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Yang J, Cao C, Liu J, Liu Y, Lu J, Yu H, Li X, Wu J, Yu Z, Li H, Chen G. Dystrophin 71 deficiency causes impaired aquaporin-4 polarization contributing to glymphatic dysfunction and brain edema in cerebral ischemia. Neurobiol Dis 2024; 199:106586. [PMID: 38950712 DOI: 10.1016/j.nbd.2024.106586] [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: 03/27/2024] [Revised: 06/28/2024] [Accepted: 06/28/2024] [Indexed: 07/03/2024] Open
Abstract
OBJECTIVE The glymphatic system serves as a perivascular pathway that aids in clearing liquid and solute waste from the brain, thereby enhancing neurological function. Disorders in glymphatic drainage contribute to the development of vasogenic edema following cerebral ischemia, although the molecular mechanisms involved remain poorly understood. This study aims to determine whether a deficiency in dystrophin 71 (DP71) leads to aquaporin-4 (AQP4) depolarization, contributing to glymphatic dysfunction in cerebral ischemia and resulting in brain edema. METHODS A mice model of middle cerebral artery occlusion and reperfusion was used. A fluorescence tracer was injected into the cortex and evaluated glymphatic clearance. To investigate the role of DP71 in maintaining AQP4 polarization, an adeno-associated virus with the astrocyte promoter was used to overexpress Dp71. The expression and distribution of DP71 and AQP4 were analyzed using immunoblotting, immunofluorescence, and co-immunoprecipitation techniques. The behavior ability of mice was evaluated by open field test. Open-access transcriptome sequencing data were used to analyze the functional changes of astrocytes after cerebral ischemia. MG132 was used to inhibit the ubiquitin-proteasome system. The ubiquitination of DP71 was detected by immunoblotting and co-immunoprecipitation. RESULTS During the vasogenic edema stage following cerebral ischemia, a decline in the efflux of interstitial fluid tracer was observed. DP71 and AQP4 were co-localized and interacted with each other in the perivascular astrocyte endfeet. After cerebral ischemia, there was a notable reduction in DP71 protein expression, accompanied by AQP4 depolarization and proliferation of reactive astrocytes. Increased DP71 expression restored glymphatic drainage and reduced brain edema. AQP4 depolarization, reactive astrocyte proliferation, and the behavior of mice were improved. After cerebral ischemia, DP71 was degraded by ubiquitination, and MG132 inhibited the decrease of DP71 protein level. CONCLUSION AQP4 depolarization after cerebral ischemia leads to glymphatic clearance disorder and aggravates cerebral edema. DP71 plays a pivotal role in regulating AQP4 polarization and consequently influences glymphatic function. Changes in DP71 expression are associated with the ubiquitin-proteasome system. This study offers a novel perspective on the pathogenesis of brain edema following cerebral ischemia.
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Affiliation(s)
- Jian Yang
- Department of Neurosurgery & Brain and Nerve Research Laboratory, The First Affiliated Hospital of Soochow University, Suzhou, Jiangsu Province, China; Institute of Stroke Research, Soochow University, Suzhou, Jiangsu Province, China
| | - Chang Cao
- Department of Neurosurgery & Brain and Nerve Research Laboratory, The First Affiliated Hospital of Soochow University, Suzhou, Jiangsu Province, China; Institute of Stroke Research, Soochow University, Suzhou, Jiangsu Province, China
| | - Jiale Liu
- Department of Neurosurgery & Brain and Nerve Research Laboratory, The First Affiliated Hospital of Soochow University, Suzhou, Jiangsu Province, China; Institute of Stroke Research, Soochow University, Suzhou, Jiangsu Province, China
| | - Yangyang Liu
- Department of Neurosurgery & Brain and Nerve Research Laboratory, The First Affiliated Hospital of Soochow University, Suzhou, Jiangsu Province, China; Institute of Stroke Research, Soochow University, Suzhou, Jiangsu Province, China
| | - Jinxin Lu
- Department of Neurosurgery & Brain and Nerve Research Laboratory, The First Affiliated Hospital of Soochow University, Suzhou, Jiangsu Province, China; Institute of Stroke Research, Soochow University, Suzhou, Jiangsu Province, China
| | - HaoYun Yu
- Suzhou Medical College, Soochow University, Suzhou, Jiangsu Province, China
| | - Xiang Li
- Department of Neurosurgery & Brain and Nerve Research Laboratory, The First Affiliated Hospital of Soochow University, Suzhou, Jiangsu Province, China; Institute of Stroke Research, Soochow University, Suzhou, Jiangsu Province, China
| | - Jiang Wu
- Department of Neurosurgery & Brain and Nerve Research Laboratory, The First Affiliated Hospital of Soochow University, Suzhou, Jiangsu Province, China; Institute of Stroke Research, Soochow University, Suzhou, Jiangsu Province, China.
