1
|
Espay AJ, Lees AJ. Loss of monomeric alpha-synuclein (synucleinopenia) and the origin of Parkinson's disease. Parkinsonism Relat Disord 2024; 122:106077. [PMID: 38461037 DOI: 10.1016/j.parkreldis.2024.106077] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/18/2024] [Revised: 02/26/2024] [Accepted: 02/27/2024] [Indexed: 03/11/2024]
Abstract
These facts argue against the gain-of-function synucleinopathy hypothesis, which proposes that Lewy pathology causes Parkinson's disease: (1) most brains from people without neurological symptoms have multiple pathologies; (2) neither pathology type nor distribution correlate with disease severity or progression in Parkinson's disease; (3) aggregated α-synuclein in the form of Lewy bodies is not a space-occupying lesion but the insoluble fraction of its precursor, soluble monomeric α-synuclein; (4) pathology spread is passive, occurring by irreversible nucleation, not active replication; and (5) low cerebrospinal fluid α-synuclein levels predict brain atrophy and clinical disease progression. The transformation of α-synuclein into Lewy pathology may occur as a response to biological, toxic, or infectious stressors whose persistence perpetuates the nucleation process, depleting normal α-synuclein and eventually leading to Parkinson's symptoms from neuronal death. We propose testing the loss-of-function synucleinopenia hypothesis by evaluating the clinical and neurodegenerative rescue effect of replenishing the levels of monomeric α-synuclein.
Collapse
Affiliation(s)
- Alberto J Espay
- James J. and Joan A. Gardner Family Center for Parkinson's Disease and Movement Disorders, Department of Neurology, University of Cincinnati, Cincinnati, OH, USA.
| | - Andrew J Lees
- The National Hospital, Queen Square and Reta Lila Weston Institute for Neurological Studies University College London, London, UK
| |
Collapse
|
2
|
Abioye A, Akintade D, Mitchell J, Olorode S, Adejare A. Nonintuitive Immunogenicity and Plasticity of Alpha-Synuclein Conformers: A Paradigm for Smart Delivery of Neuro-Immunotherapeutics. Pharmaceutics 2024; 16:609. [PMID: 38794271 PMCID: PMC11124533 DOI: 10.3390/pharmaceutics16050609] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2024] [Revised: 04/25/2024] [Accepted: 04/26/2024] [Indexed: 05/26/2024] Open
Abstract
Despite the extensive research successes and continuous developments in modern medicine in terms of diagnosis, prevention, and treatment, the lack of clinically useful disease-modifying drugs or immunotherapeutic agents that can successfully treat or prevent neurodegenerative diseases is an ongoing challenge. To date, only one of the 244 drugs in clinical trials for the treatment of neurodegenerative diseases has been approved in the past decade, indicating a failure rate of 99.6%. In corollary, the approved monoclonal antibody did not demonstrate significant cognitive benefits. Thus, the prevalence of neurodegenerative diseases is increasing rapidly. Therefore, there is an urgent need for creative approaches to identifying and testing biomarkers for better diagnosis, prevention, and disease-modifying strategies for the treatment of neurodegenerative diseases. Overexpression of the endogenous α-synuclein has been identified as the driving force for the formation of the pathogenic α-synuclein (α-Syn) conformers, resulting in neuroinflammation, hypersensitivity, endogenous homeostatic responses, oxidative dysfunction, and degeneration of dopaminergic neurons in Parkinson's disease (PD). However, the conformational plasticity of α-Syn proffers that a certain level of α-Syn is essential for the survival of neurons. Thus, it exerts both neuroprotective and neurotoxic (regulatory) functions on neighboring neuronal cells. Furthermore, the aberrant metastable α-Syn conformers may be subtle and difficult to detect but may trigger cellular and molecular events including immune responses. It is well documented in literature that the misfolded α-Syn and its conformers that are released into the extracellular space from damaged or dead neurons trigger the innate and adaptive immune responses in PD. Thus, in this review, we discuss the nonintuitive plasticity and immunogenicity of the α-Syn conformers in the brain immune cells and their physiological and pathological consequences on the neuroimmune responses including neuroinflammation, homeostatic remodeling, and cell-specific interactions that promote neuroprotection in PD. We also critically reviewed the novel strategies for immunotherapeutic delivery interventions in PD pathogenesis including immunotherapeutic targets and potential nanoparticle-based smart drug delivery systems. It is envisioned that a greater understanding of the nonintuitive immunogenicity of aberrant α-Syn conformers in the brain's microenvironment would provide a platform for identifying valid therapeutic targets and developing smart brain delivery systems for clinically effective disease-modifying immunotherapeutics that can aid in the prevention and treatment of PD in the future.
