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Gonzalez JC, Lee H, Vincent AM, Hill AL, Goode LK, King GD, Gamble KL, Wadiche JI, Overstreet-Wadiche L. Circadian regulation of dentate gyrus excitability mediated by G-protein signaling. Cell Rep 2023; 42:112039. [PMID: 36749664 PMCID: PMC10404305 DOI: 10.1016/j.celrep.2023.112039] [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: 05/11/2022] [Revised: 10/27/2022] [Accepted: 01/12/2023] [Indexed: 02/08/2023] Open
Abstract
The central circadian regulator within the suprachiasmatic nucleus transmits time of day information by a diurnal spiking rhythm driven by molecular clock genes controlling membrane excitability. Most brain regions, including the hippocampus, harbor similar intrinsic circadian transcriptional machinery, but whether these molecular programs generate oscillations of membrane properties is unclear. Here, we show that intrinsic excitability of mouse dentate granule neurons exhibits a 24-h oscillation that controls spiking probability. Diurnal changes in excitability are mediated by antiphase G-protein regulation of potassium and sodium currents that reduce excitability during the Light phase. Disruption of the circadian transcriptional machinery by conditional deletion of Bmal1 enhances excitability selectively during the Light phase by removing G-protein regulation. These results reveal that circadian transcriptional machinery regulates intrinsic excitability by coordinated regulation of ion channels by G-protein signaling, highlighting a potential novel mechanism of cell-autonomous oscillations.
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Affiliation(s)
- Jose Carlos Gonzalez
- Department of Neurobiology and McKnight Brain Institute, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Haeun Lee
- Department of Neurobiology and McKnight Brain Institute, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Angela M Vincent
- Department of Neurobiology and McKnight Brain Institute, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Angela L Hill
- Department of Neurobiology and McKnight Brain Institute, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Lacy K Goode
- Department of Psychiatry and Behavioral Neurobiology, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Gwendalyn D King
- Department of Biology, Creighton University, Omaha, NE 68178, USA
| | - Karen L Gamble
- Department of Psychiatry and Behavioral Neurobiology, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Jacques I Wadiche
- Department of Neurobiology and McKnight Brain Institute, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
| | - Linda Overstreet-Wadiche
- Department of Neurobiology and McKnight Brain Institute, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
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2
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Endogenous functioning and light response of the retinal clock in vertebrates. PROGRESS IN BRAIN RESEARCH 2022; 273:49-69. [DOI: 10.1016/bs.pbr.2022.04.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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3
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Öztürk M, Ingenwerth M, Sager M, von Gall C, Ali AAH. Does a Red House Affect Rhythms in Mice with a Corrupted Circadian System? Int J Mol Sci 2021; 22:2288. [PMID: 33669004 PMCID: PMC7956239 DOI: 10.3390/ijms22052288] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2021] [Revised: 02/12/2021] [Accepted: 02/24/2021] [Indexed: 02/05/2023] Open
Abstract
The circadian rhythms of body functions in mammals are controlled by the circadian system. The suprachiasmatic nucleus (SCN) in the hypothalamus orchestrates subordinate oscillators. Time information is conveyed from the retina to the SCN to coordinate an organism's physiology and behavior with the light/dark cycle. At the cellular level, molecular clockwork composed of interlocked transcriptional/translational feedback loops of clock genes drives rhythmic gene expression. Mice with targeted deletion of the essential clock gene Bmal1 (Bmal1-/-) have an impaired light input pathway into the circadian system and show a loss of circadian rhythms. The red house (RH) is an animal welfare measure widely used for rodents as a hiding place. Red plastic provides light at a low irradiance and long wavelength-conditions which affect the circadian system. It is not known yet whether the RH affects rhythmic behavior in mice with a corrupted circadian system. Here, we analyzed whether the RH affects spontaneous locomotor activity in Bmal1-/- mice under standard laboratory light conditions. In addition, mPER1- and p-ERK-immunoreactions, as markers for rhythmic SCN neuronal activity, and day/night plasma corticosterone levels were evaluated. Our findings indicate that application of the RH to Bmal1-/- abolishes rhythmic locomotor behavior and dampens rhythmic SCN neuronal activity. However, RH had no effect on the day/night difference in corticosterone levels.