| | - Zhengquan Yu
- Department of Neurosurgery & Brain and Nerve Research Laboratory, The First Affiliated Hospital of Soochow University, Suzhou, Jiangsu Province, China; Institute of Stroke Research, Soochow University, Suzhou, Jiangsu Province, China.
| | - Haiying Li
- Department of Neurosurgery & Brain and Nerve Research Laboratory, The First Affiliated Hospital of Soochow University, Suzhou, Jiangsu Province, China; Institute of Stroke Research, Soochow University, Suzhou, Jiangsu Province, China.
| | - Gang Chen
- Department of Neurosurgery & Brain and Nerve Research Laboratory, The First Affiliated Hospital of Soochow University, Suzhou, Jiangsu Province, China; Institute of Stroke Research, Soochow University, Suzhou, Jiangsu Province, China
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Hladky SB, Barrand MA. Alterations in brain fluid physiology during the early stages of development of ischaemic oedema. Fluids Barriers CNS 2024; 21:51. [PMID: 38858667 PMCID: PMC11163777 DOI: 10.1186/s12987-024-00534-8] [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: 02/01/2024] [Accepted: 03/22/2024] [Indexed: 06/12/2024] Open
Abstract
Oedema occurs when higher than normal amounts of solutes and water accumulate in tissues. In brain parenchymal tissue, vasogenic oedema arises from changes in blood-brain barrier permeability, e.g. in peritumoral oedema. Cytotoxic oedema arises from excess accumulation of solutes within cells, e.g. ischaemic oedema following stroke. This type of oedema is initiated when blood flow in the affected core region falls sufficiently to deprive brain cells of the ATP needed to maintain ion gradients. As a consequence, there is: depolarization of neurons; neural uptake of Na+ and Cl- and loss of K+; neuronal swelling; astrocytic uptake of Na+, K+ and anions; swelling of astrocytes; and reduction in ISF volume by fluid uptake into neurons and astrocytes. There is increased parenchymal solute content due to metabolic osmolyte production and solute influx from CSF and blood. The greatly increased [K+]isf triggers spreading depolarizations into the surrounding penumbra increasing metabolic load leading to increased size of the ischaemic core. Water enters the parenchyma primarily from blood, some passing into astrocyte endfeet via AQP4. In the medium term, e.g. after three hours, NaCl permeability and swelling rate increase with partial opening of tight junctions between blood-brain barrier endothelial cells and opening of SUR1-TPRM4 channels. Swelling is then driven by a Donnan-like effect. Longer term, there is gross failure of the blood-brain barrier. Oedema resolution is slower than its formation. Fluids without colloid, e.g. infused mock CSF, can be reabsorbed across the blood-brain barrier by a Starling-like mechanism whereas infused serum with its colloids must be removed by even slower extravascular means. Large scale oedema can increase intracranial pressure (ICP) sufficiently to cause fatal brain herniation. The potentially lethal increase in ICP can be avoided by craniectomy or by aspiration of the osmotically active infarcted region. However, the only satisfactory treatment resulting in retention of function is restoration of blood flow, providing this can be achieved relatively quickly. One important objective of current research is to find treatments that increase the time during which reperfusion is successful. Questions still to be resolved are discussed.
