Antioxidant enzymes--superoxide dismutase and glutathione peroxidase--in haemodialyzed patients

Fourier-Transform Infrared Imaging Spectroscopy and Laser Ablation -ICPMS New Vistas for Biochemical Analyses of Ischemic Stroke in Rat Brain

Objective: Stroke is the main cause of adult disability in the world, leaving more than half of the patients dependent on daily assistance. Understanding the post-stroke biochemical and molecular changes are critical for patient survival and stroke management. The aim of this work was to investigate the photo-thrombotic ischemic stroke in male rats with particular focus on biochemical and elemental changes in the primary stroke lesion in the somatosensory cortex and surrounding areas, including the corpus callosum.

Materials and Methods: FT-IR imaging spectroscopy and LA-ICPMS techniques examined stroke brain samples, which were compared with standard immunohistochemistry studies.

Results: The FTIR results revealed that in the lesioned gray matter the relative distribution of lipid, lipid acyl and protein contents decreased significantly. Also at this locus, there was a significant increase in aggregated protein as detected by high-levels Aβ_1-42. Areas close to the stroke focus experienced decrease in the lipid and lipid acyl contents associated with an increase in lipid ester, olefin, and methyl bio-contents with a novel finding of Aβ_1-42 in the PL-GM and L-WM. Elemental analyses realized major changes in the different brain structures that may underscore functionality.

Conclusion: In conclusion, FTIR bio-spectroscopy is a non-destructive, rapid, and a refined technique to characterize oxidative stress markers associated with lipid degradation and protein denaturation not characterized by routine approaches. This technique may expedite research into stroke and offer new approaches for neurodegenerative disorders. The results suggest that a good therapeutic strategy should include a mechanism that provides protective effect from brain swelling (edema) and neurotoxicity by scavenging the lipid peroxidation end products.

[Importance of selenium homeostasis in chronic and end-stage kidney diseases]

Selenium is an essential trace element for the human body with a significant antioxidant effect. Selenium deficiency and excess are both detrimental for proper functioning of the human body. The possible association between selenium deficiency and acute or chronic renal disease, along with their complications has been less intensively investigated, however, there are firm data showing that selenium deficiency and renal failure increase the risk of both coronary artery disease and total mortality. Further studies revealed that selenium deficiency increases the risk of death due to infection in patients treated with hemodialysis through dysfunction of the immune system. However, there are no data whether the imbalance of selenium metabolism, especially selenium deficiency, could cause chronic kidney disease or renal failure. As far as results of selenium measurements, there is convincing evidence that protein loss and renal replacement treatment reduce serum selenium levels. Despite some contradictory results obtained from various studies regarding selenium deficiency in chronic kidney diseases, it seems that selenium supplementation may be beneficial in many patients with severe or end-stage kidney disease including those treated with dialysis.

Effect of reuse of polysulfone membrane on oxidative stress during hemodialysis

Patients with chronic renal failure, especially those on long-term hemodialysis (HD), have a high incidence of premature cardiovascular disease. Oxidative stress, which occurs when there is an excessive free radical production or low antioxidant level, has recently been implicated as a causative factor in atherogenesis. Hourly changes in malondialdehyde (MDA) and antioxidant enzymes, vitamins, lipid profile and ferric reducing ability of plasma (FRAP) were studied with the first use and immediate subsequent reuse of polysulfone dialysis membrane in 27 patients on regular HD treatment. Data were corrected for hemoconcentration and standardized to measure the rate of change. Increase in MDA and erythrocyte catalase along with decrease in plasma vitamin E and FRAP levels and no change in glutathione peroxidase levels were observed as a result of both fresh and reuse dialysis. These findings indicate a net oxidative stress in both fresh as well as dialyzer reuse sessions. There was no significant change in oxidative stress in both fresh and reuse sessions. The oxidative stress with reuse dialysis was less when compared to first use dialysis, but the difference was not statistically significant.

Glutathione and Glutathione Peroxidase Activities in Blood of Patients in Early Stages Following Kidney Transplantation

This study focuses on glutathione (GSH) level in red blood cells, as well as on glutathione peroxidases (GSH-Px) activities in red blood cells and in plasma of chronic renal failure (CRF) patients following renal transplantation. We want to focus our main attention on plasma GSH-Px, the selenoenzyme that is synthesized primarily in the kidney. In CRF patients, activity of this enzyme is significantly reduced, and the reduction decreases with the progress of the disease, reaching in the end-stage 20% to 30% of the activity of healthy patients. We have shown that following renal transplantation the activity of plasma GSH-Px is restored very rapidly, and 2 weeks after surgery it reached the value of the control group. Red blood cell GSH level is significantly higher in CRF patients, and following transplantation, no significant changes were observed. Red blood cell GSH-Px activity before transplantation was the same as in healthy patients and did not change significantly after surgery.

Expression of catalase and glutathione peroxidase in renal insufficiency

Chronic renal failure (CRF) is associated with oxidative stress, the precise mechanism of which is yet to be elucidated. The present study was undertaken to investigate in renal insufficiency the expression of catalase and glutathione peroxidase, which play a critical role in antioxidant defense system by catalyzing detoxification of hydrogen peroxide (H2O2) and organic hydroperoxides. Rats were randomly assigned to the CRF (5/6 nephrectomized) and sham-operated control groups and observed for 6 weeks. Renal and thoracic aortic catalase and glutathione peroxidase protein abundance was measured by Western blotting. The enzyme activities in the renal and aortic extracts, hepatic glutathione levels, blood pressure and urinary nitric oxide metabolites (NO(x)) excretion were also measured. Blood pressure and urinary nitric oxide metabolite (NO(x)) excretion were also measured. The CRF group showed a significant down-regulation of both immunodetectable catalase and glutathione peroxidase proteins in the remnant kidney. Catalase activity was also significantly decreased in the remnant kidney whereas glutathione peroxidase activity was not significantly affected. Furthermore, the protein abundance of catalase was unchanged whereas the enzyme activity was significantly decreased in the thoracic aorta of CRF animals compared to the sham-operated controls. By contrast, both the protein abundance and the enzyme activity of glutathione peroxidase were not significantly affected in the aorta of CRF animals compared to the sham-operated controls. This was coupled with marked arterial hypertension, significant reduction of hepatic glutathione levels and urinary NO(x) excretion pointing to increased inactivation and sequestration of NO by superoxide. These events point to the role of impaired antioxidant defense system in the pathogenesis of oxidative stress in CRF.

