Preformed Fibrils Research Articles

USP19 deubiquitinase inactivation regulates α-synuclein ubiquitination and inhibits accumulation of Lewy body-like aggregates in mice

The USP19 deubiquitinase is found in a locus associated with Parkinson’s Disease (PD), interacts with chaperonins, and promotes secretion of α-synuclein (α-syn) through the misfolding-associated protein secretion (MAPS) pathway. Since these processes might modulate the processing of α-syn aggregates in PD, we inactivated USP19 (KO) in mice expressing the A53T mutation of α-syn and in whom α-syn preformed fibrils (PFF) had been injected in the striatum. Compared to WT, KO brains showed decreased accumulation of phospho-synuclein (pSyn) positive aggregates. This improvement was associated with less activation of microglia and improved performance in a tail-suspension test. Exposure of primary neurons from WT and KO mice to PFF in vitro also led to decreased accumulation of pSyn aggregates. KO did not affect uptake of PFF nor propagation of aggregates in the cultured neurons. We conclude that USP19 instead modulates intracellular dynamics of aggregates. At an early time following PFF injection when the number of pSyn-positive neurons were similar in WT and KO brains, the KO neurons contained less aggregates. KO brain aggregates stained more intensely with anti-ubiquitin antibodies. Immunoprecipitation of soluble proteins from WT and KO brains with antibodies to pSyn showed higher levels of ubiquitinated oligomeric species in the KO samples. We propose that the improved pathology in USP19 KO brains may arise from decreased formation or enhanced clearance of the more ubiquitinated aggregates and/or enhanced disassembly towards more soluble oligomeric species. USP19 inhibition may represent a novel therapeutic approach that targets the intracellular dynamics of α-syn complexes.

The potential of Rhein's aromatic amines for Parkinson's disease prevention and treatment: α-Synuclein aggregation inhibition and disaggregation of preformed fibers

The aggregation of α-Syn is a pivotal mechanism in Parkinson's disease (PD). Effectively maintaining α-Syn proteostasis involves both inhibiting its aggregation and promoting disaggregation. In this study, we developed a series of aromatic amide derivatives based on Rhein. Two of these compounds, 4,5-dihydroxy-N-(3-hydroxyphenyl)-9,10-dioxo-9,10-dihydroanthracene-2-carboxamide (a5) and 4,5-dihydroxy-N-(2-hydroxy-4-chlorophenyl)-9,10-dioxo-9,10-dihydroanthracene-2-carboxamide (a8), exhibited good binding affinities to α-Syn residues, demonstrating promising inhibitory activity against α-Syn aggregation in vitro, with low IC50 values (1.35 and 1.08 μM, respectivly). These inhibitors acted throughout the entire aggregation process by stabilizing α-Syn's conformation and preventing the formation of β-sheet aggregates. They also effectively disassembled preformed α-Syn oligomers and fibrils. Preliminary mechanistic insights indicated that they bound to the specific domain within fibrils, inducing fibril instability, collapse, and the formation of smaller aggregates and monomeric α-Syn units. This research underscores the therapeutic potential of Rhein's aromatic amides in targeting α-Syn aggregation for PD treatment and suggests broader applications in managing and preventing neurodegenerative diseases.

4-Arylidene curcumin derivatives in vitro inhibit α-Synuclein aggregation and disaggregate the preformed fibril

This study focuses on the misfolding and aggregation of α-Syn as a central mechanism linking various pathological processes in PD. Maintaining α-Syn proteostasis through suitable inhibitors emerges as an effective approach to prevent PD. A more efficient strategy for PD treatment involves disintegrating neurotoxic oligomers and fibrils into normal functional α-Syn using inhibitors. To this end, a series of 4-arylidene curcumin derivatives were synthesized with a sheet-like conjugated skeleton and higher binding energies with α-Syn residues. Among these derivatives, three candidate compounds exhibited promising α-Syn aggregation inhibitory activities in vitro, with IC50 values as low as 0.61 μM. The inhibitory action extended throughout the entire aggregation process, stabilizing α-Syn proteostasis conformation and preventing β-sheets aggregation. Furthermore, the candidate compounds demonstrated effective disintegration capabilities against preformed α-Syn oligomers and fibrils. Initial mechanistic investigations indicated that the inhibitors may bind to a specific domain within the fibril, inducing fibril instability and subsequent collapse. This process resulted in the formation of a complex system of aggregates with smaller sizes and monomers. Overall, these findings provide valuable insights into the potential of 4-arylidene curcumin derivatives as therapeutic agents for targeting α-Syn aggregation in PD treatment.

