A Mouse Model to Test Novel Therapeutics for Parkinson's Disease: an Update on the Thy1-aSyn ("line 61") Mice

Application of IVDr NMR spectroscopy to stratify Parkinson's disease with absolute quantitation of blood serum metabolites and lipoproteins

The challenge of early detection and stratification in Parkinson's disease (PD) is urgent due to the current emergence of mechanism-based disease-modifying treatments. In here, metabolomic and lipidomic parameters obtained by a standardized and targeted in vitro diagnostic research (IVDr) platform have a significant potential to address therapy-related questions and generate improved biomarker panels. Our study aimed to use IVDr nuclear magnetic resonance (NMR) spectroscopy to quantify metabolites and lipoproteins in PD blood serum from different cohorts to stratify metabolically driven subtypes of idiopathic and genetic PD. Serum aliquots from three neurodegeneration biobank cohorts (287 samples in total, including 62 PD patient samples with GBA mutation, 98/43 PD patient samples of early/late stages of disease duration, 20 PD samples from patients with mutations in recessive PD genes and some smaller subgroups of mitochondrial and double mutation cases) were prepared and analyzed with IVDr NMR spectroscopy, covering 39 blood serum metabolites and 112 lipoprotein parameters. Uni- and multivariate statistics were used to identify metabolism-driven changes under consideration of typical confounders such as age, sex and disease duration and set into context with clinical biomarkers such as CSF concentrations of alpha-synuclein, neurofilament light chain, and tau protein. Based on the different PD subgroups we performed a total of eight different comparisons. Highlights from these comparisons include increased citrate and dimethylglycine with a decrease of creatinine and methionine in healthy controls and early PD group compared to GBA, PD late and recessive PD. We furthermore identified decreased HDL-3 free cholesterol in genetic PD cases compared to sporadic subject samples (sum of the PD early and PD late groups). Considering medication, we found that the levodopa equivalent daily dose (LEDD) is mostly positively correlated with tyrosine and citrate in sporadic PD compared to pyruvate and phenylalanine in genetic PD. Cerebrospinal fluid levels of alpha-synuclein were negatively correlated with alanine. Further metabolites and lipoproteins with discriminatory power for double mutation PD cases involved ornithine, 2-aminobutyrate and 2-hydroxybutyrate as well as for mitochondrial phenotypes via LDL phospholipid, apolipoprotein and cholesterol subfractions. Quantitative IVDr NMR serum spectroscopy is able to stratify PD patient samples of different etiology and can contribute to a wider understanding of the underlying metabolism-driven alterations e.g. in energy, amino acid, and lipoprotein metabolism. Though our overall cohort was large, major confounders such as age, sex and medication have a strong impact. That is why absolute quantification and detailed patient knowledge about metabolic confounders, is a premise for future translation of NMR serum spectroscopy to routine PD diagnostics.

Intravenous SARS-CoV-2 Spike protein induces neuroinflammation and alpha-synuclein accumulation in brain regions relevant to Parkinson's disease

BACKGROUND

Coronavirus disease 2019 (COVID-19) frequently presents with neurological symptoms in human patients and leads to long-lasting brain pathology in a hamster model. There is no overt SARS-CoV-2 virus replication in central neurons. Whether viral proteins are sufficient to cause this pathology requires further investigations. The SARS-CoV-2 Spike-protein S1-subunit (S1-protein) has recently gained interest for causing neuroinflammation and accelerating aggregation of alpha-synuclein (aSyn) in vitro. Here, we show the impact of S1-protein in a broad spectrum of brain regions after injection via three different application routes in C57/BL6 mice.

METHODS

S1-protein was administered either intranasally, intravenously or intracerebrally. We quantified aSyn immunoreactivity and phosphorylated aSyn (pS129), microglia and astrocyte reactivity, ACE2/Neuropilin-1 receptor expression, and parvalbumin-positive interneurons in limbic system, basal ganglia, and cortical regions 14 days post-application. Plasma cytokine profiles were assessed 6 days post-injection.

RESULTS

While intracerebral injection resulted in decreased aSyn immunoreactivity with increased pS129 in males, intravenous injection led to increased levels of aSyn immunoreactivity and microglia cell density, predominantly in brain regions associated with Parkinson's disease pathology. Intranasal application of S1-protein induced microgliosis in some brain regions but resulted in sex-dependent alterations of aSyn levels, with increases in females and decreases in males. All routes showed sex-dependent alterations in astrocytic reactivity, receptor expression, and parvalbumin-positive interneurons.

