Coupling Osmotic Efficacy with Biocompatibility in Peritoneal Dialysis: A Stiff Challenge.

Peritoneal dialysis (PD) is a home-based efficacious modality for the replacement of renal function in end-stage kidney failure patients, but it is still under-prescribed. A major limitation is the durability of the dialytic technique. Continuous exposure of the peritoneum to bioincompatible conventional glucose-based solutions is thought to be the main cause of the long-term morpho-functional peritoneal changes that eventually result in ultrafiltration failure. Poor PD solution biocompatibility is primarily related to the high glucose content, which is not only detrimental to the peritoneal membrane but has many potential metabolic side effects. To improve the clinical outcome and prolong the survival of the treatment, PD-related bioincompatibility urgently needs to be overcome. However, combining dialytic and osmotic efficacy with a satisfactory biocompatible profile is proving to be quite difficult. New approaches targeting the composition of the PD solution include the replacement of glucose with other osmotic agents, and the addition of cytoprotective or osmo-metabolic compounds. Other strategies include the infusion of mesenchymal cells or the administration of orally active agents. In the present article, we review the current evidence on efforts to improve the biocompatible and functional performance of PD, focusing on studies performed in vivo (animal models of PD, human subjects on PD).

Compatibility and stability of non-ionic iodinated contrast media in peritoneal dialysis solution and safe practice considerations for CT peritoneography.

BACKGROUND: Computerised tomographic (CT) peritoneography is performed on peritoneal dialysis (PD) patients to identify peritoneal boundary defects, dialysate maldistributions and loculated fluid collections. Iodinated contrast media are added to dialysate and infused through the dialysis catheter, and CT images are obtained. Chemical compatibility of contrast media with dialysis solutions has not been studied. In some institutions, pharmacists charged with oversight of compounded sterile preparations have placed a moratorium on the use of contrast media-dialysate mixtures until compatibility data become available. This study was undertaken to examine the compatibility of non-ionic iodinated contrast agents added to PD solution for the performance of CT peritoneography. METHODS: 100 mL of three non-ionic iodinated contrast agents, iopamidol 370 mgI/mL, iohexol 300 mgI/mL and iodixanol 320 mgI/mL, were mixed with 2 L 1.5% dextrose PD solution and stored at 2-8°C, 25°C and 40°C. Observations at predefined intervals were made over 5 days for visual appearance, turbidity, pH, drug concentration and chemical degradation. RESULTS: Iopamidol, iohexol and iodixanol were stable for 5 days under study conditions. The contrast-dialysate mixture remained clear and colourless, no turbidity changes observed, pH and drug concentrations were stable and no increase in existing impurities or new impurities were detected. CONCLUSIONS: The addition of commonly used non-ionic iodinated contrast agents to 1.5% dextrose dialysis solution is chemically stable, meeting the criteria set forth in the standards and guidelines of the US Pharmacopeia and the Institute of Safe Medication Practices. A protocol for performing CT peritoneography is recommended herein to facilitate patient safety and diagnostic reliability of the imaging study.

Advantages of pyruvate-based fluids in preclinical shock resuscitation-A narrative review.

This review focuses on the innate beneficial effects of sodium pyruvate-based fluids, including pyruvate in intravenous solutions, oral rehydration solutions, and peritoneal dialysis solutions, on shock resuscitation with various animal models relative to current commercial fluids over the last two decades. Due to its superior pharmacological properties, pyruvate effectively sustains cytosolic glycolytic pathways and mitochondrial oxidative phosphorylation by restoration of redox potentials and reactivation of pyruvate dehydrogenase in hypoxia, even anoxia, and diabetes, reversing the Warburg effect and diabetic glucometabolic aberration. Pyruvate has been demonstrated to protect against multiorgan dysfunction and metabolic disturbance in numerous preclinical studies with various pathogenic injuries. The unique features of pyruvate potential clinical benefits encompass to efficiently correct lethal lactic acidosis via metabolically rapid consumption of intracellular [H+] and robustly protect multiorgan metabolism and function, particularly visceral organs in addition to the heart and brain, significantly prolonging survival in various animal models. Pyruvate protection of red blood cell function and preservation of the partial pressure of arterial oxygen should be highly concerned in further studies. Pyruvate is much advantageous over existing anions such as acetate, bicarbonate, chloride, and lactate in commercial fluids. Pyruvate-based fluids act as a therapeutic agent without causing iatrogenic resuscitation injury in addition to being a volume expander, indicating a potential novel generation of resuscitation fluids, including crystalloids and colloids. Pyruvate-based fluids have an enormous potential appeal for clinicians who face the ongoing fluid debate to readily select as the first resuscitation fluid. Clinical trials with pyruvate-based fluids in shock resuscitation are urgently warranted.

