Gene expression patterns in the hippocampus and amygdala of endogenous depression and chronic stress models

Bioenergetic-related gene expression in the hippocampus predicts internalizing vs. externalizing behavior in an animal model of temperament

Externalizing and internalizing behavioral tendencies underlie many psychiatric and substance use disorders. These tendencies are associated with differences in temperament that emerge early in development via the interplay of genetic and environmental factors. To better understand the neurobiology of temperament, we have selectively bred rats for generations to produce two lines with highly divergent behavior: bred Low Responders (bLRs) are highly inhibited and anxious in novel environments, whereas bred High Responders (bHRs) are highly exploratory, sensation-seeking, and prone to drug-seeking behavior. Recently, we delineated these heritable differences by intercrossing bHRs and bLRs (F0-F1-F2) to produce a heterogeneous F2 sample with well-characterized lineage and behavior (exploratory locomotion, anxiety-like behavior, Pavlovian conditioning). The identified genetic loci encompassed variants that could influence behavior via many mechanisms, including proximal effects on gene expression. Here we measured gene expression in male and female F0s (n = 12 bHRs, 12 bLRs) and in a large sample of heterogeneous F2s (n = 250) using hippocampal RNA-Seq. This enabled triangulation of behavior with both genetic and functional genomic data to implicate specific genes and biological pathways. Our results show that bHR/bLR differential gene expression is robust, surpassing sex differences in expression, and predicts expression associated with F2 behavior. In F0 and F2 samples, gene sets related to growth/proliferation are upregulated with bHR-like behavior, whereas gene sets related to mitochondrial function, oxidative stress, and microglial activation are upregulated with bLR-like behavior. Integrating our F2 RNA-Seq data with previously-collected whole genome sequencing data identified genes with hippocampal expression correlated with proximal genetic variation (cis-expression quantitative trait loci or cis-eQTLs). These cis-eQTLs successfully predict bHR/bLR differential gene expression based on F0 genotype. Sixteen of these genes are associated with cis-eQTLs colocalized within loci we previously linked to behavior and are strong candidates for mediating the influence of genetic variation on behavioral temperament. Eight of these genes are related to bioenergetics. Convergence between our study and others targeting similar behavioral traits revealed five more genes consistently related to temperament. Overall, our results implicate hippocampal bioenergetic regulation of oxidative stress, microglial activation, and growth-related processes in shaping behavioral temperament, thereby modulating vulnerability to psychiatric and addictive disorders.

Depletion of the paternal gut microbiome alters sperm small RNAs and impacts offspring physiology and behavior in mice

The paternal environment prior to conception has been demonstrated to influence offspring physiology and behavior, with the sperm epigenome (including noncoding RNAs) proposed as a potential facilitator of non-genetic inheritance. Whilst the maternal gut microbiome has been established as an important influence on offspring development, the impact of the paternal gut microbiome on offspring development, health and behavior is largely unknown. Gut microbiota have major influences on immunity, and thus we hypothesized that they may be relevant to paternal immune activation (PIA) modulating epigenetic inheritance in mice. Therefore, male C57BL/6J mice (F0) were orally administered non-absorbable antibiotics via drinking water in order to substantially deplete their gut microbiome. Four weeks after administration of the antibiotics (gut microbiome depletion), F0 male mice were then mated with naïve female mice. The F1 offspring of the microbiome-depleted males had reduced body weight as well as altered gut morphology (shortened colon length). F1 females showed significant alterations in affective behaviors, including measures of anxiety and depressive-like behaviors, indicating altered development. Analysis of small noncoding RNAs in the sperm of F0 mice revealed that gut microbiome depletion is associated with differential expression of 8 different PIWI-interacting RNAs (piRNAs), each of which has the potential to modulate the expression of multiple downstream gene targets, and thus influence epigenetic inheritance and offspring development. This study demonstrates that the gut-germline axis influences sperm small RNA profiles and offspring physiology, with specific impacts on offspring affective and/or coping behaviors. These findings may have broader implications for other animal species with comparable gut microbiota, intergenerational epigenetics and developmental biology, including humans.

Female Wistar Kyoto More Immobile rats with genetic stress hyper-reactivity show enhanced contextual fear memory without deficit in extinction of fear

The prevalence of post-traumatic stress disorder (PTSD) is higher in females than males, but pre-clinical models are established almost exclusively in males. This study is aimed to investigate the stress-enhanced fear learning model of PTSD in females. The model mirrors PTSD symptomology in males, whereby prior stress leads to extinction resistant exaggerated contextual fear memory. As stress reactivity is highly relevant to the study and risk for PTSD, females of the stress hyper-reactive Wistar Kyoto More Immobile (WMI) and its nearly isogenic control the Wistar Kyoto Less Immobile (WLI) strains were employed. Prior studies have shown WMI females presenting unchanged or enhanced fear memory in the stress-enhanced fear learning paradigm compared WLIs. The present study confirmed the enhanced fear memory following contextual fear conditioning in WMIs compared to WLI females, but this increased fear memory was neither exaggerated by prior stress nor showed extinction deficit. The novel stressor of a glucose challenge test resulted in subtle strain- and prior stress-induced differences in plasma glucose responses. However, fasting plasma corticosterone levels were lower, and rose slower in response to glucose challenge in WMI females, suggesting a PTSD-like dysfunctional stress response. Hippocampal expressions of genes relevant to both learning and memory and the stress response were decreased in stressed WMIs compared to WLI females, further suggesting a marked dysregulation in stress-related functions like in PTSD. Thus, although WMI females do not show extinction-resistant enhanced fear memory, they do present other characteristics that are relevant to PTSD in women.

Resource: A curated database of brain-related functional gene sets (Brain.GMT)

Transcriptional profiling has become a common tool for investigating the nervous system. During analysis, differential expression results are often compared to functional ontology databases, which contain curated gene sets representing well-studied pathways. This dependence can cause neuroscience studies to be interpreted in terms of functional pathways documented in better studied tissues (e.g., liver) and topics (e.g., cancer), and systematically emphasizes well-studied genes, leaving other findings in the obscurity of the brain "ignorome". To address this issue, we compiled a curated database of 918 gene sets related to nervous system function, tissue, and cell types ("Brain.GMT") that can be used within common analysis pipelines (GSEA, limma, edgeR) to interpret results from three species (rat, mouse, human). Brain.GMT includes brain-related gene sets curated from the Molecular Signatures Database (MSigDB) and extracted from public databases (GeneWeaver, Gemma, DropViz, BrainInABlender, HippoSeq) and published studies containing differential expression results. Although Brain.GMT is still undergoing development and currently only represents a fraction of available brain gene sets, "brain ignorome" genes are already better represented than in traditional Gene Ontology databases. Moreover, Brain.GMT substantially improves the quantity and quality of gene sets identified as enriched with differential expression in neuroscience studies, enhancing interpretation. •We compiled a curated database of 918 gene sets related to nervous system function, tissue, and cell types ("Brain.GMT").•Brain.GMT can be used within common analysis pipelines (GSEA, limma, edgeR) to interpret neuroscience transcriptional profiling results from three species (rat, mouse, human).•Although Brain.GMT is still undergoing development, it substantially improved the interpretation of differential expression results within our initial use cases.

Transcriptomics and psychotherapy: An integrative review

Gold-standard psychotherapies like cognitive-behavioral therapy (CBT) show beneficial effects, but patient responses vary, indicating a need to predict and optimize treatment efficacy. Gene expression analysis may offer insights into the interplay between psychosocial processes and biological factors that impact psychopathology and therapeutic response. This integrative review examines 17 studies that assess gene expression in the context of psychotherapy, highlighting innovative frameworks for incorporating gene expression analysis in diagnosis, predicting treatment response, and monitoring treatment progress. Current evidence points to transcriptional control pathways downstream of the hypothalamic-pituitary-adrenal (HPA)-axis and sympathetic nervous system (SNS) signaling pathways, particularly their effects on immune cells (e.g., pro-inflammatory processes and wound healing), as key areas for future research. Higher-level pathway analyses, whether theory-based or empirically driven, appear to offer the most robust framework for future studies. This review also discusses significant limitations of current literature and proposes directions for future research.

Stress enhances aggression in male rats with genetic stress hyper-reactivity

The current study investigated stress-induced aggressive behavior in the resident-intruder test in males of the genetically stress hyper-reactive Wistar Kyoto More Immobile (WMI), and the nearly isogenic, control Wistar Kyoto Less Immobile (WLI) strains. Tests were carried out against same-age intruders during adolescence, and same-age and juvenile intruders in adulthood. In adolescence and adulthood, prior acute restraint stress decreased social interactions and decreased aggressive behaviors of adolescents and adult WLIs. However, prior stress precipitated aggression in the adult WMI males toward both same-age, and juvenile intruders compared with control WMIs and WLIs. Trunk blood levels of testosterone and androstenedione increased in stressed WLIs, but not in WMIs, suggesting no direct role of androgens in the increased aggression of WMIs. Expressions of aggression-relevant genes showed patterns commensurate with being causative in aggressive behavior. The methyl-CpG binding protein 2 was lower in the frontal cortex of control WMIs, and in the amygdala of stressed WMIs compared with their respective WLIs. Frontal cortex expression of vasopressin receptor 1a and serotonin transporter increased, solely in WMI males after stress. As behaviors were the same toward same-age and non-threatening juvenile intruders, the stress-induced increase in confrontational behavior of the adult WMI male was not because of enhanced fear or anxiety. These results suggest that genetic stress hyper-reactivity is a risk factor for stress-induced increases in aggression in males. Additionally, as known aggression-related genes showed expression patterns paralleling aggressive behavior, this model system could identify novel molecular pathways leading to stress-enhanced aggression.

