Selenium and glutathione peroxidases in blood of patients with different stages of chronic renal failure

In patients with chronic renal failure (CRF) Se concentration in blood components is usually lower as compared with healthy controls. One of the five known forms of Se-dependent glutathione peroxidases (GSH-Px), the plasma GSH-Px, is synthesized primarily in the kidney. In CRF patients, plasma GSH-Px activity is reduced and the reduction increases with the progress of the disease.

The Se concentration in blood components was measured spectrofluorometrically with 2,3-diaminonaphthalene as complexing reagent. Activities of GSH-Px in red cells and in plasma were assayed by the coupled method with t-butyl hydroperoxide as substrate. The study group consisted of 150 patients in different stages of CRF. The results were compared with the values for 30 healthy subjects.

Se concentrations in whole blood and plasma of the entire group of patients were significantly lower (p < 0.01) as compared with the healthy subjects. In the incipient stage, however, the Se levels in all blood components were non-significantly lower. In whole blood and plasma the Se levels gradually decreased, reaching in the end stage values that were lower by 29 to 32% (p < 0.0001) as compared with the control group. Total protein and albumin levels in plasma of patients were significantly lower (p < 0.0001) as compared with healthy subjects and they decreased linearly with the progress of the disease. Positive and highly significant correlations were noted between total plasma protein and plasma Se concentrations (p < 0.0001) as well as between plasma albumin and plasma Se concentrations (p < 0.0001).

Red cell GSH-Px activity in the entire group of patients was lower (p < 0.05) than in the control group and did not change significantly with the progress of the disease. In plasma, however, GSH-Px activity of the entire group was lower by 33% (p < 0.0001) as compared with healthy subjects and decreased gradually with increasing renal failure. Highly significant, inverse correlations were seen between creatinine levels and plasma GSH-Px activities (p < 0.0001) as well as between urea nitrogen levels and plasma GSH-Px activities (p < 0.0001) when all stages of the disease were included.

In conclusion, patients with CRF exhibit lower Se levels in blood components as compared with healthy subjects. In whole blood and plasma these levels decrease with the progress of the disease. Plasma GSH-Px activity in patients was extremely reduced and it dramatically decreased with the progress of the illness.     

Selenium and glutathione levels, and glutathione peroxidase activities in blood components of uremic patients on hemodialysis supplemented with selenium and treated with erythropoietin

Patients with chronic renal failure (CRF) often have reduced concentrations of selenium (Se) and lowered activities of glutathione peroxidase (GSH-Px) in blood components. The kidney is a major source of plasma GSH-Px. We measured Se and glutathione levels in blood components and red cell and plasma GSH-Px activities in 58 uremic patients on regular (3 times a week) hemodialysis (HD). The dialyzed patients were divided in 4 subgroups and were supplemented for 3 months with: 1) placebo (bakers yeast), 2) erythropoietin (EPO; 3 times a week with 2,000 U after each HD session), 3) Se-rich yeast (300 μg 3 times a week after each HD), and 4) Se-rich yeast plus EPO in doses as above. The results were compared with those for 25 healthy subjects. The Se concentrations and GSH-Px activities in the blood components of dialyzed uremic patients were significantly lower compared with the control group. Treatment of the HD patients with placebo and EPO only did not change the parameters studied. The treatment with Se as well as with Se and EPO caused an increase in Se levels and red cell GSH-Px activity. Plasma GSH-Px activity, however, increased only slowly or did not change after treatment with Se and with Se plus EPO. In the group treated with Se plus EPO the element concentration in blood components was higher compared with the group supplemented with Se alone. The weak or absence of response in plasma GSH-Px activity to Se supply indicates that the impaired kidney of uremic HD patients has reduced possibilities to synthesize this enzyme.     

