Role of bioincompatibility in dialysis morbidity and mortality

Transcriptomics: A Step behind the Comprehension of the Polygenic Influence on Oxidative Stress, Immune Deregulation, and Mitochondrial Dysfunction in Chronic Kidney Disease

Chronic kidney disease (CKD) is an increasing and global health problem with a great economic burden for healthcare system. Therefore to slow down the progression of this condition is a main objective in nephrology. It has been extensively reported that microinflammation, immune system deregulation, and oxidative stress contribute to CKD progression. Additionally, dialysis worsens this clinical condition because of the contact of blood with bioincompatible dialytic devices. Numerous studies have shown the close link between immune system impairment and CKD but most have been performed using classical biomolecular strategies. These methodologies are limited in their ability to discover new elements and enable measuring the simultaneous influence of multiple factors. The “omics” techniques could overcome these gaps. For example, transcriptomics has revealed that mitochondria and inflammasome have a role in pathogenesis of CKD and are pivotal elements in the cellular alterations leading to systemic complications. We believe that a larger employment of this technique, together with other “omics” methodologies, could help clinicians to obtain new pathogenetic insights, novel diagnostic biomarkers, and therapeutic targets. Finally, transcriptomics could allow clinicians to personalize therapeutic strategies according to individual genetic background (nutrigenomic and pharmacogenomic). In this review, we analyzed the available transcriptomic studies involving CKD patients.

Mitochondria: a new therapeutic target in chronic kidney disease

Cellular metabolic changes during chronic kidney disease (CKD) may induce higher production of oxygen radicals that play a significant role in the progression of renal damage and in the onset of important comorbidities. This condition seems to be in part related to dysfunctional mitochondria that cause an increased electron "leakage" from the respiratory chain during oxidative phosphorylation with a consequent generation of reactive oxygen species (ROS). ROS are highly active molecules that may oxidize proteins, lipids and nucleic acids with a consequent damage of cells and tissues. To mitigate this mitochondria-related functional impairment, a variety of agents (including endogenous and food derived antioxidants, natural plants extracts, mitochondria-targeted molecules) combined with conventional therapies could be employed. However, although the anti-oxidant properties of these substances are well known, their use in clinical practice has been only partially investigated. Additionally, for their correct utilization is extremely important to understand their effects, to identify the correct target of intervention and to minimize adverse effects. Therefore, in this manuscript, we reviewed the characteristics of the available mitochondria-targeted anti-oxidant compounds that could be employed routinely in our nephrology, internal medicine and renal transplant centers. Nevertheless, large clinical trials are needed to provide more definitive information about their use and to assess their overall efficacy or toxicity.

NLRP3 inflammasome activation in dialyzed chronic kidney disease patients

To assess whether NLR pyrin domain-containing protein 3 (NLRP3) inflammasome, a multiprotein complex that mediates the activation of caspase-1 (CASP-1) and pro-inflammatory cytokines IL-18 and IL-1β, could be involved in the chronic inflammatory state observed in chronic kidney disease patients undergoing hemodialysis treatment (CKD-HD), we employed several biomolecular techniques including RT-PCR, western blot, FACS analysis, confocal microscopy and microarray. Interestingly, peripheral blood mononuclear cells from 15 CKD-HD patients showed higher mRNA levels of NLRP3, CASP-1, ASC, IL-1β, IL-18 and P2X7receptor compared to 15 healthy subjects. Western blotting analysis confirmed the above results. In particular, active forms of CASP-1, IL1-β and IL-18 resulted significantly up-regulated in CKD-HD versus controls. Additionally, elevated mitochondrial ROS level, colocalization of NLRP3/ASC/mitochondria in peripheral blood mononuclear cells from CKD-HD patients and down-regulation of CASP-1, IL1-β and IL-18 protein levels in immune-cells of CKD-HD patients stimulated with LPS/ATP in presence of mitoTEMPO, inhibitor of mitochondrial ROS production, suggested a possible role of this organelle in the aforementioned CKD-associated inflammasome activation. Then, microarray analysis confirmed, in an independent microarray study cohort, that NLRP3 and CASP-1, along with other inflammasome-related genes, were up-regulated in 17 CKD-HD patients and they were able to clearly discriminate these patients from 5 healthy subjects. All together these data showed, for the first time, that NLRP3 inflammasome was activated in uremic patients undergoing dialysis treatment and they suggested that this unphysiological condition could be possibly induced by mitochondrial dysfunction.