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Affiliation(s)
- Stephen B Hladky
- Department of Pharmacology, Tennis Court Rd., Cambridge, CB2 1PD, UK.
| | - Margery A Barrand
- Department of Pharmacology, Tennis Court Rd., Cambridge, CB2 1PD, UK
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Bojarskaite L, Nafari S, Ravnanger AK, Frey MM, Skauli N, Åbjørsbråten KS, Roth LC, Amiry-Moghaddam M, Nagelhus EA, Ottersen OP, Bogen IL, Thoren AE, Enger R. Role of aquaporin-4 polarization in extracellular solute clearance. Fluids Barriers CNS 2024; 21:28. [PMID: 38532513 DOI: 10.1186/s12987-024-00527-7] [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: 11/23/2023] [Accepted: 03/02/2024] [Indexed: 03/28/2024] Open
Abstract
Waste from the brain has been shown to be cleared via the perivascular spaces through the so-called glymphatic system. According to this model the cerebrospinal fluid (CSF) enters the brain in perivascular spaces of arteries, crosses the astrocyte endfoot layer, flows through the parenchyma collecting waste that is subsequently drained along veins. Glymphatic clearance is dependent on astrocytic aquaporin-4 (AQP4) water channels that are highly enriched in the endfeet. Even though the polarized expression of AQP4 in endfeet is thought to be of crucial importance for glymphatic CSF influx, its role in extracellular solute clearance has only been evaluated using non-quantitative fluorescence measurements. Here we have quantitatively evaluated clearance of intrastriatally infused small and large radioactively labeled solutes in mice lacking AQP4 (Aqp4-/-) or lacking the endfoot pool of AQP4 (Snta1-/-). We confirm that Aqp4-/- mice show reduced clearance of both small and large extracellular solutes. Moreover, we find that the Snta1-/- mice have reduced clearance only for the 500 kDa [3H]dextran, but not 0.18 kDa [3H]mannitol suggesting that polarization of AQP4 to the endfeet is primarily important for clearance of large, but not small molecules. Lastly, we observed that clearance of 500 kDa [3H]dextran increased with age in adult mice. Based on our quantitative measurements, we confirm that presence of AQP4 is important for clearance of extracellular solutes, while the perivascular AQP4 localization seems to have a greater impact on clearance of large versus small molecules.
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Affiliation(s)
- Laura Bojarskaite
- GliaLab and Letten Centre, Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, P.O.B. 1103, Oslo, 0317, Norway
- Department of Neurology, Oslo University Hospital, Oslo, 0027, Norway
| | - Sahar Nafari
- GliaLab and Letten Centre, Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, P.O.B. 1103, Oslo, 0317, Norway
| | - Anne Katrine Ravnanger
- GliaLab and Letten Centre, Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, P.O.B. 1103, Oslo, 0317, Norway
| | - Mina Martine Frey
- Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, 0317, Norway
| | - Nadia Skauli
- Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, 0317, Norway
| | - Knut Sindre Åbjørsbråten
- GliaLab and Letten Centre, Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, P.O.B. 1103, Oslo, 0317, Norway
| | - Lena Catherine Roth
- GliaLab and Letten Centre, Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, P.O.B. 1103, Oslo, 0317, Norway
| | - Mahmood Amiry-Moghaddam
- Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, 0317, Norway
| | - Erlend A Nagelhus
- GliaLab and Letten Centre, Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, P.O.B. 1103, Oslo, 0317, Norway
| | - Ole Petter Ottersen
- GliaLab and Letten Centre, Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, P.O.B. 1103, Oslo, 0317, Norway
| | - Inger Lise Bogen
- GliaLab and Letten Centre, Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, P.O.B. 1103, Oslo, 0317, Norway
- Section for Drug Abuse Research, Department of Forensic Sciences, Oslo University Hospital, P.O. Box N-4950, Nydalen, Oslo, 0424, Norway
| | - Anna E Thoren
- GliaLab and Letten Centre, Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, P.O.B. 1103, Oslo, 0317, Norway
| | - Rune Enger
- GliaLab and Letten Centre, Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, P.O.B. 1103, Oslo, 0317, Norway.
