The role of selenium in cadmium toxicity: interactions with essential and toxic elements

Cadmium exposure is associated with testosterone levels in men: A cross-sectional study from the China National Human Biomonitoring

BACKGROUND

Sex hormone disorders can cause adverse health consequences. While experimental data suggests that cadmium (Cd) disrupts the endocrine system, little is known about the link between Cd exposure and sex hormones in men.

METHODS

We measured blood cadmium (B-Cd), urine cadmium (U-Cd), serum testosterone and serum estradiol in men aged ≥18 years old participating in the China National Human Biomonitoring program, from 2017 to 2018. Urine cadmium adjusted for creatinine (Ucr-Cd) and the serum testosterone to serum estradiol ratio (T/E₂) were calculated. The association of Cd exposure to serum testosterone and T/E₂ in men was analyzed with multiple linear regression models.

RESULTS

Among Chinese men ≥18 years old, the weighted geometric mean (95% CI) of B-Cd and Ucr-Cd levels were 1.23 (1.12-1.35) μg/L and 0.53 (0.47-0.59) μg/g, respectively. The geometric means (95% CI) of serum testosterone and T/E₂ were 18.56 (17.92-19.22) nmol/L and 143.86 (137.24-150.80). After adjusting for all covariates, each doubling of B-Cd level was associated with a 5.04% increase in serum testosterone levels (β = 0.071; 95%CI: 0.057-0.086) and a 4.03% increase in T/E₂ (β = 0.057; 95%CI: 0.040-0.075); similar findings were found in Ucr-Cd.

CONCLUSIONS

In Chinese men, Cd may be an endocrine disruptor, which is positively associated with serum testosterone and T/E₂.

Transcriptomics and transmission ultrastructural examination reveals the nephrotoxicity of cadmium in laying hens

The objective of this study was to reveal the effects of cadmium (Cd) on ultrastructural changes, oxidative stress, and transcriptome expression in the kidneys of laying hens. Seventy-two healthy Hy-Line brown laying hens at 41 weeks old were randomly allocated to four treatment groups with six replicates. The control group received a basal diet without additional Cd incorporation, and the other three treatment groups received diets supplemented with 15, 30, or 60 mg Cd /kg of feed. After 6 weeks of exposure, the results show that administration of 60 mg/kg Cd significantly reduced (P < 0.05) eggshell thickness. With an increase in the Cd concentration in feed, the concentrations of renal Zn and Fe also had changed. Renal histopathology and ultrastructure also showed aggravated damage to glomeruli and renal tubules and the deformation of nuclei and mitochondria in all Cd treatment groups. With an increase in Cd in feed, the activity of glutathione peroxide (GPX) and catalase (CAT) was significantly reduced (P < 0.05), while the activity of total antioxidant capacity (T -AOC) was decreased (P < 0.05) only in the 60 mg/kg Cd group. RNA-seq analysis revealed that 410 genes displayed differential expression (≥ 1.5-fold) in the 60 mg/kg supplementation group, compared to the control group. GO and KEGG pathway analysis results showed that Cd affected many genes involved in mitochondria and ion transport. In conclusion, this study elaborates the mechanisms underlying renal toxicity caused by Cd, which might provide target candidate genes for alleviating Cd poisoning in laying hens.

Effect of occupational cadmium exposure on the thyroid gland and associated inflammatory markers among workers of the electroplating industry

Cadmium (Cd) is widespread throughout the environment and is used in the electroplating industry. It has been found to have an effect on the endocrine system. However, its effects and their underlying mechanisms are still not clear. The aim of this study was to evaluate how cadmium exposure at work affected the levels of thyroid hormones and the associated inflammatory and oxidative markers. This study was conducted in an electroplating industry in Cairo, Egypt. Ninety male cadmium-exposed workers were matched with 90 male unexposed participants. A detailed questionnaire was designed and given to every participant in the study, and full clinical examinations were carried out. Blood samples were collected from all participants for determination of levels of serum cadmium, thyroid hormones, anti-thyroid peroxidase antibody (anti-TPO), interleukin-6 (IL-6), malondialdehyde (MDA), and tumor necrosis factor-alpha (TNF-α). Morning midstream urine samples were obtained to measure urine cadmium levels. Results showed that the total blood and urinary cadmium levels were significantly higher in the exposed group (2.38 ± 0.94 μg/L and 5.45 ± 1.92 μg/g creatinine, respectively) than in the unexposed group. The serum levels of anti-TPO antibody, TSH, MDA, IL-6, and TNF-α also were significantly higher in the cadmium-exposed group than in the unexposed group. Significant direct relationships were seen between the biological indices of cadmium exposure and anti-TPO antibodies, TSH, IL-6, TNF-α, and MDA. It was concluded that there is a link between occupational cadmium exposure and autoimmune hypothyroidism, inflammatory, and oxidative stress markers.

