Possible Mechanisms of Mercury Toxicity and Cancer Promotion: Involvement of Gap Junction Intercellular Communications and Inflammatory Cytokines

The preventive and carcinogenic effect of metals on cancer: a systematic review

BACKGROUND

Many studies have investigated the role of metals in various types of malignancies. Considering the wide range of studies conducted in this field and the achievement of different results, the presented systematic review was performed to obtain the results of investigations on the prevention and occurrence of various types of cancer associated with metal exposures.

METHODS

In this review, research was conducted in the three databases: Scopus, PubMed, and Web of Science without historical restrictions until May 31, 2024. Animal studies, books, review articles, conference papers, and letters to the editors were omitted. The special checklist of Joanna Briggs Institute (JBI) was used for the quality assessment of the articles. Finally, the findings were classified according to the effect of the metal as preventive or carcinogenic.

RESULTS

The total number of retrieved articles was 4695, and 71 eligible results were used for further investigation. In most studies, the concentration of toxic metals such as lead (Pb), chromium (Cr (VI)), arsenic (As), cadmium (Cd), and nickel (Ni) in the biological and clinical samples of cancer patients was higher than that of healthy people. In addition, the presence of essential elements, such as selenium (Se), zinc (Zn), iron (Fe), and manganese (Mn) in tolerable low concentrations was revealed to have anti-cancer properties, while exposure to high concentrations has detrimental health effects.

CONCLUSIONS

Metals have carcinogenic effects at high levels of exposure. Taking preventive measures, implementing timely screening, and reducing the emission of metal-associated pollutants can play an effective role in reducing cancer rates around the world.

Biomonitoring Study of Toxic Metal(loid)s: Levels in Lung Adenocarcinoma Patients

Lung cancer is a leading cause of cancer deaths worldwide. The aim of this study was to investigate heavy metal(loid)s (Cd, Pb, Hg, Cr, Mn, Mo, Ni, and As) in lung cancer patients in order to elucidate their role as lung cancer environmental risk factors. Sixty-three patients of both sexes with adenocarcinoma stage IIIB or IV were enrolled in this research. The heavy metal(loid) urine concentrations were measured using ICP-MS. Arsenic was quantified above 10 μg/L in 44.44% of the samples. Nickel urinary concentrations above the ToxGuide reference levels were found in 50.79% of the samples, while lead was quantified in 9.52% of the urine samples. The urinary chromium levels were above the mean ToxGuide levels in 41.27% of the patients and were significantly higher in men in comparison with women (p = 0.035). The chromium urinary concentrations were positively associated with the CRP serum levels (p = 0.037). Cadmium was quantified in 61.90% of the samples with levels significantly higher in females than in males (p = 0.023), which was associated with smoking habits. Mercury was measured above the limit of quantification in 63.49% of the samples and was not associated with amalgam dental fillings. However, the Hg urinary concentrations were correlated positively with the ALT (p = 0.02), AST (p < 0.001), and GGT (p < 0.001) serum levels. In 46.03% of the samples, the Mo concentrations were above 32 μg/L, the mean value for healthy adults according to the ToxGuide, and 9.52% of the patients had Mn levels higher than 8 μg/L, the reference value for healthy adults based on ToxGuide data. The obtained results are preliminary, and further studies are needed to have a deeper insight into metal(loid) exposure's association with lung cancer development, progression, and survival prediction.

Omics technology draws a comprehensive heavy metal resistance strategy in bacteria

The rapid industrial revolution significantly increased heavy metal pollution, becoming a major global environmental concern. This pollution is considered as one of the most harmful and toxic threats to all environmental components (air, soil, water, animals, and plants until reaching to human). Therefore, scientists try to find a promising and eco-friendly technique to solve this problem i.e., bacterial bioremediation. Various heavy metal resistance mechanisms were reported. Omics technologies can significantly improve our understanding of heavy metal resistant bacteria and their communities. They are a potent tool for investigating the adaptation processes of microbes in severe conditions. These omics methods provide unique benefits for investigating metabolic alterations, microbial diversity, and mechanisms of resistance of individual strains or communities to harsh conditions. Starting with genome sequencing which provides us with complete and comprehensive insight into the resistance mechanism of heavy metal resistant bacteria. Moreover, genome sequencing facilitates the opportunities to identify specific metal resistance genes, operons, and regulatory elements in the genomes of individual bacteria, understand the genetic mechanisms and variations responsible for heavy metal resistance within and between bacterial species in addition to the transcriptome, proteome that obtain the real expressed genes. Moreover, at the community level, metagenome, meta transcriptome and meta proteome participate in understanding the microbial interactive network potentially novel metabolic pathways, enzymes and gene species can all be found using these methods. This review presents the state of the art and anticipated developments in the use of omics technologies in the investigation of microbes used for heavy metal bioremediation.

