Evidence of an increased susceptibility to lipid peroxidation in red blood cells of chronic renal failure patients

Assessment of Oxidative Stress Markers in Hypothermic Preservation of Transplanted Kidneys

Ischemia-reperfusion injury (IRI) after renal transplantation is a complex biochemical process. The first component is an ischemic phase during kidney storage. The second is reperfusion, the main source of oxidative stress. This study aimed to analyze the activity of enzymes and concentrations of non-enzymatic compounds involved in the antioxidant defense mechanisms: glutathione (GSH), glutathione peroxidase (GPX), catalase (CAT), superoxide dismutase (SOD), glutathione reductase (GR), glutathione transferase (GST), thiobarbituric acid reactive substances (TBARS), malondialdehyde (MDA), measured in preservation fluid before transplantation of human kidneys (KTx) grafted from brain dead donors. The study group (N = 66) was divided according to the method of kidney storage: Group 1—hypothermic machine perfusion (HMP) in LifePort perfusion pump, n1 = 26, and Group 2—static cold storage (SCS), n2 = 40. The measurements of kidney function parameters, blood count, and adverse events were performed at constant time points during 7-day hospitalization and 3-month follow-up. Kidney perfusate in Group 2 was characterized by significantly more acidic pH (p < 0.0001), higher activity of GPX [U/mgHb] (p < 0.05) and higher concentration of MDA [μmol/L] (p < 0.05). There was a statistically significant improvement of kidney function and specific blood count alterations concerning storage method in repeated measures. There were aggregations of significant correlations (p < 0.05) between kidney function parameters after KTx and oxidative stress markers: diuresis & CAT, Na⁺ & CAT, K⁺ & GPX, urea & GR. There were aggregations of significant correlations (p < 0.05) between recipient blood count and oxidative stress markers: CAT & MON, SOD & WBC, SOD & MON. Study groups demonstrated differences concerning the method of kidney storage. A significant role of recipient’s gender, gender matching, preservation solution, and perfusate pH was not confirmed, however, basing on analyzed data, the well-established long-term beneficial impact of HMP on the outcome of transplanted kidneys might partially depend on the intensity of IRI ischemic phase and oxidative stress, reflected by the examined biomarkers.

Lipid Perxidtion and Antioxidants in Continuous Ambulatory Dialysis Patients

Objective

Oxidative cell damage due to the production of free radical species has been implicated in the pathogenesis of cardiovascular disease for which dialysis patients are at increased risk. Plasma lipid peroxides (malon-dialdehyde), the antioxidants plasma albumin thiol, and red cell superoxide dismutase (SOD) were therefore measured in 18 patients undergoing continuous ambulatory peritoneal dialysis (CAPD), 20 hemodialysis patients, and 30 normal controls.

Setting

Renal dialysis unit.

Results

Malondialdehyde(MDA)concentrationswere significantly higher in dialysis patients compared to controls (p<0.001 ) and were significantly higher in CAPD patients compared to hemodialysis patients, p<0.001 (CAPD, median and range: 11.25 (8.4–15.5) nmol/mL; hemodialysis: 8.75 (7.0–12.6) nmol/mL; controls: 6.65 (5.2–9.6) nmol/mL). Plasma thiol and red cell SOD were significantly lower in dialysis patients compared to controls, but there was no significant difference between CAPD and hemodialysis patients (CAPD thiol: 333.5 (282480) μmol/L; hemodialysis thiol: 344 (203–468) μmol/L; control thiol: 421.5 (351 -504) μmol/L; CAPD SOD: 78.2 (42.4 -112.8) u//2 mL red cells; hemodialysis SOD: 89.4 (44.6–121.1) u//2 mL red cells; control SOD: 96.8 (66.8153.4) u//2 mL red cells). Red cell SOD was significantly negatively correlated with duration of dialysis in CAPD patients (r=-0.683, p<0.01 ).

Conclusion

In dialysis patients there is indirect evidence for increased free radical activity, which may be further influenced by the mode of dialysis.

Association of interleukin 18-607A/C and -137C/G polymorphisms with oxidative stress in renal transplant recipients

Objectives IL-18 mediates various inflammatory and oxidative responses including renal injury, fibrosis, and graft rejection. It has been reported that the promoter -607 and -137 polymorphisms of IL-18 influence the level of IL-18. This prospective observational study investigated the association between oxidative stress with IL-18-607 and -137 polymorphisms in renal transplant recipients. Patients and methods This study included 75 renal transplant recipients (28 female, 47 male) from living-related donors. Blood samples were collected immediately before and after transplantation at day 7 and month 1. Serum IL-18, creatinine, cystatin C, CRP, and oxidative stress markers (TOS, TAC) were measured. The Oxidative Stress Index (OSI) was calculated. Polymorphisms of the promoter region of the IL-18 gene, IL18-607A/C, and -137C/G were determined by analysis of a "real-time PCR/Melting curve". Results Serum creatinine, cystatin C, CRP, IL-18, TOS, and OSI levels significantly decreased after transplantation. Post-transplant levels of serum TAC and estimated GFR demonstrated consistent significant increases. Serum IL-18 levels were significantly higher in patients with IL-18-137 GG and IL-18-607 CC genotypes before transplantation. Conclusion Our results indicate that the IL-18-137 GG and -607 CC genotypes contribute to higher IL-18 levels; however, the influence of these polymorphisms on oxidative stress has not been observed.

