Positive versus negative effects of VEGF165 on Ca2+ signaling and NO production in human endothelial cells

The role increased vascular endothelial growth factor (VEGF) plays in vascular function during normal vs. preeclamptic pregnancy has been a source of some controversy of late. In this study, we seek to understand how VEGF influences vasodilator production via Ca signaling mechanisms in human endothelial cells. We utilize human umbilical vein endothelial cells (HUVEC) as well as intact ex vivo human umbilical vein (HUV Endo) to address direct stimulation of Ca and NO by VEGF alone, as well as the effect of VEGF on subsequent ATP-stimulated Ca signaling and NO production. We show that VEGF stimulates Ca responses in both HUVEC and HUV Endo, which results in a corresponding increase in NO production in HUV Endo. Longer-term VEGF pretreatment then inhibits sustained Ca burst responses to ATP in HUVEC and HUV Endo. This is paralleled by a corresponding drop in ATP-stimulated NO production in HUV Endo, likely through inhibition of Cx43 gap-junction function. Thus, although VEGF makes a small initial positive impact on vasodilator production via direct stimulation of Ca responses, this is outweighed by the greater subsequent negative impact on Ca bursts and vasodilator production promoted by more potent agonists such as ATP. Overall, elevated levels of VEGF associated with preeclampsia could contribute to the endothelial dysfunction by preventing Ca bursts to other agonists including but not limited to ATP. In this manuscript, we show that VEGF levels associated with preeclampsia are a net negative contributor to potential vasodilator production in both a human ex vivo and in vitro endothelial cell model. Therefore, pharmacological targeting of VEGF-stimulated signaling pathways could be a novel treatment modality for preeclampsia-related hypertension.