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Tong XJ, Akdemir G, Wadhwa M, Verkman AS, Smith AJ. Large molecules from the cerebrospinal fluid enter the optic nerve but not the retina of mice. Fluids Barriers CNS 2024; 21:1. [PMID: 38178155 PMCID: PMC10768282 DOI: 10.1186/s12987-023-00506-4] [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: 10/24/2023] [Accepted: 12/21/2023] [Indexed: 01/06/2024] Open
Abstract
It has been proposed that cerebrospinal fluid (CSF) can enter and leave the retina and optic nerve along perivascular spaces surrounding the central retinal vessels as part of an aquaporin-4 (AQP4) dependent ocular 'glymphatic' system. Here, we injected fluorescent dextrans and antibodies into the CSF of mice at the cisterna magna and measured their distribution in the optic nerve and retina. We found that uptake of dextrans in the perivascular spaces and parenchyma of the optic nerve is highly sensitive to the cisternal injection rate, where high injection rates, in which dextran disperses fully in the sub-arachnoid space, led to uptake along the full length of the optic nerve. Accumulation of dextrans in the optic nerve did not differ significantly in wild-type and AQP4 knockout mice. Dextrans did not enter the retina, even when intracranial pressure was greatly increased over intraocular pressure. However, elevation of intraocular pressure reduced accumulation of fluorescent dextrans in the optic nerve head, and intravitreally injected dextrans left the retina via perivascular spaces surrounding the central retinal vessels. Human IgG distributed throughout the perivascular and parenchymal areas of the optic nerve to a similar extent as dextran following cisternal injection. However, uptake of a cisternally injected AQP4-IgG antibody, derived from a seropositive neuromyelitis optica spectrum disorder subject, was limited by AQP4 binding. We conclude that large molecules injected in the CSF can accumulate along the length of the optic nerve if they are fully dispersed in the optic nerve sub-arachnoid space but that they do not enter the retina.
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Affiliation(s)
- Xiao J Tong
- Department of Ophthalmology, University of California San Francisco, San Francisco, CA, 94131, USA
| | - Gokhan Akdemir
- Departments of Medicine and Physiology, University of California San Francisco, San Francisco, CA, 94131, USA
| | - Meetu Wadhwa
- Departments of Medicine and Physiology, University of California San Francisco, San Francisco, CA, 94131, USA
| | - Alan S Verkman
- Departments of Medicine and Physiology, University of California San Francisco, San Francisco, CA, 94131, USA
| | - Alex J Smith
- Department of Ophthalmology, University of California San Francisco, San Francisco, CA, 94131, USA.
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Yoo SS, Kim E, Kowsari K, Van Reet J, Kim HC, Yoon K. Non-invasive enhancement of intracortical solute clearance using transcranial focused ultrasound. Sci Rep 2023; 13:12339. [PMID: 37524783 PMCID: PMC10390479 DOI: 10.1038/s41598-023-39640-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2023] [Accepted: 07/28/2023] [Indexed: 08/02/2023] Open
Abstract
Transport of interstitial fluid and solutes plays a critical role in clearing metabolic waste from the brain. Transcranial application of focused ultrasound (FUS) has been shown to promote localized cerebrospinal fluid solute uptake into the brain parenchyma; however, its effects on the transport and clearance of interstitial solutes remain unknown. We demonstrate that pulsed application of low-intensity FUS to the rat brain enhances the transport of intracortically injected fluorescent tracers (ovalbumin and high molecular-weight dextran), yielding greater parenchymal tracer volume distribution compared to the unsonicated control group (ovalbumin by 40.1% and dextran by 34.6%). Furthermore, FUS promoted the drainage of injected interstitial ovalbumin to both superficial and deep cervical lymph nodes (cLNs) ipsilateral to sonication, with 78.3% higher drainage observed in the superficial cLNs compared to the non-sonicated hemisphere. The application of FUS increased the level of solute transport visible from the dorsal brain surface, with ~ 43% greater area and ~ 19% higher fluorescence intensity than the unsonicated group, especially in the pial surface ipsilateral to sonication. The sonication did not elicit tissue-level neuronal excitation, measured by an electroencephalogram, nor did it alter the molecular weight of the tracers. These findings suggest that nonthermal transcranial FUS can enhance advective transport of interstitial solutes and their subsequent removal in a completely non-invasive fashion, offering its potential non-pharmacological utility in facilitating clearance of waste from the brain.
