Prospective crossover trial of the influence of vitamin E-coated dialyzer membranes on T-cell activation and cytokine induction

Immune System Dysfunction and Inflammation in Hemodialysis Patients: Two Sides of the Same Coin

Biocompatibility in hemodialysis (HD) has considerably improved in recent decades, but remains an open issue to be solved, appearing essential to reduce systemic inflammation and enhance patients’ clinical outcomes. Clotting prevention, reduction in complement and leukocyte activation, and improvement of antioxidant effect represent the main goals. This review aims to analyze the different pathways involved in HD patients, leading to immune system dysfunction and inflammation. In particular, we mostly review the evidence about thrombogenicity, which probably represents the most important characteristic of bio-incompatibility. Platelet activation is one of the first steps occurring in HD patients, determining several events causing chronic sub-clinical inflammation and immune dysfunction involvement. Moreover, oxidative stress processes, resulting from a loss of balance between pro-oxidant factors and antioxidant mechanisms, have been described, highlighting the link with inflammation. We updated both innate and acquired immune system dysfunctions and their close link with uremic toxins occurring in HD patients, with several consequences leading to increased mortality. The elucidation of the role of immune dysfunction and inflammation in HD patients would enhance not only the understanding of disease physiopathology, but also has the potential to provide new insights into the development of therapeutic strategies.

Monocytes in Uremia

Monocytes play an important role in both innate immunity and antigen presentation for specific cellular immune defense. In patients with chronic renal failure, as well as those treated with maintenance hemodialysis, these cells are largely dysregulated. There is a large body of literature on monocyte alterations in such patients. However, most of the publications report on small series, there is a vast spectrum of different methods and the heterogeneity of the data prevents any meta-analytic approach. Thus, a narrative review was performed to describe the current knowledge. Monocytes from patients with chronic renal failure differ from those of healthy individuals in the pattern of surface molecule expression, cytokine and mediator production, and function. If these findings can be summarized at all, they might be subsumed as showing chronic inflammation in resting cells together with limited activation upon immunologic challenge. The picture is complicated by the fact that monocytes fall into morphologically and functionally different populations and population shifts interact heavily with dysregulation of the individual cells. Severe complications of chronic renal failure such as impaired immune defense, inflammation, and atherosclerosis can be related to several aspects of monocyte dysfunction. Therefore, this review aims to provide an overview about the impairment and activation of monocytes by uremia and the resulting clinical consequences for renal failure patients.

A Retrospective Study on Erythropoiesis Stimulating Agent Dose Reducing Potential of an Anti-Platelet Activation Membrane Dialyzer in Hemodialysis Patients

Our previous small‐scale trial demonstrated an erythropoiesis stimulating agent (ESA)‐sparing potential of the TORAYLIGHT NV (NV) dialyzer in hemodialysis patients with high interleukin‐6 levels. We now retrospectively explored this ESA‐sparing potential of the NV dialyzer in 122 and 129 prevalent dialysis patients who were on the NV and conventional polysulfone (PS) dialyzers, respectively, for 12 months. ESA resistance index (ERI) increased with the PS dialyzers whereas neither ERI nor ESA dose changed with the NV dialyzer. Analyses of baseline ERI or ESA dose‐based subgroups revealed a decrease in ERI and ESA dose with the NV dialyzer in patients with a baseline ERI ≥12 IU·dL/week·kg·g Hb (P < 0.05) and in those with a baseline ESA dose >6000 IU/week (P < 0.001), respectively. Neither ERI nor ESA dose improved in the corresponding subgroups on the PS dialyzers. These findings suggest that NV dialyzer can improve ESA responsiveness in hemodialysis patients with advanced ESA resistance.

Effect of Vitamin E-Coated Dialysis Membranes on Anemia in Patients with Chronic Kidney Disease: An Italian Multicenter Study

Background

Increased oxidant stress is increasingly recognized as a crucial factor in anemia in patients with chronic kidney disease. Vitamin E-coated membranes (VECMs) consist of a multilayer membrane with liposoluble vitamin E on the blood surface allowing direct free radical scavenging at the membrane site, which is of potential clinical benefit. Our objective was to examine the effect of VECMs on anemia in chronic hemodialysis (HD).

Methods

We enrolled 172 stable chronic HD patients (94 men, 78 women, age 65.4 ± 13.4 years) in an open-label multicenter study. They were shifted from their previous dialyzer to VECM for 1 year. Hemoglobin (Hb) levels and recombinant human erythropoietin (rHuEpo) dosage were analyzed after 4, 8, and 12 months on the VECM and compared with baseline values using paired tests.

Results

Hb significantly increased from 10.9 ± 1.2 g/dL at baseline to 11.7 ± 1.2 g/dL after 12 months (p<0.001) on VECMs. Conversely, the rHuEpo dosage decreased from 7,762 ± 5,865 IU/week at baseline to 6,390 ± 5,679 IU/week after 12 months (p<0.001). The proportion of patients who were at target Hb levels (European Best Practice Guidelines) increased from 49.4% at baseline to 80% after 12 months (p<0.001).

Conclusions

Dialysis with VECM in stable chronic HD patients was associated with significantly improved Hb levels and lower rHuEpo requirements. These results suggest that the antioxidant properties of VECMs may impact favorably on anemia management in chronic HD patients. Possible mechanisms include enhanced membrane biocompatibility, reduced oxidative stress and inflammation with VECMs, resulting in improved red blood cell survival and/or rHuEpo responsiveness. This therapy may potentially contribute to more effective anemia management in hemodialysis patients, and merits further rigorous study.

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.

Dendritic Cell Dysfunction in Patients with End-stage Renal Disease

End-stage renal disease (ESRD) with immune disorder involves complex interactions between the innate and adaptive immune responses. ESRD is associated with various alterations in immune function such as a reduction in polymorphonuclear leukocyte bactericidal activity, a suppression of lymphocyte proliferative response to stimuli, and a malfunction of cell-mediated immunity at the molecular level. ESRD also increases patients' propensity for infections and malignancies as well as causing a diminished response to vaccination. Several factors influence the immunodeficiency in patients with ESRD, including uremic toxins, malnutrition, chronic inflammation, and the therapeutic dialysis modality. The alteration of T-cell function in ESRD has been considered to be a major factor underlying the impaired adaptive cellular immunity in these patients. However, cumulative evidence has suggested that the immune defect in ESRD can be caused by an Ag-presenting dendritic cell (DC) dysfunction in addition to a T-cell defect. It has been reported that ESRD has a deleterious effect on DCs both in terms of their number and function, although the precise mechanism by which DC function becomes altered in these patients is unclear. In this review, we discuss the effects of ESRD on the number and function of DCs and propose a possible molecular mechanism for DC dysfunction. We also address therapeutic approaches to improve immune function by optimally activating DCs in patients with ESRD.

