Intratracheally instillated diesel PM2.5 significantly altered the structure and composition of indigenous murine gut microbiota

A multi-omics investigation of the lung injury induced by PM2.5 at environmental levels via the lung-gut axis

Long-term exposure to fine particulate matter (PM2.5) posed injury for gastrointestinal and respiratory systems, ascribing with the lung-gut axis. However, the cross-talk mechanisms remain unclear. Here, we attempted to establish the response networks of lung-gut axis in mice exposed to PM2.5 at environmental levels. Male Balb/c mice were exposed to PM2.5 (dose of 0.1, 0.5, and 1.0 mg/kg) collected from Chengdu, China for 10 weeks, through intratracheally instillation, and examined the effect of PM2.5 on lung functions of mice. The changes of lung and gut microbiota and metabolic profiles of mice in different groups were determined. Furthermore, the results of multi-omics were conjointly analyzed to elucidate the primary microbes and the associated metabolites in lung and gut responsible for PM2.5 exposure. Accordingly, the cross-talk network and key pathways between lung-gut axis were established. The results indicated that exposed to PM2.5 0.1 mg/kg induced obvious inflammations in mice lung, while emphysema was observed at 1.0 mg/kg. The levels of metabolites guanosine, hypoxanthine, and hepoxilin B3 increased in the lung might contribute to lung inflammations in exposure groups. For microbiotas in lung, PM2.5 exposure significantly declined the proportions of Halomonas and Lactobacillus. Meanwhile, the metabolites in gut including L-tryptophan, serotonin, and spermidine were up-regulated in exposure groups, which were linked to the decreasing of Oscillospira and Helicobacter in gut. Via lung-gut axis, the activations of pathways including Tryptophan metabolism, ABC transporters, Serotonergic synapse, and Linoleic acid metabolism contributed to the cross-talk between lung and gut tissues of mice mediated by PM2.5. In summary, the microbes including Lactobacillus, Oscillospira, and Parabacteroides, and metabolites including hepoxilin B3, guanosine, hypoxanthine, L-tryptophan, and spermidine were the main drivers. In this lung-gut axis study, we elucidated some pro- and pre-biotics in lung and gut microenvironments contributed to the adverse effects on lung functions induced by PM2.5 exposure.

Effects of inhaled fine particulate matter on the lung injury as well as gut microbiota in broilers

Fine particulate matter (PM2.5) has been widely regarded as an important environmental risk factor that has widely influenced health of both animals and humans. Lung injury is the main cause of PM2.5 affecting respiratory tract health. Gut microbiota participates in the development of lung injury in many pathological processes. However, there is still unknown the specific effects of PM2.5 on the gut-lung axis in broilers. Thus, we conducted a broiler model based on 3-wk-old male Arbor Acres broiler to explore the underlying mechanism. Our results showed that PM2.5 exposure triggered TLR4 signaling pathway and induced the increase of IL-6, IFN-γ, TNF-α expression as well as the decrease of IL-10 expression in the lung. Inhaled PM2.5 exposure significantly altered the gut microbiota diversity and community. Specifically, PM2.5 exposure decreased α diversity and altered β diversity of gut microbiota, and reduced the abundance of DTU089, Oscillospirales, Staphylococcus, and increased the Escherichia-Shigella abundance, leading to the increase of gut-derived lipopolysaccharides (LPS). Moreover, PM2.5 significantly disrupted the intestinal epithelial barrier by reducing the expression of muc2 and claudin-1 to increase intestinal permeability, which possibly facilitated the LPS translocation into the blood. Spearman analysis revealed that gut microbiota dysbiosis was positively related to TLR4, TNF-α, and IFN-γ expression in the lung. In summary, our results showed that PM2.5 exposure induced lung injury by causing inflammation and triggering TLR4 signaling pathway, and also induced gut microbiota dysbiosis resulting in the overproduction of gut-derived LPS. And gut microbiota dysbiosis may be associated with lung injury. The above results provide basis data to comprehend the potential role of gut microbiota dysbiosis in the lung injury as well as providing a new regulatory target for alleviating lung injury associated with environmental pollutants.

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.

