Effect of renal replacement therapy on cellular cytokine production in patients with renal disease

Inflammasome assembly is required for intracellular formation of β2-microglobulin amyloid fibrils, leading to IL-1β secretion

INTRODUCTION

Dialysis-related amyloidosis (DRA) caused by β2-microgloblin (B2M) fibrils is a serious complication for patients with kidney failure on long-term dialysis. Deposition of B2M amyloid fibrils is thought to be due not only to serum extracellular B2M but also to infiltrating inflammatory cells, which may have an important role in B2M amyloid deposition in osteoarticular tissues in patients with DRA. Here, we asked whether B2M amyloid fibrils activate the inflammasome and contribute to formation and deposition of amyloid fibrils in cells.

METHODS

Amyloid formation was confirmed by a thioflavin T (ThT) spectroscopic assay and scanning electron microscopy (SEM). Activation of inflammasomes was assessed by detecting interleukin (IL)-1β in culture supernatants from human embryonic kidney (HEK) 293T cells ectopically expressing inflammasome components. IL-1β secretion was measured by enzyme-linked immunosorbent assay. Expression and co-localization were analyzed by immunohistochemistry and dual immunofluorescence microscopy.

RESULTS

B2M amyloid fibrils interacted directly with NLRP3/Pyrin and to activate the NLRP3/Pyrin inflammasomes, resulting in IL-1β secretion. When HEK293T cells were transfected with inflammasome components NLRP3 or Pyrin, along with ASC, pro-caspase-1, pro-IL-1β, and B2M, ThT fluorescence intensity increased. This was accompanied by IL-1β secretion, which increased in line with the amount of transfected B2M. In this case, morphological glowing of amyloid fibrils was observed by SEM. In the absence of ASC, there was no increase in ThT fluorescence intensity or IL-1β secretion, or any morphological glowing of amyloid fibrils. NLRP3 or Pyrin and B2M were co-localized in a "speck" in HEK293T cells, and co-expressed in infiltrated monocytes/macrophages in the osteoarticular synovial tissues in a patient with DRA.

CONCLUSION

Taken together, these data suggest that inflammasome assembly is required for the subsequent triggering of intracellular formation of B2M amyloid fibrils, which may contribute to osteoarticular deposition of B2M amyloid fibrils and inflammation in patients with DRA.

Peritoneal Sclerosis: Role of Plasticizers in Stimulating Interleukin-1 Production

The role of plasticizers (PLS) in inducing water flow inhibition and peritoneal sclerosis has been demonstrated in both In vivo and In vitro studies. Interleukin-1 (IL-1) has been shown to be a regulator of fibroblast proliferation as well as collagenase production.

The aim of this study was to evaluate the role of PLS in stimulating mononuclear ce1l1L-1 secretion.

Two cultures containing 103 cells/mL were obtained from 14 healthy subjects. One was used as the control, and the other was mixed with diethylhexylphthalate (DEHP) to reach a final concentration of 2.8x10” M. After 4 hours the samples were centrifuged, and the supernatants were tested by radioimmunoassay for IL-1α and IL-1β.

The results showed a significant increase In both IL-1α and IL-1 β production In DEHP-stimulated cells in comparIson to the controls: 42.6±15.4 versus 29.3±10 ng/L (p<0.015) for IL-1α. and 153.6±55 versus 113.6±32 ng/L (p<0.03) for IL-1β

In conclusion, PLS added to mononuclear cells were able to Induce IL-1 secretion. This mechanism could be responsible, at least in part, for the development of peritoneal sclerosis. Thus the employment of plasticlzer-free bags should be elective in peritoneal dialysis.

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.

Chronic Induction of C-Reactive Protein by Hemodialysis, but Not by Peritoneal Dialysis Therapy

Objective

Evaluation of the inflammatory activity in patients on chronic peritoneal dialysis (PD) and patients on chronic hemodialysis (HD) in comparison to patients with chronic renal insufficiency without dialysis treatment and healthy volunteers.

Design

Open, non randomized prospective study.

Setting

Nephrology Department, including HD and PD therapy in a university hospital.

Patients

Twenty -four patients on chronic PD, 21 patients on chronic HD therapy using a cuprophan dialyzer, 16 patients with chronic renal insufficiency without dialysis treatment, and 33 healthy volunteers; 8 additional patients before and after initiation of chronic HD therapy. All patients and controls were without infection or immunosuppressive therapy.

Main Outcome Measures

As a marker of the inflammatory activity in the different patient groups, C-reactive protein (CAP) was measured serially using a sensitive, enzyme-Iinked, immunosorbent assay in order to detect values below the detection limit of standard assays.

Results

All patient groups had CAP levels higher than the normal controls (p < 0.01). Patients on HD had CAP levels significantly higher than PD patients (p < 0.01) whose levels were comparable to patients without dialysis therapy. Accordingly, longitudinal measurements before and after initiation of chronic HD showed a significant increase in CAP levels after the beginning of HD treatment (p < 0.04).