Cadmium promotes apoptosis and inflammation via the circ08409/miR-133a/TGFB2 axis in bovine mammary epithelial cells and mouse mammary gland

Cadmium is a common environmental heavy metal pollutant that can accumulate over long periods of time and cause disease. Thus, analysis of the molecular mechanisms affected by cadmium in the body could be of great significance for the prevention and treatment of cadmium-related diseases. In this study, flow cytometry, immunofluorescence, transmission electron microscopy, H&E (Hematoxylin Eosin) staining and TUNEL (TdT-mediated dUTP Nick-End Labeling) assays were used to verify that cadmium induced apoptosis and immune responses in bovine mammary epithelial cells (BMECs) and in mouse mammary gland. Isolated BMECs cultured with or without cadmium were collected to screen miRNA (microRNA) using high-throughput sequencing. There were 42 differentially-expressed miRNAs among which 27 were upregulated and 15 downregulated including bta-miR-133a, bta-miR-23b-5p, bta-miR-29e, bta-miR-365-5p, bta-miR-615, bta-miR-7, bta-miR-11975, bta-miR-127, and bta-miR-411a. Among those, miR-133a (which can specifically target TGFB2 (Recombinant Transforming Growth Factor Beta 2) was the most significantly downregulated with a fold-change of 5.27 in BMECs cultured with cadmium. Application of the double luciferase reporter system, western blotting, and qRT-PCR (Quantitative Real-time PCR) revealed that circ08409 can directly bind to miR-133a. Experiments demonstrated that circRNA-08409 could adsorb bta-miR-133a. Both circ08409 and TGFB2 significantly increased apoptosis and altered expression level of a series of inflammatory factors in BMECs. In contrast, miR-133a decreased significantly apoptosis and inflammation in the cells. Compared with cultures receiving only cadmium, the miR-133a+cadmium cultures exhibited significant reductions in the occurrence of late apoptosis. Overall, results indicated that circ08409 could relieve the inhibitory effect of miR-133a on TGFB2 expression by combining with miR-133a and subsequently modulating cell proliferation, apoptosis and inflammation. Overall, the data suggested that the circ08409/miR-133a/TGFB2 axis might play a role in mediating the effect of cadmium on BMECs. As such, data provide novel insights into controlling hazards that cadmium could induce in the mammary gland.

Nano Selenium-Enriched Probiotics as Functional Food Products against Cadmium Liver Toxicity

Since cadmium is a toxic metal that can cause serious health problems for humans, it is necessary to find bioremediation solutions to reduce its harmful effects. The main goal of our work was to develop a functional food based on elemental selenium nanoparticles (SeNPs) obtained by green synthesis using Lactobacillus casei and to validate their ability to annihilate the hepatic toxic effects induced by cadmium. The characterization of SeNPs was assessed by UV-Vis spectroscopy, FTIR, XRD, DLS and TEM. In order to investigate the dose-dependent protective effects of SeNPs on Cd liver toxicity, mice were assigned to eight experimental groups and fed by gavage, with 5 mg/kg b.w. cadmium, respectively, with co-administration with SeNPs or lacto-SeNPs (LSeNPs) in 3 doses (0.1, 0.2 and 0.4 mg/kg b.w.) for 30 days. The protective effect was demonstrated by the restoration of blood hepatic markers (AST, ALT, GGT and total bilirubin) and antioxidant enzymes, such as catalase (CAT) and glutathione peroxidase (GPx). Moreover, the antioxidant capacity of mice plasma by the FRAP assay, revealed the highest antioxidant capacity for the 0.2 mg/kg LSeNPs group. Histopathological analysis demonstrated the morphological alteration in the group that received only cadmium and was restored after the administration of SeNPs or LSeNPs, while the immunohistochemical analysis of the bcl family revealed anti-apoptotic effects; the Q-PCR analysis showed an upregulation of hepatic inflammatory markers for the group exposed to Cd and a decreased value for the groups receiving oral SeNPs/ LSeNPs in a dose-dependent manner. The best protective effects were obtained for LSeNPs. A functional food that includes both probiotic bacteria and elemental SeNPs could be successfully used to annihilate Cd-induced liver toxicity, and to improve both nutritional values and health benefits.

