Hemodialysis related induction of interleukin-6 production by peripheral blood mononuclear cells

Immune-Related Genes and Immune Cell Infiltration Characterize the Maturation Status of Arteriovenous Fistulas: An Integrative Bioinformatics Study and Experimental Validation Based on Transcriptome Sequencing

Purpose

Arteriovenous fistula (AVF) is the preferred vascular access for hemodialysis, but the low maturation rate is concerning. Immune cells' impact on AVF maturation lacks bioinformatics research. The study aims to investigate the potential predictive role of immune-related genes and immune cell infiltration characteristics in AVF maturation.

Patients and Methods

We analyzed the high-throughput sequencing dataset to identify differentially expressed genes (DEGs). Then, we performed enrichment analyses (GO, KEGG, GSEA) on immune-related genes and pathways in mature AVF. We focused on differentially expressed immune-related genes (DEIRGs) and constructed a PPI network to identify hub genes. These hub genes were validated in other databases and experiments, including qPCR and immunohistochemistry (IHC). The immune cell infiltration characteristics in native veins, failed AVFs, and matured AVFs were analyzed by cibersortX. Partial experimental validation was conducted using clinical samples.

Results

Our results showed that immune-related genes and signaling pathways are significantly enriched in mature AVF. We validated this in other databases and ultimately identified three hub genes (IL1B, IL6, CXCR4) in combination with experiments. Significant differences in immune cell infiltration characteristics were observed among native veins, failed AVFs, and matured AVFs. Immune cell infiltration analysis revealed that accumulation of CD4+ T cells, dendritic cells, mast cells and M2 macrophages contribute to AVF maturation. These immune-related genes and immune cells have the potential to serve as predictive factors for AVF maturation. We partially validated this experimentally.

Conclusion

From a bioinformatics perspective, our results have identified, for the first time, a set of immune-related genes and immune cell infiltration features that can characterize the maturation of AVF and significantly impact AVF maturation. These features hold potential as predictive indicators for AVF maturation outcomes.

Effects of Medium Cut-Off Polyarylethersulfone and Polyvinylpyrrolidone Blend Membrane Dialyzers in Hemodialysis Patients: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

The use of medium cut-off (MCO) polyarylethersulfone and polyvinylpyrrolidone blend membrane is an emerging mode in hemodialysis. Recent studies have shown that MCO membranes exhibit a middle high molecular weight uremic toxin clearance superior to standard high flux hemodialysis. We conducted a systematic literature review and meta-analysis of randomized controlled trials to investigate whether MCO membranes efficiently increase the reduction ratio of middle molecules, and to explore the potential clinical applications of MCO membranes. We selected articles that compared beta 2-microglobulin (β2M), kappa free light chain (κFLC), lambda free light chain (λFLC), interleukin-6 (IL-6), and albumin levels among patients undergoing hemodialysis. Five randomized studies with 328 patients were included. The meta-analysis demonstrated a significantly higher reduction ratio of serum β2M (p < 0.0001), κFLC (p < 0.0001), and λFLC (p = 0.02) in the MCO group. No significant difference was found in serum IL-6 levels after hemodialysis. Albumin loss was observed in the MCO group (p = 0.04). In conclusion, this meta-analysis study demonstrated the MCO membranes’ superior ability to clear β2M, κFLC, and λFLC. Serum albumin loss is an issue and should be monitored. Further studies are expected to identify whether MCO membranes could significantly improve clinical outcomes and overall survival.

Differential Glucocorticoid Responsiveness of Dialysis Patients’ Lymphocytes

Objectives

To evaluate in vitro glucocorticoid responsiveness of phytohemagglutinin (PHA)-stimulated lymphocytes from peritoneal dialysis (PO) patients compared to hemodialysis (HO) patients.

Design

Cross-sectional study of prevalent PO and HO patients and concurrent control subjects.

Setting

Urban outpatient dialysis unit.

Patients

20 HO, 14 PO, and 20 control subjects.

Measurements

Using standard lymphocyte culture techniques, the concentration of prednisolone (P) and methylprednisolone (MP) required to cause 50% inhibition (ICso) of the proliferative response to phytohemagglutinin (PHA) was determined from dose-response curves.

Results

There was considerable heterogeneity in the sensitivities of individual patients’ PBMC to glucocorticoid inhibition, especially those of HO patients’ cells to P. The mean: i: SO ICso for MP was significantly (p ≤ 0.001) lower than that for P in each cohort: PO 11 ± 5 vs. 34 ± 18 ng/mL; HO 22 ± 14 vs. 89 ± 43 ng/mL; control subjects 14 ± 11 vs. 55 ± 56 ng/mL. Interestingly, the ICSO for both P and MP was significantly higher in HO than in either PO or controls (ANOVA, P: F = 6.56, p = 0.003; MP: F = 3.77, p = 0.03), indicating decreased sensitivity of HO lymphocytes to both drugs. There were no significant differences in mean ICSO values for either P or MP between PO and controls. No correlations were found between ICSO for either P or MP and patient age, gender, duration of dialysis, serum creatinine, serum albumin, or parathyroid hormone level.

Conclusions

In vitro glucocorticoid responsiveness of dialysis patients’ lymphocytes appears to be influenced by dialysis modality, butthefactor(s) involved remains to be determined. Thegreater sensitivity of PO lymphocytes to both P and MP might result in better immunosuppression and less severe rejection after renal transplantation. MP may be particularly advantageous following renal transplantation for any patient manifesting relative or absolute in vitro resistance to P.

Alteration of HDL Protein Composition with Hemodialysis Initiation

BACKGROUND AND OBJECTIVES

HDL particles obtained from patients on chronic hemodialysis exhibit lower cholesterol efflux capacity and are enriched in inflammatory proteins compared with those in healthy individuals. Observed alterations in HDL proteins could be due to effects of CKD, but also may be influenced by the hemodialysis procedure, which stimulates proinflammatory and prothrombotic pathways.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We compared HDL-associated proteins in 143 participants who initiated hemodialysis within the previous year with those of 110 participants with advanced CKD from the Hemodialysis Fistula Maturation Study. We quantified concentrations of 38 HDL-associated proteins relative to total HDL protein using targeted mass spectrometry assays that included a stable isotope-labeled internal standard. We used linear regression to compare the relative abundances of HDL-associated proteins after adjustment and required a false discovery rate q value ≤10% to control for multiple testing. We further assessed the association between hemodialysis initiation and cholesterol efflux capacity in a subset of 80 participants.

RESULTS

After adjustment for demographics, comorbidities, and other clinical characteristics, eight HDL-associated proteins met the prespecified false discovery threshold for association. Recent hemodialysis initiation was associated with higher HDL-associated concentrations of serum amyloid A1, A2, and A4; hemoglobin-β; haptoglobin-related protein; cholesterylester transfer protein; phospholipid transfer protein; and apo E. The trend for participants recently initiating hemodialysis for lower cholesterol efflux capacity compared with individuals with advanced CKD did not reach statistical significance.

CONCLUSIONS

Compared with advanced CKD, hemodialysis initiation within the previous year is associated with higher concentrations of eight HDL proteins related to inflammation and lipid metabolism. Identified associations differ from those recently observed for nondialysis-requiring CKD. Hemodialysis initiation may further impair cholesterol efflux capacity. Further work is needed to clarify the clinical significance of the identified proteins with respect to cardiovascular risk.

PODCAST

This article contains a podcast at https://www.asn-online.org/media/podcast/CJASN/2018_07_25_CJASNPodcast_18_8_W.mp3.

