Alpha-synuclein in Lewy bodies

Adeno-associated viral vectors for modeling Parkinson's disease in non-human primates

The development of clinical candidates that modify the natural progression of sporadic Parkinson's disease and related synucleinopathies is a praiseworthy endeavor, but extremely challenging. Therapeutic candidates that were successful in preclinical Parkinson's disease animal models have repeatedly failed when tested in clinical trials. While these failures have many possible explanations, it is perhaps time to recognize that the problem lies with the animal models rather than the putative candidate. In other words, the lack of adequate animal models of Parkinson's disease currently represents the main barrier to preclinical identification of potential disease-modifying therapies likely to succeed in clinical trials. However, this barrier may be overcome by the recent introduction of novel generations of viral vectors coding for different forms of alpha-synuclein species and related genes. Although still facing several limitations, these models have managed to mimic the known neuropathological hallmarks of Parkinson's disease with unprecedented accuracy, delineating a more optimistic scenario for the near future.

Gut-brain axis and environmental factors in Parkinson's disease: bidirectional link between disease onset and progression

Parkinson's disease has long been considered a disorder that primarily affects the brain, as it is defined by the dopaminergic neurodegeneration in the substantia nigra and the brain accumulation of Lewy bodies containing α-synuclein protein. In recent decades, however, accumulating research has revealed that Parkinson's disease also involves the gut and uncovered an intimate and important bidirectional link between the brain and the gut, called the "gut-brain axis." Numerous clinical studies demonstrate that gut dysfunction frequently precedes motor symptoms in Parkinson's disease patients, with findings including impaired intestinal permeability, heightened inflammation, and distinct gut microbiome profiles and metabolites. Furthermore, α-synuclein deposition has been consistently observed in the gut of Parkinson's disease patients, suggesting a potential role in disease initiation. Importantly, individuals with vagotomy have a reduced Parkinson's disease risk. From these observations, researchers have hypothesized that α-synuclein accumulation may initiate in the gut and subsequently propagate to the central dopaminergic neurons through the gut-brain axis, leading to Parkinson's disease. This review comprehensively examines the gut's involvement in Parkinson's disease, focusing on the concept of a gut-origin for the disease. We also examine the interplay between altered gut-related factors and the accumulation of pathological α-synuclein in the gut of Parkinson's disease patients. Given the accessibility of the gut to both dietary and pharmacological interventions, targeting gut-localized α-synuclein represents a promising avenue for developing effective Parkinson's disease therapies.

A model of L-DOPA-induced dyskinesia in parkinsonian mice produced by AAV vector-mediated overexpression of α-synuclein

L-3,4-dihydroxyphenylalanin (L-DOPA) is the most effective drug for treating Parkinson's disease (PD); however, long-term L-DOPA therapy can lead to L-DOPA-induced dyskinesia (LID). While the 6-hydroxydopamine-lesioned rodent model for LID fails to reproduce the pathological hallmarks of PD, a newly introduced rodent model using adeno-associated virus (AAV)-mediated overexpression of α-synuclein results in α-synuclein aggregation and progressive loss of dopaminergic neurons. The present study aimed to provoke LID in parkinsonian mice generated by AAV vector-mediated overexpression of α-synuclein and to explore histologic features associated with LID. A recombinant AAV2/7 vector containing the human α-synuclein transgene was injected into the substantia nigra (SN) of wild-type mice. Eight weeks later, mice received daily injections of 10 mg/kg of L-DOPA for one week, followed by 25 mg/kg of L-DOPA daily for the subsequent week. LID was observed in 3 out of 19 mice at the 10 mg/kg L-DOPA dose and in 14 mice at 25 mg/kg dose. The number of tyrosine hydroxylase (TH)-positive neurons in the AAV vector-injected side of the SN was reduced to an average of 59 % of the intact side, and the optical density of TH-positive fibers in the ipsilateral striatum was reduced to an average of 37 %. Abnormal Involuntary Movement scores were correlated with decrease in both the number of TH-positive neurons in SN and optical density of striatal TH-positive fibers. This study establishes a mouse model for LID using AAV vector-mediated overexpression of α-synuclein, providing a useful tool for investigating the progressive changes and associated pathophysiology during occurrence of LID.

Early α-synuclein aggregation decreases corticostriatal glutamate drive and synapse density

Neuronal inclusions of α-synuclein (α-syn) are pathological hallmarks of Parkinson's disease (PD) and Dementia with Lewy Bodies (DLB). α-Syn pathology accumulates in cortical neurons which project to the striatum. To understand how α-syn pathology affects cortico-striatal synapses at early time points before significant dopamine neuron loss, pre-formed α-syn fibrils (PFF) were injected into the striatum to induce endogenous α-syn aggregation in corticostriatal-projecting neurons. Electrophysiological recordings of striatal spiny projection neurons (SPNs) from acute slices found a significant decrease in evoked corticostriatal glutamate release and corticostriatal synaptic release sites in mice with PFF-induced aggregates compared to monomer injected mice. Expansion microscopy, confocal microscopy and Imaris reconstructions were used to identify VGLUT1 positive presynaptic terminals juxtaposed to Homer1 positive postsynaptic densities, termed synaptic loci. Quantitation of synaptic loci density revealed an early loss of corticostriatal synapses. Immunoblots of the striatum showed reductions in expression of pre-synaptic proteins VGLUT1, VAMP2 and Snap25, in mice with α-syn aggregates compared to controls. Paradoxically, a small percentage of remaining VGLUT1+ synaptic loci positive for pS129-α-syn aggregates showed enlarged volumes compared to nearby synapses without α-syn aggregates. Our combined physiology and high-resolution imaging data point to an early loss of corticostriatal synapses in mice harboring α-synuclein inclusions, which may contribute to impaired basal ganglia circuitry in PD and DLB.

Allium sativum-Derived Alliin and Allicin Stably Bind to α-Synuclein and Prevent Its Cytotoxic Aggregation

Neurodegenerative diseases such as Parkinson's disease are characterized by the pathological aggregation of α-synuclein. Targeting α-synuclein aggregation through natural bioactive compounds offers a promising therapeutic strategy. In this study, sulfur-containing compounds derived from Allium sativum were evaluated for their drug-likeness, pharmacokinetic properties, and ability to inhibit α-synuclein aggregation using a combination of in silico and in vitro approaches. ADMET profiling indicated high gastrointestinal absorption for nine compounds, supporting their drug-like properties. Six compounds were predicted to cross the blood-brain barrier, suggesting potential efficacy in the central nervous system. Molecular docking identified alliin, allicin, E-ajoene, and diallyl disulfide as top binders to α-synuclein, forming stable interactions with key aggregation-prone regions. Molecular dynamics simulations over 100 ns confirmed the structural stability of alliin- and allicin-α-synuclein complexes, with minimal residue fluctuations and persistent hydrogen bonding. MM-GBSA binding energy analysis corroborated these results, showing favorable binding free energies, particularly for alliin and E-ajoene. Principal component analysis (PCA) further supported the role of alliin in stabilizing α-synuclein dynamics. In vitro cellular assays further validated these computational findings. Using an SH-SY5Y cell-based α-synuclein aggregation model, treatment with alliin and allicin significantly reduced α-synuclein aggregation. Furthermore, MTT-based cytotoxicity assays in SH-SY5Y neuroblastoma cells overexpressing α-synuclein revealed that alliin and allicin conferred notable cytoprotective effects by reducing α-synuclein-induced toxicity. Taken together, these findings highlight alliin and allicin as potent lead compounds that not only bind and stabilize α-synuclein but also attenuate its aggregation and associated cytotoxicity.

Ligands for Protein Fibrils of Amyloid-β, α-Synuclein, and Tau

Amyloid fibrils are characteristic features of many neurodegenerative diseases, including Alzheimer's disease and Parkinson's disease. The use of small molecule ligands that bind to amyloid fibrils underpins both fundamental research aiming to better understand the pathology of neurodegenerative disease, and clinical research aiming to develop diagnostic tools for these diseases. To date, a large number of amyloid-binding ligands have been reported in the literature, predominantly targeting protein fibrils composed of amyloid-β (Aβ), tau, and α-synuclein (αSyn) fibrils. Fibrils formed by a particular protein can adopt a range of possible morphologies, but protein fibrils formed in vivo possess disease-specific morphologies, highlighting the need for morphology-specific amyloid-binding ligands. This review details the morphologies of Aβ, tau, and αSyn fibril polymorphs that have been reported as a result of structural work and describes a database of amyloid-binding ligands containing 4,288 binding measurements for 2,404 unique compounds targeting Aβ, tau, or αSyn fibrils.

