SRF and SRFΔ5 Splicing Isoform Recruit Corepressor LSD1/KDM1A Modifying Structural Neuroplasticity and Environmental Stress Response.

Ten to 20% of western countries population suffers from major depression disorder (MDD). Stressful life events represent the main environmental risk factor contributing to the onset of MDD and other stress-related neuropsychiatric disorders. In this regard, investigating brain physiology of stress response underlying the remarkable individual variability in terms of behavioral outcome may uncover stress-vulnerability pathways as a source of candidate targets for conceptually new antidepressant treatments.

Global epigenetic analysis of BDNF Val66Met mice hippocampus reveals changes in dendrite and spine remodeling genes.

Brain-derived neurotrophic factor (BDNF), a neurotrophin highly expressed in the hippocampus, plays crucial roles in cognition, neuroplasticity, synaptic function, and dendritic remodeling. The common human Val66Met polymorphism of BDNF has been implicated in the pathophysiology of neuropsychiatric and neurodegenerative disorders, and in the outcome of pro-adaptive and therapeutic treatments. Altered gene-expression profile has been previously shown in BDNF Val66Met knock-in mice, which recapitulate the phenotypic hallmarks of individuals carrying the BDNF Met allele.

Chronic social defeat stress differentially regulates the expression of transcripts and epigenetic modifying enzymes in susceptible and resilient mice.

Although stress is considered a primary risk factor for neuropsychiatric disorders, a majority of individuals are resilient to the effects of stress exposure and successfully adapt to adverse life events, while others, the so-called susceptible individuals, may have problems to properly adapt to environmental changes. However, the mechanisms underlying these different responses to stress exposure are poorly understood. Adult male C57BL/6J mice were exposed to chronic social defeat stress protocol and levels of brain derived neurotrophic factor () transcripts and epigenetic modifying enzymes were analysed by real-time PCR in the hippocampus (HPC) and prefrontal cortex (PFC) of susceptible and resilient mice.

Brain-Derived Neurotrophic Factor Val66Met Human Polymorphism Impairs the Beneficial Exercise-Induced Neurobiological Changes in Mice.

Several studies have shown that exercise improves cognitive functions and emotional behaviors. Positive effects of exercise have been associated with enhanced brain plasticity, adult hippocampal neurogenesis, and increased levels of brain-derived neurotrophic factor (BDNF). However, a substantial variability of individual response to exercise has been described, which may be accounted for by individual genetic variants.

LSD1 modulates stress-evoked transcription of immediate early genes and emotional behavior.

Behavioral changes in response to stressful stimuli can be controlled via adaptive epigenetic changes in neuronal gene expression. Here we indicate a role for the transcriptional corepressor Lysine-Specific Demethylase 1 (LSD1) and its dominant-negative splicing isoform neuroLSD1, in the modulation of emotional behavior. In mouse hippocampus, we show that LSD1 and neuroLSD1 can interact with transcription factor serum response factor (SRF) and set the chromatin state of SRF-targeted genes early growth response 1 (egr1) and c-fos Deletion or reduction of neuro LSD1 in mutant mice translates into decreased levels of activating histone marks at egr1 and c-fos promoters, dampening their psychosocial stress-induced transcription and resulting in low anxiety-like behavior.

Social Isolation Stress Induces Anxious-Depressive-Like Behavior and Alterations of Neuroplasticity-Related Genes in Adult Male Mice.

Stress is a major risk factor in the onset of several neuropsychiatric disorders including anxiety and depression. Although several studies have shown that social isolation stress during postweaning period induces behavioral and brain molecular changes, the effects of social isolation on behavior during adulthood have been less characterized. Aim of this work was to investigate the relationship between the behavioral alterations and brain molecular changes induced by chronic social isolation stress in adult male mice.

Expression and Dendritic Trafficking of BDNF-6 Splice Variant are Impaired in Knock-In Mice Carrying Human BDNF Val66Met Polymorphism.

Background: The human Val66Met polymorphism in brain-derived neurotrophic factor (BDNF), a key factor in neuroplasticity, synaptic function, and cognition, has been implicated in the pathophysiology of neuropsychiatric and neurodegenerative disorders. BDNF is encoded by multiple transcripts with distinct regulation and localization, but the impact of the Val66Met polymorphism on BDNF regulation remains unclear.

Methods: In BDNF Val66Met knock-in mice, which recapitulate the phenotypic hallmarks of individuals carrying the BDNF(Met) allele, we measured expression levels, epigenetic changes at promoters, and dendritic trafficking of distinct BDNF transcripts using quantitative PCR, chromatin immunoprecipitation (ChIP), and in situ hybridization.

Physical exercise and acute restraint stress differentially modulate hippocampal brain-derived neurotrophic factor transcripts and epigenetic mechanisms in mice.