Red Cell Distribution Width and Mean Corpuscular Volume Alterations: Detecting Inflammation Early in Occupational Cement Dust Exposure

Introduction Cement dust emitted during cement manufacture consists of toxic components. Occupational cement dust exposure may cause inflammation in the human body, which may be detected early by observing changes in blood parameters such as red blood cell distribution width (RDW) and mean corpuscular volume (MCV). Objectives The study aims to observe the effect of occupational cement dust exposure on RDW and MCV. Methods This study was performed in the Department of Physiology of Dhaka Medical College, Dhaka, Bangladesh, and a factory in Munshiganj, Bangladesh, from September 2017 to August 2018. Ninety-two participants between 20 and 50 years were included (46 subjects were occupationally exposed to cement dust, and 46 were not exposed to cement dust). A pre-designed questionnaire was used for data collection. An independent sample t-test was used to analyze basic information, such as blood pressure and BMI. The multivariate regression model was used to analyze the effect of cement dust exposure on the study group. The impact of cement dust exposure duration was analyzed using the multivariate regression model. The level of significance was p < 0.05. The statistical analysis was performed using STATA-15 (StataCorp, College Station, TX), and the graphical presentation used GraphPad Prism v8.3.2. Results The cement dust-exposed participants had a significantly higher value of MCV by 1.19 fi (95% CI = 0.02, 4.84; p = 0.049) and a 5.92% increase in RDW (95% CI = 5.29, 6.55; p < 0.001) than that of the control group. Conclusion The study reveals that exposure to cement dust causes significant changes in RDW and MCV. These changes may indicate hemolysis due to inflammation.

Exposure to heavy metal elements may significantly increase serum prostate-specific antigen levels with overdosed dietary zinc

BACKGROUND

Serum prostate-specific antigen (PSA) is a primary metric for diagnosis and prognosis of prostate cancer (PCa). Exposure to heavy metals, such as lead, cadmium, mercury, and zinc can impact PSA levels in PCa patients. However, it is unclear whether this effect also occurs in men without PCa, which may lead to the overdiagnosis of PCa.

METHOD

Data on a total of 5089 American men who had never been diagnosed with PCa were obtained from the National Health and Nutrition Examination Survey performed from 2003-2010. The relationship between serum PSA levels (dependent variable) and concentrations of lead (μmol/L), cadmium (nmol/L), and mercury (μmol/L) were investigated with dietary zinc intake being used as a potential modifier or covariate in a weighted linear regression model and a generalized additive model. A series of bootstrapping analyses were performed to evaluate sensitivity and specificity using these models.

RESULTS

Regression analyses suggested that, in general, lead, cadmium, or mercury did not show an association with PSA levels, which was consistent with the results of the bootstrapping analyses. However, in a subgroup of participants with a high level of dietary zinc intake (≥14.12 mg/day), a significant positive association between cadmium and serum PSA was identified (1.06, 95% CI, P = 0.0268, P for interaction=0.0249).

CONCLUSIONS

With high-level zinc intake, serum PSA levels may rise in PCa-free men as the exposure to cadmium increases, leading to a potential risk of an overdiagnosis of PCa and unnecessary treatment. Therefore, environmental variables should be factored in the current diagnostic model for PCa that is solely based on PSA measurements. Different criteria for PSA screening are necessary based on geographical variables. Further investigations are needed to uncover the biological and biochemical relationship between zinc, cadmium, and serum PSA levels to more precisely diagnose PCa.

Genome-Wide Association Study of Blood Mercury in European Pregnant Women and Children

Mercury has high industrial utility and is present in many products, and environmental contamination and occupational exposure are widespread. There are numerous biological systems involved in the absorption, metabolism, and excretion of Hg, and it is possible that some systems may be impacted by genetic variation. If so, genotype may affect tissue concentrations of Hg and subsequent toxic effects. Genome-wide association testing was performed on blood Hg samples from pregnant women of the Avon Longitudinal Study of Parents and Children (n = 2893) and children of the Human Early Life Exposome (n = 1042). Directly-genotyped single-nucleotide polymorphisms (SNPs) were imputed to the Haplotype Reference Consortium r1.1 panel of whole genotypes and modelled againstlog-transformed Hg. Heritability was estimated using linkage disequilibrium score regression. The heritability of Hg was estimated as 24.0% (95% CI: 16.9% to 46.4%) in pregnant women, but could not be determined in children. There were 16 SNPs associated with Hg in pregnant women above a suggestive p-value threshold (p < 1 × 10-5), and 21 for children. However, no SNP passed this threshold in both studies, and none were genome-wide significant (p < 5 × 10-8). SNP-Hg associations were highly discordant between women and children, and this may reflect differences in metabolism, a gene-age interaction, or dose-response effects. Several suggestive variants had plausible links to Hg metabolism, such as rs146099921 in metal transporter SLC39A14, and two variants (rs28618224, rs7154700) in potassium voltage-gated channel genes. The findings would benefit from external validation, as suggestive results may contain both true associations and false positives.

