Prevention of membrane damage in patient on peritoneal dialysis with new peritoneal dialysis solutions

1,25(OH)2D3 inhibits high glucose-induced apoptosis and ROS production in human peritoneal mesothelial cells via the MAPK/P38 pathway

The regulation of cell proliferation, differentiation and immunomodulation are affected by 1,25(OH)2D3. However, its function during apoptosis and oxidative stress in human peritoneal mesothelial cells (HPMCs) remains unknown. The aim of the present study was to investigate whether the regulation of apoptosis and oxidative stress have therapeutic relevance in peritoneal dialysis (PD) therapy. The present study investigated the effects of 1,25(OH)2D3 on high glucose (HG)-induced apoptosis and reactive oxygen species (ROS) production in HPMCs, and examined the underlying molecular mechanisms. Flow cytometry and western blotting were performed to detect cell apoptosis, 2,7-dichlorofluorescein diacetate was used to measure reactive oxygen species production and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide was used to measure cell viability. The results of the present study demonstrated that exposure to HG increased apoptosis and ROS production in HPMCs, whereas pretreatment with 1,25(OH)2D3 significantly inhibited HG‑induced apoptosis and ROS production. Further analysis revealed that 1,25(OH)2D3 facilitated cell survival via the MAPK/P38 pathway. The results of the present study indicate that 1,25(OH)2D3 inhibits apoptosis and ROS production in HG‑induced HPMCs via inhibition of the MAPK/P38 pathway.

Zinc transporter 5 and zinc transporter 7 induced by high glucose protects peritoneal mesothelial cells from undergoing apoptosis

Zinc is an essential micronutrient and cytoprotectant involved in many types of apoptosis. The zinc transporter family SLC30A (ZnTs) is an important factor in the regulation of zinc homeostasis; however, its function in apoptosis in peritoneal mesothelial cells (PMCs) remains unknown. This study explores the regulation of zinc transporters and how they play a role in cell survival, particularly in rat peritoneal mesothelial cells (RPMCs), surrounding glucose concentrations, and the molecular mechanism involved. The messenger RNA (mRNA) transcripts were quantitatively measured by real-time polymerase chain reaction for all known nine zinc transport exporters (SLC30A1-8,10), as well as in primary RPMCs and the cells cultured under nonstimulated and HG-stimulated conditions. While many zinc transporters were constitutively expressed, ZnT5 mRNA and ZnT7 mRNA were strongly induced by HG. Overexpression of ZnT5 and ZnT7 respectively resulted in a decrease in the expression of caspace 3, caspace 8, BAX, and AIF and coincided with cell survival in the presence of HG. Inhibition of ZnT5 and ZnT7 expression using considerable siRNA-mediated knockdown of RPMCs was examined and, afterwards, the impact on cell apoptosis was investigated. Increased levels of apoptosis were observed after knockdown of ZnT5 and ZnT7. Furthermore, overexpression of ZnT5 and ZnT7 is accompanied by activation of PI3K/Akt pathway and inhibiting HG-induced apoptosis. This study suggests that the zinc transporting system in RPMCs is influenced by exposure to HG, particularly ZnT5 and ZnT7. This may account for the inhibition of HG-induced RPMC apoptosis and peritoneum injury, likely through targeting PI3K/Akt pathway-mediated cell survival.

Zinc inhibits high glucose-induced apoptosis in peritoneal mesothelial cells

Zinc (Zn) plays an important role in influencing many types of apoptosis. However, its function in apoptosis in peritoneal mesothelial cells (PMCs) remains unknown. Here, we studied the effects of Zn on high glucose (HG)-induced apoptosis in rat PMCs (RPMCs) and examined the underlying molecular mechanisms. We found that Zn supplementation inhibited HG-induced RPMC apoptosis significantly, by attenuating reactive oxygen species (ROS) production, inhibiting HG-induced sFasR and sFasL over-expression, caspase-8 and caspase-3 activation, and inhibiting release of cytochrome c from mitochondria to the cytosol. Further analysis revealed that Zn supplementation facilitated cell survival through activation of the phosphatidylinositol 3-kinase/Akt signaling pathway and MAPK/ERK pathways. These results indicate that Zn can inhibit apoptosis in HG-induced RPMCs by several independent mechanisms, including an indirect antioxidative effect and probably by inhibition of caspase-8 and caspase-3 activation.

