Cytokine patterns in the effluent of continuous ambulatory peritoneal dialysis: relationship to peritoneal permeability.

Cytokines are pluripotent pleiotropic agents that have received widespread attention over the last few years. Not surprisingly, the have also been studied in the context of continuous ambulatory peritoneal dialysis. Cytokines play a central role in this treatment modality for uremic patients, because these inflammatory mediators act upon the biological dialysis membrane, i.e. the peritoneum, while simultaneously they participate in host defense mechanisms. This review describes which cytokines are present in dialysate, whether there is support for intraperitoneal release, and under which circumstances. If focuses particularly on the relationship between cytokines in peritoneal effluent and peritoneal permeability to macromolecules. In addition, the presence of prostanoids in dialysate and their role in the local regulation of peritoneal permeability are discussed, because cyclooxygenase products are tightly linked to cytokine networks.

Impaired initial cell reaction in CAPD-related peritonitis.

Our objective was to determine the incidence of peritonitis episodes with an impaired initial cell reaction (IICR:neutrophil number < 100 x 10(6)/L) over a period of ten years, and to find possible explanations for this unusual presentation of peritonitis. A retrospective review of the files of continuous ambulatory peritoneal dialysis (CAPD) patients included in the CAPD program 1984 and 1993 was done. Analysis of cytokine and prostanoid patterns during four peritonitis episodes with an IICR was compared to 12 episodes with a normal initial cell reaction (NICR). Dialysate cell numbers and immunoeffector characteristics of peritoneal cells were compared in 7 IICR patients in a stable situation and a control group of 70 stable CAPD patients. The setting was a CAPD unit in the Academic Medical Center in Amsterdam. Thirty-five CAPD patients who had one or more peritonitis episodes with an IICR and a control group of 249 CAPD patients were included in the study. The incidence of peritonitis with an IICR was 6%. These episodes occurred more than once in 51% of the patients who presented with IICR. In 72% the cell reaction was only delayed: a cell number exceeding 100 x 10(6)/L was reached later. Staphylococcus aureus was significantly more frequently the causative microorganism compared to all peritonitis episodes (PE) that occurred during the study period. Patients with IICR had lower dialysate cell counts in a stable situation, compared to a control group (p < 0.01). This was caused by a lower number of macrophages and CD4 positive lymphocytes. The phagocytosis capacity of the macrophages appeared to be normal. In a comparison of four PE with an IICR and 12 episodes with an NICR, the tumor necrosis factor-alpha (TNF-alpha) response was similar and occurred on day 1, also pointing to normally functioning macrophages. However, the maximal appearance rates of interleukin-6 (IL-6) and IL-8 occurred later in the episodes with IICR compared to NICR (day 2 vs day 1, p < 0.05). No differences were found in vasodilating prostaglandins, mesothelial cell markers (cancer antigen 125, phospholipids, hyaluronan), and mesothelial cell numbers in the stable situation nor during peritonitis. Peritonitis can present as abdominal pain in the absence of a cloudy dialysate. In some of the patients this presentation occurred more than once. This impaired, most often delayed, cell reaction was associated with a delayed secondary cytokine response. As IL-6 and IL-8 can be synthesized by mesothelial cells, this suggests an impaired functioning mesothelium. This could not be confirmed, however, by a lower number of mesothelial cells in effluent or lower dialysate levels of mesothelial cell markers.

Effects of intraperitoneal cyclooxygenase inhibition on inflammatory mediators in dialysate and peritoneal membrane characteristics during peritonitis in continuous ambulatory peritoneal dialysis.

