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Avilez-Avilez JJ, Medina-Flores MF, Gómez-Gonzalez B. Sleep loss impairs blood-brain barrier function: Cellular and molecular mechanisms. VITAMINS AND HORMONES 2024; 126:77-96. [PMID: 39029977 DOI: 10.1016/bs.vh.2024.02.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/21/2024]
Abstract
Sleep is a physiological process that preserves the integrity of the neuro-immune-endocrine network to maintain homeostasis. Sleep regulates the production and secretion of hormones, neurotransmitters, cytokines and other inflammatory mediators, both at the central nervous system (CNS) and at the periphery. Sleep promotes the removal of potentially toxic metabolites out of the brain through specialized systems such as the glymphatic system, as well as the expression of specific transporters in the blood-brain barrier. The blood-brain barrier maintains CNS homeostasis by selectively transporting metabolic substrates and nutrients into the brain, by regulating the efflux of metabolic waste products, and maintaining bidirectional communication between the periphery and the CNS. All those processes are disrupted during sleep loss. Brain endothelial cells express the blood-brain barrier phenotype, which arises after cell-to-cell interactions with mural cells, like pericytes, and after the release of soluble factors by astroglial endfeet. Astroglia, pericytes and brain endothelial cells respond differently to sleep loss; evidence has shown that sleep loss induces a chronic low-grade inflammatory state at the CNS, which is associated with blood-brain barrier dysfunction. In animal models, blood-brain barrier dysfunction is characterized by increased blood-brain barrier permeability, decreased tight junction protein expression and pericyte detachment from the capillary wall. Blood-brain barrier dysfunction may promote defects in brain clearance of potentially neurotoxic metabolites and byproducts of neural physiology, which may eventually contribute to neurodegenerative diseases. This chapter aims to describe the cellular and molecular mechanisms by which sleep loss modifies the function of the blood-brain barrier.
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Affiliation(s)
- Jessica Janeth Avilez-Avilez
- Graduate Program in Experimental Biology, Universidad Autónoma Metropolitana, Mexico City, Mexico; Area of Neurosciences, Department of Biology of Reproduction, Universidad Autónoma Metropolitana, Mexico City, Mexico
| | - María Fernanda Medina-Flores
- Graduate Program in Experimental Biology, Universidad Autónoma Metropolitana, Mexico City, Mexico; Area of Neurosciences, Department of Biology of Reproduction, Universidad Autónoma Metropolitana, Mexico City, Mexico
| | - Beatriz Gómez-Gonzalez
- Area of Neurosciences, Department of Biology of Reproduction, Universidad Autónoma Metropolitana, Mexico City, Mexico.
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Yang Y, Feng Y, Hu Y, Liu J, Shi H, Zhao R. Exposure to constant light impairs cognition with FTO inhibition and m 6A-dependent TrκB repression in mouse hippocampus. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2021; 283:117037. [PMID: 33866220 DOI: 10.1016/j.envpol.2021.117037] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2020] [Revised: 03/16/2021] [Accepted: 03/27/2021] [Indexed: 06/12/2023]
Abstract
N6-methyladenosine (m6A) mRNA methylation plays a role in various brain functions. Exposure to chronic constant light (CCL) has been reported to impair cognition, yet whether the underlying mechanism involves m6A remains unknown. In this study, mice exposed to CCL for 3 weeks show impaired cognitive behavior, which was associated with increased m6A level in hippocampus. Accordingly, the m6A demethylase FTO was inhibited while the methyltransferases METTL3, METTL14 and WTAP, as well as the reader protein YTHDF2, were elevated in the hippocampus of CCL-exposed mice. CCL exposure significantly activated hippocampal expression of circadian regulator cryptochrome 1 and 2 (CRY1 and 2). Meanwhile, hippocampal neurogenesis was impaired with suppression of BDNF/TrκB/ERK pathway. To further delineate the signaling pathway and the role of m6A, we altered the expression of CRY1/2 in hippocampus neuron cells. CRY1/2 overexpression inhibited FTO and increased m6A levels, while CRY1/2 knockdown led to opposite results. Luciferase reporter analysis further confirmed CRY1/2-induced FTO suppression. Furthermore, FTO knockdown increased m6A on 3'UTR of TrκB mRNA, and decreased TrκB mRNA stability and TrκB protein expression, in a YTHDF2-dependent manner. These results indicate that CCL-activated CRY1/2 causes transcriptional inhibition of FTO, which suppresses TrκB expression in hippocampus via m6A-dependent post-transcriptional regulation and contributes to impaired cognitive behavior in mice exposed to constant light.
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Affiliation(s)
- Yang Yang
- MOE Joint International Research Laboratory of Animal Health & Food Safety, Nanjing Agricultural University, Nanjing, 210095, PR China; Key Laboratory of Animal Physiology & Biochemistry, Nanjing Agricultural University, Nanjing, 210095, PR China
| | - Yue Feng
- MOE Joint International Research Laboratory of Animal Health & Food Safety, Nanjing Agricultural University, Nanjing, 210095, PR China; Key Laboratory of Animal Physiology & Biochemistry, Nanjing Agricultural University, Nanjing, 210095, PR China
| | - Yun Hu
- MOE Joint International Research Laboratory of Animal Health & Food Safety, Nanjing Agricultural University, Nanjing, 210095, PR China; Key Laboratory of Animal Physiology & Biochemistry, Nanjing Agricultural University, Nanjing, 210095, PR China
| | - Jie Liu
- MOE Joint International Research Laboratory of Animal Health & Food Safety, Nanjing Agricultural University, Nanjing, 210095, PR China; Key Laboratory of Animal Physiology & Biochemistry, Nanjing Agricultural University, Nanjing, 210095, PR China
| | - Hailing Shi
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, USA; Howard Hughes Medical Institute, The University of Chicago, Chicago, IL, USA
| | - Ruqian Zhao
- MOE Joint International Research Laboratory of Animal Health & Food Safety, Nanjing Agricultural University, Nanjing, 210095, PR China; Key Laboratory of Animal Physiology & Biochemistry, Nanjing Agricultural University, Nanjing, 210095, PR China.
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Vega-Rivera NM, Ortiz-López L, Granados-Juárez A, Estrada-Camarena EM, Ramírez-Rodríguez GB. Melatonin Reverses the Depression-associated Behaviour and Regulates Microglia, Fractalkine Expression and Neurogenesis in Adult Mice Exposed to Chronic Mild Stress. Neuroscience 2020; 440:316-336. [PMID: 32417342 DOI: 10.1016/j.neuroscience.2020.05.014] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Revised: 05/05/2020] [Accepted: 05/07/2020] [Indexed: 02/08/2023]
Abstract
Depression may be precipitated by the negative impact of chronic stress, which is considered to play a key role in this neuropsychiatric disorder. Interestingly, depressed patients show decreased levels of melatonin. This hormone acts pro-neurogenic and exhibits anti-depressant effects in rodent models of predictive antidepressant-like effects. However, the benefits of melatonin in reversing the deleterious effects of chronic mild stress on the alterations in behaviour and in the neurogenic niche of the hippocampus in male BALB/c mice are unknown. In this study, we compared the effects of melatonin (2.5 mg/kg) and citalopram (5 mg/kg), an antidepressant drug belonging to the selective serotonin reuptake inhibitors, in male BALB/c mice exposed to chronic mild stress (CMS). We also investigated the potential effects of melatonin and citalopram on microglial cells, hippocampal neurogenesis and peripheral cytokine profiles. Melatonin and citalopram induced similar antidepressant-like activities that occurred with some of the the following findings: (1) reversal of the morphological alterations in microglia; (2) reversal of the decreased immunoreactivity to CX3CL1 and CX3CR1 in the dentate gyrus; (3) positive regulation of cell proliferation, survival and complexity of the dendritic trees of doublecortin-cells; and (4) modifications of peripheral CX3CL1 expression. This outcome is consistent with the hypothesis about the antidepressant-like effect of melatonin and supports its relevance as a modulator of the niche in the dentate gyrus.
