Axonopathy in an α-synuclein transgenic model of Lewy body disease is associated with extensive accumulation of C-terminal-truncated α-synuclein

Recombinant Antibody Fragments for Immunotherapy of Parkinson's Disease

Parkinson's disease (PD) is the second most common age-related neurodegenerative disorder. Multiple genetic and environmental factors leading to progressive loss of dopaminergic neurons in the substantia nigra pars compacta (SN) and consequent depletion of dopamine were described. Current clinical approaches, such as dopamine replacement or deep brain stimulation using surgically implanted probes, provide symptomatic relief but cannot modify disease progression. Therefore, disease-modifying therapeutic tools are urgently needed. Immunotherapy approaches, including passive transfer of protective antibodies and their fragments, have shown therapeutic efficacy in several animal models of neurodegenerative diseases, including PD. Recombinant antibody fragments are promising alternatives to conventional full-length antibodies. Modern computational approaches and molecular biology tools, directed evolution methodology, and the design of tissue-penetrating fusion peptides allowed for the development of recombinant antibody fragments with superior specificity and affinity, reduced immunogenicity, the capacity to target hidden epitopes and cross the blood-brain barrier (BBB), higher solubility and stability, the ability to refold after heat denaturation, and inexpensive large-scale production. In addition, antibody fragments do not induce microglia Fcγ receptor (FcγR)-mediated proinflammatory response and tissue damage in the central nervous system (CNS), because they lack the Fc portion of the immunoglobulin molecule. In the present review, we summarized data on recombinant antibody fragments evaluated as immunotherapeutics in preclinical models of PD and discussed their potential for developing therapeutic and preventive protocols for patients with PD.

Computational investigation on the effect of the peptidomimetic inhibitors (NPT100-18A and NPT200-11) on the α-synuclein and lipid membrane interactions

Parkinson's disease (PD) is associated with α-synuclein (α-Syn), a presynaptic protein that binds to cell membranes. The molecular pathophysiology of PD most likely begins with the binding of α-Syn to membranes. Recently, two peptidomimetic inhibitors (NPT100-18A and NPT200-11) were identified to potentially interact with α-Syn and affect the interaction of α-Syn with the membrane. In this study, the effect of the two peptidomimetic inhibitors on the α-Syn-membrane interaction was demonstrated. DFT calculations were performed for optimization of the two inhibitors, and the nucleophilicity (N) and electrophilicity (ω) of NPT100-18A and NPT200-11 were calculated to be 3.90 and 3.86 (N); 1.06 and 1.04 (ω), respectively. Using the docking tool (CB-dock2), the two α-Syn-peptidomimetic inhibitor complexes (α-Syn-NPT100-18A and α-Syn-NPT200-11) have been prepared. Then all-atom molecular dynamics (MD) simulation was carried out on the α-Syn (control), α-Syn-NPT100-18A and α-Syn-NPT200-11 complex systems in presence of DOPE: DOPS: DOPC (5:3:2) lipid bilayer. From the conformational dynamics analysis, the 3-D structure of α-Syn was found to be stable, and the helices present in the regions (1-37) and (45-95) of α-Syn were found to be retained in the presence of the two peptidomimetic inhibitors. The electron density profile analysis revealed the binding modes of NAC and C-terminal region of α-Syn (in the presence of NPT200-11 inhibitor) with lipid membrane are in the close vicinity from the lipid bilayer centre. Our findings in this study on α-Syn-membrane interactions may be useful for developing a new therapeutic approach for treating PD and other neurodegenerative disorders.Communicated by Ramaswamy H. Sarma.

Truncation or proteolysis of α-synuclein in Parkinsonism

Posttranslational modifications of α-synuclein, such as truncation or abnormal proteolysis, are implicated in Parkinson's disease (PD), dementia with Lewy bodies (DLB), and multiple system atrophy (MSA). A key focus of this article includes the proteases responsible for inducing truncation, the specific sites susceptible to truncation, and the resultant influence of these truncated species on the seeding and aggregation of endogenous α-synuclein. We also shed light on the unique structural attributes of these truncated species, and how these modifications can lead to distinctive forms of synucleinopathies. In addition, we explore the comparative toxic potentials of various α-synuclein species. An extensive analysis of available evidence of truncated α-synuclein species in human-synucleinopathy brains is also provided. Lastly, we delve into the detrimental impact of truncated species on key cellular structures such as the mitochondria and endoplasmic reticulum. Our article discusses enzymes involved in α-synuclein truncation, including 20 S proteasome, cathepsins, asparagine endopeptidase, caspase-1, calpain-1, neurosin/kallikrein-6, matrix metalloproteinase-1/-3, and plasmin. Truncation patterns impact α-synuclein aggregation - C-terminal truncation accelerates aggregation with larger truncations correlated with shortened aggregation lag times. N-terminal truncation affects aggregation differently based on the truncation location. C-terminally truncated α-synuclein forms compact, shorter fibrils compared to the full-length (FL) protein. N-terminally truncated monomers form fibrils similar in length to FL α-synuclein. Truncated forms show distinct fibril morphologies, increased β-sheet structures, and greater protease resistance. Misfolded α-synuclein can adopt various conformations, leading to unique aggregates and distinct synucleinopathies. Fibrils, with prion-like transmission, are potentially more toxic than oligomers, though this is still debated. Different α-synuclein variants with N- and C-terminal truncations, namely 5-140, 39-140, 65-140, 66-140, 68-140, 71-140, 1-139, 1-135, 1-133, 1-122, 1-119, 1-115, 1-110, and 1-103 have been found in PD, DLB, and MSA patients' brains. In Parkinsonism, excess misfolded α-synuclein overwhelms the proteasome degradation system, resulting in truncated protein production and accumulation in the mitochondria and endoplasmic reticulum.

Cogs in the autophagic machine-equipped to combat dementia-prone neurodegenerative diseases

Neurodegenerative diseases are often characterized by hydrophobic inclusion bodies, and it may be the case that the aggregate-prone proteins that comprise these inclusion bodies are in fact the cause of neurotoxicity. Indeed, the appearance of protein aggregates leads to a proteostatic imbalance that causes various interruptions in physiological cellular processes, including lysosomal and mitochondrial dysfunction, as well as break down in calcium homeostasis. Oftentimes the approach to counteract proteotoxicity is taken to merely upregulate autophagy, measured by an increase in autophagosomes, without a deeper assessment of contributors toward effective turnover through autophagy. There are various ways in which autophagy is regulated ranging from the mammalian target of rapamycin (mTOR) to acetylation status of proteins. Healthy mitochondria and the intracellular energetic charge they preserve are key for the acidification status of lysosomes and thus ensuring effective clearance of components through the autophagy pathway. Both mitochondria and lysosomes have been shown to bear functional protein complexes that aid in the regulation of autophagy. Indeed, it may be the case that minimizing the proteins associated with the respective neurodegenerative pathology may be of greater importance than addressing molecularly their resulting inclusion bodies. It is in this context that this review will dissect the autophagy signaling pathway, its control and the manner in which it is molecularly and functionally connected with the mitochondrial and lysosomal system, as well as provide a summary of the role of autophagy dysfunction in driving neurodegenerative disease as a means to better position the potential of rapamycin-mediated bioactivities to control autophagy favorably.

In vivo effects of the alpha-synuclein misfolding inhibitor minzasolmin supports clinical development in Parkinson's disease

Direct targeting of alpha-synuclein (ASYN) has emerged as a disease-modifying strategy for Parkinson's disease and other synucleinopathies which is being approached using both small molecule compounds and ASYN-targeted biologics. Minzasolmin (UCB0599) is an orally bioavailable and brain-penetrant small molecule ASYN misfolding inhibitor in clinical development as a disease-modifying therapeutic for Parkinson's disease. Herein the results of preclinical evaluations of minzasolmin that formed the basis for subsequent clinical development are described. Pharmacokinetic evaluations of intraperitoneal 1 and 5 mg/kg minzasolmin in wildtype mice revealed parallel and dose-proportional exposures in brain and plasma. Three-month administration studies in the Line 61 transgenic mouse model of PD were conducted to measure ASYN pathology and other PD-relevant endpoints including markers of CNS inflammation, striatal DAT labeling and gait. Reductions in ASYN pathology were correlated with improved aspects of gait and balance, reductions in CNS inflammation marker abundance, and normalized striatal DAT levels. These findings provide support for human dose determinations and have informed the translational strategy for clinical trial design and biomarker selection for the ongoing clinical studies of minzasolmin in patients living with early-stage Parkinson's disease (ClinicalTrials.gov ID: NCT04658186; EudraCT Number 2020-003265).

Salivary Biomarkers: Noninvasive Ways for Diagnosis of Parkinson's Disease

Finding reliable biomarkers has a crucial role in Parkinson's disease (PD) assessments. Saliva is a bodily fluid, which might be used as a source of biomarkers for PD. Our article has reviewed several publications on salivary proteins in PD patients and their potential as biomarkers. We find out that α-Syn's proportion in oligomeric form is higher in PD patients' saliva, which is potent to use as a biomarker for PD. The salivary concentration of DJ-1 and alpha-amylase is lower in PD patients. Also, substance P level is more moderate in PD patients. Although salivary flow rate is decreased in PD patients, high levels of heme oxygenase and acetylcholinesterase might be used as noninvasive biomarkers. Salivary miRNAs (miR-153, miR-223, miR-874, and miR-145-3p) are novel diagnostic biomarkers that should be given more attention.

