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Suzuki Y, Nakamura Y, Igarashi H. Interstitial fluid flow decreases with age, especially after 50 years. Neurobiol Aging 2024; 141:14-20. [PMID: 38796942 DOI: 10.1016/j.neurobiolaging.2024.05.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2023] [Revised: 05/08/2024] [Accepted: 05/09/2024] [Indexed: 05/29/2024]
Abstract
Physiological age-related alterations in the interstitial flow in the brain, which plays an important role in waste product removal, remain unclear. Using [15O]H2O positron emission tomography (PET), water dynamics were evaluated in 63 healthy adult participants aged between 20 and 80 years. Interstitial flow was assessed by influx ratio (IR) and drain rate (DR), using time-activity concentration data. Participants were divided into four age groups with 15-year ranges, to evaluate age-related functional alterations. At least one of the indices declined significantly with age across all groups. A significant linear negative correlation between age and both indicators was found in the scatter plots (IR: R2 = 0.54, DR: R2 = 0.44); both indicators were predominantly lower after age 50 years. These results suggest interstitial flow decreases with age, especially after 50 years. These important findings can contribute to devising therapeutic interventions for neurological diseases characterized by abnormal accumulation of waste products, and suggest the need for taking measures to maintain interstitial flow starting around the age of 50 years.
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Affiliation(s)
- Yuji Suzuki
- Center for Integrated Human Brain Science, Brain Research Institute, Niigata University, Niigata, Japan.
| | - Yukimi Nakamura
- Center for Integrated Human Brain Science, Brain Research Institute, Niigata University, Niigata, Japan
| | - Hironaka Igarashi
- Center for Integrated Human Brain Science, Brain Research Institute, Niigata University, Niigata, Japan
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2
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Yue Y, Zhang X, Lv W, Lai HY, Shen T. Interplay between the glymphatic system and neurotoxic proteins in Parkinson's disease and related disorders: current knowledge and future directions. Neural Regen Res 2024; 19:1973-1980. [PMID: 38227524 DOI: 10.4103/1673-5374.390970] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2023] [Accepted: 10/26/2023] [Indexed: 01/17/2024] Open
Abstract
Parkinson's disease is a common neurodegenerative disorder that is associated with abnormal aggregation and accumulation of neurotoxic proteins, including α-synuclein, amyloid-β, and tau, in addition to the impaired elimination of these neurotoxic protein. Atypical parkinsonism, which has the same clinical presentation and neuropathology as Parkinson's disease, expands the disease landscape within the continuum of Parkinson's disease and related disorders. The glymphatic system is a waste clearance system in the brain, which is responsible for eliminating the neurotoxic proteins from the interstitial fluid. Impairment of the glymphatic system has been proposed as a significant contributor to the development and progression of neurodegenerative disease, as it exacerbates the aggregation of neurotoxic proteins and deteriorates neuronal damage. Therefore, impairment of the glymphatic system could be considered as the final common pathway to neurodegeneration. Previous evidence has provided initial insights into the potential effect of the impaired glymphatic system on Parkinson's disease and related disorders; however, many unanswered questions remain. This review aims to provide a comprehensive summary of the growing literature on the glymphatic system in Parkinson's disease and related disorders. The focus of this review is on identifying the manifestations and mechanisms of interplay between the glymphatic system and neurotoxic proteins, including loss of polarization of aquaporin-4 in astrocytic endfeet, sleep and circadian rhythms, neuroinflammation, astrogliosis, and gliosis. This review further delves into the underlying pathophysiology of the glymphatic system in Parkinson's disease and related disorders, and the potential implications of targeting the glymphatic system as a novel and promising therapeutic strategy.
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Affiliation(s)
- Yumei Yue
- Department of Neurology of Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Zhejiang University, Hangzhou, Zhejiang Province, China
| | - Xiaodan Zhang
- Department of Emergency Medicine, The University of Hong Kong, Hong Kong Special Administrative Region, China
| | - Wen Lv
- Department of Neurology of Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Zhejiang University, Hangzhou, Zhejiang Province, China
| | - Hsin-Yi Lai
- Department of Neurology of the Second Affiliated Hospital and School of Brain Science and Brain Medicine, Interdisciplinary Institute of Neuroscience and Technology, Key Laboratory of Medical Neurobiology of Zhejiang Province, Zhejiang University School of Medicine, Hangzhou, Zhejiang Province, China
- College of Biomedical Engineering and Instrument Science, Zhejiang University, Hangzhou, Zhejiang Province, China
- MOE Frontier Science Center for Brain Science and Brain-Machine Integration, State Key Laboratory of Brain-machine Intelligence, School of Brain Science and Brain Medicine, Zhejiang University, Hangzhou, Zhejiang Province, China
| | - Ting Shen
- Department of Neurology of the Second Affiliated Hospital and School of Brain Science and Brain Medicine, Interdisciplinary Institute of Neuroscience and Technology, Key Laboratory of Medical Neurobiology of Zhejiang Province, Zhejiang University School of Medicine, Hangzhou, Zhejiang Province, China
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3
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Peng W, Yuan Y, Lei J, Zhao Y, Li Y, Qu Q, Wang J. Long-Term High-Fat Diet Impairs AQP4-Mediated Glymphatic Clearance of Amyloid Beta. Mol Neurobiol 2024:10.1007/s12035-024-04320-3. [PMID: 38958889 DOI: 10.1007/s12035-024-04320-3] [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: 03/04/2024] [Accepted: 06/19/2024] [Indexed: 07/04/2024]
Abstract
As a risk factor for Alzheimer's disease (AD), studies have demonstrated that long-term high-fat diet (HFD) could accelerate the deposition of amyloid beta (Aβ) in the brain. The glymphatic system plays a critical role in Aβ clearance from the brain. However, studies investigating the effects of long-term HFD on glymphatic function have reported paradoxical outcomes, and whether glymphatic dysfunction is involved in the disturbance of Aβ clearance in long-term HFD-fed mice has not been determined. In the present study, we injected fluorescently labeled Aβ into the hippocampus and found that Aβ clearance was decreased in HFD-fed mice. We found that long-term HFD-fed mice had decreased glymphatic function by injecting fluorescent tracers into the cisterna magna and corpus striatum. In long-term HFD-fed mice, aquaporin-4 (AQP4) polarization in the cortex was disrupted, and glymphatic clearance activity was positively correlated with the AQP4 polarization index. In HFD-fed mice, the disturbance of Aβ clearance from the hippocampus was exacerbated by TGN-020, a specific inhibitor of AQP4, whereas TGN-073, an enhancer of AQP4, ameliorated it. These findings suggest that long-term HFD disrupts Aβ clearance by inhibiting AQP4-mediated glymphatic function. The underlying mechanism may involve the disruption of AQP4 polarization.
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Affiliation(s)
- Wei Peng
- Department of Neurology, The First Affiliated Hospital of Xi'an Jiaotong University, 277 West Yanta Rd, Xi'an, 710061, China
| | - Ye Yuan
- Department of Neurology, The First Affiliated Hospital of Xi'an Jiaotong University, 277 West Yanta Rd, Xi'an, 710061, China
| | - Jingna Lei
- Department of Neurology, The First Affiliated Hospital of Xi'an Jiaotong University, 277 West Yanta Rd, Xi'an, 710061, China
| | - Yi Zhao
- Department of Neurology, The First Affiliated Hospital of Xi'an Jiaotong University, 277 West Yanta Rd, Xi'an, 710061, China
| | - Yan Li
- Center for Brain Science, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China
| | - Qiumin Qu
- Department of Neurology, The First Affiliated Hospital of Xi'an Jiaotong University, 277 West Yanta Rd, Xi'an, 710061, China.
- Center for Brain Science, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China.
| | - Jin Wang
- Department of Neurology, The First Affiliated Hospital of Xi'an Jiaotong University, 277 West Yanta Rd, Xi'an, 710061, China.
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Taoka T, Ito R, Nakamichi R, Nakane T, Kawai H, Naganawa S. Diffusion Tensor Image Analysis ALong the Perivascular Space (DTI-ALPS): Revisiting the Meaning and Significance of the Method. Magn Reson Med Sci 2024; 23:268-290. [PMID: 38569866 PMCID: PMC11234944 DOI: 10.2463/mrms.rev.2023-0175] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/05/2024] Open
Abstract
More than 5 years have passed since the Diffusion Tensor Image Analysis ALong the Perivascular Space (DTI-ALPS) method was proposed with the intention of evaluating the glymphatic system. This method is handy due to its noninvasiveness, provision of a simple index in a straightforward formula, and the possibility of retrospective analysis. Therefore, the ALPS method was adopted to evaluate the glymphatic system for many disorders in many studies. The purpose of this review is to look back and discuss the ALPS method at this moment.The ALPS-index was found to be an indicator of a number of conditions related to the glymphatic system. Thus, although this was expected in the original report, the results of the ALPS method are often interpreted as uniquely corresponding to the function of the glymphatic system. However, a number of subsequent studies have pointed out the problems on the data interpretation. As they rightly point out, a higher ALPS-index indicates predominant Brownian motion of water molecules in the radial direction at the lateral ventricular body level, no more and no less. Fortunately, the term "ALPS-index" has become common and is now known as a common term by many researchers. Therefore, the ALPS-index should simply be expressed as high or low, and whether it reflects a glymphatic system is better to be discussed carefully. In other words, when a decreased ALPS-index is observed, it should be expressed as "decreased ALPS-index" and not directly as "glymphatic dysfunction". Recently, various methods have been proposed to evaluate the glymphatic system. It has become clear that these methods also do not seem to reflect the entirety of the extremely complex glymphatic system. This means that it would be desirable to use various methods in combination to evaluate the glymphatic system in a comprehensive manner.
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Affiliation(s)
- Toshiaki Taoka
- Department of Innovative Biomedical Visualization (iBMV), Nagoya University Graduate School of Medicine, Nagoya, Aichi, Japan
- Department of Radiology, Nagoya University, Nagoya, Aichi, Japan
| | - Rintaro Ito
- Department of Innovative Biomedical Visualization (iBMV), Nagoya University Graduate School of Medicine, Nagoya, Aichi, Japan
- Department of Radiology, Nagoya University, Nagoya, Aichi, Japan
| | - Rei Nakamichi
- Department of Radiology, Nagoya University, Nagoya, Aichi, Japan
| | - Toshiki Nakane
- Department of Radiology, Nagoya University, Nagoya, Aichi, Japan
| | - Hisashi Kawai
- Department of Radiology, Aichi Medical University, Nagakute, Aichi, Japan
| | - Shinji Naganawa
- Department of Radiology, Nagoya University, Nagoya, Aichi, Japan
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Sriram S, Carstens K, Dewing W, Fiacco TA. Astrocyte regulation of extracellular space parameters across the sleep-wake cycle. Front Cell Neurosci 2024; 18:1401698. [PMID: 38988660 PMCID: PMC11233815 DOI: 10.3389/fncel.2024.1401698] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2024] [Accepted: 06/07/2024] [Indexed: 07/12/2024] Open
Abstract
Multiple subfields of neuroscience research are beginning to incorporate astrocytes into current frameworks of understanding overall brain physiology, neuronal circuitry, and disease etiology that underlie sleep and sleep-related disorders. Astrocytes have emerged as a dynamic regulator of neuronal activity through control of extracellular space (ECS) volume and composition, both of which can vary dramatically during different levels of sleep and arousal. Astrocytes are also an attractive target of sleep research due to their prominent role in the glymphatic system, a method by which toxic metabolites generated during wakefulness are cleared away. In this review we assess the literature surrounding glial influences on fluctuations in ECS volume and composition across the sleep-wake cycle. We also examine mechanisms of astrocyte volume regulation in glymphatic solute clearance and their role in sleep and wake states. Overall, findings highlight the importance of astrocytes in sleep and sleep research.
