Disease duration and the integrity of the nigrostriatal system in Parkinson's disease

Ceftriaxone affects ferroptosis and alleviates glial cell activation in Parkinson's disease

Parkinson's disease (PD) is the second most common neurodegenerative disorder, which is characterized by the death of dopaminergic neurons. It has been reported that ceftriaxone (CEF) exerts promising effects on alleviating dopaminergic neuron death in PD models. However, the neuroprotective mechanisms of CEF in PD have not been well understood. In the present study, to investigate the neuroprotective effects of CEF through western blot and immunofluorescence assays, two in vivo models were established, namely the 1‑methyl‑4‑phenyl‑1,2,3,6‑tetrahydropyridine (MPTP)‑ and lipopolysaccharide (LPS)‑induced models. Additionally, three in vitro models were used to explore the neuroprotective mechanisms of CEF, namely the 1‑methyl‑4‑phenylpyridinium ion (MPP+)‑induced dopaminergic neuron injury, LPS‑induced microglia activation and TNFα‑induced astrocyte activation models, with key insights derived from western blot and qPCR experiments. The in vivo studies demonstrated that CEF exerted neuroprotective effects and reduced glial cell activation. Additionally, CEF reversed the reduction of tyrosine hydroxylase and suppressed the activation of microglia and astrocytes. Furthermore, the in vitro experiments revealed that CEF could display both direct and indirect neuroprotective effects and could directly alleviate MPP+‑induced neuronal toxicity and suppress the activation of microglia and astrocytes. In addition, CEF indirectly reduced neuronal injury caused by conditioned medium from activated microglia and astrocytes. Mechanistic studies revealed that CEF inhibited the ferroptosis pathway via regulating the expression of solute carrier family 7 member 11 and glutathione peroxidase 4 in a non‑cell‑specific manner. Via inhibiting ferroptosis, CEF could directly protect dopaminergic neurons and prevent glial cell activation, and indirectly impair neurons. In conclusion, the results of the current study highlighted the potential research and therapeutic value of CEF in regulating ferroptosis in PD.

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.

Neuromelanin and selective neuronal vulnerability to Parkinson's disease

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

Emergent glutamate & dopamine dysfunction in VPS35(D620N) knock-in mice and rapid reversal by LRRK2 inhibition

The D620N variant in Vacuolar Protein Sorting 35 (VPS35) causes autosomal-dominant, late-onset Parkinson's disease. VPS35 is a core subunit of the retromer complex that canonically recycles transmembrane cargo from sorting endosomes. Although retromer cargoes include many synaptic proteins, VPS35's neuronal functions are poorly understood. To investigate the consequences of the Parkinson's mutation, striatal neurotransmission was assessed in 1- to 6-month-old VPS35 D620N knock-in (VKI) mice. Spontaneous and optogenetically-evoked corticostriatal glutamate transmission was increased in VKI spiny projection neurons by 6 months and was unaffected by acute leucine-rich repeat kinase 2 (LRRK2) inhibition. Total striatal glutamate release by iGluSnFR imaging was similar to wild-type. dLight imaging revealed robust increases in VKI striatal dopamine release by 6 months, which were reversed with acute LRRK2 kinase inhibition. We conclude that increased striatal neurotransmission in VKI mice progressively emerges in young-adulthood, and that dopamine dysfunction is likely the result of sustained, rapidly-reversible, LRRK2 hyperactivity.

Biological effects of pathologies in Lewy body diseases: why timing matters

The emergence of promising biomarkers of α-synuclein Lewy pathology has led to new biological definitions and staging systems for Parkinson's disease and dementia with Lewy bodies. These research frameworks aim to enhance patient selection for studies of biomarkers and disease-modifying therapies. Building on approaches developed for Alzheimer's disease, these new frameworks focus on hallmark neuropathological findings in Lewy body diseases, including abnormal α-synuclein aggregates and neurodegeneration, particularly nigrostriatal dopaminergic loss. Understanding the temporal inter-relationships between Lewy pathology, Alzheimer's disease, and other co-pathologies and symptom manifestation is central to any biological staging system. Neuropathological and in vivo evidence demonstrates substantial temporal and biological heterogeneity in the progression of clinical and pathological events across Lewy body disorders, highlighting knowledge gaps. Staging systems must incorporate this evidence into a nuanced conceptual framework of biological progression. Such revision will be crucial for the appropriate selection of participants and correct timing of targeted interventions in clinical research.

The neurotoxicity of pesticides: Implications for Parkinson's disease

Parkinson's disease (PD) is the fastest-growing neurodegenerative disorder worldwide, and no effective cure is currently available. Neuropathologically, PD is characterized by the selective degeneration of dopaminergic neurons in the substantia nigra and by the accumulation of alpha-synuclein (aSyn)-rich proteinaceous inclusions within surviving neurons. As a multifactorial disorder, approximately 85 % of PD cases are sporadic with unknown etiology. Among the many risk factors implicated in PD, exposure to neurotoxic pesticides stands out as a significant contributor. While the effects of many are still uncharacterized, it has already been shown that rotenone, paraquat, maneb, and dieldrin affect critical cellular pathways, including mitochondrial and proteasomal dysfunction, aSyn aggregation, autophagy dysregulation, and disruption of dopamine metabolism. With the constant rise in pesticide usage to meet the demands of a growing human population, the risk of environmental contamination and subsequent PD development is also increasing. This review explores the molecular mechanisms by which pesticide exposure influences PD development, shedding light on their role in the pathogenesis of PD and highlighting the need for preventative measures and regulatory oversight to mitigate these risks.

Disrupted Paraventricular Hypothalamic Nucleus Functional Connectivity in Parkinson's Disease With Constipation

BACKGROUND

Constipation is one of the most common non-motor symptoms in patients with Parkinson's disease (PD), which could manifest during the early stage of the disease. However, the etiology of constipation in PD remains largely unknown. Previous studies supported that gastrointestinal dysfunction may be associated with functional connectivity alterations in paraventricular hypothalamic nucleus (PVN). Therefore, this study aimed to investigate the potential contribution of the PVN to the pathogenesis of constipation in a cohort of early-stage patients with PD and to compare brain network organization between PD patients with and without constipation.

METHODS

A total of 66 PD patients (PD with constipation and without constipation) and 30 healthy controls were prospectively enrolled. All participants acquired T1-weighted and resting-state fMRI scans. Then we employed voxel-based morphometry analysis and functional connectivity analysis.

RESULTS

We observed a decreased functional connectivity in the PVN-pontine tegmentum pathway in PD patients with constipation compared to the patients without constipation (p = 0.006, t = 5.37), while we did not find any changes in basal ganglia circuitry between these two groups. In addition, we found that the functional connectivity between PVN and pontine tegmentum was negatively associated with the UPDRS I, II, III and NMSS scores (p < 0.05). Meanwhile, these two types of patients also showed substantial differences in functional connections linking the inferior frontal gyrus and cerebellum with multiple brain regions. We discovered no statistical difference in gray matter volume among these two groups.

CONCLUSIONS

Our study provides further insights into the dysfunctional mechanisms of constipation, suggesting that abnormal PVN functional connectivity may be related to the mechanism of constipation in PD. Meanwhile, the inferior frontal gyrus and cerebellum may be involved in the occurrence of constipation in PD patients.

Harnessing routine MRI for the early screening of Parkinson's disease: a multicenter machine learning study using T2-weighted FLAIR imaging

OBJECTIVE

To explore the potential of radiomics features derived from T2-weighted fluid-attenuated inversion recovery (T2W FLAIR) images to distinguish idiopathic Parkinson's disease (PD) patients from healthy controls (HCs).

METHODS

T2W FLAIR images from 1727 subjects were retrospectively obtained from five cohorts and divided into a training set (395 PD/574 HC), an internal test set (99 PD/144 HC) and an external test set (295 PD/220 HC). Regions of interest (ROIs), including bilateral globus pallidus (GP), putamen (PU), substantia nigra (SN), and red nucleus (RN), were manually delineated. The radiomics features were extracted from ROIs. Six independent machine learning (ML) classifiers were trained on the training set, and validated on the internal and external test sets.

RESULTS

A selection of five, two, three, and ten highly correlated diagnostic features were identified from SN, RN, GP, and PU regions, respectively. Six ML classifiers were implemented based on the combined 20 radiomics features. In the internal test cohort, the six models achieved AUC of 0.96-0.98 with the accuracy ranging from 0.80 to 0.90. In the external test cohort, the multilayer perceptron model demonstrated the highest AUC of 0.85 (95% CI: 0.80-0.89) with an accuracy of 0.78.

