| 1. |
- Brandi, Edoardo, et al.
(författare)
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Brain region-specific microglial and astrocytic activation in response to systemic lipopolysaccharides exposure
- 2022
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Ingår i: Frontiers in Aging Neuroscience. - : Frontiers Media SA. - 1663-4365. ; 14
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Tidskriftsartikel (refereegranskat)abstract
- Microglia cells are the macrophage population within the central nervous system, which acts as the first line of the immune defense. These cells present a high level of heterogeneity among different brain regions regarding morphology, cell density, transcriptomes, and expression of different inflammatory mediators. This region-specific heterogeneity may lead to different neuroinflammatory responses, influencing the regional involvement in several neurodegenerative diseases. In this study, we aimed to evaluate microglial response in 16 brain regions. We compared different aspects of the microglial response, such as the extension of their morphological changes, sensitivity, and ability to convert an acute inflammatory response to a chronic one. Then, we investigated the synaptic alterations followed by acute and chronic inflammation in substantia nigra. Moreover, we estimated the effect of partial ablation of fractalkine CX3C receptor 1 (CX3CR1) on microglial response. In the end, we briefly investigated astrocytic heterogeneity and activation. To evaluate microglial response in different brain regions and under the same stimulus, we induced a systemic inflammatory reaction through a single intraperitoneal (i.p.) injection of lipopolysaccharides (LPS). We performed our study using C57BL6 and CX3CR1+/GFP mice to investigate microglial response in different regions and the impact of CX3CR1 partial ablation. We conducted a topographic study quantifying microglia alterations in 16 brain regions through immunohistochemical examination and computational image analysis. Assessing Iba1-immunopositive profiles and the density of the microglia cells, we have observed significant differences in region-specific responses of microglia populations in all parameters considered. Our results underline the peculiar microglial inflammation in the substantia nigra pars reticulata (SNpr). Here and in concomitance with the acute inflammatory response, we observed a transient decrease of dopaminergic dendrites and an alteration of the striato-nigral projections. Additionally, we found a significant decrease in microglia response and the absence of chronic inflammation in CX3CR1+/GFP mice compared to the wild-type ones, suggesting the CX3C axis as a possible pharmacological target against neuroinflammation induced by an increase of systemic tumor necrosis factor-alpha (TNFα) or/and LPS. Finally, we investigated astrocytic heterogeneity in this model. We observed different distribution and morphology of GFAP-positive astrocytes, a heterogeneous response under inflammatory conditions, and a decrease in their activation in CX3CR1 partially ablated mice compared with C57BL6 mice. Altogether, our data confirm that microglia and astrocytes heterogeneity lead to a region-specific inflammatory response in presence of a systemic TNFα or/and LPS treatment.
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| 2. |
- Davidsson, Marcus, et al.
(författare)
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A comparison of AAV-vector production methods for gene therapy and preclinical assessment
- 2020
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 10:1
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Tidskriftsartikel (refereegranskat)abstract
- Adeno Associated Virus (AAV)-mediated gene expression in the brain is widely applied in the preclinical setting to investigate the therapeutic potential of specific molecular targets, characterize various cellular functions, and model central nervous system (CNS) diseases. In therapeutic applications in the clinical setting, gene therapy offers several advantages over traditional pharmacological based therapies, including the ability to directly manipulate disease mechanisms, selectively target disease-afflicted regions, and achieve long-term therapeutic protein expression in the absence of repeated administration of pharmacological agents. Next to the gold-standard iodixanol-based AAV vector production, we recently published a protocol for AAV production based on chloroform-precipitation, which allows for fast in-house production of small quantities of AAV vector without the need for specialized equipment. To validate our recent protocol, we present here a direct side-by-side comparison between vectors produced with either method in a series of in vitro and in vivo assays with a focus on transgene expression, cell loss, and neuroinflammatory responses in the brain. We do not find differences in transduction efficiency nor in any other parameter in our in vivo and in vitro panel of assessment. These results suggest that our novel protocol enables most standardly equipped laboratories to produce small batches of high quality and high titer AAV vectors for their experimental needs.
