Background: Elevated levels of homocysteine (Hcy) and/or homocysteine thiolactone (HTL) are linked to neurodegenerative diseases, including Alzheimer’s disease (AD). Hyperphosphorylation or elevated acetylation of TAU protein are hallmarks of AD. However, the mechanistic roles of Hcy and HTL in the development and progression of AD are not fully understood.

Aim: We tested a hypothesis that Hcy and HTL promote TAU accumulation via hyperphosphorylation and acetylation of TAU in mouse neuroblastoma N2A-APPswe cells.

Methods: Neuroblastoma N2A-APPswe cells (N2A-APPswe) harboring a human transgene with mutation in the amyloid precursor protein (APP) gene were grown on the complete DMEM/F12 medium. Cells were treated with 20-200 μM Hcy or HTL. Phosphorylation and acetylation of TAU, as well as selected enzymes involved in TAU modification, were quantified by Immunofluorescence and Western blotting.

Results: Immunofluorescent analysis showed that Hcy and HTL upregulate phosphorylated TAU at threonine 205 and serine 396 and acetylated TAU at lysine 174, relative to untreated cells. However levels of total TAU were not affected in cells after Hcy and HTL treatment compared to control cells. At the same time, Western blots showed upregulation of CDK5 and GSK3α after Hcy and HTL treatments compared to untreated cells, while GSK3β level was not affected.

Conclusion: Treatment with Hcy or HTL affects TAU modifications which, in turn, promote TAU aggregation in mouse neuroblastoma N2A-APPswe cells. The hyperphosphorylated TAU at Ser396 and at Thr205 results from elevated levels of TAU kinases, CDK5 and GSK3α, which are upregulated by Hcy and HTL treatments.

Acknowledgements: This work was supported by NCN grant 2021/43/B/NZ4/00339 and by Prof. Daniel Lipiński, Dean of the Faculty of Agriculture, Horticulture and Biotechnology, PULS, on the occasion of the 20th anniversary of the establishment of the Operon Scientific Club.

* First seven authors contributed equally to this work

Beyond its hallmark motor symptoms, Huntington’s disease (HD) involves early and progressive disruption of cognitive and psychiatric functions critical for social interaction. Theory of Mind (ToM), the ability to infer one’s own and others’ mental states, is particularly vulnerable in HD. The present study investigated cognitive and affective ToM across disease stages and their association with neuropsychiatric symptoms.

A total of 24 HD patients (12 stage I, 12 stage II) and 24 healthy controls completed the Yoni Task, assessing cognitive and affective ToM. Neuropsychiatric symptoms were evaluated using the Problem Behaviors Assessment—short version, and quality of life with the 12-item Short Form Health Survey.

Cognitive ToM was significantly impaired already in stage I HD compared to controls (mean accuracy: 68.5% vs. 87.6%, p = 0.004), while affective ToM was relatively preserved (76.4% vs. 86.2%, p = 0.095). Stage II patients showed marked deficits in both domains (cognitive ToM: 46.3%; affective ToM: 52.3%), performing significantly worse than controls (p < 0.001). Total ToM performance declined progressively across stages (p < 0.001). Lower affective ToM scores were associated with greater irritability/aggression (ρ = –0.40, p = 0.049), obsessive–compulsive symptoms (ρ = –0.51, p = 0.015), and poorer self-reported physical functioning (ρ = 0.42, p = 0.049).

ToM impairments in HD are stage-dependent, with early cognitive deficits and later involvement of affective processes. Decline in ToM performance is clinically meaningful and associated with neuropsychiatric symptoms, particularly irritability. ToM assessment may therefore provide a sensitive marker of socio-cognitive dysfunction and disease progression in HD.

Introduction: The global rise in age-related neurodegenerative disorders, including Alzheimer’s, Huntington’s, and Parkinson’s diseases, represents a major health challenge, as existing therapies are largely symptomatic and fail to prevent progressive neuronal loss. Consequently, increasing attention has focused on natural compounds with neuroprotective and antioxidant properties. This study investigated the neuroprotective potential of Persea americana (avocado) seed extract (ASD) against 3-nitropropionic acid (3-NPA)-induced neurotoxicity, with emphasis on its antioxidant, anti-inflammatory, and anti-apoptotic mechanisms.

Methods: Methanol-extracted P. americana seed powder was orally administered to thirty-six male Wistar rats (150–200 g), randomly divided into six groups (n = 6): control, 3-NPA only, 3-NPA + 300 mg/kg ASD, 3-NPA + 600 mg/kg ASD, 300 mg/kg ASD only, and 600 mg/kg ASD only. The extract was administered for one week prior to 3-NPA exposure (10 mg/kg, intraperitoneally) and continued for two additional weeks. Behavioural, biochemical, and histopathological evaluations were performed. Oxidative stress indices, antioxidant enzyme activities, and succinate dehydrogenase (SDH) activity were measured, alongside gene expression analyses of Keap1, NF-κB, TNF-α, COX-2, Bad, and Bcl2.

