Subchronic oral mercury caused intestinal injury and changed gut microbiota in mice

Metal(loid)-gut microbiota interactions and microbiota-related protective strategies: A review

Human exposure to metal(loid)s has dramatically increased over the past five decades, which has triggered public concern worldwide. Recently, gut microbiota has been considered a target for metal(loid)s, and some literature has reviewed the interactions between gut microbiota and heavy metal(loid)s (HMs) with high toxicity. However, whether there is an interaction between gut microbiota and metal(loid)s with essential roles or some normal functions are far from clear to date. Importantly, in addition to traditional probiotics that have been clarified to alleviate the adverse effect of HMs on the body, some novel probiotics, prebiotics, synbiotics, and postbiotics may also exhibit comparable or even better abilities of metal(loid) remediation. In this review, we mainly outline and discuss recent research findings on the metal(loid)-gut microbiota interactions and microbiota-related protective strategies.

Subchronic Chloroform Exposure Causes Intestinal Damage and Induces Gut Microbiota Disruption and Metabolic Dysregulation in Mice

Chloroform is a prevalent toxic environmental pollutant in urban settings, posing risks to human health through exposure via various mediums such as air and tap water. The gut microbiota plays a pivotal role in maintaining host health. However, there is a paucity of research elucidating the impact of chloroform exposure on the gut microbiota. In this investigation, 18 SPF Kunming female mice were stratified into three groups (n = 6) and subjected to oral gavage with chloroform doses equivalent to 0, 50, and 150 mg/kg of body weight over 30 days. Our findings demonstrate that subchronic chloroform exposure significantly perturbs hematological parameters in mice and induces histopathological alterations in cecal tissues, consequently engendering marked disparities in the functional composition of cecal microbiota and metabolic equilibrium of cecal contents. Ultimately, our investigation revealed a statistically robust correlation, exhibiting a high degree of significance, between the intestinal microbiome composition and the metabolites that were differentially expressed consequent to chloroform exposure.

Is There an Interplay between Environmental Factors, Microbiota Imbalance, and Cancer Chemotherapy-Associated Intestinal Mucositis?

Interindividual variation in drug efficacy and toxicity is a significant problem, potentially leading to adverse clinical and economic public health outcomes. While pharmacogenetics and pharmacogenomics have long been considered the primary causes of such heterogeneous responses, pharmacomicrobiomics has recently gained attention. The microbiome, a community of microorganisms living in or on the human body, is a critical determinant of drug response and toxicity. Factors such as diet, lifestyle, exposure to xenobiotics, antibiotics use, illness, and genetics can influence the composition of the microbiota. Changes in the intestinal microbiota are particularly influential in drug responsiveness, especially in cancer chemotherapy. The microbiota can modulate an individual's response to a drug, affecting its bioavailability, clinical effect, and toxicity, affecting treatment outcomes and patient quality of life. For instance, the microbiota can convert drugs into active or toxic metabolites, influencing their efficacy and side effects. Alternatively, chemotherapy can also alter the microbiota, creating a bidirectional interplay. Probiotics have shown promise in modulating the microbiome and ameliorating chemotherapy side effects, highlighting the potential for microbiota-targeted interventions in improving cancer treatment outcomes. This opinion paper addresses how environmental factors and chemotherapy-induced dysbiosis impact cancer chemotherapy gastrointestinal toxicity.

Toxic and essential metals: metabolic interactions with the gut microbiota and health implications

Human exposure to heavy metals, which encompasses both essential and toxic varieties, is widespread. The intestine functions as a critical organ for absorption and metabolism of heavy metals. Gut microbiota plays a crucial role in heavy metal absorption, metabolism, and related processes. Toxic heavy metals (THMs), such as arsenic (As), mercury (Hg), lead (Pb), and cadmium (Cd), can cause damage to multiple organs even at low levels of exposure, and it is crucial to emphasize their potential high toxicity. Nevertheless, certain essential trace elements, including iron (Fe), copper (Cu), and manganese (Mn), play vital roles in the biochemical and physiological functions of organisms at low concentrations but can exert toxic effects on the gut microbiota at higher levels. Some potentially essential micronutrients, such as chromium (Cr), silicon (Si), and nickel (Ni), which were considered to be intermediate in terms of their essentiality and toxicity, had different effects on the gut microbiota and their metabolites. Bidirectional relationships between heavy metals and gut microbiota have been found. Heavy metal exposure disrupts gut microbiota and influences its metabolism and physiological functions, potentially contributing to metabolic and other disorders. Furthermore, gut microbiota influences the absorption and metabolism of heavy metals by serving as a physical barrier against heavy metal absorption and modulating the pH, oxidative balance, and concentrations of detoxification enzymes or proteins involved in heavy metal metabolism. The interactions between heavy metals and gut microbiota might be positive or negative according to different valence states, concentrations, and forms of the same heavy metal. This paper reviews the metabolic interactions of 10 common heavy metals with the gut microbiota and their health implications. This collated information could provide novel insights into the disruption of the intestinal microbiota caused by heavy metals as a potential contributing factor to human diseases.

