Impaired polymorphonuclear neutrophil function in end-stage renal failure and its correction by continuous ambulatory peritoneal dialysis

Oxidative Metabolism of Polymorphonuclear Leukocytes in Continuous Ambulatory Peritoneal Dialysis

Objective

To evaluate the oxidative metabolism of polymorphonuclear leukocytes (PMNL) in continuous ambulatory peritoneal dialysis (CAPD) patients compared with those of hemodialysis (HD) patients, chronic renal failure (CRF) patients not yet on dialysis, and healthy controls; and to discover factors contributing to the oxidative function in CAPD patients.

Patients

Thirty-five CAPD, 22 HD, 11 CRF patients were assessed; all were free from infections at the time of examination. Thirty-one healthy volunteers served as controls.

Methods

The oxidative metabolism was estimated by the production of superoxide anion, which was detected by luminol-dependent zymosan stimulated chemiluminescence (CL) with whole blood assessment. The volume of superoxide production equivalent to 1 mL of circulating blood (T-CL), that equivalent to 104 neutrophils (CL/N) and the velocity of superoxide production (V-CL), were measured as parameters for the oxidative function of PMNL.

Results

There were no differences in all CL parameters between CAPD and HD patients. T -CL and CL/N of dialysis patients were equal to controls but those of CRF patients were significantly decreased. V-CL of dialysis patients, as well as CRF patients, was smaller than that of controls but the difference was not significant. Among nutritional status, degree of anemia, dialytic efficacy and duration of dialysis in CAPD patients, only serum albumin concentration (Alb) correlated well to all CL parameters. Hypoalbuminemic patients(Alb <3.6 gldL, n=20) had significantly decreased T -CL and CL/N compared to normoalbuminemic patients(Alb ?: 3.6 g/dL, n=15), and decreased CL/N and V-CL compared to controls. No differences in CL parameters were observed between the patients with a history of peritonitis (n=15) and without a history of peritonitis (n=20).

Conclusions

Oxidative metabolism of PMNL in CAPD patients was maintained with respect to superoxide productive volume, while the oxidative velocity was relatively impaired. Furthermore, it seems that albumin has a great influence on the oxidative metabolism of PMNL in CAPD patients.

Phospholipases and the Activation and Priming of Neutrophils by Peritoneal Dialysis Effluent

Objective

To investigate the role of phospholipases during the activation and priming of neutrophil nicotinamide adenine dinucleotide phosphate (NADPH) oxidase by peritoneal dialysis effluent (PDE).

Design

Examine the action of 4-hour dwell PDE upon phospholipase activation in the circulating neutrophils obtained from healthy individuals.

Results

We have previously reported that PDE stimulated superoxide release by the NADPH oxidase of human neutrophils and primed the response to the bacterial peptide, fMLP (fMetLeuPhe). To elucidate the biochemical mechanisms underlying these observations, we have examined the roles of phospholipases (PL) C, D, and A2, whose activation causes the release of a range of intracellular secondary messengers. Following fMLP stimulation, we observed a rapid activation of both PLC and PLD as well as a small but nonsignificant increase in PLA2 activity. Peritoneal dialysis effluent alone failed to stimulate either PLC or PLD, while pre-incubation with PDE had no affect upon fMLP-induced PLC and PLD activation. However, PDE caused a small but nonsignificant increase in PLA2 activity (which was comparable to that observed with fMLP) and primed the fMLP-induced response. In common with a role for PLA2 and the subsequent release of arachidonic acid (AA), we have demonstrated dose-dependent inhibition of PDE-induced superoxide release by the PLA2 inhibitor mepacrine, as well as activation and priming of the fMLP-induced superoxide generation by AA.

Conclusions

These results imply that PDE-induced NADPH-oxidase activation and priming in human neutrophils is mediated via a PLA2-dependent but PLC and PLD-independent mechanism.

Characterization of the biological anti-staphylococcal functionality of hUK-66 IgG1, a humanized monoclonal antibody as substantial component for an immunotherapeutic approach

Multi-antigen immunotherapy approaches against Staphylococcus aureus are expected to have the best chance of clinical success when used in combinatorial therapy, potentially incorporating opsonic killing of bacteria and toxin neutralization. We recently reported the development of a murine monoclonal antibody specific for the immunodominant staphylococcal antigen A (IsaA), which showed highly efficient staphylococcal killing in experimental infection models of S. aureus. If IsaA-specific antibodies are to be used as a component of combination therapy in humans, the binding specificity and biological activity of the humanized variant must be preserved. Here, we describe the functional characterization of a humanized monoclonal IgG1 variant designated, hUK-66. The humanized antibody showed comparable binding kinetics to those of its murine parent, and recognized the target antigen IsaA on the surface of clinically relevant S. aureus lineages. Furthermore, hUK-66 enhances the killing of S. aureus in whole blood (a physiological environment) samples from healthy subjects and patients prone to staphylococcal infections such as diabetes and dialysis patients, and patients with generalized artery occlusive disease indicating no interference with already present natural antibodies. Taken together, these data indicate that hUK-66 mediates bacterial killing even in high risk patients and thus, could play a role for immunotherapy strategies to combat severe S. aureus infections.

