High selenium status in individuals exposed to arsenic through coal-burning in Shaanxi (PR of China) modulates antioxidant enzymes, heme oxygenase-1 and DNA damage

Comparative study on protective effect of different selenium sources against cadmium-induced nephrotoxicity via regulating the transcriptions of selenoproteome

Cadmium (Cd) is a ubiquitous environmental pollutant, which mainly input to the aquatic environment through discharge of industrial and agricultural waste, can be a threat to human and animal health. Selenium (Se) possesses a beneficial role in protecting animals and ameliorating the toxic effects of Cd. However, the comparative antagonistic effects of different Se sources such as inorganic, organic Se and nano-form Se on Cd toxicity are still under-investigated. Hence, the purpose of this study was to evaluate the comparative of Se sources antagonism on Cd-induced nephrotoxicity via oxidative stress and selenoproteome transcription. In the present study, Cd-diet disturbed in the system balance of 5 trace elements (Zinc (Zn), copper (Cu), Iron (Fe), Se, Cd) and impaired renal function. Se sources, including nano- Se (NS), Se- yeast (SY), sodium selenite (SS) and mixed selenium (MS) significantly recovered the balance of 4 trace elements (Zn, Cu, Cd, Se) and renal impaired indexes (blood urea nitrogen (BUN) and creatinine (CREA)). Histological appearance of Cd-treated kidney indicated renal tubular epithelial vacuoles, particle degeneration and enlarged capsular space. Ultrastructure observation results illustrated that Cd-induced mitochondrial cristae reduction, membrane disappearance, and nuclear deformation. Treatment with Se sources, NS appeared a better impact on improving kidney tissues against the pathological alterations resulting from Cd administration. Meanwhile, NS reflected a significant impact on relieving Cd-induced kidney oxidative damage, and significantly restored the antioxidant defense system of the body. Our findings also showed NS ameliorated the Cd-induced downtrends expression of selenoproteome and selenoprotein synthesis related transcription factors. Overall, NS was the most effective Se source in avoiding of Cd cumulative toxicity, improving antioxidant capacity and regulating of selenoproteome transcriptome and selenoprotein synthesis related transcription factors expression, which contributes to ameliorate Cd-induced nephrotoxicity in chickens. These results demonstrated diet supplement with NS may prove to be an effective approach for alleviating Cd toxicity and minimizing Cd -induced health risk.

Protective effects of selenium in tacrolimus-induced lung toxicity: potential role of heme oxygenase 1

The present study aimed to evaluate the protective effects of selenium (Sel) administration against tacrolimus (Tac) - induced lung toxicity and to assess the relation between heme oxygenase 1 (HO-1) and these effects. The study was conducted on 36 Wistar male albino rats equally divided into four groups: (i) normal control; (ii) Sel (0.1 mg/kg per day p.o. for four weeks); (iii) TAC 3 mg/mL as single oral dose on 27th day; and (iv) Tac + Sel. Lung tissues, lung homogenate, and bronchoalveolar lavage of the sacrificed animals were investigated biochemically and histopathologically, by immunohistochemistry or by PCR. The Tac group showed significantly lower expression of HO-1. Administration of Sel was associated with increased HO-1 expression. Oxidative (malondialdehyde, reduced glutathione, superoxide dismutase, myeloperoxidase, and glutathione peroxidase activity) and nitrosative stress (nitric oxide) markers and markers of inflammation (interleukin 1β (IL-1β), IL-6, and IL-10) showed changes corresponding to HO-1 levels in rat groups. Tac group showed the highest expression of caspase-3. Sel exerted a protective role against Tac-induced lung toxicity.