Conclusions

The results suggest that induction of the inflammatory activity is lower during PD compared to HD, since stimulation by the dialyzer membrane, dialysate buffer, or bacterial fragments in the dialysate is avoided. This observation might indicate a possible lower risk of long-term complications in patients with PD.

Serum C-Reactive Protein: A Predictor of Mortality in Continuous Ambulatory Peritoneal Dialysis Patients

Objective

To evaluate the predictive value of a single baseline serum C-reactive protein (sCRP) as a marker of mortality in continuous ambulatory peritoneal dialysis (CAPD) patients.

Design

A review of prospectively collected data in a 2-year follow-up study.

Setting

Tertiary medical center.

Patients

The study included 106 patients who were stable and had been on CAPD for a minimum of 3 months.

Main Outcome Measures

Patient survival rate was the main outcome measure of this study. Other outcome measures were technique survival rate, peritonitis rate, and hospitalized days. Covariables used in the survival analysis were age, sex, the presence of cardiovascular disease or diabetes mellitus, sCRP, serum albumin, hematocrit, cholesterol, HDL-cholesterol, malnutrition by subjective global assessment (SGA), weekly Kt/V urea, and weekly standardized creatinine clearance (SCCr).

Results

The 2-year patient survival rate was significantly lower in the increased sCRP group than in the normal sCRP group (66.7% vs 94.1%, p = 0.001), although there was no significant difference in technique failure, peritonitis rate, and hospitalized days between the two groups. By Cox proportional hazards analysis, independent predictors of mortality were: cardiovascular disease (relative risk, RR = 8.96, p < 0.005); increased sCRP level (RR = 1.19, p < 0.05); and high hematocrit (RR = 1.18, p < 0.05).

← Conclusion

Serum CRP at enrollment is an independent predictor of 2-year patient survival in CAPD patients.

Monocyte Activation and Humoral Immune Response to Endotoxins in Patients Receiving On-Line Hemodiafiltration Therapy

With the on-line preparation of substitution fluid, an easy-to-operate and cost-effective alter-native to conventional hemodiafiltration (HDF) has been realized. The continuous filtration of dialysis fluid, furthermore, allows high volumes of exchange. Microbial contamination and subsequently endotoxins, however, may be present in dialysis fluid, and thus the microbiological safety has become a pivotal issue.

In this clinical study we evaluated the safety of the Fresenius Medical Care on-line HDF system which is based on a two-stage filtration of dialysis fluid with upstream DIASAFE® and downstream on-line HDF filter. During the three-month study period we failed to detect germs or endotoxins in the substitution fluid. Augmented plasma interleukin-1β (IL-1β) and tumor necrosis factor α (TNFα) concentrations were found neither during the intradialytic period nor when pre-session values at study begin and study end were compared. In addition, changes in the anti-endotoxin core antibody levels and soluble CD14 (sCD14) concentration, or pyrogenic episodes were not observed.

On-line HDF with DIASAFE® and on-line HDF filter thus represents a safe treatment modality by effectively depleting dialysis fluid of cytokine-inducing substances.

Race modifies the association between adiposity and inflammation in patients with chronic kidney disease: findings from the chronic renal insufficiency cohort study

OBJECTIVE

The race-specific association of inflammation with adiposity and muscle mass in subjects with chronic kidney disease (CKD) was examined.

METHODS

Plasma concentration of interleukin (IL)-1β, IL-1 receptor antagonist (IL-1RA), IL-6, IL-10, tumor necrosis factor (TNF)-α, TGF-β, high-sensitivity C-reactive protein (hs-CRP), fibrinogen, and serum albumin was measured in 3,939 Chronic Renal Insufficiency Cohort study participants. Bioelectric impedance analysis was used to determine body fat mass (BFM) and fat-free mass (FFM).

RESULTS

Plasma levels of hs-CRP, fibrinogen, IL-1RA, IL-6, and TNF-α increased and serum albumin decreased across the quartiles of body mass index. In multivariable analysis, BFM and FFM were positively associated with hs-CRP, fibrinogen, IL-1β, IL-1RA, and IL-6. One standard deviation (SD) increase in BFM and FFM was associated with 0.36 (95% confidence interval [CI] = 0.33, 0.39) and 0.26 (95% CI = 0.22, 0.30) SD increase in log-transformed hs-CRP, respectively (P < 0.001). Race stratified analysis showed that the association between biomarkers and BFM and FFM differed by race, with Caucasians, demonstrating a stronger association with markers of inflammation than African Americans.

CONCLUSIONS

BFA and FFM are positively associated with markers of inflammation in patients with CKD. Race stratified analysis showed that Caucasians have a stronger association with markers of inflammation compared to African Americans.

Increased risk of Parkinson's disease in patients with end-stage renal disease: a retrospective cohort study

BACKGROUND

Studies on dyskinesia and Parkinson's syndrome associated with chronic kidney disease or end-stage renal disease (ESRD) have been mainly limited to case reports or case series studies. This population-based study investigated the risk of Parkinson's disease in patients with ESRD.

