Α-syn Aggregation Research Articles

The PM20D1-NADA pathway protects against Parkinson's disease.

Parkinson's disease (PD) is characterized by the selective loss of dopaminergic neurons in the substantia nigra and the accumulation of α-synuclein (α-Syn) aggregates. However, the molecular mechanisms regulating α-Syn aggregation and neuronal degeneration remain poorly understood. The peptidase M20 domain containing 1 (PM20D1) gene lies within the PARK16 locus genetically linked to PD. Single nucleotide polymorphisms regulating PM20D1 expressionare associated with changed risk of PD. Dopamine (DA) metabolism and DA metabolites have been reported to regulate α-Syn pathology. Here we report that PM20D1 catalyzes the conversion of DA to N-arachidonoyl dopamine (NADA), which interacts with α-Syn and inhibits its aggregation. Simultaneously, NADA competes with α-Syn fibrils to regulate TRPV4-mediated calcium influx and downstream phosphatases, thus alleviating α-Syn phosphorylation. The expression of PM20D1 decreases during aging. Overexpression of PM20D1 or the administration of NADA in a mouse model of synucleinopathy alleviated α-Syn pathology, dopaminergic neurodegeneration, and motor impairments. These observations support the protective effect of the PM20D1-NADA pathway against the progression of α-Syn pathology in PD.

Neuroprotection of low dose carbon monoxide in Parkinson’s disease models commensurate with the reduced risk of Parkinson’s among smokers

Paradoxically, cigarette smoking is associated with a reduced risk of Parkinson’s Disease (PD). This led us to hypothesize that carbon monoxide (CO) levels, which are constitutively but modestly elevated in smokers, might contribute to neuroprotection. Using rodent models of PD based on α-synuclein (αSyn) accumulation and oxidative stress, we show that low-dose CO mitigates neurodegeneration and reduces αSyn pathology. Oral CO administration activated signaling cascades mediated by heme oxygenase-1 (HO-1), which have been implicated in limiting oxidative stress, and in promoting αSyn degradation, thereby conferring neuroprotection. Consistent with the neuroprotective effect of smoking, HO-1 levels in cerebrospinal fluid were higher in human smokers compared to nonsmokers. Moreover, in PD brain samples, HO-1 levels were higher in neurons without αSyn pathology. Thus, CO in rodent PD models reduces pathology and increases oxidative stress responses, phenocopying possible protective effects of smoking evident in PD patients. These data highlight the potential for low-dose CO-modulated pathways to slow symptom onset and limit pathology in PD patients.

Microglia-specific IL-10 gene delivery inhibits neuroinflammation and neurodegeneration in a mouse model of Parkinson's disease.

Neuroinflammation plays a key role in exacerbating dopaminergic neuron (DAN) loss in Parkinson's disease (PD). However, it remains unresolved how to effectively normalize this immune response given the complex interplay between the innate and adaptive immune responses occurring within a scarcely accessible organ like the brain. In this study, we uncovered a consistent correlation between neuroinflammation, brain parenchymal lymphocytes, and DAN loss among several commonly used mouse models of PD generated by a variety of pathological triggers. We validated a viral therapeutic approach for the microglia-specific expression of interleukin 10 (IL-10) to selectively mitigate the excessive inflammatory response. We found that this approach induced a local nigral IL-10 release that alleviated DAN loss in mice overexpressing the human SNCA gene in the substantia nigra. Single-cell transcriptomics revealed that IL-10 induced the emergence of a molecularly distinct microglial cell state, enriched in markers of cell activation with enhanced expression of prophagocytic pathways. IL-10 promoted microglial phagocytotic and clearance activities in vitro and reduced αSYN aggregate burden in the nigral area in mice overexpressing SNCA. Furthermore, IL-10 stimulated the differentiation of CD4+ T lymphocytes into active T regulatory cells and promoted inhibitory characteristics in CD8+ T cells. In summary, our results show that local and microglia-specific IL-10 transduction elicited strong immunomodulation in the nigral tissue with enhanced suppression of lymphocyte toxicity that was associated with DAN survival. These results offer insights into the therapeutic benefits of IL-10 and showcase a promising gene delivery approach that could minimize undesired side effects.

Posttranslational Modifications of α-Synuclein, Their Therapeutic Potential, and Crosstalk in Health and Neurodegenerative Diseases.