Membrane Distillation of Human Plasma Ultrafiltrate and its Theoretical Applications to Haemodialysis Techniques

Membrane Distillation (MD) is a technique that allows the extraction of water from aqueous solutions. The basic principle is that vapour, but not liquid water, can pass through hydrophobic micro-porous membranes, along a temperature gradient, with consequent separation of water from solutes. In this study we evaluated the possibility to utilise MD to extract water from Plasma Ultrafiltrate (PU) of patients with Chronic Renal Failure (CRF). The experiments were carried out in vitro by a hydro-phobic polypropylene hollow-fibre distillation module; PU was obtained by a CRF patient utilising a high permeability polisulphone membrane. The results show that water can be extracted by MD from PU of CRF subjects at a constant rate and that none of the substances analysed in PU was able to pass through the polypropilene membrane. In the future MD could integrate extra-corporeal blood purification techniques allowing the re-utilisation of plasmatic water thus ameliorating the treatment of uraemia.

Rediscovering Beta-2 Microglobulin As a Biomarker across the Spectrum of Kidney Diseases

There is currently an unmet need for better biomarkers across the spectrum of renal diseases. In this paper, we revisit the role of beta-2 microglobulin (β₂M) as a biomarker in patients with chronic kidney disease and end-stage renal disease. Prior to reviewing the numerous clinical studies in the area, we describe the basic biology of β₂M, focusing in particular on its role in maintaining the serum albumin levels and reclaiming the albumin in tubular fluid through the actions of the neonatal Fc receptor. Disorders of abnormal β₂M function arise as a result of altered binding of β₂M to its protein cofactors and the clinical manifestations are exemplified by rare human genetic conditions and mice knockouts. We highlight the utility of β₂M as a predictor of renal function and clinical outcomes in recent large database studies against predictions made by recently developed whole body population kinetic models. Furthermore, we discuss recent animal data suggesting that contrary to textbook dogma urinary β₂M may be a marker for glomerular rather than tubular pathology. We review the existing literature about β₂M as a biomarker in patients receiving renal replacement therapy, with particular emphasis on large outcome trials. We note emerging proteomic data suggesting that β₂M is a promising marker of chronic allograft nephropathy. Finally, we present data about the role of β₂M as a biomarker in a number of non-renal diseases. The goal of this comprehensive review is to direct attention to the multifaceted role of β₂M as a biomarker, and its exciting biology in order to propose the next steps required to bring this recently rediscovered biomarker into the twenty-first century.

Antineutrophil cytoplasmic antibody-associated renal vasculitis treated with autologous mesenchymal stromal cells: evaluation of the contribution of immune-mediated mechanisms

We report the first case of renal antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis treated with autologous mesenchymal stromal cells (MSCs). A 73-year-old man was admitted to the hospital for malaise, weight loss, and oliguria. His serum creatinine level was 2.7 mg/dL but it rapidly increased to 7.8 mg/dL; urinalysis showed proteinuria and hematuria, and the ANCA to myeloperoxidase with a perinuclear pattern (pANCA) titer was high (132 IU/mL). Renal biopsy showed necrotizing crescentic glomerulonephritis. Standard immunosuppressive therapy (cyclophosphamide and corticosteroids) was ineffective. Rituximab therapy was started, but it was discontinued after the third dose to minimize the risk of systemic spread of a severe oral Candida infection and to prevent superinfections that were facilitated by leukopenia. The patient received autologous MSCs, 1.5 × 10(6) cells/kg body weight, intravenously. After 7 days, his serum creatinine level decreased to 2.2 mg/dL, pANCA titer decreased to 75 IU/mL, and urinalysis findings normalized. Eight months later, he received a second MSC infusion because his serum creatinine level increased. In 1 week, his creatinine level decreased to 1.9 mg/dL and his pANCA titer decreased to 14 IU/mL. Immunosuppressive therapy was subsequently withdrawn. At the last follow-up visit, 12 months after the second MSC infusion, the patient remained in clinical remission without any therapy. Infusion of MSCs induced expansion of the T-lymphocyte subset expressing a regulatory T-cell phenotype (CD4(+)CD25(+)Foxp3(+)) and a notable reduction in interferon-γ, interleukin 6, and tumor necrosis factor serum levels.

Immunomodulatory effect of continuous venovenous hemofiltration during sepsis: preliminary data

INTRODUCTION

Severe sepsis and septic shock are the primary causes of multiple organ dysfunction syndrome (MODS), which is the most frequent cause of death in intensive care unit patients. Many pro- and anti-inflammatory mediators, such as interleukin-6 (IL-6), play a strategic role in septic syndrome. Continuous renal replacement therapy (CRRT) removes in a nonselective way pro- and anti-inflammatory mediators.

OBJECTIVE

To investigate the effects of continuous venovenous hemofiltration (CVVH) as an immunomodulatory treatment of sepsis in a prospective clinical study.

METHODS

High flux hemofiltration (Qf = 60 ml/Kg/hr) was performed for 72 hr in thirteen critically ill patients suffering from severe sepsis or septic shock with acute renal failure (ARF). IL-6 gene expression was measured by real-time PCR analysis on RNA extracted from peripheral blood mononuclear cell before beginning of treatment (T0) and after 12, 24, 48, and 72 hours (T1-4).

RESULTS

Real-time PCR analysis demonstrated in twelve patients IL-6 mRNA reduction after 12 hours of treatment and a progressive increase after 24, 48, and 72 hours.

CONCLUSIONS

We suggest that an immunomodulatory effect might exist during CVVH performed in critically ill patients with severe sepsis and septic shock. Our data show that the transcriptional activity of IL-6 increases during CVVH.

Acute kidney injury: effect of hemodialysis membrane on Hgf and recovery of renal function

OBJECTIVES

Acute kidney injury (AKI) is associated with a high mortality and morbidity rate. In this study we investigated whether dialysis membranes influence the recovery of renal function, through the regulation of hepatocyte growth factor (HGF).

DESIGN AND METHODS

21 patients were enrolled and assigned to hemodialysis (HD) with cellulose (CE, N=11) versus polymethylacrylate (PMMA, N=10) membranes in alternating order. HGF and IL-1 were measured in serum and in peripheral blood mononuclear cells (PBMC) supernatants collected immediately before the first HD session (T0), at 15 minutes (T15), at 240 minutes (T240) and after the last HD, when renal recovery occurred. Eight healthy volunteers were the controls (CON).

RESULTS

Time to renal function recovery was lower in CE than in PMMA patients. Serum HGF in HD patients was significantly higher than in CON. HGF levels were higher in CE than in PMMA patients at T15 (13.4±2.7 vs 8.9±3.0 ng/mL, P=0.004) and T240. At recovery, HGF levels decreased. IL-1 serum levels showed a similar trend (at T15 CE: 20.5±2.9 vs PMMA: 16.9±3.2 pg/mL, P=0.005). HGF release significantly increased in the course of HD, resulting in higher levels in CE than that in PMMA patients. Considering all the patients, basal HGF release negatively correlated with time to renal recovery (r2=0.42, P<0.01).

CONCLUSIONS

Here we demonstrated that dialysis membranes influence the cytokine profile in AKI patients, HGF release being higher in patients treated with the CE membrane, in comparison to PMMA. Our results suggest that treatment with CE might improve clinical outcomes, possibly through increased release of HGF.

Water quality in conventional and home haemodialysis

Dialysis water can be contaminated by chemical and microbiological factors, all of which are potentially hazardous to patients on haemodialysis. The quality of dialysis water has seen incremental improvements over the years, with advances in water preparation, monitoring and disinfection methods, and high standards are now readily achievable in clinical practice. Advances in dialysis membrane technology have refocused attention on water quality and its potential role in the bioincompatibility of haemodialysis circuits and adverse patient outcomes. The role of ultrapure dialysate is increasingly being advocated, given its proposed clinical benefits and relative ease of production as a result of the widespread use of reverse osmosis and ultrafiltration. Many of the issues pertaining to water quality in hospital-based dialysis units are also pertinent to haemodialysis in the home. Furthermore, an increased awareness of the environmental and financial consequences of home haemodialysis has resulted in the development of automated and more efficient dialysis machines. These new machines have an increased emphasis on water conservation and recycling along with a decreased need for a complex infrastructure for water purification and maintenance.