The Parkinson-Associated Toxin Paraquat Shifts Physiological α-Synuclein Tetramers toward Monomers That Can Be Calpain-Truncated and Form Oligomers

Abnormal aggregation of α-synuclein (αS) is thought to initiate neuronal dysfunction and death in Parkinson disease (PD). In addition to higher-molecular-weight, oligomeric, and polymeric forms of αS associated with neurotoxicity and disease, recent findings indicate the occurrence of physiological tetrameric assemblies in healthy neurons in culture and in brain. Herein, the PD-associated neurotoxin paraquat reduced physiological tetramers and led to calpain-truncated monomers and an approximately 70-kDa apparent oligomer different in size from physiological αS multimers. These truncated and oligomeric forms could also be generated by calpain cleavage of pure, recombinant human αS in vitro. Moreover, they were detected in the brains of tetramer-abrogating, E46K-amplified (3K) mice that model PD. These results indicate that paraquat triggers membrane damage and aberrant calpain activity that can induce a pathologic shift of tetramers toward an excess of full-length and truncated monomers, the accumulation of αS oligomers, and insoluble cytoplasmic αS puncta. The findings suggest that an environmental precipitant of PD can alter αS tetramer/monomer equilibrium, as already shown for several genetically caused forms of PD.

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

Development of neuroprotective therapeutics for Parkinson's disease (PD) is facing a lack of translation from pre-clinical to clinical trials. One strategy for improvement is to increase predictive validity of pre-clinical studies by using extensively characterized animal models with a comprehensive set of validated pharmacodynamic readouts. Mice over-expressing full-length, human, wild-type alpha-synuclein under the Thy-1 promoter (Thy1-aSyn line 61) reproduce key features of sporadic PD, such as progressive loss of striatal dopamine, alpha-synuclein pathology, deficits in motor and non-motor functions, and elevation of inflammatory markers. Extensive work with this model by multiple laboratories over the past decade further increased confidence in its robustness and validity, especially for analyzing pathomechanisms of alpha-synuclein pathology and down-stream pathways, and for pre-clinical drug testing. Interestingly, while postnatal transgene expression is widespread in central and peripheral neurons, the extent and progression of down-stream pathology differs between brain regions, thereby replicating the characteristic selective vulnerability of neurodegenerative diseases. In-depth characterization of these readouts in conjunction with behavioral deficits has led to more informative endpoints for pre-clinical trials. Each drug tested in Thy1-aSyn line 61 enhances knowledge on how molecular targets, pathology, and functional behavioral readouts are interconnected, thereby further optimizing the platform towards predictive validity for clinical trials. Here, we present the current state of the art using Thy1-aSyn line 61 for drug target discovery, validation, and pre-clinical testing.

Therapeutic Approaches to Non-Motor Symptoms of Parkinson's Disease: A Current Update on Preclinical Evidence

Despite being classified as a movement disorder, Parkinson's disease (PD) is characterized by a wide range of non-motor symptoms that significantly affect the patients' quality of life. However, clear evidence-based therapy recommendations for non-motor symptoms of PD are uncommon. Animal models of PD have previously been shown to be useful for advancing the knowledge and treatment of motor symptoms. However, these models may provide insight into and assess therapies for non-motor symptoms in PD. This paper highlights non-motor symptoms in preclinical models of PD and the current position regarding preclinical therapeutic approaches for these non-motor symptoms. This information may be relevant for designing future preclinical investigations of therapies for nonmotor symptoms in PD.

Implications of fractalkine on glial function, ablation and glial proteins/receptors/markers—understanding its therapeutic usefulness in neurological settings: a narrative review

Background

Fractalkine (CX3CL1) is a chemokine predominantly released by neurons. As a signaling molecule, CX3CL1 facilitates talk between neurons and glia. CX3CL1 is considered as a potential target which could alleviate neuroinflammation. However, certain controversial results and ambiguous role of CX3CL1 make it inexorable to decipher the overall effects of CX3CL1 on the physiopathology of glial cells.

Main body of the abstract

Implications of cross-talk between CX3CL1 and different glial proteins/receptors/markers will give a bird eye view of the therapeutic significance of CX3CL1. Keeping with the need, this review identifies the effects of CX3CL1 on glial physiopathology, glial ablation, and gives a wide coverage on the effects of CX3CL1 on certain glial proteins/receptors/markers.

Short conclusion

Pinpoint prediction of the therapeutic effect of CX3CL1 on neuroinflammation needs further research. This is owing to certain obscure roles and implications of CX3CL1 on different glial proteins/receptors/markers, which are crucial under neurological settings. Further challenges are imposed due to the dichotomous roles played by CX3CL1. The age-old chemokine shows many newer scopes of research in near future. Thus, overall assessment of the effect of CX3CL1 becomes crucial prior to its administration in neuroinflammation.

Neuronal Oxidative Stress Promotes α-Synuclein Aggregation In Vivo

Both genetic and environmental factors increase risk for Parkinson's disease. Many of the known genetic factors influence α-synuclein aggregation or degradation, whereas most of the identified environmental factors produce oxidative stress. Studies using in vitro approaches have identified mechanisms by which oxidative stress can accelerate the formation of α-synuclein aggregates, but there is a paucity of evidence supporting the importance of these processes over extended time periods in brain. To assess this issue, we evaluated α-synuclein aggregates in brains of three transgenic mouse strains: hSyn mice, which overexpress human α-synuclein in neurons and spontaneously develop α-synuclein aggregates; EAAT3^-/- mice, which exhibit a neuron-specific impairment in cysteine uptake and resultant neuron-selective chronic oxidative stress; and double-transgenic hSyn/EAAT3^-/- mice. Aggregate formation was evaluated by quantitative immunohistochemistry for phosphoserine 129 α-synuclein and by an α-synuclein proximity ligation assay. Both methods showed that the double transgenic hSyn/EAAT3^-/- mice exhibited a significantly higher α-synuclein aggregate density than littermate hSyn mice in each brain region examined. Negligible aggregate formation was observed in the EAAT3^-/- mouse strain, suggesting a synergistic rather than additive interaction between the two genotypes. A similar pattern of results was observed in assessments of motor function: the pole test and rotarod test. Together, these observations indicate that chronic, low-grade neuronal oxidative stress promotes α-synuclein aggregate formation in vivo. This process may contribute to the mechanism by which environmentally induced oxidative stress contributes to α-synuclein pathology in idiopathic Parkinson's disease.

Thiocyanate Reduces Motor Impairment in the hMPO-A53T PD Mouse Model While Reducing MPO-Oxidation of Alpha Synuclein in Enlarged LYVE1/AQP4 Positive Periventricular Glymphatic Vessels

Parkinson's disease (PD) is due to the oxidation of alpha synuclein (αSyn) contributing to motor impairment. We developed a transgenic mouse model of PD that overexpresses the mutated human αSyn gene (A53T) crossed to a mouse expressing the human MPO gene. This model exhibits increased oxidation and chlorination of αSyn leading to greater motor impairment. In the current study, the hMPO-A53T mice were treated with thiocyanate (SCN^-) which is a favored substrate of MPO as compared to chlorine. We show that hMPO-A53T mice treated with SCN^- have less chlorination in the brain and show an improvement in motor skills compared to the nontreated hMPO-A53T mice. Interestingly, in the hMPO-A53T mice we found a possible link between MPO-related disease and the glymphatic system which clears waste including αSyn from the brain. The untreated hMPO-A53T mice exhibited an increase in the size of periventricular glymphatic vessels expressing the glymphatic marker LYVE1 and aquaporin 4 (AQP4). These vessels also exhibited an increase in MPO and HOCl-modified epitopes in the glymphatic vessels correlating with loss of ependymal cells lining the ventricles. These findings suggest that MPO may significantly promote the impairment of the glymphatic waste removal system thus contributing to neurodegeneration in PD. Moreover, the inhibition of MPO chlorination/oxidation by SCN^- may provide a potential therapeutic approach to this disease.

Therapeutic Strategies for Immune Transformation in Parkinson’s Disease

Dysregulation of innate and adaptive immunity can lead to alpha-synuclein (α-syn) misfolding, aggregation, and post-translational modifications in Parkinson’s disease (PD). This process is driven by neuroinflammation and oxidative stress, which can contribute to the release of neurotoxic oligomers that facilitate dopaminergic neurodegeneration. Strategies that promote vaccines and antibodies target the clearance of misfolded, modified α-syn, while gene therapy approaches propose to deliver intracellular single chain nanobodies to mitigate α-syn misfolding, or to deliver neurotrophic factors that support neuronal viability in an otherwise neurotoxic environment. Additionally, transformative immune responses provide potential targets for PD therapeutics. Anti-inflammatory drugs represent one strategy that principally affects innate immunity. Considerable research efforts have focused on transforming the balance of pro-inflammatory effector T cells (Teffs) to favor regulatory T cell (Treg) activity, which aims to attenuate neuroinflammation and support reparative and neurotrophic homeostasis. This approach serves to control innate microglial neurotoxic activities and may facilitate clearance of α-syn aggregates accordingly. More recently, changes in the intestinal microbiome have been shown to alter the gut-immune-brain axis leading to suppressed leakage of bacterial products that can promote peripheral inflammation and α-syn misfolding. Together, each of the approaches serves to interdict chronic inflammation associated with disordered immunity and neurodegeneration. Herein, we examine research strategies aimed at improving clinical outcomes in PD.

