Parkinson's disease: mechanisms and models

Recovery of the injured neural system through gene delivery to surviving neurons in Parkinson's disease

A critical unaddressed problem in Parkinson's disease is the lack of therapy that slows or hampers neurodegeneration. While medications effectively manage symptoms, they offer no long-term benefit because they fail to address the underlying neuronal loss. This highlights that the elusive goals of halting progression and restoring damaged neurons limit the long-term impact of current approaches. Recent clinical trials using gene therapy have demonstrated the safety of various vector delivery systems, dosages, and transgenes expressed in the central nervous system, signifying tangible and substantial progress in applying gene therapy as a promising Parkinson's disease treatment. Intriguingly, at diagnosis, many dopamine neurons remain in the substantia nigra, offering a potential window for recovery and survival. We propose that modulating these surviving dopamine neurons and axons in the substantia nigra and striatum using gene therapy offers a potentially more impactful therapeutic approach for future research. Moreover, innovative gene therapies that focus on preserving the remaining elements may have significant potential for enhancing long-term outcomes and the quality of life for patients with Parkinson's disease. In this review, we provide a perspective on how gene therapy can protect vulnerable elements in the substantia nigra and striatum, offering a novel approach to addressing Parkinson's disease at its core.

Multiparametric analysis based on 18F-AV133 PET/MR imaging for clinical application in Parkinson's disease

OBJECTIVE

The progressive loss of dopaminergic neurons and abnormal iron deposition in the central nervous system (CNS) are key pathogenic mechanisms of Parkinson's disease (PD). This study aimed to explore the relationship between iron deposition in specific CNS regions and striatal dysfunction using 18F-AV133 PET/MR imaging.

METHODS

Based on the Hoehn-Yahr stage, 24 patients with early-stage PD (EPD, stage ≤ 2.5), 17 patients with late-stage PD (LPD, stage ≥ 3), and 30 healthy controls (HCs) were recruited for scale evaluation. The specific uptake ratio (SUR) of striatal subregions was calculated using the occipital cortex as the reference region. Quantitative Susceptibility Mapping (QSM) values of major subcortical nuclei were derived through QSM imaging. Spearman correlation analysis was conducted to assess the relationships between SUR in striatal subregions, QSM values in nuclear groups, and PD clinical symptoms, as well as the correlation between SUR and QSM values.

RESULTS

Compared to HC, EPD and LPD patients showed significantly reduced VMAT2 distribution in the bilateral caudate nuclei and anteroposterior putamen, particularly in the contralateral posterior putamen. In PD patients, the SUR of striatal subregions and QSM values of the substantia nigra (SN), globus pallidus (GP), and external segment of the GP (GPe) were significantly correlated with disease duration, H&Y stage, UPDRS III score, and NMSS score. Moreover, SUR of striatal subregions was negatively correlated with QSM values in the SN, GP, internal segment of the GP (GPi), and GPe.

CONCLUSION

Multi-parameter analysis revealed a region-specific correlation between striatal dysfunction and iron deposition in PD, offering new avenues to elucidate the underlying mechanisms of the disease.

DRN-SNc serotonergic circuit drives stress-induced motor deficits and Parkinson's disease vulnerability

Stress is a recognized risk factor for Parkinson's disease (PD), but the mechanisms by which stress exacerbates PD symptoms through the serotonergic system are not fully understood. This study investigates the role of serotonergic (5-HT) neurons in the dorsal raphe nucleus (DRN) in mediating stress-induced motor deficits and PD progression. Acute and chronic stress were induced in mice using an elevated platform (EP) and combined with MPTP administration to model early-stage PD. Acute EP stress caused transient motor deficits and significant activation of DRN5-HT neurons projecting to substantia nigra compacta (SNc) dopaminergic (DA) neurons. Manipulating the DRN-SNc pathway with optogenetics and chemogenetics confirmed its critical role in stress-induced motor deficits. Activation of the SNc 5-HT2C receptor with an agonist replicated these deficits, while receptor inhibition prevented them, underscoring its importance. Chronic EP stress worsened MPTP-induced deficits and caused significant SNcDA neurons loss, suggesting it accelerates PD progression. Prolonged chemogenetic inhibition of the DRN-SNc circuit mitigated chronic stress effects in MPTP-treated mice. These findings highlight the crucial role of the DRN-SNc serotonergic circuit and 5-HT2C receptors in stress-related motor deficits, suggesting potential targets for therapies aimed at treating both stress-related motor disorders and Parkinson's disease.

Sitagliptin attenuates L-dopa-induced dyskinesia by regulating mitochondrial proteins and neuronal activity in a 6-OHDA-induced mouse model of Parkinson's disease

L-dopa-induced dyskinesia (LID) is an incapacitating complication of long-term administration of L-dopa therapy that commonly affects patients with Parkinson's disease (PD) due to the widespread use of the causative drug. Herein, we investigated the therapeutic potential of sitagliptin, a drug used to treat type 2 diabetes mellitus, to treat LID. 6-hydroxydopamine (6-OHDA) was unilaterally injected into the left side of the substantia nigra pas compacta to induce a mouse model of PD. After four weeks of 6-OHDA induction, L-dopa was administered with or without sitagliptin for 11 consecutive days. LID was monitored using abnormal involuntary movement (AIM) scoring, conducted on days 5 and 10 of L-dopa treatment. Comparative proteomic analysis was performed on the 6-OHDA-lesioned striatum by comparing groups treated with vehicle + L-dopa and sitagliptin + L-dopa. Sitagliptin combined with L-dopa significantly attenuated AIM scores in 6-OHDA-lesioned mice. Proteomic analysis following sitagliptin treatment showed an increase in proteins involved in mitochondrial function regulation and a decrease in proteins associated with cytoskeleton function regulation. Changes in the expression of Ndufb2, a subunit of NADH: ubiquinone oxidoreductase (complex I), and Arc, an immediate early gene (IEG), which showed the most significant increase and decrease, respectively, were validated using western blotting and RT-PCR analysis. These findings suggest that sitagliptin may have therapeutic potential by enhancing mitochondrial functions and suppressing neuronal activity in the striatum, thereby mitigating the incapacitating complications associated with long-term L-dopa use in patients with PD.

Assessing Laryngeal Neuromotor Activity from Phonation

Neurodegenerative motor disorders affect the neuromuscular system challenging daily life and normal activity. Parkinson's Disease (PD) is among the most prevalent ones, with a large impact and rising prevalence rates. Speech is most affected by PD as far as phonatory and articulatory performance is concerned. Neuromotor activity (NMA) alterations have an impact on larynx muscles responsible for vocal fold adduction and abduction, hampering phonation stability and regularity. The main muscular articulators involved in phonation control are the cricothyroid (tensor) and thyroarytenoid (relaxer) systems, regulated by two distinct direct neuromotor pathways, activated by the precentral gyrus laryngeal control areas. These articulations control the musculus vocalis, directly responsible for regular vocal fold vibration. An indirect estimation of the muscular tension produced by inverse filtering may split into two independent channels, assumed to be the tensor and relaxer neuromotor pathways such as the differential neuromotor activity (DNMA). The amplitude distributions of both DNMA channels allow comparing phonations from PD-affected persons (PDPs) and age-matched healthy control participants (HCPs) with respect to a set of reference mid-age normative participants (RSPs). The comparisons are carried out by Jensen-Shannon distributions of PDP and HCP phonations with respect to those of RSPs. A dataset of 96 phonation samples from participants balanced by gender is used to train a set of decision tree classifiers (DTCs) to distinguish PDP from HCP phonation. The best results from 10-fold cross-validation offered accumulated mismatches of 0.09 and 0.1292 for male and female subsets. The sensitivity, specificity, and accuracy of the classification results when separating PDP from HCP phonatios were 93.33%, 88.23%, and 90.63% (male PDP versus HCP) and 92.86%, 83.33%, and 87.50% (female PDP versus HCP), providing a stratification of PDPs and HCPs by objective disease grading from explainable AI (XAI) methods.

Exploring the dynamic pathogenesis of Parkinson's disease by case-control and longitudinal blood transcriptome analyses

The pathogenesis of Parkinson's disease (PD) was recently hypothesized to change along with the disease course. Given the fact that transcriptional changes in blood can provide insightful clues for PD pathogenesis, we performed case-control and longitudinal whole blood transcriptome analyses to identify the signature genes underlying the hypothesized dynamic pathogenesis of PD. In the case-control study, we compared the gene expression patterns in healthy control (N = 189), prodromal (N = 58) and de novo idiopathic PD subjects (N = 390). The results showed that the prodromal subjects were at the tipping-point stage, which is characterized by the abnormal expression patterns of 414 genes associated with oxygen transport and reactive oxygen species metabolic process. We next performed a longitudinal transcriptome analysis on 255 PD patients from the baseline to the third year, and identified 203 genes related to immune and inflammatory responses during disease progression. These findings not just offer deeper insights into the dynamic pathogenesis of PD, but also help to find potential drugs to prevent the early neurodegeneration process.

