Effect of selenium on lead-induced alterations in rat brain

Possible role of selenium in ameliorating lead-induced neurotoxicity in the cerebrum of adult male rats: an experimental study

Chronic lead (Pb) poisoning is one of the greatest public health risks. The nervous system is the primary and most vulnerable target of Pb poisoning. Selenium (Se) has been shown to be a potential protection against heavy metal toxicity through anti-inflammatory and antioxidant properties. Therefore, the present study aimed to elucidate the possible protective role of Se in ameliorating the effects of Pb on rat cerebral structure by examining oxidative stress and markers of apoptosis. The rats were divided into 6 groups: control group, Se group, low Pb group, high Pb group, low Pb + Se group, high Pb + Se group. After the 4-week experiment period, cerebral samples were examined using biochemical and histological techniques. Pb ingestion especially when administered in high doses resulted in cerebral injury manifested by a significant increase in glial fibrillary acidic protein, malondialdehyde (MDA) marker of brain oxidation and DNA fragmentation. Moreover, Pb produced alteration of the normal cerebral structure and cellular degeneration with a significant reduction in the total number of neurons and thickness of the frontal cortex with separation of meninges from the cerebral surface. There was also a decrease in total antioxidant capacity. All these changes are greatly improved by adding Se especially in the low Pb + Se group. The cerebral structure showed a relatively normal histological appearance with normally attached pia and an improvement in neuronal structure. There was also a decrease in MDA and DNA fragmentation and an increase TAC. Selenium is suggested to reduce Pb-induced neurotoxicity due to its modulation of oxidative stress and apoptosis.

Selenium attenuates the association of co-exposure to arsenic, cadmium, and lead with cognitive function among Chinese community-dwelling older adults

The effects of interactions between the toxic and essential metal mixtures on cognitive function are poorly understood. This study aims to identify the joint association of arsenic (As), cadmium (Cd), and lead (Pb) with cognitive function in older adults and the moderating role of selenium (Se), zinc (Zn), and copper (Cu) in this association. This study included 1000 community-dwelling older adults. Cognitive function was assessed by the Mini-Mental State Examination (MMSE). Blood concentrations of As, Cd, Pb, Se, Zn, and Cu were measured using inductively coupled plasma mass spectrometry. Linear regression and Bayesian kernel machine regression (BKMR) models were applied to assess the individual and joint associations of As, Cd, and Pb with cognitive function and to examine whether Se, Zn, and Cu (individually and as a mixture) modified these associations. In the adjusted single-metal models, both Cd (β = - 0.37, 95% CI: - 0.73 to - 0.01) and Pb (β = - 0.44, 95% CI: - 0.86 to - 0.02) were associated with MMSE scores, while Se (β = 0.71, 95% CI: 0.30 to 1.13) exhibited a positive relationship with MMSE scores. Univariate exposure-response functions from BKMR models showed similar results. Moreover, the toxic metal mixture (As, Cd, and Pb) exhibited a significant negative association with MMSE scores in a dose-response pattern, with Pb being the greatest contributor within the mixture. The negative association of Pb alone or the toxic metal mixture with MMSE scores became weaker at higher concentrations of Se within its normal range, especially when Se levels were greater than the median (89.18 μg/L). Our findings support that Se can attenuate the negative associations of exposure to single Pb or the As, Cd, and Pb mixtures with cognitive function. Future prospective studies are needed to replicate our findings.

