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The role of Triggering Receptor Expressed on Myeloid Cells 2 in Parkinson's disease and other neurodegenerative disorders. Behav Brain Res 2022; 433:113977. [PMID: 35752274 DOI: 10.1016/j.bbr.2022.113977] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Revised: 06/09/2022] [Accepted: 06/21/2022] [Indexed: 11/23/2022]
Abstract
Parkinson's disease (PD) is a progressive neurological disorder marked by cardinal clinical symptoms such as rigor, tremor, and akinesia. Albeit a loss of dopaminergic neurons from the substantia nigra pars compacta is causative for the movement impairments found in patients, molecular reasoning for this loss is still incomplete. In recent years, triggering factor expressed on myeloid cells (TREM2) gained attention in the field of neurodegeneration as it could be associated with different neurodegenerative disorders. Primarily identified as a risk factor in Alzheimer's disease, variants in TREM2 were linked to PD and multiple sclerosis, too. Expressed on phagocytic cells, such as macrophages and microglia, TREM2 puts the focus on inflammation associated conditions in PD and provides a molecular target that could at least partly explain the role of immune cells in PD. Here, we summarize expression patterns and molecular functions of TREM2, recapitulate on its role in inflammation, phagocytosis and cell survival, before turning to neurodegenerative disorders with an emphasis on PD.
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Qin Q, Wan H, Wang D, Li J, Qu Y, Zhao J, Li J, Xue Z. The Association of CSF sTREM2 With Cognitive Decline and Its Dynamic Change in Parkinson's Disease: Analysis of the PPMI Cohort. Front Aging Neurosci 2022; 14:892493. [PMID: 35783125 PMCID: PMC9245456 DOI: 10.3389/fnagi.2022.892493] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2022] [Accepted: 05/24/2022] [Indexed: 01/20/2023] Open
Abstract
Background Soluble fragment of triggering receptor expressed on myeloid cells 2 (sTREM2) in cerebrospinal fluid (CSF) is a biomarker of microglial activation and increased in several neurodegenerative diseases. However, the role of sTREM2 in Parkinson's diseases (PDs) remains unclear. This study aims to investigate whether CSF sTREM2 is changed during the pathology of PD and its association with cognitive decline. Methods We recruited 219 de novo patients with PD and 100 healthy controls from Parkinson's Progression Markers Initiative (PPMI). Cross-sectional and longitudinal associations between cognition and CSF sTREM2 were evaluated using multivariable-adjusted models. To assess the changes in CSF sTREM2 during the pathology of PD, patients were classified through the A/T classification framework with addition of α-synuclein (α-syn), which we implemented based on the CSF amyloid β-peptide 1−42 (A) and phosphorylated tau (T) and α-syn (S). Results The CSF sTREM2 did not differ between healthy controls and patients with PD or between PD clinical subgroups (p > 0.05). However, higher baseline CSF sTREM2 predicted greater global cognitive decline in patients with PD (β = −0.585, p = 0.039). Moreover, after a mean follow-up of 5.51 ± 1.31 years, baseline CSF sTREM2 that elevated in the middle tertile (HR = 2.426, 95% CI: 1.023–5.754, p = 0.044) and highest tertile (HR = 2.833, 95% CI: 1.226–6.547, p = 0.015) were associated with a future high risk of cognitive decline. Additionally, CSF sTREM2 decreased in abnormal Aβ pathology (A+) and α-syn pathology (S+) but normal tau pathology, while increased in abnormal phosphorylated tau (T+) (p < 0.05). Conclusion CSF sTREM2 may be a promising predictor for the cognitive decline in PD rather than a diagnostic biomarker. The dynamic change in CSF sTREM2 in PD may help to the monitor of neuronal injury and microglial activity.