Functional mannose-binding lectin levels in patients with end-stage renal disease on maintenance hemodialysis

BACKGROUND

Innate immunity is generally impaired in chronic renal failure (CRF). Mannose-binding lectin (MBL) has an important role in first-line host defense against pathogens via the lectin pathway. We recently reported that functional MBL was significantly lower in CRF patients than in healthy subjects. In this study, we aimed to determine whether functional MBL would be improved following hemodialysis (HD) therapy.

METHODS

This study included 22 patients with end-stage renal disease (ESRD) on maintenance HD. Functional MBL was measured every 6 months for 1 year after HD using an enzyme-linked immunosorbent assay.

RESULTS

Median serum functional MBL levels of ESRD patients were significantly higher after 6 and 12 months than at the start of HD therapy (p < 0.05 and p < 0.01, respectively). Furthermore, median functional MBL levels at 12 months were significantly higher than those at 6 months (p < 0.05).

CONCLUSIONS

We found significant increases in serum functional MBL levels in patients on HD. Our results indicated that HD tailored to remove uremic toxins could improve functional MBL levels in these patients.

Uremia impairs monocyte and monocyte-derived dendritic cell function in hemodialysis patients

Patients with chronic renal failure maintained on intermittent hemodialysis have frequent infections and a suboptimal response to vaccinations. Dendritic cells are potent antigen-presenting cells essential for the initiation and maintenance of innate and adaptive immunity. In this study we used uremic sera from hemodialysis patients to measure its impact on monocyte and monocyte-derived dendritic cell function in vitro. Monocytes from healthy and uremic subjects were isolated using immunomagnetic beads and differentiated into dendritic cells in the presence of either complete sera or sera from hemodialysis patients. Dendritic cells from normal patients cultured in uremic sera had decreased endocytosis and impaired maturation. These cells, however, had enhanced IL-12p70 production and increased allogeneic T-cell proliferation compared to cells of normal subjects cultured in normal sera. Monocyte derived dendritic cells of hemodialysis patients cultured in either normal or uremic sera were functionally impaired for endocytosis and maturation but had enhanced IL-12p70 production and allogeneic T-cell proliferation only when cultured with uremic sera. High concentrations of urea in normal sera inhibited all aspects of normal dendritic cell function in vitro. Our study suggests that hemodialysis regimes tailored to remove uremic toxins more efficiently may improve immune functions of these patients.

Uremia impairs blood dendritic cell function in hemodialysis patients

Patients on hemodialysis have a general immunodeficiency involving both innate and adaptive responses. As the mechanisms contributing to this defect are uncertain, we sought to study the effects of uremia on circulating dendritic cells (DC) in hemodialysis patients. Immunomagnetic beads were used to isolate myeloid and plasmacytoid DCs from healthy donors. Immune-related functions were determined in these cells cultured in either a complete media containing ABO-compatible serum or media containing sera from uremic patients. The myeloid cells were analyzed for costimulatory molecule expression and allo-stimulatory capability following lipopolysaccharide stimulation. The production of interferon-alpha following herpes-simplex virus stimulation by the plasmacytoid cells was also measured. Myeloid DCs incubated with uremic sera demonstrated impaired maturation and decreased allo-stimulatory capacity. Similarly, herpes virus-stimulated plasmacytoid DCs incubated with uremic sera produced significantly less interferon-alpha compared with cells incubated in the complete media. Both small and large molecule uremic toxins inhibited DC functions in vitro. Use of more efficient dialysis to improve small molecule clearance reversed the inhibition of uremic sera on myeloid but not plasmacytoid DC function. We have shown that the immunodeficiency of hemodialysis patients is due to dialyzable uremic toxins.

Uremic concentrations of guanidino compounds inhibit neutrophil superoxide production

BACKGROUND

In uremia, diminished reactive oxygen intermediate (ROI) production is an important consequence of impaired neutrophil function. We have studied the effect of guanidino compounds, known uremic toxins, on neutrophil ROI production in vitro.

METHODS

Neutrophils from healthy volunteers were exposed for three hours to individual or mixed guanidino compounds (GCmix) at concentrations encountered in uremic plasma. After removal of guanidino compounds, neutrophils were activated by adhesion, N-formyl-methionyl-leucyl-phenyalanine (fMLP), phorbol 12-myristate 13-acetate (PMA), or opsonized zymosan, and superoxide production was measured by lucigenin chemiluminescence (CL). The direct effect of guanidino compounds on superoxide production in activated neutrophils was also measured. The energy status (ATP and creatine phosphate), antioxidant status (total glutathione), and glycolytic flux (lactate production) were measured.

RESULTS

The GCmix pretreatment decreased the superoxide production in activated neutrophils (fMLP or zymosan) by 50% (P < 0.01) and the ATP concentration by 60% (P < 0.05), and it inhibited glycolytic flux (lactate production) by 45% (P < 0.01), but did not alter glutathione concentration. Simultaneous exposure to GCmix and activation did not inhibit nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity in cell lysates, but inhibited superoxide formation in zymosan-activated intact neutrophils, and this inhibition was reversed following removal of the guanidino compounds.

