Perfluorooctane sulfonate alters gut microbiota-host metabolic homeostasis in mice

Perinatal Exposure to Phenols and Poly- and Perfluoroalkyl Substances and Gut Microbiota in One-Year-Old Children

The role of the gut microbiota in human health calls for a better understanding of its determinants. In particular, the possible effects of chemicals with widespread exposure other than pharmaceuticals are little known. Our aim was to characterize the sensitivity of the early-life gut microbiota to specific chemicals with possible antimicrobial action. Within the SEPAGES French couple-child cohort, we assessed 12 phenols in repeated urine samples from 356 pregnant women and their offspring and 19 poly- and perfluoroalkyl substances (PFASs) in serum from the pregnant women. We collected stool samples from the children at one year of age, in which the V3-V4 region of the 16S rRNA gene was sequenced, allowing for gut bacterial profiling. Associations of each chemical with α- and β-diversity indices of the gut microbiota and with the relative abundance of the most abundant taxa were assessed using single-pollutant and mixture (BKMR) models. Perinatal exposure to certain parabens was associated with gut microbiota α- and β-diversity and with Firmicutes and Proteobacteria. Suggestive associations of certain phenols with genera of the Lachnospiraceae and Enterobacteriaceae families were observed, but these were not maintained after correction for multiple testing. Parabens, which have known antimicrobial properties, might disrupt the child gut microbiota, but larger studies are required to confirm these findings.

Impacts of PFOS, PFOA and their alternatives on the gut, intestinal barriers and gut-organ axis

With the restricted use of perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA), a number of alternatives to PFOS and PFOA have attracted great interest. Most of the alternatives are still characterized by persistence, bioaccumulation, and a variety of toxicity. Due to the production and use of these substances, they can be detected in the atmosphere, soil and water body. They affect human health through several exposure pathways and especially enter the gut by drinking water and eating food, which results in gut toxicity. In this review, we summarized the effects of PFOS, PFOA and 9 alternatives on pathological changes in the gut, the disruption of physical, chemical, biological and immune barriers of the intestine, and the gut-organ axis. This review provides a valuable understanding of the gut toxicity of PFOS, PFOA and their alternatives as well as the human health risks of emerging contaminants.

Contributions of Synthetic Chemicals to Autoimmune Disease Development and Occurrence

PURPOSE OF REVIEW

Exposure to many synthetic chemicals has been linked to a variety of adverse human health effects, including autoimmune diseases. In this scoping review, we summarize recent evidence detailing the effects of synthetic environmental chemicals on autoimmune diseases and highlight current research gaps and recommendations for future studies.

RECENT FINDINGS

We identified 68 recent publications related to environmental chemical exposures and autoimmune diseases. Most studies evaluated exposure to persistent environmental chemicals and autoimmune conditions including rheumatoid arthritis (RA), systemic lupus (SLE), systemic sclerosis (SSc), and ulcerative colitis (UC) and Crohn's disease. Results of recent original research studies were mixed, and available data for some exposure-outcome associations were particularly limited. PFAS and autoimmune inflammatory bowel diseases (UC and CD) and pesticides and RA appeared to be the most frequently studied exposure-outcome associations among recent publications, despite a historical research focus on solvents. Recent studies have provided additional evidence for the associations of exposure to synthetic chemicals with certain autoimmune conditions. However, impacts on other autoimmune outcomes, particularly less prevalent conditions, remain unclear. Owing to the ubiquitous nature of many of these exposures and their potential impacts on autoimmune risk, additional studies are needed to better evaluate these relationships, particularly for understudied autoimmune conditions. Future research should include larger longitudinal studies and studies among more diverse populations to elucidate the temporal relationships between exposure-outcome pairs and to identify potential population subgroups that may be more adversely impacted by immune modulation caused by exposure to these chemicals.

Maternal PFOS exposure in mice induces hepatic lipid accumulation and inflammation in adult female offspring: Involvement of microbiome-gut-liver axis and autophagy

Perfluorooctane sulfonates (PFOS) are the persistent organic pollutants. In the present study, 0, 0.3, or 3-mg/kg PFOS were administered to pregnant mice from GD 11 to GD 18. The histopathology of liver and intestine, serum and hepatic lipid levels, lipid metabolism related genes, and gut microbiota were examined in adult female offspring. The results suggested that maternal PFOS exposure increased serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), and induced F4/80+ macrophage infiltration in adult female offspring, in addition to the elevation of TNF-α and IL-1β mRNA levels in low-dose and high-dose groups, respectively. Furthermore, maternal exposure to PFOS increased serum triglyceride (TG) and hepatic total cholesterol (TC) levels, which was associated with the alteration of the process of fatty acid transport and β-oxidation, TG synthesis and transport, cholesterol synthesis and excretion in the liver. The AMPK/mTOR/autophagy signaling was also inhibited in the liver of adult female offspring. Moreover, changes in gut microbiota were also related to lipid metabolism, especially for the Desulfovibrio, Ligilactobacillus, Enterorhabdus, HT002 and Peptococcaceae_unclassified. Additionally, maternal exposure to PFOS decreased mRNA expressions of the tight junction protein and AB+ goblet cells in the colon, while increasing the overproduction of lipopolysaccharides (LPS) and F4/80+ macrophage infiltration. Collectively, maternal PFOS exposure induced liver lipid accumulation and inflammation, which strongly correlated with the disruption of the gut-liver axis and autophagy in adult female offspring, highlighting the persistent adverse effects in offspring exposed to PFOS.

Prenatal PFAS exposure, gut microbiota dysbiosis, and neurobehavioral development in childhood

Studies on the role of the gut microbiota in the associations between per- and polyfluoroalkyl substance (PFAS) exposure and adverse neurodevelopment are limited. Umbilical cord serum and faeces samples were collected from children, and the Strengths and Difficulties Questionnaire (SDQ) was conducted. Generalized linear models, linear mixed-effects models, multivariate analysis by linear models and microbiome regression-based kernel association tests were used to evaluate the associations among PFAS exposure, the gut microbiota, and neurobehavioural development. Perfluorohexane sulfonic acid (PFHxS) exposure was associated with increased scores for conduct problems and externalizing problems, as well as altered gut microbiota alpha and beta diversity. PFHxS concentrations were associated with higher relative abundances of Enterococcus spp. but lower relative abundances of several short-chain fatty acid-producing genera (e.g., Ruminococcus gauvreauii group spp.). PFHxS exposure was also associated with increased oxidative phosphorylation. Alpha and beta diversity were found significantly associated with conduct problems and externalizing problems. Ruminococcus gauvreauii group spp. abundance was positively correlated with prosocial behavior scores. Increased alpha diversity played a mediating role in the associations of PFHxS exposure with conduct problems. Our results suggest that the gut microbiota might play an important role in PFAS neurotoxicity, which may have implications for PFAS control.