The hidden threat: Environmental toxins and their effects on gut microbiota

The human gut microbiota (GM), which consists of a complex and diverse ecosystem of bacteria, plays a vital role in overall wellness. However, the delicate balance of this intricate system is being compromised by the widespread presence of environmental toxins. The intricate connection between contaminants in the environment and human well-being has garnered significant attention in recent times. Although many environmental pollutants and their toxicity have been identified and studied in laboratory settings and animal models, there is insufficient data concerning their relevance to human physiology. Consequently, research on the toxicity of environmental toxins in GM has gained prominence in recent years. Various factors, such as air pollution, chemicals, heavy metals, and pesticides, have a detrimental impact on the composition and functioning of the GM. This comprehensive review aims to comprehend the toxic effects of numerous environmental pollutants, including antibiotics, endocrine-disrupting chemicals, heavy metals, and pesticides, on GM by examining recent research findings. The current analysis concludes that different types of environmental toxins can lead to GM dysbiosis and have various potential adverse effects on the well-being of animals. We investigate the alterations to the GM composition induced by contaminants and their impact on overall well-being, providing a fresh perspective on research related to pollutant exposure.

Could the gut microbiota be capable of making individuals more or less susceptible to environmental toxicants?

Environmental toxicants are chemical substances capable to impair environmental quality and exert adverse effects on humans and other animals. The main routes of exposure to these pollutants are through the respiratory tract, skin, and oral ingestion. When ingested orally, they will encounter trillions of microorganisms that live in a community - the gut microbiota (GM). While pollutants can disrupt the GM balance, GM plays an essential role in the metabolism and bioavailability of these chemical compounds. Under physiological conditions, strategies used by the GM for metabolism and/or excretion of xenobiotics include reductive and hydrolytic transformations, lyase and functional group transfer reactions, and enzyme-mediated functional transformations. Simultaneously, the host performs metabolic processes based mainly on conjugation, oxidation, and hydrolysis reactions. Thus, due to the broad variety of bacterial enzymes present in GM, the repertoire of microbial transformations of chemicals is considered a key component of the machinery involved in the metabolism of pollutants in humans and other mammals. Among pollutants, metals deserve special attention once contamination by metals is a worldwide problem, and their adverse effects can be observed even at very low concentrations due to their toxic properties. In this review, bidirectional interaction between lead, arsenic, cadmium, and mercury and the host organism and its GM will be discussed given the most recent literature, presenting an analysis of the ability of GM to alter the host organism's susceptibility to the toxic effects of heavy metals, as well as evaluating the extent to which interventions targeting the microbiota could be potential initiatives to mitigate the adverse effects resulting from poisoning by heavy metals. This study is the first to highlight the overlap between some of the bacteria found to be altered by metal exposure and the bacteria that also aid the host organism in the metabolism of these metals. This could be a key factor to determine the beneficial species able to minimize the toxicity of metals in future therapeutic approaches.

Dissecting the role of cadmium, lead, arsenic, and mercury in non-alcoholic fatty liver disease and non-alcoholic steatohepatitis

The objective of the present study was to review the existing epidemiological and laboratory findings supporting the role of toxic metal exposure in non-alcoholic fatty liver disease (NAFLD). The existing epidemiological studies demonstrate that cadmium (Cd), lead (Pb), arsenic (As), and mercury (Hg) exposure was associated both with an increased risk of NAFLD and altered biochemical markers of liver injury. Laboratory studies demonstrated that metal exposure induces hepatic lipid accumulation resulting from activation of lipogenesis and inhibition of fatty acid β-oxidation due to up-regulation of sterol regulatory element-binding protein 1 (SREBP-1), carbohydrate response element binding protein (ChREBP), peroxisome proliferator-activated receptor γ (PPARγ), and down-regulation of PPARα. Other metabolic pathways involved in this effect may include activation of reactive oxygen species (ROS)/extracellular signal-regulated kinase (ERK) and inhibition of AMP-activated protein kinase (AMPK) signaling. The mechanisms of hepatocyte damage during development of metal-induced hepatic steatosis were shown to involve oxidative stress, endoplasmic reticulum stress, pyroptosis, ferroptosis, and dysregulation of autophagy. Induction of inflammatory response contributing to progression of NAFLD to non-alcoholic steatohepatitis (NASH) upon toxic metal exposure was shown to be mediated by up-regulation of nuclear factor κB (NF-κB) and activation of NRLP3 inflammasome. Moreover, epigenetic effects of the metals, as well as their effect on gut microbiota and gut wall integrity were also shown to mediate their role in NAFLD development. Despite being demonstrated for Cd, Pb, and As, the contribution of these mechanisms into Hg-induced NAFLD is yet to be estimated. Therefore, further studies are required to clarify the intimate mechanisms underlying the relationship between heavy metal and metalloid exposure and NAFLD/NASH to reveal the potential targets for treatment and prevention of metal-induced NAFLD.

Challenges and strategies for preventing intestinal damage associated to mercury dietary exposure

Food represents the major risk factor for exposure to mercury in most human populations. Therefore, passage through the gastrointestinal tract plays a fundamental role in its entry into the organism. Despite the intense research carried out on the toxicity of Hg, the effects at the intestinal level have received increased attention only recently. In this review we first provide a critical appraisal of the recent advances on the toxic effects of Hg at the intestinal epithelium. Next, dietary strategies aimed to diminish Hg bioavailability or modulate the epithelial and microbiota responses will be revised. Food components and additives, including probiotics, will be considered. Finally, limitations of current approaches to tackle this problem and future lines of research will be discussed.

