title: FTY720 ameliorates acute ischemic stroke in mice by reducing thrombo-inflammation but not by direct neuroprotection.
abstract: OBJECTIVE
  Lymphocytes are important players in the pathophysiology of acute ischemic stroke. The interaction of lymphocytes with endothelial cells and platelets, termed thrombo-inflammation, fosters microvascular dysfunction and secondary infarct growth. FTY720, a sphingosine-1-phosphate receptor modulator, blocks the egress of lymphocytes from lymphoid organs and has been shown to reduce ischemic neurodegeneration; however, the underlying mechanisms are unclear. We investigated the mode of FTY720 action in models of cerebral ischemia.
  
  
  METHODS
  Transient middle cerebral artery occlusion (tMCAO) was induced in wild-type and lymphocyte-deficient Rag1(-/-) mice treated with FTY720 (1 mg/kg) or vehicle immediately before reperfusion. Stroke outcome was assessed 24 hours later. Immune cells in the blood and brain were counted by flow cytometry. The integrity of the blood-brain barrier was analyzed using Evans Blue dye. Thrombus formation was determined by immunohistochemistry and Western blot, and was correlated with cerebral perfusion.
  
  
  RESULTS
  FTY720 significantly reduced stroke size and improved functional outcome in wild-type mice on day 1 and day 3 after transient middle cerebral artery occlusion. This protective effect was lost in lymphocyte-deficient Rag1(-/-) mice and in cultured neurons subjected to hypoxia. Less lymphocytes were present in the cerebral vasculature of FTY720-treated wild-type mice, which in turn reduced thrombosis and increased cerebral perfusion. In contrast, FTY720 was unable to prevent blood-brain barrier breakdown and transendothelial immune cell trafficking after transient middle cerebral artery occlusion.
  
  
  CONCLUSIONS
  Induction of lymphocytopenia and concomitant reduction of microvascular thrombosis are key modes of FTY720 action in stroke. In contrast, our findings in Rag1(-/-) mice and cultured neurons argue against direct neuroprotective effects of FTY720.
authors.affiliation: From the University Clinic Würzburg, Departments of Neurology (P.K., E.G., M.K.S., G.S., C.K.) and Anesthesiology and Critical Care (M.B.), Rudolf Virchow Center, the Deutsche Forschungsgemeinschaft Research Center for Experimental Biomedicine (C.D., I.T., B.N.), Institute of Pharmacology and Toxicology, University of Würzburg (K.L.), Würzburg, Germany; Department of Neurology (K.G., A.M.H., S.G.M.), Institute of Physiology and Neuropathophysiology (S.G.M.), University of Münster, Germany; and University Clinic Frankfurt, Department of Neurology, Frankfurt, Germany (W.P.).
authors.forename: Peter
authors.initials: P
authors.lastname: Kraft
authors.forename: Eva
authors.initials: E
authors.lastname: Göb
authors.forename: Michael K
authors.initials: MK
authors.lastname: Schuhmann
authors.forename: Kerstin
authors.initials: K
authors.lastname: Göbel
authors.forename: Carsten
authors.initials: C
authors.lastname: Deppermann
authors.forename: Ina
authors.initials: I
authors.lastname: Thielmann
authors.forename: Alexander M
authors.initials: AM
authors.lastname: Herrmann
authors.forename: Kristina
authors.initials: K
authors.lastname: Lorenz
authors.forename: Marc
authors.initials: M
authors.lastname: Brede
authors.forename: Guido
authors.initials: G
authors.lastname: Stoll
authors.forename: Sven G
authors.initials: SG
authors.lastname: Meuth
authors.forename: Bernhard
authors.initials: B
authors.lastname: Nieswandt
authors.forename: Waltraud
authors.initials: W
authors.lastname: Pfeilschifter
authors.forename: Christoph
authors.initials: C
authors.lastname: Kleinschnitz
mesh_terms: D000818:Animals; D002545:Brain Ischemia / Q000628:therapy*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D000068876:Fingolimod Hydrochloride; D018398:Homeodomain Proteins / Q000235:genetics; D000860:Hypoxia; D007166:Immunosuppressive Agents / Q000494:pharmacology*; D007249:Inflammation / Q000628:therapy*; D008214:Lymphocytes / Q000187:drug effects; D008231:Lymphopenia / Q000473:pathology; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D020768:Middle Cerebral Artery / Q000473:pathology; D009474:Neurons / Q000473:pathology; D018696:Neuroprotective Agents / Q000627:therapeutic use; D011409:Propylene Glycols / Q000494:pharmacology*; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D020521:Stroke / Q000628:therapy*; D013927:Thrombosis / Q000628:therapy*
chemical_list: D004791:Enzyme Inhibitors; D018398:Homeodomain Proteins; D007166:Immunosuppressive Agents; D018696:Neuroprotective Agents; D011409:Propylene Glycols; C064658:RAG-1 protein; D000068876:Fingolimod Hydrochloride; D013110:Sphingosine
keywords: FTY720; MCAO; inflammation; ischemic stroke; microvascular dysfunction; thrombo-inflammation