Potent and specific inhibition of VEGF signalling mediated by slow tight‐binding of flavonoids to VEGF (1045.33)

Abstract

Potent and specific inhibition of VEGF signalling mediated by slow tight‐binding of flavonoids to VEGF Paul A. Kroon1, Christina W.A. Moyle1, Ana B. Cerezo1, Mark S. Winterbone1, Paul W. Needs1, Wendy J. Hollands1, Rebecca L. Edwards1: Institute of Food Research, Norwich Research Park, Norwich NR4 7UA, UK.Background: Previously, we reported that the predominant effect of a low dose of an apple procyanidin extract on gene expression in cultured human vascular endothelial cells was inhibition of angiogenic functions and associated signalling pathways. Vascular endothelial growth factor (VEGF) is the dominant driver of vascular angiogenesis, and excessive concentrations of VEGF drive angiogenesis and cause complications such as age‐related macular degeneration and increased growth of tumours and atherosclerotic plaques. Since VEGF signalling plays crucial roles in diseases for which flavonoids have been shown to be protective, we further investigated the interactions of flavonoids with VEGF signalling.Methods and Results: Polyphenols such as EGCg (green tea) and procyanidin oligomers (cocoa, apples) potently inhibited VEGFA‐mediated phosphorylation of VEGF receptor‐2 in HUVECs with IC50 values of 89 and 280 nM, respectively. Many other polyphenols including (‐)‐epicatechin were completely ineffective. We show that EGCg and a procyanidin tetramer inhibited VEGFR2 activation by directly binding to VEGFA and preventing ligand‐receptor binding. The polyphenol‐VEGFA complexes were formed as a result of slow, tight‐binding reactions from which VEGF activity could not be recovered by dialysis. Remarkably, even though VEGFR‐2 signalling was completely inhibited at 1 µM concentrations of EGCg and procyanidins, endothelial NO synthase (eNOS) was shown to still be activated via the PI3K/pAkt signalling pathway.Conclusion: These data show that polyphenols can potently inhibit VEGFR‐2 signalling while retaining the pro‐endothelial functions that occur downstream of PI3K/Akt.Grant Funding Source: Supported by the BBSRC (UK), EU FP7 (BACCHUS‐312090, VegFenol‐274885) and Coressence Ltd.