Amphiphilic Distyrylbenzene Derivatives as Potential Therapeutic and Imaging Agents for the Soluble Amyloid-β Oligomers in Alzheimer’s Disease

Alzheimer’s Diseases (AD) is the most common neurodegenerative disease, but efficient therapeutic and early diagnosis agents for this neurological disorder are still lacking. Herein, we report the development of a novel amphiphilic compound, LS-4, generated linking a hydrophobic amyloid fibril-binding fragment with a hydrophilic azamacrocycle that can dramatically increase the binding affinity towards various amyloid β (Aβ) peptide aggregates. The developed compound exhibits uncommon fluorescence turn-on and high binding affinity for Aβ aggregates, especially for soluble Aβ oligomers. Moreover, upon the administration of LS-4 to 5xFAD mice, fluorescence imaging of the LS-4-treated brain sections reveals that LS-4 can readily penetrate the blood-brain-barrier (BBB) and bind to the Aβ oligomers in vivo, as confirmed by immunostaining with an Aβ oligomer-specific antibody. In addition, the treatment of 5xFAD mice with LS-4 significantly reduces the amount of both amyloid plaques and associated phosphorylated tau (p-tau) aggregates vs. the vehicle-treated 5xFAD mice, while microglia activation is also reduced. Furthermore, molecular dynamics simulations corroborate the observation that introducing a hydrophilic moiety into the molecular structure can significantly enhance the electrostatic interactions with the polar residues of the Aβ peptide species. Finally, taking advantage of the strong Cu-chelating property of the azamacrocycle, we performed a series of radioimaging and biodistribution studies that show the ⁶⁴Cu-LS-4 complex binds to the amyloid plaques and can accumulate a significantly larger extent in the 5xFAD mice brains vs. the WT controls. Overall, these in vitro and in vivo studies illustrate that the novel strategy to employ an amphiphilic molecule containing a hydrophilic fragment attached to a hydrophobic amyloid fibril-binding fragment can increase the binding affinity of these compounds for the soluble Aβ oligomers and can thus be used to detect and regulate the soluble Aβ species in AD.