title: Extracellular cyclophilin A activates platelets via EMMPRIN (CD147) and PI3K/Akt signaling, which promotes platelet adhesion and thrombus formation in vitro and in vivo.
abstract: OBJECTIVE
  Cyclophilin A (CyPA) is secreted under inflammatory conditions by various cell types. Whereas the important role of intracellular CyPA for platelet function has been reported, the effect of extracellular CyPA on platelet function has not been investigated yet.
  
  
  RESULTS
  Inhibition of extracellular CyPA through a novel specific inhibitor MM284 reduced thrombus after ferric chloride-induced injury in vivo. In vitro extracellular CyPA enhanced thrombus formation even in CyPA(-/-) platelets. Treatment of isolated platelets with recombinant CyPA resulted in platelet degranulation in a time- and dose-dependent manner. Inhibition of the platelet surface receptor extracellular matrix metalloproteinase inducer (cluster of differentiation 147) by an anticluster of differentiation 147 monoclonal antibody significantly reduced CyPA-dependent platelet degranulation. Pretreatment of platelets with CyPA enhanced their recruitment to mouse carotid arteries after arterial injury, which could be inhibited by an anticluster of differentiation 147 monoclonal antibody (intravital microscopy). The role of extracellular CyPA in adhesion could be confirmed by infusing CyPA(-/-) platelets in CyPA(+/+) mice and by infusing CyPA(+/+) platelets in CyPA(-/-) mice. Stimulation of platelets with CyPA induced phosphorylation of Akt, which could in turn be inhibited in the presence of phosphoinositid-3-kinase inhibitors. Akt-1(-/-) platelets revealed a markedly decreased degranulation on CyPA stimulation. Finally, ADP-induced platelet aggregation was attenuated by MM284, as well as by inhibiting paracrine-secreted CyPA without directly affecting Ca(2+)-signaling.
  
  
  CONCLUSIONS
  Extracellular CyPA activates platelets via cluster of differentiation 147-mediated phosphoinositid-3-kinase/Akt-signaling, leading to enhanced adhesion and thrombus formation independently of intracellular CyPA. Targeting extracellular CyPA via a specific inhibitor may be a promising strategy for platelet inhibition without affecting critical functions of intracellular CyPA.
authors.affiliation: From the Medizinische Klinik III, Kardiologie und Kreislauferkrankungen (P.S., S.N.I.v.U.-S., T.S., O.B., D.H., M.C., H.L., M.G., A.E.M.), Institute of Physiology (P.M., E.-M.S., F.L.), and Institute of Anatomy (A.F.M.), Eberhard Karls-University Tübingen, Tübingen, Germany; Institute of Biochemistry, Abteilung Enzymology, Martin-Luther-University Halle-Wittenberg, Halle, Germany (M.M.); and Max-Planck-Institute für Biophysikalische Chemie Göttingen, BO Halle (Saale), Germany (G.F.). peter.seizer@med.uni-tuebingen.de.
authors.forename: Peter
authors.initials: P
authors.lastname: Seizer
authors.affiliation: From the Medizinische Klinik III, Kardiologie und Kreislauferkrankungen (P.S., S.N.I.v.U.-S., T.S., O.B., D.H., M.C., H.L., M.G., A.E.M.), Institute of Physiology (P.M., E.-M.S., F.L.), and Institute of Anatomy (A.F.M.), Eberhard Karls-University Tübingen, Tübingen, Germany; Institute of Biochemistry, Abteilung Enzymology, Martin-Luther-University Halle-Wittenberg, Halle, Germany (M.M.); and Max-Planck-Institute für Biophysikalische Chemie Göttingen, BO Halle (Saale), Germany (G.F.).
authors.forename: Saskia N I V
authors.initials: SN
authors.lastname: Ungern-Sternberg
authors.affiliation: From the Medizinische Klinik III, Kardiologie und Kreislauferkrankungen (P.S., S.N.I.v.U.-S., T.S., O.B., D.H., M.C., H.L., M.G., A.E.M.), Institute of Physiology (P.M., E.-M.S., F.L.), and Institute of Anatomy (A.F.M.), Eberhard Karls-University Tübingen, Tübingen, Germany; Institute of Biochemistry, Abteilung Enzymology, Martin-Luther-University Halle-Wittenberg, Halle, Germany (M.M.); and Max-Planck-Institute für Biophysikalische Chemie Göttingen, BO Halle (Saale), Germany (G.F.).
authors.forename: Tanja
authors.initials: T
authors.lastname: Schönberger
authors.affiliation: From the Medizinische Klinik III, Kardiologie und Kreislauferkrankungen (P.S., S.N.I.v.U.-S., T.S., O.B., D.H., M.C., H.L., M.G., A.E.M.), Institute of Physiology (P.M., E.-M.S., F.L.), and Institute of Anatomy (A.F.M.), Eberhard Karls-University Tübingen, Tübingen, Germany; Institute of Biochemistry, Abteilung Enzymology, Martin-Luther-University Halle-Wittenberg, Halle, Germany (M.M.); and Max-Planck-Institute für Biophysikalische Chemie Göttingen, BO Halle (Saale), Germany (G.F.).
