Identifying plasma-based biomarkers that can accurately differentiate Lewy body disease (LBD) from Alzheimer's disease (AD) remains a major challenge. Extracellular vesicles (EVs), which carry molecular cargo from their parent cells and can cross the blood-brain barrier, offer a new path forward. We developed the multiplexed Track-Etch magnetic NanoPOre (mTENPO) platform, a highly parallelized microfluidic technology for cell-specific EV isolation, and demonstrated independent enrichment of GluR2+ (neuron-derived) and GLAST+ (astrocyte-derived) EVs from the antemortem plasma of 137 autopsy-confirmed LBD, AD, mixed pathology, and control subjects. By integrating miRNA sequencing of GluR2+ and GLAST + EV cargo with plasma measurements of Aβ40, Aβ42, tau, p-Tau181, and p-Tau231, we identified a multimodal 15-feature panel that more comprehensively reflects brain pathology than conventional biomarkers. Using tenfold cross-validation to mitigate overfitting, the panel achieved an accuracy of 0.95 and an area under the curve of 0.96 for distinguishing LBD versus AD.

Neurodegenerative diseases (NDs) pose clinical challenges due to their complexity and molecular heterogeneity. Here, we present a pan-neurodegeneration atlas (PanNDA) from multilayer, deep proteomic analysis of 2,279 human brain samples spanning 6 major NDs: Alzheimer’s disease (AD), Lewy body dementia (LBD), frontotemporal lobar degeneration with TDP-43 pathology, progressive supranuclear palsy with tau pathology, vascular dementia, and Parkinson’s disease. PanNDA integrates data from whole proteome, detergent-insoluble proteome, and posttranslational modifications (phosphorylation and ubiquitination), enabling intra- and inter-disease comparisons. Intra-disease analyses uncover distinct molecular subtypes (e.g., three in AD and four in LBD), reveal dysregulated pathways, and prioritize top-ranked proteins. Inter-disease comparisons identify shared alterations in NDs, such as GPNMB in microglial and lysosomal activation and NPTX2 in synaptic regulation, alongside disease-specific changes and hub regulators within protein networks. Overall, PanNDA provides a systems-level framework for understanding ND mechanisms and serves as a foundational resource that is accessible via an interactive website: https://penglab.shinyapps.io/pannda.

Parkinson’s disease (PD) is neuropathologically characterized by the abnormal accumulation of fibrillar alpha-synuclein (aSyn) within selectively vulnerable neuronal populations. Although this pathological hallmark is shared across individuals with PD, the disease presents with marked clinical heterogeneity in age of onset, progression rate, and clinical symptoms, the molecular basis of which remains incompletely understood. In this study, we examined whether biochemical and seeding-related properties of aSyn vary across clinically defined PD subgroups. Using well-characterized, autopsy-confirmed PD cases and matched controls we applied complementary biochemical, cell-based aggregation, and cell-free seed amplification assays (SAA) to investigate aSyn molecular heterogeneity and its potential contribution to disease diversity. Autopsy-confirmed PD cases were classified as early-onset (< 60 years) or late-onset (> 60 years), with the late-onset group further subdivided into fast-progressing (< 5 years duration) and slow-progressing (> 10 years duration). Analysis of detergent-insoluble fractions from PD brains revealed significantly elevated pSer129-aSyn levels compared to controls, while total aSyn was highest in late-onset PD. Seeding bioactivity measured via FRET-based biosensor cells was significantly increased in PD, albeit with substantial inter-individual variability; late-onset and slow-progressing groups exhibited the strongest activity. Seeding activity correlated positively with pSer129-aSyn levels. These findings were supported by high-content imaging, which demonstrated increased intracellular aggregate burden in PD samples. SAA confirmed robust seeding activity in PD, with shorter lag times relative to controls. Finally, proteinase K digestion of amplified products revealed differences in proteolytic resistance between PD and control samples, consistent with biochemical heterogeneity of seeding-competent species. Collectively, these findings suggest that aSyn pathology in PD is associated with marked inter-individual variability in biochemical and seeding properties. Our results highlight the importance of considering molecular heterogeneity at the individual patient level when investigating PD pathobiology and supports the need for precision medicine approaches for PD patients.