Peritonitis complicating continuous ambulatory peritoneal dialysis (CAPD) can be used as an in vivo model to study the contribution of mediators in dialysate to the regulation of peritoneal permeability. Previously we reported that changes in the peritoneal appearance rates of the cytokines interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF alpha) were related to alterations in the effective peritoneal surface area. Changes in the intrinsic peritoneal permeability were mainly related to those in the peritoneal appearance rate of the prostanoid prostaglandin E2 (PGE2) and partly also to that of IL-6. In this intervention study the role of these mediators was further analyzed. Eleven peritonitis episodes were followed on 8 consecutive days from the start of the infection and once after recovery. Indomethacin was given intraperitoneally during the first 3 days. beta 2-Microglobulin clearance was used as indicator of the effective peritoneal surface area. The intrinsic peritoneal permeability was characterized functionally by the restriction coefficient. The 15 peritonitis episodes studied previously served as the control group. This study supports the formerly obtained relationships in two ways. First, significant reductions were observed for peritoneal PGE2, 6-keto-PGF1 alpha, and TxB2 during cyclooxygenase inhibition to 6%, 0.6%, and 9% of the values on day 1, whereas simultaneously the intrinsic permeability was less increased. This indomethacin effect on intrinsic permeability was not entirely significant, probably because of the additional role of IL-6, which was not influenced by indomethacin. Also, the appearance rate of TNF alpha in the effluent was not affected by cyclooxygenase inhibition. Accordingly, the changes in the effective surface area were similar to those in the control group. Second, in 8 of the 11 cases, new rises both in peritoneal PGE2 and in intrinsic permeability occurred after discontinuation of indomethacin. Rebounds were not seen for TNF alpha or IL-6, and, consistently, not for the effective surface area. In conclusion, local cyclooxygenase inhibition results in a less-increased intrinsic permeability during peritonitis but has no effect on the effective surface area. These data support our previous finding that IL-6 and TNF alpha contribute to alterations in surface area, whereas PGE2 is more involved in intrinsic peritoneal permeability changes.

Dialysate markers of peritoneal tissue during peritonitis and in stable CAPD.

OBJECTIVE: To investigate whether dialysate concentrations of substances that are locally produced within the peritoneal cavity can be used to study the effects of inflammation on peritoneal tissue. DESIGN: We followed the appearance rates (AR) of concentrations of cancer antigen (CA) 125, phospholipids (PHL), hyaluronan (HA), and the procollagen peptides PICP (procollagen 1 C-terminal) and PIIINP (procollagen 3 N-terminal) in dialysate during peritonitis (8 consecutive days) and after recovery. Data were compared with the stable situation. SETTING: CAPD (continuous ambulatory peritoneal dialysis) unit in the Academic Medical Center in Amsterdam. PATIENTS: Twelve CAPD patients with a total of 16 episodes of peritonitis and 10 clinically stable CAPD patients were studied. RESULTS: All substances showed temporal increments in dialysate during peritonitis compared to control. No difference was found between the control day of peritonitis and the stable patients. Maximum AR were reached in the acute phase of peritonitis for CA125, PHL, and HA and on day 4 for both PICP and PIIINP. A second increment in CA125 occurred on days 4 to 6. These findings indicate acute damage to the mesothelium (CA125) and other cells (PHL) by the infection. HA may reflect stromal changes. Subsequently, peritoneal healing (PICP,PIIINP) and remesothelialization (second peak CA125) are likely to occur. CONCLUSIONS: Dialysate concentrations of these substances can be used as markers for the effects of peritonitis on the peritoneum of CAPD patients in vivo. The similarity between the marker concentrations in the effluent after recovery from peritonitis and those in stable CAPD patients implies that complete peritoneal healing is likely to occur after uncomplicated peritonitis.

Nitrate in stable CAPD patients and during peritonitis.

During continuous ambulatory peritoneal dialysis (CAPD) peritoneal vessels are dilated. Nitric oxide (NO) causes vasodilation in many organs. Nitrate, a stable metabolite of NO, was measured in plasma and dialysate. In 6 stable CAPD patients standard peritoneal analyses were performed. The mass transfer area coefficient (MTAC) of nitrate was 11.5 mL/min (10.0-17.0 mL/min) (median and range). The MTAC of creatinine was of the same order of magnitude: 10.7 mL/min (8.0-14.2 mL/min), although the molecular weight of nitrate is lower (62 vs 113 dalton). The correlation between the MTAC of nitrate and the MTAC of creatinine indicated diffusion from the circulation and not local production of NO (r = 0.71; p = 0.11). Peritoneal permeability is increased in the acute phase of peritonitis, partly caused by extensive vasodilation. The potential role of NO during peritonitis was investigated in 8 CAPD patients with 11 peritonitis episodes in the acute phase and after recovery. The median dialysate/plasma (D/P) ratio of nitrate in the acute phase was 1.47 (range 0.96-2.55), which was higher than after recovery: 1.07 (0.99-1.75), p < 0.05. No relation was found between the D/P ratio of nitrate and the D/P ratio of TNF alpha (tumor necrosis factor). In conclusion, dialysate nitrate levels in stable CAPD patients are likely to be determined by diffusion from the circulation. D/P ratios exceeding 1.0 during the acute phase of peritonitis are probably the result of local NO production. This may contribute to the marked vasodilation during peritonitis.

