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Skauli N, Zohoorian N, Banitalebi S, Geiseler S, Salameh M, Rao SB, Morland C, Ottersen OP, Amiry-Moghaddam M. Aquaporin-4 deletion leads to reduced infarct volume and increased peri-infarct astrocyte reactivity in a mouse model of cortical stroke. J Physiol 2024; 602:3151-3168. [PMID: 38924526 DOI: 10.1113/jp284099] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2023] [Accepted: 05/29/2024] [Indexed: 06/28/2024] Open
Abstract
Aquaporin-4 (AQP4) is the main water channel in brain and is enriched in perivascular astrocyte processes abutting brain microvessels. There is a rich literature on the role of AQP4 in experimental stroke. While its role in oedema formation following middle cerebral artery occlusion (MCAO) has been studied extensively, its specific impact on infarct volume remains unclear. This study investigated the effects of total and partial AQP4 deletion on infarct volume in mice subjected to distal medial cerebral artery (dMCAO) occlusion. Compared to MCAO, this model induces smaller infarcts confined to neocortex, and less oedema. We show that AQP4 deletion significantly reduced infarct volume as assessed 1 week after dMCAO, suggesting that the role of AQP4 in stroke goes beyond its effect on oedema formation and dissolution. The reduction in infarct volume was associated with increased astrocyte reactivity in the peri-infarct areas. No significant differences were observed in the number of microglia among the genotypes. These findings provide new insights in the role of AQP4 in ischaemic injury indicating that AQP4 affects both infarct volume and astrocyte reactivity in the peri-infarct zone. KEY POINTS: Aquaporin-4 (AQP4) is the main water channel in brain and is enriched in perivascular astrocyte processes abutting microvessels. A rich literature exists on the role of AQP4 in oedema formation following middle cerebral artery occlusion (MCAO). We investigated the effects of total and partial AQP4 deletion on infarct volume in mice subjected to distal medial cerebral artery occlusion (dMCAO), a model inducing smaller infarcts confined to neocortex and less oedema compared to MCAO. AQP4 deletion significantly reduced infarct volume 1 week after dMCAO, suggesting a broader role for AQP4 in stroke beyond oedema formation. The reduction in infarct volume was associated with increased astrocyte reactivity in the peri-infarct areas, while no significant differences were observed in the number of microglia among the genotypes. These findings provide new insights into the role of AQP4 in stroke, indicating that AQP4 affects both infarct volume and astrocyte reactivity in the peri-infarct zone.
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Affiliation(s)
- Nadia Skauli
- Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Blindern, Oslo, Norway
| | - Negar Zohoorian
- Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Blindern, Oslo, Norway
| | - Shervin Banitalebi
- Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Blindern, Oslo, Norway
| | - Samuel Geiseler
- Cardiovascular Research Group IMB, Department of Medical Biology, Faculty of Health Sciences, UiT - The Arctic University of Norway, Tromsø, Norway
| | - Maher Salameh
- Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Blindern, Oslo, Norway
| | - Shreyas B Rao
- Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Blindern, Oslo, Norway
| | - Cecilie Morland
- Section for Pharmacology and Pharmaceutical Biosciences, Department of Pharmacy, The Faculty of Mathematics and Natural Sciences, University of Oslo, Oslo, Norway
| | - Ole P Ottersen
- Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Blindern, Oslo, Norway
| | - Mahmood Amiry-Moghaddam
- Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Blindern, Oslo, Norway
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2
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Yang S, Qi S, Wang C. The role of retinal Müller cells in diabetic retinopathy and related therapeutic advances. Front Cell Dev Biol 2022; 10:1047487. [PMID: 36531955 PMCID: PMC9757137 DOI: 10.3389/fcell.2022.1047487] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2022] [Accepted: 11/24/2022] [Indexed: 11/19/2023] Open
Abstract
Diabetic retinopathy (DR) is a significant complication of diabetes. During the pathogenesis of retinal microangiopathy and neuronopathy, activated retinal Müller cells (RMCs) undergo morphological and structural changes such as increased expression of glial fibrillary acidic protein, disturbance of potassium and water transport regulation, and onset of production of a large number of inflammatory and vascular growth factors as well as chemokines. Evidently, activated RMCs are necessary for the pathogenesis of DR; therefore, exploring the role of RMCs in DR may provide a new target for the treatment thereof. This article reviews the mechanism of RMCs involvement in DR and the progress in related treatments.