Lewy pathology can form over decades in patients with Lewy body diseases, but the causal cellular mechanisms associated with this process remain unclear. This project aims to discover proteins that associate with monomeric and/or oligomeric alpha-synuclein during early stages of the aggregation process. To mimic aggregation processes, cells expressing a synuclein-biotin ligase fusion protein were treated with human recombinant pre-formed fibrils and subjected to BioSITe and mass spectrometry. Using a novel split biotin ligase fused to alpha-synuclein facilitated the identification of proteins specifically associated with multimeric alpha-synuclein. A total of 581 proteins were differentiated into potential interactors of monomeric versus multimeric alpha-synuclein in physiological versus aggregated conditions. The data reveal potentially relevant phosphorylation mechanisms, connections to insulin processing, and a potential interaction with ALS/FTD-associated FUS. Interestingly, we propose that loss of specific interactions may contribute to pathology in patients with sporadic onset of Lewy body diseases. Future studies will validate both true interaction of highlighted proteins with alpha-synuclein, and the impact of such proteins on alpha-synuclein aggregation.

Lewy body dementia and Alzheimer's disease (AD) are leading causes of cognitive impairment, characterized by distinct but overlapping neuropathological hallmarks. Lewy body disease (LBD) is characterized by α-synuclein aggregates in the form of Lewy bodies as well as the deposition of extracellular amyloid plaques, with many cases also exhibiting neurofibrillary tangle (NFT) pathology. In contrast, AD is characterized by amyloid plaques and neurofibrillary tangles. Both conditions often co-occur with additional neuropathological changes, such as vascular disease and TDP-43 pathology. To elucidate shared and distinct molecular signatures underlying these mixed neuropathologies, we extensively analysed transcriptional changes in the anterior cingulate cortex, a brain region critically involved in cognitive processes. We performed bulk tissue RNA sequencing from the anterior cingulate cortex and determined differentially expressed genes (q-value <0.05) in control (n = 81), LBD (n = 436), AD (n = 53) and pathological amyloid cases consisting of amyloid pathology with minimal or no tau pathology (n = 39). We used gene set enrichment and weighted gene correlation network analysis to understand the pathways associated with each neuropathologically defined group. LBD cases had strong upregulation of inflammatory pathways and downregulation of metabolic pathways. The LBD cases were further subdivided into either high Thal amyloid, Braak NFT, or low pathological burden cohorts. Compared to the control cases, the LBD cohorts consistently showed upregulation for genes involved in protein folding and cytokine immune response, as well as downregulation of fatty acid metabolism. Surprisingly, concomitant tau pathology within the LBD cases resulted in no additional changes. Some core inflammatory pathways were shared between AD and LBD but with numerous disease-specific changes. Direct comparison of LBD cohorts versus AD cases revealed strong enrichment of synaptic signalling, behaviour and neuronal system pathways. Females had a stronger response overall in both LBD and AD, with several sex-specific changes. Overall, the results identify genes commonly and uniquely dysregulated in neuropathologically defined LBD and AD cases, shedding light on shared and distinct molecular pathways. Additionally, the study underscores the importance of considering sex-specific changes in understanding the complex transcriptional landscape of these neurodegenerative diseases.

Parkinson's disease (PD) is one of the most devastating neurodegenerative disorders, influenced by a complex interplay of genetic, epigenetic, and environmental factors. Genetic studies and neuropathological evidence suggest that there may be two main forms of early-onset PD driven centrally by either alpha-synuclein aggregation (Lewy bodies) or mitochondrial dysfunction. While numerous studies have utilized omics approaches to investigate the pathogenesis of PD, the role of mitochondrial DNA remains to be fully resolved, in part due to the finite resolution of short-read sequencing technologies. Integrating variations in nuclear and mitochondrial DNA is critical to understanding the etiology of PD and assessing the potential contribution of mitochondrial variation and age-related accumulation of mutations to disease risk. In this review, we explore the role of mitochondrial genetics in PD utilizing long-read sequencing, highlighting its unprecedented versatility in resolving difficult genomic regions and providing critical insights into complex cases of PD.

