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The role of Aquaporins in Hearing Function and Dysfunction. Eur J Cell Biol 2022; 101:151252. [DOI: 10.1016/j.ejcb.2022.151252] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Revised: 06/09/2022] [Accepted: 06/22/2022] [Indexed: 11/23/2022] Open
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Löscher W, Kaila K. CNS pharmacology of NKCC1 inhibitors. Neuropharmacology 2021; 205:108910. [PMID: 34883135 DOI: 10.1016/j.neuropharm.2021.108910] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2021] [Revised: 11/25/2021] [Accepted: 11/26/2021] [Indexed: 12/21/2022]
Abstract
The Na-K-2Cl cotransporter NKCC1 and the neuron-specific K-Cl cotransporter KCC2 are considered attractive CNS drug targets because altered neuronal chloride regulation and consequent effects on GABAergic signaling have been implicated in numerous CNS disorders. While KCC2 modulators are not yet clinically available, the loop diuretic bumetanide has been used off-label in attempts to treat brain disorders and as a tool for NKCC1 inhibition in preclinical models. Bumetanide is known to have anticonvulsant and neuroprotective effects under some pathophysiological conditions. However, as shown in several species from neonates to adults (mice, rats, dogs, and by extrapolation in humans), at the low clinical doses of bumetanide approved for diuresis, this drug has negligible access into the CNS, reaching levels that are much lower than what is needed to inhibit NKCC1 in cells within the brain parenchyma. Several drug discovery strategies have been initiated over the last ∼15 years to develop brain-permeant compounds that, ideally, should be selective for NKCC1 to eliminate the diuresis mediated by inhibition of renal NKCC2. The strategies employed to improve the pharmacokinetic and pharmacodynamic properties of NKCC1 blockers include evaluation of other clinically approved loop diuretics; development of lipophilic prodrugs of bumetanide; development of side-chain derivatives of bumetanide; and unbiased high-throughput screening approaches of drug discovery based on large chemical compound libraries. The main outcomes are that (1), non-acidic loop diuretics such as azosemide and torasemide may have advantages as NKCC1 inhibitors vs. bumetanide; (2), bumetanide prodrugs lead to significantly higher brain levels than the parent drug and have lower diuretic activity; (3), the novel bumetanide side-chain derivatives do not exhibit any functionally relevant improvement of CNS accessibility or NKCC1 selectivity vs. bumetanide; (4) novel compounds discovered by high-throughput screening may resolve some of the inherent problems of bumetanide, but as yet this has not been achieved. Thus, further research is needed to optimize the design of brain-permeant NKCC1 inhibitors. In parallel, a major challenge is to identify the mechanisms whereby various NKCC1-expressing cellular targets of these drugs within (e.g., neurons, oligodendrocytes or astrocytes) and outside the brain parenchyma (e.g., the blood-brain barrier, the choroid plexus, and the endocrine system), as well as molecular off-target effects, might contribute to their reported therapeutic and adverse effects.
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Affiliation(s)
- Wolfgang Löscher
- Dept. of Pharmacology, Toxicology, and Pharmacy, University of Veterinary Medicine Hannover, Germany; Center for Systems Neuroscience Hannover, Germany.
| | - Kai Kaila
- Molecular and Integrative Biosciences and Neuroscience Center (HiLIFE), University of Helsinki, Finland
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Klug NR, Chechneva OV, Hung BY, O'Donnell ME. High glucose-induced effects on Na +-K +-2Cl - cotransport and Na +/H + exchange of blood-brain barrier endothelial cells: involvement of SGK1, PKCβII, and SPAK/OSR1. Am J Physiol Cell Physiol 2021; 320:C619-C634. [PMID: 33406028 DOI: 10.1152/ajpcell.00177.2019] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Hyperglycemia exacerbates edema formation and worsens neurological outcome in ischemic stroke. Edema formation in the early hours of stroke involves transport of ions and water across an intact blood-brain barrier (BBB), and swelling of astrocytes. We showed previously that high glucose (HG) exposures of 24 hours to 7 days increase abundance and activity of BBB Na+-K+-2Cl- cotransport (NKCC) and Na+/H+ exchange 1 (NHE1). Further, bumetanide and HOE-642 inhibition of these transporters significantly reduces edema and infarct following middle cerebral artery occlusion in hyperglycemic rats, suggesting that NKCC and NHE1 are effective therapeutic targets for reducing edema in hyperglycemic stroke. The mechanisms underlying hyperglycemia effects on BBB NKCC and NHE1 are not known. In the present study we investigated whether serum-glucocorticoid regulated kinase 1 (SGK1) and protein kinase C beta II (PKCβII) are involved in HG effects on BBB NKCC and NHE1. We found transient increases in phosphorylated SGK1 and PKCβII within the first hour of HG exposure, after 5-60 min for SGK1 and 5 min for PKCβII. However, no changes were observed in cerebral microvascular endothelial cell SGK1 or PKCβII abundance or phosphorylation (activity) after 24 or 48 h HG exposures. Further, we found that HG-induced increases in NKCC and NHE1 abundance were abolished by inhibition of SGK1 but not PKCβII, whereas the increases in NKCC and NHE activity were abolished by inhibition of either kinase. Finally, we found evidence that STE20/SPS1-related proline/alanine-rich kinase and oxidative stress-responsive kinase-1 (SPAK/OSR1) participate in the HG-induced effects on BBB NKCC.
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Affiliation(s)
- Nicholas R Klug
- Department of Physiology and Membrane Biology, University of California, Davis, California
| | - Olga V Chechneva
- Department of Physiology and Membrane Biology, University of California, Davis, California
| | - Benjamin Y Hung
- Department of Physiology and Membrane Biology, University of California, Davis, California
| | - Martha E O'Donnell
- Department of Physiology and Membrane Biology, University of California, Davis, California
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Kakigi A, Egami N, Uehara N, Fujita T, Nibu KI, Yamashita S, Yamasoba T. Live imaging and functional changes of the inner ear in an animal model of Meniere's disease. Sci Rep 2020; 10:12271. [PMID: 32704101 PMCID: PMC7378199 DOI: 10.1038/s41598-020-68352-0] [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: 03/09/2020] [Accepted: 06/23/2020] [Indexed: 11/20/2022] Open
Abstract
The symptoms of Meniere's disease (MD) are generally considered to be related to endolymphatic hydrops (EH). There are many recent reports supporting the possibility that vasopressin (VP) is closely linked to the formation of EH in Meniere's disease. Based on this, we developed a clinically relevant animal model of Meniere's disease in which a VP type 2 receptor agonist was administered after electrocauterization of the endolymphatic sac. We report live imaging of the internal structure, and functional changes of the inner ear after electrocauterization of the endolymphatic sac and administration of a VP type 2 receptor agonist. In this model, the development of EH was visualized in vivo using optical coherence tomography, there was no rupture of Reissner's membrane, and low-tone hearing loss and vertiginous attacks were observed. This study suggested that acute attacks are caused by the abrupt development of EH. This is the first report of live imaging of the development of EH induced by the administration of a VP type 2 receptor agonist.