Elemental distribution and source analysis of atmospheric aerosols from Meycauayan, Bulacan, Philippines

One of the industrialized cities in the Philippines is Meycauayan, Bulacan. This study reports the elemental distribution and source apportionment in eight varying land cover-land use type sampling points located along the Marilao-Meycauayan- Obando Rivers System. Elemental analysis was conducted using a scanning electron microscope coupled with energy dispersive x-ray. Cu, Pb, Zn, Cr, Mn, As, Cd, Co, Fe, Ni, Ti, and V concentrations were determined using Inductively Coupled Plasma Mass Spectrometry, and Hg concentrations by Mercury analyzer. Principal component analysis (PCA), hierarchical cluster analysis (HCA), and Pearson's r correlation were used to analyze different sources of heavy metals and its corresponding land use-land cover type. The aerosol samples showed the presence of heavy metals Pb and Hg, elements that were also detected in trace amounts in the water measurements. Concentrations of heavy metals such as Cu, Fe, Pb, Zn, V, Ni, and As found in the atmospheric aerosols and urban dusts were attributed to anthropogenic sources such as residential, commercial and industrial wastes. Other source of aerosols in the area were traffic and crustal emissions in Meycauayan. Using HCA, there are 3 clusters observed based on the similar sets of heavy metals: (1) AQS1 (Caingin), AQS2 (Banga), and AQS8 (Malhacan); (2) AQS3(Calvario), AQS4 (Camalig), and AQS5(Langka); (3) AQS1(Sto Nino-Perez), and (AQS7) (Sterling). These groups are related based on different land use setting such as residential/commercial, agricultural, and commercial/industrial areas. Our study recommends the need to address heavy metal pollution in Meycauayan in support to the ongoing implementation of laws and regulations by the local and private sectors.

Interaction of mercury species with proteins: towards possible mechanism of mercurial toxicology

The nature of the binding of mercurials (organic and inorganic) and their subsequent transformations in biological systems is a matter of great debate as several different hypotheses have been proposed and none of them has been conclusively proven to explain the characteristics of Hg binding with the proteins. Thus, the chemical nature of Hg-protein binding through the possible transportation mechanism in living tissues is critically reviewed herein. Emphasis is given to the process of transportation, and binding of Hg species with selenol-containing biomolecules that are appealing for toxicological studies as well as the advancement of environmental and biological research.

Disease-associated metabolic pathways affected by heavy metals and metalloid

Increased exposure to environmental heavy metals and metalloids and their associated toxicities has become a major threat to human health. Hence, the association of these metals and metalloids with chronic, age-related metabolic disorders has gained much interest. The underlying molecular mechanisms that mediate these effects are often complex and incompletely understood. In this review, we summarize the currently known disease-associated metabolic and signaling pathways that are altered following different heavy metals and metalloids exposure, alongside a brief summary of the mechanisms of their impacts. The main focus of this study is to explore how these affected pathways are associated with chronic multifactorial diseases including diabetes, cardiovascular diseases, cancer, neurodegeneration, inflammation, and allergic responses upon exposure to arsenic (As), cadmium (Cd), chromium (Cr), iron (Fe), mercury (Hg), nickel (Ni), and vanadium (V). Although there is considerable overlap among the different heavy metals and metalloids-affected cellular pathways, these affect distinct metabolic pathways as well. The common pathways may be explored further to find common targets for treatment of the associated pathologic conditions.

Integrated review of the nexus between toxic elements in the environment and human health

Emerging pollutants in the environment due to economic development have become a global challenge for environmental and human health management. Potentially toxic elements (PTEs), a major group of pollutants, have been detected in soil, air, water and food crops. Humans are exposed to PTEs through soil ingestion, consumption of water, uptake of food crop products originating from polluted fields, breathing of dust and fumes, and direct contact of the skin with contaminated soil and water. The dose absorbed by humans, the exposure route and the duration (i.e., acute or chronic) determine the toxicity of PTEs. Poisoning by PTEs can lead to excessive damage to health as a consequence of oxidative stress produced by the formation of free radicals and, as a consequence, to various disorders. The toxicity of certain organs includes neurotoxicity, nephrotoxicity, hepatotoxicity, skin toxicity, and cardiovascular toxicity. In the treatment of PTE toxicity, synthetic chelating agents and symptomatic supportive procedures have been conventionally used. In addition, there are new insights concerning natural products which may be a powerful option to treat several adverse consequences. Health policy implications need to include monitoring air, water, soil, food products, and individuals at risk, as well as environmental manipulation of soil, water, and sewage. The overall goal of this review is to present an integrated view of human exposure, risk assessment, clinical effects, as well as therapy, including new treatment options, related to highly toxic PTEs.

Environmental Exposure to Metals, Parameters of Oxidative Stress in Blood and Prostate Cancer: Results from Two Cohorts

We studied the potential role of exposure to various metal(oid)s (As, Cd, Cr, Hg, Ni, and Pb) in prostate cancer. Two cohorts were established: the Croatian cohort, consisting of 62 cases and 30 controls, and the Serbian cohort, consisting of 41 cases and 61 controls. Blood/serum samples were collected. Levels of investigated metal(oid)s, various parameters of oxidative stress, and prostate-specific antigen (PSA) were determined in collected samples. A comparison of the measured parameters between 103 prostate cancer patients and 91 control men from both Croatian and Serbian cohorts showed significantly higher blood Hg, SOD, and GPx levels and significantly lower serum SH levels in prostate cancer patients than in controls. Correlation analyses revealed the significant relationship between certain parameters of oxidative stress and the concentrations of the measured metal(loid)s, pointing to the possible role of metal(oid)-induced oxidative stress imbalance. Furthermore, a significant inverse relationship was found between the blood Pb and the serum PSA in prostate cancer patients, but when the model was adjusted for the impacts of remaining parameters, no significant association between the serum PSA and the measured parameters was found. The results of the overall study indicate a substantial contribution of the measured metal(loid)s to the imbalance of the oxidant/antioxidant system. Although somewhat conflicting, the results of the present study point to the possible role of investigated metal(oid)s in prostate cancer, especially for Hg, since the obtained relationship was observed for both cohorts, followed by the disturbances in oxidative stress status, which were found to be correlated with Hg levels. Nevertheless, further studies in larger cohorts are warranted to explain and confirm the obtained results.

