Hemodialysis membrane-induced activation of phagocyte oxidative metabolism detected in vivo and in vitro within microamounts of whole blood

The impacts of dietary antioxidants on cardiovascular events in hemodialysis patients: An update on the cellular and molecular mechanisms

Cardiovascular-related complications (CVCs) are the primary cause of death in patients undergoing hemodialysis (HD), accounting for greater than half of all deaths. Beyond traditional risk factors, chronic inflammation, extreme oxidative stress (OS), and endothelial dysfunction emerge as major contributors to accelerated CVCs in HD patients. Ample evidence shows that HD patients are constantly exposed to excessive OS, due to uremic toxins and pro-oxidant molecules that overwhelm the defense antioxidant mechanisms. The present study highlights the efficiency of natural antioxidant supplementation in managing HD-induced inflammation, OS, and consequently CVCs. Moreover, it discusses the underlying molecular mechanisms by which these antioxidants can decrease mitochondrial and endothelial dysfunction and ameliorate CVCs in HD patients. Given the complex nature of OS and its molecular pathways, the utilization of specific antioxidants as a polypharmacotherapy may be necessary for targeting each dysregulated signaling pathway and reducing the burden of CVCs.

Design of the Functional Dialysis Membrane with a Catalase Pseudoactive Center on the Surface

Here, we have designed a functional dialysis membrane with a catalase pseudoactive center on the surface. To make the catalase pseudoactive center, we have modified the regenerated cellulose dialysis membrane with methylated or octylated poly(1-vinylimidazole) (PVIm-Me or PVIm-Oc), followed by manganese or iron tetrakis(4-carboxyphenyl)porphyrin (Mn- or Fe-TCPP), using the layer-by-layer (LbL) method. As a result of the optimization, the dialysis membrane modified with 25 mol % methylated poly(1-vinylimidazole) [PVIm-Me(25)] and Mn-TCPP produced the highest amount of oxygen (O2) from hydrogen peroxide (H2O2) without the decomposition of Mn-TCPP. Conversely, Mn- and Fe-TCPP were decomposed under other experimental conditions in the presence of H2O2. These results suggest the conversion of H2O2 to O2 by catalase catalytic activity on the surface coated with PVIm-Me(25) and Mn-TCPP.

Biomonitoring of Oxidative-Stress-Related Genotoxic Damage in Patients with End-Stage Renal Disease

Chronic kidney disease (CKD), a common progressive renal failure characterized by the permanent loss of functional nephrons can rapidly progress to end-stage renal disease, which is known to be an irreversible renal failure. In the therapy of ESRD, there are controversial suggestions about the use of regular dialysis, since it is claimed to increase oxidative stress, which may increase mortality in patients. In ESRD, oxidative-stress-related DNA damage is expected to occur, along with increased inflammation. Many factors, including heavy metals, have been suggested to exacerbate the damage in kidneys; therefore, it is important to reveal the relationship between these factors in ESRD patients. There are very few studies showing the role of oxidative-stress-related genotoxic events in the progression of ESRD patients. Within the scope of this study, genotoxic damage was evaluated using the comet assay and 8-OHdG measurement in patients with ESRD who were undergoing hemodialysis. The biochemical changes, the levels of heavy metals (aluminum, arsenic, cadmium, lead, and mercury) in the blood, and the oxidative biomarkers, including superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and malondialdehyde (MDA) levels were evaluated, and their relationship with genotoxic damages was revealed. Genotoxicity, oxidative stress, and heavy-metal levels, except mercury, increased significantly in all renal patients. DNA damage, 8OHdG, and MDA significantly increased, and GSH significantly decreased in patients undergoing dialysis, compared with those not having dialysis. The duration and the severity of disease was positively correlated with increased aluminum levels and moderate positively correlated with increased DNA damage and cadmium levels. In conclusion, this study revealed that the oxidative-stress-related DNA damage, and also the levels of Al and Cd, increased in ESRD patients. It is assumed that these changes may play an important role in the progression of renal damage. Approaches for reducing oxidative-stress-related DNA damage and heavy-metal load in ESRD patients are recommended.

Alleviation of Oxidative Stress during Hemodialysis Sessions by Hemodialysis Membrane Innovation: A Multidisciplinary Perspective

Oxidative stress is prevalent in end-stage kidney disease patients receiving chronic hemodialysis and is associated with heavy cardiovascular disease burdens and increased mortality risks. Hemoincompatible hemodialysis membranes per se contribute to the activation of oxidative reactions and the generation of oxygen free radicals. Since the early 1990s, vitamin E-coated membranes have been extensively used in hemodialysis patients to reduce oxidative stress during hemodialysis sessions. However, the beneficial effects of vitamin E-coated membranes versus unmodified synthetic membranes on long-term patient-centered outcomes, such as survival, quality of life, and prevalence of cardiovascular diseases, remain controversial. Accordingly, novel antioxidant hemodialysis membranes were prepared to replace the use of vitamin E-coated membranes despite the translational research on these membranes unfortunately coming to a standstill. In this review, we first summarize the state-of-the-art on the use of vitamin E-coated membranes in hemodialysis patients to highlight their strengths and limitations. Then, we discuss the latest advances in fabricating antioxidant hemodialysis membranes and provide perspectives to bridge knowledge gaps between laboratorial investigations and clinical practice in fabricating antioxidant hemodialysis membranes.

Albumin redox state of maintenance haemodialysis patients is positively altered after treatment

BACKGROUND AND AIM

Maintenance haemodialysis patients have increased morbidity and mortality which is mainly driven by an elevated inflammation level due to the uraemic milieu. A major part of this increased inflammation level is the degree of oxidative stress which can be assessed by albumin redox state (ARS). Aim of this study was to evaluate how the ARS is affected by a haemodialysis treatment and different dialyzer properties.

METHODS

ARS was determined before and after haemodialysis treatment by fractionating it into reduced human mercaptalbumin (HMA), reversibly oxidized human non-mercaptalbumin 1 (HNA-1), and irreversibly oxidized human non-mercaptalbumin 2 (HNA-2) by high-performance liquid chromatography. In healthy individuals, albumin circulates in the following proportions: HMA 70-80%, HNA-1 20-30% and HNA-2 2-5%. High flux (FX 100 [Fresenius Medical Care], BG 1.8 [Toray], Xevonta Hi 18 [B. Braun], CTA-2000 [Kawasumi]) and low flux FX10 [Fresenius Medical Care] dialyzers were used.

