scholarly journals The Glymphatic System and Waste Clearance with Brain Aging: A Review

Gerontology ◽  
2018 ◽  
Vol 65 (2) ◽  
pp. 106-119 ◽  
Author(s):  
Helene Benveniste ◽  
Xiaodan Liu ◽  
Sunil Koundal ◽  
Simon Sanggaard ◽  
Hedok Lee ◽  
...  
Keyword(s):  
Healthy Aging ◽  
Brain Aging ◽  
Cranial Nerves ◽  
Lymphatic Vessels ◽  
Current Evidence ◽  
Glymphatic System ◽  
Physiological Processes ◽  
Metabolic Products ◽  
Lymphatic Network ◽  
The Brain

The glymphatic system is a glial-dependent waste clearance pathway in the brain, in place of lymphatic vessels, dedicated to drain away soluble waste proteins and metabolic products. Specifically, the glymphatic network serves as a “front end” for waste clearance, and is connected downstream to an authentic lymphatic network, associated with dura covering the brain as well as cranial nerves and large vessels at the skull exits. The anatomical and functional interconnections between these two networks are not completely understood. Several key physiological processes have been identified that control glymphatic transport function and waste clearance from brain. In this review, we aim to provide an overview and discussion of the concept behind the glymphatic system, current evidence, and controversies, while specifically focusing on the consequences of aging and evidence of its existence in human brain. Discovering novel strategies for optimizing and maintaining efficient brain waste clearance across the lifespan may in the future prove to be important for preventing cognitive decline and sustaining healthy aging.

scholarly journals Xueshuantong Improves Functions of Lymphatic Ducts and Modulates Inflammatory Responses in Alzheimer’s Disease Mice

2021 ◽  
Vol 12 ◽  
Author(s):  
Rui Zheng ◽  
Yang-mei Huang ◽  
Qiang Zhou
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Healthy Aging ◽  
Inflammatory Responses ◽  
Brain Aging ◽  
Lymphatic Vessels ◽  
Amyloid Β ◽  
Brain Functions ◽  
Vital Functions ◽  
The Brain

Recent studies have revealed significant contributions of lymphatic vessels (LVs) to vital functions of the brain, especially related to clearance of waste from the brain and immune responses in the brain. These studies collectively indicate that enhancing the functions of LVs may improve brain functions during brain aging and in Alzheimer’s disease (AD) where LV functions are impaired. However, it is currently unknown whether this enhancement can be achieved using small molecules. We have previously shown that a widely used Chinese herbal medicine Xueshuantong (XST) significantly improves functions and reduces pathology in AD transgenic mice associated with elevated cerebral blood flow (CBF). Here, we show that XST partially rescues deficits in lymphatic structures, improves clearance of amyloid-β (Aβ) from the brain, and reduces the inflammatory responses in the serum and brains of transgenic AD mice. In addition, we showed that this improvement in the lymphatic system occurs independently of elevated CBF, suggesting independent modulation and limited interaction between blood circulation and lymphatic systems. Moreover, XST treatment leads to a significant increase in GLT-1 level and a significantly lower level of MMP-9 and restores AQP4 polarity in APP/PS1 mice. These results provide the basis for further exploration of XST to enhance or restore LV functions, which may be beneficial to treat neurodegenerative diseases or promote healthy aging.

Longitudinal Changes in Individual BrainAGE in Healthy Aging, Mild Cognitive Impairment, and Alzheimer’s Disease

GeroPsych ◽  
2012 ◽  
Vol 25 (4) ◽  
pp. 235-245 ◽  
Author(s):  
Katja Franke ◽  
Christian Gaser
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Healthy Aging ◽  
Brain Aging ◽  
Elderly Subjects ◽  
Additional Increase ◽  
Longitudinal Changes ◽  
Novel Method ◽  
The Brain

We recently proposed a novel method that aggregates the multidimensional aging pattern across the brain to a single value. This method proved to provide stable and reliable estimates of brain aging – even across different scanners. While investigating longitudinal changes in BrainAGE in about 400 elderly subjects, we discovered that patients with Alzheimer’s disease and subjects who had converted to AD within 3 years showed accelerated brain atrophy by +6 years at baseline. An additional increase in BrainAGE accumulated to a score of about +9 years during follow-up. Accelerated brain aging was related to prospective cognitive decline and disease severity. In conclusion, the BrainAGE framework indicates discrepancies in brain aging and could thus serve as an indicator for cognitive functioning in the future.