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Affiliation(s)
- Akinobu Kakigi
- Department of Otolaryngology-Head and Neck Surgery, Kobe University, Graduate School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe, Hyogo, 650-0017, Japan.
| | - Naoya Egami
- Department of Otolaryngology, Faculty of Medicine, The University of Tokyo, Tokyo, 113-8655, Japan
| | - Natsumi Uehara
- Department of Otolaryngology-Head and Neck Surgery, Kobe University, Graduate School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe, Hyogo, 650-0017, Japan
| | - Takeshi Fujita
- Department of Otolaryngology-Head and Neck Surgery, Kobe University, Graduate School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe, Hyogo, 650-0017, Japan
| | - Ken-Ichi Nibu
- Department of Otolaryngology-Head and Neck Surgery, Kobe University, Graduate School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe, Hyogo, 650-0017, Japan
| | - Shinji Yamashita
- Research Center for Advanced Science and Technology, The University of Tokyo, Tokyo, 153-8904, Japan
| | - Tatsuya Yamasoba
- Department of Otolaryngology, Faculty of Medicine, The University of Tokyo, Tokyo, 113-8655, Japan
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Xu LH, Yang Y, Liu HX, Xiao SF, Qiu WX, Wang JX, Zhao CC, Gui YH, Liu GZ, Peng B, Li X, Wang GH, Zhou X, Jiang ZL. Inner Ear Arginine Vasopressin-Vasopressin Receptor 2-Aquaporin 2 Signaling Pathway Is Involved in the Induction of Motion Sickness. J Pharmacol Exp Ther 2020; 373:248-260. [PMID: 32165443 DOI: 10.1124/jpet.119.264390] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2019] [Accepted: 02/24/2020] [Indexed: 11/22/2022] Open
Abstract
It has been identified that arginine vasopressin (AVP), vasopressin receptor 2(V2R), and the aquaporin 2 (AQP2) signaling pathway in the inner ear play important roles in hearing and balance functions through regulating the endolymph equilibrium; however, the contributions of this signaling pathway to the development of motion sickness are unclear. The present study was designed to investigate whether the activation of the AVP-V2R-AQP2 signaling pathway in the inner ear is involved in the induction of motion sickness and whether mozavaptan, a V2R antagonist, could reduce motion sickness. We found that both rotatory stimulus and intraperitoneal AVP injection induced conditioned taste aversion (a confirmed behavioral index for motion sickness) in rats and activated the AVP-V2R-AQP2 signaling pathway with a responsive V2R downregulation in the inner ears, and AVP perfusion in cultured epithelial cells from rat endolymphatic sacs induced similar changes in this pathway signaling. Vestibular training, V2R antagonist mozavaptan, or PKA inhibitor H89 blunted these changes in the V2R-AQP2 pathway signaling while reducing rotatory stimulus- or DDAVP (a V2R agonist)-induced motion sickness in rats and dogs. Therefore, our results suggest that activation of the inner ear AVP-V2R-AQP2 signaling pathway is potentially involved in the development of motion sickness; thus, mozavaptan targeting AVP V2Rs in the inner ear may provide us with a new application option to reduce motion sickness. SIGNIFICANCE STATEMENT: Motion sickness affects many people traveling or working. In the present study our results showed that activation of the inner ear arginine vasopressin-vaspopressin receptor 2 (V2R)-aquaporin 2 signaling pathway was potentially involved in the development of motion sickness and that blocking V2R with mozavaptan, a V2R antagonist, was much more effective in reducing motion sickness in both rat and dog; therefore, we demonstrated a new mechanism to underlie motion sickness and a new candidate drug to reduce motion sickness.
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Affiliation(s)
- Li-Hua Xu
- Department of Neurophysiology and Neuropharmacology, Institute of Special Environmental Medicine, Institute of Nautical Medicine and Co-innovation Center of Neuroregeneration, Nantong University, Nantong, Jiangsu, China
| | - Yao Yang
- Department of Neurophysiology and Neuropharmacology, Institute of Special Environmental Medicine, Institute of Nautical Medicine and Co-innovation Center of Neuroregeneration, Nantong University, Nantong, Jiangsu, China
| | - Hong-Xia Liu
- Department of Neurophysiology and Neuropharmacology, Institute of Special Environmental Medicine, Institute of Nautical Medicine and Co-innovation Center of Neuroregeneration, Nantong University, Nantong, Jiangsu, China
| | - Shui-Feng Xiao
- Department of Neurophysiology and Neuropharmacology, Institute of Special Environmental Medicine, Institute of Nautical Medicine and Co-innovation Center of Neuroregeneration, Nantong University, Nantong, Jiangsu, China
| | - Wen-Xia Qiu
- Department of Neurophysiology and Neuropharmacology, Institute of Special Environmental Medicine, Institute of Nautical Medicine and Co-innovation Center of Neuroregeneration, Nantong University, Nantong, Jiangsu, China
| | - Jin-Xing Wang
- Department of Neurophysiology and Neuropharmacology, Institute of Special Environmental Medicine, Institute of Nautical Medicine and Co-innovation Center of Neuroregeneration, Nantong University, Nantong, Jiangsu, China
| | - Chen-Chen Zhao
- Department of Neurophysiology and Neuropharmacology, Institute of Special Environmental Medicine, Institute of Nautical Medicine and Co-innovation Center of Neuroregeneration, Nantong University, Nantong, Jiangsu, China
| | - Yuan-Hong Gui
- Department of Neurophysiology and Neuropharmacology, Institute of Special Environmental Medicine, Institute of Nautical Medicine and Co-innovation Center of Neuroregeneration, Nantong University, Nantong, Jiangsu, China
| | - Gui-Zhu Liu
- Department of Neurophysiology and Neuropharmacology, Institute of Special Environmental Medicine, Institute of Nautical Medicine and Co-innovation Center of Neuroregeneration, Nantong University, Nantong, Jiangsu, China
| | - Bin Peng
- Department of Neurophysiology and Neuropharmacology, Institute of Special Environmental Medicine, Institute of Nautical Medicine and Co-innovation Center of Neuroregeneration, Nantong University, Nantong, Jiangsu, China
| | - Xia Li
- Department of Neurophysiology and Neuropharmacology, Institute of Special Environmental Medicine, Institute of Nautical Medicine and Co-innovation Center of Neuroregeneration, Nantong University, Nantong, Jiangsu, China
| | - Guo-Hua Wang
- Department of Neurophysiology and Neuropharmacology, Institute of Special Environmental Medicine, Institute of Nautical Medicine and Co-innovation Center of Neuroregeneration, Nantong University, Nantong, Jiangsu, China
| | - Xin Zhou
- Department of Neurophysiology and Neuropharmacology, Institute of Special Environmental Medicine, Institute of Nautical Medicine and Co-innovation Center of Neuroregeneration, Nantong University, Nantong, Jiangsu, China
| | - Zheng-Lin Jiang