Subchronic exposure to PM2.5 induced renal function damage and intestinal microflora changes in rats

BACKGROUND

Exposure to inhalable environmental particulate matter with a diameter of 2.5 µm or smaller (PM2.5) is associated with decreased or impaired kidney function, but the underlying biological mechanisms are not fully understood. Gut microbiota is an emerging key player in the homeostasis regulation of the gut-kidney axis. Few studies have investigated its role in PM2.5 exposure-induced gut-kidney axis homeostasis abnormalities.

METHODS

In this study, a versatile aerosol concentration enrichment system for medium- to long-term whole-body exposure was used to expose Sprague-Dawley rats to filtered air (FA) or concentrated ambient PM2.5 for 12 weeks. A correlation analysis of renal impairment and the intestinal microbiome was performed.

RESULTS

The urine flow rate calculation and renal function analysis showed that PM2.5 exposure significantly impaired renal function and increased the urine flow rate. The fecal microbiota analysis showed that renal impairment and increased urine flow rates were consistent with the reduced estimates of the fecal bacteria Chao1, observed-species, Shannon, and Simpson (richness and diversity indices). Pearson's correlation analysis showed that the estimated bacterial richness and diversity were correlated with the urine flow rate and renal function. The linear discriminant analysis effect size (LEfSe) analysis revealed differences between animals exposed to PM2.5 and FA in 25 bacterial groups. Further correlation of a single bacterial taxon with the urine flow rate and renal function showed that the relative abundances of 30, 29, 21, and 50 distinct bacterial groups were significantly correlated with the urine flow rate, estimated glomerular filtration rate (eGFR), serum cystatin C (CysC), and beta-2 microglobulin (β2-MG), respectively.

CONCLUSION

Subchronic exposure to PM2.5 can cause intestinal ecological disorders, which may, in turn, lead to decreased kidney function or the development of impaired kidney function.

Does PM1 exposure during pregnancy impact the gut microbiota of mothers and neonates?

BACKGROUND

Ambient air pollutant exposure can change the composition of gut microbiota at 6-months of age, but there is no epidemiological evidence on the impacts of exposure to particulate matter with an aerodynamic diameter ≤1 μm (PM1) during pregnancy on gut microbiota in mothers and neonates. We aimed to determine if gestational PM1 exposure is associated with the gut microbiota of mothers and neonates.

METHODS

Leveraging a mother-infant cohort from the central region of China, we estimated the exposure concentrations of PM1 during pregnancy based on residential address records. The gut microbiota of mothers and neonates was analyzed using 16 S rRNA V3-V4 gene sequences. Functional pathway analyses of 16 S rRNA V3-V4 bacterial communities were conducted using Tax4fun. The impact of PM1 exposure on α-diversity, composition, and function of gut microbiota in mothers and neonates was evaluated using multiple linear regression, controlling for nitrogen dioxide (NO2) and ozone (O3). Permutation multivariate analysis of variance (PERMANOVA) was used to analyze the interpretation degree of PM1 on the sample differences at the OTU level using the Bray-Curtis distance algorithm.

RESULTS

Gestational PM1 exposure was positively associated with the α-diversity of gut microbiota in neonates and explained 14.8% (adj. P = 0.026) of the differences in community composition among neonatal samples. In contrast, gestational PM1 exposure had no impact on the α- and β-diversity of gut microbiota in mothers. Gestational PM1 exposure was positively associated with phylum Actinobacteria of gut microbiota in mothers, and genera Clostridium_sensu_stricto_1, Streptococcus, Faecalibacterium of gut microbiota in neonates. At Kyoto Encyclopedia of Genes and Genomes pathway level 3, the functional analysis results showed that gestational PM1 exposure significantly down-regulated Nitrogen metabolism in mothers, as well as Two-component system and Pyruvate metabolism in neonates. While Purine metabolism, Aminoacyl-tRNA biosynthesis, Pyrimidine metabolism, and Ribosome in neonates were significantly up-regulated.

CONCLUSIONS

Our study provides the first evidence that exposure to PM1 has a significant impact on the gut microbiota of mothers and neonates, especially on the diversity, composition, and function of neonatal meconium microbiota, which may have important significance for maternal health management in the future.