Neural glymphatic system: Clinical implications and potential importance of melatonin

2021 ◽  
Vol 4 (4) ◽  
pp. 551-565
Author(s):  
Ryan D Bitar ◽  
Jorge L Torres-Garza ◽  
Russel J Reiter ◽  
William T Phillips
Keyword(s):  
Lymph Nodes ◽  
Subarachnoid Space ◽  
Slow Wave Sleep ◽  
Lymphatic Vessels ◽  
Amyloid Β ◽  
Secretory Product ◽  
Cervical Lymph Nodes ◽  
Waste Products ◽  
Glymphatic System ◽  
The Brain

The central nervous system was thought to lack a lymphatic drainage until the recent discovery of the neural glymphatic system.  This highly specialized waste disposal network includes classical lymphatic vessels in the dura that absorb fluid and metabolic by-products and debris from the underlying cerebrospinal fluid (CSF) in the subarachnoid space. The subarachnoid space is continuous with the Virchow-Robin peri-arterial and peri-vascular spaces which surround the arteries and veins that penetrate into the neural tissue, respectively.  The dural lymphatic vessels exit the cranial vault via an anterior and a posterior route and eventually drain into the deep cervical lymph nodes. Aided by the presence of aquaporin 4 on the perivascular endfeet of astrocytes, nutrients and other molecules enter the brain from peri-arterial spaces and form interstitial fluid (ISF) that baths neurons and glia before being released into peri-venous spaces.  Melatonin, a pineal-derived secretory product which is in much higher concentration in the CSF than in the blood, is believed to follow this route and to clear waste products such as amyloid-β from the interstitial space. The clearance of amyloid-β reportedly occurs especially during slow wave sleep which happens concurrently with highest CSF levels of melatonin.  Experimentally, exogenously-administered melatonin defers amyloid-β buildup in the brain of animals and causes its accumulation in the cervical lymph nodes. Clinically, with increased age CSF melatonin levels decrease markedly, co-incident with neurodegeneration and dementia.  Collectively, these findings suggest a potential association between the loss of melatonin, decreased glymphatic drainage and neurocognitive decline in the elderly.

scholarly journals Brain lymphatic drainage system – visualization opportunities and current state of the art

2020 ◽  
Vol 9 (3) ◽  
pp. 81-89
Author(s):  
G. S. Yankova ◽  
O. B. Bogomyakova
Keyword(s):  
Neurodegenerative Diseases ◽  
Immune Surveillance ◽  
Lymphatic Vessels ◽  
Drainage System ◽  
Lymphatic Drainage ◽  
Waste Products ◽  
Glymphatic System ◽  
Age Related ◽  
The Central Nervous System ◽  
The Brain

The lymphatic drainage system of the brain is assumed to consist of the lymphatic system and a network of meningeal lymphatic vessels. This system supports brain homeostasis, participates in immune surveillance and presents a new therapeutic target in the treatment of neurological disorders.The article analyzes and systematizes data on the brain lymphatic drainage system. The key components of this system are considered: recently described meningeal lymphatic vessels and their relationship with the glymphatic system, which provides perfusion of the central nervous system with cerebrospinal and interstitial fluids. The lymphatic drainage system helps to maintain water and ion balances of the interstitial fluid and to remove metabolic waste products, assists in reabsorption of macromolecules. Disorders in its work play a crucial role in age-related changes in the brain, the pathogenesis of neurovascular and neurodegenerative diseases, as well as injuries and brain tumors. The review also presents the results of human studies concerning the presence, anatomy and structure of meningeal lymphatic vessels and the glymphatic system. The discovery of the brain lymphatic drainage system has not only changed our understanding of cerebrospinal fluid circulation, but also contributed to understanding the pathology and mechanisms of neurodegenerative diseases.

scholarly journals Brain Energy Metabolism and Blood Flow Differences in Healthy Aging

