Lewy pathology in Parkinson's disease consists of crowded organelles and lipid membranes

Neuronal regulated cell death in aging-related neurodegenerative diseases: key pathways and therapeutic potentials

Regulated cell death (such as apoptosis, necroptosis, pyroptosis, autophagy, cuproptosis, ferroptosis, disulfidptosis) involves complex signaling pathways and molecular effectors, and has been proven to be an important regulatory mechanism for regulating neuronal aging and death. However, excessive activation of regulated cell death may lead to the progression of aging-related diseases. This review summarizes recent advances in the understanding of seven forms of regulated cell death in age-related diseases. Notably, the newly identified ferroptosis and cuproptosis have been implicated in the risk of cognitive impairment and neurodegenerative diseases. These forms of cell death exacerbate disease progression by promoting inflammation, oxidative stress, and pathological protein aggregation. The review also provides an overview of key signaling pathways and crosstalk mechanisms among these regulated cell death forms, with a focus on ferroptosis, cuproptosis, and disulfidptosis. For instance, FDX1 directly induces cuproptosis by regulating copper ion valency and dihydrolipoamide S-acetyltransferase aggregation, while copper mediates glutathione peroxidase 4 degradation, enhancing ferroptosis sensitivity. Additionally, inhibiting the Xc- transport system to prevent ferroptosis can increase disulfide formation and shift the NADP + /NADPH ratio, transitioning ferroptosis to disulfidptosis. These insights help to uncover the potential connections among these novel regulated cell death forms and differentiate them from traditional regulated cell death mechanisms. In conclusion, identifying key targets and their crosstalk points among various regulated cell death pathways may aid in developing specific biomarkers to reverse the aging clock and treat age-related neurodegenerative conditions.

Raman spectroscopy and imaging of protein droplet formation and aggregation

Raman microscopy offers a unique combination of chemical and spatial resolution with structural sensitivity. This makes it an ideal tool for studies of protein structural changes in heterogenous samples such as protein liquid-liquid phase separation (LLPS) and amyloid formation. These processes are characterized by the spontaneous assembly of proteins to form either microscopic liquid droplets or insoluble filaments stabilized by β-sheets. LLPS and amyloid formation are closely related, with many proteins that undergo LLPS also forming amyloids. This has led to the proposal that development of β-sheets in droplets is an initiating event in toxic amyloid formation. This review surveys recent applications of Raman microscopic methods to studies of LLPS and amyloid formation both in vitro and in cellulo.

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.

COVID-19 Alters Inflammatory, Mitochondrial, and Protein Clearance Pathway Genes: Potential Implications for New-onset Parkinsonism in Patients

Several preclinical and clinical studies have shown that SARS-CoV-2 infection is associated with new-onset Parkinson's disease (PD). The overall goal of this study is to uncover how the COVID-19 severity gradient impacts the conventional pathological pathway of PD to inform the identification of at-risk patients and the development of personalized treatment strategies. Transcriptomics analysis of 43 PD pathogenic genes was conducted on nasopharyngeal swabs from 50 COVID-19 patients with varying severity including 17 outpatients, 16 non-ICU, and 17 ICU patients, compared to 13 SARS-CoV-2 negative individuals. The study shows that COVID-19 severity gradient differentially dysregulates PD pathological genes. Dysfunctional lysosomal and mitochondrial processes in outpatients and non-ICU COVID-19 patients was identified as the convergent network of COVID-19-PD interactions. These dysfunctions were later abrogated by the upregulation of the ubiquitin-proteasome system and autophagy-lysosome system in ICU COVID-19 patients. A potential synergistic co-expression and clustering of protein clearance pathway genes with other pathological genes was observed in ICU patients, indicating a possible overlap in biological pathways. Dysregulation of the PD pathopharmacogene, SLC6A3 was observed in ICU patients, suggesting potential COVID-19-gene-drug interactions. Nasopharyngeal swabs express major PD pathological genes as well as clinically relevant drug processing genes, which could advance studies on PD, including diagnosis, pathogenesis, and the development of disease-modifying treatments. Outpatients and non-ICU COVID-19 patients may face a higher risk of developing new-onset PD, whereas ICU COVID-19 patients may be more susceptible to COVID-19-gene-drug interactions.

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.

Artificial intelligence and omics-based autoantibody profiling in dementia

Introduction

Dementia is a neurodegenerative syndrome marked by the accumulation of disease-specific proteins and immune dysregulation, including autoimmune mechanisms involving autoantibodies. Current diagnostic methods are often invasive, time-consuming, or costly.

Methods

This study explores the use of proteome-wide autoantibody screening (PWAbS) for noninvasive dementia diagnosis by analyzing serum samples from Alzheimer's disease (AD), dementia with Lewy bodies (DLB), and age-matched cognitively normal individuals (CNIs). Serum samples from 35 subjects were analyzed utilizing our original wet protein arrays displaying more than 13,000 human proteins.

Results

PWAbS revealed elevated gross autoantibody levels in AD and DLB patients compared to CNIs. A total of 229 autoantibodies were differentially elevated in AD and/or DLB, effectively distinguishing between patient groups. Machine learning models showed high accuracy in classifying AD, DLB, and CNIs. Gene ontology analysis highlighted autoantibodies targeting neuroactive ligands/receptors in AD and lipid metabolism proteins in DLB. Notably, autoantibodies targeting neuropeptide B (NPB) and adhesion G protein-coupled receptor F5 (ADGRF5) showed significant correlations with clinical traits including Mini Mental State Examination scores.

Discussion

The study demonstrates the potential of PWAbS and artificial intelligence integration as a noninvasive diagnostic tool for dementia, uncovering biomarkers that could enhance understanding of disease mechanisms. Limitations include demographic differences, small sample size, and lack of external validation. Future research should involve longitudinal observation in larger, diverse cohorts and functional studies to clarify autoantibodies' roles in dementia pathogenesis and their diagnostic and therapeutic potential.

Protein kinases in neurodegenerative diseases: current understandings and implications for drug discovery

Neurodegenerative diseases (e.g., Alzheimer's, Parkinson's, Huntington's disease, and Amyotrophic Lateral Sclerosis) are major health threats for the aging population and their prevalences continue to rise with the increasing of life expectancy. Although progress has been made, there is still a lack of effective cures to date, and an in-depth understanding of the molecular and cellular mechanisms of these neurodegenerative diseases is imperative for drug development. Protein phosphorylation, regulated by protein kinases and protein phosphatases, participates in most cellular events, whereas aberrant phosphorylation manifests as a main cause of diseases. As evidenced by pharmacological and pathological studies, protein kinases are proven to be promising therapeutic targets for various diseases, such as cancers, central nervous system disorders, and cardiovascular diseases. The mechanisms of protein phosphatases in pathophysiology have been extensively reviewed, but a systematic summary of the role of protein kinases in the nervous system is lacking. Here, we focus on the involvement of protein kinases in neurodegenerative diseases, by summarizing the current knowledge on the major kinases and related regulatory signal transduction pathways implicated in diseases. We further discuss the role and complexity of kinase-kinase networks in the pathogenesis of neurodegenerative diseases, illustrate the advances of clinical applications of protein kinase inhibitors or novel kinase-targeted therapeutic strategies (such as antisense oligonucleotides and gene therapy) for effective prevention and early intervention.

Modification of membrane properties using ionic liquids investigated with Langmuir monolayers and bilayers in vesicles

Biocompatible and bioavailable ionic liquids (ILs) are generally used to modify the physicochemical properties of lipid monolayers and bilayers. Understanding the influence of ILs on lipid properties and the molecular level mechanism is crucial for applying ILs in lipid membrane modifications. Here the modification of a lipid membrane composed of 1,2-dioleoyl-sn-glycero-3-phosphoglycerol (DOPG) and cholesterol using alkyl methyl imidazolium-based ILs [Cnmim]Cl with varied alkyl chains (n = 4, 6, 8 and 10) was investigated. Langmuir monolayers were used to evaluate the influence of the ILs on the rigidity and robustness of the membranes. Then, selected compositions were used to prepare small unilamellar vesicles (SUVs) as nanocarriers. A small amphiphilic molecule (4-(4-diethylaminostyry)-1-methyl-pyridinium iodide, D289) was used as a probe to investigate the loading capability and encapsulation efficiency of the SUVs. The permeability of the lipid membrane to small molecules was also evaluated using second harmonic generation spectroscopy analysis. The different effects of the ILs with increasing chain length imposed on the membranes were compared and analyzed.