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Affiliation(s)
- Qixiong Qin
- Department of Neurology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Hengming Wan
- Department of General Family Medicine, Liuzhou Worker's Hospital, The Fourth Affiliated Hospital of Guangxi Medical University, Liuzhou, China
| | - Danlei Wang
- Department of Neurology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Jingyi Li
- Department of Neurology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Yi Qu
- Department of Neurology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Jingwei Zhao
- Department of Neurology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Jiangting Li
- Department of Neurology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Zheng Xue
- Department of Neurology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
- *Correspondence: Zheng Xue
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Mo M, Tang Y, Wei L, Qiu J, Peng G, Lin Y, Zhou M, Dai W, Zhang Z, Chen X, Liu H, Ding L, Ye P, Wu Y, Zhu X, Wu Z, Guo W, Xu P. Soluble Triggering Receptor Expressed on Myeloid Cells 2 From Cerebrospinal Fluid in Sleep Disorders Related to Parkinson's Disease. Front Aging Neurosci 2021; 13:753210. [PMID: 34658845 PMCID: PMC8511683 DOI: 10.3389/fnagi.2021.753210] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2021] [Accepted: 09/07/2021] [Indexed: 01/04/2023] Open
Abstract
Background: Triggering receptor expressed on myeloid cells 2 (TREM2) is a microglial receptor exclusively expressed in the central nervous system (CNS). It contributes to abnormal protein aggregation in neurodegenerative disorders, but its role in Parkinson’s disease (PD) is still unclear. Methods: In this case-control study, we measured the concentration of the soluble fragment of TREM2 (sTREM2) in PD patients, evaluated their sleep conditions by the PD sleep scale (PDSS), and analyzed the relationship between sTREM2 and PD symptoms. Results: We recruited 80 sporadic PD patients and 65 healthy controls without disease-related variants in TREM2. The concentration of sTREM2 in the CSF was significantly higher in PD patients than in healthy controls (p < 0.01). In the PD group, the concentration of sTREM2 had a positive correlation with α-syn in the CSF (Pearson r = 0.248, p = 0.027). Receiver operating characteristic curve (ROC) analyses showed that sTREM2 in the CSF had a significant diagnostic value for PD (AUC, 0.791; 95% CI, 0.711–0.871, p < 0.05). The subgroup analysis showed that PD patients with sleep disorders had a significantly higher concentration of sTREM2 in their CSF (p < 0.01). The concentration of sTREM2 in the CSF had a negative correlation with the PDSS score in PD patients (Pearson r = −0.555, p < 0.01). The ROC analyses showed that sTREM2 in the CSF had a significant diagnostic value for sleep disorders in PD (AUC, 0.733; 95% CI, 0.619–0.846, p < 0.05). Conclusion: Our findings suggest that CSF sTREM2 may be a potential biomarker for PD and it could help predict sleep disorders in PD patients, but multicenter prospective studies with more participants are still needed to confirm its diagnostic value in future.
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Affiliation(s)
- Mingshu Mo
- Department of Neurology, The First Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
| | - Yuting Tang
- Department of Neurology, The First Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
| | - Lijian Wei
- Department of Neurology, The First Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
| | - Jiewen Qiu
- Department of Neurology, The First Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
| | - Guoyou Peng
- Department of Neurology, The First Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
| | - Yuwan Lin
- Department of Neurology, The First Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
| | - Miaomiao Zhou
- Department of Neurology, The First Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
| | - Wei Dai
- Department of Neurology, The First Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
| | - Zhiling Zhang
- Department of Neurology, The First Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
| | - Xiang Chen
- Department of Neurology, The First Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
| | - Hanqun Liu
- Department of Neurology, The First Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
| | - Liuyan Ding
- Department of Neurology, The First Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
| | - Panghai Ye
- Department of Neurology, The First Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
| | - Yijuan Wu
- Department of Neurology, The First Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
| | - Xiaoqin Zhu
- Department of Physiology, School of Basic Medical Sciences, Guangzhou Medical University, Guangzhou, China
| | - Zhuohua Wu
- Department of Neurology, The First Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
| | - Wenyuan Guo
- Department of Neurology, The First Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
| | - Pingyi Xu
- Department of Neurology, The First Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
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Vieira SRL, Morris HR. Neurodegenerative Disease Risk in Carriers of Autosomal Recessive Disease. Front Neurol 2021; 12:679927. [PMID: 34149605 PMCID: PMC8211888 DOI: 10.3389/fneur.2021.679927] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2021] [Accepted: 05/14/2021] [Indexed: 01/19/2023] Open
Abstract
Genetics has driven significant discoveries in the field of neurodegenerative diseases (NDDs). An emerging theme in neurodegeneration warrants an urgent and comprehensive update: that carrier status of early-onset autosomal recessive (AR) disease, typically considered benign, is associated with an increased risk of a spectrum of late-onset NDDs. Glucosylceramidase beta (GBA1) gene mutations, responsible for the AR lysosomal storage disorder Gaucher disease, are a prominent example of this principle, having been identified as an important genetic risk factor for Parkinson disease. Genetic analyses have revealed further examples, notably GRN, TREM2, EIF2AK3, and several other LSD and mitochondria function genes. In this Review, we discuss the evidence supporting the strikingly distinct allele-dependent clinical phenotypes observed in carriers of such gene mutations and its impact on the wider field of neurodegeneration.
