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Uva L, Bruno G, de Curtis M. Activity-dependent extracellular potassium changes in unmyelinated versus myelinated areas in olfactory regions of the isolated female guinea-pig brain. Exp Neurol 2024; 379:114884. [PMID: 38992824 DOI: 10.1016/j.expneurol.2024.114884] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2024] [Revised: 06/26/2024] [Accepted: 07/08/2024] [Indexed: 07/13/2024]
Abstract
The potassium released in the extracellular space during neuronal activity is rapidly removed by glia and neurons to maintain tissue homeostasis. Oligodendrocyte-derived myelin axonal coating contributes to potassium buffering and is therefore crucial to control brain excitability. We studied activity-dependent extracellular potassium ([K+]o) changes in the piriform cortex (PC), a region that features highly segregated bundles of myelinated and unmyelinated fibers. Four-aminopyridine (4AP; 50 μM) treatment or patterned high-frequency stimulations (hfST) were utilized to generate [K+]o changes measured with potassium-sensitive electrodes in the myelinated lateral olfactory tract (LOT), in the unmyelinated PC layer I and in the myelinated deep PC layers in the ex vivo isolated guinea-pig brain. Seizure-like events induced by 4AP are initiated by the abrupt [K+]o rise in the layer I formed by unmyelinated fibers (Uva et al., 2017). Larger [K+]o shifts occurred in unmyelinated layers compared to the myelinated LOT. LOT hfST that mimicks pre-seizure discharges also generated higher [K+]o changes in unmyelinated PC layer I than in LOT and deep PC layers. The treatment with the Kir4.1 potassium channel blocker BaCl2 (100 μM) enhanced the [K+]o changes generated by hfST in myelinated structures. Our data show that activity-dependent [K+]o changes are intrinsically different in myelinated vs unmyelinated cortical regions. The larger [K+]o shifts generated in unmyelinated structures may represent a vehicle for seizure generation.
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Affiliation(s)
- Laura Uva
- Epilepsy Unit, Fondazione IRCCS Istituto Neurologico Carlo Besta, via Celoria 11/via Amadeo 42, Milano, Italy..
| | - Gaia Bruno
- Epilepsy Unit, Fondazione IRCCS Istituto Neurologico Carlo Besta, via Celoria 11/via Amadeo 42, Milano, Italy.; Dipartimento di Biologia e Biotecnologia, via Forlanini, 6, Università di Pavia, 27100, Pavia, Italy..
| | - Marco de Curtis
- Epilepsy Unit, Fondazione IRCCS Istituto Neurologico Carlo Besta, via Celoria 11/via Amadeo 42, Milano, Italy..
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2
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Dhanapalaratnam R, Issar T, Poynten AM, Milner KL, Kwai NCG, Krishnan AV. Progression of axonal excitability abnormalities with increasing clinical severity of diabetic peripheral neuropathy. Clin Neurophysiol 2024; 160:12-18. [PMID: 38367309 DOI: 10.1016/j.clinph.2024.02.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2023] [Revised: 01/18/2024] [Accepted: 02/05/2024] [Indexed: 02/19/2024]
Abstract
OBJECTIVE Diabetic peripheral neuropathy (DPN) is a frequent complication for persons with type 2 diabetes. Previous studies have failed to demonstrate any significant impact of treatment for DPN. The present study assessed the role of axonal ion channel dysfunction in DPN and explored the hypothesis that there may be a progressive change in ion channel abnormalities that varied with disease stage. METHODS Neurophysiological studies were conducted using axonal excitability techniques, a clinical method of assessing ion channel dysfunction. Studies were conducted in 178 persons with type 2 diabetes, with participants allocated into four groups according to clinical severity of neuropathy, assessed using the Total Neuropathy Grade. RESULTS Analysis of excitability data demonstrated a progressive and stepwise reduction in two parameters that are related to the activity of Kv1.1 channels, namely superexcitability and depolarizing threshold electrotonus at 10-20 ms (p < 0.001), and mathematical modelling of axonal excitability findings supported progressive upregulation of Kv1.1 conductances with increasing greater disease severity. CONCLUSION The findings are consistent with a progressive upregulation of juxtaparanodal Kv1.1 conductances with increasing clinical severity of diabetic peripheral neuropathy. SIGNIFICANCE From a translational perspective, the study suggests that blockade of Kv1.1 channels using 4-aminopyridine derivatives such as fampridine may be a potential treatment for DPN.
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Affiliation(s)
- Roshan Dhanapalaratnam
- School of Clinical Medicine, UNSW Sydney, NSW 2031, Australia; Department of Neurology, Prince of Wales Hospital, Sydney, NSW 2031, Australia
| | - Tushar Issar
- School of Clinical Medicine, UNSW Sydney, NSW 2031, Australia
| | - Ann M Poynten
- School of Clinical Medicine, UNSW Sydney, NSW 2031, Australia; Department of Endocrinology, Prince of Wales Hospital, Sydney, NSW 2031, Australia
| | - Kerry-Lee Milner
- School of Clinical Medicine, UNSW Sydney, NSW 2031, Australia; Department of Endocrinology, Prince of Wales Hospital, Sydney, NSW 2031, Australia
| | - Natalie C G Kwai
- School of Medical, Indigenous and Health Sciences, University of Wollongong, Australia
| | - Arun V Krishnan
- School of Clinical Medicine, UNSW Sydney, NSW 2031, Australia; Department of Neurology, Prince of Wales Hospital, Sydney, NSW 2031, Australia.
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3
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Zhao R, Qasim A, Sophanpanichkul P, Dai H, Nayak M, Sher I, Chill J, Goldstein SAN. Selective block of human Kv1.1 channels and an epilepsy-associated gain-of-function mutation by AETX-K peptide. FASEB J 2024; 38:e23381. [PMID: 38102952 PMCID: PMC10754259 DOI: 10.1096/fj.202302061r] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2023] [Revised: 11/11/2023] [Accepted: 12/05/2023] [Indexed: 12/17/2023]
Abstract
Dysfunction of the human voltage-gated K+ channel Kv1.1 has been associated with epilepsy, multiple sclerosis, episodic ataxia, myokymia, and cardiorespiratory dysregulation. We report here that AETX-K, a sea anemone type I (SAK1) peptide toxin we isolated from a phage display library, blocks Kv1.1 with high affinity (Ki ~ 1.6 pM) and notable specificity, inhibiting other Kv channels we tested a million-fold less well. Nuclear magnetic resonance (NMR) was employed both to determine the three-dimensional structure of AETX-K, showing it to employ a classic SAK1 scaffold while exhibiting a unique electrostatic potential surface, and to visualize AETX-K bound to the Kv1.1 pore domain embedded in lipoprotein nanodiscs. Study of Kv1.1 in Xenopus oocytes with AETX-K and point variants using electrophysiology demonstrated the blocking mechanism to employ a toxin-channel configuration we have described before whereby AETX-K Lys23 , two positions away on the toxin interaction surface from the classical blocking residue, enters the pore deeply enough to interact with K+ ions traversing the pathway from the opposite side of the membrane. The mutant channel Kv1.1-L296 F is associated with pharmaco-resistant multifocal epilepsy in infants because it significantly increases K+ currents by facilitating opening and slowing closure of the channels. Consistent with the therapeutic potential of AETX-K for Kv1.1 gain-of-function-associated diseases, AETX-K at 4 pM decreased Kv1.1-L296 F currents to wild-type levels; further, populations of heteromeric channels formed by co-expression Kv1.1 and Kv1.2, as found in many neurons, showed a Ki of ~10 nM even though homomeric Kv1.2 channels were insensitive to the toxin (Ki > 2000 nM).
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Affiliation(s)
- Ruiming Zhao
- Departments of Pediatrics, Physiology & Biophysics, and Pharmaceutical Sciences, Susan and Henry Samueli College of Health Sciences, University of California, Irvine, Irvine, CA 92697, USA
| | - Arwa Qasim
- Department of Chemistry, Bar Ilan University, Ramat Gan, 52900, Israel
| | - Punyanuch Sophanpanichkul
- Departments of Pediatrics, Physiology & Biophysics, and Pharmaceutical Sciences, Susan and Henry Samueli College of Health Sciences, University of California, Irvine, Irvine, CA 92697, USA
| | - Hui Dai
- Departments of Pediatrics, Physiology & Biophysics, and Pharmaceutical Sciences, Susan and Henry Samueli College of Health Sciences, University of California, Irvine, Irvine, CA 92697, USA
| | - Maha Nayak
- Departments of Pediatrics, Physiology & Biophysics, and Pharmaceutical Sciences, Susan and Henry Samueli College of Health Sciences, University of California, Irvine, Irvine, CA 92697, USA
| | - Inbal Sher
- Department of Chemistry, Bar Ilan University, Ramat Gan, 52900, Israel
| | - Jordan Chill
- Department of Chemistry, Bar Ilan University, Ramat Gan, 52900, Israel
| | - Steve A. N. Goldstein
- Departments of Pediatrics, Physiology & Biophysics, and Pharmaceutical Sciences, Susan and Henry Samueli College of Health Sciences, University of California, Irvine, Irvine, CA 92697, USA
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AlShammari AK, Abd El-Aziz TM, Al-Sabi A. Snake Venom: A Promising Source of Neurotoxins Targeting Voltage-Gated Potassium Channels. Toxins (Basel) 2023; 16:12. [PMID: 38251229 PMCID: PMC10820993 DOI: 10.3390/toxins16010012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2023] [Revised: 12/11/2023] [Accepted: 12/19/2023] [Indexed: 01/23/2024] Open
Abstract
The venom derived from various sources of snakes represents a vast collection of predominantly protein-based toxins that exhibit a wide range of biological actions, including but not limited to inflammation, pain, cytotoxicity, cardiotoxicity, and neurotoxicity. The venom of a particular snake species is composed of several toxins, while the venoms of around 600 venomous snake species collectively encompass a substantial reservoir of pharmacologically intriguing compounds. Despite extensive research efforts, a significant portion of snake venoms remains uncharacterized. Recent findings have demonstrated the potential application of neurotoxins derived from snake venom in selectively targeting voltage-gated potassium channels (Kv). These neurotoxins include BPTI-Kunitz polypeptides, PLA2 neurotoxins, CRISPs, SVSPs, and various others. This study provides a comprehensive analysis of the existing literature on the significance of Kv channels in various tissues, highlighting their crucial role as proteins susceptible to modulation by diverse snake venoms. These toxins have demonstrated potential as valuable pharmacological resources and research tools for investigating the structural and functional characteristics of Kv channels.
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Affiliation(s)
- Altaf K. AlShammari
- College of Engineering and Technology, American University of the Middle East, Egaila 54200, Kuwait;
| | - Tarek Mohamed Abd El-Aziz
- Zoology Department, Faculty of Science, Minia University, El-Minia 61519, Egypt
- Department of Cellular and Integrative Physiology, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA
| | - Ahmed Al-Sabi
- College of Engineering and Technology, American University of the Middle East, Egaila 54200, Kuwait;
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Dustin E, McQuiston AR, Honke K, Palavicini JP, Han X, Dupree JL. Adult-onset depletion of sulfatide leads to axonal degeneration with relative myelin sparing. Glia 2023; 71:2285-2303. [PMID: 37283058 PMCID: PMC11007682 DOI: 10.1002/glia.24423] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2022] [Revised: 05/10/2023] [Accepted: 05/12/2023] [Indexed: 06/08/2023]
Abstract
3-O-sulfogalactosylceramide (sulfatide) constitutes a class of sphingolipids that comprise about 4% of myelin lipids in the central nervous system. Previously, our group characterized a mouse with sulfatide's synthesizing enzyme, cerebroside sulfotransferase (CST), constitutively disrupted. Using these mice, we demonstrated that sulfatide is required for establishment and maintenance of myelin, axoglial junctions, and axonal domains and that sulfatide depletion results in structural pathologies commonly observed in Multiple Sclerosis (MS). Interestingly, sulfatide is reduced in regions of normal appearing white matter (NAWM) of MS patients. Sulfatide reduction in NAWM suggests depletion occurs early in disease development and consistent with functioning as a driving force of disease progression. To closely model MS, an adult-onset disease, our lab generated a "floxed" CST mouse and mated it against the PLP-creERT mouse, resulting in a double transgenic mouse that provides temporal and cell-type specific ablation of the Cst gene (Gal3st1). Using this mouse, we demonstrate adult-onset sulfatide depletion has limited effects on myelin structure but results in the loss of axonal integrity including deterioration of domain organization accompanied by axonal degeneration. Moreover, structurally preserved myelinated axons progressively lose the ability to function as myelinated axons, indicated by the loss of the N1 peak. Together, our findings indicate that sulfatide depletion, which occurs in the early stages of MS progression, is sufficient to drive the loss of axonal function independent of demyelination and that axonal pathology, which is responsible for the irreversible loss of neuronal function that is prevalent in MS, may occur earlier than previously recognized.