Hepatic injury and ileitis associated with gut microbiota dysbiosis in mice upon F-53B exposure

Chlorinated polyfluorinated ether sulfonate (F-53B), a substitute of perfluorooctane sulfonic acid (PFOS), has attracted significant attention for its link to hepatotoxicity and enterotoxicity. Nevertheless, the underlying mechanisms of F-53B-induced enterohepatic toxicity remain incompletely understood. This study aimed to explore the role of F-53B exposure on enterohepatic injury based on the gut microbiota, pathological and molecular analysis in mice. Here, we exposed C57BL/6 mice to F-53B (0, 4, 40, and 400 μg/L) for 28 days. Our findings revealed a significant accumulation of F-53B in the liver, followed by small intestines, and feces. In addition, F-53B induced pathological collagen fiber deposition and lipoid degeneration, up-regulated the expression of fatty acid β-oxidation-related genes (PPARα and PPARγ, etc), while simultaneously down-regulating pro-inflammatory genes (Nlrp3, IL-1β, and Mcp1) in the liver. Meanwhile, F-53B induced ileal mucosal barrier damage, and an up-regulation of pro-inflammatory genes and mucosal barrier-related genes (Muc1, Muc2, Claudin1, Occludin, Mct1, and ZO-1) in the ileum. Importantly, F-53B distinctly altered gut microbiota compositions by increasing the abundance of Akkermansia and decreasing the abundance of Prevotellaceae_NK3B31_group in the feces. F-53B-altered microbiota compositions were significantly associated with genes related to fatty acid β-oxidation, inflammation, and mucosal barrier. In summary, our results demonstrate that F-53B is capable of inducing hepatic injury, ileitis, and gut microbiota dysbiosis in mice, and the gut microbiota dysbiosis may play an important role in the F-53B-induced enterohepatic toxicity.

Exposure to environmental toxicants is associated with gut microbiome dysbiosis, insulin resistance and obesity

Environmental toxicants (ETs) are associated with adverse health outcomes. Here we hypothesized that exposures to ETs are linked with obesity and insulin resistance partly through a dysbiotic gut microbiota and changes in the serum levels of secondary bile acids (BAs). Serum BAs, per- and polyfluoroalkyl substances (PFAS) and additional twenty-seven ETs were measured by mass spectrometry in 264 Danes (121 men and 143 women, aged 56.6 ± 7.3 years, BMI 29.7 ± 6.0 kg/m2) using a combination of targeted and suspect screening approaches. Bacterial species were identified based on whole-genome shotgun sequencing (WGS) of DNA extracted from stool samples. Personalized genome-scale metabolic models (GEMs) of gut microbial communities were developed to elucidate regulation of BA pathways. Subsequently, we compared findings from the human study with metabolic implications of exposure to perfluorooctanoic acid (PFOA) in PPARα-humanized mice. Serum levels of twelve ETs were associated with obesity and insulin resistance. High chemical exposure was associated with increased abundance of several bacterial species (spp.) of genus (Anaerotruncus, Alistipes, Bacteroides, Bifidobacterium, Clostridium, Dorea, Eubacterium, Escherichia, Prevotella, Ruminococcus, Roseburia, Subdoligranulum, and Veillonella), particularly in men. Conversely, females in the higher exposure group, showed a decrease abundance of Prevotella copri. High concentrations of ETs were correlated with increased levels of secondary BAs including lithocholic acid (LCA), and decreased levels of ursodeoxycholic acid (UDCA). In silico causal inference analyses suggested that microbiome-derived secondary BAs may act as mediators between ETs and obesity or insulin resistance. Furthermore, these findings were substantiated by the outcome of the murine exposure study. Our combined epidemiological and mechanistic studies suggest that multiple ETs may play a role in the etiology of obesity and insulin resistance. These effects may arise from disruptions in the microbial biosynthesis of secondary BAs.

Transcriptomic and metabolomic profile changes in the liver of Sprague Dawley rat offspring after maternal PFOS exposure during gestation and lactation

Epidemiological and experimental research has indicated an association between perfluorooctane sulfonate (PFOS) exposure and liver disease. However, the potential hepatotoxic effects and mechanisms of low-level prenatal PFOS exposure in offspring remain ambiguous. The objective of this research was to examine the alterations in liver transcriptomic and metabolomic profiles in offspring rats at postnatal day (PND) 30 following gestational and lactational exposure to PFOS (from gestational day 1 to 20 and PND 1 to 21). Pregnant Sprague-Dawley rats were separated into a control group (3% starch gel solution, oral gavage) and a PFOS exposure group (0.03 mg/kg body weight per day, oral gavage). Histopathological changes in liver sections were observed by hematoxylin and eosin staining. Biochemical analysis was conducted to evaluate changes in glucose and lipid metabolism. Transcriptomic and metabolomic analyses were utilized to identify significant genes and metabolites associated with alterations of liver glucose and lipid metabolism through an integrated multi-omics analysis. No significant differences were found in the measured biochemical parameters. In total, 167 significant differentially expressed genes (DEGs) related to processes such as steroid biosynthesis, PPAR signaling pathway, and fat digestion and absorption were identified in offspring rats in the PFOS exposure group. Ninety-five altered metabolites were exhibited in the PFOS exposure group, such as heptaethylene glycol, lysoPE (0:0/18:0), lucidenic acid K, and p-Cresol sulfate. DEGs associated with steroid biosynthesis, PPAR signaling pathway, fat digestion and absorption were significantly upregulated in the PFOS exposure group (P < 0.05). The analysis of correlations indicated that there was a significant inverse correlation between all identified differential metabolites and the levels of fasting blood glucose, high-density lipoprotein, and triglycerides in the PFOS exposure group (P < 0.05). Our findings demystify that early-life PFOS exposure can lead to alterations in transcriptomic and metabolomic profiles in the offspring's liver, which provided mechanistic insights into the potential hepatotoxicity and developmental toxicity associated with environmentally relevant levels of PFOS exposure.

Interaction between Per- and Polyfluorinated Substances (PFAS) and Acetaminophen in Disease Exacerbation-Focusing on Autism and the Gut-Liver-Brain Axis

This review presents a new perspective on the exacerbation of autism spectrum disorder (ASD) by per- and polyfluoroalkyl substances (PFAS) through the gut-liver-brain axis. We have summarized evidence reported on the involvement of the gut microbiome and liver inflammation that led to the onset and exacerbation of ASD symptoms. As PFAS are toxicants that particularly target liver, this review has comprehensively explored the possible interaction between PFAS and acetaminophen, another liver toxicant, as the chemicals of interest for future toxicology research. Our hypothesis is that, at acute dosages, acetaminophen has the ability to aggravate the impaired conditions of the PFAS-exposed liver, which would further exacerbate neurological symptoms such as lack of social communication and interest, and repetitive behaviors using mechanisms related to the gut-liver-brain axis. This review discusses their potential interactions in terms of the gut-liver-brain axis and signaling pathways that may contribute to neurological diseases.

Gut microbiota related response of Oryzias melastigma to combined exposure of polystyrene microplastics and tetracycline

The co-existence of microplastics (MPs) and antibiotics in the coastal environment poses a combined ecological risk. Single toxic effects of MPs or antibiotics on aquatic organisms have been verified, however, the exploration of their combined toxic effects remains limited. Here, foodborne polystyrene microplastics (PS-MPs, 10 μm, 0.1 % w/w in food) and waterborne tetracyclines (TC, 50 μg/L) were used to expose an estuarine fish Oryzias melastigma for four weeks. We found that the aqueous availability of TC was not significantly altered coexisting with MPs. The fish body weight gain was significantly slower in TC alone or combined groups than the control group, consistent with the lower lipid content in livers. The body length gain was significantly inhibited by the combined presence compared to the single exposure. Both exposures led to a shift of gut microbiota composition and diversity. TC and the combined group possessed similar gut microbiota which is distinct from PS-MPs and the control group. The Firmicutes/Bacteroidetes (F/B) ratio in the TC and combined groups were significantly lower compared to the control, while the PS-MPs group showed no significant impact. Metabolomic analysis of the fish liver confirmed the shift of metabolites in specific pathways after different exposures. More, a number of gut microbiota-related metabolites on lipid metabolism was perturbed, which were annotated in arachidonic acid metabolism and linoleic acid metabolism. In all, TC modulates bacterial composition in the fish gut and disturbs their liver metabolites via the gut-liver axis, which led to the slower growth of O. melastigma. More, the adverse impact was aggravated by the co-exposure to foodborne PS-MPs.

