201
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Astroglial water channel aquaporin 4-mediated glymphatic clearance function: A determined factor for time-sensitive treatment of aerobic exercise in patients with Alzheimer's disease. Med Hypotheses 2018; 119:18-21. [PMID: 30122483 DOI: 10.1016/j.mehy.2018.07.016] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2018] [Revised: 07/05/2018] [Accepted: 07/21/2018] [Indexed: 11/21/2022]
Abstract
Currently, there are no effective drug therapies for Alzheimer's disease (AD). Thus, exploring new non-pharmacological strategies, including the neuroprotective mechanisms of aerobic exercise, to enhance therapeutic treatment of AD are essential. Previous studies have shown that the beneficial efficiency of aerobic exercise in the prevention and treatment of AD is time-sensitive, but its mechanism is not clear. Recent studies revealed that the water channel protein aquaporin 4 (AQP4) mediates the glymphatic system to clear interstitial solutes, including β-amyloid, from the brain. More recently, voluntary exercise has been shown to promote glymphatic clearance function in mice. However, glymphatic function is reduced in the mid- or late-stage of AD due to the loss of the polarity distribution of AQP4. Based on this, we hypothesized that AQP4-mediated glymphatic system clearance function is a determining factor for time-sensitive treatment of aerobic exercise in patients with AD. While further studies are necessary, the potential results are important for elucidating the new pro-cognitive mechanism of aerobic exercise, but also help to establish a new strategy for treatment of AD via regulation of glymphatic clearance function by targeting AQP4.
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202
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Ringstad G, Valnes LM, Dale AM, Pripp AH, Vatnehol SAS, Emblem KE, Mardal KA, Eide PK. Brain-wide glymphatic enhancement and clearance in humans assessed with MRI. JCI Insight 2018; 3:121537. [PMID: 29997300 DOI: 10.1172/jci.insight.121537] [Citation(s) in RCA: 263] [Impact Index Per Article: 43.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2018] [Accepted: 05/31/2018] [Indexed: 12/21/2022] Open
Abstract
To what extent does the subarachnoid cerebrospinal fluid (CSF) compartment communicate directly with the extravascular compartment of human brain tissue? Interconnection between the subarachnoid CSF compartment and brain perivascular spaces is reported in some animal studies, but with controversy, and in vivo CSF tracer studies in humans are lacking. In the present work, we examined the distribution of a CSF tracer in the human brain by MRI over a prolonged time span. For this, we included a reference cohort, representing close to healthy individuals, and a cohort of patients with dementia and anticipated compromise of CSF circulation (idiopathic normal pressure hydrocephalus). The MRI contrast agent gadobutrol, which is confined to the extravascular brain compartment by the intact blood-brain barrier, was used as a CSF tracer. Standardized T1-weighted MRI scans were performed before and after intrathecal gadobutrol at defined time points, including at 24 hours, 48 hours, and 4 weeks. All MRI scans were aligned and brain regions were segmented using FreeSurfer, and changes in normalized T1 signals over time were quantified as percentage change from baseline. The study provides in vivo evidence of access to all human brain subregions of a substance administered intrathecally. Clearance of the tracer substance was delayed in the dementia cohort. These observations translate previous findings in animal studies into humans and open new prospects concerning intrathecal treatment regimens, extravascular contrast-enhanced MRI, and assessment of brain clearance function.
