Mercuric chloride enhances immunoglobulin E-dependent mediator release from human basophils

The Associations between Exposure to Multiple Heavy Metals and Total Immunoglobulin E in U.S. Adults

Immunoglobulin E (IgE) is a type of immunoglobulin, and elevated serum total IgE is often present in allergic diseases. Exposure to environmental heavy metals has been markedly linked to allergic diseases, leading to elevated total IgE levels. However, studies concerning the effects of multiple metal exposures on total IgE levels are limited. Therefore, the current study seeks to explore the correlation between heavy-metal co-exposure and total IgE levels based on the National Health and Nutrition Examination Survey (NHANES, 2005-2006). Participants possessed complete data on total IgE levels, 11 urinary metal concentrations and other covariates. The correlations between 11 metals and total IgE levels were analyzed using multiple linear regression, and total IgE levels were a continuous variable. Total IgE levels exceeding 150 kU/L were considered sensitized. Binary logistic regression analyses were employed to assess the correlation between metal exposure and the occurrence of an allergic state. Then, the association between co-exposure to the 11 metals and total IgE levels or the occurrence of sensitization status was further analyzed by Bayesian kernel machine regression (BKMR), a multi-contaminant model. There were 1429 adults with complete data included. Based on the median concentration, molybdenum (Mo) had the highest concentration (46.60 μg/L), followed by cesium (Cs), barium (Ba), lead (Pb), and mercury (Hg). And the median (interquartile range) for total IgE levels was 43.7 (17.3, 126.0) kU/L. Multiple linear regression results showed that Pb was significantly and positively associated with total IgE levels (β = 0.165; 95% CI: 0.046, 0.284). Binary logistic regression showed a significant positive correlation between urinary Pb (OR: 1.258; 95% CI: 1.052, 1.510) and tungsten (W) (OR: 1.251; 95% CI: 1.082, 1.447). Importantly, the BKMR model found a positive correlation between combined-metal exposure and total IgE levels and the occurrence of sensitization status. The mixed heavy-metal exposure was associated with increased total IgE levels, and this association may be driven primarily by the exposure of Pb and W. This study provides new insights into the relationship between heavy-metal exposure and allergic diseases. More research is needed to confirm these findings.

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.

Heavy metals in contact dermatitis: A review

Contact dermatitis is an inflammatory skin reaction caused by direct contact with chemical substances in the environment and can either be irritant or allergic in nature. The clinical symptoms of contact dermatitis, include local skin rash, itching, redness, swelling, and lesions. Nowadays, 15-20% of people have some degree of contact dermatitis, which can be more or less severe. Immune responses in allergic contact dermatitis (ACD) are due to the effects of cytokines and allergen-specific CD4⁺ and CD8⁺ T cells on the skin. Acids and alkalis such as drain cleaners, plants such as poinsettias, hair colors, and nail polish remover, are all prominent causes of irritant contact dermatitis (ICDs). Heavy metals are metallic elements with a high atomic weight that are hazardous in low quantities and are known to cause dermatitis after systemic or local exposure. Nickel (Ni), chromium (Cr), lead (Pb), and copper (Cu) are among the most common heavy metals used in various industries. Metal allergies may cause ACD and also systemic contact dermatitis (SCD). Contact dermatitis is detected by laboratory tests such as patch testing, lymphocyte stimulation test (LST), and evaluation of cytokine production by primary cultures of peripheral blood mononuclear cells. This article presents an update on the epidemiological and clinical characteristics of ACD and SCD caused by three heavy metals (Cr, Cu, and Pb). Ni is not discussed due to recent coverage. Furthermore, the effects of contact sensitivity to some other heavy metals, such as gold (Au), cobalt (Co), palladium (Pd), and mercury (Hg) are discussed.

