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Lagarde S, Modolo J, Yochum M, Carvallo A, Ballabeni A, Scavarda D, Carron R, Villeneuve N, Bartolomei F, Wendling F. Modification of brain conductivity in human focal epilepsy: A model-based estimation from stereoelectroencephalography. Epilepsia 2024; 65:1744-1755. [PMID: 38491955 DOI: 10.1111/epi.17957] [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: 12/18/2023] [Revised: 03/04/2024] [Accepted: 03/05/2024] [Indexed: 03/18/2024]
Abstract
OBJECTIVE We have developed a novel method for estimating brain tissue electrical conductivity using low-intensity pulse stereoelectroencephalography (SEEG) stimulation coupled with biophysical modeling. We evaluated the hypothesis that brain conductivity is correlated with the degree of epileptogenicity in patients with drug-resistant focal epilepsy. METHODS We used bipolar low-intensity biphasic pulse stimulation (.2 mA) followed by a postprocessing pipeline for estimating brain conductivity. This processing is based on biophysical modeling of the electrical potential induced in brain tissue between the stimulated contacts in response to pulse stimulation. We estimated the degree of epileptogenicity using a semi-automatic method quantifying the dynamic of fast discharge at seizure onset: the epileptogenicity index (EI). We also investigated how the location of stimulation within specific anatomical brain regions or within lesional tissue impacts brain conductivity. RESULTS We performed 1034 stimulations of 511 bipolar channels in 16 patients. We found that brain conductivity was lower in the epileptogenic zone (EZ; unpaired median difference = .064, p < .001) and inversely correlated with the epileptogenic index value (p < .001, Spearman rho = -.32). Conductivity values were also influenced by anatomical site, location within lesion, and delay between SEEG electrode implantation and stimulation, and had significant interpatient variability. Mixed model multivariate analysis showed that conductivity is significantly associated with EI (F = 13.45, p < .001), anatomical regions (F = 5.586, p < .001), delay since implantation (F = 14.71, p = .003), and age at SEEG (F = 6.591, p = .027), but not with the type of lesion (F = .372, p = .773) or the delay since last seizure (F = 1.592, p = .235). SIGNIFICANCE We provide a novel model-based method for estimating brain conductivity from SEEG low-intensity pulse stimulations. The brain tissue conductivity is lower in EZ as compared to non-EZ. Conductivity also varies significantly across anatomical brain regions. Involved pathophysiological processes may include changes in the extracellular space (especially volume or tortuosity) in epileptic tissue.
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Affiliation(s)
- Stanislas Lagarde
- Epileptology and Cerebral Rhythmology Department (member of the ERN EpiCARE Network), APHM, Timone Hospital, Marseille, France
- INS, Institut de Neurosciences des Systèmes, Aix Marseille University, INSERM, Marseille, France
- University Hospitals (HUG) and University of Geneva (UNIGE), Geneva, Switzerland
| | - Julien Modolo
- LTSI - U1099, University of Rennes, INSERM, Rennes, France
| | - Maxime Yochum
- LTSI - U1099, University of Rennes, INSERM, Rennes, France
| | | | - Alice Ballabeni
- Epileptology and Cerebral Rhythmology Department (member of the ERN EpiCARE Network), APHM, Timone Hospital, Marseille, France
- University of Modena and Reggio-Emilia, Modena, Italy
| | - Didier Scavarda
- INS, Institut de Neurosciences des Systèmes, Aix Marseille University, INSERM, Marseille, France
- Pediatric Neurosurgery Department, APHM, Timone Hospital, Marseille, France
| | - Romain Carron
- INS, Institut de Neurosciences des Systèmes, Aix Marseille University, INSERM, Marseille, France
- Stereotactic and Functional Neurosurgery Department, APHM, Timone Hospital, Marseille, France
| | | | - Fabrice Bartolomei
- Epileptology and Cerebral Rhythmology Department (member of the ERN EpiCARE Network), APHM, Timone Hospital, Marseille, France
- INS, Institut de Neurosciences des Systèmes, Aix Marseille University, INSERM, Marseille, France
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Xie J, Li H, Su S, Cheng J, Cai Q, Tan H, Zu L, Qu X, Han H. Quantitative analysis of molecular transport in the extracellular space using physics-informed neural network. Comput Biol Med 2024; 171:108133. [PMID: 38364661 DOI: 10.1016/j.compbiomed.2024.108133] [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: 01/23/2024] [Revised: 02/06/2024] [Accepted: 02/12/2024] [Indexed: 02/18/2024]
Abstract
The brain extracellular space (ECS), an irregular, extremely tortuous nanoscale space located between cells or between cells and blood vessels, is crucial for nerve cell survival. It plays a pivotal role in high-level brain functions such as memory, emotion, and sensation. However, the specific form of molecular transport within the ECS remain elusive. To address this challenge, this paper proposes a novel approach to quantitatively analyze the molecular transport within the ECS by solving an inverse problem derived from the advection-diffusion equation (ADE) using a physics-informed neural network (PINN). PINN provides a streamlined solution to the ADE without the need for intricate mathematical formulations or grid settings. Additionally, the optimization of PINN facilitates the automatic computation of the diffusion coefficient governing long-term molecule transport and the velocity of molecules driven by advection. Consequently, the proposed method allows for the quantitative analysis and identification of the specific pattern of molecular transport within the ECS through the calculation of the Péclet number. Experimental validation on two datasets of magnetic resonance images (MRIs) captured at different time points showcases the effectiveness of the proposed method. Notably, our simulations reveal identical molecular transport patterns between datasets representing rats with tracer injected into the same brain region. These findings highlight the potential of PINN as a promising tool for comprehensively exploring molecular transport within the ECS.
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Affiliation(s)
- Jiayi Xie
- Department of Automation, Tsinghua University, Beijing 100084, China; Institute of Medical Technology, Peking University Health Science Center, Beijing 100191, China
| | - Hongfeng Li
- Institute of Medical Technology, Peking University Health Science Center, Beijing 100191, China
| | - Shaoyi Su
- Institute of Medical Technology, Peking University Health Science Center, Beijing 100191, China
| | - Jin Cheng
- School of Mathematical Sciences, Fudan University, Shanghai 200433, China
| | - Qingrui Cai
- National Integrated Circuit Industry Education Integration Innovation Platform, School of Electronic Science and Engineering (National Model Microelectronics College), Xiamen University, Xiamen 361102, China; Department of Electronic Science, Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance, Xiamen University, Xiamen 361102, China
| | - Hanbo Tan
- Institute of Medical Technology, Peking University Health Science Center, Beijing 100191, China
| | - Lingyun Zu
- Department of Endocrinology and Metabolism, Department of Cardiology and Institute of Vascular Medicine, Peking University Third Hospital, Beijing 100191, China
| | - Xiaobo Qu
- National Integrated Circuit Industry Education Integration Innovation Platform, School of Electronic Science and Engineering (National Model Microelectronics College), Xiamen University, Xiamen 361102, China; Department of Electronic Science, Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance, Xiamen University, Xiamen 361102, China
| | - Hongbin Han
- Institute of Medical Technology, Peking University Health Science Center, Beijing 100191, China; Department of Radiology, Peking University Third Hospital, Beijing 100191, China; Peking University Third Hospital, Beijing Key Laboratory of Magnetic Resonance Imaging Devices and Technology, Beijing 100191, China; NMPA key Laboratory of Evaluation of Medical Imaging Equipment and Technique, Beijing 100191, China.
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3
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Mivalt F, Kremen V, Sladky V, Cui J, Gregg NM, Balzekas I, Marks V, St Louis EK, Croarkin P, Lundstrom BN, Nelson N, Kim J, Hermes D, Messina S, Worrell S, Richner T, Brinkmann BH, Denison T, Miller KJ, Van Gompel J, Stead M, Worrell GA. Impedance Rhythms in Human Limbic System. J Neurosci 2023; 43:6653-6666. [PMID: 37620157 PMCID: PMC10538585 DOI: 10.1523/jneurosci.0241-23.2023] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2023] [Revised: 08/09/2023] [Accepted: 08/14/2023] [Indexed: 08/26/2023] Open
Abstract
The impedance is a fundamental electrical property of brain tissue, playing a crucial role in shaping the characteristics of local field potentials, the extent of ephaptic coupling, and the volume of tissue activated by externally applied electrical brain stimulation. We tracked brain impedance, sleep-wake behavioral state, and epileptiform activity in five people with epilepsy living in their natural environment using an investigational device. The study identified impedance oscillations that span hours to weeks in the amygdala, hippocampus, and anterior nucleus thalamus. The impedance in these limbic brain regions exhibit multiscale cycles with ultradian (∼1.5-1.7 h), circadian (∼21.6-26.4 h), and infradian (∼20-33 d) periods. The ultradian and circadian period cycles are driven by sleep-wake state transitions between wakefulness, nonrapid eye movement (NREM) sleep, and rapid eye movement (REM) sleep. Limbic brain tissue impedance reaches a minimum value in NREM sleep, intermediate values in REM sleep, and rises through the day during wakefulness, reaching a maximum in the early evening before sleep onset. Infradian (∼20-33 d) impedance cycles were not associated with a distinct behavioral correlate. Brain tissue impedance is known to strongly depend on the extracellular space (ECS) volume, and the findings reported here are consistent with sleep-wake-dependent ECS volume changes recently observed in the rodent cortex related to the brain glymphatic system. We hypothesize that human limbic brain ECS changes during sleep-wake state transitions underlie the observed multiscale impedance cycles. Impedance is a simple electrophysiological biomarker that could prove useful for tracking ECS dynamics in human health, disease, and therapy.SIGNIFICANCE STATEMENT The electrical impedance in limbic brain structures (amygdala, hippocampus, anterior nucleus thalamus) is shown to exhibit oscillations over multiple timescales. We observe that impedance oscillations with ultradian and circadian periodicities are associated with transitions between wakefulness, NREM, and REM sleep states. There are also impedance oscillations spanning multiple weeks that do not have a clear behavioral correlate and whose origin remains unclear. These multiscale impedance oscillations will have an impact on extracellular ionic currents that give rise to local field potentials, ephaptic coupling, and the tissue activated by electrical brain stimulation. The approach for measuring tissue impedance using perturbational electrical currents is an established engineering technique that may be useful for tracking ECS volume.
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Affiliation(s)
- Filip Mivalt
- Bioelectronics Neurophysiology and Engineering Laboratory, Department of Neurology, Mayo Clinic, Rochester, Minnesota 55905
- Department of Biomedical Engineering, Faculty of Electrical Engineering and Communication, Brno University of Technology, 61600 Brno, Czech Republic
- International Clinical Research Center, St. Anne's University Hospital, 60200 Brno, Czech Republic
| | - Vaclav Kremen
- Bioelectronics Neurophysiology and Engineering Laboratory, Department of Neurology, Mayo Clinic, Rochester, Minnesota 55905
- Czech Institute of Informatics, Robotics, and Cybernetics, Czech Technical University, 16000 Prague, Czech Republic
| | - Vladimir Sladky
- Bioelectronics Neurophysiology and Engineering Laboratory, Department of Neurology, Mayo Clinic, Rochester, Minnesota 55905
- International Clinical Research Center, St. Anne's University Hospital, 60200 Brno, Czech Republic
- Faculty of Biomedical Engineering, Czech Technical University, 16000 Prague, Czech Republic
| | - Jie Cui
- Bioelectronics Neurophysiology and Engineering Laboratory, Department of Neurology, Mayo Clinic, Rochester, Minnesota 55905
| | - Nicholas M Gregg
- Bioelectronics Neurophysiology and Engineering Laboratory, Department of Neurology, Mayo Clinic, Rochester, Minnesota 55905
| | - Irena Balzekas
- Bioelectronics Neurophysiology and Engineering Laboratory, Department of Neurology, Mayo Clinic, Rochester, Minnesota 55905
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota 55905
| | - Victoria Marks
- Bioelectronics Neurophysiology and Engineering Laboratory, Department of Neurology, Mayo Clinic, Rochester, Minnesota 55905
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota 55905
| | - Erik K St Louis
- Center for Sleep Medicine, Departments of Neurology and Medicine, Divisions of Sleep Neurology and Pulmonary and Critical Care Medicine, Mayo Clinic, Rochester, Minnesota 55905
| | | | - Brian Nils Lundstrom
- Bioelectronics Neurophysiology and Engineering Laboratory, Department of Neurology, Mayo Clinic, Rochester, Minnesota 55905
| | - Noelle Nelson
- Bioelectronics Neurophysiology and Engineering Laboratory, Department of Neurology, Mayo Clinic, Rochester, Minnesota 55905
| | - Jiwon Kim
- Bioelectronics Neurophysiology and Engineering Laboratory, Department of Neurology, Mayo Clinic, Rochester, Minnesota 55905
| | - Dora Hermes
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota 55905
| | - Steven Messina
- Department of Radiology, Mayo Clinic Rochester, Minnesota 55905
| | - Samuel Worrell
- Bioelectronics Neurophysiology and Engineering Laboratory, Department of Neurology, Mayo Clinic, Rochester, Minnesota 55905
| | - Thomas Richner
- Bioelectronics Neurophysiology and Engineering Laboratory, Department of Neurology, Mayo Clinic, Rochester, Minnesota 55905
| | - Benjamin H Brinkmann
- Bioelectronics Neurophysiology and Engineering Laboratory, Department of Neurology, Mayo Clinic, Rochester, Minnesota 55905
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota 55905
| | - Timothy Denison
- Department of Engineering Science, Medical Research Council Brain Network Dynamics Unit, University of Oxford, Oxford OX3 7DQ, United Kingdom
| | - Kai J Miller
- Department of Neurologic Surgery, Mayo Clinic, Rochester, Minnesota 55905
| | - Jamie Van Gompel
- Department of Neurologic Surgery, Mayo Clinic, Rochester, Minnesota 55905
| | - Matthew Stead
- Bioelectronics Neurophysiology and Engineering Laboratory, Department of Neurology, Mayo Clinic, Rochester, Minnesota 55905
| | - Gregory A Worrell
- Bioelectronics Neurophysiology and Engineering Laboratory, Department of Neurology, Mayo Clinic, Rochester, Minnesota 55905
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota 55905
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Toader C, Tataru CP, Florian IA, Covache-Busuioc RA, Dumitrascu DI, Glavan LA, Costin HP, Bratu BG, Ciurea AV. From Homeostasis to Pathology: Decoding the Multifaceted Impact of Aquaporins in the Central Nervous System. Int J Mol Sci 2023; 24:14340. [PMID: 37762642 PMCID: PMC10531540 DOI: 10.3390/ijms241814340] [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: 09/02/2023] [Revised: 09/15/2023] [Accepted: 09/18/2023] [Indexed: 09/29/2023] Open
Abstract
Aquaporins (AQPs), integral membrane proteins facilitating selective water and solute transport across cell membranes, have been the focus of extensive research over the past few decades. Particularly noteworthy is their role in maintaining cellular homeostasis and fluid balance in neural compartments, as dysregulated AQP expression is implicated in various degenerative and acute brain pathologies. This article provides an exhaustive review on the evolutionary history, molecular classification, and physiological relevance of aquaporins, emphasizing their significance in the central nervous system (CNS). The paper journeys through the early studies of water transport to the groundbreaking discovery of Aquaporin 1, charting the molecular intricacies that make AQPs unique. It delves into AQP distribution in mammalian systems, detailing their selective permeability through permeability assays. The article provides an in-depth exploration of AQP4 and AQP1 in the brain, examining their contribution to fluid homeostasis. Furthermore, it elucidates the interplay between AQPs and the glymphatic system, a critical framework for waste clearance and fluid balance in the brain. The dysregulation of AQP-mediated processes in this system hints at a strong association with neurodegenerative disorders such as Parkinson's Disease, idiopathic normal pressure hydrocephalus, and Alzheimer's Disease. This relationship is further explored in the context of acute cerebral events such as stroke and autoimmune conditions such as neuromyelitis optica (NMO). Moreover, the article scrutinizes AQPs at the intersection of oncology and neurology, exploring their role in tumorigenesis, cell migration, invasiveness, and angiogenesis. Lastly, the article outlines emerging aquaporin-targeted therapies, offering a glimpse into future directions in combatting CNS malignancies and neurodegenerative diseases.
