Glucose Peritoneal Dialysis Fluid Research Articles

Differential effects of biocompatible peritoneal dialysis fluids on human mesothelial and endothelial cells in 2D and 3D phenotypes.

Peritoneal dialysis (PD) is a life maintaining treatment in patients with end-stage renal disease. Its chronic application leads to peritoneal mesothelial layer denudation and fibrotic transformation along with vascular activation of inflammatory pathways. The impact of different PD fluids (PDF) on mesothelial and endothelial cell function and repair mechanisms are not comprehensively described. Mesothelial (MeT-5A) and endothelial cells (EA.hy926) were cultured in 1:1 ratio with cell medium and different PDF (icodextrin-based, amino acid-based, and glucose-based). Cell adhesion, cell migration, and cell proliferation in 2D and spheroid formation and collagen gel contraction assays in 3D cell cultures were performed. Cell proliferation and cell-mediated gel contraction were both significantly decreased in all conditions. 3D spheroid formation was significantly reduced with icodextrin and amino acid PDF, but unchanged with glucose PDF. Adhesion was significantly increased by amino acid PDF in mesothelial cells and decreased by icodextrin and amino acid PDF in endothelial cells. Migration capacity was significantly decreased in mesothelial cells by all three PDF, while endothelial cells remained unaffected. In 3D phenotypes the effects of PDF are more uniform in both mesothelial and endothelial cells, mitigating spheroid formation and gel contraction. On the contrary, effects on 2D phenotypes are more uniform in the icodextrin and amino acid PDF as opposed to glucose ones and affect mesothelial cells more variably. 2D and 3D comparative assessments of PDF effects on the main peritoneal membrane cell barriers, the mesothelial and endothelial, could provide useful translational information for PD studies.

N-methylpiperazine-diepoxyovatodiolide ameliorates peritoneal fibrosis via suppressing TGF-β/Smad and JAK/STAT signaling pathway

Peritoneal fibrosis (PF) is the main cause of peritoneal ultrafiltration failure in patients undergoing long-term peritoneal dialysis (PD). Epithelial–mesenchymal transition (EMT) is the key pathogenesis of PF. However, currently, no specific treatments are available to suppress PF. N-methylpiperazine-diepoxyovatodiolide (NMPDOva) is a newly synthesized compound that involves a chemical modification of ovatodiolide. In this study, we aimed to explore the antifibrotic effects of NMPDOva in PD-related PF and underlying mechanisms. A mouse model of PD-related PF was established via daily intraperitoneal injection of 4.25% glucose PD fluid. In vitro studies were performed using the transforming growth factor-beta1 (TGF-β1)-stimulated HMrSV5 cell line. Pathological changes were observed, and fibrotic markers were significantly elevated in the peritoneal membrane in mice model of PD-related PF. However, NMPDOva treatment significantly alleviated PD-related PF by decreasing the extracellular matrix accumulation. NMPDOva treatment decreased the expression of fibronectin, collagen Ⅰ, and alpha-smooth muscle actin (α-SMA) in mice with PD-related PF. Moreover, NMPDOva could alleviate TGF-β1-induced EMT in HMrSV5 cells, inhibited phosphorylation and nuclear translocation of Smad2/3, and increased the expression of Smad7. Meanwhile, NMPDOva inhibited phosphorylation of JAK2 and STAT3. Collectively, these results indicated that NMPDOva prevents PD-related PF by inhibiting the TGF-β1/Smad and JAK/STAT signaling pathway. Therefore, because of these antifibrotic effects, NMPDOva may be a promising therapeutic agent for PD-related PF.

Histone deacetylase 8 inhibition prevents the progression of peritoneal fibrosis by counteracting the epithelial-mesenchymal transition and blockade of M2 macrophage polarization.

