title: Brain pericytes among cells constituting the blood-brain barrier are highly sensitive to tumor necrosis factor-α, releasing matrix metalloproteinase-9 and migrating in vitro.
abstract: BACKGROUND
  Increased matrix metalloproteinase (MMP)-9 in the plasma and brain is associated with blood-brain barrier (BBB) disruption through proteolytic activity in neuroinflammatory diseases. MMP-9 is present in the brain microvasculature and its vicinity, where brain microvascular endothelial cells (BMECs), pericytes and astrocytes constitute the BBB. Little is known about the cellular source and role of MMP-9 at the BBB. Here, we examined the ability of pericytes to release MMP-9 and migrate in response to inflammatory mediators in comparison with BMECs and astrocytes, using primary cultures isolated from rat brains.
  
  
  METHODS
  The culture supernatants were collected from primary cultures of rat brain endothelial cells, pericytes, or astrocytes. MMP-9 activities and levels in the supernatants were measured by gelatin zymography and western blot, respectively. The involvement of signaling molecules including mitogen-activated protein kinases (MAPKs) and phosphoinositide-3-kinase (PI3K)/Akt in the mediation of tumor necrosis factor (TNF)-α-induced MMP-9 release was examined using specific inhibitors. The functional activity of MMP-9 was evaluated by a cell migration assay.
  
  
  RESULTS
  Zymographic and western blot analyses demonstrated that TNF-α stimulated pericytes to release MMP-9, and this release was much higher than from BMECs or astrocytes. Other inflammatory mediators [interleukin (IL)-1β, interferon-γ, IL-6 and lipopolysaccharide] failed to induce MMP-9 release from pericytes. TNF-α-induced MMP-9 release from pericytes was found to be mediated by MAPKs and PI3K. Scratch wound healing assay showed that in contrast to BMECs and astrocytes the extent of pericyte migration was significantly increased by TNF-α. This pericyte migration was inhibited by anti-MMP-9 antibody.
  
  
  CONCLUSIONS
  These findings suggest that pericytes are most sensitive to TNF-α in terms of MMP-9 release, and are the major source of MMP-9 at the BBB. This pericyte-derived MMP-9 initiated cellular migration of pericytes, which might be involved in pericyte loss in the damaged BBB.
authors.affiliation: Department of Pharmaceutical Care and Health Sciences, Faculty of Pharmaceutical Sciences, Fukuoka University, Fukuoka, Japan.
authors.forename: Fuyuko
authors.initials: F
authors.lastname: Takata
authors.forename: Shinya
authors.initials: S
authors.lastname: Dohgu
authors.forename: Junichi
authors.initials: J
authors.lastname: Matsumoto
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Takahashi
authors.forename: Takashi
authors.initials: T
authors.lastname: Machida
authors.forename: Tomoya
authors.initials: T
authors.lastname: Wakigawa
authors.forename: Eriko
authors.initials: E
authors.lastname: Harada
authors.forename: Haruki
authors.initials: H
authors.lastname: Miyaji
authors.forename: Mitsuhisa
authors.initials: M
authors.lastname: Koga
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Nishioku
authors.forename: Atsushi
authors.initials: A
authors.lastname: Yamauchi
authors.forename: Yasufumi
authors.initials: Y
authors.lastname: Kataoka
mesh_terms: D000818:Animals; D001812:Blood-Brain Barrier / Q000166:cytology* / Q000378:metabolism*; D002465:Cell Movement / Q000502:physiology*; D002478:Cells, Cultured; D003470:Culture Media / Q000737:chemistry; D004791:Enzyme Inhibitors / Q000378:metabolism; D020935:MAP Kinase Signaling System / Q000502:physiology; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D020286:Pericytes / Q000166:cytology / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051381:Rats; D017208:Rats, Wistar; D047888:Receptors, Tumor Necrosis Factor, Type I / Q000378:metabolism; D047889:Receptors, Tumor Necrosis Factor, Type II / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*
chemical_list: D003470:Culture Media; D004791:Enzyme Inhibitors; D020780:Matrix Metalloproteinase 9; D020928:Mitogen-Activated Protein Kinases; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D047888:Receptors, Tumor Necrosis Factor, Type I; D047889:Receptors, Tumor Necrosis Factor, Type II; D014409:Tumor Necrosis Factor-alpha