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

The major pathological feature of Alzheimer's disease (AD) is the aggregation of amyloid beta peptide (A beta) in the brain. Inhibition of A beta(42) aggregation may prevent the advancement of AD. This study employed molecular dynamics, molecular docking, electron microscopy, circular dichroism, staining of aggregated A beta with ThT, cell viability, and flow cytometry for the detection of reactive oxygen species (ROS) and apoptosis. A beta(42) polymerizes into fibrils due to hydrophobic interactions to minimize free energy, adopting a beta-strand structure and forming three hydrophobic areas. Eight dipeptides were screened by molecular docking from a structural database of 20 L-alpha-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 A beta(42) aggregation the most. The ThT assay and EM revealed that RR reduced A beta(42) aggregation, whereas the circular dichroism spectroscopy analysis showed a 62.8% decrease in beta-sheet conformation and a 39.3% increase in random coiling of A beta(42) in the presence of RR. RR also significantly reduced the toxicity of A beta(42) secreted by SH-SY5Y cells, including cell death, ROS production, and apoptosis. The formation of three hydrophobic regions and polymerization of A beta(42) reduced the Gibbs free energy, and RR was the most effective dipeptide at interfering with polymerization.

Automated summary

The major pathological feature of Alzheimer's disease (AD) is the aggregation of amyloid beta peptide (A beta) in the brain. Inhibition of A beta(42) aggregation may prevent the advancement of AD. This study found that arginine dipeptide (RR) was the most effective at interfering with A beta(42) polymerization and reducing its toxicity, including cell death, reactive oxygen species (ROS) production, and apoptosis.