Exposure to Heavy Metals and Allergic Outcomes in Children: a Systematic Review and Meta-analysis

It has been reported that heavy metals have adverse effects on the immune system. However, the relationship between heavy metal exposure and allergic outcomes remains unclear. This systematic review was conducted to examine whether heavy metal exposure is associated with allergic outcomes during childhood. We performed a systematic search of all relevant articles in Web of Science, EMBASE, and PubMed, from inception through to November 2020. We used odds ratio (OR) and the standard mean differences (SMDs) with 95% confidence intervals (CIs) to present estimates from individual studies. In addition, random-effects meta-analysis was used to pool the data. We also conducted the meta-regression and subgroup analysis to explore potential sources of heterogeneity. After duplicate removal, we finally included 35 articles in the systematic review and meta-analysis from an initial 11,181 articles. The overall results showed that copper (Cu) was associated with asthma (pooled SMD = 1.50, 95% CI = 0.13-2.86); in the subgroup analysis, the results indicated that lead (Pb) was associated with asthma (pooled OR = 6.27, 95% CI = 2.24-17.56), and Cu and Pb were connected with atopic dermatitis (SMD =  - 1.05, 95% CI =  - 1.45 to - 0.65; SMD = 5.68, 95% CI = 5.05-6.32), respectively. Mercury (Hg) was associated with atopic dermatitis (pooled OR = 1.13, 95% CI = 1.04-1.22) and wheeze (OR = 1.20, 95% CI = 1.05-1.37). The meta-analysis results indicate that Cu might be connected with childhood asthma, but not with other allergic diseases; Hg and Pb may have no association with allergic diseases during childhood. Given some limits observed in the current studies, more prospective cohort studies are still needed to verify our findings. Review registration: PROSPERO CRD42020222167.

Prenatal Exposure to Lead and Chromium is Associated with IL-13 Levels in Umbilical Cord Blood and Severity of Atopic Dermatitis: COCOA Study

There have been few studies investigating the association between atopic dermatitis (AD) and prenatal exposure to heavy metals. We aimed to evaluate whether prenatal exposure to heavy metals is associated with the development or severity of AD in a birth cohort study. A total of 331 subjects were followed from birth for a median duration of 60.0 months. The presence and severity of AD were evaluated at ages 6 and 12 months, and regularly once a year thereafter. The concentrations of lead, mercury, chromium, and cadmium in umbilical cord blood were measured by inductively coupled plasma mass spectrometry. Cord blood mononuclear cells (CBMCs) were isolated and stimulated for analysis of cytokine production using ELISA. Heavy metal levels in cord blood were not associated with the development of AD until 24 months of age. However, a positive correlation was observed between the duration of AD and lead levels in cord blood (p=0.002). AD severity was also positively associated with chromium concentrations in cord blood (p=0.037), while cord blood levels of lead, mercury, and cadmium were not significantly associated with AD severity (p=0.562, p=0.054, and p=0.055, respectively). Interleukin-13 production in CBMCs was positively related with lead and chromium levels in cord blood (p=0.021 and p=0.015, respectively). Prenatal exposure to lead and chromium is associated with the persistence and severity of AD, and the immune reaction toward a Th2 polarization.

The effects of environmental toxins on allergic inflammation

The prevalence of asthma and allergic disease has increased worldwide over the last few decades. Many common environmental factors are associated with this increase. Several theories have been proposed to account for this trend, especially those concerning the impact of environmental toxicants. The development of the immune system, particularly in the prenatal period, has far-reaching consequences for health during early childhood, and throughout adult life. One underlying mechanism for the increased levels of allergic responses, secondary to exposure, appears to be an imbalance in the T-helper function caused by exposure to the toxicants. Exposure to environmental endocrine-disrupting chemicals can result in dramatic changes in cytokine production, the activity of the immune system, the overall Th1 and Th2 balance, and in mediators of type 1 hypersensitivity mediators, such as IgE. Passive exposure to tobacco smoke is a common risk factor for wheezing and asthma in children. People living in urban areas and close to roads with a high volume of traffic, and high levels of diesel exhaust fumes, have the highest exposure to environmental compounds, and these people are strongly linked with type 1 hypersensitivity disorders and enhanced Th2 responses. These data are consistent with epidemiological research that has consistently detected increased incidences of allergies and asthma in people living in these locations. During recent decades more than 100,000 new chemicals have been used in common consumer products and are released into the everyday environment. Therefore, in this review, we discuss the environmental effects on allergies of indoor and outside exposure.