Impact of inflammation on anti-oxidative effects of vitamin E-coated membrane dialyzer in patients on chronic hemodialysis

Hemodialysis (HD) with the use of vitamin E-coated membrane (VEM) dialyzers is shown to exert anti-inflammatory and antioxidative effects in patients with end-stage renal disease on HD. However, the association of baseline inflammatory status with the antioxidative effects of VEM has not been investigated thus far. Thirty-five stable end-stage renal disease patients treated with VEM for 6 months were enrolled in the present prospective, observational cohort study. For the previous 3 months minimum, 17 (48%) patients were dialyzed with a cellulose, eight (23%) patients with a hemophane, and 10 (29%) patients with a polysulfone 1.2 to 1.5 m(2) hollow fiber dialyzer. The effects of treatment on oxidized low-density lipoprotein (oxLDL) were stratified according to half percentiles of baseline serum logC-reactive protein and interleukin-6, and the association between treatment goal, arbitrarily defined as a minimum 30% decrease in baseline oxLDL, was assessed with the use of logistic regression analysis. The higher C-reactive protein and interleukin-6 half percentiles were independently and additively associated with a higher odds ratio for achieving treatment goal. Adjustment for baseline oxLDL, age, sex, HD duration, smoking, and body mass index did not attenuate the odds ratios, whereas the history of diabetes, as primary renal disease, significantly decreased the odds ratio for achieving treatment goal. Increased baseline C-reactive protein and interleukin-6 are independent, additive factors associated with the effect of VEM on oxLDL in HD patients.

Effect of different hemodialyzers on serum levels of interleukin-6, interleukin-10 and interleukin-18

BACKGROUND

The blood and membrane contact during dialysis may elicit an immune reaction. The current study looked at the impact of different dialyzers on blood levels of cytokines.

METHODS

During the first month, randomly selected patients were treated with one dialyzer (PF-170H) and then crossed over to another dialyzer (FLX-18GW) during the next month. Pre- and postdialysis blood samples were assayed for interleukin (IL)-6, IL-10 and IL-18.

RESULTS

A significant drop of postdialysis systolic blood pressure (pre vs. post 156.4 ± 31.8 vs. 143.1 ± 24.8 mm Hg, p = 0.014) and diastolic pressure (80.7 ± 12.7 vs. 73.4 ± 10.9 mm Hg, p = 0.002) were found when patients were dialyzed with PF-170H. A significant increase of postdialysis IL-18 levels was found in both groups (pre vs. post 605.5 ± 278.6 vs. 690.6 ± 315.3 pg/ml, p = 0.016, for PF-170H and 556.4 ± 231.0 vs. 647.3 ± 282.6 pg/ml, p = 0.067, for FLX-18GW). There was a positive correlation between IL-6 and IL-10 levels (p < 0.0001).

CONCLUSION

We demonstrated a significant increase of postdialysis serum IL-18 level when either dialyzer was used. There is a strong correlation between serum levels of IL-6 and IL-10.

A randomized controlled trial evaluating the erythropoiesis stimulating agent sparing potential of a vitamin E-bonded polysulfone dialysis membrane

Background

Vitamin E (VE) bonded polysulfone dialysis membranes have putative erythropoiesis stimulating agent (ESA)-sparing and anti-inflammatory properties based on data from a small number of studies. We sought to investigate this in a large, prospective 12-month randomized controlled trial.

Methods

Two-hundred and sixty prevalent haemodialysis (HD) patients were randomized to dialysis with VE-bonded polysulfone membranes or non-VE-bonded equivalents. All ESA-dosing was performed by means of a computer-based anaemia management decision support system. Monthly data were used to calculate the ESA resistance index (ERI) and blood tests were performed at baseline, 6 and 12 months for measurement of C-reactive protein (CRP) levels.

Results

Of the 260 patients, 123 were randomized to dialysis with the VE-membrane and 12-month data was available for 220 patients. At the study population level, no beneficial effect of the VE membranes on the ERI or CRP levels was observed. Post hoc analyses indicated that there was a significant fall in ERI for patients with the highest baseline ESA resistance dialysed with the VE (9.28 [7.70–12.5] versus 7.70 [5.34–12.7] IU/week/kg/g/dL Hb, P = 0.01) but not the control membranes (9.45 [7.62–12.3] versus 8.14 [4.44–15.6] IU/week/kg/g/dL Hb, P = 0.41); this was not attributable to changes in CRP levels.

Conclusions

Wholesale switching of all chronic HD patients to dialysis with VE-bonded polysulfone membranes appears not to be associated with improvements in ESA-responsiveness or CRP. These membranes may have utility in patients with heightened ESA resistance.

Oxidative stress and inflammation: Implications in uremia and hemodialysis

Oxidative response and inflammation constitute a major defense against infections, but if not properly regulated they could also lead to a number of deleterious effects. Patients affected by different stages of acute and chronic kidney disease, particularly patients on hemodialysis, present a marked activation of oxidative and inflammatory processes. This condition exposes these patients to an elevated risk of morbidity and mortality. This Review is up to date and it analyses the newest notions about pathophysiological mechanisms of oxidative stress and inflammation in patients with renal diseases, also considering the different strategies studied to counterbalance this high risk state.

Antiatherogenic effects of vitamin E: the search for the Holy Grail

Vitamin E, a naturally occurring antioxidant, has been found to reduce atherosclerotic lesion formation in animal models as well as cardiovascular morbidity in several observational studies. However, a number of case-control and prospective cohort studies failed to confirm its value in the primary and secondary prevention of morbidity and mortality from coronary artery disease. Several small or larger randomized interventional trials completed to date failed to resolve the conflict. Notably, even in large, well-conducted prospective epidemiologic studies, the potential effects of residual confounding may be on the same order of magnitude as the reported benefit. The response to vitamin E supplementation in specific patient subpopulations with chronic inflammation and/or higher degrees of oxidative stress has not been studied as yet. Therefore, further large randomized interventional trials are warranted to clarify accurately the role of vitamin E in the primary and secondary prevention of atherosclerotic coronary disease in these patient groups.

Serum vitamin E and oxidative protein modification in hemodialysis: a randomized clinical trial

BACKGROUND

Patients with end-stage renal disease have increased circulating concentrations of oxidatively modified circulating proteins. Therefore, we examined the ability of vitamin E alpha (alpha-tocopherol) to alter levels of these modified proteins.

STUDY DESIGN

Randomized clinical trial.

SETTING & PARTICIPANTS

27 clinically stable patients treated by means of hemodialysis in 4 freestanding outpatient dialysis units.

INTERVENTION

Oral administration of 800 IU of vitamin E alpha or placebo daily.