α-Synuclein pathology from the body to the brain: so many seeds so close to the central soil.

α-Synuclein is a protein that mainly exists in the presynaptic terminals. Abnormal folding and accumulation of α-synuclein are found in several neurodegenerative diseases, including Parkinson's disease. Aggregated and highly phosphorylated α-synuclein constitutes the main component of Lewy bodies in the brain, the pathological hallmark of Parkinson's disease. For decades, much attention has been focused on the accumulation of α-synuclein in the brain parenchyma rather than considering Parkinson's disease as a systemic disease. Recent evidence demonstrates that, at least in some patients, the initial α-synuclein pathology originates in the peripheral organs and spreads to the brain. Injection of α-synuclein preformed fibrils into the gastrointestinal tract triggers the gut-to-brain propagation of α-synuclein pathology. However, whether α-synuclein pathology can occur spontaneously in peripheral organs independent of exogenous α-synuclein preformed fibrils or pathological α-synuclein leakage from the central nervous system remains under investigation. In this review, we aimed to summarize the role of peripheral α-synuclein pathology in the pathogenesis of Parkinson's disease. We also discuss the pathways by which α-synuclein pathology spreads from the body to the brain.

Synaptotagmin-11 regulates immune functions of microglia invivo.

Membrane trafficking pathways mediate key microglial activities such as cell migration, cytokine secretion, and phagocytosis. However, the underlying molecular mechanism remains poorly understood. Previously, we found that synaptotagmin-11 (Syt11), a non-Ca2+ -binding Syt associated with Parkinson's disease (PD) and schizophrenia, inhibits cytokine release and phagocytosis in primary microglia. Here we reported the invivo function of Syt11 in microglial immune responses using an inducible microglia-specific Syt11-conditional-knockout (cKO) mouse strain. Syt11-cKO resulted in activation of microglia and elevated mRNA levels of IL-6, TNF-α, IL-1β, and iNOS in various brain regions under both resting state and LPS-induced acute inflammation state in adult mice. In a PD mouse model generated by microinjection of preformed α-synuclein fibrils into the striatum, a reduced number of microglia migrated toward the injection sites and an enhanced phagocytosis of α-synuclein fibrils by microglia were found in Syt11-cKO mice. To understand the molecular mechanism of Syt11 function, we identified its direct binding proteins vps10p-tail-interactor-1a (vti1a) and vti1b. The linker domain of Syt11 interacted with both proteins and a peptide derived from it competitively inhibited the interaction of Syt11 with vti1a/vti1b invitro and in cells. Importantly, application of this peptide induced more cytokine secretion in wild-type microglia upon LPS treatment, phenocopying defects in Syt11 knockdown cells. Altogether, we propose that Syt11 inhibits microglial activation invivo and regulates cytokine secretion through interactions with vti1a and vti1b.

Chitosan oligosaccharides inhibit the fibrillation of insulin and disassemble its preformed fibrils

In the current study, we first established that chitosan oligosaccharides (COS) have significant anti-fibrillogenic and fibril-destabilising effects on bovine insulin in vitro that proportionally expand with concentration growth. The obtained data were supported by the Thioflavin T (ThT) assay, circular dichroism (CD), attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy, and atomic force microscopy (AFM). Interestingly, coincubation of insulin with COS in the ratio of 1 to 10 over 48 h at 37 °C leads to full prevention of insulin aggregation, and in the case of preformed fibrils, results in their destabilisation and disaggregation. Moreover, both a cationic polymer of allylamine (PAH) and a sulphated oligosaccharide (CROS) prepared from carrageenan had no inhibitory effect on insulin amyloid formation. Thus, we proposed that COS modulates insulin amyloid formation due to the presence of linear sugar units, the degree of polymerization, and the free amino group providing a positive charge. These findings highlight the potential implications of COS as a promising substance for the treatment of insulin-dependent diabetes mellitus and localised insulin-derived amyloidosis and, moreover, provide a new insight into the mechanism of the anti-diabetic and antitoxic properties of chitosan and chitosan-based agents.

