Metabolomics,Unknown,Transcriptomics,Genomics,Proteomics

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Transcription profiling of mouse hippocampus after chronic fluoxetine treatment

ABSTRACT: Both the mechanism of action and the factors determining the behavioral response to antidepressants are unknown. It has been shown that antidepressant treatment promotes the proliferation and survival of hippocampal neurons via enhanced serotonergic signaling, but it is still unclear whether hippocampal neurogenesis is responsible for the behavioral response to antidepressants. Furthermore, a large subpopulation of patients fails to respond to antidepressant treatment due to presumed underlying genetic factors. In the present study, we have used the phenotypic and genotypic variability of inbred mouse strains to show that there is a genetic component to both the behavioral and neurogenic effects of chronic fluoxetine treatment, and that this antidepressant induces an increase in hippocampal cell proliferation only in the strains that also show a positive behavioral response to treatment. The behavioral and neurogenic responses are associated with an upregulation of genes known to promote neuronal proliferation and survival. These results suggest that inherent genetic predisposition to increased serotonin-induced neurogenesis is a determinant of antidepressant efficacy. Experiment Overall Design: Male DBA/2J, age 3-5 weeks, were obtained from The Jackson Laboratory (Bar Harbor, ME) and maintained on a 12:12 light:dark cycle with lights on at 0700 hours. Following at least one week of acclimation, mice were provided with either untreated or fluoxetine-treated drinking water, available ad libitum. Fluoxetine-HCl was obtained from Spectrum Chemicals (Gardena, CA). Differences in daily water consumption were previously determined by measuring water intake for three weeks from at least 12 mice (6.4 mL (+/- .58 mL) per day). We also determined the average weight at 10 weeks of age (25.5 g +/- 1.4 g), and used this information to dilute fluoxetine in the water in order to provide a daily dosage of 0 or 18 mg/kg/mouse. Experiment Overall Design: Mice were 8-12 weeks of age at the time of behavioral testing, which was performed during the light phase between 1300h and 1600h. Behavioral despair was measured using a mouse Tail Suspension apparatus from Med Associates (Georgia, VT). Experiment Overall Design: Individual bilateral hippocampii from 21-day-treatment 0 and 18 mg/kg/day DBA/2J mice were homogenized in 500 Âµl TRIzol using a QIAgen Tissuelyser (15 minutes at 30 Hz, QIAgen, Chatsworth, CA). RNA was extracted by phenol-chloroform phase separation and further processed using the RNAeasy miniprep kit (QIAgen). For each treatment group of 12 animals, separate RNA pools were made using hippocampal RNA from 6 mice per pool. These biological replicates were processed separately through the entirety of the microarray procedure. Five Âµg of total RNA from each pool was used as a template to synthesize complementary DNA (cDNA) and biotinylated cRNA (Enzo kit, Affymetrix, Santa Clara, CA) using standard Affymetrix protocols. cRNA was hybridized to Affymetrix GeneChip Mouse Genome 430 2.0 Array. Data were analyzed using ArrayAssist software (Stratagene, La Jolla, CA) and normalized with the GCRMA algorithm. A probeset had to obtain a minimal intensity value 100 to be considered as detecting expression above background. Therefore, any probeset that failed to meet this cutoff was removed from the analysis. Ratios of intensity differences were generated and genes showing at least a two-fold difference between experimental conditions were identified for further analysis.

ORGANISM(S): Mus musculus

SUBMITTER: Mathew Pletcher

PROVIDER: E-GEOD-6476 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Publications

Genetic regulation of behavioral and neuronal responses to fluoxetine.

Miller Brooke H BH Schultz Laura E LE Gulati Anisha A Cameron Michael D MD Pletcher Mathew T MT

Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology 20070704 6

Despite widespread use of antidepressants, the factors underlying the behavioral response to antidepressants are unknown. It has been shown that antidepressant treatment promotes the proliferation and survival of neurons in the adult hippocampus via enhanced serotonergic signaling, but it is unclear whether hippocampal neurogenesis is responsible for the behavioral response to antidepressants. Furthermore, a large subpopulation of patients fails to respond to antidepressant treatment due to pres ...[more]

