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Hippocampal CA1 transcriptional profile of sleep deprivation: relation to aging and stress.

ABSTRACT: Many aging changes seem similar to those elicited by sleep-deprivation and psychosocial stress. Further, sleep architecture changes with age suggest an age-related loss of sleep. Here, we hypothesized that sleep deprivation in young subjects would elicit both stress and aging-like transcriptional responses.F344 rats were divided into control and sleep deprivation groups. Body weight, adrenal weight, corticosterone level and hippocampal CA1 transcriptional profiles were measured. A second group of animals was exposed to novel environment stress (NES), and their hippocampal transcriptional profiles measured. A third cohort exposed to control or SD was used to validate transcriptional results with Western blots. Microarray results were statistically contrasted with prior transcriptional studies. Microarray results pointed to sleep pressure signaling and macromolecular synthesis disruptions in the hippocampal CA1 region. Animals exposed to NES recapitulated nearly one third of the SD transcriptional profile. However, the SD-aging relationship was more complex. Compared to aging, SD profiles influenced a significant subset of genes. mRNA associated with neurogenesis and energy pathways showed agreement between aging and SD, while immune, glial, and macromolecular synthesis pathways showed SD profiles that opposed those seen in aging.We conclude that although NES and SD exert similar transcriptional changes, selective presynaptic release machinery and Homer1 expression changes are seen in SD. Among other changes, the marked decrease in Homer1 expression with age may represent an important divergence between young and aged brain response to SD. Based on this, it seems reasonable to conclude that therapeutic strategies designed to promote sleep in young subjects may have off-target effects in the aged. Finally, this work identifies presynaptic vesicular release and intercellular adhesion molecular signatures as novel therapeutic targets to counter effects of SD in young subjects.

SUBMITTER: Porter NM

PROVIDER: S-EPMC3390348 | biostudies-literature | 2012

REPOSITORIES: biostudies-literature

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Hippocampal CA1 transcriptional profile of sleep deprivation: relation to aging and stress.

Porter Nada M NM Bohannon Julia H JH Curran-Rauhut Meredith M Buechel Heather M HM Dowling Amy L S AL Brewer Lawrence D LD Popovic Jelena J Thibault Veronique V Kraner Susan D SD Chen Kuey Chu KC Blalock Eric M EM

PloS one 20120705 7

<h4>Background</h4>Many aging changes seem similar to those elicited by sleep-deprivation and psychosocial stress. Further, sleep architecture changes with age suggest an age-related loss of sleep. Here, we hypothesized that sleep deprivation in young subjects would elicit both stress and aging-like transcriptional responses.<h4>Methodology/principal findings</h4>F344 rats were divided into control and sleep deprivation groups. Body weight, adrenal weight, corticosterone level and hippocampal CA ...[more]

