Vanillin Mitigates the MPTP-Induced α-Synucleinopathy in a Mouse Model of Parkinson's Disease: Insights into the Involvement of Wnt/ß-Catenin Signaling.

BACKGROUND: The abnormal aggregation of α-synuclein (α-syn) in the substantia nigra pars compacta (SNpc) region of the brain is characteristic of Parkinson's disease (PD), leading to the selective demise of neurons. Modifications in the post-translational processing of α-syn, phosphorylation at Ser129 in particular, are implicated in α-syn aggregation and are considered key hallmarks of PD. Furthermore, dysregulated Wnt/ß-catenin signaling, influenced by glycogen synthase kinase-3 beta (GSK-3ß), is implicated in PD pathogenesis. Inhibition of GSK-3ß holds promise in promoting neuroprotection by enhancing the Wnt/ß-catenin pathway. METHODS: In our previous study utilizing 1-methyl-4-phenylpyridinium (MPP+)-administered differentiated SH-SY5Y cells and a PD mouse model, we explored Vanillin's neuroprotective properties and related mechanisms against neuronal loss induced by MPP+/1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) administration. In the current study, we elucidated the mitigating effects of Vanillin on motor impairments, P-Ser129-α-syn expression, Wnt/ß-catenin signaling, and autophagic neuron death induced by MPTP in a mouse model of PD by performing motor function tests, western blot analysis and immunostaining. RESULTS: Our results show that Vanillin effectively modulated the motor dysfunctions, GSK-3ß expression, and activity, activated the Wnt/ß-catenin signaling, and reduced autophagic neuronal demise in the MPTP-lesioned mice, highlighting its neuroprotective effects. CONCLUSIONS: These findings underscore the complex interplay between α-syn pathology, GSK-3ß, Wnt/ß-catenin signaling, and autophagic-cell death in PD pathogenesis. Targeting these pathways, particularly with Vanillin, can be a promising therapeutic strategy for restoring dopaminergic (DA-ergic) neuronal homeostasis and slowing the progression of PD. Further research is crucial to resolving existing disputes and translating these discoveries into effective therapeutic interventions for PD patients.

Design, Synthesis, and Evaluation of a Novel Conjugate Molecule with Dopaminergic and Neuroprotective Activities for Parkinson's Disease.

The escalating prevalence of Parkinson's disease (PD) underscores the need for innovative therapeutic interventions since current palliative measures, including the standard l-Dopa formulations, face challenges of tolerance and side effects while failing to address the underlying neurodegenerative processes. Here, we introduce DAD9, a novel conjugate molecule that aims to combine symptomatic relief with disease-modifying strategies for PD. Crafted through knowledge-guided chemistry, the molecule combines a nonantibiotic doxycycline derivative with dopamine, preserving neuroprotective attributes while maintaining dopaminergic agonism. This compound exhibited no off-target effects on PD-relevant cell functions and sustained antioxidant and anti-inflammatory properties of the tetracycline precursor. Furthermore, it effectively interfered with the formation and seeding of toxic α-synuclein aggregates without producing detrimental oxidative species. In addition, DAD9 was able to activate dopamine receptors, and docking simulations shed light onto the molecular details of this interaction. These findings position DAD9 as a potential neuroprotective dopaminergic agonist, promising advancements in PD therapeutics.

Antimicrobial drugs for Parkinson's disease: Existing therapeutic strategies and novel drugs exploration.

Parkinson's disease (PD), the second most common neurodegenerative disorder, is characterized by loss of dopaminergic neurons in the substantia nigra, as well as the abnormal accumulation of misfolded α-synuclein. Clinically, PD is featured by typical motor symptoms and some non-motor symptoms. Up to now, although considerable progress has been made in understanding the pathogenesis of PD, there is still no effective therapeutic treatment for the disease. Thus, exploring new therapeutic strategies has been a topic that needs to be addressed urgently. Noteworthy, with the proposal of the microbiota-gut-brain axis theory, antimicrobial drugs have received significant attention due to their effects on regulating the intestinal microbiota. Nowadays, there is growing evidence showing that some antimicrobial drugs may be promising drugs for the treatment of PD. Data from pre-clinical and clinical studies have shown that some antimicrobial drugs may play neuroprotective roles in PD by modulating multiple biochemical and molecular pathways, including reducing α-synuclein aggregation, inhibiting neuroinflammation, regulating mitochondrial structure and function, as well as suppressing oxidative stress. In this paper, we summarized the effects of some antimicrobial drugs on PD treatment from recent pre-clinical and clinical studies. Then, we further discussed the potential of a few antimicrobial drugs for treating PD based on molecular docking and molecular dynamics simulation. Importantly, we highlighted the potential of clorobiocin as the therapeutic strategy for PD owing to its ability to inhibit α-synuclein aggregation. These results will help us to better understand the potential of antimicrobial drugs in treating PD and how antimicrobial drugs may alleviate or reverse the pathological symptoms of PD.