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Affiliation(s)
- E Dustin
- Department of Anatomy and Neurobiology, Virginia Commonwealth University, Richmond, Virginia, USA
- Research Service, Central Virginia Veterans Affairs Health Care Systems, Richmond, Virginia, USA
| | - A R McQuiston
- Department of Anatomy and Neurobiology, Virginia Commonwealth University, Richmond, Virginia, USA
| | - K Honke
- Department of Biochemistry, Kochi University Medical School, Kochi, Japan
| | - J P Palavicini
- Department of Medicine, University of Texas Health San Antonio, San Antonio, Texas, USA
- Barshop Institute for Longevity and Aging Studies, University of Texas Health San Antonio, San Antonio, Texas, USA
| | - X Han
- Department of Medicine, University of Texas Health San Antonio, San Antonio, Texas, USA
- Barshop Institute for Longevity and Aging Studies, University of Texas Health San Antonio, San Antonio, Texas, USA
| | - J L Dupree
- Department of Anatomy and Neurobiology, Virginia Commonwealth University, Richmond, Virginia, USA
- Research Service, Central Virginia Veterans Affairs Health Care Systems, Richmond, Virginia, USA
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6
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Orlov NA, Kryukova EV, Efremenko AV, Yakimov SA, Toporova VA, Kirpichnikov MP, Nekrasova OV, Feofanov AV. Interactions of the Kv1.1 Channel with Peptide Pore Blockers: A Fluorescent Analysis on Mammalian Cells. MEMBRANES 2023; 13:645. [PMID: 37505011 PMCID: PMC10383195 DOI: 10.3390/membranes13070645] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2023] [Revised: 06/23/2023] [Accepted: 06/27/2023] [Indexed: 07/29/2023]
Abstract
The voltage-gated potassium channel Kv1.1, which is abundant in the CNS and peripheral nervous system, controls neuronal excitability and neuromuscular transmission and mediates a number of physiological functions in non-excitable cells. The development of some diseases is accompanied by changes in the expression level and/or activity of the channels in particular types of cells. To meet the requirements of studies related to the expression and localization of the Kv1.1 channels, we report on the subnanomolar affinity of hongotoxin 1 N-terminally labeled with Atto 488 fluorophore (A-HgTx) for the Kv1.1 channel and its applicability for fluorescent imaging of the channel in living cells. Taking into consideration the pharmacological potential of the Kv1.1 channel, a fluorescence-based analytical system was developed for the study of peptide ligands that block the ion conductivity of Kv1.1 and are potentially able to correct abnormal activity of the channel. The system is based on analysis of the competitive binding of the studied compounds and A-HgTx to the mKate2-tagged human Kv1.1 (S369T) channel, expressed in the plasma membrane of Neuro2a cells. The system was validated by measuring the affinities of the known Kv1.1-channel peptide blockers, such as agitoxin 2, kaliotoxin 1, hongotoxin 1, and margatoxin. Peptide pore blocker Ce1, from the venom of the scorpion Centruroides elegans, was shown to possess a nanomolar affinity for the Kv1.1 channel. It is reported that interactions of the Kv1.1 channel with the studied peptide blockers are not affected by the transition of the channel from the closed to open state. The conclusion is made that the structural rearrangements accompanying the channel transition into the open state do not change the conformation of the P-loop (including the selectivity filter) involved in the formation of the binding site of the peptide pore blockers.
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Affiliation(s)
- Nikita A Orlov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 117997 Moscow, Russia
- Faculty of Biology, Lomonosov Moscow State University, 119234 Moscow, Russia
| | - Elena V Kryukova
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 117997 Moscow, Russia
| | - Anastasia V Efremenko
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 117997 Moscow, Russia
| | - Sergey A Yakimov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 117997 Moscow, Russia
| | - Victoria A Toporova
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 117997 Moscow, Russia
| | - Mikhail P Kirpichnikov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 117997 Moscow, Russia
- Faculty of Biology, Lomonosov Moscow State University, 119234 Moscow, Russia
| | - Oksana V Nekrasova
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 117997 Moscow, Russia
| | - Alexey V Feofanov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 117997 Moscow, Russia
- Faculty of Biology, Lomonosov Moscow State University, 119234 Moscow, Russia
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7
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Balraj A, Clarkson-Paredes C, Miller RH. Loss of optic nerve oligodendrocytes during maturation alters retinal organization. Exp Eye Res 2023:109540. [PMID: 37364629 DOI: 10.1016/j.exer.2023.109540] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Revised: 06/01/2023] [Accepted: 06/12/2023] [Indexed: 06/28/2023]
Abstract
The myelin sheath facilitates signal conduction along axons in white matter tracts, and when disrupted, can result in significant functional deficits. Demyelination, observed in diseases like multiple sclerosis and optic neuritis, are associated with neural degeneration, however the extent of this damage on upstream circuitry is not well understood. Here we use the MBP-iCP9 mouse model to induce selective oligodendrocyte ablation in the optic nerve at P14 via a chemical inducer of dimerization (CID), resulting in partial demyelination of retinal ganglion cell (RGC) axons with minimal inflammation after two weeks. Oligodendrocyte loss reduced axon diameter and altered compound action potential waveforms, blocking conduction in the slowest-conducting axon populations. Demyelination resulted in disruptions to the normal composition of the retina, including reduced density of RBPMS+, Brn3a+, and OFF-transient RGCs, thinning of the IPL, and reduced density of displaced amacrine cells. The INL and ONL were unaffected by oligodendrocyte loss, suggesting that demyelination-induced deficits in this model are specific to the IPL and GCL. These results show that a partial demyelination of a subpopulation of RGC axons disrupts optic nerve function and affects the organization of the retinal network. This study highlights the significance of myelination in maintaining upstream neural connectivity and provides support for targeting neuronal degeneration in treatments of demyelinating diseases.
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Affiliation(s)
- Annika Balraj
- Department of Anatomy and Cell Biology, The George Washington University, School of Medicine and Health Sciences, Washington, D.C., USA
| | - Cheryl Clarkson-Paredes
- Department of Anatomy and Cell Biology, The George Washington University, School of Medicine and Health Sciences, Washington, D.C., USA
| | - Robert H Miller
- Department of Anatomy and Cell Biology, The George Washington University, School of Medicine and Health Sciences, Washington, D.C., USA.
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8
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ELBini I, Neili NE. Potassium channels at the crossroads of neuroinflammation and myelination in experimental models of multiple sclerosis. Biochem Biophys Res Commun 2023; 653:140-146. [PMID: 36870238 DOI: 10.1016/j.bbrc.2023.02.066] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Revised: 02/16/2023] [Accepted: 02/23/2023] [Indexed: 03/06/2023]
Abstract
Multiple sclerosis (MS) is a chronic demyelinating disease of the central nervous system (CNS), characterized by the presence of localized demyelinating lesions accompanied by an inflammatory reaction, evidently leading to neurodegeneration. A number of ion channels have been implicated in the progression of MS, most notably in cell types involved in the immune response. In the present study, we investigated the implication of two ion channel isoforms, Kv1.1 and Kv1.3, in experimental models of neuroinflammation and demyelination. Immunohistochemical staining of brain sections from the mouse cuprizone model displayed high levels Kv1.3 expression. In an astroglial cellular model of inflammation, stimulation with LPS resulted also in a higher expression of Kv1.1 and Kv1.3, while the introduction of 4-Aminopyridine (4-AP) exacerbated the release of pro-inflammatory chemokine CXCL10. In the oligodendroglial cellular model of demyelination, the alteration in expression levels of Kv1.1 and Kv1.3 may be correlated with that of MBP levels. Indirect co-culture was attempted to further understand the communication between astrocytes and oligodendrocytes, The addition of reactive astrocytes' secretome significantly inhibited the production of MBP, this inhibition was accompanied by an alteration in the expression of Kv1.1 and Kv1.3. The addition of 4-AP in this case did not alleviate the decrease in MBP production. In conclusion, the use of 4-AP generated controversial results, suggesting 4-AP may be used in the early stages of the disease or in the remission phases to stimulate myelination, yet in induced toxic inflammatory environment, 4-AP exacerbated this effect.
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Affiliation(s)
- Ines ELBini
- Laboratoire des Biomolécules, Venins et Applications Théranostiques (LR20IPT01), Institut Pasteur de Tunis, Université de Tunis El Manar, Tunis, 1002, Tunisia.
| | - Nour-Elhouda Neili
- Laboratoire des Biomolécules, Venins et Applications Théranostiques (LR20IPT01), Institut Pasteur de Tunis, Université de Tunis El Manar, Tunis, 1002, Tunisia.
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9
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Sun Y, Guehl NJ, Zhou YP, Takahashi K, Belov V, Dhaynaut M, Moon SH, El Fakhri G, Normandin MD, Brugarolas P. Radiochemical Synthesis and Evaluation of 3-[ 11C]Methyl-4-aminopyridine in Rodents and Nonhuman Primates for Imaging Potassium Channels in the CNS. ACS Chem Neurosci 2022; 13:3342-3351. [PMID: 36417797 PMCID: PMC9732819 DOI: 10.1021/acschemneuro.2c00364] [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] [Indexed: 11/24/2022] Open
Abstract
Demyelination, the loss of the insulating sheath of neurons, causes failed or slowed neuronal conduction and contributes to the neurological symptoms in multiple sclerosis, traumatic brain and spinal cord injuries, stroke, and dementia. In demyelinated neurons, the axonal potassium channels Kv1.1 and Kv1.2, generally under the myelin sheath, become exposed and upregulated. Therefore, imaging these channels using positron emission tomography can provide valuable information for disease diagnosis and monitoring. Here, we describe a novel tracer for Kv1 channels, [11C]3-methyl-4-aminopyridine ([11C]3Me4AP). [11C]3Me4AP was efficiently synthesized via Pd(0)-Cu(I) comediated Stille cross-coupling of a stannyl precursor containing a free amino group. Evaluation of its imaging properties in rats and nonhuman primates showed that [11C]3Me4AP has a moderate brain permeability and slow kinetics. Additional evaluation in monkeys showed that the tracer is metabolically stable and that a one-tissue compartment model can accurately model the regional brain time-activity curves. Compared to the related tracers [18F]3-fluoro-4-aminopyridine ([18F]3F4AP) and [11C]3-methoxy-4-aminopyridine ([11C]3MeO4AP), [11C]3Me4AP shows lower initial brain uptake, which indicates reduced permeability to the blood-brain barrier and slower kinetics, suggesting higher binding affinity consistent with in vitro studies. While the slow kinetics and strong binding affinity resulted in a tracer with less favorable properties for imaging the brain than its predecessors, these properties may make 3Me4AP useful as a therapeutic.
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Cordano C, Sin JH, Timmons G, Yiu HH, Stebbins K, Guglielmetti C, Cruz-Herranz A, Xin W, Lorrain D, Chan JR, Green AJ. Validating visual evoked potentials as a preclinical, quantitative biomarker for remyelination efficacy. Brain 2022; 145:3943-3952. [PMID: 35678509 DOI: 10.1093/brain/awac207] [Citation(s) in RCA: 22] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2022] [Revised: 05/19/2022] [Accepted: 05/30/2022] [Indexed: 11/14/2022] Open
Abstract
Many biomarkers in clinical neuroscience lack pathological certification. This issue is potentially a significant contributor to the limited success of neuroprotective and neurorestorative therapies for human neurological disease - and is evident even in areas with therapeutic promise such as myelin repair. Despite the identification of promising remyelinating candidates, biologically validated methods to demonstrate therapeutic efficacy or provide robust preclinical evidence of remyelination in the central nervous system are lacking. Therapies with potential to remyelinate the central nervous system constitute one of the most promising and highly anticipated therapeutic developments in the pipeline to treat multiple sclerosis and other demyelinating diseases. The optic nerve has been proposed as an informative pathway to monitor remyelination in animals and human subjects. Recent clinical trials using visual evoked potential (VEP) have had promising results, but without unequivocal evidence about the cellular and molecular basis for signal changes on VEP, the interpretation of these trials is constrained. The VEP was originally developed and utilized in the clinic as a diagnostic tool but its use as a quantitative method for assessing therapeutic response requires certification of its biological specificity. Here, using the tools of experimental pathology we demonstrate that quantitative measurements of myelination using both histopathological measures of nodal structure and ultrastructural assessments correspond to VEP latency in both inflammatory and chemical models of demyelination. VEP latency improves after treatment with a tool remyelinating compound (clemastine), mirroring both quantitative and qualitative myelin assessment. Furthermore, clemastine does not improve VEP latency following demyelinating injury when administered to a transgenic animal incapable of forming new myelin. Therefore, using the capacity for therapeutic enhancement and biological loss of function we demonstrate conclusively that VEP measures myelin status and is thereby a validated tool for preclinical verification of remyelination.