RIPK1: A Promising Target for Intervention Neuroinflammation

Necroptosis is a novel mode of cell death that differs from traditional apoptosis, characterized by distinct molecular mechanisms and physiopathological features. Recent research has increasingly underscored the pivotal role of necroptosis in various neurological diseases, including stroke, Alzheimer's disease and multiple sclerosis. A defining hallmark of these conditions is neuroinflammation, a complex inflammatory response that critically influences neuronal survival. This review provides a comprehensive analysis of the mechanistic underpinnings of necroptosis and its intricate interplay with neuroinflammation, exploring the interrelationship between the two processes and their impact on neurological disorders. In addition, we discuss potential therapeutic strategies that target the intervention of necroptosis and neuroinflammation, offering novel avenues for intervention. By deepening our understanding of these interconnected processes, the development of more effective treatments approaches holds significant promise for improving patient outcomes in neurological disorders.

Oligodendrocyte-astrocyte crosstalk in Parkinson's disease mediates neuronal ferroptosis via the FGF signaling pathway

Parkinson's disease (PD), as a neurodegenerative disorder, is characterized primarily by damage to the central nervous system, accompanied by astrocyte dysfunction and the activation of ferroptosis. Recent studies have shown that oligodendrocytes also exhibit functional abnormalities in the brains of PD patients and are involved in the ferroptotic process. However, it remains unclear whether there is an interaction between oligodendrocytes and astrocytes and how they induce neuronal ferroptosis. Here, we employed single-nucleus sequencing and spatial transcriptomics to characterize the intercellular communication network between oligodendrocytes and astrocytes in the PD environment. Among these, astrocytes are the primary recipients of signals sent by oligodendrocytes in the FGF (Fibroblast growth factors) signaling pathway. In PD, the communication intensity is weakened, involving FGF1 and FGF9 and their receptors FGFR1, FGFR2, and FGFR3. Subsequently, we further validated the significant activation of mitochondrial oxidative phosphorylation processes within oligodendrocytes and astrocytes in PD mice, and that astrocytes might also involve the interaction of Mt1 and Ca2+. Additionally, we demonstrated a significant reduction in the number of DA neurons in the SN region and a notable activation of ferroptosis, alongside a significant decrease in the antioxidant pathway NRF2/SLC7A11/GPX4. In summary, our data elucidate that ferroptosis in the midbrain SN region preferentially occurs in astrocytes under the dysregulation of oligodendrocytes, leading to ferroptosis in DA neurons. Thus, our study highlights the crucial role of oligodendrocyte-astrocyte crosstalk in driving neuronal inactivation and inflammatory expansion in PD.

Exploring the interactions of urinary metals and the mediating role of oxidative stress in Parkinson's disease risk: an epidemiological study in the elderly

Parkinson's disease (PD) ranks as the second most prevalent neurodegenerative disorder, often leading to significant disability in affected individuals. Metal exposure has been implicated in PD, but the overall role, interactions among metal mixtures, and underlying mechanisms remain unclear. In this study, we measured 8 essential and 2 potentially harmful metal trace elements in urine samples from PD patients (n = 96) and healthy controls (n = 162). The concentration of 8-hydroxy-2'-deoxyguanosine (8-OHdG), a marker of oxidative damage, was also measured. Logistic regression and restricted cubic spline (RCS) regression analyses revealed that both increased exposure to manganese (Mn) and lead (Pb), and insufficient intake of chromium (Cr), nickel (Ni), selenium (Se), and cadmium (Cd) may increase the risk of PD. However, smoking may mediate the relationship between Cd and PD, and Cd itself may not exert a protective effect against PD. Bayesian kernel machine regression (BKMR) and quantile-based g-calculation (QGC) models demonstrated that both metal deficiencies and excesses could increase the risk of PD, with Mn (73.7%) and Pb (9.3%) identified as the main contributors to PD risk. Furthermore, we observed an interaction between Mn and Cr, with Cr amplifying the promoting effect of Mn. Mediation analysis indicated that 8-OHdG mediated 11.6% of the total effect of Mn and Pb exposure on PD risk. Further research is required to explore specific metals' protective mechanisms and elucidate the interactions among different metals. Further longitudinal and cohort studies are required to better verify the causal link between metal exposure and PD.

A Levodopa-Encapsulated Poly-ε-Caprolactone Nanocomposite Improves the Motor Symptoms and Neurochemical Changes in a Rotenone-Induced Mouse Model of Parkinson's Disease

Parkinson's disease (PD) is the most common neurodegenerative disorder; in this condition, patients lose dopamine (DA), which leads to abnormal motor functions. Levodopa (LD) is the most effective drug used for the treatment of PD; however, LD shows poor plasma bioavailability and limited brain uptake and induces peripheral side effects. Due to its poor brain availability and short half-life, prolonged treatment must be repeated with a dosing schedule, which leads to long-term side effects, including dyskinesia, stomatitis, anxiety, and depression. An LD-encapsulated polymer nanocomposite has been reported to overcome these problems. The present study aims to improve the bioavailability and efficiency of LD to an effective treatment strategy for PD. Herein, we report the newly synthesized LD-encapsulated poly-ε-caprolactone (PCL) nanocomposite (LD-PCL-PVA NC), and its chemical and physical properties were analyzed. The LD-PCL-PVA NC exhibits no toxicity on the SH-SY5Y cell line and shows improved bioavailability of the LD in mouse plasma. Furthermore, we found that LD-PCL-PVA NC showed a significant improvement in motor symptoms in the rotenone (RT)-induced PD mouse model compared to the LD treatment. In addition, LD-PCL-PVA NC significantly increased the DA and homovanillic acid compared to LD and restored the total glutathione level and malonaldehyde and catalase activity in mouse brain. The histopathology studies reveal that LD-PCL-PVA NC did not exhibit toxicity in treated mice. The study suggested that LD-PCL-PVA NC can be used for the effective and promising treatment of PD.

URB597 downregulates DJ-1 expression in the mouse striatum and induces neurodegeneration

DJ-1 is a multifunctional protein involved in diverse cellular processes, including defense against oxidative stress, regulation of gene transcription, and maintenance of mitochondrial function. Mutations in the DJ-1 gene are closely associated with early-onset Parkinson's disease, and loss of DJ-1 function increases the susceptibility of dopaminergic neurons to oxidative damage, potentially driving neurodegeneration. Therefore, DJ-1 represents an attractive therapeutic target for PD. In this study, we screened a library of blood-brain barrier-permeable small molecules to identify compounds that modulate DJ-1 expression in the mouse brain. Through molecular docking, we discovered that URB597, a selective fatty acid amide hydrolase inhibitor, binds to DJ-1 and forms a stable complex. URB597 treatment markedly reduced DJ-1 protein levels in SH-SY5Y cells, leading to decreased cell survival and impaired mitochondrial function under oxidative stress conditions. In addition, URB597-treated mice exhibited motor deficits and dopaminergic neuron loss, indicating that suppressing DJ-1 expression may adversely affect neuronal function. Gene expression and pathway enrichment analyses revealed that URB597 targets DJ-1 in the mouse striatum and regulates the expression of genes involved in protein acetylation. Collectively, these findings underscore the critical role of DJ-1 in protecting dopaminergic neurons from oxidative damage and uncover its potential implications in regulating protein acetylation.

Impact of canny edge detection preprocessing on performance of machine learning models for Parkinson's disease classification

This study investigates the classification of individuals as healthy or at risk of Parkinson's disease using machine learning (ML) models, focusing on the impact of dataset size and preprocessing techniques on model performance. Four datasets are created from an original dataset: [Formula: see text] (normal dataset), [Formula: see text] ([Formula: see text] subjected to Canny edge detection and Hessian filtering), [Formula: see text] (augmented [Formula: see text]), and [Formula: see text] (augmented [Formula: see text]). We evaluate a range of ML models-Logistic Regression (LR), Decision Tree (DT), Random Forest (RF), Gradient Boosting (GB), XGBoost (XBG), Naive Bayes (NB), Support Vector Machine (SVM), and AdaBoost (AdB)-on these datasets, analyzing prediction accuracy, model size, and prediction latency. The results show that while larger datasets lead to increased model memory footprints and prediction latencies, the Canny edge detection preprocessing supplemented by Hessian filtering (used in [Formula: see text] and [Formula: see text]) degrades the performance of most models. In our experiment, we observe that Random Forest (RF) maintains a stable memory footprint of 61 KB across all datasets, while models like KNN and SVM show significant increases in memory usage, from 5.7-7 KB on [Formula: see text] to 102-220 KB on [Formula: see text], and similar increases in prediction time. Logistic Regression, Decision Tree, and Naive Bayes show stable memory footprints and fast prediction times across all datasets. XGBoost's prediction time increases from 180-200 ms on [Formula: see text] to 700-3000 ms on [Formula: see text]. Statistical analysis using the Mann-Whitney U test with 100 prediction accuracy observations per model (98 degrees of freedom) reveals significant differences in performance between models trained on [Formula: see text] and [Formula: see text] (p-values < 1e-34 for most models), while the effect sizes measured by estimating Cliff's delta values (approaching [Formula: see text]) indicate large shifts in performance, especially for SVM and XGBoost. These findings highlight the importance of selecting lightweight models like LR and DT for deployment in resource-constrained healthcare applications, as models like KNN, SVM, and XGBoost show significant increases in resource demands with larger datasets, particularly when Canny preprocessing is applied.

