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

Effect of different dialysis duration on the prognosis of peritoneal dialysis-associated peritonitis: a single-center, retrospective study

BACKGROUND

Peritoneal dialysis (PD)-associated peritonitis is a serious complication observed in peritoneal dialysis patients. Herein, we investigated the clinical characteristics and treatment outcomes of PD peritonitis in patients with different PD durations.

METHODS

All peritonitis episodes from January 2007 to December 2020 at Peking University People's hospital PD center were retrospectively analyzed and divided into the long-dialysis duration (≥60 months, LDD) and short-dialysis duration (<60 months, SDD) groups. Clinical characteristics and outcomes were compared between these groups. The risk factors for treatment failure were analyzed using a logistic regression model.

RESULTS

During 14 years, 156 patients had 267 peritonitis episodes. There were 83 (31.1%) peritonitis episodes in the LDD group and 184 (68.9%) in the SDD group. No statistical difference was noted in peritonitis causes and the composition of causative pathogens between the two groups. The hospitalization, treatment failure, and transfer-to-hemodialysis rates, and peritonitis-related mortality were significantly higher in the LDD group than in the SDD group (all p < .05). Logistic regression analysis revealed that PD duration was an independent risk factor for PD-associated hospitalization, treatment failure and peritonitis-related death (p < .05). The receiver operating characteristic curve analysis results showed that when the cutoff value of PD duration was 5.5 years, the sensitivity of predicting PD peritonitis treatment failure was 51.1%, specificity was 78.8%, and the area under the curve was 0.679 (95% confidence interval: 0.594-0.765, p < .001).

CONCLUSIONS

PD duration is an independent risk factor for poor prognosis in PD peritonitis. Careful and active attention should be paid to the prevention of peritonitis in PD patients with long PD duration.

Protein kinase C beta deficiency increases glucose-mediated peritoneal damage via M1 macrophage polarization and up-regulation of mesothelial protein kinase C alpha

BACKGROUND

Peritoneal membrane (PM) damage during peritoneal dialysis (PD) is mediated largely by high glucose (HG)-induced pro-inflammatory and neo-angiogenic processes, resulting in PM fibrosis and ultrafiltration failure. We recently demonstrated a crucial role for protein kinase C (PKC) isoform α in mesothelial cells.

METHODS

In this study we investigate the role of PKCβ in PM damage in vitro using primary mouse peritoneal macrophages (MPMΦ), human macrophages (HMΦ) and immortalized mouse peritoneal mesothelial cells (MPMCs), as well as in vivo using a chronic PD mouse model.

RESULTS

We demonstrate that PKCβ is the predominant classical PKC isoform expressed in primary MPMΦ and its expression is up-regulated in vitro under HG conditions. After in vitro lipopolysaccharides stimulation PKCβ-/- MPMΦ demonstrates increased levels of interleukin 6 (IL-6), tumour necrosis factor α, and monocyte chemoattractant protein-1 and drastically decrease IL-10 release compared with wild-type (WT) cells. In vivo, catheter-delivered treatment with HG PD fluid for 5 weeks induces PKCβ up-regulation in omentum of WT mice and results in inflammatory response and PM damage characterized by fibrosis and neo-angiogenesis. In comparison to WT mice, all pathological changes are strongly aggravated in PKCβ-/- animals. Underlying molecular mechanisms involve a pro-inflammatory M1 polarization shift of MPMΦ and up-regulation of PKCα in MPMCs of PKCβ-/- mice. Finally, we demonstrate PKCβ involvement in HG-induced polarization processes in HMΦ.

CONCLUSIONS

PKCβ as the dominant PKC isoform in MPMΦ is up-regulated by HG PD fluid and exerts anti-inflammatory effects during PD through regulation of MPMΦ M1/M2 polarization and control of the dominant mesothelial PKC isoform α.

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

Objective

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

Design

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

Results

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

Conclusions

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

Effect of Duration of Chronic Peritoneal Dialysis Therapy on the Development of Peritonitis

Objective

Long-term chronic peritoneal dialysis (CPD) therapy has been associated with alterations in peritoneal membrane structure and peritoneal macrophage function. We thus reviewed our experience with the development of peritonitis among patients maintained on CPD therapy for various time periods to determine if the spectrum of organisms, rates of peritonitis, and outcome changed with the duration of CPD therapy.

Setting and Patients

Patients maintained on CPD therapy in our out-patient unit in New Haven, Connecticut.

Design

Retrospective review of the charts of patients maintained on CPD therapy (HomeChoice Cycler or Ultrabag, Baxter, McGaw Park, IL, U.S.A.) between 1 January 1997 and 31 March 1998. These patients were divided into three groups: group 1, patients maintained on CPD therapy < 12 months; group 2, patients maintained on CPD therapy for 13 - 36 months; and group 3, patients maintained on CPD therapy for ≥ 37 months.