Effects of organic selenium on absorption and bioaccessibility of arsenic in radish under arsenic stress

Arsenic (As) exposure poses a serious threat to human health. The present study investigated the effects of organic Se on As accumulation, migration, and As bioaccessibility in As-stressed radish. The results showed that organic Se can effectively block the accumulation of As in radish, reduce As bioaccessibility, and promote the conversion of As from inorganic to organic form. The total As content decreased with increasing Se application in raw radish roots, the gastric fraction and the gastrointestinal fraction. Compared to the control (CK) group, the As bioaccessibility in the 24Se treatment of the yeast Se and malt Se groups decreased by 26% and 37%, respectively. These findings provide new comprehensive information for the application of organic Se to alleviate the toxicological effects of As and reduce the health risks of As in edible plants. In the future, it is necessary to carry out a deeper study of the interaction between Se and As through advanced analytical methods.

Effects of selenium on antioxidant enzyme activity and bioaccessibility of arsenic in arsenic-stressed radish

Consuming arsenic (As)-contaminated vegetables is the main route of As exposure in humans. The present study focused on the alterations in antioxidant enzymatic activities and As bioaccessibility in As-contaminated radish subjected to Se. Compared to the CK group, the total As content in raw radish was reduced by 27.5 ± 1.3%, and the bioaccessibility of As was reduced by 21.9 ± 2.3% in the 6 mg Se kg^-1 treatment group. The total As content in the treatment groups decreased first but then increased with increasing Se application in raw radish, gastric (G) fraction and gastrointestinal (GI) fraction, while the antioxidant activity exhibited the opposite trend. The results revealed that a low amount of Se effectively blocks the accumulation of As in radish, improves the antioxidant activity in radish and reduces the bioaccessibility of As. These findings provide new ideas for effectively alleviating the spread of As to the human body through the food chain.

Selenium may suppress peripheral blood mononuclear cell apoptosis by modulating HSP70 and regulate levels of SIRT1 through reproductive hormone secretion and oxidant stress in women suffering fluorosis

Excessive taking fluoride (F) causes severe damage to reproductive system through stimulation of apoptosis and oxidant stress. Selenium (Se) may promote anti-oxidant enzymes and invert cell apoptosis. The aim of this study was to investigate the effect of Se on peripheral blood mononuclear cell (PBMC) apoptosis and oxidant stress in women with fluorosis. Sixty women were divided into three groups according to serum and urine fluoride and hair Se as High F + high Se group, High F group and Control group. The activities of anti-oxidant enzymes, malondialdehyde (MDA) and Se were measured. The levels of sirtuin type 1 (SIRT1), estradiol (E₂), follicle-stimulating hormone (FSH) and luteinizing hormone (LH) were measured by enzyme-linked immune sorbent assay (ELISA) kits. The expression of protein and apoptosis rate were detected by Western blot and Flow cytometry. The levels of E₂, anti-oxidant enzymes in High F group were significantly lower than that in Control group, while the levels of SIRT1 and MDA were significantly higher. The levels of anti-oxidant enzymes and heat shock protein 70 (HSP70) were significantly increased in High Se + high F group while the expression of caspase-3 was significantly increased in high F group. The levels of LH and FSH in serum were significantly increased in High F group and High Se + high F group. Therefore, Se alleviates apoptosis induced by F through improving the expression of HSP70 and reduces oxidative stress by regulating levels of SIRT1 and anti-oxidant enzymes, and the secretion of certain reproductive hormones.

The Role of Selenium in Arsenic and Cadmium Toxicity: an Updated Review of Scientific Literature

Arsenic (As) and cadmium (Cd) are elements arousing major public health concerns associated with environmental pollution, high toxicity potential, and carcinogenic nature. However, selenium (Se) at low doses and incorporated into enzymes and proteins has antioxidant properties and protects animals and humans from the risk of various diseases. It also has an exceptionally narrow range between necessary and toxic concentrations, which is a well-known hindrance in its use as a dietary supplement. The present article aims to update and expand the role of Se in As and Cd toxicity discussed in our earlier paper. In general, recent reports show that Se, regardless of its form (as selenite, selenomethionine, nanoSe, or Se from lentils), can reduce As- or Cd-mediated toxicity in the liver, kidney, spleen, brain, or heart in animal models and in cell culture studies. As was suggested in our earlier review, Se antagonizes the toxicity of As and Cd mainly through sequestration of these elements into biologically inert complexes and/or through the action of Se-dependent antioxidant enzymes. An increase in the As methylation efficiency is proposed as a possible mechanism by which Se can reduce As toxicity. However, new studies indicate that Se may also diminish As or Cd toxicity by activation of the Nrf2 pathway. In addition, this paper discusses possible signs of Se toxic effects, which may be a challenge for its future use in the therapy of As and Cd poisoning and provide future directions to address this issue.