α-Synuclein (α-Syn) aggregation in Lewy bodies and Lewy neurites has emerged as a key pathogenetic feature in Parkinson's disease, dementia with Lewy bodies, and multiple system atrophy. Various factors, including posttranslational modifications (PTMs), can influence the propensity of α-Syn to misfold and aggregate. PTMs are biochemical modifications of a protein that occur during or after translation and are typically mediated by enzymes. PTMs modulate several characteristics of proteins including their structure, activity, localization, and stability. α-Syn undergoes various posttranslational modifications, including phosphorylation, ubiquitination, SUMOylation, acetylation, glycation, O-GlcNAcylation, nitration, oxidation, polyamination, arginylation, and truncation. Different PTMs of a protein can physically interact with one another or work together to influence a particular physiological or pathological feature in a process known as PTMs crosstalk. The development of detection techniques for the cooccurrence of PTMs in recent years has uncovered previously unappreciated mechanisms of their crosstalk. This has led to the emergence of evidence supporting an association between α-Syn PTMs crosstalk and synucleinopathies. In this review, we provide a comprehensive evaluation of α-Syn PTMs, their impact on misfolding and pathogenicity, the pharmacological means of targeting them, and their potential as biomarkers of disease. We also highlight the importance of the crosstalk between these PTMs in α-Syn function and aggregation. Insight into these PTMS and the complexities of their crosstalk can improve our understanding of the pathogenesis of synucleinopathies and identify novel targets of therapeutic potential. SIGNIFICANCE STATEMENT: α-Synuclein is a key pathogenic protein in Parkinson's disease and other synucleinopathies, making it a leading therapeutic target for disease modification. Multiple posttranslational modifications occur at various sites in α-Synuclein and alter its biophysical and pathological properties, some interacting with one another to add to the complexity of the pathogenicity of this protein. This review details these modifications, their implications in disease, and potential therapeutic opportunities.

Role of Lipids in the Pathogenesis of Parkinson's Disease.

Aggregation of α-synuclein (αSyn) and its accumulation as Lewy bodies play a central role in the pathogenesis of Parkinson's disease (PD). However, the mechanism by which αSyn aggregates in the brain remains unclear. Biochemical studies have demonstrated that αSyn interacts with lipids, and these interactions affect the aggregation process of αSyn. Furthermore, genetic studies have identified mutations in lipid metabolism-associated genes such as glucocerebrosidase 1 (GBA1) and synaptojanin 1 (SYNJ1) in sporadic and familial forms of PD, respectively. In this review, we focus on the role of lipids in triggering αSyn aggregation in the pathogenesis of PD and propose the possibility of modulating the interaction of lipids with αSyn as a potential therapy for PD.

Motor Cortical Neuronal Hyperexcitability Associated with α-Synuclein Aggregation.

Dysfunction of the cerebral cortex is thought to underlie motor and cognitive impairments in Parkinson disease (PD). While cortical function is known to be suppressed by abnormal basal ganglia output following dopaminergic degeneration, it remains to be determined how the deposition of Lewy pathology disrupts cortical circuit integrity and function. Moreover, it is also unknown whether cortical Lewy pathology and midbrain dopaminergic degeneration interact to disrupt cortical function in late-stage. To begin to address these questions, we injected α-synuclein (αSyn) preformed fibrils (PFFs) into the dorsolateral striatum of mice to seed αSyn pathology in the cortical cortex and induce degeneration of midbrain dopaminergic neurons. Using this model system, we reported that αSyn aggregates accumulate in the motor cortex in a layer- and cell-subtype-specific pattern. Particularly, intratelencephalic neurons (ITNs) showed earlier accumulation and greater extent of αSyn aggregates relative to corticospinal neurons (CSNs). Moreover, we demonstrated that the intrinsic excitability and inputs resistance of αSyn aggregates-bearing ITNs in the secondary motor cortex (M2) are increased, along with a noticeable shrinkage of cell bodies and loss of dendritic spines. Last, neither the intrinsic excitability of CSNs nor their thalamocortical input was altered by a partial striatal dopamine depletion associated with αSyn pathology. Our results documented motor cortical neuronal hyperexcitability associated with αSyn aggregation and provided a novel mechanistic understanding of cortical circuit dysfunction in PD.