Oxidative stress in kidney transplantation: malondialdehyde is an early predictive marker of graft dysfunction

BACKGROUND

Oxidative stress is one of the most important components of the ischemia-reperfusion process after kidney transplantation (KTx) and increases with graft dysfunction.

METHODS

This prospective study was conducted on 40 consecutive KTx recipients to evaluate time-dependent changes in oxidative stress-related parameters within the first week after KTx and to assess their performance in predicting delayed graft function (DGF=dialysis requirement during initial posttransplant week) and graft function at 1 year. Blood samples were collected before (day 0) and after KTx (days 1, 2, 4, and 7). Total antioxidant capacity, plasma levels of malondialdehyde (MDA), and activities of glutathione peroxidase, glutathione reductase and superoxide dismutase were measured. Multivariable linear mixed and linear regression models, receiver-operating characteristic (ROC), and areas under ROC curves (AUC-ROC) were used.

RESULTS

At all time points after KTx, mean MDA levels were significantly higher in patients developing DGF (n=18). Shortly after KTx (8-12 hr), MDA values were higher in DGF recipients (on average, +0.16 μmol/L) and increased further on following day, contrasting with prompt functioning recipients. Day 1 MDA levels accurately predicted DGF (AUC-ROC=0.90), with a performance higher than SCr (AUC-ROC=0.73) and similar to cystatin C (AUC-ROC=0.91). Multivariable analysis revealed that MDA levels on day 7 represented an independent predictor of 1-year graft function. Antioxidant enzyme activities were not significantly changed during the study period and were not predictors of 1-year graft function.

CONCLUSIONS

Increased MDA levels on day 1 after KTx might be an early prognostic indicator of DGF, and levels on day 7 might represent a useful predictor of 1-year graft function.

Comparison of vitamin e and L-carnitine, separately or in combination in patients with intradialytic complications

BACKGROUND

The most common complications during dialysis are hypotension and muscle cramps. There are many strategies to prevent and treat these complications.

OBJECTIVES

The aim of this study is to evaluate effects of vitamin E and L-carnitine supplementation alone and in combination on intradialytic complications.

PATIENTS AND METHODS

In a prospective study, 20 patients with end stage renal disease on chronic hemodialysis that had intradialytic complications such as hypotension, muscle cramp, nausea, vomiting and headache were studied. These patients were studied in four 45 day periods, beginning with no treatment (step 1), receiving vitamin E (200 IU/d) (step 2), receiving L-carnitine (500 mg/d) (step 3) and their combination (step 4). Intradialytic complications were recorded in each step and compared between treatments.

RESULTS

All three treatments significantly reduced frequency of muscle cramps in comparison to baseline values. Vitamin E alone and in combination with L-carnitine reduced the frequency of muscle cramps more effectively. Hypotension was significantly lower in combination therapy in comparison to baseline values and vitamin E treatment.

CONCLUSIONS

Vitamin E and L-carnitine both have comparative effects on intradialytic complications. As the combination use of vitamin E and L-carnitine could more effectively reduce the intradialytic complications, it is recommended for daily use in hemodialysis patients.

Anemia of renal disease: what it is, what to do and what's new

PATIENT GROUP

It is estimated that 15-30% of geriatric cats will develop chronic kidney disease (CKD), and that 30-65% of these cats will develop anemia as their renal disease worsens. Anemia of renal disease is multifactorial in its pathogenesis, but the main cause is reduced production of erythropoietin, a renal hormone that controls the bone marrow's production of red blood cells, as kidney disease progresses.

PRACTICAL RELEVANCE

It is important to recognize the presence of anemia of renal disease so that adequate treatment may be instituted to improve quality of life and metabolic function. Erythrocyte-stimulating agents (ESAs), such as epoetin alfa, epoetin beta and darbepoetin alfa, have been developed to counteract the effects of decreased erythropoietin production by the kidneys. These treatments, which are the focus of this review, have 83% similarity in amino acid sequence to the feline hormone. On average, the target packed cell volume (>25%) is reached within 3-4 weeks of ESA therapy.

CLINICAL CHALLENGES

The use of ESAs has been associated with a number of complications, such as iron deficiency, hypertension, arthralgia, fever, seizures, polycythemia and pure red cell aplasia (PRCA). Darbepoetin has a prolonged half-life compared with epoetin and thus can be given only once a week, instead of three times a week. The incidence of PRCA appears to be decreased with darbepoetin use when compared with epoetin use in cats.

EVIDENCE BASE

There is limited published evidence to date to underpin the use of ESAs in cats. This review draws on the relevant publications that currently exist, and the authors' personal experience of using these therapies for over 5 years.

Comparative effects of silymarin and vitamin E supplementation on oxidative stress markers, and hemoglobin levels among patients on hemodialysis

BACKGROUND

The incidence of accelerated atherosclerosis among patients on hemodialysis is very high and oxidative stress (OS) is a potentially major contributor to their morbidity and mortality.

OBJECTIVE

To evaluate the effects of Silymarin and/or vitamin E on OS markers and hemoglobin levels in patients on hemodialysis.

METHODS

Eighty patients on hemodialysis were randomized into four groups: Group 1 received silymarin 140 mg 3 times daily; Group 2 received vitamin E 400 IU/day; Group 3 received silymarin 140 mg 3 times daily and vitamin E 400 IU/day; and Group 4 was the control. Samples were obtained at baseline and on day 21 for measurement of malondialdehyde (MDA), red blood cell (RBC) glutathione peroxidase (GPX), and hemoglobin.

