfilin-1, leading to TWMP-induced pulmonary fibrotic injury. While we are in the very early stages of explaining the role of epigenetics in TWMP-induced lung injury, the potential for the use of epigenetic marks as biomarkers is high and discoveries made in this field will likely bring us closer to better understanding this crucial mechanism.

Study on Lung Injury Caused by Fine Particulate Matter and Intervention Effect of Rhodiola wallichiana

Objective

The objective of this study was to observe the protective effect of Rhodiola wallichiana drops in a rat model of fine particulate matter (PM2.5) lung injury.

Methods

Forty male Wistar rats were randomly divided into blank control (NC), normal saline (NS), PM2.5-infected (PM), and Rhodiola wallichiana (RW) groups. Rats in the NC group were not provided any interventions, whereas those in the NS and PM groups were administered normal saline and PM2.5 suspension by trachea drip once a week for four weeks. Rats in the RW group were intraperitoneally administered Rhodiola wallichiana for 14 days and then administered PM2.5 suspension by trachea drip 7 days after drug delivery. The levels of inflammatory factors such as interleukin-6, interleukin-1β, and tumor necrosis factor-alpha and oxidative stress biomarkers such as 8-hydroxy-2′-deoxyguanosine, 4-hydroxynonenal, and protein carbonyl content were determined in the serum and bronchoalveolar lavage fluid by ELISA. The level of 4-hydroxynonenal in the lung was also determined using Western blotting and immunohistochemical staining.

Results

Levels of inflammatory factors and oxidative stress biomarkers were all increased in the PM group but decreased in the RW group. Western blotting revealed increased 4-hydroxynonenal levels in the PM group but decreased levels in the RW group. Immunohistochemical staining also provided similar results.

Conclusion

Rhodiola wallichiana could protect rats from inflammation and oxidative stress injury caused by PM2.5.

High throughput data-based, toxicity pathway-oriented development of a quantitative adverse outcome pathway network linking AHR activation to lung damages

The quantitative adverse outcome pathway (qAOP) is proposed to inform dose-responses at multiple biological levels for the purpose of toxicity prediction. So far, qAOP models concerning human health are scarce. Previously, we proposed 5 key molecular pathways that led aryl hydrogen receptor (AHR) activation to lung damages. The present study assembled an AOP network based on the gene expression signatures of these toxicity pathways, and validated the network using publicly available high throughput data combined with machine learning models. In addition, the AOP network was quantitatively evaluated with omics approaches and bioassays, using 16HBE-CYP1A1 cells exposed to benzo(a)pyrene (BaP), a prototypical AHR activator. Benchmark dose (BMD) analysis of transcriptomics revealed that AHR gene held the lowest BMD value, whereas AHR pathway held the lowest point of departure (PoD) compared to the other 4 pathways. Targeted bioassays were further performed to quantitatively understand the cellular responses, including ROS generation, DNA damage, interleukin-6 production, and extracellular matrix increase marked by collagen expression. Eventually, response-response relationships were plotted using nonlinear model fitting. The present study developed a highly reliable AOP model concerning human health, and validated as well as quantitatively evaluated it, and such a method is likely to be adoptable for risk assessment.

Multi-omics analysis to reveal disorders of cell metabolism and integrin signaling pathways induced by PM2.5

Atmospheric fine particle pollution is known to cause many adverse health effects. However, the potential mechanisms of PM_2.5-induced cytotoxicity still needs further understanding. Herein, we integrated cytotoxicity, component profiling, metabolomics and proteomics data to deeply explain the biological responses of human bronchial epithelial cells exposed to PM_2.5. We observed that PM_2.5 caused cell cycle arrest, calcium influx, cell damage and further induced cell apoptosis. The contents of heavy metals and 4-6 rings PAHs in PM_2.5 were positively correlated with intracellular ROS, indicating that they might be the important components to induce the above cytotoxicity. Integrated metabolomics and proteomics analysis revealed the significant alterations of many metabolic processes, such as glycolysis, the citric acid cycle, amino acid metabolism and lipid metabolism. Notably, we found that PM_2.5 inhibited the integrin signaling pathway, including down-regulating the protein expression of integrins and the phosphorylation of downstream signaling kinases, which might ultimately affect cell cycle progression, cell metabolism and apoptosis. This study provided a comprehensive data resource for the deep understanding of biological toxicity mechanisms caused by atmospheric fine particles in human lung-bronchial epithelium cells.