CONCLUSION

ML models based on the conventional T2W FLAIR images demonstrated promising diagnostic performance for PD and those models may serve as a basis for future investigations on PD diagnosis with the aid of ML methods.

CRITICAL RELEVANCE STATEMENT

Our study confirmed that early screening of Parkinson's Disease based on the conventional T2W FLAIR images was feasible with the aid of machine learning algorithms in a large multicenter cohort and those models had certain generalization.

KEY POINTS

Conventional head MRI is routinely performed in Parkinson's disease (PD) but exhibits inadequate specificity for diagnosis. Machine learning (ML) models based on conventional T2W FLAIR images showed favorable accuracy for PD diagnosis. ML algorithm enables early screening of PD on routine T2W FLAIR sequence.

Machine Learning-Based Diagnostic Prediction Model Using T1-Weighted Striatal Magnetic Resonance Imaging for Early-Stage Parkinson's Disease Detection

RATIONALE AND OBJECTIVES

Diagnosing Parkinson's disease (PD) typically relies on clinical evaluations, often detecting it in advanced stages. Recently, artificial intelligence has increasingly been applied to imaging for neurodegenerative disorders. This study aims to develop a diagnostic prediction model using T1-weighted magnetic resonance imaging (T1-MRI) data from the caudate and putamen in individuals with early-stage PD.

MATERIALS AND METHODS

This retrospective case-control study included 69 early-stage PD patients and 22 controls, recruited through the Parkinson's Progression Markers Initiative. T1-MRI scans were acquired using a 3-tesla system. 432 radiomic features were extracted from images of the segmented caudate and putâmen in an automated way. Feature selection was performed using Pearson's correlation and recursive feature elimination to identify the most relevant variables. Three machine learning algorithms-random forest (RF), support vector machine and logistic regression-were evaluated for diagnostic prediction effectiveness using a cross-validation method. The Shapley Additive Explanations technique identified the most significant features distinguishing between the groups. The metrics used to evaluate the performance were discrimination, expressed in area under the ROC curve (AUC), sensitivity and specificity; and calibration, expressed as accuracy.

RESULTS

The RF algorithm showed superior performance with an average accuracy of 92.85%, precision of 100.00%, sensitivity of 86.66%, specificity of 96.65% and AUC of 0.93. The three most influential features were contrast, elongation, and gray-level non-uniformity, all from the putamen.

CONCLUSION

Machine learning-based models can differentiate early-stage PD from controls using T1-weighted MRI radiomic features.

Eye movements during the Iowa Gambling Task in Parkinson's disease: a brief report

Parkinson's disease (PD) is characterized by motor and cognitive impairments. Subtle cognitive impairment may precede motor impairment. There is a substantial need for innovative assessments, such as those involving decision-making, to detect PD in the premotor phase. Evidence suggests executive dysfunction in PD can impede strategic decision-making relying on learning and applying feedback. The Iowa Gambling Task (IGT), when combined with eye-tracking, may be a valuable synergistic strategy for predicting impaired decision-making and therapeutic non-compliance. Participants with PD and matched healthy controls completed the Movement Disorders Society's modified Unified Parkinson's Disease Rating Scale (UPDRS-MDS), 6-min Walk Test (6MWT), Timed Up and Go Test (TUG), Trail Making Test A and B (TMT A and B), Controlled Oral Word Association Test (COWAT), and the Barratt Impulsiveness Scale (BIS). Eye tracking was recorded during the IGT. The PD group scored significantly higher on UPDRS subscales and travelled less distance during the 6MWT despite equivalent performance on the TUG. The PD group also had longer completion times on TMT A and B and more errors on TMT B. Overall IGT winning scores were marginally worse in PD. However, when analyzed as a function of performance over time, the PD group performed significantly worse by task end, thus suggesting impaired decision-making. PD participants exhibited a 72% reduction in blinks despite equivalent outcomes in other eye-movements. Combined with established motor and executive function tests, the inclusion of eye-tracking with the IGT may represent a powerful combination of noninvasive methods to detect and monitor PD early in progression.

Central Involvement in Pure Autonomic Failure: Insights from Neuromelanin-Sensitive Magnetic Resonance Imaging and 18F-Fluorodopa-Positron Emission Tomography

BACKGROUND

Central synucleinopathies, including Parkinson's disease (PD), dementia with Lewy bodies (DLB), and multiple system atrophy (MSA), involve alpha-synuclein accumulation and dopaminergic cell loss in the substantia nigra (SN) and locus coeruleus (LC). Pure autonomic failure (PAF), a peripheral synucleinopathy, often precedes central synucleinopathies.

OBJECTIVES

To assess early brain involvement in PAF using neuromelanin-sensitive magnetic resonance imaging (NM-MRI) and fluorodopa-positron emission tomography (FDOPA-PET), and to determine whether PAF patients with a high likelihood ratio (LR) for conversion to a central synucleinopathy exhibit reduced NM-MRI contrast in the LC and SN compared with controls and low-LR patients.

METHODS

Participants with PAF (n = 23) were categorized as high-LR (n = 13) or low-LR (n = 10) for conversion to central synucleinopathy. Additional participants included PD (n = 22), DLB (n = 8), and age- and sex-matched healthy controls (n = 23). NM-MRI at 3 T was used to quantify contrast ratios in the LC and SN, while FDOPA-PET measured presynaptic dopamine synthesis. Linear regression analyses, adjusted for age and sex, were used to compare NM-MRI contrast across groups.

RESULTS

High-LR PAF patients showed reduced contrast in the LC and SN compared with controls and low-LR PAF patients, with values similar to PD and DLB. The NM-MRI contrast in the SN correlated with dopamine uptake in the striatum. Longitudinal imaging in PAF patients (n = 6) demonstrated reduced NM-MRI and PET values in individuals who developed central synucleinopathies.

CONCLUSIONS

NM-MRI and FDOPA-PET may serve as potential biomarkers for early brain involvement and predicting progression to central synucleinopathies in PAF and could help identify patients for early intervention. © 2025 The Author(s). Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Microstructural patterns in substantia nigra subregions are associated with depression and olfactory impairments in Parkinson's disease

OBJECTIVE

Parkinson's Disease (PD) manifests with both motor and non-motor symptoms, with non-motor symptoms often appearing first. The link between non-motor symptoms, particularly depression, and olfactory dysfunction, and substantia nigra (SN) subregions has been studied less. By utilizing Diffusion tensor imaging (DTI), we investigated the associations between microstructural patterns in the SN's subregions and motor and non-motor symptoms in patients with PD, including those without evident dopaminergic deficits, compared to healthy controls (HC).

METHODS

Complete baseline demographic data, motor assessments, full-scale non-motor tests, and DTI of SN subregions for 260 participants, including 156 with PD, 36 with scans without evidence of dopaminergic deficit (SWEDD), and 68 HC, were extracted from the PPMI database. Multiple linear regression models were used to evaluate the associations between symptom scores and DTI findings.

RESULTS

A significant difference in depression between the groups was found (p < 0.01), with patients with SWEDD having the highest rate of depression (approximately 36.1 %). Depressed SWEDD patients, compared to non-depressed ones, had higher FA values in the right rostral part of SN (p = 0.03, adjusted p = 0.15). Anxiety scores were significantly higher in both PD and SWEDD groups compared to HCs. PD patients exhibited a significantly higher prevalence of olfactory dysfunction compared to SWEDD and HCs (p < 0.001, adjusted p = 0.03), with 54.5 % of PD patients experiencing hyposmia and 34 % of them suffering from anosmia. PD patients with normosmia and hyposmia had higher FA in the right caudal SN than those with anosmia.

CONCLUSION

Our findings suggest significant brain microstructural differences in SN associated with depression and olfactory dysfunction in patients with PD with or without evident dopaminergic deficits. This finding highlights the advantage of DTI in detecting microstructural changes in patients with SWEDD.

Gluten and its relationship with inflammation and Parkinson's Disease: A literature review

Parkinson's Disease is a neurodegenerative central nervous system (CNS) disease that primarily affects the dopaminergic cells of the Substantia Nigra in the midbrain and causes a diverse array of symptoms, including dystonia, a loss of balance, difficulty initiating movements, akinesia, muscle spasms, and tremors. It has long been known that environmental and commercial compounds are linked to an increased risk of Parkinson's Disease. Of importance, gluten, a complex polysaccharide, has been hypothesized to cause some of the symptoms related to Parkinson's Disease. It is hypothesized that gluten causes a chronic inflammatory state which may lead to plaque formation and neuronal cell death in the substantia nigra, alongside the symptoms of Parkinson's Disease. This literature review hopes to explore the relationship gluten has as an inflammatory molecule and its role in the production and prolongation of the disease processes in Parkinson's Disease.

