Chronic Exposure to Drinking Water As, Pb, and Cd at Provisional Guideline Values Reduces Weight Gain in Male Mice via Gut Microflora Alterations and Intestinal Inflammation

Chlorella vulgaris Supplementation Attenuates Lead Accumulation, Oxidative Stress, and Memory Impairment in Rats

Lead is a harmful heavy metal known to alter the environment and affect human health. Several industries have contributed to the increase in lead contamination, making it a major global concern. Thus, remediation strategies are necessary to prevent lead bioaccumulation and deleterious health effects. The aim of this study was to determine the capacity of the green microalga Chlorella vulgaris (C. vulgaris or CV) to remove lead in an animal model and prevent the accumulation of this heavy metal in the principal organs (brain, liver, and kidney) and blood. Forty male Wistar rats were randomly assigned to four groups (n = 10): control group (CT); C. vulgaris supplementation group, 5% of the diet (CV); lead acetate administration group, 500 ppm (Pb); and C. vulgaris supplementation group, 5% of the diet plus lead acetate administration group, 500 ppm (CV-Pb). After 4 weeks of exposure, we measured lead accumulation, memory function, oxidative stress, and antioxidant activity (SOD and GSH). Lead exposure altered memory function, increased oxidative stress in the brain and kidney, and increased SOD activity in the brain. Supplementation with C. vulgaris restored memory function to control levels; reduced oxidative stress in the brain and kidney; and decreased the accumulation of lead in the liver, kidney, and blood of rats exposed to lead. Based on our results, C. vulgaris is a lead chelating and antioxidant agent in animal models.

Nano-Scale Insights into Clay Minerals Regulating the Fe(II)-Catalyzed Ferrihydrite Transformation under Anoxic Conditions

Metastable ferrihydrite nanoparticles and clay minerals always coexist as heteroaggregates in nature due to their abundance, opposite charge, and large interface energy. However, the impact of clay minerals on the transformation of ferrihydrite under anoxic conditions remains elusive. This study systematically investigated the effect of distinct clay minerals on the Fe(II)-catalyzed transformation of ferrihydrite and clarifying the underlying nanoscale mechanisms for the first time. Our results demonstrated that clay minerals could affect the production and recrystallization of labile Fe(III) (an active Fe(III) intermediate species formed by oxidation of Fe(II) at the ferrihydrite surface) by dispersing ferrihydrite aggregates. This modulation led to different transformation rates, higher crystallinity of formed lepidocrocite, and enhanced goethite formation in the heteroaggregates. Importantly, montmorillonite can accommodate Fe(II) and labile Fe(III) within its interlayer spaces, which further led to the inhibited crystallization of Fe(II) to magnetite and long-term preservation of labile Fe(III). Additionally, clay minerals served as templates for forming dendritic goethite and hexagonal magnetite nanoplates. Our findings provide new insights into the complicated roles of clay minerals in controlling the ferrihydrite transformation and other iron (oxyhydr)oxides formation, which is significant for predicting the bioavailability of iron and the fate of other coexisting contaminants.

Metal Dyshomeostasis as a Driver of Gut Pathology in Autism Spectrum Disorders

Despite being classified as neurodevelopmental disorders, in recent years, there has been a growing interest in the association between autism spectrum disorders (ASDs) and gut pathology. This comprehensive and systematic review explores a potential mechanism underlying gut pathology in ASDs, including alterations in gut microbiota, intestinal permeability, immune dysregulation, and gastrointestinal (GI) symptoms. Specifically, it delves into the role of toxic and essential metals and their interplay, affecting the development and function of the GI tract. The review also discusses the potential implications of this gut pathology in the development and management of ASDs. Studies have shown that heavy metal exposure, whether through environmental sources or dietary intake, can disrupt the delicate balance of trace elements in the gut. This disruption can adversely affect zinc homeostasis, potentially exacerbating gut pathology in individuals with ASDs. The impaired zinc absorption resulting from heavy metal exposure may contribute to the immune dysregulation, oxidative stress, and inflammation observed in the gut of individuals with ASDs. By shedding light on the multifaceted nature of gut pathology, including the impact of metal dyshomeostasis as a non-genetic factor in ASD, this review underscores the significance of the gut-brain axis in the etiology and management of ASDs.

