Study of alpha-synuclein fibrillation: state of the art and expectations

Since the discovery of the presence of fibrillary forms ofα-synuclein(α-syn)in Lewy bodies(LB)and Lewy neurites in the brain of patients affected by Parkinson’s disease(PD)and dementia with LB,great effort has been dedicated to study the features ofα-syn fibrillation.In parallel,the pathological relevance of the different toxic forms ofα-syn has been also matter of investigation.In the last twenty years,scientists have been able to single out thatα-syn fibrillation initiates pathological mechanisms that by contributing to or triggering neurodegeneration/neuroinflammation,may lead to PD pathogenesis.This notwithstanding,we still ignore the reasons whyα-syn shifts from its natively unfolded conformation to toxic oligomeric and fibrillary forms.The chameleonic nature of monomericα-syn,and the extremely polymorphic characteristics of aggregated strains,renders it difficult to picture the real nature ofα-syn fibrils,their exact composition and formation dynamics.Recently,sophisticated biophysical methods and microscopy techniques have been exploited to studyα-syn fibrillation.Here,we provide an overview of the most relevant advancement in our understanding ofα-syn fibrils formation and conformation.

Anionic liposomes for small interfering ribonucleic acid （siRNA） delivery to primary neuronal cells： Evaluation of alpha-synuclein knockdown efficacy

Alpha-synuclein （a-syn） deposition in Lewy bodies （LB） is one of the main neuropathological hallmarks of Parkinson＇s disease （PD）. LB accumulation is considered a causative factor of PD, which suggests that strategies aimed at reducing a-syn levels could be relevant for its treatment. In the present study, we developed novel nanocarriers suitable for systemic delivery of small interfering ribonucleic acid （siRNA） that were specifically designed to reduce neuronal α-syn by RNA interference. Anionic liposomes loaded with an siRNA-protamine complex for α-syn gene silencing and decorated with a rabies virus glycoprotein （RVG）-derived peptide as a targeting agent were prepared. The nanoparticles were characterized for their ability to load, protect, and deliver the functional siRNA to mouse primary hippocampal and cortical neurons as well as their efficiency to induce gene silencing in these cells. Moreover, the nanocarriers were evaluated for their stability in serum. The RVG-decorated liposomes displayed suitable characteristics for future in vivo applications and successfully induced α-syn gene silencing in primary neurons without altering cell viability. Collectively, our results indicate that RVG-decorated liposomes may be an ideal tool for further studies aimed at achieving efficient in vivo α-syn gene silencing in mouse models of PD.

NF-κB/c-Rel deficiency causes Parkinson’s disease-like prodromal symptoms and progressive pathology in mice

Background:Parkinson’s disease(PD),the most common neurodegenerative movement disorder,is characterized by dopaminergic nigrostriatal neuron loss and brain accumulation of Lewy bodies,protein aggregates mainly composed ofα-synuclein.We reported that mice deficient for NF-κB/c-Rel(c-rel^(-/-))develop a late-onset parkinsonism.At 18 months of age,c-rel^(-/-)mice showed nigrostriatal degeneration and accumulation ofα-synuclein aggregates associated with a motor impairment responsive to L-DOPA administration.Being c-Rel protein a transcriptional regulator for mitochondrial anti-oxidant and antiapoptotic factors,it has been inferred that its deficiency may affect the resilience of“energy demanding”nigral dopaminergic neurons to the aging process.PD patients manifest a prodromal syndrome that includes olfactory and gastrointestinal dysfunctions years before the frank degeneration of nigrostriatal neurons and appearance of motor symptoms.According to the Braak staging,the onset of non-motor and motor symptoms relates to progressive ascendant diffusion ofα-synuclein pathology in the brain.The aim of this study was to identify whether c-rel^(-/-)deficiency is associated with the onset of premotor signs of PD and spatio-temporal progression of cerebralα-synuclein deposition.Methods:Intestinal and olfactory functions,intestine and brainα-synuclein deposition as well as striatal alterations,were assessed in c-rel^(-/-)and control mice from 2 to 18 months of age.Results:From 2 months of age,c-rel^(-/-)mice displayed intestinal constipation and increasing olfactory impairment.At 2 months,c-rel^(-/-)mice exhibited a mildα-synuclein accumulation in the distal colon.Moreover,they developed an agedependent deposition of fibrillaryα-synuclein that,starting at 5 months from the olfactory bulbs,dorsal motor nucleus of vagus and locus coeruleus,reached the substantia nigra at 12 months.At this age,theα-synuclein pathology associated with a drop of dopamine transporter in the striatum that anticipated by 6 months the axonal degeneration.From 12 months onwards oxidative/nitrosative stress developed in the striatum in parallel with altered expression of mitochondrial homeostasis regulators in the substantia nigra.Conclusions:In c-rel^(-/-)mice,reproducing a parkinsonian progressive pathology with non-motor and motor symptoms,a Braak-like pattern of brain ascendingα-synuclein deposition occurs.The peculiar phenotype of c-rel^(-/-)mice envisages a potential contribution of c-Rel dysregulation to the pathogenesis of PD.