Formation of templated inclusions in a forebrain α-synuclein mouse model is independent of LRRK2

Leucine-rich repeat kinase 2 (LRRK2) and α-synuclein share enigmatic roles in the pathobiology of Parkinson's disease (PD). LRRK2 mutations are a common genetic cause of PD which, in addition to neurodegeneration, often present with abnormal deposits of α-synuclein in the form of Lewy-related pathology. As Lewy-related pathology is a prominent neuropathologic finding in sporadic PD, the relationship between LRRK2 and α-synuclein has garnered considerable interest. However, whether and how LRRK2 might influence the accumulation of Lewy-related pathology remains poorly understood. Through stereotactic injection of mouse α-synuclein pre-formed fibrils (PFF), we modeled the spread of Lewy-related pathology within forebrain regions where LRRK2 is most highly expressed. The impact of LRRK2 genotype on the formation of α-synuclein inclusions was evaluated at 1-month post-injection. Neither deletion of LRRK2 nor G2019S LRRK2 knockin appreciably altered the burden of α-synuclein pathology at this early timepoint. These observations fail to provide support for a robust pathophysiologic interaction between LRRK2 and α-synuclein in the forebrain in vivo. There was, however, a modest reduction in microglial activation induced by PFF delivery in the hippocampus of LRRK2 knockout mice, suggesting that LRRK2 may contribute to α-synuclein-induced neuroinflammation. Collectively, our data indicate that the pathological accumulation of α-synuclein in the mouse forebrain is largely independent of LRRK2.

α-Synuclein aggregates amplified from patient-derived Lewy bodies recapitulate Lewy body diseases in mice

Extraction of α-Synuclein (αSyn) aggregates from Lewy body disease (LBD) brains has been widely described yet templated fibrillization of LB-αSyn often fails to propagate its structural and functional properties. We recently demonstrated that aggregates amplified from LB-αSyn (ampLB) show distinct biological activities in vitro compared to human αSyn preformed fibrils (hPFF) formed de novo. Here we compare the in vivo biological activities of hPFF and ampLB regarding seeding activity, latency in inducing pathology, distribution of pathology, inclusion morphology, and cell-type preference. Injection of ampLB into mice expressing only human αSyn (male Thy1:SNCA/Snca–/– mice) induced pathologies similar to those of LBD subjects that were distinct from those induced by hPFF-injection or developing spontaneously with aging. Importantly, αSyn aggregates in ampLB-injected Thy1:SNCA/Snca–/– mice maintained the unique biological and conformational features of original LB-αSyn. These results indicate that ampLB-injection, rather than conventional PFF-injection or αSyn overexpression, faithfully models key aspects of LBD.

Modelling α-synuclein processing in primary patient cells for pharmacological intervention

Aim: Parkinson’s disease (PD) is a complex, chronic neurodegenerative disorder with predominately sporadic etiology. Intricate genetic-environmental interactions lead to the hallmarks of the disease: degeneration of dopaminergic neurons and the deposition of α-synuclein aggregates. The aim of this study was to establish a novel primary patient cell model as an in vitro screen to study α-synuclein processing for drug screening. Methods: Primary patient olfactory neuroepithelial-derived cells (ONS) were exposed to α-synuclein and examined for cytotoxicity, processing, and solubility over 48 h. Epigallocatechin gallate (EGCG), which is known to destabilise α-synuclein fibrils, was used to investigate the solubilisation of α-synuclein in the model system. Results: Exposure to 0.1 μmol/L α-synuclein preformed fibrils was not toxic to ONS over 48 h. ONS processing of α-synuclein was observed to be different in PD cells by their increased accumulation in the cytoplasm. Processing deficits in the PD ONS were confirmed by immunoblotting with an increase in sodium dodecyl sulfate (SDS)-insoluble α-synuclein after 48 h. Conclusions: The data has illustrated the utility of primary patient ONS as a model system to understand the processing of α-synuclein. Considerable differences in α-synuclein processing were identified in PD ONS. Furthermore, the data suggests that primary patient ONS are a viable in vitro drug screening platform for α-synuclein pathology in PD.

