Cuprammonium membranes stimulate interleukin 1 release and arachidonic acid metabolism in monocytes in the absence of complement

Increased Endothelin-1 Mrna Expression in Peripheral Blood Monocytes of Dialysis Patients

Objective

To compare plasma endothelin (ET)-1 level and ET-1 mRNA level in peripheral blood monocytes of patients undergoing hemodialysis (HD) or continuous ambulatory peritoneal dialysis (CAPD).

Design

Endothelin-1 mRNA level in peripheral blood monocytes and plasma ET -1 level were studied in 30 HD patients, 15 CAPD patients, 20 chronic renal failure patients not being dialyzed, and 20 normal healthy controls. Hemodialysis patients were dialyzed three times per week with a bicarbonate dialysate. Different types of dialyzer membrane, viz., cellulose triacetate, cuprophane, poly-sulfone, polyacrylonitrile, and ethylenevinylalcohol were used in 8,6,6,5, and 5 patients, respectively. Continuous ambulatory peritoneal dialysis patients were dialyzed with four daily exchanges of a 2-L dialysate containing glucose at a concentration of 1.5% to 2.5%.

Results

Higher levels of ET -1 mRNA in monocytes were observed in HD patients than in CAPD patients (p < 0.01), chronic renal failure patients (p < 0.01), or normal healthy controls (p < 0.001). The level of ET -1 mRNA in monocytes at the end of HD was not significantly higher than that at the start of HD. ln addition, these mRNA levels in HD patients showed littledifference with different types of dialysis membrane. Plasma ET -1 level in HD patients (10.2 ± 2.4 pg/mL) was also higher than that in CAPD patients (7.8 ± 1.6 pg/mL, p < 0.01), in chronic renal failure patients (4.8 ± 1.2 pg/mL, p < 0.01), or in normal controls (2.6 ± 0.8 pg/mL, p < 0.001).

Conclusion

Dialysis itself did not significantly affect ET -1 mRNA levels in monocytes. Chronic stimulation of peripheral blood monocytes may be associated with higher levels of ET -1 mRNA and plasma ET -1 in HD patients than in CAPD patients.

Biocompatibility of High-Flux Membranes

Standard dialysis with cuprophane membranes is known to stimulate the immune system. As a result of activation of macrophages various interleukins and tumor necrosis factor (TNF) are secreted, presenting further evidence of the poor biocompatibility of cuprophane. We investigated the immunogenic properties of three modern high-flux membranes. Seven patients were studied during hemodiafiltration sessions using either a polysulfone (F60, Fresenius), a polymethylmetacrylate (BK 2.1, Toray) or a cellulose triacetate (FB-210 U, Nipro) dialyzer in a hemodiafiltration procedure. Serial measurements were made during each treatment of interleukin-1β (II-1β), TNF, soluble IL-2 receptor (sII-2r), soluble CD4 (sCD4), soluble CD8 (sCD8), interferon gamma (IFNg) and neopterin. In contrast to the known increase of IL-1β, IL-2r and TNF with cuprophane membranes, none of the modern high-flux dialyzers stimulated the production of these factors. Significant decreases of neopterin and sCD4 were observed. IFNg and sCD8 did not change significantly. Our results suggest that the modern high-flux dialyzers are non-immunogenic, and thus provide further evidence of the superior biocompatibility of synthetic or semisynthetic membranes over the conventional cuprophane.

Oxidative stress and inflammation: Implications in uremia and hemodialysis

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

Bio-incompatibility and Th2 polarization during regular dialysis treatment

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

Some relations among the dialysis membrane, metastatic cells and the immune system

Since results in the literature show that series of patients with kidney cancer on hemodialysis present at the postmortem examination an incidence of metastases significantly lower than such patients not on hemodialysis, the author asks what part of this favorable prognostic result is due to the dialysis membrane and what part is due to the immune system. The part due to the dialysis membrane is with every probability a blockade of metastatic cancer cells. This block, very likely consequent to phenomena of adhesion of cells to the dialysis membrane, allows a selection in that it blocks those cells that have the greatest possibility of adhesion also to the endothelium of capillaries in sites of potential colonization. The immune system would thus have, in the presence of the dialysis membrane, a greater possibility to concentrate its action on residual metastatic cells, even though uremia can have a negative influence on the clinical result. The possibility is discussed that among the various therapies of neoplasms, that for melanoma in particular may benefit from the presence of the dialysis membrane. Melanoma has demonstrated a certain sensitivity to the action of cytokines, in part also due to the presence of receptors for the latter in melanoma cells. However, the early and intense metastatic diffusion worsens the prognosis in the course of the neoplasm, and an eventual blockade, although partial, of metastatic cells could thus lead to a positive clinical result. An increase in cytokines, verified in patients on hemodialysis, does not appear to have any particular affect on the course of the disease. No signs of particular activity of the cytokines most active in an antineoplastic sense or in the sense of immune tolerance have been observed.

Disturbances of acquired immunity in hemodialysis patients

Acquired immunity disturbances in hemodialysis (HD) patients are many and diverse. They are caused by uremia per se, the HD procedure, chronic renal failure complications, and therapeutic interventions for their treatment. Current data suggest that acquired immunity disturbances in HD patients concern mainly the T-lymphocyte and the antigen-presenting cell (APC). The T-lymphocyte-dependent immune response is deficient, predisposing to infections and inadequate response to vaccinations. In addition, APCs are preactivated, which seems to be responsible for the malnutrition-inflammation-atherosclerosis syndrome, and also affects T-lymphocyte function. At the molecular level it is assumed that the interaction between the APC and the T-lymphocyte is impaired. This disturbance is likely to concern the signal that results from the interaction between the major histocompatibility complex:peptide complex on APC surfaces and T-cell receptors on T-lymphocyte surfaces, or the signal that results from the interaction among the co-receptors of these two cells. The aim of the present review was to collect and classify the available clinical and experimental data in this area. Although many pieces are still missing from the puzzle, a better understanding of the responsible molecular mechanisms, will potentially lead to increased survival and a better quality of life in HD patients.

Impairment of innate cellular response to in vitro stimuli in patients on continuous ambulatory peritoneal dialysis

BACKGROUND

Most crucial in the initial stages of host defence against invading micro-organisms is innate immunity, in which peripheral mononuclear cells, in particular cytokines, are pivotal. Mortality from infections is high in dialysis patients, but it remains unclear if this arises from the ineffectiveness of innate immune mechanisms.

METHODS

In 20 haemodialysis (HD) patients, 20 patients on continuous ambulatory peritoneal dialysis (CAPD), and 15 age-matched controls, we studied cytokine production by monocytes and helper T-cells in response to in vitro stimuli. The most important early-response cytokines for innate immunity, tumour necrosis factor (TNF)-alpha and interleukin (IL)-1beta, were tested in monocytes, and interferon-gamma and IL-4 were studied as indicators of polarization of helper T-cells into type 1 and type 2 cells. Peripheral blood cells stimulated with lipopolysaccharide or mitogen were labelled with anti-CD14+ and -CD4+ antibodies and then subjected to intracellular cytokine staining and flow cytometry.