The protective role of Coenzyme Q10 in metallothionein-3 expression in liver and kidney upon rats' exposure to lead acetate

Metallothionein-3 (MT3) is an antioxidant protein that alters after exposure to heavy metals. In this study, we investigated the hepatic and renal expression of MT3 gene following exposure to lead acetate (PbAc) alone and PbAc plus CoQ10 as an adjuvant antioxidant. Twenty-four rats were allocated into three groups, including control, PbAc (free access to drinking water contaminated with PbAc at 1 g/100 ml), and PbAc plus CoQ10 (10 mg/kg/day Oral). After 28 consecutive days of treatment, the mRNA expression of MT3 and Cyt-c genes and MT3 protein levels were assessed using real-time PCR and immunosorbent assay. The serum lipid profile was also monitored in the three groups. PbAc exposure significantly reduced the hepatic and renal MT3 mRNA and protein expression compared to the control group. This reduction was significantly increased with addition of CoQ10 to levels near those of the control group. The hepatic and renal expression of Cyt-c mRNA increased after treatment with PbAc, while such effect was reversed after addition of CoQ10. Alteration in lipid profile including increased cholesterol and low-density lipoprotein levels were observed after PbAc exposure which were counteracted by CoQ10. Our results confirm the cytotoxic effects of acute lead exposure manifested as changes in the serum lipid profile and cellular levels of Cyt-c mRNA. These cytotoxic effects may have been caused by decreased MT3 gene expression and be reduced by the protective role of CoQ10.

The Activation of Heat-Shock Protein After Copper(II) and/or Arsenic(III)-Induced Imbalance of Homeostasis, Inflammatory Response in Chicken Rectum

Arsenic and copper, two toxic pollutants, are powerful inducers of oxidative stress. Exposure to copper and arsenic can cause intestinal injury in cockerel. This study was carried out to investigate the effects of these two pollutants on the gastrointestinal tract of cockerels. Experimental results showed that the activity of antioxidant enzymes (catalase and glutathione peroxidase) was inhibited and the ionic balance was destroyed after exposure to copper sulfate (300 mg/kg) and/or arsenic trioxide (30 mg/kg). However, the expression of pro-inflammatory cytokines (nuclear factor kappa-B, cyclooxygenase-2, tumor necrosis factor-α, and prostaglandin E2 synthases) increased markedly. Damages to the biofilm structure and inflammatory cell infiltration were simultaneously observed during histological examination. Heat-shock proteins were also expressed in large quantities after exposure to the poisons. Collectively, exposure to arsenite and/or Cu²⁺ can cause rectal damage in cockerels, inducing inflammation and an imbalance in immune system responses. Sometimes, exposure to both pollutants can produce even more toxic effects. Heat-shock proteins can protect the tissue from the exotoxins but the specific mechanisms require exploration. After oral ingestion of toxins, the rectum can still be damaged, necessitating attention to the safety of poultry breeding, human food safety, and environmental protection.

The threshold effect between the soil bioavailable molar Se:Cd ratio and the accumulation of Cd in corn (Zea mays L.) from natural Se-Cd rich soils

There is little available information about the important interactions between selenium and cadmium (Se-Cd) in crops grown on natural Se-Cd rich soils. We investigated their interactive effects on the translocation and uptake of Se and Cd from soils to crops. Corn (Zea mays L.) roots, stems, leaves, and grains, and their corresponding rhizosphere soils were collected from naturally Se-Cd rich areas in Wumeng Mountain, Guizhou, China. The Se and Cd levels were determined in the soils, roots, stems, leaves, and grains. Soil bioavailable Se and Cd were also determined. The low soil bioavailable molar ratios for Se and Cd (Se:Cd) (≤0.7) improved Cd accumulation in the plants. However, relatively high Se:Cd molar ratios (>0.7) in the soils prevented Cd from entering the plants, but the effect of the soil Se:Cd on Se accumulation in corn was not significant. The strong anion exchange-high performance liquid chromatography-inductively coupled plasma mass spectroscopy (SAX-HPLC-ICP-MS) chromatograms showed that Se-Cd complexes occurred in the leaves, which likely indicated that direct interactions between Se and Cd happened there. The results suggested that thresholds for soil bioavailable Se:Cd molar ratios played a role in the interaction between Se and Cd in corn under natural conditions.

Avian Stress-Related Transcriptome and Selenotranscriptome: Role during Exposure to Heavy Metals and Heat Stress

Selenium, through incorporation into selenoproteins, is one of the key elements of the antioxidant system. Over the past few years there has been increased interest in exploring those molecular mechanisms in chicken, responsible for the development of this protection system. In more detail, Cd/Pb poisoning and heat stress increase oxidation, mRNA levels of inflammatory proteins, and apoptotic proteins. Selenium seems to enhance the antioxidant status and alleviates these effects via upregulation of antioxidant proteins and other molecular effects. In this review, we analyze avian transcriptome key elements with particular emphasis on interactions with heavy metals and on relation to heat stress.

