Early glycated albumin, but not advanced glycated albumin, methylglyoxal, or 3-deoxyglucosone increases the expression of PAI-1 in human peritoneal mesothelial cells

Objective:The continuous contact of glucose-containing peritoneal dialysis (PD) fluids with the peritoneum results in the intraperitoneal formation of early and advanced glycation end-products. This nonenzymatic glycation of proteins may cause morphological and functional alterations to the peritone um, which may contribute to patient dropout from PD therapy. Because fibrin olytic system components have been demonstrated to play an important role i n the balance of intraperitoneal generation and degradation of fibrin, we s tudied the effect of early and advanced glycated human serum albumin, methy lglyoxal, and 3-deoxyglucosone on the synthesis of tissue-type plasminogen activator (WA), as well as its specific inhibitor (PAI-1), in human periton eal mesothelial cells (HPMC). Methods: Antigen concentrations in the supernatants of cultured HPMC were m easured by ELISA. Northern blot analysis was conducted for mRNA expression. Electrophoretic mobility shift assays were applied to demonstrate the invo lvement of the transcription factors nuclear factor kappa B (NF-kappaB) and activator protein-1 (AP-1) in signal transduction. Results: Incubation of HPMC with early glycated albumin (GHSA) resulted in a time- and concentration-dependent increase in PAI-1 mRNA expression and a ntigen secretion. In contrast, no changes in PAI-1 synthesis occurred after stimulation with either the 1,2-dicarbonyl compounds methylglyoxal and 3-d eoxyglucosone, or with late advanced glycation end-products. tPA synthesis was not affected by any of the tested components. Furthermore, HPMC exposed to GHSA induced NF-kappaB and AP-1 DNA binding activity, suggesting that G HSA-induced overexpression of PAI-1 is transcriptionally regulated by both transcription factors. Conclusions: We conclude that Amadori modified glycated albumin upregulates PAI-1 synthesis in HPMC, possibly mediated through the activation of the t ranscription factors NF-kappaB and AP-1. The present data support the clini cal relevance of the formation of glycated proteins and their involvement i n pathological processes in PD patients. Thus, glycated albumin may contrib ute to an imbalance between intraperitoneal formation and degradation of fi brin that causes peritoneal structural alterations, with subsequent membran e failure.