FXa-induced responses in vascular wall cells are PAR-mediated and inhibited by ZK-807834.
During thrombosis, vascular wall cells are exposed to clotting factors, including the procoagulant proteases thrombin and factor Xa (FXa), both known to induce cell signaling. FXa shows dose-dependent induction of intracellular Ca(2+) transients in vascular wall cells that is active-site-dependent, Gla-domain-independent, and enhanced by FXa assembly into the prothrombinase complex. FXa signaling is independent of prothrombin activation as shown by the lack of inhibition by argatroban, hirudin and the sulfated C-terminal peptide of hirudin (Hir(54-65)(SO3(-))). This peptide binds to both proexosite I in prothrombin and exosite I in thrombin. In contrast, signaling is completely blocked by the FXa inhibitor ZK-807834 (CI-1031). No inhibition is observed by peptides which block interaction of FXa with effector cell protease 1 receptor (EPR-1), indicating that this receptor does not mediate signaling in the cells assayed. Receptor desensitization studies with thrombin or peptide agonists (PAR-1 or PAR-2) and experiments with PAR-1-blocking antibodies indicate that signaling by FXa is mediated by both PAR-1 and PAR-2. Potential pathophysiological responses to FXa include increased cell proliferation, increased production of the proinflammatory cytokine IL-6 and increased production of prothrombotic tissue factor. These cellular responses, which may complicate vascular disease, are inhibited by ZK-807834.
McLean
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K
Berlex Biosciences, Richmond, CA 94804, USA. kirk_mclean@berlex.com
Schirm
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Johns
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Morser
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J
Light
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DR
D000578:Amidines / Q000494:pharmacology; D020013:Calcium Signaling / Q000187:drug effects; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects*; D005165:Factor V / Q000494:pharmacology; D015951:Factor Xa / Q000494:pharmacology*; D065427:Factor Xa Inhibitors; D006801:Humans; D051034:Inhibitor of Apoptosis Proteins; D011725:Pyridines / Q000494:pharmacology; D044463:Receptor, PAR-1; D044464:Receptor, PAR-2; D011956:Receptors, Cell Surface; D018179:Receptors, Thrombin / Q000502:physiology*; D015842:Serine Proteinase Inhibitors / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects*; D000077022:Survivin; D013917:Thrombin / Q000494:pharmacology
D000578:Amidines; C107489:BIRC5 protein, human; D065427:Factor Xa Inhibitors; D051034:Inhibitor of Apoptosis Proteins; D011725:Pyridines; D044463:Receptor, PAR-1; D044464:Receptor, PAR-2; D011956:Receptors, Cell Surface; D018179:Receptors, Thrombin; D015842:Serine Proteinase Inhibitors; D000077022:Survivin; C022475:prothrombinase complex; C114592:Fidexaban; D005165:Factor V; D013917:Thrombin; D015951:Factor Xa