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Akyuz E, Villa C, Beker M, Elibol B. Unraveling the Role of Inwardly Rectifying Potassium Channels in the Hippocampus of an Aβ (1-42)-Infused Rat Model of Alzheimer's Disease. Biomedicines 2020; 8:biomedicines8030058. [PMID: 32183098 PMCID: PMC7148495 DOI: 10.3390/biomedicines8030058] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2020] [Revised: 03/10/2020] [Accepted: 03/12/2020] [Indexed: 11/24/2022] Open
Abstract
Alzheimer’s disease (AD) is a progressive neurodegenerative disorder with a complex etiology and characterized by cognitive deficits and memory loss. The pathogenesis of AD is not yet completely elucidated, and no curative treatment is currently available. Inwardly rectifying potassium (Kir) channels are important for playing a key role in maintaining the resting membrane potential and controlling cell excitability, being largely expressed in both excitable and non-excitable tissues, including neurons. Accordingly, the aim of the study is to investigate the role of neuronal Kir channels in AD pathophysiology. The mRNA and protein levels of neuronal Kir2.1, Kir3.1, and Kir6.2 were evaluated by real-time PCR and Western blot analysis from the hippocampus of an amyloid-β(Aβ)(1-42)-infused rat model of AD. Extracellular deposition of Aβ was confirmed by both histological Congo red staining and immunofluorescence analysis. Significant decreased mRNA and protein levels of Kir2.1 and Kir6.2 channels were observed in the rat model of AD, whereas no differences were found in Kir3.1 channel levels as compared with controls. Our results provide in vivo evidence that Aβ can modulate the expression of these channels, which may represent novel potential therapeutic targets in the treatment of AD.
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Affiliation(s)
- Enes Akyuz
- Department of Biophysics, Faculty of Medicine, Yozgat Bozok University, Yozgat 66100, Turkey
- Correspondence: (E.A.); (C.V.)
| | - Chiara Villa
- School of Medicine and Surgery, University of Milano-Bicocca, 20900 Monza, Italy
- Correspondence: (E.A.); (C.V.)
| | - Merve Beker
- Department of Medical Biology, Faculty of Medicine, Bezmialem Vakif University, Istanbul 34093, Turkey; (M.B.); (B.E.)
| | - Birsen Elibol
- Department of Medical Biology, Faculty of Medicine, Bezmialem Vakif University, Istanbul 34093, Turkey; (M.B.); (B.E.)
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Villa C, Suphesiz H, Combi R, Akyuz E. Potassium channels in the neuronal homeostasis and neurodegenerative pathways underlying Alzheimer's disease: An update. Mech Ageing Dev 2019; 185:111197. [PMID: 31862274 DOI: 10.1016/j.mad.2019.111197] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2019] [Revised: 11/27/2019] [Accepted: 12/12/2019] [Indexed: 02/06/2023]
Abstract
With more than 80 subunits, potassium (K+) channels represent a group of ion channels showing high degree of diversity and ubiquity. They play important role in the control of membrane depolarization and cell excitability in several tissues, including the brain. Controlling the intracellular and extracellular K+ flow in cells, they also modulate the hormone and neurotransmitter release, apoptosis and cell proliferation. It is therefore not surprising that an improper functioning of K+ channels in neurons has been associated with pathophysiology of a wide range of neurological disorders, especially Alzheimer's disease (AD). This review aims to give a comprehensive overview of the basic properties and pathophysiological functions of the main classes of K+ channels in the context of disease processes, also discussing the progress, challenges and opportunities to develop drugs targeting these channels as potential pharmacological approach for AD treatment.
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Affiliation(s)
- Chiara Villa
- School of Medicine and Surgery, University of Milano-Bicocca, Italy
| | | | - Romina Combi
- School of Medicine and Surgery, University of Milano-Bicocca, Italy
| | - Enes Akyuz
- Yozgat Bozok University, Medical Faculty, Department of Biophysics, Yozgat, Turkey.
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Moriguchi S, Ishizuka T, Yabuki Y, Shioda N, Sasaki Y, Tagashira H, Yawo H, Yeh JZ, Sakagami H, Narahashi T, Fukunaga K. Blockade of the K ATP channel Kir6.2 by memantine represents a novel mechanism relevant to Alzheimer's disease therapy. Mol Psychiatry 2018; 23:211-221. [PMID: 27777420 DOI: 10.1038/mp.2016.187] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/24/2015] [Revised: 08/11/2016] [Accepted: 08/22/2016] [Indexed: 01/09/2023]
Abstract
Here, we report a novel target of the drug memantine, ATP-sensitive K+ (KATP) channels, potentially relevant to memory improvement. We confirmed that memantine antagonizes memory impairment in Alzheimer's model APP23 mice. Memantine increased CaMKII activity in the APP23 mouse hippocampus, and memantine-induced enhancement of hippocampal long-term potentiation (LTP) and CaMKII activity was totally abolished by treatment with pinacidil, a specific opener of KATP channels. Memantine also inhibited Kir6.1 and Kir6.2 KATP channels and elevated intracellular Ca2+ concentrations in neuro2A cells overexpressing Kir6.1 or Kir6.2. Kir6.2 was preferentially expressed at postsynaptic regions of hippocampal neurons, whereas Kir6.1 was predominant in dendrites and cell bodies of pyramidal neurons. Finally, we confirmed that Kir6.2 mutant mice exhibit severe memory deficits and impaired hippocampal LTP, impairments that cannot be rescued by memantine administration. Altogether, our studies show that memantine modulates Kir6.2 activity, and that the Kir6.2 channel is a novel target for therapeutics to improve memory impairment in Alzheimer disease patients.