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Affiliation(s)
- Corneliu Toader
- Department of Neurosurgery, “Carol Davila” University of Medicine and Pharmacy, 020021 Bucharest, Romania; (C.T.); (R.-A.C.-B.); (D.-I.D.); (L.A.G.); (H.P.C.); (B.-G.B.); (A.V.C.)
- Department of Vascular Neurosurgery, National Institute of Neurology and Neurovascular Diseases, 077160 Bucharest, Romania
| | - Calin Petru Tataru
- Department of Opthamology, “Carol Davila” University of Medicine and Pharmacy, 020021 Bucharest, Romania
- Central Military Emergency Hospital “Dr. Carol Davila”, 010825 Bucharest, Romania
| | - Ioan-Alexandru Florian
- Department of Neurosciences, “Iuliu Hatieganu” University of Medicine and Pharmacy, 400012 Cluj-Napoca, Romania
| | - Razvan-Adrian Covache-Busuioc
- Department of Neurosurgery, “Carol Davila” University of Medicine and Pharmacy, 020021 Bucharest, Romania; (C.T.); (R.-A.C.-B.); (D.-I.D.); (L.A.G.); (H.P.C.); (B.-G.B.); (A.V.C.)
| | - David-Ioan Dumitrascu
- Department of Neurosurgery, “Carol Davila” University of Medicine and Pharmacy, 020021 Bucharest, Romania; (C.T.); (R.-A.C.-B.); (D.-I.D.); (L.A.G.); (H.P.C.); (B.-G.B.); (A.V.C.)
| | - Luca Andrei Glavan
- Department of Neurosurgery, “Carol Davila” University of Medicine and Pharmacy, 020021 Bucharest, Romania; (C.T.); (R.-A.C.-B.); (D.-I.D.); (L.A.G.); (H.P.C.); (B.-G.B.); (A.V.C.)
| | - Horia Petre Costin
- Department of Neurosurgery, “Carol Davila” University of Medicine and Pharmacy, 020021 Bucharest, Romania; (C.T.); (R.-A.C.-B.); (D.-I.D.); (L.A.G.); (H.P.C.); (B.-G.B.); (A.V.C.)
| | - Bogdan-Gabriel Bratu
- Department of Neurosurgery, “Carol Davila” University of Medicine and Pharmacy, 020021 Bucharest, Romania; (C.T.); (R.-A.C.-B.); (D.-I.D.); (L.A.G.); (H.P.C.); (B.-G.B.); (A.V.C.)
| | - Alexandru Vlad Ciurea
- Department of Neurosurgery, “Carol Davila” University of Medicine and Pharmacy, 020021 Bucharest, Romania; (C.T.); (R.-A.C.-B.); (D.-I.D.); (L.A.G.); (H.P.C.); (B.-G.B.); (A.V.C.)
- Neurosurgery Department, Sanador Clinical Hospital, 010991 Bucharest, Romania
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Warren KE, Coupland KG, Hood RJ, Kang L, Walker FR, Spratt NJ. Movement of cerebrospinal fluid tracer into brain parenchyma and outflow to nasal mucosa is reduced at 24 h but not 2 weeks post-stroke in mice. Fluids Barriers CNS 2023; 20:27. [PMID: 37041551 PMCID: PMC10088200 DOI: 10.1186/s12987-023-00427-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2022] [Accepted: 03/27/2023] [Indexed: 04/13/2023] Open
Abstract
BACKGROUND Recent data indicates that cerebrospinal fluid (CSF) dynamics are disturbed after stroke. Our lab has previously shown that intracranial pressure rises dramatically 24 h after experimental stroke and that this reduces blood flow to ischaemic tissue. CSF outflow resistance is increased at this time point. We hypothesised that reduced transit of CSF through brain parenchyma and reduced outflow of CSF via the cribriform plate at 24 h after stroke may contribute to the previously identified post-stroke intracranial pressure elevation. METHODS Using a photothrombotic permanent occlusion model of stroke in C57BL/6 adult male mice, we examined the movement of an intracisternally infused 0.5% Texas Red dextran throughout the brain and measured tracer efflux into the nasal mucosa via the cribriform plate at 24 h or two weeks after stroke. Brain tissue and nasal mucosa were collected ex vivo and imaged using fluorescent microscopy to determine the change in CSF tracer intensity in these tissues. RESULTS At 24 h after stroke, we found that CSF tracer load was significantly reduced in brain tissue from stroke animals in both the ipsilateral and contralateral hemispheres when compared to sham. CSF tracer load was also reduced in the lateral region of the ipsilateral hemisphere when compared to the contralateral hemisphere in stroke brains. In addition, we identified an 81% reduction in CSF tracer load in the nasal mucosa in stroke animals compared to sham. These alterations to the movement of CSF-borne tracer were not present at two weeks after stroke. CONCLUSIONS Our data indicates that influx of CSF into the brain tissue and efflux via the cribriform plate are reduced 24 h after stroke. This may contribute to reported increases in intracranial pressure at 24 h after stroke and thus worsen stroke outcomes.
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Affiliation(s)
- K E Warren
- School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan and Hunter Medical Research Institute, University Drive, Callaghan, New Lambton Heights, NSW, 2308, Australia
- Hunter New England Health District, New Lambton Heights, NSW, Australia
| | - K G Coupland
- School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan and Hunter Medical Research Institute, University Drive, Callaghan, New Lambton Heights, NSW, 2308, Australia
- Hunter New England Health District, New Lambton Heights, NSW, Australia
| | - R J Hood
- School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan and Hunter Medical Research Institute, University Drive, Callaghan, New Lambton Heights, NSW, 2308, Australia
- Hunter New England Health District, New Lambton Heights, NSW, Australia
| | - L Kang
- School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan and Hunter Medical Research Institute, University Drive, Callaghan, New Lambton Heights, NSW, 2308, Australia
- Hunter New England Health District, New Lambton Heights, NSW, Australia
| | - F R Walker
- School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan and Hunter Medical Research Institute, University Drive, Callaghan, New Lambton Heights, NSW, 2308, Australia
- Hunter New England Health District, New Lambton Heights, NSW, Australia
| | - N J Spratt
- School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan and Hunter Medical Research Institute, University Drive, Callaghan, New Lambton Heights, NSW, 2308, Australia.
- Hunter New England Health District, New Lambton Heights, NSW, Australia.
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Nieves Torres D, Lee SH. Inter-neuronal signaling mediated by small extracellular vesicles: wireless communication? Front Mol Neurosci 2023; 16:1187300. [PMID: 37181650 PMCID: PMC10172472 DOI: 10.3389/fnmol.2023.1187300] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2023] [Accepted: 04/03/2023] [Indexed: 05/16/2023] Open
Abstract
Conventional inter-neuronal communication conceptualizes the wired method of chemical synapses that physically connect pre-and post-synaptic neurons. In contrast, recent studies indicate that neurons also utilize synapse-independent, hence "wireless" broadcasting-type communications via small extracellular vesicles (EVs). Small EVs including exosomes are secreted vesicles released by cells and contain a variety of signaling molecules including mRNAs, miRNAs, lipids, and proteins. Small EVs are subsequently absorbed by local recipient cells via either membrane fusion or endocytic processes. Therefore, small EVs enable cells to exchange a "packet" of active biomolecules for communication purposes. It is now well established that central neurons also secrete and uptake small EVs, especially exosomes, a type of small EVs that are derived from the intraluminal vesicles of multivesicular bodies. Specific molecules carried by neuronal small EVs are shown to affect a variety of neuronal functions including axon guidance, synapse formation, synapse elimination, neuronal firing, and potentiation. Therefore, this type of volume transmission mediated by small EVs is thought to play important roles not only in activity-dependent changes in neuronal function but also in the maintenance and homeostatic control of local circuitry. In this review, we summarize recent discoveries, catalog neuronal small EV-specific biomolecules, and discuss the potential scope of small EV-mediated inter-neuronal signaling.
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Affiliation(s)
- Damaris Nieves Torres
- Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, WI, United States
| | - Sang H Lee
- Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, WI, United States
- Neuroscience Research Institute, Medical College of Wisconsin, Milwaukee, WI, United States
- *Correspondence: Sang H. Lee,
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7
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Walch E, Fiacco TA. Honey, I shrunk the extracellular space: Measurements and mechanisms of astrocyte swelling. Glia 2022; 70:2013-2031. [PMID: 35635369 PMCID: PMC9474570 DOI: 10.1002/glia.24224] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2022] [Revised: 05/17/2022] [Accepted: 05/17/2022] [Indexed: 12/16/2022]
Abstract
Astrocyte volume fluctuation is a physiological phenomenon tied closely to the activation of neural circuits. Identification of underlying mechanisms has been challenging due in part to use of a wide range of experimental approaches that vary between research groups. Here, we first review the many methods that have been used to measure astrocyte volume changes directly or indirectly. While the field has recently shifted towards volume analysis using fluorescence microscopy to record cell volume changes directly, established metrics corresponding to extracellular space dynamics have also yielded valuable insights. We then turn to analysis of mechanisms of astrocyte swelling derived from many studies, with a focus on volume changes tied to increases in extracellular potassium concentration ([K+ ]o ). The diverse methods that have been utilized to generate the external [K+ ]o environment highlight multiple scenarios of astrocyte swelling mediated by different mechanisms. Classical potassium buffering theories are tempered by many recent studies that point to different swelling pathways optimized at particular [K+ ]o and that depend on local/transient versus more sustained increases in [K+ ]o .
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Affiliation(s)
- Erin Walch
- Division of Biomedical Sciences, School of MedicineUniversity of California, RiversideRiversideCaliforniaUSA
| | - Todd A. Fiacco
- Department of Molecular, Cell and Systems BiologyUniversity of California, RiversideRiversideCaliforniaUSA
- Center for Glial‐Neuronal InteractionsUniversity of California, RiversideRiversideCaliforniaUSA
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8
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Plá V, Bork P, Harnpramukkul A, Olveda G, Ladrón-de-Guevara A, Giannetto MJ, Hussain R, Wang W, Kelley DH, Hablitz LM, Nedergaard M. A real-time in vivo clearance assay for quantification of glymphatic efflux. Cell Rep 2022; 40:111320. [PMID: 36103828 DOI: 10.1016/j.celrep.2022.111320] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2021] [Revised: 02/05/2022] [Accepted: 08/16/2022] [Indexed: 11/03/2022] Open
Abstract
Glymphatic fluid transport eliminates metabolic waste from the brain including amyloid-β, yet the methodology for studying efflux remains rudimentary. Here, we develop a method to evaluate glymphatic real-time clearance. Efflux of Direct Blue 53 (DB53, also T-1824 or Evans Blue) injected into the striatum is quantified by imaging the DB53 signal in the vascular compartment, where it is retained due to its high affinity to albumin. The DB53 signal is detectable as early as 15 min after injection and the efflux kinetics are sharply reduced in mice lacking the water channel aquaporin 4 (AQP4). Pharmacokinetic modeling reveal that DB53 efflux is consistent with the existence of two efflux paths, one with fast kinetics (T1/2 = 50 min) and another with slow kinetics (T1/2 = 240 min), in wild-type mice. This in vivo methodology will aid in defining the physiological variables that drive efflux, as well as the impact of brain states or disorders on clearance kinetics.
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Affiliation(s)
- Virginia Plá
- Center for Translational Neuromedicine, University of Rochester Medical Center, Rochester, NY 14642, USA
| | - Peter Bork
- Center for Translational Neuromedicine, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Aurakoch Harnpramukkul
- Center for Translational Neuromedicine, University of Rochester Medical Center, Rochester, NY 14642, USA
| | - Genaro Olveda
- Center for Translational Neuromedicine, University of Rochester Medical Center, Rochester, NY 14642, USA
| | - Antonio Ladrón-de-Guevara
- Center for Translational Neuromedicine, University of Rochester Medical Center, Rochester, NY 14642, USA
| | - Michael J Giannetto
- Center for Translational Neuromedicine, University of Rochester Medical Center, Rochester, NY 14642, USA
| | - Rashad Hussain
- Center for Translational Neuromedicine, University of Rochester Medical Center, Rochester, NY 14642, USA
| | - Wei Wang
- Center for Translational Neuromedicine, University of Rochester Medical Center, Rochester, NY 14642, USA
| | - Douglas H Kelley
- Department of Mechanical Engineering, University of Rochester, Rochester, NY 14627, USA
| | - Lauren M Hablitz
- Center for Translational Neuromedicine, University of Rochester Medical Center, Rochester, NY 14642, USA
| | - Maiken Nedergaard
- Center for Translational Neuromedicine, University of Rochester Medical Center, Rochester, NY 14642, USA; Center for Translational Neuromedicine, University of Copenhagen, 2200 Copenhagen, Denmark.
