Glycation of fibronectin inhibits VEGF-induced angiogenesis by uncoupling VEGF receptor-2-c-Src crosstalk

Glycation of extracellular matrix proteins has been demonstrated to contribute to the pathogenesis of vascular complications. However, no previous report has shown the role of glycated fibronectin (FN) in vascular endothelial growth factor (VEGF)-induced angiogenesis. Thus, this study aimed to investigate the effects of glycated FN on VEGF signalling and to clarify the molecular mechanisms involved. FN was incubated with methylglyoxal (MGO) in vitro to synthesize glycated FN, and human umbilical vein endothelial cells (HUVECs) were seeded onto unmodified and MGO-glycated FN. Then, VEGF-induced angiogenesis and VEGF-induced VEGF receptor-2 (VEGFR-2) signalling activation were measured. The results demonstrated that normal FN-positive bands (260 kD) vanished and advanced glycation end products (AGEs) appeared in MGO-glycated FN and glycated FN clearly changed to a higher molecular mass. The glycation of FN inhibited VEGF-induced VEGF receptor-2 (VEGFR-2), Akt and ERK1/2 activation and VEGF-induced cell migration, proliferation and tube formation. The glycation of FN also inhibited the recruitment of c-Src to VEGFR-2 by sequestering c-Src through receptor for AGEs (RAGE) and the anti-RAGE antibody restored VEGF-induced VEGFR-2, Akt and ERK1/2 phosphorylation, endothelial cell migration, proliferation and tube formation. Furthermore, the glycation of FN significantly inhibited VEGF-induced neovascularization in the Matrigel plugs implanted into subcutaneous tissue of mice. Taken together, these data suggest that the glycation of FN may inhibit VEGF signalling and VEGF-induced angiogenesis by uncoupling VEGFR-2-c-Src interaction. This may provide a novel mechanism for the impaired angiogenesis in diabetic ischaemic diseases.