Biocompatibility of bicarbonate buffered peritoneal dialysis fluids: influence on mesothelial cell and neutrophil function

Peritoneal Dialysis Solutions Low in Glucose Degradation Products—evidence for Clinical Benefits

In Japan, two types of new peritoneal dialysis fluid (PDF) are ordinarily used: two-chambered PDF, and icodextrin PDF. Two-chambered PDF has several biocompatible characteristics, one being low glucose degradation products (GDPs). Of the several GDPs in PDF, 3,4-dideoxyglucosone-3-ene (3,4-DGE) is thought to be strongly associated with the cytotoxicity of standard PDF. Using a PDF low in GDPs may reduce exposure of the peritoneum to 3,4-DGE, helping to preserve peritoneal function in PD patients. Additionally, use of a PDF low in GDPs may reduce plasma levels of advanced glycosylation end-products in PD patients, a change that may help to preserve vascular function in PD patients.

Peritoneal rest for 24 hours after exposure to a PDF with low GDPs improves the activity of human peritoneal mesothelial cells. As compared with the use of standard PDF, the use of low-GDP PDF in combination therapy (peritoneal dialysis plus hemodialysis) may more effectively preserve peritoneal function. The new PDF low in GDPs has bio-compatible characteristics relative to peritoneum and system that may help to preserve peritoneal function or reduce complications such as atherosclerosis or dialysis-related amyloidosis in dialysis patients.

Bicarbonate/Lactate Dialysis Solution ImprovesIn VivoFunction of Peritoneal Host Defense in Rats

Objective

To assess the in vivo peritoneal inflammatory reaction in rats dialyzed with neutral, bicarbonatelactate-buffered dialysis fluid.

Methods

Chronic peritoneal dialysis was performed for 4 weeks in Wistar rats with two solutions: (1) 40 mmol/l lactate-buffered fluid, pH 5.2, with a glucose concentration of 2.27 gldl (lac); and, (2) 15 mmolll lactate and 25 mmolll bicarbonate-buffered fluid, pH 7.0 -7.5, with a glucose concentration of 2.27gldl (Bic-lac). After 4 weeks, two peritoneal equilibration tests (PET 1 and PET 2) were performed in all animals with each respective solution. PET 1 was done with test solutions alone, whereas, on a subsequent day, PET 2 was performed with test solutions supplemented with endotoxin [lipopolysaccharide (IPS)] to induce peritonitis.

Results

During PET 1 no consistent differences were detected in peritoneal permeability between the lac and Bic-lac groups. Total dialysate cell count in the Bic-lac animals was lower than in rats treated with lac fluid: that is, at 8 hours, the respective counts were 1858 ± 524 cellslμl versus 2785 ± 1162 cellslμl (p < 0.01). Dialysate from animals dialyzed with Bic-lac contained more macrophages (at 4 hours: 53.6% ± 35.8% versus 35.8% ± 8.8%, p < 0.001) and fewer neutrophils (at 4 hours: 3.6% ± 1.8% versus 15.4%± 6.1%, p < 0.001) as compared to those dialyzed with the lac solution. Concentration of nitrites in 8-hour dwell dialysate samples from Bic-lac rats was lower than that in the lac group (0.98 ± 0.28 μmollml versus 2.32 ± 0.87 μmollml, p < 0.002), but cytokine levels in the dialysates were comparable. During PET 2, the in -crease in peritoneal permeability resulting from the lPS induced inflammatory response was similar for both test solutions. Dialysate cell count was higher in the lac group versus the Bic-lac group (at 8 hours: 8789 ± 4862 cellslμl versus 3961 ± 581 cellslμl, p < 0.001), contained more neutrophils (at 8 hours: 80.0% ± 11.3% versus 54.8% ± 4.4%, p < 0.001) and fewer macrophages (at 8 hours: 6.8% ± 5.6% versus 21.2% ± 3.3%, p < 0.05). During peritonitis, we found a higher overall dialysate concentration of both tumor necrosis factor (TNFα: +53%, p < 0.05) and of interferon gamma (lFN-y: +303%, p < 0.02), in the Bic-lac group than in the lac group.

Conclusions

A lower dialysate cell count, higher percentage of macrophages, and lower percentage of neutrophils in dialysate suggest that Bic-lac fluid induces a diminished nonspecific inflammatory response of the peritoneal cavity during dialysis. However, after in vivo stimulation, peritoneal cells from animals dialyzed with Bic-lac solution possess an augmented ability to produce inflammatory cytokines.

Generation of TNFα and Interleukin-6 by Peritoneal Macrophages after Overnight Dwells with Bicarbonate- or Lactate-Buffered Dialysis Fluid

Objective

In order to evaluate the biocompatibility profile of a newly designed peritoneal dialysis fluid (PDF), we evaluated peritoneal leukocyte (PMΦ) cytokine release following overnight in vivo dwells using standard, lactate-buffered, single-chamber bag PDF (Lac-PDF) and purely bicarbonate-buffered, double-chamber bag PDF containing 34 (Bic-PDF) or 39 (Bic Hi-PDF) mmol/L bicarbonate.

Design

A randomized, open, crossover clinical trial with single weekly test dwells was performed in stable, long-term continuous ambulatory PD patients ( n = 8). During 8-hour overnight dwells, PMΦ were exposed to different PDF containing 1.5% glucose. After drainage, peritoneal cells were isolated and incubated with RPMI 1640 medium for 2 or 3 hours, with and without stimulation by lipopolysaccharide (LPS). Ex vivo release of tumor necrosis factor (TNF)-α and interleukin (IL)-6 was measured by specific ELISA technique.

Results

After pre-exposure to Lac-PDF, PMΦ generated 242 ± 279 pg TNFα/106 cells and 157 ± 105 pg IL-6/106 cells. When pre-exposed to Bic-PDF and Bic Hi-PDF, TNFα and IL-6 production of PMΦ was not significantly different from Lac-PDF. After LPS stimulation (100 ng/mL), PMΦ secretion of TNFα and IL-6 pre-exposed to three PDF revealed no significant differences between groups: TNFα was 2864 ± 1216, 2910 ± 1202, and 3291 ± 558 pg/106 cells after overnight dwells with Lac-PDF, Bic-PDF, and Bic Hi-PDF, respectively. Comparably, LPS-stimulated (100 pg/mL) PMΦ showed IL-6 secretion of 891 ± 335, 1380 ± 1149, and 1442 ± 966 pg/106 cells for Lac-PDF, Bic-PDF, and Bic Hi-PDF.

Conclusion

After long-term overnight dwells, initial pH, the different buffers, and varying glucose degradation product levels of PDF do not strongly affect PMΦ function with respect to cytokine release. The lack of significant differences between fluids may result from the complete dialysate equilibration achieved during the overnight intraperitoneal dwell.

Peritoneal Dialysis in Japan: The Issue of Encapsulating Peritoneal Sclerosis and Future Challenges

Encapsulating peritoneal sclerosis (EPS) is a life-threatening complication of peritoneal dialysis (PD). The overall prevalence of EPS in Japanese PD patients is 2.3%. Among patients on PD for less than 5 years, the rate is 0.9%; among patients on PD for 5 – 10 years, the rate is 3.8%; and among patients on PD for >10 years, it is 11.5%. Thus, the longer the treatment duration, the higher the prevalence of EPS.

Encapsulating peritoneal sclerosis does not result solely from the natural progression of peritoneal sclerosis. A “second hit” event, such as bacterial peritonitis, abdominal bleeding, or abdominal surgery may be needed to trigger the onset of EPS in the face of advanced peritoneal sclerosis.

To prevent development of EPS, PD treatment is replaced by other treatments when patients reached high-transport status. Peritoneal lavage and prednisolone administration have been reported to be effective in preventing or stopping the progress of EPS. When bowel obstruction has occurred, total enterolysis to remove the fibrous capsule from the bowel is indicated.

To maximize overall quality of life, patients with end-stage renal disease (ESRD) should have the choice to make use of all the treatment modalities available: PD, hemodialysis (HD), and transplantation. Furthermore, the development of truly biocompatible PD equipment—including peritoneal catheters, solutions, and systems—are desirable to extend PD treatment for the long term. The cost of individual products could decrease significantly if PD use were to increase to 30% from 10% among ESRD patients worldwide. As practitioners, we have to further improve the technical survival rate and functional duration of PD treatment so that adequate peritoneal function can be maintained for 10 years in at least 40% of PD patients. The goal is to place PD on par with HD using high-flux dialysis membranes and ultrapure dialysis solution.

