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Geisler SM, Ottaviani MM, Jacobo-Piqueras N, Theiner T, Mastrolia V, Guarina L, Ebner K, Obermair GJ, Carbone E, Tuluc P. Deletion of the α 2δ-1 calcium channel subunit increases excitability of mouse chromaffin cells. J Physiol 2024. [PMID: 39004870 DOI: 10.1113/jp285681] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2023] [Accepted: 06/26/2024] [Indexed: 07/16/2024] Open
Abstract
High voltage-gated Ca2+ channels (HVCCs) shape the electrical activity and control hormone release in most endocrine cells. HVCCs are multi-subunit protein complexes formed by the pore-forming α1 and the auxiliary β, α2δ and γ subunits. Four genes code for the α2δ isoforms. At the mRNA level, mouse chromaffin cells (MCCs) express predominantly the CACNA2D1 gene coding for the α2δ-1 isoform. Here we show that α2δ-1 deletion led to ∼60% reduced HVCC Ca2+ influx with slower inactivation kinetics. Pharmacological dissection showed that HVCC composition remained similar in α2δ-1-/- MCCs compared to wild-type (WT), demonstrating that α2δ-1 exerts similar functional effects on all HVCC isoforms. Consistent with reduced HVCC Ca2+ influx, α2δ-1-/- MCCs showed reduced spontaneous electrical activity with action potentials (APs) having a shorter half-maximal duration caused by faster rising and decay slopes. However, the induced electrical activity showed opposite effects with α2δ-1-/- MCCs displaying significantly higher AP frequency in the tonic firing mode as well as an increase in the number of cells firing AP bursts compared to WT. This gain-of-function phenotype was caused by reduced functional activation of Ca2+-dependent K+ currents. Additionally, despite the reduced HVCC Ca2+ influx, the intracellular Ca2+ transients and vesicle exocytosis or endocytosis were unaltered in α2δ-1-/- MCCs compared to WT during sustained stimulation. In conclusion, our study shows that α2δ-1 genetic deletion reduces Ca2+ influx in cultured MCCs but leads to a paradoxical increase in catecholamine secretion due to increased excitability. KEY POINTS: Deletion of the α2δ-1 high voltage-gated Ca2+ channel (HVCC) subunit reduces mouse chromaffin cell (MCC) Ca2+ influx by ∼60% but causes a paradoxical increase in induced excitability. MCC intracellular Ca2+ transients are unaffected by the reduced HVCC Ca2+ influx. Deletion of α2δ-1 reduces the immediately releasable pool vesicle exocytosis but has no effect on catecholamine (CA) release in response to sustained stimuli. The increased electrical activity and CA release from MCCs might contribute to the previously reported cardiovascular phenotype of patients carrying α2δ-1 loss-of-function mutations.
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Affiliation(s)
- Stefanie M Geisler
- Department of Pharmacology and Toxicology, Centre for Molecular Biosciences, University of Innsbruck, Innsbruck, Austria
| | - Matteo M Ottaviani
- Department of Drug Science, NIS Centre, University of Torino, Torino, Italy
| | - Noelia Jacobo-Piqueras
- Department of Pharmacology and Toxicology, Centre for Molecular Biosciences, University of Innsbruck, Innsbruck, Austria
| | - Tamara Theiner
- Department of Pharmacology and Toxicology, Centre for Molecular Biosciences, University of Innsbruck, Innsbruck, Austria
| | - Vincenzo Mastrolia
- Department of Pharmacology and Toxicology, Centre for Molecular Biosciences, University of Innsbruck, Innsbruck, Austria
| | - Laura Guarina
- Department of Drug Science, NIS Centre, University of Torino, Torino, Italy
| | - Karl Ebner
- Department of Pharmacology and Toxicology, Centre for Molecular Biosciences, University of Innsbruck, Innsbruck, Austria
| | - Gerald J Obermair
- Division of Physiology, Karl Landsteiner University of Health Sciences, Krems, Austria
| | - Emilio Carbone
- Department of Drug Science, NIS Centre, University of Torino, Torino, Italy
| | - Petronel Tuluc
- Department of Pharmacology and Toxicology, Centre for Molecular Biosciences, University of Innsbruck, Innsbruck, Austria
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Yun SH, Mansurov V, Yang L, Yoon J, Leblanc N, Craviso GL, Zaklit J. Modulating Ca 2+ influx into adrenal chromaffin cells with short-duration nanosecond electric pulses. Biophys J 2024:S0006-3495(24)00418-1. [PMID: 38909279 DOI: 10.1016/j.bpj.2024.06.021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2023] [Revised: 05/07/2024] [Accepted: 06/20/2024] [Indexed: 06/24/2024] Open
Abstract
Isolated bovine adrenal chromaffin cells exposed to single 2-, 4-, or 5-ns pulses undergo a rapid, transient rise in intracellular Ca2+ mediated by Ca2+ entry via voltage-gated Ca2+ channels (VGCCs), mimicking the activation of these cells in vivo by acetylcholine. However, pulse durations 150 ns or longer elicit larger amplitude and longer-lived Ca2+ responses due to Ca2+ influx via both VGCCs and a yet to be identified plasma membrane pathway(s). To further our understanding of the differential effects of ultrashort versus longer pulse durations on Ca2+ influx, chromaffin cells were loaded with calcium green-1 and exposed to single 3-, 5-, 11-, 25-, or 50-ns pulses applied at their respective Ca2+ activation threshold electric fields. Increasing pulse duration from 3 or 5 ns to only 11 ns was sufficient to elicit increased amplitude and longer-lived Ca2+ responses in the majority of cells, a trend that continued as pulse duration increased to 50 ns. The amplification of Ca2+ responses was not the result of Ca2+ release from intracellular stores and was accompanied by a decreased effectiveness of VGCC inhibitors to block the responses and a reduced reliance on extracellular Na+ and membrane depolarization to evoke the responses. Inhibitors of pannexin channels, P2X receptors, or non-selective cation channels failed to attenuate 50-ns-elicited Ca2+ responses, ruling out these Ca2+-permeable channels as secondary Ca2+ entry pathways. Analytical calculations and numerical modeling suggest that the parameter that best determines the response of chromaffin cells to increasing pulse durations is the time the membrane charges to its peak voltage. These results highlight the pronounced sensitivity of a neuroendocrine cell to pulse durations differing by only tens of nanoseconds, which has important implications for the future development of nanosecond pulse technologies enabling electrostimulation applications for spatially focused and graded in vivo neuromodulation.
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Affiliation(s)
- Sung Hae Yun
- Department of Electrical and Biomedical Engineering, College of Engineering, University of Nevada, Reno, Nevada
| | - Vasilii Mansurov
- Department of Electrical and Biomedical Engineering, College of Engineering, University of Nevada, Reno, Nevada
| | - Lisha Yang
- Department of Pharmacology, University of Nevada, Reno School of Medicine, Reno, Nevada
| | - Jihwan Yoon
- Department of Electrical and Biomedical Engineering, College of Engineering, University of Nevada, Reno, Nevada
| | - Normand Leblanc
- Department of Pharmacology, University of Nevada, Reno School of Medicine, Reno, Nevada
| | - Gale L Craviso
- Department of Pharmacology, University of Nevada, Reno School of Medicine, Reno, Nevada
| | - Josette Zaklit
- Department of Electrical and Biomedical Engineering, College of Engineering, University of Nevada, Reno, Nevada.
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3
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Carretero VJ, Liccardi N, Tejedor MA, de Pascual R, Campano JH, Hernández-Guijo JM. Lead exerts a depression of neurotransmitter release through a blockade of voltage dependent calcium channels in chromaffin cells. Toxicology 2024; 505:153809. [PMID: 38648961 DOI: 10.1016/j.tox.2024.153809] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2024] [Revised: 04/08/2024] [Accepted: 04/17/2024] [Indexed: 04/25/2024]
Abstract
The present work, using chromaffin cells of bovine adrenal medullae (BCCs), aims to describe what type of ionic current alterations induced by lead (Pb2+) underlies its effects reported on synaptic transmission. We observed that the acute application of Pb2+ lead to a drastic depression of neurotransmitters release in a concentration-dependent manner when the cells were stimulated with both K+ or acetylcholine, with an IC50 of 119,57 μM and of 5,19 μM, respectively. This effect was fully recovered after washout. Pb2+ also blocked calcium channels of BCCs in a time- and concentration-dependent manner with an IC50 of 6,87 μM. This blockade was partially reversed upon washout. This compound inhibited the calcium current at all test potentials and shows a shift of the I-V curve to more negative values of about 8 mV. The sodium current was not blocked by acute application of high Pb2+ concentrations. Voltage-dependent potassium current was also shortly affected by high Pb2+. Nevertheless, the calcium- and voltage-dependent potassium current was drastically depressed in a dose-dependent manner, with an IC50 of 24,49 μM. This blockade was related to the prevention of Ca2+ influx through voltage-dependent calcium channels coupled to Ca2+-activated K+-channels (BK) instead a direct linking to these channels. Under current-clamp conditions, BCCs exhibit a resting potential of -52.7 mV, firing spontaneous APs (1-2 spikes/s) generated by the opening of Na+ and Ca2+-channels, and terminated by the activation of K+ channels. In spite of the effect on ionic channels exerted by Pb2+, we found that Pb2+ didn't alter cellular excitability, no modification of the membrane potential, and no effect on action potential firing. Taken together, these results point to a neurotoxic action evoked by Pb2+ that is associated with changes in neurotransmitter release by blocking the ionic currents responsible for the calcium influx.