Iron-lead mixed exposure causes bone damage in mice: A multi-omics analysis

Excessive intake of essential and toxic metals affects the pathological process of osteoporosis. At present, the effects of single forms of iron (Fe), lead (Pb) and other metals on bone injury have been widely studied. However, these metal elements usually do not exist in the environment in a separate form. They are ingested in various ways and are often found together in the human body. However, the mechanism of bone damage caused by Fe and Pb mixed exposure is still unclear at this stage. At present, the combined analysis of multi-omics is the conventional method to explore the molecular mechanism behind the disease. Therefore, we attempted to combine proteomics and metabolomics to explain the mechanism of bone damage caused by mixed Fe and Pb exposure. Differential proteins and metabolites were found to be predominantly enriched in the JAK-STAT signalling pathway, inflammatory bowel disease (IBD), and osteoclast differentiation. Combined analysis showed that Fpr2, Lifr, Lisofylline, 7-Ketocholesterol, LacCer (d18: 1/14:0) and other substances may be involved in the process of bone injury mediated by mixed metal exposure. In summary, we hypothesise that mixed exposure to Fe and Pb leads to osteoclast activation via the JAK-STAT signalling pathway in situ and indirectly via the gut-bone axis, resulting in bone damage. In general, our study potentially suggests that bone injury induced by mixed exposure of Fe and Pb may be related to osteoclast proliferation mediated by changes in inflammatory levels in vivo.

Gut Dysbiosis Exacerbates Intestinal Absorption of Cadmium and Arsenic from Cocontaminated Rice in Mice Due to Impaired Intestinal Barrier Functions

Globally, humans face gut microbiota dysbiosis; however, its impact on the bioavailability of cadmium (Cd) and arsenic (As) from rice consumption─a major source of human exposure to these metals─remains unclear. In this study, we compared Cd and As accumulation in the liver and kidneys of mice with disrupted gut microbiota (administered cefoperazone sodium), restored microbiota (administered probiotics and prebiotics following antibiotic exposure), and normal microbiota, all after consuming cocontaminated rice. Compared to normal mice, microbiota-disrupted mice exhibited 30.9-119% and 30.0-100% (p < 0.05) higher Cd and As levels in tissues after a 3 week exposure period. The increased Cd and As bioavailability was not due to changes in the duodenal expression of Cd-related transporters or As speciation biotransformation in the intestine. Instead, it was primarily attributed to a damaged mucus layer and depleted tight junctions associated with gut dysbiosis, which increased intestinal permeability. These mechanisms were confirmed by observing 34.3-74.3% and 25.0-75.0% (p < 0.05) lower Cd and As levels in the tissues of microbiota-restored mice with rebuilt intestinal barrier functions. This study enhances our understanding of the increased risk of dietary metal(loid) exposure in individuals with gut microbiota dysbiosis due to impaired intestinal barrier functions.

RNA m6A involves in regulation of oxidative stress and apoptosis may via NF-kB pathway in cadmium-induced lung cells

Cadmium has been identified as an environmental pollutant and a carcinogen. N6-methyladenosine (m6A) plays a crucial role in the development of lung tumors, but the mechanisms remain incompletely clarified. In present study, our data demonstrated that prolonged treatment of 1 μmol/L CdSO4 for 40 passages in bronchial epithelial cells (Beas-2B cells) resulted in the development of a malignant phenotype, which manifested as boosted proliferation, migration and invasion capacity as well as apoptosis reduction. Proteomic assay revealed that in passage 40 cells, 350 proteins showed differentially expressed in comparison to control, and these proteins were primarily enriched in Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways of "pathways in cancer" and "Chemical carcinoma-reactive oxygen species". Moreover, the mRNAs of Nuclear factor kappa B (NF-κB) p65 and NAD(P)H: quinone oxidoreductase 1 (NQO1), the key signaling molecules in these two signaling pathways, were predicted to contain m6A modification sites with high confidence. The subsequent experimental results indicated that levels of m6A and Fat mass and obesity associated protein (FTO) elevated, while Alkylated DNA repair protein alkB homolog 5 (ALKBH5) and YTH Domain Containing Protein 2 (YTHDC2) reduced with the increasing of cadmium treatment generations. Furthermore, the reduction of m6A levels by 3-deazide adenosine (DAA, m6A inhibitor) was found to significantly inhibit malignant characteristics of cadmium-induced cells, activate molecules involved in the nuclear factor erythroid 2-related factor 2 (NRF2) signaling pathway, and inhibit the activity of NF-κB. It is also noteworthy that the results based on animals indicate that the relevant indicators and biological changes are partially similar to cell experiments. In detail, m6A modification levels in lung tissue were observed to increase while the expressions of FTO, ALKBH5 and YTHDC2 were found to drop. Additionally, immunofluorescence examination illustrated the co-localization of the m6A regulatory proteins FTO and YTHDC2 with NF-κB. The presented data collectively suggest that chronic cadmium treatment may impact the m6A level through influencing regulatory proteins, which could potentially trigger oxidative stress and apoptosis by regulating transcription factors such as NF-κB and NRF2. In conclusion, our study provides a scientific foundation for understanding cadmium toxicity and offers novel insights for treating cadmium-induced lung diseases.

