Influence of chronic stress on brain corticosteroid receptors and HPA axis activity

Complement C5a Receptor Signaling Alters Stress Responsiveness and Modulates Microglia Following Chronic Stress Exposure

Background

Accumulating evidence underscores the pivotal role of heightened inflammation in the pathophysiology of stress-related diseases, but the underlying mechanisms remain elusive. The complement system, a key effector of the innate immune system, produces the C5-cleaved activation product C5a upon activation, initiating inflammatory responses through the canonical C5a receptor 1 (C5aR1). While C5aR1 is expressed in stress-responsive brain regions, its role in stress responsiveness remains unknown.

Methods

To investigate C5a-C5aR1 signaling in stress responses, mice underwent acute and chronic stress paradigms. Circulating C5a levels and messenger RNA expression of C5aR1 in the hippocampus and adrenal gland were measured. C5aR1-deficient mice were used to elucidate the effects of disrupted C5a-C5aR1 signaling across behavioral, hormonal, metabolic, and inflammation parameters.

Results

Chronic restraint stress elevated circulating C5a levels while reducing C5aR1 messenger RNA expression in the hippocampus and adrenal gland. Notably, the absence of C5aR1 signaling enhanced adrenal sensitivity to adrenocorticotropic hormone, concurrently reducing pituitary adrenocorticotropic hormone production and enhancing the response to acute stress. C5aR1-deficient mice exhibited attenuated reductions in locomotor activity and body weight under chronic stress. Additionally, these mice displayed increased glucocorticoid receptor sensitivity and disrupted glucose and insulin homeostasis. Chronic stress induced an increase in C5aR1-expressing microglia in the hippocampus, a response mitigated in C5aR1-deficient mice.

Conclusions

C5a-C5aR1 signaling emerges as a key metabolic regulator during stress, suggesting that complement activation and dysfunctional C5aR1 signaling may contribute to neuroinflammatory phenotypes in stress-related disorders. The results advocate for further exploration of complement C5aR1 as a potential therapeutic target for stress-related conditions.

The Influence of Social Dynamics on Biological Aging and the Health of Historically Marginalized Populations: A Biopsychosocial Model for Health Disparities

Historically marginalized populations are susceptible to social isolation resulting from their unique social dynamics; thus, they incur a higher risk of developing chronic diseases across the course of life. Research has suggested that the cumulative effect of aging trajectories per se, across the lifespan, determines later-in-life disease risks. Emerging evidence has shown the biopsychosocial effects of social stress and social support on one's wellbeing in terms of inflammation. Built upon previous multidisciplinary findings, here, we provide an overarching model that explains how the social dynamics of marginalized populations shape their rate of biological aging through the inflammatory process. Under the framework of social stress and social support theories, this model aims to facilitate our understanding of the biopsychosocial impacts of social dynamics on the wellbeing of historically marginalized individuals, with a special emphasis on biological aging. We leverage this model to advance our mechanistic understanding of the health disparity observed in historically marginalized populations and inform future remediation strategies.

Structural and biochemical alterations in dendritic spines as key mechanisms for severe mental illnesses

Severe mental illnesses (SMI) collectively affect approximately 20% of the global population, as estimated by the World Health Organization (WHO). Despite having diverse etiologies, clinical symptoms, and pharmacotherapies, these diseases share a common pathophysiological characteristic: the misconnection of brain areas involved in reality perception, executive control, and cognition, including the corticolimbic system. Dendritic spines play a crucial role in excitatory neurotransmission within the central nervous system. These small structures exhibit remarkable plasticity, regulated by factors such as neurotransmitter tone, neurotrophic factors, and innate immunity-related molecules, and other mechanisms - all of which are associated with the pathophysiology of SMI. However, studying dendritic spine mechanisms in both healthy and pathological conditions in patients is fraught with technical limitations. This is where animal models related to these diseases become indispensable. They have played a pivotal role in elucidating the significance of dendritic spines in SMI. In this review, the information regarding the potential role of dendritic spines in SMI was summarized, drawing from clinical and animal model reports. Also, the implications of targeting dendritic spine-related molecules for SMI treatment were explored. Specifically, our focus is on major depressive disorder and the neurodevelopmental disorders schizophrenia and autism spectrum disorder. Abundant clinical and basic research has studied the functional and structural plasticity of dendritic spines in these diseases, along with potential pharmacological targets that modulate the dynamics of these structures. These targets may be associated with the clinical efficacy of the pharmacotherapy.

