title: Hyperoxia causes inducible nitric oxide synthase-mediated cellular damage to the immature rat brain.
abstract: Relative hyperoxia is a condition frequently encountered in premature infants, either spontaneously or during treatment in the Neonatal Intensive Care Unit. The effects of high inspiratory oxygen concentrations on immature brain cells and their signaling cascades are largely unknown. The aim of the study was to investigate the effect of hyperoxia on the amount and topographic distribution of iNOS-expression (inducible nitric oxide synthase) in the immature rat brain, and to localize hyperoxia-induced formation of peroxynitrite as a potential marker of cellular damage to immature cerebral structures. Seven-day-old Wistar rat pups were exposed to >80% oxygen for 24 h and were then transcardially perfused. Following paraformaldehyde fixation, brains were paraffin-embedded and immunohistochemically stained for iNOS and nitrotyrosine. iNOS protein was quantified by Western blot; iNOS mRNA expression was studied by RT-PCR. Total brain iNOS mRNA was up-regulated, demonstrating a peak at 6 h following the onset of hyperoxia. Immunohistochemical staining was predominantly observed in microglial cells of hippocampus and frontal cortex with some iNOS reactivity in endothelial and perivascular cells. Nitrotyrosine staining was positive in apical dendrites of neurons in the frontal cortex. There was no positive staining for iNOS or nitrotyrosine in control animals. Hyperoxia causes iNOS mRNA and protein up-regulation in microglial cells of the immature rat brain. Positive neuronal nitrotyrosine staining indicates formation of peroxynitrite with potential deleterious effects for immature cellular structures in the neonatal brain.
authors.affiliation: Neonatology and Pediatric Intensive Care, University Children's Hospital, Heinrich-Heine-University, Moorenstr. 5, 40225 Düsseldorf, Germany. thomas.hoehn@uni-duesseldorf.de
authors.forename: Thomas
authors.initials: T
authors.lastname: Hoehn
authors.forename: Ursula
authors.initials: U
authors.lastname: Felderhoff-Mueser
authors.forename: Katja
authors.initials: K
authors.lastname: Maschewski
authors.forename: Christine
authors.initials: C
authors.lastname: Stadelmann
authors.forename: Marco
authors.initials: M
authors.lastname: Sifringer
authors.forename: Petra
authors.initials: P
authors.lastname: Bittigau
authors.forename: Petra
authors.initials: P
authors.lastname: Koehne
authors.forename: Marc
authors.initials: M
authors.lastname: Hoppenz
authors.forename: Michael
authors.initials: M
authors.lastname: Obladen
authors.forename: Christoph
authors.initials: C
authors.lastname: Bührer
mesh_terms: D000818:Animals; D015153:Blotting, Western; D001921:Brain / Q000201:enzymology / Q000254:growth & development / Q000473:pathology; D001927:Brain Diseases / Q000378:metabolism* / Q000473:pathology*; D018496:Hyperoxia / Q000378:metabolism* / Q000473:pathology*; D007150:Immunohistochemistry; D019001:Nitric Oxide Synthase / Q000235:genetics / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000378:metabolism
chemical_list: C002744:3-nitrotyrosine; D014443:Tyrosine; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496318:Nos2 protein, rat