Basic Science and Dialysis: Response of the Peritoneal Membrane to Injury

Protein-Losing Enteropathy is Associated with Peritoneal Functional Abnormalities in Peritoneal Dialysis Patients

Objective

To evaluate the relationship between acquired peritoneal transport disorders and the presence of protein-losing enteropathy (PLE), and their contribution to the protein malnutrition in peritoneal dialysis (PD) patients.

Patients and Methods

We studied 31 clinically stable PD patients that received a fat overload diet for 3 days. We measured intestinal absorption of fecal fat (normal < 6 g/24-hour stool) and nitrogen (normal < 2 g/24-hr stool), intestinal protein permeability [fecal clearance of α1-antitrypsin (Cα1AT) (normal < 12 mL/24-hr stool)], and nutritional markers [normalized protein nitrogen appearance (nPNA), half-life medium-term proteins, and body mass index]. Peritoneal solute transport was measured by mass transfer coefficient (MTC), and water transport by peritoneal ultrafiltration (UF) capacity. To define protein maldigestion it was necessary to find high fecal nitrogen values with normal Cα1AT; PLE was defined when both values were elevated.

Results

High fecal nitrogen (mean 2.1 ± 1 g/24-hr stool) and fat (mean 5.8 ± 3.6 g/24-hr stool) were found in 15 patients; 6 patients had high Cα1AT levels (PLE). These 6 patients showed a worse nutritional status: lower albumin (3.57 ± 0.57 g/dL vs 3.98 ± 0.38 g/dL, p < 0.05) and transferrin (243 ± 70 mg/dL vs 272 ± 44.3 mg/dL, p < 0.05), as well as lower triglycerides (131.3 ± 31.7 mg/dL vs 187 ± 116 mg/dL, p < 0.05). Higher urea MTCs were found in 10 patients, normal in 7, and lower in 14. Higher creatinine MTCs were found in 8 patients, normal in 15, and lower in 8. Normal peritoneal UF capacity was found in 25 and lower in 6 patients. These 6 patients showed higher urea and creatinine MTCs and Cα1AT. A positive linear correlation between Cα1AT, urea MTC ( r = 0.56, p < 0.01), and creatinine MTC ( r = 0.46, p < 0.01) was found. A similar situation occurred between Cα1AT, fecal fat ( r = 0.45, p < 0.05), and fecal nitrogen ( r = 0.43, p < 0.05). Thirteen patients with previous history of peritonitis showed higher Cα1AT than those without peritonitis (10.2 ± 8 mL/24-hr stool vs 5.2 ± 4.4 mL/24-hr stool, p < 0.05).

Conclusions

We confirm that protein and fat malabsorption, maldigestion, and PLE are present in some PD patients. Higher fecal Cα1AT is associated with malnutrition and poorer showings of the viability markers of peritoneal membrane function.

The Potential of Gene Therapy in the Peritoneal Cavity

Gene therapy is a promising new treatment modality based on molecular genetic modification to achieve a therapeutic benefit. We believe that gene therapy in the peritoneal cavity holds considerable promise, and we describe strategies by which genetic modification can be used to treat a variety of disease states or conditions. First, we can envision a strategy, based on genetic modification of the peritoneal membrane, to improve the practice of peritoneal dialysis through the production of proteins that would be of therapeutic value in preventing membrane damage and in preserving or enhancing its function as a dialyzing membrane. Second, the membrane could be genetically modified for either local or systemic delivery of therapeutic proteins. This approach could be applied to a variety of pathologies or conditions that require either sustained or transient delivery of therapeutic proteins, such as enzymes or growth factors. Third, gene transfer has already been incorporated into several strategies for the treatment of intra-abdominal carcinomas, and it has been effective in animal models of ovarian and bladder cancer and of peritoneal mesothelioma. Finally, gene transfer can be a valuable tool in increasing our understanding of the biology of the peritoneal membrane. By being able to manipulate the expression of specific genes through gene transfer, their role in various (patho)physiological processes can be identified. In summary, gene therapy in the peritoneal cavity has significant potential to address a variety of diseases or pathophysiological conditions, and to further our knowledge of peritoneal cavity biology.

Inflammatory cytokines stimulate the adhesion of colon carcinoma cells to mesothelial monolayers

Surgical handling of the peritoneum causes an inflammatory reaction, during which a potentially lethal cocktail of active mediators is produced, including cytokines and growth factors. The aim of this study was to investigate the effects of inflammatory cytokines on the interaction between tumor and mesothelial cells. Tumor cell adhesion to a mesothelial monolayer was assessed after preincubation of the mesothelium with interleukin (IL)-1beta, IL-6, and tumor necrosis factor (TNF)-alpha. Preincubation of the mesothelial monolayer with IL-1beta or TNF-alpha resulted in enhanced tumor cell adhesion of Caco2 and HT29 colon carcinoma cells. The amount of stimulation for the Caco2 cells was between 20% and 40% and for HT29 cells between 30% and 70%. Blocking experiments with anti-IL-1beta and anti-TNF-alpha resulted in significant inhibition of the cytokine-stimulated tumor cell adhesion. The presented results prove that IL-1beta and TNF-alpha are significant stimulating factors in tumor cell adhesion in vitro and may therefore account for tumor recurrence to the peritoneum in vivo.

