Immunology of mercury

Prenatal heavy metal exposure and pediatric asthma, allergic rhinitis, atopic dermatitis: a systematic review and meta-analysis

OBJECTIVE

We review the prevalence of allergic diseases in children across prenatal exposures to heavy metals.

METHODS

This systematic review and meta-analysis is registered in the PROSPERO database (CRD42023478471). A comprehensive search of PubMed, Web of Science, Medline and Cochrane library was conducted from the database inception until 31 October 2023. The Newcastle-Ottawa Quality Assessment Scale (NOS) was used to assess the quality of included studies. We used a random-effects model to summarize the effects from the studies.

RESULTS

A total of 16 studies were included, 120,065 mother-child pairs enrolled. The NOS scores indicated that the quality of the literature included in the study was of a high standard.

CONCLUSION

The final results indicate that prenatal exposure to Pb increased the incidence of wheeze and Eczema in infants, and exposure to Ni and CD increased the incidence of AD in infants.

Mercury-induced toxicity: Mechanisms, molecular pathways, and gene regulation

Mercury is a well-known neurotoxicant for humans and wildlife. The epidemic of mercury poisoning in Japan has clearly demonstrated that chronic exposure to methylmercury (MeHg) results in serious neurological damage to the cerebral and cerebellar cortex, leading to the dysfunction of the central nervous system (CNS), especially in infants exposed to MeHg in utero. The occurrences of poisoning have caused a wide public concern regarding the health risk emanating from MeHg exposure; particularly those eating large amounts of fish may experience the low-level and long-term exposure. There is growing evidence that MeHg at environmentally relevant concentrations can affect the health of biota in the ecosystem. Although extensive in vivo and in vitro studies have demonstrated that the disruption of redox homeostasis and microtube assembly is mainly responsible for mercurial toxicity leading to adverse health outcomes, it is still unclear whether we could quantitively determine the occurrence of interaction between mercurial and thiols and/or selenols groups of proteins linked directly to outcomes, especially at very low levels of exposure. Furthermore, intracellular calcium homeostasis, cytoskeleton, mitochondrial function, oxidative stress, neurotransmitter release, and DNA methylation may be the targets of mercury compounds; however, the primary targets associated with the adverse outcomes remain to be elucidated. Considering these knowledge gaps, in this article, we conducted a comprehensive review of mercurial toxicity, focusing mainly on the mechanism, and genes/proteins expression. We speculated that comprehensive analyses of transcriptomics, proteomics, and metabolomics could enhance interpretation of "omics" profiles, which may reveal specific biomarkers obviously correlated with specific pathways that mediate selective neurotoxicity.

Complementary and Alternative Medicine Use and Glomerular Disease: A Contemporary Case Series

Rationale & Objective

Complementary and alternative medicine (CAM) intake is widely prevalent in many parts of India. Heavy metals are known ingredients in some of these formulations. We studied the spectrum of glomerular diseases in patients using CAM.

Study Design

Case series.

Setting & Participants

Patients with proteinuria or unexplained acute kidney injury, who underwent a kidney biopsy between May 2021 and September 2022, and who provided a history of recent CAM intake were included in the study. For patients enrolled prospectively, blood and urine samples were analyzed using mass spectrometry for the presence of mercury, lead, arsenic and cadmium. The CAM formulation, when available, was analyzed using inductively coupled plasma-optical emission spectroscopy.

Results

Twenty-eight patients were enrolled in the study, with a median duration of CAM intake of 4 months (interquartile range, 2-6 months). Heavy metal screening was performed in 17 patients, of whom 15 had elevated urine mercury levels, 10 had elevated blood mercury levels, and 1 had elevated blood and urine arsenic levels. Of the 6 CAM formulations that were analyzed, all had high levels of mercury. Kidney biopsy findings were membranous nephropathy (n = 19), minimal change disease (n = 8), and mesangial proliferative glomerulonephritis (n = 1). Of the 19 patients with membranous nephropathy, 14 were associated with neural epidermal growth factor-like protein 1 (NELL-1). With conservative management alone, 17 patients achieved complete remission.

Limitations

Not all patients underwent blood and urine mercury testing, and only 6 patients provided the CAM samples for analysis. Furthermore, occupational and residential exposure to mercury could not be excluded.

Conclusions

The most common kidney pathology noted in our study was membranous nephropathy, which was predominantly associated with neural epidermal growth factor-like protein 1. A significant proportion of the patients recovered completely after withdrawal of the offending agent and initiation of renin-angiotensin system blockade.

Association between environmental mercury exposure and allergic disorders in Korean children: Korean National Environmental Health Survey (KoNEHS) cycles 3-4 (2015-2020)

Although previous studies have suggested potential adverse effects of mercury on a child's immune system, the associations have been inconsistent. We aimed to determine the association between urinary mercury levels and allergic diseases in Korean children with high mercury exposure. Data from 853 and 710 children aged 6-11 years in the Korean National Environmental Health Survey (KoNEHS) cycle 3 (2015-2017) and cycle 4 (2018-2020) were analyzed. We examined the association between mercury exposure and the prevalence of atopic dermatitis (AD), asthma, allergic rhinitis (AR), and allergic multimorbidity. After adjusting for all covariates, the urinary mercury level was positively associated with AD in the 2015-2017 study (OR = 1.34, 95% CI = 1.01, 1.79) and AR in 2018-2020 study (OR = 1.46, 95% CI = 1.01, 2.10). Pooled effects showed OR of 1.34 (95% CI = 1.01, 1.79) for AD and 1.47 (95% CI = 1.01, 2.12) for allergic multimorbidity. The association with allergic multimorbidity was greater in boys (OR = 1.88, 95% CI = 1.01, 3.49) than in girls (OR = 1.25, 95% CI = 0.73, 2.14). These results suggest that environmental mercury exposure may exacerbate symptoms of atopic dermatitis and allergic multimorbidity in children.

Mercury chloride activates the IFNγ-IRF1 signaling in myeloid progenitors and promotes monopoiesis in mice

Inorganic mercury (Hg2+) is a highly toxic heavy metal in the environment. To date, the impacts of Hg2+ on the development of monocytes, or monopoiesis, have not been fully addressed. The aim of the present study was to investigate the impact of Hg2+ on monopoiesis. In this study, we treated B10.S mice and DBA/2 mice with 10 μM or 50 μM HgCl2 via drinking water for 4 wk, and we then evaluated the development of monocytes. Treatment with 50 μM HgCl2, but not 10 μM HgCl2, increased the number of monocytes in the blood, spleen and bone marrow (BM) of B10.S mice. Accordingly, treatment with 50 μM HgCl2, but not 10 μM HgCl2, increased the number of common myeloid progenitors (CMP) and granulocyte-macrophage progenitors (GMP) in the BM. Functional analyses indicated that treatment with 50 μM HgCl2 promoted the differentiation of CMP and GMP to monocytes in the BM of B10.S mice. Mechanistically, treatment with 50 μM HgCl2 induced the production of IFNγ, which activated the Jak1/3-STAT1/3-IRF1 signaling in CMP and GMP and enhanced their differentiation potential for monocytes in the BM, thus likely leading to increased number of mature monocytes in B10.S mice. Moreover, the increased monopoiesis by Hg2+ was associated with the increased inflammatory status in B10.S mice. In contrast, treatment with 50 μM HgCl2 did not impact the monopoiesis in DBA/2 mice. Our study reveals the impact of Hg on the development of monocytes.