Peritoneal Kinetics and Mesothelial Markers in CCPD Using Icodextrin for Daytime Dwell for Two Years

Objective

To evaluate the safety, efficacy, and biocompatibility of icodextrin (Ico), continuous cycling peritoneal dialysis (CCPD) patients were treated for 2 years with either Ico- or glucose (Glu)-containing dialysis fluid for their daytime dwell (14 – 15 hours). Prior to entry into the study, all patients used standard Glu solutions (Dianeal, Baxter BV, Utrecht, The Netherlands).

Design

Open, randomized, prospective two-center study.

Setting

University hospital and teaching hospital.

Patients

Both established patients and patients new to CCPD were included. A life expectancy of more than 2 years, a stable clinical condition, and written informed consent were necessary before entry. Patients aged under 18 years or with peritonitis in the previous month, and women of childbearing potential unless taking adequate contraceptive precautions, were excluded. Thirty-eight patients entered the study (19 Glu, 19 Ico).

Main Outcome Measures

Daytime dwell peritoneal effluents were collected every 3 months in combination with other study variables (clinical data, laboratory measurements, dialysis-related data, and urine collection). Peritoneal transport studies were carried out every 6 months.

Results

In Glu- and Ico-treated patients, peritoneal transport of low molecular weight solutes and protein clearances neither changed during follow-up nor differed between the two groups. Peritoneal membrane markers (CA125, interleukin-8, carboxyterminal propeptide of type I procollagen, and aminoterminal propeptide of type III procollagen) measured in effluents did not differ between the groups and did not change over time. All these markers showed a dialysate/plasma ratio of more than 1, suggesting local production. Residual renal function remained stable during follow-up and adverse clinical effects were not observed.

Conclusions

Peritoneal membrane transport kinetics and markers remained stable in both groups over a 2-year follow-up period. Membrane markers were higher in effluents than in serum, suggesting local production. No clinical side effects were demonstrated. Icodextrin was a well-tolerated effective treatment.

The Choice of Dialysis Solutions in Pediatric Chronic Peritoneal Dialysis: Guidelines by AnAD HOCEuropean Committee

Objective

To provide guidelines on choosing dialysis solutions for children on chronic peritoneal dialysis (PD).

Setting

European Paediatric Peritoneal Dialysis Working Group.

Data Source

Literature on the application of PD solutions in children ( Evidence), and discussions within the group ( Opinion).

Conclusions

Glucose is the standard osmotic agent for PD in children ( Evidence). The lowest glucose concentration needed should be used ( Opinion). Low calcium solution (1.25 mmol/L) should be applied, wherever possible, with careful monitoring of parathyroid hormone levels ( Opinion). The use of amino acid-containing dialysis fluids can be considered in malnourished children, although aggressive enteral nutrition is preferred ( Opinion). There is insufficient evidence documenting the efficacy of intraperitoneally administered amino acids ( Evidence). When ultrafiltration and/or solute removal are insufficient, poly-glucose solutions are a welcome addition to the treatment of children on nocturnal intermittent PD ( Evidence). However, in the absence of any reported long-term experience with children, their use must be closely monitored ( Opinion). Bicarbonate would appear to be the preferred buffer for PD in children, but more in vivo studies are required before it replaces the present lactate-containing solutions ( Evidence/Opinion).

An Amino Acid-Based Peritoneal Dialysis Fluid Buffered with Bicarbonate versus Glucose/Bicarbonate and Glucose/Lactate Solutions: An Intraindividual Randomized Study

Objective

In order to study acute metabolic changes and peritoneal transport, amino acids as osmotic agent and bicarbonate as buffer were tested as new agents in peritoneal dialysis (PD) solutions.

Design

In a prospective, cross-over, randomized, intraindividual study, we investigated the acute metabolic changes following the application of three different PD fluids: (1) a 1% amino acid-based PD solution buffered with bicarbonate (34 mmol/L) (Amino/Bic); (2) a 1.5% glucose anhydrous-containing bicarbonate-buffered solution (34 mmol/L) (Glu/Bic); and (3) a conventional 1.5% glucose anhydrous-based dialysis solution with lactate (35 mmol/L) (Glu/Lac).

Setting

University medical center.

Patients

Ten nondiabetic patients stable on continuous ambulatory peritoneal dialysis (time on dialysis, 42.5 ± 21.5 months) were treated and monitored with the test solutions over a 6-hour dwell. Three different study days followed in a randomized order for each patient (interval of 1 – 3 weeks). Blood and dialysate samples were taken at 0.25, 0.5, 1, 2, 4, and 6 hours. Immediately after the 1-hr dwell (and after sampling), the patients received a standardized breakfast, thereby simulating usual food intake.

Results

Following the application of Amino/Bic a significant increase in plasma amino acids occurred, with peak levels (maximum 250% increase) after either the 1-hr or the 2-hr dwell. Before taking the standard meal (0.5 hr, 1 hr), the mean serum glucose level with Amino/Bic was 8% ± 13% lower than with Glu/Bic ( p = 0.06) and 14% ± 8% lower than with Glu/Lac ( p < 0.01). This difference was still significant after the standard breakfast and also for the whole dwell (average serum glucose 0.5 – 6 hr: Amino/Bic, 91 ± 6 mg/dL; Glu/Bic, 100 ± 8 mg/dL; Glu/Lac, 102 ± 7 mg/dL; p < 0.01 MANOVA). The serum insulin profiles did not differ between the fluids. A transperitoneal protein- and amino acid-related nitrogen loss of 0.49 ± 0.18 g and 0.48 ± 0.12 g per dwell was measured using Glu/Bic and Glu/Lac, while a positive balance of 1.80 ± 0.43 g was achieved with Amino/ Bic. The parameters of acid-base status (pH, HCO3, pCO2) remained nearly unchanged in the blood, irrespective of the solution used, while dialysate values differed markedly. No significant differences with respect to ultrafiltration (Amino/Bic, –68 ± 199 mL/6hr; Glu/Bic, –51 ± 89 mL/6hr; Glu/ Lac, –2 ± 134 mL/6hr) and peritoneal creatinine clearance (Amino/Bic, 4.9 ± 0.6 mL/min; Glu/Bic, 5.1 ± 0.6 mL/min; Glu/ Lac, 4.8 ± 0.5 mL/min) were measured.

Conclusions

Our results demonstrate that ultrafiltration and small solute clearance over a 6-hour dwell with a 1% Amino/Bic solution were comparable to those of 1.5% Glu/Bic and 1.5% Glu/Lac. Reduced serum glucose concentrations were found with Amino/Bic and this fluid compensated the transperitoneal protein-nitrogen loss of about three glucose dwells. Bicarbonate buffering (34 mmol/L) did not change blood acid-base status combined with either glucose or amino acids.

The Effects of Peritoneal Dialysis Solutions on Peritoneal Host Defense

Conventional peritoneal dialysis fluid (PDF) is a bioincompatible solution owing to the acidic pH, the high glucose concentrations and the associated hyperosmolarity, the high lactate concentrations, and the presence of glucose degradation products (GDPs). This unphysiologic composition adversely affects peritoneal host defense and may thus contribute to the development of PD-related peritonitis. The viability of polymorphonuclear leukocytes, monocytes, peritoneal macrophages, and mesothelial cells is severely depressed in the presence of conventional PDF. In addition, the production of inflammatory cytokines and chemoattractants by these cells is markedly affected by conventional PDF. Further, conventional PDF hampers the recruitment of circulating leukocytes in response to an infectious stimulus. Finally, phagocytosis, respiratory burst, and bacterial killing are markedly lower when polymorphonuclear leukocytes, monocytes, and peritoneal macrophages are exposed to conventional PDF. Although there are a few discrepant results, all major PDF components have been implicated as causative factors. Generally, novel PDF with alternative osmotic agents or with alternative buffers, neutral pH, and low GDP content have much milder inhibitory effects on peritoneal host defense. Clinical studies, however, still need to demonstrate their superiority with respect to the incidence of PD-related peritonitis.