Neuroprotective effects of indole-3-carbinol on the rotenone rat model of Parkinson's disease: Impact of the SIRT1-AMPK signaling pathway.

Parkinson's disease (PD) is the second most common progressive neurodegenerative disorder. Although mounting studies have been conducted, no effective therapy is available to halt its progression. Indole-3-carbinol (I3C) is a naturally occurring compound obtained by ß-thioglucosidase-mediated autolysis of glucobrassicin in cruciferous vegetables. Besides its powerful antioxidant activity, I3C has shown neuroprotection against depression and chemically induced neurotoxicity via its anti-inflammatory and antiapoptotic effects. This study aimed to investigate the neuroprotective effects of I3C against rotenone (ROT)-induced PD in male albino rats. The possible protective mechanisms were also explored. PD was induced by subcutaneous administration of ROT (2 mg/kg) for 28 days. The effects of I3C (25, 50, and 100 mg/kg/day) were assessed by catalepsy test (bar test), spontaneous locomotor activity, rotarod test, weight change, tyrosine hydroxylase (TH) expression, α-synuclein (α-Syn) expression, striatal dopamine (DA) content, and histological examination. The highest dose of I3C (100 mg/kg) was the most effective to prevent ROT-mediated motor dysfunctions and amend striatal DA decrease, weight loss, neurodegeneration, TH expression reduction, and α-Syn expression increase in both the midbrain and striatum. Further mechanistic investigations revealed that the neuroprotective effects of I3C are partially attributed to its anti-inflammatory and antiapoptotic effects and the activation of the sirtuin 1/AMP-activated protein kinase pathway. Altogether, these results suggested that I3C could attenuate biochemical, molecular, and functional changes in a rat PD model with following repeated rotenone exposures.

Ferruginol prevents degeneration of dopaminergic neurons by enhancing clearance of α-synuclein in neuronal cells.

Lewy bodies are characteristic spherical inclusions in Parkinson's disease (PD) that are formed by α-synuclein fibrils. Ferruginol (Fer) is an amonomeric compound isolated from a traditional Chinese herb. Here, we show that Fer exerted potent neuroprotective effects in both in vitro and in vivo PD models. Neuronal cells transfected with A53T mutant (A53T) α-synuclein plasmids and treated with Fer exhibited attenuated the cytotoxicity induced by pathogenic A53T α-synuclein overexpression. Further, when we transfected neuronal cells with siRNA-SNCA (alpha-synuclein) plasmids and incubated them with Fer, the protective role of Fer decreased. We also found that Fer was a potent α-synuclein inhibitor in neuronal cells, which promotes the clearance of αsynuclein in dopaminergic neurons exposed to 1-Methyl-4-phenylpyridinium (MPP +). Fer could inhibit abnormal α-synuclein aggregation and dopaminergic neuron depletion in A53T-Tg mice, suggesting that a role for Fer in α-synuclein accumulation and nigrostriatal pathway injury. Our study revealed that Fer strongly alleviated neurodegeneration by promoting α-synuclein clearance, indicating a neuroprotective role against α-synuclein oligomer-induced neurodegeneration, which makes it a promising candidate for the treatment of PD and other neurodegenerative diseases.

Effects of the Toxic Metals Arsenite and Cadmium on α-Synuclein Aggregation In Vitro and in Cells.

