Effects of Grape Seed-derived Polyphenols on Amyloid β-Protein Self-assembly and CytotoxicityJ. Biol. Chem., Vol. 283, Issue 47, 32176-32187, November 21, 2008Epidemiological evidence suggests that moderate consumption
of red wine reduces the incidence of Alzheimer disease (AD).
To study the protective effects of red wine, experiments recently
were executed in the Tg2576 mouse model of AD.
These studies
showed that a commercially available grape seed polyphenolic
extract, MegaNatural-AZ (MN), significantly attenuated AD-type
cognitive deterioration and reduced cerebral amyloid deposition
(Wang, J., Ho, L., Zhao, W., Ono, K., Rosensweig, C., Chen,
L., Humala, N., Teplow, D. B., and Pasinetti, G. M. (2008)
J. Neurosci. 28, 6388–6392).
To elucidate the mechanistic
bases for these observations, here we used CD spectroscopy,
photo-induced cross-linking of unmodified proteins, thioflavin
T fluorescence, size exclusion chromatography, and electron
microscopy to examine the effects of MN on the assembly of the
two predominant disease-related amyloid β-protein alloforms,
Aβ40 and Aβ42.
We also examined the effects of MN
on Aβ-induced cytotoxicity by assaying 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium
bromide metabolism and lactate dehydrogenase activity in Aβ-treated,
differentiated pheochromocytoma (PC12) cells.
Initial studies
revealed that MN blocked Aβ fibril formation. Subsequent
evaluation of the assembly stage specificity of the effect showed
that MN was able to inhibit protofibril formation, pre-protofibrillar
oligomerization, and initial coil
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-helix/β-sheet secondary
structure transitions.
Importantly, MN had protective effects
in assays of cytotoxicity in which MN was mixed with Aβ
prior to peptide assembly or following assembly and just prior
to peptide addition to cells.
These data suggest that MN is
worthy of consideration as a therapeutic agent for AD.
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