Inflammation and cardiometabolic diseases induced by persistent organic pollutants and nutritional interventions: Effects of multi-organ interactions

The development and outcome of inflammatory diseases are associated with genetic and lifestyle factors, which include chemical and nonchemical stressors. Persistent organic pollutants (POPs) are major groups of chemical stressors. For example, dioxin-like polychlorinated biphenyls (PCBs), per- and polyfluoroalkyl substances (PFASs), and polybrominated diphenyl ethers (PBDEs) are closely associated with the incidence of inflammatory diseases. The pathology of environmental chemical-mediated inflammatory diseases is complex and may involve disturbances in multiple organs, including the gut, liver, brain, vascular tissues, and immune systems. Recent studies suggested that diet-derived nutrients (e.g., phytochemicals, vitamins, unsaturated fatty acids, dietary fibers) could modulate environmental insults and affect disease development, progression, and outcome. In this article, mechanisms of environmental pollutant-induced inflammation and cardiometabolic diseases are reviewed, focusing on multi-organ interplays and highlighting recent advances in nutritional strategies to improve the outcome of cardiometabolic diseases associated with environmental exposures. In addition, advanced system biology approaches are discussed, which present unique opportunities to unveil the complex interactions among multiple organs and to fuel the development of precision intervention strategies in exposed individuals.

Per- and Poly-fluoroalkyl Substances and Bile Acid Profiles in Pregnant Women

Alterations in bile acid (BA) profiles are closely associated with adverse outcomes in pregnant women and their offspring and may be one potential pathway underlying the related metabolic effects of per- and poly-fluoroalkyl substances (PFAS) exposure. However, evidence of associations between PFAS exposure and BA profiles in pregnant women is scarce. This study examined the associations of individual PFAS and PFAS mixture with BA profiles of pregnant women. We obtained quantitative data on the plasma concentrations of 13 PFAS and 15 BAs in 645 pregnant women from the Jiashan birth cohort. In Bayesian kernel machine regression models, the PFAS mixture was associated with increased plasma CA, TCA, TCDCA, and GLCA levels but with decreased GCA and LCA concentrations. Furthermore, the PFAS mixture was associated with increased concentrations of total BAs and the secondary/primary BA ratio but with decreased conjugated/unconjugated and glycine/taurine-conjugated BA ratios. PFHxS, PFUdA, PFOS, PFNA, and PFDA were the dominant contributors. The results of the linear regression analysis of individual PFAS were generally similar. Our findings provide the first epidemiological evidence for the associations of a PFAS mixture with BA profiles in pregnant women and may provide explanatory insights into the biological pathways underlying the related metabolic effects of PFAS exposure.

Antibiotic induced restructuring of the gut microbiota does not affect oral uptake and accumulation of perfluorooctane sulfonic acid (PFOS) in rats

Perfluorooctane sulfonic acid (PFOS) is a manmade legacy compound belonging to the group of persistent per- and polyfluorinated substances (PFAS). While many adverse health effects of PFOS have been identified, knowledge about its effect on the intestinal microbiota is scarce. The microbial community inhabiting the gut of mammals plays an important role in health, for instance by affecting the uptake, excretion, and bioavailability of some xenobiotic toxicants. Here, we investigated (i) the effect of vancomycin-mediated microbiota modulation on the uptake of PFOS in adult Sprague-Dawley rats, and (ii) the effects of PFOS exposure on the rat microbiota composition. Four groups of twelve rats were exposed daily for 7 days with either 3 mg/kg PFOS plus 8 mg/kg vancomycin, only PFOS, only vancomycin, or a corn oil control. Vancomycin-induced modulation of the gut microbiota composition did not affect uptake of branched and linear PFOS over a period of 7 days, measured in serum samples. 16S rRNA amplicon sequencing of faecal and intestinal samples revealed that vancomycin treatment lowered microbial alpha-diversity, while PFOS increased the microbial diversity in vancomycin-treated as well as in non-antibiotic treated animals, possibly because an observed decrease in the Enterobacteriaceae abundance allows other microbial species to propagate. Colonic short-chain fatty acids were significantly lower in vancomycin-treated animals but remained unaffected by PFOS. Our results suggest that PFOS exposure may disturb the intestinal microbiota, but that antibiotic-induced modulation of the intestinal ecosystem does not affect systemic uptake of PFOS in rats.

Recent Review on Selected Xenobiotics and Their Impacts on Gut Microbiome and Metabolome

As it is well known, the gut is one of the primary sites in any host for xenobiotics, and the many microbial metabolites responsible for the interactions between the gut microbiome and the host. However, there is a growing concern about the negative impacts on human health induced by toxic xenobiotics. Metabolomics, broadly including lipidomics, is an emerging approach to studying thousands of metabolites in parallel. In this review, we summarized recent advancements in mass spectrometry (MS) technologies in metabolomics. In addition, we reviewed recent applications of MS-based metabolomics for the investigation of toxic effects of xenobiotics on microbial and host metabolism. It was demonstrated that metabolomics, gut microbiome profiling, and their combination have a high potential to identify metabolic and microbial markers of xenobiotic exposure and determine its mechanism. Further, there is increasing evidence supporting that reprogramming the gut microbiome could be a promising approach to the intervention of xenobiotic toxicity.

Accumulation of Linoleic Acid by Altered Peroxisome Proliferator-Activated Receptor-α Signaling Is Associated with Age-Dependent Hepatocarcinogenesis in Ppara Transgenic Mice

Long-term ligand activation of PPARα in mice causes hepatocarcinogenesis through a mechanism that requires functional PPARα. However, hepatocarcinogenesis is diminished in both Ppara-null and PPARA-humanized mice, yet both lines develop age-related liver cancer independently of treatment with a PPARα agonist. Since PPARα is a master regulator of liver lipid metabolism in the liver, lipidomic analyses were carried out in wild-type, Ppara-null, and PPARA-humanized mice treated with and without the potent agonist GW7647. The levels of hepatic linoleic acid in Ppara-null and PPARA-humanized mice were markedly higher compared to wild-type controls, along with overall fatty liver. The number of liver CD4+ T cells was also lower in Ppara-null and PPARA-humanized mice and was negatively correlated with the elevated linoleic acid. Moreover, more senescent hepatocytes and lower serum TNFα and IFNγ levels were observed in Ppara-null and PPARA-humanized mice with age. These studies suggest a new role for PPARα in age-associated hepatocarcinogenesis due to altered lipid metabolism in Ppara-null and PPARA-humanized mice and the accumulation of linoleic acid as part of an overall fatty liver that is associated with loss of CD4+ T cells in the liver in both transgenic models. Since fatty liver is a known causal risk factor for liver cancer, Ppara-null and PPARA-humanized mice are valuable models for examining the mechanisms of PPARα and age-dependent hepatocarcinogenesis.

