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

Background:Progressive accumulation ofα-synuclein is a key step in the pathological development of Parkinson’s disease.Impaired protein degradation and increased levels ofα-synuclein may trigger a pathological aggregation in vitro and in vivo.The chaperone-mediated autophagy(CMA)pathway is involved in the intracellular degradation processes ofα-synuclein.Dysfunction of the CMA pathway impairsα-synuclein degradation and causes cytotoxicity.Results:In the present study,we investigated the effects on the CMA pathway andα-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 ofα-synuclein aggregation,after administration of DHM and Sal B,we observed significant inhibition ofα-synuclein accumulation and aggregation.Cells were co-transfected with a Cterminal modifiedα-synuclein(SynT)and synphilin-1,and then treated with DHM(10μM)and Sal B(50μM)16 hours after transfection;levels ofα-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 withα-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 ofα-synuclein.Moreover,DHM and Sal B treatments exhibited anti-inflammatory activities,preventing astroglia-and microglia-mediated neuroinflammation in BAC-α-syn-GFP transgenic mice.Conclusions:Our data indicate that DHM and Sal B are effective in modulatingα-synuclein accumulation and aggregate formation and augmenting activation of CMA,holding potential for the treatment of Parkinson’s disease.

Magnesium ion influx reduces neuroinflammation in Aβ precursor protein/Presenilin 1 transgenic mice by suppressing the expression of interleukin-1β

Alzheimer＇s disease （AD） has been associated with magnesium ion （Mg2＋） deficits and interleukin-1β（IL-1β） elevations in the serum or brains of AD patients. However, the mechanisms regulating IL-1β expression during Mg2＋ dyshomeostasis in AD remain unknown. We herein studied the mechanism of IL-1β reduction using a recently developed compound, magnesium-L-threonate （MgT）. Using human glioblastoma A172 and mouse brain DIA glial cells as an in vitro model system, we delineated the signaling pathways by which MgT suppressed the expression of IL-1β in glial cells. In detail, we found that MgT incubation stimulated the activity of extracellular signal-regulated protein kinases I and 2 （ERK1/2） and peroxisome proliferator-activated receptor gamma （PPARγ） signaling pathways by phosphorylation, which resulted in IL-1β suppression. Simultaneous inhibition of the phosphorylation of ERK1/2 and PPARγ, induced IL-1β upregulation in MgT-stimulated glial cells. In accordance with our in vitrodata, the intracerebroventricular （i.c.v） injection of MgT into the ventricles of APP/PS1 transgenic mice and treatment of Aβ precursor protein （APP）/PS1 brain slices suppressed the mRNA and protein expression of IL-1β. These in vivo observations were further supported by the oral administration of MgT for 5 months. Importantly, Mg2＋ influx into the ventricles of the mice blocked the effects of IL-1β or amyloid p-protein oligomers in the cerebrospinal fluid. This reduced the stimulation of IL-1β expression in the cerebral cortex of APP/PS1 transgenic mice, which potentially contributed to the inhibition of neuroinflammation.

Age-dependent alpha-synuclein accumulation and aggregation in the colon of a transgenic mouse model of Parkinson’s disease

Background:Parkinson’s disease(PD)is one of the most common neurodegenerative diseases,neuropathologically characterized by misfolded protein aggregation,called Lewy bodies and Lewy neurites.PD is a slow-progressive disease with colonic dysfunction appearing in the prodromal stage and lasting throughout the course of the disease.Methods:In order to study PD pathology in the colon,we examined the age-dependent morphological and pathological changes in the colon of a PD mouse model expressing human wildtype α-synuclein(α-syn)fused with the green fluorescent protein(GFP),under the endogenous mouse α-syn promoter.Results:We observed an age-dependent progressive expression and accumulation of α-syn-GFP in the enteric neurons of Meissner’s(submucosal)and Auerbach’s(myenteric)plexuses of the colon.Additionally,the phosphorylation of α-syn at serine 129 also increased with age and the aggregation ofα-syn-GFP coincided with the appearance of motor deficits at 9 months of age.Furthermore,α-syn(-GFP)distinctly co-localized with different subtypes of neurons,as identified by immunohistochemical labeling of vasoactive intestinal peptide(VIP),neuronal nitric oxide synthase(nNOS),and calretinin.Conclusions:Our results show the development of α-syn pathology in the enteric neurons of the colon in a PD mouse model,which coincide with the appearance of motor deficits.Our mouse model possesses the potential and uniqueness for studying PD gastrointestinal dysfunction.