Biocompatibility of New Peritoneal Dialysis Solutions: What Can We Hope to Achieve?

Despite the bioincompatibility of the “old”, standard, high glucose, lactate-buffered peritoneal dialysis (PD) solutions, PD is itself a highly successful dialysis modality with patient survival equivalent to that of hemodialysis (HD) during the initial 3 – 5 years of dialysis therapy. Nevertheless, PD technique survival is often limited by infectious complications and alterations in the structure and function of the peritoneal membrane. These local changes also have a negative impact on patient survival owing to systemic effects such as those often seen in patients with high peritoneal transport rate and loss of ultrafiltration (UF) capacity.

Patient mortality remains unacceptably high in both HD and PD patients, with most premature deaths being associated with signs of malnutrition, inflammation, and atherosclerotic cardiovascular disease (MIA syndrome). These systemic signs are likely to be influenced by PD solutions both directly and indirectly (via changes in the peritoneal membrane). New, biocompatible PD solutions may have favorable local effects (viability and function of the peritoneal membrane) and systemic effects (for example, on MIA syndrome). Amino acid–based solution [Nutrineal (N): Baxter Healthcare Corporation, Deerfield, IL, U.S.A.] may improve nutritional status as well as peritoneal membrane viability. Bicarbonate/lactate–buffered solution [Physioneal (P): Baxter Healthcare Corporation] may ameliorate local and systemic effects of low pH, high lactate, and high glucose degradation products. Icodextrin-based solution [Extraneal (E): Baxter Healthcare SA, Castlebar, Ireland] may improve hypertension and cardiovascular problems associated with fluid overload and may extend time on therapy in patients with loss of UF capacity.

The positive effects of each of these new, biocompatible solutions have been demonstrated in several studies. It is likely that the combined use of N, P, and E solutions will produce favorable synergies in regard to both local effects (peritoneal viability) and systemic effects (less malnutrition, inflammation, and fluid overload). Solution combination is an exciting area for clinical study in the coming years. Furthermore, dialysis fluid additives such as hyaluronan, which protects and improves the function of the peritoneal membrane, may further improve PD solutions. The new, biocompatible PD solutions represent an entirely new era in the evolution of the PD therapy; they are likely to have markedly positive effects on both PD technique and PD patient survival in coming years.

Glucose Dialysate Induces Mitochondrial DNA Damage in Peritoneal Mesothelial Cells

Background

It is known that peritoneal mesothelial cells (PMCs) are denuded in patients undergoing long-term continuous ambulatory peritoneal dialysis (CAPD); the mechanism of damage is not well known. A high quantity of glucose loaded onto PMCs in these patients may generate toxic radicals during the mitochondrial metabolism, leading to mitochondrial DNA damage that accumulates due to the incomplete repair system of this DNA.

Objective

To study damage to the PMCs of long-term CAPD patients, and to examine whether glucose overload accelerates this damage in vitro.

Design

Descriptive clinical and in vitro study.

Participants

Stable CAPD patients and nonuremic patients undergoing elective abdominal surgery.

Methods

( 1 ) Clinical Samples: 13 peritoneal tissue samples from CAPD patients and 5 omental tissue samples from patients with normal renal function were investigated. PMCs in dialysate effluent were collected from another 13 stable CAPD patients. ( 2 ) In Vitro Samples: Primary cultured PMCs were incubated for up to 144 hours in medium containing one of the following: 5.6 mmol/L glucose (control), 56 mmol/L glucose (G), 222 mmol/L glucose (high G), or 222 mmol/L mannitol (high M; osmolar control for high G). The tissues and cells of clinical and in vitro samples were stained for light and immunoelectron microscopy with anti–8-hydroxy-2'-deoxyguanosine (anti–8-OH-dG) antibody, a marker of oxidative DNA damage. In vitro cells were also studied using transmission electron microscopy. Cellular ATP content, mitochondrial membrane potential, and intracellular generation of reactive oxygen species (ROS) were analyzed by luciferase–luciferin system, or by flow cytometry using rhodamine 123 and 2',7'-dichlorodihydrofluorescein diacetate (DCFH-DA).

Results

Biopsy specimens showed strong cytoplasmic staining with 8-OH-dG in patients on long-term CAPD, but only faint staining in patients with end-stage renal disease before the initiation of CAPD, and no staining in patients with normal renal function. Dialysate effluent showed strong granular staining with 8-OH-dG in most PMCs in all long-term CAPD patients, but only faint and focal staining in patients at the start and after 3 – 5 months of CAPD. In vitro experiments also showed strong granular staining by 8-OH-dG in most PMCs cultured in high G, weak staining in G and high M, and no staining in the control. Immunoelectron microscopy revealed the localization of 8-OH-dG to mitochondria. Transmission electron microscopy showed swelling of mitochondria, with decreased cristae, in PMCs cultured in high G. However, only partial expansion of mitochondria was seen in G and high M, and no changes were seen in the control. Cellular ATP content and mitochondrial membrane potential were reduced early, followed by an increase when cultured in high G. Intracellular ROS production was also increased in PMCs cultured in high G and high M.

Conclusions

These data suggest that high-glucose peritoneal dialysate may promote oxidative mitochondrial DNA damage in PMCs in CAPD patients.

Reduced Glucose Degradation Products in Bicarbonate/Lactate-Buffered Peritoneal Dialysis Solutions Produced in Two-Chambered Bags

Objectives

The aims of the current study were: (1) to determine the effects of peritoneal dialysis (PD) solutions at different glucose concentrations on the growth of cultured cells; (2) to determine whether a bicarbonate/ lactate-based solution, as a result of the configuration of its components during heat sterilization in a two-chambered bag, was lower in glucose degradation products than a corresponding lactate-based PD solution; and (3) to determine whether lower glucose degradation corresponded to a decreased inhibition of cell growth.

Design

Growth inhibition of cells exposed to lactatebased PD solutions at three different glucose concentrations was determined. Bicarbonate/lactate-based and lactate-based solutions at high glucose concentration (3.86%) were further analyzed for presence of glucose degradation products and inhibition of cell growth.

Methods

Cell growth was determined by neutral red uptake, measured by optical density at 540 nm. Glucose degradation to acetaldehyde or fructose was determined by gas chromatographymass spectroscopy and highperformance liquid chromatography.

Results

Only 3.86% glucose lactate-based PD solution caused significant inhibition of cell growth (p < 0.05). The heat-sterilized, bicarbonate/lactate-based solution (3.86% glucose) had lower levels of fructose and acetaldehyde than a conventional heat-sterilized, lactatebased solution with the same glucose concentration. Growth of cultured cells exposed to the bicarbonate/ lactate-based solution was significantly improved (p < 0.05) over growth in the conventional solution.

Conclusions

The bicarbonate/lactate-based solutions, manufactured and heat-sterilized in two-chambered bags, were lower in glucose degradation products than the corresponding lactate-based PD solutions, and demonstrated improvedin vitrobiocompatibility as measured by the growth of cultured cells.

Effect of Bicarbonate-Based Dialysis Solutions on Intracellular Ph (Phi) and Tnfα Production by Peritoneal Macrophages

Objective

To compare the effect of Dianeal and two newly-formulated bicarbonate-based peritoneal solutions on intracellular pH (pHi), tumor necrosis factor-α (TNFα) mRNA level, and TNFα secretion by peritoneal macrophages (PMΦ).

Design and Measurements

Peritoneal macrophages were isolated from dialysates collected after overnight dwells in peritonitis -free continuous ambulatory peritoneal dialysis patients. Dialysis solutions contained 1.5% or 4.25% dextrose. HCO3 concentrations of bicarbonate(TB)and bicarbonate/lactate-buffered (TBL) solution were 38 mM and 25 mM, respectively. TBL also contained lactate at a concentration of 15 mM. pCO2 levels were 78 mmHg and 51 mmHg, respectively. In all experiments pC02 was carefully maintained at a stable level. The pHi was measured by spectrofluorometry in BCECF-Ioaded PMΦ exposed to different dialysis solutions or Hank's balanced salt solution. TNFα levels were measured by ELISA in the supernatant of lipopolysaccharide (LPS) stimulated PMΦ after their incubation in different solutions for 15 and 30 minutes. TNFα mRNA was measured by reverse transcriptase polymerase chain reaction (RT PCR) of total RNA extracted from LPS-stimulated PMΦ after their incubation in different solutions for 30 minutes. β-actin mRNA was used as the control.

