Intracellular crowding by age-dependent neuromelanin accumulation disrupts neuronal proteostasis and triggers Parkinson disease pathology

In Parkinson disease (PD), there is a preferential degeneration of neurons that contain the dark-brown cytoplasmic pigment neuromelanin, in particular dopaminergic neurons of the substantia nigra (SN), the loss of which leads to the typical motor symptoms of the disease and constitutes the cardinal pathological diagnostic criterion for PD. Neuromelanin is generally considered a byproduct of dopamine oxidative metabolism and, in humans, it is first detected in early childhood and accumulates progressively with age until occupying most of the neuronal cytoplasm, as neurons apparently lack the means to degrade or eliminate this pigment. Aging is the main risk factor for developing PD, but the molecular substrate underlying this link remains unknown. Despite the close and long-established association between neuromelanin and PD, the potential contribution of neuromelanin to PD pathogenesis has remained elusive because, in contrast to humans, common laboratory animal species, such as rodents, lack neuromelanin. To overcome this major limitation, we have recently generated the first experimental in vivo rodent model exhibiting age-dependent production and accumulation of human-like neuromelanin within PD-vulnerable dopaminergic nigral neurons, at levels up to those reached in elderly humans

Chitinase 3-like 1 is neurotoxic in primary cultured neurons

Chitinase 3-like 1 (CHI3L1) is known to play a role as prognostic biomarker in the early stages of multiple sclerosis (MS), and patients with high cerebrospinal fluid CHI3L1 levels have an increased risk for the development of neurological disability. Here, we investigated its potential neurotoxic effect by adding recombinant CHI3L1 in vitro to primary cultures of mouse cortical neurons and evaluating both neuronal functionality and survival by immunofluorescence. CHI3L1 induced a significant neurite length retraction after 24 and 48 hours of exposure and significantly reduced neuronal survival at 48 hours. The cytotoxic effect of CHI3L1 was neuron-specific and was not observed in mouse immune or other central nervous system cells. These results point to a selective neurotoxic effect of CHI3L1 in vitro and suggest a potential role of CHI3L1 as therapeutic target in MS patients

Selective suppression of α-Synuclein in monoaminergic neurons of mice by intranasal delivery of targeted small interfering RNA or antisense oligonucleotides: Potential therapy for Parkinson's disease

Póster presentado en: ACNP (American College of Neuropsychopharmacology) 52nd Annual Conference, celebrada del 8 al 12 de diciembre de 2013 en Hollywood, Florida (Estados Unidos)Abstract publicado en: Neuropsychopharmacology 38:S419-S420 (2013). ISSN: 0893-133X. eISSN: 1740-634X. DOI:10.1038/npp.2013.280α-Synuclein (α-Syn) appears to play a crucial role in the pathogenesis of several neurodegenerative disorders including Parkinson's disease (PD). The brains of Parkinson patients typically contain insoluble intracellular protein inclusions called Lewy bodies. Increased neuronal α-Syn levels represent a major component of Lewy bodies and therefore, the suppression of α-Syn expression provides a valid therapeutic target for PD. The goal of this study was to assess the ability of various small interfering RNA (siRNA) and antisense oligonucleotide (ASO) sequences directed against α-Syn to downregulate endogenous or overexpressed α-Syn mRNA levels in BE-M17 neuroblastoma cells. Moreover, we evaluated the feasibility of reducing α-Syn expression selectively in PD-vulnerable brain areas including substantia nigra pars compacta (SNc), ventral tegmental area (VTA), locus coeruleus (LC) and dorsal raphe nucleus (DR) of mice after the internalization of conjugated siRNA/ASO molecules into monoamine neurons following intranasal administration. Conclusions: These results set the stage for the testing of these molecules as potential disease-modifying agents in neurotoxin-based and genetic models of PD linked to pathogenic increases in α-Syn. In this study we have characterized conjugated siRNA and ASO molecules that actively reduce endogenous α-Syn expression in vivo using the intranasal route to deliver directly siRNA/ASO into the brainPeer Reviewe

Age-dependent multisystem parkinsonian features in a novel neuromelanin-producing transgenic mouse model