High mobility group box protein-1 correlates with microinflammatory state and nutritional status in continuous ambulatory peritoneal dialysis patients

High mobility group box protein-1 (HMGB-1) was recently identified as a new type of inflammatory cytokine. Inflammation can lead to malnutrition to some extent. Our study was aimed to clarify the relationship between serum HMGB-1 level with microinflammatory state and nutritional status in continuous ambulatory peritoneal dialysis (CAPD) patients. Patients in the treatment of maintenance of peritoneal dialysis for >6 months were included. HMGB-1, interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) were measured by enzyme-linked immunosorbent assay (ELISA). High-sensitivity C-reactive-protein (hs-CRP), prealbumin (PA), serum albumin (S-Alb), hemoglobin (Hb), subjective global nutritional assessment (SGA), and CAPD presents' urea clearance rate (Kt/V), creatinine clearance (CrCl), residual glomerular filtration rate (rGFR), and dialysate-to-plasma ratio of creatinine after 4 h (D/P(4Cr)) were analyzed. The Independent-samples t test and Pearson's rank correlation test were used. Serum HMGB-1, IL-6, and TNF-α of CAPD patients were significantly higher than in the control group (P < 0.05); Serum HMGB-1 levels had positive relationships with TNF-α (r = 0.730, P < 0.01), hs-CRP (r = 0.361, P < 0.01), and IL-6 (r = 0.865, P < 0.01), and had negative relationships with Hb (r = -0.59, P < 0.01), Alb (r = -0.34, P < 0.05), and PA (r = -0.44, P < 0.01); no significant relationships were found between serum HMGB-1 with SGA, peritoneal dialysis age, Kt/V, CrCl, rGFR, and D/P(4Cr). Our study revealed that HMGB-1 was elevated significantly in CAPD patients and correlated with indicators of inflammation and malnutrition. Serum HMGB-1 could be used as a marker for evaluating inflammation and malnutrition in CAPD patients.

Mitochondrial dysregulation and oxidative stress in patients with chronic kidney disease

Background

Chronic renal disease (CKD) is characterized by complex changes in cell metabolism leading to an increased production of oxygen radicals, that, in turn has been suggested to play a key role in numerous clinical complications of this pathological condition. Several reports have focused on the identification of biological elements involved in the development of systemic biochemical alterations in CKD, but this abundant literature results fragmented and not exhaustive.

Results

To better define the cellular machinery associated to this condition, we employed a high-throughput genomic approach based on a whole transcriptomic analysis associated with classical molecular methodologies. The genomic screening of peripheral blood mononuclear cells revealed that 44 genes were up-regulated in both CKD patients in conservative treatment (CKD, n = 9) and hemodialysis (HD, n = 17) compared to healthy subjects (HS, n = 8) (p < 0.001, FDR = 1%). Functional analysis demonstrated that 11/44 genes were involved in the oxidative phosphorylation system. Western blotting for COXI and COXIV, key constituents of the complex IV of oxidative phosphorylation system, performed on an independent testing-group (12 healthy subjects, 10 CKD and 14 HD) confirmed an higher synthesis of these subunits in CKD/HD patients compared to the control group. Only for COXI, the comparison between CKD and healthy subjects reached the statistical significance. However, complex IV activity was significantly reduced in CKD/HD patients compared to healthy subjects (p < 0.01). Finally, CKD/HD patients presented higher reactive oxygen species and 8-hydroxydeoxyguanosine levels compared to controls.

Conclusion

Taken together these results suggest, for the first time, that CKD/HD patients may have an impaired mitochondrial respiratory system and this condition may be both the consequence and the cause of an enhanced oxidative stress.

Plasma gelsolin and circulating actin correlate with hemodialysis mortality

Plasma gelsolin (pGSN) binds actin and bioactive mediators to localize inflammation. Low pGSN correlates with adverse outcomes in acute injury, whereas administration of recombinant pGSN reduces mortality in experimental sepsis. We found that mean pGSN levels of 150 patients randomly selected from 10,044 starting chronic hemodialysis were 140 +/- 42 mg/L, 30 to 50% lower than levels reported for healthy individuals. In a larger sample, we performed a case-control analysis to evaluate the relationship of pGSN and circulating actin with mortality; pGSN levels were significantly lower in 114 patients who died within 1 yr of dialysis initiation than in 109 survivors (117 +/- 38 mg/L versus 147 +/- 42 mg/L, P < 0.001). pGSN levels had a graded, inverse relationship with 1-yr mortality, such that patients with pGSN < 130 mg/L experienced a > 3-fold risk for mortality compared with those with pGSN > or = 150 mg/L. The 69% of patients with detectable circulating actin had lower pGSN levels than those without (127 +/- 45 mg/L versus 141 +/- 36 mg/L, P = 0.026). Compared with patients who had elevated pGSN and no detectable actin, those with low pGSN levels and detectable actin had markedly increased mortality (odds ratio 9.8, 95% confidence interval 2.9 to 33.5). Worsening renal function correlated with pGSN decline in 53 subjects with CKD not on dialysis. In summary, low pGSN and detectable circulating actin identify chronic hemodialysis patients at highest risk for 1-yr mortality.

