Lysophagy protects against propagation of α-synuclein aggregation through ruptured lysosomal vesicles.

The neuron-to-neuron propagation of misfolded α-synuclein (αSyn) aggregates is thought to be key to the pathogenesis of synucleinopathies. Recent studies have shown that extracellular αSyn aggregates taken up by the endosomal-lysosomal system can rupture the lysosomal vesicular membrane; however, it remains unclear whether lysosomal rupture leads to the transmission of αSyn aggregation. Here, we applied cell-based αSyn propagation models to show that ruptured lysosomes are the pathway through which exogenous αSyn aggregates transmit aggregation, and furthermore, this process was prevented by lysophagy, i.e., selective autophagy of damaged lysosomes. αSyn aggregates accumulated predominantly in lysosomes, causing their rupture, and seeded the aggregation of endogenous αSyn, initially around damaged lysosomes. Exogenous αSyn aggregates induced the accumulation of LC3 on lysosomes. This LC3 accumulation was not observed in cells in which a key regulator of autophagy, RB1CC1/FIP200, was knocked out and was confirmed as lysophagy by transmission electron microscopy. Importantly, RB1CC1/FIP200-deficient cells treated with αSyn aggregates had increased numbers of ruptured lysosomes and enhanced propagation of αSyn aggregation. Furthermore, various types of lysosomal damage induced using lysosomotropic reagents, depletion of lysosomal enzymes, or more toxic species of αSyn fibrils also exacerbated the propagation of αSyn aggregation, and impaired lysophagy and lysosomal membrane damage synergistically enhanced propagation. These results indicate that lysophagy prevents exogenous αSyn aggregates from escaping the endosomal-lysosomal system and transmitting aggregation to endogenous cytosolic αSyn via ruptured lysosomal vesicles. Our findings suggest that the progression and severity of synucleinopathies are associated with damage to lysosomal membranes and impaired lysophagy.

Phosphatidylinositol-3,4,5-trisphosphate interacts with alpha-synuclein and initiates its aggregation and formation of Parkinson's disease-related fibril polymorphism.

Lipid interaction with α-synuclein (αSyn) has been long implicated in the pathogenesis of Parkinson's disease (PD). However, it has not been fully determined which lipids are involved in the initiation of αSyn aggregation in PD. Here exploiting genetic understanding associating the loss-of-function mutation in Synaptojanin 1 (SYNJ1), a phosphoinositide phosphatase, with familial PD and analysis of postmortem PD brains, we identified a novel lipid molecule involved in the toxic conversion of αSyn and its relation to PD. We first established a SYNJ1 knockout cell model and found SYNJ1 depletion increases the accumulation of pathological αSyn. Lipidomic analysis revealed SYNJ1 depletion elevates the level of its substrate phosphatidylinositol-3,4,5-trisphosphate (PIP3). We then employed Caenorhabditis elegans model to examine the effect of SYNJ1 defect on the neurotoxicity of αSyn. Mutations in SYNJ1 accelerated the accumulation of αSyn aggregation and induced locomotory defects in the nematodes. These results indicate that functional loss of SYNJ1 promotes the pathological aggregation of αSyn via the dysregulation of its substrate PIP3, leading to the aggravation of αSyn-mediated neurodegeneration. Treatment of cultured cell line and primary neurons with PIP3 itself or with PIP3 phosphatase inhibitor resulted in intracellular formation of αSyn inclusions. Indeed, in vitro protein-lipid overlay assay validated that phosphoinositides, especially PIP3, strongly interact with αSyn. Furthermore, the aggregation assay revealed that PIP3 not only accelerates the fibrillation of αSyn, but also induces the formation of fibrils sharing conformational and biochemical characteristics similar to the fibrils amplified from the brains of PD patients. Notably, the immunohistochemical and lipidomic analyses on postmortem brain of patients with sporadic PD showed increased PIP3 level and its colocalization with αSyn. Taken together, PIP3 dysregulation promotes the pathological aggregation of αSyn and increases the risk of developing PD, and PIP3 represents a potent target for intervention in PD.