RESULTS

CAPD patients showed significantly reduced synthesis of TNF-alpha and IL-1beta and inhibited T helper phenotype development compared with HD patients and control subjects. In contrast, HD patients showed an unaltered monokine response and a marked polarization of helper T-cells towards the type 1 phenotype. We also found that a single HD treatment potentiated monocytes to synthesize TNF-alpha.

CONCLUSIONS

Circulating immune cells in CAPD patients may be hyporeactive against infections, indicating an unfavourable innate host defence.

Complement inhibition reduces material-induced leukocyte activation with PEG modified polystyrene beads (Tentagel™) but not polystyrene beads

With isolated leukocytes, inhibiting complement reduced material-induced leukocyte activation (CD11b) with polyethylene glycol modified polystyrene beads (PS-PEG), but not with polystyrene beads (PS). The PS-PEG beads (TentaGel) were complement activating as measured by SC5b-9 levels consistent with the sensitivity of these beads to leukocyte inhibition with complement inhibitors. Following contact with PS and PS-PEG beads, isolated leukocytes in plasma and in the absence in platelets were found to significantly upregulate CD11b, while TF expression and exposure of phosphatidylserine remained at background levels. Complement inhibition by means of sCR1 partially reduced CD11b upregulation on PS-PEG beads, but had no effect with PS beads. Pyridoxal-5-phosphate (P5P) was able to significantly reduce both CD11b upregulation and exposure of phosphatidylserine with PS-PEG beads, although it did not appear to inhibit SC5b-9 production. Pentamidine and NAAGA inhibited complement and were effective in reducing CD11b upregulation with both PS and PS-PEG. However, they also had an inhibitory effect on leukocyte signaling mechanisms, precluding their utility for further study in this context. Leukocyte adhesion occurred to similar extents on both PS and PS-PEG beads. While sCR1 and P5P blocked adhesion and activation (for adherent leukocytes) on PS-PEG beads, they had no effect on leukocytes adherent to PS beads. The role of complement in leukocyte activation and adhesion was found to be material-dependent. Thus, leukocyte-material compatibility may be resolved by complement inhibition in some but not all cases. For these other materials (example here was PS), other mechanisms, such as fibrinogen adsorption and direct leukocyte release, may need exploitation to minimize leukocyte activation and adhesion.

Serum Growth Factors in Hemodialyzed Patients

The contact of chronic hemodialysis patients' blood with components of extracorporeal circulation leads to mobilization of several systemic reactions. The purpose of this study was to determine the activity of transforming growth factor (TGF-beta1) and platelet derived growth factor (PDGF) in serum of patients on long-term hemodialysis program and to compare these results with ones obtained in healthy volunteers. Twenty-five patients on dialysis carried out on polysulfone membrane dialyzer, and 16 patients on dialysis with the used of cuprophan membrane dialyzer on long-term hemodialysis program participated in the study. TGF-beta1 level in serum of healthy volunteers (12.06 +/- 7.56 ng/mL) was lower than in serum of patients dialyzed on polysulfone membrane dialyzers (26.56 +/- 14.83 ng/mL). Differences in PDGF concentrations in serum of control group and hemodialyzed patients were not statistically significant. The strong correlation between TGF-beta1 and PDGF in serum of both studied groups of patients was demonstrated.

Is steam sterilization really making any difference in dialysis-induced cytokine release?

Ethylene oxide (ETO) is presently the most commonly used sterilization method for medical devices. Although alternative sterilization modes such as steam sterilization have been suggested, the effect of steam on dialysis-induced cytokine release is unknown. We enrolled 9 patients on chronic hemodialysis and evaluated at different intervals IL-1beta production while treated with ETO (NC 1785-Bellco) and steam sterilized NC 1785S-Bellco) Synthetically Modified Cellulose (SMC). A basal test during treatment with NC 1785 was performed (A); the same test was set up 4 weeks after treatment with NC 1785S (B) and, lastly, 4 weeks after returning to NC 1785 (C). Peripheral blood mononuclear cells (PBMC) were purified before and after the dialysis session, were isolated on a Ficoll/Hypaque gradient and incubated for 24 h. Spontaneous IL-1beta release was evaluated in the supernatant and in the lysate. In A, IL-1beta levels were (in pg/ml/10(6) cells, in supematant and lysate, respectively): 5.8 +/- 4.8 and 7.6+/-5.2 in pre-HD and 4.68 +/- 3.6 and 9.7 +/- 6.65 in post-HD. These levels showed a clear reduction in B: 2.5 +/- 2.2 and 4.4 +/- 3.1 in pre-HD, and 4.35+/- 6.6 and 7.52 +/- 7.22 in post-HD. In the C test, 4 weeks after the return to the ETO membrane, IL-1beta levels remained unchanged: 2.9 +/- 1.8 and 4.5 +/- 3.1 in pre-HD; and 2.6 +/- 3 and 5.7 +/- 6.6 in post-HD. Statistical analysis showed significant changes in the pre-HD levels both in supematant (p < 0.04) and in lysate (p < 0.04). Steam sterilization of SMC induced a lower spontaneous IL-1beta release, but this effect was not statistically significant due to the large inter-individual variation. Hence, contrary to claims of better biocompatibility, steam sterilization does not result in a reduced production of pro-inflammatory IL-1beta.

Strong depletion of CD14(+)CD16(+) monocytes during haemodialysis treatment

BACKGROUND

The immune defect in haemodialysis (HD) patients is associated with a monocytic dysfunction, including an increased production of proinflammatory cytokines. Monocytes fall into subpopulations comprising CD14(++)CD16(-) and CD14(+)CD16(+) cells. Circulating numbers of the latter can rapidly increase during infectious episodes and inflammation.

METHODS

We determined the amount of CD14(+)CD16(+) monocytes in HD patients and characterized their fate during HD treatment. In 34 HD patients and 17 healthy controls, the distinct cell populations were determined by differential blood counts and flow cytometry. Cells from 14 HD patients were analysed at the start, 10, 30 and 120 min thereafter, and at the end of HD treatment.

RESULTS

Before HD, patients show a monocytosis with a strongly increased CD14(+)CD16(+) subpopulation. Early during HD treatment, circulating leukocyte numbers decrease, with monocytes being most profoundly influenced. Interestingly, among them, sequestration is most pronounced in the CD14(+) CD16(+) subpopulation. After 30 min, approximately 83+/-9% of CD14(+)CD16(+) cells are removed from circulation. This sequestration does not differ between patients treated with polyamide or haemophan membranes. The sequestration is a short-lived temporary effect and cell numbers are replenished within 120 min of treatment for the entire monocyte population. Beyond that time point, cellular activation by the dialyser membrane becomes visible. Reappearence kinetics of CD14(+)CD16(+) monocytes is slower; however, initial numbers are reached by the end of treatment.

CONCLUSION

Haemodiaysis leads to temporary removal of monocytes from the bloodstream followed by the reappearance of activated cells. This might contribute to the state of chronic microinflammation, which is reflected by high levels of CD14(+)CD16(+) monocytes.