Acetate-free hemodialysis: a feasibility study on a technical alternative to bicarbonate dialysis

This study aimed at evaluating the feasibility of an acetate-free hemodialysis (AFHD) technique, comparing it with acetate-free biofiltration (AFB) and bicarbonate dialysis (BD). The assessment of the parameters concerned: electrolyte kinetics (Na+, K+), acid-base balance (HCO3-, pH), dialysis efficiency (Kt/V), serum beta2-microglobulin reduction ratio, nutritional status (normalized protein catabolic rate, serum albumin and total proteins, body mass index), hemopoietic status (hemoglobin, hematocrit), and some clinical parameters (systolic and diastolic blood pressures, heart rate, percent blood volume reduction measured by Hemoscan). Nine patients participated in this study which was conducted using a Latin square randomized experimental design. The results of the last week of each month of the study (1 month for each technique) were analyzed by means of Anova for repeated measures. The different treatments were comparable with regard to the main dialysis parameters such as blood flow (320 ml/min) and weight loss rate (0.6 +/- 0.1 kg/h), while dialysis length and dialysate conductivities were different, depending on the dialysis technique. Electrolyte kinetics and acid-base balance were similar during the three periods. The dialysis efficiency for small molecules (Kt/V of urea) was similar (between 1.4 and 1.6); however, AFB seemed to show a higher beta2-microglobulin reduction rate (47.6 +/- 4 vs. 4.3 +/- 10% for AFHD and vs. 9.9 +/- 5% for BD; p < 0.001). The nutritional and hemopoietic status maintained stable, and the hemodynamic parameters were comparable during all periods. The percent blood volume reduction at the end of the treatments was not statistically different (-14.9 +/- 9.4% in AFB, -12.1 +/- 5.1% in AFHD, and -12.2 +/- 4.4% in BD), and these results could explain the similar hemodynamic behavior during the three periods. In conclusion, AFHD appears to be a safe technique which has all positive effects of AFB and the low costs of BD. In our opinion, it could be used in patients with few clinical impairments, usually treated with hemodialysis, in whom a biocompatible treatment is indicated.

Angiographical severity of coronary atherosclerosis predicts death in the first year of hemodialysis

BACKGROUND

Cardiac deaths and events tend to cluster within the early-phase after starting dialysis. Our goal is to clarify the influence of severity of coronary atherosclerosis on early-phase death after starting hemodialysis (HD) therapy.

PATIENTS AND METHODS

Eighty-three consecutive patients [mean age 62 years; male/female 64/19; diabetic nephropathy in 50 (54%)] with end-stage renal disease who admitted to our hospital to initiate regular HD treatment, and then received coronary angiography within 3 months after first dialysis therapy, were eligible for this study. Angiographical severity of coronary atherosclerosis was scored by numerically using Gensini scoring system. The patients who died within one year from starting HD were compared with those who survived as control by means of logistic regression analysis.

RESULTS

Of 83 patients, 12 (14%) died less than one year after starting dialysis therapy. Of these 12 patients, nine died for cardiac causes. Confirmed predictors of death from cardiac cause were older age (>70 years), lower mean blood pressure (<100 mmHg), presence of ischemic heart disease (IHD), myocardial infarction (MI), angina pectoris (AP), chronic heart failure (CHF), poor cardiac function, abnormal wall motion of left ventricule (LV) and angiographical severity of coronary atherosclerosis by univariate model. Adjusting for confounding variables by multivariate model, only severity of coronary atherosclerosis (Gensini score >40 points) had a powerful influence, increasing risk for cardiac cause of early-phase death by about 17 times.

CONCLUSIONS

Severity of coronary atherosclerosis predicts death in the first year of HD. These findings suggest that the strategy for prevention of coronary atherosclerosis should be instituted during the early phase of chronic renal failure.

The evaluation of oxidative stress in patients with chronic renal failure

BACKGROUND

Free radical-mediated changes are thought to be involved with atherosclerosis in patients with chronic renal failure.

METHODS

The protein carbonyl and malondialdehyde (MDA) levels in serum as the markers of radical-induced protein and lipid oxidations were measured in chronic renal failure patients.

RESULTS

Serum carbonyl and MDA levels in both hemodialysis and peritoneal dialysis patients were not found to be different as compared with healthy subjects. In both patient groups, the approximately twofold increment in total antioxidant activity (ferric reducing/antioxidant power; FRAP) and uric acid values in serum were found. The high uric acid levels in both patient groups might be partly responsible for the increment in FRAP values. In addition, all patients received multivitamin preparations including ascorbate, which was also a major antioxidant in serum.

CONCLUSIONS

Our data suggest that oxidative stress does not become the major threat for patients with chronic renal failure. The increment in endogenous and exogenous antioxidant capacities in serum might be thought to prevent any possible radical-induced damage in patients with chronic renal failure. In addition, the increased nitric oxide (NO) levels especially in hemodialysis patients might likely favor an antioxidant effect.