Ambient particulate air pollution and the intestinal microbiome; a systematic review of epidemiological, in vivo and, in vitro studies

A healthy indigenous intestinal microbiome is indispensable for intra- and extra-intestinal human health. Since well-established factors such as diet and antibiotic use only explain 16 % of the inter-individual variation in gut microbiome composition, recent studies have focused on the association between ambient particulate air pollution and the intestinal microbiome. We systematically summarize and discuss all evidence concerning the effect of particulate air pollution on intestinal bacterial diversity indices, specific bacterial taxa, and potential underlying intestinal mechanisms. To this end, all possibly relevant publications published between February 1982 and January 2023 were screened, and eventually, 48 articles were included. The vast majority (n = 35) of these studies were animal studies. The exposure periods investigated in the human epidemiological studies (n = 12) ranged from infancy through elderly. This systematic review found that intestinal microbiome diversity indices were generally negatively associated with particulate air pollution in epidemiological studies, with an increase in taxa belonging to Bacteroidetes (two studies), Deferribacterota (one study), and Proteobacteria (four studies), a decrease in taxa belonging to Verrucomicrobiota (one study), and no consensus for taxa belonging to Actinobacteria (six studies) and Firmicutes (seven studies). There was no unequivocal effect of ambient particulate air pollution exposure on bacterial indices and taxa in animal studies. Only one study in humans examined a possible underlying mechanism; yet, the included in vitro and animal studies depicted higher gut damage, inflammation, oxidative stress, and permeability in exposed versus unexposed animals. Overall, the population-based studies showed a dose-related continuum of short- and long-term ambient particulate air pollution exposure on lower gut diversity and shifts in taxa over the entire life course.

Pectin alleviates the pulmonary inflammatory response induced by PM2.5 from a pig house by modulating intestinal microbiota

This study aimed to investigate whether dietary fiber pectin can alleviate PM_2.5-induced pulmonary inflammation and the potential mechanism. PM_2.5 samples were collected from a nursery pig house. The mice were divided into three groups: the control group, PM_2.5 group and PM_2.5 + pectin group. The mice in the PM_2.5 group were intratracheally instilled with PM_2.5 suspension twice a week for four consecutive weeks, and those in the PM_2.5 + pectin group were subject to the same PM_2.5 exposure, but fed with a basal diet supplemented with 5% pectin. The results showed that body weight and feed intake were not different among the treatments (p > 0.05). However, supplementation with pectin relieved PM_2.5-induced pulmonary inflammation, presenting as slightly restored lung morphology, decreased mRNA expression levels of IL-1β, IL-6 and IL-17 in the lung, decreased MPO content in bronchoalveolar lavage fluid (BLAF), and even decreased protein levels of IL-1β and IL-6 in the serum (p < 0.05). Dietary pectin altered the composition of the intestinal microbiota, increasing the relative abundance of Bacteroidetes and decreasing the ratio of Firmicutes/Bacteroidetes. At the genus level, short-chain fatty acid (SCFA)-producing bacteria, such as Bacteroides, Anaerotruncus, Prevotella 2, Parabacteroides, Ruminococcus 2 and Butyricimonas, were enriched in the PM_2.5 +pectin group. Accordingly, dietary pectin increased the concentrations of SCFAs, including acetate, propionate, butyrate and valerate, in mice. In conclusion, dietary fermentable fiber pectin can relieve PM_2.5-induced pulmonary inflammation via alteration of intestinal microbiota composition and SCFA production. This study provides a new insight into reducing the health risk associated with PM_2.5 exposure.