Is motor reserve associated with a rapid progression of Parkinson disease?

BackgroundThe motor reserve estimates (MRes) derived from a residual approach correlate with motor severity in Parkinson's disease (PD), leaving the independent effect of motor reserve on clinical outcomes unclear.ObjectiveInvestigate the independent influence of motor reserve on the long-term outcome.MethodsUsing the Parkinson's Progression Markers Initiative (PPMI) and Pusan National University Hospital (PNUH) datasets, we investigated the association of MRes with progression of motor severity as well as risk of phenoconversion to Hoehn & Yahr (H&Y) stage 3. Two MRes types were calculated: (1) original MRes, negative conversion of standardized residuals from a generalized linear model (GLM) between putaminal dopamine transporter (DAT) levels and motor severity, and (2) modified MRes, standardized residuals from the GLM between original MRes and motor scores.ResultsOriginal MRes correlated with baseline motor scores, while modified MRes did not. Modified MRes in both cohorts were associated with a rapid increase in motor severity (linear mixed effect model, interaction between MRes and disease duration; PPMI, Movement Disorder Society sponsored Unified Parkinson Disease Rating Scale part III [MDS-UPDRS III], estimate 2.248 × 10-3, p < 0.001; PNUH, UPDRS III, estimate 0.027, p = 0.014) In both cohorts, Kaplan-Meier plots showed high modified MRes indicated higher risk of progression to H&Y stage 3. Mediation models using original MRes agreed that high MRes were associated with an accelerated increase in motor scores.ConclusionsIndependent of baseline motor severity, MRes were associated with rapid motor deterioration and high risk of progression to H&Y stage 3.

Multifaceted therapeutic potentials of catalpol, an iridoid glycoside: an updated comprehensive review

Catalpol, classified as an iridoid glucoside, is recognized for its significant role in medicine, particularly in the treatment of various conditions such as diabetes mellitus, neuronal disorders, and inflammatory diseases. This review aims to evaluate the biological implications of catalpol and the mechanisms underlying its diverse pharmacological effects. A thorough exploration of existing literature was conducted utilizing the keyword "Catalpol" across prominent public domains like Google Scholar, PubMed, and EKB. Catalpol has demonstrated a diverse array of pharmacological effects in experimental models, showcasing its anti-diabetic, cardiovascular-protective, neuroprotective, anticancer, hepatoprotective, anti-inflammatory, and antioxidant properties. In summary, catalpol manifests a spectrum of biological effects through a myriad of mechanisms, prominently featuring its anti-inflammatory and antioxidant capabilities. Its diverse pharmacological profile underscores its potential for therapeutic applications across a range of conditions. Further research is warranted to fully elucidate the clinical implications of catalpol and optimize its use in medical practice.

Fully automatic categorical analysis of striatal subregions in dopamine transporter SPECT using a convolutional neural network

OBJECTIVE

To provide fully automatic scanner-independent 5-level categorization of the [123I]FP-CIT uptake in striatal subregions in dopamine transporter SPECT.

METHODS

A total of 3500 [123I]FP-CIT SPECT scans from two in house (n = 1740, n = 640) and two external (n = 645, n = 475) datasets were used for this study. A convolutional neural network (CNN) was trained for the categorization of the [123I]FP-CIT uptake in unilateral caudate and putamen in both hemispheres according to 5 levels: normal, borderline, moderate reduction, strong reduction, almost missing. Reference standard labels for the network training were created automatically by fitting a Gaussian mixture model to histograms of the specific [123I]FP-CIT binding ratio, separately for caudate and putamen and separately for each dataset. The CNN was trained on a mixed-scanner subsample (n = 1957) and tested on one independent identically distributed (IID, n = 1068) and one out-of-distribution (OOD, n = 475) test dataset.

RESULTS

The accuracy of the CNN for the 5-level prediction of the [123I]FP-CIT uptake in caudate/putamen was 80.1/78.0% in the IID test dataset and 78.1/76.5% in the OOD test dataset. All 4 regional 5-level predictions were correct in 54.3/52.6% of the cases in the IID/OOD test dataset. A global binary score automatically derived from the regional 5-scores achieved 97.4/96.2% accuracy for automatic classification of the scans as normal or reduced relative to visual expert read as reference standard.

CONCLUSIONS

Automatic scanner-independent 5-level categorization of the [123I]FP-CIT uptake in striatal subregions by a CNN model is feasible with clinically useful accuracy.

Exploring the active ingredients and potential mechanisms of Pingchan granules in Parkinson's disease treatment through network pharmacology and transcriptomics

Parkinson's disease (PD), the second most prevalent neurodegenerative disorder, poses significant challenges to single-target therapeutic strategies due to its complex etiology. This has driven interest in multi-target approaches, particularly those leveraging natural compounds. Pingchan granules (PCG), a traditional Chinese medicine composed of plant- and animal-derived compounds, have shown efficacy in alleviating PD symptoms. Here, we identify 96 PCG-associated anti-PD targets, enriched in neuronal synaptic signaling and G protein-coupled receptor pathways. Through protein-protein interaction network analysis of anti-PD targets and random forest modeling of substantia nigra transcriptomic data from PD patients, SLC6A3 and SRC emerged as central hub targets, with Mendelian randomization further validating SRC as a potential therapeutic target. Molecular docking and single-cell sequencing reveal that dauricine, PCG's principal active compound, binds strongly to SLC6A3 and SRC, modulating glucose metabolism pathways in dopaminergic neurons. These findings illuminate the molecular basis of PCG's therapeutic effects, offer a foundation for future drug development, and underscore the potential of dauricine as a targeted treatment for PD.

Chronic hyperactivation of midbrain dopamine neurons causes preferential dopamine neuron degeneration

Parkinson's disease (PD) is characterized by the death of substantia nigra (SNc) dopamine (DA) neurons, but the pathophysiological mechanisms that precede and drive their death remain unknown. The activity of DA neurons is likely altered in PD, but we understand little about if or how chronic changes in activity may contribute to degeneration. To address this question, we developed a chemogenetic (DREADD) mouse model to chronically increase DA neuron activity, and confirmed this increase using ex vivo electrophysiology. Chronic hyperactivation of DA neurons resulted in prolonged increases in locomotor activity during the light cycle and decreases during the dark cycle, consistent with chronic changes in DA release and circadian disturbances. We also observed early, preferential degeneration of SNc projections, recapitulating the PD hallmarks of selective vulnerability of SNc axons and the comparative resilience of ventral tegmental area axons. This was followed by eventual loss of midbrain DA neurons. Continuous DREADD activation resulted in a sustained increase in baseline calcium levels, supporting a role for increased calcium in the neurodegeneration process. Finally, spatial transcriptomics from DREADD mice examining midbrain DA neurons and striatal targets, and cross-validation with human patient samples, provided insights into potential mechanisms of hyperactivity-induced toxicity and PD. Our results thus reveal the preferential vulnerability of SNc DA neurons to increased neural activity, and support a potential role for increased neural activity in driving degeneration in PD.

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.

Early alterations of functional connectivity, regional brain volumes and astrocyte markers in the beta-sitosterol beta-d-glucoside (BSSG) rat model of parkinsonism

The β-sitosterol-β-ᴅ-glucoside (BSSG) rat model of experimental parkinsonism develops pathological behaviour and motor changes that progress over time. The purpose of this study was to identify early changes in structure and function of the brain of rats treated with BSSG using both structural and resting-state functional MRI. BSSG and non-BSSG rats were fed five days a week for sixteen weeks, then underwent in vivo MRI scans and an assessment of motor performance 2 and 8 weeks later (18 and week 24 from BSSG). Groups of rats were killed at weeks 19 and 25, then imaged again with MR ex vivo, and immunostained for tyrosine hydroxylase (TH). Since BSSG may interfere with cholesterol metabolism in astrocytes, we also studied potential target engagement and measured levels of astrocyte markers GFAP and S100b. At both studied timepoints, functional connectivity (FC) between brain areas with intermediate connectivity was decreased, but brain volumes increased in the BSSG-treated rats. At week 18/19, fine movements were normal, whereas TH and GFAP were decreased in the striatum, but not in the substantia nigra. At week 24/25, fine movements were impaired, and TH was decreased both in the striatum and the substantia nigra and S100b was increased in the substantia nigra. Astrogliosis may contribute to the increased brain volume found after BSSG exposure. Using the BSSG model of parkinsonism, the results demonstrate early functional and structural alterations in MRI imaging that occur before the appearance of detectable motor symptoms.