Hierarchical porous loofah-like carbon with sulfhydryl functionality for electrochemical detection of trace mercury in water

Mercury is a common contaminant found in natural waters, which is highly toxic to human health. Thus, the facile and reliable monitoring of mercury in waters is of great significance. In this study, we fabricated a novel loofah-like hierarchical porous carbon with sulfhydryl functionality (S-LHC), and applied it as an ultrasensitive sensor for the electrochemical detection of mercury in water. The S-LHC was prepared through the direct pyrolysis of a triazole-rich metal-organic framework (MOF), followed by chemical modification using thioglycolic acid. The highly conductive N-doped carbon framework of S-LHC facilitated the electron transfer in mercury electrochemical sensing. Meanwhile, the open hierarchical pore structure and abundant sulfhydryl groups allowed the fast diffusion and effective enrichment of mercury ions. Consequently, the S-LHC sensor exhibited an exceptionally high sensitivity for mercury ions, with the mercury detection limit (0.36 nM) orders of magnitude lower than the regulated values in drinking water (typically 10∼30 nM). The constructed sensor also afforded good anti-interference ability and excellent stability for long-term detection of mercury in a variety of complex real water samples. The present study provides not only a facile method for mercury detection, but also a new idea for the construction of highly sensitive electrochemical sensors.

Prenatal exposure to selenium, mercury, and manganese during pregnancy and allergic diseases in early childhood: The Japan Environment and Children's study

BACKGROUND

Prenatal exposure to metallic elements may adversely affect early childhood health. However, more evidence is needed as population-based cohort studies are currently limited.

OBJECTIVES

We aimed to examine the associations between prenatal metallic (mercury, selenium, and manganese) exposure and the risk of allergic diseases in early childhood until three years of age.

METHODS

The data from 94,794 mother-infant pairs, who participated in the Japan Environment and Children's study, were used in this study. Prenatal metallic element exposure was measured in maternal blood collected during mid-pregnancy. The incidence of atopic dermatitis, food allergies, asthma, and allergic rhinitis during the first three years of life was prospectively investigated using self-reports of physician-diagnosed allergies. A multivariable modified Poisson regression model was used to estimate the cumulative incidence ratio and their 95% confidence intervals of allergic diseases associated with prenatal exposure to mercury, selenium, and manganese. We further evaluated the interaction between mercury and selenium exposures in this association.

RESULTS

We confirmed 26,238 cases of childhood allergic diseases: atopic dermatitis, food allergies, asthma, and allergic rhinitis in 9,715 (10.3%), 10,897 (11.5%), and 9,857 (10.4%), 4,630 (4.9%), respectively. No association was found between prenatal mercury or manganese exposure and the risk of allergic diseases. Prenatal selenium exposure was inversely associated with atopic dermatitis, food allergies, allergic rhinitis, and any allergic diseases, but not with asthma. These inverse associations were more pronounced for lower mercury exposures than for higher exposures.

CONCLUSIONS

Our findings suggest that prenatal exposure to selenium may be beneficial for reducing the risk of atopic dermatitis, food allergies, allergic rhinitis, and any allergic diseases in early childhood, especially with lower prenatal mercury exposure.

Metabolomics: a promising tool for deciphering metabolic impairment in heavy metal toxicities

Heavy metals are the metal compounds found in earth's crust and have densities higher than that of water. Common heavy metals include the lead, arsenic, mercury, cadmium, copper, manganese, chromium, nickel, and aluminum. Their environmental levels are consistently rising above the permissible limits and they are highly toxic as enter living systems via inhalation, ingestion, or inoculation. Prolonged exposures cause the disruption of metabolism, altered gene and/or protein expression, and dysregulated metabolite profiles. Metabolomics is a state of the art analytical tool widely used for pathomolecular inv22estigations, biomarkers, drug discovery and validation of biotransformation pathways in the fields of biomedicine, nutrition, agriculture, and industry. Here, we overview studies using metabolomics as a dynamic tool to decipher the mechanisms of metabolic impairment related to heavy metal toxicities caused by the environmental or experimental exposures in different living systems. These investigations highlight the key role of metabolomics in identifying perturbations in pathways of lipid and amino acid metabolism, with a critical role of oxidative stress in metabolic impairment. We present the conclusions with future perspectives on metabolomics applications in meeting emerging needs.

Potentially toxic elements in the brains of people with multiple sclerosis

Potentially toxic elements such as lead and aluminium have been proposed to play a role in the pathogenesis of multiple sclerosis (MS), since their neurotoxic mechanisms mimic many of the pathogenetic processes in MS. We therefore examined the distribution of several potentially toxic elements in the autopsied brains of people with and without MS, using two methods of elemental bio-imaging. Toxicants detected in the locus ceruleus were used as indicators of past exposures. Autometallography of paraffin sections from multiple brain regions of 21 MS patients and 109 controls detected inorganic mercury, silver, or bismuth in many locus ceruleus neurons of both groups, and in widespread blood vessels, oligodendrocytes, astrocytes, and neurons of four MS patients and one control. Laser ablation-inductively coupled plasma-mass spectrometry imaging of pons paraffin sections from all MS patients and 12 controls showed that combinations of iron, silver, lead, aluminium, mercury, nickel, and bismuth were present more often in the locus ceruleus of MS patients and were located predominantly in white matter tracts. Based on these results, we propose that metal toxicants in locus ceruleus neurons weaken the blood-brain barrier, enabling multiple interacting toxicants to pass through blood vessels and enter astrocytes and oligodendroglia, leading to demyelination.

Mercury increases IL-1β and IL-18 secretion and intensifies coronary arteritis in an animal model of Kawasaki disease

Kawasaki disease (KD) is a multisystem vasculitis that predominantly targets the coronary arteries in young children. Epidemiological data suggest both environmental and genetic factors contribute to the susceptibility and severity of the disease. Mercury (Hg) is a known environmental pollutant and a Ca²⁺ signaling modulator. Ca²⁺ signaling regulates the activation of NLRP3 inflammasome. Using the Lactobacillus casei cell wall extract (LCWE) induced coronary arteritis mouse model of KD; we studied the effect of mercury on inflammasome activation and its impact on the immunopathogenesis of KD. Mercury enhances the expression of inflammasome activation resulting in caspase-1 mediated secretion of IL-1β and IL-18 cytokines. In vivo, the administration of mercury together with disease inducing LCWE exacerbates disease resulting in increased incidence and severity of coronary arteritis compared to LCWE alone. Mercury can act as a novel danger signal modulating Ca²⁺ signaling to increase IL-1β and IL-18 secretion and intensifies coronary arteritis in an animal model of KD.

Mercury Chloride Impacts on the Development of Erythrocytes and Megakaryocytes in Mice

Inorganic mercury (Hg²⁺) is a highly toxic heavy metal. The aim of this study was to investigate the impact of Hg²⁺ on the development of erythrocytes and megakaryocytes. B10.S mice (H-2^s) and DBA/2 mice (H-2^d) were administrated with 10 μM HgCl₂ or 50 μM HgCl₂ via drinking water for four weeks, and erythro-megakaryopoiesis was evaluated thereafter. The administration of 50 μM HgCl₂ increased the number of erythrocytes and platelets in B10.S mice, which was not due to a reduced clearance for mature erythrocytes. The administration of 50 μM HgCl₂, but not 10 μM HgCl₂, increased the number of progenitors for erythrocytes and megakaryocytes in the bone marrow (BM) of B10.S mice, including erythroid-megakaryocyte progenitors (EMPs), burst-forming unit-erythroid progenitors (BFU-Es), colony-forming unit-erythroid progenitors (CFU-Es), and megakaryocyte progenitors (MkPs). Moreover, 50 μM HgCl₂ caused EMPs to be more proliferative and possess an increased potential for differentiation into committed progenies in B10.S mice. Mechanistically, 50 μM HgCl₂ increased the expression of the erythropoietin receptor (EPOR) in EMPs, thus enhancing the Jak2/STAT5 signaling pathway to promote erythro-megakaryopoiesis in B10.S mice. Conversely, 50 μM HgCl₂ did not impact erythro-megakaryopoiesis in DBA/2 mice. This study may extend our current understanding for hematopoietic toxicology of Hg.

