Regulation of heparanase by albumin and advanced glycation end products in proximal tubular cells.

Diabetic nephropathy is one of the main causes of end-stage renal disease, in which the development of tubular damage depends on factors such as high glucose levels, albuminuria and advanced glycation end-product. In this study, we analyzed the involvement of heparanase, a heparan sulfate glycosidase, in the homeostasis of proximal tubular epithelial cells in the diabetic milieu. In vitro studies were performed on a wild-type and stably heparanase-silenced adult tubular line (HK2) and HEK293. Gene and protein expression analyses were performed in the presence and absence of diabetic mediators. Albumin and advanced glycation end-product, but not high glucose levels, increased heparanase expression in adult tubular cells via the AKT/PI3K signaling pathway. This over-expression of heparanase is then responsible for heparan sulfate reduction via its endoglycosidase activity and its capacity to regulate the heparan sulfate-proteoglycans core protein. In fact, heparanase regulates the gene expression of syndecan-1, the most abundant heparan sulfate-proteoglycans in tubular cells. We showed that heparanase is a target gene of the diabetic nephropathy mediators albumin and advanced glycation end-product, so it may be relevant to the progression of diabetic nephropathy. It could take part in several processes, e.g. extracellular-matrix remodeling and cell-cell crosstalk, via its heparan sulfate endoglycosidase activity and capacity to regulate the expression of the heparan sulfate-proteoglycan syndecan-1.