Effects of physiological concentrations of heavy metals both individually and in mixtures on the viability and function of peripheral blood human leukocytes in vitro

Integrative investigation of hematotoxic effects induced by low doses of lead, cadmium, mercury and arsenic mixture: In vivo and in silico approach

The effect of the lead (Pb), cadmium (Cd), mercury (Hg) and arsenic (As) mixture (MIX) on hematotoxicity development was investigated trough combined approach. In vivo subacute study (28 days) was performed on rats (5 per group): a control group and five groups orally exposed to increasing metal(loid) mixture doses, MIX 1- MIX 5 (mg/kg bw./day) (Pb: 0.003, 0.01, 0.1, 0.3, 1; Cd: 0.01, 0.03, 0.3, 0.9, 3; Hg: 0.0002, 0.0006, 0.006, 0.018, 0.06; As: 0.002, 0.006, 0.06, 0.18, 0.6). Blood was taken for analysis of hematological parameters and serum iron (Fe) analysis. MIX treatment increased thrombocyte/platelet count and MCHC and decreased Hb, HCT, MCV and MCH values compared to control, indicating the development of anemia and thrombocytosis. BMDIs with the narrowest width were identified for MCH [pg] (6.030E-03 - 1.287E-01 mg Pb/kg bw./day; 2.010E-02 - 4.290E-01 mg Cd/kg bw./day; 4.020E-04 - 8.580E-03 mg Hg/kg bw./day; 4.020E-03 - 8.580E-02 mg As/kg bw./day). In silico analysis showed target genes connected with MIX and the development of: anemia - ACHE, GSR, PARP1, TNF; thrombocytosis - JAK2, CALR, MPL, THPO; hematological diseases - FAS and ALAD. The main extracted pathways for anemia were related to apoptosis and oxidative stress; for thrombocytosis were signaling pathways of Jak-STAT and TPO. Changes in miRNAs and transcription factors enabled the mode of action (MoA) development based on the obtained results, contributing to mechanistic understanding and hematological risk related to MIX exposure.

Pb and Cd exposure linked with Il-10 and Il-13 gene polymorphisms in asthma risk relevant immunomodulation in children

Genetic variants and environmental factor of heavy metal exposure accelerate the risk of immune-mediated respiratory diseases, including asthma in children. This study aims to investigate the effects and interaction of Pb, Cd exposure from e-waste and interleukin (IL)-10, IL-13 gene polymorphisms on interleukin expressions in children. Pb, Cd levels, Il-10 (rs1800871, rs1800872, rs1800896) and Il-13 (rs20541, rs1800925) polymorphisms were determined in blood or urine of 155 children (75 from e-waste-exposed area, Guiyu and 80 from reference area, Haojiang). Blood Pb and urine Cd levels of e-waste-exposed children were both higher (mean: 5.89 vs. 3.35 μg/dL; 6.04 vs. 1.82 μg/g, both P < 0.05). Exposed children had a larger proportion of high blood Pb level (> 5.00 μg/dL) (66.67% vs. 4.11%, P < 0.001), but they had no statistically different proportion of high urine Cd level (> 1.00 μg/g creatinine). Median levels of IL-13 decreased (3.674 vs. 4.410 ng/L, P < 0.01), but of IL-10 did not vary in serum of exposed children. The analyses revealed no significant associations of Pb or Cd with Il-10 or Il-13 gene polymorphisms. The high blood Pb and urine Cd level were respectively associated with the low IL-13 ( < 3.696 ng/L) and low IL-10 ( < 0.361 ng/L) level, after adjustment for children's age, gender, and BMI (both P ≤ 0.05). Children homozygous carrying major allele for Il-13 (rs20541 and rs1800925) had additive interactions with high blood Pb level on low IL-13 expression (OR = 5.37, 95% CI: 1.96, 14.73 and OR = 8.45, 95% CI: 2.61, 27.32; both P ≤ 0.001). In contrast, no interaction was observed amongst Pb or Cd with Il-10 gene polymorphisms on its expression. Our findings suggest that Pb exposure interacting with Il-13 gene polymorphisms negatively regulates IL-13 expression, which may pose a risk to abnormal asthma-relevant immunomodulation in preschool children.