Diesel exhaust exposure in mice induces pulmonary fibrosis by TGF-β/Smad3 signaling pathway

BACKGROUND

Epidemiological studies suggest increased risk of lung cancer associated with diesel exhaust (DE) exposure. However, DE-induced lung fibrosis may lead to cancer and needs investigation.

OBJECTIVES

To study the mechanism involved in the initiation of DE- induced lung fibrosis.

METHODS

C57BL/6 mice were exposed to DE for 30 min/day for 5 days/weeks for 8 weeks. Pulmonary function test was performed to measure lung function. Mice were euthanized to collect BALF, blood, and lung tissue. BALF was used for cell count and cytokine analysis. Lung tissue slides were stained to examine structural integrity. RNA from lung tissue was used for RT-PCR. Immunoblots were performed to study fibrosis and EMT pathway.

RESULTS

Mice exposed to DE increase lung resistance and tissue elastance with decrease in inspiratory capacity (p < 0.05) suggesting lung function impairment. BALF showed significantly increased macrophages, neutrophils and monocytes (p < 0.01). Additionally, there was an increase in inflammation and alveolar wall thickening in lungs (p < 0.01) correlates with cellular infiltration. Macrophages had black soot deposition in lung tissue of DE exposed mice. Lung section staining revealed increase in mucus producing goblet cells for clearance of soot in lung. DE exposed lung showed increased collagen deposition and hydroxyproline residue (p < 0.01). Repetitive exposure of DE in mice lead to tissue remodeling in lung, demonstrated by fibrotic foci and smooth muscles. A significant increase in α-SMA and fibronectin (p < 0.05) in lung indicate progression of pulmonary fibrosis. TGF-β/Smad3 signaling was activated with increase in P-smad3 expression in DE exposed mice. Decreased expression of E-cadherin and increased vimentin (p < 0.05) in lungs of DE exposed mice indicate epithelial to mesenchymal transition.

CONCLUSION

DE exposure to mice induced lung injury and pulmonary fibrosis thereby remodeling tissue. The study demonstrates TGF-β/SMAD3 pathway involvement with an activation of EMT in DE exposed mice.

Exposure to ambient fine particulate matter impedes the function of spleen in the mouse metabolism of high-fat diet

Epidemiological and experimental evidence has been associating the exposure with ambient fine particulate matter (PM_2.5) with metabolic malfunctions such as obesity and cardiovascular disease. As the blood-filter and the important lymphatic organ, spleen participates in the regulation of metabolic balance. In this work, liquid chromatography-mass spectrometry (LC-MS)-based lipidomics, metabolomics and proteomics were performed to study the effects of PM_2.5 exposure and high-fat diet (HFD) induced obesity on mice spleen. By comparing the differences in lipids, metabolites, and proteins in the spleens from PM_2.5 and HFD treated mice, we discovered the individual and combined effects of the two risk factors. The results showed the PM_2.5 exposure altered energy metabolism of the mice, as evidenced by the upregulation of TCA cycle. In addition, the metabolism of branched-chain amino acids was also significantly changed, which might be related to the preventive function of spleen in lipid metabolism. The PM_2.5-induced metabolic changes in spleen could further aggravate the adverse impacts of HFD on mice, resulting in impeded splenic metabolism of lipids. This study revealed the effects of PM_2.5 and obesity mice spleen, which might be of great significance to public health.

Biomarkers for the adverse effects on respiratory system health associated with atmospheric particulate matter exposure