Peritoneal dialysis (PD) is an effective replacement therapy for end-stage renal disease patients. However, long-term exposure to peritoneal dialysate will lead to the development of peritoneal fibrosis. Epigenetics has been shown to play an important role in peritoneal fibrosis, but the role of histone deacetylases 8 (HDAC8) in peritoneal fibrosis have not been elucidated. In this research, we focused on the role and mechanisms of HDAC8 in peritoneal fibrosis and discussed the mechanisms involved. We examined the expression of HDAC8 in the peritoneum and dialysis effluent of continuous PD patients. Then we assessed the role and mechanism of HDAC8 in peritoneal fibrosis progression in mouse model of peritoneal fibrosis induced by high glucose peritoneal dialysis fluid by using PCI-34051. In vitro, TGF-β1 or IL-4 were used to stimulate human peritoneal mesothelial cells (HPMCs) or RAW264.7 cells to establish two cell injury models to further explore the role and mechanism of HDAC8 in epithelial-mesenchymal transition (EMT) and macrophage polarization. We found that HDAC8 expressed highly in the peritoneum from patients with PD-related peritonitis. We further revealed that the level of HDAC8 in the dialysate increased over time, and HDAC8 was positively correlated with TGF-β1 and vascular endothelial growth factor (VEGF), and negatively correlated with cancer antigen 125. In mouse model of peritoneal fibrosis induced by high glucose dialysate, administration of PCI-34051 (a selective HDAC8 inhibitor) significantly prevented the progression of peritoneal fibrosis. Treatment with PCI-34051 blocked the phosphorylation of epidermal growth factor receptor (EGFR) and the activation of its downstream signaling pathways ERK1/2 and STAT3/HIF-1α. Inhibition of HDAC8 also reduced apoptosis. In vitro, HDAC8 silencing with PCI-34051 or siRNA inhibited TGF-β1-induced EMT and apoptosis in HPMCs. In addition, continuous high glucose dialysate or IL-4 stimulation induced M2 macrophage polarization. Blockade of HDAC8 reduced M2 macrophage polarization by inhibiting the activation of STAT6 and PI3K/Akt signaling pathways. We demonstrated that HDAC8 promoted the EMT of HPMCs via EGFR/ERK1/2/STAT3/HIF-1α, induced M2 macrophage polarization via STAT6 and PI3K/Akt signaling pathways, and ultimately accelerated the process of peritoneal fibrosis.

Pharmacologic Inhibition of Histone Deacetylase 6 Prevents the Progression of Chlorhexidine Gluconate-Induced Peritoneal Fibrosis by Blockade of M2 Macrophage Polarization.

Peritoneal fibrosis contributes to ultrafiltration failure in peritoneal dialysis (PD) patients and thus restricts the wide application of PD in clinic. Recently we have demonstrated that histone deacetylase 6 (HDAC6) is critically implicated in high glucose peritoneal dialysis fluid (HG-PDF) induced peritoneal fibrosis, however, the precise mechanisms of HDAC6 in peritoneal fibrosis have not been elucidated. Here, we focused on the role and mechanisms of HDAC6 in chlorhexidine gluconate (CG) induced peritoneal fibrosis and discussed the mechanisms involved. We found Tubastatin A (TA), a selective inhibitor of HDAC6, significantly prevented the progression of peritoneal fibrosis, as characterized by reduction of epithelial-mesenchymal transition (EMT) and extracellular matrix (ECM) protein deposition. Inhibition of HDAC6 remarkably suppressed the expression of matrix metalloproteinases-2 (MMP2) and MMP-9. Administration of TA also increased the expression of acetylation Histone H3 and acetylation α-tubulin. Moreover, our results revealed that blockade of HDAC6 inhibited alternatively M2 macrophages polarization by suppressing the activation of TGF-β/Smad3, PI3K/AKT, and STAT3, STAT6 pathways. To give a better understanding of the mechanisms, we further established two cell injured models in Raw264.7 cells by using IL-4 and HG-PDF. Our in vitro experiments illustrated that both IL-4 and HG-PDF could induce M2 macrophage polarization, as demonstrated by upregulation of CD163 and Arginase-1. Inhibition of HDAC6 by TA significantly abrogated M2 macrophage polarization dose-dependently by suppressing TGF-β/Smad, IL4/STAT6, and PI3K/AKT signaling pathways. Collectively, our study revealed that blockade of HDAC6 by TA could suppress the progression of CG-induced peritoneal fibrosis by blockade of M2 macrophage polarization. Thus, HDAC6 may be a promising target in peritoneal fibrosis treatment.

Intermittent hypoxia in rat enhancing peritoneal membrane thickening through HIF-1α-induced cytokines in peritoneum.