METHODS

From a universal insurance claims database of Taiwan, we established a cohort of 8,325 adults with newly diagnosed ESRD from 1997 to 2010 without a history of Parkinson's disease. A control cohort of 33,382 insured subjects without a history of kidney disease or Parkinson's disease was also selected, with frequency matched for age, sex and index date of the patients with ESRD. Both cohorts were followed up until the end of 2010.

RESULTS

The Parkinson's disease incidence was 1.55-fold higher in the cohort with ESRD than in the comparison cohort (48.8 vs. 31.7 per 10,000 person-years) with an adjusted hazard ratio of 1.73 (95% confidence interval, 1.39-2.15). Sex-specific and age-specific analysis showed a higher relative risk for women and younger patients with ESRD compared to the control cohort.

CONCLUSIONS

ESRD is significantly associated with an increased risk of Parkinson's disease. Close surveillance for Parkinson's disease should be considered for patients with ESRD.

Leukocyte proliferation and immune modulator production in patients with chronic kidney disease

INTRODUCTION

In Chronic Kidney Disease (CKD), immune cells are affected by uremic retention toxins. Given this effect, we analyzed lymphocyte proliferative response and immune modulators production following in vitro stimulation.

METHODS

Whole blood was drawn from healthy controls, patients with eGFR <20 ml/min/1.73 m(2) (Pre-dialysis, CKD stages 4 and 5) and hemodialysis patients (stage 5D). Peripheral cells were incubated for six days with pokeweed mitogen, concanavalin A, Staphylococcus enterotoxin A or influenza A vaccine. Peripheral lymphocyte proliferation was then analyzed by the "Flow-cytometric Assay of Specific Cell-mediated Immune response in Activated whole blood" (FASCIA) method, and cytokine profile in the cell supernatants was analyzed by the Milliplex multi-array method.

RESULTS

The absolute number of lymphoblasts in response to mitogenic stimulation and the number of cells in each CD4+ and CD8+ subpopulation were similar comparing the three groups, except for a single decline in number of lymphoblasts after stimulation with Staphylococcus enterotoxin A, comparing dialysis patients with healthy controls. Levels of interleukin (IL)-2 (p=0.026), -10 (p=0.019) and -15 (p=0.027) in the Staphylococcus enterotoxin A-stimulated supernatant were lower in hemodialysis patients compared to healthy controls. Levels of IL-15 (p=0.017) from pre-dialysis patients and levels of IL-5 (p=0.019) from hemodialysis patients in influenza A vaccine-stimulated supernatants were also lower compared to controls. In pokeweed mitogen-stimulated supernatant, IL-2 levels (p=0.013) were lower in hemodialysis patients compared to pre-dialysis patients. TNF-α, IL-10, IL-12, IL-15, IL-8, MCP-1, IP-10, IFN-α2, IL-1α and eotaxin levels were all significantly higher in plasma obtained from CKD patients.

CONCLUSION

Our results suggest that T-cells from CKD patients have similar proliferative response to stimulation compared with healthy individuals. Moreover, however the immune cells show inability to produce selected cytokines, most likely due to the uremic milieu or dialysis procedure.

Association between albuminuria, kidney function, and inflammatory biomarker profile in CKD in CRIC

BACKGROUND AND OBJECTIVES

Increased risk of mortality in patients with CKD has been attributed to inflammation. However, the association between kidney function, albuminuria, and biomarkers of inflammation has not been examined in a large cohort of CKD patients.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This study measured the plasma levels of IL-1β, IL-1 receptor antagonist (IL-1RA), IL-6, TNF-α, TGF-β, high-sensitivity C-reactive protein (hs-CRP), fibrinogen, and serum albumin in 3939 participants enrolled in the Chronic Renal Insufficiency Cohort study between June 2003 and September 2008. An inflammation score was established based on plasma levels of IL-1β, IL-6, TNF-α, hs-CRP, and fibrinogen. Estimated GFR (eGFR) and serum cystatin C were used as measures of kidney function. Albuminuria was quantitated by urine albumin to creatinine ratio (UACR).

RESULTS

Plasma levels of IL-1β, IL-1RA, IL-6, TNF-α, hs-CRP, and fibrinogen were higher among participants with lower levels of eGFR. Inflammation score was higher among those with lower eGFR and higher UACR. In regression analysis adjusted for multiple covariates, eGFR, cystatin C, and UACR were strongly associated with fibrinogen, serum albumin, IL-6, and TNF-α. Each unit increase in eGFR, cystatin C, and UACR was associated with a -1.2% (95% confidence interval, -1.4, -1), 64.9% (56.8, 73.3) and 0.6% (0.4, 0.8) change in IL-6, respectively (P<0.001).

CONCLUSIONS

Biomarkers of inflammation were inversely associated with measures of kidney function and positively with albuminuria.