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9
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Xu X, Ge X, Xiong H, Qin Z. Toward dynamic, anisotropic, high-resolution, and functional measurement in the brain extracellular space. NEUROPHOTONICS 2022; 9:032210. [PMID: 35573823 PMCID: PMC9094757 DOI: 10.1117/1.nph.9.3.032210] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/01/2022] [Accepted: 03/31/2022] [Indexed: 06/15/2023]
Abstract
Diffusion of substances in the brain extracellular space (ECS) is important for extrasynaptic communication, extracellular ionic homeostasis, drug delivery, and metabolic waste clearance. However, substance diffusion is largely constrained by the geometry of brain ECS and the extracellular matrix. Investigating the diffusion properties of substances not only reveals the structural information of the brain ECS but also advances the understanding of intercellular signaling of brain cells. Among different techniques for substance diffusion measurement, the optical imaging method is sensitive and straightforward for measuring the dynamics and distribution of fluorescent molecules or sensors and has been used for molecular diffusion measurement in the brain. We mainly discuss recent advances of optical imaging-enabled measurements toward dynamic, anisotropic, high-resolution, and functional aspects of the brain ECS diffusion within the last 5 to 10 years. These developments are made possible by advanced imaging, such as light-sheet microscopy and single-particle tracking in tissue, and new fluorescent biosensors for neurotransmitters. We envision future efforts to map the ECS diffusivity across the brain under healthy and diseased conditions to guide the therapeutic delivery and better understand neurochemical transmissions that are relevant to physiological signaling and functions in brain circuits.
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Affiliation(s)
- Xueqi Xu
- University of Texas at Dallas, Department of Mechanical Engineering, Richardson, Texas, United States
| | - Xiaoqian Ge
- University of Texas at Dallas, Department of Mechanical Engineering, Richardson, Texas, United States
| | - Hejian Xiong
- University of Texas at Dallas, Department of Mechanical Engineering, Richardson, Texas, United States
| | - Zhenpeng Qin
- University of Texas at Dallas, Department of Mechanical Engineering, Richardson, Texas, United States
- University of Texas at Dallas, Department of Bioengineering, Richardson, Texas, United States
- University of Texas at Southwestern Medical Center, Department of Surgery, Richardson, Texas, United States
- University of Texas at Dallas, The Center for Advanced Pain Studies, Richardson, Texas, United States
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10
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Alarcan H, Al Ojaimi Y, Lanznaster D, Escoffre JM, Corcia P, Vourc'h P, Andres CR, Veyrat-Durebex C, Blasco H. Taking Advantages of Blood–Brain or Spinal Cord Barrier Alterations or Restoring Them to Optimize Therapy in ALS? J Pers Med 2022; 12:jpm12071071. [PMID: 35887567 PMCID: PMC9319288 DOI: 10.3390/jpm12071071] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Revised: 06/23/2022] [Accepted: 06/27/2022] [Indexed: 11/21/2022] Open
Abstract
Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disorder that still lacks an efficient therapy. The barriers between the central nervous system (CNS) and the blood represent a major limiting factor to the development of drugs for CNS diseases, including ALS. Alterations of the blood–brain barrier (BBB) or blood–spinal cord barrier (BSCB) have been reported in this disease but still require further investigations. Interestingly, these alterations might be involved in the complex etiology and pathogenesis of ALS. Moreover, they can have potential consequences on the diffusion of candidate drugs across the brain. The development of techniques to bypass these barriers is continuously evolving and might open the door for personalized medical approaches. Therefore, identifying robust and non-invasive markers of BBB and BSCB alterations can help distinguish different subgroups of patients, such as those in whom barrier disruption can negatively affect the delivery of drugs to their CNS targets. The restoration of CNS barriers using innovative therapies could consequently present the advantage of both alleviating the disease progression and optimizing the safety and efficiency of ALS-specific therapies.
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Affiliation(s)
- Hugo Alarcan
- Laboratoire de Biochimie et Biologie Moleculaire, CHRU Bretonneau, 2 Boulevard Tonnellé, 37000 Tours, France
- UMR 1253 iBrain, Université de Tours, Inserm, 10 Boulevard Tonnellé, 37000 Tours, France
| | - Yara Al Ojaimi
- UMR 1253 iBrain, Université de Tours, Inserm, 10 Boulevard Tonnellé, 37000 Tours, France
| | - Debora Lanznaster
- UMR 1253 iBrain, Université de Tours, Inserm, 10 Boulevard Tonnellé, 37000 Tours, France
| | - Jean-Michel Escoffre
- UMR 1253 iBrain, Université de Tours, Inserm, 10 Boulevard Tonnellé, 37000 Tours, France
| | - Philippe Corcia
- UMR 1253 iBrain, Université de Tours, Inserm, 10 Boulevard Tonnellé, 37000 Tours, France
- Service de Neurologie, CHRU Bretonneau, 2 Boulevard Tonnellé, 37000 Tours, France
| | - Patrick Vourc'h
- Laboratoire de Biochimie et Biologie Moleculaire, CHRU Bretonneau, 2 Boulevard Tonnellé, 37000 Tours, France
- UMR 1253 iBrain, Université de Tours, Inserm, 10 Boulevard Tonnellé, 37000 Tours, France
| | - Christian R Andres
- Laboratoire de Biochimie et Biologie Moleculaire, CHRU Bretonneau, 2 Boulevard Tonnellé, 37000 Tours, France
- UMR 1253 iBrain, Université de Tours, Inserm, 10 Boulevard Tonnellé, 37000 Tours, France
| | - Charlotte Veyrat-Durebex
- Laboratoire de Biochimie et Biologie Moleculaire, CHRU Bretonneau, 2 Boulevard Tonnellé, 37000 Tours, France
- UMR 1253 iBrain, Université de Tours, Inserm, 10 Boulevard Tonnellé, 37000 Tours, France
| | - Hélène Blasco
- Laboratoire de Biochimie et Biologie Moleculaire, CHRU Bretonneau, 2 Boulevard Tonnellé, 37000 Tours, France
- UMR 1253 iBrain, Université de Tours, Inserm, 10 Boulevard Tonnellé, 37000 Tours, France
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11
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Hills KE, Kostarelos K, Wykes RC. Converging Mechanisms of Epileptogenesis and Their Insight in Glioblastoma. Front Mol Neurosci 2022; 15:903115. [PMID: 35832394 PMCID: PMC9271928 DOI: 10.3389/fnmol.2022.903115] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2022] [Accepted: 05/25/2022] [Indexed: 12/15/2022] Open
Abstract
Glioblastoma (GBM) is the most common and advanced form of primary malignant tumor occurring in the adult central nervous system, and it is frequently associated with epilepsy, a debilitating comorbidity. Seizures are observed both pre- and post-surgical resection, indicating that several pathophysiological mechanisms are shared but also prompting questions about how the process of epileptogenesis evolves throughout GBM progression. Molecular mutations commonly seen in primary GBM, i.e., in PTEN and p53, and their associated downstream effects are known to influence seizure likelihood. Similarly, various intratumoral mechanisms, such as GBM-induced blood-brain barrier breakdown and glioma-immune cell interactions within the tumor microenvironment are also cited as contributing to network hyperexcitability. Substantial alterations to peri-tumoral glutamate and chloride transporter expressions, as well as widespread dysregulation of GABAergic signaling are known to confer increased epileptogenicity and excitotoxicity. The abnormal characteristics of GBM alter neuronal network function to result in metabolically vulnerable and hyperexcitable peri-tumoral tissue, properties the tumor then exploits to favor its own growth even post-resection. It is evident that there is a complex, dynamic interplay between GBM and epilepsy that promotes the progression of both pathologies. This interaction is only more complicated by the concomitant presence of spreading depolarization (SD). The spontaneous, high-frequency nature of GBM-associated epileptiform activity and SD-associated direct current (DC) shifts require technologies capable of recording brain signals over a wide bandwidth, presenting major challenges for comprehensive electrophysiological investigations. This review will initially provide a detailed examination of the underlying mechanisms that promote network hyperexcitability in GBM. We will then discuss how an investigation of these pathologies from a network level, and utilization of novel electrophysiological tools, will yield a more-effective, clinically-relevant understanding of GBM-related epileptogenesis. Further to this, we will evaluate the clinical relevance of current preclinical research and consider how future therapeutic advancements may impact the bidirectional relationship between GBM, SDs, and seizures.
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Affiliation(s)
- Kate E. Hills
- Nanomedicine Lab, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, United Kingdom
| | - Kostas Kostarelos
- Nanomedicine Lab, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, United Kingdom
- Catalan Institute for Nanoscience and Nanotechnology (ICN2), Edifici ICN2, Campus UAB, Barcelona, Spain
| | - Robert C. Wykes
- Nanomedicine Lab, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, United Kingdom
- Department of Clinical and Experimental Epilepsy, UCL Queen Square Institute of Neurology, London, United Kingdom
- *Correspondence: Robert C. Wykes
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12
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Szu JI, Binder DK. Mechanisms Underlying Aquaporin-4 Subcellular Mislocalization in Epilepsy. Front Cell Neurosci 2022; 16:900588. [PMID: 35734218 PMCID: PMC9207308 DOI: 10.3389/fncel.2022.900588] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2022] [Accepted: 05/10/2022] [Indexed: 11/13/2022] Open
Abstract
Epilepsy is a chronic brain disorder characterized by unprovoked seizures. Mechanisms underlying seizure activity have been intensely investigated. Alterations in astrocytic channels and transporters have shown to be a critical player in seizure generation and epileptogenesis. One key protein involved in such processes is the astrocyte water channel aquaporin-4 (AQP4). Studies have revealed that perivascular AQP4 redistributes away from astrocyte endfeet and toward the neuropil in both clinical and preclinical studies. This subcellular mislocalization significantly impacts neuronal hyperexcitability and understanding how AQP4 becomes dysregulated in epilepsy is beginning to emerge. In this review, we evaluate the role of AQP4 dysregulation and mislocalization in epilepsy.
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13
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Abstract
The brain harbors a unique ability to, figuratively speaking, shift its gears. During wakefulness, the brain is geared fully toward processing information and behaving, while homeostatic functions predominate during sleep. The blood-brain barrier establishes a stable environment that is optimal for neuronal function, yet the barrier imposes a physiological problem; transcapillary filtration that forms extracellular fluid in other organs is reduced to a minimum in brain. Consequently, the brain depends on a special fluid [the cerebrospinal fluid (CSF)] that is flushed into brain along the unique perivascular spaces created by astrocytic vascular endfeet. We describe this pathway, coined the term glymphatic system, based on its dependency on astrocytic vascular endfeet and their adluminal expression of aquaporin-4 water channels facing toward CSF-filled perivascular spaces. Glymphatic clearance of potentially harmful metabolic or protein waste products, such as amyloid-β, is primarily active during sleep, when its physiological drivers, the cardiac cycle, respiration, and slow vasomotion, together efficiently propel CSF inflow along periarterial spaces. The brain's extracellular space contains an abundance of proteoglycans and hyaluronan, which provide a low-resistance hydraulic conduit that rapidly can expand and shrink during the sleep-wake cycle. We describe this unique fluid system of the brain, which meets the brain's requisites to maintain homeostasis similar to peripheral organs, considering the blood-brain-barrier and the paths for formation and egress of the CSF.
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Affiliation(s)
- Martin Kaag Rasmussen
- Center for Translational Neuromedicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Humberto Mestre
- Center for Translational Neuromedicine, University of Rochester Medical Center, Rochester, New York
| | - Maiken Nedergaard
- Center for Translational Neuromedicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
- Center for Translational Neuromedicine, University of Rochester Medical Center, Rochester, New York
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14
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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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15
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Muñoz Y, Cuevas-Pacheco F, Quesseveur G, Murai KK. Light microscopic and heterogeneity analysis of astrocytes in the common marmoset brain. J Neurosci Res 2021; 99:3121-3147. [PMID: 34716617 PMCID: PMC9541330 DOI: 10.1002/jnr.24967] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Revised: 08/19/2021] [Accepted: 08/30/2021] [Indexed: 12/12/2022]
Abstract
Astrocytes are abundant cells of the central nervous system (CNS) and are involved in processes including synapse formation/function, ion homeostasis, neurotransmitter uptake, and neurovascular coupling. Recent evidence indicates that astrocytes show diverse molecular, structural, and physiological properties within the CNS. This heterogeneity is reflected in differences in astrocyte structure, gene expression, functional properties, and responsiveness to injury/pathological conditions. Deeper investigation of astrocytic heterogeneity is needed to understand how astrocytes are configured to enable diverse roles in the CNS. While much has been learned about astrocytic heterogeneity in rodents, much less is known about astrocytic heterogeneity in the primate brain where astrocytes have greater size and complexity. The common marmoset (Callithrix jacchus) is a promising non‐human primate model because of similarities between marmosets and humans with respect to genetics, brain anatomy, and cognition/behavior. Here, we investigated the molecular and structural heterogeneity of marmoset astrocytes using an array of astrocytic markers, multi‐label confocal microscopy, and quantitative analysis. We used male and female marmosets and found that marmoset astrocytes show differences in expression of astrocytic markers in cortex, hippocampus, and cerebellum. These differences were accompanied by intra‐regional variation in expression of markers for glutamate/GABA transporters, and potassium and water channels. Differences in astrocyte structure were also found, along with complex interactions with blood vessels, microglia, and neurons. This study contributes to our knowledge of the cellular and molecular features of marmoset astrocytes and is useful for understanding the complex properties of astrocytes in the primate CNS.
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Affiliation(s)
- Yorka Muñoz
- Centre for Research in Neuroscience, Department of Neurology & Neurosurgery, Brain Repair and Integrative Neuroscience Program, Research Institute of the McGill University Health Centre, Montreal General Hospital, Montreal, QC, Canada
| | - Francisco Cuevas-Pacheco
- Department of Mathematics, Universidad Técnica Federico Santa Maria, Valparaiso, Chile.,Advanced Center for Electrical and Electronic Engineering, Universidad Técnica Federico Santa Maria, Valparaiso, Chile
| | - Gaël Quesseveur
- Centre for Research in Neuroscience, Department of Neurology & Neurosurgery, Brain Repair and Integrative Neuroscience Program, Research Institute of the McGill University Health Centre, Montreal General Hospital, Montreal, QC, Canada
| | - Keith K Murai
- Centre for Research in Neuroscience, Department of Neurology & Neurosurgery, Brain Repair and Integrative Neuroscience Program, Research Institute of the McGill University Health Centre, Montreal General Hospital, Montreal, QC, Canada.,Quantitative Life Sciences Graduate Program, McGill University, Montreal, QC, Canada
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16
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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: 12] [Impact Index Per Article: 4.0] [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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17
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Savtchenko LP, Zheng K, Rusakov DA. Conductance of porous media depends on external electric fields. Biophys J 2021; 120:1431-1442. [PMID: 33609495 PMCID: PMC8105728 DOI: 10.1016/j.bpj.2021.02.012] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Revised: 01/12/2021] [Accepted: 02/01/2021] [Indexed: 11/28/2022] Open
Abstract
In obstacle-filled media, such as extracellular or intracellular lumen of brain tissue, effective ion-diffusion permeability is a key determinant of electrogenic reactions. Although this diffusion permeability is thought to depend entirely on structural features of the medium, such as porosity and tortuosity, brain tissue shows prominent nonohmic properties, the origins of which remain poorly understood. Here, we explore Monte Carlo simulations of ion diffusion in a space filled with overlapping spheres to predict that diffusion permeability of such media decreases with stronger external electric fields. This dependence increases with lower medium porosity while decreasing with radial (two-dimensional or three-dimensional) compared with homogenous (one-dimensional) fields. We test our predictions empirically in an electrolyte chamber filled with microscopic glass spheres and find good correspondence with our predictions. A theoretical insight relates this phenomenon to a disproportionately increased dwell time of diffusing ions at potential barriers (or traps) representing geometric obstacles when the field strength increases. The dependence of medium ion-diffusion permeability on electric field could be important for understanding conductivity properties of porous materials, in particular for the accurate interpretation of electric activity recordings in brain tissue.