Emerging issues in the genetics of dyslexia: a methodological preview

A review of the classic and recent evidence on the genetics of reading disability (RD) shows encouraging progress, and accumulating evidence of genetic risk factors that operate within families and are separately localizable to more than one chromosomal region. The accelerating pace of these findings, however, suggests the need to consider some methodological issues about the design and interpretation of current and future studies. A major issue is the shape of the distribution of reading ability in the population, and we offer three tests of increasing rigor for determining whether those distributions are categorical, and hence not suitable for analyses that depend on the assumption of a continuous normal distribution. These tests are as follows: a nonnormal preponderance of cases with RD (i.e., the hump in the lower end of the distribution); a difference in the within-group variance-covariance matrices for typical readers compared to those with RD; and a correlation between a neurogenetically relevant criterion and a categorical reading variable that is larger than the correlation between the same criterion and a continuous version of the same reading variable. We emphasize also the importance of interactive relationships between multiple genetic loci, the variations in genotypic range as well as type of affectedness, the need to account for remediation variance, and the importance of lifespan changes in the phenotypes.

Implications for the role of endogenous nitric oxide inhibitors in hemodialysis hypotension

Hypotensive episodes during hemodialysis in patients with end-stage renal disease in the absence of inadequate maintenance of the plasma volume, pre-existence of cardiovascular disease, or autonomic nervous system dysfunction is accompanied by increase in the plasma concentrations of the end-products of nitric oxide metabolism, above the levels expected based on the reduction of urea. Factors that can influence the synthesis of nitric oxide or the regulation of the effects of this free radical in patients with chronic renal failure are reviewed. Convergence of these factors and their interactions during the hemodialysis procedure are discussed as the basis for the generation of excessive amounts of nitric oxide that serves as an important contributing factor in the development of symptomatic hypotension.

8-hydroxy-2'-deoxyguanosine of leukocyte DNA as a marker of oxidative stress in chronic hemodialysis patients

In contrast to proteins and lipids, oxidative damage to DNA has not been well studied in patients undergoing hemodialysis (HD). We hypothesized that phagocytes are activated after blood-membrane contact during HD, and oxidants from metabolic activation can damage leukocyte DNA. To test this hypothesis, the 8-hydroxy-2'-deoxyguanosine (8-OHdG) content of leukocyte DNA was measured by high-performance liquid chromatography electrochemical detection method in 35 age- and sex-matched healthy subjects, 22 undialyzed patients with advanced renal failure, and 109 HD patients to assess the relation between oxidative DNA damage and complement-activating membranes, blood antioxidants, and iron status. Dialysis membranes were classified into complement-activating (cellulose; n = 55) and non-complement-activating (polymethylmethacrylate [PMMA]; n = 35; polysulfone [PS]; n = 19) membranes. We found increased oxidative stress in undialyzed and HD patients based on a decrease in plasma levels of ascorbate and alpha-tocopherol adjusted for blood lipid (alpha-tocopherol/lipid), serum albumin, and reduced glutathione levels in whole blood and an increase in oxidized glutathione levels in whole blood compared with controls (P < 0.001). The greatest 8-OHdG level in leukocyte DNA was in HD patients, followed by undialyzed patients and healthy controls (P < 0.001), and was significantly greater in HD patients using cellulose membranes than those using PMMA or PS membranes (P < 0.001). 8-OHdG levels correlated with plasma alpha-tocopherol/lipid (r = -0.314; P < 0.005), serum iron (r = 0. 446; P < 0.001), and transferrin saturation values (r = 0.202; P < 0.05) in the analysis of all HD patients. In a 6-week crossover study, 8-OHdG levels significantly decreased after the switch from cellulose to synthetic membranes for 2 weeks and increased after the shift from synthetic to cellulose membranes (P < 0.05). Iron metabolism indices and plasma alpha-tocopherol/lipid values did not change significantly in the study period. We conclude that 8-OHdG content in leukocyte DNA is a biomarker of oxidant-induced DNA damage in HD patients. Oxidative DNA damage is a consequence of uremia, further augmented by complement-activating membranes.

Effect of vitamin E-bonded membrane on the 8-hydroxy 2'-deoxyguanosine level in leukocyte DNA of hemodialysis patients

BACKGROUND

8-Hydroxy 2'-deoxyguanosine (8-OHdG) of leukocyte DNA has been identified as a surrogate marker of oxidative stress in chronic hemodialysis (HD) patients. In this study, we focused on the determinants of the 8-OHdG level in leukocyte DNA of HD patients. We further investigated the influence of vitamin E-modified, regenerated cellulose (CL-E) membrane on the oxidative DNA damage, intracellular reactive oxygen species (ROS) production of granulocytes, and plasma alpha-tocopherol concentration.

