Effect of high glucose concentration on the synthesis of monocyte chemoattractant protein-1 in human peritoneal mesothelial cells: involvement of protein kinase C.

Human peritoneal mesothelial cells (HMC) contribute to the activation and control of inflammatory processes in the peritoneum by their potential to produce various inflammatory mediators. The present study was designed to assess the effect of glucose, the osmotic active compound in most commercially available peritoneal dialysis fluids, on the synthesis of the C-C chemokine monocyte chemoattractant protein-1 (MCP-1) in cultured HMC. The MCP-1 concentration in the cell supernatants was determined by enzyme-linked immunosorbent assay and the MCP-1 mRNA expression was examined using Northern blot analysis. Incubation of HMC with glucose (30-120 mM) resulted in a time- and concentration-dependent increase in MCP-1 protein secretion and mRNA expression. After 24 h the MCP-1 synthesis was increased from 2.8 +/- 0.46 to 4.2 +/- 0.32 ng/10(5) cells (n = 5, p < 0.05) in HMC treated with 60 mM glucose. In contrast, osmotic control media containing either the metabolically inert monosaccharide mannitol or NaCl did not influence MCP-1 production. The stimulating effect of high glucose on MCP-1 expression in HMC was mimicked by activation of protein kinase C (PKC) with the phorbol ester PMA (20 nM). Coincubation of the cells with glucose and the specific PKC inhibitor Ro 31-8220 completely blunted glucose-mediated MCP-1 expression. In summary, our results indicate that glucose induces MCP-1 synthesis by a PKC-dependent pathway. Since osmotic control media did not increase MCP-1 release, it is suggested that the effect of glucose is mainly related to metabolism and not to hyperosmolarity. These data may in part explain elevated steady-state levels of MCP-1 found in the dialysis effluent of continuous ambulatory peritoneal dialysis patients.