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.

Bio-incompatibility and Th2 polarization during regular dialysis treatment

Long-term hemodialysis treatment results in chronic monocyte activation with cytokine release. It generates Treg induction with potential immune dysfunction and associated clinical complications. Recent immunological data and preliminary clinical evidence suggest that synthetic polymers and vitamin E coated membranes are associated with a significant improvement in hemodialysis tolerance when compared to cellulose membranes. The aim of this review is to update cytokine release, T-cell polarization, and its clinical impact in patients under extracorporeal hemodialysis comparing traditional cellulose to synthetic/vitamin E coated membranes.

Effect of hemodialysis schedules and membranes on hepatocyte growth factor and hepatitis C virus RNA levels

Hemodialysis induces production of the hepatocyte growth factor (HGF) and decrease of serum hepatitis C virus (HCV) RNA in patients with HCV infection, but it is not known if the hemodialysis schedule or type of membrane affect both the HGF production and HCV viremia. The effects on both parameters of alternate-day intermittent hemodialysis and short-daily hemodialysis and high and low flux membranes were investigated in 41 patients treated by hemodialysis. Sixteen (39%) patients were anti-HCV positive and 11 (69%) had HCV RNA. Twenty-six patients were on alternate-day intermittent and 15 on short-daily hemodialysis. High flux membranes were used for 29 patients and low flux membranes for 12 patients. A decrease in HCV RNA was observed at the end of hemodialysis (8.6 x 10(5) +/- 1.1 x 10(6) IU/ml vs. 4.4 x 10(5) +/- 7.3 x 10(5) IU/ml, P = 0.003). The proportion of HCV RNA decrease was similar in patients dialyzed with both schedules and with both types of membranes. The HGF levels increased from 2,605.9 +/- 1,428.7 to >8,000 pg/ml at 15 min. At the end of the session, the HGF levels decreased to 5,106.7 +/- 2,533.9 pg/ml. The HGF levels at the start of the next session were similar to those at baseline (2,680.0 +/- 1,209.3 pg/ml). The increase and dynamics of the HGF levels were similar in patient's hemodialyzed with both schedules and with both types of membranes. These results suggest that changes in HCV RNA and HGF levels during hemodialysis are not influenced by the schedule or type of membrane used.

A translational approach to micro-inflammation in end-stage renal disease: molecular effects of low levels of interleukin-6

Inflammation plays a key role in the progression of cardiovascular disease, the leading cause of mortality in ESRD (end-stage renal disease). Over recent years, inflammation has been greatly reduced with treatment, but mortality remains high. The aim of the present study was to assess whether low (<2 pg/ml) circulating levels of IL-6 (interleukin-6) are necessary and sufficient to activate the transcription factor STAT3 (signal transducer and activator of transcription 3) in human hepatocytes, and if this micro-inflammatory state was associated with changes in gene expression of some acute-phase proteins involved in cardiovascular mortality in ESRD. Human hepatocytes were treated for 24 h in the presence and absence of serum fractions from ESRD patients and healthy subjects with different concentrations of IL-6. The specific role of the cytokine was also evaluated by cell experiments with serum containing blocked IL-6. Furthermore, a comparison of the effects of IL-6 from patient serum and rIL-6 (recombinant IL-6) at increasing concentrations was performed. Confocal microscopy and Western blotting demonstrated that STAT3 activation was associated with IL-6 cell-membrane-bound receptor overexpression only in hepatocytes cultured with 1.8 pg/ml serum IL-6. A linear activation of STAT3 and IL-6 receptor expression was also observed after incubation with rIL-6. Treatment of hepatocytes with 1.8 pg/ml serum IL-6 was also associated with a 31.6-fold up-regulation of hepcidin gene expression and a 8.9-fold down-regulation of fetuin-A gene expression. In conclusion, these results demonstrated that low (<2 pg/ml) circulating levels of IL-6, as present in non-inflamed ESRD patients, are sufficient to activate some inflammatory pathways and can differentially regulate hepcidin and fetuin-A gene expression.

Elevated hepatocyte growth factor levels at the beginning of high-flux hemodialysis are due to heparin administration

BACKGROUND

It has been reported that hemodialysis (HD) stimulates hepatocyte growth factor (HGF) release, but it is not clear if this stimulation is due to HD itself or to heparin used during HD. To clarify this issue, we undertook the present study.

METHODS

We studied 18 HD patients using high-flux dialyzers, during a single 4-hr hemodialysis session (session A). The dialyzers were pre-rinse with normal saline without heparin, and HD was started with zero ultrafiltration and without anticoagulation. Anticoagulation was administered as IV injection (80 IU/kg of LMWH enoxaparin sodium) 10 min after the beginning of HD. HD was continued for 10 more minutes and then as prescribed. HGF serum levels were measured before the beginning of the HD session (sample t0) as well as 10 and 20 minutes after the beginning of the session (samples t10 and t20). In six more patients (controls), the same study was repeated but without the administration of LMWH during the first 20 min of HD initiation (session B).

RESULTS

In comparison with t0, t10 HGF serum levels changed significantly in neither session A nor in session B. However, at t20, HGF levels increased significantly in session A compared with t0 (increment 666.3 +/- 211.0%, p < 0.0001) and t10 (increment 894.2 +/- 506.0%, p < 0.0001), but not in session B. No differences were found between sessions A and B at samples t0 and t10 (p = NS). HGF serum levels at t20 in session A were found to be higher compared with corresponding levels in session B (p < 0.0001).

CONCLUSION

Elevated HGF serum levels at the beginning of high-flux HD session are due to LMWH administration.

Fatigue in patients receiving maintenance dialysis: a review of definitions, measures, and contributing factors

Fatigue is a debilitating symptom or side effect experienced by many patients on long-term dialysis therapy. Fatigue has a considerable effect on patient health-related quality of life and is viewed as being more important than survival by some patients. Renal providers face many challenges when attempting to reduce fatigue in dialysis patients. The lack of a reliable, valid, and sensitive fatigue scale complicates the accurate identification of this symptom. Symptoms of daytime sleepiness and depression overlap with fatigue, making it difficult to target specific therapies. Moreover, many chronic health conditions common in the long-term dialysis population may lead to the development of fatigue and contribute to the day-to-day and diurnal variation in fatigue in patients. Key to improving the assessment and treatment of fatigue is improving our understanding of potential mediators, as well as potential therapies. Cytokines have emerged as an important mediator of fatigue and have been studied extensively in patients with cancer-related fatigue. In addition, although erythropoietin-stimulating agents have been shown to mitigate fatigue, the recent controversy regarding erythropoietin-stimulating agent dosing in patients with chronic kidney disease suggests that erythropoietin-stimulating agent therapy may not serve as the sole therapy to improve fatigue in this population. In conclusion, fatigue is an important and often underrecognized symptom in the dialysis population. Possible interventions for minimizing fatigue in patients on long-term dialysis therapy should aim at improving health care provider awareness, developing improved methods of measurement, understanding the pathogenesis better, and managing known contributing factors.

Quotidian hemodialysis and inflammation associated with chronic kidney disease

The mortality rate of chronic dialysis patients in the United States is 24% per year per the 2006 United States Renal Data System. Although there have been marked improvements in dialysis technology, cardiovascular disease is the principal cause of mortality in end-stage renal disease patients. Inflammation and left ventricular hypertrophy both contribute to atherosclerosis. Hemodialysis 3 times a week is the most commonly used form of dialysis in the United States. The multicenter hemodialysis (HEMO) study hypothesized that an increase in dialysis dose and use of high-flux membranes would improve mortality and decrease morbidity. This study failed to show decreases in mortality. In other studies, however, there appears to be improved morbidity with more frequent dialysis including daily nocturnal hemodialysis and short-daily hemodialysis. The more frequent dialysis may have some beneficial effect on the inflammatory process that occurs in end-stage renal disease.