Oral exposure to inorganic mercury or methylmercury elicits distinct pro-inflammatory and pro-oxidant intestinal responses in a mouse model system

Humans are mainly exposed to mercury (Hg) through contaminated foodstuffs. However, the effects of Hg on the intestinal tract have received little attention. We performed a subchronic exposure to inorganic mercury or methylmercury in mice through drinking water (1, 5 or 10 mg/L for four months) to evaluate their intestinal impact. Histological, biochemical and gene expression analyses showed that both Hg species induced oxidative stress in small intestine and colon, while inflammation was mainly detected in the colon. Increased fecal albumin content indicated a compromised epithelial barrier. Mucus production was possibly also affected, as an increase in Muc2 expression was detected. However, differential effects were detected between both Hg species. Activation of p38 MAPK and increased crypt depth were detected in colon only with MeHg. Minor differences in microbiota composition were detected between unexposed and exposed mice. Although significant differences were detected between both Hg species at 10 mg/L, only the relative abundances of low abundance taxa were affected. Concentrations of microbial-derived short-chain fatty acids were decreased, suggesting an effect on microbial metabolism or increased demand by the intestinal epithelium. Results obtained confirm previous in vitro studies and highlights the intestinal mucosa as an initial target of Hg.

Lactic acid bacteria strains reduce in vitro mercury toxicity on the intestinal mucosa

A bicameral model consisting of Caco-2 and HT29-MTX intestinal epithelial cells and THP-1-derived macrophages has been used to test the ability of two strains of Lactobacillus to protect from damage caused by mercury. Exposure to 1 mg/ml mercury [Hg(II) or methyl-Hg] for seven days in this model resulted in an inflammatory and pro-oxidant response mainly driven by macrophages. This led to an impairment in the intestinal barrier, defective tight-junctions, increased permeability and mucus hypersecretion. In addition, the wound-healing capacity of the epithelial monolayer was also diminished. However, the presence of heat-killed Lactobacillus intestinalis or Lactobacillus johnsonii cells during Hg exposure reverted these effects, and most of the parameters recovered values similar to control cells. Both lactobacilli showed the capacity to bind Hg(II) and methyl-Hg under the cell culture conditions. This points to Hg sequestration as a likely mechanism that counteracted Hg toxicity. However, differences in the Hg binding capacity and in the effects between both strains suggest that other probiotic-mediated mechanisms may play a role in the alleviation of the damage elicited by Hg. These results show the potential of the bicameral intestinal epithelial model for screening of effective strains for their use in later in vivo studies.

Response of earthworms to microplastics in soil under biogas slurry irrigation: Toxicity comparison of conventional and biodegradable microplastics

As a reliable environment-friendly alternative, biodegradable plastic mulching films have been introduced into agricultural practice to reduce the adverse threats posed by conventional plastic products. Information regarding whether potential untoward effects of biodegradable plastics exist in soil and how strong are such effects on terrestrial organisms, however, still remains unknown. This study examined differences in the responses of earthworm, represented by Eisenia fetida, to exposure to biodegradable (PLA: polylactic acid) and conventional microplastics (PVC: polyvinylchloride, LDPE: low-density polyethylene) in soil with biogas slurry irrigation. Mortality, growth, histopathology and biochemical enzymes of the earthworms exposed to different concentrations of microplastics (5, 20 and 50 g/kg wet weight of soil, respectively) were investigated after 28 days of incubation in the experiment. The obtained results showed that the ecotoxicity of microplastics (MPs) to earthworms was time-dependent. Regardless of MPs type, continuous exposure to MPs at the concentration of 50 g/kg induced mucous vacuolization, longitude muscle disorder, and granular lipofuscin-like deposits generation in the epithelium. Moreover, tissue fibrosis and cavity formation were also observed in intestinal tissue. The presence of MPs stimulated the oxidative stress system of the earthworms, as indicated by the enhancement of malonaldehyde (MDA) content in vivo. The antioxidative defense system in earthworms was supposed to collapse at the MPs concentration of 50 g/kg after 28 days of exposure. Interestingly, PLA exhibited similar ecotoxicity effects with LDPE, which might violate the original intention of biodegradable plastics with less harmful or nontoxic influence on the terrestrial biotas. Thus, knowledge regarding the molecular and genetic mechanisms of the earthworms in soil containing biodegradable plastics should be further explored to better understand the risk posed by biodegradable plastics in the agroecosystem.

Gut as the target tissue of mercury and the extraintestinal effects

Mercury (Hg) is harmful to the environment and human health. The gut plays important roles as the biological, chemical, mechanical, and immune barriers in animals and human beings. It has been known that Hg can be absorbed and methylated/demethylated in the gut, on the other hand, the impacts of Hg to the gut (especially the gut microbiota) is less studied. This review paper summarizes the impacts of inorganic Hg (IHg) and methyl Hg (MeHg) on gut barriers and the extraintestinal effects (damage to other organs such as the liver and brain). Both IHg and MeHg were found to cause intestinal microbial disorders, abnormal metabolites production, tight junction damage, and immune responses in the gut. The damage to the gut also contributed to the extraintestinal effects like the hepatotoxicity by IHg and the neurotoxicity by MeHg. In all, it is proposed that the gut should be considered as an important target tissue of Hg exposure, and the regulation of gut microbiota may have the potential for the prevention and control of the toxicity of Hg.

Adverse health effects of emerging contaminants on inflammatory bowel disease

Inflammatory bowel disease (IBD) is becoming increasingly prevalent with the improvement of people's living standards in recent years, especially in urban areas. The emerging environmental contaminant is a newly-proposed concept in the progress of industrialization and modernization, referring to synthetic chemicals that were not noticed or researched before, which may lead to many chronic diseases, including IBD. The emerging contaminants mainly include microplastics, endocrine-disrupting chemicals, chemical herbicides, heavy metals, and persisting organic pollutants. In this review, we summarize the adverse health effect of these emerging contaminants on humans and their relationships with IBD. Therefore, we can better understand the impact of these new emerging contaminants on IBD, minimize their exposures, and lower the future incidence of IBD.