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Affiliation(s)
- Victoria Jiménez Carretero
- Department of Pharmacology and Therapeutic, Facultad de Medicina, Univ. Autónoma de Madrid, Av. Arzobispo Morcillo 4, Madrid 28029, Spain
| | - Ninfa Liccardi
- Department of Pharmacology and Therapeutic, Facultad de Medicina, Univ. Autónoma de Madrid, Av. Arzobispo Morcillo 4, Madrid 28029, Spain
| | - Maria Arribas Tejedor
- Department of Pharmacology and Therapeutic, Facultad de Medicina, Univ. Autónoma de Madrid, Av. Arzobispo Morcillo 4, Madrid 28029, Spain
| | - Ricardo de Pascual
- Department of Pharmacology and Therapeutic, Facultad de Medicina, Univ. Autónoma de Madrid, Av. Arzobispo Morcillo 4, Madrid 28029, Spain
| | - Jorge Hernández Campano
- Department of Pharmacology and Therapeutic, Facultad de Medicina, Univ. Autónoma de Madrid, Av. Arzobispo Morcillo 4, Madrid 28029, Spain
| | - Jesús M Hernández-Guijo
- Department of Pharmacology and Therapeutic, Facultad de Medicina, Univ. Autónoma de Madrid, Av. Arzobispo Morcillo 4, Madrid 28029, Spain; Ramón y Cajal Institute for Health Research, IRYCIS, Hospital Ramón y Cajal, Ctra. de Colmenar Viejo, Km. 9,100, Madrid 28029, Spain.
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Borges JI, Ferraino KE, Cora N, Nagliya D, Suster MS, Carbone AM, Lymperopoulos A. Adrenal G Protein-Coupled Receptors and the Failing Heart: A Long-distance, Yet Intimate Affair. J Cardiovasc Pharmacol 2022; 80:386-392. [PMID: 34983911 PMCID: PMC9294064 DOI: 10.1097/fjc.0000000000001213] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/30/2021] [Accepted: 12/11/2021] [Indexed: 01/31/2023]
Abstract
ABSTRACT Systolic heart failure (HF) is a chronic clinical syndrome characterized by the reduction in cardiac function and still remains the disease with the highest mortality worldwide. Despite considerable advances in pharmacological treatment, HF represents a severe clinical and social burden. Chronic human HF is characterized by several important neurohormonal perturbations, emanating from both the autonomic nervous system and the adrenal glands. Circulating catecholamines (norepinephrine and epinephrine) and aldosterone elevations are among the salient alterations that confer significant hormonal burden on the already compromised function of the failing heart. This is why sympatholytic treatments (such as β-blockers) and renin-angiotensin system inhibitors or mineralocorticoid receptor antagonists, which block the effects of angiotensin II (AngII) and aldosterone on the failing heart, are part of the mainstay HF pharmacotherapy presently. The adrenal gland plays an important role in the modulation of cardiac neurohormonal stress because it is the source of almost all aldosterone, of all epinephrine, and of a significant amount of norepinephrine reaching the failing myocardium from the blood circulation. Synthesis and release of these hormones in the adrenals is tightly regulated by adrenal G protein-coupled receptors (GPCRs), such as adrenergic receptors and AngII receptors. In this review, we discuss important aspects of adrenal GPCR signaling and regulation, as they pertain to modulation of cardiac function in the context of chronic HF, by focusing on the 2 best studied adrenal GPCR types in that context, adrenergic receptors and AngII receptors (AT 1 Rs). Particular emphasis is given to findings from the past decade and a half that highlight the emerging roles of the GPCR-kinases and the β-arrestins in the adrenals, 2 protein families that regulate the signaling and functioning of GPCRs in all tissues, including the myocardium and the adrenal gland.
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Affiliation(s)
- Jordana I. Borges
- Laboratory for the Study of Neurohormonal Control of the Circulation, Department of Pharmaceutical Sciences, Nova Southeastern University, Fort Lauderdale, FL 33328-2018, USA
| | - Krysten E. Ferraino
- Laboratory for the Study of Neurohormonal Control of the Circulation, Department of Pharmaceutical Sciences, Nova Southeastern University, Fort Lauderdale, FL 33328-2018, USA
| | - Natalie Cora
- Laboratory for the Study of Neurohormonal Control of the Circulation, Department of Pharmaceutical Sciences, Nova Southeastern University, Fort Lauderdale, FL 33328-2018, USA
| | - Deepika Nagliya
- Laboratory for the Study of Neurohormonal Control of the Circulation, Department of Pharmaceutical Sciences, Nova Southeastern University, Fort Lauderdale, FL 33328-2018, USA
| | - Malka S. Suster
- Laboratory for the Study of Neurohormonal Control of the Circulation, Department of Pharmaceutical Sciences, Nova Southeastern University, Fort Lauderdale, FL 33328-2018, USA
| | - Alexandra M. Carbone
- Laboratory for the Study of Neurohormonal Control of the Circulation, Department of Pharmaceutical Sciences, Nova Southeastern University, Fort Lauderdale, FL 33328-2018, USA
| | - Anastasios Lymperopoulos
- Laboratory for the Study of Neurohormonal Control of the Circulation, Department of Pharmaceutical Sciences, Nova Southeastern University, Fort Lauderdale, FL 33328-2018, USA
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5
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Yang L, Pierce S, Gould TW, Craviso GL, Leblanc N. Ultrashort nanosecond electric pulses activate a conductance in bovine adrenal chromaffin cells that involves cation entry through TRPC and NALCN channels. Arch Biochem Biophys 2022; 723:109252. [DOI: 10.1016/j.abb.2022.109252] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2021] [Revised: 03/25/2022] [Accepted: 04/12/2022] [Indexed: 12/14/2022]
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Sodium background currents in endocrine/neuroendocrine cells: Towards unraveling channel identity and contribution in hormone secretion. Front Neuroendocrinol 2021; 63:100947. [PMID: 34592201 DOI: 10.1016/j.yfrne.2021.100947] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Revised: 09/03/2021] [Accepted: 09/23/2021] [Indexed: 02/04/2023]
Abstract
In endocrine/neuroendocrine tissues, excitability of secretory cells is patterned by the repertoire of ion channels and there is clear evidence that extracellular sodium (Na+) ions contribute to hormone secretion. While voltage-gated channels involved in action potential generation are well-described, the background 'leak' channels operating near the resting membrane potential are much less known, and in particular the channels supporting a background entry of Na+ ions. These background Na+ currents (called here 'INab') have the ability to modulate the resting membrane potential and subsequently affect action potential firing. Here we compile and analyze the data collected from three endocrine/neuroendocrine tissues: the anterior pituitary gland, the adrenal medulla and the endocrine pancreas. We also model how INab can be functionally involved in cellular excitability. Finally, towards deciphering the physiological role of INab in endocrine/neuroendocrine cells, its implication in hormone release is also discussed.
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7
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Carbone E. Fast inactivation of Nav1.3 channels by FGF14 proteins: An unconventional way to regulate the slow firing of adrenal chromaffin cells. J Gen Physiol 2021; 153:211934. [PMID: 33792614 PMCID: PMC8020463 DOI: 10.1085/jgp.202112879] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Using Nav1.3 and FGF14 KO mice, Martinez-Espinosa et al. provide new findings on how intracellular FGF14 proteins interfere with the endogenous fast inactivation gating and regulate the “long-term inactivation” of Nav1.3 channels that sets Nav channel availability and spike adaptation during sustained stimulation in adrenal chromaffin cells.
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Affiliation(s)
- Emilio Carbone
- Department of Drug Science, Lab of Cell Physiology and Molecular Neuroscience, University of Torino, Torino, Italy
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8
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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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Montenegro M, Bayonés L, Moya-Díaz J, Borassi C, Martín Toscani A, Gallo LI, Marengo FD. Rapid vesicle replenishment after the immediately releasable pool exocytosis is tightly linked to fast endocytosis, and depends on basal calcium and cortical actin in chromaffin cells. J Neurochem 2021; 157:1069-1085. [PMID: 33338257 DOI: 10.1111/jnc.15276] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Revised: 11/25/2020] [Accepted: 12/12/2020] [Indexed: 01/06/2023]
Abstract
The maintenance of the secretory response requires a continuous replenishment of releasable vesicles. It was proposed that the immediately releasable pool (IRP) is important in chromaffin cell secretion during action potentials applied at basal physiological frequencies, because of the proximity of IRP vesicles to voltage-dependent Ca2+ channels. However, previous reports showed that IRP replenishment after depletion is too slow to manage such a situation. In this work, we used patch-clamp measurements of membrane capacitance, confocal imaging of F-actin distribution, and cytosolic Ca2+ measurements with Fura-2 to re-analyze this problem in primary cultures of mouse chromaffin cells. We provide evidence that IRP replenishment has one slow (time constant between 5 and 10 s) and one rapid component (time constant between 0.5 and 1.5 s) linked to a dynamin-dependent fast endocytosis. Both, the fast endocytosis and the rapid replenishment component were eliminated when 500 nM Ca2+ was added to the internal solution during patch-clamp experiments, but they became dominant and accelerated when the cytosolic Ca2+ buffer capacity was increased. In addition, both rapid replenishment and fast endocytosis were retarded when cortical F-actin cytoskeleton was disrupted with cytochalasin D. Finally, in permeabilized chromaffin cells stained with rhodamine-phalloidin, the cortical F-actin density was reduced when the Ca2+ concentration was increased in a range of 10-1000 nM. We conclude that low cytosolic Ca2+ concentrations, which favor cortical F-actin stabilization, allow the activation of a fast endocytosis mechanism linked to a rapid replenishment component of IRP.