Neuromelanin and selective neuronal vulnerability to Parkinson's disease

Neuromelanin is a unique pigment made by some human catecholamine neurons. These neurons survive with their neuromelanin content for a lifetime but can also be affected by age-related neurodegenerative conditions, as observed using new neuromelanin imaging techniques. The limited quantities of neuromelanin has made understanding its normal biology difficult, but recent rodent and primate models, as well as omics studies, have confirmed its importance for selective neuronal loss in Parkinson's disease (PD). We review the development of neuromelanin in dopamine versus noradrenaline neurons and focus on previously overlooked cellular organelles in neuromelanin formation and function. We discuss the role of neuromelanin in stimulating endogenous α-synuclein misfolding in PD which renders neuromelanin granules vulnerable, and can exacerbates other pathogenic processes.

Abundant non-inclusion α-synuclein pathology in Lewy body-negative LRRK2-mutant cases

Lewy body diseases are common neurodegenerative diseases, including Parkinson's disease (PD) and dementia with Lewy bodies, which lead to both motor and non-motor symptoms. They are neuropathologically characterized by loss of neuromelanized neurons in the substantia nigra pars compacta and α-synuclein-immunopositive inclusions (Lewy bodies) in several types of neurons in the brain. A fraction of monogenic PD cases, however, represent a conundrum, as they can present with clinical Lewy body disease but do not have Lewy bodies upon neuropathological examination. For LRRK2, the presence or absence of Lewy bodies is not related to any specific mutation in the gene and different clinical presentation and neuropathology can be present even in the same family. Here, we present the first evidence of widespread α-synuclein accumulation detected with proximity ligation assay (PLA) using the MJFR14-6-4-2 antibody in six Lewy body-negative LRRK2 cases and compare the levels with five patients with neuropathologically verified Lewy body disease and six healthy controls. We show that non-inclusion aggregated α-synuclein in the form of particulate PLA signal is dominant in the LRRK2 cases, while both Lewy-like and particulate PLA signal is found in late-stage Lewy body disease. Furthermore, LRRK2 cases displayed prominent particulate PLA signal in pontocerebellar tracts and inferior olivary nuclei in the brainstem, which was not seen in idiopathic Lewy body disease cases. These results suggest that Lewy-body negative LRRK2-related PD is not associated with a lack of α-synuclein aggregation in neurons but rather a deficiency in the formation of inclusions.

Increased burden of rare risk variants across gene expression networks predisposes to sporadic Parkinson's disease

Alpha-synuclein (αSyn) is an intrinsically disordered protein that accumulates in the brains of patients with Parkinson's disease (PD). Through a high-throughput screen, we recently identified 38 genes whose knockdown modulates αSyn propagation. Here, we show that, among those, TAX1BP1 regulates how αSyn interacts with lipids, and ADAMTS19 modulates how αSyn phase separates into inclusions, adding to the growing body of evidence implicating those processes in PD. Through RNA sequencing, we identify several genes that are differentially expressed after knockdown of TAX1BP1 or ADAMTS19 and carry an increased frequency of rare risk variants in patients with PD versus healthy controls. Those differentially expressed genes cluster within modules in regions of the brain that develop high degrees of αSyn pathology. We propose a model for the genetic architecture of sporadic PD: increased burden of risk variants across genetic networks dysregulates pathways underlying αSyn homeostasis and leads to pathology and neurodegeneration.

GDNF reduces fibril-induced early-stage alpha-synuclein pathology after delivery of 20S proteasome inhibitor lactacystin

Failures in protein homeostasis are linked to Parkinson's disease (PD) and other neurodegenerative diseases. Lewy bodies, proteinaceous inclusions rich in phosphorylated alpha-synuclein are a hallmark of PD. Glial cell line-derived neurotrophic factor (GDNF) can eliminate Lewy body-like inclusions in mouse dopamine neurons. This study explores whether GDNF has protective effects against alpha-synuclein protofibril toxicity under proteasome inhibition by lactacystin, both in vitro and in vivo. GDNF did not shield midbrain dopamine neurons from lactacystin-induced neurodegeneration, but still prevented phosphorylated alpha-synuclein accumulation. In vivo experiment with control or GDNF-expressing viral vectors assessed alpha-synuclein pathology spread in the nigrostriatal pathway and lactacystin-caused damage in the midbrain. GDNF overexpression reduced phosphorylated alpha-synuclein inclusions. Lactacystin-treated mice showed motor asymmetry and decreased spontaneous activity, exacerbated without AAV-GDNF pre-treatment. However, GDNF's neuroprotective effect could not be confirmed in vivo, due to side-effects from overexpression in the midbrain. Importantly, these findings show that GDNF continues to eliminate alpha-synuclein aggregation despite lactacystin-induced proteasome inhibition. Activating neurotrophic signaling pathways may protect against alpha-synuclein pathology in PD, even with impaired protein degradation mechanisms.

Monitoring neurodegeneration through brain-derived extracellular vesicles in biofluids

The identification of neurodegenerative disease (ND) biomarkers in easily accessible body fluids is crucial in the fight against this class of disorders. Brain-derived extracellular vesicles (BDEVs) have gained attention as nanoscale carriers of molecular information and bioactive molecules that reflect the status of their source cells. By crossing the blood-brain barrier (BBB), BDEVs can transfer these biomolecular signatures to peripheral biofluids, setting the scene for their use as ND biomarkers. In this review, we explore the role of BDEVs in liquid biopsy as a promising route for early ND diagnosis, as well as patient stratification and follow-up, with a particular focus on their ability to transport misfolded proteins and protein aggregates, major actors in neurodegeneration development. We also discuss the link between the physicochemical properties of BDEVs and the potential insights gained into NDs, highlighting both challenges and opportunities associated with the use of BDEVs for ND diagnostics.

Pathogenesis of Parkinson's Disease

Both genetic and environmental factors modulate the risk of Parkinson's disease. In this article, all these pathophysiologic processes that contribute to damages at the tissue, cellular, organelle, and molecular levels, and their effects are talked about.

Investigating the causal relationships between mitochondrial proteins and dementia with Lewy bodies

BackgroundDisruptions in mitochondrial function have been implicated in various neurodegenerative diseases. However, the specific role of mitochondrial proteins in the pathogenesis of dementia with Lewy bodies (DLB) remains poorly understood.ObjectiveThis study aims to investigate potential causal relationships between mitochondrial proteins and DLB risk using Mendelian randomization (MR) analysis.MethodsCausal associations between 66 mitochondrial proteins (MPs) and DLB were assessed by MR analysis, utilizing data from comprehensive genome-wide association studies (GWAS), with various analytical methods, including the inverse variance weighted, MR-Egger, and weighted median. Cochran's Q statistics assessed the heterogeneity of instrumental variables.ResultsGenetic predispositions to increased levels of ES1 protein homolog and apoptosis-inducing factor 1 (AIF-1) were associated with an elevated risk of DLB. Conversely, genetic predispositions to increased levels of glutaredoxin-2 (GLRX-2), complement component 1 Q subcomponent-binding protein (C1QBP), and mitochondrial glutamate carrier 2 (GC2) were found to be protective against DLB. Sensitivity analyses revealed no heterogeneity or horizontal pleiotropy among the selected instrumental variables.ConclusionsOur MR study identifies specific MPs potentially causally linked to DLB risk. These findings offer new insights into the MP-related mechanisms underlying DLB pathogenesis and highlight potential therapeutic targets.

