1
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Tomagra G, Franchino C, Carbone E, Marcantoni A, Pasquarelli A, Picollo F, Carabelli V. Methodologies for Detecting Quantal Exocytosis in Adrenal Chromaffin Cells Through Diamond-Based MEAs. Methods Mol Biol 2023; 2565:213-221. [PMID: 36205897 DOI: 10.1007/978-1-0716-2671-9_15] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Diamond-based multiarray sensors are suitable to detect in real-time exocytosis and action potentials from cultured, spontaneously firing chromaffin cells, primary hippocampal neurons, and midbrain dopaminergic neurons. Here, we focus on how amperometric measurements of catecholamine release are performed on micrographitic diamond multiarrays (μG-D-MEAs) with high temporal and spatial resolution by 16 electrodes simultaneously.
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Affiliation(s)
- Giulia Tomagra
- Department of Drug Science and Technology and "NIS" Inter-departmental Centre, University of Torino, Turin, Italy.
| | - Claudio Franchino
- Department of Drug Science and Technology, University of Torino, Turin, Italy
| | - Emilio Carbone
- Department of Drug Science and Technology and "NIS" Inter-departmental Centre, University of Torino, Turin, Italy
| | - Andrea Marcantoni
- Department of Drug Science and Technology and "NIS" Inter-departmental Centre, University of Torino, Turin, Italy
| | | | - Federico Picollo
- Department of Physics and "NIS" Inter-departmental Centre, University of Torino, Istituto Nazionale di Fisica Nucleare - Sezione di Torino, Turin, Italy
| | - Valentina Carabelli
- Department of Drug Science and Technology and "NIS" Inter-departmental Centre, University of Torino, Turin, Italy
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2
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Mi X, Ding WG, Toyoda F, Kojima A, Omatsu-Kanbe M, Matsuura H. Selective activation of adrenoceptors potentiates I Ks current in pulmonary vein cardiomyocytes through the protein kinase A and C signaling pathways. J Mol Cell Cardiol 2021; 161:86-97. [PMID: 34375616 DOI: 10.1016/j.yjmcc.2021.08.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Revised: 07/19/2021] [Accepted: 08/04/2021] [Indexed: 10/20/2022]
Abstract
Delayed rectifier K+ current (IKs) is a key contributor to repolarization of action potentials. This study investigated the mechanisms underlying the adrenoceptor-induced potentiation of IKs in pulmonary vein cardiomyocytes (PVC). PVC were isolated from guinea pig pulmonary vein. The action potentials and IKs current were recorded using perforated and conventional whole-cell patch-clamp techniques. The expression of IKs was examined using immunocytochemistry and Western blotting. KCNQ1, a IKs pore-forming protein was detected as a signal band approximately 100 kDa in size, and its immunofluorescence signal was found to be mainly localized on the cell membrane. The IKs current in PVC was markedly enhanced by both β1- and β2-adrenoceptor stimulation with a negative voltage shift in the current activation, although the potentiation was more effectively induced by β2-adrenoceptor stimulation than β1-adrenoceptor stimulation. Both β-adrenoceptor-mediated increases in IKs were attenuated by treatment with the adenylyl cyclase (AC) inhibitor or protein kinase A (PKA) inhibitor. Furthermore, the IKs current was increased by α1-adrenoceptor agonist but attenuated by the protein kinase C (PKC) inhibitor. PVC exhibited action potentials in normal Tyrode solution which was slightly reduced by HMR-1556 a selective IKs blocker. However, HMR-1556 markedly reduced the β-adrenoceptor-potentiated firing rate. The stimulatory effects of β- and α1-adrenoceptor on IKs in PVC are mediated via the PKA and PKC signal pathways. HMR-1556 effectively reduced the firing rate under β-adrenoceptor activation, suggesting that the functional role of IKs might increase during sympathetic excitation under in vivo conditions.
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Affiliation(s)
- Xinya Mi
- Department of Physiology, Shiga University of Medical Science, Otsu, Shiga, Japan
| | - Wei-Guang Ding
- Department of Physiology, Shiga University of Medical Science, Otsu, Shiga, Japan.
| | - Futoshi Toyoda
- Department of Physiology, Shiga University of Medical Science, Otsu, Shiga, Japan
| | - Akiko Kojima
- Department of Anesthesiology, Shiga University of Medical Science, Otsu, Shiga, Japan
| | - Mariko Omatsu-Kanbe
- Department of Physiology, Shiga University of Medical Science, Otsu, Shiga, Japan
| | - Hiroshi Matsuura
- Department of Physiology, Shiga University of Medical Science, Otsu, Shiga, Japan
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3
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Milman A, Ventéo S, Bossu JL, Fontanaud P, Monteil A, Lory P, Guérineau NC. A sodium background conductance controls the spiking pattern of mouse adrenal chromaffin cells in situ. J Physiol 2021; 599:1855-1883. [PMID: 33450050 PMCID: PMC7986707 DOI: 10.1113/jp281044] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Accepted: 01/04/2021] [Indexed: 12/11/2022] Open
Abstract
KEY POINTS Mouse chromaffin cells in acute adrenal slices exhibit two distinct spiking patterns, a repetitive mode and a bursting mode. A sodium background conductance operates at rest as demonstrated by the membrane hyperpolarization evoked by a low Na+ -containing extracellular saline. This sodium background current is insensitive to TTX, is not blocked by Cs+ ions and displays a linear I-V relationship at potentials close to chromaffin cell resting potential. Its properties are reminiscent of those of the sodium leak channel NALCN. In the adrenal gland, Nalcn mRNA is selectively expressed in chromaffin cells. The study fosters our understanding of how the spiking pattern of chromaffin cells is regulated and adds a sodium background conductance to the list of players involved in the stimulus-secretion coupling of the adrenomedullary tissue. ABSTRACT Chromaffin cells (CCs) are the master neuroendocrine units for the secretory function of the adrenal medulla and a finely-tuned regulation of their electrical activity is required for appropriate catecholamine secretion in response to the organismal demand. Here, we aim at deciphering how the spiking pattern of mouse CCs is regulated by the ion conductances operating near the resting membrane potential (RMP). At RMP, mouse CCs display a composite firing pattern, alternating between active periods composed of action potentials spiking with a regular or a bursting mode, and silent periods. RMP is sensitive to changes in extracellular sodium concentration, and a low Na+ -containing saline hyperpolarizes the membrane, regardless of the discharge pattern. This RMP drive reflects the contribution of a depolarizing conductance, which is (i) not blocked by tetrodotoxin or caesium, (ii) displays a linear I-V relationship between -110 and -40 mV, and (iii) is carried by cations with a conductance sequence gNa > gK > gCs . These biophysical attributes, together with the expression of the sodium-leak channel Nalcn transcript in CCs, state credible the contribution of NALCN. This inaugural report opens new research routes in the field of CC stimulus-secretion coupling, and extends the inventory of tissues in which NALCN is expressed to neuroendocrine glands.
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Affiliation(s)
- Alexandre Milman
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, Montpellier, France.,LabEx "Ion Channel Science and Therapeutics", Montpellier, France
| | | | - Jean-Louis Bossu
- Institut des Neurosciences Cellulaires et Intégratives, CNRS UPR 3212, Strasbourg, France
| | - Pierre Fontanaud
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, Montpellier, France
| | - Arnaud Monteil
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, Montpellier, France.,LabEx "Ion Channel Science and Therapeutics", Montpellier, France
| | - Philippe Lory
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, Montpellier, France.,LabEx "Ion Channel Science and Therapeutics", Montpellier, France
| | - Nathalie C Guérineau
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, Montpellier, France.,LabEx "Ion Channel Science and Therapeutics", Montpellier, France
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4
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Marcantoni A, Calorio C, Hidisoglu E, Chiantia G, Carbone E. Cav1.2 channelopathies causing autism: new hallmarks on Timothy syndrome. Pflugers Arch 2020; 472:775-789. [PMID: 32621084 DOI: 10.1007/s00424-020-02430-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Revised: 06/23/2020] [Accepted: 06/26/2020] [Indexed: 02/07/2023]
Abstract
Cav1.2 L-type calcium channels play key roles in long-term synaptic plasticity, sensory transduction, muscle contraction, and hormone release. De novo mutations in the gene encoding Cav1.2 (CACNA1C) causes two forms of Timothy syndrome (TS1, TS2), characterized by a multisystem disorder inclusive of cardiac arrhythmias, long QT, autism, and adrenal gland dysfunction. In both TS1 and TS2, the missense mutation G406R is on the alternatively spliced exon 8 and 8A coding for the IS6-helix of Cav1.2 and is responsible for the penetrant form of autism in most TS individuals. The mutation causes specific gain-of-function changes to Cav1.2 channel gating: a "leftward shift" of voltage-dependent activation, reduced voltage-dependent inactivation, and a "leftward shift" of steady-state inactivation. How this occurs and how Cav1.2 gating changes alter neuronal firing and synaptic plasticity is still largely unexplained. Trying to better understanding the molecular basis of Cav1.2 gating dysfunctions leading to autism, here, we will present and discuss the properties of recently reported typical and atypical TS phenotypes and the effective gating changes exhibited by missense mutations associated with long QTs without extracardiac symptoms, unrelated to TS. We will also discuss new emerging views achieved from using iPSCs-derived neurons and the newly available autistic TS2-neo mouse model, both appearing promising for understanding neuronal mistuning in autistic TS patients. We will also analyze and describe recent proposals of molecular pathways that might explain mistuned Ca2+-mediated and Ca2+-independent excitation-transcription signals to the nucleus. Briefly, we will also discuss possible pharmacological approaches to treat autism associated with L-type channelopathies.
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Affiliation(s)
- Andrea Marcantoni
- Department of Drug Science, Laboratory of Cellular and Molecular Neuroscience, N.I.S. Centre, Corso Raffaello 30, 10125, Torino, Italy
| | - Chiara Calorio
- Department of Drug Science, Laboratory of Cellular and Molecular Neuroscience, N.I.S. Centre, Corso Raffaello 30, 10125, Torino, Italy
| | - Enis Hidisoglu
- Department of Biophysics, Faculty of Medicine, Akdeniz University, Antalya, Turkey
| | - Giuseppe Chiantia
- Department of Drug Science, Laboratory of Cellular and Molecular Neuroscience, N.I.S. Centre, Corso Raffaello 30, 10125, Torino, Italy
| | - Emilio Carbone
- Department of Drug Science, Laboratory of Cellular and Molecular Neuroscience, N.I.S. Centre, Corso Raffaello 30, 10125, Torino, Italy.
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5
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Russo I, Gavello D, Menna E, Vandael D, Veglia C, Morello N, Corradini I, Focchi E, Alfieri A, Angelini C, Bianchi FT, Morellato A, Marcantoni A, Sassoè-Pognetto M, Ottaviani MM, Yekhlef L, Giustetto M, Taverna S, Carabelli V, Matteoli M, Carbone E, Turco E, Defilippi P. p140Cap Regulates GABAergic Synaptogenesis and Development of Hippocampal Inhibitory Circuits. Cereb Cortex 2020; 29:91-105. [PMID: 29161354 DOI: 10.1093/cercor/bhx306] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2017] [Accepted: 10/23/2017] [Indexed: 01/19/2023] Open
Abstract
The neuronal scaffold protein p140Cap was investigated during hippocampal network formation. p140Cap is present in presynaptic GABAergic terminals and its genetic depletion results in a marked alteration of inhibitory synaptic activity. p140Cap-/- cultured neurons display higher frequency of miniature inhibitory postsynaptic currents (mIPSCs) with no changes of their mean amplitude. Consistent with a potential presynaptic alteration of basal GABA release, p140Cap-/- neurons exhibit a larger synaptic vesicle readily releasable pool, without any variation of single GABAA receptor unitary currents and number of postsynaptic channels. Furthermore, p140Cap-/- neurons show a premature and enhanced network synchronization and appear more susceptible to 4-aminopyridine-induced seizures in vitro and to kainate-induced seizures in vivo. The hippocampus of p140Cap-/- mice showed a significant increase in the number of both inhibitory synapses and of parvalbumin- and somatostatin-expressing interneurons. Specific deletion of p140Cap in forebrain interneurons resulted in increased susceptibility to in vitro epileptic events and increased inhibitory synaptogenesis, comparable to those observed in p140Cap-/- mice. Altogether, our data demonstrate that p140Cap finely tunes inhibitory synaptogenesis and GABAergic neurotransmission, thus regulating the establishment and maintenance of the proper hippocampal excitatory/inhibitory balance.