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Affiliation(s)
| | - Shounan Qi
- Department of Ophthalmology, The Second Hospital of Jilin University, Changchun, China
| | - Chenguang Wang
- Department of Ophthalmology, The Second Hospital of Jilin University, Changchun, China
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Beverley KM, Pattnaik BR. Inward rectifier potassium (Kir) channels in the retina: living our vision. Am J Physiol Cell Physiol 2022; 323:C772-C782. [PMID: 35912989 PMCID: PMC9448332 DOI: 10.1152/ajpcell.00112.2022] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2022] [Revised: 07/25/2022] [Accepted: 07/25/2022] [Indexed: 11/22/2022]
Abstract
Channel proteins are vital for conducting ions throughout the body and are especially relevant to retina physiology. Inward rectifier potassium (Kir) channels are a class of K+ channels responsible for maintaining membrane potential and extracellular K+ concentrations. Studies of the KCNJ gene (that encodes Kir protein) expression identified the presence of all of the subclasses (Kir 1-7) of Kir channels in the retina or retinal-pigmented epithelium (RPE). However, functional studies have established the involvement of the Kir4.1 homotetramer and Kir4.1/5.1 heterotetramer in Müller glial cells, Kir2.1 in bipolar cells, and Kir7.1 in the RPE cell physiology. Here, we propose the potential roles of Kir channels in the retina based on the physiological contributions to the brain, pancreatic, and cardiac tissue functions. There are several open questions regarding the expressed KCNJ genes in the retina and RPE. For example, why does not the Kir channel subtype gene expression correspond with protein expression? Catching up with multiomics or functional "omics" approaches might shed light on posttranscriptional changes that might influence Kir subunit mRNA translation within the retina that guides our vision.
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Affiliation(s)
- Katie M Beverley
- Endocrinology and Reproductive Physiology Graduate Program, School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin
- Department of Pediatrics, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin
- McPherson Eye Research Institute, University of Wisconsin, Madison, Wisconsin
| | - Bikash R Pattnaik
- Endocrinology and Reproductive Physiology Graduate Program, School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin
- Department of Pediatrics, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin
- McPherson Eye Research Institute, University of Wisconsin, Madison, Wisconsin
- Department of Ophthalmology and Visual Sciences, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin
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4
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Skauli N, Savchenko E, Ottersen OP, Roybon L, Amiry-Moghaddam M. Canonical Bone Morphogenetic Protein Signaling Regulates Expression of Aquaporin-4 and Its Anchoring Complex in Mouse Astrocytes. Front Cell Neurosci 2022; 16:878154. [PMID: 35518645 PMCID: PMC9067306 DOI: 10.3389/fncel.2022.878154] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2022] [Accepted: 03/22/2022] [Indexed: 11/13/2022] Open
Abstract
Aquaporin-4 (AQP4) is the predominant water channel in the brain; it is enriched in astrocytic foot processes abutting vessels where it is anchored through an interaction with the dystrophin-associated protein (DAP) complex. Enhanced expression with concomitant mislocalization of AQP4 along astrocyte plasma membranes is a hallmark of several neurological conditions. Thus, there is an urgent need to identify which signaling pathways dictate AQP4 microdistribution. Here we show that canonical bone morphogenetic proteins (BMPs), particularly BMP2 and 4, upregulate AQP4 expression in astrocytes and dysregulate the associated DAP complex by differentially affecting its individual members. We further demonstrate the presence of BMP receptors and Smad1/5/9 pathway activation in BMP treated astrocytes. Our analysis of adult mouse brain reveals BMP2 and 4 in neurons and in a subclass of endothelial cells and activated Smad1/5/9 in astrocytes. We conclude that the canonical BMP-signaling pathway might be responsible for regulating the expression of AQP4 and of DAP complex proteins that govern the subcellular compartmentation of this aquaporin.