RESULTS

58 patients (59% male, median age 68 years, median time on haemodialysis 32 month) were included in the study. Before haemodialysis treatment, HMA (median 55.9%, IQR 50.1-61.2%) was substantially lower than in healthy individuals. Accordingly, oxidized albumin fractions were above the level of healthy individuals (median HNA-1 38.5%, IQR 33.3-43.2%; median HNA-2 5.8%, IQR 5.1-6.7%). Before haemodialysis treatment HMA was significantly higher in patients usually treated with high flux membranes (p < 0.01). After haemodialysis treatment there was a significant increase of HMA and a decrease of HNA-1 and HNA-2 (p < 0.01). These effects were more pronounced in patients treated with high flux dialyzers (p < 0.01). There were no differences of ARS alteration with regard to the dialyzer´s sterilization mode or the presence of diabetes.

CONCLUSION

The study confirms that the ARS is positively altered by haemodialysis and shows for the first time that this effect depends on dialyzer properties.

The Role of Oxidative Stress in Kidney Injury

Acute kidney injury and chronic kidney disease are among the most common non-communicable diseases in the developed world, with increasing prevalence. Patients with acute kidney injury are at an increased risk of developing chronic kidney disease. One of kidney injury's most common clinical sequelae is increased cardiovascular morbidity and mortality. In recent years, new insights into the pathophysiology of renal damage have been made. Oxidative stress is the imbalance favoring the increased generation of ROS and/or reduced body's innate antioxidant defense mechanisms and is of pivotal importance, not only in the development and progression of kidney disease but also in understanding the enhanced cardiovascular risk in these patients. This article summarizes and emphasizes the role of oxidative stress in acute kidney injury, various forms of chronic kidney disease, and also in patients on renal replacement therapy (hemodialysis, peritoneal dialysis, and after kidney transplant). Additionally, the role of oxidative stress in the development of drug-related nephrotoxicity and also in the development after exposure to various environmental and occupational pollutants is presented.

Hemodialysis raises oxidative stress through carbon-centered radicals despite improved biocompatibility

Leukocyte activation and the resulting oxidative stress induced by bioincompatible materials during hemodialysis impact the prognosis of patients. Despite multiple advances in hemodialysis dialyzers, the prognosis of hemodialysis patients with complications deeply related to oxidative stress, such as diabetes mellitus, remains poor. Thus, we re-evaluated the effects of hemodialysis on multiple reactive oxygen species using electron spin resonance-based methods for further improvement of biocompatibility in hemodialysis. We enrolled 31 patients in a stable condition undergoing hemodialysis using high-flux polysulfone dialyzers. The effects of hemodialysis on reactive oxygen species were evaluated by two methods: MULTIS, which evaluates serum scavenging activities against multiple hydrophilic reactive oxygen species, and i-STrap, which detects lipophilic carbon-center radicals. Similar to previous studies, we found that serum hydroxyl radical scavenging activity significantly improved after hemodialysis. Unlike previous studies, we discovered that scavenging activity against alkoxyl radical was significantly reduced after hemodialysis. Moreover, patients with diabetes mellitus showed a decrease in serum scavenging activity against alkyl peroxyl radicals and an increase in lipophilic carbon-center radicals after hemodialysis. These results suggest that despite extensive improvements in dialyzer membranes, the forms of reactive oxygen species that can be eliminated during dialysis are limited, and multiple reactive oxygen species still remain at increased levels during hemodialysis.

Association between serum advanced oxidation protein products and mortality risk in maintenance hemodialysis patients

BACKGROUND

The association between serum advanced oxidation protein products (AOPP) and mortality risk remains equivocal. We aimed to assess the correlation of serum AOPP levels with the risk of all-cause mortality in hemodialysis (HD) patients.

METHODS

A total of 1394 maintenance HD patients with complete data on AOPP and related parameters were included from China Collaborative Study on Dialysis (CCSD), a multi-center, prospective cohort study. The primary outcome was all-cause mortality, the secondary outcome was cardiovascular disease (CVD) mortality.

RESULTS

During a median follow-up duration of 5.2 years (IQR, 2.1-5.4), all-cause mortality occurred in 492 (31.4%) participants. Overall, there was a reversed L-shaped association between serum AOPP and all-cause mortality in HD patients (P for nonlinearity = 0.04), with an inflection point at 87 µmol/L. Accordingly, there was no significant association between serum AOPP and all-cause mortality (per SD increment; HR, 0.94; 95%CI, 0.84, 1.05) in participants with AOPP < 87 µmol/L. However, there was a positive relationship of serum AOPP and all-cause mortality (per SD increment; HR, 1.24; 95%CI, 1.08, 1.42) in those with AOPP ≥ 87 µmol/L. Moreover, a similar trend was found for CVD mortality.

CONCLUSIONS

Elevated serum AOPP levels were associated with higher risk of all-cause mortality in Chinese maintenance HD patients.

Plasma Catestatin Levels and Advanced Glycation End Products in Patients on Hemodialysis

Catestatin (CST) is a pleiotropic peptide involved in cardiovascular protection with its antihypertensive and angiogenic effects. Considering that patients with end-stage renal disease (ESRD) who are undergoing hemodialysis (HD) are associated with higher cardiovascular risk, the aim of this study was to investigate plasma CST levels in HD patients, compare them to healthy controls and evaluate possible CST associations with advanced glycation end products (AGEs) and laboratory, anthropometric and clinical parameters. The study included 91 patients on HD and 70 healthy controls. Plasma CST levels were determined by an enzyme-linked immunosorbent assay in a commercially available diagnostic kit, while AGEs were determined using skin autofluorescence. Plasma CST levels were significantly higher in the HD group compared to the controls (32.85 ± 20.18 vs. 5.39 ± 1.24 ng/mL, p < 0.001) and there was a significant positive correlation between CST and AGEs (r = 0.492, p < 0.001). Furthermore, there was a significant positive correlation between plasma CST levels with both the Dialysis Malnutrition Score (r = 0.295, p = 0.004) and Malnutrition-Inflammation Score (r = 0.290, p = 0.005). These results suggest that CST could be playing a role in the complex pathophysiology of ESRD/HD and that it could affect the higher cardiovascular risk of patients on HD.

