The Role of the Glyoxalase Pathway in Reducing Mesothelial Toxicity of Glucose Degradation Products

Abstract

BackgroundThe glucose degradation products (GDP) present in conventional peritoneal dialysis fluids (PDF) may exert adverse effects toward human peritoneal mesothelial cells (HPMC). Some GDP can be detoxified by the glyoxalase/glutathione pathway. It has been shown that the addition of glyoxalase I (GLO-I) and reduced glutathione (GSH) to PDF effectively eliminates GDP. We have therefore examined the GLO-I/GSH system in HPMC and assessed the impact of GLO-I/GSH-treated PDF on the viability and function of HPMC.MethodsHeat-sterilized PDF (H-PDF) was incubated in the presence or absence of GLO-I and GSH for 1 hour at 37°C, and then mixed with an equal volume of serum-free M199 medium and applied to HPMC in culture. After 24 hours, HPMC were assessed for viability, the release of interleukin-6, GLO-I activity, and cellular glutathione. The effects were compared to those exerted by filter-sterilized PDF (F-PDF), which was devoid of GDP.ResultsExposure of HPMC to H-PDF resulted in reduced GLO-I activity, GSH depletion, and a decrease in cell viability. Pretreatment of H-PDF with either a combination of GLO-I and GSH or GSH alone markedly reduced inhibitory effects of H-PDF toward HPMC, as measured by cell viability and interleukin-6 generation. Exposure of HPMC to the GSH precursor L-2-oxothiazolidine-carboxylic acid increased cellular GSH and prevented the loss of GLO-I activity in response to H-PDF.ConclusionsExposure to conventional GDP-rich PDF impairs the activity of the glyoxalase/glutathione system in HPMC. Pretreatment of PDF with GSH or replenishment of cellular GSH protects HPMC against GDP-mediated toxicity.