Chronic Social Instability Stress Research Articles

Transmission of reduced levels of miR-34/449 from sperm to preimplantation embryos is a key step in the transgenerational epigenetic inheritance of the effects of paternal chronic social instability stress

ABSTRACT The transgenerational effects of exposing male mice to chronic social instability (CSI) stress are associated with decreased sperm levels of multiple members of the miR-34/449 family that persist after their mating through preimplantation embryo (PIE) development. Here we demonstrate the importance of these miRNA changes by showing that restoring miR-34c levels in PIEs derived from CSI stressed males prevents elevated anxiety and defective sociability normally found specifically in their adult female offspring. It also restores, at least partially, levels of sperm miR-34/449 normally reduced in their male offspring who transmit these sex-specific traits to their offspring. Strikingly, these experiments also revealed that inducing miR-34c levels in PIEs enhances the expression of its own gene and that of miR-449 in these cells. The same induction of embryo miR-34/449 gene expression likely occurs after sperm-derived miR-34c is introduced into oocytes upon fertilization. Thus, suppression of this miRNA amplification system when sperm miR-34c levels are reduced in CSI stressed mice can explain how a comparable fold-suppression of miR-34/449 levels can be found in PIEs derived from them, despite sperm containing ~50-fold lower levels of these miRNAs than those already present in PIEs. We previously found that men exposed to early life trauma also display reduced sperm levels of miR-34/449. And here we show that miR-34c can also increase the expression of its own gene, and that of miR-449 in human embryonic stem cells, suggesting that human PIEs derived from men with low sperm miR-34/449 levels may also contain this potentially harmful defect.

468. Sex-Dependent Differences in Intra-Hippocampal and Hippocampal-Prefrontal Coherence, Microglial Activation, and Perineuronal Nets Following Chronic Social Instability Stress in Mice

468. Sex-Dependent Differences in Intra-Hippocampal and Hippocampal-Prefrontal Coherence, Microglial Activation, and Perineuronal Nets Following Chronic Social Instability Stress in Mice

The role of sociability in social instability stress: Behavioral, neuroendocrine and monoaminergic effects

Extensive literature has reported a link between social stress and mental health. In this complex relationship, individual strategies for coping with social stress are thought to have a possible modulating effect, with sociability being a key factor. Despite the higher incidence of affective disorders in females and sex-related neurochemical differences, female populations have been understudied. The aim of the present study was, therefore, to analyze the behavioral, neuroendocrine, and neurochemical effects of stress in female OF1 mice, paying special attention to social connectedness (female mice with high vs low sociability). To this end, subjects were exposed to the Chronic Social Instability Stress (CSIS) model for four weeks. Although female mice exposed to CSIS had increased arousal, there was no evidence of depressive-like behavior. Neither did exposure to CSIS affect corticosterone levels, although it did increase the MR/GR ratio by decreasing GR expression. Female mice exposed to CSIS had higher noradrenaline and dopamine levels in the hippocampus and striatum respectively, with a lower monoaminergic turnover, resulting in an increased arousal. CSIS increased serotonin levels in both the hippocampus and striatum. Similarly, CSIS was found to reduce kynurenic acid, 3-HK, and IDO and iNOS enzyme levels in the hippocampus. Interestingly, the observed decrease in IDO synthesis and the increased serotonin and dopamine levels in the striatum were only found in subjects with high sociability. These highly sociable female mice also had significantly lower levels of noradrenaline in the striatum after CSIS application. Overall, our model has produced neuroendocrine and neurochemical but not behavioral changes, so it has not allowed us to study sociability in depth. Therefore, a model that induces both molecular and behavioral phenotypes should be applied to determine the role of sociability.