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Affiliation(s)
- Isabella Russo
- Department of Molecular Biotechnology and Health Sciences, University of Torino, Torino, Italy
| | - Daniela Gavello
- Department of Drug Science, University of Torino, Torino, Italy.,NIS Centre of Excellence, Torino, Italy
| | - Elisabetta Menna
- Institute of Neuroscience, CNR, Milano, Italy.,Istituto Clinico Humanitas, IRCCS, Rozzano, Italy
| | - David Vandael
- Department of Drug Science, University of Torino, Torino, Italy.,NIS Centre of Excellence, Torino, Italy
| | - Carola Veglia
- Department of Molecular Biotechnology and Health Sciences, University of Torino, Torino, Italy
| | - Noemi Morello
- Department of Neuroscience, University of Torino, Torino, Italy
| | - Irene Corradini
- Institute of Neuroscience, CNR, Milano, Italy.,Istituto Clinico Humanitas, IRCCS, Rozzano, Italy
| | | | - Annalisa Alfieri
- Department of Molecular Biotechnology and Health Sciences, University of Torino, Torino, Italy
| | - Costanza Angelini
- Department of Molecular Biotechnology and Health Sciences, University of Torino, Torino, Italy
| | - Federico Tommaso Bianchi
- Department of Molecular Biotechnology and Health Sciences, University of Torino, Torino, Italy.,Neuroscience Institute Cavalieri Ottolenghi, University of Torino, Orbassano, Italy
| | - Alessandro Morellato
- Department of Molecular Biotechnology and Health Sciences, University of Torino, Torino, Italy
| | - Andrea Marcantoni
- Department of Drug Science, University of Torino, Torino, Italy.,NIS Centre of Excellence, Torino, Italy
| | - Marco Sassoè-Pognetto
- Department of Neuroscience, University of Torino, Torino, Italy.,National Institute of Neuroscience-Italy, Torino, Italy
| | | | - Latefa Yekhlef
- Division of Neuroscience, San Raffaele Scientific Institute, Milano, Italy
| | - Maurizio Giustetto
- Department of Neuroscience, University of Torino, Torino, Italy.,National Institute of Neuroscience-Italy, Torino, Italy
| | - Stefano Taverna
- Division of Neuroscience, San Raffaele Scientific Institute, Milano, Italy
| | - Valentina Carabelli
- Department of Drug Science, University of Torino, Torino, Italy.,NIS Centre of Excellence, Torino, Italy
| | - Michela Matteoli
- Institute of Neuroscience, CNR, Milano, Italy.,Istituto Clinico Humanitas, IRCCS, Rozzano, Italy
| | - Emilio Carbone
- Department of Drug Science, University of Torino, Torino, Italy.,NIS Centre of Excellence, Torino, Italy
| | - Emilia Turco
- Department of Molecular Biotechnology and Health Sciences, University of Torino, Torino, Italy
| | - Paola Defilippi
- Department of Molecular Biotechnology and Health Sciences, University of Torino, Torino, Italy
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6
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Carbone E, Borges R, Eiden LE, García AG, Hernández‐Cruz A. Chromaffin Cells of the Adrenal Medulla: Physiology, Pharmacology, and Disease. Compr Physiol 2019; 9:1443-1502. [DOI: 10.1002/cphy.c190003] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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7
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Tomagra G, Franchino C, Pasquarelli A, Carbone E, Olivero P, Carabelli V, Picollo F. Simultaneous multisite detection of quantal release from PC12 cells using micro graphitic-diamond multi electrode arrays. Biophys Chem 2019; 253:106241. [PMID: 31398633 DOI: 10.1016/j.bpc.2019.106241] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2019] [Revised: 07/29/2019] [Accepted: 07/29/2019] [Indexed: 12/28/2022]
Abstract
Micro graphitic - diamond - multi electrode arrays (μG-D-MEAs) are suitable for measuring multisite quantal dopamine (DA) release from PC12 cells. Following cell stimulation with high extracellular KCl and electrode polarization at +650 mV, amperometric spikes are detected with a mean frequency of 0.60 ± 0.16 Hz. In each recording, simultaneous detection of secretory events is occurred in approximately 50% of the electrodes. Kinetic spike parameters and background noise are preserved among the different electrodes. Comparing the amperometric spikes recorder under control conditions with those recorders from PC12 cells previously incubated for 30 min with the dopamine precursor Levodopa (L-DOPA, 20 μM) it appears that the quantal size of amperometric spikes is increased by 250% and the half-time width (t1/2) by over 120%. On the contrary, L-DOPA has no effect on the frequency of secretory events. Overall, these data demonstrate that the μG-D-MEAs represent a reliable bio-sensor to simultaneously monitor quantal exocytotic events from different cells and in perspective can be exploited as a drug-screening tool.
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Affiliation(s)
- Giulia Tomagra
- Department of Drug and Science Technology, NIS Inter-departmental Centre, University of Torino, Corso Raffaello 30, 10125 Torino, Italy.
| | - Claudio Franchino
- Department of Drug and Science Technology, NIS Inter-departmental Centre, University of Torino, Corso Raffaello 30, 10125 Torino, Italy
| | - Alberto Pasquarelli
- Institute of Electron Devices and Circuits, University of Ulm, 89069 Ulm, Germany
| | - Emilio Carbone
- Department of Drug and Science Technology, NIS Inter-departmental Centre, University of Torino, Corso Raffaello 30, 10125 Torino, Italy
| | - Paolo Olivero
- Department of Physics, NIS Inter-departmental Centre, University of Torino, Italian Institute of Nuclear Physics, via Giuria 1, 10125 Torino, Italy
| | - Valentina Carabelli
- Department of Drug and Science Technology, NIS Inter-departmental Centre, University of Torino, Corso Raffaello 30, 10125 Torino, Italy
| | - Federico Picollo
- Department of Physics, NIS Inter-departmental Centre, University of Torino, Italian Institute of Nuclear Physics, via Giuria 1, 10125 Torino, Italy
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8
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Gavello D, Calorio C, Franchino C, Cesano F, Carabelli V, Carbone E, Marcantoni A. Early Alterations of Hippocampal Neuronal Firing Induced by Abeta42. Cereb Cortex 2019; 28:433-446. [PMID: 27999123 DOI: 10.1093/cercor/bhw377] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2016] [Indexed: 12/11/2022] Open
Abstract
We studied the effect of Amyloid β 1-42 oligomers (Abeta42) on Ca2+ dependent excitability profile of hippocampal neurons. Abeta42 is one of the Amyloid beta peptides produced by the proteolytic processing of the amyloid precursor protein and participates in the initiating event triggering the progressive dismantling of synapses and neuronal circuits. Our experiments on cultured hippocampal network reveal that Abeta42 increases intracellular Ca2+ concentration by 46% and inhibits firing discharge by 19%. More precisely, Abeta42 differently regulates ryanodine (RyRs), NMDA receptors (NMDARs), and voltage gated calcium channels (VGCCs) by increasing Ca2+ release through RyRs and inhibiting Ca2+ influx through NMDARs and VGCCs. The overall increased intracellular Ca2+ concentration causes stimulation of K+ current carried by big conductance Ca2+ activated potassium (BK) channels and hippocampal network firing inhibition. We conclude that Abeta42 alters neuronal function by means of at least 4 main targets: RyRs, NMDARs, VGCCs, and BK channels. The development of selective modulators of these channels may in turn be useful for developing effective therapies that could enhance the quality of life of AD patients during the early onset of the pathology.
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Affiliation(s)
- Daniela Gavello
- Department of Drug Science and Technology, Torino University, Corso Raffaello 30, 10125 Torino, Italy
| | - Chiara Calorio
- Department of Drug Science and Technology, Torino University, Corso Raffaello 30, 10125 Torino, Italy
| | - Claudio Franchino
- Department of Drug Science and Technology, Torino University, Corso Raffaello 30, 10125 Torino, Italy
| | - Federico Cesano
- Department of Chemistry Via Pietro Giuria 7, Torino University, 10125 Torino, Italy
| | - Valentina Carabelli
- Department of Drug Science and Technology, Torino University, Corso Raffaello 30, 10125 Torino, Italy
| | - Emilio Carbone
- Department of Drug Science and Technology, Torino University, Corso Raffaello 30, 10125 Torino, Italy
| | - Andrea Marcantoni
- Department of Drug Science and Technology, Torino University, Corso Raffaello 30, 10125 Torino, Italy
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9
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Calorio C, Gavello D, Guarina L, Salio C, Sassoè-Pognetto M, Riganti C, Bianchi FT, Hofer NT, Tuluc P, Obermair GJ, Defilippi P, Balzac F, Turco E, Bett GC, Rasmusson RL, Carbone E. Impaired chromaffin cell excitability and exocytosis in autistic Timothy syndrome TS2-neo mouse rescued by L-type calcium channel blockers. J Physiol 2019; 597:1705-1733. [PMID: 30629744 DOI: 10.1113/jp277487] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2018] [Accepted: 12/19/2018] [Indexed: 12/30/2022] Open
Abstract
KEY POINTS Tymothy syndrome (TS) is a multisystem disorder featuring cardiac arrhythmias, autism and adrenal gland dysfunction that originates from a de novo point mutation in the gene encoding the Cav1.2 (CACNA1C) L-type channel. To study the role of Cav1.2 channel signals in autism, the autistic TS2-neo mouse has been generated bearing the G406R point-mutation associated with TS type-2. Using heterozygous TS2-neo mice, we report that the G406R mutation reduces the rate of inactivation and shifts leftward the activation and inactivation of L-type channels, causing marked increase of resting Ca2+ influx ('window' Ca2+ current). The increased 'window current' causes marked reduction of NaV channel density, switches normal tonic firing to abnormal burst firing, reduces mitochondrial metabolism, induces cell swelling and decreases catecholamine release. Overnight incubations with nifedipine rescue NaV channel density, normal firing and the quantity of catecholamine released. We provide evidence that chromaffin cell malfunction derives from altered Cav1.2 channel gating. ABSTRACT L-type voltage-gated calcium (Cav1) channels have a key role in long-term synaptic plasticity, sensory transduction, muscle contraction and hormone release. A point mutation in the gene encoding Cav1.2 (CACNA1C) causes Tymothy syndrome (TS), a multisystem disorder featuring cardiac arrhythmias, autism spectrum disorder (ASD) and adrenal gland dysfunction. In the more severe type-2 form (TS2), the missense mutation G406R is on exon 8 coding for the IS6-helix of the Cav1.2 channel. The mutation causes reduced inactivation and induces autism. How this occurs and how Cav1.2 gating-changes alter cell excitability, neuronal firing and hormone release on a molecular basis is still largely unknown. Here, using the TS2-neo mouse model of TS we show that the G406R mutation altered excitability and reduced secretory activity in adrenal chromaffin cells (CCs). Specifically, the TS2 mutation reduced the rate of voltage-dependent inactivation and shifted leftward the activation and steady-state inactivation of L-type channels. This markedly increased the resting 'window' Ca2+ current that caused an increased percentage of CCs undergoing abnormal action potential (AP) burst firing, cell swelling, reduced mitochondrial metabolism and decreased catecholamine release. The increased 'window' Ca2+ current caused also decreased NaV channel density and increased steady-state inactivation, which contributed to the increased abnormal burst firing. Overnight incubation with the L-type channel blocker nifedipine rescued the normal AP firing of CCs, the density of functioning NaV channels and their steady-state inactivation. We provide evidence that CC malfunction derives from the altered Cav1.2 channel gating and that dihydropyridines are potential therapeutics for ASD.
