Cyclooxygenase-2 Mediates Dialysate-Induced Alterations of the Peritoneal Membrane

Abstract

During peritoneal dialysis (PD), exposure of the peritoneal membrane to nonphysiologic solutions causes inflammation, ultimately leading to altered structure and function. Myofibroblasts, one of the cell types that contribute to dysfunction of the peritoneal membrane, can originate from mesothelial cells (MCs) by epithelial-to-mesenchymal transition (EMT), a process that has been associated with an increased rate of peritoneal transport. Because cyclooxygenase-2 (COX-2) is induced by inflammation, we studied the role of COX-2 in the deterioration of the peritoneal membrane. We observed that nonepithelioid MCs found in peritoneal effluent expressed higher levels of COX-2 than epithelioid MCs. The mass transfer coefficient for creatinine correlated with MC phenotype and with COX-2 levels. Although COX-2 was upregulated during EMT of MCs in vitro, COX-2 inhibition did not prevent EMT. In a mouse model of PD, however, COX-2 inhibition with Celecoxib resulted in reduced fibrosis and in partial recovery of ultrafiltration, outcomes that were associated with a reduction of inflammatory cells. Furthermore, PD fluid with a low content of glucose degradation products did not induce EMT or COX-2; the peritoneal membranes of mice treated with this fluid showed less worsening than mice exposed to standard fluid. In conclusion, upregulation of COX-2 during EMT may mediate peritoneal inflammation, suggesting COX-2 inhibition as a potential strategy to ameliorate peritoneal deterioration in PD patients.

PPAR-γ agonist rosiglitazone protects peritoneal membrane from dialysis fluid-induced damage

“…PD fluid or saline solution were instilled via a peritoneal catheter connected to an implanted subcutaneous mini access port (Access Technologies, Skokie, IL, USA) as previously described. 15,35 Mice that were not treated surgically and that received no fluid, served as control group (Control; n ¼ 5). During the first week after surgery, the animals implanted with a peritoneal access port (n ¼ 37) received 0.2 ml of saline with 1 IU/ml heparin to facilitate wound healing.…”

“…10,14,15 Cells were cultured in Earle's M199 medium supplemented with 20% fetal calf serum, 50 U/ml penicillin, 50 mg/ml streptomycin, and 2% Biogro-2 (containing insulin, transferrin, ethanolamine, and putrescine: Biological Industries, Beit Haemek, Israel). The purity of omentum and effluentderived mesothelial cell cultures was determined through the expression of the standard mesothelial markers, intercellular adhesion molecule (ICAM)-1, calretinine and cytokeratins.…”

“…To induce MMT in vitro, omentum-derived mesothelial cells were seeded on wells coated with 50 mg/ml of collagen I (Roche Diagnostics GmbH, Mannheim, Germany) and treated for 48 h with 1 ng/ml of human-recombinant transforming growth factor b1 (TGF-b1: R&D Systems), which has been proven to be a good in vitro model of MMT. 10,14,15 Where indicated, RSG (GlaxoSmithKline, Brentford, Middlesex, UK) was used at concentrations ranging from 0.1 to 10 mM. This study adjusts to the Declaration of Helsinki and it was approved by the Ethics Committee of 'Hospital Universitario de la Princesa' (Madrid, Spain).…”

“…Quantitative PCR was carried out in a LightCycler 2.0 using a SYBR Green kit (Roche Diagnostics GmbH) and specific primers for Snail, E-cadherin, Cox-2, and histone H3. 10,15 Samples were normalized with respect to the value obtained for H3. Vascular endothelial growth factor (VEGF) concentration in culture supernatants was measured by ELISA (R&D Systems).…”

“…In this context, it has been shown that the presence of trans-differentiated mesothelial cells, either in the PD effluent or peritoneal tissue of PD patients, is correlated with high transport rates. [14][15][16] Glucose, used as an osmotic agent in most common PD fluids, and glucose degradation products, generated during heat sterilization and storage, induce a local diabetic environment within the peritoneal cavity through the generation of advanced glycation end products (AGEs). 17 AGEs have been associated with the progress and complications of diabetes, 18 and they may act directly to induce cross-linking of long-lived proteins like collagen, altering vascular structure and function.…”