OUTCOMES & MEASUREMENTS

Plasma levels of alpha- and gamma-tocopherol and oxidative protein modifications reflecting 2 pathways for protein-oxidant damage. The advanced glycation end product pentosidine reflects glycoxidation. The lipid peroxidation products iso[4]-levuglandin E(2), (E)-4-hydroxy-2-nonenal, and (E)-4-oxo-2-nonenal are formed through covalent adduction.

RESULTS

Circulating levels of all oxidative protein modifications were increased in patients with end-stage renal disease. Supplementation with alpha-tocopherol caused alpha-tocopherol levels to rise (13.2 +/- 3.7 to 27.3 +/- 14 mug/mL), but gamma-tocopherol levels to decrease (4.1 +/- 1.6 to 3.5 +/- 1.1 mug/mL). Control values were unchanged. There was no effect on oxidative protein modifications (placebo versus treatment; mean for pentosidine, 15.6 +/- 11.4 (SD): 95% confidence interval (CI), 8.2 to 23.1 versus 21.3 +/- 9.0 pg/mg protein; 95% CI, 16.1 to 26.6; iso[4]-levuglandin E(2), 8.31 +/- 2.55; 95% CI, 6.77 to 9.85 versus 8.46 +/- 2.37 nmol/mL; 95% CI, 7.09 to 9.84; (E)-4-hydroxy-2-nonenal, 0.51 +/- 0.11; 95% CI, 0.45 to 0.57 versus 0.51 +/- 0.08 nmol/mL; 95% CI, 0.46 to 0.56; (E)-4-oxo-2-nonenal, 189 +/- 44; 95% CI, 162 to 215 vs 227 +/- 72 pmol/mL; 95% CI, 183 to 271).

LIMITATIONS

Sample size was adequate to show changes in alpha- and gamma-tocopherol levels in response to treatment. However, power was insufficient to show an effect on oxidative protein modifications.

CONCLUSIONS

Intervention of oral supplementation with alpha-tocopherol did not result in changes in circulating oxidative protein modifications. A larger study may be required to show an effect in this clinical setting.

Vitamin E in renal therapeutic regiments

Administration of vitamin E in children with immunoglobulin A (IgA) nephropathy, focal segmental glomerulosclerosis (FSGS) and type I diabetes demonstrated potential towards ameliorating progression. Oral vitamin E therapy reduced endothelial dysfunction, lipid peroxidation and oxidative stress in patients with chronic kidney failure (CKF). Moreover, the use of vitamin E-bonded hemodialyzers reduced atherosclerotic changes, erythropoietin dosage and muscular cramps in patients on hemodialysis (HD). However, several controlled clinical trials failed to document beneficial effects on the study subjects' cardiovascular and renal outcomes. A recent report of increased all-cause mortality in adult patients receiving high dose vitamin E therapy has caused considerable concern and debate. These issues regarding the efficacy and safety of vitamin E in renal therapeutic regimens will be reviewed in this article.

A systematic review of the effect of the Excebrane dialyser on biomarkers of lipid peroxidation

BACKGROUND

Oxidative stress is prevalent in dialysis patients and has been implicated in the pathogenesis of cardiovascular disease and anaemia. We conducted a systematic review and meta-analysis to examine the effect of Excebrane, a vitamin E-coated cellulose-based dialyser, on circulating biomarkers of lipid peroxidation, as surrogate markers of oxidative stress.

METHODS

The primary sources used to identify candidate studies included PubMed, the Cochrane Central Register of Controlled Trials, a bibliography provided by the dialyser manufacturer, and a manual search of abstracts from proceedings of scientific meetings and review articles. Studies were selected for analysis if their design included a comparator group (primarily within patient comparison, i.e. pre- and post-study evaluations). For the meta-analysis, we computed the overall change of the outcome from baseline using a random-effects model. A supplemental analysis was performed in which the absolute levels of these biomarkers of lipid peroxidation were converted to a common unit by calculating standardized effect sizes.

RESULTS

Fourteen peer-reviewed articles met the criteria. The studies consisted of 11 single arm, one randomized crossover and two randomized controlled trials, with a total of 37 to 158 evaluable patients, according to the outcome of interest analysed. Due to the paucity of randomized trials, the meta-analysis was limited to the Excebrane arm of each study. When the studies were combined according to similar measurement units, the overall mean decrease in malondialdehyde (MDA) level was -0.3 mM (95% CI, -0.5 to -0.1 mM; seven studies) and -0.8 nmol/mg low-density lipoprotein (LDL) (95% CI, -1.3 to -0.4 nmol/mg LDL; three studies), respectively. The summary estimate revealed a non-significant decrease in pre-dialysis thiobarbituric acid reactive substances (TBARS) level of 0.4 microM (95% CI, -1.2 to 0.4 microM; three studies). When the MDA and TBARS studies were combined using the standardized effect size, the mean decrease in these biomarkers of lipid peroxidation was statistically significant at -1.7 units (95% CI, -2.7, -0.7 units; 13 studies). A meta-analysis on the effect of Excebrane on pre-dialysis levels of oxidized-LDL could not be performed due to study heterogeneity.

CONCLUSION

The conversion of dialysis patients to a vitamin E-coated dialyser is associated with an improvement in circulating biomarkers of lipid peroxidation, which is of potential clinical benefit.

Hollow-fiber blood-dialysis membranes: superoxide generation, permeation, and dismutation measured by chemiluminescence

The interaction of blood with a material surface results in activation of the body's humoral immune system and the generation of reactive oxygen species (ROS). It has recently become clear that ROS are central to the pathology of many diseases. In this study, we evaluated the superoxide generation, permeation, and dismutation in hollow-fiber dialysis membranes by using 2-methyl-6-p-methoxyphenylethynyl-imidazopyrazinone (MPEC) as a superoxide-reactive chemiluminescence producer and an optical fiber probe to detect the resulting chemiluminescence in the hollow fiber lumen. We measured the superoxide generated when bovine blood leukocytes were brought into contact with dialysis membranes. Superoxide permeation was determined by measuring MPEC chemiluminescence in the hollow fiber lumen using an optical fiber probe. Additionally, superoxide dismutation was evaluated by examining the difference in superoxide permeability for membranes with and without vitamin E coating. Superoxide generation varies for different membrane materials, depending on the membrane's biocompatibility. Superoxide permeability depends on the diffusive permeability of membranes. No marked decrease in superoxide permeability was observed among membrane materials. The superoxide permeability of vitamin E-coated membrane was smaller than that of uncoated membrane. The antioxidant property of vitamin E-coated membranes is hence effective in causing superoxide dismutation.

Cellulose, modified cellulose and synthetic membranes in the haemodialysis of patients with end-stage renal disease

BACKGROUND

When the kidney fails the blood-borne metabolites of protein breakdown and water cannot be excreted. The principle of haemodialysis is that such substances can be removed when blood is passed over a semipermeable membrane. Natural membrane materials include cellulose or modified cellulose, more recently various synthetic membranes have been developed. Synthetic membranes are regarded as being more "biocompatible" in that they incite less of an immune response than cellulose-based membranes.

