In Alzheimer's disease (AD), tau pathology is more strongly linked to neurodegeneration than amyloid-β and better predicts brain atrophy. The spatial extent of tauopathy (SEOT) has shown promise as an earlier and more sensitive marker of AD severity than tau load, but how these complementary dimensions relate to neurodegeneration remains unclear. Here, we compared the in vivo associations of tau-PET extent versus load with cross-sectional and longitudinal neurodegeneration. We studied 367 participants across the healthy-aging to AD continuum (mean age 69.3 years; 61% female) from the TRIAD cohort who underwent [18F]MK-6240 tau-PET. Tau load was quantified as regional standardized uptake value ratio (SUVR), and SEOT as the proportion of abnormal voxels, within a temporal meta-region of interest (ROI) and a full-cortex ROI. Neurodegeneration markers included cortical thickness, hippocampal volume (HCV), medial temporal atrophy (MTA) visual ratings, plasma neurofilament light (NfL), and CSF total tau (t-tau). Cross-sectional associations were evaluated using multiple linear regression or covariate-adjusted Spearman correlations. We also compared local correlations of tau load and extent with cortical thickness across all cortical regions. Longitudinal predictive value for neurodegeneration was tested using linear mixed-effects models. Cross-sectionally, all tau-PET metrics were significantly associated with neurodegeneration across imaging and fluid biomarkers. Full-cortex SEOT provided the best model fit for cortical thinning. SEOT outperformed tau load for associations with HCV and for predicting MTA, whereas SEOT and SUVR showed comparable associations with plasma NfL and CSF t-tau. Tau extent was equal or superior to tau load in its correlation with local cortical thickness across all cortical regions. Longitudinally, baseline full-cortex SEOT best predicted future cortical thinning, while temporal SEOT best predicted future hippocampal atrophy. Across cross-sectional and longitudinal analyses, tau extent provided superior predictive value for imaging-based neurodegeneration compared with tau load. By enabling a spatially unbiased, whole-brain assessment of tau burden that accommodates heterogeneous topographies, SEOT represents a promising complementary tau-PET metric for staging and tracking disease progression in AD.
Can we decode Alzheimer's disease (AD) heterogeneity into a few portable axes that capture how amyloid-β, tau and neurodegeneration (A-T-N) spatially co vary in vivo? To answer this question, we built a pipeline that harmonizes longitudinal amyloid-β/tau PET and T1 MRI (gray matter) from ADNI cohort (12,430 images) with mixed effects modeling and then derived stage specific multimodal axes (mVCs) using linked component analysis, with robustness tested in simulations and external validation in the OASIS cohort (4,958 images). We identified a small set of multimodal axes that (i) recapitulate early tau weighted variation in cognitively unimpaired (CU) individuals, AD like A -T-N coupling in cognitively impaired (CI) individuals and atypical CU and CI participants with posterior (precuneus/occipitoparietal) and fronto insular/frontal weighted patterns, (ii) map onto domain specific cognition, APOE e4, and blood/CSF biomarkers of neurodegeneration, neuroaxonal injury and astrocyte activation, (iii) predict clinical transitions, (iv) generalize in an independent cohort, and (v) demonstrate modelling robustness to missing data, high dimensionality, and cross-cohort variability, enabling direct application of the extracted axes to new datasets for biomarker discovery and stratification. Multimodal axes provide a portable, interpretable layer for quantifying amyloid-β-tau-neurodegeneration coupling at the individual level, complementing current biomarker-based staging frameworks based on A-T-N status and tau PET topography, and can be computed on new datasets to aid clinical assessment and trial enrichment. We developed and validated a multimodal statistical pipeline to identify individualized patterns of association among core Alzheimer's disease biomarkers: amyloid-β deposition, tau accumulation, and neurodegeneration. Applied to longitudinal PET and MRI data, the approach revealed distinct, reproducible axes of biomarker coupling across cognitively unimpaired and impaired individuals, linked to cognitive performance and clinical progression. By providing subject -level scores that quantify how pathologies co-express across brain regions, this framework supports fine-grained biomarker discovery, improves interpretation of Alzheimer's disease heterogeneity, and can be extended to high -dimensional multimodal datasets in future biomarker studies.
