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

The Effect of Advanced Glycation End-Products and Aminoguanidine on Tnfα Production by Rat Peritoneal Macrophages

Objective

To evaluate the effect of advanced glycation end-products (AGEs) and the inhibitor of their formation, aminoguanidine, on tumor necrosis factor-α (TNFα) production (as a functional marker) by rat peritoneal macrophages (PMΦ).

Design

Charles River rats underwent a daily intraperitoneal injection of peritoneal dialysis solution [(PDS), 4.25 g/dL dextrose; Dialine, Travenol, Ashdod, Israel] for a 2-month period (group E). Another group of rats was subjected to the same protocol with the addition of 25 mg/kg aminoguanidine (group A). Three control groups were utilized: ( 1 ) rats that were injected daily with aminoguanidine only (group AO), ( 2 ) rats that were injected with Dulbecco's phosphate-buffered saline (group D), and ( 3 ) rats in which no intervention was carried out (group C). After 2 months, PMΦ were isolated from rat peritoneal effluent and their TNFα production measured by ELISA in cell-free culture supernatants, in both the basal state and after 24-hour stimulation with lipopolysaccharide (LPS). The concentrations of AGEs in peritoneal effluent were assayed and correlated to TNFα levels. PMΦ obtained from normal rats were then incubated for 24 hours with ( 1 ) the peritoneal effluent of each of the above respective groups, with or without LPS; ( 2 ) increasing concentrations of AGEs (0 - 250 μg/mL); and ( 3 ) increasing concentrations of aminoguanidine (0 - 7.5 mg/mL), and TNFα secretion again determined.

Results

After 2 months of daily intraperitoneal injection of PDS, in the basal state, TNFα production was significantly higher in PMΦ isolated from the peritoneal effluent groups (groups E, A, and AO) compared to controls (group C). Following LPS stimulation, a further increase in TNFα secretion was seen, with a significantly greater response in group AO versus groups E, A, and D. Effluent AGEs were markedly elevated only in group E. No correlation was found between TNFα secretion by these PMΦ and the concentration of AGEs. On incubation with the respective peritoneal effluents (groups E, A, and AO), in both the basal and stimulated state, TNFα production by PMΦ from normal rats was significantly enhanced compared to group C. Incubation with increasing concentrations of AGEs or aminoguanidine resulted in an increase of TNFα secretion by these PMΦ.

Conclusions

Following intermittent intraperitoneal administration of glucose-based PDS, rat PMΦ are chronically activated, as evidenced by increased basal TNFα secretion. The peritoneal effluent of such treated animals is capable of stimulating TNFα production by normal rat PMΦ. These data suggest that glucose-based PDS acts as a primer of PMΦ, which retain their ability to further stimulation by LPS. Although, in vitro, AGEs promote TNFα secretion by normal rat PMΦ, in vivo, their influence is probably modulated by other factors. Aminoguanidine has a specific inducing effect on rat PMΦ, independent of glucose-based PDS.

Dendritic Cells as Arbiters of Peritoneal Immune Responses

During the past few years, there has been a substantial increase in the understanding of innate immunity. Dendritic cells are emerging as key players in the orchestration of this early phase of immune responses, with a role that will translate into the subsequent type of adaptive immune response against infection. Here we provide an overview of dendritic cell differentiation and function, with particular emphasis on those features unique to the immune defense of the peritoneal cavity and in the context of peritoneal dialysis-associated immune responses. The reader is referred to the primary references included in the accompanying list for specific details in this fascinating field.

Peritoneal M2 macrophage transplantation as a potential cell therapy for enhancing renal repair in acute kidney injury

Acute kidney injury (AKI) is a clinical condition that is associated with high morbidity and mortality. Inflammation is reported to play a key role in AKI. Although the M2 macrophages exhibit antimicrobial and anti‐inflammatory activities, their therapeutic potential has not been evaluated for AKI. This study aimed to investigate the protective effect of peritoneal M2 macrophage transplantation on AKI in mice. The macrophages were isolated from peritoneal dialysates of mice. The macrophages were induced to undergo M2 polarization using interleukin (IL)‐4/IL‐13. AKI was induced in mice by restoring the blood supply after bilateral renal artery occlusion for 30 minutes. The macrophages were injected into the renal cortex of mice. The changes in renal function, inflammation and tubular proliferation were measured. The M2 macrophages were co‐cultured with the mouse primary proximal tubular epithelial cells (PTECs) under hypoxia/reoxygenation conditions in vitro. The PTEC apoptosis and proliferation were analysed. The peritoneal M2 macrophages effectively alleviated the renal injury and inflammatory response in mice with ischaemia‐reperfusion injury (IRI) and promoted the PTEC proliferation in vivo and in vitro. These results indicated that the peritoneal M2 macrophages ameliorated AKI by decreasing inflammatory response and promoting PTEC proliferation. Hence, the peritoneal M2 macrophage transplantation can serve as a potential cell therapy for renal diseases.