CONCLUSION

Our results demonstrate that S1-protein itself leads to neuroinflammation, altered aSyn homeostasis, and disruption of inhibitory circuits in a route- and sex-dependent manner. These findings indicate the possibility of S1-protein being a crucial agent for both neuroinflammatory processes and altered protein regulation mechanisms. S1-protein trapped in tissue reservoirs could therefore explain symptoms occurring or persisting beyond viral clearance (Post COVID-19 condition).

Nose-to-brain drug delivery: from bench to bedside

There is increasing interest in nose-to-brain delivery as an innovative drug delivery strategy for neurodegenerative disorders such as Parkinson's or Alzheimer's disease. The unique anatomy of the nose-brain interface facilitates direct drug transport via the olfactory and trigeminal pathways to the brain, bypassing the blood-brain barrier. Different administration techniques as well as advanced drug formulations like targeted nanoparticles and thermoresponsive systems have been explored to improve the delivery efficiency and the therapeutic efficacy. This review provides an up-to-date perspective on this fast-developing field, and discusses different studies on safety and pharmacokinetic properties. A thorough evaluation of preclinical and clinical studies reveals both promises and challenges of this delivery method, highlighting approved drugs for the treatment of epilepsy and migraine that successfully utilize intranasal routes. The current landscape of research on nose-to-brain delivery is critically discussed, and a rationale is provided for ongoing research to optimize therapeutic strategies.

Leveraging animal models to understand non-motor symptoms of Parkinson's disease

Parkinson's disease is diagnosed based on motor symptoms, but non-motor symptoms of the disease, such as cognitive impairment, autonomic dysfunction, hyposmia, sleep disorders, and psychiatric disorders heavily impact patient and caregiver quality of life. It has proven challenging to faithfully reproduce and quantify these non-motor phenotypes. Indeed, many non-motor signs in animals that may phenotypically resemble features in patients may be caused by different mechanisms or may not be consistent within the same or similar models. In this review, we survey the existing literature on the assessment of non-motor signs in parkinsonian rodents and non-human primates. We highlight the gaps in our understanding and suggest how researchers might improve experimental designs to produce more meaningful results with the hope of better understanding the disease and developing better therapies.

The basolateral amygdala and striatum propagate alpha-synuclein pathology causing increased fear response in a Parkinson's disease model

Alpha-synuclein (aSyn)-related pathology crucially contributes to the pathogenesis of Parkinson's disease, a frequent and incurable neurodegenerative disease characterized by progressive motor and non-motor symptoms. Anxiety and fear- related neuropsychiatric symptoms develop frequently and early in the disease, but a lack of understanding of pathogenesis hampers rational therapy. This study aimed to decipher whether aSyn pathology in the basolateral amygdala (BLA) is causative of fear and anxiety. Bilateral stereotaxic injections of human aSyn-preformed amyloid fibrils (PFF) in BLA, striatum, or substantia nigra were conducted in female mice overexpressing human aSyn (Thy1-aSyn) and in wildtype littermates (WT). We characterized the propagation of aSyn pathology and related neuropathological changes across brain regions and examined the behavioral and fear responses in mice up to 2 months post-injection of PFF. While PFF injections induced local aSyn fibril pathology close to all respective injection sites in transgenic mice, we observed differences in propagation, downstream pathology and behavioral alterations. The BLA and the striatum, but not the substantia nigra, effectively propagated aSyn pathology to connected brain regions at 2.5 months post injection. This involved enhanced microgliosis and astrogliosis in the nigrostriatal system and loss of GABAergic parvalbuminergic interneurons in the striatum and corticolimbic brain regions. Intra-BLA PFF injections resulted in increased cued fear response in both transgenic mice and WT mice at 1 month post injection. The effect was more pronounced in the transgenic mice. Conversely, intra-striatal PFF injections enhanced contextual fear in WT at 2 months post injection. These findings imply that increased fear is inducible by aSyn pathology, especially if originating in the BLA or striatum. Furthermore, both regions are hub regions of aSyn pathology propagation, thereby contributing to disease progression. These insights provide mechanisms that can guide rational therapeutic development.