Atorvastatin Reduces High Glucose Toxicity in Rat Peritoneal Mesothelial Cells

Objective

Continuous exposure of the peritoneal membrane to high glucose dialysis solutions can produce functional alterations in this membrane. We studied the toxic effects of high glucose (50 mmol/L and 83 mmol/L) and its reversal by atorvastatin (0.5 – 5 μmol/L) on cultures of rat peritoneal mesothelial cells (PMCs).

Methods

Rat PMCs were harvested from the peritonea of male Sprague–Dawley rats and grown in M199 medium supplemented with 10% fetal bovine serum. The effects of high glucose (50 mmol/L and 83 mmol/L) on levels of reactive oxygen species (ROS), on caspase 3 activity, and on phospho-p38 mitogen-activated protein kinase (MAPK) in the cultures were evaluated.

Results

Exposure to high glucose (for 4, 8, and 24 hours) increased intracellular levels of ROS and phospho-p38 MAPK (indices of cellular toxicity). Atorvastatin blocked these toxic effects of high glucose, being more effective against 50 mmol/L glucose (protective effects were observed above 0.5 μmol/L) than against 83 mmol/L (protective effects were observed above 2.5 μmol/L). Atorvastatin was also able to prevent glucose-induced increase in caspase 3 activity.

Conclusions

The present study shows that high glucose may promote oxidative stress and may activate apoptotic pathways in rat PMCs. These toxic effects could be reversed by atorvastatin.

3-Deoxygalactosone, a new glucose degradation product in peritoneal dialysis fluids: identification, quantification by HPLC/DAD/MSMS and its pathway of formation

Heat sterilization of peritoneal dialysis (PD) fluids leads to the formation of glucose degradation products (GDPs), which considerably impair long-term application of PD. Knowledge of the exact composition of GDPs present in a PD fluid is important to improve the biocompatibility of dialysis solutions. The present study conducted a targeted screening for novel GDPs with α-dicarbonyl structure in PD fluids. Thus, 3-deoxygalactosone (3-DGal) was identified for the first time in PD fluids. Quantification of 3-DGal was achieved by high-performance liquid chromatography (HPLC)/DAD/MSMS after derivatization with o-phenylendiamine to yield the quinoxaline derivative. Baseline separation of all α-dicarbonyl GDPs, particularly of the diastereomers 3-deoxyglucosone (3-DG) and 3-DGal, required the application of a polar, phenyl-based RP column for HPLC and additional pH-gradient elution. Concentrations of 3-DGal ranged between 55.8 and 136.9 μM in single-chamber PD fluids, and between 2.5 and 12.4 μM in double-chamber PD fluids. In solutions containing glucose, 3-DGal is formed from 3-DG via the intermediate 3,4-dideoxyglucosone-3-ene (3,4-DGE). Further studies are now required to determine the (patho-)physiological properties of 3-DGal.

Peritoneal dialysis fluid bioincompatibility and new vessel formation promote leukocyte-endothelium interactions in a chronic rat model for peritoneal dialysis

Peritoneal dialysis (PD)-induced peritonitis leads to dysfunction of the peritoneal membrane. During peritonitis, neutrophils are recruited to the inflammation site by rolling along the endothelium, adhesion, and transmigration through vessel walls. In a rat PD-model, long-term effects of PD-fluids (PDF) on leukocyte-endothelium interactions and neutrophil migration were studied under baseline and inflammatory conditions. Rats received daily conventional-lactate-buffered PDF (Dianeal), bicarbonate/lactate-buffered PDF (Physioneal) or bicarbonate/lactate buffer (Buffer) during five weeks. Untreated rats served as control. Baseline leukocyte rolling and N-formylmethionyl-leucyl-phenylalanine (fMLP) induced levels of transmigration in the mesentery were evaluated and quantified by intra-vital videomicroscopy and immunohistochemistry. Baseline leukocyte rolling was unaffected by buffer treatment, approximately 2-fold increased after Physioneal and 4-7-fold after Dianeal treatment. After starting fMLP superfusion, transmigrated leukocytes appeared outside the venules firstly after Dianeal treatment (15 minutes), thereafter in Physioneal and Buffer groups (20-22 minutes), and finally in control rats (>25 minutes). Newly formed vessels and total number of transmigrated neutrophils were highest in Dianeal-treated animals, followed by Physioneal and Buffer, and lowest in control rats and correlated for all groups to baseline leukocyte rolling (r = 0.78, P < 0.003). This study indicates that the start of inflammatory neutrophil transmigration is related to PDF bio(in)compatibility, whereas over time neutrophil transmigration is determined by the degree of neo-angiogenesis.