Therapeutic potential of regulatory macrophages generated from peritoneal dialysate in adriamycin nephropathy

Cell therapy using macrophages requires large amounts of cells, which are difficult to collect from patients. Patients undergoing peritoneal dialysis (PD) discard huge numbers of peritoneal macrophages in dialysate daily. Macrophages can be modulated to become regulatory macrophages, which have shown great promise as a therapeutic strategy in experimental kidney disease and human kidney transplantation. This study aimed to examine the potential of using peritoneal macrophages (PMs) from peritoneal dialysate to treat kidney disease. Monocytes/macrophages accounted for >40% of total peritoneal leukocytes in both patients and mice undergoing PD. PMs from patients and mice undergoing PD were more mature than peripheral monocytes/macrophages, as shown by low expression of C-C motif chemokine receptor 2 (CCR2) and morphological changes during in vitro culture. PMs from patients and mice undergoing PD displayed normal macrophage function and could be modulated into a regulatory (M2) phenotype. In vivo, adoptive transfer of peritoneal M2 macrophages derived from PD mice effectively protected against kidney injury in mice with adriamycin nephropathy (AN). Importantly, the transfused peritoneal M2 macrophages maintained their M2 phenotype in kidney of AN mice. In conclusion, PMs derived from patients and mice undergoing PD exhibited conventional macrophage features. Peritoneal M2 macrophages derived from PD mice are able to reduce kidney injury in AN, suggesting that peritoneal macrophages from patients undergoing PD may have the potential for clinical therapeutic application.

The Measurement of Cytokine Production Capacity during Dialysis - a New Dynamic Method for the Evaluation of Biocompatibility?

The activation of monocytes and other immunocompetent cells during hemodialysis can be attributed to their contact with immunogenic structures such as membranes, blood lines, and endotoxins. The simple measurement of cytokines in blood cannot completely describe the whole dimension of this event. Stimulation of monocytes and other immunocompetent cells in whole blood with lipopolysaccharides (LPS) for IL-6 and phytohemagglutinine (PHA) for TNF at the start and end of dialysis may make it possible to better analyze cellular response during dialysis. Ten healthy volunteers and 10 patients suffering from chronic renal failure were tested with the commercial whole-blood stimulation assays “Dynamix”-IL-6-DIA and -TNF-alpha-DIA (Biosource Diagnostics, Ratingen, Germany). Then 24 patients undergoing hemodialysis with hemophane (n=12) and polyamide (n=12) membranes were examined before and after dialysis treatment. The unpaired Wilcoxon t- test was used for statistical analysis. Healthy volunteers and patients with chronic renal failure showed no statistical differences in concentrations of TNF-alpha and IL-6 before or after whole blood stimulation (WBS). In comparison to patients with chronic renal failure, pre-WBS concentrations of both cytokines (p<0.034) were increased in patients of each membrane group before dialysis. After whole blood stimulation, no differences were observed. At the end of dialysis treatment, the pre- and post-WBS IL-6 values were both significantly higher in the hemophane group (p=0.049 and p=0.0038, respectively) TNF-alpha concentrations were unchanged. No significant differences in the polyamide group were found between the start and end of treatment for either cytokine. A comparison of these membrane groups showed that only the pre-WBS IL-6 concentration in the hemophane group was elevated (p=0.022) after dialysis. In conclusion, the presence of uremia alone could not influence the cytokine production and release capacity. In our patients, dialysis elevated pre-WBS concentrations of TNF-alpha and IL-6, and increased IL-6 release from immunocompetent cells after whole blood stimulation in the hemophane group. The use of polyamide membranes decreased the action of monocytes and other immunocompetent cells, but could not completely prevent this phenomenon. The whole blood stimulation assays for measurement of TNF-alpha and IL-6 may represent a new, dynamic method for evaluating biocompatibility.