Serum asymmetric dimethylarginine level correlates with the progression and prognosis of amyotrophic lateral sclerosis.

BACKGROUND AND PURPOSE: The aim was to investigate the association between serum asymmetric dimethylarginine (ADMA) levels and the progression and prognosis of amyotrophic lateral sclerosis (ALS), and to compare cerebrospinal fluid (CSF) and serum ADMA levels with other biomarkers of ALS. METHODS: Serum ADMA levels of sporadic ALS patients (n = 68), disease control patients (n = 54) and healthy controls (n = 20) were measured using liquid chromatography tandem mass spectrometry. Correlations of the ADMA level and other markers (nitric oxide and neurofilament light chain levels) were analyzed. Changes in the ALS Functional Rating Scale Revised (ALSFRS-R) score from the onset of disease (ALSFRS-R pre-slope) was used to assess disease progression. Survival was evaluated using the Cox proportional hazards model and Kaplan-Meier analysis. RESULTS: The serum ADMA level was substantially higher in patients with ALS than in healthy controls and disease controls. Serum ADMA level correlated with CSF ADMA level (r = 0.591, p < 0.0001) and was independently associated with the ALSFRS-R pre-slope (r = 0.505, p < 0.0001). Patients with higher serum ADMA levels had less favorable prognoses. CSF ADMA level significantly correlated with CSF neurofilament light chain level (r = 0.456, p = 0.0002) but not with nitric oxide level (r = 0.194, p = 0.219). CONCLUSION: Serum ADMA level is an independent biomarker of ALS disease progression and prognosis and reflects the degree of motor neuron degeneration.

Increased Expression of Fibronectin Leucine-Rich Transmembrane Protein 3 in the Dorsal Root Ganglion Induces Neuropathic Pain in Rats.

Neuropathic pain is a chronic condition that occurs frequently after nerve injury and induces hypersensitivity or allodynia characterized by aberrant neuronal excitability in the spinal cord dorsal horn. Fibronectin leucine-rich transmembrane protein 3 (FLRT3) is a modulator of neurite outgrowth, axon pathfinding, and cell adhesion, which is upregulated in the dorsal horn following peripheral nerve injury. However, the function of FLRT3 in adults remains unknown. Therefore, we aimed to investigate the involvement of spinal FLRT3 in neuropathic pain using rodent models. In the dorsal horns of male rats, FLRT3 protein levels increased at day 4 after peripheral nerve injury. In the DRG, FLRT3 was expressed in activating transcription factor 3-positive, injured sensory neurons. Peripheral nerve injury stimulated Flrt3 transcription in the DRG but not in the spinal cord. Intrathecal administration of FLRT3 protein to naive rats induced mechanical allodynia and GluN2B phosphorylation in the spinal cord. DRG-specific FLRT3 overexpression using adeno-associated virus also produced mechanical allodynia. Conversely, a function-blocking FLRT3 antibody attenuated mechanical allodynia after partial sciatic nerve ligation. Therefore, FLRT3 derived from injured DRG neurons increases dorsal horn excitability and induces mechanical allodynia.SIGNIFICANCE STATEMENT Neuropathic pain occurs frequently after nerve injury and is associated with abnormal neuronal excitability in the spinal cord. Fibronectin leucine-rich transmembrane protein 3 (FLRT3) regulates neurite outgrowth and cell adhesion. Here, nerve injury increased FLRT3 protein levels in the spinal cord dorsal root, despite the fact that Flrt3 transcripts were only induced in the DRG. FLRT3 protein injection into the rat spinal cord induced mechanical hypersensitivity, as did virus-mediated FLRT3 overexpression in DRG. Conversely, FLRT3 inhibition with antibodies attenuated mechanically induced pain after nerve damage. These findings suggest that FLRT3 is produced by injured DRG neurons and increases neuronal excitability in the dorsal horn, leading to pain sensitization. Neuropathic pain induction is a novel function of FLRT3.