The benefits of peritoneal dialysis (PD) solution with low-glucose degradation product in residual renal function and dialysis adequacy in PD patients: A meta-analysis / Beneficios de la solución de diálisis peritoneal (DP), con producto de degradación bajo en glucosa, en la función renal residual y la adecuación de la diálisis en pacientes en DP: un metanálisis

Abstract The peritoneal effects of low-glucose degradation product (GDP)-containing peritoneal dialysis (PD) solutions have been extensively described. To systematically evaluate the efficacy and safety of low GDP solution for PD patients, specifically the effect on residual renal function (RRF) and dialysis adequacy, we conducted a meta-analysis of the published randomized controlled trials (RCTs). Different databases were searched for RCTs that compared low GDP-PD solutions with conventional PD solutions in the treatment of PD patients with continuous ambulatory peritoneal dialysis (CAPD) and automated peritoneal dialysis (APD). The outcomes of RCTs should include RRF and may include small solute clearance, peritoneal transport status, nutritional status, and all-cause mortality. Seven studies (632 patients) were included. Compared with the conventional solution, low-GDP solution preserved RRF in PD patients over time (MD 0.66 mL/min, 95% CI 0.34 to 0.99; p<0.0001), particularly in one year of treatment (p<0.01), and improved weekly Kt/V (MD 0.11, 95% CI 0.05 to 0.17; p=0.0007) without an increased 4-hour D/Pcr (MD 0.00, 95% CI -0.02 to 0.02; p=1.00). Notably, the MD of RRF and urine volume between the two groups tended to decrease as time on PD progressed up to 24 months. Patients using low GDP PD solutions did not have an increased risk of all-cause mortality (MD 0.97, 95% CI 0.50 to 1.88; p=0.93). Our meta-analysis confirms that the low GDP PD solution preserves RRF, improves the dialysis adequacy without increasing the peritoneal solute transport rate and all-cause mortality. Further trials are needed to determine whether this beneficial effect can affect long-term clinical outcomes.

Resumen Los efectos peritoneales de las soluciones de diálisis peritoneal (DP) que contienen productos de degradación bajos en glucosa (PIB) se han descrito ampliamente. Para evaluar sistemáticamente la eficacia y la seguridad de la solución de PIB bajo para pacientes en DP, específicamente el efecto sobre la función renal residual (RRF) y la adecuación de la diálisis, realizamos un metanálisis de los ensayos controlados aleatorios (ECA) publicados. Se realizaron búsquedas en diferentes bases de datos de ECA que compararan la solución de DP de bajo PIB con la solución de DP convencional en el tratamiento de pacientes con EP con CAPD y APD. Los resultados de los ECA deben incluir la RRF y pueden incluir la depuración de solutos pequeños, el estado nutricional, el estado del transporte peritoneal y la mortalidad por todas las causas. Se incluyeron siete estudios (632 pacientes). En comparación con la solución convencional, la solución de bajo PIB preservó la FRR en pacientes con EP a lo largo del tiempo (DM 0,66 mL/min, IC del 95%: 0,34 a 0,99; p<0,0001), particularmente en un año de tratamiento (p<0,01), y mejoró el Kt/V semanal (DM 0,11, IC del 95%: 0,05 a 0,17; p = 0,0007), sin un aumento de D/Pcr a las 4 horas (DM 0,00, IC del 95%: -0,02 a 0,02; p = 1,00). Los pacientes que usaron una solución para DP con bajo contenido de GDP no tuvieron un mayor riesgo de mortalidad por todas las causas (DM 0,97; IC del 95%: 0,50 a 1,88; p = 0,93). Nuestro metanálisis confirma que la solución de DP de bajo PIB preserva la FRR, mejora la adecuación de la diálisis sin aumentar la tasa de transporte peritoneal de solutos y la mortalidad por todas las causas. Se necesitan más ensayos para determinar si este efecto beneficioso puede afectar los resultados clínicos a largo plazo.