Collapse
Affiliation(s)
- Amos Abioye
- College of Pharmacy and Health Sciences, Belmont University, Nashville, TN 37212, USA
| | - Damilare Akintade
- Department of Biomedical Sciences, School of Health, Leeds Beckett University, Leeds LS1 3HE, UK; (D.A.); (J.M.); (S.O.)
| | - James Mitchell
- Department of Biomedical Sciences, School of Health, Leeds Beckett University, Leeds LS1 3HE, UK; (D.A.); (J.M.); (S.O.)
| | - Simisade Olorode
- Department of Biomedical Sciences, School of Health, Leeds Beckett University, Leeds LS1 3HE, UK; (D.A.); (J.M.); (S.O.)
| | - Adeboye Adejare
- Department of Pharmaceutical Sciences, Philadelphia College of Pharmacy, Saint Joseph’s University, Philadelphia, PA 19131, USA;
| |
Collapse
|
3
|
Mills KA, Phillips O, Mahajan A. Hope vs. Hype I: Spreading alpha-synuclein explains cognitive deficits in Parkinson disease. Parkinsonism Relat Disord 2024:106042. [PMID: 38365523 DOI: 10.1016/j.parkreldis.2024.106042] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/06/2024] [Accepted: 02/09/2024] [Indexed: 02/18/2024]
Abstract
The Parkinson Study Group (PSG) gathered North American experts in Parkinson disease during the 9th Annual Symposium on "Shaping the Management of Parkinson Disease: Debating Current Controversies". Debaters were tasked with agree or disagree positions to a particular prompt. This is the first in three-part series of "Hype vs. Hope" debates involving current trends and advances in Parkinson disease. With the prompt of "Spreading alpha-synuclein explains cognitive deficits in Parkinson disease," Dr. Kelly Mills, MD, MHS was tasked with the "agree" stance and Dr. Abhimanyu Mahajan, MD, MHS was tasked with the "disagree" stance. The following point-of-view article is an adaptation of this debate.
Collapse
Affiliation(s)
- Kelly A Mills
- Johns Hopkins Department of Neurology, Baltimore, MD600 N. Wolfe Street, Meyer 6-181D, 21287, United States.
| | - Oliver Phillips
- Geisel School of Medicine at Dartmouth, Hanover, NH, 18 Old Etna Road, 03756, United States.
| | - Abhimanyu Mahajan
- The University of Cincinnati James J. and Joan A. Gardner Family Center for Parkinson's Disease and Movement Disorders, OH, 260 Stetson St., Suite 2300, Cincinnati, 45219, United States.
| |
Collapse
|
4
|
Zenuni H, Bovenzi R, Bissacco J, Grillo P, Simonetta C, Mascioli D, Pieri M, Bernardini S, Sancesario GM, Stefani A, Mercuri NB, Schirinzi T. Clinical and neurochemical correlates of the APOE genotype in early-stage Parkinson's disease. Neurobiol Aging 2023; 131:24-28. [PMID: 37572524 DOI: 10.1016/j.neurobiolaging.2023.07.011] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2023] [Revised: 07/14/2023] [Accepted: 07/15/2023] [Indexed: 08/14/2023]
Abstract
Emerging evidence indicates that apolipoprotein E (APOE) genotype may influence Parkinson's disease (PD) course, although clinical and neurochemical correlates have not been completely established. This study aimed to determine the associations of APOE genotypes (ε4 vs. non-ε4) with cerebrospinal fluid (CSF) neurodegeneration biomarkers and clinical parameters in early-stage PD patients. One hundred and seventy-five PD patients and 89 non-neurodegenerative controls grouped in APOE-ε4 carriers (28 PD; 12 controls) and non-APOE-ε4 carriers (147 PD; 78 controls) were enrolled. CSF levels of amyloid-β-42, amyloid-β-40, total and 181-phosphorylated tau, and clinical scores were compared among groups adjusting for main covariates. APOE genotypes prevalence was similar in PD and controls. PD APOE-ε4 carriers had lower amyloid-β-42 CSF levels than PD non-APOE-ε4 carriers and controls, independently from age. PD APOE-ε4 carriers also had higher total and "item 5" (attention and memory) non-motor symptoms scale scores than PD non-APOE-ε4 carriers, independently from confounding factors. APOE-ε4 genotype might thus account for a more vulnerable PD subtype characterized by prominent amyloidopathy and a greater burden of non-motor symptoms in the early disease stages. DATA AVAILABILITY: Data are available upon reasonable request.