Synergistic effects of combined lead and iprodione exposure on P53 signaling-mediated hepatotoxicity, enterotoxicity and transgenerational toxicity in zebrafish

Environmental heavy metal contamination, combined with inappropriate use of fungicides, has led to the co-existence of lead (Pb) and iprodione (IPR), presenting signification risks to ecosystems and human health. The toxic effects resulting from concurrent exposure to Pb and IPR, however, remain poorly understood. In the study, we conducted a comprehensive 60-day subchronic study to investigate the toxic effects on the liver and gut in parental male zebrafish through employing multi-omics analyses. We also explored the potential transgenerational toxicity to unexposed offspring embryos. The results demonstrated that exposure to both Pb and IPR exacerbated intestinal pathological damage, decreased the expression of intestinal tight junction molecules, and activated the expression of intestinal inflammatory molecules in the gut. Metabolic and microbial analyses, utilizing 16S rRNA sequencing and non-targeted metabolic profiling, revealed alterations in the intestinal flora structure and disruptions in metabolite synthesis. Notably, we observed a significant negative correlation between the abundance of the Lactobacillus genus and uracil synthesis. Furthermore, liver RNA-seq analysis identified a marked enrichment of the P53 signaling pathway, confirmed by the activation of P53-mediated apoptotic markers, which was consistent with the observed increase in inflammatory infiltration and pathological damage within the liver. Importantly, P53-mediated apoptosis and inflammatory responses were activated in offspring embryos, suggesting that long-term parental exposure to Pb and IPR may induce transgenerational toxicity, potentially impacting offspring health. Despite the identification of these molecular changes, the phenotypic effects remain to be elucidated. Future studies are necessary to evaluate the potential phenotypic changes in offspring to fully understand the long-term effects of Pb and IPR exposure. Overall, these findings enhance the understanding of the molecular mechanisms underlying the toxic effects of Pb and IPR and emphasize the importance of a comprehensive risk assessment of environmental pollutants.

Toxic Metals and Metalloids in Food: Current Status, Health Risks, and Mitigation Strategies

PURPOSE OF REVIEW

Exposure to toxic metals/metalloids, such as arsenic (As), cadmium (Cd), and lead (Pb), through food consumption is a global public health concern. This review examines the contamination status of these metals/metalloids in food, assesses dietary intake across different populations, and proposes strategies to reduce metal/metalloid exposures throughout the food chain.

RECENT FINDINGS

For the general population, dietary intake of metals/metalloids is generally lower than health-based guidance values. However, for vulnerable populations, such as infants, children, and pregnant women, their dietary intake levels are close to or even higher than the guidance values. Among different food categories, seafood shows higher total As, but largely present as organic species. Rice accumulates higher As concentration than other cereals, with inorganic As (iAs) and dimethylarsinic acid (DMA) being the main As species. Methylated thioarsenate species, such as dimethylmonothioarsenate, have also been detected in rice. The distribution of iAs and DMA in rice shows geographical variation. Additionally, seafood and cocoa products generally contain more Cd than other food, but seafood consumption does not significantly increase in adverse health effects due to its high zinc and iron content. Compared to As and Cd, Pb concentrations in food are generally lower. To minimize the health risks of metal/metalloid exposure, several strategies are proposed. Food contamination with toxic metals/metalloids poses significant concerns for human health, particularly for vulnerable populations. This review provides scientific evidence and suggestions for policy makers to reduce human exposure of metals/metalloids via dietary intake.

