on September 15, 2005
Published online before print September 15, 2005, doi: 10.1161/01.ATV.0000186182.14908.7b
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Submitted on July 13, 2005
Accepted on August 15, 2005
Integrin 
V
3 as a Target for Blocking HIV-1 Tat-Induced Endothelial Cell Activation In Vitro and Angiogenesis In Vivo
Chiara Urbinati ;
From the Chair of General Pathology and Immunology, Department of Biomedical Sciences and Biotechnology (C.U., S.M., E.T., M.P., M.R.), University of Brescia, Italy; the Department of Tumor Biology (C.K.), Schering-Plough Research Institute, Kenilworth, New Jersey; the Department of Cardiology (J.W.), University Hospital Maastricht, The Netherlands; and the Institute of Human Anatomy, Histology, and Embryology (D.R.), University of Bari, Italy.
* To whom correspondence should be addressed. E-mail: rusnati{at}med.unibs.it.
Objective--The transactivating factor (Tat) of HIV-1 binds to 
v
3 integrin present on endothelial cells contributing to neovascularization. Here, we investigated the biological consequences of Tat/v3 interaction and the antagonist effect of an RGD-based peptidomimetic.
Methods and Results--Binding of Tat to endothelial v3 triggers focal adhesion kinase and nuclear factor-
B activation, leading to endothelial cell proliferation, membrane ruffling, and motility in vitro and neovascularization in vivo. The RGD-peptidomimetic SCH221153 inhibits Tat/v3 interaction in a solid phase binding assay and endothelial cell adhesion to immobilized Tat with a potency higher than that of RGD-containing peptides. Accordingly, SCH221153 inhibits Tat/v3-dependent focal adhesion kinase and nuclear factor-B activation, proliferation, membrane ruffling, and motility in endothelial cells. Finally, SCH221153 inhibits the angiogenic response triggered by Tat in the chick-embryo chorioallantoic membrane without affecting physiological vascularization. SCH221153 exerts these inhibitory effects without affecting the interaction of Tat with endothelial heparan sulfate proteoglycan or with the vascular endothelial growth factor receptor-2/KDR. In all the assays the negative control SCH216687 was ineffective.
Conclusion--These data provide new insights on the mechanism of endothelial cell activation by Tat and point to RGD peptidomimetics as prototypes for the development of novel Tat antagonists.
Key words: HIV-1 • Tat • endothelium • integrin • angiogenesis
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