The fibrillogenesis of amyloid-β protein (Aβ) is considered a crucial factor in the pathogenesis of Alzheimer’s disease (AD). Hence, inhibiting Aβ fibrillogenesis is regarded as the primary therapeutic strategy for the prevention and treatment of AD. However, the development of effective inhibitors against Aβ fibrillogenesis has faced significant challenges. Previous studies have shown that pristine single-walled carbon nanotubes (SWNTs) can inhibit fibrillogenesis of some amyloid proteins. However, the poor dispersibility of SWNTs in an aqueous environment greatly hinders their inhibitory efficacy. Here, we examined the inhibitory activity of hydroxylated SWNTs (SWNT-OH) on the aggregation and cytotoxicity of Aβ42 using thioflavin T (ThT) fluorescence, atomic force microscopy (AFM), cellular viability assays, and molecular dynamics (MD) simulations. ThT and AFM results showed that SWNT-OH inhibits Aβ42 fibrillogenesis and disaggregates preformed amyloid fibrils in a dose-dependent manner. Furthermore, the ratio of hydroxyl groups in SWNT-OH is crucial for their effect against Aβ42 aggregation. SWNT-OH exerted cytoprotective effects against Aβ42 fibrillation-induced cytotoxicity. The results of free-energy decomposition studies based on MD simulations revealed that nonpolar interactions, and especially van der Waals forces, contributed most of the free energy of binding in the SWNT-OH–Aβ complex. Two regions of the Aβ pentamer were identified to interact with SWNT-OH, spanning H13–Q15 and V36–G38. The findings presented here will contribute to a comprehensive understanding of the inhibitory effect of hydroxylated nanoparticles against Aβ fibrillogenesis, which is critical for the search for more effective agents that can counteract amyloid-mediated pathologies.

Misfolding and fibrillogenesis of amyloid-β protein (Aβ) play a key role in the onset and progression of Alzheimer’s disease (AD). Screening for inhibitors against Aβ amyloidogenesis is helpful for rational designing and developing new anti-AD drugs and therapeutic strategies. Dihydromyricetin, a natural flavonoid extracted from a Chinese herb, Ampelopsis grossedentata, has been proven with antioxidative, anti-inflammatory, and neuroprotective effects against neurodegenerative disease. Herein, we found that dihydromyricetin could inhibit Aβ40 aggregation, impede the protofibril formation, disassemble preformed Aβ40 fibrils, and protect PC12 cells from the Aβ40-induced cytotoxicity using a series of biochemical and biophysical assays, including thioflavin T fluorescence, atomic force microscopy, and cell toxicity assays. Circular dichroism spectroscopy data proved that dihydromyricetin delayed the Aβ40 conformational conversion. In addition, the results of molecular dynamics simulations indicated that the interaction between dihydromyricetin and Aβ40 trimer is mainly nonpolar interactions. Key residues (i.e., V18, A21, and D23) of the Aβ40 interacting with dihydromyricetin were also identified. This study suggested that dihydromyricetin shows great potential to be developed as a novel Aβ40 inhibitor.

The inhibitory effect of brazilin against α-synuclein (α-syn) fibrillogenesis, disruption effect against mature fibrils, and the following cytotoxicity were examined by systematical biochemical, biophysical, cellular biological, and molecular simulation experiments. It is found that brazilin inhibited α-syn fibrillogenesis and disrupted the performed fibrils with a concentration-dependent manner. Moreover, cellular experimental data showed that brazilin effectively reduced the cytotoxicity induced by α-syn aggregates. Finally, molecular dynamics simulations were performed to explore the interactions between brazilin and α-syn pentamer. It is found that brazilin directly interacts with α-syn pentamer, and the hydrophobic interactions are favorable for brazilin binding with the α-syn pentamer, while the electrostatic part provides adverse effects. Three binding regions were identified to inhibit α-syn fibrillogenesis or disrupt the preformed aggregates. Furthermore, six important residues (i.e., G51, V52, A53, E61, V66, and K80) of α-syn were also identified. We expected that brazilin is an effective agent against α-syn fibrillogenesis and associated cytotoxicity.

Fibrillogenesis of α-synuclein (αSN) is associated with the onset and progression of Parkinson's disease (PD). Dihydromyricetin (DHM), a natural flavonoid compound extracted from Ampelopsis grossedentata, has proven antioxidative, antineuroinflammatory, and neuroprotective effects in dementia. However, it remains unclear if DHM can impede αSN fibrillogenesis and attenuate the corresponding cytotoxicity. Herein, we found that DHM could inhibit αSN fibrillogenesis and destabilize mature αSN fibrils in a dose-dependent manner. Moreover, DHM protected against αSN-induced cytotoxicity by improving the cell viability by 34.73 ± 3.68% at a 1:1 molar ratio of αSN to DHM. Molecular dynamics simulations showed that DHM interacts with the αSN trimer mainly via nonpolar mechanisms. The key residues by which αSN interacts with DHM were hydrophobic, and their side chains and main chains showed a synergistic effect via hydrophobic and hydrogen-bonding interactions. These findings suggest that DHM possesses great potential to be developed into a new aggregation inhibitor for αSN.

Amyloid self-assembly is pathologically linked to many neurodegenerative diseases, including Alzheimer’s disease (AD) and Parkinson’s disease (PD). While many inhibitors have been developed individually for specific amyloid proteins, there are a few effective platforms to screen on a large scale general amyloid inhibitors against different amyloid proteins. Herein, we developed a new class of amyloid inhibitor probes by site-specific conjugation of aggregation-induced emission (AIE) molecules with amyloid proteins (i.e., AIE@amyloid probes) to realize a high-throughput screening of small-molecule inhibitors. Optimization of site-specific AIE conjugation with two amyloid proteins, amyloid-β protein (Aβ) and α-synuclein (αSN), enabled us to retain their high amyloidogenic properties; i.e., AIE-amyloid probes alone exhibited strong fluorescence due to amyloid-like aggregation, but they showed no fluorescence in the presence of amyloid inhibitors to prevent amyloid aggregation. From integration of AIE@amyloid probes and computational virtual screening from a large drug database, it was found that tolcapone possessed a dual inhibition against the aggregation and cytotoxicity of both Aβ and αSN. More importantly, tolcapone significantly improved the spatial cognition and recognition of Aβ-treated mice. This work represents an innovative attempt to design an AIE-based anti-amyloid drug platform for identifying new small-molecule inhibitors against amyloidogenesis in both AD and PD or other amyloid diseases.