Results: Persea americana seed extract significantly attenuated 3-NPA-induced behavioural deficits and restored SDH and antioxidant enzyme activities. The extract reduced lipid peroxidation and markedly downregulated the expression of NF-κB, TNF-α, COX-2, Bad, and Keap1, while upregulating the anti-apoptotic gene Bcl2. Histopathological examination further demonstrated reduced neuronal degeneration in extract-treated groups.

Conclusion: These findings indicate that Persea americana seed extract confers substantial neuroprotection against 3-NPA-induced neurotoxicity through antioxidant, anti-inflammatory, and anti-apoptotic mechanisms. The results suggest that the extract holds promise as a natural therapeutic candidate for oxidative stress-associated neurodegenerative disorders.

Introduction: Huntington disease (HD) is an autosomal dominant neurodegenerative disorder caused by an expanded CAG repeat in the HTT gene. Although disease onset and progression are known to vary between individuals, recent research has highlighted the role of genetic modifiers—both cis- and trans-acting—in influencing somatic instability, neuronal vulnerability, and age of onset. However, the extent to which these modifiers affect cross-sectional clinical severity and neuroimaging markers remains unclear. This study evaluates the phenotypic impact of genetic modifier categories in a large real-world HD dataset.

Methods: We analyzed a cohort of 48,536 genetically confirmed HD cases containing demographic variables, HTT CAG repeat length, motor severity (Chorea Score), functional impairment (Functional Capacity), and a quantitative neurodegeneration index (Brain Volume Loss). Genetic information included HTT (primary cause), trans-acting modifiers (e.g., MSH3, MLH1), and cis-acting somatic expansion events, classified into three categories. We compared clinical and MRI variables across categories using ANOVA and assessed correlations between CAG length, age, and severity measures using Pearson coefficients.

Results: The distribution of modifier categories was balanced (primary: 25.2%; trans-acting: 50.0%; cis-acting: 24.8%). Mean values of Chorea Score, Brain Volume Loss, and Functional Capacity were nearly identical across groups, with no statistically significant differences (p = 0.27, p = 0.48, p = 0.10, respectively). CAG repeat length was not correlated with motor severity, neurodegeneration, or functional status (all r ≈ 0; p > 0.05). Similarly, age showed no significant associations with any clinical variable. Disease stage (pre-symptomatic, early, middle, late) did not yield significant group differences.

Conclusions: Across this large real-world cohort, genetic modifier categories did not produce meaningful differences in cross-sectional clinical severity or MRI-based neurodegeneration. These findings suggest that modifier effects are subtle and likely act on longitudinal trajectories, age of onset, or progression rates rather than on isolated clinical snapshots. Longitudinal modeling is warranted to capture their true phenotypic impact.

Introduction: Clinically isolated syndrome (CIS) represents the first demyelinating event suggestive of multiple sclerosis (MS). However, the risk of conversion to MS varies widely among individuals. Identifying clinical and paraclinical predictors of conversion is essential for early risk stratification and timely therapeutic decision-making. This study aimed to evaluate the clinical, neuroimaging, laboratory, and neurophysiological factors associated with MS conversion in a real-world CIS cohort.

Methods: A retrospective analysis was conducted with 273 patients diagnosed with CIS. The primary outcome was conversion to MS, defined by the treating neurologist using standard diagnostic criteria. Bivariate analyses (t-tests, χ², and Fisher’s exact test) were used to compare clinical and paraclinical variables between converters and non-converters. Predictors with p < 0.20 and clinically relevant variables were included in a multivariate logistic regression model to identify independent predictors of conversion.

Results: Of the 273 patients included, 148 (54.2%) converted to MS. Age did not differ significantly between converters and non-converters (33.4 vs. 34.8 years, p=0.29). Neuroimaging markers were strongly associated with conversion: periventricular lesions (74.3% vs. 20.0%; OR_adj ≈ 8.1, 95%CI 4.0–16.1), infratentorial lesions (88.5% vs. 49.6%; OR_adj ≈ 4.8, 95%CI 2.2–10.3), and spinal cord lesions (73.6% vs. 62.4%; OR_adj ≈ 2.16, 95%CI 1.02–4.59). Oligoclonal bands in CSF were significantly different across groups (χ²=48.3; p≈3.3×10⁻¹¹) and remained an independent predictor (p≈0.014). Gender exhibited a trend toward significance after adjustment (p≈0.051). Initial EDSS could not be reliably compared due to missing data.