Plasma Metal Concentrations and Incident Coronary Heart Disease in Chinese Adults: The Dongfeng-Tongji Cohort

BACKGROUND

Circulating metals from both the natural environment and pollution have been linked to cardiovascular disease. However, few prospective studies have investigated the associations between exposure to multiple metals and incident coronary heart disease (CHD).

OBJECTIVES

We conducted a nested case-control study in the prospective Dongfeng-Tongji cohort, to investigate the prospective association between plasma metal concentrations and incident CHD.

METHODS

A total of 1,621 incident CHD cases and 1,621 controls free of major cardiovascular disease at baseline and follow-up visits were matched on age (±5 years) and sex. We measured baseline fasting plasma concentrations of 23 metals and used conditional logistic regression models to estimate odds ratios (ORs) of CHD for metal concentrations categorized according to quartiles in controls.

RESULTS

Five metals (titanium, arsenic, selenium, aluminum, and barium) were significantly associated with CHD based on trend tests from single-metal multivariable models adjusted for established cardiovascular risk factors. When all five were included in the same model, adjusted ORs for barium and aluminum were close to the null, whereas associations with titanium, arsenic, and selenium were similar to estimates from single-metal models, and ORs comparing extreme quartiles were 1.32 (95% CI: 1.03, 1.69; p-trend=0.04), 1.78 (95% CI: 1.29, 2.46; p-trend=0.001), and 0.67 (95% CI: 0.52, 0.85; p-trend=0.001), respectively.

CONCLUSIONS

Our study suggested that incident CHD was positively associated with plasma levels of titanium and arsenic, and inversely associated with selenium. Additional research is needed to confirm these findings in other populations. https://doi.org/10.1289/EHP1521.

Hydrochemical characteristics of natural water and selenium-rich water resources in the Northern Daba Mountains, China

The Northern Daba Mountains (NDM) of Shaanxi Province, China, are a well-known selenium (Se)-rich area, and the area is also known for endemic fluorine (F) and arsenic (As) poisoning. In order to study the hydrochemical characteristics and trace element contents of the natural waters of this region, 62 water samples were collected from Lan'gao area in the NDM. The hydrochemical composition was principally characterized by Ca·Mg-HCO₃·SO₄. F and As concentrations ranged from 0.01 to 0.67 mg/L and from 0.33 to 6.29 μg/L, respectively, lower than Chinese national standard and international guidelines for drinking water quality. One year of monitoring proved that F and As in natural water were not the sources of the local fluorosis and arseniasis in the NDM. The average Se concentration in fissure water was 5.20 μg/L. The average Se content of river water was 2.82 μg/L, 14 times that of the world's surface level (0.2 μg/L). The Se content in eight samples reached the Chinese national standards for mineral drinking water quality (>10 μg/L). Contrasting the water samples of May, July, and September in 2015 shows that the Se content is relatively stable and the increase of humidity might be beneficial to increase the content of selenium and strontium in water.

Effect of vitamin E supplementation on arsenic induced alteration in blood biochemical profile, oxidant/antioxidant status, serum cortisol level and retention of arsenic and selenium in goats