A pilot study for foetal exposure to multiple persistent organic pollutants and the development of infant atopic dermatitis in modern Japanese society

Increasing evidence supports that harmful chemicals accumulating in the human body may pose a significant threat to infant health through foetal exposure. Persistent organic pollutants (POPs) are thought to enhance the risk for later development of allergic disease like atopic dermatitis (AD). However, few studies have evaluated the effect of foetal exposure to various POPs on the development of AD in early infancy. Here, we describe the impact of foetal exposure to a number of POPs on the occurrence of AD in 7-month-old infants. The participants were 81 infants with or without AD who participated in a birth cohort study, where the concentrations of 15 polychlorinated biphenyl (PCBs) congeners, dichlorodiphenyltrichloroethane (p,p'-DDT), dichlorodiphenyldichloroethylene (p,p'-DDE), β-hexachlorocyclohexane (β-HCH), hexachlorobenzene (HCB), cis-nonachlor, trans-nonachlor, mirex, oxychlordane, and 27 polybrominated diphenyl ether (PBDEs) congeners were measured in the umbilical cord tissues collected immediately after birth. At 7 months, 27 of the 81 infants (33.8%) were diagnosed with AD. Of all POPs examined, total concentrations of 27 PBDE congeners were associated with a significantly decreased incidence of AD. Notably, the concentration of 27 PBDEs was significantly lower in AD infants than in non-AD infants (P<0.01), and the risk of AD development decreased with increasing PBDE levels. These results suggest that foetal exposure to PBDEs is a possible contributing factor to reducing AD in early infancy.

Pyrrolidine dithiocarbamate augments Hg(2+)-mediated induction of macrophage cell death via oxidative stress-induced apoptosis and necrosis signaling pathways

Exposure to mercury can lead to several injuries in mammals, including immune system dysfunction, and pyrrolidine dithiocarbamate (PDTC), as a metal chelator and antioxidant, has been indicated to increase the cytotoxic effects of toxic metals. However, the toxicological effects and possible mechanisms of mercury in combination with PDTC are mostly unclear. In this study, we showed that PDTC dramatically increase the cytotoxic effect of HgCl(2) on cultured murine macrophages (RAW 264.7 cells). PDTC augmented HgCl(2)-induced cytotoxic effects by facilitating the entry of mercury into the cells. The Hg(2+)/PDTC complex significantly and rapidly increased the formation of reactive oxygen species (ROS) and decreased intracellular glutathione (GSH) levels in these cells. Flow cytometry analysis showed that the numbers of sub-G1 hypodiploid cells and annexin V-FITC binding cells increased after Hg(2+)/PDTC complex exposure, and several features of mitochondria-dependent apoptosis were also induced, including mitochondrial membrane depolarization, cytosolic cytochrome c release, poly(ADP-ribose) polymerase (PARP) and caspase 3/7 activation, and DNA fragmentation. Moreover, both apoptotic and necrotic cells were detected using acridine orange/ethidium bromide dual staining. Meanwhile, depleted intracellular ATP levels and increased lactate dehydrogenase (LDH) release were observed, suggesting the induction of necrotic cell death processes. These Hg(2+)/PDTC complex-induced cytotoxicity-related signals could be reversed by pretreatment with the antioxidant N-acetylcysteine. In conclusion, these results suggest that Hg(2+)/PDTC complex-induced oxidative stress causes macrophage cell death via both apoptosis and necrosis. These findings imply for the first time that PDTC dramatically increases the uptake and toxicological effects of Hg(2+) instead of detoxification.