OBJECTIVES

To assess the effects of different haemodialysis membrane material in patients with end-stage renal disease (ESRD).

SEARCH STRATEGY

We searched MEDLINE, EMBASE, PreMEDLINE, HealthStar CINAHL, the Cochrane Central Register of Controlled Trials (CENTRAL), Biosis, SIGLE, CRIB, UK National Research Register and reference lists of relevant articles. We contacted biomedical companies, known investigators and handsearched selected journals and conference proceedings. Date of most recent search: June 2004.

SELECTION CRITERIA

All randomised controlled trials (RCTs) or quasi-RCTs comparing different haemodialysis membrane material in patients with ESRD.

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed the methodological quality of studies. Data was abstracted onto a standard form by one reviewer and checked by another. Relative Risk (RR) and weighted mean difference (WMD) with 95% confidence intervals (CI)) MAIN RESULTS: Thirty two studies were identified. Pre-dialysis ss(2) microglobulin concentrations were not significantly lower in patients treated with synthetic membranes (WMD -14.67, 95% CI -33.10 to 4.05). When analysed for change in ss(2) microglobulin, a fall was only noted with high-flux membranes. The incidence of amyloid was less in patients who were dialysed for six years with high-flux synthetic membranes (one study, RR 0.03, 95% CI 0.00 to 0.54). There was a significant difference in favour of the synthetic (high-flux) membrane in comparison to cellulose membranes for triglycerides (WMD -0.66; 95% CI -1.18 to -0.14) but not for modified cellulose membranes. Dialysis adequacy measured by Kt/V was marginally higher when cellulose membranes were used (WMD -0.10; 95% CI -0.16 to 0.04), whereas synthetic membranes achieved significantly higher Kt/V values when compared with modified cellulose membranes (WMD 0.20, 95% 0.11 to 0.29) . There were no data on quality of life measures.

AUTHORS' CONCLUSIONS

We found no evidence of benefit when synthetic membranes were compared with cellulose/modified cellulose membranes in terms of reduced mortality no reduction in dialysis-related adverse symptoms. Despite the relatively large number of RCTs undertaken in this area none of the included studies reported any measures of quality of life.

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.

Antioxidant therapy in uremia: evidence-based medicine?

Because of correlations between cardiovascular disease, inflammation, and renal failure, many investigators are pursuing nontraditional risk factors and therapies in order to reduce cardiovascular morbidity and mortality in the end-stage renal disease (ESRD) population. Despite the disappointing lack of clinical effects with antioxidative therapies seen in large studies of the general population, some studies suggest a diminished cardiovascular risk in individuals with renal failure. This expanding new line of evidence is promising as a method to help alleviate the more than 20-fold increase in risk of cardiovascular events in the ESRD population. Most of the current available studies have evaluated laboratory or physiologic endpoints, such as endothelial function and measures of oxidative burden, and have evaluated relatively small numbers of patients. However, it is currently premature to initiate widespread clinical therapy with antioxidants. Further investigation in this area should be supported to see if reported benefits can be duplicated in more widespread study populations, and to more accurately define the most appropriate choice of therapy, mode of therapy, and dose.

Vitamin E-coated dialyzer membranes downregulate expression of monocyte adhesion and co-stimulatory molecules

BACKGROUND

In patients on chronic hemodialysis leukocyte activation has been related to the impaired function of the immune system. In this study we investigated if the vitamin E-coated dialyzer membrane could reduce monocyte activation thereby improving cellular immunity.

METHODS

This hypothesis was tested in a prospective crossover trial in which 14 stable hemodialysis patients were switched from the baseline hemophane dialyzer to a vitamin E-coated and thereafter a polysulphone dialyzer membrane or vice versa.

RESULTS

Monocyte MHC class I, CD54 and ICAM-1 expression was significantly downregulated when a vitamin E-coated or polysulphone dialyzer was used. The use of a vitamin E membrane specifically decreased monocyte CD40 and CD86 expression. Lectin induced T cell proliferation increased with the use of the vitamin E-coated membrane as compared to polysulphone and hemophane dialyzers.

CONCLUSION

Vitamin E-coated dialyzers induced a less-activated phenotype of monocytes and may improve cellular immunity.

Vitamin E–loaded dialyzer resets PBMC-operated cytokine network in dialysis patients

BACKGROUND

In hemodialysis patients the activity of stimulated Th1 lymphocytes is depressed, while Th2 cells are constitutively primed. Such phenomena may depend on monocyte activation and altered release of interleukin (IL)-12 and IL-18, which regulate Th cell differentiation. Reactive oxygen species (ROS) activate monocytes; therefore, a hemodialyzer with antioxidant activity would contrast ROS, prevent monocyte activation, reset IL-12 and IL-18 release, and restore Th1/Th2 balance.

METHODS

Ten patients on regular dialysis treatment (RDT) with cellulosic membrane (CM) were shifted to vitamin E-coated dialyzer (VE). During treatment with CM and after 3, 6, and 12 months of treatment with VE, peripheral blood mononuclear cells (PBMC) and purified CD4+ cells were isolated, and cultured, resting, mitogen-stimulated, and interferon gamma (IFNgamma), IL-4, IL-10, IL-12, and IL-18 release was measured. Vitamin E and A plasma levels and the effects of a single dialysis session on peripheral blood NO levels were assayed.

RESULTS

The constitutive release of IL-4 and IL-10 by CD4+ cells was abated significantly by treatment with VE (nadir -77.8% and -55.3%, respectively, at 12 months). INFgamma release by mitogen-stimulated CD4+ recovered with VE (zenith +501% at 12 months). PBMC constitutive production of IL-12 and IL-18 was significantly reduced by VE (nadir at 12 months -64.7% and -51.3%, respectively). VE increased plasma levels of vitamins E and A. NO plasma levels fell after a single dialysis treatment with VE (-17%, P < 0.05) in contrast with CU (+27.1%, P < 0.05).

CONCLUSION

The network of cytokines released by monocytes and Th cells is reset toward normality by treatment with vitamin E-coated dialyzer.

Management of hemodialysis access infections

Management of hemodialysis (HD) access infection is one of the most challenging and most common problems faced by surgeons, interventional radiologists, and nephrologists. The goal to eradicate infection is often at odds with the need to maintain access. Patients on HD are immunocompromised and typically have significant comorbid conditions placing them at high risk for the occurrence of access infection. Infection is most common with central-vein catheter access, followed by prosthetic arteriovenous grafts (AVG) and is rare with autogenous fistulas. The diagnosis is usually evident on physical exam, but it is not uncommon for these patients to present with atypical symptoms and lack of clinical findings. Although Staphylococcal species are the most common organism to cause infection, early empiric antimicrobial therapy should also include coverage for Gram-negative organisms. Management of central-vein catheter infection includes removal and delayed replacement or, in patients with mild clinical symptoms, catheter exchange over a guide wire. Our management of AVG infection includes total graft excision when patients present with sepsis or the entire graft is bathed in pus, subtotal graft excision when all of the graft is removed except a small oversewn cuff of prosthetic material on an underlying patent artery, and partial graft excision when only a limited infected portion of the graft is removed and a new graft is rerouted in adjacent sterile tissue to maintain patency of the original graft. This strategy has proven to be highly successful in the management of these complicated cases.

