Exploring the mechanism of transcutaneous auricular vagus nerve stimulation on improving post-stroke cognitive impairment in MCAO rats using RNA-seq
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ABSTRACT: Our previous findings have shown that taVNS is effective in improving PSCI. However, its specific mechanism and the target genes, biological processes, and signaling pathways it regulates are still unclear and require more in-depth research. We established a cognitive impairment model in MCAO rats and administered taVNS treatment. Cognitive function was assessed using Y-maze and novel object recognition (NOR) experiments. Pathological changes in hippocampal tissue were observed through HE and Nissl staining. RNA-seq was conducted on hippocampal tissue from each group, and differentially expressed genes (DEGs) were performed for GO and KEGG enrichment. Hub genes were identified using the STRING database and betweenness centrality values. taVNS treatment significantly improved cognitive function (Y-maze and NOR) and pathological morphology of hippocampal tissue (HE and Nissl staining) in the PSCI model rats. A total of 341 taVNS targeted DEGs were identified, and they may be implicated in chromosome segregation, mitotic nuclear division, cell cycle, NOD-like receptor signaling pathway, NF-kappa B signaling pathway, and Toll-like receptor signaling pathway, etc. The expression trends of TLR4, Myd88, and NF-κB mRNAs in the Hub genes were significantly inhibited by taVNS.
Project description:In this study, we investigated the miRNA and mRNA profiling of the cortex of rat model of vascular dementia (VaD) to analyze the regulatory mechanism in the pathology of VaD involved by miRNAs, transcription factors (TFs), and corresponding target genes. As a validated model of VaD, rats suffering from bilateral common carotid artery occlusion (2VO) were used in the present study and the reliability of this model was examined by the Morris water maze (MWM) test and the Nissl staining. Overall, results showed that rats with 2VO presented declined learning and memory capabilities in the MWM test and neuronal loss in the hippocampus and cortex indicated by Nissl-staining compared to sham rats. DEGs, DEMs, and DETFs were discriminated between rats with 2VO and sham rats in the cortex, illustrated by 13 aberrantly-expressed miRNAs, 805 mRNAs, and 63 TFs. Further network analysis revealed that 7 target genes, 5 miRNAs, and 10 TFs were the key molecule in the miRNA-TF-gene network related to VaD. Gene Ontology (GO) and pathway enrichment analyses of these VaD-related transcripts showed that these differently changed genes mostly got involved in PI3K-Akt signaling pathway, neuroactive ligand-receptor interaction, calcium signaling pathway, and Wnt signaling pathway, along with central locations around cell membrane, exerting function such as growth factor binding, integrin binding, and extracellular matrix structural constituent, with representative biological processes like vasculature development, cell-substrate adhesion, cellular response to growth factor stimulus, and synaptic transmission. In conclusion, these results will help us understand the underlying regulatory mechanisms of miRNA-TF-genes in pathogenesis and provide potential therapeutic targets for the treatment of VaD.
Project description:Although immediate early genes (IEGs) such as Bdnf, Arc and Egr1, have been implicated in plasticity, the larger pathways related to memory and memory disorders are not well understood. Here, we combined statistical Affymetrix microarray and behavioral analyses to identify key genes and pathways associated with aging-related cognitive impairment. Aged rats were separated into cognitively unimpaired (AU) or impaired (AI) groups, based on their Morris water maze performance relative to young-adult (Y) animals. Hippocampal gene expression was assessed in Y, AU and AI on the fifth (last) day of maze training or 21 days posttraining, and in non-trained aged and young animals (eight groups, overall n = 78, one chip/animal). ANOVA, linear contrasts, and overrepresentation analyses identified genes and pathways that differed from Y generally with aging (in both AU and AI) or selectively with cognitive status (only in AI or AU). Plasticity pathways, including insulin/cAMP/IEG signaling, and glycogenolytic and lipogenic pathways, were selectively downregulated (5 days) in AI, whereas Notch2 (regulating oligodendrocyte differentiation) and myelination pathways were upregulated (particularly at 21 days). Downregulation with general aging occurred in signal transduction and axonal growth/transport pathways, whereas upegulation occurred in immune/inflammatory, lipid metabolism/transport (e.g., Lxr-Srebf1), and lysosomal pathways. In AU, receptor/signal transduction genes were selectively upregulated, suggesting possible compensatory mechanisms. Immunohistochemistry confirmed and extended results to the protein level. Thus, this study identified novel cognition-linked processes, suggesting a new model in which energy-intensive, plasticity/lipogenic processes and energy-generating pathways necessary for learning are coordinately downregulated during training, while myelinogenic programs that impair cognition are concurrently activated. Experiment Overall Design: Aged rats were separated into cognitively unimpaired (AU) or impaired (AI) groups, based on their Morris water maze performance relative to young-adult (Y) animals (NT, 5D, and 21D, N=10/group). Hippocampal gene expression was assessed in Y, AU and AI on the fifth (last) day of maze training or 21 days posttraining, and in non-trained aged and young animals (eight groups, overall n = 78, one chip/animal)
