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Gil-Rivera M, Medina-Gali RM, Martínez-Pinna J, Soriano S. Physiology of pancreatic β-cells: Ion channels and molecular mechanisms implicated in stimulus-secretion coupling. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2021; 359:287-323. [PMID: 33832651 DOI: 10.1016/bs.ircmb.2021.02.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The human and mouse islet of Langerhans is an endocrine organ composed of five different cells types; insulin-secreting β-cells, glucagon-producing α-cells, somatostatin-producing δ-cells, pancreatic polypeptide-secreting PP cells and ɛ-cells that secretes ghrelin. The most important cells are the pancreatic β-cells that comprise around 45-50% of human islets and 75-80% in the mouse. Pancreatic β-cells secrete insulin at high glucose concentration, thereby finely regulating glycaemia by the hypoglycaemic effects of this hormone. Different ion channels are implicated in the stimulus-secretion coupling of insulin. An increase in the intracellular ATP concentration leads to closure KATP channels, depolarizing the cell and opening voltage-gated calcium channels. The increase of intracellular calcium concentration induced by calcium entry through voltage-gated calcium channels promotes insulin secretion. Here, we briefly describe the diversity of ion channels present in pancreatic β-cells and the different mechanisms that are responsible to induce insulin secretion in human and mouse cells. Moreover, we described the pathophysiology due to alterations in the physiology of the main ion channels present in pancreatic β-cell and its implication to predispose metabolic disorders as type 2 diabetes mellitus.
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Affiliation(s)
- Minerva Gil-Rivera
- Departamento de Fisiología, Genética y Microbiología, Universidad de Alicante, Alicante, Spain.
| | - Regla M Medina-Gali
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Madrid, Spain; Instituto de Investigación, Desarrollo e Innovación en Biotecnología Sanitaria de Elche (IDiBE), Universidad Miguel Hernández, Elche, Spain
| | - Juan Martínez-Pinna
- Departamento de Fisiología, Genética y Microbiología, Universidad de Alicante, Alicante, Spain; Instituto de Investigación, Desarrollo e Innovación en Biotecnología Sanitaria de Elche (IDiBE), Universidad Miguel Hernández, Elche, Spain
| | - Sergi Soriano
- Departamento de Fisiología, Genética y Microbiología, Universidad de Alicante, Alicante, Spain; Instituto de Investigación, Desarrollo e Innovación en Biotecnología Sanitaria de Elche (IDiBE), Universidad Miguel Hernández, Elche, Spain.
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152
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Glycinergic Inhibition Targets Specific Off Cone Bipolar Cells in Primate Retina. eNeuro 2021; 8:ENEURO.0432-20.2020. [PMID: 33188005 PMCID: PMC7920536 DOI: 10.1523/eneuro.0432-20.2020] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2020] [Accepted: 11/06/2020] [Indexed: 11/21/2022] Open
Abstract
Adapting between scotopic and photopic illumination involves switching the routing of retinal signals between rod and cone-dominated circuits. In the daytime, cone signals pass through parallel On and Off cone bipolar cells (CBCs), that are sensitive to increments and decrements in luminance, respectively. At night, rod signals are routed into these cone-pathways via a key glycinergic interneuron, the AII amacrine cell (AII-AC). AII-ACs also provide On-pathway-driven crossover inhibition to Off-CBCs under photopic conditions. In primates, it is not known whether all Off-bipolar cell types receive functional inputs from AII-ACs. Here, we show that select Off-CBC types receive significantly higher levels of On-pathway-driven glycinergic input than others. The rise and decay kinetics of the glycinergic events are consistent with involvement of the α1 glycine receptor (GlyR) subunit, a result supported by a higher level of GLRA1 transcript in these cells. The Off-bipolar types that receive glycinergic input have sustained physiological properties and include the flat midget bipolar (FMB) cells, which provide excitatory input to the Off-midget ganglion cells (GCs; parvocellular pathway). Our results suggest that only a subset of Off-bipolar cells have the requisite receptors to respond to AII-AC input. Taken together with results in mouse retina, our findings suggest a conserved motif whereby signal output from AII-ACs is preferentially routed into sustained Off-bipolar signaling pathways.
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153
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Rapid effects of neurosteroids on neuronal plasticity and their physiological and pathological implications. Neurosci Lett 2021; 750:135771. [PMID: 33636284 DOI: 10.1016/j.neulet.2021.135771] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2020] [Revised: 02/15/2021] [Accepted: 02/20/2021] [Indexed: 11/22/2022]
Abstract
Current neuroscience research on neurosteroids and their synthetic analogues - neuroactive steroids - clearly demonstrate their drug likeness in a variety of neurological and psychiatric conditions. Moreover, research on neurosteroids continues to provide novel mechanistic insights into receptor activation or inhibition of various receptors. This mini-review will provide a high-level overview of the research area and discuss the various classes of potential physiological and pathological implications discovered so far.
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154
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Rangel-Galván M, Rangel A, Romero-Méndez C, Dávila EM, Castro ME, Caballero NA, Meléndez Bustamante FJ, Sanchez-Gaytan BL, Meza U, Perez-Aguilar JM. Inhibitory Mechanism of the Isoflavone Derivative Genistein in the Human Ca V3.3 Channel. ACS Chem Neurosci 2021; 12:651-659. [PMID: 33507062 DOI: 10.1021/acschemneuro.0c00684] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Regulation of cellular excitability and oscillatory behavior of resting membrane potential in nerve cells are largely mediated by the low-voltage activated T-type calcium channels. This calcium channel family is constituted by three isoforms, namely, CaV3.1, CaV3.2, and CaV3.3, that are largely distributed in the nervous system and other parts of the body. Dysfunction of T-type calcium channels is associated with a wide range of pathophysiologies including epilepsy, neuropathic pain, cardiac problems, and major depressive disorders. Due to their pharmacological relevance, finding molecular agents able to modulate the channel's function may provide therapeutic means to ameliorate their related disorders. Here we used electrophysiological experiments to show that genistein, a canonical tyrosine kinase inhibitor, reduces the activity of the human CaV3.3 channel in a concentration-dependent manner. The inhibitory effect of genistein is independent of tyrosine kinase modulation and does not affect the voltage-dependent gating of the channel. Subsequently, we used computational methods to identify plausible molecular poses for the interaction of genistein and the CaV3.3 channel. Starting from different molecular poses, we carried out all-atom molecular dynamics (MD) simulations to identify the interacting determinants for the CaV3.3/genistein complex formation. Our extensive (microsecond-length) simulations suggest specific binding interactions that seem to stabilize the protein/inhibitor complex. Furthermore, our results from the unbiased MD simulations are in good agreement with the recently solved cryoelectron microscopy structure of the CaV3.1/Z944 complex in terms of both the location of the ligand binding site and the role of several equivalent amino acid residues. Proposed interacting complex loci were subsequently tested and corroborated by electrophysiological experiments using another naturally occurring isoflavone derivative, daidzein. Thus, by using a combination of in vitro and in silico techniques, we have identified interacting determinants relevant to the CaV3.3/genistein complex formation and propose that genistein directly blocks the function of the human CaV3.3 channel as a result of such interaction. Specifically, we proposed that a combination of polar interactions involving the three hydroxyl groups of genistein and an aromatic interaction with the fused rings are the main binding interactions in the complex formation. Our results pave the way for the rational development of improved and novel low-voltage activated T-type calcium channel inhibitors.
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Affiliation(s)
- Maricruz Rangel-Galván
- School of Chemical Sciences, Meritorious Autonomous University of Puebla (BUAP), University City, Puebla 72570, Mexico
| | - Azahel Rangel
- Coordinación Académica Región Altiplano, Universidad Autónoma de San Luis Potosí, San Luis Potosí 78700, México
| | - Catalina Romero-Méndez
- Departamento de Fisiología y Biofísica, Facultad de Medicina Universidad Autónoma de San Luis Potosí, San Luis Potosí 78210, México
| | - Eliud Morales Dávila
- School of Chemical Sciences, Meritorious Autonomous University of Puebla (BUAP), University City, Puebla 72570, Mexico
| | - María Eugenia Castro
- Chemistry Center, Science Institute, Meritorious Autonomous University of Puebla (BUAP), University City, Puebla 72570, Mexico
| | - Norma A. Caballero
- School of Biological Sciences, Meritorious Autonomous University of Puebla (BUAP), University City, Puebla 72570, Mexico
| | | | - Brenda L. Sanchez-Gaytan
- Chemistry Center, Science Institute, Meritorious Autonomous University of Puebla (BUAP), University City, Puebla 72570, Mexico
| | - Ulises Meza
- Departamento de Fisiología y Biofísica, Facultad de Medicina Universidad Autónoma de San Luis Potosí, San Luis Potosí 78210, México
| | - Jose Manuel Perez-Aguilar
- School of Chemical Sciences, Meritorious Autonomous University of Puebla (BUAP), University City, Puebla 72570, Mexico
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155
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Bladen C, Mirlohi S, Santiago M, Longworth M, Kassiou M, Banister S, Connor M. Modulation of human T-type calcium channels by synthetic cannabinoid receptor agonists in vitro. Neuropharmacology 2021; 187:108478. [PMID: 33600843 DOI: 10.1016/j.neuropharm.2021.108478] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2020] [Revised: 01/07/2021] [Accepted: 01/26/2021] [Indexed: 01/01/2023]
Abstract
BACKGROUND AND PURPOSE Consumption of Synthetic Cannabinoid Receptor agonists (SCRAs) is associated with severe adverse reactions including seizures, arrhythmias and death, but the molecular mechanisms surrounding SCRA toxicity are not yet established. These disease-like symptoms are also synonymous with altered T-type calcium channel activity which controls rhythmicity in the heart and brain. This study examined whether SCRAs alter T-type activity and whether this represents a possible mechanism of toxicity. EXPERIMENTAL APPROACH Fluorescence-based and electrophysiology assays were used to screen 16 structurally related synthetic cannabinoids for their ability to inhibit human T-type calcium channels expressed in HEK293 cells. The most potent compounds were then further examined using patch clamp electrophysiology. KEY RESULTS MDMB-CHMICA and AMB-CHMINACA potently blocked Cav3.2 with IC50 values of 1.5 and 0.74 μM respectively. Current inhibition increased from 47 to 80% and 45-87% respectively when the channel was in slow-inactivated state. Both SCRAs had little effect on steady state inactivation, however MDMB-CHMICA significantly shifted the half activation potential by -7mV. Neither drug produced frequency dependent block, in contrast to the phytocannabinoid Δ9-THC. CONCLUSIONS AND IMPLICATIONS SCRAs are potent agonists of CB1 receptors and can be extremely toxic, but observed toxicity also resembles symptoms associated with altered Cav3.2 activity. Many SCRAs tested were potent modulators of Cav3.2, raising the possibility that SC toxicity may be due in part to Cav3.2 modulation. This potent T-type channel modulation suggests the possibility of SCRAs as a new drug class with potential to treat diseases associated with altered T-type channel activity. This article is part of the special issue on 'Cannabinoids'.
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Affiliation(s)
- Chris Bladen
- Biomedical Sciences, Macquarie University, Sydney, NSW, Australia.
| | - Somayeh Mirlohi
- Biomedical Sciences, Macquarie University, Sydney, NSW, Australia
| | - Marina Santiago
- Biomedical Sciences, Macquarie University, Sydney, NSW, Australia
| | | | - Michael Kassiou
- School of Chemistry, University of Sydney, Sydney, NSW, 2006, Australia
| | - Sam Banister
- School of Chemistry, University of Sydney, Sydney, NSW, 2006, Australia; The Lambert Initiative for Cannabinoid Therapeutics, University of Sydney, Sydney, NSW, 2006, Australia
| | - Mark Connor
- Biomedical Sciences, Macquarie University, Sydney, NSW, Australia
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156
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Xu J, He M, Wang W, Hou J, Chen X, Ding X, Zhang J. siRNA-mediated Eppin testicular silencing causes changes in sperm motility and calcium currents in mice. Reprod Biol 2021; 21:100485. [PMID: 33607572 DOI: 10.1016/j.repbio.2021.100485] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2020] [Revised: 12/24/2020] [Accepted: 01/30/2021] [Indexed: 10/22/2022]
Abstract
Epididymal protease inhibitor (EPPIN) is differentially expressed in the reproductive tissues (such as testicles, outlet tubes, epididymis, vas deferens, and seminal vesicles). Its critical role in sperm function and male reproduction has shed light on EPPIN as a candidate target for male contraceptive vaccines. In this study, we endeavored to further reveal the mechanism through which EPPIN exerts its function. We created a mouse model of reduced Eppin expression by microinjecting small interfering RNA targeting Eppin expression into seminiferous tubules of mice. This mouse model was then used to explore the effects of low Eppin expression on sperm function, which was assessed by Computer Assisted Semen Analysis and patch clamp recording of T-type Ca2+ current in spermatogenic cells. We found that the sperm motility significantly declined when Eppin was downregulated. Further investigation demonstrated that Eppin downregulation significantly affected T-type Ca2+ currents and messenger RNA expression of three subtypes of T-type Ca2+ channels in spermatogenic cells. These findings indicate that low Eppin gene expression induces decreased T-type Ca2+ currents and mRNA expression, which in turn results in the reduced sperm motility.
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Affiliation(s)
- Jie Xu
- Department of Toxicology, School of Public Health, Medical College of Soochow University, Suzhou, China
| | - Mengting He
- Department of Toxicology, School of Public Health, Medical College of Soochow University, Suzhou, China
| | - Wei Wang
- Department of Toxicology, School of Public Health, Medical College of Soochow University, Suzhou, China
| | - Jiaojiao Hou
- Department of Toxicology, School of Public Health, Medical College of Soochow University, Suzhou, China
| | - Xiaoyi Chen
- Department of Toxicology, School of Public Health, Medical College of Soochow University, Suzhou, China
| | - Xinliang Ding
- Department of Public Health, Wuxi Center for Disease Control and Prevention, Wuxi, China.
| | - Jie Zhang
- Department of Toxicology, School of Public Health, Medical College of Soochow University, Suzhou, China; Jiangsu Key Laboratory of Preventive and Translational Medicine for Geriatric Diseases, School of Public Health, Medical College of Soochow University, Suzhou, China.
