N-acetylcysteine modulates effect of the iron isomaltoside on peritoneal mesothelial cells.

Intravenous (i.v.) iron supplementation is used in patients on chronic peritoneal dialysis (pd). Iron induced intraperitoneal inflammation observed in our previous studies with iron sucrose may deteriorate the function of the peritoneum as the dialysis membrane. We evaluated effect iron compound, iron-isomaltoside-100 (IIS) on the peritoneal mesothelial cells (MC). We studied the effect of iv treatment with IIS ± N-acetylcysteine (NAC) on the dialysate parameters and function of MC. In 7 uremic pd patients IIS 200 mg was infused i.v. ± NAC 600 mg. Afterward, a 4 hours exchange was performed with Dianeal 1.5%. As a control dialysate exchange preceding IIS treatment was used. Inflammatory parameters of the drained dialysates as well as the dialysates and IIS effects on MC were evaluated in ex vivo experiments. Intravenous infusion of IIS resulted in an increase of the dialysate Fe (+147%, P < 0.01). Concentrations of the dialysates inflammatory mediators were increased: interleukin-6 (IL-6) +39%, P < 0.02, monocyte chemoattractant protein-1(MCP1) +50%, P < 0.02, and hyaluronan (HA) +64%, P < 0.02. Simultaneous i.v. infusion of NAC prevented increase of the dialysate inflammatory mediators. Dialysates collected after IIS treatment induced oxidative stress in MC (+29%, P < 0.05) and stimulated IL-6 synthesis (+64%, P < 0.05) in MC; no such effect was seen in dialysates obtained after simultaneous IIS and NAC i.v. treatment. IIS used as the additive to culture medium stimulated synthesis in MC of IL6 (+76%, P < 0.001) and plasminogen activator inhibitor-1 (PAI-1) (28%, P < 0.001) whereas synthesis of tissue plasminogen activator (t-PA) was reduced (-16%, P < 0.001). These changes were prevented in the presence of NAC 1 mmol/L. Intravenous administration of IIS results in the mild stimulation of intraperitoneal inflammation. IIS changes MC phenotype to the inflammatory one with reduced fibrinolytic activity. These effects are prevented by NAC.

L-2-oxothiazolidine-4-carboxylic acids slow down dialysate-induced senescence in human peritoneal mesothelial cells.

Peritoneal dialysis induces an intraperitoneal inflammatory reaction, which in the long term may cause deterioration of the peritoneal structure and function as the dialysis membrane. We studied the effect of the overnight effluent dialysate from patients on chronic peritoneal dialysis on aging of the human peritoneal mesothelial cells in an in vitro model of replicative cellular senescence. In the control group cells were cultured in the standard medium and in the studied groups in culture medium mixed 1:1 v/v with the dialysate ± L-2-oxothiazolodine-4-carboxylic acid 1 mmol/L (OTZ). OTZ was used as the precursor for the synthesis of glutathione in these cells. Dialysate accelerated senescence of the mesothelial cells as reflected by elongation of their population doubling time, reduced expression of KI-67 gene, and increased ß-galactosidase activity. Also, expression of the genes regulating the production of the inflammatory mediators (interleukin-6, monocyte chemoattractant protein-1, metalloproteinase-2, hyaluronan), proangiogenic (VEGF) and profibrotic (fibronectin) factors was increased in that group. At the same time, these cells secreted more inflammatory mediators. Simultaneous treatment of the cells with the dialysate and OTZ slowed down their senescence, whose intensity was similar to that in the control group. The results presented in this manuscript prove that the intraperitoneal inflammatory reaction induced by repeated infusions of the dialysis fluid accelerates the senescence of the mesothelial cells, which may result in fibrosis and neoangiogenesis within the peritoneum. Simultaneous supplementation of the cells with a glutathione precursor (OTZ) may prevent the development of these pathological changes.

Intravenous iron sucrose changes the intraperitoneal homeostasis.