[Which future solutions for peritoneal dialysis?]

Peritoneal dialysis is an efficient renal replacement therapy for uremic patients but is currently under-prescribed. This is partly due to the unfavorable effects on peritoneal morphology and function (bioincompatibility) of current glucose-based solutions. Use of standard solutions can cause several peritoneal alterations including inflammation, mesothelial to mesenchymal transition, and neo-angiogenesis. The final step is fibrosis, which reduces the peritoneal filtration capacity and can lead to ultrafiltration failure and transfer of the patient to hemodialysis. Bioincompatibility can be local (peritoneum) but also systemic, due to the excessive absorption of glucose from the dialysate. Several strategies have been adopted to improve the biocompatibility of peritoneal dialysis solutions, based on the alleged causal factors. Some new solutions available on the market contain low glucose degradation products and neutral pH, others contain icodextrin or aminoacids. Clinical benefits have been associated with the use of these solutions, which however have some limitations and a debated biocompatibility profile. More recent strategies include the use of cytoprotective agents or osmo-metabolic agents in the dialysate. In this article, we review the different approaches currently under development to improve the biocompatibility of peritoneal dialysis solution and hence the clinical outcome and the viability of the technique.

A Novel Formulation of Glucose-Sparing Peritoneal Dialysis Solutions with l-Carnitine Improves Biocompatibility on Human Mesothelial Cells.

The main reason why peritoneal dialysis (PD) still has limited use in the management of patients with end-stage renal disease (ESRD) lies in the fact that the currently used glucose-based PD solutions are not completely biocompatible and determine, over time, the degeneration of the peritoneal membrane (PM) and consequent loss of ultrafiltration (UF). Here we evaluated the biocompatibility of a novel formulation of dialytic solutions, in which a substantial amount of glucose is replaced by two osmometabolic agents, xylitol and l-carnitine. The effect of this novel formulation on cell viability, the integrity of the mesothelial barrier and secretion of pro-inflammatory cytokines was evaluated on human mesothelial cells grown on cell culture inserts and exposed to the PD solution only at the apical side, mimicking the condition of a PD dwell. The results were compared to those obtained after exposure to a panel of dialytic solutions commonly used in clinical practice. We report here compelling evidence that this novel formulation shows better performance in terms of higher cell viability, better preservation of the integrity of the mesothelial layer and reduced release of pro-inflammatory cytokines. This new formulation could represent a step forward towards obtaining PD solutions with high biocompatibility.

Valsartan ameliorates high glucose-induced peritoneal fibrosis by blocking mTORC1 signaling.

IMPACT STATEMENT: Our study provided new insight into the mechanism underlying the preservation of the peritoneum by valsartan. The results demonstrated that the mice receiving chronic high glucose (HG) peritoneal dialysis solution infusion showed a typical feature of peritoneal fibrosis (PF), as well as higher expression of α-smooth muscle actin (α-SMA) and collagen I. In vitro, HG increased the protein expression of α-SMA and collagen I in a dose-dependent manner, while valsartan significantly ameliorated these pathological changes. Interestingly, there was a parallel decrease in the activity of mammalian target of rapamycin complex 1 (mTORC1) and the protein expression levels of α-SMA and collagen I upon treatment with valsartan in vivo and in vitro. Moreover, the mTOR agonist MHY1485 reversed the downregulation of α-SMA and collagen I in vitro, even in the presence of valsartan. Altogether, our findings reported for the first time that valsartan exerts a protective effect against HG-induced PF by inhibiting the activity of the mTORC1 pathway.

Removal of Protein-Bound Uremic Toxins by Liposome-Supported Peritoneal Dialysis.