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Affiliation(s)
- Nelly Maritza Vega-Rivera
- Laboratorio de Neuropsicofarmacología, Dirección de Neurociencias, Instituto Nacional de Psiquiatría "Ramón de la Fuente Muñiz", Calz. México-Xochimilco 101, 14370 Ciudad de México, Mexico
| | - Leonardo Ortiz-López
- Laboratorio de Neurogénesis, Subdirección de Investigaciones Clínicas, Instituto Nacional de Psiquiatría "Ramón de la Fuente Muñiz", Calzada México-Xochimilco 101, 14370 Ciudad de México, Mexico
| | - Andrea Granados-Juárez
- Laboratorio de Neurogénesis, Subdirección de Investigaciones Clínicas, Instituto Nacional de Psiquiatría "Ramón de la Fuente Muñiz", Calzada México-Xochimilco 101, 14370 Ciudad de México, Mexico
| | - Erika Monserrat Estrada-Camarena
- Laboratorio de Neuropsicofarmacología, Dirección de Neurociencias, Instituto Nacional de Psiquiatría "Ramón de la Fuente Muñiz", Calz. México-Xochimilco 101, 14370 Ciudad de México, Mexico
| | - Gerardo Bernabé Ramírez-Rodríguez
- Laboratorio de Neurogénesis, Subdirección de Investigaciones Clínicas, Instituto Nacional de Psiquiatría "Ramón de la Fuente Muñiz", Calzada México-Xochimilco 101, 14370 Ciudad de México, Mexico.
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Gao T, Wang Z, Dong Y, Cao J, Lin R, Wang X, Yu Z, Chen Y. Role of melatonin in sleep deprivation-induced intestinal barrier dysfunction in mice. J Pineal Res 2019; 67:e12574. [PMID: 30929267 DOI: 10.1111/jpi.12574] [Citation(s) in RCA: 127] [Impact Index Per Article: 25.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/15/2018] [Revised: 03/20/2019] [Accepted: 03/21/2019] [Indexed: 12/18/2022]
Abstract
Intestinal diseases caused by sleep deprivation (SD) are severe public health threats worldwide. This study focuses on the effect of melatonin on intestinal mucosal injury and microbiota dysbiosis in sleep-deprived mice. Mice subjected to SD had significantly elevated norepinephrine levels and decreased melatonin content in plasma. Consistent with the decrease in melatonin levels, we observed a decrease of antioxidant ability, down-regulation of anti-inflammatory cytokines and up-regulation of pro-inflammatory cytokines in sleep-deprived mice, which resulted in colonic mucosal injury, including a reduced number of goblet cells, proliferating cell nuclear antigen-positive cells, expression of MUC2 and tight junction proteins and elevated expression of ATG5, Beclin1, p-P65 and p-IκB. High-throughput pyrosequencing of 16S rRNA demonstrated that the diversity and richness of the colonic microbiota were decreased in sleep-deprived mice, especially in probiotics, including Akkermansia, Bacteroides and Faecalibacterium. However, the pathogen Aeromonas was markedly increased. By contrast, supplementation with 20 and 40 mg/kg melatonin reversed these SD-induced changes and improved the mucosal injury and dysbiosis of the microbiota in the colon. Our results suggest that the effect of SD on intestinal barrier dysfunction might be an outcome of melatonin suppression rather than a loss of sleep per se. SD-induced intestinal barrier dysfunction involved the suppression of melatonin production and activation of the NF-κB pathway by oxidative stress.
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Affiliation(s)
- Ting Gao
- Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Animal Medicine, China Agricultural University, Beijing, China
| | - Zixu Wang
- Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Animal Medicine, China Agricultural University, Beijing, China
| | - Yulan Dong
- Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Animal Medicine, China Agricultural University, Beijing, China
| | - Jing Cao
- Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Animal Medicine, China Agricultural University, Beijing, China
| | - Rutao Lin
- Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Animal Medicine, China Agricultural University, Beijing, China
| | - Xintong Wang
- Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Animal Medicine, China Agricultural University, Beijing, China
| | - Zhengquan Yu
- Beijing Advanced Innovation Center for Food Nutrition and Human Health, Beijing, China
| | - Yaoxing Chen
- Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Animal Medicine, China Agricultural University, Beijing, China
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5
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Sleep deprivation inhibits proliferation of adult hippocampal neural progenitor cells by a mechanism involving IL-17 and p38 MAPK. Brain Res 2019; 1714:81-87. [DOI: 10.1016/j.brainres.2019.01.024] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2018] [Revised: 01/20/2019] [Accepted: 01/20/2019] [Indexed: 01/12/2023]
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Hinojosa-Godinez A, Jave-Suarez LF, Flores-Soto M, Gálvez-Contreras AY, Luquín S, Oregon-Romero E, González-Pérez O, González-Castañeda RE. Melatonin modifies SOX2 + cell proliferation in dentate gyrus and modulates SIRT1 and MECP2 in long-term sleep deprivation. Neural Regen Res 2019; 14:1787-1795. [PMID: 31169197 PMCID: PMC6585545 DOI: 10.4103/1673-5374.257537] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Melatonin is a pleiotropic molecule that, after a short-term sleep deprivation, promotes the proliferation of neural stem cells in the adult hippocampus. However, this effect has not been observed in long-term sleep deprivation. The precise mechanism exerted by melatonin on the modulation of neural stem cells is not entirely elucidated, but evidence indicates that epigenetic regulators may be involved in this process. In this study, we investigated the effect of melatonin treatment during a 96-hour sleep deprivation and analyzed the expression of epigenetic modulators predicted by computational text mining and keyword clusterization. Our results showed that the administration of melatonin under sleep-deprived conditions increased the MECP2 expression and reduced the SIRT1 expression in the dentate gyrus. We observed that let-7b, mir-132, and mir-124 were highly expressed in the dentate gyrus after melatonin administration, but they were not modified by sleep deprivation. In addition, we found more Sox2+/5-bromo-2′-deoxyuridine (BrdU)+ cells in the subgranular zone of the sleep-deprived group treated with melatonin than in the untreated group. These findings may support the notion that melatonin modifies the expression of epigenetic mediators that, in turn, regulate the proliferation of neural progenitor cells in the adult dentate gyrus under long-term sleep-deprived conditions. All procedures performed in this study were approved by the Animal Ethics Committee of the University of Guadalajara, Mexico (approval No. CI-16610) on January 2, 2016.
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Affiliation(s)
- Alan Hinojosa-Godinez
- Laboratorio de Microscopía de Alta Resolución, Departamento de Neurociencias, Centro Universitario de Ciencias de la Salud, Universidad de Guadalajara, Guadalajara, México
| | - Luis F Jave-Suarez
- División de Inmunología, Centro de Investigación Biomédica de Occidente, Instituto Mexicano del Seguro Social, Guadalajara, México
| | - Mario Flores-Soto
- División de Neurociencias, Centro de Investigación Biomédica de Occidente, Instituto Mexicano del Seguro Social, Guadalajara, México
| | - Alma Y Gálvez-Contreras
- Laboratorio de Microscopía de Alta Resolución, Departamento de Neurociencias; Unidad de Atención en Neurociencias, Departamento de Neurociencias, Centro Universitario de Ciencias de la Salud, Universidad de Guadalajara, Guadalajara, México
| | - Sonia Luquín
- Laboratorio de Microscopía de Alta Resolución, Departamento de Neurociencias, Centro Universitario de Ciencias de la Salud, Universidad de Guadalajara, Guadalajara, México
| | - Edith Oregon-Romero
- Instituto de Investigación en Ciencias Biomédicas (IICB), Departamento de Biología Molecular y Genómica, Centro Universitario de Ciencias de la Salud, Universidad de Guadalajara, Guadalajara, México
| | - Oscar González-Pérez
- Laboratorio de Neurociencias, Facultad de Psicología, Universidad de Colima, Colima, México
| | - Rocio E González-Castañeda
- Laboratorio de Microscopía de Alta Resolución, Departamento de Neurociencias; Unidad de Atención en Neurociencias, Departamento de Neurociencias, Centro Universitario de Ciencias de la Salud, Universidad de Guadalajara, Guadalajara, México
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Draijer S, Chaves I, Hoekman MFM. The circadian clock in adult neural stem cell maintenance. Prog Neurobiol 2018; 173:41-53. [PMID: 29886147 DOI: 10.1016/j.pneurobio.2018.05.007] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Revised: 05/14/2018] [Accepted: 05/29/2018] [Indexed: 12/25/2022]
Abstract
Neural stem cells persist in the adult central nervous system as a continuing source of astrocytes, oligodendrocytes and neurons. Various signalling pathways and transcription factors actively maintain this population by regulating cell cycle entry and exit. Similarly, the circadian clock is interconnected with the cell cycle and actively maintains stem cell populations in various tissues. Here, we discuss emerging evidence for an important role of the circadian clock in neural stem cell maintenance. We propose that the NAD+-dependent deacetylase SIRT1 exerts control over the circadian clock in adult neural stem cell function to limit exhaustion of their population. Conversely, disruption of the circadian clock may compromise neural stem cell quiescence resulting in a premature decline of the neural stem cell population. As such, energy metabolism and the circadian clock converge in adult neural stem cell maintenance.