Selenium modifies glutathione peroxidase activity and glutathione concentration in mice exposed to ozone-provoked oxidative stress

The aim of this study was to show the direct effect of selenium on glutathione peroxidase (GSH-Px) activity and GSH/GSSG concentrations in 3- and 6-month-old mice. An ozone-oxygen mixture was used to provoke an oxygen stress. To measure the Se-effect mice were gavaged with sodium selenite. GSH-Px activity and total glutathione concentrations were determined in serum and in the postnuclear fraction of liver and lungs. Additionally glutathione concentrations were determined in whole blood. Both ozone and selenium, administered separately, reduced GSH-Px activity in lungs of 6-month-old animals, while in young mice an opposite effect of Se was observed. Ozone administered jointly with Se did not influence GSH-Px activity in 6-month-old mice, while in young, 3-month-old mice, a stimulatory effect in lungs was observed. There were no significant changes in GSH-Px activity in the liver of 6-month-old mice, but the stimulatory effect occurred in young mice treated with Se and Se & ozone jointly. In young mice, ozone (also ozone with Se) augmented glutathione concentrations. The response to ozone and selenium strictly depended on age and the antagonism between selenium and ozone was observed only in a few cases.     

Effects of dietary selenium supplementation on tissue selenium distribution and glutathione peroxidase activity in Chinese Ring Necked Pheasants

The objective of this study was to determine the concentration of total selenium (Se) and the proportions of total Se comprised as selenomethionine (SeMet) and selenocysteine (SeCys) in the postmortem tissues of female pheasants (Phasianus Colchicus Torquator) offered diets that contained graded additions of selenised-enriched yeast (SY) or a single comparative dose of sodium selenite (SS). Thiobarbituric acid reactive substances (TBARS) and tissue glutathione peroxidase (GSH-Px) activity of breast (Pectoralis Major) were assessed at 0 and 5 days postmortem. A total of 216 female pheasant chicks were enrolled into the study. Twenty-four birds were euthanased at the start of the study, and samples of blood, breast muscle, leg muscle (M. Peroneus Longus and M. Gastrocnemius), heart, liver, kidney and gizzard were collected for determination of total Se. Remaining birds were blocked by live weight and randomly allocated to one of four dietary treatments (n = 48 birds/treatment) that either differed in Se source (SY v. SS) or dose (control (0.17 mg total Se/kg), SY-L and SS-L (0.3 mg/kg total Se as SY and SS, respectively) and SY-H (0.45 mg total Se/kg)). Following 42 and 91 days of treatment, 24 birds per treatment were euthanased, and samples of blood, breast muscle, leg muscle, heart, liver, kidney and gizzard were retained for determination of total Se and the proportion of total Se comprised as SeMet or SeCys. Whole blood GSH-Px activity was determined at each time point. Tissue GSH-Px activity and TBARS were determined in breast tissue at the end of the study. There were increases in both blood and tissues to the graded addition of SY to the diet (P < 0.001), but the same responses were not apparent with the blood and tissues of selenite-supplemented birds receiving a comparable dose (SY-L v. SS-L). Although there were differences between tissue types in the distribution of SeMet and SeCys, there were few differences between treatments. There were effects of treatment on erythrocyte GSH-Px activity (P = 0.012) with values being higher in treatments SY-H and SS-L when compared with the negative control and treatment SY-L. There were no effects of treatment on tissue GSH-Px activity, which is reflected in the overall lack of any treatment effects on TBARS.     

Effect of supplementation with selenium on whole blood glutathione peroxidase activities and on plasma and tissue selenium concentrations in lambs

In recent years the selenium (Se) intake of the human population of the UK has shown a marked decline from 60 μg/d in 1978 to around 30 μg/d in 1990 owing largely to a significant reduction in the importation of North American wheat for bread-making fluor. Other countries (Finland, for example) in similar situations have instituted fertilization programs in order to raise cereal Se concentrations and thus boost dietary intakes. An alternative approach would be to increase the Se concentration of carcass meat by supplementation of meat animals for a limited period prior to slaughter. A trial was set up with store lambs to evaluate this approach. Sixteen Scottish Blackface lambs were stratified according to live weight and then randomly allocated to one of four treatments: unsupplemented, or 3.5, 7, or 10.5 mg. Se/head/wk. After 14 wk, the lambs were sacrificed and samples of shoulder and thigh muscle, liver, and kidney were obtained for analysis. All three treatments effected an increase in whole blood glutathione peroxidase (GSH-Px) and plasma Se concentrations over controls. Shoulder, thigh, and liver Se exhibited a dose-response relationship to treatment, but kidney Se concentrations were unaffected by treatment. Muscle and some organ meat Se concentrations can therefore be increased by supplementation and could contribute to increased human dietary intakes of the element.     