Collapse
Affiliation(s)
- Henri Zenuni
- Unit of Neurology, Department of Systems Medicine, University of Roma Tor Vergata, Rome, Italy
| | - Roberta Bovenzi
- Unit of Neurology, Department of Systems Medicine, University of Roma Tor Vergata, Rome, Italy
| | - Jacopo Bissacco
- Unit of Neurology, Department of Systems Medicine, University of Roma Tor Vergata, Rome, Italy
| | - Piergiorgio Grillo
- Unit of Neurology, Department of Systems Medicine, University of Roma Tor Vergata, Rome, Italy
| | - Clara Simonetta
- Unit of Neurology, Department of Systems Medicine, University of Roma Tor Vergata, Rome, Italy
| | - Davide Mascioli
- Unit of Neurology, Department of Systems Medicine, University of Roma Tor Vergata, Rome, Italy
| | - Massimo Pieri
- Clinical Biochemistry Unit, Department of Experimental Medicine, University of Roma Tor Vergata, Rome, Italy
| | - Segio Bernardini
- Clinical Biochemistry Unit, Department of Experimental Medicine, University of Roma Tor Vergata, Rome, Italy
| | | | - Alessandro Stefani
- Unit of Neurology, Department of Systems Medicine, University of Roma Tor Vergata, Rome, Italy
| | - Nicola Biagio Mercuri
- Unit of Neurology, Department of Systems Medicine, University of Roma Tor Vergata, Rome, Italy
| | - Tommaso Schirinzi
- Unit of Neurology, Department of Systems Medicine, University of Roma Tor Vergata, Rome, Italy.
| |
Collapse
|
5
|
Espay AJ, McFarthing K. Alpha-synuclein and the Parkinson's disease drug pipeline. Parkinsonism Relat Disord 2023:105432. [PMID: 37244791 DOI: 10.1016/j.parkreldis.2023.105432] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/19/2023] [Revised: 04/20/2023] [Accepted: 04/28/2023] [Indexed: 05/29/2023]
Abstract
The process of protein aggregation involves the transformation of soluble peptides into insoluble cross-beta amyloids. In Parkinson's disease (PD), soluble monomeric α-synuclein transforms into the amyloid state known as Lewy pathology. Monomeric (functional) α-synuclein depletes as the fraction of Lewy pathology increases. We examined the allocation of disease-modifying projects in the PD therapeutic pipeline classified based on whether they aimed to reduce directly or indirectly the insoluble or increase the soluble α-synuclein. A project was defined as a drug development program that may include more than one registered clinical trial, according to the Parkinson's Hope List, a database of therapies under development for PD. Of 67 projects, 46 aimed to reduce α-synuclein, 15 (22.4%) directly and 31 (46.3%) indirectly, amounting to 68.7% of all disease-modifying projects. No projects explicitly aimed to increase soluble α-synuclein levels. Altogether, α-synuclein is the target of more than two-thirds of the disease-modifying pipeline, with treatments aimed at reducing or preventing an increase in its insoluble fraction. As no treatments aim to restore soluble α-synuclein levels within a normal range, we propose rebalancing the therapeutic PD pipeline.
Collapse
Affiliation(s)
- Alberto J Espay
- Department of Neurology, James J. and Joan A. Gardner Family Center for Parkinson's Disease and Movement Disorders, University of Cincinnati, Cincinnati, OH, USA.
| | | |
Collapse
|
6
|
Ezzat K, Sturchio A, Espay AJ. The shift to a proteinopenia paradigm in neurodegeneration. HANDBOOK OF CLINICAL NEUROLOGY 2023; 193:23-32. [PMID: 36803814 DOI: 10.1016/b978-0-323-85555-6.00001-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/18/2023]
Abstract
The toxic proteinopathy paradigm has defined neurodegenerative disorders for over a century. This gain-of-function (GOF) framework posited that proteins become toxic when turned into amyloids (pathology), predicting that lowering its levels would translate into clinical benefits. Genetic observations used to support a GOF framework are equally compatible with a loss-of-function (LOF) framework, as the soluble pool of proteins rendered unstable by these mutations (e.g., APP in Alzheimer's disease, SNCA in Parkinson's disease) aggregate, becoming depleted. In this review, we highlight misconceptions that have prevented LOF from gaining currency. Some of these misconceptions include no phenotype in knock-out animals (there is neurodegenerative phenotype in knock-out animals) and high levels of proteins in patients (patients have lower levels of the proteins involved in neurodegeneration than healthy age-matched controls). We also expose the internal contradictions within the GOF framework, namely that (1) pathology can have both pathogenic and protective roles; (2) the neuropathology gold standard for diagnosis can be present in normal individuals and absent in those affected; (3) oligomers are the toxic species even if they are ephemeral and decrease over time. We therefore advocate for a paradigm shift from proteinopathy (GOF) to proteinopenia (LOF) based on the universal depletion of soluble functional proteins in neurodegenerative diseases (low amyloid-β 42 in Alzheimer's disease, low α-synuclein in Parkinson's disease, and low tau in progressive supranuclear palsy) and supported by the confluence of biologic, thermodynamic, and evolutionary principles with proteins having evolved to perform a function, not to become toxic, and where protein depletion is consequential. Such shift to a Proteinopenia paradigm is necessary to examining the safety and efficacy of protein replacement strategies instead of perpetuating a therapeutic paradigm with further antiprotein permutations.