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Affiliation(s)
- Christian Cordano
- Department of Neurology, Weill Institute for Neuroscience, University of California, San Francisco; San Francisco, CA 94158, USA
| | - Jung H Sin
- Department of Neurology, Weill Institute for Neuroscience, University of California, San Francisco; San Francisco, CA 94158, USA
| | - Garrett Timmons
- Department of Neurology, Weill Institute for Neuroscience, University of California, San Francisco; San Francisco, CA 94158, USA
| | - Hao H Yiu
- Department of Neurology, Weill Institute for Neuroscience, University of California, San Francisco; San Francisco, CA 94158, USA
| | | | - Caroline Guglielmetti
- Department of Physical Therapy, University of California, San Francisco; San Francisco, CA 94158, USA
| | - Andres Cruz-Herranz
- Department of Neurology, Weill Institute for Neuroscience, University of California, San Francisco; San Francisco, CA 94158, USA
| | - Wendy Xin
- Department of Neurology, Weill Institute for Neuroscience, University of California, San Francisco; San Francisco, CA 94158, USA
| | | | - Jonah R Chan
- Department of Neurology, Weill Institute for Neuroscience, University of California, San Francisco; San Francisco, CA 94158, USA
| | - Ari J Green
- Department of Neurology, Weill Institute for Neuroscience, University of California, San Francisco; San Francisco, CA 94158, USA
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11
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Oniani T, Vinnenberg L, Chaudhary R, Schreiber JA, Riske K, Williams B, Pape HC, White JA, Junker A, Seebohm G, Meuth SG, Hundehege P, Budde T, Zobeiri M. Effects of Axonal Demyelination, Inflammatory Cytokines and Divalent Cation Chelators on Thalamic HCN Channels and Oscillatory Bursting. Int J Mol Sci 2022; 23:ijms23116285. [PMID: 35682964 PMCID: PMC9181513 DOI: 10.3390/ijms23116285] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2022] [Revised: 05/31/2022] [Accepted: 05/31/2022] [Indexed: 12/13/2022] Open
Abstract
Multiple sclerosis (MS) is a demyelinating disease of the central nervous system that is characterized by the progressive loss of oligodendrocytes and myelin and is associated with thalamic dysfunction. Cuprizone (CPZ)-induced general demyelination in rodents is a valuable model for studying different aspects of MS pathology. CPZ feeding is associated with the altered distribution and expression of different ion channels along neuronal somata and axons. However, it is largely unknown whether the copper chelator CPZ directly influences ion channels. Therefore, we assessed the effects of different divalent cations (copper; zinc) and trace metal chelators (EDTA; Tricine; the water-soluble derivative of CPZ, BiMPi) on hyperpolarization-activated cyclic nucleotide-gated (HCN) channels that are major mediators of thalamic function and pathology. In addition, alterations of HCN channels induced by CPZ treatment and MS-related proinflammatory cytokines (IL-1β; IL-6; INF-α; INF-β) were characterized in C57Bl/6J mice. Thus, the hyperpolarization-activated inward current (Ih) was recorded in thalamocortical (TC) neurons and heterologous expression systems (mHCN2 expressing HEK cells; hHCN4 expressing oocytes). A number of electrophysiological characteristics of Ih (potential of half-maximal activation (V0.5); current density; activation kinetics) were unchanged following the extracellular application of trace metals and divalent cation chelators to native neurons, cell cultures or oocytes. Mice were fed a diet containing 0.2% CPZ for 35 days, resulting in general demyelination in the brain. Withdrawal of CPZ from the diet resulted in rapid remyelination, the effects of which were assessed at three time points after stopping CPZ feeding (Day1, Day7, Day25). In TC neurons, Ih was decreased on Day1 and Day25 and revealed a transient increased availability on Day7. In addition, we challenged naive TC neurons with INF-α and IL-1β. It was found that Ih parameters were differentially altered by the application of the two cytokines to thalamic cells, while IL-1β increased the availability of HCN channels (depolarized V0.5; increased current density) and the excitability of TC neurons (depolarized resting membrane potential (RMP); increased the number of action potentials (APs); produced a larger voltage sag; promoted higher input resistance; increased the number of burst spikes; hyperpolarized the AP threshold), INF-α mediated contrary effects. The effect of cytokine modulation on thalamic bursting was further assessed in horizontal slices and a computational model of slow thalamic oscillations. Here, IL-1β and INF-α increased and reduced oscillatory bursting, respectively. We conclude that HCN channels are not directly modulated by trace metals and divalent cation chelators but are subject to modulation by different MS-related cytokines.
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Affiliation(s)
- Tengiz Oniani
- Institute of Physiology I, Westfälische Wilhelms-Universität, Robert-Koch-Str. 27a, D-48149 Münster, Germany; (T.O.); (R.C.); (H.-C.P.); (M.Z.)
| | - Laura Vinnenberg
- Department of Neurology with Institute of Translational Neurology, Albert-Schweitzer-Campus 1, D-48149 Münster, Germany; (L.V.); (P.H.)
| | - Rahul Chaudhary
- Institute of Physiology I, Westfälische Wilhelms-Universität, Robert-Koch-Str. 27a, D-48149 Münster, Germany; (T.O.); (R.C.); (H.-C.P.); (M.Z.)
| | - Julian A. Schreiber
- Institute of Pharmaceutical and Medicinal Chemistry, Westfälische Wilhelms-Universität, Corren-Str. 48, D-48149 Münster, Germany;
- Cellular Electrophysiology and Molecular Biology, Department of Cardiovascular Medicine, Institute for Genetics of Heart Diseases (IfGH), University Hospital Münster, Robert-Koch-Str. 45, D-48149 Münster, Germany;
| | - Kathrin Riske
- European Institute for Molecular Imaging (EIMI), Westfälische Wilhelms-Universität, Waldeyer-Str. 15, D-48149 Münster, Germany; (K.R.); (A.J.)
| | - Brandon Williams
- Center for Systems Neuroscience, Neurophotonics Center, Department of Biomedical Engineering, Boston University, 610 Commonwealth Ave., Boston, MA 02215, USA; (B.W.); (J.A.W.)
| | - Hans-Christian Pape
- Institute of Physiology I, Westfälische Wilhelms-Universität, Robert-Koch-Str. 27a, D-48149 Münster, Germany; (T.O.); (R.C.); (H.-C.P.); (M.Z.)
| | - John A. White
- Center for Systems Neuroscience, Neurophotonics Center, Department of Biomedical Engineering, Boston University, 610 Commonwealth Ave., Boston, MA 02215, USA; (B.W.); (J.A.W.)
| | - Anna Junker
- European Institute for Molecular Imaging (EIMI), Westfälische Wilhelms-Universität, Waldeyer-Str. 15, D-48149 Münster, Germany; (K.R.); (A.J.)
| | - Guiscard Seebohm
- Cellular Electrophysiology and Molecular Biology, Department of Cardiovascular Medicine, Institute for Genetics of Heart Diseases (IfGH), University Hospital Münster, Robert-Koch-Str. 45, D-48149 Münster, Germany;
| | - Sven G. Meuth
- Neurology Clinic, University Clinic Düsseldorf, Moorenstraße 5, D-40225 Düsseldorf, Germany;
| | - Petra Hundehege
- Department of Neurology with Institute of Translational Neurology, Albert-Schweitzer-Campus 1, D-48149 Münster, Germany; (L.V.); (P.H.)
| | - Thomas Budde
- Institute of Physiology I, Westfälische Wilhelms-Universität, Robert-Koch-Str. 27a, D-48149 Münster, Germany; (T.O.); (R.C.); (H.-C.P.); (M.Z.)
- Correspondence:
| | - Mehrnoush Zobeiri
- Institute of Physiology I, Westfälische Wilhelms-Universität, Robert-Koch-Str. 27a, D-48149 Münster, Germany; (T.O.); (R.C.); (H.-C.P.); (M.Z.)
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12
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Marenna S, Huang SC, Dalla Costa G, d’Isa R, Castoldi V, Rossi E, Comi G, Leocani L. Visual Evoked Potentials to Monitor Myelin Cuprizone-Induced Functional Changes. Front Neurosci 2022; 16:820155. [PMID: 35495042 PMCID: PMC9051229 DOI: 10.3389/fnins.2022.820155] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2021] [Accepted: 03/07/2022] [Indexed: 11/17/2022] Open
Abstract
The visual system is one of the most accessible routes to study the central nervous system under pathological conditions, such as in multiple sclerosis (MS). Non-invasive visual evoked potential (VEP) and optical coherence tomography (OCT) were used to assess visual function and neuroretinal thickness in C57BL/6 taking 0.2% cuprizone for 7 weeks and at 5, 8, 12, and 15 days after returning to a normal diet. VEPs were significantly delayed starting from 4 weeks on cuprizone, with progressive recovery off cuprizone, becoming significant at day 8, complete at day 15. In contrast, OCT and neurofilament staining showed no significant axonal thinning. Optic nerve histology indicated that whilst there was significant myelin loss at 7 weeks on the cuprizone diet compared with healthy mice, at 15 days off cuprizone diet demyelination was significantly less severe. The number of Iba 1+ cells was found increased in cuprizone mice at 7 weeks on and 15 days off cuprizone. The combined use of VEPs and OCT allowed us to characterize non-invasively, in vivo, the functional and structural changes associated with demyelination and remyelination in a preclinical model of MS. This approach contributes to the non-invasive study of possible effective treatments to promote remyelination in demyelinating pathologies.