Unraveling psilocybin's therapeutic potential: behavioral and neuroplasticity insights in Wistar-Kyoto and Wistar male rat models of treatment-resistant depression

RATIONALE

Our study aimed to unravel the unknown mechanisms behind the exceptional efficacy of Psilocybin (PSI) in treating treatment-resistant depression (TRD). Focusing on Wistar-Kyoto (WKY) rats with a TRD phenotype and Wistar (WIS) rats as a normative comparison, we investigated behavioral and neuroplasticity-related responses to PSI, striving to shed light on the distinctive features of its antidepressant effects.

OBJECTIVES

We set out to assess the behavioral impact of acute and prolonged PSI administration on WKY and WIS rats, employing Novel Object Recognition (NORT), Social Interaction (SI), and Forced Swimming Test (FST). Our secondary objectives involved exploring strain-specific alterations in neuroplasticity-related parameters, including brain-derived neurotrophic factor (BDNF) and activity-regulated cytoskeleton-associated protein (Arc).

METHODS

Conducting post-acute and extended assessments after a single PSI administration, we applied behavioral tests and biochemical analyses to measure serum BDNF levels and neuroplasticity-related parameters in the prefrontal cortex. Statistical analyses were deployed to discern significant differences between the rat strains and assess the impact of PSI on behavioral and biochemical outcomes.

RESULTS

Our findings uncovered significant behavioral disparities between WKY and WIS rats, indicating passive behavior and social withdrawal in the former. PSI demonstrated pronounced pro-social and antidepressant effects in both strains, each with its distinctive temporal trajectory. Notably, we identified strain-specific variations in BDNF-related signaling and observed the modulation of Arc expression in WKY rats.

CONCLUSIONS

Our study delineated mood-related behavioral nuances between WKY and WIS rat strains, underscoring the antidepressant and pro-social properties of PSI in both groups. The distinct temporal patterns of observed changes and the identified strain-specific neuroplasticity alterations provide valuable insights into the TRD phenotype and the mechanisms underpinning the efficacy of PSI.

Resource: A Curated Database of Brain-Related Functional Gene Sets (Brain.GMT)

Transcriptional profiling has become a common tool for investigating the nervous system. During analysis, differential expression results are often compared to functional ontology databases, which contain curated gene sets representing well-studied pathways. This dependence can cause neuroscience studies to be interpreted in terms of functional pathways documented in better studied tissues (e.g., liver) and topics (e.g., cancer), and systematically emphasizes well-studied genes, leaving other findings in the obscurity of the brain "ignorome". To address this issue, we compiled a curated database of 918 gene sets related to nervous system function, tissue, and cell types ("Brain.GMT") that can be used within common analysis pipelines (GSEA, limma, edgeR) to interpret results from three species (rat, mouse, human). Brain.GMT includes brain-related gene sets curated from the Molecular Signatures Database (MSigDB) and extracted from public databases (GeneWeaver, Gemma, DropViz, BrainInABlender, HippoSeq) and published studies containing differential expression results. Although Brain.GMT is still undergoing development and currently only represents a fraction of available brain gene sets, "brain ignorome" genes are already better represented than in traditional Gene Ontology databases. Moreover, Brain.GMT substantially improves the quantity and quality of gene sets identified as enriched with differential expression in neuroscience studies, enhancing interpretation.

Limited WKY chromosomal regions confer increases in anxiety and fear memory in a F344 congenic rat strain

This study investigated the interaction between genetic differences in stress reactivity/coping and environmental challenges, such as acute stress during adolescence on adult contextual fear memory and anxiety-like behaviors. Fischer 344 (F344) and the inbred F344;WKY-Stresp3/Eer congenic strain (congenic), in which chromosomal regions from the Wistar-Kyoto (WKY) strain were introgressed into the F344 background, were exposed to a modified forced swim test during adolescence, while controls were undisturbed. In adulthood, fear learning and memory, assessed by contextual fear conditioning, were significantly greater in congenic animals compared with F344 animals, and stress during adolescence increased them even further in males of both strains. Anxiety-like behavior, measured by the open field test, was also greater in congenic than F344 animals, and stress during adolescence increased it further in both strains of adult males. Whole genome sequencing of the F344;WKY-Stresp3/Eer strain revealed an enrichment of WKY genotypes in chromosomes 9, 14, and 15. An example of functional WKY sequence variations in the congenic strain, cannabinoid receptor interacting protein 1 (Cnrip1) had a Cnrip1 transcript isoform that lacked two exons. Although the original hypothesis that the genetic predisposition to increased anxiety of the WKY donor strain would exaggerate fear memory relative to the background strain was confirmed, the consequences of adolescent stress were strain independent but sex dependent in adulthood. Molecular genomic approaches combined with genetic mapping of WKY sequence variations in chromosomes 9, 14, and 15 could aid in finding quantitative trait genes contributing to the variation in fear memory.NEW & NOTEWORTHY This study found that 1) whole genome sequencing of congenic strains should be a criterion for their recognition; 2) sequence variations between Wistar-Kyoto and Fischer 344 strains at regions of chromosomes 9, 14, and 15 contribute to differences in contextual fear memory and anxiety-like behaviors; and 3) stress during adolescence affects these behaviors in males, but not females, and is independent of strain.

Interventionism and Intelligibility: Why Depression Is Not (Always) a Brain Disease

Major depressive disorder (MDD) is a serious condition with a large disease burden. It is often claimed that MDD is a "brain disease." What would it mean for MDD to be a brain disease? I argue that the best interpretation of this claim is as offering a substantive empirical hypothesis about the causes of the syndrome of depression. This syndrome-causal conception of disease, combined with the idea that MDD is a disease of the brain, commits the brain disease conception of MDD to the claim that brain dysfunction causes the symptoms of MDD. I argue that this consequence of the brain disease conception of MDD is false. It incorrectly rules out genuine instances of content-sensitive causation between adverse conditions in the world and the characteristic symptoms of MDD. Empirical evidence shows that the major causes of depression are genuinely psychological causes of the symptoms of MDD. This rules out, in many cases, the "brute" causation required by the brain disease conception. The existence of cases of MDD with non-brute causes supports the reinstatement of the old nosological distinction between endogenous and exogenous depression.

Paternal immune activation by Poly I:C modulates sperm noncoding RNA profiles and causes transgenerational changes in offspring behavior

Paternal pre-conceptual environmental experiences, such as stress and diet, can affect offspring brain and behavioral phenotypes via epigenetic modifications in sperm. Furthermore, maternal immune activation due to infection during gestation can reprogram offspring behavior and brain functioning in adulthood. However, the effects of paternal pre-conceptual exposure to immune activation on the behavior and physiology of offspring (F1) and grand-offspring (F2) are not currently known. We explored effects of paternal pre-conceptual exposure to viral-like immune activation on F1 and F2 behavioral and physiological phenotypes using a C57BL/6J mouse model. Males were treated with a single injection (intraperitoneal) of the viral mimetic polyinosinic:polycytidylic acid (Poly I:C: 12 mg/kg) then bred with naïve female mice four weeks after the Poly I:C (or 0.9% saline control) injection. The F1 offspring of Poly I:C treated fathers displayed increased depression-like behavior in the Porsolt swim test, an altered stress response in the novelty-suppressed feeding test, and significant transcriptomic changes in their hippocampus. Additionally, the F1 male offspring of Poly I:C treated F0 males showed significantly increased immune responsivity after a Poly I:C immune challenge (12 mg/kg). Furthermore, the F2 male grand-offspring took longer to enter and travelled significantly shorter distances in the light zone of the light/dark box. An analysis of the small noncoding RNA profiles in sperm from Poly I:C treated males and their male offspring revealed significant effects of Poly I:C on the sperm microRNA content at the time of conception and on the sperm PIWI-interacting RNA content of the male offspring. Notably, eight miRNAs with an FDR < 0.05 (miR-141-3p, miR-126b-5p, miR-669o-5p, miR-10b-3p, miR-471-5p, miR-463-5p, miR-148b-3p, and miR-181c-5p) were found to be significantly downregulated in the sperm of Poly I:C treated males. Collectively, we demonstrate that paternal pre-conceptual exposure to a viral immune challenge results in both intergenerational and transgenerational effects on brain and behavior that may be mediated by alterations in the sperm small noncoding RNA content.