RESULTS

Combination of silymarin and vitamin E led to a reduction in the MDA levels (7.84 ± 1.84 vs. 9.20 ± 2.74 nmol/mL; p = 0.008). There was a significant increase in RBC GPX levels in all treatment groups compared with controls after 3 weeks. This was more pronounced in the group receiving combination compared with the group receiving vitamin E or the control group (5.78 ± 3.51, 4.22 ± 1.63, and 3.16 ± 1.89 IU/grHb, respectively; p < 0.001). There was also a significant increase in mean hemoglobin of all treatment groups compared with the control.

CONCLUSIONS

Oral supplementation with silymarin and vitamin E leads to reduction in MDA, increase in RBC GPX, and increase in hemoglobin levels in patients with end-stage renal disease. Studies with larger sample sizes and longer follow-up are required to investigate the effect of silymarin on cardiovascular outcomes and erythropoietin requirement.

Antioxidant micronutrient supplementation increases erythrocyte membrane fluidity in adults from a rural Chinese community

The objective of the present study was to investigate age-related differences in erythrocyte membrane fluidity (EMF) and changes in antioxidant capacity following supplementation. A total of seventy-four children were randomly divided into two groups: group A1 was the placebo-controlled group and group A2 was supplemented daily with 600 μg retinol, 1·0 mg β-carotene, 100 mg tocopherol, 300 mg ascorbic acid and 200 μg Se. A total of ninety young people were randomly divided into B1 and B2 groups, and ninety-one elderly subjects were divided into C1 and C2 groups. Groups B1 and C1 were placebo-controlled groups, and groups B2 and C2 were daily supplemented with 900 μg retinol, 1·5 mg β-carotene, 200 mg tocopherol, 500 mg ascorbic acid and 400 μg Se. Results showed that plasma malondialdehyde (MDA) was 5·35 μmol/l in children, which was lower than in young and elderly people. The MDA levels of the young and elderly individuals in the treated groups were significantly lower compared with the control groups, but the supplementation did not alter MDA levels in children. At baseline, there was a lower value of polarisation (ρ) and microviscosity (η) in children, indicating a higher EMF, than in both the young and elderly subjects. After the 2-month trial, the ρ and η values of young and elderly subjects in the treated groups decreased significantly in comparison with the placebo groups, indicating an increase in EMF. In conclusion, there was a background of higher MDA levels and lower EMF in young and elderly people than in children, which could be improved by antioxidant supplementation.

Effect of vitamin E supplementation on oxidative stress in hemodialysis patients

Hemodialysis represents a chronic stress status for its recipients. Many hypotheses state that this may be associated with oxidative stress. Thus, there may be deficiency of antioxidants like erythrocytic superoxide dismutase, catalase, vitamin E or increased generation of free radicals like superoxide anions. A study was carried out to investigate oxidant and antioxidant status in chronic renal failure patients undergoing hemodialysis and effect of vitamin E supplementation on these two status. Blood samples were collected from patients before and after hemodialysis and from controls. The samples were analyzed for quantitation of MDA as index of lipid peroxide, nitric oxide, vitamin E, vitamin C and enzymatic antioxidants namely erythrocyte SOD and catalase. As compared to controls, the levels of serum MDA were significantly increased and activities of erythrocyte SOD and catalase, levels of serum nitric oxide, serum vitamin E and plasma vitamin C were significantly decreased both before and after hemodialysis. The efficiency of vitamin E therapy in hemodialysis patients was assessed by re-evaluating oxidant and antioxidant status of same patients after supplementation of vitamin E. Vitamin E supplementation caused decrease in serum MDA and increase in levels of serum nitric oxide, vitamin E, vitamin C and activities of erythrocytic SOD and catalase. Our results suggest the presence of oxidative stress and the possible preventive role of vitamin E therapy in hemodialysis patients.

Reassessing the increased glycation of hemoglobin in nondiabetic chronic renal failure patients: a hypothesis on the role of lipid peroxides

BACKGROUND

Glycated hemoglobin (HbA(1C)) is considered clinically useful for assessing long-term integrated control of blood glucose in diabetes. However, an increased HbA(1C) concentration has been documented in chronic renal failure (CRF) patients without any history of diabetes. Collective evidences reveal that lipid peroxidation (MDA) can modulate protein glycation. We evaluated the relationship between glycated hemoglobin (HbA(1C)) and lipid peroxidation in non-diabetic CRF patients.

METHODS

Twenty-eight nondiabetic CRF and 23 age- and sex-matched healthy subjects were enrolled for this study. Plasma urea, creatinine, lipid peroxides, fasting glucose and HbA(1C) were analyzed in both the groups. The in-vitro effect of MDA on glycation of hemoglobin was studied by incubating healthy erythrocytes with either 5 or 50 mmol/l glucose concentration.

RESULTS

The percentage of HbA(1C) concentrations and plasma malondialdehyde (MDA) were significantly increased in CRF patients compared to control subjects. When the effects of uremia and blood glucose on the concentration of HbA(1C) was refuted by partial correlation analysis, MDA was found to be a significant determinant of HbA(1C) (r=0.41, p=0.04) in patients with renal failure. In-vitro incubation of RBC with glucose along with MDA was found to enhance the process of hemoglobin glycation.