authors.forename: Oliver
authors.initials: O
authors.lastname: Borst
authors.affiliation: From the Medizinische Klinik III, Kardiologie und Kreislauferkrankungen (P.S., S.N.I.v.U.-S., T.S., O.B., D.H., M.C., H.L., M.G., A.E.M.), Institute of Physiology (P.M., E.-M.S., F.L.), and Institute of Anatomy (A.F.M.), Eberhard Karls-University Tübingen, Tübingen, Germany; Institute of Biochemistry, Abteilung Enzymology, Martin-Luther-University Halle-Wittenberg, Halle, Germany (M.M.); and Max-Planck-Institute für Biophysikalische Chemie Göttingen, BO Halle (Saale), Germany (G.F.).
authors.forename: Patrick
authors.initials: P
authors.lastname: Münzer
authors.affiliation: From the Medizinische Klinik III, Kardiologie und Kreislauferkrankungen (P.S., S.N.I.v.U.-S., T.S., O.B., D.H., M.C., H.L., M.G., A.E.M.), Institute of Physiology (P.M., E.-M.S., F.L.), and Institute of Anatomy (A.F.M.), Eberhard Karls-University Tübingen, Tübingen, Germany; Institute of Biochemistry, Abteilung Enzymology, Martin-Luther-University Halle-Wittenberg, Halle, Germany (M.M.); and Max-Planck-Institute für Biophysikalische Chemie Göttingen, BO Halle (Saale), Germany (G.F.).
authors.forename: Eva-Maria
authors.initials: EM
authors.lastname: Schmidt
authors.affiliation: From the Medizinische Klinik III, Kardiologie und Kreislauferkrankungen (P.S., S.N.I.v.U.-S., T.S., O.B., D.H., M.C., H.L., M.G., A.E.M.), Institute of Physiology (P.M., E.-M.S., F.L.), and Institute of Anatomy (A.F.M.), Eberhard Karls-University Tübingen, Tübingen, Germany; Institute of Biochemistry, Abteilung Enzymology, Martin-Luther-University Halle-Wittenberg, Halle, Germany (M.M.); and Max-Planck-Institute für Biophysikalische Chemie Göttingen, BO Halle (Saale), Germany (G.F.).
authors.forename: Andreas F
authors.initials: AF
authors.lastname: Mack
authors.affiliation: From the Medizinische Klinik III, Kardiologie und Kreislauferkrankungen (P.S., S.N.I.v.U.-S., T.S., O.B., D.H., M.C., H.L., M.G., A.E.M.), Institute of Physiology (P.M., E.-M.S., F.L.), and Institute of Anatomy (A.F.M.), Eberhard Karls-University Tübingen, Tübingen, Germany; Institute of Biochemistry, Abteilung Enzymology, Martin-Luther-University Halle-Wittenberg, Halle, Germany (M.M.); and Max-Planck-Institute für Biophysikalische Chemie Göttingen, BO Halle (Saale), Germany (G.F.).
authors.forename: David
authors.initials: D
authors.lastname: Heinzmann
authors.affiliation: From the Medizinische Klinik III, Kardiologie und Kreislauferkrankungen (P.S., S.N.I.v.U.-S., T.S., O.B., D.H., M.C., H.L., M.G., A.E.M.), Institute of Physiology (P.M., E.-M.S., F.L.), and Institute of Anatomy (A.F.M.), Eberhard Karls-University Tübingen, Tübingen, Germany; Institute of Biochemistry, Abteilung Enzymology, Martin-Luther-University Halle-Wittenberg, Halle, Germany (M.M.); and Max-Planck-Institute für Biophysikalische Chemie Göttingen, BO Halle (Saale), Germany (G.F.).
authors.forename: Madhumita
authors.initials: M
authors.lastname: Chatterjee
authors.affiliation: From the Medizinische Klinik III, Kardiologie und Kreislauferkrankungen (P.S., S.N.I.v.U.-S., T.S., O.B., D.H., M.C., H.L., M.G., A.E.M.), Institute of Physiology (P.M., E.-M.S., F.L.), and Institute of Anatomy (A.F.M.), Eberhard Karls-University Tübingen, Tübingen, Germany; Institute of Biochemistry, Abteilung Enzymology, Martin-Luther-University Halle-Wittenberg, Halle, Germany (M.M.); and Max-Planck-Institute für Biophysikalische Chemie Göttingen, BO Halle (Saale), Germany (G.F.).
authors.forename: Harald
authors.initials: H
authors.lastname: Langer
authors.affiliation: From the Medizinische Klinik III, Kardiologie und Kreislauferkrankungen (P.S., S.N.I.v.U.-S., T.S., O.B., D.H., M.C., H.L., M.G., A.E.M.), Institute of Physiology (P.M., E.-M.S., F.L.), and Institute of Anatomy (A.F.M.), Eberhard Karls-University Tübingen, Tübingen, Germany; Institute of Biochemistry, Abteilung Enzymology, Martin-Luther-University Halle-Wittenberg, Halle, Germany (M.M.); and Max-Planck-Institute für Biophysikalische Chemie Göttingen, BO Halle (Saale), Germany (G.F.).