Results

Dianeal caused a profound drop in pHi to below 6.2. Following an initial drop, pHi stabilized after 4 minutes at levels of 6.96 and 6.8 after incubation in TB and TBL, respectively. In comparison to the control solution, a fall of 11% and 21% in TNFα secretion was seen after incubation in TB for 15 and 30 minutes, respectively, and 15% and 26% after incubation in TBL. Under identical conditions, Dianeal (Baxter, McGaw Park, IL, U.S.A.) caused 59% and >95% suppression of TNFα secretion. Accordingly, TNFα mRNA level in PMΦ was severely depressed by Dianeal but no detectable inhibition was observed following incubation for 30 minutes in TB and TBL. When dextrose concentration in TB and TBL was increased from 1.5% to 4.25%, TNFα secretion by PMΦ was not suppressed by more than 49%, even after 30 minutes incubation. Moreover, suppression of TNFα mRNA levels could not be detected with TB or TBL even at high dextrose concentrations.

Conclusions

In contrast to Dianeal, both bicarbonate based solutions caused only a mild drop in pHi of PMΦ. We postulate this effect to be responsible for the improved capacity of PMΦ to secrete TNFα when incubated in bicarbonate-based solutions compared to Dianeal. Reflecting its known cytotoxicity, dextrose in high concentrations diminishes the protective effect of TB and TBL on immune function of PMΦ. TBL is as effective as TB in preventing the deleterious effect of Dianeal on PMΦ function.

N-Acetylglucosamine Changes Permeability of Peritoneum during Chronic Peritoneal Dialysis in Rats

Objective

To evaluate the effect of supplementation of dialysis fluid with N-acetylglucosamine (NAG) on the permeability of peritoneum during chronic peritoneal dialysis in rats.

Design

Experiments were performed on rats with surgically implanted peritoneal catheters. Dialysis solution [DianeaI1.5% (Baxter, Deerfield, IL, U.S.A.) supplemented with either NAG 50 mmol/L or glucose 50 mmol/L (control)] was infused intraperitoneally twice, every day, for 8 weeks. Peritoneal equilibration tests (PET) were performed in all animals at the beginning of the study and after 8 weeks of dialysis. Additionally, at the end of each week, dialysis solution infused in the morning was drained after 4 hours of intraperitoneal dwell. White blood cell count, creatinine, and total protein concentrations were measured in the effluent dialysate. After 8 weeks of dialysis, the morphology of the peritoneum was studied.

Results

In rats exposed to dialysis fluid supplemented with NAG, peritoneal permeability to creatinine and proteins was reduced when compared to animals dialyzed with glucose solution. In NAG treated animals, staining with alcian blue for polyanions in the peritoneal interstitium was significantly stronger than in rats dialyzed with glucose solution.

Conclusions

Chronic peritoneal dialysis with dialysis solution supplemented with N-acetylglucosamine causes accumulation of glycosaminoglycans in the peritoneal interstitium, which results in a change of peritoneal permeability.

Long-Term Clinical Experience with Pure Bicarbonate Peritoneal Dialysis Solutions

Objectives

The aim of this prospective study was to collect long-term experience in incident peritoneal dialysis (PD) patients treated with pure bicarbonate-buffered PD fluids.

Methods

The metabolic parameters acidosis, acid–base status, adequacy, fluid balance, nutritional markers, calcium, phosphorus, parathyroid hormone (PTH), and general laboratory work and medication were compared between incident PD patients in two groups: one treated with a 34 mmol/L bicarbonate-buffered PD fluid (BIC), the other with a 35 mmol/L lactate-buffered PD fluid (LAC). The observation period included 5 visits from 1 month (visit 1) until 12 months (visit 5) after the start of dialysis treatment. For the descriptive analysis, means and standard deviations were calculated. Student's t-test and linear mixed models were used to compare the two treatment groups.

Results

36 patients were followed for 12 months, 18 in the BIC group and 18 in the LAC group. Statistically significant differences between the groups (at the end of study) were found. In BIC group, venous plasma bicarbonate was 27.4 ± 2.3 mmol/L, base excess 0.8 ± 2.2 mmol/L, and pH 7.31 ± 0.05; in LAC group, venous bicarbonate was 25.9 ± 2.4 mmol/L, base excess –0.6 ± 2.1 mmol/L, and pH 7.30 ± 0.04. No patient from the BIC group needed oral bicarbonate, in contrast to 4 patients in the LAC group. Whereas peritoneal urea and creatinine clearances did not differ between the groups, there was better renal solute clearance in the BIC group, accompanied by better-preserved diuresis at 12 months (1333 ± 935 mL with BIC vs 839 ± 556 mL with LAC). The reverse was true for ultrafiltration.

Conclusions

Pure bicarbonate-buffered PD solutions were superior in correcting metabolic acidosis and they allowed omission of oral bicarbonate. The minor ultrafiltration with bicarbonate-buffered PD solutions was counterbalanced by better-preserved residual renal function with these solutions.

Variations of Cytokine Levels and Production in CAPD Patients

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

"Biocompatible" Neutral pH Low-GDP Peritoneal Dialysis Solutions: Much Ado About Nothing?

Adverse outcomes in peritoneal dialysis (PD), including PD related infections, the loss of residual kidney function (RKF), and longitudinal, deleterious changes in peritoneal membrane function continue to limit the long-term success of PD therapy. The observation that these deleterious changes occur upon exposure to conventional glucose-based PD solutions fuels the search for a more biocompatible PD solution. The development of a novel PD solution with a neutral pH, and lower in glucose degradation products (GDPs) compared to its conventional predecessors has been labeled a "biocompatible" solution. While considerable evidence in support of these novel solutions' biocompatibility has emerged from cell culture and animal studies, the clinical benefits as compared to conventional PD solutions are less clear. Neutral pH low GDP (NpHLGDP) PD solutions appear to be effective in reducing infusion pain, but their effects on other clinical endpoints including peritoneal membrane function, preservation of RKF, PD-related infections, and technique and patient survival are less clear. The literature is limited by studies characterized by relatively few patients, short follow-up time, heterogeneity with regards to the novel PD solution type under study, and the different patient populations under study. Nonetheless, the search for a more biocompatible PD solution continues with emerging data on promising non glucose-based solutions.

Functional and Transcriptomic Characterization of Peritoneal Immune-Modulation by Addition of Alanyl-Glutamine to Dialysis Fluid

Peritonitis remains a major cause of morbidity and mortality during chronic peritoneal dialysis (PD). Glucose-based PD fluids reduce immunological defenses in the peritoneal cavity. Low concentrations of peritoneal extracellular glutamine during PD may contribute to this immune deficit. For these reasons we have developed a clinical assay to measure the function of the immune-competent cells in PD effluent from PD patients. We then applied this assay to test the impact on peritoneal immune-competence of PD fluid supplementation with alanyl-glutamine (AlaGln) in 6 patients in an open-label, randomized, crossover pilot trial (EudraCT 2012-004004-36), and related the functional results to transcriptome changes in PD effluent cells. Ex-vivo stimulation of PD effluent peritoneal cells increased release of interleukin (IL) 6 and tumor necrosis factor (TNF) α. Both IL-6 and TNF-α were lower at 1 h than at 4 h of the peritoneal equilibration test but the reductions in cytokine release were attenuated in AlaGln-supplemented samples. AlaGln-supplemented samples exhibited priming of IL-6-related pathways and downregulation of TNF-α upstream elements. Results from measurement of cytokine release and transcriptome analysis in this pilot clinical study support the conclusion that suppression of PD effluent cell immune function in human subjects by standard PD fluid is attenuated by AlaGln supplementation.