Effects of Lifetime Exposures to Environmental Contaminants on the Adult Gut Microbiome

Emerging experimental evidence indicates that toxicant-induced alterations in gut microbiota composition and activity may affect host homeostasis. However, data from human studies are scarce; to our knowledge, no previous studies have quantified the association of lifetime exposure to environmental chemicals, across multiple time points, with the composition of the adult gut microbiome. Here we studied 124 individuals born in the Faroe Islands in 1986-1987 who were followed approximately every seven years from birth through age 28 years. Organochlorine compounds, including polychlorinated biphenyls (PCBs) and pesticides, perfluoroalkyl substances (PFAS), and mercury (Hg), were measured in cord blood and longitudinally in participants' blood. At age 28, the gut microbiome was assessed using shotgun metagenomic sequencing. Historical contaminant exposures had little direct effect on the adult gut microbiome, while a small number of fastidious anaerobes were weakly linked to recent PFAS/PFOS exposures at age 28. In this cohort, our findings suggest no lasting effects of early life exposures on adult gut microbial composition, but proximal exposures may contribute to gut microbiome alterations. The methods developed and used for this investigation may help in future identification of small but lasting impacts of environmental toxicant exposure on the gut microbiome.

Thallium(I) exposure perturbs the gut microbiota and metabolic profile as well as the regional immune function of C57BL/6 J mice

Intestinal microbes regulate the development of diseases induced by environmental exposure. Thallium (Tl) is a highly toxic heavy metal, and its toxicity is rarely discussed in relation to gut microbes. Herein, we showed that Tl(I) exposure (10 ppm for 2 weeks) affected the alpha diversity of bacteria in the ileum, colon, and feces, but had little effect on the beta diversity of bacteria through 16S rRNA sequencing. LEfSe analysis revealed that Tl(I) exposure changed the abundance of intestinal microbiota along the digestive tract. Cecum metabolomic detection and analysis showed that Tl(I) exposure altered the abundance and composition of metabolites. In addition, the Kyoto Encyclopaedia of Genes and Genomes (KEGG) enrichment analysis revealed that Tl(I) exposure impaired amino acid, lipid, purine metabolism, and G protein-coupled receptor signalling pathways. A consistency test revealed a strong correlation, and a Pearson's correlation analysis showed an extensive interaction, between microorganisms and metabolites. Analysis of the intestinal immunity revealed that Tl(I) exposure suppressed the immune responses, which also had regional differences. These results identify the perturbation of the intestinal microenvironment by Tl exposure and provide a new explanation for Tl toxicity.

Antioxidative and anti-inflammatory effects of vitamin C on the liver of laying hens under chronic heat stress

In this study, we investigated the therapeutic effect and mechanism of action of vitamin C on chronic heat stress (CHS)-induced liver oxidative damage and inflammation in laying hens. The thermoneutral control group (TN group) was kept at a constant temperature of 22 ± 1°C, while the chronic heat stress group (CHS group) and the vitamin C supplemented group (HSV group) were exposed to heat stress (HS) (36 ± 1°C, 8 h/d). The TN and HS groups were fed the basic diet at will, and the HSV group was supplemented with 300 mg/kg of vitamin C on top of the basic diet. The experimental results showed a significant improvement in body weight and feed intake in the HSV group compared to the HS group. A significantly lower pH and higher HCO3- and PCO₂ levels were observed in the HSV group compared to the CHS group. As laying hens were supplemented with vitamin C, serum malondialdehyde (MDA) level was declined, superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities were increased, and total antioxidant capacity (T-AOC) was increased. Further, CHS induced an increase in the expression of inflammation-related genes and a decrease in the expression of antioxidant-related genes. In contrast, the addition of vitamin C reversed the effects of CHS, resulting in an increase in the expression of antioxidant-related genes and a decrease in the expression of inflammation-related genes. In conclusion, vitamin C can effectively alleviate CHS-induced acid-base imbalance in body fluids of laying hens and the oxidative damage and inflammatory response caused to the liver. Therefore, vitamin C can be used clinically as an effective drug to alleviate chronic heat stress in laying hens. This experiment provides clinical evidence and theoretical basis for the use of vitamin C as an effective drug to alleviate chronic heat stress in laying hens.

Bioactive compounds, antibiotics and heavy metals: effects on the intestinal structure and microbiome of monogastric animals – a non-systematic review

The intestinal structure and gut microbiota are essential for the animals‘ health. Chemical components taken with food provide the right environment for a specific microbiome which, together with its metabolites and the products of digestion, create an environment, which in turn is affects the population size of specific bacteria. Disturbances in the composition of the gut microbiota can be a reason for the malformation of guts, which has a decisive impact on the animal‘ health. This review aimed to analyse scientific literature, published over the past 20 years, concerning the effect of nutritional factors on gut health, determined by the intestinal structure and microbiota of monogastric animals. Several topics have been investigated: bioactive compounds (probiotics, prebiotics, organic acids, and herbal active substances), antibiotics and heavy metals (essentaial minerals and toxic heavy metals).