Lymphocyte glutathione peroxidase activity during exacerbations in multiple sclerosis

Glutathione peroxidase, one of the major antioxidants in the human brain, has been found to have decreased activity in patients suffering from multiple sclerosis (MS). This study compares the activity of lymphocyte glutathione peroxidase (L-GSH-px) in MS patients suffering from acute relapses with clinically stable MS patients and with control patients referred with nondemyelinating neurological diseases. All three groups showed an increase of mean enzymatic activity (MEA) during the observation period. The highest MEA in this study was observed in the MS groups. However, there were no significant differences in the L-GSH-px activity in the three groups. These results are not in accordance with previous investigations, and the need for further research in this field is emphasized.     

Selenium concentrations and glutathione peroxidase activities in blood of patients before and after allogenic kidney transplantation

In animals and humans, the highest level of selenium (Se) occurs in the kidney. This organ is also the major site of the synthesis of the selenoenzyme glutathione peroxidase (GSH-Px). Decreased Se levels and GSH-Px activities in blood are common symptoms in the advanced stage of chronic renal failure (CRF). Blood samples for Se levels and GSH-Px activities measurements from patients were collected just before transplantation and 3, 7, 14, 30, and 90 d posttransplant. The Se levels in whole blood and plasma of patients before transplantation (79.5 and 64.5 ng/mL, respectively) were lower by 23% and 21%, respectively, as compared with controls (p<0.0001), and 7 d after operation, it further decreased in both components (p<0.01). Fourteen days after surgery, the levels reached the initial values and increased slowly in the later period. Red blood cell GSH-Px activity in patients in the entire period of the study did not differ from the control group. Plasma GSH-Px of patients before the surgery was extremely low (76 U/L) as compared with controls (243 U/L; p<0.0001) but increased rapidly to 115 U/L after 3 d, to 164 U/L after 14 d, and to 208 U/L after 3 mo posttransplant. In CRF patients, after kidney transplantation, plasma GSH-Px activity increased rapidly, approaching, after 3 mo, the values that were close to the normal levels. A negative correlation between creatinine level and plasma GSH-Px activity is observed in patients after kidney transplantation. Monitoring of plasma GSH-Px activity may be a useful additional marker of the transplanted kidney function.     

Accumulation of plasma N-methyl-2-pyridone-5-carboxamide in patients with chronic renal failure

Intracellular catabolism of NAD in mammalian cells occurs mainly via reaction catalyzed by poly(ADP-ribose) polymerase (PARP) with the release of nicotinamide, which is then metabolized predominantly to N-methyl-2-pyridone-5-carboxamide (2PY). PARP could be activated by binding to broken DNA and is known to be involved in DNA repair mechanisms, cell stress response and regulation of apoptosis. 2PY may accumulate under disease conditions resulting in accelerated DNA damage and retention of catabolic products. Our hypothesis was that chronic renal failure would lead to elevation of 2PY and potentially to inhibition of PARP and related physiological mechanisms. In the present study we: (a) compared plasma 2PY concentration in healthy subjects and in patients with chronic renal failure (CRF); (b) evaluated the relationship between plasma 2PY concentration and the severity of CRF; (c) evaluated the effect of hemodialysis treatment and kidney transplantation on 2PY concentration.We found that the plasma 2PY concentration in healthy subjects is 0.83 ± 0.18 M but it could increase up to 40 M in patients with CRF. A significant correlation was found in CRF between plasma 2PY and creatinine concentration. A single hemodialysis treatment was associated with significant reduction of plasma 2PY concentration after the hemodialysis, but it increased rapidly 48 h after the end of treatment. Successful kidney transplantation was associated with return of 2PY concentration to the normal range.In conclusion, our results indicated significant production of 2PY in humans. In healthy subjects 2PY is cleared from the plasma by excretion in the urine. Altered excretion by the kidney leads to increase in plasma concentration of 2PY. It is possible that 2PY may play a significant role in the development of uremic toxemia, especially as an inhibitor of poly(ADP-ribose)polymerase.     