Large amounts of epidemiological evidence have confirmed the atmospheric particulate matter (PM_2.5) exposure was positively correlated with the morbidity and mortality of respiratory diseases. Nevertheless, its pathogenesis remains incompletely understood, probably resulting from the activation of oxidative stress, inflammation, altered genetic and epigenetic modifications in the lung upon PM_2.5 exposure. Currently, biomarker investigations have been widely used in epidemiological and toxicological studies, which may help in understanding the biologic mechanisms underlying PM_2.5-elicited adverse health outcomes. Here, the emerging biomarkers to indicate PM_2.5-respiratory system interactions were summarized, primarily related to oxidative stress (ROS, MDA, GSH, etc.), inflammation (Interleukins, FE_NO, CC16, etc.), DNA damage (8-OHdG, γH2AX, OGG1) and also epigenetic modulation (DNA methylation, histone modification, microRNAs). The identified biomarkers shed light on PM_2.5-elicited inflammation, fibrogenesis and carcinogenesis, thus may favor more precise interventions in public health. It is worth noting that some inconsistent findings may possibly relate to the inter-study differentials in the airborne PM_2.5 sample, exposure mode and targeted subjects, as well as methodological issues. Further research, particularly by -omics technique to identify novel, specific biomarkers, is warranted to illuminate the causal relationship between PM_2.5 pollution and deleterious lung outcomes.

Epigenetic regulation is involved in traffic-related PM2.5 aggravating allergic airway inflammation in rats

Increasing fine particulate matter (PM_2.5) and epigenetic modifications are closely associated with the pathogenesis of asthma, but the definite mechanism remains unclear. The traffic-related PM_2.5 exposure aggravated pulmonary inflammation and changed the methylation level of interferon gamma (Ifng) and interleukin (Il)4 genes, and then altered levels of affiliated cytokines of IFN-γ and IL-4 in rats with allergic airway inflammation. It also increased the level of miR146a and decreased the level of miR31. In addition, transcription factors of nuclear factor kappa B (NF-κB) and signal transducer and activator of transcription 6 (Stat6) rose; forkhead box P3 (Foxp3) and signal transducer and activator of transcription 4 (Stat4) lowered. The traffic-related PM_2.5 altered epigenetic modifications in allergic airway inflammation of rats leading to inflammation exacerbation through impaired regulatory T (Treg) cells function and T-helper type 1 (Th1)/Th2 cells imbalance, which provided a new target for the treatment and control of asthma.

PM2.5 Induces Airway Remodeling in Chronic Obstructive Pulmonary Diseases via the Wnt5a/β-Catenin Pathway

Background

Fine-particulate matter ≤2.5 μm in diameter (PM2.5)-associated airway remodeling has recently been recognized as a central feature of COPD. Activation of the Wnt/β-catenin pathway is closely related to the occurrence of airway remodeling. Accordingly, the goal of this study was to determine whether the Wnt5a/β-Catenin pathway is involved in PM2.5-induced smooth muscle proliferation in vivo and in vitro, which promotes the development of airway remodeling in subjects with COPD.

Methods

The effect of Wnt5a on β-Catenin-mediated airway remodeling was assessed using an in vivo model of PM2.5-induced COPD and PM2.5-exposed human bronchial smooth muscle cells (HBSMCs) in vitro. Small animal spirometry was used to measure lung function in mice. H&E staining and immunohistochemistry were performed to inspect emphysema and airway remodeling indices. Real-time PCR was used to detect Wnt5a, β-Catenin, TGF-β1, CyclinD1 and c-myc mRNA expression. The CCK8 assay was performed to detect cellular activity. Western blotting was performed to assess PCNA, α-SMA, Wnt5a, β-Catenin, PDGFRβ and TenascinC protein expression. β-Catenin expression was detected using cellular immunofluorescence.

Results

Exposure to PM2.5 led to emphysema, airway wall thickening, an increased smooth muscle layer thickness, decreased lung function and increased expression of the Wnt5a, β-Catenin, PDGFRβ and Tenascin C proteins in the mouse lung tissue. BOX5 (a Wnt5a antagonist) alleviated these PM2.5-induced outcomes in mice. Moreover, PM2.5 induced the expression of the Wnt5a, β-Catenin, TGF-β1, CyclinD1 and c-myc mRNAs in HBSMCs. BOX5 also inhibited the PM2.5-induced increases in PCNA, α-SMA, Wnt5a, β-Catenin, PDGFRβ and Tenascin C protein expression in HBSMCs.

Conclusion

Our findings suggest that PM2.5 exposure induces HBSMC proliferation, contributing to airway remodeling via the Wnt5a/β-Catenin signaling pathway in vivo and in vitro, which might be a target for COPD treatment.