Results

The study included 256 patients: 101 patients in group 1, 110 patients in group 2, and 45 patients in group 3. All groups of patients were similar in age. There were significantly fewer Caucasians and fewer males in group 3 in comparison to groups 1 and 2. The incidence of diabetes mellitus, coronary artery disease, and peripheral vascular disease was significantly lower among patients in group 3 in comparison to groups 1 and 2. There were 155 episodes of peritonitis during the study period for an overall rate of 1 episode in 18.7 patient-months. The overall, gram-positive, and gram-negative rates of peritonitis were not significantly different among the patients in groups 1, 2, and 3. There were more episodes of Staphylococcus aureus peritonitis among patients in group 3 in comparison to group 2 (1 episode in 59.6 vs 1 episode in 280.2 patient-months, respectively). Two weeks after the development of peritonitis, 94.6% of the patients in group 3 continued CPD therapy, while 79.4% of the patients in group 1 continued CPD therapy ( p < 0.05). No patient in group 3 transferred to hemodialysis, while 10.3% and 8.2% of the patients in groups 1 and 2 transferred to hemodialysis ( p < 0.05). The death rate 2 weeks after the onset of peritonitis was 10.3%, 9.8%, and 5.4% in groups 1, 2, and 3, respectively ( p = NS).

Conclusions

Despite the immunological and morphological changes that occur in the peritoneal cavity with increased time on CPD therapy, there was no difference in the overall, gram-positive, or gram-negative rates of peritonitis for patients maintained on CPD therapy for various time periods. Patients in group 3 continued CPD therapy more often than did patients in group 1. Patients in group 3 transferred to hemodialysis less often than did the remaining patients in the study period. The incidence of death was not significantly different for the three groups of patients.

Hyperleptinemia in Patients with End-Stage Renal Disease Undergoing Continuous Ambulatory Peritoneal Dialysis

Objective

To determine whether the increased plasma leptin levels reported in hemodialyzed patients is a feature of end-stage renal disease or an artifact of hemodialysis, we studied plasma levels in patients treated exclusively by continuous ambulatory peritoneal dialysis (CAPD).

Design

Prospective comparison of end points in CAPD patients and matched healthy subjects.

Setting

Tertiary care institutional dialysis center.

Participants

Fifty-six healthy subjects, age 50.8 ± 2.3 years, body mass index (BMI) 27.7 ± 1.3 kg/m2, recruited through public announcement, and 36 patients with end-stage renal disease, age 51.0 ± 2.4 yr, BM128.2 ± 1.3 kg/m2, enrolled in a CAPD treatment program.

Intervention

Four exchanges of CAPD per day, using 2.0, 2.5, or 3.0 L of dialysate over a period of 1 -96 months (median 22 mth).

Main Outcome Measures

The primary outcome measure was plasma leptin concentration. Secondary measures included plasma glucose, insulin, C-peptide, and cortisol concentrations; and residual renal function and dialysis adequacy (Kt/V).

Results

Plasma leptin levels in CAPD patients were 27.1 -490 ng/mL(women)and 1.3 -355 ng/mL(men); the levels in healthy subjects were 2.0 84.7 ng/mL (women) and 1.8 -55.4 ng/mL (men). The mean leptin levels were 5-fold higher among CAPD-treated men than control men (49.9 ± 18.4 vs 9.8 ± 2.5 ng/mL, p < 0.001) and 7.5-fold higher among CAPD-treated women than control women (220 ± 28.1 vs 29.3 ± 3.7 ng/mL, p < 0.0001). Female gender and BMI were the strongest predictors of hyperleptinemia in CAPD patients.

Conclusion

These results indicate that hyperleptinemia is a feature of terminal renal failure, not an artifact of hemodialysis.

Transmigration of Blood Leukocytes into the Peritoneal Cavity is Related to the Upregulation of ICAM-1 (CD54) and MAC-1 (CD11b/CD18) Adhesion Molecules

Background

Migration of blood leukocytes into the peritoneal cavity of patients treated with peritoneal dialysis appears to be an important mechanism to prevent and fight peritonitis. To study the role of adhesion molecules in the process of leukocyte transmigration, we compared the expression of several adhesion receptors between peripheral blood monocytes and macrophages isolated from overnight dwell effluents.

Methods

The study was performed in 12, stable, infection-free patients treated with continuous ambulatory peritoneal dialysis (CAPD) and in 9 patients during peritonitis. In another set of experiments, we analyzed the expression of these molecules on blood leukocytes in 10 predialysis chronic renal failure (CRF) patients and 9 healthy controls. Peritoneal cells from an 8-hour dwell were isolated by centrifugation. Expression of adhesion receptors CD11a, CD11b, CD18, CD49d, and CD54 on blood and peritoneal leukocytes was measured using flow cytometry.

Results

In macrophages from the uninfected effluents, expression of both subunits of Mac-1 integrin receptor (CD11b and CD18) and intercellular adhesion molecule (ICAM)-1 receptor (CD54) was upregulated compared to peripheral blood monocytes from the same patients. The median value of mean fluorescence intensity in blood and effluent was 760.3 versus 1085.8 for CD11b ( p = 0.013), 288.8 versus 448.6 for CD18 ( p = 0.003), and 186.1 versus 365.7 for CD54 ( p = 0.001). The same adhesion receptors were also significantly upregulated on peritoneal macrophages and neutrophils during peritonitis compared to blood leukocytes. Blood leukocytes from CAPD and CRF patients showed higher expression of CD54 and CD49d molecules compared to leukocytes from healthy controls.