CONCLUSION

Our results suggest that lipid peroxidation per se can contribute to glycation of hemoglobin, warranting extra-precaution in interpreting HbA(1C) as a measure of glycemic control in CRF.

Erythrocyte susceptibility to oxidative stress in chronic renal failure patients under different substitutive treatments

An increased oxidative stress is now considered one of the major risk factors in chronic renal failure (CRF) patients that may be exacerbated by dialysis. It has been postulated that this increased oxidative stress might cause an augmented red blood cell (RBC) membrane lipid peroxidation with the consequent alteration in membrane deformability. The aim of this study was to evaluate RBC susceptibility to an in vitro induced oxidative stress and RBC antioxidant potential in different groups of CRF patients undergoing different substitutive treatment modalities. Fifteen end-stage CRF patients were evaluated in conservative treatment, 23 hemodialysis (HD) patients, 15 continuous ambulatory peritoneal dialysis (CAPD) patients, 15 kidney transplanted patients, and 16 controls. Their RBCs were incubated with the oxidative stress-inducing agent tert-butylhydroperoxide both in the presence and in the absence of the catalase inhibitor sodium azide, and the level of malondialdehyde (MDA) (a product of lipid peroxidation), was measured at 0, 5, 10, 15, and 30 min of incubation. In addition, the RBC content of reduced glutathione (GSH) was measured by HPLC. As opposed to the controls, RBCs from end-stage CRF patients exhibited an increased sensitivity to oxidative stress induced in vitro, both in the absence and presence of a catalase inhibitor, as demonstrated by a significantly higher level of MDA production at all the incubation times (P < 0.05). Different substitutive treatments had different impacts on this phenomenon; CAPD and kidney transplantation were able to normalize this alteration while HD was not. GSH appeared to be related to the increase in RBC susceptibility to oxidative stress; its content being significantly elevated in end-stage CRF and HD patients as compared with CAPD and transplanted patients and controls (P < 0.05). No significant changes were observed in the RBC glutathione content during the HD session. The increase of GSH in RBCs of end-stage CRF and HD patients seems to indicate the existence of an adaptive mechanism under increased oxidative stress occurring in vivo. Unlike HD, the beneficial effect of CAPD on the anemia of dialysis patients might partly be due to a condition of lower oxidative stress that might in addition counterbalance the cardiovascular negative effects of dislipidemia of CAPD patients.

The effect of different dialysis membranes on oxidative stress and selenium status

BACKGROUND

Oxidative stress is an important risk factor for the development and progression of several complications in hemodialysis patients. The aim of this study was to evaluate the effects of two different dialysis membranes on oxidative stress and selenium status.

METHODS

Forty long-term dialysis patients and 20 age-matched healthy controls were enrolled into our study. Serum malondialdehyde (MDA) and selenium (Se) concentrations, and glutathione peroxidase (GSH-Px) activities were determined before and after hemodialysis (HD) using a hemophan (H) or a polysulfone (PS) membrane.

RESULTS

MDA levels in the HD patients were significantly higher than those in the control group (p < 0.001). GSH-Px activity and selenium concentrations were significantly lower in HD patients compared to the control group (p < 0.001). MDA levels were significantly increased (p < 0.05); GSH-Px activity and selenium concentrations were significantly reduced (p < 0.001) in the PS membrane group compared to H membrane group after HD.

CONCLUSIONS

Comparing with H membrane, PS membrane caused more oxidative stress and lower levels of Se in HD patients.

Lipid peroxidation in vitamin E-deficient rats submitted to subtotal nephrectomy

Clinical and experimental evidence has indicated that chronic renal failure (CRF) is related to increased free radical production. CRF patients show increased lipid peroxidation after a progressive reduction in vitamin E, one of the most important antioxidants. In the present study the role of vitamin E deficiency in lipid peroxidation was investigated in rats submitted to subtotal nephrectomy. Male Wistar rats were divided into groups receiving different diets for a period of 45 days: SND - sham rats submitted to a regular diet containing vitamin E; ERD nephrectomized rats submitted to a regular diet containing vitamin E; SDD - sham rats submitted to a vitamin E-deficient diet; EDD nephrectomized rats submitted to a vitamin E-deficient diet. After 30 days the Experimental animals were submitted to 5/6 nephrectomy and the Controls were submitted to sham operation. The vitamin E levels of the SDD and EDD groups were significantly reduced (p < 0.05) in plasma (4.92 +/- 1.22 and 8.37 +/- 2.09 mmol/L, respectively), liver (7.57 +/- 2.72 and 9.44 +/- 2.55mg/g tissue, respectively) and kidney (8.17 +/- 2.38 and 9.40 +/- 3.10 mg/g tissue, respectively) when compared to the SRD and ERD groups. In contrast, in the EDD group the levels of thiobarbituric acid-reactive substances, expressed as nmol/mg protein, were significantly increased (p < 0.05) in the liver (1.41 +/- 0.27) and kidney (1.67 +/- 0.47), and superoxide dismutase activity was significantly increased in the erythrocytes (4455.80 +/- 1322.63 Ug/Hb) compared to all other groups. The vitamin E-deficient diet associated with subtotal nephrectomy determined an increase in lipid peroxidation, suggesting an important role of free radicals in the development of chronic renal failure.

Do different dialytic techniques have different atherosclerotic and antioxidant activities?