Due to the high prevalence of both obstructive sleep apnea syndrome (OSA) and end-stage renal disease (ESRD), the co-existence of both conditions in peritoneal dialysis is demonstrated. Because OSA-induced chronic intermittent hypoxia is well-known, the hypoxia might worsen peritoneal membrane. We tested the influence of chronic intermittent hypoxia upon peritoneal membrane in a Sprague-Dawley rat model. Normal saline or 3.86% glucose peritoneal dialysis fluid (PDF) were intra-peritoneally administered twice a day as negative (NSS group) and positive controls (PDF group), respectively. Intermittent hypoxia was induced by using a hypoxic chamber with 10% O2 for 8 hours a day plus twice-daily NSS injection (IH group). At 12 weeks of the experiments, high serum TNF-α and IL-6 (but not IL-10) with normal renal and liver functions were demonstrated in the IH group (but not the PDF group). In parallel, local cytokines (TNF-α, IL-6, and IL10 in peritoneal membrane) and peritoneal membrane thickness were increased whereas peritoneal membrane hypoxia (hypoxyprobeTM and hypoxia-inducible factor-1α; HIF-1α) was induced in both PDF and IH groups (more prominent in the PDF group). However, the increased vascular density in submesothelial area was established only in the PDF group. Intermittent hypoxia model induced local peritoneal membrane inflammation and enhanced peritoneal membrane thickness, at least in part, through a mechanism of hypoxia-induced HIF-1α. Although peritoneal membrane alterations from PDF were more prominent than intermittent hypoxia, the combination between intermittent hypoxia with PDF utilization might facilitate peritoneal membrane failure, which will need more study.

Trimethylamine-N-Oxide Aggravates Kidney Injury via Activation of p38/MAPK Signaling and Upregulation of HuR

Background: Trimethylamine-N-oxide (TMAO) is an intestinal metabolic toxin, which is produced by gut flora via metabolizing high-choline foods. TMAO is known to increase the risk of atherosclerosis and cardiovascular events in chronic kidney disease (CKD) patients. Objectives: The objective of this study was to explore the role and mechanism of TMAO aggravating kidney injury. Method: We used the five-sixths nephrectomy (5/6 Nx)-induced CKD rats to investigate whether TMAO could aggravate kidney damage and its possible mechanisms. Six weeks after the operation, the two groups of 5/6 Nx rats were subjected to intraperitoneal injection with 2.5% glucose peritoneal dialysis fluid (2.5% PDF) and 2.5% PDF plus TMAO 20 mg/kg/day. Results: In this study, we provided evidence showing TMAO significantly aggravated renal failure as well as inflammatory cell infiltration and in five-sixths nephrectomy-induced CKD rats. We found that TMAO could upregulate inflammatory factors including MCP-1, TNF-α, IL-6, IL-1β, and IL-18 by activating p38 phosphorylation and upregulation of human antigen R. TMAO could aggravate oxidative stress by upregulating NOX4 and downregulating SOD. The result also confirmed that TMAO promoted NLRP3 inflammasome formation as well as cleaved caspase-1 and IL-1β activation in the kidney tissue. Conclusions: Taken together, the present study validates TMAO as a pro-inflammatory factor that causes renal inflammatory injury and renal function impairment. Inhibition of TMAO synthesis or promoting its clearance may be a potential therapeutic approach of CKD in the future.

A Sweet Dream with SGLT2 Inhibitors

Glucose is an osmotic agent in the peritoneal dialysis fluid (PDF) to absorb water, sodium and other toxins. Glucose absorption from PDF to blood impairs peritoneal dialysis (PD) efficiency and cause glycemic burden. This extra glycemic load leads to poor glycemic control in diabetic dialysis patients with PD program. Studies have shown sodium-glucose co-transporter (SGLT)-2 expression in peritoneal mesothelial cells. Blockade of peritoneal SGLT reduced blood glucose increment and increased peritoneal glucose retention in mice. In rat models, it was shown that high glucose PDF promotes the peritoneal fibrosis by upregulating the expression of glucose transporter (GLUT) and SGLT, and addition of phlorizin to PDF leads to downregulation of GLUT and SGLT expression and reduced peritoneal degeneration. According to these information, we want to share our experience of using empagliflozin in a poor glycemic controlled type 2 diabetic patient, who was on PD program for end-stage renal disease. We hypothesized that if we administer empagliflozin to our patient we can reduce glycemic burden caused by PDF and increase the ultrafiltration volume.