Conclusions: In this CIS cohort, the strongest independent predictors of conversion to MS were periventricular, infratentorial, and spinal cord lesions, along with the presence of oligoclonal bands. These findings support the central prognostic role of MRI and CSF biomarkers in early MS risk stratification and highlight the need for prompt monitoring and therapeutic considerations in high-risk CIS patients.

Introduction: Multiple sclerosis (MS) is characterized by neuroinflammation, autonomic dysfunction, and alterations in the hypothalamic–pituitary–adrenal (HPA) axis. Salivary cortisol is a useful biomarker of physiological stress, while xerostomia and nitric oxide (NO) dysregulation may reflect autonomic or inflammatory changes frequently observed in MS. However, the relationship between cortisol, NO, xerostomia, and anxiety symptoms remains unclear. This study aimed to evaluate the associations among these biomarkers and clinical features in patients with MS.

Methods: A cross-sectional study was conducted in 39 patients with MS. Salivary cortisol and NO were measured through validated assays. Xerostomia was assessed using the Abslang Test (0 = no xerostomia, 1 = xerostomia). Anxiety levels were measured using the Beck Anxiety Inventory (BAI). MS duration was converted to years for analysis. Due to non-normal distributions, Spearman correlations and Mann–Whitney U tests were applied. Logistic regression was performed to examine the predictive value of cortisol for xerostomia, expressed as odds ratios (OR).

Results: Xerostomia was present in 41% of participants. Cortisol levels were higher in patients with xerostomia compared with those without (median 6.02 vs. 4.56; p = 0.050). Logistic regression showed that cortisol increased the odds of xerostomia by 33% per unit increase (OR = 1.33; 95% CI: 0.96–1.85; p = 0.085). Cortisol showed a weak-to-moderate positive correlation with xerostomia (ρ = 0.32; p = 0.047) and a moderate negative correlation with NO (ρ = –0.46; p = 0.0035). No associations were found between cortisol and age, MS duration, or anxiety scores.

Conclusions: Salivary cortisol is associated with xerostomia and lower NO levels in MS, suggesting a possible neuroendocrine–salivary pathway. Although the predictive effect of cortisol on xerostomia did not reach statistical significance, the consistent trends across analyses support a potential physiological link. Larger studies are warranted to further explore these interactions.

Alzheimer’s disease (AD) features a range of pathological hallmarks that are multifactorial, including the buildup of amyloid-β (Aβ) plaques, neuronal cell death, oxidative stress, and dysfunctions in cholinergic and mitochondrial systems. In this study, the curcumin-functionalized chitosan–PLGA nanocomposite embedded with gold nanoparticles (CS-PLGA@AuNCs) was synthesized via co-precipitation to enhance targeted neuroprotection. Detailed physicochemical characterization using FT-IR, XRD, and HRTEM-EDX confirmed the successful creation, structural stability, and consistent morphology of CS-PLGA@AuNCs. In vitro studies using neuronal cell models showed excellent compatibility, effective cellular uptake, and a notable reduction in Aβ protein expression. CS-PLGA@AuNCs significantly reduced neuronal apoptosis and oxidative damage. Confocal microscopy further confirmed the downregulation of both Aβ and tau proteins, suggesting strong potential to alleviate AD-related pathological signaling. To assess in vivo effectiveness, we treated ICV-STZ-induced AD rats with CS-PLGA@AuNCs. Behavioral evaluations indicated enhanced learning and memory, supporting the compound’s neuroprotective function in reducing cognitive and synaptic deficits. Biochemical assessments revealed significant decreases in acetylcholinesterase (AChE) and malondialdehyde (MDA) levels, reflecting restored cholinergic function and reduced lipid peroxidation. Additionally, the activities of antioxidant enzymes, including SOD, CAT, and GPx, were substantially increased in the cortex and hippocampus, indicating enhanced internal defense mechanisms. The activities of mitochondrial complexes were also positively adjusted, suggesting improved cellular respiration and diminished mitochondrial dysfunction. Overall, these results underscore CS-PLGA@AuNCs as promising in multifunctional nanotherapy, capable of targeting critical features of AD. The findings support their potential for further preclinical development and eventual clinical application for the management of AD.

Neurodegenerative diseases with a dementia component, such as Alzheimer’s disease (AD) and C9orf72-associated ALS/FTD (C9-ALS/FTD), exhibit genomic instability and aberrant activation of transposable elements. Our previous work in AD uncovered a pathogenic mechanism whereby retrotransposon (RTE) mobilization generates RNA::DNA hybrids that trigger innate immunity through the cGAS–STING pathway. Here, we aim to determine whether this RTE-RNA::DNA hybrid-STING axis is also engaged in C9-ALS/FTD, and to determine its clinical relevance while assessing its potential as a therapeutic target using patient-derived cerebral organoids.