Alpha-Synuclein Phosphomimetic Y39E and S129D Knock-In Mice Show Cytosolic Alpha-Synuclein Localization without Developing Neurodegeneration or Motor Deficits

Parkinson's disease (PD) is a progressive neurodegenerative disorder characterized by motor and nonmotor symptoms. Its pathological hallmarks include the accumulation of misfolded alpha-synuclein (α-Syn) in Lewy bodies and Lewy neurites. Phosphorylation of α-Syn is a prominent feature of these inclusions, but its role in disease pathogenesis remains unclear. To identify the role of α-Syn phosphorylation in synucleinopathy, we generated two Snca knock-in (KI) mouse models carrying phosphomimetic mutations at SncaY39 or SncaS129 (SncaY39E or SncaS129D ) which manipulated epitopes phosphorylated in the PD brain. Both SncaY39E and SncaS129D KI mice displayed increased α-Syn phosphorylation, enhanced oligomer formation, and a shift of α-Syn localization from membrane-bound to cytoplasm. However, neurodegeneration in the substantia nigra was not observed up to 24 months of age. These findings demonstrate that mimicking the phosphorylation of Y39 or S129 can induce endogenous α-Syn phosphorylation. Still, a single phosphomimetic mutation alone is insufficient to induce PD-like behavior and pathology in the mouse's lifespan. Overall, our study provides a mouse model for investigating the role of phosphorylation at Y39 and S129 α-Syn epitopes in vivo.

Alterations in non-REM sleep and EEG spectra precede REM-sleep deficits in a model of synucleinopathy

BackgroundSleep disturbances often precede motor symptoms in neurodegenerative diseases like Parkinson's disease (PD) and dementia with Lewy bodies (DLB). Neuroinflammation is implicated in PD pathophysiology and may contribute to non-motor symptoms such as sleep disturbances. The Thy1-αSyn mouse model, overexpressing human alpha-synuclein (αSyn), mimics key aspects of PD and DLB, making it valuable for studying related sleep disturbances and neuroinflammatory changes.ObjectiveTo investigate early-stage alterations in sleep architecture, electroencephalographic (EEG) patterns, and neuroinflammation in Thy1-αSyn mice.MethodsWe used telemetric EEG/electromyography (EMG) with video surveillance to compare sleep patterns and EEG spectral power between 2.5- and 4.5-month-old male Thy1-αSyn transgenic mice and wild-type littermates. Neuroinflammation was assessed by examining microglial (Iba1) and astrocytic (GFAP) activation in key sleep-regulating brain regions.ResultsThy1-αSyn mice showed decreased resting wake time and increased non-REM sleep, with altered sleep bout frequency and length, indicating significant sleep architecture changes. Spectral analysis revealed a shift from higher to lower frequency bands, suggesting early neural circuitry disruptions due to αSyn overexpression. Significant microglial activation was observed at 3 months, with astrogliosis progressing by 5 months in key sleep-regulating regions, indicating that neuroinflammation may contribute to the observed sleep disturbances.ConclusionsEarly-stage Thy1-αSyn mice exhibit significant sleep architecture changes, EEG spectral shifts, and neuroinflammatory alterations. These findings suggest that neuroinflammation may play a role in the initial pathophysiological changes in PD and related synucleinopathies. Sleep, EEG, and neuroinflammatory changes could serve as early biomarkers for these diseases.

Deciphering motor dysfunction and microglial activation in mThy1-α-synuclein mice: a comprehensive study of behavioral, gene expression, and methylation changes

Introduction

Growing recognition of microglia's role in neurodegenerative disorders has accentuated the need to characterize microglia profiles and their influence on pathogenesis. To understand changes observed in the microglial profile during the progression of synucleinopathies, microglial gene expression and DNA methylation were examined in the mThy1-α-synuclein mouse model.

Methods

Disease progression was determined using behavioral tests evaluating locomotor deficits before DNA and RNA extraction at 7 and 10 months from isolated microglia for enzymatic methyl-sequencing and RNA-sequencing.

Results

Pathway analysis of these changes at 7 months indicates a pro-inflammatory profile and changes in terms related to synaptic maintenance. Expression and methylation at both 7 and 10 months included terms regarding mitochondrial and metabolic stress. While behavior symptoms progressed at 10 months, we see many previously activated pathways being inhibited in microglia at a later stage, with only 8 of 53 shared pathways predicted to be directionally concordant. Despite the difference in pathway directionality, 21 of the 22 genes that were differentially expressed and annotated to differentially methylated regions at both 7 and 10 months had conserved directionality changes.

Discussion

These results highlight a critical period in disease progression, during which the microglia respond to α-synuclein, suggesting a transition in the role of microglia from the early to late stages of the disease.

