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.

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.