BACKGROUND/AIMS: Intravenous iron infusion is the accepted way of supplementation of that compound in uremic patients. The aim of the study was to evaluate whether this treatment affects intraperitoneal homeostasis in patients on peritoneal dialysis. METHODS: Blood and peritoneal dialysate samples were collected from 10 patients treated with continuous ambulatory peritoneal dialysis who were given 100 mg iron sucrose (IS) intravenously. Systemic and peritoneal permeability as well as transperitoneal transport were studied. The effect of spent dialysate was tested in vitro on human peritoneal mesothelial cells (MCs). RESULTS: Dialysate total iron was increased (+19%, p < 0.01) during intravenous infusion of IS. Immediately after infusion the concentration of 8-OHdG was increased in plasma (+10%, p < 0.01) and in dialysate (+5%, p < 0.05). IS infusion caused a transient decrease in peritoneal permeability to protein (-42%, p < 0.05) and glucose (-30%, p < 0.01) and a reduction in dialysate cell count (-58%, p < 0.05). During the exchange dialysate hyaluronan was increased by 27% (p < 0.01). Spent dialysate, tested ex vivo on cultured MC, induced oxidative stress (+39%, p < 0.01), slowed their proliferation (-20%, p < 0.01), and stimulated MCP-1 synthesis (+46%, p < 0.01). Iron content in MCs exposed to dialysate obtained after IS infusion was increased by 32% (p < 0.01). CONCLUSION: Intravenous infusion of IS causes oxidative stress and inflammation within peritoneal MCs which may impair viability of the peritoneum.

Effect of iron sucrose on human peritoneal mesothelial cells.

BACKGROUND: Iron supplementation is often required in uraemic patients with anaemia. Peritoneal cavity was proposed as an alternative intravenous route for iron infusion in patients treated with peritoneal dialysis. We studied the effect of iron sucrose (Venofer) on the function of human peritoneal mesothelial cells maintained in in vitro culture. MATERIALS AND METHODS: In in vitro experiments on human peritoneal, the mesothelial effect of elemental iron (in conc. 0.0001-1 mg mL-1) present in Venofer on their viability, growth and synthesis of IL-6 was studied. Additionally we evaluated with a fluorescent probe (2',7'-dichlorodihydro-fluorescein diacatate) generation of reactive oxygen species in cells exposed to iron sucrose. We also measured accumulation of iron in the cytoplasm of mesothelial cells after their in vitro exposure to Venofer. RESULTS: In in vitro conditions iron induces a dose-dependent inhibition of viability of the mesothelial cells as reflected by inhibition of the cells growth by 34% at Fe 0.1 mg mL-1 vs. control (P < 0.05) increased release of lactate dehydrogenase (LDH) from the cytosol: 67.1 +/- 30.3 mU mL-1 at Fe 1 mg mL-1 vs. 7.9 +/- 6.4 in control group (P < 0.001), and reduced synthesis of IL-6: 209 +/- 378 pg mg-1 cell protein at Fe 1 mg mL-1 vs. 38674 +/- 4146 pg mg-1 cell protein in controls (P < 0.001). Cytotoxicity of iron towards mesothelial cells was enhanced in vitro when it was tested in presence of the dialysis fluid. Iron used in vitro at concentration 0.0001 mg mL-1 and greater induces generation of oxygen-derived free radicals in mesothelial cells. Furthermore, iron is taken by these cells and stored in their cytosol, resulting in stimulation of the intracellular generation of free radicals. CONCLUSIONS: We conclude that iron used in the form of iron sucrose is cytotoxic to human peritoneal mesothelial cells. Accumulation of iron sucrose within cytoplasm of these cells may lead to induction of its chronic cytotoxic effect.

Comparison of the biocompatibility of phosphate-buffered saline alone, phosphate-buffered saline supplemented with glucose, and dianeal 3.86%.

OBJECTIVE: We compared the effects of intraperitoneal infusion of phosphate-buffered saline (PBS, pH 7.4), of PBS supplemented with 3.86% glucose (G), and of standard dialysis solution [Dianeal 3.86%: Baxter Healthcare Corporation, Deerfield, IL, U.S.A. (D)] on intraperitoneal inflammation in dialyzed rats. METHODS: After catheter implantation, rats were infused on day 1 with PBS, on day 3 with PBS+G, on day 5 with D, and on day 7 again with PBS (PBS-2). After a 4-hour dwell, dialysate samples were collected and analyzed. RESULTS: All dialysate parameters studied [dialysate cell count, neutrophil:macrophage ratio (Ne:Ma), and total protein], except tumor necrosis factor alpha (TNFalpha), were comparable during both PBS infusions. During dialysis with PBS+G, the inflammatory response was suppressed as compared with the first dialysis with PBS (cell count, p < 0.001; Ne:Ma, p < 0.05; TNFalpha, p < 0.001; total protein, p < 0.001). During dialysis with D, peritoneal inflammatory parameters were further suppressed (cell count, p < 0.001 vs PBS and p < 0.01 vs PBS+G; Ne:Ma, p < 0.001 vs PBS and p < 0.05 vs PBS+G; TNFalpha, p < 0.001 vs PBS and p < 0.001 vs PBS+G; total protein, p < 0.001 vs PBS and p < 0.01 vs PBS+G). CONCLUSIONS: Hypertonicity of the dialysis fluid suppresses intraperitoneal inflammatory parameters in rats. The suppression was even more severe when Dianeal 3.86% was used. That finding could be due to the low pH and presence of GDPs in the fluid.