Pre and postnatal exposure to mercury and respiratory health in preschool children from the Spanish INMA Birth Cohort Study

Effects of mercury on maturing immune system have been reported, however the association with respiratory and allergy problems during infancy remains unclear. The aim of this study is to evaluate the association between pre and postnatal mercury exposure and respiratory and allergy problems among preschool children and to examine the role of potential modifying factors. Study subjects were children participant in Spanish Childhood and Environment Project (INMA, 2003-2008). We measured total mercury levels in cord blood (n = 1868) and hair at 4 years of age (n = 1347). Respiratory outcomes (wheezing, severe wheezing, chestiness, persistent cough, eczema and otitis) were obtained by questionnaires administered to parents. Associations were investigated by logistic regression adjusted for socio-demographic and lifestyle-related variables in each cohort and subsequent meta-analysis. We tested effect modification by factors related to individual susceptibility, diet and co-exposure with other pollutants. The geometric mean of cord blood and hair total mercury was 8.20 μg/L and 0.97 μg/g, respectively. No statistically significant association between pre or postnatal mercury exposure and respiratory and allergy outcomes was found. Notwithstanding, lower maternal intake of fruits and vegetables increased the risk of some respiratory outcomes due to the prenatal exposure to mercury (p_int < 0.05). Moreover, an inverse association between prenatal mercury exposure and some respiratory outcomes was observed among children with higher maternal exposure to organocholorine compounds or smoking (p_int < 0.05). Also, sex and postnatal smoking exposure modulated mercury postnatal effects on persistent cough (p_int < 0.05). In conclusion, no association between pre and postnatal mercury exposure and respiratory and allergy problems among the whole population at study was found. However, diet and other toxicants could modulate this relation, especially during prenatal period. More research on this topic is warranted due to the limited evidence.

A novel coumarin-based colorimetric and fluorescent probe for detecting increasing concentrations of Hg2+ in vitro and in vivo

Mercury has complex biological toxicity and can cause a variety of physiological diseases and even death, so it is of great importance to develop novel strategies for detecting trace mercury in environmental and biological samples. In this work, we designed a new coumarin-based colorimetric and fluorescent probe CNS, which could be obtained from inexpensive starting materials with high overall yield in three steps. Probe CNS could selectively respond to Hg²⁺ with obvious color and fluorescence changes, and the presence of other metal ions had no effect on the fluorescence changes. Probe CNS also exhibited high sensitivity against Hg²⁺, with a detection limit as low as 2.78 × 10^-8 M. More importantly, the behavioral tracks of zebrafish had no obvious changes upon treatment with 10 μM probe CNS, thus indicating its low toxicity. The probe showed potential application value and was successfully used for detecting Hg²⁺ in a test strip, HeLa cells and living zebrafish larvae.

Are cysteine residues of human phospholipid scramblase 1 essential for Pb2+ and Hg2+ binding-induced scrambling of phospholipids?

Lead and mercury being common environmental pollutants are often associated with erythrocytes, where phosphatidylserine (PS) exposure-mediated procoagulant activation is induced. Human phospholipid scramblase 1 (hPLSCR1) identified in the erythrocyte membrane is a type II transmembrane protein involved in Ca²⁺-dependent bidirectional scrambling of phospholipids (PL) during blood coagulation, cell activation, and apoptosis. The prominent role of hPLSCR1 in Pb²⁺ and Hg²⁺ poisoning was demonstrated by a biochemical assay, where recombinant hPLSCR1 induced PL scrambling across bilayer with a higher binding affinity (K_d) towards Hg²⁺ (4.1 µM) and Pb²⁺ (5.8 µM) than Ca²⁺ (25.6 mM). The increased affinity could be the outcome of heavy metals interacting at auxiliary sites other than the calcium-binding motif of hPLSCR1. Similar to other metal-binding proteins, cysteine-based metal-binding motifs could be the potential additional binding sites in hPLSCR1. To explore the hypothesis, the cysteines were chemically modified, which significantly reduced only the Hg²⁺- and Pb²⁺-induced scrambling activity leaving Ca²⁺-induced activity unaltered. Recombinant constructs with deletion of prominent cysteine residues and point mutation in the calcium-binding motif including Δ100-hPLSCR1, Δ160-hPLSCR1, and D275A-hPLSCR1 were generated, purified, and assayed for scramblase activity. The cysteine-deleted constructs of hPLSCR1 showed reduced binding affinity (K_d) for Hg²⁺ and Pb²⁺ without altering the Ca²⁺-binding affinity whereas the point mutant had completely lost its affinity for Ca²⁺ and reduced affinities for Hg²⁺ and Pb²⁺. The results accentuated the significance of cysteine residues as additional binding sites for heavy metal ions in hPLSCR1.

Mercury Toxicity and Detection Using Chromo-Fluorogenic Chemosensors

Mercury (Hg), this non-essential heavy metal released from both industrial and natural sources entered into living bodies, and cause grievous detrimental effects to the human health and ecosystem. The monitoring of Hg2+ excessive accumulation can be beneficial to fight against the risk associated with mercury toxicity to living systems. Therefore, there is an emergent need of novel and facile analytical approaches for the monitoring of mercury levels in various environmental, industrial, and biological samples. The chromo-fluorogenic chemosensors possess the attractive analytical parameters of low-cost, enhanced detection ability with high sensitivity, simplicity, rapid on-site monitoring ability, etc. This review was narrated to summarize the mercuric ion selective chromo-fluorogenic chemosensors reported in the year 2020. The design of sensors, mechanisms, fluorophores used, analytical performance, etc. are summarized and discussed.

Neurotoxicity of mercury: an old issue with contemporary significance

Mercury exerts a variety of toxic effects, depending on the specific compound and route of exposure. However, neurotoxicity in virtue of its consequence to health causes the greatest concern for toxicologists. This is particularly true regarding fetal development, where neurotoxic effects are much more severe than in adults, and the toxicity threshold is lower. Here, we review the major concepts regarding the neurotoxicity of mercury compounds (mercury vapor; methylmercury and ethylmercury), from exposure routes to toxicokinetic particularities leading to brain deposition and the development of neurotoxic effects. Albeit research on the neurotoxicity of mercury compounds has significantly advanced from the second half of the twentieth century onwards, several grey areas regarding the mechanism of toxicity still exist. Thus, we emphasize research advances during the last two decades concerning the molecular interactions of mercury which cause neurotoxic effects. Highlights include the disruption of glutamate signaling and excitotoxicity resulting from exposure to mercury and the interaction with redox active residues such as cysteines and selenocysteines which are the premise accounting for the disruption of redox homeostasis caused by mercurials. We also address how immunotoxic effects at the CNS, namely microglia and astrocyte activation modulate developmental neurotoxicity, a major topic in contemporary research.

Mercury as a hapten: A review of the role of toxicant-induced brain autoantibodies in autism and possible treatment considerations

BACKGROUND

Mercury has many direct and well-recognized neurotoxic effects. However, its immune effects causing secondary neurotoxicity are less well-recognized. Mercury exposure can induce immunologic changes in the brain indicative of autoimmune dysfunction, including the production of highly specific brain autoantibodies. Mercury, and in particular, Thimerosal, can combine with a larger carrier, such as an endogenous protein, thereby acting as a hapten, and this new molecule can then elicit the production of antibodies.