Novel co-culture model of T cells and midbrain organoids for investigating neurodegeneration in Parkinson's disease

Recent studies demonstrate that brain infiltration of peripheral immune cells and their interaction with brain-resident cells contribute to Parkinson's disease (PD). However, mechanisms of T cell-brain cell communication are not fully elucidated and models allowing investigation of interaction between T cells and brain-resident cells are required. In this study, we developed a three-dimensional (3D) model composed of stem cell-derived human midbrain organoids (hMO) and peripheral blood T cells. We demonstrated that organoids consist of multiple midbrain-specific cell types, allowing to study T cell motility and interactions with midbrain tissue in a spatially organized microenvironment. We optimized co-culture conditions and demonstrated that T cells infiltrate hMO tissue, leading to neural cell loss. Our work establishes a novel 3D cell co-culture model as a promising tool to investigate the effect of the adaptive immune system on the midbrain and can be used in future studies to address these processes in the context of PD.

Bradykinesia and postural instability in a model of prodromal synucleinopathy with α-synuclein aggregation initiated in the gigantocellular nuclei

α-Synuclein (aSyn) accumulation within the extra-nigral neuronal populations in the brainstem, including the gigantocellular nuclei (GRN/Gi) of reticular formation, is a recognized feature during the prodromal phase of Parkinson disease (PD). Accordingly, there is a burgeoning interest in animal model development for understanding the pathological significance of extra-nigral synucleinopathy, in relation to motor and/or non-motor symptomatology in PD. Here, we report an experimental paradigm for the induction of aSyn aggregation in brainstem, with stereotaxic delivery of pre-formed fibrillar (PFF) aSyn in the pontine GRN of transgenic mice expressing the mutant human Ala53Thr aSyn (M83 line). Our data show that PFF aSyn-induced aggregate pathology in GRN and distinct nuclei of subcortical motor system leads to progressive decline in home cage activity, which was accompanied by postural instability and impaired motor coordination. The progressive accumulation of aSyn pathology in brainstem and motor neurons in lumbar spinal cord heralded the onset of a moribund stage, which culminated in impaired survival. Collectively, our observations suggest an experimental framework for studying the pathological significance of aSyn aggregation in GRN in relation to features of movement disability in PD. With further refinements, we anticipate that this model holds promise as a test-bed for translational research in PD and related disorders.

α-Synuclein orchestrates Th17 responses as antigen and adjuvant in Parkinson's disease

Recently, the role of T cells in the pathology of α-synuclein (αS)-mediated neurodegenerative disorders called synucleinopathies, including Parkinson's disease (PD), dementia with Lewy bodies (DLB), and multiple system atrophy, has attracted increasing attention. Although the existence of αS-specific T cells and the immunogenicity of the post-translationally modified αS fragment have been reported in PD and DLB, the key cellular subset associated with disease progression and its induction mechanism remain largely unknown.Peripheral blood mononuclear cells (PBMCs) from synucleinopathy patients and healthy controls were cultured in the presence of the αS peptide pools. Cytokine analysis using culture supernatants revealed that C-terminal αS peptides with a phosphorylated serine 129 residue (pS129), a feature of pathological αS aggregates, promoted the production of IL-17A, IL-17F, IL-22, IFN-γ and IL-13 in PD patients compared with that in controls. In pS129 peptide-reactive PD cases, Ki67 expression was increased in CD4 T cells but not in CD8 T cells, and intracellular cytokine staining assay revealed the existence of pS129 peptide-specific Th1 and Th17 cells. The pS129 peptide-specific Th17 responses, but not Th1 responses, demonstrated a positive correlation with the Movement Disorder Society-Unified Parkinson's Disease Rating Scale (MDS-UPDRS) Part III scores. A similar correlation was observed for IL-17A levels in the culture supernatant of PBMCs from PD patients with disease duration < 10 years. Interestingly, enhanced Th17 responses to pS129 peptides were uniquely found in PD patients among the synucleinopathies, suggesting that Th17 responses are amplified by certain mechanisms in PD patients. To investigate such mechanisms, we analyzed Th17-inducible capacity of αS-exposed dendritic cells (DCs). In vitro stimulation with αS aggregates generated Th17-inducible DCs with IL-6 and IL-23 production through the signaling of TLR4 and spliced X-box binding protein-1 (XBP1s). In fact, the levels of IL-6 and IL-23 in plasma, and the XBP1s ratio in type 2 conventional DCs were increased in PD patients compared with those in controls.Here, we propose the importance of αS-specific Th17 responses in the progression of PD and the underlying mechanisms inducing Th17 responses. These findings may provide novel therapeutic strategies to prevent disease development through the suppression of TLR4-XBP1s-IL-23 signaling in DCs.

Magnetic susceptibility components reveal different aspects of neurodegeneration in alpha-synucleinopathies

Nigrostriatal dopaminergic degeneration in alpha-synucleinopathies is indirectly reflected by low dopamine transporter (DaT) uptake through [123I]FP-CIT-SPECT. Bulk magnetic susceptibility (χ) in the substantia nigra, from MRI-based quantitative susceptibility mapping (QSM), is a potential biomarker of nigrostriatal degeneration, however, QSM cannot disentangle paramagnetic (e.g. iron) and diamagnetic (e.g. myelin) sources. Using the susceptibility source-separation technique DECOMPOSE, paramagnetic component susceptibility (PCS) and diamagnetic component susceptibility (DCS) were studied in prodromal and overt alpha-synucleinopathies, and their relationships with DaT-SPECT specific binding ratio (SBR) and clinical scores. 78 participants were included (23 controls, 30 prodromal and 25 overt alpha-synucleinopathies). Prodromal patients were subdivided into groups with positive or negative DaT-SPECT (SBR Z-scores below or above -1, respectively). Correlations of putamen and caudate SBR Z-scores with PCS and DCS in the substantia nigra, putamen, and caudate were investigated. Increased PCS was observed in the substantia nigra of prodromal alpha-synucleinopathy patients with positive DaT-SPECT compared to controls and prodromal patients with negative DaT-SPECT. SBR Z-scores in the putamen correlated with increased PCS in the substantia nigra and reduced |DCS| in the putamen, which may reflect dopaminergic degeneration ascribable to iron accumulation and nigrostriatal neuron axonal loss, respectively.

Longitudinal Trajectory of Dopamine and Serotonin Transporters in Parkinson Disease

Parkinson disease (PD) is a multisystem disorder marked by progressive dopaminergic neuronal degeneration in the substantia nigra, as well as nondopaminergic systems. Our aim was to investigate longitudinal changes in N-(3-[18F]fluoropropyl-2β-carbomethoxy-3β-(4-iodophenyl)nortropane (18F-FP-CIT) binding at the putamen, substantia nigra, and raphe nuclei in PD. Methods: This retrospective cohort study enrolled 127 patients with PD, who underwent 18F-FP-CIT PET scans twice or more, and 71 age- and sex-matched healthy controls. A temporal trajectory model was created to estimate the longitudinal trajectories of 18F-FP-CIT PET specific binding ratios (SBRs) of the putamen, substantia nigra, and raphe nuclei from the prodromal to advanced stages. Associations between SBRs and age and motor severity were evaluated. Results: At baseline, the PD group showed significantly lower 18F-FP-CIT SBR of the putamen and substantia nigra and higher 18F-FP-CIT SBR of the median raphe than did the control group. Longitudinally, 18F-FP-CIT decline of the putamen and substantia nigra began 11.3 and 3.4 y, respectively, before clinical onset on the more affected side. 18F-FP-CIT decline of the raphe nuclei remained constant for up to 20 y of disease duration. Topographically, 18F-FP-CIT SBR of the substantia nigra progressed from the caudal and anterolateral to the rostral and posteromedial regions. Conclusion: These results provide in vivo evidence of decreased striatal synaptic dopamine transporter availability approximately 8 y before decreased nigral neuronal dopamine transporter availability, which is strongly correlated with motor deficit. Serotonin transporter availability in the raphe nuclei was elevated in and remained largely unchanged during the disease span.