Analysis of inflammatory mediators and peritoneal permeability to macromolecules shortly before the onset of overt peritonitis in patients treated with CAPD.

OBJECTIVE: To investigate whether changes in peritoneal membrane characteristics and inflammatory mediators in dialysate precede the onset of overt infection during continuous ambulatory peritoneal dialysis (CAPD)-related peritonitis. DESIGN: CAPD patients with a high peritonitis incidence stored every night bag at 4 degrees C. Routinely, each bag was thrown away after two days. Only if patients developed peritonitis, all bags were delivered for study. Thus, two night bags immediately prior to the first peritonitis bag were available for analysis. A control study was done 14 days after recovery. Dialysate samples were measured for TNF alpha, IL-6, PGE2, 6-keto-PGF1 alpha, TxB2, and serum proteins. The clearance of beta 2-microglobulin was used as an indicator of the effective peritoneal surface area. The intrinsic peritoneal permeability was characterized by the restriction coefficient. RESULTS: Eight episodes occurred in 5 patients. The night dwells available prior to the first peritonitis effluent were drained maximally nine dwells and minimally one dwell before the first peritonitis bag. Dialysate leukocyte counts exceeded 100 x 10(6)/L only on the day of manifest infection. However, bacterial cultures were already positive at least one day before overt infection in four episodes and in three of these cases two days before. No changes were observed prior to peritonitis for the clearance of beta 2-microglobulin or the restriction coefficient. In contrast to these permeability characteristics, the cytokines, TNF alpha and, though less significant, also IL-6, were increased in dialysate one day prior to overt infection, when compared to the values obtained at the control investigation. This was especially evident in effluents drained no longer than two dwells before the first peritonitis bag. Prostaglandin concentrations in dialysate were not different before the onset of manifest peritonitis from the values measured after recovery. CONCLUSION: In this study, the increased effective peritoneal surface area and intrinsic peritoneal permeability during acute infection appeared to be preceded by elevations in the cytokines TNF alpha and, to a lesser extent, IL-6. These increments occurred only very shortly before the onset of clinical symptoms.

Appearance of tumor necrosis factor-alpha and soluble TNF-receptors I and II in peritoneal effluent of CAPD.

Dialysate and serum concentrations of tumor necrosis factor-alpha (TNF-alpha), soluble TNF-receptor I (sTNFRI) and soluble TNF-receptor II (sTNFRII) were measured during stable and infectious CAPD to determine whether these mediators are released intraperitoneally or derived from the circulation. Dialysate/serum ratios were compared to those of various marker proteins for peritoneal transport and to interleukin-6 (IL-6), which is locally produced. Peritoneal immunoreactive TNF-alpha could be detected in 19 of 20 stable CAPD patients after a night dwell, but only occasionally and in lower concentrations during and after a standard four-hour peritoneal permeability test. Both sTNFRs highly exceeded TNF-alpha dialysate concentrations. In case of peritonitis a median 16-fold increase in dialysate TNF-alpha occurred on the first day, which declined towards control values during a longitudinal follow-up of eight consecutive days. sTNFRI and sTNFRII in dialysate increased three- to fourfold. Their peaks, however, appeared on the second peritonitis day. Bioactive TNF-alpha was only detected when immunoreactive levels exceeded 1000 pg/ml. Serum values of all variables were not altered during infection; sTNFRs exceeded TNF-alpha 300- to 400-fold. During stable CAPD indirect evidence was obtained for transperitoneal transport from plasma to dialysate of TNF-alpha (molecular wt 17 kD), sTNFRI (55 kD) and sTNFRII (75 kD). Dialysate/serum (D/S) ratios were higher, the lower the molecular weight; they were related to D/S ratios of those marker proteins with the nearest molecular weight; D/S ratios were unrelated to the intraperitoneally produced IL-6. Furthermore, the observed D/S ratios were as expected theoretically for their molecular weights.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of the peritoneal cellular immune system during CAPD shortly before a clinical peritonitis.