Microbial modulation via cross-fostering prevents the effects of pervasive environmental stressors on microglia and social behavior, but not the dopamine system

Environmental toxicant exposure, including air pollution, is increasing worldwide. However, toxicant exposures are not equitably distributed. Rather, low-income and minority communities bear the greatest burden, along with higher levels of psychosocial stress. Both air pollution and maternal stress during pregnancy have been linked to neurodevelopmental disorders such as autism, but biological mechanisms and targets for therapeutic intervention remain poorly understood. We demonstrate that combined prenatal exposure to air pollution (diesel exhaust particles, DEP) and maternal stress (MS) in mice induces social behavior deficits only in male offspring, in line with the male bias in autism. These behavioral deficits are accompanied by changes in microglial morphology and gene expression as well as decreased dopamine receptor expression and dopaminergic fiber input in the nucleus accumbens (NAc). Importantly, the gut-brain axis has been implicated in ASD, and both microglia and the dopamine system are sensitive to the composition of the gut microbiome. In line with this, we find that the composition of the gut microbiome and the structure of the intestinal epithelium are significantly shifted in DEP/MS-exposed males. Excitingly, both the DEP/MS-induced social deficits and microglial alterations in males are prevented by shifting the gut microbiome at birth via a cross-fostering procedure. However, while social deficits in DEP/MS males can be reversed by chemogenetic activation of dopamine neurons in the ventral tegmental area, modulation of the gut microbiome does not impact dopamine endpoints. These findings demonstrate male-specific changes in the gut-brain axis following DEP/MS and suggest that the gut microbiome is an important modulator of both social behavior and microglia.

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.

Association of long-term exposure to ambient PM2.5 and its constituents with gut microbiota: Evidence from a China cohort

Accumulating animal experiments and epidemiological studies have found that exposure to fine particulate matter (PM_2.5) is associated with altered gut microbiota (GM). However, it is unclear what kind of role the PM_2.5 constituents play in the PM_2.5-GM association. Therefore, this study aimed to investigate the association of long-term exposure to PM_2.5 and its constituents (PM_cons) with GM. This study included 1583 participants from a cohort in Southwest China. Satellite remote sensing and chemical transport modelling were used to determine the yearly average concentrations of PM_cons. GM data were derived from 16 s sequencing based on stool samples. Generalized propensity score weighting regression and Bayesian Kernel Machine Regression (BKMR) were used to estimate the individual and joint association of exposure to PM_cons with the Shannon index. The weighted correlation analysis was used to estimate the association of PM_cons with the composition of GM. The result showed that an interquartile range increase of 3-year average black carbon (BC), ammonium, nitrate, organic matter (OM), sulfate, and soil particles (SOIL) were negatively associated with Shannon index with mean difference (95 % confidence interval) being -0.144 (-0.208, -0.080), -0.141 (-0.205, -0.078), -0.126 (-0.184, -0.068), -0.117 (-0.172, -0.062), -0.153 (-0.221, -0.085), and - 0.153 (-0.222, -0.085). BKMR indicated joint exposure to PM_cons was associated with decreased Shannon index, and BC had the largest posterior inclusion probability (0.578). Weighted correlation analyses indicated PM_cons were associated with decreased Bacteroidetes (r = -0.204, P < 0.001 for PM_2.5) and increased Proteobacteria (r = 0.273, P < 0.001 for PM_2.5). These results revealed that long-term exposure to PM_cons was associated with GM. BC was the most important constituent in the association, indicating that the source of BC should be controlled to mitigate the negative effects of PM_2.5 on GM.

The effect of real-ambient PM2.5 exposure on the lung and gut microbiomes and the regulation of Nrf2

The influence of air pollution on human health has sparked widespread concerns across the world. Previously, we found that exposure to ambient fine particulate matter (PM2.5) in our "real-ambient exposure" system can result in reduced lung function. However, the mechanism of organ-specific toxicity is still not fully elucidated. The balance of the microbiome contributes to maintaining lung and gut health, but the changes in the microbiome under PM2.5 exposure are not fully understood. Recently, crosstalk between nuclear factor E2-related factor 2 (Nrf2) and the microbiome was reported. However, it is unclear whether Nrf2 affects the lung and gut microbiomes under PM2.5 exposure. In this study, wild-type (WT) and Nrf2^-/- (KO) mice were exposed to filtered air (FA) and real ambient PM2.5 (PM) in the " real-ambient exposure" system to examine changes in the lung and gut microbiomes. Here, our data suggested microbiome dysbiosis in lung and gut of KO mice under PM2.5 exposure, and Nrf2 ameliorated the microbiome disorder. Our study demonstrated the detrimental impacts of PM2.5 on the lung and gut microbiome by inhaled exposure to air pollution and supported the protective role of Nrf2 in maintaining microbiome homeostasis under PM2.5 exposure.