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Affiliation(s)
- Geir Ringstad
- Division of Radiology and Nuclear Medicine, Department of Radiology, Oslo University Hospital - Rikshospitalet, Oslo, Norway.,Institute of Clinical Medicine, Faculty of Medicine, and
| | - Lars M Valnes
- Department of Mathematics, University of Oslo, Oslo, Norway
| | - Anders M Dale
- Department of Neurosciences.,Department of Radiology, and.,Multimodal Imaging Laboratory, UCSD, La Jolla, California, USA
| | - Are H Pripp
- Oslo Centre of Biostatistics and Epidemiology, Research Support Services, Oslo University Hospital, Oslo, Norway
| | - Svein-Are S Vatnehol
- The Intervention Centre, Oslo University Hospital - Rikshospitalet, Oslo, Norway
| | - Kyrre E Emblem
- Department of Diagnostic Physics, Oslo University Hospital, Oslo, Norway
| | - Kent-Andre Mardal
- Department of Mathematics, University of Oslo, Oslo, Norway.,Center for Biomedical Computing, Simula Research Laboratory, Lysaker, Norway
| | - Per K Eide
- Institute of Clinical Medicine, Faculty of Medicine, and.,Department of Neurosurgery, Oslo University Hospital - Rikshospitalet, Oslo, Norway
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203
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Verheggen I, Van Boxtel M, Verhey F, Jansen J, Backes W. Interaction between blood-brain barrier and glymphatic system in solute clearance. Neurosci Biobehav Rev 2018; 90:26-33. [DOI: 10.1016/j.neubiorev.2018.03.028] [Citation(s) in RCA: 55] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2017] [Revised: 03/22/2018] [Accepted: 03/25/2018] [Indexed: 02/03/2023]
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204
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Xiong Y, Mahmood A, Chopp M. Current understanding of neuroinflammation after traumatic brain injury and cell-based therapeutic opportunities. Chin J Traumatol 2018; 21:137-151. [PMID: 29764704 PMCID: PMC6034172 DOI: 10.1016/j.cjtee.2018.02.003] [Citation(s) in RCA: 117] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/13/2018] [Revised: 03/02/2018] [Accepted: 03/05/2018] [Indexed: 02/04/2023] Open
Abstract
Traumatic brain injury (TBI) remains a major cause of death and disability worldwide. Increasing evidence indicates that TBI is an important risk factor for neurodegenerative diseases including Alzheimer's disease, Parkinson's disease, and chronic traumatic encephalopathy. Despite improved supportive and rehabilitative care of TBI patients, unfortunately, all late phase clinical trials in TBI have yet to yield a safe and effective neuroprotective treatment. The disappointing clinical trials may be attributed to variability in treatment approaches and heterogeneity of the population of TBI patients as well as a race against time to prevent or reduce inexorable cell death. TBI is not just an acute event but a chronic disease. Among many mechanisms involved in secondary injury after TBI, emerging preclinical studies indicate that posttraumatic prolonged and progressive neuroinflammation is associated with neurodegeneration which may be treatable long after the initiating brain injury. This review provides an overview of recent understanding of neuroinflammation in TBI and preclinical cell-based therapies that target neuroinflammation and promote functional recovery after TBI.
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Affiliation(s)
- Ye Xiong
- Department of Neurosurgery Henry Ford Health System, 2799 West Grand Boulevard, Detroit, MI, 48202, USA.
| | - Asim Mahmood
- Department of Neurosurgery Henry Ford Health System, 2799 West Grand Boulevard, Detroit, MI, 48202, USA
| | - Michael Chopp
- Department of Neurology, Henry Ford Health System, 2799 West Grand Boulevard, Detroit, MI, 48202, USA; Department of Physics, Oakland University, Rochester, MI, 48309, USA
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205
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Abstract
Alzheimer's disease (AD) is a debilitating disease influencing a multitude of outcomes, including memory function. Recent work suggests that memory may be influenced by exercise ('memorcise'), even among those with AD. The present narrative review details (1) the underlying mechanisms of AD; (2) whether exercise has a protective effect in preventing AD; (3) the mechanisms through which exercise may help to prevent AD; (4) the mechanisms through which exercise may help attenuate the progression of AD severity among those with existing AD; (5) the effects and mechanisms through which exercise is associated with memory among those with existing AD; and (6) exercise recommendations for those with existing AD. Such an understanding will aid clinicians in their ability to use exercise as a potential behavioral strategy to help prevent and treat AD.
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Affiliation(s)
- Paul D Loprinzi
- a Physical Activity Epidemiology Laboratory, Exercise Psychology Laboratory, Department of Health, Exercise Science and Recreation Management , The University of Mississippi , University , MS , USA
| | - Emily Frith
- a Physical Activity Epidemiology Laboratory, Exercise Psychology Laboratory, Department of Health, Exercise Science and Recreation Management , The University of Mississippi , University , MS , USA
| | - Pamela Ponce
- a Physical Activity Epidemiology Laboratory, Exercise Psychology Laboratory, Department of Health, Exercise Science and Recreation Management , The University of Mississippi , University , MS , USA
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206
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Perez-Nievas BG, Serrano-Pozo A. Deciphering the Astrocyte Reaction in Alzheimer's Disease. Front Aging Neurosci 2018; 10:114. [PMID: 29922147 PMCID: PMC5996928 DOI: 10.3389/fnagi.2018.00114] [Citation(s) in RCA: 174] [Impact Index Per Article: 29.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2018] [Accepted: 04/03/2018] [Indexed: 12/24/2022] Open
Abstract
Reactive astrocytes were identified as a component of senile amyloid plaques in the cortex of Alzheimer's disease (AD) patients several decades ago. However, their role in AD pathophysiology has remained elusive ever since, in part owing to the extrapolation of the literature from primary astrocyte cultures and acute brain injury models to a chronic neurodegenerative scenario. Recent accumulating evidence supports the idea that reactive astrocytes in AD acquire neurotoxic properties, likely due to both a gain of toxic function and a loss of their neurotrophic effects. However, the diversity and complexity of this glial cell is only beginning to be unveiled, anticipating that astrocyte reaction might be heterogeneous as well. Herein we review the evidence from mouse models of AD and human neuropathological studies and attempt to decipher the main conundrums that astrocytes pose to our understanding of AD development and progression. We discuss the morphological features that characterize astrocyte reaction in the AD brain, the consequences of astrocyte reaction for both astrocyte biology and AD pathological hallmarks, and the molecular pathways that have been implicated in this reaction.