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Affiliation(s)
- Leonid P Savtchenko
- UCL Queen Square Institute of Neurology, University College London, London, United Kingdom.
| | - Kaiyu Zheng
- UCL Queen Square Institute of Neurology, University College London, London, United Kingdom
| | - Dmitri A Rusakov
- UCL Queen Square Institute of Neurology, University College London, London, United Kingdom.
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18
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Rao SB, Skauli N, Jovanovic N, Katoozi S, Frigeri A, Froehner SC, Adams ME, Ottersen OP, Amiry-Moghaddam M. Orchestrating aquaporin-4 and connexin-43 expression in brain: Differential roles of α1- and β1-syntrophin. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2021; 1863:183616. [PMID: 33872576 DOI: 10.1016/j.bbamem.2021.183616] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Revised: 03/22/2021] [Accepted: 03/25/2021] [Indexed: 01/09/2023]
Abstract
Aquaporin-4 (AQP4) water channels and gap junction proteins (connexins) are two classes of astrocytic membrane proteins critically involved in brain water and ion homeostasis. AQP4 channels are anchored by α1-syntrophin to the perivascular astrocytic endfoot membrane domains where they control water flux at the blood-brain interface while connexins cluster at the lateral aspects of the astrocytic endfeet forming gap junctions that allow water and ions to dissipate through the astrocyte syncytium. Recent studies have pointed to an interdependence between astrocytic AQP4 and astrocytic gap junctions but the underlying mechanism remains to be explored. Here we use a novel transgenic mouse line to unravel whether β1-syntrophin (coexpressed with α1-syntrophin in astrocytic plasma membranes) is implicated in the expression of AQP4 isoforms and formation of gap junctions in brain. Our results show that while the effect of β1-syntrophin deletion is rather limited, double knockout of α1- and β1-syntrophin causes a downregulation of the novel AQP4 isoform AQP4ex and an increase in the number of astrocytic gap junctions. The present study highlight the importance of syntrophins in orchestrating specialized functional domains of brain astrocytes.
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Affiliation(s)
- Shreyas B Rao
- Laboratory of Molecular Neuroscience, Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Post box 1105, Blindern, 0317 Oslo, Norway.
| | - Nadia Skauli
- Laboratory of Molecular Neuroscience, Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Post box 1105, Blindern, 0317 Oslo, Norway.
| | - Nenad Jovanovic
- Laboratory of Molecular Neuroscience, Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Post box 1105, Blindern, 0317 Oslo, Norway
| | - Shirin Katoozi
- Laboratory of Molecular Neuroscience, Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Post box 1105, Blindern, 0317 Oslo, Norway
| | - Antonio Frigeri
- School of Medicine, Department of Basic Medical Sciences, Neuroscience and Sense Organs, University of Bari Aldo Moro, Bari, Italy.
| | - Stanley C Froehner
- Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195-7290, USA.
| | - Marvin E Adams
- Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195-7290, USA.
| | - Ole Petter Ottersen
- Laboratory of Molecular Neuroscience, Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Post box 1105, Blindern, 0317 Oslo, Norway.
| | - Mahmood Amiry-Moghaddam
- Laboratory of Molecular Neuroscience, Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Post box 1105, Blindern, 0317 Oslo, Norway.
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19
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Alcoreza OB, Patel DC, Tewari BP, Sontheimer H. Dysregulation of Ambient Glutamate and Glutamate Receptors in Epilepsy: An Astrocytic Perspective. Front Neurol 2021; 12:652159. [PMID: 33828523 PMCID: PMC8019783 DOI: 10.3389/fneur.2021.652159] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Accepted: 02/24/2021] [Indexed: 12/16/2022] Open
Abstract
Given the important functions that glutamate serves in excitatory neurotransmission, understanding the regulation of glutamate in physiological and pathological states is critical to devising novel therapies to treat epilepsy. Exclusive expression of pyruvate carboxylase and glutamine synthetase in astrocytes positions astrocytes as essential regulators of glutamate in the central nervous system (CNS). Additionally, astrocytes can significantly alter the volume of the extracellular space (ECS) in the CNS due to their expression of the bi-directional water channel, aquaporin-4, which are enriched at perivascular endfeet. Rapid ECS shrinkage has been observed following epileptiform activity and can inherently concentrate ions and neurotransmitters including glutamate. This review highlights our emerging knowledge on the various potential contributions of astrocytes to epilepsy, particularly supporting the notion that astrocytes may be involved in seizure initiation via failure of homeostatic responses that lead to increased ambient glutamate. We also review the mechanisms whereby ambient glutamate can influence neuronal excitability, including via generation of the glutamate receptor subunit GluN2B-mediated slow inward currents, as well as indirectly affect neuronal excitability via actions on metabotropic glutamate receptors that can potentiate GluN2B currents and influence neuronal glutamate release probabilities. Additionally, we discuss evidence for upregulation of System x c - , a cystine/glutamate antiporter expressed on astrocytes, in epileptic tissue and changes in expression patterns of glutamate receptors.
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Affiliation(s)
- Oscar B Alcoreza
- Glial Biology in Health, Disease, and Cancer Center, Fralin Biomedical Research Institute, Virginia Tech Carilion, Roanoke, VA, United States.,School of Medicine, Virginia Tech Carilion, Roanoke, VA, United States.,Translational Biology, Medicine and Health, Virginia Tech, Blacksburg, VA, United States
| | - Dipan C Patel
- Glial Biology in Health, Disease, and Cancer Center, Fralin Biomedical Research Institute, Virginia Tech Carilion, Roanoke, VA, United States
| | - Bhanu P Tewari
- Glial Biology in Health, Disease, and Cancer Center, Fralin Biomedical Research Institute, Virginia Tech Carilion, Roanoke, VA, United States
| | - Harald Sontheimer
- Glial Biology in Health, Disease, and Cancer Center, Fralin Biomedical Research Institute, Virginia Tech Carilion, Roanoke, VA, United States
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20
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Paviolo C, Cognet L. Near-infrared nanoscopy with carbon-based nanoparticles for the exploration of the brain extracellular space. Neurobiol Dis 2021; 153:105328. [PMID: 33713842 DOI: 10.1016/j.nbd.2021.105328] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2020] [Revised: 03/04/2021] [Accepted: 03/06/2021] [Indexed: 12/19/2022] Open
Abstract
Understanding the physiology and pathology of the brain requires detailed knowledge of its complex structures as well as dynamic internal processes at very different scales from the macro down to the molecular dimensions. A major yet poorly described brain compartment is the brain extracellular space (ECS). Signalling molecules rapidly diffuse through the brain ECS which is complex and dynamic structure at numerous lengths and time scales. In recent years, characterization of the ECS using nanomaterials has made remarkable progress, including local analysis of nanoscopic dimensions and diffusivity as well as local chemical sensing. In particular, carbon nanomaterials combined with advanced optical technologies, biochemical and biophysical analysis, offer novel promises for understanding the ECS morphology as well as neuron connectivity and neurochemistry. In this review, we present the state-of-the-art in this quest, which mainly focuses on a type of carbon nanomaterial, single walled carbon nanotubes, as fluorescent nanoprobes to unveil the ECS features in the nanometre domain.
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Affiliation(s)
- Chiara Paviolo
- LP2N, Institut d'Optique Graduate School, CNRS, Université de Bordeaux, 33400 Talence, France
| | - Laurent Cognet
- LP2N, Institut d'Optique Graduate School, CNRS, Université de Bordeaux, 33400 Talence, France.
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21
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Wang ZX, Zhu WZ, Zhang S, Shaghaghi M, Cai KJ. Neurite Orientation Dispersion and Density Imaging of Rat Brain Microstructural Changes due to Middle Cerebral Artery Occlusion at a 3T MRI. Curr Med Sci 2021; 41:167-172. [PMID: 33582922 DOI: 10.1007/s11596-021-2332-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2020] [Accepted: 07/07/2020] [Indexed: 12/11/2022]
Abstract
The purpose of this work was to demonstrate the feasibility of neurite orientation dispersion and density imaging (NODDI) in characterizing the brain tissue microstructural changes of middle cerebral artery occlusion (MCAO) in rats at 3T MRI, and to validate NODDI metrics with histology. A multi-shell diffusion MRI protocol was performed on 11 MCAO rats and 10 control rats at different post-operation time points of 0.5, 2, 6, 12, 24 and 72 h. NODDI orientation dispersion index (ODI) and intracellular volume fraction (Vic) metrics were compared between MCAO group and control group. The evolution of NODDI metrics was characterized and validated by histology. Infarction was consistent with significantly increased ODI and Vic in comparison to control tissues at all time points (P<0.001). Lesion ODI increased gradually from 0.5 to 72 h, while its Vic showed a more complicated and fluctuated evolution. ODI and Vic were significantly different between hyperacute and acute stroke periods (P<0.001). The NODDI metrics were found to be consistent with the histological findings. In conclusion, NODDI can reflect microstructural changes of brain tissues in MCAO rats at 3T MRI and the metrics are consistent with histology. This study helps to prepare NODDI for the diagnosis and management of ischemic stroke in translational research and clinical practice.
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Affiliation(s)
- Zhen-Xiong Wang
- Department of Radiology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China.,Department of Radiology, Department of Bioengineering, and the Center for MR Research, University of Illinois at Chicago, Chicago, 60612, USA
| | - Wen-Zhen Zhu
- Department of Radiology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Shun Zhang
- Department of Radiology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China.
| | - Mehran Shaghaghi
- Department of Radiology, Department of Bioengineering, and the Center for MR Research, University of Illinois at Chicago, Chicago, 60612, USA
| | - Ke-Jia Cai
- Department of Radiology, Department of Bioengineering, and the Center for MR Research, University of Illinois at Chicago, Chicago, 60612, USA
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22
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Kimball E, Schaub J, Quillen S, Keuthan C, Pease ME, Korneva A, Quigley H. The role of aquaporin-4 in optic nerve head astrocytes in experimental glaucoma. PLoS One 2021; 16:e0244123. [PMID: 33529207 PMCID: PMC7853498 DOI: 10.1371/journal.pone.0244123] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Accepted: 01/11/2021] [Indexed: 02/04/2023] Open
Abstract
PURPOSE To study aquaporin channel expression in astrocytes of the mouse optic nerve (ON) and the response to IOP elevation in mice lacking aquaporin 4 (AQP4 null). METHODS C57BL/6 (B6) and AQP4 null mice were exposed to bead-induced IOP elevation for 3 days (3D-IOP), 1 and 6 weeks. Mouse ocular tissue sections were immunolabeled against aquaporins 1(AQP1), 4(AQP4), and 9(AQP9). Ocular tissue was imaged to identify normal AQP distribution, ON changes, and axon loss after IOP elevation. Ultrastructure examination, cell proliferation, gene expression, and transport block were also analyzed. RESULTS B6 mice had abundant AQP4 expression in Müller cells, astrocytes of retina and myelinated ON (MON), but minimal AQP4in prelaminar and unmyelinated ON (UON). MON of AQP4 nulls had smaller ON area, smaller axon diameter, higher axon density, and larger proportionate axon area than B6 (all p≤0.05). Bead-injection led to comparable 3D-IOP elevation (p = 0.42) and axonal transport blockade in both strains. In B6, AQP4 distribution was unchanged after 3D-IOP. At baseline, AQP1 and AQP9 were present in retina, but not in UON and this was unaffected after IOP elevation in both strains. In 3D-IOP mice, ON astrocytes and microglia proliferated, more in B6 than AQP4 null. After 6 week IOP elevation, axon loss occurred equally in the two mouse types (24.6%, AQP4 null vs. 23.3%, B6). CONCLUSION Lack of AQP4 was neither protective nor detrimental to the effects of IOP elevation. The minimal presence of AQP4 in UON may be a vital aspect of the regionally specific phenotype of astrocytes in the mouse optic nerve head.
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Affiliation(s)
- Elizabeth Kimball
- Glaucoma Center of Excellence, Wilmer Eye Institute, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Julie Schaub
- Glaucoma Center of Excellence, Wilmer Eye Institute, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Sarah Quillen
- Glaucoma Center of Excellence, Wilmer Eye Institute, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Casey Keuthan
- Glaucoma Center of Excellence, Wilmer Eye Institute, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Mary Ellen Pease
- Glaucoma Center of Excellence, Wilmer Eye Institute, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Arina Korneva
- Glaucoma Center of Excellence, Wilmer Eye Institute, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Harry Quigley
- Glaucoma Center of Excellence, Wilmer Eye Institute, Johns Hopkins University, Baltimore, Maryland, United States of America
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23
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Zannetti A, Benga G, Brunetti A, Napolitano F, Avallone L, Pelagalli A. Role of Aquaporins in the Physiological Functions of Mesenchymal Stem Cells. Cells 2020; 9:cells9122678. [PMID: 33322145 PMCID: PMC7763964 DOI: 10.3390/cells9122678] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2020] [Revised: 12/09/2020] [Accepted: 12/11/2020] [Indexed: 12/13/2022] Open
Abstract
Aquaporins (AQPs) are a family of membrane water channel proteins that control osmotically-driven water transport across cell membranes. Recent studies have focused on the assessment of fluid flux regulation in relation to the biological processes that maintain mesenchymal stem cell (MSC) physiology. In particular, AQPs seem to regulate MSC proliferation through rapid regulation of the cell volume. Furthermore, several reports have shown that AQPs play a crucial role in modulating MSC attachment to the extracellular matrix, their spread, and migration. Shedding light on how AQPs are able to regulate MSC physiological functions can increase our knowledge of their biological behaviours and improve their application in regenerative and reparative medicine.