Effects of Selenium and Cadmium on Breast Muscle Fatty-Acid Composition and Gene Expression of Liver Antioxidant Proteins in Broilers

The present work was part of a project intended to evaluate whether organic selenium (Se) has the potential to protect against toxic effects exerted by cadmium (Cd). For this reason, 300 as-hatched, one-day-old broiler chickens were randomly allocated in four dietary treatments with five replicate pens per treatment. Chickens in T1 treatment, were offered a diet supplemented with 0.3 ppm Se (as Se-yeast), without added Cd; in T2 treatment, they were offered a diet with 0.3 ppm Se and 10 ppm Cd; in T3 treatment, they were offered a diet with 0.3 ppm Se and 100 ppm Cd; in T4 treatment, chickens were offered a diet supplemented with 3 ppm Se and 100 ppm Cd. Cadmium was added to the diets in T2, T3, and T4 as CdCl₂. On the fourth and sixth weeks, liver and breast samples were obtained from two broilers per replicate pen. Relative gene expression levels of catalase (CAT), superoxide dismutase 1 (SOD1) and 2 (SOD2), methionine sulfoxide reductase A (MSRA) and B3 (MSRB3), iodothyronine deiodinase 1 (DIO1), 2 (DIO2), and 3 (DIO3), glutathione peroxidase 1 (GPX1) and 4 (GPX4), thioredoxin reductase 1 (TXNRD1) and 3 (TXNRD3), and metallothionein 3 (MT3) were analyzed by real-time quantitative PCR in liver, whereas the fatty-acid (FA) profile of breast muscle was determined by gas chromatography. Broilers supplemented with 0.3 ppm Se could tolerate low levels of Cd present in the diets, as there were no significant changes in the breast muscle FA profile, whereas excess Cd led to decreased polyunsaturated fatty acids (PUFAs), and in particular n-6 PUFA. Furthermore, treatments mainly affected the messenger RNA (mRNA) expression of SOD2, TXNRD3, and MT3, while age affected CAT, MSRB3, DIO2, DIO3, GPX4, TXNRD1, and MT3. In conclusion, dietary Se may help against the negative effects of Cd, but cannot be effective when Cd is present at excessive amounts in the diet.

Airborne metals and polycyclic aromatic hydrocarbons in relation to mammographic breast density

BACKGROUND

Breast density is strongly related to breast cancer. Identifying associations between environmental exposures and density may elucidate relationships with breast cancer. Metals and polycyclic aromatic hydrocarbons (PAHs) may influence breast density via oxidative stress or endocrine disruption.

METHODS

Study participants (n = 222,581) underwent a screening mammogram in 2011 at a radiology facility in the Breast Cancer Surveillance Consortium. Zip code residential levels of airborne PAHs and metals (arsenic, cadmium, chromium, cobalt, lead, manganese, mercury, nickel, and selenium) were assessed using the 2011 EPA National Air Toxics Assessment. Breast density was measured using the Breast Imaging-Reporting and Data System (BI-RADS) lexicon. Logistic regression was used to estimate adjusted odds ratios (ORs) and 95% confidence intervals (CI) for the individual air toxics and dense breasts (BI-RADS 3 or 4). Weighted quantile sum (WQS) regression was used to model the association between the air toxic mixture and density.

RESULTS

Higher residential levels of arsenic, cobalt, lead, manganese, nickel, or PAHs were individually associated with breast density. Comparing the highest to the lowest quartile, higher odds of having dense breasts were observed for cobalt (OR = 1.60, 95% CI 1.56-1.64) and lead (OR = 1.56, 95% CI 1.52-1.64). Associations were stronger for premenopausal women. The WQS index was associated with density overall (OR = 1.22, 95% CI 1.20-1.24); the most heavily weighted air toxics were lead and cobalt.

CONCLUSIONS

In this first study to evaluate the association between air toxics and breast density, women living in areas with higher concentrations of lead and cobalt were more likely to have dense breasts.

The protective role of selenium against cadmium-induced hepatotoxicity in laying hens: Expression of Hsps and inflammation-related genes and modulation of elements homeostasis

The purpose of this study was to examine the potential role of high selenium (Se) diets in alleviating chronic cadmium (Cd) hepatic toxicity in laying hens. In the present study, 128 healthy 31-week-old laying hens were fed a diet supplemented with Se (Na₂SeO₃, 2 mg/kg), Cd (CdCl₂, 150 mg/kg), or both Se and Cd (150 mg/kg of CdCl₂ and 2 mg/kg of Na₂SeO₃) for 90 days. The expression levels of heat shock proteins (Hsps, including Hsp60, Hsp70 and Hsp90) and inflammation-related factors, including nuclear factor-kappa B p50 (NF-κB), cyclooxygenase-2 (COX-2), prostaglandin E synthases (PTGES), interleukin 1-beta (IL-1β), and tumor necrosis factor-α (TNF-α) were investigated. The concentrations of 28 elements were also determined. The results indicated that Cd treatment significantly increased the mRNA and protein expression levels of Hsps and significantly improved the expression of inflammation-related genes. Moreover, Cd addition to the diets resulted in disturbances in the systemic balance of 13 elements, leading to decrease in the concentrations of Cr, Mn, Sr, Ba, and Hg and increase in Li, B, Ca, Ti, Fe, Cu, Mo, and Cd concentrations. Treatment with Se significantly alleviated Cd-induced hepatic toxicity, as evidenced by a reduction in Hsp60, Hsp70, Hsp90, NF-κB, COX-2, PTGES, TNF-α, and IL-1β expression. Additionally, Se and Cd co-treatment alleviated the changes in Li, B, Ca, Fe, Ti, Cu, Mo, Cd, Cr, Se, Sr, Ba, and Hg concentrations, which was in contrast to that upon Cd induction. The study indicated that Se could help against the negative effects of Cd and may be related to the alleviation of Cd-induced Hsps stress and the inflammatory responses along with modulating the element homeostasis.