Variations of Cytokine Levels and Production in CAPD Patients

Macrophages, predominant cells in dialysates of patients on CAPD without peritonitis, produce a wide variety of substances including cytokines. The aim of this study was to examine the cytokine production in five uninfected patients. This work investigated the presence in dialysates of interleukin-1ß, interleukin-6, interleukin-8, tumor necrosis factor α and the ability of peritoneal macrophages to produce these cytokines. These results were compared with values obtained from control group in non-uremic conditions (peritoneal lavage with isotonic saline or dialysis fluid). All cytokines were detectable in dialysates. Interindividual variations in cytokine concentration in dialysates were wider than variations of production of cytokines ex vivo by stimulated and unstimulated cells. In control group, dialysis fluid inhibited the cytokine production and with isotonic saline, cells produced less cytokines than dialysis patients'cells. The highest levels of interleukin-1 and tumor necrosis factor in dialysates and the highest capacity to respond to LPS were observed in patients having the shortest duration of dialysis. The variability observed did not seem to be due to cells themselves but to their environment.

On-line production of ultrapure substitution fluid reduces TNF-alpha- and IL-6 release in patients on hemodiafiltration therapy

On-line hemodiafiltration (HDF) has been introduced into clinical practice in the last few years. The most important technical and regulatory challenges were the safety and microbiological quality of ultrafiltrated substitution/replacement fluid. The application of ultrafilters in a different technical arrangement in the fluid path based on polysulfone or polyamide membranes should prevent patient contact with endotoxins and other pyrogenic or bacteria-derived substances. After resolving these problems and providing clinically safe and technically robust product solutions, increasing numbers of patients have been treated, especially those with severe clinical conditions, e.g., diabetes, hypo- or hypertension. The benefit for patients was brought about by the increase of substitution rate in hemodiafiltration and enhancing convective mass transfer. The impact of highly convective therapy modes on the state of immunomodulation towards the syndrome of microinflammation has not been investigated in a systematic prospective manner. In this study, 8 patients undergoing bag-HDF treatment with lactate buffered solution were investigated before on-line HDF treatment with commercially available whole blood stimulation assays testing for TNF-alpha and IL-6 release. Both assays are based on phytohemagglutinine (for TNF) and lipo-polysaccharide stimulation (for IL-6). Thereafter the patients were switched to on-line production of substitution fluid. After a wash-out period of 2 sessions the whole blood stimulation assays were applied to the same patients. The Wilcoxon test (for paired analysis) was done, revealing a statistically significant lower release of proinflammtory cytokines from patients' blood upon stimulation with PHA or LPS. The reduction of IL-6 and TNF concentration and release capacity in whole blood may be attributed to the use of high quality ultrapure substitution fluid and dialysate in on-line treatment instead of lactate buffer bag solution. These results indicate that not only an increase of convective mass transfer by higher volume exchange, but also a decrease in unspecific activation of immunocompetent cells may have advantages for HDF-treated patients.

Production of monokines in patients under polysulphone haemodiafiltration is influenced by the ultrafiltration flow rate

BACKGROUND

Chronic haemodialysis patients show various clinical signs of immunodeficiency and there is growing evidence that a dysregulated monocyte cytokine production is heavily involved in this deficiency. The production of monokines in vitro has been proposed to correlate closely with the in vivo immune status and to be of high clinical relevance in cuprophane haemodialysis. Even though it is well known that the biocompatibility of dialyser membranes has a significant impact on immune functions, little is known about the influence of the ultrafiltration flow rate (UFR). The aim of this study was to investigate the potential long-term effects of UFR on the production of interleukin-10 (IL-10), interleukin-1beta (IL-1beta) and interleukin-6 (IL-6) in an intra-individual study design.

METHODS

In 11 patients previously treated with polysulphone haemodiafiltration, UFR was reduced from 40-46 ml/min to 24-28 ml/min, then to 7-10 ml/min before it was reinstated at 40-46 ml/min for periods of 4 weeks each. Monokine secretion into culture supernatants and mRNA expression (assessed using a novel Taqman PCR technique), were determined in a whole blood assay after lipopolysaccharide stimulation.