METHODS

A comprehensive search using PubMed and Google Scholar for original studies and reviews related to autism, mercury, autoantibodies, autoimmune dysfunction, and haptens was undertaken. All articles providing relevant information from 1985 to date were examined. Twenty-three studies were identified showing autoantibodies in the brains of individuals diagnosed with autism and all were included and discussed in this review.

RESULTS

Research shows mercury exposure can result in an autoimmune reaction that may be causal or contributory to autism, especially in children with a family history of autoimmunity. The autoimmune pathogenesis in autism is demonstrated by the presence of brain autoantibodies (neuroantibodies), which include autoantibodies to: (1) human neuronal progenitor cells; (2) myelin basic protein (MBP); (3) neuron-axon filament protein (NAFP); (4) brain endothelial cells; (5) serotonin receptors; (6) glial fibrillary acidic protein (GFAP); (7) brain derived neurotrophic factor (BDNF); (8) myelin associated glycoprotein (MAG); and (9) various brain proteins in the cerebellum, hypothalamus, prefrontal cortex, cingulate gyrus, caudate putamen, cerebral cortex and caudate nucleus.

CONCLUSION

Recent evidence suggests a relationship between mercury exposure and brain autoantibodies in individuals diagnosed with autism. Moreover, brain autoantibody levels in autism are found to correlate with both autism severity and blood mercury levels. Treatments to reduce mercury levels and/or brain autoantibody formation should be considered in autism.

The distribution of toxic metals in the human retina and optic nerve head: Implications for age-related macular degeneration

Objective

Toxic metals are suspected to play a role in the pathogenesis of age-related macular degeneration. However, difficulties in detecting the presence of multiple toxic metals within the intact human retina, and in separating primary metal toxicity from the secondary uptake of metals in damaged tissue, have hindered progress in this field. We therefore looked for the presence of several toxic metals in the posterior segment of normal adult eyes using elemental bioimaging.

Methods

Paraffin sections of the posterior segment of the eye from seven tissue donors (age range 54–74 years) to an eye bank were examined for toxic metals in situ using laser ablation-inductively coupled plasma-mass spectrometry, a technique that detects multiple elements in tissues, as well as the histochemical technique of autometallography that demonstrates inorganic mercury, silver, and bismuth. No donor had a visual impairment, and no significant retinal abnormalities were seen on post mortem fundoscopy and histology.

Results

Metals found by laser ablation-inductively coupled plasma-mass spectrometry in the retinal pigment epithelium and choriocapillaris were lead (n = 7), nickel (n = 7), iron (n = 7), cadmium (n = 6), mercury (n = 6), bismuth (n = 5), aluminium (n = 3), and silver (n = 1). In the neural retina, mercury was present in six samples, and iron in one. Metals detected in the optic nerve head were iron (N = 7), mercury (N = 7), nickel (N = 4), and aluminium (N = 1). No gold or chromium was seen. Autometallography demonstrated probable inorganic mercury in the retinal pigment epithelium of one donor.

Conclusion

Several toxic metals are taken up by the human retina and optic nerve head. Injury to the retinal pigment epithelium from toxic metals could damage the neuroprotective functions of the retinal pigment epithelium and allow toxic metals to enter the outer neural retina. These findings support the hypothesis that accumulations of toxic metals in the retina could contribute to the pathogenesis of age-related macular degeneration.

The Association Between Mercury Exposure and Atopic Dermatitis in Early Childhood: A Mothers and Children's Environmental Health Study

BACKGROUND

Atopic dermatitis is a chronic and relapsing inflammatory skin disease. Although mercury has been suggested as a risk factor, the underlying mechanism and the relationship between mercury and atopic dermatitis remains unclear. The objective of the present study was to investigate the relationship between mercury exposure and the presence of atopic dermatitis in early childhood.

METHODS

This study is part of the prospective Mothers and Children's Environmental Health cohort study. A total of 1,751 pregnant women were enrolled in Mothers and Children's Environmental Health. After delivery, children were followed up. Blood samples were collected and mothers were asked about the presence of atopic dermatitis in their children via a questionnaire at 6, 12, 24, 36, and 60 months of age.

RESULTS

After excluding participants who did not meet the inclusion criteria, a total of 1,061 mother-children pairs were included in the analysis. The geometric mean of mercury concentrations in cord blood was 5.1 µg/L. In adjusted models, cord blood mercury exposure (odds ratio [OR] = 1.1; 95% confidence interval [CI] = 1.0, 1.2 at 12-24 months) and postnatal mercury exposure (OR = 1.2; 95% CI = 1.0, 1.5 at 24-36 months, OR = 1.4; 95% CI = 1.1, 1.8 at 48-60 months) were associated with the presence of atopic dermatitis in children.

CONCLUSIONS

Postnatal mercury exposure at 24 months of age increases the risk of atopic dermatitis in children.

Toxicity of mercury: Molecular evidence

Minamata disease in Japan and the large-scale poisoning by methylmercury (MeHg) in Iraq caused wide public concerns about the risk emanating from mercury for human health. Nowadays, it is widely known that all forms of mercury induce toxic effects in mammals, and increasing evidence supports the concern that environmentally relevant levels of MeHg could impact normal biological functions in wildlife. The information of mechanism involved in mercurial toxicity is growing but knowledge gaps still exist between the adverse effects and mechanisms of action, especially at the molecular level. A body of data obtained from experimental studies on mechanisms of mercurial toxicity in vivo and in vitro points to that disruption of the antioxidant system may play an important role in the mercurial toxic effects. Moreover, the accumulating evidence indicates that signaling transduction, protein or/and enzyme activity, and gene regulation are involving in mediating toxic and adaptive response to mercury exposure. We conducted here a comprehensive review of mercurial toxic effects on wildlife and human, in particular synthesized key findings of molecular pathways involved in mercurial toxicity from the cells to human. We discuss the molecular evidence related mercurial toxicity to the adverse effects, with particular emphasis on the gene regulation. The further studies relying on Omic analysis connected to adverse effects and modes of action of mercury will aid in the evaluation and validation of causative relationship between health outcomes and gene expression.

Mercury-induced autoimmunity: Report of two adolescent siblings with Morvan syndrome "plus" and review of the literature

Heavy metal toxicity is a global health concern. Mercury intoxication has been implicated in the etiology and pathogenesis of autoimmune disease, including Morvan syndrome. We describe two siblings with overlapping features of distinct autoimmune syndromes following accidental exposure to elemental mercury. Morvan syndrome was the predominant clinical phenotype. In addition to the characteristic anti-leucine-rich glioma-inactivated protein 1 (LGI1) and anti-contactin-associated protein-like 2 (Caspr2) autoantibodies, glutamic acid decarboxylase 65-kilodalton isoform (GAD65), and N-type and P/Q-type voltage-gated calcium channel (VGCC) antibodies were detected. Treatment with chelation therapy, glucocorticoids, and intravenous immunoglobulin was unsuccessful, but complete resolution of symptoms was achieved following treatment with rituximab. Herein, we perform an extensive review of the literature with a focus on the emerging concepts of mercury-induced autoimmunity and the role of mercury in the etiopathogenesis of autoimmune diseases of the nervous system.