Effect of Selenium on Ion Profiles and Antioxidant Defense in Mice Livers

Se entering the mammalian body from diverse sources shows different liver accumulation patterns. However, the effects of Se from diverse sources on the body's I on spectrum and the relationship between the changes in the ion spectrum and antioxidant function are not clear. In this study, 80 3-week-old female mice were randomly divided into four groups: a control group, sodium selenite group, yeast Se group, and seaweed Se group. The estimated Se contents were 0.03, 0.23, 0.23, and 0.23 mg/kg, respectively. The liver was collected from mice on day 60. The results showed that, compared with the control group, sodium selenite significantly reduced Na and Li contents and significantly increased Cr, Ni, Se, and Sb contents (P < 0.05); yeast Se significantly increased Mg, Ca, Si, Cr, Fe, Co, Cu, Se, Sb, and Al contents, and significantly reduced Tl, As, and Hg contents (P < 0.05); seaweed Se significantly increased B, Si, Cr, Fe, Se, As, and Hg contents, and significantly reduced Zn and Tl contents (P < 0.05). The results of antioxidant parameter analysis showed that Se from three sources increased total superoxide dismutase content and significantly reduced malondialdehyde content (P < 0.05), whereas no clear effect was observed on total antioxidant capacity (P > 0.05). Combined with the ion spectrum and antioxidant test results, yeast Se was found to most effectively promote the accumulation of beneficial elements, enhance antioxidant capacity, and reduce the concentration of toxic elements. The variety of ion spectrum antioxidants followed a similar trend, which indicated that the ion spectrum might be related to antioxidant activity.

Overview of Cadmium Thyroid Disrupting Effects and Mechanisms

Humans are exposed to a significant number of chemicals that are suspected to produce disturbances in hormone homeostasis. Hence, in recent decades, there has been a growing interest in endocrine disruptive chemicals. One of the alleged thyroid disrupting substances is cadmium (Cd), a ubiquitous toxic metal shown to act as a thyroid disruptor and carcinogen in both animals and humans. Multiple PubMed searches with core keywords were performed to identify and evaluate appropriate studies which revealed literature suggesting evidence for the link between exposure to Cd and histological and metabolic changes in the thyroid gland. Furthermore, Cd influence on thyroid homeostasis at the peripheral level has also been hypothesized. Both in vivo and in vitro studies revealed that a Cd exposure at environmentally relevant concentrations results in biphasic Cd dose-thyroid response relationships. Development of thyroid tumors following exposure to Cd has been studied mainly using in vitro methodologies. In the thyroid, Cd has been shown to activate or stimulate the activity of various factors, leading to increased cell proliferation and a reduction in normal apoptotic activity. Evidence establishing the association between Cd and thyroid disruption remains ambiguous, with further studies needed to elucidate the issue and improve our understanding of Cd-mediated effects on the thyroid gland.

Effects of Se and Cd Co-treatment on the Morphology, Oxidative Stress, and Ion Concentrations in the Ovaries of Laying Hens

This study aims at revealing the effects of the combined treatment of selenium and cadmium on ovary morphology, oxidative stress, and 28 kinds of ion concentrations in laying hens. In this experiment, 128 healthy 31-week-old chickens were selected and divided into four treatment groups, three of which were separately fed the basic diets supplemented with either Se or Cd or both Se and Cd for 90 days, and the remaining group was fed the basic diet and treated as a control. The chickens were sacrificed for collecting ovarian tissues. Morphological structure and ultrastructure analysis of ovaries in the Cd-treated group revealed ovarian damage, with decreased activities of SOD and GPx, along with increased levels of MDA and H₂O₂. Cd treatment also resulted in disturbances in ion balance. The concentrations of Ca, Ti, Cu, Zn, and Ba were significantly reduced, while the concentrations of Fe, Mo, and Cd were significantly increased when compared with the control group. Interestingly, the damages caused by cadmium were alleviated in the Se+Cd-treated group. These results indicate that selenium can alleviate cadmium-induced ovarian damages.