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Affiliation(s)
- Menekse Öztürk
- Institute for Anatomy II, Medical Faculty, Heinrich-Heine-University, Moorenstrasse 5, 40225 Dusseldorf, Germany; (M.Ö.); (M.I.); (A.A.H.A.)
| | - Marc Ingenwerth
- Institute for Anatomy II, Medical Faculty, Heinrich-Heine-University, Moorenstrasse 5, 40225 Dusseldorf, Germany; (M.Ö.); (M.I.); (A.A.H.A.)
- Institute of Pathology, Medical Faculty, University Duisburg-Essen, Hufelandstrasse 55, 45147 Essen, Germany
| | - Martin Sager
- Central Institute for Animal Research and Animal Protection (ZETT), Medical Faculty, Heinrich Heine University, Moorenstrasse 5, 40225 Dusseldorf, Germany;
| | - Charlotte von Gall
- Institute for Anatomy II, Medical Faculty, Heinrich-Heine-University, Moorenstrasse 5, 40225 Dusseldorf, Germany; (M.Ö.); (M.I.); (A.A.H.A.)
| | - Amira A. H. Ali
- Institute for Anatomy II, Medical Faculty, Heinrich-Heine-University, Moorenstrasse 5, 40225 Dusseldorf, Germany; (M.Ö.); (M.I.); (A.A.H.A.)
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4
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Lim ASP. Diurnal and seasonal molecular rhythms in the human brain and their relation to Alzheimer disease. HANDBOOK OF CLINICAL NEUROLOGY 2021; 179:271-284. [PMID: 34225968 DOI: 10.1016/b978-0-12-819975-6.00017-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Diurnal and seasonal rhythms influence many aspects of human physiology including brain function. Moreover, altered diurnal and seasonal behavioral and physiological rhythms have been linked to Alzheimer's disease and related dementias (ADRD). Understanding the molecular basis for these links may lead to identification of novel targets to mitigate the negative impact of normal and abnormal diurnal and seasonal rhythms on ADRD or to alleviate the adverse consequences of ADRD on normal diurnal and seasonal rhythms. Diurnally and seasonally rhythmic gene expression and epigenetic modification in the human neocortex may be a key mechanism underlying these links. This chapter will first review the observed epidemiological links between normal and abnormal diurnal and seasonal rhythmicity, cognitive impairment, and ADRD. Then it will review normal diurnal and seasonal rhythms of brain epigenetic modification and gene expression in model organisms. Finally, it will review evidence for diurnal and seasonal rhythms of epigenetic modification and gene expression the human brain in aging, Alzheimer's disease, and other brain disorders.
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Affiliation(s)
- Andrew S P Lim
- Division of Neurology, Department of Medicine, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, ON, Canada.