Neural stem cells of the subventricular zone: A potential stem cell pool for brain repair in Parkinson's disease

Parkinson's disease is a neurodegenerative disease caused by the degeneration of dopaminergic neurons in the substantia nigra. There are no curative treatments, and therefore, there is an urgent need for new approaches. One potential strategy being investigated is stem cell-based approaches to replace lost neurons, by, for example, harnessing endogenous neural stem cells (NSCs). These cells are found in the subventricular zone (SVZ) aligning the lateral ventricles and remain in a dormant state in the aged and diseased mammalian brain. However, with the appropriate stimuli, NSCs can shift into an activated state, proliferate, and differentiate. In this review, we discuss how PD pathology affects the behavior of NSCs and current pharmacological strategies to boost regeneration in PD. NSCs of the SVZ could be a stem cell source for brain repair, and future studies should shed light on whether these stem cells have the potential to produce functional neuronal cells.

α-Synuclein Pathology in Synucleinopathies: Mechanisms, Biomarkers, and Therapeutic Challenges

Parkinson's disease and related synucleinopathies, including dementia with Lewy bodies and multiple system atrophy, are characterised by the pathological aggregation of the α-synuclein (aSyn) protein in neuronal and glial cells, leading to cellular dysfunction and neurodegeneration. This review synthesizes knowledge of aSyn biology, including its structure, aggregation mechanisms, cellular interactions, and systemic influences. We highlight the structural diversity of aSyn aggregates, ranging from oligomers to fibrils, their strain-like properties, and their prion-like propagation. While the role of prion-like mechanisms in disease progression remains a topic of ongoing debate, these processes may contribute to the clinical heterogeneity of synucleinopathies. Dysregulation of protein clearance pathways, including chaperone-mediated autophagy and the ubiquitin-proteasome system, exacerbates aSyn accumulation, while post-translational modifications influence its toxicity and aggregation propensity. Emerging evidence suggests that immune responses and alterations in the gut microbiome are key modulators of aSyn pathology, linking peripheral processes-particularly those of intestinal origin-to central neurodegeneration. Advances in biomarker development, such as cerebrospinal fluid assays, post-translationally modified aSyn, and real-time quaking-induced conversion technology, hold promise for early diagnosis and disease monitoring. Furthermore, positron emission tomography imaging and conformation-specific antibodies offer innovative tools for visualising and targeting aSyn pathology in vivo. Despite significant progress, challenges remain in accurately modelling human synucleinopathies, as existing animal and cellular models capture only specific aspects of the disease. This review underscores the need for more reliable aSyn biomarkers to facilitate the development of effective treatments. Achieving this goal requires an interdisciplinary approach integrating genetic, epigenetic, and environmental insights.

E2 conjugating enzymes: A silent but crucial player in ubiquitin biology

E2 conjugating enzymes serve as the linchpin of the Ubiquitin-Proteasome System (UPS), facilitating ubiquitin (Ub) transfer to substrate proteins and regulating diverse processes critical to cellular homeostasis. The interaction of E2s with E1 activating enzymes and E3 ligases singularly positions them as middlemen of the ubiquitin machinery that guides protein turnover. Structural determinants of E2 enzymes play a pivotal role in these interactions, enabling precise ubiquitin transfer and substrate specificity. Regulation of E2 enzymes is tightly controlled through mechanisms such as post-translational modifications (PTMs), allosteric control, and gene expression modulation. Specific residues that undergo PTMs highlight their impact on E2 function and their role in ubiquitin dynamics. E2 enzymes also cooperate with deubiquitinases (DUBs) to maintain proteostasis. Design of small molecule inhibitors to modulate E2 activity is emerging as promising avenue to restrict ubiquitination as a potential therapeutic intervention. Additionally, E2 enzymes have been implicated in the pathogenesis and progression of neurodegenerative disorders (NDDs), where their dysfunction contributes to disease mechanisms. In summary, examining E2 enzymes from structural and functional perspectives offers potential to advance our understanding of cellular processes and assist in discovery of new therapeutic targets.

α-Synuclein pathology and mitochondrial dysfunction: Toxic partners in Parkinson's disease

Two major neuropathological features of Parkinson's disease (PD) are α-synuclein Lewy pathology and mitochondrial dysfunction. Although both α-synuclein pathology and mitochondrial dysfunction may independently contribute to PD pathogenesis, the interaction between these two factors is not yet fully understood. In this review, we discuss the physiological functions of α-synuclein and mitochondrial homeostasis in neurons as well as the pathological defects that ensue when these functions are disturbed in PD. Recent studies have highlighted that dysfunctional mitochondria can become sequestered within Lewy bodies, and cell biology studies have suggested that α-synuclein can directly impair mitochondrial function. There are also PD cases caused by genetic or environmental perturbation of mitochondrial homeostasis. Together, these studies suggest that mitochondrial dysfunction may be a common pathway to neurodegeneration in PD, triggered by multiple insults. We review the literature surrounding the interaction between α-synuclein and mitochondria and highlight open questions in the field that may be explored to advance our understanding of PD and develop novel, disease-modifying therapies.

CSF α-synuclein aggregation is associated with APOE ε4 and progressive cognitive decline in Alzheimer's disease

At autopsy, around half of the Alzheimer's disease (AD) brains exhibit Lewy body pathology, and the main component of Lewy body pathology is α-synuclein aggregates. This study investigated the prevalence of cerebrospinal fluid (CSF) α-synuclein aggregation and its association with demographic factors and cognitive decline among 1619 participants from the Alzheimer's Disease Neuroimaging Initiative (ADNI), with the test for α-synuclein aggregation by seed amplification assay (SAA). This cohort consisted of 595 cognitively normal (CN) individuals, 765 with mild cognitive impairment (MCI), and 259 with AD dementia. The results showed a higher prevalence of positive α-synuclein aggregation status in the AD dementia group (37.07 %) and the MCI group (22.75 %) compared to CN controls (16.13 %). Additionally, APOE ε4 carriers exhibited a higher prevalence of α-synuclein aggregation compared to non-carriers: 20.12 % for APOE ε4-/- (non-carriers), 24.82 % for APOE ε4 + /-, and 30.92 % for APOE ε4 + /+ . Longitudinally, positive CSF α-synuclein aggregation associated with accelerated cognitive decline, especially in the MCI and AD groups. Notably, positive aggregation status did not significantly affect cognitive trajectories in CN individuals. Moreover, APOE ε4 carriers with positive CSF α-synuclein aggregation experienced more pronounced cognitive decline. This study provides evidence that CSF α-synuclein aggregation is associated with cognitive function and the APOE ε4 allele. These findings suggest that CSF α-synuclein SAA, in combination with APOE ε4 status, could serve as biomarkers for predicting cognitive decline in AD.

Alpha-Synuclein as a Potential Biomarker for Inclusion Body Myositis in Blood and Muscle

AIMS

Diagnosis of inclusion body myositis (IBM) is difficult and currently based on a combination of clinical and (immuno)histological findings. Biomarkers facilitating the diagnostic process are needed. Alpha-synuclein (αSN) aggregates are a known histological feature of IBM, but there is a lack of information on their diagnostic relevance. Furthermore, serum αSN concentrations in IBM have not been investigated.

METHODS

Immunohistochemical staining for αSN was performed on 63 biopsies (19 IBM, 21 other inflammatory myopathies, 20 other myopathies and 3 healthy controls), and αSN reactive fibres were quantified. The serum concentration of αSN was determined by ELISA in 156 serum samples (11 IBM, 25 other inflammatory myopathies, 53 hereditary myopathies, 30 mitochondriopathies and 37 healthy controls).

RESULTS

The proportion of fibres with αSN immunoreactivity was significantly higher in IBM compared to all groups (p < 0.001) and discriminated IBM against all other neuromuscular disorders with a sensitivity of 79% and a specificity of 85%, which further improved when only non-regenerating fibres were examined. In serum, αSN concentrations in IBM were generally not different from healthy controls. However, serum concentrations were inversely correlated with disease duration (r = -0.62, p = 0.04) and positively correlated with the IBM functional rating scale (r = 0.74, p = 0.01). Consequently, stratification according to these clinical parameters showed significantly lower serum αSN concentrations in late-stage, more severely affected patients.