To compare the chronic effect of several dialytic techniques (bicarbonate dialysis, BHD; acetate free biofiltration, AFB; hemodiafiltration, HDF; paired filtration dialysis, PFD) on atherosclerosis and antioxidant activity, three different indices were created. The first (atherosclerotic index = AI) is formed using the sum of three plasma substances: MDA, Hcy, and Cys (malondialdehyde, homocysteine, cysteine). The second (antioxidant activity index = AOAI) is the sum of five erythrocyte (E) parameters: E-GSH, GPx, CAT, SOD, GR (E-glutathione, E-glutathione peroxidase, E-catalase, E-superoxide dismutase, E-glutathione reductase). The third (defense index = DI) is derived from the previous two: (AOAI - AI). The indices were so expressed as AI in mmol/L, AOAI in U/g hemoglobin (Hb), and DI in arbitrary units. These indices were calculated in 20 controls and 51 chronic HD patients (26 female, 25 male) before, during, and after the first session of the week. HD patients were divided according to their dialytic technique: BHD, n = 35; AFB, n = 5 patients; HDF, n = 7 patients; or PFD = 4 patients. All patients had been treated with a given technique for at least 12 months, before entering the study. As expected, HD patients had AI values higher than controls, both before and after the session, with a mean value of 541 (before) and 331 (after), whereas controls had a mean value of 205. The AOAI was lower than controls, both before and after the session, the mean value being 1,122 (before) and 1,582 (after), that of controls being 2,424. In all cases, PFD gave the best "acute" results; at the end of a PFD session, near normal values of AI, AOAI, and DI (defensive index = AOAI - AI) were obtained.

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.

Evaluation of a novel vitamin E coated cellulosic membrane hollow fiber dialyzer

Adverse physiologic effects accompany hemodialysis. Biocompatible dialyzer membranes may both limit oxidative stress and decrease beta2-microglobulin production, thereby reducing patient morbidity. We compared standard solute clearance, lipid, and antioxidant effects of a novel cellulosic membrane dialyzer modified with covalently bonded vitamin E (Excebrane Clirans E15, Terumo Australia) with standard cellulosic and polysulphone membrane dialyzers. Stable adult hemodialysis patients taking no lipid lowering or antioxidant therapy (n = 17; 9 male, 8 female) were recruited into a 10 week, prospective, unblinded study. Measurements were made at baseline on their usual dialyzer and after 2, 4, and 10 weeks of Excebrane use. Excebrane demonstrated good in vivo clearance of standard solutes relative to surface area. Predialysis beta2-microglobulin levels were unchanged with time and were significantly lower postdialysis than with cellulose acetate (p < 0.05). Oxidized low density lipoprotein levels as measured by nitrotyrosine residues were high predialysis, but tended to decrease with both membranes (p > 0.05). Total antioxidant status fell during dialysis (p < 0.0005), but plasma vitamin A and E concentrations increased (p = 0.007 and p = 0.02, respectively). Baseline vitamin A levels were high in all patients and, along with vitamin E, total antioxidant status and lipid profiles did not change over time with Excebrane use. Excebrane is an efficient, biocompatible membrane with no deleterious effects on beta2-microglobulin or lipids. More long-term study is merited.

Plasma and erythrocytes antioxidant status and trace element levels in proteinuric patients with moderate glomerular function

The objective of the study was to investigate the effect of moderate glomerular dysfunction on oxidative stress. We determined the plasma and erythrocyte malondialdehyde (MDA) levels, as a marker of lipid peroxidation, erythrocyte glutathione (GSH) levels and activities of GSH-Px, GSH Red and SOD as an antioxidant enzymes, and plasma trace element levels containing Fe, Cu and Zn in twenty proteinuric patients (6.8 +/- 5.1 g/day) with moderate glomerular function and in 20 anemic control subjects. We found that the erythrocyte and plasma MDA levels and erythrocyte GSH-Px activities were significantly higher (p < 0.001, p < 0.001, p < 0.001, respectively) and the erythrocyte GSH levels and activities of GSH-Red and SOD activities were significantly lower (p < 0.001, p < 0.001, p < 0.001, respectively) in the patients than in the anemic subjects. Plasma Fe and Zn levels were not to be found significantly different in the patients compared to the anemic subjects. But plasma Cu levels were significantly higher in the patients (p < 0.05) when compared with the levels of anemic subjects. This study was concluded that cellular antioxidant activity decreases in proteinuric patients with moderate glomerular function. This may increase lipid peroxidation reactions by causing oxidative stress in erythrocyte membranes.

Role of cellulosic and noncellulosic membranes in hyperhomocysteinemia and oxidative stress

Hyperhomocysteinemia is an independent risk factor for cardiovascular morbidity and mortality in end-stage renal disease (ESRD) with an increased relative risk (RR) of 1% per micromol/L in total homocysteine concentration. In ESRD patients who undergo hemodialysis (HD), the antioxidant system is largely inadequate in correcting the imbalance between generation and scavenging of reactive oxygen species (ROS). To clarify the role of several cellulosic (CMs) and noncellulosic of synthetic membranes (NCMs) upon hyperhomocysteinemia and the oxidative stress, we measured plasma (P) homocysteine (t-HCY), plasma lipid peroxidation (LPO), and erythrocyte (E) concentration of several antioxidant enzymes in 20 normal subjects, in 35 HD patients treated with CMs, and in 29 patients treated with NCMs. Before, during, and after the first session of the week (at times 0', 120', end, 30' after HD end), blood samples were drawn. Plasma (P) homocysteine (t-HCY), cysteine (CYS), malondialdehyde (MDA), erythrocyte (E)-glutathione (GSH), glucose-6-phosphodehydrogenase (G6PD), glutathione reductase (GR), glutathione peroxidase (GPx), catalase (CAT), and superoxide-dismutase (SOD) were determined. The dialytic procedure significantly decreased the three plasma parameters, but none normalized (as a mean). The E-enzymes scavenging ROS (lower than normal before session) increased throughout the session, but the normal range of activity was never reached. Different membranes have shown different effects. When these effects on P and E spaces were pooled, we were able to classify the membranes as follows. In a general sense, cellulosic membranes are less effective than synthetic membranes both on lipoperoxides (LPO) and antioxidant activity (AOA). Among synthetic membranes, PMMA is the best membrane both for plasma values and lesser enzymatic derangement during the session. A practical system for classifying the anti-atherosclerotic action and antioxidant activity of dialytic membranes is proposed.