Amyotrophic Lateral Sclerosis and Parkinson's Disease: Brain Tissue Transcriptome Analysis Reveals Interactions

This study utilises amyotrophic lateral sclerosis (ALS) and Parkinson's disease (PD) human brain samples from the GEO database and employs differential expression gene (DEG) analysis to identify genes that are pivotal in both neurodegenerative diseases. Through in depth GO and KEGG enrichment analyses, we elucidated the biological functions and potential pathways associated with these DEGs. Furthermore, by constructing protein‒protein interaction networks, we highlight the significance of shared DEGs in both cellular physiology and disease contexts. Analysis of drug‒gene associations revealed potential therapeutic compounds linked to ALS and PD treatment. Additionally, we explored the interactions between transcription factors, miRNAs, and common DEGs, revealing aspects of gene regulatory networks. This study provides insights into the molecular mechanisms of ALS and PD, offering valuable contributions to ongoing research and potential therapeutic avenues.

Massage-Mimicking Nanosheets Mechanically Reorganize Inter-organelle Contacts to Restore Mitochondrial Functions in Parkinson's Disease

Parkinson's disease (PD) is exacerbated by dysfunction of inter-organelle contact, which depends on cellular responses to the mechanical microenvironment and can be regulated by external mechanical forces. Delivering dynamic mechanical forces to neural cells proves challenging due to the skull. Inspired by the effects of massage; here PEGylated black phosphorus nanosheets (PEG-BPNS), known for their excellent biocompatibility, biodegradability, specific surface area, mechanical strength, and flexibility, are introduced, which are capable of adhering to neural cell membrane and generating mechanical stimulation with their lateral size of 200 nm, exhibiting therapeutic potential in a 1-methyl-4-phenyl-1,2,3,6-te-trahydropyridine-induced PD mouse model by regulating inter-organelle contacts. Specifically, it is found that 200 nm PEG-BPNS, acting as "NanoMassage," significantly increase  plasma membrane tension, as evidenced by fluorescent lipid tension reporter fluorescence lifetime analysis. This mechanical force modulates actin reorganization, subsequently regulating the contacts between actin, mitochondria, and endoplasmic reticulum, further controlling mitochondrial fission and mitigating mitochondrial dysfunction in PD, exhibiting therapeutic efficacy via intranasal administration. These findings provide a noninvasive strategy for applying mechanical stimulation to deep brain areas and elucidate the mechanism of NanoMassage mediating inter-organelle contacts, suggesting the rational design of "NanoMassage" to remodel inter-organelle communications in neurodegenerative disease treatment.

Alpha-synuclein misfolding as fluid biomarker for Parkinson's disease measured with the iRS platform

Misfolding and aggregation of alpha-synuclein (αSyn) play a key role in the pathophysiology of Parkinson's disease (PD). Despite considerable advances in diagnostics, an early and differential diagnosis of PD still represents a major challenge. We innovated the immuno-infrared sensor (iRS) platform for measuring αSyn misfolding. We analyzed cerebrospinal fluid (CSF) from two cohorts comprising PD cases, atypical Parkinsonian disorders, and disease controls. We obtained an AUC of 0.90 (n = 134, 95% CI 0.85-0.96) for separating PD/MSA from controls by determination of the αSyn misfolding by iRS. Using two thresholds divided individuals as unaffected/affected by misfolding with an intermediate area in between. Comparing the affected/unaffected cases, controls versus PD/MSA cases were classified with 97% sensitivity and 92% specificity. The spectral data revealed misfolding from an α-helical/random-coil αSyn in controls to β-sheet enriched αSyn in PD and MSA cases. Moreover, a first subgroup analysis implied the potential for patient stratification in clinically overlapping cases. The iRS, directly measuring all αSyn conformers, is complementary to the αSyn seed-amplification assays (SAAs), which however only amplify seeding competent conformers.

Role and mechanism of molecular hydrogen in the treatment of Parkinson's diseases

Parkinson's disease (PD) is a complex neurodegenerative disorder characterized by a pathology that includes the aggregation of alpha-synuclein (α-syn), oxidative stress, and neuroinflammation. While existing treatments can alleviate motor symptoms, they have limited efficacy in slowing disease progression and improving non-motor symptoms. In recent years, molecular hydrogen has been recognized for its potential neuroprotective effects, attributed to its selective antioxidant and anti-inflammatory properties. While preclinical studies demonstrate promising results, clinical trials conducted thus far have yielded mixed outcomes, with some trials reporting limited or no therapeutic benefit. This review systematically analyzes the mechanisms of action of molecular hydrogen in PD and related neurodegenerative disorders, emphasizing its antioxidant, anti-inflammatory, and anti-apoptotic properties. By evaluating evidence from both preclinical and clinical studies, this paper explores the potential of molecular hydrogen to attenuate oxidative stress, modulate inflammatory responses, and inhibit apoptosis in neuronal cells, while also identifying key gaps in current research. As a novel neuroprotective agent, molecular hydrogen holds potential in PD and other neurodegenerative diseases, but further well-designed clinical trials are needed to validate its efficacy. Future studies should focus on elucidating the mechanisms through which hydrogen exerts its neuroprotective effects, particularly concerning α-syn aggregation and its clearance pathways, as well as Nrf2-mediated immunomodulation. Furthermore, large-scale, multicenter clinical trials are necessary to establish efficacy benchmarks and personalized delivery protocols.

Green tea polyphenol EGCG acts differentially on end-stage amyloid polymorphs of α-synuclein formed in different polyol osmolytes

Synucleinopathies are heterogenous group of disorders characterized by α-synuclein amyloid aggregates in the nervous system. Different synucleinopathy clinical subtypes are encoded by structurally diverse α-synuclein amyloid polymorphs referred to as 'strains'. The underlying structural differences between polymorphs can potentially hamper the drug design against synucleinopathies. Polyphenolic compounds like EGCG have shown promise in inhibiting and remodeling of α-synuclein amyloid aggregates, but their effects on different polymorphs are not well-studied. The cellular environment is one factor contributing to the heterogeneity in the amyloid landscape. Herein, we generated diverse polymorphs of α-synuclein by fine-tuning its aggregation using different polyol osmolytes, varying in their physicochemical properties. These osmolytes act as globular protein stabilizers and conformational modulators of intrinsically disordered proteins. While the buffer control α-synuclein aggregates were evenly dispersed, the polyol-induced aggregate solutions contained a heterogeneous mixture of co-existing polymorphs, as evidenced by AFM and TEM measurements. The polyol-induced aggregated solutions consisted of a mixture of both fibrillar and nonfibrillar cross-β-rich species. Using various spectroscopic tools, we observed differences in the structures of osmolyte-induced polymorphic aggregates. We incubated these aggregates with EGCG and observed its disparate action over polymorphs wherein the treated species were either disintegrated or structurally altered. Contrary to previous reports, all EGCG-treated polymorphs were β-sheet-rich and seeding-competent. Our findings are relevant in assessing the efficacy of polyphenolic compounds on diverse aggregate strains encoding different proteinopathy variants. The formation of β-sheet-rich species in our study also engenders a more critical examination of EGCG's mode of action on diverse classes of amyloids.

Alpha-synuclein aggregation induces prominent cellular lipid changes as revealed by Raman spectroscopy and machine learning analysis

The aggregation of α-synuclein is a central neuropathological hallmark in neurodegenerative disorders known as Lewy body diseases, including Parkinson's disease and dementia with Lewy bodies. In the aggregation process, α-synuclein transitions from its native disordered/α-helical form to a β-sheet-rich structure, forming oligomers and protofibrils that accumulate into Lewy bodies, in a process that is thought to underlie neurodegeneration. Lipids are thought to play a critical role in this process by facilitating α-synuclein aggregation and contributing to cell toxicity, possibly through ceramide production. This study aimed to investigate biochemical changes associated with α-synuclein aggregation, focusing on lipid changes, using Raman spectroscopy coupled with machine learning. HEK293, Neuro2a and SH-SY5Y expressing increased levels of α-synuclein were treated with sonicated α-synuclein pre-formed fibrils, to model seeded aggregation. Raman spectroscopy, complemented by an in-house lipid spectral library, was used to monitor the aggregation process and its effects on cellular viability over 14 days. We detected α-synuclein aggregation by assessing β-sheet peaks at 1045 cm⁻1, in cells treated with α-synuclein pre-formed fibrils, using machine learning (principal component analysis and uniform manifold approximation and projection) analysis based on Raman spectral features. Changes in lipid profiles, and especially sphingolipids, including a decrease in sphingomyelin and increase in ceramides, were observed, consistent with oxidative stress and apoptosis. Altogether, our study informs on biochemical alterations that can be considered for the design of therapeutic strategies for Parkinson's disease and related synucleinopathies.