CONCLUSIONS

αSN reactivity may serve as an additional immunohistochemical marker for IBM diagnosis. Furthermore, this study indicates that αSN serum concentrations decrease with disease duration and clinical deterioration. Therefore, serum αSN may be provisionally considered a monitoring biomarker in IBM, pending further studies.

Unlocking Parkinson's disease: the role of microRNAs in regulation, diagnosis, and therapy

Parkinson's disease (PD), the second most prevalent neurodegenerative disorder globally, imposes substantial healthcare burdens on aging populations. The pathogenesis of PD is complex and multifaceted. Emerging evidence highlights microRNA (miRNA) dysregulation as a critical regulatory layer that drives PD progression. These small noncoding RNAs mediate posttranscriptional gene regulation through target mRNA binding, inducing either transcript degradation or translational repression. This article reviews the distinct miRNAs that orchestrate PD pathogenesis by disrupting mitochondrial homeostasis, lysosomal clearance pathways, ferroptosis regulation, and neuroinflammatory responses. Notably, some miRNAs achieve these effects by selectively targeting risk genes central to PD pathology. Crucially, certain miRNAs exhibit aberrant expression patterns in the brain tissues and biofluids of PD patients or models, highlighting their potential as minimally invasive diagnostic or prognostic biomarkers. Furthermore, this review highlights the novel role of exosomes as miRNA carriers, offering innovative possibilities for PD therapeutic interventions. With the deepening understanding of miRNA research advances in PD, we propose that these insights may not only inform PD treatment strategies but also hold relevance for addressing other genetic disorders.

Clearance Pathways for α-Synuclein in Parkinson's Disease

Protein aggregation and accumulation are hallmark features of neurodegenerative diseases. In Parkinson's disease, the progressive formation and propagation of α-synuclein aggregates-found in Lewy bodies and Lewy neurites-are closely linked to widespread neuronal dysfunction, dopaminergic neuron loss, and the emergence of both motor and nonmotor symptoms, including anosmia, cognitive decline, and depression. Despite their pathological significance, the mechanisms underlying the formation, spread, and clearance of these aggregates remain incompletely understood. In this review, we examine the cellular and molecular pathways responsible for the elimination of protein aggregates in the diseased brain. We first summarize various experimental models of α-synuclein pathology, followed by a discussion of the degradation mechanisms in neurons and glial cells under pathological conditions. These findings offer new insights into cell type-specific clearance pathways and highlight potential therapeutic targets for mitigating α-synuclein-associated toxicity in Parkinson's disease.

Identification of novel small molecule chaperone activators for neurodegenerative disease treatment

A pathological hallmark of neurodegenerative disease is the accumulation of aberrant protein aggregates which contribute to the cytotoxicity and are therefore a target for therapy development. One key mechanism to manage cellular protein homeostasis is heat shock proteins (HSPs), protein chaperones which are known to target aberrant protein accumulation. Activation of HSPs target aberrant TDP-43, tau and amyloid to rescue neurodegenerative disease. As an attempt to target HSP activation for neurodegeneration therapy, we here develop a drug screening assay to identify compounds that will activate the master regulator of HSPs, the transcription factor heat shock factor 1 (HSF1). As HSF1 is bound by HSP90 which prevents its activation, we developed a NanoBRET assay, which allows us to monitor and quantify the HSF1-HSP90 interaction in living cells to screen for compounds disrupting this interaction and thereby releasing HSF1 for activation. After the optimisation and validation of the assay, a two thousand compound library was screened which produced 10 hits including two known HSP90 inhibitors. Follow-up functional study showed that one of the hits oxyphenbutazone (OPB) significantly reduces the accumulation of insoluble TDP-43 in a cell model, eliciting no signs of stress or toxicity. Overall, this study demonstrates a viable strategy for new drug discovery in targeting aberrant proteins and identifies potential candidates for translation into neurodegenerative disease treatment.

Global and local effects in lipid-mediated interactions between peripheral and integral membrane proteins

Amphitropic proteins (APs) are a subfamily of water-soluble peripherally membrane-bound proteins that interact directly with the lipid membrane rather than with intrinsic membrane proteins and are therefore strongly influenced by membrane properties. When an AP interacts with a membrane containing an integral membrane protein, a ternary protein-lipid-protein system is created. Even in the absence of direct interactions between the amphitropic and integral proteins, the two proteins can affect each other by modifying lipid membrane properties, either at the global (i.e., whole-membrane) or local (i.e., confined to a small area around the bound or integrated protein) scale. These lipid-mediated protein-protein interactions are indirect and, therefore, difficult to elucidate; independent experimental data are required to report on each individual interaction to comprehend the whole system. Examples for which comprehensive data are available are remarkably rare. In this article, we describe how these difficulties could be surmounted by using the channel-forming integral membrane protein gramicidin A (grA) reconstituted in a planar lipid membrane and exposed to the amphitropic proteins dimeric tubulin or α-synuclein. Importantly, there are no known direct interactions between these APs and grA, thus revealing the role of the lipid membrane. Here, grA serves a dual role. First, grA reports on the global properties of the lipid membrane; grA results, combined with the well-understood tubulin-lipid interaction, yield a complete picture of the mutual effect of tubulin binding on the lipid membrane. Second, the presence of the grA conducting dimer alters the local membrane curvature and creates binding sites for tubulin in an otherwise inert membrane composition.

Multimodal markers of immune activation predict cognitive outcomes in Parkinson's disease

BACKGROUND

Inflammation is well described in the central nervous system (CNS) and the periphery in Parkinson's disease (PD) and has been implicated in dementia risk. Longitudinal studies to identify immune/inflammatory biomarkers predicting cognitive decline are lacking.

METHODS

Peripheral blood mononuclear cells and cerebrospinal fluid (CSF)-derived immune cells were obtained from newly-diagnosed PD cases and healthy controls as part of the NET-PDD study. Immunophenotyping was performed using flow cytometry. CSF:blood ratios were calculated as a index of cell ingress to the CNS. Neuroinflammation was evaluated using 11C-PK11195 positron emission tomography (PET) MRI scanning. Participants were then followed-up clinically for 3 years to determine cognitive outcomes.

RESULTS

Bivariate comparisons between PD cases who were cognitively impaired at 3 years (PD-CI N = 10), PD non cognitively impaired (PD-NCI, N = 25) and controls (N = 36) identified 22 blood/CSF immune variables that differed between groups. The differences with the largest effect sizes (Cliff's d) were a higher proportion of activated CD4 T cells in the blood (CD4 + CD28+, d = 0.63) and a higher CSF:blood ratio of memory B cells (d = 0.63) in PD-CI versus controls. The substantia nigra was the only brain region in which PD-CI versus controls showed a higher 11C-PK11195 non-displaceable binding potential (BPND) (d = 0.45). In a multivariate regression model including age and gender, the CSF:blood memory B cell ratio and substantia nigra 11C-PK11195 BPND at baseline predicted cognitive decline over 3 years. ROC analysis demonstrated that the lead blood, CSF and imaging markers individually predicted cognitive status at 3 years with good accuracy (AUC 0.79-0.85).

CONCLUSIONS

An increase in activated CD4 cells in the blood, transition of B cells to the CNS and inflammation in the substantia nigra were predictive of longitudinal cognitive outcomes in PD. These markers warrant further validation as biomarkers for immune/inflammatory stratification and add to the evidence supporting development of therapeutic strategies to reduce microglial inflammation or the recruitment of lymphocytes to the CNS in early PD.

Resveratrol Attenuates CSF Markers of Neurodegeneration and Neuroinflammation in Individuals with Alzheimer's Disease

Alzheimer's disease (AD) is a progressive neurodegenerative disorder that is characterized by amyloid-beta (Aβ) accumulation and neuroinflammation. A previous multicenter, phase 2, double-blind, placebo-controlled trial randomized 179 participants into placebo or resveratrol over 52 weeks. Sub-analysis of CSF biomarkers of neuronal damage, inflammation, and microglial activity was performed in a subset of patients treated with a placebo (n = 21) versus resveratrol (n = 30). Markers of neuronal damage, including neuron-specific enolase and hyperphosphorylated neurofilaments, were reduced. Microglial activation was measured via a triggering receptor expressed on myeloid cells (TREM)-2 at baseline and after resveratrol treatment. Resveratrol significantly reduced CSF TREM2 levels and decreased inflammation and tissue damage, including matrix metalloprotease (MMP)-9. Cathepsin D, a lysosomal marker of autophagy, was reduced in the resveratrol group compared with placebo, while angiogenin, a marker of vascular angiogenesis, was increased. These data suggest that resveratrol may exert anti-inflammatory and neuroprotective effects in AD by reducing CSF TREM2 and other markers of neuronal damage. Further research is needed to assess the significance of these biomarker changes on clinical outcomes in patients with neurodegenerative diseases.

