In vitro amyloid-β binding and inhibition of amyloid-β self-association by therapeutic albumin

J Alzheimers Dis. 2014;38(4):753-65. doi: 10.3233/JAD-131169.

Abstract

Background: A promising approach for treating Alzheimer's disease relies on the net efflux of the amyloid-β (Aβ) peptide from the brain to peripheral plasma, as a result of plasma Aβ clearance promoted by plasma removal and therapeutic albumin replacement.

Objective: To assess the binding of therapeutic albumin (Albutein, Grifols) to monomeric and aggregated Aβ according to methods previously tested on the interactions between Aβ and research-grade albumin.

Methods: Albumin integrity and the interactions with albumin stabilizers (octanoic acid and N-Ac-Trp) were assessed through one-dimensional (1D) 1H-NMR and saturation transfer difference (STD) NMR spectra. The interactions between monomeric Aβ1-40 and albumin were probed by 2D 1H-15 N HSQC spectra of labeled Aβ1-40. The formation of cross-β structured Aβ1-42 assemblies was monitored by ThT fluorescence. The interactions between self-assembled Aβ1-42 and albumin were probed by Trp fluorescence.

Results: NMR spectra indicated that both therapeutic and research-grade albumin are similarly well-folded proteins. No significant changes in either HSQC peak position or intensity were observed upon addition of albumin to 15N-labeled Aβ1-40, which rules out binding of albumin to monomeric Aβ with dissociation constant in the μM or lower range. When aggregated Aβ1-42 was added to albumin, quenching of Trp fluorescence was observed, which indicates albumin binding to Aβ1-42 aggregates. The relative potency of therapeutic albumin as an Aβ self-association inhibitor was in the same order of magnitude as research-grade albumin.

Conclusions: Albutein inhibited Aβ self-association by selectively binding Aβ aggregates rather than monomers and by preventing further growth of the Aβ assemblies.

Keywords: Alzheimer's disease; NMR; amyloid; amyloid-β peptide; oligomers; therapeutic albumin.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alzheimer Disease / drug therapy
  • Alzheimer Disease / metabolism
  • Amyloid beta-Peptides / antagonists & inhibitors*
  • Amyloid beta-Peptides / metabolism*
  • Humans
  • Nuclear Magnetic Resonance, Biomolecular / methods
  • Peptide Fragments / antagonists & inhibitors*
  • Peptide Fragments / metabolism*
  • Protein Binding / physiology
  • Serum Albumin / metabolism*
  • Serum Albumin / physiology
  • Serum Albumin / therapeutic use*

Substances

  • Amyloid beta-Peptides
  • Peptide Fragments
  • Serum Albumin
  • amyloid beta-protein (1-42)