In vivo modulation of soluble "antagonistic" IL-6 receptor synthesis and release in ESRD

Soluble gp130 (sgp130) is a soluble circulating receptor of IL-6 with "antagonistic" biologic activity. It is generated independently by either shedding of the extracellular domain of membrane gp130 or alternative mRNA splicing. This study was addressed to clarify the mechanisms underlying sgp130 synthesis and release in patients who undergo regular dialysis treatment (RDT) using dialytic membranes with different biocompatibility. Two groups of RDT patients were enrolled: 11 patients who were treated with cellulosic membranes (C) and 10 patients who were treated with synthetic membranes (S). Ten healthy subjects constituted the control group. Serum samples and peripheral blood mononuclear cells (PBMC) were harvested in all groups (before dialysis in RDT patients). PBMC were cultured for 24 h in the absence or presence of LPS. The serum levels of sgp130 were significantly higher in C group than in control and S patients (C, 603.1 +/- 89.9; control, 396 +/- 49.5; S, 423.4 +/- 27.7 ng/ml; P < 0.01). PBMC from C patients, in the absence of any mitogenic stimulation, released a significantly greater amount of sgp130 as compared with S and control groups (C, 532.6 +/- 161.2; S, 332.4 +/- 148.6; control, 341.4 +/- 125.4 pg/ml; P < 0.01). The sgp130 release was positively correlated with the release of both IL-6 (r = 0.336, P < 0.05) and sIL-6R receptor (r = 0.324, P < 0.05). A significantly higher gp130 gene expression was also observed in unstimulated PBMC from C patients when compared with control and S groups. It is interesting that the expression of the 85-bp exon characteristic of the alternative splicing mRNA for sgp130 was low in all groups. Finally, confocal microscopy analysis showed an increased expression of gp130 on cell surface in unstimulated PBMC from C patients as compared with control and S groups. Our results demonstrate that in patients on RDT with C membranes, the synthesis and release of sgp130 "antagonistic" receptor is significantly increased. This release is seemingly due to a shedding of membrane-bound gp130 receptor. The increased sgp130 release may partially counteract the inflammatory effects caused by IL-6.

The role of interleukin-6 and of its soluble receptors in the biocompatibility of dialysis treatment

Proinflammatory cytokines, in addition to their role in host defence, may be considered mediators of disease; a reduction of cytokine synthesis or effects is, therefore, becoming a target of many diseases. IL-6 is a pro-inflammatory cytokine that may play a role in several clinical problems related to dialysis treatment. An enhanced spontaneous production of IL-6 by Peripheral Blood Mononuclear Cells (PBMC) harvested from ESRD patients dialyzed with a poor biocompatible membrane has been first demonstrated by our group. These results were also obtained in patients undergoing continuous peritoneal dialysis, in absence of peritonitis. We have also demonstrated that IL-6 release was inversely correlated with serum albumin changes. Biological activities of IL-6 may be modulated by two soluble circulating receptors, namely sIL-6R and sgp130. sIL-6R may enhance the inflammatory effects of IL-6 and is, therefore, an "agonistically" acting molecule. We have recently studied sIL-6R production in ESRD patients dialyzed with different membranes; the conclusion was that poor biocompatible membranes, via the sIL-6R, might further increase the inflammatory effects of IL-6. On the contrary, sgp130 can efficiently bind the IL-6/sIL-6R complex with "antagonistic" effects. We have evaluated plasma levels of sgp130 in 18 ESRD patients regularly dialyzed with hemophan membranes (HE) and in 15 patients dialyzed with more biocompatible synthetic membranes (BIO). Our results demonstrate that plasma levels of sgp130 in HE are 33% higher than in both healthy controls and BIO. Circulating levels of sgp130 were correlated positively with C-reactive protein (r: 0.338, p<0.05) and negatively with serum albumin (r: -0.334, p<0.05). These results suggest that higher circulating levels of sgp130 are likely associated with higher IL-6 levels. These higher amounts are probably insufficient to control the activity of IL-6 and may be considered only as a marker of PBMC activation.

Characteristics and effects of inflammation in end-stage renal disease

Malnutrition and cardiovascular disease are associated with end-stage renal disease (ESRD) and both are closely associated with one another, both in cross-sectional analysis and when the courses of individual patients are followed over time. Inflammation, by suppressing synthesis of albumin, transferrin, and other negative acute-phase proteins and increasing their catabolic rates, either combines with modest malnutrition or mimics malnutrition, resulting in decreased levels of these proteins in dialysis patients. Inflammation also leads to reduced muscle mass by increasing muscle protein catabolism and blocking synthesis of muscle protein. More importantly, inflammation alters plasma protein composition and endothelial structure and function so as to promote vascular disease. Markers of inflammation, C-reactive protein (CRP), and interleukin (IL)-6 powerfully predict death from all causes and from cardiovascular disease in dialysis patients as well as progression of vascular injury. The causes of inflammation are likely multifactorial, including oxidative modification of plasma proteins, interaction of blood with nonbiocompatible membranes and lipopolysaccharides in dialysate, subclinical infection of vascular access materials, oxidative catabolism of endothelium-derived nitric oxide, and other infectious processes. Treatment should be focused on identifying potential causes of inflammation, if obvious, and reduction of other risk factor for cardiovascular disease.

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.

Rights of chronic renal failure patients undergoing chronic dialysis therapy

The Patient Advocacy Committee of the International Federation of Kidney Foundations (IFKF) has developed a document proposing a set of rights for individuals with end stage renal failure (ESRF). These rights have been approved by the Board of Directors of the IFKF. Twenty rights have been developed and are organized into the following categories: (i) need of treatment and choice of patients; (ii) treatment of ESRF by haemodialysis; (iii) treatment of ESRF by peritoneal dialysis; and (iv) renal transplantation. It is the hope of this Committee and the IFKF that this document will provide a stimulus to more scientific inquiry and discussion as to what rights do patients possess with regard to treatment of chronic kidney disease, regardless of where they live or what may be their economic, social, ethnic or political status.

Changes in C-reactive protein plasma levels during low-density lipoprotein apheresis

C-reactive protein (CRP) is one of the important risk factors for atherosclerosis, and its serum level is lowered by popular cholesterol-lowering drugs, statins. This study was undertaken to examine the changes of CRP levels during dextran-sulfate (DS) low-density lipoprotein (LDL) apheresis. In 15 apheresis sessions in seven patients with severe hypercholesterolemia (four men and three women, aged between 36 and 70 years), changes in CRP levels were examined. The efficiency in adsorption of CRP with DS column was evaluated by measuring CRP levels in both pre- and post-column plasma. In one patient, the effect of repeated apheresis sessions on CRP preapheresis levels was examined. The changes in interleukin (IL)-6 plasma levels were also examined in six sessions. Although IL-6 levels after 3,000 mL-plasma treatment rose to 170% of preapheresis levels, CRP levels decreased significantly (from 1.91 +/- 0.49 mg/L to 0.89 +/- 0.24, P < 0.01). C-reactive protein was almost completely adsorbed by the DS column and CRP preapheresis levels were decreased gradually by repetition of apheresis. CRP, a novel risk factor of atherosclerosis, was effectively removed by DS-LDL apheresis. The decrease in CRP plasma levels may be involved in prevention of atherosclerotic vascular diseases due to DS-LDL apheresis.