PM2.5 Induces Early Epithelial Mesenchymal Transition in Human Proximal Tubular Epithelial Cells through Activation of IL-6/STAT3 Pathway

Particulate matter exposure has been known as a potential risk for the global burden of disease, such as respiratory and cardiovascular diseases. Accumulating evidence suggests that PM2.5 (particulate matter with a diameter less than 2.5 μm) is associated with increased risk of kidney disease, but the mechanisms underlying the renal injury caused by PM2.5 remain to be elucidated. This study investigated the effects of PM2.5 on human proximal tubular epithelial (HK-2) cells by monolayer and 3D spheroid cultures and explored the potential mechanisms. The typical morphology of HK-2 cells showed epithelial–mesenchymal transition (EMT), resulting in reduced adhesion and enhanced migration after PM2.5 exposure, and was accompanied by decreased E-cadherin expression and increased vimentin and α-SMA expressions. Exposure to PM2.5 in the HK-2 cells could lead to an increase in interleukin-6 (IL-6) levels and cause the activation of signal transducer and activator of transcription 3 (STAT3), which is involved in EMT features of HK-2 cells. Furthermore, blocking IL-6/STAT3 signaling by an IL-6 neutralizing antibody or STAT3 inhibitor was sufficient to reverse PM2.5-induced EMT characteristics of the HK-2 cells. Our study suggests that PM2.5 could induce early renal tubule cell injury, contributing to EMT change, and the induction of IL-6/STAT3 pathway may play an important role in this process.

Evaluation of the effect of filtered ultrafine particulate matter on bleomycin-induced lung fibrosis in a rat model using computed tomography, histopathologic analysis, and RNA sequencing

We aimed to investigate the effect of chronic particulate matter (PM) exposure on bleomycin-induced lung fibrosis in a rat model using chest CT, histopathologic evaluation, and RNA-sequencing. A bleomycin solution was intratracheally administrated to 20 male rats. For chronic PM exposure, after four weeks of bleomycin treatment to induce lung fibrosis, PM suspension (experimental group) or normal saline (control group) was intratracheally administrated for 10 weeks. Chest CT was carried out in all rats, and then both lungs were extracted for histopathologic evaluation. One lobe from three rats in each group underwent RNA sequencing, and one lobe from five rats in each group was evaluated by western blotting. Inflammation and fibrosis scores in both chest CT and pathologic analysis were significantly more aggravated in rats with chronic PM exposure than in the control group. Several genes associated with inflammation and immunity were also upregulated with chronic PM exposure. Our study revealed that chronic PM exposure in a bleomycin-induced lung fibrosis rat model aggravated pulmonary fibrosis and inflammation, proven by chest CT, pathologic analysis, and RNA sequencing.

N6-methyladenosine modification of CDH1 mRNA promotes PM2.5-induced pulmonary fibrosis via mediating epithelial mesenchymal transition

The association between ambient airborne fine particulate matter (PM2.5) exposure and respiratory diseases has been investigated in epidemiological studies. To explore the potential mechanism of PM2.5-induced pulmonary fibrosis, sixty mice were divided into 3 groups to expose to different levels of PM2.5 for 8 and 16 weeks: filtered air (FA), unfiltered air (UA) and concentrated PM2.5 air (CA), respectively. BEAS-2B cells were treated with 0, 25, 50 and 100 μg/ml PM2.5 for 24 h. The biomarkers of pulmonary fibrosis, epithelial-mesenchymal transition (EMT), N6-methyladenosine (m6A) modification and metabolism of mRNAs were detected to characterize the effect of PM2.5 exposure. The results illustrated that PM2.5 exposure induced pathological alteration and pulmonary fibrosis in mice. The expression of E-cadherin (E-cad) was decreased whereas vimentin and N-cadherin (N-cad) expression were increased in a dose- and time-dependent manner after PM2.5 exposure. Mechanistically, PM2.5 exposure increased the levels of METTL3-mediated m6A modification of CDH1 mRNA. As a target gene of miR-494-3p, YTHDF2 was up-regulated by miR-494-3p down-regulation and then recognized m6A-modified CDH1 mRNA to inhibit the E-cad expression, consequently induced the EMT progression after PM2.5 exposure. Our study indicated that PM2.5 exposure triggered EMT progression to promote the pulmonary fibrosis via miR-494-3p/YTHDF2 recognized and METTL3 mediated m6A modification.

