Positive versus negative effects of VEGF sub( 165) on Ca super( 2+) 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 sub( 165) influences vasodilator production via Ca2+ 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 Ca2+ and NO by VEGF sub( 165) alone, as well as the effect of VEGF sub( 165) on subsequent ATP-stimulated Ca2+ signaling and NO production. We show that VEGF sub( 165) stimulates Ca2+ responses in both HUVEC and HUV Endo, which results in a corresponding increase in NO production in HUV Endo. Longer-term VEGF sub( 165) pretreatment then inhibits sustained Ca2+ 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 sub( 165) makes a small initial positive impact on vasodilator production via direct stimulation of Ca2+ responses, this is outweighed by the greater subsequent negative impact on Ca2+ bursts and vasodilator production promoted by more potent agonists such as ATP. Overall, elevated levels of VEGF sub( 165) associated with preeclampsia could contribute to the endothelial dysfunction by preventing Ca2+ bursts to other agonists including but not limited to ATP.