1
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Bonnefont X. Cell Signaling in the Circadian Pacemaker: New Insights from in vivo Imaging. Neuroendocrinology 2024:1-8. [PMID: 38754404 DOI: 10.1159/000539344] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/29/2024] [Accepted: 05/12/2024] [Indexed: 05/18/2024]
Abstract
BACKGROUND "One for all, and all for one," the famous rallying cry of the Three Musketeers, in Alexandre Dumas's popular novel, certainly applies to the 20,000 cells composing the suprachiasmatic nuclei (SCN). These cells work together to form the central clock that coordinates body rhythms in tune with the day-night cycle. Like virtually every body cell, individual SCN cells exhibit autonomous circadian oscillations, but this rhythmicity only reaches a high level of precision and robustness when the cells are coupled with their neighbors. Therefore, understanding the functional network organization of SCN cells beyond their core rhythmicity is an important issue in circadian biology. SUMMARY The present review summarizes the main results from our recent study demonstrating the feasibility of recording SCN cells in freely moving mice and the significance of variations in intracellular calcium over several timescales. KEY MESSAGE We discuss how in vivo imaging at the cell level will be pivotal to interrogate the mammalian master clock, in an integrated context that preserves the SCN network organization, with intact inputs and outputs.
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Affiliation(s)
- Xavier Bonnefont
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, Montpellier, France
- BioCampus Montpellier, Université de Montpellier, CNRS, INSERM, Montpellier, France
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2
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Rodan AR. Circadian Rhythm Regulation by Pacemaker Neuron Chloride Oscillation in Flies. Physiology (Bethesda) 2024; 39:0. [PMID: 38411570 DOI: 10.1152/physiol.00006.2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2024] [Revised: 02/14/2024] [Accepted: 02/15/2024] [Indexed: 02/28/2024] Open
Abstract
Circadian rhythms in physiology and behavior sync organisms to external environmental cycles. Here, circadian oscillation in intracellular chloride in central pacemaker neurons of the fly, Drosophila melanogaster, is reviewed. Intracellular chloride links SLC12 cation-coupled chloride transporter function with kinase signaling and the regulation of inwardly rectifying potassium channels.
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Affiliation(s)
- Aylin R Rodan
- Molecular Medicine Program, University of Utah, Salt Lake City, Utah, United States
- Department of Internal Medicine, Division of Nephrology and Hypertension, University of Utah, Salt Lake City, Utah, United States
- Department of Human Genetics, University of Utah, Salt Lake City, Utah, United States
- Medical Service, Veterans Affairs Salt Lake City Health Care System, Salt Lake City, Utah, United States
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3
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Ragozzino FJ, Karatsoreos IN, Peters JH. Principles of synaptic encoding of brainstem circadian rhythms. Exp Physiol 2024. [PMID: 38308846 DOI: 10.1113/ep090867] [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: 10/15/2023] [Accepted: 01/16/2024] [Indexed: 02/05/2024]
Abstract
Circadian regulation of autonomic tone and reflex pathways pairs physiological processes with the daily light cycle. However, the underlying mechanisms mediating these changes on autonomic neurocircuitry are only beginning to be understood. The brainstem nucleus of the solitary tract (NTS) and adjacent nuclei, including the area postrema and dorsal motor nucleus of the vagus, are key candidates for rhythmic control of some aspects of the autonomic nervous system. Recent findings have contributed to a working model of circadian regulation in the brainstem which manifests from the transcriptional, to synaptic, to circuit levels of organization. Vagal afferent neurons and the NTS possess rhythmic clock gene expression, rhythmic action potential firing, and our recent findings demonstrate rhythmic spontaneous glutamate release. In addition, postsynaptic conductances also vary across the day producing subtle changes in membrane depolarization which govern synaptic efficacy. Together these coordinated pre- and postsynaptic changes provide nuanced control of synaptic transmission across the day to tune the sensitivity of primary afferent input and likely govern reflex output. Further, given the important role for the brainstem in integrating cues such as feeding, cardiovascular function and temperature, it may also be an underappreciated locus in mediating the effects of such non-photic entraining cues. This short review focuses on the neurophysiological principles that govern NTS synaptic transmission and how circadian rhythms impacted them across the day.
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Affiliation(s)
- Forrest J Ragozzino
- Department of Integrative Physiology and Neuroscience, College of Veterinary Medicine, Washington State University, Pullman, Washington, USA
| | - Ilia N Karatsoreos
- Department of Psychological and Brain Sciences, University of Massachusetts Amherst, Amherst, Massachusetts, USA
| | - James H Peters
- Department of Integrative Physiology and Neuroscience, College of Veterinary Medicine, Washington State University, Pullman, Washington, USA
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4
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Hiro S, Kobayashi K, Nemoto T, Enoki R. In-phasic cytosolic-nuclear Ca 2+ rhythms in suprachiasmatic nucleus neurons. Front Neurosci 2023; 17:1323565. [PMID: 38178840 PMCID: PMC10765503 DOI: 10.3389/fnins.2023.1323565] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2023] [Accepted: 11/30/2023] [Indexed: 01/06/2024] Open
Abstract
The suprachiasmatic nucleus (SCN) of the hypothalamus is the master circadian clock in mammals. SCN neurons exhibit circadian Ca2+ rhythms in the cytosol, which is thought to act as a messenger linking the transcriptional/translational feedback loop (TTFL) and physiological activities. Transcriptional regulation occurs in the nucleus in the TTFL model, and Ca2+-dependent kinase regulates the clock gene transcription. However, the Ca2+ regulatory mechanisms between cytosol and nucleus as well as the ionic origin of Ca2+ rhythms remain unclear. In the present study, we monitored circadian-timescale Ca2+ dynamics in the nucleus and cytosol of SCN neurons at the single-cell and network levels. We observed robust nuclear Ca2+ rhythm in the same phase as the cytosolic rhythm in single SCN neurons and entire regions. Neuronal firing inhibition reduced the amplitude of both nuclear and cytosolic Ca2+ rhythms, whereas blocking of Ca2+ release from the endoplasmic reticulum (ER) via ryanodine and inositol 1,4,5-trisphosphate (IP3) receptors had a minor effect on either Ca2+ rhythms. We conclude that the in-phasic circadian Ca2+ rhythms in the cytosol and nucleus are mainly driven by Ca2+ influx from the extracellular space, likely through the nuclear pore. It also raises the possibility that nuclear Ca2+ rhythms directly regulate transcription in situ.
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Affiliation(s)
- Sota Hiro
- Biophotonics Research Group, Exploratory Research Center on Life and Living Systems (ExCELLS), National Institutes of Natural Sciences, Okazaki, Aichi, Japan
- Division of Biophotonics, National Institute for Physiological Sciences, National Institutes of Natural Sciences, Okazaki, Aichi, Japan
- School of Life Science, The Graduate University for Advanced Studies (SOKENDAI), Okazaki, Aichi, Japan
| | - Kenta Kobayashi
- School of Life Science, The Graduate University for Advanced Studies (SOKENDAI), Okazaki, Aichi, Japan
- Section of Viral Vector Development, National Institute for Physiological Sciences, Okazaki, Aichi, Japan
| | - Tomomi Nemoto
- Biophotonics Research Group, Exploratory Research Center on Life and Living Systems (ExCELLS), National Institutes of Natural Sciences, Okazaki, Aichi, Japan
- Division of Biophotonics, National Institute for Physiological Sciences, National Institutes of Natural Sciences, Okazaki, Aichi, Japan
- School of Life Science, The Graduate University for Advanced Studies (SOKENDAI), Okazaki, Aichi, Japan
| | - Ryosuke Enoki
- Biophotonics Research Group, Exploratory Research Center on Life and Living Systems (ExCELLS), National Institutes of Natural Sciences, Okazaki, Aichi, Japan
- Division of Biophotonics, National Institute for Physiological Sciences, National Institutes of Natural Sciences, Okazaki, Aichi, Japan
- School of Life Science, The Graduate University for Advanced Studies (SOKENDAI), Okazaki, Aichi, Japan
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5
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Davidson AJ, Beckner D, Bonnefont X. A Journey in the Brain's Clock: In Vivo Veritas? BIOLOGY 2023; 12:1136. [PMID: 37627020 PMCID: PMC10452196 DOI: 10.3390/biology12081136] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2023] [Revised: 08/12/2023] [Accepted: 08/14/2023] [Indexed: 08/27/2023]
Abstract
The suprachiasmatic nuclei (SCN) of the hypothalamus contain the circadian pacemaker that coordinates mammalian rhythms in tune with the day-night cycle. Understanding the determinants of the intrinsic rhythmicity of this biological clock, its outputs, and resetting by environmental cues, has been a longstanding goal of the field. Integrated techniques of neurophysiology, including lesion studies and in vivo multi-unit electrophysiology, have been key to characterizing the rhythmic nature and outputs of the SCN in animal models. In parallel, reduced ex vivo and in vitro approaches have permitted us to unravel molecular, cellular, and multicellular mechanisms underlying the pacemaker properties of the SCN. New questions have emerged in recent years that will require combining investigation at a cell resolution within the physiological context of the living animal: What is the role of specific cell subpopulations in the SCN neural network? How do they integrate various external and internal inputs? What are the circuits involved in controlling other body rhythms? Here, we review what we have already learned about the SCN from in vivo studies, and how the recent development of new genetically encoded tools and cutting-edge imaging technology in neuroscience offers chronobiologists the opportunity to meet these challenges.
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Affiliation(s)
- Alec J. Davidson
- Neuroscience Institute, Morehouse School of Medicine, Atlanta, GA 30310, USA;
| | - Delaney Beckner
- Neuroscience Institute, Morehouse School of Medicine, Atlanta, GA 30310, USA;
| | - Xavier Bonnefont
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, 34094 Montpellier, France
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6
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Ragozzino FJ, Peterson B, Karatsoreos IN, Peters JH. Circadian regulation of glutamate release pathways shapes synaptic throughput in the brainstem nucleus of the solitary tract (NTS). J Physiol 2023; 601:1881-1896. [PMID: 36975145 PMCID: PMC10192157 DOI: 10.1113/jp284370] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2023] [Accepted: 03/06/2023] [Indexed: 03/29/2023] Open
Abstract
Circadian regulation of autonomic reflex pathways pairs physiological function with the daily light cycle. The brainstem nucleus of the solitary tract (NTS) is a key candidate for rhythmic control of the autonomic nervous system. Here we investigated circadian regulation of NTS neurotransmission and synaptic throughput using patch-clamp electrophysiology in brainstem slices from mice. We found that spontaneous quantal glutamate release onto NTS neurons showed strong circadian rhythmicity, with the highest rate of release during the light phase and the lowest in the dark, that were sufficient to drive day/night differences in constitutive postsynaptic action potential firing. In contrast, afferent evoked action potential throughput was enhanced during the dark and diminished in the light. Afferent-driven synchronous release pathways showed a similar decrease in release probability that did not explain the enhanced synaptic throughput during the night. However, analysis of postsynaptic membrane properties revealed diurnal changes in conductance, which, when coupled with the circadian changes in glutamate release pathways, tuned synaptic throughput between the light and dark phases. These coordinated pre-/postsynaptic changes encode nuanced control over synaptic performance and pair NTS action potential firing and vagal throughput with time of day. KEY POINTS: Vagal afferent neurons relay information from peripheral organs to the brainstem nucleus of the solitary tract (NTS) to initiate autonomic reflex pathways as well as providing important controls of food intake, digestive function and energy balance. Vagally mediated reflexes and behaviours are under strong circadian regulation. Diurnal fluctuations in presynaptic vesicle release pathways and postsynaptic membrane conductances provide nuanced control over NTS action potential firing and vagal synaptic throughput. Coordinated pre-/postsynaptic changes represent a fundamental mechanism mediating daily changes in vagal afferent signalling and autonomic function.
