title: Blockade of angiogenesis by small molecule antagonists to protease-activated receptor-1: association with endothelial cell growth suppression and induction of apoptosis.
abstract: Many studies support the notion that protease-activated receptor (PAR)-1 plays a pivotal role in angiogenesis. However, direct evidence and understanding the molecular mechanisms involved were limited because PAR-1-specific antagonists have been developed only recently. In the present study, we evaluated the effects of two well characterized PAR-1 antagonists, SCH79797 ((N-3-cyclopropyl-7-{[4-(1-methylethyl)phenyl]-methyl}-7H-pyrrolo[3,2-f]quinazoline-1,3-diamine)) and RWJ56110 [(alphaS)-N-[(1S)-3-amino-1-[[(phenylmethyl)amino]carbonyl]propyl]-alpha-[[[[[1-(2,6-dichlorophenyl)methyl]-3-(1-pyrrolidinylmethyl)-1H-indol-6-yl]amino]carbonyl]amino]-3,4-difluorobenzenepropanamide], in the angiogenic cascade. These antagonists suppressed both the basic angiogenesis and that stimulated by thrombin in the chick chorioallantoic membrane model in vivo. PAR-1 antagonists also abrogated tube formation in the in vitro Matrigel system. These inhibitory effects were dose-dependent and well correlated with the inhibitory effects of SCH79797 and RWJ56110 on primary endothelial cell proliferation and on the initiation of apoptosis. PAR-1 blockage resulted in inhibition of endothelial cell growth by increasing the sub-G0/G1 fraction and reducing the percentage of cells in the S phase. Consistent with this, PAR-1 antagonists reduced incorporation of [3H]thymidine in endothelial cells and blocked the phosphorylation of extracellular signal-regulated kinases in a fashion depending specifically on PAR-1 activation. Analysis by annexin V/propidium iodide staining and poly(ADP-ribose) polymerase cleavage revealed that PAR-1 blockage increased apoptotic cell death by a mechanism involving caspases. These results provide further evidence that PAR-1 is a key receptor that mediates angiogenesis and suggest PAR-1 as target for developing antiangiogenic agents with potential therapeutic application in cancer and other angiogenesis-related diseases.
authors.affiliation: Department of Pharmacology, Medical School, University of Patras, 26500, Patras, Greece.
authors.forename: Panagiota
authors.initials: P
authors.lastname: Zania
authors.forename: Sosanna
authors.initials: S
authors.lastname: Kritikou
authors.forename: Christodoulos S
authors.initials: CS
authors.lastname: Flordellis
authors.forename: Michael E
authors.initials: ME
authors.lastname: Maragoudakis
authors.forename: Nikos E
authors.initials: NE
authors.lastname: Tsopanoglou
mesh_terms: D020533:Angiogenesis Inhibitors / Q000494:pharmacology*; D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D002642:Chick Embryo; D004305:Dose-Response Relationship, Drug; D042783:Endothelial Cells / Q000187:drug effects / Q000502:physiology*; D018919:Neovascularization, Physiologic / Q000187:drug effects / Q000502:physiology*; D011758:Pyrroles / Q000494:pharmacology; D011799:Quinazolines / Q000494:pharmacology; D044463:Receptor, PAR-1 / Q000502:physiology; D010975:Platelet Aggregation Inhibitors
chemical_list: D020533:Angiogenesis Inhibitors; C415424:N3-cyclopropyl-7-((4-(1-methylethyl)phenyl)methyl)-7H-pyrrolo(3, 2-f)quinazoline-1,3-diamine; D011758:Pyrroles; D011799:Quinazolines; D044463:Receptor, PAR-1; D010975:Platelet Aggregation Inhibitors