Targeting Lung-Gut Axis for Regulating Pollution Particle-Mediated Inflammation and Metabolic Disorders

Cigarette smoking (CS) or ambient particulate matter (PM) exposure is a risk factor for metabolic disorders, such as insulin resistance (IR), increased plasma triglycerides, hyperglycemia, and diabetes mellitus (DM); it can also cause gut microbiota dysbiosis. In smokers with metabolic disorders, CS cessation decreases the risks of serious pulmonary events, inflammation, and metabolic disorder. This review included recent studies examining the mechanisms underlying the effects of CS and PM on gut microbiota dysbiosis and metabolic disorder development; one of the potential mechanisms is the disruption of the lung-gut axis, leading to gut microbiota dysbiosis, intestinal dysfunction, systemic inflammation, and metabolic disease. Short-chain fatty acids (SCFAs) are the primary metabolites of gut bacteria, which are derived from the fermentation of dietary fibers. They activate G-protein-coupled receptor (GPCR) signaling, suppress histone deacetylase (HDAC) activity, and inhibit inflammation, facilitating the maintenance of gut health and biofunction. The aforementioned gut microbiota dysbiosis reduces SCFA levels. Treatment targeting SCFA/GPCR signaling may alleviate air pollution-associated inflammation and metabolic disorders, which involve lung-gut axis disruption.

Omega-3 polyunsaturated fatty acids ameliorate PM2.5 exposure induced lung injury in mice through remodeling the gut microbiota and modulating the lung metabolism

Short-term or long-term exposure to fine particulate matter (PM2.5) is related to increased incidences of respiratory diseases. This study aimed to investigate the influences of omega-3 polyunsaturated fatty acids (ω-3 PUFAs) supplementation on oxidative stress, inflammation, lung metabolic profile, and gut microbiota in PM2.5-induced lung injury mice. Mice were divided into four groups (n = 15, per group): two unsupplemented groups, control group and PM2.5 group, and two supplemented groups with ω-3 PUFAs, ω-3 PUFAs group, and ω-3 PUFAs + PM2.5 group. Mice in the supplemented groups were placed on an ω-3 PUFAs-enriched diet (ω-3 PUFAs, 21 g/kg). During the 5th to 6th week of dietary supplementation, mice were exposed to PM2.5 by intra-tracheal instillation. ω-3 PUFAs ameliorate lung histopathological injury, reduce inflammatory responses and oxidative stress, affect lung metabolite profile, and modulate gut microbiota in PM2.5-induced lung injury mice. Thus, supplementary ω-3 PUFAs showed effectiveness in attenuation of PM2.5-induced lung injury, indicating that the interventions exhibited preventive and therapeutic potential.

Effects of urban particulate matter on gut microbiome and partial schizophrenia-like symptoms in mice: Evidence from shotgun metagenomic and metabolomic profiling

BACKGROUND

Epidemiological evidence reported that particulate matter (PM) was associated with increased schizophrenia (SCZ) risk. Disturbance of gut microbiome was involved in SCZ. However, it remains unclear whether PM induces SCZ-like symptoms and how gut microbiome regulates them. Therefore, a multi-omics animal experiment was conducted to verify how urban PM induces SCZ-like behavior and altered gut microbiota and metabolic pathways.

METHODS

Using a completely random design, mice were divided into three groups: PM group, control group and MK801 group, which received daily tracheal instillation of PM solution, sterile PBS solution and intraperitoneal injection of MK801 (establish SCZ model), respectively. After a 14-day intervention, feces were collected for multi-omics testing (shotgun metagenomic sequencing and untargeted metabolomic profiling), followed by open field test, tail suspension test, and passive avoidance test. Besides, fecal microbiome of PM group and control group were transplanted into "pseudo-sterile" mice, then behavioral tests were conducted.