Project description:Objective Obesity is a multidimensional condition that is treatable by the restoration of a lean phenotype; however, some obesity-related outcomes may persist after weight normalization. Among the organs of the human body, the brain possesses a relatively low regenerative capacity and could retain perturbations established as a result of developmental obesity. Calorie restriction (CR) or a restricted ketogenic diet (KD) are successfully used as weight loss approaches, but their impact on obesity-related effects in the brain have not been previously evaluated. Methods We performed a series of experiments in a rat model of developmental obesity induced by a 12-week cafeteria diet, followed by CR to implement weight loss. First, we assessed the impact of obesity on neurogenesis (BrdU incorporation into the hippocampus), cognitive function (water maze), and concomitant changes in hippocampal protein expression (GC/MS-MS, western blot). Next, we repeated these experiments in a rat model of weight loss induced by CR. We also measured mitochondrial enzyme activity in rats after weight loss during the fed or fasting state. By using a modified version of the water maze we evaluated cognitive abilities in rats subjected to weight loss by CR or a restricted KD. Results In this study, obesity affected metabolic processes, upregulated hippocampal NF-κB, and induced proteomic differences which were associated with impaired cognition and neurogenesis. Weight loss improved neurogenesis and enhanced cognition. While the expression pattern of some proteins persisted after weight loss, most of the changes appeared de novo revealing metabolic adjustment by overactivation of citrate synthase and downregulation of ATP synthase. As a consequence of fasting, the activity of these enzymes indicated hippocampal adaptation to negative energy balance during the weight loss phase of CR. Moreover, the effects on cognitive abilities measured after weight loss were negatively correlated with the obesity level and were alleviated by KD, which improved cognition when used as a weight loss approach. Conclusions The study shows that cognition and mitochondrial metabolism in the hippocampus are affected by CR- or KD-induced weight loss.
Project description:Vitamin D is an important calcium-regulating hormone with diverse functions in numerous tissues including the brain. Increasing evidence suggests that vitamin D may play a role in maintaining cognitive function and that vitamin D deficiency may accelerate age-related cognitive decline. Using aging rodents, we attempted to model the range of human serum vitamin D levels, from deficient to sufficient, to test whether vitamin D could preserve or improve cognitive function with aging. For 5-6 months, middle-aged F344 rats were fed diets containing low, medium (typical amount) or high vitamin D3 (100, 1000 or 10,000 IU/kg diet, respectively) and then hippocampal-dependent learning and memory were tested in the Morris water maze. Rats on high vitamin D achieved the highest blood levels (in the sufficient range) and significantly outperformed low and medium groups on maze reversal, a particularly challenging task that detects more subtle changes in memory. In addition to calcium-related processes, hippocampal gene expression microarrays identified pathways pertaining to synaptic transmission, cell communication and G-protein function as being up-regulated with high vitamin D. Basal synaptic transmission also was enhanced corroborating observed effects on gene expression and learning and memory. Our studies demonstrate a causal relationship between vitamin D status and cognitive function and suggest that vitamin D-mediated changes in hippocampal gene expression may improve the likelihood of successful brain aging.
Project description:Repeated excessive alcohol consumption increases the risk of developing cognitive decline and dementia. Hazardous drinking among older adults further increases such vulnerabilities. In order to understand the molecular mechanisms underlying alcohol-induced cognitive deficits in older adults, we performed a chronic intermittent ethanol exposure paradigm (ethanol or water gavage every other day 10 times) in 8-week-old young adult and 70-week-old aged rats. While spatial memory retrieval ascertained by probe trials in the Morris water maze was not significantly different between ethanol-treated and water-treated rats in both age groups after the fifth and tenth gavages, behavioral flexibility was impaired in ethanol-treated rats than water-treated rats in the aged group but not in the young adult group. Further proteomic and phosphoproteomic analyses on their hippocampal tissues by tandem mass tag mass spectrometry revealed ethanol-treatment-associated proteomic and phosphoproteomic differences distinct to the aged rats, including the upregulations of Prkcd protein level, several of its phosphosites, and its kinase activity and the same aspects in Camk2a but downregulated, and were enriched in pathways involved in neurotransmission regulation, synaptic plasticity, neuronal apoptosis, and insulin receptor signaling. In conclusion, our behavioral and proteomic results added several candidate proteins and pathways potentially associated with alcohol-induced cognitive decline in aged adults.
Project description:The aim of this study was to identify alterations in hippocampal synaptic mRNA expression with aging and cognitive decline. Transcriptional profiling and subsequent bioinformatic analysis was performed to identify the most highly regulated pathways of genes. Interestingly, the antigen processing and presentation pathway was identified as the most highly regulated pathway with aging. Adult (12 month) and aged (28 month) Fischer 344 x Brown Norway (F1) hybrid rats were assessed for cognitive performance using the Morris water maze task and were divided into Adult (n=5), Aged Cognitively Intact (n=8), and Aged Cognitively Impaired (n=7) groups. One week following testing, all animals were sacrificed, the hippocampi were dissected, and synaptosomes were isolated for subsequent transcriptomic profiling. Only 5 cognitively intact animals were processed on the arrays.