Arsenic (As) exerts oxidative stress with depletion of body selenium in monogastric animals. But in ruminants this fact is not yet verified. Vitamin E is an effective dietary antioxidant. Thus, in this experiment, the protective effect of vitamin E against arsenic toxicity induced by sodium arsenite (60mg As/kg diet) was investigated in goat kids. For this, 21 male kids were divided into three equal groups and fed either basal diet as such (control), or supplemented with 60mg As/kg diet and 60mg As/kg diet+250IU vitamin E/kg diet for 180 days. Vitamin E supplementation alleviated the toxic effects caused by arsenic on serum alanine aminotransferase and aspartate aminotransferase and lipid peroxidation. It also prevented the depletion of reduced glutathione content and reduction in activity of catalase, superoxide dismutase and glutathione-s-transferase in erythrocytes resulted from arsenic intoxication. The elevated levels of arsenic and reduced levels of selenium in the serum and tissues in arsenic treated animals were attenuated by vitamin E supplementation, though not completely. However, serum cortisol level was not affected by arsenic. It was concluded that arsenic exerts cortisol independent stressor mechanism and supplementation of vitamin E at a level of 250IU/kg diet was partially effective in reducing tissue accumulation of arsenic in the body and protect the kids from oxidative stress induced by arsenic.

Protective effects of selenium on oxidative damage and oxidative stress related gene expression in rat liver under chronic poisoning of arsenic

Arsenic (As) is a toxic metalloid existing widely in the environment, and chronic exposure to it through contaminated drinking water has become a global problem of public health. The present study focused on the protective effects of selenium on oxidative damage of chronic arsenic poisoning in rat liver. Rats were divided into four groups at random and given designed treatments for 20 weeks. The oxidative damage of liver tissue was evaluated by lipid peroxidation and antioxidant enzymes. Oxidative stress related genes were detected to reflect the liver stress state at the molecular level. Compared to the control and Na2SeO3 groups, the MDA content in liver tissue was decreased and the activities of antioxidant enzymes were increased in the Na2SeO3 intervention group. The mRNA levels of SOD1, CAT, GPx and Txnrd1 were increased significantly (P<0.05) in the combined Na2SeO3+NaAsO2 treatment group. The expressions of HSP70 and HO-1 were significantly (P<0.05) increased in the NaAsO2 group and reduced in the combined treatment group. The results indicate that long-term intake of NaAsO2 causes oxidative damage in the rat liver, and Na2SeO3 protects liver cells by adjusting the expression of oxidative stress related genes to improve the activities of antioxidant enzymes.

Blood Arsenic and Cadmium Concentrations in End-Stage Renal Disease Patients who were on Maintenance Haemodialysis

BACKGROUND

In India, there is a rising burden of chronic diseases like hypertension and diabetes. It has been estimated that 25-40% of these patients are likely to develop chronic kidney disease (CKD), with a significant percentage requiring renal replacement therapy. Haemodialysis is the most common method which is used to treat advanced and permanent kidney failure. Derangements in the metabolism of several toxic and trace elements such as antimony, arsenic cadmium, molybdenum, nickel, and selenium have been reported for several decades in patients with chronically reduced renal functions. Overall, the available literature suggests that the blood levels of some elements such as cadmium, chromium, fluorine, iodine, lead, or vanadium are high in end-stage renal disease (ESRD).

AIM AND OBJECTIVES

Our aim was to study the levels of blood arsenic and cadmium in ESRD patients who were on maintenance haemodialysis (MHD), and to study whether there was any relationship between their concentrations and the duration of the MHD.

METHODS

The blood lead levels were determined in 50 healthy subjects with normal renal functions and in 50 patients with ESRD, who were on MHD. None of them had any history of smoking or any industrial exposure.

RESULTS

The results of the study revealed that the blood arsenic and cadmium concentrations were higher in the ESRD patients who were on MHD than in the healthy adults. The blood arsenic and cadmium concentrations were found to increase with the duration of the MHD.

CONCLUSION

The mild increase in the blood arsenic and cadmium concentrations, with an increase in the duration of the MHD in the study population, may be viewed in the wider context, that a prolonged exposure to arsenic and cadmium, even at low levels, may result in renal damage and/or progression of an already existing CKD.

Hair analysis in health assessment

BACKGROUND

Hair analysis is used for estimation of the nutritional status of individuals. In the present work, a systematic review on the relation between the mineral composition of hair and the physical or mental disorders is discussed. Detailed information of examined populations, methods of sample preparations and analytical techniques are presented.