Trabajo presentado en el 19th National Meeting of the Spanish Society of Neuroscience, celebrado en Lleida (España), del 3 al 5 de noviembre de 2021Parkinson’s disease (PD) is characterized by a preferential degeneration of neurons that accumulate with age the pigment neuromelanin, especially neurons from substantia nigra (SN) and locus coeruleus (LC). We aim to characterize the consequences of age-dependent intracellular neuromelanin accumulation in catecholaminergic neuronal populations to understand the relationship between this process and the vulnerability of these cells in PD, as well as its impact on healthy brain aging. We previously generated a rat model exhibiting progressive unilateral SN production of neuromelanin that showed parkinsonian-like neuropathology and motor deficits1. Here, we generated a new neuromelanin-producing rodent model, based on the tissue-specific constitutive expression of human tyrosinase (hTyr) under the tyrosine hydroxylase (TH) promoter (Tg-TH-hTyr), that mimics the bilateral distribution of pigmentation within the aging human brain (i.e. catecholaminergic groups A1-A142). In parallel to neuromelanin intracellular buildup, Tg-TH-hTyr mice exhibited major PD features, including motor and non-motor behavioral alterations, inclusion body formation and degeneration of specific catecholaminergic neuronal groups. Genome-wide transcriptomic analysis of neuromelanin-laden neurons revealed alterations in PD-related biological pathways that correlate with human PD postmortem studies. Our results show that modelling human neuromelanin accumulation in rodents leads to age-dependent catecholaminergic dysfunction and molecular alterations resulting in motor and non-motor deficits, which is relevant to PD pathology and brain aging.Peer reviewe

Advances in Parkinson’s Disease: 200 Years Later

When James Parkinson described the classical symptoms of the disease he could hardly foresee the evolution of our understanding over the next two hundred years. Nowadays, Parkinson’s disease is considered a complex multifactorial disease in which genetic factors, either causative or susceptibility variants, unknown environmental cues, and the potential interaction of both could ultimately trigger the pathology. Noteworthy advances have been made in different fields from the clinical phenotype to the decoding of some potential neuropathological features, among which are the fields of genetics, drug discovery or biomaterials for drug delivery, which, though recent in origin, have evolved swiftly to become the basis of research into the disease today. In this review, we highlight some of the key advances in the field over the past two centuries and discuss the current challenges focusing on exciting new research developments likely to come in the next few years. Also, the importance of pre-motor symptoms and early diagnosis in the search for more effective therapeutic options is discussed

Brain tyrosinase overexpression implicates age-dependent neuromelanin production in Parkinson's disease pathogenesis

Brain tyrosinase; Neuromelanin production; Parkinson’sTirosinasa cerebral; Producció de neuromelanina; ParkinsonTirosinasa cerebral; Producción de neuromelanina; ParkinsonIn Parkinson's disease (PD) there is a selective degeneration of neuromelanin-containing neurons, especially substantia nigra dopaminergic neurons. In humans, neuromelanin accumulates with age, the latter being the main risk factor for PD. The contribution of neuromelanin to PD pathogenesis remains unknown because, unlike humans, common laboratory animals lack neuromelanin. Synthesis of peripheral melanins is mediated by tyrosinase, an enzyme also present at low levels in the brain. Here we report that overexpression of human tyrosinase in rat substantia nigra results in age-dependent production of human-like neuromelanin within nigral dopaminergic neurons, up to levels reached in elderly humans. In these animals, intracellular neuromelanin accumulation above a specific threshold is associated to an age-dependent PD phenotype, including hypokinesia, Lewy body-like formation and nigrostriatal neurodegeneration. Enhancing lysosomal proteostasis reduces intracellular neuromelanin and prevents neurodegeneration in tyrosinase-overexpressing animals. Our results suggest that intracellular neuromelanin levels may set the threshold for the initiation of PD

Transcriptomic changes linked to age-dependent neuromelanin accumulation in a new Parkinson's disease mouse model