PMID: 22792227

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Project description:Sleep deprivation (SD) in young adults is associated with metabolic, stress and cognitive responses that are also characteristic of brain aging. Given that sleep architecture changes with age, including increased fragmentation and decreased slow wave activity, it seems reasonable to investigate potential molecular relationships between SD and aging in brain tissue. Here, we tested the hypothesis that young rats exposed to 24 or 72 hour SD would respond with stress and aging-like shifts in brain hippocampal CA1 gene expression. SD animals showed blood corticosterone and weight changes consistent with a stress response. Microarray results, validated by Western blot and comparison to prior SD studies, pointed to disruptions in neurotransmission, sleep pressure signaling, and macromolecular synthesis. In a separate experiment, animals exposed to 24 or 72 hour novel environment stress recapitulated nearly one third of the SD transcriptional profile, particularly upregulated apoptotic and immune signaling pathways. Compared to aging (based on three previously published independent hippocampal aging studies), SD transcriptional profiles agreed for neurogenesis and energy pathways. However, immune signaling, glial activity, macromolecular synthesis and neuronal function all showed an SD profile that was, at least in part, opposed by aging. We conclude that while stress and SD have discrete molecular signatures, they do show a subset of highly similar changes. However, the same could not be said of aging and SD, where a similar subset of genes is changed, but in partially divergent directions. Finally, this work identifies presynaptic vesicular release and intercellular adhesion molecular signatures as novel targets for future SD-countering therapeutics. Subjects: Male Fischer 344 rats (3-5 months old, Harlan, Indianapolis): 37 in cohort 1 and 32 in cohort 2. Subjects were assigned to one of 5 treatment groups: Home Cage-HC n =17; 24 hour sleep deprivation- 24SD n = 16; 72 hour sleep deprivation- 72SD n = 20; 24 hour novel environment stress- 24NES n = 10; 72 hour novel environment stress- 72NES n = 6. Cohorts 1 and 2 were combined for microarray analyses. Sleep Deprivation: The multiple platform modification (Coenen and van Luijtelaar, 1985) of the classic 'flower pot' (Mendelson et al., 1974) technique in which animals are placed on an elevated platform over water was used. Pairs of SD animals (cage mates) were sleep deprived for 24 or 72 hours. Novel Environment Stress (NES): NES animals were exposed to a novel environment, but were not constrained from sleeping. These NES animals paralleled the sleep deprivation exposure duration (24 hour- n = 10, and 72 hour- n = 6). Tissue Isolation: On the day that animals were removed from the SD chambers, they were anesthetized with CO2 gas and decapitated. Brains were removed and immediately placed in oxygenated artificial cerebrospinal fluid (aCSF) containing (in mM) 114NaCl, 2.5 KCl, 2MgCl2, 30 NaHCO3, 10 Glucose and 2.2CaCl2. Hippocampi were dissected as described previously (Blalock et al., 2003; Kadish et al., 2009). Briefly, dissected hippocampi were immersed in 0C oxygenated aCSF and placed on a chilled glass petri dish. The CA1 region was dissected along the long axis of the hippocampus. CA1 tissue was flash frozen and stored at -80C until further use. Microarray Protocol: GCOS quality control measures of background signal (74.9 ¬± 2.1 cohort 1; 59.8 ¬± 2.3 cohort 2) and RawQ (2.3 ¬± 0.1 cohort 1; 1.9 ¬± 0.1 cohort 2), as well as a chip x chip correlation matrix of signal intensity data pointed to a global decrease in background signal intensity in Cohort 2. To control for this, each gene expression values for HC, 24SD and 72SD was standardized separately within cohort 1 and cohort 2, and then the two cohorts were combined. This retained the variability of each cohort, but removed the 'cohort effect' from the data. Pre-statistical filtering retained 'A' grade probe sets that were uniquely annotated (Affymetrix, June 2011) with gene symbols and had at least 6 presence calls across all 71 chips. This criterion was selected based on factorial analysis demonstrating < 5% probability of 6 or more chips being rated present for a given probe set by chance (Blalock, unpublished observations).

Project description:Sleep has been hypothesized to rebalance overall synaptic strength after ongoing learning during waking leads to net synaptic potentiation. If so, because synaptic strength and size are correlated, synapses on average should be larger after wake and smaller after sleep. This prediction was recently confirmed in mouse cerebral cortex using serial block-face electron microscopy (SBEM). However, whether these findings extend to other brain regions is unknown. Moreover, sleep deprivation by gentle handling was reported to produce hippocampal spine loss, raising the question of whether synapse size and number are differentially affected by sleep and waking. Here we applied SBEM to measure axon-spine interface (ASI), the contact area between pre-synapse and post-synapse, and synapse density in CA1 stratum radiatum. Adolescent YFP-H mice were studied after 6-8 h of sleep (S = 6), spontaneous wake at night (W = 4) or wake enforced during the day by novelty exposure (EW = 4; males/females balanced). In each animal ?425 ASIs were measured and synaptic vesicles were counted in ~100 synapses/mouse. Reconstructed dendrites included many small, nonperforated synapses and fewer large, perforated synapses. Relative to S, ASI sizes in perforated synapses shifted toward higher values after W and more so after EW. ASI sizes in nonperforated synapses grew after EW relative to S and W, and so did their density. ASI size correlated with presynaptic vesicle number but the proportion of readily available vesicles decreased after EW, suggesting presynaptic fatigue. Thus, CA1 synapses undergo changes consistent with sleep-dependent synaptic renormalization and their number increases after extended wake.SIGNIFICANCE STATEMENT Sleep benefits learning, memory consolidation, and the integration of new with old memories, but the underlying mechanisms remain highly debated. One hypothesis suggests that sleep's cognitive benefits stem from its ability to renormalize total synaptic strength, after ongoing learning during wake leads to net synaptic potentiation. Supporting evidence for this hypothesis mainly comes from the cerebral cortex, including the observation that cortical synapses are larger after wake and smaller after sleep. Using serial electron microscopy, we find here that sleep/wake synaptic changes consistent with sleep-dependent synaptic renormalization also occur in the CA1 region. Thus, the role of sleep in maintaining synaptic homeostasis may extend to the hippocampus, a key area for learning and synaptic plasticity.