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Affiliation(s)
- Nadia Skauli
- Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
| | - Ekaterina Savchenko
- Stem Cell Laboratory for CNS Disease Modeling, Department of Experimental Medical Science, BMC D10, Lund University, Lund, Sweden
| | - Ole Petter Ottersen
- Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway.,Karolinska Institutet, Stockholm, Sweden
| | - Laurent Roybon
- Stem Cell Laboratory for CNS Disease Modeling, Department of Experimental Medical Science, BMC D10, Lund University, Lund, Sweden
| | - Mahmood Amiry-Moghaddam
- Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
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5
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Li X, Lv J, Li J, Ren X. Kir4.1 may represent a novel therapeutic target for diabetic retinopathy (Review). Exp Ther Med 2021; 22:1021. [PMID: 34373707 PMCID: PMC8343704 DOI: 10.3892/etm.2021.10453] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2021] [Accepted: 05/28/2021] [Indexed: 12/27/2022] Open
Abstract
As the major cause of irreversible loss of vision in adults, diabetic retinopathy (DR) is one of the most serious complications of diabetes. The imbalance of the retinal microenvironment and destruction of the blood-retinal barrier have a significant role in the progression of DR. Inward rectifying potassium channel 4.1 (Kir4.1) is located on Müller cells and is closely related to potassium homeostasis, water balance and glutamate clearance in the whole retina. The present review discusses the functions of Kir4.1 in regulating the retinal microenvironment and related biological mechanisms in DR. In the future, Kir4.1 may represent a novel alternative therapeutic target for DR through affecting the retinal microenvironment.
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Affiliation(s)
- Xiaoyu Li
- Department of Histology and Embryology, Dalian Medical University, Dalian, Liaoning 116044, P.R. China.,Department of Radiotherapy Oncology, The Second Hospital of Dalian Medical University, Dalian, Liaoning 116023, P.R. China
| | - Jiajun Lv
- Department of Histology and Embryology, Dalian Medical University, Dalian, Liaoning 116044, P.R. China.,Department of Radiotherapy Oncology, The Second Hospital of Dalian Medical University, Dalian, Liaoning 116023, P.R. China
| | - Jiazhi Li
- Department of Radiotherapy Oncology, The Second Hospital of Dalian Medical University, Dalian, Liaoning 116023, P.R. China
| | - Xiang Ren
- Department of Histology and Embryology, Dalian Medical University, Dalian, Liaoning 116044, P.R. China
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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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Katoozi S, Rao SB, Skauli N, Froehner SC, Ottersen OP, Adams ME, Amiry-Moghaddam M. Functional specialization of retinal Müller cell endfeet depends on an interplay between two syntrophin isoforms. Mol Brain 2020; 13:40. [PMID: 32178707 PMCID: PMC7074989 DOI: 10.1186/s13041-020-00581-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2020] [Accepted: 03/06/2020] [Indexed: 11/10/2022] Open
Abstract
Retinal Müller cells are highly polarized macroglial cells with accumulation of the aquaporin-4 (AQP4) water channel and the inwardly rectifying potassium channel Kir4.1 at specialized endfoot membrane domains abutting microvessels and corpus vitreum. Proper water and potassium homeostasis in retina depends on these membrane specializations. Here we show that targeted deletion of β1-syntrophin leads to a partial loss of AQP4 from perivascular Müller cell endfeet and that a concomitant deletion of both α1- and β1-syntrophin causes a near complete loss of AQP4 from both perivascular and subvitreal endfoot membranes. α1-syntrophin is normally very weakly expressed in Müller cell endfeet but β1-syntrophin knockout mice display an increased amount of α1-syntrophin at these sites. We suggest that upregulation of perivascular α1-syntrophin restricts the effect of β1-syntrophin deletion. The present findings indicate that β1-syntrophin plays an important role in maintaining the functional polarity of Müller cells and that α1-syntrophin can partially substitute for β1-syntrophin in AQP4 anchoring. Functional polarization of Müller cells thus depends on an interplay between two syntrophin isoforms.