Early life exposure to low-dose perfluorooctane sulfonate disturbs gut barrier homeostasis and increases the risk of intestinal inflammation in offspring

Perfluorooctane sulfonate (PFOS), one of the legacy per- and poly-fluoroalkyl substances (PFAS), is associated with multiple adverse health effects on children. However, much remains to be known about its potential impacts on intestinal immune homeostasis during early life. Our study found that PFOS exposure during pregnancy in rats significantly increased the maternal serum levels of interleukin-6 (IL-6) and zonulin, a gut permeability biomarker, and decreased gene expressions of Tight junction protein 1 (Tjp1) and Claudin-4 (Cldn4), the tight junction proteins, in maternal colons on gestation day 20 (GD20). Being exposed to PFOS during pregnancy and lactation in rats significantly decreased the body weight of pups and increased the offspring's serum levels of IL-6 and tumor necrosis factor-α (TNF-α) on postnatal day 14 (PND14), and induced a disrupted gut tight junction, manifested by decreased expressions of Tjp1 in pup's colons on PND14 and increased pup's serum concentrations of zonulin on PND28. By integrating high-throughput 16S rRNA sequencing and metabolomics, we demonstrated that early-life PFOS exposure altered the diversity and composition of gut microbiota that were correlated with the changed metabolites in serum. The altered blood metabolome was associated with increased proinflammatory cytokines in offspring. These changes and correlations were divergent at each developmental stage, and pathways underlying immune homeostasis imbalance were significantly enriched in the PFOS-exposed gut. Our findings provide new evidence for the developmental toxicity of PFOS and its underlying mechanism and explain in part the epidemiological observation of its immunotoxicity.

Investigating fatty liver disease-associated adverse outcome pathways of perfluorooctane sulfonate using a systems toxicology approach

Adverse outcome pathway (AOP) frameworks help elucidate toxic mechanisms and support chemical regulation. AOPs link a molecular initiating event (MIE), key events (KEs), and an adverse outcome by key event relationships (KERs), which assess the biological plausibility, essentiality, and empirical evidence involved. Perfluorooctane sulfonate (PFOS), a hazardous poly-fluoroalkyl substance, demonstrates hepatotoxicity in rodents. PFOS may induce fatty liver disease (FLD) in humans; however, the underlying mechanism remains unclear. In this study, we evaluated the toxic mechanisms of PFOS-associated FLD by developing an AOP using publicly available data. We identified MIE and KEs by performing GO enrichment analysis on PFOS- and FLD-associated target genes collected from public databases. The MIEs and KEs were then prioritized by PFOS-gene-phenotype-FLD networks, AOP-helpFinder, and KEGG pathway analyses. Following a comprehensive literature review, an AOP was then developed. Finally, six KEs for the AOP of FLD were identified. This AOP indicated that toxicological processes initiated by SIRT1 inhibition led to SREBP-1c activation, de novo fatty acid synthesis, and fatty acid and triglyceride accumulation, culminating in liver steatosis. Our study provides insights into the toxic mechanism of PFOS-induced FLD and suggests approaches to assessing the risk of toxic chemicals.

Gut Microbiome-Host Metabolome Homeostasis upon Exposure to PFOS and GenX in Male Mice

Alterations of the normal gut microbiota can cause various human health concerns. Environmental chemicals are one of the drivers of such disturbances. The aim of our study was to examine the effects of exposure to perfluoroalkyl and polyfluoroalkyl substances (PFAS)-specifically, perfluorooctane sulfonate (PFOS) and 2,3,3,3-tetrafluoro-2-(heptafluoropropoxy) propanoic acid (GenX)-on the microbiome of the small intestine and colon, as well as on liver metabolism. Male CD-1 mice were exposed to PFOS and GenX in different concentrations and compared to controls. GenX and PFOS were found to have different effects on the bacterial community in both the small intestine and colon based on 16S rRNA profiles. High GenX doses predominantly led to increases in the abundance of Clostridium sensu stricto, Alistipes, and Ruminococcus, while PFOS generally altered Lactobacillus, Limosilactobacillus, Parabacteroides, Staphylococcus, and Ligilactobacillus. These treatments were associated with alterations in several important microbial metabolic pathways in both the small intestine and colon. Untargeted LC-MS/MS metabolomic analysis of the liver, small intestine, and colon yielded a set of compounds significantly altered by PFOS and GenX. In the liver, these metabolites were associated with the important host metabolic pathways implicated in the synthesis of lipids, steroidogenesis, and in the metabolism of amino acids, nitrogen, and bile acids. Collectively, our results suggest that PFOS and GenX exposure can cause major perturbations in the gastrointestinal tract, aggravating microbiome toxicity, hepatotoxicity, and metabolic disorders.

Curbing per- and polyfluoroalkyl substances (PFASs): First investigation in a constructed wetland-microbial fuel cell system

The presence of per- and polyfluoroalkyl substances (PFASs) in water environments has been linked to a slew of negative health effects in both animals and humans, but the green and eco-sustainable removal technologies remain largely unknown. Constructed wetland coupled microbial fuel cell (CW-MFC) is termed a "green process" to control pollutants and recover energy. However, so far, no study has investigated the removal of PFASs and their effects on the performance of the CW-MFC systems. Here, we investigated the removal performance of PFOA and PFOS in the CW-MFC systems both in the absence and presence of electricity circuit, and explored the distribution and fate of PFASs and their interactions with other elements in the systems. Our findings demonstrated excellent removal efficiency of >96% PFOA and PFOS in CW-MFC systems. PFOA and PFOS were distributed throughout the system via wastewater flow, while electrode material and plants are the main enrichment sites in which MFC enhanced up to 10% PFASs removal. However, a loss of 7.2-13.5% of nitrogen removal and a decrease of 7.3% in bioelectricity output were observed when PFASs were introduced in the system. The driven force led to the loss of nitrogen removal and bioelectricity generation lies in the accumulation of PFASs in system composition, which affected microbial activity and community composition, damaging the health of the plant, and in turn reducing CW-MFC's functioning. No doubt, CW-MFC systems provide an alternative technique for PFASs removal, alleviating some limitations to the physical and chemical techniques, but further investigation is highly needed.

Research Progress on Up-Conversion Fluorescence Probe for Detection of Perfluorooctanoic Acid in Water Treatment

Perfluorooctanoic acid (PFOA) is a new type of organic pollutant in wastewater that is persistent, toxic, and accumulates in living organisms. The development of rapid and sensitive analytical methods to detect PFOA in environmental media is of great importance. Fluorescence detection has the advantages of high efficiency and low cost, in which fluorescent probes have excellent fluorescence properties, excellent bio-solubility, and remarkable photostability. It is necessary to review the fluorescence detection routes for PFOA. In addition, the up-conversion of fluorescent materials (UCNPs), as fluorescent materials to prepare fluorescent probes with, has significant advantages and also attracts the attention of researchers, however, reviews related to their application in detecting PFOA and comparing them with other routes are rare. Furthermore, there are many strategies to improve the performance of up-conversion fluorescent probes including SiO₂ modification and amino modification. These strategies can enhance the detection effect of PFOA. Thus, this work reviews the types of fluorescence detection, the design, and synthesis of UCNPs, their recognition mechanism, properties, and their application progress. Moreover, the development trend and prospects of these detection probes are given.