METHODS

A systematic literature search in four electronic databases Scopus, PubMed, Web of Science and Medline (from 1997 to 2012/01/31) for English language articles was performed. In addition, a reference list and manual search was undertaken.

RESULTS

The following number of studies was included: 66. Most of the authors reported that there exists a correlation between deficiency or excess of some elements in hair and occurrence of some diseases, such as: autism, cancer, hypertension, myocardial infarction, kidney disease and diabetes mellitus. However, not all results were consistent.

CONCLUSIONS

Most of the authors concluded that the profile of hair mineral imbalance might be useful as a diagnostic tool for the early diagnosis of many diseases. However, it seems that there is a need to standardize sample preparation procedures, in particular washing and mineralization methods.

Protective and antioxidant role of selenium on arsenic trioxide-induced oxidative stress and genotoxicity in the fish hepatoma cell line PLHC-1

In vitro models are useful tools for rapid screening for toxicity, elucidation of mechanisms of toxicity, and understanding complex interactions among environmental toxicants. These evaluations may provide useful information for ecological evaluations if the relationship between in vitro and in vivo effects is established. The present study was undertaken to evaluate the protective effect of selenium on arsenic trioxide (As(2) O(3) )-induced cytotoxicity, DNA damage, and apoptosis. N-acetylcysteine (NAC), a free radical scavenger, was used to determine the involvement of reactive oxygen species (ROS) in As(2) O(3) -induced DNA damage and apoptosis. Poeciliopsis lucida hepatocellular carcinoma line 1 (PLHC-1) cells were pretreated with selenium (1, 5, and 10 µM) and NAC (50 and 100 µM) for 2 h. After pretreatment, cells were exposed to 100 µM of As(2) O(3) for 10-, 20-, and 40-h intervals. The As(2) O(3) exposure promoted extensive DNA damage and apoptosis compared to control, while selenium- and NAC-pretreated cells improved cell survival rate against As(2) O(3) -induced cell death. Improved survival likely resulted from increasing glutathione peroxidase activity and reduction of ROS formation, reduction of mitochondrial membrane potential damage, DNA damage, and caspase-3 activity. During As(2) O(3) exposure, selenium played the same role as NAC. The authors conclude that As(2) O(3) -induced DNA damage and apoptosis are mediated by oxidative stress and selenium and that, although toxic at higher concentrations, selenium provides significant protection against As(2) O(3) effects in PLHC-1 cells.

Probing the bioinorganic chemistry of toxic metals in the mammalian bloodstream to advance human health

The etiology of numerous grievous human diseases, including Alzheimer's and Parkinson's Disease is not well understood. Conversely, the concentration toxic metals and metalloids, such as As, Cd, Hg and Pb in human blood of the average population is well established, yet we know strikingly little about the role that they might play in the etiology of disease processes. Establishing functional connections between the chronic exposure of humans to these and other inorganic pollutants and the etiology of certain human diseases is therefore viewed by many as one of the greatest challenges in the post-genomic era. Conceptually, this task requires us to uncover hitherto unknown biomolecular mechanisms which must explain how small doses of a toxic metal/metalloid compound (low μg per day) - or mixtures thereof - may eventually result in a particular human disease. The biological complexity that is inherently associated with mammals, however, makes the discovery of these mechanisms a truly monumental task. Recent findings suggest that a better understanding of the bioinorganic chemistry of inorganic pollutants in the mammalian bloodstream represents a fruitful strategy to unravel relevant biomolecular mechanisms. The adverse effect(s) that toxic metals/metalloid compounds exert on the transport of essential ultratrace elements to internal organs appear particularly pertinent. A brief overview of the effect that arsenite and Hg(2+) exert on the mammalian metabolism of selenium is presented.