Monomers, Dimers, and Oligomers of Pyroglutamate-Modified α-Synuclein Fragments Exhibit Distinct Biophysical Characteristics

α-Synuclein (aSyn) aggregation represents a key event in the neurodegenerative cascade of synucleinopathies. Initially, aSyn appears as an intrinsically disordered protein. However, its structural flexibility allows aSyn to either adopt α-helical conformations, relevant for physiological functions at presynaptic vesicles, or form β-strand-rich aggregates, leading to toxic oligomers. This relation between structure, function, and toxicity can be influenced by post-translational modifications such as the recently identified glutaminyl cyclase-catalyzed pyroglutamate (pE) modification. Here, we investigated (i) structural characteristics of monomeric, dimeric, and oligomeric states of N-terminal truncated, pE-modified aSyn variants, pE24-, pE62-, and pE79-aSyn by a complementary biophysical approach including DLS, SEC-MALS, SRCD, SEC-SAXS, and AUC and (ii) the toxicity of oligomeric pE-aSyn variants compared to full-length aSyn. Overall, pE62-aSyn showed an immediate fibril formation, reflecting the aggregation-prone properties of this particular variant. Furthermore, in a membrane-like environment, the secondary aSyn structure shifted toward α-helical folding depending on the degree of N-terminal truncation. pE79-aSyn showed a significantly reduced level of structural adaptation, reflecting compromised functions at presynaptic vesicles. In addition, the comparative analysis indicates the presence of a dimeric aSyn intermediate, the initial and potentially crucial step in aSyn aggregation, and supports the hypothesis of a toxic porous oligomeric state. For the first time, based on SAXS data, EOM models of the dimeric aSyn state are proposed.

Trehalose-releasing nanogels reduce α-synuclein-induced Lewy body-like inclusions in primary mouse hippocampal neurons

Parkinson's disease (PD) is the second most prevalent age-related neurodegenerative disorder, clinically characterized by both motor and non-motor symptoms. A key hallmark of PD is the accumulation of misfolded α-synuclein, which aggregates to Lewy bodies (LB) formed inside neurons. Trehalose, a disaccharide that induces autophagy, has been demonstrated to reduce α-synuclein aggregation in vivo. However, the enzyme trehalase rapidly degrades free trehalose, and its hydrophilicity causes poor penetration through the cell membrane. Thus, advanced trehalose delivery strategies are urgently needed. Herein, we investigated the effects of trehalose-bearing nanogels for reducing α-synuclein protein-induced perinuclear LB-like pathology in primary mouse hippocampal neurons. The study compares the effects of trehalose-releasing nanogel (TR) and trehalose-non releasing nanogel (TNR). The results showed that TR, but not TNR, nor free trehalose reduced LB-like inclusions in primary hippocampal neurons. The neuroprotective effects of TR may result from the synergistic effects of direct limitation of α-synuclein aggregates formation and trehalose release-induced autophagy promoting aggregates clearance. Overall, enhancing trehalose delivery with nanogels that can sustainably release trehalose could be worth further investigation as a new potential option for reducing α-synuclein aggregation in neurons affected by neurodegenerative diseases.

Accurate prediction of the kinetic sequence of physicochemical states using generative artificial intelligence

Capturing the time evolution and predicting kinetic sequences of states of physicochemical systems present significant challenges due to the precision and computational effort required. In this study, we demonstrate that 'Generative Pre-trained Transformer (GPT)', an artificial intelligence model renowned for machine translation and natural language processing, can be effectively adapted to predict the dynamical state-to-state transition kinetics of biologically relevant physicochemical systems. Specifically, by using sequences of time-discretized states from Molecular Dynamics (MD) simulation trajectories akin to the vocabulary corpus of a language, we show that a GPT-based model can learn the complex syntactic and semantic relationships within the trajectory. This enables GPT to predict kinetically accurate sequences of states for a diverse set of biomolecules of varying complexity, at a much quicker pace than traditional MD simulations and with a better efficiency than other baseline time-series prediction approaches. More significantly, the approach is found to be equally adept at forecasting the time evolution of out-of-equilibrium active systems that do not maintain detailed balance. An analysis of the mechanism inherent in GPT reveals the crucial role of the 'self-attention mechanism' in capturing the long-range correlations necessary for accurate state-to-state transition predictions. Together, our results highlight generative artificial intelligence's ability to generate kinetic sequences of states of physicochemical systems with statistical precision.

Plasma α-synuclein domain profiles across α-synucleinopathies

The differential diagnosis of α-synucleinopathies, including Parkinson's disease, dementia with Lewy bodies (DLB) and multiple system atrophy (MSA), remains challenging due to overlapping clinical features and the absence of reliable biomarkers. We developed a targeted mass spectrometry assay to profile α-synuclein peptides in plasma from Parkinson's disease (n = 82), DLB (n = 32), MSA (n = 8) and controls (n = 21). We hypothesized that disease-specific truncations or post-translational modifications would alter levels of non-modified α-synuclein peptides across α-synucleinopathies. The assay quantified non-modified peptides derived from the N-terminus and non-amyloid component (NAC) domain, regions implicated in aggregate formation. Although peptide levels were consistent across disease groups, a distinct NAC domain pattern observed in MSA may reflect unique pathological processes. This study presents the first blood-based profiling of α-synuclein peptides in these disorders, offering a basis for further investigation into disease mechanisms. Refinement of the assay to include post-translational modifications could enhance understanding of α-synucleinopathies and support future biomarker development.

Exploring α-Syn's Functions Through Ablation Models: Physiological and Pathological Implications

A significant advancement in neurodegenerative research was the discovery that α-synuclein (α-Syn/SNCA) plays a part in the pathophysiology of Parkinson's disease (PD). Decades later, the protein's significant impacts on various brain disorders are still being extensively explored. In disease conditions, α-Syn misfolds and forms abnormal aggregates that accumulate in neurons, thus triggering various organellar dysfunctions and ultimately neurodegeneration. These misfolded forms are highly heterogeneous and vary significantly among different synucleinopathies, such as PD, Multiple System Atrophy, or Dementia with Lewy bodies. Though initially believed to be exclusively localized in the brain, numerous pieces of evidence suggest that α-Syn functions transcend the central nervous system, with roles in peripheral functions, such as modulation of immune responses, hematopoiesis, and gastrointestinal regulation. Here, we aim to provide a detailed compilation of cellular functions and pathological phenotypes that are altered upon attenuation of α-Syn function in vitro and in vivo and explore the effects of SNCA gene silencing in healthy and disease states using cellular and animal models.

Autophagy Dysfunction and Neurodegeneration: Where Does It Go Wrong?

An infamous hallmark of neurodegenerative diseases is the accumulation of misfolded or unfolded proteins forming inclusions in the brain. The accumulation of these abnormal structures is a mysterious one, given that cells devote significant resources to integrate complementary pathways to ensure proteome integrity and proper protein folding. Aberrantly folded protein species are rapidly targeted for disposal by the ubiquitin-proteasome system (UPS), and even if this should fail, and the species accumulates, the cell can also rely on the lysosome-mediated degradation pathways of autophagy. Despite the many safeguards in place, failure to maintain protein homeostasis commonly occurs during, or preceding, the onset of disease. Over the last decade and a half, studies suggest that the failure of autophagy may explain the disruption in protein homeostasis observed in disease. In this review, we will examine how the highly complex cells of the brain can become vulnerable to failure of aggregate clearance at specific points during the processive pathway of autophagy, contributing to aggregate accumulation in brains with neurodegenerative disease.