RESULTS

Reduction of UFR led to a significant increase in IL-10 secretion and mRNA expression (P=0.012, P=0.001). Conversely, a substantial (but not complete) decrease was observed when UFR returned to initial levels. In contrast, supernatant concentrations of IL-1beta (P=0.04) and IL-6 (P=0.003), and mRNA expression of both monokines (P<0.001, P<0.001) decreased significantly when UFR was reduced. Calculation of the IL-1beta/IL-10 ratio also revealed a decrease when UFR was reduced, with an increase again being observed when the initial degree of UFR was reinstated (P<0.001).

CONCLUSIONS

These results indicate a significant impact of UFR on the production of monokines at both the transcriptional and the protein level. We suggest that middle molecule removal has to be considered as a possible pathophysiological mechanism to explain our findings. Since monokine production in vitro was shown to be closely correlated with the in vivo immune status in patients on cuprophane haemodialysis, further investigations are necessary to clarify the impact of UFR on the immunocompetence of patients under polysulphone haemodiafiltration.

Selective sequestration of cytokine-producing monocytes during hemodialysis treatment

Hemodialysis treatment leads to leukocyte activation and cytokine production. Studying this effect has been complicated because cell activation by blood membrane contact also induces adherence factors on leukocytes, leading to margination of cells to the endothelium of the lung. Using single-cell cytokine determination, we studied the relation between cytokine production and cell sequestration during dialysis therapy. Blood was sampled in 11 chronic hemodialysis patients using hemophane dialyzers before hemodialysis and at 20 and 120 minutes of treatment. Lipopolysaccharide (LPS)-induced cytokine production in monocytes was studied by intracellular staining for interleukin-6 (IL-6) and IL-10 and flow cytometry. Results obtained in dialysis patients were compared with samples from an ex vivo dialysis system. Monocyte maturation stage was evaluated by detection of several surface markers through flow cytometry. Within 20 minutes of hemodialysis, the numbers of circulating monocytes decreased to one third of initial values. Before dialysis, 56.7% +/- 15.7% of circulating monocytes responded to LPS by the production of IL-6. This fraction decreased to 21.1% +/- 17.3% (P < 0.001 versus before hemodialysis) at 20 minutes and 32.3% +/- 13.8% (P < 0.001 versus before hemodialysis) at 120 minutes of treatment. A similar decrease occurred for IL-10. Cytokine-positive cells did not decrease during ex vivo dialysis. Surface marker studies showed that mature monocytes expressing HLA-DR or CD86 were predominantly removed. We provide the first evidence for a subtype-specific sequestration of monocytes caused by dialysis treatment. Fully differentiated cells capable of cytokine production and antigen presentation are removed and relatively immature cells remain in circulation.

Impact of dialyzer membrane selection on cellular responses in acute renal failure: a crossover study

BACKGROUND

When acute renal failure (ARF) is severe enough to require dialysis, in-hospital mortality rates approach 60%. These alarming figures have been ascribed in part to advanced age and the high prevalence of comorbid conditions. In the past several years, a number of attempts have been made to investigate the impact of dialyzer membrane type on clinical outcomes. Unfortunately, to date, clinical studies addressing this question have reported conflicting results.

METHODS

This crossover study examined the effect of dialyzer membrane type on cytokine synthesis by peripheral blood mononuclear cells (PBMCs), superoxide release by neutrophils, and apoptosis or programmed cell death of neutrophils in 24 patients with ARF requiring intermittent hemodialysis. The patients were assigned in an alternate order to a low-flux cellulose acetate (CA) or polysulfone (PS) dialyzer. After three consecutive dialysis sessions, patients were crossed over to the second dialyzer for three additional treatments. These cellular responses were measured upon dialyzer assignment and at the third and sixth dialysis session in relationship to the dialyzer type.

RESULTS

The results of the study showed no impact of dialyzer biocompatibility on synthesis of tumor necrosis factor-alpha (TNF-alpha) or interleukin 10 (IL-10) by PBMCs, superoxide release by neutrophils, or neutrophil apoptosis. This held true regardless of the initial dialyzer assignment. Furthermore, there was no correlation between dialysis adequacy (measured by single-pool Kt/V) and postdialysis cellular responses.

CONCLUSIONS

In summary, this study refines the question of biocompatibility by comparing a substituted cellulose rather than unsubstituted cellulose dialyzer to a PS dialyzer in the setting of ARF. The results failed to demonstrate a dialyzer advantage on the selected cellular responses.

