Vascular endothelial growth factor receptor-2 and low affinity VEGF binding sites on human glomerular endothelial cells: Biological effects and advanced glycosilation end products modulation

Vascular Endothelial Growth Factor (VEGF), binding to its receptor in endothelial cells, seems to modulate the increased blood flow in the early phase of diabetic renal disease. The aim of the study was to evaluate, in a diabetic milieu, the expression, biological function and modulation of VEGF binding sites in human glomerular endothelial cells (GENC). We demonstrated the presence of VEGF binding sites with high (VEGFR-2) and low (heparan sulfate proteoglycans, HSPG) affinity. VEGF165 and VEGF121 working through VEGFR-2 stimulated nitric oxide (NO) production at low doses (0.1-1 nM), whereas only VEGF165 at high doses (10-100 nM) increased thymidine incorporation. 1 nM VEGF165 and VEGF121 induced in GENC a significant peak of inducible NO synthase (iNOS) production and, at a lower level, of endothelial NOS (eNOS). The copresence of VEGF165 with aminoguanidine (iNOS inhibitor) determined an increase of eNOS and a significant increase in thymidine incorporation. Advanced glycation end products (AGEs) working through specific receptors (RAGE) up-regulated the expression of VEGFR-2, decreased the expression of HSPG sites and reduced GENC growth. These results identify in GENC VEGFR-2 as a mediator of iNOS and eNOS release under control of VEGF, whereas HSPG binding sites seem to mediate the weak growth effect. The presence of AGEs, up-regulating the VEGFR-2 and decreasing HSPG sites might participate to the block of glomerular angiogenesis addressing the VEGF effects on glomerular permeability.