Reversing the Fold: Polyanionic Macrocycle Dissolves αA66-80 Crystallin Peptide Aggregates

Cataract is a leading cause of blindness worldwide, with no clear pharmacological agent for treatment. An octa-sulfonated polyanionic resorcinarene MR-8S was synthesized and investigated for its ability to inhibit the aggregation of αA66-80-Crystallin peptide, a key peptide of the αA-Crystallin protein involved in cataract formation. Nuclear magnetic resonance (NMR) and isothermal titration calorimetry (ITC) experiments revealed strong interactions between MR-8S and the nine amino acids that make up the αA66-80-Crystallin peptide as well as the peptide. ITC revealed dissociation constants ranging between 1 nm and 1000 μM. Fluorescence aggregation assays, dynamic light scattering (DLS) experiments, and transmission electron microscopy (TEM) graphs illustrated a concentration-dependent deaggregation ability of MR-8S toward αA66-80-Crystallin peptide in physiological solutions. At 1:1 equivalence of αA66-80-Crystallin and MR-8S, the average particle size of αA66-80 peptide aggregate dropped almost 9-fold (from 13293 ± 1072 d.nm to 1483 ± 15 d.nm), which was less than that determined for previously reported macrocycles with the same batch of peptide at a similar concentration. Evident from TEM imaging, varying ratios of MR-8S and αA66-80-Crystallin peptide produced fibrillar aggregates of the peptide when compared to pure αA66-80 Crystallin peptide. A concentration of 44 ± 1 μM of MR-8S was needed to break down 50% of αA66-80 peptide aggregates, which was significantly lower than reported IC₅₀ values for two reported functionalized resorcinarenes and doubles that of a third macrocycle. Molecular dynamics (MD) simulations further showed that aggregation of the αA66-80 peptide was driven by core hydrophobic residues, which were effectively shielded by MR-8S, thereby inhibiting the formation of peptide aggregates. Among the four polyionic resorcinarenes tested, MR-8S displayed the strongest deaggregation effects, highlighting its potential as a molecular scaffold for the development of anticataract therapeutics.