Lasting Impact: Exploring the Brain Mechanisms that Link Traumatic Brain Injury to Parkinson's Disease

Development of Parkinson's Disease (PD) is linked with a history of traumatic brain injury (TBI), although the mechanisms driving this remain unclear. Of note, many key parallels have been identified between the pathologies of PD and TBI; in particular, PD is characterised by loss of dopaminergic neurons from the substantia nigra (SN), accompanied by broader changes to dopaminergic signalling, disruption of the Locus Coeruleus (LC) and noradrenergic system, and accumulation of aggregated α-synuclein in Lewy Bodies, which spreads in a stereotypical pattern throughout the brain. Widespread disruptions to the dopaminergic and noradrenergic systems, including progressive neuronal loss from the SN and LC, have been observed acutely following injury, some of which have also been identified chronically in TBI patients and preclinical models. Furthermore, changes to α-synuclein expression are also seen both acutely and chronically following injury throughout the brain, although detailed characterisation of these changes and spread of pathology is limited. In this review, we detail the current literature regarding dopaminergic and noradrenergic disruption and α-synuclein pathology following injury, with particular focus on how these changes may predispose individuals to prolonged pathology and progressive neurodegeneration, particularly the development of PD. While it is increasingly clear that TBI is a key risk factor for the development of PD, significant gaps remain in current understanding of neurodegenerative pathology following TBI, particularly chronic manifestations of injury.

TMS and tDCS as potential tools for the treatment of cognitive deficits in Parkinson's disease: a meta-analysis

BACKGROUND

Cognitive deficits are common nonmotor symptoms in Parkinson's disease (PD). Non-Invasive Brain Stimulation (NIBS) could be a potential aid to prevent or delay dementia progression in this clinical population. However, previous studies reported controversial results concerning their efficacy on cognitive symptoms of PD. Hence, the present meta-analysis aims to systematically examine the effects of NIBS as possible treatments for PD cognitive impairments. Understanding NIBS' impact on these symptoms may be of outstanding importance to implement new therapeutic strategies and improve the patients' quality of life.

METHODS

EMBASE, Scopus, and PubMed databases were systematically searched for consecutive studies published from 2000 to March 2023 describing Randomized Controlled Trials studies evaluating the effect of NIBS on PD cognitive symptoms. From the included studies, data concerning neuropsychological tests were extracted and grouped into six cognitive domains, separately analyzed. Hedge's method was computed as the effect size measure of the extracted data; heterogeneity among studies and publication bias were also assessed. The Cochrane's RoB2 tool was used to evaluate the risk of bias for each of the included studies.

RESULTS

After database searching and screening of texts, sixteen studies met the inclusion criteria. No significant results emerged from any investigated cognitive domain when comparing NIBS and sham treatments.

CONCLUSION

Several factors may have contributed to the lack of effects; among these, methodological choices, the small sample of studies, the high heterogeneity of data and stimulation protocols pose the need for more controlled studies to highlight the potentiality of NIBS as a future treatment for PD cognitive impairments.

Changes in Action Tremor in Parkinson's Disease over Time: Clinical and Neuroimaging Correlates

BACKGROUND

The various symptoms of Parkinson's disease (PD) may change differently over time as the disease progresses. Tremor usually manifests early in the disease, but unlike other motor symptoms, its severity may diminish over time. The cerebral mechanisms underlying these symptom-specific longitudinal trajectories are unclear. Previous magnetic resonance imaging (MRI) studies have shown structural changes in brain regions associated with PD tremor, suggesting that structural changes over time may define clinical trajectories.

OBJECTIVES

The aims were to investigate the longitudinal trajectory of PD tremor in relation to bradykinesia and rigidity, and assess whether tremor progression is related to structural changes in tremor-related areas.

METHODS

We used data from the Personalized Parkinson Project: a two-year longitudinal study involving 520 PD patients and 60 healthy controls, who were measured twice clinically and with MRI. Mixed-effects models were used to compare tremor, bradykinesia, and rigidity progression; investigate gray matter changes in tremor-related regions (cerebello-thalamo-cortical circuit and pallidum); and calculate associations between symptom severity and brain structure. Associations across the whole brain were included to assess anatomical specificity.

RESULTS

Bradykinesia and rigidity worsened over 2 years, whereas tremor behaved differently: resting tremor severity remained stable, whereas postural and kinetic tremor severity decreased. Attenuation of postural and kinetic tremor was associated with, but not restricted to, atrophy in tremor-related areas. Opposite relationships were observed for bradykinesia and rigidity.

CONCLUSIONS

Action tremor (postural and kinetic) is an early symptom of PD, which reduces with disease progression. Longitudinal brain atrophy correlates with tremor and other motor symptoms in opposite ways. © 2024 The Author(s). Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Neurofilament heavy phosphorylated epitopes as biomarkers in ageing and neurodegenerative disease

From the day we are born, the nervous system is subject to insult, disease and degeneration. Aberrant phosphorylation states in neurofilaments, the major intermediate filaments of the neuronal cytoskeleton, accompany and mediate many pathological processes in degenerative disease. Neuronal damage, degeneration and death can release these internal components to the extracellular space and eventually the cerebrospinal fluid and blood. Sophisticated assay techniques are increasingly able to detect their presence and phosphorylation states at very low levels, increasing their utility as biomarkers and providing insights and differential diagnosis for the earliest stages of disease. Although a variety of studies focus on single or small clusters of neurofilament phosphorylated epitopes, this review offers a wider perspective of the phosphorylation landscape of the neurofilament heavy subunit, a major intermediate filament component in both ageing and disease.

Predictive potential of circular walking in prodromal Parkinson's disease

BackgroundDevelopment of objective, reliable and easy-to-use methods to detect the onset of motor changes in Parkinson's disease (PD) is required to identify the temporal window in which neuromodulatory therapies could be implemented. Turning impairments are present at early stages of PD. However, it is unclear, to date, whether circular walking is also altered in prodromal PD.ObjectiveExplore the predictive potential of circular walking in prodromal PD.MethodsWe included 102 subjects from a nine-year prospective cohort study (with 712 participants) in the current nested case-control analysis: 16 diagnosed with PD during follow-up (incident PD) and 96 healthy controls, matched in gender, age, and education with a 1:6 ratio. Forty-one gait features were extracted from baseline assessments with accelerometers under single and dual-tasking conditions. A Cox proportional hazards regression analysis was used to test the temporal association of non-correlated gait features to the probability of being diagnosed with PD.ResultsWe identified associations between time from baseline measurement to PD diagnosis for eleven gait features, mostly based on harmonic ratios, step and stride variability, and index of harmonicity, partially in combination with gait speed. Most significant associations indicated that low gait symmetry and low rhythmicity were associated with larger hazard of being diagnosed with PD. Area under the curve ranged 0.63-0.69.ConclusionsDespite low sensitivity and specificity, the findings potentially reflect prodromal motor impairments of PD manifested during circular walking, assessed quantitatively with a low-cost and wearable instrument. This will contribute to the characterization of pre-diagnostic PD motor symptoms.

Iron(ing) out parkinsonisms: The interplay of proteinopathy and ferroptosis in Parkinson's disease and tau-related parkinsonisms

Parkinsonian syndromes are characterised by similar motor-related symptomology resulting from dopaminergic neuron damage. While Parkinson's disease (PD) is the most prevalent parkinsonism, we also focus on two other variants, Progressive supranuclear palsy (PSP) and Corticobasal degeneration (CBD). Due to the clinical similarities of these parkinsonisms, and since definite diagnoses are only possible post-mortem, effective therapies and novel biomarkers of disease are scarce. Thus, we explore the current findings relating to the relationship of parkinsonism proteinopathy (α-synuclein in PD, and tau in PSP/CBD) paralleled to a specific form of cell death, ferroptosis. Ferroptosis is characterised by iron-induced lipid peroxidation and several markers of this pathway have been identified to control intracellular iron fluctuations. However, in parkinsonism, these mechanisms are thought to become dysfunctional. Although both proteinopathies have been linked to ferroptosis, much less is known about ferroptotic cell death and tau in the context of PSP/CBD. Interestingly, clinical trials targeting iron have recently shown conflicting results which begs to question the complexity of the ferroptotic pathway and alludes to the need for exploring other ferroptosis-related machinery as possible therapeutic targets. Overall, we address the literature gap in parkinsonism proteinopathy and ferroptosis, and its relevance to understanding disease pathophysiology and aetiology.