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Affiliation(s)
- Swip Draijer
- Swammerdam Institute for Life Sciences, University of Amsterdam, 1098 XH Amsterdam, The Netherlands
| | - Inês Chaves
- Department of Molecular Genetics, Erasmus University Medical Center, 3000 CA Rotterdam, The Netherlands
| | - Marco F M Hoekman
- Swammerdam Institute for Life Sciences, University of Amsterdam, 1098 XH Amsterdam, The Netherlands.
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Chronic Circadian Misalignment without Circadian Arrhythmicity or Sleep Deprivation Does Not Impair Adult Hippocampal Neurogenesis. J Biol Rhythms 2017; 32:621-626. [DOI: 10.1177/0748730417736960] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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9
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Navarro-Sanchis C, Brock O, Winsky-Sommerer R, Thuret S. Modulation of Adult Hippocampal Neurogenesis by Sleep: Impact on Mental Health. Front Neural Circuits 2017; 11:74. [PMID: 29075182 PMCID: PMC5643465 DOI: 10.3389/fncir.2017.00074] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Accepted: 09/26/2017] [Indexed: 12/27/2022] Open
Abstract
The process of neurogenesis has been demonstrated to occur throughout life in the subgranular zone (SGZ) of the hippocampal dentate gyrus of several mammals, including humans. The basal rate of adult hippocampal neurogenesis can be altered by lifestyle and environmental factors. In this perspective review, the evidence for sleep as a modulator of adult hippocampal neurogenesis is first summarized. Following this, the impacts of sleep and sleep disturbances on hippocampal-dependent functions, including learning and memory, and depression are critically evaluated. Finally, we postulate that the effects of sleep on hippocampal-dependent functions may possibly be mediated by a change in adult hippocampal neurogenesis. This could provide a route to new treatments for cognitive impairments and psychiatric disorders.
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Affiliation(s)
- Cristina Navarro-Sanchis
- Department of Basic and Clinical Neuroscience, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, United Kingdom
| | - Olivier Brock
- Department of Basic and Clinical Neuroscience, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, United Kingdom
| | - Raphaelle Winsky-Sommerer
- Surrey Sleep Research Centre, Department of Clinical and Experimental Medicine, Faculty of Health and Medical Science, University of Surrey, Guildford, United Kingdom
| | - Sandrine Thuret
- Department of Basic and Clinical Neuroscience, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, United Kingdom
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Wilcox ME, Lim AS, McAndrews MP, Wennberg RA, Pinto RL, Black SE, Walczak KD, Friedrich JO, Taglione MS, Rubenfeld GD. A study protocol for an observational cohort investigating COGnitive outcomes and WELLness in survivors of critical illness: the COGWELL study. BMJ Open 2017; 7:e015600. [PMID: 28710215 PMCID: PMC5734403 DOI: 10.1136/bmjopen-2016-015600] [Citation(s) in RCA: 9] [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] [Indexed: 01/07/2023] Open
Abstract
INTRODUCTION Up to 9 out of 10 intensive care unit (ICU) survivors will suffer some degree of cognitive impairment at hospital discharge and approximately half will have decrements that persist for years. The mechanisms for this newly acquired brain injury are poorly understood. The purpose of this study is to describe the prevalence of sleep abnormalities and their association with cognitive impairment, examine a well-known genetic risk factor for dementia (Apolipoprotein E ε4) that may allow for genetic risk stratification of ICU survivors at greatest risk of cognitive impairment and determine if electroencephalography (EEG) is an independent predictor of long-term cognitive impairment and possibly a candidate intermediate end point for future clinical trials. METHODS AND ANALYSIS This is a multisite, prospective, observational cohort study. The setting for this trial will be medical and surgical ICUs of five large tertiary care referral centres. The participants will be adult patients admitted to a study ICU and invasively ventilated for ≥3 days . Participants will undergo follow-up within 7 days of ICU discharge, 6 months and 1 year. At each time point, patients will have an EEG, blood work (biomarkers; gene studies), sleep study (actigraphy), complete a number of questionnaires as well as undergo neuropsychological testing. The primary outcome of this study will be long-term cognitive function at 12 months follow-up as measured by the Repeatable Battery for the Assessment of Neuropsychological Status and Trails Making Test B. ETHICS AND DISSEMINATION The study has received the following approvals: University Health Network Research Ethics Committee (13-6425-BE), Sunnybrook Health Centre Research Ethics Committee (365-2013), Mount Sinai Research Ethics Committee (14-0194-E) and St. Michael's Hospital Research Ethics Committee (14-295). Results will be made available to critical care survivors, their caregivers, the funders, the critical care societies and other researchers. TRIAL REGISTRATION NUMBER NCT02086877; Pre-results.
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Affiliation(s)
- M Elizabeth Wilcox
- Department of Medicine (Critical Care Medicine), University of Toronto, University Health Network, Toronto, Canada
| | - Andrew S Lim
- Department of Medicine (Neurology), University of Toronto, Sunnybrook Health Sciences Centre, Toronto, Canada
| | - Mary P McAndrews
- Department of Psychology, University of Toronto, University Health Network, Toronto, Canada
| | - Richard A Wennberg
- Department of Medicine (Neurology), University of Toronto, University Health Network, Toronto, Canada
| | - Ruxandra L Pinto
- Department of Medicine (Critical Care Medicine), University of Toronto, Sunnybrook Health Sciences Centre, Toronto, Canada
| | - Sandra E Black
- Department of Medicine (Neurology), University of Toronto, Sunnybrook Health Sciences Centre, Toronto, Canada
| | - Karolina D Walczak
- Department of Medicine (Critical Care Medicine), University of Toronto, University Health Network, Toronto, Canada
| | - Jan O Friedrich
- Department of Medicine (Critical Care Medicine), University of Toronto, St. Michael’s Hospital, Toronto, Canada
| | - Michael S Taglione
- Department of Medicine (Critical Care Medicine), University of Toronto, University Health Network, Toronto, Canada
| | - Gordon D Rubenfeld
- Department of Medicine (Critical Care Medicine), University of Toronto, Sunnybrook Health Sciences Centre, Toronto, Canada
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Petersen CC, Mistlberger RE. Interval Timing Is Preserved Despite Circadian Desynchrony in Rats: Constant Light and Heavy Water Studies. J Biol Rhythms 2017. [DOI: 10.1177/0748730417716231] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The mechanisms that enable mammals to time events that recur at 24-h intervals (circadian timing) and at arbitrary intervals in the seconds-to-minutes range (interval timing) are thought to be distinct at the computational and neurobiological levels. Recent evidence that disruption of circadian rhythmicity by constant light (LL) abolishes interval timing in mice challenges this assumption and suggests a critical role for circadian clocks in short interval timing. We sought to confirm and extend this finding by examining interval timing in rats in which circadian rhythmicity was disrupted by long-term exposure to LL or by chronic intake of 25% D2O. Adult, male Sprague-Dawley rats were housed in a light-dark (LD) cycle or in LL until free-running circadian rhythmicity was markedly disrupted or abolished. The rats were then trained and tested on 15- and 30-sec peak-interval procedures, with water restriction used to motivate task performance. Interval timing was found to be unimpaired in LL rats, but a weak circadian activity rhythm was apparently rescued by the training procedure, possibly due to binge feeding that occurred during the 15-min water access period that followed training each day. A second group of rats in LL were therefore restricted to 6 daily meals scheduled at 4-h intervals. Despite a complete absence of circadian rhythmicity in this group, interval timing was again unaffected. To eliminate all possible temporal cues, we tested a third group of rats in LL by using a pseudo-randomized schedule. Again, interval timing remained accurate. Finally, rats tested in LD received 25% D2O in place of drinking water. This markedly lengthened the circadian period and caused a failure of LD entrainment but did not disrupt interval timing. These results indicate that interval timing in rats is resistant to disruption by manipulations of circadian timekeeping previously shown to impair interval timing in mice.