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| 3. |
- Haikal, Caroline, et al.
(författare)
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The bacterial amyloids phenol soluble modulins from staphylococcus aureus catalyze alpha-synuclein aggregation
- 2021
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Ingår i: International Journal of Molecular Sciences. - : MDPI AG. - 1661-6596 .- 1422-0067. ; 22:21
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Tidskriftsartikel (refereegranskat)abstract
- Aggregated α-synuclein (α-syn) is the main constituent of Lewy bodies, which are a pathological hallmark of Parkinson’s disease (PD). Environmental factors are thought to be potential triggers capable of initiating the aggregation of the otherwise monomeric α-syn. Braak’s seminal work redirected attention to the intestine and recent reports of dysbiosis have highlighted the potential causative role of the microbiome in the initiation of pathology of PD. Staphylococcus aureus is a bacterium carried by 30–70% of the general population. It has been shown to produce functional amy-loids, called phenol soluble modulins (PSMαs). Here, we studied the kinetics of α-syn aggregation under quiescent conditions in the presence or absence of four different PSMα peptides and observed a remarkable shortening of the lag phase in their presence. Whereas pure α-syn monomer did not aggregate up to 450 h after initiation of the experiment in neither neutral nor mildly acidic buffer, the addition of different PSMα peptides resulted in an almost immediate increase in the Thioflavin T (ThT) fluorescence. Despite similar peptide sequences, the different PSMα peptides displayed distinct effects on the kinetics of α-syn aggregation. Kinetic analyses of the data suggest that all four peptides catalyze α-syn aggregation through heterogeneous primary nucleation. The immunogold electron microscopic analyses showed that the aggregates were fibrillar and composed of α-syn. In addition of the co-aggregated materials to a cell model expressing the A53T α-syn variant fused to GFP was found to catalyze α-syn aggregation and phosphorylation in the cells. Our results provide evidence of a potential trigger of synucleinopathies and could have implications for the prevention of the diseases.
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| 4. |
- Liu, Di, et al.
(författare)
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Differential seeding and propagating efficiency of α-synuclein strains generated in different conditions
- 2021
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Ingår i: Translational Neurodegeneration. - : Springer Science and Business Media LLC. - 2047-9158. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Background: Accumulation of alpha-synuclein (α-syn) is a main pathological hallmark of Parkinson’s and related diseases, which are collectively known as synucleinopathies. Growing evidence has supported that the same protein can induce remarkably distinct pathological progresses and disease phenotypes, suggesting the existence of strain difference among α-syn fibrils. Previous studies have shown that α-syn pathology can propagate from the peripheral nervous system (PNS) to the central nervous system (CNS) in a “prion-like” manner. However, the difference of the propagation potency from the periphery to CNS among different α-syn strains remains unknown and the effect of different generation processes of these strains on the potency of seeding and propagation remains to be revealed in more detail. Methods: Three strains of preformed α-syn fibrils (PFFs) were generated in different buffer conditions which varied in pH and ionic concentrations. The α-syn PFFs were intramuscularly (IM) injected into a novel bacterial artificial chromosome (BAC) transgenic mouse line that expresses wild-type human α-syn, and the efficiency of seeding and propagation of these PFFs from the PNS to the CNS was evaluated. Results: The three strains of α-syn PFFs triggered distinct propagation patterns. The fibrils generated in mildly acidic buffer led to the most severe α-syn pathology, degeneration of motor neurons and microgliosis in the spinal cord. Conclusions: The different α-syn conformers generated in different conditions exhibited strain-specific pathology and propagation patterns from the periphery to the CNS, which further supports the view that α-syn strains may be responsible for the heterogeneity of pathological features and disease progresses among synucleinopathies.
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| 5. |
- Martinsson, Isak, et al.
