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Figueira da Costa TN, Andreotti S, de Farias TDSM, Lima FB, Bargi-Souza P. The Influence of Melatonin on the Daily 24-h Rhythm of Putative Reference Gene Expression in White Adipose Tissues. J Biol Rhythms 2020; 35:530-541. [PMID: 32886018 DOI: 10.1177/0748730420949337] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
In adipose tissue, the expression of hundreds of genes exhibits circadian oscillation, which may or may not be affected by circulating melatonin levels. Using control and pinealectomized rats, we investigated the daily expression profile of Actb, Hprt-1, B2m, and Rpl37a, genes that are commonly used as reference genes for reverse transcription quantitative polymerase chain reaction (RT-qPCR), in epididymal (EP), retroperitoneal (RP), and subcutaneous (SC) adipose tissues. In control rats, Actb expression presented a daily oscillation in all adipose tissues investigated, Hprt-1 showed 24-h fluctuations in only RP and SC depots, B2m was stable over 24 h for EP and RP but oscillated over 24 h in SC adipose tissue, and Rpl37a presented a daily oscillation in only RP fat. In the absence of melatonin, the rhythmicity of Actb in all adipose depots was abolished, the daily rhythmicity of Hprt-1 and B2m was disrupted in SC fat, the peak expression of Rpl37a and Hprt-1 was delayed, and the amplitude of Rpl37a was reduced in RP adipose tissue. Collectively, our results demonstrate that the expression of putative reference genes displays a daily rhythm influenced by melatonin levels in a manner specific to the adipose depot. Thus, the proper standardization and daily profile expression of reference genes should be performed carefully in temporal studies using RT-qPCR analysis.
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Affiliation(s)
- Tatienne Neder Figueira da Costa
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, SP, Brazil.,Federal University of Tocantins, Palmas, TO, Brazil
| | - Sandra Andreotti
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, SP, Brazil
| | | | - Fábio Bessa Lima
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, SP, Brazil
| | - Paula Bargi-Souza
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, SP, Brazil.,Department of Physiology and Biophysics, Institute of Biological Sciences, Federal University of Minas Gerais, Campus Pampulha, Belo Horizonte, MG, Brazil
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2
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Cleal JK, Bruce KD, Shearer JL, Thomas H, Plume J, Gregory L, Shepard JN, Spiers-Fitzgerald KL, Mani R, Lewis RM, Lillycrop KA, Hanson MA, Byrne CD, Cagampang FR. Maternal Obesity during Pregnancy Alters Daily Activity and Feeding Cycles, and Hypothalamic Clock Gene Expression in Adult Male Mouse Offspring. Int J Mol Sci 2019; 20:E5408. [PMID: 31671625 PMCID: PMC6862679 DOI: 10.3390/ijms20215408] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2019] [Revised: 10/12/2019] [Accepted: 10/28/2019] [Indexed: 02/07/2023] Open
Abstract
An obesogenic diet adversely affects the endogenous mammalian circadian clock, altering daily activity and metabolism, and resulting in obesity. We investigated whether an obese pregnancy can alter the molecular clock in the offspring hypothalamus, resulting in changes to their activity and feeding rhythms. Female mice were fed a control (C, 7% kcal fat) or high fat diet (HF, 45% kcal fat) before mating and throughout pregnancy. Male offspring were fed the C or HF diet postweaning, resulting in four offspring groups: C/C, C/HF, HF/C, and HF/HF. Daily activity and food intake were monitored, and at 15 weeks of age were killed at six time-points over 24 h. The clock genes Clock, Bmal1, Per2, and Cry2 in the suprachiasmatic nucleus (SCN) and appetite genes Npy and Pomc in the arcuate nucleus (ARC) were measured. Daily activity and feeding cycles in the HF/C, C/HF, and HF/HF offspring were altered, with increased feeding bouts and activity during the day and increased food intake but reduced activity at night. Gene expression patterns and levels of Clock, Bmal1, Per2, and Cry2 in the SCN and Npy and Pomc in the ARC were altered in HF diet-exposed offspring. The altered expression of hypothalamic molecular clock components and appetite genes, together with changes in activity and feeding rhythms, could be contributing to offspring obesity.