AKT and MAPK signaling pathways in hippocampus reveals the pathogenesis of depression in four stress-induced models

Major depressive disorder (MDD) is a highly heterogeneous psychiatric disorder. The pathogenesis of MDD remained unclear, and it may be associated with exposure to different stressors. Most previous studies have focused on molecular changes in a single stress-induced depression model, which limited the identification of the pathogenesis of MDD. The depressive-like behaviors were induced by four well-validated stress models in rats, including chronic unpredictable mild stress, learned helplessness stress, chronic restraint stress and social defeat stress. We applied proteomic and metabolomic to investigate molecular changes in the hippocampus of those four models and revealed 529 proteins and 98 metabolites. Ingenuity Pathways Analysis (IPA) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis identified differentially regulated canonical pathways, and then we presented a schematic model that simulates AKT and MAPK signaling pathways network and their interactions and revealed the cascade reactions. Further, the western blot confirmed that p-AKT, p-ERK12, GluA1, p-MEK1, p-MEK2, p-P38, Syn1, and TrkB, which were changed in at least one depression model. Importantly, p-AKT, p-ERK12, p-MEK1 and p-P38 were identified as common alterations in four depression models. The molecular level changes caused by different stressors may be dramatically different, and even opposite, between four depression models. However, the different molecular alterations converge on a common AKT and MAPK molecular pathway. Further studies of these pathways could contribute to a better understanding of the pathogenesis of depression, with the ultimate goal of helping to develop or select more effective treatment strategies for MDD.

Aberrant Histone Modification of TNFAIP3, TLR4, TNIP2, miR-146a, and miR-155 in Major Depressive Disorder

Activated toll-like receptor (TLR) signaling has been well investigated in major depressive disorder (MDD). We previously reported that TNFAIP3, TLR4, TNIP2, miR-146a, and miR-155 play important roles in regulating the toll-like receptor 4 (TLR4) signaling pathway and may serve as novel targets in the pathogenesis of MDD. Recently, aberrant histone modification has been implicated in several psychiatric disorders, including schizophrenia and mood disorder; the most thoroughly studied modification is histone 3 lysine 4 tri-methylation (H3K4me3). In this work, we aimed to explore H3K4me3 differences in the promotors of genes encoding the abovementioned factors in patients with MDD, and whether they were altered after antidepressant treatment. A total of 30 MDD patients and 28 healthy controls were recruited. Peripheral blood mononuclear cells (PBMCs) were collected. The levels of H3K4me3 in the promoters of TNFAIP3, TLR4, TNIP2, miR-146a, and miR-155 were measured through chromatin immunoprecipitation (ChIP) followed by DNA methylation assay. Analysis of covariance was used to evaluate between-group differences after adjusting for age, sex, BMI, and smoking. In comparison with healthy controls, patients with MDD showed significantly lower H3K4me3 levels in the promoters of TNFAIP3, TLR4, TNIP2, miR-146a, and miR-155 in PBMCs. These levels were not significantly altered after completion of a 4-week antidepressant treatment. To explore the association between depression severity and H3K4me3 levels, a multiple linear regression model was generated. The results revealed that levels of H3K4me3 in the TNIP2 promoters a negative correlation with the 17-item Hamilton Depression Rating Scale (HAND-17) score, whereas that of TLR4 had a positive correlation with this score. The present results suggest that decreased H3K4me3 levels in the promoters of the genes encoding TNFAIP3, TLR4, miR-146a, miR-155, and TNIP2 are involved in psychopathology of major depressive disorder.

Structural changes and neurotrophic factors upregulation in submandibular gland in a rat model of depression: proposed correlation with stress indicators during and after the relief of depression

This study evaluated the structural changes, the immunohistochemical and gene expression of neurotrophic factors in submandibular gland in a rat model of depression, and their correlation with depression parameters during and after relief of depression by voluntary running. Forty-eight male Wistar rats were divided into control, control-exercise, depression, and depression-exercise groups. Depression was induced using forced swimming protocol, while the relief of depression was induced using the rat voluntary running wheels. The depressive state of rats was evaluated by measuring the immobility duration and the serum corticosterone level. The immune expression was evaluated by measuring the optical densities (ODs) using ImageJ software, and the gene expression levels were investigated. In the depression group, the convoluted ducts appeared dilated with numerous secretory granules. The number of PCNA-stained cells was significantly decreased in the depression group as compared to control group and then significantly increased in the depression-exercise group when compared to the depression group with a negative correlation to stress indicator. The ODs of immuno-expression for the brain-derived neurotrophic factor (BDNF) and vascular endothelial growth factor (VEGF) increased significantly in the depression group as compared to control group. Both BDNF and VEGF immuno-expression displayed positive correlation with the stress indicators. Both BDNF and VEGF gene expression results confirmed their immunohistochemical results. The findings of this study explored the role of submandibular gland in secreting neurotrophic factors and raise a flag for the possibility of using salivary secretions as dependable and easy parameter for estimation of chronic stressed patients.Mini AbstractThe submandibular gland neurotrophic factors immuno-expression can be used in estimating chronic depressive disorders as they are correlated with stress indicators during and after the relief of depression.

Role of neurotrophic and growth factors in the rapid and sustained antidepressant actions of ketamine

The neurotrophic hypothesis of depression proposes that reduced levels of brain-derived neurotrophic factor (BDNF) and vascular endothelial growth factor (VEGF) contribute to neuronal atrophy or loss in the prefrontal cortex (PFC) and hippocampus and impaired hippocampal adult neurogenesis, which are associated with depressive symptoms. Chronic, but acute, treatment with typical monoaminergic antidepressants can at least partially reverse these deficits, in part via induction of BDNF and/or VEGF expression, consistent with their delayed onset of action. Ketamine, an N-methyl-d-aspartate receptor antagonist, exerts rapid and sustained antidepressant effects. Rodent studies have revealed that ketamine rapidly increases BDNF and VEGF release and/or expression in the PFC and hippocampus, which in turn increases the number and function of spine synapses in the PFC and hippocampal neurogenesis. Ketamine also induces the persistent release of insulin-like growth factor 1 (IGF-1) in the PFC of male mice. These neurotrophic effects of ketamine are associated with its rapid and sustained antidepressant effects. In this review, we first provide an overview of the neurotrophic hypothesis of depression and then discuss the role of BDNF, VEGF, IGF-1, and other growth factors (IGF-2 and transforming growth factor-β1) in the antidepressant effects of ketamine and its enantiomers. This article is part of the Special Issue on 'Ketamine and its Metabolites'.

Current State of Modeling Human Psychiatric Disorders Using Zebrafish

Psychiatric disorders are highly prevalent brain pathologies that represent an urgent, unmet biomedical problem. Since reliable clinical diagnoses are essential for the treatment of psychiatric disorders, their animal models with robust, relevant behavioral and physiological endpoints become necessary. Zebrafish (Danio rerio) display well-defined, complex behaviors in major neurobehavioral domains which are evolutionarily conserved and strikingly parallel to those seen in rodents and humans. Although zebrafish are increasingly often used to model psychiatric disorders, there are also multiple challenges with such models as well. The field may therefore benefit from a balanced, disease-oriented discussion that considers the clinical prevalence, the pathological complexity, and societal importance of the disorders in question, and the extent of its detalization in zebrafish central nervous system (CNS) studies. Here, we critically discuss the use of zebrafish for modeling human psychiatric disorders in general, and highlight the topics for further in-depth consideration, in order to foster and (re)focus translational biological neuroscience research utilizing zebrafish. Recent developments in molecular biology research utilizing this model species have also been summarized here, collectively calling for a wider use of zebrafish in translational CNS disease modeling.

Chronic restraint stress-induced depression-like behavior is mediated by upregulation of melanopsin expression in C57BL/6 mice retina

BACKGROUND

Depression is associated with circadian disturbances in which melanopsin was a key mechanism. Further studies have demonstrated that melanopsin gene variations are associated with some depressive disorders and aberrant light can impair mood through melanopsin-expressing retinal ganglion cells (mRGCs). The goal of this study was to explore the direct relationship between depression and melanopsin.

METHODS

Adult C57BL/6 male mice were physically restrained for 16 h in a 50-ml polypropylene centrifuge tube and all behavioral tests were performed after CRS treatment. Western blot analysis and immunofluorescence were used to detect melanopsin expression in the retina of C57BL/6 mice. And we observed the change of the electrophysiological function and release of glutamate of mRGCs.

RESULTS

The melanopsin expression upregulate in mRGCs of chronic restraint stress (CRS)-treating mice which exhibit depression-like behavior. The frequency of blue light-induced action potentials and light-induced glutamate release mediated by melanopsin also increase significantly. This change of melanopsin is mediated by the CRS-induced glucocorticoid.

CONCLUSIONS

CRS may induce the depression-like behavior in mice via glucocorticoid-melanopsin pathway. Our findings provide a novel mechanistic link between CRS-induced depression and melanopsin in mice.