Wistar-Kyoto rats and chronically stressed Wistar rats present similar depression- and anxiety-like behaviors but different corticosterone and endocannabinoid system modulation

The interplay of social, psychological, and biological stresses can trigger mental health conditions such as major depressive disorder (MDD), adjustment disorder, and posttraumatic stress disorder (PTSD). The endocannabinoid system (ECS), comprising endocannabinoids and cannabinoid receptors, is the critical pathway that mediates responses to stress stimuli. This study aimed to investigate the ECS's impact on responding to chronic social instability stress (SIS). Wistar (WIS) rats and an endogenously depressed rat model, Wistar-Kyoto (WKY), were used to evaluate depression- and anxiety-like behavioral responses, cognitive function, hormone levels, and ECS function. The animals in the stress group (WIS-STS and WKY-STS) were exposed to TMT (predator odor) for 10 mins (two exposures in total: one in light cycle and one in dark cycle) and daily roommate changes (30 days in total), while the control group (CTL) rats were exposed to a sham odor stimulus (distilled water) and did not undergo roommate changes.The results in the open field test suggest that WKY rats had significantly lower locomotor activity than WIS rats. In contrast, WKY rats and chronically stressed WIS rats presented similar depression- and anxiety-like behaviors and impaired cognitive function in the elevated plus maze, forced swimming test, and novel objective recognition test. However, chronic SIS did not exacerbate these behavioral changes in WKY rats. ELISA and Western blot analysis indicated that chronic SIS did not induce further upregulation of endocannabinoids and CB1R downregulation in WKY rats compared to WIS rats. In addition, the Luminex assay revealed that WKY rats showed a higher resilience on the HPA-axis modulation towards chronic SIS, distinguished by the hyperactivity of the HPA-axis modulation in WIS rats.Overall, the study revealed that the chronic SIS animal model (stressed WIS rats) and an animal model of endogenous depression (WKY rats) can generate similar behavioral changes in anxious behavior, behavioral despair, and cognitive impairment. Both animal models present hyperactivity of the ACTH modulation and ECS activity, while WKY rats are more resilient on CORT modulation towards chronic SIS.

Chronic Social Instability Stress in female mice inoculated with melanoma tumor cells: neurochemical and behavioral effects

Chronic Social Instability Stress in female mice inoculated with melanoma tumor cells: neurochemical and behavioral effects

Chronic social instability stress increases the arousal and alters the inflammatory response in OF1 female mice

Chronic social instability stress increases the arousal and alters the inflammatory response in OF1 female mice

Chronic social instability stress down-regulates IL-10 and up-regulates CX3CR1 in tumor-bearing and non-tumor-bearing female mice

Extensive literature has reported a link between stress and tumor progression, and between both of these factors and mental health. Despite the higher incidence of affective disorders in females and the neurochemical differences according to sex, female populations have been understudied. The aim of this study was therefore to analyze the effect of stress on tumor development in female OF1 mice. For this purpose, subjects were inoculated with B16F10 melanoma cells and exposed to the Chronic Social Instability Stress (CSIS) model. Behavioral, neurochemical and neuroendocrine parameters were analyzed. Female mice exposed to CSIS exhibited reduced body weight and increased arousal, but there was no evidence of depressive behavior or anxiety. Exposure to CSIS did not affect either corticosterone levels or tumor development, although it did provoke an imbalance in cerebral inflammatory cytokines, decreasing IL-10 expression (IL-6/IL-10 and TNF-α/IL-10); chemokines, increasing CX3CR1 expression (CX3CL1/CX3CR1); and glucocorticoid receptors, decreasing GR expression (MR/GR). In contrast, tumor development did not alter body weight and, although it did alter behavior, it did so to a much lesser extent. Tumor inoculation did not affect corticosterone levels, but increased the MR/GR ratio in the hippocampus and provoked an imbalance in cerebral inflammatory cytokines and chemokines, although differently from stress. These results underscore the need for experimental approaches that allow us to take sex differences into account when exploring this issue, since these results appear to indicate that the female response to stress is mediated by mechanisms different from those often proposed in relation to male mice.

P406. Chronic Adolescent Social Instability Stress Leads to Impaired Recognition Memory and Increased Hippocampal FKBP5 and CRHR2 Expression in Adulthood

Recently published studies indicate that the Covid-19 pandemic has dramatically increased rates of anxiety, depression, and suicide in adolescents and young adults. Human and animal studies strongly indicate that early life stress leads to lasting changes to cognition and psychiatric outcomes, but less is known about how chronic adolescent stress may alter brain function across the lifespan.