authors.forename: Miroslav
authors.initials: M
authors.lastname: Malešević
authors.affiliation: From the Medizinische Klinik III, Kardiologie und Kreislauferkrankungen (P.S., S.N.I.v.U.-S., T.S., O.B., D.H., M.C., H.L., M.G., A.E.M.), Institute of Physiology (P.M., E.-M.S., F.L.), and Institute of Anatomy (A.F.M.), Eberhard Karls-University Tübingen, Tübingen, Germany; Institute of Biochemistry, Abteilung Enzymology, Martin-Luther-University Halle-Wittenberg, Halle, Germany (M.M.); and Max-Planck-Institute für Biophysikalische Chemie Göttingen, BO Halle (Saale), Germany (G.F.).
authors.forename: Florian
authors.initials: F
authors.lastname: Lang
authors.affiliation: From the Medizinische Klinik III, Kardiologie und Kreislauferkrankungen (P.S., S.N.I.v.U.-S., T.S., O.B., D.H., M.C., H.L., M.G., A.E.M.), Institute of Physiology (P.M., E.-M.S., F.L.), and Institute of Anatomy (A.F.M.), Eberhard Karls-University Tübingen, Tübingen, Germany; Institute of Biochemistry, Abteilung Enzymology, Martin-Luther-University Halle-Wittenberg, Halle, Germany (M.M.); and Max-Planck-Institute für Biophysikalische Chemie Göttingen, BO Halle (Saale), Germany (G.F.).
authors.forename: Meinrad
authors.initials: M
authors.lastname: Gawaz
authors.affiliation: From the Medizinische Klinik III, Kardiologie und Kreislauferkrankungen (P.S., S.N.I.v.U.-S., T.S., O.B., D.H., M.C., H.L., M.G., A.E.M.), Institute of Physiology (P.M., E.-M.S., F.L.), and Institute of Anatomy (A.F.M.), Eberhard Karls-University Tübingen, Tübingen, Germany; Institute of Biochemistry, Abteilung Enzymology, Martin-Luther-University Halle-Wittenberg, Halle, Germany (M.M.); and Max-Planck-Institute für Biophysikalische Chemie Göttingen, BO Halle (Saale), Germany (G.F.).
authors.forename: Gunter
authors.initials: G
authors.lastname: Fischer
authors.affiliation: From the Medizinische Klinik III, Kardiologie und Kreislauferkrankungen (P.S., S.N.I.v.U.-S., T.S., O.B., D.H., M.C., H.L., M.G., A.E.M.), Institute of Physiology (P.M., E.-M.S., F.L.), and Institute of Anatomy (A.F.M.), Eberhard Karls-University Tübingen, Tübingen, Germany; Institute of Biochemistry, Abteilung Enzymology, Martin-Luther-University Halle-Wittenberg, Halle, Germany (M.M.); and Max-Planck-Institute für Biophysikalische Chemie Göttingen, BO Halle (Saale), Germany (G.F.).
authors.forename: Andreas E
authors.initials: AE
authors.lastname: May
mesh_terms: D000818:Animals; D051926:Basigin / Q000097:blood*; D001792:Blood Platelets / Q000187:drug effects / Q000201:enzymology*; D020212:Carotid Artery Injuries / Q000097:blood / Q000201:enzymology / Q000235:genetics; D015550:Cell Degranulation / Q000187:drug effects; D002712:Chlorides; D021984:Cyclophilin A / Q000037:antagonists & inhibitors / Q000097:blood* / Q000235:genetics; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D005290:Ferric Compounds; D005343:Fibrinolytic Agents / Q000494:pharmacology; D006801:Humans; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D019869:Phosphatidylinositol 3-Kinases / Q000097:blood*; D010973:Platelet Adhesiveness / Q000187:drug effects; D010974:Platelet Aggregation / Q000187:drug effects; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D051057:Proto-Oncogene Proteins c-akt / Q000097:blood* / Q000172:deficiency / Q000235:genetics; D015398:Signal Transduction / Q000187:drug effects; D013927:Thrombosis / Q000097:blood / Q000139:chemically induced / Q000201:enzymology* / Q000235:genetics / Q000517:prevention & control; D013997:Time Factors
chemical_list: C497886:BSG protein, human; C497887:Bsg protein, mouse; D002712:Chlorides; D005290:Ferric Compounds; D005343:Fibrinolytic Agents; D010975:Platelet Aggregation Inhibitors; D051926:Basigin; D019869:Phosphatidylinositol 3-Kinases; C514862:Akt1 protein, mouse; D051057:Proto-Oncogene Proteins c-akt; D021984:Cyclophilin A; C024555:ferric chloride
keywords: antigens, CD147; blood platelets; cyclophilin A