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Affiliation(s)
- Silvia Marenna
- Experimental Neurophysiology Unit, Institute of Experimental Neurology (INSPE), IRCCS-Scientific Institute San Raffaele, Milan, Italy
| | - Su-Chun Huang
- Experimental Neurophysiology Unit, Institute of Experimental Neurology (INSPE), IRCCS-Scientific Institute San Raffaele, Milan, Italy
| | - Gloria Dalla Costa
- Experimental Neurophysiology Unit, Institute of Experimental Neurology (INSPE), IRCCS-Scientific Institute San Raffaele, Milan, Italy
- Faculty of Medicine, Vita-Salute San Raffaele University, Milan, Italy
| | - Raffaele d’Isa
- Experimental Neurophysiology Unit, Institute of Experimental Neurology (INSPE), IRCCS-Scientific Institute San Raffaele, Milan, Italy
| | - Valerio Castoldi
- Experimental Neurophysiology Unit, Institute of Experimental Neurology (INSPE), IRCCS-Scientific Institute San Raffaele, Milan, Italy
| | - Elena Rossi
- Experimental Neurophysiology Unit, Institute of Experimental Neurology (INSPE), IRCCS-Scientific Institute San Raffaele, Milan, Italy
| | - Giancarlo Comi
- Faculty of Medicine, Vita-Salute San Raffaele University, Milan, Italy
- Casa di Cura Privata del Policlinico, Milan, Italy
| | - Letizia Leocani
- Experimental Neurophysiology Unit, Institute of Experimental Neurology (INSPE), IRCCS-Scientific Institute San Raffaele, Milan, Italy
- Faculty of Medicine, Vita-Salute San Raffaele University, Milan, Italy
- *Correspondence: Letizia Leocani,
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13
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Balraj A, Clarkson-Paredes C, Pajoohesh-Ganji A, Kay MW, Mendelowitz D, Miller RH. Refinement of axonal conduction and myelination in the mouse optic nerve indicate an extended period of postnatal developmental plasticity. Dev Neurobiol 2022; 82:308-325. [PMID: 35403346 PMCID: PMC9128412 DOI: 10.1002/dneu.22875] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2021] [Revised: 02/18/2022] [Accepted: 03/17/2022] [Indexed: 11/07/2022]
Abstract
Retinal ganglion cells generate a pattern of action potentials to communicate visual information from the retina to cortical areas. Myelin, an insulating sheath, wraps axonal segments to facilitate signal propagation and when deficient, can impair visual function. Optic nerve development and initial myelination has largely been considered complete by the fifth postnatal week. However, the relationship between the extent of myelination and axonal signaling in the maturing optic nerve is not well characterized. Here, we examine the relationship between axon conduction and elements of myelination using extracellular nerve recordings, immunohistochemistry, western blot analysis, scanning electron microscopy, and simulations of nerve responses. Comparing compound action potentials from mice aged 4-12 weeks revealed five functional distinct axonal populations, an increase in the number of functional axons, and shifts toward fast-conducting axon populations at 5 and 8 weeks postnatal. At these ages, our analysis revealed increased myelin thickness, lower g-ratios and changes in the 14 kDa MBP isoform, while the density of axons and nodes of Ranvier remained constant. At 5 postnatal weeks, axon diameter increased, while at 8 weeks, increased expression of a mature sodium ion channel subtype, Nav 1.6, was observed at nodes of Ranvier. A simulation model of nerve conduction suggests that ion channel subtype, axon diameter, and myelin thickness are more likely to be key regulators of nerve function than g-ratio. Such refinement of axonal function and myelin rearrangement identified an extended period of maturation in the normal optic nerve that may facilitate the development of visual signaling patterns. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Annika Balraj
- Department of Anatomy, The George Washington University School of Medicine and Health Sciences, Washington, District of Columbia, USA
| | - Cheryl Clarkson-Paredes
- Nanofabrication and Imaging Center, The George Washington University School of Medicine and Health Sciences, Washington, District of Columbia, USA
| | - Ahdeah Pajoohesh-Ganji
- Department of Anatomy, The George Washington University School of Medicine and Health Sciences, Washington, District of Columbia, USA
| | - Matthew W. Kay
- Department of Biomedical Engineering, The George Washington University, Washington, District of Columbia, USA
| | - David Mendelowitz
- Department of Pharmacology and Physiology, The George Washington University School of Medicine and Health Sciences, Washington, District of Columbia, USA
| | - Robert H. Miller
- Department of Anatomy, The George Washington University School of Medicine and Health Sciences, Washington, District of Columbia, USA
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14
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Moussaoui H, Ladjel-Mendil A, Laraba-Djebari F. Neuromodulation of neurological disorders in a demyelination model: effect of a potassium channel inhibitor from Androctonus scorpion venom. TOXIN REV 2022. [DOI: 10.1080/15569543.2021.2022698] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Affiliation(s)
- Hadjila Moussaoui
- Faculty of Biological Sciences, USTHB, Laboratory of Cellular and Molecular Biology, Algiers, Algeria
| | - Amina Ladjel-Mendil
- Faculty of Biological Sciences, USTHB, Laboratory of Cellular and Molecular Biology, Algiers, Algeria
| | - Fatima Laraba-Djebari
- Faculty of Biological Sciences, USTHB, Laboratory of Cellular and Molecular Biology, Algiers, Algeria
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15
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Guehl NJ, Ramos-Torres KM, Linnman C, Moon SH, Dhaynaut M, Wilks MQ, Han PK, Ma C, Neelamegam R, Zhou YP, Popko B, Correia JA, Reich DS, Fakhri GE, Herscovitch P, Normandin MD, Brugarolas P. Evaluation of the potassium channel tracer [ 18F]3F4AP in rhesus macaques. J Cereb Blood Flow Metab 2021; 41:1721-1733. [PMID: 33090071 PMCID: PMC8221756 DOI: 10.1177/0271678x20963404] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Demyelination causes slowed or failed neuronal conduction and is a driver of disability in multiple sclerosis and other neurological diseases. Currently, the gold standard for imaging demyelination is MRI, but despite its high spatial resolution and sensitivity to demyelinated lesions, it remains challenging to obtain specific and quantitative measures of molecular changes involved in demyelination. To understand the contribution of demyelination in different diseases and to assess the efficacy of myelin-repair therapies, it is critical to develop new in vivo imaging tools sensitive to changes induced by demyelination. Upon demyelination, axonal K+ channels, normally located underneath the myelin sheath, become exposed and increase in expression, causing impaired conduction. Here, we investigate the properties of the K+ channel PET tracer [18F]3F4AP in primates and its sensitivity to a focal brain injury that occurred three years prior to imaging. [18F]3F4AP exhibited favorable properties for brain imaging including high brain penetration, high metabolic stability, high plasma availability, high reproducibility, high specificity, and fast kinetics. [18F]3F4AP showed preferential binding in areas of low myelin content as well as in the previously injured area. Sensitivity of [18F]3F4AP for the focal brain injury was higher than [18F]FDG, [11C]PiB, and [11C]PBR28, and compared favorably to currently used MRI methods.
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Affiliation(s)
- Nicolas J Guehl
- Gordon Center for Medical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA
| | - Karla M Ramos-Torres
- Gordon Center for Medical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA
| | - Clas Linnman
- Spaulding Neuroimaging Lab, Spaulding Rehabilitation Hospital and Harvard Medical School, Charlestown, MA, USA
| | - Sung-Hyun Moon
- Gordon Center for Medical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA
| | - Maeva Dhaynaut
- Gordon Center for Medical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA
| | - Moses Q Wilks
- Gordon Center for Medical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA
| | - Paul K Han
- Gordon Center for Medical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA
| | - Chao Ma
- Gordon Center for Medical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA
| | - Ramesh Neelamegam
- Gordon Center for Medical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA
| | - Yu-Peng Zhou
- Gordon Center for Medical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA
| | - Brian Popko
- Department of Neurology, Northwestern Feinberg School of Medicine, Chicago, IL, USA
| | - John A Correia
- Gordon Center for Medical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA
| | - Daniel S Reich
- Translational Neuroradiology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA
| | - Georges El Fakhri
- Gordon Center for Medical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA
| | - Peter Herscovitch
- Positron Emission Tomography Department, NIH Clinical Center, National Institutes of Health, Bethesda, MD, USA
| | - Marc D Normandin
- Gordon Center for Medical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA
| | - Pedro Brugarolas
- Gordon Center for Medical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA
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16
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Guehl NJ, Neelamegam R, Zhou YP, Moon SH, Dhaynaut M, El Fakhri G, Normandin MD, Brugarolas P. Radiochemical Synthesis and Evaluation in Non-Human Primates of 3-[ 11C]methoxy-4-aminopyridine: A Novel PET Tracer for Imaging Potassium Channels in the CNS. ACS Chem Neurosci 2021; 12:756-765. [PMID: 33539063 DOI: 10.1021/acschemneuro.0c00791] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Demyelination, the loss of the protecting sheath of neurons, contributes to disability in many neurological diseases. In order to fully understand its role in different diseases and to monitor treatments aiming at reversing this process, it would be valuable to have PET radiotracers that can detect and quantify molecular changes involved in demyelination such as the uncovering and upregulation of the axonal potassium channels Kv1.1 and Kv1.2. Carbon-11 labeled radiotracers present the advantage of allowing for multiple scans on the same subject in the same day. Here, we describe [11C]3MeO4AP, a novel 11C-labeled version of the K+ channel tracer [18F]3F4AP, and characterize its imaging properties in two non-human primates including a monkey with a focal brain injury sustained during a surgical procedure 3 years prior to imaging. Our findings show that [11C]3MeO4AP is brain permeable, metabolically stable and has high plasma availability. When compared with [18F]3F4AP, [11C]3MeO4AP shows very high correlation in volumes of distribution (VT), confirming a common target. [11C]3MeO4AP shows slower washout than [18F]3F4AP, suggesting stronger binding. Finally, similar to [18F]3F4AP, [11C]3MeO4AP is highly sensitive to the focal brain injury. All these features make it a promising radioligand for imaging demyelinated lesions.
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Affiliation(s)
- Nicolas J. Guehl
- Gordon Center for Medical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114, United States
| | - Ramesh Neelamegam
- Gordon Center for Medical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114, United States
| | - Yu-Peng Zhou
- Gordon Center for Medical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114, United States
| | - Sung-Hyun Moon
- Gordon Center for Medical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114, United States
| | - Maeva Dhaynaut
- Gordon Center for Medical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114, United States
| | - Georges El Fakhri
- Gordon Center for Medical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114, United States
| | - Marc D. Normandin
- Gordon Center for Medical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114, United States
| | - Pedro Brugarolas
- Gordon Center for Medical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114, United States
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17
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de Curtis M, Garbelli R, Uva L. A hypothesis for the role of axon demyelination in seizure generation. Epilepsia 2021; 62:583-595. [PMID: 33493363 DOI: 10.1111/epi.16824] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2020] [Revised: 01/04/2021] [Accepted: 01/05/2021] [Indexed: 01/06/2023]
Abstract
Loss of myelin and altered oligodendrocyte distribution in the cerebral cortex are commonly observed both in postsurgical tissue derived from different focal epilepsies (such as focal cortical dysplasias and tuberous sclerosis) and in animal models of focal epilepsy. Moreover, seizures are a frequent symptom in demyelinating diseases, such as multiple sclerosis, and in animal models of demyelination and oligodendrocyte dysfunction. Finally, the excessive activity reported in demyelinated axons may promote hyperexcitability. We hypothesize that the extracellular potassium rise generated during epileptiform activity may be amplified by the presence of axons without appropriate myelin coating and by alterations in oligodendrocyte function. This process could facilitate the triggering of recurrent spontaneous seizures in areas of altered myelination and could result in further demyelination, thus promoting epileptogenesis.
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Affiliation(s)
- Marco de Curtis
- Epilepsy Unit, IRCCS Foundation Carlo Besta Neurological Institute, Milan, Italy
| | - Rita Garbelli
- Epilepsy Unit, IRCCS Foundation Carlo Besta Neurological Institute, Milan, Italy
| | - Laura Uva
- Epilepsy Unit, IRCCS Foundation Carlo Besta Neurological Institute, Milan, Italy
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18
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Cañas CA, Castaño-Valencia S, Castro-Herrera F, Cañas F, Tobón GJ. Biomedical applications of snake venom: from basic science to autoimmunity and rheumatology. J Transl Autoimmun 2020; 4:100076. [PMID: 33385156 PMCID: PMC7772571 DOI: 10.1016/j.jtauto.2020.100076] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2020] [Revised: 12/08/2020] [Accepted: 12/09/2020] [Indexed: 12/26/2022] Open
Abstract
Snake venoms have components with diverse biological actions that are extensively studied to identify elements that may be useful in biomedical sciences. In the field of autoimmunity and rheumatology, various findings useful for the study of diseases and potential drug development have been reported. The study of disintegrins, proteins that block the action of integrins, has been useful for the development of antiplatelet agents and principles for the development of immunosuppressants and antineoplastics. Several proteins in snake venoms act on the coagulation cascade, activating factors that have allowed the development of tests for the study of coagulation, including Russell's viper venom time, which is useful in the diagnosis of antiphospholipid syndrome. Neurotoxins with either pre- or postsynaptic effects have been used to study neurogenic synapses and neuromuscular plaques and the development of analgesics, muscle relaxants and drugs for neurodegenerative diseases. Various components act by inhibiting cells and proteins of the immune system, which will allow the development of anti-inflammatory and immunosuppressive drugs. This review summarizes the usefulness of the components of snake venoms in the fields of autoimmunity and rheumatology, which can serve as a basis for diverse translational research.