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Affiliation(s)
| | - Huw R. Morris
- Department of Clinical and Movement Neurosciences, University College London, Queen Square Institute of Neurology, London, United Kingdom
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Shafi S, Singh A, Ibrahim AM, Alhajri N, Abu Izneid T, Pottoo FH. Role of triggering receptor expressed on myeloid cells 2 (TREM2) in neurodegenerative dementias. Eur J Neurosci 2021; 53:3294-3310. [PMID: 33786894 DOI: 10.1111/ejn.15215] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Accepted: 03/22/2021] [Indexed: 01/04/2023]
Abstract
Neurodegeneration is a debilitating condition that causes nerve cell degeneration or death. Neurodegenerative diseases (NDDs) such as Alzheimer's disease (AD), Parkinson's disease (PD), frontotemporal dementia (FTD), and Lewy body dementia (LBD) are posing a larger population burden of dementia worldwide. Neurodegenerative dementia is one of the main challenges in public health with its main characteristics being permanent loss of memory, impairment in cognition, and impaired daily functions. The published literature about genetic studies of these disorders suggests genetic underpinning in the pathogenesis of neurodegenerative dementia. In the process of underlining the pathogenesis of NDD, growing evidence has related genetic variations in the triggering receptor expressed on myeloid cells 2 (TREM2). This review paper aims to provide a detailed information regarding the association of TREM2 and NDDs leading to dementia. A central consideration is AD that accounts for almost 50%-70% of all late-life dementias alone or in combination with other neurological disorders. Other prevalent neurodegenerative conditions that lead to dementia are also discussed. Such studies are important as they can give a comprehensive knowledge of TREM2's role in various NDDs, in order to maximize the potential for developing new therapeutic approaches.
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Affiliation(s)
- Sadat Shafi
- Pharmaceutical Medicine, Department of Pharmacology, School of Pharmaceutical Education and Research, Jamia Hamdard, New Delhi, India
| | - Archu Singh
- Department of Pharmaceutics, School of Pharmaceutical Education and Research, Jamia Hamdard, New Delhi, India
| | - Abdallah Mohammad Ibrahim
- Fundamentals of Nursing Department, College of Nursing, Imam Abdul Rahman Bin Faisal University, Dammam, Saudi Arabia
| | - Noora Alhajri
- Department of Epidemiology and Population Health, College of Medicine and Health Science, Khalifa University, Abu Dhabi, UAE
| | | | - Faheem Hyder Pottoo
- Department of Pharmacology, College of Clinical Pharmacy, Imam Abdulrahman Bin Faisal University, Damman, Saudi Arabia
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Sanghvi H, Singh R, Morrin H, Rajkumar AP. Systematic review of genetic association studies in people with Lewy body dementia. Int J Geriatr Psychiatry 2020; 35:436-448. [PMID: 31898332 DOI: 10.1002/gps.5260] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Accepted: 12/21/2019] [Indexed: 12/29/2022]
Abstract
OBJECTIVES Lewy body dementia (LBD) causes more morbidity, disability, and earlier mortality than Alzheimer disease. Molecular mechanisms underlying neurodegeneration in LBD are poorly understood. We aimed to do a systematic review of all genetic association studies that investigated people with LBD for improving our understanding of LBD molecular genetics and for facilitating discovery of novel biomarkers and therapeutic targets for LBD. METHODS We systematically reviewed five online databases (PROSPERO protocol: CRD42018087114) and completed the quality assessment using the quality of genetic association studies tool. RESULTS Eight thousand five hundred twenty-one articles were screened, and 75 articles were eligible to be included. Genetic associations of LBD with APOE, GBA, and SNCA variants have been replicated by two or more good quality studies. Our meta-analyses confirmed that APOE-ε4 is significantly associated with dementia with Lewy bodies (pooled odds ratio [POR] = 2.70; 95% CI, 2.37-3.07; P < .001) and Parkinson's disease dementia (POR = 1.60; 95% CI, 1.21-2.11; P = .001). Other reported genetic associations that need further replication include variants in A2M, BCHE-K, BCL7C, CHRFAM7A, CNTN1, ESR1, GABRB3, MAPT, mitochondrial DNA (mtDNA) haplogroup H, NOS2A, PSEN1, SCARB2, TFAM, TREM2, and UCHL1. CONCLUSIONS The reported genetic associations and their potential interactions indicate the importance of α-synuclein, amyloid, and tau pathology, autophagy lysosomal pathway, ubiquitin proteasome system, oxidative stress, and mitochondrial dysfunction in LBD. There is a need for larger genome-wide association study (GWAS) for identifying more LBD-associated genes. Future hypothesis-driven studies should aim to replicate reported genetic associations of LBD and to explore their functional implications.