Mutations in leucine-rich repeat kinase 2 (LRRK2) are the most common cause of familial and sporadic Parkinson’s disease (PD). While the clinical features of patients with LRRK2-PD resemble those of typical PD, there are significant differences in the pathological findings. The pathological hallmark of definite PD is the presence of α-synuclein (αSYN)-positive Lewy-related pathology; however, approximately half of patients with LRRK2-PD do not have Lewy-related pathology. Lewy-related pathology is a late-stage αSYN aggregation that can be visualized with hematoxylin and eosin stains or conventional immunohistochemistry (IHC). Increasing evidence has indicated that αSYN oligomers, which represent the early-stage of αSYN aggregation, may have neurotoxicity. Visualization of αSYN oligomers requires specialized staining techniques, such as αSYN-proximity ligation assay (PLA). Distribution and severity of αSYN oligomers in the brain of patients with LRRK2-PD remain unknown. In this study, we performed phosphorylated αSYN-IHC and αSYN-PLA staining on postmortem brain sections of patients with three pathogenic LRRK2 mutants: p.G2019S (n = 5), p.I2020T (n = 5), and p.R1441C (n = 4). The severity of Lewy-related pathology and αSYN oligomers was assessed semi-quantitatively in the brainstem, limbic lobe, basal ganglia, and cerebral cortex. αSYN oligomers were detected in patients with LRRK2-PD even in those without Lewy-related pathology; a negative correlation was observed between Lewy-related pathology and αSYN oligomers (r = − 0.26 [− 0.39, − 0.12]; P < 0.0001). Our findings suggest that αSYN oligomers may represent a common pathological feature of LRRK2-PD. Notably, patients harboring p.G2019S and p.I2020T had significantly higher levels of αSYN oligomers in those without Lewy-related pathology compared to those with Lewy-related pathology. These patients also had a trend toward shorter disease duration. These results imply that in LRRK2-PD, αSYN oligomers may initially accumulate in the brain but do not progress to form Lewy-related pathology. The present study suggests that targeting αSYN oligomers may be a therapeutic strategy for LRRK2-PD even if there is no Lewy-related pathology.

INTRODUCTION:Visual hallucinations (VHs) represent one of the core clinical features of dementia with Lewy bodies (DLB); however, their underlying pathology remains unclear. METHODS:We employed proximity ligation assay (PLA) and phosphorylated α-synuclein (αSYN) immunohistochemistry to compare αSYN oligomers and Lewy-related pathology across brain regions along the ventral visual pathway in patients with and without VHs (five patients each). RESULTS:Greater αSYN oligomer burden in the parahippocampal cortex was observed in patients with VHs compared to those without (p = 0.041), whereas the burden of Lewy-related pathology was similar between groups. DISCUSSION:Our findings suggest that αSYN oligomers, rather than conventional Lewy-related pathology, may be more closely associated with VHs in DLB. This provides novel evidence linking αSYN oligomers to a core clinical feature in DLB and suggests potential therapeutic targets for managing VH in these patients. HIGHLIGHTS:Visualization of αSYN oligomers by PLA and quantitative neuropathologic analysis. Abundant αSYN oligomers in parahippocampal cortex of DLB with VHs. First human brain study linking αSYN oligomers to VHs. Potential oligomer-targeted therapy for managing VH in DLB.

INTRODUCTION:Increasing evidence indicates that α-synuclein (αSYN) oligomers are toxic. We sought to determine whether αSYN oligomers were associated with faster cognitive decline in prospectively-followed patients with dementia with Lewy bodies (DLB). METHODS:Eight autopsy-confirmed patients with DLB were selected based on rapid or slow cognitive decline determined by the rate of change of Mini-Mental State Examination (MMSE) scores. Quantitative neuropathologic analysis of αSYN oligomers, Lewy-related pathology, phosphorylated tau, and amyloid-β was conducted in hippocampal subfields (CA1-4 and subiculum) and the entorhinal cortex. RESULTS:DLB with rapid cognitive decline showed greater CA1 αSYN oligomer burden (p = 0.029) and tau burden (p = 0.029) than DLB with slow decline. The groups showed comparable burden of Lewy-related pathology and amyloid-β pathology in the hippocampal formation and entorhinal cortex. DISCUSSION:Hippocampal accumulation of αSYN oligomers and phosphorylated tau is associated with rapid cognitive decline in DLB. Therapeutic strategies targeting αSYN oligomers warrant further investigation. HIGHLIGHTS:Proximity ligation assay (PLA) and digital pathology for oligomer quantification. Abundant α-synuclein (αSYN) oligomers in CA1 of patients with dementia with Lewy bodies (DLB) with rapid decline. First human brain study linking αSYN oligomers to cognitive trajectory. Potential therapeutic implications of targeting αSYN oligomers in DLB.