Renal replacement therapies

Slow continuous renal replacement therapy is more hemodynamically stabilizing and is replacing conventional hemodialysis as the therapy of choice for acute renal failure in the intensive care unit. This article presents practical information, including basic terminology, basic physiology, technical aspects, and indications for and application of this technique.

Interleukin-1 receptor antagonist synthesis by peripheral blood mononuclear cells in hemodialysis patients

BACKGROUND

Pro-inflammatory cytokines like interleukin (IL)-1 beta and tumor necrosis factor-alpha (TANF-alpha) are believed to play a significant role in dialysis-related morbidity. It has been previously demonstrated that the endogenous synthesis of interleukin-1 receptor antagonist (IL-1Ra) is a reliable marker of the level of IL-1 beta synthesis in hemodialysis (HD) patients. In this study, we assessed the impact of clinical and laboratory variables on IL-1Ra synthesis by peripheral blood mononuclear cells (PBMC) in patients on HD with unsubstituted cellulose dialyzers.

METHODS

IL-1Ra by PBMC was measured by a specific non-cross-reactive radioimmunoassay. Day to day variation in cytokine synthesis, the correlation between cytokine synthesis under different in vitro stimulatory conditions, and the influence of clinical and laboratory variables on cytokine synthesis were studied.

RESULTS

Although there was a trend towards greater IL-1Ra synthesis by unstimulated, endotoxin-stimulated and IgG-stimulated PBMC drawn before the second and third dialysis sessions of the week when compared to the first dialysis treatment, this was not statistically significant. There was a strong correlation between IL-1Ra synthesis by PBMC cultured under different stimulatory conditions that was best observed between IL-1Ra cell content and from endotoxin-stimulated PBMC (r = 0.51, P = 0.0001), and endotoxin- and IgG-stimulated PBMC (r = 0.44, P = 0.0001). In addition, there was a close correlation between total synthesis (cell associated and secreted) and secreted levels of IL-1Ra in unstimulated (r = 0.59, P = 0.0001) and endotoxin-stimulated PBMC (r = 0.69, P = 0.0001). Interestingly, there was an inverse correlation between IL-1Ra synthesis and duration of dialysis that was strongest for secreted IL-1Ra from unstimulated (r = -0.50, P = 0.002) and endotoxin-stimulated PBMC (r = -0.34, P = 0.04). There was no significant correlation between IL-1Ra synthesis by PBMC and other clinical and laboratory indices.

CONCLUSIONS

The observations from this study indicate that: (1) in HD patients, there were no significant differences in cytokine synthesis by PBMC drawn before the three different dialysis treatments during the week; (2) there is a close relationship between IL-1Ra synthesis from PBMC cultured under different stimulatory conditions; (3) the secreted levels of IL-1Ra correlate directly with total synthesis (cell-associated and secreted); (4) with the exception of duration of dialysis, none of the other clinical or laboratory parameters correlated with cytokine synthesis; and (5) the diminished endotoxin- or IgG-stimulated IL-1Ra synthesis with increasing time on dialysis is possibly another sign of the impaired host-defense system in patients on long-term hemodialysis.

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.

Differential Effects of Chondroitin Sulfates A and B on Monocyte and B-Cell Activation: Evidence for B-Cell Activation Via a CD44-Dependent Pathway

At inflammatory sites, proteoglycans are both secreted by activated mononuclear leukocytes and released as a consequence of extracellular matrix degradation. Chondroitin 4-sulfate proteoglycans constitute the predominant ones produced by activated human monocytes/macrophages. In this study, we show that two chondroitin 4-sulfate forms, CSA and CSB, can activate distinct peripheral blood mononuclear cell types. Whereas CSA activates monocytes (to secrete monokines), CSB activates B-cells (to proliferate). In contrast, the chondroitin 6-sulfate CSC and heparin do not exert these functional effects. We further show that CD44 monoclonal antibodies block CSB-induced B-cell proliferation. These findings point to glycosaminoglycans, and specifically chondroitin 4-sulfates, as a novel class of immunological mediators at inflammatory sites. Furthermore, the data link CD44 to B-cell activation, paralleling the established roles of CD44 in T-cell and monocyte activation.

