A nanoconjugate Apaf-1 inhibitor protects mesothelial cells from cytokine-induced injury.

BACKGROUND: Inflammation may lead to tissue injury. We have studied the modulation of inflammatory milieu-induced tissue injury, as exemplified by the mesothelium. Peritoneal dialysis is complicated by peritonitis episodes that cause loss of mesothelium. Proinflammatory cytokines are increased in the peritoneal cavity during peritonitis episodes. However there is scarce information on the modulation of cell death by combinations of cytokines and on the therapeutic targets to prevent desmesothelization. METHODOLOGY: Human mesothelial cells were cultured from effluents of stable peritoneal dialysis patients and from omentum of non-dialysis patients. Mesothelial cell death was studied in mice with S. aureus peritonitis and in mice injected with tumor necrosis factor alpha and interferon gamma. Tumor necrosis factor alpha and interferon gamma alone do not induce apoptosis in cultured mesothelial cells. By contrast, the cytokine combination increased the rate of apoptosis 2 to 3-fold over control. Cell death was associated with the activation of caspases and a pancaspase inhibitor prevented apoptosis. Specific caspase-8 and caspase-3 inhibitors were similarly effective. Co-incubation with both cytokines also impaired mesothelial wound healing in an in vitro model. However, inhibition of caspases did not improve wound healing and even impaired the long-term recovery from injury. By contrast, a polymeric nanoconjugate Apaf-1 inhibitor protected from apoptosis and allowed wound healing and long-term recovery. The Apaf-1 inhibitor also protected mesothelial cells from inflammation-induced injury in vivo in mice. CONCLUSION: Cooperation between tumor necrosis factor alpha and interferon gamma contributes to mesothelial injury and impairs the regenerative capacity of the monolayer. Caspase inhibition attenuates mesothelial cell apoptosis but does not facilitate regeneration. A drug targeting Apaf-1 allows protection from apoptosis as well as regeneration in the course of inflammation-induced tissue injury.

Bcl-xL prevents peritoneal dialysis solution-induced leukocyte apoptosis.

Conventional glucose-containing peritoneal dialysis solutions (PDS) with a high glucose degradation product content accelerate leukocyte apoptosis and impair peritoneal defense. Mononuclear cells are less sensitive than neutrophils to PDS-induced apoptosis, suggesting that they may express antiapoptotic molecules. Since apoptosis induced by PDS requires Bax, we explored the role of an antiapoptotic protein of the same family, Bcl-xL, in PDS-induced apoptosis in cultured peripheral blood mononuclear cells and monocytic THP-1 cells. In these cells, conventional PDS decreased the expression of Bcl-xL protein with a temporal pattern compatible with their lethal effect. Inhibition of Bcl-xL also induced mononuclear cell apoptosis. A cell-permeable TAT-BH4 peptide that contains the BH4 domain of Bcl-xL prevented mononuclear cell apoptosis induced by PDS. These data suggest that Bcl-xL protects mononuclear cells from apoptosis induced by bioincompatible PDS and that Bcl-xL-like molecules should be explored to prolong leukocyte survival and potentiate peritoneal defense during peritonitis.

3,4-Dideoxyglucosone-3-ene as a mediator of peritoneal demesothelization.

BACKGROUND: The mesothelium contributes significantly to the functional, structural and homeostatic properties of the peritoneum. Bioincompatible peritoneal dialysis solutions contribute to mesothelial cell loss during chronic peritoneal dialysis. Cell death has been implicated in mesothelial cell loss, but the molecular mechanisms have not been adequately characterized. We now report the modulation of mesothelial cell death by the glucose degradation product 3,4-dideoxyglucosone-3-ene (3,4-DGE). METHODS: Human mesothelial cells were cultured from the effluents of stable dialysis patients. Apoptosis was quantified in cultured mesothelial cells and in peritoneal effluents. Confocal microscopy and inhibitors were used to assess molecular mechanisms. RESULTS: Peritoneal dialysis solutions with a high content of both glucose and glucose degradation products, but not those with low glucose degradation product content, induced mesothelial cell apoptosis and loss of cell viability in culture and in vivo. 3,4-DGE also induced mesothelial cell apoptosis. Apoptosis induced by peritoneal dialysis solutions and 3,4-DGE was associated with oligomerization of Bax at mitochondria and caspase activation. Bax antagonism prevented caspase activation, apoptosis and cell death. The pancaspase inhibitor zVAD was also protective. CONCLUSION: 3,4-DGE and peritoneal dialysis solutions with a high content in glucose degradation products induce mesothelial cell apoptosis by a Bax-dependent mechanism. This could contribute to chronic demesothelization in peritoneal dialysis.

