The ADMA/DDAH Pathway Regulates VEGF-Mediated Angiogenesis

Objectives-Asymmetrical dimethylarginine ( ADMA) is a nitric oxide synthase (NOS) inhibitor and cardiovascular risk factor associated with angiogenic disorders. Enzymes metabolising ADMA, dimethylarginine dimethylaminohydrolases ( DDAH) promote angiogenesis, but the mechanisms are not clear. We hypothesized that ADMA/DDAH modifies endothelial responses to vascular endothelial growth factor ( VEGF) by affecting activity of Rho GTPases, regulators of actin polymerization, and focal adhesion dynamics. Methods and Results-The effects of ADMA on VEGF-induced endothelial cell motility, focal adhesion turnover, and angiogenesis were studied in human umbilical vein endothelial cells (HUVECs) and DDAH I heterozygous knockout mice. ADMA inhibited VEGF-induced chemotaxis in vitro and angiogenesis in vitro and in vivo in an NO-dependent way. ADMA effects were prevented by overexpression of DDAH but were not associated with decreased proliferation, increased apoptosis, or changes in VEGFR-2 activity or expression. ADMA inhibited endothelial cell polarization, protrusion formation, and decreased focal adhesion dynamics, resulting from Rac1 inhibition after decrease in phosphorylation of vasodilator stimulated phosphoprotein ( VASP). Constitutively active Rac1, and to a lesser extent dominant negative RhoA, abrogated ADMA effects in vitro and in vivo. Conclusion-The ADMA/DDAH pathway regulates VEGF-induced angiogenesis in an NO- and Rac1-dependent manner. (Arterioscler Thromb Vasc Biol. 2009;29:2117-2124.)