METHODS

8-OHdG content in cellular DNA of leukocytes was measured by a high-performance liquid chromatography-electrochemical detection (HPLC-ECD) method. Intracellular production of ROS, H2O2 and O2-. were analyzed by flow cytometry in leukocytes with and without phorbol-12-myristate-13-acetate (PMA) stimulation before dialysis, as well as at 15 and 30 minutes of dialysis. Plasma alpha-tocopherol concentration was measured by a HPLC method, and the value of alpha-tocopherol was corrected by total blood lipid concentration.

RESULTS

In the prospective cross sectional study, the mean 8-OHdG level in leukocyte DNA was equally lower in the patients of the CL-E, polymethylmethacrylate (PMMA), and polysulfone (PS) groups as compared with the cellulosic group (ANOVA, P < 0.001). The leukocyte 8-OHdG level correlated negatively with plasma alpha-tocopherol and blood lipid-adjusted plasma alpha-tocopherol, but correlated positively with serum iron and percentage of transferrin saturation. Forward stepwise multiple regression showed that dialysis membrane type, serum iron, and blood lipid-adjusted plasma alpha-tocopherol were the independent determinants of the leukocyte 8-OHdG level in HD patients. Like synthetic membranes, granulocyte ROS production was less augmented during dialysis with the CL-E membrane as compared with the cellulose membrane. Exposure to cellulose membrane impaired intracellular ROS production of granulocytes in response to PMA challenge, whereas the CL-E and synthetic membranes improved the granulocyte responsiveness to PMA. In the longitudinal cross-over study, the 8-OHdG level significantly decreased, and blood lipid-adjusted plasma alpha-tocopherol increased after switching the cellulose membrane to CL-E or synthetic membrane for eight weeks. In contrast, the 8-OHdG level dramatically rose, and blood lipid-adjusted plasma alpha-tocopherol declined after shift of CL-E or synthetic membrane to the cellulose membrane.

CONCLUSIONS

CL-E membrane exhibited biocompatible and bioactive characteristics. Like synthetic membranes, treatment with a CL-E dialyzer effectively reduced the 8-OHdG content in leukocyte DNA, suppressed intracellular ROS production of granulocytes, and preserved the plasma level of vitamin E. It could further improve granulocyte responsiveness to a PMA challenge. Reduced DNA damage and improved immune function of leukocytes may reduce the cancer and infection risks in chronic HD patients.

Hemodialysis impairs endothelial function via oxidative stress: effects of vitamin E-coated dialyzer

BACKGROUND

Patients who undergo hemodialysis experience accelerated atherosclerosis and premature death. Recent evidence suggests that endothelial dysfunction proceeds to and exacerbates atherosclerosis. It remains unknown whether hemodialysis per se causes endothelial dysfunction.

METHODS AND RESULTS

We evaluated endothelial function estimated by flow-mediated vasodilation during reactive hyperemia using high-resolution ultrasound Doppler echocardiography before and after a single session in patients on maintenance hemodialysis. Several studies have shown that the imbalance between pro-oxidant and antioxidant activities in hemodialyzed patients results in high oxidative stress, which causes lipid peroxidation and endothelial injury. Accordingly, we investigated the effects of antioxidative modification during hemodialysis on endothelial function using a vitamin E-coated cellulose membrane dialyzer. Nonspecific endothelium-independent vasodilation was measured after administration of a sublingual glyceryl trinitrate spray (0.3 mg). A single session of hemodialysis by noncoated dialyzer impaired flow-mediated vasodilation (P<0.05) associated with increased plasma levels of oxidized LDL (P<0.05), an index of oxidative stress. Hemodialysis by vitamin E-coated membrane prevented dialysis-induced endothelial dysfunction and increases in oxidized LDL. Plasma levels of oxidized LDL were inversely correlated with the magnitudes of flow-mediated vasodilation (r=-0.53, P< 0.001). Hemodialysis by noncoated or vitamin E-coated membrane did not affect glyceryl trinitrate-induced endothelium-independent vasodilation.

CONCLUSIONS

Our findings indicate that hemodialysis per se impairs endothelial function, possibly by increasing oxidative stress.

Polymorphonuclear granulocyte stimulation by cellulose-based hemodialysis membranes

Hemodialysis with cellulose-based membranes is associated with an array of adverse reactions, including leukopenia, pulmonary sequestration and dysfunction of leukocytes. Activation of the alternative pathway of complement due to direct contact of plasma with dialysis membrane is considered to be responsible for the induction of these side effects. In recent years, evidence has accumulated that other neutrophil effector functions such as reactive oxygen intermediate production play an important role as well. Here the importance of burst formation in cooperation with other inflammatory effector functions in the mechanisms of hemodialysis-related adverse effects will be discussed.