Understanding alpha-synuclein aggregation propensity in animals and humans

Alpha-synuclein (α-syn) aggregation plays a critical role in the pathogenicity of Parkinson's Disease (PD). This study aims to evaluate the aggregation propensity of α-syn fragment peptides designed using the variability found in humans and animals. Thioflavin T (ThT) and transmission electron microscopy (TEM) were used to validate the formation of fibrils to identify important amino acid residues. Human α-syn fragments 51–75, 37–61, 62–86, 76–100, and 116–140 demonstrate a significantly higher tendency to aggregate compared to fragments 1–25, 26–50, and 91–115. All species analyzed of the α-syn 37–61 and 62–86 regions were shown to form fibrils on both ThT and TEM. The α-syn 37–61 and 62–86 fragment regions exhibited a high susceptibility to aggregation, with fibril formation observed in all species. The A53T mutation in several α-syn 37–61 fragments may enhance their propensity for aggregation, suggesting a correlation between this mutation and the capacity for fibril formation. Furthermore, the presence of the non-amyloid-β component (NAC) region, specifically in α-syn 62–86, was consistently observed in several fragments that displayed fibril formation, indicating a potential correlation between the NAC region and the process of fibril formation in α-syn. Finally, the combination of a high quantity of valine and a low quantity of acidic amino acids in these fragments may serve as indicators of α-syn fibril formation.

Lipids and α-Synuclein: adding further variables to the equation.

Aggregation of alpha-Synuclein (αSyn) has been connected to several neurodegenerative diseases, such as Parkinson's disease (PD), dementia with Lewy Bodies (DLB), and multiple system atrophy (MSA), that are collected under the umbrella term synucleinopathies. The membrane binding abilities of αSyn to negatively charged phospholipids have been well described and are connected to putative physiological functions of αSyn. Consequently, αSyn-related neurodegeneration has been increasingly connected to changes in lipid metabolism and membrane lipid composition. Indeed, αSyn aggregation has been shown to be triggered by the presence of membranes in vitro, and some genetic risk factors for PD and DLB are associated with genes coding for proteins directly involved in lipid metabolism. At the same time, αSyn aggregation itself can cause alterations of cellular lipid composition and brain samples of patients also show altered lipid compositions. Thus, it is likely that there is a reciprocal influence between cellular lipid composition and αSyn aggregation, which can be further affected by environmental or genetic factors and ageing. Little is known about lipid changes during physiological ageing and regional differences of the lipid composition of the aged brain. In this review, we aim to summarise our current understanding of lipid changes in connection to αSyn and discuss open questions that need to be answered to further our knowledge of αSyn related neurodegeneration.

Different neurotoxicity and seeding activity between α-synuclein oligomers formed in plasma of patients with Parkinson’s disease and multiple system atrophy

Previous studies have shown that α-synuclein (α-Syn) aggregates derived from the brains of patients with Parkinson’s disease (PD) and multiple system atrophy (MSA) exhibit different phosphorylation, cytotoxicity, and seeding activity. However, the mechanism underlying the differences remains poorly understood. Here, recombinant human α-Syn was incubated in the plasma of patients with PD and MSA, and the oligomers formed in the plasma (PD-O-α-Syn and MSA-O-α-Syn) were purified and analyzed for their phosphorylation, cytotoxicity and seeding activity. In vitro assays revealed that both PD-O-α-Syn and MSA-O-α-Syn were phosphorylated at serine 129. However, the phosphorylation degree of MSA-O-α-Syn was significantly higher than that of PD-O-α-Syn. In addition, MSA-O-α-Syn exhibited stronger cytotoxicity and seeding activity compared with PD-O-α-Syn. In vivo experiments showed that mice receiving intrastriatal inoculation of MSA-O-α-Syn developed more severe motor dysfunction and dopaminergic degeneration than mice receiving intrastriatal inoculation of PD-O-α-Syn. Compared with the mice inoculated with PD-O-α-Syn, the mice inoculated with MSA-O-α-Syn accumulated more phosphorylated and oligomerized α-Syn in the striatum and brain regions (substantia nigra, hippocampus and prefrontal cortex) away from the inoculated site. The results obtained suggest that α-Syn oligomers formed in PD and MSA plasma are different in phosphorylation, cytotoxicity, and seeding activity.

Novel Therapeutic Horizons: SNCA Targeting in Parkinson's Disease.