Conclusions

These data suggest that transmigration of blood leukocytes into the peritoneal cavity during uncomplicated dialysis and in peritonitis is related to selective upregulation of ICAM-1 (CD54) and Mac-1 (CD18/CD11b) receptors.

Intraperitoneal Hyaluronan Production in Stable Continuous Ambulatory Peritoneal Dialysis Patients

Objective

Several cytokines and proteins are excreted intraperitoneally during the course of peritonitis and stable states in continuous ambulatory peritoneal dialysis (CAPD) patients. Dialysate hyaluronan (HYA) is also regarded as a marker of peritoneal healing during bacterial peritonitis. We examined here, intraperitoneal HYA production in stable CAPD patients and compared the results to those of the peritoneal equilibration test (PET), the length of time on dialysis, and other marker proteins.

Design

We determined the concentration of HYA and other marker proteins in the 4-hour-dwell dialysate at 1-year intervals.

Setting

CAPD unit in Hitachi General Hospital.

Patients

The subjects were 46 stable CAPD patients who underwent 104 PETs.

Results

A correlation was found between the length of time on dialysis and the amount of HYA excretion in the 4-hr-dwell dialysate ( r = 0.403, p < 0.001). A positive but weak correlation was found between the dialysate-to-plasma ratio of the creatinine concentration and dialysate HYA excretion ( r = 0.229, p < 0.05). Seven patients were over the 90th percentile in both the concentration of HYA (>349.2 ng/mL) and the amount of HYA (>743.6 μg/4-hr dwell). Five patients exceeded 1000 μg of HYA excretion in the 4-hr-dwell dialysate, 4 of whom showed an abrupt increase of HYA excretion to more than 1000 μg/4-hr dwell, and discontinued CAPD within 6 months due to ultrafiltration failure. Two of these 4 patients were diagnosed with sclerosing encapsulating peritonitis at autopsy.

Conclusion

Intraperitoneal HYA production increased with both higher permeable membrane and the length of time on CAPD. Monitoring of HYA in the peritoneal dialysate may be useful as a marker to assess functional and morphological changes in the peritoneum in long-term CAPD patients.

Capd Peritonitis Induces the Production of a Novel Peptide, Daintain/Allograft Inflammatory Factor-1

← Objectives

To study the occurrence of a novel macrophage-derived peptide, daintain/allograft inflammatory factor-1 (AIF-1), in dialysate from continuous ambulatory peritoneal dialysis (CAPD) patients at commencement and after a follow-up period of therapy and during peritonitis. In addition, we studied peptide production in response to bacterial stimulation of monocytes and macrophages.

← Design

Peritoneal fluid and supernatants from cells stimulated with different bacteria were analyzed for daintain/AIF-1.

← Patients and Setting

Peritoneal fluid was obtained from 5 patients at commencement of CAPD therapy and during 8 weeks follow-up, and from 14 patients (10 males, 4 females) during CAPD peritonitis and during the noninfected steady state. All patients were admitted to the Karolinska Hospital. A human monocyte cell-line, THP-1 was differentiated to macrophages, and both monocytes and macrophages were stimulated with live and heat-inactivated Escherichia coli, Staphylococcus aureus, and S. epidermidis Cells were also stimulated with interleukin (IL)-1β and interferon gamma (IFNγ). Daintain/AIF-1 was analyzed with radioimmunoassay technique and IL-8 with enzyme immunoassay technique.

← Results

An increased production of daintain/AIF-1 was observed in the first spent dialysate in the newly started CAPD patients, with a decrease during the follow-up period ( p < 0.05). During peritonitis, the first spent dialysate revealed significantly higher levels of daintain/AIF-1 (3.9 ng/mL) compared to the noninfected state (0.8 ng/mL), with production normalizing after 9 – 12 days. Bacterial stimulation with E. coli, S. aureus or S. epidermidi sinduced higher daintain/AIF-1 response in monocytes compared to macrophages ( p < 0.05). Live bacteria induced higher production of the peptide compared to heat-inactivated bacteria ( p < 0.05). Interleukin-1β and IFNγ were used to stimulate monocytes and macrophages; however, no daintain/AIF-1 production was found, although increased IL-8 levels were detected.

← Conclusion

CAPD peritonitis induces a high and prominent daintain/AIF-1 response. Bacteria are able to induce a response of the peptide from monocytes and macrophages, and it is likely that the virulent parts of the bacteria are heat-labile structures. The early rise in daintain/AIF-1 might be used as a marker of CAPD peritonitis.

Leukocyte CD11b and CD62L Expression in Response to Interstitial Inflammation in CAPD Patients

Objective

Very little is known about the kinetics of leukocyte recruitment and the modulation of adhesion molecules on leukocytes in the interstitium at the site of inflammation outside the peritoneal cavity in patients on peritoneal dialysis. These issues were addressed in the present study.

Patients and Methods

Two skin blisters were raised in 10 patients on peritoneal dialysis and in 19 healthy subjects. After 12 hours, blister exudates were collected and the blisters were thereafter challenged with buffer or autologous serum in order to establish an intermediate and an intense cutaneous inflammation. Leukocyte count, leukocyte CD11b/CD62L expression, monocyte chemotactic protein-1 (MCP-1), and interleukin-8 (IL-8) were determined in blood and at the three sites of interstitial inflammation by immunostaining, flow cytometry, and ELISA.