Lewy pathology formation in patient-derived GBA1 Parkinson's disease midbrain organoids

Fibrillary aggregation of α-synuclein in Lewy body inclusions and nigrostriatal dopaminergic neuron degeneration define Parkinson's disease neuropathology. Mutations in GBA1, encoding glucocerebrosidase, are the most frequent genetic risk factor for Parkinson's disease. However, the lack of reliable experimental models able to reproduce key neuropathological signatures has hampered clarification of the link between mutant glucocerebrosidase and Parkinson's disease pathology. Here, we describe an innovative protocol for the generation of human induced pluripotent stem cell-derived midbrain organoids containing dopaminergic neurons with nigral identity that reproduce characteristics of advanced maturation. When applied to patients with GBA1-related Parkinson's disease, this method enabled the differentiation of midbrain organoids recapitulating dopaminergic neuron loss and fundamental features of Lewy pathology observed in human brains, including the generation of α-synuclein fibrillary aggregates with seeding activity that also propagate pathology in healthy control organoids. Concurrently, we found that the retention of mutant glucocerebrosidase in the endoplasmic reticulum and increased levels of its substrate, glucosylceramide, are determinants of α-synuclein aggregation into Lewy body-like inclusions, and the reduction of glucocerebrosidase activity accelerated α-synuclein pathology by promoting fibrillary α-synuclein deposition. Finally, we demonstrated the efficacy of ambroxol and GZ667161 (two modulators of the glucocerebrosidase pathway in clinical development for the treatment of GBA1-related Parkinson's disease) in reducing α-synuclein pathology in this model, supporting the use of midbrain organoids as a relevant preclinical platform for investigational drug screening.

Synapses-associated research in Parkinson's disease: an explored trends analysis

Background

The pathological features of Parkinson's disease (PD) include the formation of Lewy bodies composed mainly of aggregated alpha-synuclein (α-Syn) and extensive neurodegeneration. Synaptic dysfunction is a key factor contributing to disease progression among the various cellular and molecular mechanisms of PD. This study aims to analyze the research hotspots, frontier trends, and future directions of PD and synapses.

Method

Relevant publications were obtained using the Web of Science database. Software CiteSpace, VOSviewer, and bibliometrix were used for visualization and quantitative analysis.

Results

A total of 3,823 publications were included for analysis, and the number of publications related to the research topic showed an increasing trend from 2001 to 2024. North America, Asia, and Europe were the main research forces with high activity. The United States was the main leader in this field, followed by China and Italy. Emory University was the institution with the largest number of publications. Journal of Neuroscience was the core journal with a large number of publications. Dr. Calabresi, Paolo was a leader in the field of research. High-frequency keywords included PD, α-Syn, synaptic plasticity, basal ganglia, dopamine, substantia-nigra. In recent years, neuroinflammation has been the subject of active research.

Conclusion

Communication and collaboration between different countries, institutions, and authors have promoted the development of this field. The research content mainly focused on α-Syn, synaptic plasticity, and mouse model. Neuroinflammation may be the direction of future research.

Deciphering protein aggregation: Insights into morphology, contributing factors, and molecular pathologies

Protein aggregation research stands at the cutting edge of biomedical science, offering crucial insights into the molecular underpinnings of neurodegenerative and amyloid-associated diseases. Significant advancements in deciphering the structural, biophysical, and molecular intricacies of protein misfolding are driving the development of innovative therapies. Emerging approaches, from small molecule inhibitors to sophisticated polymer-based therapeutics, hold great promise for alleviating the toxic impacts of aggregation with the potential to prevent, delay, or even reverse disease progression. Despite these advances, the field contends with substantial challenges. The polymorphic and complex nature of protein aggregates poses major obstacles to both research and therapeutic design. Yet, interdisciplinary methodologies-integrating advanced spectroscopic, imaging, and computational tools-are creating new pathways to address these complexities, effectively bridging molecular breakthroughs and practical therapeutic applications. The rapid shift of foundational discoveries to clinical trials marks a pivotal step forward, instilling new hope for patients with protein aggregation disorders. Each breakthrough propels us closer to life-changing therapies that may reshape the outlook for these patients. The promise of precise and effective treatments is driving a transformative shift in medical science, establishing protein aggregation research as a crucial pillar in combating these challenging diseases and offering a beacon of hope for the future of neurodegenerative care.

Expression analysis of molecular chaperones associated with disaggregation complex in rotenone-induced Parkinsonian rat model

Parkinson's disease (PD) is a progressive neurodegenerative disorder characterized by the aberrant aggregation and phosphorylation (ser129) of α-synuclein (α-syn, a presynaptic protein) which leads to the formation of pathogenic Lewy bodies. A critical factor in the pathogenesis of PD is the disruption of the cellular protein quality control system, where molecular chaperones and their co-chaperones are integral for mitigating proteotoxic stress. Although the role of molecular chaperones in PD and other protein aggregation diseases has been extensively investigated, the in vivo investigation of disaggregation chaperones, including HSP70, HSP105, and co-chaperone DNAJBs, remains relatively limited. The present study aims to elucidate the expression dynamics of the disaggregation molecular chaperones within the substantia nigra pars compacta of the rotenone-induced Parkinsonian rat model and its association with α-syn aggregation. The rotenone-treated rats exhibited significant behavioural symptoms, α-syn aggregation and degeneration of dopaminergic neurons, confirming the development of Parkinsonism. Significant upregulation of α-syn expression/phosphorylation and co-localization in TH+ve neurons in the SNpc of treated rats was observed. Further, the gene and protein analysis of HSP70, DNAJB6, and HSP105 were found to be upregulated and TH+ve neurons showed their co-localization with p-α-synser129 expression. The total proteomic analysis of SNpc correlated the altered cellular processes with cellular homeostasis imbalance. The observations of the present study provide an in vivo analysis of disaggregation-associated molecular chaperones in Parkinsonian or α-syn related conditions. The study can be helpful for further manipulation in the expression or activity of disaggregation-related chaperones for advanced therapeutic strategies and mechanistic studies in protein aggregation-associated diseases.

Down-regulation of platelet-derived growth factor receptor β in pericytes increases blood-brain barrier permeability and significantly enhances α-synuclein in a Parkinson's Disease 3D cell model in vitro under hyperglycemic condition

BACKGROUND

Parkinson's Disease (PD) often presents with a compromised blood-brain barrier (BBB), which hyperglycemia may exacerbate. Pericytes, a key cell for BBB integrity, are potential therapeutic targets for neurodegenerative disorders. Few studies have developed 3D PD cell models incorporating neurovascular units (NVU) through the co-culture of human endothelial, pericytes, astrocytes, and SH-SY5Y cells to evaluate BBB impairment and the role of pericytes under hyperglycemic condition.

METHOD

A 3D PD like cell model was developed using 6-OHDA-affected SH-SY5Y cells, combined with endothelial cells, pericytes, and astrocytes through the Real Architecture for Tissue (RAFT) 3D co-culture system. PD incorporating reduced (30 % and 89 %) PDGFRβ NVU (RPN) with or without hyperglycemic model (HM) were also established. BBB permeability to sodium fluorescein was assessed, and BBB impairment was evaluated using BBB-associated proteins (ZO-1, CD54, CD144), cell-specific proteins (CD31, GFAP, PDGFRβ, CD13), tyrosine hydroxylase (TH), α-synuclein, oligomeric α-synuclein, and α-synuclein (ser9).

RESULTS

PD 3D cell models incorporating RPN with or without hyperglycemia were successfully established in vitro. Graduately increased BBB impairment was observed in PD, PD with RPN, and PD with RPN combined with HM, indicated by decreased BBB-associated and cell-specific proteins, reduced TH, and increased α-synuclein, oligomeric α-synuclein, and α-synuclein (ser9) compared to the NVU model.