Exposure to heavy metals, including arsenic and cadmium, is associated with neurodegenerative disorders such as Parkinson's disease. However, the mechanistic details of how these metals contribute to pathogenesis are not well understood. To search for underlying mechanisms involving α-synuclein, the protein that forms amyloids in Parkinson's disease, we here assessed the effects of arsenic and cadmium on α-synuclein amyloid formation in vitro and in Saccharomyces cerevisiae (budding yeast) cells. Atomic force microscopy experiments with acetylated human α-synuclein demonstrated that amyloid fibers formed in the presence of the metals have a different fiber pitch compared to those formed without metals. Both metal ions become incorporated into the amyloid fibers, and cadmium also accelerated the nucleation step in the amyloid formation process, likely via binding to intermediate species. Fluorescence microscopy analyses of yeast cells expressing fluorescently tagged α-synuclein demonstrated that arsenic and cadmium affected the distribution of α-synuclein aggregates within the cells, reduced aggregate clearance, and aggravated α-synuclein toxicity. Taken together, our in vitro data demonstrate that interactions between these two metals and α-synuclein modulate the resulting amyloid fiber structures, which, in turn, might relate to the observed effects in the yeast cells. Whilst our study advances our understanding of how these metals affect α-synuclein biophysics, further in vitro characterization as well as human cell studies are desired to fully appreciate their role in the progression of Parkinson's disease.

Neuroprotective effect of paeoniflorin in the mouse model of Parkinson's disease through α-synuclein/protein kinase C δ subtype signaling pathway.

OBJECTIVES: Paeoniflorin, an active component of Radix Paeoniae Alba, has a neuroprotective effect in Parkinson's animal models. However, its mechanism of action remains to be determined. METHODS: In this study, we hypothesized that the neuroprotective effect of paeoniflorin occurs through the α-synuclein/protein kinase C δ subtype (PKC-δ) signaling pathway. We tested our hypothesis in the 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP)-induced mouse model of Parkinson's disease. We evaluated the effects of paeoniflorin on the expression levels of signal components of the α-synuclein/PKC-δ pathway, cellular apoptosis and motor performance. RESULTS: Our results demonstrated that paeoniflorin restored the motor performance impairment caused by MPTP, inhibited apoptosis, and protected the ultrastructure of neurons. Paeoniflorin treatment also resulted in the dose-dependent upregulation of an antiapoptotic protein, B-cell lymphoma-2, at the mRNA and protein levels, similar to the effects of the positive control, selegiline. In contrast, paeoniflorin treatment downregulated the expression of pro-apoptotic proteins BCL2-Associated X2, α-synuclein, and PKC-δ at the mRNA and protein levels, as well as the level of the activated form of nuclear factor kappa B (p-NF-κB p65). CONCLUSIONS: Thus, our results showed that paeoniflorin exerts its neuroprotective effect by regulating the α-synuclein/PKC-δ signaling pathway to reduce neuronal apoptosis.

Direct targeting of wild-type glucocerebrosidase by antipsychotic quetiapine improves pathogenic phenotypes in Parkinson's disease models.

Current treatments for Parkinson's disease (PD) provide only symptomatic relief, with no disease-modifying therapies identified to date. Repurposing FDA-approved drugs to treat PD could significantly shorten the time needed for and reduce the costs of drug development compared with conventional approaches. We developed an efficient strategy to screen for modulators of ß-glucocerebrosidase (GCase), a lysosomal enzyme that exhibits decreased activity in patients with PD, leading to accumulation of the substrate glucosylceramide and oxidized dopamine and α-synuclein, which contribute to PD pathogenesis. Using a GCase fluorescent probe and affinity-based fluorescence polarization assay, we screened 1280 structurally diverse, bioactive, and cell-permeable FDA-approved drugs and found that the antipsychotic quetiapine bound GCase with high affinity. Moreover, quetiapine treatment of induced pluripotent stem cell-derived (iPSC-derived) dopaminergic neurons from patients carrying mutations in GBA1 or LRRK2 led to increased wild-type GCase protein levels and activity and partially lowered accumulation of oxidized dopamine, glucosylceramide, and α-synuclein. Similarly, quetiapine led to activation of wild-type GCase and reduction of α-synuclein in a GBA mutant mouse model (Gba1D409V/+ mice). Together, these results suggest that repurposing quetiapine as a modulator of GCase may be beneficial for patients with PD exhibiting decreased GCase activity.