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Affiliation(s)
- Jane K Cleal
- School of Human Development and Health, Faculty of Medicine, University of Southampton, Southampton General Hospital, Southampton SO16 6YD, UK.
| | - Kimberley D Bruce
- School of Human Development and Health, Faculty of Medicine, University of Southampton, Southampton General Hospital, Southampton SO16 6YD, UK.
| | - Jasmin L Shearer
- School of Human Development and Health, Faculty of Medicine, University of Southampton, Southampton General Hospital, Southampton SO16 6YD, UK.
| | - Hugh Thomas
- School of Human Development and Health, Faculty of Medicine, University of Southampton, Southampton General Hospital, Southampton SO16 6YD, UK.
| | - Jack Plume
- Centre for Biological Sciences, Faculty of Natural and Environmental Sciences, University of Southampton, Southampton SO17 1BJ, UK.
| | - Louise Gregory
- Centre for Biological Sciences, Faculty of Natural and Environmental Sciences, University of Southampton, Southampton SO17 1BJ, UK.
| | - James N Shepard
- Centre for Biological Sciences, Faculty of Natural and Environmental Sciences, University of Southampton, Southampton SO17 1BJ, UK.
| | - Kerry L Spiers-Fitzgerald
- School of Human Development and Health, Faculty of Medicine, University of Southampton, Southampton General Hospital, Southampton SO16 6YD, UK.
| | - Ravi Mani
- School of Human Development and Health, Faculty of Medicine, University of Southampton, Southampton General Hospital, Southampton SO16 6YD, UK.
| | - Rohan M Lewis
- School of Human Development and Health, Faculty of Medicine, University of Southampton, Southampton General Hospital, Southampton SO16 6YD, UK.
| | - Karen A Lillycrop
- Centre for Biological Sciences, Faculty of Natural and Environmental Sciences, University of Southampton, Southampton SO17 1BJ, UK.
| | - Mark A Hanson
- School of Human Development and Health, Faculty of Medicine, University of Southampton, Southampton General Hospital, Southampton SO16 6YD, UK.
| | - Christopher D Byrne
- School of Human Development and Health, Faculty of Medicine, University of Southampton, Southampton General Hospital, Southampton SO16 6YD, UK.
| | - Felino R Cagampang
- School of Human Development and Health, Faculty of Medicine, University of Southampton, Southampton General Hospital, Southampton SO16 6YD, UK.
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Shrestha TC, Šuchmanová K, Houdek P, Sumová A, Ralph MR. Implicit time-place conditioning alters Per2 mRNA expression selectively in striatum without shifting its circadian clocks. Sci Rep 2018; 8:15547. [PMID: 30341352 PMCID: PMC6195625 DOI: 10.1038/s41598-018-33637-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2018] [Accepted: 10/02/2018] [Indexed: 11/30/2022] Open
Abstract
Animals create implicit memories of the time of day that significant events occur then anticipate the recurrence of those conditions at the same time on subsequent days. We tested the hypothesis that implicit time memory for daily encounters relies on the setting of the canonical circadian clockwork in brain areas involved in the formation or expression of context memories. We conditioned mice to avoid locations paired with a mild foot shock at one of two Zeitgeber times set 8 hours apart. Place avoidance was exhibited only when testing time matched the prior training time. The suprachiasmatic nucleus, dorsal striatum, nucleus accumbens, cingulate cortex, hippocampal complex, and amygdala were assessed for clock gene expression. Baseline phase dependent differences in clock gene expression were found in most tissues. Evidence for conditioned resetting of a molecular circadian oscillation was found only in the striatum (dorsal striatum and nucleus accumbens shell), and specifically for Per2 expression. There was no evidence of glucocorticoid stress response in any tissue. The results are consistent with a model where temporal conditioning promotes a selective Per2 response in dopamine-targeted brain regions responsible for sensorimotor integration, without resetting the entire circadian clockwork.
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Affiliation(s)
- Tenjin C Shrestha
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada
| | - Karolína Šuchmanová
- Department of Neurohumoral Regulations, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Pavel Houdek
- Department of Neurohumoral Regulations, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Alena Sumová
- Department of Neurohumoral Regulations, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Martin R Ralph
- Department of Psychology, University of Toronto, Toronto, Ontario, Canada.