Low-Level Environmental Mercury Exposure and Thyroid Cancer Risk Among Residents Living Near National Industrial Complexes in South Korea: A Population-Based Cohort Study

Background: Previous studies suggested that mercury may be linked to thyroid cancer due to its bioaccumulation in the thyroid gland, but no studies have evaluated the association between mercury exposure and thyroid cancer risk. We examined the relationship between mercury exposure and thyroid cancer risk, with the potential modification of hematological parameters. Methods: We performed a secondary analysis of a prospective cohort study among residents living near industrial complexes in South Korea (recruited from 2003 to 2011). Incident thyroid cancer cases (C73, ICD-10 code) were identified from the National Cancer Registry and Statistics Korea. Urinary mercury concentrations were measured using thermal decomposition amalgamation atomic absorption spectrometry (TDA-AAS). Cox proportional hazards regression models (adjusted for age, sex, educational level, smoking status, and employment) were used to estimate the hazard ratio (HR) and confidence interval [CI] between mercury exposure and the incidence of thyroid cancer. Results: We documented 69 cases of thyroid cancer in a total of 5213 participants during follow-up (median 8.7 years). The geometric mean of urinary mercury concentration was 1.8 μg/L for thyroid cancer cases and 1.2 μg/L for noncases (p for difference = 0.001). After adjusting for potential confounders, those in the highest tertile of urinary mercury levels had a twofold higher risk of thyroid cancer (HR = 1.97 [CI 1.03 - 3.80] in the highest tertile vs. the lowest tertile, p for trend = 0.043). This association was stronger for those with lower mean corpuscular volume and mean corpuscular hemoglobin status. Conclusions: Urinary mercury concentration was positively associated with the risk of thyroid cancer among residents living near national industrial complexes, and this association was influenced by red blood cell indices status. These results provide some evidence suggesting the adverse effects of environmental metal pollution in the development of thyroid cancer.

Plant-mediated gold and silver nanoparticles as detectors of heavy metal contamination

Heavy metals are dumped into the environment as a result of human activities, posing a serious threat to ecology and human health. Surface water, potable drinking water, potable groundwater, and majority of wastewater include their traces, due to which, their detection by nanoparticles has received a lot of attention in recent years. Although microorganisms are utilised for green nanoparticle production, plant materials have recently been explored because they are more environmentally friendly, easier to scale up, and require fewer specific growth conditions. The production and attributes of nanoparticles synthesized by plant mediation could be enhanced through design of experiments approach, extending their feasibility in the detection of heavy metals in polluted environmental samples. A concise review on green synthesis of silver and gold nanoparticles utilizing plant phytochemicals, its mechanism of synthesis along with significance of design of experiments for enhancement, and their use as heavy metal contamination detectors is presented in the current study.

Potential Application of Living Microorganisms in the Detoxification of Heavy Metals

Heavy metal (HM) exposure remains a global occupational and environmental problem that creates a hazard to general health. Even low-level exposure to toxic metals contributes to the pathogenesis of various metabolic and immunological diseases, whereas, in this process, the gut microbiota serves as a major target and mediator of HM bioavailability and toxicity. Specifically, a picture is emerging from recent investigations identifying specific probiotic species to counteract the noxious effect of HM within the intestinal tract via a series of HM-resistant mechanisms. More encouragingly, aided by genetic engineering techniques, novel HM-bioremediation strategies using recombinant microorganisms have been fruitful and may provide access to promising biological medicines for HM poisoning. In this review, we summarized the pivotal mutualistic relationship between HM exposure and the gut microbiota, the probiotic-based protective strategies against HM-induced gut dysbiosis, with reference to recent advancements in developing engineered microorganisms for medically alleviating HM toxicity.

A high-throughput screening assay for identification of chemicals with liver tumor promoting potential using a transgenic zebrafish line

Traditional high-throughput methods for identification of chemicals with liver tumor promotion potentials are based on established cancer cell lines, and rapid and cost-effective high-throughput screening assays in whole organisms are presently lacking. In this study, a transgenic zebrafish liver cancer model was employed to develop a method that could be used to identify chemicals with liver tumor promotion effect quickly and accurately. The method consisted of three parts, including exposure preparation, exposure process and image acquisition. In brief, after chemical exposure for 7 days, 96-well plate exposure system for zebrafish larvae was assessed by microplate reader. Then, the liver cancer promoting potential chemicals were evaluated by field area and field average intensity of fluorescence. The results were further validated by conducting histopathological examination. Our data demonstrated that the high-throughput screening assay developed in this study was reproducible and could be used to rapidly screen chemicals with liver tumor promoting potentials by using tris-(2-chloropropyl)-phosphate (TDCIPP) as a positive control. Furthermore, some other positive chemicals found in previous studies and environmental compounds were assessed using the established method. Results indicated that 86.7% of the positive chemicals and five environmental compounds out of seventeen compounds could enhance liver tumor progression.

