title: Age-dependent neuroplasticity mechanisms in Alzheimer Tg2576 mice following modulation of brain amyloid-β levels.
abstract: The objective of this study was to investigate the effects of modulating brain amyloid-β (Aβ) levels at different stages of amyloid pathology on synaptic function, inflammatory cell changes and hippocampal neurogenesis, i.e. processes perturbed in Alzheimer's disease (AD). Young (4- to 6-month-old) and older (15- to 18-month-old) APP(SWE) transgenic (Tg2576) mice were treated with the AD candidate drug (+)-phenserine for 16 consecutive days. We found significant reductions in insoluble Aβ1-42 levels in the cortices of both young and older transgenic mice, while significant reductions in soluble Aβ1-42 levels and insoluble Aβ1-40 levels were only found in animals aged 15-18 months. Autoradiography binding with the amyloid ligand Pittsburgh Compound B ((3)H-PIB) revealed a trend for reduced fibrillar Aβ deposition in the brains of older phenserine-treated Tg2576 mice. Phenserine treatment increased cortical synaptophysin levels in younger mice, while decreased interleukin-1β and increased monocyte chemoattractant protein-1 and tumor necrosis factor-alpha levels were detected in the cortices of older mice. The reduction in Aβ1-42 levels was associated with an increased number of bromodeoxyuridine-positive proliferating cells in the hippocampi of both young and older Tg2576 mice. To determine whether the increased cell proliferation was accompanied by increased neuronal production, the endogenous early neuronal marker doublecortin (DCX) was examined in the dentate gyrus (DG) using immunohistochemical detection. Although no changes in the total number of DCX(+)-expressing neurons were detected in the DG in Tg2576 mice at either age following (+)-phenserine treatment, dendritic arborization was increased in differentiating neurons in young Tg2576 mice. Collectively, these findings indicate that reducing Aβ1-42 levels in Tg2576 mice at an early pathological stage affects synaptic function by modulating the maturation and plasticity of newborn neurons in the brain. In contrast, lowering Aβ levels in Tg2576 mice when Aβ plaque pathology is prominent mainly alters the levels of proinflammatory cytokines and chemokines.
authors.affiliation: Alzheimer Neurobiology Center, Department of Neurobiology, Care Sciences and Society, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Anna M
authors.initials: AM
authors.lastname: Lilja
authors.forename: Jennie
authors.initials: J
authors.lastname: Röjdner
authors.forename: Tamanna
authors.initials: T
authors.lastname: Mustafiz
authors.forename: Carina M
authors.initials: CM
authors.lastname: Thomé
authors.forename: Elisa
authors.initials: E
authors.lastname: Storelli
authors.forename: Daniel
authors.initials: D
authors.lastname: Gonzalez
authors.forename: Christina
authors.initials: C
authors.lastname: Unger-Lithner
authors.forename: Nigel H
authors.initials: NH
authors.lastname: Greig
authors.forename: Agneta
authors.initials: A
authors.lastname: Nordberg
authors.forename: Amelia
authors.initials: A
authors.lastname: Marutle
mesh_terms: D000367:Age Factors; D000544:Alzheimer Disease / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D016229:Amyloid beta-Peptides / Q000378:metabolism*; D000818:Animals; D001921:Brain / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology*; D049109:Cell Proliferation / Q000187:drug effects; D004195:Disease Models, Animal; D000089662:Doublecortin Protein; D005260:Female; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism; D053583:Interleukin-1beta / Q000378:metabolism; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D009473:Neuronal Plasticity; D009474:Neurons / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D010830:Physostigmine / Q000008:administration & dosage / Q000031:analogs & derivatives; D058225:Plaque, Amyloid; D013569:Synapses / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D016229:Amyloid beta-Peptides; C000714847:Dcx protein, mouse; D000089662:Doublecortin Protein; D053583:Interleukin-1beta; D014409:Tumor Necrosis Factor-alpha; D010830:Physostigmine; C092280:phenserine
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