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Affiliation(s)
- Mauricio Montenegro
- Instituto de Fisiología, Biología Molecular y Neurociencias (IFIByNE). CONICET, Departamento de Fisiología y Biología Molecular y Celular. Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Lucas Bayonés
- Instituto de Fisiología, Biología Molecular y Neurociencias (IFIByNE). CONICET, Departamento de Fisiología y Biología Molecular y Celular. Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - José Moya-Díaz
- Instituto de Fisiología, Biología Molecular y Neurociencias (IFIByNE). CONICET, Departamento de Fisiología y Biología Molecular y Celular. Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina.,School of Life Sciences, University of Sussex, Brighton, UK
| | - Cecilia Borassi
- Fundación Instituto Leloir, Instituto de Investigaciones Bioquímicas de Buenos Aires (IIBBA), CONICET, Buenos Aires, Argentina
| | - Andrés Martín Toscani
- Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales (IQUIBICEN). CONICET, Departamento de Química Biológica. Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina.,Instituto de Investigaciones Bioquímicas de La Plata (INIBIOLP), Centro Científico Tecnológico -, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), La Plata, Argentina
| | - Luciana I Gallo
- Instituto de Fisiología, Biología Molecular y Neurociencias (IFIByNE). CONICET, Departamento de Fisiología y Biología Molecular y Celular. Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Fernando D Marengo
- Instituto de Fisiología, Biología Molecular y Neurociencias (IFIByNE). CONICET, Departamento de Fisiología y Biología Molecular y Celular. Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina
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Abstract
Kv7.1-Kv7.5 (KCNQ1-5) K+ channels are voltage-gated K+ channels with major roles in neurons, muscle cells and epithelia where they underlie physiologically important K+ currents, such as neuronal M current and cardiac IKs. Specific biophysical properties of Kv7 channels make them particularly well placed to control the activity of excitable cells. Indeed, these channels often work as 'excitability breaks' and are targeted by various hormones and modulators to regulate cellular activity outputs. Genetic deficiencies in all five KCNQ genes result in human excitability disorders, including epilepsy, arrhythmias, deafness and some others. Not surprisingly, this channel family attracts considerable attention as potential drug targets. Here we will review biophysical properties and tissue expression profile of Kv7 channels, discuss recent advances in the understanding of their structure as well as their role in various neurological, cardiovascular and other diseases and pathologies. We will also consider a scope for therapeutic targeting of Kv7 channels for treatment of the above health conditions.
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11
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Moya‐Díaz J, Bayonés L, Montenegro M, Cárdenas AM, Koch H, Doi A, Marengo FD. Ca 2+ -independent and voltage-dependent exocytosis in mouse chromaffin cells. Acta Physiol (Oxf) 2020; 228:e13417. [PMID: 31769918 DOI: 10.1111/apha.13417] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2019] [Revised: 11/19/2019] [Accepted: 11/20/2019] [Indexed: 12/11/2022]
Abstract
AIM It is widely accepted that the exocytosis of synaptic and secretory vesicles is triggered by Ca2+ entry through voltage-dependent Ca2+ channels. However, there is evidence of an alternative mode of exocytosis induced by membrane depolarization but lacking Ca2+ current and intracellular Ca2+ increase. In this work we investigated if such a mechanism contributes to secretory vesicle exocytosis in mouse chromaffin cells. METHODS Exocytosis was evaluated by patch-clamp membrane capacitance measurements, carbon fibre amperometry and TIRF. Cytosolic Ca2+ was estimated using epifluorescence microscopy and fluo-8 (salt form). RESULTS Cells stimulated by brief depolatizations in absence of extracellular Ca+2 show moderate but consistent exocytosis, even in presence of high cytosolic BAPTA concentration and pharmacological inhibition of Ca+2 release from intracellular stores. This exocytosis is tightly dependent on membrane potential, is inhibited by neurotoxin Bont-B (cleaves the v-SNARE synaptobrevin), is very fast (saturates with time constant <10 ms), it is followed by a fast endocytosis sensitive to the application of an anti-dynamin monoclonal antibody, and recovers after depletion in <5 s. Finally, this exocytosis was inhibited by: (i) ω-agatoxin IVA (blocks P/Q-type Ca2+ channel gating), (ii) in cells from knock-out P/Q-type Ca2+ channel mice, and (iii) transfection of free synprint peptide (interferes in P/Q channel-exocytic proteins association). CONCLUSION We demonstrated that Ca2+ -independent and voltage-dependent exocytosis is present in chromaffin cells. This process is tightly coupled to membrane depolarization, and is able to support secretion during action potentials at low basal rates. P/Q-type Ca2+ channels can operate as voltage sensors of this process.
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Affiliation(s)
- José Moya‐Díaz
- Instituto de Fisiología, Biología Molecular y Neurociencias Departamento de Fisiología y Biología Molecular y Celular Facultad de Ciencias Exactas y Naturales Universidad de Buenos AiresConsejo Nacional de Investigaciones Científicas y Técnicas Buenos Aires Argentina
| | - Lucas Bayonés
- Instituto de Fisiología, Biología Molecular y Neurociencias Departamento de Fisiología y Biología Molecular y Celular Facultad de Ciencias Exactas y Naturales Universidad de Buenos AiresConsejo Nacional de Investigaciones Científicas y Técnicas Buenos Aires Argentina
| | - Mauricio Montenegro
- Instituto de Fisiología, Biología Molecular y Neurociencias Departamento de Fisiología y Biología Molecular y Celular Facultad de Ciencias Exactas y Naturales Universidad de Buenos AiresConsejo Nacional de Investigaciones Científicas y Técnicas Buenos Aires Argentina
| | - Ana M. Cárdenas
- Centro Interdisciplinario de Neurociencia de Valparaíso Facultad de Ciencias Universidad de Valparaíso Valparaíso Chile
| | - Henner Koch
- Center for Integrative Brain Research Seattle Children's Research Institute Seattle WA USA
- Department of Neurology and Epileptology Hertie‐Institute for Clinical Brain ResearchUniversity of Tübingen Tübingen Germany
| | - Atsushi Doi
- Department of Rehabilitation Graduate School of Health Science Kumamoto Health Science University Kumamoto Japan
| | - Fernando D. Marengo
- Instituto de Fisiología, Biología Molecular y Neurociencias Departamento de Fisiología y Biología Molecular y Celular Facultad de Ciencias Exactas y Naturales Universidad de Buenos AiresConsejo Nacional de Investigaciones Científicas y Técnicas Buenos Aires Argentina
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12
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Yang L, Fomina AF. Ca 2+ influx and clearance at hyperpolarized membrane potentials modulate spontaneous and stimulated exocytosis in neuroendocrine cells. Cell Calcium 2020; 87:102184. [PMID: 32151786 DOI: 10.1016/j.ceca.2020.102184] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2019] [Revised: 02/10/2020] [Accepted: 02/21/2020] [Indexed: 01/09/2023]
Abstract
Neuroendocrine adrenal chromaffin cells release neurohormones catecholamines in response to Ca2+ entry via voltage-gated Ca2+ channels (VGCCs). Adrenal chromaffin cells also express non-voltage-gated channels, which may conduct Ca2+ at negative membrane potentials, whose role in regulation of exocytosis is poorly understood. We explored how modulation of Ca2+ influx at negative membrane potentials affects basal cytosolic Ca2+ concentration ([Ca2+]i) and exocytosis in metabolically intact voltage-clamped bovine adrenal chromaffin cells. We found that in these cells, Ca2+ entry at negative membrane potentials is balanced by Ca2+ extrusion by the Na+/Ca2+ exchanger and that this balance can be altered by membrane hyperpolarization or stimulation with an inflammatory hormone bradykinin. Membrane hyperpolarization or application of bradykinin augmented Ca2+-carrying current at negative membrane potentials, elevated basal [Ca2+]i, and facilitated synchronous exocytosis evoked by the small amounts of Ca2+ injected into the cell via VGCCs (up to 20 pC). Exocytotic responses evoked by the injections of the larger amounts of Ca2+ via VGCCs (> 20 pC) were suppressed by preceding hyperpolarization. In the absence of Ca2+ entry via VGCCs and Ca2+ extrusion via the Na+/Ca2+ exchanger, membrane hyperpolarization induced a significant elevation in [Ca2+]i and asynchronous exocytosis. Our results indicate that physiological interferences, such as membrane hyperpolarization and/or activation of non-voltage-gated Ca2+ channels, modulate basal [Ca2+]i and, consequently, segregation of exocytotic vesicles and their readiness to be released spontaneously and in response to Ca2+ entry via VGCCs. These mechanisms may play role in homeostatic plasticity of neuronal and endocrine cells.
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Affiliation(s)
- Lukun Yang
- Department of Physiology and Membrane Biology, University of California, Davis, Davis, CA, 95616, USA; Department of Anesthesiology, The 5th Affiliated Hospital of SUN YAT-SEN University, Zhuhai, 519000, China.
| | - Alla F Fomina
- Department of Physiology and Membrane Biology, University of California, Davis, Davis, CA, 95616, USA.
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13
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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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14
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Byron KL, Brueggemann LI. Kv7 potassium channels as signal transduction intermediates in the control of microvascular tone. Microcirculation 2018; 25. [PMID: 28976052 DOI: 10.1111/micc.12419] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2017] [Accepted: 09/27/2017] [Indexed: 12/18/2022]
Abstract
Potassium channels are recognized as important regulators of cellular functions in most, if not all cell types. These cellular proteins assemble to form gated pores in the plasma membrane, which serve to regulate the flow of potassium ions (K+ ) from the cytosol to the extracellular space. In VSMCs, the open state of potassium channels enables the efflux of K+ and thereby establishes a negative resting voltage across the plasma membrane that inhibits the opening of VSCCs. Under these conditions, cytosolic Ca2+ concentrations are relatively low and Ca2+ -dependent contraction is inhibited. Recent research has identified Kv7 family potassium channels as important contributors to resting membrane voltage in VSMCs, with much of the research focusing on the effects of drugs that specifically activate or block these channels to produce corresponding effects on VSMC contraction and vascular tone. Increasingly, evidence is emerging that these channels are not just good drug targets-they are also essential intermediates in vascular signal transduction, mediating vasoconstrictor or vasodilator responses to a variety of physiological stimuli. This review will summarize recent research findings that support a crucial function of Kv7 channels in both positive (vasoconstrictive) and negative (vasorelaxant) regulation of microvascular tone.