Effect of chronic unpredictable stress in female Wistar-Kyoto rats subjected to progesterone withdrawal: Relevance for Premenstrual Dysphoric Disorder neurobiology

Premenstrual Dysphoric Disorder (PMDD) is related to an abrupt drop in progesterone and impairments in the HPA axis that cause anxiety. Suffering persons report higher daily-life stress and anxiety proneness that may contribute to developing PMDD, considered a chronic stress-related disorder. Here, we explored the effect of chronic unpredictable stress (CUS) in rats subjected to progesterone withdrawal (PW) and evaluated gene expression of HPA axis activation in the stress-vulnerable Wistar-Kyoto (WKY) rat strain that is prone to anxiety. Ovariectomized WKY rats were randomly assigned to CUS or Standard-housed conditions (SHC) for 30 days. To induce PW, animals received 2 mg/kg of progesterone on day 25th for 5 days; 24 h later, they were tested using the anxiety-like burying behavior test (BBT). After behavioral completion, rats were euthanized, and brains were extracted to measure Crh (PVN) and Nr3c1 (hippocampus) mRNA. Blood corticosterone and vasopressin levels were determined. Results showed that PW exacerbated anxiety-like behaviors through passive coping in CUS-WKY. PW decreased Crh-PVN mRNA and the Nr3c1-hippocampal mRNA expression in SHC. CUS decreased Crh-PVN mRNA compared to SHC, and no further changes were observed by PW or BBT exposure. CUS reduced Nr3c1-hippocampal gene expression compared to SHC animals, and lower Nr3c1 mRNA was detected due to BBT. The PW increased corticosterone in SHC and CUS rats; however, CUS blunted corticosterone when combined with PW+BBT and similarly occurred in vasopressin concentrations. Chronic stress blunts the response of components of the HPA axis regulation when PW and BBT (systemic and psychogenic stressors, respectively) are presented. This response may facilitate less adaptive behaviors through passive coping in stress-vulnerable subjects in a preclinical model of premenstrual anxiety.

Inflammation, stress and depression: An exploration of ketamine's therapeutic profile

Well-established animal models of depression have described a proximal relationship between stress and central nervous system (CNS) inflammation - a relationship mirrored in the peripheral inflammatory biomarkers of individuals with depression. Evidence also suggests that stress-induced proinflammatory states can contribute to the neurobiology of treatment-resistant depression. Interestingly, ketamine, a rapid-acting antidepressant, can partially exert its therapeutic effects via anti-inflammatory actions on the hypothalamic-pituitary adrenal (HPA) axis, the kynurenine pathway or by cytokine suppression. Further investigations into the relationship between ketamine, inflammation and stress could provide insight into ketamine's unique therapeutic mechanisms and stimulate efforts to develop rapid-acting, anti-inflammatory-based antidepressants.

Chronic stress induced loudness hyperacusis, sound avoidance and auditory cortex hyperactivity

Hyperacusis, a debilitating loudness intolerance disorder, has been linked to chronic stress and adrenal insufficiency. To investigate the role of chronic stress, rats were chronically treated with corticosterone (CORT) stress hormone. Chronic CORT produced behavioral evidence of loudness hyperacusis, sound avoidance hyperacusis, and abnormal temporal integration of loudness. CORT treatment did not disrupt cochlear or brainstem function as reflected by normal distortion product otoacoustic emissions, compound action potentials, acoustic startle reflexex, and auditory brainstem responses. In contrast, the evoked response from the auditory cortex was enhanced up to three fold after CORT treatment. This hyperactivity was associated with a significant increase in glucocorticoid receptors in auditory cortex layers II/III and VI. Basal serum CORT levels remained normal after chronic CORT stress whereas reactive serum CORT levels evoked by acute restraint stress were blunted (reduced) after chronic CORT stress; similar changes were observed after chronic, intense noise stress. Taken together, our results show for the first time that chronic stress can induce hyperacusis and sound avoidance. A model is proposed in which chronic stress creates a subclinical state of adrenal insufficiency that establishes the necessary conditions for inducing hyperacusis.

Restraint Stress and Repeated Corticosterone Administration Differentially Affect Neuronal Excitability, Synaptic Transmission and 5-HT7 Receptor Reactivity in the Dorsal Raphe Nucleus of Young Adult Male Rats

