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(Arteriosclerosis, Thrombosis, and Vascular Biology. 2009;29:2117.)
© 2009 American Heart Association, Inc.

Cell Biology/Signaling

The ADMA/DDAH Pathway Regulates VEGF-Mediated Angiogenesis

Lorna R Fiedler; Tiziana Bachetti; James Leiper; Ian Zachary; Lihua Chen; Thomas Renné; Beata Wojciak-Stothard

From the National Heart and Lung Institute, Faculty of Medicine (L.R.F.), Imperial College London, UK; the Department of Medicine (T.B.), BHF Laboratories, Rayne Institute, University College London; MRC Clinical Sciences Centre (J.L.), Imperial College London, UK; the Department of Cardiovascular Science (I.Z.), BHF Laboratories, Rayne Institute, University College London, UK; the Center for Cardiovascular Biology (L.C.), University of Washington, Seattle; the Department of Molecular Medicine and Surgery; and Center for Molecular Medicine (T.R.), Karolinska Institutet, Stockholm, Sweden; and the Department of Experimental Medicine and Toxicology, Division of Investigative Science (B.W.-S.), Imperial College London, UK.

Correspondence to Beata Wojciak-Stothard, Department of Experimental Medicine and Toxicology, Division of Investigative Science, Imperial College London, Hammersmith Hospital Campus, DuCane Road, London W12 0NN, UK. E-mail b.wojciak-stothard{at}imperial.ac.uk

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.

The endogenous NO synthase inhibitor and cardiovascular risk factor ADMA inhibits angiogenesis. We show for the first time that ADMA inhibits VEGF-induced endothelial cell motility and angiogenesis by modulating NO-dependent Rho GTPase activity. Further, normal angiogenic responses to VEGF are restored by overexpression of DDAH or active Rac1.

Key Words: Rho GTPase • ADMA • DDAH I • VEGF • angiogenesis