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Affiliation(s)
- Sandhya Sriram
- Interdepartmental Graduate Program in Neuroscience, University of California, Riverside, Riverside, CA, United States
- Department of Biochemistry and Molecular Biology, University of California, Riverside, Riverside, CA, United States
| | - Kaira Carstens
- Department of Biochemistry and Molecular Biology, University of California, Riverside, Riverside, CA, United States
| | - Wayne Dewing
- Undergraduate Major in Neuroscience, University of California, Riverside, Riverside, CA, United States
| | - Todd A Fiacco
- Interdepartmental Graduate Program in Neuroscience, University of California, Riverside, Riverside, CA, United States
- Department of Biochemistry and Molecular Biology, University of California, Riverside, Riverside, CA, United States
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6
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Arms LM, Duchatel RJ, Jackson ER, Sobrinho PG, Dun MD, Hua S. Current status and advances to improving drug delivery in diffuse intrinsic pontine glioma. J Control Release 2024; 370:835-865. [PMID: 38744345 DOI: 10.1016/j.jconrel.2024.05.018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2023] [Revised: 05/06/2024] [Accepted: 05/09/2024] [Indexed: 05/16/2024]
Abstract
Diffuse midline glioma (DMG), including tumors diagnosed in the brainstem (diffuse intrinsic pontine glioma - DIPG), is the primary cause of brain tumor-related death in pediatric patients. DIPG is characterized by a median survival of <12 months from diagnosis, harboring the worst 5-year survival rate of any cancer. Corticosteroids and radiation are the mainstay of therapy; however, they only provide transient relief from the devastating neurological symptoms. Numerous therapies have been investigated for DIPG, but the majority have been unsuccessful in demonstrating a survival benefit beyond radiation alone. Although many barriers hinder brain drug delivery in DIPG, one of the most significant challenges is the blood-brain barrier (BBB). Therapeutic compounds must possess specific properties to enable efficient passage across the BBB. In brain cancer, the BBB is referred to as the blood-brain tumor barrier (BBTB), where tumors disrupt the structure and function of the BBB, which may provide opportunities for drug delivery. However, the biological characteristics of the brainstem's BBB/BBTB, both under normal physiological conditions and in response to DIPG, are poorly understood, which further complicates treatment. Better characterization of the changes that occur in the BBB/BBTB of DIPG patients is essential, as this informs future treatment strategies. Many novel drug delivery technologies have been investigated to bypass or disrupt the BBB/BBTB, including convection enhanced delivery, focused ultrasound, nanoparticle-mediated delivery, and intranasal delivery, all of which are yet to be clinically established for the treatment of DIPG. Herein, we review what is known about the BBB/BBTB and discuss the current status, limitations, and advances of conventional and novel treatments to improving brain drug delivery in DIPG.
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Affiliation(s)
- Lauren M Arms
- Therapeutic Targeting Research Group, School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan, NSW, Australia; Precision Medicine Research Program, Hunter Medical Research Institute, New Lambton Heights, NSW, Australia; Paediatric Program, Mark Hughes Foundation Centre for Brain Cancer Research, College of Health, Medicine & Wellbeing, University of Newcastle, Callaghan, NSW, Australia
| | - Ryan J Duchatel
- Precision Medicine Research Program, Hunter Medical Research Institute, New Lambton Heights, NSW, Australia; Cancer Signalling Research Group, School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan, NSW, Australia; Paediatric Program, Mark Hughes Foundation Centre for Brain Cancer Research, College of Health, Medicine & Wellbeing, University of Newcastle, Callaghan, NSW, Australia
| | - Evangeline R Jackson
- Precision Medicine Research Program, Hunter Medical Research Institute, New Lambton Heights, NSW, Australia; Cancer Signalling Research Group, School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan, NSW, Australia; Paediatric Program, Mark Hughes Foundation Centre for Brain Cancer Research, College of Health, Medicine & Wellbeing, University of Newcastle, Callaghan, NSW, Australia
| | - Pedro Garcia Sobrinho
- Therapeutic Targeting Research Group, School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan, NSW, Australia; Precision Medicine Research Program, Hunter Medical Research Institute, New Lambton Heights, NSW, Australia
| | - Matthew D Dun
- Precision Medicine Research Program, Hunter Medical Research Institute, New Lambton Heights, NSW, Australia; Cancer Signalling Research Group, School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan, NSW, Australia; Paediatric Program, Mark Hughes Foundation Centre for Brain Cancer Research, College of Health, Medicine & Wellbeing, University of Newcastle, Callaghan, NSW, Australia
| | - Susan Hua
- Therapeutic Targeting Research Group, School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan, NSW, Australia; Precision Medicine Research Program, Hunter Medical Research Institute, New Lambton Heights, NSW, Australia; Paediatric Program, Mark Hughes Foundation Centre for Brain Cancer Research, College of Health, Medicine & Wellbeing, University of Newcastle, Callaghan, NSW, Australia.
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7
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Thipani Madhu M, Balaji O, Kandi V, Ca J, Harikrishna GV, Metta N, Mudamanchu VK, Sanjay BG, Bhupathiraju P. Role of the Glymphatic System in Alzheimer's Disease and Treatment Approaches: A Narrative Review. Cureus 2024; 16:e63448. [PMID: 39077280 PMCID: PMC11285013 DOI: 10.7759/cureus.63448] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/29/2024] [Indexed: 07/31/2024] Open
Abstract
Currently, there is unavailability of disease-modifying medication for Alzheimer's disease (AD), a debilitating neurological disorder. The pathogenesis of AD appears to be complex and could be influenced by the glymphatic system present in the central nervous system (CNS). Amyloid-beta (Aβ) and other metabolic wastes are eliminated from the brain interstitium by the glymphatic system, which encompasses perivascular channels and astroglial cells. Dysfunction of the glymphatic system, which could occur due to decreased aquaporin 4 (AQP4) expression, aging-related alterations in the human brain, and sleep disruptions, may contribute to the pathogenesis of AD and also accelerate the development of AD by causing a buildup of harmful proteins like Aβ. Promising approaches have been examined for reducing AD pathology, including non-pharmacological therapies that target glymphatic function, like exercise and sleep regulation. In addition, preclinical research has also demonstrated the therapeutic potential of pharmaceutical approaches targeted at augmenting AQP4-mediated glymphatic flow. To identify the precise processes driving glymphatic dysfunction in AD and to find new treatment targets, more research is required. Innovative diagnostic and treatment approaches for AD could be made possible by techniques such as dynamic contrast-enhanced MRI, which promises to evaluate glymphatic function in neurodegenerative diseases. Treatment options for AD and other neurodegenerative diseases may be improved by comprehending and utilizing the glymphatic system's function in preserving brain homeostasis and targeting the mechanisms involved in glymphatic functioning. This review intends to enhance the understanding of the complex link between AD and the glymphatic system and focuses on the function of AQP4 channels in promoting waste clearance and fluid exchange.
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Affiliation(s)
- Mansi Thipani Madhu
- Internal Medicine, Vydehi Institute of Medical Sciences and Research Centre, Bangalore, IND
| | - Ojas Balaji
- Medicine, Vydehi Institute of Medical Sciences and Research Centre, Bangalore, IND
| | - Venkataramana Kandi
- Clinical Microbiology, Prathima Institute of Medical Sciences, Karimnagar, IND
| | - Jayashankar Ca
- Internal Medicine, Vydehi Institute of Medical Sciences and Research Centre, Bangalore, IND
| | | | - Nirosha Metta
- Neurology, Vydehi Institute of Medical Sciences and Research Centre, Bangalore, IND
| | | | - Bhangdiya G Sanjay
- Internal Medicine, Vydehi Institute of Medical Sciences and Research Centre, Bangalore, IND
| | - Praful Bhupathiraju
- Internal Medicine, Vydehi Institute of Medical Sciences and Research Centre, Bangalore, IND
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8
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Chen Y, He X, Cai J, Li Q. Functional aspects of the brain lymphatic drainage system in aging and neurodegenerative diseases. J Biomed Res 2024; 38:206-221. [PMID: 38430054 PMCID: PMC11144931 DOI: 10.7555/jbr.37.20230264] [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: 10/31/2023] [Revised: 12/30/2023] [Accepted: 02/29/2024] [Indexed: 03/03/2024] Open
Abstract
The phenomenon of an aging population is advancing at a precipitous rate. Alzheimer's disease (AD) and Parkinson's disease (PD) are two of the most common age-associated neurodegenerative diseases, both of which are primarily characterized by the accumulation of toxic proteins and the progressive demise of neuronal structures. Recent discoveries about the brain lymphatic drainage system have precipitated a growing body of investigations substantiating its novel roles, including the clearance of macromolecular waste and the trafficking of immune cells. Notably, aquaporin 4-mediated glymphatic transport, crucial for maintaining neural homeostasis, becomes disrupted during the aging process and is further compromised in the pathogenesis of AD and PD. Functional meningeal lymphatic vessels, which facilitate the drainage of cerebrospinal fluid into the deep cervical lymph nodes, are integral in bridging the central nervous system with peripheral immune responses. Dysfunction in these meningeal lymphatic vessels exacerbates pathological trajectory of the age-related neurodegenerative disease. This review explores modulatory influence of the glymphatic system and meningeal lymphatic vessels on the aging brain and its associated neurodegenerative disorders. It also encapsulates the insights of potential mechanisms and prospects of the targeted non-pharmacological interventions.
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Affiliation(s)
- Yan Chen
- Jiangsu Key Laboratory of Neurodegeneration, Nanjing Medical University, Nanjing, Jiangsu 211166, China
- Shandong Institute of Brain Science and Brain-inspired Research, Shandong First Medical University & Shandong Academy of Medical Sciences, Jinan, Shandong 250117, China
| | - Xiaoxin He
- Jiangsu Key Laboratory of Neurodegeneration, Nanjing Medical University, Nanjing, Jiangsu 211166, China
- Center for Global Health, Nanjing Medical University, Nanjing, Jiangsu 211166, China
| | - Jiachen Cai
- Jiangsu Key Laboratory of Neurodegeneration, Nanjing Medical University, Nanjing, Jiangsu 211166, China
- Center for Global Health, Nanjing Medical University, Nanjing, Jiangsu 211166, China
| | - Qian Li
- Jiangsu Key Laboratory of Neurodegeneration, Nanjing Medical University, Nanjing, Jiangsu 211166, China
- Center for Global Health, Nanjing Medical University, Nanjing, Jiangsu 211166, China
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9
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Zhao H, Sun M, Zhang Y, Kong W, Fan L, Wang K, Xu Q, Chen B, Dong J, Shi Y, Wang Z, Wang S, Zhuang X, Li Q, Lin F, Yao X, Zhang W, Kong C, Zhang R, Feng D, Zhao X. Connecting the Dots: The Cerebral Lymphatic System as a Bridge Between the Central Nervous System and Peripheral System in Health and Disease. Aging Dis 2024; 15:115-152. [PMID: 37307828 PMCID: PMC10796102 DOI: 10.14336/ad.2023.0516] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2023] [Accepted: 05/16/2023] [Indexed: 06/14/2023] Open
Abstract
As a recently discovered waste removal system in the brain, cerebral lymphatic system is thought to play an important role in regulating the homeostasis of the central nervous system. Currently, more and more attention is being focused on the cerebral lymphatic system. Further understanding of the structural and functional characteristics of cerebral lymphatic system is essential to better understand the pathogenesis of diseases and to explore therapeutic approaches. In this review, we summarize the structural components and functional characteristics of cerebral lymphatic system. More importantly, it is closely associated with peripheral system diseases in the gastrointestinal tract, liver, and kidney. However, there is still a gap in the study of the cerebral lymphatic system. However, we believe that it is a critical mediator of the interactions between the central nervous system and the peripheral system.