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Touati H, Ouali-Hassenaoui S, Dekar-Madoui A, Challet E, Pévet P, Vuillez P. Diet-induced insulin resistance state disturbs brain clock processes and alters tuning of clock outputs in the Sand rat, Psammomys obesus. Brain Res 2017; 1679:116-124. [PMID: 29196219 DOI: 10.1016/j.brainres.2017.11.018] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2017] [Revised: 11/16/2017] [Accepted: 11/18/2017] [Indexed: 01/16/2023]
Abstract
Reciprocal interactions closely connect energy metabolism with circadian rhythmicity. Altered clockwork and circadian desynchronization are often linked with impaired energy regulation. Conversely, metabolic disturbances have been associated with altered autonomic and hormonal rhythms. The effects of high-energy (HE) diet on the master clock in the suprachiasmatic nuclei (SCN) remain unclear.This question was addressed in the Sand rat (Psammomys obesus), a non-insulin-dependent diabetes mellitus (NIDDM) animal model. The aim of this work was to determine whether enriched diet in Psammomys affects locomotor activity rhythm, as well as daily oscillations in the master clock of the SCN and in an extra-SCN brain oscillator, the piriform cortex. Sand rats were fed during 3 months with either low or HE diet. Vasoactive intestinal peptide (VIP), vasopressin (AVP) and CLOCK protein cycling were studied by immunohistochemistry and running wheel protocol was used for behavioral analysis. High energy feeding dietary triggered hyperinsulinemia, impaired insulin/glucose ratio and disruption in pancreatic hormonal rhythms. Circadian disturbances in hyper-insulinemic animals include a lengthened rest/activity rhythm in constant darkness, as well as disappearance of daily rhythmicity of VIP, AVP and the circadian transcription factor CLOCK within the suprachiasmatic clock. In addition, daily rhythmicity of VIP and CLOCK was abolished by HE diet in a secondary brain oscillator, the piriform cortex. Our findings highlight a major impact of diabetogenic diet on central and peripheral rhythmicity. The Psammomys model will be instrumental to better understand the functional links between circadian clocks, glucose intolerance and insulin resistance state.
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Affiliation(s)
- Hanane Touati
- Regulation of Circadian Clocks Team, Institute of Cellular and Integrative Neurosciences, UPR3212, CNRS, University of Strasbourg, Strasbourg, France; USTHB, Faculty of Biological Sciences, Laboratory of Biology and Physiology of Organisms, Neurobiology Team, BP 32, El Alia, 16111 Bab Ezzouar, Algiers, Algeria.
| | - Saliha Ouali-Hassenaoui
- USTHB, Faculty of Biological Sciences, Laboratory of Biology and Physiology of Organisms, Neurobiology Team, BP 32, El Alia, 16111 Bab Ezzouar, Algiers, Algeria.
| | - Aicha Dekar-Madoui
- USTHB, Faculty of Biological Sciences, Laboratory of Biology and Physiology of Organisms, Neurobiology Team, BP 32, El Alia, 16111 Bab Ezzouar, Algiers, Algeria.
| | - Etienne Challet
- Regulation of Circadian Clocks Team, Institute of Cellular and Integrative Neurosciences, UPR3212, CNRS, University of Strasbourg, Strasbourg, France.
| | - Paul Pévet
- Regulation of Circadian Clocks Team, Institute of Cellular and Integrative Neurosciences, UPR3212, CNRS, University of Strasbourg, Strasbourg, France.
| | - Patrick Vuillez
- Regulation of Circadian Clocks Team, Institute of Cellular and Integrative Neurosciences, UPR3212, CNRS, University of Strasbourg, Strasbourg, France.