CONCLUSION

Reduced pericyte PDGFRβ could increase BBB permeability, accelerate PD progression, and exacerbate under hyperglycemic condition.

Criterion for Assessing Accumulated Neurotoxicity of Alpha-Synuclein Oligomers in Parkinson's Disease

The paper introduces a parameter called "accumulated neurotoxicity" of α-syn oligomers, which measures the cumulative damage these toxic species inflict on neurons over time, given the years it typically takes for such damage to manifest. A threshold value for accumulated neurotoxicity is estimated, beyond which neuron death is likely. Numerical results suggest that rapid deposition of α-syn oligomers into fibrils minimizes neurotoxicity, indicating that the formation of Lewy bodies might play a neuroprotective role. Strategies such as reducing α-syn monomer production or enhancing degradation can decrease accumulated neurotoxicity. In contrast, slower degradation (reflected by longer half-lives of monomers and free aggregates) increases neurotoxicity, supporting the idea that impaired protein degradation may contribute to Parkinson's disease progression. Accumulated neurotoxicity is highly sensitive to the half-deposition time of free α-syn aggregates into fibrils, exhibiting a sharp increase as it transitions from negligible to elevated levels, indicative of neural damage.

Correlative light and electron microscopy for human brain and other biological models

Correlative light and electron microscopy (CLEM) combines light microscopy, for identifying a target via genetic labels, dyes, antibodies and morphological features, with electron microscopy, for analyzing high-resolution subcellular ultrastructures. Here, we describe step-by-step instructions to perform a CLEM experiment, optimized for the investigation of ultrastructural features in human brain tissue. The procedure is carried out at room temperature and can be adapted to other human and animal tissue samples. The procedure requires 8 d to complete and includes the stages of sample fixation for optimal ultrastructural preservation, immunofluorescence staining, image acquisition and multimodal image correlation and is executable within standard electron microscopy laboratories. Serving as a critical tool for characterizing human tissue and disease models, room-temperature CLEM facilitates the identification and quantification of subcellular morphological features across brain regions.

Stepwise recruitment of chaperone Hsc70 by DNAJB1 produces ordered arrays primed for bursts of amyloid fibril disassembly

The Hsp70 chaperone system is capable of disassembling pathological aggregates such as amyloid fibres associated with serious degenerative diseases. Here we examine the role of the J-domain protein co-factor in amyloid disaggregation by the Hsc70 system. We used cryo-EM and tomography to compare the assemblies with wild-type DNAJB1 or inactive mutants. We show that DNAJB1 binds regularly along α-synuclein amyloid fibrils and acts in a 2-step recruitment of Hsc70, releasing DNAJB1 auto-inhibition before activating Hsc70 ATPase. The wild-type DNAJB1:Hsc70:Apg2 complex forms dense arrays of chaperones on the fibrils, with Hsc70 on the outer surface. When the auto-inhibition is removed by mutating DNAJB1 (ΔH5 DNAJB1), Hsc70 is recruited to the fibrils at a similar level, but the ΔH5 DNAJB1:Ηsc70:Apg2 complex is inactive, binds less regularly to the fibrils and lacks the ordered clusters. Therefore, we propose that 2-step activation of DNAJB1 regulates the ordered assembly of Hsc70 on the fibril. The localised, dense packing of chaperones could trigger a cascade of recruitment and activation to give coordinated, sequential binding and disaggregation from an exposed fibril end, as previously observed in AFM videos. This mechanism is likely to be important in maintaining a healthy cellular proteome into old age.

Advances in autonomic dysfunction research in Parkinson's disease

Parkinson's disease (PD) is a prevalent neurodegenerative disorder, best known for its motor symptoms such as resting tremor, muscle rigidity, and bradykinesia. However, autonomic dysfunction is an important non-motor aspect that often brings considerable discomfort and distress to both patients and their families. In this review, we summarize recent advances in understanding the pathophysiological mechanisms of autonomic dysfunction and explore its relationship with other clinical features. Our aim is to discover novel potential diagnostic and therapeutic strategies, alleviate patient suffering, and pave the way for future clinical and basic research.

Correlative light and electron microscopy imaging of proteinaceous deposits in cell cultures and brain tissues

Identifying protein deposits and associated components is crucial for understanding the pathogenesis of neurodegenerative disorders with intracellular or extracellular deposits. Correlative light and electron microscopy (CLEM) has emerged as a powerful tool to accurately study tissue and cellular pathology by examination of the same target at both microstructural and ultrastructural levels. However, the technical challenges with CLEM have limited its application to neuropathology. Here, we developed a simplified efficient CLEM method and applied it to a cell model that produces a high proportion of α-synuclein (αS) inclusions with immunopositivity to phosphorylated αS and the synaptic vesicle marker SV2A and synaptophysin. This approach incorporates modifications in sample processing and innovative fiducial marking techniques, which enhance antigen preservation and improve target registration, respectively. These advancements achieve an optimal balance in sensitivity, accuracy, efficiency, and cost-effectiveness compared to current CLEM methods employing different strategies. Using this method, we identified and analyzed αS inclusions in cell cultures, as well as various pathological protein deposits in postmortem brain tissues from individuals with a range of neurodegenerative disorders. Our findings replicate recently reported new features of αS pathology and also reveal unrecognized a variety forms of small αS inclusions in human brain, which provide valuable insights into mechanisms underlying Lewy-related pathology. Application of this enhanced CLEM method is a powerful tool in research on neurodegenerative disorders, including αS-opathies.

Super-resolution microscopy as a drug discovery tool

At the turn of the century a fundamental resolution barrier in fluorescence microscopy known as the diffraction limit was broken, giving rise to the field of super-resolution microscopy. Subsequent nanoscopic investigation with visible light revolutionised our understanding of how previously unknown molecular features give rise to the emergent behaviour of cells. It transpires that the devil is in these fine molecular details, and essential nanoscale processes were found everywhere researchers chose to look. Now, after nearly two decades, super-resolution microscopy has begun to address previously unmet challenges in the study of human disease and is poised to become a pivotal tool in drug discovery.

Identifying potential genes driving ferroptosis in the substantia nigra and dopaminergic neurons in Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disorder marked by dopaminergic (DA) neuron degeneration in the substantia nigra (SN). Conventional dopamine replacement therapies provide limited long-term efficacy and significant side effects. Emerging evidence suggests ferroptosis-a form of cell death driven by iron-dependent lipid peroxidation-contributes to PD pathology, though direct evidence linking dysregulation of ferroptosis-related genes in DA neuron loss in PD remains limited. This study explores the expression of ferroptosis-associated genes in the SN and DA neurons of PD patients, identifying potential therapeutic targets. We analyzed two independent RNA-seq datasets, GSE7621 and GSE8397 (GPL-96), from the GEO database to identify common differentially expressed ferroptosis-related genes in the SN of PD patients. We also conducted Gene Ontology and pathway enrichment analyses of these genes to explore the underlying mechanisms and constructed a protein-protein interaction network. The findings were further validated using an additional dataset, GSE49036. We further explored the dysregulation of these ferroptosis-related genes in DA neurons using RNA-seq data GSE169755, derived from DA neurons isolated from the SN of PD patients and controls. Lastly, the proposed hypothesis was experimentally validated in an in vitro PD model. This comprehensive multi-dataset analysis uncovers novel insights into the expression of ferroptosis-related genes in PD, suggesting potential biomarkers and therapeutic targets for mitigating DA neuron loss and PD progression.

