title: Enhanced proteolytic clearance of plasma Aβ by peripherally administered neprilysin does not result in reduced levels of brain Aβ in mice.
abstract: Accumulation of β-amyloid (Aβ) in the brain is believed to contribute to the pathology of Alzheimer's Disease (AD). Aβ levels are controlled by the production of Aβ from amyloid precursor protein, degradation by proteases, and peripheral clearance. In this study we sought to determine whether enhancing clearance of plasma Aβ with a peripherally administered Aβ-degrading protease would reduce brain Aβ levels through a peripheral sink. Neprilysin (NEP) is a zinc-dependent metalloprotease that is one of the key Aβ-degrading enzymes in the brain. We developed a NEP fusion protein with in vitro degradation of Aβ and a 10 day plasma half-life in mouse. Intravenous administration of NEP to wild-type and APP23 transgenic mice resulted in dose-dependent clearance of plasma Aβ. However, this did not correspond to reduced levels of soluble brain Aβ with treatment up to 5 weeks in WT mice or formic acid-extractable brain Aβ with 3 month treatment in aged APP23. In contrast, intracranial injection of NEP resulted in an acute decrease in soluble brain Aβ. We found no change in amyloid precursor protein gene expression in mice treated with intravenous NEP, suggesting that the lack of effects in the brain following this route of administration was not caused by compensatory upregulation of Aβ production. Taken together, these results suggest a lack of a robust peripheral Aβ efflux sink through which brain amyloid burdens can be therapeutically reduced.
authors: Genomics Institute of the Novartis Research Foundation, San Diego, California 92121, USA.
authors: John R
authors: JR
authors: Walker
authors: Reynand
authors: R
authors: Pacoma
authors: James
authors: J
authors: Watson
authors: Weijia
authors: W
authors: Ou
authors: Juliano
authors: J
authors: Alves
authors: Daniel E
authors: DE
authors: Mason
authors: Eric C
authors: EC
authors: Peters
authors: Hugo D
authors: HD
authors: Urbina
authors: Gus
authors: G
authors: Welzel
authors: Alana
authors: A
authors: Althage
authors: Bo
authors: B
authors: Liu
authors: Tove
authors: T
authors: Tuntland
authors: Laura H
authors: LH
authors: Jacobson
authors: Jennifer L
authors: JL
authors: Harris
authors: Andrew M
authors: AM
authors: Schumacher
mesh_terms: D000595:Amino Acid Sequence; D016229:Amyloid beta-Peptides / Q000097:blood*; D016564:Amyloid beta-Protein Precursor / Q000097:blood*; D000818:Animals; D001921:Brain / Q000187:drug effects* / Q000378:metabolism* / Q000473:pathology; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D015260:Neprilysin / Q000494:pharmacology*; D059748:Proteolysis / Q000187:drug effects*
chemical_list: D016229:Amyloid beta-Peptides; D016564:Amyloid beta-Protein Precursor; D015260:Neprilysin
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