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

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

Machine learning-based meta-analysis reveals gut microbiome alterations associated with Parkinson's disease

There is strong interest in using the gut microbiome for Parkinson's disease (PD) diagnosis and treatment. However, a consensus on PD-associated microbiome features and a multi-study assessment of their diagnostic value is lacking. Here, we present a machine learning meta-analysis of PD microbiome studies of unprecedented scale (4489 samples). Within most studies, microbiome-based machine learning models accurately classify PD patients (average AUC 71.9%). However, these models are study-specific and do not generalise well across other studies (average AUC 61%). Training models on multiple datasets improves their generalizability (average LOSO AUC 68%) and disease specificity as assessed against microbiomes from other neurodegenerative diseases. Moreover, meta-analysis of shotgun metagenomes delineates PD-associated microbial pathways potentially contributing to gut health deterioration and favouring the translocation of pathogenic molecules along the gut-brain axis. Strikingly, microbial pathways for solvent and pesticide biotransformation are enriched in PD. These results align with epidemiological evidence that exposure to these molecules increases PD risk and raise the question of whether gut microbes modulate their toxicity. Here, we offer the most comprehensive overview to date about the PD gut microbiome and provide future reference for its diagnostic and functional potential.

Invasive laser acupuncture targeting muscle: a novel approach to protect dopaminergic neurons and reduce neuroinflammation in a brain of Parkinson's disease model

Parkinson's disease (PD) affects 1-2% of the global population and presents significant therapeutic challenges. Due to the limitations of existing treatments, there is a pressing need for alternative approaches. This study investigated the effects of invasive laser acupuncture (ILA), which combines acupuncture and photobiomodulation. In this method, optical fibers are inserted into the muscle layers of the acupoint to enhance therapeutic outcomes. Mice with MPTP-induced PD were treated with ILA at 830 nm or 650 nm. Protective effects of nigrostriatal dopaminergic neurons and fibers were assessed by examining TH immunoreactivity in the brain. Neuroinflammation markers in the brain and muscle metabolomic profiles were also analyzed. Comparisons between invasive and non-invasive laser application, as well as the impact of nerve blocking with lidocaine, were also evaluated. ILA at 830 nm (ILA830) significantly improved motor performance and increased the nigrostriatal TH-positive immunoreactivities. It reduced the levels of α-synuclein, apoptotic proteins, and inflammatory cytokines, while increasing anti-inflammatory in the brain. ILA830 also decreased nigrostriatal astrocyte and microglia activation. Muscle metabolomic analysis showed distinct group clustering and significant changes in metabolites like glucose and galactose, correlating with improved motor functions. Invasive laser treatment was more effective than non-invasive, and lidocaine pre-treatment did not block its effects. ILA at 830 nm effectively ameliorates PD symptoms by protecting dopaminergic neurons, and reducing neuroinflammation in the brain. Muscle metabolomic changes by ILA830, such as increased glucose and galactose, correlate with motor improvement. This approach offers a promising strategy for PD treatment, warranting further research to optimize its use in clinical settings.

Dopamine D2 receptor upregulation in dorsal striatum in the LRRK2-R1441C rat model of early Parkinson's disease revealed by in vivo PET imaging

We conducted PET imaging with [18F]FDOPA and dopamine D2/3 receptor ligand [18F]fallypride in aged transgenic rats carrying human pathogenic LRRK2 R1441C or G2019S mutations. These rats have mild age-dependent deficits in dopamine release restricted to dorsal striatum despite no overt loss of dopamine neurons or dopamine content and demonstrate L-DOPA-responsive movement deficits.LRRK2 mutant rats displayed no deficit in [18F]FDOPA uptake, consistent with intact dopamine synthesis in striatal axons. However, LRRK2-R1441C rats demonstrated greater binding of [18F]fallypride than LRRK2-G2019S or non-transgenic controls, from a regionally selective increase in dorsal striatum. Immunocytochemical labelling post-mortem confirmed a greater density of D2 receptors in LRRK2-R1441C than other genotypes restricted to dorsal striatum, consistent with upregulation of D2-receptors as a compensatory response to the greater dopamine release deficit previously demonstrated in this genotype.These results show that [18F]fallypride PET imaging is sensitive to dysregulation of dopamine signalling in the LRRK2-R1441C rat, revealing upregulation of D2 receptors that parallels observations in human putamen in early sporadic PD. Future studies of candidate therapies could exploit this non-invasive approach to assess treatment efficacy.

Evaluation of the Protective Effects of Noscapine on Paraquat-Induced Parkinson's Disease in Rats

Parkinson's disease (PD) is a degenerative central nervous system disease pathologically attributed to dopaminergic neuron damage in the substantia nigra. Noscapine is a natural alkaloid with several benefits, including anti-inflammatory, neural protection, and anti-oxidant effects. Hence, the current study evaluated the protective effects of Noscapine against paraquat (PQ)-induced Parkinson's disease model in rats. Male Wistar rats were into six groups: sham and PQ-induced models treated with vehicle, vitamin-E (20 mg/kg/d), or Noscapine (6, 18, and 55 mg/kg/d) for four weeks. Meanwhile, the rats were assessed for weight and food consumption (FC) daily and PD-associated behavior changes using rotarod, bar, and parallel bar tests every week. The animals were ethically sacrificed at the end of the study, and biochemical, immunological, and histopathological markers were measured in the brain. As a result, the levels of weight, FC, parallel bar, and rotarod test (both speed and latency), number of neurons, total thiol content, and interleukin-10 (IL-10) were significantly reduced. In contrast, the levels of dark neurons, TNF-α, bar test, and malondialdehyde (MDA) were markedly increased in the PQ-vehicle group compared to the sham group (P < 0.001-0.5). In contrast, comedication with Noscapine significantly reversed the histological damages and improved deteriorated behavioral, biochemical, and immunological parameters in a dose-dependent manner compared to the PQ-vehicle group (0.001-0.05). Taken together, it was determined that using Noscapine has antiparkinsonian effects and improved behavioral tests, catalepsy, bradykinesia, and motor dysfunction and has a protective impact on the brain's neurons through its anti-oxidant and anti-inflammatory properties.

Can the Pupillary Light Reflex and Pupillary Unrest Be Used as Biomarkers of Parkinson's Disease? A Systematic Review and Meta-Analysis

Background/Objectives: The pathological changes preceding the onset of Parkinson's disease (PD) commence several decades before motor symptoms manifest, offering a potential window for identifying objective biomarkers for early diagnosis and disease monitoring. Among the primary non-motor features of PD is autonomic dysfunction; however, its precise assessment remains challenging, limiting its viability as a reliable biomarker. Both the pupillary light reflex (PLR) and pupillary unrest are regulated by autonomic pathways suggesting their potential as objective non-invasive indicators of the PD prodromal phase. This review systematically evaluates studies that compare PLR and pupillary unrest in individuals with PD and healthy controls to determine their utility as potential biomarkers of the disease. Methods: A systematic search strategy was designed to identify studies reporting PLR and pupillary unrest findings in PD patients. Searches were conducted across three databases (MEDLINE, Embase PsycINFO), supplemented by cross-referencing relevant studies found on Google Scholar. The literature search was last updated on 7 December 2020. Pupillometric parameters that permitted statistical synthesis included maximum constriction velocity (VMax), constriction amplitude (CAmp), and constriction latency (CL). Pooled incidence and effect sizes were determined using a random-effects model with an inverse variance DerSimonian-Laird estimator. The I2 statistic was used to assess study heterogeneity. When meta-analysis was not feasible, a qualitative analysis was undertaken. Results: The initial search yielded 219 references. Following deduplication and exclusion of ineligible studies, 31 papers were selected for review. Pupillometric data from 11 studies were incorporated into the meta-analysis. Effect sizes for PD patients were significant for VMax -0.92, (p < 0.01), CAmp -0.58, (p < 0.05), and CL 0.46, (p < 0.05). Measures of pupillary unrest were elevated in PD patients compared to controls, but evidence was limited to two studies. Conclusions: Pupillary constriction in response to light is characterised by reduced speed and amplitude in PD, with effect sizes suggesting potential clinical applicability. However, evidence regarding baseline pupillary variability remains insufficient, underlining the necessity for further research. Pupillary metrics represent a promising avenue for early PD detection, though their clinical utility is constrained by methodological heterogeneity and variations in disease duration among studies.