The Wistar Kyoto Rat: A Model of Depression Traits

There is an ongoing debate about the value of animal research in psychiatry with valid lines of reasoning stating the limits of individual animal models compared to human psychiatric illnesses. Human depression is not a homogenous disorder; therefore, one cannot expect a single animal model to reflect depression heterogeneity. This limited review presents arguments that the Wistar Kyoto (WKY) rats show intrinsic depression traits. The phenotypes of WKY do not completely mirror those of human depression but clearly indicate characteristics that are common with it. WKYs present despair- like behavior, passive coping with stress, comorbid anxiety, and enhanced drug use compared to other routinely used inbred or outbred strains of rats. The commonly used tests identifying these phenotypes reflect exploratory, escape-oriented, and withdrawal-like behaviors. The WKYs consistently choose withdrawal or avoidance in novel environments and freezing behaviors in response to a challenge in these tests. The physiological response to a stressful environment is exaggerated in WKYs. Selective breeding generated two WKY substrains that are nearly isogenic but show clear behavioral differences, including that of depression-like behavior. WKY and its substrains may share characteristics of subgroups of depressed individuals with social withdrawal, low energy, weight loss, sleep disturbances, and specific cognitive dysfunction. The genomes of the WKY and WKY substrains contain variations that impact the function of many genes identified in recent human genetic studies of depression. Thus, these strains of rats share characteristics of human depression at both phenotypic and genetic levels, making them a model of depression traits.

Circuit-wide proteomics profiling reveals brain region-specific protein signatures in the male WKY rats with endogenous depression

BACKGROUND

Although the Wistar Kyoto (WKY) rat has been consistently recognized as an animal model with endogenous depression, the exact molecular mechanisms underlying its genetic susceptibility to depression remain undetermined.

METHODS

Compared with the Wistar rats, the depression-like behaviors of the male WKY ones were evaluated by both the sucrose preference test and forced swimming test. Golgi staining analysis was conducted to access the dendritic morphology. TMT-labelled quantitative proteomics analyses were respectively performed in the medial prefrontal cortex (mPFC), nucleus accumbens (NAc), and hippocampus (Hip), followed by KEGG enrichment-based clustering analysis, Venn diagram analysis, and Pearson correlation analysis.

RESULTS

The WKY strain showed significant differences in both the depression-like behaviors and synaptic plasticity. Moreover, the WKY model displayed markedly distinct differentially-expressed protein (DEP) profiles, with minor differences between the WKY subgroups. A cerebral regional commonality and specificity were evident in the signaling pathways enriched in the WKY model, and a total of 15 brain region-specific DEPs were identified to closely correlate with the depression-like phenotypes (in the mPFC: Lrrc8d, Dcun1d2, and Mtnd5; in the NAc: Ccdc154, Sec14l2, Kif2a, LOC680322, Me1, Mknk1, and Ret7; in the Hip: Sec14l2, Serpinf2, LOC103694855, Fam13c, and Loxl1). Data were available via ProteomeXchange with identifier PXD029079.

LIMITATIONS

Female WKY rats are not included, and the roles of these candidate DEPs in depression remain further elucidation.

CONCLUSION

The present study further evidences the brain region-specific protein signatures in the male WKY model with endogenous depression, providing novel insights into the pathogenesis of depression in males.

Molecular regulation, breed differences and genes involved in stress control in farm animals

Stress is a state of disturbed homeostasis evoking a multiplicity of somatic and mental adaptive reactions resulting from any of the 5 freedoms of animals being violated. Many environmental forces disrupt homeostasis in farm animals, such as extreme temperatures, poor nutrition, noise, hunger, and thirst. During stressful situations, neuronal circuits in the limbic system and prefrontal cortex are activated, which lead to the release of adrenalin and noradrenalin. The hormones released during stress are needed for adaptation to acute stress and are regulated by many genes. This review examined molecular regulation, breed differences, and genes involved in stress control in farm animals. Major molecular regulation of stress, such as oxidative, cytosolic heat shock, unfolded protein, and hypoxic responses, were discussed. The responses of various poultry, ruminant, and pig breeds to different stress types were also discussed. Gene expressions and polymorphisms in the neuroendocrine and neurotransmitter pathways were also elucidated. The information obtained from this review will help farmers mitigate stress in farm animals through appropriate breed and gene-assisted selection. Also, information obtained from this review will add to the field of stress genetics since stress is a serious welfare issue in farm animals.

Stress and the brain transcriptome: Identifying commonalities and clusters in standardized data from published experiments

Interpretation of transcriptomic experiments is hindered by many problems including false positives/negatives inherent to big-data methods and changes in gene nomenclature. To find the most consistent effect of stress on brain transcriptome, we retrieved data from 79 studies applying animal models and 3 human studies investigating post-traumatic stress disorder (PTSD). The analyzed data were obtained either with microarrays or RNA sequencing applied to samples collected from more than 1887 laboratory animals and from 121 human subjects. Based on the initial database containing a quarter million differential expression effect sizes representing transcripts in three species, we identified the most frequently reported genes in 223 stress-control comparisons. Additionally, the analysis considers sex, individual vulnerability and contribution of glucocorticoids. We also found an overlap between gene expression in PTSD patients and animals which indicates relevance of laboratory models for human stress response. Our analysis points to genes that, as far as we know, were not specifically tested for their role in stress response (Pllp, Arrdc2, Midn, Mfsd2a, Ccn1, Htra1, Csrnp1, Tenm4, Tnfrsf25, Sema3b, Fmo2, Adamts4, Gjb1, Errfi1, Fgf18, Galnt6, Slc25a42, Ifi30, Slc4a1, Cemip, Klf10, Tom1, Dcdc2c, Fancd2, Luzp2, Trpm1, Abcc12, Osbpl1a, Ptp4a2). Provided transcriptomic resource will be useful for guiding the new research.

Gene Expression Profiling of the Habenula in Rats Exposed to Chronic Restraint Stress

Chronic stress contributes to the risk of developing depression; the habenula, a nucleus in epithalamus, is associated with many neuropsychiatric disorders. Using genome-wide gene expression analysis, we analyzed the transcriptome of the habenula in rats exposed to chronic restraint stress for 14 days. We identified 379 differentially expressed genes (DEGs) that were affected by chronic stress. These genes were enriched in neuroactive ligand-receptor interaction, the cAMP (cyclic adenosine monophosphate) signaling pathway, circadian entrainment, and synaptic signaling from the Kyoto Encyclopedia of Genes and Genomes pathway analysis and responded to corticosteroids, positive regulation of lipid transport, anterograde trans-synaptic signaling, and chemical synapse transmission from the Gene Ontology analysis. Based on protein-protein interaction network analysis of the DEGs, we identified neuroactive ligand-receptor interactions, circadian entrainment, and cholinergic synapse-related subclusters. Additionally, cell type and habenular regional expression of DEGs, evaluated using a recently published single-cell RNA sequencing study (GSE137478), strongly suggest that DEGs related to neuroactive ligand-receptor interaction and trans-synaptic signaling are highly enriched in medial habenular neurons. Taken together, our findings provide a valuable set of molecular targets that may play important roles in mediating the habenular response to stress and the onset of chronic stress-induced depressive behaviors.

Stress Elicits Contrasting Effects on Rac1-Cofilin Signaling in the Hippocampus and Amygdala

There is accumulating evidence for contrasting patterns of stress-induced morphological and physiological plasticity in glutamatergic synapses of the hippocampus and amygdala. The same chronic stress that leads to the formation of dendritic spines in the basolateral amygdala (BLA) of rats, leads to a loss of spines in the hippocampus. However, the molecular underpinnings of these divergent effects of stress on dendritic spines are not well understood. Since the activity of the Rho GTPase Rac1 and the actin-depolymerizing factor cofilin are known to play a pivotal role in spine morphogenesis, we investigated if alterations in this signaling pathway reflect the differential effects of stress on spine plasticity in the hippocampus and amygdala. A day after the end of chronic immobilization stress (2 h/day for 10 days), we found a reduction in the activity of Rac1, as well as its effector p21-activated kinase 1 (PAK1), in the rat hippocampus. These changes, in turn, decreased cofilin phosphorylation alongside a reduction in the levels of profilin isoforms. In striking contrast, the same chronic stress increased Rac1, PAK1 activity, cofilin phosphorylation, and profilin levels in the BLA, which is consistent with enhanced actin polymerization leading to spinogenesis in the BLA. In the hippocampus, on the other hand, the same stress caused the opposite changes, the functional consequences of which would be actin depolymerization leading to the elimination of spines. Together, these findings reveal a role for brain-region specific differences in the dysregulation of Rac1-to-cofilin signaling in the effects of repeated stress on two brain areas that are implicated in the emotional and cognitive symptoms of stress-related psychiatric disorders.