Secondary Dysfunction of the Intestinal Barrier in the Pathogenesis of Complications of Acute Poisoning

The last decade has been marked by an exponential increase in the number of publications on the physiological role of the normal human gut microbiota. The idea of a symbiotic relationship between the human organism and normal microbiota of its gastrointestinal tract has been firmly established as an integral part of the current biomedical paradigm. However, the type of this symbiosis varies from mutualism to parasitism and depends on the functional state of the host organism. Damage caused to the organism by external agents can lead to the emergence of conditionally pathogenic properties in the normal gut microbiota, mediated by humoral factors and affecting the outcome of exogenous exposure. Among the substances produced by symbiotic microbiota, there are an indefinite number of compounds with systemic toxicity. Some occur in the intestinal chyme in potentially lethal amounts in the case they enter the bloodstream quickly. The quick entry of potential toxicants is prevented by the intestinal barrier (IB), a set of structural elements separating the intestinal chyme from the blood. Hypothetically, severe damage to the IB caused by exogenous toxicants can trigger a leakage and subsequent systemic redistribution of toxic substances of bacterial origin. Until recently, the impact of such a redistribution on the outcome of acute exogenous poisoning remained outside the view of toxicology. The present review addresses causal relationships between the secondary dysfunction of the IB and complications of acute poisoning. We characterize acute systemic toxicity of such waste products of the normal gut microflora as ammonia and endotoxins, and demonstrate their involvement in the formation of such complications of acute poisoning as shock, sepsis, cerebral insufficiency and secondary lung injuries. The principles of assessing the functional state of the IB and the approaches to its protection in acute poisoning are briefly considered.

Effects of N-Acetyl-L-Cysteine on Serum Indices and Hypothalamic AMPK-Related Gene Expression Under Chronic Heat Stress

This study aims to investigate the effect of heat stress on the physiological metabolism of young laying hens and whether N-acetyl-l-cysteine (NAC) can effectively alleviate heat stress. 120 Hy-Line Brown laying hens aged 12 weeks were randomly divided into four groups: the control group (fed on basal diet under thermal neutral condition), HS group (fed on basal diet under heat stress condition), CN group (fed on the basic meal supplemented with 1,000 mg NAC per kg under thermal neutral condition), and HS+N group (fed on the basic meal was supplemented with 1000 mg NAC per kg under heat stress condition). The HS and HS+N groups were exposed to 36 ± 1°C for 10 h/day. The effects of NAC on the changes of serum concentrations of T3, T4, and CORT and hypothalamic gene and protein expressions induced by heat stress were measured. Results showed that heat stress upregulated the contents of T3, T4, and CORT, while NAC reduced the contents of T3, T4, and CORT. In addition, NAC downregulated AgRP expression, while upregulated the expression of POMC. Moreover, the expressions of AMPKα1, LKB1, and CPT1 were inhibited by NAC, while the expressions of AKT1, ACC, GPAT, and PPARα were increased after NAC treatment, and HMGR did not change significantly. Western blot and comprehensive immunofluorescence section of AMPK in the hypothalamus showed that NAC attenuated the activity of AMPK. In conclusion, NAC can enhance the resistance of laying hens to heat stress by alleviating the metabolic disorders of serum T3, T4, and CORT induced by heat stress, inhibiting the activation of the AMPK pathway and regulating the expression of appetite-related genes in the hypothalamus.

Contamination, exposure, and health risk assessment of Hg in Pakistan: A review

Mercury is a highly toxic and highly mobile heavy metal. It has been regarded as more toxic than other nonessential and toxic nonradioactive heavy metals. Moreover, it has a high tendency of bioaccumulation and biomagnification in the ecosystem. This study aimed to assess the environmental and health risks related to Hg. Seventy studies related to Hg in environmental media, aquatic biota, and food stuffs across Pakistan were reviewed, and their concentrations were used for ecological and human health risk assessments. High concentrations of Hg were reported in the environment, with maximum concentrations of 72 mg L^-1, 144 mg kg^-1, 887 mg kg^-1, and 49,807 ng m^-3 in surface water, surface soil, surface sediments, and urban atmosphere, respectively. The possible non-carcinogenic health risk (hazard quotient) of Hg was assessed in soil, water, and fish. High risks were calculated for seafood and vegetable consumption, while low risks were estimated for soils and groundwater ingestion and exposure. Overall, children showed higher risks than adults. Last, the risk quotient analysis (RQ) revealed significant risks for aquatic species. RQs showed that multiple species, especially those with smaller resilience, could face long-term detrimental impacts. High, medium, and low risks were calculated from 66.66, 16.17, and 16.17% of the reported Hg concentrations.

Impact of Cumulative Environmental and Dietary Xenobiotics on Human Microbiota: Risk Assessment for One Health

Chemical risk assessment in the context of the risk analysis framework was initially designed to evaluate the impact of hazardous substances or xenobiotics on human health. As the need of multiple stressors assessment was revealed to be more reliable regarding the occurrence and severity of the adverse effects in the exposed organisms, the cumulative risk assessment started to be the recommended approach. As toxicant mixtures and their "cocktail effects" are considered to be main hazards, the most important exposure for these xenobiotics would be of dietary and environmental origin. In fact, even a more holistic prism should currently be considered. In this sense, the definition of One Health refers to simultaneous actions for improving human, animal, and environmental health through transdisciplinary cooperation. Global policies necessitate going beyond the classical risk assessment for guaranteeing human health through actions and implementation of the One Health approach. In this context, a new perspective is proposed for the integration of microbiome biomarkers and next generation probiotics potentially impacting and modulating not only human health, but plant, animal health, and the environment.

Role-Playing Between Environmental Pollutants and Human Gut Microbiota: A Complex Bidirectional Interaction

There is a growing interest in the characterization of the involvement of toxicant and pollutant exposures in the development and the progression of several diseases such as obesity, diabetes, cancer, as well as in the disruption of the immune and reproductive homeostasis. The gut microbiota is considered a pivotal player against the toxic properties of chemicals with the establishment of a dynamic bidirectional relationship, underlining the toxicological significance of this mutual interplay. In fact, several environmental chemicals have been demonstrated to affect the composition, the biodiversity of the intestinal microbiota together with the underlining modulated metabolic pathways, which may play an important role in tailoring the microbiotype of an individual. In this review, we aimed to discuss the latest updates concerning the environmental chemicals–microbiota dual interaction, toward the identification of a distinctiveness of the gut microbial community, which, in turn, may allow to adopt personalized preventive strategies to improve risk assessment for more susceptible workers.

