Effects of Grape Seed-derived Polyphenols on Amyloid -Protein Self-assembly and Cytotoxicity

Department of Neurology, David Geffen School of Medicine, University of California, Los Angeles, California 90095-7334, USA.
Journal of Biological Chemistry (Impact Factor: 4.57). 10/2008; 283(47):32176-87. DOI: 10.1074/jbc.M806154200
Source: PubMed


Epidemiological 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 beta-protein alloforms, Abeta40 and Abeta42. We also examined the effects of MN on Abeta-induced cytotoxicity by assaying 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide metabolism and lactate dehydrogenase activity in Abeta-treated, differentiated pheochromocytoma (PC12) cells. Initial studies revealed that MN blocked Abeta 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 --> alpha-helix/beta-sheet secondary structure transitions. Importantly, MN had protective effects in assays of cytotoxicity in which MN was mixed with Abeta 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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    • "Noncross-linked samples were used as controls in each experiment. Glutathione S-transferase (GST) (Sigma-Aldrich, St. Louis, MO) was used as a control for the PICUP chemistry (Ono et al. 2008). GST was dissolved in 10 mM sodium phosphate buffer, pH 7.4, at a concentration of 40 µM. "
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    ABSTRACT: Epidemiological evidence that red wine consumption negatively correlates with risk of AD 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 AD. 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. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.
    Full-text · Article · Jul 2015 · Journal of Neurochemistry
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    • "Similar findings have been reported in animals after consumption of red wine in moderate quantities [15] and on administration of a polyphenolic extract from grape seed [16]. Data from preclinical studies support the theory that resveratrol could be a useful therapeutic agent for Alzheimer's disease [14] [17]. Similarly, a previous study in our laboratory showed that resveratrol improved cognitive deficits induced by scopolamine [18]. "
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    ABSTRACT: A number of studies have recently focused on the neuroprotective and anti-inflammatory effects of resveratrol. In prior studies, we described its beneficial effects on scopolamine-induced learning deficits in rats. The aim of this study was to investigate the effects of resveratrol on emotional and spatial cognitive functions, neurotropic factor expression, and plasma levels of proinflammatory cytokines in rats exposed to chronic unpredictable mild stress (CUMS), which is known to induce cognitive deficits. Resveratrol (5 or 20 mg/kg) was administered intraperitoneally for 35 days. Rats in the CUMS group and in the 5 mg/kg resveratrol + CUMS group performed poorly in tasks designed to assess emotional and spatial learning and memory. The 20 mg/kg resveratrol + CUMS group showed improved performance compared to the CUMS group. In addition, the CUMS procedure induced lower expression of brain-derived neurotrophic factor and c-Fos in hippocampal CA1 and CA3 and in the amygdala of stressed rats. These effects were reversed by chronic administration of resveratrol (20 mg/kg). In addition, plasma levels of tumor necrosis factor-alpha and interleukin-1 beta were increased by CUMS, but were restored to normal by resveratrol. These results indicate that resveratrol significantly attenuates the deficits in emotional learning and spatial memory seen in chronically stressed rats. These effects may be related to resveratrol-mediated changes in neurotrophin factor expression in hippocampus and in levels of proinflammatory cytokines in circulation.
    Full-text · Article · Oct 2014 · Physiology & Behavior
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    • "Treatment with cocoa polyphenols resulted in reduced oligomer formation of both A␤ 42 and A␤ 40 (Fig. 1A, B). A␤ 42 formed monomers and trimers in the absence of cross-linking (Fig. 1A, Lane 1); the trimer being an artifact introduced in the presence of SDS [21]. Following cross-linking, A␤ 42 formed a mixture of monomers and oligomers in the orders of 2–6 (Fig. 1A, Lane 2). "
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    ABSTRACT: Background: Alzheimer's disease (AD) is the most common age-related neurodegenerative disorder, characterized by pathological aggregates of amyloid peptide-β (Aβ) and tau protein. Currently available therapies mediate AD symptoms without modifying disease progression. Polyphenol-rich diets are reported to reduce the risk for AD. Objective: In the present study, we investigated the AD disease-modifying effects of cocoa, a rich source of flavanols, which are a class of polyphenols. We hypothesized that cocoa extracts interfere with amyloid-β oligomerization to prevent synaptic deficits. Methods: We tested the effects of three different cocoa extracts, viz. Natural, Dutched, and Lavado extracts, on Aβ42 and Aβ40 oligomerization, using photo-induced cross-linking of unmodified proteins technique. To assess the effects of cocoa extracts on synaptic function, we measured long term potentiation in mouse brain hippocampal slices exposed to oligomeric Aβ. Results: Our results indicate that cocoa extracts are effective in preventing the oligomerization of Aβ, with Lavado extract being most effective. Lavado extract, but not Dutched extract, was effective in restoring the long term potentiation response reduced by oligomeric Aβ. Conclusion: Our findings indicate that cocoa extracts have multiple disease-modifying properties in AD and present a promising route of therapeutic and/or preventative initiatives.
    Full-text · Article · Jun 2014 · Journal of Alzheimer's disease: JAD
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