Neuronal hyperactivity-induced oxidant stress promotes in vivo α-synuclein brain spreading

Interneuronal transfer and brain spreading of pathogenic proteins are features of neurodegenerative diseases. Pathophysiological conditions and mechanisms affecting this spreading remain poorly understood. This study investigated the relationship between neuronal activity and interneuronal transfer of α-synuclein, a Parkinson-associated protein, and elucidated mechanisms underlying this relationship. In a mouse model of α-synuclein brain spreading, hyperactivity augmented and hypoactivity attenuated protein transfer. Important features of neuronal hyperactivity reported here were an exacerbation of oxidative and nitrative reactions, pronounced accumulation of nitrated α-synuclein, and increased protein aggregation. Data also pointed to mitochondria as key targets and likely sources of reactive oxygen and nitrogen species within hyperactive neurons. Rescue experiments designed to counteract the increased burden of reactive oxygen species reversed hyperactivity-induced α-synuclein nitration, aggregation, and interneuronal transfer, providing first evidence of a causal link between these pathological effects of neuronal stimulation and indicating a mechanistic role of oxidant stress in hyperactivity-induced α-synuclein spreading.

Alpha-synucleinopathy reduces NMNAT3 protein levels and neurite formation that can be rescued by targeting the NAD+ pathway

Parkinson's disease is characterized by the deposition of α-synuclein, which leads to synaptic dysfunction, the loss of neuronal connections and ultimately progressive neurodegeneration. Despite extensive research into Parkinson's disease pathogenesis, the mechanisms underlying α-synuclein-mediated synaptopathy have remained elusive. Several lines of evidence suggest that altered nicotinamide adenine dinucleotide (NAD+) metabolism might be causally related to synucleinopathies, including Parkinson's disease. NAD+ metabolism is central to the maintenance of synaptic structure and function. Its synthesis is mediated by nicotinamide mononucleotide adenylyltransferases (NMNATs), but their role in Parkinson's disease is not known. Here we report significantly decreased levels of NMNAT3 protein in the caudate nucleus of patients who have died with Parkinson's disease, which inversely correlated with the amount of monomeric α-synuclein. The detected alterations were specific and significant as the expression levels of NMNAT1, NMNAT2 and sterile alpha and TIR motif containing 1 (SARM1) were not significantly different in Parkinson's disease patients compared to controls. To test the functional significance of these findings, we ectopically expressed wild-type α-synuclein in retinoic acid-differentiated dopaminergic SH-SY5Y cells that resulted in decreased levels of NMNAT3 protein plus a neurite pathology, which could be rescued by FK866, an inhibitor of nicotinamide phosphoribosyltransferase that acts as a key enzyme in the regulation of NAD+ synthesis. Our results establish, for the first time, NMNAT3 alterations in Parkinson's disease and demonstrate in human cells that this phenotype together with neurite pathology is causally related to α-synucleinopathy. These findings identify alterations in the NAD+ biosynthetic pathway as a pathogenic mechanism underlying α-synuclein-mediated synaptopathy.

Diagnostic and therapeutic agents that target alpha-synuclein in Parkinson's disease

The development of disease-modifying drugs and differential diagnostic agents is an urgent medical need in Parkinson’s disease. Despite the complex pathophysiological pathway, the misfolding of alpha-synuclein has been identified as a putative biomarker for detecting the onset and progression of the neurodegeneration associated with Parkinson’s disease. Identifying the most appropriate alpha-synuclein-based diagnostic modality with clinical translation will revolutionize the diagnosis of Parkinson’s. Likewise, molecules that target alpha-synuclein could alter the disease pathway that leads to Parkinson’s and may serve as first-in class therapeutics compared to existing treatment options such as levodopa and dopamine agonist that do not necessarily modify the disease pathway. Notwithstanding the promising benefits that alpha-synuclein presents to therapeutics and diagnostics development for Parkinson’s disease, finding ways to address potential challenges such as inadequate preclinical models, safety and efficacy will be paramount to achieving clinical translation. In this comprehensive review paper, we described the role of alpha-synuclein in the pathogenesis of Parkinson’s disease, as well as how its structure and function relationship delineate disease onset and progression. We further discussed different alpha-synuclein-based diagnostic modalities including biomolecular assays and molecular imaging. Finally, we presented current small molecules and biologics that are being developed as disease-modifying drugs or positron emission tomography imaging probes for Parkinson’s disease.

Multi-platform quantitation of alpha-synuclein human brain proteoforms suggests disease-specific biochemical profiles of synucleinopathies

Based on immunostainings and biochemical analyses, certain post-translationally modified alpha-synuclein (aSyn) variants, including C-terminally truncated (CTT) and Serine-129 phosphorylated (pSer129) aSyn, are proposed to be involved in the pathogenesis of synucleinopathies such as Parkinson’s disease with (PDD) and without dementia (PD), dementia with Lewy bodies (DLB), and multiple system atrophy (MSA). However, quantitative information about aSyn proteoforms in the human brain in physiological and different pathological conditions is still limited. To address this, we generated sequential biochemical extracts of the substantia nigra, putamen and hippocampus from 28 donors diagnosed and neuropathologically-confirmed with different synucleinopathies (PD/PDD/DLB/MSA), as well as Alzheimer’s disease, progressive supranuclear palsy, and aged normal subjects. The tissue extracts were used to build a reverse phase array including 65 aSyn antibodies for detection. In this multiplex approach, we observed increased immunoreactivity in donors with synucleinopathies compared to controls in detergent-insoluble fractions, mainly for antibodies against CT aSyn and pSer129 aSyn. In addition, despite of the restricted sample size, clustering analysis suggested disease-specific immunoreactivity signatures in patient groups with different synucleinopathies. We aimed to validate and quantify these findings using newly developed immunoassays towards total, 119 and 122 CTT, and pSer129 aSyn. In line with previous studies, we found that synucleinopathies shared an enrichment of post-translationally modified aSyn in detergent-insoluble fractions compared to the other analyzed groups. Our measurements allowed for a quantitative separation of PDD/DLB patients from other synucleinopathies based on higher detergent-insoluble pSer129 aSyn concentrations in the hippocampus. In addition, we found that MSA stood out due to enrichment of CTT and pSer129 aSyn also in the detergent-soluble fraction of the SN and putamen. Together, our results achieved by multiplexed and quantitative immunoassay-based approaches in human brain extracts of a limited sample set point to disease-specific biochemical aSyn proteoform profiles in distinct neurodegenerative disorders.

Efficacy and immunogenicity of MultiTEP-based DNA vaccines targeting human α-synuclein: prelude for IND enabling studies

Accumulation of misfolded proteins such as amyloid-β (Aβ), tau, and α-synuclein (α-Syn) in the brain leads to synaptic dysfunction, neuronal damage, and the onset of relevant neurodegenerative disorder/s. Dementia with Lewy bodies (DLB) and Parkinson’s disease (PD) are characterized by the aberrant accumulation of α-Syn intracytoplasmic Lewy body inclusions and dystrophic Lewy neurites resulting in neurodegeneration associated with inflammation. Cell to cell propagation of α-Syn aggregates is implicated in the progression of PD/DLB, and high concentrations of anti-α-Syn antibodies could inhibit/reduce the spreading of this pathological molecule in the brain. To ensure sufficient therapeutic concentrations of anti-α-Syn antibodies in the periphery and CNS, we developed four α-Syn DNA vaccines based on the universal MultiTEP platform technology designed especially for the elderly with immunosenescence. Here, we are reporting on the efficacy and immunogenicity of these vaccines targeting three B-cell epitopes of hα-Syn aa85–99 (PV-1947D), aa109–126 (PV-1948D), aa126–140 (PV-1949D) separately or simultaneously (PV-1950D) in a mouse model of synucleinopathies mimicking PD/DLB. All vaccines induced high titers of antibodies specific to hα-Syn that significantly reduced PD/DLB-like pathology in hα-Syn D line mice. The most significant reduction of the total and protein kinase resistant hα-Syn, as well as neurodegeneration, were observed in various brain regions of mice vaccinated with PV-1949D and PV-1950D in a sex-dependent manner. Based on these preclinical data, we selected the PV-1950D vaccine for future IND enabling preclinical studies and clinical development.

Calpain Inhibitors as Potential Therapeutic Modulators in Neurodegenerative Diseases

It is considered a significant challenge to understand the neuronal cell death mechanisms with a suitable cure for neurodegenerative disorders in the coming years. Calpains are one of the best-considered "cysteine proteases activated" in brain disorders. Calpain is an important marker and mediator in the pathophysiology of neurodegeneration. Calpain activation being the essential neurodegenerative factor causing apoptotic machinery activation, it is crucial to develop reliable and effective approaches to prevent calpain-mediated apoptosis in degenerating neurons. It has been recently seen that the "inhibition of calpain activation" has appeared as a possible therapeutic target for managing neurodegenerative diseases. A systematic literature review of PubMed, Medline, Bentham, Scopus, and EMBASE (Elsevier) databases was conducted. The present article reviews the basic pathobiology and role of selective calpain inhibitors used in various neurodegenerative diseases as a therapeutic target.