Genetic or pharmacologic blockade of enhancer of zeste homolog 2 inhibits the progression of peritoneal fibrosis.

Dysregulation of histone methyltransferase enhancer of zeste homolog 2 (EZH2) has been implicated in the pathogenesis of many cancers. However, the role of EZH2 in peritoneal fibrosis remains unknown. We investigated EZH2 expression in peritoneal dialysis (PD) patients and assessed its role in peritoneal fibrosis in cultured human peritoneal mesothelial cells (HPMCs) and murine models of peritoneal fibrosis induced by chlorhexidine gluconate (CG) or high glucose peritoneal dialysis fluid (PDF) by using 3-deazaneplanocin A (3-DZNeP), and EZH2 conditional knockout mice. An abundance of EZH2 was detected in the peritoneum of patients with PD associated peritonitis and the dialysis effluent of long-term PD patients, which was positively correlated with expression of TGF-β1, vascular endothelial growth factor, and IL-6. EZH2 was found highly expressed in the peritoneum of mice following injury by CG or PDF. In both mouse models, treatment with 3-DZNeP attenuated peritoneal fibrosis and inhibited activation of several profibrotic signaling pathways, including TGF-β1/Smad3, Notch1, epidermal growth factor receptor and Src. EZH2 inhibition also inhibited STAT3 and nuclear factor-κB phosphorylation, and reduced lymphocyte and macrophage infiltration and angiogenesis in the injured peritoneum. 3-DZNeP effectively improved high glucose PDF-associated peritoneal dysfunction by decreasing the dialysate-to-plasma ratio of blood urea nitrogen and increasing the ratio of dialysate glucose at 2h after PDF injection to initial dialysate glucose. Moreover, delayed administration of 3-DZNeP inhibited peritoneal fibrosis progression, reversed established peritoneal fibrosis and reduced expression of tissue inhibitor of metalloproteinase 2, and matrix metalloproteinase-2 and -9. Finally, EZH2-KO mice exhibited less peritoneal fibrosis than EZH2-WT mice. In HPMCs, treatment with EZH2 siRNA or 3-DZNeP suppressed TGF-β1-induced upregulation of α-SMA and Collagen I and preserved E-cadherin. These results indicate that EZH2 is a key epigenetic regulator that promotes peritoneal fibrosis. Targeting EZH2 may have the potential to prevent and treat peritoneal fibrosis. © 2019 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

SUN-074 Icodextrin- vs. Either Single or Dual Compartment Glucose-Based Solutions for Peritoneal Dialysis – A Systematic Review and Meta-Analysis

Patients with end-stage renal disease (ESRD) undergoing peritoneal dialysis (PD) have options regarding the osmotic agents used in PD fluids (PDFs). These include hyper-osmolar glucose, as well as iso-osmolar icodextrin, a soluble glucose polymer. In addition to the randomized, controlled trials (RCT) published over the past two decades, there is a significant body of unpublished evidence also comparing icodextrin to glucose PDFs. The aim of our systematic review was to synthesize evidence from RCT comparing the efficacy and safety profile of icodextrin-inclusive vs.

Tamoxifen attenuates dialysate-induced peritoneal fibrosis by inhibiting GSK-3β/β-catenin axis activation

Peritoneal fibrosis is a severe complication arising from long-term peritoneal dialysis (PD). Tamoxifen (Tamo) has been clinically proven effective in a series of fibrotic diseases, such as PD-associated encapsulating peritoneal sclerosis (EPS), but the mechanisms underlying Tamoxifen’s protective effects are yet to be defined. In the present study, C57BL/6 mice received intraperitoneal injections of either saline, 4.25% high glucose (HG) PD fluid (PDF) or PDF plus Tamoxifen each day for 30 days. Tamoxifen attenuated thickening of the peritoneum, and reversed PDF-induced peritoneal expression of E-cadherin, Vimentin, matrix metalloproteinase 9 (MMP9), Snail, and β-catenin. Mouse peritoneal mesothelial cells (mPMCs) were cultured in 4.25% glucose or 4.25% glucose plus Tamoxifen for 48 h. Tamoxifen inhibited epithelial-to-mesenchymal transition (EMT) as well as phosphorylation of glycogen synthase kinase-3β (GSK-3β), nuclear β-catenin, and Snail induced by exposure to HG. TWS119 reversed the effects of Tamoxifen on β-catenin and Snail expression. In conclusion, Tamoxifen significantly attenuated EMT during peritoneal epithelial fibrosis, in part by inhibiting GSK-3β/β-catenin activation.