Lewy body diseases and the gut

Gastrointestinal (GI) involvement in Lewy body diseases (LBDs) has been observed since the initial descriptions of patients by James Parkinson. Recent experimental and human observational studies raise the possibility that pathogenic alpha-synuclein (⍺-syn) might develop in the GI tract and subsequently spread to susceptible brain regions. The cellular and mechanistic origins of ⍺-syn propagation in disease are under intense investigation. Experimental LBD models have implicated important contributions from the intrinsic gut microbiome, the intestinal immune system, and environmental toxicants, acting as triggers and modifiers to GI pathologies. Here, we review the primary clinical observations that link GI dysfunctions to LBDs. We first provide an overview of GI anatomy and the cellular repertoire relevant for disease, with a focus on luminal-sensing cells of the intestinal epithelium including enteroendocrine cells that express ⍺-syn and make direct contact with nerves. We describe interactions within the GI tract with resident microbes and exogenous toxicants, and how these may directly contribute to ⍺-syn pathology along with related metabolic and immunological responses. Finally, critical knowledge gaps in the field are highlighted, focusing on pivotal questions that remain some 200 years after the first descriptions of GI tract dysfunction in LBDs. We predict that a better understanding of how pathophysiologies in the gut influence disease risk and progression will accelerate discoveries that will lead to a deeper overall mechanistic understanding of disease and potential therapeutic strategies targeting the gut-brain axis to delay, arrest, or prevent disease progression.

Morphological and functional decline of the SNc in a model of progressive parkinsonism

The motor symptoms of Parkinson's Disease are attributed to the degeneration of dopamine neurons in the substantia nigra pars compacta (SNc). Previous work in the MCI-Park mouse model has suggested that the loss of somatodendritic dopamine transmission predicts the development of motor deficits. In the current study, brain slices from MCI-Park mice were used to investigate dopamine signaling in the SNc prior to and through the onset of movement deficits. Electrophysiological properties were impaired by p30 and somatic volume was decreased at all time points. The D2 receptor activated potassium current evoked by quinpirole was present initially, but declined after p30. In contrast, D2-IPSCs were absent at all time points. The decrease in GPCR-mediated inhibition was met with increased spontaneous GABAA signaling. Dendro-dendritic synapses are identified as an early locus of dysfunction in response to bioenergetic decline and suggest that dendritic release sites may contribute to the induction of degeneration.

NPT100-18A rescues mitochondrial oxidative stress and neuronal degeneration in human iPSC-based Parkinson's model

BACKGROUND

Parkinson's disease (PD) is a neurodegenerative disorder characterized by protein aggregates mostly consisting of misfolded alpha-synuclein (αSyn). Progressive degeneration of midbrain dopaminergic neurons (mDANs) and nigrostriatal projections results in severe motor symptoms. While the preferential loss of mDANs has not been fully understood yet, the cell type-specific vulnerability has been linked to a unique intracellular milieu, influenced by dopamine metabolism, high demand for mitochondrial activity, and increased level of oxidative stress (OS). These factors have been shown to adversely impact αSyn aggregation. Reciprocally, αSyn aggregates, in particular oligomers, can impair mitochondrial functions and exacerbate OS. Recent drug-discovery studies have identified a series of small molecules, including NPT100-18A, which reduce αSyn oligomerization by preventing misfolding and dimerization. NPT100-18A and structurally similar compounds (such as NPT200-11/UCB0599, currently being assessed in clinical studies) point towards a promising new approach for disease-modification.

METHODS

Induced pluripotent stem cell (iPSC)-derived mDANs from PD patients with a monoallelic SNCA locus duplication and unaffected controls were treated with NPT100-18A. αSyn aggregation was evaluated biochemically and reactive oxygen species (ROS) levels were assessed in living mDANs using fluorescent dyes. Adenosine triphosphate (ATP) levels were measured using a luminescence-based assay, and neuronal cell death was evaluated by immunocytochemistry.

RESULTS

Compared to controls, patient-derived mDANs exhibited higher cytoplasmic and mitochondrial ROS probe levels, reduced ATP-related signals, and increased activation of caspase-3, reflecting early neuronal cell death. NPT100-18A-treatment rescued cleaved caspase-3 levels to control levels and, importantly, attenuated mitochondrial oxidative stress probe levels in a compartment-specific manner and, at higher concentrations, increased ATP signals.

CONCLUSIONS

Our findings demonstrate that NPT100-18A limits neuronal degeneration in a human in vitro model of PD. In addition, we provide first mechanistic insights into how a compartment-specific antioxidant effect in mitochondria might contribute to the neuroprotective effects of NPT100-18A.

Present insights into the progress in gene therapy delivery systems for central nervous system diseases

Central nervous system (CNS) diseases, including Alzheimer's disease (AD), Parkinson's disease (PD), spinal cord injury (SCI), and ischemic strokes and certain rare diseases, such as amyotrophic lateral sclerosis (ALS) and ataxia, present significant obstacles to treatment using conventional molecular pharmaceuticals. Gene therapy, with its ability to target previously "undruggable" proteins with high specificity and safety, is increasingly utilized in both preclinical and clinical research for CNS ailments. As our comprehension of the pathophysiology of these conditions deepens, gene therapy stands out as a versatile and promising strategy with the potential to both prevent and treat these diseases. Despite the remarkable progress in refining and enhancing the structural design of gene therapy agents, substantial obstacles persist in their effective and safe delivery within living systems. To surmount these obstacles, a diverse array of gene delivery systems has been devised and continuously improved. Notably, Adeno-Associated Virus (AAVs)-based viral gene vectors and lipid-based nanocarriers have each advanced the in vivo delivery of gene therapies to various extents. This review aims to concisely summarize the pathophysiological foundations of CNS diseases and to shed light on the latest advancements in gene delivery vector technologies. It discusses the primary categories of these vectors, their respective advantages and limitations, and their specialized uses in the context of gene therapy delivery.

Combined quantitative analysis of the nigro-striata system in multiple system atrophy and Parkinson's disease

Degeneration of the nigrostriatal system occurs in multiple system atrophy (MSA) and Parkinson's disease (PD) via distinct pathological mechanisms. Here, we investigated nigrostriatal degeneration in MSA and PD by combining a newly developed method for evaluating the regional accumulation of dopamine transporter single-photon emission computed tomography (DAT SPECT) and individual voxel-based morphometry adjusting covariates (iVAC). We recruited 17 MSA patients and 13 PD patients, and compared their clinical and imaging indices. All patients underwent DAT SPECT and head three-dimensional T1-weighted magnetic resonance imaging. We calculated the specific binding ratio (SBR) of the putamen and caudate separately using a region-based method, and evaluated the association between the SBR and iVAC Z-score. SBR values of the putamen and caudate were lower in the PD group than in the MSA group (p < 0.001 for both). The MSA and PD groups had lower SBR values in the putamen than in the caudate (p < 0.05 and p < 0.001, respectively). We found a negative correlation between the putamen SBR and iVAC Z-score in MSA (p < 0.001, r = -0.775), but such a correlation was not detected in PD. For the caudate, there was no correlation between the SBR and iVAC Z-score in MSA and PD. Our results indicate different mechanisms of reduced uptake of DATs in MSA and PD. The association between the striatal SBR and iVAC Z-score suggests parallel degeneration in the substantia nigra and striatum in MSA.

Delivery of small interfering RNA by hydrogen sulfide-releasing nanomotor for the treatment of Parkinson's disease

Small interfering RNA (siRNA) that inhibit the formation of α-synuclein (α-syn) aggregates is considered very promising therapeutic agents for the treatment of Parkinson's disease (PD). However, the low stability and the difficulty in crossing the blood-brain barrier (BBB) of free siRNA has severely limited their therapeutic effects. Here, we developed an H2S donor nanomotor that can encapsulate siRNA, which can both protect the activity of siRNA and help siRNA to be effectively targeted to the mitochondria of damaged neuronal cells, in order to promote the effective therapeutic effect of siRNA for PD. Specifically, the cysteine monomer-modified polyethylene glycol (PEG-Cys) and the amphiphilic ionic monomer 2-methacryloyloxyethylphosphorylcholine (MPC) that can effectively penetrate the BBB, were selected to form a polymer protective layer on the surface of siRNA in a free-radical polymerization reaction, to construct the H2S donor nanomotor encapsulating siRNA (PCM@siRNA). Among them, MPC can help PCM@siRNA to break through the BBB by interacting with nicotinic acetylcholine receptor or choline transporter on the surface of cerebrovascular endothelial cells, while PEG-Cys can undergo chemotactic effect by specifically recognizing 3-thiopyruvate thioltransferase and thus achieve effective targeting of damaged mitochondria in neuronal cells. PCM@siRNA that reached neuronal cells can not only be utilized to play the role of silencing the α-syn gene to inhibit the formation of α-syn aggregates by siRNA, but also to degrade the formed α-syn aggregates by using the H2S produced by its chemotaxis process to achieve an effective treatment for PD. This therapeutic modality, which can simultaneously inhibit the formation of α-syn aggregates and promote their degradation, has the therapeutic potential to reverse the pathological state of α-syn, which is important for the treatment of PD.

