Inhibition of aggregation of amyloid-β through covalent modification with benzylpenicillin; potential relevance to Alzheimer’s disease

The pathogenesis of Alzheimer’s disease (AD) is correlated with the misfolding and aggregation of amyloid-beta
protein (Aβ). Here we report that the antibiotic benzylpenicillin (BP) can specifically bind to Aβ, modulate the
process of aggregation and supress its cytotoxic effect, initially via a reversible binding interaction, followed by
covalent bonding between specific functional groups (nucleophiles) within the Aβ peptide and the beta-lactam
ring. Mass spectrometry and computational docking supported covalent modification of Aβ by BP. BP was found
to inhibit aggregation of Aβ as revealed by the Thioflavin T (ThT) fluorescence assay and atomic force microscopy (AFM). In addition, BP treatment was found to have a cytoprotective activity against Aβ-induced cell
cytotoxicity as shown by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) cell toxicity
assay. The specific interaction of BP with Aβ suggests the possibility of structure-based drug design, leading to the
identification of new drug candidates against AD. Moreover, good pharmacokinetics of beta-lactam antibiotics
and safety on long-time use make them valuable candidates for drug repurposing towards neurological disorders
such as AD.