Hydrogen sulfide inhibits epithelial-mesenchymal transition in peritoneal mesothelial cells

Peritoneal fibrosis (PS) determines the long-term outcome of peritoneal dialysis (PD). We previous confirmed that hydrogen sulfide (H2S) inhibited PS, but its cellular mechanism was not fully elucidated. Epithelial-mesenchymal transition (EMT) of mesothelial cells (MCs) is an important cellular event of PS, we therefore investigated whether EMT can be affected by H2S in MCs. Rats were treated with 4.25% -glucose PD fluids plus lipopolysaccharide for 28 days to produce PS, and NaHS (56 μg/kg.d) was given simultaneously. NaHS (56 μg/kg.d) reduced the deposition of collagen in the submesothelial zone compared with the PS group. In primarily cultured rat MCs, 4.25% -glucose PD fluid induced EMT in MCs featured as loss of ZO-1 and Cytokeratin, and increase of α-SMA, plasminogen activator inhibitor 1, fibronectin and TGF-β1 proteins. PD fluid also increased IL-6 and monocyte chemotactic protein-1 mRNA expressions as well as the phosphorylation of Smad2/3 and Smad3. NaHS (50–300 μmol/L) reversed the above alterations with the optimal dose at 100 μmol/L. Thus, exogenous H2S improves PS by inhibiting EMT in MCs. The anti-EMT effect of H2S is associated with the inhibition of inflammation and TGF-β1-Smad signal pathway.

Beta-catenin participates in dialysate-induced peritoneal fibrosis via enhanced peritoneal cell epithelial-to-mesenchymal transition.

Long‐term exposure to peritoneal dialysate with high glucose (HG) leads to peritoneal fibrosis and thus decreases dialysis efficiency. In this study, we explored the role of β‐catenin in this process. C57BL/6 mice received daily intraperitoneal injection with 10% of the body weight of saline (control), 4.25% glucose peritoneal dialysis fluid (PDF), or PDF combined with 5 mg·kg−1 of the β‐catenin inhibitor ICG‐001 (PDF+ICG) for 30 days. Also, mice peritoneal epithelial cells (mPECs) were cultured in 4.25% glucose (HG) or combined with 10 μm ICG‐001 (HG+ICG) for 48 h. We found greater thickness of the parietal peritoneum in the PDF‐treated mice. Additionally, lower expression of E‐cadherin, higher expression of Vimentin, β‐catenin, and Snail, and activation of β‐catenin was observed in the mice and in HG‐treated mPECs, all of which were reversed by ICG‐001. The changes in E‐cadherin and Vimentin indicated occurrence of the epithelial‐to‐mesenchymal transition (EMT). Thus, β‐catenin signaling participates in the process of HG‐induced peritoneal fibrosis, and the EMT of peritoneal epithelial cells is one of the underlying mechanisms of this pathological change.

Addition of Alanyl-Glutamine to Dialysis Fluid Restores Peritoneal Cellular Stress Responses - A First-In-Man Trial.