Temporal and Geographical Variation of Intestinal Ulcers in Grey Seals (Halichoerus grypus) and Environmental Contaminants in Baltic Biota during Four Decades

Simple Summary

In the 1970s it was discovered that seal populations in the Baltic Sea had decreased severely due to hunting and high levels of contaminants. Lesions were found in several organs and many of the females became sterile. Since then, most of the organ lesions have decreased and so have the levels of some pollutants. However, ulcers in the large intestines of the grey seals increased in the early 1980s and decreased after the mid-1990s. The aims of this study were to: (1) describe the ulcers and investigate if there is a trend over time that coincides with concentrations of some pollutants in Baltic biota; (2) evaluate the significance of different sea areas in the Baltic, grade of parasite intensity, as well as the sex and age of the seals. The results show that seals with ulcers had, in general, higher parasite intensity. Ulcers were more common in older seals and in the Bothnian Sea. The time trend of ulcers coincides with the trend of certain contaminant levels (BDE-47, PFOS and cadmium). The high prevalence of intestinal ulcers and the high intensity of acanthocephalan parasites appear to be unique to the Baltic population of grey seals.

Abstract

The prevalence of intestinal ulcers and parasites was investigated in 2172 grey seals (Halichoerus grypus) collected in the Baltic Sea and 49 grey seals collected outside the Baltic Sea (i.e., the Atlantic). An increase in frequency of ileocaeco-colonic ulcers was observed in the early 1980s, followed by a decrease in the mid-1990s. At the same time, there was an increase followed by a decrease in brominated flame retardants, Perfluorooctanesulfonic acid (PFOS) and cadmium levels in herring (Clupea harengus), the most common prey item in Baltic grey seal diet, as well as in another top predator in the Baltic, the common guillemot (Uria aalge). The frequency of intestinal ulcers was significantly related to the intensity of acanthocephalan parasites, the age of the seal and the region of the Baltic Sea. Perforation of the intestinal wall was the cause of death in 26 of the investigated Baltic grey seals. In contrast, none of the investigated Atlantic grey seals had intestinal ulcers. They showed a thin colonic wall and very few acanthocephalan parasites. The high prevalence of intestinal ulcers and the high parasite intensity appear to be unique to the Baltic population of grey seals.

Exposure to multiple heavy metals associate with aberrant immune homeostasis and inflammatory activation in preschool children

Heavy metals generate adverse health effects by interfering with immune homeostasis and promoting inflammation in individuals. Our objective was to explore the induction of immune and inflammatory responses by multiple heavy metals in children living in the e-waste contaminated area. A total of 147 preschool children were recruited, including 73 children from Guiyu, a typical e-waste recycling area, and 74 from a reference group. Blood levels of heavy metals, including lead (Pb), cadmium (Cd), mercury (Hg) and arsenic (As), were detected using an inductively coupled plasma mass spectrometry (ICP-MS). Immune cell counts (neutrophils, monocytes, lymphocytes) were determined by an automatic blood cell analyzer, pro-inflammatory cytokines (IL-1β, IL-6, IL-8, TNF-α) and anti-inflammatory cytokines (IL-1RA, IL-4, IL-10, IL-13) were analyzed by a Luminex 200 multiplex immunoassay instrument. Multiple correspondences and linear regression analyses were applied to investigate the relationships between heavy metal exposure and relevant parameters. Results shows Guiyu children had higher levels of Pb, Cd, Hg, As, IL-1β and IL-6, but decreased lymphocyte, IL-1RA and IL-13. Neutrophil count was positively correlated with Pb, Cd and Hg exposure. Anti-inflammatory IL-1RA concentration was negatively related with Pb, Cd, Hg and As, while pro-inflammatory IL-1β and IL-6 were positively correlated with Pb. Guiyu children may have dysregulated immune response and high inflammation risk. Exposure to Pb, Cd, Hg and As could be harmful for immune response and inflammatory regulation. Our finding of decreased IL-RA production in children exposed to Pb, Cd, Hg, and As is novel and could be an opportunity for future research.

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.