Insulin stimulates the activity of Na+/K(+)-ATPase in human peritoneal mesothelial cells.

OBJECTIVE: To assess the effect of insulin on the Na+/K(+)-ATPase expression and activity in human peritoneal mesothelial cells (HPMC). METHODS: HPMC were isolated from the omental tissue of non-uremic patients, grown to confluence and rendered quiescent by serum deprivation for 24 hours. The activity of Na+/K(+)-ATPase was determined by measuring the ouabain-sensitive 86Rb uptake. To assess whether the effect of insulin was related to changes in [Na+]i the sodium influx was measured with 22Na and the activity of Na+/K(+)-ATPase was assessed in the presence of amiloride. Expression of Na+/K(+)-ATPase alpha 1,alpha 2 and beta 1-subunit mRNAs was determined by RT/PCR. RESULTS: Exposure of HPMC to insulin resulted in a time- and dose-dependent increase in the Na+/K(+)-ATPase activity. After 60 minutes the ouabain-sensitive 86Rb uptake (cpm/10(4) cells) was increased from 6650 +/- 796 in control cells to 9763 +/- 1212 in HPMC exposed to 100 mU/mL insulin (1.5-fold increase; n = 4, P < 0.05). In addition, incubation of HPMC with 100 mU/mL insulin resulted in a time-dependent increase in the 22Na influx. Pre-exposure of HPMC to 1mM amiloride reduced the activity of Na+/K(+)-ATPase but did not block the stimulatory effect of insulin. RT/PCR analysis revealed that HPMC constitutively expressed alpha 1- and beta 1-subunit mRNAs while the alpha 2-subunit mRNA was barely detectable. Exposure of HPMC to insulin for up to 24 hours was not associated with any changes in the expression of either alpha 1, alpha 2 or beta 1-subunit. CONCLUSION: Insulin stimulates the Na+/K(+)-ATPase activity in HPMC in a time- and dose-dependent manner. This effect appears to mediated by an increase in [Na+]i and is not related to alterations in Na+/K(+)-ATPase subunit mRNAs expression.

Alterations of intraperitoneal inflammation by the addition of L-2-oxothiazolidine-carboxylate.

The authors studied the effect of L-2-oxothiazolidine-carboxylate (OTZ), a substrate for intracellular glutathione synthesis, in an in vivo model of lipopolysaccharide (LPS)-induced peritonitis in rats. The addition of LPS to dialysis fluid increased the white blood cell (WBC) count and the nitrite (index of NO synthesis) level in the dialysate. The simultaneous addition of OTZ to the dialysis fluid prevented an increase of WBCs but not of nitrites in the dialysate. Intraperitoneal inflammation was accompanied by a decrease in net transperitoneal ultrafiltration, an increase in the absorption of glucose, and a loss of protein into the dialysate. OTZ partially reversed the effect of peritonitis on net ultrafiltration. Peritoneal leukocytes from rats exposed to LPS showed a reduced concentration of glutathione, an effect that was reversed in the presence of OTZ. These results show that the supplementation of dialysis fluid with OTZ modified the peritoneal reaction to acute inflammation.

Effect of vitamin E on peroxidation and permeability of the peritoneum.

Because of the evidence that peritoneal macrophages are activated during peritoneal dialysis, we hypothesised that the injury of the peritoneum is, at least in part, dependent on the intraperitoneal generation of free radicals. The aim of the study was to evaluate the effect of vitamin E on the peroxidation and permeability of the peritoneum during chronic peritoneal dialysis in rats. Supplementation of the intraperitoneally infused saline with vitamin E decreased the peroxidation of peritoneum estimated as the malondialdehyde (MDA) level in rats' omentum. However the permeability of the peritoneum to glucose and protein in vitamin E treated rats was increased. In in vitro study we have found that vitamin E is cytotoxic to human mesothelial cells (HMC) as measured by inhibition of their proliferation and this effect was irreversible. We conclude that vitamin E, despite its antioxidant effect, causes the changes of the peritoneum permeability which could decrease the effectiveness of peritoneal dialysis.