A novel glucosylceramide synthase inhibitor attenuates alpha synuclein pathology and lysosomal dysfunction in preclinical models of synucleinopathy.

Mutations in the lysosomal enzyme glucocerebrosidase (GCase, GBA1 gene) are the most common genetic risk factor for developing Parkinson's disease (PD). GCase metabolizes the glycosphingolipids glucosylceramide (GlcCer) and glucosylsphingosine (GlcSph). Mutations in GBA1 reduce enzyme activity and the resulting accumulation of glycosphingolipids may contribute to the underlying pathology of PD, possibly via altering lysosomal function. While reduction of GCase activity exacerbates α-synuclein (α-syn) aggregation, it has not been determined that this effect is the result of altered glycosphingolipid levels and lysosome function or some other effect of altering GCase. The glycosphingolipid GlcCer is synthesized by a single enzyme, glucosylceramide synthase (GCS), and small molecule inhibitors (GCSi) reduce cellular glycosphingolipid levels. In the present studies, we utilize a preformed fibril (PFF) rodent primary neuron in vitro model of α-syn pathology to investigate the relationship between glycosphingolipid levels, α-syn pathology, and lysosomal function. In primary cultures, pharmacological inhibition of GCase and D409V GBA1 mutation enhanced accumulation of glycosphingolipids and insoluble phosphorylated α-syn. Administration of a novel small molecule GCSi, benzoxazole 1 (BZ1), significantly decreased glycosphingolipid concentrations in rodent primary neurons and reduced α-syn pathology. BZ1 rescued lysosomal deficits associated with the D409V GBA1 mutation and α-syn PFF administration, and attenuated α-syn induced neurodegeneration of dopamine neurons. In vivo studies revealed BZ1 had pharmacological activity and reduced glycosphingolipids in the mouse brain to a similar extent observed in neuronal cultures. These data support the hypothesis that reduction of glycosphingolipids through GCS inhibition may impact progression of synucleinopathy and BZ1 is useful tool to further examine this important biology.

Memantine exerts neuroprotective effects by modulating α-synuclein transmission in a parkinsonian model.

Ample evidence has demonstrated that α-Synuclein can propagate from one area of the brain to others via cell-to-cell transmission, which might be the underlying mechanism for pathological propagation and the disease progression of Parkinson's disease (PD). Recent reports have demonstrated cell surface receptor-mediated cell-to-cell transmission of α-synuclein. Memantine decreased the levels of internalized cytosolic α-synuclein and led to attenuation in α-synuclein-induced cell death. Specifically, memantine attenuated α-synuclein-induced expression of clathrin and EEA1, and increased expression of NR2A subunits. Moreover, memantine inhibited propagation of extracellular α-synuclein and thus, decreased the expression of the phosphorylated form of α-synuclein in dopaminergic neurons of the substantia nigra, which was accompanied by increased survival of dopaminergic neurons with functional improvement of motor deficits. The present study demonstrated that memantine modulates extracellular α-synuclein propagation by inhibiting interactions between α-synuclein and NR2A subunits, which leads to neuroprotective effects on nigral dopaminergic neurons against α-synuclein-enriched conditions. The repositioning use of memantine in α-synuclein propagation needs to be further evaluated in patients with α-synucleinopathies as an effective therapeutic approach.

Protective effect of plastrum testudinis extract on dopaminergic neurons in a Parkinson's disease model through DNMT1 nuclear translocation and SNCA's methylation.

