title: Hypoxia Potentiates LPS-Mediated Cytotoxicity of BV2 Microglial Cells In Vitro by Synergistic Effects on Glial Cytokine and Nitric Oxide System.
abstract: BACKGROUND
  Microglial activation due to a variety of stimuli induces secretion of neurotoxic substances including inflammatory cytokines and nitric oxide (NO). Clinical studies indicate a cross-link between inflammatory and hypoxia-regulated pathways suggesting that bacterial infections markedly sensitize the immature brain to hypoxic injury.
  
  
  METHODS
  The impact of inflammation and hypoxia on interleukin (IL)-1β, IL-6, tumor necrosis factor α (TNF-α), and NO secretion and microglia-induced cytotoxicity was investigated exposing BV2 cells to lipopolysaccharides (LPS) and hypoxia (1% O2). Cytotoxicity, NO, and cytokine release was quantified by MTS and Griess assays and by enzyme-linked immunosorbent assays, respectively.
  
  
  RESULTS
  LPS exposure of BV2 cells induced a significant, persistent production of NO, IL-1β, IL-6, and TNF-α. Even after LPS removal, ongoing NO and cytokine secretion was observed. Hypoxia mediated exclusively a significant, short-term IL-1β increase, but enhanced LPS-induced cytokine and NO secretion significantly. In addition, LPS-induced supernatants exhibited a stronger cytotoxic effect in glial and neuronal cells than LPS exposition (p < 0.001). Hypoxia potentiated LPS-induced cytotoxicity.
  
  
  CONCLUSIONS
  Present data prove that LPS-induced soluble factors rather than LPS exposure mediate microglial toxicity under conditions of hypoxia in vitro. Apart from potential protective effects of the hypoxia-inducible transcription factor (HIF)-1α system, activation of proinflammatory pathways may markedly sensitize microglial cells to promote hypoxia-induced injuries of the developing brain.
authors.affiliation: Department of Pediatrics, University Hospital for Children and Adolescents, Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen, Germany.
authors.forename: Daniel
authors.initials: D
authors.lastname: Frey
authors.affiliation: Department of Pediatrics, University Hospital for Children and Adolescents, Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen, Germany.
authors.forename: Susan
authors.initials: S
authors.lastname: Jung
authors.affiliation: Department of Pediatrics, University Hospital for Children and Adolescents, Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen, Germany.
authors.forename: Florian
authors.initials: F
authors.lastname: Brackmann
authors.affiliation: Department of Pediatrics, University Hospital for Children and Adolescents, Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen, Germany.
authors.forename: Mandy
authors.initials: M
authors.lastname: Richter-Kraus
authors.affiliation: Department of Pediatrics, University Hospital for Children and Adolescents, Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen, Germany.
authors.forename: Regina
authors.initials: R
authors.lastname: Trollmann
mesh_terms: D000818:Animals; D015687:Cell Hypoxia; D002478:Cells, Cultured; D018925:Chemokines / Q000378:metabolism*; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism; D066298:In Vitro Techniques; D007249:Inflammation / Q000139:chemically induced / Q000378:metabolism*; D053583:Interleukin-1beta / Q000378:metabolism; D015850:Interleukin-6 / Q000378:metabolism; D008070:Lipopolysaccharides; D051379:Mice; D017628:Microglia / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D018925:Chemokines; C497443:Hif1a protein, mouse; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D053583:Interleukin-1beta; D015850:Interleukin-6; D008070:Lipopolysaccharides; D014409:Tumor Necrosis Factor-alpha; D009569:Nitric Oxide