The importance of polymorphisms of regulatory and catalytic antioxidant proteins in chronic kidney disease

Both excessive production of reactive oxygen species (ROS) and impaired antioxidant function are found in patients with chronic kidney disease (CKD). Therefore, individual susceptibility towards CKD can be induced by functional variations of genes encoding antioxidant regulatory (nuclear factor erythroid 2 - related factor 2 (Nrf2)) and catalytic (superoxide dismutase (SOD2) and glutathione peroxidase (GPX1)) proteins. Several types of single nucleotide polymorphisms (SNPs) have been found within the genes encoding these proteins, with Nrf2 (-617C/A), SOD2 (Ala16Val) and GPX1 (Pro198Leu) conferring impaired catalytic activity. The most unexplored gene polymorphism in CKD susceptibility, progression and survival, with only two original studies published, is the Nrf2 (-617C/A) polymorphism. The results of these studies showed that there was no individual impact of this polymorphism on the susceptibility towards end stage renal disease (ESRD) development, oxidative phenotype and mortality. However, Nrf2 had a significant role in ESRD risk and survival, when combined with other antioxidant genes. The results regarding the impact of SOD2 (Ala16Val) and GPX1 (Pro198Leu) polymorphisms on either CKD or ESRD are still inconclusive. Namely, some studies showed that patients having variant SOD2 (Val) or GPX1 (Leu) allele were at increased risk of CKD development and progression, while other studies reported only weak or no association between these polymorphisms and CKD. Surprisingly, the only study that reported an association of GPX1 polymorphism with overall/cardiovascular survival in ESRD patients showed a significant impact of low activity GPX1 (Leu/Leu) genotype on better survival. In this review, we comprehensively and critically appraise the literature on these polymorphisms related to oxidative stress in CKD patients, in order to identify gaps and provide recommendations for further clinical research and translation. New developments in the field of antioxidant polymorphisms in CKD patients could lead to better stratification of CKD patients, based on a prognostic antioxidant gene panel, and provide a more personalised medicine approach for the need of antioxidant therapy in these patients.

Neutrophil Activation and Neutrophil Extracellular Trap Formation in Dialysis Patients

Rationale & Objective

The removal of metabolic waste by passing blood through synthetic tubing and membranes generates an immune response, even with the most biocompatible materials available. We evaluated blood levels of neutrophil activation and cell death during dialysis to devise a set of markers by which future dialysis interventions might be measured for biocompatibility.

Study Design

Observational, case control.

Setting & Participants

30 patients with end-stage kidney disease in Seattle, WA, evaluated during 30 dialysis procedures in out- and inpatient settings were compared with 27 healthy (negative) controls and 20 nondialysis patients with systemic lupus erythematosus as positive controls.

Predictor(s)

Blood levels of neutrophil activation (calprotectin and peroxidase activity) and cell death (cell-free DNA and neutrophil extracellular traps) were assayed.

Outcome(s)

Markers of neutrophil activation and cell death can be used to assess immune response during dialysis.

Analytical Approach

Descriptive analysis and group comparisons.

Results

Intradialytic levels of neutrophil activation markers are higher than prehemodialysis levels (P < 0.05), demonstrating neutrophil activation during hemodialysis. Less neutrophil activation occurs with peritoneal dialysis (P < 0.05). Immunosuppressive treatment and anticoagulant therapy did not seem to affect the capacity of neutrophils to undergo activation with hemodialysis. Finally, levels of hemodialysis-induced neutrophil activation correlated with markers of endothelial activation (r = 0.44; P = 0.01).

Limitations

Low sample size with heterogeneous patient cohort.

Conclusions

Neutrophil activation occurs during hemodialysis, potentially contributing to endothelial inflammation and damage. Neutrophil activation markers are novel and sensitive measures of biocompatibility for improving dialysis.

Cardiovascular disease in dialysis patients

Cardiovascular disease (CVD) is a highly common complication and the first cause of death in patients with end-stage renal disease (ESRD) on haemodialysis (HD). In this population, mortality due to CVD is 20 times higher than in the general population and the majority of maintenance HD patients have CVD. This is likely due to ventricular hypertrophy as well as non-traditional risk factors, such as chronic volume overload, anaemia, inflammation, oxidative stress, chronic kidney disease–mineral bone disorder and other aspects of the ‘uraemic milieu’. Better understanding the impact of these numerous factors on CVD would be an important step for prevention and treatment. In this review we focus non-traditional CVD risk factors in HD patients.

Antioxidant Supplementation in Renal Replacement Therapy Patients: Is There Evidence?

The disruption of balance between production of reactive oxygen species and antioxidant systems in favor of the oxidants is termed oxidative stress (OS). To counteract the damaging effects of prooxidant free radicals, all aerobic organisms have antioxidant defense mechanisms that are aimed at neutralizing the circulating oxidants and repair the resulting injuries. Antioxidants are either endogenous (the natural defense mechanisms produced by the human body) or exogenous, found in supplements and foods. OS is present at the early stages of chronic kidney disease, augments progressively with renal function deterioration, and is further exacerbated by renal replacement therapy. End-stage renal disease patients, on hemodialysis (HD) or peritoneal dialysis (PD), suffer from accelerated OS, which has been associated with increased risk for mortality and cardiovascular disease. During HD sessions, the bioincompatibility of dialyzers and dialysate trigger activation of white blood cells and formation of free radicals, while a significant loss of antioxidants is also present. In PD, the bioincompatibility of solutions, including high osmolality, elevated lactate levels, low pH, and accumulation of advanced glycation end-products trigger formation of prooxidants, while there is significant loss of vitamins in the ultrafiltrate. A number of exogenous antioxidants have been suggested to ameliorate OS in dialysis patients. Vitamins B, C, D, and E, coenzyme Q10, L-carnitine, a-lipoic acid, curcumin, green tea, flavonoids, polyphenols, omega-3 polyunsaturated fatty acids, statins, trace elements, and N-acetylcysteine have been studied as exogenous antioxidant supplements in both PD and HD patients.

Changes in antioxidant status associated with haemodialysis in chronic kidney disease

Oxidative stress has been implicated in the pathogenesis, progression of chronic kidney disease (CKD) and development of cardiovascular complications. Hemodialysis (HD) has also been described to contribute significantly to oxidative stress in CKD patients, though reports are conflicting.

Objective

We evaluated the effects of one session of HD on the antioxidant capacity and lipid peroxidation in CKD patients.

Method

Thirty-six CKD patients requiring HD were recruited into this study. Participants were naïve to HD and each completed a session of three hours using polysulfone membrane dialyzers. Blood samples were collected before and after dialysis. Total antioxidant capacity (TAC) was measured by ferric reducing antioxidant power (FRAP) while malondialdehyde (MDA) was measured using thiobarbituric acid-reactive substance (TBARS). Comparison was made between pre-HD and post-HD values of TAC and MDA respectively, p value of <0.05 was taken as significant.