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Affiliation(s)
- Christian C. Petersen
- Department of Psychology, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Ralph E. Mistlberger
- Department of Psychology, Simon Fraser University, Burnaby, British Columbia, Canada
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Kent BA, Mistlberger RE. Sleep and hippocampal neurogenesis: Implications for Alzheimer's disease. Front Neuroendocrinol 2017; 45:35-52. [PMID: 28249715 DOI: 10.1016/j.yfrne.2017.02.004] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/25/2016] [Revised: 01/23/2017] [Accepted: 02/24/2017] [Indexed: 01/29/2023]
Abstract
Alzheimer's disease (AD) is the most common cause of dementia and currently there are no effective disease-modifying treatments available. Hallmark symptoms of AD include impaired hippocampus-dependent episodic memory and disrupted sleep and circadian rhythms. The pathways connecting these symptoms are of particular interest because it is well established that sleep and circadian disruption can impair hippocampus-dependent learning and memory. In rodents, these procedures also markedly suppress adult hippocampal neurogenesis, a form of brain plasticity that is believed to play an important role in pattern separation, and thus episodic memory. A causal role for sleep disruptions in AD pathophysiology is suggested by evidence for sleep-dependent glymphatic clearance of metabolic waste products from the brain. This review explores a complementary hypothesis that sleep and circadian disruptions in AD contribute to cognitive decline by activating neuroendocrine and neuroinflammatory signaling pathways that suppress hippocampal neurogenesis. Evidence for this hypothesis underscores the promise of sleep, circadian rhythms, and neurogenesis as therapeutic targets for remediation of memory impairment in AD.
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Affiliation(s)
- Brianne A Kent
- Division of Neurology and Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, Canada
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13
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Abstract
Reward-related learning, including that associated with drugs of abuse, is largely mediated by the dopaminergic mesolimbic pathway. Mesolimbic neurophysiology and motivated behavior, in turn, are modulated by the circadian timing system which generates ∼24-h rhythms in cellular activity. Both drug taking and seeking and mesolimbic dopaminergic neurotransmission can vary widely over the day. Moreover, circadian clock genes are expressed in ventral tegmental area dopaminergic cells and in mesolimbic target regions where they can directly modulate reward-related neurophysiology and behavior. There also exists a reciprocal influence between drug taking and circadian timing as the administration of drugs of abuse can alter behavioral rhythms and circadian clock gene expression in mesocorticolimbic structures. These interactions suggest that manipulations of the circadian timing system may have some utility in the treatment of substance abuse disorders. Here, the literature on bidirectional interactions between the circadian timing system and drug taking is briefly reviewed, and potential chronotherapeutic considerations for the treatment of addiction are discussed.
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14
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Coppin G. The anterior medial temporal lobes: Their role in food intake and body weight regulation. Physiol Behav 2016; 167:60-70. [PMID: 27591841 DOI: 10.1016/j.physbeh.2016.08.028] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2016] [Revised: 07/22/2016] [Accepted: 08/29/2016] [Indexed: 11/25/2022]
Abstract
The anterior medial temporal lobes are one of the most studied parts of the brain. Classically, their two main structures - the amygdalae and the hippocampi - have been linked to key cognitive and affective functions, related in particular to learning and memory. Based on abundant evidence, we will argue for an alternative but complementary point of view: they may also play a major role in food intake and body weight regulation. First, an overview is given of early clinical evidence in this line of thought. Subsequently, empirical evidence is presented on how food intake, including in the extreme case of obesity, may relate to amygdalian and hippocampal functioning. The focus is on the amygdala's role in processing the relevance of food stimuli, cue-induced feeding, and stress-induced eating and on the hippocampus' involvement in the use of interoceptive signals of hunger and satiety, as well as memory and inhibitory processes related to food intake. Additionally, an elaboration takes place on possible reciprocal links between food intake, body weight, and amygdala and hippocampus functioning. Finally, issues that seemed particularly critical for future research in the field are discussed.
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Affiliation(s)
- Géraldine Coppin
- The John B. Pierce Laboratory, School of Medicine, Yale University, 290 Congress Avenue, New Haven, CT 06519, USA; Department of Psychiatry, School of Medicine, Yale University, 300 George Street, Suite 901, New Haven, CT 06511, USA.
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Prophylactic Role of Oral Melatonin Administration on Neurogenesis in Adult Balb/C Mice during REM Sleep Deprivation. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2016; 2016:2136902. [PMID: 27579149 PMCID: PMC4992538 DOI: 10.1155/2016/2136902] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/06/2016] [Revised: 06/10/2016] [Accepted: 06/20/2016] [Indexed: 12/17/2022]
Abstract
Purpose. The aim of this study was to assess the effect of melatonin in the proliferation of neural progenitors, melatonin concentration, and antiapoptotic proteins in the hippocampus of adult mice exposed to 96 h REM sleep deprivation (REMSD) prophylactic administration of melatonin for 14 days. Material and Methods. Five groups of Balb/C mice were used: (1) control, (2) REMSD, (3) melatonin (10 mg/kg) plus REMSD, (4) melatonin and intraperitoneal luzindole (once a day at 5 mg/kg) plus REMSD, and (5) luzindole plus REMSD. To measure melatonin content in hippocampal tissue we used HPLC. Bcl-2 and Bcl-xL proteins were measured by Western Blot and neurogenesis was determined by injecting 5-bromo-2-deoxyuridine (BrdU) and BrdU/nestin expressing cells in the subgranular zone of the dentate gyrus were quantified by epifluorescence. Results. The melatonin-treated REMSD group showed an increased neural precursor in 44% with respect to the REMSD group and in 28% when contrasted with the control group (P < 0.021). The melatonin-treated REMSD group also showed the highest expression of Bcl-2 and Bcl-xL as compared to the rest of the groups. Conclusion. The exogenous administration of melatonin restores the tissue levels of sleep-deprived group and appears to be an efficient neuroprotective agent against the deleterious effects of REMSD.
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Piromelatine ameliorates memory deficits associated with chronic mild stress-induced anhedonia in rats. Psychopharmacology (Berl) 2016; 233:2229-39. [PMID: 27007604 DOI: 10.1007/s00213-016-4272-3] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/25/2015] [Accepted: 03/08/2016] [Indexed: 12/15/2022]
Abstract
RATIONALE Previous studies have demonstrated that piromelatine (a melatonin and serotonin 5-HT1A and 5-HT1D agonist) exerts an antidepressant activity in rodent models of acute stress and improves cognitive impairments in a rat model of Alzheimer's disease (AD). However, the role of piromelatine in chronic stress-induced memory dysfunction remains unclear. OBJECTIVE The aim of this study was to determine whether piromelatine ameliorates chronic mild stress (CMS)-induced memory deficits and explore the underlying mechanisms. METHODS Rats were exposed randomly to chronic mild stressors for 7 weeks to induce anhedonia (reflected by a significant decrease in sucrose intake), which was used to select rats vulnerable (CMS-anhedonic, CMSA) or resistant (CMS-resistant, CMSR) to stress. Piromelatine (50 mg/kg) was administered daily during the last 2 weeks of CMS. The tail suspension and forced swimming tests were adopted to further characterize vulnerable and resilient rats. The Y-maze and novel object recognition (NOR) tests were used to evaluate memory performance. Brain-derived neurotrophic factor (BDNF), cAMP response element-binding protein (CREB), phosphorylated CREB (pCREB), and cytogenesis were measured in the hippocampus. RESULTS We found that only CMSA rats displayed significant increases in immobility time in the tail suspension and forced swimming tests; memory deficits in the Y-maze and NOR tests; significant decreases in hippocampal BDNF, CREB, and pCREB expression; and cytogenesis. All these anhedonia-associated effects were reversed by piromelatine. CONCLUSIONS Piromelatine ameliorates memory deficits associated with CMS-induced anhedonia in rats and this effect may be mediated by restoring hippocampal BDNF, CREB, and cytogenesis deficits.
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Kim HS, Paik MJ, Lee YH, Lee YS, Choi HD, Pack JK, Kim N, Ahn YH. Eight hours of nocturnal 915 MHz radiofrequency identification (RFID) exposure reduces urinary levels of melatonin and its metabolite via pineal arylalkylamine N-acetyltransferase activity in male rats. Int J Radiat Biol 2016; 91:898-907. [PMID: 26189731 DOI: 10.3109/09553002.2015.1075075] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
PURPOSE We investigated the effects of whole-body exposure to the 915 MHz radiofrequency identification (RFID) on melatonin biosynthesis and the activity of rat pineal arylalkylamine N-acetyltransferase (AANAT). MATERIALS AND METHODS Rats were exposed to RFID (whole-body specific absorption rate, 4 W/kg) for 8 h/day, 5 days/week, for weeks during the nighttime. Total volume of urine excreted during a 24-h period was collected after RFID exposure. Urinary melatonin and 6-hydroxymelatonin sulfate (6-OHMS) was measured by gas chromatography-mass spectrometry (GC-MS) and enzyme-linked immunosorbent assay (ELISA), respectively. AANAT enzyme activity was measured using liquid biphasic dif-13 fusion assay. Protein levels and mRNA expression of AANAT was 14 measured by Western blot and reverse transcription polymerase 15 chain reaction (RT-PCR) analysis, respectively. RESULTS Eight hours of nocturnal RFID exposure caused a significant reduction in both urinary melatonin (p = 0. 003) and 6-OHMS (p = 0. 026). Activity, protein levels, and mRNA expression of AANAT were suppressed by exposure to RFID (p < 0. 05). CONCLUSIONS Our results suggest that nocturnal RFID exposure can cause reductions in the levels of both urinary melatonin and 6-OHMS, possibly due to decreased melatonin biosynthesis via suppression of Aanat gene transcription in the rat pineal gland.