The Role of Natural Antioxidants Against Reactive Oxygen Species Produced by Cadmium Toxicity: A Review

Cadmium (Cd) is a significant ecotoxic heavy metal that adversely affects all biological processes of humans, animals and plants. Exposure to acute and chronic Cd damages many organs in humans and animals (e.g. lung, liver, brain, kidney, and testes). In humans, the Cd concentration at birth is zero, but because the biological half-life is long (about 30 years in humans), the concentration increases with age. The industrial developments of the last century have significantly increased the use of this metal. Especially in developing countries, this consumption is higher. Oxidative stress is the imbalance between antioxidants and oxidants. Cd increases reactive oxygen species (ROS) production and causes oxidative stress. Excess cellular levels of ROS cause damage to proteins, nucleic acids, lipids, membranes and organelles. This damage has been associated with various diseases. These include cancer, hypertension, ischemia/perfusion, cardiovascular diseases, chronic obstructive pulmonary disease, diabetes, insulin resistance, acute respiratory distress syndrome, idiopathic pulmonary fibrosis, asthma, skin diseases, chronic kidney disease, eye diseases, neurodegenerative diseases (amyotrophic lateral sclerosis, Parkinson's disease, Alzheimer's disease, and Huntington disease). Natural antioxidants are popular drugs that are used by the majority of people and have few side effects. Natural antioxidants play an important role in reducing free radicals caused by Cd toxicity. Our goal in this review is to establish the relationship between Cd and oxidative stress and to discuss the role of natural antioxidants in reducing Cd toxicity.

Potential Health Risk Assessment of Different Heavy Metals in Wheat Products

In the present work, health risk of heavy metals such as As, Cd, Co, Cr, Cu, Hg, Ni, Pb, and Zn in Iranian urban and rural samples including wheat, wheat flour, bread, pasta and sweets were assessed. The real amount of heavy metals in target samples were determined by inductively coupled plasma-atomic emission spectrometry (ICP-AES) and atomic absorption spectroscopy (AAS). Wet ashing and hydride generation techniques were used in sample preparation step. Results demonstrated that heavy metal contaminations in cereal samples were significant. The average concentrations of heavy metals in wheat products were between 0.01 mg kg-1 to 46 mg kg-1. Finally, the health risk assessment results showed that heavy metal contents in rural samples were higher than those in urban samples. The risk of Cu and Zn was significant in two areas and risk of Cr and Cd was not significant.

Alteration of the number and percentage of innate immune cells in preschool children from an e-waste recycling area

Heavy metal lead (Pb) and cadmium (Cd) are widespread environmental contaminants and exert detrimental effects on the immune system. We evaluated the association between Pb/Cd exposures and innate immune cells in children from an electronic waste (e-waste) recycling area. A total number of 294 preschool children were recruited, including 153 children from Guiyu (e-waste exposed group), and 141 from Haojiang (reference group). Pb and Cd levels in peripheral blood were measured by graphite furnace atomic absorption spectrophotometer, NK cell percentages were detected by flow cytometer, and other innate immune cells including monocytes, eosinophils, neutrophils and basophils were immediately measured by automated hematology analyzer. Results showed children in Guiyu had significantly higher Pb and Cd levels than in reference group. Absolute counts of monocytes, eosinophils, neutrophils and basophils, as well as percentages of eosinophils and neutrophils were significantly higher in the Guiyu group. In contrast, NK cell percentages were significantly lower in Guiyu group. Pb elicited significant escalation in counts of monocytes, eosinophils and basophils, as well as percentages of monocytes, but decline in percentages of neutrophils in different quintiles with respect to the first quintile of Pb concentrations. Cd induced significant increase in counts and percentages of neutrophils in the highest quintile compared with the first quintile of Cd concentrations. We concluded alteration of the number and percentage of innate immune cells are linked to higher levels of Pb and Cd, which indicates Pb and Cd exposures might affect the innate and adaptive immune response in Guiyu children.

Cadmium-induced toxicity is rescued by curcumin: A review

Cadmium (Cd) is one of the most common environmental and occupational heavy metals with extended distribution. Exposure to Cd may be associated with several deleterious consequences on the liver, bones, kidneys, lungs, testes, brain, immunological, and cardiovascular systems. Overproduction of reactive oxygen species (ROS) as the main mechanism behind its toxicity causes oxidative stress and subsequent damages to lipids, proteins, and DNA. Therefore, antioxidants along with chelating agents have shown promising outcomes against Cd-induced toxicity. Curcumin with various beneficial effects and medical efficacy has been evaluated for its inhibitory activities against biological impairments caused by Cd. Thus, this article is intended to address the effectiveness of curcumin against toxicity following Cd entry. Curcumin can afford to attenuate lipid peroxidation, glutathione depletion, alterations in antioxidant enzyme, and so forth through scavenging and chelating activities or Nrf2/Keap1/ARE pathway induction. © 2017 BioFactors, 43(5):645-661, 2017.