ZSCAN21 mediates the pathogenic transcriptional induction of α-synuclein in cellular and animal models of Parkinson's disease

The expression level of α-synuclein is thought to play a crucial role in the pathogenesis of Parkinson's disease. However, little is known about the molecular mechanisms regulating the transcription of its gene, SNCA, particularly in the context of the disease. The transcription factor ZSCAN21 has been shown to act on SNCA, but whether ZSCAN21 is actually involved in the induction of SNCA transcription in Parkinson's disease is unknown. To address this question, we used the MPTP mouse model and LUHMES-derived dopaminergic neuronal spheroids, subjected to Parkinson's disease-related neurotoxins and mutations. We show that MPP+-treated spheroids recapitulate the main features of α-synuclein pathology and that MPP+-triggered transcriptional induction of SNCA is associated with ZSCAN21 stabilisation. Importantly, knock-down of ZSCAN21 prevents both the MPP+-triggered increase in α-synuclein mRNA and pre-mRNA levels in LUHMES-derived spheroids and the death of dopaminergic neurons in the substantia nigra of MPTP-treated mice. These effects are recapitulated by knockdown of TRIM17, a ZSCAN21 stabiliser which prevents its ubiquitination and degradation mediated by TRIM41. Moreover, reducing the interaction between ZSCAN21 and TRIM41, either by inserting Parkinson's disease-associated mutations into the TRIM41 gene or by preventing SUMOylation of ZSCAN21, results in both stabilisation of ZSCAN21 and induction of SNCA. Taken together, our data strongly suggest that ZSCAN21 is a crucial transcription factor for pathogenic α-synuclein expression and neurodegeneration in Parkinson's disease, pointing to its regulators, TRIM17 and TRIM41, as original therapeutic targets for a neuroprotective treatment of Parkinson's disease.

Chiral Carbon Nanodots Modulate α-Synuclein Homeostasis to Combat Parkinson's Disease

Inhibiting α-synuclein (α-syn) aggregation is an effective treatment for Parkinson's disease (PD), and chiral recognition of proteins offers a novel strategy for designing efficient inhibitors. However, the impact of chiral selectivity on α-syn aggregation and its regulatory mechanisms remain ambiguous. In this work, it is synthesized chiral carbon nanodots (CNDs), including L-CNDs, D-CNDs, and DL-CNDs, and found that D-CNDs exhibited the most potent inhibitory effect on α-syn aggregation. ¹H-¹⁵N heteronuclear single quantum coherence nuclear magnetic resonance spectroscopy revealed that CNDs primarily interact with α-syn through electrostatic interactions, with D-CNDs specifically targeting key aggregation-prone residues, thereby disrupting β-sheet formation and reducing fibril assembly. In contrast, L-CNDs and DL-CNDs exhibited limited inhibitory effects, attributed to their weak affinity for the non-amyloid-β component region. Moreover, CNDs efficiently crossed the blood-brain barrier, and D-CNDs significantly reduced α-syn accumulation, alleviated neuronal damage, and ameliorated cognitive function. This work underlines the critical role of chirality in modulating α-syn aggregation and provides a novel strategy for developing enantiomer-selective inhibitors for PD therapy.

Intermittent fasting reduces alpha-synuclein pathology and functional decline in a mouse model of Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disorder characterized by dopaminergic neuron degeneration and α-synuclein (aSyn) accumulation. Environmental factors play a significant role in PD progression, highlighting the potential of non-pharmacological interventions. This study investigates the therapeutic effects of intermittent fasting (IF) in an rAAV-aSyn mouse model of PD. IF, initiated four weeks post-induction of aSyn pathology, improved motor function and reduced dopaminergic neuron and axon terminal degeneration. Additionally, IF preserved dopamine levels and synaptic integrity in the striatum. Mechanistically, IF enhanced autophagic activity, promoting phosphorylated-aSyn clearance and reducing its accumulation in insoluble brain fractions. Transcriptome analysis revealed IF-induced modulation of inflammation-related genes and microglial activation. Validation in primary cultures confirmed that autophagy activation and inflammatory modulators (CCL17, IL-36RN) mitigate aSyn pathology. These findings suggest that IF exerts neuroprotective effects, supporting further exploration of IF and IF-mimicking therapies as potential PD treatments.

Astrocytes carrying LRRK2 G2019S exhibit increased levels of clusterin chaperone via miR-22-5p and reduced ability to take up α-synuclein fibrils

Accumulating evidence highlights that dysfunction of astrocyte biology might contribute to Parkinson's disease (PD) onset and progression. Leucine-rich repeat kinase 2 (LRRK2), a gene linked to genetic and familial PD, has been reported to affect astrocytic-related functions, including the ingestion of alpha-synuclein (α-syn) aggregates. In this context, we recently showed that the extracellular chaperone clusterin (Clu) binds to and limits the uptake of alpha-syn fibrils by astrocytes. Thus, starting from these premises, we explored whether LRRK2 G2019S affects aggregated α-syn ingestion through the Clu-related pathway and the underlying molecular mechanisms. We first validated in our LRRK2 G2019S knock-in (KI) mouse strain that primary astrocytes exhibited an impaired ability to ingest fibrillary α-syn. Then, we investigated whether LRRK2 G2019S affects this pathway through the modulation of Clu. In this regard, we collected several results showing that LRRK2 regulates Clu levels in astrocytes. Specifically, brain slices and primary astrocytes from KI mice with the LRRK2 G2019S pathological mutation exhibit increased levels of Clu protein compared to their respective wild-type (WT). Accordingly, we observed an opposite effect in brain slices and primary astrocytes from LRRK2 knock-out (KO) mice in comparison to their respective WT. To gain insights into the molecular mechanism underlying LRRK2-dependent Clu modulation, we found that LRRK2 controls Clu expression at the translation level through the action of miR-22-5p. In addition, we demonstrated that treatment with miR-22-5p mimic improves the ability of LRRK2 G2019S-KI astrocytes to take up α-syn pffs. Taken together, our findings indicate that the LRRK2-Clu pathway is involved in the ingestion of a-syn fibrils and that the impairment of α-syn uptake in LRRK2 G2019S-KI astrocytes is associated to Clu levels. Future studies will allow us to understand whether the modulation of astrocytic LRRK2 G2019S-Clu pathway might attenuate the neuronal spreading of α-syn pathology in PD.

An approach to characterize mechanisms of action of anti-amyloidogenic compounds in vitro and in situ

Amyloid aggregation is associated with neurodegenerative disease and its modulation is a focus of drug development. We developed a chemical proteomics pipeline to probe the mechanism of action of anti-amyloidogenic compounds. Our approach identifies putative interaction sites with high resolution, can probe compound interactions with specific target conformations and directly in cell and brain extracts, and identifies off-targets. We analysed interactions of six anti-amyloidogenic compounds and the amyloid binder Thioflavin T with different conformations of the Parkinson's disease protein α-Synuclein and tested specific compounds in cell or brain lysates. AC Immune compound 2 interacted with α-Synuclein in vitro, in intact neurons and in neuronal lysates, reduced neuronal α-Synuclein levels in a seeded model, and had protective effects. EGCG, Baicalein, ThT and doxycycline interacted with α-Synuclein in vitro but not substantially in cell lysates, with many additional putative targets, underscoring the importance of testing compounds in situ. Our pipeline will enable screening of compounds against any amyloidogenic proteins in cell and patient brain extracts and mechanistic studies of compound action.

Intracellular Inclusions Induced by Patient-Derived and Amplified α-Synuclein Aggregates Are Morphologically Indistinguishable

Lewy Body Disease (LBD) and Multiple System Atrophy (MSA) are synucleinopathies with distinct prognoses and neuropathologies, however, with overlapping clinical symptoms. Different disease characteristics are proposed to be determined by distinct conformations of alpha-synuclein (α-Syn) aggregates, which can self-propagate and spread between cells via a prion-like mechanism. The goal of this study is to investigate whether α-syn aggregates amplified from brain and CSF samples of LBD and MSA patients using the Seed Amplification Assay (SAA) maintain α-Syn seeding properties similar to those of α-syn aggregates derived from patients' brains. To address this, SAA-amplified and un-amplified α-Syn aggregates from LBD and MSA patients' brains, as well as SAA-amplified α-Syn aggregates from LBD and MSA patients' CSF samples, were used to treat synuclein biosensor cells, and induced intracellular α-Syn inclusions were analyzed by confocal microscopy. Our data indicate that induced α-Syn aggregates from LBD and MSA patients' brains have similar seeding properties and morphological characteristics in the α-Syn biosensor cells as those amplified from LBD and MSA patients' brains, as well as those amplified from LBD and MSA patients' CSF samples. In this study, we demonstrated that, regardless of the source of aggregates, the seeds from LBD and MSA produce cellular accumulation of α-Syn with distinct morphologies, confirming the presence of different conformational strains of α-Syn in LBD and MSA and allowing us to differentiate synucleinopathies based on the morphology of aggregates and seeding properties.