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Affiliation(s)
- Hazel Sanghvi
- GKT School of Medical Education, King's College London, London, UK
| | - Ricky Singh
- GKT School of Medical Education, King's College London, London, UK
| | - Hamilton Morrin
- GKT School of Medical Education, King's College London, London, UK
| | - Anto P Rajkumar
- Department of Old Age Psychiatry, Institute of Psychiatry, Psychology & Neuroscience, King's College London, London, UK
- Institute of Mental Health, Division of Psychiatry and Applied Psychology, University of Nottingham, Nottingham, UK
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7
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Dardiotis E, Rikos D, Siokas V, Aloizou AM, Tsouris Z, Sakalakis E, Brotis AG, Bogdanos DP, Hadjigeorgiou GM. Assessment of TREM2 rs75932628 variant's association with Parkinson's disease in a Greek population and Meta-analysis of current data. Int J Neurosci 2020; 131:544-548. [PMID: 32250197 DOI: 10.1080/00207454.2020.1750388] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
BACKGROUND Α number of genetic variants are considered to confer susceptibility to Parkinson's disease (PD). Rs75392628 (R47H), a rare variant of TREM2 gene, has been linked to PD, although its role on PD remains conflicting. OBJECTIVE Detection of a possible contribution of rs75392628 variant of TREM2 gene to PD risk. METHODS A total of 358 PD patients and 358 healthy controls genotyped for rs75392628. In addition, a meta-analysis was performed by merging our results with those from previous studies. RESULTS The rare variant of rs75932628 (47H) of TREM2 gene was not detected on cohort. Meta-analysis of a total of 9271 PD cases and 9777 controls across 14 independent PD data sets from 9 studies, including the present study, did not show any statistically significant effect of rs75392628 on PD risk (ORFE:1.54 95% CI:0.87-2.73. ORRE: 1.54, 95%CI: 0.71-3.32). CONCLUSIONS Rs75392628 TREM2 variant is rather unlikely to be a major genetic risk contributor of PD.