The pathological characteristics of Parkinson's disease (PD) include dopaminergic neuron damage, specifically disorders caused by dopamine synthesis, in vivo. Plastrum testudinis extract (PTE) and its bioactive ingredient ethyl stearate (PubChem CID: 8122) were reported to be correlated with tyrosine hydroxylase (TH), which is a biomarker of dopaminergic neurons. This suggests that PTE and its small-molecule active ingredient ethyl stearate have potential for development as a therapeutic drug for PD. In this study, we treated 6-hydroxydopamine (6-OHDA)-induced model rats and PC12 cells with PTE. The mechanism of action of PTE and ethyl stearate was investigated by western blotting, bisulfite sequencing PCR (BSP), real-time PCR, immunofluorescence and siRNA transfection. PTE effectively upregulated the TH expression and downregulated the alpha-synuclein expression in both the substantia nigra and the striatum of the midbrain in a PD model rat. The PC12 cell model showed that both PTE and its active monomer ethyl stearate significantly promoted TH expression and blocked alpha-synuclein, agreeing with the in vivo results. BSP showed that PTE and ethyl stearate increased the methylation level of the Snca intron 1 region. These findings suggest that some of the protective effects of PTE on dopaminergic neurons are mediated by ethyl stearate. The mechanism of ethyl stearate may involve disrupting the abnormal aggregation of DNA (cytosine-5)-methyltransferase 1 (DNMT1) with alpha-synuclein by releasing DNMT1, upregulating Snca intron 1 CpG island methylation, and ultimately, reducing the expression of alpha-synuclein.

Green Tea Epigallocatechin-3-gallate (EGCG) Targeting Protein Misfolding in Drug Discovery for Neurodegenerative Diseases.

The potential to treat neurodegenerative diseases (NDs) of the major bioactive compound of green tea, epigallocatechin-3-gallate (EGCG), is well documented. Numerous findings now suggest that EGCG targets protein misfolding and aggregation, a common cause and pathological mechanism in many NDs. Several studies have shown that EGCG interacts with misfolded proteins such as amyloid beta-peptide (Aß), linked to Alzheimer's disease (AD), and α-synuclein, linked to Parkinson's disease (PD). To date, NDs constitute a serious public health problem, causing a financial burden for health care systems worldwide. Although current treatments provide symptomatic relief, they do not stop or even slow the progression of these devastating disorders. Therefore, there is an urgent need to develop effective drugs for these incurable ailments. It is expected that targeting protein misfolding can serve as a therapeutic strategy for many NDs since protein misfolding is a common cause of neurodegeneration. In this context, EGCG may offer great potential opportunities in drug discovery for NDs. Therefore, this review critically discusses the role of EGCG in NDs drug discovery and provides updated information on the scientific evidence that EGCG can potentially be used to treat many of these fatal brain disorders.

The food additive fast green FCF inhibits α-synuclein aggregation, disassembles mature fibrils and protects against amyloid-induced neurotoxicity.

α-Synuclein (α-syn) aggregates into cytotoxic amyloid fibrils, which are recognized as the defining neuropathological feature of Parkinson's disease (PD). Therefore, inhibiting α-syn fibrillogenesis and disrupting the preformed fibrils are both considered attractive strategies to cure PD. We discovered that a safe food additive, fast green FCF, is capable of inhibiting α-synuclein fibrillogenesis and reducing the related cytotoxicity. Thioflavin T fluorescence assays demonstrated that fast green FCF could inhibit the fibrillogenesis α-synuclein. In the presence of 100 µM fast green FCF, amorphous aggregates were formed and observed by atomic force microscopy. Toxicity assays in cell cultures revealed that fast green FCF significantly reduced the cytotoxicity of α-syn. Molecular dynamics simulations revealed the potential mechanism of the interactions between fast green FCF and α-synuclein. Fast green FCF greatly disrupted the α-synuclein pentamer and reduced the ß-sheet content by reducing both nonpolar and polar interactions. Furthermore, two binding sites were identified, named region I (Y39-K45) and region II (H50-Q62). Our data reveal that electrostatic interactions, hydrogen bonds, and π-π interactions synergistically contribute to the binding of fast green FCF to the α-synuclein pentamer. These results indicate that fast green FCF is a candidate prototype for the development of drugs against the aggregation of amyloid fibrils in PD.

Doxycycline inhibits α-synuclein-associated pathologies in vitro and in vivo.