Functional properties of mesothelial cells after prolonged exposure to dialysate effluent.

The authors tested in vitro the effect of glucose-based and amino acid-based dialysate effluent on the function of human peritoneal mesothelial cells. After 9 days of exposure to the tested effluents with medium (1:1 v/v) or to a medium supplemented with 10% fetal calf serum (FCS) (control), several functional properties of the cells were studied. The synthesis of DNA measured by incorporation of 3H-methyl-thymidine was higher in mesothelial-cell monolayers exposed to the dialysates than in the controls. Synthesis of hyaluronic acid was similar in all three groups, but after stimulation with Il-1 the cells exposed to the dialysates produced more hyaluronic acid. Synthesis of tissue plasminogen activator (t-PA) and plasminogen activator inhibitor-1 (PAI-1) was higher in the control cells. However, after stimulation with IL-1, the cells exposed to the dialysate showed greater synthesis of PAI-1 than of t-PA. Also, procoagulant activity of the control cells was higher than that of the cells exposed to the dialysates. We have concluded that the functional properties of the mesothelial cells may be altered in vitro during prolonged exposure to the dialysate, something that may also occur in vivo.

Glycosaminoglycan chondroitin sulphate prevents loss of ultrafiltration during peritoneal dialysis in rats.

We evaluated the effect of 6 days of intraperitoneal saline infusion on peritoneal peroxidation and permeability in rats. Peroxidation of the peritoneum as measured by malondialdehyde concentration in the omentum was increased and there was a concomitant augmented membrane permeability to glucose and resulted in a loss of ultrafiltration. In vitro experiments with mesothelial cells showed that glycosaminoglycan chondroitin sulphate appears to act as a scavenger of free radicals and so protects the mesothelial cells against injury. Thus, in rats, supplementation of the infused saline with chondroitin sulphate reduces peroxidation of the peritoneum and prevents loss of ultrafiltration during peritoneal dialysis. These results suggest that chondroitin sulphate may be effective in preventing the deterioration of peritoneal permeability during chronic peritoneal dialysis. This beneficial effect probably derives from the scavenging of free radicals by chondroitin sulphate.

In vitro study of the mechanism of potassium transport into human mesothelial cells. I: Effect of hyperosmolality.

OBJECTIVE: To study the mechanism(s) of potassium transport into human mesothelial cells (HMC) exposed to osmotic solutes. DESIGN: Using potassium analog 86Rb, we evaluated its intracellular transport through three pathways: 1. blocked by ouabain; 2. blocked by furosemide but not by ouabain; 3. blocked by neither furosemide nor ouabain. Experiments were performed in a normotonic medium (control) or in a medium supplemented with osmotic solutes (glucose, glycerol, mannitol). Both the acute and chronic effects of osmotic solutes on potassium transport were studied. RESULTS: The acute exposure of mesothelial cells to osmotic solutes modifies the intracellular transport of potassium through all studied channels, and the effect is specific for every solute. In mesothelial cells exposed over 7 days to glucose (90 mM), the intracellular transport via ouabain- and furosemide-blocked channels is decreased, whereas it is increased through the third pathway. Total intracellular accumulation of 86Rb (potassium) ions in mesothelial cells cultured in a medium supplemented with various concentrations of glucose is decreased, and this effect is proportional to the concentration of glucose in the medium. CONCLUSIONS: The intracellular transport of potassium in mesothelial cells is regulated through at least three independent mechanisms. Acute or chronic exposure of mesothelial cells to a hypertonic medium affects the intracellular accumulation of potassium, and this effect is specific for the various osmotic solutes.

Chondroitin sulphate and peritoneal permeability.

We studied the effect of chronic intraperitoneal (ip) infusion of saline supplemented with the glycosaminoglycan-chondroitin sulphate 0.1% on the permeability and peroxidation of the peritoneal membrane in rats and compared this with the effect of saline infusion alone. Animals treated with chondroitin sulphate had a higher net ultrafiltration (uf), a slower glucose absorption from the dialysate and less trans-peritoneal loss of proteins. Chronic ip infusion of chondroitin sulphate reduced peroxidation of the peritoneum. These observations suggest that chondroitin may effect the peritoneal interstitium-an important barrier of fluid and solutes transport.