Effects of methyl and inorganic mercury exposure on genome homeostasis and mitochondrial function in Caenorhabditis elegans

Mercury toxicity mechanisms have the potential to induce DNA damage and disrupt cellular processes, like mitochondrial function. Proper mitochondrial function is important for cellular bioenergetics and immune signaling and function. Reported impacts of mercury on the nuclear genome (nDNA) are conflicting and inconclusive, and mitochondrial DNA (mtDNA) impacts are relatively unknown. In this study, we assessed genotoxic (mtDNA and nDNA), metabolic, and innate immune impacts of inorganic and organic mercury exposure in Caenorhabditis elegans. Genotoxic outcomes measured included DNA damage, DNA damage repair (nucleotide excision repair, NER; base excision repair, BER), and genomic copy number following MeHg and HgCl2 exposure alone and in combination with known DNA damage-inducing agents ultraviolet C radiation (UVC) and hydrogen peroxide (H2O2), which cause bulky DNA lesions and oxidative DNA damage, respectively. Following exposure to both MeHg and HgCl2, low-level DNA damage (∼0.25 lesions/10kb mtDNA and nDNA) was observed. Unexpectedly, a higher MeHg concentration reduced damage in both genomes compared to controls. However, this observation was likely the result of developmental delay. In co-exposure treatments, both mercury compounds increased initial DNA damage (mtDNA and nDNA) in combination with H2O2 exposure, but had no impact in combination with UVC exposure. Mercury exposure both increased and decreased DNA damage removal via BER. DNA repair after H2O2 exposure in mercury-exposed nematodes resulted in damage levels lower than measured in controls. Impacts to NER were not detected. mtDNA copy number was significantly decreased in the MeHg-UVC and MeHg-H2O2 co-exposure treatments. Mercury exposure had metabolic impacts (steady-state ATP levels) that differed between the compounds; HgCl2 exposure decreased these levels, while MeHg slightly increased levels or had no impact. Both mercury species reduced mRNA levels for immune signaling-related genes, but had mild or no effects on survival on pathogenic bacteria. Overall, mercury exposure disrupted mitochondrial endpoints in a mercury-compound dependent fashion.

Elevated lead levels and adverse effects on natural killer cells in children from an electronic waste recycling area

Lead (Pb) has been proved to exert immunotoxicity to influence immune homeostasis in humans. To monitor the internal Pb level and evaluate its effect on natural killer (NK) cells and cytokine/chemokine concentrations, we recruited 285 preschool children from Guiyu, one of the largest electronic waste (e-waste) destinations and recycling areas in the world, and known to have high concentrations of Pb in the air, soil, water, sediment and plants. A total of 126 preschool children were selected from Haojiang as a reference group. Results showed that children in Guiyu, the exposed area, had higher blood Pb levels and lower percentages of NK cells than children from the reference area. A significantly negative association was found between the percentage of NK cells and increasing Pb levels. Moreover, children in Guiyu area had higher platelet counts and IL-1β concentrations, and lower levels of IL-2, IL-27, MIP-1α and MIP-1β were observed in the exposed children. These changes might not be conducive to the development and differentiation of NK cells. Taken together, the elevated Pb levels result in the lower percentages of NK cells, but also alter the levels of platelets, IL-1β and IL-27, which might be unconducive to the activity and function of NK cells.

Comparative analysis of hemocyte properties from Mytilus edulis desolationis and Aulacomya ater in the Kerguelen Islands

The capability of bivalve molluscs to respond to environmental stresses largely depends upon their cellular immunity. Accordingly, shift in habitat conditions following thermal stress or exposure to pollutants may harm sensitive species differently, thereby modulating the biodiversity of a given ecosystem by favoring stress-tolerant species. Here, we have compared the sensitivity of hemocytes from Mytilus edulis desolationis (M. edulis desolationis) and Aulacomya ater (A. ater) to acute thermal stress and exposure to cadmium. The two subantarctic species are commonly found in the same habitat in the isolated Kerguelen archipelago. Our results showed that the phagocytic activity and viability of hemocytes from both species were equally sensitive to increasing concentrations of cadmium. However, although in vitro exposure to cadmium induced apoptosis in hemocytes of M. edulis desolationis and A. ater, flow cytometric analyses showed that the apoptotic profile of both species differed greatly when using Annexin V and YO-PRO-1 as apoptotic markers. We also found that the total hemocyte counts decreased strongly in A. ater but not in M. edulis desolationis following an acute thermal stress. Taken together, these results showed that stress responses differed significantly in hemocytes from both species. This suggests that the co-existence of both species may be at risk following exposure to pollutants and/or changes in temperature.