In silico drug screening by using genome-wide association study data repurposed dabrafenib, an anti-melanoma drug, for Parkinson's disease.

Parkinson's disease (PD) is a neurodegenerative disorder characterized by dopaminergic neuron loss. At present, there are no drugs that stop the progression of PD. As with other multifactorial genetic disorders, genome-wide association studies (GWASs) found multiple risk loci for PD, although their clinical significance remains uncertain. Here, we report the identification of candidate drugs for PD by a method using GWAS data and in silico databases. We identified 57 Food and Drug Administration-approved drug families as candidate neuroprotective drugs for PD. Among them, dabrafenib, which is known as a B-Raf kinase inhibitor and is approved for the treatment of malignant melanoma, showed remarkable cytoprotective effects in neurotoxin-treated SH-SY5Y cells and mice. Dabrafenib was found to inhibit apoptosis, and to enhance the phosphorylation of extracellular signal-regulated kinase (ERK), and inhibit the phosphorylation of c-Jun NH2-terminal kinase. Dabrafenib targets B-Raf, and we confirmed a protein-protein interaction between B-Raf and Rit2, which is coded by RIT2, a PD risk gene in Asians and Caucasians. In RIT2-knockout cells, the phosphorylation of ERK was reduced, and dabrafenib treatment improved the ERK phosphorylation. These data indicated that dabrafenib exerts protective effects against neurotoxicity associated with PD. By using animal model, we confirmed the effectiveness of this in silico screening method. Furthermore, our results suggest that this in silico drug screening system is useful in not only neurodegenerative diseases but also other common diseases such as diabetes mellitus and hypertension.

Structurally distinct α-synuclein fibrils induce robust parkinsonian pathology.

OBJECTIVE: Alpha-synuclein (α-syn) is a major component of Lewy bodies, which are the pathological hallmark in Parkinson's disease, and its genetic mutations cause familial forms of Parkinson's disease. Patients with α-syn G51D mutation exhibit severe clinical symptoms. However, in vitro studies showed low propensity for α-syn with the G51D mutation. We studied the mechanisms associated with severe neurotoxicity of α-syn G51D mutation using a murine model generated by G51D α-syn fibril injection into the brain. METHODS: Structural analysis of wild-type and G51D α-syn-fibrils were performed using Fourier transform infrared spectroscopy. The ability of α-syn fibrils forming aggregates was first assessed in in vitro mammalian cells. An in vivo mouse model with an intranigral injection of α-syn fibrils was then used to evaluate the propagation pattern of α-syn and related cellular changes. RESULTS: We found that G51D α-syn fibrils have higher ß-sheet contents than wild-type α-syn fibrils. The addition of G51D α-syn fibrils to mammalian cells overexpressing α-syn resulted in the formation of phosphorylated α-syn inclusions at a higher rate. Similarly, an injection of G51D α-syn fibrils into the substantia nigra of a mouse brain induced more widespread phosphorylated α-syn pathology. Notably, the mice injected with G51D α-syn fibrils exhibited progressive nigral neuronal loss accompanied with mitochondrial abnormalities and motor impairment. CONCLUSION: Our findings indicate that the structural difference of G51D α-syn fibrils plays an important role in the rapidly developed and more severe neurotoxicity of G51D mutation-linked Parkinson's disease. © 2019 International Parkinson and Movement Disorder Society.

Parkinson's disease and iron.

While the initial causes of Parkinson's disease (PD) are not clearly defined, iron deposition has long been implicated in the pathogenesis of PD. The substantia nigra of PD patients, where the selective loss of dopaminergic neurons occurs, show a fairly selective and significant elevation in iron contents. However, the question remains whether iron deposition represents the initiation cause or merely the consequence of nigral degeneration. Here, we describe existing findings regarding the interaction of iron with neuromelanin and alpha synuclein, the iron deposition in experimental animal model of PD and sporadic and familial PD patients, and the treatment option involving the use of iron chelators for targeting the aberration of iron level in brain. This review may provide us a better understanding of the role of iron in PD to address the question of cause or consequence.