Newly Developed Neutralized pH Icodextrin Dialysis Fluid: Nonclinical Evaluation

A two-compartment system (NICOPELIQ; NICO, Terumo Co., Tokyo, Japan) has recently been developed to neutralize icodextrin peritoneal dialysis fluid (PDF). In this study, a nonclinical evaluation of NICO was carried out to evaluate biocompatibility as well as water transport ability. Glucose degradation products (GDPs) in the icodextrin PDFs were analyzed via high-performance liquid chromatography (HPLC). The cell viability of human peritoneal mesothelial cells derived from peritoneal dialysis effluent (PDE-HPMCs) was evaluated as well as the amount of lactate dehydrogenase (LDH) released after exposure to different PDFs (NICO and EXTRANEAL [EX, Baxter Healthcare Corp., Chicago, IL, USA]) and neutralized pH glucose PDF MIDPELIQ 250 (M250, Terumo). The water transport ability of NICO, EX, and M250 was tested using dialysis tube membranes with various pore sizes: 1, 2, 6-8, and 12-16 kDa. Although cell viability decreased by 30% after 30 min exposure to NICO, it was maintained for 6 h while a significant decrease was observed after 6 h exposure to EX. However, following adjustment of the pH to the same pre-exposure pH value, there was no significant difference in cell viability within the same pH group despite a doubling of the difference in the total amount of GDPs (44.6 ± 8.6 µM in NICO and 91.9 ± 9.5 µM in EX, respectively). In contrast, a significant decrease in cell viability was observed when the pH decreased to less than pH 6. Levels of released LDH, a cytotoxic marker, were within 5% after a 6-h exposure of NICO to PDE-HPMCs. There was no significant difference in water transport ability represented as overall osmotic gradients between NICO and EX. In conclusion, neutralization of icodextrin PDF is beneficial for maintaining cell viability and minimizing LDH release while water transport ability is comparable to the conventional icodextrin PDF.

A new peritoneal dialysis fluid for Japanese patients: a randomized non-inferiority clinical trial of safety and efficacy

BACKGROUND

We report here two new peritoneal dialysis fluids (PDFs) for Japan [BLR 250, BLR 350 (Baxter Limited, Japan)]. The PDFs use two-chamber systems, and have bicarbonate and lactate buffer to a total of 35 mmol/L. In separate trials, the new PDFs were compared to two "standard" systems [PD-4, PD-2 (Baxter Limited, Japan)]. The trials aimed to demonstrate non-inferiority of peritoneal creatinine clearance (pCcr), peritoneal urea clearance (pCurea) and ultrafiltration volume (UF), and compare acid-base and electrolyte balance.

METHODS

We performed randomized, multicenter, parallel group, controlled, open-label clinical trials in stable continuous ambulatory peritoneal dialysis (CAPD) patients. The primary endpoints were pCcr and UF. The secondary endpoints were serum bicarbonate and peritoneal urea clearance. The active phase was 8 weeks. These trials were performed as non-inferiority studies, with the lower limit of non-inferiority for pCcr and UF set at 3.2 L/week/1.73 m² and 0.12 L/day, respectively.

RESULTS

108 patients (28 centers) and 103 patients (29 centers) took part in the two trials. Groups were well balanced at baseline. The investigative PDFs were non-inferior to the "standard" ones in terms of primary endpoints, comparable in terms of pCurea, and superior in terms acid-base balance, especially correcting those with over-alkalinization at baseline.

CONCLUSIONS

We demonstrated fundamental functionality of two new PDFs and showed superior acid-base balance. Given the propensity of Japanese CAPD patients for alkalosis, it is important to avoid metabolic alkalosis which is associated with increased cardiovascular mortality risk and accelerated vascular calcification. The new PDFs are important progress of CAPD treatment for Japanese patients.

Fluid dwell impact induces peritoneal fibrosis in the peritoneal cavity reconstructed in vitro

Peritoneal fluid dwell impacts the peritoneum by creating an abnormal physiological microenvironment. Little is known about the precise effects of fluid dwell on the peritoneum, and no adequate in vitro models to analyze the impact of fluid dwell have been established. In this study, we developed a peritoneal fluid dwell model combined with an artificial peritoneal cavity and fluid stirring generation system to clarify the effects of different dwelling solutions on the peritoneum over time. To replicate the peritoneal cavity, we devised a reconstructed peritoneal cavity utilizing a mesothelial layer, endothelial layer, and collagen membrane chamber. The reconstructed peritoneal cavity was infused with Dulbecco's modified Eagle's medium, saline, lactated Ringer's solution or peritoneal dialysis solution with repeated 4-h dwells for 10 or 20 consecutive days. The above-described solutions induced epithelial-mesenchymal transition (EMT) and hyperplasia of mesothelial cells. All solution types modulated nitric oxide synthase activities in mesothelial and endothelial cells and nitric oxide concentrations in dwelling solutions. Inhibition of nitric oxide synthase activity acted synergistically on mesothelial EMT and hyperplasia. The present findings suggest that solutions infused into the peritoneal cavity are likely to affect nitric oxide production in the peritoneum and promote peritoneal fibrosis. Our newly devised peritoneal cavity model should be a promising tool for understanding peritoneal cellular kinetics and homeostasis.

Dynamic O-linked N-acetylglucosamine modification of proteins affects stress responses and survival of mesothelial cells exposed to peritoneal dialysis fluids

The ability of cells to respond and survive stressful conditions is determined, in part, by the attachment of O-linked N-acetylglucosamine (O-GlcNAc) to proteins (O-GlcNAcylation), a post-translational modification dependent on glucose and glutamine. This study investigates the role of dynamic O-GlcNAcylation of mesothelial cell proteins in cell survival during exposure to glucose-based peritoneal dialysis fluid (PDF). Immortalized human mesothelial cells and primary mesothelial cells, cultured from human omentum or clinical effluent of PD patients, were assessed for O-GlcNAcylation under normal conditions or after exposure to PDF. The dynamic status of O-GlcNAcylation and effects on cellular survival were investigated by chemical modulation with 6-diazo-5-oxo-L-norleucine (DON) to decrease or O-(2-acetamido-2-deoxy-D-glucopyranosylidene)amino N-phenyl carbamate (PUGNAc) to increase O-GlcNAc levels. Viability was decreased by reducing O-GlcNAc levels by DON, which also led to suppressed expression of the cytoprotective heat shock protein 72. In contrast, increasing O-GlcNAc levels by PUGNAc or alanyl-glutamine led to significantly improved cell survival paralleled by higher heat shock protein 72 levels during PDF treatment. Addition of alanyl-glutamine increased O-GlcNAcylation and partly counteracted its inhibition by DON, also leading to improved cell survival. Immunofluorescent analysis of clinical samples showed that the O-GlcNAc signal primarily originates from mesothelial cells. In conclusion, this study identified O-GlcNAcylation in mesothelial cells as a potentially important molecular mechanism after exposure to PDF. Modulating O-GlcNAc levels by clinically feasible interventions might evolve as a novel therapeutic target for the preservation of peritoneal membrane integrity in PD.

[Peritoneal dialysis from the beginnings up to today: which developments of the last decades were important?]

During the past years new developments in peritoneal dialysis (PD) technique have resulted in continuous improvement of patient outcome. The importance of salt and fluid balance, residual renal function and peritoneal glucose load are of increasing interest, whereas small solute clearances have lost importance. In patients with high peritoneal transport rates automated PD (APD) is indicated. However, APD can also be chosen as initial PD treatment since recent studies show comparable or even better survival as compared to continuous ambulatory PD patients. Alternative PD solutions improve peritoneal ultrafiltration (icodextrin), reduce peritoneal glucose load (amino acid solution, icodextrin) and protect the peritoneal membrane (solutions with low concentration of glucose degradation products). Infection risk can be reduced when using antibiotic creams, but resistances should be considered. Ongoing studies will clarify if non-antibiotic agents, e.g. medihoney, are effective in preventing PD-associated infections. Due to these improvements PD and hemodialysis have become equivalent treatments.

HSP induction in mesothelial cells by peritoneal dialysis fluid depends on biocompatibility test system

BACKGROUND

We have previously shown that exposure of mesothelial cells (MC) to peritoneal dialysis fluids (PDF) not only caused toxic injury, but also induced cytoprotective heat shock proteins (HSP). This study was performed in order to compare HSP expression in MC upon PDF exposure in three currently used biocompatibility test systems.

METHODS

Omentum-derived human peritoneal MC underwent 3 modalities of exposure to heat- or filter-sterilized PDF: (A) pure PDF for 60 minutes followed by a recovery-period in pure culture medium for 24 hours; (B) 1:1 mixture of PDF and culture medium for 24 hours or (C) pure PDF for 60 minutes followed by a recovery-period in a 1:1 mixture of PDF and culture medium for 24 hours. Biocompatibility was assessed by LDH-release into the supernatant and HSP-72 expression in MC lysates.

