Intracellular Ca2+ can compensate for the lack of NADPH oxidase-derived ROS in endothelial cells

The aim of the present study is to determine the role of intracellular Ca2+ in VEGF signaling. We demonstrate that reduction in Ca2+ by chelating compound BAPTA-AM or by IP3-endoplasmic reticulum blocker 2-APB selectively inhibited VEGF-induced activation of c-Src-PI3K-Akt but not ERK1/2 in human coronary artery endothelial cells (HCAEC). We also show that the selective inhibitory effects of NADPH oxidase knockdown on VEGF-mediated activation of c-Src-PI3K-Akt signaling and cell proliferation in HCAEC can be reversed by increase in intracellular Ca2+. These results suggest an essential role for Ca2+ in redox-dependent selective activation of c-Src-PI3K-Akt and endothelial cell proliferation.