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Affiliation(s)
- Hye Sun Kim
- a Department of Neurosurgery , Ajou University School of Medicine , Suwon
| | - Man-Jeong Paik
- b College of Pharmacy , Sunchon National University , Sunchon
| | - Yu Hee Lee
- a Department of Neurosurgery , Ajou University School of Medicine , Suwon ;,c Neuroscience Graduate Program, Department of Biomedical Sciences , Graduate School of Ajou University , Suwon
| | - Yun-Sil Lee
- d Division of Life Science and Pharmaceuticals, College of Pharmacy , Ewha Woman's University , Seoul
| | - Hyung Do Choi
- e Radio Technology Research Department , Electronics and Telecommunications Research Institute , Daejeon
| | - Jeong-Ki Pack
- f Department of Radio Sciences and Engineering, College of Engineering , Chungnam National University , Daejeon
| | - Nam Kim
- g School of Electrical and Computer Engineering , Chungbuk National University , Cheongju , Republic of Korea
| | - Young Hwan Ahn
- a Department of Neurosurgery , Ajou University School of Medicine , Suwon ;,c Neuroscience Graduate Program, Department of Biomedical Sciences , Graduate School of Ajou University , Suwon
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18
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Fitzsimons CP, Herbert J, Schouten M, Meijer OC, Lucassen PJ, Lightman S. Circadian and ultradian glucocorticoid rhythmicity: Implications for the effects of glucocorticoids on neural stem cells and adult hippocampal neurogenesis. Front Neuroendocrinol 2016; 41:44-58. [PMID: 27234350 DOI: 10.1016/j.yfrne.2016.05.001] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/04/2016] [Revised: 05/01/2016] [Accepted: 05/03/2016] [Indexed: 01/01/2023]
Abstract
Psychosocial stress, and within the neuroendocrine reaction to stress specifically the glucocorticoid hormones, are well-characterized inhibitors of neural stem/progenitor cell proliferation in the adult hippocampus, resulting in a marked reduction in the production of new neurons in this brain area relevant for learning and memory. However, the mechanisms by which stress, and particularly glucocorticoids, inhibit neural stem/progenitor cell proliferation remain unclear and under debate. Here we review the literature on the topic and discuss the evidence for direct and indirect effects of glucocorticoids on neural stem/progenitor cell proliferation and adult neurogenesis. Further, we discuss the hypothesis that glucocorticoid rhythmicity and oscillations originating from the activity of the hypothalamus-pituitary-adrenal axis, may be crucial for the regulation of neural stem/progenitor cells in the hippocampus, as well as the implications of this hypothesis for pathophysiological conditions in which glucocorticoid oscillations are affected.
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Affiliation(s)
- Carlos P Fitzsimons
- Neuroscience Program, Swammerdam Institute for Life Sciences, University of Amsterdam, Science Park 904, 1098XH Amsterdam, The Netherlands.
| | - Joe Herbert
- John van Geest Centre for Brain Repair, Department of Clinical Neurosciences, University of Cambridge, United Kingdom
| | - Marijn Schouten
- Neuroscience Program, Swammerdam Institute for Life Sciences, University of Amsterdam, Science Park 904, 1098XH Amsterdam, The Netherlands
| | - Onno C Meijer
- Leiden University Medical Centre, Department of Endocrinology, Leiden, The Netherlands
| | - Paul J Lucassen
- Neuroscience Program, Swammerdam Institute for Life Sciences, University of Amsterdam, Science Park 904, 1098XH Amsterdam, The Netherlands.
| | - Stafford Lightman
- Henry Wellcome Laboratories for Integrative Neuroscience and Endocrinology, School of Clinical Sciences, Faculty of Medicine and Dentistry, University of Bristol, United Kingdom
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19
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Li D, Ma S, Guo D, Cheng T, Li H, Tian Y, Li J, Guan F, Yang B, Wang J. Environmental Circadian Disruption Worsens Neurologic Impairment and Inhibits Hippocampal Neurogenesis in Adult Rats After Traumatic Brain Injury. Cell Mol Neurobiol 2016; 36:1045-55. [PMID: 26886755 DOI: 10.1007/s10571-015-0295-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2015] [Accepted: 10/23/2015] [Indexed: 11/29/2022]
Abstract
Circadian rhythms modulate many physiologic processes and behaviors. Therefore, their disruption causes a variety of potential adverse effects in humans and animals. Circadian disruption induced by constant light exposure has been discovered to produce pathophysiologic consequences after brain injury. However, the underlying mechanisms that lead to more severe impairment and disruption of neurophysiologic processes are not well understood. Here, we evaluated the effect of constant light exposure on the neurobehavioral impairment and survival of neurons in rats after traumatic brain injury (TBI). Sixty adult male Sprague-Dawley rats were subjected to a weight-drop model of TBI and then exposed to either a standard 12-/12-h light/dark cycle or a constant 24-h light/light cycle for 14 days. Our results showed that 14 days of constant light exposure after TBI significantly worsened the sensorimotor and cognitive deficits, which were associated with decreased body weight, impaired water and food intake, increased cortical lesion volume, and decreased neuronal survival. Furthermore, environmental circadian disruption inhibited cell proliferation and newborn cell survival and decreased immature cell production in rats subjected to the TBI model. We conclude that circadian disruption induced by constant light exposure worsens histologic and neurobehavioral impairment and inhibits neurogenesis in adult TBI rats. Our novel findings suggest that light exposure should be decreased and circadian rhythm reestablished in hospitalized TBI patients and that drugs and strategies that maintain circadian rhythm would offer a novel therapeutic option.
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Affiliation(s)
- Dongpeng Li
- Department of Neurosurgery, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, 450052, People's Republic of China.,Henan Province Red Cross Blood Center, Zhengzhou, Henan, 450014, People's Republic of China
| | - Shanshan Ma
- School of Life Sciences, Zhengzhou University, Zhengzhou, 450001, People's Republic of China
| | - Dewei Guo
- Department of Neurosurgery, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, 450052, People's Republic of China
| | - Tian Cheng
- Department of Neurosurgery, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, 450052, People's Republic of China.,Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, MD, 21205, USA
| | - Hongwei Li
- Department of Neurosurgery, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, 450052, People's Republic of China
| | - Yi Tian
- Department of Neurosurgery, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, 450052, People's Republic of China
| | - Jianbin Li
- Henan Province Red Cross Blood Center, Zhengzhou, Henan, 450014, People's Republic of China
| | - Fangxia Guan
- School of Life Sciences, Zhengzhou University, Zhengzhou, 450001, People's Republic of China.
| | - Bo Yang
- Department of Neurosurgery, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, 450052, People's Republic of China.
| | - Jian Wang
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, MD, 21205, USA
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Kreutzmann JC, Havekes R, Abel T, Meerlo P. Sleep deprivation and hippocampal vulnerability: changes in neuronal plasticity, neurogenesis and cognitive function. Neuroscience 2015; 309:173-90. [PMID: 25937398 DOI: 10.1016/j.neuroscience.2015.04.053] [Citation(s) in RCA: 192] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2015] [Revised: 03/31/2015] [Accepted: 04/21/2015] [Indexed: 01/19/2023]
Abstract
Despite the ongoing fundamental controversy about the physiological function of sleep, there is general consensus that sleep benefits neuronal plasticity, which ultimately supports brain function and cognition. In agreement with this are numerous studies showing that sleep deprivation (SD) results in learning and memory impairments. Interestingly, such impairments appear to occur particularly when these learning and memory processes require the hippocampus, suggesting that this brain region may be particularly sensitive to the consequences of sleep loss. Although the molecular mechanisms underlying sleep and memory formation remain to be investigated, available evidence suggests that SD may impair hippocampal neuronal plasticity and memory processes by attenuating intracellular cyclic adenosine monophosphate (cAMP)-protein kinase A (PKA) signaling which may lead to alterations in cAMP response element binding protein (CREB)-mediated gene transcription, neurotrophic signaling, and glutamate receptor expression. When restricted sleep becomes a chronic condition, it causes a reduction of hippocampal cell proliferation and neurogenesis, which may eventually lead to a reduction in hippocampal volume. Ultimately, by impairing hippocampal plasticity and function, chronically restricted and disrupted sleep contributes to cognitive disorders and psychiatric diseases.