Lack of association of mercury with risk of wheeze and eczema in Japanese children: the Osaka Maternal and Child Health Study

Mercury can have profound and complicated effects on the immune system, and epidemiological evidence regarding the relationship between mercury exposure and allergic disorders has been sparse. We investigated the associations between mercury levels in maternal and children's hair and the risk of wheeze and eczema in Japanese children at 29-39 months of age. Study subjects were 582 Japanese mother-child pairs. Presence or absence of wheeze and eczema symptoms was determined based on the criteria of the International Study of Asthma and Allergies in Childhood. Adjustment was made for maternal age; residential municipality at baseline; maternal and paternal education; maternal and paternal history of allergic disorders; maternal energy-adjusted fish intake during pregnancy; maternal smoking during pregnancy; number of child's older siblings; child's sex; household smoking in the same room as the child; breastfeeding duration; and children's fish intake at the fourth survey. The prevalence of wheeze and eczema was 18.6% and 17.2%, respectively. The range of hair mercury levels was 0.26-6.05 μg/g in mothers and 0.13-9.51 μg/g in children. Neither maternal nor children's hair mercury levels were related to the risk of wheeze or eczema. Maternal and children's hair mercury levels in the second quartile were non-significantly inversely related to the risk of wheeze (adjusted odds ratios [95% confidence intervals] were 0.77 [0.41-1.44] and 0.57 [0.29-1.11], respectively) while those in the third quartile were non-significantly inversely associated with the risk of eczema (adjusted odds ratios [95% confidence intervals] were 0.77 [0.40-1.45] and 0.66 [0.33-1.30], respectively). The current study provides no evidence that hair mercury levels in either mothers or children are positively associated with the risk of wheeze or eczema in children aged 29-39 months in Japan, where fish intake is high.

Serum heavy metal and antioxidant element levels of children with recurrent wheezing

STUDY OBJECTIVES

The aim of the study is to investigate the levels of toxic heavy metals related with environmental pollution and trace elements involved in antioxidant system in children suffering from recurrent wheezing.

STUDY DESIGN

One hundred children with recurrent wheezing (at least three recurrences) between the ages from 1 to 6 years took part in the study, and also 116 age- and sex- matched healthy children were involved in the study as a control group. Venous blood samples were collected and serum mercury, lead, aluminium, zinc, selenium, and copper levels were studied using ICP-MS.

RESULTS

Serum lead (0.76±0.15 vs. 0.27±0.01, p:0.001) and mercury levels (1.31±0.15 vs 0.71±0.05, p<0.001) were higher in wheezy group than those acquired from the control group. Serum zinc (69.4±1.65 vs. 78.9±2.78, p:0.005) and selenium (115.6±1.87 vs. 125.4±2.94, p:0.008) levels were lower in wheezy group than those acquired from the control group. Serum zinc levels were found to be correlated with number of ARTIs (r(p):-0.332, p:0.001) and the number of wheezy attacks (r(p):-0.776, p<0.001) during the previous year in the wheezy group.

CONCLUSION

Elevated levels of serum lead and mercury and low levels of zinc and selenium may suggest some disturbances in the antioxidant system in children with recurrent wheezing. This means that children with recurrent wheezing are much more susceptible to environmental pollutants and respiratory tract infections than healthy children and this heavy metal-antioxidant relationship may play a role as a contributing factor in the pathogenesis of recurrent wheezing in children.

Mercury induces inflammatory mediator release from human mast cells

Background

Mercury is known to be neurotoxic, but its effects on the immune system are less well known. Mast cells are involved in allergic reactions, but also in innate and acquired immunity, as well as in inflammation. Many patients with Autism Spectrum Disorders (ASD) have "allergic" symptoms; moreover, the prevalence of ASD in patients with mastocytosis, characterized by numerous hyperactive mast cells in most tissues, is 10-fold higher than the general population suggesting mast cell involvement. We, therefore, investigated the effect of mercuric chloride (HgCl₂) on human mast cell activation.

Methods

Human leukemic cultured LAD2 mast cells and normal human umbilical cord blood-derived cultured mast cells (hCBMCs) were stimulated by HgCl2 (0.1-10 μM) for either 10 min for beta-hexosaminidase release or 24 hr for measuring vascular endothelial growth factor (VEGF) and IL-6 release by ELISA.