The modifying effect of mutant LRRK2 on mutant GBA1-associated Parkinson disease

Parkinson disease (PD) is the second most common neurodegenerative disease. While most cases are sporadic, in ~ 5%-10% of PD patients the disease is caused by mutations in several genes, among them GBA1 (glucocerebrosidase beta 1) and LRRK2 (leucine-rich repeat kinase 2), both prevalent among the Ashkenazi Jewish population. LRRK2-associated PD tends to be milder than GBA1-associated PD. Several recent clinical studies have suggested that carriers of both GBA1 and LRRK2 mutations develop milder PD compared to that observed among GBA1 carriers. These findings strongly suggested an interplay between the two genes in the development and progression of PD. In the present study Drosophila was employed as a model to investigate the impact of mutations in the LRRK2 gene on mutant GBA1-associated PD. Our results strongly indicated that flies expressing both mutant genes exhibited milder parkinsonian signs compared to the disease developed in flies expressing only a GBA1 mutation. This was corroborated by a decrease in the ER stress response, increase in the number of dopaminergic cells, elevated levels of tyrosine hydroxylase, reduced neuroinflammation, improved locomotion and extended survival. Furthermore, a significant decrease in the steady-state levels of mutant GBA1-encoded GCase was observed in the presence of mutant LRRK2, strongly implying a role for mutant LRRK2 in degradation of mutant GCase.

Neuroprotective effect of Thymus vulgaris on paraquat induced Parkinson's disease

The dramatic surge of neurodegenerative disorders among elderly population underscore the pressing demand for development of optimal and evidence based noninvasive natural treatment strategies. Paraquat exposure in animal models used in scientific studies can cause a variety of clinical signs of Parkinson disease (PD). The health benefits of thyme include antioxidant, anti-inflammatory, pulmonary, and neurological benefits. Thyme and other herbal treatments are frequently used to treat a variety of conditions, including neurological issues. The primary factor in the etiology of neurodegeneration is oxidative stress. Conventional treatments are indicated to potentially have negative side effects. The primary phytochemicals of Thymus vulgaris (TV), which are responsible for its unique therapeutic property of neuro-protection, include hydrocarbon and phenolic compounds like thymol and carvacrol. The goal of the current investigation was to examine T. vulgaris' potential for neuroprotection while also ensuring its safety. Analyses of the plant's physicochemical and phytochemical composition were performed by liquid chromatographic analysis. Neuro-behavioral and biochemical parameters were evaluated to determine the impact of T. vulgaris in paraquat induced parkinsonian rodents model. The neurobehavioral tests include open field tests for movement and exploration, Y maze test and elevated plus maze test for natural behavior, memory, and anxiety, hole board tests for exploratory behavior, ladder climbing, foot printing, and wire hanging tests for estimating neuromuscular coordination. T. vulgaris treatment significantly improved neurobehavioral parameters dose-dependently, Biochemical analysis revealed that extract treatment mitigated the declined level of antioxidant enzymes. RT-PCR analysis showed that in paraquat treated group mRNA expression of IL-1α, IL-1β, Alpha-Synuclein, TNF-α, and IL-6 was upregulated markedly. However, T. vulgaris treatment dose dependently down-regulated the mRNA expression of these genes. The groundbreaking results of current study revealed that T. vulgaris restored the degenerative alterations, neuro-inflammation, and nerve loss in the brain structure, as evident by histopathological investigation. Particularly remarkable restoration in neuropsychological and biochemical markers emphasize the medicinal potential of T. vulgaris as a revolutionary treatment for neurodegenerative disorders, offering new hope for millions worldwide afflicted by these devastating conditions.

Dectin-1 participates in neuroinflammation and dopaminergic neurodegeneration through synergistic signaling crosstalk with TLR4

Neuroinflammation mediated by microglial activation plays a prominent role in the pathogenesis of Parkinson's disease (PD). Dendritic cell-associated C-type lectin-1 (Dectin-1) is a pattern recognition receptor that is involved in innate immunity. However, the role of Dectin-1 on dopaminergic neuronal damage remains unclear. Our results demonstrated that the expression of Dectin-1 was significantly increased in the microglia of the LPS-induced PD mouse model. Inhibition of Dectin-1 by laminarin (LAM) attenuated LPS-induced dopaminergic neuronal damage in substantia nigra (SN) and behavioral deficits and promoted the phenotypic transformation of microglia from M1 to M2. Moreover, inhibition or knockdown of Dectin-1 significantly decreased LPS-induced phosphorylation of Syk and P65 as well as the production of COX-2 and iNOS in BV2 cells. Knockdown of Syk also significantly decreased LPS-induced protein expressions of COX-2 and iNOS. Mechanistically, both TLR4 inhibitor and NF-κB inhibitor could antagonize LPS-induced Dectin-1 expression. Chromatin immunoprecipitation (ChIP) assays showed a physical binding of NF-κB/P65 to Dectin-1 promoter, which further indicated the regulatory effect of toll-like receptor 4 (TLR4)/NF-κB signaling pathway on Dectin-1 expression. Furthermore, the present study provided the first evidence that Dectin-1 activation by hot-alkali treated depleted zymosan (d-Zymosan) could induce dopaminergic neurotoxicity and motor dysfunction, and promote up-regulation of TLR4, iNOS and Iba-1 in C57BL/6J mice. In conclusion, Dectin-1-Syk synergistic signaling crosstalk with TLR4/NF-κB promotes and maintains inflammatory phenotypes of M1 microglia which induces dopaminergic neuronal damage in SN. These findings provide novel insights into the pivotal role of Dectin-1 in neuroinflammation, suggesting its potential as a novel therapeutic target for PD.

Clinical predictors of freezing of gait in patients with Parkinson's disease: A systematic review

BACKGROUND

Freezing of gait (FOG) is a debilitating motor symptom of Parkinson's disease (PD) that markedly impacts patients' quality of life. This review aims to identify clinical predictors of FOG to facilitate early prediction and future interventions.

METHODS

A systematic review adhering to PRISMA guidelines was conducted. Comprehensive searches in PubMed, EBSCO, and Web of Science yielded 1761 records. After removing duplicates, 1558 records were screened by title and abstract, and 92 full-text articles were assessed. Nine studies met the inclusion criteria and were qualitatively synthesized.

RESULTS

Our systematic review indicates that higher baseline MDS-UPDRS scores, which reflect greater disease severity, alongside elevated doses and early use of levodopa, are predictive of FOG in patients with PD. Additionally, higher Postural Instability and Gait Disorder (PIGD) scores, motor fluctuations, and lower limb disease onset further increase the risk of FOG. Other factors associated with an increased risk of FOG include older age, longer disease duration, anxiety, hyposmia, cognitive deficits, and sleep disorders. Furthermore, decreased step initiation duration when using visual cues serves as a predictor for the development of FOG. Early treatment with amantadine, selegiline, and dopamine agonists may help reduce the risk of developing FOG.

CONCLUSION

A combination of motor and non-motor factors predicts the development of FOG. Understanding FOG predictors is crucial for developing future therapeutics and personalized management plans, enabling targeted interventions and improved outcomes.

Mode and Mechanism of Action of Omega-3 and Omega-6 Unsaturated Fatty Acids in Chronic Diseases

Unsaturated fatty acids, particularly omega-3 and omega-6 polyunsaturated fatty acids, have garnered increasing scientific interest due to their therapeutic potential in chronic disease management. Dietary sources such as milk provide essential unsaturated fatty acids, including linoleic acid and α-linolenic acid. Current evidence indicates that these compounds and their derivatives regulate critical physiological processes, such as neurodevelopment, visual function, immune modulation, and cardiovascular homeostasis. Their multifunctional roles encompass the structural maintenance of biological membranes, cardioprotective effects, anti-inflammatory and anti-tumor activities, and metabolic regulation. However, despite established associations between unsaturated fatty acids and chronic diseases, the mechanistic contributions of omega-3 and omega-6 polyunsaturated fatty acids to complex neuropsychiatric disorders remain poorly characterized. Furthermore, the controversial role of omega-6 polyunsaturated fatty acids in chronic disease pathogenesis necessitates urgent clarification. This review systematically examines the structural properties, molecular mechanisms, and therapeutic applications of omega-3 and omega-6 polyunsaturated fatty acids in cardiovascular diseases, diabetes, cancer, dermatological conditions, neurodegenerative disorders, and depression. By integrating recent advances in dietary science, this work aims to address knowledge gaps in their neuropsychiatric implications and refine evidence-based strategies for chronic disease intervention through optimized nutritional approaches.