Alpha-synuclein (αSyn) aggregates are the primary component of Lewy bodies, which are pathological hallmarks of Parkinson's disease (PD). The toxicity of αSyn seems to increase with its elevated expression during injury, suggesting that therapeutic approaches focused on reducing αSyn burden in neurons could be beneficial. Additionally, studies have shown higher levels of SNCA mRNA in the midbrain tissues and substantia nigra dopaminergic neurons of sporadic PD post-mortem brains compared to controls. Therefore, the regulation of SNCA expression and inhibition of αSyn synthesis could play an important role in the pathogenesis of injury, resulting in an effective treatment approach for PD. In this context, we summarized the most recent and innovative strategies proposed that exploit the targeting of SNCA to regulate translation and efficiently knock down cytoplasmatic levels of αSyn. Significant progress has been made in developing antisense technologies for treating PD in recent years, with a focus on antisense oligonucleotides and short-interfering RNAs, which achieve high specificity towards the desired target. To provide a more exhaustive picture of this research field, we also reported less common but highly innovative strategies, including small molecules, designed to specifically bind 5'-untranslated regions and, targeting secondary nucleic acid structures present in the SNCA gene, whose formation can be modulated, acting as a transcription and translation control. To fully describe the efficiency of the reported strategies, the effect of αSyn reduction on cellular viability and dopamine homeostasis was also considered.

Rotenone and Its Derivative, Rotenoisin A, Induce Neurodegeneration Differentially in SH-SY5Y Cells.

Rotenone (ROT), the most significant rotenoid, which has shown anticancer activity, has also been reported to be toxic to normal cells, inducing Parkinson's disease (PD)-like neuronal loss with aggregation of α-synuclein (α-syn). To reduce the adverse effects of ROT, its derivative, rotenoisin A (ROA), is obtained by directly irradiating a ROT solution in methanol using γ-rays, which has been reported for potential anticancer properties. However, its PD-inducing effects have not yet been researched or reported. This study sought to compare the activities of ROA and ROT on the aggregation of α-syn, apoptosis, and autophagy in SH-SY5Y cells. ROA decreased cell survival less when compared with ROT on SH-SY5Y cells at 48 h in a dose-dependent manner. ROT (0.5 and 1 μM) and ROA (4 and 5 μM) decreased the expression of tyrosine hydroxylase. Western blot analysis of the Triton X-100 insoluble fraction revealed that both ROT and ROA significantly increased the levels of oligomeric, dimeric, and monomeric phosphorylated Serine129 α-syn and total monomeric α-syn. Moreover, both compounds decreased the proportion of neuronal nuclei, the neurofilament-heavy chain, and β3-tubulin. The phosphorylation of ERK and SAPK were reduced, whereas ROA did not act on Akt. Additionally, the increased Bax/Bcl-2 ratio further activated the downstream caspases cascade. ROT promoted the LC3BII/I ratio and p62 levels; however, different ROA doses resulted in different effects on autophagy while inducing PD-like impairments in SH-SY5Y cells.

THE EFFECTS OF DIFFERENT SONICATION METHODS ON ALPHA-SYNUCLEIN PRE-FORMED FIBRILS

Alpha-synuclein (α-syn) aggregation is associated with neuronal death and the pathological hallmark of Parkinson's disease (PD). The α-syn preformed fibril model (α-syn-PFFs), reflects α-syn aggregation and is currently used in PD studies. To pass through the cell membrane, long fibrils should be fragmented by sonication. In our study, the effects of temperature, pulse modifications and/or device type on the sonication of α-syn-PFFs were investigated. Sonication was performed ultrasonic bath and in laminar-flow cabinet with probe sonicator. Dilutions were made from 5 µg/µl α-syn-PFFs stock in sterile-filtered dH2O to a final concentration and volume of 0.1 µg/µl and 200µl, respectively. Sonication was performed in an ultrasonic bath containing water at 10°C for 1 hour. All probe sonications were performed at 30% amplitude for 1 minute and 20 repetitions. The effect of temperature on sonication has been evaluated by performing sonication at room temperature (RT), in ice and in ice surrounded by dry ice. Also, the effects of pulse duration on sonication were evaluated using pulse durations of 1second(sec) on/1sec off, 3sec on/3sec off and 5sec on/5sec off. Furthermore, by waiting one minute between each sonication cycle, the heat released by the probe was prevented from affecting the fibrillar structure. The particle size was measured in triplicate by dynamic light scattering method. For transmission electron microscopy, formvar/carbon-coated grids were run through ddH2O-sonicated fibril-uranyl acetate solutions and kept dry until examined. Due to the variation in breakage of long α-syn fibrils, the effect of different parameters on sonication was investigated. In comparison of pulse durations, 5sec on/5sec off application produced shorter fibrils. Comparing the temperature interventions, lowering the temperature decreased the fibril size at 1sec on/1sec off settings but increased it at 3sec on/3sec off and 5sec on/5sec off. However, the shortest fibrils were obtained by sonication for 5sec on/5sec off at RT