Per- and polyfluoroalkyl substances exposure and its influence on the intestinal barrier: An overview on the advances

Per- and polyfluoroalkyl substances (PFAS) are a class of artificially synthetic organic compounds that are hardly degraded in the natural environment. PFAS have been widely used for many decades, and the persistence and potential toxicity of PFAS are an emerging concern in the world. PFAS exposed via diet can be readily absorbed by the intestine and enter the circulatory system or accumulate directly at intestinal sites, which could interact with the intestine and cause the destruction of intestinal barrier. This review summarizes current relationships between PFAS exposure and intestinal barrier damage with a focus on more recent toxicological studies. Exposure to PFAS could cause inflammation in the gut, destruction of the gut epithelium and tight junction structure, reduction of the mucus layer, and induction of the toxicity of immune cells. PFAS accumulation could also induce microbial disorders and metabolic products changes. In addition, there are limited studies currently, and most available studies converge on the health risk of PFAS exposure for human intestinal disease. Therefore, more efforts are deserved to further understand potential associations between PFAS exposure and intestinal dysfunction and enable better assessment of exposomic toxicology and health risks for humans in the future.

Metabolomic, Lipidomic, Transcriptomic, and Metagenomic Analyses in Mice Exposed to PFOS and Fed Soluble and Insoluble Dietary Fibers

BACKGROUND

Perfluorooctane sulfonate (PFOS) is a persistent environmental pollutant that has become a significant concern around the world. Exposure to PFOS may alter gut microbiota and liver metabolic homeostasis in mammals, thereby increasing the risk of cardiometabolic diseases. Diets high in soluble fibers can ameliorate metabolic disease risks.

OBJECTIVES

We aimed to test the hypothesis that soluble fibers (inulin or pectin) could modulate the adverse metabolic effects of PFOS by affecting microbe-liver metabolism and interactions.

METHODS

Male C57BL/6J mice were fed an isocaloric diet containing different fibers: a) inulin (soluble), b) pectin (soluble), or c) cellulose (control, insoluble). The mice were exposed to PFOS in drinking water (3 μ g / g  per day ) for 7 wk. Multi-omics was used to analyze mouse liver and cecum contents.

RESULTS

In PFOS-exposed mice, the number of differentially expressed genes associated with atherogenesis and hepatic hyperlipidemia were lower in those that were fed soluble fiber than those fed insoluble fiber. Shotgun metagenomics showed that inulin and pectin protected against differences in microbiome community in PFOS-exposed vs. control mice. It was found that the plasma PFOS levels were lower in inulin-fed mice, and there was a trend of lower liver accumulation of PFOS in soluble fiber-fed mice compared with the control group. Soluble fiber intake ameliorated the effects of PFOS on host hepatic metabolism gene expression and cecal content microbiome structure.

DISCUSSIONS

Results from metabolomic, lipidomic, and transcriptomic studies suggest that inulin- and pectin-fed mice were less susceptible to PFOS-induced liver metabolic disturbance, hepatic lipid accumulation, and transcriptional changes compared with control diet-fed mice. Our study advances the understanding of interaction between microbes and host under the influences of environmental pollutants and nutrients. The results provide new insights into the microbe-liver metabolic network and the protection against environmental pollutant-induced metabolic diseases by high-fiber diets. https://doi.org/10.1289/EHP11360.

Perturbation of the gut microbiome in wild-caught freshwater turtles (Emydura macquarii macquarii) exposed to elevated PFAS levels

Per- and polyfluoroalkyl substances (PFAS) are environmentally persistent and pervasive. Understanding the toxicity of PFAS to wildlife is difficult, both due to the complexity of biotic and abiotic perturbations in the taxa under study and the practical and ethical problems associated with studying the impacts of environmental pollutants on free living wildlife. One avenue of inquiry into the effects of environmental pollutants, such as PFAS, is assessing the impact on the host gut microbiome. Here we show the microbial composition and biochemical functional outputs from the gut microbiome of sampled faeces from euthanised and necropsied wild-caught freshwater turtles (Emydura macquarii macquarii) exposed to elevated PFAS levels. The microbial community composition was profiled by 16S rRNA gene sequencing using a Nanopore MinION and the biochemical functional outputs of the gut microbiome were profiled using a combination of targeted central carbon metabolism metabolomics using liquid chromatography coupled to a triple quadrupole mass spectrometer (LC-QqQ-MS) and untargeted metabolomics using liquid chromatography coupled to a quadrupole time of flight mass spectrometer (LC-QToF-MS). Total PFAS was measured in the turtle serum using standard methods. These preliminary data demonstrated a 60-fold PFAS increase in impacted turtles compared to the sampled aquatic environment. The microbiome community was also impacted in the PFAS exposed turtles, with the ratio of Firmicutes-to-Bacteroidetes rising from 1.4 at the reference site to 5.5 at the PFAS impacted site. This ratio increase is indicative of host stress and dysfunction of the gut microbiome that was correlated with the biochemical metabolic function data, metabolites observed that are indications of stress and inflammation in the gut microbiome. Utilising the gut microbiome of sampled faeces collected from freshwater turtles provides a non-destructive avenue for investigating the impacts of PFAS in native wildlife, and provides an avenue to explore other contaminants in higher-order taxa within the environment.

Characterization of triclosan-induced hepatotoxicity and triclocarban-triggered enterotoxicity in mice by multiple omics screening

Triclosan (2,4,4'-trichloro-2'-hydroxydiphenyl ether, TCS) and triclocarban (3,4,4'-trichloro-carbanilide, TCC) are two antimicrobial agents commonly used for personal care products. Previous studies primarily focused on respective harmful effects of TCS and TCC. In terms of their structural similarities and differences, however, the structure-toxicity relationships on health effects of TCS and TCC exposure remain unclear. Herein, global ¹H NMR-based metabolomics was employed to screen the changes of metabolic profiling in various biological matrices including liver, serum, urine, feces and intestine of mice exposed to TCS and TCC at chronic and acute dosages. Metagenomics was also applied to analyze the gut microbiota modulation by TCS and TCC exposure. Targeted MS-based metabolites quantification, histopathological examination and biological assays were subsequently conducted to supply confirmatory information on respective toxicity of TCS and TCC. We found that oral administration of TCS mainly induced significant liver injuries accompanied with inflammation and dysfunction, hepatic steatosis fatty acids and bile acids metabolism disorders; while TCC exposure caused marked intestine injuries leading to striking disruption of colonic morphology, inflammatory status and intestinal barrier integrity, intestinal bile acids metabolism and microbial community. These comparative results provide novel insights into structure-dependent mechanisms of TCS-induced hepatotoxicity and TCC-triggered enterotoxicity in mice.

Persistent organic pollutants in foods, their interplay with gut microbiota and resultant toxicity

Persistent Organic Pollutants (POPs) have become immensely prevalent in the environment as a result of their unique chemical properties (persistent, semi-volatile and bioaccumulative nature). Their occurrence in the soil, water and subsequently in food has become a matter of concern. With food being one of the major sources of exposure, the detrimental impact of these chemicals on the gut microbiome is inevitable. The gut microbiome is considered as an important integrant for human health. It participates in various physiological, biochemical and immunological activities; thus, affects the metabolism and physiology of the host. A myriad of studies have corroborated an association between POP-induced gut microbial dysbiosis and prevalence of disorders. For instance, ingestion of polychlorinated biphenyls, polybrominated diphenyl ethers or organochlorine pesticides influenced bile acid metabolism via alteration of bile salt hydrolase activity of Lactobacillus, Clostridium or Bacteroides genus. At the same time, some chemicals such as DDE have the potential to elevate Proteobacteria and Firmicutes/Bacteriodetes ratio influencing their metabolic activity leading to enhanced short-chain fatty acid synthesis, ensuing obesity or a pre-diabetic state. This review highlights the impact of POPs exposure on the gut microbiota composition and metabolic activity, along with an account of its corresponding consequences on the host physiology. The critical role of gut microbiota in impeding the POPs excretion out of the body resulting in their prolonged exposure and consequently, enhanced degree of toxicity is also emphasized.