We analysed the peritoneal cellular immune system 24-48 h before the onset of a clinical peritonitis. Peritoneal cells were obtained from the overnight dialysis effluents 1 or 2 days (day-1 and day-2) preceding the day of peritonitis, the last overnight effluent before the peritonitis effluent (day P), and the first peritonitis effluent. Nine peritonitis episodes of six patients were studied. The number of Fc receptor positive cells, the chemotactic activity, and immunophenotype of the peritoneal cell population at day-2 and day-1 were similar to the postperitonitis control effluent. However, immunophagocytosis and phagocytosis capacity of the peritoneal macrophages was decreased in five of six episodes at day-2 and -1 compared to control peritoneal macrophages. The overnight effluents of day P revealed a moderate influx of neutrophilic granulocytes and an increase of bacterial killing capacity and chemotactic activity. Activation of the peritoneal T cells at day P was shown by the increase in MHC class II positive T cells and an increase in the CD4/CD8 ratio. Bacterial cell cultures of the effluents were positive in three episodes 24-48 h before peritonitis, and of all overnight effluents at day P. These results indicate that malfunctioning of phagocytosis by peritoneal macrophages may contribute to the development of a CAPD peritonitis.

Cancer antigen 125 is locally produced in the peritoneal cavity during continuous ambulatory peritoneal dialysis.

The local production of cancer antigen (CA) 125 in the peritoneal cavity of 14 continuous ambulatory peritoneal dialysis patients was studied. In addition, the relationship between the concentration of mesothelial cells and CA 125 in the peritoneal dialysate effluent was examined. The median results and ranges were as follows: plasma CA 125 14 U/mL (range 10-23), dialysate CA 125 18 U/mL (range 5.2-76), dialysate/plasma ratio 1.9 (range 0.61-5.4), and number of mesothelial cells 400/mL (range 10-5000). Peritoneal concentrations of mesothelial cells and CA 125 were positively correlated (r = 0.50, p < 0.01). Using a monoclonal antibody, CA 125-positive cells were found in the cytospin preparations of the cells of dialysis effluents. All these CA 125 positive cells were also positive for cytokeratin used as a mesothelial cell marker. In vitro experiments using mesothelial cells in monolayers showed a linear increase in CA 125 concentration both in time and in relation to the number of mesothelial cells. From these experiments a production rate of 24 U/hour/10(6) cells could be calculated. It is therefore concluded that CA 125 is locally produced in the peritoneal cavity during CAPD and that the mesothelial cells are the major source of this CA 125.

Interleukin-8 during peritonitis in patients treated with CAPD; an in-vivo model of acute inflammation.

CAPD-related peritonitis was used as an in-vivo model to study Il-8 during peritoneal inflammation. Eleven episodes were studied in nine patients, who were followed on 8 consecutive days from the start of peritonitis and once after recovery (control). Il-8 was measured in dialysate (night dwells) and serum. The Il-8 time course was compared to Il-6 and TNF alpha. In addition, an in-vivo relationship between dialysate Il-8 and intraperitoneal accumulation of neutrophils was studied. A highly increased peritoneal appearance rate of Il-8 was found in the acute phase that decreased to control values during recovery. A remarkable parallelism was observed for dialysate Il-8 and Il-6 with respect to the time course and the peritoneal appearance rate. In contrast, the appearance rate of TNF alpha was much less and had a different time course. In three of four cases where the dialysate Il-8 peak occurred on day 2, the dialysate Il-6 peak still coincided with Il-8, in contrast to TNF alpha (always day 1). Dialysate Il-8 generally exceeded serum concentrations during the entire follow-up, indicating intraperitoneal Il-8 synthesis. A positive correlation was present between the dialysate Il-8 peak and the maximal number of neutrophils in dialysate. This relationship was absent for Il-6 and TNF alpha. In five of six episodes where neutrophils were quantified on both day 1 and 2, the Il-8 peak occurred simultaneously with the neutrophil peak. These findings suggest that Il-8 is involved in the recruitment of neutrophils towards the dialysate during peritonitis.