Galantamine suppresses α-synuclein aggregation by inducing autophagy via the activation of α7 nicotinic acetylcholine receptors

Synucleinopathies, including Parkinson's disease and dementia with Lewy bodies, are neurodegenerative disorders characterized by the aberrant accumulation of α-synuclein (α-syn). Although no treatment is effective for synucleinopathies, the suppression of α-syn aggregation may contribute to the development of numerous novel therapeutic targets. Recent research revealed that nicotinic acetylcholine (nACh) receptor activation has neuroprotective effects and promotes the degradation of amyloid protein by activating autophagy. In an in vitro human-derived cell line model, we demonstrated that galantamine, the nAChR allosteric potentiating ligand, significantly reduced the cell number of SH-SY5Y cells with intracellular Lewy body-like aggregates by enhancing the sensitivity of α7-nAChR. In addition, galantamine promoted autophagic flux, and prevented the formation of Lewy body-resembled aggregates. In an in vivo synucleinopathy mouse model, the propagation of α-syn aggregation in the cerebral cortex was inhibited by galantamine administration for 90 days. These results suggest that α7-nAChR is expected to be a novel therapeutic target, and galantamine is a potential agent for synucleinopathies.

Microglia rescue neurons from aggregate-induced neuronal dysfunction and death through tunneling nanotubes

Microglia are crucial for maintaining brain health and neuron function. Here, we report that microglia establish connections with neurons using tunneling nanotubes (TNTs) in both physiological and pathological conditions. These TNTs facilitate the rapid exchange of organelles, vesicles, and proteins. In neurodegenerative diseases like Parkinson's and Alzheimer's disease, toxic aggregates of alpha-synuclein (α-syn) and tau accumulate within neurons. Our research demonstrates that microglia useTNTsto extract neurons from these aggregates, restoring neuronal health. Additionally, microglia sharetheir healthy mitochondria with burdened neurons, reducing oxidative stress and normalizing gene expression. Disrupting mitochondrial function with antimycin A before TNT formation eliminates this neuroprotection. Moreover, co-culturing neurons with microglia and promoting TNT formation rescuessuppressed neuronal activity caused by α-syn or tau aggregates. Notably, TNT-mediated aggregate transfer is compromised in microglia carrying Lrrk22(Gly2019Ser) or Trem2(T66M) and (R47H)mutations, suggesting a role in the pathology of these gene variants in neurodegenerative diseases.

A dual target molecular magnetic resonance imaging probe for noninvasive profiling of pathologic alpha-synuclein and microgliosis in a mouse model of Parkinson's disease.

The pathogenesis of Parkinson's disease (PD) is characterized by progressive deposition of alpha-synuclein (α-syn) aggregates in dopaminergic neurons and neuroinflammation. Noninvasive in vivo imaging of α-syn aggregate accumulation and neuroinflammation can elicit the underlying mechanisms involved in disease progression and facilitate the development of effective treatment as well as disease diagnosis and prognosis. Here we present a novel approach to simultaneously profile α-syn aggregation and reactive microgliosis in vivo, by targeting oligomeric α-syn in cerebrospinal fluid with nanoparticle bearing a magnetic resonance imaging (MRI), contrast payload. In this proof-of-concept report we demonstrate, in vitro, that microglia and neuroblastoma cell lines internalize agglomerates formed by cross-linking the nanoparticles with oligomeric α-syn. Delayed in vivo MRI scans following intravenous administration of the nanoparticles in the M83 α-syn transgenic mouse line show statistically significant MR signal enhancement in test mice versus controls. The in vivo data were validated by ex-vivo immunohistochemical analysis which show strong correlation between in vivo MRI signal enhancement, Lewy pathology distribution, and microglia activity in the treated brain tissue. Furthermore, neuronal and microglial cells in brain tissue from treated mice display strong cytosolic signal originating from the nanoparticles, attributed to in vivo cell uptake of nanoparticle/oligomeric α-syn agglomerates.

