Study of A beta Aggregation Inhibitors Based on Multiple Weak Interactions

Zhang, Q (Zhang, Qian)^[ 1 ] ; Yuan, Z (Yuan, Zhi)^[ 1,2 ]

ACTA POLYMERICA SINICA, 2018, 7: 776-785

DOI: 10.11777/j.issn1000-3304.2018.18025

 WOS:000446262600002

Abstract

Alzheimer 's disease (AD) is a neurodegenerative disorder associated with the loss of memory, cognitive decline, and behavioral disability, leading to dementia and death ultimately. The pathogenesis of AD is still unclear, but it is generally accepted that the occurrence of AD is related to the accumulation of amyloid beta (A beta) in the brain and the oxidative stress effect caused by the enrichment of metal ions. In our previous work, we expanded the targeting site from A beta 16-22 to A beta 11-23 (EVHHQKLVFFAED), which could offer multiple weak interaction sites, such as the electrostatic, hydrophobic interactions and hydrogen bonding. We designed and screened a novel A beta aggregation inhibitory peptide (RR) by computer simulation. The tripeptide chelator GGH, selected by ITC experiment with selectively Cu ion chelating ability, was introduced into RR to get the bifunctional peptide inhibitor GR, which have the ability to inhibit A beta aggregation and produce the oxygen species (ROS) production at the same time. The results of ThT fluorescence, turbidity analysis, MTT methods showed that GR can inhibit the aggregation of A beta and A beta-Cu complex (A beta:Cu = 1:0.25) to form amorphous aggregates, and the cell survival of GR group can reach 88%, significantly higher than chelator GGH (49%) and single functional inhibitor RR (68%). Moreover, it is proposed for the first time that the endocytosis of A beta aggregates in the brain could be promoted by the disaggregation of A beta or A beta-Cu complex fibrils to achieve the effect of treating AD. The results showed that RR and GR can disaggregate A beta and A beta-Cu complex fibrils to nanorod-like structure with a length of 200 - 250 nm (rA beta), and beta-sheet structure content in the system was reduced by 45%. rA beta more easily to PC12 cell endocytosis, and it can enter the cells and further into the cell lysosomes. The in vitro lysosomal cathepsin B (CatB) degradation experimental results showed that, compared to fA beta, rA beta is more susceptible to CatB degradation, and its degradation products have no longer full hydrophobic core region, thereby greatly reducing their chances of re-aggregation. Finally the feasibility of GR and RR has been verified in Morris water maze test.