PARIS undergoes liquid-liquid phase separation and poly(ADP-ribose)-mediated solidification.

ZNF746 was identified as parkin-interacting substrate (PARIS). Investigating its pathophysiological properties, we find that PARIS undergoes liquid-liquid phase separation (LLPS) and amorphous solid formation. The N-terminal low complexity domain 1 (LCD1) of PARIS is required for LLPS, whereas the C-terminal prion-like domain (PrLD) drives the transition from liquid to solid phase. In addition, we observe that poly(ADP-ribose) (PAR) strongly binds to the C-terminus of PARIS near the PrLD, accelerating its LLPS andsolidification. N-Methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced PAR formation leads to PARIS oligomerization in human iPSC-derived dopaminergic neurons that is prevented by the PARP inhibitor, ABT-888. Furthermore, SDS-resistant PARIS species are observed in the substantia nigra (SN) of aged mice overexpressing wild-type PARIS, but not with a PAR binding-deficient PARIS mutant. PARIS solidification is also found in the SN of mice injected with preformed fibrils of α-synuclein (α-syn PFF) and adult mice with a conditional knockout (KO) of parkin, but not if α-syn PFF is injected into mice deficient for PARP1. Herein, we demonstrate that PARIS undergoes LLPS and PAR-mediated solidification in models of Parkinson's disease.

Dopaminergic neurodegeneration in the substantia nigra is associated with olfactory dysfunction in mice models of Parkinson’s disease

Olfactory dysfunction represents a prodromal stage in Parkinson’s disease (PD). However, the mechanisms underlying hyposmia are not specified yet. In this study, we first observed an early olfactory dysfunction in mice with intragastric rotenone administration, consistent with dopaminergic neurons loss and α-synuclein pathology in the olfactory bulb. However, a much severer olfactory dysfunction was observed without severer pathology in olfactory bulb when the loss of dopaminergic neurons in the substantia nigra occurred. Then, we established the mice models by intrastriatal α-synuclein preformed fibrils injection and demonstrated the performance in the olfactory discrimination test was correlated to the loss of dopaminergic neurons in the substantia nigra, without any changes in the olfactory bulb analyzed by RNA-sequence. In mice with intranasal ferric ammonium citrate administration, we observed olfactory dysfunction when dopaminergic neurodegeneration in substantia nigra occurred and was restored when dopaminergic neurons were rescued. Finally we demonstrated that chemogenetic inhibition of dopaminergic neurons in the substantia nigra was sufficient to cause hyposmia and motor incoordination. Taken together, this study shows a direct relationship between nigral dopaminergic neurodegeneration and olfactory dysfunction in PD models and put forward the understandings that olfactory dysfunction represents the early stage of neurodegeneration in PD progression.

α-Synuclein propagation leads to synaptic abnormalities in the cortex through microglial synapse phagocytosis

The major neuropathologic feature of Parkinson’s disease is the presence of widespread intracellular inclusions of α-synuclein known as Lewy bodies. Evidence suggests that these misfolded protein inclusions spread through the brain with disease progression. Changes in synaptic function precede neurodegeneration, and this extracellular α-synuclein can affect synaptic transmission. However, whether and how the spreading of α-synuclein aggregates modulates synaptic function before neuronal loss remains unknown. In the present study, we investigated the effect of intrastriatal injection of α-synuclein preformed fibrils (PFFs) on synaptic activity in the somatosensory cortex using a combination of whole-cell patch-clamp electrophysiology, histology, and Golgi-Cox staining. Intrastriatal PFF injection was followed by formation of phosphorylated α-synuclein inclusions in layer 5 of the somatosensory cortex, leading to a decrease in synapse density, dendritic spines, and spontaneous excitatory post-synaptic currents, without apparent neuronal loss. Additionally, three-dimensional reconstruction of microglia using confocal imaging showed an increase in the engulfment of synapses. Collectively, our data indicate that propagation of α-synuclein through neural networks causes abnormalities in synaptic structure and dynamics prior to neuronal loss.