Knockdown of the mitochondria-localized protein p13 protects against experimental parkinsonism.

Mitochondrial dysfunction in the nigrostriatal dopaminergic system is a critical hallmark of Parkinson's disease (PD). Mitochondrial toxins produce cellular and behavioural dysfunctions resembling those in patients with PD Causative gene products for familial PD play important roles in mitochondrial function. Therefore, targeting proteins that regulate mitochondrial integrity could provide convincing strategies for PD therapeutics. We have recently identified a novel 13-kDa protein (p13) that may be involved in mitochondrial oxidative phosphorylation. In the current study, we examine the mitochondrial function of p13 and its involvement in PD pathogenesis using mitochondrial toxin-induced PD models. We show that p13 overexpression induces mitochondrial dysfunction and apoptosis. p13 knockdown attenuates toxin-induced mitochondrial dysfunction and apoptosis in dopaminergic SH-SY5Y cells via the regulation of complex I. Importantly, we generate p13-deficient mice using the CRISPR/Cas9 system and observe that heterozygous p13 knockout prevents toxin-induced motor deficits and the loss of dopaminergic neurons in the substantia nigra. Taken together, our results suggest that manipulating p13 expression may be a promising avenue for therapeutic intervention in PD.

Go-sha-jinki-Gan (GJG) ameliorates allodynia in chronic constriction injury-model mice via suppression of TNF-α expression in the spinal cord.

BACKGROUND: Alternative medicine is noted for its clinical effect and minimal invasiveness in the treatment of neuropathic pain. Go-sha-jinki-Gan, a traditional Japanese herbal medicine, has been used for meralgia and numbness in elderly patients. However, the exact mechanism of GJG is unclear. This study aimed to investigate the molecular mechanism of the analgesic effect of GJG in a chronic constriction injury model. RESULTS: GJG significantly reduced allodynia and hyperalgesia from the early phase (von Frey test, p<0.0001; cold-plate test, p<0.0001; hot-plate test p»0.011; two-way repeated measures ANOVA). Immunohistochemistry and Western blot analysis revealed that GJG decreased the expression of Iba1 and tumor necrosis factor-a in the spinal cord. Double staining immunohistochemistry showed that most of the tumor necrosis factor-a was co-expressed in Iba1-positive cells at day 3 post-operation. GJG decreased the phosphorylation of p38 in the ipsilateral dorsal horn. Moreover, intrathecal injection of tumor necrosis factor-a opposed the anti-allodynic effect of GJG in the cold-plate test. CONCLUSIONS: Our data suggest that GJG ameliorates allodynia in chronic constriction injury model mice via suppression of tumor necrosis factor-a expression derived from activated microglia. GJG is a promising drug for the treatment of neuropathic pain induced by neuro-inflammation.

Lung Cancer Wherein Durvalumab Induced Both Anti-CRMP-5 Antibody-related Paraneoplastic Neurological Syndromes and Neurological Adverse Events.

A 68-year-old man with small-cell lung cancer developed anti-collapsin response-mediator protein (CRMP)-5 antibody-related paraneoplastic neurological syndrome (PNS) presenting with ataxia and chorea during treatment with durvalumab. As a result of steroid therapy, anti-CRMP-5 antibodies became negative, hyperintense lesions on brain magnetic resonance imaging disappeared, and neurological symptoms improved. After resuming durvalumab, he became unable to walk due to neurological adverse events (nAEs). There have been no reported cases manifesting PNSs and nAEs as a result of the same immune checkpoint inhibitors (ICIs) administered at different times. Resuming ICIs in patients diagnosed with PNSs should be performed with prudence.