BackgroundPeritonitis and ultrafiltration failure remain serious complications of chronic peritoneal dialysis (PD). Dysfunctional cellular stress responses aggravate peritoneal injury associated with PD fluid exposure, potentially due to peritoneal glutamine depletion. In this randomized cross-over phase I/II trial we investigated cytoprotective effects of alanyl-glutamine (AlaGln) addition to glucose-based PDF.MethodsIn a prospective randomized cross-over design, 20 stable PD outpatients underwent paired peritoneal equilibration tests 4 weeks apart, using conventional acidic, single chamber 3.86% glucose PD fluid, with and without 8 mM supplemental AlaGln. Heat-shock protein 72 expression was assessed in peritoneal effluent cells as surrogate parameter of cellular stress responses, complemented by metabolomics and functional immunocompetence assays.ResultsAlaGln restored peritoneal glutamine levels and increased the primary outcome heat-shock protein expression (effect 1.51-fold, CI 1.07–2.14; p = 0.022), without changes in peritoneal ultrafiltration, small solute transport, or biomarkers reflecting cell mass and inflammation. Further effects were glutamine-like metabolomic changes and increased ex-vivo LPS-stimulated cytokine release from healthy donor peripheral blood monocytes. In patients with a history of peritonitis (5 of 20), AlaGln supplementation decreased dialysate interleukin-8 levels. Supplemented PD fluid also attenuated inflammation and enhanced stimulated cytokine release in a mouse model of PD-associated peritonitis.ConclusionWe conclude that AlaGln-supplemented, glucose-based PD fluid can restore peritoneal cellular stress responses with attenuation of sterile inflammation, and may improve peritoneal host-defense in the setting of PD.

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.

High glucose dialysate enhances peritoneal fibrosis through upregulating glucose transporters GLUT1 and SGLT1

Objective: To investigate the role of glucose transporter 1 (GLUT1) and sodium-glucose cotransporter 1 (SGLT1) in high glucose dialysate-induced peritoneal fibrosis. Methods: Thirty six male SD rats were randomly divided into 6 groups (6 in each):normal control group, sham operation group, peritoneal dialysis group (PD group), PD+phloretin group (PD+T group), PD+phlorizin group (PD+Z group), PD+phloretin+phlorizin group (PD+T+Z group). Rat model of uraemia was established using 5/6 nephrotomy, and 2.5% dextrose peritoneal dialysis solution was used in peritoneal dialysis. Peritoneal equilibration test was performed 24 h after dialysis to evaluate transport function of peritoneum in rats; HE staining was used to observe the morphology of peritoneal tissue; and immunohistochemistry was used to detect the expression of GLUT1, SGLT1, TGF-β1 and connective tissue growth factor (CTGF) in peritoneum. Human peritoneal microvascular endothelial cells (HPECs) were divided into 5 groups:normal control group, peritoneal dialysis group (PD group), PD+phloretin group (PD+T group), PD+phlorezin group (PD+Z group), and PD+phloretin+phlorezin group (PD+T+Z group). Real time PCR and Western blotting were used to detect mRNA and protein expressions of GLUT1, SGLT1, TGF-β1, CTGF in peritoneal membrane and HPECs. Results:In vivo, compared with sham operation group, rats in PD group had thickened peritoneum, higher ultrafiltration volume, and the mRNA and protein expressions of GLUT1, SGLT1, CTGF, TGF-β1 were significantly increased (all P<0.05); compared with PD group, thickened peritoneum was attenuated, and the mRNA and protein expressions of GLUT1, SGLT1, CTGF, TGF-β1 were significantly decreased in PD+T, PD+Z and PD+T+Z groups (all P<0.05). Pearson's correlation analysis showed that the expressions of GLUT1, SGLT1 in peritoneum were positively correlated with the expressions of TGF-β1 and CTGF (all P<0.05). In vitro, the mRNA and protein expressions of GLUT1, SGLT1, TGF-β1, CTGF were significantly increased in HPECs of peritoneal dialysis group (all P<0.05), and those in PD+T, PD+Z, and PD+T+Z groups were decreased (all P<0.05). Pearson's correlation analysis showed that the expressions of GLUT1, SGLT1 in HPECs were positively correlated with the expressions of TGF-β1 and CTGF (all P<0.05). Conclusion: High glucose peritoneal dialysis fluid may promote peritoneal fibrosis by upregulating the expressions of GLUT1 and SGLT1.