Studies assessing genetic associations with neuropathological features in Lewy body disease (LBD) have been limited to candidate gene investigations, and therefore, information is lacking regarding the genetic architecture of the neuropathology of LBD. In the current study, we examined a large series of neuropathologically confirmed LBD cases (n = 980 in the discovery series, n = 503 in the replication series) and performed genome-wide association studies of 11 different neuropathological outcome measures. The 11 neuropathological outcomes included Braak neurofibrillary tangle (NFT) stage, Thal amyloid phase, LBD subtype, Lewy body (LB) counts in five different brain regions, dorsolateral and ventromedial putaminal tyrosine hydroxylase immunoreactivity and neuronal loss in the ventrolateral part of the substantia nigra. Associations between variants and outcomes were assessed using regression models appropriate for the nature of the given neuropathological outcome and that were adjusted for age at death, sex and top principal components of genetic data. In the discovery series, APOE rs429358 (i.e. APOE ε4) was associated with a greater severity of each of Braak NFT stage [odds ratio (OR) = 3.07, P = 2.34 × 10-32], Thal amyloid phase (OR = 3.57, P = 3.28 × 10-29) and LBD subtype (OR = 1.78, P = 9.85 × 10-9), with similar findings observed in the independent replication series (Braak NFT stage, OR = 2.30, P = 2.70 × 10-11; Thal amyloid phase, OR = 3.17, P = 6.39 × 10-18; LBD subtype, OR = 2.68, P = 3.85 × 10-10). In the subgroup of cases with lower levels of Alzheimer's disease pathology (Braak NFT stage ≤ III and Thal amyloid phase ≤2), there was a strong association between APOE rs429358 and LBD subtype even when adjusting for Braak stage and Thal phase in the discovery series (n = 218, OR = 2.47, P = 0.007) and the replication series (n = 141, OR = 3.60, P = 0.006). Although additional genome-wide significant associations were identified in the discovery series between LINC01581/MCTP2 rs547411734 and lower middle frontal LB counts, between TLE3 rs3743309 and lower cingulate LB counts, and between GRIN2A/ATF7IP2 rs1097915 and lower parahippocampal LB counts, these findings were not observed in the replication series. Our results indicate that the APOE ε4 allele is the most prominent genetic determinant of severity of neuropathology in LBD. These findings represent a key step forward in our understanding of genetic drivers of neuropathological features in LBD. Future studies utilizing meta-analytical approaches will be important to more precisely assess other associations that were not quite genome-wide significant in the discovery series.

INTRODUCTION:Robust plasma-based biomarkers to distinguish Lewy body disease (LBD) and Alzheimer's disease (AD) are currently lacking. We applied track-etch magnetic nanopore (TENPO) sorting for enrichment of brain-derived extracellular vesicle (EV) signatures as potential biomarkers to address this gap. METHODS:We analyzed plasma from 137 autopsy-confirmed patients [30 LBD, 31 AD, 30 AD/LBD, 19 AD with amygdala Lewy bodies (AD/ALB), and 27 controls], sequencing miRNAs from TENPO-isolated GluR2-positive (neuron-enriched) and GLAST-positive (astrocyte-enriched) EVs, and measuring plasma proteins (Aβ40, Aβ42, tau, p-Tau181, p-Tau231) via SIMOA. RESULTS:We identified 16 GluR2+, 8 GLAST+, and 4 protein biomarkers with differential expression (false discovery rate-corrected P value < .1) between LBD and AD. A multimodal 15-feature panel classified LBD versus AD with 10-fold crossvalidated accuracy = 0.95 and area under the curve (AUC) = 0.96. DISCUSSION:Brain-derived EVs offer accurate and accessible miRNA biomarkers for the differential diagnosis of LBD and AD.

Lewy body dementia (LBD), which includes dementia with Lewy bodies (DLB) and Parkinson's disease dementia (PDD), is characterized by cognitive decline, sleep disturbances, motor dysfunction, and other debilitating clinical symptoms. Neuropathologically, LBD is characterized by the progressive accumulation of alpha-synuclein (aSYN) in vulnerable cellular populations in the brain. Diagnosing LBD is challenging due to the overlap of clinical symptoms with Alzheimer's disease (AD) and other neurodegenerative disorders with current diagnostic tools, including clinical examinations by specialized neurologists and brain imaging, limited by accessibility. Taken together, LBD is often misdiagnosed, especially at early disease stages. Seed amplification assays to detect pathogenic aSYN (aSYN SAAs) are emerging as promising tools to detect aSYN pathology in biological specimens. These assays amplify trace amounts of misfolded aSYN, enabling their potential detection in brain, CSF, saliva, skin, and blood. This review compares the sensitivity and specificity of aSYN SAAs across different biological samples and explores the potential of the assay as a diagnostic in LBD. We also highlight challenges that will need to be addressed going forward if the aSYN SAA is to be widely adopted as a diagnostic test. Despite current limitations, aSYN SAAs hold promise for early and precise diagnosis, paving the way for targeted treatments that could significantly improve patient care and outcomes.