Project description:We found that a klotho protein fragment (KL-F), administered peripherally, induced cognitive enhancement and neural resilience. Here we report a proteomic analysis of whole hippocampal homogenates from mice treated with vehicle or KL-F (10 µg/kg, i.p.) four hours prior to exploration in the small Y-maze. The proteomic results showed glutamate receptor signaling as the top enriched canonical pathway by Ingenuity Pathway Analysis.
Project description:Vitamin D is an important calcium-regulating hormone with diverse functions in numerous tissues including the brain. Increasing evidence suggests that vitamin D may play a role in maintaining cognitive function and that vitamin D deficiency may accelerate age-related cognitive decline. Using aging rodents, we attempted to model the range of human serum vitamin D levels, from deficient to sufficient, to test whether vitamin D could preserve or improve cognitive function with aging. For 5-6 months, middle-aged F344 rats were fed diets containing low, medium (typical amount) or high vitamin D3 (100, 1000 or 10,000 IU/kg diet, respectively) and then hippocampal-dependent learning and memory were tested in the Morris water maze. Rats on high vitamin D achieved the highest blood levels (in the sufficient range) and significantly outperformed low and medium groups on maze reversal, a particularly challenging task that detects more subtle changes in memory. In addition to calcium-related processes, hippocampal gene expression microarrays identified pathways pertaining to synaptic transmission, cell communication and G-protein function as being up-regulated with high vitamin D. Basal synaptic transmission also was enhanced corroborating observed effects on gene expression and learning and memory. Our studies demonstrate a causal relationship between vitamin D status and cognitive function and suggest that vitamin D-mediated changes in hippocampal gene expression may improve the likelihood of successful brain aging. Sixty, middle-aged male F344 rats were divided into three groups, each receiving for 5-6 months a different dietary amount of cholecalciferol (vitamin D3; VitD3). Purified AIN-93G (Harlan-Teklad) diet was modified to contain low, medium or high VitD3 (IU/kg diet): High = 10,000, Standard (Control) = 1000; Low = 100. Animal weight and amount of food consumed was recorded 2-3 times/week. Serum levels of 25-hydroxy vitamin D were determined using liquid chromatography/tandem mass spectrometry (ZRT Laboratory). Hippocampal RNA was isolated, quantified and checked for RNA integrity. One low VitD3 sample failed RNA quality control. Remaining RNA samples were applied to Affymetrix Rat Gene 1.0 ST arrays (one array/subject). Pre-statistical filtering removed poorly annotated probe sets, low intensity signals, and outlier values (>2SD of the group mean). Filtered data were analyzed by 1-way ANOVA to identify significant differences and the False Discovery Rate (FDR) procedure was used to estimate the error of multiple testing. FDR was compared at 0.31 and 0.17. Significant genes were assigned to one of four idealized expression patterns using Pearson’s test and separated by the sign of their correlation; relative gene expression values are provided on the log-2 scale. Functional categorization for significant genes was determined using DAVID bioinformatic tools. Please note that 'Marked' and 'Unmarked' (in the sample titles) refers to whether the rat had a mark on its tail. The rats were pair-housed and this is how two rats in one cage were distinguished.
Project description:Analyzing changes in gene expression in liver and skeletal muscle from streptozotocin-diabetic rats. From the 9,929 expressed genes across the genome, 1,305 and 997 differentially expressed genes (DEGs, P < 0.01) were identified in comparisons of skeletal muscle and liver, respectively. Interestingly, large numbers of DEGs (200) were common to both comparisons, which was clearly more than the predicted number (131 genes, P < 10−4). Further interpretation of gene ontology used three over-representation analysis software (WebGestalt, Expander and GATHER). All the tools detected one KEGG pathway (MAPK signaling) and two GO biological processes (response to stress and cell death), with enrichment of DEGs in both tissues. In addition, PPI (protein-protein interaction) networks constructed using human homologs not only revealed the tendency of DEGs to form a highly connected module, but also suggested a “hub” role of MAPK related genes (such as MAPK14) in the pathogenesis of T2D. Total RNA obtained from liver and skeletal muscle of streptozotocin-diabetic rats and controls, respectivly.
Project description:We carried out a global survey of age-related changes in mRNA levels in the C57BL/6NIA mouse hippocampus and found a difference in the hippocampal gene expression profile between 2-month-old young mice and 15-month-old middle-aged mice correlated with an age-related cognitive deficit in hippocampal-based explicit memory formation. Middle-aged mice displayed a mild but specific deficit in spatial memory in the Morris water maze. Experiment Overall Design: No technical replicates; 14 biological replicates for 15-month-old mice, 9 biological replicates for 2-month-old mice. Whole hippocampus.