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157
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Hasan MM, Starobova H, Mueller A, Vetter I, Lewis RJ. Subcutaneous ω-Conotoxins Alleviate Mechanical Pain in Rodent Models of Acute Peripheral Neuropathy. Mar Drugs 2021; 19:106. [PMID: 33670311 PMCID: PMC7917901 DOI: 10.3390/md19020106] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2020] [Revised: 02/05/2021] [Accepted: 02/07/2021] [Indexed: 11/16/2022] Open
Abstract
The peripheral effects of ω-conotoxins, selective blockers of N-type voltage-gated calcium channels (CaV2.2), have not been characterised across different clinically relevant pain models. This study examines the effects of locally administered ω-conotoxin MVIIA, GVIA, and CVIF on mechanical and thermal paw withdrawal threshold (PWT) in postsurgical pain (PSP), cisplatin-induced neuropathy (CisIPN), and oxaliplatin-induced neuropathy (OIPN) rodent models. Intraplantar injection of 300, 100 and 30 nM MVIIA significantly (p < 0.0001, p < 0.0001, and p < 0.05, respectively) alleviated mechanical allodynia of mice in PSP model compared to vehicle control group. Similarly, intraplantar injection of 300, 100, and 30 nM MVIIA (p < 0.0001, p < 0.01, and p < 0.05, respectively), and 300 nM and 100 nM GVIA (p < 0.0001 and p < 0.05, respectively) significantly increased mechanical thresholds of mice in OIPN model. The ED50 of GVIA and MVIIA in OIPN was found to be 1.8 pmol/paw and 0.8 pmol/paw, respectively. However, none of the ω-conotoxins were effective in a mouse model of CisIPN. The intraplantar administration of 300 nM GVIA, MVIIA, and CVIF did not cause any locomotor side effects. The intraplantar administration of MVIIA can alleviate incision-induced mechanical allodynia, and GVIA and MVIIA effectively reduce OIPN associated mechanical pain, without locomotor side effects, in rodent models. In contrast, CVIF was inactive in these pain models, suggesting it is unable to block a subset of N-type voltage-gated calcium channels associated with nociceptors in the skin.
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Affiliation(s)
- Md. Mahadhi Hasan
- Division of Chemistry and Structural Biology, Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD 4072, Australia; (M.M.H.); (H.S.); (A.M.); (I.V.)
| | - Hana Starobova
- Division of Chemistry and Structural Biology, Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD 4072, Australia; (M.M.H.); (H.S.); (A.M.); (I.V.)
| | - Alexander Mueller
- Division of Chemistry and Structural Biology, Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD 4072, Australia; (M.M.H.); (H.S.); (A.M.); (I.V.)
| | - Irina Vetter
- Division of Chemistry and Structural Biology, Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD 4072, Australia; (M.M.H.); (H.S.); (A.M.); (I.V.)
- School of Pharmacy, The University of Queensland, Brisbane, QLD 4102, Australia
| | - Richard J. Lewis
- Division of Chemistry and Structural Biology, Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD 4072, Australia; (M.M.H.); (H.S.); (A.M.); (I.V.)
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158
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Li K, Abbott SBG, Shi Y, Eggan P, Gonye EC, Bayliss DA. TRPM4 mediates a subthreshold membrane potential oscillation in respiratory chemoreceptor neurons that drives pacemaker firing and breathing. Cell Rep 2021; 34:108714. [PMID: 33535052 PMCID: PMC7888550 DOI: 10.1016/j.celrep.2021.108714] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Revised: 12/04/2020] [Accepted: 01/12/2021] [Indexed: 12/01/2022] Open
Abstract
Brainstem networks that control regular tidal breathing depend on excitatory drive, including from tonically active, CO2/H+-sensitive neurons of the retrotrapezoid nucleus (RTN). Here, we examine intrinsic ionic mechanisms underlying the metronomic firing activity characteristic of RTN neurons. In mouse brainstem slices, large-amplitude membrane potential oscillations are evident in synaptically isolated RTN neurons after blocking action potentials. The voltage-dependent oscillations are abolished by sodium replacement; blocking calcium channels (primarily L-type); chelating intracellular Ca2+; and inhibiting TRPM4, a Ca2+-dependent cationic channel. Likewise, oscillation voltage waveform currents are sensitive to calcium and TRPM4 channel blockers. Extracellular acidification and serotonin (5-HT) evoke membrane depolarization that augments TRPM4-dependent oscillatory activity and action potential discharge. Finally, inhibition of TRPM4 channels in the RTN of anesthetized mice reduces central respiratory output. These data implicate TRPM4 in a subthreshold oscillation that supports the pacemaker-like firing of RTN neurons required for basal, CO2-stimulated, and state-dependent breathing.
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Affiliation(s)
- Keyong Li
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA
| | - Stephen B G Abbott
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA
| | - Yingtang Shi
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA
| | - Pierce Eggan
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA
| | - Elizabeth C Gonye
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA
| | - Douglas A Bayliss
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA.
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159
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Dhanalakshmi C, Janakiraman U, Moutal A, Fukunaga K, Khanna R, Nelson MA. Evaluation of the effects of the T-type calcium channel enhancer SAK3 in a rat model of TAF1 deficiency. Neurobiol Dis 2021; 149:105224. [PMID: 33359140 PMCID: PMC8230513 DOI: 10.1016/j.nbd.2020.105224] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Revised: 12/03/2020] [Accepted: 12/16/2020] [Indexed: 11/18/2022] Open
Abstract
The TATA-box binding protein associated factor 1 (TAF1) is part of the TFIID complex that plays a key role during the initiation of transcription. Variants of TAF1 are associated with neurodevelopmental disorders. Previously, we found that CRISPR/Cas9 based editing of the TAF1 gene disrupts the morphology of the cerebral cortex and blunts the expression as well as the function of the CaV3.1 (T-type) voltage gated calcium channel. Here, we tested the efficacy of SAK3 (ethyl 8'-methyl-2', 4-dioxo-2-(piperidin-1-yl)-2'H-spiro [cyclopentane-1, 3'-imidazo [1, 2-a] pyridine]-2-ene-3-carboxylate), a T-type calcium channel enhancer, in an animal model of TAF1 intellectual disability (ID) syndrome. At post-natal day 3, rat pups were subjected to intracerebroventricular (ICV) injection of either gRNA-control or gRNA-TAF1 CRISPR/Cas9 viruses. At post-natal day 21, the rat pups were given SAK3 (0.25 mg/kg, p.o.) or vehicle for 14 days (i.e. till post-natal day 35) and then subjected to behavioral, morphological, and molecular studies. Oral administration of SAK3 (0.25 mg/kg, p.o.) significantly rescued locomotion abnormalities associated with TAF1 gene editing. SAK3 treatment prevented the loss of cortical neurons and GFAP-positive astrocytes observed after TAF1 gene editing. In addition, SAK3 protected cells from apoptosis. SAK3 also restored the Brain-derived neurotrophic factor/protein kinase B/Glycogen Synthase Kinase 3 Beta (BDNF/AKT/GSK3β) signaling axis in TAF1 edited animals. Finally, SAK3 normalized the levels of three GSK3β substrates - CaV3.1, FOXP2, and CRMP2. We conclude that the T-type calcium channel enhancer SAK3 is beneficial against the deleterious effects of TAF1 gene-editing, in part, by stimulating the BDNF/AKT/GSK3β signaling pathway.
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Affiliation(s)
- Chinnasamy Dhanalakshmi
- Department of Pathology, University of Arizona College of Medicine and College of Pharmacy, Tucson, AZ, USA
| | - Udaiyappan Janakiraman
- Department of Pathology, University of Arizona College of Medicine and College of Pharmacy, Tucson, AZ, USA
| | - Aubin Moutal
- Department of Pharmacology, University of Arizona College of Medicine and College of Pharmacy, Tucson, AZ, USA; The Center for Innovation in Brain Sciences, The University of Arizona Health Sciences, Tucson, AZ, United States; The BIO5 Institute, University of Arizona, United States
| | - Kohji Fukunaga
- Department of Pharmacology, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan
| | - Rajesh Khanna
- Department of Pharmacology, University of Arizona College of Medicine and College of Pharmacy, Tucson, AZ, USA; The Center for Innovation in Brain Sciences, The University of Arizona Health Sciences, Tucson, AZ, United States; The BIO5 Institute, University of Arizona, United States
| | - Mark A Nelson
- Department of Pathology, University of Arizona College of Medicine and College of Pharmacy, Tucson, AZ, USA.
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160
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Arshaad MI, Siwek ME, Henseler C, Daubner J, Ehninger D, Hescheler J, Sachinidis A, Broich K, Papazoglou A, Weiergräber M. Enhanced hippocampal type II theta activity AND altered theta architecture in mice lacking the Ca v3.2 T-type voltage-gated calcium channel. Sci Rep 2021; 11:1099. [PMID: 33441788 PMCID: PMC7806756 DOI: 10.1038/s41598-020-79763-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2020] [Accepted: 12/08/2020] [Indexed: 12/20/2022] Open
Abstract
T-type Ca2+ channels are assumed to contribute to hippocampal theta oscillations. We used implantable video-EEG radiotelemetry and qPCR to unravel the role of Cav3.2 Ca2+ channels in hippocampal theta genesis. Frequency analysis of spontaneous long-term recordings in controls and Cav3.2-/- mice revealed robust increase in relative power in the theta (4-8 Hz) and theta-alpha (4-12 Hz) ranges, which was most prominent during the inactive stages of the dark cycles. Urethane injection experiments also showed enhanced type II theta activity and altered theta architecture following Cav3.2 ablation. Next, gene candidates from hippocampal transcriptome analysis of control and Cav3.2-/- mice were evaluated using qPCR. Dynein light chain Tctex-Type 1 (Dynlt1b) was significantly reduced in Cav3.2-/- mice. Furthermore, a significant reduction of GABA A receptor δ subunits and GABA B1 receptor subunits was observed in the septohippocampal GABAergic system. Our results demonstrate that ablation of Cav3.2 significantly alters type II theta activity and theta architecture. Transcriptional changes in synaptic transporter proteins and GABA receptors might be functionally linked to the electrophysiological phenotype.
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Affiliation(s)
- Muhammad Imran Arshaad
- Experimental Neuropsychopharmacology, Federal Institute for Drugs and Medical Devices (Bundesinstitut für Arzneimittel und Medizinprodukte, BfArM), Kurt-Georg-Kiesinger-Allee 3, 53175, Bonn, Germany
| | - Magdalena Elisabeth Siwek
- Experimental Neuropsychopharmacology, Federal Institute for Drugs and Medical Devices (Bundesinstitut für Arzneimittel und Medizinprodukte, BfArM), Kurt-Georg-Kiesinger-Allee 3, 53175, Bonn, Germany
| | - Christina Henseler
- Experimental Neuropsychopharmacology, Federal Institute for Drugs and Medical Devices (Bundesinstitut für Arzneimittel und Medizinprodukte, BfArM), Kurt-Georg-Kiesinger-Allee 3, 53175, Bonn, Germany
| | - Johanna Daubner
- Experimental Neuropsychopharmacology, Federal Institute for Drugs and Medical Devices (Bundesinstitut für Arzneimittel und Medizinprodukte, BfArM), Kurt-Georg-Kiesinger-Allee 3, 53175, Bonn, Germany
| | - Dan Ehninger
- Molecular and Cellular Cognition, German Center for Neurodegenerative Diseases (Deutsches Zentrum für Neurodegenerative Erkrankungen, DZNE), Sigmund-Freud-Str. 27, 53127, Bonn, Germany
| | - Jürgen Hescheler
- Institute of Neurophysiology, University of Cologne, Faculty of Medicine, Robert-Koch-Str. 39, 50931, Cologne, Germany
| | - Agapios Sachinidis
- Institute of Neurophysiology, University of Cologne, Faculty of Medicine, Robert-Koch-Str. 39, 50931, Cologne, Germany
| | - Karl Broich
- Federal Institute for Drugs and Medical Devices (Bundesinstitut für Arzneimittel und Medizinprodukte, BfArM), Kurt-Georg-Kiesinger-Allee 3, 53175, Bonn, Germany
| | - Anna Papazoglou
- Experimental Neuropsychopharmacology, Federal Institute for Drugs and Medical Devices (Bundesinstitut für Arzneimittel und Medizinprodukte, BfArM), Kurt-Georg-Kiesinger-Allee 3, 53175, Bonn, Germany
| | - Marco Weiergräber
- Experimental Neuropsychopharmacology, Federal Institute for Drugs and Medical Devices (Bundesinstitut für Arzneimittel und Medizinprodukte, BfArM), Kurt-Georg-Kiesinger-Allee 3, 53175, Bonn, Germany.
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161
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Przybyła GW, Szychowski KA, Gmiński J. Paracetamol - An old drug with new mechanisms of action. Clin Exp Pharmacol Physiol 2021; 48:3-19. [PMID: 32767405 DOI: 10.1111/1440-1681.13392] [Citation(s) in RCA: 60] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2020] [Revised: 07/09/2020] [Accepted: 08/02/2020] [Indexed: 12/26/2022]
Abstract
Paracetamol (acetaminophen) is the most commonly used over-the-counter (OTC) drug in the world. Despite its popularity and use for many years, the safety of its application and its mechanism of action are still unclear. Currently, it is believed that paracetamol is a multidirectional drug and at least several metabolic pathways are involved in its analgesic and antipyretic action. The mechanism of paracetamol action consists in inhibition of cyclooxygenases (COX-1, COX-2, and COX-3) and involvement in the endocannabinoid system and serotonergic pathways. Additionally, paracetamol influences transient receptor potential (TRP) channels and voltage-gated Kv7 potassium channels and inhibits T-type Cav3.2 calcium channels. It also exerts an impact on L-arginine in the nitric oxide (NO) synthesis pathway. However, not all of these effects have been clearly confirmed. Therefore, the aim of our paper was to summarize the current state of knowledge of the mechanism of paracetamol action with special attention to its safety concerns.