Haemodialysis induces mitochondrial dysfunction and apoptosis

BACKGROUND

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

Nutritional status and immune functions in maintenance hemodialysis patients

Epidemiological studies suggest various kinds of immune dysregulation in hemodialysis (HD) patients. The aim of this study was to investigate the relationship between immune functions and nutritional status of HD patients. We studied 54 patients with ESRD on chronic HD, included 34 females and 20 males with mean age 46.6 ± 16.3 (18–77) years. We measured the height and dry weight of all patients. The BMI was calculated by dividing weight (kg) by height squared (m²). In all patients serum urea, creatinine, albumin, iron, cholesterol, triglyceride, CRP, IgG, IgM, IgA, CD4, CD8, CD19, CD16-56 lymphocytes were measured. Kt/V values were calculated according to DOQI guideline. In this study, a positive correlation between albumin, cholesterol, and triglyceride levels as nutritional parameters and immune functions in terms of total and subtype lymphocyte counts was observed. Further prospective studies are needed to determine the clinical importance of this finding and the appropriate means of measurement and effects of nutrition on immune function in hemodialysis patients.

Children with chronic renal failure have reduced numbers of memory B cells

Reduced serum IgG and subclass levels have been demonstrated in children with chronic renal failure. To study possible causes of this reduction, we analysed B cell subset composition, T helper cell frequencies and immunoglobulin (Ig) production capacity in vitro in children with chronic renal failure, with or without dialysis treatment. B cell subsets were characterized by determining CD27, IgM, IgD and CD5 expression within the CD19(+) population. Intracellular expression of interferon (IFN)-gamma, interleukin (IL)-2 and IL-4 in PMA/ionomycin-stimulated peripheral blood mononuclear cells (PBMC) was used to evaluate T helper frequencies. The capacity of B cells to secrete Ig in vitro was determined by measuring IgG(1), IgG(2) and IgM in culture supernatants of anti-CD2/CD28 monoclonal antibody (MoAb)- or SAC/IL-2-stimulated PBMC. Memory B cell numbers (identified as percentage or absolute number of CD19(+) IgM-IgD- or CD19(+)CD27(+) lymphocytes) were lower in children treated with haemodialysis (HD), peritoneal dialysis (PD) and children with chronic renal failure before starting dialysis treatment (CRF) compared to healthy controls (HC) (P < 0.05). Compared with HC, CD5(+) (naive) B cells were reduced in HD-treated patients but not for PD or for children with chronic renal failure before starting dialysis treatment (CRF). No significant differences in CD4(+) T helper cell subsets were found between the groups. However, CRF children had a higher percentage of IFN-gamma producing CD8(+) T lymphocytes compared to HC (P = 0.02). Finally, IgG(1), IgG(2) and IgM production in vitro was similar in the four groups. In conclusion, significantly lower numbers of memory type B cells were found in children with chronic renal failure compared to healthy controls. This reduction may contribute to the low Ig levels found in these children.

Interleukin-1 receptor antagonist synthesis by peripheral blood mononuclear cells: a novel predictor of morbidity among hemodialysis patients

Proinflammatory cytokines have been implicated in the short- and long-term morbidity experienced by hemodialysis (HD) patients. The present study, which is based on long-term follow-up of a cohort of 37 patients, relates peripheral blood mononuclear cell (PBMC) interleukin-1 receptor antagonist (IL-1Ra) synthesis (a reliable marker of IL-1beta synthesis in HD patients) and plasma levels of an acute phase reactant, lipopolysaccharide binding protein (LBP), to clinical outcomes. In July 1993, predialysis blood samples from these patients were collected and IL-1Ra synthesis by PBMC and plasma LBP was measured. Hospital records were reviewed and patient follow-up data were obtained until December 1997 (54 mo) or death, whichever occurred earlier. The effect of age, diabetes, endotoxin- and IgG-stimulated IL-1Ra synthesis, and plasma LBP levels on mortality was assessed using the Cox proportional hazard regression model. Poisson regression was used to determine potential relationships between the number of outcome events and each continuous risk factor. Twenty-two patients (59%) died during the follow-up period. Mortality was unrelated to IL-1Ra synthesis but did increase with age (relative risk, 1.05/yr; P: = 0.01) and diabetes (relative risk, 3.00/yr; P: = 0.03). Cardiovascular event rates were higher among older individuals and in those with higher endotoxin-stimulated PBMC IL-1Ra synthesis. Cardiovascular events increased with plasma LBP levels in the range of 9,000 to 12,000 pg/ml but then seemed to decrease. In contrast, older age and low IgG-stimulated IL-1Ra synthesis were associated with an increased risk of infectious events. The results of this study demonstrate an interesting link between stimulus-dependent variability in IL-1Ra synthesis by PBMC and clinical outcomes among patients on chronic HD and provide interesting targets for therapeutic interventions in this vulnerable patient population.