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Affiliation(s)
- Chiara Calorio
- Department of Drug Science, NIS Centre, University of Torino, Torino, Italy
| | - Daniela Gavello
- Department of Drug Science, NIS Centre, University of Torino, Torino, Italy
| | - Laura Guarina
- Department of Drug Science, NIS Centre, University of Torino, Torino, Italy
| | - Chiara Salio
- Department of Veterinary Sciences, University of Torino, Torino, Italy
| | - Marco Sassoè-Pognetto
- Department of Neuroscience Rita Levi Montalcini, University of Torino, Torino, Italy
| | - Chiara Riganti
- Department of Oncology, University of Torino, Torino, Italy
| | | | - Nadja T Hofer
- Department of Pharmacology and Toxicology, Center for Molecular Biosciences, University of Innsbruck, Innsbruck, Austria
| | - Petronel Tuluc
- Department of Pharmacology and Toxicology, Center for Molecular Biosciences, University of Innsbruck, Innsbruck, Austria
| | - Gerald J Obermair
- Department of Physiology & Medical Physics, Medical University of Innsbruck, Innsbruck, Austria
| | - Paola Defilippi
- Department of Molecular Biotechnology and Health Sciences, University of Torino, Torino, Italy
| | - Fiorella Balzac
- Department of Molecular Biotechnology and Health Sciences, University of Torino, Torino, Italy
| | - Emilia Turco
- Department of Molecular Biotechnology and Health Sciences, University of Torino, Torino, Italy
| | - Glenna C Bett
- Department of Physiology & Biophysics, State University of New York, Buffalo, NY, USA
| | - Randall L Rasmusson
- Department of Physiology & Biophysics, State University of New York, Buffalo, NY, USA
| | - Emilio Carbone
- Department of Drug Science, NIS Centre, University of Torino, Torino, Italy
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10
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Sanz-Lázaro S, Jiménez-Pompa A, Carmona-Hidalgo B, Ubeda M, Muñoz L, Caba-González JC, Hernández-Vivanco A, López-García S, Albillos A, Albillos A. The firing frequency of spontaneous action potentials and their corresponding evoked exocytosis are increased in chromaffin cells of CCl 4 -induced cirrhotic rats with respect to control rats. J Neurochem 2018; 148:359-372. [PMID: 30347483 DOI: 10.1111/jnc.14618] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2018] [Revised: 10/09/2018] [Accepted: 10/18/2018] [Indexed: 11/29/2022]
Abstract
High catecolamine plasma levels because of sympathetic nervous system over-activity contribute to cirrhosis progression. The aim of this study was to investigate whether chromaffin cells of the adrenal gland might potentiate the deleterious effect exerted by this over-activity. Electrophysiological patch-clamp and amperometric experiments with carbon-fibre electrodes were conducted in single chromaffin cells of control and CCl4 -induced cirrhotic rats. The spontaneous action potential firing frequency was increased in chromaffin cells of cirrhotic rats with respect to control rats. The exocytosis evoked by that firing was also increased. However, exocytosis elicited by ACh did not vary between control and cirrhotic rats. Exocytosis triggered by depolarizing pulses was also unchanged. Amperometric recordings confirmed the lack of increased catecholamine charge released in cirrhosis after ACh or depolarization stimuli. However, the amperometric spikes exhibited faster kinetics of release. The overall Ca2+ entry through voltage-dependent Ca2+ channels (VDCC), or in particular through Cav1 channels, did not vary between chromaffin cells of control and cirrhotic rats. The inhibition of VDCC by methionine-enkephaline or ATP was not either altered, but it was increased by adrenaline in cells of cirrhotic rats. When a cocktail composed by the three neurotransmitters was tested in order to approach a situation closer to the physiological condition, the inhibition of VDCC was similar between both types of cells. In summary, chromaffin cells of the adrenal gland might contribute to exacerbate the sympathetic nervous system over-activity in cirrhosis because of an increased exocytosis elicited by an enhanced spontaneous electrical activity.
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Affiliation(s)
- Sara Sanz-Lázaro
- Departamento de Farmacología y Terapéutica, Facultad de Medicina, Universidad Autónoma de Madrid, Madrid, Spain
| | - Amanda Jiménez-Pompa
- Departamento de Farmacología y Terapéutica, Facultad de Medicina, Universidad Autónoma de Madrid, Madrid, Spain
| | - Beatriz Carmona-Hidalgo
- Departamento de Farmacología y Terapéutica, Facultad de Medicina, Universidad Autónoma de Madrid, Madrid, Spain
| | - María Ubeda
- Laboratorio de Enfermedades del Sistema Inmune, Departamento de Medicina, Universidad de Alcalá, Alcalá de Henares, Madrid, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBERehd), Instituto de Salud Carlos III, Madrid, Spain
| | - Leticia Muñoz
- Laboratorio de Enfermedades del Sistema Inmune, Departamento de Medicina, Universidad de Alcalá, Alcalá de Henares, Madrid, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBERehd), Instituto de Salud Carlos III, Madrid, Spain
| | - Jose Carlos Caba-González
- Departamento de Farmacología y Terapéutica, Facultad de Medicina, Universidad Autónoma de Madrid, Madrid, Spain
| | - Alicia Hernández-Vivanco
- Departamento de Farmacología y Terapéutica, Facultad de Medicina, Universidad Autónoma de Madrid, Madrid, Spain
| | - Sarai López-García
- Departamento de Farmacología y Terapéutica, Facultad de Medicina, Universidad Autónoma de Madrid, Madrid, Spain
| | - Agustín Albillos
- Departamento de Farmacología y Terapéutica, Facultad de Medicina, Universidad Autónoma de Madrid, Madrid, Spain.,Laboratorio de Enfermedades del Sistema Inmune, Departamento de Medicina, Universidad de Alcalá, Alcalá de Henares, Madrid, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBERehd), Instituto de Salud Carlos III, Madrid, Spain.,Servicio de Gastroenterología y Hepatología, Hospital Universitario Ramón y Cajal, IRYCIS, Madrid, Spain
| | - Almudena Albillos
- Departamento de Farmacología y Terapéutica, Facultad de Medicina, Universidad Autónoma de Madrid, Madrid, Spain
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11
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Baraibar AM, de Pascual R, Camacho M, Domínguez N, David Machado J, Gandía L, Borges R. Distinct patterns of exocytosis elicited by Ca 2+, Sr 2+ and Ba 2+ in bovine chromaffin cells. Pflugers Arch 2018; 470:1459-1471. [PMID: 29926228 DOI: 10.1007/s00424-018-2166-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2018] [Revised: 05/24/2018] [Accepted: 06/07/2018] [Indexed: 10/28/2022]
Abstract
Three divalent cations can elicit secretory responses in most neuroendocrine cells, including chromaffin cells. The extent to which secretion is elicited by the cations in intact depolarized cells was Ba2+ > Sr2+ ≥ Ca2+, contrasting with that elicited by these cations in permeabilized cells (Ca2+ > Sr2+ > Ba2+). Current-clamp recordings show that extracellular Sr2+ and Ba2+ cause membrane depolarization and action potentials, which are not blocked by Cd2+ but that can be mimicked by tetra-ethyl-ammonium. When applied intracellularly, only Ba2+ provokes action potentials. Voltage-clamp monitoring of Ca2+-activated K+ channels (KCa) shows that Ba2+ reduces outward currents, which were enhanced by Sr2+. Extracellular Ba2+ increases cytosolic Ca2+ concentrations in Fura-2-loaded intact cells, and it induces long-lasting catecholamine release. Conversely, amperometric recordings of permeabilized cells show that Ca2+ promotes the longest lasting secretion, as Ba2+ only provokes secretion while it is present and Sr2+ induces intermediate-lasting secretion. Intracellular Ba2+ dialysis provokes exocytosis at concentrations 100-fold higher than those of Ca2+, whereas Sr2+ exhibits an intermediate sensitivity. These results are compatible with the following sequence of events: Ba2+ blocks KCa channels from both the outside and inside of the cell, causing membrane depolarization that, in turn, opens voltage-sensitive Ca2+ channels and favors the entry of Ca2+ and Ba2+. Although Ca2+ is less permeable through its own channels, it is more efficient in triggering exocytosis. Strontium possesses both an intermediate permeability and an intermediate ability to induce secretion.
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Affiliation(s)
- Andrés M Baraibar
- Instituto Teófilo Hernando, Departamento de Farmacología y Terapéutica, Facultad de Medicina, Universidad Autónoma de Madrid, Arzobispo Morcillo 4, 28029, Madrid, Spain
| | - Ricardo de Pascual
- Instituto Teófilo Hernando, Departamento de Farmacología y Terapéutica, Facultad de Medicina, Universidad Autónoma de Madrid, Arzobispo Morcillo 4, 28029, Madrid, Spain
| | - Marcial Camacho
- Unidad de Farmacología, Facultad de Medicina, Universidad de La Laguna, 38200, La Laguna, Tenerife, Spain.,Institute of Neurophysiology, Charité-Universitätsmedizin Berlin, 10117, Berlin, Germany
| | - Natalia Domínguez
- Unidad de Farmacología, Facultad de Medicina, Universidad de La Laguna, 38200, La Laguna, Tenerife, Spain.,INTEGRARE, Généthon, Inserm, Univ Evry, Université Paris-Saclay, 91002, Evry, France
| | - J David Machado
- Unidad de Farmacología, Facultad de Medicina, Universidad de La Laguna, 38200, La Laguna, Tenerife, Spain
| | - Luis Gandía
- Instituto Teófilo Hernando, Departamento de Farmacología y Terapéutica, Facultad de Medicina, Universidad Autónoma de Madrid, Arzobispo Morcillo 4, 28029, Madrid, Spain
| | - Ricardo Borges
- Unidad de Farmacología, Facultad de Medicina, Universidad de La Laguna, 38200, La Laguna, Tenerife, Spain. .,Instituto Universitario de BioOrgánica Antonio González, Universidad de La Laguna, 38200, La Laguna, Tenerife, Spain.
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12
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Calorio C, Donno D, Franchino C, Carabelli V, Marcantoni A. Bud extracts from Salix caprea L. inhibit voltage gated calcium channels and catecholamines secretion in mouse chromaffin cells. PHYTOMEDICINE : INTERNATIONAL JOURNAL OF PHYTOTHERAPY AND PHYTOPHARMACOLOGY 2017; 36:168-175. [PMID: 29157811 DOI: 10.1016/j.phymed.2017.09.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2017] [Revised: 07/07/2017] [Accepted: 09/21/2017] [Indexed: 06/07/2023]
Abstract
BACKGROUND Salix caprea L. is an ornamental plant with prominent antioxidant activity. In the last decades Salix caprea bud extracts (SCBEs) have been used for the treatment of oxidative stress related disorders. PURPOSE A large part of cellular functions depends on the amount of intracellular Ca2+ concentration which in turn is mainly determined by Ca2+ ions movements across plasma membrane as well as by Ca2+ released from the stores. For better evaluating the mechanism of action of SCBEs, we focused on the effect of SCBEs on voltage gated Ca2+ channels (VGCCs) functioning and related catecholamines secretion in mouse chromaffin cells (MCCs). These latter are neuroendocrine cells that share a wide variety of functions with neurons. They are particularly interesting for studying the relationship between VGCCs activation and catecholamines secretion both in control and under stressful conditions. STUDY DESIGN AND METHODS We focused on the effect of SCBEs on VGCCs being these latter considered one of the main pathway of Ca2+ influx across plasma membrane. Ca2+ currents and capacitance changes were measured in patch clamp experiments performed in voltage clamp configuration. RESULTS We show that SCBEs inhibited VGCCs in a dose dependent manner. On average, the saturating concentration of SCBEs (SCBEsmax) is able to block 36% of the maximum Ca2+ current amplitude (ICa) without selectivity for L (ICa, L) or non-L type (ICa, non-L) Ca2+ channels. Furthermore, ICa inhibition is not followed by alteration of VGCCs gating kinetics, but is responsible for a marked decrease of Ca2+ dependent catecholamines secretion. CONCLUSION We conclude that the ability of SCBEs to inhibit VGCCs function, known to be potentiated during oxidative stress, could contribute to the already known antioxidant properties of Salix caprea L. We finally suggest that the inhibitory effect of SCBEs on catecholamines secretion may contribute to treat stress dependent cellular dysfunctions.