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Affiliation(s)
| | - Konrad A Szychowski
- Department of Lifestyle Disorders and Regenerative Medicine, University of Information Technology and Management in Rzeszow, Rzeszow, Poland
| | - Jan Gmiński
- Department of Lifestyle Disorders and Regenerative Medicine, University of Information Technology and Management in Rzeszow, Rzeszow, Poland
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162
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Gauberg J, Abdallah S, Elkhatib W, Harracksingh AN, Piekut T, Stanley EF, Senatore A. Conserved biophysical features of the Ca V2 presynaptic Ca 2+ channel homologue from the early-diverging animal Trichoplax adhaerens. J Biol Chem 2020; 295:18553-18578. [PMID: 33097592 PMCID: PMC7939481 DOI: 10.1074/jbc.ra120.015725] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2020] [Revised: 10/21/2020] [Indexed: 12/20/2022] Open
Abstract
The dominant role of CaV2 voltage-gated calcium channels for driving neurotransmitter release is broadly conserved. Given the overlapping functional properties of CaV2 and CaV1 channels, and less so CaV3 channels, it is unclear why there have not been major shifts toward dependence on other CaV channels for synaptic transmission. Here, we provide a structural and functional profile of the CaV2 channel cloned from the early-diverging animal Trichoplax adhaerens, which lacks a nervous system but possesses single gene homologues for CaV1-CaV3 channels. Remarkably, the highly divergent channel possesses similar features as human CaV2.1 and other CaV2 channels, including high voltage-activated currents that are larger in external Ba2+ than in Ca2+; voltage-dependent kinetics of activation, inactivation, and deactivation; and bimodal recovery from inactivation. Altogether, the functional profile of Trichoplax CaV2 suggests that the core features of presynaptic CaV2 channels were established early during animal evolution, after CaV1 and CaV2 channels emerged via proposed gene duplication from an ancestral CaV1/2 type channel. The Trichoplax channel was relatively insensitive to mammalian CaV2 channel blockers ω-agatoxin-IVA and ω-conotoxin-GVIA and to metal cation blockers Cd2+ and Ni2+ Also absent was the capacity for voltage-dependent G-protein inhibition by co-expressed Trichoplax Gβγ subunits, which nevertheless inhibited the human CaV2.1 channel, suggesting that this modulatory capacity evolved via changes in channel sequence/structure, and not G proteins. Last, the Trichoplax channel was immunolocalized in cells that express an endomorphin-like peptide implicated in cell signaling and locomotive behavior and other likely secretory cells, suggesting contributions to regulated exocytosis.
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Affiliation(s)
- Julia Gauberg
- Department of Biology, University of Toronto Mississauga, Mississauga, Ontario, Canada
| | - Salsabil Abdallah
- Department of Biology, University of Toronto Mississauga, Mississauga, Ontario, Canada
| | - Wassim Elkhatib
- Department of Biology, University of Toronto Mississauga, Mississauga, Ontario, Canada
| | - Alicia N Harracksingh
- Department of Biology, University of Toronto Mississauga, Mississauga, Ontario, Canada
| | - Thomas Piekut
- Department of Biology, University of Toronto Mississauga, Mississauga, Ontario, Canada
| | - Elise F Stanley
- Laboratory of Synaptic Transmission, Krembil Research Institute, Toronto, Ontario, Canada
| | - Adriano Senatore
- Department of Biology, University of Toronto Mississauga, Mississauga, Ontario, Canada.
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163
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Hariharan A, Weir N, Robertson C, He L, Betsholtz C, Longden TA. The Ion Channel and GPCR Toolkit of Brain Capillary Pericytes. Front Cell Neurosci 2020; 14:601324. [PMID: 33390906 PMCID: PMC7775489 DOI: 10.3389/fncel.2020.601324] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Accepted: 11/13/2020] [Indexed: 12/14/2022] Open
Abstract
Brain pericytes reside on the abluminal surface of capillaries, and their processes cover ~90% of the length of the capillary bed. These cells were first described almost 150 years ago (Eberth, 1871; Rouget, 1873) and have been the subject of intense experimental scrutiny in recent years, but their physiological roles remain uncertain and little is known of the complement of signaling elements that they employ to carry out their functions. In this review, we synthesize functional data with single-cell RNAseq screens to explore the ion channel and G protein-coupled receptor (GPCR) toolkit of mesh and thin-strand pericytes of the brain, with the aim of providing a framework for deeper explorations of the molecular mechanisms that govern pericyte physiology. We argue that their complement of channels and receptors ideally positions capillary pericytes to play a central role in adapting blood flow to meet the challenge of satisfying neuronal energy requirements from deep within the capillary bed, by enabling dynamic regulation of their membrane potential to influence the electrical output of the cell. In particular, we outline how genetic and functional evidence suggest an important role for Gs-coupled GPCRs and ATP-sensitive potassium (KATP) channels in this context. We put forth a predictive model for long-range hyperpolarizing electrical signaling from pericytes to upstream arterioles, and detail the TRP and Ca2+ channels and Gq, Gi/o, and G12/13 signaling processes that counterbalance this. We underscore critical questions that need to be addressed to further advance our understanding of the signaling topology of capillary pericytes, and how this contributes to their physiological roles and their dysfunction in disease.
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Affiliation(s)
- Ashwini Hariharan
- Department of Physiology, School of Medicine, University of Maryland, Baltimore, MD, United States
| | - Nick Weir
- Department of Physiology, School of Medicine, University of Maryland, Baltimore, MD, United States
| | - Colin Robertson
- Department of Physiology, School of Medicine, University of Maryland, Baltimore, MD, United States
| | - Liqun He
- Rudbeck Laboratory, Department of Immunology, Genetics and Pathology, Uppsala University, Uppsala, Sweden
| | - Christer Betsholtz
- Rudbeck Laboratory, Department of Immunology, Genetics and Pathology, Uppsala University, Uppsala, Sweden.,Department of Medicine Huddinge (MedH), Karolinska Institutet & Integrated Cardio Metabolic Centre, Huddinge, Sweden
| | - Thomas A Longden
- Department of Physiology, School of Medicine, University of Maryland, Baltimore, MD, United States
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164
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Wang M, Thyagarajan B. Pain pathways and potential new targets for pain relief. Biotechnol Appl Biochem 2020; 69:110-123. [PMID: 33316085 DOI: 10.1002/bab.2086] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Accepted: 12/06/2020] [Indexed: 12/15/2022]
Abstract
Pain is an unpleasant sensory and emotional experience that affects a sizable percentage of people on a daily basis. Sensory neurons known as nociceptors built specifically to detect damaging stimuli can be found throughout the body. They transmit information about noxious stimuli from mechanical, thermal, and chemical sources to the central nervous system and higher brain centers via electrical signals. Nociceptors express various channels and receptors such as voltage-gated sodium and calcium channels, transient receptor potential channels, and opioid receptors that allow them to respond in a highly specific manner to noxious stimuli. Attenuating the pain response can be achieved by inhibiting or altering the expression of these pain targets. Achieving a deeper understanding of how these receptors can be affected at the molecular level can lead to the development of novel pain therapies. This review will discuss the mechanisms of pain, introduce the various receptors that are responsible for detecting pain, and future directions in pharmacological therapies.
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Affiliation(s)
- Menglan Wang
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Wyoming, Laramie, WY, USA
| | - Baskaran Thyagarajan
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Wyoming, Laramie, WY, USA
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165
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Global genetic deletion of Ca V3.3 channels facilitates anaesthetic induction and enhances isoflurane-sparing effects of T-type calcium channel blockers. Sci Rep 2020; 10:21510. [PMID: 33299036 PMCID: PMC7725806 DOI: 10.1038/s41598-020-78488-8] [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: 06/02/2020] [Accepted: 11/13/2020] [Indexed: 01/02/2023] Open
Abstract
We previously documented that the CaV3.3 isoform of T-type calcium channels (T-channels) is inhibited by clinically relevant concentrations of volatile anaesthetics, including isoflurane. However, little is understood about the functional role of CaV3.3 channels in anaesthetic-induced hypnosis and underlying neuronal oscillations. To address this issue, we used CaV3.3 knock-out (KO) mice and a panselective T-channel blocker 3,5-dichloro-N-[1-(2,2-dimethyltetrahydro-pyran-4-ylmethyl)-4-fluoro-piperidin-4-ylmethyl]-benzamide (TTA-P2). We found that mutant mice injected with the vehicle showed faster induction of hypnosis than wild-type (WT) mice, while the percent isoflurane at which hypnosis and immobility occurred was not different between two genotypes. Furthermore, we found that TTA-P2 facilitated isoflurane induction of hypnosis in the CaV3.3 KO mice more robustly than in the WT mice. Isoflurane-induced hypnosis following injections of TTA-P2 was accompanied with more prominent delta and theta EEG oscillations in the mutant mice, and reached burst-suppression pattern earlier when compared to the WT mice. Our findings point to a relatively specific value of CaV3.3 channels in anaesthetic induced hypnosis. Furthermore, we propose that T-channel blockers may be further explored as a valuable adjunct to reducing the usage of potent volatile anaesthetics, thereby improving their safety.
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166
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T-type calcium channels blockers inhibit HSV-2 infection at the late stage of genome replication. Eur J Pharmacol 2020; 892:173782. [PMID: 33279521 DOI: 10.1016/j.ejphar.2020.173782] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2020] [Revised: 11/19/2020] [Accepted: 12/01/2020] [Indexed: 12/19/2022]
Abstract
Herpes simplex virus type 2 (HSV-2) is a highly contagious sexually transmitted virus. The increasing emergence of drug-resistant viral strains has highlighted the crucial need for the development of new anti-HSV-2 drugs with different mechanisms. Ion channels that govern a wide range of cellular functions represent attractive targets for viral manipulation. Here, we tried to identify novel compounds to suppress HSV-2 infection in vitro by screening a small library with ion channels modulators. We found that several T-type calcium channel blockers including benidipine, lercanidipine, lomerizine and mibefradil inhibited HSV-2 infection, while L-type calcium channel blockers nifedipine and nitrendipine showed no significant effect on HSV-2 infection. Furthermore, we found that benidipine exerted the antiviral effect by suppressing the expression of viral genes in the late stage of viral infection. In conclusion, our study suggested that T-type calcium channel blockers, which are clinically wide used, could effectively inhibit HSV-2 infection. These findings could shed light on the mechanism and pharmacological study for HSV-2 infection in the future.
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167
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Guidelli R. The common features of tetrameric ion channels and the role of electrostatic interactions. Electrochem commun 2020. [DOI: 10.1016/j.elecom.2020.106866] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
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168
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Agarwala S, Veerappa AM, Ramachandra NB. Identification of primary copy number variations reveal enrichment of Calcium, and MAPK pathways sensitizing secondary sites for autism. EGYPTIAN JOURNAL OF MEDICAL HUMAN GENETICS 2020. [DOI: 10.1186/s43042-020-00091-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Abstract
Background
Autism is a neurodevelopmental condition with genetic heterogeneity. It is characterized by difficulties in reciprocal social interactions with strong repetitive behaviors and stereotyped interests. Copy number variations (CNVs) are genomic structural variations altering the genomic structure either by duplication or deletion. De novo or inherited CNVs are found in 5–10% of autistic subjects with a size range of few kilobases to several megabases. CNVs predispose humans to various diseases by altering gene regulation, generation of chimeric genes, and disruption of the coding region or through position effect. Although, CNVs are not the initiating event in pathogenesis; additional preceding mutations might be essential for disease manifestation. The present study is aimed to identify the primary CNVs responsible for autism susceptibility in healthy cohorts to sensitize secondary-hits. In the current investigation, primary-hit autism gene CNVs are characterized in 1715 healthy cohorts of varying ethnicities across 12 populations using Affymetrix high-resolution array study. Thirty-eight individuals from twelve families residing in Karnataka, India, with the age group of 13–73 years are included for the comparative CNV analysis. The findings are validated against global 179 autism whole-exome sequence datasets derived from Simons Simplex Collection. These datasets are deposited at the Simons Foundation Autism Research Initiative (SFARI) database.
Results
The study revealed that 34.8% of the subjects carried 2% primary-hit CNV burden with 73 singleton-autism genes in different clusters. Of these, three conserved CNV breakpoints were identified with ARHGAP11B, DUSP22, and CHRNA7 as the target genes across 12 populations. Enrichment analysis of the population-specific autism genes revealed two signaling pathways—calcium and mitogen-activated protein kinases (MAPK) in the CNV identified regions. These impaired pathways affected the downstream cascades of neuronal function and physiology, leading to autism behavior. The pathway analysis of enriched genes unravelled complex protein interaction networks, which sensitized secondary sites for autism. Further, the identification of miRNA targets associated with autism gene CNVs added severity to the condition.
Conclusion
These findings contribute to an atlas of primary-hit genes to detect autism susceptibility in healthy cohorts, indicating their impact on secondary sites for manifestation.