Dyadic relationship conflict, gender, and mortality in urban hemodialysis patients

The effects of dyadic satisfaction and conflict have not been well defined in the hemodialysis (HD) population. The aim of this study was to determine whether the perception of decreased dyadic satisfaction was associated with mortality in patients treated with HD, and if so, whether there were different relationships between risk factors, and differential outcomes in men and women. A total of 174 HD patients, primarily African-Americans, involved in dyadic relationships for more than 6 mo had indices of dyadic satisfaction, depression, perception of illness effects, social support, behavioral compliance with the dialysis prescription, and plasma interleukin-1 (IL-1) and beta-endorphin levels measured. Cox proportional hazards models assessed relative mortality risks. Patients' dyadic satisfaction scores correlated with beta-endorphin levels. There was no correlation of IL-1 or beta-endorphin with any psychosocial or behavioral compliance measure in the group as a whole. Correlations between psychosocial, medical, and neuroimmunologic variables were different in men and women. For women, dyadic satisfaction correlated with beta-endorphin levels, depression, and perception of illness. Women with higher dyadic satisfaction and decreased dyadic conflict were at decreased mortality risk, but dyadic adjustment indices were unassociated with differential survival in the larger group of men. Correlations between neuroendocrine and immune markers are different in African-American male and female HD patients. Greater dyadic satisfaction and lower dyadic conflict are independently associated with decreased mortality in female African-American HD patients, of the same order of magnitude as medical risk factors. Such effects may be attributable to a relationship between dyadic satisfaction and conflict and health-related behaviors, or through an effect on neuroendocrine or immunologic status.

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.

Interleukin-6 gene expression in peripheral blood mononuclear cells from patients undergoing hemodialysis or continuous ambulatory peritoneal dialysis

To compare the interleukin-6 (IL-6) gene expression in the peripheral blood mononuclear cells (PBMCs) and plasma IL-6 levels in patients undergoing continuous ambulatory peritoneal dialysis (CAPD) with those in patients undergoing hemodialysis. Eleven hemodialysis patients, 10 CAPD patients, 15 non-dialyzed patients with end-stage kidney disease (ESKD), and 7 healthy controls were included in this study. PBMCs were collected by differential centrifugation. Plasma IL-6 concentration was measured by enzyme immunoassay. Plasma IL-6 levels were significantly increased in the hemodialysis and CAPD patients as compared with non-dialyzed ESKD patients and normal subjects (p < 0.01). Following hemodialysis, plasma IL-6 levels exceeded those before hemodialysis. No significant difference was found in plasma IL-6 levels in CAPD patients and in hemodialysis patients when blood was drawn before hemodialysis. Low but steady-state levels of IL-6 mRNA expression were observed in the non-dialyzed ESKD patients. The expression of IL-6 mRNA in PBMCs was significantly increased in the patients undergoing hemodialysis or CAPD as compared with the non-dialyzed ESKD patients. The PBMC IL-6 mRNA was significantly lower in CAPD patients than in hemodialysis patients (p < 0.01). A significant correlation was found between the plasma concentration of IL-6 and the expression of IL-6 mRNA in PBMCs from patients undergoing hemodialysis or CAPD (p < 0.01). The hemodialysis or CAPD procedure contributed to the increase in PBMC IL-6 mRNA expression and plasma IL-6 concentration. CAPD treatment stimulated the production of IL-6 to a lesser extent than hemodialysis treatment.

Immunologic function and survival in hemodialysis patients

BACKGROUND

Although the medical determinants of mortality in patients with end-stage renal disease (ESRD) treated with hemodialysis (HD) are well appreciated, the contribution of immunologic parameters to survival in such patients is unclear, especially when variations in age, medical comorbidity and nutrition are controlled. In addition, although dysregulation of cytokine metabolism has been appreciated in patients with ESRD, the association of these parameters with outcomes has not been established. Recently, the type of dialyzer used in patients' treatment has been associated with survival, but the mechanisms underlying these findings, including their immune effects, have not been established. We conducted a prospective, cross-sectional, observational multicenter study of urban HD patients to determine the contribution of immunological factors to patient survival. We hypothesized increased proinflammatory cytokines would be associated with increased mortality, and that improved immune function would be associated with survival.

METHODS

Patients were assessed using demographic and anthropometric indices, Kt/V, protein catabolic rate (PCR) and immunologic variables including circulating cytokine [interleukin (IL)-1, IL-2, IL-4, IL-5, IL-6, IL-12, IL-13 and tumor necrosis factor (TNF)-alpha] levels, total hemolytic complement activity (CH50), and T cell number and function. A severity index, previously demonstrated to be a mortality marker, was used to grade medical comorbidity. A Cox proportional hazards model, controlling for patients' age, severity index, level of serum albumin concentration, dialyzer type and dialysis site was used to asses relative survival risk.

RESULTS

Two hundred and thirty patients entered the study. The mean (+/- SD) age of the population was 54.4 +/- 14.2 years, mean serum albumin concentration was 3.86 +/- 0.47 g/dl, mean PCR was 1.1 +/- 0.28 g/kg/day, and mean Kt/V 1.2 +/- 0.3. Patients' serum albumin concentration was correlated with levels of Kt/V and PCR, and their circulating IL-13 and TNF-alpha levels, but negatively with their circulating IL-2 levels, T-cell number and T-cell antigen recall function. T-cell antigen recall function correlated negatively with PCR, but not Kt/V. There was no correlation of any other immune parameter and medical or demographic factor. Immune parameters, were all highly intercorrelated. Mean level of circulating cytokines in HD patients were in all cases greater than those of a normal control group. There were few differences in medical risk factors or immune parameters between patients treated with different types of dialyzers. After an almost three-year mean follow-up period, increased IL-1, TNF-alpha, IL-6, and IL-13 levels were significantly associated with increased relative mortality risk, while higher levels of IL-2, IL-4, IL-5, IL-12, T-cell number and function, and CH50 were associated with improved survival. The difference in survival between patients treated with unmodified cellulose dialyzers and modified or synthetic dialyzers approached the level of statistical significance, but there were no differences in levels of circulating cytokines between these two groups.

