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Role of the glial glutamate exchanger xCT in ventral hippocampus in resilience to stress

ABSTRACT: We demonstrate that stress differentially regulates glutamate homeostasis in the dorsal and ventral hippocampus and established a previously unknown role for the glial marker xCT in the homeostatic regulation of the ventral dentate gyrus (vDG) in stress resilience and antidepressant responses. We provide RNAseq roadmap for the stress-sensitive vDG and show that the transcription factor REST binds to xCT promoter in co-occupancy with the epigenetic marker H3K27acet, to negatively regulate xCT expression. Reduced xCT was also observed in a genetic mouse model of inherent susceptibility to depression. Pharmacologically modulating histone acetylation with next-generation therapeutics, such as acetyl-N-cysteine (NAC) or acetyl-L-carnitine (LAC), rapidly increased xCT reduction and activated a network that included mGlu2 receptors to prime an enhanced glutamate homeostasis that promoted stress resilience and antidepressant-like responses. Moreover, pharmacological xCT blockage counteracted NAC prophylactic effects. Anatomical (vDG) and cell-type specific (GFAP+) virus-overexpression mimicked the effects of pharmacological treatments in increasing stress resilience. These findings establish xCT as critical regulator of the glutamate system in a network with mGlu2 receptors. These studies also point to a role of histone acetylation as mediator of stress resilience.

ORGANISM(S): Mus musculus

PROVIDER: GSE103435 | GEO | 2017/10/11

SECONDARY ACCESSION(S): PRJNA401858

REPOSITORIES: GEO

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Project description:Background: Examining transcriptional regulation by existing antidepressants in key neural circuits implicated in depression, and understanding the relationship to transcriptional mechanisms of susceptibility and natural resilience, may help in the search for new therapeutics. Further, given the heterogeneity of treatment response in human populations, examining both treatment response and non-response is critical. Methods: We compared the effects of a conventional monoamine-based tricyclic antidepressant, imipramine (14 daily injections), and a rapidly acting, experimental, non-monoamine-based antidepressant, ketamine (single injection), in mice subjected to chronic social defeat stress, a validated model of depression, and used RNA-sequencing to analyze transcriptional profiles associated with susceptibility, resilience and antidepressant response and non-response in prefrontal cortex (PFC), nucleus accumbens, hippocampus, and amygdala. Results: We identified approximately equal numbers of responder and non-responder mice following ketamine or imipramine treatment. Ketamine induced more expression changes in hippocampus than other brain regions; imipramine induced more expression changes in nucleus accumbens and amygdala. Transcriptional profiles in ketamine and imipramine responders were most similar in PFC, where the least transcriptional regulation occurred for each drug. Non-response reflected both the lack of response-associated gene expression changes and unique gene regulation. In responders, both drugs reversed susceptible associated transcriptional changes as well as induced resilient associated transcription in PFC, with effects varying by drug and brain region studied. Conclusions: We generated a uniquely large resource of gene expression data in four inter-connected limbic brain regions implicated in depression and its treatment with imipramine or ketamine. Our analyses highlight the PFC as a key site of common transcriptional regulation by both antidepressant drugs and in both reversing susceptibility and inducing resilience associated molecular adaptations. In addition, we found region-specific effects of each drug suggesting both common and unique effects of imipramine versus ketamine. mRNA profiles of susceptibility to chronic social defeat stress as well as treatment response were generated across 4 separate brain regions, with a sample size of 3-5 per group.

Project description:Although regulation of energy metabolism has been linked with multiple disorders, its role in depression and responsiveness to antidepressants is less-known. We found that an epigenetic and energetic agent, acetyl-L-carnitine (LAC, oral administration), rapidly rescued the depressive- and central and systemic metabolic-like phenotype of LAC-deficient Flinders Sensitive Line (FSL) rats. After acute stress during LAC treatment, a subset of FSL continued to respond to LAC (rFSL), whereas the other subset did not respond (nrFSL). RNAseq for the ventral dentate-gyrus (vDG), a mood-regulatory region, identified metabolic factors as key markers predisposing to depression (insulin receptors Insr, glucose transporters Glut-4 and Glut-12, the regulator of appetite Cartpt) and to LAC responsiveness (leptin receptors Lepr, metabotropic glutamate receptors-2 mGlu2, neuropeptide-Y NPY, and mineralocorticoid receptors MR). Furthermore, we found that stress-induced treatment-resistance in nrFSL shows a new gene profile, including the metabolic regulator factors Elovl7 and Cyb5r2 and the synaptic regulator NPAS4. Finally, while improving central energy regulation and exerting rapid antidepressant-like effects, LAC corrected a systemic hyperinsulinemia and hyperglycemia.tance in rFSL and failed to do that in nrFSL. These findings establish CNS energy regulation as factor to be considered for the development of better therapeutics. Agents, like LAC, which regulate metabolic factors and reduce glutamate overflow, could rapidly ameliorate depression and could also be considered for treatment of insulin-resistance in depressed subjects. The approach here serves as a model for identifying markers and underlying mechanisms of predisposition to diseases and treatment responsiveness that may be useful in translation to human behavior and psychopathology. Ventral dentate gyrus RNA from 3 biological replicates per group (vehicle-FRL, vehicle-FSL, LAC-treated not-responder FSL, LAC-treated responder FSL, all males) was used for library prep (TruSeq Stranded Total RNA with Ribo-Zero Human/Mouse/Rat) and sequenced on Illumina HiSeq2500 at the Genomic Core facility at The Rockefeller University. Each sample was provided with a unique adapter and all samples were put in the same pool and run in multiple lanes to control for lane effects with a sequencing depth of about 30M (100bp, single).

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Role of the glial glutamate exchanger xCT in ventral hippocampus in resilience to stress

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