A Review on Therapeutic Strategies against Parkinson's Disease: Current Trends and Future Perspectives

Parkinson's Disease (PD) is the most common neurodegenerative disorder after Alzheimer's Disease and is clinically expressed by movement disorders, such as tremor, bradykinesia, and rigidity. It occurs mainly in the extrapyramidal system of the brain and is characterized by dopaminergic neuron degeneration. L-DOPA, dopaminergic agonists, anticholinergic drugs, and MAO-B inhibitors are currently used as therapeutic agents against PD, however, they have only symptomatic efficacy, mainly due to the complex pathophysiology of the disease. This review summarizes the main aspects of PD pathology, as well as, discusses the most important biochemical dysfunctions during PD, and presents novel multi-targeting compounds, which have been tested for their activity against various targets related to PD. This review selects various research articles from main databases concerning multi-targeting compounds against PD. Molecules targeting more than one biochemical pathway involved in PD, expected to be more effective than the current treatment options, are discussed. A great number of research groups have designed novel compounds following the multi-targeting drug approach. They include structures combining antioxidant, antiinflammatory, and metal-chelating properties. These compounds could be proven useful for effective multi-targeted PD treatment. Multi-targeting drugs could be a useful tool for the design of effective antiparkinson agents. Their efficacy towards various targets implicated in PD could be the key to the radical treatment of this neurodegenerative disorder.

Molecular and spatial transcriptomic classification of midbrain dopamine neurons and their alterations in a LRRK2G2019S model of Parkinson's disease

Several studies have revealed that midbrain dopamine (DA) neurons, even within a single neuroanatomical area, display heterogeneous properties. In parallel, studies using single cell profiling techniques have begun to cluster DA neurons into subtypes based on their molecular signatures. Recent work has shown that molecularly defined DA subtypes within the substantia nigra (SNc) display distinctive anatomic and functional properties, and differential vulnerability in Parkinson's disease (PD). Based on these provocative results, a granular understanding of these putative subtypes and their alterations in PD models, is imperative. We developed an optimized pipeline for single-nuclear RNA sequencing (snRNA-seq) and generated a high-resolution hierarchically organized map revealing 20 molecularly distinct DA neuron subtypes belonging to three main families. We integrated this data with spatial MERFISH technology to map, with high definition, the location of these subtypes in the mouse midbrain, revealing heterogeneity even within neuroanatomical sub-structures. Finally, we demonstrate that in the preclinical LRRK2G2019S knock-in mouse model of PD, subtype organization and proportions are preserved. Transcriptional alterations occur in many subtypes including those localized to the ventral tier SNc, where differential expression is observed in synaptic pathways, which might account for previously described DA release deficits in this model. Our work provides an advancement of current taxonomic schemes of the mouse midbrain DA neuron subtypes, a high-resolution view of their spatial locations, and their alterations in a prodromal mouse model of PD.

LRRK2 mutation contributes to decreased free water in the nucleus basalis of Meynert in manifest and premanifest Parkinson's disease

BACKGROUND

Free-water imaging can predict and monitor dopamine system degeneration in patients with Parkinson's disease (PD). However, brain cholinergic function has not been investigated to date in LRRK2 mutation carriers with or without PD using free-water imaging.

OBJECTIVES

To investigate the effect of LRRK2 mutations on the cholinergic system in manifest and premanifest stages of PD using free-water imaging.

METHODS

We recruited participants from the Parkinson's Progression Markers Initiative (PPMI) data set. We evaluated the effect of LRRK2 mutations on the cholinergic nuclei (i.e., cholinergic nuclei 1, 2, and 3 (Ch123), Ch4, and pedunculopontine nucleus) in manifest and premanifest stages of PD using free-water imaging. We compared free-water values between groups using ANCOVA with adjustment for age. Then, the discriminative power of the free-water content was evaluated by receiver operating characteristic curve (ROC) analysis.

RESULTS

We included 27 patients with LRRK2 PD, 33 LRRK2 mutation carriers without PD, 281 patients with idiopathic PD, and 98 healthy controls. We noted significant between-group differences in free-water content in Ch4 (p = 0.003). LRRK2 mutation carriers without PD had decreased free-water content in the Ch4 compared with healthy controls (p = 0.036) and idiopathic patients with PD (p = 0.001); LRRK2 patients with PD showed decreased tendency of free-water content in the Ch4 compared with idiopathic patients with PD (p = 0.074). Furthermore, ROC analysis showed that free-water content in the Ch4 identified asymptomatic LRRK2 mutation carriers with a high specificity (84.7%).

CONCLUSIONS

LRRK2 mutation is associated with decreased free-water content in the Ch4 (also referred to as nucleus basalis of Meynert, nbM), which might suggest early and sustained attempts to compensate for LRRK2-related dysfunction.

Revolutionizing our understanding of Parkinson's disease: Dr. Heinz Reichmann's pioneering research and future research direction

Millions of individuals around the world are afflicted with Parkinson's disease (PD), a prevalent and incapacitating neurodegenerative disorder. Dr. Reichmann, a distinguished professor and neurologist, has made substantial advancements in the domain of PD research, encompassing both fundamental scientific investigations and practical applications. His research has illuminated the etiology and treatment of PD, as well as the function of energy metabolism and premotor symptoms. As a precursor to a number of neurotransmitters and neuromodulators that are implicated in the pathophysiology of PD, he has also investigated the application of tryptophan (Trp) derivatives in the disease. His principal findings and insights are summarized and synthesized in this narrative review article, which also emphasizes the challenges and implications for future PD research. This narrative review aims to identify and analyze the key contributions of Reichmann to the field of PD research, with the ultimate goal of informing future research directions in the domain. By examining Reichmann's work, the study seeks to provide a comprehensive understanding of his major contributions and how they can be applied to advance the diagnosis and treatment of PD. This paper also explores the potential intersection of Reichmann's findings with emerging avenues, such as the investigation of Trp and its metabolites, particularly kynurenines, which could lead to new insights and potential therapeutic strategies for managing neurodegenerative disorders like PD.

Uncovering the genetic basis of Parkinson's disease globally: from discoveries to the clinic

Knowledge on the genetic basis of Parkinson's disease has grown tremendously since the discovery of the first monogenic form, caused by a mutation in α-synuclein, and with the subsequent identification of multiple other causative genes and associated loci. Genetic studies provide insights into the phenotypic heterogeneity and global distribution of Parkinson's disease. By shedding light on the underlying biological mechanisms, genetics facilitates the identification of new biomarkers and therapeutic targets. Several clinical trials of genetics-informed therapies are ongoing or imminent. International programmes in populations who have been under-represented in Parkinson's disease genetics research are fostering collaboration and capacity-building, and have already generated novel findings. Many challenges remain for genetics research in these populations, but addressing them provides opportunities to obtain a more complete and equitable understanding of Parkinson's disease globally. These advances facilitate the integration of genetics into the clinic, to improve patient management and personalised medicine.

Developmental and Adult Striatal Patterning of Nociceptin Ligand Marks Striosomal Population With Direct Dopamine Projections

Circuit influences on the midbrain dopamine system are crucial to adaptive behavior and cognition. Recent developments in the study of neuropeptide systems have enabled high-resolution investigations of the intersection of neuromodulatory signals with basal ganglia circuitry, identifying the nociceptin/orphanin FQ (N/OFQ) endogenous opioid peptide system as a prospective regulator of striatal dopamine signaling. Using a prepronociceptin-Cre reporter mouse line, we characterized highly selective striosomal patterning of Pnoc mRNA expression in mouse dorsal striatum, reflecting the early developmental expression of Pnoc. In the ventral striatum, Pnoc expression in the nucleus accumbens core was grouped in clusters akin to the distribution found in striosomes. We found that PnoctdTomato reporter cells largely comprise a population of dopamine receptor D1 (Drd1) expressing medium spiny projection neurons localized in dorsal striosomes, known to be unique among striatal projection neurons for their direct innervation of midbrain dopamine neurons. These findings provide a new understanding of the intersection of the N/OFQ system among basal ganglia circuits with particular implications for developmental regulation or wiring of striato-nigral circuits.

A framework for translational therapy development in deep brain stimulation

Deep brain stimulation (DBS) is an established treatment for motor disorders like Parkinson's disease, but its mechanisms and effects on neurons and networks are not fully understood, limiting research-driven progress. This review presents a framework that combines neurophysiological insights and translational research to enhance DBS therapy, emphasizing biomarkers, device technology, and symptom-specific neuromodulation. It also examines the role of animal research in improving DBS, while acknowledging challenges in clinical translation.