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Affiliation(s)
- Seung-Schik Yoo
- Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, 75 Francis Street, MA, 02115, Boston, USA.
| | - Evgenii Kim
- Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, 75 Francis Street, MA, 02115, Boston, USA
| | - Kavin Kowsari
- Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, 75 Francis Street, MA, 02115, Boston, USA
| | - Jared Van Reet
- Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, 75 Francis Street, MA, 02115, Boston, USA
| | - Hyun-Chul Kim
- Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, 75 Francis Street, MA, 02115, Boston, USA
- Department of Artificial Intelligence, Kyungpook National University, Daegu, Republic of Korea
| | - Kyungho Yoon
- School of Computational Science and Engineering, Yonsei University, Seoul, Republic of Korea
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6
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Formolo DA, Yu J, Lin K, Tsang HWH, Ou H, Kranz GS, Yau SY. Leveraging the glymphatic and meningeal lymphatic systems as therapeutic strategies in Alzheimer's disease: an updated overview of nonpharmacological therapies. Mol Neurodegener 2023; 18:26. [PMID: 37081555 PMCID: PMC10116684 DOI: 10.1186/s13024-023-00618-3] [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: 08/29/2022] [Accepted: 04/05/2023] [Indexed: 04/22/2023] Open
Abstract
Understanding and treating Alzheimer's disease (AD) has been a remarkable challenge for both scientists and physicians. Although the amyloid-beta and tau protein hypothesis have largely explained the key pathological features of the disease, the mechanisms by which such proteins accumulate and lead to disease progression are still unknown. Such lack of understanding disrupts the development of disease-modifying interventions, leaving a therapeutic gap that remains unsolved. Nonetheless, the recent discoveries of the glymphatic pathway and the meningeal lymphatic system as key components driving central solute clearance revealed another mechanism underlying AD pathogenesis. In this regard, this narrative review integrates the glymphatic and meningeal lymphatic systems as essential components involved in AD pathogenesis. Moreover, it discusses the emerging evidence suggesting that nutritional supplementation, non-invasive brain stimulation, and traditional Chinese medicine can improve the pathophysiology of the disease by increasing glymphatic and/or meningeal lymphatic function. Given that physical exercise is a well-regarded preventive and pro-cognitive intervention for dementia, we summarize the evidence suggesting the glymphatic system as a mediating mechanism of the physical exercise therapeutic effects in AD. Targeting these central solute clearance systems holds the promise of more effective treatment strategies.
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Affiliation(s)
- Douglas A Formolo
- Department of Rehabilitation Sciences, Faculty of Health and Social Sciences, The Hong Kong Polytechnic University, 11 Yuk Choi Road, Hung Hom, Kowloon, Hong Kong, S.A.R, China
- Research Institute for Smart Ageing (RISA), The Hong Kong Polytechnic University, Hong Kong S.A.R, China
- Mental Health Research Center (MHRC), The Hong Kong Polytechnic University, Hong Kong S.A.R, China
| | - Jiasui Yu
- Department of Rehabilitation Sciences, Faculty of Health and Social Sciences, The Hong Kong Polytechnic University, 11 Yuk Choi Road, Hung Hom, Kowloon, Hong Kong, S.A.R, China
- Research Institute for Smart Ageing (RISA), The Hong Kong Polytechnic University, Hong Kong S.A.R, China
- Mental Health Research Center (MHRC), The Hong Kong Polytechnic University, Hong Kong S.A.R, China
| | - Kangguang Lin
- Department of Affective Disorders, The Affiliated Brain Hospital of Guangzhou Medical University, Guangzhou, Guangdong Province, China
- School of Health and Life Sciences, University of Health and Rehabilitation Sciences, Qingdao City, Shandong Province, China
| | - Hector W H Tsang
- Department of Rehabilitation Sciences, Faculty of Health and Social Sciences, The Hong Kong Polytechnic University, 11 Yuk Choi Road, Hung Hom, Kowloon, Hong Kong, S.A.R, China
- Mental Health Research Center (MHRC), The Hong Kong Polytechnic University, Hong Kong S.A.R, China
| | - Haining Ou
- Department of Rehabilitation, The Fifth Affiliated Hospital of Guangzhou Medical University, Guangzhou, Guangdong Province, China
| | - Georg S Kranz
- Department of Rehabilitation Sciences, Faculty of Health and Social Sciences, The Hong Kong Polytechnic University, 11 Yuk Choi Road, Hung Hom, Kowloon, Hong Kong, S.A.R, China
- Mental Health Research Center (MHRC), The Hong Kong Polytechnic University, Hong Kong S.A.R, China
- Department of Psychiatry and Psychotherapy, Comprehensive Center for Clinical Neurosciences and Mental Health (C3NMH), Medical University of Vienna, Vienna, Austria
- The State Key Laboratory of Brain and Cognitive Sciences, The University of Hong Kong, Hong Kong S.A.R, China
| | - Suk-Yu Yau
- Department of Rehabilitation Sciences, Faculty of Health and Social Sciences, The Hong Kong Polytechnic University, 11 Yuk Choi Road, Hung Hom, Kowloon, Hong Kong, S.A.R, China.