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Affiliation(s)
- Kenneth L Byron
- Department of Molecular Pharmacology & Therapeutics, Loyola University Chicago, Maywood, IL, USA
| | - Lyubov I Brueggemann
- Department of Molecular Pharmacology & Therapeutics, Loyola University Chicago, Maywood, IL, USA
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15
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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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16
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Harada K, Matsuoka H, Inoue M. Expression and regulation of M-type K+ channel in PC12 cells and rat adrenal medullary cells. Cell Tissue Res 2018; 372:457-468. [DOI: 10.1007/s00441-018-2809-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2017] [Accepted: 01/24/2018] [Indexed: 11/30/2022]
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17
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Roles of Na +, Ca 2+, and K + channels in the generation of repetitive firing and rhythmic bursting in adrenal chromaffin cells. Pflugers Arch 2017; 470:39-52. [PMID: 28776261 DOI: 10.1007/s00424-017-2048-1] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2017] [Accepted: 07/23/2017] [Indexed: 12/30/2022]
Abstract
Adrenal chromaffin cells (CCs) are the main source of circulating catecholamines (CAs) that regulate the body response to stress. Release of CAs is controlled neurogenically by the activity of preganglionic sympathetic neurons through trains of action potentials (APs). APs in CCs are generated by robust depolarization following the activation of nicotinic and muscarinic receptors that are highly expressed in CCs. Bovine, rat, mouse, and human CCs also express a composite array of Na+, K+, and Ca2+ channels that regulate the resting potential, shape the APs, and set the frequency of AP trains. AP trains of increasing frequency induce enhanced release of CAs. If the primary role of CCs is simply to relay preganglionic nerve commands to CA secretion, why should they express such a diverse set of ion channels? An answer to this comes from recent observations that, like in neurons, CCs undergo complex firing patterns of APs suggesting the existence of an intrinsic CC excitability (non-neurogenically controlled). Recent work has shown that CCs undergo occasional or persistent burst firing elicited by altered physiological conditions or deletion of pore-regulating auxiliary subunits. In this review, we aim to give a rationale to the role of the many ion channel types regulating CC excitability. We will first describe their functional properties and then analyze how they contribute to pacemaking, AP shape, and burst waveforms. We will also furnish clear indications on missing ion conductances that may be involved in pacemaking and highlight the contribution of the crucial channels involved in burst firing.
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18
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Muscarinic receptors in adrenal chromaffin cells: physiological role and regulation of ion channels. Pflugers Arch 2017; 470:29-38. [DOI: 10.1007/s00424-017-2047-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2017] [Revised: 07/21/2017] [Accepted: 07/23/2017] [Indexed: 10/19/2022]
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19
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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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20
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Lymperopoulos A, Brill A, McCrink KA. GPCRs of adrenal chromaffin cells & catecholamines: The plot thickens. Int J Biochem Cell Biol 2016; 77:213-9. [PMID: 26851510 DOI: 10.1016/j.biocel.2016.02.003] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2015] [Revised: 02/01/2016] [Accepted: 02/02/2016] [Indexed: 12/14/2022]
Abstract
The circulating catecholamines (CAs) epinephrine (Epi) and norepinephrine (NE) derive from two major sources in the whole organism: the sympathetic nerve endings, which release NE on effector organs, and the chromaffin cells of the adrenal medulla, which are cells that synthesize, store and release Epi (mainly) and NE. All of the Epi in the body and a significant amount of circulating NE derive from the adrenal medulla. The secretion of CAs from adrenal chromaffin cells is regulated in a complex way by a variety of membrane receptors, the vast majority of which are G protein-coupled receptors (GPCRs), including adrenergic receptors (ARs), which act as "presynaptic autoreceptors" in this regard. There is a plethora of CA-secretagogue signals acting on these receptors but some of them, most notably the α2ARs, inhibit CA secretion. Over the past few years, however, a few new proteins present in chromaffin cells have been uncovered to participate in CA secretion regulation. Most prominent among these are GRK2 and β-arrestin1, which are known to interact with GPCRs regulating receptor signaling and function. The present review will discuss the molecular and signaling mechanisms by which adrenal chromaffin cell-residing GPCRs and their regulatory proteins modulate CA synthesis and secretion. Particular emphasis will be given to the newly discovered roles of GRK2 and β-arrestins in these processes and particular points of focus for future research will be highlighted, as well.
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Affiliation(s)
- Anastasios Lymperopoulos
- From the Laboratory for the Study of Neurohormonal Control of the Circulation, Department of Pharmaceutical Sciences, Nova Southeastern University, College of Pharmacy, 3200 S. University Dr., Fort Lauderdale, FL 33328-2018, USA.
| | - Ava Brill
- From the Laboratory for the Study of Neurohormonal Control of the Circulation, Department of Pharmaceutical Sciences, Nova Southeastern University, College of Pharmacy, 3200 S. University Dr., Fort Lauderdale, FL 33328-2018, USA
| | - Katie A McCrink
- From the Laboratory for the Study of Neurohormonal Control of the Circulation, Department of Pharmaceutical Sciences, Nova Southeastern University, College of Pharmacy, 3200 S. University Dr., Fort Lauderdale, FL 33328-2018, USA
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21
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Podvin S, Bundey R, Toneff T, Ziegler M, Hook V. Profiles of secreted neuropeptides and catecholamines illustrate similarities and differences in response to stimulation by distinct secretagogues. Mol Cell Neurosci 2015; 68:177-85. [PMID: 26092702 DOI: 10.1016/j.mcn.2015.06.008] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2015] [Revised: 05/12/2015] [Accepted: 06/01/2015] [Indexed: 12/20/2022] Open
Abstract
The goal of this study was to define profiles of secreted neuropeptide and catecholamine neurotransmitters that undergo co-release from sympathoadrenal chromaffin cells upon stimulation by distinct secretagogues. Chromaffin cells of the adrenal medulla participate in the dynamic responses to stress, especially that of 'fight and flight', and, thus, analyses of the co-release of multiple neurotransmitters is necessary to gain knowledge of how the stress response regulates cell-cell communication among physiological systems. Results of this study demonstrated that six different secretagogues stimulated the co-release of the neuropeptides Met-enkephalin, galanin, NPY, and VIP with the catecholamines dopamine, norepinephrine, and epinephrine. Importantly, the quantitative profiles of the secreted neurotransmitters showed similarities and differences upon stimulation by the different secretagogues evaluated, composed of KCl depolarization, nicotine, carbachol, PACAP, bradykinin, and histamine. The rank-orders of the secreted profiles of the neurotransmitters were generally similar among these secretagogues, but differences in the secreted amounts of each neurotransmitter occurred with different secretagogues. Epinephrine among the catecholamines showed the highest level of secretion. (Met)enkephalin showed the largest levels of secretion compared to the other neuropeptides examined. Levels of secreted catecholamines were greater than that of the neuropeptides. These data support the hypothesis that profiles of secreted neuropeptide and catecholamine neurotransmitters show similarities and differences upon stimulation by distinct secretagogues. These results illustrate the co-release of concerted neurotransmitter profiles that participate in the stress response of the sympathoadrenal nervous system.
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Affiliation(s)
- Sonia Podvin
- Skaggs School of Pharmacy and Pharmaceutical Sciences, Univ. of Calif.-San Diego, La Jolla, CA 92093, United States
| | - Richard Bundey
- Dept. of Medicine, Univ. of Calif.-San Diego, La Jolla, CA 92093, United States
| | - Thomas Toneff
- Skaggs School of Pharmacy and Pharmaceutical Sciences, Univ. of Calif.-San Diego, La Jolla, CA 92093, United States
| | - Michael Ziegler
- Dept. of Medicine, Univ. of Calif.-San Diego, La Jolla, CA 92093, United States
| | - Vivian Hook
- Skaggs School of Pharmacy and Pharmaceutical Sciences, Univ. of Calif.-San Diego, La Jolla, CA 92093, United States; Dept. of Neuroscience and Dept. of Pharmacology, School of Medicine, Univ. of Calif.-San Diego, La Jolla, CA 92093, United States.
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22
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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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23
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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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24
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de Lucia C, Femminella GD, Gambino G, Pagano G, Allocca E, Rengo C, Silvestri C, Leosco D, Ferrara N, Rengo G. Adrenal adrenoceptors in heart failure. Front Physiol 2014; 5:246. [PMID: 25071591 PMCID: PMC4084669 DOI: 10.3389/fphys.2014.00246] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2013] [Accepted: 06/13/2014] [Indexed: 01/08/2023] Open
Abstract
Heart failure (HF) is a chronic clinical syndrome characterized by the reduction in left ventricular (LV) function and it represents one of the most important causes of morbidity and mortality worldwide. Despite considerable advances in pharmacological treatment, HF represents a severe clinical and social burden. Sympathetic outflow, characterized by increased circulating catecholamines (CA) biosynthesis and secretion, is peculiar in HF and sympatholytic treatments (as β-blockers) are presently being used for the treatment of this disease. Adrenal gland secretes Epinephrine (80%) and Norepinephrine (20%) in response to acetylcholine stimulation of nicotinic cholinergic receptors on the chromaffin cell membranes. This process is regulated by adrenergic receptors (ARs): α2ARs inhibit CA release through coupling to inhibitory Gi-proteins, and β ARs (mainly β2ARs) stimulate CA release through coupling to stimulatory Gs-proteins. All ARs are G-protein-coupled receptors (GPCRs) and GPCR kinases (GRKs) regulate their signaling and function. Adrenal GRK2-mediated α2AR desensitization and downregulation are increased in HF and seem to be a fundamental regulator of CA secretion from the adrenal gland. Consequently, restoration of adrenal α2AR signaling through the inhibition of GRK2 is a fascinating sympatholytic therapeutic strategy for chronic HF. This strategy could have several significant advantages over existing HF pharmacotherapies minimizing side-effects on extra-cardiac tissues and reducing the chronic activation of the renin–angiotensin–aldosterone and endothelin systems. The role of adrenal ARs in regulation of sympathetic hyperactivity opens interesting perspectives in understanding HF pathophysiology and in the identification of new therapeutic targets.