Structural and functional insights into the nuclear role of Parkinson's disease-associated α-synuclein as a histone chaperone

α-Synuclein (αSyn) plays a critical role in the pathogenesis of 'Synucleinopathies'. Although increased nuclear αSyn localization induces neurotoxicity, its definitive physiological role remains elusive. Previous studies on nuclear αSyn are limited to its interactions with individual histones and dsDNA, leaving a significant gap in understanding its interactions with assembled histone H2a-H2b dimer and (H3-H4)2 tetramer, as well as its role in chromatin regulation. Here, we demonstrate that αSyn binds specifically to both H2a-H2b and (H3-H4)2 with high affinity. Truncation studies reveal that αSyn(1-103) region interacts with (H3-H4)2, while the acidic (121-140) C-terminal end is crucial for H2a-H2b binding and contains a conserved DEF/YxP motif present in other dimer-binding histone chaperones. High-resolution structure of αSyn(121-140) with H2a-H2b complex reveals that αSyn adopts two binding modes (BM-1 and BM-2). Nonetheless, the αSyn C-terminal end in both modes overlap but runs in opposite orientations, specifically interacting with the H2a-L2 and H2b-L1 loop regions of the dimer and cap the H2a-R78 residue. Mutational analysis confirms that αSyn-Y136 and P138 residues, part of the DEF/YxP motif, together with H2a-R78, are critical for αSyn-(H2a-H2b) interaction. The chaperoning assay supports αSyn's function as a histone chaperone, suggesting the potential role of αSyn in the nucleosome assembly/disassembly process.

Parishin C modulates the amyloid transformation of alpha-synuclein protein by apparently interacting with the NAC domain

Parkinson's disease (PD) is a neurodegenerative disorder marked by the gradual deterioration of dopaminergic neurons in the brain and the presence of Lewy bodies (LB) within the remaining affected neurons, comprised of α-synuclein protein aggregates. Herein, we report a novel amyloid inhibitory potential of Parishin C on the amyloid transformation of the α-synuclein protein. Our studies involving computational screening and REMD simulation analysis revealed a strong interaction between Parishin C and the non-amyloid component (NAC domain), a known aggregation-prone region of the α-synuclein protein. Thioflavin T fluorescence assay demonstrated the inhibitory effect of Parishin C on amyloid transformation kinetics of α-synuclein, where even at the lowest concentration of Parishin C there was a 72 % reduction in the ThT maxima. ANS binding assay further revealed its ability to alter the surface hydrophobicity of the protein. An extensive evaluation using biophysical techniques indicated that Parishin C effectively prevented the formation of mature fibrillar species and promoted the formation of lower order aggregates with reduced cross-β-sheet signatures compared to the native α-synuclein aggregates. Collectively, our research highlights Parishin C's potential as a structural blueprint for developing new therapeutic compounds aimed at preventing the amyloidogenic transition in Parkinson's disease and related disorders.

Mitochondrial Dysfunction in Genetic and Non-Genetic Parkinson's Disease

Mitochondrial dysfunction is a hallmark of Parkinson's disease (PD) pathogenesis, contributing to increased oxidative stress and impaired endo-lysosomal-proteasome system efficiency underlying neuronal injury. Genetic studies have identified 19 monogenic mutations-accounting for ~10% of PD cases-that affect mitochondrial function and are associated with early- or late-onset PD. Early-onset forms typically involve genes encoding proteins essential for mitochondrial quality control, including mitophagy and structural maintenance, while late-onset mutations impair mitochondrial dynamics, bioenergetics, and trafficking. Atypical juvenile genetic syndromes also exhibit mitochondrial abnormalities. In idiopathic PD, environmental neurotoxins such as pesticides and MPTP act as mitochondrial inhibitors, disrupting complex I activity and increasing reactive oxygen species. These converging pathways underscore mitochondria as a central node in PD pathology. This review explores the overlapping and distinct mitochondrial mechanisms in genetic and non-genetic PD, emphasizing their role in neuronal vulnerability. Targeting mitochondrial dysfunction finally offers a promising therapeutic avenue to slow or modify disease progression by intervening at a key point of neurodegenerative convergence.

Delineating the Mechanistic Insight of Inhibition of α-Synuclein Fibrillation by Neuro Metabolite, Myo-inositol: Implications in Synucleopathies-Related Disorders

The fibrillation of α-synuclein (α-syn) is a major factor contributing to neuronal damage and is critical in developing synucleopathies-related disorders. Considering this, the discovery of new compounds that can inhibit or modulate α-syn aggregation is a significant area of research. While polyol osmolytes have been shown to reduce α-syn fibrillation, the impact of brain metabolites such as myo-inositol (MI) on α-syn aggregation has not yet been explored. This study is the first to examine the effects of MI on α-syn aggregation, utilizing spectroscopic, microscopic, and cell cytotoxicity assay. Various aggregation assays revealed that MI inhibits the α-syn fibrillation in a dose-dependent manner. Fluorescence microscopy observations suggest that MI inhibits the α-syn fibrillation by forming amorphous aggregates. MTT assay revealed that α-syn aggregates in the presence of different concentrations of MI were not toxic as compared to α-syn fibrils. Thus, the mechanistic insight of inhibition of α-syn fibrillation by MI was explored by employing interaction studies using spectroscopic, calorimetric, and in silico approaches. Surface plasmon resonance and isothermal titration calorimetry suggest that MI-α-syn interacted with significant binding affinity, and the reaction was spontaneous. Molecular docking results depict that MI interacted with the aggregation-prone residues (36-42) at the N-terminal of α-syn, thereby stabilizing the α-syn and preventing the fibril formation. Molecular dynamics simulation results demonstrate the stability of the complex formation of MI with α-syn. This study highlighted the mechanistic insight of MI on preventing the α-syn from forming amyloid fibril, which could be further explored for therapeutic management of synucleopathies-related disorders.

The multifaceted roles of Akkermansia muciniphila in neurological disorders

Gut commensals regulate neurological disorders through dynamic bidirectional communication along the gut-brain axis. Recent evidence has highlighted the well-documented beneficial role of the commensal gut bacterium Akkermansia muciniphila and its components in promoting host health. However, numerous clinical studies have demonstrated a paradoxical role of A. muciniphila in individuals with various neurological conditions. In this opinion article, we review the correlation between the prevalence of this gut commensal and the development of several disorders, including stroke, multiple sclerosis (MS), Parkinson's disease (PD), and Alzheimer's disease (AD). We focus on the potential mechanisms by which A. muciniphila may contribute to these diseases. An in-depth understanding of these correlations and the underlying pathogenic mechanisms could shed new light on the mechanisms of disease pathogenesis and provide a logical rationale for developing new therapies for these neurological conditions.

Rationally designed peptides inhibit the formation of α-synuclein fibrils and oligomers

Parkinson's Disease (PD) is characterized by the pathological aggregation of α-synuclein (αSyn) into oligomers and amyloid fibrils, making αSyn aggregation a key target for drug development. Peptides have gained recent attention as potential agents to inhibit aggregation. Two previously identified peptide inhibitors, discovered through large-scale yeast screening, were used as templates for in silico mutagenesis aimed at designing novel peptides with improved efficacy in inhibiting αSyn aggregation and cytotoxicity. The newly designed peptides underwent in silico docking analysis, and the most promising candidates were tested in vitro and in cellular models. Peptides T02 and T05 emerged as the most effective inhibitors, with T02 binding αSyn monomers and T05 targeting lower-order oligomers. Both peptides reduce αSyn fibril and oligomer formation in vitro and significantly suppress αSyn aggregation and cytotoxicity in yeast and human H4 cells. These novel peptides represent antagonists of αSyn aggregation with promising potential for therapeutic intervention for PD.

New insights into pathogenisis and therapies of P2X7R in Parkinson's disease

Parkinson's disease (PD), a prevalent neurodegenerative disorder, is linked to genetics and environment, but its mechanisms remain unclear. Emerging evidence connects purinergic signaling-particularly ATP-sensitive P2X7 receptor (P2X7R)-to PD. P2X7R expression is elevated in PD patients, and its antagonist BBG mitigates 6-OHDA-induced dopaminergic neuron death. This review discusses P2X7R's structure, neural functions, PD-related mechanisms, and therapeutic potential as a targert.

