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Alzheimer's Research & Therapy
Published in: Alzheimer's Research & Therapy 1/2017

Open Access 01-12-2017 | Research

Serotonin augmentation therapy by escitalopram has minimal effects on amyloid-β levels in early-stage Alzheimer’s-like disease in mice

Authors: Christian Ulrich von Linstow, Jonas Waider, Manuela Grebing, Athanasios Metaxas, Klaus Peter Lesch, Bente Finsen

Published in: Alzheimer's Research & Therapy | Issue 1/2017

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Abstract

Background

Dysfunction of the serotonergic (5-HTergic) system has been implicated in the cognitive and behavioural symptoms of Alzheimer’s disease (AD). Accumulation of toxic amyloid-β (Aβ) species is a hallmark of AD and an instigator of pathology. Serotonin (5-HT) augmentation therapy by treatment with selective serotonin reuptake inhibitors (SSRIs) in patients with AD has had mixed success in improving cognitive function, whereas SSRI administration to mice with AD-like disease has been shown to reduce Aβ pathology. The objective of this study was to investigate whether an increase in extracellular levels of 5-HT induced by chronic SSRI treatment reduces Aβ pathology and whether 5-HTergic deafferentation of the cerebral cortex could worsen Aβ pathology in the APPswe/PS1ΔE9 (APP/PS1) mouse model of AD.

Methods

We administered a therapeutic dose of the SSRI escitalopram (5 mg/kg/day) in the drinking water of 3-month-old APP/PS1 mice to increase levels of 5-HT, and we performed intracerebroventricular injections of the neurotoxin 5,7-dihydroxytryptamine (DHT) to remove 5-HTergic afferents. We validated the effectiveness of these interventions by serotonin transporter autoradiography (neocortex 79.7 ± 7.6%) and by high-performance liquid chromatography for 5-HT (neocortex 64% reduction). After 6 months of escitalopram treatment or housing after DHT-induced lesion, we evaluated brain tissue by mesoscale multiplex analysis and sections by IHC analysis.

Results

Amyloid-β-containing plaques had formed in the neocortex and hippocampus of 9-month-old APP/PS1 mice after 6 months of escitalopram treatment and 5-HTergic deafferentation. Unexpectedly, levels of insoluble Aβ42 were unaffected in the neocortex and hippocampus after both types of interventions. Levels of insoluble Aβ40 increased in the neocortex of SSRI-treated mice compared with those treated with vehicle control, but they were unaffected in the hippocampus. 5-HTergic deafferentation was without effect on the levels of insoluble/soluble Aβ42 and Aβ40 in both the neocortex and hippocampus. However, levels of soluble amyloid precursor protein α were reduced in the neocortex after 5-HTergic deafferentation.

Conclusions

Because this study shows that modulation of the 5-HTergic system has either no effect or increases levels of insoluble/soluble Aβ42 and Aβ40 in the cerebral cortex of APP/PS1 mice, our observations do not support 5-HT augmentation therapy as a preventive strategy for reducing Aβ pathology.
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Metadata
Title
Serotonin augmentation therapy by escitalopram has minimal effects on amyloid-β levels in early-stage Alzheimer’s-like disease in mice
Authors
Christian Ulrich von Linstow
Jonas Waider
Manuela Grebing
Athanasios Metaxas
Klaus Peter Lesch
Bente Finsen
Publication date
01-12-2017
Publisher
BioMed Central
Published in
Alzheimer's Research & Therapy / Issue 1/2017
Electronic ISSN: 1758-9193
DOI
https://doi.org/10.1186/s13195-017-0298-y

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