In the quest to unravel the mysteries of neurological diseases, comprehending the underlying mechanisms is supreme. The SH-SY5Y human neuroblastoma cell line serves as a crucial tool in this endeavor; however, the cells are known for its sensitivity and slow proliferation rates. Typically, this cell line is cultured with 10% Fetal Bovine Serum (FBS) supplement. Nu-Serum (NuS), a low-protein alternative to FBS, is promising to advance cell culture practices. Herein, we evaluated the substitution of NuS for FBS to test the hypothesis that an alternative serum supplement can aid and promote SH-SY5Y cell proliferation and differentiation. Our findings revealed that the NuS-supplemented group exhibited a notable increase in adhered cells compared to both the FBS and serum-free (SF) groups. Importantly, cell viability remained high in both sera treated groups, with the NuS-supplemented cells displaying significantly larger cell sizes compared to the SF-treated group. Furthermore, cell proliferation rates were higher in the NuS-treated group, and neuroblast-like morphology was observed earlier than FBS group. Notably, both FBS and NuS supported the differentiation of these cells into mature neurons. Our data supports NuS as an alternative for SH-SY5Y cell culture, with the potential to elevate the quality of research in the neuroscience field.

Aggregated α-synuclein (α-SYN) proteins, encoded by the SNCA gene, are hallmarks of Lewy body disease (LBD), affecting multiple brain regions. However, the specific mechanisms underlying α-SYN pathology in cortical neurons, crucial for LBD-associated dementia, remain unclear. Here, we recapitulated α-SYN pathologies in human induced pluripotent stem cells (iPSCs)–derived cortical organoids generated from patients with LBD with SNCA gene triplication. Single-cell RNA sequencing, combined with functional and molecular validation, identified synaptic and mitochondrial dysfunction in excitatory neurons exhibiting high expression of the SNCA gene, aligning with observations in the cortex of autopsy-confirmed LBD human brains. Furthermore, we screened 1280 Food and Drug Administration–approved drugs and identified four candidates (entacapone, tolcapone, phenazopyridine hydrochloride, and zalcitabine) that inhibited α-SYN seeding activity in real-time quaking-induced conversion assays with human brains, reduced α-SYN aggregation, and alleviated mitochondrial dysfunction in SNCA triplication organoids and excitatory neurons. Our findings establish human cortical LBD models and suggest potential therapeutic drugs targeting α-SYN aggregation for LBD.

Despite its high prevalence among dementias, Lewy body dementia (LBD) remains poorly understood with a limited, albeit growing, evidence base. The public-health burden that LBD imposes is worsened by overlapping pathologies, which contribute to misdiagnosis, and lack of treatments. For this report, we gathered and analyzed public-domain information on advocacy, funding, research outputs, and the therapeutic pipeline to identify gaps in each of these key elements. To further understand the current gaps, we also conducted interviews with leading experts in regulatory/governmental agencies, LBD advocacy, academic research, and biopharmaceutical research, as well as with funding sources. We identified wide gaps across the entire landscape, the most critical being in research. Many of the experts participated in a workshop to discuss the prioritization of research areas with a view to accelerating therapeutic development and improving patient care. This white paper outlines the opportunities for bridging the major LBD gaps and creates the framework for collaboration in that endeavor.HighlightsA group representing academia, government, industry, and consulting expertise was convened to discuss current progress in Dementia with Lewy Body care and research.Consideration of expert opinion,natural language processing of the literature as well as publicly available data bases, and Delphi inspired discussion led to a proposed consensus document of priorities for the field.