RESULTS

Short-term exposure of MC to pure PDF (Modality A) resulted in concordant LDH release and upregulation of HSP-72, regardless of heat or filter sterilization. In contrast, both test systems that exposed MC to heat-sterilized PDF during the recovery period (Modalities B and C) resulted in severe cellular lethality but low HSP-72 expression.

CONCLUSIONS

This study clearly shows that HSP expression in MC upon PDF exposure depends on the biocompatibility test system. The presence of heat-sterilized PDF during recovery resulted in significant downregulation of Hsp-72 despite severe cell injury. Therefore, Hsp-72 expression reflects adequate cellular stress responses rather than PDF cytotoxicity.

Solutions for peritoneal dialysis in children: recommendations by the European Pediatric Dialysis Working Group

The purpose of this article is to provide recommendations on the choice of peritoneal dialysis (PD) fluids in children by the European Pediatric Dialysis Working Group. The literature on experimental and clinical studies with PD solutions in children and adults was analyzed together with consensus discussions within the group. A grading was performed based on the international KDIGO nomenclature and methods. The lowest glucose concentration possible should be used. Icodextrin may be applied once daily during the long dwell, in particular in children with insufficient ultrafiltration. Infants on PD are at risk of ultrafiltration-associated sodium depletion, while anuric adolescents may have water and salt overload. Hence, the sodium chloride balance needs to be closely monitored. In growing children, the calcium balance should be positive and dialysate calcium adapted according to individual needs. Limited clinical experience with amino acid-based PD fluids in children suggests good tolerability. The anabolic effect, however, is small; adequate enteral nutrition is preferred. CPD fluids with reduced glucose degradation products (GDP) content reduce local and systemic toxicity and should be preferred whenever possible. Correction of metabolic acidosis is superior with pH neutral bicarbonate-based fluids compared with single-chamber, acidic, lactate-based solutions. Prospective comparisons of low GDP solutions with different buffer compositions are still few, and firm recommendations cannot yet be given, except when hepatic lactate metabolism is severely compromised.

Peritoneal dialysis tailored to pediatric needs

Consideration of specific pediatric aspects is essential to achieve adequate peritoneal dialysis (PD) treatment in children. These are first of all the rapid growth, in particular during infancy and puberty, which must be accompanied by a positive calcium balance, and the age dependent changes in body composition. The high total body water content and the high ultrafiltration rates required in anuric infants for adequate nutrition predispose to overshooting convective sodium losses and severe hypotension. Tissue fragility and rapid increases in intraabdominal fat mass predispose to hernia and dialysate leaks. Peritoneal equilibration tests should repeatedly been performed to optimize individual dwell time. Intraperitoneal pressure measurements give an objective measure of intraperitoneal filling, which allow for an optimized dwell volume, that is, increased dialysis efficiency without increasing the risk of hernias, leaks, and retrofiltration. We present the concept of adapted PD, that is, the combination of short dwells with low fill volume to promote ultrafiltration and long dwells with a high fill volume to improve purification within one PD session. The use of PD solutions with low glucose degradation product content is recommended in children, but unfortunately still not feasible in many countries.

Biocompatibility and Tolerability of a Purely Bicarbonate-Buffered Peritoneal Dialysis Solution

Background

Novel peritoneal dialysis solutions are characterized by a minimal content of glucose degradation products and a neutral pH. Many studies have shown the biocompatibility of neutral lactate-buffered solutions; however, until now, the effect of purely bicarbonate-buffered solutions has not been intensively studied in vivo.

Methods

This study was an open label, prospective, crossover multicenter trial to investigate the biocompatibility of a purely bicarbonate-buffered solution (bicPDF) by measuring biocompatibility parameters such as cancer antigen 125 (CA125) in peritoneal effluent. 55 patients were enrolled in the study. After a 2-week run-in phase, 53 patients could be randomized into 2 groups, starting with either standard lactate-buffered peritoneal dialysis fluid (SPDF) for 12 weeks (phase 1) and then switching to bicPDF for 12 weeks (phase 2), or vice versa. Overnight peritoneal effluents were collected at baseline and at the end of phases 1 and 2 and were tested for CA125, hyaluronic acid, vascular endothelial growth factor (VEGF), tumor necrosis factor-alpha (TNF-α), interleukin 6 (IL-6), interferon gamma (IFNγ), and transforming growth factor-beta1 (TGF-β1). Total ultrafiltration and residual renal function were also assessed. At the end of the study, pain during fluid exchange and dwell was evaluated using special questionnaires.

Results

34 patients completed the study; 27 of them provided data for analysis of the biocompatibility parameters. CA125 levels in overnight effluent were significantly higher with bicPDF (61.9 ± 33.2 U/L) than with SPDF (18.6 ± 18.2 U/L, p < 0.001). Hyaluronic acid levels were significantly lower after the use of bicPDF (185.0 ± 119.6 ng/mL) than after SPDF (257.4 ± 174.0 ng/mL, p = 0.013). Both TNF-α and TGF-β1 showed higher levels with the use of bicPDF than with SPDF. No differences were observed for IL-6, VEGF, or IFNγ levels. We observed an improvement in the glomerular filtration rate with the use of bicPDF but no differences were observed for total fluid loss. Pain scores could be analyzed in 23 patients: there was no difference between the solutions.

Conclusions

The use of a purely bicarbonate-buffered low-glucose degradation product solution significantly changes most of the peritoneal effluent markers measured, suggesting an improvement in peritoneal membrane integrity. Additionally, it seems to have a positive effect on residual renal function.

Use of new peritoneal dialysis solutions in children

Standard peritoneal dialysis (PD) solutions with low pH and containing high concentrations of lactate and glucose have been demonstrated to negatively affect the peritoneal membrane, mesothelial cell viability, residential peritoneal cells, and also to inhibit phagocytic functions. An increasing body of experimental evidence supports the idea that the peritoneal hypervascularization and fibrosis observed in long-term PD are causally related to the acute and chronic toxicity of conventional PD solutions. A Physioneal (lactate/bicarbonate mixed buffer pH 7-7.4), Physioneal, Extraneal (7.5% icodextrin), Nutrineal (1.1% amino-acid-containing solution) regimen, for example, offers a significant reduction in carbohydrate load (approximately 40-50%), lower exposure to and absorption of glucose degradation products, reduced oxidative stress, and improved volume control when compared with a first-generation DDDD (4 x Dianeal) regimen. The positive aspects of each solution that we have observed in our patients allow a recommendation on the potential benefit of using these solutions in children treated with PD. In fact, data from the literature as well as the results of the studies reported in this paper show that in children the application of neutral pH bicarbonate/lactate-buffered solution for the standard nighttime APD prescription, icodextrin solution for a long daytime dwell, and AA-based solution in malnourished patients is safe and effective. Extended clinical trials should be encouraged to better define the PD schedules for the combined use of these solutions that may be associated with the best clinical efficacy and the highest level of biocompatibility.

Impact of new dialysis solutions on peritonitis rates

Peritonitis remains a major cause of morbidity among patients on peritoneal dialysis (PD), yet there is little information about the effect of new biocompatible dialysis solutions on peritonitis rates and treatment. In our unit, information on each peritonitis episode is prospectively collected. Since 2003, bicarbonate/lactate dialysate has been gradually introduced for new patients and for patients experiencing abdominal pain with conventional lactate solutions. From 2002 to 2005, data from 121 episodes of peritonitis (71 automated PD and 50 continuous ambulatory PD) were analyzed; 107 episodes occurred in patients using standard lactate dialysate and 14 episodes in patients using bicarbonate/lactate solution. Patients using bicarbonate/lactate had a significantly lower peritonitis rate of 1 per 52.5 patient-months compared to those using standard lactate dialysate (1 per 26.9 patient-months) (P=0.0179). Response to treatment, however, was not affected by the type of dialysate; cure rates (71.4 and 69.1%, respectively) and recurrence rates (21.4 and 15.8%, respectively) were not significantly different. Catheter removal was required in three (21.4%) patients using bicarbonate/lactate and 23 (22.4%) patients using lactate solution. Use of biocompatible dialysate appears to reduce the peritonitis rate by 50%, although this has to be confirmed in a randomized study. The type of dialysate, on the other hand, does not affect response to treatment.