Resumen del trabajo presentado en el 50th Annual Meeting Society for Neuroscience, celebrado de forma virtual del 8 al 11 de noviembre de 2021In Parkinson's disease (PD) there is a preferential degeneration of neuromelanin (NM)-containing neurons, especially neurons from the Substantia Nigra (SN) but also from the Ventral Tegmental Area (VTA) and Locus Coeruleus (LC). We generated a new NM-producing mouse model, based on the tissue-specific constitutive expression of human tyrosinase (hTyr) under the tyrosine hydroxylase (TH) promoter (tgNM), that mimics the distribution and age-dependent accumulation of NM in the human brain (i.e. catecholaminergic groups A1-A14). TgNM mice exhibited major PD features, including both motor and non-motor behavioral alterations, inclusion body formation, neuronal degeneration in lower brainstem areas (LC) together with neuronal dysfunction in higher brainstem areas (SN and VTA). In order to understand the mechanisms by which NM accumulation in specific brain areas ultimately interferes with the normal functioning of cells, we characterized genome-wide transcriptomic changes linked to the intracellular presence and progressive accumulation of NM in two NM-accumulating neuronal subpopulations (SN and VTA) that are known to be differentially susceptible to PD pathology. We selectively isolated single dopaminergic NM-containing neurons by laser capture microdissection from male and female wild-type and tgNM animals at 3 months, 12 months and 20 months of age (n=4-6 mice per group). We performed differential expression analysis, resulting in statistically significant differentially expressed genes at all ages (p-value<0.5). Gene-set enrichment analysis (GSEA) with Reactome Pathway Database led to the identification of altered biological pathways in tgNM related to neuroinflammation, vesicle-mediated transport and lipid metabolism, transcription and translation, mitochondrial function and cell cycle (senescence) (False Discovery Rate<0.05). Targeted-based validation of candidate RNA species was performed in microdissected samples by quantitative real-time PCR and candidate biological pathways were validated at the protein level by western blot in dissected ventral midbrain tissues from biological replicates. The transcriptomic profiles identified in this project contribute to our understanding of selective vulnerability in PD and brain aging, and points to key biological pathways and molecular targets in prodromal and early PD

Correction to : The Small GTPase RAC1/CED-10 Is Essential in Maintaining Dopaminergic Neuron Function and Survival Against α-Synuclein-Induced Toxicity

With the author(s)' decision to opt for Open Choice the copyright of the article changed on March 2018 t

Disease-specific phenotypes in dopamine neurons from human iPS-based models of genetic and sporadic Parkinson's disease

Induced pluripotent stem cells (iPSC) offer an unprecedented opportunity to model human disease in relevant cell types, but it is unclear whether they could successfully model age-related diseases such as Parkinson's disease (PD). Here, we generated iPSC lines from seven patients with idiopathic PD (ID-PD), four patients with familial PD associated to the G2019S mutation in the Leucine-Rich Repeat Kinase 2 (LRRK2) gene (LRRK2-PD) and four age- and sex-matched healthy individuals (Ctrl). Over long-time culture, dopaminergic neurons (DAn) differentiated from either ID-PD- or LRRK2-PD-iPSC showed morphological alterations, including reduced numbers of neurites and neurite arborization, as well as accumulation of autophagic vacuoles, which were not evident in DAn differentiated from Ctrl-iPSC. Further induction of autophagy and/or inhibition of lysosomal proteolysis greatly exacerbated the DAn morphological alterations, indicating autophagic compromise in DAn from ID-PD- and LRRK2-PD-iPSC, which we demonstrate occurs at the level of autophagosome clearance. Our study provides an iPSC-based in vitro model that captures the patients' genetic complexity and allows investigation of the pathogenesis of both sporadic and familial PD cases in a disease-relevant cell type

Aberrant epigenome in iPSC-derived dopaminergic neurons from Parkinson's disease patients

The epigenomic landscape of Parkinson's disease (PD) remains unknown. We performed a genomewide DNA methylation and a transcriptome studies in induced pluripotent stem cell (iPSC)-derived dopaminergic neurons (DAn) generated by cell reprogramming of somatic skin cells from patients with monogenic LRRK2-associated PD (L2PD) or sporadic PD (sPD), and healthy subjects. We observed extensive DNA methylation changes in PD DAn, and of RNA expression, which were common in L2PD and sPD. No significant methylation differences were present in parental skin cells, undifferentiated iPSCs nor iPSC-derived neural cultures not-enriched-in-DAn. These findings suggest the presence of molecular defects in PD somatic cells which manifest only upon differentiation into the DAn cells targeted in PD. The methylation profile from PD DAn, but not from controls, resembled that of neural cultures not-enriched-in-DAn indicating a failure to fully acquire the epigenetic identity own to healthy DAn in PD. The PD-associated hypermethylation was prominent in gene regulatory regions such as enhancers and was related to the RNA and/or protein downregulation of a network of transcription factors relevant to PD (FOXA1, NR3C1, HNF4A, and FOSL2). Using a patient-specific iPSC-based DAn model, our study provides the first evidence that epigenetic deregulation is associated with monogenic and sporadic PD