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Affiliation(s)
- Forrest J. Ragozzino
- Department of Integrative Physiology and Neuroscience, College of Veterinary Medicine, Washington State University, Pullman, WA, USA
| | - BreeAnne Peterson
- Department of Integrative Physiology and Neuroscience, College of Veterinary Medicine, Washington State University, Pullman, WA, USA
| | - Ilia N. Karatsoreos
- Department of Psychological and Brain Sciences, University of Massachusetts Amherst, Amherst, MA, 01003, USA
| | - James H. Peters
- Department of Integrative Physiology and Neuroscience, College of Veterinary Medicine, Washington State University, Pullman, WA, USA
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7
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Cheng PC, Cheng RC, Huang RC. Glutamate-Evoked Ca2+ Responses in the Rat Suprachiasmatic Nucleus: Involvement of Na+/K+-ATPase and Na+/Ca2+-Exchanger. Int J Mol Sci 2023; 24:ijms24076444. [PMID: 37047417 PMCID: PMC10095050 DOI: 10.3390/ijms24076444] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2023] [Revised: 03/22/2023] [Accepted: 03/28/2023] [Indexed: 03/31/2023] Open
Abstract
Glutamate mediates photic entrainment of the central clock in the suprachiasmatic nucleus (SCN) by evoking intracellular Ca2+ signaling mechanisms. However, the detailed mechanisms of glutamate-evoked Ca2+ signals are not entirely clear. Here, we used a ratiometric Ca2+ and Na+ imaging technique to investigate glutamate-evoked Ca2+ responses. The comparison of Ca2+ responses to glutamate (100 μM) and high (20 mM) K+ solution indicated slower Ca2+ clearance, along with rebound Ca2+ suppression for glutamate-evoked Ca2+ transients. Increasing the length of exposure time in glutamate, but not in 20 mM K+, slowed Ca2+ clearance and increased rebound Ca2+ suppression, a result correlated with glutamate-induced Na+ loads. The rebound Ca2+ suppression was abolished by ouabain, monensin, Na+-free solution, or nimodipine, suggesting an origin of activated Na+/K+-ATPase (NKA) by glutamate-induced Na+ loads. Ouabain or Na+-free solution also slowed Ca2+ clearance, apparently by retarding Na+/Ca2+-exchanger (NCX)-mediated Ca2+ extrusion. Together, our results indicated the involvement of glutamate-induced Na+ loads, NKA, and NCX in shaping the Ca2+ response to glutamate. Nevertheless, in the absence of external Na+ (NMDG substituted), Ca2+ clearance was still slower for the Ca2+ response to glutamate than for 20 mM K+, suggesting participation of additional Ca2+ handlers to the slower Ca2+ clearance under this condition.
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8
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Stangherlin A. Ion dynamics and the regulation of circadian cellular physiology. Am J Physiol Cell Physiol 2023; 324:C632-C643. [PMID: 36689675 DOI: 10.1152/ajpcell.00378.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Circadian rhythms in physiology and behavior allow organisms to anticipate the daily environmental changes imposed by the rotation of our planet around its axis. Although these rhythms eventually manifest at the organismal level, a cellular basis for circadian rhythms has been demonstrated. Significant contributors to these cell-autonomous rhythms are daily cycles in gene expression and protein translation. However, recent data revealed cellular rhythms in other biological processes, including ionic currents, ion transport, and cytosolic ion abundance. Circadian rhythms in ion currents sustain circadian variation in action potential firing rate, which coordinates neuronal behavior and activity. Circadian regulation of metal ions abundance and dynamics is implicated in distinct cellular processes, from protein translation to membrane activity and osmotic homeostasis. In turn, studies showed that manipulating ion abundance affects the expression of core clock genes and proteins, suggestive of a close interplay. However, the relationship between gene expression cycles, ion dynamics, and cellular function is still poorly characterized. In this review, I will discuss the mechanisms that generate ion rhythms, the cellular functions they govern, and how they feed back to regulate the core clock machinery.
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Affiliation(s)
- Alessandra Stangherlin
- Faculty of Medicine and University Hospital Cologne, Cluster of Excellence Cellular Stress Responses in Aging-associated Diseases (CECAD), Institute for Mitochondrial Diseases and Ageing, University of Cologne, Cologne, Germany
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9
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Van Drunen R, Eckel-Mahan K. Circadian rhythms as modulators of brain health during development and throughout aging. Front Neural Circuits 2023; 16:1059229. [PMID: 36741032 PMCID: PMC9893507 DOI: 10.3389/fncir.2022.1059229] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2022] [Accepted: 12/08/2022] [Indexed: 01/20/2023] Open
Abstract
The circadian clock plays a prominent role in neurons during development and throughout aging. This review covers topics pertinent to the role of 24-h rhythms in neuronal development and function, and their tendency to decline with aging. Pharmacological or behavioral modification that augment the function of our internal clock may be central to decline of cognitive disease and to future chronotherapy for aging-related diseases of the central nervous system.
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10
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ISX-9 potentiates CaMKIIδ-mediated BMAL1 activation to enhance circadian amplitude. Commun Biol 2022; 5:750. [PMID: 35902736 PMCID: PMC9334596 DOI: 10.1038/s42003-022-03725-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2021] [Accepted: 07/15/2022] [Indexed: 11/09/2022] Open
Abstract
Circadian dysregulation associates with numerous diseases including metabolic dysfunction, sleep disorder, depression and aging. Given that declined circadian amplitude is a trait commonly found with compromised health, interventions that design in precluding circadian amplitude from dampening will aid to mitigate complex, circadian-related diseases. Here we identify a neurogenic small molecule ISX-9 that is able to support persistent and higher amplitude of circadian oscillations. ISX-9 improves diurnal metabolic rhythms in middle-aged mice. Moreover, the ISX-9-treated mice show better sleep homeostasis with increased delta power during the day time and higher locomotive activity in the dark period. ISX-9 augments CaMKIIδ expression and increases BMAL1 activity via eliciting CaMKIIδ-mediated phosphorylation on BMAL1 residues S513/S515/S516, accordingly composes a positive feedback effect on enhancing circadian amplitude. CaMKIIδ-targeting, and the use of ISX-9 may serve as decent choices for treating circadian-related disorders.
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11
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El Cheikh Hussein L, Fontanaud P, Mollard P, Bonnefont X. Nested calcium dynamics support daily cell unity and diversity in the suprachiasmatic nuclei of free-behaving mice. PNAS NEXUS 2022; 1:pgac112. [PMID: 36741435 PMCID: PMC9896879 DOI: 10.1093/pnasnexus/pgac112] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/11/2022] [Accepted: 07/05/2022] [Indexed: 02/07/2023]
Abstract
The suprachiasmatic nuclei (SCN) of the anterior hypothalamus host the circadian pacemaker that synchronizes mammalian rhythms with the day-night cycle. SCN neurons are intrinsically rhythmic, thanks to a conserved cell-autonomous clock mechanism. In addition, circuit-level emergent properties confer a unique degree of precision and robustness to SCN neuronal rhythmicity. However, the multicellular functional organization of the SCN is not yet fully understood. Indeed, although SCN neurons are well-coordinated, experimental evidences indicate that some neurons oscillate out of phase in SCN explants, and possibly to a larger extent in vivo. Here, to tackle this issue we used microendoscopic Ca2+ i imaging and investigated SCN rhythmicity at a single cell resolution in free-behaving mice. We found that SCN neurons in vivo exhibited fast Ca2+ i spikes superimposed upon slow changes in baseline Ca2+ i levels. Both spikes and baseline followed a time-of-day modulation in many neurons, but independently from each other. Daily rhythms in basal Ca2+ i were highly coordinated, while spike activity from the same neurons peaked at multiple times of the light cycle, and unveiled clock-independent coactivity in neuron subsets. Hence, fast Ca2+ i spikes and slow changes in baseline Ca2+ i levels highlighted how multiple individual activity patterns could articulate within the temporal unity of the SCN cell network in vivo, and provided support for a multiplex neuronal code in the circadian pacemaker.
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Affiliation(s)
- Lama El Cheikh Hussein
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, IGF, 141 Rue de la Cardonille, F-34094 Montpellier, Cedex 5, France,BioCampus Montpellier, Université de Montpellier, CNRS, INSERM, 141 Rue de la Cardonille, F-34094 Montpellier, Cedex 5, France
| | - Pierre Fontanaud
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, IGF, 141 Rue de la Cardonille, F-34094 Montpellier, Cedex 5, France,BioCampus Montpellier, Université de Montpellier, CNRS, INSERM, 141 Rue de la Cardonille, F-34094 Montpellier, Cedex 5, France
| | - Patrice Mollard
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, IGF, 141 Rue de la Cardonille, F-34094 Montpellier, Cedex 5, France,BioCampus Montpellier, Université de Montpellier, CNRS, INSERM, 141 Rue de la Cardonille, F-34094 Montpellier, Cedex 5, France
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12
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Liang X, Holy TE, Taghert PH. Circadian pacemaker neurons display cophasic rhythms in basal calcium level and in fast calcium fluctuations. Proc Natl Acad Sci U S A 2022; 119:e2109969119. [PMID: 35446620 PMCID: PMC9173584 DOI: 10.1073/pnas.2109969119] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Accepted: 03/17/2022] [Indexed: 12/02/2022] Open
Abstract
Circadian pacemaker neurons in the Drosophila brain display daily rhythms in the levels of intracellular calcium. These calcium rhythms are driven by molecular clocks and are required for normal circadian behavior. To study their biological basis, we employed genetic manipulations in conjunction with improved methods of in vivo light-sheet microscopy to measure calcium dynamics in individual pacemaker neurons over complete 24-h durations at sampling frequencies as high as 5 Hz. This technological advance unexpectedly revealed cophasic daily rhythms in basal calcium levels and in high-frequency calcium fluctuations. Further, we found that the rhythms of basal calcium levels and of fast calcium fluctuations reflect the activities of two proteins that mediate distinct forms of calcium fluxes. One is the inositol trisphosphate receptor (ITPR), a channel that mediates calcium fluxes from internal endoplasmic reticulum calcium stores, and the other is a T-type voltage-gated calcium channel, which mediates extracellular calcium influx. These results suggest that Drosophila molecular clocks regulate ITPR and T-type channels to generate two distinct but coupled rhythms in basal calcium and in fast calcium fluctuations. We propose that both internal and external calcium fluxes are essential for circadian pacemaker neurons to provide rhythmic outputs and thereby, regulate the activities of downstream brain centers.
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Affiliation(s)
- Xitong Liang
- Department of Neuroscience, Washington University in St. Louis, St. Louis, MO 63110
| | - Timothy E. Holy
- Department of Neuroscience, Washington University in St. Louis, St. Louis, MO 63110
| | - Paul H. Taghert
- Department of Neuroscience, Washington University in St. Louis, St. Louis, MO 63110
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13
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14
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Plante AE, Rao VP, Rizzo MA, Meredith AL. Comparative Ca 2+ channel contributions to intracellular Ca 2+ levels in the circadian clock. BIOPHYSICAL REPORTS 2021; 1:100005. [PMID: 35330949 PMCID: PMC8942421 DOI: 10.1016/j.bpr.2021.100005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/27/2021] [Accepted: 07/08/2021] [Indexed: 11/22/2022]
Abstract
Circadian rhythms in mammals are coordinated by the central clock in the brain, located in the suprachiasmatic nucleus (SCN). Multiple molecular and cellular signals display a circadian variation within SCN neurons, including intracellular Ca2+, but the mechanisms are not definitively established. SCN cytosolic Ca2+ levels exhibit a peak during the day, when both action potential firing and Ca2+ channel activity are increased, and are decreased at night, correlating with a reduction in firing rate. In this study, we employ a single-color fluorescence anisotropy reporter (FLARE), Venus FLARE-Cameleon, and polarization inverted selective-plane illumination microscopy to measure rhythmic changes in cytosolic Ca2+ in SCN neurons. Using this technique, the Ca2+ channel subtypes contributing to intracellular Ca2+ at the peak and trough of the circadian cycle were assessed using a pharmacological approach with Ca2+ channel inhibitors. Peak (218 ± 16 nM) and trough (172 ± 13 nM) Ca2+ levels were quantified, indicating a 1.3-fold circadian variance in Ca2+ concentration. Inhibition of ryanodine-receptor-mediated Ca2+ release produced a larger relative decrease in cytosolic Ca2+ at both time points compared to voltage-gated Ca2+channels. These results support the hypothesis that circadian Ca2+ rhythms in SCN neurons are predominantly driven by intracellular Ca2+ channels, although not exclusively so. The study provides a foundation for future experiments to probe Ca2+ signaling in a dynamic biological context using FLAREs.