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Affiliation(s)
- Antonella Zannetti
- Institute of Biostructure and Bioimaging, CNR, Via T. De Amicis 95, 80145 Naples, Italy
| | - Gheorghe Benga
- Romanian Academy, Cluj-Napoca Branch, Strada Republicii 9, 400015 Cluj-Napoca, Romania
| | - Arturo Brunetti
- Department of Advanced Biomedical Sciences, University of Naples Federico II, via Pansini 5, 80131 Naples, Italy
| | - Francesco Napolitano
- Department of Veterinary Medicine and Animal Production, University of Naples Federico II, via Veterinaria 1, 80137 Naples, Italy
- CEINGE-Biotecnologie Avanzate, Via Gaetano Salvatore 486, 80145 Naples, Italy
| | - Luigi Avallone
- Department of Veterinary Medicine and Animal Production, University of Naples Federico II, via Veterinaria 1, 80137 Naples, Italy
| | - Alessandra Pelagalli
- Institute of Biostructure and Bioimaging, CNR, Via T. De Amicis 95, 80145 Naples, Italy
- Department of Advanced Biomedical Sciences, University of Naples Federico II, via Pansini 5, 80131 Naples, Italy
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24
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Kedarasetti RT, Turner KL, Echagarruga C, Gluckman BJ, Drew PJ, Costanzo F. Functional hyperemia drives fluid exchange in the paravascular space. Fluids Barriers CNS 2020; 17:52. [PMID: 32819402 PMCID: PMC7441569 DOI: 10.1186/s12987-020-00214-3] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Accepted: 08/09/2020] [Indexed: 12/20/2022] Open
Abstract
The brain lacks a conventional lymphatic system to remove metabolic waste. It has been proposed that directional fluid movement through the arteriolar paravascular space (PVS) promotes metabolite clearance. We performed simulations to examine if arteriolar pulsations and dilations can drive directional CSF flow in the PVS and found that arteriolar wall movements do not drive directional CSF flow. We propose an alternative method of metabolite clearance from the PVS, namely fluid exchange between the PVS and the subarachnoid space (SAS). In simulations with compliant brain tissue, arteriolar pulsations did not drive appreciable fluid exchange between the PVS and the SAS. However, when the arteriole dilated, as seen during functional hyperemia, there was a marked exchange of fluid. Simulations suggest that functional hyperemia may serve to increase metabolite clearance from the PVS. We measured blood vessels and brain tissue displacement simultaneously in awake, head-fixed mice using two-photon microscopy. These measurements showed that brain deforms in response to pressure changes in PVS, consistent with our simulations. Our results show that the deformability of the brain tissue needs to be accounted for when studying fluid flow and metabolite transport.
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Affiliation(s)
- Ravi Teja Kedarasetti
- Center for Neural Engineering, The Pennsylvania State University, University Park, PA, USA
- Department of Engineering Science and Mechanics, The Pennsylvania State University, University Park, PA, USA
| | - Kevin L Turner
- Center for Neural Engineering, The Pennsylvania State University, University Park, PA, USA
- Department of Biomedical Engineering, The Pennsylvania State University, University Park, PA, USA
| | - Christina Echagarruga
- Center for Neural Engineering, The Pennsylvania State University, University Park, PA, USA
- Department of Biomedical Engineering, The Pennsylvania State University, University Park, PA, USA
| | - Bruce J Gluckman
- Center for Neural Engineering, The Pennsylvania State University, University Park, PA, USA
- Department of Engineering Science and Mechanics, The Pennsylvania State University, University Park, PA, USA
- Department of Neurosurgery, The Pennsylvania State University, University Park, PA, USA
- Department of Biomedical Engineering, The Pennsylvania State University, University Park, PA, USA
| | - Patrick J Drew
- Center for Neural Engineering, The Pennsylvania State University, University Park, PA, USA.
- Department of Engineering Science and Mechanics, The Pennsylvania State University, University Park, PA, USA.
- Department of Neurosurgery, The Pennsylvania State University, University Park, PA, USA.
- Department of Biomedical Engineering, The Pennsylvania State University, University Park, PA, USA.
| | - Francesco Costanzo
- Center for Neural Engineering, The Pennsylvania State University, University Park, PA, USA.
- Department of Engineering Science and Mechanics, The Pennsylvania State University, University Park, PA, USA.
- Department of Biomedical Engineering, The Pennsylvania State University, University Park, PA, USA.
- Department of Mathematics, The Pennsylvania State University, University Park, PA, USA.
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25
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Szu JI, Patel DD, Chaturvedi S, Lovelace JW, Binder DK. Modulation of posttraumatic epileptogenesis in aquaporin-4 knockout mice. Epilepsia 2020; 61:1503-1514. [PMID: 32484924 DOI: 10.1111/epi.16551] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2019] [Revised: 05/05/2020] [Accepted: 05/05/2020] [Indexed: 11/27/2022]
Abstract
OBJECTIVE To determine the role of aquaporin-4 (AQP4) in posttraumatic epileptogenesis using long-term video-electroencephalographic (vEEG) recordings. Here, differences in EEG were analyzed between wild-type (WT) and AQP4 knockout (KO) mice and between mice with and without posttraumatic epilepsy (PTE). METHODS WT and AQP4 KO mice were subjected to a single controlled cortical impact traumatic brain injury (TBI) in the frontal cortex, and vEEG was recorded in the ipsilateral hippocampus at 14, 30, 60, and 90 days postinjury (dpi). Intrahippocampal electrical stimulation was also used to assess electrographic seizure threshold and electrographic seizure duration (ESD). RESULTS The mean seizure frequency per day for WT mice was 0.07 ± 0.07, 0.11 ± 0.07, 0.26 ± 0.13, and 0.12 ± 0.10 at 14, 30, 60, and 90 dpi, respectively. The mean seizure frequency per day for AQP4 KO mice was 0.45 ± 0.27, 0.29 ± 0.12, and 0.26 ± 0.19 at 14, 30, and 60 dpi, respectively. The mean seizure duration was 15 ± 2 seconds and 24 ± 3 seconds for WT and AQP4 KO mice, respectively. The percentage of mice that developed PTE were 28% and 37% for WT and AQP4 KO mice, respectively. Power spectral density (PSD) analysis revealed alterations in EEG frequency bands between sham and TBI in both genotypes. Additionally, PSD analysis of spontaneous recurrent seizures revealed alterations in delta power between genotypes. Morlet wavelet analysis detected heterogeneity in EEG seizure subtypes and dynamic EEG power patterns after TBI. Compared with AQP4 KO mice, a significant increase in ESD was observed in WT mice at 14 dpi. SIGNIFICANCE Posttraumatic seizures (PTSs) may be modulated by the astrocyte water channel AQP4. Absence of AQP4 increases the number of spontaneous seizures, increases seizure duration, and alters EEG power patterns of PTSs.
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Affiliation(s)
- Jenny I Szu
- Center for Glial-Neuronal Interactions, Division of Biomedical Sciences, School of Medicine, University of California, Riverside, Riverside, California, USA
| | - Dillon D Patel
- Center for Glial-Neuronal Interactions, Division of Biomedical Sciences, School of Medicine, University of California, Riverside, Riverside, California, USA
| | - Som Chaturvedi
- Center for Glial-Neuronal Interactions, Division of Biomedical Sciences, School of Medicine, University of California, Riverside, Riverside, California, USA
| | - Jonathan W Lovelace
- Center for Glial-Neuronal Interactions, Division of Biomedical Sciences, School of Medicine, University of California, Riverside, Riverside, California, USA
| | - Devin K Binder
- Center for Glial-Neuronal Interactions, Division of Biomedical Sciences, School of Medicine, University of California, Riverside, Riverside, California, USA
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26
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Walch E, Murphy TR, Cuvelier N, Aldoghmi M, Morozova C, Donohue J, Young G, Samant A, Garcia S, Alvarez C, Bilas A, Davila D, Binder DK, Fiacco TA. Astrocyte-Selective Volume Increase in Elevated Extracellular Potassium Conditions Is Mediated by the Na +/K + ATPase and Occurs Independently of Aquaporin 4. ASN Neuro 2020; 12:1759091420967152. [PMID: 33092407 PMCID: PMC7586494 DOI: 10.1177/1759091420967152] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2020] [Accepted: 09/23/2020] [Indexed: 12/26/2022] Open
Abstract
Astrocytes and neurons have been shown to swell across a variety of different conditions, including increases in extracellular potassium concentration (^[K+]o). The mechanisms involved in the coupling of K+ influx to water movement into cells leading to cell swelling are not well understood and remain controversial. Here, we set out to determine the effects of ^[K+]o on rapid volume responses of hippocampal CA1 pyramidal neurons and stratum radiatum astrocytes using real-time confocal volume imaging. First, we found that elevating [K+]o within a physiological range (to 6.5 mM and 10.5 mM from a baseline of 2.5 mM), and even up to pathological levels (26 mM), produced dose-dependent increases in astrocyte volume, with absolutely no effect on neuronal volume. In the absence of compensating for addition of KCl by removal of an equal amount of NaCl, neurons actually shrank in ^[K+]o, while astrocytes continued to exhibit rapid volume increases. Astrocyte swelling in ^[K+]o was not dependent on neuronal firing, aquaporin 4, the inwardly rectifying potassium channel Kir 4.1, the sodium bicarbonate cotransporter NBCe1, , or the electroneutral cotransporter, sodium-potassium-chloride cotransporter type 1 (NKCC1), but was significantly attenuated in 1 mM barium chloride (BaCl2) and by the Na+/K+ ATPase inhibitor ouabain. Effects of 1 mM BaCl2 and ouabain applied together were not additive and, together with reports that BaCl2 can inhibit the NKA at high concentrations, suggests a prominent role for the astrocyte NKA in rapid astrocyte volume increases occurring in ^[K+]o. These findings carry important implications for understanding mechanisms of cellular edema, regulation of the brain extracellular space, and brain tissue excitability.
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Affiliation(s)
- Erin Walch
- Division of Biomedical Sciences, School of Medicine, University of California, Riverside, Riverside, United States
- Center for Glial-Neuronal Interactions, University of California, Riverside, Riverside, United States
| | - Thomas R. Murphy
- Department of Molecular, Cell and Systems Biology, University of California, Riverside, Riverside, United States
| | - Nicholas Cuvelier
- Department of Molecular, Cell and Systems Biology, University of California, Riverside, Riverside, United States
- Interdepartmental Graduate Program in Neuroscience, University of California, Riverside, Riverside, United States
| | - Murad Aldoghmi
- Department of Molecular, Cell and Systems Biology, University of California, Riverside, Riverside, United States
| | - Cristine Morozova
- Department of Molecular, Cell and Systems Biology, University of California, Riverside, Riverside, United States
- Undergraduate Major in Neuroscience, University of California, Riverside, Riverside, United States
| | - Jordan Donohue
- Department of Molecular, Cell and Systems Biology, University of California, Riverside, Riverside, United States
- Interdepartmental Graduate Program in Neuroscience, University of California, Riverside, Riverside, United States
| | - Gaby Young
- Department of Molecular, Cell and Systems Biology, University of California, Riverside, Riverside, United States
- Undergraduate Major in Neuroscience, University of California, Riverside, Riverside, United States
| | - Anuja Samant
- Department of Molecular, Cell and Systems Biology, University of California, Riverside, Riverside, United States
- Undergraduate Major in Neuroscience, University of California, Riverside, Riverside, United States
| | - Stacy Garcia
- Department of Molecular, Cell and Systems Biology, University of California, Riverside, Riverside, United States
- Undergraduate Major in Neuroscience, University of California, Riverside, Riverside, United States
| | - Camila Alvarez
- Department of Molecular, Cell and Systems Biology, University of California, Riverside, Riverside, United States
- Undergraduate Major in Neuroscience, University of California, Riverside, Riverside, United States
| | - Alex Bilas
- Department of Molecular, Cell and Systems Biology, University of California, Riverside, Riverside, United States
- Interdepartmental Graduate Program in Neuroscience, University of California, Riverside, Riverside, United States
| | - David Davila
- Department of Molecular, Cell and Systems Biology, University of California, Riverside, Riverside, United States
| | - Devin K. Binder
- Division of Biomedical Sciences, School of Medicine, University of California, Riverside, Riverside, United States
- Center for Glial-Neuronal Interactions, University of California, Riverside, Riverside, United States
- Interdepartmental Graduate Program in Neuroscience, University of California, Riverside, Riverside, United States
| | - Todd A. Fiacco
- Center for Glial-Neuronal Interactions, University of California, Riverside, Riverside, United States
- Department of Molecular, Cell and Systems Biology, University of California, Riverside, Riverside, United States
- Interdepartmental Graduate Program in Neuroscience, University of California, Riverside, Riverside, United States
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27
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Wood T, Nance E. Disease-directed engineering for physiology-driven treatment interventions in neurological disorders. APL Bioeng 2019; 3:040901. [PMID: 31673672 PMCID: PMC6811362 DOI: 10.1063/1.5117299] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2019] [Accepted: 10/02/2019] [Indexed: 02/06/2023] Open
Abstract
Neurological disease is killing us. While there have long been attempts to develop therapies for both acute and chronic neurological diseases, no current treatments are curative. Additionally, therapeutic development for neurological disease takes 15 years and often costs several billion dollars. More than 96% of these therapies will fail in late stage clinical trials. Engineering novel treatment interventions for neurological disease can improve outcomes and quality of life for millions; however, therapeutics should be designed with the underlying physiology and pathology in mind. In this perspective, we aim to unpack the importance of, and need to understand, the physiology of neurological disease. We first dive into the normal physiological considerations that should guide experimental design, and then assess the pathophysiological factors of acute and chronic neurological disease that should direct treatment design. We provide an analysis of a nanobased therapeutic intervention that proved successful in translation due to incorporation of physiology at all stages of the research process. We also provide an opinion on the importance of keeping a high-level view to designing and administering treatment interventions. Finally, we close with an implementation strategy for applying a disease-directed engineering approach. Our assessment encourages embracing the complexity of neurological disease, as well as increasing efforts to provide system-level thinking in our development of therapeutics for neurological disease.
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Abstract
Despite its small size, the brain consumes 25% of the body’s energy, generating its own weight in potentially toxic proteins and biological debris each year. The brain is also the only organ lacking lymph vessels to assist in removal of interstitial waste. Over the past 50 years, a picture has been developing of the brain’s unique waste removal system. Experimental observations show cerebrospinal fluid, which surrounds the brain, enters the brain along discrete pathways, crosses a barrier into the spaces between brain cells, and flushes the tissue, carrying wastes to routes exiting the brain. Dysfunction of this cerebral waste clearance system has been demonstrated in Alzheimer’s disease, traumatic brain injury, diabetes, and stroke. The activity of the system is observed to increase during sleep. In addition to waste clearance, this circuit of flow may also deliver nutrients and neurotransmitters. Here, we review the relevant literature with a focus on transport processes, especially the potential role of diffusion and advective flows.