Background:Protein-bound uremic toxins (PBUTs) are poorly cleared by peritoneal dialysis (PD). This study aimed to enhance PBUT removal in PD by adding a binder to the peritoneal dialysate and to evaluate the feasibility and efficacy of liposome-supported PD (LSPD) to increase the removal of PBUTs compared with albumin PD.Methods:Removal of p-cresyl sulfate (PCS), indoxyl sulfate (IS), and indole-3-acetic acid (3-IAA) was first evaluated in an in vitro PD model using artificial plasma preloaded with test solutes. Male Sprague-Dawley rats (n = 24) were then subjected to 5/6 nephrectomy and fed for 16 weeks to establish end-stage renal failure, after which they were treated with either conventional glucose-based PD, albumin-based PD, or liposome-based PD. Removal of PBUTs and small water-soluble solutes was determined during a 6-hour PD dwell.Results:In vitro experiments showed that adding albumin as a toxin binder to the dialysate markedly increased the removal of PCS, IS, and 3-IAA compared with the control. The uptake capacity of liposomes was comparable with that of albumin for PCS and 3-IAA, though slightly inferior for IS. In vivo PD in uremic rats demonstrated that LSPD resulted in higher intraperitoneal concentrations and more total mass removal for PBUTs than the conventional glucose-based PD, which was comparable with albumin PD.Conclusions:Supplementing conventional glucose-based PD solutions with a binder could efficiently increase the removal of PBUTs. This preliminary study suggested that LSPD may be a promising alternative to albumin PD for increasing PBUT removal in the development of next-generation PD solutions for PD patients.

Rapamycin inhibits peritoneal fibrosis by modifying lipid homeostasis in the peritoneum.

Peritoneal fibrosis (PF) is characterized by progressive accumulation of extracellular matrix (ECM) components in the peritoneum under high glucose conditions. Rapamycin has previously been shown to inhibit ECM accumulation of peritoneal mesothelial cells (PMCs) and prevent PF. Here we explored the undefined mechanisms by which rapamycin inhibits ECM accumulation of PMCs. We used high-glucose peritoneal dialysis solution (PDS) in a mouse peritoneal dialysis model to induce in vivo PF and in human PMCs in vitro to stimulate ECM accumulation. The mice that received chronic PDS infusions showed typical features of PF, including markedly increased peritoneal thickness, excessive matrix deposition, increased peritoneal permeability, and higher expressions of α-smooth muscle actin and collagen I. Rapamycin significantly ameliorated these pathological changes. There was a parallel decrease in lipid accumulation in the peritoneum of rapamycin-treated mice. Rapamycin significantly inhibited high-glucose PDS-induced ECM accumulation and reduced the lipid droplet in human PMCs in the presence of PDS. The effects of rapamycin on intracellular lipid metabolism correlated with a series of steps in lipid homeostasis; namely, a decrease in low density lipoprotein receptor-mediated lipid influx, which was mediated through the downregulation of sterol regulatory element-binding protein-2 (SREBP-2) and SREBP cleavage-activating protein (SCAP), and an increase in adenosine triphosphate-binding cassette transporter A1-mediated lipid efflux, which was mediated through the upregulation of the liver X receptor α and peroxisome proliferator-activated receptor α. We conclude that rapamycin shows a clear protective effect on high-glucose PDS-induced PF by improving the disruption of intracellular lipid homeostasis.

Mammalian Target of Rapamycin Complex 1 Activation Disrupts the Low-Density Lipoprotein Receptor Pathway: A Novel Mechanism for Extracellular Matrix Accumulation in Human Peritoneal Mesothelial Cells.