Vitamin E-coated membrane dialyzer and beta2-microglobulin removal

This study was designed to test the removal of beta2-microglobulin (beta2M) in a vitamin E-modified membrane. We investigated in vivo the dialyzer (Excebrane, series EE, 1.8 m2) with respect to hydraulic permeability (Kuf), maximum ultrafiltration rate (UF max), sieving coefficient (Sc), and solute clearances in hemodialysis (HD) and in soft hemodiafiltration (HDF). Kuf was 18.4 ml/h/mmHg, UF max was 75 ml/min, and Sc for beta2M was 0.45. Clearance values at 400 ml/min of Qb in HD were 258 ml/min for urea, 201 ml/min for creatinine, and 135 ml/min for phosphate. In soft HDF, clearances were slightly higher. beta2M clearance was 26 ml/min in HD and 43 ml/min in soft HDF. In conclusion, Excebrane (series EE) procures a soft HDF with an amount of substitution fluid in post dilution mode of over 60 ml/min. Remarkable small solute clearances were obtained when the blood flow was raised to 400 ml/min. A significant reduction of beta2M is demonstrated by HDF.

Vitamin E-bonded hemodialyzer improves atherosclerosis associated with a rheological improvement of circulating red blood cells

BACKGROUND

Vitamin E-bonded hemodialyzer is known to improve oxidative stress in patients with hemodialysis. However, there is little information available as to whether or not this membrane clinically improves atherosclerosis. Furthermore, it remains unknown whether there is any effect of the membrane on rheology of circulating red blood cells.

METHOD

We conducted a randomized, open-labeled, prospective control study (N = 34) for 1 year to investigate the effect of vitamin E-bonded cellulose membrane dialyzer (EE) (N = 17) on carotid atherosclerotic changes [intima-media thickness (IMT) of carotid arteries] and the viscosity, percentage of dysmorphism (%DMR) of red blood cells (RBCs) and their distribution width-standard deviation (RDW-SD), in comparison with cellulose membrane (SU) (N = 17) identical to EE without vitamin E-bonded membrane. Erythropoietin (EPO) dose used for the treatment of uremic anemia was also calculated.

RESULTS

The IMT significantly decreased in the EE group, while in the SU group the IMT significantly increased. The viscosity of RBCs in hemodialysis patients (4.70 +/- 0.45 cP) was greater than that in healthy individuals (3.73 +/- 0.15 cP). EE significantly improved the viscosity (from 4.84 +/- 0.41 cP to 4.51 +/- 0.54 cP, P < 0.01), %DMR (from 2.29 +/- 2.17% to 1.90 +/- 1.49%, P < 0.01), and RDW-SD (from 54.4 +/- 7.6 fL to 49.3 +/- 5.9 fL, P < 0.01). On the contrary, these parameters all worsened in the SU group. EPO dose needed for the treatment of anemia was significantly (P < 0.05) reduced from 5383 +/- 2655 U/week to 4235 +/- 3103 U/week in the EE group. During these period, mean blood pressure, Kt/V urea, and serum beta2-microglobulin were not changed between the two groups.

CONCLUSION

These findings suggest that vitamin E-bonded hemodialyzer is very useful for improving atherosclerosis from a clinical point of view. As one of the underlying mechanisms, as well as antioxidant effects, we want to address an important role of the improvement of rheology of circulating RBCs, which may also help to reduce the requirement of EPO dose in the treatment of anemia of ESRD patients.

5-Lipoxygenase-mediated mitochondrial damage and apoptosis of mononuclear cells in ESRD patients

BACKGROUND

5-Lipoxygenase activity is enhanced in peripheral blood mononuclear cells (PBMC) from end-stage renal disease (ESRD) patients on maintenance hemodialysis (HD), leading to lipoperoxidation and reactive oxygen species formation. These effects are prevented by vitamin E, which inhibits 5-lipoxygenase activity. The present study was designed to test the possibility that 5-lipoxygenase activation might cause mitochondrial damage and cytochrome c release, ultimately leading PBMC to apoptosis.

METHODS

Apoptosis, mitochondrial uncoupling, and cytochrome c release were investigated in PBMC from 16 healthy volunteers and 16 ESRD patients on maintenance HD with cuprammonium rayon (CL-S) membranes in a two-step crossover study: after a four-week treatment with vitamin E-coated cuprammonium rayon (CL-E) membranes, and again after a four-week treatment with oral vitamin E.

RESULTS

Compared to healthy controls, PBMC from ESRD patients showed an approximately threefold increase in mitochondrial uncoupling and cytochrome c release (within 4 and 8 hours, respectively), followed by an approximately threefold increase in apoptotic body formation (within 48 hours). Regardless of the administration route, vitamin E reduced mitochondrial uncoupling, cytochrome c release and apoptosis of mononuclear cells, as did the 5-lipoxygenase inhibitor eicosatetraynoic acid. Conversely, the cyclooxygenase inhibitor indomethacin was ineffective.

CONCLUSIONS

Reported data suggest that the 5-lipoxygenase branch of the arachidonate cascade is only responsible for mitochondrial disruption and apoptosis of PBMC of ESRD patients, and that vitamin E may be helpful in the control of oxidative stress-related disease in these subjects, independent of the administration route.

Effects of erythropoietin and vitamin E-modified membrane on plasma oxidative stress markers and anemia of hemodialyzed patients

BACKGROUND

Oxidant stress has a pathogenic role in uremic anemia, possibly interfering with erythropoietin (EPO) function and red blood cell (RBC) survival. Therefore, it is expected that antioxidant therapy might exert a beneficial effect on these parameters.

METHODS

To test this hypothesis, we investigated some oxidant stress indices, anemia levels, and RBC survival in 47 hemodialysis (HD) patients randomly assigned to three groups. Patients in groups A (n = l8) and B (n = 20) were on dialysis therapy using conventional cellulosic and synthetic membranes and were administered high and low doses of recombinant human EPO (rHuEPO), respectively. Patients in group C (n = 9) were dialyzed with vitamin E-modified membranes (CL-Es) and investigated in a two-step prospective study. In step Cl, patients were administered rHuEPO doses similar to those of group A. In step C2, rHuEPO doses were reduced to those of group B. As oxidant stress markers, we determined in plasma the susceptibility of lipids to undergo iron-catalyzed oxidation (reactive oxygen molecules [ROMs] test) and malondialdehyde-4-hydroxynonenal (MDA-4HNE), alpha-tocopherol (alpha-T), total thiol (-SH), and total antioxidant activity. RBC survival was measured using the chromium 51 T/2 technique in 22 patients.