Differentially Expressed Genes in Period 2-Overexpressing Mice Striatum May Underlie Their Lower Sensitivity to Methamphetamine Addiction-Like Behavior

Previous reports have demonstrated that genetic mechanisms greatly mediate responses to drugs of abuse, including methamphetamine (METH). The circadian gene Period 2 (Per2) has been previously associated with differential responses towards METH in mice. While the behavioral consequences of eliminating Per2 have been illustrated previously, Per2 overexpression has not yet been comprehensively described; although, Per2-overexpressing (Per2 OE) mice previously showed reduced sensitivity towards METH-induced addiction-like behaviors. To further elucidate this distinct behavior of Per2 OE mice to METH, we identified possible candidate biomarkers by determining striatal differentially expressed genes (DEGs) in both drug-naïve and METH-treated Per2 OE mice relative to wild-type (WT), through RNA sequencing. Of the several DEGs in drug naïve Per2 OE mice, we identified six genes that were altered after repeated METH treatment in WT mice, but not in Per2 OE mice. These results, validated by quantitative real-time polymerase chain reaction, could suggest that the identified DEGs might underlie the previously reported weaker METH-induced responses of Per2 OE mice compared to WT. Gene network analysis also revealed that Asic3, Hba-a1, and Rnf17 are possibly associated with Per2 through physical interactions and predicted correlations, and might potentially participate in addiction. Inhibiting the functional protein of Asic3 prior to METH administration resulted in the partial reduction of METH-induced conditioned place preference in WT mice, supporting a possible involvement of Asic3 in METH-induced reward. Although encouraging further investigations, our findings suggest that these DEGs, including Asic3, may play significant roles in the lower sensitivity of Per2 OE mice to METH.

Beyond the neuron: Role of non-neuronal cells in stress disorders

Stress disorders are leading causes of disease burden in the U.S. and worldwide, yet available therapies are fully effective in less than half of all individuals with these disorders. Although to date, much of the focus has been on neuron-intrinsic mechanisms, emerging evidence suggests that chronic stress can affect a wide range of cell types in the brain and periphery, which are linked to maladaptive behavioral outcomes. Here, we synthesize emerging literature and discuss mechanisms of how non-neuronal cells in limbic regions of brain interface at synapses, the neurovascular unit, and other sites of intercellular communication to mediate the deleterious, or adaptive (i.e., pro-resilient), effects of chronic stress in rodent models and in human stress-related disorders. We believe that such an approach may one day allow us to adopt a holistic "whole body" approach to stress disorder research, which could lead to more precise diagnostic tests and personalized treatment strategies. Stress is a major risk factor for many psychiatric disorders. Cathomas et al. review new insight into how non-neuronal cells mediate the deleterious effects, as well as the adaptive, protective effects, of stress in rodent models and human stress-related disorders.

Circulating hsa-let-7e-5p and hsa-miR-125a-5p as Possible Biomarkers in the Diagnosis of Major Depression and Bipolar Disorders

Background. Evidence shows that microRNAs (miRNAs) could play a key role in the homeostasis and development of major depressive disorder and bipolar disorder. The present study is aimed at investigating the changes in circulating miRNA expression profiles in a plasma of patients suffering from major depressive disorder (MDD) and bipolar disorder (BD) to distinguish and evaluate these molecules as biomarkers for mood disorders. Methods. A study enrolled a total of 184 subjects: 74 controls, 84 MDD patients, and 26 BD patients. Small RNA sequencing revealed 11 deregulated circulating miRNAs in MDD and BD plasma, of which expression of 5, hsa-miR-139-3p, miRNAs hsa-let-7e-5p, hsa-let-7f-5p, hsa-miR-125a-5p, and hsa-miR-483-5p, were further verified using qPCR. miRNA gene expression data was evaluated alongside the data from clinical assessment questionnaires. Results. hsa-let-7e-5p and hsa-miR-125a-5p were both confirmed upregulated: 0.75-fold and 0.25-fold, respectively, in the MDD group as well as 1.36-fold and 0.68-fold in the BD group. Receiver operating curve (ROC) analysis showed mediocre diagnostic sensitivity and specificity of both hsa-let-7e-5p and hsa-miR-125a-5p with approximate area under the curve (AOC) of 0.66. ROC analysis of combined miRNA and clinical assessment data showed that hsa-let-7e-5p and hsa-miR-125a-5p testing could improve MDD and BD diagnostic accuracy by approximately 10%. Conclusions. Circulating hsa-let-7e-5 and hsa-miR-125a-5p could serve as additional peripheral biomarkers for mood disorders; however, suicidal ideation remains the major diagnostic factor for MDD and BD.

Specific and cumulative lifetime stressors in the aetiology of major depression: A longitudinal community-based population study

AIMS

Early-life stressful circumstances (i.e. childhood maltreatment) coupled with stressful events later in life increase the likelihood of subsequent depression. However, very few studies have been conducted to examine the specific and cumulative effects of these stressors in the development of depression. There is also a paucity of research that simultaneously considers the role of biological factors combined with psychosocial stressors in the aetiology of depression. Guided by the biopsychosocial model proposed by Engel, the present study aims to examine to what extent the experience of stressors across the lifespan is associated with depression while taking into account the role of genetic predispositions.

METHODS

Data analysed were from the Social and Psychiatric Epidemiology Catchment Area of the Southwest of Montreal (ZEPSOM), a large-scale, longitudinal community-based cohort study. A total of 1351 participants with complete information on the lifetime diagnoses of depression over a 10-year follow-up period were included in the study. Stressful events across the lifespan were operationalised as specific, cumulative and latent profiles of stressful experiences. Latent profile analysis (LPA) was used to explore the clustering of studied stressors including childhood maltreatment, poor parent-child relationship, and stressful life events. A polygenetic risk score was calculated for each participant to provide information on genetic liability. Multivariate logistic regression was used to examine the association between specific, cumulative and latent profiles of stressors and subsequent depression.

RESULTS

We found that different subtypes of childhood maltreatment, child-parent bonding and stressful life events predicted subsequent depression. Furthermore, a significant association between combined effects of cumulative stressful experiences and depression was found [odds ratio (OR) = 1.20, 95% confidence interval (CI): 1.12-1.28]. Three latent profiles of lifetime stressors were identified in the present study and named as 'low-level of stress' (75.1%), 'moderate-level of stress' (6.8%) and 'high-level of stress' (18.1%). Individuals with a 'high-level of stress' had a substantially higher risk of depression (OR = 1.80, 95% CI: 1.08-3.00) than the other two profiles after adjusting for genetic predispositions, socio-demographic characteristics, and health-related factors.

CONCLUSIONS

While controlling for genetic predispositions, the present study provides robust evidence to support the independent and cumulative as well as compositional effects of early- and later-on lifetime psychosocial stressors in the subsequent development of depression. Consequently, mental illness prevention and mental health promotion should target the occurrence of stressful events as well as build resilience in people so they can better cope with stress when it inevitably occurs.

Sex-Specific Behavioral Response to Early Adolescent Stress in the Genetically More Stress-Reactive Wistar Kyoto More Immobile, and Its Nearly Isogenic Wistar Kyoto Less Immobile Control Strain

Genetic predisposition and environmental stress are known etiologies of stress-related psychiatric disorders. Environmental stress during adolescence is assumed to be particularly detrimental for adult affective behaviors. To investigate how genetic stress-reactivity differences modify the effects of stress during adolescence on adult affective behaviors we employed two inbred strains with differing stress reactivity. The Wistar Kyoto More Immobile (WMI) rat strain show increased stress-reactivity and despair-like behaviors as well as passive coping compared to the nearly isogenic control strain, the Wistar Kyoto Less Immobile (WLI). Males and females of these strains were exposed to contextual fear conditioning (CFC) during early adolescence (EA), between 32 and 34 postnatal days (PND), and were tested for the consequences of this mild EA stress in adulthood. Early adolescent stress significantly decreased anxiety-like behavior, measured in the open field test (OFT) and increased social interaction and recognition in adult males of both strains compared to controls. In contrast, no significant effects of EA stress were observed in adult females in these behaviors. Both males and females of the genetically less stress-reactive WLI strain showed significantly increased immobility in the forced swim test (FST) after EA stress compared to controls. In contrast, immobility was significantly attenuated by EA stress in adult WMI females compared to controls. Transcriptomic changes of the glucocorticoid receptor (Nr3c1, GR) and the brain-derived neurotrophic factor (Bdnf) illuminate primarily strain and stress-dependent changes, respectively, in the prefrontal cortex and hippocampus of adults. These results suggest that contrary to expectations, limited adolescent stress is beneficial to males thru decreasing anxiety and enhancing social behaviors, and to the stress more-reactive WMI females by way of decreasing passive coping.

Immediate stress alters social and object interaction and recognition memory in nearly isogenic rat strains with differing stress reactivity

Stress prior to learning and recall is known to affect both processes depending on the learning paradigm, the sex of the animal, and their reactivity to stress. Male and female animals of the inbred Wistar-Kyoto More Immobile (WMI) and Less Immobile (WLI) strains were tested in the modified novel object and spatial recognition paradigm and in the social interaction-recognition paradigm immediately after a 30 min restraint stress. The WMI strain shows enhanced stress reactivity compared to its near isogenic WLI control and thus, represents a genetically stress-susceptible rodent model. Without stress, there were no strain differences in social or object recognition, but there were sex differences in both types of investigation. Immediate stress generally increased object investigation, but decreased social interaction in all groups, except the WMI males, who exhibited increased aggression toward the juveniles. While stress increased plasma corticosterone and decreased testosterone levels in WLI males as expected, it increased testosterone in the aggressive WMI males, despite elevated levels of corticosterone. Stress generally decreased recognition, except the spatial recognition of WMI females, which paradoxically improved after stress. The strain-specific effects of immediate stress indicate that stress unlocks the vulnerability encoded by the stable genetic differences between WLIs and WMIs to result in the observed phenotypes.