Radiation therapy is the standard of care for central nervous system tumours. Despite the success of radiation therapy in reducing tumour mass, irradiation (IR)-induced vasculopathies and neuroinflammation contribute to late-delayed complications, neurodegeneration, and premature ageing in long-term cancer survivors. Mesenchymal stromal cells (MSCs) are adult stem cells that facilitate tissue integrity, homeostasis, and repair. Here, we investigated the potential of the iPSC-derived MSC (iMSC) secretome in immunomodulation and vasculature repair in response to radiation injury utilizing human cell lines. We generated iPSC-derived iMSC lines and evaluated the potential of their conditioned media (iMSC CM) to treat IR-induced injuries in human monocytes (THP1) and brain vascular endothelial cells (hCMEC/D3). We further assessed factors in the iMSC secretome, their modulation, and the molecular pathways they elicit. Increasing doses of IR disturbed endothelial tube and spheroid formation in hCMEC/D3. When IR-injured hCMEC/D3 (IR ≤ 5 Gy) were treated with iMSC CM, endothelial cell viability, adherence, spheroid compactness, and proangiogenic sprout formation were significantly ameliorated, and IR-induced ROS levels were reduced. iMSC CM augmented tube formation in cocultures of hCMEC/D3 and iMSCs. Consistently, iMSC CM facilitated angiogenesis in a zebrafish model in vivo. Furthermore, iMSC CM suppressed IR-induced NFκB activation, TNF-α release, and ROS production in THP1 cells. Additionally, iMSC CM diminished NF-kB activation in THP1 cells cocultured with irradiated hCMEC/D3, iMSCs, or HMC3 microglial lines. The cytokine array revealed that iMSC CM contains the proangiogenic and immunosuppressive factors MCP1/CCL2, IL6, IL8/CXCL8, ANG (Angiogenin), GROα/CXCL1, and RANTES/CCL5. Common promoter regulatory elements were enriched in TF-binding motifs such as androgen receptor (ANDR) and GATA2. hCMEC/D3 phosphokinome profiling revealed increased expression of pro-survival factors, the PI3K/AKT/mTOR modulator PRAS40 and β-catenin in response to CM. The transcriptome analysis revealed increased expression of GATA2 in iMSCs and the enrichment of pathways involved in RNA metabolism, translation, mitochondrial respiration, DNA damage repair, and neurodevelopment. The iMSC secretome is a comodulated composite of proangiogenic and immunosuppressive factors that has the potential to alleviate radiation-induced vascular endothelial cell damage and immune activation.

The precise neurophysiological changes prompted by meningeal lymphatic dysfunction remain unclear. Here, we showed that inducing meningeal lymphatic vessel ablation in adult mice led to gene expression changes in glial cells, followed by reductions in mature oligodendrocyte numbers and specific lipid species in the brain. These phenomena were accompanied by altered meningeal adaptive immunity and brain myeloid cell activation. During brain remyelination, meningeal lymphatic dysfunction provoked a state of immunosuppression that contributed to delayed spontaneous oligodendrocyte replenishment and axonal loss. The deficiencies in mature oligodendrocytes and neuroinflammation due to impaired meningeal lymphatic function were solely recapitulated in immunocompetent mice. Patients diagnosed with multiple sclerosis presented reduced vascular endothelial growth factor C in the cerebrospinal fluid, particularly shortly after clinical relapses, possibly indicative of poor meningeal lymphatic function. These data demonstrate that meningeal lymphatics regulate oligodendrocyte function and brain myelination, which might have implications for human demyelinating diseases.

Parkinson's disease (PD) is a complex, multifactorial neurodegenerative disease with a prevalence of 1% over the age of 55. Neuropathological hallmarks of PD include the loss of dopaminergic neurons in the substantia nigra pars compacta and the accumulation of Lewy bodies that contain a variety of proteins and lipids including alpha‐synuclein (α‐syn). Although the formation of α‐syn occurs intracellularly, it can also be found in the extracellular space where it can be taken up by neighboring cells. Toll‐like receptor 2 (TLR2) is an immune system receptor that has been shown to recognize extracellular α‐syn and modulate its uptake by other cells. Lymphocyte‐activation gene 3 (LAG3), an immune checkpoint receptor, has also been proposed to play a role in extracellular α‐syn internalization; however, a recent study has disputed this role. Internalized α‐syn can trigger expression and secretion of inflammatory cytokines such as tumor necrosis factor alpha (TNF‐α), interleukin (IL)‐1β, IL‐2, and IL‐6 and induce neuroinflammation, apoptosis, and mitophagy that results in cellular death. In this study, we tested if N ‐acetylcysteine (NAC), an anti‐inflammatory and anti‐carcinogenic drug, can circumvent the detrimental effects of neuroinflammation and induce an anti‐inflammatory response by modulating transcription and expression of TLR2 and LAG3 receptors. Cells overexpressing wild‐type α‐syn were treated with TNF‐α to induce inflammation followed by NAC to inhibit the deleterious effects of TNF‐α‐induced inflammation and apoptosis. SNCA gene transcription and α‐syn protein expression were validated by q‐PCR and Western blot (WB), respectively. Cell viability was measured, and apoptosis was evaluated by WB and terminal deoxynucleotidyl transferase nick end labeling methods. Alterations in LAG3 and TLR2 receptor levels were evaluated by immunofluorescent labeling, WB, and q‐PCR. TNF‐α not only increased inflammation but also increased endogenous and overexpressed α‐syn levels. NAC treatment decreased expression of TLR2 and increased transcription of LAG3 receptor and diminished inflammation‐mediated toxicity and cell death. Here, we demonstrate that NAC can reduce neuroinflammation that occurs as a result of alpha‐synuclein overexpression, via a TLR2‐associated pathway, making it a promising candidate for therapeutic intervention. Further studies are needed to elucidate molecular mechanisms and pathways related to neuroinflammation in PD and to develop possible new therapeutic approaches to slow the clinical progression of PD.