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5
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Crislip GR, Douma LG, Masten SH, Cheng KY, Lynch IJ, Johnston JG, Barral D, Glasford KB, Holzworth MR, Verlander JW, Wingo CS, Gumz ML. Differences in renal BMAL1 contribution to Na + homeostasis and blood pressure control in male and female mice. Am J Physiol Renal Physiol 2020; 318:F1463-F1477. [PMID: 32338037 PMCID: PMC7311713 DOI: 10.1152/ajprenal.00014.2020] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2020] [Revised: 04/07/2020] [Accepted: 04/20/2020] [Indexed: 12/27/2022] Open
Abstract
The renal circadian clock has a major influence on the function of the kidney. Aryl hydrocarbon receptor nuclear translocator-like protein 1 [ARNTL; also known as brain and muscle ARNT-like 1 (BMAL1)] is a core clock protein and transcription factor that regulates the expression of nearly half of all genes. Using male and female kidney-specific cadherin BMAL1 knockout (KS-BMAL1 KO) mice, we examined the role of renal distal segment BMAL1 in blood pressure control and solute handling. We confirmed that this mouse model does not express BMAL1 in thick ascending limb, distal convoluted tubule, and collecting duct cells, which are the final locations for solute and fluid regulation. Male KS-BMAL1 KO mice displayed a substantially lower basal systolic blood pressure compared with littermate control mice, yet their circadian rhythm in pressure remained unchanged [male control mice: 127 ± 0.7 mmHg (n = 4) vs. male KS-BMAL KO mice: 119 ± 2.3 mmHg (n = 5), P < 0.05]. Female mice, however, did not display a genotype difference in basal systolic blood pressure [female control mice: 120 ± 1.6 mmHg (n = 5) vs. female KS-BMAL1 KO mice: 119 ± 1.5 mmHg (n = 7), P = 0.4]. In addition, male KS-BMAL1 KO mice had less Na+ retention compared with control mice in response to a K+-restricted diet (15% less following 5 days of treatment). However, there was no genotype difference in Na+ handling after a K+-restricted diet in female mice. Furthermore, there was evidence indicating a sex-specific response to K+ restriction where female mice reabsorbed less Na+ in response to this dietary challenge compared with male mice. We propose that BMAL1 in the distal nephron and collecting duct contributes to blood pressure regulation and Na+ handling in a sex-specific manner.
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Affiliation(s)
- G Ryan Crislip
- Department of Medicine, Division of Nephrology, Hypertension, and Renal Transplantation, University of Florida, Gainesville, Florida
| | - Lauren G Douma
- Department of Medicine, Division of Nephrology, Hypertension, and Renal Transplantation, University of Florida, Gainesville, Florida
- Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, Florida
| | - Sarah H Masten
- Department of Medicine, Division of Nephrology, Hypertension, and Renal Transplantation, University of Florida, Gainesville, Florida
| | - Kit-Yan Cheng
- Department of Medicine, Division of Nephrology, Hypertension, and Renal Transplantation, University of Florida, Gainesville, Florida
| | - I Jeanette Lynch
- Department of Medicine, Division of Nephrology, Hypertension, and Renal Transplantation, University of Florida, Gainesville, Florida
- North Florida/South Georgia Veterans Health System, Gainesville, Florida
| | - Jermaine G Johnston
- Department of Medicine, Division of Nephrology, Hypertension, and Renal Transplantation, University of Florida, Gainesville, Florida
| | - Dominique Barral
- Department of Medicine, Division of Nephrology, Hypertension, and Renal Transplantation, University of Florida, Gainesville, Florida
| | - Krystal B Glasford
- Department of Medicine, Division of Nephrology, Hypertension, and Renal Transplantation, University of Florida, Gainesville, Florida
| | - Meaghan R Holzworth
- Department of Medicine, Division of Nephrology, Hypertension, and Renal Transplantation, University of Florida, Gainesville, Florida
| | - Jill W Verlander
- Department of Medicine, Division of Nephrology, Hypertension, and Renal Transplantation, University of Florida, Gainesville, Florida
| | - Charles S Wingo