Temporal Evolution of Inflammation and Neurodegeneration With Alpha-Synuclein Propagation in Parkinson's Disease Mouse Model

According to a few studies, α-synuclein (αSyn) propagation has been suggested to play a key role in the pathomechanism of Parkinson's disease (PD), but neurodegeneration and the involvement of inflammation in its pathologic progression are not well understood with regard to temporal relationship. In this study, with the help of the PD mouse model injected with intrastriatal αSyn preformed fibril (PFF), the temporal evolution of αSyn propagation, inflammation, and neurodegeneration was explored in the perspective of the striatum and the whole brain. In the PFF-injected striatum, inflammatory response cells, including microglia and astrocytes, were activated at the earliest stage and reduced with time, and the phosphorylated form of αSyn accumulation increased behind it. Afterward, the degeneration of striatal dopaminergic neurons became significant with the conspicuity of behavioral phenotype. Similar patterns of forefront eruption of inflammation and then followed by αSyn propagation were noted in the opposite striatum, which were not injured by PFF injection. In analyzing the whole brain, inflammatory responses were activated at the earliest stage, and the soluble αSyn expression increased concurrently. The inflammatory response decreased afterward, and the accumulation of the insoluble form of αSyn increased behind it. Our results suggested that the inflammatory response may precede the accumulation of the pathologic form of αSyn; thereafter, the neurodegeneration and motor dysfunction followed αSyn proliferation in the PD mouse model. From this model, recognizing the temporal relationship between inflammation, αSyn propagation, and neurodegeneration may be helpful in establishing the PD animal model and monitoring the effect of interventional therapy.

A Phase II Study to Evaluate the Safety and Efficacy of Prasinezumab in Early Parkinson's Disease (PASADENA): Rationale, Design, and Baseline Data

Background: Currently available treatments for Parkinson's disease (PD) do not slow clinical progression nor target alpha-synuclein, a key protein associated with the disease. Objective: The study objective was to evaluate the efficacy and safety of prasinezumab, a humanized monoclonal antibody that binds aggregated alpha-synuclein, in individuals with early PD. Methods: The PASADENA study is a multicenter, randomized, double-blind, placebo-controlled treatment study. Individuals with early PD, recruited across the US and Europe, received monthly intravenous doses of prasinezumab (1,500 or 4,500 mg) or placebo for a 52-week period (Part 1), followed by a 52-week extension (Part 2) in which all participants received active treatment. Key inclusion criteria were: aged 40-80 years; Hoehn & Yahr (H&Y) Stage I or II; time from diagnosis ≤2 years; having bradykinesia plus one other cardinal sign of PD (e.g., resting tremor, rigidity); DAT-SPECT imaging consistent with PD; and either treatment naïve or on a stable monoamine oxidase B (MAO-B) inhibitor dose. Study design assumptions for sample size and study duration were built using a patient cohort from the Parkinson's Progression Marker Initiative (PPMI). In this report, baseline characteristics are compared between the treatment-naïve and MAO-B inhibitor-treated PASADENA cohorts and between the PASADENA and PPMI populations. Results: Of the 443 patients screened, 316 were enrolled into the PASADENA study between June 2017 and November 2018, with an average age of 59.9 years and 67.4% being male. Mean time from diagnosis at baseline was 10.11 months, with 75.3% in H&Y Stage II. Baseline motor and non-motor symptoms (assessed using Movement Disorder Society-Unified Parkinson's Disease Rating Scale [MDS-UPDRS]) were similar in severity between the MAO-B inhibitor-treated and treatment-naïve PASADENA cohorts (MDS-UPDRS sum of Parts I + II + III [standard deviation (SD)]; 30.21 [11.96], 32.10 [13.20], respectively). The overall PASADENA population (63.6% treatment naïve and 36.4% on MAO-B inhibitor) showed a similar severity in MDS-UPDRS scores (e.g., MDS-UPDRS sum of Parts I + II + III [SD]; 31.41 [12.78], 32.63 [13.04], respectively) to the PPMI cohort (all treatment naïve). Conclusions: The PASADENA study population is suitable to investigate the potential of prasinezumab to slow disease progression in individuals with early PD. Trial Registration: NCT03100149.

The subcellular arrangement of alpha-synuclein proteoforms in the Parkinson's disease brain as revealed by multicolor STED microscopy

Various post-translationally modified (PTM) proteoforms of alpha-synuclein (aSyn)-including C-terminally truncated (CTT) and Serine 129 phosphorylated (Ser129-p) aSyn-accumulate in Lewy bodies (LBs) in different regions of the Parkinson's disease (PD) brain. Insight into the distribution of these proteoforms within LBs and subcellular compartments may aid in understanding the orchestration of Lewy pathology in PD. We applied epitope-specific antibodies against CTT and Ser129-p aSyn proteoforms and different aSyn domains in immunohistochemical multiple labelings on post-mortem brain tissue from PD patients and non-neurological, aged controls, which were scanned using high-resolution 3D multicolor confocal and stimulated emission depletion (STED) microscopy. Our multiple labeling setup highlighted a consistent onion skin-type 3D architecture in mature nigral LBs in which an intricate and structured-appearing framework of Ser129-p aSyn and cytoskeletal elements encapsulates a core enriched in CTT aSyn species. By label-free CARS microscopy we found that enrichments of proteins and lipids were mainly localized to the central portion of nigral aSyn-immunopositive (aSyn+) inclusions. Outside LBs, we observed that 122CTT aSyn+ punctae localized at mitochondrial membranes in the cytoplasm of neurons in PD and control brains, suggesting a physiological role for 122CTT aSyn outside of LBs. In contrast, very limited to no Ser129-p aSyn immunoreactivity was observed in brains of non-neurological controls, while the alignment of Ser129-p aSyn in a neuronal cytoplasmic network was characteristic for brains with (incidental) LB disease. Interestingly, Ser129-p aSyn+ network profiles were not only observed in neurons containing LBs but also in neurons without LBs particularly in donors at early disease stage, pointing towards a possible subcellular pathological phenotype preceding LB formation. Together, our high-resolution and 3D multicolor microscopy observations in the post-mortem human brain provide insights into potential mechanisms underlying a regulated LB morphogenesis.

Safety and Tolerability of Active Immunotherapy Targeting α-Synuclein with PD03A in Patients with Early Parkinson's Disease: A Randomized, Placebo-Controlled, Phase 1 Study

Background:

Immunotherapies targeting α-synuclein aim to limit its extracellular spread in the brain and prevent progression of pathology in Parkinson’s disease (PD). PD03A is a specific active immunotherapy (SAIT) involving immunization with a short peptide formulation.

Objective:

This phase 1 study characterized the safety and tolerability of PD03A in patients with early PD. A key secondary objective was to evaluate immunological activity following immunization.

Methods:

This was a phase 1 study of two different doses of PD03A versus placebo in PD patients. Patients were randomized (1:1:1) to receive four priming plus one booster vaccination of PD03A 15μg, PD03A 75μg or placebo and were followed for 52 weeks.

Results:

Overall, 36 patients were randomized, of which 35 received five immunizations and completed the study. All patients experienced at least one adverse event. Transient local injection site reactions affected all but two patients; otherwise most AEs were considered unrelated to study treatment. A substantial IgG antibody response against PD03 was observed with a maximum titer achieved at Week-12. Differences in titers between both active groups versus placebo were statistically significant from the second immunization at Week-8 until Week-52.

Conclusion:

The safety profile and positive antibody response of PD03A supports the further development of active immunotherapeutic approaches for the treatment of PD.

Modulation of the Interactions Between α-Synuclein and Lipid Membranes by Post-translational Modifications

Parkinson's disease is characterised by the presence in brain tissue of aberrant inclusions known as Lewy bodies and Lewy neurites, which are deposits composed by α-synuclein and a variety of other cellular components, including in particular lipid membranes. The dysregulation of the balance between lipid homeostasis and α-synuclein homeostasis is therefore likely to be closely involved in the onset and progression of Parkinson's disease and related synucleinopathies. As our understanding of this balance is increasing, we describe recent advances in the characterisation of the role of post-translational modifications in modulating the interactions of α-synuclein with lipid membranes. We then discuss the impact of these advances on the development of novel diagnostic and therapeutic tools for synucleinopathies.

NPT520-34 improves neuropathology and motor deficits in a transgenic mouse model of Parkinson's disease

NPT520-34 is a clinical-stage, small molecule being developed for the treatment of Parkinson's disease and other neurodegenerative disorders. The therapeutic potential of NPT520-34 was first suggested by findings from cell-based assays of alpha-synuclein (ASYN) clearance. As reported here, NPT520-34 was subsequently evaluated for therapeutically relevant actions in a transgenic animal model of Parkinson's disease that overexpresses human ASYN and in an acute lipopolysaccharide (LPS)-challenge model using wild-type mice. Daily administration of NPT520-34 to mThy1-ASYN (Line 61) transgenic mice for one or three months resulted in reduced ASYN pathology, reduced expression of markers of neuroinflammation, and improvements in multiple indices of motor function. In an LPS-challenge model using wild-type mice, a single-dose of NPT520-34 reduced LPS-evoked increases in the expression of several pro-inflammatory cytokines in plasma. These findings demonstrate the beneficial effects of NPT520-34 on both inflammation and protein-pathology endpoints, with consequent improvements in motor function in an animal model of Parkinson's disease. These findings further suggest that NPT520-34 may have two complementary actions: (1) to increase the clearance of neurotoxic protein aggregates and (2) to directly attenuate inflammation. NPT520-34 treatment may thereby address two of the predominate underlying pathophysiological aspects of neurodegenerative disorders such as Parkinson's disease.

