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Hippocamus of SAMR1 and SAMP8 mice [microRNA]

ABSTRACT: A growing body of research shows that epigenetic mechanisms are critically involved in normal and pathological aging. The Senescence-Accelerated Mouse Prone 8 (SAMP8) can be considered an useful tool to better understand the dynamics of the global epigenetic landscape during the aging process since its phenotype is not fully explained by genetic factors. Here we investigated dysfunctional age-related transcriptional profiles and epigenetic programming enzymes in the hippocampus of 2- and 9-month-old SAMP8 female mice using the Senescent-Accelerated Resistant 1 (SAMR1) mouse strain as control. SAMP8 mice presented 1,062 genes dysregulated at 2 months of age, and 1,033 genes at 9 months, with 92 genes concurrently dysregulated at both ages in reference to age mated SAMR1. SAMP8 mice showed a significant decrease in global DNA methylation (5-mC) at 2 months while hydroxymethylation (5-hmC) levels were increased in SAMP8 mice at 2 and 9 months of age compared to SAMR1. These changes were accompanied by changes in the expression of several enzymes that regulate 5-mC and methylcytosine oxidation. Acetylated H3 and H4 histone levels were significantly diminished in SAMP8 mice at 2-month-old compared to SAMR1 and altered Histone DeACetylase (HDACs) profiles were detected in both young and old SAMP8 mice. We analyzed 84 different mouse miRNAs known to be altered in neurological diseases or involved in neuronal development. Compared with SAMR1, SAMP8 mice showed 28 and 17 miRNAs differentially expressed at 2 and 9 months of age, respectively, 6 of these miRNAs overlapped at both ages. We used several bioinformatic approaches to integrate our data in mRNA:miRNA regulatory networks and functional predictions for young and aged animals. In sum, our study reveals interplay between epigenetic mechanisms and gene networks that seems to be relevant for the progression towards a pathological aging and provides several potential markers and therapeutic candidates for Alzheimer’s Disease (AD) and age-related cognitive impairment.

ORGANISM(S): Mus musculus

PROVIDER: GSE121769 | GEO | 2018/10/26

REPOSITORIES: GEO

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Project description:A growing body of research shows that epigenetic mechanisms are critically involved in normal and pathological aging. The Senescence-Accelerated Mouse Prone 8 (SAMP8) can be considered an useful tool to better understand the dynamics of the global epigenetic landscape during the aging process since its phenotype is not fully explained by genetic factors. Here we investigated dysfunctional age-related transcriptional profiles and epigenetic programming enzymes in the hippocampus of 2- and 9-month-old SAMP8 female mice using the Senescent-Accelerated Resistant 1 (SAMR1) mouse strain as control. SAMP8 mice presented 1,062 genes dysregulated at 2 months of age, and 1,033 genes at 9 months, with 92 genes concurrently dysregulated at both ages in reference to age mated SAMR1. SAMP8 mice showed a significant decrease in global DNA methylation (5-mC) at 2 months while hydroxymethylation (5-hmC) levels were increased in SAMP8 mice at 2 and 9 months of age compared to SAMR1. These changes were accompanied by changes in the expression of several enzymes that regulate 5-mC and methylcytosine oxidation. Acetylated H3 and H4 histone levels were significantly diminished in SAMP8 mice at 2-month-old compared to SAMR1 and altered Histone DeACetylase (HDACs) profiles were detected in both young and old SAMP8 mice. We analyzed 84 different mouse miRNAs known to be altered in neurological diseases or involved in neuronal development. Compared with SAMR1, SAMP8 mice showed 28 and 17 miRNAs differentially expressed at 2 and 9 months of age, respectively, 6 of these miRNAs overlapped at both ages. We used several bioinformatic approaches to integrate our data in mRNA:miRNA regulatory networks and functional predictions for young and aged animals. In sum, our study reveals interplay between epigenetic mechanisms and gene networks that seems to be relevant for the progression towards a pathological aging and provides several potential markers and therapeutic candidates for Alzheimer’s Disease (AD) and age-related cognitive impairment.