Epigenetic Regulation in Exposome-Induced Tumorigenesis: Emerging Roles of ncRNAs

Environmental factors, including pollutants and lifestyle, constitute a significant role in severe, chronic pathologies with an essential societal, economic burden. The measurement of all environmental exposures and assessing their correlation with effects on individual health is defined as the exposome, which interacts with our unique characteristics such as genetics, physiology, and epigenetics. Epigenetics investigates modifications in the expression of genes that do not depend on the underlying DNA sequence. Some studies have confirmed that environmental factors may promote disease in individuals or subsequent progeny through epigenetic alterations. Variations in the epigenetic machinery cause a spectrum of different disorders since these mechanisms are more sensitive to the environment than the genome, due to the inherent reversible nature of the epigenetic landscape. Several epigenetic mechanisms, including modifications in DNA (e.g., methylation), histones, and noncoding RNAs can change genome expression under the exogenous influence. Notably, the role of long noncoding RNAs in epigenetic processes has not been well explored in the context of exposome-induced tumorigenesis. In the present review, our scope is to provide relevant evidence indicating that epigenetic alterations mediate those detrimental effects caused by exposure to environmental toxicants, focusing mainly on a multi-step regulation by diverse noncoding RNAs subtypes.

Role of Nanoparticles in Environmental Remediation: An Insight into Heavy Metal Pollution from Dentistry

Environmental damage is without a doubt one of the most serious issues confronting society today. As dental professionals, we must recognize that some of the procedures and techniques we have been using may pose environmental risks. The usage and discharge of heavy metals from dental set-ups pollute the environment and pose a serious threat to the ecosystem. Due to the exclusive properties of nanosized particles, nanotechnology is a booming field that is being extensively studied for the remediation of pollutants. Given that the nanoparticles have a high surface area to volume ratio and significantly greater reactivity, they have been greatly considered for environmental remediation. This review aims at identifying the heavy metal sources and their environmental impact in dentistry and provides insights into the usage of nanoparticles in environmental remediation. Although the literature on various functions of inorganic nanoparticles in environmental remediation was reviewed, the research is still confined to laboratory set-ups and there is a need for more studies on the usage of nanoparticles in environmental remediation.

Multivariate Investigation of Toxic and Essential Metals in the Serum from Various Types and Stages of Colorectal Cancer Patients

Colorectal cancer (CRC) is currently one of the most frequent malignant neoplasms, ranking 3rd in incidence and 2nd in mortality both in the USA and across the world. The pathogenesis of CRC is a complex interaction between genetic susceptibility and environmental factors such as exposure to metals. Therefore, the present study was intended to assess the imbalances in the concentrations of selected essential/toxic elements (Pb, Cr, Fe, Zn, As, Cd, Cu, Se, Ni, and Hg) in the serum of newly diagnosed colorectal carcinoma patients (n = 165) in comparison with counterpart controls (n = 151) by atomic absorption spectrometry after wet-acid digestion method. Serum carcinoembryonic antigen (CEA) of the CRC patients was determined using immunoradiometric method. Body mass index (BMI) which is an established risk factor for CRC was also calculated for patients and healthy controls. Conversely, average Ni (2.721 μg/g), Cd (0.563 μg/g), As (0.539 μg/g), and Pb (1.273 μg/g) levels were significantly elevated in the serum of CRC patients compared to the healthy donors, while the average Se (7.052 μg/g), Fe (15.67 μg/g), Cu (2.033 μg/g), and Zn (8.059 μg/g) concentrations were elevated in controls. The correlation coefficients between the elements in the cancerous patients demonstrated significantly dissimilar communal relationships compared with the healthy subjects. Significant differences in the elemental levels were also showed for CRC types (primary colorectal lymphoma, gastrointestinal stromal tumor, and adenocarcinoma) and CRC stages (stage-I, stage-II, stage-III, and stage-IV) among the patients. Majority of the elements demonstrated perceptible disparities in their levels based on dietary, habitat, gender, and smoking habits of the malignant patients and healthy subjects. Multivariate methods revealed noticeably divergent apportionment among the toxic/essential elements in the cancerous patients than the healthy counterparts. Overall, the study showed significantly divergent distribution and associations of the essential and toxic elemental levels in the serum of the CRC patients in comparison with the healthy donors.

Probiotics and gut microbiome - Prospects and challenges in remediating heavy metal toxicity

The gut microbiome, often referred to as "super organ", comprises up to a hundred trillion microorganisms, and the species diversity may vary from person to person. They perform a decisive role in diverse biological functions related to metabolism, immunity and neurological responses. However, the microbiome is sensitive to environmental pollutants, especially heavy metals. There is continuous interaction between heavy metals and the microbiome. Heavy metal exposure retards the growth and changes the structure of the phyla involved in the gut microbiome. Meanwhile, the gut microbiome tries to detoxify the heavy metals by altering the physiological conditions, intestinal permeability, enhancing enzymes for metabolizing heavy metals. This review summarizes the effect of heavy metals in altering the gut microbiome, the mechanism by which gut microbiota detoxifies heavy metals, diseases developed due to heavy metal-induced dysbiosis of the gut microbiome, and the usage of probiotics along with advancements in developing improved recombinant probiotic strains for the remediation of heavy metal toxicity.

