title: Translocation of inhaled ultrafine manganese oxide particles to the central nervous system.
abstract: BACKGROUND
  Studies in monkeys with intranasally instilled gold ultrafine particles (UFPs; <100 nm) and in rats with inhaled carbon UFPs suggested that solid UFPs deposited in the nose travel along the olfactory nerve to the olfactory bulb.
  
  
  METHODS
  To determine if olfactory translocation occurs for other solid metal UFPs and assess potential health effects, we exposed groups of rats to manganese (Mn) oxide UFPs (30 nm; approximately 500 microg/m(superscript)3(/superscript)) with either both nostrils patent or the right nostril occluded. We analyzed Mn in lung, liver, olfactory bulb, and other brain regions, and we performed gene and protein analyses.
  
  
  RESULTS
  After 12 days of exposure with both nostrils patent, Mn concentrations in the olfactory bulb increased 3.5-fold, whereas lung Mn concentrations doubled; there were also increases in striatum, frontal cortex, and cerebellum. Lung lavage analysis showed no indications of lung inflammation, whereas increases in olfactory bulb tumor necrosis factor-alpha mRNA (approximately 8-fold) and protein (approximately 30-fold) were found after 11 days of exposure and, to a lesser degree, in other brain regions with increased Mn levels. Macrophage inflammatory protein-2, glial fibrillary acidic protein, and neuronal cell adhesion molecule mRNA were also increased in olfactory bulb. With the right nostril occluded for a 2-day exposure, Mn accumulated only in the left olfactory bulb. Solubilization of the Mn oxide UFPs was <1.5% per day.
  
  
  CONCLUSIONS
  We conclude that the olfactory neuronal pathway is efficient for translocating inhaled Mn oxide as solid UFPs to the central nervous system and that this can result in inflammatory changes. We suggest that despite differences between human and rodent olfactory systems, this pathway is relevant in humans.
authors.affiliation: Department of Environmental Medicine, University of Rochester, Rochester, New York 14642, USA. Alison_Elder@urmc.rochester.edu
authors.forename: Alison
authors.initials: A
authors.lastname: Elder
authors.forename: Robert
authors.initials: R
authors.lastname: Gelein
authors.forename: Vanessa
authors.initials: V
authors.lastname: Silva
authors.forename: Tessa
authors.initials: T
authors.lastname: Feikert
authors.forename: Lisa
authors.initials: L
authors.lastname: Opanashuk
authors.forename: Janet
authors.initials: J
authors.lastname: Carter
authors.forename: Russell
authors.initials: R
authors.lastname: Potter
authors.forename: Andrew
authors.initials: A
authors.lastname: Maynard
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Ito
authors.forename: Jacob
authors.initials: J
authors.lastname: Finkelstein
authors.forename: Günter
authors.initials: G
authors.lastname: Oberdörster
mesh_terms: D000818:Animals; D015153:Blotting, Western; D001921:Brain / Q000378:metabolism; D001992:Bronchoalveolar Lavage Fluid / Q000166:cytology; D002490:Central Nervous System / Q000378:metabolism*; D002712:Chlorides / Q000737:chemistry / Q000493:pharmacokinetics; D008297:Male; D017895:Manganese Compounds / Q000737:chemistry / Q000493:pharmacokinetics*; D046529:Microscopy, Electron, Transmission; D053758:Nanoparticles; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009830:Olfactory Bulb / Q000378:metabolism; D010084:Oxidation-Reduction; D010087:Oxides / Q000737:chemistry / Q000493:pharmacokinetics*; D012313:RNA / Q000096:biosynthesis / Q000302:isolation & purification; D051381:Rats; D011916:Rats, Inbred F344; D012995:Solubility; D014018:Tissue Distribution
chemical_list: D002712:Chlorides; D017895:Manganese Compounds; D009419:Nerve Tissue Proteins; D010087:Oxides; D012313:RNA; C027424:manganese oxide; C025340:manganese chloride