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Affiliation(s)
- S Moriguchi
- Department of Pharmacology, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan
| | - T Ishizuka
- Department of Developmental Biology and Neuroscience, Graduate School of Life Sciences, Tohoku University, Sendai, Japan
| | - Y Yabuki
- Department of Pharmacology, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan
| | - N Shioda
- Department of Pharmacology, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan
| | - Y Sasaki
- Department of Pharmacology, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan
| | - H Tagashira
- Department of Pharmacology, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan
| | - H Yawo
- Department of Developmental Biology and Neuroscience, Graduate School of Life Sciences, Tohoku University, Sendai, Japan
| | - J Z Yeh
- Department of Molecular Pharmacology and Biological Chemistry, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - H Sakagami
- Department of Anatomy, Kitasato University School of Medicine, Sagamihara, Japan
| | - T Narahashi
- Department of Molecular Pharmacology and Biological Chemistry, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - K Fukunaga
- Department of Pharmacology, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan
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Dallérac G, Rouach N. Astrocytes as new targets to improve cognitive functions. Prog Neurobiol 2016; 144:48-67. [PMID: 26969413 DOI: 10.1016/j.pneurobio.2016.01.003] [Citation(s) in RCA: 97] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2015] [Revised: 01/07/2016] [Accepted: 01/24/2016] [Indexed: 01/09/2023]
Abstract
Astrocytes are now viewed as key elements of brain wiring as well as neuronal communication. Indeed, they not only bridge the gap between metabolic supplies by blood vessels and neurons, but also allow fine control of neurotransmission by providing appropriate signaling molecules and insulation through a tight enwrapping of synapses. Recognition that astroglia is essential to neuronal communication is nevertheless fairly recent and the large body of evidence dissecting such role has focused on the synaptic level by identifying neuro- and gliotransmitters uptaken and released at synaptic or extrasynaptic sites. Yet, more integrated research deciphering the impact of astroglial functions on neuronal network activity have led to the reasonable assumption that the role of astrocytes in supervising synaptic activity translates in influencing neuronal processing and cognitive functions. Several investigations using recent genetic tools now support this notion by showing that inactivating or boosting astroglial function directly affects cognitive abilities. Accordingly, brain diseases resulting in impaired cognitive functions have seen their physiopathological mechanisms revisited in light of this primary protagonist of brain processing. We here provide a review of the current knowledge on the role of astrocytes in cognition and in several brain diseases including neurodegenerative disorders, psychiatric illnesses, as well as other conditions such as epilepsy. Potential astroglial therapeutic targets are also discussed.
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Affiliation(s)
- Glenn Dallérac
- Neuroglial Interactions in Cerebral Physiopathology, Center for Interdisciplinary Research in Biology, Collège de France, Centre National de la Recherche Scientifique UMR 7241, Institut National de la Santé et de la Recherche Médicale U1050, Labex Memolife, PSL Research University, Paris, France.
| | - Nathalie Rouach
- Neuroglial Interactions in Cerebral Physiopathology, Center for Interdisciplinary Research in Biology, Collège de France, Centre National de la Recherche Scientifique UMR 7241, Institut National de la Santé et de la Recherche Médicale U1050, Labex Memolife, PSL Research University, Paris, France.
