A Molecular Integrative Study on the Inhibitory Effects of WRR and ERW on Amyloid ß Peptide (1-42) Polymerization and Cell Toxicity.

Alzheimer's disease (AD) is a neurodegenerative disease and the main pathological characteristic of AD is the deposition of Aß42 in the brain. Inhibition of Aß42 polymerization is one of the important research directions. Due to the pathological complexity of Alzheimer's disease, studies on Aß42 polymerization inhibitors have not made significant progress worldwide. Using an independently constructed structure database of oligopeptides, in this study, molecular docking, umbrella sampling analysis of free energy, ThT fluorescence detection of Aß42 polymerization, transmission electron microscopy, and flow cytometry detection of reactive oxygen species (ROS) and apoptosis were performed to screen tripeptides and pentapeptides that inhibit polymerization. It was found that two tripeptides, i.e., WRR and ERW, bind stably to the core of Aß42 polymerization in the molecular dynamics analysis, and they significantly inhibited the aggregation of Aß42 and reduced their cell toxicity in vitro.

Molecular Integrative Analysis of the Inhibitory Effects of Dipeptides on Amyloid ß Peptide 1-42 Polymerization.

The major pathological feature of Alzheimer's disease (AD) is the aggregation of amyloid ß peptide (Aß) in the brain. Inhibition of Aß42 aggregation may prevent the advancement of AD. This study employed molecular dynamics, molecular docking, electron microscopy, circular dichroism, staining of aggregated Aß with ThT, cell viability, and flow cytometry for the detection of reactive oxygen species (ROS) and apoptosis. Aß42 polymerizes into fibrils due to hydrophobic interactions to minimize free energy, adopting a ß-strand structure and forming three hydrophobic areas. Eight dipeptides were screened by molecular docking from a structural database of 20 L-α-amino acids, and the docking was validated by molecular dynamics (MD) analysis of binding stability and interaction potential energy. Among the dipeptides, arginine dipeptide (RR) inhibited Aß42 aggregation the most. The ThT assay and EM revealed that RR reduced Aß42 aggregation, whereas the circular dichroism spectroscopy analysis showed a 62.8% decrease in ß-sheet conformation and a 39.3% increase in random coiling of Aß42 in the presence of RR. RR also significantly reduced the toxicity of Aß42 secreted by SH-SY5Y cells, including cell death, ROS production, and apoptosis. The formation of three hydrophobic regions and polymerization of Aß42 reduced the Gibbs free energy, and RR was the most effective dipeptide at interfering with polymerization.