3,4-di-deoxyglucosone-3-ene promotes leukocyte apoptosis.

BACKGROUND: Heat-sterilized, single-chambered, glucose-containing peritoneal dialysis solutions promote neutrophil apoptosis and impair the peritoneal antibacterial response. It has been proposed that glucose degradation products may be responsible for this effect. However, the precise contribution of individual glucose degradation products had not been addressed. METHODS: The effect of individual glucose degradation products on apoptosis in cultured human neutrophils and peripheral blood mononuclear cells was studied. RESULTS: Peritoneal dialysis solutions with a high content of both glucose and glucose degradation products accelerated neutrophil and mononuclear cell apoptosis. Among the different glucose degradation products, 3,4-di-deoxyglucosone-3-ene (3,4-DGE) accelerated apoptosis in neutrophils and peripheral blood mononuclear cells at concentrations (25 micromol/L) in the range found in heat-sterilized, single-chambered, 4.25% glucose peritoneal dialysis fluids. Apoptosis induced by 3,4-DGE was caspase-dependent and could be prevented by the broad-spectrum caspase inhibitor benzyloxycarbonyl-Val-Ala-DL-Asp-fluoromethylketone (zVAD-fmk). By contrast, no cytotoxicity was observed following the addition of methylglyoxal, acetaldehyde, formaldehyde, or 3-deoxyglucosone at concentrations found in peritoneal dialysis solutions. CONCLUSION: 3,4-DGE appears to be the main proapoptotic factor in high glucose peritoneal dialysis solutions. 3,4-DGE may impair peritoneal defenses by accelerating leukocyte apoptosis.

Regulation of apoptosis by lethal cytokines in human mesothelial cells.

BACKGROUND: Dysregulation of peritoneal cell death may contribute to the complications of peritoneal dialysis (PD). Chronic peritoneal dialysis and acute peritonitis are both associated with loss of mesothelial cells. In addition, acute peritonitis is characterized by sudden changes in the number of peritoneal leukocytes. However, the factors regulating peritoneal cell survival are poorly understood. METHODS: Peritoneal effluent cells and mesothelial cells cultured from peritoneal dialysis patients were studied. Reverse transcriptase-polymerase chain reaction (RT-PCR) and flow cytometry were used to assess the expression of FasL and Fas mRNA and protein. Western blot was used to assess FasL and tumor necrosis factor (TNF)-related apoptosis inducing ligand (TRAIL). RT-PCR was used to study TRAIL and TRAIL receptor mRNA. Apoptosis was quantified by flow cytometry of DNA content and confirmed by morphology. RESULTS: Apoptotic cells, including apoptotic mesothelial cells, were present in the peritoneal effluent of stable peritoneal dialysis patients and patients with bacterial peritonitis. The lethal cytokines FasL and TRAIL were expressed by peritoneal effluent cells, while cultured mesothelial cells expressed FasL, Fas, and TRAIL receptors. Cultured mesothelial cells were sensitive to FasL-induced apoptosis. IFNgamma increased the cell surface expression of Fas and the sensitivity of mesothelial cells to FasL-induced apoptosis. In contrast to the effect of FasL, TNFalpha and TRAIL did not induce apoptosis in human mesothelial cells from peritoneal dialysis patients. CONCLUSION: Lethal cytokines, such as FasL, may contribute to peritoneal cell turnover and the loss of mesothelium in peritoneal dialysis. The role of other cytokines, such as TRAIL, remains undefined. Approaches in limiting mesothelial cell injury that interferes with apoptosis should be considered.

Peritoneal dialysis retardation of progression of advanced renal failure.

OBJECTIVES: The rate of decline of residual renal function is slower in peritoneal dialysis (PD) than in hemodialysis. However, it is unclear which and whether either of the two techniques modifies the natural course of renal failure. We tested whether PD influences the natural course of the progression of chronic renal failure in humans. DESIGN: Retrospective review of clinical charts. SETTING: Tertiary-care center. PATIENTS: Fourteen patients were selected from the 36 patients that were treated with PD in our center from January 1997 to June 2000, applying the following criteria: predialysis follow-up longer than 12 months, renal creatinine clearance 20 mL/minute or more at the start of predialysis follow-up, follow-up while on PD longer than 6 months, and renal creatinine clearance above 0 mL/minute at the start of PD. MAIN OUTCOME MEASURE: Residual renal function calculated as renal creatinine clearance obtained from 24-hour urine samples. RESULTS: A lower mean rate of decline of residual renal function was observed during PD than during the predialysis period (-0.06 +/- 0.16 vs -0.94 +/- 0.74 mL/min/month, p < 0.0005). The rate of decline in renal creatinine clearance was faster in every patient during the predialysis period than during his or her time on PD. CONCLUSIONS: These preliminary data support the hypothesis that PD may contribute to the slowing of the natural progression of renal disease in humans, as it does in rodents. Prospective studies involving a larger number of patients are needed to settle the question.