Factors Modulating COVID-19: A Mechanistic Understanding Based on the Adverse Outcome Pathway Framework

Addressing factors modulating COVID-19 is crucial since abundant clinical evidence shows that outcomes are markedly heterogeneous between patients. This requires identifying the factors and understanding how they mechanistically influence COVID-19. Here, we describe how eleven selected factors (age, sex, genetic factors, lipid disorders, heart failure, gut dysbiosis, diet, vitamin D deficiency, air pollution and exposure to chemicals) influence COVID-19 by applying the Adverse Outcome Pathway (AOP), which is well-established in regulatory toxicology. This framework aims to model the sequence of events leading to an adverse health outcome. Several linear AOPs depicting pathways from the binding of the virus to ACE2 up to clinical outcomes observed in COVID-19 have been developed and integrated into a network offering a unique overview of the mechanisms underlying the disease. As SARS-CoV-2 infectibility and ACE2 activity are the major starting points and inflammatory response is central in the development of COVID-19, we evaluated how those eleven intrinsic and extrinsic factors modulate those processes impacting clinical outcomes. Applying this AOP-aligned approach enables the identification of current knowledge gaps orientating for further research and allows to propose biomarkers to identify of high-risk patients. This approach also facilitates expertise synergy from different disciplines to address public health issues.

Challenges of fluoride pollution in environment: Mechanisms and pathological significance of toxicity - A review

Fluoride is an important trace element in the living body. A suitable amount of fluoride has a beneficial effect on the body, but disproportionate fluoride entering the body will affect various organs and systems, especially the liver, kidneys, nervous system, endocrine system, reproductive system, bone, and intestinal system. In recent years, with the rapid development of agriculture and industry, fluoride pollution has become one of the important factors of environmental pollution, and fluoride pollution in any form is becoming a serious problem. Although countries around the world have made great breakthroughs in controlling fluoride pollution, however fluorosis still exists. A large amount of fluoride accumulated in animals will not only produce the toxic effects, but it also causes cell damage and affect the normal physiological activities of the body. There is no systematic description of the damage mechanism of fluoride. Therefore, the study on the toxicity mechanism of fluoride is still in progress. This review summarizes the existing information of several molecular mechanisms of the fluoride toxicity comprehensively, aiming to clarify the toxic mechanism of fluoride on various body systems. We have also summerized the pathological changes of those organ systems after fluoride poisoning in order to provide some ideas and solutions to the reader for the prevention and control of modern fluoride pollution.

The Role of Fecal Microbiota in Liver Toxicity Induced by Perfluorooctane Sulfonate in Male and Female Mice

BACKGROUND

Perfluorooctane sulfonate (PFOS) is a persistent organic pollutant that can cause hepatotoxicity. The underlying toxicological mechanism remains to be investigated. Given the critical role of fecal microbiota in liver function, it is possible that fecal microbiota may contribute to the liver toxicity induced by PFOS.

OBJECTIVES

We aimed to investigate the role of liver-fecal microbiota axis in modulating PFOS-induced liver injury in mice.

METHODS

Male and female mice were exposed to PFOS or vehicle for 14 d. In this investigation, 16S rDNA sequencing and metabolomic profiling were performed to identify the perturbed fecal microbiota and altered metabolites with PFOS exposure. In addition, antibiotic treatment, fecal microbiota transplantation, and bacterial administration were conducted to validate the causal role of fecal microbiota in mediating PFOS-induced liver injury and explore the potential underlying mechanisms.

RESULTS

Both male and female mice exposed to PFOS exhibited liver inflammation and steatosis, which were accompanied by fecal microbiota dysbiosis and the disturbance of amino acid metabolism in comparison with control groups. The hepatic lesions were fecal microbiota-dependent, as supported by antibiotic treatment and fecal microbiota transplantation. Mice with altered fecal microbiota in antibiotic treatment or fecal microbiota transplantation experiments exhibited altered arginine concentrations in the liver and feces. Notably, we observed sex-specific lower levels of key microbiota, including Lactobacillus, Enterococcus, and Akkermansia. Mice treated with specific bacteria showed lower arginine levels and lower expression of the phosphorylated mTOR and P70S6K, suggesting lower activity of the related pathway and mitigation of the pathological differences observed in PFOS-exposed mice.

CONCLUSIONS

Our study demonstrated the critical role of the fecal microbiota in PFOS-induced liver injury in mice. We also identified several critical bacteria that could protect against liver injury induced by PFOS in male and female mice. Our present research provided novel insights into the mechanism of PFOS-induced liver injury in mice. https://doi.org/10.1289/EHP10281.

Immunotoxicity mechanisms of perfluorinated compounds PFOA and PFOS

Perfluorinated and polyfluorinated compounds (PFASs) are a class of synthetic chemical substances that are widely used in human production and life, such as fire-fighting foams, textiles and clothing, surfactants, and surface protective agents. Perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) are the most abundant and common perfluorinated compounds in biota and humans. Currently, PFOA and PFOS have been listed in the Stockholm Convention on Persistent Organic Pollutants, and their production has been halted in many countries. However, because the high-energy carbon-fluorine bond can make it resistant to hydrolysis, photolysis, microbial degradation, and vertebrate metabolism, PFOA and PFOS show environmental persistence and bioaccumulation and hence, are of great concern to humans and wildlife. PFOA and PFOS have toxic effects on the immune system of the body. This article reviewed the effects of PFOA and PFOS on immune organs such as the spleen, bone marrow, and thymus of mice and zebrafish, and the effects on non-specific immune functions such as the skin barrier, intestinal mucosal barrier, and humoral immunity. We also reviewed the influence of specific immune functions based on cellular immunity, and further summarized the possible immune toxicity mechanisms such as AIM2 inflammasome activation, gene dysregulation, and signal pathway disorders caused by PFOA and PFOS. The aim of this review was to provide a reference for further understanding of the immunotoxicity and the responsible mechanism of PFOA and PFOS.

Effects of long-term perfluorooctane sulfonate (PFOS) exposure on activated sludge performance, composition, and its microbial community

The widespread presence and persistence of perfluorooctane sulfonate (PFOS) in wastewater treatment plants, as well as its toxicity and bioaccumulation potential, necessitates the investigation on their impact on bioreactor performance. A 48-day exposure test was adopted to study the effects of low (10 μg L-1) and high (1000 μg L-1) PFOS concentrations in a sequencing batch reactor on the performance, composition, and microbial community of activated sludge. The results suggested that adding PFOS at low and high concentrations lowered the removal efficiency of total nitrogen by 22.48% (p < 0.01) and 16.30% (p < 0.01) respectively, while enhanced that of total phosphorus by 1.87% (p > 0.05) and 7.07% (p < 0.05) respectively, compared with the control group. The addition of PFOS also led to the deterioration of activated sludge dewatering performance. Composition and spectroscopic measurements revealed that the PFOS dosage changed the composition of the activated sludge. Furthermore, the PFOS altered the structure and function of the activated sludge microbial community as well as key enzyme activities.