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Affiliation(s)
- Carlos A Cañas
- GIRAT: Grupo de Investigación en Reumatología, Autoimunidad y Medicina Traslacional, Fundación Valle Del Lili and Universidad Icesi, Cali, Colombia.,Fundación Valle Del Lili, Rheumatology Unit, Cra 98 No. 18 - 49, Cali, 760032, Colombia
| | - Santiago Castaño-Valencia
- Department of Physiological Sciences, Department of Health Sciences, Universidad Del Valle, Cali, Colombia
| | - Fernando Castro-Herrera
- Department of Physiological Sciences, Department of Health Sciences, Universidad Del Valle, Cali, Colombia
| | - Felipe Cañas
- Department of Cardiology, Clínica Medellín, Medellín, Colombia
| | - Gabriel J Tobón
- GIRAT: Grupo de Investigación en Reumatología, Autoimunidad y Medicina Traslacional, Fundación Valle Del Lili and Universidad Icesi, Cali, Colombia.,Fundación Valle Del Lili, Rheumatology Unit, Cra 98 No. 18 - 49, Cali, 760032, Colombia
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19
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Al-Sabi A, Daly D, Rooney M, Hughes C, Kinsella GK, Kaza SK, Nolan K, Oliver Dolly J. Development of a selective inhibitor for Kv1.1 channels prevalent in demyelinated nerves. Bioorg Chem 2020; 100:103918. [PMID: 32428746 DOI: 10.1016/j.bioorg.2020.103918] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2019] [Revised: 03/23/2020] [Accepted: 05/05/2020] [Indexed: 11/19/2022]
Abstract
Members of the voltage-gated K+ channel subfamily (Kv1), involved in regulating transmission between neurons or to muscles, are associated with human diseases and, thus, putative targets for neurotherapeutics. This applies especially to those containing Kv1.1 α subunits which become prevalent in murine demyelinated axons and appear abnormally at inter-nodes, underlying the perturbed propagation of nerve signals. To overcome this dysfunction, akin to the consequential debilitation in multiple sclerosis (MS), small inhibitors were sought that are selective for the culpable hyper-polarising K+ currents. Herein, we report a new semi-podand - compound 3 - that was designed based on the modelling of its interactions with the extracellular pore region in a deduced Kv1.1 channel structure. After synthesis, purification, and structural characterisation, compound 3 was found to potently (IC50 = 8 µM) and selectively block Kv1.1 and 1.6 channels. The tested compound showed no apparent effect on native Nav and Cav channels expressed in F-11 cells. Compound 3 also extensively and selectively inhibited MS-related Kv1.1 homomer but not the brain native Kv1.1- or 1.6-containing channels. These collective findings highlight the therapeutic potential of compound 3 to block currents mediated by Kv1.1 channels enriched in demyelinated central neurons.
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Affiliation(s)
- Ahmed Al-Sabi
- College of Engineering and Technology, American University of the Middle East, Kuwait; International Centre for Neurotherapeutics, Dublin City University, Glasnevin, Dublin 9, Ireland
| | - Declan Daly
- School of Chemical Sciences, Dublin City University, Glasnevin, Dublin 9, Ireland
| | - Myles Rooney
- School of Chemical Sciences, Dublin City University, Glasnevin, Dublin 9, Ireland
| | - Cian Hughes
- School of Chemical Sciences, Dublin City University, Glasnevin, Dublin 9, Ireland
| | - Gemma K Kinsella
- School of Food Science and Environmental Health, College of Sciences and Health, Technological University Dublin, Cathal Brugha Street, Dublin 1, Ireland
| | - Seshu K Kaza
- International Centre for Neurotherapeutics, Dublin City University, Glasnevin, Dublin 9, Ireland
| | - Kieran Nolan
- School of Chemical Sciences, Dublin City University, Glasnevin, Dublin 9, Ireland.
| | - J Oliver Dolly
- International Centre for Neurotherapeutics, Dublin City University, Glasnevin, Dublin 9, Ireland
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20
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Kopanitsa MV, Lehtimäki KK, Forsman M, Suhonen A, Koponen J, Piiponniemi TO, Kärkkäinen AM, Pavlidi P, Shatillo A, Sweeney PJ, Merenlender-Wagner A, Kaye J, Orbach A, Nurmi A. Cognitive disturbances in the cuprizone model of multiple sclerosis. GENES BRAIN AND BEHAVIOR 2020; 20:e12663. [PMID: 32372528 DOI: 10.1111/gbb.12663] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2019] [Revised: 04/29/2020] [Accepted: 04/29/2020] [Indexed: 12/19/2022]
Abstract
Cognitive problems frequently accompany neurological manifestations of multiple sclerosis (MS). However, during screening of preclinical candidates, assessments of behaviour in mouse models of MS typically focus on locomotor activity. In the present study, we analysed cognitive behaviour of 9 to 10-week-old female C57Bl/6J mice orally administered with the toxin cuprizone that induces demyelination, a characteristic feature of MS. Animals received 400 mg/kg cuprizone daily for 2 or 4 weeks, and their performance was compared with that of vehicle-treated mice. Cuprizone-treated animals showed multiple deficits in short touchscreen-based operant tasks: they responded more slowly to visual stimuli, rewards and made more errors in a simple rule-learning task. In contextual/cued fear conditioning experiments, cuprizone-treated mice showed significantly lower levels of contextual freezing than vehicle-treated mice. Diffusion tensor imaging showed treatment-dependent changes in fractional anisotropy as well as in axial and mean diffusivities in different white matter areas. Lower values of fractional anisotropy and axial diffusivity in cuprizone-treated mice indicated developing demyelination and/or axonal damage. Several diffusion tensor imaging measurements correlated with learning parameters. Our results show that translational touchscreen operant tests and fear conditioning paradigms can reliably detect cognitive consequences of cuprizone treatment. The suggested experimental approach enables screening novel MS drug candidates in longitudinal experiments for their ability to improve pathological changes in brain structure and reverse cognitive deficits.
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Affiliation(s)
- Maksym V Kopanitsa
- Charles River Discovery Services, Kuopio, Finland.,UK Dementia Research Institute, Department of Brain Sciences, Imperial College, London, UK
| | | | | | - Ari Suhonen
- Charles River Discovery Services, Kuopio, Finland
| | - Juho Koponen
- Charles River Discovery Services, Kuopio, Finland
| | | | | | - Pavlina Pavlidi
- MSc Programme in Translational Neuroscience, Imperial College, London, UK
| | | | | | | | - Joel Kaye
- Teva Pharmaceutical Industries Ltd, Netanya, Israel
| | - Aric Orbach
- Teva Pharmaceutical Industries Ltd, Netanya, Israel
| | - Antti Nurmi
- Charles River Discovery Services, Kuopio, Finland
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21
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Sen MK, Mahns DA, Coorssen JR, Shortland PJ. Behavioural phenotypes in the cuprizone model of central nervous system demyelination. Neurosci Biobehav Rev 2019; 107:23-46. [PMID: 31442519 DOI: 10.1016/j.neubiorev.2019.08.008] [Citation(s) in RCA: 46] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2019] [Revised: 08/01/2019] [Accepted: 08/12/2019] [Indexed: 12/14/2022]
Abstract
The feeding of cuprizone (CPZ) to animals has been extensively used to model the processes of demyelination and remyelination, with many papers adopting a narrative linked to demyelinating conditions like multiple sclerosis (MS), the aetiology of which is unknown. However, no current animal model faithfully replicates the myriad of symptoms seen in the clinical condition of MS. CPZ ingestion causes mitochondrial and endoplasmic reticulum stress and subsequent apoptosis of oligodendrocytes leads to central nervous system demyelination and glial cell activation. Although there are a wide variety of behavioural tests available for characterizing the functional deficits in animal models of disease, including that of CPZ-induced deficits, they have focused on a narrow subset of outcomes such as motor performance, cognition, and anxiety. The literature has not been systematically reviewed in relation to these or other symptoms associated with clinical MS. This paper reviews these tests and makes recommendations as to which are the most important in order to better understand the role of this model in examining aspects of demyelinating diseases like MS.
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Affiliation(s)
- Monokesh K Sen
- School of Medicine, Western Sydney University, New South Wales, Australia
| | - David A Mahns
- School of Medicine, Western Sydney University, New South Wales, Australia
| | - Jens R Coorssen
- Departments of Health Sciences and Biological Sciences, Faculties of Applied Health Sciences and Mathematics & Science, Brock University, Ontario, Canada.
| | - Peter J Shortland
- Science and Health, Western Sydney University, New South Wales, Australia.
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22
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Stumpf SK, Berghoff SA, Trevisiol A, Spieth L, Düking T, Schneider LV, Schlaphoff L, Dreha-Kulaczewski S, Bley A, Burfeind D, Kusch K, Mitkovski M, Ruhwedel T, Guder P, Röhse H, Denecke J, Gärtner J, Möbius W, Nave KA, Saher G. Ketogenic diet ameliorates axonal defects and promotes myelination in Pelizaeus-Merzbacher disease. Acta Neuropathol 2019; 138:147-161. [PMID: 30919030 PMCID: PMC6570703 DOI: 10.1007/s00401-019-01985-2] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2018] [Revised: 02/25/2019] [Accepted: 03/01/2019] [Indexed: 12/24/2022]
Abstract
Pelizaeus-Merzbacher disease (PMD) is an untreatable and fatal leukodystrophy. In a model of PMD with perturbed blood-brain barrier integrity, cholesterol supplementation promotes myelin membrane growth. Here, we show that in contrast to the mouse model, dietary cholesterol in two PMD patients did not lead to a major advancement of hypomyelination, potentially because the intact blood-brain barrier precludes its entry into the CNS. We therefore turned to a PMD mouse model with preserved blood-brain barrier integrity and show that a high-fat/low-carbohydrate ketogenic diet restored oligodendrocyte integrity and increased CNS myelination. This dietary intervention also ameliorated axonal degeneration and normalized motor functions. Moreover, in a paradigm of adult remyelination, ketogenic diet facilitated repair and attenuated axon damage. We suggest that a therapy with lipids such as ketone bodies, that readily enter the brain, can circumvent the requirement of a disrupted blood-brain barrier in the treatment of myelin disease.
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Affiliation(s)
- Sina K Stumpf
- Department of Neurogenetics, Max-Planck-Institute of Experimental Medicine, Hermann-Rein-Str. 3, 37075, Göttingen, Germany
| | - Stefan A Berghoff
- Department of Neurogenetics, Max-Planck-Institute of Experimental Medicine, Hermann-Rein-Str. 3, 37075, Göttingen, Germany
| | - Andrea Trevisiol
- Department of Neurogenetics, Max-Planck-Institute of Experimental Medicine, Hermann-Rein-Str. 3, 37075, Göttingen, Germany
| | - Lena Spieth
- Department of Neurogenetics, Max-Planck-Institute of Experimental Medicine, Hermann-Rein-Str. 3, 37075, Göttingen, Germany
| | - Tim Düking
- Department of Neurogenetics, Max-Planck-Institute of Experimental Medicine, Hermann-Rein-Str. 3, 37075, Göttingen, Germany
| | - Lennart V Schneider
- Department of Neurogenetics, Max-Planck-Institute of Experimental Medicine, Hermann-Rein-Str. 3, 37075, Göttingen, Germany
| | - Lennart Schlaphoff
- Department of Neurogenetics, Max-Planck-Institute of Experimental Medicine, Hermann-Rein-Str. 3, 37075, Göttingen, Germany
| | - Steffi Dreha-Kulaczewski
- Division of Pediatric Neurology, Department of Pediatrics and Adolescent Medicine, University Medical Center, 37075, Göttingen, Germany
| | - Annette Bley
- University Children's Hospital, University Medical Center Hamburg-Eppendorf, 20246, Hamburg, Germany
| | - Dinah Burfeind
- Department of Neurogenetics, Max-Planck-Institute of Experimental Medicine, Hermann-Rein-Str. 3, 37075, Göttingen, Germany
| | - Kathrin Kusch
- Department of Neurogenetics, Max-Planck-Institute of Experimental Medicine, Hermann-Rein-Str. 3, 37075, Göttingen, Germany
| | - Miso Mitkovski
- Light Microscopy Facility, Max-Planck-Institute of Experimental Medicine, 37075, Göttingen, Germany
| | - Torben Ruhwedel
- Department of Neurogenetics, Max-Planck-Institute of Experimental Medicine, Hermann-Rein-Str. 3, 37075, Göttingen, Germany
- Electron Microscopy Core Unit, Max-Planck-Institute of Experimental Medicine, 37075, Göttingen, Germany
| | - Philipp Guder
- University Children's Hospital, University Medical Center Hamburg-Eppendorf, 20246, Hamburg, Germany
| | - Heiko Röhse
- Light Microscopy Facility, Max-Planck-Institute of Experimental Medicine, 37075, Göttingen, Germany
| | - Jonas Denecke
- University Children's Hospital, University Medical Center Hamburg-Eppendorf, 20246, Hamburg, Germany
| | - Jutta Gärtner
- Division of Pediatric Neurology, Department of Pediatrics and Adolescent Medicine, University Medical Center, 37075, Göttingen, Germany
| | - Wiebke Möbius
- Department of Neurogenetics, Max-Planck-Institute of Experimental Medicine, Hermann-Rein-Str. 3, 37075, Göttingen, Germany
- Electron Microscopy Core Unit, Max-Planck-Institute of Experimental Medicine, 37075, Göttingen, Germany
- Center Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB), 37073, Göttingen, Germany
| | - Klaus-Armin Nave
- Department of Neurogenetics, Max-Planck-Institute of Experimental Medicine, Hermann-Rein-Str. 3, 37075, Göttingen, Germany
- Electron Microscopy Core Unit, Max-Planck-Institute of Experimental Medicine, 37075, Göttingen, Germany
- Center Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB), 37073, Göttingen, Germany
| | - Gesine Saher
- Department of Neurogenetics, Max-Planck-Institute of Experimental Medicine, Hermann-Rein-Str. 3, 37075, Göttingen, Germany.