Effect of vitamin E and selenium supplementation of cockerel diets on glutathione peroxidase activity and lipid peroxidation susceptibility in sperm, testes, and liver

The phospholipids of avian spermatozoa are characterized by high proportions of arachidonic (20:4n-6) and docosatetraenoic (22:4n-6) fatty acids and are therefore sensitive to lipid peroxidation. α-Tocopherol and glutathione peroxidase [GSH-Px] are believed to be the primary components of the antioxidant system of the spermatozoa. The present study evaluates the effect of vitamin E and vitamin E plus Se supplementation of the cockerel diet on GSH-Px activity, vitamin E accumulation, and lipid peroxidation in the spermatozoa, testes, and liver. At the beginning of the experiment 75 Rhode Island Red cockerels were divided into five groups, kept in individual cages, and fed a wheat-barley-based ration balanced in all nutrients. Supplements fed to the different groups were as follows: vitamin E, 0, 20, 200, 20, and 200 mg/kg to groups 1–5, respectively, with groups 4 and 5 also receiving 0. 3 mg Se/kg. The vitamin E supplementation produced increased levels of α-tocopherol in semen, testes, and liver. The inclusion of the Se into the cock diet had a significant (P < 0.01) stimulating effect on GSH-Px activity in seminal plasma, spermatozoa, testes, and liver. The increased vitamin E concentration in the spermatozoa was associated with a reduction in their susceptibility to lipid peroxidation. Similarly, the increased GSH-Px activity provided enhanced protection against lipid peroxidation.     

Investigation of albumin properties in patients with chronic renal failure

The aim of this study was the investigation of HSA properties and its structural changes after modification induced in vivo among patients with CRF who underwent haemodialysis. Application of different fluorescent dyes allowed the investigation of different regions of albumin molecule using ANS, bis-ANS, piren, piren maleimide and fluorescein isothiocyanate. As markers of oxidative modification, the total protein thiol, carbonyls, glycosylated plasma proteins and hydroperoxide were estimated in plasma. Additionally, this study investigated plasma viscosity and total antioxidant capacity (TAC) of the plasma. Results show that haemodialysis provoked significant changes in conformational properties of plasma albumin, which resulted in the loss of its biological functions. These findings suggest that oxidative stress and glycation of proteins in plasma are developed during haemodialysis. The results depict that one of the features of uraemia is the presence of signs of oxidative stress before haemodialysis. Nevertheless, oxidative stress and glycation of proteins in plasma are exacerbated during haemodialysis and are a complex process.     

Oxidative stress in patients with cardiovascular disease and chronic renal failure

Abstract

Oxidative response regulates many physiological response in human health, but if not properly regulated it could also lead to a number of deleterious effects. The importance of oxidative stress injury depends on the molecular target, the severity of the stress, and the mechanism by which the oxidative stress is imposed: it has been implicated in several diseases including cancer, neurodegenerative diseases, malaria, rheumatoid arthritis and cardiovascular and kidney disease. Most of the common diseases, such as hypertension, atherosclerosis, heart failure, and renal dysfunction, are associated with vascular functional and structural alterations including endothelial dysfunction, altered contractility, and vascular remodeling. Common to these processes is increased bioavailability of reactive oxygen species (ROS), decreased nitric oxide (NO) levels, and reduced antioxidant capacity. Oxidative processes are up-regulated also in patients with chronic renal failure (CRF) and seem to be a cause of elevated risk of morbidity and mortality in these patients.

In this review, we highlight the role of oxidative stress in cardiovascular and renal disease.     

Selenium status is decreased in patients with intrinsic asthma

Lowered selenium (Se) status has been observed in asthma patients. An increased production of reactive oxygen species (ROS) owing to inflammatory condition has also been found in these patients and thus antioxidant properties of Se via glutathione peroxidase (GPx) activity are of great importance. Concentrations of Se in plasma and erythrocytes as well as eryth-rocyte GPx activity in 22 intrinsic asthma patients (five patients; all women were aspirin-sensitive) were compared with those of 33 control subjects. Se concentrations in both plasma and erythrocytes and GPx activity were decreased in intrinsic asthma patients. There were no significant differences in investigated parameters of Se status between aspirin-tolerant and aspirin-intolerant patients within intrinsic asthma group. Significantly high positive correlation between plasma and erythrocyte Se concentrations was found when regarding all subjects as a whole. Se supplementation might be beneficial to patients with intrinsic asthma, which may be at risk of Se deficiency.     