Alpha synuclein overexpression can drive microbiome dysbiosis in mice

Growing evidence indicates that persons with Parkinson disease (PD), have a unique composition of indigenous gut microbes. Given the long prodromal or pre-diagnosed period, longitudinal studies of the human and rodent gut microbiome before symptomatic onset and for the duration of the disease are currently lacking. PD is partially characterized by the accumulation of the protein α-synuclein (α-syn) into insoluble aggregates, in both the central and enteric nervous systems. As such, several experimental rodent and non-human primate models of α-syn overexpression recapitulate some of the hallmark pathophysiologies of PD. These animal models provide an opportunity to assess how the gut microbiome changes with age under disease-relevant conditions. Here, we used a transgenic mouse strain, which overexpress wild-type human α-syn to test how the gut microbiome composition responds in this model of PD pathology during aging. Using shotgun metagenomics, we find significant, age and genotype-dependent bacterial taxa whose abundance becomes altered with age. We reveal that α-syn overexpression can drive alterations to the gut microbiome composition and suggest that it limits diversity through age. Taxa that were most affected by genotype-age interaction were Lactobacillus and Bifidobacteria. In a mouse model, we showed direct link between alpha synuclein geneotype (hallmark of PD), a dysbiotic and low-diversity gut microbiome, and dysbiotic levels of Bifidobacteria and Lactobacillus (most robust features of PD microbiome). Given emerging data on the potential contributions of the gut microbiome to PD pathologies, our data provide an experimental foundation to understand how the PD-associated microbiome may arise as a trigger or co-pathology to disease.

Alpha-synuclein pathology enhances peripheral and CNS immune responses to bacterial endotoxins

Increasing evidence points to infectious diseases as contributor to the pathogenesis of neurodegeneration in Parkinson's disease (PD), probably driven by a peripheral and CNS inflammatory response together with alpha-synuclein (aSyn) pathology. Pro-inflammatory lipopolysaccharide (LPS) endotoxin is suggested as a risk factor, and LPS shedding gram-negative bacteria are more prevalent in the gut-microbiome of PD patients. Here, we investigated whether LPS could contribute to the neurodegenerative disease progression via neuroinflammation, especially under conditions of aSyn pathology. To investigate this, we created a double-hit model based on the Thy1-aSyn mouse line (line 61), an established aSyn-overexpression model of PD, exposed to a single intraperitoneal injection of LPS at a dose of 0.8 mg/kg (equivalent to approximately 1,200,000 EU/kg). Clinical parameters, flow cytometry of blood and immune cells in the brain, brain immunohistology and motor behavior were evaluated over time. As expected, the LPS dosage induced transient acute symptoms and mild weight loss in mice, with full recovery after 7 days. In aSyn over-expressing mice, this single low dose of LPS was sufficient to alter the expression of specific markers on blood and brain immune cells and induced brain region-specific microgliosis that were present at 7 days post LPS injection. At 14 days post injection of LPS, aSyn expression was reduced in wild-type mice, indicating a specific response of the endogenous protein to the endotoxin. At this early time point, motor behavior is not yet robustly impacted by the observed pathological alterations. In conclusion, aSyn pathology renders the peripheral and central immune response more sensitive to a single low dose of bacterial endotoxin, which mimics a transient dysbiosis or gut infection. Thus, this data suggests that such peripheral triggers should be monitored in PD patients for instance by blood immune cell response as biomarkers. Furthermore, results from this study lend further support to the development of treatments aiming to reduce the impact of bacterial dysbiosis as a promising strategy to mitigate PD progression.

The role of amphipathic and cationic helical peptides in Parkinson's disease

Peptides are attracting a growing interest for therapeutic applications in biomedicine. In Parkinson's disease (PD), different human endogenous peptides have been associated with beneficial effects, including protein aggregation inhibition, reduced inflammation, or the protection of dopaminergic neurons. Such effects seem to be connected to the spatial arrangement of peptide side chains, and many of these human molecules share common conformational traits, displaying a distinctive amphipathic and cationic helical structure, which is believed to be crucial for their activities. This review delves into the relationship between these structural properties and the current evidence connecting biogenic peptides to the amelioration of PD symptoms. We discuss their implications in the disease, the different mechanisms of action, their state of validation, and their therapeutic potential.