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Affiliation(s)
- Amber E. Plante
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Vishnu P. Rao
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Megan A. Rizzo
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Andrea L. Meredith
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland
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15
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Cavieres-Lepe J, Ewer J. Reciprocal Relationship Between Calcium Signaling and Circadian Clocks: Implications for Calcium Homeostasis, Clock Function, and Therapeutics. Front Mol Neurosci 2021; 14:666673. [PMID: 34045944 PMCID: PMC8144308 DOI: 10.3389/fnmol.2021.666673] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2021] [Accepted: 04/09/2021] [Indexed: 12/03/2022] Open
Abstract
In animals, circadian clocks impose a daily rhythmicity to many behaviors and physiological processes. At the molecular level, circadian rhythms are driven by intracellular transcriptional/translational feedback loops (TTFL). Interestingly, emerging evidence indicates that they can also be modulated by multiple signaling pathways. Among these, Ca2+ signaling plays a key role in regulating the molecular rhythms of clock genes and of the resulting circadian behavior. In addition, the application of in vivo imaging approaches has revealed that Ca2+ is fundamental to the synchronization of the neuronal networks that make up circadian pacemakers. Conversely, the activity of circadian clocks may influence Ca2+ signaling. For instance, several genes that encode Ca2+ channels and Ca2+-binding proteins display a rhythmic expression, and a disruption of this cycling affects circadian function, underscoring their reciprocal relationship. Here, we review recent advances in our understanding of how Ca2+ signaling both modulates and is modulated by circadian clocks, focusing on the regulatory mechanisms described in Drosophila and mice. In particular, we examine findings related to the oscillations in intracellular Ca2+ levels in circadian pacemakers and how they are regulated by canonical clock genes, neuropeptides, and light stimuli. In addition, we discuss how Ca2+ rhythms and their associated signaling pathways modulate clock gene expression at the transcriptional and post-translational levels. We also review evidence based on transcriptomic analyzes that suggests that mammalian Ca2+ channels and transporters (e.g., ryanodine receptor, ip3r, serca, L- and T-type Ca2+ channels) as well as Ca2+-binding proteins (e.g., camk, cask, and calcineurin) show rhythmic expression in the central brain clock and in peripheral tissues such as the heart and skeletal muscles. Finally, we discuss how the discovery that Ca2+ signaling is regulated by the circadian clock could influence the efficacy of pharmacotherapy and the outcomes of clinical interventions.
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Affiliation(s)
- Javier Cavieres-Lepe
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencias, Universidad de Valparaíso, Valparaíso, Chile.,Programa de Doctorado en Ciencias, Mención Neurociencia, Universidad de Valparaíso, Valparaíso, Chile
| | - John Ewer
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencias, Universidad de Valparaíso, Valparaíso, Chile
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16
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Cluster headache pathophysiology - insights from current and emerging treatments. Nat Rev Neurol 2021; 17:308-324. [PMID: 33782592 DOI: 10.1038/s41582-021-00477-w] [Citation(s) in RCA: 46] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/24/2021] [Indexed: 02/01/2023]
Abstract
Cluster headache is a debilitating primary headache disorder that affects approximately 0.1% of the population worldwide. Cluster headache attacks involve severe unilateral pain in the trigeminal distribution together with ipsilateral cranial autonomic features and a sense of agitation. Acute treatments are available and are effective in just over half of the patients. Until recently, preventive medications were borrowed from non-headache indications, so management of cluster headache is challenging. However, as our understanding of cluster headache pathophysiology has evolved on the basis of key bench and neuroimaging studies, crucial neuropeptides and brain structures have been identified as emerging treatment targets. In this Review, we provide an overview of what is known about the pathophysiology of cluster headache and discuss the existing treatment options and their mechanisms of action. Existing acute treatments include triptans and high-flow oxygen, interim treatment options include corticosteroids in oral form or for greater occipital nerve block, and preventive treatments include verapamil, lithium, melatonin and topiramate. We also consider emerging treatment options, including calcitonin gene-related peptide antibodies, non-invasive vagus nerve stimulation, sphenopalatine ganglion stimulation and somatostatin receptor agonists, discuss how evidence from trials of these emerging treatments provides insights into the pathophysiology of cluster headache and highlight areas for future research.
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17
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Buijink MR, Michel S. A multi-level assessment of the bidirectional relationship between aging and the circadian clock. J Neurochem 2021; 157:73-94. [PMID: 33370457 PMCID: PMC8048448 DOI: 10.1111/jnc.15286] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2020] [Revised: 12/23/2020] [Accepted: 12/23/2020] [Indexed: 12/15/2022]
Abstract
The daily temporal order of physiological processes and behavior contribute to the wellbeing of many organisms including humans. The central circadian clock, which coordinates the timing within our body, is located in the suprachiasmatic nucleus (SCN) of the hypothalamus. Like in other parts of the brain, aging impairs the SCN function, which in turn promotes the development and progression of aging-related diseases. We here review the impact of aging on the different levels of the circadian clock machinery-from molecules to organs-with a focus on the role of the SCN. We find that the molecular clock is less effected by aging compared to other cellular components of the clock. Proper rhythmic regulation of intracellular signaling, ion channels and neuronal excitability of SCN neurons are greatly disturbed in aging. This suggests a disconnection between the molecular clock and the electrophysiology of these cells. The neuronal network of the SCN is able to compensate for some of these cellular deficits. However, it still results in a clear reduction in the amplitude of the SCN electrical rhythm, suggesting a weakening of the output timing signal. Consequently, other brain areas and organs not only show aging-related deficits in their own local clocks, but also receive a weaker systemic timing signal. The negative spiral completes with the weakening of positive feedback from the periphery to the SCN. Consequently, chronotherapeutic interventions should aim at strengthening overall synchrony in the circadian system using life-style and/or pharmacological approaches.
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Affiliation(s)
- M. Renate Buijink
- Department of Cellular and Chemical BiologyLaboratory for NeurophysiologyLeiden University Medical CenterLeidenthe Netherlands
| | - Stephan Michel
- Department of Cellular and Chemical BiologyLaboratory for NeurophysiologyLeiden University Medical CenterLeidenthe Netherlands
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18
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Lin HY, Huang RC. Glycolytic metabolism and activation of Na + pumping contribute to extracellular acidification in the central clock of the suprachiasmatic nucleus: Differential glucose sensitivity and utilization between oxidative and non-oxidative glycolytic pathways. Biomed J 2021; 45:143-154. [PMID: 35341719 PMCID: PMC9133309 DOI: 10.1016/j.bj.2021.02.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2020] [Revised: 02/02/2021] [Accepted: 02/07/2021] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND The central clock of the suprachiasmatic nucleus (SCN) controls the metabolism of glucose and is sensitive to glucose shortage. However, it is only beginning to be understood how metabolic signals such as glucose availability regulate the SCN physiology. We previously showed that the ATP-sensitive K+ channel plays a glucose-sensing role in regulating SCN neuronal firing at times of glucose shortage. Nevertheless, it is unknown whether the energy-demanding Na+/K+-ATPase (NKA) is also sensitive to glucose availability. Furthermore, we recently showed that the metabolically active SCN constantly extrudes H+ to acidify extracellular pH (pHe). This study investigated whether the standing acidification is associated with Na+ pumping activity, energy metabolism, and glucose utilization, and whether glycolysis- and mitochondria-fueled NKAs may be differentially sensitive to glucose shortage. METHODS Double-barreled pH-selective microelectrodes were used to determine the pHe in the SCN in hypothalamic slices. RESULTS NKA inhibition with K+-free (0-K+) solution rapidly and reversibly alkalinized the pHe, an effect abolished by ouabain. Mitochondrial inhibition with cyanide acidified the pHe but did not inhibit 0-K+-induced alkalinization. Glycolytic inhibition with iodoacetate alkalinized the pHe, completely blocked cyanide-induced acidification, and nearly completely blocked 0-K+-induced alkalinization. The results indicate that glycolytic metabolism and activation of Na+ pumping contribute to the standing acidification. Glucoprivation also alkalinized the pHe, nearly completely eliminated cyanide-induced acidification, but only partially reduced 0-K+-induced alkalinization. In contrast, hypoglycemia preferentially and partially blocked cyanide-induced acidification. The result indicates sensitivity to glucose shortage for the mitochondria-associated oxidative glycolytic pathway. CONCLUSION Glycolytic metabolism and activation of glycolysis-fueled NKA Na+ pumping activity contribute to the standing acidification in the SCN. Furthermore, the oxidative and non-oxidative glycolytic pathways differ in their glucose sensitivity and utilization, with the oxidative glycolytic pathway susceptible to glucose shortage, and the non-oxidative glycolytic pathway able to maintain Na+ pumping even in glucoprivation.
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Affiliation(s)
- Hsin-Yi Lin
- Department of Physiology and Pharmacology, College of Medicine, Chang Gung University, Taoyuan, Taiwan
| | - Rong-Chi Huang
- Department of Physiology and Pharmacology, College of Medicine, Chang Gung University, Taoyuan, Taiwan; Healthy Aging Research Center, Chang Gung University, Taoyuan, Taiwan; Neuroscience Research Center, Chang Gung Memorial Hospital at Linkou, Taoyuan, Taiwan.
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19
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Michel S, Nakamura TJ, Meijer JH, Colwell CS. Electrophysiological Approaches to Studying the Suprachiasmatic Nucleus. Methods Mol Biol 2021; 2130:303-324. [PMID: 33284454 DOI: 10.1007/978-1-0716-0381-9_23] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
In mammals, the part of the nervous system responsible for most circadian behavior can be localized to a bilaterally paired structure in the hypothalamus known as the suprachiasmatic nucleus (SCN). Understanding the mammalian circadian system will require a detailed multilevel analysis of neural SCN circuits ex vivo and in vivo. Many of the techniques and approaches that are used for the analysis of the circuitry driving circadian oscillations in the SCN are similar to those employed in other brain regions. There is, however, one fundamental difference that needs to be taken into consideration, that is, the physiological, cell, and molecular properties of SCN neurons vary with the time of day. In this chapter, we will consider the preparations and electrophysiological techniques that we have used to analyze the SCN circuit focusing on the acute brain slice and intact, freely moving animal.
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Affiliation(s)
- Stephan Michel
- Laboratory for Neurophysiology, Department of Cell and Chemical Biology, Leiden University Medical Center, Leiden, The Netherlands.
| | - Takahiro J Nakamura
- Laboratory of Animal Physiology, Department of Life Sciences, School of Agriculture, Meiji University, Tama-ku Kawasaki, Kanagawa, Japan
| | - Johanna H Meijer
- Laboratory for Neurophysiology, Department of Cell and Chemical Biology, Leiden University Medical Center, Leiden, The Netherlands
| | - Christopher S Colwell
- Department of Psychiatry and Biobehavioral Sciences, University of California, Los Angeles, Los Angeles, CA, USA
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20
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Hartsock MJ, Spencer RL. Memory and the circadian system: Identifying candidate mechanisms by which local clocks in the brain may regulate synaptic plasticity. Neurosci Biobehav Rev 2020; 118:134-162. [PMID: 32712278 DOI: 10.1016/j.neubiorev.2020.07.023] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2019] [Revised: 07/14/2020] [Accepted: 07/18/2020] [Indexed: 12/11/2022]
Abstract
The circadian system is an endogenous biological network responsible for coordinating near-24-h cycles in behavior and physiology with daily timing cues from the external environment. In this review, we explore how the circadian system regulates memory formation, retention, and recall. Circadian rhythms in these memory processes may arise through several endogenous pathways, and recent work highlights the importance of genetic timekeepers found locally within tissues, called local clocks. We evaluate the circadian memory literature for evidence of local clock involvement in memory, identifying potential nodes for direct interactions between local clock components and mechanisms of synaptic plasticity. Our discussion illustrates how local clocks may pervasively modulate neuronal plastic capacity, a phenomenon that we designate here as circadian metaplasticity. We suggest that this function of local clocks supports the temporal optimization of memory processes, illuminating the potential for circadian therapeutic strategies in the prevention and treatment of memory impairment.