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

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

Complement components as uremic toxins and their potential role as mediators of microinflammation

Cardiovascular disease is the major cause of death in end-stage renal disease (ESRD) patients. There is growing evidence that atherogenesis is an inflammatory rather than a purely degenerative process leading to a state of microinflammation. This raises the issue of whether treatment modalities of ESRD contribute to the microinflammatory state. One potential candidate in this context is the complement system. Here we consider three potential pathways linking complement activation to progression of atherosclerosis: (1) complement activation on artificial surfaces depends on their physicochemical characteristics, the effect of which is amplified because of the accumulation of complement factor D; (2) the exposure of ESRD patients to endotoxin creates a microinflammatory state, and this may amplify complement-induced damage; exposure to endotoxin may result from frequent infections because of the impairment of host-defense mechanisms or from transfer of bacterial contaminants across dialysis membranes into the blood stream; and (3) direct transduction of proinflammatory signals from blood-material interactions to the vascular system. We conclude that the complement system is an important candidate system in the genesis of microinflammation and accelerated atherogenesis in ESRD. We advance the hypothesis that the generation of proinflammatory signals, in which the complement system appears to be involved--both through systemic and local activation--plays a role in the development of late complications of uremia, including coronary heart disease. This hypothesis provides a rationale to maximize the biocompatibility of the dialysis procedure, that is, selection of nonactivating materials, use of ultrapure dialysis fluid, and--still theoretical--high-flux dialysis to remove factor D.

T-cell activation follows Th1 rather than Th2 pattern in haemodialysis patients

BACKGROUND

Patients on chronic intermittent haemodialysis (HD) show an impaired cellular and humoral immune response that clinically appears with frequent infectious complications and low vaccination responses. This immune defect strongly correlates with reduced in vitro proliferative responses of T cells. The defect is localized in antigen presenting cells, which show a decreased co-stimulatory activity. Furthermore, the impaired immune response correlates with an increased production of pro-inflammatory cytokines. In response to primary activation, CD4 positive T helper (Th) cells mainly differentiate into either Th1 or Th2 cells. Th1 cells support cell mediated immunity whereas Th2 cells enhance humoral immune responses. Since both types of responses mutually inhibit each other, the impaired humoral immune response seen in HD patients could either be due to a reduced number of Th2 cells or to a predominant Th1 response.

METHODS

We analysed the Th cell profile in HD patients using flow cytometry. Monocytic cytokine expression was analysed using both flow cytometry and enzyme linked immunoadsorbant assays.

RESULTS

Our data demonstrate that the cytokine differentiation profile in circulating T cells from HD patients is dysregulated and characterized by an increase in Th1 cells, but a normal amount of Th2 cells. Moreover, the skewed helper cell responses correlate with a higher percentage of monocytes capable of secreting the Th1 promoting cytokine interleukin 12 (IL-12).

CONCLUSIONS

Our findings contribute to a better understanding of the pathogenesis of impaired cellular immune functions in dialysis patients and, in particular, the decreased antibody production after vaccination. They provide a link between overproduction of pro-inflammatory cytokines (IL-12) and imbalanced T-cell activation.

Clinical relevance of cytokine production in hemodialysis

Blood-dialyzer interaction in hemodialysis has the potential to activate mononuclear cells leading to the production of inflammatory cytokines. The extent of activation is dependent on the dialyzer material used and is considered an index of biocompatibility. Cytokines, such as interleukin-1 beta (IL-1 beta), tumor necrosis factor-alpha (TNF-alpha), and IL-6, may induce an inflammatory state and are believed to play a significant role in dialysis-related morbidity. The interleukin hypothesis suggests that the release of proinflammatory cytokines acts as an underlying pathophysiologic event in hemodialysis-related acute manifestations, such as fever and hypotension. Nevertheless, a cytokine overproduction may alter sleep pattern in chronic hemodialyzed patients, thus explaining the presence of sleep disorders in these patients. A potential role of cytokines in chronic-related morbidity has also been suggested. High levels of some inflammatory cytokines are often associated with anemia caused by hyporesponsiveness to erythropoietin. Cytokine production may also play a relevant role in bone remodeling by regulating osteoblast/osteoclast cell functions and parathyroid hormone (PTH). Finally, cytokine release may have a long-term deleterious effect on mortality of uremic patients by altering immune response and increasing susceptibility to infections. Bioincompatibility of dialytic membranes may also contribute to malnutrition in dialysis patients by increasing the monocyte release of catabolic cytokines such as TNF-alpha and IL-6. Bioincompatible dialytic treatment may induce an inappropriate monocyte activation and cytokine production, which, in turn, may mediate some of the immune and metabolic dysfunction associated with hemodialysis. The use of biocompatible dialytic membranes appears to reduce the monocyte activation and to improve the survival of hemodialysis patients.

Initiation of hemodialysis treatment leads to improvement of T-cell activation in patients with end-stage renal disease

Patients with chronic renal failure show an immunodeficiency characterized by frequent infectious complications and a low response to vaccinations. This is paralleled in vitro by a low T-cell proliferation on mitogenic stimuli because of an impaired costimulation by accessory cells. Furthermore, alterations of the cytokine profile are correlated with impaired immune function. The immune system is influenced by both uremia and renal replacement therapy. To evaluate the influence of hemodialysis on immune parameters, we studied patients before and after the initiation of chronic hemodialysis therapy. Fourteen patients with end-stage renal failure were tested before dialysis initiation and during the first 6 weeks of hemodialysis treatment. We determined the in vitro T-cell proliferation, as well as plasma levels of interleukin-6 (IL-6) and the release of IL-6 and IL-10 into culture supernatant poststimulation with lipopolysaccharide. After 6 weeks of intermittent hemodialysis, in vitro T-cell proliferation on stimulation improved significantly (stimulation index, 21.6 +/- 18.5 versus 58.1 +/- 45.5; P < 0.01). This improvement occurred regardless of whether synthetic dialyzers or cellulosic membranes were used for the initiation of dialysis. Plasma IL-6 levels, as well as IL-6 and IL-10 secretion, did not change during the study period. In patients with end-stage renal disease, the initiation of hemodialysis led to a significant improvement of in vitro T-cell proliferation. This effect may have a role for an improvement of immune function in vivo. The expected normalization of IL-6 and IL-10 production may be masked by cytokine induction through hemodialysis membranes.

Whole blood production of monocytic cytokines (IL-1beta, IL-6, TNF-alpha, sIL-6R, IL-1Ra) in haemodialysed patients

BACKGROUND

The production of monocytic cytokines by isolated mononuclear cells after stimulation by phytohaemagglutinin (PHA) and lipopolysaccharide (LPS) is generally increased in haemodialysed (HD) patients. We performed whole blood (WB) cultures to evaluate cytokine production by blood cells inside their complex cellular and humoral network.

METHODS

Diluted whole blood from HD patients (collected before dialysis) and controls was cultured alone with PHA (2.5 microg/ml) or LPS (1 and 3 microg/ml). Supernatants were collected after 24 and 48 h of culture, and concentrations of IL-1 beta, IL-6, TNF-alpha, sIL-6R and IL-1Ra were determined by ELISA.

RESULTS

The low spontaneous production of IL-1beta, IL-6 and TNF-alpha in both patients and controls was not significantly modified by PHA. The lower dose of LPS (1 microg/ml) induced a significant but lower increase in production of IL-1beta, IL-6 and TNF-alpha in patients than in controls. In contrast, while it did not further increase their production in controls, the higher concentration of LPS (3 microg/ml) still increased their production in patients to the same level than in controls. The plasma concentrations of sIL-6R were higher in patients than in controls. In both groups, the sIL-6R concentration did not vary during the culture period whether the cells were stimulated or not with LPS or PHA. This suggests that the increased plasma levels of sIL-6R were not produced by blood cells. Despite a similar significant LPS and PHA induced production of IL-1Ra, the IL-1Ra/IL-1beta ratio was always higher in patients than in controls.