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Affiliation(s)
- J C Kreutzmann
- Center for Behavior and Neurosciences, University of Groningen, The Netherlands; Department of Biology, University of Pennsylvania, Philadelphia, United States
| | - R Havekes
- Department of Biology, University of Pennsylvania, Philadelphia, United States
| | - T Abel
- Department of Biology, University of Pennsylvania, Philadelphia, United States
| | - P Meerlo
- Center for Behavior and Neurosciences, University of Groningen, The Netherlands.
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Fernandes C, Rocha NBF, Rocha S, Herrera-Solís A, Salas-Pacheco J, García-García F, Murillo-Rodríguez E, Yuan TF, Machado S, Arias-Carrión O. Detrimental role of prolonged sleep deprivation on adult neurogenesis. Front Cell Neurosci 2015; 9:140. [PMID: 25926773 PMCID: PMC4396387 DOI: 10.3389/fncel.2015.00140] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2014] [Accepted: 03/24/2015] [Indexed: 01/17/2023] Open
Abstract
Adult mammalian brains continuously generate new neurons, a phenomenon called adult neurogenesis. Both environmental stimuli and endogenous factors are important regulators of adult neurogenesis. Sleep has an important role in normal brain physiology and its disturbance causes very stressful conditions, which disrupt normal brain physiology. Recently, an influence of sleep in adult neurogenesis has been established, mainly based on sleep deprivation studies. This review provides an overview on how rhythms and sleep cycles regulate hippocampal and subventricular zone neurogenesis, discussing some potential underlying mechanisms. In addition, our review highlights some interacting points between sleep and adult neurogenesis in brain function, such as learning, memory, and mood states, and provides some insights on the effects of antidepressants and hypnotic drugs on adult neurogenesis.
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Affiliation(s)
- Carina Fernandes
- Faculty of Medicine, University of PortoPorto, Portugal
- Laboratory of Neuropsychophysiology, Faculty of Psychology and Education Sciences, University of PortoPorto, Portugal
| | | | - Susana Rocha
- School of Accounting and Administration of Porto, Polytechnic Institute of PortoPorto, Portugal
| | - Andrea Herrera-Solís
- Unidad de Trastornos del Movimiento y Sueño, Hospital General Dr. Manuel Gea González/Instituto de Fisiología Celular, Universidad Nacional Autónoma de MéxicoMexico City, Mexico
| | - José Salas-Pacheco
- Instituto de Investigación Científica, Universidad Juárez del Estado de DurangoDurango, Mexico
| | - Fabio García-García
- Departamento de Biomedicina, Instituto de Ciencias de la Salud, Universidad VeracruzanaXalapa, Mexico
| | - Eric Murillo-Rodríguez
- División Ciencias de la Salud, Laboratorio de Neurociencias Moleculares e Integrativas, Escuela de Medicina, Universidad Anáhuac MayabMérida, México
| | - Ti-Fei Yuan
- School of Psychology, Nanjing Normal UniversityNanjing, China
| | - Sergio Machado
- Panic and Respiration, Institute of Psychiatry of Federal University of Rio de JaneiroRio de Janeiro, Brazil
- Physical Activity Neuroscience, Physical Activity Sciences Postgraduate Program, Salgado de Oliveira UniversityNiterói, Brazil
| | - Oscar Arias-Carrión
- Unidad de Trastornos del Movimiento y Sueño, Hospital General Dr. Manuel Gea González/Instituto de Fisiología Celular, Universidad Nacional Autónoma de MéxicoMexico City, Mexico
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23
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Martynhak BJ, Kanazawa LKS, Messias do Nascimento G, Andreatini R. Social interaction with rat exposed to constant light during lactation prevents depressive-like behavior induced by constant light in adulthood. Neurosci Lett 2014; 588:7-11. [PMID: 25545554 DOI: 10.1016/j.neulet.2014.12.042] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2014] [Revised: 12/02/2014] [Accepted: 12/19/2014] [Indexed: 11/17/2022]
Abstract
Circadian rhythm disruptions are often observed in depressed patients, and changes in the light/dark cycle promote depressive-like behavior in animal models. Prolonged exposure to constant light (LL) is known to lead to arrhythmicity of circadian locomotor activity and depressive-like behavior in rats. Interestingly, neonatal exposure to LL prevents both arrhythmicity and depressive behavior in adulthood. Arrhythmic rats under LL conditions that cohabitate with a rhythmic rat exhibit improvement in circadian rhythms. We tested whether such cohabitation also protects against LL-induced depressive-like behavior. Wistar rats were assigned to conditions of either neonatal constant light (neonatal-LL) on postnatal days 10-22 or a regular light/dark cycle (neonatal-LD). On day 45, the animals were assigned to three possible pair combinations. After a baseline sucrose preference test, half of the pairs were placed under LL conditions. Weekly sucrose preference tests were conducted to evaluate depressive-like behavior. The animals were isolated by an aluminum wall on the test day. At week 2 of LL, sucrose preference was reduced in neonatal-LD/neonatal-LD pairs of animals. At week 5, neonatal-LD/neonatal-LD pairs exhibited anhedonic-like behavior, but the pairs with at least one neonatal-LL rat did not. The LL cycle was returned to an LD cycle, and the neonatal-LD/neonatal-LD pairs exhibited a restoration of sucrose preference 2 weeks later. We conclude that social interaction can prevent depressive-like behavior induced by circadian rhythm disruption as long as one of the animals is more prone to present a strong rhythm.
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Affiliation(s)
- Bruno Jacson Martynhak
- Departamento de Farmacologia, Universidade Federal do Paraná Cel. Francisco H. dos Santos, Centro Politécnico, Curitiba, Paraná 81530-900, Brazil.
| | - Luiz Kae Sales Kanazawa
- Departamento de Farmacologia, Universidade Federal do Paraná Cel. Francisco H. dos Santos, Centro Politécnico, Curitiba, Paraná 81530-900, Brazil
| | - Guilherme Messias do Nascimento
- Departamento de Farmacologia, Universidade Federal do Paraná Cel. Francisco H. dos Santos, Centro Politécnico, Curitiba, Paraná 81530-900, Brazil
| | - Roberto Andreatini
- Departamento de Farmacologia, Universidade Federal do Paraná Cel. Francisco H. dos Santos, Centro Politécnico, Curitiba, Paraná 81530-900, Brazil
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ZHU LITING, YU JUN, ZHANG WENYI, XIE BIN, ZHU YI. Research progress on the central mechanism underlying regulation of visceral biological rhythm by per2 (Review). Mol Med Rep 2014; 10:2241-8. [DOI: 10.3892/mmr.2014.2559] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2013] [Accepted: 04/25/2014] [Indexed: 11/05/2022] Open
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Rakai BD, Chrusch MJ, Spanswick SC, Dyck RH, Antle MC. Survival of adult generated hippocampal neurons is altered in circadian arrhythmic mice. PLoS One 2014; 9:e99527. [PMID: 24941219 PMCID: PMC4062413 DOI: 10.1371/journal.pone.0099527] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2014] [Accepted: 05/15/2014] [Indexed: 01/25/2023] Open
Abstract
The subgranular zone of the hippocampal formation gives rise to new neurons that populate the dentate gyrus throughout life. Cells in the hippocampus exhibit rhythmic clock gene expression and the circadian clock is known to regulate the cycle of cell division in other areas of the body. These facts suggest that the circadian clock may regulate adult neurogenesis in the hippocampus as well. In the present study, neurogenesis in the hippocampal subgranular zone was examined in arrhythmic Bmal1 knockout (-KO) mice and their rhythmic heterozygous and wildtype littermates. Proliferation and survival of newly generated subgranular zone cells were examined using bromodeoxyuridine labelling, while pyknosis (a measure of cell death) and hippocampal volume were examined in cresyl violet stained sections. There was no significant difference in cellular proliferation between any of the groups, yet survival of proliferating cells, 6 weeks after the bromodeoxyuridine injection, was significantly greater in the BMAL1-KO animals. The number of pyknotic cells was significantly decreased in Bmal1-KO animals, yet hippocampal volume remained the same across genotypes. These findings suggest that while a functional circadian clock is not necessary for normal proliferation of neuronal precursor cells, the normal pruning of newly generated neurons in the hippocampus may require a functional circadian clock.
