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J Neurochem. 2015 Oct;135(2):416-30. doi: 10.1111/jnc.13270. Epub 2015 Sep 2.

Inhibiting amyloid β-protein assembly: Size-activity relationships among grape seed-derived polyphenols.

Author information

  • 1Department of Neurology, David Geffen School of Medicine, University of California, Los Angeles, California, USA.
  • 2Medical Scientist Training Program, Neuroscience Interdepartmental Ph.D. Program, University of California, Los Angeles, California, USA.
  • 3Departments of Psychiatry and Neuroscience, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, New York, USA.
  • 4Department of Neurology, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, New York, USA.
  • 5Geriatric Research, Education and Clinical Center (GRECC), James J. Peters Veterans Affairs Medical Center, 130 West Kingsbridge Road, Bronx, New York, USA.
  • 6Molecular Biology Institute (MBI), and Brain Research Institute (BRI), David Geffen School of Medicine, University of California, Los Angeles, California, USA.

Abstract

Epidemiological evidence that red wine consumption negatively correlates with risk of Alzheimer's disease has led to experimental studies demonstrating that grape seed extracts inhibit the aggregation and oligomerization of Aβ in vitro and ameliorate neuropathology and behavioral deficits in a mouse model of Alzheimer's disease. The active agent in the extracts is a mixed population of polyphenolic compounds. To evaluate the relative potency of each of these compounds, HPLC was used to fractionate the mixture into monomers, dimers, and oligomers. Each fraction was analyzed for its effect on Aβ conformational dynamics (circular dichroism), oligomerization (zero-length photochemical cross-linking), aggregation kinetics (Thioflavin T fluorescence), and morphology (electron microscopy). The relative activities of each fraction were determined on the basis of molar concentration (mol/L) or mass concentration (g/L). When molar concentration, the number concentration of each polyphenolic compound, was considered, the oligomer fraction was the most potent inhibitor of Aβ oligomerization and aggregation. However, when mass concentration, the number concentration of phenolic groups, was considered, monomers were the most potent inhibitors. To understand these ostensibly contradictory results, a model of polyphenol:Aβ complexation was developed. This model, which was found to be consistent with published X-ray crystallographic studies, offers an explanation for the effects of functional group polyvalency on inhibitor activity. Our data emphasize the importance of an in-depth understanding of the mechanism(s) underlying 'concentration dependence' in inhibitor systems involving polyfunctional agents.

KEYWORDS:

Alzheimer's disease; amyloid β-protein (Aβ); grape seeds; inhibitors; oligomers; polyphenols

PMID:
26228682
DOI:
10.1111/jnc.13270
[PubMed - indexed for MEDLINE]
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