Mercury in the retina and optic nerve following prenatal exposure to mercury vapor

Damage to the retina and optic nerve is found in some neurodegenerative disorders, but it is unclear whether the optic pathway and central nervous system (CNS) are affected by the same injurious agent, or whether optic pathway damage is due to retrograde degeneration following the CNS damage. Finding an environmental agent that could be responsible for the optic pathway damage would support the hypothesis that this environmental toxicant also triggers the CNS lesions. Toxic metals have been implicated in neurodegenerative disorders, and mercury has been found in the retina and optic nerve of experimentally-exposed animals. Therefore, to see if mercury exposure in the prenatal period could be one link between optic pathway damage and human CNS disorders of later life, we examined the retina and optic nerve of neonatal mice that had been exposed prenatally to mercury vapor, using a technique, autometallography, that detects the presence of mercury within cells. Pregnant mice were exposed to a non-toxic dose of mercury vapor for four hours a day for five days in late gestation, when the mouse placenta most closely resembles the human placenta. The neonatal offspring were sacrificed one day after birth and gapless serial sections of formalin-fixed paraffin-embedded blocks containing the eyes were stained with silver nitrate autometallography to detect inorganic mercury. Mercury was seen in the nuclear membranes of retinal ganglion cells and endothelial cells. A smaller amount of mercury was present in the retinal inner plexiform and inner nuclear layers. Mercury was conspicuous in the peripapillary retinal pigment epithelium. In the optic nerve, mercury was seen in the nuclear membranes and processes of glia and in endothelial cells. Optic pathway and CNS endothelial cells contained mercury. In conclusion, mercury is taken up preferentially by fetal retinal ganglion cells, optic nerve glial cells, the retinal pigment epithelium, and endothelial cells. Mercury induces free radical formation, autoimmunity, and genetic and epigenetic changes, so these findings raise the possibility that mercury plays a part in the pathogenesis of degenerative CNS disorders that also affect the retina and optic nerve.

Mercury Is Taken Up Selectively by Cells Involved in Joint, Bone, and Connective Tissue Disorders

Background: The causes of most arthropathies, osteoarthritis, and connective tissue disorders remain unknown, but exposure to toxic metals could play a part in their pathogenesis. Human exposure to mercury is common, so to determine whether mercury could be affecting joints, bones, and connective tissues we used a histochemical method to determine the cellular uptake of mercury in mice. Whole neonatal mice were examined since this allowed histological assessment of mercury in joint, bone, and connective tissue cells. Materials and Methods: Pregnant mice were exposed to a non-toxic dose of 0.5 mg/m3 of mercury vapor for 4 h a day on gestational days 14-18. Neonates were sacrificed at postnatal day 1, fixed in formalin, and transverse blocks of the body were processed for paraffin embedding. Seven micrometer sections were stained for inorganic mercury using silver nitrate autometallography, either alone or combined with CD44 immunostaining to detect progenitor cells. Control neonates were not exposed to mercury during gestation. Results: Uptake of mercury was marked in synovial cells, articular chondrocytes, and periosteal and tracheal cartilage cells. Mercury was seen in fibroblasts in the dermis, aorta, esophagus and striated muscle, some of which were CD44-positive progenitor cells, and in the endothelial cells of small blood vessels. Mercury was also present in renal tubules and liver periportal cells. Conclusions: Mercury is taken up selectively by cells that are predominantly affected in rheumatoid arthritis and osteoarthritis. In addition, fibroblasts in several organs often involved in multisystem connective tissue disorders take up mercury. Mercury provokes the autoimmune, inflammatory, genetic, and epigenetic changes that have been described in a range of arthropathies and bone and connective tissue disorders. These findings support the hypothesis that mercury exposure could trigger some of these disorders, particularly in people with a genetic susceptibility to autoimmunity.

Mercury-associated glomerulonephritis: a retrospective study of 35 cases in a single Chinese center

Background

Long-term exposure of mercury may induce glomerulonephritis. Clinical and pathological features of mercury-associated glomerulonephritis are not fully clear. This study retrospectively analyzed 35 cases of mercury-associated glomerulonephritis in a single Chinese center.

Methods

Thirty-five patients of mercury-associated glomerulonephritis were enrolled. Clinical data on diagnosis and during follow-up were collected. Plasma anti-phospholipase A2 receptor (PLA2R) antibody, glomerular PLA2R and glomerular IgG subclasses deposition were detected in the cases with membranous nephropathy (MN).

Results

Mercury exposure was caused by skin lighting cream (20 patients), mercury-containing pills (9 patients), hair-dyeing agents (4 patients), and unidentified reasons (2 patients). All patients presented with proteinuria and normal renal function. The median of urinary protein was 4.6 (range 1.6~19.7) g/24 h. Twenty-two patients (62.9%) had nephrotic syndrome. Renal histopathology showed minimal change disease (MCD) in 21 patients (60.0%), MN in 13 (37.1%) and focal segmental glomerular sclerosis (FSGS) in 1 patient (2.9%). The proportion of MCD increased along with urinary mercury concentration (P = 0.024). In 13 cases of MN, all patients were negative for plasma anti-PLA2R antibody and glomerular PLA2R antigen. IgG1 (61.5%) and IgG4 (46.2%) deposits were noted along the glomerular capillary loops. Among the 16 patients received mercury detoxification monotherapy, 14 patients received 4.5 ± 2.8 (range 1~12) rounds of regimen and achieved complete remission in 4.5 (range 0.3~23.0) months, 2 patients stayed no remission.

Conclusions

MCD was the most common pathological type of mercury-associated glomerulonephritis, followed by MN. The proportion of MCD increased along with the increase of urinary mercury concentration. Most patients could achieve complete remission after mercury detoxification.

Developmental exposure to mercury chloride impairs social behavior in male offspring dependent on genetic background and maternal autoimmune environment

To date, the connection between inorganic mercury (Hg) and social behavior remains incompletely understood. The aim of this study was to investigate the influence of maternal autoimmunity by inorganic Hg (Hg²⁺) exposure on social behavior of offspring. Wild-type (WT) and immunoglobulin deficient (Ig^-/-) B10.S dams fertilized by male WT B10.S or SJL mice were treated with 50 μM Hg chloride (HgCl₂). Non-pregnant female WT B10.S mice were used to investigate factors regulating HgCl₂-induced autoimmunity to brain. HgCl₂ selectively impaired social behavior in male offspring, but not female offspring from WT B10.S dams × male SJL, in that only male offspring displayed reduced time distribution with the stranger mouse, decreased sniffing to the stranger mouse and increased self-grooming. HgCl₂ did not disrupt social behavior of male or female offspring from WT B10.S dams × male WT B10.S or Ig^-/- B10.S dams × male SJL. The offspring from WT and Ig^-/- B10.S dams × male SJL had equivalent autoimmunity to brain antigens during HgCl₂ exposure, indicating that maternal, but not offspring-derived anti-brain antibodies (Ab) impaired social behavior of the offspring. Non-pregnant WT B10.S mice treated with HgCl₂ had increased anti-brain Ab dependent on increase in CD4 T cell activation and IFNγ signaling to macrophages. IFNγ interaction with macrophages drove B cells and plasma cells to produce IgG. Therefore, HgCl₂ selectively impaired social behavior in males with certain genetic background via maternally derived anti-brain Ab production, thus providing a novel insight into our current understanding of Hg toxicity.

Inorganic mercury in human astrocytes, oligodendrocytes, corticomotoneurons and the locus ceruleus: implications for multiple sclerosis, neurodegenerative disorders and gliomas

Neurotoxic metals have been implicated in the pathogenesis of multiple sclerosis, neurodegenerative disorders and brain tumours but studies of the location of heavy metals in human brains are rare. In a man who injected himself with metallic mercury the cellular location of mercury in his brain was studied after 5 months of continuous exposure to inorganic mercury arising from metallic mercury deposits in his organs. Paraffin sections from the primary motor and sensory cortices and the locus ceruleus in the pons were stained with autometallography to detect inorganic mercury and combined with glial fibrillary acidic protein immunohistochemistry to identify astrocytes. Inorganic mercury was found in grey matter subpial, interlaminar, protoplasmic and varicose astrocytes, white matter fibrous astrocytes, grey but not white matter oligodendrocytes, corticomotoneurons and some locus ceruleus neurons. In summary, inorganic mercury is taken up by five types of human brain astrocytes, as well as by cortical oligodendrocytes, corticomotoneurons and locus ceruleus neurons. Mercury can induce oxidative stress, stimulate autoimmunity and damage DNA, mitochondria and lipid membranes, so its location in these CNS cells suggests it could play a role in the pathogenesis of multiple sclerosis, neurodegenerative conditions such as Alzheimer's disease and amyotrophic lateral sclerosis, and glial tumours.