- Department of Medicine, Division of Nephrology, Hypertension, and Renal Transplantation, University of Florida, Gainesville, Florida
- North Florida/South Georgia Veterans Health System, Gainesville, Florida
| | - Michelle L Gumz
- Department of Medicine, Division of Nephrology, Hypertension, and Renal Transplantation, University of Florida, Gainesville, Florida
- Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, Florida
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Sondereker KB, Stabio ME, Renna JM. Crosstalk: The diversity of melanopsin ganglion cell types has begun to challenge the canonical divide between image-forming and non-image-forming vision. J Comp Neurol 2020; 528:2044-2067. [PMID: 32003463 DOI: 10.1002/cne.24873] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Revised: 01/22/2020] [Accepted: 01/22/2020] [Indexed: 12/15/2022]
Abstract
Melanopsin ganglion cells have defied convention since their discovery almost 20 years ago. In the years following, many types of these intrinsically photosensitive retinal ganglion cells (ipRGCs) have emerged. In the mouse retina, there are currently six known types (M1-M6) of melanopsin ganglion cells, each with unique morphology, mosaics, connections, physiology, projections, and functions. While melanopsin-expressing cells are usually associated with behaviors like circadian photoentrainment and the pupillary light reflex, the characterization of multiple types has demonstrated a reach that may extend far beyond non-image-forming vision. In fact, studies have shown that individual types of melanopsin ganglion cells have the potential to impact image-forming functions like contrast sensitivity and color opponency. Thus, the goal of this review is to summarize the morphological and functional aspects of the six known types of melanopsin ganglion cells in the mouse retina and to highlight their respective roles in non-image-forming and image-forming vision. Although many melanopsin ganglion cell types do project to image-forming brain targets, it is important to note that this is only the first step in determining their influence on image-forming vision. Even so, the visual system has canonically been divided into these two functional realms and melanopsin ganglion cells have begun to challenge the boundary between them, providing an overlap of visual information that is complementary rather than redundant. Further studies on these ganglion cell photoreceptors will no doubt continue to illustrate an ever-expanding role for melanopsin ganglion cells in image-forming vision.
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Affiliation(s)
| | - Maureen E Stabio
- Department of Cell & Developmental Biology, University of Colorado School of Medicine, Aurora, Colorado
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Chaix A, Lin T, Le HD, Chang MW, Panda S. Time-Restricted Feeding Prevents Obesity and Metabolic Syndrome in Mice Lacking a Circadian Clock. Cell Metab 2019; 29:303-319.e4. [PMID: 30174302 PMCID: PMC7751278 DOI: 10.1016/j.cmet.2018.08.004] [Citation(s) in RCA: 395] [Impact Index Per Article: 79.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/30/2017] [Revised: 04/25/2018] [Accepted: 08/01/2018] [Indexed: 12/21/2022]
Abstract
Increased susceptibility of circadian clock mutant mice to metabolic diseases has led to the idea that a molecular clock is necessary for metabolic homeostasis. However, these mice often lack a normal feeding-fasting cycle. We tested whether time-restricted feeding (TRF) could prevent obesity and metabolic syndrome in whole-body Cry1;Cry2 and in liver-specific Bmal1 and Rev-erbα/β knockout mice. When provided access to food ad libitum, these mice rapidly gained weight and showed genotype-specific metabolic defects. However, when fed the same diet under TRF (food access restricted to 10 hr during the dark phase) they were protected from excessive weight gain and metabolic diseases. Transcriptome and metabolome analyses showed that TRF reduced the accumulation of hepatic lipids and enhanced cellular defenses against metabolic stress. These results suggest that the circadian clock maintains metabolic homeostasis by sustaining daily rhythms in feeding and fasting and by maintaining balance between nutrient and cellular stress responses.