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Affiliation(s)
- Matthew J Hartsock
- Department of Psychology and Neuroscience, University of Colorado Boulder, Boulder, Colorado 80309, United States.
| | - Robert L Spencer
- Department of Psychology and Neuroscience, University of Colorado Boulder, Boulder, Colorado 80309, United States.
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21
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Monfredi O, Lakatta EG. Complexities in cardiovascular rhythmicity: perspectives on circadian normality, ageing and disease. Cardiovasc Res 2020; 115:1576-1595. [PMID: 31150049 DOI: 10.1093/cvr/cvz112] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/27/2018] [Revised: 02/06/2019] [Accepted: 05/25/2019] [Indexed: 12/13/2022] Open
Abstract
Biological rhythms exist in organisms at all levels of complexity, in most organs and at myriad time scales. Our own biological rhythms are driven by energy emitted by the sun, interacting via our retinas with brain stem centres, which then send out complex messages designed to synchronize the behaviour of peripheral non-light sensing organs, to ensure optimal physiological responsiveness and performance of the organism based on the time of day. Peripheral organs themselves have autonomous rhythmic behaviours that can act independently from central nervous system control but is entrainable. Dysregulation of biological rhythms either through environment or disease has far-reaching consequences on health that we are only now beginning to appreciate. In this review, we focus on cardiovascular rhythms in health, with ageing and under disease conditions.
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Affiliation(s)
- Oliver Monfredi
- Division of Medicine, Department of Cardiology, The Johns Hopkins Hospital, 1800 Orleans Street, Baltimore, MD, USA.,Laboratory of Cardiovascular Sciences, Intramural Research Program, National Institute on Aging, National Institutes of Health, 251 Bayview Blvd, Baltimore, MD, USA
| | - Edward G Lakatta
- Laboratory of Cardiovascular Sciences, Intramural Research Program, National Institute on Aging, National Institutes of Health, 251 Bayview Blvd, Baltimore, MD, USA
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22
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Harvey JRM, Plante AE, Meredith AL. Ion Channels Controlling Circadian Rhythms in Suprachiasmatic Nucleus Excitability. Physiol Rev 2020; 100:1415-1454. [PMID: 32163720 DOI: 10.1152/physrev.00027.2019] [Citation(s) in RCA: 50] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Animals synchronize to the environmental day-night cycle by means of an internal circadian clock in the brain. In mammals, this timekeeping mechanism is housed in the suprachiasmatic nucleus (SCN) of the hypothalamus and is entrained by light input from the retina. One output of the SCN is a neural code for circadian time, which arises from the collective activity of neurons within the SCN circuit and comprises two fundamental components: 1) periodic alterations in the spontaneous excitability of individual neurons that result in higher firing rates during the day and lower firing rates at night, and 2) synchronization of these cellular oscillations throughout the SCN. In this review, we summarize current evidence for the identity of ion channels in SCN neurons and the mechanisms by which they set the rhythmic parameters of the time code. During the day, voltage-dependent and independent Na+ and Ca2+ currents, as well as several K+ currents, contribute to increased membrane excitability and therefore higher firing frequency. At night, an increase in different K+ currents, including Ca2+-activated BK currents, contribute to membrane hyperpolarization and decreased firing. Layered on top of these intrinsically regulated changes in membrane excitability, more than a dozen neuromodulators influence action potential activity and rhythmicity in SCN neurons, facilitating both synchronization and plasticity of the neural code.
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Affiliation(s)
- Jenna R M Harvey
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Amber E Plante
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Andrea L Meredith
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland
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23
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Zakhvataev VE. Tidal variations of background ionizing radiation and circadian timing of the suprachiasmatic nucleus clock. Med Hypotheses 2020; 140:109667. [PMID: 32182557 DOI: 10.1016/j.mehy.2020.109667] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2020] [Revised: 03/03/2020] [Accepted: 03/05/2020] [Indexed: 02/06/2023]
Abstract
Recently, correlations of different physiological processes in humans with variations in the local lunisolar gravitational tide force have been observed under highly controlled laboratory conditions. Understanding of the physical nature of this phenomenon needs a comprehensive study of its possible molecular mechanisms. One of the possible timing cues is the strong periodic variation of the emanation fields of radon-222 and its progeny produced by tidal deformations of geological environment. In the present work, we argue that this variation could induce temporal modulation of radiation-induced bystander signaling pathways associated with fundamental regulators of gene expression in the suprachiasmatic nucleus clock.
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Affiliation(s)
- V E Zakhvataev
- Federal Research Center "Krasnoyarsk Scientific Center of the Siberian Branch of the Russian Academy of Sciences", 660036 Krasnoyarsk, Russia; Siberian Federal University, 660041 Krasnoyarsk, Russia.
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24
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Szibor M, Gizatullina Z, Gainutdinov T, Endres T, Debska-Vielhaber G, Kunz M, Karavasili N, Hallmann K, Schreiber F, Bamberger A, Schwarzer M, Doenst T, Heinze HJ, Lessmann V, Vielhaber S, Kunz WS, Gellerich FN. Cytosolic, but not matrix, calcium is essential for adjustment of mitochondrial pyruvate supply. J Biol Chem 2020; 295:4383-4397. [PMID: 32094224 PMCID: PMC7135991 DOI: 10.1074/jbc.ra119.011902] [Citation(s) in RCA: 43] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2019] [Revised: 02/19/2020] [Indexed: 12/12/2022] Open
Abstract
Mitochondrial oxidative phosphorylation (OXPHOS) and cellular workload are tightly balanced by the key cellular regulator, calcium (Ca2+). Current models assume that cytosolic Ca2+ regulates workload and that mitochondrial Ca2+ uptake precedes activation of matrix dehydrogenases, thereby matching OXPHOS substrate supply to ATP demand. Surprisingly, knockout (KO) of the mitochondrial Ca2+ uniporter (MCU) in mice results in only minimal phenotypic changes and does not alter OXPHOS. This implies that adaptive activation of mitochondrial dehydrogenases by intramitochondrial Ca2+ cannot be the exclusive mechanism for OXPHOS control. We hypothesized that cytosolic Ca2+, but not mitochondrial matrix Ca2+, may adapt OXPHOS to workload by adjusting the rate of pyruvate supply from the cytosol to the mitochondria. Here, we studied the role of malate-aspartate shuttle (MAS)-dependent substrate supply in OXPHOS responses to changing Ca2+ concentrations in isolated brain and heart mitochondria, synaptosomes, fibroblasts, and thymocytes from WT and MCU KO mice and the isolated working rat heart. Our results indicate that extramitochondrial Ca2+ controls up to 85% of maximal pyruvate-driven OXPHOS rates, mediated by the activity of the complete MAS, and that intramitochondrial Ca2+ accounts for the remaining 15%. Of note, the complete MAS, as applied here, included besides its classical NADH oxidation reaction the generation of cytosolic pyruvate. Part of this largely neglected mechanism has previously been described as the “mitochondrial gas pedal.” Its implementation into OXPHOS control models integrates seemingly contradictory results and warrants a critical reappraisal of metabolic control mechanisms in health and disease.
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Affiliation(s)
- Marten Szibor
- Faculty of Medicine and Health Technology, Tampere University, FI-33520 Tampere, Finland.,Department of Cardiothoracic Surgery, Jena University Hospital, D-07747 Jena, Germany
| | - Zemfira Gizatullina
- Department of Neurology, Otto-von-Guericke-University, D-39120 Magdeburg, Germany.,Leibniz-Institute for Neurobiology, D-39120 Magdeburg, Germany
| | - Timur Gainutdinov
- Department of Neurology, Otto-von-Guericke-University, D-39120 Magdeburg, Germany.,Leibniz-Institute for Neurobiology, D-39120 Magdeburg, Germany.,Research Institute for Problems of Ecology and Mineral Wealth Use, Tatarstan Academy of Sciences, Kazan 420087, Russia
| | - Thomas Endres
- Faculty of Medicine and Health Technology, Tampere University, FI-33520 Tampere, Finland
| | | | - Matthias Kunz
- Department of Neurology, Otto-von-Guericke-University, D-39120 Magdeburg, Germany
| | - Niki Karavasili
- Department of Neurology, Otto-von-Guericke-University, D-39120 Magdeburg, Germany
| | - Kerstin Hallmann
- Department of Cardiothoracic Surgery, Jena University Hospital, D-07747 Jena, Germany
| | - Frank Schreiber
- Department of Neurology, Otto-von-Guericke-University, D-39120 Magdeburg, Germany.,German Center for Neurodegenerative Diseases, D-39120 Magdeburg, Germany
| | - Alexandra Bamberger
- Department of Cardiothoracic Surgery, Jena University Hospital, D-07747 Jena, Germany
| | - Michael Schwarzer
- Department of Cardiothoracic Surgery, Jena University Hospital, D-07747 Jena, Germany
| | - Torsten Doenst
- Department of Cardiothoracic Surgery, Jena University Hospital, D-07747 Jena, Germany
| | - Hans-Jochen Heinze
- Department of Neurology, Otto-von-Guericke-University, D-39120 Magdeburg, Germany.,German Center for Neurodegenerative Diseases, D-39120 Magdeburg, Germany.,Center for Behavioral Brain Sciences (CBBS), D-39120 Magdeburg, Germany
| | - Volkmar Lessmann
- Faculty of Medicine and Health Technology, Tampere University, FI-33520 Tampere, Finland.,Center for Behavioral Brain Sciences (CBBS), D-39120 Magdeburg, Germany
| | - Stefan Vielhaber
- Department of Neurology, Otto-von-Guericke-University, D-39120 Magdeburg, Germany.,German Center for Neurodegenerative Diseases, D-39120 Magdeburg, Germany
| | - Wolfram S Kunz
- Department of Cardiothoracic Surgery, Jena University Hospital, D-07747 Jena, Germany
| | - Frank N Gellerich
- Department of Neurology, Otto-von-Guericke-University, D-39120 Magdeburg, Germany .,Leibniz-Institute for Neurobiology, D-39120 Magdeburg, Germany
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25
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Eugenin EA, Valdebenito S, Gorska AM, Martínez AD, Bitran M, Sáez JC. Gap junctions coordinate the propagation of glycogenolysis induced by norepinephrine in the pineal gland. J Neurochem 2019; 151:558-569. [PMID: 31381153 DOI: 10.1111/jnc.14846] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2019] [Revised: 06/15/2019] [Accepted: 07/29/2019] [Indexed: 11/26/2022]
Abstract
Chemical and electrical synapses are the two major communication systems that permit cell-to-cell communication within the nervous system. Although most studies are focused on chemical synapses (glutamate, γ-aminobutyric acid, and other neurotransmitters), clearly both types of synapses interact and cooperate to allow the coordination of several cell functions within the nervous system. The pineal gland has limited independent axonal innervation and not every cell has access to nerve terminals. Thus, additional communication systems, such as gap junctions, have been postulated to coordinate metabolism and signaling. Using acutely isolated glands and dissociated cells, we found that gap junctions spread glycogenolytic signals from cells containing adrenoreceptors to the entire gland lacking these receptors. Our data using glycogen and lactate quantification, electrical stimulation, and high-performance liquid chromatography with electrochemical detection, demonstrate that gap junctional communication between cells of the rat pineal gland allows cell-to-cell propagation of norepinephrine-induced signal that promotes glycogenolysis throughout the entire gland. Thus, the interplay of both synapses is essential for coordinating glycogen metabolism and lactate production in the pineal gland.