The pathogenesis of Multiple Sclerosis (MS) involves a dynamic interplay between (auto-)inflammation and neurodegeneration, driving its relapsing and progressive course. While both processes have been shown to be involved throughout disease with different emphasis, relapsing MS (RMS) is characterized by acute inflammatory activity, and secondary progressive MS (SPMS) involves chronic, diffuse neurodegeneration. Identifying biomarkers to predict progression independent of relapse activity (PIRA) is critical for improving diagnostic accuracy and treatment strategies. This study aimed to integrate inflammatory and neurodegenerative biomarkers into a Classification And Regression Tree (CART) model to distinguish RMS from SPMS. We employed a multimodal approach by combining functional as well as structural retinal assessment via multifocal electroretinography (mfERG) and optical coherence tomography (OCT), serum neurofilament light chain (sNfL) and glial fibrillary acidic protein (GFAP) levels via multiplex technology, and subsequent deep immunophenotyping. A CART model was constructed and trained to classify people with MS (PwMS) into RMS or SPMS categories based on these biomarkers. Our results revealed significant thinning of the retinal nerve fiber layer (RNFL) and ganglion cell-inner plexiform layer (GCIPL) in pwMS, with more pronounced reductions in SPMS, while functional mfERG-readouts did not differ between MS subgroups. Neurodegenerative markers sNfL and GFAP were elevated in pwMS compared to healthy controls, with higher levels in SPMS. Immunophenotyping showed increased levels of non-classic and intermediate monocytes in SPMS. The CART and Random Forest models identified sNfL, GCIPL thickness, and frequency of intermediate monocytes as the most accurate predictors, achieving approximately 80% accuracy in distinguishing RMS from SPMS. These findings suggest that combining sNfL, GCIPL thickness, and monocyte subsets provides an experimental, but robust diagnostic framework for differentiating RMS from SPMS. This approach could enable earlier identification of disease progression, facilitating tailored therapeutic interventions. Future studies should validate this model in larger cohorts to enhance its clinical applicability.
Phosphatidylinositol 3,5-bisphosphate [PI(3,5)P2] is a lysosomal signaling lipid whose deficiency, caused by mutations in the PIKfyve complex subunits Fig. 4 or VAC14, underlies a spectrum of fatal neurologic diseases including Charcot-Marie-Tooth type 4 J (CMT4J) and amyotrophic lateral sclerosis (ALS). To map the molecular consequences of PI(3,5)P2 insufficiency in the brain, we performed quantitative proteomic and transcriptomic analyses of three mouse lines bearing distinct loss-of-function mutations in Fig. 4 or Vac14, examining the brain at the presymptomatic and end stages. Strikingly, profound neuroinflammation was already present at postnatal day 5 (before significant neurodegeneration), characterized by complement activation, interferon signaling, and parenchymal infiltration of peripheral myeloid cells and T-cells. Isolated mutant microglia exhibited a markedly pro-oxidative transcriptional state with elevated reactive oxygen species, a partly non-cell-autonomous phenotype, being present in microglia from mice with conditional Fig. 4 inactivation in just neurons and astrocytes. Comparison of early (P5) and late (P25) proteomics data revealed that PI(3,5)P2 insufficiency impairs developmental remodeling of the brain proteome: proteins typically upregulated during postnatal maturation failed to accumulate, implicating lysosomal function in neurodevelopment. We identify coordinated elevation of p53, Fas receptor, inflammatory caspases, Gasdermin D, RIPK1, and ZBP1, consistent with multifactorial inflammatory cell death with features of apoptosis, pyroptosis, and necroptosis. Many of the dysregulated proteins are encoded by genes mutated in lysosomal storage disorders, ALS, CMT, Alzheimer's and Parkinson diseases, extending the pathogenic relevance of PI(3,5)P2 insufficiency. Together, these findings establish that early neuroinflammation is a defining - and likely initiating - feature of neurodegeneration caused by disruption of lysosomal PI(3,5)P2.