RESULTS

Similar to MK801 group, mice in PM group showed SCZ-like symptoms, including increased spontaneous activity, excitability, anxiety and decreased learning and spatial memory. PM exposure significantly increased the relative abundance of Verrucomicrobia and decreased that of Fibrobacteres et al. The metabolism pathways of estrogen signaling (estriol, 16-glucuronide-estriol and 21-desoxycortisol) and choline metabolism (phosphocholine) were significantly altered by PM exposure. Verrucomicrobia was negatively correlated with the level of estriol, which was correlated with decreased learning and spatial memory. Fibrobacteres and Deinococcus-Thermus were positively correlated with the level of phosphocholine, which was correlated with increased spontaneous activity, excitability and anxiety. Fecal microbiome transplantation from PM group mice reproduced excitability and anxiety symptoms.

CONCLUSIONS

Exposure to PM may affect composition of gut microbiome and alterations of estrogen signaling pathway and choline metabolism pathway, which were associated with partial SCZ-like behaviors. But whether gut microbiome regulates these metabolic pathways and behaviors remains to be determined.

Cell-Free Supernatant from Lactobacillus and Streptococcus Strains Modulate Mucus Production via Nf-κB/CREB Pathway in Diesel Particle Matter-Stimulated NCI-H292 Airway Epithelial Cells

Airway epithelial cells are a major site of airway inflammation and may play an important role in the pathogenesis of chronic obstructive pulmonary disease (COPD). Diesel particulate matter (DPM) is associated with mucus hypersecretion and airway inflammation and has been reported to overexpress airway mucin in the NCI-H292 airway epithelial cells. Therefore, regulation of mucin hypersecretion is essential for developing novel anti-inflammatory agents. This study aimed to investigate the effects of cell-free supernatant (CFS) from Lactobacillus and Streptococcus on nitro oxide (NO) production in RAW264.7 and proteins associated with mucus production in NCI-H292 cells. We observed that NO production was reduced by CFS from Lactobacillus and Streptococcus in RAW 264.7, and MUC4, MUC5AC, and MUC5B gene expression was increased by phosphorylation of nuclear factor kappa B (NF-κB) p65 and cAMP response element-binding protein (CREB) in DPM-stimulated NCI-H292 cells. However, CFS from L. paracasei MG4272, MG4577, L. gasseri MG4247, and S. thermophilus MG5140 inhibited mRNA expression related to mucus production by downregulating the CREB/NfκB signaling pathway. These results suggest that CFS from L. paracasei MG4272, MG4577, L. gasseri MG4247, and S. thermophilus MG5140 can contribute as a strategic candidate to the prevention of airway inflammatory diseases caused by DPM.

Water Extract of Ecklonia cava Protects against Fine Dust (PM2.5)-Induced Health Damage by Regulating Gut Health

To confirm the therapeutic effect of the water extract from Ecklonia cava (WEE) against PM_2.5 induced systemic health damage, we evaluated gut health with a focus on the microbiota and metabolites. Systemic damage in mice was induced through PM_2.5 exposure for 12 weeks in a whole-body chamber. After exposure for 12 weeks, body weight and food intake decreased, and WEE at 200 mg/kg body weight (mpk) alleviated these metabolic efficiency changes. In addition, PM_2.5 induced changes in the length of the colon and fecal water content. The administration of the WEE at 200 mpk oral dose effectively reduced changes in the colon caused by PM_2.5 exposure. We also attempted to confirm whether the effect of the WEE is mediated via regulation of the microbiota-gut-brain axis in mice with PM_2.5 induced systemic damage. We examined changes in the fecal microbiota and gut metabolites such as short-chain fatty acids (SCFAs) and kynurenine metabolites. In the PM_2.5 exposed group, a decrease in the abundance of Lactobacillus (Family: Lactobacillaceae) and an increase in the abundance of Alistipes (Family: Rikenellaceae) were observed, and the administration of the WEE showed a beneficial effect on the gut microbiota. In addition, the WEE effectively increased the levels of SCFAs (acetate, propionate, and butyrate). Furthermore, kynurenic acid (KYNA), which is a critical neuroprotective metabolite in the gut-brain axis, was increased by the administration of the WEE. Our findings suggest that the WEE could be used as a potential therapeutic against PM_2.5 induced health damage by regulating gut function.