Results

In monocytes and granulocytes, expression of CD11b increased and CD62L decreased significantly during the transmigration process from the peripheral blood into the three sites of interstitial inflammation. In the nonstimulated blister, expression of CD11b on both monocytes and granulocytes was similar in patients and healthy subjects. At the site of intermediate inflammation, expression of CD11b on both monocytes and granulocytes was significantly higher in healthy subjects compared to patients ( p < 0.05 and p < 0.001 respectively). At the site of intense inflammation, expression of CD11b on granulocytes was significantly lower ( p < 0.001), and CD62L significantly higher ( p < 0.001) in patients. Interstitial concentrations of MCP-1 and IL-8 at the sites of intermediate inflammation were significantly higher in healthy subjects compared to patients ( p < 0.05 and p < 0.05 respectively). However, at the site of intense inflammation, similar concentrations of MCP-1 and IL-8 were observed. Furthermore, there were no significant correlations between concentrations of MCP-1 and IL-8 in blister exudates and expression of CD11b on monocytes and granulocytes at the sites of interstitial inflammation.

Conclusion

The ability of monocytes and granulocytes to modulate the expression of adhesion molecule in response to interstitial inflammation was significantly impaired in patients on peritoneal dialysis. Furthermore, these data suggest that the expression of CD11b on leukocytes is not dependent on concentrations of IL-8 and MCP-1 in interstitium in this patient group.

Dendritic Cells as Arbiters of Peritoneal Immune Responses

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

Acute cholecystitis in end-stage renal disease patients: a nation-wide longitudinal study

BACKGROUND

The objective of this study was to evaluate the risks of acute cholecystitis among end-stage renal disease patients and compare the incidence between two dialysis modality.

STUDY DESIGN

In this retrospective cohort study, records of fifty thousand end-stage renal disease patients older than 20 years of age from 1998 to 2007 and an age, gender, Charlson's score, diabetes, and dyslipidemia matched control cohort were retrieved from Taiwan National Health Insurance Research Database. Hospitalizations for acute cholecystitis were retrieved using ICD-9-CM diagnosis codes and ICD-9-CM operation codes from in-patient claims.

RESULTS

The incidence rates were 5.8 per 1000 patient-years in the end-stage renal disease patients and 0.92 per 1000 patient-years in the control group. End-stage renal disease was an independent risk factor for acute cholecystitis. In the end-stage renal disease patients, independent risk factors were old age, higher Charlson's score, diabetes, severe liver disease, atrial fibrillation, and haemodialysis (all p<0.05). However, the peritoneal dialysis patients had a higher mortality rate after developing acute cholecystitis.

CONCLUSION

Acute cholecystitis is not uncommon in end-stage renal disease patients. The independent risk factors were older age, higher Charlson's score, atrial fibrillation, severe liver disease, diabetes, and dialysis modality. Haemodialysis patients had a higher risk of acute cholecystitis than PD patients.

Pathophysiological changes to the peritoneal membrane during PD-related peritonitis: the role of mesothelial cells

The success of peritoneal dialysis (PD) is dependent on the structural and functional integrity of the peritoneal membrane. The mesothelium lines the peritoneal membrane and is the first line of defense against chemical and/or bacterial insult. Peritonitis remains a major complication of PD and is a predominant cause of technique failure, morbidity and mortality amongst PD patients. With appropriate antibiotic treatment, peritonitis resolves without further complications, but in some PD patients excessive peritoneal inflammatory responses lead to mesothelial cell exfoliation and thickening of the submesothelium, resulting in peritoneal fibrosis and sclerosis. The detrimental changes in the peritoneal membrane structure and function correlate with the number and severity of peritonitis episodes and the need for catheter removal. There is evidence that despite clinical resolution of peritonitis, increased levels of inflammatory and fibrotic mediators may persist in the peritoneal cavity, signifying persistent injury to the mesothelial cells. This review will describe the structural and functional changes that occur in the peritoneal membrane during peritonitis and how mesothelial cells contribute to these changes and respond to infection. The latter part of the review discusses the potential of mesothelial cell transplantation and genetic manipulation in the preservation of the peritoneal membrane.

Functional effector memory T cells enrich the peritoneal cavity of patients treated with peritoneal dialysis

The frequency and severity of episodes of peritonitis adversely affect the structure and function of the peritoneal membrane in patients treated with peritoneal dialysis (PD), but the underlying mechanisms are not well understood. Alterations in the phenotype and function of resident peritoneal cells may contribute. Because effector memory T cells play a pivotal role in maintaining peripheral tissue immunity, we hypothesized that these cells may initiate or perpetuate the peritoneal inflammatory response. Here, we characterized the phenotype and effector function of peritoneal memory T cells. We found that functional effector memory T cells capable of mounting long-term recall responses enrich the peritoneal cavity of PD patients. Peritoneal T cells were able to mount a Th1-polarized response to recall antigens, and these responses were greater in peritoneal T cells compared with T cells in the peripheral blood. We also observed that the peritoneal T cells had altered telomeres; some cells had ultrashort telomeres, suggesting a highly differentiated local population. In summary, we describe a resident population of memory T cells in the peritoneum of PD patients and speculate that these cells form part of the first line of defense against invading pathogens.