Ultrasensitive detection of aggregated α-synuclein using quiescent seed amplification assay for the diagnosis of Parkinson’s disease

BackgroundSeed amplification assays (SAA) enable the amplification of pathological misfolded proteins, including α-synuclein (αSyn), in both tissue homogenates and body fluids of Parkinson’s disease (PD) patients. SAA involves repeated cycles of shaking or sonication coupled with incubation periods. However, this amplification scheme has limitations in tracking protein propagation due to repeated fragmentation.MethodsWe introduced a modified form of SAA, known as Quiescent SAA (QSAA), and evaluated biopsy and autopsy samples from individuals clinically diagnosed with PD and those without synucleinopathies (control group). Brain biopsy samples were obtained from 14 PD patients and 6 controls without synucleinopathies. Additionally, skin samples were collected from 214 PD patients and 208 control subjects. Data were analyzed from April 2019 to May 2023.ResultsQSAA successfully amplified αSyn aggregates in brain tissue sections from mice inoculated with pre-formed fibrils. In the skin samples from 214 PD cases and 208 non-PD cases, QSAA demonstrated high sensitivity (90.2%) and specificity (91.4%) in differentiating between PD and non-PD cases. Notably, more αSyn aggregates were detected by QSAA compared to immunofluorescence with the pS129-αSyn antibody in consecutive slices of both brain and skin samples.ConclusionWe introduced the new QSAA method tailored for in situ amplification of αSyn aggregates in brain and skin samples while maintaining tissue integrity, providing a streamlined approach to diagnosing PD with individual variability. The integration of seeding activities with the location of deposition of αSyn seeds advances our understanding of the mechanism underlying αSyn misfolding in PD.

Wild-Type α-Synuclein Structure and Aggregation: A Comprehensive Coarse-Grained and All-Atom Molecular Dynamics Study.

α-Synuclein (α-syn) is a 140 amino acid intrinsically disordered protein (IDP) and the primary component of cytotoxic oligomers implicated in the etiology of Parkinson's disease (PD). While IDPs lack a stable three-dimensional structure, they sample a heterogeneous ensemble of conformations that can, in principle, be assessed through molecular dynamics simulations. However, describing the structure and aggregation of large IDPs is challenging due to force field (FF) accuracy and sampling limitations. To cope with the latter, coarse-grained (CG) FFs emerge as a potential alternative at the expense of atomic detail loss. Whereas CG models can accurately describe the structure of the monomer, less is known about aggregation. The latter is key for assessing aggregation pathways and designing aggregation inhibitor drugs. Herein, we investigate the structure and dynamics of α-syn using different resolution CG (Martini3 and Sirah2) and all-atom (Amber99sb and Charmm36m) FFs to gain insight into the differences and resemblances between these models. The dependence of the magnitude of protein-water interactions and the putative need for enhanced sampling (replica exchange) methods in CG simulations are analyzed to distinguish between force field accuracy and sampling limitations. The stability of the CG models of an α-syn fibril was also investigated. Additionally, α-syn aggregation was studied through umbrella sampling for the CG models and CG/all-atom models for an 11-mer peptide (NACore) from an amyloidogenic domain of α-syn. Our results show that despite the α-syn structures of Martini3 and Sirah2 with enhanced protein-water interactions being similar, major differences exist concerning aggregation. The Martini3 fibril is not stable, and the binding free energy of α-syn and NACore is positive, opposite to Sirah2. Sirah2 peptides in a zwitterionic form, in turn, display termini interactions that are too strong, resulting in end-to-end orientation. Sirah2, with enhanced protein-water interactions and neutral termini, provides, however, a peptide aggregation free energy profile similar to that found with all-atom models. Overall, we find that Sirah2 with enhanced protein-water interactions is suitable for studying protein-protein and protein-drug aggregation.

The Aggregation of α-Synuclein in the Dorsomedial Striatum Significantly Impairs Cognitive Flexibility in Parkinson's Disease Mice.