Chronic Social Instability Stress in Tumor-Bearing and Non-Tumor-Bearing Female Mice: Protective Effects of Reduced IL-10 and Increased CX3CR1 Expression

Chronic Social Instability Stress in Tumor-Bearing and Non-Tumor-Bearing Female Mice: Protective Effects of Reduced IL-10 and Increased CX3CR1 Expression

Venlafaxine reduces the striatal il6/il10 ratio and increases hippocampal GR expression in female mice subjected to chronic social instability stress

Women are twice as likely as men to develop depression and antidepressant treatment is more frequent in females. Moreover, neuroinflammatory changes related to affective disorders differ in accordance with sex. Despite this evidence, female populations have been largely omitted from preclinical experiments studying antidepressants. The aim of this work is to analyze the potential restorative effect of venlafaxine on an animal model of depression. Female CD1 mice were subjected to chronic social instability (CSI) stress for 7 weeks, and were administered venlafaxine during the last 3 weeks of the stress period. Behavioral and physiological parameters were then analyzed. Stressed mice showed a decreased sucrose preference and increased whisking behavior, and had a lower body weight, higher plasma corticosterone levels and increased hypothalamic GR expression. They also had lower levels of 5-HT, 5-HIAA and NA and a higher KYN/TRYP ratio in the hippocampus. Moreover, CSI increased striatal IL-6 mRNA expression levels. Venlafaxine treatment reduced the striatal IL-6/IL-10 ratio and increased hippocampal GR expression, although it did not reverse stress-induced behavioral changes. In conclusion, seven weeks of exposure to CSI produced depressive-like alterations in female mice. The venlafaxine treatment regimen was found to have a modest anti-inflammatory effect in the striatum and increased hippocampal GR mRNA, although it failed to redress stress-induced behavioral disturbances.

Behavioral response to fluoxetine in both female and male mice is modulated by dentate gyrus granule cell activity

Depression is a complex psychiatric disorder that is a major burden on society, with only ~33% of depressed patients attaining remission upon initial monotherapy with a selective serotonin reuptake inhibitor (SSRI). In preclinical studies using rodents, chronic stress paradigms, such as chronic corticosterone and social instability stress, are used to induce avoidance behaviors associated with negative affective states. Chronic fluoxetine (FLX; an SSRI) treatment reverses these chronic stress-induced behavioral changes in some, but not all mice, permitting stratification of mice into behavioral responders and non-responders to FLX. We previously reported that 5-HT1A receptors, which are Gi-coupled inhibitory receptors, on mature granule cells (GCs) in the dentate gyrus (DG) are necessary and sufficient for the behavioral, neurogenic, and neuroendocrine response to chronic SSRI treatment. Since inhibition of mature DG GCs through cell autonomous Gi-coupled receptors is critical for mounting an antidepressant response, we assessed the relationship between behavioral response to FLX and DG GC activation in FLX responders, non-responders, and stress controls in both male and female mice. Intriguingly, using disparate stress paradigms, we found that male and female behavioral FLX responders show decreased DG GC activation (as measured by cFos immunostaining) relative to non-responders and stress controls. We then show in both sexes that chronic inhibition of ventral DG GCs (through usage of Gi-DREADDs) results in a decrease in maladaptive avoidance behaviors, while ventral DG GCs stimulation with Gq-DREADDs increases maladaptive behaviors. Finally, we were able to bidirectionally control the behavioral response to FLX through modulation of DG GCs. Chronic inhibition of ventral DG GCs with Gi-DREADDs converted FLX non-responders into responders, while activation of ventral DG GCs with Gq-DREADDs converted FLX responders into non-responders. This study illustrates ventral DG GC activity is a major modulator of the behavioral response to FLX in both male and female mice.