- Department of Neurophysiology and Neuropharmacology, Institute of Special Environmental Medicine, Institute of Nautical Medicine and Co-innovation Center of Neuroregeneration, Nantong University, Nantong, Jiangsu, China
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“Reversed polarization” of Na/K-ATPase—a sign of inverted transport in the human endolymphatic sac: a super-resolution structured illumination microscopy (SR-SIM) study. Cell Tissue Res 2019; 379:445-457. [DOI: 10.1007/s00441-019-03106-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Accepted: 09/15/2019] [Indexed: 02/06/2023]
Abstract
AbstractThe human endolymphatic sac (ES) is believed to regulate inner ear fluid homeostasis and to be associated with Meniere’s disease (MD). We analyzed the ion transport protein sodium/potassium-ATPase (Na/K-ATPase) and its isoforms in the human ES using super-resolution structured illumination microscopy (SR-SIM). Human vestibular aqueducts were collected during trans-labyrinthine vestibular schwannoma surgery after obtaining ethical permission. Antibodies against various isoforms of Na/K-ATPase and additional solute-transporting proteins, believed to be essential for ion and fluid transport, were used for immunohistochemistry. A population of epithelial cells of the human ES strongly expressed Na/K-ATPase α1, β1, and β3 subunit isoforms in either the lateral/basolateral or apical plasma membrane domains. The β1 isoform was expressed in the lateral/basolateral plasma membranes in mostly large cylindrical cells, while β3 and α1 both were expressed with “reversed polarity” in the apical cell membrane in lower epithelial cells. The heterogeneous expression of Na/K-ATPase subunits substantiates earlier notions that the ES is a dynamic structure where epithelial cells show inverted epithelial transport. Dual absorption and secretion processes may regulate and maintain inner ear fluid homeostasis. These findings may shed new light on the etiology of endolymphatic hydrops and MD.
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Dong SH, Kim SS, Kim SH, Yeo SG. Expression of aquaporins in inner ear disease. Laryngoscope 2019; 130:1532-1539. [PMID: 31593306 DOI: 10.1002/lary.28334] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2019] [Revised: 09/05/2019] [Accepted: 09/10/2019] [Indexed: 12/22/2022]
Abstract
The inner ear is responsible for hearing and balance and consists of a membranous labyrinth within a bony labyrinth. The balance structure is divided into the otolith organ that recognizes linear acceleration and the semicircular canal that is responsible for rotational movement. The cochlea is the hearing organ. The external and middle ear are covered with skin and mucosa, respectively, and the space is filled with air, whereas the inner ear is composed of endolymph and perilymph. The inner ear is a fluid-filled sensory organ composed of hair cells with cilia on the upper part of the cells that convert changes in sound energy and balance into electric energy through the hair cells to transmit signals to the auditory nerve through synapses. Aquaporins (AQPs) are a family of transmembrane proteins present in all species that can be roughly divided into three subfamilies according to structure and function: 1) classical AQP, 2) aquaglyceroporin, and 3) superaquaporin. Currently, the subfamily of mammalian species is known to include 13 AQP members (AQP0-AQP12). AQPs have a variety of functions depending on their structure and are related to inner ear diseases such as Meniere's disease, sensorineural hearing loss, and presbycusis. Additional studies on the relationship between the inner ear and AQPs may be helpful in the diagnosis and treatment of inner ear disease. Laryngoscope, 130:1532-1539, 2020.
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Affiliation(s)
- Sung Hwa Dong
- Department of Otorhinolaryngology-Head and Neck Surgery, Graduate School, Kyung Hee University, Seoul, South Korea
| | - Sung Su Kim
- Medical Research Center for Bioreaction to Reactive Oxygen Species and Biomedical Science Institute, School of Medicine, Graduate School, Kyung Hee University, Seoul, South Korea
| | - Sang Hoon Kim
- Department of Otorhinolaryngology-Head and Neck Surgery, Graduate School, Kyung Hee University, Seoul, South Korea
| | - Seung Geun Yeo
- Department of Otorhinolaryngology-Head and Neck Surgery, Graduate School, Kyung Hee University, Seoul, South Korea.,Medical Research Center for Bioreaction to Reactive Oxygen Species and Biomedical Science Institute, School of Medicine, Graduate School, Kyung Hee University, Seoul, South Korea
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JIANG LY, CHEN XX, HE JJ, CHEN HD. Effects of electroacupuncture on cochlear morphology and expression of aquaporins in rats with AVP-induced endolymphatic hydrops. WORLD JOURNAL OF ACUPUNCTURE-MOXIBUSTION 2019. [DOI: 10.1016/j.wjam.2019.03.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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Delpire E, Gagnon KB. Na + -K + -2Cl - Cotransporter (NKCC) Physiological Function in Nonpolarized Cells and Transporting Epithelia. Compr Physiol 2018; 8:871-901. [PMID: 29687903 DOI: 10.1002/cphy.c170018] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Two genes encode the Na+ -K+ -2Cl- cotransporters, NKCC1 and NKCC2, that mediate the tightly coupled movement of 1Na+ , 1K+ , and 2Cl- across the plasma membrane of cells. Na+ -K+ -2Cl- cotransport is driven by the chemical gradient of the three ionic species across the membrane, two of them maintained by the action of the Na+ /K+ pump. In many cells, NKCC1 accumulates Cl- above its electrochemical potential equilibrium, thereby facilitating Cl- channel-mediated membrane depolarization. In smooth muscle cells, this depolarization facilitates the opening of voltage-sensitive Ca2+ channels, leading to Ca2+ influx, and cell contraction. In immature neurons, the depolarization due to a GABA-mediated Cl- conductance produces an excitatory rather than inhibitory response. In many cell types that have lost water, NKCC is activated to help the cells recover their volume. This is specially the case if the cells have also lost Cl- . In combination with the Na+ /K+ pump, the NKCC's move ions across various specialized epithelia. NKCC1 is involved in Cl- -driven fluid secretion in many exocrine glands, such as sweat, lacrimal, salivary, stomach, pancreas, and intestine. NKCC1 is also involved in K+ -driven fluid secretion in inner ear, and possibly in Na+ -driven fluid secretion in choroid plexus. In the thick ascending limb of Henle, NKCC2 activity in combination with the Na+ /K+ pump participates in reabsorbing 30% of the glomerular-filtered Na+ . Overall, many critical physiological functions are maintained by the activity of the two Na+ -K+ -2Cl- cotransporters. In this overview article, we focus on the functional roles of the cotransporters in nonpolarized cells and in epithelia. © 2018 American Physiological Society. Compr Physiol 8:871-901, 2018.