Genetic stress-reactivity, sex, and conditioning intensity affect stress-enhanced fear learning

The Stress-Enhanced Fear Learning (SEFL) model of posttraumatic stress disorder (PTSD) reveals increased fear memory in animals exposed to stress prior to contextual fear conditioning (CFC), similar to the increased likelihood of developing PTSD in humans after prior stress. The present study utilized the SEFL model by exposing animals to restraint stress as the first stressor, followed by CFC using foot-shocks with 0.6 mA or 0.8 mA intensity. Adult males and females from the two nearly isogenic rat strains, the genetically more stress-reactive Wistar Kyoto (WKY) More Immobile (WMI), and the less stress-reactive WKY Less Immobile (WLI) were employed. Percent time spent freezing at acquisition and at recall differed between these strains in both prior stress and no stress conditions. The significant correlations between percent freezing at acquisition and at recall suggest that fear memory differences represent a true phenotype related to the stress-reactivity differences between the strains. This assumption is further substantiated by the lack of effect of either conditioning intensity on percent freezing in WLI males, while WMI males were affected by both intensities albeit with opposite directional changes after prior stress. Differences between the sexes in sensitivity to the two conditioning intensities became apparent by the opposite directional and inverse relationship between fear memory and the intensity of conditioning in WMI males and females. The present data also illustrate that although corticosterone (CORT) responses to prior stress are known to be necessary for SEFL, plasma CORT and percent freezing were positively correlated only in the stress less-reactive WLI strain. These differences in baseline fear acquisition, fear memory, and the percent freezing responses to the SEFL paradigm in the two genetically close inbred WMI and WLI strains provide a unique opportunity to study the genetic contribution to the variation in these phenotypes.

Antidepressant-like effects of albiflorin involved the NO signaling pathway in rats model of chronic restraint stress

The depressant-like effects of albiflorin (AF) were studied on stressed chronic restraint stress (CRS) rats. Experimental rats were subjected to immobilization stress for a daily 6 h-restraining in a plastic restrainer for continuous 21 d and were treated with 30 or 15 mg·kg^-1 of AF for 21 d. Control rats were maintained in completely non stressed conditions. Behavioral tests and biochemical analysis were applied to investigating a regulatory mechanism of anti-stress of AF. Treatment with AF significantly restored the depressant-like behaviors. Besides, AF increased the levels of 5-hydroxytryptophan (5-HT), 5-hydroxyindoleacetic acid (5-HIAA), noradrenaline (NE) and dopamine (DA) in the hippocampus and increased the level of brain-derived neurotrophic factor (BDNF) in serum and protein expression in hippocampus. In addition, AF decreased the levels of hypothalamo-pituitary-adrenal (HPA) cascade, reduced the level of NO and cGMP in serum and inhibited the overexpression of 5-HT_2AR mRNA and protein expression. Taken together, AF can modulate the NO-mediated network pathway in the hippocampus against stress-induced depressive-like behaviors. These physiological and behavioral changes allow rats to avoid potential deleterious effects of stress that may result from chronically elevated levels of glucocorticosteroids over days.

Whole genome sequencing of nearly isogenic WMI and WLI inbred rats identifies genes potentially involved in depression and stress reactivity

The WMI and WLI inbred rats were generated from the stress-prone, and not yet fully inbred, Wistar Kyoto (WKY) strain. These were selected using bi-directional selection for immobility in the forced swim test and were then sib-mated for over 38 generations. Despite the low level of genetic diversity among WKY progenitors, the WMI substrain is significantly more vulnerable to stress relative to the counter-selected WLI strain. Here we quantify numbers and classes of genomic sequence variants distinguishing these substrains with the long term goal of uncovering functional and behavioral polymorphism that modulate sensitivity to stress and depression-like phenotypes. DNA from WLI and WMI was sequenced using Illumina xTen, IonTorrent, and 10X Chromium linked-read platforms to obtain a combined coverage of ~ 100X for each strain. We identified 4,296 high quality homozygous SNPs and indels between the WMI and WLI. We detected high impact variants in genes previously implicated in depression (e.g. Gnat2), depression-like behavior (e.g. Prlr, Nlrp1a), other psychiatric disease (e.g. Pou6f2, Kdm5a, Reep3, Wdfy3), and responses to psychological stressors (e.g. Pigr). High coverage sequencing data confirm that the two substrains are nearly coisogenic. Nonetheless, the small number of sequence variants contributes to numerous well characterized differences including depression-like behavior, stress reactivity, and addiction related phenotypes. These selected substrains are an ideal resource for forward and reverse genetic studies using a reduced complexity cross.

Elucidating the Possible Role of FoxO in Depression

Forkhead box-O (FoxO) transcriptional factors perform essential functions in several physiological and biological processes. Recent studies have shown that FoxO is implicated in the pathophysiology of depression. Changes in the upstream mediators of FoxOs including brain-derived neurotrophic factor (BDNF) and protein kinase B have been associated with depressive disorder and the antidepressant agents are known to alter the phosphorylation of FoxOs. Moreover, FoxOs might be regulated by serotonin or noradrenaline signaling and the hypothalamic-pituitary-adrenal (HPA)-axis,both of them are associated with the development of the depressive disorder. FoxO also regulates neural morphology, synaptogenesis, and neurogenesis in the hippocampus, which accounts for the pathogenesis of the depressive disorder. The current article underlined the potential functions of FoxOs in the etiology of depressive disorder and formulate few essential proposals for further investigation. The review also proposes that FoxO and its signal pathway might establish possible therapeutic mediators for the management of depressive disorder.

Blood and affective markers of stress in Elite Airmen during a preparatory training course: A pilot study

In highly stressful environments, individuals with diverging stress-reactivity can perform differently. Identification of blood markers of stress-reactivity is of major significance to help human performance during stress. Candidate transcripts were identified between stressed and non-stressed strains of rats’ blood and brain, and overlapping significant differentially expressed genes were selected. Serum levels of human orthologues of these proteins, in lieu of blood RNA, in addition to classic stress and general clinical markers, were measured in 33 Battlefield Airmen undergoing a 52 day long preparatory training course before their course of initial entry (COIE). Blood samples and factors of affective state, negative valence “Threat” and positive valence “Challenge”, were obtained five times across different days of training which included either routine physical exercise or prolonged and intense physical and mental training. During training, levels of chloride (Cl), dehydroepiandrosterone-sulfate (DHEA-S), creatinine kinase (CK), and total carbon dioxide (TCO2) differed between airmen who subsequently graduated from their COIE and those who did not. Time dependent changes of serum TCO2 and neuropeptide Y (NPY), as well as the affective factor Challenge differed by future graduation status throughout the training. Serum levels of parvin beta (PARVB) correlated with the affective factor Threat, while those of NPY, testosterone, coactosin like F-actin binding protein 1 (COTL1) and C-reactive protein (CRP) correlated with factor Challenge during the extended, intensive periods of training, consistently. These pilot data suggest that the identified panel of blood markers can measure stress responsiveness, which has the potential to advance individualized stress-management strategies.

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Levels of novel and classical serum markers signal stress severity in men.

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Biomarker levels reflect stress reactivity of Battlefield Airmen in training.

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Affective measures correlate with serum biomarkers after extended stress.

Nonhuman Primate Models to Explore Mechanisms Underlying Early-Life Temperamental Anxiety

Anxiety disorders are among the most prevalent psychiatric disorders, causing significant suffering and disability. Behavioral inhibition is a temperament that is linked to an increased risk for the later development of anxiety disorders and other stress-related psychopathology, and understanding the neural systems underlying this dispositional risk could provide insight into novel treatment targets for anxiety disorders. Nonhuman primates (NHPs) have anxiety-related temperaments that are similar to those of humans with behavioral inhibition, facilitating the design of translational models related to human psychopathology. Characterization of our NHP model of behavioral inhibition, which we term anxious temperament (AT), reveals that it is trait-like. Exploration of the neural substrates of AT in NHPs has revealed a distributed neural circuit that is linked to individual differences in AT, which includes the dorsal amygdala. AT-related metabolism in the dorsal amygdala, including the central nucleus, is stable across time and can be detected even in safe contexts, suggesting that AT has trait-like neural signatures within the brain. The use of lesioning and novel chemogenetic methods allows for mechanistic perturbation of the amygdala to determine its causal contribution to AT. Studies characterizing the molecular bases for individual differences in AT in the dorsal amygdala, which take advantage of novel methods for probing cellular and molecular systems, suggest involvement of neurotrophic systems, which point to the importance of neuroplasticity in AT. These novel methods, when used in combination with translational NHP models such as AT, promise to provide insights into the brain systems underlying the early risk for anxiety disorder development.

Transcription Factor TWIST1 Integrates Dendritic Remodeling and Chronic Stress to Promote Depressive-like Behaviors

BACKGROUND

Deficiency in neuronal structural plasticity is involved in the development of major depressive disorder. TWIST1, a helix-loop-helix transcription factor that is essential for morphogenesis and organogenesis, is normally expressed at low levels in mature neurons. However, it is poorly understood what role TWIST1 plays in the brain and whether it is involved in the pathophysiology of depression.