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Affiliation(s)
- Chiara Calorio
- Department of Drug Science and Technology, University of Torino, Corso Raffaello 30, 10125 Torino, Italy.
| | - Dario Donno
- Department of Agricultural, Forest and Food Sciences (DiSAFA), University of Torino, Largo Braccini 2, 10095 Grugliasco, To, Italy.
| | - Claudio Franchino
- Department of Drug Science and Technology, University of Torino, Corso Raffaello 30, 10125 Torino, Italy.
| | - Valentina Carabelli
- Department of Drug Science and Technology, University of Torino, Corso Raffaello 30, 10125 Torino, Italy.
| | - Andrea Marcantoni
- Department of Drug Science and Technology, University of Torino, Corso Raffaello 30, 10125 Torino, Italy.
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13
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L-type calcium channels in exocytosis and endocytosis of chromaffin cells. Pflugers Arch 2017; 470:53-60. [DOI: 10.1007/s00424-017-2064-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2017] [Revised: 08/22/2017] [Accepted: 08/23/2017] [Indexed: 11/25/2022]
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14
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Guarina L, Vandael DHF, Carabelli V, Carbone E. Low pH o boosts burst firing and catecholamine release by blocking TASK-1 and BK channels while preserving Cav1 channels in mouse chromaffin cells. J Physiol 2017; 595:2587-2609. [PMID: 28026020 DOI: 10.1113/jp273735] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2016] [Accepted: 12/07/2016] [Indexed: 12/19/2022] Open
Abstract
KEY POINTS Mouse chromaffin cells (MCCs) generate spontaneous burst-firing that causes large increases of Ca2+ -dependent catecholamine release, and is thus a key mechanism for regulating the functions of MCCs. With the aim to uncover a physiological role for burst-firing we investigated the effects of acidosis on MCC activity. Lowering the extracellular pH (pHo ) from 7.4 to 6.6 induces cell depolarizations of 10-15 mV that generate bursts of ∼330 ms at 1-2 Hz and a 7.4-fold increase of cumulative catecholamine-release. Burst-firing originates from the inhibition of the pH-sensitive TASK-1-channels and a 60% reduction of BK-channel conductance at pHo 6.6. Blockers of the two channels (A1899 and paxilline) mimic the effects of pHo 6.6, and this is reverted by the Cav1 channel blocker nifedipine. MCCs act as pH-sensors. At low pHo , they depolarize, undergo burst-firing and increase catecholamine-secretion, generating an effective physiological response that may compensate for the acute acidosis and hyperkalaemia generated during heavy exercise and muscle fatigue. ABSTRACT Mouse chromaffin cells (MCCs) generate action potential (AP) firing that regulates the Ca2+ -dependent release of catecholamines (CAs). Recent findings indicate that MCCs possess a variety of spontaneous firing modes that span from the common 'tonic-irregular' to the less frequent 'burst' firing. This latter is evident in a small fraction of MCCs but occurs regularly when Nav1.3/1.7 channels are made less available or when the Slo1β2-subunit responsible for BK channel inactivation is deleted. Burst firing causes large increases of Ca2+ -entry and potentiates CA release by ∼3.5-fold and thus may be a key mechanism for regulating MCC function. With the aim to uncover a physiological role for burst-firing we investigated the effects of acidosis on MCC activity. Lowering the extracellular pH (pHo ) from 7.4 to 7.0 and 6.6 induces cell depolarizations of 10-15 mV that generate repeated bursts. Bursts at pHo 6.6 lasted ∼330 ms, occurred at 1-2 Hz and caused an ∼7-fold increase of CA cumulative release. Burst firing originates from the inhibition of the pH-sensitive TASK-1/TASK-3 channels and from a 40% BK channel conductance reduction at pHo 7.0. The same pHo had little or no effect on Nav, Cav, Kv and SK channels that support AP firing in MCCs. Burst firing of pHo 6.6 could be mimicked by mixtures of the TASK-1 blocker A1899 (300 nm) and BK blocker paxilline (300 nm) and could be prevented by blocking L-type channels by adding 3 μm nifedipine. Mixtures of the two blockers raised cumulative CA-secretion even more than low pHo (∼12-fold), showing that the action of protons on vesicle release is mainly a result of the ionic conductance changes that increase Ca2+ -entry during bursts. Our data provide direct evidence suggesting that MCCs respond to low pHo with sustained depolarization, burst firing and enhanced CA-secretion, thus mimicking the physiological response of CCs to acute acidosis and hyperkalaemia generated during heavy exercise and muscle fatigue.
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Affiliation(s)
- Laura Guarina
- Department of Drug Science, Laboratory of Cellular and Molecular Neuroscience, NIS Centre, CNISM Unit, Torino, Italy
| | - David H F Vandael
- Department of Drug Science, Laboratory of Cellular and Molecular Neuroscience, NIS Centre, CNISM Unit, Torino, Italy.,Present address: Institute of Science and Technology Austria, Am Campus 1, Klosterneuburg, Austria
| | - Valentina Carabelli
- Department of Drug Science, Laboratory of Cellular and Molecular Neuroscience, NIS Centre, CNISM Unit, Torino, Italy
| | - Emilio Carbone
- Department of Drug Science, Laboratory of Cellular and Molecular Neuroscience, NIS Centre, CNISM Unit, Torino, Italy
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15
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Human native Ca v1 channels in chromaffin cells: contribution to exocytosis and firing of spontaneous action potentials. Eur J Pharmacol 2017; 796:115-121. [PMID: 27988286 DOI: 10.1016/j.ejphar.2016.12.009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2016] [Revised: 12/02/2016] [Accepted: 12/05/2016] [Indexed: 01/31/2023]
Abstract
The present study was performed to evaluate the Cav1 channel subtypes expressed in human chromaffin cells and the role that these channels play in exocytosis and cell excitability. Here we show that human chromaffin cells obtained from organ donors express Cav1.2 and Cav1.3 subtypes using molecular and pharmacological techniques. Immunocytochemical data demonstrated the presence of Cav1.2 and Cav1.3 subtypes, but not Cav1.1 or Cav1.4. Electrophysiological experiments were conducted to investigate the contribution of Cav1 channels to the exocytotic process and cell excitability. Cav1 channels contribute to the exocytosis of secretory vesicles, evidenced by the block of 3μM nifedipine (36.5±2%) of membrane capacitance increment elicited by 200ms depolarizing pulses. These channels show a minor contribution to the initiation of spontaneous action potential firing, as shown by the 2.5 pA of current at the threshold potential (-34mV), which elicits 10.4mV of potential increment. In addition, we found that only 8% of human chromaffin cells exhibit spontaneous action potentials. These data offer novel information regarding human chromaffin cells and the role of human native Cav1 channels in exocytosis and cell excitability.
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16
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Picollo F, Battiato A, Bernardi E, Marcantoni A, Pasquarelli A, Carbone E, Olivero P, Carabelli V. Microelectrode Arrays of Diamond-Insulated Graphitic Channels for Real-Time Detection of Exocytotic Events from Cultured Chromaffin Cells and Slices of Adrenal Glands. Anal Chem 2016; 88:7493-9. [DOI: 10.1021/acs.analchem.5b04449] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Federico Picollo
- Istituto Nazionale di Fisica Nucleare (INFN), 10125 Torino, Italy
- Physics
Department, University of Torino, 10125 Torino, Italy
- “Nanostructured
Interfaces and Surfaces” Inter-departmental Centre, University of Torino, 10125 Torino, Italy
- Consorzio Nazionale Interuniversitario per le Scienze Fisiche della Materia (CNISM), Torino Unit, 10125 Torino, Italy
| | - Alfio Battiato
- Istituto Nazionale di Fisica Nucleare (INFN), 10125 Torino, Italy
- Physics
Department, University of Torino, 10125 Torino, Italy
- “Nanostructured
Interfaces and Surfaces” Inter-departmental Centre, University of Torino, 10125 Torino, Italy
- Consorzio Nazionale Interuniversitario per le Scienze Fisiche della Materia (CNISM), Torino Unit, 10125 Torino, Italy
| | - Ettore Bernardi
- Istituto Nazionale di Fisica Nucleare (INFN), 10125 Torino, Italy
- Physics
Department, University of Torino, 10125 Torino, Italy
- “Nanostructured
Interfaces and Surfaces” Inter-departmental Centre, University of Torino, 10125 Torino, Italy
- Consorzio Nazionale Interuniversitario per le Scienze Fisiche della Materia (CNISM), Torino Unit, 10125 Torino, Italy
| | - Andrea Marcantoni
- “Nanostructured
Interfaces and Surfaces” Inter-departmental Centre, University of Torino, 10125 Torino, Italy
- Consorzio Nazionale Interuniversitario per le Scienze Fisiche della Materia (CNISM), Torino Unit, 10125 Torino, Italy
- Department
of Drug Science and Technology, University of Torino, 10125 Torino, Italy
| | - Alberto Pasquarelli
- Institute
of Electron Devices and Circuits, Ulm University, 89081 Ulm, Germany
| | - Emilio Carbone
- “Nanostructured
Interfaces and Surfaces” Inter-departmental Centre, University of Torino, 10125 Torino, Italy
- Consorzio Nazionale Interuniversitario per le Scienze Fisiche della Materia (CNISM), Torino Unit, 10125 Torino, Italy
- Department
of Drug Science and Technology, University of Torino, 10125 Torino, Italy
| | - Paolo Olivero
- Istituto Nazionale di Fisica Nucleare (INFN), 10125 Torino, Italy
- Physics
Department, University of Torino, 10125 Torino, Italy
- “Nanostructured
Interfaces and Surfaces” Inter-departmental Centre, University of Torino, 10125 Torino, Italy
- Consorzio Nazionale Interuniversitario per le Scienze Fisiche della Materia (CNISM), Torino Unit, 10125 Torino, Italy
| | - Valentina Carabelli
- “Nanostructured
Interfaces and Surfaces” Inter-departmental Centre, University of Torino, 10125 Torino, Italy
- Consorzio Nazionale Interuniversitario per le Scienze Fisiche della Materia (CNISM), Torino Unit, 10125 Torino, Italy
- Department
of Drug Science and Technology, University of Torino, 10125 Torino, Italy
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17
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Knock-down of synapsin alters cell excitability and action potential waveform by potentiating BK and voltage-gated Ca(2+) currents in Helix serotonergic neurons. Neuroscience 2015; 311:430-43. [PMID: 26522789 DOI: 10.1016/j.neuroscience.2015.10.046] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2015] [Revised: 09/23/2015] [Accepted: 10/25/2015] [Indexed: 11/21/2022]
Abstract
Synapsins (Syns) are an evolutionarily conserved family of presynaptic proteins crucial for the fine-tuning of synaptic function. A large amount of experimental evidences has shown that Syns are involved in the development of epileptic phenotypes and several mutations in Syn genes have been associated with epilepsy in humans and animal models. Syn mutations induce alterations in circuitry and neurotransmitter release, differentially affecting excitatory and inhibitory synapses, thus causing an excitation/inhibition imbalance in network excitability toward hyperexcitability that may be a determinant with regard to the development of epilepsy. Another approach to investigate epileptogenic mechanisms is to understand how silencing Syn affects the cellular behavior of single neurons and is associated with the hyperexcitable phenotypes observed in epilepsy. Here, we examined the functional effects of antisense-RNA inhibition of Syn expression on individually identified and isolated serotonergic cells of the Helix land snail. We found that Helix synapsin silencing increases cell excitability characterized by a slightly depolarized resting membrane potential, decreases the rheobase, reduces the threshold for action potential (AP) firing and increases the mean and instantaneous firing rates, with respect to control cells. The observed increase of Ca(2+) and BK currents in Syn-silenced cells seems to be related to changes in the shape of the AP waveform. These currents sustain the faster spiking in Syn-deficient cells by increasing the after hyperpolarization and limiting the Na(+) and Ca(2+) channel inactivation during repetitive firing. This in turn speeds up the depolarization phase by reaching the AP threshold faster. Our results provide evidence that Syn silencing increases intrinsic cell excitability associated with increased Ca(2+) and Ca(2+)-dependent BK currents in the absence of excitatory or inhibitory inputs.
