A Novel Peptide Derived From Tissue‐Type Plasminogen Activator Potently Inhibits Angiogenesis and Corneal Neovascularization

ABSTRACT The recombinant protein TK1‐2, which consists of two kringle domains of tissue‐type plasminogen activator (t‐PA), inhibits angiogenesis and tumor growth. ɪn this study, we examined the anti‐angiogenic activities of peptides derived from kringle 2 domain of t‐PA to identify the functional core sequence. Seven peptides were constructed from the kringle 2 sequence, based on the structure and characteristics of amino acid residues, and were analyzed for their inhibitory effects on endothelial cells (ECs). Among them, TP‐7 (derived from a β‐sheet motif) potently inhibited proliferation, tube formation, and migration of ECs in a dose‐dependent manner, whereas truncation of 3–9 amino acid residues from either N or C terminus of TP‐7 abrogated its inhibitory effects on ECs. TP‐7 also potently inhibited angiogenesis in a Matrigel plug assay in vivo. Moreover, TP‐7 dose‐dependently suppressed corneal neovascularization induced by an acute chemical burn in a rat model. At the molecular level, TP‐7 inhibited VEGF‐ or bFGF‐induced phosphorylation of FAK and ERK1/2 and drastically disrupted VEGF‐ or bFGF‐induced formation of stress fibers and focal adhesion complexes. In addition, TP‐7 markedly suppressed attachment and spreading of ECs on a collagen type I or fibronectin matrix. Adhesion of ECs to immobilized TP‐7 increased dose‐dependently, which was disrupted strongly by pretreatment with soluble TP‐7 and slightly by an integrin α2β1‐blocking antibody. These results suggest that TP‐7 is a potent anti‐angiogenic peptide in part affecting the integrin α2β1‐dependent pathway and that it can be used for treatment of corneal neovascularization by targeting VEGF and non‐VEGF pathways. J. Cell. Biochem. 118: 1132–1143, 2017. © 2016 Wiley Periodicals, Inc.