Trace elements in the hair of hemodialysis patients

Trace element disturbance is often observed in hemodialysis patients. While trace element concentrations have been reported in blood samples from hemodialysis patients, they have not been well investigated in scalp hair. In the present study, 22 trace elemental concentrations were measured by inductively coupled plasma-atomic emission spectrometry in the scalp hair of 80 male hemodialysis patients and compared with those of 100 healthy male subjects. In hemodialysis patients, the concentrations of beryllium, arsenic, magnesium, chromium, manganese, iron, selenium, molybdenum, iodine, vanadium, and cobalt were significantly higher than those in healthy subjects, while lead, mercury, copper, germanium, and bromine were significantly lower than those in the former group. No significant differences were observed for lithium, aluminum, cadmium, zinc, boron, or nickel. There were significant positive correlations between the duration of hemodialysis and the magnesium and manganese concentrations. There was a significant negative correlation between cadmium concentration and the duration of hemodialysis. There were significant positive correlations between dialysis efficacy (Kt/V) and magnesium, manganese, zinc, and selenium concentrations. In conclusion, trace element concentrations of the scalp hair are different between hemodialysis patients and healthy subjects. Essential trace elements, such as magnesium, manganese, zinc, and selenium, may be affected by the duration of hemodialysis and Kt/V.

Protective role of Moringa oleifera (Sajina) seed on arsenic-induced hepatocellular degeneration in female albino rats

In an attempt to develop new herbal therapy, an aqueous extract of the seed of Moringa oleifera was used to screen the effect on arsenic-induced hepatic toxicity in female rat of Wistar strain. Subchronic exposure to sodium arsenite (0.4 ppm/100 g body weight/day via drinking water for a period of 24 days) significantly increased activities of hepatic and lipid function markers such as alanine transaminase, aspartate transaminase, cholesterol, triglycerides, LDL along with a decrease in total protein and HDL. A notable distortion of hepatocellular histoarchitecture was prominent with a concomitant increase in DNA fragmentation following arsenic exposure. A marked elevation of lipid peroxidation in hepatic tissue was also evident from the hepatic accumulation of malondialdehyde and conjugated dienes along with suppressed activities in the antioxidant enzymes such as superoxide dismutase and catalase. However, co-administration of aqueous seed extract of M. oleifera (500 mg/100 g body weight/day for a period of 24 days) was found to significantly prevent the arsenic-induced alteration of hepatic function markers and lipid profile. Moreover, the degeneration of histoarchitecture of liver found in arsenic-treated rats was protected along with partial but definite prevention against DNA fragmentation induction. Similarly, generation of reactive oxygen species and free radicals were found to be significantly less along with restored activities of antioxidant enzymes in M. oleifera co-administered group with comparison to arsenic alone treatment group. The present investigation offers strong evidence for the hepato-protective and antioxidative efficiencies of M. oleifera seed extract against oxidative stress induced by arsenic.

Nutrigenetics, nutrigenomics, and selenium

Selenium (Se) is an important micronutrient that, as a component of selenoproteins, influences oxidative and inflammatory processes. Its’ levels vary considerably, with different ethnic and geographic population groups showing varied conditions, ranging from frank Se deficiencies to toxic effects. An optimum Se level is essential for the maintenance of homeostasis, and this optimum may vary according to life stage, general state of health, and genotype. Nutrigenetic studies of different Se levels, in the presence of genetic variants in selenoproteins, suggest that an effective dietary Se intake for one individual may be very different from that for others. However, we are just starting to learn the significance of various genes in selenoprotein pathways, functional variants in these, and how to combine such data from genes into pathways, alongside dietary intake or serum levels of Se. Advances in systems biology, genetics, and genomics technologies, including genetic/genomic, epigenetic/epigenomic, transcriptomic, proteomic, and metabolomic information, start to make it feasible to assess a comprehensive spectrum of the biological activity of Se. Such nutrigenomic approaches may prove very sensitive biomarkers of optimal Se status at the individual or population level. The premature cessation of a major human Se intervention trial has led to considerable controversy as to the value of Se supplementation at the population level. New websites provide convenient links to current information on methodologies available for nutrigenetics and nutrigenomics. These new technologies will increasingly become an essential tool in optimizing the level of Se and other micronutrients for optimal health, in individuals and in population groups. However, definitive proof of such effects will require very large collaborative studies, international agreement on study design, and innovative approaches to data analysis.