RESULTS

Results show that: (1) high rHuEPO doses (groups A and C1) were associated with decreased ROM production, low alpha-T levels, and slightly increased -SH levels compared with corresponding groups on low rHuEPO doses (groups B and C2); (2) treatment with CL-Es (group C) increased plasma alpha-T and decreased -SH levels; these data were associated with decreased indices of lipid peroxidation, particularly MDA-4HNE 1evels, only in patients administered low rHuEPO doses; (3) alpha-T concentration influenced RBC survival, which was remarkably decreased in HD patients; patients treated with CL-Es showed a better degree of anemia correction; and (4) alpha-T level correlated negatively with -SH level and seemed to be independent of the extent of peroxidation and oxidizability of plasma lipids.

CONCLUSION

Both EPO and CL-E can influence plasma antioxidants and, to an extent, lipid peroxidation processes. However, this study shows that even in patients treated with low rHuEPO doses, RBC survival close to normal and sufficient correction of anemia are achieved only when appropriate alpha-T levels are reached.

Arachidonate cascade, apoptosis, and vitamin E in peripheral blood mononuclear cells from hemodialysis patients

BACKGROUND

Lipid peroxidation and oxidative stress are enhanced in peripheral blood mononuclear cells (PBMCs) from hemodialysis (HD) patients because of upregulation of the 5-lipoxygenase pathway of the arachidonate cascade. 5-Lipoxygenase activity is specifically inhibited by vitamin E both in vitro and in vivo regardless of its administration route.

METHODS

The effect of arachidonate cascade enzymes and vitamin E on oxidative stress and apoptosis was investigated in PBMCs from 16 maintenance HD patients treated for at least 6 months with cuprammonium rayon membranes in a two-step crossover study: after a 4-week treatment with vitamin E-coated cuprammonium rayon membranes and again after a 4-week treatment with oral vitamin E. Control PBMCs were obtained from 16 healthy volunteers.

RESULTS

Membrane lipoperoxidation, cellular luminescence, membrane fluidity, and leukotriene B(4) content were significantly greater in PBMCs from HD patients; lipoxygenase was upregulated, but prostaglandin H synthase (PHS) was not affected. Regardless of administration route, vitamin E partially controlled lipid peroxidation and oxidative stress through direct inhibition of 5-lipoxygenase. Cultured PBMCs from HD patients showed a significant increase in apoptotic cells compared with controls. Vitamin E markedly reduced cell luminescence, membrane fluidity, and apoptosis, whereas the PHS inhibitor indomethacin was ineffective. Similar results were obtained with control PBMCs induced to apoptosis by hydrogen peroxide.

CONCLUSION

Reported data suggest that the 5-lipoxygenase branch of the arachidonate cascade is only responsible for membrane peroxidation, oxidative stress, and apoptosis of PBMCs of HD patients, and administration of vitamin E may be helpful in the control of oxidative stress-related disease in these subjects.

Vitamin E-modified filters modulate Jun N-terminal kinase activation in peripheral blood mononuclear cells

BACKGROUND

The generation during hemodialysis of activated complement fragments and reactive oxygen species, including nitric oxide (NO), may affect peripheral blood mononuclear cell (PBMC) function. Currently, little is known about signal transduction pathways involved in PBMC activation. Jun N-terminal kinase (JNK) is a novel mitogen-activated protein (MAP) kinase phosphorylated and activated in response to oxidative stress and directly involved in cell activation.

METHODS

The present study evaluated the activation of JNK in PBMCs isolated from eight uremic patients undergoing, in a randomized manner, three month-subsequent periods of hemodialysis with a low-flux cellulose acetate (CA) and a vitamin E-modified cellulose membrane (CL-E). After each period of treatment, PBMCs were harvested before (T0), during (T15) and after three hours (T180) of dialysis. At the indicated time points, plasma C5b-9 generation by ELISA and inducible NO synthase (iNOS) gene expression by in situ hybridization were evaluated also. The activation of JNK was studied by Western blotting using a specific monoclonal anti-phospho-JNK antibody, which recognizes the activated form of JNK.

RESULTS

At T0, a significant increase in plasma C5b-9 levels was found in CA patients compared to CL-E-treated patients. During hemodialysis, C5b-9 levels rose more significantly in CA patients than in CL-E patients and returned to baseline values only in CL-E patients. At the same time, in CA patients an increased iNOS gene expression was observed at T180 together with a striking activation of JNK. By contrast, PBMC from CL-E-treated patients showed undetectable levels of phospho-JNK and a significant reduction in iNOS expression. Interestingly, incubation of PBMCs with normal human plasma (10%), activated by contact with a cellulosic membrane, induced a time-dependent increase in JNK phosphorylation that was completely inhibited by blocking complement cascade activation.

CONCLUSION

Our data suggest that JNK phosphorylation is strikingly increased in PBMCs obtained from CA-treated patients and may represent a key cellular event in PBMC activation during dialysis with bioincompatible membranes. The activation of this signaling enzyme, mediated by active complement fragments and PBMC-dialyzer interaction, can be significantly reduced by the use of vitamin E-coated membrane.

Hemodialysis Membranes: Interleukins, Biocompatibility, and Middle Molecules

ABSTRACT. Maintenance hemodialysis patients display evidence of elevated interleukin-1 (IL-1) and tumor necrosis factor alpha release after stimulation either by contaminated dialysate, bioincompatible membrane material, or both. This release is followed by the stimulated secretion of a large number of other interleukins, particularly IL-6, the cytokine principally responsible for acute-phase protein synthesis. It has been shown that high levels of the circulating proinflammatory cytokines IL-1, tumor necrosis factor alpha, IL-6, and IL-13 are associated with mortality in hemodialysis patients. Essential functions of polymorphonuclear leukocytes—that is, phagocytosis, oxygen species production, upregulation of specific cell surface receptor proteins, or apoptosis—are disturbed in patients with end-stage renal disease. These are further altered as a result of complement activation by the hemodialysis procedure, particularly if bioincompatible dialyzers are used. Polymorphonuclear leukocyte degranulation occurring during extracorporeal circulation does not depend on complement activation but rather on intracellular calcium and the presence or absence of the degranulation inhibitory proteins angiogenin and complement factor D. Clinical signs and symptoms of end-stage renal disease patients are at least in part related to the accumulation of middle molecules such as β2-microglobulin, parathyroid hormone, advanced glycation end products, advanced lipoxidation end products, advanced oxidation protein products (formed as a result of oxidative stress, carbonyl stress, or both), granulocyte inhibitory proteins, or leptin. Currently available membrane materials do not provide long-lasting, effective reduction of middle molecules in patients who require maintenance hemodialysis.