(författare)
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Aβ/Amyloid Precursor Protein-Induced Hyperexcitability and Dysregulation of Homeostatic Synaptic Plasticity in Neuron Models of Alzheimer’s Disease
- 2022
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Ingår i: Frontiers in Aging Neuroscience. - : Frontiers Media SA. - 1663-4365. ; 14, s. 1-16
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Tidskriftsartikel (refereegranskat)abstract
- Alzheimer’s disease (AD) is increasingly seen as a disease of synapses and diverse evidence has implicated the amyloid-β peptide (Aβ) in synapse damage. The molecular and cellular mechanism(s) by which Aβ and/or its precursor protein, the amyloid precursor protein (APP) can affect synapses remains unclear. Interestingly, early hyperexcitability has been described in human AD and mouse models of AD, which precedes later hypoactivity. Here we show that neurons in culture with either elevated levels of Aβ or with human APP mutated to prevent Aβ generation can both induce hyperactivity as detected by elevated calcium transient frequency and amplitude. Since homeostatic synaptic plasticity (HSP) mechanisms normally maintain a setpoint of activity, we examined whether HSP was altered in AD transgenic neurons. Using methods known to induce HSP, we demonstrate that APP protein levels are regulated by chronic modulation of activity and that AD transgenic neurons have an impaired adaptation of calcium transients to global changes in activity. Further, AD transgenic compared to WT neurons failed to adjust the length of their axon initial segments (AIS), an adaptation known to alter excitability. Thus, we show that both APP and Aβ influence neuronal activity and that mechanisms of HSP are disrupted in primary neuron models of AD.
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| 6. |
- Martinsson, I, et al.
(författare)
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Aβ/APP-induced hyperexcitability and dysregulation of homeostatic synaptic plasticity in models of Alzheimer’s disease
- 2022
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The proper function of the nervous system is dependent on the appropriate timing of neuronal firing. Synapses continually undergo rapid activity-dependent modifications that require feedback mechanisms to maintain network activity within a window in which communication is energy efficient and meaningful. Homeostatic synaptic plasticity (HSP) and homeostatic intrinsic plasticity (HIP) are such negative feedback mechanisms. Accumulating evidence implicates that Alzheimer’s disease (AD)-related amyloid precursor protein (APP) and its cleavage product amyloid-beta (Aβ) play a role in the regulation of neuronal network activity, and in particular HSP. AD features impaired neuronal activity with regional early hyper-activity and Aβ-dependent hyperexcitability has also been demonstrated in AD transgenic mice. We demonstrate similar hyper-activity in AD transgenic neurons in culture that have elevated levels of both human APP and Aβ. To examine the individual roles of APP and Aβ in promoting hyperexcitability we used an APP construct that does not generate Aβ, or elevated Aβ levels independently of APP. Increasing either APP or Aβ in wild type (WT) neurons leads to increased frequency and amplitude of calcium transients. Since HSP/HIP mechanisms normally maintain a setpoint of activity, we examined whether homeostatic synaptic/intrinsic plasticity was altered in AD transgenic neurons. Using methods known to induce HSP/HIP, we demonstrate that APP protein levels are regulated by chronic modulation of activity and show that AD transgenic neurons have an impaired response to global changes in activity. Further, AD transgenic compared to WT neurons failed to adjust the length of their axon initial segments (AIS), an adaptation known to alter excitability. Thus, we present evidence that both APP and Aβ influence neuronal activity and that mechanisms of HSP/HIP are disrupted in neuronal models of AD.Competing Interest StatementThe authors have declared no competing interest.
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| 7. |
- Paulus, Agnes, et al.
