title: Blocking endothelial protein C receptor (EPCR) accelerates thrombus development in vivo.
abstract: The endothelial protein C receptor (EPCR) plays an anticoagulant role by improving protein C activation. Although low levels of activated protein C (APC) constitute a thrombosis risk factor, the relationship between modulating EPCR function and thrombosis has not been addressed so far. Monoclonal antibodies (mAb) against murine EPCR were raised, and their ability to block protein C/APC binding was tested. The ferric chloride carotid artery injury model in mice was chosen to test the effect of anti-EPCR mAb on thrombus formation. The time to total occlusion of the vessel was analysed in three groups, given an isotype control mAb (IC), a blocking (RCR-16) or a non-blocking (RCR-20) anti-EPCR mAb. RCR-16 prevented the interaction between protein C/APC and EPCR as demonstrated by surface plasmon resonance and flow cytometry, and inhibited the activation of protein C on the endothelium. IC and RCR-20 were unable to induce such effects. In vivo , RCR-16 shortened the time to total vessel occlusion with respect to IC [13.4 +/- 1.0 (mean +/- SD) and 17.8 +/- 3.2 minutes, respectively, p<0.001]. Occlusive thrombi lasting for more than one hour were observed in all RCR-16-treated animals, but only in 43% of IC-treated ones. Results with RCR-20 were indistinguishable from those observed with IC. For the first time, a direct relationship between blocking EPCR and thrombosis is demonstrated. Blocking anti-EPCR autoantibodies can predispose to thrombosis episodes and may constitute a new therapeutic target.
authors.affiliation: Division of Cardiovascular Sciences, Centre for Applied Medical Research (CIMA), University of Navarra, Pamplona, Spain.
authors.forename: Miguel N
authors.initials: MN
authors.lastname: Centelles
authors.forename: Cristina
authors.initials: C
authors.lastname: Puy
authors.forename: Jacinto
authors.initials: J
authors.lastname: López-Sagaseta
authors.forename: Kenji
authors.initials: K
authors.lastname: Fukudome
authors.forename: Ramón
authors.initials: R
authors.lastname: Montes
authors.forename: José
authors.initials: J
authors.lastname: Hermida
mesh_terms: D000818:Animals; D019138:Antibodies, Blocking / Q000494:pharmacology*; D000911:Antibodies, Monoclonal / Q000302:isolation & purification / Q000494:pharmacology*; D002339:Carotid Arteries / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D002341:Carotid Artery Thrombosis; D002460:Cell Line; D004195:Disease Models, Animal; D000074283:Endothelial Protein C Receptor; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D005290:Ferric Compounds / Q000378:metabolism; D006023:Glycoproteins / Q000037:antagonists & inhibitors* / Q000276:immunology; D006801:Humans; D051379:Mice; D011485:Protein Binding / Q000187:drug effects; D011486:Protein C / Q000378:metabolism; D011956:Receptors, Cell Surface; D020349:Surface Plasmon Resonance
chemical_list: D019138:Antibodies, Blocking; D000911:Antibodies, Monoclonal; D000074283:Endothelial Protein C Receptor; D005290:Ferric Compounds; D006023:Glycoproteins; C080248:Procr protein, mouse; D011486:Protein C; D011956:Receptors, Cell Surface