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Affiliation(s)
- Hongxiang Zhao
- Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, Shandong, China.
- Shandong Provincial Medicine and Health Key Laboratory of Clinical Anesthesia, School of Anesthesiology, Weifang Medical University, Weifang, China.
| | - Meiyan Sun
- Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, Shandong, China.
- Shandong Provincial Medicine and Health Key Laboratory of Clinical Anesthesia, School of Anesthesiology, Weifang Medical University, Weifang, China.
| | - Yue Zhang
- Shandong Provincial Medicine and Health Key Laboratory of Clinical Anesthesia, School of Anesthesiology, Weifang Medical University, Weifang, China.
| | - Wenwen Kong
- Shandong Provincial Medicine and Health Key Laboratory of Clinical Anesthesia, School of Anesthesiology, Weifang Medical University, Weifang, China.
| | - Lulu Fan
- Shandong Provincial Medicine and Health Key Laboratory of Clinical Anesthesia, School of Anesthesiology, Weifang Medical University, Weifang, China.
| | - Kaifang Wang
- Shandong Provincial Medicine and Health Key Laboratory of Clinical Anesthesia, School of Anesthesiology, Weifang Medical University, Weifang, China.
| | - Qing Xu
- Department of Anesthesiology, Affiliated Hangzhou First People's Hospital, Zhejiang University School of Medicine, Hangzhou, China.
| | - Baiyan Chen
- Shandong Provincial Medicine and Health Key Laboratory of Clinical Anesthesia, School of Anesthesiology, Weifang Medical University, Weifang, China.
| | - Jianxin Dong
- Shandong Provincial Medicine and Health Key Laboratory of Clinical Anesthesia, School of Anesthesiology, Weifang Medical University, Weifang, China.
| | - Yanan Shi
- Shandong Provincial Medicine and Health Key Laboratory of Clinical Anesthesia, School of Anesthesiology, Weifang Medical University, Weifang, China.
| | - Zhengyan Wang
- Shandong Provincial Medicine and Health Key Laboratory of Clinical Anesthesia, School of Anesthesiology, Weifang Medical University, Weifang, China.
| | - ShiQi Wang
- Shandong Provincial Medicine and Health Key Laboratory of Clinical Anesthesia, School of Anesthesiology, Weifang Medical University, Weifang, China.
| | - Xiaoli Zhuang
- Department of Anesthesiology, Beijing Anzhen Hospital, Capital Medical University, Beijing, China.
| | - Qi Li
- Department of Anesthesiology, Ninth People's Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China.
| | - Feihong Lin
- Department of Anesthesiology, Shanghai Pulmonary Hospital, School of Medicine, Tongji University, Shanghai, China.
| | - Xinyu Yao
- Department of Anesthesiology, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou, China.
| | - WenBo Zhang
- Department of Neurosurgery, The Children’s Hospital of Zhejiang University School of Medicine, National Clinical Research Center for Child Health, Hangzhou, China.
| | - Chang Kong
- Department of Anesthesiology and Critical Care Medicine, Tianjin Nankai Hospital, Tianjin Medical University, Tianjin, China.
| | - Rui Zhang
- Department of Anesthesiology, Affiliated Hospital of Weifang Medical University, Weifang, China.
- Shandong Provincial Medicine and Health Key Laboratory of Clinical Anesthesia, School of Anesthesiology, Weifang Medical University, Weifang, China.
| | - Dayun Feng
- Department of neurosurgery, Tangdu hospital, Fourth Military Medical University, Xi'an, China.
| | - Xiaoyong Zhao
- Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, Shandong, China.
- Department of Anesthesiology, Affiliated Hospital of Weifang Medical University, Weifang, China.
- Shandong Provincial Medicine and Health Key Laboratory of Clinical Anesthesia, School of Anesthesiology, Weifang Medical University, Weifang, China.
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10
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Lapshina KV, Ekimova IV. Aquaporin-4 and Parkinson's Disease. Int J Mol Sci 2024; 25:1672. [PMID: 38338949 PMCID: PMC10855351 DOI: 10.3390/ijms25031672] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2023] [Revised: 01/15/2024] [Accepted: 01/26/2024] [Indexed: 02/12/2024] Open
Abstract
The water-selective channel aquaporin-4 (AQP4) is implicated in water homeostasis and the functioning of the glymphatic system, which eliminates various metabolites from the brain tissue, including amyloidogenic proteins. Misfolding of the α-synuclein protein and its post-translational modifications play a crucial role in the development of Parkinson's disease (PD) and other synucleopathies, leading to the formation of cytotoxic oligomers and aggregates that cause neurodegeneration. Human and animal studies have shown an interconnection between AQP4 dysfunction and α-synuclein accumulation; however, the specific role of AQP4 in these mechanisms remains unclear. This review summarizes the current knowledge on the role of AQP4 dysfunction in the progression of α-synuclein pathology, considering the possible effects of AQP4 dysregulation on brain molecular mechanisms that can impact α-synuclein modification, accumulation and aggregation. It also highlights future directions that can help study the role of AQP4 in the functioning of the protective mechanisms of the brain during the development of PD and other neurodegenerative diseases.
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Affiliation(s)
- Ksenia V. Lapshina
- Laboratory of Comparative Thermophysiology, Sechenov Institute of Evolutionary Physiology and Biochemistry of RAS, 194223 Saint Petersburg, Russia;
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11
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Gao Y, Liu K, Zhu J. Glymphatic system: an emerging therapeutic approach for neurological disorders. Front Mol Neurosci 2023; 16:1138769. [PMID: 37485040 PMCID: PMC10359151 DOI: 10.3389/fnmol.2023.1138769] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2023] [Accepted: 06/21/2023] [Indexed: 07/25/2023] Open
Abstract
The functions of the glymphatic system include clearance of the metabolic waste and modulation of the water transport in the brain, and it forms a brain-wide fluid network along with cerebrospinal fluid (CSF) and interstitial fluid (ISF). The glymphatic pathway consists of periarterial influx of CSF, astrocyte-mediated interchange between ISF and CSF supported by aquaporin-4 (AQP4) on the endfeet of astrocyte around the periarterioles, and perivenous efflux of CSF. Finally, CSF is absorbed by the arachnoid granules or flows into the cervical lymphatic vessels. There is growing evidence from animal experiments that the glymphatic system dysfunction is involved in many neurological disorders, such as Alzheimer's disease, stroke, epilepsy, traumatic brain injury and meningitis. In this review, we summarize the latest progress on the glymphatic system and its driving factors, as well as changes in the glymphatic pathway in different neurological diseases. We significantly highlight the likely therapeutic approaches for glymphatic pathway in neurological diseases, and the importance of AQP4 and normal sleep architecture in this process.
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Affiliation(s)
- Ying Gao
- Department of Neurology, Neuroscience Centre, The First Hospital of Jilin University, Changchun, China
| | - Kangding Liu
- Department of Neurology, Neuroscience Centre, The First Hospital of Jilin University, Changchun, China
| | - Jie Zhu
- Department of Neurology, Neuroscience Centre, The First Hospital of Jilin University, Changchun, China
- Department of Neurobiology, Care Sciences and Society, Karolinska Institute, Karolinska University Hospital, Solna, Sweden
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12
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Sigurdsson B, Hauglund NL, Lilius TO, Mogensen FLH, Mortensen KN, Beschorner N, Klinger L, Bærentzen SL, Rosenholm MP, Shalgunov V, Herth M, Mori Y, Nedergaard M. A SPECT-based method for dynamic imaging of the glymphatic system in rats. J Cereb Blood Flow Metab 2023; 43:1153-1165. [PMID: 36809165 PMCID: PMC10291457 DOI: 10.1177/0271678x231156982] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/10/2022] [Revised: 11/17/2022] [Accepted: 12/07/2022] [Indexed: 02/23/2023]
Abstract
The glymphatic system is a brain-wide waste drainage system that promotes cerebrospinal fluid circulation through the brain to remove waste metabolites. Currently, the most common methods for assessing glymphatic function are ex vivo fluorescence microscopy of brain slices, macroscopic cortical imaging, and MRI. While all these methods have been crucial for expanding our understanding of the glymphatic system, new techniques are required to overcome their specific drawbacks. Here, we evaluate SPECT/CT imaging as a tool to assess glymphatic function in different anesthesia-induced brain states using two radiolabeled tracers, [111In]-DTPA and [99mTc]-NanoScan. Using SPECT, we confirmed the existence of brain state-dependent differences in glymphatic flow and we show brain state-dependent differences of CSF flow kinetics and CSF egress to the lymph nodes. We compare SPECT and MRI for imaging glymphatic flow and find that the two imaging modalities show the same overall pattern of CSF flow, but that SPECT was specific across a greater range of tracer concentrations than MRI. Overall, we find that SPECT imaging is a promising tool for imaging the glymphatic system, and that qualities such as high sensitivity and the variety of available tracers make SPECT imaging a good alternative for glymphatic research.