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18
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Gavello D, Vandael D, Gosso S, Carbone E, Carabelli V. Dual action of leptin on rest-firing and stimulated catecholamine release via phosphoinositide 3-kinase-driven BK channel up-regulation in mouse chromaffin cells. J Physiol 2015; 593:4835-53. [PMID: 26282459 DOI: 10.1113/jp271078] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Accepted: 08/12/2015] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Leptin is an adipokine produced by the adipose tissue regulating body weight through its appetite-suppressing effect and, as such, exerts a relevant action on the adipo-adrenal axis. Leptin has a dual action on adrenal mouse chromaffin cells both at rest and during stimulation. At rest, the adipokine inhibits the spontaneous firing of most cells by enhancing the probability of BK channel opening through the phosphoinositide 3-kinase signalling cascade. This inhibitory effect is absent in db(-) /db(-) mice deprived of Ob receptors. During sustained stimulation, leptin preserves cell excitability by generating well-adapted action potential (AP) trains of lower frequency and broader width and increases catecholamine secretion by increasing the size of the ready-releasable pool and the rate of vesicle release. In conclusion, leptin dampens AP firing at rest but preserves AP firing and enhances catecholamine release during sustained stimulation, highlighting the importance of the adipo-adrenal axis in the leptin-mediated increase of sympathetic tone and catecholamine release. ABSTRACT Leptin is an adipokine produced by the adipose tissue regulating body weight through its appetite-suppressing effect. Besides being expressed in the hypothalamus and hippocampus, leptin receptors (ObRs) are also present in chromaffin cells of the adrenal medulla. In the present study, we report the effect of leptin on mouse chromaffin cell (MCC) functionality, focusing on cell excitability and catecholamine secretion. Acute application of leptin (1 nm) on spontaneously firing MCCs caused a slowly developing membrane hyperpolarization followed by complete blockade of action potential (AP) firing. This inhibitory effect at rest was abolished by the BK channel blocker paxilline (1 μm), suggesting the involvement of BK potassium channels. Single-channel recordings in 'perforated microvesicles' confirmed that leptin increased BK channel open probability without altering its unitary conductance. BK channel up-regulation was associated with the phosphoinositide 3-kinase (PI3K) signalling cascade because the PI3K specific inhibitor wortmannin (100 nm) fully prevented BK current increase. We also tested the effect of leptin on evoked AP firing and Ca(2+) -driven exocytosis. Although leptin preserves well-adapted AP trains of lower frequency, APs are broader and depolarization-evoked exocytosis is increased as a result of the larger size of the ready-releasable pool and higher frequency of vesicle release. The kinetics and quantal size of single secretory events remained unaltered. Leptin had no effect on firing and secretion in db(-) /db(-) mice lacking the ObR gene, confirming its specificity. In conclusion, leptin exhibits a dual action on MCC activity. It dampens AP firing at rest but preserves AP firing and increases catecholamine secretion during sustained stimulation, highlighting the importance of the adipo-adrenal axis in the leptin-mediated increase of sympathetic tone and catecholamine release.
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Affiliation(s)
- Daniela Gavello
- Department of Drug Science and Technology, University of Torino, Torino, Italy.,NIS Center, CNISM, University of Torino, Torino, Italy
| | - David Vandael
- Department of Drug Science and Technology, University of Torino, Torino, Italy.,NIS Center, CNISM, University of Torino, Torino, Italy.,Institute of Science and Technology Austria, Am Campus 1, Klosterneuburg, Austria
| | - Sara Gosso
- Department of Drug Science and Technology, University of Torino, Torino, Italy.,NIS Center, CNISM, University of Torino, Torino, Italy
| | - Emilio Carbone
- Department of Drug Science and Technology, University of Torino, Torino, Italy.,NIS Center, CNISM, University of Torino, Torino, Italy
| | - Valentina Carabelli
- Department of Drug Science and Technology, University of Torino, Torino, Italy.,NIS Center, CNISM, University of Torino, Torino, Italy
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19
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Caricati-Neto A, García AG, Bergantin LB. Pharmacological implications of the Ca(2+)/cAMP signaling interaction: from risk for antihypertensive therapy to potential beneficial for neurological and psychiatric disorders. Pharmacol Res Perspect 2015; 3:e00181. [PMID: 26516591 PMCID: PMC4618650 DOI: 10.1002/prp2.181] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2015] [Accepted: 08/10/2015] [Indexed: 11/25/2022] Open
Abstract
In this review, we discussed pharmacological implications of the Ca2+/cAMP signaling interaction in the antihypertensive and neurological/psychiatric disorders therapies. Since 1975, several clinical studies have reported that acute and chronic administration of L-type voltage-activated Ca2+ channels (VACCs) blockers, such as nifedipine, produces reduction in peripheral vascular resistance and arterial pressure associated with an increase in plasma noradrenaline levels and heart rate, typical of sympathetic hyperactivity. Despite this sympathetic hyperactivity has been initially attributed to adjust reflex of arterial pressure, the cellular and molecular mechanisms involved in this apparent sympathomimetic effect of the L-type VACCs blockers remained unclear for decades. In addition, experimental studies using isolated tissues richly innervated by sympathetic nerves (to exclude the influence of adjusting reflex) showed that neurogenic responses were completely inhibited by L-type VACCs blockers in concentrations above 1 μmol/L, but paradoxically potentiated in concentrations below 1 μmol/L. During almost four decades, these enigmatic phenomena remained unclear. In 2013, we discovered that this paradoxical increase in sympathetic activity produced by L-type VACCs blocker is due to interaction of the Ca2+/cAMP signaling pathways. Then, the pharmacological manipulation of the Ca2+/cAMP interaction produced by combination of the L-type VACCs blockers used in the antihypertensive therapy, and cAMP accumulating compounds used in the antidepressive therapy, could represent a potential cardiovascular risk for hypertensive patients due to increase in sympathetic hyperactivity. In contrast, this pharmacological manipulation could be a new therapeutic strategy for increasing neurotransmission in psychiatric disorders, and producing neuroprotection in the neurodegenerative diseases.
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Affiliation(s)
- Afonso Caricati-Neto
- Department of Pharmacology, Universidade Federal de São Paulo, Escola Paulista de Medicina São Paulo, Brazil
| | - Antonio G García
- Instituto Teófilo Hernando de I+D del Medicamento, Universidad Autónoma de Madrid Madrid, Spain
| | - Leandro Bueno Bergantin
- Department of Pharmacology, Universidade Federal de São Paulo, Escola Paulista de Medicina São Paulo, Brazil
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20
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Allio A, Calorio C, Franchino C, Gavello D, Carbone E, Marcantoni A. Bud extracts from Tilia tomentosa Moench inhibit hippocampal neuronal firing through GABAA and benzodiazepine receptors activation. JOURNAL OF ETHNOPHARMACOLOGY 2015; 172:288-296. [PMID: 26144285 DOI: 10.1016/j.jep.2015.06.016] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2015] [Revised: 06/10/2015] [Accepted: 06/14/2015] [Indexed: 06/04/2023]
Abstract
ETHNOPHARMACOLOGICAL RELEVANCE Tilia tomentosa Moench bud extracts (TTBEs) is used in traditional medicine for centuries as sedative compound. Different plants belonging to the Tilia genus have shown their efficacy in the treatment of anxiety but still little is known about the mechanism of action of their bud extracts. AIM OF THE STUDY To evaluate the action of TTBEs as anxiolytic and sedative compound on in vitro hippocampal neurons. MATERIAL AND METHODS The anxiolytic effect of TTBEs was assayed by testing the effects of these compounds on GABAA receptor-activated chloride current of hippocampal neurons by means of the patch-clamp technique and microelectrode-arrays (MEAs). RESULTS TTBEs acutely administered on mouse hippocampal neurons, activated a chloride current comparable to that measured in the presence of GABA (100 µM). Bicuculline (100 µM) and picrotoxin (100 µM) blocked about 90% of this current, while the remaining 10% was blocked by adding the benzodiazepine (BDZ) antagonist flumazenil (30 µM). Flumazenil alone blocked nearly 60% of the TTBEs activated current, suggesting that TTBEs binds to both GABAA and BDZ receptor sites. Application of high-doses of TTBEs on spontaneous active hippocampal neurons grown for 3 weeks on MEAs blocked the synchronous activity of these neurons. The effects were mimicked by GABA and prevented by picrotoxin (100µM) and flumazenil (30 µM). At minimal doses, TTBEs reduced the frequency of synchronized bursts and increased the cross-correlation index of synchronized neuronal firing. CONCLUSIONS Our data suggest that TTBEs mimics GABA and BDZ agonists by targeting hippocampal GABAergic synapses and inhibiting network excitability by increasing the strength of inhibitory synaptic outputs. Our results contribute toward the validation of TTBEs as effective sedative and anxiolytic compound.
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Affiliation(s)
- Arianna Allio
- Department of Drug Science and Technology, University of Torino, Corso Raffaello 30, 10125 Torino, Italy.
| | - Chiara Calorio
- Department of Drug Science and Technology, University of Torino, Corso Raffaello 30, 10125 Torino, Italy.
| | - Claudio Franchino
- Department of Drug Science and Technology, University of Torino, Corso Raffaello 30, 10125 Torino, Italy.
| | - Daniela Gavello
- Department of Drug Science and Technology, University of Torino, Corso Raffaello 30, 10125 Torino, Italy.
| | - Emilio Carbone
- Department of Drug Science and Technology, University of Torino, Corso Raffaello 30, 10125 Torino, Italy.
| | - Andrea Marcantoni
- Department of Drug Science and Technology, University of Torino, Corso Raffaello 30, 10125 Torino, Italy.
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Vandael DHF, Ottaviani MM, Legros C, Lefort C, Guérineau NC, Allio A, Carabelli V, Carbone E. Reduced availability of voltage-gated sodium channels by depolarization or blockade by tetrodotoxin boosts burst firing and catecholamine release in mouse chromaffin cells. J Physiol 2015; 593:905-27. [PMID: 25620605 DOI: 10.1113/jphysiol.2014.283374] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2014] [Accepted: 12/05/2014] [Indexed: 01/09/2023] Open
Abstract
KEY POINTS Mouse chromaffin cells (MCCs) of the adrenal medulla possess fast-inactivating Nav channels whose availability alters spontaneous action potential firing patterns and the Ca(2+)-dependent secretion of catecholamines. Here, we report MCCs expressing large densities of neuronal fast-inactivating Nav1.3 and Nav1.7 channels that carry little or no subthreshold pacemaker currents and can be slowly inactivated by 50% upon slight membrane depolarization. Reducing Nav1.3/Nav1.7 availability by tetrodotoxin or by sustained depolarization near rest leads to a switch from tonic to burst-firing patterns that give rise to elevated Ca(2+)-influx and increased catecholamine release. Spontaneous burst firing is also evident in a small percentage of control MCCs. Our results establish that burst firing comprises an intrinsic firing mode of MCCs that boosts their output. This occurs particularly when Nav channel availability is reduced by sustained splanchnic nerve stimulation or prolonged cell depolarizations induced by acidosis, hyperkalaemia and increased muscarine levels. ABSTRACT Action potential (AP) firing in mouse chromaffin cells (MCCs) is mainly sustained by Cav1.3 L-type channels that drive BK and SK currents and regulate the pacemaking cycle. As secretory units, CCs optimally recruit Ca(2+) channels when stimulated, a process potentially dependent on the modulation of the AP waveform. Our previous work has shown that a critical determinant of AP shape is voltage-gated sodium channel (Nav) channel availability. Here, we studied the contribution of Nav channels to firing patterns and AP shapes at rest (-50 mV) and upon stimulation (-40 mV). Using quantitative RT-PCR and immunoblotting, we show that MCCs mainly express tetrodotoxin (TTX)-sensitive, fast-inactivating Nav1.3 and Nav1.7 channels that carry little or no Na(+) current during slow ramp depolarizations. Time constants and the percentage of recovery from fast inactivation and slow entry into closed-state inactivation are similar to that of brain Nav1.3 and Nav1.7 channels. The fraction of available Nav channels is reduced by half after 10 mV depolarization from -50 to -40 mV. This leads to low amplitude spikes and a reduction in repolarizing K(+) currents inverting the net current from outward to inward during the after-hyperpolarization. When Nav channel availability is reduced by up to 20% of total, either by TTX block or steady depolarization, a switch from tonic to burst firing is observed. The spontaneous occurrence of high frequency bursts is rare under control conditions (14% of cells) but leads to major Ca(2+)-entry and increased catecholamine release. Thus, Nav1.3/Nav1.7 channel availability sets the AP shape, burst-firing initiation and regulates catecholamine secretion in MCCs. Nav channel inactivation becomes important during periods of high activity, mimicking stress responses.