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169
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Hara N, Morino H, Matsuda Y, Satoh K, Hashimoto K, Maruyama H, Kawakami H. Zonisamide can ameliorate the voltage-dependence alteration of the T-type calcium channel Ca V3.1 caused by a mutation responsible for spinocerebellar ataxia. Mol Brain 2020; 13:163. [PMID: 33243296 PMCID: PMC7690142 DOI: 10.1186/s13041-020-00700-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Accepted: 11/16/2020] [Indexed: 11/25/2022] Open
Abstract
Spinocerebellar ataxia (SCA) 42 is caused by a mutation in CACNA1G, which encodes the low voltage-gated calcium channel CaV3.1 (T-type). Patients with SCA42 exhibit a pure form of cerebellar ataxia. We encountered a patient with the p.Arg1715His mutation, suffering from intractable resting tremor, particularly head tremor. This symptom improved with the administration of low-dose of zonisamide (ZNS), a T-type calcium channel blocker effective for treating Parkinson’s disease and epilepsy. Previous electrophysiological studies showed that the voltage dependence of this mutant CaV3.1 was shifted toward the positive potential. This abnormal shift was considered a factor related to disease onset and symptoms. In this study, we performed whole-cell recordings of GFP-expressing HEK293T cells that expressed wild-type or mutant CaV3.1 and investigated the changes in the abnormal shift of voltage dependence of the mutant CaV3.1. The results showed that ZNS in an amount equivalent to the patient’s internal dose significantly ameliorated the abnormal shift in the mutant CaV3.1, giving values close to those in the wild-type. On the other hand, ZNS did not affect the voltage dependence of wild-type CaV3.1. Because CaV3.1 is known to be involved in tremogenesis, modulation of the voltage dependence of mutant CaV3.1 by ZNS might have contributed to improvement in the intractable tremor of our patient with SCA42. Moreover, efonidipine, another T-type calcium channel blocker, had no effect on tremors in our patient with SCA42 and did not improve the abnormal shift in the voltage dependence of the mutant CaV3.1. This indicates that ZNS is distinct from other T-type calcium channel blockers in terms of modulation of the voltage dependence of the mutant CaV3.1.
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Affiliation(s)
- Naoyuki Hara
- Department of Clinical Neuroscience and Therapeutics, Graduate School of Biomedical and Health Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima, Hiroshima, 734-8551, Japan
| | - Hiroyuki Morino
- Department of Epidemiology, Research Institute for Radiation Biology and Medicine, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima, Hiroshima, 734-8553, Japan.
| | - Yukiko Matsuda
- Department of Epidemiology, Research Institute for Radiation Biology and Medicine, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima, Hiroshima, 734-8553, Japan
| | - Kenichi Satoh
- The Center for Data Science Education and Research, Shiga University, 1-1-1 Banba, Hikone, Shiga, 522-8522, Japan
| | - Kouichi Hashimoto
- Department of Neurophysiology, Graduate School of Biomedical and Health Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima, Hiroshima, 734-8551, Japan
| | - Hirofumi Maruyama
- Department of Clinical Neuroscience and Therapeutics, Graduate School of Biomedical and Health Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima, Hiroshima, 734-8551, Japan
| | - Hideshi Kawakami
- Department of Epidemiology, Research Institute for Radiation Biology and Medicine, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima, Hiroshima, 734-8553, Japan
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170
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Barrett PQ, Guagliardo NA, Bayliss DA. Ion Channel Function and Electrical Excitability in the Zona Glomerulosa: A Network Perspective on Aldosterone Regulation. Annu Rev Physiol 2020; 83:451-475. [PMID: 33176563 DOI: 10.1146/annurev-physiol-030220-113038] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Aldosterone excess is a pathogenic factor in many hypertensive disorders. The discovery of numerous somatic and germline mutations in ion channels in primary hyperaldosteronism underscores the importance of plasma membrane conductances in determining the activation state of zona glomerulosa (zG) cells. Electrophysiological recordings describe an electrically quiescent behavior for dispersed zG cells. Yet, emerging data indicate that in native rosette structures in situ, zG cells are electrically excitable, generating slow periodic voltage spikes and coordinated bursts of Ca2+ oscillations. We revisit data to understand how a multitude of conductances may underlie voltage/Ca2+ oscillations, recognizing that zG layer self-renewal and cell heterogeneity may complicate this task. We review recent data to understand rosette architecture and apply maxims derived from computational network modeling to understand rosette function. The challenge going forward is to uncover how the rosette orchestrates the behavior of a functional network of conditional oscillators to control zG layer performance and aldosterone secretion.
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Affiliation(s)
- Paula Q Barrett
- Department of Pharmacology, University of Virginia School of Medicine, Charlottesville, Virginia 22908, USA; , ,
| | - Nick A Guagliardo
- Department of Pharmacology, University of Virginia School of Medicine, Charlottesville, Virginia 22908, USA; , ,
| | - Douglas A Bayliss
- Department of Pharmacology, University of Virginia School of Medicine, Charlottesville, Virginia 22908, USA; , ,
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171
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Timic Stamenic T, Feseha S, Valdez R, Zhao W, Klawitter J, Todorovic SM. Alterations in Oscillatory Behavior of Central Medial Thalamic Neurons Demonstrate a Key Role of CaV3.1 Isoform of T-Channels During Isoflurane-Induced Anesthesia. Cereb Cortex 2020; 29:4679-4696. [PMID: 30715245 DOI: 10.1093/cercor/bhz002] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2018] [Revised: 01/04/2019] [Accepted: 01/08/2019] [Indexed: 11/14/2022] Open
Abstract
Although the central medial nucleus (CeM) of the thalamus is an essential part of the arousal system for sleep and anesthesia initiation, the precise mechanisms that regulate its activity are not well studied. We examined the role of CaV3.1 isoform of T-type calcium channels (T-channels) in the excitability and rhythmic activity of CeM neurons during isoflurane (ISO)-induced anesthesia by using mouse genetics and selective pharmacology. Patch-clamp recordings taken from acute brain slices revealed that CaV3.1 channels in CeM are inhibited by prototypical volatile anesthetic ISO (250 and 500 μM) and selective T-channels blocker 3,5-dichloro-N-[1-(2,2-dimethyl-tetrahydro-pyran-4-ylmethyl)-4-fluoro-piperidin-4-ylmethyl]-benzamide (TTA-P2). Both TTA-P2 and ISO attenuated tonic and burst firing modes, and hyperpolarized CeM neurons from wild type (WT) mice. These effects were greatly diminished or abolished in CaV3.1 null mice. Our ensuing in vivo local field potential (LFP) recordings from CeM indicated that the ability of TTA-P2 and anesthetic concentrations of ISO to promote δ oscillation was substantially weakened in CaV3.1 null mice. Furthermore, escalating ISO concentrations induced stronger burst-suppression LFP pattern in mutant than in WT mice. Our results demonstrate for the first time the importance of CaV3.1 channels in thalamocortical oscillations from the non-specific thalamic nuclei that underlie clinically important effects of ISO.
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Affiliation(s)
- Tamara Timic Stamenic
- Department of Anesthesiology, University of Colorado, Anschutz Medical Campus, Aurora, CO, USA
| | - Simon Feseha
- Department of Anesthesiology, University of Colorado, Anschutz Medical Campus, Aurora, CO, USA
| | - Robert Valdez
- Department of Pediatrics, Division of Neurology, School of Medicine, Translational Epilepsy Research Program, University of Colorado, Anschutz Medical Campus, Aurora, CO, USA
| | - Wanzhu Zhao
- Department of Anesthesiology, University of Colorado, Anschutz Medical Campus, Aurora, CO, USA
| | - Jost Klawitter
- Department of Anesthesiology, University of Colorado, Anschutz Medical Campus, Aurora, CO, USA
| | - Slobodan M Todorovic
- Department of Anesthesiology, University of Colorado, Anschutz Medical Campus, Aurora, CO, USA.,Neuroscience Graduate Program, University of Colorado, Anschutz Medical Campus, Aurora, CO, USA
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172
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Jain PP, Hosokawa S, Xiong M, Babicheva A, Zhao T, Rodriguez M, Rahimi S, Pourhashemi K, Balistrieri F, Lai N, Malhotra A, Shyy JYJ, Valdez-Jasso D, Thistlethwaite PA, Makino A, Yuan JXJ. Revisiting the mechanism of hypoxic pulmonary vasoconstriction using isolated perfused/ventilated mouse lung. Pulm Circ 2020; 10:2045894020956592. [PMID: 33282184 PMCID: PMC7691930 DOI: 10.1177/2045894020956592] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Accepted: 08/16/2020] [Indexed: 12/13/2022] Open
Abstract
Hypoxic Pulmonary Vasoconstriction (HPV) is an important physiological mechanism of the lungs that matches perfusion to ventilation thus maximizing O2 saturation of the venous blood within the lungs. This study emphasizes on principal pathways in the initiation and modulation of hypoxic pulmonary vasoconstriction with a primary focus on the role of Ca2+ signaling and Ca2+ influx pathways in hypoxic pulmonary vasoconstriction. We used an ex vivo model, isolated perfused/ventilated mouse lung to evaluate hypoxic pulmonary vasoconstriction. Alveolar hypoxia (utilizing a mini ventilator) rapidly and reversibly increased pulmonary arterial pressure due to hypoxic pulmonary vasoconstriction in the isolated perfused/ventilated lung. By applying specific inhibitors for different membrane receptors and ion channels through intrapulmonary perfusion solution in isolated lung, we were able to define the targeted receptors and channels that regulate hypoxic pulmonary vasoconstriction. We show that extracellular Ca2+ or Ca2+ influx through various Ca2+-permeable channels in the plasma membrane is required for hypoxic pulmonary vasoconstriction. Removal of extracellular Ca2+ abolished hypoxic pulmonary vasoconstriction, while blockade of L-type voltage-dependent Ca2+ channels (with nifedipine), non-selective cation channels (with 30 µM SKF-96365), and TRPC6/TRPV1 channels (with 1 µM SAR-7334 and 30 µM capsazepine, respectively) significantly and reversibly inhibited hypoxic pulmonary vasoconstriction. Furthermore, blockers of Ca2+-sensing receptors (by 30 µM NPS2143, an allosteric Ca2+-sensing receptors inhibitor) and Notch (by 30 µM DAPT, a γ-secretase inhibitor) also attenuated hypoxic pulmonary vasoconstriction. These data indicate that Ca2+ influx in pulmonary arterial smooth muscle cells through voltage-dependent, receptor-operated, and store-operated Ca2+ entry pathways all contribute to initiation of hypoxic pulmonary vasoconstriction. The extracellular Ca2+-mediated activation of Ca2+-sensing receptors and the cell-cell interaction via Notch ligands and receptors contribute to the regulation of hypoxic pulmonary vasoconstriction.
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Affiliation(s)
- Pritesh P. Jain
- Section of Physiology, Division of
Pulmonary, Critical Care and Sleep Medicine, University of California, San Diego,
CA, USA
| | - Susumu Hosokawa
- Section of Physiology, Division of
Pulmonary, Critical Care and Sleep Medicine, University of California, San Diego,
CA, USA
- Department of Pediatrics, Tokyo Medical
and Dental University, Tokyo, Japan
| | - Mingmei Xiong
- Section of Physiology, Division of
Pulmonary, Critical Care and Sleep Medicine, University of California, San Diego,
CA, USA
- Department of Critical Medicine, The
Third Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
| | - Aleksandra Babicheva
- Section of Physiology, Division of
Pulmonary, Critical Care and Sleep Medicine, University of California, San Diego,
CA, USA
| | - Tengteng Zhao
- Section of Physiology, Division of
Pulmonary, Critical Care and Sleep Medicine, University of California, San Diego,
CA, USA
| | - Marisela Rodriguez
- Section of Physiology, Division of
Pulmonary, Critical Care and Sleep Medicine, University of California, San Diego,
CA, USA
| | - Shamin Rahimi
- Section of Physiology, Division of
Pulmonary, Critical Care and Sleep Medicine, University of California, San Diego,
CA, USA
| | - Kiana Pourhashemi
- Section of Physiology, Division of
Pulmonary, Critical Care and Sleep Medicine, University of California, San Diego,
CA, USA
| | - Francesca Balistrieri
- Section of Physiology, Division of
Pulmonary, Critical Care and Sleep Medicine, University of California, San Diego,
CA, USA
| | - Ning Lai
- Section of Physiology, Division of
Pulmonary, Critical Care and Sleep Medicine, University of California, San Diego,
CA, USA
| | - Atul Malhotra
- Section of Physiology, Division of
Pulmonary, Critical Care and Sleep Medicine, University of California, San Diego,
CA, USA
| | - John Y.-J. Shyy
- Division of Cardiovascular Medicine,
Department of Medicine, University of California, San Diego, USA
| | | | | | - Ayako Makino
- Division of Endocrinology and
Metabolism, University of California, San Diego, CA, USA
| | - Jason X.-J. Yuan
- Section of Physiology, Division of
Pulmonary, Critical Care and Sleep Medicine, University of California, San Diego,
CA, USA
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173
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DEMİRTAŞ ŞAHİN T, UTKAN T, KARSON A, YAZIR Y, KARAOZ E. Genetik absans epilepsili WAG/Rij sıçanlarda kardiyovasküler değişiklikler: Kronik etosüksimid tedavisinin etkileri. CUKUROVA MEDICAL JOURNAL 2020. [DOI: 10.17826/cumj.724491] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Catacuzzeno L, Sforna L, Esposito V, Limatola C, Franciolini F. Ion Channels in Glioma Malignancy. Rev Physiol Biochem Pharmacol 2020; 181:223-267. [DOI: 10.1007/112_2020_44] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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175
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Firsov AM, Popova LB, Khailova LS, Nazarov PA, Kotova EA, Antonenko YN. Protonophoric action of BAM15 on planar bilayers, liposomes, mitochondria, bacteria and neurons. Bioelectrochemistry 2020; 137:107673. [PMID: 32971482 DOI: 10.1016/j.bioelechem.2020.107673] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2020] [Revised: 09/04/2020] [Accepted: 09/07/2020] [Indexed: 12/30/2022]
Abstract
Small molecules capable of uncoupling respiration and ATP synthesis in mitochondria are protective towards various cell malfunctions. Recently (2-fluorophenyl){6-[(2-fluorophenyl)amino](1,2,5-oxadiazolo[3,4-e]pyrazin-5-yl)}amine (BAM15), a new compound of this type, has become popular as a potent mitochondria-selective depolarizing agent producing minimal adverse effects. To validate protonophoric mechanism of BAM15 action, we examined its behavior in bilayer lipid membranes (BLM). BAM15 proved to be a typical anionic protonophore with the activity on planar membranes being suppressed upon decreasing membrane dipole potential. In both planar BLM and liposomes, BAM15 induced proton conductance with the potency close to that of the classical protonophoric uncoupler carbonyl cyanide m-chlorophenyl hydrazone (CCCP). In isolated rat liver mitochondria (RLM), BAM15 caused membrane potential collapse, increased respiration rate and induced Ca2+ efflux at concentrations slightly higher than those for CCCP. Surprisingly, the uncoupling action of BAM15 on isolated RLM, in contrast to that of CCCP, was partially reversed by carboxyatractyloside (CATR), an inhibitor of adenine nucleotide translocase, thereby indicating involvement of this protein in the BAM15-induced uncoupling. BAM15 inhibited growth of Bacillus subtilis at micromolar concentrations. In electrophysiological experiments on molluscan neurons, BAM15 caused plasma membrane depolarization and suppression of electrical activity, but the effect developed more slowly than that of CCCP.