Impact of 3,4-dideoxyglucosone-3-ene (3,4-DGE) on cytotoxicity of acidic heat-sterilized peritoneal dialysis fluid

Of the glucose degradation products (GDPs) in glucose-rich peritoneal dialysate, we investigated the influence of 3,4-dideoxyglucosone-3-ene (3,4-DGE) on the cytotoxicity of acidic heat-sterilized peritoneal dialysis fluid (L-H PDF) using human peritoneal mesothelial cells (HPMC). We prepared acidified filtration-sterilized PDF (glucose concentration 3.86%) containing eight types of added GDP [3,4-DGE, glyoxal (GO), methylglyoxal (MGO), 3-deoxyglucosone (3-DG), formaldehyde (FA), acetaldehyde (AA), 5-hydroxymethyl-2-furaldehyde (5-HMF), and furfural (FF)] or seven types of GDP (GO, MGO, 3-DG, FA, AA, 5-HMF, and FF). HPMC were exposed to these two types of solution and acidic heat-sterilized PDF (glucose concentration 3.86%, L-H 3.86) for 4 h. Cell viability was determined by 3,(4,5-dimethythiazol-2-yl)2,5-diphenyl-terazolium bromide (MTT) assay. MTT viability was decreased significantly compared with the control when treated with L-H 3.86 or acidified neutral filtration-sterilized PDF (glucose concentration 3.86%) containing eight GDPs. However, no significant decrease in MTT viability was observed when HPMC were treated with acidified neutral filtration-sterilized PDF (glucose concentration 3.86%) containing seven GDPs. Thus, 3,4-DGE strongly affects the cytotoxicity of L-H PDF. It is suggested that the cytotoxicity of L-H PDF is based on the presence of 3,4-DGE.

Effects of new peritoneal dialysis solutions on leukocyte recruitment in the rat peritoneal membrane

OBJECTIVES

Peritonitis remains a principal cause of dropout in peritoneal dialysis (PD). The physiological host response to a peritoneal infection involves a rise in numbers of circulating leukocytes to the peritoneal cavity. We evaluated the effects of (1) conventional peritoneal dialysis fluid (PDF), (2) bicarbonate-based PDF, low in glucose degradation products, and (3) non-glucose PDF on peritoneal leukocyte recruitment in response to an inflammatory stimulus using intravital microscopy.

METHODS

The visceral peritoneum was exposed to EBSS, conventional lactate-buffered and bicarbonate/lactate-buffered glucose-based PDF and three lactate-buffered non-glucose PDF-icodextrin, amino acid-based PDF and amino acid/glycerol-based PDF. The number of rolling, adhering and extravasated leukocytes and leukocyte rolling velocity was assessed at different time intervals after stimulation with lipopolysaccharide (LPS).

RESULTS

Exposure to LPS dissolved in EBSS dramatically increased the number of rolling, adhering and extravasated leukocytes and decreased leukocyte rolling velocity. Conventional PDF completely abolished LPS-induced leukocyte recruitment. Bicarbonate/lactate-buffered PDF only minimally affected the process of leukocyte recruitment, whereas icodextrin PDF resulted in partial inhibition of the immune response. The amino acid-based and the amino acid/glycerol-based PDF inhibited leukocyte recruitment to a similar extent as conventional PDF.

CONCLUSIONS

Bicarbonate/lactate-buffered PDF has superior biocompatibility towards peritoneal host defense, in spite of its high glucose concentrations. Lactate-buffered non-glucose containing PDF has substantial inhibitory effects on leukocyte recruitment, indicating that the bioincompatibility of high lactate concentrations and/or low pH may not be underestimated.

The effect of peritoneal rest in combination therapy of peritoneal dialysis and hemodialysis: using the cultured human peritoneal mesothelial cell model

The effects of peritoneal rest for 24 h during peritoneal dialysis and hemodialysis combination therapy were investigated using cultured human peritoneal mesothelial cell (HPMC) models. Cell activity was investigated by 3-[4,5-dimethylthiazol-2-yl]-2, 5-diphenylterazolium bromide (MTT) assay after exposing HPMCs to peritoneal dialysis fluids (PDFs) with different pH levels. The following PDFs (50 microl/well) were used for exposure durations of 30 or 240 min: acidic heat-sterilized PDFs (L-H PDF, pH 5.5) and neutral heat-sterilized PDFs (N-H PDF, pH 6.7). Control wells were exposed to M-199 Hanks medium containing 20% fetal bovine serum (FBS) for 30 or 240 min. Supernatants were then aspirated from each well and M-199 culture medium containing 20% FBS (50 microl) was added to each well to rest HPMCs for 24 h before investigation of MTT activity. The activity of HPMCs exposed to L-H PDF for 240 min decreased to approximately 20% and 15% when compared with controls (glucose concentrations of 1.36% and 3.86%, respectively; P < 0.01 versus control, Tukey-Kramer test), and to approximately 60% and 40% after exposure to N-H PDF for 240 min (glucose: 1.36% and 3.86%; P < 0.01). The activity of HPMCs exposed to L-H PDF for 240 min followed by rest was approximately 20% and 4% when compared with controls (glucose: 1.36% and 3.86%; P < 0.01) and was 93% and 96% when compared with controls after exposure to N-H PDF for 240 min followed by rest (glucose: 1.36% and 3.86%). These findings suggest that rest for 24 h after exposure to N-H PDF improves the activity of HPMCs.

Synergistic Cytotoxicity of Acidity and 3,4-Dideoxyglucosone-3-ene Under the Existence of Lactate in Peritoneal Dialysis Fluid

Of the non-physiological compounds in glucose-rich peritoneal dialysis fluid, we investigated the synergistic cytotoxicity of acidity and 3,4-Dideoxyglucosone-3-ene(3,4-DGE) under the existence of lactate using human peritoneal mesothelial cells (HPMC). The effect of pH on cell viability at various levels of pH (5.5, 6.7, 7.15), with or without lactate was examined by adding 1N-HCl to phosphate buffer solution. We also examined the cytotoxic effects of 3,4-DGE and pH (5.5, 6.7 or 7.15). Additionally, we compared the cytotoxic effects of 3,4-DGE and pH (5.5, 6.7 or 7.15) under existence of lactate (40 meq/L) or absence of lactate. The cells were exposed to these solutions for 2 or 4 h. Cell viability was determined by MTT (3-[4, 5-dimethylthiazol-2-yl]-2, 5-diphenylterazolium bromide) assay. 3,4-DGE or acidic solution alone had no significant effects on MTT viability under the absence of lactate. However, acidic solutions containing 3,4-DGE significantly decreased MTT viability under the existence of lactate. The MTT viability of HPMC was not decreased by 3,4-DGE or acidity alone under the absence of lactate. However, the combination of acidity and 3,4-DGE markedly decreased MTT viability under the existence of lactate, strongly suggesting the synergistic cytotoxicity of 3,4-DGE and acidity under the existence of lactate.

Effect of glucose concentration on peritoneal inflammatory cytokines in continuous ambulatory peritoneal dialysis patients

OBJECTIVE: It is known that glucose concentrations of peritoneal dialysis solutions are detrimental to the peritoneal membrane. In order to determine the effect of glucose concentration on cytokine levels of peritoneal fluid of continuous ambulatory peritoneal dialysis (CAPD) patients, a cross-sectional study was performed. METHODS: Nine non-diabetic CAPD patients participated in two 8-h dwell sessions of overnight exchanges in consecutive days, with 1.36% and 3.86% glucose containing peritoneal dialysis solutions (Baxter-Eczacibas). Peritoneal dialysis fluid tumor necrosis factor (TNF)-alpha and interleukin (IL)-6 levels were measured. RESULTS: TNF-alpha levels after 1.36% and 3.86% glucose used dwells were 23+/-14 pg/ml and 28+/-4 pg/ml, respectively (p=0.78). The IL-6 levels were 106+/-57 pg/ml and 115+/-63 pg/ml (p=0.81), respectively. CONCLUSION: In our in vivo study we found that the glucose concentration of the conventional lactate-based CAPD solution has no effect on basal IL-6 and TNF-alpha levels of peritoneal fluid. Further in vivo studies with non-lactate-based CAPD solutions are needed in order to determine the effect of glucose concentration per se on cytokine release.