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Affiliation(s)
- David H F Vandael
- Department of Drug Science, Laboratory of Cellular and Molecular Neuroscience, NIS Center, CNISM Unit, Torino, Italy
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22
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Vandael DHF, Marcantoni A, Carbone E. Cav1.3 Channels as Key Regulators of Neuron-Like Firings and Catecholamine Release in Chromaffin Cells. Curr Mol Pharmacol 2015; 8:149-61. [PMID: 25966692 PMCID: PMC5384372 DOI: 10.2174/1874467208666150507105443] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2014] [Revised: 01/31/2015] [Accepted: 04/20/2015] [Indexed: 12/19/2022]
Abstract
Neuronal and neuroendocrine L-type calcium channels (Cav1.2, Cav1.3) open readily at relatively low membrane potentials and allow Ca(2+) to enter the cells near resting potentials. In this way, Cav1.2 and Cav1.3 shape the action potential waveform, contribute to gene expression, synaptic plasticity, neuronal differentiation, hormone secretion and pacemaker activity. In the chromaffin cells (CCs) of the adrenal medulla, Cav1.3 is highly expressed and is shown to support most of the pacemaking current that sustains action potential (AP) firings and part of the catecholamine secretion. Cav1.3 forms Ca(2+)-nanodomains with the fast inactivating BK channels and drives the resting SK currents. These latter set the inter-spike interval duration between consecutive spikes during spontaneous firing and the rate of spike adaptation during sustained depolarizations. Cav1.3 plays also a primary role in the switch from "tonic" to "burst" firing that occurs in mouse CCs when either the availability of voltage-gated Na channels (Nav) is reduced or the β2 subunit featuring the fast inactivating BK channels is deleted. Here, we discuss the functional role of these "neuron-like" firing modes in CCs and how Cav1.3 contributes to them. The open issue is to understand how these novel firing patterns are adapted to regulate the quantity of circulating catecholamines during resting condition or in response to acute and chronic stress.
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Affiliation(s)
| | | | - Emilio Carbone
- Department of Drug Science, Corso Raffaello 30, I - 10125 Torino, Italy.
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23
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Baliño P, Ledesma JC, Aragon CMG. Role of CA2+/calmodulin on ethanol neurobehavioral effects. Psychopharmacology (Berl) 2014; 231:4611-21. [PMID: 24853690 DOI: 10.1007/s00213-014-3610-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/24/2013] [Accepted: 04/29/2014] [Indexed: 01/13/2023]
Abstract
RATIONALE The cAMP-dependent protein kinase A (PKA) signaling transduction pathway has been shown to play an important role in the modulation of several ethanol-induced behaviors. Different studies have demonstrated intracellular calcium (Ca(2+))-dependent activation of the PKA cascade after ethanol administration. Thus, the cAMP cascade mediator Ca(2+)-dependent calmodulin (CaM) has been strongly implicated in the central effects of ethanol. OBJECTIVES In this study, we assessed the role of the CaM inhibitor W7 on ethanol-induced stimulation, ethanol intake, and ethanol-induced activation of PKA. METHODS Swiss mice were pretreated with W7 (0-10 mg/kg) 30 min before ethanol (0-3.75 g/kg) administration. Immediately, animals were placed during 20 min in an open-field chamber. Ethanol (10 %, v/v) intake in 2 h was assessed using a limited access paradigm. Experiments with caffeine (0-15 mg/kg), cocaine (0-4 mg/kg), and saccharine (0.1 %, w/v) were designed to compare their results to those obtained with ethanol. Western blot was assayed 45 min after ethanol administration. RESULTS Results showed that pretreatment with W7, reduced selectively in a dose-dependent fashion ethanol-induced locomotor stimulation and ethanol intake. The ethanol-induced activation of PKA was also prevented by W7 administration. CONCLUSIONS These results demonstrate that CaM inhibition resulted in a selective reduction of ethanol-stimulating effects and ethanol intake. The PKA activation induced by ethanol was blocked after the CaM blockade with W7. These results provide further evidence of the key role of cellular Ca(2+)-dependent pathways on the central effects of ethanol.
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Affiliation(s)
- Pablo Baliño
- Área de Psicobiología, Universtitat Jaume I, Avda. Sos Baynat s/n, 12071, Castellón, Spain,
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Gosso S, Turturici M, Franchino C, Colombo E, Pasquarelli A, Carbone E, Carabelli V. Heterogeneous distribution of exocytotic microdomains in adrenal chromaffin cells resolved by high-density diamond ultra-microelectrode arrays. J Physiol 2014; 592:3215-30. [PMID: 24879870 DOI: 10.1113/jphysiol.2014.274951] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Here we describe the ability of a high-density diamond microelectrode array targeted to resolve multi-site detection of fast exocytotic events from single cells. The array consists of nine boron-doped nanocrystalline diamond ultra-microelectrodes (9-Ch NCD-UMEA) radially distributed within a circular area of the dimensions of a single cell. The device can be operated in voltammetric or chronoamperometric configuration. Sensitivity to catecholamines, tested by dose-response calibrations, set the lowest detectable concentration of adrenaline to ∼5 μm. Catecholamine release from bovine or mouse chromaffin cells could be triggered by electrical stimulation or external KCl-enriched solutions. Spikes detected from the cell apex using carbon fibre microelectrodes showed an excellent correspondence with events measured at the bottom of the cell by the 9-Ch NCD-UMEA, confirming the ability of the array to resolve single quantal secretory events. Subcellular localization of exocytosis was provided by assigning each quantal event to one of the nine channels based on its location. The resulting mapping highlights the heterogeneous distribution of secretory activity in cell microdomains of 12-27 μm2. In bovine chromaffin cells, secretion was highly heterogeneous with zones of high and medium activity in 54% of the cell surface and zones of low or no activity in the remainder. The 'non-active' ('silent') zones covered 24% of the total and persisted for 6-8 min, indicating stable location. The 9-Ch NCD-UMEA therefore appears suitable for investigating the microdomain organization of neurosecretion with high spatial resolution.
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Affiliation(s)
- Sara Gosso
- Department of Drug Science and Technology, NIS Center, University of Turin, 10125, Turin, Italy
| | - Marco Turturici
- Department of Drug Science and Technology, NIS Center, University of Turin, 10125, Turin, Italy Department of Neuroscience, University of Turin, 10125, Turin, Italy
| | - Claudio Franchino
- Department of Drug Science and Technology, NIS Center, University of Turin, 10125, Turin, Italy
| | - Elisabetta Colombo
- Department of Drug Science and Technology, NIS Center, University of Turin, 10125, Turin, Italy Institute of Electron Devices and Circuits, University of Ulm, 89069, Ulm, Germany
| | - Alberto Pasquarelli
- Institute of Electron Devices and Circuits, University of Ulm, 89069, Ulm, Germany
| | - Emilio Carbone
- Department of Drug Science and Technology, NIS Center, University of Turin, 10125, Turin, Italy
| | - Valentina Carabelli
- Department of Drug Science and Technology, NIS Center, University of Turin, 10125, Turin, Italy
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25
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T-type channel-mediated neurotransmitter release. Pflugers Arch 2014; 466:677-87. [PMID: 24595475 DOI: 10.1007/s00424-014-1489-z] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2014] [Accepted: 02/18/2014] [Indexed: 10/25/2022]
Abstract
Besides controlling a wide variety of cell functions, T-type channels have been shown to regulate neurotransmitter release in peripheral and central synapses and neuroendocrine cells. Growing evidence over the last 10 years suggests a key role of Cav3.2 and Cav3.1 channels in controlling basal neurosecretion near resting conditions and sustained release during mild stimulations. In some cases, the contribution of low-voltage-activated (LVA) channels is not directly evident but requires either the activation of coupled presynaptic receptors, block of ion channels, or chelation of metal ions. Concerning the coupling to the secretory machinery, T-type channels appear loosely coupled to neurotransmitter and hormone release. In neurons, Cav3.2 and Cav3.1 channels mainly control the asynchronous appearance of "minis" [miniature inhibitory postsynaptic currents (mIPSCs) and miniature excitatory postsynaptic currents (mEPSCs)]. The same loose coupling is evident from membrane capacity and amperometric recordings in chromaffin cells and melanotropes where the low-threshold-driven exocytosis possesses the same linear Ca(2+) dependence of the other voltage-gated Ca(2+) channels (Cav1 and Cav2) that is strongly attenuated by slow calcium buffers. The intriguing issue is that, despite not expressing a consensus "synprint" site, Cav3.2 channels do interact with syntaxin 1A and SNAP-25 and, thus, may form nanodomains with secretory vesicles that can be regulated at low voltages. In this review, we discuss all the past and recent issues related to T-type channel-secretion coupling in neurons and neuroendocrine cells.
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Inhibition of catecholamine secretion by iron-rich and iron-deprived multiwalled carbon nanotubes in chromaffin cells. Neurotoxicology 2013; 39:84-94. [PMID: 23999117 DOI: 10.1016/j.neuro.2013.08.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2013] [Revised: 07/23/2013] [Accepted: 08/21/2013] [Indexed: 01/26/2023]
Abstract
The assay of the toxic effects of carbon nanotubes (CNTs) on human health is a stringent need in view of their expected increasing exploitation in industrial and biomedical applications. Most studies so far have been focused on lung toxicity, as the respiratory tract is the main entry of airborne particulate, but there is also recent evidence on the existence of toxic effects of multiwalled carbon nanotubes (MWCNTs) on neuronal and neuroendocrine cells (Belyanskaya et al., 2009; Xu et al., 2009; Gavello et al., 2012). Commercial MWCNTs often contain large amounts of metals deriving from the catalyst used during their synthesis. Since metals, particularly iron, may contribute to the toxicity of MWCNTs, we compared here the effects of two short MWCNTs samples (<5μm length), differing only in their iron content (0.5 versus 0.05% w/w) on the secretory responses of neurotransmitters in mouse chromaffin cells. We found that both iron-rich (MWCNT+Fe) and iron-deprived (MWCNT-Fe) samples enter chromaffin cells after 24h exposure, even though incorporation was attenuated in the latter case (40% versus 78% of cells). As a consequence of MWCNT+Fe or MWCNT-Fe exposure (50-263μg/ml, 24h), catecholamine secretion of chromaffin cells is drastically impaired because of the decreased Ca(2+)-dependence of exocytosis, reduced size of ready-releasable pool and lowered rate of vesicle release. On the contrary, both MWCNTs were ineffective in changing the kinetics of neurotransmitter release of single chromaffin granules and their quantal content. Overall, our data indicate that both MWCNT samples dramatically impair secretion in chromaffin cells, thus uncovering a true depressive action of CNTs mainly associated to their structure and degree of aggregation. This cellular "loss-of-function" is only partially attenuated in iron-deprived samples, suggesting a minor role of iron impurities on MWCNTs toxicity in chromaffin cells exocytosis.
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Bergantin LB, Souza CF, Ferreira RM, Smaili SS, Jurkiewicz NH, Caricati-Neto A, Jurkiewicz A. Novel model for "calcium paradox" in sympathetic transmission of smooth muscles: role of cyclic AMP pathway. Cell Calcium 2013; 54:202-12. [PMID: 23849429 DOI: 10.1016/j.ceca.2013.06.004] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2013] [Revised: 06/03/2013] [Accepted: 06/11/2013] [Indexed: 01/25/2023]
Abstract
It is well established that reduction of Ca2+ influx through L-type voltage-dependent Ca2+ channel (L-type VDCC), or increase of cytosolic cAMP concentration ([cAMP]c), inhibit contractile activity of smooth muscles in response to transmitters released from sympathetic nerves. Surprisingly, in this work we observed that simultaneous administration of L-type VDCC blocker (verapamil) and [cAMP]c enhancers (rolipram, IBMX and forskolin) potentiated purinergic contractions evoked by electrical field stimulation of rat vas deferens, instead of inhibiting them. These results, including its role in sympathetic transmission, can be considered as a "calcium paradox". On the other hand, this potentiation was prevented by reduction of [cAMP]c by inhibition of adenylyl cyclase (SQ 22536) or depletion of Ca2+ storage of sarco-endoplasmic reticulum by blockade of Ca2+ reuptake (thapsigargin). In addition, cytosolic Ca2+ concentration ([Ca2+]c) evaluated by fluorescence microscopy in rat adrenal medullary slices was significantly reduced by verapamil or rolipram. In contrast, simultaneous incubation of adrenal slices with these compounds significantly increased [Ca2+]c. This effect was prevented by thapsigargin. Thus, a reduction of [Ca2+]c due to blockade of Ca2+ influx through L-type VDCC could stimulate adenylyl cyclase activity increasing [cAMP]c thereby stimulating Ca2+ release from endoplasmic reticulum, resulting in augmented transmitter release in sympathetic nerves and contraction.