Antioxidant Status of Patients on Peritoneal Dialysis: Associations with Inflammation and Glycoxidative Stress

Background

Patients on peritoneal dialysis (PD) frequently exhibit oxidant–antioxidant imbalance, advanced glycation end-product overload, and subclinical inflammation but the interrelations between these pathophysiological changes have not been fully elucidated.

Subjects and Methods

To study possible associations, a cross-sectional study of antioxidant status, glycoxidative stress, and inflammation, using HPLC and ELISA methods, was undertaken in 37 PD patients and age- and sex-matched healthy controls.

Results

Plasma ascorbate concentrations were low in patients not taking at least low-dose vitamin C supplements. In patients taking vitamin C supplements, there was a positive relation between ascorbate and pentosidine concentrations. Vitamin E and carotenoid concentrations were comparable between patients and controls, while lycopene and lutein/zeaxanthin concentrations were lower. Interleukin-6, C-reactive protein (CRP), and pentosidine concentrations were elevated in PD patients. β–Cryptoxanthin, lycopene, and lutein/zeaxanthin concentrations were inversely related to interleukin-6 concentrations. β–Cryptoxanthin concentrations were also inversely related to CRP concentrations. Pentosidine showed a low dialysate-to-plasma ratio, indicating low peritoneal clearance. Pentosidine concentrations increased with duration of PD therapy, while α– and β–carotene concentrations decreased. Malondialdehyde concentrations were elevated compared to controls but remained within the normal range. Retinol concentrations decreased with PD therapy and were inversely related to interleukin-6 and CRP concentrations.

Conclusions

Low-dose vitamin C supplements and a carotenoid-rich diet should be recommended for PD patients to maintain normal antioxidant status and efficiently counteract the chronic inflammatory response, rather than high doses of vitamin C, which could play a role as a precursor of pentosidine.

Fas expression on peritoneal macrophages during continuous ambulatory peritoneal dialysis peritonitis

BACKGROUND

Peritonitis is a common complication of end stage renal failure (ESRF) patients receiving continuous ambulatory peritoneal dialysis (CAPD). Peritoneal macrophage may participate in the activation of specific T cells and in the generation of local cell-mediated immunity to various pathogens. The purpose of this study is to investigate the possible role of macrophage in CAPD patients with peritonitis.

METHODS

We evaluated the expression of Fas receptor (CD95), ICAM-1 (CD54), CD25, and CD69 by two-color flow cytometry on extravasted macrophages from 16 ESRF patients on CAPD with peritonitis (peritonitis-positive) and compared them to 11 ESRF patients on CAPD without peritonitis (peritonitis-negative) and normal controls.

RESULTS

We found an increased expression of CD95, CD54, and CD25 on macrophage in peritonitis-positive group compared to controls (all p < 0.001). In the peritonitis-positive group, the CD95 expression was significantly higher than that of the peritonitis-negative group (p < 0.001). The expression of CD54, CD25, and CD69, however, was not significantly different between the peritonitis-positive and peritonitis-negative CAPD subgroups.

CONCLUSION

We found an abnormally increased percentage of macrophage-expressing Fas receptor and ICAM-1, and the percentage of CD95+ macrophage, but not those of other markers, were increased among the subset of CAPD patients with peritonitis. The later finding suggests that this macrophage phenotype is associated with peritonitis occurring in CAPD.

Clinical indices of in vivo biocompatibility: The role of ex vivo cell function studies and effluent markers in peritoneal dialysis patients

Clinical indices of in vivo biocompatibility: The role of ex vivo cell function studies and effluent markers in peritoneal dialysis patients. Over the past 20 years, studies of the biocompatibility profile of peritoneal dialysis solutions (PDF) have evolved from initial in vitro studies assessing the impact of solutions on leukocyte function to evaluations of mesothelial cell behavior. More recent biocompatibility evaluations have involved assessments of the impact of PDF on membrane integrity and cell function in peritoneal dialysis (PD) patients. The development of ex vivo systems for the evaluation of in vivo cell function, and effluent markers of membrane integrity and inflammation in patients exposed both acutely and chronically to conventional and new PDF will be interpreted in the context of our current understanding of the biology of the dialyzed peritoneum. The available data indicate that exposure of the peritoneal environment to more biocompatible PDF is associated with improvements in peritoneal cell function, alterations in markers of membrane integrity, and reduced local inflammation. These data suggest that more biocompatible PDF will have a positive impact on host defense, peritoneal homeostasis, and the long-term preservation of peritoneal membrane function in PD patients.

Host defenses in APD

The incidence of peritonitis in peritoneal dialysis (PD) has further decreased after the introduction of automated peritoneal dialysis (APD) into clinical routine. Technical advances such as a reduction in the number of connections, more motivated patients, and improved host defense mechanisms in APD have been described. We found that the long daytime interval without dialysate exchanges leads to a higher absolute number of peritoneal macrophages which are capable of an improved first-line host defense. This is demonstrated by a higher release of cytokines of peritoneal macrophages after stimulation with lipopolysaccharides. The dry "day" in nightly intermittent PD seems to have no relevant additional positive effects on peritoneal host defense compared to continuous cyclic peritoneal dialysis. The regeneration of peritoneal cell populations induced by intervals without PD remains relevant even in times when more "biocompatible" PD solutions become available.

