Human umbilical vein endothelial cells accelerate oxalate-induced apoptosis of human renal proximal tubule epithelial cells in co-culture system which is prevented by pyrrolidine dithiocarbamate

Oxalate is the most common component of kidney stones and elevated urinary levels induce renal tubular cell toxicity and death which is essential for crystal attachment. Endothelial cells, in some studies have been shown to regulate certain functions of renal proximal tubule cells. The aim of this study was to evaluate the effect of endothelial cells on tubular cell apoptosis in a co-culture system mimicking the in vivo renal physiological settings. The human umbilical vein endothelial cells (HUVEC) and human renal proximal tubule epithelial cells (RPTEC) were exposed to increasing concentrations (0-1.0 mM) of oxalate with or without 10 mu M PDTC pretreatment for 24 h. In HUVEC, RPTEC and HUVEC-RPTEC co-cultures, the cell viability was measured using the WST-1 assay and cell death with the TUNEL analysis using the flow cytometry. The treatment of RPTECs with oxalate lead to 8.9-26.2% cell death which was reduced to 0-1.6% with the PDTC pretreatment. The death rate of RPTECs was significantly increased by 15-19% at different oxalate concentrations when co-cultured with HUVECs. In contrast, cell viability was not substantially altered in PDTC pretreated RPTECs that were co-cultured with HUVECs. Apoptosis was the way of cell death as similar rate of apoptosis was observed in cell culture systems. Although cell viability of RPTECs was further reduced when co-cultured with HUVECs, it was restored with the pretreatment of PDTC. This is the first study focusing on the role of endothelial cells on RPTEC apoptosis following hyperoxaluria.