Imaging spatial transcriptomics reveals molecular patterns of vulnerability to pathology in a transgenic α-synucleinopathy model

In Parkinson's disease and dementia with Lewy bodies, aggregated and phosphorylated α-synuclein pathology appears in select neurons throughout cortical and subcortical regions, but little is currently known about why certain populations are selectively vulnerable. Here, using imaging spatial transcriptomics (IST) coupled with downstream immunofluorescence for α-synuclein phosphorylated at Ser129 (pSyn) in the same tissue sections, we identified neuronal subtypes in the cortex and hippocampus of transgenic human α-synuclein-overexpressing mice that preferentially developed pSyn pathology. Additionally, we investigated the transcriptional underpinnings of this vulnerability, pointing to expression of Plk2, which phosphorylates α-synuclein at Ser129, and human SNCA (hSNCA), as key to pSyn pathology development. Finally, we performed differential expression analysis, revealing gene expression changes broadly downstream of hSNCA overexpression, as well as pSyn-dependent alterations in mitochondrial and endolysosomal genes. Overall, this study yields new insights into the formation of α-synuclein pathology and its downstream effects in a synucleinopathy mouse model.

α-synuclein overexpression and the microbiome shape the gut and brain metabolome in mice

Pathological forms of α-synuclein contribute to synucleinopathies, including Parkinson's disease (PD). Most cases of PD arise from gene-environment interactions. Microbiome composition is altered in PD, and gut bacteria are causal to symptoms in animal models. We quantitatively profiled nearly 630 metabolites in the gut, plasma, and brain of α-synuclein-overexpressing (ASO) mice, compared to wild-type (WT) animals, and comparing germ-free (GF) to specific pathogen-free (SPF) animals (n = 5 WT-SPF; n = 6 ASO-SPF; n = 6 WT-GF; n = 6 ASO-GF). Many differentially expressed metabolites in ASO mice are also dysregulated in human PD patients, including amine oxides, bile acids and indoles. The microbial metabolite trimethylamine N-oxide (TMAO) strongly correlates from the gut to the plasma to the brain in mice, notable since TMAO is elevated in the blood and cerebrospinal fluid of PD patients. These findings uncover broad metabolomic changes that are influenced by the intersection of host genetics and microbiome in a mouse model of PD.

Olfactory deficit and gastrointestinal dysfunction precede motor abnormalities in alpha-Synuclein G51D knock-in mice

Parkinson's disease (PD) is typically a sporadic late-onset disorder, which has made it difficult to model in mice. Several transgenic mouse models bearing mutations in SNCA, which encodes alpha-Synuclein (α-Syn), have been made, but these lines do not express SNCA in a physiologically accurate spatiotemporal pattern, which limits the ability of the mice to recapitulate the features of human PD. Here, we generated knock-in mice bearing the G51D SNCA mutation. After establishing that their motor symptoms begin at 9 mo of age, we then sought earlier pathologies. We assessed the phosphorylation at Serine 129 of α-Syn in different tissues and detected phospho-α-Syn in the olfactory bulb and enteric nervous system at 3 mo of age. Olfactory deficit and impaired gut transit followed at 6 mo, preceding motor symptoms. The SncaG51D mice thus parallel the progression of human PD and will enable us to study PD pathogenesis and test future therapies.

Suppression of the JAK/STAT pathway inhibits neuroinflammation in the line 61-PFF mouse model of Parkinson's disease

Parkinson's disease (PD) is characterized by neuroinflammation, progressive loss of dopaminergic neurons, and accumulation of α-synuclein (α-Syn) into insoluble aggregates called Lewy pathology. The Line 61 α-Syn mouse is an established preclinical model of PD; Thy-1 is used to promote human α-Syn expression, and features of sporadic PD develop at 9-18 months of age. To accelerate the PD phenotypes, we injected sonicated human α-Syn preformed fibrils (PFFs) into the striatum, which produced phospho-Syn (p-α-Syn) inclusions in the substantia nigra pars compacta and significantly increased MHC Class II-positive immune cells. Additionally, there was enhanced infiltration and activation of innate and adaptive immune cells in the midbrain. We then used this new model, Line 61-PFF, to investigate the effect of inhibiting the JAK/STAT signaling pathway, which is critical for regulation of innate and adaptive immune responses. After administration of the JAK1/2 inhibitor AZD1480, immunofluorescence staining showed a significant decrease in p-α-Syn inclusions and MHC Class II expression. Flow cytometry showed reduced infiltration of CD4+ T-cells, CD8+ T-cells, CD19+ B-cells, dendritic cells, macrophages, and endogenous microglia into the midbrain. Importantly, single-cell RNA-Sequencing analysis of CD45+ cells from the midbrain identified 9 microglia clusters, 5 monocyte/macrophage (MM) clusters, and 5 T-cell (T) clusters, in which potentially pathogenic MM4 and T3 clusters were associated with neuroinflammatory responses in Line 61-PFF mice. AZD1480 treatment reduced cell numbers and cluster-specific expression of the antigen-presentation genes H2-Eb1, H2-Aa, H2-Ab1, and Cd74 in the MM4 cluster and proinflammatory genes such as Tnf, Il1b, C1qa, and C1qc in the T3 cluster. Together, these results indicate that inhibiting the JAK/STAT pathway suppresses the activation and infiltration of innate and adaptive cells, reducing neuroinflammation in the Line 61-PFF mouse model.