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Affiliation(s)
- Amandine Chaix
- The Salk Institute for Biological Studies, La Jolla, CA 92037, USA
| | - Terry Lin
- The Salk Institute for Biological Studies, La Jolla, CA 92037, USA
| | - Hiep D Le
- The Salk Institute for Biological Studies, La Jolla, CA 92037, USA
| | - Max W Chang
- Department of Medicine, University of California, San Diego, La Jolla, CA 92093, USA
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8
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Price KH, Dziema H, Aten S, Loeser J, Norona FE, Hoyt K, Obrietan K. Modulation of learning and memory by the targeted deletion of the circadian clock gene Bmal1 in forebrain circuits. Behav Brain Res 2016; 308:222-35. [PMID: 27091299 PMCID: PMC5344043 DOI: 10.1016/j.bbr.2016.04.027] [Citation(s) in RCA: 69] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2015] [Revised: 03/27/2016] [Accepted: 04/14/2016] [Indexed: 02/06/2023]
Abstract
A large body of literature has shown that the disruption of circadian clock timing has profound effects on mood, memory and complex thinking. Central to this time keeping process is the master circadian pacemaker located within the suprachiasmatic nucleus (SCN). Of note, within the central nervous system, clock timing is not exclusive to the SCN, but rather, ancillary oscillatory capacity has been detected in a wide range of cell types and brain regions, including forebrain circuits that underlie complex cognitive processes. These observations raise questions about the hierarchical and functional relationship between the SCN and forebrain oscillators, and, relatedly, about the underlying clock-gated synaptic circuitry that modulates cognition. Here, we utilized a clock knockout strategy in which the essential circadian timing gene Bmal1 was selectively deleted from excitatory forebrain neurons, whilst the SCN clock remained intact, to test the role of forebrain clock timing in learning, memory, anxiety, and behavioral despair. With this model system, we observed numerous effects on hippocampus-dependent measures of cognition. Mice lacking forebrain Bmal1 exhibited deficits in both acquisition and recall on the Barnes maze. Notably, loss of forebrain Bmal1 abrogated time-of-day dependent novel object location memory. However, the loss of Bmal1 did not alter performance on the elevated plus maze, open field assay, and tail suspension test, indicating that this phenotype specifically impairs cognition but not affect. Together, these data suggest that forebrain clock timing plays a critical role in shaping the efficiency of learning and memory retrieval over the circadian day.
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Affiliation(s)
- Kaiden H Price
- Department of Neuroscience, Ohio State University, Columbus, OH, USA
| | - Heather Dziema
- Department of Neuroscience, Ohio State University, Columbus, OH, USA
| | - Sydney Aten
- Department of Neuroscience, Ohio State University, Columbus, OH, USA
| | - Jacob Loeser
- Department of Neuroscience, Ohio State University, Columbus, OH, USA
| | - Frances E Norona
- Department of Neuroscience, Ohio State University, Columbus, OH, USA
| | - Kari Hoyt
- Division of Pharmacology, Ohio State University, Columbus, OH, USA
| | - Karl Obrietan
- Department of Neuroscience, Ohio State University, Columbus, OH, USA.
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Dyar KA, Ciciliot S, Tagliazucchi GM, Pallafacchina G, Tothova J, Argentini C, Agatea L, Abraham R, Ahdesmäki M, Forcato M, Bicciato S, Schiaffino S, Blaauw B. The calcineurin-NFAT pathway controls activity-dependent circadian gene expression in slow skeletal muscle. Mol Metab 2015; 4:823-33. [PMID: 26629406 PMCID: PMC4632177 DOI: 10.1016/j.molmet.2015.09.004] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/04/2015] [Accepted: 09/15/2015] [Indexed: 12/17/2022] Open
Abstract
Objective Physical activity and circadian rhythms are well-established determinants of human health and disease, but the relationship between muscle activity and the circadian regulation of muscle genes is a relatively new area of research. It is unknown whether muscle activity and muscle clock rhythms are coupled together, nor whether activity rhythms can drive circadian gene expression in skeletal muscle. Methods We compared the circadian transcriptomes of two mouse hindlimb muscles with vastly different circadian activity patterns, the continuously active slow soleus and the sporadically active fast tibialis anterior, in the presence or absence of a functional skeletal muscle clock (skeletal muscle-specific Bmal1 KO). In addition, we compared the effect of denervation on muscle circadian gene expression. Results We found that different skeletal muscles exhibit major differences in their circadian transcriptomes, yet core clock gene oscillations were essentially identical in fast and slow muscles. Furthermore, denervation caused relatively minor changes in circadian expression of most core clock genes, yet major differences in expression level, phase and amplitude of many muscle circadian genes. Conclusions We report that activity controls the oscillation of around 15% of skeletal muscle circadian genes independently of the core muscle clock, and we have identified the Ca2+-dependent calcineurin-NFAT pathway as an important mediator of activity-dependent circadian gene expression, showing that circadian locomotor activity rhythms drive circadian rhythms of NFAT nuclear translocation and target gene expression. Activity is a major extrinsic factor driving ∼15% of muscle circadian genes. Calcineurin-NFAT drives activity-dependent circadian gene expression in muscle. The majority of skeletal muscle circadian genes are muscle type-specific. A common set of skeletal muscle circadian genes are clock-dependent.