The Effects of Pb on TNF-R1-RIPK1/RIPK3 Signaling Pathway in the Hippocampus of Mice

Lead (Pb), a dense, soft, blue-gray metal, is widely used in metallurgy, cables, storage batteries, pigments, and other industrial applications. Pb has been shown to cause degenerative changes in the nervous system. Necroptosis, a form of non-apoptotic programmed cell death modality, is closely associated with neurodegenerative diseases. Whether the TNF-R1-RIPK1/RIPK3 pathway is involved in the neurodegeneration induced by Pb has yet to be determined. Here, we explored the role of the TNF-R1-RIPK1/RIPK3 signaling pathway in the Pb-induced necroptosis by using HT-22 cells, primary mouse hippocampal neurons, and C57BL/6 mice models, demonstrating that Pb exposure elevated lead levels in murine whole blood and hippocampal tissue in a dose-response relationship. Protein expression levels of PARP, c-PARP, RIPK1, p-RIPK1, RIPK3, MLKL, and p-MLKL in the hippocampal tissues were elevated, while the protein expression of caspase-8 was decreased. Furthermore, Pb exposure reduced the survival rates in HT-22 cells and primary mouse hippocampal neurons, while increasing the protein expressions of RIPK1 and p-MLKL. Collectively, these novel findings suggest that the TNF-R1/RIPK1/RIPK3 signaling pathway is associated with Pb-induced neurotoxicity in hippocampal neurons in mice.

Impaired learning and memory in male mice induced by sodium arsenite was associated with MMP-2/MMP-9-mediated blood-brain barrier disruption and neuronal apoptosis

Arsenic is a widespread environmental contaminant known to accumulate in the brain, leading to cognitive impairment. However, the exact mechanisms by which arsenic causes cognitive deficits remain unclear. The present study aims to discover whether the destruction of the blood-brain barrier (BBB) mediated by matrix metalloproteinases 2 and matrix metalloproteinases 9 (MMP-2 and MMP-9) and subsequent neuronal apoptosis are involved in arsenic-induced cognitive impairment. Ninety male mice were given 0, 25, and 50 mg/L NaAsO2 in drinking water and 30 mg/kg doxycycline hyclate (DOX, an inhibitor of MMPs) gavage for 12 weeks to observe the alterations in learning and memory of mice, the morphology of hippocampal neurons, as well as the BBB permeability and ultrastructure, the localization and expression of tight junction proteins, MMP-2, and MMP-9. Our findings indicated that arsenic exposure induced learning and memory impairment in mice, accompanied by neuronal loss and apoptosis. Furthermore, arsenic exposure increased hematogenous IgG leakage into the brain, disrupted the tight junctions, reduced the expression of Claudin5, Occludin, and ZO1 in the endothelial cells, and increased the expression of MMP-2 and MMP-9 in the endothelial cells and astrocytes. Finally, DOX intervention preserved BBB integrity, alleviated hippocampal neuronal apoptosis, and improved cognitive impairment in mice caused by arsenic exposure. Our research demonstrates that cognitive disfunction in mice induced by arsenic exposure is associated with MMP-2 and MMP-9-mediated BBB destruction and neuronal apoptosis. The current investigation provides new insights into mechanisms of arsenic neurotoxicity and suggests that MMP-2 and MMP-9 may serve as potential therapeutic targets for treating arsenic-induced cognitive dysfunction in the future.

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.

Cadmium in Market Pork Kidneys: A Study on Cadmium Bioavailability and the Health Effects Based on Mouse Models

Edible offal of farmed animals can accumulate cadmium (Cd). However, no studies have investigated Cd bioavailability and its health effects. Here, based on mouse models, market pork kidney samples exhibited high Cd relative bioavailability of 74.5 ± 11.2% (n = 26), close to 83.8 ± 7.80% in Cd-rice (n = 5). This was mainly due to high vitamin D3 content in pork kidney, causing 1.7-2.3-fold up-regulated expression of duodenal Ca transporter genes in mice fed pork kidney compared to mice fed Cd-rice, favoring Cd intestinal absorption via Ca transporters. However, although pork kidney was high in Cd bioavailability, subchronic low-dose (5% in diet) consumption of two pork kidney samples having 0.48 and 0.97 μg Cd g-1 dw over 35 d did not lead to significant Cd accumulation in the tissue of mice fed Cd-free rice but instead remarkably decreased Cd accumulation in the tissue of mice fed Cd-rice (0.48 μg Cd g-1) by ∼50% and increased abundance of gut probiotics (Faecalibaculum and Lactobacillus). Overall, this study contributed to our understanding of the bioavailability and health effects associated with Cd in edible offal, providing mechanistic insights into pork kidney consumption safety based on Cd bioavailability.