Mercury impact on hematopoietic stem cells is regulated by IFNγ-dependent bone marrow-resident macrophages in mice

, but not MeHg, affects HSC through regulating IFNγ-dependent BM-resident macrophages in mice. These findings reveal a previously unknown toxicity of Hg.

Arsenic, Cadmium and Lead Exposure and Immunologic Function in Workers in Taiwan

There has been growing concern over the impact of environmental exposure to heavy metals and other trace elements on immunologic functions. This study investigated men’s arsenic (As), cadmium (Cd) and lead (Pb) contents in hair samples and their associations with immunological indicators, including white blood cell (WBC), lymphocyte and monocyte counts, and the immunoglobulin (Ig) levels including IgA, IgG and IgE. We recruited 133 men from one antimony trioxide manufacturing plant, two glass manufacturing plants and two plastics manufacturing plants. The mean concentration of Cd [0.16 (SD = 0.03) ug/g] was lower than means of As [0.86 (SD = 0.16) ug/g] and Pb [0.91 (SD = 0.22) ug/g] in hair samples, exerting no relationship with immunologic functions for Cd. The Spearman’s correlation analysis showed a positive relationship between monocyte counts and hair Pb levels, but negative relations between As and IgG and between As and IgE. In conclusion, findings from these industry workers suggest that As levels in hair may have a stronger relation with immunologic function than Cd and PB have. Further research is needed to confirm the negative relationship.

Increased memory T cell populations in Pb-exposed children from an e-waste-recycling area

Chronic exposure to heavy metals could affect cell-mediated immunity. The aim of this study was to explore the status of memory T cell development in preschool children from an e-waste recycling area. Blood lead (Pb) levels, peripheral T cell subpopulations, and serum levels of cytokines (IL-2/IL-7/IL-15), relevant to generation and homeostasis of memory T cells were evaluated in preschool children from Guiyu (e-waste-exposed group) and Haojiang (reference group). The correlations between blood Pb levels and percentages of memory T cell subpopulations were also evaluated. Guiyu children had higher blood Pb levels and increased percentages of CD4⁺ central memory T cells and CD8⁺ central memory T cells than in the Haojiang group. Moreover, blood Pb levels were positively associated with the percentages of CD4⁺ central memory T cells. In contrast, Pb exposure contributed marginally in the change of percentages of CD8⁺ central memory T cells in children. There was no significant difference in the serum cytokine levels between the e-waste-exposed and reference children. Taken together, preschool children from an e-waste recycling area suffer from relatively higher levels of Pb exposure, which might facilitate the development of CD4⁺ central memory T cells in these children.

The toxicology of mercury: Current research and emerging trends

Mercury (Hg) is a persistent bio-accumulative toxic metal with unique physicochemical properties of public health concern since their natural and anthropogenic diffusions still induce high risk to human and environmental health. The goal of this review was to analyze scientific literature evaluating the role of global concerns over Hg exposure due to human exposure to ingestion of contaminated seafood (methyl-Hg) as well as elemental Hg levels of dental amalgam fillings (metallic Hg), vaccines (ethyl-Hg) and contaminated water and air (Hg chloride). Mercury has been recognized as a neurotoxicant as well as immunotoxic and designated by the World Health Organization as one of the ten most dangerous chemicals to public health. It has been shown that the half-life of inorganic Hg in human brains is several years to several decades. Mercury occurs in the environment under different chemical forms as elemental Hg (metallic), inorganic and organic Hg. Despite the raising understanding of the Hg toxicokinetics, there is still fully justified to further explore the emerging theories about its bioavailability and adverse effects in humans. In this review, we describe current research and emerging trends in Hg toxicity with the purpose of providing up-to-date information for a better understanding of the kinetics of this metal, presenting comprehensive knowledge on published data analyzing its metabolism, interaction with other metals, distribution, internal doses and targets, and reservoir organs.

Pre-acclimation to low copper mitigated immunotoxic effects in spleen and head-kidney of large yellow croaker (Pseudosciaena crocea) when exposed subsequently to high copper

The hypothesis tested in this study was that Cu pre-acclimation would mitigate high Cu induced immunotoxic effects in large yellow croaker Pseudosciaena crocea. To the end, fish were pre-acclimation to 0 and 84μg CuL^-1 for 48h and then exposed to 0 and 420μg CuL^-1 for another 48h. Survival rate, Cu content, ROS, NO, activities and mRNA levels of inflammatory genes (iNOS and COX-2), and gene expressions of transcription factor NF-κB and its inhibitor IκBα were determined in spleen and head-kidney of large yellow croaker. Cu pre-acclimation significantly reduced mortality of fish exposed to 420μg CuL^-1. Cu pre-acclimation triggered the up-regulation of both enzyme activities and express levels of iNOS and COX-2 in spleen under 420μg CuL^-1 exposure, resulting in remarkable reduction of Cu content and ROS in this tissue. Contrast to spleen, iNOS activity remained unchanged but the mRNA level of iNOS increased, and the mRNA level of COX-2 remained constant though COX-2 activity enhanced in head-kidney, suggesting iNOS and COX-2 may be modulated by Cu at a post-transcriptional level. In this process, NF-κB/IκBα signaling molecules may play a vital role in the transcriptional activation of inflammatory genes in both spleen and head-kidney. In conclusion, low Cu pre-acclimation alleviated high Cu induced immunotoxicity in spleen and head-kidney of large yellow croaker by enhancing the activities and mRNA levels of inflammatory genes.

Biomarkers of mercury toxicity: Past, present, and future trends

Mercury (Hg) toxicity continues to represent a global health concern. Given that human populations are mostly exposed to low chronic levels of mercurial compounds (methylmercury through fish, mercury vapor from dental amalgams, and ethylmercury from vaccines), the need for more sensitive and refined tools to assess the effects and/or susceptibility to adverse metal-mediated health risks remains. Traditional biomarkers, such as hair or blood Hg levels, are practical and provide a reliable measure of exposure, but given intra-population variability, it is difficult to establish accurate cause-effect relationships. It is therefore important to identify and validate biomarkers that are predictive of early adverse effects prior to adverse health outcomes becoming irreversible. This review describes the predominant biomarkers used by toxicologists and epidemiologists to evaluate exposure, effect and susceptibility to Hg compounds, weighing on their advantages and disadvantages. Most importantly, and in light of recent findings on the molecular mechanisms underlying Hg-mediated toxicity, potential novel biomarkers that might be predictive of toxic effect are presented, and the applicability of these parameters in risk assessment is examined.

Predictors and immunological correlates of sublethal mercury exposure in vampire bats

Mercury (Hg) is a pervasive heavy metal that often enters the environment from anthropogenic sources such as gold mining and agriculture. Chronic exposure to Hg can impair immune function, reducing the ability of animals to resist or recover from infections. How Hg influences immunity and susceptibility remains unknown for bats, which appear immunologically distinct from other mammals and are reservoir hosts of many pathogens of importance to human and animal health. We here quantify total Hg (THg) in hair collected from common vampire bats (Desmodus rotundus), which feed on blood and are the main reservoir hosts of rabies virus in Latin America. We examine how diet, sampling site and year, and bat demography influence THg and test the consequences of this variation for eight immune measures. In two populations from Belize, THg concentrations in bats were best explained by an interaction between long-term diet inferred from stable isotopes and year. Bats that foraged more consistently on domestic animals exhibited higher THg. However, relationships between diet and THg were evident only in 2015 but not in 2014, which could reflect recent environmental perturbations associated with agriculture. THg concentrations were low relative to values previously observed in other bat species but still correlated with bat immunity. Bats with higher THg had more neutrophils, weaker bacterial killing ability and impaired innate immunity. These patterns suggest that temporal variation in Hg exposure may impair bat innate immunity and increase susceptibility to pathogens such as bacteria. Unexpected associations between low-level Hg exposure and immune function underscore the need to better understand the environmental sources of Hg exposure in bats and the consequences for bat immunity and susceptibility.