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Affiliation(s)
- Björn Sigurdsson
- Center for Translational Neuromedicine, University of Copenhagen, Denmark
| | - Natalie L Hauglund
- Center for Translational Neuromedicine, University of Copenhagen, Denmark
| | - Tuomas O Lilius
- Center for Translational Neuromedicine, University of Copenhagen, Denmark
- INDIVIDRUG Research Program, University of Helsinki, Finland
- Department of Pharmacology, University of Helsinki, Finland
- Department of Emergency Medicine and Services, Helsinki University Hospital and University of Helsinki, Finland
| | - Frida L-H Mogensen
- Center for Translational Neuromedicine, University of Copenhagen, Denmark
- Neuro-Immunology Group, Department of Cancer Research, Luxembourg Institute of Health, Luxembourg, Luxembourg
- Doctoral School of Science and Technology, University of Luxembourg, Esch-sur-Alzette, Luxembourg
| | | | - Natalie Beschorner
- Center for Translational Neuromedicine, University of Copenhagen, Denmark
| | - Laura Klinger
- Center for Translational Neuromedicine, University of Copenhagen, Denmark
| | - Simone L Bærentzen
- Translational Neuropsychiatry Unit, Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
- Department of Nuclear Medicine and PET Center, Aarhus University Hospital, Aarhus, Denmark
| | - Marko P Rosenholm
- Center for Translational Neuromedicine, University of Copenhagen, Denmark
| | - Vladimir Shalgunov
- Department of Drug Design and Pharmacology, University of Copenhagen, Denmark
| | - Matthias Herth
- Department of Drug Design and Pharmacology, University of Copenhagen, Denmark
- Department of Clinical Physiology, Copenhagen University Hospital, Denmark
| | - Yuki Mori
- Center for Translational Neuromedicine, University of Copenhagen, Denmark
| | - Maiken Nedergaard
- Center for Translational Neuromedicine, University of Copenhagen, Denmark
- Center for Translational Neuromedicine, University of Rochester Medical Center, USA
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13
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Mohamed W, Kumar J, Alghamdi BS, Soliman AH, Toshihide Y. Neurodegeneration and inflammation crosstalk: Therapeutic targets and perspectives. IBRO Neurosci Rep 2023; 14:95-110. [PMID: 37388502 PMCID: PMC10300452 DOI: 10.1016/j.ibneur.2022.12.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2022] [Revised: 11/19/2022] [Accepted: 12/08/2022] [Indexed: 12/23/2022] Open
Abstract
Glia, which was formerly considered to exist just to connect neurons, now plays a key function in a wide range of physiological events, including formation of memory, learning, neuroplasticity, synaptic plasticity, energy consumption, and homeostasis of ions. Glial cells regulate the brain's immune responses and confers nutritional and structural aid to neurons, making them an important player in a broad range of neurological disorders. Alzheimer's, ALS, Parkinson's, frontotemporal dementia (FTD), and epilepsy are a few of the neurodegenerative diseases that have been linked to microglia and astroglia cells, in particular. Synapse growth is aided by glial cell activity, and this activity has an effect on neuronal signalling. Each glial malfunction in diverse neurodegenerative diseases is distinct, and we will discuss its significance in the progression of the illness, as well as its potential for future treatment.
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Affiliation(s)
- Wael Mohamed
- Department of Basic Medical Sciences, Kulliyyah of Medicine, International Islamic University Malaysia (IIUM), Kuantan, Malaysia
- Clinical Pharmacology Department, Menoufia Medical School, Menoufia University, Menoufia, Egypt
| | - Jaya Kumar
- Department of Physiology, Faculty of Medicine, UKM Medical Centre (UKMMC), Kuala Lumpur, Malaysia
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14
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Liu H, Chen L, Zhang C, Liu C, Li Y, Cheng L, Wei Z, Zhang Z, Lu H, van Zijl PCM, Iliff JJ, Xu J, Duan W. Interrogation of dynamic glucose-enhanced MRI and fluorescence-based imaging reveals a perturbed glymphatic network in Huntington's disease. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.04.03.535397. [PMID: 37066166 PMCID: PMC10103957 DOI: 10.1101/2023.04.03.535397] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
Huntington's disease (HD) is a neurodegenerative disorder that presents with progressive motor, mental, and cognitive impairment leading to early disability and mortality. The accumulation of mutant huntingtin protein aggregates in neurons is a pathological hallmark of HD. The glymphatic system, a brain-wide perivascular network, facilitates the exchange of interstitial fluid (ISF) and cerebrospinal fluid (CSF), supporting interstitial solute clearance including abnormal proteins from mammalian brains. In this study, we employed dynamic glucose-enhanced (DGE) MRI to measure D-glucose clearance from CSF as a tool to assess CSF clearance capacity to predict glymphatic function in a mouse model of HD. Our results demonstrate significantly diminished CSF clearance efficiency in premanifest zQ175 HD mice. The impairment of CSF clearance of D-glucose, measured by DGE MRI, worsened with disease progression. These DGE MRI findings in compromised glymphatic function in HD mice were further confirmed with fluorescence-based imaging of glymphatic CSF tracer influx, suggesting an impaired glymphatic function in premanifest stage of HD. Moreover, expression of the astroglial water channel aquaporin-4 (AQP4) in the perivascular compartment, a key mediator of glymphatic function, was significantly diminished in both HD mouse brain as well as postmortem human HD brain. Our data, acquired using a clinically translatable MRI approach, indicate a perturbed glymphatic network in the HD brain as early as in the premanifest stage. Further validation of these findings in clinical studies should provide insights into potential of glymphatic clearance as a HD biomarker and for glymphatic functioning as a disease-modifying therapeutic target for HD.
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15
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Peng S, Liu J, Liang C, Yang L, Wang G. Aquaporin-4 in glymphatic system, and its implication for central nervous system disorders. Neurobiol Dis 2023; 179:106035. [PMID: 36796590 DOI: 10.1016/j.nbd.2023.106035] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2022] [Revised: 02/06/2023] [Accepted: 02/08/2023] [Indexed: 02/17/2023] Open
Abstract
The clearance function is essential for maintaining brain tissue homeostasis, and the glymphatic system is the main pathway for removing brain interstitial solutes. Aquaporin-4 (AQP4) is the most abundantly expressed aquaporin in the central nervous system (CNS) and is an integral component of the glymphatic system. In recent years, many studies have shown that AQP4 affects the morbidity and recovery process of CNS disorders through the glymphatic system, and AQP4 shows notable variability in CNS disorders and is part of the pathogenesis of these diseases. Therefore, there has been considerable interest in AQP4 as a potential and promising target for regulating and improving neurological impairment. This review aims to summarize the pathophysiological role that AQP4 plays in several CNS disorders by affecting the clearance function of the glymphatic system. The findings can contribute to a better understanding of the self-regulatory functions in CNS disorders that AQP4 were involved in and provide new therapeutic alternatives for incurable debilitating neurodegenerative disorders of CNS in the future.
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Affiliation(s)
- Shasha Peng
- 56 Xinjian southern St, Department of Pharmacology, School of Basical Medical Sciences, Shanxi Medical University, Taiyuan, Shanxi 030001, China
| | - Jiachen Liu
- 172 Tongzipo Rd, Xiangya Medical College of Central South University, Changsha, Hunan 410013, China
| | - Chuntian Liang
- 56 Xinjian southern St, Department of Neurology, Shanxi Medical University, Taiyuan, Shanxi 030001, China
| | - Lijun Yang
- 56 Xinjian southern St, Department of Pharmacology, School of Basical Medical Sciences, Shanxi Medical University, Taiyuan, Shanxi 030001, China
| | - Gaiqing Wang
- 56 Xinjian southern St, Department of Neurology, Shanxi Medical University, Taiyuan, Shanxi 030001, China; 146 JieFang forth Rd, Department of Neurology, SanYa Central Hospital (Hainan Third People's Hospital), Hainan Medical University, SanYa, Hainan 572000, China.
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16
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Yamada K. Multifaceted Roles of Aquaporins in the Pathogenesis of Alzheimer’s Disease. Int J Mol Sci 2023; 24:ijms24076528. [PMID: 37047501 PMCID: PMC10095057 DOI: 10.3390/ijms24076528] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2023] [Revised: 03/29/2023] [Accepted: 03/29/2023] [Indexed: 04/03/2023] Open
Abstract
The central nervous system is highly dependent on water, and disturbances in water homeostasis can have a significant impact on its normal functions. The regulation of water balance is, at least in part, carried out via specialized water channels called aquaporins. In the central nervous system, two major aquaporins (AQPs), AQP1 and AQP4, and their potential involvements have been long implicated in the pathophysiology of many brain disorders such as brain edema and Neuromyelitis optica. In addition to these diseases, there is growing attention to the involvement of AQPs in the removal of waste products in Alzheimer’s disease (AD). This indicates that targeting fluid homeostasis is a novel and attractive approach for AD. This review article aims to summarize recent knowledge on the pathological implications of AQPs in AD, discussing unsolved questions and future prospects.
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Affiliation(s)
- Kaoru Yamada
- Department of Neuropathology, Graduate School of Medicine, The University of Tokyo, Tokyo 113-0033, Japan
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17
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Alghanimy A, Martin C, Gallagher L, Holmes WM. The effect of a novel AQP4 facilitator, TGN-073, on glymphatic transport captured by diffusion MRI and DCE-MRI. PLoS One 2023; 18:e0282955. [PMID: 36920936 PMCID: PMC10016657 DOI: 10.1371/journal.pone.0282955] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2022] [Accepted: 02/27/2023] [Indexed: 03/16/2023] Open
Abstract
The glymphatic system is a low resistance pathway, by which cerebrospinal fluid enters the brain parenchyma along perivascular spaces via AQP4 channels. It is hypothesised that the resulting convective flow of the interstitial fluid provides an efficient mechanism for the removal of waste toxins from the brain. Therefore, enhancing AQP4 function might protect against neurodegenerative diseases such as Alzheimer's disease (AD), in which the accumulation of harmful proteins and solutes is a hallmark feature. Here, we test the effect of a putative AQP4 facilitator, TGN-073, on glymphatic transport in a normal rat brain by employing different MRI techniques. Surgical procedures were undertaken to catheterise the cisterna magna, thereby enabling infusion of the MRI tracer. Followed by the intraperitoneal injection of either TGN-073, or the vehicle. Using a paramagnetic contrast agent (Gd-DTPA) as the MRI tracer, dynamic 3D T1 weighted imaging of the glymphatic system was undertaken over two hours. Further, the apparent diffusion coefficient was measured in different brain regions using diffusion-weighted imaging (DWI). While physiological parameters and arterial blood gas analysis were monitored continuously. We found that rats treated with TGN-073 showed the distribution of Gd-DTPA was more extensive and parenchymal uptake was higher compared with the vehicle group. Water diffusivity was increased in the brain of TGN-073 treated group, which indicates greater water flux. Also, MRI showed the glymphatic transport and distribution in the brain is naturally heterogeneous, which is consistent with previous studies. Our results indicate that compounds such as TGN-073 can improve glymphatic function in the brain. Since glymphatic impairment due to AQP4 dysfunction is potentially associated with several neurological disorders such as AD, dementia and traumatic brain injury, enhancing AQP4 functionality might be a promising therapeutic target.
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Affiliation(s)
- Alaa Alghanimy
- Institute of Neuroscience and Psychology, College of Medicine, Veterinary and Life Science, University of Glasgow, Glasgow, United Kingdom
- Radiological Sciences Department, College of Applied Medical Sciences, King Saud University, Riyadh, Saudi Arabia
| | - Conor Martin
- Institute of Neuroscience and Psychology, College of Medicine, Veterinary and Life Science, University of Glasgow, Glasgow, United Kingdom
| | - Lindsay Gallagher
- Institute of Neuroscience and Psychology, College of Medicine, Veterinary and Life Science, University of Glasgow, Glasgow, United Kingdom
| | - William M. Holmes
- Institute of Neuroscience and Psychology, College of Medicine, Veterinary and Life Science, University of Glasgow, Glasgow, United Kingdom
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18
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Verghese JP, Terry A, de Natale ER, Politis M. Research Evidence of the Role of the Glymphatic System and Its Potential Pharmacological Modulation in Neurodegenerative Diseases. J Clin Med 2022; 11:jcm11236964. [PMID: 36498538 PMCID: PMC9735716 DOI: 10.3390/jcm11236964] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Revised: 11/07/2022] [Accepted: 11/24/2022] [Indexed: 11/29/2022] Open
Abstract
The glymphatic system is a unique pathway that utilises end-feet Aquaporin 4 (AQP4) channels within perivascular astrocytes, which is believed to cause cerebrospinal fluid (CSF) inflow into perivascular space (PVS), providing nutrients and waste disposal of the brain parenchyma. It is theorised that the bulk flow of CSF within the PVS removes waste products, soluble proteins, and products of metabolic activity, such as amyloid-β (Aβ). In the experimental model, the glymphatic system is selectively active during slow-wave sleep, and its activity is affected by both sleep dysfunction and deprivation. Dysfunction of the glymphatic system has been proposed as a potential key driver of neurodegeneration. This hypothesis is indirectly supported by the close relationship between neurodegenerative diseases and sleep alterations, frequently occurring years before the clinical diagnosis. Therefore, a detailed characterisation of the function of the glymphatic system in human physiology and disease would shed light on its early stage pathophysiology. The study of the glymphatic system is also critical to identifying means for its pharmacological modulation, which may have the potential for disease modification. This review will critically outline the primary evidence from literature about the dysfunction of the glymphatic system in neurodegeneration and discuss the rationale and current knowledge about pharmacological modulation of the glymphatic system in the animal model and its potential clinical applications in human clinical trials.