Analysis of 7-ketocholesterol in low density lipoprotein and fatty acid composition in erythrocyte membranes of patients on maintenance hemodialysis and healthy controls

We established a method to quantify 7-ketocholesterol (7-KC) in low density lipoprotein by using the heparin-citrate method and gas chromatography-mass spectrometry. We examined the concentration of 7-ketocholesterol in LDL using this method to assess the pathological conditions in uremic patients with hemodialysis and healthy controls. We also examined the fatty acid composition in erythrocyte membranes to estimate the modification of biological membranes. We showed that the concentrations of 7-KC/cholesterol in LDL were significantly increased in hemodialysis patients compared to healthy controls (3.68+/-0.45 vs. 2.41+/-0.19, P<0.05) and the ratio of polyunsaturated fatty acids to saturated fatty acids in erythrocyte membranes was significantly decreased in hemodialysis patients compared to healthy controls (0.499+/-0.014 vs. 0.655+/-0. 017, P<0.001). There was no significant difference in 7-KC concentration in LDL or fatty acid composition in erythrocyte membranes between pre- and post-intervention of hemodialysis. We concluded that hemodialysis patients are under oxidative stress, which modifies LDL and erythrocyte membranes and we speculated these modifications may participate in the process of atherosclerosis. We believe that the method to quantify 7-KC in this study is concise and reliable and may be used to investigate various diseases.

Peroxidação lipídica em pacientes com insuficiência renal crônica

Trabalhos demonstram desequilíbrio entre atividade oxidante/antioxidante e um aumento nos níveis de radicais livres em pacientes com insuficiência renal crônica. Várias pesquisas mostram uma maior peroxidação lipídica em eritrócitos e outras células do sangue com implicações importantes na morbidade destes pacientes, principalmente por doenças cardiovasculares. Os níveis de antioxidantes enzimáticos como a glutationa peroxidase, superóxido dismutase e catalase estão reduzidos, bem como os dos elementos traço (Selênio, Zinco). A diminuição das defesas antioxidantes permite o aumento da formação de espécies reativas de oxigênio, o que caracteriza a condição de estresse oxidativo. Em decorrência disto, ocorrem lesões oxidativas que podem alterar a fluidez da membrana dos eritrócitos, contribuindo para a hemólise e piora da anemia, além de causar a oxidação das lipoproteínas de baixa densidade do colesterol, a qual tem um papel importante na patogênese da aterosclerose, que ocorre freqüentemente nos pacientes com insuficiência renal crônica. O objetivo deste trabalho é discutir a relação da peroxidação lipídica e da diminuição das defesas antioxidantes do organismo como fatores importantes na patogênese da insuficiência renal crônica e suas complicações.

Oxidation of low density lipoprotein in hemodialysis patients: effect of dialysis and comparison with matched controls

End stage renal failure is associated with lipoprotein abnormalities and a high prevalence of premature atherosclerosis. Oxidative modification of low density lipoprotein (LDL) may be promoted by hemodialysis increasing its atherogenicity. The oxidative status of LDL was therefore examined in female subjects before and after routine hemodialysis (HD; n = 10) and compared with women of similar age without significant renal disease (n = 19). There were no significant differences between the groups in the LDL fatty acid composition, or in the content of reactive amino acid groups (lysine) before or after exposure to Cu2+. The kinetics of LDL oxidation by Cu2+ showed no significant differences between the groups with respect to the lag time, the level of conjugated dienes before and after oxidation, or the maximal rate of oxidation during the propagation phase. No acute effects of HD were demonstrated. The present study provides no evidence that circulating LDL isolated from HD patients is more extensively modified or more susceptible to oxidation in vitro than gender-matched controls without renal failure.

Lipid abnormalities of erythrocyte membranes in hemodialysis patients with chronic renal failure

Lipids in erythrocyte membranes from 16 hemodialysis patients and 16 healthy volunteers were studied using gas chromatographic mass spectrometry. 7-keto cholestadiene was first reported in this study. The ratios of 7-keto cholestadiene to cholesterol, the ratios of arachidonate to cholesterol and the ratios of dochosahexanate to cholesterol in peak heights of chromatograms were measured in both groups as the markers of lipid peroxidation. Higher 7-keto cholestadiene/cholesterol ratios and lower arachidonate/cholesterol and dochosahexanate/cholesterol ratios were significantly observed in hemodialysis patients compared with healthy subjects. Our results are evidence that hemodialysis patients are exposed to much oxidative stress. It has been suggested that, during hemodialysis, leukocytes are activated by contract with non-physiological surfaces of the blood line tubing and produce oxygen free radicals. Oxygen free radicals attach cholesterol, arachidonate and dochosahexanate to produce lipid peroxides. In this study, this cell activation may be responsible for the increased lipid peroxidation of hemodialysis patients, 7-Keto cholestadiene, arachidonate and dochosahexanate can be used as markers of lipid peroxidation in hemodialysis patients.