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Affiliation(s)
- Brooke D. Rakai
- Department of Psychology, University of Calgary, Calgary, Alberta, Canada
- Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada
| | - Michael J. Chrusch
- Department of Psychology, University of Calgary, Calgary, Alberta, Canada
- Department of Neuroscience, University of Calgary, Calgary, Alberta, Canada
| | - Simon C. Spanswick
- Department of Psychology, University of Calgary, Calgary, Alberta, Canada
- Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada
| | - Richard H. Dyck
- Department of Psychology, University of Calgary, Calgary, Alberta, Canada
- Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada
- Department of Cell Biology and Anatomy, University of Calgary, Calgary, Alberta, Canada
| | - Michael C. Antle
- Department of Psychology, University of Calgary, Calgary, Alberta, Canada
- Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada
- Pharmacology & Therapeutics, University of Calgary, Calgary, Alberta, Canada
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Smarr BL, Jennings KJ, Driscoll JR, Kriegsfeld LJ. A time to remember: the role of circadian clocks in learning and memory. Behav Neurosci 2014; 128:283-303. [PMID: 24708297 PMCID: PMC4385793 DOI: 10.1037/a0035963] [Citation(s) in RCA: 113] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The circadian system has pronounced influence on learning and memory, manifesting as marked changes in memory acquisition and recall across the day. From a mechanistic perspective, the majority of studies have investigated mammalian hippocampal-dependent learning and memory, as this system is highly tractable. The hippocampus plays a major role in learning and memory, and has the potential to integrate circadian information in many ways, including information from local, independent oscillators, and through circadian modulation of neurogenesis, synaptic remodeling, intracellular cascades, and epigenetic regulation of gene expression. These local processes are combined with input from other oscillatory systems to synergistically augment hippocampal rhythmic function. This overview presents an account of the current state of knowledge on circadian interactions with learning and memory circuitry and provides a framework for those interested in further exploring these interactions.
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Affiliation(s)
- Benjamin L. Smarr
- Department of Psychology, University of California, Berkeley, CA, 94720 USA
| | | | - Joseph R. Driscoll
- The Helen Wills Neuroscience Institute, University of California, Berkeley, CA, 94720 USA
| | - Lance J. Kriegsfeld
- Department of Psychology, University of California, Berkeley, CA, 94720 USA
- The Helen Wills Neuroscience Institute, University of California, Berkeley, CA, 94720 USA
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27
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Mueller AD, Parfyonov M, Pavlovski I, Marchant EG, Mistlberger RE. The inhibitory effect of sleep deprivation on cell proliferation in the hippocampus of adult mice is eliminated by corticosterone clamp combined with interleukin-1 receptor 1 knockout. Brain Behav Immun 2014; 35:182-8. [PMID: 24121035 DOI: 10.1016/j.bbi.2013.10.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/26/2013] [Revised: 09/22/2013] [Accepted: 10/01/2013] [Indexed: 11/17/2022] Open
Abstract
Deprivation or fragmentation of sleep for longer than 2days significantly inhibits cell proliferation and neurogenesis in the hippocampus of adult rats and mice. Signaling pathways that mediate these effects have yet to be clarified. Although deprivation procedures can stimulate adrenal corticosterone (CORT) release, suppression of cell proliferation by sleep deprivation does not require elevated CORT. We examined a role for interleukin-1β (IL-1β), a pro-inflammatory cytokine that is increased by sleep loss and that mediates effects of stress on hippocampal neurogenesis. Wild type (WT) and IL-1 receptor 1 knockout (IL1RI-KO) mice were subjected to rapid-eye-movement sleep deprivation (RSD) for 72-h using the multiple platform-over-water method. Mice were administered BrdU (100mg/kg) i.p. at hour 70 of RSD and were sacrificed 2-h later. New cells were identified by immunoreactivity (ir) for BrdU and Ki67 in the granular cell layer/subgranular zone (GCL/SGZ) and the hilus. In Experiment 1, WT and IL1RI-KO mice, by contrast with respective control groups, exhibited significantly fewer BrdU-ir and Ki67-ir cells. In Experiment 2, WT and IL1RI-KO mice were adrenalectomized (ADX) and maintained on constant low-dose CORT by osmotic minipumps. RSD reduced cell proliferation by 32% (p<0.01) in ADX-WT animals but did not significantly reduce proliferation in ADX IL1RI-KO animals (p>0.1). These results imply that RSD suppresses cell proliferation by the presence of wake-dependent factors (either elevated CORT or IL-1β signaling are sufficient), rather than the absence of a REM sleep-dependent process. The generality of these findings to other sleep deprivation methods and durations remains to be established.
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Affiliation(s)
- Anka D Mueller
- Cognitive and Neural Sciences Program, Department of Psychology, Simon Fraser University, Burnaby, BC V5A1S6, Canada
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Weber M, Killgore WDS. What are the emerging therapeutic uses of bright light therapy for neurological disorders? FUTURE NEUROLOGY 2013. [DOI: 10.2217/fnl.13.33] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Affiliation(s)
- Mareen Weber
- Center for Depression, Anxiety & Stress Research, McLean Hospital, Harvard Medical School, 115 Mill Street, Belmont, MA 02478, USA
| | - William DS Killgore
- Center for Depression, Anxiety & Stress Research, McLean Hospital, Harvard Medical School, 115 Mill Street, Belmont, MA 02478, USA
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Daulatzai MA. Neurotoxic Saboteurs: Straws that Break the Hippo’s (Hippocampus) Back Drive Cognitive Impairment and Alzheimer’s Disease. Neurotox Res 2013; 24:407-59. [DOI: 10.1007/s12640-013-9407-2] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2013] [Revised: 06/06/2013] [Accepted: 06/17/2013] [Indexed: 12/29/2022]
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Weber M, Webb CA, Deldonno SR, Kipman M, Schwab ZJ, Weiner MR, Killgore WDS. Habitual 'sleep credit' is associated with greater grey matter volume of the medial prefrontal cortex, higher emotional intelligence and better mental health. J Sleep Res 2013; 22:527-34. [PMID: 23593990 DOI: 10.1111/jsr.12056] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2012] [Accepted: 03/09/2013] [Indexed: 11/26/2022]
Abstract
In modern society, people often fail to obtain the amount of sleep that experts recommend for good health and performance. Insufficient sleep can lead to degraded cognitive performance and alterations in emotional functioning. However, most people also acknowledge that on a regular basis they obtain more sleep than they subjectively perceive they need at a minimum to stave off performance decrements, a construct we describe as subjective 'sleep credit'. Few people would contest the notion that getting more sleep is better, but data on both behavioural and neuroanatomical correlates of 'sleep credit' are surprisingly limited. We conducted a voxel-based morphometric study to assess cerebral grey matter correlates of habitually sleeping more than one's subjective requirements. We further tested whether these structural correlates are associated with perceived emotional intelligence and indices of psychopathology while controlling for age, gender, and total intracranial volume. In a sample of 55 healthy adults aged 18-45 years (28 males, 27 females), whole-brain multiple regression showed that habitual subjective 'sleep credit' was correlated positively with grey matter volume within regions of the left medial prefrontal cortex and right orbitofrontal gyrus. Volumes were extracted and regressed against self-report emotion and psychopathology indices. Only grey matter volume of the medial prefrontal cortex cluster correlated with greater emotional intelligence and lower scores on several indices of psychopathology. Findings converge with previous evidence of the role of the medial prefrontal cortex in the relationship between sleep and emotional functioning, and suggest that behaviour and brain structure vary with habitual 'sleep credit'.