Project description:Astrocytes are key cells in brain aging, helping neurons to undertake healthy aging or otherwise letting them enter into a spiral of neurodegeneration. We aimed to characterize astrocytes cultured from senescence-accelerated prone 8 (SAMP8) mice, a mouse model of brain pathological aging, along with the effects of caloric restriction, the most effective rejuvenating treatment known so far. Analysis of the transcriptomic profiles of SAMP8 astrocytes cultured in control conditions and treated with caloric restriction serum was performed using mRNA microarrays. A decrease in mitochondrial and ribosome mRNA, which was restored by caloric restriction, confirmed the age-related profile of SAMP8 astrocytes and the benefits of caloric restriction. An amelioration of antioxidant and neurodegeneration-related path- ways confirmed the brain benefits of caloric restriction. Studies of oxidative stress and mitochondrial function demonstrated a reduction of oxidative damage and partial improvement of mito- chondria after caloric restriction. In summary, caloric restriction showed a significant tendency to normalize pathologically aged astrocytes through the activation of pathways that are protective against the age-related deterioration of brain physiology. Key words: astrocytes; caloric restriction; mitochondria; oxidative stress; RNA microarrays; SAMP8. Primary cultures enriched in astrocytes were obtained from cerebral cortical tissue from 2-day-old SAMP8 and SAMR1 mice. Astrocyte cultures were established and experiments were routinely carried out after 21 days in culture. Established astrocyte cultures of both SAMR1 and SAMP8 consisted of 85-90% astrocytes, 10-15% microglia and 0.1-1% oligodendroglia. Sera from rats subjected to ad libitum (AL) diet and to CR were obtained as described for the establishment of the CR in vitro model (de Cabo et al., 2003). Serum was heat inactivated at 56°C prior to use in astrocyte culture experiments. Treatment in vitro was performed by adding 10% volume CR or AL serum onto the astrocyte culture medium for 48 h, the cells were harvested and RNA was extracted for the microarray studies. Three biological replicates for each condition were done and RNA was extracted for the microarray studies. Please note that SAM models were developed from AKR/J by Kyoto University. Five litters with severe senescence were selected to further propagate and examine these characteristics. Litters that showed normal aging were selected as a senescence-resistant series (R-series). The genetic background of the SAM mice became suspect after the pathological findings were different from the AKR/J mouse. Each SAM model is genetically different. Each SAM colony was acquired by Harlan by Takeda Chemical Ltd. in 2002. And here is the link to the company site. http://www.harlan.com/products_and_services/research_models_and_services/research_models/sam_inbred_mice/samp8tahsd.hl

Project description:The present study examines the effects of whale meat extract (WME) supplementation on the senescence-accelerated mouse prone 8 (SAMP8) model at the level of learning memory formation and gene expression profiles genome-wide. Our present study builds up on these previous studies by focusing on two sets of experiments examining WME-supplemented diet, on SAMP8 and SAMR1 (senescence-accelerated mouse resistant 1) learning and memory deficits (experiment 1) and whole-genome DNA microarray-based transcriptomics profiling in conjunction with Ingenuity Pathway Analysis (IPA) (experiment 2). We also examined the SAMP8 and SAMR1 mice fed with the regular (control; low-safflower oil, LSO) diets specifically to know the gene profiles in the brain of the SAMP8 mouse. Results revealed that WME supplementation on SAMP8 mouse resulted in an increase in the level of learning memory formation and positive changes in the transcriptome of the brain, suggested through the observation of recovery of gene expressions in the SAMP8 model over the not-supplemented mouse. 6-week-old mice (SAMP8 and SAMR1; CLEA, Tokyo, Japan) were housed at the Animal Institution Facility in Showa University, and maintained in individual cages in a ventilated animal room with controlled temperature and relative humidity under a 12-h light: 12-h dark regime (8:00 AM, lights turned on). Mice were fed chow (CE-2, CLEA Japan) and tap water ad libitum until 24-weeks-old. Then, 24-week-old SAMs mice were given experimental diet, LSO diet as a control diet and WME-supplemented diet, both in a powder form. The WME was made from red meat of Antarctic minke whale (Balaenoptera bonaerensis), taken from the Japanese Whale Research Program under Special Permit in the Antarctic-Phase II in 2009/2010 by heat, enzyme and drying treatments. The quality standard of WE were measured by Marugei Co. Ltd. (Hyogo, Japan). SAMP8 mice were randomly given LSO or WME diet, respectively. SAMR1 mice were given LSO diet only until 50-weeks-old. The behavioral tests were performed at the timing of 49-weeks-old for 8 days. At the end of the experiment (50 weeks of age) following the behavioral analysis (open field test, Y-maze test, new object recognition test (NOR), and water-filled multiple T-maze) and the last day of the feeding, the mice were removed from their cages, decapitated and their brains carefully removed on ice. The whole brains were quickly frozen in liquid nitrogen in a sterile freeze tube and stored at -80ÂºC till extraction of total RNA followed by DNA microarray analysis using a whole-genome mouse chip (Agilent-014868, 4 x 44K (G4122F)) with two-color dye-swap approach in conjunction with IPA bioinformatic analysis. All animal studies were conducted in accordance with the Standards Relating to the Care Management of Experimental Animalsâ (Notice No. 6 of the Office of Prime Minister dated March 27, 1980) and with approval from the Animal Use Committee of Showa University (Approval Number: #04093).