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29
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Smith AJ, Verkman AS. CrossTalk opposing view: Going against the flow: interstitial solute transport in brain is diffusive and aquaporin-4 independent. J Physiol 2019; 597:4421-4424. [PMID: 31389038 DOI: 10.1113/jp277636] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Affiliation(s)
- Alex J Smith
- Departments of Medicine and Physiology, University of California San Francisco, San Francisco, CA, 94143, USA
| | - Alan S Verkman
- Departments of Medicine and Physiology, University of California San Francisco, San Francisco, CA, 94143, USA
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30
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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: 342] [Impact Index Per Article: 57.0] [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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31
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Clément T, Rodriguez-Grande B, Badaut J. Aquaporins in brain edema. J Neurosci Res 2018; 98:9-18. [DOI: 10.1002/jnr.24354] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2018] [Accepted: 10/15/2018] [Indexed: 01/08/2023]
Affiliation(s)
- Tifenn Clément
- CNRS UMR 5287, INCIA, University of Bordeaux; Bordeaux France
| | | | - Jérôme Badaut
- CNRS UMR 5287, INCIA, University of Bordeaux; Bordeaux France
- Department of Basic Science; Loma Linda University School of Medicine; Loma Linda California
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32
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Wilson CS, Mongin AA. Cell Volume Control in Healthy Brain and Neuropathologies. CURRENT TOPICS IN MEMBRANES 2018; 81:385-455. [PMID: 30243438 DOI: 10.1016/bs.ctm.2018.07.006] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Regulation of cellular volume is a critical homeostatic process that is intimately linked to ionic and osmotic balance in the brain tissue. Because the brain is encased in the rigid skull and has a very complex cellular architecture, even minute changes in the volume of extracellular and intracellular compartments have a very strong impact on tissue excitability and function. The failure of cell volume control is a major feature of several neuropathologies, such as hyponatremia, stroke, epilepsy, hyperammonemia, and others. There is strong evidence that such dysregulation, especially uncontrolled cell swelling, plays a major role in adverse pathological outcomes. To protect themselves, brain cells utilize a variety of mechanisms to maintain their optimal volume, primarily by releasing or taking in ions and small organic molecules through diverse volume-sensitive ion channels and transporters. In principle, the mechanisms of cell volume regulation are not unique to the brain and share many commonalities with other tissues. However, because ions and some organic osmolytes (e.g., major amino acid neurotransmitters) have a strong impact on neuronal excitability, cell volume regulation in the brain is a surprisingly treacherous process, which may cause more harm than good. This topical review covers the established and emerging information in this rapidly developing area of physiology.
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Affiliation(s)
- Corinne S Wilson
- Department of Neuroscience and Experimental Therapeutics, Albany Medical College, Albany, NY, United States
| | - Alexander A Mongin
- Department of Neuroscience and Experimental Therapeutics, Albany Medical College, Albany, NY, United States; Department of Biophysics and Functional Diagnostics, Siberian State Medical University, Tomsk, Russian Federation
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Zhang C, Lin J, Wei F, Song J, Chen W, Shan L, Xue R, Wang G, Tao J, Zhang G, Xu GY, Wang L. Characterizing the glymphatic influx by utilizing intracisternal infusion of fluorescently conjugated cadaverine. Life Sci 2018; 201:150-160. [PMID: 29605446 DOI: 10.1016/j.lfs.2018.03.057] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2018] [Revised: 03/21/2018] [Accepted: 03/29/2018] [Indexed: 12/31/2022]
Abstract
AIMS Accumulating evidence supports that cerebrospinal fluid (CSF) in the subarachnoid space (SAS) could reenter the brain parenchyma via the glymphatic influx. The present study was designed to characterize the detailed pathway of subarachnoid CSF influx by using a novel CSF tracer. MAIN METHODS Fluorescently conjugated cadaverine (A488-ca), for the first time, was employed to investigate CSF movement in the brain. Following intracisternal infusion of CSF tracers, mice brain was sliced and prepared for fluorescence imaging. Some brain sections were immunostained in order to observe tracer distribution and cellular uptake. KEY FINDINGS A488-ca moved into the brain parenchyma rapidly, and the influx was time and region dependent. A488-ca entered the mice brain more readily and spread more widely than another commonly used CSF tracer-fluorescently conjugated ovalbumin (OA-45). Furthermore, A488-ca could enter the brain parenchyma either along the paravascular space or across the pial surface. Suppression of glymphatic transport by administration with acetazolamide strikingly reduced the influx of A488-ca. More importantly, relative to OA-45 largely remained in the extracellular space, A488-ca exhibited obvious cellular uptake by astrocytes surrounding the blood vessels and neurons in the cerebral cortex. SIGNIFICANCE Subarachnoid CSF could flow into the brain parenchyma via the glymphatic influx, in which the transcellular pathway was faithfully traced by intracisternal infusion with fluorescently conjugated cadaverine. These observations extend our comprehension on the glymphatic influx pathway.
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Affiliation(s)
- Cui Zhang
- Department of Physiology and Neurobiology, Medical College of Soochow University, 199 Ren-Ai Road, Suzhou 215123, PR China
| | - Jun Lin
- Department of Orthopaedics, The First Affiliated Hospital of Soochow University, 188 Shi-Zi Street, Suzhou 215006, PR China
| | - Fang Wei
- Department of Physiology and Neurobiology, Medical College of Soochow University, 199 Ren-Ai Road, Suzhou 215123, PR China
| | - Jian Song
- Department of Physiology and Neurobiology, Medical College of Soochow University, 199 Ren-Ai Road, Suzhou 215123, PR China
| | - Wenyue Chen
- Department of Physiology and Neurobiology, Medical College of Soochow University, 199 Ren-Ai Road, Suzhou 215123, PR China
| | - Lidong Shan
- Department of Physiology and Neurobiology, Medical College of Soochow University, 199 Ren-Ai Road, Suzhou 215123, PR China
| | - Rong Xue
- Department of Physiology and Neurobiology, Medical College of Soochow University, 199 Ren-Ai Road, Suzhou 215123, PR China
| | - Guoqing Wang
- Department of Physiology and Neurobiology, Medical College of Soochow University, 199 Ren-Ai Road, Suzhou 215123, PR China
| | - Jin Tao
- Department of Physiology and Neurobiology, Medical College of Soochow University, 199 Ren-Ai Road, Suzhou 215123, PR China
| | - Guoxing Zhang
- Department of Physiology and Neurobiology, Medical College of Soochow University, 199 Ren-Ai Road, Suzhou 215123, PR China
| | - Guang-Yin Xu
- Institute of Neuroscience, Soochow University, 199 Ren-Ai Road, Suzhou 215123, PR China.
| | - Linhui Wang
- Department of Physiology and Neurobiology, Medical College of Soochow University, 199 Ren-Ai Road, Suzhou 215123, PR China.
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Tomasetti L, Breunig M. Preventing Obstructions of Nanosized Drug Delivery Systems by the Extracellular Matrix. Adv Healthc Mater 2018; 7. [PMID: 29121453 DOI: 10.1002/adhm.201700739] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2017] [Revised: 08/25/2017] [Indexed: 12/13/2022]
Abstract
Although nanosized drug delivery systems are promising tools for the treatment of severe diseases, the extracellular matrix (ECM) constitutes a major obstacle that endangers therapeutic success. Mobility of diffusing species is restricted not only by small pore size (down to as low as 3 nm) but also by electrostatic interactions with the network. This article evaluates commonly used in vitro models of ECM, analytical methods, and particle types with respect to their similarity to native conditions in the target tissue. In this cross-study evaluation, results from a wide variety of mobility studies are analyzed to discern general principles of particle-ECM interactions. For instance, cross-linked networks and a negative network charge are essential to reliably recapitulate key features of the native ECM. Commonly used ECM mimics comprised of one or two components can lead to mobility calculations which have low fidelity to in vivo results. In addition, analytical methods must be tailored to the properties of both the matrix and the diffusing species to deliver accurate results. Finally, nanoparticles must be sufficiently small to penetrate the matrix pores (ideally Rd/p < 0.5; d = particle diameter, p = pore size) and carry a neutral surface charge to avoid obstructions. Larger (Rd/p >> 1) or positively charged particles are trapped.
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Affiliation(s)
- Luise Tomasetti
- Department of Pharmaceutical Technology; University of Regensburg; Universitaetsstrasse 31 93040 Regensburg Germany
| | - Miriam Breunig
- Department of Pharmaceutical Technology; University of Regensburg; Universitaetsstrasse 31 93040 Regensburg Germany
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35
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Smith AJ, Verkman AS. The "glymphatic" mechanism for solute clearance in Alzheimer's disease: game changer or unproven speculation? FASEB J 2018; 32:543-551. [PMID: 29101220 DOI: 10.1096/fj.201700999] [Citation(s) in RCA: 98] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
How solutes and macromolecules are removed from brain tissue is of central importance in normal brain physiology and in how toxic protein aggregates are cleared in neurodegenerative conditions, including Alzheimer's disease (AD). Conventionally, solute transport in the narrow and tortuous extracellular space in brain parenchyma has been thought to be primarily diffusive and nondirectional. The recently proposed "glymphatic" (glial-lymphatic) hypothesis posits that solute clearance is convective and driven by active fluid transport from para-arterial to paravenous spaces though aquaporin-4 water channels in astrocyte endfeet. Glymphatic, convective solute clearance has received much attention because of its broad implications for AD and other brain pathologies and even the function of sleep. However, the theoretical plausibility of glymphatic transport has been questioned, and recent data have challenged its experimental underpinnings. A substantiated mechanism of solute clearance in the brain is of considerable importance because of its implications for pathogenic mechanisms of neurologic diseases and delivery of therapeutics.-Smith, A. J., Verkman, A. S. The "glymphatic" mechanism for solute clearance in Alzheimer's disease: game changer or unproven speculation?
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Affiliation(s)
- Alex J Smith
- Department of Medicine, University of California San Francisco, San Francisco, California, USA.,Department of Physiology, University of California San Francisco, San Francisco, California, USA
| | - Alan S Verkman
- Department of Medicine, University of California San Francisco, San Francisco, California, USA.,Department of Physiology, University of California San Francisco, San Francisco, California, USA
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36
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Ross AE, Pompano RR. Diffusion of cytokines in live lymph node tissue using microfluidic integrated optical imaging. Anal Chim Acta 2017; 1000:205-213. [PMID: 29289312 DOI: 10.1016/j.aca.2017.11.048] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2017] [Revised: 11/15/2017] [Accepted: 11/17/2017] [Indexed: 12/21/2022]
Abstract
Communication and drug efficacy in the immune system rely heavily on diffusion of proteins such as cytokines through the tissue matrix. Available methods to analyze diffusion in tissue require microinjection or saturating the tissue in protein, which may alter local transport properties due to damage or rapid cellular responses. Here, we developed a novel, user-friendly method - Microfluidic Integrated Optical Imaging (micro-IOI) - to quantify the effective diffusion coefficient of bioactive proteins in live tissue samples ex vivo. A microfluidic platform was used to deliver picograms of fluorescently labelled cytokines to microscale regions within slices of murine lymph node, and diffusion was monitored by widefield fluorescence microscopy. Micro-IOI was validated against theory and existing methods. Free diffusion coefficients were within 8% and 24% of Stokes-Einstein predictions for dextrans and cytokines, respectively. Furthermore, diffusion coefficients for dextrans and proteins in a model matrix were within 1.5-fold of reported results from fluorescence recovery after photobleaching (FRAP). We used micro-IOI to quantify the effective diffusion of three cytokines from different structural classes and two different expression systems - tumor necrosis factor alpha (TNF-α), interferon gamma (IFN-γ), and interleukin-2 (IL-2), from human and mouse - through live lymph node tissue. This is the first method to directly measure cytokine transport in live tissue slices, and in the future, it should promote a deeper understanding of the dynamics of cell-cell communication and enable targeted immunotherapy design.
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Affiliation(s)
- A E Ross
- Department of Chemistry, University of Virginia, McCormick Rd., PO Box 400319, Charlottesville, VA 22904, USA
| | - R R Pompano
- Department of Chemistry, University of Virginia, McCormick Rd., PO Box 400319, Charlottesville, VA 22904, USA.
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37
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Hubbard JA, Binder DK. Unaltered Glutamate Transporter-1 Protein Levels in Aquaporin-4 Knockout Mice. ASN Neuro 2017; 9:1759091416687846. [PMID: 28078912 PMCID: PMC5315234 DOI: 10.1177/1759091416687846] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Maintenance of glutamate and water homeostasis in the brain is crucial to healthy brain activity. Astrocytic glutamate transporter-1 (GLT1) and aquaporin-4 (AQP4) are the main regulators of extracellular glutamate and osmolarity, respectively. Several studies have reported colocalization of GLT1 and AQP4, but the existence of a physical interaction between the two has not been well studied. Therefore, we used coimmunoprecipitation to determine whether a strong interaction exists between these two important molecules in mice on both a CD1 and C57BL/6 background. Furthermore, we used Western blot and immunohistochemistry to examine GLT1 levels in AQP4 knockout (AQP4−/−) mice. An AQP4-GLT1 precipitate was not detected, suggesting the lack of a strong physical interaction between AQP4 and GLT1. In addition, GLT1 protein levels remained unaltered in tissue from CD1 and C57BL/6 AQP4−/− mice. Finally, immunohistochemical analysis revealed that AQP4 and GLT1 do colocalize, but only in a region-specific manner. Taken together, these findings suggest that AQP4 and GLT1 do not have a strong physical interaction between them and are, instead, differentially regulated.