Preparation of a JAZF1 protein polyclonal antibody and its potential role in broiler ascites syndrome

As a novel functional protein, juxtaposed with another zinc finger protein 1 (JAZF1) can regulate the growth and apoptosis through various pathways, and maintain the body's normal physiological metabolism. To explore the important role of JAZF1 in broiler ascites syndrome (BAS), we analysed the expression and distribution of the protein in poultry and mammal tissues based on the prepared polyclonal antibody. In this study, the recombinant plasmid PET32a-JAZF1 was constructed by TA cloning, subcloning and other technical methods, and the fusion protein His-JAZF1 was successfully expressed. After purification, His-JAZF1 was used as the antigen to prepare high-quality chicken-derived antibodies. Subsequently, the results showed that JAZF1 protein in broiler tissues could be specifically recognized by this antibody. Immunofluorescence showed that JAZF1 protein mainly exists in the cytoplasm of pulmonary artery, liver, kidney, heart and lung tissue cells of various animals. The expression of this protein was more obvious in broiler and duck tissues than in mammalian tissues. In addition, western blotting combined with immunofluorescence showed that BAS caused a significant decrease in JAZF1 protein in tissue cells. This effect further indicated that JAZF1 protein was closely related to the occurrence of BAS and provided a new entry point for the functional study of JAZF1 protein.

Chronic lead exposure induces fatty liver disease associated with the variations of gut microbiota

BACKGROUND

Lead (Pb) has been suggested as an endocrine-disrupting chemical. However, few studies have investigated the association between chronic Pb exposure and fatty liver disease.

OBJECTIVES

We aimed to investigate the association of chronic Pb exposure with fatty liver disease and whether the variations of the gut microbiota involve in the mechanism of the fatty liver disease induced by chronic Pb exposure.

METHODS

We conducted a cross-sectional study of 3066 rural participants in East China. Blood lead level (BLL) was detected, and abdominal ultrasonography was used to diagnose hepatic steatosis. Both the definition of non-alcoholic fatty liver disease (NAFLD) and metabolic dysfunction-associated fatty liver disease (MAFLD) were used. Wistar rats were randomly divided into two groups and each group was exposed to 0 or 0.05% w/v Pb through drinking water for 28 weeks. The relevant parameters of hepatic lipid metabolism and gut microbiota were analyzed.

RESULTS

In humans, after adjusting for potential confounders, the odds of having NAFLD and MAFLD were significantly increased by 54% and 52% in the participants in the fourth BLL quartile (OR 1.54, 95% CI 1.24, 1.91 and OR 1.52, 95% CI 1.22, 1.89). In the rats, chronic Pb exposure induced the increased visceral fat, hepatic steatosis, and dysbiosis of the gut microbiota, including the decrease of richness, diversity, evenness and phylogenetic diversity of the gut microbiota and the significant alternations of the gut microbiota composition, particularly, the decrease of the relative abundance of Coprococcus and Oscillospira at the genus level.

CONCLUSIONS

Chronic Pb exposure could induce fatty liver disease, which may be associated with the variations of the gut microbiota.

Comprehensive Review Regarding Mercury Poisoning and Its Complex Involvement in Alzheimer's Disease

Mercury (Hg) is considered one of the most widespread toxic environmental pollutants, which seems to have multiple effects on organisms even at low concentrations. It has a critical role in many health problems with harmful consequences, with Hg primarily targeting the brain and its components, such as the central nervous system (CNS). Hg exposure was associated with numerous CNS disorders that frequently trigger Alzheimer's disease (AD). Patients with AD have higher concentrations of Hg in blood and brain tissue. This paper aims to emphasize a correlation between Hg and AD based on the known literature in the occupational field. The outcome shows that all these concerning elements could get attributed to Hg. However, recent studies did not investigate the molecular level of Hg exposure in AD. The present review highlights the interactions between Hg and AD in neuronal degenerations, apoptosis, autophagy, oxidative stress (OS), mitochondrial malfunctions, gastrointestinal (GI) microflora, infertility and altering gene expression.

Oscillospira - a candidate for the next-generation probiotics

Oscillospira is a class of organism that often appears in high-throughput sequencing data but has not been purely cultured and is widely present in the animal and human intestines. There is a strong association between variation in Oscillospira abundance and obesity, leanness, and human health. In addition, a growing body of studies has shown that Oscillospira is also implicated in other diseases, such as gallstones and chronic constipation, and has shown some correlation with the positive or negative changes in its course. Sequencing data combined with metabolic profiling indicate that Oscillospira is likely to be a genus capable of producing short-chain fatty acids (SCFAs) such as butyrate, which is an important reference indicator for screening "next-generation probiotics ". Considering the positive effects of Oscillospira in some specific diseases, such as obesity-related metabolic diseases, it has already been characterized as one of the next-generation probiotic candidates and therefore has great potential for development and application in the future food, health care, and biopharmaceutical products.