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Bonetto G, Hivert B, Goutebroze L, Karagogeos D, Crépel V, Faivre-Sarrailh C. Selective Axonal Expression of the Kv1 Channel Complex in Pre-myelinated GABAergic Hippocampal Neurons. Front Cell Neurosci 2019; 13:222. [PMID: 31164806 PMCID: PMC6535494 DOI: 10.3389/fncel.2019.00222] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2019] [Accepted: 05/02/2019] [Indexed: 01/01/2023] Open
Abstract
In myelinated fibers, the voltage-gated sodium channels Nav1 are concentrated at the nodal gap to ensure the saltatory propagation of action potentials. The voltage-gated potassium channels Kv1 are segregated at the juxtaparanodes under the compact myelin sheath and may stabilize axonal conduction. It has been recently reported that hippocampal GABAergic neurons display high density of Nav1 channels remarkably in clusters along the axon before myelination (Freeman et al., 2015). In inhibitory neurons, the Nav1 channels are trapped by the ankyrinG scaffold at the axon initial segment (AIS) as observed in pyramidal and granule neurons, but are also forming “pre-nodes,” which may accelerate conduction velocity in pre-myelinated axons. However, the distribution of the Kv1 channels along the pre-myelinated inhibitory axons is still unknown. In the present study, we show that two subtypes of hippocampal GABAergic neurons, namely the somatostatin and parvalbumin positive cells, display a selective high expression of Kv1 channels at the AIS and all along the unmyelinated axons. These inhibitory axons are also highly enriched in molecules belonging to the juxtaparanodal Kv1 complex, including the cell adhesion molecules (CAMs) TAG-1, Caspr2, and ADAM22 and the scaffolding protein 4.1B. Here, taking advantage of hippocampal cultures from 4.1B and TAG-1 knock-out mice, we observed that 4.1B is required for the proper positioning of Caspr2 and TAG-1 along the distal axon, and that TAG-1 deficiency induces alterations in the axonal distribution of Caspr2. However, the axonal expression of Kv1 channels and clustering of ankyrinG were not modified. In conclusion, this study allowed the analysis of the hierarchy between channels, CAMs and scaffolding proteins for their expression along hippocampal inhibitory axons before myelination. The early steps of channel compartmentalization preceding myelination may be crucial for stabilizing nerve impulses switching from a continuous to saltatory conduction during network development.
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Affiliation(s)
- Giulia Bonetto
- INSERM UMR1249, Institut de Neurobiologie de la Méditerranée, Aix-Marseille Université, Marseille, France
| | - Bruno Hivert
- INSERM UMR1249, Institut de Neurobiologie de la Méditerranée, Aix-Marseille Université, Marseille, France
| | - Laurence Goutebroze
- INSERM UMR-S 1270, Institut du Fer à Moulin, Faculté des Sciences et Ingénierie, Sorbonne Université, Paris, France
| | - Domna Karagogeos
- Department of Basic Sciences, Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology, University of Crete Medical School - University of Crete, Heraklion, Greece
| | - Valérie Crépel
- INSERM UMR1249, Institut de Neurobiologie de la Méditerranée, Aix-Marseille Université, Marseille, France
| | - Catherine Faivre-Sarrailh
- INSERM UMR1249, Institut de Neurobiologie de la Méditerranée, Aix-Marseille Université, Marseille, France
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24
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Neurobiology and therapeutic applications of neurotoxins targeting transmitter release. Pharmacol Ther 2019; 193:135-155. [DOI: 10.1016/j.pharmthera.2018.08.016] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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25
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Zhu P, Li J, Zhang L, Liang Z, Tang B, Liao WP, Yi YH, Su T. Development-related aberrations in Kv1.1 α-subunit exert disruptive effects on bioelectrical activities of neurons in a mouse model of fragile X syndrome. Prog Neuropsychopharmacol Biol Psychiatry 2018; 84:140-151. [PMID: 29481897 DOI: 10.1016/j.pnpbp.2018.02.011] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/27/2017] [Revised: 02/22/2018] [Accepted: 02/22/2018] [Indexed: 10/18/2022]
Abstract
Kv1.1, a Shaker homologue potassium channel, plays a critical role in homeostatic regulation of neuronal excitability. Aberrations in the functional properties of Kv1.1 have been implicated in several neurological disorders featured by neuronal hyperexcitability. Fragile X syndrome (FXS), the most common form of inherited mental retardation, is characterized by hyperexcitability in neural network and intrinsic membrane properties. The Kv1.1 channel provides an intriguing mechanistic candidate for FXS. We investigated the development-related expression pattern of the Kv1.1 α-subunit by using a Fmr1 knockout (KO) mouse model of FXS. Markedly decreased protein expression of Kv1.1 was found in neonatal and adult stages when compared to age-matched wild-type (WT) mice. Immunohistochemical investigations supported the delayed development-related increases in Kv1.1 expression, especially in CA3 pyramidal neurons. By applying a Kv1.1-specific blocker, dendrotoxin-κ (DTX-κ), we isolated the Kv1.1-mediated currents in the CA3 pyramidal neurons. The isolated DTX-κ-sensitive current of neurons from KO mice exhibited decreased amplitude, lower threshold of activation, and faster recovery from inactivation. The equivalent reduction in potassium current in the WT neurons following application of the appropriate amount of DTX-κ reproduced the enhanced firing abilities of KO neurons, suggesting the Kv1.1 channel as a critical contributor to the hyperexcitability of KO neurons. The role of Kv1.1 in controlling neuronal discharges was further supported by the parallel developmental trajectories of Kv1.1 expression, current amplitude, and discharge impacts, with a significant correlation between the amplitude of Kv1.1-mediated currents and Kv1.1-blocking-induced firing enhancement. These data suggest that the expression of the Kv1.1 α-subunit has a profound pathological relevance to hyperexcitability in FXS, as well as implications for normal development, maintenance, and control of neuronal activities.
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Affiliation(s)
- Pingping Zhu
- Institute of Neuroscience and the Second Affiliated Hospital of Guangzhou Medical University, Guangzhou, China; Key Laboratory of Neurogenetics and Channelopathies of the Ministry of Education of China, Guangzhou, China; Department of Neurology, Guangzhou Red Cross Hospital, Medical College, Jinan University, Guangzhou, China
| | - Jialing Li
- Institute of Neuroscience and the Second Affiliated Hospital of Guangzhou Medical University, Guangzhou, China; Key Laboratory of Neurogenetics and Channelopathies of the Ministry of Education of China, Guangzhou, China
| | - Liting Zhang
- Institute of Neuroscience and the Second Affiliated Hospital of Guangzhou Medical University, Guangzhou, China; Key Laboratory of Neurogenetics and Channelopathies of the Ministry of Education of China, Guangzhou, China
| | - Zhanrong Liang
- Institute of Neuroscience and the Second Affiliated Hospital of Guangzhou Medical University, Guangzhou, China; Key Laboratory of Neurogenetics and Channelopathies of the Ministry of Education of China, Guangzhou, China
| | - Bin Tang
- Institute of Neuroscience and the Second Affiliated Hospital of Guangzhou Medical University, Guangzhou, China; Key Laboratory of Neurogenetics and Channelopathies of the Ministry of Education of China, Guangzhou, China
| | - Wei-Ping Liao
- Institute of Neuroscience and the Second Affiliated Hospital of Guangzhou Medical University, Guangzhou, China; Key Laboratory of Neurogenetics and Channelopathies of the Ministry of Education of China, Guangzhou, China
| | - Yong-Hong Yi
- Institute of Neuroscience and the Second Affiliated Hospital of Guangzhou Medical University, Guangzhou, China; Key Laboratory of Neurogenetics and Channelopathies of the Ministry of Education of China, Guangzhou, China
| | - Tao Su
- Institute of Neuroscience and the Second Affiliated Hospital of Guangzhou Medical University, Guangzhou, China; Key Laboratory of Neurogenetics and Channelopathies of the Ministry of Education of China, Guangzhou, China.
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26
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Correale J, Ysrraelit MC, Benarroch EE. Metabolic coupling of axons and glial cells. Neurology 2018; 90:737-744. [DOI: 10.1212/wnl.0000000000005339] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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27
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Kojima W, Hayashi K. Changes in the axo-glial junctions of the optic nerves of cuprizone-treated mice. Histochem Cell Biol 2018; 149:529-536. [PMID: 29460173 DOI: 10.1007/s00418-018-1654-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/15/2018] [Indexed: 10/18/2022]
Abstract
Demyelination induced by cuprizone in mice has served a useful model system for the study of demyelinating diseases, such as multiple sclerosis. Severity of demyelination by cuprizone, however, varies across different regions of the central nervous system; the corpus callosum is sensitive, while the optic nerves are resistant. Here, we investigated the effects of cuprizone on optic nerves, focusing on the axo-glial junctions. Immunostaining for sodium channels, contactin-associated protein, neurofascins, and potassium channels revealed that there were no massive changes in the density and morphology of the axo-glial junctions in cuprizone-treated optic nerves. However, when we counted the number of incomplete junctional complexes, we observed increased numbers of isolated paranodes. These isolated paranodes were immunopositive for both axonal and glial membrane proteins, indicating that they were the contact sites between axons and glia. These were not associated with sodium channels or potassium channels, suggesting the absence of physiological functions. When teased axons from cuprizone-treated optic nerves were immunostained, the isolated paranodes were found at the internode region of the myelin. From these observations, we conclude that cuprizone induces new contacts between axons and myelins at the internode region.
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Affiliation(s)
- Wataru Kojima
- Department of Materials and Life Sciences, Faculty of Science and Technology, Sophia University, 7-1 Kioicho, Chiyoda-ku, Tokyo, Japan
| | - Kensuke Hayashi
- Department of Materials and Life Sciences, Faculty of Science and Technology, Sophia University, 7-1 Kioicho, Chiyoda-ku, Tokyo, Japan.
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28
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Jackson J, Bianco G, Rosa AO, Cowan K, Bond P, Anichtchik O, Fern R. White matter tauopathy: Transient functional loss and novel myelin remodeling. Glia 2018; 66:813-827. [PMID: 29315804 DOI: 10.1002/glia.23286] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Revised: 12/08/2017] [Accepted: 12/11/2017] [Indexed: 01/03/2023]
Abstract
Early white matter (WM) changes are common in dementia and may contribute to functional decline. We here examine this phenomenon in an induced dementia model for the first time. We report a novel and selective form of myelin injury as the first manifestation of tauopathy in the adult central nervous system. Myelin pathology rapidly followed the induction of a P301 tau mutation associated with fronto-temporal dementia in humans (rTG4510 line). Damage involved focal disruption of the ad-axonal myelin lamella and internal oligodendrocyte tongue process, followed by myelin remodeling with features of re-myelination that included myelin thinning and internodal shortening. The evolution of the re-myelinated phenotype was complete in the molecular layer of the dentate gyrus after 1 month and in the optic nerve (ON) after 9 months of transgene induction and proceeded in the absence of actual demyelination, reactive glial changes or inflammatory response. The initial rapid myelin pathology was associated with loss of WM function and performance decline in a novel recognition test and both these effects largely reversed during the myelin re-modeling phase. The initial phase of myelin injury was accompanied by disruption of the vesicle population present in the axoplasm of hippocampal and ON axons. Axoplasmic vesicle release is significant for the regulation of myelin plasticity and disruption of this pathway may underlie the myelin damage and remodeling evoked by tauopathy. WM dysfunction early in tauopathy will disorder neural circuits, the current findings suggest this event may make a significant contribution to early clinical deficit in dementia.