Changes of serum albumin and C-reactive protein are related to changes of interleukin-6 release by peripheral blood mononuclear cells in hemodialysis patients treated with different membranes

Protein malnutrition, a condition associated with an albumin concentration less than 3.5 g/dL, has been shown to be a major risk factor for increased mortality in hemodialysis patients. The aim of this cross-over study was to evaluate the relationship between the type of membrane adopted and serum albumin changes by measuring peripheral blood mononuclear cells (PBMC) interleukin-6 (IL-6) release, serum albumin, and plasma concentrations of C-reactive protein (CRP) in 18 patients dialyzed with different membranes. During the study, all patients were dialyzed with cuprophan (CU), synthetically modified cellulosic (SMC) membrane (a new cellulosic membrane with lesser complement activation), and cellulose diacetate (CD) membrane, and have served as their own controls. IL-6 spontaneous release by PBMC resulted after 3 months of SMC (436.2 +/- 47.4 pg/mL) significantly (P < 0.05) reduced as compared with CU (569.3 +/- 24.5 pg/mL). This effect was more evident after 6 months of dialysis with SMC (220 +/- 35.3 pg/mL, P < 0.01 versus CU and versus 3 months of SMC). The passage to CD membrane was followed by a progressive new increase in the IL-6 PBMC release (332.3 +/- 30.7 after 3 months, and 351.2 +/- 35.8 pg/mL after 6 months, respectively) that, however, remained significantly (P < 0.05) lower than CU. The behavior of CRP plasma levels resembled that of IL-6 PBMC release (23.3 +/- 4.7 in CU, 11.0 +/- 2.1 after 3 months in SMC, and 7.9 +/- 1.5 after 6 months in SMC, respectively). IL-6 release values were positively correlated with circulating levels of CRP (r = 0.3264, P < 0.002). Serum albumin increased after 6 months of dialysis with SMC membranes (3.25 +/- 0.09 g/dL in CU and 3.64 +/- 0.07 g/dL in SMC, P < 0.05). When the patients were switched to CD, serum albumin showed a slight, though not statistically significant, decrease. Serum albumin concentrations negatively correlated with both IL-6 release values (r = -0.247, P < 0.05) and CRP plasma levels (r = -0.433, P < 0.001). In conclusion, our data clearly show that a significant relationship exists between biocompatibility of the membranes and serum albumin changes; serum albumin levels, in fact, are negatively correlated with the PBMC spontaneous IL-6 release values and CRP circulating levels.

Effects of ultrapure dialysis fluid on nutritional status and inflammatory parameters

BACKGROUND

Malnutrition and chronic systemic inflammatory response syndrome not only coexist in uraemia, but may also have a bi-directional cause-and-effect relationship. To evaluate the role of dialysate-related cytokine induction in inflammatory response and nutritional status, we conducted a prospective comparison of two dialysis fluids differing in their microbiological quality.

METHODS

Forty-eight early haemodialysis patients were assigned to either treatment with conventional (potentially microbiologically contaminated) or on-line produced ultrapure dialysis fluid. Study parameters were bacterial growth, markers of systemic inflammation (C-reactive protein (CRP) and interleukin 6), and parameters of nutritional status (estimated dry weight, upper mid-arm muscle circumference, serum albumin concentration, insulin-like growth factor 1, leptin, and protein catabolic rate). Patients were followed for 12 months.

RESULTS

There were no statistically significant differences in demographic and treatment characteristics, degree of bacterial contamination of the dialysate, markers of systemic inflammation, or parameters of nutritional status among the two treatment groups at recruitment. Changing from conventional to ultrapure dialysis fluid reduced significantly the levels of IL-6 (19+/-3 pg/ml to 13+/-3 pg/ml) and CRP (1.0+/- 0.4 mg/dl to 0.5+/-0.2 mg/dl), and resulted in significant increases in estimated dry body weight, mid-arm muscle circumference, serum albumin concentration, levels of the humoral factors, and in protein catabolic rate after 12 months. Continuous use of conventional dialysis fluid (median 40-60 c.f.u./ml) was not associated with significant alterations in markers of inflammation (IL-6 21+/-4 pg/ml vs 24+/-6 pg/ml, CRP 0.9+/-0.3 mg/dl vs 1.1+/-0.4 mg/dl) or of nutritional status at any time of the study. All differences in systemic inflammation and nutritional parameters observed during the study period (from recruitment to month 12) were significant between the two patient groups.

CONCLUSIONS

Cytokine induction by microbiologically contaminated dialysis fluid has a negative impact on nutritional parameters of early haemodialysis patients. The microbiological quality of the dialysis fluid represents an independent determinant of the nutritional status in addition to known factors, such as dose of dialysis and biocompatibility of the dialyser membrane. Ultrapure dialysis fluid adds to the cost of the dialytic treatment, but may improve the nutritional status in long-term haemodialysis patients.

Role of lipoprotein (a) and TGF-beta 1 in atherosclerosis of hemodialysis patients

Atherosclerotic vascular disease is a major cause of death for uremic patients who are on hemodialysis (HD). Recent evidence suggests that lipoprotein (a) [Lp(a)] may aggravate atherosclerosis by inhibiting activation of transforming growth factor-beta 1 (TGF-beta 1). Plasma Lp(a) and plasma TGF-beta 1 activation in HD patients (n = 51), chronic renal failure patients not subjected to hemodialysis (non-HD-CRF; n = 12), and healthy volunteers (control; n = 13) were investigated. Plasma Lp(a) was significantly higher in HD (18.75 +/- 1.62 mg/ml) and non-HD-CRF patients (25.0 +/- 8.4 mg/ml) than in control subjects (10.9 +/- 5.8 mg/ml). The degree of atherosclerosis in HD patients was assessed by measuring the intima-media thickness (IMT) and plaque score with the use of an ultrasound scanner. IMT and plaque score were higher in HD and non-HD-CRF patients than in controls. A significant positive correlation was found in HD patients between Lp(a) and IMT (r = 0. 377, P < 0.01) as well as between Lp(a) and plaque score (r = 0.43, P < 0.01). Plasma total TGF-beta 1 significantly increased in HD (119.8 +/- 53.5 ng/ml) and non-HD-CRF patients (93.2 +/- 25.0 ng/ml) compared with control subjects (17.7 +/- 6.4 ng/ml), whereas the plasma level of mature (active) TGF-beta1 did not differ among the groups. When plasma TGF-beta 1 and supernatant TGF-beta 1 from cultured peripheral mononuclear cells were compared before and after an HD session, neither total nor mature TGF-beta 1 showed a significant difference between the values before and after an HD session. There were no significant relationships between plasma total TGF-beta 1 and IMT or plaque score, between mature TGF-beta 1 and IMT or plaque score, or between mature TGF-beta 1 and Lp(a). In conclusion, Lp(a) may be an important atherogenic factor in CRF patients. However, it was not clarified whether Lp(a) exerts its effect by inhibiting TGF-beta 1 activation in CRF patients.

Temporal changes of cytokines and nitric oxide products in urine from renal transplant patients

BACKGROUND

Acute rejection and urinary tract infection (UTI) both increase nitric oxide synthase (NOS) activity in urine from renal transplant patients. Also, with rejection, a regulatory interplay between nitric oxide (NO) and cytokines has been suggested. Thus, measurement of the temporal changes of NOS products and cytokines in urine will provide a strategy for the diagnosis of acute rejection and for its differentiation from UTI.

METHODS

Soluble interleukins (ILs) and NOS-related products, cyclic GMP (cGMP), nitrate, and nitrite were measured in 192 urine samples consecutively collected from 13 patients within the first three months of transplantation. Sixty-seven additional urine specimens were collected randomly from 24 patients for follow-up analysis of the nitrate test.

