title: Evidence That Ly6C(hi) Monocytes are Protective in Acute Ischemic Stroke by Promoting M2 Macrophage Polarization.
abstract: OBJECTIVE
  Ly6C(hi) monocytes are generally thought to exert a proinflammatory role in acute tissue injury, although their impact after injuries to the central nervous system is poorly defined. CC chemokine receptor 2 is expressed on Ly6C(hi) monocytes and plays an essential role in their extravasation and transmigration into the brain after cerebral ischemia. We used a selective CC chemokine receptor 2 antagonist, INCB3344, to assess the effect of Ly6C(hi) monocytes recruited into the brain early after ischemic stroke.
  
  
  METHODS
  Male C57Bl/6J mice underwent occlusion of the middle cerebral artery for 1 hour followed by 23 hours of reperfusion. Mice were administered either vehicle (dimethyl sulfoxide/carboxymethylcellulose) or INCB3344 (10, 30 or 100 mg/kg IP) 1 hour before ischemia and at 2 and 6 hours after ischemia. At 24 hours, we assessed functional outcomes, infarct volume, and quantified the immune cells in blood and brain by flow cytometry or immunofluorescence. Gene expression of selected inflammatory markers was assessed by quantitative polymerase chain reaction.
  
  
  RESULTS
  Ly6C(hi) monocytes were increased 3-fold in the blood and 10-fold in the brain after stroke, and these increases were selectively prevented by INCB3344 in a dose-dependent manner. Mice treated with INCB3344 exhibited markedly worse functional outcomes and larger infarct volumes, in association with reduced M2 polarization and increased peroxynitrite production in macrophages, compared with vehicle-treated mice.
  
  
  CONCLUSIONS
  Our data suggest that Ly6C(hi) monocytes exert an acute protective effect after ischemic stroke to limit brain injury and functional deficit that involves promotion of M2 macrophage polarization.
authors.affiliation: From the Vascular Biology and Immunopharmacology Group, Department of Pharmacology (H.X.C., B.R.S.B., H.A.K., S.L., G.R.D., C.G.S.) and Vascular Biology and Immunopharmacology Group, Department of Surgery, Southern Clinical School (G.R.D., C.G.S.), Monash University, Clayton, Victoria, Australia.
authors.forename: Hannah X
authors.initials: HX
authors.lastname: Chu
authors.affiliation: From the Vascular Biology and Immunopharmacology Group, Department of Pharmacology (H.X.C., B.R.S.B., H.A.K., S.L., G.R.D., C.G.S.) and Vascular Biology and Immunopharmacology Group, Department of Surgery, Southern Clinical School (G.R.D., C.G.S.), Monash University, Clayton, Victoria, Australia.
authors.forename: Brad R S
authors.initials: BR
authors.lastname: Broughton
authors.affiliation: From the Vascular Biology and Immunopharmacology Group, Department of Pharmacology (H.X.C., B.R.S.B., H.A.K., S.L., G.R.D., C.G.S.) and Vascular Biology and Immunopharmacology Group, Department of Surgery, Southern Clinical School (G.R.D., C.G.S.), Monash University, Clayton, Victoria, Australia.
authors.forename: Hyun Ah
authors.initials: HA
authors.lastname: Kim
authors.affiliation: From the Vascular Biology and Immunopharmacology Group, Department of Pharmacology (H.X.C., B.R.S.B., H.A.K., S.L., G.R.D., C.G.S.) and Vascular Biology and Immunopharmacology Group, Department of Surgery, Southern Clinical School (G.R.D., C.G.S.), Monash University, Clayton, Victoria, Australia.
authors.forename: Seyoung
authors.initials: S
authors.lastname: Lee
authors.affiliation: From the Vascular Biology and Immunopharmacology Group, Department of Pharmacology (H.X.C., B.R.S.B., H.A.K., S.L., G.R.D., C.G.S.) and Vascular Biology and Immunopharmacology Group, Department of Surgery, Southern Clinical School (G.R.D., C.G.S.), Monash University, Clayton, Victoria, Australia.
authors.forename: Grant R
authors.initials: GR
authors.lastname: Drummond
authors.affiliation: From the Vascular Biology and Immunopharmacology Group, Department of Pharmacology (H.X.C., B.R.S.B., H.A.K., S.L., G.R.D., C.G.S.) and Vascular Biology and Immunopharmacology Group, Department of Surgery, Southern Clinical School (G.R.D., C.G.S.), Monash University, Clayton, Victoria, Australia. chris.sobey@monash.edu.
authors.forename: Christopher G
authors.initials: CG
authors.lastname: Sobey
mesh_terms: D000818:Animals; D000950:Antigens, Ly / Q000378:metabolism*; D002545:Brain Ischemia / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D016764:Cell Polarity / Q000187:drug effects / Q000502:physiology*; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009000:Monocytes / Q000187:drug effects / Q000378:metabolism*; D011759:Pyrrolidines / Q000494:pharmacology / Q000627:therapeutic use; D011897:Random Allocation; D054390:Receptors, CCR2 / Q000037:antagonists & inhibitors / Q000378:metabolism; D020521:Stroke / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology
chemical_list: D000950:Antigens, Ly; C515335:Ccr2 protein, mouse; C505875:INCB3344; C494192:Ly-6C antigen, mouse; D011759:Pyrrolidines; D054390:Receptors, CCR2
keywords: ischemia; monocytes; receptors, CCR2; stroke