Hemodialysis hypotension: interaction of inhibitors, iNOS, and the interdialytic period

Hypotension during hemodialysis in end-stage renal disease (ESRD) not explained by excessive ultrafiltration has been linked to an apparent increase in the synthesis of nitric oxide (NO). The authors tested whether the induction of NO synthase (iNOS) by cytokines or differences in the concentrations of inhibitors of NOS or both could account for variability in the amount of NO synthesized during hemodialysis. Plasma levels of an inhibitor of NOS, asymmetric dimethylarginine (ADMA), L-arginine, the substrate for NOS, the end-products N02+N03, iNOS activity in circulating buffy coat cells, and their interdialytic changes were measured in 10 patients during three treatments. Predialysis (0') levels of ADMA were markedly elevated with a mean of 0.008+/-0.002 micromol/mL of deproteinized plasma, compared to controls where ADMA is present in trace amounts. ADMA levels from 30 minutes to the end of dialysis correlated directly with the drop in blood pressure (BP), with levels being much higher in patients with severe hypotension. Postdialysis ADMA levels correlated directly with the 0' systolic BP and the drop in BP at the next dialysis treatment. NOS activity was detected in two thirds of the predialysis buffy coat samples, and appeared to increase as dialysis progressed. 0' iNOS activity correlated inversely with the 0' BP, but activities did not differ based on percent drop in BP. iNOS activity in the 0' samples correlated inversely with the time since the last dialysis, reflecting the greater accumulation of dialyzable inhibitors of NOS as the interval is prolonged. The interdialytic change in iNOS activity correlated inversely with the drop in BP. The isoform detected immunochemically in the buffy coat samples had an Mr of 130 kDa and was reactive with antihuman iNOS. Thus, iNOS is already induced in the cells of the buffy coat in many intermittently hemodialyzed ESRD subjects, but its expression may be masked by inhibitors. After 60 minutes of dialysis (too brief a time for the de novo induction of iNOS,) the appearance of or increase in iNOS activity suggests that an inhibitor had been removed. Because ADMA levels are associated with higher predialysis systolic BPs that result in a greater severity of hypotension, reduction in ADMA concentrations would appear to play a major role in the resumption of NO synthesis by various isoforms.

Improved biochemical variables, nutrient intake, and hormonal factors in slow nocturnal hemodialysis: a pilot study

OBJECTIVE

To determine whether slow nocturnal hemodialysis (SNHD) can be safely performed in patients with end-stage renal disease to improve the biochemical and clinical outcome.

MATERIAL AND METHODS

We conducted an 8-week pilot study in nondiabetic adult patients, who underwent dialysis 6 nights per week for 8 hours each night. A dialysate flow rate of 300 mL/min and a blood flow rate of 250 mL/min, through an internal jugular dual-lumen venous catheter, were used. The equipment used was a COBE Centry System 3 dialysis machine and Fresenius F-80 (1.8 m2) or Baxter CT 190 (1.9 m2) dialyzers. Five patients were enrolled in the study.

RESULTS

Two patients did not complete the study because of catheter-related infections--one at day 7 and one after 4 weeks of SNHD. All patients had improved blood pressure control, and no intradialytic adverse events occurred. Dietary intake improved, urea and creatinine levels significantly decreased, and weekly delivery of dialysate increased on SNHD. Potassium, chloride, beta 2-microglobulin, phosphorus, calcium, and high-density lipoprotein cholesterol all improved on SNHD. Serum testosterone increased in the three men on SNHD, but parathyroid hormone, luteinizing hormone, and follicle-stimulating hormone remained unchanged. Erythropoietin levels increased on SNHD, despite no change in exogenous erythropoietin doses in three patients and discontinuation of administration of erythropoietin in one. The following biochemical factors did not change significantly: serum sodium, bicarbonate, vitamin B12, folate, alkaline phosphatase, total cholesterol, triglycerides, and albumin.

CONCLUSION

Higher doses of hemodialysis benefit nutrition, improve biochemical variables, and may improve many hormonal systems.

Biocompatibility Evaluation of Polyamide Hemofiltration

Introduction

Postdilution hemofiltration with a polyamide membrane is a renal replacement technique widely used, but very little information is available regarding the biocompatibility of this treatment. In this paper we report the results of an acute study of the biocompatibility of polyamide hemofiltration.

Patients and methods

Complement activation such as C3a and C5a Des Arg (RIA), granulocyte degranulation like alpha 1 elastase intradialytic increase (ELISA) and the expression of high affinity membrane receptors for IL-2 (anti-TAC) were determined. Beta 2-microglobulin (RIA) intradialytic decrease, as well as its convective removal, was evaluated. The nature of protein layer adsorbed onto the polyamide membrane, at the end of the dialytic session was investigated with a new immunohistochemical tecnique. Cell-associated cytokine concentration (like IL-1 beta and IL-1Ra - ELISA) was determined on mononuclear cell lysates.