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Affiliation(s)
- Jacqueline A Hubbard
- 1 Center for Glial-Neuronal Interactions, Division of Biomedical Sciences, University of California, Riverside, CA, USA
| | - Devin K Binder
- 1 Center for Glial-Neuronal Interactions, Division of Biomedical Sciences, University of California, Riverside, CA, USA
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38
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Murphy TR, Davila D, Cuvelier N, Young LR, Lauderdale K, Binder DK, Fiacco TA. Hippocampal and Cortical Pyramidal Neurons Swell in Parallel with Astrocytes during Acute Hypoosmolar Stress. Front Cell Neurosci 2017; 11:275. [PMID: 28979186 PMCID: PMC5611379 DOI: 10.3389/fncel.2017.00275] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2017] [Accepted: 08/28/2017] [Indexed: 01/08/2023] Open
Abstract
Normal nervous system function is critically dependent on the balance of water and ions in the extracellular space (ECS). Pathological reduction in brain interstitial osmolarity results in osmotically-driven flux of water into cells, causing cellular edema which reduces the ECS and increases neuronal excitability and risk of seizures. Astrocytes are widely considered to be particularly susceptible to cellular edema due to selective expression of the water channel aquaporin-4 (AQP4). The apparent resistance of pyramidal neurons to osmotic swelling has been attributed to lack of functional water channels. In this study we report rapid volume changes in CA1 pyramidal cells in hypoosmolar ACSF (hACSF) that are equivalent to volume changes in astrocytes across a variety of conditions. Astrocyte and neuronal swelling was significant within 1 min of exposure to 17 or 40% hACSF, was rapidly reversible upon return to normosmolar ACSF, and repeatable upon re-exposure to hACSF. Neuronal swelling was not an artifact of patch clamp, occurred deep in tissue, was similar at physiological vs. room temperature, and occurred in both juvenile and adult hippocampal slices. Neuronal swelling was neither inhibited by TTX, nor by antagonists of NMDA or AMPA receptors, suggesting that it was not occurring as a result of excitotoxicity. Surprisingly, genetic deletion of AQP4 did not inhibit, but rather augmented, astrocyte swelling in severe hypoosmolar conditions. Taken together, our results indicate that neurons are not osmoresistant as previously reported, and that osmotic swelling is driven by an AQP4-independent mechanism.
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Affiliation(s)
- Thomas R. Murphy
- Division of Biomedical Sciences, School of Medicine, University of California, RiversideRiverside, CA, United States
- Center for Glial-Neuronal Interactions, University of California, RiversideRiverside, CA, United States
| | - David Davila
- Center for Glial-Neuronal Interactions, University of California, RiversideRiverside, CA, United States
- Department of Cell Biology and Neuroscience, University of California, RiversideRiverside, CA, United States
| | - Nicholas Cuvelier
- Center for Glial-Neuronal Interactions, University of California, RiversideRiverside, CA, United States
- Department of Cell Biology and Neuroscience, University of California, RiversideRiverside, CA, United States
| | - Leslie R. Young
- Center for Glial-Neuronal Interactions, University of California, RiversideRiverside, CA, United States
- Department of Cell Biology and Neuroscience, University of California, RiversideRiverside, CA, United States
| | - Kelli Lauderdale
- Division of Biomedical Sciences, School of Medicine, University of California, RiversideRiverside, CA, United States
- Center for Glial-Neuronal Interactions, University of California, RiversideRiverside, CA, United States
| | - Devin K. Binder
- Division of Biomedical Sciences, School of Medicine, University of California, RiversideRiverside, CA, United States
- Center for Glial-Neuronal Interactions, University of California, RiversideRiverside, CA, United States
| | - Todd A. Fiacco
- Center for Glial-Neuronal Interactions, University of California, RiversideRiverside, CA, United States
- Department of Cell Biology and Neuroscience, University of California, RiversideRiverside, CA, United States
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Smith AJ, Yao X, Dix JA, Jin BJ, Verkman AS. Test of the 'glymphatic' hypothesis demonstrates diffusive and aquaporin-4-independent solute transport in rodent brain parenchyma. eLife 2017; 6:27679. [PMID: 28826498 PMCID: PMC5578736 DOI: 10.7554/elife.27679] [Citation(s) in RCA: 233] [Impact Index Per Article: 33.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2017] [Accepted: 08/18/2017] [Indexed: 12/11/2022] Open
Abstract
Transport of solutes through brain involves diffusion and convection. The importance of convective flow in the subarachnoid and paravascular spaces has long been recognized; a recently proposed ‘glymphatic’ clearance mechanism additionally suggests that aquaporin-4 (AQP4) water channels facilitate convective transport through brain parenchyma. Here, the major experimental underpinnings of the glymphatic mechanism were re-examined by measurements of solute movement in mouse brain following intracisternal or intraparenchymal solute injection. We found that: (i) transport of fluorescent dextrans in brain parenchyma depended on dextran size in a manner consistent with diffusive rather than convective transport; (ii) transport of dextrans in the parenchymal extracellular space, measured by 2-photon fluorescence recovery after photobleaching, was not affected just after cardiorespiratory arrest; and (iii) Aqp4 gene deletion did not impair transport of fluorescent solutes from sub-arachnoid space to brain in mice or rats. Our results do not support the proposed glymphatic mechanism of convective solute transport in brain parenchyma.
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Affiliation(s)
- Alex J Smith
- Department of Medicine, University of California, San Francisco, San Francisco, United States.,Department of Physiology, University of California, San Francisco, San Francisco, United States
| | - Xiaoming Yao
- Department of Medicine, University of California, San Francisco, San Francisco, United States.,Department of Physiology, University of California, San Francisco, San Francisco, United States
| | - James A Dix
- Department of Medicine, University of California, San Francisco, San Francisco, United States.,Department of Physiology, University of California, San Francisco, San Francisco, United States
| | - Byung-Ju Jin
- Department of Medicine, University of California, San Francisco, San Francisco, United States.,Department of Physiology, University of California, San Francisco, San Francisco, United States
| | - Alan S Verkman
- Department of Medicine, University of California, San Francisco, San Francisco, United States.,Department of Physiology, University of California, San Francisco, San Francisco, United States
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40
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Turning down the volume: Astrocyte volume change in the generation and termination of epileptic seizures. Neurobiol Dis 2017; 104:24-32. [PMID: 28438505 DOI: 10.1016/j.nbd.2017.04.016] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2017] [Revised: 04/18/2017] [Accepted: 04/20/2017] [Indexed: 12/20/2022] Open
Abstract
Approximately 1% of the global population suffers from epilepsy, a class of disorders characterized by recurrent and unpredictable seizures. Of these cases roughly one-third are refractory to current antiepileptic drugs, which typically target neuronal excitability directly. The events leading to seizure generation and epileptogenesis remain largely unknown, hindering development of new treatments. Some recent experimental models of epilepsy have provided compelling evidence that glial cells, especially astrocytes, could be central to seizure development. One of the proposed mechanisms for astrocyte involvement in seizures is astrocyte swelling, which may promote pathological neuronal firing and synchrony through reduction of the extracellular space and elevated glutamate concentrations. In this review, we discuss the common conditions under which astrocytes swell, the resultant effects on neural excitability, and how seizure development may ultimately be influenced by these effects.
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41
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Hubbard JA, Szu JI, Binder DK. The role of aquaporin-4 in synaptic plasticity, memory and disease. Brain Res Bull 2017; 136:118-129. [PMID: 28274814 DOI: 10.1016/j.brainresbull.2017.02.011] [Citation(s) in RCA: 86] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2016] [Revised: 02/27/2017] [Accepted: 02/28/2017] [Indexed: 12/25/2022]
Abstract
Since the discovery of aquaporins, it has become clear that the various mammalian aquaporins play critical physiological roles in water and ion balance in multiple tissues. Aquaporin-4 (AQP4), the principal aquaporin expressed in the central nervous system (CNS, brain and spinal cord), has been shown to mediate CNS water homeostasis. In this review, we summarize new and exciting studies indicating that AQP4 also plays critical and unanticipated roles in synaptic plasticity and memory formation. Next, we consider the role of AQP4 in Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS), Parkinson's disease (PD), multiple sclerosis (MS), neuromyelitis optica (NMO), epilepsy, traumatic brain injury (TBI), and stroke. Each of these conditions involves changes in AQP4 expression and/or distribution that may be functionally relevant to disease physiology. Insofar as AQP4 is exclusively expressed on astrocytes, these data provide new evidence of "astrocytopathy" in the etiology of diverse neurological diseases.
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Affiliation(s)
- Jacqueline A Hubbard
- Center for Glial-Neuronal Interactions, Division of Biomedical Sciences, School of Medicine, University of California, Riverside, United States
| | - Jenny I Szu
- Center for Glial-Neuronal Interactions, Division of Biomedical Sciences, School of Medicine, University of California, Riverside, United States
| | - Devin K Binder
- Center for Glial-Neuronal Interactions, Division of Biomedical Sciences, School of Medicine, University of California, Riverside, United States.
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42
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Hirt L, Fukuda AM, Ambadipudi K, Rashid F, Binder D, Verkman A, Ashwal S, Obenaus A, Badaut J. Improved long-term outcome after transient cerebral ischemia in aquaporin-4 knockout mice. J Cereb Blood Flow Metab 2017; 37:277-290. [PMID: 26767580 PMCID: PMC5363745 DOI: 10.1177/0271678x15623290] [Citation(s) in RCA: 73] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/27/2015] [Revised: 10/23/2015] [Accepted: 10/26/2015] [Indexed: 01/07/2023]
Abstract
A hallmark of stroke is water accumulation (edema) resulting from dysregulation of osmotic homeostasis. Brain edema contributes to tissue demise and may lead to increased intracranial pressure and lethal herniation. Currently, there are only limited treatments to prevent edema formation following stroke. Aquaporin 4 (AQP4), a brain water channel, has become a focus of interest for therapeutic approaches targeting edema. At present, there are no pharmacological tools to block AQP4. The role of AQP4 in edema after brain injury remains unclear with conflicting results from studies using AQP4-/- mice and of AQP4 expression following stroke. Here, we studied AQP4 and its role in edema formation by testing AQP4-/- mice in a model of middle cerebral artery occlusion using novel quantitative MRI water content measurements, histology and behavioral changes as outcome measures. Absence of AQP4 was associated with decreased mortality and increased motor recovery 3 to 14 days after stroke. Behavioral improvement was associated with decreased lesion volume, neuronal cell death and neuroinflammation in AQP4-/- compared to wild type mice. Our data suggest that the lack of AQP4 confers an overall beneficial role at long term with improved neuronal survival and reduced neuroinflammation, but without a direct effect on edema formation.
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Affiliation(s)
- Lorenz Hirt
- Department of Clinical Neurosciences, Neurology Service, Centre Hospitalier Universitaire Vaudois and Lausanne University, Switzerland
| | - Andrew M Fukuda
- Department of Physiology, Loma Linda University School of Medicine, Loma Linda, CA, USA
| | - Kamalakar Ambadipudi
- Department of Pediatrics, Loma Linda University School of Medicine, Loma Linda, CA, USA
| | - Faisil Rashid
- Department of Physiology, Loma Linda University School of Medicine, Loma Linda, CA, USA
| | - Devin Binder
- Center for Glial-Neuronal Interactions, Division of Biomedical Sciences, University of California, Riverside, Riverside, CA, USA
| | - Alan Verkman
- Medicine and Physiology, Cardiovascular Research Institute, University of California San Francisco, CA, USA
| | - Stephen Ashwal
- Department of Pediatrics, Loma Linda University School of Medicine, Loma Linda, CA, USA
| | - Andre Obenaus
- Department of Physiology, Loma Linda University School of Medicine, Loma Linda, CA, USA.,Department of Pediatrics, Loma Linda University School of Medicine, Loma Linda, CA, USA.,Center for Glial-Neuronal Interactions, Division of Biomedical Sciences, University of California, Riverside, Riverside, CA, USA
| | - Jerome Badaut
- Department of Physiology, Loma Linda University School of Medicine, Loma Linda, CA, USA .,Department of Pediatrics, Loma Linda University School of Medicine, Loma Linda, CA, USA.,CNRS UMR5287, University of Bordeaux, Bordeaux, France
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43
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Yamashiro K, Morita M. Novel aspects of extracellular adenosine dynamics revealed by adenosine sensor cells. Neural Regen Res 2017; 12:881-885. [PMID: 28761414 PMCID: PMC5514856 DOI: 10.4103/1673-5374.208544] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Adenosine modulates diverse physiological and pathological processes in the brain, including neuronal activities, blood flow, and inflammation. However, the mechanisms underlying the dynamics of extracellular adenosine are not fully understood. We have recently developed a novel biosensor, called an adenosine sensor cell, and we have characterized the neuronal and astrocytic pathways for elevating extracellular adenosine. In this review, the physiological implications and therapeutic potential of the pathways revealed by the adenosine sensor cells are discussed. We propose that the multiple pathways regulating extracellular adenosine allow for the diverse functions of this neuromodulator, and their malfunctions cause various neurological and psychiatric disorders.
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Affiliation(s)
- Kunihiko Yamashiro
- Department of Biochemistry and Cellular Biology, National Institute of Neuroscience, National Center of Neurology and Psychiatry (NCNP), Tokyo, Japan.,Department of NCNP Brain Physiology and Pathology, Tokyo Medical and Dental University Graduate School of Medical and Dental Sciences, Tokyo, Japan.,Department of Biology, Kobe University Graduate School of Sciences, Kobe, Japan
| | - Mitsuhiro Morita
- Department of Biology, Kobe University Graduate School of Sciences, Kobe, Japan
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44
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Verkman AS, Tradtrantip L, Smith AJ, Yao X. Aquaporin Water Channels and Hydrocephalus. Pediatr Neurosurg 2017; 52:409-416. [PMID: 27978530 PMCID: PMC5969073 DOI: 10.1159/000452168] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/18/2016] [Accepted: 09/21/2016] [Indexed: 01/10/2023]
Abstract
The aquaporins (AQPs) are a family of water-transporting proteins that are broadly expressed in mammalian cells. Two AQPs in the central nervous system, AQP1 and AQP4, might play a role in hydrocephalus and are thus potential drug targets. AQP1 is expressed in the ventricular-facing membrane of choroid plexus epithelial cells, where it facilitates the secretion of cerebrospinal fluid (CSF). AQP4 is expressed in astrocyte foot processes and ependymal cells lining ventricles, where it appears to facilitate the transport of excess water out of the brain. Altered expression of these AQPs in experimental animal models of hydrocephalus and limited human specimens suggests their involvement in the pathophysiology of hydrocephalus, as do data in knockout mice demonstrating a protective effect of AQP1 deletion and a deleterious effect of AQP4 deletion in hydrocephalus. Though significant questions remain, including the precise contribution of AQP1 to CSF secretion in humans and the mechanisms by which AQP4 facilitates clearance of excess brain water, AQP1 and AQP4 have been proposed as potential drug targets to reduce ventricular enlargement in hydrocephalus.