Peritoneal fibrosis (PF) is characterized by progressive extracellular matrix (ECM) accumulation. Increasing evidence has suggested that ECM synthesis was increased in human peritoneal mesothelial cells (HPMCs) under high-glucose conditions, but the effects of high-glucose peritoneal dialysis solution (PDS) on ECM synthesis have not been fully elucidated. The aim of this study was to explore the potential mechanisms of high-glucose PDS-induced production of ECM in HPMCs. HPMCs were stimulated by high-glucose PDS. The activity of mammalian target of rapamycin complex 1 (mTORC1) was inhibited by rapamycin or regulatory-associated protein of mTOR (raptor) siRNA. Morphological changes in the cells were observed under an inverted microscope. Oil red O, filipin staining and high-performance liquid chromatography were used to examine lipid accumulation. The expression of low-density lipoprotein receptor (LDLr) regulation, the mTORC1 pathway and ECM-associated markers were assessed by real-time polymerase chain reaction and western blot analysis. The results showed that after treatment with PDS, HPMCs showed notable elongation consistent with the morphology of myofibroblasts, and the expression of ECM proteins such as α-smooth muscle actin, fibroblast specific protein-1 and collagen I was increased. In addition, there was a parallel increase in the ECM and lipid accumulation. Moreover, the effect of intracellular lipid deposition was closely correlated with the dysregulation of LDLr, which was mediated through the upregulation of LDLr, sterol regulatory element-binding protein (SREBP) cleavage-activating protein (SCAP), and SREBP-2 and through the enhanced coexpression of the SCAP with the Golgin. Further analysis showed that PDS enhanced the protein phosphorylation of mTOR, eukaryotic initiation factor 4E-binding protein 1, and p70 S6 kinase. Interestingly, blocking mTORC1 activity reversed the dysregulation of LDLr, even in the presence of PDS. These effects were also accompanied by a decrease in the expression of ECM components. Our findings demonstrated that increased mTORC1 activity exacerbated ECM formation in HPMCs by disrupting LDLr regulation, which contributed to lipid disorder-mediated PF.

Associations Between Peritoneal Glucose Exposure, Glucose Degradation Product Exposure, and Peritoneal Membrane Transport Characteristics in Peritoneal Dialysis Patients: Secondary Analysis of the balANZ Trial.

BACKGROUND: Glucose is the most commonly used osmotic medium in peritoneal dialysis (PD) solutions, and its use has been associated with both local and systemic adverse effects. Previous, single-center, observational cohort studies have reported conflicting findings regarding whether a relationship exists between peritoneal glucose exposure and peritoneal small solute transport rate. METHODS: In this secondary analysis of the balANZ multicenter, multinational, randomized controlled trial of a neutral pH, ultra-low glucose degradation product (biocompatible) versus conventional PD solutions over a 2-year period, the relationship between time varying peritoneal glucose exposure and change in peritoneal solute transport rate, (measured as dialysate to plasma creatinine ratio at 4 hours [D:PCr4h]), was evaluated using multivariable, multilevel linear regression. Baseline peritoneal glucose exposure was also assessed as either a continuous or categorical variable. RESULTS: The study included 165 patients (age 58.1 ± 14.2 years, 55% male, 33% diabetic). Peritoneal glucose exposure increased over time (coefficient 1.49, 95% confidence interval [CI] 1.07 - 1.92 and was not significantly associated with change in D:PCr4h (coefficient 0.00004, 95% CI -0.0001 - 0.0002, p = 0.68). Similar results were found when peritoneal glucose exposure was examined as a baseline continuous or categorical variable. A significant 2-way interaction was observed with PD solution type, whereby a progressive increase in D:PCr4h was seen in the patients receiving conventional PD solution, but not in those receiving biocompatible solution. CONCLUSIONS: Increases in peritoneal solute transport rate in PD patients over time were not associated with peritoneal glucose exposure, although a strong and positive association with PD solution glucose degradation product content was identified. Peritoneal glucose exposure may be a less important consideration than peritoneal glucose degradation product exposure with respect to peritoneal membrane function over time.

Autophagy promotes fibrosis and apoptosis in the peritoneum during long-term peritoneal dialysis.