Detection of oxidants in uremic plasma by electron spin resonance spectroscopy

Depletion of antioxidants and the presence of products of free radical damage in plasma suggest that oxidative stress is increased in uremia. We have developed an application of electron spin resonance spectroscopy, and used this method to show that a stable oxidizing component or components of plasma accumulate in uremia. No oxidizing activity was detectable in plasma from subjects with normal renal function. The oxidant was detected by its capacity to oxidize the spin trap 3,5-dibromo-4-nitrosobenzene sulphonate (DBNBS). The oxidant was dialyzable from plasma, had an upper molecular weight limit of about 3,000 Daltons and was stable over many months. Physiological plasma concentrations of vitamin C, a water soluble congener of vitamin E and reduced glutathione were unable to inhibit the oxidizing capacity of uremic plasma. Thus, uremia is associated with accumulation of an endogenous oxidizing activity at much higher concentrations than in subjects with normal renal function.

Oxidative stress and erythrocyte membrane fluidity in patients undergoing regular dialysis

Oxidative damage due to free radical production is increased in uraemic patients and has been suggested as a possible factor contributing to the anaemia of chronic renal failure (CRF) and the pathogenesis of atherosclerosis. Oxidative stress was assessed in 40 patients with CRF maintained by either haemodialysis (HD) or continuous ambulatory peritoneal dialysis (CAPD) and in 18 healthy controls. Lipid peroxidation (assessed as malondialdehyde, MDA), total glutathione (TG), antioxidant enzyme (glutathione reductase (GSHRx), glutathione peroxidase (GSHPx) and superoxide dismutase (SOD)) activity and antioxidant associated trace metal (selenium, copper, zinc) levels were studied. Erythrocyte membrane fluidity was examined using the fluorescent probe 1,6 diphenyl-1,3,5-hexatriene (DPH). The results indicate increased levels of oxidative stress and altered erythrocyte membrane fluidity in patients treated with CAPD compared with controls and patients treated with HD. Only minor changes were observed in patients treated with HD. Altered free radical activity, oxidative stress and altered erythrocyte membrane fluidity observed in patients with CRF may contribute to the increase in vascular disease in such patients and to the anaemia of CRF.

Evaluation of oxidant stress in chronic hemodialysis patients: use of different parameters

Patients with chronic renal failure, particularly those undergoing regular dialysis treatment (RDT) are candidates for free radical damage. It is difficult to quantitate free radicals because of their short half-lives and reactive nature. Therefore, indirect methods measuring products of lipid peroxidation and protein oxidation are preferred. The present study displays a profile of lipid peroxidation and protein oxidation parameters, which are more sensitive and specific than the widely used method measuring thiobarbituric acid reactive substances (TBARS), adapted to the plasma and erythrocyte samples of RDT patients. We have observed increased levels of plasma and erythrocyte lipid peroxidation and also demonstrated increased protein oxidation in erythrocyte membranes of RDT patients.

Lipoperoxidation in plasma and red blood cells of patients undergoing haemodialysis: vitamins A, E, and iron status

In 14 patients undergoing haemodialysis, lipoperoxidation (LPO) processes were determined in plasma and red blood cells (RBC) before and after a dialysis session by determining (a) the direct substrate, polyunsaturated fatty acids (PUFA); (b) the end product of LPO, malondialdehyde (MDA); and (c) the hydrophobic antioxidant systems, vitamins A and E. In plasma before dialysis, linoleic and arachidonic acid, and the antioxidant vitamin E, were significantly lowered as compared to the healthy controls (p < 0.05). On the contrary, the free MDA level was enhanced (p < 0.05). These results were emphasized by a dialysis session. In RBC of these patients, no difference in linoleic acid, free MDA, or vitamin E level were observed before or after dialysis when compared to controls. However, only vitamin A was significantly higher in haemodialysis patients (before and after dialysis) and in renal failure patients (p < 0.05) than in the healthy control group. The present results suggest that increased RBC vitamin A may offer some degree of protection against oxidative stress in erythrocytes, but not in plasma where LPO is demonstrated.

Red blood cells and platelet membrane fatty acids in non-dialyzed and dialyzed uremics

Three groups of patients with chronic renal failure (CRF), 16 non-dialyzed, 16 undergoing haemodialysis (HD), 16 undergoing continuous ambulatory peritoneal dialysis (CAPD), and 48 controls were examined. We analyzed the fatty acid composition in membranes from erythrocytes and platelets and the platelet malondialdehyde (MDA) production as an index of thromboxane metabolism. Marked differences in erythrocytes fatty acid composition were observed between patients with CRF and controls and, particularly, among the three groups of patients with CRF. Patients on CAPD were characterized by an increase in oleic acid, while haemodialyzed had a marked increase in arachidonic acid. Platelet fatty acid composition showed similar differences, suggesting a 'systemic' membrane abnormality. Platelet MDA was increased in haemodialyzed and positively correlated with the platelet arachidonate content.