PMID: 17609676

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Project description:Adult Neurogenesis and Gene Expression Changes in 5-HT7 Receptor Knockout Mice: In the adult, the formation of new nerve cells in the CNS is restricted to the subependymal layer and to the subgranular zone of the hippocampus (Duman et al., 2001). Clinically adult neurogenesis has received most attention for its possible role in major depression. Depressed patients have reduced hippocampal neurogenesis (Kasper & McEwen, 2008) and hippocampal volume (Colla et al., 2007). It has also been shown that chronic, but not acute, treatment with currently widely used antidepressants, most notably fluoxetine, results in increased hippocampal neurogenesis (Malberg et al., 2000; Miller et al., 2007). Pharmacologically antidepressants act by elevating the amount of synaptic serotonin (5-HT) and they do that within minutes of administration, but the clinical effect is often delayed, sometimes for weeks (Miller et al., 2007). This delay is believed to involve changes in plasticity and neurogenesis. With currently available treatment options for depression 20% or more of patients do not respond to the therapy. Thus, there is a need for an increased understanding of the mechanism behind plasticity and neurogenesis, and for the development of improved therapies for depression. We have in an ongoing project with the aim to functionally characterize the 5-HT7 receptor, one of the most recently discovered receptor subtypes for 5-HT (Lovenberg et al., 1993). Interestingly, we have found that this receptor might be a new target for the treatment of depression. Inactivation or pharmacological blockade of this receptor induces an antidepressant-like profile in several preclinical models of depression (Hedlund et al., 2005; Guscott et al., 2005; Wesolowska et al., 2006a, 2006b) and in sleep patterns (Thomas et al., 2003; Hedlund et al., 2005). Of special interest is also the finding that inhibition of the 5-HT7 receptor potentiates the effect of antidepressants in behavioral models of depression (Wesolowska et al., 2007; Bonaventure et al., 2007). We have recently determined that mice lacking lacking the 5-HT7 receptor show a 25% decrease in the number of proliferating cells in the subgranular zone of the hippocampus compared to wildtype mice. The mice were treated with BrdU, a thymidine analog that is incorporated into the DNA of cells undergoing mitosis. BrdU was then detected immunohistochemically. Both wildtype and knockout mice responded to fluoxetine treatment with an increase in the number of dividing cells. The reduction in the number of dividing cells in the 5-HT7 receptor knockout mice seemingly contradicts the antidepressant-like profile previously observed in these mice, but might on the other hand help to explain previously observed impairments in hippocampus-dependent learning seen in the knockout mice (Roberts et al., 2004) and after pharmacological blockade (Meneses, 2004). The observation that 5-HT7 receptors influence neurogenesis constitutes an entirely new regulatory mechanism for this physiologically and pathophysiologically important process. In order to further understand hippocampal neurogenesis and how it is influenced by 5-HT in general and 5-HT7 receptors in particular we propose to perform a microarray study using the glycogene array designed by the Consortium for Functional Glycomics using total RNA from the hippocampus. A comparison will be made between young adult male mice lacking the 5-HT7 receptor and wildtype sibling controls. Such a study should yield new valuable insights into the pathways regulating neurogenesis. The glycogene array is of particular interest as it includes several genes that have been shown to be either directly or indirectly involved in adult neurogenesis and to be regulated by 5-HT and antidepressants. Of particular interest are cell adhesion molecules which are glycoproteins. One such molecule is NCAM, a marker for immature neurons undergoing remodeling and plasticity (Nakagawa et al., 2002), which is upregulated by fluoxetine treatment (Varea et al., 2006). In contrast, NCAM is downregulated following 5-HT depletion (Brezun & Daszuta, 1999). Chronic fluoxetine treatment has also been shown to upregulate neuropeptide Y, Galectin I, Activin A receptor and Inhibin beta-A, all included in the glycogene array (Miller et al., 2007). Another relevant gene on the glycogene chip is ST8SiaIV (Nakagawa et al., 2002). Experimental Design: The hippocampus will be dissected and total RNA will be extracted according to recommended protocols for array studies. RNA from a sufficient number (2-3 animals) of male 5-HT7 receptor knockout mice will be pooled for each of the three replicates. Control samples will be similarly generated from wildtype siblings. The 5-HT7 receptor mice are on a genetically homogeneous background (backcrossed for 16 generation on a C57BL6/J background) so inter-animal variability should be negligible. The RNA will be analyzed on the glycogene array. 3 KO replicates + 3 WT replicates per glycogene array = 6 arrays

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Project description:Major depression is a multidimensional disorder highly prevalent in modern society. Although several classes of antidepressants (ADs) are currently available to treat depression, the effectiveness of treatment is still limited, as many patients do not show full remission; thus, there is a need to find better patients’ directed therapeutic strategies. Neuroplastic changes in several brain regions, namely in the hippocampal dentate gyrus (DG), are amongst the best correlates of depression and of ADs actions. In this study the targets and molecular mediators of chronic stress and of four ADs from different pharmacological classes (fluoxetine, imipramine, tianeptine and agomelatine) were investigated in the DG. Using the unpredictable chronic mild stress (uCMS) animal model of depression, the molecular commonalities and specificities of the ADs were determined. All ADs, except agomelatine, could reverse the behavioral deficits produced by uCMS, and the neuroplastic changes in the DG; agomelatine reversed only the anhedonic profile in the sucrose consumption test. Chronic stress induced mild but relevant molecular changes that were mostly reversed by fluoxetine, imipramine and tianeptine. Fluoxetine reduced pro-inflammatory response and increased cell metabolism pathways. Its actions were mostly dependent on molecular changes occurring in neurons. Similarities were found between imipramine and tianeptine molecular actions and targets, as both activated pathways related to cellular protection. Moreover, no particular neural cell type enrichment was found with both treatments. Agomelatine presented a very dissimilar molecular pattern impacting greatly on Rho-GTPases-related pathways in oligodendrocytes and neurons. The recognition of these molecular alterations contributes to the understanding of the processes implicated in the onset and treatment of depression and may pave the way for more effective therapeutic interventions. We compared gene expresssion in the dentate gyros of rats which were either untreated, exposed to unpredictable chronic mild stress, or exposed to the same stress and treated with either fluoxetine, imipramine, tianeptine, or agomelatine

Dataset Information

Transcription profiling of mouse hippocampus after chronic fluoxetine treatment

Publications

Genetic regulation of behavioral and neuronal responses to fluoxetine.

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