- Research Institute for Smart Ageing (RISA), The Hong Kong Polytechnic University, Hong Kong S.A.R, China.
- Mental Health Research Center (MHRC), The Hong Kong Polytechnic University, Hong Kong S.A.R, China.
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Bah TM, Siler DA, Ibrahim AH, Cetas JS, Alkayed NJ. Fluid dynamics in aging-related dementias. Neurobiol Dis 2023; 177:105986. [PMID: 36603747 DOI: 10.1016/j.nbd.2022.105986] [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: 10/31/2022] [Revised: 12/22/2022] [Accepted: 12/31/2022] [Indexed: 01/03/2023] Open
Abstract
Recent human and animal model experimental studies revealed novel pathways for fluid movement, immune cell trafficking and metabolic waste clearance in CNS. These studies raise the intriguing possibility that the newly discovered pathways, including the glymphatic system, lymphatic meningeal vessels and skull-brain communication channels, are impaired in aging and neurovascular and neurodegenerative diseases associated with dementia, including Alzheimer's disease (AD) and AD-related dementia. We provide an overview of the glymphatic and dural meningeal lymphatic systems, review current methods and approaches used to study glymphatic flow in humans and animals, and discuss current evidence and controversies related to its role in CNS flow homeostasis under physiological and pathophysiological conditions. Non-invasive imaging approaches are needed to fully understand the mechanisms and pathways driving fluid movement in CNS and their roles across lifespan including healthy aging and aging-related dementia.
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Affiliation(s)
- Thierno M Bah
- Department of Anesthesiology and Perioperative Medicine, Oregon Health & Science University, Portland, OR, USA
| | - Dominic A Siler
- Department of Neurological Surgery, Oregon Health & Science University, Portland, OR, USA
| | - Aseel H Ibrahim
- Department of Neurosurgery, University of Arizona, Tucson, AZ, USA
| | - Justin S Cetas
- Department of Neurosurgery, University of Arizona, Tucson, AZ, USA
| | - Nabil J Alkayed
- Department of Anesthesiology and Perioperative Medicine, Oregon Health & Science University, Portland, OR, USA; Knight Cardiovascular Institute, Oregon Health & Science University, Portland, OR, USA.
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Semyachkina-Glushkovskaya OV, Postnov DE, Khorovodov AP, Navolokin NA, Kurthz JHG. Lymphatic Drainage System of the Brain: a New Player in Neuroscience. J EVOL BIOCHEM PHYS+ 2023. [DOI: 10.1134/s0022093023010015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/16/2023]
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9
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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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Aryal M, Azadian MM, Hart AR, Macedo N, Zhou Q, Rosenthal EL, Airan RD. Noninvasive ultrasonic induction of cerebrospinal fluid flow enhances intrathecal drug delivery. J Control Release 2022; 349:434-442. [PMID: 35798095 DOI: 10.1016/j.jconrel.2022.06.067] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2021] [Revised: 06/15/2022] [Accepted: 06/30/2022] [Indexed: 10/17/2022]
Abstract
Intrathecal drug delivery is routinely used in the treatment and prophylaxis of varied central nervous system conditions, as doing so allows drugs to directly bypass the blood-brain barrier. However, the utility of this route of administration is limited by poor brain and spinal cord parenchymal drug uptake from the cerebrospinal fluid. We demonstrate that a simple noninvasive transcranial ultrasound protocol can significantly increase influx of cerebrospinal fluid into the perivascular spaces of the brain, to enhance the uptake of intrathecally administered drugs. Specifically, we administered small (~1 kDa) and large (~155 kDa) molecule agents into the cisterna magna of rats and then applied low, diagnostic-intensity focused ultrasound in a scanning protocol throughout the brain. Using real-time magnetic resonance imaging and ex vivo histologic analyses, we observed significantly increased uptake of small molecule agents into the brain parenchyma, and of both small and large molecule agents into the perivascular space from the cerebrospinal fluid. Notably, there was no evidence of brain parenchymal damage following this intervention. The low intensity and noninvasive approach of transcranial ultrasound in this protocol underscores the ready path to clinical translation of this technique. In this manner, this protocol can be used to directly bypass the blood-brain barrier for whole-brain delivery of a variety of agents. Additionally, this technique can potentially be used as a means to probe the causal role of the glymphatic system in the variety of disease and physiologic processes to which it has been correlated.