PM2.5 promotes Drp1-mediated mitophagy to induce hepatic stellate cell activation and hepatic fibrosis via regulating miR-411

BACKGROUND

Particulate matter≤ 2.5 μm (PM_2.5) is a type of environmental agent associated with air pollution, which induces hepatic fibrosis. However, the function and mechanism of PM_2.5 on hepatic stellate cell (HSC) proliferation and fibrosis remain largely unknown.

METHODS

Human HSC line (LX-2) and murine HSCs were exposed to various doses of PM_2.5. microRNA (miR)-411 expression was detected via quantitative reverse transcription polymerase chain reaction (qRT-PCR). Cell proliferation, fibrosis, mitochondrial dynamics dysfunction and mitophagy were determined via cell counting kit-8 (CCK-8), qRT-PCR, Western blotting and immunofluorescence.

RESULTS

PM_2.5 facilitated HSC proliferation and fibrosis via increasing the levels of ACTA2, Collagen 1, TIMP1 and TGF-β1. PM_2.5 reduced miR-411 expression, and contributed to mitochondrial dynamics dysfunction via increasing Drp1 and decreasing OPA1, TOM20 and PGC-1α levels. PM_2.5 promoted mitophagy by upregulating the levels of Beclin-1, LC3II/I, PINK1 and Parkin. miR-411 overexpression or autophagy blockage using 3-methyladenine (3-MA) relieved PM_2.5-mediated cell proliferation and fibrosis-associated factor expression in HSCs. Drp1 was targeted by miR-411. miR-411 mitigated PM_2.5-induced mitophagy via targeting Drp1. Drp1 overexpression abolished the inhibitory role of miR-411 in cell proliferation and fibrosis-associated factor levels in HSCs.

CONCLUSION

PM_2.5 induced HSC activation and fibrosis via promoting Drp1-mediated mitophagy by decreasing miR-411, thereby causing liver fibrosis.

Pharmacological inhibition of PAI-1 alleviates cardiopulmonary pathologies induced by exposure to air pollutants PM2.5

Numerous studies have established that acute or chronic exposure to environmental pollutants like particulate matter (PM) leads to the development of accelerated aging related pathologies including pulmonary and cardiovascular diseases, and thus air pollution is one of the major global threats to human health. Air pollutant particulate matter 2.5 (PM_2.5)-induced cellular dysfunction impairs tissue homeostasis and causes vascular and cardiopulmonary damage. To test a hypothesis that elevated plasminogen activator inhibitor-1 (PAI-1) levels play a pivotal role in air pollutant-induced cardiopulmonary pathologies, we examined the efficacy of a drug-like novel inhibitor of PAI-1, TM5614, in treating PM_2.5-induced vascular and cardiopulmonary pathologies. Results from biochemical, histological, and immunohistochemical studies revealed that PM_2.5 increases the circulating levels of PAI-1 and thrombin and that TM5614 treatment completely abrogates these effects in plasma. PM_2.5 significantly augments the levels of pro-inflammatory cytokine interleukin-6 (IL-6) in bronchoalveolar lavage fluid (BALF), and this also can be reversed by TM5614, indicating its efficacy in amelioration of PM_2.5-induced increases in inflammatory and pro-thrombotic factors. TM5614 reduces PM_2.5-induced increased levels of inflammatory markers cluster of differentiation 107 b (Mac3) and phospho-signal transducer and activator of transcription-3 (pSTAT3), adhesion molecule vascular cell adhesion molecule 1 (VCAM1), and apoptotic marker cleaved caspase 3. Longer exposure to PM_2.5 induces pulmonary and cardiac thrombosis, but TM5614 significantly ameliorates PM_2.5-induced vascular thrombosis. TM5614 also reduces PM_2.5-induced increased blood pressure and heart weight. In vitro cell culture studies revealed that PM_2.5 induces the levels of PAI-1, type I collagen, fibronectin (Millipore), and sterol regulatory element binding protein-1 and 2 (SREBP-1 and SREBP-2), transcription factors that mediate profibrogenic signaling, in cardiac fibroblasts. TM5614 abrogated that stimulation, indicating that it may block PM_2.5-induced PAI-1 and profibrogenic signaling through suppression of SREBP-1 and 2. Furthermore, TM5614 blocked PM_2.5-mediated suppression of nuclear factor erythroid related factor 2 (Nrf2), a major antioxidant regulator, in cardiac fibroblasts. Pharmacological inhibition of PAI-1 with TM5614 is a promising therapeutic approach to control air pollutant PM_2.5-induced cardiopulmonary and vascular pathologies.