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

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

Advances in research on mitochondrial dysfunction in neurodegenerative diseases

Given the high energy demand of the nervous system, mitochondrial dysfunction is a key factor in the pathogenesis of neurodegenerative diseases. Thus, a comprehensive understanding of its mechanisms and potential therapeutic targets is essential. This review discusses the roles of mitochondrial oxidative stress, mitochondrial dynamics alterations, and mtDNA damage in Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), and multiple sclerosis (MS). In addition, it summarizes the contributions of novel technological approaches in detecting mitochondrial dysfunction, which assist in disease diagnosis. We also emphasize emerging therapeutic strategies and drugs aimed at enhancing mitochondrial quality control and reducing oxidative stress, thereby laying the groundwork for innovative therapeutic approaches in neurodegenerative disease treatment.

L-DOPA Induces Spatially Discrete Changes in Gene Expression in the Forebrain of Mice with a Progressive Loss of Dopaminergic Neurons

L-3,4-Dihydroxyphenylalanine (L-DOPA) is effective at alleviating motor impairments in Parkinson's disease (PD) patients but has mixed effects on nonmotor symptoms and causes adverse effects after prolonged treatment. Here, we analyzed the spatial profile of L-DOPA-induced gene expression in the forebrain of mice with an inducible progressive loss of dopaminergic neurons (the TIF-IADATCreERT2 strain), with a focus on the similarities and differences in areas relevant to different PD symptoms. The animals received a 14-day L-DOPA treatment, and 1 h after the final drug injection, a spatial transcriptome analysis was performed on coronal forebrain sections. A total of 121 genes were identified as being regulated by L-DOPA. We found that the treatment had widespread effects extending beyond the primary areas involved in dopamine-dependent movement control. An unsupervised clustering analysis of the transcripts recapitulated the forebrain anatomy and indicated both ubiquitous and region-specific effects on transcription. The changes were most pronounced in layers 2/3 and 5 of the dorsal cortex and the dorsal striatum, where a robust increase in the abundance of activity-regulated transcripts, including Fos, Egr1, and Junb, was observed. Conversely, transcripts with a decreased abundance, e.g., Plekhm2 or Pgs1, were identified primarily in the piriform cortex, the adjacent endopiriform nucleus, and the claustrum. Taken together, our spatial analysis of L-DOPA-induced alterations in gene expression reveals the anatomical complexity of treatment effects, identifying novel genes affected by the drug, as well as molecular activation in brain areas relevant to the nonmotor symptoms of PD.

The Virtual Parkinsonian patient

This study investigates the influence of the pharmacological nigrostriatal dopaminergic stimulation on the entire brain by analyzing EEG and deep electrodes, placed near the subthalamic nuclei, from 10 Parkinsonian patients before (OFF) and after (ON) L-Dopa administration. We characterize large-scale brain dynamics as the spatio-temporal spreading of aperiodic bursts. We then simulate the effects of L-Dopa utilizing a novel neural-mass model that includes the local dopamine concentration. Whole-brain dynamics are simulated for different dopaminergic tones, generating predictions for the expected dynamics, to be compared with empirical EEG and deep electrode data. To this end, we invert the model and infer the most likely dopaminergic tone from empirical data, correctly identifying a higher Dopaminergic tone in the ON-state, and a lower dopaminergic tone in the OFF-state, for each patient. In conclusion, we successfully infer the dopaminergic tone by integrating anatomical and functional knowledge into physiological predictions, using solid ground truth to validate our findings.

Loss of intracellular ATP affects axoplasmic viscosity and pathological protein aggregation in mammalian neurons

Neurodegenerative diseases display synaptic deficits, mitochondrial defects, and protein aggregation. We show that intracellular adenosine triphosphate (ATP) regulates axoplasmic viscosity and protein aggregation in mammalian neurons. Decreased intracellular ATP upon mitochondrial inhibition leads to axoterminal cytosol, synaptic vesicles, and active zone component condensation, modulating the functional organization of mouse glutamatergic synapses. Proteins involved in the pathogenesis of Parkinson's disease (PD), Alzheimer's disease (AD), and amyotrophic lateral sclerosis (ALS) condensed and underwent ATP-dependent liquid phase separation in vitro. Human inducible pluripotent stem cell-derived neurons from patients with PD and ALS displayed reduced axoplasmic fluidity and decreased intracellular ATP. Last, nicotinamide mononucleotide treatment successfully rescued intracellular ATP levels and axoplasmic viscosity in neurons from patients with PD and ALS and reduced TAR DNA-binding protein 43 (TDP-43) aggregation in human motor neurons derived from a patient with ALS. Thus, our data suggest that the hydrotropic activity of ATP contributes to the regulation of neuronal homeostasis under both physiological and pathological conditions.

A Review of the Neuroprotective Properties of Exosomes Derived from Stem Cells and Exosome-Coated Nanoparticles for Treating Neurodegenerative Diseases and Stroke

Neurological diseases, including neurodegenerative disorders and stroke, represent significant medical challenges due to their complexity and the limitations of current treatment approaches. This review explores the potential of stem cell (SC)-derived exosomes (Exos) as a transformative therapeutic strategy for these diseases. Exos, especially those derived from SCs, exhibit natural targeting ability, biocompatibility, and the capacity to cross the blood-brain barrier (BBB), making them ideal vehicles for drug delivery. This review provides an in-depth discussion of the properties and advantages of SC-Exos. It highlights their potential synergistic benefits in therapeutic approaches to treat neurological diseases. This article discusses the mechanisms of action of SC-Exos, highlighting their ability to target specific cells, modulate disease pathways, and provide controlled release of therapeutic agents. Applications in specific neurological disorders have been investigated, demonstrating the potential to improve outcomes in conditions such as Alzheimer's Disease (AD), Parkinson's Disease (PD), and stroke. Moreover, Exos-coated nanoparticles (NPs) combine the natural properties of Exos with the multifunctionality of NPs. This integration takes advantage of exosome membrane biocompatibility and targeting capabilities while preserving NPs' beneficial features, such as drug loading and controlled release. As a result, Exos-coated NPs may enhance the precision, efficacy, and safety of therapeutic interventions. In conclusion, SC-Exos represent a promising and innovative approach to treating neurological diseases.

Aptamer single-molecule dispersion on single-atom anchoring sites for high-selectivity in vivo detection

Traditional aptasensors struggle to distinguish molecules with highly similar chemical structures due to the inherent flexibility of aptamers, which form 'nano-bushes' causing non-specific adsorption and reducing sensor specificity. To address this, we propose a novel strategy of anchoring aptamers at the single-molecule level onto atomic anchoring sites. We have designed a gold single-atom/titanium dioxide (Au SA/TiO2) photoelectrode to immobilize a dopamine (DA)-selective aptamer, enabling the fabrication of a photoelectrochemical single-molecule aptamer sensor (PEC-sm-aptasensor). This sensor can selectively detect DA in vivo in different brain regions of living mice. This advancement has revolutionized our understanding of DA variation in the prefrontal cortex of Parkinson's disease (PD) mice. In contrast to previous beliefs, we have discovered a new neurotransmitter dynamic pattern: while the total concentration of neurotransmitters decreases, the concentration of DA remains constant, thus not affecting cognitive levels. This finding is crucial for a more targeted understanding of PD and opens avenues for more effective treatments and diagnostic methods.

Parkinson's disease and gut microbiota metabolites: The dual impact of vitamins and functional amyloids

Parkinson's disease (PD) is a neurodegenerative disorder characterized by the abnormal accumulation of alpha-synuclein (α-Syn). Recent research emphasizes the significant role of the gut microbiota, the diverse community of microbes living in the intestines, in modulating α-Syn pathology. This review explores the bi-directional communication along the microbiota-gut-brain axis, highlighting the paradoxical impact of two gut microbiota metabolites-functional bacterial amyloids (FuBA) and vitamins-on neurodegenerative diseases, particularly PD. FuBA contributes to PD pathogenesis by promoting α-Syn aggregation, while vitamins offer neuroprotection through their anti-amyloidogenic, antioxidant, and anti-inflammatory properties. Understanding these processes could lead to precision clinical approaches and novel strategies for managing and preventing PD.

Reduced composite dietary antioxidant index increases the risk of Parkinson's disease and all-cause mortality in Parkinson's disease patients: evidence from the NHANES database

Background

This study aimed to investigate the relationship between the Composite Dietary Antioxidant Index (CDAI) and the prevalence of Parkinson's disease (PD), as well as to explore its relationship with all-cause mortality risk in PD patients.

