Effects of the Polyphenols Delphinidin and Rosmarinic Acid on the Inducible Intra-cellular Aggregation of Alpha-Synuclein in Model Neuron Cells.

Intracellular aggregation of α-synuclein is a major pathological feature of Parkinson's disease. In this study, we show that the polyphenols delphinidin and rosmarinic acid suppress intracellular aggregation of α-synuclein in a mouse neuron cell model when added under oxidative stress conditions. To enhance the detection threshold of this preventive effect of the two polyphenols, we generated a new strain of "aggregation prone model cells" that tended to show prominent α-synuclein aggregation even under normal conditions. Using this new highly sensitive cell line, we demonstrate that addition of delphinidin to model cell cultures effectively suppresses the formation of intracellular α-synuclein aggregates. Flow cytometric analysis shows that adding delphinidin decreases the fraction of "dying cells," cells that were alive but in a damaged state. Our findings suggest the possibility of using polyphenols to prevent and treat the symptoms correlated with the onset of Parkinson's disease. Additionally, our aggregation-prone cell model may be used in future studies to probe numerous neurodegenerative diseases with high sensitivity.

Human Molecular Chaperone Hsp60 and Its Apical Domain Suppress Amyloid Fibril Formation of α-Synuclein.

Heat shock proteins play roles in assisting other proteins to fold correctly and in preventing the aggregation and accumulation of proteins in misfolded conformations. However, the process of aging significantly degrades this ability to maintain protein homeostasis. Consequently, proteins with incorrect conformations are prone to aggregate and accumulate in cells, and this aberrant aggregation of misfolded proteins may trigger various neurodegenerative diseases, such as Parkinson's disease. Here, we investigated the possibilities of suppressing α-synuclein aggregation by using a mutant form of human chaperonin Hsp60, and a derivative of the isolated apical domain of Hsp60 (Hsp60 AD(Cys)). In vitro measurements were used to detect the effects of chaperonin on amyloid fibril formation, and interactions between Hsp60 proteins and α-synuclein were probed by quartz crystal microbalance analysis. The ability of Hsp60 AD(Cys) to suppress α-synuclein intracellular aggregation and cytotoxicity was also demonstrated. We show that Hsp60 mutant and Hsp60 AD(Cys) both effectively suppress α-synuclein amyloid fibril formation, and also demonstrate for the first time the ability of Hsp60 AD(Cys) to function as a mini-chaperone inside cells. These results highlight the possibility of using Hsp60 AD as a method of prevention and treatment of neurodegenerative diseases.