RESULTS

Among patients who experienced rejection, the percentage (%) binding of IL-2 increased within the first five days (P = 0.0004) after transplantation and one to five days prior to the clinical diagnosis (dx) of rejection (P = 0.02). Tumor necrosis factor-alpha, IL-6, and IL-8 increased at the time of rejection dx (P < or = 0.01). With UTI, IL-2 (P = 0.01) decreased one to five days prior to dx, and IL-10 (P = 0.003) increased one to five days after dx. Although cGMP and nitrate are dependent variables, cGMP increased (P < or =0.0009) with both rejection and UTI, and nitrate increased (P = 0.0001) with rejection and decreased (P = 0.0001) with UTI. Prior to formal dx (1 to 5 days), urine nitrate clearly differentiated rejection (3004 to 7451 micromol/L) from UTI (90 to 885 micromol/L) and controls (1059 to 3235 micromol/L). The additional 67 urines demonstrated that the sensitivity of the nitrate test for rejection and UTI was 100%.

CONCLUSIONS

In renal transplant patients, specific temporal changes in urine cytokine levels do occur with acute rejection and UTI, but urine nitrate levels are the most precise at differentiating rejection from UTI.

Role of different dialysis membranes in the release of interleukin-6-soluble receptor in uremic patients

BACKGROUND

Interleukin-6 (IL-6) exerts its actions through a cell-surface receptor system that consists of two transmembrane subunits: the IL-6 binding glycoprotein gp 80 (IL-6R) and the signal-transducing component (gp 130). Soluble forms of the IL-6R (sIL-6R) are generated by shedding of the membrane-associated proteins. The sIL-6R binds the ligand IL-6 with comparable affinity as the membrane-associated IL-6R and enhances the actions of IL-6.

METHODS

Our aim was to evaluate the role of both uremia and different dialysis membranes on peripheral blood mononuclear cell (PBMC) release (either in absence or in presence of mitogen stimulation) and plasma levels of sIL-6R. Ten patients chronically dialyzed with cuprophan membranes (CU), eight patients on regular dialysis treatment with polymethylmethacrylate (PMMA) membranes, 11 uremic nondialyzed patients (UR), and 12 healthy subjects (CON) were included in the study.

RESULTS

PBMCs harvested from CU spontaneously released significantly (P < 0.01) greater amounts of sIL-6R (881.8 +/- 80.1 pg/mL), as compared with CON (267.5 +/- 26.5 pg/mL), UR (258.4 +/- 38.1 pg/mL), and PMMA (288.4 +/- 24.6 pg/mL). Under mitogenic stimulation, the sIL-6R release was significantly (P < 0.01) increased in all groups. The greater PBMC production of sIL-6R in CU was followed by significantly (P < 0.01) higher levels of circulating soluble receptors (48.7 +/- 2.5 ng/mL, 60%), as compared with CON (30.5 +/- 1.9 ng/mL). UR also showed high circulating levels of sIL-6R (53.3 +/- 5.9 ng/mL), probably secondary to an impaired urinary excretion. Circulating levels of sIL-6R in PMMA were comparable to CON (30.3 +/- 3.3 ng/mL). Either the absence of monocyte activation or the adsorption of sIL-6R on the hydrophobic PMMA surface could explain this finding.

CONCLUSIONS

These results suggest an important role for poor dialysis biocompatibility of CU on the release of sIL-6R, which increases sIL-6R plasma levels, thereby enhancing the inflammatory effects of IL-6.

Effects of dialyser and dialysate on the acute phase reaction in clinical bicarbonate dialysis

BACKGROUND

In chronic haemodialysis (HD), morbidity may result from repetitive induction of the acute phase response, caused by a bioincompatible dialysis membrane and/or contaminated dialysate. In the present study, cytokine release (interleukin-6, IL-6) and subsequent production of acute phase proteins (C-reactive protein, CRP and secretory phospholipase A(2), sPLA(2)) were assessed to investigate whether the HD-induced acute phase reaction depends mainly on the type of membrane or on the sterility of the dialysate.

METHODS

In 11 patients, IL-6, CRP and sPLA(2) levels were assessed in blood samples drawn before (t(0)), at the end (t(180)) and 24 h after the start of HD (t(1440)). All patients were dialysed on Cuprammonium (CU) and Polysulphon (PS) dialysers and seven patients underwent an additional HD session on CU plus a dialysate filter (CUf).

RESULTS

IL-6 levels were increased significantly at t(180) compared with t(0) (P<0.02) with both CU and CUf. At t(1440), IL-6 levels had returned to baseline. In contrast, marked fluctuations did not occur during HD with PS. At t(180), IL-6 was significantly greater with CU and CUf devices, than with PS (P<0.02). Following HD with CU and CUf, a significant increase in CRP was observed at t(1440), compared with postdialysis values (P</=0.05). In addition, sPLA(2) values were markedly increased at t(1440), compared with t(180), but only significant in the case of CU (P=0.01). IL-6 levels at t(180) were significantly correlated with CRP (r=0.50, P<0.01) and sPLA(2) (r=0.47, P=0.01) values at t(1440). During HD with PS membranes, neither CRP nor sPLA(2) values were markedly changed.

CONCLUSIONS

In contrast to PS, both CU and CUf resulted in elevated IL-6 plasma levels at the end of HD, compared with t(0), which correlated with increased CRP and sPLA(2) values 24 h later. Therefore, the type of membrane, rather than the bacterial quality of the dialysate, seems to be responsible for the induction of the acute phase response during clinical bicarbonate HD.

Hemodialysis-related lymphomononuclear release of interleukin-12 in patients with end-stage renal disease

Interleukin-12 (IL-12) is a cytokine produced by peripheral blood mononuclear cells (PBMC) that causes interferon-gamma (IFN-gamma) production and enhancement of cell-mediated cytotoxicity. To clarify the role of hemodialysis biocompatibility on IL-12 production and uremic immunodeficiency, we have studied the IL-12 and IFN-gamma release by PBMC harvested from 12 patients dialyzed with cuprophan membrane (CU), eight patients dialyzed with polymethylmethacrylate membrane (PMMA), and eight nondialyzed uremic patients (UR). Ten healthy subjects constituted the control group (CON). PBMC were cultured for 48 h with and without nonspecific mitogen stimulation. In unstimulated conditions, CU showed an IL-12 PBMC production higher than CON, UR, and PMMA (46.67 +/- 30.13 versus 2.56 +/- 1.38, 6.16 +/- 7.09, and 4.62 +/- 4.76 pg/ml, respectively; P < 0.01). IL-12 production was correlated with C3a concentration measured at the outlet of hemodialyzer after 15 min of dialysis (r = 0.69, P < 0.01). IL-12 release in CU remained unchanged under mitogen stimulation (44.34 +/- 23.86 pg/ml) and was lower than in CON, UR, and PMMA (66.0 +/- 12.41, 68.37 +/- 25.78, and 67.75 +/- 22.61 pg/ml, respectively; P < 0.05). IFN-gamma production was similar, in unstimulated conditions, in all groups. Under stimulation, IFN-gamma release was lower in CU (13.42 +/- 12.04 IU/ml) than in CON, UR, and PMMA (51.84 +/- 30.74, 32.16 +/- 13.86, and 32.16 +/- 13.86 IU/ml, respectively; P < 0.01). These results demonstrate that hemodialysis with CU induces monocyte activation with an enhanced release of IL-12. On the contrary, stimulated PBMC production of both IL-12 and IFN-gamma is lower in these patients than in CON, UR, and PMMA. The altered release of these cytokines could play a role in cell-mediated immunodeficiency of the uremic patients dialyzed with CU.

Regulation of beta2-microglobulin expression in different human cell lines by proinflammatory cytokines

BACKGROUND

Proinflammatory monocytic cytokines such as interleukin-1 (IL-1), tumour necrosis factor-alpha (TNF-alpha) and IL-6 have been incriminated in the pathogenesis of elevated beta2-microglobulin (beta2M) serum concentrations in patients undergoing haemodialysis with so-called bioincompatible dialyser membranes. However, neither the source of the elevated serum beta2M nor the precise role of monocytic cytokines in the expression of the beta2M gene have been elucidated conclusively. The aim of the current study was to evaluate whether monocytic cytokines, and in particular IL-6, are regulators of beta2M gene expression in human hepatoma cells, T-lymphocytes and monocytes.