Methods

Data from the National Health and Nutrition Examination Survey (NHANES) database spanning from 2007 to 2018 were used, including 119,609 participants. After excluding individuals aged <18 years, those with incomplete follow-up data, and those missing critical variables such as CDAI and covariates, the final cohort consisted of 34,133 participants. Participants were categorized into a PD group (510 individuals) and a non-PD group (33,623 individuals). The CDAI values were calculated, and participants were divided into three groups based on the tertile distribution of their CDAI scores: Q1 (CDAI < -1.07), Q2 (-1.07 to 1.74), and Q3 (CDAI >1.74). Weighted logistic regression and weighted Cox regression analyses were employed to evaluate the associations between CDAI and the prevalence of PD, as well as between CDAI and all-cause mortality risk. Restricted cubic spline regression analysis was used to further elucidate the precise relationship between CDAI and outcome events.

Results

CDAI values were significantly lower in the PD group compared to the non-PD group. After adjusting for age, sex, comorbid conditions (hypertension and diabetes), blood lipid and glucose levels, a reduction in CDAI was associated with an increased risk of PD (Q3 vs. Q1, OR = 0.72, p = 0.035). In patients with PD, a decrease in CDAI was significantly associated with a higher risk of all-cause mortality (Q3 vs. Q1, HR = 0.53, p = 0.018). This association was particularly pronounced in those over 60 years old, smokers, and those with hypertension. Restricted cubic spline regression analysis identified CDAI <0.471 as a risk factor for PD, and CDAI <0.527 as a risk factor for all-cause mortality in PD patients.

Conclusion

CDAI reduction is an independent risk factor for both PD risk in the general population and all-cause mortality in PD patients, with amplified predictive power in older adults, smokers, and hypertensive individuals. Our findings support developing personalized antioxidant-enhancing nutritional interventions for both high-risk populations with suboptimal CDAI and established PD patients.

Mitochondrial stress disassembles nuclear architecture through proteolytic activation of PKCδ and Lamin B1 phosphorylation in neuronal cells: implications for pathogenesis of age-related neurodegenerative diseases

Mitochondrial dysfunction and oxidative stress are central to the pathogenesis of neurodegenerative diseases, including Parkinson's, Alzheimer's and Huntington's diseases. Neurons, particularly dopaminergic (DAergic) ones, are highly vulnerable to mitochondrial stress; however, the cellular and molecular mechanisms underlying this vulnerability remain poorly understood. Previously, we demonstrated that protein kinase C delta (PKCδ) is highly expressed in DAergic neurons and mediates apoptotic cell death during neurotoxic stress via caspase-3-mediated proteolytic activation. Herein, we further uncovered a key downstream molecular event of PKCδ signaling following mitochondrial dysfunction that governs neuronal cell death by dissembling nuclear architecture. Exposing N27 DAergic cells to the mitochondrial complex-1 inhibitor tebufenpyrad (Tebu) induced PKCδ phosphorylation at the T505 activation loop accompanied by caspase-3-dependent proteolytic activation. High-resolution 3D confocal microscopy revealed that proteolytically activated cleaved PKCδ translocates to the nucleus, colocalizing with Lamin B1. Electron microscopy also visualized nuclear membrane damage in Tebu-treated N27 cells. In silico analyses identified threonine site on Lamin B1 (T575) as a phosphorylation site of PKCδ. Interestingly, N27 DAergic cells stably expressing a PKCδ cleavage-resistant mutant failed to induce nuclear damage, PKCδ activation, and Lamin B1 phosphorylation. Furthermore, CRISPR/Cas9-based stable knockdown of PKCδ greatly attenuated Tebu-induced Lamin B1 phosphorylation. Also, studies using the Lamin B1T575G phosphorylation mutant and PKCδ-ΔNLS-overexpressing N27 cells showed that PKCδ activation and translocation to the nuclear membrane are essential for phosphorylating Lamin B1 at T575 to induce nuclear membrane damage during Tebu insult. Additionally, Tebu failed to induce Lamin B1 damage and Lamin B1 phosphorylation in organotypic midbrain slices cultured from PKCδ-/- mouse pups. Postmortem analyses of PD brains revealed significantly higher PKCδ activation, Lamin B1 phosphorylation, and Lamin B1 loss in nigral DAergic neurons compared to age-matched healthy controls, demonstrating the translational relevance of these findings. Collectively, our data reveal that PKCδ functions as a Lamin B1 kinase to disassemble the nuclear membrane during mitochondrial stress-induced neuronal death. This mechanistic insight may have important implications for the etiology of age-related neurodegenerative diseases resulting from mitochondrial dysfunction as well as for the development of novel treatment strategies.

Enhanced alpha-synuclein pathology and exacerbated motor dysfunction in alpha-synuclein transgenic mice with autophagy deficiency

Alpha-synuclein (α-synuclein), a key component of Lewy body pathology, is a hallmark of Parkinson's disease. In previous studies, we examined dopaminergic neuron-specific Atg7 autophagy-deficient mice and observed α-synuclein aggregation in vivo. Notably, p62 accumulation preceded synuclein deposition, resulting in the formation of inclusions containing both α-synuclein and p62. This pathological process led to dopamine neuron loss and age-related motor impairments, such as hindlimb defects in 120-week-old mice. In this study, we developed a mouse model by crossing human α-synuclein bacterial artificial chromosome transgenic mice with dopaminergic neuron-specific Atg7 conditional knockout mice to investigate these mechanisms further. The mice exhibited accelerated Lewy body-like pathology and motor dysfunction, providing additional evidence that autophagy deficiency exacerbates synuclein toxicity in vivo. Phosphorylated synuclein deposits were detected in the substantia nigra, hippocampus, and cortical regions reliant on dopaminergic pathways. Degeneration of dopaminergic neurons in the substantia nigra pars compacta was also observed, with neuron numbers declining with age. Interestingly, this mouse model displayed more severe motor deficits than Atg7 autophagy-deficient mice. This novel model offers a valuable platform for studying the interplay between α-synuclein expression, autophagy dysfunction, and neurodegeneration, as well as for testing therapeutic strategies targeting synucleinopathies. Our findings highlight the importance of aging in the manifestation of synuclein toxicity, mirroring the progression observed in patients with Parkinson's disease.

Erasing "bad memories": reversing aberrant synaptic plasticity as therapy for neurological and psychiatric disorders

Dopamine modulates corticostriatal plasticity in both the direct and indirect pathways of the cortico-striato-thalamo-cortical (CSTC) loops. These gradual changes in corticostriatal synaptic strengths produce long-lasting changes in behavioral responses. Under normal conditions, these mechanisms enable the selection of the most appropriate responses while inhibiting others. However, under dysregulated dopamine conditions, including a lack of dopamine release or dopamine signaling, these mechanisms could lead to the selection of maladaptive responses and/or the inhibition of appropriate responses in an experience-dependent and task-specific manner. In this review, we propose that preventing or reversing such maladaptive synaptic strengths and erasing such aberrant "memories" could be a disease-modifying therapeutic strategy for many neurological and psychiatric disorders. We review evidence from Parkinson's disease, drug-induced parkinsonism, L-DOPA-induced dyskinesia, obsessive-compulsive disorder, substance use disorders, and depression as well as research findings on animal disease models. Altogether, these studies allude to an emerging theme in translational neuroscience and promising new directions for therapy development. Specifically, we propose that combining pharmacotherapy with behavioral therapy or with deep brain stimulation (DBS) could potentially cause desired changes in specific neural circuits. If successful, one important advantage of correcting aberrant synaptic plasticity is long-lasting therapeutic effects even after treatment has ended. We will also discuss the potential molecular targets for these therapeutic approaches, including the cAMP pathway, proteins involved in synaptic plasticity as well as pathways involved in new protein synthesis. We place special emphasis on RNA binding proteins and epitranscriptomic mechanisms, as they represent a new frontier with the distinct advantage of rapidly and simultaneously altering the synthesis of many proteins locally.

Fucoxanthinol Mitigates the Cytotoxic Effect of Chlorpyrifos and MPTP on the Dopaminergic Differentiation of SH-SY5Y Human Neuroblastoma Cells

This study investigates the neuroprotective effects of fucoxanthinol (FXL) against the toxic activities of two compounds known to induce neurotoxic effects in humans and animals. MPTP (1-methyl- 4-phenyl- 1,2,3,6-tetrahydropyridine) induces Parkinson's disease (PD)-like phenotypes by inhibiting mitochondrial complex I in dopaminergic neurons. Chlorpyrifos (CPF), another neurotoxic agent, is associated with acute and long-term neurotoxicity primarily through acetylcholinesterase (AChE) inhibition. FXL demonstrated the ability to reverse the neurotoxic effects of CPF and MPTP in SH-SY5Y dopaminergic neuronal cell models. Treatment with FXL enhances mitochondrial function in SH-SY5Y cells exposed to CPF and MPTP, as demonstrated by increased levels of Adenosine triphosphate (ATP), mitochondrial membrane potential (MMP), mitochondrial complexes activities, and oxygen consumption rates, pyruvate dehydrogenase (PDH) activities, and mitophagy pathways. This improvement highlights FXL's ability to counteract the mitochondrial dysfunction induced by these neurotoxic agents. Additionally, FXL reduces oxidative damage and enhances cell viability. At the molecular level, the neuroprotective effects were also associated with the modulation of apoptotic cell markers, including Bcl- 2 and the oxidative damage markers. Molecular docking data further support the outcomes of our in vitro studies. Multivariable analysis highlights the neuroprotective effects of FXL. These findings indicate the potential of FXL to mitigate CPF- and MPTP-induced neurotoxicity, suggesting its promise as a therapeutic agent for managing neuronal damage observe in PD.