CONCLUSIONS

Higher levels of circulating proinflammatory cytokines are associated with mortality, while immune parameters reflecting improved T-cell function are associated with survival in ESRD patients treated with HD, independent of other medical risk factors. These factors may serve as markers for outcome. The mechanism underlying the relationship of immune function and survival, and the effect of interventions to normalize immune function in HD patients should be studied.

Zinc modulates mononuclear cellular calcitriol metabolism in peritoneal dialysis patients

Zinc has long been known to play a role in maintaining immunologic function. Hypozincemia, however, is common in patients with end-stage renal disease (ESRD) treated with continuous ambulatory peritoneal dialysis (CAPD). We previously demonstrated that zinc depletion limits the ability of animals to achieve maximum circulating calcitriol levels in response to the stress of calcium or phosphorus depletion. It was unclear, however, whether changes in the circulating levels of calcitriol in these settings was associated with a direct effect on renal 1-alpha hydroxylase activity, or whether the zinc dependence of the stimulated calcitriol response involved an integrated systemic response in intact animals. In addition it was unclear whether circulating zinc levels or zinc nutritional status modified calcitriol metabolism in humans. To better understand the role zinc plays in the immune response in patients with ESRD, we studied IL-1, calcitriol and tumor necrosis factor-alpha production by mononuclear cells from blood and peritoneal effluents of 22 patients with ESRD treated with CAPD. Macrophages from peritoneal effluents and peripheral blood mononuclear cells were isolated and pulsed with phytohemagglutinin in medium to which different concentrations of zinc chloride, copper chloride, and carbonyl cyanide p-(trifluoromethoxy)-phenyl-hydrazone (FCCP), an inhibitor of mitochondrial function were added. Supernatant interleukin-1, calcitriol, and tumor necrosis factor-alpha levels were subsequently measured. We demonstrated a zinc concentration dependent increase in stimulated IL-1 alpha and -beta, and TNF-alpha release in both peripheral mononuclear cells and peritoneal macrophages from patients with ESRD treated with CAPD. The effect is zinc specific, as it is not reproduced by copper or chloride supplementation. A zinc concentration dependent increase in peritoneal macrophage calcitriol release was also noted. FCCP blocked the cellular production of IL-1 alpha, IL-1 beta, and TNF-alpha, but had little effect on zinc-induced stimulated mononuclear cell supernatant calcitriol levels. The different shape of the zinc dose response curve, and the lack of correlation between paired IL-1 and calcitriol supernatant levels suggests the effect of zinc on mononuclear cellular cytokine and calcitriol production is mediated through different pathways.

Apoptosis of monocytes cultured from long-term hemodialysis patients

Monocyte apoptosis in vitro was studied in patients on long-term hemodialysis, CAPD, and in predialytic uremia to gain insight into the high susceptibility of these patients to infections. Monocytes from dialysis and control subjects were cultured for 24 to 120 hours in vitro to analyze the level and progression of DNA fragmentation as a hallmark of apoptosis. After an incubation time of 48 hours chromatin fragmentation of 48.5 +/- 7.7% was found in monocytes from dialysis patients, which significantly exceeded DNA fragmentation of control monocytes (23.1 +/- 9.1%; N = 12; P < 0.01). Over longer culture periods of up to 5 days, a continuous progression of apoptosis occurred with a similar slope of percent DNA fragmentation in the two studied groups. Monocyte viability was > 95% both in the dialysis and control group. Hemodialysis patients also showed elevated levels of monocyte apoptosis when programmed cell death was evaluated by transmission electron microscopy or DNA electrophoresis of cleaved chromatin. To test the functional relevance of monocyte apoptosis, a significant reduction of Candida growth inhibition by monocytes of dialysis patients was found with a strong linkage between percentage of DNA fragmentation and impaired microbicidal capacity. Monocytes obtained from patients after the hemodialysis session and from CAPD patients showed normal DNA fragmentation levels similar to controls. Differences of monocyte apoptosis between patients on cuprophane and high-flux polysulphone dialysis were not found. Uremic predialytic patients also exerted an increased monocyte DNA fragmentation of 44.2 +/- 1.5% (N = 7; P < 0.05 compared to controls). Enhanced apoptosis of uremic monocytes was accompanied by a reduced formation of TNF-alpha over 48 hours, revealing a significant negative correlation between chromatin fragmentation and monokine synthesis. Supplementation of monocyte cultures from dialysis patients with exogenous TNF-alpha turned increased apoptosis back to baseline levels, suggesting that inflammatory mediators may modulate monocyte senescence. In summary, the elevated degree of monocyte apoptosis in end-stage renal failure may contribute to the impaired cellular host defense seen in these patients.

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.

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.

