title: Accumulation of natural killer cells in ischemic brain tissues and the chemotactic effect of IP-10.
abstract: BACKGROUND
  Stroke is accompanied by a distinguished inflammatory reaction that is initiated by the infiltration of immunocytes, expression of cytokines, and other inflammatory mediators. As natural killer cells (NK cells) are a type of cytotoxic lymphocyte critical to the innate immune system, we investigated the mechanism of NK cells-induced brain injuries after cerebral ischemia and the chemotactic effect of IP-10 simultaneously.
  
  
  METHODS
  NK cells infiltration, interferon-gamma (IFN-γ) and IP-10 expression were detected by immunohistochemistry, immunofluorescence, PCR and flow cytometry in human and C57/BL6 wild type mouse ischemic brain tissues. The ischemia area was detected via 2,3,5-triphenyltetrazolium chloride staining. CXCR3 mean fluorescence intensity of isolated NK cells was measured by flow cytometry. The neuronal injury made by NK cells was examined via apoptosis experiment. The chemotactic of IP-10 was detected by migration and permeability assays.
  
  
  RESULTS
  In human ischemic brain tissue, infiltrations of NK cells were observed and reached a peak at 2 to 5 days. In a permanent middle cerebral artery occlusion (pMCAO) model, infiltration of NK cells into the ischemic infarct region reached their highest levels 12 hours after ischemia. IFN-γ-positive NK cells and levels of the chemokine IP-10 were also detected within the ischemic region, from 6 hours up to 4 days after pMCAO was performed, and IFN-γ levels decreased after NK cells depletion in vivo. Co-culture experiments of neural cells with NK cells also showed that neural necrosis was induced via IFN-γ. In parallel experiments with IP-10, the presence of CXCR3 indicates that NK cells were affected by IP-10 via CXCR3, and the effect was dose-dependent. After IP-10 depletion in vivo, NK cells decreased. In migration assays and permeability experiments, disintegration of the blood-brain barrier (BBB) was observed following the addition of NK cells. Moreover, in the presence of IP-10 this injury was aggravated.
  
  
  CONCLUSIONS
  All findings support the hypothesis that NK cells participate in cerebral ischemia and promote neural cells necrosis via IFN-γ. Moreover, IP-10 intensifies injury to the BBB by NK cells via CXCR3.
authors.forename: Yao
authors.initials: Y
authors.lastname: Zhang
authors.forename: Zhongming
authors.initials: Z
authors.lastname: Gao
authors.forename: Dandan
authors.initials: D
authors.lastname: Wang
authors.forename: Tongshuai
authors.initials: T
authors.lastname: Zhang
authors.forename: Bo
authors.initials: B
authors.lastname: Sun
authors.forename: Lili
authors.initials: L
authors.lastname: Mu
authors.forename: Jinghua
authors.initials: J
authors.lastname: Wang
authors.forename: Yumei
authors.initials: Y
authors.lastname: Liu
authors.forename: Qingfei
authors.initials: Q
authors.lastname: Kong
authors.forename: Xijun
authors.initials: X
authors.lastname: Liu
authors.forename: Yue
authors.initials: Y
authors.lastname: Zhang
authors.forename: Haoqiang
authors.initials: H
authors.lastname: Zhang
authors.forename: Jiqing
authors.initials: J
authors.lastname: He
authors.affiliation: Department of Neurobiology, Harbin Medical University Provincial Key Lab of Neurobiology, Harbin Medical University, Xuefu Road, 150081, Heilongjiang, People's Republic of China. lihulun@aliyun.com.
authors.forename: Hulun
authors.initials: H
authors.lastname: Li
authors.forename: Guangyou
authors.initials: G
authors.lastname: Wang
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D000950:Antigens, Ly / Q000378:metabolism; D017209:Apoptosis / Q000502:physiology; D001812:Blood-Brain Barrier / Q000378:metabolism / Q000473:pathology; D001921:Brain / Q000166:cytology / Q000473:pathology*; D002545:Brain Ischemia / Q000473:pathology*; D002465:Cell Movement / Q000502:physiology; D002478:Cells, Cultured; D054357:Chemokine CXCL10 / Q000378:metabolism*; D004195:Disease Models, Animal; D006801:Humans; D020244:Infarction, Middle Cerebral Artery / Q000473:pathology; D007371:Interferon-gamma / Q000378:metabolism; D007694:Killer Cells, Natural / Q000502:physiology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D055627:Natural Cytotoxicity Triggering Receptor 1 / Q000378:metabolism; D054367:Receptors, CXCR3 / Q000378:metabolism
chemical_list: D000950:Antigens, Ly; D054357:Chemokine CXCL10; C515188:Cxcr3 protein, mouse; D055627:Natural Cytotoxicity Triggering Receptor 1; C118384:Ncr1 protein, mouse; D054367:Receptors, CXCR3; D007371:Interferon-gamma
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