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19
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Ocular Lymphatic and Glymphatic Systems: Implications for Retinal Health and Disease. Int J Mol Sci 2022; 23:ijms231710139. [PMID: 36077535 PMCID: PMC9456449 DOI: 10.3390/ijms231710139] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2022] [Revised: 09/01/2022] [Accepted: 09/02/2022] [Indexed: 11/17/2022] Open
Abstract
Clearance of ocular fluid and metabolic waste is a critical function of the eye in health and disease. The eye has distinct fluid outflow pathways in both the anterior and posterior segments. Although the anterior outflow pathway is well characterized, little is known about posterior outflow routes. Recent studies suggest that lymphatic and glymphatic systems play an important role in the clearance of fluid and waste products from the posterior segment of the eye. The lymphatic system is a vascular network that runs parallel to the blood circulatory system. It plays an essential role in maintenance of fluid homeostasis and immune surveillance in the body. Recent studies have reported lymphatics in the cornea (under pathological conditions), ciliary body, choroid, and optic nerve meninges. The evidence of lymphatics in optic nerve meninges is, however, limited. An alternative lymphatic system termed the glymphatic system was recently discovered in the rodent eye and brain. This system is a glial cell-based perivascular network responsible for the clearance of interstitial fluid and metabolic waste. In this review, we will discuss our current knowledge of ocular lymphatic and glymphatic systems and their role in retinal degenerative diseases.
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20
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Need for a Paradigm Shift in the Treatment of Ischemic Stroke: The Blood-Brain Barrier. Int J Mol Sci 2022; 23:ijms23169486. [PMID: 36012745 PMCID: PMC9409167 DOI: 10.3390/ijms23169486] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2022] [Revised: 08/04/2022] [Accepted: 08/18/2022] [Indexed: 11/17/2022] Open
Abstract
Blood-brain barrier (BBB) integrity is essential to maintaining brain health. Aging-related alterations could lead to chronic progressive leakiness of the BBB, which is directly correlated with cerebrovascular diseases. Indeed, the BBB breakdown during acute ischemic stroke is critical. It remains unclear, however, whether BBB dysfunction is one of the first events that leads to brain disease or a down-stream consequence. This review will focus on the BBB dysfunction associated with cerebrovascular disease. An added difficulty is its association with the deleterious or reparative effect, which depends on the stroke phase. We will first outline the BBB structure and function. Then, we will focus on the spatiotemporal chronic, slow, and progressive BBB alteration related to ischemic stroke. Finally, we will propose a new perspective on preventive therapeutic strategies associated with brain aging based on targeting specific components of the BBB. Understanding BBB age-evolutions will be beneficial for new drug development and the identification of the best performance window times. This could have a direct impact on clinical translation and personalised medicine.
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21
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The glymphatic system: implications for drugs for central nervous system diseases. Nat Rev Drug Discov 2022; 21:763-779. [PMID: 35948785 DOI: 10.1038/s41573-022-00500-9] [Citation(s) in RCA: 38] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/22/2022] [Indexed: 12/14/2022]
Abstract
In the past decade, evidence for a fluid clearance pathway in the central nervous system known as the glymphatic system has grown. According to the glymphatic system concept, cerebrospinal fluid flows directionally through the brain and non-selectively clears the interstitium of metabolic waste. Importantly, the glymphatic system may be modulated by particular drugs such as anaesthetics, as well as by non-pharmacological factors such as sleep, and its dysfunction has been implicated in central nervous system disorders such as Alzheimer disease. Although the glymphatic system is best described in rodents, reports using multiple neuroimaging modalities indicate that a similar transport system exists in the human brain. Here, we overview the evidence for the glymphatic system and its role in disease and discuss opportunities to harness the glymphatic system therapeutically; for example, by improving the effectiveness of intrathecally delivered drugs.
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22
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Lopes DM, Llewellyn SK, Harrison IF. Propagation of tau and α-synuclein in the brain: therapeutic potential of the glymphatic system. Transl Neurodegener 2022; 11:19. [PMID: 35314000 PMCID: PMC8935752 DOI: 10.1186/s40035-022-00293-2] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Accepted: 03/03/2022] [Indexed: 12/12/2022] Open
Abstract
Many neurodegenerative diseases, including Alzheimer’s disease and Parkinson’s disease, are characterised by the accumulation of misfolded protein deposits in the brain, leading to a progressive destabilisation of the neuronal network and neuronal death. Among the proteins that can abnormally accumulate are tau and α-synuclein, which can propagate in a prion-like manner and which upon aggregation, represent the most common intracellular proteinaceous lesions associated with neurodegeneration. For years it was thought that these intracellular proteins and their accumulation had no immediate relationship with extracellular homeostasis pathways such as the glymphatic clearance system; however, mounting evidence has now suggested that this is not the case. The involvement of the glymphatic system in neurodegenerative disease is yet to be fully defined; however, it is becoming increasingly clear that this pathway contributes to parenchymal solute clearance. Importantly, recent data show that proteins prone to intracellular accumulation are subject to glymphatic clearance, suggesting that this system plays a key role in many neurological disorders. In this review, we provide a background on the biology of tau and α-synuclein and discuss the latest findings on the cell-to-cell propagation mechanisms of these proteins. Importantly, we discuss recent data demonstrating that manipulation of the glymphatic system may have the potential to alleviate and reduce pathogenic accumulation of propagation-prone intracellular cytotoxic proteins. Furthermore, we will allude to the latest potential therapeutic opportunities targeting the glymphatic system that might have an impact as disease modifiers in neurodegenerative diseases.
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23
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Hladky SB, Barrand MA. The glymphatic hypothesis: the theory and the evidence. Fluids Barriers CNS 2022; 19:9. [PMID: 35115036 PMCID: PMC8815211 DOI: 10.1186/s12987-021-00282-z] [Citation(s) in RCA: 80] [Impact Index Per Article: 40.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2021] [Accepted: 10/15/2021] [Indexed: 12/13/2022] Open
Abstract
The glymphatic hypothesis proposes a mechanism for extravascular transport into and out of the brain of hydrophilic solutes unable to cross the blood-brain barrier. It suggests that there is a circulation of fluid carrying solutes inwards via periarterial routes, through the interstitium and outwards via perivenous routes. This review critically analyses the evidence surrounding the mechanisms involved in each of these stages. There is good evidence that both influx and efflux of solutes occur along periarterial routes but no evidence that the principal route of outflow is perivenous. Furthermore, periarterial inflow of fluid is unlikely to be adequate to provide the outflow that would be needed to account for solute efflux. A tenet of the hypothesis is that flow sweeps solutes through the parenchyma. However, the velocity of any possible circulatory flow within the interstitium is too small compared to diffusion to provide effective solute movement. By comparison the earlier classical hypothesis describing extravascular transport proposed fluid entry into the parenchyma across the blood-brain barrier, solute movements within the parenchyma by diffusion, and solute efflux partly by diffusion near brain surfaces and partly carried by flow along "preferred routes" including perivascular spaces, white matter tracts and subependymal spaces. It did not suggest fluid entry via periarterial routes. Evidence is still incomplete concerning the routes and fate of solutes leaving the brain. A large proportion of the solutes eliminated from the parenchyma go to lymph nodes before reaching blood but the proportions delivered directly to lymph or indirectly via CSF which then enters lymph are as yet unclear. In addition, still not understood is why and how the absence of AQP4 which is normally highly expressed on glial endfeet lining periarterial and perivenous routes reduces rates of solute elimination from the parenchyma and of solute delivery to it from remote sites of injection. Neither the glymphatic hypothesis nor the earlier classical hypothesis adequately explain how solutes and fluid move into, through and out of the brain parenchyma. Features of a more complete description are discussed. All aspects of extravascular transport require further study.
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Affiliation(s)
- Stephen B. Hladky
- Department of Pharmacology, University of Cambridge, Cambridge, CB2 1PD UK
| | - Margery A. Barrand
- Department of Pharmacology, University of Cambridge, Cambridge, CB2 1PD UK
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24
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Sfera A, Osorio C, Rahman L, Zapata-Martín del Campo CM, Maldonado JC, Jafri N, Cummings MA, Maurer S, Kozlakidis Z. PTSD as an Endothelial Disease: Insights From COVID-19. Front Cell Neurosci 2021; 15:770387. [PMID: 34776871 PMCID: PMC8586713 DOI: 10.3389/fncel.2021.770387] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2021] [Accepted: 10/11/2021] [Indexed: 12/15/2022] Open
Abstract
SARS-CoV-2 virus, the etiologic agent of COVID-19, has affected almost every aspect of human life, precipitating stress-related pathology in vulnerable individuals. As the prevalence rate of posttraumatic stress disorder in pandemic survivors exceeds that of the general and special populations, the virus may predispose to this disorder by directly interfering with the stress-processing pathways. The SARS-CoV-2 interactome has identified several antigens that may disrupt the blood-brain-barrier by inducing premature senescence in many cell types, including the cerebral endothelial cells. This enables the stress molecules, including angiotensin II, endothelin-1 and plasminogen activator inhibitor 1, to aberrantly activate the amygdala, hippocampus, and medial prefrontal cortex, increasing the vulnerability to stress related disorders. This is supported by observing the beneficial effects of angiotensin receptor blockers and angiotensin converting enzyme inhibitors in both posttraumatic stress disorder and SARS-CoV-2 critical illness. In this narrative review, we take a closer look at the virus-host dialog and its impact on the renin-angiotensin system, mitochondrial fitness, and brain-derived neurotrophic factor. We discuss the role of furin cleaving site, the fibrinolytic system, and Sigma-1 receptor in the pathogenesis of psychological trauma. In other words, learning from the virus, clarify the molecular underpinnings of stress related disorders, and design better therapies for these conditions. In this context, we emphasize new potential treatments, including furin and bromodomains inhibitors.