Alpha-synuclein increases in rodent and human spinal cord injury and promotes inflammation and tissue loss

Synucleinopathies are neurodegenerative diseases in which α-synuclein protein accumulates in neurons and glia. In these diseases, α-synuclein forms dense intracellular aggregates that are disease hallmarks and actively contribute to tissue pathology. Interestingly, many pathological mechanisms, including iron accumulation and lipid peroxidation, are shared between classical synucleinopathies such as Alzheimer’s disease, Parkinson’s disease and traumatic spinal cord injury (SCI). However, to date, no studies have determined if α-synuclein accumulation occurs after human SCI. To examine this, cross-sections from injured and non-injured human spinal cords were immunolabeled for α-synuclein. This showed robust α-synuclein accumulation in profiles resembling axons and astrocytes in tissue surrounding the injury, revealing that α-synuclein markedly aggregates in traumatically injured human spinal cords. We also detected significant iron deposition in the injury site, a known catalyst for α-synuclein aggregation. Next a rodent SCI model mimicking the histological features of human SCI revealed aggregates and structurally altered monomers of α-synuclein are present after SCI. To determine if α-synuclein exacerbates SCI pathology, α-synuclein knockout mice were tested. Compared to wild type mice, α-synuclein knockout mice had significantly more spared axons and neurons and lower pro-inflammatory mediators, macrophage accumulation, and iron deposition in the injured spinal cord. Interestingly, locomotor analysis revealed that α-synuclein may be essential for dopamine-mediated hindlimb function after SCI. Collectively, the marked upregulation and long-lasting accumulation of α-synuclein and iron suggests that SCI may fit within the family of synucleinopathies and offer new therapeutic targets for promoting neuron preservation and improving function after spinal trauma.

Targeted de-repression of neuronal Nrf2 inhibits α-synuclein accumulation

Many neurodegenerative diseases are associated with neuronal misfolded protein accumulation, indicating a need for proteostasis-promoting strategies. Here we show that de-repressing the transcription factor Nrf2, epigenetically shut-off in early neuronal development, can prevent protein aggregate accumulation. Using a paradigm of α-synuclein accumulation and clearance, we find that the classical electrophilic Nrf2 activator tBHQ promotes endogenous Nrf2-dependent α-synuclein clearance in astrocytes, but not cortical neurons, which mount no Nrf2-dependent transcriptional response. Moreover, due to neuronal Nrf2 shut-off and consequent weak antioxidant defences, electrophilic tBHQ actually induces oxidative neurotoxicity, via Nrf2-independent Jun induction. However, we find that epigenetic de-repression of neuronal Nrf2 enables them to respond to Nrf2 activators to drive α-synuclein clearance. Moreover, activation of neuronal Nrf2 expression using gRNA-targeted dCas9-based transcriptional activation complexes is sufficient to trigger Nrf2-dependent α-synuclein clearance. Thus, targeting reversal of the developmental shut-off of Nrf2 in forebrain neurons may alter neurodegenerative disease trajectory by boosting proteostasis.

Amyloid Oligomers: A Joint Experimental/Computational Perspective on Alzheimer's Disease, Parkinson's Disease, Type II Diabetes, and Amyotrophic Lateral Sclerosis

Protein misfolding and aggregation is observed in many amyloidogenic diseases affecting either the central nervous system or a variety of peripheral tissues. Structural and dynamic characterization of all species along the pathways from monomers to fibrils is challenging by experimental and computational means because they involve intrinsically disordered proteins in most diseases. Yet understanding how amyloid species become toxic is the challenge in developing a treatment for these diseases. Here we review what computer, in vitro, in vivo, and pharmacological experiments tell us about the accumulation and deposition of the oligomers of the (Aβ, tau), α-synuclein, IAPP, and superoxide dismutase 1 proteins, which have been the mainstream concept underlying Alzheimer's disease (AD), Parkinson's disease (PD), type II diabetes (T2D), and amyotrophic lateral sclerosis (ALS) research, respectively, for many years.

Glial cells in Parkinson´s disease: protective or deleterious?

Glial cells have been identified more than 100 years ago, and are known to play a key role in the central nervous system (CNS) function. A recent piece of evidence is emerging showing that in addition to the capacity of CNS modulation and homeostasis, glial cells are also being looked like as a promising cell source not only to study CNS pathologies initiation and progression but also to the establishment and development of new therapeutic strategies. Thus, in the present review, we will discuss the current evidence regarding glial cells' contribution to neurodegenerative diseases as Parkinson's disease, providing cellular, molecular, functional, and behavioral data supporting its active role in disease initiation, progression, and treatment. As so, considering their functional relevance, glial cells may be important to the understanding of the underlying mechanisms regarding neuronal-glial networks in neurodegeneration/regeneration processes, which may open new research opportunities for their future use as a target or treatment in human clinical trials.

α-Synuclein in traumatic and vascular diseases of the central nervous system

α-Synuclein (α-Syn) is a small, soluble, disordered protein that is widely expressed in the nervous system. Although its physiological functions are not yet fully understood, it is mainly involved in synaptic vesicle transport, neurotransmitter synthesis and release, cell membrane homeostasis, lipid synthesis, mitochondrial and lysosomal activities, and heavy metal removal. The complex and inconsistent pathological manifestations of α-Syn are attributed to its structural instability, mutational complexity, misfolding, and diverse posttranslational modifications. These effects trigger mitochondrial dysfunction, oxidative stress, and neuroinflammatory responses, resulting in neuronal death and neurodegeneration. Several recent studies have discovered the pathogenic roles of α-Syn in traumatic and vascular central nervous system diseases, such as traumatic spinal cord injury, brain injury, and stroke, and in aggravating the processes of neurodegeneration. This review aims to highlight the structural and pathophysiological changes in α-Syn and its mechanism of action in traumatic and vascular diseases of the central nervous system.

Safety and immunogenicity of the α-synuclein active immunotherapeutic PD01A in patients with Parkinson's disease: a randomised, single-blinded, phase 1 trial

BACKGROUND

Robust evidence supports the role of α-synuclein pathology as a driver of neuronal dysfunction in Parkinson's disease. PD01A is a specific active immunotherapy with a short peptide formulation targeted against oligomeric α-synuclein. This phase 1 study assessed the safety and tolerability of the PD01A immunotherapeutic in patients with Parkinson's disease.

METHODS

We did a first-in-human, randomised, phase 1 study of immunisations with PD01A, followed by three consecutive study extensions. Patients aged 45-65 years with a clinical diagnosis of Parkinson's disease (≤4 years since diagnosis and Hoehn and Yahr Stage 1 to 2), imaging results (dopamine transporter single photon emission CT and MRI) consistent with their Parkinson's disease diagnosis, and on stable doses of Parkinson's disease medications for at least 3 months were recruited at a single private clinic in Vienna, Austria. Patients were randomly assigned (1:1), using a computer-generated sequence with varying block size, to receive four subcutaneous immunisations with either 15 μg or 75 μg PD01A injected into the upper arms and followed up initially for 52 weeks, followed by a further 39 weeks' follow-up. Patients were then randomly assigned (1:1) again to receive the first booster immunisation at 15 μg or 75 μg and were followed up for 24 weeks. All patients received a second booster immunisation of 75 μg and were followed up for an additional 52 weeks. Patients were masked to dose allocation. Primary (safety) analyses included all treated patients. These four studies were registered with EU Clinical Trials Register, EudraCT numbers 2011-002650-31, 2013-001774-20, 2014-002489-54, and 2015-004854-16.

FINDINGS

32 patients were recruited between Feb 14, 2012, and Feb 6, 2013, and 24 were deemed eligible and randomly assigned to receive four PD01A priming immunisations. One patient had a diagnosis change to multiple system atrophy and was withdrawn and two patients withdrew consent during the studies. 21 (87%) of 24 patients received all six immunisations and completed 221-259 weeks in-study (two patients in the 15 μg dose group and one patient in the 75 μg dose group discontinued). All patients experienced at least one adverse event, but most of them were considered unrelated to study treatment (except for transient local injection site reactions, which affected all but one patient). Serial MRI assessments also ruled out inflammatory processes. Systemic treatment-related adverse events were fatigue (n=4), headache (n=3), myalgia (n=3), muscle rigidity (n=2), and tremor (n=2). The geometric group mean titre of antibodies against the immunising peptide PD01 increased from 1:46 at baseline to 1:3580 at week 12 in the 15 μg dose group, and from 1:76 to 1:2462 at week 12 in the 75 μg dose group. Antibody titres returned to baseline over 2 years, but could be rapidly reactivated after booster immunisation from week 116 onwards, reaching geometric group mean titres up to 1:20218.

INTERPRETATION

Repeated administrations of PD01A were safe and well tolerated over an extended period. Specific active immunotherapy resulted in a substantial humoral immune response with target engagement. Phase 2 studies are needed to further assess the safety and efficacy of PD01A for the treatment of Parkinson's disease.

FUNDING

AFFiRiS, Michael J Fox Foundation.