Relationship of TNF-alpha, interleukin-6, and prostaglandins to peritoneal permeability for macromolecules during longitudinal follow-up of peritonitis in continuous ambulatory peritoneal dialysis.

Infectious reactions are known to comprise changes in vasopermeability and inflammatory mediators. We used peritonitis that complicated continuous ambulatory peritoneal dialysis (CAPD) as an in vivo inflammation model to study the time courses of peritoneal permeability characteristics and mediators in dialysate. Sixteen episodes of peritonitis were prospectively followed on eight consecutive days from the onset of the infection and once after recovery (control). Dialysate night dwells were examined for marker proteins of peritoneal permeability, cytokines (tumor necrosis factor-alpha [TNF-alpha], interleukin-6 [IL-6] and prostaglandins (PGE2, 6-keto-PGF1 alpha, and thromboxane B2 [TxB2]). The clearance of beta 2-microglobulin was used as indicator of the effective peritoneal surface area. The intrinsic permeability was characterized functionally by the peritoneal restriction coefficient. All protein clearances were increased during the acute phase of peritonitis and subsequently decreased to control. Likewise, the intrinsic peritoneal permeability was elevated, as demonstrated by a decrease of the peritoneal restriction coefficient. Peritoneal appearance rates of TNF-alpha, IL-6, and prostaglandins were also increased during the acute phase. Peak values were reached on day 1. The largest increase was observed for IL-6 (median 854-fold), followed by TNF-alpha (35-fold). The vasodilating PGE2 and 6-keto-PGF1 alpha were increased 12-fold and the vasoconstricting TxB2 was increased threefold. Evidence was obtained for local intraperitoneal synthesis of IL-6 and prostaglandins. TNF-alpha production appeared to be present only during the early acute inflammatory response. Analysis of variance for repeated measurements revealed that changes in the clearance of beta 2-microglobulin were related to those in IL-6 and marginally also to TNF-alpha in dialysate. Changes in the peritoneal restriction coefficient were also related to IL-6, but were more closely related to alterations in dialysate PGE2. These findings suggest that TNF-alpha, IL-6, and PGE2 are involved in the changes in permeability characteristics during CAPD-related peritonitis.

Interleukin-6 in CAPD patients without peritonitis: relationship to the intrinsic permeability of the peritoneal membrane.

We investigated whether day to day changes in the transport characteristics of the peritoneal membrane to macromolecules in patients treated with CAPD, were related to the levels of interleukin-6 (IL-6) in the effluent of an overnight dwell. Four stable CAPD patients without peritonitis collected all "nightbags" on consecutive days during 2 months for the determination of peritoneal IgG clearance. Serum samples were obtained weekly. IL-6 was determined in the effluent on all occasions where the IgG clearance was less than mean - SD or greater than mean + SD. On these days clearances of beta 2-microglobulin, albumin and alpha 2-macroglobulin were determined as well, to calculate the peritoneal restriction coefficient, i.e. the slope of the power relationship between protein clearances and their free diffusion coefficient in water. This coefficient was used as a parameter of the intrinsic permeability of the membrane. IL-6 was measured by a sensitive and specific bioassay, using the B13.29, subclone 9.9 hybridoma cell assay. Dialysate IL-6 was measured on 43 occasions when IgG clearance was high and on 37 occasions when IgG clearance was low. In all 4 patients indirect evidence was found for local production of IL-6 within the peritoneal cavity: mean dialysate/serum ratios were 15 to 452 times higher than could be expected when IL-6 would enter the dialysate by diffusion only. The patient with the highest dialysate/serum ratio showed higher clearances of albumin, IgG and alpha 2-macroglobulin than the other 3 patients (p less than 0.001) and a lower restriction coefficient (p less than 0.001), indicating a high intrinsic permeability.(ABSTRACT TRUNCATED AT 250 WORDS)