The pathophysiology of neurodegenerative illnesses is increasingly understood to be influenced by vascular aging, with blood-brain barrier (BBB) disruption emerging as a crucial mechanistic connection. Comprising endothelial cells, pericytes, astrocytes, and microglia, the BBB is a complex neurovascular unit (NVU) that strictly regulates molecular trafficking and shields neural tissue from circulating toxins and immune cells, therefore maintaining central nervous system homeostasis. The integrity of the BBB is compromised as people age due to structural and functional changes in the cerebrovasculature, such as endothelial senescence, pericyte loss, mitochondrial dysfunction, and persistent low-grade inflammation. These alterations speed up neuronal damage and encourage the development of classical proteinopathies like tau aggregation and amyloid-β by making it easier for neurotoxic proteins, immunological mediators, and metabolic waste to enter the brain parenchyma. BBB disruption is both an early occurrence and a factor in the development of neurodegenerative diseases including Alzheimer's disease, cerebral amyloid angiopathy, and vascular dementia. It exacerbates neuroinflammation, hinders clearance processes, and contributes to cognitive decline. Recent developments in single-cell omics, fluid biomarkers, and molecular imaging have made it possible to identify and characterize BBB failure in preclinical and clinical contexts, creating new opportunities for early diagnosis and treatment. Restoring BBB function and addressing vascular aging are two viable approaches to alter the course of neurodegenerative illnesses and enhance their prognoses. The processes, effects, and translational potential of vascular aging and BBB degradation in neurodegeneration are summarized in this review, which also identifies new treatment targets and research objectives for the future.
Neurodegeneration has traditionally been largely attributed to protein aggregation, yet ribonucleic acid (RNA) has emerged as an active driver of pathology. Expanded repeat RNAs, misregulated RNA-binding proteins, and aberrant RNA-protein interactions can directly or indirectly trigger neuronal dysfunction, although the distinction between the two mechanisms might, in some cases, be loose. RNA modulates prion-like aggregation, scaffolds liquid-liquid phase separation, and either promotes or inhibits protein assembly, depending on RNA sequence and structure. The aim of this review is to discuss our current understanding of RNA's dual role-as a facilitator of aggregation or as a potential therapeutic target-revealing new mechanistic insights into diseases such as amyotrophic lateral sclerosis (ALS), frontotemporal dementia (FTD), and spinocerebellar ataxias. We highlight RNA metabolism as a central determinant of neuronal vulnerability.
Parkinson's disease (PD) is a neurological disorder with the fastest global growth rate, marked by the deterioration of dopaminergic neurons in the substantia nigra pars compacta (SNpc) and the accumulation of α-synuclein (α-syn) deposits in neuronal cells. This progressive neurodegenerative disorder impacts both peripheral organs and the central nervous system (CNS), with neuroinflammation playing a pivotal role in its pathophysiological mechanisms. Research indicates that the adaptive immune response, particularly neuroinflammation mediated by T helper 17 (Th17) cells, a subset of CD4⁺ T cells characterized primarily by their secretion of interleukin-17 (IL-17), is strongly implicated in the pathological process of PD. Despite significant recent advances in mechanistic and translational research, a comprehensive synthesis integrating Th17 activation mechanisms, pathogenic crosstalk with other immune subsets, and the resultant Th17/Treg imbalance is currently lacking, thereby hindering the translation of immunological findings into targeted therapeutic interventions. This review considers in detail the mechanistic roles of Th17 cells in PD, including their activation mechanisms, pathogenic pathways, crosstalk with other immune cell subsets, and immune dysregulation with Tregs. Our analysis aims to offer an integrated perspective on the immunological mechanisms underlying Th17 cells in PD, thereby facilitating a deeper comprehension of disease pathogenesis and guiding the development of future immune-based therapeutic strategies.