Recent advances in environmentally benign hierarchical inorganic nano-adsorbents for the removal of poisonous metal ions in water: a review with mechanistic insight into toxicity and adsorption

Recent developments in nanoscience and technology have addressed many of the problems associated with water quality. Accordingly, using the technological outputs of the recent research on nanomaterials, the best solution for the purification of water is highlighted in this review. Herein, the main objective is to provide mechanistic insight into the synthesis of various inorganic nanoadsorbents and their adsorption chemistry for poisonous metal ions present in polluted water. Initially, the toxicity and carcinogenicity of As3+, Pb2+, Cr6+, Cd2+, and Hg2+ metal ions are highlighted. For the removal of these toxic ions, this review focuses on eco-friendly nanoadsorbents. The various preparation procedures utilized for the preparation of nanoadsorbents are briefly discussed. Generally, this is because of the adsorption capacity of nanoadsorbents depends on their morphology, shape, size, surface area, surface active sites, functional groups, and quantization effect. Also, due to the importance of their mechanism of action, the recent developments and challenges of novel nanoadsorbents such as metal oxides, core shell nanoparticles, magnetic nano ferrates, and functionalized core shell magnetic oxides and the processes for the treatment of water contaminated by toxic metal ions such as As3+, Pb2+, Cr6+, Cd2+, and Hg2+ are exclusively reviewed. Further, the adsorption efficiency of inorganic nanoadsorbents is also compared with that of activated carbon derived from various sources for all the above-mentioned metal ions.

Mercury in Pancreatic Cells of People with and without Pancreatic Cancer

Toxic metals have been implicated in the pathogenesis of pancreatic cancer. Human exposure to mercury is widespread, but it is not known how often mercury is present in the human pancreas and which cells might contain mercury. We therefore aimed to determine, in people with and without pancreatic cancer, the distribution and prevalence of mercury in pancreatic cells. Paraffin-embedded sections of normal pancreatic tissue were obtained from pancreatectomy samples of 45 people who had pancreatic adenocarcinoma, and from autopsy samples of 38 people without pancreatic cancer. Mercury was identified using two methods of elemental bio-imaging: (1) With autometallography, inorganic mercury was seen in islet cells in 14 of 30 males (47%) with pancreatic cancer compared to two of 17 males (12%) without pancreatic cancer (p = 0.024), and in 10 of 15 females (67%) with pancreatic cancer compared to four of 21 females (19%) without pancreatic cancer (p = 0.006). Autometallographic mercury was present in acinar cells in 24% and in periductal cells in 11% of people with pancreatic cancer, but not in those without pancreatic cancer. (2) Laser ablation-inductively coupled plasma-mass spectrometry confirmed the presence of mercury in islets that stained with autometallography and detected cadmium, lead, chromium, iron, nickel and aluminium in some samples. In conclusion, the genotoxic metal mercury is found in normal pancreatic cells in more people with, than without, pancreatic cancer. These findings support the hypothesis that toxic metals such as mercury contribute to the pathogenesis of pancreatic cancer.

Lycopene enriched tomato extract suppresses chemically induced skin tumorigenesis in mice

Abstract. The present study revealed the effects of Lycopene enriched tomato extract (LycT) on chemically induced skin cancer in mice. Skin tumors were induced by topical application of 7,12-Dimethylbenz(a)anthracene (DMBA) [500 nmol/100 ul of acetone, twice a week for two weeks] and 12-O-tetradecanoyl phorbol-13-acetate (TPA) [1.7 nmol/100 ul of acetone, twice a week for eighteen weeks] and LycT (5 mg/kg b.w.) was administered orally. Male Balb/c mice were divided into four groups (n = 15 per group): control, DMBA/TPA, LycT and LycT + DMBA/TPA. The chemopreventive response of LycT to skin tumorigenesis was evident by inhibition in tumor incidence, number, size, burden and volume in LycT + DMBA/TPA group when compared to DMBA/TPA group. This was associated with inhibition of cell proliferation in LycT + DMBA/TPA group as observed by the decrease in epidermal morphometric parameters and mRNA and protein expression of proliferating cell nuclear antigen when compared to DMBA/TPA group (p ≤ 0.05). LycT decreased (p ≤ 0.05) the mRNA and protein expression of angiogenic genes (vascular endothelial growth factor, angiopoietin-2, basic fibroblast growth factor) in LycT + DMBA/TPA group, suggesting its anti-angiogenic effects. The increase (p ≤ 0.05) in protein expression of connexin-32 and 43 in LycT + DMBA/TPA group suggests improved inter cellular communication when compared to DMBA/TPA group. Histochemical studies demonstrated that the components of extracellular matrix (fibrous proteins and mucopolysaccharides) were also modulated during skin carcinogenesis and its chemoprevention by LycT. The decrease in cell proliferation parameters and expression of angiogenesis associated genes, modulation of ECM components and increase in expression of connexins suggest that LycT improved multiple dysregulated processes during chemoprevention of skin cancer.