The expression of adhesion molecules and the influence of inflammatory cytokines on the adhesion of human pancreatic carcinoma cells to mesothelial monolayers

OBJECTIVES

Pancreatic cancer has a tremendously deplorable prognosis. Peritoneal dissemination frequently occurs after surgical resection of the tumor. Specific adhesion molecules may be of great importance in local tumor recurrence. These adhesion molecules may be influenced by inflammatory cytokines produced during surgery. The aim of this study was to investigate the effects of inflammatory cytokines, interleukin-1beta (IL-1beta), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-alpha), on the interaction between pancreatic tumor cells and mesothelial cells.

METHODS

An experimental in vitro model was designed using Panc-1, MiaPaCa-2, and BxPC-3 pancreatic carcinoma cell lines. Primary cultures of mesothelial cells were incubated with the inflammatory cytokines, and after the incubation, the adherence of the different pancreatic cell lines was measured. By means of immunocytochemical staining and enzyme immunoassay, the expression of adhesion molecules (ICAM-1, VCAM-1, and CD44) and counterparts (LFA-1 and VLA-4) was investigated.

RESULTS

Preincubation of the mesothelial monolayer with IL-1beta or TNF-alpha resulted in enhanced tumor cell adhesion of the MiaPaCa-2 and BxPC-3 cells. The amount of stimulation for the MiaPaCa-2 cells was more than 100% versus the control situation and for BxPC-3 cells between 20% to 35%. IL-6 did not affect the tumor cell adhesion of the MiaPaCa-2 and BxPC-3 cells. The adherence of Panc-1 was not enhanced after preincubation of the mesothelial monolayers with the inflammatory cytokines. Mesothelial cells show a significant enhancement of expression of ICAM-1, VCAM-1, and CD44 after stimulation with IL-1beta and TNF-alpha.

CONCLUSIONS

The presented results prove that IL-1beta and TNF-alpha are significant stimulating factors in pancreatic tumor cell adhesion in vitro and may therefore account for tumor recurrence to the peritoneum in vivo. The immunocytochemical staining results demonstrate that ICAM-1 and CD44 important adhesion molecules and interference with their function may decrease the incidence of peritoneal tumor recurrence after curative resection of pancreatic cancer.

Effects of Neutral pH and Reduced Glucose Degradation Products in a New Peritoneal Dialysis Solution on Morphology of Peritoneal Membrane in Rats

BACKGROUND

In vitro studies have shown that pH and glucose degradation products (GDPs) in the dialysate are determinant factors for the biocompatibility of peritoneal dialysis (PD) treatment. The present study was thus designed to evaluate whether a newly developed PD solution, which features neutral pH levels and a low GDP concentration, influences tissue damage of the peritoneal membrane in an in vivo setting, and which factor is more critical to the histological changes.

METHODS

Rats were injected 3 times per day during 1 or 4 weeks with 10 ml of various PD fluids (group G, acidic pH, high GDPs; group S, neutral pH, low GDPs; or group A, acidic pH, low GDPs). When the experimental period was over, the mesothelial cell monolayers of the animals were taken and studied with population analysis, and peritoneal membranes were obtained from the abdominal wall for immunohistochemical examination with proliferating cell nuclear antigen (PCNA) and for measurement of thickness of the peritoneal specimens.

RESULTS

The density of the mesothelial cell monolayer and the number of fibroblast-like cells in group S were significantly less than in group G at 1 and 4 weeks' injection. PCNA-positive nuclei in group S were significantly less than in group G for only the 1-week injection set (group G, 2.03 +/- 0.95; group S, 0.85 +/- 1.18 nuclei/1 x 10(4) microm2). At 4 weeks, the peritoneal thickness of group S (6.32 +/- 0.53 microm) was significantly less than that of group G (7.94 +/- 0.77 microm), There was no significant difference between groups S and A throughout the whole study period except for the result of the number of fibroblast-like cells.

CONCLUSION

These results indicate that a PD solution with a neutral pH and low GDPs proved more biocompatible with the peritoneal membrane than a solution with an acidic pH and high GDPs. Furthermore, the level of the GDPs has more impact on tissue damage of the peritoneal membrane than the pH in the short term.