2012 ◽  
Vol 32 (7) ◽  
pp. 1177-1187 ◽  
Author(s):  
Joel Aanerud ◽  
Per Borghammer ◽  
M Mallar Chakravarty ◽  
Kim Vang ◽  
Anders B Rodell ◽  
...  
Keyword(s):  
Blood Flow ◽  
Healthy Volunteers ◽  
Healthy Aging ◽  
Brain Aging ◽  
Temporal Cortex ◽  
Oxygen Extraction Fraction ◽  
Positron Emission ◽  
Rate Of Oxygen Consumption ◽  
Parietal Cortices ◽  
The Brain

Cerebral metabolic rate of oxygen consumption ( CMRO 2), cerebral blood flow ( CBF), and oxygen extraction fraction ( OEF) are important indices of healthy aging of the brain. Although a frequent topic of study, changes of CBF and CMRO 2 during normal aging are still controversial, as some authors find decreases of both CBF and CMRO 2 but increased OEF, while others find no change, and yet other find divergent changes. In this reanalysis of previously published results from positron emission tomography of healthy volunteers, we determined CMRO 2 and CBF in 66 healthy volunteers aged 21 to 81 years. The magnitudes of CMRO 2 and CBF declined in large parts of the cerebral cortex, including association areas, but the primary motor and sensory areas were relatively spared. We found significant increases of OEF in frontal and parietal cortices, excluding primary motor and somatosensory regions, and in the temporal cortex. Because of the inverse relation between OEF and capillary oxygen tension, increased OEF can compromise oxygen delivery to neurons, with possible perturbation of energy turnover. The results establish a possible mechanism of progression from healthy to unhealthy brain aging, as the regions most affected by age are the areas that are most vulnerable to neurodegeneration.

scholarly journals Magnetic Resonance Imaging and Modeling of the Glymphatic System

Diagnostics ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 344 ◽  
Author(s):  
Jasleen Kaur ◽  
Esmaeil Davoodi-Bojd ◽  
Lara M Fahmy ◽  
Li Zhang ◽  
Guangliang Ding ◽  
...  
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Imaging Techniques ◽  
Neurological Diseases ◽  
Current Evidence ◽  
Resonance Imaging ◽  
Ongoing Research ◽  
Glymphatic System ◽  
Modeling Techniques ◽  
The Brain

The glymphatic system is a newly discovered waste drainage pathway in the brain; it plays an important role in many neurological diseases. Ongoing research utilizing various cerebrospinal fluid tracer infusions, either directly or indirectly into the brain parenchyma, is investigating clearance pathways by using distinct imaging techniques. In the present review, we discuss the role of the glymphatic system in various neurological diseases and efflux pathways of brain waste clearance based on current evidence and controversies. We mainly focus on new magnetic resonance imaging (MRI) modeling techniques, along with traditional computational modeling, for a better understanding of the glymphatic system function. Future sophisticated modeling techniques hold the potential to generate quantitative maps for glymphatic system parameters that could contribute to the diagnosis, monitoring, and prognosis of neurological diseases. The non-invasive nature of MRI may provide a safe and effective way to translate glymphatic system measurements from bench-to-bedside.

The glymphatic system and meningeal lymphatics of the brain: new understanding of brain clearance

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Galina Yankova ◽  
Olga Bogomyakova ◽  
Andrey Tulupov
Keyword(s):  
Neurodegenerative Diseases ◽  
Brain Injuries ◽  
Immune Surveillance ◽  
Lymphatic Vessels ◽  
Drainage System ◽  
Waste Products ◽  
Glymphatic System ◽  
System A ◽  
Age Related ◽  
The Brain

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.

scholarly journals Gut Microbiota: Critical Controller and Intervention Target in Brain Aging and Cognitive Impairment

2021 ◽  
Vol 13 ◽  
Author(s):  
Hui Li ◽  
Junjun Ni ◽  
Hong Qing
Keyword(s):  
Cognitive Impairment ◽  
Gut Microbiota ◽  
Healthy Aging ◽  
Brain Aging ◽  
Current Trend ◽  
The Body ◽  
Dietary Interventions ◽  
Age Related ◽  
Functional Features ◽  
The Brain