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Affiliation(s)
| | | | | | - Agustin D Martínez
- Instituto de Neurociencias, Centro interdisciplinario de Neurociencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Marcela Bitran
- Departamento de Fisiologia, Pontificia Universidad Catolica de Chile, Santiago, Chile
| | - Juan C Sáez
- Instituto de Neurociencias, Centro interdisciplinario de Neurociencias, Universidad de Valparaíso, Valparaíso, Chile.,Departamento de Fisiologia, Pontificia Universidad Catolica de Chile, Santiago, Chile
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26
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Role of Intracellular Na + in the Regulation of [Ca 2+] i in the Rat Suprachiasmatic Nucleus Neurons. Int J Mol Sci 2019; 20:ijms20194868. [PMID: 31575032 PMCID: PMC6801571 DOI: 10.3390/ijms20194868] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2019] [Accepted: 09/28/2019] [Indexed: 12/17/2022] Open
Abstract
Transmembrane Ca2+ influx is essential to the proper functioning of the central clock in the suprachiasmatic nucleus (SCN). In the rat SCN neurons, the clearance of somatic Ca2+ following depolarization-induced Ca2+ transients involves Ca2+ extrusion via Na+/Ca2+ exchanger (NCX) and mitochondrial Ca2+ buffering. Here we show an important role of intracellular Na+ in the regulation of [Ca2+]i in these neurons. The effect of Na+ loading on [Ca2+]i was determined with the Na+ ionophore monensin and the cardiac glycoside ouabain to block Na+/K+-ATPase (NKA). Ratiometric Na+ and Ca2+ imaging was used to measure the change in [Na+]i and [Ca2+]i, and cell-attached recordings to investigate the effects of monensin and ouabain on spontaneous firing. Our results show that in spite of opposite effects on spontaneous firing and basal [Ca2+], both monensin and ouabain induced Na+ loading, and increased the peak amplitude, slowed the fast decay rate, and enhanced the slow decay phase of 20 mM K+-evoked Ca2+ transients. Furthermore, both ouabain and monensin preferentially enhanced nimodipine-insensitive Ca2+ transients. Together, our results indicate that in the SCN neurons the NKA plays an important role in regulating [Ca2+]i, in particular, associated with nimodipine-insensitive Ca2+ channels.
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27
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Petersen AS, Barloese MCJ, Snoer A, Soerensen AMS, Jensen RH. Verapamil and Cluster Headache: Still a Mystery. A Narrative Review of Efficacy, Mechanisms and Perspectives. Headache 2019; 59:1198-1211. [DOI: 10.1111/head.13603] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/27/2019] [Indexed: 01/04/2023]
Affiliation(s)
- Anja S. Petersen
- Department of Neurology, Danish Headache Center Rigshospitalet‐Glostrup Glostrup Denmark
| | - Mads C. J. Barloese
- Department of Neurology, Danish Headache Center Rigshospitalet‐Glostrup Glostrup Denmark
- Department of Clinical Physiology and Nuclear Medicine, Center for Functional and Diagnostic Imaging Hvidovre Hospital Hvidovre Denmark
| | - Agneta Snoer
- Department of Neurology, Danish Headache Center Rigshospitalet‐Glostrup Glostrup Denmark
| | - Anne Mette S. Soerensen
- Department of Clinical Pharmacology Bispebjerg and Frederiksberg Hospital Copenhagen Denmark
| | - Rigmor H. Jensen
- Department of Neurology, Danish Headache Center Rigshospitalet‐Glostrup Glostrup Denmark
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28
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El Cheikh Hussein L, Mollard P, Bonnefont X. Molecular and Cellular Networks in The Suprachiasmatic Nuclei. Int J Mol Sci 2019; 20:ijms20082052. [PMID: 31027315 PMCID: PMC6514755 DOI: 10.3390/ijms20082052] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Revised: 04/18/2019] [Accepted: 04/23/2019] [Indexed: 12/20/2022] Open
Abstract
Why do we experience the ailments of jetlag when we travel across time zones? Why is working night-shifts so detrimental to our health? In other words, why can’t we readily choose and stick to non-24 h rhythms? Actually, our daily behavior and physiology do not simply result from the passive reaction of our organism to the external cycle of days and nights. Instead, an internal clock drives the variations in our bodily functions with a period close to 24 h, which is supposed to enhance fitness to regular and predictable changes of our natural environment. This so-called circadian clock relies on a molecular mechanism that generates rhythmicity in virtually all of our cells. However, the robustness of the circadian clock and its resilience to phase shifts emerge from the interaction between cell-autonomous oscillators within the suprachiasmatic nuclei (SCN) of the hypothalamus. Thus, managing jetlag and other circadian disorders will undoubtedly require extensive knowledge of the functional organization of SCN cell networks. Here, we review the molecular and cellular principles of circadian timekeeping, and their integration in the multi-cellular complexity of the SCN. We propose that new, in vivo imaging techniques now enable to address these questions directly in freely moving animals.
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Affiliation(s)
- Lama El Cheikh Hussein
- Institut de Génomique Fonctionnelle (IGF), University Montpellier, CNRS, INSERM, 34094 Montpellier, France.
| | - Patrice Mollard
- Institut de Génomique Fonctionnelle (IGF), University Montpellier, CNRS, INSERM, 34094 Montpellier, France.
| | - Xavier Bonnefont
- Institut de Génomique Fonctionnelle (IGF), University Montpellier, CNRS, INSERM, 34094 Montpellier, France.
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29
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Song Q, Feng G, Zhang J, Xia X, Ji M, Lv L, Ping Y. NMDA Receptor-mediated Ca2+ Influx in the Absence of Mg2+ Block Disrupts Rest: Activity Rhythms in Drosophila. Sleep 2018; 40:4330652. [PMID: 29029290 DOI: 10.1093/sleep/zsx166] [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] [Indexed: 12/12/2022] Open
Abstract
Study Objectives The correlated activation of pre- and postsynaptic neurons is essential for the NMDA receptor-mediated Ca2+ influx by removing Mg2+ from block site and NMDA receptors have been implicated in phase resetting of circadian clocks. So we assessed rest:activity rhythms in Mg2+ block defective animals. Methods Using Drosophila locomotor monitoring system, we checked circadian rest:activity rhythms of different mutants under constant darkness (DD) and light:dark (LD) conditions. We recorded NMDA receptor-mediated currents or Ca2+ increase in neurons using patch-clamp and Ca2+ imaging techniques. Results We found that Mg2+ block defective mutant flies were completely arrhythmic under DD. To further understand the role of Mg2+ block in daily circadian rest:activity, we observed the mutant files under LD cycles, and we found severely reduced morning anticipation and advanced evening peak compared to control flies. We also used tissue-specific expression of Mg2+ block defective NMDA receptors and demonstrated pigment-dispersing factor receptor (PDFR)-expressing circadian neurons were implicated in mediating the circadian rest:activity deficits. Endogenous functional NMDA receptors are expressed in most Drosophila neurons, including in a subgroup of dorsal neurons (DN1s). Subsequently, we determined that the uncorrelated extra Ca2+ influx may act in part through Ca2+/Calmodulin (CaM)-stimulated PDE1c pathway leading to morning behavior phenotypes. Conclusions These results demonstrate that Mg2+ block of NMDA receptors at resting potential is essential for the daily circadian rest:activity rhythms and we propose that Mg2+ block functions to suppress CaM-stimulated PDE1c activation at resting potential, thus regulating Ca2+ and cyclic AMP oscillations in circadian and sleep circuits.
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Affiliation(s)
- Qian Song
- Bio-X Institutes, Shanghai Jiao Tong University, Shanghai, China
| | - Ge Feng
- Bio-X Institutes, Shanghai Jiao Tong University, Shanghai, China
| | - Jiaxing Zhang
- Bio-X Institutes, Shanghai Jiao Tong University, Shanghai, China
| | - Xuechun Xia
- Bio-X Institutes, Shanghai Jiao Tong University, Shanghai, China
| | - Min Ji
- Affiliated Hospital of Nantong University, Nantong, Jiangsu, China
| | - Lei Lv
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC
| | - Yong Ping
- Bio-X Institutes, Shanghai Jiao Tong University, Shanghai, China.,Shanghai Key Laboratory of Psychotic Disorders (No.13dz2260500), Shanghai Mental Health Center, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
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30
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SCN VIP Neurons Are Essential for Normal Light-Mediated Resetting of the Circadian System. J Neurosci 2018; 38:7986-7995. [PMID: 30082421 DOI: 10.1523/jneurosci.1322-18.2018] [Citation(s) in RCA: 86] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2018] [Revised: 07/10/2018] [Accepted: 07/14/2018] [Indexed: 12/21/2022] Open
Abstract
The suprachiasmatic nucleus (SCN) synchronizes circadian rhythms in behavior and physiology to the external light cycle, but the mechanisms by which this occurs are unclear. As the neuropeptide vasoactive intestinal peptide (VIP) is important for circadian light responses, we tested the hypothesis that rhythmic VIP-producing SCN neurons mediate circadian light responses in male and female mice. Using in vivo fiber photometry over multiple days, we found daily rhythms in spontaneous calcium events of SCN VIP neurons that peaked during the subjective day and were disrupted by constant light. The light-evoked calcium responses peaked around subjective dusk and were greater during the subjective night. Using novel VIP sensor cells, we found that the activity patterns in SCN VIP neurons correlated tightly with spontaneous and NMDA-evoked VIP release. Finally, in vivo hyperpolarization of VIP neurons attenuated light-induced shifts of daily rhythms in locomotion. We conclude that SCN VIP neurons exhibit circadian rhythms in spontaneous and light-responsive activity and are essential for the normal resetting of daily rhythms by environmental light.SIGNIFICANCE STATEMENT Daily rhythms in behavior and physiology, including sleep/wake and hormone release, are synchronized to local time by the master circadian pacemaker, the suprachiasmatic nucleus (SCN). The advent of artificial lighting and, consequently, light exposure at night, is associated with an increased risk of disease due to disrupted circadian rhythms. However, the mechanisms by which the SCN encodes normal and pathological light information are unclear. Here, we find that vasoactive intestinal peptide (VIP)-producing SCN neurons exhibit daily rhythms in neuronal activity and VIP release, and that blocking the activity of these neurons attenuates light-induced phase shifts. We conclude that rhythmic VIP neurons are an essential component of the circadian light transduction pathway.
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31
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Cheng PC, Wang YC, Chen YS, Cheng RC, Yang JJ, Huang RC. Differential regulation of nimodipine-sensitive and -insensitive Ca 2+ influx by the Na +/Ca 2+ exchanger and mitochondria in the rat suprachiasmatic nucleus neurons. J Biomed Sci 2018; 25:44. [PMID: 29788971 PMCID: PMC5964920 DOI: 10.1186/s12929-018-0447-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2018] [Accepted: 05/14/2018] [Indexed: 11/25/2022] Open
Abstract
Background Transmembrane Ca2+ influx is critical for molecular rhythmicity, metabolic activity, and neuropeptide release in the central clock of the suprachiasmatic nucleus (SCN). We previously reported that both the Na+/Ca2+ exchanger (NCX) and mitochondria play a role in regulating intracellular Ca2+ homeostasis in the rat SCN neurons. Here we present evidence to show differential regulation by NCX and mitochondria of nimodipine-sensitive and -insensitive Ca2+ influx. Methods Ratiometric Ca2+ imaging was used to measure change in [Ca2+]i and patch clamp recordings to study spontaneous firing, membrane potential, and voltage-dependent Ca2+ channels in neurons from reduced SCN slice preparations. Immunofluorescent staining was used to determine the distribution pattern of CaV1.2 and CaV1.3 and their colocalization with NCX1. Results Ratiometric Ca2+ imaging indicates that nimodipine (2 μM) blocked most of 20 (mM) K+-induced, but less so of 50 K+-induced, Ca2+ rise. The nimodipine-sensitive 50 K+-induced Ca2+ transient rose more rapidly but decayed similarly with the nimodipine-insensitive component, suggesting both components were extruded by NCX. Immunofluorescent stains showed the expression of both CaV1.2 and CaV1.3 and their colocalization with NCX1, whereas functional studies suggest that CaV1.2 mediated most of the nimodipine-sensitive Ca2+ rise but had insignificant effect on spontaneous firing. After normalization relative to the Ca2+-free solution, nimodipine reduced ~ 65% of basal Ca2+ influx, and TTX lowered it by ~ 35%, leaving ~ 25% basal Ca2+ influx in the combined presence of TTX and nimodipine. With the mitochondrial uncoupler carbonyl cyanide-p-trifluoromethoxyphenylhydrazone (FCCP) to inhibit mitochondrial Ca2+ uptake, 20 K+-induced Ca2+ transients became larger and slower, both in the absence and presence of nimodipine. FCCP markedly enhanced nimodipine-insensitive, but not nimodipine-sensitive, Ca2+ transients, suggesting that mitochondria preferentially buffer nimodipine-insensitive Ca2+ influx. Results from using CaV2 channel blockers further indicate that FCCP enhanced Ca2+ transients mediated by N-, P/Q-, and the blocker cocktail-insensitive Ca2+ channels. Conclusions The differential regulation of transmembrane Ca2+ influx by NCX and mitochondria suggests that Ca2+ entry via different sources may be regulated differently to play different roles in SCN physiology.