Result

Mean age and estimated glomerular filtration rate of subjects were 45 ±15 years and 6.3± 4.7mls/1.73m² respectively. There was significant decrease in the mean TAC from 1232.2 ± 495.6 µmol Trolox equiv/ to 832.4 ± 325.7 µmol Trolox equiv/L post-dialysis (p< 0.001) while MDA values were similar before and after HD (11.8 ± 1.8 vs 11.8 ± 2.331)µmol/L (p> 0.05). There was no significant association between changes in antioxidant status following HD with blood flow rate, ultrafiltration volume nor dialyzer per size.

Conclusion

A session of HD in patients with CKD is associated with significant reduction of the total antioxidants capacity; and no effect on MDA levels.

Funding

No external funding received.

Oxidative stress in hemodialysis: Causative mechanisms, clinical implications, and possible therapeutic interventions

Oxidative stress (OS) is the result of prooxidant molecules overwhelming the antioxidant defense mechanisms. Hemodialysis (HD) constitutes a state of elevated inflammation and OS, due to loss of antioxidants during dialysis and activation of white blood cells triggering production of reactive oxygen species. Dialysis vintage, dialysis methods, and type and condition of vascular access, biocompatibility of dialyzer membrane and dialysate, iron administration, and anemia all can play a role in aggravating OS, which in turn has been associated with increased morbidity and mortality. Oral or intravenous administration of antioxidants may detoxify the oxidative molecules and at least in part repair OS-mediated tissue damage. Lifestyle interventions and optimization of a highly biocompatible HD procedure might ameliorate OS development in dialysis.

Preserved Respiratory and Phagocytic Functions of Phagocytes Exposed to Flat Sheet Plasmapheresis Equipment

Monocytes and polymorphonuclear leukocytes (PMN) were tested for functional integrity after exposure to flat sheet plasmapheresis equipment. Purified PMN were tested for chemiluminescence activity in response to a variety of triggers of the respiratory burst. Monocytes were assessed for their capacity to ingest erythrocytes sensitized with varying amounts of IgG antibodies. Both assays were demonstrated to be sensitive hallmarks of functional modulation. However, no functional differences were noted between phagocytes from blood collected prior to pheresis and those exposed to flat sheet plasmapheresis cylinders. These data suggest that plasmapheresis with the Au-topheresis C system does not influence the respiratory and phagocytic function of phagocytes returned back to the donor and implies that contact of phagocytes with artificial surfaces and/or their exposure to surface-activated plasma factors generated in the collection cylinder are minimal when using this plasmapheresis method.

Kinetics of Pulmonary Leukocyte Sequestration in Man during Hemodialysis with Different Membrane-Types

Although it has been suggested that pulmonary sequestration of leukocytes could account for membrane-dependent white blood cell depletion in HD, direct evidence in patients is still lacking. Therefore a study was initiated to test whether and how leukocytes distribute in the lung circulation during HD with different membranes. Thirteen patients suffering from chronic renal failure underwent lung scintigraphy during HD with cuprophane (n = 3), hemophane (n = 8) and polysulfone (n = 2) lowflux capillary dialyzers. Isolated autologous leukocytes were labelled with 99m-Technetium and reinfused before starting HD. Distribution of leukocyte related activity was registered by lung scintigraphy. In comparison to normal lung scintigraphy performed without HD, an impressive redistribution peak was demonstrated 10-20 min after the start of HD with cuprophane and also to a lesser extent with hemophane. When HD was performed with polysulfone the decrease in activity was delayed but no real redistribution was obtained.

In accordance with other phenomena, such as peripheral leukopenia and changes in granulocyte oxidative metabolism, pulmonary sequestration of leukocytes takes place in man in the initial phase of HD and appears to be strongly dependent on the type of membrane. (Int J Artif Organs 1990; 13: 729-36)

Phagocyte Metabolic Activity during Hemodialysis with Different Dialyzers Not Affecting the Number of Circulating Phagocytes

Overall leukocyte counts decrease during certain forms of hemodialysis, but little information is available on the intradialytic evolution of phagocytic metabolic function, especially during dialysis with dialyzers not affecting the number of circulating phagocytes. This study evaluated the phagocytic capacity of granulocytes and monocytes to generate CO2 out of glucose under basic unchallenged conditions and after stimulation with latex or zymosan, before and after 15, 60 and 240 minutes of dialysis with reused cuprophan, AN69S, polysulphone, polymethylmethacrylate and hemophan hemodialyzers. Phagocytic metabolic function was assessed in whole blood on the basis of 14CO2-production from labelled glucose during the phagocytic process. There were no changes in basic unchallenged CO2-production with any of the dialyzers. Reactivity to latex and zymosan, expressed per number of phagocytes, showed no decrease, irrespective of the membrane type. For polymethylmethacrylate and reused cuprophan, a slight but significant increase in metabolic reactivity was observed in response to latex and zymosan. The test employed may give a screening picture of the phagocytic reaction to contact with dialyzers and membranes and thus of their degree of biocompatibility towards the phagocyte system.

Amyloid Bone Disease and Highly Permeable Synthetic Membranes

The effect of different highly permeable membranes on amyloid bone disease (ABD) was retrospectively evaluated in patients on renal replacement therapy (RRT) in our Unit with a dialytic age of more than 4 years. A group of 36 patients (age 60 ± 12 years) after a variable period (28 ± 29 months) on hemodialysis with cuprophane membrane (CU-HD), were moved to HDF with a reinfusate volume of 22 ± 1 1/session, for a period of 65 ± 26 months using the following membranes: AN69 1.6 m2, PAN 1.8, PMMA 2.1, PS 1.3, polyamide (PA) 1.3 and 1.6. Bone x-rays of wrists, hips and shoulders were taken annually and the presence of ABD was evaluated according to generally accepted criteria. ABD occurred in 4 patients after a period of 73 ± 30 months on CU-HD only; it developed in 4/7 patients an AN69, in 4/6 on PAN, in 3/5 on PMMA, in 3/5 on PS; no patient of the 13 on PA developed ABD. Comparing patients on PA with those on other synthetic membranes, no significant difference was found in dialysis time (73 ± 19 vs 83 ± 28 months) as well as in age (59 ± 13 vs 61 ± 11 years) at ABD on set, when present. These data strongly encourage prospective studies enrolling more patients for a longer period of observation in order to evaluate possible differences on ABD development among various synthetic membranes.