Arginine decarboxylase: A novel biological target of mercury compounds identified in PC12 cells

Mercury compounds are well-known toxic environmental pollutants and potently induce severe neurotoxicological effects in human and experimental animals. Previous studies showed that one of the mechanisms of mercury compounds neurotoxicity arose from the over-activation of the N-methyl d-aspartate (NMDA)-type glutamate receptor induced by increased glutamate release. In this work, we aimed to investigate the molecular mechanisms of Hg compounds neurotoxicities by identifying their biological targets in cells. Firstly, the inhibitory effects of four Hg compounds, including three organic (methyl-, ethyl- and phenyl-mercury) and one inorganic (Hg²⁺) Hg compounds, on the activity of arginine decarboxylase (ADC), a key enzyme in the central agmatinergic system, were evaluated. They were found to inhibit the ADC activity significantly with methylmercury (MeHg) being the strongest (IC₅₀=7.96nM). Furthermore, they showed remarkable inhibitory effects on ADC activity in PC12 cells (MeHg>EtHg>PhHg>HgCl₂), and led to a marked loss in the level of agmatine, an endogenous neuromodulatory and neuroprotective agent that selectively blocks the activation of NMDA receptors. MeHg was detected in the immunoprecipitated ADC from the cells, providing unequivocal evidence for the direct binding of MeHg with ADC in the cell. Molecular dynamics simulation revealed that Hg compounds could form the coordination bond not only with cofactor PLP of ADC, but also with substrate arginine. Our finding indicated that MeHg could attenuate the neuroprotective effects of agmatine by the inhibition of ADC, a new cellular target of MeHg, which might be implicated in molecular mechanism of MeHg neurotoxicity.

Children's white blood cell counts in relation to developmental exposures to methylmercury and persistent organic pollutants

BACKGROUND

To explore possible markers of developmental immunotoxicity, we prospectively examined 56 children to determine associations between exposures to methylmercury and persistent organic pollutants since birth and the comprehensive differential counts of white blood cells (WBC) at age 5 years.

MATERIALS AND METHODS

Extended differential count included: neutrophils, eosinophils, basophils, lymphocytes (includingT cells, NK cells, and B cells), and monocytes. Organochlorine compounds (OCs) including polychlorinated biphenyls (PCBs) and pesticides, five perfluoroalkyl substances (PFASs), and total mercury (Hg) were measured in maternal (n=56) and children's blood at 18 months (n=42) and 5 years (n=54). We constructed latent functions for exposures at three different ages using factor analyses and applied structural equation models adjusted for covariates.

RESULTS

Prenatal mercury exposure was associated with depleted total WBC, especially for lymphocytes, where a one standard deviation (SD) increase in the exposure was associated with a decrease by 23% SD (95% CI: -43, -4) in the cell count. Prenatal exposure to OCs was marginally associated with decreases in neutrophil counts. In contrast, the 5-year PFASs concentrations were associated with higher basophil counts (B=46% SD, 95% CI: 13, 79). Significantly reduced subpopulations of lymphocytes such as B cells, CD4-positive T helper cells and CD4 positive recent thymic emigrants may suggest cellular immunity effects and dysregulation of T-cell mediated immunity.

CONCLUSION

Developmental exposure to environmental immunotoxicants appears to have different impacts on WBC counts in childhood.

Low-level Mercury Exposure and Risk of Asthma in School-age Children

BACKGROUND

Mercury (Hg) has been reported to have adverse effects on the immune system. However, the association between Hg exposure and asthma remains unclear. We hypothesized that blood Hg concentrations are associated with asthma and immune system blood profile changes in school-age children.

METHODS

Between 2005 and 2010, we evaluated 4,350 Korean children at 7-8 years of age with no previous asthma diagnosis. Follow-up surveys were conducted twice, each 2 years apart, until 11-12 years of age. For every survey, we evaluated asthma through a questionnaire and blood profile. We analyzed the association of Hg concentration with asthma by logistic and Cox regression models and the association with blood profile by generalized additive and linear mixed models.

RESULTS

Blood Hg concentrations at 7-8 years of age were associated with an increased risk of asthma (odds ratio [OR] = 1.3; 95% confidence interval [CI] = 1.0, 1.6) at ages up to 11-12 years (n = 191). Hg concentration was also associated with wheezing (OR = 1.2; 95% CI = 1.0, 1.3), asthma medication use (OR = 1.4; 95% CI = 0.97, 2.0), and airway hyperresponsiveness (OR = 1.2; 95% CI = 1.0, 1.3). Further adjustment for fish consumption did not change the results appreciably.

CONCLUSIONS

Low-level Hg exposure was associated with asthma and blood profile changes in school-age children.

Mercury Exposure and Antinuclear Antibodies among Females of Reproductive Age in the United States: NHANES

BACKGROUND

Immune dysregulation associated with mercury has been suggested, although data in the general population are lacking. Chronic exposure to low levels of methylmercury (organic) and inorganic mercury is common, such as through fish consumption and dental amalgams.

OBJECTIVE

We examined associations between mercury biomarkers and antinuclear antibody (ANA) positivity and titer strength.

METHODS

Among females 16-49 years of age (n = 1,352) from the National Health and Nutrition Examination Survey (NHANES) 1999-2004, we examined cross-sectional associations between mercury and ANAs (indirect immunofluorescence; cutoff ≥ 1:80). Three biomarkers of mercury exposure were used: hair (available 1999-2000) and total blood (1999-2004) predominantly represented methylmercury, and urine (1999-2002) represented inorganic mercury. Survey statistics were used. Multivariable modeling adjusted for several covariates, including age and omega-3 fatty acids.

RESULTS

Sixteen percent of females were ANA positive; 96% of ANA positives had a nuclear speckled staining pattern. Geometric mean (geometric SD) mercury concentrations were 0.22 (0.03) ppm in hair, 0.92 (0.05) μg/L blood, and 0.62 (0.04) μg/L urine. Hair and blood, but not urinary, mercury were associated with ANA positivity (sample sizes 452, 1,352, and 804, respectively), after adjusting for confounders: for hair, odds ratio (OR) = 4.10 (95% CI: 1.66, 10.13); for blood, OR = 2.32 (95% CI: 1.07, 5.03) comparing highest versus lowest quantiles. Magnitudes of association were strongest for high-titer (≥ 1:1,280) ANA: hair, OR = 11.41 (95% CI: 1.60, 81.23); blood, OR = 5.93 (95% CI: 1.57, 22.47).

CONCLUSIONS

Methylmercury, at low levels generally considered safe, was associated with subclinical autoimmunity among reproductive-age females. Autoantibodies may predate clinical disease by years; thus, methylmercury exposure may be relevant to future autoimmune disease risk.