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Affiliation(s)
- Alexander M Firsov
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991 Moscow, Russia
| | - Lyudmila B Popova
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991 Moscow, Russia
| | - Ljudmila S Khailova
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991 Moscow, Russia
| | - Pavel A Nazarov
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991 Moscow, Russia
| | - Elena A Kotova
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991 Moscow, Russia
| | - Yuri N Antonenko
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991 Moscow, Russia.
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176
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Zampese E, Surmeier DJ. Calcium, Bioenergetics, and Parkinson's Disease. Cells 2020; 9:cells9092045. [PMID: 32911641 PMCID: PMC7564460 DOI: 10.3390/cells9092045] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2020] [Revised: 09/04/2020] [Accepted: 09/07/2020] [Indexed: 12/12/2022] Open
Abstract
Degeneration of substantia nigra (SN) dopaminergic (DAergic) neurons is responsible for the core motor deficits of Parkinson’s disease (PD). These neurons are autonomous pacemakers that have large cytosolic Ca2+ oscillations that have been linked to basal mitochondrial oxidant stress and turnover. This review explores the origin of Ca2+ oscillations and their role in the control of mitochondrial respiration, bioenergetics, and mitochondrial oxidant stress.
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Interneuron-specific plasticity at parvalbumin and somatostatin inhibitory synapses onto CA1 pyramidal neurons shapes hippocampal output. Nat Commun 2020; 11:4395. [PMID: 32879322 PMCID: PMC7467931 DOI: 10.1038/s41467-020-18074-8] [Citation(s) in RCA: 94] [Impact Index Per Article: 23.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2019] [Accepted: 07/31/2020] [Indexed: 12/22/2022] Open
Abstract
The formation and maintenance of spatial representations within hippocampal cell assemblies is strongly dictated by patterns of inhibition from diverse interneuron populations. Although it is known that inhibitory synaptic strength is malleable, induction of long-term plasticity at distinct inhibitory synapses and its regulation of hippocampal network activity is not well understood. Here, we show that inhibitory synapses from parvalbumin and somatostatin expressing interneurons undergo long-term depression and potentiation respectively (PV-iLTD and SST-iLTP) during physiological activity patterns. Both forms of plasticity rely on T-type calcium channel activation to confer synapse specificity but otherwise employ distinct mechanisms. Since parvalbumin and somatostatin interneurons preferentially target perisomatic and distal dendritic regions respectively of CA1 pyramidal cells, PV-iLTD and SST-iLTP coordinate a reprioritisation of excitatory inputs from entorhinal cortex and CA3. Furthermore, circuit-level modelling reveals that PV-iLTD and SST-iLTP cooperate to stabilise place cells while facilitating representation of multiple unique environments within the hippocampal network. Inhibitory interneuron subtypes differentially control place cell representations in CA1. Here, the authors show that parvalbumin and somatostatin interneuron synapses onto CA1 pyramidal neurons exhibit distinct plasticity mechanisms and incorporating this insight into circuit-level modeling leads to stable place cell representations.
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178
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Ghasemzadeh Rahbardar M, Hosseinzadeh H. Therapeutic effects of rosemary ( Rosmarinus officinalis L.) and its active constituents on nervous system disorders. IRANIAN JOURNAL OF BASIC MEDICAL SCIENCES 2020; 23:1100-1112. [PMID: 32963731 PMCID: PMC7491497 DOI: 10.22038/ijbms.2020.45269.10541] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/23/2019] [Accepted: 04/28/2020] [Indexed: 12/19/2022]
Abstract
Rosemary (Rosmarinus officinalis L.) is an evergreen bushy shrub which grows along the Mediterranean Sea, and sub-Himalayan areas. In folk medicine, it has been used as an antispasmodic, mild analgesic, to cure intercostal neuralgia, headaches, migraine, insomnia emotional upset, and depression. Different investigations have highlighted rosemary neuropharmacological properties as their main topics. Rosemary has significant antimicrobial, anti-inflammatory, anti-oxidant, anti-apoptotic, anti-tumorigenic, antinociceptive, and neuroprotective properties. Furthermore, it shows important clinical effects on mood, learning, memory, pain, anxiety, and sleep. The aim of the current work is to review the potential neuropharmacological effects of different rosemary extracts and its active constituents on nervous system disorders, their relevant mechanisms and its preclinical application to recall the therapeutic potential of this herb and more directions of future research projects. The data were gathered by searching the English articles in PubMed, Scopus, Google Scholar, and Web of Science. The keywords used as search terms were 'Rosmarinus officinalis', 'rosemary', 'nervous system', 'depression', 'memory', 'Alzheimer's disease' 'epilepsy', 'addiction', 'neuropathic pain', and 'disorders'. All kinds of related articles, abstracts and books were included. No time limitation was considered. Both in vitro and in vivo studies were subjected to this investigation. This review authenticates that rosemary has appeared as a worthy source for curing inflammation, analgesic, anti-anxiety, and memory boosting. It also arranges new perception for further investigations on isolated constituents, especially carnosic acid, rosmarinic acid, and essential oil to find exquisite therapeutics and support drug discovery with fewer side effects to help people suffering from nervous system disorders.
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Affiliation(s)
| | - Hossein Hosseinzadeh
- Pharmaceutical Research Center, Pharmaceutical Technology Institute, Mashhad University of Medical Sciences, Mashhad, Iran
- Department of Pharmacodynamics and Toxicology, School of Pharmacy, Mashhad University of Medical Sciences, Mashhad, Iran
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Kunii M, Doi H, Hashiguchi S, Matsuishi T, Sakai Y, Iai M, Okubo M, Nakamura H, Takahashi K, Katsumoto A, Tada M, Takeuchi H, Ishikawa T, Miyake N, Saitsu H, Matsumoto N, Tanaka F. De novo CACNA1G variants in developmental delay and early-onset epileptic encephalopathies. J Neurol Sci 2020; 416:117047. [DOI: 10.1016/j.jns.2020.117047] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2020] [Revised: 06/22/2020] [Accepted: 07/14/2020] [Indexed: 11/16/2022]
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Janakiraman U, Dhanalakshmi C, Yu J, Moutal A, Boinon L, Fukunaga K, Khanna R, Nelson MA. The investigation of the T-type calcium channel enhancer SAK3 in an animal model of TAF1 intellectual disability syndrome. Neurobiol Dis 2020; 143:105006. [PMID: 32622085 PMCID: PMC7422587 DOI: 10.1016/j.nbd.2020.105006] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Revised: 06/17/2020] [Accepted: 06/27/2020] [Indexed: 01/21/2023] Open
Abstract
T-type calcium channels, in the central nervous system, are involved in the pathogenesis of many neurodegenerative diseases, including TAF1 intellectual disability syndrome (TAF1 ID syndrome). Here, we evaluated the efficacy of a novel T-type Ca2+ channel enhancer, SAK3 (ethyl 8'-methyl-2', 4-dioxo-2-(piperidin-1-yl)-2'H-spiro [cyclopentane-1, 3'-imidazo [1, 2-a] pyridine]-2-ene-3-carboxylate) in an animal model of TAF1 ID syndrome. At post-natal day 3, rat pups were subjected to intracerebroventricular (ICV) injection of either gRNA-control or gRNA-TAF1 CRISPR/Cas9 viruses. At post-natal day 21 animals were given SAK3 (0.25 mg/kg, p.o.) or vehicle up to post-natal day 35 (i.e. 14 days). Rats were subjected to behavioral, morphological, electrophysiological, and molecular studies. Oral administration of SAK3 (0.25 mg/kg, p.o.) significantly rescued the behavior abnormalities in beam walking test and open field test caused by TAF1 gene editing. We observed an increase in calbindin-positive Purkinje cells and GFAP-positive astrocytes as well as a decrease in IBA1-positive microglia cells in SAK3-treated animals. In addition, SAK3 protected the Purkinje and granule cells from apoptosis induced by TAF-1 gene editing. SAK3 also restored the excitatory post synaptic current (sEPSCs) in TAF1 edited Purkinje cells. Finally, SAK3 normalized the BDNF/AKT signaling axis in TAF1 edited animals. Altogether, these observations suggest that SAK3 could be a novel therapeutic agent for TAF1 ID syndrome.
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Affiliation(s)
- Udaiyappan Janakiraman
- Department of Pathology, University of Arizona College of Medicine, College of Pharmacy, Tucson, AZ, USA
| | - Chinnasamy Dhanalakshmi
- Department of Pathology, University of Arizona College of Medicine, College of Pharmacy, Tucson, AZ, USA
| | - Jie Yu
- Department of Pharmacology, University of Arizona College of Medicine, College of Pharmacy, Tucson, AZ, USA; College of Basic Medical Science, Zhejiang Chinese Medical University, Hangzhou 310058, China
| | - Aubin Moutal
- Department of Pharmacology, University of Arizona College of Medicine, College of Pharmacy, Tucson, AZ, USA
| | - Lisa Boinon
- Department of Pharmacology, University of Arizona College of Medicine, College of Pharmacy, Tucson, AZ, USA
| | - Kohji Fukunaga
- Department of Pharmacology, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan
| | - Rajesh Khanna
- Department of Pathology, University of Arizona College of Medicine, College of Pharmacy, Tucson, AZ, USA; Department of Pharmacology, University of Arizona College of Medicine, College of Pharmacy, Tucson, AZ, USA; The Center for Innovation in Brain Sciences, The University of Arizona Health Sciences, Tucson, AZ, USA; The BIO5 Institute, University of Arizona, USA
| | - Mark A Nelson
- Department of Pathology, University of Arizona College of Medicine, College of Pharmacy, Tucson, AZ, USA.
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181
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Novel Missense CACNA1G Mutations Associated with Infantile-Onset Developmental and Epileptic Encephalopathy. Int J Mol Sci 2020; 21:ijms21176333. [PMID: 32878331 PMCID: PMC7503748 DOI: 10.3390/ijms21176333] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Revised: 08/29/2020] [Accepted: 08/29/2020] [Indexed: 11/17/2022] Open
Abstract
The CACNA1G gene encodes the low-voltage-activated Cav3.1 channel, which is expressed in various areas of the CNS, including the cerebellum. We studied two missense CACNA1G variants, p.L208P and p.L909F, and evaluated the relationships between the severity of Cav3.1 dysfunction and the clinical phenotype. The presentation was of a developmental and epileptic encephalopathy without evident cerebellar atrophy. Both patients exhibited axial hypotonia, developmental delay, and severe to profound cognitive impairment. The patient with the L909F mutation had initially refractory seizures and cerebellar ataxia, whereas the L208P patient had seizures only transiently but was overall more severely affected. In transfected mammalian cells, we determined the biophysical characteristics of L208P and L909F variants, relative to the wild-type channel and a previously reported gain-of-function Cav3.1 variant. The L208P mutation shifted the activation and inactivation curves to the hyperpolarized direction, slowed the kinetics of inactivation and deactivation, and reduced the availability of Ca2+ current during repetitive stimuli. The L909F mutation impacted channel function less severely, resulting in a hyperpolarizing shift of the activation curve and slower deactivation. These data suggest that L909F results in gain-of-function, whereas L208P exhibits mixed gain-of-function and loss-of-function effects due to opposing changes in the biophysical properties. Our study expands the clinical spectrum associated with CACNA1G mutations, corroborating further the causal association with distinct complex phenotypes.
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182
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Sun H, Zhang H, Ross A, Wang TT, Al-Chami A, Wu SH. Developmentally Regulated Rebound Depolarization Enhances Spike Timing Precision in Auditory Midbrain Neurons. Front Cell Neurosci 2020; 14:236. [PMID: 32848625 PMCID: PMC7424072 DOI: 10.3389/fncel.2020.00236] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2020] [Accepted: 07/06/2020] [Indexed: 12/23/2022] Open
Abstract
The inferior colliculus (IC) is an auditory midbrain structure involved in processing biologically important temporal features of sounds. The responses of IC neurons to these temporal features reflect an interaction of synaptic inputs and neuronal biophysical properties. One striking biophysical property of IC neurons is the rebound depolarization produced following membrane hyperpolarization. To understand how the rebound depolarization is involved in spike timing, we made whole-cell patch clamp recordings from IC neurons in brain slices of P9-21 rats. We found that the percentage of rebound neurons was developmentally regulated. The precision of the timing of the first spike on the rebound increased when the neuron was repetitively injected with a depolarizing current following membrane hyperpolarization. The average jitter of the first spikes was only 0.5 ms. The selective T-type Ca2+ channel antagonist, mibefradil, significantly increased the jitter of the first spike of neurons in response to repetitive depolarization following membrane hyperpolarization. Furthermore, the rebound was potentiated by one to two preceding rebounds within a few hundred milliseconds. The first spike generated on the potentiated rebound was more precise than that on the non-potentiated rebound. With the addition of a calcium chelator, BAPTA, into the cell, the rebound potentiation no longer occurred, and the precision of the first spike on the rebound was not improved. These results suggest that the postinhibitory rebound mediated by T-type Ca2+ channel promotes spike timing precision in IC neurons. The rebound potentiation and precise spikes may be induced by increases in intracellular calcium levels.