Synaptic vesicle-omics in mice captures signatures of aging and synucleinopathy

Neurotransmitter release occurs through exocytosis of synaptic vesicles. α-Synuclein's function and dysfunction in Parkinson's disease and other synucleinopathies is thought to be tightly linked to synaptic vesicle binding. Age is the biggest risk factor for synucleinopathy, and ~15% of synaptic vesicle proteins have been linked to central nervous system diseases. Yet, age- and disease-induced changes in synaptic vesicles remain unexplored. Via systematic analysis of synaptic vesicles at the ultrastructural, protein, and lipid levels, we reveal specific changes in synaptic vesicle populations, proteins, and lipids over age in wild-type mice and in α-synuclein knockout mice with and without expression of human α-synuclein. Strikingly, we find several previously undescribed synaptic changes in mice lacking α-synuclein, suggesting that loss of α-synuclein function contributes to synaptic dysfunction. These findings not only provide insights into synaptic vesicle biology and disease mechanisms in synucleinopathy, but also serve as a baseline for further mechanistic exploration of age- and disease-related alterations in synaptic vesicles.

HMGA1 deficiency: a pathogenic link between tau pathology and insulin resistance

BACKGROUND

Growing evidence links tau-related neurodegeneration with insulin resistance and type 2 diabetes (T2D), though the underlying mechanisms remain unclear. Our previous research identified HMGA1 as crucial for insulin receptor (INSR) expression, with defects in the HMGA1 gene associated with insulin resistance and T2D. Here, we explore HMGA1 deficiency as a potential contributor to tauopathies, such as Alzheimer's disease (AD), and its connection to insulin resistance.

METHODS

Immunoblot analyses, protein-DNA interaction studies, ChIP-qPCR, and reporter gene assays were conducted in human and mouse neuronal cell models. Tau immunohistochemistry, behavioural studies, and brain glucose metabolism were analysed in Hmga1-knockout mice. Additionally, a case-control study investigated the relationship between HMGA1 and tau pathology in patients with tauopathy, carrying or not the HMGA1 rs146052672 variant, known to reduce HMGA1 protein levels and increase the risk of insulin resistance and T2D.

FINDINGS

We show that HMGA1 regulates tau protein expression primarily through the specific repression of MAPT gene transcription. In both human neuronal cells and primary mouse neurons, tau mRNA and protein levels were inversely correlated with HMGA1 expression. This inverse relationship was further confirmed in the brain of Hmga1-knockout mice, where tau was overexpressed, INSR was downregulated, and brain glucose uptake was impaired. Additionally, the rs146052672 variant was more common in patients with tauopathy (12/69, 17.4%) than in controls (10/200, 5.0%) (p = 0.001), and carriers of this variant exhibited more severe disease progression and poorer therapeutic outcomes.

INTERPRETATION

These findings suggest that HMGA1 deficiency may drive tau pathology, linking tauopathies to insulin resistance and providing new insights into the relationship between metabolic and neurodegenerative disorders. Furthermore, our observation that over 17% of individuals with tauopathy exhibit a deficit in HMGA1 protein production could have significant clinical implications, potentially guiding the development of therapeutic strategies targeting this specific defect.

FUNDING

See acknowledgements section.

α-Synuclein in Parkinson's Disease: From Bench to Bedside

α-Synuclein (α-syn), a pathological hallmark of PD, is emerging as a bridging element at the crossroads between neuro/immune-inflammatory responses and neurodegeneration in PD. Several evidence show that pathological α-syn accumulates in neuronal and non-neuronal cells (i.e., neurons, microglia, macrophages, skin cells, and intestinal cells) in central and peripheral tissues since the prodromal phase of the disease, contributing to brain pathology. Indeed, pathological α-syn deposition can promote neurogenic/immune-inflammatory responses that contribute to systemic and central neuroinflammation associated with PD. After providing an overview of the structure and functions of physiological α-syn as well as its pathological forms, we review current studies about the role of neuronal and non-neuronal α-syn at the crossroads between neuroinflammation and neurodegeneration in PD. In addition, we provide an overview of the correlation between the accumulation of α-syn in central and peripheral tissues and PD, related symptoms, and neuroinflammation. Special attention was paid to discussing whether targeting α-syn can represent a suitable therapeutical approach for PD.

α-Synuclein Pathology Spreads in a Midbrain-Hindbrain Assembloid Model

Understanding the progression of α-synuclein pathology in neurodegenerative diseases such as Parkinson's disease (PD) is a longstanding challenge. Here, a novel midbrain-hindbrain-assembloid model that recapitulates the spread of α-synuclein pathology observed in PD patients, akin to Braak's hypothesis, is presented. Initially, the presence α-synuclein pathology is demonstrated in the hindbrain organoids. Subsequently, sophisticated tissue engineering methods are employed to create midbrain-hindbrain assembloids. These assembloids allow investigation and description of the spreading of α-synuclein pathology, as it progresses from the hindbrain components to the midbrain regions within the integrated structure. It is observed that an increase in α-synuclein in the hindbrain can induce transfer of the pathology into the healthy midbrain, as well as cause changes at the synapse level. The presented model constitutes a robust in vitro platform for investigating the mechanisms underlying α-synuclein spreading and disease progression, and holding potential for the screening of prospective therapeutics targeting the pathological propagation in PD and related synucleinopathies.

Nicotine Ameliorates α-Synuclein Preformed Fibril-Induced Behavioral Deficits and Pathological Features in Mice

Epidemiologic study suggests that nicotine reduces the risk of Parkinson's disease (PD) and thus could serve as a potential treatment. In this study, we aimed to investigate the effect of nicotine on the behavioral phenotypes and pathological characteristics of mice induced by human alpha-synuclein preformed fibers (α-syn-PFF). Mice were injected with 5 µg of human α-syn-PFF in the hippocampus while administering nicotine-containing drinking water (200 µg/mL). After 1 month, the motor ability, mood, spatial learning, and memory ability of the PD phenotype-like model mice were detected using open field, rotarod, Y maze, and O maze tests. The expression of pathological α-syn and apoptotic proteins, as well as the number of glial and neural stem cells in the hippocampus of mice, was detected using western blot and immunofluorescence. The results demonstrated that nicotine significantly reduced pathological α-syn accumulation, α-syn serine 129 phosphorylation, and apoptosis induced by α-syn-PFF injection in the hippocampus of mice. Nicotine also inhibited the increase in the number of glia, microglia, and neuronal apoptotic cells, and it decreased the expression of PI3K and Akt while also exhibiting significant memory impairment, motor deficits, and anxiety-like behavior. In conclusion, our findings suggest that nicotine ameliorates behavioral deficits and pathological changes in mice by inhibiting human α-syn-PFF-induced neuroinflammation and apoptosis.

Exogenous α-Synuclein Induces Oxidative Damage to Dopaminergic Neurons Through p-NMDAR2B/Nur77

Alpha-synuclein (α-syn) is a major pathological marker of Parkinson's disease (PD), and its abnormal expression and aggregation lead to dopaminergic neuron degeneration, in which oxidative stress plays an important role. However, the exact molecular mechanism by which α-syn causes PD remains unclear. In this study, exogenous α-syn, also known as α-syn preformed fibrils (α-syn PFFs), was used to construct in vivo and in vitro models of PD. Behavioral, Western blotting, biochemical, immunofluorescence, flow cytometry, electron microscopy, etc. were used to investigate the pathological mechanism of PD induced by α-syn. We found that 6 months after striatum injection of α-syn PFFs, mice exhibited motor deficits. Meanwhile, the protein expression of pS129-α-syn (p-α-syn) and α-syn oligomer significantly increased, while the expression of TH significantly decreased, and the oxidative stress in the substantia nigra was aggravated. In addition, we found an increase in the protein expression of NMDAR2B and p-Tyr1472-NMDAR2B (p-NMDAR2B) and a decrease in the protein expression of Nur77. However, in α-syn PFFs-induced SH-SY5Y cells, we found that inhibiting p-NMDAR2B increased the protein expression of Nur77, while overexpression of Nur77 did not affect the expression of p-NMDAR2B. Inhibition of p-NMDAR2B and overexpression of Nur77 reversed α-syn PFF-induced oxidative stress, thus reducing mitochondrial damage and cytotoxicity. Therefore, we speculate that α-syn PFF-induced oxidative stress in dopaminergic neurons may be mediated by p-NMDAR2B/Nur77. Our study provides novel insights into the pathology mechanism underlying α-syn-induced PD.