This study focused on α-synuclein (α-syn) aggregation in the dorsomedial striatum (DMS) so as to investigate its role in the cognitive flexibility of Parkinson's disease (PD). Here, we investigated the cognitive flexibility by assessing reversal learning abilities in MPTP-induced subacute PD model mice and in C57BL/6J mice with α-syn aggregation in the DMS induced by adenovirus (AAV-SNCA) injection, followed by an analysis of the target protein's expression and distribution. PD mice exhibited impairments in reversal learning, positively correlated with the expression of phosphorylated α-syn in the DMS. Furthermore, the mice in the AAV-SNCA group exhibited reversal learning deficits and a reduction in acetylcholine levels, accompanied by protein alterations within the DMS. Notably, the administration of a muscarinic receptor 1 (M1R) agonist was able to alleviate the aforementioned phenomenon. These findings suggest that the impaired cognitive flexibility in PD may be attributed to the diminished activation of acetylcholine to M1R caused by α-syn aggregation.

Rosmarinic acid turned α-syn oligomers into non-toxic species preserving microtubules in Raw 264.7 cells

Parkinson’s disease (PD) is the second most prevalent neurodegenerative disorder worldwide, and the therapeutic is focused on several approaches including the inhibition of fibril formation by small compounds, avoiding the formation of cytotoxic oligomers. Thus, we decided to explore the capacity of compounds carrying catechol moieties to inhibit the progression of α-synuclein. Overall, the compounds rosmarinic acid (1), carnosic acid (2), carnosol (3), epiisorosmanol (4), and rosmanol (5) avoid the progression of fibril formation assessed by Thiofavine T (ThT), and atomic force microscopy images showed that morphology is influenced for the actions of compounds over fibrillization. Moreover, ITC experiments showed a Kd varying from 28 to 51 µM, the ΔG showed that the reaction between compounds and α-syn is spontaneous, and ΔH is associated with an exothermic reaction, suggesting the interactions of hydrogen bonds among compounds and α-syn. Docking experiments reinforce this idea showing the intermolecular interactions are mostly hydrogen bonding within the sites 2, 9, and 3/13 of α-synuclein, and compounds 1 and 5. Thus, compound 1, rosmarinic acid, interestingly interacts better with site 9 through catechol and Lysines. In cultured Raw 264. 7 cells, the presence of compounds showed that most of them can promote cell differentiation, especially rosmarinic acid, and rosmanol, both preserving tubulin cytoskeleton. However, once we evaluated whether or not the aggregates pre-treated with compounds could prevent the disruption of microtubules of Raw 264.7 cells, only pre-treated aggregates with rosmarinic acid prevented the disruption of the cytoskeleton. Altogether, we showed that especially rosmarinic acid not only inhibits α-syn but stabilizes the remaining aggregates turning them into not-toxic to Raw 264.7 cells suggesting a main role in cell survival and antigen processing in response to external α-syn aggregates.

Immunomodulator-Derived Nanoparticles Induce Neuroprotection and Regulatory T Cell Action to Alleviate Parkinsonism.

Post-translational modification, mitochondrial abruptions, neuroinflammation, and α-synuclein (α-Syn) aggregation are considered as major causes of Parkinson's disease (PD) pathogenesis. The recent literature highlights neuroimmune cross talk and the negative role of immune effector T (Teff) and positive regulation by regulatory T (Treg) cells in PD treatment. Herein, a strategy to endow Treg action paves the path for development of PD treatment. Thus, we explored the neuroprotective efficiency of the immunomodulator and PP2A (protein phosphatase 2) activator, FTY720 nanoparticles in in vivo experimental PD models. Repurposing of FTY720 for PD is known due to its protective effect by reducing PD and its camouflaged role in endowing EZH2-mediated epigenetic regulation of PD. EZH2-FOXP3 interaction is necessary for the neuroprotective Treg cell activity. Therefore, we synthesized FTY720 nanoparticles to improve FTY720 protective efficacy in an in vivo PD model to explore the PP2A mediated signaling. We confirmed the formation of FTY720NPs, and the results of the behavioral and protein expression study showed the significant neuroprotective efficiency of our nanoformulations. In the exploration of neuroprotective mechanism, several lines of evidence confirmed FTY720NPs mediated induction of PP2A/EZH2/FOXP3 signaling in the induction of Treg cells effect in in vivo PD treatment. In summary, our nanoformulations have novel potential to alleviate PD by inducing PP2A-induced epigenetic regulation-mediated neuroimmunomodulation at the clinical setup.