CONCLUSION

Monocytes from HD patients in WB cultures are hyporesponsive to PHA and LPS for their IL-1beta, TNFalpha and IL-6 production in contrast to isolated monocytes that demonstrate signs of activation. If it reflects the in vivo situation it could partly explain the immune defect in uraemic and haemodialysed patients. Higher sIL-6R/IL-6 and IL-1Ra/IL-1beta ratios could also participate to the complex immune disturbances of HD patients by reducing the biological activity of two cytokines playing a major role in the immune and inflammatory network.

Novel C5-dependent mechanism of neutrophil stimulation by bioincompatible dialyzer membranes

The objective of the study was to evaluate the contribution of reactive oxygen intermediate formation for receptor modulation on neutrophils by the cellulosic dialyzer membrane cuprophan (CU). In patients dialyzed with CU, CD11b and CD66b upregulation on neutrophils (by 104.3 +/- 37.9% and 85.7 +/- 31.1%, respectively), and a downregulation of L-selectin (by 44.9 +/- 26.9%) was seen, whereas expression of CD11a remained unaltered. Hemodialysis with polysulfone did not bring about major changes in surface receptor expression. In vitro incubation of isolated neutrophils in the presence of serum with hollow fibers of CU or polysulfone showed similar results: Only CU resulted in upregulation of CD11b and CD66b expression (by 65.5 +/- 18.7% and 60.1 +/- 24%) and a decrease in CD62L expression (by 60.6 +/- 18.2%). In contrast to receptor alterations, generation of reactive oxygen intermediate by CU occurred in the absence of serum. Inhibition experiments with soluble complement receptor 1, which produced only partial inhibition of receptor up-/down-regulation, indicated the existence of also other than alternate complement-dependent mechanisms for neutrophil activation. By using C5-depleted serum instead of normal human serum, up-/down-regulation of CD11b, CD62L, and CD66b by CU was dramatically reduced, whereas C3-depleted serum did not produce that effect. C5-deficient serum repleted with purified C5, as well as purified C5 alone, was able to induce receptor modulation by CU comparable to normal human serum. L-Methionine, a specific inhibitor for the oxidative activation of C5, blocked the modulatory effect of CU in assays with purified C5 as well as with serum. As a result, in addition to the alternative pathway of complement, a C5-dependent mechanism probably activated by neutrophil-derived reactive oxygen intermediate leads to receptor modulation and subsequent generation of the well known side effects of bioincompatible dialyzer membranes.

Calcium channel blockers correct in vitro mitochondrial toxicity of cellulose acetate

We studied the action of rinse solutions from cellulose acetate hemodialyzers on isolated mitochondria. We showed that concentrates from the rinses impaired the adenosine 5'-triphosphate (ATP) synthesis as reflected by the decrease in respiration during state 3 and in P/O ratio. This impairment results from a calcium release from mitochondria that is induced by rinse solution concentrates. The release, triggering the mitochondrial calcium carrier, would explain the decrease in ATP synthesis. Moreover, rinse solution concentrates hinder mitochondrial calcium storage. The rise in cytosolic calcium in hemodialyzed patients may be related, at least in part, to these findings, since a lack of ATP impairs the ATP-dependent cellular calcium-extrusion pumps. We also showed that calcium channel blockers, at therapeutically relevant doses, restore ATP synthesis and calcium storage in mitochondria impaired by rinse solution concentrates. Finally, these in vitro results were confirmed by experiments on cells in culture proving that Diltiazem counteracts the cytotoxicity of rinse solution concentrates. These findings are consistent with observations that these drugs suppress the increase in leukocyte cytosolic calcium in dialyzed patients. Moreover, this would help explain the efficiency of calcium channel blockers in cells without L-calcium channels.

Exposure of blood to biomaterial surfaces liberates substances that activate polymorphonuclear granulocytes

Human whole blood, anticoagulated or not, was exposed to hydrophilic glass surfaces or methylated hydrophobic glass surfaces under saline cover. Platelet-poor plasma or serum was prepared after 10 minutes of exposure, measured in respect to complement activation, and transferred to a suspension of granulocytes, which acted as bioprobes. The granulocytes were prepared from blood, anticoagulated with ethylenediaminetetraacetic acid, and evaluated regarding intracellular Ca2+ concentration (Calcium Green-1 fluorescence), integrin expression (CD-11b immunohistochemistry), respiratory burst (chemiluminescence), and priming (increase in N-formyl-methionyl-leucyl-phenylalanine-induced respiratory burst). The results indicate that humoral factors formed during the surface exposure of blood were able to activate the probe granulocytes. The exposure to hydrophilic surfaces led to a calcium transient three times the magnitude of that of hydrophobic surfaces. This response could be blocked by the presence of heparin during the blood-surface exposure but was not affected by the addition of heparin to the probe granulocytes. Hirudin, a specific thrombin blocker, had no effect. The exposure to hydrophobic surfaces led to complement activation in serum that induced priming and respiratory burst of the probe granulocytes. In conclusion, the study provides evidence that hydrophilic-hydrophobic surface treatment significantly affects the immediate inflammatory response of a blood-biomaterial interaction that is moderated by the presence of heparin.

Macrophage colony stimulating factor involvement in uremic patients

The immunodeficiency of patients with chronic renal failure (CRF) is related to multiple and complex alterations of the cytokine network and of its target cells such as T or B lymphocytes, monocytes, fibroblasts or endothelial cells. Chronic activation of monocytic functions is recognized as a key factor in these immunological disorders. Since macrophage colony stimulating factor (M-CSF) is essential for the activation of several functions of monocytes and macrophages and their production of cytokines such as interleukin-1, interleukin-6, and tumor necrosis factor alpha, we investigated its involvement in patients with CRF. When measured by ELISA, M-CSF serum levels were significantly higher in patients with progressive CRF and those on hemodialysis (HD) and continuous ambulatory peritoneal dialysis (CAPD) than in controls. M-CSF serum levels did not correlate with the degree of renal insufficiency and were probably related to complex alterations in its production and/or degradation by the specific M-CSF receptors of macrophages. In HD patients the M-CSF serum concentrations inversely correlated with the number of circulating lymphocytes and were significantly higher in anemic patients requiring treatment with erythropoietin. Our results suggest that M-CSF may play a role in altering the immune system in uremic patients by maintaining in the circulation and tissues permanently primed monocytes and/or macrophages that can then be triggered to an activated state by secondary stimuli such as endotoxins, complement components, other cytokines or contact with foreign surfaces.