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Affiliation(s)
- Kenneth A Dyar
- Venetian Institute of Molecular Medicine (VIMM), Padova, Italy
| | | | - Guidantonio Malagoli Tagliazucchi
- Center for Genome Research, Department of Life Sciences, University of Modena and Reggio Emilia, Modena, Italy ; Istituto Nazionale Genetica Molecolare 'Romeo ed Enrica Invernizzi', Via F. Sforza 35, 20122 Milan, Italy
| | - Giorgia Pallafacchina
- Venetian Institute of Molecular Medicine (VIMM), Padova, Italy ; Institute of Neurosciences, Consiglio Nazionale delle Ricerche (CNR), Padova, Italy
| | - Jana Tothova
- Venetian Institute of Molecular Medicine (VIMM), Padova, Italy
| | - Carla Argentini
- Venetian Institute of Molecular Medicine (VIMM), Padova, Italy
| | - Lisa Agatea
- Venetian Institute of Molecular Medicine (VIMM), Padova, Italy
| | - Reimar Abraham
- Venetian Institute of Molecular Medicine (VIMM), Padova, Italy
| | - Miika Ahdesmäki
- Institute for Medical Informatics, Statistics and Epidemiology, University of Leipzig, Germany
| | - Mattia Forcato
- Center for Genome Research, Department of Life Sciences, University of Modena and Reggio Emilia, Modena, Italy
| | - Silvio Bicciato
- Center for Genome Research, Department of Life Sciences, University of Modena and Reggio Emilia, Modena, Italy
| | - Stefano Schiaffino
- Venetian Institute of Molecular Medicine (VIMM), Padova, Italy ; Institute of Neurosciences, Consiglio Nazionale delle Ricerche (CNR), Padova, Italy
| | - Bert Blaauw
- Venetian Institute of Molecular Medicine (VIMM), Padova, Italy ; Department of Biomedical Sciences, University of Padova, Italy
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Hardeland R. Chronobiology of Melatonin beyond the Feedback to the Suprachiasmatic Nucleus-Consequences to Melatonin Dysfunction. Int J Mol Sci 2013; 14:5817-41. [PMID: 23481642 PMCID: PMC3634486 DOI: 10.3390/ijms14035817] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2013] [Revised: 03/01/2013] [Accepted: 03/04/2013] [Indexed: 12/28/2022] Open
Abstract
The mammalian circadian system is composed of numerous oscillators, which gradually differ with regard to their dependence on the pacemaker, the suprachiasmatic nucleus (SCN). Actions of melatonin on extra-SCN oscillators represent an emerging field. Melatonin receptors are widely expressed in numerous peripheral and central nervous tissues. Therefore, the circadian rhythm of circulating, pineal-derived melatonin can have profound consequences for the temporal organization of almost all organs, without necessarily involving the melatonin feedback to the suprachiasmatic nucleus. Experiments with melatonin-deficient mouse strains, pinealectomized animals and melatonin receptor knockouts, as well as phase-shifting experiments with explants, reveal a chronobiological role of melatonin in various tissues. In addition to directly steering melatonin-regulated gene expression, the pineal hormone is required for the rhythmic expression of circadian oscillator genes in peripheral organs and to enhance the coupling of parallel oscillators within the same tissue. It exerts additional effects by modulating the secretion of other hormones. The importance of melatonin for numerous organs is underlined by the association of various diseases with gene polymorphisms concerning melatonin receptors and the melatonin biosynthetic pathway. The possibilities and limits of melatonergic treatment are discussed with regard to reductions of melatonin during aging and in various diseases.
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Affiliation(s)
- Rüdiger Hardeland
- Johann Friedrich Blumenbach Institute of Zoology and Anthropology, University of Göttingen, Berliner Str. 28, Göttingen D-37073, Germany.
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