Exogenous corticosterone administration reduces GABAergic transmission and impairs its 5-HT₇ receptor-dependent modulation in the rat dorsal raphe nucleus (DRN), but it is largely unknown how neuronal functions of the DRN are affected by repeated physical and psychological stress. This study compared the effects of repeated restraint stress and corticosterone injections on DRN neuronal excitability, spontaneous synaptic transmission, and its 5-HT₇ receptor-dependent modulation. Male Wistar rats received corticosterone injections for 7 or 14 days or were restrained for 10 min twice daily for 3 days. Repeated restraint stress and repeated corticosterone administration evoked similar changes in performance in the forced swim test. They increased the frequency of spontaneous excitatory postsynaptic currents (sEPSCs) recorded from DRN neurons. In contrast to the treatment with corticosterone, restraint stress-induced changes in sEPSC kinetics and decreased intrinsic excitability of DRN neurons did not modify inhibitory transmission. Repeated injections of the 5-HT₇ receptor antagonist SB 269970 ameliorated the effects of restraint on excitability and sEPSC frequency but did not restore the altered kinetics of sEPSCs. Thus, repeated restraint stress and repeated corticosterone administration differ in consequences for the intrinsic excitability of DRN projection neurons and their excitatory and inhibitory synaptic inputs. Effects of repeated restraint stress on DRN neurons can be partially abrogated by blocking the 5-HT₇ receptor.

New View on the Impact of the Low-Frequency Electromagnetic Field (50 Hz) on Stress Responses: Hormesis Effect

INTRODUCTION

Low-frequency electromagnetic field (50 Hz) (EMF) can modify crucial neuronal processes. Existing data indicate that exposure to EMF may represent a mild stressor and contribute to disturbances of the hypothalamic-pituitary-adrenal (HPA) axis. The important regulatory pathways controlling HPA axis activity include two types of corticosteroid receptors: mineralocorticoid receptors (MRs) and glucocorticoid receptors. They are particularly abundant in the hippocampus, a key locus of HPA axis feedback control. The research aimed at determining whether (1) EMF exhibits hormesis, it means bidirectional action depending on EMF intensity (1 or 7 mT) and (2) repeated EMF exposure changes stress response to subsequent stress factors.

METHODS

The exposure (7 days, 1 h/day) of adult rats to EMF (1 mT and 7 mT) was repeated 3 times. HPA axis hormones and their receptors were analysed after each following exposure. Moreover, the impact of EMF exposure on hormonal and behavioural responses to subsequent stress factor - open-field test was evaluated.

RESULTS

Our data suggest that exposure to EMF can establish a new "set-point" for HPA axis activity. The direction and dynamics of this process depend on the intensity of EMF and the number of exposures. EMF of 1 mT induced an adaptive stress response, but 7 mT EMF caused sensitization. Consequently, EMF changed the vulnerability of the organism to a subsequent stress factor. We have also shown the increase in MR mRNA abundance in the hippocampus of 1 mT EMF-exposed rats, which can represent the possible neuroprotective response and suggest therapeutic properties of EMFs.

Early-life maternal deprivation affects the mother-offspring relationship in domestic pigs, as well as the neuroendocrine development and coping behavior of piglets

Early-life adversity may have programming effects on the psychological and physiological development of offspring. Domestic pigs (Sus scrofa) are an excellent model species for studying these effects because of their many physiological similarities to humans. Piglets from 10 sows were subjected to daily 2-h maternal deprivation on postnatal days (PND) 2–15 alone (DA) or in a group of littermates (DG). Control piglets (C) from 10 sows stayed with their mothers. Mother-offspring interaction, milk oxytocin, and cortisol were analyzed. An open-field/novel-object (OF/NO) test was performed with piglets on PNDs 16 and 40. Plasma cortisol and immune parameters were determined on PND 5 and 16. Two piglets from each group and sow were sacrificed on PND 20 and stress-related gene expression in the limbic system and prefrontal cortex (PFC), as well as splenic lymphocyte proliferative abilities, were examined. The milk cortisol of sows increased during the first separation of mother and offspring on the second day of lactation, whereas milk oxytocin did not change. The increase in cortisol by the OF/NO test on PND 16 was greater in C piglets than in DA and DG ones. DA piglets showed less agitated behavior than DG and C piglets in the OF/NO test at PND 16, but appeared more fearful. On PND 40, DA piglets showed more arousal than DG and C piglets in the OF/NO test. Neither plasma IgA nor N/L ratios in blood nor mitogen-induced proliferation of spleen lymphocytes were affected by deprivation. We found a higher mRNA expression of CRHR1 in the hypothalamus and a higher expression of MR in the hippocampus in DA piglets than in DG ones. The expression of GR, MR, and CRHR1 genes in the PFC was reduced by maternal deprivation, however, the expression of arginine vasopressin and oxytocin receptors was not affected. Repeated maternal deprivation induces sustained effects on stress reactivity and behavior of domestic piglets. Some of these effects were buffered by the presence of littermates. In addition, we found sex-specific differences in behavior and gene expression.

