Effects of an Aβ-antibody fragment on Aβ aggregation and astrocytic uptake are modulated by apolipoprotein E and J mimetic peptides.

Laia Montoliu-Gaya,Robert Veerhuis,Sandra D Mulder,Sandra Villegas,Israel Silman

doi:10.1371/journal.pone.0188191

Laia Montoliu-Gaya, Robert Veerhuis + Show 3 more

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https://doi.org/10.1371/journal.pone.0188191

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Abstract

Aβ-Immunotherapy has long been studied in the treatment of Alzheimer’s disease (AD), but not how other molecules involved in the disease can affect antibody performance. We previously designed an antibody fragment, scFv-h3D6, and showed that it precludes Aβ-induced cytotoxicity by withdrawing Aβ oligomers from the amyloid pathway towards a non-toxic, worm-like pathway. ScFv-h3D6 was effective at the behavioral, cellular, and molecular levels in the 3xTg-AD mouse model. Because scFv-h3D6 treatment restored apolipoprotein E (apoE) and J (apoJ) concentrations to non-pathological values, and Aβ internalization by glial cells was found to be decreased in the presence of these apolipoproteins, we now aimed to test the influence of scFv-h3D6 on Aβ aggregation and cellular uptake by primary human astrocytes in the presence of therapeutic apoE and apoJ mimetic peptides (MPs). Firstly, we demonstrated by CD and FTIR that the molecules used in this work were well folded. Next, interactions between apoE or apoJ-MP, scFv-h3D6 and Aβ were studied by CD. The conformational change induced by the interaction of Aβ with apoE-MP was much bigger than the induced with apoJ-MP, in line with the observed formation of protective worm-like fibrils by the scFv-h3D6/Aβ complex in the presence of apoJ-MP, but not of apoE-MP. ScFv-h3D6, apoJ-MP, and apoE-MP to a different extent reduced Aβ uptake by astrocytes, and apoE-MP partially interfered with the dramatic reduction by scFv-h3D6 while apoJ-MP had no effect on scFv-h3D6 action. As sustained Aβ uptake by astrocytes may impair their normal functions, and ultimately neuronal viability, this work shows another beneficence of scFv-h3D6 treatment, which is not further improved by the use of apoE or apoJ mimetic peptides.

Highlights

Alzheimer’s disease (AD) is a neurodegenerative disorder characterized by a progressive decline in cognitive functions
When pre-incubated at 4 ̊C, the scFv-h3D6 spectrum is centered at 1638 cm-1, which is indicative of the prevalence of the native β-sheet component, as we previously described in depth[28,37]
We have studied the interaction among scFv-h3D6, the Aβ peptide, and apolipoprotein E (apoE)-mimetic peptides (MPs) or apoJ-MP to test the influence of scFv-h3D6 in combination with these MPs on Aβ aggregation and cellular uptake by primary human astrocytes

Summary

Introduction

Alzheimer’s disease (AD) is a neurodegenerative disorder characterized by a progressive decline in cognitive functions. Aggregation and accumulation of Aβ result in alterations in synaptic function, activation of glial cells, release of inflammatory mediators, and oxidative stress[4,5]. This accumulation may lead to the deposition of amyloid plaques in the brain, one of the histological hallmarks of AD[6]. Human apoE is a 299-residue glycoprotein composed of two separate domains joined by a flexible hinge region: the N-terminal domain, which constitutes the receptor-binding region, and the C-terminal domain, the lipid-binding region[10]. Human apoE exists in three isoforms, apoE2, apoE3 and apoE4, with apoE3 as the most common form and apoE4 being the major genetic risk factor for AD[12]

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