A Case of Liver Cancer with Overlapping Myasthenia Gravis, Myocarditis, Seronegative Autoimmune Autonomic Ganglionopathy, and Myositis Symptoms Induced by Atezolizumab: A Case Report.

An 83-year-old man with hepatocellular carcinoma developed muscle weakness, ptosis, and dyspnea 3 weeks after receiving atezolizumab. Soon after, mechanical ventilation was initiated, which was followed by marked blood pressure spikes. The levels of creatine kinase and troponin-I were significantly elevated, and acetylcholine receptor antibodies were positive. The patient was diagnosed with immune checkpoint inhibitor (ICI)-induced myositis, myasthenia gravis (MG), myocarditis, and suspected autoimmune autonomic ganglionopathy (AAG). After immunotherapy, the serum markers and blood pressure normalized, and he was weaned from the ventilator after five months. To our knowledge, this is the first reported case of AAG secondary to ICI-induced myositis, MG, and myocarditis.

Elevated Serum Xanthine Oxidase and Its Correlation with Antioxidant Status in Patients with Parkinson's Disease.

Parkinson's disease (PD) is a neurodegenerative movement disorder associated with a loss of dopamine neurons in the substantia nigra. The diagnosis of PD is sensitive since it shows clinical features that are common with other neurodegenerative diseases. In addition, most symptoms arise at the late stage of the disease, where most dopaminergic neurons are already damaged. Several studies reported that oxidative stress is a key modulator in the development of PD. This condition occurs due to excess reactive oxygen species (ROS) production in the cellular system and the incapability of antioxidants to neutralize it. In this study, we focused on the pathology of PD by measuring serum xanthine oxidase (XO) activity, which is an enzyme that generates ROS. Interestingly, the serum XO activity of patients with PD was markedly upregulated compared to patients with other neurological diseases (ONDs) as a control. Moreover, serum XO activity in patients with PD showed a significant correlation with the disease severity based on the Hoehn and Yahr (HY) stages. The investigation of antioxidant status also revealed that serum uric acid levels were significantly lower in the severe group (HY ≥ 3) than in the ONDs group. Together, these results suggest that XO activity may contribute to the development of PD and might potentially be a biomarker for determining disease severity in patients with PD.

Deciphering social traits and pathophysiological conditions from natural behaviors in common marmosets.

Nonhuman primates (NHPs) are indispensable animal models by virtue of the continuity of behavioral repertoires across primates, including humans. However, behavioral assessment at the laboratory level has so far been limited. Employing the application of three-dimensional (3D) pose estimation and the optimal integration of subsequent analytic methodologies, we demonstrate that our artificial intelligence (AI)-based approach has successfully deciphered the ethological, cognitive, and pathological traits of common marmosets from their natural behaviors. By applying multiple deep neural networks trained with large-scale datasets, we established an evaluation system that could reconstruct and estimate the 3D poses of the marmosets, a small NHP that is suitable for analyzing complex natural behaviors in laboratory setups. We further developed downstream analytic methodologies to quantify a variety of behavioral parameters beyond motion kinematics. We revealed the distinct parental roles of male and female marmosets through automated detections of food-sharing behaviors using a spatial-temporal filter on 3D poses. Employing a recurrent neural network to analyze 3D pose time series data during social interactions, we additionally discovered that marmosets adjusted their behaviors based on others' internal state, which is not directly observable but can be inferred from the sequence of others' actions. Moreover, a fully unsupervised approach enabled us to detect progressively appearing symptomatic behaviors over a year in a Parkinson's disease model. The high-throughput and versatile nature of an AI-driven approach to analyze natural behaviors will open a new avenue for neuroscience research dealing with big-data analyses of social and pathophysiological behaviors in NHPs.

Human induced pluripotent stem cell line (ONHi001-A) generated from a patient with infantile neuroaxonal dystrophy having PLA2G6 c.517C > T (p.Q173X) and c.1634A > G (p.K545R) compound heterozygous mutations.