Arginine-rich poly-glycine-arginine (poly-GR), a toxic dipeptide repeat protein generated from C9orf72 hexanucleotide repeat expansion, drives mitochondrial dysfunction, oxidative stress, and neuronal loss in amyotrophic lateral sclerosis (ALS). Hyperoside, a bioactive flavonoid, exhibits antioxidant and cytoprotective properties, but its therapeutic relevance to C9orf72-associated ALS remains unclear. To determine whether hyperoside attenuates poly-GR-induced mitochondrial and oxidative injury and improves neuronal survival in cellular and animal models of C9orf72-ALS. A combined in vitro and in vivo experimental study using motor neuron-like cells and an AAV-mediated neonatal mouse model of poly-GR toxicity. NSC34 cells expressing EGFP-GR50 were analyzed for mitochondrial morphology, membrane potential, ROS generation, antioxidant signaling, and apoptosis using confocal microscopy, CellROX/MitoTracker assays, Western blot analysis, and viability testing. For in vivo assessment, neonatal mice received intracerebroventricular AAV9-EGFP-GR50 followed by intraperitoneal hyperoside (10 mg/kg). Survival, cerebral hemisphere length, and cortical NeuN⁺ neuron numbers were quantified. Poly-GR expression induced pronounced mitochondrial fragmentation, reduced membrane potential, elevated ROS, and suppressed Nrf2/HO-1/GPx4 signaling, accompanied by increased Drp1 and reduced Opa1 expression. Hyperoside reversed these abnormalities by restoring mitochondrial integrity, normalizing the Drp1/Opa1 balance, enhancing Nrf2 nuclear accumulation, and increasing the expression of HO-1 and GPx4. Hyperoside also reduced cleaved caspase-3 and corrected the Bax/Bcl-2 ratio, improving cell viability under basal and oxidative stress conditions. In vivo, hyperoside modestly prolonged survival, increased cerebral hemisphere length, and significantly preserved cortical neuronal numbers in AAV9-EGFP-GR50 mice. Hyperoside mitigates poly-GR-induced neurotoxicity by alleviating excessive mitochondrial fission, strengthening Nrf2-dependent antioxidant defenses, and suppressing apoptosis. These findings support hyperoside as a promising multi-target therapeutic candidate for C9orf72-associated ALS.
Neurodegenerative diseases with prominent motor symptoms converge on mitochondrial and lysosomal bottlenecks in selectively vulnerable neurons. Deubiquitinases regulate ubiquitin-dependent organelle fate at these decision points. Emerging evidence suggests that modulating deubiquitinase activity can restore organelle quality control and represents a promising therapeutic strategy.
The ageing population and the increasing prevalence of age-related diseases underscore the urgent need for targeted therapeutic strategies. Accumulating evidence indicates that quinolinic acid (QA), a neuroinflammatory neurotoxin, contributes to the pathogenesis of neurodegenerative disorders. In this study, using Caenorhabditis elegans as a model organism, we demonstrate that chronic QA exposure acts as a robust driver of accelerated aging, significantly reducing overall healthspan. This pro-aging effect is accompanied by the premature onset of decreased locomotor function, enhanced lipofuscin accumulation, and decreased thermotolerance. Beyond these systemic aging phenotypes, QA induced pronounced cognitive deficits, including impaired short- and long-term associative memory and structural damage to dopaminergic neurons. Using this QA-induced injury model, we investigated the therapeutic potential of the clinical compound dimethyl fumarate (DMF), a derivative of a tricarboxylic acid cycle intermediate, and revealed that DMF's protective effects are partially dependent on the activation of the nuclear factor erythroid 2-related factor 2 (Nrf2) pathway. In summary, our results demonstrate the therapeutic efficacy of DMF as a highly effective geroprotector and neuroprotector against QA-induced toxicity and define the Nrf2 pathway as a crucial mediator of the cognitive benefits of DMF, thus establishing its therapeutic repurposing potential for age-related neurodegenerative diseases.