Physical exercise and stressful experiences have been shown to exert opposite effects on behavioral functions and brain plasticity, partly by involving the action of brain-derived neurotrophic factor (BDNF). Although epigenetic modifications are known to play a pivotal role in the regulation of the different BDNF transcripts, it is poorly understood whether epigenetic mechanisms are also implied in the BDNF modulation induced by physical exercise and stress. Here, we show that total BDNF mRNA levels and BDNF transcripts 1, 2, 3, 4, 6, and 7 were reduced immediately after acute restraint stress (RS) in the hippocampus of mice, and returned to control levels 24 h after the stress session.

Synaptoproteomic analysis of a rat gene-environment model of depression reveals involvement of energy metabolism and cellular remodeling pathways.

Background: Major depression is a severe mental illness that causes heavy social and economic burdens worldwide. A number of studies have shown that interaction between individual genetic vulnerability and environmental risk factors, such as stress, is crucial in psychiatric pathophysiology. In particular, the experience of stressful events in childhood, such as neglect, abuse, or parental loss, was found to increase the risk for development of depression in adult life.

Time-dependent activation of MAPK/Erk1/2 and Akt/GSK3 cascades: modulation by agomelatine.

Background: The novel antidepressant agomelatine, a melatonergic MT1/MT2 agonist combined with 5-HT2c serotonin antagonist properties, showed antidepressant action in preclinical and clinical studies. There is a general agreement that the therapeutic action of antidepressants needs the activation of slow-onset adaptations in downstream signalling pathways finally regulating neuroplasticity. In the last several years, particular attention was given to cAMP-responsive element binding protein (CREB)-related pathways, since it was shown that chronic antidepressants increase CREB phosphorylation and transcriptional activity, through the activation of calcium/calmodulin-dependent (CaM) and mitogen activated protein kinase cascades (MAPK/Erk1/2).

Chronic treatment with agomelatine or venlafaxine reduces depolarization-evoked glutamate release from hippocampal synaptosomes.

Background: Growing compelling evidence from clinical and preclinical studies has demonstrated the primary role of alterations of glutamatergic transmission in cortical and limbic areas in the pathophysiology of mood disorders. Chronic antidepressants have been shown to dampen endogenous glutamate release from rat hippocampal synaptic terminals and to prevent the marked increase of glutamate overflow induced by acute behavioral stress in frontal/prefrontal cortex. Agomelatine, a new antidepressant endowed with MT1/MT2 agonist and 5-HT2C serotonergic antagonist properties, has shown efficacy at both preclinical and clinical levels.

The action of antidepressants on the glutamate system: regulation of glutamate release and glutamate receptors.

Recent compelling evidence has suggested that the glutamate system is a primary mediator of psychiatric pathology and also a target for rapid-acting antidepressants. Clinical research in mood and anxiety disorders has shown alterations in levels, clearance, and metabolism of glutamate and consistent volumetric changes in brain areas where glutamate neurons predominate. In parallel, preclinical studies with rodent stress and depression models have found dendritic remodeling and synaptic spines reduction in corresponding areas, suggesting these as major factors in psychopathology.

Lost in translation. New unexplored avenues for neuropsychopharmacology: epigenetics and microRNAs.

Introduction: Mood and anxiety disorders are among the major causes of disability worldwide. Despite clear need for better therapies, efforts to develop novel drugs have been relatively unsuccessful. One major reason is lack of translation into neuropsychopharmacology of the impressive recent array of knowledge accrued by clinical and preclinical researches on the brain.

ErbB3 mRNA leukocyte levels as a biomarker for major depressive disorder.

Background: In recent years, the identification of peripheral biomarkers that are associated with psychiatric diseases, such as Major Depressive Disorder (MDD), has become relevant because these biomarkers may improve the efficiency of the differential diagnosis process and indicate targets for new antidepressant drugs. Two recent candidate genes, ErbB3 and Fgfr1, are growth factors whose mRNA levels have been found to be altered in the leukocytes of patients that are affected by bipolar disorder in a depressive state. On this basis, the aim of the study was to determine if ErbB3 and Fgfr1 mRNA levels could be a biomarkers of MDD.

Physical exercise and antidepressants enhance BDNF targeting in hippocampal CA3 dendrites: further evidence of a spatial code for BDNF splice variants.

Brain-derived neurotrophic factor (BDNF) is encoded by multiple BDNF transcripts, whose function is unclear. We recently showed that a subset of BDNF transcripts can traffic into distal dendrites in response to electrical activity, while others are segregated into the somatoproximal domains. Physical exercise and antidepressant treatments exert their beneficial effects through upregulation of BDNF, which is required to support survival and differentiation of newborn dentate gyrus (DG) neurons.

Chronic antidepressant treatments induce a time-dependent up-regulation of AMPA receptor subunit protein levels.

Growing evidence suggests a pivotal role for glutamatergic neurotransmission in the pathophysiology of major depressive disorder and in the action of antidepressants. The main aim of this study was to elucidate the temporal profile of α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptors expression and their functional regulation in prefrontal/frontal cortex (P/FC) and hippocampus (HC) of rats chronically treated with two different antidepressants: fluoxetine (FLX) and reboxetine (RBX). Rat groups were treated for 1, 2 or 3 weeks with the two drugs and, in additional groups, the treatments were followed by 1 week of drug washout (3+1).