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Affiliation(s)
- Efthimios Dardiotis
- Department of Neurology, Laboratory of Neurogenetics, University of Thessaly, University Hospital of Larissa, Larissa, Greece
| | - Dimitrios Rikos
- Department of Neurology, Laboratory of Neurogenetics, University of Thessaly, University Hospital of Larissa, Larissa, Greece
| | - Vasileios Siokas
- Department of Neurology, Laboratory of Neurogenetics, University of Thessaly, University Hospital of Larissa, Larissa, Greece
| | - Athina-Maria Aloizou
- Department of Neurology, Laboratory of Neurogenetics, University of Thessaly, University Hospital of Larissa, Larissa, Greece
| | - Zisis Tsouris
- Department of Neurology, Laboratory of Neurogenetics, University of Thessaly, University Hospital of Larissa, Larissa, Greece
| | - Evagelos Sakalakis
- Department of Neurology, Laboratory of Neurogenetics, University of Thessaly, University Hospital of Larissa, Larissa, Greece
| | - Alexandros G Brotis
- Department of Neurosurgery, University of Thessaly, University Hospital of Larissa, Larissa, Greece
| | - Dimitrios P Bogdanos
- Department of Rheumatology and Clinical Immunology, University General Hospital of Larissa, Faculty of Medicine, School of Health Sciences, University of Thessaly, Larissa, Greece.,Cellular Immunotherapy & Molecular Immunodiagnostics, Biomedical Section, Centre for Research and Technology-Hellas (CERTH), Institute for Research and Technology-Thessaly (IRETETH), Larissa, Greece
| | - Georgios M Hadjigeorgiou
- Department of Neurology, Laboratory of Neurogenetics, University of Thessaly, University Hospital of Larissa, Larissa, Greece.,Department of Neurology, Medical School, University of Cyprus, Nicosia, Cyprus
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Zhang B, Li R, Zhang Y, Gao X. Differential role of triggering receptors expressed on myeloid cells 2 R47H in 3 neurodegenerative diseases based on a systematic review and meta-analysis. Medicine (Baltimore) 2020; 99:e18921. [PMID: 32000403 PMCID: PMC7004756 DOI: 10.1097/md.0000000000018921] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
BACKGROUND Recent studies have suggested that the potential functional polymorphism R47H in triggering receptors expressed on myeloid cells 2 (TREM2) is associated with several neurodegenerative diseases, however, the results remain inconclusive. This meta-analysis aimed to investigate the association between TREM2 R47H and the risk for 3 typical neurodegenerative diseases: Alzheimer disease (AD), Parkinson disease (PD), and amyotrophic lateral sclerosis (ALS). METHODS A literature review was carried out using PubMed, Medline, and Embase. Data analysis was conducted using Stata 15.0 software. The pooled odds ratio (ORs) and 95% confidence interval (CIs) were calculated. RESULTS A total of 35 articles were identified as eligible: 22 on AD, 3 on ALS, 7 on PD, 2 on AD and ALS, and 1 on ALS and PD. The AD set included 23,092 cases and 30,920 controls, the ALS set included 7391 cases and 12,442 controls, and the PD set included 8498 patients and 9161 controls. We found that R47H was associated with an increased risk of AD in the total pooled population (P < .001, OR = 4.02, 95% CI = 3.15-5.13). However, this significant difference existed for Caucasian people (OR = 4.16, 95% CI = 3.24-5.33) but not for Asian or African people. Moreover, we did not find any significant differences in minor allele frequency distribution between the PD and control groups or between the ALS and control groups, not only for the total pooled population but also for the subgroups of different ethnicities. CONCLUSION Our study suggested that R47H in the TREM2 gene leads to an increased risk for developing AD, but not for ALS and PD, which adds evidence to the notion that diverse pathogenesis may be involved in different neurogenerative diseases.
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Affiliation(s)
- Bin Zhang
- Department of Neurology, the First Hospital of Yulin, Yulin, Shaanxi
| | - Rui Li
- Department of Neurology, the First Hospital of Yulin, Yulin, Shaanxi
| | - Yufan Zhang
- Department of Neurology, the First Hospital of Yulin, Yulin, Shaanxi
| | - Xia Gao
- Department of Geriatrics, Dazhou Central Hospital, Dazhou, Sichuan, China
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Tremblay ME, Cookson MR, Civiero L. Glial phagocytic clearance in Parkinson's disease. Mol Neurodegener 2019; 14:16. [PMID: 30953527 PMCID: PMC6451240 DOI: 10.1186/s13024-019-0314-8] [Citation(s) in RCA: 94] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2018] [Accepted: 03/15/2019] [Indexed: 12/21/2022] Open
Abstract
An emerging picture suggests that glial cells' loss of beneficial roles or gain of toxic functions can contribute to neurodegenerative conditions. Among glial cells, microglia and astrocytes have been shown to play phagocytic roles by engulfing synapses, apoptotic cells, cell debris, and released toxic proteins. As pathogenic protein accumulation is a key feature in Parkinson's disease (PD), compromised phagocytic clearance might participate in PD pathogenesis. In contrast, enhanced, uncontrolled and potentially toxic glial clearance capacity could contribute to synaptic degeneration. Here, we summarize the current knowledge of the molecular mechanisms underlying microglial and astrocytic phagocytosis, focusing on the possible implication of phagocytic dysfunction in neuronal degeneration. Several endo-lysosomal proteins displaying genetic variants in PD are highly expressed by microglia and astrocytes. We also present the evidence that lysosomal defects can affect phagocytic clearance and discuss the therapeutic relevance of restoring or enhancing lysosomal function in PD.