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Affiliation(s)
- Leandro Bueno Bergantin
- Department of Pharmacology, INFAR--Escola Paulista de Medicina, Federal University of São Paulo, Brazil
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Ca(V)1.3-driven SK channel activation regulates pacemaking and spike frequency adaptation in mouse chromaffin cells. J Neurosci 2013; 32:16345-59. [PMID: 23152617 DOI: 10.1523/jneurosci.3715-12.2012] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Mouse chromaffin cells (MCCs) fire spontaneous action potentials (APs) at rest. Ca(v)1.3 L-type calcium channels sustain the pacemaker current, and their loss results in depolarized resting potentials (V(rest)), spike broadening, and remarkable switches into depolarization block after BayK 8644 application. A functional coupling between Ca(v)1.3 and BK channels has been reported but cannot fully account for the aforementioned observations. Here, using Ca(v)1.3(-/-) mice, we investigated the role of Ca(v)1.3 on SK channel activation and how this functional coupling affects the firing patterns induced by sustained current injections. MCCs express SK1-3 channels whose tonic currents are responsible for the slow irregular firing observed at rest. Percentage of frequency increase induced by apamin was found inversely correlated to basal firing frequency. Upon stimulation, MCCs build-up Ca(v)1.3-dependent SK currents during the interspike intervals that lead to a notable degree of spike frequency adaptation (SFA). The major contribution of Ca(v)1.3 to the subthreshold Ca(2+) charge during an AP-train rather than a specific molecular coupling to SK channels accounts for the reduced SFA of Ca(v)1.3(-/-) MCCs. Low adaptation ratios due to reduced SK activation associated with Ca(v)1.3 deficiency prevent the efficient recovery of Na(V) channels from inactivation. This promotes a rapid decline of AP amplitudes and facilitates early onset of depolarization block following prolonged stimulation. Thus, besides serving as pacemaker, Ca(v)1.3 slows down MCC firing by activating SK channels that maintain Na(V) channel availability high enough to preserve stable AP waveforms, even upon high-frequency stimulation of chromaffin cells during stress responses.
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Vandael DHF, Mahapatra S, Calorio C, Marcantoni A, Carbone E. Cav1.3 and Cav1.2 channels of adrenal chromaffin cells: emerging views on cAMP/cGMP-mediated phosphorylation and role in pacemaking. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1828:1608-18. [PMID: 23159773 DOI: 10.1016/j.bbamem.2012.11.013] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2012] [Revised: 11/05/2012] [Accepted: 11/08/2012] [Indexed: 12/21/2022]
Abstract
Voltage-gated Ca²⁺ channels (VGCCs) are voltage sensors that convert membrane depolarizations into Ca²⁺ signals. In the chromaffin cells of the adrenal medulla, the Ca²⁺ signals driven by VGCCs regulate catecholamine secretion, vesicle retrievals, action potential shape and firing frequency. Among the VGCC-types expressed in these cells (N-, L-, P/Q-, R- and T-types), the two L-type isoforms, Ca(v)1.2 and Ca(v)1.3, control key activities due to their particular activation-inactivation gating and high-density of expression in rodents and humans. The two isoforms are also effectively modulated by G protein-coupled receptor pathways delimited in membrane micro-domains and by the cAMP/PKA and NO/cGMP/PKG phosphorylation pathways which induce prominent Ca²⁺ current changes if opposingly regulated. The two L-type isoforms shape the action potential and directly participate to vesicle exocytosis and endocytosis. The low-threshold of activation and slow rate of inactivation of Ca(v)1.3 confer to this channel the unique property of carrying sufficient inward current at subthreshold potentials able to activate BK and SK channels which set the resting potential, the action potential shape, the cell firing mode and the degree of spike frequency adaptation during spontaneous firing or sustained depolarizations. These properties help chromaffin cells to optimally adapt when switching from normal to stress-mimicking conditions. Here, we will review past and recent findings on cAMP- and cGMP-mediated modulations of Ca(v)1.2 and Ca(v)1.3 and the role that these channels play in the control of chromaffin cell firing. This article is part of a Special Issue entitled: Calcium channels.
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Affiliation(s)
- D H F Vandael
- Department of Drug Science, Laboratory of Cellular & Molecular Neuroscience, NIS Center, CNISM, University of Torino, Italy
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30
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Mahapatra S, Marcantoni A, Zuccotti A, Carabelli V, Carbone E. Equal sensitivity of Cav1.2 and Cav1.3 channels to the opposing modulations of PKA and PKG in mouse chromaffin cells. J Physiol 2012; 590:5053-73. [PMID: 22826131 DOI: 10.1113/jphysiol.2012.236729] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Mouse chromaffin cells (MCCs) express high densities of L-type Ca2+ channels (LTCCs), which control pacemaking activity and catecholamine secretion proportionally to their density of expression. In vivo phosphorylation of LTCCs by cAMP-PKA and cGMP–PKG, regulate LTCC gating in two opposing ways: the cAMP-PKA pathway potentiates while the cGMP–PKG cascade inhibits LTCCs. Despite this, no attempts have been made to answer three key questions related to the two Cav1 isoforms expressed in MCCs (Cav1.2 and Cav1.3): (i) how much are the two Cav1 channels basally modulated by PKA and PKG?, (ii) to what extent can Cav1.2 and Cav1.3 be further regulated by PKA or PKG activation?, and (iii) are the effects of both kinases cumulative when simultaneously active? Here, by comparing the size of L-type currents of wild-type (WT; Cav1.2+Cav1.3) and Cav1.3−/− KO (Cav1.2) MCCs, we provide new evidence that both PKA and PKG pathways affect Cav1.2 and Cav1.3 to the same extent either under basal conditions or induced stimulation. Inhibition of PKA by H89 (5 μM) reduced the L-type current in WT and KO MCCs by∼60%,while inhibition of PKG by KT 5823 (1 μM) increased by∼40% the same current in both cell types. Given that Cav1.2 and Cav1.3 carry the same quantity of Ca2+ currents, this suggests equal sensitivity of Cav1.2 and Cav1.3 to the two basal modulatory pathways. Maximal stimulation of cAMP–PKA by forskolin (100 μM) and activation of cGMP–PKG by pCPT-cGMP (1mM) uncovered a∼25% increase of L-type currents in the first case and∼65% inhibition in the second case in both WT and KO MCCs, suggesting equal sensitivity of Cav1.2 and Cav1.3 during maximal PKA or PKG stimulation. The effects of PKA and PKG were cumulative and most evident when one pathway was activated and the other was inhibited. The two extreme combinations(PKA activation–PKG inhibition vs. PKG activation-PKA inhibition) varied the size of L-type currents by one order of magnitude (from 180% to 18% of control size). Taken together our data suggest that: (i) Cav1.2 and Cav1.3 are equally sensitive to PKA and PKG action under both basal conditions and maximal stimulation, and (ii) PKA and PKG act independently on both Cav1.2 and Cav1.3, producing cumulative effects when opposingly activated. These extreme Cav1 channel modulations may occur either during high-frequency sympathetic stimulation to sustain prolonged catecholamine release (maximal L-type current) or following activation of the NO–cGMP–PKG signalling pathway (minimal L-type current) to limit the steady release of catecholamines.
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Abstract
BACKGROUND Gabapentin is most commonly prescribed for chronic pain, but acute perioperative effects, including preemptive analgesia and hemodynamic stabilization, have been reported. Adrenal chromaffin cells are a widely used model to investigate neurosecretion, and adrenal catecholamines play important physiologic roles and contribute to the acute stress response. However, the effects of gabapentin on adrenal catecholamine release have never been tested. METHODS Primary cultures of bovine adrenal chromaffin cells were treated with gabapentin or vehicle for 18-24 h. The authors quantified catecholamine secretion from dishes of cells using high-performance liquid chromatography and resolved exocytosis of individual secretory vesicles from single cells using carbon fiber amperometry. Voltage-gated calcium channel currents were recorded using patch clamp electrophysiology and intracellular [Ca2+] using fluorescent imaging. RESULTS Gabapentin produced statistically significant reductions in catecholamine secretion evoked by cholinergic agonists (24 ± 3%, n = 12) or KCl (16 ± 4%, n = 8) (mean ± SEM) but did not inhibit Ca2+ entry or calcium channel currents. Amperometry (n = 51 cells) revealed that gabapentin inhibited the number of vesicles released upon stimulation, with no change in quantal size or kinetics of these unitary events. CONCLUSIONS The authors show Ca2+ entry was not inhibited by gabapentin but was less effective at triggering vesicle fusion. The work also demonstrates that chromaffin cells are a useful model for additional investigation of the cellular mechanism(s) by which gabapentin controls neurosecretion. In addition, it identifies altered adrenal catecholamine release as a potential contributor to some of the beneficial perioperative effects of gabapentin.
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Calcium channel types contributing to chromaffin cell excitability, exocytosis and endocytosis. Cell Calcium 2012; 51:321-30. [DOI: 10.1016/j.ceca.2012.01.005] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2011] [Revised: 01/10/2012] [Accepted: 01/12/2012] [Indexed: 11/18/2022]
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Functional chromaffin cell plasticity in response to stress: focus on nicotinic, gap junction, and voltage-gated Ca2+ channels. J Mol Neurosci 2012; 48:368-86. [PMID: 22252244 DOI: 10.1007/s12031-012-9707-7] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2011] [Accepted: 01/04/2012] [Indexed: 10/14/2022]
Abstract
An increase in circulating catecholamines constitutes one of the mechanisms whereby human body responds to stress. In response to chronic stressful situations, the adrenal medullary tissue exhibits crucial morphological and functional changes that are consistent with an improvement of chromaffin cell stimulus-secretion coupling efficiency. Stimulus-secretion coupling encompasses multiple intracellular (chromaffin cell excitability, Ca(2+) signaling, exocytosis, endocytosis) and intercellular pathways (splanchnic nerve-mediated synaptic transmission, paracrine and endocrine communication, gap junctional coupling), each of them being potentially subjected to functional remodeling upon stress. This review focuses on three chromaffin cell incontrovertible actors, the cholinergic nicotinic receptors and the voltage-dependent T-type Ca(2+) channels that are directly involved in Ca(2+)-dependent events controlling catecholamine secretion and electrical activity, and the gap junctional communication involved in the modulation of catecholamine secretion. We show here that these three actors react differently to various stressors, sometimes independently, sometimes in concert or in opposition.