Prefrontal Nectin3 Reduction Mediates Adolescent Stress-Induced Deficits of Social Memory, Spatial Working Memory, and Dendritic Structure in Mice

Chronic stress may disrupt the normal neurodevelopmental trajectory of the adolescent brain (especially the prefrontal cortex) and contribute to the pathophysiology of stress-related mental illnesses, but the underlying molecular mechanisms remain unclear. Here, we investigated how synaptic cell adhesion molecules (e.g., nectin3) are involved in the effects of adolescent chronic stress on mouse medial prefrontal cortex (mPFC). Male C57BL/6N mice were subjected to chronic social instability stress from postnatal days 29 to 77. One week later, the mice exposed to chronic stress exhibited impaired social recognition and spatial working memory, simplified dendritic structure, and reduced spine density in the mPFC. Membrane localization of nectin3 was also altered, and was significantly correlated with behavioral performance. Furthermore, knocking down mPFC nectin3 expression by adeno-associated virus in adolescent mice reproduced the stress-induced changes in behavior and mPFC morphology. These results support the hypothesis that nectin3 is a potential mediator of the effects of adolescent chronic stress on prefrontal structural and functional abnormalities.

Involvement of early embryonic miR-409-3p in the establishment of anxiety levels in female mice.

Small RNA molecules in early embryos, delivered from sperm to zygotes upon fertilization, are required for normal mouse embryonic development. Even modest changes in the levels of sperm-derived miRNAs appear to influence early embryos and subsequent development. For example, stress-associated behaviors develop in mice after injection into normal zygotes sets of sperm miRNAs elevated in stressed male mice. Here, we implicate early embryonic miR-409-3p in establishing anxiety levels in adult female, but not male mice. First, we found that exposure of male mice to chronic social instability stress, which leads to elevated anxiety in their female offspring across at least three generations through the paternal lineage, elevates sperm miR-409-3p levels not only in exposed males, but also in sperm of their F1 and F2 male offspring. Second, we observed that while injection of a mimic of miR-409-3p into zygotes from mating control males was incapable of mimicking this effect in offspring derived from them, injection of a specific inhibitor of this miRNA led to the opposite, anxiolytic effect in female, but not male, and offspring. These findings imply that baseline miR-409-3p activity in early female embryos is necessary for the expression of normal anxiety levels when they develop into adult females. In addition, elevated embryo miR-409-3p activity, possibly as a consequence of stress-induced elevation of its expression in sperm, may participate in, but may not be sufficient for, the induction of enhanced anxiety.

Benlafaxinaren eragina ezegonkortasun sozial kronikoa jasandako sagu emeen sistema serotoninergiko zentralean eta jokabidean

Bi bider ohikoagoa da depresioaren diagnosia emakumeengan gizonezkoetan baino, eta, ondorioz, baita farmako antidepresiboen erabilera ere. Hala ere, estresarekin lotutako nahasteen eta haien tratamenduaren inguruko ikerketa gehienak animalia arretan egiten dira, eta ikerketetako emaitzak gizon nahiz emakumeetara orokortzen dira gero. Ildo horretatik, antsietatearen eta depresioaren aurkako tratamenduen eraginkortasuna sexuaren araberakoa da, berezitasun biologikoak izaki. Hori dela-eta, lan honek ezegonkortasun sozial kronikoaren estresa bizi duten sagu emeen jokabidean eta garuneko bide serotoninergikoan benlafaxinak —serotoninaren eta noradrenalinaren birkaptazioaren inhibitzailea— duen eragina du aztergai.

Reduced levels of miRNAs 449 and 34 in sperm of mice and men exposed to early life stress