Osmotic agents and buffers in peritoneal dialysis solution: monocyte cytokine release and in vitro cytotoxicity

Peritonitis remains a major problem in peritoneal dialysis. The incidence of peritonitis may be reduced by the use of more "biocompatible" peritoneal dialysis solutions that do not impair local host defense mechanisms, such as occurs with conventional lactate-buffered glucose solutions. In the present study, we investigated the use of bicarbonate and lactate as buffer systems and glucose, amino acids, and glucose polymer as osmotic agents on specific cellular functions of isolated fresh blood monocytes in vitro. The bicarbonate-buffered solutions had a physiologic pH (7.0 to 7.6). Lactate-buffered solutions were tested with a pH between 5.5 and 7.3. RPMI 1640 (Roswell Park Memorial Institute, supplied by Biochrom, Berlin, Germany) and phosphate-buffered saline were used as control mediums. The test solutions were incubated with 200,000 monocytes/mL for 45 minutes followed by a 1:1 mix with RPMI 1640 (with supplements) during a 24- or 4-hour tetrazolium bromide test (MTT test) recovery period. Constitutive and lipopolysaccharide (LPS)-stimulated release of interleukin-1beta (IL-1beta) and IL-6 in the supernatants as parameters of cellular host defense and lactate dehydrogenase concentrations and MTT-formazan production as parameters for cell cytotoxicity were measured. Significantly higher IL-6 and IL-1beta release was found in the bicarbonate-buffered solutions, both under basal conditions and after LPS stimulation, compared with the lactate-buffered solutions (LPS stimulation: 1% amino acids/34 mmol/L bicarbonate, IL-1beta: 1,166 +/- 192 pg/mL; 1.5% glucose/34 mmol/L bicarbonate, IL-1beta: 752 +/- 107 pg/mL; 1.5% glucose/35 mmol/L lactate/pH 5.5, IL-1beta: 174 +/- 51 pg/mL). Some of these differences could even be detected in spent dialysate after a 6-hour dwell in continuous ambulatory peritoneal dialysis patients (n = 10). A lower degree of cellular cytotoxicity (lactate dehydrogenase activity) and better-preserved metabolic activity (MTT test) also were found for the bicarbonate-buffered solutions. Amino acids (1%) proved to be comparable to glucose (1.5%) as an osmotic agent at a neutral pH with regard to LPS-stimulated cytokine release and cytotoxicity. The incubation with a glucose polymer solution (7.5% glucose polymer in phosphate-buffered saline, pH 7.3) resulted in a significantly lowered cytokine release (LPS stimulation: IL-1beta, 69 +/- 19 pg/mL) compared with the other solutions with neutral pH (P < 0.01). These results suggest that bicarbonate as a buffer provided better biocompatibility with regard to mononuclear cytokine release and viability compared with lactate. Amino acids and glucose were equivalent to these parameters at a physiologic pH. The glucose polymer solution, however, was associated with a marked depression of cytokine release.

Plasminogen activator inhibitor-1 activity in chronic renal disease and dialysis

The activity of plasminogen activator inhibitor-1 (PAI-1), an inhibitor of fibrinolysis, is associated with insulin resistance (IR) and the risk of venous and arterial thrombotic cardiovascular disease (CVD) in the general population, and may behave as an acute-phase reactant. PAI-1 activity was measured in 124 patients with chronic renal disease, and its relationship with alterations in metabolic, lipid, and cytokine parameters and the prevalence of CVD complications was explored. Patients with chronic renal disease not requiring dialysis were divided into a low proteinuric ([LP]n = 30) or high proteinuric ([HP]n = 31) group and compared with patients on continuous ambulatory peritoneal dialysis ([CAPD]n = 32) or hemodialysis([HD]n = 31) and with 31 healthy controls. Patients on HD had significantly lower PAI-1 activity than HP, CAPD, and control groups, but no group had significantly higher values than the controls (AU/mL: 7.4 +/- 3.8 HD, 11.2 +/- 8.4 CAPD, 9.4 +/- 5.4 LP, 12.1 +/- 8.0 HP, 11.4 +/- 6.6 controls, P = .04). Interleukin-6 (IL-6), the mediator of the acute-phase response, was determined in a subset of patients and was significantly increased in HD, CAPD, and LP groups compared with the controls (median, pg/mL: 4.6 HD, 4.0 CAPD, 2.9 LP, 2.4 HP, and 1.5 controls, P < .001), but did not correlate with PAI-1. PAI-1 independently correlated with body mass index (BMI), triglycerides, and lipoprotein(a) [Lp(a)] in stepwise regression for all patients. Dividing the whole patient group by tertiles of triglycerides and BMI, increased PAI-1 was confined to the subgroup of patients with both obesity (BMI > 26.7 kg/m2) and hypertriglyceridemia (triglycerides > 2.5 mmol/L). These data suggest that PAI-1 activity in chronic renal disease and dialysis was more strongly associated with the common metabolic abnormalities of obesity and hypertriglyceridemia than with renal disease status, dialysis, or a chronic inflammatory state. This study does not support but does not exclude a major role for increased PAI-1 activity in CVD risk in chronic renal disease.