Long-term peritoneal dialysis is accompanied by functional and histopathological alterations in the peritoneal membrane. In the long process of peritoneal dialysis, high-glucose peritoneal dialysis solution (HGPDS) will aggravate the peritoneal fibrosis, leading to decreased effectiveness of peritoneal dialysis and ultrafiltration failure. In this study, we found that the coincidence of elevated TGF-ß1 expression, autophagy, apoptosis and fibrosis in peritoneal membrane from patients with peritoneal dialysis. The peritoneal membranes from patients were performed with immunocytochemistry and transmission electron microscopy. Human peritoneal mesothelial cells were treated with 1.5%, 2.5% and 4.25% HGPDS for 24 hrs; Human peritoneal mesothelial cells pre-treated with TGF-ß1 (10 ng/ml) or transfected with siRNA Beclin1 were treated with 4.25% HGPDS or vehicle for 24 hrs. We further detected the production of TGF-ß1, activation of TGF-ß1/Smad2/3 signalling, induction of autophagy, EMT, fibrosis and apoptosis. We also explored whether autophagy inhibition by siRNA targeting Beclin 1 reduces EMT, fibrosis and apoptosis in human peritoneal mesothelial cells. HGPDS increased TGF-ß1 production, activated TGF-ß1/Smad2/3 signalling and induced autophagy, fibrosis and apoptosis hallmarks in human peritoneal mesothelial cells; HGPDS-induced Beclin 1-dependent autophagy in human peritoneal mesothelial cells; Autophagy inhibition by siRNA Beclin 1 reduced EMT, fibrosis and apoptosis in human peritoneal mesothelial cells. Taken all together, these studies are expected to open a new avenue in the understanding of peritoneal fibrosis, which may guide us to explore the compounds targeting autophagy and achieve the therapeutic improvement of PD.

Peritoneal Equilibration Test Reference Values Using a 3.86% Glucose Solution During the First Year of Peritoneal Dialysis: Results of a Multicenter Study of a Large Patient Population.

BACKGROUND: The original peritoneal equilibration test (PET) was used to classify peritoneal dialysis (PD) patients using a 2.27% glucose solution. It has since been suggested that a 3.86% glucose solution be used because this provides better information about ultrafiltration (UF) capacity and the sodium (Na) sieving of the peritoneal membrane. OBJECTIVE: The aim of this study was to determine reference values for a PET using a 3.86% glucose solution (PET-3.86%). METHODS: We evaluated the PET-3.86% in a large population of incident PD patients attending 27 Italian dialysis centers. RESULTS: We evaluated the results of 758 PET-3.86% in 758 incident PD patients (1 test per patient). The mean duration of PD was 5 ± 3 months. The ratio of the concentrations of creatinine in dialysate/plasma (D/PCreat) was 0.73 ± 0.1 (median 0.74). The ratio between the concentrations of glucose at the end/beginning of the test (D/D0) was 0.25 ± 0.08 (median 0.24). Ultrafiltration uncorrected and corrected for bag overfill was respectively 776 ± 295 mL (median 781 mL) and 675 ± 308 mL (median 689 mL). Sodium sieving was 8.4 ± 3.8 mmol/L (median 8.0 mmol/L). CONCLUSION: The results of the study provide PET-3.86% reference values for the beginning of PD that can be used to classify PD patients into transport classes and monitor them over time.

Effect of peritoneal dialysis fluid containing osmo-metabolic agents on human endothelial cells.

BACKGROUND: The use of glucose as the only osmotic agent in peritoneal dialysis (PD) solutions (PDSs) is believed to exert local (peritoneal) and systemic detrimental actions, particularly in diabetic PD patients. To improve peritoneal biocompatibility, we have developed more biocompatible PDSs containing xylitol and carnitine along with significantly less amounts of glucose and have tested them in cultured Human Vein Endothelial Cells (HUVECs) obtained from the umbilical cords of healthy (C) and gestational diabetic (GD) mothers. METHODS: Primary C- and GD-HUVECs were treated for 72 hours with our PDSs (xylitol 0.7% and 1.5%, whereas carnitine and glucose were fixed at 0.02% and 0.5%, respectively) and two glucose-based PDSs (glucose 1.36% or 2.27%). We examined their effects on endothelial cell proliferation (cell count), viability (3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide assay), intracellular nitro-oxidative stress (peroxynitrite levels), Vascular Cell Adhesion Molecule-1 and Intercellular Adhesion Molecule-1 membrane exposure (flow cytometry), and HUVEC-monocyte interactions (U937 adhesion assay). RESULTS: Compared to glucose-based PDSs, our in vitro studies demonstrated that the tested PDSs did not change the proliferative potential both in C- and GD-HUVECs. Moreover, our PDSs significantly improved endothelial cell viability, compared to glucose-based PDSs and basal condition. Notably, glucose-based PDSs significantly increased the intracellular peroxynitrite levels, Vascular Cell Adhesion Molecule-1 and Intercellular Adhesion Molecule-1 membrane exposure, and endothelial cell-monocyte interactions in both C- and GD-HUVECs, as compared with our experimental PDSs. CONCLUSION: Present results show that in control and diabetic human endothelial cell models, xylitol-carnitine-based PDSs do not cause cytotoxicity, nitro-oxidative stress, and inflammation as caused by hypertonic glucose-based PDSs. Since xylitol and carnitine are also known to favorably affect glucose homeostasis, these findings suggest that our PDSs may represent a desirable hypertonic solution even for diabetic patients in PD.