Results

HgCl₂ induced a 2-fold increase in β-hexosaminidase release, and also significant VEGF release at 0.1 and 1 μM (311 ± 32 pg/10⁶ cells and 443 ± 143 pg/10⁶ cells, respectively) from LAD2 mast cells compared to control cells (227 ± 17 pg/10⁶ cells, n = 5, p < 0.05). Addition of HgCl₂ (0.1 μM) to the proinflammatory neuropeptide substance P (SP, 0.1 μM) had synergestic action in inducing VEGF from LAD2 mast cells. HgCl₂ also stimulated significant VEGF release (360 ± 100 pg/10⁶ cells at 1 μM, n = 5, p < 0.05) from hCBMCs compared to control cells (182 ± 57 pg/10⁶ cells), and IL-6 release (466 ± 57 pg/10⁶ cells at 0.1 μM) compared to untreated cells (13 ± 25 pg/10⁶ cells, n = 5, p < 0.05). Addition of HgCl₂ (0.1 μM) to SP (5 μM) further increased IL-6 release.

Conclusions

HgCl₂ stimulates VEGF and IL-6 release from human mast cells. This phenomenon could disrupt the blood-brain-barrier and permit brain inflammation. As a result, the findings of the present study provide a biological mechanism for how low levels of mercury may contribute to ASD pathogenesis.

Autism: an emerging 'neuroimmune disorder' in search of therapy

BACKGROUND

Autism spectrum disorders (ASDs) are neurodevelopmental disorders characterized by difficulties in communication and by repetitive and stereotypic behaviors, as well as by social impairment, attention, cognitive, and learning defects. ASDs present in early childhood and their prevalence has increased significantly to 1/150 children. Despite a number of theories, the actual reasons for this increase are still not clear. There is no reliable screening test, and no definite pathogenesis or curative therapy. Consequently, there is a major gap hampering development of effective treatments.

OBJECTIVE

To review recent publications on ASDs pathogenesis and treatment with emphasis on neuroimmune processes and new therapeutic approaches.

METHODS

Mostly original papers (450) on epidemiology, possible pathogenesis or treatment of ASDs in Medline from 1990 to May 2009 were reviewed. All authors contributed to this review.

RESULTS/CONCLUSION

Increased oxidative stress and immune dysregulation are present in ASDs. Mast-cell activation may contribute to gut-blood-brain barrier disruption and brain inflammation. No effective treatments have emerged. Well-designed clinical trials with nonpsychotropic drugs were few and ASD characteristics varied considerably, making conclusions difficult. Psychotropic drugs are often used for stereotypic and aggressive behaviors. Unique combinations with antioxidant and anti-inflammatory flavonoids hold promise. New potential translational research areas and possible treatments are suggested.

Selective effect of mercury on Th2-type cytokine production in humans

Mercury induces autoimmune disease and increases IL-4 production and IgE levels in certain rodent strains. The object of this study was to determine if mercury was capable of inducing Th2 cytokine production in human leucocytes. Human peripheral blood mononuclear cells (PBMC) were incubated with PMA/ionomycin or Con A in the presence or absence of methyl mercury (CH(3)Hg) or mercuric chloride (HgCl(2)). IL-4 and gamma-IFN were measured by ELISA.

RESULTS

IL-4 production significantly increased at low concentrations of CH(3)Hg (0.5 uM, p < 0.01), while gamma-IFN production was suppressed starting at CH(3)Hg 2 uM (p = 0.004). Inorganic mercury (HgCl(2)) increased IL-4 only at concentrations 10-20 times higher than CH(3)Hg. These findings suggest a mechanism by which mercury could trigger or potentiate TH2 cytokine production in humans.