Effect of selenium and protein deficiency on selenium and glutathione peroxidase in rats

Twenty-four weanling male Wistar rats were divided into four groups fed diets containing adequate or deficient levels of selenium (0.5 ppm [+ Se] or <0.02 ppm [−Se] and protein (15% [+Pro] or 5% [−Pro]), but adequate levels of all other nutrients for 4 wk to determine the effects of Se deficiency and protein deficiency on tissue Se and glutathione peroxidase (GSHPx) activity in rats. Plasma, heart, liver, and kidney Se and GSHPx were significantly lower in Se-deficient groups in relation to Se-sufficient groups. In Se-deficient groups, Se and GSHPx were significantly higher in −Se−Pro rats in heart, liver, and kidney. Data analysis showed that there were significant interaction effects between dietary Se and protein on Se and GSHPx of rats. It is assumed that under the condition of Se deficiency. a low level of protein may decrease Se and GSHPx utilization, increase GSHPx synthesis, and result in Se redistribution. This could account for high levels of Se and GSHPx in the −Se−Pro rats compared to −Se+Pro rats.     

Human catalytic antibody Se-scFv-B3 with high glutathione peroxidase activity

In order to generate catalytic antibodies with glutathione peroxidase (GPX) activity, we prepared GSH-S-2,4-dinitrophenyl t-butyl ester (GSH-S-DNPBu) as target antigen. Three clones (A11, B3, and D5) that bound specifically to the antigen were selected from the phage display antibody library (human synthetic VH + VL single-chain Fv fragment (scFv) library). Analysis of PCR products using gel electrophoresis and sequencing showed that only clone B3 beared intact scFv-encoding gene, which was cloned into the expression vector pPELB and expressed as soluble form (scFv-B3) in Escherichia coli Rosetta. The scFv-B3 was purified by Ni(2+)-immobilized metal affinity chromatography (IMAC). The yield of purified proteins was about 2.0-3.0 mg of proteins from 1 L culture. After the active site serines of scFv-B3 were converted into selenocysteines (Secs) with the chemical modification method, we obtained the human catalytic antibody (Se-scFv-B3) with GPX activity of 1288 U/micromol. Copyright (c) 2008 John Wiley & Sons, Ltd.     

Selenium depletion in patients on home parenteral nutrition

Severe selenium (Se) depletion was found in nine patients receiving long-term home parenteral nutrition because of short bowel syndrome. Plasma Se ranged from 0–0.51 (median 0.21 μmol/L) and erythrocyte Se ranged from 0.7–2.6 (median 1.8 μmol/gHgb), which was significantly lower than in the controls. Glutathione peroxidase (GSHPx) in plasma and erythrocytes was also decreased. After bolus injections with 200 μg Se/d in the form of sodium selenite for 4 mo, followed by 100 μg/d for 8 mo, plasma Se increased to values slightly but significantly higher than in the controls. Erythrocyte Se reached normal levels in most of the patients after 4 mo substitution, but it remained lower than in the controls. Following Se supplementation, plasma and erythrocyte GSHPx did not differ between patients and controls. These data suggest that all patients receiving long-term parenteral nutrition because of short bowel syndrome should receive at least 100 μg sodium selenite/d when given as bolus injections to avoid Se depletion.     

Anti-apoptotic activity of the glutathione peroxidase homologue encoded by HIV-1

The third reading frame of the envelope gene from HIV-1 codes for a protein homologous to the human selenoprotein glutathione peroxidase (GPX). Cells stably or transiently transfected with a HIV-1 GPX construct are protected against the loss of the mitochondrial transmembrane potential and subsequent cell death induced by exogenous reactive oxygen species (ROS) as well as mitochondrion-generated ROS. However, HIV-1 GPX does not confer a general apoptosis resistance, because HIV-1 GPX-transfected cells were not protected against cell death induced by staurosporine or oligomycin. The inhibition of cell death induced by the ROS donor tert-butylhydroperoxide was also observed in cells depleted from endogenous glutathione (GSH), suggesting that GSH is not the sole electron acceptor for HIV-1 GPX. Clinical HIV-1 isolates from long-term non-progressors (untreated patients with diagnosed HIV-1 infection for > 10 years, with CD4 T cell count of > 500 cells/mm3) mostly possess an intact GPX gene (with only 18% of loss-of-function mutations), while HIV-1 isolates from patients developing AIDS contain non-functional GPX mutants in 9 out of 17 cases (53%). Altogether, these data suggest that HIV-1 GPX possesses a cytoprotective, pathophysiologically relevant function.     