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Tuckwell HC. Quantitative aspects of L-type Ca2+ currents. Prog Neurobiol 2012; 96:1-31. [DOI: 10.1016/j.pneurobio.2011.09.010] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2010] [Revised: 09/16/2011] [Accepted: 09/23/2011] [Indexed: 12/24/2022]
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Gosso S, Gavello D, Giachello CN, Franchino C, Carbone E, Carabelli V. The effect of CdSe–ZnS quantum dots on calcium currents and catecholamine secretion in mouse chromaffin cells. Biomaterials 2011; 32:9040-50. [DOI: 10.1016/j.biomaterials.2011.08.031] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2011] [Accepted: 08/10/2011] [Indexed: 01/10/2023]
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Mahapatra S, Marcantoni A, Vandael DH, Striessnig J, Carbone E. Are Ca(v)1.3 pacemaker channels in chromaffin cells? Possible bias from resting cell conditions and DHP blockers usage. Channels (Austin) 2011; 5:219-24. [PMID: 21406973 DOI: 10.4161/chan.5.3.15271] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Mouse and rat chromaffin cells (MCCs, RCCs) fire spontaneously at rest and their activity is mainly supported by the two L-type Ca(2+) channels expressed in these cells (Ca(v)1.2 and Ca(v)1.3). Using Ca(v)1.3(-/-) KO MCCs we have shown that Ca(v)1.3 possess all the prerequisites for carrying subthreshold currents that sustain low frequency cell firing near resting (0.5 to 2 Hz at -50 mV): low-threshold and steep voltage dependence of activation, slow and incomplete inactivation during pulses of several hundreds of milliseconds. Ca(v)1.2 contributes also to pacemaking MCCs and possibly even Na(+) channels may participate in the firing of a small percentage of cells. We now show that at potentials near resting (-50 mV), Ca(v)1.3 carries equal amounts of Ca(2+) current to Ca(v)1.2 but activates at 9 mV more negative potentials. MCCs express only TTX-sensitive Na(v)1 channels that activate at 24 mV more positive potentials than Ca(v)1.3 and are fully inactivating. Their blockade prevents the firing only in a small percentage of cells (13%). This suggests that the order of importance with regard to pacemaking MCCs is: Ca(v)1.3, Ca(v)1.2 and Na(v)1. The above conclusions, however, rely on the proper use of DHPs, whose blocking potency is strongly holding potential dependent. We also show that small increases of KCl concentration steadily depolarize the MCCs causing abnormally increased firing frequencies, lowered and broadened AP waveforms and an increased facility of switching "non-firing" into "firing" cells that may lead to erroneous conclusions about the role of Ca(v)1.3 and Ca(v)1.2 as pacemaker channels in MCCs.
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Affiliation(s)
- Satyajit Mahapatra
- Department of Neuroscience, NIS Center, CNISM Research Unit, Torino, Italy
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Gavello D, Vandael DHF, Cesa R, Premoselli F, Marcantoni A, Cesano F, Scarano D, Fubini B, Carbone E, Fenoglio I, Carabelli V. Altered excitability of cultured chromaffin cells following exposure to multi-walled carbon nanotubes. Nanotoxicology 2011; 6:47-60. [DOI: 10.3109/17435390.2011.553294] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
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Pérez-Alvarez A, Hernández-Vivanco A, Caba-González JC, Albillos A. Different roles attributed to Cav1 channel subtypes in spontaneous action potential firing and fine tuning of exocytosis in mouse chromaffin cells. J Neurochem 2010; 116:105-21. [PMID: 21054386 PMCID: PMC7197458 DOI: 10.1111/j.1471-4159.2010.07089.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
J. Neurochem. (2011) 116, 105–121. Abstract This study examines the Cav1 isoforms expressed in mouse chromaffin cells and compares their biophysical properties and roles played in cell excitability and exocytosis. Using immunocytochemical and electrophysiological techniques in mice lacking the Cav1.3α1 subunit (Cav1.3−/−) or the high sensitivity of Cav1.2α1 subunits to dihydropyridines, Cav1.2 and Cav1.3 channels were identified as the only Cav1 channel subtypes expressed in mouse chromaffin cells. Cav1.3 channels were activated at more negative membrane potentials and inactivated more slowly than Cav1.2 channels. Cav1 channels, mainly Cav1.2, control cell excitability by functional coupling to BK channels, revealed by nifedipine blockade of BK channels in wild type (WT) and Cav1.3−/− cells (53% and 35%, respectively), and by the identical change in the shape of the spontaneous action potentials elicited by the dihydropyridine in both strains of mice. Cav1.2 channels also play a major role in spontaneous action potential firing, supported by the following evidence: (i) a similar percentage of WT and Cav1.3−/− cells fired spontaneous action potentials; (ii) firing frequency did not vary between WT and Cav1.3−/− cells; (iii) mostly Cav1.2 channels contributed to the inward current preceding the action potential threshold; and (iv) in the presence of tetrodotoxin, WT or Cav1.3−/− cells exhibited spontaneous oscillatory activity, which was fully abolished by nifedipine perfusion. Finally, Cav1.2 and Cav1.3 channels were essential for controlling the exocytotic process at potentials above and below −10 mV, respectively. Our data reveal the key yet differential roles of Cav1.2 and Cav1.3 channels in mediating action potential firing and exocytotic events in the neuroendocrine chromaffin cell.
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Affiliation(s)
- Alberto Pérez-Alvarez
- Department of Pharmacology and Therapeutics, Faculty of Medicine, Universidad Autónoma de Madrid, Madrid, Spain
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Vandael DH, Marcantoni A, Mahapatra S, Caro A, Ruth P, Zuccotti A, Knipper M, Carbone E. Ca(v)1.3 and BK channels for timing and regulating cell firing. Mol Neurobiol 2010; 42:185-98. [PMID: 21088933 DOI: 10.1007/s12035-010-8151-3] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2010] [Accepted: 11/09/2010] [Indexed: 12/20/2022]
Abstract
L-type Ca(2+) channels (LTCCs, Ca(v)1) open readily during membrane depolarization and allow Ca(2+) to enter the cell. In this way, LTCCs regulate cell excitability and trigger a variety of Ca(2+)-dependent physiological processes such as: excitation-contraction coupling in muscle cells, gene expression, synaptic plasticity, neuronal differentiation, hormone secretion, and pacemaker activity in heart, neurons, and endocrine cells. Among the two major isoforms of LTCCs expressed in excitable tissues (Ca(v)1.2 and Ca(v)1.3), Ca(v)1.3 appears suitable for supporting a pacemaker current in spontaneously firing cells. It has steep voltage dependence and low threshold of activation and inactivates slowly. Using Ca(v)1.3(-/-) KO mice and membrane current recording techniques such as the dynamic and the action potential clamp, it has been possible to resolve the time course of Ca(v)1.3 pacemaker currents that regulate the spontaneous firing of dopaminergic neurons and adrenal chromaffin cells. In several cell types, Ca(v)1.3 is selectively coupled to BK channels within membrane nanodomains and controls both the firing frequency and the action potential repolarization phase. Here we review the most critical aspects of Ca(v)1.3 channel gating and its coupling to large conductance BK channels recently discovered in spontaneously firing neurons and neuroendocrine cells with the aim of furnishing a converging view of the role that these two channel types play in the regulation of cell excitability.
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Affiliation(s)
- David Henry Vandael
- Department of Neuroscience, NIS Centre, CNISM, Corso Raffaello 30, 10125 Turin, Italy
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Loss of Cav1.3 channels reveals the critical role of L-type and BK channel coupling in pacemaking mouse adrenal chromaffin cells. J Neurosci 2010; 30:491-504. [PMID: 20071512 DOI: 10.1523/jneurosci.4961-09.2010] [Citation(s) in RCA: 129] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
We studied wild-type (WT) and Cav1.3(-/-) mouse chromaffin cells (MCCs) with the aim to determine the isoform of L-type Ca(2+) channel (LTCC) and BK channels that underlie the pacemaker current controlling spontaneous firing. Most WT-MCCs (80%) were spontaneously active (1.5 Hz) and highly sensitive to nifedipine and BayK-8644 (1,4-dihydro-2,6-dimethyl-5-nitro-4-[2-(trifluoromethyl)phenyl]-3-pyridinecarboxylic acid, methyl ester). Nifedipine blocked the firing, whereas BayK-8644 increased threefold the firing rate. The two dihydropyridines and the BK channel blocker paxilline altered the shape of action potentials (APs), suggesting close coupling of LTCCs to BK channels. WT-MCCs expressed equal fractions of functionally active Cav1.2 and Cav1.3 channels. Cav1.3 channel deficiency decreased the number of normally firing MCCs (30%; 2.0 Hz), suggesting a critical role of these channels on firing, which derived from their slow inactivation rate, sizeable activation at subthreshold potentials, and close coupling to fast inactivating BK channels as determined by using EGTA and BAPTA Ca(2+) buffering. By means of the action potential clamp, in TTX-treated WT-MCCs, we found that the interpulse pacemaker current was always net inward and dominated by LTCCs. Fast inactivating and non-inactivating BK currents sustained mainly the afterhyperpolarization of the short APs (2-3 ms) and only partially the pacemaker current during the long interspike (300-500 ms). Deletion of Cav1.3 channels reduced drastically the inward Ca(2+) current and the corresponding Ca(2+)-activated BK current during spikes. Our data highlight the role of Cav1.3, and to a minor degree of Cav1.2, as subthreshold pacemaker channels in MCCs and open new interesting features about their role in the control of firing and catecholamine secretion at rest and during sustained stimulations matching acute stress.
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de Diego AMG. Electrophysiological and morphological features underlying neurotransmission efficacy at the splanchnic nerve-chromaffin cell synapse of bovine adrenal medulla. Am J Physiol Cell Physiol 2009; 298:C397-405. [PMID: 19940070 DOI: 10.1152/ajpcell.00440.2009] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The ability of adrenal chromaffin cells to fast-release catecholamines relies on their capacity to fire action potentials (APs). However, little attention has been paid to the requirements needed to evoke the controlled firing of APs. Few data are available in rodents and none on the bovine chromaffin cell, a model extensively used by researchers. The aim of this work was to clarify this issue. Short puffs of acetylcholine (ACh) were fast perifused to current-clamped chromaffin cells and produced the firing of single APs. Based on the currents generated by such ACh applications and previous literature, current waveforms that efficiently elicited APs at frequencies up to 20 Hz were generated. Complex waveforms were also generated by adding simple waveforms with different delays; these waveforms aimed at modeling the stimulation patterns that a chromaffin cell would conceivably undergo upon strong synaptic stimulation. Cholinergic innervation was assessed using the acetylcholinesterase staining technique on the supposition that the innervation pattern is a determinant of the kind of stimuli chromaffin cells can receive. It is concluded that 1) a reliable method to produce frequency-controlled APs by applying defined current injection waveforms is achieved; 2) the APs thus generated have essentially the same features as those spontaneously emitted by the cell and those elicited by fast-ACh perifusion; 3) the higher frequencies attainable peak at around 30 Hz; and 4) the bovine adrenal medulla shows abundant cholinergic innervation, and chromaffin cells show strong acetylcholinesterase staining, consistent with a tight cholinergic presynaptic control of firing frequency.
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Affiliation(s)
- Antonio M G de Diego
- Departamento de Farmacología y Terapéutica, Facultad de Medicina, Instituto Teófilo Hernando, Universidad Autónoma de Madrid, Arzobispo Morcillo, 4, 28029 Madrid, Spain.
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L-type channel inhibition by CB1 cannabinoid receptors is mediated by PTX-sensitive G proteins and cAMP/PKA in GT1-7 hypothalamic neurons. Cell Calcium 2009; 46:303-12. [PMID: 19818494 DOI: 10.1016/j.ceca.2009.08.007] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2009] [Accepted: 08/31/2009] [Indexed: 12/31/2022]
Abstract
Using immortalized hypothalamic GT1-7 neurons, which express the CB1 cannabinoid receptor (CB1R) and three Ca2+ channel types (T, R and L), we found that the CB1R agonist WIN 55,212-2 inhibited the voltage-gated Ca2+ currents by about 35%. The inhibition by WIN 55,212-2 (10 microM) was reversible and prevented by nifedipine (3 microM), suggesting a selective action on L-type Ca2+ channels (LTCCs). WIN 55,212-2 action exhibited all the features of voltage-independent Ca2+ channel modulation: (1) no changes of the activation kinetics, (2) equal depressive action at all potentials and (3) no facilitation following strong prepulses. At variance with WIN 55,212-2, the CB1R inverse agonist AM-251 (10 microM) caused 20% increase of Ca2+ currents. The inhibition of LTCCs by WIN 55,212-2 was prevented by overnight PTX-incubation and by intracellular perfusion with GDP-beta-S. The latter caused also a 20% Ca2+ current up-regulation. WIN 55,212-2 action was also prevented by application of the PKA-blocker H89 or by loading the neurons with 8-CPT-cAMP. Our results suggest that LTCCs in GT1-7 neurons are partially inhibited at rest due to a constitutive CB1R activity removed by AM-251 and GDP-beta-S. Activation of CB1R via PTX-sensitive G proteins and cAMP/PKA pathway selectively depresses LTCCs that critically control the synchronized spontaneous firing and pulsatile release of gonadotropin-releasing hormone in GT1-7 neurons.
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