Immunomodulation by mercuric chloride in vitro: application of different cell activation pathways

Evidence is emerging that exposure to mercury (Hg) may elicit many pathological manifestations, including immunomodulation. We tested whether changing cellular activation pathways may affect the immunomodulation by Hg. Human cell cultures were set up where isolated peripheral blood mononuclear cells, activated by monoclonal antibodies (MoAb: anti-CD3/-CD28/-CD40) or heat-killed Salmonella enterica serovar Enteritidis (hk-SE), exposed to mercuric chloride (HgCl2) for 24 h. Cell vitality was assessed by MTT assay, and modulation of cytokine profiles were monitored by enzyme-linked immunosorbent assay (ELISA), intracellular cytokine staining and reverse transcription-polymerase chain reaction (RT-PCR). Results show that Hg doses above 15 ng/ml significantly reduced cell vitality (P < 0.05). Lower doses elicited distinct effects on T helper 1 (Th1) and Th2 cytokine expression depending on cellular activation pathways. In MoAb-stimulated cells, interferon (IFN)-gamma, tumour necrosis factor (TNF)-alpha and interleukin (IL)-6 production was reduced. Doses up to 0.150 and 0.5 microg/ml increased IL-10 and IL-4 production, respectively, resulting in significantly reduced Th1/Th2 ratios. Stimulation by hk-SE, however, elevated Th1/Th2 ratios due to induction of IFN-gamma versus IL-10 production. Taken together, we conclude that low-level exposure to Hg, in the absence of inflammation, polarizes the immune response toward Th2, but not in the case of Th1-polarized responses elicited by Salmonella antigens that can be promoted instead. This demonstrates differential in vitro effects of Hg on the Th1/Th2 balance produced by different stimuli, which may have important experimental and scientific implications.

Low dose mercury toxicity and human health

Post Minamata incident there has been awareness about mercury toxicity even among the general public. Previous researches contributed a vast amount of data regarding acute mercury exposure, but gradually information about the low dose [Ninomiya, T., Ohmori, H., Hashimoto, K., Tsuruta, K., Ekino, S., 1995. Expansion of methylmercury poisoning outside minamata: an epidemiological study on chronic methylmercury poisoninig outside of Minamata. Environ. Res. 70 (1) 47-50; Lebel, J., Mergler, D., Lucotte, M., Amorim, M., Dolbec, J., Miranda, D., Arantes, G., Rheault, I., Pichet, P., 1996. Evidence of early nervous system dysfunction in Amazonian populations exposed to low-levels of methylmercury. Neurotoxicology 17 (1) 157-167] of mercury toxicity has been trickling in. With mercury contaminating rain-, ground- and sea-water no one is safe. Polluted water leads to mercury laced fish, meat and vegetable. In aquatic environments, inorganic mercury is microbiologically transformed into lipophilic organic compound 'methylmercury'. This transformation makes mercury more prone to biomagnification in food chains. Consequently, populations with traditionally high dietary intake of food originating from fresh or marine environment have highest dietary exposure to mercury. Extensive research done on locals across the globe have already established this, persons who routinely consume fish or a particular species of fish are at an increased risk of methylmercury poisoning. The easy access of the toxicant to man through multiple pathways air, water, food, cosmetic products and even vaccines increase the exposure. Foetus and children are more susceptible towards mercury toxicity. Mothers consuming diet containing mercury pass the toxicant to foetus and to infants through breast milk. Decreased performance in areas of motor function and memory has been reported among children exposed to presumably safe mercury levels. Similarly, disruption of attention, fine motor function and verbal memory was also found in adults on exposure to low mercury levels. It is an occupational hazard for dental staff, chloralkali factory workers and goldminers, etc. Mercury has been found to be a causative agent of various sorts of disorders, including neurological, nephrological, immunological, cardiac, motor, reproductive and even genetic. Recently heavy metal mediated toxicity has been linked to diseases like Alzeihemer's, Parkinson's, Autism, Lupus, Amyotrophic lateral sclerosis, etc. Besides this, it poses danger to wildlife. Therefore, it becomes imperative to spread the information regarding the threat of mercury exposure amongst the scientists and masses.