Emodin inhibits aggregation of amyloid-β peptide 1-42 and improves cognitive deficits in Alzheimer's disease transgenic mice

Aggregation of amyloid-beta peptide 1-42 (A beta 42) initiates the onset of Alzheimer's disease (AD), and all the drugs designed to attenuate AD have failed in clinical trials. Emodin reduces levels of beta-amyloid, tau aggregation, oxidative stress, and inflammatory response, demonstrating AD therapeutic potential, whereas its effect on the accumulation of the amyloid-beta protein is not well understood. In this work, we investigated emodin activity on A beta aggregation using a range of biochemical, biophysical, and cell-based approaches. We provide evidence to suggest that emodin blocks A beta 42 fibrillogenesis and A beta-induced cytotoxicity, displaying a greater effect than that of curcumin. Through adopting three short peptides (A beta 1-16, A beta 17-33, and A beta 28-42), it was proven that emodin interacts with the Leu17-Gly33 sequence. Furthermore, our findings indicated that Val18 and Phe19 in A beta 42 are the target residues with which emodin interacts according amino acid mutation experiments. When fed to 8-month-old B6C3-Tg mice for 2 months, high-dose emodin ameliorates cognitive impairment by 60%-70%. Pathological results revealed that levels of A beta deposition in the brains of AD mice treated with a high dose of emodin decreased by 50%-70%. Therefore, our study indicates that emodin may represent a promising drug for AD treatment.