Oxidative Stress in Hemodialysis Patients: A Review of the Literature

Hemodialysis (HD) patients are at high risk for all-cause mortality and cardiovascular events. In addition to traditional risk factors, excessive oxidative stress (OS) and chronic inflammation emerge as novel and major contributors to accelerated atherosclerosis and elevated mortality. OS is defined as the imbalance between antioxidant defense mechanisms and oxidant products, the latter overwhelming the former. OS appears in early stages of chronic kidney disease (CKD), advances along with worsening of renal failure, and is further exacerbated by the HD process per se. HD patients manifest excessive OS status due to retention of a plethora of toxins, subsidized under uremia, nutrition lacking antioxidants and turn-over of antioxidants, loss of antioxidants during renal replacement therapy, and leukocyte activation that leads to accumulation of oxidative products. Duration of dialysis therapy, iron infusion, anemia, presence of central venous catheter, and bioincompatible dialyzers are several factors triggering the development of OS. Antioxidant supplementation may take an overall protective role, even at early stages of CKD, to halt the deterioration of kidney function and antagonize systemic inflammation. Unfortunately, clinical studies have not yielded unequivocal positive outcomes when antioxidants have been administered to hemodialysis patients, likely due to their heterogeneous clinical conditions and underlying risk profile.

Correlation of bioelectrical impedance analysis phase angle with changes in oxidative stress on end-stage renal disease patients, before, during, and after dialysis

Chronic kidney disease is a condition that promotes oxidative stress. There are conflicting evidence about the role of hemodialysis on oxidative stress, that are mostly related with the various types of membrane materials used, the quality and type of dialysate, the method used, etc. The phase angle (PhA), which is determined with bioelectrical impedance analysis (BIA), measures the functionality of cell membranes. In this study, the correlation of the PhA with parameters of oxidative stress is attempted for the first time. We evaluated parameters of oxidative status as total antioxidant capacity (TAC) in erythrocytes (RBCs) and plasma of patients with ESRD undergoing hemodialysis with low flux synthetic polysulfone membranes. Measurements were recorded from 30 patients (16 men and 14 women) aged 64 ± 14 years before, during, and after dialysis, and in 15 healthy volunteers aged 56 ± 12 years The PhA was obtained by BIA. The plasma TAC increased significantly (41%, p < 0.05). Intracellular TAC noted a non-significant increase. Total antioxidant capacity of the patients before and after hemodialysis was significantly lower from the healthy volunteers (p < 0.05) showing that ESRD patients are at the state of increased oxidative stress. The PhA increased in significantly positive correlation with plasma TAC at the end of hemodialysis. The process of hemodialysis with biocompatible synthetic membranes and bicarbonate dialysate improved plasma TAC. The positive correlation of PhA with extracellular TAC could evolve to a method of oxidative stress estimation by BIA but further research is needed.

Evaluation of a polynephron dialysis membrane considering new aspects of biocompatibility

PURPOSE

The biocompatibility of dialyzers may influence the inflammatory state of hemodialysis patients. This study compares the effect of a high-flux polynephron membrane with other high-flux membranes, helixone and polyamide, on some inflammation biomarkers based on the analysis of circulating mononuclear cells (MC).

METHODS

The study included 47 patients on hemodialysis with helixone and polyamide; 9 formed the control group, without changes in their dialyzers throughout the study, and 38 formed the intervention group, in which their dialyzers were replaced by polynephron. In both groups, blood samples were taken at the beginning of the study before and after hemodialysis session, and at the end of the study 4 months later. In each extraction, biochemical parameters were determined, and MC isolated using Ficoll gradient. Production of reactive oxygen species and the percentage of activated MC (CD14+CD16+) were measured by flow cytometry, and protein levels of heat-shock proteins (Hsp70/Hsp90) studied by Western blot.

RESULTS

After 1 hemodialysis session with different membranes, no significant differences were observed in the different parameters considered. After 4 months of dialysis with polynephron, a significant reduction in the percentage of CD14+CD16+ and in the β2-microglobulin reduction ratio were found, with respect to helixone and polyamide, without changes in the other parameters analyzed.

CONCLUSIONS

The use of polynephron for 4 months reduces the percentage of CD14+CD16+ compared to helixone and polyamide, suggesting a better profile regarding activation of the inflammatory response. These findings could be explained by a better biocompatibility or an increased reduction of medium-sized toxic molecules.

Evaluation of neutrophil function during hemodialysis treatment in healthy dogs under anesthesia with sevoflurane

This study evaluated the number and function of neutrophils during 3 hr of hemodialysis in healthy dogs under anesthesia. Isolated neutrophils were used to assess neutrophil adhesion, phagocytosis and the oxidative burst. At 0.5 and 3 hr after the start of hemodialysis treatment, there was a decrease in neutrophil number. The phagocytic ability of neutrophils was decreased 3 hr after the start of hemodialysis. In conclusion, this study demonstrated that hemodialysis reduces the number and phagocytic ability of neutrophils during treatment. However, these changes recover within 24 hr of hemodialysis.

Oxidative stress and nucleic acid oxidation in patients with chronic kidney disease

Patients with chronic kidney disease (CKD) have high cardiovascular mortality and morbidity and a high risk for developing malignancy. Excessive oxidative stress is thought to play a major role in elevating these risks by increasing oxidative nucleic acid damage. Oxidative stress results from an imbalance between reactive oxygen/nitrogen species (RONS) production and antioxidant defense mechanisms and can cause vascular and tissue injuries as well as nucleic acid damage in CKD patients. The increased production of RONS, impaired nonenzymatic or enzymatic antioxidant defense mechanisms, and other risk factors including gene polymorphisms, uremic toxins (indoxyl sulfate), deficiency of arylesterase/paraoxonase, hyperhomocysteinemia, dialysis-associated membrane bioincompatibility, and endotoxin in patients with CKD can inhibit normal cell function by damaging cell lipids, arachidonic acid derivatives, carbohydrates, proteins, amino acids, and nucleic acids. Several clinical biomarkers and techniques have been used to detect the antioxidant status and oxidative stress/oxidative nucleic acid damage associated with long-term complications such as inflammation, atherosclerosis, amyloidosis, and malignancy in CKD patients. Antioxidant therapies have been studied to reduce the oxidative stress and nucleic acid oxidation in patients with CKD, including alpha-tocopherol, N-acetylcysteine, ascorbic acid, glutathione, folic acid, bardoxolone methyl, angiotensin-converting enzyme inhibitor, and providing better dialysis strategies. This paper provides an overview of radical production, antioxidant defence, pathogenesis and biomarkers of oxidative stress in patients with CKD, and possible antioxidant therapies.