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Figueredo DDS, Barbosa MR, Coimbra DG, Dos Santos JLA, Costa EFL, Koike BDV, Alexandre Moreira MS, de Andrade TG. Usual normalization strategies for gene expression studies impair the detection and analysis of circadian patterns. Chronobiol Int 2017; 35:378-391. [PMID: 29219623 DOI: 10.1080/07420528.2017.1410168] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Recent studies have shown that transcriptomes from different tissues present circadian oscillations. Therefore, the endogenous variation of total RNA should be considered as a potential bias in circadian studies of gene expression. However, normalization strategies generally include the equalization of total RNA concentration between samples prior to cDNA synthesis. Moreover, endogenous housekeeping genes (HKGs) frequently used for data normalization may exhibit circadian variation and distort experimental results if not detected or considered. In this study, we controlled experimental conditions from the amount of initial brain tissue samples through extraction steps, cDNA synthesis, and quantitative real time PCR (qPCR) to demonstrate a circadian oscillation of total RNA concentration. We also identified that the normalization of the RNA's yield affected the rhythmic profiles of different genes, including Per1-2 and Bmal1. Five widely used HKGs (Actb, Eif2a, Gapdh, Hprt1, and B2m) also presented rhythmic variations not detected by geNorm algorithm. In addition, the analysis of exogenous microRNAs (Cel-miR-54 and Cel-miR-39) spiked during RNA extraction suggests that the yield was affected by total RNA concentration, which may impact circadian studies of small RNAs. The results indicate that the approach of tissue normalization without total RNA equalization prior to cDNA synthesis can avoid bias from endogenous broad variations in transcript levels. Also, the circadian analysis of 2-Cycle threshold (Ct) data, without HKGs, may be an alternative for chronobiological studies under controlled experimental conditions.
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Affiliation(s)
- Diego de Siqueira Figueredo
- a Laboratory of Molecular Chronobiology , Federal University of Alagoas (UFAL) , Arapiraca , Alagoas , Brazil
| | - Mayara Rodrigues Barbosa
- a Laboratory of Molecular Chronobiology , Federal University of Alagoas (UFAL) , Arapiraca , Alagoas , Brazil
| | - Daniel Gomes Coimbra
- a Laboratory of Molecular Chronobiology , Federal University of Alagoas (UFAL) , Arapiraca , Alagoas , Brazil.,c Faculty of Medicine , Federal University of Alagoas (UFAL) , Maceió , Alagoas , Brazil
| | - José Luiz Araújo Dos Santos
- a Laboratory of Molecular Chronobiology , Federal University of Alagoas (UFAL) , Arapiraca , Alagoas , Brazil
| | - Ellyda Fernanda Lopes Costa
- a Laboratory of Molecular Chronobiology , Federal University of Alagoas (UFAL) , Arapiraca , Alagoas , Brazil
| | - Bruna Del Vechio Koike
- a Laboratory of Molecular Chronobiology , Federal University of Alagoas (UFAL) , Arapiraca , Alagoas , Brazil
| | | | - Tiago Gomes de Andrade
- a Laboratory of Molecular Chronobiology , Federal University of Alagoas (UFAL) , Arapiraca , Alagoas , Brazil.,c Faculty of Medicine , Federal University of Alagoas (UFAL) , Maceió , Alagoas , Brazil
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6
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Park J, Zhu H, O'Sullivan S, Ogunnaike BA, Weaver DR, Schwaber JS, Vadigepalli R. Single-Cell Transcriptional Analysis Reveals Novel Neuronal Phenotypes and Interaction Networks Involved in the Central Circadian Clock. Front Neurosci 2016; 10:481. [PMID: 27826225 PMCID: PMC5079116 DOI: 10.3389/fnins.2016.00481] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2016] [Accepted: 10/07/2016] [Indexed: 12/31/2022] Open
Abstract
Single-cell heterogeneity confounds efforts to understand how a population of cells organizes into cellular networks that underlie tissue-level function. This complexity is prominent in the mammalian suprachiasmatic nucleus (SCN). Here, individual neurons exhibit a remarkable amount of asynchronous behavior and transcriptional heterogeneity. However, SCN neurons are able to generate precisely coordinated synaptic and molecular outputs that synchronize the body to a common circadian cycle by organizing into cellular networks. To understand this emergent cellular network property, it is important to reconcile single-neuron heterogeneity with network organization. In light of recent studies suggesting that transcriptionally heterogeneous cells organize into distinct cellular phenotypes, we characterized the transcriptional, spatial, and functional organization of 352 SCN neurons from mice experiencing phase-shifts in their circadian cycle. Using the community structure detection method and multivariate analytical techniques, we identified previously undescribed neuronal phenotypes that are likely to participate in regulatory networks with known SCN cell types. Based on the newly discovered neuronal phenotypes, we developed a data-driven neuronal network structure in which multiple cell types interact through known synaptic and paracrine signaling mechanisms. These results provide a basis from which to interpret the functional variability of SCN neurons and describe methodologies toward understanding how a population of heterogeneous single cells organizes into cellular networks that underlie tissue-level function.