DOPAC as a modulator of α-Synuclein and E46K interactions with membrane: Insights into binding dynamics

α-Synuclein (Syn) is an intrinsically disordered protein, abundant in presynaptic neurons. It is a constituent of the Lewis Body inclusions as amyloid fibrils, in Parkinson's disease patients. It populates an ensemble of conformations and floats between the free random coil and the membrane-bound α-helical species. E46K is a pathogenic mutant of Syn able to accelerate the formation of fibrils. The lysine in position 46 affects several protein structural properties including its interaction with membranes. We have shown that 3,4-dihydroxyphenylacetic acid (DOPAC), a dopamine metabolite, hampers Syn to form fibrils, interfering with the aggregation process and alters the interaction of the protein and its aggregates with membranes. To understand the mechanism of such alteration, we studied the interplay between Syn and E46K, lipid membranes and DOPAC. The ability of DOPAC to displace the proteins bound to membrane was also tested. Our findings provided a dynamic model of interaction able to explain the different effects of DOPAC on lipid binding properties of Syn and E46K, shedding light on the conformational changes induced by the catechol, which may destabilize the protein interactions with membranes. Understanding these mechanisms could have implications for therapeutic strategies targeting Syn aggregation and membrane interactions in neurodegenerative diseases.

Molecular Insights into α-Synuclein Fibrillation: A Raman Spectroscopy and Machine Learning Approach

The aggregation of α-synuclein is crucial to the development of Lewy body diseases, including Parkinson's disease and dementia with Lewy bodies. The aggregation pathway of α-synuclein typically involves a defined sequence of nucleation, elongation, and secondary nucleation, exhibiting prion-like spreading. This study employed Raman spectroscopy and machine learning analysis, alongside complementary techniques, to characterize the biomolecular changes during the fibrillation of purified recombinant wild-type α-synuclein protein. Monomeric α-synuclein was produced, purified, and subjected to a 7-day fibrillation assay to generate preformed fibrils. Stages of α-synuclein fibrillation were analyzed using Raman spectroscopy, with aggregation confirmed through negative staining transmission electron microscopy, mass spectrometry, and light scattering analyses. A machine learning pipeline incorporating principal component analysis and uniform manifold approximation and projection was used to analyze the Raman spectral data and identify significant peaks, resulting in differentiation between sample groups. Notable spectral shifts in α-synuclein were found in various stages of aggregation. Early changes (D1) included increases in α-helical structures (1303, 1330 cm-1) and β-sheet formation (1045 cm-1), with reductions in COO- and CH2 bond regions (1406, 1445 cm-1). By D4, these structural shifts persist with additional β-sheet features. At D7, a decrease in β-sheet H-bonding (1625 cm-1) and tyrosine ring breathing (830 cm-1) indicates further structural stabilization, suggesting a shift from initial helical structures to stabilized β-sheets and aggregated fibrils. Additionally, alterations in peaks related to tyrosine, alanine, proline, and glutamic acid were identified, emphasizing the role of these amino acids in intramolecular interactions during the transition from α-helical to β-sheet conformational states in α-synuclein fibrillation. This approach offers insight into α-synuclein aggregation, enhancing the understanding of its role in Lewy body disease pathophysiology and potential diagnostic relevance.

Increased α-synuclein phosphorylation and oligomerization and altered enzymes in plasma of patients with Parkinson's disease

The brain of patients with Parkinson's disease (PD) was characterized by increased phosphorylation and oligomerization of α-synuclein (α-syn) and altered activity of enzymes regulating α-syn phosphorylation and oligomerization. Whether increased α-syn phosphorylation and oligomerization as well as related enzyme changes can be detected in the plasma of PD patients remains unclear. Here, we showed that human α-syn proteins incubated in PD plasma formed more oligomerized α-syn (O-α-syn) and phosphorylated α-syn (pS-α-syn) than those in healthy control (HC) plasma. Receiver operating characteristic (ROC) curve indicated that α-syn oligomerization rate and phosphorylation rate discriminated PD patients well from HC subjects. Moreover, they were both positively correlated with Hoehn and Yahr staging and polo-like kinase 2 (PLK2, an enzyme promoting α-syn phosphorylation) levels, and negatively correlated with protein phosphatase 2A levels (PP2A, an enzyme dephosphorylating α-syn) and glucocerebrosidase (GCase, an enzyme whose deficiency causes α-syn oligomerization) activity and ceramide (a product of GCase and a natural PP2A activator) levels. The above results suggest that increased α-syn oligomerization and phosphorylation rates and related enzyme changes can be detected in PD plasma and used to discriminate PD patients from HC subjects and predict PD progression.

The cholesterol 24-hydroxylase CYP46A1 promotes α-synuclein pathology in Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disease characterized by the death of dopaminergic neurons in the substantia nigra and the formation of Lewy bodies that are composed of aggregated α-synuclein (α-Syn). However, the factors that regulate α-Syn pathology and nigrostriatal dopaminergic degeneration remain poorly understood. Previous studies demonstrate cholesterol 24-hydroxylase (CYP46A1) increases the risk for PD. Moreover, 24-hydroxycholesterol (24-OHC), a brain-specific oxysterol that is catalyzed by CYP46A1, is elevated in the cerebrospinal fluid of PD patients. Herein, we show that the levels of CYP46A1 and 24-OHC are elevated in PD patients and increase with age in a mouse model. Overexpression of CYP46A1 intensifies α-Syn pathology, whereas genetic removal of CYP46A1 attenuates α-Syn neurotoxicity and nigrostriatal dopaminergic degeneration in the brain. Moreover, supplementation with exogenous 24-OHC exacerbates the mitochondrial dysfunction induced by α-Syn fibrils. Intracerebral injection of 24-OHC enhances the spread of α-Syn pathology and dopaminergic neurodegeneration via elevated X-box binding protein 1 (XBP1) and lymphocyte-activation gene 3 (LAG3) levels. Thus, elevated CYP46A1 and 24-OHC promote neurotoxicity and the spread of α-Syn via the XBP1-LAG3 axis. Strategies aimed at inhibiting the CYP46A1-24-OHC axis and LAG3 could hold promise as disease-modifying therapies for PD.

Elucidation of cytotoxicity of α-Synuclein fibrils on immune cells

Progressive aggregation of α-synuclein (α-Syn), a small cytosolic protein involved in cell vesicle trafficking, in the midbrain, hypothalamus, and thalamus is linked to Parkinson's disease (PD). Amyloid oligomers and fibrils formed as a result of such aggregation are highly toxic to neurons. However, it remains unclear whether amyloid-induced toxicity of neurons is the primary mechanism of the progressive neurodegeneration observed upon PD. In the current study, we investigated cytotoxicity exerted by α-Syn fibrils formed in the lipid-free environment, as well as in the presence of two phospholipids, on macrophages, dendritic cells, and microglia. We found that α-Syn fibrils are far more toxic to dendritic cells and microglia compared to neurons. We also observe low toxicity levels of such amyloids to macrophages. Real-time polymerase chain reaction (RT-PCR) results suggest that toxicity of amyloids aggregates is linked to the levels of autophagy in cells. These results suggest that a strong impairment of the immune system in the brain may be the first stop of neurodegenerative processes that are taking place upon the onset of PD.

New insights into the molecular architecture of neurons by cryo-electron tomography

Cryo-electron tomography (cryo-ET) visualizes natively preserved cellular ultrastructure at molecular resolution. Recent developments in sample preparation workflows and image processing tools enable growing applications of cryo-ET in cellular neurobiology. As such, cryo-ET is beginning to unravel the in situ macromolecular organization of neurons using samples of increasing complexity. Here, we highlight advances in cryo-ET technology and review its recent use to study neuronal architecture and its alterations under disease conditions.

Investigating the causal relationships between lipid traits and dementia with lewy bodies: A mendelian randomization study

BACKGROUND

Disruptions in lipid metabolism have been implicated in various neurodegenerative diseases. However, the specific role of lipid species in the pathogenesis of dementia with Lewy bodies (DLB) remains poorly understood. This study aims to investigate potential causal relationships between lipid traits and DLB risk using Mendelian randomization (MR).

METHODS

We employed MR analysis to assess causal associations between 179 lipid traits and DLB, utilizing data from comprehensive genome-wide association studies (GWAS). The lipid-related GWAS included 7174 participants, and the DLB-related GWAS included 2981 DLB cases and 4391 healthy controls.