The Level of Selenium and Oxidative Stress in Workers Chronically Exposed to Lead

The possible beneficial role of selenium (Se) on the oxidative stress induced by lead (Pb) is still unclear in humans. Therefore, the aim of the present study was to explore the associations among the Se levels, chronic Pb exposure, oxidative stress parameters, and parameters characterizing the function of the antioxidant defense system in men who are occupationally exposed to Pb. Based on the median serum Se concentrations, the 324 study subjects were divided into two subgroups: a subgroup with a low Se level (L-Se) and a subgroup with a high Se level (H-Se). The levels of lead (PbB) and zinc protoporphyrin (ZPP) in the blood and the delta-aminolevulinic acid (ALA) level in the urine served as indices of Pb exposure. The PbB level was significantly lower in the H-Se group compared to that in the L-Se group by 6 %. The levels of 8-hydroxyguanosine and lipofuscin (LPS) and the activity of superoxide dismutase were significantly lower in the H-Se group compared to that in the L-Se group by 17, 19, and 11 %, respectively. However, the glutathione level (GSH) and the activities of glutathione peroxidase (GPx) and catalase were significantly higher by 9, 23, and 3 %. Spearman correlations showed positive associations between the Se level and GPx activity and GSH level. A lower serum Se level in chronically Pb-exposed subjects is associated with higher Pb blood levels and an elevated erythrocyte LPS level, which reflects the intensity of oxidative stress. Besides, in a group of Pb-exposed subjects with lower serum Se level, depleted GSH pool and decreased activity of GPx in erythrocytes were reported. However, the present results are inadequate to recommend Se supplementation for chronic lead exposure at higher doses than would be included in a normal diet except for selenium deficiency.

Effects of low-level organic selenium on lead-induced alterations in neural cell adhesion molecules

Low-level lead (Pb) exposure has been reported to impair the formation and consolidation of learning and memory by inhibiting the expression of neural cell adhesion molecules (NCAMs) and altering the temporal profile of its polysialylation state. In this study, we investigated whether administration of low-level organic selenium (selenomethionine, Se) at different time points could affect Pb-induced changes of NCAMs in female Wistar rats. Here we reported that the exposure of Se (60μg/kg body weight/day) at different time points significantly alleviated Pb-induced reductions in the mRNA and protein levels of NCAMs, and increases in the mRNA levels of two polysialyltransferases (St8sia II, Stx; St8sia IV, Pst) as well as the sialyltransferase activity (p<0.05). The concentrations of Pb in blood and hippocampi of Wistar rats treated with the combination of Se and Pb were significantly lower than those treated with Pb alone (p<0.05). Our results suggest that low-level organic Se can not only prevent but also reverse Pb-induced alterations in the expression and polysialylated state of NCAMs as well as the concentration of Pb in rat blood and hippocampus.

The effect of occupational lead exposure on blood levels of zinc, iron, copper, selenium and related proteins

The study objective was to evaluate the effect of occupational lead exposure on blood concentrations of zinc, iron, copper, selenium and proteins related to them, such as transferrin, caeruloplasmin and haptoglobin. The examined group consisted of 192 healthy male employees of zinc-lead works. By the degree of lead exposure, the exposed group was subdivided into three subgroups. The control group was composed of 73 healthy male administrative workers. The markers of lead exposure (blood levels of lead and zinc protoporphyrin) were significantly elevated in the exposed group compared with the control group. Additionally, concentrations of copper and caeruloplasmin were raised. The significant increase in haptoglobin level was observed only in the low exposure group. Selenium levels were significantly decreased, whereas iron, zinc and transferrin levels were unchanged in the exposed group compared with the control group. There were positive correlations between the lead toxicity parameters and the copper and caeruloplasmin levels. In conclusion, the effect of occupational exposure to lead on the metabolism of trace metals appears to be limited. However, significant associations between lead exposure and levels of copper and selenium were shown. Changed levels of positive acute-phase proteins, such as caeruloplasmin and haptoglobin, were also observed.