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Affiliation(s)
- James Park
- Department of Pathology, Anatomy and Cell Biology, Daniel Baugh Institute for Functional Genomics and Computational Biology, Sidney Kimmel Medical College, Thomas Jefferson UniversityPhiladelphia, PA, USA; Department of Chemical and Biomolecular Engineering, University of DelawareNewark, NJ, USA
| | - Haisun Zhu
- Department of Pathology, Anatomy and Cell Biology, Daniel Baugh Institute for Functional Genomics and Computational Biology, Sidney Kimmel Medical College, Thomas Jefferson University Philadelphia, PA, USA
| | - Sean O'Sullivan
- Department of Pathology, Anatomy and Cell Biology, Daniel Baugh Institute for Functional Genomics and Computational Biology, Sidney Kimmel Medical College, Thomas Jefferson University Philadelphia, PA, USA
| | - Babatunde A Ogunnaike
- Department of Chemical and Biomolecular Engineering, University of Delaware Newark, NJ, USA
| | - David R Weaver
- Department of Neurobiology, University of Massachusetts Medical School Worcester, MA, USA
| | - James S Schwaber
- Department of Pathology, Anatomy and Cell Biology, Daniel Baugh Institute for Functional Genomics and Computational Biology, Sidney Kimmel Medical College, Thomas Jefferson UniversityPhiladelphia, PA, USA; Department of Chemical and Biomolecular Engineering, University of DelawareNewark, NJ, USA
| | - Rajanikanth Vadigepalli
- Department of Pathology, Anatomy and Cell Biology, Daniel Baugh Institute for Functional Genomics and Computational Biology, Sidney Kimmel Medical College, Thomas Jefferson UniversityPhiladelphia, PA, USA; Department of Chemical and Biomolecular Engineering, University of DelawareNewark, NJ, USA
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7
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Harrison OJ, Moorjani N, Torrens C, Ohri SK, Cagampang FR. Endogenous Reference Genes for Gene Expression Studies on Bicuspid Aortic Valve Associated Aortopathy in Humans. PLoS One 2016; 11:e0164329. [PMID: 27727313 PMCID: PMC5058495 DOI: 10.1371/journal.pone.0164329] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Accepted: 09/25/2016] [Indexed: 01/18/2023] Open
Abstract
Bicuspid aortic valve (BAV) disease is the most common congenital cardiac abnormality and predisposes patients to life-threatening aortic complications including aortic aneurysm. Quantitative real-time reverse transcription PCR (qRT-PCR) is one of the most commonly used methods to investigate underlying molecular mechanisms involved in aortopathy. The accuracy of the gene expression data is dependent on normalization by appropriate housekeeping (HK) genes, whose expression should remain constant regardless of aortic valve morphology, aortic diameter and other factors associated with aortopathy. Here, we identified an appropriate set of HK genes to be used as endogenous reference for quantifying gene expression in ascending aortic tissue using a spin column-based RNA extraction method. Ascending aortic biopsies were collected intra-operatively from patients undergoing aortic valve and/or ascending aortic surgery. These patients had BAV or tricuspid aortic valve (TAV), and the aortas were either dilated (≥4.5cm) or undilated. The cohort had an even distribution of gender, valve disease and hypertension. The expression stability of 12 reference genes were investigated (ATP5B, ACTB, B2M, CYC1, EIF4A2, GAPDH, SDHA, RPL13A, TOP1, UBC, YWHAZ, and 18S) using geNorm software. The most stable HK genes were found to be GAPDH, UBC and ACTB. Both GAPDH and UBC demonstrated relative stability regardless of valve morphology, aortic diameter, gender and age. The expression of B2M and SDHA were found to be the least stable HK genes. We propose the use of GAPDH, UBC and ACTB as reference genes for gene expression studies of BAV aortopathy using ascending aortic tissue.