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Affiliation(s)
- Pi-Cheng Cheng
- Department of Physiology and Pharmacology, College of Medicine, Chang Gung University, 259 Wen-Hwa 1st Road, Kwei-San, Tao-Yuan, 33302, Taiwan
| | - Yi-Chi Wang
- Department of Physiology and Pharmacology, College of Medicine, Chang Gung University, 259 Wen-Hwa 1st Road, Kwei-San, Tao-Yuan, 33302, Taiwan
| | - Ya-Shuan Chen
- Department of Physiology and Pharmacology, College of Medicine, Chang Gung University, 259 Wen-Hwa 1st Road, Kwei-San, Tao-Yuan, 33302, Taiwan
| | - Ruo-Ciao Cheng
- Department of Physiology and Pharmacology, College of Medicine, Chang Gung University, 259 Wen-Hwa 1st Road, Kwei-San, Tao-Yuan, 33302, Taiwan
| | - Jyh-Jeen Yang
- Department of Physiology and Pharmacology, College of Medicine, Chang Gung University, 259 Wen-Hwa 1st Road, Kwei-San, Tao-Yuan, 33302, Taiwan
| | - Rong-Chi Huang
- Department of Physiology and Pharmacology, College of Medicine, Chang Gung University, 259 Wen-Hwa 1st Road, Kwei-San, Tao-Yuan, 33302, Taiwan. .,Healthy Aging Research Center, Chang Gung University, Tao-Yuan, 33302, Taiwan. .,Neuroscience Research Center, Chang Gung Memorial Hospital, Linkou Medical Center, Tao-Yuan, 33305, Taiwan.
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32
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Belle MDC, Diekman CO. Neuronal oscillations on an ultra-slow timescale: daily rhythms in electrical activity and gene expression in the mammalian master circadian clockwork. Eur J Neurosci 2018; 48:2696-2717. [PMID: 29396876 DOI: 10.1111/ejn.13856] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2017] [Revised: 01/16/2018] [Accepted: 01/28/2018] [Indexed: 12/17/2022]
Abstract
Neuronal oscillations of the brain, such as those observed in the cortices and hippocampi of behaving animals and humans, span across wide frequency bands, from slow delta waves (0.1 Hz) to ultra-fast ripples (600 Hz). Here, we focus on ultra-slow neuronal oscillators in the hypothalamic suprachiasmatic nuclei (SCN), the master daily clock that operates on interlocking transcription-translation feedback loops to produce circadian rhythms in clock gene expression with a period of near 24 h (< 0.001 Hz). This intracellular molecular clock interacts with the cell's membrane through poorly understood mechanisms to drive the daily pattern in the electrical excitability of SCN neurons, exhibiting an up-state during the day and a down-state at night. In turn, the membrane activity feeds back to regulate the oscillatory activity of clock gene programs. In this review, we emphasise the circadian processes that drive daily electrical oscillations in SCN neurons, and highlight how mathematical modelling contributes to our increasing understanding of circadian rhythm generation, synchronisation and communication within this hypothalamic region and across other brain circuits.
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Affiliation(s)
- Mino D C Belle
- Institute of Clinical and Biomedical Sciences, University of Exeter Medical School, University of Exeter, Exeter, EX4 4PS, UK
| | - Casey O Diekman
- Department of Mathematical Sciences, New Jersey Institute of Technology, Newark, NJ, USA.,Institute for Brain and Neuroscience Research, New Jersey Institute of Technology, Newark, NJ, USA
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33
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Whitt JP, McNally BA, Meredith AL. Differential contribution of Ca 2+ sources to day and night BK current activation in the circadian clock. J Gen Physiol 2017; 150:259-275. [PMID: 29237755 PMCID: PMC5806683 DOI: 10.1085/jgp.201711945] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2017] [Accepted: 11/28/2017] [Indexed: 01/16/2023] Open
Abstract
Large conductance K+ (BK) channels are expressed widely in neurons, where their activation is regulated by membrane depolarization and intracellular Ca2+ (Ca2+i). To enable this regulation, BK channels functionally couple to both voltage-gated Ca2+ channels (VGCCs) and channels mediating Ca2+ release from intracellular stores. However, the relationship between BK channels and their specific Ca2+ source for particular patterns of excitability is not well understood. In neurons within the suprachiasmatic nucleus (SCN)-the brain's circadian clock-BK current, VGCC current, and Ca2+i are diurnally regulated, but paradoxically, BK current is greatest at night when VGCC current and Ca2+i are reduced. Here, to determine whether diurnal regulation of Ca2+ is relevant for BK channel activation, we combine pharmacology with day and night patch-clamp recordings in acute slices of SCN. We find that activation of BK current depends primarily on three types of channels but that the relative contribution changes between day and night. BK current can be abrogated with nimodipine during the day but not at night, establishing that L-type Ca2+ channels (LTCCs) are the primary daytime Ca2+ source for BK activation. In contrast, dantrolene causes a significant decrease in BK current at night, suggesting that nighttime BK activation is driven by ryanodine receptor (RyR)-mediated Ca2+i release. The N- and P/Q-type Ca2+ channel blocker ω-conotoxin MVIIC causes a smaller reduction of BK current that does not differ between day and night. Finally, inhibition of LTCCs, but not RyRs, eliminates BK inactivation, but the BK β2 subunit was not required for activation of BK current by LTCCs. These data reveal a dynamic coupling strategy between BK channels and their Ca2+ sources in the SCN, contributing to diurnal regulation of SCN excitability.
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Affiliation(s)
- Joshua P Whitt
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD
| | - Beth A McNally
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD
| | - Andrea L Meredith
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD
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34
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Calcium Circadian Rhythmicity in the Suprachiasmatic Nucleus: Cell Autonomy and Network Modulation. eNeuro 2017; 4:eN-NWR-0160-17. [PMID: 28828400 PMCID: PMC5562299 DOI: 10.1523/eneuro.0160-17.2017] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2017] [Accepted: 07/26/2017] [Indexed: 11/25/2022] Open
Abstract
Circadian rhythms of mammalian physiology and behavior are coordinated by the suprachiasmatic nucleus (SCN) in the hypothalamus. Within SCN neurons, various aspects of cell physiology exhibit circadian oscillations, including circadian clock gene expression, levels of intracellular Ca2+ ([Ca2+]i), and neuronal firing rate. [Ca2+]i oscillates in SCN neurons even in the absence of neuronal firing. To determine the causal relationship between circadian clock gene expression and [Ca2+]i rhythms in the SCN, as well as the SCN neuronal network dependence of [Ca2+]i rhythms, we introduced GCaMP3, a genetically encoded fluorescent Ca2+ indicator, into SCN neurons from PER2::LUC knock-in reporter mice. Then, PER2 and [Ca2+]i were imaged in SCN dispersed and organotypic slice cultures. In dispersed cells, PER2 and [Ca2+]i both exhibited cell autonomous circadian rhythms, but [Ca2+]i rhythms were typically weaker than PER2 rhythms. This result matches the predictions of a detailed mathematical model in which clock gene rhythms drive [Ca2+]i rhythms. As predicted by the model, PER2 and [Ca2+]i rhythms were both stronger in SCN slices than in dispersed cells and were weakened by blocking neuronal firing in slices but not in dispersed cells. The phase relationship between [Ca2+]i and PER2 rhythms was more variable in cells within slices than in dispersed cells. Both PER2 and [Ca2+]i rhythms were abolished in SCN cells deficient in the essential clock gene Bmal1. These results suggest that the circadian rhythm of [Ca2+]i in SCN neurons is cell autonomous and dependent on clock gene rhythms, but reinforced and modulated by a synchronized SCN neuronal network.
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35
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Allen CN, Nitabach MN, Colwell CS. Membrane Currents, Gene Expression, and Circadian Clocks. Cold Spring Harb Perspect Biol 2017; 9:cshperspect.a027714. [PMID: 28246182 DOI: 10.1101/cshperspect.a027714] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Neuronal circadian oscillators in the mammalian and Drosophila brain express a circadian clock comprised of interlocking gene transcription feedback loops. The genetic clock regulates the membrane electrical activity by poorly understood signaling pathways to generate a circadian pattern of action potential firing. During the day, Na+ channels contribute an excitatory drive for the spontaneous activity of circadian clock neurons. Multiple types of K+ channels regulate the action potential firing pattern and the nightly reduction in neuronal activity. The membrane electrical activity possibly signaling by changes in intracellular Ca2+ and cyclic adenosine monophosphate (cAMP) regulates the activity of the gene clock. A decline in the signaling pathways that link the gene clock and neural activity during aging and disease may weaken the circadian output and generate significant impacts on human health.
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Affiliation(s)
- Charles N Allen
- Oregon Institute of Occupational Health Sciences and Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, Oregon 97239
| | - Michael N Nitabach
- Department of Cellular and Molecular Physiology and Department of Genetics, Yale School of Medicine, New Haven, Connecticut 06520
| | - Christopher S Colwell
- Department of Psychiatry & Biobehavioral Sciences, University of California, Los Angeles, Los Angeles, California 90024
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36
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Kiehn JT, Tsang AH, Heyde I, Leinweber B, Kolbe I, Leliavski A, Oster H. Circadian Rhythms in Adipose Tissue Physiology. Compr Physiol 2017; 7:383-427. [PMID: 28333377 DOI: 10.1002/cphy.c160017] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The different types of adipose tissues fulfill a wide range of biological functions-from energy storage to hormone secretion and thermogenesis-many of which show pronounced variations over the course of the day. Such 24-h rhythms in physiology and behavior are coordinated by endogenous circadian clocks found in all tissues and cells, including adipocytes. At the molecular level, these clocks are based on interlocked transcriptional-translational feedback loops comprised of a set of clock genes/proteins. Tissue-specific clock-controlled transcriptional programs translate time-of-day information into physiologically relevant signals. In adipose tissues, clock gene control has been documented for adipocyte proliferation and differentiation, lipid metabolism as well as endocrine function and other adipose oscillations are under control of systemic signals tied to endocrine, neuronal, or behavioral rhythms. Circadian rhythm disruption, for example, by night shift work or through genetic alterations, is associated with changes in adipocyte metabolism and hormone secretion. At the same time, adipose metabolic state feeds back to central and peripheral clocks, adjusting behavioral and physiological rhythms. In this overview article, we summarize our current knowledge about the crosstalk between circadian clocks and energy metabolism with a focus on adipose physiology. © 2017 American Physiological Society. Compr Physiol 7:383-427, 2017.