Immunomodulation of peritoneal macrophages by granulocyte-macrophage colony-stimulating factor in humans

Colony-stimulating factors are growth factors which induce differentiation of the hematopoietic stem cells. Granulocyte-macrophage colony-stimulating factor (GM-CSF) stimulates proliferation and improves functions of neutrophils and monocyte/macrophages. A macrophage submesothelial stratum has been suggested to constitute the first line of peritoneal defense. We have tested whether intraperitoneally administered GM-CSF could increase the number and activation of peritoneal macrophages in peritoneal dialysis patients. Eight stable patients injected 17 micrograms of GM-CSF in each of their four daily CAPD bags over three days. The clinical status, the peritoneal effluent and peripheral blood cell count, membrane receptor expression, phagocytosis activity and cytokine levels were monitored at days 0, 1, 3, 10 and 28. GM-CSF administration caused a large increase in peritoneal macrophage number (89-fold mean increase after 72 hr), returning to baseline seven days after withdrawal. GM-CSF triggered an increase in the expression of CD11b/CD18 (CR3) and its counterreceptor CD54, indicating the cellular progression into a more activated state. Both the number of phagocytic cells (55 +/- 15% to 83 +/- 10%, P < 0.05) and the phagocytic index (137 +/- 29 to 255 +/- 61, P < 0.01) were also augmented. Peritoneal effluent cytokine-chemokine levels demonstrated an increase in IL-6 and MCP-1 levels while TNF-alpha, IL-1, IL-8, MIP-1 alpha and RANTES were not significantly altered. GM-CSF administration did not affect the peritoneal transport of water or solutes. Minor side-effects were registered in two patients. In conclusion, intraperitoneal GM-CSF causes a marked and transient recruitment of primed macrophages into the peritoneum without inducing inflammatory parameters. GM-CSF should improve the peritoneal defensive capacity through potentiation of the effector functions of resident and newly-recruited macrophages.

Longitudinal evaluation of peritoneal macrophage function and activation during CAPD: maturity, cytokine synthesis and arachidonic acid metabolism

The release of cytokines and prostaglandins (PG) by peritoneal macrophages (PM luminal diameter of) may influence the cytokine network controlling peritoneal inflammation and in the long-term the function of the peritoneum as a dialysis membrane. In the present study, an evaluation of the long-term effects of peritoneal dialysis on the release of cytokines and prostaglandins, and the expression of surface markers of cellular maturation on blood and mononuclear cells has been performed in patients during their first year on CAPD. Spontaneous release of tumour necrosis factor alpha (TNF alpha) and interleukins 6 (IL-6) by PM luminal diameter of, after 4 or 24 hours in culture, increased significantly with time on CAPD, while there was a small but significant decrease in release of prostaglandin E2 (PGE2). Production of TNF alpha and IL-6 was enhanced following incubation of the cells with lipopolysaccharide (LPS), but the effect of LPS was proportionally greater on blood monocytes than on PM luminal diameter of. There was a significant increase in the concentrations of PGE2 and 6-keto-prostaglandin F1 alpha in overnight dwell peritoneal dialysis effluent with time on CAPD. The levels of TNF alpha and IL-6 in uninfected PDE were below the detection limit of the immunoassay over the whole time period studied. Expression of CD15, which correlates with immaturity, by PM luminal diameter of and blood monocytes increased with time on CAPD, while expression of CD11c, a marker of maturation, decreased on blood monocytes, but did not change significantly on PM luminal diameter of. There was also a slight increase in expression of transferrin receptor in both PM luminal diameter of and monocytes, but this did not reach statistical significance. These findings suggest that peritoneal macrophages and blood monocytes isolated from CAPD patients over a one year period become increasingly immature with time, and this is accompanied by a significant modulation of their ability to secrete inflammatory cytokines. Dysregulation of macrophage function may have important consequences with respect to inflammatory processes and the long-term function of the peritoneal membrane in CAPD patients.