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Affiliation(s)
- Eric Delpire
- Department of Anesthesiology, Vanderbilt University Medical School, Nashville, Tennessee, USA
| | - Kenneth B Gagnon
- Division of Nephrology and Hypertension, Department of Medicine, University of Louisville School of Medicine, Louisville, Keystone, USA
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Asmar MH, Gaboury L, Saliba I. Ménière’s Disease Pathophysiology: Endolymphatic Sac Immunohistochemical Study of Aquaporin-2, V2R Vasopressin Receptor, NKCC2, and TRPV4. Otolaryngol Head Neck Surg 2018; 158:721-728. [DOI: 10.1177/0194599818756829] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Objectives Endolymphatic sac (ELS) pathophysiology in Ménière’s disease (MD) remains poorly understood. We identified from the literature a group of proteins expressed on the ELS and involved in endolymph volume regulation: aquaporin-2 (AQP2), vasopressin receptor V2R, sodium potassium chloride cotransporter 2 (NKCC2), and transient receptor potential cation channel V4 (TRPV4). Our objective was to determine whether their ELS expression was altered in MD, to better understand the pathophysiology of endolymphatic hydrops. Study Design Prospective case-control study. Setting Tertiary care center. Subjects Twenty-four patients with definite MD undergoing endolymphatic duct blockage surgery were recruited, as well as 23 controls with no history of MD undergoing surgery for vestibular schwannoma (VS). Methods ELS biopsies and blood samples for plasma arginine vasopressin (AVP) were obtained. Immunohistochemistry for AQP2, V2R, NKCC2, and TRPV4 was performed. Slides were scanned digitally for highly sensitive pixel density analysis by specialized software (VIS; Visiopharm). Results Global scores generated by the software represent total and relative protein expression density of 3 staining intensity levels, exclusively on ELS epithelium. AQP2 expression density was significantly elevated in MD compared to VS ( P = .003). There was no significant difference in plasma AVP, V2R, NKCC2, and TRPV4 expression. Conclusion This original study evaluates simultaneous in situ expression of AQP2, V2R, NKCC2, and TRPV4 on the human ELS in MD, with a control group. Our results show only AQP2 upregulation on the ELS of patients with MD. We suggest a constitutively increased expression of AQP2 in MD, independent of its regulatory axis (AVP-V2R). Acquired regulator sequence mutations could support this model.
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Affiliation(s)
- Marc-Henri Asmar
- University of Montreal Hospital Centre Research Centre (CRCHUM), Montreal, QC, Canada
| | - Louis Gaboury
- University of Montreal Hospital Centre Research Centre (CRCHUM), Montreal, QC, Canada
- Department of Pathology and Cell Biology, University of Montreal Hospital Centre (CHUM), Montreal, QC, Canada
| | - Issam Saliba
- University of Montreal Hospital Centre Research Centre (CRCHUM), Montreal, QC, Canada
- Division of Otolaryngology–Head & Neck Surgery, University of Montreal Hospital Centre (CHUM), Montreal, QC, Canada
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Ménière's Disease: Molecular Analysis of Aquaporins 2, 3 and Potassium Channel KCNE1 Genes in Brazilian Patients. Otol Neurotol 2017; 37:1117-21. [PMID: 27509294 DOI: 10.1097/mao.0000000000001136] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
OBJECTIVES Ménière's disease (MD) is a complex disease of unknown etiology characterized by a symptomatic tetrad of vertigo, hearing loss, tinnitus, and aural fullness. In addition to factors related to homeostasis of the inner ear, genetic factors have been implicated in its pathophysiology, including genes related to the transport of water and ionic composition maintenance of the endolymph, such as the aquaporin genes AQP2 and AQP3, and the potassium channel gene KCNE1. The aim of this study was to identify polymorphisms of these genes and determine their association with clinical characteristics of patients with MD. DESIGN A case-control genetic association study was carried out, including 30 patients with definite Ménière's disease and 30 healthy controls. The coding regions of the target genes were amplified from blood samples by polymerase chain reaction (PCR), followed by direct sequencing. The associations of polymorphisms with clinical characteristics were analyzed with logistic regression. RESULTS Five polymorphisms were identified: rs426496 in AQP2; rs591810 in AQP3; and rs1805127, rs1805128, and rs17173510 in KCNE1. After adjustment, rs426496 was significantly associated with tinnitus during the initial crisis and with altered electronystagmography, and rs1805127 was significantly associated with nephropathy. CONCLUSIONS The genetic variant rs426496 in AQP2; rs591810 in AQP3 and rs1805127, rs1805128, and rs17173510, in KCNE1 were found in patients with Ménière's disease. The polymorphism rs426496, in AQP2, is associated with tinnitus at the onset of Ménière's disease and altered electronystagmography. In addition, rs1805127, in KCNE1, is associated with the presence of nephropathy.
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Takumida M, Takumida H, Anniko M. Gastric-type H +,K +-ATPase in mouse vestibular end organs. Acta Otolaryngol 2017; 137:455-459. [PMID: 27768854 DOI: 10.1080/00016489.2016.1245865] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
CONCLUSION Gastric type H+,K+-ATPase in the vestibular end organs may be of importance for K+ circulation and may also be related to pH regulation in vestibular end organs and endolymphatic sac. OBJECTIVE To analyze the expression of gastric-type H+,K+-ATPase in normal mouse vestibular end organs. METHODS 8 weeks old CBA/J mice were used in this study. The presence of gastric-type H+,K+-ATPase α and β in the vestibular end organs, viz. utricle, saccule, ampulla, vestibular ganglion, and endolymphatic sac, was investigated using immunohistochemistry. RESULTS In the vestibular end organs, H+,K+-ATPase α and β were almost identical. H+,K+-ATPase was expressed in sensory cells, the basolateral surface of dark cells, fibrocytes, in vestibular ganglion cells, and in the upper region of the endolymphatic sac epithelial cells.