Restoration of the cellular thiol status of peritoneal macrophages from CAPD patients by the flavonoids silibinin and silymarin

During continuous ambulatory peritoneal dialysis (CAPD) the peritoneal immune cells, mainly macrophages, are highly compromised by multiple factors including oxidative stress, resulting in a loss of functional activity. One reason for the increase of inflammatory reactions could be an imbalance in the thiol-disulfide status. Here, the possible protective effects of the antioxidant flavonoid complex silymarin and its major component silibinin on the cellular thiol status were investigated. Peritoneal macrophages from dialysis fluid of 30 CAPD patients were treated with silymarin or silibinin up to 35 days. A time-dependent increase of intracellular thiols was observed with a nearly linear increment up to 2.5-fold after 96 hours, reaching a maximum of 3.5-fold after 20 days of culture. Surface-located thiols were also elevated. The stabilization of the cellular thiol status was followed by an improvement of phagocytosis and the degree of maturation as well as significant changes in the synthesis of IL-6 and IL-1ra. Furthermore, the treatment of peritoneal macrophages with flavonoids in combination with cysteine donors resulted in a shortened and more efficient time course of thiol normalization as well as in a further increased phagocytosis. In addition, GSH-depletion in thiol-deficient media simulating CAPD procedures led to intracellular thiol deficiency similar to the in vivo situation. It is concluded that treatment with milk thistle extracts silymarin and silibinin alone or, more effectively in combination with cysteine donors, provide a benefit for peritoneal macrophages of CAPD-patients due to a normalization and activation of the cellular thiol status followed by a restoration of specific functional capabilities.

Stimulated IFNgamma and IL-10 secretion of blood mononuclear cells in patients on renal replacement therapies show different secretion patterns

Infection is still a leading cause of morbidity and mortality in patients on renal replacement therapy (RRT). Although the role of the immune system is of great importance, little is known about the influence of the mode of RRT to the preferential excretions of regulator cytokines of mononuclear cells. Therefore, we investigated the stimulated IFNgamma (Th1) and IL-10 (Th2) secretions of mononuclear cells from patients on RRT. Blood was drawn from 10 controls, 15 patients on hemodialysis (HD), 15 on peritoneal dialysis (PD), and 10 after kidney transplantation (Tx). The cells were separated, and phytohemagglutinine (PHA) was added for stimulation. After 0, 6, and 24 h, IFNgamma and IL-10 (pg/ml) were measured by enzyme-linked immunosorbent assay. IFNgamma secretion was significantly enhanced 6 (p < 0.001) and 24 h (p = 0.002) after stimulation in all groups (in mean +/- SEM). The analysis of the subgroups 6 h after adding PHA showed significant differences (p = 0.0239) with the lowest IFNgamma in Tx (16 +/- 5) and the highest in PD (79 +/- 30). For IL-10, secretion was enhanced in all groups 6 h after stimulation (p < 0.0116). The lowest secretions were seen in HD (18 +/- 8) and controls (27 +/- 9); the highest secretions were in Tx (98 +/- 20) and PD (57 +/- 12). The differences between HD and Tx (p < 0.01) and HD versus PD (p = 0.05) were significant. The stimulated cytokine secretion of blood mononuclear cells is preserved with RRT. The modes of RRT could influence the pattern of cytokine secretion. Surprisingly, the cells from patients on PD showed enhanced IL-10 secretion compared to HD. Presumably, this is due to the chronic contact of peritoneal dialysis fluids with monocytes and the lymphatic system in PD.

In vivo exposure to bicarbonate/lactate- and bicarbonate-buffered peritoneal dialysis fluids improves ex vivo peritoneal macrophage function

The impact on peritoneal macrophage (PMO) function of acidic lactate-buffered (Lac-PDF [PD4]; 40 mmol/L of lactate; pH 5.2) and neutral-pH, bicarbonate-buffered (TB; 38 mmol/L of bicarbonate; pH 7. 3) and bicarbonate/lactate-buffered (TBL; 25 mmol/L of bicarbonate/15 mmol/L of lactate; pH 7.3) peritoneal dialysis fluids (PDFs) was compared during a study of continuous therapy with PD4, TB, or TBL. During a run-in phase of 6 weeks when all patients (n = 15) were treated with their regular dialysis regimen with Lac-PDF, median PMO tumor necrosis factor alpha (TNFalpha) release values were 203.6, 89.9, and 115.5 pg TNFalpha/10(6) PMO in the patients subsequently randomized to the PD4, TB, and TBL treatment groups, respectively. Median stimulated TNFalpha values (serum-treated zymosan [STZ], 10 microgram/mL) were 1,894.6, 567.3, and 554.5 pg TNFalpha/10(6) PMO in the same groups, respectively. During the trial phase of 12 weeks, when the three groups of patients (n = 5 per group) were randomized to continuous treatment with PD4, TB, or TBL, median constitutive TNFalpha release values were 204.7, 131.4, and 155.4 pg TNFalpha/10(6) PMO, respectively. Stimulated TNFalpha values (STZ, 10 microgram/mL) were 1,911, 1,832, and 1,378 pg TNFalpha/10(6) PMO in the same groups, respectively. Repeated-measures analysis of variance comparing the run-in phase with the trial phase showed that PMO TNFalpha release was significantly elevated in patients treated with both TB (P = 0.040) and TBL (P = 0.014) but not in patients treated with Lac-PDF (P = 0. 795). These data suggest that patients continuously exposed to bicarbonate- and bicarbonate/lactate-buffered PDFs might have better preserved PMO function and thus improved host defense status.