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Affiliation(s)
| | | | - Angelo O Rosa
- Plymouth Electron Microscopy Centre, University of Plymouth, Plymouth, United Kingdom
| | - Katrina Cowan
- Peninsula School of Medicine and Dentistry, University of Plymouth, PUPSMD, Plymouth, United Kingdom
| | - Peter Bond
- Plymouth Electron Microscopy Centre, University of Plymouth, Plymouth, United Kingdom
| | - Oleg Anichtchik
- Peninsula School of Medicine and Dentistry, University of Plymouth, PUPSMD, Plymouth, United Kingdom
| | - Robert Fern
- Peninsula School of Medicine and Dentistry, University of Plymouth, PUPSMD, Plymouth, United Kingdom
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29
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Araújo SES, Mendonça HR, Wheeler NA, Campello-Costa P, Jacobs KM, Gomes FCA, Fox MA, Fuss B. Inflammatory demyelination alters subcortical visual circuits. J Neuroinflammation 2017; 14:162. [PMID: 28821276 PMCID: PMC5562979 DOI: 10.1186/s12974-017-0936-0] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2017] [Accepted: 08/07/2017] [Indexed: 11/13/2022] Open
Abstract
Background Multiple sclerosis (MS) is an inflammatory demyelinating disease classically associated with axonal damage and loss; more recently, however, synaptic changes have been recognized as additional contributing factors. An anatomical area commonly affected in MS is the visual pathway; yet, changes other than those associated with inflammatory demyelination of the optic nerve, i.e., optic neuritis, have not been described in detail. Methods Adult mice were subjected to a diet containing cuprizone to mimic certain aspects of inflammatory demyelination as seen in MS. Demyelination and inflammation were assessed by real-time polymerase chain reaction and immunohistochemistry. Synaptic changes associated with inflammatory demyelination in the dorsal lateral geniculate nucleus (dLGN) were determined by immunohistochemistry, Western blot analysis, and electrophysiological field potential recordings. Results In the cuprizone model, demyelination was observed in retinorecipient regions of the subcortical visual system, in particular the dLGN, where it was found accompanied by microglia activation and astrogliosis. In contrast, anterior parts of the pathway, i.e., the optic nerve and tract, appeared largely unaffected. Under the inflammatory demyelinating conditions, as seen in the dLGN of cuprizone-treated mice, there was an overall decrease in excitatory synaptic inputs from retinal ganglion cells. At the same time, the number of synaptic complexes arising from gamma-aminobutyric acid (GABA)-generating inhibitory neurons was found increased, as were the synapses that contain the N-methyl-d-aspartate receptor (NMDAR) subunit GluN2B and converge onto inhibitory neurons. These synaptic changes were functionally found associated with a shift toward an overall increase in network inhibition. Conclusions Using the cuprizone model of inflammatory demyelination, our data reveal a novel form of synaptic (mal)adaption in the CNS that is characterized by a shift of the excitation/inhibition balance toward inhibitory network activity associated with an increase in GABAergic inhibitory synapses and a possible increase in excitatory input onto inhibitory interneurons. In addition, our data recognize the cuprizone model as a suitable tool in which to assess the effects of inflammatory demyelination on subcortical retinorecipient regions of the visual system, such as the dLGN, in the absence of overt optic neuritis.
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Affiliation(s)
- Sheila Espírito Santo Araújo
- Department of Anatomy and Neurobiology, Virginia Commonwealth University School of Medicine, Richmond, VA, USA.,Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.,Instituto de Biologia, Programa de Neurociências, Universidade Federal Fluminense, Niterói, Brazil.,Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Henrique Rocha Mendonça
- Department of Anatomy and Neurobiology, Virginia Commonwealth University School of Medicine, Richmond, VA, USA.,Instituto de Biologia, Programa de Neurociências, Universidade Federal Fluminense, Niterói, Brazil
| | - Natalie A Wheeler
- Department of Anatomy and Neurobiology, Virginia Commonwealth University School of Medicine, Richmond, VA, USA
| | - Paula Campello-Costa
- Instituto de Biologia, Programa de Neurociências, Universidade Federal Fluminense, Niterói, Brazil
| | - Kimberle M Jacobs
- Department of Anatomy and Neurobiology, Virginia Commonwealth University School of Medicine, Richmond, VA, USA
| | - Flávia C A Gomes
- Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Michael A Fox
- Developmental and Translational Neurobiology Center, Virginia Tech Carilion Research Institute, Roanoke, VA, USA
| | - Babette Fuss
- Department of Anatomy and Neurobiology, Virginia Commonwealth University School of Medicine, Richmond, VA, USA.
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30
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Hasan S, Bove C, Silvestri G, Mantuano E, Modoni A, Veneziano L, Macchioni L, Hunter T, Hunter G, Pessia M, D'Adamo MC. A channelopathy mutation in the voltage-sensor discloses contributions of a conserved phenylalanine to gating properties of Kv1.1 channels and ataxia. Sci Rep 2017; 7:4583. [PMID: 28676720 PMCID: PMC5496848 DOI: 10.1038/s41598-017-03041-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2017] [Accepted: 04/21/2017] [Indexed: 01/21/2023] Open
Abstract
Channelopathy mutations prove informative on disease causing mechanisms and channel gating dynamics. We have identified a novel heterozygous mutation in the KCNA1 gene of a young proband displaying typical signs and symptoms of Episodic Ataxia type 1 (EA1). This mutation is in the S4 helix of the voltage-sensing domain and results in the substitution of the highly conserved phenylalanine 303 by valine (p.F303V). The contributions of F303 towards K+ channel voltage gating are unclear and here have been assessed biophysically and by performing structural analysis using rat Kv1.2 coordinates. We observed significant positive shifts of voltage-dependence, changes in the activation, deactivation and slow inactivation kinetics, reduced window currents, and decreased current amplitudes of both Kv1.1 and Kv1.1/1.2 channels. Structural analysis revealed altered interactions between F303V and L339 and I335 of the S5 helix of a neighboring subunit. The substitution of an aromatic phenylalanine with an aliphatic valine within the voltage-sensor destabilizes the open state of the channel. Thus, F303 fine-tunes the Kv1.1 gating properties and contributes to the interactions between the S4 segment and neighboring alpha helices. The resulting channel's loss of function validates the clinical relevance of the mutation for EA1 pathogenesis.
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Affiliation(s)
- Sonia Hasan
- Department of Physiology, Faculty of Medicine, Kuwait University, Safat, 13110, Kuwait
| | - Cecilia Bove
- Section of Physiology and Biochemistry, Department of Experimental Medicine, School of Medicine, University of Perugia, Perugia, Italy
| | - Gabriella Silvestri
- Institute of Neurology, Catholic University of Sacred Heart, Fondazione Gemelli, Rome, Italy
| | - Elide Mantuano
- Institute of Translational Pharmacology, National Research Council of Italy, Rome, Italy
| | - Anna Modoni
- Institute of Neurology, Catholic University of Sacred Heart, Fondazione Gemelli, Rome, Italy
| | - Liana Veneziano
- Institute of Translational Pharmacology, National Research Council of Italy, Rome, Italy
| | - Lara Macchioni
- Section of Physiology and Biochemistry, Department of Experimental Medicine, School of Medicine, University of Perugia, Perugia, Italy
| | - Therese Hunter
- Faculty of Medicine & Surgery, Department of Physiology & Biochemistry, University of Malta, MSD 2080, Msida, Malta
| | - Gary Hunter
- Faculty of Medicine & Surgery, Department of Physiology & Biochemistry, University of Malta, MSD 2080, Msida, Malta
| | - Mauro Pessia
- Section of Physiology and Biochemistry, Department of Experimental Medicine, School of Medicine, University of Perugia, Perugia, Italy.,Faculty of Medicine & Surgery, Department of Physiology & Biochemistry, University of Malta, MSD 2080, Msida, Malta
| | - Maria Cristina D'Adamo
- Faculty of Medicine & Surgery, Department of Physiology & Biochemistry, University of Malta, MSD 2080, Msida, Malta.
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Al-Sabi A, Daly D, Hoefer P, Kinsella GK, Metais C, Pickering M, Herron C, Kaza SK, Nolan K, Dolly JO. A Rational Design of a Selective Inhibitor for Kv1.1 Channels Prevalent in Demyelinated Nerves That Improves Their Impaired Axonal Conduction. J Med Chem 2017; 60:2245-2256. [PMID: 28225274 DOI: 10.1021/acs.jmedchem.6b01262] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
K+ channels containing Kv1.1 α subunits, which become prevalent at internodes in demyelinated axons, may underlie their dysfunctional conduction akin to muscle weakness in multiple sclerosis. Small inhibitors were sought with selectivity for the culpable hyper-polarizing K+ currents. Modeling of interactions with the extracellular pore in a Kv1.1-deduced structure identified diaryldi(2-pyrrolyl)methane as a suitable scaffold with optimized alkyl ammonium side chains. The resultant synthesized candidate [2,2'-((5,5'(di-p-topyldiaryldi(2-pyrrolyl)methane)bis(2,2'carbonyl)bis(azanediyl)) diethaneamine·2HCl] (8) selectively blocked Kv1.1 channels (IC50 ≈ 15 μM) recombinantly expressed in mammalian cells, induced a positive shift in the voltage dependency of K+ current activation, and slowed its kinetics. It preferentially inhibited channels containing two or more Kv1.1 subunits regardless of their positioning in concatenated tetramers. In slices of corpus callosum from mice subjected to a demyelination protocol, this novel inhibitor improved neuronal conduction, highlighting its potential for alleviating symptoms in multiple sclerosis.
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Affiliation(s)
| | | | | | - Gemma K Kinsella
- School of Food Science and Environmental Health, College of Sciences and Health, Dublin Institute of Technology , Cathal Brugha Street, Dublin 1, Ireland
| | | | - Mark Pickering
- UCD School of Medicine, University College Dublin , Dublin, Ireland
| | - Caroline Herron
- School of Biomolecular and Biomed Science, Conway Institute , Belfield, Dublin 4, Ireland
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Alteration of Neuronal Excitability and Short-Term Synaptic Plasticity in the Prefrontal Cortex of a Mouse Model of Mental Illness. J Neurosci 2017; 37:4158-4180. [PMID: 28283561 DOI: 10.1523/jneurosci.4345-15.2017] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2015] [Revised: 02/17/2017] [Accepted: 02/22/2017] [Indexed: 01/28/2023] Open
Abstract
Using a genetic mouse model that faithfully recapitulates a DISC1 genetic alteration strongly associated with schizophrenia and other psychiatric disorders, we examined the impact of this mutation within the prefrontal cortex. Although cortical layering, cytoarchitecture, and proteome were found to be largely unaffected, electrophysiological examination of the mPFC revealed both neuronal hyperexcitability and alterations in short-term synaptic plasticity consistent with enhanced neurotransmitter release. Increased excitability of layer II/III pyramidal neurons was accompanied by consistent reductions in voltage-activated potassium currents near the action potential threshold as well as by enhanced recruitment of inputs arising from superficial layers to layer V. We further observed reductions in both the paired-pulse ratios and the enhanced short-term depression of layer V synapses arising from superficial layers consistent with enhanced neurotransmitter release at these synapses. Recordings from layer II/III pyramidal neurons revealed action potential widening that could account for enhanced neurotransmitter release. Significantly, we found that reduced functional expression of the voltage-dependent potassium channel subunit Kv1.1 substantially contributes to both the excitability and short-term plasticity alterations that we observed. The underlying dysregulation of Kv1.1 expression was attributable to cAMP elevations in the PFC secondary to reduced phosphodiesterase 4 activity present in Disc1 deficiency and was rescued by pharmacological blockade of adenylate cyclase. Our results demonstrate a potentially devastating impact of Disc1 deficiency on neural circuit function, partly due to Kv1.1 dysregulation that leads to a dual dysfunction consisting of enhanced neuronal excitability and altered short-term synaptic plasticity.SIGNIFICANCE STATEMENT Schizophrenia is a profoundly disabling psychiatric illness with a devastating impact not only upon the afflicted but also upon their families and the broader society. Although the underlying causes of schizophrenia remain poorly understood, a growing body of studies has identified and strongly implicated various specific risk genes in schizophrenia pathogenesis. Here, using a genetic mouse model, we explored the impact of one of the most highly penetrant schizophrenia risk genes, DISC1, upon the medial prefrontal cortex, the region believed to be most prominently dysfunctional in schizophrenia. We found substantial derangements in both neuronal excitability and short-term synaptic plasticity-parameters that critically govern neural circuit information processing-suggesting that similar changes may critically, and more broadly, underlie the neural computational dysfunction prototypical of schizophrenia.