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Affiliation(s)
- Mareen Weber
- Social, Cognitive and Affective Neuroscience Laboratory, McLean Hospital, Harvard Medical School, Belmont, MA, USA
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Golombek DA, Casiraghi LP, Agostino PV, Paladino N, Duhart JM, Plano SA, Chiesa JJ. The times they're a-changing: effects of circadian desynchronization on physiology and disease. ACTA ACUST UNITED AC 2013; 107:310-22. [PMID: 23545147 DOI: 10.1016/j.jphysparis.2013.03.007] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Circadian rhythms are endogenous and need to be continuously entrained (synchronized) with the environment. Entrainment includes both coupling internal oscillators to external periodic changes as well as synchrony between the central clock and peripheral oscillators, which have been shown to exhibit different phases and resynchronization speed. Temporal desynchronization induces diverse physiological alterations that ultimately decrease quality of life and induces pathological situations. Indeed, there is a considerable amount of evidence regarding the deleterious effect of circadian dysfunction on overall health or on disease onset and progression, both in human studies and in animal models. In this review we discuss the general features of circadian entrainment and introduce diverse experimental models of desynchronization. In addition, we focus on metabolic, immune and cognitive alterations under situations of acute or chronic circadian desynchronization, as exemplified by jet-lag and shiftwork schedules. Moreover, such situations might lead to an enhanced susceptibility to diverse cancer types. Possible interventions (including light exposure, scheduled timing for meals and use of chronobiotics) are also discussed.
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Affiliation(s)
- Diego A Golombek
- Laboratory of Chronobiology, National University of Quilmes/CONICET, Buenos Aires, Argentina.
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Mueller AD, Meerlo P, McGinty D, Mistlberger RE. Sleep and adult neurogenesis: implications for cognition and mood. Curr Top Behav Neurosci 2013; 25:151-81. [PMID: 24218292 DOI: 10.1007/7854_2013_251] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The hippocampal dentate gyrus plays a critical role in learning and memory throughout life, in part by the integration of adult-born neurons into existing circuits. Neurogenesis in the adult hippocampus is regulated by numerous environmental, physiological, and behavioral factors known to affect learning and memory. Sleep is also important for learning and memory. Here we critically examine evidence from correlation, deprivation, and stimulation studies that sleep may be among those factors that regulate hippocampal neurogenesis. There is mixed evidence for correlations between sleep variables and rates of hippocampal cell proliferation across the day, the year, and the lifespan. There is modest evidence that periods of increased sleep are associated with increased cell proliferation or survival. There is strong evidence that disruptions of sleep exceeding 24 h, by total deprivation, selective REM sleep deprivation, and chronic restriction or fragmentation, significantly inhibit cell proliferation and in some cases neurogenesis. The mechanisms by which sleep disruption inhibits neurogenesis are not fully understood. Although sleep disruption procedures are typically at least mildly stressful, elevated adrenal corticosterone secretion is not necessary for this effect. However, procedures that prevent both elevated corticosterone and interleukin 1β signaling have been found to block the effect of sleep deprivation on cell proliferation. This result suggests that sleep loss impairs hippocampal neurogenesis by the presence of wake-dependent factors, rather than by the absence of sleep-specific processes. This would weigh against a hypothesis that regulation of neurogenesis is a function of sleep. Nonetheless, impaired neurogenesis may underlie some of the memory and mood effects associated with acute and chronic sleep disruptions.
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Affiliation(s)
- Anka D Mueller
- Department of Psychology, Simon Fraser University, 8888 University Drive, Burnaby, BC, V5A 1S6, Canada
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Abstract
INTRODUCTION Over the last 8 years, emerging studies bridging the gap between nutrition and mental health have resolutely established that learning and memory abilities as well as mood can be influenced by diet. However, the mechanisms by which diet modulates mental health are still not well understood. Sources of data In this article, a review of the literature was conducted using PubMed to identify studies that provide functional implications of adult hippocampal neurogenesis (AHN) and its modulation by diet. AREAS OF AGREEMENT One of the brain structures associated with learning and memory as well as mood is the hippocampus. Importantly, the hippocampus is one of the two structures in the adult brain where the formation of newborn neurons, or neurogenesis, persists. AREAS OF CONTROVERSY The exact roles of these newborn neurons in learning, memory formation and mood regulation remain elusive. GROWING POINTS Nevertheless, there has been accumulating evidence linking cognition and mood to neurogenesis occurring in the adult hippocampus. Therefore, modulation of AHN by diet emerges as a possible mechanism by which nutrition impacts on mental health. AREAS TIMELY FOR DEVELOPING RESEARCH This area of investigation is new and needs attention because a better understanding of the neurological mechanisms by which nutrition affect mental health may lead to novel dietary approaches for disease prevention, healthier ageing and discovery of new therapeutic targets for mental illnesses.
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Neuroimmunomodulation in unipolar depression: a focus on chronobiology and chronotherapeutics. J Neural Transm (Vienna) 2012; 119:1147-66. [PMID: 22653515 DOI: 10.1007/s00702-012-0819-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2012] [Accepted: 05/05/2012] [Indexed: 12/21/2022]
Abstract
The rising burden of unipolar depression along with its often related sleep disturbances, as well as increasing rates of sleep restriction in modern society, make the search for an extended understanding of the aetiology and pathophysiology of depression necessary. Accumulating evidence suggests an important role for the immune system in mediating disrupted neurobiological and chronobiological processes in depression. This review aims to provide an overview of the neuroimmunomodulatory processes involved with depression and antidepressant treatments with a special focus on chronobiology, chronotherapeutics and the emerging field of immune-circadian bi-directional crosstalk. Increasing evidence suggests that chronobiological disruption can mediate immune changes in depression, and likewise, immune processes can mediate chronobiological disruption. This may suggest a bi-directional relationship in immune-circadian crosstalk. Furthermore, given the immunomodulatory effects of antidepressants and chronotherapeutics, as well as their associated beneficial effects on circadian disturbance, we--and others--suggest that these therapeutic agents may exert their chronobiotic effects partially via the neuroimmune system. Further research is required to better elucidate the mechanisms of immune involvement in the chronobiology of depression.
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Tosini G, Ye K, Iuvone PM. N-acetylserotonin: neuroprotection, neurogenesis, and the sleepy brain. Neuroscientist 2012; 18:645-53. [PMID: 22585341 DOI: 10.1177/1073858412446634] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
N-Acetylserotonin (NAS) is a naturally occurring chemical intermediate in biosynthesis of melatonin. Previous studies have shown that NAS has different brain distribution patterns from those of serotonin and melatonin, suggesting that NAS might have functions other than as a precursor or metabolite of melatonin. Indeed, several studies have now shown that NAS may play an important role in mood regulation and may have antidepressant activity. Additional studies have shown that NAS stimulates proliferation of neuroprogenitor cells and prevents some of the negative effects of sleep deprivation. It is believed that the antidepressant and neurotrophic actions of NAS are due at least in part to the capability on this molecule to activate the TrkB receptor in a brain-derived neurotrophic factor-independent manner. Emerging evidence also indicates that NAS and its derivatives have neuroprotective properties and protect retinal photoreceptor cells from light-induced degeneration. In this review, the authors discuss the literature about this exciting and underappreciated molecule.
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Kott J, Leach G, Yan L. Direction-dependent effects of chronic "jet-lag" on hippocampal neurogenesis. Neurosci Lett 2012; 515:177-80. [PMID: 22465247 DOI: 10.1016/j.neulet.2012.03.048] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2012] [Revised: 03/02/2012] [Accepted: 03/15/2012] [Indexed: 10/28/2022]
Abstract
Disruptions in circadian rhythms, as seen in human shift workers, are often associated with many health consequences including impairments in cognitive functions. However, the mechanisms underlying these affects are not well understood. The objective of the present study is to explore the effects of circadian disruption on hippocampal neurogenesis, which has been implicated in learning and memory and could serve as a potential pathway mediating the cognitive consequences associated with rhythm disruption. Circadian rhythm disruptions were introduced using a weekly 6 h phase shifting paradigm, in which male Wistar rats were subjected to either 6 h phase advances (i.e. traveling eastbound from New York to Paris) or 6 h phase delays (i.e. traveling westbound from Paris to New York) in their light/dark schedule every week. The effects of chronic phase shifts on hippocampal neurogenesis were assessed using doublecortin (DCX), a microtubule binding protein expressed in immature neurons. The results revealed that chronic disruption in circadian rhythms inhibits hippocampal neurogenesis, and the degree of reduction in neurogenesis depends upon the direction and duration of the shifts. In two cohorts of animals that experienced phase shifts for either 4 or 8 weeks, a greater decrease in neurogenesis was observed when the phase was advanced versus delayed in both groups. The direction-dependent effect mirrors the findings on clock gene expression in the SCN, suggesting a causal link between the reduction in hippocampal neurogenesis and a disrupted SCN circadian clock.
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Affiliation(s)
- Jennifer Kott
- Department of Psychology, Michigan State University, East Lansing, MI 48824, USA
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