Developmental toxicity of Nafion byproduct 2 (NBP2) in the Sprague-Dawley rat with comparisons to hexafluoropropylene oxide-dimer acid (HFPO-DA or GenX) and perfluorooctane sulfonate (PFOS)

Nafion byproduct 2 (NBP2) is a polyfluoroalkyl ether sulfonic acid that was recently detected in surface water, drinking water, and human serum samples from monitoring studies in North Carolina, USA. We orally exposed pregnant Sprague-Dawley rats to NBP2 from gestation day (GD) 14-18 (0.1-30 mg/kg/d), GD17-21, and GD8 to postnatal day (PND) 2 (0.3-30 mg/kg/d) to characterize maternal, fetal, and postnatal effects. GD14-18 exposures were also conducted with perfluorooctane sulfonate (PFOS) for comparison to NBP2, as well as data previously published for hexafluoropropylene oxide-dimer acid (HFPO-DA or GenX). NBP2 produced stillbirth (30 mg/kg), reduced pup survival shortly after birth (10 mg/kg), and reduced pup body weight (10 mg/kg). Histopathological evaluation identified reduced glycogen stores in newborn pup livers and hepatocyte hypertrophy in maternal livers at ≥ 10 mg/kg. Exposure to NBP2 from GD14-18 reduced maternal serum total T₃ and cholesterol concentrations (30 mg/kg). Maternal, fetal, and neonatal liver gene expression was investigated using RT-qPCR pathway arrays, while maternal and fetal livers were also analyzed using TempO-Seq transcriptomic profiling. Overall, there was limited alteration of genes in maternal or F1 livers from NBP2 exposure with significant changes mostly occurring in the top dose group (30 mg/kg) associated with lipid and carbohydrate metabolism. Metabolomic profiling indicated elevated maternal bile acids for NBP2, but not HFPO-DA or PFOS, while all three reduced 3-indolepropionic acid. Maternal and fetal serum and liver NBP2 concentrations were similar to PFOS, but ∼10-30-fold greater than HFPO-DA concentrations at a given maternal oral dose. NBP2 is a developmental toxicant in the rat, producing neonatal mortality, reduced pup body weight, reduced pup liver glycogen, reduced maternal thyroid hormones, and altered maternal and offspring lipid and carbohydrate metabolism similar to other studied PFAS, with oral toxicity for pup loss that is slightly less potent than PFOS but more potent than HFPO-DA.

Impact of Contaminants on Microbiota: Linking the Gut-Brain Axis with Neurotoxicity

Over the last years, research has focused on microbiota to establish a missing link between neuronal health and intestine imbalance. Many studies have considered microbiota as critical regulators of the gut–brain axis. The crosstalk between microbiota and the central nervous system is mainly explained through three different pathways: the neural, endocrine, and immune pathways, intricately interconnected with each other. In day-to-day life, human beings are exposed to a wide variety of contaminants that affect our intestinal microbiota and alter the bidirectional communication between the gut and brain, causing neuronal disorders. The interplay between xenobiotics, microbiota and neurotoxicity is still not fully explored, especially for susceptible populations such as pregnant women, neonates, and developing children. Precisely, early exposure to contaminants can trigger neurodevelopmental toxicity and long-term diseases. There is growing but limited research on the specific mechanisms of the microbiota–gut–brain axis (MGBA), making it challenging to understand the effect of environmental pollutants. In this review, we discuss the biological interplay between microbiota–gut–brain and analyse the role of endocrine-disrupting chemicals: Bisphenol A (BPA), Chlorpyrifos (CPF), Diethylhexyl phthalate (DEHP), and Per- and polyfluoroalkyl substances (PFAS) in MGBA perturbations and subsequent neurotoxicity. The complexity of the MGBA and the changing nature of the gut microbiota pose significant challenges for future research. However, emerging in-silico models able to analyse and interpret meta-omics data are a promising option for understanding the processes in this axis and can help prevent neurotoxicity.

The new PFAS C6O4 and its effects on marine invertebrates: First evidence of transcriptional and microbiota changes in the Manila clam Ruditapes philippinarum

There is growing concern for the wide use ofperfluorooctanoic acid (PFOA) because of its toxic effects on the environment and on human health. A new compound - the so called C6O4 (perfluoro ([5-methoxy-1,3-dioxolan-4-yl]oxy) acetic acid) - was recently introduced as one of the alternative to traditional PFOA, however this was done without any scientific evidence of the effects of C6O4 when dispersed into the environment. Recently, the Regional Agency for the Protection of the Environment of Veneto (Italy) detected high levels of C6O4 in groundwater and in the Po river, increasing the alarm for the potential effects of this chemical into the natural environment. The present study investigates for the first time the effects of C6O4 on the Manila clam Ruditapes philippinarum exposed to environmental realistic concentrations of C6O4 (0.1 µg/L and 1 µg/L) for 7 and 21 days. Furthermore, in order to better understand if C6O4 is a valid and less hazardous alternative to its substitute, microbial and transcriptomic alterations were also investigated in clams exposed to 1 µg/L ofPFOA. Results indicate that C6O4 may cause significant perturbations to the digestive gland microbiota, likely determining the impairment of host physiological homeostasis. Despite chemical analyses suggest a 5 times lower accumulation potential of C604 as compared to PFOA in clam soft tissues, transcriptional analyses reveal several alterations of gene expression profile. A large part of the altered pathways, including immune response, apoptosis regulation, nervous system development, lipid metabolism and cell membrane is the same in C6O4 and PFOA exposed clams. In addition, clams exposed to C6O4 showed dose-dependent responses as well as possible narcotic or neurotoxic effects and reduced activation of genes involved in xenobiotic metabolism. Overall, the present study suggests that the potential risks for marine organism following environmental contamination are not reduced by replacing PFOA with C6O4. In addition, the detection of both C6O4 and PFOA into tissues of clams inhabiting the Lagoon of Venice - where there are no point sources of either compounds - recommends a similar capacity to spread throughout the environment. These results prompt the urgent need to re-evaluate the use of C6O4 as it may represent not only an environmental hazard but also a potential risk for human health.

Effect of an Antibacterial Polysaccharide Produced by Chaetomium globosum CGMCC 6882 on the Gut Microbiota of Mice

Previously, a polysaccharide produced by Chaetomiumglobosum CGMCC 6882 was found to have antibacterial activity, but its toxic effects on body health and gut microbiota were concealed. Recent results showed that this polysaccharide was safe to Caco-2 cells and mice, while it reduced the body weight gain of mice from 10.5 ± 1.21 g to 8.4 ± 1.17 g after 28 days administration. Acetate, propionate, butyrate and total short-chain fatty acids concentrations increased from 23.85 ± 1.37 μmol/g, 10.23 ± 0.78 μmol/g, 7.15 ± 0.35 μmol/g and 41.23 ± 0.86 μmol/g to 42.77 ± 1.29 μmol/g, 20.03 ± 1.44 μmol/g, 12.06 ± 0.51 μmol/g and 74.86 ± 2.07 μmol/g, respectively. Furthermore, this polysaccharide enriched the abundance of gut microbiota and the Firmicutes/Bacteroidetes ratio was increased from 0.5172 to 0.7238. Overall, this study provides good guidance for the promising application of polysaccharides as preservatives in foods and in other fields in the future.

Impacts of radiation exposure on the bacterial and fungal microbiome of small mammals in the Chernobyl Exclusion Zone

Environmental impacts of the 1986 Chernobyl Nuclear Power Plant accident are much debated, but the effects of radiation on host microbiomes have received little attention to date. We present the first analysis of small mammal gut microbiomes from the Chernobyl Exclusion Zone in relation to total absorbed dose rate, including both caecum and faeces samples. We provide novel evidence that host species determines fungal community composition, and that associations between microbiome (both bacterial and fungal) communities and radiation exposure vary between host species. Using ambient versus total weighted absorbed dose rates in analyses produced different results, with the latter more robust for interpreting microbiome changes at the individual level. We found considerable variation between results for faecal and gut samples of bank voles, suggesting faecal samples are not an accurate indicator of gut composition. Associations between radiation exposure and microbiome composition of gut samples were not robust against geographical variation, although we identified families of bacteria (Lachnospiraceae and Muribaculaceae) and fungi (Steccherinaceae and Strophariaceae) in the guts of bank voles that may serve as biomarkers of radiation exposure. Further studies considering a range of small mammal species are needed to establish the robustness of these potential biomarkers.