Collapse
Affiliation(s)
- Kariem Ezzat
- Department of Laboratory Medicine, Biomolecular and Cellular Medicine, Karolinska Institutet, Stockholm, Sweden.
| | - Andrea Sturchio
- Department of Clinical Neuroscience, Neuro Svenningsson, Karolinska Institutet, Stockholm, Sweden; James J. and Joan A. Gardner Family Center for Parkinson's Disease and Movement Disorders, Department of Neurology, University of Cincinnati, Cincinnati, OH, United States
| | - Alberto J Espay
- James J. and Joan A. Gardner Family Center for Parkinson's Disease and Movement Disorders, Department of Neurology, University of Cincinnati, Cincinnati, OH, United States
| |
Collapse
|
7
|
Donadio V, Sturchio A, Rizzo G, Abu Rumeileh S, Liguori R, Espay AJ. Pathology vs pathogenesis: Rationale and pitfalls in the clinicopathology model of neurodegeneration. HANDBOOK OF CLINICAL NEUROLOGY 2023; 192:35-55. [PMID: 36796947 DOI: 10.1016/b978-0-323-85538-9.00001-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/16/2023]
Abstract
In neurodegenerative disorders, the term pathology is often implicitly referred to as pathogenesis. Pathology has been conceived as a window into the pathogenesis of neurodegenerative disorders. This clinicopathologic framework posits that what can be identified and quantified in postmortem brain tissue can explain both premortem clinical manifestations and the cause of death, a forensic approach to understanding neurodegeneration. As the century-old clinicopathology framework has yielded little correlation between pathology and clinical features or neuronal loss, the relationship between proteins and degeneration is ripe for revisitation. There are indeed two synchronous consequences of protein aggregation in neurodegeneration: the loss of the soluble/normal proteins on one; the accrual of the insoluble/abnormal fraction of these proteins on the other. The omission of the first part in the protein aggregation process is an artifact of the early autopsy studies: soluble, normal proteins have disappeared, with only the remaining insoluble fraction amenable to quantification. We here review the collective evidence from human data suggesting that protein aggregates, known collectively as pathology, are the consequence of many biological, toxic, and infectious exposures, but may not explain alone the cause or pathogenesis of neurodegenerative disorders.
Collapse
Affiliation(s)
- Vincenzo Donadio
- IRCCS Istituto delle Scienze Neurologiche di Bologna, UOC Clinica Neurologica, Bologna, Italy.
| | - Andrea Sturchio
- Department of Clinical Neuroscience, Neuro Svenningsson, Karolinska Institutet, Stockholm, Sweden; James J. and Joan A. Gardner Family Center for Parkinson's Disease and Movement Disorders, Department of Neurology, University of Cincinnati, Cincinnati, OH, United States
| | - Giovanni Rizzo
- IRCCS Istituto delle Scienze Neurologiche di Bologna, UOC Clinica Neurologica, Bologna, Italy
| | - Samir Abu Rumeileh
- Department of Neurology, Martin-Luther-University Halle-Wittenberg, Halle, Germany
| | - Rocco Liguori
- IRCCS Istituto delle Scienze Neurologiche di Bologna, UOC Clinica Neurologica, Bologna, Italy
| | - Alberto J Espay
- James J. and Joan A. Gardner Family Center for Parkinson's Disease and Movement Disorders, Department of Neurology, University of Cincinnati, Cincinnati, OH, United States
| |
Collapse
|
8
|
Abstract
This Viewpoint makes a case for changing the approach in Parkinson disease research efforts from one of proteinopathy (accrual of amyloids) to proteinopenia (depletion of normal proteins).
Collapse
Affiliation(s)
- Alberto J Espay
- James J. and Joan A. Gardner Family Center for Parkinson's Disease and Movement Disorders, Department of Neurology, University of Cincinnati, Cincinnati, Ohio
| | - Michael S Okun
- Department of Neurology, Norman Fixel Institute for Neurological Diseases, Gainesville, Florida
| |
Collapse
|
9
|
Espay AJ. Movement disorders research in 2021: cracking the paradigm. Lancet Neurol 2021; 21:10-11. [PMID: 34942122 DOI: 10.1016/s1474-4422(21)00413-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Accepted: 11/15/2021] [Indexed: 11/27/2022]
Affiliation(s)
- Alberto J Espay
- James J and Joan A Gardner Family Center for Parkinson's Disease and Movement Disorders, Department of Neurology, University of Cincinnati, Cincinnati, OH 45219, USA.
| |
Collapse
|