Assessment on the lung injury of mice posed by airborne PM2.5 collected from developing area in China and associated molecular mechanisms by integrated analysis of mRNA-seq and miRNA-seq

Some epidemiological evidences showed exposure of airborne fine particulate matter (PM2.5) was associated with lung dysfunction. However, the adverse effects of PM2.5 from mid-scale city of China on the respiratory system were unknown. Correspondingly, the mechanisms, especially the epigenetic mechanism regulated by miRNAs, involved in PM2.5-induced lung injury has not been fully understood. In this study, male Balb/C mice were exposed to PM2.5 collected from mid-scale city (Baoji), China for 8 weeks (mean concentration 298.52 ± 25.86 μg/m3 at exposure chamber) using a whole-body exposure system. The carbon component was the main ingredient (45.80%) of PM2.5 followed by ions (43.19%). Meanwhile, the sum concentrations of polycyclic aromatic hydrocarbons (PAHs) and n-alkanes (C18-C33) were 570.48 and 2029.13 ng/m3 in the exposure chamber, respectively. Obvious lung injury including pulmonary inflammation and fibrosis (p < 0.05 compared with the control) were found from PM2.5 exposure group determined by micro-CT and histopathological assays, respectively, suggesting the health risk posed by PM2.5 from mid-scale city of China should be concerned. The integrated analysis between mRNA-seq and miRNA-seq revealed the differentially expression genes in lung tissues were enriched in immune pathways including B cell receptor signaling (p = 0.078) and cell adhesion molecules (CAMs) (p = 0.0068). The expression profiles of the genes and corresponding mRNAs involved into the immune pathways determined by RT-qPCR analysis were consistent with them conducted by transcriptome. Moreover, the expression levels of the proteins (i.e., CD19, CD81, PIK3CD, and CD22) involved into B cell receptor signaling pathway from exposure group were 1.71- to 6.948- folds compared with the control, validating the results of the genes expression profiles. Further, canonical correlation analysis (CCA) and multiple correlation analysis between the target genes and components of PM2.5 documented the organic compounds (i.e., Benzo(a)pyrene (p = 0.012) and octadecane (p = 0.05)) and inorganic elements (i.e., Cl-, Ti, Al, and Zn) was the key environmental factors. Cd19, Pik3cd, and Cd8b1 might be the key genes for lung dysfunction induced by PM2.5 illuminated using interactive analysis (p < 0.05). This work for the first time showed the adverse effects of PM2.5 in mid-scale city in China on respiratory system should be concerned, and the associated epigenetic mechanism regulated by miRNA were revealed. These results may provide new insight into the development of future assessment on the air pollution associated respiratory disease.

Chronic lung inflammation and pulmonary fibrosis after multiple intranasal instillation of PM2 .5 in mice

Fine particulate matter (PM_2.5 ) is an important component of air pollution and can induce lung inflammation and oxidative stress. We hypothesized that PM_2.5 could play a role in the induction of pulmonary fibrosis. We examined whether multiple intranasal instillation of PM_2.5 can induce pulmonary fibrosis in the mouse, and also investigated the underlying pro-fibrotic signaling pathways. C57/BL6 mice were intranasally instilled with 50 μl of PM_2.5 suspension (7.8 μg/g body weight) or PBS three times a week over 3 weeks, 6 weeks or 9 weeks. To observe the recovery of pulmonary fibrosis after the termination of PM_2.5 exposure, 9 week-PM_2.5 instilled mice were also studied at 3 weeks after termination of instillation. There were significant decreases in total lung capacity (TLC) and compliance (Cchord) in the 9-week PM_2.5 -instilled mice, while there were increased histological fibrosis scores with enhanced type I collagen and hydroxyproline deposition, increased mitochondrial ROS levels and NOX activity, decreased total SOD and GSH levels, accompanied by decreased mitochondrial number and aberrant mitochondrial morphology (swelling, vacuolization, cristal disruption, reduced matrix density) in PM_2.5 -instilled mice. Multiple PM_2.5 instillation resulted in increased expression of TGFβ1, increases of N-Cadherin and Vimentin and a decrease of E-Cadherin. It also led to decreases in OPA1 and MFN2, and increases in Parkin, SQSTM1/p62, the ratio of light china (LC) 3B II to LC3B I, PI3k/Akt phosphorylation, and NLRP3 expression. Intranasal instillation of PM_2.5 for 9 weeks induced lung inflammation and pulmonary fibrosis, which was linked with aberrant epithelial-mesenchymal transition, oxidative stress, mitochondrial damage and mitophagy, as well as activation of TGFβ1-PI3K/Akt, TGFβ1- NOX and TGFβ1-NLRP3 pathways.