Role of dialysis modality in responses of blood monocytes and peritoneal macrophages to endotoxin stimulation

Constitutive and endotoxin (lipopolysaccharide [LPS])-stimulated release of interleukin-1 beta (IL-1 beta), interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-alpha), and prostaglandin E2 (PGE2) by blood monocytes and peritoneal cell preparations from patients on various forms of dialysis was measured. Monocytes were obtained from healthy controls (n = 20), and from patients on peritoneal dialysis (n = 8), on hemodialysis with cellulose ester membranes (n = 9), and on hemodialysis with polysulfone membranes (n = 8). Peritoneal macrophages were recovered by lavage during laparoscopic surgery from 11 healthy controls, from dialysate in 37 patients on peritoneal dialysis, and at catheter placement for transfer to peritoneal dialysis from eight patients on hemodialysis with polysulfone membranes. Peak LPS-induced production of TNF-alpha, IL-1 beta, and IL-6 by monocytes from patients on peritoneal dialysis and cellulose ester hemodialysis was less than that by monocytes from healthy controls. In contrast, monocytes from patients treated with polysulfone hemodialysis produced amounts of cytokine not different from controls. Lipopolysaccharide-stimulated PGE2 production by monocytes was the same in both patient and control groups. Peritoneal cell preparations from patients on peritoneal dialysis showed decreased release of IL-1 beta and TNF-alpha as compared with control peritoneal cells and with their own blood monocytes. To determine whether the decreased response to LPS by peritoneal cells compared with their own blood monocytes could be attributed to lower numbers of macrophages in the peritoneal cell preparations, adherence of peritoneal cells to plastic was performed. Adherence increased the percentage of macrophages from 70% to more than 90%. In monocytes and adherence purified peritoneal macrophages from peritoneal dialysis patients, no significant difference between monocytes and adherent peritoneal macrophages could be found for TNF-alpha and PGE2. Interleukin-1 beta production by the adherent peritoneal macrophages, as by total peritoneal cells, was significantly lower than that by monocytes. Constitutive production of PGE2 and IL-6 by peritoneal cells from patients on peritoneal dialysis was significantly increased. In contrast, LPS-stimulated production of TNF-alpha, IL-1 beta, and IL-6 by blood monocytes and peritoneal cells from patients receiving hemodialysis with polysulfone membranes was comparable to that produced by monocytes and peritoneal cells obtained from healthy controls. Thus, blood monocytes and peritoneal cells from patients on peritoneal dialysis and from patients on hemodialysis with cellulose-ester membranes demonstrate a decreased cytokine response to LPS, suggesting a state similar to endotoxin tolerance.(ABSTRACT TRUNCATED AT 250 WORDS)

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

Interleukin-6 (IL-6) has a complex spectrum of biological activities, for example, growth and differentiation of B cells and synthesis of acute-phase proteins by the liver. To evaluate the role of this cytokine in the inflammatory response induced by blood interaction with hemodialysis membranes, we have investigated the IL-6 synthesis and release in supernatant of 24-hour cultured peripheral blood mononuclear cells (PBMC) isolated from: (a) 10 hemodialyzed patients, (b) seven patients with advanced chronic renal failure (GFR less than or equal to 10 ml/min), and (c) eight healthy control subjects. In the same groups of subjects we evaluated the relationship between IL-6 synthesis and release and beta-2-microglobulin (beta 2m) production. Before and after dialytic treatment hemodialysis patient blood samples were drawn using the following criteria: (1) after two months of dialysis with cuprophan membranes, (2) after one and two months of dialysis with polymethylmethacrylate (PMMA) membranes, and finally, (3) after one further month of dialysis with cuprophan membranes. IL-6 was determined after 72 hours of incubation of PBMC supernatant serial dilutions with IL-6-dependent hybridoma cell line, 7TD1. Compared to IL-6 synthesis in control subjects (6.0 +/- 5.6 U/3 x 10(6) PBMC/24 hr), hemodialyzed patients, when treated with cuprophan membranes, showed significantly higher value of IL-6 production both before (23 +/- 13 U/3 x 10(6) PBMC/24 hr) and after (26.2 +/- 11.3 U/3 x 10(6) PBMC/24 hr) the dialytic session.(ABSTRACT TRUNCATED AT 250 WORDS)

Soluble interleukin 2 receptor (Tac chain) is not a reliable marker in kidney transplant recipient monitoring

T lymphocyte expansion is triggered through interaction of interleukin 2 (IL-2) with its high-affinity receptor (IL-2R). This molecule is a heterodimer comprising an antigen-inducible component, the Tac chain (P55). Activation of T lymphocytes also generates a soluble form of this P55 called S-IL-2R. S-IL-2R is elevated in many T-cell-related pathologies (leukemia, autoimmunity, etc.). In graft recipients, rejection is a result of T-cell activation by graft antigens and therefore might induce a release of S-IL-2R in the circulation; this parameter is now said to be a good indicator of rejection. We have performed a study in renal graft recipients in order to assess the usefulness of circulating S-IL-2R particularly to discriminate the origin of renal failure in cases of rejection or of cyclosporin-A (CsA)-induced nephrotoxicity. We demonstrated that there are no differences between isolated values in the clinical groups at the time of diagnosis. Variations in S-IL-2R are increased compared to steady-state periods during rejection and cytomegalovirus infections, although not in CsA toxicity episodes. However, at the individual level there are too many false-positive and false-negative results, making this parameter no more meaningful than serum creatinine levels alone or even in association (as tested in logistic discriminant analysis). In addition, it seems that the variations in S-IL-2R are partly related to renal function itself, as suggested by the correlation between S-IL-2R levels and serum creatinine levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Interleukin-2 deficit in hemodialysis patients. Role of prostaglandins