METHODS

Depressive-like behaviors in C57BL/6J mice were developed by chronic social defeat stress. Genetic and pharmacological approaches were used to investigate the role of the TWIST1-miR-214-PPAR-δ signaling pathway in depressive-like behaviors. Molecular biological and morphological studies were performed to define the molecular mechanisms downstream of TWIST1.

RESULTS

The expression of TWIST1 was positively correlated with depressive behaviors in humans and mice. Chronic stress elevated TWIST1 expression in the medial prefrontal cortex of mice, which was reversed by fluoxetine treatment. While the overexpression of TWIST1 increased susceptibility to stress, the knockdown of TWIST1 prevented the defective morphogenesis of dendrites of pyramidal neurons in layer II/III of the medial prefrontal cortex and alleviated depressive-like behaviors. Mechanistically, this prodepressant property of TWIST1 was mediated, at least in part, through the repression of miR-214-PPAR-δ signaling and mitochondrial function, which was also mimicked by genetic and pharmacological inhibition of PPAR-δ.

CONCLUSIONS

These results suggest that TWIST1 in the medial prefrontal cortex mediates chronic stress-induced dendritic remodeling and facilitates the occurrence of depressive-like behavior, providing new information for developing drug targets for depression therapy.

Genetic Liability for Internalizing Versus Externalizing Behavior Manifests in the Developing and Adult Hippocampus: Insight From a Meta-analysis of Transcriptional Profiling Studies in a Selectively Bred Rat Model

BACKGROUND

For more than 16 years, we have selectively bred rats for either high or low levels of exploratory activity within a novel environment. These bred high-responder (bHR) and bred low-responder (bLR) rats model temperamental extremes, exhibiting large differences in internalizing and externalizing behaviors relevant to mood and substance use disorders.

METHODS

We characterized persistent differences in gene expression related to bHR/bLR phenotype across development and adulthood in the hippocampus, a region critical for emotional regulation, by meta-analyzing 8 transcriptional profiling datasets (microarray and RNA sequencing) spanning 43 generations of selective breeding (postnatal day 7: n = 22; postnatal day 14: n = 49; postnatal day 21: n = 21; adult: n = 46; all male). We cross-referenced expression differences with exome sequencing within our colony to pinpoint candidates likely to mediate the effect of selective breeding on behavioral phenotype. The results were compared with hippocampal profiling from other bred rat models.

RESULTS

Genetic and transcriptional profiling results converged to implicate multiple candidate genes, including two previously associated with metabolism and mood: Trhr and Ucp2. Results also highlighted bHR/bLR functional differences in the hippocampus, including a network essential for neurodevelopmental programming, proliferation, and differentiation, centering on Bmp4 and Mki67. Finally, we observed differential expression related to microglial activation, which is important for synaptic pruning, including 2 genes within implicated chromosomal regions: C1qa and Mfge8.

CONCLUSIONS

These candidate genes and functional pathways may direct bHR/bLR rats along divergent developmental trajectories and promote a widely different reactivity to the environment.

Protective effects of duloxetine against chronic immobilisation stress-induced anxiety, depression, cognitive impairment and neurodegeneration in mice

OBJECTIVES

This study aimed to evaluate the effect of duloxetine (10 and 20 mg/kg) against chronic immobilisation stress (CIS)-induced anxiety, depression, cognitive impairment and neurodegeneration in mice.

METHODS

CIS, 2 h/10 days (11:00 AM-1:00 PM) was applied after 30 min of pretreatment with saline, duloxetine 10 mg/kg and 20 mg/kg to the respective groups of animals, except the control group. Animals were examined for physiological (body weight, locomotion and grip strength), psychological (memory impairment, anxiety and depression), neurochemical (GABA and glutamate), biochemical (MDA, catalase, glutathione, superoxide dismutase) and histopathological changes.

KEY FINDINGS

CIS exposure revealed anxiety-like behaviour, depression-like behaviour, motor in-coordination and learning and memory impairment in mice. Besides, CIS induction decreased the antioxidant enzymes (GSH, SOD and catalase), GABA and the viable neuronal cell count, whereas CIS exposure significantly elevated the MDA, AChE activity and glutamate content in the cortex and hippocampus. Pretreatment with duloxetine10 and 20 mg/kg showed dose-dependent ameliorated effect against the CIS-induced alterations in mice.

CONCLUSION

In conclusion, the results of this study demonstrated the protective effect of duloxetine against neuropsychiatric symptoms, memory impairment caused by CIS-induction through inhibition of oxidative stress, AChE activity and glutamate release.

Transcriptional and morphological profiling of parvalbumin interneuron subpopulations in the mouse hippocampus

The diversity reflected by >100 different neural cell types fundamentally contributes to brain function and a central idea is that neuronal identity can be inferred from genetic information. Recent large-scale transcriptomic assays seem to confirm this hypothesis, but a lack of morphological information has limited the identification of several known cell types. In this study, we used single-cell RNA-seq in morphologically identified parvalbumin interneurons (PV-INs), and studied their transcriptomic states in the morphological, physiological, and developmental domains. Overall, we find high transcriptomic similarity among PV-INs, with few genes showing divergent expression between morphologically different types. Furthermore, PV-INs show a uniform synaptic cell adhesion molecule (CAM) profile, suggesting that CAM expression in mature PV cells does not reflect wiring specificity after development. Together, our results suggest that while PV-INs differ in anatomy and in vivo activity, their continuous transcriptomic and homogenous biophysical landscapes are not predictive of these distinct identities.

IGF2 improves the developmental competency and meiotic structure of oocytes from aged mice

Advanced maternal-age is a major factor adversely affecting oocyte quality, consequently worsening pregnancy outcomes. Thus, developing strategies to reduce the developmental defects associated with advanced maternal-age would benefit older mothers. Multiple growth factors involved in female fertility have been extensively studied; however, the age-related impacts of various growth factors remain poorly studied. In the present study, we identified that levels of insulin-like growth factor 2 (IGF2) are significantly reduced in the serum and oocytes of aged mice. We found that adding IGF2 in culture medium promotes oocyte maturation and significantly increases the proportion of blastocysts: from 41% in the untreated control group to 64% (50 nM IGF2) in aged mice (p < 0.05). Additionally, IGF2 supplementation of the culture medium reduced reactive oxygen species production and the incidence of spindle/chromosome defects. IGF2 increases mitochondrial functional activity in oocytes from aged mice: we detected increased ATP levels, elevated fluorescence intensity of mitochondria, higher mitochondrial membrane potentials, and increased overall protein synthesis, as well as increased autophagy activity and decreased apoptosis. Collectively, our findings demonstrate that IGF2 supplementation in culture media improves oocyte developmental competence and reduces meiotic structure defects in oocytes from aged mice.

Paroxetine combined with fluorouracil plays a therapeutic role in mouse models of colorectal cancer with depression through inhibiting IL-22 expression to regulate the MAPK signaling pathway

The objective of the present study was to observe the therapeutic effect of paroxetine combined with fluorouracil on mice with colorectal cancer (CRC) complicated with depression and to explore its mechanism of action. Using chronic mild stress and xenograft tumor methods to model CRC complicated with depression, 60 BALB/c mice were randomly divided into control, tumor model, tumor depression model, tumor depression antidepressant, tumor depression chemotherapy and tumor depression antidepressant plus chemotherapeutic drug groups. Changes in mouse sucrose preference and forced swimming tests were tracked. Changes in tumor volume and weight were compared, the tumor inhibition rate was calculated, Ki-67 expression in tumor tissues was detected using immunohistochemistry and IL-22 levels in peripheral blood were detected using ELISAs. Additionally, protein expression levels of IL-22, Bcl-2, Bax, caspase-3, p38, phosphorylated (p)-p38, ERK, p-ERK, JNK and p-JNK in tumor tissue were detected using western blotting. Following treatment with paroxetine and chemotherapy drugs, the sucrose preference index was increased, autonomic behavior dysfunction was alleviated and tumor growth was significantly inhibited. Furthermore, the expression levels of Ki-67 and apoptosis-related proteins, Bax and caspase-3, increased in tumor tissues, anti-apoptosis protein Bcl2 expression levels decreased significantly, IL-22 levels in the blood and tumor tissues were reduced and p-p38, p-ERK and p-JNK proteins were significantly reduced. It was concluded that paroxetine combined with chemotherapy drugs improved depressive behavior and promoted the survival state in a mouse model of CRC and depression, possibly through inhibiting IL-22 expression to regulate the activity of the MAPK signaling pathway.