Bile acid metabolism is altered in learning and memory impairment induced by chronic lead exposure

Lead is a neurotoxic contaminant that exists widely in the environment. Although lead neurotoxicity has been found to be tightly linked to gut microbiota disturbance, the effect of host metabolic disorders caused by gut microbiota disturbance on lead neurotoxicity has not been investigated. In this work, the results of new object recognition tests and Morris water maze tests showed that chronic low-dose lead exposure caused learning and memory dysfunction in mice. The results of 16 S rRNA sequencing of cecal contents and fecal microbiota transplantation showed that the neurotoxicity of lead could be transmitted through gut microbiota. The results of untargeted metabolomics and bile acid targeted metabolism analysis showed that the serum bile acid metabolism profile of lead-exposed mice was significantly changed. In addition, supplementation with TUDCA or INT-777 significantly alleviated chronic lead exposure-induced learning and memory impairment, primarily through inhibition of the NLRP3 inflammasome in the hippocampus to relieve neuroinflammation. In conclusion, our findings suggested that dysregulation of host bile acid metabolism may be one of the mechanisms of lead-induced neurotoxicity, and supplementation of specific bile acids may be a possible therapeutic strategy for lead-induced neurotoxicity.

Fe(II)-catalyzed phase transformation of Cd(II)-bearing ferrihydrite-kaolinite associations under anoxic conditions: New insights to role of kaolinite and fate of Cd(II)

Cadmium-bearing ferrihydrite-kaolinite associations (Cd-associations) are commonly found in cadmium-contaminated paddy soils in tropical and subtropical regions. In the presence of anaerobic conditions caused by flooding, the creation of Fe(II) can facilitate the transformation of ferrihydrite into secondary Fe (hydr)oxides, resulting in the redistribution of Cd. However, the role of kaolinite in iron oxides transformation and changes in Cd chemical species have largely not been determined. In this study, Cd-associations were prepared for reaction with Fe(II) under anoxic conditions. The results obtained from powder XRD and EXAFS indicated that the presence of kaolinite association noticeably hastened the transformation of ferrihydrite into crystalline goethite. Specific surface area and electrochemical analyses revealed that smaller particle sizes and higher reactivity of ferrihydrite within Cd-associations collaboratively contribute to the acceleration. Chemical analyses demonstrated a significant negative correlation between ferrihydrite-Fe and aqueous-Cd, and a significant positive correlation between crystalline-Fe and residual-Cd. HRTEM analyses indicated that a portion of the Cd was incorporated into the crystal lattices of lepidocrocite and goethite, with the majority of Cd being sequestered within goethite lattice. These findings provide new insights into the roles of clay minerals in the geochemical cycling of Fe and Cd in paddy soils under anoxic conditions.

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.

Waterborne Tebuconazole Exposure Induces Male-Biased Sex Differentiation in Zebrafish (Danio rerio) Larvae via Aromatase Inhibition

Tebuconazole is a widely used fungicide for various crops that targets sterol 14-α-demethylase (CYP51) in fungi. However, attention has shifted to aromatase (CYP19) due to limited research indicating its reproductive impact on aquatic organisms. Herein, zebrafish were exposed to 0.5 mg/L tebuconazole at different developmental stages. The proportion of males increased significantly after long-term exposure during the sex differentiation phase (0-60, 5-60, and 19-60 days postfertilization (dpf)). Testosterone levels increased and 17β-estradiol and cyp19a1a expression levels decreased during the 5-60 dpf exposure, while the sex ratio was equally distributed on coexposure with 50 ng/L 17β-estradiol. Chemically activated luciferase gene expression bioassays determined that the male-biased sex differentiation was not caused by tebuconazole directly binding to sex hormone receptors. Protein expression and phosphorylation levels were specifically altered in the vascular endothelial growth factor signaling pathway despite excluding the possibility of tebuconazole directly interacting with kinases. Aromatase was selected for potential target analysis. Molecular docking and aromatase activity assays demonstrated the interactions between tebuconazole and aromatase, highlighting that tebuconazole poses a threat to fish populations by inducing a gender imbalance.