Increased levels of transforming growth factor beta 1 and basic fibroblast growth factor in patients on CAPD: a study during non-infected steady state and peritonitis

Long-term influence of continuous ambulatory peritoneal dialysis (CAPD) on concentrations of transforming growth factor beta1 (TGF-beta1) and basic fibroblast growth factor (bFGF) in the peritoneal effluent, and the effect of peritonitis on these cytokines were investigated. TGF-beta1 and bFGF were assayed in effluent samples from dialysate bags collected during the initial week of treatment with CAPD and at 5 months. To determine the effect of peritonitis, dialysate bags were collected on admission to the hospital and on days 3 and 10 and also during non-infected steady state. Serum was drawn prior to infection and on days 1 and 10. TGF-beta1 increased more than threefold during the longitudinal follow-up period, median concentrations of 35 pg/ml to 106 pg/ml (P<0.05). No change in bFGF was seen during this initial 5 months. TGF-beta1 was increased on the first day of peritonitis (median concentration 169 pg/ml) and reached its maximum on day 3 of infection, (median concentration 216 pg/ml) (P<0.05 vs non-infected state, median concentration 39 pg/ml). Basic FGF reached a maximum on day three of infection (median concentration 7.7 pg/ml; P=0.01 vs non-infected state) and then slowly declined. In conclusion, TGF-beta1 is influenced by CAPD treatment per se, and together with bFGF is increased during peritonitis, indicating its importance in the peritoneum and its potential involvement in the development of tissue fibrosis and eventually ultrafiltration failure.

Biocompatibility and buffers: effect of bicarbonate-buffered peritoneal dialysis fluids on peritoneal cell function

BACKGROUND

Conventional peritoneal dialysis fluids (PDF) have been shown to compromise the function of both leukocytes and human peritoneal mesothelial cells (HPMC). Various in vitro studies have identified the low initial pH in combination with high lactate content, as well as the hyperosmolality and high glucose concentration present in currently used solutions as the primary determinants of their bioincompatibility. Bicarbonate buffered PDF (at neutral pH) display improved in vitro biocompatibility as compared to conventional, lactate buffered PDF. However, little information is currently available regarding the potential impact of PDF on the function of human peritoneal fibroblasts (HPFB), the major cell population present in peritoneal interstitium.

METHODS

The current study compares the effect of bicarbonate and lactate buffered PDF in a model system of resting peritoneal mesothelial cells and fibroblasts cultured from human omentum. Interleukin-1 beta-stimulated IL-6 release from HPMC and HPFB was used as the cell functional parameter.

RESULTS

While short (30 min) pre-exposure to lactate buffered PDF significantly reduced the IL-1 beta-stimulated IL-6 release from HPMC during a subsequent recovery period (24 hr), a significant decrease in HPMC IL-6 secretion with bicarbonate buffered PDF was only observed after prolonged (> or = 60 min) exposure. In contrast, no significant IL-6 inhibition was detected with HPFB pre-exposed to PDF for up to 90 minutes. A significant suppression of HPFB IL-6 secretion was only observed in coincubation experiments (24 hr) with dilutions of both types of PDF.

CONCLUSIONS

These results indicate that (i) bicarbonate buffered PDF are less inhibitory to peritoneal cell function as compared to conventional, lactate buffered PDF; and (ii) HPFB may be more resistant than HPMC to bioincompatible PDF.

Membrane longevity in peritoneal dialysis: impact of infection and bio-incompatible solutions

As experience with peritoneal dialysis (PD) has improved and peritonitis rates have decreased, more patients are surviving for long periods on PD. Associated with this has been the recognition that there are unique complications of PD, specifically sclerosing syndromes and membrane failure that are most common in the long-term patient. Although anecdotal data would suggest that the long-term exposure to "bio-incompatable" fluids and or the occurrence of severe episodes of peritonitis are contributory in the pathogenesis of these diseases, cause and effect have not been proven. Normal peritoneal structure, changes that occur over time, and how the normal resident immune defense systems are altered with PD are reviewed. It is known that the continued loss of macrophages in the PD fluid results in an ever increasing percentage of immature cells in the peritoneum, which paradoxically are more reactive in terms of cytokine generation and less effective in host defense. The potential harmful effects of glucose and advanced glycosylation end products are also explored. The review concludes stating that further research is needed to better link the clinical syndromes with alterations in membrane structure/function.