L-fucose residues on cellulose-based dialysis membranes: quantification of membrane-associated L-fucose and analysis of specific lectin binding

Contact of mononuclear human leukocytes with cellulose dialysis membranes may result in complement-independent cell activation, i.e. enhanced synthesis of cytokines, prostaglandins and an increase in beta 2-micro-globulin synthesis. Cellular contact activation is specifically inhibited by the monosaccharide L-fucose suggesting that dialysis membrane associated L-fucose residues are involved in leukocyte activation. In this study we have detected and quantitated L-fucose on commercially-available cellulose dialysis membranes using two approaches. A sensitive enzymatic fluorescence assay detected L-fucose after acid hydrolysis of flat sheet membranes. Values ranged from 79.3 +/- 3.6 to 90.2 +/- 5.0 pmol cm-2 for Hemophan or Cuprophan respectively. Enzymatic cleavage of terminal alpha-L-fucopyranoses with alpha-L-fucosidase yielded 7.7 +/- 3.3 pmol L-fucose per cm2 for Cuprophan. Enzymatic hydrolysis of the synthetic polymer membranes AN-69 and PC-PE did not yield detectable amounts of L-fucose. In a second approach, binding of the fucose specific lectins of Lotus tetragonolobus and Ulex europaeus (UEAI) demonstrated the presence of biologically accessible L-fucose on the surface of cellulose membranes. Specific binding was observed with Cuprophan, and up to 2.6 +/- 0.3 pmol L-fucose per cm2 was calculated to be present from Langmuir-type adsorption isotherms. The data presented are in line with the hypothesis that surface-associated L-fucose residues on cellulose dialysis membranes participate in leukocyte contact activation.

Influence of hemodialysis membranes on gene expression and plasma levels of interleukin-1 beta

Plasma levels of interleukin-1 beta (IL-1 beta) were measured in 10 normal subjects, in 11 nondialyzed end-stage renal failure (ESRD) patients, and in 22 hemodialysis (HD) patients. Of the HD patients, 7 were dialyzed with Cuprophan (CU), 7 with polymethylmethacrylate (PMMA), and 8 with polysulphone (PS) dialyzers. In normal controls, nondialyzed ESRD patients, and HD equipped with CU, PAMM, and PS dialyzers, plasma levels of IL-1 beta were 10.73 +/- 5.24 pg/ml, 9.97 +/- 3.61 pg/ml, 13.17 +/- 4.04 pg/ml, 15.16 +/- 6.16 pg/ml, and 13.96 +/- 5.47 pg/ml, respectively. There were no statistically significant differences among the groups (p > or = 0.05). In contrast, the gene expression of IL-1 beta for peripheral blood mononuclear cells (PBMC) by in situ hybridization showed differences among the groups. The gene for IL-1 beta for PBMC appears in HD equipped with different membranes, but not in cases of nondialyzed uremic patients and normal subjects. With computer imaging analysis, we carried out quantitative analysis of cells in in situ hybridization with an area of positive spots to an area of total cells. In HD with CU, PMMA, and PS, the results were 10.64 +/- 1.07, 3.34 +/- 0.74, and 3.27 +/- 0.64%, respectively. The levels of IL-1 beta gene expression in CU were higher than that in PMMA or PS. There were statistically significant differences (p < or = 0.001) between CU and PMMA or PS and no significant difference between the PMMA and PS (p > or = 0.05). We suggest measuring the gene expression of cytokines for PBMC and which may be better than measuring cytokine levels only for investigating the blood compatibility of dialyzers, which may help in understanding chronic complications of the dialysis procedure.

Cytokine induction during cardiac surgery: analysis of TNF-alpha expression pre- and postcardiopulmonary bypass

Cytokines are soluble mediators that possess both intra- and intercellular signaling properties. Their function has been investigated most thoroughly in the context of immune reactions. Cytokines, however, form an important component of the inflammatory response to trauma and are found in elevated concentrations following cardiopulmonary bypass (CPB). We were, therefore, interested in studying mRNA expression for the cytokine tumor necrosis factor alpha (TNF-alpha) in patients undergoing cardiac surgery. White cells isolated from the circulation of seven patients before and after CPB were assayed for the expression of mRNA with TNF-alpha specific primers using the polymerase chain reaction. Message for TNF-alpha was found in all patients, with the highest values demonstrated in patients whose CPB times exceeded 1 1/2 hours. Enhanced message expression was seen as early as 1 hour after the start of CPB. Genes responsible for cytokine (TNF-alpha) expression and production are activated during cardiac surgery.

Why are dialysis patients malnourished?

There are multiple causes of protein-energy malnutrition in maintenance dialysis patients. The requirements of protein in dialysis patients are higher than in healthy individuals, and the intake of protein and energy in relation to the requirements is frequently low. Anorexia may be caused by uremia and underdialysis. There is experimental evidence that dialyzable uremic toxins accumulate in renal failure and suppress the appetite. In addition there are several psychosocial and comorbidity factors that may hamper adequate nutrition. There are also several factors in dialysis patients that may enhance protein catabolism and increase protein requirements, such as low energy intake, metabolic acidosis, dialytic loss of glucose, protein and amino acids and other catabolic effects of the dialytic procedures, as well as effects of infections and other comorbidity factors. The relative importance of the various factors that cause anorexia and stimulate protein catabolism is still not well understood.

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.

Reactive oxygen product formation by human neutrophils as an early marker for biocompatibility of dialysis membranes

Production of reactive oxygen intermediates (ROI) by neutrophils (PMN) in vivo was examined by a whole blood assay using dichlorofluorescein-diacetate (DCFH-DA) in 10 patients each dialysed consecutively with two different dialyser membranes. Haemodialysis (HD) with cuprophan membrane (CM) led to a significantly (P < 0.001) more pronounced ROI production by PMN (2.4 +/- 0.5-fold increase in intracellular oxidation of DCFH-DA) compared with HD with polysulfone membranes (PM; 1.5 +/- 0.2-fold). HD with CM induced a decrease in PMN count by about 90%, whereas PM induced a decrease by only 25% (P < 0.001). In CM patients maximal ROI production coincided with the nadir in PMN count. All patients dialysed with CM showed a clear increase in serum levels of Bb fragments, whereas PM-dialysed patients did not. In this respect, however, no clear time relationship was seen to the kinetics of ROI production, nor to the disappearance of neutrophils from the circulation. Evaluating a direct effect of the dialysis membranes on PMN demonstrated that incubation of neutrophils with hollow fibres of the CM but not of the PM in the absence of plasma induces significant ROI production by PMN. Our study thus indicates that ROI production by PMN during HD correlates to membrane biocompatibility. Furthermore, one might speculate that also independently from but perhaps in addition to complement activation, reactive oxygen products are critically involved in the generation of haemodialysis-associated neutrophil emigration.

