title: Extracellular hemoglobin - mediator of inflammation and cell death in the choroid plexus following preterm intraventricular hemorrhage.
abstract: BACKGROUND
  Intraventricular hemorrhage (IVH) with post-hemorrhagic ventricular dilatation (PHVD) is a major cause of neurodevelopmental impairment and mortality in preterm infants. The mechanisms leading to PHVD and brain damage remain largely unknown. The choroid plexus and the ependyma, which constitute an essential part of the blood-brain barrier (BBB), are the first structures to encounter the damaging effects of extravasated blood. The breakdown of the BBB is a critical upstream event leading to brain damage following IVH. In this study we investigated the impact of hemorrhage and hemoglobin (Hb) metabolites on the choroid plexus epithelium.
  
  
  METHODS
  Using a preterm rabbit pup model of IVH, the structural and functional integrity, cellular, inflammatory and oxidative response of the choroid plexus, at 24 and 72 hours following IVH + PHVD, were investigated. In order to further characterize cellular and molecular mechanisms, primary human choroid plexus epithelial cells were exposed to cerebrospinal fluid (CSF) from preterm infants with IVH as well as to Hb-metabolites. Finally, the blocking effects of the Hb-scavenger haptoglobin (Hp) were investigated both in vivo and in vitro.
  
  
  RESULTS
  Following IVH + PHVD, an up-regulation of mRNA for the receptor-related genes TLR-4, IL1R1, FAS, the transcription factor NF-Κβ and for the pro-inflammatory and chemotactic effector molecules, IL-1β, TNFα, MCP-1, IL-8, and IL-6 was observed in the choroid plexus at 24 and 72 hours. This was associated with structural disintegration, caspase activation and cell death in the choroid plexus epithelium. In vitro characterization of choroid plexus epithelial cells, following exposure to hemorrhagic CSF and to the Hb-metabolites metHb and heme, displayed apoptotic and necrotic cell death and an up-regulation of receptor-related and inflammatory effector molecules similar to that observed in vivo following IVH + PHVD. Intraventricular injection of the Hb-scavenger Hp in vivo and co-incubation with Hp in vitro reversed or reduced the cellular activation, inflammatory response, structural damage and cell death.
  
  
  CONCLUSIONS
  Hb-metabolites are important causal initiators of cell death following IVH and removal or scavenging of Hb-metabolites may present an efficient means to reduce the damage to the immature brain following IVH.
authors.affiliation: Department of Pediatrics, Lund University, Lund, S-221 84, Sweden. magnus.gram@med.lu.se.|Division of Infection Medicine, Lund University, Lund, S-221 84, Sweden. magnus.gram@med.lu.se.
authors.forename: Magnus
authors.initials: M
authors.lastname: Gram
authors.affiliation: Department of Pediatrics, Lund University, Lund, S-221 84, Sweden. snjolaug.sveinsdottir@med.lu.se.
authors.forename: Snjolaug
authors.initials: S
authors.lastname: Sveinsdottir
authors.affiliation: Department of Electrical Measurements, Lund University, Lund, S-221 84, Sweden. magnus.cinthio@elmat.lth.se.
authors.forename: Magnus
authors.initials: M
authors.lastname: Cinthio
authors.affiliation: Department of Pediatrics, Lund University, Lund, S-221 84, Sweden. kristbjorg.sveinsdottir@med.lu.se.
authors.forename: Kristbjörg
authors.initials: K
authors.lastname: Sveinsdottir
authors.affiliation: Department of Obstetrics and Gynaecology, Lund University, Lund, S-221 84, Sweden. stefan.hansson@med.lu.se.
authors.forename: Stefan R
authors.initials: SR
authors.lastname: Hansson
authors.affiliation: Division of Infection Medicine, Lund University, Lund, S-221 84, Sweden. matthias.morgelin@med.lu.se.
authors.forename: Matthias
authors.initials: M
authors.lastname: Mörgelin
authors.affiliation: Division of Infection Medicine, Lund University, Lund, S-221 84, Sweden. bo.akerstrom@med.lu.se.
authors.forename: Bo
authors.initials: B
authors.lastname: Åkerström
authors.affiliation: Department of Pediatrics, Lund University, Lund, S-221 84, Sweden. david.ley@med.lu.se.
authors.forename: David
authors.initials: D
authors.lastname: Ley
mesh_terms: D000818:Animals; D016923:Cell Death / Q000502:physiology; D002543:Cerebral Hemorrhage / Q000378:metabolism* / Q000473:pathology; D002831:Choroid Plexus / Q000378:metabolism* / Q000473:pathology; D045604:Extracellular Fluid / Q000378:metabolism*; D005260:Female; D006454:Hemoglobins / Q000378:metabolism*; D006801:Humans; D007234:Infant, Premature / Q000378:metabolism; D007249:Inflammation / Q000378:metabolism / Q000473:pathology; D018836:Inflammation Mediators / Q000378:metabolism*; D011247:Pregnancy; D011817:Rabbits; D011897:Random Allocation
chemical_list: D006454:Hemoglobins; D018836:Inflammation Mediators