RESULTS

Genetic predispositions to increased levels of phosphatidylinositol (PI) (18:1_20:4) were associated with an elevated risk of DLB. Conversely, genetic predispositions to increased levels of specific phosphatidylcholine (PC) species, including PC (O-18:1_20:4), PC (O-16:0_20:4) and PC (O-18:0_20:4), were found to be protective against DLB. Sensitivity analyses revealed no evidence of heterogeneity or horizontal pleiotropy among the selected instrumental variables.

CONCLUSIONS

Our MR study identifies specific lipid species potentially causally linked to DLB risk. Elevated levels of PI (18:1_20:4) were associated with increased DLB risk, while higher levels of certain PC species were found to be protective. These findings offer new insights into the lipid-related mechanisms underlying DLB pathogenesis and highlight potential therapeutic targets.

Pharmacological Targeting of the NMDAR/TRPM4 Death Signaling Complex with a TwinF Interface Inhibitor Prevents Excitotoxicity-Associated Dendritic Blebbing and Organelle Damage

Focal swellings of dendrites ("dendritic blebbing") together with structural damage of mitochondria and the endoplasmic reticulum (ER) are morphological hallmarks of glutamate neurotoxicity, also known as excitotoxicity. These pathological alterations are generally thought to be caused by the so-called "overactivation" of N-methyl-D-aspartate receptors (NMDARs). Here, we demonstrate that the activation of extrasynaptic NMDARs, specifically when forming a protein-protein complex with TRPM4, drives these pathological traits. In contrast, strong activation of synaptic NMDARs fails to induce cell damage despite evoking plateau-type calcium signals that are comparable to those generated by activation of the NMDAR/TRPM4 complex, indicating that high intracellular calcium levels per se are not toxic to neurons. Using confocal laser scanning microscopy and transmission electron microscopy, we show that disrupting the NMDAR/TRPM4 complex using the recently discovered small-molecule TwinF interface inhibitor FP802 inhibits the NMDA-induced neurotoxicity-associated dendritic blebbing and structural damage to mitochondria and the ER. It also prevents, at least in part, the disruption of ER-mitochondria contact sites. These findings establish the NMDAR/TRPM4 complex as the trigger for the structural damage of dendrites and intracellular organelles associated with excitotoxicity. They also suggest that activation of the NMDAR/TRPM4 complex, in addition to inducing high-amplitude, plateau-type calcium signals, generates a second signal required for glutamate neurotoxicity ("two-hit hypothesis"). As structural damage to organelles, particularly mitochondria, is a common feature of many human neurodegenerative diseases, including Alzheimer's disease and amyotrophic lateral sclerosis (ALS), TwinF interface inhibitors have the potential to provide neuroprotection across a broad spectrum of these diseases.

Alpha-Synuclein Fails to Form Aggregates in Endocytosis-Defective Fission Yeast Strains, ∆ myo1 and ∆ end4

Alpha-Synuclein (α-Syn) is a soluble neuronal protein whose aggregation is one of the hallmarks of Parkinson's disease (PD). We previously developed a fission yeast model of PD that recapitulates α-Syn aggregation upon high-level expression of human α-Syn. Here, we show that α-Syn aggregate formation in yeast requires Myo1 and End4 , proteins essential for the early steps of endocytosis. α-Syn expression levels in Δ myo1 and ∆end4 cells were comparable to wild-type cells, suggesting that defects in endocytosis disrupt α-Syn aggregation. These findings highlight the critical role of endocytosis in α-Syn aggregation and PD pathology.

Lipidic folding pathway of α-Synuclein via a toxic oligomer

Aggregation intermediates play a pivotal role in the assembly of amyloid fibrils, which are central to the pathogenesis of neurodegenerative diseases. The structures of filamentous intermediates and mature fibrils are now efficiently determined by single-particle cryo-electron microscopy. By contrast, smaller pre-fibrillar α-Synuclein (αS) oligomers, crucial for initiating amyloidogenesis, remain largely uncharacterized. We report an atomic-resolution structural characterization of a toxic pre-fibrillar aggregation intermediate (I1) on pathway to the formation of lipidic fibrils, which incorporate lipid molecules on protofilament surfaces during fibril growth on membranes. Super-resolution microscopy reveals a tetrameric state, providing insights into the early oligomeric assembly. Time resolved nuclear magnetic resonance (NMR) measurements uncover a structural reorganization essential for the transition of I1 to mature lipidic L2 fibrils. The reorganization involves the transformation of anti-parallel β-strands during the pre-fibrillar I1 state into a β-arc characteristic of amyloid fibrils. This structural reconfiguration occurs in a conserved structural kernel shared by a vast number of αS-fibril polymorphs including extracted fibrils from Parkinson's and Lewy Body Dementia patients. Consistent with reports of anti-parallel β-strands being a defining feature of toxic αS pre-fibrillar intermediates, I1 impacts viability of neuroblasts and disrupts cell membranes, resulting in an increased calcium influx. Our results integrate the occurrence of anti-parallel β-strands as salient features of toxic oligomers with their significant role in the amyloid fibril assembly pathway. These structural insights have implications for the development of therapies and biomarkers.

PLK2 disrupts autophagic flux to promote SNCA/α-synuclein pathology

The aggregation and transmission of SNCA/α-synuclein (synuclein, alpha) is a hallmark pathology of Parkinson disease (PD). PLK2 (polo like kinase 2) is an evolutionarily conserved serine/threonine kinase that is more abundant in the brains of all family members, is highly expressed in PD, and is linked to SNCA deposition. However, in addition to its role in phosphorylating SNCA, the role of PLK2 in PD and the mechanisms involved in triggering neurodegeneration remain unclear. Here, we found that PLK2 regulated SNCA pathology independently of S129. Overexpression of PLK2 promoted SNCA preformed fibril (PFF)-induced aggregation of wild-type SNCA and mutant SNCAS129A. Genetic or pharmacological inhibition of PLK2 attenuated SNCA deposition and neurotoxicity. Mechanistically, PLK2 exacerbated the propagation of SNCA pathology by impeding the clearance of SNCA aggregates by blocking macroautophagic/autophagic flux. We further showed that PLK2 phosphorylated S1098 of DCTN1 (dynactin 1), a protein that controls the movement of organelles, leading to impaired autophagosome-lysosome fusion. Furthermore, genetic suppression of PLK2 alleviated SNCA aggregation and motor dysfunction in vivo. Our findings suggest that PLK2 negatively regulates autophagy, promoting SNCA pathology, suggesting a role for PLK2 in PD.Abbreviation: AD: Alzheimer disease; AMPK: AMP-activated protein kinase; CASP3: caspase 3; DCTN1: dynactin 1; LBs: lewy bodies; LDH: lactate dehydrogenase; LAMP1: lysosomal associated membrane protein 1; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MAP2: microtubule associated protein 2; MTOR: mechanistic target of rapamycin kinase; NH4Cl: ammonium chloride; p-SNCA: phosphorylation of SNCA at S129; PD: Parkinson disease; PFF: preformed fibril; PI: propidium iodide; PLK2: polo like kinase 2; PRKAA/AMPK: protein kinase AMP-activated catalytic subunit alpha; shRNA: short hairpin RNA; SNCA: synuclein, alpha; SQSTM1/p62: sequestosome 1; TH: tyrosine hydroxylase; TX: Triton X-100; ULK1: unc-51 like autophagy activating kinase 1.

Prospects for Disease Slowing in Parkinson Disease

The increasing prevalence of Parkinson disease (PD) highlights the need to develop interventions aimed at slowing or halting its progression. As a result of sophisticated disease modeling in preclinical studies, and refinement of specific clinical/genetic/pathological profiles, our understanding of PD pathogenesis has grown over the years, leading to the identification of several targets for disease modification. This has translated to the development of targeted therapies, many of which have entered clinical trials. Nonetheless, up until now, none of these treatments have satisfactorily shown disease-modifying effects in PD. In this review, we present the most up-to-date disease-modifying pharmacological interventions in the clinical trial pipeline for PD. We focus on agents that have reached more advanced stages of clinical trials testing, highlighting both positive and negative results, and critically reflect on strengths, weaknesses, and challenges of current disease-modifying therapeutic avenues in PD.

