Abstract
Resveratrol (trans-3,5,4'-trihydroxystilbene), a compound found largely in the skins of red grapes and wines, possesses anti-cancer and anti-angiogenic properties and protects the cardiovascular system. However, the molecular mechanisms by which resveratrol inhibits angiogenesis are currently subjects of intense investigation. The purpose of this study was to examine whether FOXO transcription factors mediate anti-angiogenic effects of resveratrol, and whether vascular endothelial growth factor (VEGF) neutralizing antibody can enhance these effects of resveratrol. Inhibition of PI3 kinase (PI3K)/AKT and MEK/ERK pathways synergistically inhibited migration and capillary tube formation of Human Umbilical Vein Endothelial Cells (HUVECs) and further enhanced the anti-angiogenic effects of resveratrol. Inhibitors of AKT and MEK kinase synergistically inhibited cytoplasmic FOXO3a phosphorylation, which was accompanied by its nuclear translocation in HUVECs. Interestingly, inhibition of PI3K/AKT and MEK/ERK pathways synergistically induced FOXO transcriptional activity and inhibited cell migration and capillary tube formation. Antiangiogenic effects of resveratrol were enhanced by inhibitors of AKT and MEK. Phosphorylation-deficient mutants of FOXOs induced FOXO transcriptional activity, inhibited HUVEC cell migration, and capillary tube formation, and also enhanced antiangiogenic effects of resveratrol. Finally, VEGF neutralizing antibody enhanced the anti-proliferative and anti-angiogenic effects of resveratrol. In conclusion, regulation of FOXO transcription factors by resveratrol may play an important role in angiogenesis which is critical for cancer, diabetic retinopathy, rheumatoid arthritis, psoriasis, and cardiovascular disorders.