Dihydromyricetin and Salvianolic acid B inhibit alpha-synuclein aggregation and enhance chaperone-mediated autophagy

Jia-Zhen Wu,Nishant N Vaikath,Omar M El-Agnaf,Tiago F Outeiro,Mustafa Ardah,Caroline Haikal,Alexander Svanbergsson,Wen Li,Jia-Yi Li,Zhan-You Wang,Meike Diepenbroek

doi:10.1186/s40035-019-0159-7

Abstract

BackgroundProgressive accumulation of α-synuclein is a key step in the pathological development of Parkinson’s disease. Impaired protein degradation and increased levels of α-synuclein may trigger a pathological aggregation in vitro and in vivo. The chaperone-mediated autophagy (CMA) pathway is involved in the intracellular degradation processes of α-synuclein. Dysfunction of the CMA pathway impairs α-synuclein degradation and causes cytotoxicity.ResultsIn the present study, we investigated the effects on the CMA pathway and α-synuclein aggregation using bioactive ingredients (Dihydromyricetin (DHM) and Salvianolic acid B (Sal B)) extracted from natural medicinal plants. In both cell-free and cellular models of α-synuclein aggregation, after administration of DHM and Sal B, we observed significant inhibition of α-synuclein accumulation and aggregation. Cells were co-transfected with a C-terminal modified α-synuclein (SynT) and synphilin-1, and then treated with DHM (10 μM) and Sal B (50 μM) 16 hours after transfection; levels of α-synuclein aggregation decreased significantly (68% for DHM and 75% for Sal B). Concomitantly, we detected increased levels of LAMP-1 (a marker of lysosomal homeostasis) and LAMP-2A (a key marker of CMA). Immunofluorescence analyses showed increased colocalization between LAMP-1 and LAMP-2A with α-synuclein inclusions after treatment with DHM and Sal B. We also found increased levels of LAMP-1 and LAMP-2A both in vitro and in vivo, along with decreased levels of α-synuclein. Moreover, DHM and Sal B treatments exhibited anti-inflammatory activities, preventing astroglia- and microglia-mediated neuroinflammation in BAC-α-syn-GFP transgenic mice.ConclusionsOur data indicate that DHM and Sal B are effective in modulating α-synuclein accumulation and aggregate formation and augmenting activation of CMA, holding potential for the treatment of Parkinson’s disease.

Highlights

Progressive accumulation of α-synuclein is a key step in the pathological development of Parkinson’s disease
The treatment with 3-MA alone resulted in a reduction of LC3-II levels, whereas an increase in expression levels of LC3-II and Lysosomalassociated membrane protein 1 (LAMP-1)/2A was observed after DHM or Salvianolic acid B (Sal B) treatment (Additional file 2). These findings suggest that DHM and Sal B lead to an up-regulation of the LC3-II and Lysosomal-associated membrane protein 2 (LAMP-2A) proteins reflecting the involvement of chaperone-mediated autophagy (CMA) and macroautophagy after treatments with DHM and Sal B
Quantification of the Iba1 (Fig. 8e, f ) and Glial fibrillary acidic protein (GFAP) (Fig. 8g, h) signal intensity of IHC staining revealed a deactivation of astroglia and Discussion In this study, we have shown that DHM and Sal B induce the degradation of α-syn aggregates and we attribute this to the observed activation of the CMA

Summary

Introduction

Progressive accumulation of α-synuclein is a key step in the pathological development of Parkinson’s disease. Impaired protein degradation and increased levels of α-synuclein may trigger a pathological aggregation in vitro and in vivo. The chaperone-mediated autophagy (CMA) pathway is involved in the intracellular degradation processes of α-synuclein. Sal B has recently been associated with preventing fibril aggregation of amyloid proteins and inhibiting neuroinflammation, thereby improving neurological function in animal models of neurodegenerative diseases [23, 24]. It is not clear whether DHM and Sal B have any effects on α-syn accumulation and aggregation in synucleinopathies, such as PD

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