Exposure of male mice to early life stress alters the levels of specific sperm miRNAs that promote stress-associated behaviors in their offspring. To begin to evaluate whether similar phenomena occur in men, we searched for sperm miRNA changes that occur in both mice and men exposed to early life stressors that have long-lasting effects. For men, we used the Adverse Childhood Experience (ACE) questionnaire. It reveals the degree of abusive and/or dysfunctional family experiences when young, which increases risks of developing future psychological and physical disorders. For male mice, we used adolescent chronic social instability (CSI) stress, which not only enhances sociability defects for >1 year, but also anxiety and defective sociability in female offspring for multiple generations through the male lineage. Here we found a statistically significant inverse correlation between levels of multiple miRNAs of the miR-449/34 family and ACE scores of Caucasian males. Remarkably, we found members of the same sperm miRNA family are also reduced in mice exposed to CSI stress. Thus, future studies should be designed to directly test whether reduced levels of these miRNAs could be used as unbiased indicators of current and/or early life exposure to severe stress. Moreover, after mating stressed male mice, these sperm miRNA reductions persist in both early embryos through at least the morula stage and in sperm of males derived from them, suggesting these miRNA changes contribute to transmission of stress phenotypes across generations. Since offspring of men exposed to early life trauma have elevated risks for psychological disorders, these findings raise the possibility that a portion of this risk may be derived from epigenetic regulation of these sperm miRNAs.

Reduced hippocampal IL-10 expression, altered monoaminergic activity and anxiety and depressive-like behavior in female mice subjected to chronic social instability stress

Evidence indicates that release of pro-inflammatory cytokines induced by social stress contributes to affective disorders. Additionally, there are known sex differences in both the stress response and the stressors that can elicit this response. In this regard, the chronic social instability (CSI) rodent model of stress appears to be the best fit for the social nature of females. This study analyzed the effects of CSI on female mouse behavior, hippocampal cytokine expression, tryptophan metabolism and monoaminergic activity. The activity of hypothalamic-pituitary-adrenal (HPA) and hypothalamic-pituitary-gonadal (HPG) axes were also measured. Results showed a decrease in sucrose consumption in stressed subjects, indicative of anhedonic behavior and an increase in climbing activity in the forced swimming test (FST) and in whisking behavior, which have been associated with anxiety. Decreased interleukin-10 (IL-10) expression was found in the hippocampus of the stressed mice, while no differences in pro-inflammatory cytokine expression and tryptophan (TRYP), kynurenine (KYN) or 3-hydroxy kynurenine (3-HK) levels were found. Increased hippocampal serotoninergic and noradrenergic activity was observed in stressed mice. The higher plasma corticosterone and lower hypothalamic glucocorticoid receptor (GR) expression levels showed an increase in HPA activity after CSI. No differences were found in the plasma estradiol levels or the central estrogen receptors (ERα and ERβ) expression levels. These data indicate that the CSI stress-induced behavioral and physiological changes associated with anxiety and depressive disorders. Although additional studies are warranted, the results suggest an involvement of anti-inflammatory cytokines in the biobehavioral effects of social stress in female mice.

Abstract # 1734 Effect of chronic social instability stress on behavior, cytokine and GR receptor expression and monoaminergic brain activity in female mice

Studies show that women are at greater risk of developing stress related disorders such as depression or anxiety. It is also known that sex differences exist in the inflammatory response and that altered inflammatory signaling in the brain is involved in the development of affective disorders, possibly through its effect on neurotransmitter metabolism. This study analyzes changes in pro and anti-inflammatory cytokine expression and monoaminergic activity in the hippocampus, as well as changes in the HPA axis and behavior after exposure to chronic social instability stress in female mice. Results indicate increased HPA axis activity in stressed mice, manifested by higher plasma corticosterone levels and lower GR expression levels in the hypothalamus. No differences were found in hippocampal Il-6 and TNF-alpha proinflammatory cytokines, although a reduction was observed in IL-10 expression, accompanied by increased serotoninergic and noradrenergic activity. Stressed mice also showed a decrease in sucrose consumption, supporting the idea that in addition to proinflammatory cytokines, depressive behavior may also be influenced independently by the suppression of anti-inflammatory agents. Nevertheless, in the forced swimming test only was observed an increase in climbing behavior. This finding, alongside the increased noradrenergic and serotoninergic activity observed, may be indicative of anxiety. Data suggest that the social instability model may be useful to study different mechanisms involved in the development of stress-related psychopathologies in females.