Hypothalamic Gene Expression and Postpartum Behavior in a Genetic Rat Model of Depression

Postpartum depression is a complex illness that often occurs in genetically predisposed individuals. Closely related inbred rat strains are a great resource to identify novel causative genes and mechanisms underlying complex traits such as postpartum behavior. We report differences in these behaviors between the inbred depression model, Wistar Kyoto (WKY) More Immobile (WMI), and the isogenic control Wistar Kyoto Less Immobile (WLI) dams. WMI dams showed significantly lower litter survival rate and frequency of arched back and blanket nursing, but increased pup-directed licking, grooming, and retrieval during postpartum days (PPD) 1-10, compared to control WLIs. This increased pup-directed behavior and the frequency of self-directed behaviors segregated during selective breeding of the progenitor strain of WKY, which is also a depression model. These behaviors are manifested in the WMIs in contrast to those of WLIs. Furthermore, habitual differences in the self-directed behavior between light and dark cycles present in WLIs were missing in WMI dams. Hypothalamic transcript levels of the circadian rhythm-related gene Lysine Demethylase 5A (Kdm5a), period 2 (Per2), and the maternal behavior-related oxytocin receptor (Oxtr), vasopressin (Avp), and vasopressin receptor 1a (Avpr1a) were significantly greater in the post-weaning WMI dams at PPD 24 compared to those of WLIs, and also to those of WMI dams whose litter died before PPD 5. Expression correlation amongst genes differed in WLI and WMI dams and between the two time-points postpartum, suggesting genetic and litter-survival differences between these strains affect transcript levels. These data demonstrate that the genetically close, but behaviorally disparate WMI and WLI strains would be suitable for investigating the underlying genetic basis of postpartum behavior.

Race, Ethnicity, Family Socioeconomic Status, and Children's Hippocampus Volume

Introduction

The hippocampus has a significant role in memory, learning, and cognition. Although hippocampal size is highly susceptible to family socioeconomic status (SES) and associated stress, very little is known on racial and ethnic group differences in the effects of SES indicators on hippocampus volume among American children.

Purpose

This study explored the multiplicative effects of race, ethnicity, and family SES on hippocampus volume among American children.

Methods

Using data from the Adolescent Brain Cognitive Development (ABCD), we analyzed the functional Magnetic Resonance Imaging (fMRI) data of 9390 9-10 years old children. The main outcome was hippocampus volume. The predictor was parental education. Subjective family SES was the independent variable. Age, sex, and marital status were the covariates. Racial and ethnic group membership were the moderators. To analyze the data, we used regression models.

Results

High subjective family SES was associated with larger hippocampus volume. This effect was significantly larger for Whites than Black families.

Conclusions

The effect of subjective family SES on children's hippocampus volume is weaker in Black than White families.

Family Income Mediates the Effect of Parental Education on Adolescents' Hippocampus Activation During an N-Back Memory Task

Introduction: Hippocampus, a medial temporal lobe structure, has significant implications in memory formation and learning. Although hippocampus activity is believed to be affected by socioeconomic status (SES), limited knowledge exists on which SES indicators influence hippocampus function. Purpose: This study explored the separate and combined effects of three SES indicators, namely parental education, family income, and neighborhood income, on adolescents’ hippocampus activation during an N-Back memory task. As some of the effects of parental education may be through income, we also tested if the effect of parental education on hippocampus activation during our N-Back memory task is mediated by family or neighborhood income. Methods: The Adolescent Brain Cognitive Development (ABCD) study is a national multi-center investigation of American adolescents’ brain development. Functional magnetic resonance imaging (fMRI) data of a total sample of 3067 9–10-year-old adolescents were used. The primary outcome was left- hippocampus activation during the N-Back memory task (mean beta weight for N-Back run 1 2 back versus 0 back contrast in left hippocampus). The independent variable was parental education. Family income and neighborhood income were two possible mediators. Age, sex, and marital status were the covariates. To test mediation, we used hierarchical linear regression models first without and then with our mediators. Full mediation was defined according to Kenny. The Sobel test was used to confirm statistical mediation. Results: In the absence of family and neighborhood income in the model, higher parental educational attainment was associated with lower level of left hippocampus activation during the N-Back memory task. This effect was significant while age, sex, and marital status were controlled. The association between parental educational attainment and hippocampus activation during the N-Back memory task was no more significant when we controlled for family and neighborhood income. Instead, family income was associated with hippocampus activation during the N-Back memory task. These findings suggested that family income fully mediates the effect of parental educational attainment on left hippocampus activation during the N-Back memory task. Conclusions: The effect of parental educational attainment on adolescents’ hippocampus activation during an N-Back memory task is fully explained by family income. That means low family income is why adolescents with low-educated parents show highlighted hippocampus activation during an N-Back memory task. Given the central role of the hippocampus in learning and memory and as income is a modifiable factor by tax and economic policies, income-redistribution policies, fair taxation, and higher minimum wage may have implications for promotion of adolescent equality and social justice. There is a need to focus on family-level economic needs across all levels of neighborhood income.

Facilitating Complex Trait Analysis via Reduced Complexity Crosses

Genetically diverse inbred strains are frequently used in quantitative trait mapping to identify sequence variants underlying trait variation. Poor locus resolution and high genetic complexity impede variant discovery. As a solution, we explore reduced complexity crosses (RCCs) between phenotypically divergent, yet genetically similar, rodent substrains. RCCs accelerate functional variant discovery via decreasing the number of segregating variants by orders of magnitude. The simplified genetic architecture of RCCs often permit immediate identification of causal variants or rapid fine-mapping of broad loci to smaller intervals. Whole-genome sequences of substrains make RCCs possible by supporting the development of array- and targeted sequencing-based genotyping platforms, coupled with rapid genome editing for variant validation. In summary, RCCs enhance discovery-based genetics of complex traits.

Co-expression Network of mRNAs and lncRNAs Regulated by Stress-Linked Behavioral Assays

RATIONALE

Mood-related behavioral assays, designed typically on rodents' natural aversion to certain threats, are useful in studying the mechanisms of mood and in discovering effective treatments for neuropsychiatric disorders.

OBJECTIVES

Although reasonable attention has been paid to the conducted sequence, few studies address the argument whether a behavioral assay itself affects the intrinsic signaling, gene expression, and the subsequent performance of mice.

METHODS

We examined the short- (1 day) and long-term effects (7 and 14 days) of commonly used behavioral assays for anxiety and depression, including the elevated plus maze test (EPM), forced swimming test (FST), and tail suspension test (TST), on behaviors. We also investigated the effects of repeated behavioral assays on behaviors. The alterations in the expression profiles in the hippocampus experienced behavioral assays were explored via the integrative analysis of mRNA and lncRNA transcriptomes generated by RNA sequencing.

RESULTS

We found that one FST or TST can induce anxiety-related behaviors, while repeated FST or TST resulted in depression-related behaviors in mice. The altered behaviors were associated with extensive transcriptional alterations in the FST and TST hippocampus of mice. KEGG pathway analyses indicated that differentially expressed genes (DEGs) in the FST and TST hippocampus were enriched in anxiety- and metabolic-related pathways, respectively. Moreover, differentially expressed lncRNAs, showing correlations with DEGs, were linked to anxiety-related pathways in the FST hippocampus and metabolic-related pathways in the TST hippocampus.

CONCLUSIONS

Our study identified the unique and shared mRNAs and lncRNAs regulated by mood-related behavioral assays, emphasizing the importance of the sequence of and intervals between them.

Effects of aging on the motor, cognitive and affective behaviors, neuroimmune responses and hippocampal gene expression

The known effects of aging on the brain and behavior include impaired cognition, increases in anxiety and depressive-like behaviors, and reduced locomotor activity. Environmental exposures and interventions also influence brain functions during aging. We investigated the effects of normal aging under controlled environmental conditions and in the absence of external interventions on locomotor activity, cognition, anxiety and depressive-like behaviors, immune function and hippocampal gene expression in C57BL/6 mice. Healthy mice at 4, 9, and 14 months of age underwent behavioral testing using an established behavioral battery, followed by cellular and molecular analysis using flow cytometry, immunohistochemistry, and quantitative PCR. We found that 14-month-old mice showed significantly reduced baseline locomotion, increased anxiety, and impaired spatial memory compared to younger counterparts. However, no significant differences were observed for depressive-like behavior in the forced-swim test. Microglia numbers in the dentate gyrus, as well as CD8+ memory T cells increased towards late middle age. Aging processes exerted a significant effect on the expression of 43 genes of interest in the hippocampus. We conclude that aging is associated with specific changes in locomotor activity, cognition, anxiety-like behaviors, neuroimmune responses and hippocampal gene expression.

Insulin growth factor 2 (IGF2) as an emergent target in psychiatric and neurological disorders. Review

Insulin-like growth factor 2 (IGF2) is abundantly expressed in the central nervous system (CNS). Recent evidence highlights the role of IGF2 in the brain, sustained by data showing its alterations as a common feature across a variety of psychiatric and neurological disorders. Previous studies emphasize the potential role of IGF2 in psychiatric and neurological conditions as well as in memory impairments, targeting IGF2 as a pro-cognitive agent. New research on animal models supports that upcoming investigations should explore IGF2's strong promising role as a memory enhancer. The lack of effective treatments for cognitive disturbances as a result of psychiatric diseases lead to further explore IGF2 as a promising target for the development of new pharmacology for the treatment of memory dysfunctions. In this review, we aim at gathering all recent relevant studies and findings on the role of IGF2 in the development of psychiatric diseases that occur with cognitive problems.