ObjectiveRecent evidence supports a link between increased TDP‐43 burden and the presence of an APOE4 gene allele in Alzheimer's disease (AD); however, it is difficult to conclude the direct effect of APOE on TDP‐43 pathology due to the presence of mixed AD pathologies. The goal of this study is to address how APOE isoforms impact TDP‐43 pathology and related neurodegeneration in the absence of typical AD pathologies.MethodsWe overexpressed human TDP‐43 via viral transduction in humanized APOE2, APOE3, APOE4 mice, and murine Apoe‐knockout (Apoe‐KO) mice. Behavior tests were performed across ages. Animals were harvested at 11 months of age and TDP‐43 overexpression‐related neurodegeneration and gliosis were assessed. To further address the human relevance, we analyzed the association of APOE with TDP‐43 pathology in 160 postmortem brains from autopsy‐confirmed amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration with motor neuron disease (FTLD‐MND) in the Mayo Clinic Brain Bank.ResultsWe found that TDP‐43 overexpression induced motor function deficits, neuronal loss, and gliosis in the motor cortex, especially in APOE2 mice, with much milder or absent effects in APOE3, APOE4, or Apoe‐KO mice. In the motor cortex of the ALS and FTLD‐MND postmortem human brains, we found that the APOE2 allele was associated with more severe TDP‐43‐positive dystrophic neurites.InterpretationOur data suggest a genotype‐specific effect of APOE on TDP‐43 proteinopathy and neurodegeneration in the absence of AD pathology, with the strongest association seen with APOE2. ANN NEUROL 2023;93:830–843

Background Intracytoplasmic inclusions comprised of aggregated alpha-synuclein (αsyn) represent a key histopathological feature of neurological disorders collectively termed “synucleinopathies,” which includes Parkinson’s disease (PD). Mutations and multiplications in the SNCA gene encoding αsyn cause familial forms of PD and a large body of evidence indicate a correlation between αsyn accumulation and disease. Decreasing αsyn expression is recognized as a valid target for PD therapeutics, with down-regulation of SNCA expression potentially attenuating downstream cascades of pathologic events. Here, we evaluated if Honokiol (HKL), a polyphenolic compound derived from magnolia tree bark with demonstrated neuroprotective properties, can modulate αsyn levels in multiple experimental models. Methods Human neuroglioma cells stably overexpressing αsyn, mouse primary neurons, and human iPSC-derived neurons were exposed to HKL and αsyn protein and SNCA messenger RNA levels were assessed. The effect of HKL on rotenone-induced overexpression of αsyn levels was further assessed and transcriptional profiling of mouse cortical neurons treated with HKL was performed to identify potential targets of HKL. Results We demonstrate that HKL can successfully reduce αsyn protein levels and SNCA expression in multiple in vitro models of PD with our data supporting a mechanism whereby HKL acts by post-transcriptional modulation of SNCA rather than modulating αsyn protein degradation. Transcriptional profiling of mouse cortical neurons treated with HKL identifies several differentially expressed genes (DEG) as potential targets to modulate SNCA expression. Conclusion This study supports a HKL-mediated downregulation of SNCA as a viable strategy to modify disease progression in PD and other synucleinopathies. HKL has potential as a powerful tool for investigating SNCA gene modulation and its downstream effects.