Antidepressant treatments change 5-HT2C receptor mRNA expression in rat prefrontal/frontal cortex and hippocampus.

Background/aims: Compelling evidence would suggest the involvement of the serotonin 2C receptor in the pathophysiology of affective disorders and in the action of antidepressants. We analyzed the time course of 5-HT2C receptor (5-HTR2C) mRNA expression during antidepressant treatment in the prefrontal/frontal cortex (P/FC) and in the hippocampus (HC) of rats chronically treated with fluoxetine (a selective serotonin reuptake inhibitor) and reboxetine (a selective noradrenaline reuptake inhibitor). We also analyzed the 5-HTR2C RNA-editing levels at the sites called A, B, C, C' and D, which are known to modulate 5-HTR2C receptor function.

Synaptoproteomics of learned helpless rats involve energy metabolism and cellular remodeling pathways in depressive-like behavior and antidepressant response.

Although depression is a severe and life-threatening psychiatric illness, its pathogenesis still is essentially unknown. Recent studies highlighted the influence of environmental stress factors on an individual's genetic predisposition to develop mood disorders. In the present study, we employed a well-validated stress-induced animal model of depression, Learned Helplessness paradigm, in rats.

Expression profiling of a genetic animal model of depression reveals novel molecular pathways underlying depressive-like behaviours.

Background: The Flinders model is a validated genetic rat model of depression that exhibits a number of behavioural, neurochemical and pharmacological features consistent with those observed in human depression.

Principal Findings: In this study we have used genome-wide microarray expression profiling of the hippocampus and prefrontal/frontal cortex of Flinders Depression Sensitive (FSL) and control Flinders Depression Resistant (FRL) lines to understand molecular basis for the differences between the two lines. We profiled two independent cohorts of Flinders animals derived from the same colony six months apart, each cohort statistically powered to allow independent as well as combined analysis.

Early-life stress and antidepressants modulate peripheral biomarkers in a gene-environment rat model of depression.

Background: Availability of peripheral biomarkers for depression could aid diagnosis and help to predict treatment response. The objective of this work was to analyse the peripheral biomarker response in a gene-environment interaction model of depression. Genetically selected Flinders Sensitive Line (FSL) rats were subjected to maternal separation (MS), since early-life trauma is an important antecedent of depression.

Blockade of stress-induced increase of glutamate release in the rat prefrontal/frontal cortex by agomelatine involves synergy between melatonergic and 5-HT2C receptor-dependent pathways.

Background: Agomelatine is a melatonergic receptor agonist and a 5HT2C receptor antagonist that has shown antidepressant efficacy. In order to analyze separately the effect of the two receptorial components, rats were chronically treated with agomelatine, melatonin (endogenous melatonergic agonist), or S32006 (5-HT2C antagonist), and then subjected to acute footshock-stress.

Results: Only chronic agomelatine, but not melatonin or S32006, completely prevented the stress-induced increase of glutamate release in the rat prefrontal/frontal cortex.

Acute stress increases depolarization-evoked glutamate release in the rat prefrontal/frontal cortex: the dampening action of antidepressants.

Background: Behavioral stress is recognized as a main risk factor for neuropsychiatric diseases. Converging evidence suggested that acute stress is associated with increase of excitatory transmission in certain forebrain areas. Aim of this work was to investigate the mechanism whereby acute stress increases glutamate release, and if therapeutic drugs prevent the effect of stress on glutamate release.

Early-life stress and antidepressant treatment involve synaptic signaling and Erk kinases in a gene-environment model of depression.

Stress has been shown to interact with genetic vulnerability in pathogenesis of psychiatric disorders. Here we investigated the outcome of interaction between genetic vulnerability and early-life stress, by employing a rodent model that combines an inherited trait of vulnerability in Flinders Sensitive Line (FSL) rats, with early-life stress (maternal separation). Basal differences in synaptic signaling between FSL rats and their controls were studied, as well as the consequences of early-life stress in adulthood, and their response to chronic antidepressant treatment (escitalopram).

Early induction of CREB activation and CREB-regulating signalling by antidepressants.

Converging evidence points to adaptive changes in neuroplasticity and gene expression as mediators of therapeutic action of antidepressants. Activation of cAMP response-element binding protein (CREB) and CREB-regulating signalling are considered main effectors in these mechanisms. We analysed the temporal profile of intracellular changes induced by antidepressants, by measuring activation of major CREB-regulating signalling cascades and activation (Ser133 phosphorylation) of CREB.

Remodelling by early-life stress of NMDA receptor-dependent synaptic plasticity in a gene-environment rat model of depression.

An animal model of depression combining genetic vulnerability and early-life stress (ELS) was prepared by submitting the Flinders Sensitive Line (FSL) rats to a standard paradigm of maternal separation. We analysed hippocampal synaptic transmission and plasticity in vivo and ionotropic receptors for glutamate in FSL rats, in their controls Flinders Resistant Line (FRL) rats, and in both lines subjected to ELS. A strong inhibition of long-term potentiation (LTP) and lower synaptic expression of NR1 subunit of the NMDA receptor were found in FSL rats.