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Hamada MS, Popovic MA, Kole MHP. Loss of Saltation and Presynaptic Action Potential Failure in Demyelinated Axons. Front Cell Neurosci 2017; 11:45. [PMID: 28289377 PMCID: PMC5326753 DOI: 10.3389/fncel.2017.00045] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2016] [Accepted: 02/09/2017] [Indexed: 01/09/2023] Open
Abstract
In cortical pyramidal neurons the presynaptic terminals controlling transmitter release are located along unmyelinated axon collaterals, far from the original action potential (AP) initiation site, the axon initial segment (AIS). Once initiated, APs will need to reliably propagate over long distances and regions of geometrical inhomogeneity like branch points (BPs) to rapidly depolarize the presynaptic terminals and confer temporally precise synaptic transmission. While axon pathologies such as demyelinating diseases are well established to impede the fidelity of AP propagation along internodes, to which extent myelin loss affects propagation along BPs and axon collaterals is not well understood. Here, using the cuprizone demyelination model, we performed optical voltage-sensitive dye (VSD) imaging from control and demyelinated layer 5 pyramidal neuron axons. In the main axon, we find that myelin loss switches the modality of AP propagation from rapid saltation towards a slow continuous wave. The duration of single AP waveforms at BPs or nodes was, however, only slightly briefer. In contrast, by using two-photon microscopy-guided loose-seal patch recordings from axon collaterals we revealed a presynaptic AP broadening in combination with a reduced velocity and frequency-dependent failure. Finally, internodal myelin loss was also associated with de novo sprouting of axon collaterals starting from the primary (demyelinated) axon. Thus, the loss of oligodendrocytes and myelin sheaths bears functional consequences beyond the main axon, impeding the temporal fidelity of presynaptic APs and affecting the functional and structural organization of synaptic connectivity within the neocortex.
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Affiliation(s)
- Mustafa S Hamada
- Department of Axonal Signaling, Netherlands Institute for Neuroscience, Royal Netherlands Academy of Arts and SciencesAmsterdam, Netherlands; Cell Biology, Faculty of Science, Utrecht UniversityUtrecht, Netherlands
| | - Marko A Popovic
- Department of Axonal Signaling, Netherlands Institute for Neuroscience, Royal Netherlands Academy of Arts and Sciences Amsterdam, Netherlands
| | - Maarten H P Kole
- Department of Axonal Signaling, Netherlands Institute for Neuroscience, Royal Netherlands Academy of Arts and SciencesAmsterdam, Netherlands; Cell Biology, Faculty of Science, Utrecht UniversityUtrecht, Netherlands
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Cao XJ, Oertel D. Genetic perturbations suggest a role of the resting potential in regulating the expression of the ion channels of the KCNA and HCN families in octopus cells of the ventral cochlear nucleus. Hear Res 2017; 345:57-68. [PMID: 28065805 DOI: 10.1016/j.heares.2017.01.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/20/2016] [Revised: 01/02/2017] [Accepted: 01/03/2017] [Indexed: 10/20/2022]
Abstract
Low-voltage-activated K+ (gKL) and hyperpolarization-activated mixed cation conductances (gh) mediate currents, IKL and Ih, through channels of the Kv1 (KCNA) and HCN families respectively and give auditory neurons the temporal precision required for signaling information about the onset, fine structure, and time of arrival of sounds. Being partially activated at rest, gKL and gh contribute to the resting potential and shape responses to even small subthreshold synaptic currents. Resting gKL and gh also affect the coupling of somatic depolarization with the generation of action potentials. To learn how these important conductances are regulated we have investigated how genetic perturbations affect their expression in octopus cells of the ventral cochlear nucleus (VCN). We report five new findings: First, the magnitude of gh and gKL varied over more than two-fold between wild type strains of mice. Second, average resting potentials are not different in different strains of mice even in the face of large differences in average gKL and gh. Third, IKL has two components, one being α-dendrotoxin (α-DTX)-sensitive and partially inactivating and the other being α-DTX-insensitive, tetraethylammonium (TEA)-sensitive, and non-inactivating. Fourth, the loss of Kv1.1 results in diminution of the α-DTX-sensitive IKL, and compensatory increased expression of an α-DTX-insensitive, tetraethylammonium (TEA)-sensitive IKL. Fifth, Ih and IKL are balanced at the resting potential in all wild type and mutant octopus cells even when resting potentials vary in individual cells over nearly 10 mV, indicating that the resting potential influences the expression of gh and gKL. The independence of resting potentials on gKL and gh shows that gKL and gh do not, over days or weeks, determine the resting potential but rather that the resting potential plays a role in regulating the magnitude of either or both gKL and gh.
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Affiliation(s)
- Xiao-Jie Cao
- Department of Neuroscience, School of Medicine and Public Health, University of Wisconsin, Madison, WI 53705, USA
| | - Donata Oertel
- Department of Neuroscience, School of Medicine and Public Health, University of Wisconsin, Madison, WI 53705, USA.
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Verden D, Macklin WB. Neuroprotection by central nervous system remyelination: Molecular, cellular, and functional considerations. J Neurosci Res 2016; 94:1411-1420. [PMID: 27618492 DOI: 10.1002/jnr.23923] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2016] [Revised: 08/09/2016] [Accepted: 08/24/2016] [Indexed: 12/27/2022]
Abstract
Oligodendrocytes and their myelin sheaths play an intricate role in axonal health and function. The prevalence of white matter pathology in a wide variety of central nervous system disorders has gained attention in recent years. Remyelination has therefore become a major target of therapeutic research, with the aim of protecting axons from further damage. The axon-myelin unit is elaborate, and demyelination causes profound changes in axonal molecular domains, signal transmission, and metabolism. Remyelination is known to restore some of these changes, but many of its outcomes remain unknown. Understanding how different aspects of the axon-myelin unit are restored by remyelination is important for making effective, targeted therapeutics for white matter dysfunction. Additionally, understanding how subtle deficits relate to axonal function during demyelination and remyelination may provide clues into the impact of myelin on neuronal circuits. In this review, we discuss the current knowledge of the neuroprotective effects of remyelination, as well as gaps in our knowledge. Finally, we propose systems with unique myelin profiles that may serve as useful models for investigating remyelination efficacy. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Dylan Verden
- Department of Cell and Developmental Biology, University of Colorado School of Medicine, Aurora, Colorado
| | - Wendy B Macklin
- Department of Cell and Developmental Biology, University of Colorado School of Medicine, Aurora, Colorado.
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Ovsepian SV, LeBerre M, Steuber V, O'Leary VB, Leibold C, Oliver Dolly J. Distinctive role of KV1.1 subunit in the biology and functions of low threshold K+ channels with implications for neurological disease. Pharmacol Ther 2016; 159:93-101. [DOI: 10.1016/j.pharmthera.2016.01.005] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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Normal human CD4(+) helper T cells express Kv1.1 voltage-gated K(+) channels, and selective Kv1.1 block in T cells induces by itself robust TNFα production and secretion and activation of the NFκB non-canonical pathway. J Neural Transm (Vienna) 2015; 123:137-57. [PMID: 26611796 DOI: 10.1007/s00702-015-1446-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2015] [Accepted: 08/16/2015] [Indexed: 10/22/2022]
Abstract
TNFα is a very potent and pleiotropic pro-inflammatory cytokine, essential to the immune system for eradicating cancer and microorganisms, and to the nervous system, for brain development and ongoing function. Yet, excess and/or chronic TNFα secretion causes massive tissue damage in autoimmune, inflammatory and neurological diseases and injuries. Therefore, many patients with autoimmune/inflammatory diseases receive anti-TNFα medications. TNFα is secreted primarily by CD4(+) T cells, macrophages, monocytes, neutrophils and NK cells, mainly after immune stimulation. Yet, the cause for the pathologically high and chronic TNFα secretion is unknown. Can blocking of a particular ion channel in T cells induce by itself TNFα secretion? Such phenomenon was never revealed or even hypothesized. In this interdisciplinary study we discovered that: (1) normal human T cells express Kv1.1 voltage-gated potassium channel mRNA, and the Kv1.1 membrane-anchored protein channel; (2) Kv1.1 is expressed in most CD4(+)CD3(+) helper T cells (mean CD4(+)CD3(+)Kv1.1(+) T cells of 7 healthy subjects: 53.09 ± 22.17 %), but not in CD8(+)CD3(+) cytotoxic T cells (mean CD8(+)CD3(+)Kv1.1(+) T cells: 4.12 ± 3.04 %); (3) electrophysiological whole-cell recordings in normal human T cells revealed Kv currents; (4) Dendrotoxin-K (DTX-K), a highly selective Kv1.1 blocker derived from snake toxin, increases the rate of rise and decay of Kv currents in both resting and activated T cells, without affecting the peak current; (5) DTX-K by itself induces robust TNFα production and secretion by normal human T cells, without elevating IFNγ, IL-4 and IL-10; (6) intact Ca(2+) channels are required for DTX-induced TNFα secretion; (7) selective anti-Kv1.1 antibodies also induce by themselves TNFα secretion; (8) DTX-K activates NFκB in normal human T cells via the unique non-canonical-pathway; (9) injection of Kv1.1-blocked human T cells to SCID mice, causes recruitment of resident mouse cells into the liver, alike reported after TNFα injection into the brain. Based on our discoveries we speculate that abnormally blocked Kv1.1 in T cells (and other immune cells?), due to either anti-Kv1.1 autoimmune antibodies, or Kv1.1-blocking toxins alike DTX-K, or Kv1.1-blocking genetic mutations, may be responsible for the chronic/excessive TNFα in autoimmune/inflammatory diseases. Independently, we also hypothesize that selective block of Kv1.1 in CD4(+) T cells of patients with cancer or chronic infectious diseases could be therapeutic, since it may: a. augment beneficial secretion and delivery of TNFα to the disease-affected sites; b. induce recruitment and extravasation of curative immune cells and factors; c. improve accessibility of drugs to the brain and few peripheral organs thanks to TNFα-induced increased permeability of organ's barriers.
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Praet J, Guglielmetti C, Berneman Z, Van der Linden A, Ponsaerts P. Cellular and molecular neuropathology of the cuprizone mouse model: clinical relevance for multiple sclerosis. Neurosci Biobehav Rev 2015; 47:485-505. [PMID: 25445182 DOI: 10.1016/j.neubiorev.2014.10.004] [Citation(s) in RCA: 277] [Impact Index Per Article: 30.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2014] [Revised: 09/18/2014] [Accepted: 10/01/2014] [Indexed: 01/30/2023]
Abstract
The cuprizone mouse model allows the investigation of the complex molecular mechanisms behind nonautoimmune-mediated demyelination and spontaneous remyelination. While it is generally accepted that oligodendrocytes are specifically vulnerable to cuprizone intoxication due to their high metabolic demands, a comprehensive overview of the etiology of cuprizone-induced pathology is still missing to date. In this review we extensively describe the physico-chemical mode of action of cuprizone and discuss the molecular and enzymatic mechanisms by which cuprizone induces metabolic stress, oligodendrocyte apoptosis, myelin degeneration and eventually axonal and neuronal pathology. In addition, we describe the dual effector function of the immune system which tightly controls demyelination by effective induction of oligodendrocyte apoptosis, but in contrast also paves the way for fast and efficient remyelination by the secretion of neurotrophic factors and the clearance of cellular and myelinic debris. Finally, we discuss the many clinical symptoms that can be observed following cuprizone treatment, and how these strengthened the cuprizone model as a useful tool to study human multiple sclerosis, schizophrenia and epilepsy.
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Daly D, Al-Sabi A, Kinsella GK, Nolan K, Dolly JO. Porphyrin derivatives as potent and selective blockers of neuronal Kv1 channels. Chem Commun (Camb) 2015; 51:1066-9. [DOI: 10.1039/c4cc05639f] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Docking model of compound12into the homology model of Kv1.1.
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Affiliation(s)
- D. Daly
- School of Chemical Sciences
- Dublin City University
- Dublin 9
- Ireland
| | - A. Al-Sabi
- International Centre for Neurotherapeutics
- Dublin City University
- Dublin 9
- Ireland
| | - G. K. Kinsella
- Biology Department
- National University of Ireland Maynooth
- Co. Kildare
- Ireland
| | - K. Nolan
- School of Chemical Sciences
- Dublin City University
- Dublin 9
- Ireland
| | - J. O. Dolly
- International Centre for Neurotherapeutics
- Dublin City University
- Dublin 9
- Ireland
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