title: Intracellular fibril formation, calcification, and enrichment of chaperones, cytoskeletal, and intermediate filament proteins in the adult hippocampus CA1 following neonatal exposure to the nonprotein amino acid BMAA.
abstract: The environmental neurotoxin β-N-methylamino-L-alanine (BMAA) has been implicated in the etiology of neurodegenerative disease, and recent studies indicate that BMAA can be misincorporated into proteins. BMAA is a developmental neurotoxicant that can induce long-term learning and memory deficits, as well as regionally restricted neuronal degeneration and mineralization in the hippocampal CA1. The aim of the study was to characterize long-term changes (2 weeks to 6 months) further in the brain of adult rats treated neonatally (postnatal days 9-10) with BMAA (460 mg/kg) using immunohistochemistry (IHC), transmission electron microscopy, and laser capture microdissection followed by LC-MS/MS for proteomic analysis. The histological examination demonstrated progressive neurodegenerative changes, astrogliosis, microglial activation, and calcification in the hippocampal CA1 3-6 months after exposure. The IHC showed an increased staining for α-synuclein and ubiquitin in the area. The ultrastructural examination revealed intracellular deposition of abundant bundles of closely packed parallel fibrils in neurons, axons, and astrocytes of the CA1. Proteomic analysis of the affected site demonstrated an enrichment of chaperones (e.g., clusterin, GRP-78), cytoskeletal and intermediate filament proteins, and proteins involved in the antioxidant defense system. Several of the most enriched proteins (plectin, glial fibrillar acidic protein, vimentin, Hsp 27, and ubiquitin) are known to form complex astrocytic inclusions, so-called Rosenthal fibers, in the neurodegenerative disorder Alexander disease. In addition, TDP-43 and the negative regulator of autophagy, GLIPR-2, were exclusively detected. The present study demonstrates that neonatal exposure to BMAA may offer a novel model for the study of hippocampal fibril formation in vivo.
authors.affiliation: Department of Pharmaceutical Biosciences, Uppsala University, Box 591, 751 24, Uppsala, Sweden, Oskar.Karlsson@farmbio.uu.se.
authors.forename: Oskar
authors.initials: O
authors.lastname: Karlsson
authors.forename: Anna-Lena
authors.initials: AL
authors.lastname: Berg
authors.forename: Jörg
authors.initials: J
authors.lastname: Hanrieder
authors.forename: Gunnel
authors.initials: G
authors.lastname: Arnerup
authors.forename: Anna-Karin
authors.initials: AK
authors.lastname: Lindström
authors.forename: Eva B
authors.initials: EB
authors.lastname: Brittebo
mesh_terms: D000599:Amino Acids, Diamino / Q000633:toxicity*; D000818:Animals; D000831:Animals, Newborn; D056547:CA1 Region, Hippocampal / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism / Q000648:ultrastructure; D002114:Calcinosis / Q000139:chemically induced / Q000378:metabolism*; D002853:Chromatography, Liquid; D000087522:Cyanobacteria Toxins; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D003599:Cytoskeleton / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D007150:Immunohistochemistry; D046529:Microscopy, Electron, Transmission; D018832:Molecular Chaperones / Q000378:metabolism*; D017510:Protein Folding; D017207:Rats, Sprague-Dawley; D053719:Tandem Mass Spectrometry; D025801:Ubiquitin / Q000378:metabolism; D051844:alpha-Synuclein / Q000378:metabolism
chemical_list: D000599:Amino Acids, Diamino; D000087522:Cyanobacteria Toxins; D003598:Cytoskeletal Proteins; D018832:Molecular Chaperones; D025801:Ubiquitin; D051844:alpha-Synuclein; C001824:beta-N-methylamino-L-alanine