Association of plasma manganese levels with chronic renal failure

Manganese (Mn) is an essential trace element involved in the formation of bone and in amino acid, lipid and carbohydrate metabolism. Mn excess may be neurotoxic to humans, affecting specific areas of the central nervous system. However, relatively little is known about its physiological and/or toxicological effects, and very few data are available concerning the role of Mn in chronic renal failure (CRF). This paper describes a 12-month study of the evolution of plasma Mn levels in predialysis patients with CRF and the relationship with energy and macronutrient intake. The participants in this trial were 64 patients with CRF in predialysis and 62 healthy controls. Plasma levels of creatinine, urea, uric acid, total protein and Mn were measured. The glomerular filtration rate (GFR) was calculated using the Cockcroft-Gault index. The CRF patients had higher plasma levels of creatinine, urea, uric acid and Mn and a lower GFR than the controls. Plasma Mn was positively correlated with creatinine, plasma urea and plasma uric acid and was negatively correlated with the GFR and the intake of energy and macronutrients. In conclusion, CRF in predialysis patients is associated with increases in circulating levels of Mn.     

The relative effectiveness of human plasma glutathione peroxidase as a catalyst for the reduction of hydroperoxides by glutathione

To reveal clues to the function of human plasma glutathione peroxidase (GPx), we investigated its catalytic effectiveness with a variety of hydroperoxides. Comparisons of hydroperoxides as substrates for plasma GPx based on the ratio ofV _max /K _m were blocked by the limited solubility of the organic hydroperoxides, which prevented kinetic saturation of the enzyme at the chosen glutathione concentration. Therefore, we compared the hydroperoxides by the fold increase in the apparent first-order rate constants of their reactions with glutathione owing to catalysis by plasma GPx. The reductions of aromatic and small hydrophobic hydroperoxides (cumene hydroperoxide,t-amyl hydroperoxide,t-butyl hydroperoxide, paramenthane hydroperoxide) were better catalyzed by plasma GPx than were reductions of the more “physiological” substrates (linoleic acid hydroperoxide, hydrogen peroxide, peroxidized plasma lipids, and oxidized cholesterol).     

Selenium supplementation of children in a selenium-deficient area in China

Keshan disease is a cardiomyopathy restricted to the endemic areas of China and seen in residents having an extremely low selenium (Se) status. Prophylactic administration of sodium selenite has been shown to decrease significantly the incidence of acute and subacute cases. The aim of the study was to assess the relative bioavailability of selenite versus organic Se-yeast in a Se-deficient area in China with a randomized double-blind double-dummy design. Healthy children (n=30) between 14 and 16 yr of age were randomized into three equal groups receiving either 200 μg/d selenite Se or 200 μg/d Se-yeast or placebo for 12 wk. Blood was drawn at baseline, 4, 8, and 12 wk and 4 wk postsupplementation. The plasma Se concentration (mean ± SD) was 0.16±0.03 μmol/L at baseline. Selenite and Se-yeast supplementation increased plasma Se to plateau values, 1.0±0.2 and 1.3±0.2 μmol/L, respectively. In red cells, Se-yeast increased the selenium level sixfold and selenite threefold compared to placebo. The relative bioavailability of Se-yeast versus selenite measured as glutathione peroxidase (GSHPx) activity was similar in plasma, red blood cells, and platelets. GSHPx activity reached maximal levels in plasma and platelets of 300% and 200%, respectively, after 8 wk compared to the placebo group, but continued to increase in red cells for 16 wk. Our study showed that although both forms of Se were equally effective in raising GSHPx activity, Se-yeast provided a longer lasting body pool of Se. Se-yeast may be a better alternative to selenite in the prophylaxis of Keshan disease with respect to building up of body stores.