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Affiliation(s)
- Marie-Eve Tremblay
- Axe Neurosciences, Centre de Recherche du CHU de Québec, Université Laval, Quebec, QC Canada
- Département de Médecine Moléculaire, Faculté de Médecine, Université Laval, Quebec, QC Canada
| | - Mark R. Cookson
- Laboratory of Neurogenetics, National Institute on Aging, National Institutes of Health, Bethesda, MD USA
| | - Laura Civiero
- Department of Biology, University of Padova, Via Ugo Bassi 58/B, 35131 Padova, Italy
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The role of TREM2 in Alzheimer's disease and other neurodegenerative disorders. Lancet Neurol 2018; 17:721-730. [PMID: 30033062 DOI: 10.1016/s1474-4422(18)30232-1] [Citation(s) in RCA: 156] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2018] [Revised: 06/04/2018] [Accepted: 06/06/2018] [Indexed: 12/12/2022]
Abstract
Alzheimer's disease is a genetically complex disorder; rare variants in the triggering receptor expressed on myeloid cells 2 (TREM2) gene have been shown to as much as triple an individual's risk of developing Alzheimer's disease. TREM2 is a transmembrane receptor expressed in cells of the myeloid lineage, and its association with Alzheimer's disease supports the involvement of immune and inflammatory pathways in the cause of the disease, rather than as a consequence of the disease. TREM2 variants associated with Alzheimer's disease induce partial loss of function of the TREM2 protein and alter the behaviour of microglial cells, including their response to amyloid plaques. TREM2 variants have also been shown to cause polycystic lipomembranous osteodysplasia with sclerosing leukoencephalopathy and frontotemporal dementia. Although the low frequency of TREM2 variants makes it difficult to establish robust genotype-phenotype correlations, such studies are essential to enable a comprehensive understanding of the role of TREM2 in different neurological diseases, with the ultimate goal of developing novel therapeutic approaches.
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Abstract
Microglia are a subset of tissue macrophages that constitute the major immune cell type of the central nervous system. These cells have long been known to change their morphology and functions in response to various neurological insults. Recently, a plethora of unbiased transcriptomics studies have revealed that across a broad spectrum of neurodegeneration-like disease models, microglia adopt a similar activation signature and perform similar functions. Despite these commonalities in response, the role of microglia has been described as both positive and negative in different murine disease models. In humans, genetic association studies have revealed strong connections between microglia genes and various neurodegenerative diseases, and mechanistic investigations of these mutations have added another layer of complexity. Here, we provide an overview of studies that have built a case for a common microglial response to neurodegeneration and discuss pathways that may be important to initiate and sustain this response; delineate the multifaceted functions of activated microglia spanning different diseases; and discuss insights from studying genes associated with disease in humans. We argue that strong evidence causally links activated microglia function to neurodegeneration and discuss what seems to be a conflict between mouse models and human genetics.
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Affiliation(s)
- Wilbur M Song
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO, United States
| | - Marco Colonna
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO, United States.
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12
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Let's make microglia great again in neurodegenerative disorders. J Neural Transm (Vienna) 2017; 125:751-770. [PMID: 29027011 DOI: 10.1007/s00702-017-1792-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2017] [Accepted: 09/18/2017] [Indexed: 12/12/2022]
Abstract
All of the common neurodegenerative disorders-Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis and prion diseases-are characterized by accumulation of misfolded proteins that trigger activation of microglia; brain-resident mononuclear phagocytes. This chronic form of neuroinflammation is earmarked by increased release of myriad cytokines and chemokines in patient brains and biofluids. Microglial phagocytosis is compromised early in the disease process, obfuscating clearance of abnormal proteins. This review identifies immune pathologies shared by the major neurodegenerative disorders. The overarching concept is that aberrant innate immune pathways can be targeted for return to homeostasis in hopes of coaxing microglia into clearing neurotoxic misfolded proteins.