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Affiliation(s)
- Claudio de Lucia
- Department of Medical Translational Sciences, University of Naples Federico II Naples, Italy
| | - Grazia D Femminella
- Department of Medical Translational Sciences, University of Naples Federico II Naples, Italy
| | - Giuseppina Gambino
- Department of Medical Translational Sciences, University of Naples Federico II Naples, Italy
| | - Gennaro Pagano
- Department of Medical Translational Sciences, University of Naples Federico II Naples, Italy
| | - Elena Allocca
- Department of Medical Translational Sciences, University of Naples Federico II Naples, Italy
| | - Carlo Rengo
- Department of Medical Translational Sciences, University of Naples Federico II Naples, Italy ; Salvatore Maugeri Foundation, IRCCS, Scientific Institute of Telese Terme Telese Terme, Italy
| | - Candida Silvestri
- Department of Medical Translational Sciences, University of Naples Federico II Naples, Italy
| | - Dario Leosco
- Department of Medical Translational Sciences, University of Naples Federico II Naples, Italy
| | - Nicola Ferrara
- Department of Medical Translational Sciences, University of Naples Federico II Naples, Italy ; Salvatore Maugeri Foundation, IRCCS, Scientific Institute of Telese Terme Telese Terme, Italy
| | - Giuseppe Rengo
- Salvatore Maugeri Foundation, IRCCS, Scientific Institute of Telese Terme Telese Terme, Italy
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25
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Zhang H, Liu Y, Xu J, Zhang F, Liang H, Du X, Zhang H. Membrane microdomain determines the specificity of receptor-mediated modulation of Kv7/M potassium currents. Neuroscience 2013; 254:70-9. [PMID: 24036375 DOI: 10.1016/j.neuroscience.2013.08.064] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2013] [Revised: 08/28/2013] [Accepted: 08/29/2013] [Indexed: 01/18/2023]
Abstract
The Kv7/M current is one of the major mechanisms controlling neuronal excitability, which can be modulated by activation of the G protein-coupled receptor (GPCR) via distinct signaling pathways. Membrane microdomains known as lipid rafts have been implicated in the specificity of various cell signaling pathways. The aim of this study was to understand the role of lipid rafts in the specificity of Kv7/M current modulation by activation of GPCR. Methyl-β-cyclodextrin (MβCD), often used to disrupt the integrity of lipid rafts, significantly reduced the bradykinin receptor (B2R)-induced but not muscarinic receptor (M1R)-induced inhibition of the Kv7/M current. B2R and related signaling molecules but not M1R were found in caveolin-containing raft fractions of the rat superior cervical ganglia. Furthermore, activation of B2R resulted in translocation of additional B2R into the lipid rafts, which was not observed for the activation of M1R. The increase of B2R-induced intracellular Ca(2+) was also greatly reduced after MβCD treatment. Finally, B2R but not M1R was found to interact with the IP3 receptor. In conclusion, the present study implicates an important role for lipid rafts in mediating specificity for GPCR-mediated inhibition of the Kv7/M current.
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Affiliation(s)
- H Zhang
- The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Shijiazhuang, Hebei Province, China; The Key Laboratory of New Drug Pharmacology and Toxicology, Shijiazhuang, Hebei Province, China; Department of Pharmacology, Hebei Medical University, Shijiazhuang, Hebei Province, China
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Noga BR, Pinzon A. Spontaneous and electrically-evoked catecholamine secretion from long-term cultures of bovine adrenal chromaffin cells. Brain Res 2013; 1529:209-22. [PMID: 23891791 DOI: 10.1016/j.brainres.2013.07.027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2013] [Revised: 07/03/2013] [Accepted: 07/18/2013] [Indexed: 11/19/2022]
Abstract
Catecholamine release was measured from bovine adrenal medullary chromaffin cell (CC) cultures maintained over a period of three months. Cells were plated over simple biocompatible cell platforms with electrical stimulation capability and at specified times transferred to an acrylic superfusion chamber designed to allow controlled flow of superfusate over the culture. Catecholamine release was measured from the superfusates using fast cyclic voltammetry before, during and after electrical stimulation of the cells. Immunocytochemical staining of CC cultures revealed that they were composed of epinephrine (EP) and/or norepinephrine (NE) type cells. Both spontaneous and evoked-release of catecholamines from CCs were observed throughout the testing period. EP predominated during spontaneous release, whereas NE was more prevalent during electrically-evoked release. Electrical stimulation for 20 s, increased total catecholamine release by 60-130% (measured over a period of 500 s) compared to that observed for an equivalent 20 s period of spontaneous release. Stimulus intensity was correlated with the amount of evoked release, up to a plateau which was observed near the highest intensities. Shorter intervals between stimulation trials did not significantly affect the initial amount of release, and the amount of evoked release was relatively stable over time and did not decrease significantly with age of the culture. The present study demonstrates long-term survival of CC cultures in vitro and describes a technique useful for rapid assessment of cell functionality and release properties of cultured monoaminergic cell types that later can be transplanted for neurotransmitter replacement following injury or disease.
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Affiliation(s)
- Brian R Noga
- The Miami Project to Cure Paralysis, University of Miami Miller School of Medicine, 1095 NW 14th Terrace, Miami, FL 33136, USA.
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Nerve growth factor-induced endocytosis of TWIK-related acid-sensitive K+ 1 channels in adrenal medullary cells and PC12 cells. Pflugers Arch 2013; 465:1051-64. [DOI: 10.1007/s00424-013-1222-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2012] [Revised: 01/13/2013] [Accepted: 01/20/2013] [Indexed: 11/27/2022]
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28
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Inoue M, Harada K, Matsuoka H, Nakamura J, Warashina A. Mechanisms and roles of muscarinic activation in guinea-pig adrenal medullary cells. Am J Physiol Cell Physiol 2012; 303:C635-44. [PMID: 22744007 DOI: 10.1152/ajpcell.00147.2012] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Muscarinic receptors are expressed in the adrenal medullary (AM) cells of various mammals, but their physiological roles are controversial. Therefore, the ionic mechanism for muscarinic receptor-mediated depolarization and the role of muscarinic receptors in neuronal transmission were investigated in dissociated guinea-pig AM cells and in the perfused guinea-pig adrenal gland. Bath application of muscarine induced an inward current at -60 mV. This inward current was partially suppressed by quinine with an IC(50) of 6.1 μM. The quinine-insensitive component of muscarine-induced currents changed the polarity at -78 mV and was inhibited by bupivacaine, a TWIK-related acid-sensitive K(+) (TASK) channel inhibitor. Conversely, the current-voltage relationship for the bupivacaine-insensitive component of muscarine currents showed a reversal potential of -5 mV and a negative slope below -40 mV. External application of La(3+) had a double action on muscarine currents of both enhancement and suppression. Immunoblotting and immunocytochemistry revealed expression of TASK1 channels and cononical transient receptor potential channels 1, 4, 5, and 7 in guinea-pig AM cells. Retrograde application of atropine reversibly suppressed transsynaptically evoked catecholamine secretion from the adrenal gland. The results indicate that muscarinic receptor stimulation in guinea-pig AM cells induces depolarization through inhibition of TASK channels and activation of nonselective cation channels and that muscarinic receptors are involved in neuronal transmission from the splanchnic nerve.
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Affiliation(s)
- Masumi Inoue
- Dept. of Cell and Systems Physiology, Univ. of Occupational and Environmental Health School of Medicine, Kitakyushu, Japan.
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29
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Cytosolic organelles shape calcium signals and exo–endocytotic responses of chromaffin cells. Cell Calcium 2012; 51:309-20. [DOI: 10.1016/j.ceca.2011.12.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2011] [Revised: 12/02/2011] [Accepted: 12/05/2011] [Indexed: 01/09/2023]
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Modulation of intracellular Ca2+ levels in chromaffin cells by nanoelectropulses. Bioelectrochemistry 2011; 87:244-52. [PMID: 22197468 DOI: 10.1016/j.bioelechem.2011.11.016] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2011] [Revised: 11/04/2011] [Accepted: 11/28/2011] [Indexed: 01/20/2023]
Abstract
Exposing chromaffin cells to a single 5 ns, 5 MV/m pulse causes Ca(2+) influx and a rapid, transient rise in intracellular calcium concentration ([Ca(2+)](i)). A comparison of responses at room temperature versus 37°C revealed no effect of temperature on the magnitude of the increase in [Ca(2+)](i). The Ca(2+) transient, however, was shortened in duration almost twofold at 37°C, indicating that the rate of recovery was temperature-sensitive. Temperature also affected the interval required for a second pulse to elicit another maximal rise in [Ca(2+)](i), which was shorter at the higher temperature. In addition, a second pulse applied 5s after the first pulse was sufficient to cause cells at room temperature to become refractory to subsequent stimulation. At 37°C, cells became refractory after 5 pulses regardless of whether pulse delivery was at low (1 and 10 Hz) or high (1 kHz) rates. When refractory, cells showed no signs of swelling or uptake of the impermeant dye YO-PRO-1. These results demonstrate that temperature plays a role in determining how chromaffin cells respond to and become refractory to nanoelectropulses. They also indicate that despite the ultra-short duration of the pulses, pronounced effects on cell excitability result from the application of only very few pulses.