Neurodegenerative diseases are often accompanied by systemic comorbidities, including changes in bone health, but the molecular relationship between neurodegeneration, skeletal decline, and cellular senescence remains poorly understood. In this study, we investigated sex-specific changes in circulating bone- and senescence-related proteins across the spectrum of Alzheimer's disease(AD), Lewbody dementia(LB) and Parkinson's disease(PD). Plasma proteomic profiling was performed on samples from 408 participants deeply phenotyped for neurodegenerative diseases, followed by differential protein and pathway analyses. This study reveals sex-dependent alterations in bone and senescence-related circulating proteins in AD-related, PD and LB-related neurodegenerative diseases, providing insights into the complex relationship between neurodegeneration and bone health. Several candidate proteins were also associated with established plasma neurodegeneration biomarkers, particularly pTau181. Pathway analyses revealed shared mitochondrial and metabolic dysfunction across neurodegenerative diseases, with disease-specific features including vesicle trafficking disruption in AD and inflammatory-senescence pathways in LB, plus sex-divergent patterns in inflammatory signaling and bone-related pathways.
Neurodegenerative conditions signify an irreversible, progressive loss of neurons eventually resulting in a wide array of symptoms including cognitive decline, gradual loss of memory, compromised motor functions. Conventional therapies available principally attempt to either restore neurotransmitter levels, or activate its subordinate receptors; while underlying disease pathology of neurodegeneration being overlooked. This narrowed therapeutic approach ultimately results in irreversible, augmented neurodegeneration, leading to hastened disease progression, resulting in long-term complications, and impaired quality of life. This poses an imperative need for newer treatments to curb the progression of the disease. Neurotrophins; NGF and BDNF are proteins that are classically acknowledged during the development of vertebrate nervous system. Proneurotrophins and Mature neurotrophins activate their specific p75NTR and Trk receptors, which initiate intracellular neuronal survival signaling cascades that play an imperative role in maintaining survival of neurons, apoptosis, and synaptic plasticity. Such neuroprotective effects, native neurotrophins could mainly be a potent strategy in the treatment of neurodegenerative disorders. Due to their deprived drugability, neurotrophins failed to pass on further. Hence, small molecule neurotrophin mimetics that corresponds to its receptor domains might show promising results by increasing receptor-induced neuronal survival, differentiation, and initiation of downstream signalling pathways. Prospects that these small molecule mimetics possesses influential neurotrophic effects might as well lead to the application of such compounds that might be crucial to treat the underlying pathology of neurodegeneration that extends beyond the standard symptomatic treatments of neurodegenerative disorders.
We investigated how plasma biomarkers (phosphorylated tau 217 [ptau217], glial fibrillary acidic protein [GFAP], neurofilament light chain [NfL]) relate to imaging markers of small vessel disease (SVD) and Alzheimer's disease (AD), and cognition in memory clinic patients. 76 memory clinic patients underwent plasma biomarker assessment, neuropsychological testing, and 3T MRI. SVD burden was assessed using white matter hyperintensity (WMH) volume, mean skeletonized mean diffusivity (MSMD), and fiber density. AD-related neurodegeneration was captured by AD-signature cortical thickness and fiber-bundle cross-section. Findings were validated in 41 Alzheimer's Disease Neuroimaging Initiative (ADNI) participants with amyloid-/tau-positron emission tomography (PET). Associations varied between biomarkers. NfL showed strongest associations with SVD burden, ptau217 with AD-related neurodegeneration, while GFAP was linked to both. SVD markers were associated with processing speed, whereas AD markers were most associated with memory. NfL relates to SVD burden, while ptau217 remains most sensitive to AD-related biomarkers. GFAP's dual associations suggest overlapping biological processes. Together, coexisting SVD should be considered when interpreting plasma biomarkers in memory clinic patients.
Mild cognitive impairment (MCI) is an early stage of Alzheimer's disease-related neurodegeneration and may occur in midlife. The objective of the study was to assess associations between plasma p-tau217, p-tau181, cognition, and multimorbidity. We studied 236 MCI patients and 210 controls. Cognition was assessed using the Mini-Mental State Examination and Montreal Cognitive Assessment. Multimorbidity was defined as ≥2 chronic conditions, and comorbidity as coexisting diseases. MCI was associated with lower cognition, higher p-tau levels, and greater multimorbidity. Plasma p-tau217 correlated inversely with cognition. Plasma p-tau reflects early neurodegeneration, with multimorbidity contributing to cognitive decline.