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Affiliation(s)
- Muna Aryal
- Department of Radiology, Stanford University School of Medicine, Stanford, CA, United States; Departments of Engineering and Radiation Oncology, Loyola University Chicago, Chicago, IL, United States
| | - Matine M Azadian
- Department of Radiology, Stanford University School of Medicine, Stanford, CA, United States
| | - Alex R Hart
- Department of Radiology, Stanford University School of Medicine, Stanford, CA, United States
| | - Nicholas Macedo
- Department of Radiology, Stanford University School of Medicine, Stanford, CA, United States
| | - Quan Zhou
- Department of Otolaryngology, Stanford University School of Medicine, Stanford, CA, United States; Department of Neurosurgery, Stanford University School of Medicine, Stanford, CA, United States
| | - Eben L Rosenthal
- Department of Otolaryngology, Stanford University School of Medicine, Stanford, CA, United States; Stanford Cancer Center, Stanford Medical Center, Stanford, CA, United States; Department of Otolaryngology, Vanderbilt University Medical Center, Nashville, TN, United States
| | - Raag D Airan
- Department of Radiology, Stanford University School of Medicine, Stanford, CA, United States; Department of Materials Science and Engineering, Stanford University School of Medicine, Stanford, CA, United States; Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, Stanford, CA, United States.
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11
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Buckley MW, McGavern DB. Immune dynamics in the CNS and its barriers during homeostasis and disease. Immunol Rev 2022; 306:58-75. [PMID: 35067941 PMCID: PMC8852772 DOI: 10.1111/imr.13066] [Citation(s) in RCA: 38] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2021] [Revised: 12/30/2021] [Accepted: 01/03/2022] [Indexed: 12/11/2022]
Abstract
The central nervous system (CNS) has historically been viewed as an immunologically privileged site, but recent studies have uncovered a vast landscape of immune cells that reside primarily along its borders. While microglia are largely responsible for surveying the parenchyma, CNS barrier sites are inhabited by a plethora of different innate and adaptive immune cells that participate in everything from the defense against microbes to the maintenance of neural function. Static and dynamic imaging studies have revolutionized the field of neuroimmunology by providing detailed maps of CNS immune cells as well as information about how these cells move, organize, and interact during steady-state and inflammatory conditions. These studies have also redefined our understanding of neural-immune interactions at a cellular level and reshaped our conceptual view of immune privilege in this specialized compartment. This review will focus on insights gained using imaging techniques in the field of neuroimmunology, with an emphasis on anatomy and CNS immune dynamics during homeostasis, infectious diseases, injuries, and aging.