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Scott RS, Bustillo D, Olivos-Oré LA, Cuchillo-Ibañez I, Barahona MV, Carbone E, Artalejo AR. Contribution of BK channels to action potential repolarisation at minimal cytosolic Ca2+ concentration in chromaffin cells. Pflugers Arch 2011; 462:545-57. [DOI: 10.1007/s00424-011-0991-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2011] [Accepted: 06/20/2011] [Indexed: 01/11/2023]
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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: 131] [Impact Index Per Article: 9.4] [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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Matsuoka H, Harada K, Ikeda T, Uetsuki K, Sata T, Warashina A, Inoue M. Ca2+ pathway involved in the refilling of store sites in rat adrenal medullary cells. Am J Physiol Cell Physiol 2009; 296:C889-99. [PMID: 19176761 DOI: 10.1152/ajpcell.00439.2008] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
It has been suggested that store-operated Ca(2+) entry (SOC) facilitates catecholamine secretion and synthesis in bovine adrenal medullary (AM) cells. However, there has been no experimental result clearly showing that cation channel activity is enhanced by store Ca(2+) depletion. Thus the present experiments were undertaken to address the issue of whether rat AM cells have SOC channels. Inhibition of the sarco(endo)plasmic reticulum Ca(2+) (SERCA) pump resulted in a sustained increase in intracellular Ca(2+) concentration ([Ca(2+)](i)) in rat AM cells. This increase was completely suppressed by 2 mM Ni(2+) but not by 100 muM D600. A bath application of Ni(2+), but not D600, produced an outward current at -60 mV in rat AM cells, whereas exposure to a SERCA pump inhibitor did not affect either the whole cell current level or the Ni(2+)-induced outward current. The refilling of intracellular store sites was suppressed by the addition of Ni(2+) to the perfusate. RT-PCR revealed that transcripts for transient receptor potential channels 1 (TRPC1) and 5 (TRPC5) were present in rat adrenal medullas. Immunocytochemistry showed that TRPC1 channels, which have been implicated in SOC in certain types of cells, were mainly localized in the endoplasmic reticulum (ER) and not in the plasma membrane, and that STIM1, a Ca(2+) sensor in the ER, was not expressed in rat AM cells. On the basis of these results, we conclude that rat AM cells lack the SOC mechanism.
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Affiliation(s)
- Hidetada Matsuoka
- Dept. of Cell and Systems Physiology, School of Medicine, Univ. of Occupational and Environmental Health, Kitakyushu 807-8555, Japan
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de Diego AMG, Arnáiz-Cot JJ, Hernández-Guijo JM, Gandía L, García AG. Differential variations in Ca2+ entry, cytosolic Ca2+ and membrane capacitance upon steady or action potential depolarizing stimulation of bovine chromaffin cells. Acta Physiol (Oxf) 2008; 194:97-109. [PMID: 18485124 DOI: 10.1111/j.1748-1716.2008.01871.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
AIMS This study looks into the physiology of the exocytosis of catecholamines released by adrenal medullary chromaffin cells. We have comparatively explored the exocytotic responses elicited by two different patterns of depolarizing stimulation: the widely employed square depolarizing pulses (DPs) and trains of acetylcholine-like action potentials (APs), likely the physiological mode of stimulation in the intact innervated adrenal medulla. APs were applied at 30 Hz, a frequency similar to that produced in a stressful situation. METHODS Patch-clamp, cell membrane capacitance, single cell amperometry and fluorescence were the techniques used. The variations of calcium entry measured as the integral of the calcium current, cytosolic calcium (measured with the calcium-sensitive fluorescent probe fluo-4) and exo-endocytosis (membrane capacitance variations) were the parameters measured. RESULTS Trains of AP depolarizations produced distinct responses compared to those of square depolarizations: (1) Calcium current amplitude decreased to a lesser extent along the AP train; (2) calcium entry and capacitance increments raised linearly with stimulation time whereas they deviated from linearity when square depolarizations were used; (3) slower activation and faster delayed decay phase of cytosolic calcium transients; (4) capacitance increments varied linearly with calcium entry with APs and deviated from linearity with longer depolarizations; (5) little endocytosis after stimulation with longer trains of APs and pronounced endocytosis with longer square depolarizations. CONCLUSIONS Stimulation of chromaffin cells with trains of APs produced patterns of cytosolic calcium transients, exocytotic and endocytotic responses quite different from those elicited by the widely employed DPs. Our study is relevant from the methodological and physiological points of view.
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Affiliation(s)
- A M G de Diego
- Facultad de Medicina, Instituto Teófilo Hernando, Universidad Autónoma de Madrid, Madrid, Spain.
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37
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PDE type-4 inhibition increases L-type Ca2+ currents, action potential firing, and quantal size of exocytosis in mouse chromaffin cells. Pflugers Arch 2008; 457:1093-110. [DOI: 10.1007/s00424-008-0584-4] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2008] [Accepted: 08/22/2008] [Indexed: 01/21/2023]
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38
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Inoue M, Harada K, Matsuoka H, Sata T, Warashina A. Inhibition of TASK1-like channels by muscarinic receptor stimulation in rat adrenal medullary cells. J Neurochem 2008; 106:1804-14. [DOI: 10.1111/j.1471-4159.2008.05521.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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39
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Gribkoff VK. The therapeutic potential of neuronal K V 7 (KCNQ) channel modulators: an update. Expert Opin Ther Targets 2008; 12:565-81. [PMID: 18410240 DOI: 10.1517/14728222.12.5.565] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
BACKGROUND Neuronal KCNQ channels (K(V)7.2-5) represent attractive targets for the development of therapeutics for chronic and neuropathic pain, migraine, epilepsy and other neuronal hyperexcitability disorders, although there has been only modest progress in translating this potential into useful therapeutics. OBJECTIVE Compelling evidence of the importance of K(V)7 channels as neuronal regulatory elements, readily amenable to pharmacological modulation, has sustained widespread interest in these channels as drug targets. This review will update readers on key aspects of the characterization of these important ion channel targets, and will discuss possible current barriers to their exploitation for CNS therapeutics. METHODS This article is based on a review of recent literature, with a focus on data pertaining to the roles of these channels in neurophysiology. In addition, I review some of the regulatory elements that influence the channels and how these may relate to channel pharmacology, and present a review of recent advances in neuronal K(V)7 channel pharmacology. CONCLUSIONS These channels continue to be valid and approachable targets for CNS therapeutics. However, we may need to understand more about the roles of neuronal K(V)7 channels during the development of disease states, as well as to pay more attention to a detailed analysis of the molecular pharmacology of the different channel subfamily members and the modes of interaction of individual modulators, in order to successfully target these channels for therapeutic development.
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Affiliation(s)
- Valentin K Gribkoff
- Knopp Neurosciences, Inc., 2100 Wharton Street, Suite 615, Pittsburgh, PA 15203, USA.
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40
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Dynamin I plays dual roles in the activity-dependent shift in exocytic mode in mouse adrenal chromaffin cells. Arch Biochem Biophys 2008; 477:146-54. [PMID: 18492483 DOI: 10.1016/j.abb.2008.04.039] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2008] [Revised: 04/21/2008] [Accepted: 04/23/2008] [Indexed: 11/21/2022]
Abstract
Under low stimulation, adrenal chromaffin cells release freely soluble catecholamines through a restricted granule fusion pore while retaining the large neuropeptide-containing proteinacious granule core. Elevated activity causes dilation of the pore and release of all granule contents. Thus, physiological differential transmitter release is achieved through regulation of fusion pore dilation. We examined the mechanism for pore dilation utilizing a combined approach of peptide transfection, electrophysiology, electrochemistry and quantitative imaging techniques. We report that disruption of dynamin I function alters both fusion modes. Under low stimulation, interference with dynamin I does not affect granule fusion but blocks its re-internalization. In full collapse mode, disruption of dynamin I limits fusion pore dilation, but does not block membrane re-internalization. These data suggest that dynamin I is involved in both modes of exocytosis by regulating contraction or dilation of the fusion pore and thus contributes to activity-dependent differential transmitter release from the adrenal medulla.
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Liu B, Liang H, Liu L, Zhang H. Phosphatidylinositol 4,5-bisphosphate hydrolysis mediates histamine-induced KCNQ/M current inhibition. Am J Physiol Cell Physiol 2008; 295:C81-91. [PMID: 18448631 DOI: 10.1152/ajpcell.00028.2008] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The M-type potassium channel, of which its molecular basis is constituted by KCNQ2-5 homo- or heteromultimers, plays a key role in regulating neuronal excitability and is modulated by many G protein-coupled receptors. In this study, we demonstrate that histamine inhibits KCNQ2/Q3 currents in human embryonic kidney (HEK)293 cells via phosphatidylinositol 4,5-bisphosphate (PIP(2)) hydrolysis mediated by stimulation of H(1) receptor and phospholipase C (PLC). Histamine inhibited KCNQ2/Q3 currents in HEK293 cells coexpressing H(1) receptor, and this effect was totally abolished by H(1) receptor antagonist mepyramine but not altered by H(2) receptor antagonist cimetidine. The inhibition of KCNQ currents was significantly attenuated by a PLC inhibitor U-73122 but not affected by depletion of internal Ca(2+) stores or intracellular Ca(2+) concentration ([Ca(2+)](i)) buffering via pipette dialyzing BAPTA. Moreover, histamine also concentration dependently inhibited M current in rat superior cervical ganglion (SCG) neurons by a similar mechanism. The inhibitory effect of histamine on KCNQ2/Q3 currents was entirely reversible but became irreversible when the resynthesis of PIP(2) was impaired with phosphatidylinsitol-4-kinase inhibitors. Histamine was capable of producing a reversible translocation of the PIP(2) fluorescence probe PLC(delta1)-PH-GFP from membrane to cytosol in HEK293 cells by activation of H(1) receptor and PLC. We concluded that the inhibition of KCNQ/M currents by histamine in HEK293 cells and SCG neurons is due to the consumption of membrane PIP(2) by PLC.