Cadmium induces BNIP3-dependent autophagy in chicken spleen by modulating miR-33-AMPK axis

Cadmium (Cd), a widespread environmental pollutant, has toxic effects on organs including spleen. However, the underlying mechanisms of Cd induced spleen toxicity and the roles of micro-RNA (miRNA) in this process remain poorly understood. To investigate this, cadmium chloride (CdCl₂, 10 mg/kg) was administered in the diet of chickens for 90 days. Electron microscopy, qPCR and Western blot were performed. Results showed that Cd exposure suppressed miR-33-5q which increased the levels of AMPK. Subsequently, significant decrease in AKT/mTOR signaling and HSP70 were observed. Concurrently, levels of NF-κB, p-JNK/JNK increased significantly. Moreover, the expression of BNIP3 and other autophagy markers (LC3-I, LC3-II, Beclin-1) increased significantly. Additionally, the levels of ions (Ca, Cr, Se, Sr, Sn, Ba) and (Na, Mg, V, Fe, Mo, Cu, Zn, Cd) significantly decreased and increased, respectively. Taken together, we conclude that Cd induced the deregulation of miR-33-AMPK axis led to BNIP3-dependent autophagy in chicken spleen through AKT/mTOR and HSP70-NF-κB/JNK signal pathways. In-addition Cd could affect ion homeostasis in chicken spleen.

Selenium Accumulation Characteristics and Biofortification Potentiality in Turnip (Brassica rapa var. rapa) Supplied with Selenite or Selenate

Selenium (Se) is an essential trace element for humans. About 70% of the regions in China, including most of the Tibetan Plateau, are faced with Se deficiency problems. Turnip is mainly distributed around the Tibetan Plateau and is one of the few local crops. In the present study, we compared the absorption and translocation differences of Se (IV) selenite and Se (VI) selenate in turnip. The results showed that Se treatment, either by soil addition (0.2-2 mg Se kg^-1 dry soil) or by foliar spraying (50-200 mg L^-1 Se), could significantly increase the Se concentrations in turnips, and 0.5 mg Se (IV) or Se (VI) kg^-1 dry matter in soils could improve the biomasses of turnips. Moreover, turnip absorbed significantly more Se (VI) than Se (IV) at the same concentration and also transferred much more Se (VI) from roots to leaves. Based on the Se concentrations, as well as the bioconcentration factors and translocation coefficients, we considered that turnip might be a potential Se indicator plant. Subsequently, we estimated the daily Se intake for adults based on the Se concentrations in turnip roots. The results indicated that Se (IV) should be more suitable as an artificial Se fertilizer for turnips, although the levels found in most samples in this study could cause selenosis to humans. In addition, we also estimated the optimum and maximum Se concentrations for treating turnips based on the linear relations between Se concentrations in turnip roots and Se treatment concentrations. The results provided preliminary and useful information about Se biofortification in turnips.

Ameliorative Effects of Dietary Selenium Against Cadmium Toxicity Is Related to Changes in Trace Elements in Chicken Kidneys

The ameliorative effects of selenium (Se) against cadmium (Cd)-induced toxicity have been reported extensively. However, few studies have assessed the effects of multiple ions simultaneously on the variations of elements. In this study, the changes in Se, Cd, and 26 other element concentrations were investigated in chicken kidneys. One hundred and twenty-eight 31-week-old laying hens were fed a diet supplemented with either Se, Cd, or both Se and Cd for 90 days. The ion content was analyzed by inductively coupled plasma mass spectrometry (ICP-MS). We found that the Se, Cd, and combined Se and Cd treatments significantly affected the trace elements in the chicken kidneys. The Cd supplement caused ion profile disorders, including reduced concentrations of V, Cr, Mn, Mo, As, Ba, Hg, Ti, and Pb and increased Si, Cu, Li, Cd, and Sb. The Se supplement reduced the contents of Co, Mo, and Pb and increased the contents of Cr, Fe, and Se. Moreover, Se also increased the concentrations of Cr, Mn, Zn, and Se and decreased those of Li and Pb, which in contrast were induced by Cd. Complex interactions between elements were analyzed, and both positive and negative correlations among these elements are presented. The present study indicated that Se can help against the negative effects of Cd and may be related to the homeostasis of the trace elements in chicken kidneys.