METHODS

HepG2 and HuH7 human hepatoma cells, Jurkat T-cells, monocytic MonoMac6 cells, primary human monocytes and synoviocytes were stimulated with IL-1beta, IL-6, interferon-alpha (IFN-alpha), IFN-gamma or conditioned media from lipopolysaccharide (LPS)-treated monocytes. Expression of beta2M mRNA was analysed by Northern blotting, beta2M protein synthesis was determined by metabolic labelling and immunoprecipitation, and beta2M secretion was measured by an enzyme-linked immunosorbent assay (ELISA).

RESULTS

In all cell types tested, IFN-gamma and, to a lesser extent, IFN-alpha stimulated gene expression of beta2M resulting in an increased synthesis and secretion of beta2M protein. Neither IL-1beta and IL-6 nor supernatants from LPS-treated monocytes were capable of inducing beta2M gene expression, with the exception of a small increase in HuH7 hepatoma cells upon IL-1beta treatment.

CONCLUSIONS

The present study provides evidence that interferons are important regulators of beta2M expression. It also shows that proinflammatory monocytic cytokines do not modulate directly the expression of beta2M in cells of hepatic, monocytic and T-lymphocytic origin. Whether they influence beta2M synthesis and secretion indirectly by modulating interferon synthesis needs to be elucidated.

Pathophysiology of protein-energy wasting in chronic renal failure

There is a high prevalence of protein-energy malnutrition in both nondialyzed patients with advanced chronic renal failure and in those individuals with end-stage renal disease who are receiving maintenance hemodialysis or chronic peritoneal dialysis therapy. Approximately one-third of maintenance dialysis patients have mild to moderate protein-energy malnutrition, and about 6 to 8 percent of these individuals have severe malnutrition. These statistics are of major concern because markers of protein-energy malnutrition are strong predictors of morbidity and mortality. The causes of protein-energy malnutrition in patients with chronic renal failure include: (1) decreased energy or protein intake; (2) concurrent chronic illnesses, and superimposed acute illnesses and possibly increased inflammatory cytokines; (3) the catabolic stimulus of hemodialysis; (4) losses of nutrients into dialysate, particularly amino acids, peptides, protein (with peritoneal dialysis), glucose (when hemodialysis is performed with glucose-free dialysate) and water-soluble vitamins; and (5) diagnostic or therapeutic (e.g., prednisone therapy) procedures that reduce nutrient intake or engender net protein breakdown. Other theoretically possible causes for protein-energy malnutrition include (6) chronic blood loss; (7) endocrine disorders (especially resistance to insulin and insulin-like growth factor-I, hyperglucagonemia, hyperparathyroidism and deficiency of 1,25-dihydroxycholecalciferol); (8) products of metabolism that accumulate in renal failure and may induce wasting, such as organic and inorganic acids; (9) loss of the metabolic actions of the kidney; and (10) the accumulation of toxic compounds that are taken up from the environment (e.g., aluminum).

Plasma cytokine levels and coagulation and complement activation during use of the extracorporeal liver assist device in acute liver failure

Multiple organ failure frequently occurs in patients with acute liver failure, and this has been associated with increased cytokine production. Treatment by hemoperfusion with an extracorporeal liver assist device (ELAD) containing human liver-derived cells was performed in 12 patients with acute liver failure. Over the first 6 h, there were significant increases in plasma tumor necrosis factor alpha (TNFalpha; from 114+/-54 pg/ml [mean+/-SEM] to 236+/-161 pg/ml, p < 0.05) and interleukin (IL)-6 (260+/-121 pg/ml to 445+/-149 pg/ml, p < 0.05) but not in interferon gamma (IFNgamma). A similar pattern with a small peak increase was observed for complement C5b-9 complex. Plasma C-reactive protein (CRP) and thrombin antithrombin (TAT) III complex showed small peaks after 24 h of ELAD hemoperfusion. No such changes were seen in 12 control patients with acute liver failure who were treated with intensive care alone. These transitory effects, without changes in blood pressure, are likely to be due to the contact of the blood with the dialyzer membrane. There was no evidence of the clearance of cytokines by the ELAD.

Interleukin-6, interleukin-8 and monocyte chemotactic peptide-1 gene expression and protein synthesis are independently modulated by hemodialysis membranes

BACKGROUND

Uremia produces a wide range of abnormalities of the immune system. Blood-membrane interaction in hemodialysis results in activation and severe dysfunction of peripheral blood mononuclear cells (PBMC). However, the question of whether the use of different dialytic membranes may improve PBMC dysfunctions remains unanswered.

METHODS

To address this issue, the spontaneous interleukin (IL)-6, IL-8 and monocyte chemotactic peptide-1 (MCP-1) gene expression and protein release were studied in PBMC isolated from 7 healthy subjects, 8 uremic patients on conservative therapy and 8 uremic patients undergoing subsequent one month periods of hemodialysis with cuprophan (CU) and high-flux noncomplement activating membranes, polymethylmethacrylate (PMMA) and polyamide (PA). At the end of each period of treatment, PBMC were harvested at the beginning (T0) and after 180 minutes of dialysis (T180), and then were cultured in complete medium. IL-6, IL-8 and MCP-1 mRNA expression were studied by RT-PCR. In addition, MCP-1 gene expression was evaluated also by in situ hybridization. Cytokines released in the supernatant were measured by ELISA.

RESULTS

Compared to the control group, PBMC from uremic patients on conservative therapy and treated by CU showed a clear reduction in the cytokine release, while PMMA and PA membranes were able to normalize IL-6, IL-8 and MCP-1 protein concentration, which had been reduced by CU treatment. Interestingly, at T0, mRNA expression for all three cytokines was increased in the patients treated by CU, when compared to the control group and the uremic patients on conservative therapy. A further up-regulation was observed at T180. PMMA and PA treatment, despite increasing the cytokine secretion, significantly reduced the dialysis-induced cytokine gene expression.

CONCLUSION

PBMC exposure to CU membranes results in cytokine mRNA overexpression associated with a paradoxically reduced protein release. In contrast, long-term hemodialysis with synthetic high-flux membranes reduces IL-6, IL-8 and MCP-1 gene expression and improves the ability of PBMC to secrete these cytokines. The reduced cytokine secretion during bioincompatible dialysis may reflect a PBMC adaptation that protects uremic patients against the inflammatory effects of persistent cytokine release.

Hemodialysis stimulates hepatocyte growth factor release

Studies were performed in 26 patients on regular dialysis treatment with cuprophane (CU), polymethylmetacrilate (PMMA) or cuprammonium (CAM) dialyzers. Controls were six patients with chronic renal failure but not on regular dialysis treatment (CRF) and six healthy subjects (N). Blood was collected at the start (T0), and at 15 (T15) and 240 (T240) minutes of dialysis to measure the serum hepatocyte growth factor (HGF) concentration and to study HGF production by peripheral blood mononuclear cells (PBMC) in vitro. The form of HGF (that is, inactive/monomeric, active/dimeric) present in the serum was analyzed by immunoblotting. In addition, the ability of serum to stimulate proliferation of tubular cells (HK-2) and HGF release by PBMC and fibroblasts (MRC-5) was investigated. At T0, serum HGF levels were identical to that of the controls. In patients treated with CU, serum HGF rose from 0.24 ng/ml at T0 to 7.44 ng/ml at T15, and remained high at T240. PBMC collected at T15 and T240 released significantly more HGF in vitro than those collected at T0. Serum at T15 stimulated proliferation of HK-2 cells and the release of HGF by PBMC and MRC-5 cells. The PMMA and CAM dialyzers had similar effects as the CU. These results indicate that dialysis induces a striking rise in serum HGF and a prompt circulation of factor(s) stimulating HGF release. Dialysis-activated PBMC release HGF.