Loss of UCHL1 Leads to Enhanced Mouse Osteoclast Formation

Enhanced osteoclastogenesis causes bone fragility, osteoporosis, and an increased risk of fractures. Recent studies have suggested a possible correlation between osteoporosis and the pathological features of Parkinson's disease (PD). To establish a molecular link between these conditions, we focused on the physiological function of the PD-related protein ubiquitin carboxy-terminal hydrolase L1 (UCHL1) in bone remodeling. To this end, we investigated the role of UCHL1 in regulating osteoclast differentiation in Uchl1 spontaneous mutant gad mice. We found that gad-mouse-derived osteoclast progenitors exhibit enhanced osteoclast differentiation. Likewise, CRISPR-mediated Uchl1 knockout in mouse macrophage-derived preosteoclast RAW-D cells increased RANKL-dependent osteoclastogenesis. Supporting this observation, these Uchl1-depleted cells showed elevated expression of osteoclast marker genes. To uncover the molecular mechanisms by which the loss of Uchl1 enhances osteoclast differentiation, we screened for UCHL1-interacting proteins in RAW-D preosteoclast cells and identified AKT1 as a potential UCHL1-regulated protein. UCHL1 depletion in preosteoclasts led to increased Thr308/Ser473 phosphorylation of AKT1. Furthermore, ectopic expression of UCHL1 decreased the K63-linked polyubiquitination of AKT1. These findings suggest that UCHL1 is critical in partially suppressing osteoclastogenesis through modulating AKT signaling.

The roles of intrinsically disordered proteins in neurodegeneration

Neurodegenerative diseases such as Amyotrophic Lateral Sclerosis, Alzheimer's disease, Parkinson's disease, and Huntington's disease share a common pathological hallmark: the accumulation of misfolded proteins, particularly involving intrinsically disordered proteins (IDPs) like TDP-43, FUS, Tau, α-synuclein, and Huntingtin. These proteins undergo pathological aggregation, forming toxic inclusions that disrupt cellular function. The dysregulation of proteostasis mechanisms, including the ubiquitin-proteasome system (UPS), ubiquitin-independent proteasome system (UIPS), autophagy, and molecular chaperones, exacerbates these proteinopathies by failing to clear misfolded proteins effectively. Emerging therapeutic strategies aim to restore proteostasis through proteasome activators, autophagy enhancers, and chaperone-based interventions to prevent the toxic accumulation of IDPs. Additionally, understanding liquid-liquid phase separation (LLPS) and its role in stress granule dynamics offers novel insights into how aberrant phase transitions contribute to neurodegeneration. By targeting the molecular pathways involved in IDP aggregation and proteostasis regulation, and better understanding the specificity of each component, research in this area will pave the way for innovative therapeutic approaches to combat these neurodegenerative diseases. This review discusses the molecular mechanisms underpinning IDP pathology, highlights recent advancements in drug discovery, and explores the potential of targeting proteostasis machinery to develop effective therapies.

Genetic mutations in kinases: a comprehensive review on marketed inhibitors and unexplored targets in Parkinson's disease

This comprehensive review navigates the landscape of genetic mutations in kinases, offering a thorough examination of both marketed inhibitors and unexplored targets in the context of Parkinson's Disease (PD). Although existing treatments for PD primarily center on symptom management, progress in comprehending the molecular foundations of the disease has opened avenues for targeted therapeutic approaches. This review encompasses an in-depth analysis of four key kinases-PINK1, LRRK2, GAK, and PRKRA-revealing that LRRK2 has garnered the most attention with a plethora of marketed inhibitors. However, the study underscores notable gaps in the exploration of inhibitors for PINK1, GAK, and a complete absence for PRKRA. The observed scarcity of inhibitors for these kinases emphasizes a significant area of untapped potential in PD therapeutics. By drawing attention to these unexplored targets, the review highlights the urgent need for focused research and drug development efforts to diversify the therapeutic landscape, potentially providing novel interventions for halting or slowing the progression of PD.

Differential distribution of PINK1 and Parkin in the primate brain implies distinct roles

JOURNAL/nrgr/04.03/01300535-202504000-00028/figure1/v/2024-07-06T104127Z/r/image-tiff The vast majority of in vitro studies have demonstrated that PINK1 phosphorylates Parkin to work together in mitophagy to protect against neuronal degeneration. However, it remains largely unclear how PINK1 and Parkin are expressed in mammalian brains. This has been difficult to address because of the intrinsically low levels of PINK1 and undetectable levels of phosphorylated Parkin in small animals. Understanding this issue is critical for elucidating the in vivo roles of PINK1 and Parkin. Recently, we showed that the PINK1 kinase is selectively expressed as a truncated form (PINK1-55) in the primate brain. In the present study, we used multiple antibodies, including our recently developed monoclonal anti-PINK1, to validate the selective expression of PINK1 in the primate brain. We found that PINK1 was stably expressed in the monkey brain at postnatal and adulthood stages, which is consistent with the findings that depleting PINK1 can cause neuronal loss in developing and adult monkey brains. PINK1 was enriched in the membrane-bound fractionations, whereas Parkin was soluble with a distinguishable distribution. Immunofluorescent double staining experiments showed that PINK1 and Parkin did not colocalize under physiological conditions in cultured monkey astrocytes, though they did colocalize on mitochondria when the cells were exposed to mitochondrial stress. These findings suggest that PINK1 and Parkin may have distinct roles beyond their well-known function in mitophagy during mitochondrial damage.

The effects of dynamic flamingo balance exercises and balance training with a Tetrax® posturography device on the balance performance and fall risk of patients with Parkinson's disease

BackgroundBalance disorder is more prevalent in patients with Parkinson's Disease (PD). This study aimed to examine the effects of flamingo balance exercises and balance training with Tetrax® Interactive Balance System (TIBS) (Sunlight Medical Ltd, Ramat Gan, Israel) on the balance performance and fall risk of patients with PD.MethodsThis randomized-controlled, single-blind, prospective study was performed at the Department of Physical Medicine and Rehabilitation, Istanbul Atakent Acıbadem Hospital, Turkey, between September 2022 and January 2023. One hundred twenty-four patients were randomly divided into four groups: (1) balance training group with TIBS (n = 31), (2) flamingo training group (n = 32), (3) combined training group (n = 31), and (4) control group (n = 30). All participants trained 3 days a week for 6 weeks, with patient-specific training. Trial groups were evaluated with pre-treatment and post-treatment.ResultsAfter the treatment, there was a statistically significant difference in all balance and fall scores in patients who received alternate balance training (p < 0.05). The balance and falling values in the combined training group were superior to single-type training groups (p < 0.05).ConclusionsDynamic flamingo therapy combined with balance exercises with a static posturography device improves balance disorder in PD patients compared to therapy restricted to individual training.

Nigral volume loss in prodromal, early, and moderate Parkinson's disease

The loss of melanized neurons in the substantia nigra pars compacta (SNc) is a hallmark pathology in Parkinson's disease (PD). Melanized neurons in SNc can be visualized in vivo using magnetization transfer (MT) effects. Nigral volume was extracted in data acquired with a MT-prepared gradient echo sequence in 50 controls, 90 non-manifest carriers (46 LRRK2 and 44 GBA1 nonmanifest carriers), 217 prodromal hyposmic participants, 76 participants with rapid eye movement sleep behavior disorder (RBD), 194 de novo PD patients and 26 moderate PD patients from the Parkinson's Progressive Markers Initiative. No difference in nigral volume was seen between controls and LRRK2 and GBA1 non-manifest carriers ( F =0.732; P =0.483). A significant main effect in group was observed between controls, prodromal hyposmic participants, RBD participants, and overt PD patients ( F =9.882; P <10 -3 ). This study shows that nigral depigmentation can be robustly detected in prodromal and overt PD populations.

