Red blood cell lipid peroxidation in predialysis chronic renal failure.

In hemodialysis patients the pentose-phosphate shunt activity is deficient. As a consequence, the lipid peroxidation of the erythrocyte membranes is increased as shown by the increase in malonyldialdehyde concentrations and is accompanied by a decrease of the level of vitamin E in RBC. In the present study we have found that increased lipid peroxidation of the erythrocyte membranes is present also in chronic renal failure patients in the predialysis state, provided that the serum creatinine levels are higher than 5 mg/dl.

Vitamin E supplementation in hemodialysis patients: effects on peripheral blood mononuclear cells lipid peroxidation and immune response.

Lipid peroxidation and vitamin E levels in peripheral blood mononuclear cells (PBMC) were studied in 10 patients on maintenance hemodialysis. Significant increases of PBMC malonyldialdehyde (MDA) were detected, together with low vitamin E levels. After a fifteen-day-course of parenteral vitamin E supplementation, PBMC MDA reverted to normal values, while PBMC vitamin E levels remained lower than controls. In a parallel study an immunological monitoring was performed in the same patients before and after vitamin E supplementation. NK activity and PHA blastogenesis were not influenced by treatment, while a reduction of the number of OKT8+ lymphocytes were observed after vitamin E therapy. It is tempting to speculate that peroxidative damage of PBMC cell membranes in hemodialysis patients could, by impairing their functionality, influence immune responses and expression of functionally relevant membrane determinants.

Effects of alpha-tocopherol administration on red blood cell membrane lipid peroxidation in hemodialysis patients.

The result of vitamin E treatment in 19 uremic patients in chronic hemodialysis is evaluated. In particular, the levels of erythrocyte malonyldialdehyde (MDA) and vitamin E were determined, and the fatty acid composition of red blood cell (RBC) membrane before and after treatment with parenterally administered vitamin E. A decrease of RBC MDA levels, an increase of RBC vitamin E concentrations, and a decreased saturated fatty acid to unsaturated fatty acid ratio were found after treatment with vitamin E. There was a statistically significant increase of the packed RBC volume.

Relationship between red blood cell lipid peroxidation, plasma hemoglobin, and red blood cell osmotic resistance before and after vitamin E supplementation in hemodialysis patients.

It has been reported that increased peroxidation of the polyunsaturated fatty acids in the erythrocyte membranes is one of the causes of chronic hemolysis in uremic patients on hemodialysis and that therapeutic doses of vitamin E are effective in reducing peroxidation, improving the hematocrit. The present study shows how the reduced peroxidation, induced by a course with therapeutic doses of vitamin E, is paralleled by a significant reduction of plasma hemoglobin concentrations at the end of the dialysis and by a significant improvement of erythrocyte osmotic resistance. The findings lead to the suggestion that the administration of tocopherol to patients on chronic hemodialysis for end-stage renal disease may be beneficial in improving anemia, acting via a reduction of lipid peroxidation of the red blood cell membranes. Whether this can reduce the need for the transfusions can be assessed only with a longitudinal long-term study, which is also necessary to determine whether the preliminary findings of this report have important clinical applications.

Vitamin E consumption by human blood platelets activated by latex particles.

Human blood platelet activation elicited by latex particles is associated to a 30% decrease in the cellular content of vitamin E. The vitamin E consumption is inhibited by the addition of catalase (500 U/ml) and azide (1 mM), but it is not affected by potassium cyanide (1 mM). It may be proposed that the challenge of platelets with particulate stimuli causes generation of oxygen reduction products, which leads to vitamin E depletion.

Red blood cell membrane lipid peroxidation in continuous ambulatory peritoneal dialysis patients.

We have recently described that in the erythrocytes from uremic patients on chronic hemodialysis, the pentose-phosphate shunt is defective, the membrane concentrations of malonyldialdehyde, resulting from peroxidation of polyunsaturated fatty acids in the membranes themselves, are increased, and the concentrations of vitamin E, an antioxidizing agent, are reduced. In the present study we have analyzed these same metabolic aspects in a group of uremic patients in continuous ambulatory peritoneal dialysis. We have found normal function of the pentose-phosphate shunt, slightly elevated concentrations of malonyldialdehyde compared to controls, but definitely lower than in chronic hemodialysis patients, and higher tocopherol concentrations than in both controls and chronic hemodialysis patients.

Discrepancies between serum and erythrocyte concentrations of vitamin E in hemodialysis patients: role of HDL-bound fraction of vitamin E.

Recently, we have demonstrated that hemodialysis (HD) patients have higher serum and lower erythrocyte concentrations of vitamin E than controls. It is known that transfer of vitamin E from serum to erythrocyte is mostly due to high-density lipoproteins (HDL). For a better definition of the pattern of distribution of vitamin E in HD patients, we have dosed the amount of vitamin bound to serum HDL fraction. In 8 patients and in 8 healthy controls, we have determined the concentration of serum erythrocyte and HDL-bound vitamin E. The latest was obtained on an ultracentrifuged HDL fraction. HDL fractions from HD patients have been found to contain larger amounts of vitamin E than controls. The previously described higher serum and lower erythrocyte concentrations of vitamin E in HD patients have been confirmed in the study. The deficit of vitamin E in the membranes of erythrocytes from HD patients has been shown to be the result of increased consumption of the vitamin in the erythrocyte membranes, where it represents the major antioxidant agent. However, the finding of increased amounts of vitamin bound to HDL in HD patients suggests that the transfer of the vitamin to the erythrocyte membranes may also be defective.

Evidence of red blood cell membrane lipid peroxidation in haemodialysis patients.

Some metabolic alterations of the pentose-phosphate shunt can increase susceptibility to red blood cell (RBC) lipid peroxidation in uraemic patients on maintenance haemodialysis. We investigated this phenomenon in 19 uraemic patients undergoing chronic haemodialysis by determining RBC malonyldialdehyde (MDA), a secondary product of lipid peroxidation and plasma and RBC tocopherols, which are powerful antioxidants. Evidence of RBC membrane lipid peroxidation was demonstrated by an increase of RBC MDA. RBC tocopherols were significantly decreased because of enhanced antioxidant activity. No significant variations of these parameters were found before and after dialysis.

Pentose-phosphate shunt activity and red blood cell malonyldialdehyde levels in haemodialysis and in CAPD patients.

The baseline concentrations of MDA in the RBC membranes and the MDA production in the erythrocytes following stimulation with ascorbate and cyanide are compared in a group of uraemic patients on chronic haemodialysis and in one treated with CAPD. Lower baseline concentrations and smaller production of MDA following in vitro stimulation, point to a better function of the pentose-phosphate shunt in CAPD patients than in haemodialysis.

Red blood cell membrane lipid peroxidation and chronic haemolysis in haemodialysis patients.

Pre dialysis concentrations of malonyldialdehyde (MDA) in the red blood cell membranes and pre and post dialysis percent variation of plasma haemoglobin levels are studied in a group of uraemic patients on maintenance haemodialysis both before and after a therapeutic trial with vitamin E. The findings show a significant correlation between MDA levels and percent variation of plasma haemoglobin during dialysis, thus indicating that reducing the amount of lipid peroxidation can help to reduce intradialytic chronic haemolysis.