Lactobacillus casei HY2782 and Pueraria lobata Root Extract Complex Ameliorates Particulate Matter-Induced Airway Inflammation in Mice by Inhibiting Th2 and Th17 Immune Responses

This study aimed to investigate the effects of Lactobacillus casei HY2782 and Pueraria lobata root extract complex (HY2782 complex) in mitigating airway inflammation resulting from exposure to particulate matter ≤2.5 μm in diameter (PM2.5) in an animal model. Chronic inflammatory airway disease is associated with Th2-related cytokines interleukin (IL)-4, IL-5, and IL-13 and Th17-related cytokine IL-17A, which are the major contributors to allergy and asthma. Results indicated that PM2.5 elevates allergen-related airway inflammation and respiratory hyperresponsiveness in C57BL/6 mice. The HY2782 complex significantly reduced Th2/Th17-derived cytokines IL-4, IL5, IL-13, and IL-17A; immunoglobulin E; and leukotriene C₄ in bronchoalveolar lavage fluid (BALF) and serum. Furthermore, the HY2782 complex was associated with the modulation of oxidative stress-related genes. Administration of the HY2782 complex resulted in a markedly reduced number of neutrophils and eosinophil infiltration in BALF. Histopathological observation of lung tissue also showed reduced inflammatory cell infiltration into airways and surrounding tissue. The HY2782 complex may be a promising candidate for the preventive therapy of allergic diseases and airway inflammation caused by PM2.5 inhalation.

Extracellular vesicles enclosed-miR-421 suppresses air pollution (PM2.5 )-induced cardiac dysfunction via ACE2 signalling

Air pollution, via ambient PM_2.5, is a big threat to public health since it associates with increased hospitalisation, incidence rate and  mortality of cardiopulmonary injury. However, the potential mediators of pulmonary injury in PM_2.5‐induced cardiovascular disorder are not fully understood. To investigate a potential cross talk between lung and heart upon PM_2.5 exposure, intratracheal instillation in vivo, organ culture ex vivo and human bronchial epithelial cells (Beas‐2B) culture in vitro experiments were performed respectively. The exposed supernatants of Beas‐2B were collected to treat primary neonatal rat cardiomyocytes (NRCMs). Upon intratracheal instillation, subacute PM_2.5 exposure caused cardiac dysfunction, which was time‐dependent secondary to lung injury in mice, thereby demonstrating a cross‐talk between lungs and heart potentially mediated via small extracellular vesicles (sEV). We isolated sEV from PM_2.5‐exposed mice serum and Beas‐2B supernatants to analyse the change of sEV subpopulations in response to PM_2.5. Single particle interferometric reflectance imaging sensing analysis (SP‐IRIS) demonstrated that PM_2.5 increased CD63/CD81/CD9 positive particles. Our results indicated that respiratory system‐derived sEV containing miR‐421 contributed to cardiac dysfunction post‐PM_2.5 exposure. Inhibition of miR‐421 by AAV9‐miR421‐sponge could significantly reverse PM_2.5‐induced cardiac dysfunction in mice. We identified that cardiac angiotensin converting enzyme 2 (ACE2) was a downstream target of sEV‐miR421, and induced myocardial cell apoptosis and cardiac dysfunction. In addition, we observed that GW4869 (an inhibitor of sEV release) or diminazene aceturate (DIZE, an activator of ACE2) treatment could attenuate PM_2.5‐induced cardiac dysfunction in vivo. Taken together, our results suggest that PM_2.5 exposure promotes sEV‐linked miR421 release after lung injury and hereby contributes to PM_2.5‐induced cardiac dysfunction via suppressing ACE2.