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Affiliation(s)
- Adonis Sfera
- Department of Psychiatry, Loma Linda University, Loma Linda, CA, United States
- Patton State Hospital, San Bernardino, CA, United States
| | - Carolina Osorio
- Department of Psychiatry, Loma Linda University, Loma Linda, CA, United States
| | - Leah Rahman
- Patton State Hospital, San Bernardino, CA, United States
| | | | - Jose Campo Maldonado
- Department of Medicine, The University of Texas Rio Grande Valley, Edinburg, TX, United States
| | - Nyla Jafri
- Patton State Hospital, San Bernardino, CA, United States
| | | | - Steve Maurer
- Patton State Hospital, San Bernardino, CA, United States
| | - Zisis Kozlakidis
- International Agency For Research On Cancer (IARC), Lyon, France
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25
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Abstract
Optic nerve health is essential for proper function of the visual system. However, the pathophysiology of certain neurodegenerative disease processes affecting the optic nerve, such as glaucoma, is not fully understood. Recently, it was hypothesized that a lack of proper clearance of neurotoxins contributes to neurodegenerative diseases. The ability to clear metabolic waste is essential for tissue homeostasis in mammals, including humans. While the brain lacks the traditional lymphatic drainage system identified in other anatomical regions, there is growing evidence of a glymphatic system in the central nervous system, which structurally includes the optic nerve. Named to acknowledge the supportive role of astroglial cells, this perivascular fluid drainage system is essential to remove toxic metabolites from the central nervous system. Herein, we review existing literature describing the physiology and dysfunction of the glymphatic system specifically as it relates to the optic nerve. We summarize key imaging studies demonstrating the existence of a glymphatic system in the optic nerves of wild-type rodents, aquaporin 4-null rodents, and humans; glymphatic imaging studies in diseases where the optic nerve is impaired; and current evidence regarding pharmacological and lifestyle interventions that may help promote glymphatic function to improve optic nerve health. We conclude by highlighting future research directions that could be applied to improve imaging detection and guide therapeutic interventions for diseases affecting the optic nerve.
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Affiliation(s)
- Anisha Kasi
- Department of Ophthalmology, NYU Grossman School of Medicine, NYU Langone Health, New York University, New York, NY, USA
| | - Crystal Liu
- Department of Ophthalmology, NYU Grossman School of Medicine, NYU Langone Health, New York University, New York, NY, USA
| | - Muneeb A Faiq
- Department of Ophthalmology, NYU Grossman School of Medicine, NYU Langone Health, New York University, New York, NY, USA
| | - Kevin C Chan
- Department of Ophthalmology; Department of Radiology; Neuroscience Institute, NYU Grossman School of Medicine, NYU Langone Health; Center for Neural Science, College of Arts and Science, New York University, New York, NY, USA
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26
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Anzai Y, Minoshima S. Why We Need to Sleep: Glymphatic Pathway and Neurodegenerative Disease. Radiology 2021; 300:669-670. [PMID: 34156305 DOI: 10.1148/radiol.2021211140] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Yoshimi Anzai
- From the Department of Radiology and Imaging Sciences, University of Utah, 30 N 1900 E, 1A 71, Salt Lake City, UT 84132
| | - Satoshi Minoshima
- From the Department of Radiology and Imaging Sciences, University of Utah, 30 N 1900 E, 1A 71, Salt Lake City, UT 84132
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27
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Alshuhri MS, Gallagher L, Work LM, Holmes WM. Direct imaging of glymphatic transport using H217O MRI. JCI Insight 2021; 6:141159. [PMID: 33857020 PMCID: PMC8262348 DOI: 10.1172/jci.insight.141159] [Citation(s) in RCA: 32] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2020] [Accepted: 04/07/2021] [Indexed: 12/13/2022] Open
Abstract
The recently proposed glymphatic pathway for solute transport and waste clearance from the brain has been the focus of intense debate. By exploiting an isotopically enriched MRI tracer, H217O, we directly imaged glymphatic water transport in the rat brain in vivo. Our results reveal glymphatic transport that is dramatically faster and more extensive than previously thought and unlikely to be explained by diffusion alone. Moreover, we confirm the critical role of aquaporin-4 channels in glymphatic transport.
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Affiliation(s)
- Mohammed S Alshuhri
- Institute of Neuroscience and Psychology, College of Medicine, Veterinary and Life Science, University of Glasgow, Glasgow, United Kingdom.,Radiology and Medical Imaging Department, College of Applied Medical Sciences, Prince Sattam bin Abdulaziz University, Al Kharj, Saudi Arabia
| | - Lindsay Gallagher
- Institute of Neuroscience and Psychology, College of Medicine, Veterinary and Life Science, University of Glasgow, Glasgow, United Kingdom
| | - Lorraine M Work
- Institute of Cardiovascular and Medical Sciences, College of Medicine, Veterinary and Life Science, University of Glasgow, Glasgow, United Kingdom
| | - William M Holmes
- Institute of Neuroscience and Psychology, College of Medicine, Veterinary and Life Science, University of Glasgow, Glasgow, United Kingdom
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28
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Yankova G, Bogomyakova O, Tulupov A. The glymphatic system and meningeal lymphatics of the brain: new understanding of brain clearance. Rev Neurosci 2021; 32:693-705. [PMID: 33618444 DOI: 10.1515/revneuro-2020-0106] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2020] [Accepted: 01/31/2021] [Indexed: 12/25/2022]
Abstract
The glymphatic system and meningeal lymphatics have recently been characterized. Glymphatic system is a glia-dependent system of perivascular channels, and it plays an important role in the removal of interstitial metabolic waste products. The meningeal lymphatics may be a key drainage route for cerebrospinal fluid into the peripheral blood, may contribute to inflammatory reaction and central nervous system (CNS) immune surveillance. Breakdowns and dysfunction of the glymphatic system and meningeal lymphatics play a crucial role in age-related brain changes, the pathogenesis of neurovascular and neurodegenerative diseases, as well as in brain injuries and tumors. This review discusses the relationship recently characterized meningeal lymphatic vessels with the glymphatic system, which provides perfusion of the CNS with cerebrospinal and interstitial fluids. The review also presents the results of human studies concerning both the presence of meningeal lymphatics and the glymphatic system. A new understanding of how aging, medications, sleep and wake cycles, genetic predisposition, and even body posture affect the brain drainage system has not only changed the idea of brain fluid circulation but has also contributed to an understanding of the pathology and mechanisms of neurodegenerative diseases.
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Affiliation(s)
- Galina Yankova
- Lavrentyev Institute of Hydrodynamics, Siberian Branch, Russian Academy of Sciences, Novosibirsk630090, Russia.,Novosibirsk State University, Novosibirsk630090,Russia
| | - Olga Bogomyakova
- International Tomography Center, Siberian Branch, Russian Academy of Sciences, Novosibirsk630090, Russia
| | - Andrey Tulupov
- Novosibirsk State University, Novosibirsk630090,Russia.,International Tomography Center, Siberian Branch, Russian Academy of Sciences, Novosibirsk630090, Russia.,Meshalkin National Medical Research Center, Ministry of Health of Russian Federation, Novosibirsk 630055, Russia
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29
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Tan C, Wang X, Wang Y, Wang C, Tang Z, Zhang Z, Liu J, Xiao G. The Pathogenesis Based on the Glymphatic System, Diagnosis, and Treatment of Idiopathic Normal Pressure Hydrocephalus. Clin Interv Aging 2021; 16:139-153. [PMID: 33488070 PMCID: PMC7815082 DOI: 10.2147/cia.s290709] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2020] [Accepted: 01/01/2021] [Indexed: 12/16/2022] Open
Abstract
Idiopathic normal pressure hydrocephalus (iNPH) is a rare neurological disorder with no clear prevalence factors and is a significant danger to the elderly. The intracranial glymphatic system is the internal environment that maintains brain survival and metabolism, and thus fluid exchange changes in the glymphatic system under various pathological conditions can provide important insights into the pathogenesis and differential diagnosis of many neurodegenerative diseases such as iNPH. iNPH can be diagnosed using a combination of clinical symptoms, imaging findings and history, and cerebrospinal fluid biomarkers due to the glymphatic system disorder. However, only few researchers have linked the two. Shunt surgery can improve the glymphatic system disorders in iNPH patients, and the surgical approach is determined using a combination of clinical diagnosis and trials. Therefore, we have composed this review to provide a future opportunity for elucidating the pathogenesis of iNPH based on the glymphatic system, and link the glymphatic system to the diagnosis and treatment of iNPH. The review will provide new insights into the medical research of iNPH.
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Affiliation(s)
- Changwu Tan
- Department of Neurosurgery, Xiangya Hospital, Central South University, Changsha, Hunan 410008, People's Republic of China.,Diagnosis and Treatment Center for Hydrocephalus, Xiangya Hospital, Central South University, Changsha, Hunan 410008, People's Republic of China.,National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, Hunan 410008, People's Republic of China
| | - Xiaoqiang Wang
- Pediatric Neurological Disease Center, Xinhua Hospital, Shanghai Jiaotong University School of Medicine, Shanghai 200092, People's Republic of China
| | - Yuchang Wang
- Department of Neurosurgery, Xiangya Hospital, Central South University, Changsha, Hunan 410008, People's Republic of China.,Diagnosis and Treatment Center for Hydrocephalus, Xiangya Hospital, Central South University, Changsha, Hunan 410008, People's Republic of China.,National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, Hunan 410008, People's Republic of China
| | - Chuansen Wang
- Department of Neurosurgery, Xiangya Hospital, Central South University, Changsha, Hunan 410008, People's Republic of China.,Diagnosis and Treatment Center for Hydrocephalus, Xiangya Hospital, Central South University, Changsha, Hunan 410008, People's Republic of China.,National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, Hunan 410008, People's Republic of China
| | - Zhi Tang
- Department of Neurosurgery, Hunan Cancer Hospital and the Affiliated Cancer Hospital of Xiangya School of Medicine, Central South University, Changsha, Hunan 410013, People's Republic of China
| | - Zhiping Zhang
- Department of Neurosurgery, Xiangya Hospital, Central South University, Changsha, Hunan 410008, People's Republic of China.,Diagnosis and Treatment Center for Hydrocephalus, Xiangya Hospital, Central South University, Changsha, Hunan 410008, People's Republic of China.,National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, Hunan 410008, People's Republic of China
| | - Jingping Liu
- Department of Neurosurgery, Xiangya Hospital, Central South University, Changsha, Hunan 410008, People's Republic of China.,Diagnosis and Treatment Center for Hydrocephalus, Xiangya Hospital, Central South University, Changsha, Hunan 410008, People's Republic of China.,National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, Hunan 410008, People's Republic of China
| | - Gelei Xiao
- Department of Neurosurgery, Xiangya Hospital, Central South University, Changsha, Hunan 410008, People's Republic of China.,Diagnosis and Treatment Center for Hydrocephalus, Xiangya Hospital, Central South University, Changsha, Hunan 410008, People's Republic of China.,National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, Hunan 410008, People's Republic of China
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30
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Benveniste H, Lee H, Ozturk B, Chen X, Koundal S, Vaska P, Tannenbaum A, Volkow ND. Glymphatic Cerebrospinal Fluid and Solute Transport Quantified by MRI and PET Imaging. Neuroscience 2020; 474:63-79. [PMID: 33248153 DOI: 10.1016/j.neuroscience.2020.11.014] [Citation(s) in RCA: 46] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2020] [Revised: 11/04/2020] [Accepted: 11/07/2020] [Indexed: 12/13/2022]
Abstract
Over the past decade there has been an enormous progress in our understanding of fluid and solute transport in the central nervous system (CNS). This is due to a number of factors, including important developments in whole brain imaging technology and computational fluid dynamics analysis employed for the elucidation of glymphatic transport function in the live animal and human brain. In this paper, we review the technical aspects of dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) in combination with administration of Gd-based tracers into the cerebrospinal fluid (CSF) for tracking glymphatic solute and fluid transport in the CNS as well as lymphatic drainage. Used in conjunction with advanced computational processing methods including optimal mass transport analysis, one gains new insights into the biophysical forces governing solute transport in the CNS which leads to intriguing new research directions. Considering drainage pathways, we review the novel T1 mapping technique for quantifying glymphatic transport and cervical lymph node drainage concurrently in the same subject. We provide an overview of knowledge gleaned from DCE-MRI studies of glymphatic transport and meningeal lymphatic drainage. Finally, we introduce positron emission tomography (PET) and CSF administration of radiotracers as an alternative method to explore other pharmacokinetic aspects of CSF transport into brain parenchyma as well as efflux pathways.