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Affiliation(s)
| | - Alberto Serrano-Pozo
- Alzheimer's Research Unit, MassGeneral Institute for Neurodegenerative Diseases (MIND), Department of Neurology, Massachusetts General Hospital, Boston, MA, United States
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207
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Lundgaard I, Wang W, Eberhardt A, Vinitsky HS, Reeves BC, Peng S, Lou N, Hussain R, Nedergaard M. Beneficial effects of low alcohol exposure, but adverse effects of high alcohol intake on glymphatic function. Sci Rep 2018; 8:2246. [PMID: 29396480 PMCID: PMC5797082 DOI: 10.1038/s41598-018-20424-y] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2017] [Accepted: 01/18/2018] [Indexed: 12/16/2022] Open
Abstract
Prolonged intake of excessive amounts of ethanol is known to have adverse effects on the central nervous system (CNS). Here we investigated the effects of acute and chronic ethanol exposure and withdrawal from chronic ethanol exposure on glymphatic function, which is a brain-wide metabolite clearance system connected to the peripheral lymphatic system. Acute and chronic exposure to 1.5 g/kg (binge level) ethanol dramatically suppressed glymphatic function in awake mice. Chronic exposure to 1.5 g/kg ethanol increased GFAP expression and induced mislocation of the astrocyte-specific water channel aquaporin 4 (AQP4), but decreased the levels of several cytokines. Surprisingly, glymphatic function increased in mice treated with 0.5 g/kg (low dose) ethanol following acute exposure, as well as after one month of chronic exposure. Low doses of chronic ethanol intake were associated with a significant decrease in GFAP expression, with little change in the cytokine profile compared with the saline group. These observations suggest that ethanol has a J-shaped effect on the glymphatic system whereby low doses of ethanol increase glymphatic function. Conversely, chronic 1.5 g/kg ethanol intake induced reactive gliosis and perturbed glymphatic function, which possibly may contribute to the higher risk of dementia observed in heavy drinkers.
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Affiliation(s)
- Iben Lundgaard
- Center for Translational Neuromedicine, Department of Neurosurgery, University of Rochester, Rochester, NY, 14642, USA.
| | - Wei Wang
- Center for Translational Neuromedicine, Department of Neurosurgery, University of Rochester, Rochester, NY, 14642, USA
| | - Allison Eberhardt
- Center for Translational Neuromedicine, Department of Neurosurgery, University of Rochester, Rochester, NY, 14642, USA
| | - Hanna Sophia Vinitsky
- Center for Translational Neuromedicine, Department of Neurosurgery, University of Rochester, Rochester, NY, 14642, USA
| | - Benjamin Cameron Reeves
- Center for Translational Neuromedicine, Department of Neurosurgery, University of Rochester, Rochester, NY, 14642, USA
| | - Sisi Peng
- Center for Translational Neuromedicine, Department of Neurosurgery, University of Rochester, Rochester, NY, 14642, USA
- Department of Radiology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Nanhong Lou
- Center for Translational Neuromedicine, Department of Neurosurgery, University of Rochester, Rochester, NY, 14642, USA
| | - Rashad Hussain
- Center for Translational Neuromedicine, Department of Neurosurgery, University of Rochester, Rochester, NY, 14642, USA
| | - Maiken Nedergaard
- Center for Translational Neuromedicine, Department of Neurosurgery, University of Rochester, Rochester, NY, 14642, USA
- Center for Basic and Translational Neuroscience, University of Copenhagen, 2200, Copenhagen, Denmark
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208
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Bacyinski A, Xu M, Wang W, Hu J. The Paravascular Pathway for Brain Waste Clearance: Current Understanding, Significance and Controversy. Front Neuroanat 2017; 11:101. [PMID: 29163074 PMCID: PMC5681909 DOI: 10.3389/fnana.2017.00101] [Citation(s) in RCA: 101] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2017] [Accepted: 10/24/2017] [Indexed: 12/03/2022] Open
Abstract
The paravascular pathway, also known as the “glymphatic” pathway, is a recently described system for waste clearance in the brain. According to this model, cerebrospinal fluid (CSF) enters the paravascular spaces surrounding penetrating arteries of the brain, mixes with interstitial fluid (ISF) and solutes in the parenchyma, and exits along paravascular spaces of draining veins. Studies have shown that metabolic waste products and solutes, including proteins involved in the pathogenesis of neurodegenerative diseases such as amyloid-beta, may be cleared by this pathway. Consequently, a growing body of research has begun to explore the association between glymphatic dysfunction and various disease states. However, significant controversy exists in the literature regarding both the direction of waste clearance as well as the anatomical space in which the waste-fluid mixture is contained. Some studies have found no evidence of interstitial solute clearance along the paravascular space of veins. Rather, they demonstrate a perivascular pathway in which waste is cleared from the brain along an anatomically distinct perivascular space in a direction opposite to that of paravascular flow. Although possible explanations have been offered, none have been able to fully reconcile the discrepancies in the literature, and many questions remain. Given the therapeutic potential that a comprehensive understanding of brain waste clearance pathways might offer, further research and clarification is highly warranted.