Factors increasing severity of peritonitis in long-term peritoneal dialysis patients

Peritonitis is the most frequent complication and a leading cause of discontinuation of peritoneal dialysis (PD). Intact epithelial lining, sufficient blood flow, and adequate immunologic responses are vital to eradicate infection. In long-term PD, various pathological changes such as denudation of peritoneal mesothelial cells, duplication of submesothelial and/or capillary basement membranes, submesothelial fibrin deposit, and peritoneal fibrosis have been reported. Causes of these changes of the peritoneum are multifactorial. Commonly used dialysis solutions that are acidic, hypertonic, containing high concentrations of glucose and lactate, contaminated by glucose and/or plastic degradation products are not biocompatible and may induce chronic immune reactions in the peritoneal cavity. Long-term exposure of the peritoneum to dialysis solutions, the peritoneal catheter, and recurrent episodes of peritonitis all contribute to peritoneal injury. In addition, long-term exposure of peritoneal cells such as macrophages, mesothelial cells, and fibroblasts to dialysis solutions may also alter the normal immunologic reactions against bacteria. Peritoneal concentrations of opsonins such as Ig, complement, and protease are approximately 1% of the serum levels and far below the level sufficient to eradicate bacteria due to continuous peritoneal lavage and dilution with dialysis solutions. Furthermore, glycation of IgG induces chronic activation of macrophages and decreases normal opsonic activities against bacteria. Fibrin deposits, collagen accumulation, and cellular desert of the peritoneum observed in long-term peritoneal dialysis patients may serve as a safe shelter for bacteria from contact with inflammatory cells and opsonin and delay eradication of bacteria. In conclusion, peritonitis is often more severe in patients on long-term PD. In this setting, peritonitis needs special attention to prevent life-threatening infection and further damage of the peritoneum.

Difference in the blood monocyte phenotype between uremic patients and healthy controls: its relation to monocyte differentiation into macrophages in the peritoneal cavity

The phenotypic alterations between blood monocytes from 11 patients with end-stage renal disease, who had been on peritoneal dialysis for less than one week, and blood monocytes from 10 healthy controls, were analyzed. In addition, peritoneal macrophages in the dialysate effluent were enclosed. Analysis of functional receptor density was performed using immunostaining and flow cytometry. The phenotypic characterization was selected to represent various biological functions such as adhesion, phagocytosis (CD11b/CD18, CD11c/CD18, CD16), antigen-presentation (HLA-DR, ICAM-1), differentiation (transferrin receptor, CD71), receptor for LPS (CD14) and initiation of the coagulation cascade (Tissue factor, CD142). The proportion of CD16-positive blood monocytes and the quantitative level of ICAM-1 were higher in the patient group, compared to healthy controls. A significant increase in the quantitative level of CD11b/CD18, CD11c/CD18, HLA-DR and ICAM-1, transferrin receptor, CD14 and CD16, was found on peritoneal macrophages, compared to monocytes, harvested both from the corresponding patients, as well as from healthy donors. In contrast, we did not find any significant differences in the expression of tissue factor between monocytes and peritoneal macrophages. In conclusion, phenotypic differences exist between monocyte populations in the blood circulation of CAPD patients, and healthy individuals. We also show that transmigration of monocytes into the peritoneal cavity implies a selective up-regulation of functional receptors, preferentially related to adhesion, and antigen-presentation in a steady-state situation in non-infected CAPD patients.

Macrophages and mesothelial cells in bacterial peritonitis

Research in recent years has examined the mechanisms underlying cellular host defence in the peritoneal cavity. These studies have established that the resident cells of the peritoneal cavity, the peritoneal macrophages (PM phi) and the mesothelial cells (HPMC) contribute to the initiation, amplification and resolution of peritoneal inflammation. Ex vivo measurements of intra-peritoneal inflammatory mediators during peritonitis has elucidated the time courses for the generation of proinflammatory, chemotactic and anti-inflammatory cytokines and have identified that their secretion occurs largely within the peritoneum. These studies provide evidence that both PM phi- and HPMC-derived mediators are directly involved in controlling inflammation. It has been widely accepted that resident PM phi form the first line of defence against peritoneal infection, a more contemporary view would suggest that the direct or indirect (via secreted pro-inflammatory cytokines) interaction between PM phi and HPMC is pivotal to the activation and subsequent amplification of the peritoneum's response to infection. Whilst the site of these interactions is unknown, considerable evidence suggests that it occurs on the surface of the mesothelium, where invading micro-organisms may colonize. In this respect Staphylococcal exoproducts can directly activate HPMC cytokine synthesis. Once the inflammatory response is initiated, recent evidence suggests, that mesothelial cells upon activation by PM phi-derived IL-1 beta and TNF-alpha, are capable of amplifying inflammation and generating signals (via the creation of a gradient of chemotactic cytokines, IL-8, MCP-1 and RANTES) for the recruitment of leukocytes into the peritoneum. This process is also facilitated via the cytokine driven up-regulation of adhesion molecule expression (ICAM-1 and VCAM-1) on HPMC. Much less is understood about the mechanisms by which inflammation is resolved, although the secretion of anti-inflammatory molecules (IL-6, IL-1ra and soluble TNF-p55/75) by receptors by PM phi and HPMC may be important in the process. The existence of a peritoneal cytokine network controlling inflammation is now well established, within this the interaction of PM phi and HPMC appears to play a pivotal role in the hosts response to peritoneal infection.