Influence of dialysis modality on plasma and tissue concentrations of pentosidine in patients with end-stage renal disease

Plasma and tissue concentrations of pentose-derived glycation end-products ("pentosidine") are elevated in diabetic patients with normal renal function and in both diabetic and nondiabetic patients with end-stage renal disease. To determine the influence of dialysis modality and other clinical variables on the accumulation of pentosidine, we used high-performance liquid chromatography to measure this advanced glycation end-product in plasma, skin, and peritoneal samples obtained from 65 hemodialysis and 45 peritoneal dialysis patients. Plasma pentosidine levels were significantly lower in peritoneal dialysis patients. Concentrations of pentosidine in skin were similar in the two groups. In contrast, peritoneal concentrations of pentosidine were significantly higher in the patients maintained on peritoneal dialysis. Our results demonstrate that dialysis modality influences the plasma and tissue distribution of pentosidine. Compared with hemodialysis, peritoneal dialysis is associated with lower levels of this glycation end-product in plasma, but with higher levels in the peritoneum. The mechanisms accounting for lower circulating levels of pentosidine in peritoneal dialysis patients remain to be determined. Higher levels in peritoneal tissues may reflect chronic exposure to the high concentrations of glucose in peritoneal dialysate.

Production of interleukin-6, tumor necrosis factor alpha and interleukin-10 in vitro correlates with the clinical immune defect in chronic hemodialysis patients

In patients with chronic renal failure alterations in monokine production are a common feature. Their clinical relevance has not yet been proven. We show here a correlation between an overproduction of interleukin-(IL)-6 and tumor necrosis factor alpha (TNF alpha) upon stimulation with LPS by mononuclear cells in vitro and the clinical grade of immunodeficiency found in these patients. Higher levels of IL-6 and TNF alpha were correlated with an immunocompromized state, that is, non-responsiveness to hepatitis B vaccination, whereas patients with a better immune competence showed the same levels of these cytokines as healthy controls. Only the patients with a good immune function showed a high secretion of IL-10. The feedback mechanism of IL-10 for reducing monokine synthesis seems to be intact in these patients. Thus the secretion of IL-10 might be regarded as a compensatory mechanism which controls monokine induction by chronic renal failure and hemodialysis treatment. Immunocompromized patients who are unresponsive to hepatitis B vaccination seem to be unable to enhance IL-10 synthesis for control of monokine overproduction. This results in higher levels of IL-6 and TNF alpha that might be involved in the pathogenesis of reduced immune defense.

Elevated levels of interleukin-6 in ascites and serum from women with ovarian hyperstimulation syndrome

OBJECTIVE

To examine the role of pro-inflammatory cytokines in ovarian hyperstimulation syndrome (OHSS).

DESIGN

In vitro laboratory study of serum, peritoneal cells isolated and fluid obtained from ascites removed in the therapeutic management of four patients with OHSS.

SETTING

Tertiary care referral teaching hospital.

PATIENTS

Four patients with OHSS comprised the study population. Five healthy women at the time of elective laparoscopic tubal ligation served as controls. Control serum was also obtained from healthy adult volunteers, and control peritoneal fluid (PF) was obtained from patients on peritoneal dialysis.

INTERVENTIONS

Therapeutic paracentesis was performed on four patients with OHSS.

RESULTS

Peritoneal cells were isolated and fluid obtained from ascites removed in the therapeutic management of the women with OHSS. Peritoneal cells were obtained by intraoperative lavage from the control women. The cells were incubated with various concentrations of Escherichia coli lipopolysaccharide (LPS) for 20 and 48 hours. Interleukin-1 beta (IL-1 beta), tumor necrosis factor (TNF), interleukin-6 (IL-6), and prostaglandin E2 (PGE2) were assayed in the incubation supernatants. The release of the three cytokines and PGE2 in response to LPS by peritoneal cells from women with OHSS was not different from the controls. However, both serum and ascitic fluid from women with OHSS contained significantly greater levels of IL-6 than control serum and PF. No significant differences in TNF levels in serum, ascitic fluid, or PF could be found by ELISA or bioassay.

CONCLUSIONS

Increased production of IL-6, released into the peritoneal cavity and the circulation, may mediate OHSS.