Image analysis of remesothelialization following chemical wounding of cultured human peritoneal mesothelial cells: the role of hyaluronan synthesis

BACKGROUND

To understand what happens during the wound healing process of the mesothelium, we have developed an in vitro wounding model of cultured human peritoneal mesothelial cells (HPMCs) utilizing an image acquisition and analysis system. Using this system, cell mobility and hyaluronan synthesis were quantified and their interrelationship discussed.

METHODS

1N NaOH was used to create circular wounds in cultured HPMC monolayers, which were then exposed for 30 minutes to the peritoneal dialysis solutions or fetal calf serum (FCS)-free M199 culture medium, followed by incubation with 0.3% FCS/M199 culture medium for up to 96 hours. Digitalized microscopic date was captured every 30 minutes to quantify the wound healing process. In separate experiments, the HPMC monolayers were stained with biotin-conjugated hyaluronan-binding protein (B-HABP) at a regular time interval.

RESULTS

Centripetal migration of the HPMCs into the wound area was the predominant process involved in wound repair with proliferation playing a secondary role. Two noticeable observations were made from the digital video movies: (1) cell mobility varied and was dependent upon the morphology and location of the cell relative to the wound edge, and (2) cell migration continued even after wound closure. Staining for B-HABP was confined to the remesothelialized area when wound closure was complete at 24 hours. At 48 hours after wound closure, the stained area was even more visible, although somewhat diffuse; thereafter, staining was reduced to almost background levels.

CONCLUSION

The cell culture model of wound healing used in our study has enabled us to demonstrate quantitative image data of the cellular processes that occur during wound healing. We have been able to continuously observe cell migration, proliferation, and transformation. Synthesis and subsequent decomposition of hyaluronan appears to be related to the mobility of the wounded and intact HPMCs in this model system.

Effects of customized bicarbonate buffered solutions for continuous renal replacement therapies on polymorphonuclear leukocytes function and viability

It has previously been shown that the mixture of bicarbonate and calcium in the solutions used for continuous renal replacement therapy led to crystallization and significant changes in calcium concentration and pH. The aim of this study was to investigate the impact of bicarbonate/calcium and lactate/calcium solutions for Continuous Renal Replacement Therapies (CRRT) on the viability and function of polymorphonuclear cells (PMN). We tested four customized bicarbonate buffered solutions: single bag (bicarbonate and calcium mixed 24 h before testing), double bag (mixed immediately before testing), filtered single bag and double bag solutions, and a commercial lactate buffered solution. Blood from 6 volunteers was incubated with the solutions for 30 min followed by PMN isolation. After overnight incubation, viability, phagocytosis, and peroxide production by PMN were determined by flow cytometry. There was no difference between the test solutions with respect to PMN viability and function. Therefore, the presence of microcrystals and the consequent changes in electrolyte concentrations do not seem to impair PMN function.

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.

Apoptosis of Mesothelial Cells Caused by Unphysiological Characteristics of Peritoneal Dialysis Fluids

There is an ongoing debate as to which peritoneal dialysis fluids (PDFs) provide the best preservation of peritoneal cells. To investigate this topic further, we measured apoptosis and necrosis of cultured mesothelial cells (MCs) after exposure to different single unphysiological features of PDFs and PDFs for whole. MCs were incubated in buffers containing plasticizers, high osmolarity by sodium chloride, low pH, and high glucose for 0.5, 4, and 24 h. The same procedure was repeated with different PDFs. Apoptosis and necrosis were measured by FACS-analysis (annexin-FITC and propidium iodide). We found that plasticizers were clearly able to induce apoptosis after 24 h (18 +/- 4%). The same result was observed with high osmolarity by sodium chloride (17 +/- 5%), but not for high glucose (9 +/- 8%). All fluids with low pH (5.2) caused severe and almost complete necrosis (after 4 and 24 h). Incubation in neutral, two-compartment PDFs (glucose 4.25%) without plasticizers for 4 h showed no significant necrosis (3%), but after 24 h apoptosis was detectable in 10 +/- 9% and necrosis in 29 +/- 8% of MCs. In conclusion, after improving PDFs and introducing neutral fluids, further attention should be drawn to inducers of apoptosis. Apoptosis can be detected quite early (24 h) and is caused by plasticizers and high osmolarity.

Effects of bicarbonate buffered dialysate on human peritoneal mesothelial cell intracellular calcium homeostasis

This study compares the biocompatibility of two bicarbonate-based peritoneal dialysis (PD) solutions using the measurement of intracellular free calcium (Ca(i)2+)) as a sensitive parameter of cell function in human peritoneal mesothelial cells (hPMC). Fura-2-loaded hPMC suspensions were exposed to bicarbonate (38 mmol/L) and bicarbonate (25 mmol/L), lactate-buffered PD (15 mmol/L) solutions at pH 7.4 and compared with Krebs-Ringer physiological saline (KRS; pH = 7.4). Resting Ca(i)2+ values and 4br-A23187 (1.0 micro mol/L) induced transients were compared in treatment and control groups. In separate studies, the effect that low saline pH had on Ca(i)(2+) homeostasis was examined. Suspended cells or cells attached to coverslips were bathed in citric acid-phosphate (McIllvaine's) buffered saline (MBS, pH = 7.4). Cells were acidified (pH = 5.3) with citric acid and then challenged with ionophore. Ionophore challenge produced a significantly reduced Ca(i)2+ transient response in cells exposed to the bicarbonate/lactate fluid compared with bicarbonate or KRS. Acidified cell suspensions produced a small monophasic Ca(i)2+ transient rise that was short lived. Gradual recovery of MBS to pH 7.4 produced no changes to Ca(i)2+ homeostasis of cell monolayers. Ionophore treatment produced a biphasic response identical to cells bathed in KRS. This study has demonstrated that short-term exposure to bicarbonate did not alter Ca(i)2+ homeostasis directly, or subsequent modulation of intracellular pH. The MBS system provided a reliable method of modifying the external pH during continuous Ca(i)2+ measurement.

Different effects of amino acid-based and glucose-based dialysate from peritoneal dialysis patients on mesothelial cell ultrastructure and function

BACKGROUND

Peritoneal dialysis fluid (PDF) containing amino acids has been introduced recently aiming to improve the nutritional status of PD patients. Dextrose-based PDFs have been implicated in progressive functional and structural deterioration of the peritoneal membrane. Limited data are currently available regarding the effect of amino acid-based PDF on the function and ultrastructure of human peritoneal mesothelial cells (HPMCs), which play a critical role in peritoneal membrane pathophysiology.

METHODS

We investigated the effects of two commercially available PDFs, which utilized dextrose (1.5% Dianeal) or amino acids (1.1% Nutrineal) as the osmotic agent, obtained from patients after a 4 h dwell, on HPMC proliferation (MTT assay and cell counting) and viability [lactate dehydrogenase (LDH)release], interleukin-6 (IL-6) secretion (commercial enzyme-linked immunosorbent assay) and ultrastructure (scanning and transmission electron microscopy).

RESULTS

Exposure of HPMCs to 1.5% Dianeal reduced cell proliferation, total cellular protein synthesis, IL-6 secretion and cell attachment, but prolonged the cell doubling time on recovery, and increased LDH release (P<0.001, P<0.001, P<0.0001, P<0.0001, P<0.001 and P<0.001, respectively). The 1.1% Nutrineal reduced HPMC proliferation (P<0.001) and increased IL-6 secretion (P<0.0001), but did not affect cell attachment, LDH release, protein synthesis or cell doubling time. Ultrastructural studies of HPMCs exposed to Dianeal showed cell flattening, increased cell surface area, reduced microvilli, and intracellular organelles compatible with dysfunctional mitochondria. In contrast, the ultrastructural morphology of HPMCs was relatively preserved after incubation with Nutrineal.

CONCLUSIONS

Our results showed that HPMC ultrastructure, viability and protein synthesis were better preserved with amino acid-based PDF, compared with conventional dextrose-based PDF. The significance of IL-6 induction by Nutrineal remains to be elucidated.