Effects of dietary lead and/or dimercaptosuccinic acid exposure on regional serotonin and serotonin metabolite content in rainbow trout (Oncorhynchus mykiss)

The lead (Pb) chelator, meso-2,3-dimercaptosuccinic acid (DMSA) may be effective in reversing some of the adverse effects of Pb exposure. Pb-induced behavioral deficits observed in fish are due to disruptions in the integrative functioning of the medulla, cerebellum, and optic tectum. Pb exposure increased serotonin (5-HT) content in all three brain regions without an effect on 5-hydroxy-3-indoleacetic acid (5-HIAA). Pb exposure followed by no Pb in the diet increased 5-HT and 5-HIAA content in all three brain regions. The replacement of dietary Pb with DMSA had no effect on 5-HT and increased 5-HIAA content. DMSA increased 5-HIAA content in all three brain regions and increased 5-HT content only the optic tectum. Treatment with DMSA may be more effective than removal of Pb from the diet in reversing Pb-induced alterations in 5-HT.

Selenium and the brain: a review

Similar to other tissues selenium from selenomethionine is deposited in the brain at higher concentrations than selenium in other forms. Vitamin E has a greater effect than selenium in reducing lipid peroxidation in various brain regions. Selenium does not have as great effect on glutathione peroxidase (GPX) activity in the brain as in most other organs. Prolonged selenium and iodine deficiencies will compromise thyroid hormone homeostatus in the brain and this is due to changes in deiodinases activities and lipid peroxidation. Even though selenium deficiency results in reduced GPX activity and selenium content in the brain, there is no reduction in thioredoxin reductase activity or selenoprotein W levels. Selenoprotein P is taken up in greater amounts by the brain but not by other organs in selenium deficient animals, suggesting a critical function of this selenoprotein in this organ. Selenium will influence compounds with hormonal activity (and neurotransmitters) in the brain, and this is postulated to be the reason selenium affects moods in humans and behavior in animals. Even though selenium counteracts the neurotoxicity of mercury, cadmium, lead and vanadium, it causes them to accumulate in the brain, presumably in a nontoxic complex.

The accumulation effect of lead on DNA damage in mice blood cells of three generations and the protection of selenium

The accumulation effect of lead on DNA damage and the protection of selenium against lead were studied in mice blood cells of three generations. The test animals were divided into four groups: controls, Pb group, Se group, Pb + Se group. Lead and Selenium were administered to mice in the drinking water. The concentrations of lead (in form of lead acetate) and selenium (in form of Kappa-selenocarrageenan) used in this paper were 1 microgram/ml and 0.25 microgram/ml respectively. The percentage of damaged cells (DNA comets) was examined and detected conveniently by the single-cell gel electrophoresis (comet) assay. Results showed that 1 microgram/ml lead did not damage the female mice blood cells of the first generation seriously. However, there was a significant damage effect in both sexes of the second and third generations, suggesting the accumulation effect of lead was very significant starting from the second generation. In addition, under normal physiological conditions, Kappa-Se did not appear to enhance the protective ability on DNA damage significantly, whereas under lead exposure conditions, administration of Kappa-Se displayed the occurrence of a good protection against lead intoxication which was started from the female mice of the second generation.

Protection by selenium of lead-acetate-induced alterations on rat submandibular gland function

Pure submandibular saliva was collected intraorally by micro polyethylene cannulation of anaesthetized rats using pilocarpine as a secretagogue. Twenty-four days treatment with lead acetate 0.05% in drinking water altered salivary function. Except for flow rate that was (P<0.01) increased by lead acetate, the reminder of parameters, concentrations of total protein and calcium and the activity of N-acetyl-beta-D-glucosaminidase (NAG) in submandibular secretions were decreased significantly (P<0.01) by lead acetate. Selenium (2.5 mg l(-1)) in drinking water for 24 days did not induce any significant change in saliva secretory function. Pretreatment by selenium, prevented the lead acetate-induced decrease of NAG activity and concentrations of calcium and protein (P<0.01). The increased flow rate by lead acetate was also affected by selenium pretreatment and reached the level of control. It is concluded that selenium can protect rat submandibular gland function from lead-acetate-induced adverse effects. Properties of selenium as an antioxidant, free radical scavenger and maintenance of cell membrane integrity may be possible mechanisms of its protective effects.