Project description:Recent microarray studies in the hippocampus of rodents or Alzheimer’s disease (AD) subjects have identified a substantial number of cellular pathways/processes correlated with aging and cognitive decline. However, the temporal relationships among these expression changes or with cognitive impairment have not been studied in depth. Here, using Affymetrix microarrays, immunohistochemistry and Morris water maze cognitive testing across 5 age groups of male F344 rats (n=9-15/group, one microarray per animal), we systematically analyzed the temporal sequence and cellular localization of aging changes in expression. These were correlated with performance scores on the hippocampus-dependent Morris Water Maze task. Significant microarray results were sorted in to Early, Intermediate, Midlife, and Late patterns of expression, and functionally categorized (Early- downregulated neural development, lipid synthesis and energy-utilization; upregulated ribosomal synthesis, growth, stress/inflammatory, lysosome and protein/lipid degradation. Intermediate- increased defense/inflammatory activation and decreased transporter activity; Midlife- downregulated energy-dependent signaling and neurite growth, upregulated astroglial activation, Ca2+-binding, cholesterol/lipid trafficking, myelinogenic processes and additional lysosome/inflammation; Late- further recruitment of genes in already-altered pathways). Immunohistochemistry revealed a primarily astrocytic localization of the processes upregulated in midlife, as well as increased density of myelin proteins. Evidence of cognitive impairment first appeared in the 12-month-old group (midlife) and was increased further in the 23-month-old group, exhibiting the highest correlations with some upregulated genes related to cholesterol transport (e.g., Apoe, Abca2), protein management and ion binding. Some upregulated genes for inflammation (Il6st) and myelinogenesis (Pmp22) also correlated with impairment. Together, the data are consistent with a novel sequential cascade model of brain aging in which metabolic alterations early in maturity are followed by inflammation and midlife activation of an astrocyte-centered cholesterol trafficking pathway that stimulates oligodendrocyte remyelination programs. Importantly, this cholesterol trafficking pathway also may compete for astroglial bioenergetic support of neurons, in turn, leading to downregulation of energy-dependent pathways needed to sustain cognitive functions. Keywords: aging time course

Project description:BackgroundSmaller hippocampal volume in patients with posttraumatic stress disorder (PTSD) represents the most consistently reported structural alteration in the brain. Subfields of the hippocampus play distinct roles in encoding and processing of memories, which are disrupted in PTSD. We examined PTSD-associated alterations in 12 hippocampal subfields in relation to global hippocampal shape, and clinical features.MethodsCase-control cross-sectional studies of U.S. military veterans (n = 282) from the Iraq and Afghanistan era were grouped into PTSD (n = 142) and trauma-exposed controls (n = 140). Participants underwent clinical evaluation for PTSD and associated clinical parameters followed by MRI at 3 T. Segmentation with FreeSurfer v6.0 produced hippocampal subfield volumes for the left and right CA1, CA3, CA4, DG, fimbria, fissure, hippocampus-amygdala transition area, molecular layer, parasubiculum, presubiculum, subiculum, and tail, as well as hippocampal meshes. Covariates included age, gender, trauma exposure, alcohol use, depressive symptoms, antidepressant medication use, total hippocampal volume, and MRI scanner model.ResultsSignificantly lower subfield volumes were associated with PTSD in left CA1 (P = 0.01; d = 0.21; uncorrected), CA3 (P = 0.04; d = 0.08; uncorrected), and right CA3 (P = 0.02; d = 0.07; uncorrected) only if ipsilateral whole hippocampal volume was included as a covariate. A trend level association of L-CA1 with PTSD (F4, 221 = 3.32, P = 0.07) is present and the other subfield findings are nonsignificant if ipsilateral whole hippocampal volume is not included as a covariate. PTSD-associated differences in global hippocampal shape were nonsignificant.ConclusionsThe present finding of smaller hippocampal CA1 in PTSD is consistent with model systems in rodents that exhibit increased anxiety-like behavior from repeated exposure to acute stress. Behavioral correlations with hippocampal subfield volume differences in PTSD will elucidate their relevance to PTSD, particularly behaviors of associative fear learning, extinction training, and formation of false memories.

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Hippocampal CA1 transcriptional profile of sleep deprivation: relation to aging and stress.

Publications

Hippocampal CA1 transcriptional profile of sleep deprivation: relation to aging and stress.

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