LPS reduces BDNF and VEGF expression in the structures of the HPA axis of chronic social stressed female rats

Imbalance of brain neural circuitry induced by chronic stress leads to dysregulation of the HPA axis and dysfunction of neuroplasticity. The aim of the study was to investigate the influence of acute immunostimulation on the expression and protein level of BDNF and VEGF in the hypothalamus, pituitary and plasma of female rats subjected to chronic social instability stress. Rats were subjected to 4-week stress procedure, including phases of isolation and crowding, alternated in an unpredictable manner. On the last experimental day, the rats in the estrus phase were injected ip. with LPS (1mg/kg). All experiments were performed on females being in the same phase of the estrus cycle to avoid alterations in neurotrophin expression. An increase in relative adrenal and thymus weights in the stressed rats were observed. Chronic stress affected more strongly VEGF but not BDNF in the hypothalamus and pituitary gland. In the stressed rats, LPS decreased BDNF and VEGF mRNA levels in both structures and plasma BDNF concentrations. Optical density of VEGF immunoreactivity in the supraoptic nucleus was increased after LPS administration in the stressed rats as compared to the saline-treated stressed group. It may be assumed that chronic social stress makes the SOR neurons sensitive to a peripheral proinflammatory stimulus. Our results indicate that chronic stress enhances vulnerability of BDNF and VEGF response to neuroinflammation in the examined structures, which may be one of the reasons for its role in triggering affective diseases.

Chronic social instability stress enhances vulnerability of BDNF response to LPS in the limbic structures of female rats: A protective role of antidepressants

The aim of the present study was to estimate the influence of antidepressants given chronically on brain-derived neurotrophic factor (BDNF) alterations induced by lipopolysaccharide (LPS) in the amygdala and hippocampus of female rats subjected to chronic social instability stress (CSIS) for 29–30 days. CSIS was used as a paradigm known to be more stressful for females because stress induces affective disorders more frequently in women than men. An increased relative adrenal weight and a tendency towards the enhanced plasma corticosterone concentration were found in the stressed rats. Sucrose preference was not changed. On the last experimental day, the rats in the estrus phase were injected ip with LPS (1mg/kg). In the stressed rats, LPS administration decreased BDNF mRNA levels in both limbic structures. Desipramine (10mg/kg), fluoxetine (5mg/kg) or tianeptine (10mg/kg) given ip once daily reversed the effect of the combined stress and LPS, and tianeptine induced the strongest effects. These results indicate that chronic stress enhances vulnerability of BDNF response to deleterious influence of neuroinflammation in the examined limbic structures, what may account for its role in triggering neuropsychiatric diseases. The observed effect of antidepressants may be of significance for their therapeutic effects in the stress-induced affective disorders in females.

Social instability stress differentially affects amygdalar neuron adaptations and memory performance in adolescent and adult rats

Adolescence is a time of developmental changes and reorganization in the brain. It has been hypothesized that stress has a greater neurological impact on adolescents than on adults. However, scientific evidence in support of this hypothesis is still limited. We treated adolescent (4-week-old) and adult (8-week-old) rats with social instability stress for 5 weeks and compared the subsequent structural and functional changes to amygdala neurons. In the stress-free control condition, the adolescent group showed higher fear-potentiated startle responses, larger dendritic arborization, more proximal dendritic spine distribution and lower levels of truncated TrkB than the adult rats. Social instability stress exerted opposite effects on fear-potentiated startle responses in these two groups, i.e., the stress period appeared to hamper the performance in adolescents but improved it in adult rats. Furthermore, whilst the chronic social stress applied to adolescent rats reduced their dendritic field and spine density in basal and lateral amygdala neurons, the opposite stress effects on neuron morphology were observed in the adult rats. Moreover, stress in adolescence suppressed the amygdala expression of synaptic proteins, i.e., full-length TrkB and SNAP-25, whereas, in the adult rats, chronic stress enhanced full-length and truncated TrkB expressions in the amygdala. In summary, chronic social instability stress hinders amygdala neuron development in the adolescent brain, while mature neurons in the amygdala are capable of adapting to the stress. The stress induced age-dependent effects on the fear-potentiated memory may occur by altering the brain-derived neurotrophic factor (BDNF)-TrkB signaling and neuroplasticity in the amygdala.