Experimental procedures to investigate fibrillation of proteins

The unwanted phenomenon of protein fibrillation is observed in vivo and during therapeutic protein development in the industry. Protein aggregation is associated with various degenerative disorders and might induce immune-related challenges post-administration of biopharmaceutics. A pipeline for early detection, identification, and removal of pre-formed fibrils is needed to improve the quality, efficacy, and effectiveness of the formulation. Protein fibril formation is accompanied by unfolding, secondary structural changes and the formation of larger aggregates. However, most detection processes come with extensive sample preparation steps and inefficient repeatability, incurring a financial burden on research. The current article summarizes and critically discusses six simple yet powerful methods to detect aggregation phenomena in the line of detecting fibrillar aggregates in heat-induced bovine serum albumin protein. Comparing the native and heat-induced protein samples would provide insights about aggregates. Easy, inexpensive and optimized protocols for detecting the fibrillation of proteins are explained. The procedures mentioned here detected the appearance of β-sheet-rich fibrils in the heat-induced protein sample. The aggregation is characterized by enhanced thioflavin-T fluorescence, alteration in the intrinsic fluorescence, decrease in helicity and subsequent increase in β-sheet and appearance of particles with larger hydrodynamic diameters.•This article summarizes various analytical techniques to easily characterize the fibrillation of proteins.•Various techniques to detect the formation of β-sheet rich structures, changes in the secondary structures and size of aggregates have been discussed.•The stated methodologies are validated on a model protein, albumin.

Neuroanatomical and cognitive biomarkers of alpha-synuclein propagation in a mouse model of synucleinopathy prior to onset of motor symptoms.

Significant evidence suggests that misfolded alpha-synuclein (aSyn), a major component of Lewy bodies, propagates in a prion-like manner contributing to disease progression in Parkinson's disease (PD) and other synucleinopathies. In fact, timed inoculation of M83 hemizygous mice with recombinant human aSyn preformed fibrils (PFF) has shown symptomatic deficits after substantial spreading of pathogenic alpha-synuclein, as detected by markers for the phosphorylation of S129 of aSyn. However, whether accumulated toxicity impact human-relevant cognitive and structural neuroanatomical measures is not fully understood. Here we performed a single unilateral striatal PFF injection in M83 hemizygous mice, and using two assays with translational potential, ex vivo magnetic resonance imaging (MRI) and touchscreen testing, we examined the combined neuroanatomical and behavioral impact of aSyn propagation. In PFF-injected mice, we observed widespread atrophy in bilateral regions that project to or receive input from the injection site using MRI. We also identified early deficits in reversal learning prior to the emergence of motor symptoms. Our findings highlight a network of regions with related cellular correlates of pathology that follow the progression of aSyn spreading, and that affect brain areas relevant for reversal learning. Our experiments suggest that M83 hemizygous mice injected with human PFF provides a model to understand how misfolded aSyn affects human-relevant pre-clinical measures and suggest that these pre-clinical biomarkers could be used to detect early toxicity of aSyn and provide better translational measures between mice and human disease.

Feasibility of combining alpha-synuclein aggregation and 6-OHDA in embryonic midbrain culture for modeling dopamine neuron degeneration

Parkinson’s disease (PD) is characterized by the loss of nigrostriatal dopamine (DA) neurons and the presence of alpha-synuclein (αSyn)-positive Lewy body (LB) pathology. In this study, we attempted to recapitulate both these features in a novel in vitro model for PD. To achieve this, we combined the αSyn pre-formed fibril (PFF)-seeded LB-like pathology with 6-hydroxydopamine (6-OHDA)-induced mitochondrial toxicity in mouse embryonic midbrain cultures. To pilot the model for therapeutics testing, we assessed the effects of cerebral dopamine neurotrophic factor (CDNF) on αSyn aggregation and neuron survival. PFF-seeded pathology did not lead to DA neuron loss even with the highest dose of PFFs. The combination of PFFs and 6-OHDA did not trigger additional neurodegeneration or LB–like pathology and instead presented DA neuron loss to a similar extent as with 6-OHDA only. CDNF did not affect the PFF-seeded αSyn pathology or the DA neuron survival in the combination model but showed a trend toward neuroprotection in the 6-OHDA-only cultures.

Amyloidogenic propensity of self-assembling peptides and their adjuvant potential for use as DNA vaccines.