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Affiliation(s)
- Hongyu Sun
- Department of Neuroscience, Carleton University, Ottawa, ON, Canada
| | - Hui Zhang
- Department of Neuroscience, Carleton University, Ottawa, ON, Canada
| | - Alysia Ross
- Department of Neuroscience, Carleton University, Ottawa, ON, Canada
| | - Ting Ting Wang
- Department of Neuroscience, Carleton University, Ottawa, ON, Canada
| | - Aycheh Al-Chami
- Department of Neuroscience, Carleton University, Ottawa, ON, Canada
| | - Shu Hui Wu
- Department of Neuroscience, Carleton University, Ottawa, ON, Canada
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183
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Kim JH, Won J, Oh SB. Expression of Ca V3.1 T-type Calcium Channels in Acutely Isolated Adult Rat Odontoblasts. Arch Oral Biol 2020; 118:104864. [PMID: 32847753 DOI: 10.1016/j.archoralbio.2020.104864] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2019] [Revised: 03/20/2020] [Accepted: 07/30/2020] [Indexed: 11/17/2022]
Abstract
OBJECTIVE Odontoblasts, which consist the outermost compartment of the dental pulp, are primarily engaged in dentin formation. Earlier evidence suggests that voltage-gated calcium channels, such as the high voltage-activated L-type calcium channels, serve as a calcium entry route to mediate dentin formation in odontoblasts. However, the involvement of other voltage-gated calcium channels in regulating intracellular Ca2+ remain unanswered. DESIGN The expression of voltage-gated calcium channel subtypes of the P/Q- (CaV2.1), N-(CaV2.2), R- (CaV2.3), and T- (CaV3.1-3.3) type were screened in adult rat odontoblasts by single cell RT-PCR. Among these candidates, immunopositivity against CaV3.1 was examined in the odontoblastic layer in teeth sections and dissociated odontoblasts. To confirm the functional expression of CaV3.1 in odontoblasts, intracellular Ca2+ increase in response to membrane depolarization was monitored with Fura-2-based ratiometric calcium imaging. RESULTS Among the candidate calcium channels, we found that mRNA for CaV3.1 is mainly detected in odontoblasts, with its expression being detected in the odontoblastic layer and dissociated odontoblasts. High extracellular K+-induced membrane depolarization was inhibited by pharmacological blockers for T-type calcium channels such as amiloride or ML218. CONCLUSION Our results demonstrate that among P/Q-, N-, R-, and T-type calcium channels, CaV3.1 is mainly expressed in odontoblasts to mediate intracellular Ca2+ signaling in response to membrane depolarization. These findings suggest that CaV3.1 may facilitate intracellular Ca2+ dynamics especially in the range of subliminal depolarizations near resting membrane potentials where other high voltage-gated calcium channels such as the L-type are likely to be inactive.
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Affiliation(s)
- Ji Hyun Kim
- Department of Brain and Cognitive Sciences, College of Natural Sciences, Seoul National University, Seoul, Republic of Korea
| | - Jonghwa Won
- Department of Brain and Cognitive Sciences, College of Natural Sciences, Seoul National University, Seoul, Republic of Korea
| | - Seog Bae Oh
- Department of Brain and Cognitive Sciences, College of Natural Sciences, Seoul National University, Seoul, Republic of Korea; Dental Research Institute and Department of Neurobiology & Physiology, School of Dentistry, Seoul National University, Seoul, Republic of Korea.
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184
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Contribution of T-Type Calcium Channels to Spinal Cord Injury-Induced Hyperexcitability of Nociceptors. J Neurosci 2020; 40:7229-7240. [PMID: 32839232 DOI: 10.1523/jneurosci.0517-20.2020] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2020] [Revised: 07/22/2020] [Accepted: 07/30/2020] [Indexed: 01/24/2023] Open
Abstract
A hyperexcitable state and spontaneous activity of nociceptors have been suggested to play a critical role in the development of chronic neuropathic pain following spinal cord injury (SCI). In male rats, we employed the action potential-clamp technique to determine the underlying ionic mechanisms responsible for driving SCI-nociceptors to a hyperexcitable state and for triggering their spontaneous activity. We found that the increased activity of low voltage activated T-type calcium channels induced by the injury sustains the bulk (∼60-70%) of the inward current active at subthreshold voltages during the interspike interval in SCI-nociceptors, with a modest contribution (∼10-15%) from tetrodotoxin (TTX)-sensitive and TTX-resistant sodium channels and hyperpolarization-activated cyclic nucleotide-gated (HCN) channels. In current-clamp recordings, inhibition of T-type calcium channels with 1 μm TTA-P2 reduced both the spontaneous and the evoked firing in response to current injections in SCI-nociceptors to a level similar to sham-nociceptors. Electrophysiology in vitro was then combined with the conditioned place preference (CPP) paradigm to determine the relationship between the increased activity of T-type channels in SCI-nociceptors and chronic neuropathic pain following SCI. The size of the interspike T-type calcium current recorded from nociceptors isolated from SCI rats showing TTA-P2-induced CPP (responders) was ∼6 fold greater than the interspike T-type calcium current recorded from nociceptors isolated from SCI rats without TTA-P2-induced CPP (non-responders). Taken together, our data suggest that the increased activity of T-type calcium channels induced by the injury plays a primary role in driving SCI-nociceptors to a hyperexcitable state and contributes to chronic neuropathic pain following SCI.SIGNIFICANCE STATEMENT Chronic neuropathic pain is a major comorbidity of spinal cord injury (SCI), affecting up to 70-80% of patients. Anticonvulsant and tricyclic antidepressant drugs are first line analgesics used to treat SCI-induced neuropathic pain, but their efficacy is very limited. A hyperexcitable state and spontaneous activity of SCI-nociceptors have been proposed as a possible underlying cause for the development of chronic neuropathic pain following SCI. Here, we show that the increased activity of T-type calcium channels induced by the injury plays a major role in driving SCI-nociceptors to a hyperexcitable state and for promoting their spontaneous activity, suggesting that T-type calcium channels may represent a pharmacological target to treat SCI-induced neuropathic pain.
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Guidelli R, Becucci L. Deterministic model of Ca v3.1 Ca 2+ channel and a proposed sequence of its conformations. Bioelectrochemistry 2020; 136:107618. [PMID: 32795940 DOI: 10.1016/j.bioelechem.2020.107618] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2020] [Revised: 06/29/2020] [Accepted: 07/21/2020] [Indexed: 10/23/2022]
Abstract
A family of current-time curves of T-type Cav3.1 Ca2+ channels available in the literature is simulated by a kinetic model differing from that used for the interpretation of all salient features of Na+ and Shaker K+ channels by the insertion of a multiplying factor expressing the difference between the working potential ϕ and the reversal potential ϕr. This deterministic model is also used to simulate experimental curves taken from the literature for steady-state 'fast inactivation' and for a gradual passage from fast to 'slow inactivation'. A depolarizing pulse induces fast or slow inactivation depending on whether it lasts 100-500 ms or about 1 min, and is believed to cause a collapse of the central pore near the selectivity filter (SF). A number of features of fast and slow inactivation of Cav3.1 Ca2+ channels are qualitatively interpreted on the basis of a sequence of conformational states. Briefly, the conformation responsible for 'fast inactivation' is assumed to have the activation gate open and the inactivation gate (i.e., the SF) inactive. Immediately after a depolarizing pulse, this conformation is inactive and requires a sufficiently long rest time at a far negative holding potential to recover from inactivation. 'Slow inactivation' is ascribed to a different conformation with the activation gate closed and the SF inactive.
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Affiliation(s)
- Rolando Guidelli
- Department of Chemistry "Ugo Schiff", Florence University, Via della Lastruccia 3, 50019 Sesto Fiorentino (Firenze), Italy.
| | - Lucia Becucci
- Department of Chemistry "Ugo Schiff", Florence University, Via della Lastruccia 3, 50019 Sesto Fiorentino (Firenze), Italy
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186
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T-Type Calcium Channels Contribute to Burst Firing in a Subpopulation of Medial Habenula Neurons. eNeuro 2020; 7:ENEURO.0201-20.2020. [PMID: 32719103 PMCID: PMC7433892 DOI: 10.1523/eneuro.0201-20.2020] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Revised: 07/03/2020] [Accepted: 07/06/2020] [Indexed: 11/24/2022] Open
Abstract
Action potential (AP) burst firing caused by the activation of low-voltage-activated T-type Ca2+ channels is a unique mode of neuronal firing. T-type channels have been implicated in diverse physiological and pathophysiological processes, including epilepsy, autism, and mood regulation, but the brain structures involved remain incompletely understood. The medial habenula (MHb) is an epithalamic structure implicated in anxiety-like and withdrawal behavior. Previous studies have shown that MHb neurons fire tonic APs at a frequency of ∼2–10 Hz or display depolarized low-amplitude membrane oscillations. Here, we report in C57BL/6J mice that a subpopulation of MHb neurons are capable of firing transient, high-frequency AP bursts mediated by T-type channels. Burst firing was observed following rebounding from hyperpolarizing current injections or during depolarization from hyperpolarized membrane potentials in ∼20% of MHb neurons. It was rarely observed at baseline but could be evoked in MHb neurons displaying different initial activity states. Further, we show that T-type channel mRNA, in particular Cav3.1, is expressed in the MHb in both cholinergic and substance P-ergic neurons. Pharmacological Cav3 antagonism blocked both burst firing and evoked Ca2+ currents in MHb neurons. Additionally, we observed high-frequency AP doublet firing at sustained depolarized membrane potentials that was independent of T-type channels. Thus, there is a greater diversity of AP firing patterns in MHb neurons than previously identified, including T-type channel-mediated burst firing, which may uniquely contribute to behaviors with relevance to neuropsychiatric disease.
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187
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Ma K, Zhu D, Zhang C, Lv L. Botulinum Toxin Type A Possibly Affects Ca v3.2 Calcium Channel Subunit in Rats with Spinal Cord Injury-Induced Muscle Spasticity. Drug Des Devel Ther 2020; 14:3029-3041. [PMID: 32801642 PMCID: PMC7395704 DOI: 10.2147/dddt.s256814] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2020] [Accepted: 06/26/2020] [Indexed: 12/12/2022] Open
Abstract
INTRODUCTION Spinal cord injury (SCI) often causes muscle spasticity, which can be inhibited by using calcium channel blocker. Botulinum toxin type A (BoT-A) shows therapeutic efficacy on spasticity and may exert inhibitory effects on the calcium channel. METHODS A rat model with muscle spasticity was established after SCI via contusion and compression. Different concentrations (0, 1, 3 and 6 U/kg) of BoT-A Botox were injected in the extensor digitorum longus (EDL) muscles of the right hindlimb in the muscle spasticity model. The changes of muscle spasticity and calcium level in EDL muscles were measured after the establishment of SCI-induced spasticity. Cav3.2 calcium channel subunit and its mutant (M1560V) were analyzed using Western blot before (input) or after immunoprecipitation with anti-FLAG antibody, and their currents were measured in motoneurons by using whole-cell voltage clamp recordings. RESULTS SCI induced muscle spasticity, whereas calcium level in EDL muscles and expression of Cav3.2 was increased in the SCI model when compared with the sham group (p < 0.05). BoT-A Botox treatment significantly reduced muscle spasticity and calcium level in EDL muscles and Cav3.2 expression in a dose-dependent way (p < 0.05). The ratio of biotinylated to total Cav3.2 was reduced in the mutant (M1560V) of Cav3.2 and lower than that in the wild Cav3.2. BoT-A Botox intervention also reduced the current values of calcium channel and the ratio in a dose-dependent way (p < 0.05). DISCUSSION BoT-A Botox possibly attenuates SCI-induced muscle spasticity by affecting the expression of Cav3.2 calcium channel subunit in the rat models. There may be multiple mechanisms for the function of BoT-A Botox. Further work is needed to be done to address these issues.
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Affiliation(s)
- Kening Ma
- Department of Pain Medicine, The First Hospital of Jilin University, Changchun130021, People’s Republic of China
| | - Dan Zhu
- Department of Neurologic Medicine, The First Hospital of Jilin University, Changchun130021, People’s Republic of China
| | - Chunguo Zhang
- Department of Pain Medicine, The First Hospital of Jilin University, Changchun130021, People’s Republic of China
| | - Lijie Lv
- Department of Medicine and Pension, The First Hospital of Jilin University, Changchun130021, People’s Republic of China
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Fast and synchronized fluctuations of cortical actin negatively correlate with nucleoli liquid-liquid phase separation in T cells. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2020; 49:409-423. [PMID: 32666133 DOI: 10.1007/s00249-020-01446-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 07/14/2019] [Revised: 03/10/2020] [Accepted: 07/02/2020] [Indexed: 12/11/2022]
Abstract
Liquid-liquid phase separation is an important mechanism by which eukaryotic cells functionally organize their intracellular content and has been related to cell malignancy and neurodegenerative diseases. These cells also undergo ATP-driven mechanical fluctuations, yet the effect of these fluctuations on the liquid-liquid phase separation remains poorly understood. Here, we employ high-resolution microscopy and atomic force microscopy of live Jurkat T cells to characterize the spectrum of their mechanical fluctuations, and to relate these fluctuations to the extent of nucleoli liquid-liquid phase separation (LLPS). We find distinct fluctuation of the cytoskeleton and of the cell diameter around 110 Hz, which depend on ATP and on myosin activity. Importantly, these fluctuations negatively correlate to nucleoli LLPS. According to a model of cell viscoelasticity, we propose that these fluctuations generate mechanical work that increases intracellular homogeneity by inhibiting LLPS. Thus, active mechanical fluctuations serve as an intracellular regulatory mechanism that could affect multiple pathophysiological conditions.