Project description:The purpose of this study was to determine whether there were differences in gene expression in the hippocampus, a part of the brain involved in memory consolidation, between male mice with age-related memory deficits (SAMP8 mice) and control mice with no age-related memory deficits. The senescence-accelerated mouse (SAMP8) strain exhibits decreased learning and memory and increased amyloid beta peptide (Aβ) accumulation at 12 months compared to 4 months. To detect differences in gene expression in SAMP8 mice, we used a Control mouse that was a 50% cross between SAMP8 and CD-1 mice and which showed no memory deficits (50% SAMP8 mouse). We then compared gene expression in the hippocampus of 4 month and 12 month old SAMP8 and Control mice using Affymetrix gene arrays. At 12 months, but not at 4 months, pathway analysis revealed significant differences in the Long Term Potentiation (LTP) (6 genes), Phosphatidylinositol Signaling (6 genes), and Endocytosis (10 genes) pathways. The changes in LTP included MAPK signaling (N-ras, CREB binding protein, protein phosphatase inhibitor 1) and Ca-dependent signaling (PI receptors 1 and 2 and phospholipase C). Changes in phosphatidylinositol signaling genes suggested altered signaling through PI3-kinase, and Western blotting revealed phosphorylation changes in AKT and 70S6K. Changes in the Endocytosis pathway involved genes related to clathrin-mediated endocytosis (dynamin and clathrin). Endocytosis is required for receptor recycling, is involved in Aβ metabolism, and is regulated by phosphatidylinositol signaling. In summary, these studies demonstrate altered genes expression in three SAMP8 hippocampal pathways associated with memory formation and consolidation. These pathways may provide new therapeutic targets in addition to targeting Aβ metabolism itself. Global differential profiling of hippocampal gene expression (4 month and 12 month old SAMP8 and Control mice) was performed using Affymetrix GeneChip® Mouse Genome 430 2.0 Arrays. At 12 months, but not at 4 months, pathway analysis revealed significant differences in the Long Term Potentiation (LTP) (6 genes), Phosphatidylinositol Signaling (6 genes), and Endocytosis (10 genes) pathways. The changes in LTP included MAPK signaling (N-ras, CREB binding protein, protein phosphatase inhibitor 1) and Ca-dependent signaling (PI receptors 1 and 2 and phospholipase C). Changes in phosphatidylinositol signaling genes suggested altered signaling through PI3-kinase, and Western blotting revealed phosphorylation changes in AKT and 70S6K. Changes in the Endocytosis pathway involved genes related to clathrin-mediated endocytosis (dynamin and clathrin). Endocytosis is required for receptor recycling, is involved in Aβ metabolism, and is regulated by phosphatidylinositol signaling. In summary, these studies demonstrate altered genes expression in three SAMP8 hippocampal pathways associated with memory formation and consolidation. These pathways may provide new therapeutic targets in addition to targeting Aβ metabolism itself. 2-way ANOVA (2 x 2 conditions, n=4). First variable was age (4 and 12 months) and second variable was mouse strain (Control and SAMP8). This results in 4 groups: Control-4 month, Control-12 month, SAMP8-4 month, and SAMP8-12 month. Each group had 4 biological replicates (4 mice). The ”Control” mice were a 50% backcross of the SAMP8 mice with CD-1 mice (50% SAMP8 mice). These mice were closely related to SAMP8 mice but exhibited no memory deficits at 4 or 12 months. The SAMP8 mice had memory deficits at 12 months but not at 4 months.

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Hippocamus of SAMR1 and SAMP8 mice [microRNA]

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