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Affiliation(s)
- Masaya Takumida
- Department of Otolaryngology, University Hospital, Hiroshima, Japan
| | | | - Matti Anniko
- Department of Otolaryngolog and Head & Neck Surgery, Uppsala University, Uppsala, Sweden
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13
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Runggaldier D, Pradas LG, Neckel PH, Mack AF, Hirt B, Gleiser C. Claudin expression in the rat endolymphatic duct and sac - first insights into regulation of the paracellular barrier by vasopressin. Sci Rep 2017; 7:45482. [PMID: 28374851 PMCID: PMC5379655 DOI: 10.1038/srep45482] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2016] [Accepted: 02/28/2017] [Indexed: 12/13/2022] Open
Abstract
Hearing and balance functions of the inner ear rely on the homeostasis of the endolymphatic fluid. When disturbed, pathologic endolymphatic hydrops evolves as observed in Menière’s disease. The molecular basis of inner ear fluid regulation across the endolymphatic epithelium is largely unknown. In this study we identified the specific expression of the tight junction (TJ) molecules Claudin 3, 4, 6, 7, 8, 10, and 16 in epithelial preparations of the rat inner ear endolymphatic duct (ED) and endolymphatic sac (ES) by high-throughput qPCR and immunofluorescence confocal microscopy. Further we showed that Claudin 4 in the ES is a target of arginine-vasopressin (AVP), a hormone elevated in Menière’s disease. Moreover, our transmission-electron microscopy (TEM) analysis revealed that the TJs of the ED were shallow and shorter compared to the TJ of the ES indicating facilitation of a paracellular fluid transport across the ED epithelium. The significant differences in the subcellular localization of the barrier-forming protein Claudin 3 between the ED and ES epithelium further support the TEM observations. Our results indicate a high relevance of Claudin 3 and Claudin 4 as important paracellular barrier molecules in the ED and ES epithelium with potential involvement in the pathophysiology of Menière’s disease.
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Affiliation(s)
- Daniel Runggaldier
- Institute of Clinical Anatomy and Cell Analysis, University of Tübingen, Tübingen, Germany
| | - Lidia Garcia Pradas
- Institute of Clinical Anatomy and Cell Analysis, University of Tübingen, Tübingen, Germany
| | - Peter H Neckel
- Institute of Clinical Anatomy and Cell Analysis, University of Tübingen, Tübingen, Germany
| | - Andreas F Mack
- Institute of Clinical Anatomy and Cell Analysis, University of Tübingen, Tübingen, Germany
| | - Bernhard Hirt
- Institute of Clinical Anatomy and Cell Analysis, University of Tübingen, Tübingen, Germany
| | - Corinna Gleiser
- Institute of Clinical Anatomy and Cell Analysis, University of Tübingen, Tübingen, Germany
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Singh R, Kursan S, Almiahoub MY, Almutairi MM, Garzón-Muvdi T, Alvarez-Leefmans FJ, Di Fulvio M. Plasma Membrane Targeting of Endogenous NKCC2 in COS7 Cells Bypasses Functional Golgi Cisternae and Complex N-Glycosylation. Front Cell Dev Biol 2017; 4:150. [PMID: 28101499 PMCID: PMC5209364 DOI: 10.3389/fcell.2016.00150] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Accepted: 12/14/2016] [Indexed: 12/04/2022] Open
Abstract
Na+K+2Cl− co-transporters (NKCCs) effect the electroneutral movement of Na+-K+ and 2Cl− ions across the plasma membrane of vertebrate cells. There are two known NKCC isoforms, NKCC1 (Slc12a2) and NKCC2 (Slc12a1). NKCC1 is a ubiquitously expressed transporter involved in cell volume regulation, Cl− homeostasis and epithelial salt secretion, whereas NKCC2 is abundantly expressed in kidney epithelial cells of the thick ascending loop of Henle, where it plays key roles in NaCl reabsorption and electrolyte homeostasis. Although NKCC1 and NKCC2 co-transport the same ions with identical stoichiometry, NKCC1 actively co-transports water whereas NKCC2 does not. There is growing evidence showing that NKCC2 is expressed outside the kidney, but its function in extra-renal tissues remains unknown. The present study shows molecular and functional evidence of endogenous NKCC2 expression in COS7 cells, a widely used mammalian cell model. Endogenous NKCC2 is primarily found in recycling endosomes, Golgi cisternae, Golgi-derived vesicles, and to a lesser extent in the endoplasmic reticulum. Unlike NKCC1, NKCC2 is minimally hybrid/complex N-glycosylated under basal conditions and yet it is trafficked to the plasma membrane region of hyper-osmotically challenged cells through mechanisms that require minimal complex N-glycosylation or functional Golgi cisternae. Control COS7 cells exposed to slightly hyperosmotic (~6.7%) solutions for 16 h were not shrunken, suggesting that either one or both NKCC1 and NKCC2 may participate in cell volume recovery. However, NKCC2 targeted to the plasma membrane region or transient over-expression of NKCC2 failed to rescue NKCC1 in COS7 cells where NKCC1 had been silenced. Further, COS7 cells in which NKCC1, but not NKCC2, was silenced exhibited reduced cell size compared to control cells. Altogether, these results suggest that NKCC2 does not participate in cell volume recovery and therefore, NKCC1 and NKCC2 are functionally different Na+K+2Cl− co-transporters.