Effect of dialyser membranes on extracellular and intracellular granulocyte and monocyte activation in ex vivo pyrogen-free conditions

This study examined effects of blood-contacting materials on the monocyte reaction following the first contact of human blood with hollow fibre dialyser membranes under pyrogen-free conditions. Membrane materials were the unchanged regenerated cellulose, the synthetic polysulphone (PS), a positively charged diethylaminoethyl cellulose (DEAE-C), the negatively charged carboxymethyl cellulose (CMC) and acrylonitrile copolymer (AN). The experimental system involved perfusion with human fresh venous blood through different modules containing the materials in the form of hollow fibre membranes. Extracellular and intracellular aspects of blood reactions after the first contact with the materials were investigated in Ficoll-separated granulocytes and peripheral blood mononuclear cells. Investigations were done by release reactions of platelet activating factor (PAF), oxygen radical (O2-), leukotriene B4, prostaglandin E2 (PGE2) and cytokines (IL-1 beta, TNF-alpha, IL-6). The intracellular activation of peripheral blood mononuclear cells was done by mRNA transcription of IL-1 beta, TNF-alpha, IL-6, IL-8 and beta 2-microglobulin (beta 2-MG). From the set of parameters, release reactions were only measurable for PAF, PGE2 and O2- if a second stimulus (phorbol myristate acetate, lipopolysaccharide, zymosan and calcium ionophore) was used after blood-membrane interaction. Although the extent of the release reaction was weak, negatively charged membranes were, in general, more active. All dialysers exhibited the same increase in beta 2-MG mRNA transcription, suggesting that all blood-contacting membranes initiate the gene expression of beta 2-MG at the same level. TNF-alpha, IL-6, IL-1 beta and IL-8 mRNAs were demonstrated in the AN and CMC membranes rather than the other materials, which exhibit a lower transcription than the tubing set. As has been found, an enhanced generation of PGE2 for both CMC and AN membranes supports, therefore, the concept of an effect of the negative charges of the materials in the gene expression of cytokines. However, this initiation does not lead to the generation of cytokines, even after stimulation with pyrogens.

Cuprophane but not synthetic membrane induces increases in serum tumor necrosis factor-alpha levels during hemodialysis

Cytokine synthesis and secretion by blood mononuclear cells is a well-documented phenomenon in hemodialyzed patients. The present study was conducted in 17 chronically hemodialyzed patients to test the relative effect of uremic toxicity, membrane biocompatibility, dialysate composition, and the risk of endotoxinemia on the serum level of tumor necrosis factor-alpha (TNF-alpha). The only significant parameter that influenced circulating TNF-alpha was the chemical characteristics of the dialyzer membrane. Tumor necrosis factor-alpha levels significantly increased during the session with cuprophane, whereas they decreased with AN69. The TNF-alpha increase was documented whatever the dialysate buffer and the presence or absence (negative Limulus amoebocyte lysate test) of endotoxin in the dialysate. In the subgroup of patients treated with a contaminated dialysate and AN69, none had clinical symptoms and the central body temperature remained constant throughout the session. In these patients, serum TNF-alpha levels did not change after priming the dialyzer with sterile saline. In conclusion, the serum TNF-alpha level during hemodialysis appears to be modulated by biocompatibility, permeability, and binding properties of dialysis membrane rather than dialysate composition. Endotoxin in the dialysate did not result in positive TNF-alpha balance no matter what its possible priming effect on mononucleated blood cells.

Stimulation of mononuclear cells by contact with cuprophan membranes: further increase of beta 2-microglobulin synthesis by activated late complement components

Contact of mononuclear cells (MNC) with cuprophan membranes in vitro causes an increase in beta 2-microglobulin (beta 2m) synthesis. Since in vivo the dialyzer membrane is rapidly coated with plasma proteins, contact activation of MNC was tested in the presence of normal human serum (NHS). After contact with cuprophan, deposition of C5b-9 on the cells was seen, followed by an increase in beta 2m synthesis and cytokine release, exceeding that seen after contact activation in the absence of serum. Inactivated serum or serum deficient in C8 did not increase beta 2m production, indicating that the additional activation was due to complement C5b-9. The results suggest that there are two cuprophan-related mechanisms of cell activation: one by contact of cells with the membrane, the other by the complement activation products. Both might synergistically contribute to an increased beta 2m synthesis in hemodialysis patients.

Gene expression of interleukin-1 beta during hemodialysis

It is still controversial whether the hemodialysis (HD) procedure is an inflammatory process in vivo. Therefore, we studied the gene expression of interleukin-1 beta (IL-1 beta) as a marker of inflammation in peripheral blood mononuclear cells (PBMC) of patients during HD by Northern blotting and polymerase chain reaction. Compared to PBMC separated pre-HD (1.0 densitometric units), the amount of IL-1 beta mRNA was increased in PBMC leaving the dialyzer (12.2 +/- 2 densitometric units, P < 0.01), but was not increased in PBMC re-entering the dialyzer from the systemic circulation (0.6 +/- 0.1 densitometric units) in all 12 patients studied. The maximal amount of IL-1 beta mRNA in PBMC was seen at five minutes after start of HD. There was a significant correlation between the increase in IL-1 beta mRNA and the increase in activated complement C5a (r = 0.71, P < 0.01). HD using less complement-activating membranes (hemophan, polysulfone, polyamide or polyacrylonitrile) resulted in no detectable IL-1 beta mRNA. Furthermore, a monoclonal antibody against human C5a reduced the increase in IL-1 beta mRNA by 83% (P < 0.05), indicating that C5a plays a major role for induction of IL-1 beta mRNA during HD. This study demonstrates that during HD with regenerated cellulose, gene expression for IL-1 beta takes place in PBMC.

Beta2 integrins are required for neutrophil degranulation induced by hemodialysis membranes

An untoward consequence of hemodialysis is degranulation of peripheral blood neutrophils. The mechanisms that mediate this process, however, have not been conclusively identified. In the present study, the participation of complement activation and beta 2 integrins (CD11/CD18) in hemodialysis-induced neutrophil degranulation was investigated. Incubation of neutrophils with cuprophan membrane stimulated the release of very small amounts of the cytoplasmic granular protein, elastase. This release was markedly enhanced by the addition of plasma. Inactivation of complement reduced degranulation by approximately 60%, but the contribution of anaphylatoxins C3a and C5a to the degranulation process was modest. Treatment of plasma with EDTA completely abolished neutrophil degranulation in the presence of cuprophan membrane. Further, when incubated with plasma and cuprophan membrane, neutrophils that are deficient in beta 2 integrins released only 10% as much elastase as normal cells. Together, these observations strongly suggest that one or more members of the beta 2 integrin family of receptors is essential for cuprophan membrane-induced neutrophil degranulation and that both complement-related and noncomplement-related factors serve as receptor ligands.

Alterations in mononuclear cell tumour necrosis factor-alpha (TNF-alpha) response in patients on long term cuprophane haemodialysis

We have investigated TNF-alpha secretory response of peripheral blood mononuclear cells (PBMC) from 13 uraemic patients undergoing regular haemodialysis with cuprophane membrane (CM). Sixteen healthy subjects and five uraemic patients under conservative therapy were also studied as controls. Cells of haemodialysis patients exhibited increased TNF-alpha release in vitro in the absence of activating stimuli other than culture conditions, as compared with normal and uraemic controls. In contrast to normal cells, this spontaneous secretion of TNF-alpha from dialysis PBMC could not be significantly reduced by addition of polymyxin B to culture medium, thus indicating its independence of trace amount of lipopolysaccharide (LPS) present in the medium as contaminant. Furthermore, predialysis PBMC were considerably more sensitive to stimulation with 10(7) pg/ml of LPS under in vitro culture conditions than normal and uraemic controls. To elucidate a role of direct contact with CM in stimulation of TNF-alpha release from monocytes, PBMC were cultured on CM in vitro. Contact with CM stimulated TNF-alpha secretion from PBMC above the level of cells cultured on tissue culture plastic. This response persisted with time in culture in contrast to a transient LPS-induced TNF-alpha release. Furthermore, PBMC stimulated by contact with CM for 2 days did not lose the capacity to secrete TNF-alpha in response to a subsequent LPS stimulation, while a 2-day treatment of cells with LPS was followed by LPS refractory state. Therefore, direct contact with CM induces in PBMC a long-lasting TNF-alpha response which is not down-regulated by the acquisition of refractoriness in a manner similar to that which occurs in the case of LPS stimulation. These in vitro findings provide a possible explanation of the observation that predialysis PBMC exhibit elevated TNF-alpha secretory capacity.