Parkinson's disease (PD) and dementia with Lewy bodies (DLB) are neurodegenerative disorders characterized by the misfolding and aggregation of alpha-synuclein (aSyn). Doxycycline, a tetracyclic antibiotic shows neuroprotective effects, initially proposed to be due to its anti-inflammatory properties. More recently, an additional mechanism by which doxycycline may exert its neuroprotective effects has been proposed as it has been shown that it inhibits amyloid aggregation. Here, we studied the effects of doxycycline on aSyn aggregation in vivo, in vitro and in a cell free system using real-time quaking induced conversion (RT-QuiC). Using H4, SH-SY5Y and HEK293 cells, we found that doxycycline decreases the number and size of aSyn aggregates in cells. In addition, doxycycline inhibits the aggregation and seeding of recombinant aSyn, and attenuates the production of mitochondrial-derived reactive oxygen species. Finally, we found that doxycycline induces a cellular redistribution of aggregates in a C.elegans animal model of PD, an effect that is associated with a recovery of dopaminergic function. In summary, we provide strong evidence that doxycycline treatment may be an effective strategy against synucleinopathies.

Ferroptosis and its potential role in the physiopathology of Parkinson's Disease.

Parkinson's Disease (PD) is a common and progressive neurodegenerative disorder characterised by motor impairments as well as non-motor symptoms. While dopamine-based therapies are effective in fighting the symptoms in the early stages of the disease, a lack of neuroprotective drugs means that the disease continues to progress. Along with the traditionally recognised pathological hallmarks of dopaminergic neuronal death and intracellular α-synuclein (α-syn) depositions, iron accumulation, elevated oxidative stress and lipid peroxidation damage are further conspicuous features of PD pathophysiology. However, the underlying mechanisms linking these pathological hallmarks with neurodegeneration still remain unclear. Ferroptosis, a regulated iron dependent cell death pathway involving a lethal accumulation of lipid peroxides, shares several features with PD pathophysiology. Interestingly, α-syn has been functionally linked with the metabolism of both iron and lipid, suggesting a possible interplay between dysregulated α-syn and other PD pathological hallmarks related to ferroptosis. This review will address the importance for understanding these disease mechanisms that could be targeted therapeutically. Anti-ferroptosis molecules are neuroprotective in PD animal models and the anti-ferroptotic iron chelator, deferiprone, slowed disease progression and improved motor function in two independent clinical trials for PD. An ongoing larger multi-centre phase 2 clinical trial will confirm the therapeutic potential of deferiprone and the relevance of ferroptosis in PD. This review addresses the known pathological features of PD in relation to the ferroptosis pathway with therapeutic implications of targeting this cell death pathway.

Exosome-mediated delivery of antisense oligonucleotides targeting α-synuclein ameliorates the pathology in a mouse model of Parkinson's disease.

Parkinson's disease (PD) is the second most common neurodegenerative disease. Pathologically, PD is characterized by the formation of Lewy bodies (LBs) in the brain, which mainly comprises phosphorylated and aggregated α-synuclein (α-syn). The aberrant aggregation of α-syn is believed to play a key role in the pathogenesis of PD. While α-syn expression can be reduced by antisense oligonucleotides (ASOs), the challenge to deliver ASOs safely and effectively into the neurons remains unresolved. Here, we developed a safe and highly effective ASO delivery method by using exosomes. We first identified the ASO sequence that selectively reduced α-syn expression: ASO4. Exosome-mediated delivery of ASO4 (exo-ASO4) showed high cellular uptake and low toxicity in primary neuronal cultures. Exo-ASO4 also significantly attenuated α-syn aggregation induced by pre-formed α-syn fibrils in vitro. Exo-ASO4 intracerebroventricular injection into the brains of α-syn A53T mice, a transgenic model of PD, significantly decreased the expression of α-syn and attenuated its aggregation. Furthermore, exo-ASO4 ameliorated the degeneration of dopaminergic neurons in these mice. Finally, the α-syn A53T mice showed significantly improved locomotor functions after exo-ASO4 injection. Overall, this study demonstrates that exosome-mediated ASO4 delivery may be an effective treatment option for PD.

Photoresponsive Prion-Mimic Foldamer to Induce Controlled Protein Aggregation.