De novo designed peptides that self-assemble into cross-β rich fibrillar biomaterials have been pursued as an innovative platform for the development of adjuvant- and inflammation-free vaccines. However, they share structural and morphological properties similar to amyloid species implicated in neurodegenerative diseases, which has been a long-standing concern for their successful translation. Here, we comprehensively characterize the amyloidogenic character of the amphipathic self-assembling cross-β peptide KFE8, compared to pathological amyloid and amyloid-like proteins α-synuclein (α-syn) and TDP-43. Further, we developed plasmid-based DNA vaccines with the KFE8 backbone serving as a scaffold for delivery of a GFP model antigen. We find that expression of tandem repeats of KFE8 is non-toxic and efficiently cleared by autophagy. We also demonstrate that preformed KFE8 fibrils do not cross-seed amyloid formation of α-syn in mammalian cells compared to α-syn preformed fibrils. In mice, vaccination with plasmids encoding the KFE32-GFP fusion protein elicited robust immune responses, inducing production of significantly higher levels of anti-GFP antibodies compared to soluble GFP. Antigen-specific CD8+T cells were also detected in the spleens of vaccinated mice and cytokine profiles from antigen recall assays indicate a balanced Th1/Th2 response. These findings illustrate that cross-β-rich peptide nanofibers have distinct physicochemical properties from those of pathological amyloidogenic proteins, and are an attractive platform for the development of DNA vaccines with self-adjuvanting properties and improved safety profiles. STATEMENT OF SIGNIFICANCE: Biomaterials comprised of self-assembling peptides hold great promise for the development of new vaccines that do not require use of adjuvants. However, these materials have safety concerns, as they self-assemble into cross-β rich fibrils that are structurally similar to amyloid species implicated in disease. Here, we comprehensively study the properties of these biomaterials. We demonstrate that they have distinct properties from pathological proteins. They are non-toxic and do not trigger amyloidogenesis. Vaccination of these materials in mice elicited a robust immune response. Most excitingly, our work suggests that this platform could be used to develop DNA-based vaccines, which have few storage requirements. Further, due to their genetic encoding, longer sequences can be generated and the vaccines will be amenable to modification.

Assessment of Bio-Compounds Content, Antioxidant Activity, and Neuroprotective Effect of Red Cabbage (Brassica oleracea var. Capitata rubra) Processed by Convective Drying at Different Temperatures.

Parkinson's disease (PD) is the second most common neurodegenerative disorder, and no efficient therapy able to cure or slow down PD is available. In this study, dehydrated red cabbage was evaluated as a novel source of bio-compounds with neuroprotective capacity. Convective drying was carried out at different temperatures. Total phenolics (TPC), flavonoids (TFC), anthocyanins (TAC), and glucosinolates (TGC) were determined using spectrophotometry, amino acid profile by LC-DAD and fatty acid profile by GC-FID. Phenolic characterization was determined by liquid chromatography-high-resolution mass spectrometry. Cytotoxicity and neuroprotection assays were evaluated in SH-SY5Y human cells, observing the effect on preformed fibrils of α-synuclein. Drying kinetic confirmed a shorter processing time with temperature increase. A high concentration of bio-compounds was observed, especially at 90 °C, with TPC = 1544.04 ± 11.4 mg GAE/100 g, TFC = 690.87 ± 4.0 mg QE/100 g and TGC = 5244.9 ± 260.2 µmol SngE/100 g. TAC degraded with temperature. Glutamic acid and arginine were predominant. Fatty acid profiles were relatively stable and were found to be mostly C18:3n3. The neochlorogenic acid was predominant. The extracts had no cytotoxicity and showed a neuroprotective effect at 24 h testing, which can extend in some cases to 48 h. The present findings underpin the use of red cabbage as a functional food ingredient.