We employed a translational approach combining C9-ALS/FTD patients postmortem tissue with patient-derived cerebral organoids. In human brain tissue, activation of the RTE-RNA::DNA hybrid-STING axis was assessed using single-cell transcriptomic profiling, biochemical assays and immunofluorescence microscopy. Six-month-old cerebral organoids were validated as an in vitro model recapitulating the molecular signatures observed in patient tissue and subsequently used for pharmacological testing. Organoids were treated with the FDA-approved reverse transcriptase inhibitor lamivudine, and effects on RNA::DNA hybrid accumulation and downstream signaling were quantified.

In the frontal cortex of C9-ALS/FTD patients, we observed aberrant RTE activation, accompanied by cytoplasmic RNA::DNA hybrid accumulation and STING pathway activation. Organoids faithfully recapitulated these phenotypes. Treatment with lamivudine significantly reduced RNA::DNA hybrid accumulation, demonstrating pharmacological modulation of this pathway and supporting its therapeutic potential in C9-ALS/FTD.

This study provides the first demonstration that the RTE–RNA::DNA hybrid–STING axis is aberrantly activated in C9-ALS/FTD, linking retrotransposon dysregulation to disease-relevant innate immune signaling. By showing that RNA::DNA hybrid accumulation can be reduced with lamivudine, we highlight a translatable therapeutic entry point targeting this pathway in C9-ALS/FTD and related dementias.

Huntington's Disease (HD) is a neurodegenerative condition triggered by the elongation of a polyglutamine (polyQ) segment located at the N-terminus of the huntingtin protein (HTT). This elongation leads to the aggregation of HTT, which is ubiquitously expressed, suggesting that its aggregation may have effects beyond neurodegeneration to include peripheral tissues. However, the consequences of HTT aggregation in peripheral regions are not as thoroughly understood as those in the central nervous system. In this study, we utilized a Caenorhabditis elegans (C. elegans) model of HD, which expresses either a non-pathogenic (15Q) or a pathogenic (128Q) N-terminal fragment of HTT in body-wall muscle cells, to investigate changes in the proteome. We examined four conditions—15Q and 128Q at two different time points (days 2 and 7 of adulthood, labeled as 15D2, 15D7, 128D2, and 128D7). Compared to the 15D2 worms, those with the 128Q expansion at day 2 exhibited reduced levels of ribosomal proteins and cytoskeletal elements such as actin, profilin, calponin, and myosin, alongside an increased expression of galectin, a protein linked to stress and inflammation. By day 7, the 15D7 worms displayed developmental markers indicative of ribosome biogenesis, signal transduction, and vesicle trafficking. Meanwhile, increased levels of proteins related to stress response pathways—including proteostasis, protein folding, and cytoskeletal remodeling—were observed in the 128D7 worms. These findings elucidate the complex, stage-specific disruptions within the HD proteome tied to the expression of the disease in peripheral tissues.

Alzheimer's disease (AD), the most common cause of dementia, is defined by amyloid plaques, neurofibrillary tangles (NFTs) of hyperphosphorylated tau, and neuronal loss. The traditional amyloid cascade hypothesis long held that amyloid-β (Aβ) accumulation is the primary instigating event, supported by early genetic evidence linking AD to mutations in Aβ-processing genes (APP, PSEN1/2).

However, this paradigm is challenged by clinical trial results. Approved anti-Aβ immunotherapies, despite significantly reducing plaque levels, confer only modest clinical benefits, slowing cognitive decline slightly. Tau-based therapies have also failed, though they have not yet successfully cleared NFTs from the perikarya of cortical pyramidal neurons.

This evidence supports a proposed shift to the cerebrocortical disconnection hypothesis. This theory posits that dementia results from the breakdown of neural networks, initiated when tau aggregates into NFTs. This disruption damages axonal transport, creating an energetic crisis at nerve terminals, which promotes the production of Aβ42 and subsequent amyloid plaque formation.

The neural breakdown is further worsened by the dysfunction and loss of myelin-maintaining oligodendrocytes, leading to demyelination. This forces the damaged axons to expend even more energy for signalling, severely exacerbating their bioenergetic deficit. This combination of faulty transport, amyloid pathology, and myelin loss ultimately destroys critical long corticocortical and corticofugal neurons, along with (cholinergic, noradrenergic and serotonergic) corticopetal neurons. We conclude that therapeutic focus must now shift toward protecting the integrity of neural circuitry directly to prevent disconnection and meaningfully slow cognitive decline.