Understanding the hepatoxicity of inorganic mercury through guts: Perturbance to gut microbiota, alteration of gut-liver axis related metabolites and damage to gut integrity

Mercury (Hg) brings adverse effects to the environment and human beings and inorganic mercury (IHg) is a typical hepatic toxin. This work studied the impacts of IHg on gut microbes and metabolome together with its damage to liver and gut in rats through gut microbiome, metabolomics and metallomics. Sprague Dawley (SD) rats were orally exposed to 0.4 μg/mL IHg and sacrificed after 24 h. It was found that IHg perturbed greatly on the gut microbiota, such as increased pathogenic bacteria like G. bacillus. In addition, IHg also changed gut-liver axis related metabolites, which was confirmed by the secretion of a large number of inflammatory factors in both the gut and the liver. The changed gut-liver axis related metabolites correlated well to the changes of gut microbiome. In all, besides the direct deposition in liver of Hg, the perturbance to gut microbiome and alteration of gut-liver axis related metabolites by IHg also contributed to its hepatoxicity, which provides new insights about the hepatoxicity of chemicals. The strategy applied in this work may also be used to understand the hepatoxicity of other chemicals.

Koumiss promotes Mycobacterium bovis infection by disturbing intestinal flora and inhibiting endoplasmic reticulum stress

Mycobacterium bovis is the causative agent of bovine tuberculosis and also responsible for serious threat to public health. Koumiss is a fermented mare's milk product, used as traditional drink. Here, we explored the effect of koumiss on gut microbiota and the host immune response against M bovis infection. Therefore, mice were treated with koumiss and fresh mare milk for 14 days before M bovis infection and continue for 5 weeks after infection. The results showed a clear change in the intestinal flora of mice treated with koumiss, and the lungs of mice treated with koumiss showed severe edema, inflammatory infiltration, and pulmonary nodules in M bovis-infected mice. Notably, we found that the content of short-chain fatty acids was significantly lower in the koumiss-treated group compared with the control group. However, the expression of endoplasmic reticulum stress and apoptosis-related proteins in the lungs of koumiss-treated mice were significantly decreased. Collectively, these findings suggest that koumiss treatment disturb the intestinal flora of, which is associated with disease severity and the possible mechanism that induces lungs pathology. Our current findings can be exploited further to establish the "gut-lung" axis which might be a novel strategy for the control of tuberculosis.

Dichlorvos poisoning caused chicken cerebrum tissue damage and related apoptosis-related gene changes

Dichlorvos (DDVP) is an organophosphorus compound with insecticidal effects. Organophosphorus pesticides can easily enter humans or animals through various channels, causing cerebrum nerve cell damage. The purpose of this research was to investigate whether acute dichlorvos poisoning can cause cerebrum neurotoxic injury and change the expression of apoptosis-related genes in broilers, further clarify the neurotoxic mechanism after acute dichlorvos exposure, and provide a research basis for prevention, treatment and gene drug screening in the later stage. In this experiment, healthy yellow-feathered broilers were randomly assigned to the control group, the low-dose group (1.13 mg/kg) and the high-dose group (10.2 mg/kg) for modelling observation, and detection was conducted based on H&E (haematoxylin and eosin) staining, transmission electron microscopy analysis of tissue sections, immunofluorescence techniques and real-time quantitative polymerase chain reaction (qRT-PCR). The results showed that organophosphorus poisoning was accompanied by obvious neurological symptoms such as limb twitching and massive salivation. In addition, we observed that compared with the control group, the number of lysed nuclear neurons, deformed vascular sheaths, and glial cells and the expression of glial fibrillary acidic protein (GFAP) in the poisoned group of broilers increased significantly, and the increase was more obvious in the low-dose group. However, cell apoptosis and mitochondrial structure dissolution were most pronounced in the high-dose group. Moreover, the qRT-PCR results also revealed significant changes in the expression of apoptosis-related genes. The expression levels of ACC, LKB1 and GPAT increased significantly, while the expression of HMGR, PPARα, CPT1 and AMPKα1 decreased significantly. In summary, these results indicated that dichlorvos may cause the lysis of cerebrum nerve cell nuclei, completely destroy the structure of mitochondria, change the expression of related apoptotic genes, enhance cell apoptosis, and cause neurogenic damage to the cerebrum. These research results offer a theoretical foundation for the prevention and treatment of acute organophosphate toxicosis.

Omic methodologies for assessing metal(-loid)s-host-microbiota interplay: A review

Omic methodologies have become key analytical tools in a wide number of research topics such as systems biology, environmental analysis, biomedicine or food analysis. They are especially useful when they are combined providing a new perspective and a holistic view of the analytical problem. Methodologies for microbiota analysis have been mostly focused on genome sequencing. However, information provided by these metagenomic studies is limited to the identification of the presence of genes, taxa and their inferred functionality. To achieve a deeper knowledge of microbial functionality in health and disease, especially in dysbiosis conditions related to metal and metalloid exposure, the introduction of additional meta-omic approaches including metabolomics, metallomics, metatranscriptomics and metaproteomics results essential. The possible impact of metals and metalloids on the gut microbiota and their effects on gut-brain axis (GBA) only begin to be figured out. To this end new analytical workflows combining powerful tools are claimed such as high resolution mass spectrometry and heteroatom-tagged proteomics for the absolute quantification of metal-containing biomolecules using the metal as a "tag" in a sensitive and selective detector (e.g. ICP-MS). This review focus on current analytical methodologies related with the analytical techniques and procedures available for metallomics and microbiota analysis with a special attention on their advantages and drawbacks.