Traffic-related PM2.5 and diverse constituents disturb the balance of Th17/Treg cells by STAT3/RORγt-STAT5/Foxp3 signaling pathway in a rat model of asthma

Water-soluble ions (WSI) and organic extract (OE) in traffic-related particulate matter with aerodynamic diameters ≤ 2.5 μm (TRPM2.5) are potential risk factors for asthma exacerbation. Although CD4+ T lymphocytes mediated immune response is involved in the pathogenesis of asthma, the effect of WSI-TRPM2.5 and OE-TRPM2.5 on the balance of Th17/Treg cells in asthma remains poorly understood. In this study, the ovalbumin (OVA)-sensitized rats were repeatedly exposure to TRPM2.5 (3 mg/kg·bw), WSI-TRPM2.5 (1.8 mg/kg·bw, 7.2 mg/kg·bw) and OE-TRPM2.5 (0.6 mg/kg·bw, 2.4 mg/kg·bw) every three days for five times. The inflammation response and hyperemia edema were observed in the lung and trachea tissues. DNA methylation levels of STAT3 and RORγt genes in rats with WSI-TRPM2.5 and OE-TRPM2.5 treatment were decreased. DNA methylation level in STAT5 gene tended to decrease, with no change observed on Foxp3 expression. WSI-TRPM2.5 and OE-TRPM2.5 enhanced the mRNA and protein expression of STAT3 and RORγt while inhibited the expression of STAT5 and Foxp3, which may contribute to the imbalance of Th17/Treg cells (P < 0.05). More importantly, recovered balance of Th17/Treg cell subsets, upregulated p-STAT5 and Foxp3 expression and reduced p-STAT3 and RORγt levels were observed after 5-Aza treatment. Our results demonstrate that the STAT3/RORγt-STAT5/Foxp3 signaling pathway is involved in asthma exacerbation induced by WSI-TRPM2.5 and OE-TRPM2.5 through disrupting the balance of Th17/Treg cells. The alteration of DNA methylation of STAT3, STAT5, and RORγt genes may be involved in asthma exacerbation as well.

PM2.5 and water-soluble components induce airway fibrosis through TGF-β1/Smad3 signaling pathway in asthmatic rats

Epidemiological studies have suggested that fine particulate matter (PM_2.5) and asthma have been independently associated with pulmonary fibrosis but rarely studied together. Furthermore, it is unknown whether airway fibrosis in asthma is more attributable to water-soluble ions of PM_2.5. Our current study was to explore the potential mechanism of PM_2.5 and water-soluble components on airway fibrosis in ovalbumin (OVA)-sensitized asthmatic rats. Rats were intratracheally instilled with PM_2.5 and water-soluble components every 3 days for 4 times or 8 times. Histopathological examination demonstrated that lung inflammatory and airway fibrosis were induced after PM_2.5 and water-soluble components exposure. Meanwhile, PM_2.5, in particular water-soluble extracts, increased expression of collagen 1 (COL-1), connective tissue growth factor (CTGF), interleukin-6 (IL-6), transforming growth factor-β1 (TGF-β1), Smad family member 3 (Smad3), and p-Smad3, whereas decreased secretion of heme oxygenase-1 (HO-1). However, pretreating asthmatic rats with SB432542, the inhibitor of TGF-β1, and SIS3 HCl, the antagonist of Smad3, both reversed the activation of airway fibrosis induced by water-soluble extracts. Therefore, TGF-β1/Smad3 signaling pathway may be responsible for the pathological process of airway fibrosis in asthmatic rats following PM_2.5 and water-soluble components exposure.