(författare)
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Amyloid Structural Changes Studied by Infrared Microspectroscopy in Bigenic Cellular Models of Alzheimer’s Disease
- 2021
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Ingår i: International Journal of Molecular Sciences. - : MDPI AG. - 1422-0067. ; 22:7
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Tidskriftsartikel (refereegranskat)abstract
- Alzheimer’s disease affects millions of lives worldwide. This terminal disease is characterized by the formation of amyloid aggregates, so-called amyloid oligomers. These oligomers are composed of β-sheet structures, which are believed to be neurotoxic. However, the actual secondary structure that contributes most to neurotoxicity remains unknown. This lack of knowledge is due to the challenging nature of characterizing the secondary structure of amyloids in cells. To overcome this and investigate the molecular changes in proteins directly in cells, we used synchrotron-based infrared microspectroscopy, a label-free and non-destructive technique available for in situ molecular imaging, to detect structural changes in proteins and lipids. Specifically, we evaluated the formation of β-sheet structures in different monogenic and bigenic cellular models of Alzheimer’s disease that we generated for this study. We report on the possibility to discern different amyloid signatures directly in cells using infrared microspectroscopy and demonstrate that bigenic (amyloid-β, α-synuclein) and (amyloid-β, Tau) neuron-like cells display changes in β-sheet load. Altogether, our findings support the notion that different molecular mechanisms of amyloid aggregation, as opposed to a common mechanism, are triggered by the specific cellular environment and, therefore, that various mechanisms lead to the development of Alzheimer’s disease.
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| 8. |
- Svanbergsson, Alexander, et al.
(författare)
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FRET-Based Screening Identifies p38 MAPK and PKC Inhibition as Targets for Prevention of Seeded α-Synuclein Aggregation
- 2021
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Ingår i: Neurotherapeutics. - : Springer Science and Business Media LLC. - 1878-7479 .- 1933-7213. ; 18:3, s. 1692-1709
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Tidskriftsartikel (refereegranskat)abstract
- Aggregation of α-synuclein is associated with neurodegeneration and a hallmark pathology in synucleinopathies. These aggregates are thought to function as prion-like particles where the conformation of misfolded α-synuclein determines the traits of the induced pathology, similar to prion diseases. Still, little is known about the molecular targets facilitating the conformation-specific biological effects, but their identification could form the basis for new therapeutic interventions. High-throughput screening of annotated compound libraries could facilitate mechanistic investigation by identifying targets with impact on α-synuclein aggregation. To this end, we developed a FRET-based cellular reporter in HEK293T cells, with sensitivity down to 6.5 nM α-synuclein seeds. Using this model system, we identified GF109203X, SB202190, and SB203580 as inhibitors capable of preventing induction of α-synuclein aggregation via inhibition of p38 MAPK and PKC, respectively. We further investigated the mechanisms underlying the protective effects and found alterations in the endo-lysosomal system to be likely candidates of the protection. We found the changes did not stem from a reduction in uptake but rather alteration of lysosomal abundance and degradative capacity. Our findings highlight the value high-throughput screening brings to the mechanistic investigation of α-synuclein aggregation while simultaneously identifying novel therapeutic compounds.
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| 9. |
- Svanbergsson, Alexander
(författare)
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Modeling and Mechanistic Investigation of α-synuclein aggregation
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Our understanding of the α-synuclein aggregation process and the consequences thereof is currently limited, which in turn prevents the development of targeted therapeutic interventions. The work presented here, as a part of this thesis, is focused on expanding our understanding of the molecular events involved in α-synuclein aggregation. Towards this goal we have studied the impact of pathologically relevant forms of α-synuclein, namely A53T mutant α-synuclein and fibrillar α-synuclein, and characterized their impact on N-methyl-D-aspartate receptor (NMDAR) diffusion and function. We found both mutant and fibrillar α-synuclein, decreased the NMDAR diffusion and expression at the post-synapse. Moving further towards the mechanistic investigations we investigated the effect of two neuroprotective compounds on α-synuclein aggregation and found both compounds capable of clearing α-synuclein in cell and animal models potentially through autophagy related functions. In our efforts to scale mechanistic investigations we developed a high-throughput screening (HTS) capable FRET-based reporter for detection of α-synuclein aggregation in cells. Using this model, we performed a proof-of-concept screen of kinase inhibitors from which we identified three inhibitors with potent protective effects on α-synuclein aggregation. We further showed through mechanistic investigation that the protective effects likely involved lysosomal changes. Finally, in an effort to advance our knowledge of α-synuclein aggregation, we performed a genome-wide knockout screen to identify genes in the human genome with an impact on α-synuclein aggregation. This study also highlighted among other pathways the importance of the endolysosomal system in relation to α-synuclein aggregation. Many questions remain in regard to the molecular mechanisms involved in α-synuclein aggregation, but we hope our insights and models presented here will assist in the elucidation of the underlying mechanisms of α-synuclein aggregation.