Hydrogen Sulfide Alleviates Peritoneal Fibrosis via Attenuating Inflammation and TGF-β1 Synthesis

Background/Aims: Peritoneal fibrosis is one of the long-term complications in peritoneal dialysis (PD) patients. Recent evidences have suggested that hydrogen sulfide (H₂S) is beneficial in treating various fibrotic diseases, including pulmonary fibrosis, cirrhosis, kidney fibrosis and cardiac hypertrophy. However, no information is known about the effect of H₂S on peritoneal fibrosis. In the present study, we investigated the effect of H₂S on peritoneal fibrosis and explored its potential mechanisms. Methods: We developed a model of peritoneal fibrosis by intraperitoneally injecting 4.25%-glucose PD fluids and lipopolysaccharide to Sprague-Dawley rats. The rats received daily intraperitoneal injections of NaHS (56 μg/kg), an H₂S donor. After 28 days, the peritoneal equilibration test (PET) was used to assess peritoneal function. At the end of dialysis, the rats were killed and parietal peritoneum was harvested for microscopic examination and immunohistochemistry. Results: On the 28th day, the parietal peritoneum of the PD rats markedly thickened as a result of increased depositions of type III collagen and fibronectin. Moreover, the number of ED-1-positive cells and the expressions of monocyte chemoattractant protein-1, transforming growth factor-β1 (TGF-β1), α-smooth muscle actin and CD31 were significantly increased in the fibrotic peritoneum. Administration of NaHS markedly decreased the biomarkers of inflammation, fibrosis and angiogenesis in the peritoneum. NaHS also improved peritoneal function assessed by PET. Conclusion: Exogenous H₂S ameliorates the pathologic process of peritonitis via attenuating inflammatory events and TGF-β1 synthesis. These results suggest that H₂S may be a potential therapy against peritoneal fibrosis during chronic PD. In the future, compounds releasing H₂S at controlled rate will be assessed as potential candidates to treat peritoneal fibrosis.

Hydrogen Sulfide Ameliorates High-Glucose Toxicity in Rat Peritoneal Mesothelial Cells by Attenuating Oxidative Stress

Background/Aims: Continuous exposure of the peritoneal membrane to high-glucose (HG) peritoneal dialysis fluids (PDFs) can produce peritoneal mesothelial cells (PMCs) injury. It has been demonstrated that hydrogen sulfide (H₂S), the third endogenous gaseous mediator identified after nitric oxide and carbon monoxide, exhibits a potent protective effect on cell activity. We studied the toxic effects of HG PDFs and their reversal by H₂S on cultures of rat PMCs. Methods: Synchronized confluent rat PMCs were incubated with 2.5% glucose PDFs with or without NaHS, an H₂S donor. Cell viability was assessed by methyl thiazolyl tetrazolium assay and flow cytometry. The level of phospho-p38 mitogen-activated protein kinase (MAPK) was analyzed by immunoblotting. p53, Bax and Bcl-2 mRNA expressions by rat PMCs were detected by real-time PCR. The levels of reactive oxygen species (ROS), superoxide dismutase (SOD) activity and caspase-3 activity were measured. Results: Exposure of rat PMCs to 2.5% glucose PDFs for 24 h resulted in a significant induction of apoptosis, which was attenuated by NaHS. NaHS also restored the 2.5% glucose PDF-induced increase in phospho-p38 MAPK (indices of cellular toxicity). Further investigation of the apoptotic mechanisms in rat PMCs demonstrated that HG activated caspase-3 and upregulated Bax, while it downregulated Bcl-2. All the above responses were prevented by pretreatment with NaHS. Moreover, NaHS reversed the 2.5% glucose PDF-induced increase in ROS generation and decrease in SOD activity. Conclusions: These findings suggest that HG PDFs significantly inhibit rat PMC viability, leading to peritoneal injury. H₂S exhibits a potent anti-apoptotic ability by attenuating oxidative stress and inhibiting caspase-3 activation, which in turn restores peritoneal injury.

Could mini-PET be used to instead of 4 h original-PET to assess peritoneal permeability in children on peritoneal dialysis?