Selenium relieves oxidative stress, inflammation, and apoptosis within spleen of chicken exposed to mercuric chloride

Mercuric chloride (HgCl₂) is a widely distributed environmental pollutant with multiorgan toxicity including immune organs such as spleen. Selenium (Se) is an essential trace element in animal nutrition and exerts biological activity to antagonize organ toxicity caused by heavy metals. The objective of this study was to explore the underlying mechanism of the protective effects of Se against spleen damage caused by HgCl₂ in chicken. Ninety male Hyline brown chicken were randomly divided into 3 groups namely Cont, HgCl₂, and HgCl₂+Se group. Chicken were provided with the standard diet and nontreated water, standard diet and HgCl₂-treated water (250 ppm), and sodium selenite-treated diet (10 ppm) plus HgCl₂-treated water (250 ppm), respectively. After being fed for 7 wk, the spleen tissues were collected, and spleen index, the microstructure of the spleen, and the indicators of oxidative stress, inflammation, apoptosis as well as heat shock proteins (HSP) were detected. First, the results of spleen index and pathological examination confirmed that Se exerted an antagonistic effect on the spleen injury induced by HgCl₂. Second, Se ameliorated HgCl₂-induced oxidative stress by decreasing the level of malondialdehyde and increasing the levels of glutathione, glutathione peroxidase, and total antioxidant capacity. Third, Se attenuated HgCl₂-induced inflammation by decreasing the protein expression of nuclear factor kappa-B, inducible nitric oxide synthase, and cyclooxygenase-2, and the gene expression of interleukin (IL)-1β, IL-6, IL-8, IL-12β, IL-18 as well as tumor necrosis factor-α. Fourth, Se inhibited HgCl₂-induced apoptosis by downregulating the protein expression of BCL2 antagonist/killer 1 and upregulating the protein expression of B-cell lymphoma-2. Finally, Se reversed HgCl₂-triggered activation of HSP 60, 70, and 90. In conclusion, Se antagonized HgCl₂-induced spleen damage in chicken, partially through the regulation of oxidative stress, inflammatory, and apoptotic signaling.

Nanozyme-based sensing platforms for detection of toxic mercury ions: An alternative approach to conventional methods

Mercury (Hg) is known as a poisonous heavy metal which stimulates a wide range of adverse effects on the human health. Therefore, development of some feasible, practical and highly sensitive platforms would be desirable in determination of Hg²⁺ level as low as nmol L^-1 or pmol L^-1. Different approaches such as ICP-MS, AAS/AES, and nanomaterial-based nanobiosensors have been manipulated for determination of Hg²⁺ level. However, these approaches suffer from expensive instruments and complicated sample preparation. Recently, nanozymes have been assembled to address some disadvantages of conventional methods in the detection of Hg²⁺. Along with the outstanding progress in nanotechnology and computational approaches, pronounced improvement has been attained in the field of nanozymes, recently. To accentuate these progresses, this review presents an overview on the different reports of Hg²⁺-induced toxicity on the different tissues followed by various conventional approaches validated for the determination of Hg²⁺ level. Afterwards, different types of nanozymes like AuNPs, PtNPs for quantitative detection of Hg²⁺ were surveyed. Finally, the current challenges and the future directions were explored to alleviate the limitation of nanozyme-based platforms with potential engineering in detection of heavy metals, namely Hg²⁺. The current overview can provide outstanding information to develop nano-based platforms for improvement of LOD and LOQ of analytical methods in sensitive detection of Hg²⁺ and other heavy metals.

Association of blood mercury levels with nonmelanoma skin cancer in the U.S.A. using National Health and Nutrition Examination Survey data (2003-2016)

BACKGROUND

Some studies have reported increased incidence or mortality of lung and brain cancers associated with occupations involving potential mercury exposure. Epidemiological evidence related to skin cancer is also limited.

OBJECTIVES

To investigate the association between blood mercury (Hg) levels and nonmelanoma skin cancer (NMSC).

METHODS

We used National Health and Nutrition Examination Survey data from 2003 to 2016. The exposures were blood total (tHg), inorganic (iHg) and methylmercury (MeHg). The outcome was a self-reported diagnosis of NMSC. We included participants aged ≥ 20 years who had information on blood mercury and sociodemographic factors. We conducted a logistic regression analysis to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for the risk of NMSC associated with quartiles of blood Hg, after adjusting for the sociodemographic factors and survey year.

RESULTS

The number of participants was 29 413; mean age was 49 years and 52% were female. Compared with those with a tHg ≤ 0·47 μg L^-1 (Q1), those with a tHg > 1·74 μg L^-1 (Q4) had nearly double the odds of NMSC (OR 1·79, 95% CI 1·19-2·71; P_trend = 0·004). Similarly, those in the highest quartile of MeHg (> 1·44 μg L^-1 ) had 1·7 times greater odds of NMSC (OR 1·74, 95% CI 1·13-2·70; P_trend = 0·01) than those in the lowest quartile (≤ 0·21 μg L^-1 ). iHg levels were nonsignificantly positively associated with NMSC (P_trend = 0·08).

CONCLUSIONS

We found that higher blood tHg and MeHg levels were associated with a higher prevalence of NMSC. Linked Comment: Taylor. Br J Dermatol 2020; 183:413-414.