Brain-derived neurotrophic factor (BDNF), a member of the neurotrophin family, plays essential roles in nervous system development, neuronal maintenance, and neurogenesis. Aberrant BDNF concentrations, observed both peripherally and within the central nervous system (CNS), have been consistently implicated in the pathogenesis of a spectrum of neurodegenerative disorders (NDDs), including Alzheimer's disease, Parkinson's disease, Amyotrophic lateral sclerosis, Huntington's disease, and Multiple sclerosis. Non-coding RNAs (ncRNAs), such as microRNAs (miRNAs) and long non-coding RNAs (lncRNAs), regulate gene expression and are critical factors in cellular processes relevant to neurodegenerative disease pathobiology. Consequently, ncRNAs are posited as promising biomarkers and potential therapeutic modalities for CNS-related pathologies. However, robust empirical evidence substantiating ncRNA-mediated, post-transcriptional regulation of BDNF expression in the context of neurodegeneration remains relatively scarce. The objective of this systematic review is to provide a critical synthesis of the current literature on the diagnostic and prognostic utility of ncRNAs that modulate BDNF expression, specifically within the scope of neurodegenerative disorders. Furthermore, we will explore innovative therapeutic strategies centered on targeting BDNF-associated miRNAs for the treatment of these disorders.
This review examines the bidirectional relationship between sleep instability and the pathogenesis of Alzheimer's disease, with particular emphasis on the hypothalamic orexinergic system as a key mechanistic link between these processes. Emerging evidence suggests that excessive orexin signaling contributes to insomnia and sleep fragmentation and may accelerate amyloid-β and tau accumulation by impairing glymphatic clearance and activating neurotoxic pathways. Conversely, progressive neurodegeneration can impair sleep-regulatory centers in the brainstem and hypothalamus, thereby creating a vicious cycle that may hasten cognitive decline. We further discuss therapeutic strategies targeting this pathway, with a focus on dual orexin receptor antagonists and complementary medical approaches. Notably, recent preclinical findings suggest that Panax ginseng extracts may inhibit orexin signaling and reactivate autophagy through the mammalian target of rapamycin pathway, thereby attenuating neuronal damage. By synthesizing current mechanistic insights and clinical evidence, this review proposes that modulation of the orexinergic system, through pharmacological and integrative approaches, may represent a promising strategy for delaying disease progression and improving quality of life in older adults.
Mitochondrial dysfunction has been proposed as a contributor to neurodegeneration in multiple sclerosis (MS). While the accumulation of somatic mitochondrial DNA (mtDNA) mutations with age is well documented in other neurodegenerative conditions, its role in MS progression remains largely unexplored. The aim of this study was to investigate the association between age and somatic mtDNA mutation burden in MS patients and evaluate whether any difference exists according to disease course. A total of 404 MS patients were recruited. Whole mtDNA was sequenced from blood-derived DNA using long-range PCR and the Illumina® Nextera XT kit. Somatic mutations were defined based on heteroplasmy levels between 1-5%. Linear regression models were used to assess the association between age and mutation rate. We observed a significant age-dependent increase in low-frequency non-synonymous mtDNA mutations in MS. Analyses stratified by disease course revealed that this effect was substantially driven by PPMS patients (n = 238, P = 2.71 × 10-3), while no association was seen in RRMS (n = 155, P = 0.35), suggesting course-specific mitochondrial trajectories. Furthermore, fast-progressing patients showed a positive linear relationship between age and mtDNA mutation rate (P = 0.017), while slow-progressing ones showed an opposite trend (test for interaction P = 0.013). These findings support the existence of a differential age-related accumulation of somatic mtDNA mutations detected in blood across MS courses.