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.

Evolution of oxidative stress and inflammation during hemodialysis and their contribution to cardiovascular disease

End-stage renal disease patients have increased cardiovascular morbidity and mortality. These patients have many unique risk factors, such as an accumulation of uremic toxins, electrolyte imbalances, metabolic disturbances, anemia, chronic inflammation, and thrombogenic disturbances. Oxidative stress has been implicated in many of these disturbances. This review will focus on some of the factors that may accelerate cardiovascular disease in uremic patients, with an emphasis on mechanisms and interactions of various components of oxidative stress and inflammation. Understanding the mechanisms of these pathways may be useful in developing effective prevention and treatment strategies.

Oxidative stress in haemodialysis--intradialytic changes

Oxidative stress is likely to be involved in the development of complications due to haemodialysis. Though there is evidence for production of oxygen free radicals during haemodialysis, reports on net oxidative imbalance due to a single dialysis session are conflicting. Hence, a time-course analysis of changes in lipid peroxides (LPO) along with antioxidant enzymes and vitamins was carried out. Hourly changes in LPO and antioxidants were studied during a first-use cuprophan membrane and acetate dialysis in 20 patients on regular haemodialysis treatment. Data were corrected for haemoconcentration and standardised to measure the rate of change before statistical evaluation using analysis of variance for repeated measures. The results of the study showed a net oxidative stress due to a single dialysis session in the form of increased plasma and erythrocyte lipid peroxidation, decrease in plasma vitamin E, slight increase in plasma superoxide dismutase and erythrocyte glutathione peroxidase and no change in plasma glutathione peroxidase. erythrocyte superoxide dismutase and plasma vitamin A levels. The oxygen radical production was found to be maximum in the first hour of dialysis.

Selenium, glutathione peroxidases, and some other antioxidant parameters in blood of patients with chronic renal failure

In the present study several parameters associated with oxidative stress were examined in the blood of 25 chronic renal failure (CRF) patients and the results were compared with 18 healthy subjects. Mean creatinine concentration in patients was 1,216 +/- 292 micromol/l. Selenium (Se) concentration in red cells, whole blood and in plasma of CRF patients (106 +/- 32.5, 59.0 +/- 16.7 and 42.4 +/- 13.8 ng/ml, respectively) was significantly (0.0001 < P 0.01) lower (by 20-42%) compared with the controls. Red cell and plasma glutathione peroxidase (GSH-Px) activities (16.6 +/- 3.4 U/g Hb and 93.7 +/- 32.9 U/l plasma) were lower by 12 and 53% (P < 0.05 and < 0.0001, respectively) in patients than in healthy subjects. GSH concentration in red cells of patients (2.81 +/- 0.45 mmol/l) was significantly (P < 0.001) higher (by 20%) than in control group. Malonyldialdehyde (MDA) concentration (expressed as thiobarbituric acid-reactive substances) in red cells of patients (725 +/- 155 nmol/g Hb) was significantly (P < 0.001) higher (by 28%) than in control group. No significant difference was observed in the activity of superoxide dismutase in pLasma between the two groups. In conclusion, our results confirm that the aLterations in Se levels in blood components and in GSH-Px activity in plasma show that the kidney plays an important role in Se homeostasis and in plasma GSH-Px synthesis.

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 microg 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.

Retinol and alpha-tocopherol in hemodialysis patients

The biological effects of reactive oxygen species and other radicals controlled by antioxidant mechanisms are modified by various enzymes and other substrates. Antioxidant substrates are divided into those with lipophilic and hydrophilic groups. Retinol and tocopherol are the main representations of lipophilic antioxidants. The aim of the present study was to describe the changes of retinol and alpha-tocopherol which occurred in hemodialysis (HD) patients in respect to the influence of antioxidant systems. The experimental group consisted of 14 patients on regular HD treatment. The control group consisted of 14 healthy blood donors. HPLC was used to measure retinol and alpha-tocopherol in serum. We found that the retinol concentration was significantly higher in HD patients compared to controls (2.35 +/- 0.95 versus 0.90 +/- 0.23 mg/L, p < 0.0001). The concentration of alpha-tocopherol in serum was not different in both study groups (7.32 +/- 3.01 versus. 8.94 +/- 3.57 mg/L). A review of the MEDLINE database since 1985 found a few references concerning these important antioxidant vitamins in HD patients and these contained contrasting results. It has been suggested that some of the complications related to HD including cardiovascular complications, anemia and atherosclerosis may be due to ineffective antioxidant systems and/or to increased free oxygen radical production. The question about supplementation of antioxidants in HD patients is open although there are some positive data regarding the use of moderate and safe selenium supplementation in HD patients. HD patients treated by erythropoietin had increased plasma concentration of retinol and normal level of alpha-tocopherol compared to healthy group. However, this positive finding did not affect lipid peroxidation, which is increased in HD patients and leads to some complications during HD treatment.