title: Activated factor X signaling via protease-activated receptor 2 suppresses pro-inflammatory cytokine production from lipopolysaccharide-stimulated myeloid cells.
abstract: Vitamin K-dependent proteases generated in response to vascular injury and infection enable fibrin clot formation, but also trigger distinct immuno-regulatory signaling pathways on myeloid cells. Factor Xa, a protease crucial for blood coagulation, also induces protease-activated, receptor-dependent cell signaling. Factor Xa can bind both monocytes and macrophages, but whether factor Xa-dependent signaling stimulates or suppresses myeloid cell cytokine production in response to Toll-like receptor activation is not known. In this study, exposure to factor Xa significantly impaired pro-inflammatory cytokine production from lipopolysaccharide-treated peripheral blood mononuclear cells, THP-1 monocytic cells and murine macrophages. Furthermore, factor Xa inhibited nuclear factor-kappa B activation in THP-1 reporter cells, requiring phosphatidylinositide 3-kinase activity for its anti-inflammatory effect. Active-site blockade, γ-carboxyglutamic acid domain truncation and a peptide mimic of the factor Xa inter-epidermal growth factor-like region prevented factor Xa inhibition of lipopolysaccharide-induced tumor necrosis factor-α release. In addition, factor Xa anti-inflammatory activity was markedly attenuated by the presence of an antagonist of protease-activated receptor 2, but not protease-activated receptor 1. The key role of protease-activated receptor 2 in eliciting factor Xa-dependent anti-inflammatory signaling on macrophages was further underscored by the inability of factor Xa to mediate inhibition of tumor necrosis factor-α and interleukin-6 release from murine bone marrow-derived protease-activated receptor 2-deficient macrophages. We also show for the first time that, in addition to protease-activated receptor 2, factor Xa requires a receptor-associated protein-sensitive low-density lipoprotein receptor to inhibit lipopolysaccharide-induced cytokine production. Collectively, the findings of this study support a novel function for factor Xa as an endogenous, receptor-associated protein-sensitive, protease-activated receptor 2-dependent regulator of myeloid cell pro-inflammatory cytokine production.
authors.affiliation: prestonr@tcd.ie.
authors.forename: Eimear M
authors.initials: EM
authors.lastname: Gleeson
authors.forename: James S
authors.initials: JS
authors.lastname: O'Donnell
authors.forename: Emily
authors.initials: E
authors.lastname: Hams
authors.forename: Fionnuala
authors.initials: F
authors.lastname: Ní Áinle
authors.forename: Bridget-Ann
authors.initials: BA
authors.lastname: Kenny
authors.forename: Padraic G
authors.initials: PG
authors.lastname: Fallon
authors.forename: Roger J S
authors.initials: RJ
authors.lastname: Preston
mesh_terms: D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D002460:Cell Line; D016207:Cytokines / Q000096:biosynthesis*; D004789:Enzyme Activation / Q000187:drug effects; D015951:Factor Xa / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D018836:Inflammation Mediators / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000276:immunology; D008264:Macrophages / Q000276:immunology / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D022423:Myeloid Cells / Q000276:immunology / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism; D054730:Protein Interaction Domains and Motifs; D044464:Receptor, PAR-2 / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D000077191:Wortmannin
chemical_list: D000730:Androstadienes; D016207:Cytokines; D018836:Inflammation Mediators; D008070:Lipopolysaccharides; D016328:NF-kappa B; D044464:Receptor, PAR-2; D015951:Factor Xa; D000077191:Wortmannin