Acceleration of neutrophil apoptosis by glucose-containing peritoneal dialysis solutions: role of caspases.

Commercial, glucose-containing peritoneal dialysis (PD) solutions have deleterious effects on leukocytes and mesothelial cells that contribute to an impaired peritoneal defense. However, the molecular mechanisms of these deleterious effects are poorly understood. The effect of PD solutions on neutrophil viability, the molecular mechanisms of cell death, its functional consequences, and the possibilities for pharmacologic modulation have now been studied. The effect of newly available, bicarbonate-buffered PD solutions were further investigated. Lactate-buffered, glucose-containing PD solutions increased the apoptosis rate of cultured neutrophils (control media versus 4.25% glucose PD solution: 31 +/- 3% versus 52 +/- 3% apoptosis at 24 h, P < 0.001). Bicarbonate-buffered, 4.25% glucose-containing PD solutions with low concentration of glucose degradation products did not increase the rate of apoptosis. Apoptosis induced by lactate-buffered, 4.25% glucose PD solutions was not related to hyperosmolality or acidic pH and was not reproduced by increasing the glucose concentration by the addition of glucose to a commercial, lactate-buffered fluid. Neutrophil apoptosis was associated with caspase-3 activation. Inhibition of caspase-3 by the use of the caspase-3 inhibitor acetyl-Asp-Glu-Val-Asp-fmk or the broad-spectrum caspase inhibitor benzyloxycarbonyl-Val-Ala-DL-Asp-fluoromethylketone (zVAD-fmk) prevented features of apoptosis, such as morphologic changes, internucleosomal DNA degradation, and the appearance of hypodiploid cells and increased the number of viable, trypan blue-excluding neutrophils. Furthermore, zVAD-fmk increased neutrophil phagocytosis of bacteria. However, the caspase-1 inhibitor acetyl-Tyr-Val-Ala-Asp-aldehyde did not prevent cell death. These data suggest that unidentified components in commercial, lactate-buffered, high-glucose PD fluid accelerate the rate of neutrophil apoptosis. Glucose degradation products may be such unidentified components. Acceleration of neutrophil apoptosis may contribute to the impaired local defense system of patients undergoing PD.

Expression of endothelial nitric oxide synthase in human peritoneal tissue: regulation by Escherichia coli lipopolysaccharide.

Changes in the expression of endothelial nitric oxide synthase (eNOS) in the peritoneum could be involved in the peritoneal dysfunction associated with peritoneal inflammation. Demonstrated recently in bovine endothelial cells was the existence of cytosolic proteins that bind to the 3'-untranslated region (3'-UTR) of eNOS mRNA and could be implicated in eNOS mRNA stabilization. The present work demonstrates that eNOS protein is expressed in human endothelial and mesothelial peritoneal cells. Escherichia coli lipopolysaccharide shortened the half-life of eNOS message, reducing eNOS protein expression in peritoneal mesothelial and endothelial cells. Moreover, under basal conditions, human peritoneal samples expressed cytosolic proteins that bind to the 3'-UTR of eNOS mRNA. The cytosolic proteins that directly bind to 3'-UTR were identified as a 60-kD protein. After incubation of human peritoneal samples with lipopolysaccharide, the binding activity of the cytosolic 60-kD protein increased in a time-dependent manner. Studies are now necessary to determine the involvement of this 60-kD protein in the regulation of eNOS expression in peritoneal cells and particularly its involvement in the peritoneal dysfunction associated with inflammatory reactions.

Estudio del autocuidado en los pacientes de Diálisis Peritoneal / Study of the self-care in patinets in peritoneal dialysis

Uno de los grandes retos de la enfermería nefrológica es el incremento de pacientes mayores de 65 años que se incluyen actualmente en los programas de diálisis peritonal. El objetivo de este trabajo es describir, evaluar y valorar los factores edad, autocuidado, carga familiar y tiempo de tratamiento de estos pacientes. Las enfermeras de 15 unidades de diálisis peritoneall cumplimentaron cuestionarios referidos a 300 pacientes. De los resultados cabe destacar que la edad es un factor significativo en el deterioro del autocuidado, del incremento de la sobrecarga familiar y de las cargas de trabajo de enfermería (AU)