Low-dose prostacyclin preserves renal function in high-risk patients after coronary bypass surgery

OBJECTIVE

Renal failure after bypass is still a threatening problem prolonging hospital care and reducing overall survival. The following pilot study was aimed to analyze whether perioperative low-dose prostacyclin infusion is able to preserve renal function in a selected group of patients who according to a poor cardiac function were stratified as high risk for the development of renal failure after bypass.

DESIGN

Prospective randomized study.

SETTING

Tertiary care university medical center.

PATIENTS

Thirty-four patients scheduled for primary cardiac bypass surgery were included in the study (prostacyclin n = 17, control n = 17). Inclusion criteria were normal renal function before surgery and a cardiac ejection fraction <40%.

INTERVENTIONS

Low-dose prostacyclin (2 ng/kg/min) was added to the standard anesthetic protocol. Infusion was started immediately before surgery and was continued for a maximum of 48

MEASUREMENTS AND MAIN RESULTS

Significant differences in the endogenous creatinine clearance were found between the prostacyclin and the control group. Whereas there was a significant drop in the creatinine clearance at 6 hrs after surgery in the control group with a prolonged recovery period, values in the prostacyclin group remained stable. Creatinine clearance before intervention was 100 +/- 22 mL/min in the control group and 91 +/- 22 mL/min in the prostacyclin group, values at 24 hr were 68 +/- 34 mL/min vs. 103 +/- 37 mL/min, respectively (p < .01). Significant findings in favor for the prostacyclin group were also found for urine output and the fractional excretion rate of sodium.

CONCLUSION

This first pilot study indicates that low-dose prostacyclin may be of substantial value for preserving renal function in high-risk patients after coronary bypass surgery.

Vitamin E-bonded hemodialyzer improves neutrophil function and oxidative stress in patients with end-stage renal failure

We evaluated the biocompatibility of a newly developed vitamin E hemodialyzer (CL-EE; Terumo Co Ltd, Tokyo, Japan) by neutrophil function and oxidant stress in patients with end-stage renal failure in a randomized crossover study. Ten patients underwent hemodialysis using either the CL-EE or a control dialyzer membrane identical to the CL-EE except for vitamin E binding for 12 weeks in a crossover fashion after a 1-month washout period with hemophane membranes. White blood cell counts, serum oxidized low-density lipoprotein (Ox-LDL) levels, and malondialdehyde (MDA) levels during hemodialysis sessions were measured at the initiation and end of the CL-EE and control trials. Superoxide anion production by neutrophils just before and 4 hours after starting the session also was measured. Leukocytopenia at 1 hour after starting the session was detected to a similar extent in both membranes. However, the degree of reduction was less in the CL-EE trial after repeated use. Superoxide anion production by neutrophils just before a hemodialysis session was reduced after repeated use of the CL-EE membrane. Serum Ox-LDL levels increased, whereas serum MDA levels decreased during sessions to a similar extent in both trials. However, these parameters were significantly lower in the CL-EE trial after repeated use. Serum LDL concentrations significantly decreased with repeated use of the CL-EE membrane. These data suggest that repeated use of the CL-EE membrane for 3 months improves neutrophil function, oxidant stress, and LDL concentrations in patients with renal failure. This membrane may be useful to reduce the incidence of cardiovascular events in patients with renal failure.

Effect of vitamin E modified cellulose membrane on human lymphocyte, monocyte, and granulocyte CD11b/CD18 adhesion molecule expression during hemodialysis

Chronic renal failure induces a clinical state of immunodefi ciency that also depends upon a wide spectrum of dialysis membranes used during hemodialysis. Previous studies have shown that cellular immunodeficiency is caused by malfunc tion of the antigen presenting cells (monocytes or granulocytes). Subsequent activation of rolling mononuclear leuko cytes results in up-regulated expression of CD11b/CD18 (Mac-1) on endothelial cells. It is postulated that a VitE coated dialysis membrane might minimize the membrane biocompatibility, thereby generating a smaller amount of re active oxygen species (ROS). The purpose of this study was to evaluate the expression of the CD11b/CD18 adhesion mole cule on lymphocytes, monocytes, and granulocytes during HD in 10 patients, using flow cytometric analysis. The study protocol included the measurement of molecule expression using cellulose membrane (Clirans RS15, TERUMO Corp. Japan), and the same membrane coated by vitamin E (Exce brane, Clirans E15, TERUMO Corp., Japan) during 20 dialysi sessions each. Lymphocyte CD11 b/CD1 8 (Mac-1) expression did not change with either dialyzer type. However, monocyt (p = 0.046) and granulocyte (p = 0.018) CD11b/CD18 ex pression in the post HD period was significantly lower using the vitamin E coated membrane compared with the contro cellulose membrane. Our findings suggest a significant de crease in activation and migration of monocytes and granu locytes when using a vitamin E coated cellulose membrane.

Immunologic defects and vaccination in patients with chronic renal failure

Patients with chronic renal failure suffer from defective host defenses which are directly the result of the renal impairment, in addition to those dependent on the primary illness leading to the renal failure. The mechanisms underlying the defective responses in phagocytic cells, lymphocytes and antigen processing are likely due to either failure to adequately eliminate suppressive compounds by the defective kidneys or to improper metabolic processing of the factors by the damaged renal parynchema. That some of the defects are reversed by transplantation and not dialysis suggests that renal parenchymal metabolic activities may be involved, although it is also possible that functioning glomerular cells are capable of filtering substances that membranes are not currently capable of eliminating. The current strategy for dealing with the immunodeficiency appears to be totally based on developing means to circumvent the defective function. The other approach, correction of the impaired function, cannot be even considered until the mechanisms underlying the defective function of the cells involved in defenses are better delineated. It seems possible that one or a few compounds are pivotal in altering the function of all the affected cell lines, since, with only a small amount of effort, it is possible to relate the dysfunction to abnormal cell membrane functions in phagocytic cells, dendritic cells and lymphocytes. Until the biochemical basis of the dysfunction of all the cell types affected are better defined, such exercises cannot be translated into better management of patients with chronic renal failure. Proper function of host defenses requires that appropriate cells can properly respond to threats to host viability. For the cells of the immune system (phagocytes and lymphocytes) this means that their response to regulatory molecules be appropriate, that their mobility be normal, that their adherence to substrates be preserved, and that they can generate the appropriate response to the challenge. For neutrophils, for example, it is necessary that they recognize and mobilize appropriately to chemotactic stimuli, that they be able to adhere to and migrate through endothelial lining, that their phagocytic activity be sufficient, and that they can kill and degrade endocytosed particles and generate appropriate secretions. Similar lists of requirements for good function can be generated for any cell type in the immune defense system. Uremia, as well as currently available treatments for uremia, directly or indirectly alters the function of all phases of appropriate immune cell function. Defective host responses in uremia have been recognized for decades and there has been considerable effort in the past decade to better define the extent and mechanisms of impaired defenses. Despite the multitude of major defects in humoral, cellular, and inflammatory processes, uremic patients who are cared for today, although they remain at higher risk of serious infectious complications, can and do maintain a good quality of life, with most remaining free of major infections for years and decades.