Monocyte production of transforming growth factor beta in long-term hemodialysis: modulation by hemodialysis membranes

Cytokines are likely involved in hemodialysis-associated complications such as immunodeficiency and beta 2 microglobulin amyloidosis. Because transforming growth factors beta (TGF beta) exert immunosuppressive effects on lymphocytes, down-modulate monocyte functions, and promote fibrosis, we hypothesize that they participate in the deleterious effects of hemodialysis. We investigated the production of TGF beta 1 and TGF beta 2 by monocytes from controls and patients dialyzed with high-flux cellulose triacetate (CT) and polyacrylonitrile (PAN) membranes. The detection of both TGF beta s required an acidification step, suggesting that they are secreted as latent complexes. The spontaneous production of TGF beta 1 and TGF beta 2 was significantly higher in patients dialyzed with CT or PAN than in controls, but the oversecretion of TGF beta 1 was more sustained in CT-treated patients than in PAN-dialyzed patients. The production of interleukin-6 (IL-6) was increased in both patient groups as compared with controls. In contrast to TGF beta 1, the increase was greater in PAN-treated patients than in CT-treated patients, and the release of tumor necrosis factor alpha (TNF alpha) was increased only in PAN-treated patients. Taken together, our results show that hemodialysis is associated with the oversecretion of monocyte cytokines. Moreover, the type of dialysis membrane specifically affects the balance between the secretion of suppressive cytokines such as TGF beta and that of inflammatory cytokines such as IL-6 and TNF alpha.

Inflammatory effects of peritoneal dialysis: evidence of systemic monocyte activation

We evaluated in peritonitis-free patients undergoing continuous ambulatory peritoneal dialysis (CAPD) the release of both interleukin-6 (IL-6) and beta-2-microglobulin (beta 2m) by cultured peripheral blood mononuclear cells (PBMC), as well as the levels of serum amyloid A (SAA), that is, the main hepatic acute phase protein during inflammation. The same measurements were obtained in hemodialysis (HD) patients, uremic non-dialyzed patients (ESRD) and healthy controls (CON). In CAPD, IL-6 production from PBMC was markedly increased in comparison to the control value (600.7 +/- 104.3 vs. 14.2 +/- 3.6 pg/3 x 10(6) PBMC/24 hr, P < 0.005). Similarly, a striking enhancement of the PBMC release of beta 2m was detected in CAPD with respect to CON (10.1 +/- 2.6 vs. 0.063 +/- 0.013 micrograms/3 x 10(6) PBMC/24 hr, P < 0.001). Also, the SAA levels were significantly greater in CAPD patients (21.3 +/- 8.7 micrograms/dl) than in controls (3.14 +/- 0.17 micrograms/dl, P < 0.05). Analogous increases of both IL-6 and beta 2m cell releases, as well as of SAA levels, were observed in HD patients. No difference concerning the three parameters was detected between CON and ESRD. In conclusion, CAPD induces per se PBMC activation with an enhanced release of both IL-6 and beta 2m; this is associated to higher levels of SAA. These systemic inflammatory effects are comparable to those observed in HD patients indicating that CAPD is similar to HD in terms of biocompatibility of the treatment.

Monocyte cell-surface CD14 expression and soluble CD14 antigen in hemodialysis: evidence for chronic exposure to LPS

Expression of CD14 on peripheral blood monocytes and serum levels of the 53 kD soluble CD14 antigen were investigated in patients with end-stage renal failure who were undergoing chronic hemodialysis (HD) with either cuprophane/hemophane (CU/HE) low-flux (LF) or polysulfone/polyamide (PS/PA) high-flux (HF) membranes. Baseline expression of CD14 was significantly lower in HD patients compared to uremic patients and normal controls. Patients using PS/PA membranes disclosed a further decreased CD14 expression than patients with CU/HE membranes. Specific fluorescence intensity for CD14 increased 15 minutes after the start of the dialysis session and was on average 22% higher after hemodialysis. The serum levels of sCD14 were elevated about 2.5-fold in HD patients compared to healthy controls (5.4 +/- 1.3 vs. 2.2 +/- 0.5 mg/liter, P < 0.0001) and were significantly higher compared to non-dialyzed patients with chronic renal failure (3.9 +/- 1.0 mg/liter, P < 0.001). After regular dialysis with high-flux membranes, soluble CD14 serum concentrations significantly increased (P < 0.001) compared to pre-dialysis levels. Values of soluble CD8 (54 kD) were elevated only 1.5-fold in HD patients relative to healthy controls, whereas serum levels of the low molecular weight soluble CD23 (20 kD) 12 and 19-fold in patients treated with HF-HD and LF-HD, reflecting the renal impairment and filtration through HF membranes. Thus, high sCD14 values in HD patients may stem from increased release of the up-regulated membrane antigen due to monocyte activation during hemodialysis treatment. Since the CD14 antigen is involved in LPS-induced monocyte activation, the influence of lipopolysaccharide on CD14 expression and sCD14 release was investigated in vitro. Addition of 1 ng/ml or 0.01 ng/ml LPS to whole blood significantly enhanced monocyte CD14 expression after 30 or 60 minutes of incubation. The release of soluble CD14 by cultured peripheral blood monocytes significantly increased in the presence of 0.01 ng/ml LPS during a five-day incubation experiment. Our results demonstrate an enhanced expression of CD14 by monocytes after HD and increased sCD14 serum levels possibly due to chronic exposure to trace amounts of endotoxins, as supported by in vitro experiments.

Role of bioincompatibility in dialysis morbidity and mortality

This review examines the mechanisms by which bioincompatibility in dialysis systems may have an effect on morbidity and mortality in the dialysis population. Direct toxic effects of membrane materials and various chemical substances have been well demonstrated in the chronic dialysis population. Activation of the complement cascade and stimulation of cytokine production may have autocrine effects on leukocyte function with sequelae such as enhanced rates of infection and the development of B2-microglobulin amyloidosis. The variable effect of different membrane materials on each of these effector systems is examined. Bioincompatibility may effect the incidence of infection, malignancy, cardiopulmonary disease, and malnutrition as well as induce novel disease processes. All these confounding variables must be considered when evaluating the effect of dialysis on mortality and morbidity.

Increased interleukin 6 mRNA expression by peripheral blood T cells from patients with IgA nephropathy

We investigated interleukin 6 (IL-6) mRNA expression in peripheral blood T-cells obtained from 36 patients with IgA nephropathy (IgAN), 36 patients with other glomerulonephritides and 24 healthy age-matched controls. The majority of patients with IgAN had increased IL-6 mRNA expression by their T cells; no IL-6 mRNA was detected in T cells obtained from patients with other glomerulonephritides or normal controls. A positive correlation was noted between the IL-6 mRNA level and quantity of protein excretion in the urine, histopathological findings, and renal function. However, there was no significant correlation between IL-6 mRNA expression and the IgA-immune complex titer, serum IgA level or blood pressure. mRNA levels in T cells obtained from patients with grade III or IV renal histopathological findings were significantly higher than in those with grade I or II histopathology. In addition, mRNA levels in T cells obtained from patients with more than 1.0 g/day proteinuria were markedly higher than those with less than 1.0 g/day proteinuria. We also studied the clinical course of 11 patients with IgAN during hospitalization. The IL-6 mRNA levels in these patients decreased gradually, as did proteinuria, after treatment. These studies suggest that abnormally regulated IL-6 mRNA expression in peripheral blood T cells may be associated with disease activity in IgAN.