title: CXCR2 is essential for cerebral endothelial activation and leukocyte recruitment during neuroinflammation.
abstract: BACKGROUND
  Chemokines and chemokine receptors cooperate to promote immune cell recruitment to the central nervous system (CNS). In this study, we investigated the roles of CXCR2 and CXCL1 in leukocyte recruitment to the CNS using a murine model of neuroinflammation.
  
  
  METHODS
  Wild-type (WT), CXCL1(-/-), and CXCR2(-/-) mice each received an intracerebroventricular (i.c.v.) injection of lipopolysaccharide (LPS). Esterase staining and intravital microscopy were performed to examine neutrophil recruitment to the brain. To assess endothelial activation in these mice, the expression of adhesion molecules was measured via quantitative real-time polymerase chain reaction (PCR) and Western blotting. To identify the cellular source of functional CXCR2, chimeric mice were generated by transferring bone marrow cells between the WT and CXCR2(-/-) mice.
  
  
  RESULTS
  Expression levels of the chemokines CXCL1, CXCL2, and CXCL5 were significantly increased in the brain following the i.c.v. injection of LPS. CXCR2 or CXCL1 deficiency blocked neutrophil infiltration and leukocyte recruitment in the cerebral microvessels. In the CXCR2(-/-) and CXCL1(-/-) mice, the cerebral endothelial expression of adhesion molecules such as P-selectin and VCAM-1 was dramatically reduced. Furthermore, the bone marrow transfer experiments demonstrated that CXCR2 expression on CNS-residing cells is essential for cerebral endothelial activation and leukocyte recruitment. Compared with microglia, cultured astrocytes secreted a much higher level of CXCL1 in vitro. Astrocyte culture conditioned medium significantly increased the expression of VCAM-1 and ICAM-1 in cerebral endothelial cells in a CXCR2-dependent manner. Additionally, CXCR2 messenger RNA (mRNA) expression in cerebral endothelial cells but not in microglia or astrocytes was increased following tumor necrosis factor-α (TNF-α) stimulation. The intravenous injection of the CXCR2 antagonist SB225002 significantly inhibited endothelial activation and leukocyte recruitment to cerebral microvessels.
  
  
  CONCLUSIONS
  CXCL1 secreted by astrocytes and endothelial CXCR2 play essential roles in cerebral endothelial activation and subsequent leukocyte recruitment during neuroinflammation.
authors.affiliation: Department of Immunology, Nanjing Medical University, 140 Hanzhong Road, Nanjing, JS, 210029, China. 124914924@qq.com.
authors.forename: Fengjiao
authors.initials: F
authors.lastname: Wu
authors.affiliation: Department of Immunology, Nanjing Medical University, 140 Hanzhong Road, Nanjing, JS, 210029, China. yawei_zhao@163.com.
authors.forename: Yawei
authors.initials: Y
authors.lastname: Zhao
authors.affiliation: Department of Immunology, Nanjing Medical University, 140 Hanzhong Road, Nanjing, JS, 210029, China. kisakiyuri@126.com.
authors.forename: Tian
authors.initials: T
authors.lastname: Jiao
authors.affiliation: Department of Immunology, Nanjing Medical University, 140 Hanzhong Road, Nanjing, JS, 210029, China. shidongyan1984@hotmail.com.
authors.forename: Dongyan
authors.initials: D
authors.lastname: Shi
authors.affiliation: Department of Immunology, Nanjing Medical University, 140 Hanzhong Road, Nanjing, JS, 210029, China. 809418148@qq.com.
authors.forename: Xingxing
authors.initials: X
authors.lastname: Zhu
authors.affiliation: Department of Immunology, Nanjing Medical University, 140 Hanzhong Road, Nanjing, JS, 210029, China. mingshunzhang@njmu.edu.cn.
authors.forename: Mingshun
authors.initials: M
authors.lastname: Zhang
authors.affiliation: Division of Immunology, Virginia-Maryland College of Veterinary Medicine, University of Maryland, College Park, Maryland, MD, 20742, USA. mshi@umd.edu.
authors.forename: Meiqing
authors.initials: M
authors.lastname: Shi
authors.affiliation: Department of Immunology, Nanjing Medical University, 140 Hanzhong Road, Nanjing, JS, 210029, China. hzhou@njmu.edu.cn.
authors.forename: Hong
authors.initials: H
authors.lastname: Zhou
mesh_terms: D000418:Albumins / Q000378:metabolism; D000818:Animals; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured; D054360:Chemokine CXCL1 / Q000172:deficiency / Q000235:genetics; D054365:Chemokine CXCL5 / Q000378:metabolism; D016207:Cytokines / Q000378:metabolism; D004195:Disease Models, Animal; D004660:Encephalitis / Q000139:chemically induced / Q000473:pathology*; D004727:Endothelium / Q000187:drug effects / Q000378:metabolism*; D018799:Intercellular Adhesion Molecule-1 / Q000378:metabolism; D007962:Leukocytes / Q000187:drug effects / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000633:toxicity; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D017628:Microglia / Q000187:drug effects / Q000378:metabolism; D010671:Phenylurea Compounds / Q000494:pharmacology; D023063:Receptors, Interleukin-8B / Q000235:genetics / Q000378:metabolism*; D019010:Vascular Cell Adhesion Molecule-1 / Q000378:metabolism
chemical_list: D000418:Albumins; D054360:Chemokine CXCL1; D054365:Chemokine CXCL5; C475895:Cxcl1 protein, mouse; C094739:Cxcl5 protein, mouse; D016207:Cytokines; D008070:Lipopolysaccharides; D010671:Phenylurea Compounds; D023063:Receptors, Interleukin-8B; C112019:SB 225002; D019010:Vascular Cell Adhesion Molecule-1; D018799:Intercellular Adhesion Molecule-1