Infantile neuroaxonal dystrophy (INAD) is a rare neurodegenerative disease caused mainly by homozygous or compound heterozygous mutations in the PLA2G6 gene. We generated a human induced pluripotent stem cell (hiPSC) line (ONHi001-A) using fibroblasts derived from a patient with INAD. The patient exhibited c.517C > T (p.Q173X) and c.1634A > G (p.K545R) compound heterozygous mutations in the PLA2G6 gene. This hiPSC line may be useful for studying the pathogenic mechanism underlying INAD.

A Mild Clinical Phenotype with Myopathic and Hemolytic Forms of Phosphoglycerate Kinase Deficiency (PGK Osaka): A Case Report and Literature Review.

Phosphoglycerate kinase (PGK) deficiency is an X-linked disorder characterized by a combination of hemolytic anemia, myopathy, and brain involvement. We herein report a Japanese man who had several episodes of rhabdomyolysis but was training strenuously to be a professional boxer. Mild hemolytic anemia was noted. The enzymatic activity of PGK was significantly reduced, and a novel missense mutation, p.S62N, was identified in the PGK1 gene. A literature review revealed only one case with a mixed hemolytic and myopathic phenotype like ours. This mild phenotype indicates the complex pathophysiology of PGK deficiency and suggests the benefits of dietary control and exercise.

Quantitative behavioral evaluation of a non-human primate stroke model using a new monitoring system.

Background: Recently, the common marmoset (Callithrix jacchus) has attracted significant interest as a non-human primate stroke model. Functional impairment in non-human primate stroke models should be evaluated quantitatively and successively after stroke, but conventional observational assessments of behavior cannot fully fit this purpose. In this paper, we report a behavioral analysis using MarmoDetector, a three-dimensional motion analysis, in an ischemic stroke model using photosensitive dye, along with an observational behavioral assessment and imaging examination. Methods: Ischemic stroke was induced in the left hemisphere of three marmosets. Cerebral infarction was induced by intravenous injection of rose bengal and irradiation with green light. The following day, the success of the procedure was confirmed by magnetic resonance imaging (MRI). The distance traveled, speed, activity time, and jumps/climbs were observed for 28 days after stroke using MarmoDetector. We also assessed the marmosets' specific movements and postural abnormalities using conventional neurological scores. Results: Magnetic resonance imaging diffusion-weighted and T2-weighted images showed hyperintense signals, indicating cerebral infarction in all three marmosets. MarmoDetector data showed that the both indices immediately after stroke onset and gradually improved over weeks. Neurological scores were the worst immediately after stroke and did not recover to pre-infarction levels during the observation period (28 days). A significant correlation was observed between MarmoDetector data and conventional neurological scores. Conclusion: In this study, we showed that MarmoDetector can quantitatively evaluate behavioral changes in the acute to subacute phases stroke models. This technique can be practical for research on the pathophysiology of ischemic stroke and for the development of new therapeutic methods.

Erdheim-Chester Disease Involving the Central Nervous System with Latent Toxoplasmosis.

Erdheim-Chester disease (ECD) is a rare, non-Langerhans cell histiocytosis characterized by the infiltration of foamy histiocytes into multiple organs. We herein report a case of ECD with central nervous system (CNS) involvement in a 63-year-old man who also presented a positive result for Toxoplasma gondii nested polymerase chain reaction testing of cerebrospinal fluid. Since anti-Toxoplasma treatment proved completely ineffective, we presumed latent infection of the CNS with T. gondii. This case suggests the difficulty of distinguishing ECD with CNS involvement from toxoplasmic encephalitis and the possibility of a relationship between the pathogeneses of ECD and infection with T. gondii.

piRNA/PIWI Protein Complex as a Potential Biomarker in Sporadic Amyotrophic Lateral Sclerosis.

