Functionalized Modifications Of Serum Albumin For Inhibition Of Amyloid β-protein Fibrillogenesis

Alzheimer’s disease（AD）is a kind of neurodegenerative disease.It has been clear that the pathogenesis results from the aggregation of amyloid β-proteins（Aβ）induced by metal ions,such as Zn²⁺ and Cu²⁺.Hence,it is highly desired to design multifunctional agents capable of inhibiting Aβ aggregation and modulating metal-Aβ species.Herein we developed acidulated serum albumin（A-BSA/A-HSA）for the inhibition of Aβ42 aggregation and modulating Zn²⁺-mediated Aβ42 fibrillogenesis and cytotoxicity.The A-BSA/A-HSA with more negative charges were confirmed to keep the tertiary structure and stability of native serum albumin.Extensive biophysical and biological analyses showed that A-BSA significantly inhibited Aβ42 fibrillogenesis and mitigated amyloid cytotoxicity.In addition,A-HSA could change the pathway of Zn²⁺-mediated Aβ42 aggregation and significantly mitigated the cytotoxicity presented by Zn²⁺-Aβ42 aggregates.The inhibitory effect was remarkably higher than native serum albumin at the same concentration.The studies showed that hydrophobic binding and electrostatic repulsion could work simultaneously on the bound Aβ42 on A-BSA/A-HSA surface.The two well-balanced opposite forces would make Aβ42 adopt extended conformations that were not conducive to forming toxic aggregates.Moreover,the A-HSA surface with more negative charges not only had stronger affinity for Zn²⁺ but also might decrease the binding affinity of Aβ42 for Zn²⁺.Moreover,cerebral acidosis is another common complication of AD.Under mildly acidic conditions,Cu²⁺-Aβ42 species have a higher tendency to generate neurotoxic aggregates.Herein we fabricated A-HSA to mitigate Cu²⁺-mediated Aβ42 aggregation and cytotoxicity at pH 6.6.The results showed that A-HSA could alter the pathway of Cu²⁺-mediated Aβ42 aggregation and protect SH-SY5 Y cells from cytotoxicity and oxidative damage induced by Cu²⁺-Aβ42 species.Noticeably,A-HSA changed the Cu²⁺-Aβ42 coordination mode on the millisecond timescale,which avoided the formation of aggregation-prone Cu²⁺-Aβ42 aggregates.Considering the fact that A-HSA could not bind high concentration of metal ions in vivo,we modified iminodiacetic acids（IDA）onto HSA surface.It was found that I-HSA could chelate more metal ions(Zn²⁺ and Cu²⁺)and showed more inhibitory effect on metal-mediated Aβ42 aggregation than HSA in vitro.In addition,I-HSA could remodel metal-Aβ42 fibrils and changed the aggregation pathway into unstructured aggregates.Remarkably,I-HSA could inhibit the effect of 10-fold concentration of metal ions on the Aβ42 aggregation,so that we could decrease the dosage in the treatment.The study design A-BSA,A-HSA and I-HSA to inhibit Aβ42 aggregation and modulate metal-Aβ42 species.Based on the results,we provide insights into the mechanisms of Aβ42 aggregation and this work may advance the knowledge required for developing inhibitors of Aβ42 fibrillogenesis and cytotoxicity.