Saccharides and responsive signaling pathways are important regulators of physiological and pathological processes. Saccharides can exert these functions via dedicated intracellular transporters and through binding to cellular sensors, such as saccharide-binding receptors. Glucose homeostasis and saccharide signaling are emerging as important regulators of neurodegeneration. Here, we utilized a Drosophila model of Huntington's disease to examine the role of Glut1 (homologous to multiple human glucose transporters) and saccharide-binding receptors. We find that Glut1 knockdown increases the amount of huntingtin-polyQ protein aggregates during aging, whereas Glut1 upregulation has converse effects. RNAi screening identifies several saccharide-binding receptors that either increase or decrease the levels of huntingtin-polyQ protein aggregates. In particular, pathogenic polyglutamine aggregates are reduced by knockdown of the lectin domain-containing G-protein coupled receptor Cirl (Calcium-independent receptor for α-latrotoxin), orthologous to human ADGRL1 and ADGRL2. These findings indicate that glucose transporters and saccharide-binding receptors regulate proteostasis and neurodegeneration during aging.
Neuroinflammation, especially involving NLRP3 inflammasome, has been recognized as a fundamental pathology in Alzheimer's disease (AD). Therefore, inhibiting the NLRP3 inflammasome activity can slow the development of AD. Eugenol, a natural phenolic compound, is known to inhibit or modulate the inflammatory response. Therefore, this study focuses on scrutinizing the potential neuroprotective effect of eugenol via the NLRP3 signaling pathway in aluminum chloride (AlCl3) elicited AD rats. Rats were split into four groups: olive oil, eugenol (50 mg/kg), AlCl3 (100 mg/kg), and eugenol + AlCl3, where rats received eugenol orally 2 weeks before and concurrently with oral induction by AlCl3 for 12 weeks. Behavioral, histopathological, and biochemical analyses were performed. Significant behavioral dysfunction, aluminum accumulation and pronounced neuronal damage were observed in AD rats. These were associated with increased hippocampal nitric oxide (NO), malondialdehyde (MDA) and amyloid beta protein 1-42 (Aβ 1-42) along with diminished serum total antioxidant capacity (TAC) levels. In addition, activation of NLRP3 inflammasome pathway components concomitant with upregulation of the pyroptotic marker; gasdermin D (GSDMD) was observed. Nevertheless, eugenol administration significantly improved rats' behavioral and histological aberrations, reduced NO, MDA, aluminum, and elevated TAC levels. Eugenol modulated toll like receptor 4 (TLR4)/myeloid differentiation primary response gene 88 (Myd88)/nuclear factor kappa B (NF-kB) signal transduction pathway, leading to inhibition of NLRP3 inflammasome pathway, inflammatory cytokines as interleukin 18 (IL-18) and interleukin 1 beta (IL-1β) as well as GSDMD. Eugenol may exert neuroprotective effects against AlCl3-induced neurodegeneration by modulating NLRP3 inflammasome, pyroptosis, and TLR4/MyD88/NF-kB signaling pathways.
Parkinson's disease (PD) is characterized by progressive dopaminergic neurodegeneration and chronic neuroinflammation. Increasing evidence suggests that microglial ferroptosis plays a critical role in the pathogenesis of PD. Troxerutin (TRX), a natural flavonoid derivative with potent antioxidant and anti-inflammatory activities, has shown neuroprotective potential; however, its effects on microglial ferroptosis and the underlying mechanisms in PD remain unclear. Here, we investigated the effects of TRX in a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced mouse model of PD and MPP+-stimulated BV2 cells. TRX improves motor performance, preserves nigrostriatal dopaminergic neurons, and attenuates microglial activation and pro-inflammatory cytokine expression in vivo. In BV2 cells, TRX attenuated ferroptosis-related changes, reduced lipid reactive oxygen species accumulation, and restored GPX4 and SLC7A11 expression. Furthermore, treatment with erastin, a classical ferroptosis inducer, reactivates ferroptosis-related responses and reverses the anti-inflammatory effects of TRX, linking ferroptotic stress to microglial inflammatory activation. Mechanistically, the cellular thermal shift assay supported target engagement between TRX and NOX4. TRX enhances K48-linked polyubiquitination of NOX4 and promotes its proteasomal degradation, which restores Nrf2 nuclear accumulation and activates downstream antioxidant responses. These results reveal that TRX alleviates ferroptosis-related neuroinflammation by modulating the microglial NOX4/Nrf2 axis in PD.