Dose-dependent effects of lead induced gut injuries: An in vitro and in vivo study

Lead (Pb) toxicity has been widely studied, but its dose-dependent toxic effects on the gut remain unclear, therefore, the aim of this study was to evaluate the effects of different doses of Pb exposure on the gut microbiota and gut barrier in vitro and in vivo. The HT-29 cell model was used to determine the Pb-induced effects on cell viability, reactive oxygen species (ROS), and tight junction proteins (TJPs) in vitro, and C57BL/6 mice models exposed to 0, 20, 100, 500, and 1000 mg/kg Pb were used to investigate the Pb-induced dose-dependent effects on the gut microbiota, TJP expression, and colon histopathology. Our results showed that the exposure of HT-29 cells to 8 mM Pb decreased cell viability by 50%, elevated ROS levels by 200%, and suppressed the expression of the TJPs, zonula occludens-1 (ZO-1) and occludin by 23% and 35%, respectively. Consistently, Pb-exposed mice showed significant increases in colon tissue damage and inflammation and reductions in ZO-1 mRNA levels in a dose-dependent manner. The occludin mRNA levels decreased in the 500 and 1000 mg/kg groups. At the genus level, the relative abundance of Coprococcus and Oscillospira decreased and that of Lactobacillus increased in linear manner with the Pb exposure dose. PICRUSt analysis based on 16S rRNA sequencing revealed Pb dose-dependent alterations in metabolism through the gut microbiota. These findings suggest that Pb exposure can not only disrupt the barrier by generating oxidative stress, but can also induce gut dysbiosis, colon tissue damage, and gut inflammation in a dose-dependent manner.

Diesel exhaust particles alter the profile and function of the gut microbiota upon subchronic oral administration in mice

BACKGROUND

Ambient air pollution by particulate matters, including diesel exhaust particles (DEP), is a major cause of cardiovascular and metabolic mortality worldwide. The mechanisms by which DEP cause these adverse outcomes are not completely understood. Because the gut microbiota controls cardiovascular and metabolic health, we hypothesized that the fraction of inhaled DEP which reach the gut after mucociliary clearance and swallowing might induce gut dysbiosis and, in turn, contribute to aggravate or induce cardiovascular and metabolic diseases.

RESULTS

Female ApoE^-/- mice fed a Western diet, and wild-type (C57Bl/6) mice fed standard diet were gavaged with DEP (SRM2975) doses corresponding to mucociliary clearance from inhalation exposure (200 or 1000 ng/day, 3 times a week for 3 months; and 40, 200 or 1000 ng/day, 3 times a week for 6 months, respectively). No mortality, overt systemic or digestive toxicity was observed. A dose-dependent alteration of the gut microbiota was recorded in both strains. In ApoE^-/-, β-diversity was modified by DEP, but no significant modification of the relative abundance of the phyla, families or genera was identified. In C57BL/6 mice, DEP reduced α-diversity (Shannon and Simpson indices), and modified β-diversity, including a reduction of the Proteobacteria and Patescibacteria phyla, and an increase of the Campylobacterota phylum. In both mouse models, perturbation of the gut microbiota composition was associated with a dose-dependent reduction of bacterial short chain fatty acids (butyrate and propionate) in cecal content. However, DEP ingestion did not aggravate (ApoE^-/-), or induce (C57BL/6 mice) atherosclerotic plaques, and no metabolic alteration (glucose tolerance, resistance to insulin, or lipidemia) was recorded.

CONCLUSIONS

We show here that oral exposure to DEP, at doses relevant for human health, changes the composition and function of the gut microbiota. These modifications were, however, not translated into ultimate atherosclerotic or metabolic outcomes.

Interactions between Food Hazards and Intestinal Barrier: Impact on Foodborne Diseases

The intestine is an important digestive organ of the human body, and its barrier is the guardian of the body from the external environment. The impairment of the intestinal barrier is believed to be an important determinant in various foodborne diseases. Food hazards can lead to the occurrence of many foodborne diseases represented by inflammation. Therefore, understanding the mechanisms of the impact of the food hazards on intestinal barriers is essential for promoting human health. This review examined the relationship between food hazards and the intestinal barrier in three aspects: apoptosis, imbalance of gut microbiota, and pro-inflammatory cytokines. The mechanism of dysfunctional gut microbiota caused by food hazards was also discussed. This review discusses the interaction among food hazards, intestinal barrier, and foodborne diseases and, thus, offers a new thought to deal with foodborne disease.

Endobolome, a New Concept for Determining the Influence of Microbiota Disrupting Chemicals (MDC) in Relation to Specific Endocrine Pathogenesis

Endogenous steroid hormones and Endocrine Disrupting Chemicals (EDC) interact with gut microbiota through different pathways. We suggest the use of the term "endobolome" when referring to the group of gut microbiota genes and pathways involved in the metabolism of steroid hormones and EDC. States of dysbiosis and reduced diversity of the gut microbiota may impact and modify the endobolome resulting at long-term in the development of certain pathophysiological conditions. The endobolome might play a central role in the gut microbiota as seen by the amount of potentially endobolome-mediated diseases and thereby it can be considered an useful diagnostic tool and therapeutic target for future functional research strategies that envisage the use of next generation of probiotics. In addition, we propose that EDC and other xenobiotics that alter the gut microbial composition and its metabolic capacities should be categorized into a subgroup termed "microbiota disrupting chemicals" (MDC). This will help to distinguish the role of contaminants from other microbiota natural modifiers such as those contained or released from diet, environment, physical activity and stress. These MDC might have the ability to promote specific changes in the microbiota that can ultimately result in common intestinal and chronic or long-term systemic diseases in the host. The risk of developing certain disorders associated with gut microbiota changes should be established by determining both the effects of the MDC on gut microbiota and the impact of microbiota changes on chemicals metabolism and host susceptibility. In any case, further animal controlled experiments, clinical trials and large epidemiological studies are required in order to establish the concatenated impact of the MDC-microbiota-host health axis.