Gut Microbiota Combined With Metabolomics Reveals the Repeated Dose Oral Toxicity of β-Cyclodextrin in Mice

Βeta-cyclodextrin (β-CD) with a hydrophobic cavity enables the formation of inclusion complexes with organic molecules. The formation of host–guest complexes makes the application of β-CD popular in many fields, but their interaction with organisms is poorly understood. In the present study, the effect of β-CD on gut microbiota (16S rRNA gene sequencing), serum metabolites (gas chromatography–mass spectrometry platform), and their correlation (Pearson correlation analysis) was investigated after 14 days repeated oral exposure in mice. β-CD did not significantly affect the α-diversity indexes, including Richness, Chao1, Shannon and Simpson indexes, but disturbed the structure of the gut bacteria according to the result of principal component analysis (PCA). After taxonomic assignment, 1 in 27 phyla, 2 in 48 classes, 3 in 107 orders, 6 in 192 families, and 8 in 332 genera were significantly different between control and β-CD treated groups. The serum metabolites were significantly changed after β-CD treatment according to the result of unsupervized PCA and supervised partial least squares-discriminant analysis (PLS-DA). A total of 112 differential metabolites (89 downregulated and 23 upregulated) were identified based on the VIP >1 from orthogonal PLS-DA and p <0.05 from Student’s t-test. The metabolic pathways, including ABC transporters, pyrimidine metabolism, purine metabolism, glucagon signaling pathway, insulin signaling pathway, and glycolysis/gluconeogenesis, were enriched by KEGG pathway analysis. Our study provides a general observation of gut microbiota, serum metabolites and their correlation after exposure to β-CD in mice, which will be helpful for future research and application of β-CD.

Perfluorooctane sulfonate exerts inflammatory bowel disease-like intestinal injury in rats

Background

Perfluorooctane sulfonate (PFOS), a type of perfluorinated compounds (PFCs), can induce various organ toxicity, including hepatomegaly, immunotoxicity, and gut microbiota disorder. PFCs have been associated with inflammatory bowel disease (IBD). Yet, whether PFOS exposure causes IBD-like disorder and the underlying mechanism remains undefined. Here, we investigated the influence of PFOS exposure on the development of IBD-like disorder in rats.

Methods

Sprague-Dawley rats were intraperitoneally injected with PFOS (1 or 10 mg/kg) or normal saline (NS) every other day for 15 days. Body weight, serum concentrations of serum amyloid A (SAA) and high sensitivity C reactive protein (hsCRP) were measured. Pathological assessments of villi height and crypt depth in the proximal duodenum and jejunum were performed using H&E staining. Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining was used to assay cell apoptosis in the jejunum. The infiltration of inflammatory cells and cytokines in the jejunum were detected by immunohistochemistry analysis.

Results

PFOS (10 mg/kg) significantly increased the body weight, SAA and hsCRP, whereas no significant differences were observed in PFOS 1 mg/kg group of rats. The villi height and crypt depth in the proximal duodenum and jejunum were significantly reduced upon PFOS exposure. PFOS induced higher histopathological score in intestinal tissues compared to NS. Notably, TUNEL-positive cells were significantly higher in the jejunum upon PFOS exposure. Further, neutrophil and macrophage accumulated, and inflammatory cytokines infiltration were also remarkably increased in rats exposed to PFOS.

Conclusion

PFOS induces IBD-like phenotypes in rats, with associated inflammatory infiltration to intestinal.

Exposure to Perfluorooctanoic Acid Induces Cognitive Deficits via Altering Gut Microbiota Composition, Impairing Intestinal Barrier Integrity, and Causing Inflammation in Gut and Brain

Perfluorooctanoic acid (PFOA) is an eight-carbon perfluoroalkyl chemical and has been detected widely in many media. Although the toxic effect of PFOA has been confirmed, the influence on gut and brain has not been cleared. Male C57BL/6J mice were exposed to different concentrations (0, 0.5, 1, and 3 mg/Kg (bw)/day of PFOA for 35 days in this work. The results indicate that exposure to PFOA could damage intestinal barrier integrity and impair the synaptic structure. PFOA exposure also caused inflammation in gut and brain by increasing lipopolysaccharide, tumor necrosis factor-α, interleukin-1 beta, and cyclooxygenase-2 and decreasing interleukin-10. Interestingly, fecal microbiota transplantation treatment could attenuate a series of PFOA-induced changes to a certain extent. The results suggest that exposure to PFOA has potential deleterious effects on gut and brain, and inflammation may play an essential role in evaluating the influence induced by PFOA exposure.

Metabolic Signatures of the Exposome-Quantifying the Impact of Exposure to Environmental Chemicals on Human Health

Human health and well-being are intricately linked to environmental quality. Environmental exposures can have lifelong consequences. In particular, exposures during the vulnerable fetal or early development period can affect structure, physiology and metabolism, causing potential adverse, often permanent, health effects at any point in life. External exposures, such as the “chemical exposome” (exposures to environmental chemicals), affect the host’s metabolism and immune system, which, in turn, mediate the risk of various diseases. Linking such exposures to adverse outcomes, via intermediate phenotypes such as the metabolome, is one of the central themes of exposome research. Much progress has been made in this line of research, including addressing some key challenges such as analytical coverage of the exposome and metabolome, as well as the integration of heterogeneous, multi-omics data. There is strong evidence that chemical exposures have a marked impact on the metabolome, associating with specific disease risks. Herein, we review recent progress in the field of exposome research as related to human health as well as selected metabolic and autoimmune diseases, with specific emphasis on the impacts of chemical exposures on the host metabolome.

Effect of Perfluorooctanoic Acid on the Epigenetic and Tight Junction Genes of the Mouse Intestine

Perfluorooctanoic acid (PFOA) has been implicated in various toxicities including neurotoxicity, genotoxicity, nephrotoxicity, epigenetic toxicity, immunotoxicity, reproductive toxicity, and hepatotoxicity. However, information on the accumulation of PFOA in the intestine and its toxic effects on intestinal epigenetics and tight junction (TJ) genes is sparse. CD1 mice were dosed with PFOA (1, 5, 10, or 20 mg/kg/day) for 10 days, and its accumulation and induced alterations in the expression of epigenetic and tight junction genes in the small intestine and colon were evaluated using LC-MS and qPCR techniques. PFOA reduced the expression levels of DNA methyltransferases (Dnmt1, Dnmt3a, Dnmt3b) primarily in the small intestine whereas, in the colon, a decrease was observed only at high concentrations. Moreover, ten-eleven translocation genes (Tet2 and Tet3) expression was dysregulated in the small intestine, whereas in the colon Tets remained unaffected. The tight junction genes Claudins (Cldn), Occludin (Ocln), and Tight Junction Protein (Tjp) were also heavily altered in the small intestine. TJs responded differently across the gut, in proportion to PFOA dosing. Our study reveals that PFOA triggers DNA methylation changes and alters the expression of genes essential for maintaining the physical barrier of intestine, with more profound effects in the small intestine compared to the colon.