The emerging role of α-synuclein truncation in aggregation and disease

α-Synuclein (αsyn) is an abundant brain neuronal protein that can misfold and polymerize to form toxic fibrils coalescing into pathologic inclusions in neurodegenerative diseases, including Parkinson's disease, Lewy body dementia, and multiple system atrophy. These fibrils may induce further αsyn misfolding and propagation of pathologic fibrils in a prion-like process. It is unclear why αsyn initially misfolds, but a growing body of literature suggests a critical role of partial proteolytic processing resulting in various truncations of the highly charged and flexible carboxyl-terminal region. This review aims to 1) summarize recent evidence that disease-specific proteolytic truncations of αsyn occur in Parkinson's disease, Lewy body dementia, and multiple system atrophy and animal disease models; 2) provide mechanistic insights on how truncation of the amino and carboxyl regions of αsyn may modulate the propensity of αsyn to pathologically misfold; 3) compare experiments evaluating the prion-like properties of truncated forms of αsyn in various models with implications for disease progression; 4) assess uniquely toxic properties imparted to αsyn upon truncation; and 5) discuss pathways through which truncated αsyn forms and therapies targeted to interrupt them. Cumulatively, it is evident that truncation of αsyn, particularly carboxyl truncation that can be augmented by dysfunctional proteostasis, dramatically potentiates the propensity of αsyn to pathologically misfold into uniquely toxic fibrils with modulated prion-like seeding activity. Therapeutic strategies and experimental paradigms should operate under the assumption that truncation of αsyn is likely occurring in both initial and progressive disease stages, and preventing truncation may be an effective preventative strategy against pathologic inclusion formation.

Novel approaches to counter protein aggregation pathology in Parkinson's disease

The primary neuropathological characteristics of the Parkinsonian brain are the loss of nigral dopamine neurons and the aggregation of alpha synuclein protein. Efforts to development potentially disease-modifying treatments have largely focused on correcting these aspects of the condition. In the last decade treatments targeting protein aggregation have entered the clinical pipeline. In this chapter we provide an overview of ongoing clinical trial programs for different therapies attempting to reduce protein aggregation pathology in Parkinson's disease. We will also briefly consider various novel approaches being proposed-and being developed preclinically-to inhibit/reduce aggregated protein pathology in Parkinson's.

Safety and Tolerability of Multiple Ascending Doses of PRX002/RG7935, an Anti-α-Synuclein Monoclonal Antibody, in Patients With Parkinson Disease: A Randomized Clinical Trial

Importance

Aggregated α-synuclein is believed to be central to the pathogenesis of Parkinson disease (PD). PRX002/RG7935 (PRX002) is a humanized monoclonal antibody designed to target aggregated forms of α-synuclein, thereby inhibiting neuron-to-neuron transfer of presumed pathogenic forms of α-synuclein, potentially resulting in neuronal protection and slowing disease progression.

Objective

To evaluate the safety and tolerability of multiple intravenous infusions of PRX002 in patients with idiopathic PD.

Design, Setting, and Participants

Multicenter, randomized, double-blind, placebo-controlled, multiple ascending-dose trial at 8 US study centers from July 2014 to September 2016. Eligible participants were aged 40 to 80 years with mild to moderate idiopathic PD (Hoehn and Yahr stages 1-3).

Interventions

Participants were enrolled into 6 ascending-dose cohorts and randomly assigned to receive PRX002 (0.3 mg/kg, 1.0 mg/kg, 3.0 mg/kg, 10 mg/kg, 30 mg/kg, or 60 mg/kg) or placebo. Participants received 3 intravenous infusions every 4 weeks of PRX002 or placebo and were monitored during a 24-week observational period.

Main Outcomes and Measures

Safety and tolerability assessments included physical and neurological examinations, laboratory tests, vital signs, and adverse events. Pharmacokinetic parameters included maximum PRX002 concentration, area under the curve, and half-life.

Results

Of the 80 participants, most were white (97.5%; n = 78) and male (80%; n = 64); median (SD) age was 58 (8.4) years. PRX002 was generally safe and well tolerated; no serious or severe PRX002-related treatment-emergent adverse events (TEAEs) were reported. The TEAEs experienced by at least 5% of patients receiving PRX002, irrespective of relatedness to study drug, were constipation (9.1%; n = 5), infusion reaction (7.3%; n = 4), diarrhea (5.5%; n = 3), headache (5.5%; n = 3), peripheral edema (5.5%; n = 3), post-lumbar puncture syndrome (5.5%; n = 3), and upper respiratory tract infection (5.5%; n = 3). No antidrug antibodies were detected. Serum PRX002 levels increased in an approximately dose-proportional manner; mean terminal elimination half-life was similar across all doses (10.2 days). Rapid dose- and time-dependent mean reductions from baseline vs placebo in free serum α-synuclein levels of up to 97% were seen after a single infusion at the highest dose (F78,284 = 1.66; P = .002), with similar reductions after 2 additional infusions. Mean cerebrospinal fluid PRX002 concentration increased with PRX002 dose and was approximately 0.3% relative to serum across all dose cohorts.

Conclusions and Relevance

Single and multiple doses of PRX002 were generally safe and well tolerated and resulted in robust binding of peripheral α-synuclein and dose-dependent increases of PRX002 in cerebrospinal fluid, reaching cerebrospinal fluid concentrations that may be expected to engage extracellular aggregated α-synuclein in the brain. Findings support the design of an ongoing phase 2 clinical study (NCT03100149).

Trial Registration

ClinicalTrials.gov Identifier: NCT02157714.

Human myeloperoxidase (hMPO) is expressed in neurons in the substantia nigra in Parkinson's disease and in the hMPO-α-synuclein-A53T mouse model, correlating with increased nitration and aggregation of α-synuclein and exacerbation of motor impairment

α-Synuclein (αSyn) is central to the neuropathology of Parkinson's disease (PD) due to its propensity for misfolding and aggregation into neurotoxic oligomers. Nitration/oxidation of αSyn leads to dityrosine crosslinking and aggregation. Myeloperoxidase (MPO) is an oxidant-generating enzyme implicated in neurodegenerative diseases. In the present work we have examined the impact of MPO in PD through analysis of postmortem PD brain and in a novel animal model in which we crossed a transgenic mouse expressing the human MPO (hMPO) gene to a mouse expressing human αSyn-A53T mutant (A53T) (hMPO-A53T). Surprisingly, our results show that in PD substantia nigra, the hMPO gene is expressed in neurons containing aggregates of nitrated αSyn as well as MPO-generated HOCl-modified epitopes. In our hMPO-A53T mouse model, we also saw hMPO expression in neurons but not mouse MPO. In the mouse model, hMPO was expressed in neurons colocalizing with nitrated αSyn, carbamylated lysine, nitrotyrosine, as well as HOCl-modified epitopes/proteins. RNAscope in situ hybridization confirmed hMPO mRNA expression in neurons. Interestingly, the hMPO protein expressed in hMPO-A53T brain is primarily the precursor proMPO, which enters the secretory pathway potentially resulting in interneuronal transmission of MPO and oxidative species. Importantly, the hMPO-A53T mouse model, when compared to the A53T model, exhibited significant exacerbation of motor impairment on rotating rods, balance beams, and wire hang tests. Further, hMPO expression in the A53T model resulted in earlier onset of end stage paralysis. Interestingly, there was a high concentration of αSyn aggregates in the stratum lacunosum moleculare of hippocampal CA2 region, which has been associated in humans with accumulation of αSyn pathology and neural atrophy in dementia with Lewy bodies. This accumulation of αSyn aggregates in CA2 was associated with markers of endoplasmic reticulum (ER) stress and the unfolded protein response with expression of activating transcription factor 4 (ATF4), C/EBP homologous protein (CHOP), MPO, and cleaved caspase-3. Together these findings suggest that MPO plays an important role in nitrative and oxidative damage that contributes to αSyn pathology in synucleinopathies.

Effects of single and combined immunotherapy approach targeting amyloid β protein and α-synuclein in a dementia with Lewy bodies-like model

INTRODUCTION

Immunotherapeutic approaches targeting amyloid β (Aβ) protein and tau in Alzheimer's disease and α-synuclein (α-syn) in Parkinson's disease are being developed for treating dementia with Lewy bodies. However, it is unknown if single or combined immunotherapies targeting Aβ and/or α-syn may be effective.

METHODS

Amyloid precursor protein/α-syn tg mice were immunized with AFFITOPEs® (AFF) peptides specific to Aβ (AD02) or α-syn (PD-AFF1) and the combination.

RESULTS

AD02 more effectively reduced Aβ and pTau burden; however, the combination exhibited some additive effects. Both AD02 and PD-AFF1 effectively reduced α-syn, ameliorated degeneration of pyramidal neurons, and reduced neuroinflammation. PD-AFF1 more effectively ameliorated cholinergic and dopaminergic fiber loss; the combined immunization displayed additive effects. AD02 more effectively improved buried pellet test behavior, whereas PD-AFF1 more effectively improved horizontal beam test; the combined immunization displayed additive effects.

DISCUSSION

Specific active immunotherapy targeting Aβ and/or α-syn may be of potential interest for the treatment of dementia with Lewy bodies.