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Affiliation(s)
- Alan S Verkman
- Departments of Medicine and Physiology, University of California, San Francisco, CA, USA
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45
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Glymphatic solute transport does not require bulk flow. Sci Rep 2016; 6:38635. [PMID: 27929105 PMCID: PMC5144134 DOI: 10.1038/srep38635] [Citation(s) in RCA: 178] [Impact Index Per Article: 22.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2016] [Accepted: 11/10/2016] [Indexed: 12/31/2022] Open
Abstract
Observations of fast transport of fluorescent tracers in mouse brains have led to the hypothesis of bulk water flow directed from arterial to venous paravascular spaces (PVS) through the cortical interstitium. At the same time, there is evidence for interstitial solute transport by diffusion rather than by directed bulk fluid motion. It has been shown that the two views may be consolidated by intracellular water flow through astrocyte networks combined with mainly diffusive extracellular transport of solutes. This requires the presence of a driving force that has not been determined to date, but for which arterial pulsation has been suggested as the origin. Here we show that arterial pulsation caused by pulse wave propagation is an unlikely origin of this hypothetical driving force. However, we further show that such pulsation may still lead to fast para-arterial solute transport through dispersion, that is, through the combined effect of local mixing and diffusion in the para-arterial space.
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Haenisch S, von Rüden EL, Wahmkow H, Rettenbeck ML, Michler C, Russmann V, Bruckmueller H, Waetzig V, Cascorbi I, Potschka H. miRNA-187-3p-Mediated Regulation of the KCNK10/TREK-2 Potassium Channel in a Rat Epilepsy Model. ACS Chem Neurosci 2016; 7:1585-1594. [PMID: 27609046 DOI: 10.1021/acschemneuro.6b00222] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Regulatory RNAs play a key role in the regulation of protein expression patterns in neurological diseases. Here we studied the regulation of miRNAs in a chronic rat model of temporal lobe epilepsy. The analysis was focused on a putative link with pharmacoresponsiveness as well as the functional implications of the regulation of a selected miRNA. The findings did not reveal a difference in hippocampal miRNA expression between phenobarbital responders and nonresponders. However, when comparing rats following status epilepticus with control rats we identified 13 differentially expressed miRNAs with miRNA-187-3p being most strongly regulated. mRNAs encoding KCNK10/TREK-2 as well as DYRK2 were confirmed as targets of miRNA-187-3p. Expression of the potassium channel protein KCNK10/TREK-2 negatively correlated with hippocampal miRNA-187-3p expression and proved to be upregulated in the chronic phase of the epilepsy model. In conclusion, our data do not suggest a relevant impact of miRNA expression patterns on pharmacoresponsiveness. However, we confirmed regulation of miRNA-187-3p and demonstrated that it impacts the expression of the two-pore domain potassium channel protein KCNK10/TREK-2. Considering evidence from brain ischemia models, KCNK10/TREK-2 upregulation might serve a protective function with a beneficial impact on astrocytic potassium and glutamate homeostasis.
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Affiliation(s)
- Sierk Haenisch
- Institute of Experimental and Clinical Pharmacology, University Hospital Schleswig-Holstein , 24105 Campus Kiel, Germany
| | - Eva-Lotta von Rüden
- Institute of Pharmacology, Toxicology, and Pharmacy, Ludwig-Maximilians-University (LMU) , 80539 Munich, Germany
| | - Hannes Wahmkow
- Institute of Experimental and Clinical Pharmacology, University Hospital Schleswig-Holstein , 24105 Campus Kiel, Germany
| | - Maruja L Rettenbeck
- Institute of Pharmacology, Toxicology, and Pharmacy, Ludwig-Maximilians-University (LMU) , 80539 Munich, Germany
| | - Christina Michler
- Institute of Pharmacology, Toxicology, and Pharmacy, Ludwig-Maximilians-University (LMU) , 80539 Munich, Germany
| | - Vera Russmann
- Institute of Pharmacology, Toxicology, and Pharmacy, Ludwig-Maximilians-University (LMU) , 80539 Munich, Germany
| | - Henrike Bruckmueller
- Institute of Experimental and Clinical Pharmacology, University Hospital Schleswig-Holstein , 24105 Campus Kiel, Germany
| | - Vicki Waetzig
- Institute of Experimental and Clinical Pharmacology, University Hospital Schleswig-Holstein , 24105 Campus Kiel, Germany
| | - Ingolf Cascorbi
- Institute of Experimental and Clinical Pharmacology, University Hospital Schleswig-Holstein , 24105 Campus Kiel, Germany
| | - Heidrun Potschka
- Institute of Pharmacology, Toxicology, and Pharmacy, Ludwig-Maximilians-University (LMU) , 80539 Munich, Germany
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Jin BJ, Smith AJ, Verkman AS. Spatial model of convective solute transport in brain extracellular space does not support a "glymphatic" mechanism. J Gen Physiol 2016; 148:489-501. [PMID: 27836940 PMCID: PMC5129742 DOI: 10.1085/jgp.201611684] [Citation(s) in RCA: 130] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2016] [Accepted: 10/21/2016] [Indexed: 01/12/2023] Open
Abstract
A “glymphatic mechanism” has been proposed to mediate convective fluid transport from para-arterial to paravenous extracellular space in the brain. Jin et al. model such a system and find that diffusion, rather than convection, can account for the transport of solutes. A “glymphatic system,” which involves convective fluid transport from para-arterial to paravenous cerebrospinal fluid through brain extracellular space (ECS), has been proposed to account for solute clearance in brain, and aquaporin-4 water channels in astrocyte endfeet may have a role in this process. Here, we investigate the major predictions of the glymphatic mechanism by modeling diffusive and convective transport in brain ECS and by solving the Navier–Stokes and convection–diffusion equations, using realistic ECS geometry for short-range transport between para-arterial and paravenous spaces. Major model parameters include para-arterial and paravenous pressures, ECS volume fraction, solute diffusion coefficient, and astrocyte foot-process water permeability. The model predicts solute accumulation and clearance from the ECS after a step change in solute concentration in para-arterial fluid. The principal and robust conclusions of the model are as follows: (a) significant convective transport requires a sustained pressure difference of several mmHg between the para-arterial and paravenous fluid and is not affected by pulsatile pressure fluctuations; (b) astrocyte endfoot water permeability does not substantially alter the rate of convective transport in ECS as the resistance to flow across endfeet is far greater than in the gaps surrounding them; and (c) diffusion (without convection) in the ECS is adequate to account for experimental transport studies in brain parenchyma. Therefore, our modeling results do not support a physiologically important role for local parenchymal convective flow in solute transport through brain ECS.
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Affiliation(s)
- Byung-Ju Jin
- Department of Medicine, University of California, San Francisco, San Francisco, CA 94143.,Department of Physiology, University of California, San Francisco, San Francisco, CA 94143
| | - Alex J Smith
- Department of Medicine, University of California, San Francisco, San Francisco, CA 94143.,Department of Physiology, University of California, San Francisco, San Francisco, CA 94143
| | - Alan S Verkman
- Department of Medicine, University of California, San Francisco, San Francisco, CA 94143 .,Department of Physiology, University of California, San Francisco, San Francisco, CA 94143
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Wu X, Zhang JT, Li D, Zhou J, Yang J, Zheng HL, Chen JG, Wang F. Aquaporin-4 deficiency facilitates fear memory extinction in the hippocampus through excessive activation of extrasynaptic GluN2B-containing NMDA receptors. Neuropharmacology 2016; 112:124-134. [PMID: 27373674 DOI: 10.1016/j.neuropharm.2016.06.031] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2016] [Revised: 06/11/2016] [Accepted: 06/28/2016] [Indexed: 12/22/2022]
Abstract
Aquaporin-4 (AQP-4) is the predominant water channel in the brain and primarily expressed in astrocytes. Astrocytes have been generally believed to play important roles in regulating synaptic plasticity and information processing. A growing number of evidence shows that AQP-4 plays a potential role in the regulation of astrocyte function. However, little is known about the function of AQP-4 for synaptic plasticity in the hippocampus. Therefore, we evaluated long-term depression (LTD) in the hippocampus and the extinction of fear memory of AQP-4 knockout (KO) and wild-type (WT) mice. We found that AQP-4 deficiency facilitated fear memory extinction and NMDA receptors (NMDARs)-dependent LTD in the CA3-CA1 pathway. Furthermore, AQP-4 deficiency selectively increased GluN2B-NMDAR-mediated excitatory postsynaptic currents (EPSCs). The excessive activation of extrasynaptic GluN2B-NMDAR contributed to the facilitation of NMDAR-dependent LTD and enhancement of fear memory extinction in AQP-4 KO mice. Thus, it appears that AQP-4 may be a potential target for intervention in fear memory extinction. This article is part of the Special Issue entitled 'Ionotropic glutamate receptors'.
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Affiliation(s)
- Xin Wu
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Jie-Ting Zhang
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Di Li
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Jun Zhou
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Jun Yang
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Hui-Ling Zheng
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Jian-Guo Chen
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China; The Key Laboratory of Neurological Diseases (HUST), Ministry of Education of China, Wuhan, 430030, China; The Key Laboratory for Drug Target Researches and Pharmacodynamic Evaluation of Hubei Province, Wuhan, 430030, China; Laboratory of Neuropsychiatric Diseases, The Institute of Brain Research, Huazhong University of Science and Technology, Wuhan, 430030, China; The Collaborative Innovation Center for Brain Science, Wuhan, 430030, China
| | - Fang Wang
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China; The Key Laboratory of Neurological Diseases (HUST), Ministry of Education of China, Wuhan, 430030, China; The Key Laboratory for Drug Target Researches and Pharmacodynamic Evaluation of Hubei Province, Wuhan, 430030, China; Laboratory of Neuropsychiatric Diseases, The Institute of Brain Research, Huazhong University of Science and Technology, Wuhan, 430030, China; The Collaborative Innovation Center for Brain Science, Wuhan, 430030, China.
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Yang S, Wang Y, Li K, Tang X, Zhang K, Shi C, Han H, Peng Y. Extracellular space diffusion analysis in the infant and adult rat striatum using magnetic resonance imaging. Int J Dev Neurosci 2016; 53:1-7. [PMID: 27296518 DOI: 10.1016/j.ijdevneu.2016.05.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2016] [Revised: 05/11/2016] [Accepted: 05/25/2016] [Indexed: 10/21/2022] Open
Abstract
The extracellular space (ECS) in the brain provides an extrasynaptic transfer channel among neurons, axons and glial cells. It is particularly important in the early stage after birth, when angiogenesis is not yet complete and the ECS may provide the main pathway for metabolite transport. However, the characteristics of extracellular transport remain unclear. In this study, a novel magnetic resonance imaging (MRI) method was used to perform real-time visualization and quantification of diffusion in the brain ECS of infant (postnatal day 10 (P10)) and adult rats. Using a modified diffusion equation and the linear relationship between the signal intensity and the gadolinium-diethylenetriaminepentaacetic acid (Gd-DTPA) concentration, diffusion parameters were obtained; these parameters include the effective diffusion coefficient (D*), clearance rate (k'), tortuosity (λ) and the volume fraction of distribution (Vd%). There were significant differences in the diffusion parameters between P10 and adult rats. This finding provides a reference for future treatment of brain diseases using drugs administered via interstitial pathways.
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Affiliation(s)
- Shuangfeng Yang
- Imaging Center, Beijing Children's Hospital, Capital Medical University, Beijing 100045, China
| | - Yan Wang
- Imaging Center, Beijing Children's Hospital, Capital Medical University, Beijing 100045, China
| | - Kai Li
- Department of Radiology, Beijing Jishuitan Hospital, Beijing 100035, China
| | - Xiaolu Tang
- Imaging Center, Beijing Children's Hospital, Capital Medical University, Beijing 100045, China
| | - Kuo Zhang
- Department of Laboratory Animal Science, Peking University Health Science Center, Beijing 100191, China
| | - Chunyan Shi
- Department of Radiology, Peking University Third Hospital, Beijing 100191, China; Beijing Key Lab of Magnetic Resonance Imaging Device and Technique, Beijing 100191, China
| | - Hongbin Han
- Department of Radiology, Peking University Third Hospital, Beijing 100191, China; Beijing Key Lab of Magnetic Resonance Imaging Device and Technique, Beijing 100191, China.
| | - Yun Peng
- Imaging Center, Beijing Children's Hospital, Capital Medical University, Beijing 100045, China.
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50
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Hubbard JA, Szu JI, Yonan JM, Binder DK. Regulation of astrocyte glutamate transporter-1 (GLT1) and aquaporin-4 (AQP4) expression in a model of epilepsy. Exp Neurol 2016; 283:85-96. [PMID: 27155358 DOI: 10.1016/j.expneurol.2016.05.003] [Citation(s) in RCA: 78] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2015] [Revised: 04/23/2016] [Accepted: 05/01/2016] [Indexed: 12/31/2022]
Abstract
Astrocytes regulate extracellular glutamate and water homeostasis through the astrocyte-specific membrane proteins glutamate transporter-1 (GLT1) and aquaporin-4 (AQP4), respectively. The role of astrocytes and the regulation of GLT1 and AQP4 in epilepsy are not fully understood. In this study, we investigated the expression of GLT1 and AQP4 in the intrahippocampal kainic acid (IHKA) model of temporal lobe epilepsy (TLE). We used real-time polymerase chain reaction (RT-PCR), Western blot, and immunohistochemical analysis at 1, 4, 7, and 30days after kainic acid-induced status epilepticus (SE) to determine hippocampal glial fibrillary acidic protein (GFAP, a marker for reactive astrocytes), GLT1, and AQP4 expression changes during the development of epilepsy (epileptogenesis). Following IHKA, all mice had SE and progressive increases in GFAP immunoreactivity and GFAP protein expression out to 30days post-SE. A significant initial increase in dorsal hippocampal GLT1 immunoreactivity and protein levels were observed 1day post SE and followed by a marked downregulation at 4 and 7days post SE with a return to near control levels by 30days post SE. AQP4 dorsal hippocampal protein expression was significantly downregulated at 1day post SE and was followed by a gradual return to baseline levels with a significant increase in ipsilateral protein levels by 30days post SE. Transient increases in GFAP and AQP4 mRNA were also observed. Our findings suggest that specific molecular changes in astrocyte glutamate transporters and water channels occur during epileptogenesis in this model, and suggest the novel therapeutic strategy of restoring glutamate and water homeostasis.
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Affiliation(s)
- Jacqueline A Hubbard
- Department of Biochemistry and Molecular Biology, University of California, Riverside, USA
| | - Jenny I Szu
- Neuroscience Graduate Program, University of California, Riverside, USA
| | - Jennifer M Yonan
- Neuroscience Graduate Program, University of California, Riverside, USA
| | - Devin K Binder
- Neuroscience Graduate Program, University of California, Riverside, USA; Center for Glial-Neuronal Interactions, University of California, Riverside, USA; Division of Biomedical Sciences, School of Medicine, University of California, Riverside.
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