Uremic patients suffer from various immunological alterations, whose pathogenesis is still unknown. Here, we studied 37 hemodialysis patients in order to investigate the role of prostaglandins (PGs) in uremic immunological deficiency, specifically in relation to interleukin-2 (IL-2) synthesis. We confirmed previous published data on deficient response to PHA in chronic renal failure patients (cpm, mean +/- SEM: 15,400 +/- 2,100 in uremics vs. 29,500 +/- 3,380 in controls, p < 0.04) and established a correlation between this deficiency and diminished IL-2 synthesis (r = 0.619, p < 0.05). The direct measurement of PGs in lymphocyte cultures showed greatly increased concentrations in the presence of uremic serum (US). We found that PGs synthesis can be inhibited by up to 80% if cultures are supplemented with indomethacin (IND--a cyclooxigenase inhibitor) or by removal of monocytes (producers of PGs). Both methods situated the uremic proliferative response within the normal range in cultures with FCS, and close to the normal range in cultures with US. We observed a deficit of IL-2 in hemodialysis patients (means +/- SD: 8,940 +/- 6,420 in uremics vs. 16,900 +/- 3,890 in controls). Addition of exogenous IL-2 normalized lymphocyte response even in US cultures, with no additive effect between PGs inhibition and exogenous IL-2 except in US cultures. It is suggested that IL-2 deficit of uremics depends, at least in part, on an increase in PGs synthesis induced by US.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of acetate dialysate on transforming growth factor beta 1, interleukin, and beta 2-microglobulin plasma levels

To evaluate potential adverse effects of acetate use in hemodialysis (HD), we measured plasma interleukin (IL-1 alpha, IL-1 beta, IL-6), TNF alpha, TGF beta 1, and beta 2-microglobulin levels with ELISA assays in normal (N = 9), CRF (N = 6), CAPD (N = 7) and HD (N = 8) subjects and compared the effects of acetate (Ac) and acetate-free (Ac-free) dialysate. TGF beta 1 was the only cytokine consistently detected. Compared to normals (median 57, range 53 to 68 pg/ml, one undetected; N = 8), TGF beta 1 was higher in the CRF (75, 70 to 97 pg/ml, one undetected) and CAPD (75.5, 66 to 116 pg/ml, N = 6) groups (P less than 0.05), and was somewhat higher in the HD (68, 52 to 88 pg/ml) group (P less than 0.10). Acutely, TGF beta 1 pre-HD (70, 63 to 88 pg/ml) increased above normals post AcHD [79.5, 65 to 140 pg/ml uncorrected for ultrafiltration (UF)] and was higher after AcHD versus Ac-free HD both uncorrected (79.5, 65 to 140 pg/ml vs. 70, 52 to 86 pg/ml) and corrected for UF (68, 51 to 115 pg/ml vs. 57, 43 to 69 pg/ml; P less than 0.05). beta 2-microglobulin was not different after AcHD (81.2 +/- 8.0 mg/ml) versus Ac-free HD (72.5 +/- 6.9 mg/ml). Significantly lower serum inorganic phosphorus was also found four hours post-AcHD compared to four hours post-Ac-free HD (0.87 mmol +/- 0.10 SEM vs. 1.05 mmol +/- 0.07 SEM; P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Regulation of interleukin-2 and interferon-gamma gene expression in renal failure

Regulated expression of interleukin-2 (IL-2) and interferon-gamma (IFN-gamma) genes, induced in cultured peripheral blood mononuclear cells from patients with end-stage renal disease on hemodialysis (HD; N = 13) or peritoneal dialysis (PD; N = 13), was compared to that of 32 normal donors. Culture conditions were chosen that measure the transient, phytohemagglutinin-induced expression of IL-2 and IFN-gamma messenger RNA (mRNA), as well the intactness of post-transcriptional and suppressor T cell-dependent mechanisms that control this expression. The latter was achieved by analyzing the superinduction of IL-2 and IFN-gamma mRNA occurring upon culture with cycloheximide or after low-dose gamma-irradiation, respectively. HD subjects showed a complete loss of inducibility of the IL-2 gene, concomitant with decreased inducibility of IFN-gamma mRNA. In PD subjects, by contrast, expression of IL-2 mRNA was as vigorous as in normal donors, while IFN-gamma mRNA was even more strongly inducible. This difference in gene inducibility is caused by a lack of T cell function in HD subjects. The defect in IL-2 gene expression in HD subjects, occurring most likely at transcription, may underly their impaired immune function.