Affective priming of body and facial expressions in Parkinson's disease

Patients with Parkinson's disease (PD) often experience impairments in emotion processing. Previous literature has highlighted deficits in facial expression recognition and body movement processing, including social signals. However, to date, the integration of facial and bodily expressions has been investigated in healthy populations, but not in individuals with PD. The present study assessed the reciprocal influence between facial and body emotion recognition by using subliminal priming paradigms in a sample of PD patients and in healthy controls (HC). Participants completed both a Face-Body and a Body-Face priming task, in which facial or body expressions subliminally primed the discrimination of body or face emotions, respectively. Recognition of face and body emotions was also assessed. The results revealed that the discrimination of fearful and happy body expressions was not modulated by the previous congruent, incongruent, or neutral face in PD patients, whereas a significant Face-Body priming effect was observed in HC. In contrast, body emotion did not significantly prime face expression discrimination in either group. These findings suggest an impairment in the automatic integration of emotional information from faces and bodies in PD, which may hinder the detection of mismatches between emotional information from different cues.

Transcranial magneto-acoustic stimulation enhances motor function and modulates cortical excitability of motor cortex in a Parkinson's disease mouse model

Parkinson's disease (PD) is a neurodegenerative disorder characterized primarily by motor dysfunction. Transcranial magneto-acoustic stimulation (TMAS), an emerging non-invasive brain neuromodulation technology, is increasingly being applied in the treatment of brain diseases. However, the effects of TMAS on PD are unknown, which is not well studied. Here, we utilized TMAS on PD model mice induced by MPTP to investigate the underlying mechanism of therapy. Our study found that TMAS improved the behavioral performance of PD model mice, enhancing the motor function and motivation for movement. Besides, it inhibited the increased beta oscillations in the motor cortex, while also reducing gamma oscillations. Moreover, the abnormally exaggerated beta-broad gamma phase amplitude coupling (PAC) was decreased after TMAS, and there was a significant negative correlation between PAC and both distance traveled and mean speed during the open filed test. Additionally, the ongoing stimulation could provide neuroprotection, implying that TMAS could ameliorate the loss of dopaminergic neurons, with no damage observed in the brain tissue of mice. Our findings suggest that TMAS could provide a non-invasive tool for the treatment of Parkinson's disease and beta-broad gamma phase amplitude coupling could be employed as a biomarker for PD.

Toxin-Induced Animal Models of Parkinson's Disease

The debilitating motor symptoms of Parkinson's disease (PD) result primarily from the degenerative nigrostriatal dopaminergic pathway. To elucidate pathogenic mechanisms and evaluate therapeutic strategies for PD, numerous animal models have been developed. Understanding the strengths and limitations of these models can significantly impact the choice of model, experimental design, and data interpretation. Herein, we systematically review the literature over the past decade. Some models no longer serve the purpose of PD models. The primary objectives of this review are: First, to assist new investigators in navigating through available animal models and making appropriate selections based on the objective of the study. Emphasis will be placed on common toxin-induced murine models. And second, to provide an overview of basic technical requirements for assessing the nigrostriatal pathway's pathology, structure, and function.

Advancements in PROTAC-based therapies for neurodegenerative diseases

Neurodegenerative diseases are characterized by impairments in movement and cognitive functions. These disorders are frequently associated with the accumulation of misfolded protein aggregates, which present significant challenges for treatment with conventional small-molecule inhibitors. While FDA-approved amyloid-beta-directed antibodies, such as Lecanemab, have recently shown clinical success in modifying disease progression, there are currently no treatments capable of curing neurodegenerative diseases. Emerging technologies like proteolysis-targeting chimeras (PROTACs) offer additional promise by targeting disease-causing proteins for degradation, potentially opening new therapeutic avenues. Recent experiments have demonstrated that PROTACs can specifically target and degrade pathogenic proteins associated with neurodegenerative diseases, thereby offering potential therapeutic avenues. This review discusses the latest advances in employing PROTACs for treating neurodegenerative diseases and delves into the associated challenges and opportunities. Our goal is to provide researchers in drug development with new insights on creating novel PROTACs for therapeutic applications.

Semiautomatic Quantification of 99mTc-TRODAT-1 SPECT Images in Patients With Idiopathic Parkinson's Disease

BACKGROUND AND PURPOSE

99mTc-TRODAT-1 SPECT imaging is an imaging technique, more commonly used in Asia, to diagnose Parkinson's disease (PD). This study evaluates the use of automated three-dimensional volume-of-interest (VOI) analysis in diagnosing PD.

METHODS

99mTc-TRODAT-1 SPECT images of 76 patients (50 with PD and 26 without PD) were retrospectively analyzed. The specific binding ratio (SBR) was calculated using an automated program. Multiple linear regression and receiver operating characteristic curve analyses were performed to identify the factors that affect SBR value and determine the optimal cutoff values.

RESULTS

Multiple regression analysis revealed disease status as the strongest predictor of SBR values, followed by age and sex. Receiver operating characteristic curve analysis demonstrated good diagnostic performance for the striatum (area under the curve [AUC] = 0.922), putamen (AUC = 0.922), and caudate (AUC = 0.881). Optimal cutoff values were determined for the striatum (0.515; sensitivity 88.5%, specificity 90.0%), putamen (0.445; sensitivity 92.3%, specificity 86.0%), and caudate (0.655; sensitivity 84.6%, specificity 90.0%).

CONCLUSIONS

Semiautomatic quantitative analysis of 99mTc-TRODAT-1 SPECT using automated three-dimensional VOI shows excellent diagnostic performance in differentiating PD from non-Parkinson's cases. Age and sex significantly influence SBR values, suggesting the need for demographic-adjusted cutoff values in clinical practice.

New Multiomic Studies Shed Light on Cellular Diversity and Neuronal Susceptibility in Parkinson's Disease

Parkinson's disease is a complex neurodegenerative disorder characterized by degeneration of dopaminergic neurons, with patients manifesting varying motor and nonmotor symptoms. Previous studies using single-cell RNA sequencing in rodent models and humans have identified distinct heterogeneity of neurons and glial cells with differential vulnerability. Recent studies have increasingly leveraged multiomics approaches, including spatial transcriptomics, epigenomics, and proteomics, in the study of Parkinson's disease, providing new insights into pathogenic mechanisms. Continued advancements in experimental technologies and sophisticated computational tools will be essential in uncovering a network of neuronal vulnerability and prioritizing disease modifiers for novel therapeutics development. © 2025 International Parkinson and Movement Disorder Society.

Conformationally adaptive therapeutic peptides for diseases caused by intrinsically disordered proteins (IDPs). New paradigm for drug discovery: Target the target, not the arrow

The traditional model of protein structure determined by the amino acid sequence is today seriously challenged by the fact that approximately half of the human proteome is made up of proteins that do not have a stable 3D structure, either partially or in totality. These proteins, called intrinsically disordered proteins (IDPs), are involved in numerous physiological functions and are associated with severe pathologies, e.g. Alzheimer, Parkinson, Creutzfeldt-Jakob, amyotrophic lateral sclerosis (ALS), and type 2 diabetes. Targeting these proteins is challenging for two reasons: i) we need to preserve their physiological functions, and ii) drug design by molecular docking is not possible due to the lack of reliable starting conditions. Faced with this challenge, the solutions proposed by artificial intelligence (AI) such as AlphaFold are clearly unsuitable. Instead, we suggest an innovative approach consisting of mimicking, in short synthetic peptides, the conformational flexibility of IDPs. These peptides, which we call adaptive peptides, are derived from the domains of IDPs that become structured after interacting with a ligand. Adaptive peptides are designed with the aim of selectively antagonizing the harmful effects of IDPs, without targeting them directly but through selected ligands, without affecting their physiological properties. This "target the target, not the arrow" strategy is promised to open a new route to drug discovery for currently undruggable proteins.

Association between serum IGF‑1 levels and non-motor symptoms in Parkinson's disease

AIMS

We aimed to measure serum insulin-like growth factor 1 (IGF-1) levels in Parkinson's disease (PD) patients and assess their correlation with non-motor symptoms (NMS).

BACKGROUND

Emerging evidence suggests that abnormal levels of IGF-1 play a crucial role in the development of PD.

OBJECTIVE

Further systematic research is needed to explore the potential roles of abnormal IGF-1 levels in NMS of PD.

METHODS

The study enrolled a total of 129 PD patients and 130 healthy controls (HCs). Within the PD cohort, 74 patients were classified as being in the early stage, while 55 were in the moderate stage.

RESULTS

This study found no significant difference in serum IGF-1 levels between PD patients and HC. Further analysis revealed no significant difference in IGF-1 levels between early-stage PD and those in the moderate stages. Linear regression analysis indicated a significant association between serum IGF-1 levels and Nonmotor Symptom Scale (NMSS) scores in PD patients. Linear regression analysis revealed significant correlations between serum IGF-1 levels and general cognitive function, information processing speed, and executive function in PD patients. Furthermore, lower serum IGF-1 levels were associated with fatigue in PD patients.

CONCLUSIONS

In summary, our study suggests a potential association between serum IGF-1 levels and specific NMS in patients with PD. These findings highlight the importance of long-term follow-up studies to determine whether serum biomarkers can serve as valuable tools for early detection of NMS in PD.