Fluvastatin inhibits the expression of fibronectin in human peritoneal mesothelial cells induced by high-glucose peritoneal dialysis solution via SGK1 pathway.

BACKGROUND: Previous studies showed that statins may have protective effects on peritoneal mesothelial cells (PMC) cultured in high glucose. However, the mechanisms are not clear yet. Several studies demonstrated that serum- and glucocorticoid-inducible kinase 1 (SGK1) is implicated in tissue fibrosis of liver, lung and kidney by regulating the expression of many profibrogenic cytokines and extracellular matrix (e.g., fibronectin). However, few available reports elucidated whether the SGK1 is involved in the pathogenesis of peritoneal fibrosis (PF) in patients with peritoneal dialysis (PD). So far, there is no study about the interaction between the statins and SGK1 in PMC. The purpose of this study was to identify whether fluvastatin may decrease the expression of fibronectin (FN) in human peritoneal mesothelial cells (HPMC) cultured with high-glucose peritoneal dialysis solution (HGPDS) by affecting SGK1 signal pathway. METHODS: Cultured HPMC were divided into groups of control, high-glucose peritoneal dialysis solution (HGPDS), HGPDS with fluvastatin (10(-8) mol/L ~ 10(-6) mol/L) or GSK650394 10(-5) mol/L (the competitive inhibitor of SGK1), fluvastatin 10(-6) mol/L or GSK650394 10(-5) mol/L alone. The expression of SGK1 and FN was detected by RT-PCR, western immunoblotting or ELISA. RESULTS: Compared with the control, the mRNA and protein expression of SGK1 and FN increased significantly in HPMC treated with HGPDS (p < 0.05). GSK650394 significantly decreased the upregulated mRNA and protein expression of SGK1 and FN induced by HGPDS (p < 0.05), and fluvastatin had the same effects as GSK650394 in a dose-dependent manner (p < 0.05). CONCLUSIONS: Expression of SGK1 and FN increased in HPMC induced by HGPDS. Treated with fluvastatin and the SGK1-inhibitor GSK650394, abnormalities of SGK1 and FN could be corrected partially, which suggested that the SGK1 pathway was implicated in the pathogenesis of PF, and that fluvastatin might decrease the expression of SGK1 so as to meliorate the progression of PF.

Postnatal Toxicity in Mice Attributable to Plastic Leachables in Peritoneal Dialysis Solution (PDS).

Peritoneal dialysis solution (PDS), widely used to treat uremia and renal failure, may contain toxicants that have leached from their plastic storage bags. In this study, PDS was administered intraperitoneally (i.p.) into lactating mice to investigate effects in the offspring. Treatment started from the first day of delivery until weaning. Ten lactating dams were given PDS from a bag stored at room temperature (25°C). Another 10 received PDS from a bag preheated (50°C) overnight. A third 10 were given the control PDS. Following weaning, the offspring were subjected to various biochemical and hematological tests. The significant (p≤.05) effects were elevation in alanine aminotransferase (ALT), aspartate aminotransferase (AST), nonprotein nitrogenous compounds (NPN), potassium, and triglycerides; drop in high-density lipoprotein (HDL) cholesterol; rise in monocytes and granulocytes; and drop in lymphocyte. Preheating seems to have no effect on leachability rate, producing similar effects in offspring, compared with the control. These effects could be attributable to leachables from bags of the investigated PDS.