Methylmercury Induced Neurotoxicity and the Influence of Selenium in the Brains of Adult Zebrafish (Danio rerio)

The neurotoxicity of methylmercury (MeHg) is well characterised, and the ameliorating effects of selenium have been described. However, little is known about the molecular mechanisms behind this contaminant-nutrient interaction. We investigated the influence of selenium (as selenomethionine, SeMet) and MeHg on mercury accumulation and protein expression in the brain of adult zebrafish (Danio rerio). Fish were fed diets containing elevated levels of MeHg and/or SeMet in a 2 × 2 full factorial design for eight weeks. Mercury concentrations were highest in the brain tissue of MeHg-exposed fish compared to the controls, whereas lower levels of mercury were found in the brain of zebrafish fed both MeHg and SeMet compared with the fish fed MeHg alone. The expression levels of proteins associated with gap junction signalling, oxidative phosphorylation, and mitochondrial dysfunction were significantly (p < 0.05) altered in the brain of zebrafish after exposure to MeHg and SeMet alone or in combination. Analysis of upstream regulators indicated that these changes were linked to the mammalian target of rapamycin (mTOR) pathways, which were activated by MeHg and inhibited by SeMet, possibly through a reactive oxygen species mediated differential activation of RICTOR, the rapamycin-insensitive binding partner of mTOR.

Selenium supplementation can protect from enhanced risk of keel bone damage in laying hens exposed to cadmium

The aim of this study was to investigate whether selenium (Se) supplementation can provide protection from an enhanced risk of keel bone damage (KBD) in laying hens due to the cadmium (Cd) toxicity associated with sub-chronic exposure.

Antagonistic effects of selenium against necroptosis injury via adiponectin-necrotic pathway induced by cadmium in heart of chicken

Cadmium (Cd) is one of the most toxic heavy metals having a destructive impact on various organ systems.

Effects of Selenium and Cadmium on Ion Profiles in the Brains of Chickens

Antagonistic effects of selenium (Se) in cadmium (Cd)-induced toxicity have been frequently reported in previous studies. However, little was known about the interactions of Se and Cd on ion profiles in the brains of poultry. The aim of this study was to investigate the interaction between Se and Cd in the ion profile of the chicken brain. In the present study, a total of 128 laying hens were fed a Se-, Cd-, or Se + Cd-supplemented diet for 90 days. Levels of 28 ions were detected in chicken brains using ICP-MS. We found that Cd exposure significantly increased the content of Cd in the brain; furthermore, the content of lithium (Li), stannum (Sn), and stibium (Sb) increased, but the content of kalium (K) decreased. The content of Se in the brain was not altered by Se supplementation; however, Se reduced the concentrations of Sn and Sb, which in contrast were increased by Cd exposure. Complex interactions between ions were analyzed by principal component analysis, and both positive and negative correlations between different ions were found after prolonged exposure to Se and Cd. These findings suggest that Se and Cd supplementation influences the ion profiles in the chicken brain, and moreover, Se may have an antagonistic effect under longer exposure to Cd.

Simultaneous analysis 26 mineral element contents from highly consumed cultured chicken overexposed to arsenic trioxide by inductively coupled plasma mass spectrometry

This study assessed the impacts of dietary arsenic trioxide (As₂O₃) on 26 mineral element contents in the liver and kidney of chicken. A total of 100 male Hy-line cocks were randomly divided into 2 groups (50 chickens in each group), including an arsenic-treated group (basic diet supplemented with As₂O₃ at 30 mg/kg) and a control group (basal diet). The feeding experiment lasted for 90 days and the experimental animals were given free access to feed and water. We determined 26 mineral elements in the liver and kidney by inductively coupled plasma mass spectrometry (ICP-MS). The results showed that nine element levels (Al, Mn, Co, Cu, Zn, Se, Cd, Ba, and Pb) were significantly decreased (P < 0.05) in the liver of chickens exposed to As₂O₃ compared to the control chickens where three element levels (Ni, As, and Hg) increased significantly (P < 0.05). The results in the kidney showed that nine element levels (Al, K, Ca, Cr, Mn, Ni, Sb, Ba, and Pb) were significantly decreased (P < 0.05) in the chickens exposed to As₂O₃ compared to the control chickens where four element levels (Mo, As, Cd, and Hg) increased significantly (P < 0.05). These results suggest that supplementation of high levels of arsenic affected trace mineral levels in the liver and kidney of chicken, and the effects vary from organ to organ. The aim of this study is to provide references for further study of heavy metal poisoning by detecting the contents of minerals induced by arsenic in chicken.