Investigating the potential effects of α-synuclein aggregation on susceptibility to chronic stress in a mouse Parkinson’s disease model

BackgroundParkinson’s disease (PD) is a motor disorder characterized by the degeneration of dopaminergic neurons, putatively due to the accumulation of α-synuclein (α-syn) in Lewy bodies (LBs) in Substantia Nigra. PD is also associated with the formation of LBs in brain areas responsible for emotional and cognitive regulation such as the amygdala and prefrontal cortex, and concurrent depression prevalence in PD patients. The exact link between dopaminergic cell loss, α-syn aggregation, depression, and stress, a major depression risk factor, is unclear. Therefore, we aimed to explore the interplay between sensitivity to chronic stress and α-syn aggregation.MethodsBilateral injections of α-syn preformed fibrils (PFFs) into the striatum of C57Bl/6 J mice were used to induce α-syn aggregation. Three months after injections, animals were exposed to chronic social defeat stress.Resultsα-syn aggregation did not affect stress susceptibility but independently caused increased locomotor activity in the open field test, reduced anxiety in the light–dark box test, and increased active time in the tail suspension test. Ex vivo analysis revealed modest dopaminergic neuron loss in the substantia nigra and reduced dopaminergic innervation in the dorsal striatum in PFFs injected groups. α-Syn aggregates were prominent in the amygdala, prefrontal cortex, and substantia nigra, with minimal α-syn aggregation in the raphe nuclei and locus coeruleus.ConclusionsProgressive bilateral α-syn aggregation might lead to compensatory activity increase and alterations in emotionally regulated behavior, without affecting stress susceptibility. Understanding how α-syn aggregation and degeneration in specific brain structures contribute to depression and anxiety in PD patients requires further investigation.

A Novel NOX Inhibitor Alleviates Parkinson's Disease Pathology in PFF-Injected Mice.

Oxidative stress-mediated damage is often a downstream result of Parkinson's disease (PD), which is marked by sharp decline in dopaminergic neurons within the nigrostriatal regions of the brain, accounting for the symptomatic motor deficits in patients. Regulating the level of oxidative stress may present a beneficial approach in preventing PD pathology. Here, we assessed the efficacy of a nicotinamide adenine phosphate (NADPH) oxidase (NOX) inhibitor, an exogenous reactive oxygen species (ROS) regulator synthesized by Aptabio therapeutics with the specificity to NOX-1, 2 and 4. Utilizing N27 rat dopaminergic cells and C57Bl/6 mice, we confirmed that the exposures of alpha-synuclein preformed fibrils (PFF) induced protein aggregation, a hallmark in PD pathology. In vitro assessment of the novel compound revealed an increase in cell viability and decreases in cytotoxicity, ROS, and protein aggregation (Thioflavin-T stain) against PFF exposure at the optimal concentration of 10 nM. Concomitantly, the oral treatment alleviated motor-deficits in behavioral tests, such as hindlimb clasping, rotarod, pole, nesting and grooming test, via reducing protein aggregation, based on rescued dopaminergic neuronal loss. The suppression of NOX-1, 2 and 4 within the striatum and ventral midbrain regions including Substantia Nigra compacta (SNc) contributed to neuroprotective/recovery effects, making it a potential therapeutic option for PD.

Molecular insights into the structure destabilization effects of ECG and EC on the Aβ protofilament: An all-atom molecular dynamics simulation study

The formation of Aβ into amyloid fibrils was closely connected to AD, therefore, the Aβ aggregates were the primary therapeutic targets against AD. Previous studies demonstrated that epicatechin-3-gallate (ECG), which possessed a gallate moiety, exhibited a greater ability to disrupt the preformed Aβ amyloid fibrils than epicatechin (EC), indicating that the gallate moiety was crucial. In the present study, the molecular mechanisms were investigated. Our results demonstrated that ECG had more potent disruptive impacts on the β-sheet structure and K28-A42 salt bridges than EC. We found that ECG significantly interfered the interactions between Peptide-4 and Peptide-5. However, EC could not. The disruption of K28-A42 salt bridges by ECG was mainly due to the interactions between ECG and the hydrophobic residues located at C-terminus. Interestingly, EC disrupted the K28-A42 salt bridges by the interactions with C-terminal hydrophobic residues and the cation-π interactions with K28. Moreover, our results indicated that hydrophobic interactions, H-bonds, π-π interactions and cation-π interactions between ECG and the bend of L-shaped region caused the disaggregation of interactions between Peptide-4 and Peptide-5. Significantly, gallate moiety in ECG had contributed tremendously to the disaggregation. We believed that our findings could be useful for designing prospective drug candidates targeting AD.