Inhibition Of Protein Aggregation By Macrocyclic Compounds And Dendrimers

Inhibition of amyloid ?-protein(A?)fibrillation is an effective strategy for Alzheimer's disease(AD)prevention and treatment.Here we studied the impact of para-sulfonatocalix[n]arenes(SC[n]A,n=4,6,8),a class of amphiphilic calixarene derivatives,on A?42 aggregation by using extensive biophysical and biological assays.In addition,our group recently proposed a hydrophobic binding-electrostatic repulsion(HyBER)theory based on the findings in acidulated serum albumin on A? fibrillogenesis and cytotoxicity.Inspired by HyBER theory,we designed series of phenyl derivatized carboxyl terminated PAMAM and studied their effect on A? aggregation.Here we show that through nonspecific and multipoint hydrophobic interactions,SC[n]A can significantly inhibit A? fibrillation and reduce the amyloid cytotoxicity.Further more,the ?-potential value of A? incubated with SC[6/8]A decreased,which correlated with the reduction of amyloid cytotoxicity.SC[8]A showed the best inhibitory effect among the three macrocycles,possibly owing to it having strongest interaction with A?.Based on HyBER theory,we designed and synthesized a novel class of A? aggregation inhibitors,namely dendrimers with negatively charged hydrophobic surface.To this end,we synthesized phenyl-derivatized generation 5 carboxyl terminated PAMAM,denoted as G5-Ps,with a certain degree(7.2-42.3%)of phenyl substitution(DS)by surface modification with phenethylamine(PEA).Results showed G5-Ps with DS values more than 30.5% can effectively inhibit A? aggregation and reduce amyloid cytotoxicity through the hydrophobic binding-electrostatic repulsion interactions.And G5-P with a DS value of 30.5% showed the best performance.The results verify the HyBER theory.Further studies showed that PAMAM of higher generations,such as G5 and G6,can be modified with hydorphobic groups to work as potent inhibitors of A? aggregation through HyBER theory,while PAMAM of lower generations failed to work in that way.The results indicate that the distance between the hydrophobic groups and negatively charged groups is a key factor to ensure the HyBER theory to work.It's the first time SC[n]As have been studied as A? aggregation inhibitors.The result indicates that SC[n]A with flexible structure can be more effective than the one with rigid structure.The findings can offer significance for the study of other amyloid diseases.Besides,a novel class of A? aggregation inhibitors,namely the phenyl derivatized carboxyl terminated PAMAM,based on HyBER theory were proven to be effective.The results well verify and give insight into the HyBER theory.It also suggests that rational design of inhibitors based on the HyBER theory can be an useful way to the development of potent amyloid inhibitors.