Neutrophil-derived Oxidants and Proteinases as Immunomodulatory Mediators in Inflammation

Neutrophils generate potent microbicidal molecules via the oxygen-dependent pathway, leading to the generation of reactive oxygen intermediates (ROI), and via the non-oxygen dependent pathway, consisting in the release of serine proteinases and metalloproteinases stored in granules. Over the past years, the concept has emerged that both ROI and proteinases can be viewed as mediators able to modulate neutrophil responses as well as the whole inflammatory process. This is well illustrated by the oxidative regulation of proteinase activity showing that oxidants and proteinases acts is concert to optimize the microbicidal activity and to damage host tissues. ROI and proteinases can modify the activity of several proteins involved in the control of inflammatory process. Among them, tumour necrosis factor-α and interleukin-8, are elective targets for such a modulation. Moreover, ROI and proteinases are also able to modulate the adhesion process of neutrophils to endothelial cells, which is a critical step in the inflammatory process.

HDL proteome in hemodialysis patients: a quantitative nanoflow liquid chromatography-tandem mass spectrometry approach

Aside from a decrease in the high-density lipoprotein (HDL) cholesterol levels, qualitative abnormalities of HDL can contribute to an increase in cardiovascular (CV) risk in end-stage renal disease (ESRD) patients undergoing chronic hemodialysis (HD). Dysfunctional HDL leads to an alteration of reverse cholesterol transport and the antioxidant and anti-inflammatory properties of HDL. In this study, a quantitative proteomics approach, based on iTRAQ labeling and nanoflow liquid chromatography mass spectrometry analysis, was used to generate detailed data on HDL-associated proteins. The HDL composition was compared between seven chronic HD patients and a pool of seven healthy controls. To confirm the proteomics results, specific biochemical assays were then performed in triplicate in the 14 samples as well as 46 sex-matched independent chronic HD patients and healthy volunteers. Of the 122 proteins identified in the HDL fraction, 40 were differentially expressed between the healthy volunteers and the HD patients. These proteins are involved in many HDL functions, including lipid metabolism, the acute inflammatory response, complement activation, the regulation of lipoprotein oxidation, and metal cation homeostasis. Among the identified proteins, apolipoprotein C-II and apolipoprotein C-III were significantly increased in the HDL fraction of HD patients whereas serotransferrin was decreased. In this study, we identified new markers of potential relevance to the pathways linked to HDL dysfunction in HD. Proteomic analysis of the HDL fraction provides an efficient method to identify new and uncharacterized candidate biomarkers of CV risk in HD patients.

The role of oxidative stress in chronic kidney disease

New, reliable circulating oxidative stress markers have become available in chronic kidney disease (CKD) patients and have confirmed the long held belief that CKD is a pro-oxidant state. However, several questions related to this state of oxidative stress remain largely unresolved. First, the relative importance of each type of oxidant involved has been insufficiently evaluated. Only two recent studies have addressed this issue, and both suggested that chlorinated stress played a central role. Second, as only few population-based studies are available, the prevalence of oxidative stress among CKD patients remains undetermined. Third, although the link between oxidative stress and inflammation in CKD is emerging as a key process contributing to the genesis of oxidative stress in these patients, its pathogenesis remains poorly defined. Fourth, data favoring the involvement of oxidative stress in uremic toxicity are still limited. Finally, while two recent pilot studies have demonstrated that treatment of CKD patients with antioxidants is able to reduce cardiovascular events, information related to the pharmacokinetic characteristics of antioxidants, as well as their efficacy to prevent oxidative stress, is still limited in this patient group. Thus, although existing data suggest a prominent role of CKD-associated oxidative stress in uremic toxicity, further studies are required to definitively prove this concept.

Alterations of erythrocyte structure and cellular susceptibility in patients with chronic renal failure: effect of haemodialysis and oxidative stress

The aim of this study was to investigate erythrocytes rheological behaviour, membrane dynamics and erythrocytes susceptibility to disintegration upon strong oxidative stress induced by dialysis or by external H(2)O(2) among patients with CRF. EPR spectrometry was used to investigate alterations in physical state of cellular components. Generated ROS production induced: (1) significant increase of membrane fluidity in CRF erythrocytes treated with H(2)O(2) (p<0.005) and at 60 min of haemodialysis (p<0.05), (2) significant decrease of cytoskeletal protein-protein interactions (p<0.005) and (3) cellular osmotic fragility (p<0.0005). H(2)O(2) exacerbated these changes. Erythrocytes from CRF patients have changed rheological behaviour and present higher susceptibility to disintegration. Erythrocytes membrane characteristics indicate that CRF patients possess younger and more flexible cells, which are more susceptible to oxidative stress. This may contribute to the shortened survival of young erythrocytes in CRF patients.

Haemodialysis induces mitochondrial dysfunction and apoptosis

BACKGROUND

Mitochondria play a crucial role in the regulation of the endogenous pathways of apoptosis activated by oxidant stress. Nuclear factor-kappaB (NF-kappaB) is a central integration site for pro-inflammatory signals and oxidative stress.

MATERIALS AND METHODS

Peripheral blood mononuclear cells (PBMC) were isolated from eight end-stage renal disease (ESRD) patients before haemodialysis (Pre-HD) and during the last 10 min of HD (End-HD). A new polysulfone membrane (F70, Fresenius) was used for dialysis. Intracellular generation of reactive oxygen species (ROS), mitochondrial redox potential (Deltapsim) and PBMC apoptosis were determined by flow-cytometry.

RESULTS

Plasma levels of interleukin-6 (IL-6) (24.9+/-7.0 vs. 17.4+/-5.5 pg dL(-1), P<0.05), IL-6 soluble receptor (52.2+/-4.9 vs. 37.6+/-3.2 ng dL(-1), P<0.02) and IL-6 gp130 (405.7+/-41.0 vs. 235.1+/-38.4 ng dL(-1), P<0.02) were higher end-HD compared to pre-HD. IL-6 secretion by the isolated PBMC (24.0+/-2.3 vs. 19.3+/-3.5 pg dL(-1), P<0.02) increased end-HD. Percentage of lymphocytes exhibiting collapse of mitochondrial membrane potential (43.4+/-4.6% vs. 32.6+/-2.9%, P<0.01), apoptosis (33.4+/-7.1% vs. 23.7+/-7.7%, P<0.01), and generation of superoxide (20.7+/-5.2% vs. 12.5+/-2.9%, P<0.02) and hydrogen peroxide (51.1+/-7.8% vs.38.2+/-5.9%, P<0.04) were higher at end-HD than pre-HD. NF-kappaB activation (3144.1+/-208.1 vs. 2033.4+/-454.6 pg well(-1), P<0.02), expression of B-cell lymphoma protein-2 (6494.6+/-1461 vs. 3501.5+/-796.5 ng mL(-1), P<0.03) and heat shock protein-70 (9.81+/-1.47 vs. 6.38+/-1.0 ng mL(-1), P<0.05) increased during HD.