Blood-brain barrier alterations and their impact on Parkinson's disease pathogenesis and therapy

There is increasing evidence for blood-brain barrier (BBB) alterations in Parkinson's disease (PD), the second most common neurodegenerative disorder with rapidly rising prevalence. Altered tight junction and transporter protein levels, accumulation of α-synuclein and increase in inflammatory processes lead to extravasation of blood molecules and vessel degeneration. This could result in a self-perpetuating pathophysiology of inflammation and BBB alteration, which contribute to neurodegeneration. Toxin exposure or α-synuclein over-expression in animal models has been shown to initiate similar pathologies, providing a platform to study underlying mechanisms and therapeutic interventions. Here we provide a comprehensive review of the current knowledge on BBB alterations in PD patients and how rodent models that replicate some of these changes can be used to study disease mechanisms. Specific challenges in assessing the BBB in patients and in healthy controls are discussed. Finally, a potential role of BBB alterations in disease pathogenesis and possible implications for therapy are explored. The interference of BBB alterations with current and novel therapeutic strategies requires more attention. Brain region-specific BBB alterations could also open up novel opportunities to target specifically vulnerable neuronal subpopulations.

Sex-specific biphasic alpha-synuclein response and alterations of interneurons in a COVID-19 hamster model

BACKGROUND

Coronavirus disease 2019 (COVID-19) frequently leads to neurological complications after recovery from acute infection, with higher prevalence in women. However, mechanisms by which SARS-CoV-2 disrupts brain function remain unclear and treatment strategies are lacking. We previously demonstrated neuroinflammation in the olfactory bulb of intranasally infected hamsters, followed by alpha-synuclein and tau accumulation in cortex, thus mirroring pathogenesis of neurodegenerative diseases such as Parkinson's or Alzheimer's disease.

METHODS

To uncover the sex-specific spatiotemporal profiles of neuroinflammation and neuronal dysfunction following intranasal SARS-CoV-2 infection, we quantified microglia cell density, alpha-synuclein immunoreactivity and inhibitory interneurons in cortical regions, limbic system and basal ganglia at acute and late post-recovery time points.

FINDINGS

Unexpectedly, microglia cell density and alpha-synuclein immunoreactivity decreased at 6 days post-infection, then rebounded to overt accumulation at 21 days post-infection. This biphasic response was most pronounced in amygdala and striatum, regions affected early in Parkinson's disease. Several brain regions showed altered densities of parvalbumin and calretinin interneurons which are involved in cognition and motor control. Of note, females appeared more affected.

INTERPRETATION

Our results demonstrate that SARS-CoV-2 profoundly disrupts brain homeostasis without neuroinvasion, via neuroinflammatory and protein regulation mechanisms that persist beyond viral clearance. The regional patterns and sex differences are in line with neurological deficits observed after SARS-CoV-2 infection.

FUNDING

Federal Ministry of Health, Germany (BMG; ZMV I 1-2520COR501 to G.G.), Federal Ministry of Education and Research, Germany (BMBF; 03COV06B to G.G.), Ministry of Science and Culture of Lower Saxony in Germany (14-76403-184, to G.G. and F.R.).

Cysteamine HCl Administration Impedes Motor and Olfactory Functions, Accompanied by a Reduced Number of Dopaminergic Neurons, in Experimental Mice: A Preclinical Mimetic Relevant to Parkinson's Disease