Glucoregulatory hormones and choice of osmotic agent in peritoneal dialysis

OBJECTIVE

The present study was performed to explore the range of effects of amino acid-based peritoneal dialysis (PD) solutions on glucoregulatory hormones in comparison with an osmotically equivalent glucose-based solution. ♢

METHODS

13 adult nondiabetic patients on PD underwent 2 peritoneal dwells of 2 hours' duration with either 1.5% dextrose solution or 1.1% amino acid solution. Serial sampling for glucoregulatory hormones was done throughout the duration of the dwell. ♢

RESULTS

Instillation of the 1.5% dextrose solution resulted in a modest change in plasma glucose, paralleled by a small increase in plasma insulin levels and plasma insulin-like growth factor (IGF-1). Plasma glucagon was not changed and plasma growth hormone level declined. Instillation of the 1.1% amino acid solution resulted in an increase in plasma glucose, plasma insulin, plasma glucagon, and plasma IGF-1. Plasma growth hormone level declined. Both solutions led to an increase in plasma norepinephrine but no changes were observed in epinephrine or dopamine. ♢

CONCLUSIONS

Our observations suggest that the mere replacement of glucose by amino acids in PD solutions does not necessarily imply "glucose sparing" from the perspective of induction of a glucoregulatory hormonal response because of the aminogenic stimulation of secretion of multiple hormones.

Two icodextrin exchanges per day in peritoneal dialysis patients with ultrafiltration failure: one center's experience and review of the literature

BACKGROUND

At present, only one exchange of an icodextrin-based solution is recommended to increase peritoneal ultrafiltration (UF) during long-dwell exchanges in peritoneal dialysis (PD) patients with impaired UF.

AIM

To review our experience with two icodextrin exchanges per day on net UF and body weight in PD patients with poor UF.

METHODS

Data were analyzed on nine patients with poor UF on chronic PD who were given two icodextrin exchanges per day for 6 months and had various clinical and biochemical parameters assessed monthly.

RESULTS

Administration of icodextrin twice daily reduced the body weight in six of nine patients by an average of 2.9 ± 1.2 kg, a reduction that was maintained throughout the study; two patients gained 0.5 kg; and, in one patient, the measurements were inadequate. Mean blood pressure was reduced. Mean serum creatinine increased slightly. Serum sodium levels decreased from a mean baseline level of 134 ± 3 to 132 ± 4 mmol/L at three and six months. Among the diabetics in this group, average daily insulin requirements were 44 ± 35 units/day at baseline and 40 ± 23 units/day after 6 months. Hb1Ac levels remained stable throughout the study period.

CONCLUSION

The use of two icodextrin exchanges per day reduced body weight in six of the nine patients and appeared to be safe. Long-term prospective studies are needed to assess the contribution of twice-daily icodextrin to the management of peritoneal dialysis patients with ultrafiltration failure and its long-term safety.

Prolonged use of the tyrosine kinase inhibitor in a peritoneal dialysis patient with metastatic renal cell carcinoma: possible beneficial effects on peritoneal membrane and peritonitis rates

Increased submesothelial collagen deposition, loss of mesothelial cells and increased peritoneal vascularization of peritoneal membrane with vasculopathy leads to peritoneal fibrosis in a patient on long-term peritoneal dialysis (PD). This vascular proliferation within the peritoneum is associated with an increased expression of vascular endothelial growth factor (VEGF), which in turn leads to functional loss or deterioration of the peritoneal membrane over time. Vascular endothelial growth factor inhibitors may slow or even prevent vascular proliferation and subsequent loss of membrane function in peritoneal dialysis patient. We have observed the anti-VGEF effects of a tyrosine kinase inhibitor, sunitinib maleate, in a patient who was on this medication for renal cell carcinoma with extensive abdominal metastasis. The patient had also been on PD for 26 months at the time of the study. In this patient, the tyrosine kinase inhibitor helped to stabilize the abdominal metastasis as well as the thickness of the peritoneal membrane. The D/P creatinine ratio also remained stable. These observations suggest that this tyrosine kinase inhibitor may have prevented peritoneal membrane angiogenesis. We also observed that the patient did not have any further episode of peritonitis from gut-derived organisms, suggesting that stabilization of the intestinal metastasis prevented the transmural migration of bacteria from the gut, thereby preventing peritonitis.