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Affiliation(s)
- Richa Singh
- Department of Pharmacology and Toxicology, Boonshoft School of Medicine, Wright State University Dayton, OH, USA
| | - Shams Kursan
- Department of Pharmacology and Toxicology, Boonshoft School of Medicine, Wright State University Dayton, OH, USA
| | - Mohamed Y Almiahoub
- Department of Pharmacology and Toxicology, Boonshoft School of Medicine, Wright State University Dayton, OH, USA
| | - Mohammed M Almutairi
- Department of Pharmacology and Toxicology, Boonshoft School of Medicine, Wright State University Dayton, OH, USA
| | - Tomás Garzón-Muvdi
- Department of Pharmacology and Toxicology, Boonshoft School of Medicine, Wright State University Dayton, OH, USA
| | - Francisco J Alvarez-Leefmans
- Department of Pharmacology and Toxicology, Boonshoft School of Medicine, Wright State University Dayton, OH, USA
| | - Mauricio Di Fulvio
- Department of Pharmacology and Toxicology, Boonshoft School of Medicine, Wright State University Dayton, OH, USA
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15
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Miyoshi T, Yamaguchi T, Ogita K, Tanaka Y, Ishibashi KI, Ito H, Kobayashi T, Nakagawa T, Ito J, Omori K, Yamamoto N. Quantitative Analysis of Aquaporin Expression Levels during the Development and Maturation of the Inner Ear. J Assoc Res Otolaryngol 2016; 18:247-261. [PMID: 28004290 DOI: 10.1007/s10162-016-0607-3] [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: 03/26/2016] [Accepted: 11/24/2016] [Indexed: 01/30/2023] Open
Abstract
Aquaporins (AQPs) are a family of small membrane proteins that transport water molecules across the plasma membrane along the osmotic gradient. Mammals express 13 subtypes of AQPs, including the recently reported "subcellular AQPs", AQP11 and 12. Each organ expresses specific subsets of AQP subtypes, and in the inner ear, AQPs are essential for the establishment and maintenance of two distinct fluids, endolymph and perilymph. To evaluate the contribution of AQPs during the establishment of inner ear function, we used quantitative reverse transcription polymerase chain reaction to quantify the expression levels of all known AQPs during the entire development and maturation of the inner ear. Using systematic and longitudinal quantification, we found that AQP11 was majorly and constantly expressed in the inner ear, and that the expression levels of several AQPs follow characteristic longitudinal patterns: increasing (Aqp0, 1, and 9), decreasing (Aqp6, 8, and 12), and peak of expression on E18 (Aqp2, 5, and 7). In particular, the expression level of Aqp9 increased by 70-fold during P3-P21. We also performed in situ hybridization of Aqp11, and determined the unique localization of Aqp11 in the outer hair cells. Immunohistochemistry of AQP9 revealed its localization in the supporting cells inside the organ of Corti, and in the root cells. The emergence of AQP9 expression in these cells was during P3-P21, which was coincident with the marked increase of its expression level. Combining these quantification and localization data, we discuss the possible contributions of these AQPs to inner ear function.
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Affiliation(s)
- Takushi Miyoshi
- Department of Otolaryngology, Head and Neck Surgery, Graduate School of Medicine, Kyoto University, 54 Shogoin Kawahara-cho, Sakyo-ku, Kyoto, 606-8507, Kyoto, Japan
| | - Taro Yamaguchi
- Department of Pharmacology, Faculty of Pharmaceutical Sciences, Setsunan University, Neyagawa, 572-0074, Osaka, Japan
| | - Kiyokazu Ogita
- Department of Pharmacology, Faculty of Pharmaceutical Sciences, Setsunan University, Neyagawa, 572-0074, Osaka, Japan
| | - Yasuko Tanaka
- Department of Medical Physiology, Meiji Pharmaceutical University, Kiyose, 204-0004, Tokyo, Japan
| | - Ken-Ichi Ishibashi
- Department of Medical Physiology, Meiji Pharmaceutical University, Kiyose, 204-0004, Tokyo, Japan
| | - Hiroaki Ito
- Department of Otolaryngology, Head and Neck Surgery, Kochi Medical School, Nangoku, 783-0043, Kochi, Japan
| | - Taisuke Kobayashi
- Department of Otolaryngology, Head and Neck Surgery, Kochi Medical School, Nangoku, 783-0043, Kochi, Japan
| | - Takayuki Nakagawa
- Department of Otolaryngology, Head and Neck Surgery, Graduate School of Medicine, Kyoto University, 54 Shogoin Kawahara-cho, Sakyo-ku, Kyoto, 606-8507, Kyoto, Japan
| | - Juichi Ito
- Department of Otolaryngology, Head and Neck Surgery, Graduate School of Medicine, Kyoto University, 54 Shogoin Kawahara-cho, Sakyo-ku, Kyoto, 606-8507, Kyoto, Japan.,Shiga Medical Center Research Institute, Moriyama, 524-0022, Shiga, Japan
| | - Koichi Omori
- Department of Otolaryngology, Head and Neck Surgery, Graduate School of Medicine, Kyoto University, 54 Shogoin Kawahara-cho, Sakyo-ku, Kyoto, 606-8507, Kyoto, Japan
| | - Norio Yamamoto
- Department of Otolaryngology, Head and Neck Surgery, Graduate School of Medicine, Kyoto University, 54 Shogoin Kawahara-cho, Sakyo-ku, Kyoto, 606-8507, Kyoto, Japan.
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16
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Ion transport its regulation in the endolymphatic sac: suggestions for clinical aspects of Meniere's disease. Eur Arch Otorhinolaryngol 2016; 274:1813-1820. [PMID: 27804084 PMCID: PMC5340852 DOI: 10.1007/s00405-016-4362-1] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2016] [Accepted: 10/26/2016] [Indexed: 01/22/2023]
Abstract
Ion transport and its regulation in the endolymphatic sac (ES) are reviewed on the basis of recent lines of evidence. The morphological and physiological findings demonstrate that epithelial cells in the intermediate portion of the ES are more functional in ion transport than those in the other portions. Several ion channels, ion transporters, ion exchangers, and so on have been reported to be present in epithelial cells of ES intermediate portion. An imaging study has shown that mitochondria-rich cells in the ES intermediate portion have a higher activity of Na+, K+-ATPase and a higher Na+ permeability than other type of cells, implying that molecules related to Na+ transport, such as epithelial sodium channel (ENaC), Na+–K+–2Cl− cotransporter 2 (NKCC2) and thiazide-sensitive Na+–Cl− cotransporter (NCC), may be present in mitochondria-rich cells. Accumulated lines of evidence suggests that Na+ transport is most important in the ES, and that mitochondria-rich cells play crucial roles in Na+ transport in the ES. Several lines of evidence support the hypothesis that aldosterone may regulate Na+ transport in ES, resulting in endolymph volume regulation. The presence of molecules related to acid/base transport, such as H+-ATPase, Na+–H+ exchanger (NHE), pendrin (SLC26A4), Cl−–HCO3− exchanger (SLC4A2), and carbonic anhydrase in ES epithelial cells, suggests that acid/base transport is another important one in the ES. Recent basic and clinical studies suggest that aldosterone may be involved in the effect of salt-reduced diet treatment in Meniere’s disease.