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Affiliation(s)
- Monica W. Buckley
- Viral Immunology and Intravital Imaging Section National Institute of Neurological Disorders and Stroke National Institutes of Health Bethesda Maryland USA
| | - Dorian B. McGavern
- Viral Immunology and Intravital Imaging Section National Institute of Neurological Disorders and Stroke National Institutes of Health Bethesda Maryland USA
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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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Szczygielski J, Kopańska M, Wysocka A, Oertel J. Cerebral Microcirculation, Perivascular Unit, and Glymphatic System: Role of Aquaporin-4 as the Gatekeeper for Water Homeostasis. Front Neurol 2021; 12:767470. [PMID: 34966347 PMCID: PMC8710539 DOI: 10.3389/fneur.2021.767470] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Accepted: 11/12/2021] [Indexed: 12/13/2022] Open
Abstract
In the past, water homeostasis of the brain was understood as a certain quantitative equilibrium of water content between intravascular, interstitial, and intracellular spaces governed mostly by hydrostatic effects i.e., strictly by physical laws. The recent achievements in molecular bioscience have led to substantial changes in this regard. Some new concepts elaborate the idea that all compartments involved in cerebral fluid homeostasis create a functional continuum with an active and precise regulation of fluid exchange between them rather than only serving as separate fluid receptacles with mere passive diffusion mechanisms, based on hydrostatic pressure. According to these concepts, aquaporin-4 (AQP4) plays the central role in cerebral fluid homeostasis, acting as a water channel protein. The AQP4 not only enables water permeability through the blood-brain barrier but also regulates water exchange between perivascular spaces and the rest of the glymphatic system, described as pan-cerebral fluid pathway interlacing macroscopic cerebrospinal fluid (CSF) spaces with the interstitial fluid of brain tissue. With regards to this, AQP4 makes water shift strongly dependent on active processes including changes in cerebral microcirculation and autoregulation of brain vessels capacity. In this paper, the role of the AQP4 as the gatekeeper, regulating the water exchange between intracellular space, glymphatic system (including the so-called neurovascular units), and intravascular compartment is reviewed. In addition, the new concepts of brain edema as a misbalance in water homeostasis are critically appraised based on the newly described role of AQP4 for fluid permeation. Finally, the relevance of these hypotheses for clinical conditions (including brain trauma and stroke) and for both new and old therapy concepts are analyzed.
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Affiliation(s)
- Jacek Szczygielski
- Department of Neurosurgery, Institute of Medical Sciences, University of Rzeszów, Rzeszów, Poland.,Department of Neurosurgery, Faculty of Medicine and Saarland University Medical Center, Saarland University, Homburg, Germany
| | - Marta Kopańska
- Department of Pathophysiology, Institute of Medical Sciences, University of Rzeszów, Rzeszów, Poland
| | - Anna Wysocka
- Chair of Internal Medicine and Department of Internal Medicine in Nursing, Faculty of Health Sciences, Medical University of Lublin, Lublin, Poland
| | - Joachim Oertel
- Department of Neurosurgery, Faculty of Medicine and Saarland University Medical Center, Saarland University, Homburg, Germany
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The α-dystrobrevins play a key role in maintaining the structure and function of the extracellular matrix-significance for protein elimination failure arteriopathies. Acta Neuropathol Commun 2021; 9:171. [PMID: 34674769 PMCID: PMC8532274 DOI: 10.1186/s40478-021-01274-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2021] [Accepted: 10/11/2021] [Indexed: 01/08/2023] Open
Abstract
The extracellular matrix (ECM) of the cerebral vasculature provides a pathway for the flow of interstitial fluid (ISF) and solutes out of the brain by intramural periarterial drainage (IPAD). Failure of IPAD leads to protein elimination failure arteriopathies such as cerebral amyloid angiopathy (CAA). The ECM consists of a complex network of glycoproteins and proteoglycans that form distinct basement membranes (BM) around different vascular cell types. Astrocyte endfeet that are localised against the walls of blood vessels are tethered to these BMs by dystrophin associated protein complex (DPC). Alpha-dystrobrevin (α-DB) is a key dystrophin associated protein within perivascular astrocyte endfeet; its deficiency leads to a reduction in other dystrophin associated proteins, loss of AQP4 and altered ECM. In human dementia cohorts there is a positive correlation between dystrobrevin gene expression and CAA. In the present study, we test the hypotheses that (a) the positive correlation between dystrobrevin gene expression and CAA is associated with elevated expression of α-DB at glial-vascular endfeet and (b) a deficiency in α-DB results in changes to the ECM and failure of IPAD. We used human post-mortem brain tissue with different severities of CAA and transgenic α-DB deficient mice. In human post-mortem tissue we observed a significant increase in vascular α-DB with CAA (CAA vrs. Old p < 0.005, CAA vrs. Young p < 0.005). In the mouse model of α-DB deficiency, there was early modifications to vascular ECM (collagen IV and BM thickening) that translated into reduced IPAD efficiency. Our findings highlight the important role of α-DB in maintaining structure and function of ECM, particularly as a pathway for the flow of ISF and solutes out of the brain by IPAD.
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