Progressive trends in heavy metal ions and dyes adsorption using silk fibroin composites

Thriving industrialization for human lifestyle headway has seeded the roots of water intoxication with harmful and hazardous toxic metal ions and dyes, which may ingress into food chains and become homicidal or mutation causing for creatures. The degummed functionalized silk fibroin composites with different biomaterials and synthetic materials are able to show adsorption efficiencies equivalent to 52.5%, 90%, 81.1%, 93.75%, 84.2%, and 98.9% for chromium, copper, cadmium, lead, thorium, and uranium ions, respectively, and adsorption capacity of 88.5 mg/g, 74.63 mg/g, 76.34 mg/g, and 72 mg/L for acid yellow 11, naphthol orange, direct orange S, and methylene blue, respectively, which make them desirable solution for water toxicants removal. This review is intended to describe the ability of silk fibroins to adsorb and abolish toxic heavy metal ions and dyes from water reservoirs, thus, providing a way to step toward water sanitation and wholesome living. Graphical abstract.

Critical review of mercury contamination in Sri Lankan fish and aquatic products

Mercury (Hg) in fish and aquatic products is a potential threat to human health and international trade, and guidelines of international advisory bodies are established for assessing Hg in these foods. As fish are the most consumed animal protein in Sri Lanka, this assessment summarises for the first-time total mercury concentrations in Sri Lankan marine and freshwater fish, invertebrates, aquatic plants, and fisheries products. It reveals that Hg levels in fish and other edible aquatic species are mostly below the published safety limits, except for certain top trophic level fish (swordfish, tuna, marlin). The review also highlights gaps in Sri Lankan Hg assessments such as a total lack of data for methyl‑mercury in these aquatic species and food products. This data compilation and assessment will serve as an initial baseline for comparison with results from future monitoring and research studies in Sri Lanka while adding to the world-wide Hg database.

Mercury Concentration, DNA Methylation, and Mitochondrial DNA Damage in Olive Ridley Sea Turtle Embryos With Schistosomus Reflexus Syndrome

Schistosomus reflexus syndrome (SR) is a rare and lethal congenital malformation that has been reported in the olive ridley sea turtle (Lepidochelys olivacea) in Mexico. Although the etiology remains unclear, it is presumed to be genetic. Since embryonic development in sea turtles largely depends on environmental conditions, we investigated whether sea turtle total mercury content participates in the etiology of SR. Given that several toxins are known to affect both DNA methylation and/or mitochondrial DNA (mtDNA) copy number, we also probed for associations of these parameters to SR and mercury exposure. We measured the levels of each variable in malformed olive ridley sea turtle embryos (either with SR or other non-SR malformations) and embryos without malformations. Malformed embryos (with or without SR) showed higher mercury concentrations compared to normal embryos, while only embryos with SR showed higher levels of methylation compared to embryos without malformations and those with other malformations. Furthermore, we uncovered a positive correlation between mercury concentrations and DNA methylation in SR embryos. With respect to mtDNA copy number, no differences were detected across experimental groups. Because of sample size limitations, this study is an initial attempt to understand the association of environmental toxins (such as mercury) and epigenetic alterations (DNA methylation) in the etiology of SR in sea turtles.

Gap Junction Intercellular Communication in the Carcinogenesis Hallmarks: Is This a Phenomenon or Epiphenomenon?

If occupational tumors are excluded, cancer causes are largely unknown. Therefore, it appeared useful to work out a theory explaining the complexity of this disease. More than fifty years ago the first demonstration that cells communicate with each other by exchanging ions or small molecules through the participation of connexins (Cxs) forming Gap Junctions (GJs) occurred. Then the involvement of GJ Intercellular Communication (GJIC) in numerous physiological cellular functions, especially in proliferation control, was proven and accounts for the growing attention elicited in the field of carcinogenesis. The aim of the present paper is to verify and discuss the role of Cxs, GJs, and GJIC in cancer hallmarks, pointing on the different involved mechanisms in the context of the multi-step theory of carcinogenesis. Functional GJIC acts both as a tumor suppressor and as a tumor enhancer in the metastatic stage. On the contrary, lost or non-functional GJs allow the uncontrolled proliferation of stem/progenitor initiated cells. Thus, GJIC plays a key role in many biological phenomena or epiphenomena related to cancer. Depending on this complexity, GJIC can be considered a tumor suppressor in controlling cell proliferation or a cancer ally, with possible preventive or therapeutic implications in both cases.

Capture of Pb2+ and Cu2+ Metal Cations by Neisseria meningitidis-type Capsular Polysaccharides

Heavy metal pollution of water is a significant environmental and public health concern. Current biological strategies for heavy metal removal from water are performed using microbial biopolymers, including polysaccharides, that are already fully formed. This creates limitations in adapting polysaccharides to increase binding affinity for specific metals. We propose that altering the specificity of polysaccharide-producing enzymes could be beneficial to improving metal capture by modified polysaccharides. We assess binding of Cu2+ and Pb2+ metal cations to Neisseria meningitidis-type polysaccharides. All concentrations of metal cations tested were able to completely bind to colominic acid. This polymer is equivalent to the capsular polysaccharide of N. meningitidis serogroup B comprised of a homopolymer of negatively charged sialic acid. There was slightly less binding observed with N. meningitidis serogroup W, which contains repeating units of the neutral sugar galactose and sialic acid. Our work represents the first assessment of the metal-binding properties of these capsular polysaccharides. Future work will seek to optimize metal-binding with Neisseria meningitidis serogroup W polysaccharide.