The current trend for the rapid growth of the global aging population poses substantial challenges for society. The human aging process has been demonstrated to be closely associated with changes in gut microbiota composition, diversity, and functional features. During the first 2 years of life, the gut microbiota undergoes dramatic changes in composition and metabolic functions as it colonizes and develops in the body. Although the gut microbiota is nearly established by the age of three, it continues to mature until adulthood, when it comprises more stable and diverse microbial species. Meanwhile, as the physiological functions of the human body deteriorated with age, which may be a result of immunosenescence and “inflammaging,” the guts of elderly people are generally characterized by an enrichment of pro-inflammatory microbes and a reduced abundance of beneficial species. The gut microbiota affects the development of the brain through a bidirectional communication system, called the brain-gut-microbiota (BGM) axis, and dysregulation of this communication is pivotal in aging-related cognitive impairment. Microbiota-targeted dietary interventions and the intake of probiotics/prebiotics can increase the abundance of beneficial species, boost host immunity, and prevent gut-related diseases. This review summarizes the age-related changes in the human gut microbiota based on recent research developments. Understanding these changes will likely facilitate the design of novel therapeutic strategies to achieve healthy aging.

scholarly journals Live Imaging of Intracranial Lymphatics in the Zebrafish

2020 ◽  
Author(s):  
Daniel Castranova ◽  
Bakary Samasa ◽  
Marina Venero Galanternik ◽  
Hyun Min Jung ◽  
Van N. Pham ◽  
...  
Keyword(s):  
Experimental Analysis ◽  
Immune Cell ◽  
Lymphatic Vessels ◽  
Model Organism ◽  
Live Imaging ◽  
Cell Trafficking ◽  
Lymphatic Development ◽  
Health And Disease ◽  
Lymphatic Network ◽  
The Brain

ABSTRACTRationaleThe recent discovery of meningeal lymphatics in mammals is reshaping our understanding of fluid homeostasis and cellular waste management in the brain, but visualization and experimental analysis of these vessels is challenging in mammals. Although the optical clarity and experimental advantages of zebrafish have made this an essential model organism for studying lymphatic development, the existence of meningeal lymphatics has not yet been reported in this species.ObjectiveExamine the intracranial space of larval, juvenile, and adult zebrafish to determine whether and where intracranial lymphatic vessels are present.Methods and ResultsUsing high-resolution optical imaging of the meninges in living animals, we show that zebrafish possess a meningeal lymphatic network comparable to that found in mammals. We confirm that this network is separate from the blood vascular network and that it drains interstitial fluid from the brain. We document the developmental origins and growth of these vessels into a distinct network separated from the external lymphatics. Finally we show that these vessels contain immune cells and perform live imaging of immune cell trafficking and transmigration in meningeal lymphatics.ConclusionsThis discovery establishes the zebrafish as a important new model for experimental analysis of meningeal lymphatic development, and opens up new avenues for probing meningeal lymphatic function in health and disease.

scholarly journals The Glymphatic System (En)during Inflammation

2021 ◽  
Vol 22 (14) ◽  
pp. 7491
Author(s):  
Frida Lind-Holm Mogensen ◽  
Christine Delle ◽  
Maiken Nedergaard
Keyword(s):  
Fluid Transport ◽  
Neurological Diseases ◽  
Lymphatic Vessels ◽  
Perivascular Spaces ◽  
Fluid Exchange ◽  
Glymphatic System ◽  
The Central Nervous System ◽  
The Brain ◽  
Privileged Site ◽  
Vascular Compartment

The glymphatic system is a fluid-transport system that accesses all regions of the brain. It facilitates the exchange of cerebrospinal fluid and interstitial fluid and clears waste from the metabolically active brain. Astrocytic endfeet and their dense expression of the aquaporin-4 water channels promote fluid exchange between the perivascular spaces and the neuropil. Cerebrospinal and interstitial fluids are together transported back to the vascular compartment by meningeal and cervical lymphatic vessels. Multiple lines of work show that neurological diseases in general impair glymphatic fluid transport. Insofar as the glymphatic system plays a pseudo-lymphatic role in the central nervous system, it is poised to play a role in neuroinflammation. In this review, we discuss how the association of the glymphatic system with the meningeal lymphatic vessel calls for a renewal of established concepts on the CNS as an immune-privileged site. We also discuss potential approaches to target the glymphatic system to combat neuroinflammation.

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