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Affiliation(s)
- Andrew Bacyinski
- School of Medicine, Wayne State University, Detroit, MI, United States
| | - Maosheng Xu
- Department of Radiology, The First Affiliated Hospital of Zhejiang Chinese Medical University, Hangzhou, China
| | - Wei Wang
- Department of Radiology, The First Affiliated Hospital of Zhejiang Chinese Medical University, Hangzhou, China
| | - Jiani Hu
- Department of Radiology, Wayne State University, Detroit, MI, United States
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209
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von Holstein-Rathlou S, Petersen NC, Nedergaard M. Voluntary running enhances glymphatic influx in awake behaving, young mice. Neurosci Lett 2017; 662:253-258. [PMID: 29079431 DOI: 10.1016/j.neulet.2017.10.035] [Citation(s) in RCA: 69] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2017] [Revised: 10/17/2017] [Accepted: 10/19/2017] [Indexed: 12/31/2022]
Abstract
Vascular pathology and protein accumulation contribute to cognitive decline, whereas exercise can slow vascular degeneration and improve cognitive function. Recent investigations suggest that glymphatic clearance measured in aged mice while anesthetized is enhanced following exercise. We predicted that exercise would also stimulate glymphatic activity in awake, young mice with higher baseline glymphatic function. Therefore, we assessed glymphatic function in young female C57BL/6J mice following five weeks voluntary wheel running and in sedentary mice. The active mice ran a mean distance of 6km daily. We injected fluorescent tracers in cisterna magna of awake behaving mice and in ketamine/xylazine anesthetized mice, and later assessed tracer distribution in coronal brain sections. Voluntary exercise consistently increased CSF influx during wakefulness, primarily in the hypothalamus and ventral parts of the cortex, but also in the middle cerebral artery territory. While glymphatic activity was higher under ketamine/xylazine anesthesia, we saw a decrease in glymphatic function during running in awake mice after five weeks of wheel running. In summary, daily running increases CSF flux in widespread areas of the mouse brain, which may contribute to the pro-cognitive effects of exercise.
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Affiliation(s)
| | | | - Maiken Nedergaard
- Center for Translational Neuromedicine, University of Copenhagen, 2200 Copenhagen, Denmark; Center for Translational Neuromedicine, Division of Glial Disease and Therapeutics, University of Rochester Medical Center, Rochester, New York 14642, USA
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210
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Perivascular spaces, glymphatic dysfunction, and small vessel disease. Clin Sci (Lond) 2017; 131:2257-2274. [PMID: 28798076 DOI: 10.1042/cs20160381] [Citation(s) in RCA: 217] [Impact Index Per Article: 31.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2017] [Revised: 07/09/2017] [Accepted: 07/24/2017] [Indexed: 01/12/2023]
Abstract
Cerebral small vessel diseases (SVDs) range broadly in etiology but share remarkably overlapping pathology. Features of SVD including enlarged perivascular spaces (EPVS) and formation of abluminal protein deposits cannot be completely explained by the putative pathophysiology. The recently discovered glymphatic system provides a new perspective to potentially address these gaps. This work provides a comprehensive review of the known factors that regulate glymphatic function and the disease mechanisms underlying glymphatic impairment emphasizing the role that aquaporin-4 (AQP4)-lined perivascular spaces (PVSs), cerebrovascular pulsatility, and metabolite clearance play in normal CNS physiology. This review also discusses the implications that glymphatic impairment may have on SVD inception and progression with the aim of exploring novel therapeutic targets and highlighting the key questions that remain to be answered.
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