Small concentrations of oxLDL induce capillary tube formation from endothelial cells via LOX-1-dependent redox-sensitive pathway

Objective-Vascular endothelial growth factor (VEGF), a key angiogenic growth factor, stimulates angiogenesis. Low levels of reactive oxygen species (ROS) function as signaling molecules for angiogenesis. We postulated that low concentrations of oxLDL might induce low levels of ROS and initiate angiogenesis. Methods and Results-An in vitro model of tube formation from human coronary artery endothelial cells (HCAECs) was used. oxLDL (0.1, 1, 2, 5 mu g/mL) induced VEGF expression and enhanced tube formation. oxLDL-mediated VEGF expression and tube formation were suppressed by a specific blocking anti-LOX-1 antibody. Anti-LOX-1 antibody also reduced oxLDL-induced increase in the expression of NADPH oxidase (gp91(phox) and p47(phox) subunits) and subsequent intracellular ROS generation, phosphorylation of p38 as well as p44/42MAPK, and NF-kappa B p65 expression. gp91(phox) siRNA had a similar effect. The expression of VEGF and NF-kappa B p65 induced by oxLDL was also inhibited by the specific extracellular signal-regulated kinase (ERK) 1/2 inhibitor U0126 and the p38 MAPK inhibitor SB203580. Importantly, the NADPH oxidase inhibitor apocynin, gp91(phox) siRNA, U0126, and SB203580 all reduced tube formation in response to oxLDL. Conclusions-These findings suggest that small concentrations of oxLDL promote capillary tube formation by inducing the expression of VEGF via LOX-1-mediated activation of NADPH oxidase-MAPKs-NF-kappa B pathway.