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189
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Abstract
Vascular smooth muscle cells (VSMCs) of small peripheral arteries contribute to blood pressure control by adapting their contractile state. These adaptations depend on the VSMC cytosolic Ca2+ concentration, regulated by complex local elementary Ca2+ signaling pathways. Ca2+ sparks represent local, transient, rapid calcium release events from a cluster of ryanodine receptors (RyRs) in the sarcoplasmic reticulum. In arterial SMCs, Ca2+ sparks activate nearby calcium-dependent potassium channels, cause membrane hyperpolarization and thus decrease the global intracellular [Ca2+] to oppose vasoconstriction. Arterial SMC Cav1.2 L-type channels regulate intracellular calcium stores content, which in turn modulates calcium efflux through RyRs. Cav3.2 T-type channels contribute to a minor extend to Ca2+ spark generation in certain types of arteries. Their localization within cell membrane caveolae is essential. We summarize present data on local elementary calcium signaling (Ca2+ sparks) in arterial SMCs with focus on RyR isoforms, large-conductance calcium-dependent potassium (BKCa) channels, and cell membrane-bound calcium channels (Cav1.2 and Cav3.2), particularly in caveolar microdomains.
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Affiliation(s)
- Gang Fan
- Charité - Universitätsmedizin Berlin, Experimental and Clinical Research Center (ECRC), a joint cooperation between the Charité Medical Faculty and the Max Delbrück Center for Molecular Medicine (MDC), Berlin, Germany
| | - Yingqiu Cui
- Charité - Universitätsmedizin Berlin, Experimental and Clinical Research Center (ECRC), a joint cooperation between the Charité Medical Faculty and the Max Delbrück Center for Molecular Medicine (MDC), Berlin, Germany
| | - Maik Gollasch
- Charité - Universitätsmedizin Berlin, Experimental and Clinical Research Center (ECRC), a joint cooperation between the Charité Medical Faculty and the Max Delbrück Center for Molecular Medicine (MDC), Berlin, Germany.,DZHK (German Centre for Cardiovascular Research), partner site Berlin, Germany
| | - Mario Kassmann
- Charité - Universitätsmedizin Berlin, Experimental and Clinical Research Center (ECRC), a joint cooperation between the Charité Medical Faculty and the Max Delbrück Center for Molecular Medicine (MDC), Berlin, Germany.,DZHK (German Centre for Cardiovascular Research), partner site Berlin, Germany
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190
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Lory P, Nicole S, Monteil A. Neuronal Cav3 channelopathies: recent progress and perspectives. Pflugers Arch 2020; 472:831-844. [PMID: 32638069 PMCID: PMC7351805 DOI: 10.1007/s00424-020-02429-7] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2020] [Revised: 06/08/2020] [Accepted: 06/26/2020] [Indexed: 12/22/2022]
Abstract
T-type, low-voltage activated, calcium channels, now designated Cav3 channels, are involved in a wide variety of physiological functions, especially in nervous systems. Their unique electrophysiological properties allow them to finely regulate neuronal excitability and to contribute to sensory processing, sleep, and hormone and neurotransmitter release. In the last two decades, genetic studies, including exploration of knock-out mouse models, have greatly contributed to elucidate the role of Cav3 channels in normal physiology, their regulation, and their implication in diseases. Mutations in genes encoding Cav3 channels (CACNA1G, CACNA1H, and CACNA1I) have been linked to a variety of neurodevelopmental, neurological, and psychiatric diseases designated here as neuronal Cav3 channelopathies. In this review, we describe and discuss the clinical findings and supporting in vitro and in vivo studies of the mutant channels, with a focus on de novo, gain-of-function missense mutations recently discovered in CACNA1G and CACNA1H. Overall, the studies of the Cav3 channelopathies help deciphering the pathogenic mechanisms of corresponding diseases and better delineate the properties and physiological roles Cav3 channels.
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Affiliation(s)
- Philippe Lory
- Institut de Génomique Fonctionnelle, CNRS, INSERM, University Montpellier, 141, rue de la Cardonille, 34094, Montpellier, France. .,LabEx 'Ion Channel Science and Therapeutics' (ICST), Montpellier, France.
| | - Sophie Nicole
- Institut de Génomique Fonctionnelle, CNRS, INSERM, University Montpellier, 141, rue de la Cardonille, 34094, Montpellier, France.,LabEx 'Ion Channel Science and Therapeutics' (ICST), Montpellier, France
| | - Arnaud Monteil
- Institut de Génomique Fonctionnelle, CNRS, INSERM, University Montpellier, 141, rue de la Cardonille, 34094, Montpellier, France.,LabEx 'Ion Channel Science and Therapeutics' (ICST), Montpellier, France
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191
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Homeostatic Recovery of Embryonic Spinal Activity Initiated by Compensatory Changes in Resting Membrane Potential. eNeuro 2020; 7:ENEURO.0526-19.2020. [PMID: 32540879 PMCID: PMC7340840 DOI: 10.1523/eneuro.0526-19.2020] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2019] [Revised: 05/08/2020] [Accepted: 05/22/2020] [Indexed: 01/20/2023] Open
Abstract
When baseline activity in a neuronal network is modified by external challenges, a set of mechanisms is prompted to homeostatically restore activity levels. These homeostatic mechanisms are thought to be profoundly important in the maturation of the network. It has been shown that blockade of either excitatory GABAergic or glutamatergic transmission in the living chick embryo transiently blocks the movements generated by spontaneous network activity (SNA) in the spinal cord. However, the embryonic movements then begin to recover by 2 h and are completely restored by 12 h of persistent receptor blockade. It remains unclear what mechanisms mediate this early recovery (first hours) after neurotransmitter blockade, or even if the same mechanisms are triggered following GABAergic and glutamatergic antagonists. Here we find two distinct mechanisms that could underlie this homeostatic recovery. First, we see a highly robust compensatory mechanism observed shortly after neurotransmitter receptor blockade. In the first 2 h of GABAergic or glutamatergic blockade in vitro, there was a clear depolarization of resting membrane potential (RMP) in both motoneurons and interneurons. These changes reduced threshold current and were observed in the continued presence of the antagonist. Therefore, it appears that fast changes in RMP represent a key fast homeostatic mechanism for the maintenance of network activity. Second, we see a less consistent compensatory change in the absolute threshold voltage in the first several hours of in vitro and in vivo neurotransmitter blockade. These mechanisms likely contribute to the homeostatic recovery of embryonic movements following neurotransmitter blockade.
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192
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De La Rosa JAM, García-Castañeda M, Nishigaki T, Gómora JC, Mancilla-Percino T, Ávila G. Interaction of MDIMP with the Voltage-Gated Calcium Channels. Mol Pharmacol 2020; 98:211-221. [PMID: 32587097 DOI: 10.1124/mol.120.119982] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2020] [Accepted: 06/11/2020] [Indexed: 11/22/2022] Open
Abstract
Amino acid-derived isoindolines are synthetic compounds that were created with the idea of investigating their biological actions. The amino acid moiety was included on the grounds that it may help to avoid toxic effects. Recently, the isoindoline MDIMP was shown to inhibit both cardiac excitation-contraction coupling and voltage-dependent calcium channels. Here, we revealed that MDIMP binds preferentially to low-voltage-activated (LVA) channels. Using a holding potential of -90 mV, the following IC50 values were found (in micromolars): >1000 (CaV2.3), 957 (CaV1.3), 656 (CaV1.2), 219 (CaV3.2), and 132 (CaV3.1). Moreover, the isoindoline also promoted both accelerated inactivation kinetics of high-voltage-activated Ca2+ channels and a modest upregulation of CaV1.3 and CaV2.3. Additional data indicate that although MDIMP binds to the closed state of the channels, it has more preference for the inactivated one. Concerning CaV3.1, the compound did not alter the shape of the instantaneous current-voltage curve, and substituting one or two residues in the selectivity filter drastically increased the IC50 value, suggesting that MDIMP binds to the extracellular side of the pore. However, an outward current failed in removing the inhibition, which implies an alternative mechanism may be involved. The enantiomer (R)-MDIMP [methyl (R)-2-(1,3-dihydroisoindol-2-yl)-4-methylpentanoate], on the other hand, was synthesized and evaluated, but it did not improve the affinity to LVA channels. Implications of these findings are discussed in terms of the possible underlying mechanisms and pharmacological relevance. SIGNIFICANCE STATEMENT: We have studied the regulation of voltage-gated calcium channels by MDIMP, which disrupts excitation-contraction coupling in cardiac myocytes. The latter effect is more potent in atrial than ventricular myocytes, and this could be explained by our results showing that MDIMP preferentially blocks low-voltage-activated channels. Our data also provide mechanistic insights about the blockade and suggest that MDIMP is a promising member of the family of Ca2+ channel blockers, with possible application to the inhibition of subthreshold membrane depolarizations.
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Affiliation(s)
- Juan A M De La Rosa
- Departamento de Bioquímica (J.A.M.D.L.R., M.G.-C., G.Á.) and Departamento de Química (T.M.-P.), Cinvestav-IPN, Mexico City, Mexico and Instituto de Biotecnología (T.N.) and Instituto de Fisiología Celular (J.C.G.), Universidad Nacional Autónoma de México, Cuernavaca, Mexico
| | - Maricela García-Castañeda
- Departamento de Bioquímica (J.A.M.D.L.R., M.G.-C., G.Á.) and Departamento de Química (T.M.-P.), Cinvestav-IPN, Mexico City, Mexico and Instituto de Biotecnología (T.N.) and Instituto de Fisiología Celular (J.C.G.), Universidad Nacional Autónoma de México, Cuernavaca, Mexico
| | - Takuya Nishigaki
- Departamento de Bioquímica (J.A.M.D.L.R., M.G.-C., G.Á.) and Departamento de Química (T.M.-P.), Cinvestav-IPN, Mexico City, Mexico and Instituto de Biotecnología (T.N.) and Instituto de Fisiología Celular (J.C.G.), Universidad Nacional Autónoma de México, Cuernavaca, Mexico
| | - Juan Carlos Gómora
- Departamento de Bioquímica (J.A.M.D.L.R., M.G.-C., G.Á.) and Departamento de Química (T.M.-P.), Cinvestav-IPN, Mexico City, Mexico and Instituto de Biotecnología (T.N.) and Instituto de Fisiología Celular (J.C.G.), Universidad Nacional Autónoma de México, Cuernavaca, Mexico
| | - Teresa Mancilla-Percino
- Departamento de Bioquímica (J.A.M.D.L.R., M.G.-C., G.Á.) and Departamento de Química (T.M.-P.), Cinvestav-IPN, Mexico City, Mexico and Instituto de Biotecnología (T.N.) and Instituto de Fisiología Celular (J.C.G.), Universidad Nacional Autónoma de México, Cuernavaca, Mexico
| | - Guillermo Ávila
- Departamento de Bioquímica (J.A.M.D.L.R., M.G.-C., G.Á.) and Departamento de Química (T.M.-P.), Cinvestav-IPN, Mexico City, Mexico and Instituto de Biotecnología (T.N.) and Instituto de Fisiología Celular (J.C.G.), Universidad Nacional Autónoma de México, Cuernavaca, Mexico
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193
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Liao X, Li Y. Genetic associations between voltage-gated calcium channels and autism spectrum disorder: a systematic review. Mol Brain 2020; 13:96. [PMID: 32571372 PMCID: PMC7310353 DOI: 10.1186/s13041-020-00634-0] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2020] [Accepted: 06/09/2020] [Indexed: 02/08/2023] Open
Abstract
OBJECTIVES The present review systematically summarized existing publications regarding the genetic associations between voltage-gated calcium channels (VGCCs) and autism spectrum disorder (ASD). METHODS A comprehensive literature search was conducted to gather pertinent studies in three online databases. Two authors independently screened the included records based on the selection criteria. Discrepancies in each step were settled through discussions. RESULTS From 1163 resulting searched articles, 28 were identified for inclusion. The most prominent among the VGCCs variants found in ASD were those falling within loci encoding the α subunits, CACNA1A, CACNA1B, CACNA1C, CACNA1D, CACNA1E, CACNA1F, CACNA1G, CACNA1H, and CACNA1I as well as those of their accessory subunits CACNB2, CACNA2D3, and CACNA2D4. Two signaling pathways, the IP3-Ca2+ pathway and the MAPK pathway, were identified as scaffolds that united genetic lesions into a consensus etiology of ASD. CONCLUSIONS Evidence generated from this review supports the role of VGCC genetic variants in the pathogenesis of ASD, making it a promising therapeutic target. Future research should focus on the specific mechanism that connects VGCC genetic variants to the complex ASD phenotype.
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Affiliation(s)
- Xiaoli Liao
- Xiangya Nursing School, Central South University, Changsha, Hunan, China.,Clinical Nursing Teaching and Research Section, The Second Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Yamin Li
- Clinical Nursing Teaching and Research Section, The Second Xiangya Hospital, Central South University, Changsha, Hunan, China.
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194
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Jeevakumar V, Al Sardar AK, Mohamed F, Smithhart CM, Price T, Dussor G. IL-6 induced upregulation of T-type Ca 2+ currents and sensitization of DRG nociceptors is attenuated by MNK inhibition. J Neurophysiol 2020; 124:274-283. [PMID: 32519575 DOI: 10.1152/jn.00188.2020] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Phosphorylation of the 5' cap-binding protein eIF4E by MAPK-interacting kinases (MNK1/2) is important for nociceptor sensitization and the development of chronic pain. IL-6-induced dorsal root ganglion (DRG) nociceptor excitability is attenuated in mice lacking eIF4E phosphorylation, in MNK1/2-/- mice, and by the nonselective MNK1/2 inhibitor cercosporamide. Here, we sought to better understand the neurophysiological mechanisms underlying how IL-6 causes nociceptor excitability via MNK-eIF4E signaling using the highly selective MNK inhibitor eFT508. DRG neurons were cultured from male and female ICR mice, 4-7 wk old. DRG cultures were treated with vehicle, IL-6, eFT508 (pretreat) followed by IL-6, or eFT508 alone. Whole cell patch-clamp recordings were done on small-diameter neurons (20-30 pF) to measure membrane excitability in response to ramp depolarization. IL-6 treatment (1 h) resulted in increased action potential firing compared with vehicle at all ramp intensities, an effect that was blocked by pretreatment with eFT508. Basic membrane properties, including resting membrane potential, input resistance, and rheobase, were similar across groups. Latency to the first action potential in the ramp protocol was lower in the IL-6 group and rescued by eFT508 pretreatment. We also found that the amplitudes of T-type voltage-gated calcium channels (VGCCs) were increased in the DRG following IL-6 treatment, but not in the eFT508 cotreatment group. Our findings are consistent with a model wherein MNK-eIF4E signaling controls the translation of signaling factors that regulate T-type VGCCs in response to IL-6 treatment. Inhibition of MNK with eFT508 disrupts these events, thereby preventing nociceptor hyperexcitability.NEW & NOTEWORTHY In this study, we show that the MNK inhibitor and anti-tumor agent eFT508 (tomivosertib) is effective in attenuating IL-6 induced sensitization of dorsal root ganglion (DRG) nociceptors. Pretreatment with eFT508 in DRG cultures from mice helps mitigate the development of hyperexcitability in response to IL-6. Furthermore, our data reveal that the upregulation of T-type voltage-gated calcium channels following IL-6 application can be blocked by eFT508, implicating the MNK-eIF4E signaling pathway in membrane trafficking of ion channels.
