THROMBIN RECEPTOR ACTIVATING PEPTIDES INDUCE CA-2-DERIVED GROWTH-FACTOR MESSENGER-RNA EXPRESSION IN CULTURED ENDOTHELIUM( MOBILIZATION, BARRIER DYSFUNCTION, PROSTAGLANDIN SYNTHESIS, AND PLATELET)

Endothelial cell activation by thrombin is a key event in wound healin g, inflammation, and hemostasis. To better define thrombin-endothelial cell interactions we synthesized several peptides of varying length c orresponding to the initial 14 amino acid sequence of the cloned human platelet thrombin receptor after cleavage at an arginine 41 Site (R/S FLLRNPNDKYEPF). Thrombin receptor activating peptides (TRAPs) as short as 5 amino acids induced significant levels of PGl2 synthesis and exp ression of PDGF mRNA in human endothelium and produced dose-dependent cellular contraction and permeability of confluent human umbilical vei n and bovine pulmonary artery endothelial monolayers. To explore wheth er TRAPs utilized similar signal transducing pathways as alpha-thrombi n to accomplish endothelial cell activation, phospholipase C productio n of the Ca2+ secretagogue IP3 was measured and detected 10 seconds af ter either TRAP 7 or a-thrombin. Furthermore, TRAPs ranging from 5-14 residues induced significant dose-dependent increases in Fura-2 fluore scence indicative of Ca2+, mobilization. These results indicate that t hrombin-mediated proteolytic cleavage of the human and bovine thrombin receptor initiates stimulus/coupling responses such phospholipase C a ctivation, Ca2+ mobilization, and protein kinase C activation. The fun ctional consequence of this cellular activation via the cleaved recept or is enhanced cellular contraction, barrier dysfunction, PGI2 synthes is, and expression of PDGF mRNA. (C) 1993 Wiley-Liss, Inc.