Background: Original peritoneal equilibration test (PET) is an implementation that requires hard work for peritoneal dialysis (PD) staff. Therefore, several authors have attempted to validate short and fast PET protocols, with controversial results. The aim of this study was to evaluate the concordance between the mini-PET and original PET in children. Methods: In 26 stable continuous ambulatory PD patients, we performed an original PET with 2.27% (4 h) and a mini-PET with 3.86% glucose PD fluid (1 h) and compared ultrafiltration (UF) and small solute transports obtained with the two methods. Results: Twenty-six children, 14 males, mean age 11.4 ± 5.6 (range 2.5–19 years), were included. Meantime on PD at time of enrollment was 35.2 ± 24.5 months (range 6–84 months). Based on the 4-h creatinine D/P data, the number of the patients within each transport category was as follow: high, 5; average, 18; low, 3. Kappa test showed a significant concordance between original PET and mini-PET (k = 0.610). Based on the 4-h glucose D/D0 data, the number of the patients within each transport category was as follow: high, 5; average, 17; low, 4. Kappa test showed a moderate agreement between original PET and mini-PET (0.514, p = 0.000). When Pearson correlation analysis between original PET and mini-PET was performed, there were significant positive correlations between original 2.27% PET and mini-PET (r = 0.720, p = 0.000, r = 0.638, p = 0.000, respectively). When comparing the numeric results of mini-PET and 4 h of original PET for D/Creatinine, by simple regression analysis, we found statistically significant correlation among PETs. Conclusions: In this study, we showed concordance between the mini-PET and original PET. The 3.86% mini-PET is simple and fast methods to assess free water transport. This also gives information about total UF and small solute transports and it is in good agreement with the original PET.

Neuropeptide Release Augments Serum Albumin Loss and Reduces Ultrafiltration in Peritoneal Dialysis

The triggers of the acute local inflammatory response to peritoneal dialysis (PD) fluid exposure remain unknown. In the present study, we investigated the effects of neurogenic inflammation and mast cell degranulation on water and solute transport in experimental PD. Single 2-hour dwells in rats with PD catheters were studied. Histamine and the neuropeptides substance P and calcitonin gene-related peptide (CGRP) were measured in PD fluid samples by ELISA. Radiolabeled albumin ((125)I and (131)I respectively) was used as an intraperitoneal (IP) and intravascular tracer. Glucose and urea concentrations were measured in plasma and PD fluid. The effects of varying the volume and osmolarity of a lactate-buffered PD fluid were compared and related to the effects of pharmacologic intervention. Application of 20 mL 3.9% glucose PD fluid induced an IP histamine release during the first 30 minutes, blockable by the mast cell stabilizer doxantrazole and the substance P neurokinin-1 receptor (NK1R)-blocker spantide. Histamine release was also inhibited at a reduced PD volume (14 mL), but was not affected by normalizing the PD fluid osmolarity. Blockade of NK1R also reduced plasma albumin leakage to the peritoneal cavity. Inhibition of CGRP receptors by CGRP8-37 improved osmotic (transcapillary) and net ultrafiltration and reduced the dialysate urea concentration. Neuropeptide release was not clearly related to activation of the TrpV1 receptor, the classic trigger of neurogenic inflammation. Neuropeptide release exaggerated albumin loss and reduced ultrafiltration in this rat PD model. Intervention aimed at the neuropeptide action substantially improved PD efficiency.

The impact of dialysis solution biocompatibility on ultrafiltration and on free water transport in rats

This study compares different peritoneal dialysis fluids (PDF) in rats over a short contact time. For greater accuracy, net ultrafiltration (UF) and peritoneal transport indices, mass transfer area coefficient (MTAC) were scaled for the in vivo peritoneal surface area recruited (ivPSA) measured by microcomputerized tomography. Wistar rats underwent nephrectomy (5/6ths), were randomized into two groups and given 1.5% glucose PDF, either conventional acidic lactate (n = 14) or pH neutral bicarbonate (BicaVera) (n = 13); MTAC and UF were measured using a 90-min peritoneal equilibrium test (PET), fill volume (IPV) of 10 ml/100 g; small pore fluid transport was determined from sodium balance and used to calculate free water transport (FWT). Each ivPSA value was significantly correlated with the actual IPV, which varied from one rat to another. At 90 min of contact, there was no difference in recruited ivPSA in relation to PDFs. There was a difference (p < 0.01) in net UF/ivPSA 0.45 vs. 1.41 cm(2)/ml for bicarbonate versus lactate, as there was in the proportion of FWT with bicarbonate (42 ± 5% of net UF) compared to lactate (29 ± 4% of net UF). Net UF for individual values of ivPSA differs between conventional PDF and more biocompatible solutions, such as bicarbonate PDF. This observed change in UF cannot be fully explained by differences in glucose transport. The changes in FWT may be explained by the impact of the PDF biocompatibility on aquaporin function.