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Ma G, Gao J, Fu Q, Jiang L, Wang R, Zhang Y, Liu K. Diazoxide Reverses the Enhanced Expression of KATP Subunits in Cholinergic Neurons Caused by Exposure to Aβ1-42. Neurochem Res 2009; 34:2133-40. [DOI: 10.1007/s11064-009-0007-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/19/2009] [Indexed: 10/20/2022]
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Hyland S, Muller D, Hayton S, Stoecklin E, Barella L. Cortical Gene Expression in the Vitamin E-Deficient Rat: Possible Mechanisms for the Electrophysiological Abnormalities of Visual and Neural Function. ANNALS OF NUTRITION AND METABOLISM 2006; 50:433-41. [PMID: 16847396 DOI: 10.1159/000094635] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2005] [Accepted: 04/05/2006] [Indexed: 11/19/2022]
Abstract
In mammals, severe and chronic deficiency of vitamin E (alpha-tocopherol) is associated with a characteristic neurological syndrome. Previously, we have shown that this syndrome is accompanied by electrophysiological abnormalities of neural and visual function. To investigate the molecular basis of the observed abnormalities, we used microarrays to monitor the expression of approximately 14,000 genes in the cerebral cortex from rats which had received diets containing 0, 1.25 and 5.0 mg/kg diet of all-rac-alpha-tocopheryl acetate for 14 months. Compared to the groups receiving 1.25 and 5.0 mg/kg alpha-tocopheryl acetate, a total of 11 genes were statistically significantly upregulated (> or =1.3-fold) and 34 downregulated (< or =1.3-fold) in the vitamin E-deficient group. Increased expression was observed for the genes encoding the antioxidant enzyme catalase and the axon guidance molecule tenascin-R, while decreased expression was detected for genes encoding protein components of myelin and determinants of neuronal signal propagation. Thus our observations suggest that vitamin E deficiency results in transcriptional alterations in the cerebral cortex of the rat which are consistent with the observed neurological and electrophysiological alterations.
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Affiliation(s)
- Stephen Hyland
- DSM Nutritional Products, Research and Development, Kaiseraugst, Switzerland
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Ramonet D, Rodríguez MJ, Pugliese M, Mahy N. Putative glucosensing property in rat and human activated microglia. Neurobiol Dis 2004; 17:1-9. [PMID: 15350960 DOI: 10.1016/j.nbd.2003.11.019] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2003] [Revised: 10/30/2003] [Accepted: 11/05/2003] [Indexed: 10/26/2022] Open
Abstract
Microglial cells involved in the pathogenesis of many neurodegenerative diseases acquire the features of cytotoxic and phagocytic cells in response to certain pathogens and inflammatory signals. K(ATP) channels are energy sensors of ATP availability that link the cell's metabolic state to its membrane excitability. In pancreatic beta cells, they promote glucose-dependent insulin secretion, and in neurones, hyperpolarization that protects against hypoxic damage. This study analyses activated microglia in an in vivo rat neurodegenerative model based on acute hippocampal glutamate receptor overactivation and in postmortem samples from patients with Alzheimer's disease. We demonstrate that in activated microglia the K(ATP) channel components SUR-1 or SUR-2 are present together with glucokinase. Our results indicate that, according to glucose availability, these channels may modify microglia membrane potential. The functional relevance of these channels is seen as a new mechanism modulating the effects of external signals on microglia.
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Affiliation(s)
- D Ramonet
- Unitat de Bioquímica, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Facultat de Medicina, Universitat de Barcelona, 08036 Barcelona, Spain
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Allen TGJ, Brown DA. Modulation of the excitability of cholinergic basal forebrain neurones by KATP channels. J Physiol 2004; 554:353-70. [PMID: 14578474 PMCID: PMC1664773 DOI: 10.1113/jphysiol.2003.055889] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Revised: 09/26/2003] [Accepted: 10/23/2003] [Indexed: 11/08/2022] Open
Abstract
The expression of ATP-sensitive K(+) (K(ATP)) channels by magnocellular cholinergic basal forebrain (BF) neurones was investigated in thin brain slice and dissociated cell culture preparations using a combination of whole-cell, perforated-patch and single-channel recording techniques. Greater than 95% of BF neurones expressed functional K(ATP) channels whose activation resulted in membrane hyperpolarization and a profound fall in excitability. The whole-cell K(ATP) conductance was 14.0 +/- 1.5 nS and had a reversal potential of -91.4 +/- 0.9 mV that shifted by 59.6 mV with a tenfold increase in [K(+)](o). I(KATP) was inhibited reversibly by tolbutamide (IC(50) of 34.1 microM) and irreversibly by glibenclamide (0.3-3 nM) and had a low affinity for [ATP](i) (67% reduction with 6 mm[MgATP](i)). Using perforated-patch recording, a small proportion of the conductance was found to be tonically active. This was weakly potentiated by diazoxide (0.1 mm extracellular glucose) but insensitive to pinacidil (< or =500 microM). Single-channel K(ATP) currents recorded in symmetrical 140 mm K(+)-containing solutions exhibited weak inward rectification with a mean conductance of 66.2 +/- 1.9 pS. Channel activity was inhibited by MgATP (>50 microM) and activated by MgADP (200 microM). The K(+) channels opener diazoxide (200-500 microM) increased channel opening probability (NP(o)) by 486 +/- 120% whereas pinacidil (500 microM) had no effect. In conclusion, the characteristics of the K(ATP) channels expressed by BF neurones are very similar to channels composed of SUR1 and Kir6.2 subunits. In the native cell, their affinity for ATP is close to the resting [ATP](i), potentially allowing them to be modulated by physiologically relevant changes in [ATP](i). The effect of these channels on the level of ascending cholinergic excitation of the cortex and hippocampus is discussed.
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Affiliation(s)
- T G J Allen
- Department of Pharmacology, University College London, Gower Street, London WC1E 6BT, UK.
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