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17
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Lykke K, Töllner K, Feit PW, Erker T, MacAulay N, Löscher W. The search for NKCC1-selective drugs for the treatment of epilepsy: Structure-function relationship of bumetanide and various bumetanide derivatives in inhibiting the human cation-chloride cotransporter NKCC1A. Epilepsy Behav 2016; 59:42-9. [PMID: 27088517 DOI: 10.1016/j.yebeh.2016.03.021] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/18/2016] [Revised: 03/11/2016] [Accepted: 03/12/2016] [Indexed: 11/30/2022]
Abstract
The Na(+)-K(+)-Cl(-) cotransporter NKCC1 plays a major role in the regulation of intraneuronal Cl(-) concentration. Abnormal functionality of NKCC1 has been implicated in several brain disorders, including epilepsy. Bumetanide is the only available selective NKCC1 inhibitor, but also inhibits NKCC2, which can cause severe adverse effects during treatment of brain disorders. A NKCC1-selective bumetanide derivative would therefore be a desirable option. In the present study, we used the Xenopus oocyte heterologous expression system to compare the effects of bumetanide and several derivatives on the two major human splice variants of NKCCs, hNKCC1A and hNKCC2A. The derivatives were selected from a series of ~5000 3-amino-5-sulfamoylbenzoic acid derivatives, covering a wide range of structural modifications and diuretic potencies. To our knowledge, such structure-function relationships have not been performed before for NKCC1. Half maximal inhibitory concentrations (IC50s) of bumetanide were 0.68 (hNKCC1A) and 4.0μM (hNKCC2A), respectively, indicating that this drug is 6-times more potent to inhibit hNKCC1A than hNKCC2A. Side chain substitutions in the bumetanide molecule variably affected the potency to inhibit hNKCC1A. This allowed defining the minimal structural requirements necessary for ligand interaction. Unexpectedly, only a few of the bumetanide derivatives examined were more potent than bumetanide to inhibit hNKCC1A, and most of them also inhibited hNKCC2A, with a highly significant correlation between IC50s for the two NKCC isoforms. These data indicate that the structural requirements for inhibition of NKCC1 and NKCC2 are similar, which complicates development of bumetanide-related compounds with high selectivity for NKCC1.
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Affiliation(s)
- Kasper Lykke
- Department of Neuroscience and Pharmacology, University of Copenhagen, Copenhagen, Denmark
| | - Kathrin Töllner
- Department of Pharmacology, Toxicology, and Pharmacy, University of Veterinary Medicine Hannover, Germany; Center for Systems Neuroscience, Hannover, Germany
| | - Peter W Feit
- Department of Pharmacology, Toxicology, and Pharmacy, University of Veterinary Medicine Hannover, Germany
| | - Thomas Erker
- Department of Medicinal Chemistry, University of Vienna, Vienna, Austria
| | - Nanna MacAulay
- Department of Neuroscience and Pharmacology, University of Copenhagen, Copenhagen, Denmark.
| | - Wolfgang Löscher
- Department of Pharmacology, Toxicology, and Pharmacy, University of Veterinary Medicine Hannover, Germany; Center for Systems Neuroscience, Hannover, Germany.
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18
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Egami N, Kakigi A, Takeda T, Yamasoba T. Dehydration effects of a V2 antagonist on endolymphatic hydrops in guinea pigs. Hear Res 2016; 332:151-159. [DOI: 10.1016/j.heares.2015.12.017] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/14/2015] [Revised: 12/18/2015] [Accepted: 12/18/2015] [Indexed: 10/22/2022]
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19
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Morphological and functional changes in a new animal model of Ménière's disease. J Transl Med 2013; 93:1001-11. [PMID: 23877650 DOI: 10.1038/labinvest.2013.91] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2013] [Revised: 06/20/2013] [Accepted: 06/22/2013] [Indexed: 11/09/2022] Open
Abstract
The purpose of this study was to clarify the underlying mechanism of vertiginous attacks in Ménière's disease (MD) while obtaining insight into water homeostasis in the inner ear using a new animal model. We conducted both histopathological and functional assessment of the vestibular system in the guinea-pig. In the first experiment, all animals were maintained 1 or 4 weeks after electrocauterization of the endolymphatic sac of the left ear and were given either saline or desmopressin (vasopressin type 2 receptor agonist). The temporal bones from both ears were harvested and the extent of endolymphatic hydrops was quantitatively assessed. In the second experiment, either 1 or 4 weeks after surgery, animals were assessed for balance disorders and nystagmus after the administration of saline or desmopressin. In the first experiment, the proportion of endolymphatic space in the cochlea and the saccule was significantly greater in ears that survived for 4 weeks after surgery and were given desmopressin compared with other groups. In the second experiment, all animals that underwent surgery and were given desmopressin showed spontaneous nystagmus and balance disorder, whereas all animals that had surgery but without desmopressin administration were asymptomatic. Our animal model induced severe endolymphatic hydrops in the cochlea and the saccule, and showed episodes of balance disorder along with spontaneous nystagmus. These findings suggest that administration of desmopressin can exacerbate endolymphatic hydrops because of acute V2 (vasopressin type 2 receptor)-mediated effects, and, when combined with endolymphathic sac dysfunction, can cause temporary vestibular abnormalities that are similar to the vertiginous attacks in patients with MD.
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20
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Takumida M, Takumida H, Kakigi A, Egami N, Nishioka R, Anniko M. Localization of aquaporins in the mouse vestibular end organs. Acta Otolaryngol 2013; 133:804-13. [PMID: 23628076 DOI: 10.3109/00016489.2013.783717] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
CONCLUSION We found that aquaporins (AQPs) in the fluid transporting cells, such as vestibular dark cells and endolymphatic sac epithelial cells, seem to be of importance in fluid transport in the inner ear, while those in the sensory and ganglion cells may play a functional role in sensory cell transduction. OBJECTIVE Expression of AQPs (0-12) was analyzed in normal mouse vestibular end organs. METHODS CBA/J mice were used in this study. Localization of AQPs 0-12 in the vestibular end organs and endolymphatic sac was investigated by immunohistochemistry. RESULTS The AQPs were found abundantly distributed in many structures in the vestibular end organs, i.e. vestibular sensory and supporting cells, vestibular dark cells, vestibular ganglion cells, and the endolymphatic sac.
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Affiliation(s)
- Masaya Takumida
- Department of Otolaryngology, Hiroshima University Hospital, Hiroshima, Japan.