CONCLUSIONS

Intra-dialytic activation of cytokines, together with impaired mitochondrial function, promotes generation of ROS culminating in augmented PBMC apoptosis. There is concomitant activation of pathways aimed at attenuation of cell stress and apoptosis during HD.

Oxidative stress and δ-ALA-D activity in chronic renal failure patients

In this paper, we studied the influence of uremia and hemodialysis on oxidative parameters and delta-aminolevulinic acid dehydratase (delta-ALA-D) activity in control subjects, patients with chronic renal failure (CRF) on hemodialysis treatment (HD) and in patients not undergoing hemodialysis (ND). An increased lipid peroxidation was observed in the serum of HD and ND patients, as measured by the MDA serum levels. However, the level of MDA from erythrocytes was only elevated in HD patients. Blood catalase activity was increased in HD and ND groups. This study also showed a decreased activity of blood delta-aminolevulinic acid dehydratase (delta-ALA-D) in both groups of patients. This study demonstrated a positive correlation between ALA-D activity and hemoglobin, suggesting that inhibition of this enzyme might enhance anemia in CRF. A negative correlation was found between the alteration in delta-ALA-D activity and oxidative stress, which may indicate that the inhibition of ALA-D can be used as an index of oxidative stress.

Serum matrix metalloproteinase-2 and increased oxidative stress are associated with carotid atherosclerosis in hemodialyzed patients

Matrix metalloproteinases (MMPs)/their inhibitors (TIMPs) system and elevated oxidative stress (SOX) have been implicated as important factors in atherosclerosis and vascular remodeling. The aim of the present study was to investigate whether MMPs/TIMPs system is associated with SOX in hemodialyzed (HD) patients. We compared the serum levels of metalloproteinases and their inhibitors, markers of SOX, inflammation and atherosclerosis between HD patients (n=40) with and without cardiovascular disease (CVD) and controls (n=20). Cu/Zn superoxide dismutase (Cu/Zn SOD) were elevated (all p<0.001), whereas total lipid peroxide levels were similar in HD patients and controls. The autoantibodies against oxidized LDL (OxLDL-Ab) levels were increased only in patients with CVD (p<0.05). Intima media thickness (IMT) in both CVD and in patients without CVD significantly exceeded those in the control (p<0.001 and p<0.01, respectively). Serum pre-HD values of MMP-2, TIMP-1 and TIMP-2 were significantly increased in HD patients, especially in the CVD group (all p<0.001), and they were associated with those of Cu/Zn SOD, IMT and CVD prevalence. Multiple regression analysis showed that MMP-2, Cu/Zn SOD levels and age independently and significantly predicted elevated IMT in HD patients. Our results suggest the association between SOX and the MMPs/TIMPs system in HD patients, which could represent one of the mechanisms involved in the progression of atherosclerosis in this population.

The kidney disease wasting: Inflammation, oxidative stress, and diet-gene interaction

The 350,000 maintenance hemodialysis (MHD) patients in the United States have an unacceptably high mortality rate of >20%/year. Almost half of all deaths are assumed to be cardiovascular. Markers of kidney disease wasting (KDW) such as hypoalbuminemia, anorexia, body weight and fat loss, rather than traditional cardiovascular risk factors, appear to be the strongest predictors of early death in these patients. The KDW is closely related to oxidative stress (SOX). Such SOX markers as serum myeloperoxidase are associated with pro-inflammatory cytokines and poor survival in MHD patients. Identifying the conditions that modulate the KDW/SOX-axis may be the key to improving outcomes in MHD patients. Dysfunctional lipoproteins such as a higher ratio of the high-density lipoprotein inflammatory index (HII) may engender or aggravate the KDW, whereas functionally intact or larger lipoprotein pools, as in hypercholesterolemia and obesity, may mitigate the KDW in MHD patients. Hence, a reverse epidemiology or "bad-gone-good" phenomenon may be observed. Diet and gene and their complex interaction may lead to higher proportions of pro-inflammatory or oxidative lipoproteins such as HII, resulting in the aggravation of the SOX and inflammatory processes, endothelial dysfunction, and subsequent atherosclerotic cardiovascular disease and death in MHD patients. Understanding the factors that modulate the KDW/SOX complex and their associations with genetic polymorphism, nutrition, and outcomes in MHD patients may lead to developing more effective strategies to improve outcomes in this and the 20 to 30 million Americans with chronic disease states such as individuals with chronic heart failure, advanced age, malignancies, AIDS, or cachexia.

Skeletal muscle, cytokines, and oxidative stress in end-stage renal disease

BACKGROUND

End-stage renal disease (ESRD) is a state of microinflammation, with increased activation of cytokines and augmented oxidative stress. While peripheral blood mononuclear cells are an established source of reactive oxygen species and inflammatory cytokines during hemodialysis (HD), skeletal muscle is also capable of generating these biomolecules.

METHODS

Femoral arterio-venous (A-V) balance of interleukin-1 (IL-1), IL-6, IL-10, tumor necrosis factor-alpha (TNF-alpha), malonyldialdehyde (MDA), and carbonyl protein (CP) were measured in 17 ESRD patients and 9 healthy volunteers. ESRD patients were studied before (pre-HD) and during HD. mRNA levels of cytokines, heme oxygenase-1 (HO-1), and suppressors of cytokine signaling-2 (SOCS-2) were quantitated in the skeletal muscle by real-time polymerase chain reaction (PCR).

RESULTS

Arterial concentration of MDA (pmol/mL) was higher pre-HD (325.5 +/- 19.6) compared to controls (267.7 +/- 14.7), but decreased intradialysis (248.8 +/- 16.1) (P < 0.01). Dialysis clearance of MDA was 16.9 +/- 3.1 mL/min. CP concentration (nmol/mg protein) in the artery was significantly higher pre-HD (2.29 +/- 0.09) than in controls (1.92 +/- 0.05), and remained stable during HD (2.23 +/- 0.07). Plasma cytokines increased to a variable degree in the artery and vein during HD. A-V balance studies demonstrated that the MDA (17.8%) and CP (5.1%) concentrations increased significantly in the vein intradialysis. Venous concentration of IL-6 was higher than that in the artery during dialysis (16.27 +/- 2.42 vs. 11.29 +/- 2.17 pg/dL, P < 0.01). mRNA levels of IL-6 (0.028 +/- 0.02 vs. 6.69 +/- 0.21), HO-1 (0.96 +/- 0.01 vs. 5.08 +/- 1.11), and SOCS-2 (0.63 +/- 0.12 vs. 0.82 +/- 0.14) in the muscle increased during HD (P < 0.01). Immunohistochemical studies confirmed the increase in IL-6 protein in the skeletal muscle during HD. The intradialytic increase in IL-1, IL-10, and TNF-alpha gene expression was not significant.