Uremic serum effects on peripheral blood mononuclear cell and purified T lymphocyte responses

We have studied the effects of uremic serum on the activation state and function of normal lymphocytes in vitro, by examining both accessory cell-dependent and accessory cell-independent responses. Uremic serum was obtained from patients on conservative treatment and from the same patients after they have undergone six months of maintenance hemodialysis. Uremic serum inhibited the proliferative responses to mitogens and to recombinant IL-2 (rIL-2) of both peripheral blood mononuclear cells (PBMC) and purified T cell populations. However, the responsiveness to IL-2 of pre-formed lymphoblasts, obtained from both PBMC and purified T cells, in the presence of uremic serum was similar to that obtained in the presence of normal serum, or was even enhanced. Uremic serum did not affect the cellular IL-2 receptor alpha (IL-2R) generation though it inhibited significantly the release of soluble IL-2 receptor (sIL-2R) and the production of IL-2 after mitogenic stimulation. Uremic serum from patients after six months of hemodialysis enhanced, but did not completely restore, proliferative responses and IL-2 production by control PBMC. Neither IL-1 nor IL-2R, which are present at elevated concentrations in uremic serum, appeared to be responsible for serum effects on in vitro responses of control lymphocytes. In conclusion, our results indicate that uremic serum affects both accessory cell-mediated and accessory cell-independent normal T cell responses. Uremic serum inhibition of T cell proliferation is associated with down-regulation of IL-2 synthesis by lymphocytes and the induction of an abnormal state of activation of lymphoblasts which is further enhanced following chronic hemodialysis.

Plasma tumor necrosis factor soluble receptors in chronic renal failure

Two soluble tumor necrosis factor receptors (sTNFRs) were detected in the plasma of patients with different degrees of chronic renal failure (CRF) and of long-term hemodialysis (HD) patients. In uremic undialyzed patients, plasma levels of both sTNFRs increased progressively with declining renal function. A linear correlation was found between sTNFR plasma levels and plasma creatinine concentration. sTNFR levels in end-stage uremic patients shortly before commencement of first HD treatment were approximately tenfold higher than in normal subjects. Long-term HD patients showed a further increase in plasma sTNFRs. The origin of sTNFRs, as well as their physiological role remains to be elucidated.

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)

Serum and intracellular detection of cytokines in patients undergoing chronic hemodialysis

Tumor necrosis factor (TNF) was detected, before and after dialysis, in sera from 69 patients and, at various times during dialysis, in 28 patients carefully selected for the absence of intercurrent illness. Blood samples were also sequentially collected for separation of monocytes, and cells were sonicated to detect intracellular TNF. Compared with serum levels obtained from 41 healthy subjects, basal TNF values of the unselected group of 69 patients were significantly higher (p < 0.01), independent of the dialyzer membrane. A significant increase in TNF levels by the end of dialysis was found only with Cuprophan (p < 0.01). In the selected group of 28 patients, no significant changes in TNF values were observed in sequential samples. However, a significant increase of intramonocyte TNF levels was found in Cuprophan patients (p < 0.025). Soluble interleukin-2 receptor (IL-2R) levels, measured in parallel in sera from unselected and selected patients, were found to be very much higher than healthy controls without significant changes during the dialysis procedure. While the diverse profiles of TNF obtained from differently selected patients suggest that mechanisms other than membrane biocompatibility play a role in the appearance of these low cytokine levels, the possible nature of uremic toxin for soluble IL-2R can be envisaged by detection in dialysis patients.

Biocompatibility issues in hemodialysis

Hemodialysis, as a life-saving treatment modality for uremic patients, implies a repeated and compulsory contact of blood with foreign materials. As a consequence, biocompatibility problems are unavoidable. The same applies for the material used for the creation of vascular access, and for the alternative dialysis method, CAPD (continuous ambulatory peritoneal dialysis), although each system might cause its own and specific problems. Although in early dialysis the focus has been on maintenance of life and elimination of toxins, later on the important morbid implications of this lack of biocompatibility have been recognized. Eight major problems will be discussed, especially in the perspective of recent new findings in this field: (1) coagulation and clotting; (2) complement and leukocyte activation; (3) susceptibility to infection; (4) leaching or spallation; (5) surface alterations of solid materials; (6) allergic reactions; (7) shear; (8) transfer of compounds from contaminated dialysate. After description of the major biochemical and clinical implications of these problems, ways to prevent morbid events and future perspectives will be described.

Generation of leukotriene B4 by hemodialyzer membranes: a novel index of biocompatibility

Leukotriene B4 (LTB4) plays an important role in acute and chronic inflammatory and hypersensitive reactions. We studied the time course of LTB4 biosynthesis in whole blood in 18 patients with end-stage renal failure maintained on regular hemodialysis with two different membranes, cuprophane and polyacrylonitrile (AN 69). The basal levels of LTB4 from dialysis patients did not differ significantly from a normal control group. Compared to predialytic values, the cuprophane membrane caused a maximal release of LTB4 by a factor of about 4.5 (p less than 0.01) within the first 10 to 20 minutes. Thereafter the level fell and returned to baseline range at the end of the hemodialysis session. With the use of the AN 69 membrane no significant increase of LTB4 could be demonstrated. The changes in LTB4 concentration showed a close temporal correlation to the alterations in white blood cell count. We conclude that (1) LTB4 is a biologically important mediator of neutrophil activation during hemodialysis, and (2) LTB4 may be a sensitive marker of biocompatibility in vivo.

Stimulation of beta 2-microglobulin synthesis in lymphocytes after exposure to Cuprophan dialyzer membranes

We tested beta 2-microglobulin (beta 2m) synthesis by peripheral blood lymphocytes of non-uremic donors after contact with dialyzer membranes. Under serum-free conditions, lymphocytes were incubated with different dialyzer membranes for four hours. After subsequent culture in the absence of membranes to yield an overall culture time of 24 hours, RNA was extracted. Messenger RNA for beta 2m was quantitated by Northern blotting with specific probes. Increased beta 2m mRNA was seen after a minimum of one hour contact time with Cuprophan both in the presence and absence of cycloheximide. While no consistent stimulation was seen with polyacrylonitrile or polycarbonate-polyether membranes, respectively, the stimulation of beta 2m mRNA with Cuprophan was of the same order of magnitude as that obtained with interferon gamma. Stimulation of beta 2m mRNA by Cuprophan was stereospecifically diminished by 5 mM L-fucose. Apart from stimulated transcription of beta 2m we could also show increased surface expression of MHC class I molecules, using FACS technique. The results further prove complement-independent blood cell activation by Cuprophan membranes. It is uncertain whether the results are relevant for beta 2m amyloidosis.