Effect of dialyzer geometry during hemodialysis with cuprophane membranes

The effect of dialyzer geometry, both flat plate (FP) and hollow fiber (HF), on platelet and granulocyte activation during dialysis with cuprophane membranes was studied in 12 patients. A subset of six patients was restudied after correction of their anemia with recombinant human erythropoietin (EPO). Granulocyte count and aggregation in vitro fell significantly (P less than 0.01) at 20 minutes of dialysis, followed by a gradual return towards pre-dialysis values at 240 minutes. Malondialdehyde (MDA), a product of free radical reactions generated by activated granulocytes, increased significantly during dialysis [predialysis MDA (median, range): 8.4 (5.8 to 11.6) nmol/ml, 240 minutes MDA: 9.7 (6.6 to 12.5) nmol/ml, P less than 0.01 Wilcoxon test). This increase, however, was not affected by dialyzer geometry or EPO therapy. Neither type of dialyzer was associated with significant platelet loss at the end of dialysis. Whole blood platelet aggregation in vitro (spontaneous and collagen-induced) decreased significantly, (P less than 0.01) during dialysis, the fall in spontaneous aggregation being significantly less following EPO therapy [spontaneous aggregation 240 minutes; pre-EPO: 34 (13 to 52)%; post-EPO 50: (16 to 76)%, P less than 0.01)]. The ratio of the platelet release proteins beta-thromboglobulin and platelet factor 4 increased significantly during dialysis, indicating platelet activation in vivo, although there was no effect of dialyzer geometry or EPO. Factor VIII von Willebrand Factor antigen, a putative marker of endothelial damage, was raised pre-dialysis, and increased further during dialysis, irrespective of dialyzer geometry or EPO. In conclusion, dialyzer geometry had no significant effect on granulocyte and platelet counts and activity during hemodialysis with cuprophane membranes.(ABSTRACT TRUNCATED AT 250 WORDS)

Tubulointerstitial changes as a major determinant in the progression of renal damage

Tubulointerstitial injury is an invariant finding in the chronically diseased kidney, irrespective of the type of disease or the compartment in which the disease originates. Such histologic changes are functionally significant in that scores for such damage, rather than glomerular injury, correlate with decline of renal function. This review summarizes (1) clinical evidence attesting to tubulointerstitial changes as an index of functional impairment, (2) mechanisms by which tubulointerstitial injury impairs renal function, and (3) interactions of pathologic processes in the vascular, glomerular, tubular, and interstitial compartments that culminate in tubulointerstitial injury. This report concludes with a review of interstitial fibrosis, a pathologic process regarded as an irreversible outcome from tubulointerstitial injury.

Aluminum effect on the activity of superoxide dismutase and of other antioxygenic enzymes in vitro

The effect of Al on superoxide dismutase (SOD) and on other antioxygenic enzymes: horseradish peroxidase, catalase, and glutathione peroxidase, has been investigated in vitro. In the case of SOD, the effect of metal chelators (EDTA and deferoxamine) and a possible synergistic effect with iron salts have also been tested using the pyrogallol assay. There is no significant inhibitory effect of Al on the activity of any of the above-mentioned enzymes. Noticeable increases in SOD activity were observed when metal chelators were added to the medium, but not when high concentrations of Al were present too, in the case of deferoxamine (DFO). The former fact seems to be a consequence of the chelation of transition metal ions that catalyze pyrogallol autoxidation by a mechanism not inhibitable by SOD, interfering in its action, which may account for part of the DFO antioxidant effect observed in vivo. The latter phenomenon could be owing to a saturation of the chelating capacity of DFO by an excess of Al present in the medium, which should bring the system back to the interfering conditions explained above. It can be concluded that Al, either in the presence or in the absence of iron salts, does not inhibit SOD activity in vitro. Moreover, no significant binding of Al to SOD was demonstrated, and the amounts of its metal constituents, Cu and Zn, were not affected by preincubation of the enzyme with Al. The effect of the different compounds tested on the rate of autoxidation of the indicating scavenger, pyrogallol, and a suitable hypothesis on their role in the oxidation process are also discussed.

Antioxidant enzymes and lipoperoxide in blood in uremic children and adolescents

To determine whether oxidant-antioxidant balance is altered in chronic renal failure, antioxidant enzymes and lipid peroxide in peripheral blood cells and lipid peroxide in plasma were measured. Nine children and adolescents maintained on hemodialysis (HD), 9 on continuous ambulatory peritoneal dialysis (CAPD), and 14 controls were studied. Lipid peroxide was assayed fluorimetrically as thiobarbituric acid-reactive substances, superoxide dismutases by radioimmunoassays. Both manganese and copper-zinc superoxide dismutases in lymphocytes and monocytes in the HD and CAPD patients, and manganese superoxide dismutase in polymorphs in the HD patients were higher than in the controls. Copper-zinc superoxide dismutase, glutathione peroxidase, and catalase in erythrocytes were unaltered. The lipid peroxide level in plasma in the dialyzed patients was increased, whereas those in polymorphs and lymphocytes were unaltered. Triglyceride and total cholesterol in plasma in the dialyzed patients were also increased. The plasma lipid peroxide in the patients correlated with the triglyceride and total cholesterol level. This is the first study in which manganese superoxide dismutase is measured in nucleated cells of the patients with chronic renal failure. The present results suggest that increased superoxide dismutases protect against oxidative stress induced by chronic renal failure in nucleated cells but in neither erythrocytes nor plasma.