Results

A low degree of complement activation was detected with the polyamide membrane when data were adjusted for hemoconcentration and for 1 m2of membrane surface area. An important convective removal not only of Beta 2-microglobulin (258±20 mg/session), but also of the activated anaphylatoxins (225±76 ng/ml for C3a and 22.5±4 ng/ml for C5a) was revealed. A marked deposition of all coagulation factors with no detectable amount of immunoglobulins and complement factors was revealed on the polyamide membrane at the end of the dialytic session. No intradialytic (for IL-1beta) (from 14.1±3.0 to 13.5±2.9 pg/ 2.5 x 106cell) and interdialytic (for IL-1Ra) (from 4572±1076 to 5408±615 pg/ 2.5 x 106cell) cell-associated cytokine expression was induced by hemofiltration.

Discussion and Conclusion

Polyamide hemofiltration is a highly biocompatible technique due to the use of a synthetic membrane with a sterile reinfusion fluid and the convective removal of the activated anaphylatoxins and Beta 2-microglobulin.

Improved preservation of residual renal function in chronic hemodialysis patients using polysulfone dialyzers

Our objective was to determine whether patients with chronic renal failure requiring maintenance hemodialysis retain intrinsic renal function longer when using reprocessed polysulfone (PS) membrane hemodialyzers or single-use cellulose acetate (CA) membrane hemodialyzers. Fifty consecutive patients with residual renal function (urea clearance > 2.0 mL/min) using PS dialyzers were compared with a retrospective, disease- and time-matched population of patients using CA dialyzers. Endogenous urea clearance was measured every 3 months in all patients with remaining residual function. Other data collected included age, sex, cause of chronic renal failure, use of angiotensin-converting enzyme inhibitors or calcium channel blockers, and hemodynamic stability during hemodialysis. All patients were observed for at least 6 months while using a single type of dialyzer. Study end points included loss of residual renal function (urea clearance < 1.0 mL/min), death, transplant, transfer to peritoneal dialysis, or change of dialyzer. The PS and CA groups of patients were well matched for sex, age, initial renal clearance, predialysis blood pressure, and hemodynamic stability during hemodialysis. The PS patients had a higher delivered Kt/V (1.34 +/- 0.30 [mean +/- SD]) than the CA patients (1.06 +/- 0.20). The PS group had a higher average urea clearance than the CA group after 4 to 9 months of dialysis (2.8 +/- 2.6 mL/min v 1.7 +/- 1.6 mL/min, respectively), after 10 to 15 months of chronic dialysis (2.0 +/- 2.4 mL/min v 1.1 +/- 1.5 mL/min, respectively), and after 16 to 21 months of dialysis (1.3 +/- 1.9 mL/min v 0.5 +/- 1.1 mL/min, respectively; all P < 0.03, t-test). After 22 to 24 months of dialysis, the difference between the two groups was not significant. When comparing patients with identical causes of chronic renal failure, there were no differences between the PS and CA groups for those with diabetes mellitus, tubulointerstitial disease, or polycystic disease. Patients with parenchymal renal disease (glomerulonephritis or nephrosclerosis) had markedly better retention of intrinsic renal function with PS than with CA dialyzers (all P < 0.01). Kaplan-Meier analysis for retention of intrinsic renal function showed that PS patients with parenchymal renal disease had a mean of 23 months before loss of intrinsic renal function, whereas for CA patients the mean was 11 months before loss of intrinsic renal function (P = 0.0005). Cellulose acetate patients lost renal function at an average rate of 0.27 +/- 0.22 mL/min/mo, whereas for PS patients the rate was 0.14 +/- 0.56 mL/min/mo (P = 0.06, rank sum). CA patients with parenchymal renal disease lost renal function at a rate of 0.29 +/- 0.22 mL/min/mo, whereas for PS patients the rate was 0.0 +/- 0.8 mL/min/mo (P = 0.004, rank sum). Age, sex, and the use of either angiotensin-converting enzyme inhibitors or calcium channel blockers did not have an effect on the loss of intrinsic renal function. Patients with nondiabetic parenchymal renal disease receiving chronic hemodialysis with hydrogen peroxide/peroxyacetic acid-reprocessed PS dialyzers and a higher Kt/V lose residual renal function at a slower rate than disease-matched patients using single-use CA dialyzers. Our findings provide further evidence that the choice of dialyzer membrane may have an effect on intrinsic renal function.