Alterations of polymorphonuclear leukocyte glycogen metabolism and glucose uptake in dialysis patients

Human polymorphonuclear leukocytes (PMNs) are activated during extracorporeal circulation. An indicator of PMN activation may be the glycogen-degrading enzyme phosphorylase. It is unknown whether dialysis therapy may influence PMN carbohydrate metabolism. Therefore, PMNs were isolated from healthy control subjects, patients undergoing continuous ambulatory peritoneal dialysis (CAPD), and patients undergoing regular hemodialysis therapy (RDT) before, during, and at the end of hemodialysis (HD) treatment using dialyzers made of polysulfone or polymethylmethacrylate (PMMA). Nifedipine (NIF) was continuously infused during HD with PMMA in 5 patients at a dose of 18 micrograms/kg body weight per hour. Glycogen, activity of glycogen synthetase and phosphorylase (active and inactive forms of both enzymes), and glucose uptake with and without stimulation with the chemotactic peptide FMLP were determined in these PMNs. During HD with PMMA, there was a significant increase of PMN phosphorylase "a" activity 15 and 30 minutes after the start of HD. HD with polysulfone did not stimulate the active "a" form of the glycogen-degrading enzyme in PMNs. HD with PMMA significantly inhibited the active I-form of glycogen synthetase, whereas polysulfone activated glycogen synthetase I. NIF inhibited phosphorylase "a" activation during HD with PMMA. PMN glycogen content and glucose uptake were improved during HD with polysulfone, but not with PMMA. PMN glycogen content, activity of glycogen synthetase, and glucose uptake were significantly lower also in CAPD patients compared with healthy controls. These data show that HD with PMMA activates PMN glycogenolysis. This effect can be inhibited by calcium channel blockers. PMN glycogen content of RDT and CAPD patients is significantly lower compared with healthy controls due to inhibition of glycogen synthesis. Elimination of dialyzable factor(s) improves, but does not restore, PMN glycogen synthesis and glucose uptake.

Hemodialysis with cuprophane membrane modulates interleukin-2 receptor expression

Chronic dialysis patients have several indices of immune deficiency. We examined the hypothesis that the biocompatibility of dialysis membranes may influence the ability of lymphocytes to express interleukin-2 (IL-2) receptors on their surface, a key event in cellular immune response. We investigated the potential role of the dialysis membrane in eight chronic hemodialysis patients. The study design was a cross-over study using cuprophane and polymethylmethacrylate (PMMA) membranes. Chronic dialysis with new cuprophane membrane leads to an increase in baseline expression of the two subunits of IL-2 receptors. IL2R alpha (p55, CD25) and IL-2R beta (p70), in peripheral blood mononuclear cell (PBMC). However, Phytohemagglutinin (PHA) stimulation of PBMC harvested after two weeks of dialysis with cuprophane membrane showed a markedly decreased expression of high affinity IL-2 receptors. These findings are reversed when patients were dialyzed with a PMMA membrane which is also associated with minimal complement activation. The increased expression of IL-2 receptor subunits are reproduced in vitro by direct contact of PBMC with cuprophane membrane and by the addition of the anaphylatoxin C5a. This study confirms the participation of lymphocytes in the complex blood-membrane interactions that occurs during dialysis; the results may be relevant to observations of immune deficiency in dialysis patients.

Reactive oxygen species production by monocytes and polymorphonuclear leukocytes during dialysis

Intradialytic production of reactive oxygen species (ROS) by monocytes and polymorphonuclear leukocytes (PMNL) was examined separately in six hemodialysis patients. Samples obtained 15 minutes after initiation of dialysis with new cuprophane membranes demonstrated significantly increased (P less than 0.05) ROS production in both cell populations as measured by the fluorescence of a specific intracellular marker (2',7'-dichlorofluorescein diacetate [DCFH-DA]) assayed by flow cytometry. Granulocytes harvested during dialysis also showed decreased responsiveness to exogenous C5a and F-Met-Leu-Phe (FMLP) at 15, 30, and 60 minutes after initiation of dialysis (P less than 0.05). Our data suggest that hemodialysis with cuprophane membrane is associated with monocyte and PMNL activation as shown by production of ROS coincident with peak activation of the complement cascade; these granulocytes become refractory to further stimulation with C5a and FMLP during dialysis.

Leukotriene B4 is involved in hemodialysis-associated neutropenia

Biosynthesis of leukotriene B4 (LTB4) was studied in ten patients with end-stage renal failure undergoing chronic hemodialysis with a cuprophane membrane. As compared to healthy subjects the low basal plasma levels of LTB4 quantified by radioimmunoassay after extraction and purification by HPLC showed no significant difference. The time-course of LTB4 release after contact of the blood with the dialysis membrane without further in vitro stimulation was characterized by a rapid increase by about 500% within the first 10 min, appearing approximately at the same time as the known fall of white blood cell count which reaches its nadir after 20 min. Analysis of further release showed a decline of LTB4 biosynthesis to basal levels at the end of hemodialysis. These results indicate that activation of the 5-lipoxygenase pathway is involved in hemodialysis-associated leukopenia and may contribute to the alterations in neutrophils of patients with chronic dialysis therapy.

Hemodialysis, membrane-related neutrophil dysfunctions, and pentoxifylline--a pilot study

Hemodialysis treatment is associated with activation of neutrophil granulocytes. Pentoxifylline has been shown to inhibit neutrophil activation in vitro and in vivo. We investigated the effect of pentoxifylline on leukocyte and platelet counts and on plasma levels of extracellularly released neutrophil elastase and lactoferrin during a four-hour hemodialysis treatment. Eight patients received 400 mg of pentoxifylline or placebo orally twice a day over 14 days and an additional dose of 400 mg of pentoxifylline intravenously during hemodialysis. Each subject served as his own control in a randomized, double-blind, cross-over study. Combined oral and intravenous treatment with pentoxifylline prevented neither leukopenia nor neutrophil degranulation during the time interval studied. Elastase plasma levels paralleled the drop in leucocyte counts and thereafter increased similarly in both groups. Lactoferrin plasma levels exhibited less increase in the treated group; however, this effect was not statistically significant. This may be due to the small number of cases studied and to difficulties in reaching effective plasma levels without side effects.

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

To evaluate the effect of renal replacement therapy on cellular cytokine production in patients with renal disease, we studied interleukin 1 (IL-1) and interleukin-2 (IL-2) production by target cells stimulated with supernatants from cultured peripheral blood mononuclear cells from patients with end-stage renal disease, who were treated with hemodialysis and continuous ambulatory peritoneal dialysis (CAPD) before and after hemodialysis or a peritoneal dialysate exchange, compared to normal subjects used as time controls, and patients with chronic renal insufficiency. Initial cellular IL-2 production was increased in patients with hemodialysis, compared to normal controls. The ratio of pretreatment cellular IL-2 and IL-1 production was increased in all patient groups compared to normal subjects. Both hemodialysis and CAPD treatments resulted in increased cellular IL-1 (51.7%, P less than 0.007, and 42.8%, P less than 0.002, respectively) and IL-2 production (50.5%, P less than 0.015, and 33.3%, P less than 0.0008, respectively). The hemodialysis group had significantly higher cellular IL-2 production compared with normal controls' after treatment. After treatment, the IL-2/IL-1 ratio remained elevated in all groups with renal disease compared with normal subjects. We conclude patients with renal disease have an abnormal functional relationship between IL-1 and IL-2, characterized by increased IL-2 production per level of IL-1, unaffected by type or presence of renal replacement therapy.