Acurhagin-C, an ECD disintegrin, inhibits integrin αvβ3-mediated human endothelial cell functions by inducing apoptosis via caspase-3 activation

Background and purpose: Acurhagin, a member of versatile metalloproteinase disintegrins from Agkistrodon acutus venom, has been identified as a platelet aggregation inhibitor, previously. Here, acurhagin-C, the C-terminal Glu-Cys-Asp (ECD)-containing fragment of acurhagin, was evaluated for its biological activities and potential applications in anti-angiogenic therapy. Experimental approach: Human umbilical vein endothelial cells (HUVECs) were treated with acurhagin-C to assay effects on viability, apoptosis, adhesion, migration, invasion, proliferation and angiogenesis. The recognition site and signalling involved for the interactions of acurhagin-C with HUVEC were determined using flow cytometric, electrophoresis and immunoblotting analyses. Key results: Acurhagin-C decreased viability and induced apoptosis in HUVEC. It also dose-dependently inhibited HUVEC adhesion to immobilized extracellular matrices fibronectin, collagen I and vitronectin with respective IC50 values of approximately 0.6, 0.3 and 0.1 mu M. Acurhagin-C prevented migration and invasion of HUVEC through vitronectin- and Matrigel-coated barriers respectively. Furthermore, acurhagin-C attenuated fibroblast growth factor-2-primed angiogenesis both in vitro and in vivo, and specifically blocked the binding of anti-alpha v beta 3 monoclonal antibody 23C6 to HUVEC in an ECD-dependent manner. However, purified alpha v beta 3 also dose-dependently bound to immobilized acurhagin and acurhagin-C with a saturable pattern. Interference with integrin alpha v beta 3-mediated functions and promotion of caspase-3 activation by acurhagin-C affected morphology of HUVEC and induced apoptosis. Conclusions and implications: Acurhagin-C elicited endothelial anoikis via disruption of alpha v beta 3/focal adhesion kinase/phosphatidylinositol 3-kinase/Akt survival cascade and subsequent initiation of the procaspase-3 apoptotic signalling pathway.