Proteins reconfigure their 3D-structure, and consequently their function, under the control of specific molecular interactions that sense, process and transmit information from the surrounding environment. When this fundamental process is hampered, many pathologies occur as in the case of protein misfolding diseases. In this work, we follow the early steps of α-synuclein (aS) aggregation, a process associated with Parkinson's disease etiopathogenesis, that is promptly promoted by a light-mediated binding between the protein and a photoactive foldamer. The latter can switch between two conformations, one of which generates supramolecular fibrillar seeds that act as molecular templates able to induce a fast ß-sheet transition for aS monomers that successively undergo fibrillar polymerization. The proposed method represents a powerful tool to study protein aggregation relevant to misfolding diseases in a controlled and inducible system.

Effect of Ionic Strength on Thioflavin-T Affinity to Amyloid Fibrils and Its Fluorescence Intensity.

The formation of amyloid fibrils is linked to multiple neurodegenerative disorders, including Alzheimer's and Parkinson's disease. Despite years of research and countless studies on the topic of such aggregate formation, as well as their resulting structure, the current knowledge is still fairly limited. One of the main aspects prohibiting effective aggregation tracking is the environment's effect on amyloid-specific dyes, namely thioflavin-T (ThT). Currently, there are only a few studies hinting at ionic strength being one of the factors that modulate the dye's binding affinity and fluorescence intensity. In this work we explore this effect under a range of ionic strength conditions, using insulin, lysozyme, mouse prion protein, and α-synuclein fibrils. We show that ionic strength is an extremely important factor affecting both the binding affinity, as well as the fluorescence intensity of ThT.

Effects of Detergent on α-Synuclein Structure. A Native MS-Ion Mobility Study.

The intrinsically disordered protein α-synuclein plays a major role in Parkinson's disease. The protein can oligomerize resulting in the formation of various aggregated species in neuronal cells, leading to neurodegeneration. The interaction of α-synuclein with biological cell membranes plays an important role for specific functions of α-synuclein monomers, e.g., in neurotransmitter release. Using different types of detergents to mimic lipid molecules present in biological membranes, including the presence of Ca2+ ions as an important structural factor, we aimed to gain an understanding of how α-synuclein interacts with membrane models and how this affects the protein conformation and potential oligomerization. We investigated detergent binding stoichiometry, affinity and conformational changes of α-synuclein taking detergent concentration, different detergent structures and charges into account. With native nano-electrospray ionization ion mobility-mass spectrometry, we were able to detect unique conformational patterns resulting from binding of specific detergents to α-synuclein. Our data demonstrate that α-synuclein monomers can interact with detergent molecules irrespective of their charge, that protein-micelle interactions occur and that micelle properties are an important factor.

Graphene-Based Nanoparticles as Potential Treatment Options for Parkinson's Disease: A Molecular Dynamics Study.

INTRODUCTION: The study of abnormal aggregation of proteins in different tissues of the body has recently earned great attention from researchers in various fields of science. Concerning neurological diseases, for instance, the accumulation of amyloid fibrils can contribute to Parkinson's disease, a progressively severe neurodegenerative disorder. The most prominent features of this disease are the degeneration of neurons in the substantia nigra and accumulation of α-synuclein aggregates, especially in the brainstem, spinal cord, and cortical areas. Dopamine replacement therapies and other medications have reduced motor impairment and had positive consequences on patients' quality of life. However, if these medications are stopped, symptoms of the disease will recur even more severely. Therefore, the improvement of therapies targeting more basic mechanisms like prevention of amyloid formation seems to be critical. It has been shown that the interactions between monolayers like graphene and amyloids could prevent their fibrillation. METHODS: For the first time, the impact of four types of last-generation graphene-based nanostructures on the prevention of α-synuclein amyloid fibrillation was investigated in this study by using molecular dynamics simulation tools. RESULTS: Although all monolayers were shown to prevent amyloid fibrillation, nitrogen-doped graphene (N-Graphene) caused the most instability in the secondary structure of α-synuclein amyloids. Moreover, among the four monolayers, N-Graphene was shown to present the highest absolute value of interaction energy, the lowest contact level of amyloid particles, the highest number of hydrogen bonds between water and amyloid molecules, the highest instability caused in α-synuclein particles, and the most significant decrease in the compactness of α-synuclein protein. DISCUSSION: Ultimately, it was concluded that N-Graphene could be the most effective monolayer to disrupt amyloid fibrillation, and consequently, prevent the progression of Parkinson's disease.