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Affiliation(s)
- Jana-Thabea Kiehn
- Chronophysiology Group, Medical Department I, University of Lübeck, Lübeck, Germany
| | - Anthony H Tsang
- Chronophysiology Group, Medical Department I, University of Lübeck, Lübeck, Germany
| | - Isabel Heyde
- Chronophysiology Group, Medical Department I, University of Lübeck, Lübeck, Germany
| | - Brinja Leinweber
- Chronophysiology Group, Medical Department I, University of Lübeck, Lübeck, Germany
| | - Isa Kolbe
- Chronophysiology Group, Medical Department I, University of Lübeck, Lübeck, Germany
| | - Alexei Leliavski
- Institute of Systemic Inflammation Research, University of Lübeck, Lübeck, Germany
| | - Henrik Oster
- Chronophysiology Group, Medical Department I, University of Lübeck, Lübeck, Germany
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37
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Enoki R, Ono D, Kuroda S, Honma S, Honma KI. Dual origins of the intracellular circadian calcium rhythm in the suprachiasmatic nucleus. Sci Rep 2017; 7:41733. [PMID: 28155916 PMCID: PMC5290527 DOI: 10.1038/srep41733] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Accepted: 01/03/2017] [Indexed: 12/01/2022] Open
Abstract
In mammals, the master circadian clock is located in the suprachiasmatic nucleus (SCN), where most neurons show circadian rhythms of intracellular Ca2+ levels. However, the origin of these Ca2+ rhythms remains largely unknown. In this study, we successfully monitored the intracellular circadian Ca2+ rhythms together with the circadian PER2 and firing rhythms in a single SCN slice ex vivo, which enabled us to explore the origins. The phase relation between the circadian PER2 and Ca2+ rhythms, but not between the circadian PER2 and firing rhythms, was significantly altered in Cry1/Cry2 double knockout mice, which display a loss of intercellular synchronization in the SCN. In addition, in Cry1/Cry2 double knockout mice, circadian Ca2+ rhythms were abolished in the dorsolateral SCN, but were maintained in the majority of the ventromedial SCN. These findings indicate that intracellular circadian Ca2+ rhythms are composed of an exogenous and endogenous component involving PER2 expression.
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Affiliation(s)
- Ryosuke Enoki
- Photonic Bioimaging Section, Research Center for Cooperative Projects, Hokkaido University Graduate School of Medicine, N15 W7, Kita-ku, Sapporo, 060-8638, Japan.,Department of Chronomedicine, Hokkaido University Graduate School of Medicine, N15 W7, Kita-ku, Sapporo, 060-8638, Japan.,Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency (JST), Saitama 332-0012, Japan
| | - Daisuke Ono
- Photonic Bioimaging Section, Research Center for Cooperative Projects, Hokkaido University Graduate School of Medicine, N15 W7, Kita-ku, Sapporo, 060-8638, Japan
| | - Shigeru Kuroda
- Mathematical and Physical Ethology Laboratory, Research Institute for Electrical Science, Hokkaido University, N20 W10, Kita-ku, Sapporo, Japan
| | - Sato Honma
- Department of Chronomedicine, Hokkaido University Graduate School of Medicine, N15 W7, Kita-ku, Sapporo, 060-8638, Japan
| | - Ken-Ichi Honma
- Department of Chronomedicine, Hokkaido University Graduate School of Medicine, N15 W7, Kita-ku, Sapporo, 060-8638, Japan
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38
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Yaniv Y, Lakatta EG. The end effector of circadian heart rate variation: the sinoatrial node pacemaker cell. BMB Rep 2016; 48:677-84. [PMID: 25999176 PMCID: PMC4791323 DOI: 10.5483/bmbrep.2015.48.12.061] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2015] [Indexed: 12/16/2022] Open
Abstract
Cardiovascular function is regulated by the rhythmicity of circadian, infradian and ultradian clocks. Specific time scales of different cell types drive their functions: circadian gene regulation at hours scale, activation-inactivation cycles of ion channels at millisecond scales, the heart's beating rate at hundreds of millisecond scales, and low frequency autonomic signaling at cycles of tens of seconds. Heart rate and rhythm are modulated by a hierarchical clock system: autonomic signaling from the brain releases neurotransmitters from the vagus and sympathetic nerves to the heart’s pacemaker cells and activate receptors on the cell. These receptors activating ultradian clock functions embedded within pacemaker cells include sarcoplasmic reticulum rhythmic spontaneous Ca2+ cycling, rhythmic ion channel current activation and inactivation, and rhythmic oscillatory mitochondria ATP production. Here we summarize the evidence that intrinsic pacemaker cell mechanisms are the end effector of the hierarchical brain-heart circadian clock system. [BMB Reports 2015; 48(12): 677-684]
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Affiliation(s)
- Yael Yaniv
- Biomedical Engineering Faculty, Technion-IIT, Haifa, Israel
| | - Edward G Lakatta
- Laboratory of Cardiovascular Science, Biomedical Research Center, Intramural Research Program, National Institute on Aging, NIH, Baltimore, Maryland, USA
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39
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Aguilar-Roblero R, Quinto D, Báez-Ruíz A, Chávez JL, Belin AC, Díaz-Muñoz M, Michel S, Lundkvist G. Ryanodine-sensitive intracellular Ca 2+ channels are involved in the output from the SCN circadian clock. Eur J Neurosci 2016; 44:2504-2514. [PMID: 27529310 PMCID: PMC5053303 DOI: 10.1111/ejn.13368] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2015] [Revised: 08/03/2016] [Accepted: 08/09/2016] [Indexed: 01/07/2023]
Abstract
The suprachiasmatic nuclei (SCN) contain the major circadian clock responsible for generation of circadian rhythms in mammals. The time measured by the molecular circadian clock must eventually be translated into a neuronal firing rate pattern to transmit a meaningful signal to other tissues and organs in the animal. Previous observations suggest that circadian modulation of ryanodine receptors (RyR) is a key element of the output pathway from the molecular circadian clock. To directly test this hypothesis, we studied the effects of RyR activation and inhibition on real time expression of PERIOD2::LUCIFERASE, intracellular calcium levels and spontaneous firing frequency in mouse SCN neurons. Furthermore, we determined whether the RyR-2 mRNA is expressed with a daily variation in SCN neurons. We provide evidence that pharmacological manipulation of RyR in mice SCN neurons alters the free [Ca2+ ]i in the cytoplasm and the spontaneous firing without affecting the molecular clock mechanism. Our data also show a daily variation in RyR-2 mRNA from single mouse SCN neurons with highest levels during the day. Together, these results confirm the hypothesis that RyR-2 is a key element of the circadian clock output from SCN neurons.
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Affiliation(s)
- Raúl Aguilar-Roblero
- División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Circuito Exterior s/n, Ciudad Universitaria, Coyoacan, Mexico City D.F, 04510, México.
| | - Daniel Quinto
- División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Circuito Exterior s/n, Ciudad Universitaria, Coyoacan, Mexico City D.F, 04510, México
| | - Adrian Báez-Ruíz
- Instituto de Neurobiología, Universidad Nacional Autónoma de México, Juriquilla Querétaro, México
| | - José Luis Chávez
- División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Circuito Exterior s/n, Ciudad Universitaria, Coyoacan, Mexico City D.F, 04510, México
| | | | - Mauricio Díaz-Muñoz
- Instituto de Neurobiología, Universidad Nacional Autónoma de México, Juriquilla Querétaro, México
| | - Stephan Michel
- Molecular Cell Biology, Leiden University Medical Center, Leiden, The Netherlands
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40
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Abstract
The SCN of the mammalian hypothalamus comprises a self-sustained, biological clock that generates endogenous ca. 24-h (circadian) rhythms. Circadian rhythmicity in the SCN originates from the interaction of a defined set of “clock genes” that participate in transcription/translation feedback loops. In order for the SCN to serve as an internal clock that times an internal day corresponding to the external solar day, the intracellular molecular oscillations must be output as physiological signals and be reset by appropriate environmental inputs. Here, the authors consider the mechanisms by which the SCN circadian pacemaker encodes rhythmic output and light input. In particular, they focus on the ionic mechanisms by which SCN neurons encode clock gene output as circa-dian rhythms in spike frequency, as well as cellular and molecular mechanisms by which SCN neurons encode circadian light input through phase heterogeneity in the SCN network. The authors propose that there are 2 distinct classes of ionic mechanisms supporting spike frequency rhythms output—modulation of basal membrane potential and conductance versus modulation of spike production—whereas light input is transformed by cellular communication within the SCN network and encoded by the relative phase relationships among SCN neurons.
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Affiliation(s)
- Sandra J Kuhlman
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA
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41
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Abstract
The hypothalamic suprachiasmatic nucleus (SCN) has a pivotal role in the mammalian circadian clock. SCN neurons generate circadian rhythms in action potential firing frequencies and neurotransmitter release, and the core oscillation is thought to be driven by “clock gene” transcription-translation feedback loops. Cytosolic Ca2+mobilization followed by stimulation of various receptors has been shown to reset the gene transcription cycles in SCN neurons, whereas contribution of steady-state cytosolic Ca2+levels to the rhythm generation is unclear. Recently, circadian rhythms in cytosolic Ca2+levels have been demonstrated in cultured SCN neurons. The circadian Ca2+rhythms are driven by the release of Ca2+from ryanodine-sensitive internal stores and resistant to the blockade of action potentials. These results raise the possibility that gene translation/transcription loops may interact with autonomous Ca2+oscillations in the production of circadian rhythms in SCN neurons.
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Affiliation(s)
- Masayuki Ikeda
- Department of Molecular Behavioral Biology, Osaka Bioscience Institute, Suita, Osaka, Japan.
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43
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Kudo T, Block GD, Colwell CS. The Circadian Clock Gene Period1 Connects the Molecular Clock to Neural Activity in the Suprachiasmatic Nucleus. ASN Neuro 2015; 7:7/6/1759091415610761. [PMID: 26553726 PMCID: PMC4710129 DOI: 10.1177/1759091415610761] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
The neural activity patterns of suprachiasmatic nucleus (SCN) neurons are dynamically regulated throughout the circadian cycle with highest levels of spontaneous action potentials during the day. These rhythms in electrical activity are critical for the function of the circadian timing system and yet the mechanisms by which the molecular clockwork drives changes in the membrane are not well understood. In this study, we sought to examine how the clock gene Period1 (Per1) regulates the electrical activity in the mouse SCN by transiently and selectively decreasing levels of PER1 through use of an antisense oligodeoxynucleotide. We found that this treatment effectively reduced SCN neural activity. Direct current injection to restore the normal membrane potential partially, but not completely, returned firing rate to normal levels. The antisense treatment also reduced baseline [Ca2+]i levels as measured by Fura2 imaging technique. Whole cell patch clamp recording techniques were used to examine which specific potassium currents were altered by the treatment. These recordings revealed that the large conductance [Ca2+]i-activated potassium currents were reduced in antisense-treated neurons and that blocking this current mimicked the effects of the anti-sense on SCN firing rate. These results indicate that the circadian clock gene Per1 alters firing rate in SCN neurons and raise the possibility that the large conductance [Ca2+]i-activated channel is one of the targets.
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Affiliation(s)
- Takashi Kudo
- Department of Psychiatry and Biobehavioral Sciences, University of California, Los Angeles, CA, USA
| | - Gene D Block
- Department of Psychiatry and Biobehavioral Sciences, University of California, Los Angeles, CA, USA
| | - Christopher S Colwell
- Department of Psychiatry and Biobehavioral Sciences, University of California, Los Angeles, CA, USA
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44
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Belle MDC. Circadian Tick-Talking Across the Neuroendocrine System and Suprachiasmatic Nuclei Circuits: The Enigmatic Communication Between the Molecular and Electrical Membrane Clocks. J Neuroendocrinol 2015; 27:567-76. [PMID: 25845396 PMCID: PMC4973835 DOI: 10.1111/jne.12279] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/26/2014] [Revised: 03/25/2015] [Accepted: 03/26/2015] [Indexed: 12/15/2022]
Abstract
As with many processes in nature, appropriate timing in biological systems is of paramount importance. In the neuroendocrine system, the efficacy of hormonal influence on major bodily functions, such as reproduction, metabolism and growth, relies on timely communication within and across many of the brain's homeostatic systems. The activity of these circuits is tightly orchestrated with the animal's internal physiological demands and external solar cycle by a master circadian clock. In mammals, this master clock is located in the hypothalamic suprachiasmatic nucleus (SCN), where the ensemble activity of thousands of clock neurones generates and communicates circadian time cues to the rest of the brain and body. Many regions of the brain, including areas with neuroendocrine function, also contain local daily clocks that can provide feedback signals to the SCN. Although much is known about the molecular processes underpinning endogenous circadian rhythm generation in SCN neurones and, to a lesser extent, extra-SCN cells, the electrical membrane clock that acts in partnership with the molecular clockwork to communicate circadian timing across the brain is poorly understood. The present review focuses on some circadian aspects of reproductive neuroendocrinology and processes involved in circadian rhythm communication in the SCN, aiming to identify key gaps in our knowledge of cross-talk between our daily master clock and neuroendocrine function. The intention is to highlight our surprisingly limited understanding of their interaction in the hope that this will stimulate future work in these areas.