Cysteamine hydrochloride (Cys-HCl) has been established as a potent ulcerogenic agent of the gastrointestinal (GI) system. GI dysfunction and olfactory deficits are the most common clinical symptoms of many movement disorders, including Parkinson's disease (PD). Cys-HCl has been shown to interfere with dopamine, a neurotransmitter crucial for motor, olfactory, and cognitive functions. However, the reports on the effect of Cys-HCl treatment on the behavioral aspects and functions of the dopamine system appear to be inconsistent. Therefore, we revisited the impact of Cys-HCl on the motor function in experimental mice using a battery of behavioral tests, such as the pole test (PT), beam-walking test (BWT), and rotarod test (RDT), while the olfactory ability and cognitive functions were examined through the buried-food test (BFT) and Y-maze test. Furthermore, we investigated the effect of Cys-HCl on the number of dopaminergic tyrosine hydroxylase (TH)-positive cells in the substantia nigra (SN) and olfactory bulb (OB) of the experimental mice using immunohistochemistry. The results revealed that Cys-HCl administration in the mice induced significant impairments in their motor balance and coordination, as their movement-related performances were markedly reduced in terms of the behavioral tasks. Mice exposed to Cys-HCl showed pronounced reductions in their odor discrimination abilities as well as cognitive impairments. Strikingly, the number of TH-positive neurons was found to be reduced in the SN and OB of the Cys-HCl-treated group, which is a bonafide neuropathogenic hallmark of PD. This study highlights the potential neurotoxic effects of Cys-HCl in experimental brains and suggests further investigation into its role in the pathogenesis of Parkinsonism.

Suppression of the JAK/STAT Pathway Inhibits Neuroinflammation in the Line 61-PFF Mouse Model of Parkinson's Disease

Parkinson's disease (PD) is characterized by neuroinflammation, progressive loss of dopaminergic neurons, and accumulation of a-synuclein (a-Syn) into insoluble aggregates called Lewy pathology. The Line 61 a-Syn mouse is an established preclinical model of PD; Thy-1 is used to promote human a-Syn expression, and features of sporadic PD develop at 9-18 months of age. To accelerate the PD phenotypes, we injected sonicated human a-Syn preformed fibrils (PFFs) into the striatum, which produced phospho-Syn (p-a-Syn) inclusions in the substantia nigra pars compacta and significantly increased MHC Class II-positive immune cells. Additionally, there was enhanced infiltration and activation of innate and adaptive immune cells in the midbrain. We then used this new model, Line 61-PFF, to investigate the effect of inhibiting the JAK/STAT signaling pathway, which is critical for regulation of innate and adaptive immune responses. After administration of the JAK1/2 inhibitor AZD1480, immunofluorescence staining showed a significant decrease in p-a-Syn inclusions and MHC Class II expression. Flow cytometry showed reduced infiltration of CD4+ T-cells, CD8+ T-cells, CD19+ B-cells, dendritic cells, macrophages, and endogenous microglia into the midbrain. Importantly, single-cell RNA-Sequencing analysis of CD45+ cells from the midbrain identified 9 microglia clusters, 5 monocyte/macrophage (MM) clusters, and 5 T-cell (T) clusters, in which potentially pathogenic MM4 and T3 clusters were associated with neuroinflammatory responses in Line 61-PFF mice. AZD1480 treatment reduced cell numbers and cluster-specific expression of the antigen-presentation genes H2-Eb1, H2-Aa, H2-Ab1, and Cd74 in the MM4 cluster and proinflammatory genes such as Tnf, Il1b, C1qa, and C1qc in the T3 cluster. Together, these results indicate that inhibiting the JAK/STAT pathway suppresses the activation and infiltration of innate and adaptive cells, reducing neuroinflammation in the Line 61-PFF mouse model.

Infections in the Etiology of Parkinson's Disease and Synucleinopathies: A Renewed Perspective, Mechanistic Insights, and Therapeutic Implications

Increasing evidence suggests a potential role for infectious pathogens in the etiology of synucleinopathies, a group of age-related neurodegenerative disorders including Parkinson's disease (PD), multiple system atrophy and dementia with Lewy bodies. In this review, we discuss the link between infections and synucleinopathies from a historical perspective, present emerging evidence that supports this link, and address current research challenges with a focus on neuroinflammation. Infectious pathogens can elicit a neuroinflammatory response and modulate genetic risk in PD and related synucleinopathies. The mechanisms of how infections might be linked with synucleinopathies as well as the overlap between the immune cellular pathways affected by virulent pathogens and disease-related genetic risk factors are discussed. Here, an important role for α-synuclein in the immune response against infections is emerging. Critical methodological and knowledge gaps are addressed, and we provide new future perspectives on how to address these gaps. Understanding how infections and neuroinflammation influence synucleinopathies will be essential for the development of early diagnostic tools and novel therapies.

