Abstract
Accumulation and oligomerization of amyloid-beta (Aβ) peptides have been known to be a potent cause of neurodegenerative diseases such as Alzheimer's disease (AD). To expand the possibilities of preventing AD, we investigated the effects of resveratrol dimers, gnetin C and ε-viniferin, on Aβ 1-42 (Aβ42) production and the reduced cell viability observed after Aβ42 treatment (monomers, 10 μM) in cultured SH-SY5Y human neuroblastoma cells. Among them, addition of gnetin C (20 μM) into the media reduced Aβ42 production most efficiently. Gnetin C suppressed the expression of β-site amyloid precursor protein-cleaving enzyme-1 (BACE1, β-secretase). Furthermore, gnetin C ameliorated the Aβ42-reduced cell viability most significantly. Concomitantly, gnetin C reduced intracellular Aβ oligomers (ca. 15 and 130 kDa) and elevated both levels of intracellular and extracellular Aβ monomers. Under the treatment with or without Aβ42, gnetin C upregulated the expression of matrix metalloproteinase-14 (MMP-14) which is assumed to be an Aβ-decomposing enzyme. Gnetin C may thereby prevent Aβ toxicity by suppressing BACE1 and enhancing MMP-14, together with reducing both internalization and oligomerization of exogenous Aβ monomers. The use of gnetin C may lead to the prevention of Aβ-mediated diseases, particularly AD.