Pro-inflammatory effects of metals in persons and animals exposed to tobacco smoke

Metals present in tobacco smoke have the ability to cause a pro-oxidant/antioxidant imbalance through the direct generation of free radicals in accordance with the Fenton or Haber-Weiss reaction and redox properties. Metals can also interact with antioxidant enzymes (superoxide dismutase, catalase, glutathione peroxidase) and small molecular antioxidants (glutathione) through binding to SH groups or by replacement of metals ions in the catalytic center of enzymes. Excessive free radicals production can induce an inflammatory response. The aim of this study was to review the information on the induction of inflammation by metals present in tobacco smoke such as lead (Pb), cadmium (Cd), arsenic (As), aluminum (Al), nickel (Ni) and mercury (Hg). In cellular immune response, it was demonstrated that radicals induced by metals can disrupt the transcription signaling pathway mediated by the mitogen-activated protein kinase (induced by Pb), NLRP3-ASC-caspase 1 (induced by Ni), tyrosine kinase Src (induced by As) and the nuclear factor κB (induced by Pb, Ni, Hg). The result of this is a gene transcription for early inflammatory cytokines, such as Interleukine 1β, Interleukine 6, and Tumor necrosis factor α). These cytokines can cause leukocytes recruitment and secretions of other pro-inflammatory cytokines and chemokines, which intensifies the inflammatory response. Some metals, such as cadmium (Cd), can activate an inflammatory response through tissue damage induction mediated by free radicals, which also results in leukocytes recruitment and cytokines secretions. Inflammation generated by metals can be reduced by metallothionein, which has the ability to scavenge free radicals and bind toxic metals through the release of Zn and oxidation of SH groups.

Combined exposure to lead, inorganic mercury and methylmercury shows deviation from additivity for cardiovascular toxicity in rats

Environmental exposure to metal mixtures in the human population is common. Mixture risk assessments are often challenging because of a lack of suitable data on the relevant mixture. A growing number of studies show an association between lead or mercury exposure and cardiovascular effects. We investigated the cardiovascular effects of single metal exposure or co-exposure to methylmercury [MeHg(I)], inorganic mercury [Hg(II)] and lead [Pb(II)]. Male Wistar rats received four different metal mixtures for 28 days through the drinking water. The ratios of the metals were based on reference and environmental exposure values. Blood and pulse pressure, cardiac output and electrical activity of the heart were selected as end-points. While exposure to only MeHg(I) increased the systolic blood pressure and decreased cardiac output, the effects were reversed with combined exposures (antagonism). In contrast to these effects, combined exposures negatively affected the electrical activity of the heart (synergism). Thus, it appears that estimates of blood total Hg levels need to be paired with estimates of what species of mercury dominate exposure as well as whether lead co-exposure is present to link total blood Hg levels to cardiovascular effects. Based on current human exposure data and our results, there may be an increased risk of cardiac events as a result of combined exposures to Hg(II), MeHg(I) and Pb(II). This increased risk needs to be clarified by analyzing lead and Hg exposure data in relation to cardiac electrical activity in epidemiological studies.

Gender-specific transcriptomic response to environmental exposure in Flemish adults

Flanders, Belgium, is one of the most densely populated areas in Europe. The Flemish Environment and Health Survey (2002-2006) aimed at determining exposure to pollutants of neonates, adolescents, and older adults and to assess associated biological and health effects. This study investigated genome wide gene expression changes associated with a range of environmental pollutants, including cadmium, lead, PCBs, dioxin, hexachlorobenzene, p,p'-DDE, benzene, and PAHs. Gene expression levels were measured in peripheral blood cells of 20 adults with relatively high and 20 adults with relatively low combined internal exposure levels, all non-smokers aged 50-65. Pearson correlation was used to analyze associations between pollutants and gene expression levels, separately for both genders. Pollutant- and gender-specific correlation analysis results were obtained. For organochlorine pollutants, analysis within genders revealed that genes were predominantly regulated in opposite directions in males and females. Significantly modulated pathways were found to be associated with each of the exposure biomarkers measured. Pathways and/or genes related to estrogen and STAT5 signaling were correlated to organochlorine exposures in both genders. Our work demonstrates that gene expression in peripheral blood is influenced by environmental pollutants. In particular, gender-specific changes are associated with organochlorine pollutants, including gender-specific modulation of endocrine related pathways and genes. These pathways and genes have previously been linked to endocrine disruption related disorders, which in turn have been associated with organochlorine exposure. Based on our results, we recommend that males and females be considered separately when analyzing gene expression changes associated with exposures that may include chemicals with endocrine disrupting properties.