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| 10. |
- Torres-Garcia, Laura, et al.
(författare)
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Monitoring the interactions between alpha-synuclein and Tau in vitro and in vivo using bimolecular fluorescence complementation
- 2022
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 12, s. 1-11
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Tidskriftsartikel (refereegranskat)abstract
- Parkinson’s disease (PD) and Alzheimer’s disease (AD) are characterized by pathological accumulation and aggregation of different amyloidogenic proteins, α-synuclein (aSyn) in PD, and amyloid-β (Aβ) and Tau in AD. Strikingly, few PD and AD patients’ brains exhibit pure pathology with most cases presenting mixed types of protein deposits in the brain. Bimolecular fluorescence complementation (BiFC) is a technique based on the complementation of two halves of a fluorescent protein, which allows direct visualization of protein–protein interactions. In the present study, we assessed the ability of aSyn and Tau to interact with each other. For in vitro evaluation, HEK293 and human neuroblastoma cells were used, while in vivo studies were performed by AAV6 injection in the substantia nigra pars compacta (SNpc) of mice and rats. We observed that the co-expression of aSyn and Tau led to the emergence of fluorescence, reflecting the interaction of the proteins in cell lines, as well as in mouse and rat SNpc. Thus, our data indicates that aSyn and Tau are able to interact with each other in a biologically relevant context, and that the BiFC assay is an effective tool for studying aSyn-Tau interactions in vitro and in different rodent models in vivo.
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| 11. |
- Wu, Jia-Zhen, et al.
(författare)
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Dihydromyricetin and Salvianolic acid B inhibit alpha-synuclein aggregation and enhance chaperone-mediated autophagy
- 2019
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Ingår i: Translational Neurodegeneration. - : Springer Science and Business Media LLC. - 2047-9158. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- Background: 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. Dysfunction of the CMA pathway impairs α-synuclein degradation and causes cytotoxicity.Results: In 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.Conclusions: Our 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.
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| 12. |
- Zhong, Chong Bin, et al.
(författare)
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Age-Dependent Alpha-Synuclein Accumulation and Phosphorylation in the Enteric Nervous System in a Transgenic Mouse Model of Parkinson’s Disease
- 2017
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Ingår i: Neuroscience Bulletin. - : Springer Science and Business Media LLC. - 1673-7067 .- 1995-8218. ; 33:5, s. 483-492
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Tidskriftsartikel (refereegranskat)abstract
- The enteric nervous system (ENS) controls the function of the gastrointestinal tract and has been implicated in various diseases, including Parkinson’s disease (PD). PD is a neurodegenerative disease with Lewy bodies (LBs) and Lewy neurites (LNs) as the main pathological features. In addition to the typical motor symptoms in PD, attention has been drawn to non-motor symptoms, such as constipation, implying dysfunction of the ENS. In the present study, we characterized the age-dependent morphological alterations and aggregation of α-synuclein (α-syn), the primary protein component in LBs and LNs, in the ENS in an α-syn transgenic mouse model. We found that the expression and accumulation of α-syn increased gradually in neurons of Meissner’s and Auerbach’s plexuses of the gastrointestinal tract with age (from 1 week to 2 years). In addition, α-syn was increasingly phosphorylated at the serine 129 residue, reflecting pathological alterations of the protein over time. Furthermore, α-syn was present in different subtypes of neurons expressing vasoactive intestinal polypeptide, neuronal nitric oxide synthase, or calretinin. The results indicated that BAC-α-Syn-GFP transgenic mice provide a unique model in which to study the relationship between ENS and PD pathogenesis.
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