CONCLUSION

Skeletal muscle may also contribute to the circulating plasma IL-6 and increased oxidative stress during HD.

Oxidative stress and antioxidant treatment in hypertension and the associated renal damage

Reactive oxygen species (ROS) are elevated in humans with hypertension many of which develop end-stage renal disease (ESRD), and antioxidant capacity is decreased. About one-half of essential hypertensives have a salt-sensitive type of hypertension, and the amount of renal damage that occurs in salt-sensitive hypertensives greatly exceeds that of non-salt-sensitive hypertensives. Antioxidant therapy can improve cardiovascular outcomes in humans but only if sufficient doses are used. Salt-sensitive hypertensive animal models, especially Dahl salt-sensitive rats, have been used to investigate the relationship between hypertension, ROS and end-stage renal damage. In experimental salt-sensitive hypertension, ROS increase and significant renal damage occur. In the Dahl salt-sensitive (S) rat on high Na for 3 weeks, renal damage is mild, renal levels of superoxide dismutase are decreased, and treatment with Tempol reduces arterial pressure. In the Dahl S rat on high Na for 5 weeks, renal damage is severe, GFR and renal plasma flow are decreased, and renal superoxide production is high. Treatment with vitamins C and E decreases renal superoxide production and renal damage and prevents the decrease in renal hemodynamics. Antioxidant treatment reduces arterial pressure, aortic superoxide production and renal inflammation in DOCA-salt rats, and decreases blood pressure and aortic superoxide release and increases bioactive nitric oxide in SHR stroke-prone rats. In conclusion, in both human and experimental salt-sensitive hypertension, superoxide production and renal damage are increased, antioxidant capacity is decreased, and antioxidant therapy can be helpful.

Abnormal Cytokine Synthesis as a Consequence of Increased Intracellular Oxidative Stress in Children Treated with Dialysis

BACKGROUND/AIM

End-stage renal disease (ESRD) induces a clinical state of immunodeficiency with a higher incidence of infections and higher mortality due to infectious complications compared with the normal population. The definite mechanism responsible for the host defense alterations is not well understood. The aim of the study was to investigate intracellularly the relationship between cytokine synthesis and oxidative stress in peripheral blood lymphocytes in children with ESRD.

METHODS

Twenty-one children (age 11.7 +/- 5.8 years) with ESRD treated with hemodialysis (HD; n = 10) and peritoneal dialysis (PD; n = 11) were studied. Nine healthy children of comparable age formed the control group. To determine intracellular oxidative stress we used dihydrorhodamine-123 (DHR), which after oxidation to rhodamine-123 (RHO) emitted a bright fluorescent signal. Intracellular oxidation of DHR in T lymphocytes reflected intracellular oxidative stress. The intracellular synthesis of cytokines (IL-2, IFN-gamma, IL-4, IL-6) was also measured. Both parameters were detected at a single-cell level by flow cytometry. Lymphocyte subsets were evaluated using the monoclonal antibodies conjugated with fluorochromes.

RESULTS

We found that in T lymphocytes the mean fluorescence intensity (MFI), which reflected intracellular oxidative stress, was increased in ESRD patients compared to the controls (CD3+: 34.77 +/- 11.55 vs. 22.55 +/- 4.97, p < 0.01; CD3+CD8+: 34.31 +/- 12.17 vs. 20.77 +/- 4.89, p < 0.01; CD3+CD4+: 36.06 +/- 6.98 vs. 24.44 +/- 7.68, p < 0.001). HD patients showed slightly higher MFI compared to PD patients in CD3+ cells (39.32 +/- 11.70 vs. 30.63 +/- 10.20, NS), in CD3+CD8+ cells (37.90 +/- 14.32 vs. 31.06 +/- 9.34, NS) and in CD3+CD4+ cells (40.10 +/- 2.28 vs. 29.33 +/- 7.06, p < 0.001). The intracellular synthesis of IL-2 was higher in ESRD patients compared to the controls, both in CD3+ cells (31.34 +/- 9.80 vs. 20.49 +/- 15.26%, p < 0.05) and in CD3+CD4+ cells (36.10 +/- 8.69 vs. 24.03 +/- 16.95%, p < 0.05). The intracellular synthesis of IFN-gamma, IL-4 and IL-6 was significantly lower in the ESRD group compared to the controls. Interestingly, in patients treated with HD, negative correlations between the degree of intracellular oxidative stress and intracellular cytokine synthesis in CD3+ lymphocytes were found.

CONCLUSION

Our results show that patients with ESRD, especially those treated with HD, present increased oxidative stress in T lymphocytes, which may lead to decreased cytokine synthesis and abnormal immune response.

mRNA study on Cu/Zn superoxide dismutase induction by hemodialysis treatment

BACKGROUND/AIMS

There is little or no controversy about the increased oxidative stress of hemodialysis (HD) patients. Several reports show that the activity of superoxide dismutase (SOD), one of the major endogenous antioxidant enzymes, in plasma is elevated among HD patients. It is still unclear, however, whether this elevation is due to the promotion of SOD production or a decrease in renal excretion of SOD. This study was designed to investigate the cause of the SOD activation in HD patients, and we examined the expression of SOD mRNA levels in leukocytes of patients with chronic renal failure.

METHODS

The total plasma SOD activity was determined by the nitroblue tetrazolium method, plasma SOD contents by ELISA, and SOD mRNA levels in leukocytes by RT-PCR.

RESULTS

Our results demonstrated that contents and mRNA levels of Cu/Zn SOD in HD patients are 4.4 times and 2.0 times, respectively, as large as those in healthy controls. Furthermore, in contrast to nondialyzed chronic renal failure patients, we observed higher concentrations of Cu/Zn SOD in plasma and a more enhanced mRNA expression of Cu/Zn SOD in leukocytes of HD patients.

CONCLUSION

Increased Cu/Zn SOD mRNA reflects enhanced antioxidant capacity of leukocytes and can be a promising oxidative stress marker in HD patients.