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Affiliation(s)
- Helene Benveniste
- Department of Anesthesiology, Yale School of Medicine, New Haven, CT, United States; Department of Biomedical Engineering, Yale School of Medicine, New Haven, CT, United States.
| | - Hedok Lee
- Department of Anesthesiology, Yale School of Medicine, New Haven, CT, United States
| | - Burhan Ozturk
- Department of Anesthesiology, Yale School of Medicine, New Haven, CT, United States
| | - Xinan Chen
- Departments of Computer Science and Applied Mathematics & Statistics, Stony Brook University, Stony Brook, NY, United States
| | - Sunil Koundal
- Department of Anesthesiology, Yale School of Medicine, New Haven, CT, United States
| | - Paul Vaska
- Department of Radiology and Biomedical Engineering, Renaissance School of Medicine at Stony Brook University, Stony Brook, NY, United States
| | - Allen Tannenbaum
- Departments of Computer Science and Applied Mathematics & Statistics, Stony Brook University, Stony Brook, NY, United States
| | - Nora D Volkow
- Laboratory for Neuroimaging, NIAAA, Bethesda, MD, United States
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31
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Taoka T, Naganawa S. Neurofluid Dynamics and the Glymphatic System: A Neuroimaging Perspective. Korean J Radiol 2020; 21:1199-1209. [PMID: 32783417 PMCID: PMC7462760 DOI: 10.3348/kjr.2020.0042] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2020] [Revised: 03/25/2020] [Accepted: 04/23/2020] [Indexed: 12/23/2022] Open
Abstract
The glymphatic system hypothesis is a concept describing the clearance of waste products from the brain. The term “glymphatic system” combines the glial and lymphatic systems and is typically described as follows. The perivascular space functions as a conduit that drains cerebrospinal fluid (CSF) into the brain parenchyma. CSF guided to the perivascular space around the arteries enters the interstitium of brain tissue via aquaporin-4 water channels to clear waste proteins into the perivascular space around the veins before being drained from the brain. In this review, we introduce the glymphatic system hypothesis and its association with fluid dynamics, sleep, and disease. We also discuss imaging methods to evaluate the glymphatic system.
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Affiliation(s)
- Toshiaki Taoka
- Department of Innovative Biomedical Visualization (iBMV), Nagoya University Graduate School of Medicine, Nagoya, Japan.,Department of Radiology, Nagoya University Graduate School of Medicine, Nagoya, Japan.
| | - Shinji Naganawa
- Department of Radiology, Nagoya University Graduate School of Medicine, Nagoya, Japan
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32
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Inhibition of Aquaporin 4 Decreases Amyloid Aβ40 Drainage Around Cerebral Vessels. Mol Neurobiol 2020; 57:4720-4734. [PMID: 32783141 PMCID: PMC7515968 DOI: 10.1007/s12035-020-02044-8] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2020] [Accepted: 07/24/2020] [Indexed: 01/17/2023]
Abstract
Aquaporin-4 (AQP4) is located mainly in the astrocytic end-feet around cerebral blood vessels and regulates ion and water homeostasis in the brain. While deletion of AQP4 is shown to reduce amyloid-β (Aβ) clearance and exacerbate Aβ peptide accumulation in plaques and vessels of Alzheimer's disease mouse models, the mechanism and clearing pathways involved are debated. Here, we investigated how inhibiting the function of AQP4 in healthy male C57BL/6 J mice impacts clearance of Aβ40, the more soluble Aβ isoform. Using two-photon in vivo imaging and visualizing vessels with Sulfurodamine 101 (SR101), we first showed that Aβ40 injected as a ≤ 0.5-μl volume in the cerebral cortex diffused rapidly in parenchyma and accumulated around blood vessels. In animals treated with the AQP4 inhibitor TGN-020, the perivascular Aβ40 accumulation was significantly (P < 0.001) intensified by involving four times more vessels, thus suggesting a generalized clearance defect associated with vessels. Increasing the injecting volume to ≥ 0.5 ≤ 1 μl decreased the difference of Aβ40-positive vessels observed in non-treated and AQP4 inhibitor-treated animals, although the difference was still significant (P = 0.001), suggesting that larger injection volumes could overwhelm intramural vascular clearance mechanisms. While both small and large vessels accumulated Aβ40, for the ≤ 0.5-μl volume group, the average diameter of the Aβ40-positive vessels tended to be larger in control animals compared with TGN-020-treated animals, although the difference was non-significant (P = 0.066). Using histopathology and ultrastructural microscopy, no vascular structural change was observed after a single massive dose of TGN-020. These data suggest that AQP4 deficiency is directly involved in impaired Aβ brain clearance via the peri-/para-vascular routes, and AQP4-mediated vascular clearance might counteract blood-brain barrier abnormalities and age-related vascular amyloidopathy.
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33
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Dickie BR, Parker GJM, Parkes LM. Measuring water exchange across the blood-brain barrier using MRI. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2020; 116:19-39. [PMID: 32130957 DOI: 10.1016/j.pnmrs.2019.09.002] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2019] [Revised: 09/04/2019] [Accepted: 09/09/2019] [Indexed: 05/11/2023]
Abstract
The blood-brain barrier (BBB) regulates the transfer of solutes and essential nutrients into the brain. Growing evidence supports BBB dysfunction in a range of acute and chronic brain diseases, justifying the need for novel research and clinical tools that can non-invasively detect, characterize, and quantify BBB dysfunction in-vivo. Many approaches already exist for measuring BBB dysfunction in man using positron emission tomography and magnetic resonance imaging (e.g. dynamic contrast-enhanced MRI measurements of gadolinium leakage). This review paper focusses on MRI measurements of water exchange across the BBB, which occurs through a wide range of pathways, and is likely to be a highly sensitive marker of BBB dysfunction. Key mathematical models and acquisition methods are discussed for the two main approaches: those that utilize contrast agents to enhance relaxation rate differences between the intravascular and extravascular compartments and so enhance the sensitivity of MRI signals to BBB water exchange, and those that utilize the dynamic properties of arterial spin labelling to first isolate signal from intravascular spins and then estimate the impact of water exchange on the evolving signal. Data from studies in healthy and pathological brain tissue are discussed, in addition to validation studies in rodents.
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Affiliation(s)
- Ben R Dickie
- Division of Neuroscience and Experimental Psychology, University of Manchester, Oxford Road, Manchester M13 9PT, United Kingdom.
| | - Geoff J M Parker
- Bioxydyn Limited, Manchester M15 6SZ, United Kingdom; Centre for Medical Image Computing, Department of Computer Science and Department of Neuroinflammation, University College London, London, United Kingdom
| | - Laura M Parkes
- Division of Neuroscience and Experimental Psychology, University of Manchester, Oxford Road, Manchester M13 9PT, United Kingdom
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34
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Deng W, Liu C, Parra C, Sims JR, Faiq MA, Sainulabdeen A, Song H, Chan KC. Quantitative imaging of the clearance systems in the eye and the brain. Quant Imaging Med Surg 2020; 10:1-14. [PMID: 31956524 DOI: 10.21037/qims.2019.11.18] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Wenyu Deng
- Department of Ophthalmology, New York University (NYU) School of Medicine, NYU Langone Health, New York, NY, USA
| | - Crystal Liu
- Department of Ophthalmology, New York University (NYU) School of Medicine, NYU Langone Health, New York, NY, USA
| | - Carlos Parra
- Department of Ophthalmology, New York University (NYU) School of Medicine, NYU Langone Health, New York, NY, USA
| | - Jeffrey R Sims
- Department of Ophthalmology, New York University (NYU) School of Medicine, NYU Langone Health, New York, NY, USA
| | - Muneeb A Faiq
- Department of Ophthalmology, New York University (NYU) School of Medicine, NYU Langone Health, New York, NY, USA
| | - Anoop Sainulabdeen
- Department of Ophthalmology, New York University (NYU) School of Medicine, NYU Langone Health, New York, NY, USA
| | - Hana Song
- Department of Ophthalmology, New York University (NYU) School of Medicine, NYU Langone Health, New York, NY, USA
| | - Kevin C Chan
- Department of Ophthalmology, New York University (NYU) School of Medicine, NYU Langone Health, New York, NY, USA.,Department of Radiology, New York University (NYU) School of Medicine, NYU Langone Health, New York, NY, USA.,Neuroscience Institute, New York University (NYU) School of Medicine, NYU Langone Health, New York, NY, USA.,Center for Neural Science, Faculty of Arts and Science, New York University, New York, NY, USA
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35
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Ohara S, Miyahira TA, Oguchi K, Takei YI, Yanagimura F, Kawachi I, Oyanagi K, Kakita A. Neuromyelitis optica spectrum disorder with massive basal ganglia involvement: a case report. BMC Neurol 2019; 19:351. [PMID: 31888527 PMCID: PMC6937957 DOI: 10.1186/s12883-019-1580-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2019] [Accepted: 12/19/2019] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Occurrence of basal ganglia involvement in neuromyelitis optica spectrum disorders (NMOSD) has rarely been reported and none documented pathologically. CASE PRESENTATION A 73-year-old female was clinically diagnosed with a NMOSD based on the clinical and radiological features and positive serum autoantibodies to AQP4. One month before her death, she became acutely ill with disturbed consciousness and right hemiparesis, and was diagnosed and treated as having basal ganglia infarction based on the brain CT. She made a partial recovery but later died from heart failure. At autopsy, the corresponding basal ganglia process revealed a large fresh area of necrosis. Histologically, several pathological signatures of NMOSD could be recognized in the lesion, including inflammatory cell infiltrations by B and T lymphocytes, perivascular complement and fibrinogen deposition, and the appearance of numerous phagocytosed corpora amylacea within the infiltrating macrophages. CONCLUSIONS The present case illustrates that basal ganglia may be directly involved in the pathological processes of NMOSD, although the possibility of modification of the lesions by superimposed regional ischemia could not be excluded.
