High glucose levels inhibit focal adhesion kinase-mediated wound healing of rat peritoneal mesothelial cells

Abstract

The peritoneum is progressively denuded of its mesothelial cell monolayer in patients on continuous ambulatory peritoneal dialysis (CAPD). These alterations of the mesothelium cause membrane dysfunction and progressive peritoneal fibrosis. Integrins regulate cell motility and play an important role in wound healing. We investigated the effects of high glucose on the regeneration process of the peritoneal mesothelial cell monolayer using cultured rat peritoneal mesothelial cells (RPMC). The effects of glucose or mannitol on the regeneration of RPMC and formation of focal adhesions were examined by in vitro wound healing assay and immunocytochemistry, respectively. Activities of focal adhesion kinase (FAK) and its downstream p130Cas were examined by Western blotting. Effects of wild-type and dominant-negative FAK on RPMC migration were examined by a transient transfection assay. Cell migration over fibronectin (FN) was clearly inhibited in culture media containing high glucose (28 to 140 mmol/L). RPMC formed focal adhesions on FN in the presence of a regular glucose concentration (5.6 mmol/L); however, tyrosine phosphorylation of FAK and p130Cas and formation of focal adhesions observed by FAK and vinculin staining were substantially inhibited by high glucose. Mannitol also induced significant inhibitory effects, but these were milder than those of glucose. Transfection of dominant-negative FAK inhibited cell migration in a regular glucose concentration, whereas overexpression of wild-type FAK abrogated glucose-induced inhibition of cell migration. Our results demonstrate that high glucose concentrations as well as high osmolarity inhibit FAK-mediated migration of mesothelial cells, and suggest that dialysates containing high glucose concentrations may cause peritoneal damage by inhibiting wound healing of the mesothelial cell monolayer.