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Affiliation(s)
- Oliver J. Harrison
- Institute of Developmental Sciences, University of Southampton Faculty of Medicine, Southampton, United Kingdom
- * E-mail:
| | - Narain Moorjani
- Department of Cardiac Surgery, Papworth Hospital NHS Foundation Trust, Cambridge, United Kingdom
| | - Christopher Torrens
- Institute of Developmental Sciences, University of Southampton Faculty of Medicine, Southampton, United Kingdom
| | - Sunil K. Ohri
- Department of Cardiac Surgery, University Hospital Southampton, Southampton, United Kingdom
| | - Felino R. Cagampang
- Institute of Developmental Sciences, University of Southampton Faculty of Medicine, Southampton, United Kingdom
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Diminished circadian rhythms in hippocampal microglia may contribute to age-related neuroinflammatory sensitization. Neurobiol Aging 2016; 47:102-112. [PMID: 27568094 DOI: 10.1016/j.neurobiolaging.2016.07.019] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2016] [Revised: 07/21/2016] [Accepted: 07/24/2016] [Indexed: 01/28/2023]
Abstract
Aged animals exhibit diminished circadian rhythms, and both aging and circadian disruption sensitize neuroinflammatory responses. Microglia-the innate immune cell of the central nervous system-possess endogenous timekeeping mechanisms that regulate immune responses. Here, we explored whether aging is associated with disrupted diurnal rhythms in microglia and neuroinflammatory processes. First, hippocampal microglia isolated from young rats (4 months F344XBN) rhythmically expressed circadian clock genes, whereas microglia isolated from the hippocampus of aged rats (25 months) had aberrant Per1 and Per2 rhythms. Unstimulated microglia from young rats exhibited robust rhythms of TNFα and IL-1β mRNA expression, whereas those from aged rats had flattened and tonically elevated cytokine expression. Similarly, microglial activation markers were diurnally regulated in the hippocampus of young but not aged rats and diurnal differences in responsiveness to both ex vivo and in vivo inflammatory challenges were abolished in aged rats. Corticosterone is an entraining signal for extra-suprachiasmatic nucleus circadian rhythms. Here, corticosterone stimulation elicited similar Per1 induction in aged and young microglia. Overall, these results indicate that aging dysregulates circadian regulation of neuroinflammatory functions.
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Fonken LK, Weber MD, Daut RA, Kitt MM, Frank MG, Watkins LR, Maier SF. Stress-induced neuroinflammatory priming is time of day dependent. Psychoneuroendocrinology 2016; 66:82-90. [PMID: 26799851 PMCID: PMC4788538 DOI: 10.1016/j.psyneuen.2016.01.006] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/17/2015] [Revised: 01/05/2016] [Accepted: 01/06/2016] [Indexed: 10/22/2022]
Abstract
Circadian rhythms are endogenous cycles of physiology and behavior that align with the daily rotation of the planet and resulting light-dark cycle. The circadian system ensures homeostatic balance and regulates many aspects of physiology, including the stress response and susceptibility to and/or severity of stress-related sequelae. Both acute and chronic stressors amplify neuroinflammatory responses to a subsequent immune challenge, however it is not known whether circadian timing of the stressor regulates the priming response. Here, we test whether stress-induced neuroinflammatory priming is regulated by the circadian system. As has been previously shown, exposure to 100 inescapable tails shocks (IS) increased hippocampal cytokines following a subsequent inflammatory challenge. However, this effect was limited to animals that experienced the stressor during the light phase. Rats exposed to stress during the dark phase did not alter inflammatory potential following lipopolysaccharide (LPS) challenge. To determine whether microglia might be involved in diurnal differences in neuroinflammatory priming, microglia were isolated 24h after stress that occurred either during the middle of the light or dark phase. Only microglia isolated from animals stressed during the light phase demonstrated an exaggerated inflammatory response when treated ex vivo with LPS. To determine possible circadian dependency of microglia responsiveness to glucocorticoids - the likely proximal mediator for stress associated neuroinflammatory priming - microglia were isolated during the middle of the light or dark phase and treated ex vivo with corticosterone. Glucocorticoids treatment downregulated CX3CR1 and CD200R, two genes involved in microglial inflammatory "off" signaling; however, there was no effect of time of day on expression of either gene. Importantly, while absolute concentrations of corticosterone were comparable following IS during the light and dark phase, the magnitude of change in corticosterone was greater during the light phase. This work highlights the importance of studying circadian rhythms to elucidate biological mechanisms of stress.
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Affiliation(s)
- Laura K. Fonken
- To whom correspondence should be addressed: Laura K. Fonken, Department of Psychology and Neuroscience, University of Colorado, Muenzinger Psychology D244, 1905, Colorado Ave., Boulder, CO 80309 USA.
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