Poration of mitochondrial membranes by amyloidogenic peptides and other biological toxins

Mitochondria are essential organelles known to serve broad functions, including in cellular metabolism, calcium buffering, signaling pathways and the regulation of apoptotic cell death. Maintaining the integrity of the outer (OMM) and inner mitochondrial membranes (IMM) is vital for mitochondrial health. Cardiolipin (CL), a unique dimeric glycerophospholipid, is the signature lipid of energy-converting membranes. It plays a significant role in maintaining mitochondrial architecture and function, stabilizing protein complexes and facilitating efficient oxidative phosphorylation (OXPHOS) whilst regulating cytochrome c release from mitochondria. CL is especially enriched in the IMM and at sites of contact between the OMM and IMM. Disorders of protein misfolding, such as Alzheimer's and Parkinson's diseases, involve amyloidogenic peptides like amyloid-β, tau and α-synuclein, which form metastable toxic oligomeric species that interact with biological membranes. Electrophysiological studies have shown that these oligomers form ion-conducting nanopores in membranes mimicking the IMM's phospholipid composition. Poration of mitochondrial membranes disrupts the ionic balance, causing osmotic swelling, loss of the voltage potential across the IMM, release of pro-apoptogenic factors, and leads to cell death. The interaction between CL and amyloid oligomers appears to favour their membrane insertion and pore formation, directly implicating CL in amyloid toxicity. Additionally, pore formation in mitochondrial membranes is not limited to amyloid proteins and peptides; other biological peptides, as diverse as the pro-apoptotic Bcl-2 family members, gasdermin proteins, cobra venom cardiotoxins and bacterial pathogenic toxins, have all been described to punch holes in mitochondria, contributing to cell death processes. Collectively, these findings underscore the vulnerability of mitochondria and the involvement of CL in various pathogenic mechanisms, emphasizing the need for further research on targeting CL-amyloid interactions to mitigate mitochondrial dysfunction.

α-Synuclein pathology as a target in neurodegenerative diseases

α-Synuclein misfolds into pathological forms that lead to various neurodegenerative diseases known collectively as α-synucleinopathies. In this Review, we provide a comprehensive overview of pivotal advances in α-synuclein research. We examine structural features and physiological functions of α-synuclein and summarize current insights into key post-translational modifications, such as nitration, phosphorylation, ubiquitination, sumoylation and truncation, considering their contributions to neurodegeneration. We also highlight the existence of disease-specific α-synuclein strains and their mechanisms of pathological spread, and discuss seed amplification assays and PET tracers as emerging diagnostic tools for detecting pathological α-synuclein in clinical settings. We also discuss α-synuclein aggregation and clearance mechanisms, and review cell-autonomous and non-cell-autonomous processes that contribute to neuronal death, including the roles of adaptive and innate immunity in α-synuclein-driven neurodegeneration. Finally, we highlight promising therapeutic approaches that target pathological α-synuclein and provide insights into emerging areas of research.

In situ stoichiometry amounts of p62 and poly-ubiquitin exceed the increase of alpha-synuclein during degeneration of catecholamine cells induced by autophagy inhibition in vitro

Neurodegenerative disorders are typically featured by the occurrence of neuronal inclusions. In the case of Parkinson's disease (PD) these correspond to Lewy bodies (LBs), which are routinely defined as proteinaceous inclusions composed of alpha-synuclein (alpha-syn). In turn, alpha-syn is considered to be the key protein in producing PD and fostering its progression. Recent studies challenged such a concept and emphasized the occurrence of other proteins such as p62 and poly-ubiquitin (Poly-ub) in the composition of LBs, which are also composed of large amounts of tubulo-vesicular structures. All these components, which accumulate within the cytosol of affected neurons in PD, may be the consequence of a dysfunction of major clearing pathways. In fact, autophagy-related systems are constantly impaired in inherited PD and genetic models of PD. The present study was designed to validate whether a pharmacological inhibition of autophagy within catecholamine cells produces cell damage and accumulation of specific proteins and tubulo-vesicular structures. The stoichiometry counts of single proteins, which accumulate within catecholamine neurons was carried out along with the area of tubulo-vesicular structures. In these experimental conditions p62 and Poly-ub accumulation exceeded at large the amounts of alpha-syn. In those areas where Poly-ub and p62 were highly expressed, tubulo-vesicular structures were highly represented compared with surrounding cytosol. The present study confirms new vistas about LBs composition and lends substance to the scenario that autophagy inhibition rather than a single protein dysfunction as key determinant of PD.

A systematic review of salivary biomarkers in Parkinson's disease

The search for reliable and easily accessible biomarkers in Parkinson's disease is receiving a growing emphasis, to detect neurodegeneration from the prodromal phase and to enforce disease-modifying therapies. Despite the need for non-invasively accessible biomarkers, the majority of the studies have pointed to cerebrospinal fluid or peripheral biopsies biomarkers, which require invasive collection procedures. Saliva represents an easily accessible biofluid and an incredibly wide source of molecular biomarkers. In the present study, after presenting the morphological and biological bases for looking at saliva in the search of biomarkers for Parkinson's disease, we systematically reviewed the results achieved so far in the saliva of different cohorts of Parkinson's disease patients. A comprehensive literature search on PubMed and SCOPUS led to the discovery of 289 articles. After screening and exclusion, 34 relevant articles were derived for systematic review. Alpha-synuclein, the histopathological hallmark of Parkinson's disease, has been the most investigated Parkinson's disease biomarker in saliva, with oligomeric alpha-synuclein consistently found increased in Parkinson's disease patients in comparison to healthy controls, while conflicting results have been reported regarding the levels of total alpha-synuclein and phosphorylated alpha-synuclein, and few studies described an increased oligomeric alpha-synuclein/total alpha-synuclein ratio in Parkinson's disease. Beyond alpha-synuclein, other biomarkers targeting different molecular pathways have been explored in the saliva of Parkinson's disease patients: total tau, phosphorylated tau, amyloid-β1-42 (pathological protein aggregation biomarkers); DJ-1, heme-oxygenase-1, metabolites (altered energy homeostasis biomarkers); MAPLC-3beta (aberrant proteostasis biomarker); cortisol, tumor necrosis factor-alpha (inflammation biomarkers); DNA methylation, miRNA (DNA/RNA defects biomarkers); acetylcholinesterase activity (synaptic and neuronal network dysfunction biomarkers); Raman spectra, proteome, and caffeine. Despite a few studies investigating biomarkers targeting molecular pathways different from alpha-synuclein in Parkinson's disease, these results should be replicated and observed in studies on larger cohorts, considering the potential role of these biomarkers in determining the molecular variance among Parkinson's disease subtypes. Although the need for standardization in sample collection and processing, salivary-based biomarkers studies have reported encouraging results, calling for large-scale longitudinal studies and multicentric assessments, given the great molecular potentials and the non-invasive accessibility of saliva.

Modeling Parkinson's disease pathology in human dopaminergic neurons by sequential exposure to α-synuclein fibrils and proinflammatory cytokines

Lewy bodies (LBs), α-synuclein-enriched intracellular inclusions, are a hallmark of Parkinson's disease (PD) pathology, yet a cellular model for LB formation remains elusive. Recent evidence indicates that immune dysfunction may contribute to the development of PD. In this study, we found that induced pluripotent stem cell (iPSC)-derived human dopaminergic (DA) neurons form LB-like inclusions after treatment with α-synuclein preformed fibrils (PFFs) but only when coupled to a model of immune challenge (interferon-γ or interleukin-1β treatment) or when co-cultured with activated microglia-like cells. Exposure to interferon-γ impairs lysosome function in DA neurons, contributing to LB formation. The knockdown of LAMP2 or the knockout of GBA in conjunction with PFF administration is sufficient for inclusion formation. Finally, we observed that the LB-like inclusions in iPSC-derived DA neurons are membrane bound, suggesting that they are not limited to the cytoplasmic compartment but may be formed due to dysfunctions in autophagy. Together, these data indicate that immune-triggered lysosomal dysfunction may contribute to the development of PD pathology.