A Novel Small Molecule Enhances Stable Dopamine Delivery to the Brain in Models of Parkinson's Disease

Levodopa is the gold standard symptomatic treatment for Parkinson's disease. Disease progression due to alpha-synuclein accumulation, brain inflammation, and the loss of dopamine neurons, as well as motor fluctuations, due to variations in levodopa plasma levels, remain a significant problem for Parkinson's patients. Developing a therapeutic option that can simultaneously reduce the neuropathology associated with alpha-synuclein aggregation, attenuate oxidative stress and inflammation, and overcome variations in levodopa plasma levels is an unmet need to treat Parkinson's disease. We determined the pharmacokinetics and pharmacodynamics of a small molecule, dubbed Pegasus, that conjugates dopamine with a nonantibiotic doxycycline derivative via a molecular linker. Mice harboring the human A53T mutation of alpha-synuclein or treated with MPTP were injected once daily with 50 mg/kg Pegasus for 2 weeks and assessed for motor, behavioral, and cognitive effects, followed by biochemical and histochemical analysis. Pegasus is a poor brain penetrant but it was metabolized to stable dopamine and tetracycline derivatives, and abundant plasma and brain levels of these metabolites were detected. Pegasus reduced soluble and insoluble alpha-synuclein levels, protected dopamine-producing neurons, and reduced astrocytic activation in A53T mice. Mice treated with Pegasus exhibited motor improvement (6.5 h) and reduction in anxiety-like behavior. Rotarod and grip strength improved in MPTP-treated mice when mice were treated with Pegasus or levodopa. Pegasus may be a multi-modal therapeutic option that can deliver stable dopamine into the CNS and reduce misfolded alpha-synuclein, activate dopamine receptors, and attenuate variations in dopamine levels.

α-Synuclein condensation in synaptic vesicle function and synucleinopathies

Research into the crosstalk between α-synuclein (α-syn) and synaptic vesicles (SVs) has gained considerable attention. Notably, the recently discovered liquid-liquid phase separation of α-syn involving SVs is crucial for performing their physiological functions and mediating the transition to pathological aggregates. This review first examines the functional interactions between α-syn and SVs in the context of α-syn's condensation state. It then explores how these interactions become disrupted under pathological conditions, leading to α-syn aggregation and subsequent synaptic dysfunction. Finally, the review discusses the therapeutic potential of targeting α-syn-SV interactions to restore synaptic function in diseased states. By connecting α-syn's physiological roles with its pathological effects, the article aims to shed light on its dual role as both a regulator of SVs and a driver of neurodegeneration.

Thermodynamics for reduced models of polymer aggregation based on maximum entropy principle

Polymeric aggregates play a significant role in biology and chemical engineering. In order to make a clear description of their underlying formation procedure, simplified models are crucial because the original mass-action equations involve numerous variables, complicating analysis and understanding. While the dynamical aspects of simplified models have been widely studied, their thermodynamic properties are less understood. In this study, we explore the Maximum Entropy Principle (MEP)-reduced models, initially developed for dynamical analysis, from a brand-new thermodynamic perspective. Analytical expressions, along with numerical simulations, demonstrate that the discrete MEP-reduced model strictly retains laws of thermodynamics, which holds true even when the aggregate size transits from discrete values to continuous real numbers. Our findings not only clarify the thermodynamic consistency between the MEP-reduced models and the original models of polymeric aggregates for the first time but also suggest avenues for future research into the model-reduction thermodynamics.

Alpha-synuclein pathology and Parkinson's disease-related olfactory dysfunctions: an update on preclinical models and therapeutic approaches

Olfactory dysfunction (OD) is considered one of the early signs of Parkinson's disease (PD), affecting over 90% of PD patients. OD often appears several years before the onset of motor symptoms and is therefore considered an early biomarker of PD. Recent studies have shown that COVID-19 infection might lead to worsening of symptoms and acceleration of disease progression in neurodegenerative disorders, where OD is a common symptom to both. Hence, it is essential to accurately monitor olfactory fitness in clinical settings using any of the currently available olfactory function tests. Even after a quarter of a century of the discovery of α-synuclein (α-syn) pathogenesis in PD, many aspects related to the α-syn pathogenesis in OD remain unknown. Currently, there is no definitive cure for PD; the disease management options include dopaminergic medications, deep brain stimulations, stem cells, and immunotherapy. Generating reliable PD animal models is critical for understanding the molecular pathways and neural circuits affected by disease conditions. This might contribute to the development and validation of new therapeutic approaches. This review discusses the known mechanisms of α-syn aggregated forms causing neuronal death, the recent developments in the PD preclinical models with ODs, and the treatment strategies employed.

Redefining Non-Motor Symptoms in Parkinson's Disease

Parkinson's disease involves widespread neurodegeneration that extends far beyond the basal ganglia, giving rise to a diverse range of non-motor symptoms that frequently emerge before motor onset. These include autonomic dysfunction, cognitive decline, neuropsychiatric disturbances, sleep-related disorders, and sensory deficits. Here, we synthesize current evidence on the anatomical, neurochemical, and network-level mechanisms that drive these symptoms, and we examine how they shape disease progression and clinical heterogeneity. We highlight the limitations of dopamine-centric models and advocate for a framework that treats non-motor symptoms as the disorder's primary, mechanistically distinct features. We also discuss how emerging technologies-such as multi-omic profiling, artificial intelligence, and network neuroscience-enable earlier identification, stratification of non-motor phenotypes, and the development of precision-based therapeutic strategies. Recognizing non-motor symptoms as central to Parkinson's disease redefines how the disorder should be diagnosed, studied, and treated.

Conformational plasticity of mitochondrial VDAC2 controls the kinetics of its interaction with cytosolic proteins

The voltage-dependent anion channel (VDAC) is a key conduit of the mitochondrial outer membrane for water-soluble metabolites and ions. Among the three mammalian isoforms, VDAC2 is unique because of its embryonic lethality upon knockout. Using single-molecule electrophysiology, we investigate the biophysical properties that distinguish VDAC2 from VDAC1 and VDAC3. Unlike the latter, VDAC2 exhibits dynamic switching between multiple high-conductance, anion-selective substates. Using α-synuclein (αSyn)-a known VDAC1 cytosolic regulator-we found that higher-conductance substates correlate with increased on-rates of αSyn-VDAC2 interaction but shorter blockage times, maintaining a consistent equilibrium constant across all substates. This suggests that αSyn detects VDAC2's dynamic structural variations before final binding. We explored the dependence of VDAC2's unique amino-terminal extension and cysteines on substate behavior, finding that both structural elements modulate substate occurrence. The discovered conformational flexibility enables VDAC2 recognition by diverse binding partners, explaining its critical physiological role via dynamical adaptation to mitochondrial metabolic conditions.

The Gut-Brain Axis Based on α-Synuclein Propagation-Clinical, Neuropathological, and Experimental Evidence

The cytopathological hallmark of Parkinson's disease (PD) is a neuronal cytoplasmic inclusion called Lewy body (LB). Lewy bodies are composed of alpha-synuclein (aSyn), a 140 aa protein that is predominantly expressed in the presynaptic terminal and which is implicated in neurotransmitter release. Recently, aSyn was found to propagate from neuron to neuron in a trans-synaptic manner. Although the precise molecular mechanisms are unclear, the propagation of aSyn is believed to play a major role in the progression of Lewy pathology in PD. Neuropathologically, the initial Lewy pathology has been shown to be formed in the dorsal motor nucleus of the vagus (DMV) or olfactory bulb by neuropathological studies. Since the DMV innervates the enteric nervous system (ENS) and LBs are formed in the gut nerve plexuses, it is conceivable that LBs propagate from the gut to the DMV and then to other regions of the brain. In this article, clinical, neuropathological, and experimental evidence supporting or negating the idea that aSyn propagation from the ENS to the brain leads to PD is reviewed. Moreover, the propagation of aSyn seeds through systemic circulation or multifocal generation of aSyn seeds is discussed as a potential alternative scenario for aSyn spreading.