Indexed on: 29 Jul '05Published on: 29 Jul '05Published in: FASEB journal : official publication of the Federation of American Societies for Experimental Biology
In this study we identified the involvement of reactive oxygen species (ROS) in signaling and biological effects of the angiopoietin-1 (Ang-1)/tie-2 receptor pathway. Exposure of human umbilical vein endothelial cells to Ang-1 (50 ng/ml) induced rapid and transient production of ROS, particularly superoxide anions. ROS production was attenuated by preincubation with a peptide (gp91ds-tat) that inhibits the association of the gp91(phox) subunit with the p47(phox) subunit of NADPH oxidase and by the expression of a dominant-negative form of Rac-1 (Rac1N17). These results suggest that ROS production in response to Ang-1 exposure originates mainly from a Rac-1-dependent NADPH oxidase. Overexpression of antioxidants (superoxide dismutase and catalase) and Rac1N17, as well as preincubation with selective inhibitors of NADPH oxidase augmented basal p38 phosphorylation, inhibited Ang-1-induced PAK-1 phosphorylation and potentiated Ang-1-induced Erk1/2 phosphorylation but had no influence on AKT and SAPK/JNK phosphorylation by Ang-1. Exposure to Ang-1 (100 ng/ml) for 5 h induced a threefold increase in endothelial cell migration, a response that was strongly inhibited by overexpression of antioxidants, Rac1N17, and selective NADPH oxidase inhibitors. We conclude that activation of tie-2 receptors by Ang-1 triggers the production of ROS through activation of NADPH oxidase and that ROS generation by Ang-1 promotes endothelial cell migration while negatively regulating Erk1/2 phosphorylation.