Effects of lactate peritoneal dialysis solution on apoptosis of human peritoneal mesothelial cells,expressions of bcl-2,bax and activity of caspase-3 / 吉林大学学报(医学版)

Objective To study the effects of lactate peritoneal dialysis solution(L-PDS) with different concentrations on apoptosis of human peritoneal mesothelial cells(HPMC),the expressions of bcl-2,bax and activity of caspase-3.Methods HPMC were separated using enzyme digestion and cultivated stably in vitro.After HPMC were co-cultivated with different concentrations(1.50%,2.50%,4.25%) L-PDS,flow cytometry was used to test the apoptosis of HPMC,RT-PCR was used to observe the expressions of bcl-2 and bax,fluorometric method was used to detect the activity of caspase-3.Results Compared with control group, L-PDS could induce the apoptosis of HPMC,especially in high concentration.With the increasing of L-PDS concentration,the expression of bcl-2 mRNA decreased,the expression of bax mRNA increased,the activity of caspase3 raised.There were significant differences of the indexes mentioned above between 4.25%,2.50% L-PDS groups and control group(P0.05).Conclusion L-PDS could induce HPMC apoptosis,which may be executed by alternating of the expressions of bcl-2,bax and activating of caspase3.

The Effects of Lactate and pH on Human Peritoneal Mesothelial Cell Biology / 대한신장학회잡지

Preservation of peritoneal membrane function is important in the success of long-term peritoneal dialysis (PD). During PD, human peritoneal mesothelial cells (HPMC) are continuously exposed to unphysiological peritoneal dialysis solution(PDS) charaterized by high glucose and lactate concentrations, low pH, and hyperosmolality. Since few studies have examined the effects of lactate and pH on HPMC biology, the present study investigated the effects of lactate and pH on the viability and proliferation of cultured HPMC and on the production of TGF-beta1, a fibrogenic cytokine, and fibronectin by cultured HPMC. HPMC were obtained from the omental tissue of pregnant women who were undergoing Cesarean section. Cells at confluence were utilized to determine the viability(LDH release), proliferation([3H]-thymidine incorporation), and the production of fibronectin and TGF-beta1(ELISA) after synchronizing the cell growth by incubating with serum free media for 24 hours. After exposure to the media containing lactate and pH, LDH release increased in dose- and time-dependent manner. Both 1.5% and 4.25% commercial PD solutions were cytotoxic and induced more than 80% LDH release within 24 hours. LDH release decreased with increasing dilution of commercial peritoneal dialysate, but there was no significant difference in LDH release between 1.5% and 4.25% PDS. LDH release increased in response to pH 5.5. Thymidine incorporation assay revealed that lactate and low pH significantly inhibited proliferation of HPMC. ELISA revealed that exposure of HPMC to lactate and low pH decreased fibronectin protein synthesis, when compared to cell exposed to bicarbonate containing M199 media. Our results clearly show that lactate and low pH lead to dose- and time-dependent cell death and reduce proliferation of cultured HPMC. Lactate and low pH per se appear to decrease fibronectin production by HPMC but may set a stage for other factors to promote progressive fibrosis during the healing stage in long-term PD.

Effect of 4.25% peritoneal dialysis solution on CD40 expression in rat peritoneal mesothelial cells / 中国病理生理杂志

AIM: To investigate the effect of 4.25%peritoneal dialysis solution (PDS) on CD40 expression in rat peritoneal mesothelial cells so as to reveal the potential mechanisms by which CD40-CD40 ligand (CD40L) interaction may be involved in the inflammation of peritoneal membrane. METHODS: Rat peritoneal mesothelial cells (MC) were harvested from the peritoneal cavity and maintained under defined in vitro conditions. Expression of CD40 on MC under normal culture or stimulation with 4.25%PDS or 4.25%PDS+IFN-? was detected by RT-PCR and FACS analyses. After activation of CD40 on MC with CD40 mAb, the expression of intercellular adhesion molecule-1 (ICAM-1) on MC was analyzed by FCAS. RESULTS: MC cultured in vitro expressed CD40 constitutively. 4.25%PDS markedly up-regulated the expression of CD40 mRNA and its protein. The expression of CD40 mRNA and its protein following stimulation with 4.25%PDS+IFN-? was significantly higher than 4.25%PDS alone. The expression of ICAM-1 on MC was significantly increased after activation of CD40 with CD40mAb.CONCLUSIONS: MC functionally express CD40. The up-regulated CD40 expression on MC following stimulation with 4.25%PDS may play an important role in local peritoneal defense mechanisms and may be involved in the chronic inflammatory process of the peritoneum.