Functionalized Modifications Of Serum Albumin For Inhibition Of Amyloid ?-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 ?-proteins?A??induced by metal ions,such as Zn²⁺ and Cu²⁺.Hence,it is highly desired to design multifunctional agents capable of inhibiting A? aggregation and modulating metal-A? species.Herein we developed acidulated serum albumin?A-BSA/A-HSA?for the inhibition of A?42 aggregation and modulating Zn²⁺-mediated A?42 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 A?42 fibrillogenesis and mitigated amyloid cytotoxicity.In addition,A-HSA could change the pathway of Zn²⁺-mediated A?42 aggregation and significantly mitigated the cytotoxicity presented by Zn²⁺-A?42 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 A?42 on A-BSA/A-HSA surface.The two well-balanced opposite forces would make A?42 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 A?42 for Zn²⁺.Moreover,cerebral acidosis is another common complication of AD.Under mildly acidic conditions,Cu²⁺-A?42 species have a higher tendency to generate neurotoxic aggregates.Herein we fabricated A-HSA to mitigate Cu²⁺-mediated A?42 aggregation and cytotoxicity at pH 6.6.The results showed that A-HSA could alter the pathway of Cu²⁺-mediated A?42 aggregation and protect SH-SY5 Y cells from cytotoxicity and oxidative damage induced by Cu²⁺-A?42 species.Noticeably,A-HSA changed the Cu²⁺-A?42 coordination mode on the millisecond timescale,which avoided the formation of aggregation-prone Cu²⁺-A?42 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 A?42 aggregation than HSA in vitro.In addition,I-HSA could remodel metal-A?42 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 A?42 aggregation,so that we could decrease the dosage in the treatment.The study design A-BSA,A-HSA and I-HSA to inhibit A?42 aggregation and modulate metal-A?42 species.Based on the results,we provide insights into the mechanisms of A?42 aggregation and this work may advance the knowledge required for developing inhibitors of A?42 fibrillogenesis and cytotoxicity.