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Affiliation(s)
- Boyi Liu
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, Hebei Province, China
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42
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Abstract
Excitation-secretion coupling in adrenomedullary chromaffin cells physiologically commences when acetylcholine molecules released from splanchnic nerve terminals bind to cholinergic receptors located at the cell's plasma membrane. While nicotinic acetylcholine receptors ensure a rapid and efficacious transmission of preganglionic impulses, muscarinic acetylcholine receptors are considered to play a subsidiary role mostly by facilitating the nicotinic responses. Nevertheless, the variety of effects brought about by muscarinic stimulation in chromaffin cells (release of intracellular Ca2+, activation of Ca2+ entry through non-selective cation channels and voltage-dependent Ca2+ channels, impairment and/or enhancement of action potential firing, etc.) and the long-lasting nature of many of them suggests that muscarinic receptors might contribute to the fine tuning of the catecholamine secretory response upon graded preganglionic stimulation and prolonged periods of time. Such a variety of effects probably reflects not only the diversity of muscarinic receptors expressed in chromaffin cells but also the existence of differences among the animal species employed in the reported investigations. Accordingly, we first review on an animal species-based approach the most relevant features of the muscarinic response in chromaffin cells from a set of mammals, and finally present a unified picture of the mechanisms of muscarinic excitation-secretion coupling in chromaffin cells.
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Affiliation(s)
- L Olivos
- Department of Toxicology and Pharmacology, School of Veterinary Sciences, Complutense University of Madrid, Madrid, Spain
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43
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de Diego AMG, Gandía L, García AG. A physiological view of the central and peripheral mechanisms that regulate the release of catecholamines at the adrenal medulla. Acta Physiol (Oxf) 2008; 192:287-301. [PMID: 18005392 DOI: 10.1111/j.1748-1716.2007.01807.x] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Here we review the tight neural control of the differential secretion into the circulation, of the adrenal medullary hormones adrenaline and noradrenaline. One or the other catecholamines are differentially released on various stress conditions. This is specifically controlled by central nervous system nuclei at the cortex, hypothalamus and spinal cord. Different firing patterns of splanchnic nerves and nicotinic or muscarinic receptors cause the selective release of noradrenaline or adrenaline, to adapt the body to the 'fight or flight' reaction, or during severe hypoglycaemia, haemorrhage, cold, acute myocardial infarction or other severe stressful conflicts. Endogenously acetylcholine (ACh) released at the splanchnic nerve-chromaffin cell synapse, acting on muscarinic and nicotinic receptors, causes membrane depolarization and action potentials (AP) in chromaffin cells. These changes vary with the animal species, the cell preparation (intact bisected adrenal, adrenal slices, or isolated fresh or cultured cells) or the recording technique (intracellular microelectrodes, patch-clamp, perforated-patch, cell-attached). Conflicting results leave many open questions concerning the actions of ACh on chromaffin cell excitability. The use of adrenal slices and field electrical stimulation will surely provide new insights into these mechanisms. Chromaffin cells have been thoroughly used as models to study the relationship between Ca2+ entry, cytosolic Ca2+ signals, exocytosis and endocytosis, using patch-clamp and amperometric techniques. Cells have been stimulated with single depolarizing pulses (DPs), DP trains and with simulated AP waveforms. These approaches have provided useful information but we have no data on APs generated by pulsatile secretory quanta of ACh, trying to mimic the intermittent and repetitive splanchnic nerve discharge of the neurotransmitter. We present some recent experiments using ultrashort ACh pulses (25 ms), that cause non-desensitizing repetitive APs with each ACh pulse, at low ACh concentrations (30 microM). Ultrashort pulses of a high ACh concentration (1000 microM) causes a single AP followed by a prolonged depolarization. It could be interesting trying to correlate these 'patterns of splanchnic nerve discharge' with Ca2+ signals and exocytosis. This, together with the use of adrenal slices and transmural electrical stimulation of splanchnic nerves will provide new physiologically sound data on the regulation of adrenal medullary secretion.
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Affiliation(s)
- A M G de Diego
- Instituto Teófilo Hernando, Departamento de Farmacología y Terapéutica, Facultad de Medicina, Universidad Autónoma de Madrid, Madrid, Spain
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Lymperopoulos A, Rengo G, Koch WJ. Adrenal adrenoceptors in heart failure: fine-tuning cardiac stimulation. Trends Mol Med 2007; 13:503-11. [PMID: 17981507 DOI: 10.1016/j.molmed.2007.10.005] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2007] [Revised: 09/27/2007] [Accepted: 10/01/2007] [Indexed: 12/20/2022]
Abstract
Chronic heart failure (HF) is characterized by sympathetic hyperactivity reflected by increased circulating catecholamines (CAs), which contributes significantly to its morbidity and mortality. Therefore, sympatholytic treatments, that is, treatments that reduce sympathetic hyperactivity, are being pursued currently for the treatment of HF. Secretion of CAs from the adrenal gland, which is a major source of CAs, is regulated by alpha(2)-adrenoceptors (alpha(2)ARs), which inhibit, and by beta-adrenoceptors (betaARs), which enhance CA secretion. All ARs are G-protein-coupled receptors (GPCRs), whose signaling and function are regulated tightly by the family of GPCR kinases (GRKs). Despite the enormous potential of adrenal ARs for the regulation of sympathetic outflow, elucidation of their properties has only begun recently. Here, recent advances regarding the roles of adrenal ARs in the regulation of sympathetic outflow in HF and the regulatory properties of ARs are discussed, along with the potential benefits and challenges of harnessing their function for HF therapy.
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Ardiles AO, González-Jamett AM, Maripillán J, Naranjo D, Caviedes P, Cárdenas AM. Calcium channel subtypes differentially regulate fusion pore stability and expansion. J Neurochem 2007; 103:1574-81. [PMID: 17760862 DOI: 10.1111/j.1471-4159.2007.04871.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Various studies have focused in the relative contribution of different voltage-activated Ca(2+) channels (VACC) to total transmitter release. However, how Ca(2+) entry through a given VACC subtype defines the pattern of individual exocytotic events remains unknown. To address this question, we have used amperometry in bovine chromaffin cells. L, N, and P/Q channels were individually or jointly blocked with furnidipine, omega-conotoxin GVIA, omega-agatoxin IVA, or omega-conotoxin MVIIC. The three channel types contributed similarly to cytosolic Ca(2+) signals induced by 70 mmol/L K(+). However, they exhibited different contributions to the frequency of exocytotic events and they were shown to differently regulate the final steps of the exocytosis. When compared with the other VACC subtypes, Ca(2+) entry through P/Q channels effectively induced exocytosis, it decreased fusion pore stability and accelerated its expansion. Conversely, Ca(2+) entry through N channels was less efficient in inducing exocytotic events, also slowing fusion pore expansion. Finally, Ca(2+) entry through L channels inefficiently induced exocytosis, and the individual blockade of this channel significantly modified fusion pore dynamics. The distance between a given VACC subtype and the release sites could account for the differential effects of the distinct VACC on the fusion pore dynamics.
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Affiliation(s)
- Alvaro O Ardiles
- Centro de Neurociencia de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile
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Fulop T, Smith C. Matching native electrical stimulation by graded chemical stimulation in isolated mouse adrenal chromaffin cells. J Neurosci Methods 2007; 166:195-202. [PMID: 17714791 PMCID: PMC2464294 DOI: 10.1016/j.jneumeth.2007.07.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2007] [Revised: 07/09/2007] [Accepted: 07/09/2007] [Indexed: 11/29/2022]
Abstract
Adrenal chromaffin cells release multiple transmitters in response to sympathetic stimulation. Modest cell firing, matching sympathetic tone, releases small freely soluble catecholamines. Elevated electrical firing rates matching input under sympathetic stress results in release of catecholamines as well as semi-soluble vaso- and neuro-active peptides packaged within the dense core of the secretory granule. This activity-dependent differential transmitter release has been shown to rely on a mechanistic shift in the mode of exocytosis through the regulated dilation of the secretory fusion pore between granule and cell surface membranes. However, biochemical description of the mechanism regulating fusion pore dilation remains elusive. In the experimental setting, electrical stimulation designed to mimic sympathetic input, is achieved through single-cell voltage-clamp. While precise, this approach is incompatible with biochemical and proteomic analysis, both of which require large sample sizes. We address this limitation in the current study. We describe a bulk chemical stimulation paradigm calibrated to match defined electrical activity. We utilize calcium and single-cell amperometric measurements to match extracellular potassium concentrations to physiological electrical stimulation under sympathetic tone as well as acute stress conditions. This approach provides larger samples of uniformly stimulated cells for determining molecular players in activity-dependent differential transmitter release from adrenal chromaffin cells.
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Affiliation(s)
- Tiberiu Fulop
- Department of Physiology and Biophysics, School of Medicine, 2109 Adelbert Road, Case Western Reserve University, Cleveland, OH 44106-4970, USA.
