Excessive angiogenesis is involved in many human diseases, and inhibiting angiogenesis is an important area of drug development. There have been conflicting reports as to whether decorin could function as an angiogenic inhibitor when used as an extracellular soluble factor. In this study, we demonstrated that not only purified decorin but also the 26-residue leucine-rich repeat 5 (LRR5) of decorin core protein functions as angiogenesis inhibitor by inhibiting both vascular endothelial growth factor (VEGF) and basic fibroblast growth factor-induced angiogenesis. Peptide LRR5 inhibited angiogenesis through multiple mechanisms, including inhibiting VEGF-stimulated endothelial cell (EC) migration, tube formation on Matrigel, cell attachment to fibronectin, as well as induction of EC apoptosis without significantly affecting their proliferation. We further demonstrated that different subregions of LRR5 inhibited different aspects of angiogenesis, with the middle region (LRR5M, 12 residues) inhibiting endothelial cell tube formation up to 1000 times more potently than LRR5. Although the C-terminal region (LRR5C) potently inhibited VEGF-stimulated endothelial cell migration, the N-terminal region (LRR5N) is as active as LRR5 in inhibiting endothelial cell attachment to fibronectin. Although both LRR5M and LRR5N induced EC apoptosis dose-dependently similar to LRR5 through a caspase-dependent pathway, LRR5C has no such function. We further showed that the inhibition of tube formation by LRR5 and LRR5M is linked with their ability to suppress VEGF-induced focal adhesion kinase phosphorylation and the assembly of focal adhesions and actin stress fibers in ECs, but not their ability to interfere with endothelial cell attachment to the matrix. Circular dichroism studies revealed that LRR5 undergoes an inter-conversion between 3 10 helix and -sheet structure in solution, a characteristic potentially important for its anti-angiogenic activity. Peptide LRR5 and its derivatives are therefore novel angiogenesis inhibitors that may serve as prototypes for further development into anti-angiogenic drugs.
The CD2-CD58 interaction in immune regulation and disease pathology has provided new targets for developing potential immunosuppressive agents. In the present study, we report the introduction of constraints to generate beta-hairpin structures from the strand sequences of CD2 protein. The beta-hairpin structures were induced in the designed peptides by introducing Pro-Gly sequences in the peptides. Results from NMR and MD simulation indicated that the peptides exhibited beta-turn structure at the X-Pro-Gly-Y sequence and formed the beta-hairpin structure in solution. The ability of these peptides to inhibit cell adhesion was evaluated by two cell adhesion assays. Among the peptides studied (1-4) (P1-P4), peptides 2-4 were able to inhibit cell adhesion between Jurkat cells and SRBC nearly 50% at 180 microM, and 80% inhibition between Jurkat cells and Caco-2 cells was seen at 90 microM. Peptide 1 did not show significant inhibition activity compared to control.
Anti-angiogenesis therapy is an established therapeutic strategy for cancer. The endogenous angiogenic inhibitor angiostatin contains the first 3-4 kringle domains of plasminogen and inhibits both angiogenesis and vascular permeability. We present here a 10-residue peptide, Angio-3, derived from plasminogen kringle 3, which retains the functions of angiostatin in inhibiting both angiogenesis and vascular permeability. NMR studies indicate that Angio-3 holds a solution structure similar to the corresponding region of kringle 3. Mechanistically, Angio-3 inhibited both VEGF- and bFGF-induced angiogenesis by inhibiting EC proliferation and migration while inducing apoptosis. Inhibition of VEGF-induced vascular permeability results from its ability to impede VEGF-induced dissociation of adherens junction and tight junction proteins as well as the formation of actin stress fibers. When administered intravenously, Angio-3 inhibited subcutaneous breast cancer and melanoma growth by suppressing both tumor angiogenesis and intra-tumor vascular permeability. Hence, Angio-3 is a novel dual inhibitor of angiogenesis and vascular permeability. It is valuable as a lead peptide that can be further developed as therapeutics for diseases involving excessive angiogenesis and/or vascular permeability.
Amino-substituted coumarins undergo Pictet–Spengler condensations with 3-ketosteroids to afford spirocyclic androgens for the study 17-oxidoreductases for intracrine, androgen metabolism.
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