Cadmium toxicity and treatment

Cadmium is a heavy metal of considerable toxicity with destructive impact on most organ systems. It is widely distributed in humans, the chief sources of contamination being cigarette smoke, welding, and contaminated food and beverages. Toxic impacts are discussed and appear to be proportional to body burden of cadmium. Detoxification of cadmium with EDTA and other chelators is possible and has been shown to be therapeutically beneficial in humans and animals when done using established protocols.

Mercury toxicity in beluga whale lymphocytes: limited effects of selenium protection

Increasing emissions of anthropogenic mercury represents a growing concern to the health of high trophic level marine mammals. In its organic form, this metal bioaccumulates, and can be toxic to several physiological endpoints, including the immune system. In this study, we (1) evaluated the effects of inorganic mercury (mercuric chloride, HgCl2) and organic mercury (methylmercuric chloride, MeHgCl) on the in vitro function of lymphocytes isolated from the peripheral blood of beluga whales (Delphinapterus leucas); (2) characterized the potential protective effects of sodium selenite (Na2SeO3) on cell proliferation of HgCl2 or MeHgCl-treated beluga whale lymphocytes; and (3) compared these dose-dependent effects to measurements of blood Hg in samples collected from traditionally harvested beluga whales in the western Canadian Arctic. Lymphocyte proliferative responses were reduced following exposure to 1 μM of HgCl2 and 0.33 μM of MeHgCl. Decreased intracellular thiol levels were observed at 10 μM of HgCl2 and 0.33 μM of MeHgCl. Metallothionein induction was noted at 0.33 μM of MeHgCl. Concurrent exposure of Se provided a degree of protection against the highest concentrations of inorganic Hg (3.33 and 10 μM) or organic Hg (10 μM) for T-lymphocytes. This in vitro protection of Se against Hg toxicity to lymphocytes may contribute to the in vivo protection in beluga whales exposed to high Hg concentrations. Current Hg levels in free-ranging beluga whales from the Arctic fall into the range of exposures which elicited effects on lymphocytes in our study, highlighting the potential for effects on host resistance to disease. The implications of a changing Arctic climate on Hg fate in beluga food webs and the consequences for the health of beluga whales remain pressing research needs.

Subchronic lead exposure, immunotoxicology and increased disease resistance in Japanese quail (Corturnix coturnix japonica)

The present study investigated the effects of lead (Pb) on immune responses in quail (Coturnix coturnix japonica) and the pathological impact of exposure to an infectious agent (E. coli O2). Fifty-four, 4-week-old quail were exposed to lead acetate in drinking water at 5 or 50 ppm. All birds were vaccinated with Newcastle Vaccine (NDV) during the third week of contaminant (Pb) exposure. In the fourth week, several arms of the immune response were tested using the T cell based phytohemagglutinin (PHA) skin test, the B cell mediated antibody response to NVD, and the chemiluminescence assay measuring innate immunity. Immunohistochemistry (IHC) was used to determine the expression of toll like receptor-3 (TLR-3) in the bursa of Fabricius. In the fifth week, quail were challenged with 200 μL of E. coli O2 (1×10(4) colony forming units (CFU)/mL). No clinical signs of Pb toxicity were observed. Morbidity/mortality subsequent to E. coli exposure was lowest in the high exposure group (27.8%) compared to low exposure (44.4%) and control (55.5%) groups. There was no difference in the T-cell-mediated PHA response, primary or secondary immune response or the innate response in Pb exposed groups; however, bursal TLR-3 increased (p<0.05) with higher Pb exposure. No evidence supported that subchronic Pb exposure was immunotoxic to quail at 5 or 50 ppm in drinking water. In contrast, our results provide evidence of a hormetic effect, with Pb exposed birds having lower morbidity and better survival than controls. Subchronic Pb exposure may be immunostimulatory rather than suppressive as predicted in earlier studies based on testing individual immune parameters.