Experimental Animal Models of Prodromal Parkinson's Disease

There is an estimated 35-45% loss of striatal dopamine at the time of diagnosis of Parkinson's disease (PD), and cases clinically diagnosed in the early stages may already be pathologically in advanced stages. Recent large-scale clinical trials of disease-modifying therapies (DMT) also suggest the necessity of targeting patients at earlier stages of the disease. From this perspective, the prodromal phase of PD is currently the focus of attention, emphasizing the need for a prodromal mouse model that accurately reflects the pathophysiology, along with early biomarkers. To establish prodromal animal model of PD with high face validity that reflects the disease state, the model must possess high construct validity that accurately incorporates clinical and pathological features in the prodromal phase. Furthermore, as a preclinical model of DMT, the model must possess high predictive validity to accurately evaluate the response to intervention. This review provides an overview of animal models which reflect the characteristics of prodromal PD, including alpha-synuclein (aS) accumulation and associated early non-motor symptoms, with a focus on the aS propagation model and genetic model. In addition, we discuss the challenges associated with these models. The genetic model often fails to induce motor symptoms, while aS propagation models skip the crucial step of initial aS aggregate formation, thereby not fully replicating the entire natural course of the disease. Identifying factors that induce the transition from prodromal to symptomatic phase is important as a preclinical model for DMT to prevent or delay the onset of the disease.

Anxiety in synucleinopathies: neuronal circuitry, underlying pathomechanisms and current therapeutic strategies

Synucleinopathies are neurodegenerative disorders characterized by alpha-synuclein (αSyn) accumulation in neurons or glial cells, including Parkinson's disease (PD), dementia with Lewy bodies (DLB), and multiple system atrophy (MSA). αSyn-related pathology plays a critical role in the pathogenesis of synucleinopathies leading to the progressive loss of neuronal populations in specific brain regions and the development of motor and non-motor symptoms. Anxiety is among the most frequent non-motor symptoms in patients with PD, but it remains underrecognized and undertreated, which significantly reduces the quality of life for patients. Anxiety is defined as a neuropsychiatric complication with characteristics such as nervousness, loss of concentration, and sweating due to the anticipation of impending danger. In patients with PD, neuropathology in the amygdala, a central region in the anxiety and fear circuitry, may contribute to the high prevalence of anxiety. Studies in animal models reported αSyn pathology in the amygdala together with alteration of anxiety or fear learning response. Therefore, understanding the progression, extent, and specifics of pathology in the anxiety and fear circuitry in synucleinopathies will suggest novel approaches to the diagnosis and treatment of neuropsychiatric symptoms. Here, we provide an overview of studies that address neuropsychiatric symptoms in synucleinopathies. We offer insights into anxiety and fear circuitry in animal models and the current implications for therapeutic intervention. In summary, it is apparent that anxiety is not a bystander symptom in these disorders but reflects early pathogenic mechanisms in the cortico-limbic system which may even contribute as a driver to disease progression.

Double-Edged Effects of Venglustat on Behavior and Pathology in Mice Overexpressing α-Synuclein

BACKGROUND

Venglustat is a brain-penetrant, small molecule inhibitor of glucosylceramide synthase used in clinical testing for treatment of Parkinson's disease (PD). Despite beneficial effects in certain cellular and rodent models, patients with PD with mutations in GBA, the gene for lysosomal glucocerebrosidase, experienced worsening of their motor function under venglustat treatment (NCT02906020, MOVES-PD, phase 2 trial).

OBJECTIVE

The objective of this study was to evaluate venglustat in mouse models of PD with overexpression of wild-type α-synuclein.

METHODS

Mice overexpressing α-synuclein (Thy1-aSyn line 61) or Gba-mutated mice with viral vector-induced overexpression of α-synuclein in the substantia nigra were administered venglustat as food admixture. Motor and cognitive performance, α-synuclein-related pathology, and microgliosis were compared with untreated controls.

RESULTS

Venglustat worsened motor function in Thy1-aSyn transgenics on the challenging beam and the pole test. Although venglustat did not alter the cognitive deficit in the Y-maze test, it alleviated anxiety-related behavior in the novel object recognition test. Venglustat reduced soluble and membrane-bound α-synuclein in the striatum and phosphorylated α-synuclein in limbic brain regions. Although venglustat reversed the loss of parvalbumin immunoreactivity in the basolateral amygdala, it tended to increase microgliosis and phosphorylated α-synuclein in the substantia nigra. Furthermore, venglustat also partially worsened motor performance and tended to increase neurofilament light chain in the cerebrospinal fluid in the Gba-deficient model with nigral α-synuclein overexpression and neurodegeneration.

CONCLUSIONS

Venglustat treatment in two mouse models of α-synuclein overexpression showed that glucosylceramide synthase inhibition had differential detrimental or beneficial effects on behavior and neuropathology possibly related to brain region-specific effects. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.