The Interaction among Microbiota, Epigenetic Regulation, and Air Pollutants in Disease Prevention

Environmental pollutants can influence microbiota variety, with important implications for the general wellbeing of organisms. In subjects at high-risk of cancer, gut, and lung microbiota are distinct from those of low-risk subjects, and disease progression is associated with microbiota alterations. As with many inflammatory diseases, it is the combination of specific host and environmental factors in certain individuals that provokes disease outcomes. The microbiota metabolites influence activity of epigenetic enzymes. The knowledge of the mechanisms of action of environmental pollution now includes not only the alteration of the gut microbiota but also the interaction between different human microbiota niches such as the lung–gut axis. The epigenetic regulations can reprogram differentiated cells in response to environmental changes. The microbiota can play a major role in the progression and suppression of several epigenetic diseases. Accordingly, the maintenance of a balanced microbiota by monitoring the environmental stimuli provides a novel preventive approach for disease prevention. Metagenomics technologies can be utilized to establish new mitigation approaches for diseases induced by polluted environments. The purpose of this review is to examine the effects of particulate matter exposure on the progression of disease outcomes as related to the alterations of gut and lung microbial communities and consequent epigenetic modifications.

Black Tea Alleviates Particulate Matter-Induced Lung Injury via the Gut-Lung Axis in Mice

Black tea, as the most consumed kind of tea, is shown to have beneficial effects on human health. However, its impact on particulate matter (PM) induced lung injury and the mechanisms involved have been sparsely addressed. Here, we show that PM-exposed mice exhibited oxidative stress and inflammation in the lungs, which was significantly alleviated by a daily intake of black tea infusion (TI) in a concentration-dependent manner. Interestingly, both the ethanol-soluble fraction (ES) and the ethanol precipitate fraction (EP) exhibited better effects than those of TI; moreover, EP tended to have stronger protection than ES in some indicators, implying that EP played a dominant role in the prevention effects. Furthermore, fecal microbiota transplantation (FMT) revealed that the gut microbiota was differentially reshaped by TI and its fractions were able to directly alleviate the injury induced by PMs. These results indicate that daily intake of black tea and its fractions, especially EP, may alleviate particulate matter-induced lung injury via the gut-lung axis in mice. In addition, the Lachnospiraceae_NK4A136_group could be the core gut microbe contributing to the protection of EP and thus should be further studied in the future.

The Synergistic Effects of Polysaccharides and Ginsenosides From American Ginseng (Panax quinquefolius L.) Ameliorating Cyclophosphamide-Induced Intestinal Immune Disorders and Gut Barrier Dysfunctions Based on Microbiome-Metabolomics Analysis

Cyclophosphamide (CTX), used in cancer chemotherapy, a high dose of which would cause immunosuppressive effect and intestinal mucosa damage. American ginseng (Panax quinquefolius L.) has a long history of functional food use for immunological disorder, colitis, cancer, and so on. This study aimed to illustrate the underlying mechanism of American ginseng’s immunomodulatory effect in CTX-induced mice. In this study, all groups of American ginseng (American ginseng polysaccharide [AGP], American ginseng ginsenoside [AGG], co-treated with American ginseng polysaccharide and ginsenoside [AGP_AGG]) have relieve the immune disorder by reversing the lymphocyte subsets ratio in spleen and peripheral blood, as well as stimulating CD4⁺T cells and IgA-secreting cells in small intestine. These three treatment groups, especially AGP_AGG co-treated group recovered the intestine morphology that up-regulated villus height (VH)/crypt depth (CD) ratio, areas of mucins expression, quantity of goblet cells, and expression of tight junction proteins (ZO-1, occludin). Importantly, the microbiome-metabolomics analysis was applied in this study to illustrate the possible immuno-modulating mechanism. The synergistic effect of polysaccharides and ginsenosides (AGP_AGG group) restored the gut microbiota composition and increased various beneficial mucosa-associated bacterial taxa Clostridiales, Bifidobacterium, and Lachnospiraceae, while decreased harmful bacteria Escherichia-Shigella and Peptococcaceae. Also, AGP_AGG group altered various fecal metabolites such as uric acid, xanthurenic acid, acylcarnitine, 9,10-DHOME, 13-HDoHE, LysoPE15:0, LysoPC 16:0, LysoPI 18:0, and so on, that associated with immunometabolism or protective effect of gut barrier. These results suggest AG, particularly co-treated of polysaccharide and ginsenoside may be used as immunostimulants targeting microbiome-metabolomics axis to prevent CTX-induced side effects in cancer patients.