Hypotension during hemodialysis: role for nitric oxide

Hypotensive episodes during hemodialysis are a frequent complication in patients with end-stage renal disease. The possibility that nitric oxide (NO), a major regulator of cardiovascular hemodynamics, could be a factor was explored. Pre and postdialysis plasma samples from 17 hemodialysis patients were analyzed for the stable end products of NO,nitrite + nitrate (NO2 + NO3), by the Greiss method. Predialysis NO2 + NO3 levels were significantly higher in end-stage renal disease than in nine age-matched controls (44.08 +/- standard error of mean 5.74 versus 18.67 +/- 3.56 uM, P = 0.017). In more than half of the patients, postdialysis values dropped markedly, whereas in others the value change was far less; several rose above predialysis values. Depending on the nitrite + nitrate reduction ratio (pre minus postdialysis NO2 + NO3 divided by the predialysis value) patients were separated into two groups, A (n = 9 where nitrate + nitrate reduction ratio was > 0.5 and B (n = 8 where nitrate + nitrate reduction ratio was < 0.5). Whereas the mean predialysis NO2 + NO3 values between groups A and B did not differ significantly, postdialysis levels fell from a predialysis mean of 50 uM to 12 uM in group A but rose from 37 uM to 45 uM in group B. The difference between the postdialysis values of group A and group B was significant (P = 0.0264). In group B, mean systolic blood pressure dropped more than in group A, (57.8 mm Hg compared with 21.2 mm Hg, P = 0.0078). When measured by analysis of variance for repeated measures, skin and core temperatures and blood pressures were lower in group B than in group A. The volume of the ultrafiltrate was removed and dialysis duration and mean weight loss did not differ. Thus, in group B, apparently NO formation increased during hemodialysis exceeding the rate of removal or metabolism of the end products, whereas in group A, NO2 + NO3 removal or metabolism was without apparent increase in the formation of NO. The basis for this difference is unknown. Because vasodilation is a major effect of NO, the strong association of severe reduction in blood pressures and increased NO synthesis in subset B suggests a role for NO in hypotensive episodes during hemodialysis.

Complement-mediated leukocyte adhesion on poly(etherurethane ureas) under shear stress in vitro

Blood-contacting biomaterials may activate the complement cascade, thus promoting leukocyte adhesion to the biomaterial surface. We hypothesize that the extent of complement activation is modulated by biomaterial formulation and the presence of fluid shear stress. To investigate this hypothesis, we tested base poly(etherurethane ureas) formulated with or without Santowhite antioxidant, a nucleophilic additive. We found that adherent leukocyte densities decreased with increasing shear stress. Moreover, leukocyte adhesion was decreased significantly further by Santowhite additive under shear stress but not under static conditions. Monocytes showed a higher propensity for adhesion than did neutrophils under shear and static conditions. Under static conditions, adherent cells on the Santowhite-containing polyurethane had a slightly more activated morphology than those on the base polyurethane. Cell adhesion under shear stress was significantly decreased when C3 or fibronectin was depleted from the suspension medium. Santowhite additive increased Factor B adsorption to the test surface while shear stress increased Factor H adsorption. The combination of Santowhite additive and shear stress increased the adsorption of both Factor B and Factor H and the serum protein S-terminal complement complex levels, but it did not further increase the state of activation of adherent cells. We conclude that leukocyte adhesion on poly(etherurethane urea) surfaces is sensitive to the levels of shear stress and that both C3 and fibronectin are required to maintain adhesion in the presence of shear stress. The low state of cellular activation and increased Factor H adsorption may explain the decreased adherent leukocyte density on the Santowhite-containing polyurethane.

Effects of increasing dialysis dose on serum albumin and mortality in hemodialysis patients

Dialysis dose and malnutrition have a great impact on the clinical out come of chronic hemodialysis patients. The interrelationships between them, however, remain undefined. Thus, we performed a study to determine the effects of increasing the dialysis dose on serum albumin concentrations and mortality in hemodialysis patients. We examined urea kinetic modeling, biochemical nutritional indices, comorbid conditions, patient survival time, and annual mortality rate. Dialysis dose, measured by Kt/V, significantly increased from 1.3 +/- 0.3 in 1987 to 1.5 +/- 0.4 in 1990 and to 1.7 +/- 0.4 in 1993. Serum albumin level also increased from 3.8 +/- 0.4 g/dL in 1987 to 4.0 +/- 0.4 in 1990 and to 1.7 +/- 0.4 in 1993. In 1993, 76% of patients had Kt/V > or = 1.50 compared with 45% in 1990 and 28% in 1987, whereas 82% of patients had a serum albumin level > or 4.0 g/dL in 1993 compared with 58% in 1990 and 29% in 1987. Protein catabolic rate and hematocrit also increased from 1987 to 1993, but not serum cholesterol or triglyceride. The annual mortality rate declined from 16.1% in 1987 to 13.2% in 1990 and to 8.0% in 1993. The decrease in mortality appeared to be unrelated to differences in patient selection or comorbid conditions. Serum albumin levels, hematocrit, Kt/V, and protein catabolic rate were significantly related to patient survival after age, sex, and diabetic status had been adjusted. Furthermore, there was a positive correlation between Kt/Vs and serum albumin concentration (r = 0.216, P < 0.001). Thus it appears that increasing the dose of dialysis improves serum albumin levels and perhaps survival rate in hemodialysis patients as well.