Systemic inflammation accelerates neurodegeneration in a rat model of Parkinson's disease overexpressing human alpha synuclein

Increasing efforts have been made to elucidate how genetic and environmental factors interact in Parkinson's disease (PD). In the present study, we assessed the development of symptoms on a genetic PD rat model that overexpresses human α-synuclein (Snca+/+) at a presymptomatic age, exposed to a pro-inflammatory insult by intraperitoneal injection of lipopolysaccharide (LPS), using immunohistology, high-dimensional flow cytometry, constant potential amperometry, and behavioral analyses. A single injection of LPS into WT and Snca+/+ rats triggered long-lasting increase in the activation of pro-inflammatory microglial markers, monocytes, and T lymphocytes. However, only LPS Snca+/+ rats showed dopaminergic neuronal loss in the substantia nigra pars compacta (SNpc), associated with a reduction in the release of evoked dopamine in the striatum. No significant changes were observed in the behavioral domain. We propose our double-hit animal as a reliable model to investigate the mechanisms whereby α-synuclein and inflammation interact to promote neurodegeneration in PD.

LRE-MMF: A novel multi-modal fusion algorithm for detecting neurodegeneration in Parkinson's disease among the geriatric population

Parkinson's disease (PD) is a prevalent neurological disorder characterized by progressive dopaminergic neuron loss, leading to both motor and non-motor symptoms. Early and accurate diagnosis is challenging due to the subtle and variable nature of early symptoms. This study aims to address these diagnostic challenges by proposing a novel method, Localized Region Extraction and Multi-Modal Fusion (LRE-MMF), designed to enhance diagnostic accuracy through the integration of structural MRI (sMRI) and resting-state functional MRI (rs-fMRI) data. The LRE-MMF method utilizes the complementary strengths of sMRI and rs-fMRI: sMRI provides detailed anatomical information, while rs-fMRI captures functional connectivity patterns. We applied this approach to a dataset consisting of 20 PD patients and 20 healthy controls (HC), all scanned with a 3 T MRI. The primary objective was to determine whether the integration of sMRI and rs-fMRI through the LRE-MMF method improves the classification accuracy between PD and HC subjects. LRE-MMF involves the division of imaging data into localized regions, followed by feature extraction and dimensionality reduction using Principal Component Analysis (PCA). The resulting features were fused and processed through a neural network to learn high-level representations. The model achieved an accuracy of 75 %, with a precision of 0.8125, recall of 0.65, and an AUC of 0.8875. The validation accuracy curves indicated good generalization, with significant brain regions identified, including the caudate, putamen, thalamus, supplementary motor area, and precuneus, as per the AAL atlas. These results demonstrate the potential of the LRE-MMF method for improving early diagnosis and understanding of PD by effectively utilizing both sMRI and rs-fMRI data. This approach could contribute to the development of more accurate diagnostic tools.

Visualizing lysosomes hypochlorous acid in Parkinson's disease models by a novel fluorescent probe

Heightened oxidative stress is the principal driver behind the altered metabolism of neurotransmitters within the brains of Parkinson's disease (PD). Hypochlorous acid (HClO), a variant of reactive oxygen species (ROS), plays a crucial role in several lysosomal activities. An irregular concentration of HClO may result in significant molecular damage and contribute to the onset of neurodegenerative disorders. Despite this, the precise role of lysosomal HClO in PD remains unclear, due to its fast reactivity and low levels. This is further complicated by the lack of effective in situ imaging techniques for accurately tracking its dynamics. Therefore, it is of great significance to use effective tools to map the lysosomal HClO during the pathological process of PD. In this study, we propose a fluorogenic probe named Lys-PTZ-HClO for the specific and sensitive detection of HClO. Lys-PTZ-HClO exhibits features like a fast response time (10 s) and a low detection limit (0.72 μM). Benefiting from its superior properties, the probe was used to visualize the basal HClO levels, and the variation of HClO levels in lysosomal of living cells. More importantly, this probe was successfully applied for the first time to reveal increased lysosomal HClO in a cellular model of PD.

The angiotensin (1-7) glycopeptide PNA5 improves cognition in a chronic progressive mouse model of Parkinson's disease through modulation of neuroinflammation

Cognitive decline in Parkinson's Disease (PD) is a prevalent and undertreated aspect of disease. Currently, no therapeutics adequately improve this aspect of disease. It has been previously shown that MAS receptor agonism via the glycosylated Angiotensin (1-7) peptide, PNA5, effectively reduces cognitive decline in models of vascular contributions to cognitive impairment and dementia (VCID). PNA5 has a brain/plasma ratio of 0.255 indicating good brain penetration. The goal of the present study was to determine if (1) systemic administration of PNA5 rescued cognitive decline in a mouse model of PD, and (2) if improvements in cognitive status could be correlated with changes to histopathological or blood plasma-based changes. Mice over-expressing human, wild-type α-synuclein (αSyn) under the Thy1 promoter (Thy1-αSyn mice, "line 61") were used as a model of PD with cognitive decline. Thy1-αSyn mice were treated with a systemic dose of PNA5, or saline (1 mg/kg/day) beginning at 4 months of age and underwent behavioral testing at 6 months, compared to WT. Subsequently, mice brains were analyzed for changes to brain pathology, and blood plasma was examined with a Multiplex Immunoassay for peripheral cytokine changes. Treatment with PNA5 reversed cognitive dysfunction measured by Novel Object Recognition and spontaneous alteration in a Y-maze in Thy1-αSyn mice. PNA5 treatment was specific to cognitive deficits, as fine-motor disturbances were unchanged. Enhanced cognition was associated with decreases in hippocampal inflammation and reductions in circulating levels of Macrophage Induced Protein (MIP-1β). Additionally, neuronal loss was blunted within the CA3 hippocampal region of PNA5-treated αsyn mice. These data reveal that PNA5 treatment reduces cognitive dysfunction in a mouse model of PD. These changes are associated with decreased MIP-1β levels in plasma identifying a candidate biomarker for target engagement. Thus, PNA5 treatment could potentially fill the therapeutic gap for cognitive decline in PD.

Neurotrophic factors for Parkinson's disease: Current status, progress, and remaining questions. Conclusions from a 2023 workshop

In 2023, a workshop was organized by the UK charity Cure Parkinson's with The Michael J Fox Foundation for Parkinson's Research and Parkinson's UK to review the field of growth factors (GFs) for Parkinson's disease (PD). This was a follow up to a previous meeting held in 2019.1 This 2023 workshop reviewed new relevant data that has emerged in the intervening 4 years around the development of new GFs and better models for studying them including the merit of combining treatments as well as therapies that can be modulated. We also discussed new insights into GF delivery and trial design that have emerged from the analyses of completed GDNF trials, including the patient voice, as well as the recently completed CDNF trial.2 We then concluded with our recommendations on how GF studies in PD should develop going forward.

Exploring Analysis Approaches for Using the Dopamine Transporter Striatal Binding Ratio in Early- to Mid-Stage Parkinson's Disease Modification Trials

BACKGROUND

The dopamine transporter striatal binding ratio (DAT SBR) has been used as an outcome measure in Parkinson's disease (PD) trials of potential disease-modifying therapies; however, both patient characteristics and analysis approach potentially complicate its interpretation.

OBJECTIVE

The aim was to explore how well DAT SBR reflects PD motor severity across different striatal subregions and the relationship to disease duration, and side of onset.

METHODS

DAT SBR for the anterior and posterior putamen and caudate in both hemispheres was obtained using validated automated quantitative software on baseline scans of 132 patients recruited for the Exenatide PD2 and PD3 trials. Associations between mean and lateralized SBR subregions (posterior and anterior putamen and caudate) and summed and lateralized motor characteristics were explored using regression analysis. Analyses were repeated considering disease duration and limiting analysis to the less-affected hemisphere.

RESULTS

Lateralized bradykinesia was most consistently associated with the loss of DAT uptake in the contralateral anterior putamen. There was much higher variance in the posterior putamen, and in all regions in those with longer duration disease, although bradykinesia remained robustly associated with anterior putaminal DAT uptake even in longer-duration patients. Restricting analyses to the less-affected side did not usefully reduce the variance compared to the overall cohort.

CONCLUSION

These data suggest that DAT SBR could be a useful biomarker in disease-modifying trials, but a focus on anterior striatal subregions and incorporating disease duration into analyses may improve its utility.