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Affiliation(s)
- M. D. C. Belle
- Faculty of Life SciencesUniversity of ManchesterManchesterUK
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Schmutz I, Chavan R, Ripperger JA, Maywood ES, Langwieser N, Jurik A, Stauffer A, Delorme JE, Moosmang S, Hastings MH, Hofmann F, Albrecht U. A specific role for the REV-ERBα-controlled L-Type Voltage-Gated Calcium Channel CaV1.2 in resetting the circadian clock in the late night. J Biol Rhythms 2015; 29:288-98. [PMID: 25238857 DOI: 10.1177/0748730414540453] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Within the suprachiasmatic nucleus (SCN) of the hypothalamus, circadian timekeeping and resetting have been shown to be largely dependent on both membrane depolarization and intracellular second-messenger signaling. In both of these processes, voltage-gated calcium channels (VGCCs) mediate voltage-dependent calcium influx, which propagates neural impulses by stimulating vesicle fusion and instigates intracellular pathways resulting in clock gene expression. Through the cumulative actions of these processes, the phase of the internal clock is modified to match the light cycle of the external environment. To parse out the distinct roles of the L-type VGCCs, we analyzed mice deficient in Cav1.2 (Cacna1c) in brain tissue. We found that mice deficient in the Cav1.2 channel exhibited a significant reduction in their ability to phase-advance circadian behavior when subjected to a light pulse in the late night. Furthermore, the study revealed that the expression of Cav1.2 mRNA was rhythmic (peaking during the late night) and was regulated by the circadian clock component REV-ERBα. Finally, the induction of clock genes in both the early and late subjective night was affected by the loss of Cav1.2, with reductions in Per2 and Per1 in the early and late night, respectively. In sum, these results reveal a role of the L-type VGCC Cav1.2 in mediating both clock gene expression and phase advances in response to a light pulse in the late night.
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Affiliation(s)
- Isabelle Schmutz
- Department of Biology, Unit of Biochemistry, University of Fribourg, Fribourg, Switzerland
| | - Rohit Chavan
- Department of Biology, Unit of Biochemistry, University of Fribourg, Fribourg, Switzerland
| | - Jürgen A Ripperger
- Department of Biology, Unit of Biochemistry, University of Fribourg, Fribourg, Switzerland
| | | | - Nicole Langwieser
- Institute of Pharmacology and Toxicology, TU Munich, Munich, Germany
| | - Angela Jurik
- Institute of Pharmacology and Toxicology, TU Munich, Munich, Germany
| | - Anja Stauffer
- Department of Biology, Unit of Biochemistry, University of Fribourg, Fribourg, Switzerland
| | - James E Delorme
- Department of Biology, Unit of Biochemistry, University of Fribourg, Fribourg, Switzerland
| | - Sven Moosmang
- Institute of Pharmacology and Toxicology, TU Munich, Munich, Germany
| | | | - Franz Hofmann
- Institute of Pharmacology and Toxicology, TU Munich, Munich, Germany
| | - Urs Albrecht
- Department of Biology, Unit of Biochemistry, University of Fribourg, Fribourg, Switzerland
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Rhythmic Trafficking of TRPV2 in the Suprachiasmatic Nucleus is Regulated by Prokineticin 2 Signaling. J Circadian Rhythms 2015; 13:2. [PMID: 27103928 PMCID: PMC4832818 DOI: 10.5334/jcr.ad] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
The mammalian circadian clock is composed of single-cell oscillators. Neurochemical and
electrical signaling among these oscillators is important for the normal expression of circadian
rhythms. Prokineticin 2 (PK2), encoding a cysteine-rich secreted protein, has been shown to be a
critical signaling molecule for the regulation of circadian rhythms. PK2 expression in the
suprachiasmatic nucleus (SCN) is highly rhythmic, peaking during the day and being essentially
absent during the night. Mice with disrupted PK2 gene or its receptor PKR2 display greatly reduced
rhythmicity of broad circadian parameters such as locomotor activity, body temperature and
sleep/wake patterns. PK2 has been shown to increase the firing rate of SCN neurons, with unknown
molecular mechanisms. Here we report that TRPV2, an ion channel belonging to the family of TRP, is
co-expressed with PKR2 in the SCN neurons. Further, TRPV2 protein, but not TRPV2 mRNA, was shown to
oscillate in the SCN in a PK2-dependent manner. Functional studies revealed that TRPV2 enhanced
signaling of PKR2 in calcium mobilization or ion current conductance, likely via the increased
trafficking of TRPV2 to the cell surface. Taken together, these results indicate that TRPV2 is
likely part of the downstream signaling of PK2 in the regulation of the circadian rhythms.
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Age-related changes in large-conductance calcium-activated potassium channels in mammalian circadian clock neurons. Neurobiol Aging 2015; 36:2176-83. [PMID: 25735218 DOI: 10.1016/j.neurobiolaging.2014.12.040] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2014] [Revised: 12/09/2014] [Accepted: 12/09/2014] [Indexed: 01/18/2023]
Abstract
Aging impairs the function of the suprachiasmatic nucleus (SCN, the central mammalian clock), leading to a decline in the circadian rhythm of many physiological processes, including sleep-wake rhythms. Recent studies have found evidence of age-related changes in the circadian regulation of potassium currents; these changes presumably lead to a decrease in the SCN's electrical rhythm amplitude. Current through large-conductance Ca(2+)-activated K(+) (BK) channels promote rhythmicity in both SCN neuronal activity and behavior. In many neuron types, changes in BK activity are correlated with changes in intracellular Ca(2+) concentration ([Ca(2+)]i). We performed patch-clamp recordings of SCN neurons in aged mice and observed that the circadian modulation of BK channel activity was lost because of a reduction in BK currents during the night. This reduced current diminished the afterhyperpolarization, depolarized the resting membrane potential, widened the action potential, and increased [Ca(2+)]i. These data suggest that reduced BK current increases [Ca(2+)]i by altering the action potential waveform, possibly contributing to the observed age-related phenotype.
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Wang YC, Chen YS, Cheng RC, Huang RC. Role of Na⁺/Ca²⁺ exchanger in Ca²⁺ homeostasis in rat suprachiasmatic nucleus neurons. J Neurophysiol 2015; 113:2114-26. [PMID: 25568156 DOI: 10.1152/jn.00404.2014] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2014] [Accepted: 01/02/2015] [Indexed: 12/15/2022] Open
Abstract
Intracellular Ca(2+) is critical to the central clock of the suprachiasmatic nucleus (SCN). However, the role of Na(+)/Ca(2+) exchanger (NCX) in intracellular Ca(2+) concentration ([Ca(2+)]i) homeostasis in the SCN is unknown. Here we show that NCX is an important mechanism for somatic Ca(2+) clearance in SCN neurons. In control conditions Na(+)-free solution lowered [Ca(2+)]i by inhibiting TTX-sensitive as well as nimodipine-sensitive Ca(2+) influx. With use of the Na(+) ionophore monensin to raise intracellular Na(+) concentration ([Na(+)]i), Na(+)-free solution provoked rapid Ca(2+) uptake via reverse NCX. The peak amplitude of 0 Na(+)-induced [Ca(2+)]i increase was larger during the day than at night, with no difference between dorsal and ventral SCN neurons. Ca(2+) extrusion via forward NCX was studied by determining the effect of Na(+) removal on Ca(2+) clearance after high-K(+)-induced Ca(2+) loads. The clearance of Ca(2+) proceeded with two exponential decay phases, with the fast decay having total signal amplitude of ∼85% and a time constant of ∼7 s. Na(+)-free solution slowed the fast decay rate threefold, whereas mitochondrial protonophore prolonged mostly the slow decay. In contrast, blockade of plasmalemmal and sarco(endo)plasmic reticulum Ca(2+) pumps had little effect on the kinetics of Ca(2+) clearance. RT-PCR indicated the expression of NCX1 and NCX2 mRNAs. Immunohistochemical staining showed the presence of NCX1 immunoreactivity in the whole SCN but restricted distribution of NCX2 immunoreactivity in the ventrolateral SCN. Together our results demonstrate an important role of NCX, most likely NCX1, as well as mitochondrial Ca(2+) uptake in clearing somatic Ca(2+) after depolarization-induced Ca(2+) influx in SCN neurons.
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Affiliation(s)
- Yi-Chi Wang
- Departments of Physiology and Pharmacology, Chang Gung University College of Medicine, Kwei-San, Tao-Yuan, Taiwan, Republic of China
| | - Ya-Shuan Chen
- Departments of Physiology and Pharmacology, Chang Gung University College of Medicine, Kwei-San, Tao-Yuan, Taiwan, Republic of China
| | - Ruo-Ciao Cheng
- Departments of Physiology and Pharmacology, Chang Gung University College of Medicine, Kwei-San, Tao-Yuan, Taiwan, Republic of China
| | - Rong-Chi Huang
- Departments of Physiology and Pharmacology, Chang Gung University College of Medicine, Kwei-San, Tao-Yuan, Taiwan, Republic of China
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Meijer JH, Michel S. Neurophysiological Analysis of the Suprachiasmatic Nucleus. Methods Enzymol 2015; 552:75-102. [DOI: 10.1016/bs.mie.2014.11.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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Landgraf D, McCarthy MJ, Welsh DK. Circadian clock and stress interactions in the molecular biology of psychiatric disorders. Curr Psychiatry Rep 2014; 16:483. [PMID: 25135782 DOI: 10.1007/s11920-014-0483-7] [Citation(s) in RCA: 116] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Many psychiatric disorders are characterized by circadian rhythm abnormalities, including disturbed sleep/wake cycles, changes in locomotor activity, and abnormal endocrine function. Animal models with mutations in circadian "clock genes" commonly show disturbances in reward processing, locomotor activity and novelty seeking behaviors, further supporting the idea of a connection between the circadian clock and psychiatric disorders. However, if circadian clock dysfunction is a common risk factor for multiple psychiatric disorders, it is unknown if and how these putative clock abnormalities could be expressed differently, and contribute to multiple, distinct phenotypes. One possible explanation is that the circadian clock modulates the biological responses to stressful environmental factors that vary with an individual's experience. It is known that the circadian clock and the stress response systems are closely related: Circadian clock genes regulate the physiological sensitivity to and rhythmic release of glucocorticoids (GC). In turn, GCs have reciprocal effects on the clock. Since stressful life events or increased vulnerability to stress are risk factors for multiple psychiatric disorders, including post-traumatic stress disorder (PTSD), attention deficit hyperactivity disorder (ADHD), bipolar disorder (BD), major depressive disorder (MDD), alcohol use disorder (AUD) and schizophrenia (SCZ), we propose that modulation of the stress response is a common mechanism by which circadian clock genes affect these illnesses. Presently, we review how molecular components of the circadian clock may contribute to these six psychiatric disorders, and present the hypothesis that modulation of the stress response may constitute a common mechanism by which the circadian clock affects multiple psychiatric disorders.
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Affiliation(s)
- Dominic Landgraf
- Veterans Affairs San Diego Healthcare System, San Diego, CA, USA
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