Association between serum mercury concentration and leukocyte differential count in children

There have been a number of animal studies on the immunological effects of mercury. However, there is a lack of studies investigating the effects of mercury in children. We investigated the association between serum mercury and leukocyte differential count in Korean children. The relationship between mercury and leukocyte differential count (segment, lymphocyte, monocyte, basophil, and eosinophil counts) was analyzed by multivariate linear analysis adjusted for sex, BMI, parental smoking, lead, cadmium, and allergic sensitization in 311 children. Mercury showed a positive correlation with lymphocyte count (coefficient 113.8, 95% confidence interval 26.7-200.9). However, mercury was not associated with total leukocyte, segment, monocyte, basophil, or eosinophil count. Mercury was associated with the increased of lymphocyte count in Korean children. Further studies will be required to ascertain the clinical significance of this association.

Ethylmercury and Hg2+ induce the formation of neutrophil extracellular traps (NETs) by human neutrophil granulocytes

Humans are exposed to different mercurial compounds from various sources, most frequently from dental fillings, preservatives in vaccines, or consumption of fish. Among other toxic effects, these substances interact with the immune system. In high doses, mercurials are immunosuppressive. However, lower doses of some mercurials stimulate the immune system, inducing different forms of autoimmunity, autoantibodies, and glomerulonephritis in rodents. Furthermore, some studies suggest a connection between mercury exposure and the occurrence of autoantibodies against nuclear components and granulocyte cytoplasmic proteins in humans. Still, the underlying mechanisms need to be clarified. The present study investigates the formation of neutrophil extracellular traps (NETs) in response to thimerosal and its metabolites ethyl mercury (EtHg), thiosalicylic acid, and mercuric ions (Hg(2+)). Only EtHg and Hg(2+) triggered NETosis. It was independent of PKC, ERK1/2, p38, and zinc signals and not affected by the NADPH oxidase inhibitor DPI. Instead, EtHg and Hg(2+) triggered NADPH oxidase-independent production of ROS, which are likely to be involved in mercurial-induced NET formation. This finding might help understanding the autoimmune potential of mercurial compounds. Some diseases, to which a connection with mercurials has been shown, such as Wegener's granulomatosis and systemic lupus erythematosus, are characterized by high prevalence of autoantibodies against neutrophil-specific auto-antigens. Externalization in the form of NETs may be a source for exposure to these self-antigens. In genetically susceptible individuals, this could be one step in the series of events leading to autoimmunity.

Environmental exposures, epigenetic changes and the risk of lupus

A dose-dependent combination of environmental exposures, estrogenic hormones and genetic predisposition is thought to be required for lupus to develop and flare, but how the environment modifies the immune system in genetically predisposed people is unclear. Current evidence indicates that environmental agents that inhibit DNA methylation can convert normal antigen-specific CD4+ T lymphocytes into autoreactive, cytotoxic, pro-inflammatory cells that are sufficient to cause lupus-like autoimmunity in animal models, and that the same changes in DNA methylation characterize CD4+ T cells from patients with active lupus. Environmental agents implicated in inhibiting T-cell DNA methylation include the lupus-inducing drugs procainamide and hydralazine, as well as diet, and agents causing oxidative stress, such as smoking, UV light exposure, and infections, which have been associated with lupus onset or disease activity. Other studies demonstrate that demethylated T cells cause only anti-DNA antibodies in mice lacking a genetic predisposition to lupus, but are sufficient to cause lupus-like autoimmunity in genetically predisposed mice and likely people, and that estrogens augment the disease. Collectively, these studies suggest that environmental agents that inhibit DNA methylation, together with lupus genes and estrogens or endocrine disruptors, combine in a dose-dependent fashion to cause lupus flares.

The biochemical effects of extracellular Zn(2+) and other metal ions are severely affected by their speciation in cell culture media

Investigations of physiological and toxicological effects of metal ions are frequently based on in vitro cell culture systems, in which cells are incubated with these ions in specialized culture media, instead of their physiological environment. This allows for targeted examination on the cellular or even molecular level. However, it disregards one important aspect, the different metal ion speciation under these conditions. This study explores the role of culture conditions in investigations with zinc ions (Zn(2+)). Their concentration is buffered by several orders of magnitude by fetal calf serum. Due to the complexity of serum and its many zinc-binding components, zinc speciation in culture media cannot be completely predicted. Still, the primary effect is due to the main Zn(2+)-binding protein albumin. Buffering reduces the free Zn(2+) concentration, thereby diminishing its biological effects, such as cytotoxicity and the impact on protein phosphorylation. This is not limited to Zn(2+), but is also observed with Ag(+), Cu(2+), Pb(2+), Cd(2+), Hg(2+), and Ni(2+). Usually, the serum content of culture media, and thereby their metal buffering capacity, is only a fraction of that in the physiological cellular environment. This leads to systematic over-estimation of the effects of extracellular metal ions when standard cell culture conditions are used as model systems for assessing potential in vivo effects.

Bisphenol A exposure and asthma development in school-age children: a longitudinal study

BACKGROUND

Although the effect of bisphenol A on various health outcomes has been extensively examined, few studies have investigated its effect on asthma.

OBJECTIVE

We hypothesized that exposure to bisphenol A in school-age children was associated with wheezing and asthma.

METHODS

Participants included 127 children aged 7-8 years without a previous asthma diagnosis in an elementary school in Seoul, Korea. Three surveys were conducted, each 2 years apart. Bisphenol A concentration was measured at the baseline survey, and PC20, which is defined as the methacholine concentration that induces a decrease in FEV1 of 20% from baseline, was measured at every survey. Associations between bisphenol A concentration at 7-8 years of age and wheezing, asthma, and PC20 at ages up to 11-12 years were examined using generalized estimating equations, a marginal Cox regression model, and a linear mixed model.

RESULTS

The log-transformed creatinine-adjusted urinary bisphenol A concentration at 7-8 years was positively associated with wheezing (odds ratio, 2.48; 95% confidence interval, 1.15-5.31; P = .02) and asthma (hazard ratio, 2.13; 95% confidence interval, 1.51-3.00; P<.001) at ages up to 11-12 years. Bisphenol A was also negatively associated with PC20 (ß = -2.33; P = .02). When stratified by sex, the association between bisphenol A and asthma remained significant only in girls (hazard ratio, 2.45; 95% confidence interval, 2.18-2.76; P<.001).

CONCLUSION

Increased urinary bisphenol A concentrations at 7-8 years old were positively associated with wheezing and asthma and negatively associated with PC20 at ages up to 11-12 years.

Lymphocyte Activation Gene-3 (LAG-3) negatively regulates environmentally-induced autoimmunity

Environmental factors including drugs, mineral oils and heavy metals such as lead, gold and mercury are triggers of autoimmune diseases in animal models or even in occupationally exposed humans. After exposure to subtoxic levels of mercury (Hg), genetically susceptible strains of mice develop an autoimmune disease characterized by the production of highly specific anti-nucleolar autoantibodies, hyperglobulinemia and nephritis. However, mice can be tolerized to the disease by a single low dose administration of Hg. Lymphocyte Activation Gene-3 (LAG-3) is a CD4-related, MHC-class II binding molecule expressed on activated T cells and NK cells which maintains lymphocyte homeostatic balance via various inhibitory mechanisms. In our model, administration of anti-LAG-3 monoclonal antibody broke tolerance to Hg resulting in autoantibody production and an increase in serum IgE level. In addition, LAG-3-deficient B6.SJL mice not only had increased susceptibility to Hg-induced autoimmunity but were also unresponsive to tolerance induction. Conversely, adoptive transfer of wild-type CD4⁺ T cells was able to partially rescue LAG-3-deficient mice from the autoimmune disease. Further, in LAG-3-deficient mice, mercury elicited higher amounts of IL-6, IL-4 and IFN-γ, cytokines known to play a critical role in mercury-induced autoimmunity. Therefore, we conclude that LAG-3 exerts an important regulatory effect on autoimmunity elicited by a common environmental pollutant.