Vitamin E-coated dialyzer reduces oxidative stress in hemodialysis patients

The high incidence of cardiovascular disease in hemodialyzed (HD) patients is well established and oxidative stress has been involved in this phenomenon. The aim of our study was to evaluate if a vitamin E-coated dialyzer could offer protection to HD patients against oxidative stress. Sixteen HD patients were successively assessed for one month (i) on a high biocompatible synthetic dialyzer (AN) and (ii) on a vitamin E-coated dialyzer (VE). Blood samples were taken before and after the dialysis session at the end of each treatment period. HD session conducted with the AN dialyzer was responsible for acute oxidative stress, significantly assessed after HD by a decreased plasma vitamin C level and an increased ascorbyl free radical (AFR)/vitamin C ratio used as an index of oxidative stress. Plasma elastase activity, reflecting neutrophil activation, was also increased; soluble P-selectin, reflecting platelet activation, did not show any variation. The use of the VE dialyzer was associated with a less extended oxidative stress compared with the AN membrane: basal vitamin C level was higher, and after the HD session AFR/vitamin C ratio and elastase activity were not significantly increased. Plasma vitamin E levels were not affected. Our study demonstrates that HD is associated with oxidative stress, which can be partially prevented by the use of a vitamin E-coated dialyzer. Our data suggest that this dialyzer may exert a site-specific scavenging effect on free radical species in synergy with a reduced activation of neutrophils.

Oxidative stress is reduced by the long-term use of vitamin E-coated dialysis filters

BACKGROUND

Oxidative stress during hemodialysis is thought to promote the progression of vascular complications in hemodialysis patients. The protective role of vitamin E as a lipophilic antioxidant against oxidative stress has been widely investigated. Here we investigated the effects of a vitamin E-coated regenerated cellulose hollow fiber dialyzer (CL-EE) on oxidative stress compared with a polysulfone hollow fiber (CL-PS).

METHODS

For at least three months before beginning the protocol, 10 nondiabetic (NDM) patients (70.0 +/- 7.5 years; 6 males and 4 females) and 8 diabetic (DM) patients (65.0 +/- 7.4 years; 4 males, 4 females) were dialyzed with CL-PS. After that, we treated all of the patients with CL-EE for six months. Malondialdehyde (MDA), advanced glycation end products (AGEs), and 8-hydroxydeoxyguanosine (8-OHdG) were monitored as biomarkers for oxidative stress at the start and then at one, three, and six months into treatment with CL-EE.

RESULTS

Serum MDA, AGE, and 8-OHdG levels increased after the hemodialysis with CL-PS. The increase of the biomarkers was completely prevented by a single use of CL-EE. Long-term hemodialysis with CL-EE for six months significantly reduced the basal levels of the oxidant markers at one month for AGE and at six months for 8-OHdG in both DM and NDM patients. Serum MDA was reduced in only DM patients at three months. The improvement of the oxidative stress with CL-EE was more prominent in the DM patients.

CONCLUSIONS

Long-term treatment with CL-EE efficiently improves the oxidative stress associated with hemodialysis and potentially reduces dialysis complications due to oxidative stress.

Molecular aspects of T- and B-cell function in uremia

Chronic renal failure is associated with severe alterations of the immune system. Infections are responsible for a large part of the mortality in hemodialysis patients, and vaccination is mostly ineffective. Global tests of the immune function show greatly diminished activation of T cells. However, the intrinsic function of T and B cells is normal when they are provided with normal signaling from antigen-presenting cells (APCs). Patients with chronic renal failure show a defective function of costimulation derived from APCs leading to impaired activation of effector lymphocytes. Two major components of immune deviation are relevant: reduced signaling caused by impaired expression of the costimulatory molecule B7-2 (CD86) on monocytes leads to low activation of helper T cells. This dysfunction is associated with uremia and may be improved by high-efficiency renal replacement therapy. The other component is inflammatory activation of APCs mainly due to the hemodialysis procedure. Inflammation, characterized by overproduction of cytokines such as interleukin-1beta (IL-1beta) or IL-6, correlates with low effector activation. Furthermore, inflammatory cytokines such as IL-12 deviate the functional pattern of T-cell activation toward Th1 differentiation, thus leading to an additional reduction of Th2- and B-cell function. The individual severity of inflammatory alterations is partially controlled by the negatively regulating cytokine IL-10, which, on a genetic basis, can be up-regulated to a different extent in individual patients. Therapeutic interventions to improve immune dysfunction include the enhancement of dialysis efficiency and the reduction of inflammatory alterations by the use of highly biocompatible dialyzers.

Biocompatibility of a cuprophane charcoal-based detoxification device in cirrhotic patients with hepatic encephalopathy

Extracorporeal detoxification has been proposed to treat patients with hepatic encephalopathy (HE) not responding to standard therapy. To investigate the biocompatibility of a cuprophane charcoal-based detoxification device, a prospective, randomized, controlled study was performed. Of 41 consecutive patients with cirrhosis and HE grade II or III who did not improve with conventional treatment, 20 patients (median age, 56 years; range, 33 to 71 years; 13 men) were randomly assigned to either ongoing conventional treatment or one additional 6-hour treatment with a sorbent suspension dialysis system. Main outcome parameters were physiological function and blood parameters of biocompatibility. In the 10 patients undergoing combined conventional and sorbent suspension dialysis treatment, blood pressure remained unchanged and body temperature and heart rate increased (P: < 0.01). Platelet count decreased (medians, from 75 to 26 g/L; P: < 0.001) and international normalized ratio increased after combined treatment (2.0 to 2.2; P: < 0.001). Three patients developed bleeding complications during treatment or shortly after. Treated patients showed increases in levels of plasma elastase (104 to 586 microg/L; P: = 0.001), tumor necrosis factor-alpha (5.4 to 7.5 pg/mL; P: = 0.04), and interleukin-6 (118 to 139 pg/mL; P: = 0.04), but not interferon-gamma and E-selectin. No changes were observed in the 10 patients treated conventionally. In conclusion, despite technical refinements compared with charcoal hemoperfusion, biocompatibility of sorbent suspension dialysis is still very limited. Clinical complications were apparently caused by blood-membrane interactions and disseminated intravascular coagulation. We suggest further developments in design and appropriate strategies of anticoagulation to improve the biocompatibility of artificial liver support.