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Affiliation(s)
- Shirin Katoozi
- Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Post box 1105, Blindern, 0317, Oslo, Norway
| | - Shreyas B Rao
- Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Post box 1105, Blindern, 0317, Oslo, Norway
| | - Nadia Skauli
- Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Post box 1105, Blindern, 0317, Oslo, Norway
| | - Stanley C Froehner
- Department of Physiology and Biophysics, University of Washington, Seattle, WA, 98195-7290, USA
| | - Ole Petter Ottersen
- Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Post box 1105, Blindern, 0317, Oslo, Norway.,Present Address: President's office, Karolinska Institutet, Nobels väg 6, 171 77, Stockholm, Sweden
| | - Marvin E Adams
- Department of Physiology and Biophysics, University of Washington, Seattle, WA, 98195-7290, USA
| | - Mahmood Amiry-Moghaddam
- 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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Hoddevik EH, Rao SB, Zahl S, Boldt HB, Ottersen OP, Amiry-Moghaddam M. Organisation of extracellular matrix proteins laminin and agrin in pericapillary basal laminae in mouse brain. Brain Struct Funct 2020; 225:805-816. [PMID: 32072250 PMCID: PMC7046580 DOI: 10.1007/s00429-020-02036-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2019] [Accepted: 01/29/2020] [Indexed: 01/08/2023]
Abstract
Evidence suggests that extracellular matrix molecules of perivascular basal laminae help orchestrate the molecular assemblies at the gliovascular interface. Specifically, laminin and agrin are thought to tether the dystrophin-associated protein (DAP) complex to the astrocytic basal lamina. This complex includes α-syntrophin (α-Syn), which is believed to anchor aquaporin-4 (AQP4) to astrocytic endfoot membrane domains. We have previously shown that the size of the perivascular AQP4 pool differs considerably between brain regions in an α-Syn-dependent manner. Also, both AQP4 and α-Syn occur at higher densities in endfoot membrane domains facing pericytes than in endfoot membrane domains facing endothelial cells. The heterogeneous distribution of AQP4 at the regional and capillary level has been attributed to a direct interaction between AQP4 and α-Syn. This would be challenged (1) if the microdistributions of laminin and agrin fail to align with those of DAP and AQP4 and (2) if targeted deletion of α-Syn leads to a loss of laminin and/or agrin. Here, we provide the first detailed and quantitative analysis of laminin and agrin in brain basal laminae of mice. We show that the microdistributions of these molecules vary in a fashion that is well aligned with the previously reported microdistribution of AQP4. We also demonstrate that the expression patterns of laminin and agrin are insensitive to targeted deletion of α-Syn, suggesting that α-Syn deletion affects AQP4 directly and not indirectly via laminin or agrin. These data fill remaining voids in the current model of how key molecules are assembled and tethered at the gliovascular interface.
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Affiliation(s)
- Eystein Hellstrøm Hoddevik
- Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Blindern, Post box 1105, 0317, Oslo, Norway
- Department of Pathology, Oslo University Hospital, Oslo, Norway
| | - Shreyas Balachandra Rao
- Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Blindern, Post box 1105, 0317, Oslo, Norway
| | - Soulmaz Zahl
- Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Blindern, Post box 1105, 0317, Oslo, Norway
| | - Henning Bünsow Boldt
- Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Blindern, Post box 1105, 0317, Oslo, Norway
- Department of Pathology, Odense University Hospital, Odense, Denmark
| | - Ole Petter Ottersen
- Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Blindern, Post box 1105, 0317, Oslo, Norway
- President's Office, Karolinska Institutet, Nobels väg 6, 171 77, Stockholm, Sweden
| | - Mahmood Amiry-Moghaddam
- Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Blindern, Post box 1105, 0317, Oslo, Norway.
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