Effect of combined exposure to lead and decabromodiphenyl ether on neurodevelopment of zebrafish larvae

The effect of combined exposure to decabromodiphenyl ether (BDE-209) and lead (Pb) on neurodevelopment of zebrafish (Danio rerio) larvae was investigated. Zebrafish embryos were exposed to Pb (0, 5, 10, 20 µg/L) and BDE-209 (0, 50, 100, 200 µg/L), either alone or in combination (Mix1: 5 + 50 µg/L, Mix2: 10 + 100 µg/L, Mix3: 20 + 200 µg/L) for up to 144 h post-fertilization. Growth of secondary motoneuron axons and expression of genes related to central nervous system development was significantly inhibited in Mix3 co-exposure group. A significant increase in reactive oxygen species (ROS), lipid peroxidation, DNA damage, and perturbation of the antioxidant system was detected in the Mix3 group compared to single-toxicant treatments or control. Depressed locomotor activity was recorded in the Mix2 and Mix3 groups. Addition of N-acetyl cysteine to Mix3 eliminated excessive ROS, and protected against lipid peroxidation, DNA damage, and locomotor dysfunction. Pb uptake was increased in the presence of BDE-209, but BDE-209 bioconcentration and the ability to metabolize BDE-209 were decreased in the presence of Pb. These results suggest that BDE-209 and Pb have a synergistic disruptive effect on neurodevelopment in zebrafish larvae by enhanced generation of ROS, which is a major factor that contributes to developmental neurotoxicity.

Correlation between urinary cadmium and thyroid hormones in outdoor workers exposed to urban stressors

OBJECTIVES

The aim of this study is to evaluate whether exposure to low concentrations of cadmium (Cd) can have effects on the thyroid hormone level of outdoor workers exposed to urban pollutants.

METHODS

The study was conducted on a final sample of 277 individuals (184 males and 93 females). The environmental monitoring of Cd was evaluated through the use of portable dosimeters, while the biological monitoring was achieved through the assessment of urinary Cd and thyroid hormones. The total sample was divided according to sex and task. The Pearson's correlation coefficient among the variables was calculated after subdivision on the basis of sex and task. The multiple linear regression was performed to take into account the major confounding factors.

RESULTS

Statistical tests showed a negative correlation between urinary Cd levels and free triiodothyronine and free thyroxine and a positive correlation between urinary Cd and thyroid-stimulating hormone levels.

CONCLUSIONS

Our early results seem to point out that occupational exposure to low concentrations of Cd present in urban air affects the thyroid hormone levels in exposed workers.

Effects of Dietary Cadmium and Boron Supplementation on Performance, Eggshell Quality and Mineral Concentrations of Bone in Laying Hens

This study was conducted to determine the effects of supplementation of different levels of cadmium and boron on performance, eggshell quality, and mineral concentrations of bone in layer diets. In this trial, a total of 144 layer chickens, 21 weeks old, were randomly divided into 12 experimental groups. In each experimental group, there were four replicates, and in each of the replicates, there were three hens. Experimental diets consisted of all possible combinations of four levels of added cadmium (0, 5, 15, and 45 mg/kg) and three levels of added boron (0, 60, and 120 mg/kg) to the basal diet. Added cadmium (15 or 45 mg/kg) had a significant adverse effect on performance parameters (P < 0.01). Eggshell thickness increased with the addition of 5 mg/kg level of cadmium to the diet (P < 0.01). Tibia cadmium content increased with the addition of cadmium and boron in the diet (P < 0.01). However, tibia boron content decreased with the supplementation of cadmium (P < 0.01). These results indicate that the addition of boron to the diet did not prevent adverse effect of cadmium on performance and eggshell quality, or accumulation of cadmium in bone.

Molecular cloning and sequence analysis of selenoprotein W gene and its mRNA expression patterns in response to metabolic status and cadmium exposure in goldfish, Carassius auratus

Selenoprotein W (SelW) is a low molecular weight and selenocysteine containing protein with redox activity involved in the antioxidant response. In the present study, the full-length cDNA of goldfish (Carassius auratus) selenoprotein W (gfSelW) was successfully cloned from the liver tissue by rapid amplification of cDNA ends technique. The obtained gfSelW cDNA was 730 bp long with a 79 bp 5'-untranslated region (UTR), a 390 bp 3'-UTR containing the consensus polyadenylation signal AATAAA and a 261 bp open reading frame coding a protein of 86 amino acid residues. gfSelW mRNA was observed in all regions of brain and peripheral tissues by semi-quantitative RT-PCR, and the most abundant was detected in testis. After fasting for 1 week, gfSelW mRNA expression levels were significantly decreased compared to the fed group in hypothalamus and liver. After refeeding for 7 days, gfSelW mRNA expression levels were increased back. Furthermore, the mRNA expressions of gfSelW in hypothalamus and liver were varied in periprandial changes and significantly up-regulated after meal 2 h and 4 h, respectively. With cadmium exposure for 24 h, gfSelW mRNA expression levels in gill and leucocytes were significantly decreased at different cadmium concentrations changing from 0.5 ppm to 10 ppm. However, the gfSelW mRNA expression level was sharply increased in liver, relatively to the control about 4.98-fold at 0.5 ppm. The results in this study provide molecular characterization of SelW in goldfish and imply that SelW mRNA expression may be associated with metabolic status and oxidative stress and regulated by metabolic factors and cadmium in fish.