LRRK2 kinase plays a critical role in manganese-induced inflammation and apoptosis in microglia

Long-term exposure to elevated levels of manganese (Mn) causes manganism, a neurodegenerative disorder with Parkinson's disease (PD)-like symptoms. Increasing evidence suggests that leucine-rich repeat kinase 2 (LRRK2), which is highly expressed in microglia and macrophages, contributes to the inflammation and neurotoxicity seen in autosomal dominant and sporadic PD. As gene-environment interactions have emerged as important modulators of PD-associated toxicity, LRRK2 may also mediate Mn-induced inflammation and pathogenesis. In this study, we investigated the role of LRRK2 in Mn-induced toxicity using human microglial cells (HMC3), LRRK2-wild-type (WT) and LRRK2-knockout (KO) RAW264.7 macrophage cells. Results showed that Mn activated LRRK2 kinase by phosphorylation of its serine residue at the 1292 position (S1292) as a marker of its kinase activity in macrophage and microglia, while inhibition with GSK2578215A (GSK) and MLi-2 abolished Mn-induced LRRK2 activation. LRRK2 deletion and its pharmacological inhibition attenuated Mn-induced apoptosis in macrophages and microglia, along with concomitant decreases in the pro-apoptotic Bcl-2-associated X (Bax) protein. LRRK2 deletion also attenuated Mn-induced production of reactive oxygen species (ROS) and the pro-inflammatory cytokine TNF-α. Mn-induced phosphorylation of mitogen-activated protein kinase (MAPK) p38 and ERK signaling proteins was significantly attenuated in LRRK2 KO cells and GSK-treated cells. Moreover, inhibition of MAPK p38 and ERK as well as LRRK2 attenuated Mn-induced oxidative stress and cytotoxicity. These findings suggest that LRRK2 kinase activity plays a critical role in Mn-induced toxicity via downstream activation of MAPK signaling in macrophage and microglia. Collectively, these results suggest that LRRK2 could be a potential molecular target for developing therapeutics to treat Mn-related neurodegenerative disorders.

Effects of Novel Calpain Inhibitors in Transgenic Animal Model of Parkinson's disease/dementia with Lewy bodies

Parkinson's disease (PD) and dementia with Lewy bodies (DLB) are neurodegenerative disorders of the aging population characterized by the accumulation of α-synuclein (α-syn). The mechanisms triggering α-syn toxicity are not completely understood, however, c-terminus truncation of α-syn by proteases such as calpain may have a role. Therefore, inhibition of calpain may be of value. The main objective of this study was to evaluate the effects of systemically administered novel low molecular weight calpain inhibitors on α-syn pathology in a transgenic mouse model. For this purpose, non-tg and α-syn tg mice received the calpain inhibitors - Gabadur, Neurodur or a vehicle, twice a day for 30 days. Immunocytochemical analysis showed a 60% reduction in α-syn deposition using Gabadur and a 40% reduction using Neurodur with a concomitant reduction in c-terminus α-syn and improvements in neurodegeneration. Western blot analysis showed a 77% decrease in α-spectrin breakdown products (SBDPs) SBDPs with Gabadur and 63% reduction using Neurodur. There was a 65% reduction in the active calpain form with Gabadur and a 45% reduction with Neurodur. Moreover, treatment with calpain inhibitors improved activity performance of the α-syn tg mice. Taken together, this study suggests that calpain inhibition might be considered in the treatment of synucleinopathies.

Naturally occurring autoantibodies against α-synuclein rescues memory and motor deficits and attenuates α-synuclein pathology in mouse model of Parkinson's disease

It has been suggested that aggregation of α-synuclein (α-syn) into oligomers leads to neurodegeneration in Parkinson's disease (PD), but intravenous immunoglobulin (IVIG) which contains antibodies against α-syn monomers and oligomers fails to treat PD mouse model. The reason may be because IVIG contains much low level of antibodies against α-syn, and of which only a small part can penetrate the blood-brain barrier, resulting in an extremely low level of effective antibodies in the brain, and limiting the beneficial effect of IVIG on PD mice. Here, we first isolated naturally occurring autoantibodies against α-syn (NAbs-α-syn) from IVIG. Our further investigation results showed that NAbs-α-syn inhibited α-syn aggregation and attenuated α-syn-induced cytotoxicity in vitro. Compared with vehicles, NAbs-α-syn significantly attenuated the memory and motor deficits by reducing the levels of soluble α-syn, total human α-syn and α-syn oligomers, decreasing the intracellular p-α-syn^ser129 deposits and axonal pathology, inhibiting the microgliosis and astrogliosis, as well as the production of proinflammatory cytokines, increasing the levels of PSD95, synaptophysin and TH in the brain of A53T transgenic mice. These findings suggest that NAbs-α-syn overcomes the deficiency of IVIG and exhibits a promising therapeutic potential for the treatment of PD.

Reduced Cytosolic Calcium as an Early Decisive Cellular State in Parkinson's Disease and Synucleinopathies

The more than 30-year-old Calcium hypothesis postulates that dysregulation in calcium dependent processes in the aging brain contributes to its increased vulnerability and this concept has been extended to Alzheimer’s disease and Parkinson’s disease. Central to the hypothesis is that increased levels of intracellular calcium develop and contributes to neuronal demise. We have studied the impact on cells encountering a gradual build-up of aggregated α-synuclein, which is a central process to Parkinson’s disease and other synucleinopathies. Surprisingly, we observed a yet unrecognized phase characterized by a reduced cytosolic calcium in cellular and neuronal models of Parkinson’s disease, caused by α-synuclein aggregates activating the endoplasmic calcium ATPase, SERCA. Counteracting the initial phase with low calcium rescues the subsequent degenerative phase with increased calcium and cell death – and demonstrates this early phase initiates decisive degenerative signals. In this review, we discuss our findings in relation to literature on calcium dysregulation in Parkinson’s disease and dementia.

The small molecule alpha-synuclein misfolding inhibitor, NPT200-11, produces multiple benefits in an animal model of Parkinson's disease

Accumulation of alpha-synuclein (ASYN) in neurons and other CNS cell types may contribute to the underlying pathology of synucleinopathies including Parkinson's disease (PD), dementia with Lewy bodies (DLB) and Multiple Systems Atrophy (MSA). In support of this hypothesis for PD, ASYN immunopositive aggregates are a prominent pathological feature of PD, and mutations and gene multiplications of human wild type (WT) ASYN cause rare familial autosomal-dominant forms of PD. Targeted therapeutics that reduce the accumulation of ASYN could prevent or slow the neurodegenerative processes in PD and other synucleinopathies. NPT200-11 is a novel small molecule inhibitor of ASYN misfolding and aggregation. The effects of NPT200-11 on ASYN neuropathology were evaluated in animal models over expressing human alpha synuclein. Longitudinal studies using retinal imaging in mice expressing a hASYN::GFP fusion protein revealed that 2 months of once daily administration of NPT200-11 (5 mg/kg IP) resulted in a time-dependent and progressive reduction in retinal ASYN pathology. The effects of NPT200-11 on ASYN pathology in cerebral cortex and on other disease-relevant endpoints was evaluated in the Line 61 transgenic mouse model overexpressing human wild type ASYN. Results from these studies demonstrated that NPT200-11 reduced alpha-synuclein pathology in cortex, reduced associated neuroinflammation (astrogliosis), normalized striatal levels of the dopamine transporter (DAT) and improved motor function. To gain insight into the relationship between dose, exposure, and therapeutic benefit pharmacokinetic studies were also conducted in mice. These studies demonstrated that NPT200-11 is orally bioavailable and brain penetrating and established target plasma and brain exposures for future studies of potential therapeutic benefit.

The Challenge of the Pathogenesis of Parkinson's Disease: Is Autoimmunity the Culprit?

The role of autoimmunity in Parkinson's disease (PD), as one of the most popular research subjects, has been intensively investigated in recent years. Although the ultimate cause of PD is unknown, one major area of interest remains identifying new therapeutic targets and options for patients suffering from PD. Herein, we present a comprehensive review of the impacts of autoimmunity in neurodegenerative diseases, especially PD, and we have composed a logical argument to substantiate that autoimmunity is actively involved in the pathogenesis of PD through several proteins, including α-synuclein, DJ-1, PINK1, and Parkin, as well as immune cells, such as dendritic cells, microglia, T cells, and B cells. Furthermore, a detailed analysis of the relevance of autoimmunity to the clinical symptoms of PD provides strong evidence for the close correlation of autoimmunity with PD. In addition, the previously identified relationships between other autoimmune diseases and PD help us to better understand the disease pattern, laying the foundation for new therapeutic solutions to PD. In summary, this review aims to integrate and present currently available data to clarify the pathogenesis of PD and discuss some controversial but innovative research perspectives on the involvement of autoimmunity in PD, as well as possible novel diagnostic methods and treatments based on autoimmunity targets.

Targeted Therapies for Parkinson's Disease: From Genetics to the Clinic

The greatest unmet medical need in Parkinson's disease (PD) is treatments that slow the relentless progression of symptoms. The discovery of genetic variants causing and/or increasing the risk for PD has provided the field with a new arsenal of potential therapies ready to be tested in clinical trials. We highlight 3 of the genetic discoveries (α-synuclein, glucocerebrosidase, and leucine-rich repeat kinase) that have prompted new therapeutic approaches now entering the clinical stages. We are at an exciting juncture in the journey to developing disease-modifying treatments based on knowledge of PD genetics and pathology. This review focuses on therapeutic paradigms that are under clinical development and highlights a wide range of key outstanding questions in PD. © 2018 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.