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21
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Water channel proteins in the inner ear and their link to hearing impairment and deafness. Mol Aspects Med 2012; 33:612-37. [DOI: 10.1016/j.mam.2012.06.004] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2012] [Revised: 06/11/2012] [Accepted: 06/17/2012] [Indexed: 11/24/2022]
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22
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Alshahrani S, Di Fulvio M. Enhanced insulin secretion and improved glucose tolerance in mice with homozygous inactivation of the Na(+)K(+)2Cl(-) co-transporter 1. J Endocrinol 2012; 215:59-70. [PMID: 22872759 DOI: 10.1530/joe-12-0244] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The intracellular chloride concentration ([Cl(-)](i)) in β-cells plays an important role in glucose-stimulated plasma membrane depolarisation and insulin secretion. [Cl(-)](i) is maintained above equilibrium in β-cells by the action of Cl(-) co-transporters of the solute carrier family 12 group A (Slc12a). β-Cells express Slc12a1 and Slc12a2, which are known as the bumetanide (BTD)-sensitive Na(+)-dependent K(+)2Cl(-) co-transporters 2 and 1 respectively. We show that mice lacking functional alleles of the Slc12a2 gene exhibit better fasting glycaemia, increased insulin secretion in response to glucose, and improved glucose tolerance when compared with wild-type (WT). This phenomenon correlated with increased sensitivity of β-cells to glucose in vitro and with increased β-cell mass. Further, administration of low doses of BTD to mice deficient in Slc12a2 worsened their glucose tolerance, and low concentrations of BTD directly inhibited glucose-stimulated insulin secretion from β-cells deficient in Slc12a2 but expressing intact Slc12a1 genes. Together, our results suggest for the first time that the Slc12a2 gene is not necessary for insulin secretion and that its absence increases β-cell secretory capacity. Further, impairment of insulin secretion with BTD in vivo and in vitro in islets lacking Slc12a2 genes unmasks a potential new role for Slc12a1 in β-cell physiology.
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Affiliation(s)
- Saeed Alshahrani
- Department of Pharmacology and Toxicology, School of Medicine, Wright State University, 216 HSB, Dayton, Ohio 45435, USA
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23
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Takumida M, Kakigi A, Egami N, Nishioka R, Anniko M. Localization of aquaporins 1, 2, and 3 and vasopressin type 2 receptor in the mouse inner ear. Acta Otolaryngol 2012; 132:807-13. [PMID: 22768909 DOI: 10.3109/00016489.2012.662718] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
CONCLUSION It is suggested that aquaporins (AQPs) 1, 2, and 3, and vasopressin type 2 receptors (V2Rs) in the fluid transporting cells, such as stria vascularis, vestibular dark and transitional cells, and endolymphatic sac epithelial cells, have an important role in fluid transport in the inner ear, while those in the sensory and ganglion cells may play a functional role in the sensory cell transduction system. OBJECTIVE To analyze expression of AQP1, AQP2, and AQP3 as well as V2Rs in the normal mouse inner ear. METHODS CBA/J mice were used in this study. Localization of AQP1, AQP2, AQP3, and V2Rs in the inner ear, i.e. cochlea, vestibular end organs, and endolymphatic sac, was investigated by immunohistochemistry. RESULTS The results show that AQP1, AQP2, AQP3, and V2Rs are abundantly distributed in many inner ear structures, i.e. stria vascularis, inner and outer hair cells, spiral ganglion cells, vestibular sensory and ganglion cells, vestibular dark and transitional cells, and the endolymphatic sac.
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Affiliation(s)
- Masaya Takumida
- Department of Otolaryngology, Hiroshima University Hospital, Japan.
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24
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Current Opinion in Otolaryngology & Head and Neck Surgery. Current world literature. Curr Opin Otolaryngol Head Neck Surg 2010; 18:466-74. [PMID: 20827086 DOI: 10.1097/moo.0b013e32833f3865] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Akiyama K, Miyashita T, Matsubara A, Mori N. The detailed localization pattern of Na+/K+/2Cl- cotransporter type 2 and its related ion transport system in the rat endolymphatic sac. J Histochem Cytochem 2010; 58:759-63. [PMID: 20458062 DOI: 10.1369/jhc.2010.956045] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The endolymphatic sac (ES) is a part of the membranous labyrinth. ES is believed to perform endolymph absorption, which is dependent on several ion transporters, including Na(+)/K(+)/2Cl(-) cotransporter type 2 (NKCC-2) and Na(+)/K(+)-ATPase. NKCC-2 is typically recognized as a kidney-specific ion transporter expressed in the apical membrane of the absorptive epithelium. NKCC-2 expression has been confirmed only in the rat and human ES other than the kidney, but the detailed localization features of NKCC-2 have not been investigated in the ES. Thus, we evaluated the specific site expressing NKCC-2 by immunohistochemical assessment. NKCC-2 expression was most frequently seen in the intermediate portion of the ES, where NKCC-2 is believed to play an important role in endolymph absorption. In addition, NKCC-2 expression was also observed on the apical membranes of ES epithelial cells, and Na(+)/K(+)-ATPase coexpression was observed on the basolateral membranes of ES epithelial cells. These results suggest that NKCC-2 performs an important role in endolymph absorption and that NKCC-2 in apical membranes and Na(+)/K(+)-ATPase in basolateral membranes work coordinately in the ES in a manner similar to that in renal tubules.
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Affiliation(s)
- Kosuke Akiyama
- Dept. of Otolaryngology, Faculty of Medicine, Kagawa University, Kita-gun, Kagawa, Japan.
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Abstract
The homeostasis of water in the inner ear is essential for maintaining function of hearing and equilibrium. Since the discovery of aquaporin water channels, it has become clear that these channels play a crucial role in inner ear fluid homeostasis. Indeed, proteins or mRNAs of AQP1, AQP2, AQP3, AQP4, AQP5, AQP6, AQP7 and AQP9 are expressed in the inner ear. Many of them are expressed mainly in the stria vascularis and the endolymphatic sac, which are the main sites of secretion and/or absorption of endolymph. Vasopressin type2 receptor is also expressed there. Water homeostasis of the inner ear is regulated in part via the arginine vasopressin-AQP2 system in the same fashion as in the kidney, and endolymphatic hydrops, a morphological characteristic of Meniere's disease, is thought to be caused by mal-regulation of this system. Therefore, aquaporins appear to be important for the development of novel drug therapies for Meniere's disease and related disorders.
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