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Jay TR, von Saucken VE, Landreth GE. TREM2 in Neurodegenerative Diseases. Mol Neurodegener 2017; 12:56. [PMID: 28768545 PMCID: PMC5541421 DOI: 10.1186/s13024-017-0197-5] [Citation(s) in RCA: 256] [Impact Index Per Article: 36.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Accepted: 07/20/2017] [Indexed: 12/12/2022] Open
Abstract
TREM2 variants have been identified as risk factors for Alzheimer's disease (AD) and other neurodegenerative diseases (NDDs). Because TREM2 encodes a receptor exclusively expressed on immune cells, identification of these variants conclusively demonstrates that the immune response can play an active role in the pathogenesis of NDDs. These TREM2 variants also confer the highest risk for developing Alzheimer's disease of any risk factor identified in nearly two decades, suggesting that understanding more about TREM2 function could provide key insights into NDD pathology and provide avenues for novel immune-related NDD biomarkers and therapeutics. The expression, signaling and function of TREM2 in NDDs have been extensively investigated in an effort to understand the role of immune function in disease pathogenesis and progression. We provide a comprehensive review of our current understanding of TREM2 biology, including new insights into the regulation of TREM2 expression, and TREM2 signaling and function across NDDs. While many open questions remain, the current body of literature provides clarity on several issues. While it is still often cited that TREM2 expression is decreased by pro-inflammatory stimuli, it is now clear that this is true in vitro, but inflammatory stimuli in vivo almost universally increase TREM2 expression. Likewise, while TREM2 function is classically described as promoting an anti-inflammatory phenotype, more than half of published studies demonstrate a pro-inflammatory role for TREM2, suggesting that its role in inflammation is much more complex. Finally, these components of TREM2 biology are applied to a discussion of how TREM2 impacts NDD pathologies and the latest assessment of how these findings might be applied to immune-directed clinical biomarkers and therapeutics.
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Affiliation(s)
- Taylor R. Jay
- Department of Neurosciences, Case Western Reserve University, School of Medicine, 10900 Euclid Avenue, Cleveland, OH 44106 USA
| | - Victoria E. von Saucken
- Department of Neurosciences, Case Western Reserve University, School of Medicine, 10900 Euclid Avenue, Cleveland, OH 44106 USA
- Stark Neurosciences Research Institute, Indiana University School of Medicine, 320 W 15th Street, Indianapolis, IN 46202 USA
| | - Gary E. Landreth
- Department of Neurosciences, Case Western Reserve University, School of Medicine, 10900 Euclid Avenue, Cleveland, OH 44106 USA
- Stark Neurosciences Research Institute, Indiana University School of Medicine, 320 W 15th Street, Indianapolis, IN 46202 USA
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Clark LF, Kodadek T. The Immune System and Neuroinflammation as Potential Sources of Blood-Based Biomarkers for Alzheimer's Disease, Parkinson's Disease, and Huntington's Disease. ACS Chem Neurosci 2016; 7:520-7. [PMID: 27046268 DOI: 10.1021/acschemneuro.6b00042] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Neurodegenerative diseases are characterized by a loss of neurons that leads to cognitive and behavioral dysfunction. Alzheimer's disease (AD) is the most common neurodegenerative disorder affecting millions of people in the United States and worldwide, followed by Parkinson's disease (PD). While some early onset forms of AD and PD are hereditary, the sporadic or late-onset cases are believed to result from lifestyle and environmental factors. On the contrary, Huntington's disease (HD) is a neurodegenerative disease solely caused by mutations in the gene for huntingtin protein. The disease mechanisms at play for all three disorders remain elusive, hampering efforts to develop effective therapeutic interventions. In light of this, the discovery of robust biomarkers is crucial in order to identify people at risk for AD and PD, preferably before symptoms arise. For all three diseases, the identification of biomarkers would not only allow development of treatments but also evaluation and adjustment of these with disease progression. It is now understood that neuroinflammation plays a crucial role in neurodegenerative diseases, along with subsequent immune activation. Therefore, research is actively ongoing to discover and evaluate inflammatory and immune-related biomarkers. Recent progress in this area for AD, PD, and HD is presented here.
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Affiliation(s)
- Lorraine F. Clark
- Departments
of Chemistry
and Cancer Biology, The Scripps Research Institute, Jupiter, Florida 33458, United States
| | - Thomas Kodadek
- Departments
of Chemistry
and Cancer Biology, The Scripps Research Institute, Jupiter, Florida 33458, United States
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