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Mustafa T, Grimaldi M, Eiden LE. The hop cassette of the PAC1 receptor confers coupling to Ca2+ elevation required for pituitary adenylate cyclase-activating polypeptide-evoked neurosecretion. J Biol Chem 2007; 282:8079-91. [PMID: 17213203 PMCID: PMC4183215 DOI: 10.1074/jbc.m609638200] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We have identified the single PAC1 receptor variant responsible for Ca2+ mobilization from intracellular stores and influx through voltage-gated Ca2+ channels in bovine chromaffin cells and the domain of this receptor variant that confers coupling to [Ca2+]i elevation. This receptor (bPAC1hop) contains a 28-amino acid "hop" insertion in the third intracellular loop, with a full-length 171-amino acid N terminus. Expression of the bPAC1hop receptor in NG108-15 cells, which lack endogenous PAC1 receptors, reconstituted high affinity PACAP binding and PACAP-dependent elevation of both cAMP and intracellular Ca2+ concentrations ([Ca2+]i). Removal of the hop domain and expression of this receptor (bPAC1null) in NG108-15 cells reconstituted high affinity PACAP binding and PACAP-dependent cAMP generation but without a corresponding [Ca2+]i elevation. PC12-G cells express sufficient levels of PAC1 receptors to provide PACAP-saturable coupling to adenylate cyclase and to drive PACAP-dependent differentiation but do not express PAC1 receptors at levels found in postmitotic neuronal and endocrine cells and do not support PACAP-mediated neurosecretion. Expression of bPAC1hop, but not bPAC1(null), at levels comparable with those of bPAC1hop in bovine chromaffin cells resulted in acquisition by PC12-G cells of PACAP-dependent [Ca2+]i increase and extracellular Ca2+ influx. In addition, PC12-G cells expressing bPAC1hop acquired the ability to release [3H]norepinephrine in a Ca2+ influx-dependent manner in response to PACAP. Expression of PACAP receptors in neuroendocrine rather than nonneuroendocrine cells reveals key differences between PAC1hop and PAC1null coupling, indicating an important and previously unrecognized role of the hop cassette in PAC1-mediated Ca2+ signaling in neuroendocrine cells.
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Affiliation(s)
- Tomris Mustafa
- Section on Molecular Neuroscience, Laboratory of Cellular and Molecular Regulation, National Institute of Mental Health, Bethesda, Maryland 20892
| | - Maurizio Grimaldi
- Section on Molecular Neuroscience, Laboratory of Cellular and Molecular Regulation, National Institute of Mental Health, Bethesda, Maryland 20892
- Laboratory of Neuropharmacology, Department of Biochemistry, Drug Discovery Division, Southern Research Institute, Birmingham, Alabama 35205
| | - Lee E. Eiden
- Section on Molecular Neuroscience, Laboratory of Cellular and Molecular Regulation, National Institute of Mental Health, Bethesda, Maryland 20892
- To whom correspondence should be addressed: Section on Molecular Neuroscience, Laboratory of Cellular and Molecular Regulation, National Institutes of Mental Health, Bldg. 49, Rm. 5A-68, 9000 Rockville Pike, Bethesda, MD 20892. Tel.: 301-496-4110; Fax: 301-496-1748;
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McDavid S, Currie KPM. G-proteins modulate cumulative inactivation of N-type (Cav2.2) calcium channels. J Neurosci 2007; 26:13373-83. [PMID: 17182788 PMCID: PMC6675003 DOI: 10.1523/jneurosci.3332-06.2006] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Precise regulation of N-type (Ca(V)2.2) voltage-gated calcium channels (Ca-channels) controls many cellular functions including neurotransmitter and hormone release. One important mechanism that inhibits Ca2+ entry involves binding of G-protein betagamma subunits (Gbetagamma) to the Ca-channels. This shifts the Ca-channels from "willing" to "reluctant" gating states and slows activation. Voltage-dependent reversal of the inhibition (facilitation) is thought to reflect transient dissociation of Gbetagamma from the Ca-channels and can occur during high-frequency bursts of action potential-like waveforms (APW). Inactivation of Ca-channels will also limit Ca2+ entry, but it remains unclear whether G-proteins can modulate inactivation. In part this is because of the complex nature of inactivation, and because facilitation of Ca-channel currents (I(Ca)) masks the extent and kinetics of inactivation during typical stimulation protocols. We used low-frequency trains of APW to activate I(Ca). This more closely mimics physiological stimuli and circumvents the problem of facilitation which does not occur at < or = 5 Hz. Activation of endogenous G-proteins reduced both Ca2+-dependent, and voltage-dependent inactivation of recombinant I(Ca) in human embryonic kidney 293 cells. This was mimicked by expression of wild-type Gbetagamma, but not by a point mutant of Gbetagamma with reduced affinity for Ca-channels. A similar decrease in the inactivation of I(Ca) was produced by P2Y receptors in adrenal chromaffin cells. Overall, our data identify and characterize a novel effect of G-proteins on I(Ca), and could have important implications for understanding how G-protein-coupled receptors control Ca2+ entry and Ca2+-dependent events such as neurotransmitter and hormone release.
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Affiliation(s)
- Sarah McDavid
- Department of Anesthesiology, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA
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Ma X, Bielefeldt K, Tan ZY, Whiteis CA, Snitsarev V, Abboud FM, Chapleau MW. Dual mechanisms of angiotensin-induced activation of mouse sympathetic neurones. J Physiol 2006; 573:45-63. [PMID: 16543267 PMCID: PMC1779698 DOI: 10.1113/jphysiol.2006.106716] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Ang II directly activates neurones in sympathetic ganglia. Our goal was to define the electrophysiological basis of this activation. Neurones from mouse aortic-renal and coeliac ganglia were identified as either 'tonic' or 'phasic'. With injections of depolarizing currents, action potentials (APs) were abundant and sustained in tonic neurones (TNs) and scarce or absent in phasic neurones (PNs). Resting membrane potentials were equivalent in TNs (-48 +/- 2 mV, n = 18) and PNs (-48 +/- 1 mV, n = 23) while membrane resistance was significantly higher in TNs. Ang II depolarized and increased membrane resistance equally in both TNs (n = 8) and PNs (n = 8) but it induced APs only in TNs, and enhanced current-evoked APs much more markedly in TNs (P < 0.05). The AT1 receptor antagonist losartan (2 microm, n = 6) abolished all responses to Ang II, whereas the AT2 receptor blocker PD123,319 had no effect. The transient K+ current (IA), which was more than twice as large in TNs as in PNs, was significantly inhibited by Ang II in TNs only whereas the delayed sustained K+ current (IK), which was comparable in both TNs and PNs, was not inhibited. M currents were more prominent in PNs and were inhibited by Ang II. The IA channel blocker 4-aminopyridine triggered AP generation in TNs and prevented the Ang II-induced APs but not the depolarization. Blockade of M currents by oxotremorine M or linopirdine prevented the depolarizing action of Ang II. The protein kinase C (PKC) inhibitor H7 (10 microm, n = 9) also prevented the Ang II-induced inhibition of IA and the generation APs but not the depolarization nor the inhibition of M currents. Conversely, the PKC agonist phorbol 12-myristate 13-acetate mimicked the Ang II effects by triggering APs. The results indicate that Ang II may increase AP generation in sympathetic neurones by inducing a PKC-dependent inhibition of IA currents, and a PKC-independent depolarization through inhibition of M currents. The differential expression of various K+ channels and their sensitivity to phosphorylation by PKC may determine the degree of activation of sympathetic neurones and hence may influence the severity of the hypertensive response.
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Affiliation(s)
- X Ma
- Department of Internal Medicine, 602 MRC, University of Iowa, Iowa City, IA 52242, USA.
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Dzhura EV, He W, Currie KPM. Linopirdine Modulates Calcium Signaling and Stimulus-Secretion Coupling in Adrenal Chromaffin Cells by Targeting M-Type K+Channels and Nicotinic Acetylcholine Receptors. J Pharmacol Exp Ther 2005; 316:1165-74. [PMID: 16280412 DOI: 10.1124/jpet.105.095570] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Adrenal chromaffin cells synthesize and release catecholamines and several other transmitters that play important physiological roles in the coordinated response to stress or danger. The main trigger for secretion is acetylcholine (ACh) released from splanchnic nerve terminals that activates nicotinic ACh receptors (nAChRs) on the chromaffin cells, causing membrane depolarization and Ca2+ entry primarily through voltage-gated Ca2+ channels (Ca-channels). G protein-coupled receptors (GPCRs) can also trigger secretion, and it has been suggested that closure of M-type K+ channels might contribute to this process. However, GPCRs have multiple effects on calcium signaling and secretion, including release of intracellular Ca2+ stores, activation of second messenger pathways and kinases, and Ca2+ entry through store/receptor-operated channels. Hence, the effects of M-channel closure on [Ca2+]i signaling and transmitter release remain unclear. We have investigated the effects of linopirdine, a relatively selective blocker of M-channels, on stimulus-secretion coupling in chromaffin cells. Linopirdine produced a small increase in [Ca2+]i in approximately 63% of cells because of influx through Ca-channels. However, this was not sufficient to promote catecholamine release. We also show that linopirdine reduced cholinergic-stimulated increases in [Ca2+]i and secretion, primarily through potent block of nAChRs and a subtle effect on Ca2+ entry via Ca-channels. Hence, our data support the hypothesis that M-channels help control the excitability of chromaffin cells, but additional pathways need to be recruited by GPCRs to trigger catecholamine release. Furthermore, linopirdine potently targets nAChRs to modulate stimulus-secretion coupling in adrenal chromaffin cells.
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Affiliation(s)
- Elvira V Dzhura
- Departments of Anesthesiology, Vanderbilt University Medical Center, T-4202 Medical Center North, 1161 21st Ave. South, Nashville, TN 37232-2520, USA
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