The pathological hallmark of the majority of amyotrophic lateral sclerosis (ALS) cases is the mislocalization and aggregation of TAR DNA-binding protein 43 (TDP-43), an RNA-binding protein. Several studies have attributed disease processes of ALS to abnormal RNA metabolism. However, dysregulated biogenesis of RNA, especially non-coding RNA (ncRNA), is poorly understood. To resolve it, RNA-Seq, biochemical, and immunohistochemical analyses were performed on the pyramidal tract of the medulla oblongata of sporadic ALS (sALS) and control postmortem brain samples. Here, we report perturbation of ncRNA biogenesis in PIWI-interacting RNA (piRNA) in several sALS brain samples associated with TDP-43 pathology. In addition, we confirmed the dysregulation of two PIWI homologs, PIWI-like-mediated gene silencing 1 (PIWIL1) and PIWIL4, which bind to piRNAs to regulate their expression. PIWIL1 was mislocalized and co-localized with TDP-43 in motor neurons of sporadic ALS lumbar cords. Our results imply that dysregulation of piRNA, PIWIL1, and PIWIL4 is linked to pathogenesis of ALS. Based on these results, piRNAs and PIWI proteins are potential diagnostic biomarkers and therapeutic targets of ALS.

Two-step screening method to identify α-synuclein aggregation inhibitors for Parkinson's disease.

Parkinson's disease is a neurodegenerative disease characterized by the formation of neuronal inclusions of α-synuclein in patient brains. As the disease progresses, toxic α-synuclein aggregates transmit throughout the nervous system. No effective disease-modifying therapy has been established, and preventing α-synuclein aggregation is thought to be one of the most promising approaches to ameliorate the disease. In this study, we performed a two-step screening using the thioflavin T assay and a cell-based assay to identify α-synuclein aggregation inhibitors. The first screening, thioflavin T assay, allowed the identification of 30 molecules, among a total of 1262 FDA-approved small compounds, which showed inhibitory effects on α-synuclein fibrilization. In the second screening, a cell-based aggregation assay, seven out of these 30 candidates were found to prevent α-synuclein aggregation without causing substantial toxicity. Of the seven final candidates, tannic acid was the most promising compound. The robustness of our screening method was validated by a primary neuronal cell model and a Caenorhabditis elegans model, which demonstrated the effect of tannic acid against α-synuclein aggregation. In conclusion, our two-step screening system is a powerful method for the identification of α-synuclein aggregation inhibitors, and tannic acid is a promising candidate as a disease-modifying drug for Parkinson's disease.

Inhibition of repulsive guidance molecule-a protects dopaminergic neurons in a mouse model of Parkinson's disease.

Repulsive guidance molecule-a (RGMa), a glycosylphosphatidylinositol-anchored membrane protein, has diverse functions in axon guidance, cell patterning, and cell survival. Inhibition of RGMa attenuates pathological dysfunction in animal models of central nervous system (CNS) diseases including spinal cord injury, multiple sclerosis, and neuromyelitis optica. Here, we examined whether antibody-based inhibition of RGMa had therapeutic effects in a mouse model of Parkinson's disease (PD). We treated mice with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and found increased RGMa expression in the substantia nigra (SN). Intraventricular, as well as intravenous, administration of anti-RGMa antibodies reduced the loss of tyrosine hydroxylase (TH)-positive neurons and accumulation of Iba1-positive microglia/macrophages in the SN of MPTP-treated mice. Selective expression of RGMa in TH-positive neurons in the SN-induced neuronal loss/degeneration and inflammation, resulting in a progressive movement disorder. The pathogenic effects of RGMa overexpression were attenuated by treatment with minocycline, which inhibits microglia and macrophage activation. Increased RGMa expression upregulated pro-inflammatory cytokine expression in microglia. Our observations suggest that the upregulation of RGMa is associated with the PD pathology; furthermore, inhibitory RGMa antibodies are a potential therapeutic option.