Combined Active Humoral and Cellular Immunization Approaches for the Treatment of Synucleinopathies

Dementia with Lewy bodies, Parkinson's disease, and Multiple System Atrophy are age-related neurodegenerative disorders characterized by progressive accumulation of α-synuclein (α-syn) and jointly termed synucleinopathies. Currently, no disease-modifying treatments are available for these disorders. Previous preclinical studies demonstrate that active and passive immunizations targeting α-syn partially ameliorate behavioral deficits and α-syn accumulation; however, it is unknown whether combining humoral and cellular immunization might act synergistically to reduce inflammation and improve microglial-mediated α-syn clearance. Since combined delivery of antigen plus rapamycin (RAP) in nanoparticles is known to induce antigen-specific regulatory T cells (Tregs), we adapted this approach to α-syn using the antigen-presenting cell-targeting glucan microparticle (GP) vaccine delivery system. PDGF-α-syn transgenic (tg) male and female mice were immunized with GP-alone, GP-α-syn (active humoral immunization), GP+RAP, or GP+RAP/α-syn (combined active humoral and Treg) and analyzed using neuropathological and biochemical markers. Active immunization resulted in higher serological total IgG, IgG1, and IgG2a anti-α-syn levels. Compared with mice immunized with GP-alone or GP-α-syn, mice vaccinated with GP+RAP or GP+RAP/α-syn displayed increased numbers of CD25-, FoxP3-, and CD4-positive cells in the CNS. GP-α-syn or GP+RAP/α-syn immunizations resulted in a 30-45% reduction in α-syn accumulation, neuroinflammation, and neurodegeneration. Mice immunized with GP+RAP/α-syn further rescued neurons and reduced neuroinflammation. Levels of TGF-β1 were increased with GP+RAP/α-syn immunization, while levels of TNF-α and IL-6 were reduced. We conclude that the observed effects of GP+RAP/α-syn immunization support the hypothesis that cellular immunization may enhance the effects of active immunotherapy for the treatment of synucleinopathies.SIGNIFICANCE STATEMENT We show that a novel vaccination modality combining an antigen-presenting cell-targeting glucan particle (GP) vaccine delivery system with encapsulated antigen (α-synuclein) + rapamycin (RAP) induced both strong anti-α-synuclein antibody titers and regulatory T cells (Tregs). This vaccine, collectively termed GP+RAP/α-syn, is capable of triggering neuroprotective Treg responses in synucleinopathy models, and the combined vaccine is more effective than the humoral or cellular immunization alone. Together, these results support the further development of this multifunctional vaccine approach for the treatment of synucleinopathies, such as Parkinson's disease, dementia with Lewy bodies, and multiple systems atrophy.

A refined concept: α-synuclein dysregulation disease

α-synuclein (αSyn) still remains a mysterious protein even two decades after SNCA encoding it was identified as the first causative gene of familial Parkinson's disease (PD). Accumulation of αSyn causes α-synucleinopathies including PD, dementia with Lewy bodies (DLB) and multiple system atrophy (MSA). Recent advances in therapeutic approaches offer new antibody-, vaccine-, antisense-oligonucleotide- and small molecule-based options to reduce αSyn protein levels and aggregates in patient's brain. Gathering research information of other neurological disease particularly Alzheimer's disease, recent disappointment of an experimental amyloid plaques busting antibody in clinical trials underscores the difficulty of treating people who show even mild dementia as damage in their brain may already be too extensive. Prodromal intervention to inhibit the accumulation of pathogenic protein may advantageously provide a better outcome. However, treatment prior to onset is not ethically justified as standard practice at present. In this review, we initiate a refined concept to define early pathogenic state of αSyn accumulation before occurrence of brain damage as a disease criterion for αSyn dysregulation disease.

Reducing Endogenous α-Synuclein Mitigates the Degeneration of Selective Neuronal Populations in an Alzheimer's Disease Transgenic Mouse Model

Alzheimer's disease (AD) is characterized by the progressive accumulation of amyloid β (Aβ) and microtubule associate protein tau, leading to the selective degeneration of neurons in the neocortex, limbic system, and nucleus basalis, among others. Recent studies have shown that α-synuclein (α-syn) also accumulates in the brains of patients with AD and interacts with Aβ and tau, forming toxic hetero-oligomers. Although the involvement of α-syn has been investigated extensively in Lewy body disease, less is known about the role of this synaptic protein in AD. Here, we found that reducing endogenous α-syn in an APP transgenic mouse model of AD prevented the degeneration of cholinergic neurons, ameliorated corresponding deficits, and recovered the levels of Rab3a and Rab5 proteins involved in intracellular transport and sorting of nerve growth factor and brain-derived neurotrophic factor. Together, these results suggest that α-syn might participate in mechanisms of vulnerability of selected neuronal populations in AD and that reducing α-syn might be a potential approach to protecting these populations from the toxic effects of Aβ.

SIGNIFICANCE STATEMENT

Reducing endogenous α-synuclein (α-syn) in an APP transgenic mouse model of Alzheimer's disease (AD) prevented the degeneration of cholinergic neurons, ameliorated corresponding deficits, and recovered the levels of Rab3a and Rab5 proteins involved in intracellular transport and sorting of nerve growth factor and brain-derived neurotrophic factor. These results suggest that α-syn might participate in mechanisms of vulnerability of selected neuronal populations in AD and that reducing α-syn might be a potential approach to protecting these populations from the toxic effects of amyloid β.

Differential effects of immunotherapy with antibodies targeting α-synuclein oligomers and fibrils in a transgenic model of synucleinopathy

Disorders with progressive accumulation of α-synuclein (α-syn) are a common cause of dementia and parkinsonism in the aging population. Accumulation and propagation of α-syn play a role in the pathogenesis of these disorders. Previous studies have shown that immunization with antibodies that recognize C-terminus of α-syn reduces the intra-neuronal accumulation of α-syn and related deficits in transgenic models of synucleinopathy. These studies employed antibodies that recognize epitopes within monomeric and aggregated α-syn that were generated through active immunization or administered via passive immunization. However, it is possible that more specific effects might be achieved with antibodies recognizing selective species of the α-syn aggregates. In this respect we recently developed antibodies that differentially recognized various oligomers (Syn-O1, -O2, and -O4) and fibrilar (Syn-F1 and -F2) forms of α-syn. For this purpose wild-type α-syn transgenic (line 61) mice were immunized with these 5 different antibodies and neuropathologically and biochemically analyzed to determine which was most effective at reducing α-syn accumulation and related deficits. We found that Syn-O1, -O4 and -F1 antibodies were most effective at reducing accumulation of α-syn oligomers in multiple brain regions and at preventing neurodegeneration. Together this study supports the notion that selective antibodies against α-syn might be suitable for development new treatments for synucleinopathies such as PD and DLB.

Early and progressive microstructural brain changes in mice overexpressing human α-Synuclein detected by diffusion kurtosis imaging

Diffusion kurtosis imaging (DKI) is sensitive in detecting α-Synuclein (α-Syn) accumulation-associated microstructural changes at late stages of the pathology in α-Syn overexpressing TNWT-61 mice. The aim of this study was to perform DKI in young TNWT-61 mice when α-Syn starts to accumulate and to compare the imaging results with an analysis of motor and memory impairment and α-Syn levels. Three-month-old (3mo) and six-month-old (6mo) mice underwent DKI scanning using the Bruker Avance 9.4T magnetic resonance imaging system. Region of interest (ROI) analyses were performed in the gray matter; tract-based spatial statistics (TBSS) analyses were performed in the white matter. In the same mice, α-Syn expression was evaluated using quantitative immunofluorescence. Mean kurtosis (MK) was the best differentiator between TNWT-61 mice and wildtype (WT) mice. We found increases in MK in 3mo TNWT-61 mice in the striatum and thalamus but not in the substantia nigra (SN), hippocampus, or sensorimotor cortex, even though the immunoreactivity of human α-Syn was similar or even higher in the latter regions. Increases in MK in the SN were detected in 6mo mice. These findings indicate that α-Syn accumulation-associated changes may start in areas with a high density of dopaminergic nerve terminals. We also found TBSS changes in white matter only at 6mo, suggesting α-Syn accumulation-associated changes start in the gray matter and later progress to the white matter. MK is able to detect microstructural changes induced by α-Syn overexpression in TNWT-61 mice and could be a useful clinical tool for detecting early-stage Parkinson's disease in human patients.

Anti-α-synuclein immunotherapy reduces α-synuclein propagation in the axon and degeneration in a combined viral vector and transgenic model of synucleinopathy

Neurodegenerative disorders such as Parkinson's Disease (PD), PD dementia (PDD) and Dementia with Lewy bodies (DLB) are characterized by progressive accumulation of α-synuclein (α-syn) in neurons. Recent studies have proposed that neuron-to-neuron propagation of α-syn plays a role in the pathogenesis of these disorders. We have previously shown that antibodies against the C-terminus of α-syn reduce the intra-neuronal accumulation of α-syn and related deficits in transgenic models of synucleinopathy, probably by abrogating the axonal transport and accumulation of α-syn in in vivo models. Here, we assessed the effect of passive immunization against α-syn in a new mouse model of axonal transport and accumulation of α-syn. For these purpose, non-transgenic, α-syn knock-out and mThy1-α-syn tg (line 61) mice received unilateral intra-cerebral injections with a lentiviral (LV)-α-syn vector construct followed by systemic administration of the monoclonal antibody 1H7 (recognizes amino acids 91-99) or control IgG for 3 months. Cerebral α-syn accumulation and axonopathy was assessed by immunohistochemistry and effects on behavior were assessed by Morris water maze. Unilateral LV-α-syn injection resulted in axonal propagation of α-syn in the contra-lateral site with subsequent behavioral deficits and axonal degeneration. Passive immunization with 1H7 antibody reduced the axonal accumulation of α-syn in the contra-lateral side and ameliorated the behavioral deficits. Together this study supports the notion that immunotherapy might improve the deficits in models of synucleinopathy by reducing the axonal propagation and accumulation of α-syn. This represents a potential new mode of action through which α-syn immunization might work.