Project description:Traumatic brain injury (TBI) is a global problem reaching near epidemic numbers that manifests clinically with cognitive problems that decades later may result in dementias like Alzheimer’s disease (AD). Presently, little can be done to prevent ensuing neurological dysfunctions by pharmacological means. Recently, it has become apparent that several CNS diseases share common terminal features of neuronal cell death. The effects of exendin-4 (Ex-4), a neuroprotective agent delivered via a subcutaneous micro-osmotic pump, were examined in the setting of mild TBI (mTBI). Utilizing a model of mTBI, where cognitive disturbances occur over time, animals were subjected to four treatments: sham; Ex-4; mTBI and Ex-4/mTBI. mTBI mice displayed deficits in novel object recognition, while Ex-4/mTBI mice performed similar to sham. Hippocampal gene expression, assessed by gene array methods, showed significant differences with little overlap in co-regulated genes between groups. Importantly, changes in gene expression induced by mTBI, including genes associated with AD were largely prevented by Ex-4. These data suggest a strong beneficial action of Ex-4 in managing secondary events induced by a traumatic brain injury. Male ICR mice weighing 30–40 g were kept five per cage under a constant 12-h light/dark cycle, at room temperature (23°C). Food (Purina rodent chow) and water were available ad libitum. Each mouse was used for one experiment and for one time point only. The Ethics Committee of the Sackler Faculty of Medicine approved the experimental protocol (M-09-055), in compliance with the guidelines for animal experimentation of the National Institutes of Health (DHEW publication 85–23, revised, 1995). A minimal number of mice were used for the study and all efforts were made to minimize suffering. All experimental manipulations were conducted during the light phase of the cycle. Experimental mTBI was induced using the concussive head trauma device described previously (Milman et al. 2005; Zohar et al. 2003). Briefly, mice were lightly anesthetized (Isoflurane) and placed under the weight-drop concussive head trauma instrument. The device consists of a metal tube (inner diameter 13 mm), placed vertically over the mouse head. A metal weight (30 g) was dropped from the top of the tube (80 cm) and struck the skull at the temporal right side between the corner of the eye and the ear. A sponge supported the head, allowing some antero-posterior motion without any rotational head movement at the moment of the impact. Immediately after the injury, mice were placed back in their cages for recovery. The effect of the injury upon behavior and cognition was studied from 7 days following the trauma. Sham treated mouse groups were treated identically only the weight was not dropped. The peptide Ex-4 was obtained from Bachem (Torrance, CA). In order to obtain a constant steady-state concentration of Ex-4 in mice prior to injury; Ex-4 was delivered by use of micro-osmotic pumps (7 day infusion duration), 2 days prior to the induction of mTBI. For the Ex-4 treated animals the peptide was dissolved in an equal volume of saline and dimethyl sulfoxide (DMSO) mixture and delivered from a subcutaneously implanted ALZET Micro-osmotic pump (Model 1007D, Alzet, Cupertino, CA) at a rate of 3.5 pM/kg/min. In drug treatment control groups, saline and DMSO pumps were implanted in each animal following the same surgical procedure as used for the Ex-4 treatment animals. In all animals, pumps were placed, posterior to the scapulae. Pump implantation was performed under anesthesia (ketamine/xylazine) utilizing sterile procedures. Mini pumps were implanted 48 hours prior to the weight drop injury. The number of animals from each treatment group that went on to microarray analysis were as follows, Sham, n = 5; mTBI, n = 4; Ex-4, n = 5; Ex-4/ mTBI, n = 4. Mouse cognition was assessed using the novel object recognition paradigm. After the completion of the novel object behavioral assessment, animals were euthanized and the hippocampus dissected for total RNA isolation. Total RNA was prepared using the Qiagen RNeasy Mini Kit (Qiagen, Inc. Valencia CA) following the manufacturer's specifications. Quantity and quality of the RNA was assessed using the Agilent 2100 Bioanalyzer with RNA 6000 Nano Chips. The total RNA (500 ng) was used to generate biotin-labeled cRNA using the Illumina TotalPrep RNA Amplification Kit (Ambion; Austin, TX, cat # IL1791). In short, 500 ng of total RNA was first converted into single-stranded cDNA with reverse transcriptase using an oligo-dT primer containing the T7 RNA polymerase promoter site and then copied to produce double-stranded cDNA molecules. The double stranded cDNA was cleaned and concentrated with the supplied columns and used in an overnight in vitro transcription reaction where single-stranded RNA (cRNA) was generated and labeled by incorporation of biotin-16-UTP. This cRNA was used in the hybridization reaction. Briefly, a total of 750 ng of biotin-labeled cRNA was hybridized at 58oC for 16 hours to Illumina's SentrixMouse Ref-8, v2 Expression BeadChips (Illumina, San Diego, CA). Each BeadChip has ~24,000 well-annotated RefSeq transcripts with an approximately 30-fold redundancy. The arrays were washed, blocked and the biotin labeled cRNA was detected by staining with streptavidin-Cy3. Arrays were scanned at a resolution of 0.8 m using the Beadstation 500 X from Illumina, data was extracted from the image using Illumina BeadStudio software, v3.4.0.

Project description:In order to characterize gene expression networks linked to AT1 angiotensin receptors in the kidney, we carried out genome-wide transcriptional analysis of RNA from kidneys of wild-type (WT) and AT1A receptor-deficient mice (KOs) at baseline and after 2 days of angiotensin II infusion (1 ug/kg/min), using Affymetrix GeneChip Mouse Genome 430 2.0 Arrays. At baseline, 405 genes were differentially expressed (>1.5X) between WT and KO kidneys. Of these, more than 80% were up-regulated in the KO group including genes involved in inflammation, oxidative stress, and cell proliferation. After 2 days of angiotensin II infusion in WT mice, expression of ~805 genes was altered (18% up-regulated, 82% repressed). Genes in metabolism and ion transport pathways were up-regulated while there was attenuated expression of protective genes against oxidative stress including glutathione synthetase and mitochondrial SOD2. Angiotensin II infusion has little effect on blood pressure in KOs. Nonetheless, expression of more than 250 genes was altered in kidneys from KO mice during angiotensin II infusion; 14% were up-regulated, while 86% were repressed including genes involved in immune responses, angiogenesis, and glutathione metabolism. Between WT and KO kidneys during angiotensin II infusion, 728 genes were differentially expressed; 10% were increased and 90% were decreased in the WT group. Differentially regulated pathways included those involved in ion transport, immune responses, metabolism, apoptosis, cell proliferation, and oxidative stress. This genome-wide assessment should facilitate identification of critical distal pathways linked to blood pressure regulation. To define gene expression patterns in kidney triggered by of activation AT1 receptors, we used genome-wide transcriptional analysis of RNA from kidneys of wild-type and AT1A receptor-deficient mice at baseline and after 2 days of angiotensin II infusion (1 ug/kg/min), using Affymetrix GeneChip Mouse Genome 430 2.0 Arrays. All of the experiments were conducted with male mice 2.5 months old and included 3 mice per experimental group. Synthesis of cRNA, hybridization and scanning of chips were conducted by Duke University microarray core facility (Duke University, Durham, NC).

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Comparison of transcriptomes of LOX-1 KO and WT mice and effects of angiotensin 2

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