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Clearing of toxic huntingtin protein aggregates from neuron cells is critical for treatment of Huntington's disease. However, this is very challenging and requires the control of intracellular processes and associated biochemical activities. Here, we report the designed nanoparticle-based clearing of toxic huntingtin protein aggregates via cellular autophagy induction. We have designed five different nanoparticles of 15–40 nm size that are composed of an iron oxide/zinc oxide/carbon core and a surface terminated with hemin/amine/arginine/trehalose. These nanoparticles induce cellular autophagy by three different mechanisms, and all of them clear toxic huntingtin aggregates from neuron cells. Such clearance of huntingtin aggregates by nanoparticles has shown a substantial increase in cell viability typically up to 7-fold. Our result suggests that autophagy-inducing nanodrugs may be designed for clearing toxic amyloid aggregates from the brain and treatment of neurodegenerative diseases. [ABSTRACT FROM AUTHOR]

Intracellular/extracellular protein aggregation is linked to a variety of neurodegenerative diseases. Current research focuses on identifying antiamyloidogenic small molecules to inhibit such protein aggregation and associated cytotoxicity. We have recently demonstrated that transforming these antiamyloidogenic small molecules into nanoparticle forms can greatly improve their performance, and biocompatible/biodegradable formulation of such nanoparticles is critical for therapeutic applications. Here, we report polylactide (PL)-based biodegradable nanoparticles for improved neuroprotection against polyglutamine (polyQ) aggregation that is responsible for Huntington's disease. PL is terminated with an antiamyloidogenic trehalose molecule or the neurotransmitter dopamine, and the resultant nanoparticle is loaded with the antiamyloidogenic catechin molecule. The self-assembled nanoparticle is ∼200 nm in size and enters into the neuronal cell, inhibits polyQ aggregation, lowers oxidative stress, and enhances cell proliferation against polyQ aggregates. This biodegradable polymer can be used in nanoformulation of other reported antiamyloidogenic molecules for testing various animal models of neurodegenerative diseases.

Prevention and therapeutic strategies for various neurodegenerative diseases focus on inhibiting protein fibrillation, clearing aggregated protein plaques from the brain, and lowering protein-aggregate-induced toxicity. We have designed poly(trehalose) nanoparticles that can inhibit amyloid/polyglutamine aggregation under extra-/intracellular conditions, reduce such aggregation-derived cytotoxicity, and prevent polyglutamine aggregation in a Huntington's disease (HD) model mouse brain. The nanoparticles have a hydrodynamic size of 20-30 nm and are composed of a 6 nm iron oxide core and a zwitterionic polymer shell containing ∼5-12 wt % covalently linked trehalose. The designed poly(trehalose) nanoparticles are 1000-10000 times more efficient than molecular trehalose in inhibiting protein fibrillation in extra-cellular space, in blocking aggregation of polyglutamine-containing mutant huntingtin protein in model neuronal cells, and in suppressing mutant huntingtin aggregates in HD mouse brain. We show that the nanoparticle form of trehalose with zwitterionic surface charge and a trehalose multivalency (i.e., number of trehalose molecules per nanoparticle) of ∼80-200 are crucial for efficient brain targeting, entry into neuronal cells, and suppression of mutant huntingtin aggregation. The present work shows that nanoscale trehalose can offer highly efficient antiamyloidogenic performance at micromolar concentration, compared with millimollar to molar concentrations for molecular trehalose. This approach can be extended to in vivo application to combat protein-aggregation-derived neurodegenerative diseases.

Sugar-based osmolyte molecules are known to stabilize proteins under stress, but usually they have poor chaperone performance in inhibiting protein aggregation. Here, we show that the nanoparticle form of sugars molecule can enhance their chaperone performance typically by 10 2 -10 5 times, compared to molecular sugar. Sugar-based plate-like nanoparticles of 20-40 nm hydrodynamic size have been synthesized by simple heating of acidic aqueous solution of glucose/sucrose/maltose/trehalose. These nanoparticles have excitation-dependent green/yellow/orange emission and surface chemistry identical to the respective sugar molecule. Fibrillation of lysozyme/insulin/amyloid beta in extracellular space, aggregation of mutant huntingtin protein inside model neuronal cell, and cytotoxic effect of fibrils are investigated in the presence of these sugar nanoparticles. We found that sugar nanoparticles are 10 2 -10 5 times efficient than respective sugar molecules in inhibiting protein fibrillation and preventing cytotoxicity arising of fibrils. We propose that better performance of the nanoparticle form is linked to its stronger binding with fibril structure and enhanced cell uptake. This result suggests that nanoparticle form of osmolyte can be an attractive option in prevention and curing of protein aggregation-derived diseases.

Green tea polyphenol epigallocatechin-3-gallate (EGCG) is known for its antiamyloidogenic property, and it is observed that molecular EGCG binds with amyloid structure, redirects fibrillation kinetics, remodels mature fibril, and lowers the amyloid-derived toxicity. However, this unique property of EGCG is difficult to utilize because of their poor chemical stability and substandard bioavailability. Here we report a nanoparticle form of EGCG of 25 nm size (nano-EGCG) which is 10-100 times more efficient than molecular EGCG in inhibiting protein aggregation, disintegrating mature protein aggregates, and lowering amyloidogenic cytotoxicity. The most attractive advantage of nano-EGCG is that it efficiently protects neuronal cells from the toxic effect of extracellular amyloid beta or intracellular mutant huntingtin protein aggregates by preventing their aggregation. We found that the better performance of nano-EGCG is due to the combined effect of increased chemical stability of EGCG against degradation, stronger binding with protein aggregates, and efficient entry into the cell for interaction with aggregated protein structure. This result indicates that the nanoparticle form of antiamyloidogenic molecules can be more powerful in prevention and curing of protein aggregation derived diseases.