CONCLUSION

Guanidino-succinate, -propionate, and -butyrate were individually as potent as the GCmix. Inhibition of neutrophil superoxide generation by guanidino compounds results from a depressed energy status. Uremic concentrations of guanidino compounds significantly inhibit neutrophil metabolism, and this has serious implications for their function in host defense.

Effects of a vitamin E-modified dialysis membrane on neutrophil superoxide anion radical production

Activation of neutrophil by the dialysis membrane and peroxidative stress plays an important role on the pathogenesis of complications in hemodialysis (HD) patients. Vitamin E is one of the potent scavengers for reactive oxygen species. Recent studies suggest that a vitamin E-modified multilayer membrane (Excebrane, CL-EE dialyzer) has an inhibitory effect on serum lipids peroxidation in HD patients. To determine the effect of CL-EE on biocompatibility in clinical use, we measured the superoxide anion radical producing ability (SOPA) of polymorphonuclear leukocytes (PMNLs), the plasma hydroxyl radical producing ability (OHPA) and superoxide anion radical scavenging activity (SSA). SOPA was measured after stimulation of PMNLs with phorbol myristate acetate using electron paramagnetic resonance (EPR) method. Plasma OHPA and SSA were also determined using the EPR method. In addition, the plasma concentrations of malondialdehyde (MDA) and oxidized low-density lipoprotein (LDL), as the parameters for lipid peroxidation, were measured. SOPA was decreased in patients who used conventional filter membrane compared with healthy controls. In the patients using the CL-EE membrane, SOPA gradually increased and reached control levels after six months. However, no significant increase was observed in patients who used a conventional filter membrane. OHPA of HD patients was significantly decreased compared with controls. In the CL-EE membrane patient group, OHPA was significantly increased at six months. SSA was significantly higher in the conventional filter membrane group than controls. In the CL-EE membrane patient group, SSA gradually decreased at six months. Plasma MDA and oxidized LDL levels were significantly higher in HD patients compared with controls. These values slowly decreased, and significant differences were found after nine months of using the CL-EE membrane. These findings suggest that activation of PMNLs and plasma OHPA and SSA in HD patients is attenuated by antioxidant effects of the CL-EE.

Inhibition of neutrophil superoxide production by uremic concentrations of guanidino compounds

In uremia, diminished reactive oxygen intermediate production is an important consequence of impaired neutrophil function. The effects of guanidino compounds, which are known uremic toxins, on neutrophil reactive oxygen intermediate production in vitro were studied. Neutrophils from healthy volunteers were exposed for 3 h to individual guanidino compounds or mixed guanidino compounds (GCmix), at concentrations observed in uremic plasma. After removal of the guanidino compounds, the neutrophils were activated by adhesion, N-formylmethionylleucylphenylalanine, phorbol myristate acetate, or opsonized zymosan, and superoxide production was measured by monitoring lucigenin chemiluminescence. The direct effects of guanidino compounds on superoxide production in activated neutrophils were also measured. The energy status (ATP and creatine phosphate), antioxidant status (total glutathione), and glycolytic flux (lactate production) were measured. GCmix pretreatment decreased superoxide production in activated neutrophils (activated by N-formylmethionylleucylphenylalanine or zymosan) by 50% (P < 0.01), decreased ATP concentrations by 60% (P < 0.05), and inhibited glycolytic flux (lactate production) by 45% (P < 0.01) but did not alter glutathione concentrations. Simultaneous GCmix exposure and activation did not inhibit NADPH oxidase activity in cell lysates but inhibited superoxide formation in zymosan-activated intact neutrophils; this inhibition was reversed after removal of the guanidino compounds. Guanidinosuccinic acid, guanidinopropionic acid, and guanidinobutyric acid, when tested individually, were each as potent as GCmix. The inhibition of neutrophil superoxide generation by guanidino compounds results from decreased energy status. Micromolar concentrations of guanidino compounds significantly inhibit neutrophil metabolism, with serious implications for the functions of neutrophils in host defenses.

Transplantation, not dialysis, corrects azotemia-dependent priming of the neutrophil oxidative burst

The oxidative burst of neutrophils from patients with renal failure before the initiation of dialysis is primed for an enhanced response after stimulation by phagocytosis or chemoattractants. This study shows that phagocytosis-stimulated oxidative burst activity remains primed in patients treated with both high-efficiency hemodialysis and continuous ambulatory peritoneal dialysis (CAPD), but it is normal in patients with a functioning renal transplant. Incubation of normal neutrophils or HL-60 granulocytes in azotemic plasma results in increased resting and phagocytosis-stimulated H2O2 production, which is rapidly reversible on removal of the plasma. Priming of the oxidative burst by azotemic plasma is independent of changes in opsonization and phagocytosis and does not require protein synthesis. These results suggest that azotemic plasma contains a substance or substances capable of reversibly priming oxidative burst activity in neutrophils and neutrophil-like cell lines. The Inability of high-efficiency hemodialysis and CAPD to normalize oxidative burst activity suggests that this substance is of higher molecular weight.