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Affiliation(s)
- Shinji Ohara
- Department of Neurology, Matsumoto Medical Center, Minami 2-20-30, Matsumoto, 399-8701, Japan. .,Department of Neurology, Iida Hospital, 1-15 Ohdori, Iida, 395-8505, Japan.
| | - Taka-Aki Miyahira
- Department of Neurology, Matsumoto Medical Center, Minami 2-20-30, Matsumoto, 399-8701, Japan
| | - Kenya Oguchi
- Department of Neurology, Matsumoto Medical Center, Minami 2-20-30, Matsumoto, 399-8701, Japan
| | - Yo-Ichi Takei
- Department of Neurology, Matsumoto Medical Center, Minami 2-20-30, Matsumoto, 399-8701, Japan
| | - Fumihiro Yanagimura
- Department of Neurology, Brain Research Institute, Niigata University, Niigata, Japan
| | - Izumi Kawachi
- Department of Neurology, Brain Research Institute, Niigata University, Niigata, Japan
| | - Kiyomitsu Oyanagi
- Division of Neuropathology, Brain Research Center, Shinshu University School of Medicine, Matsumoto, Japan.,Brain Research Laboratory, Hatsuishi Hospital, Chiba, Japan
| | - Akiyoshi Kakita
- Department of Neuropathology, Brain Research Institute, Niigata University, Niigata, Japan
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36
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Keep RF, Jones HC, Drewes LR. The year in review: progress in brain barriers and brain fluid research in 2018. Fluids Barriers CNS 2019; 16:4. [PMID: 30717760 PMCID: PMC6362595 DOI: 10.1186/s12987-019-0124-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2019] [Accepted: 01/17/2019] [Indexed: 12/17/2022] Open
Abstract
This editorial focuses on the progress made in brain barrier and brain fluid research in 2018. It highlights some recent advances in knowledge and techniques, as well as prevalent themes and controversies. Areas covered include: modeling, the brain endothelium, the neurovascular unit, the blood–CSF barrier and CSF, drug delivery, fluid movement within the brain, the impact of disease states, and heterogeneity.
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Affiliation(s)
- Richard F Keep
- Department of Neurosurgery, University of Michigan, R5018 BSRB, 109 Zina Pitcher Place, Ann Arbor, MI, 48109-2200, USA.
| | - Hazel C Jones
- Gagle Brook House, Chesterton, Bicester, OX26 1UF, UK
| | - Lester R Drewes
- Department of Biomedical Sciences, University of Minnesota Medical School Duluth, Duluth, MN, 55812, USA
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37
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Ramos M, Burdon Bechet N, Battistella R, Pavan C, Xavier ALR, Nedergaard M, Lundgaard I. Cisterna Magna Injection in Rats to Study Glymphatic Function. Methods Mol Biol 2019; 1938:97-104. [PMID: 30617975 PMCID: PMC6800144 DOI: 10.1007/978-1-4939-9068-9_7] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The recently discovered glymphatic system, which supports brain-wide clearance of metabolic waste, has become the subject of intense research within the past few years. Its nomenclature arose due to its functionally analogous nature to the lymphatic system in combination with glial cells that are part of its anatomical boundaries. The influx of cerebrospinal fluid (CSF) from perivascular spaces into the brain interstitium acts to clear intraparenchymal solutes. CSF is produced by the choroid plexus and flows from the ventricles to the subarachnoid space via the cisterna magna, and as such the injection of tracer molecules into any one of these spaces could be used for studying CSF movement through the glymphatic system. Of these options, the cisterna magna is most favorable as it offers a route of entry that does not involve craniotomy. Herein we describe the cisterna magna (CM) injection procedure carried out in rats, essential for studying glymphatic influx and efflux dynamics.
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Affiliation(s)
- Marta Ramos
- Department of Experimental Medical Science and Wallenberg Center for Molecular Medicine, Lund University, Lund, Sweden
| | - Nicholas Burdon Bechet
- Department of Experimental Medical Science and Wallenberg Center for Molecular Medicine, Lund University, Lund, Sweden
| | - Roberta Battistella
- Department of Experimental Medical Science and Wallenberg Center for Molecular Medicine, Lund University, Lund, Sweden
| | - Chiara Pavan
- Center for Translational Neuromedicine, Division of Glial Therapeutics, University of Copenhagen, Copenhagen, Denmark
| | - Anna L R Xavier
- Center for Translational Neuromedicine, Division of Glial Therapeutics, University of Copenhagen, Copenhagen, Denmark
| | - Maiken Nedergaard
- Center for Basic and Translational Neuroscience, University of Copenhagen, DK-2200, Copenhagen, Denmark
- Center for Translational Neuromedicine, Department of Neurosurgery, University of Rochester, Rochester, NY, 14642, USA
| | - Iben Lundgaard
- Department of Experimental Medical Science and Wallenberg Center for Molecular Medicine, Lund University, Lund, Sweden.
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38
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Mestre H, Hablitz LM, Xavier AL, Feng W, Zou W, Pu T, Monai H, Murlidharan G, Castellanos Rivera RM, Simon MJ, Pike MM, Plá V, Du T, Kress BT, Wang X, Plog BA, Thrane AS, Lundgaard I, Abe Y, Yasui M, Thomas JH, Xiao M, Hirase H, Asokan A, Iliff JJ, Nedergaard M. Aquaporin-4-dependent glymphatic solute transport in the rodent brain. eLife 2018; 7:40070. [PMID: 30561329 PMCID: PMC6307855 DOI: 10.7554/elife.40070] [Citation(s) in RCA: 347] [Impact Index Per Article: 57.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2018] [Accepted: 12/17/2018] [Indexed: 02/06/2023] Open
Abstract
The glymphatic system is a brain-wide clearance pathway; its impairment contributes to the accumulation of amyloid-β. Influx of cerebrospinal fluid (CSF) depends upon the expression and perivascular localization of the astroglial water channel aquaporin-4 (AQP4). Prompted by a recent failure to find an effect of Aqp4 knock-out (KO) on CSF and interstitial fluid (ISF) tracer transport, five groups re-examined the importance of AQP4 in glymphatic transport. We concur that CSF influx is higher in wild-type mice than in four different Aqp4 KO lines and in one line that lacks perivascular AQP4 (Snta1 KO). Meta-analysis of all studies demonstrated a significant decrease in tracer transport in KO mice and rats compared to controls. Meta-regression indicated that anesthesia, age, and tracer delivery explain the opposing results. We also report that intrastriatal injections suppress glymphatic function. This validates the role of AQP4 and shows that glymphatic studies must avoid the use of invasive procedures.
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Affiliation(s)
- Humberto Mestre
- Center for Translational Neuromedicine, University of Rochester Medical Center, Rochester, United States
| | - Lauren M Hablitz
- Center for Translational Neuromedicine, University of Rochester Medical Center, Rochester, United States
| | - Anna Lr Xavier
- Center for Translational Neuromedicine, Faculty of Medical and Health Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Weixi Feng
- Jiangsu Province Key Laboratory of Neurodegeneration, Center for Global Health, Nanjing Medical University, Nanjing, China
| | - Wenyan Zou
- Jiangsu Province Key Laboratory of Neurodegeneration, Center for Global Health, Nanjing Medical University, Nanjing, China
| | - Tinglin Pu
- Jiangsu Province Key Laboratory of Neurodegeneration, Center for Global Health, Nanjing Medical University, Nanjing, China
| | - Hiromu Monai
- RIKEN Center for Brain Science, Wako, Japan.,Ochanomizu University, Tokyo, Japan
| | - Giridhar Murlidharan
- Gene Therapy Center, The University of North Carolina, Chapel Hill, United States
| | | | - Matthew J Simon
- Department of Anesthesiology and Perioperative Medicine, Oregon Health and Science University, Portland, United States
| | - Martin M Pike
- Advanced Imaging Research Center, Oregon Health and Science University, Portland, United States
| | - Virginia Plá
- Center for Translational Neuromedicine, University of Rochester Medical Center, Rochester, United States
| | - Ting Du
- Center for Translational Neuromedicine, University of Rochester Medical Center, Rochester, United States
| | - Benjamin T Kress
- Center for Translational Neuromedicine, University of Rochester Medical Center, Rochester, United States
| | | | - Benjamin A Plog
- Center for Translational Neuromedicine, University of Rochester Medical Center, Rochester, United States
| | - Alexander S Thrane
- Center for Translational Neuromedicine, Faculty of Medical and Health Sciences, University of Copenhagen, Copenhagen, Denmark.,Department of Ophthalmology, Haukeland University Hospital, Bergen, Norway
| | - Iben Lundgaard
- Center for Translational Neuromedicine, University of Rochester Medical Center, Rochester, United States.,Department of Experimental Medical Science, Lund University, Lund, Sweden.,Wallenberg Center for Molecular Medicine, Lund University, Lund, Sweden
| | - Yoichiro Abe
- Department of Pharmacology,School of Medicine, Keio University, Tokyo, Japan
| | - Masato Yasui
- Department of Pharmacology,School of Medicine, Keio University, Tokyo, Japan
| | - John H Thomas
- Department of Mechanical Engineering, University of Rochester, Rochester, United States.,Department of Physics and Astronomy, University of Rochester, Rochester, United States
| | - Ming Xiao
- Jiangsu Province Key Laboratory of Neurodegeneration, Center for Global Health, Nanjing Medical University, Nanjing, China
| | - Hajime Hirase
- RIKEN Center for Brain Science, Wako, Japan.,Brain and Body System Science Institute, Saitama University, Saitama, Japan
| | - Aravind Asokan
- Gene Therapy Center, The University of North Carolina, Chapel Hill, United States.,Department of Molecular Genetics and Microbiology, Duke University School of Medicine, North Carolina, United States.,Department of Surgery, Duke University School of Medicine, Durham, United States
| | - Jeffrey J Iliff
- Department of Anesthesiology and Perioperative Medicine, Oregon Health and Science University, Portland, United States.,Knight Cardiovascular Institute, Oregon Health and Science University, Portland, United States
| | - Maiken Nedergaard
- Center for Translational Neuromedicine, University of Rochester Medical Center, Rochester, United States.,Center for Translational Neuromedicine, Faculty of Medical and Health Sciences, University of Copenhagen, Copenhagen, Denmark
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Nakada T, Kwee IL. Fluid Dynamics Inside the Brain Barrier: Current Concept of Interstitial Flow, Glymphatic Flow, and Cerebrospinal Fluid Circulation in the Brain. Neuroscientist 2018; 25:155-166. [PMID: 29799313 PMCID: PMC6416706 DOI: 10.1177/1073858418775027] [Citation(s) in RCA: 80] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The discovery of the water specific channel, aquaporin, and abundant expression
of its isoform, aquaporin-4 (AQP-4), on astrocyte endfeet brought about
significant advancements in the understanding of brain fluid dynamics. The brain
is protected by barriers preventing free access of systemic fluid. The same
barrier system, however, also isolates brain interstitial fluid from the
hydro-dynamic effect of the systemic circulation. The systolic force of the
heart, an essential factor for proper systemic interstitial fluid circulation,
cannot be propagated to the interstitial fluid compartment of the brain. Without
a proper alternative mechanism, brain interstitial fluid would stay stagnant.
Water influx into the peri-capillary Virchow-Robin space (VRS) through the
astrocyte AQP-4 system compensates for this hydrodynamic shortage essential for
interstitial flow, introducing the condition virtually identical to systemic
circulation, which by virtue of its fenestrated capillaries creates appropriate
interstitial fluid motion. Interstitial flow in peri-arterial VRS constitutes an
essential part of the clearance system for β-amyloid, whereas interstitial flow
in peri-venous VRS creates bulk interstitial fluid flow, which, together with
the choroid plexus, creates the necessary ventricular cerebrospinal fluid (CSF)
volume for proper CSF circulation.
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Affiliation(s)
- Tsutomu Nakada
- 1 Center for Integrated Human Brain Science, Brain Research Institute, University of Niigata, Niigata, Japan
| | - Ingrid L Kwee
- 2 Department of Neurology, University of California Davis, Sacramento, CA, USA
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