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Affiliation(s)
- Vivek Jeevakumar
- School of Behavioral and Brain Sciences, The University of Texas at Dallas, Richardson, Texas
| | - Aysha Khalid Al Sardar
- School of Behavioral and Brain Sciences, The University of Texas at Dallas, Richardson, Texas
| | - Farah Mohamed
- School of Behavioral and Brain Sciences, The University of Texas at Dallas, Richardson, Texas
| | - Clay Matthew Smithhart
- School of Behavioral and Brain Sciences, The University of Texas at Dallas, Richardson, Texas
| | - Theodore Price
- School of Behavioral and Brain Sciences, The University of Texas at Dallas, Richardson, Texas
| | - Gregory Dussor
- School of Behavioral and Brain Sciences, The University of Texas at Dallas, Richardson, Texas
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195
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Neosaxitoxin Inhibits the Expression of Inflammation Markers of the M1 Phenotype in Macrophages. Mar Drugs 2020; 18:md18060283. [PMID: 32471037 PMCID: PMC7345530 DOI: 10.3390/md18060283] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2020] [Revised: 05/19/2020] [Accepted: 05/22/2020] [Indexed: 12/19/2022] Open
Abstract
(1) Background: Neosaxitoxin (NeoSTX) has been used as a local anesthetic, but its anti-inflammatory effects have not been well defined. In the present study, we investigate the effects of NeoSTX on lipopolysaccharide (LPS)-activated macrophages. (2) Methods: Raw 264.7 and equine PBMC cells were incubated with or without 100 ng/mL LPS in the presence or absence of NeoSTX (1µM). The expression of inflammatory mediators was assessed: nitric oxide (NO) content using the Griess assay, TNF-α content using the ELISA assay, and mRNA of inducible nitric oxide synthase (iNOS), interleukin-1β (IL-1β), and tumor necrosis factor-α (TNF-α) using a real-time polymerase chain reaction. (3) Results: NeoSTX (1 μM) significantly inhibited the release of NO, TNF-α, and expression of iNOS, IL-1β, and TNF-α in LPS-activated macrophages of both species studied. Furthermore, our study shows that the LPS-induced release of inflammatory mediators was suppressed by NeoSTX. Additionally, NeoSTX deactivated polarized macrophages to M1 by LPS without compromising its polarization towards M2. (4) Conclusions: NeoSTX inhibits LPS-induced release of inflammatory mediators from macrophages, and these effects may be mediated by the blockade of voltage-gated sodium channels (VGSC).
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196
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Weir K, Dupre C, van Giesen L, Lee ASY, Bellono NW. A molecular filter for the cnidarian stinging response. eLife 2020; 9:57578. [PMID: 32452384 PMCID: PMC7250568 DOI: 10.7554/elife.57578] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2020] [Accepted: 05/09/2020] [Indexed: 01/06/2023] Open
Abstract
All animals detect and integrate diverse environmental signals to mediate behavior. Cnidarians, including jellyfish and sea anemones, both detect and capture prey using stinging cells called nematocytes which fire a venom-covered barb via an unknown triggering mechanism. Here, we show that nematocytes from Nematostella vectensis use a specialized voltage-gated calcium channel (nCaV) to distinguish salient sensory cues and control the explosive discharge response. Adaptations in nCaV confer unusually sensitive, voltage-dependent inactivation to inhibit responses to non-prey signals, such as mechanical water turbulence. Prey-derived chemosensory signals are synaptically transmitted to acutely relieve nCaV inactivation, enabling mechanosensitive-triggered predatory attack. These findings reveal a molecular basis for the cnidarian stinging response and highlight general principles by which single proteins integrate diverse signals to elicit discrete animal behaviors.
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Affiliation(s)
- Keiko Weir
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, United States
| | - Christophe Dupre
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, United States
| | - Lena van Giesen
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, United States
| | - Amy S-Y Lee
- Department of Biology, Brandeis University, Waltham, United States
| | - Nicholas W Bellono
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, United States
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197
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Chow CY, Absalom N, Biggs K, King GF, Ma L. Venom-derived modulators of epilepsy-related ion channels. Biochem Pharmacol 2020; 181:114043. [PMID: 32445870 DOI: 10.1016/j.bcp.2020.114043] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2020] [Accepted: 05/18/2020] [Indexed: 12/18/2022]
Abstract
Epilepsy is characterised by spontaneous recurrent seizures that are caused by an imbalance between neuronal excitability and inhibition. Since ion channels play fundamental roles in the generation and propagation of action potentials as well as neurotransmitter release at a subset of excitatory and inhibitory synapses, their dysfunction has been linked to a wide variety of epilepsies. Indeed, these unique proteins are the major biological targets for antiepileptic drugs. Selective targeting of a specific ion channel subtype remains challenging for small molecules, due to the high level of homology among members of the same channel family. As a consequence, there is a growing trend to target ion channels with biologics. Venoms are the best known natural source of ion channel modulators, and venom peptides are increasingly recognised as potential therapeutics due to their high selectivity and potency gained through millions of years of evolutionary selection pressure. Here we describe the major ion channel families involved in the pathogenesis of various types of epilepsy, including voltage-gated Na+, K+, Ca2+ channels, Cys-loop receptors, ionotropic glutamate receptors and P2X receptors, and currently available venom-derived peptides that target these channel proteins. Although only a small number of venom peptides have successfully progressed to the clinic, there is reason to be optimistic about their development as antiepileptic drugs, notwithstanding the challenges associated with development of any class of peptide drug.
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Affiliation(s)
- Chun Yuen Chow
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Nathan Absalom
- Brain and Mind Centre, School of Pharmacy, Faculty of Health and Medicine, The University of Sydney, Sydney, NSW 2050, Australia
| | - Kimberley Biggs
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Glenn F King
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD 4072, Australia.
| | - Linlin Ma
- Griffith Institute for Drug Discovery, Griffith University, Nathan, QLD 4111, Australia.
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198
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Cove-Smith A, Sharpe CC, Shattock MJ, Hendry BM. Ion-Channel modulator TH1177 reduces glomerular injury and serum creatinine in chronic mesangial proliferative disease in rats. BMC Nephrol 2020; 21:187. [PMID: 32429914 PMCID: PMC7236127 DOI: 10.1186/s12882-020-01842-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Accepted: 05/07/2020] [Indexed: 01/17/2023] Open
Abstract
Background T-type calcium channels (TTCC) are involved in mesangial cell proliferation. In acute thy-1 nephritis in the rat TTCC inhibition reduces glomerular damage and cell proliferation. This work is extended here by a study of the non-selective TTCC inhibitor TH1177 in a chronic model of proliferative glomerulonephritis (GN) including late treatment starting after the initial inflammation has resolved. The objective was to determine the effects of TH1177 in a model of chronic mesangioproliferative renal disease. Methods Chronic GN was induced in WKY rats by unilateral nephrectomy (day − 7) followed by day 0 injection of Ox7 thy-1 mAb. Treatment with TH1177 (10–20 mg/Kg daily IP) was started on day 2 (early treatment) or on day 14 (late treatment) and compared to vehicle-treated controls until sacrifice at day 42. Glomerular disease was assessed with a damage score, fibrosis assay, cellular counts and renal function measured by serum creatinine. Results Treatment with TH11777 was associated with reduced serum creatinine, less glomerular damage, reduced fibrosis and reduced glomerular cellularity. The results for early and late TH1177 treatments were essentially the same and differed significantly from vehicle. Conclusions The ion-channel modulator TH1177 is capable of improving glomerular outcome in chronic rat GN even when treatment starts 14 days after initiation of the disease. These data are discussed in the context of the possible targets of TH1177 including TTCC, TRP family, Stim/Orai group and other cation channels. The work supports the use of genetic models to examine the roles of individual cation channels in progressive glomerulonephritis to further define the targets of TH1177.
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Affiliation(s)
- Andrea Cove-Smith
- Renal Sciences, Department of Inflammation Biology, King's College London, Renal Medicine 10 Cutcombe Road, London, SE5 9RJ, UK.,Barts Health Renal Centre, The Royal London Hospital, E1 1BB, London, UK
| | - Claire C Sharpe
- Renal Sciences, Department of Inflammation Biology, King's College London, Renal Medicine 10 Cutcombe Road, London, SE5 9RJ, UK
| | - Michael J Shattock
- Cardiovascular Sciences, The Rayne Institute, King's College London, London, SE1 7EH, UK
| | - Bruce M Hendry
- Renal Sciences, Department of Inflammation Biology, King's College London, Renal Medicine 10 Cutcombe Road, London, SE5 9RJ, UK.
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199
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An L, Tang Y, Wang D, Jia S, Pei Q, Wang Q, Yu Z, Liu JK. Intrinsic and Synaptic Properties Shaping Diverse Behaviors of Neural Dynamics. Front Comput Neurosci 2020; 14:26. [PMID: 32372936 PMCID: PMC7187274 DOI: 10.3389/fncom.2020.00026] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2019] [Accepted: 03/18/2020] [Indexed: 12/19/2022] Open
Abstract
The majority of neurons in the neuronal system of the brain have a complex morphological structure, which diversifies the dynamics of neurons. In the granular layer of the cerebellum, there exists a unique cell type, the unipolar brush cell (UBC), that serves as an important relay cell for transferring information from outside mossy fibers to downstream granule cells. The distinguishing feature of the UBC is that it has a simple morphology, with only one short dendritic brush connected to its soma. Based on experimental evidence showing that UBCs exhibit a variety of dynamic behaviors, here we develop two simple models, one with a few detailed ion channels for simulation and the other one as a two-variable dynamical system for theoretical analysis, to characterize the intrinsic dynamics of UBCs. The reasonable values of the key channel parameters of the models can be determined by analysis of the stability of the resting membrane potential and the rebound firing properties of UBCs. Considered together with a large variety of synaptic dynamics installed on UBCs, we show that the simple-structured UBCs, as relay cells, can extend the range of dynamics and information from input mossy fibers to granule cells with low-frequency resonance and transfer stereotyped inputs to diverse amplitudes and phases of the output for downstream granule cells. These results suggest that neuronal computation, embedded within intrinsic ion channels and the diverse synaptic properties of single neurons without sophisticated morphology, can shape a large variety of dynamic behaviors to enhance the computational ability of local neuronal circuits.
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Affiliation(s)
- Lingling An
- School of Computer Science and Technology, Xidian University, Xi'an, China
| | - Yuanhong Tang
- School of Computer Science and Technology, Xidian University, Xi'an, China
| | - Doudou Wang
- School of Computer Science and Technology, Xidian University, Xi'an, China
| | - Shanshan Jia
- National Engineering Laboratory for Video Technology, Department of Computer Science and Technology, Peking University, Beijing, China
| | - Qingqi Pei
- School of Computer Science and Technology, Xidian University, Xi'an, China
| | - Quan Wang
- School of Computer Science and Technology, Xidian University, Xi'an, China
| | - Zhaofei Yu
- National Engineering Laboratory for Video Technology, Department of Computer Science and Technology, Peking University, Beijing, China
| | - Jian K Liu
- Centre for Systems Neuroscience, Department of Neuroscience, Psychology and Behaviour, University of Leicester, Leicester, United Kingdom
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Analysis of tetrodotoxin-sensitive sodium and low voltage-activated calcium channels in developing mouse retinal horizontal cells. Exp Eye Res 2020; 195:108028. [PMID: 32277973 DOI: 10.1016/j.exer.2020.108028] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2020] [Revised: 03/24/2020] [Accepted: 03/29/2020] [Indexed: 11/21/2022]
Abstract
Expression patterns of voltage-gated ion channels determine the spatio-temporal dynamics of ion currents that supply excitable neurons in developing tissue with proper electrophysiological properties. The purpose of the study was to identify fast cationic inward currents in mouse retinal horizontal cells (HCs) and describe their biophysical properties at different developmental stages. We also aimed to reveal their physiological role in shaping light responses (LRs) in adult HCs. HCs were recorded in horizontal slices of wild-type mouse retina at postnatal stages ranging from p8 through p60. Voltage-dependent inward currents were isolated with appropriate voltage protocols and blockers specific for sodium and T-type calcium channels. LRs were evoked with full-field flashes (130 μW/cm2). Transient and steady inward currents were identified at all developmental stages. Transient currents were mediated by T-type calcium and TTX-sensitive sodium channels, whereas steady currents were blocked by cadmium, indicating the presence of high voltage-activated calcium channels. Activation and steady-state inactivation kinetics of T-type calcium channels revealed a contribution to the resting membrane potential during postnatal development. Additionally, both sodium and T-type calcium channels had an impact on HC LRs at light offset in adult animals. Our results showed that the voltage-dependent inward currents of postnatally developing mouse HCs consist of T-type calcium, TTX-sensitive sodium, and high voltage-activated calcium channels, and that transient ionic currents contributed to light-evoked responses of adult HCs, suggesting a role in HC information processing.
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