Disrupted development from head to tail: Pervasive effects of postnatal restricted resources on neurobiological, behavioral, and morphometric outcomes

When a maternal rat nurtures her pups, she relies on adequate resources to provide optimal care for her offspring. Accordingly, limited environmental resources may result in atypical maternal care, disrupting various developmental outcomes. In the current study, maternal Long-Evans rats were randomly assigned to either a standard resource (SR) group, provided with four cups of bedding and two paper towels for nesting material or a limited resource (LR) group, provided with a quarter of the bedding and nesting material provided for the SR group. Offspring were monitored at various developmental phases throughout the study. After weaning, pups were housed in same-sex dyads in environments with SRs for continued observations. Subsequent behavioral tests revealed a sex × resource interaction in play behavior on PND 28; specifically, LR reduced play attacks in males while LR increased play attacks in females. A sex × resource interaction was also observed in anxiety-related responses in the open field task with an increase in thigmotaxis in LR females and, in the social interaction task, females exhibited more external rears oriented away from the social target. Focusing on morphological variables, tail length measurements of LR males and females were shorter on PND 9, 16, and 21; however, differences in tail length were no longer present at PND 35. Following the behavioral assessments, animals were perfused at 56 days of age and subsequent immunohistochemical assays indicated increased glucocorticoid receptors in the lateral habenula of LR offspring and higher c-Fos immunoreactivity in the basolateral amygdala of SR offspring. Further, when tail vertebrae and tail tendons were assessed via micro-CT and hydroxyproline assays, results indicated increased trabecular separation, decreased bone volume fraction, and decreased connectivity density in bones, along with reduced collagen concentration in tendons in the LR animals. In sum, although the restricted resources only persisted for a brief duration, the effects appear to be far-reaching and pervasive in this early life stress animal model.

The Effects of Synbiotics Administration on Stress-Related Parameters in Thai Subjects-A Preliminary Study

Urbanization influences our lifestyle, especially in fast-paced environments where we are more prone to stress. Stress management is considered advantageous in terms of longevity. The use of probiotics for psychological treatment has a small amount of diverse proven evidence to support this. However, studies on stress management in stressed subjects using synbiotics are still limited. The present study aimed to investigate the effects of synbiotics on stress in the Thai population. A total of 32 volunteers were enrolled and screened using a Thai Stress Test (TST) to determine their stress status. Participants were divided into the stressed and the non-stressed groups. Synbiotics preparation comprised a mixture of probiotics strains in a total concentration of 1 × 1010 CFU/day (5.0 × 109 CFU of Lactobacillus paracasei HII01 and 5.0 × 109 CFU of Bifidobacterium animalis subsp. lactis) and 10 g prebiotics (5 g galacto-oligosaccharides (GOS), and 5 g oligofructose (FOS)). All parameters were measured at baseline and after the 12th week of the study. In the stressed group, the administration of synbiotics significantly (p < 0.05) reduced the negative scale scores of TST, and tryptophan. In the non-stressed group, the synbiotics administration decreased tryptophan significantly (p < 0.05), whereas dehydroepiandrosterone sulfate (DHEA-S), tumor necrosis factor-α (TNF-α), 5-hydroxyindoleacetic acid (5-HIAA), and short-chain fatty acids (SCFAs), acetate and propionate were increased significantly (p < 0.05). In both groups, cortisol, and lipopolysaccharide (LPS) were reduced, whereas anti-inflammatory mediator interleukin-10 (IL-10) and immunoglobulin A (IgA) levels were increased. In conclusion, synbiotics administration attenuated the negative feelings via the negative scale scores of TST in stressed participants by modulating the HPA-axis, IL-10, IgA, and LPS. In comparison, synbiotics administration for participants without stress did not benefit stress status but showed remodeling SCFAs components, HPA-axis, and tryptophan catabolism.

Acute Inflammation Induces Neuroendocrine and Opioid Receptor Genes Responses in the Seabass Dicentrarchus labrax Brain

Simple Summary

It is generally accepted (in mammals and in teleost fish, too) that stressful conditions affect the performance of an immune response. What is still far from being known is at what extend does an immune process affects the neuroendocrine system. Vaccination for instance, is nowadays a common practice in aquaculture and little is known about its physiological implications other than immunization. Here is a first approach to the study of the European seabass’ brain gene expression patterns in response to a peripheral inflammatory process. Genes related to the stress response were focused, along with those related to the opioid system. Increased expression of certain genes suggests the activation of a stress response triggered by inflammatory signals. Additionally, contrasting expression patterns of the same gene (increased vs decreased) in the different brain regions (as well as the time needed for changes to happen) point at different functions. These results clearly show the reactivity of different brain responses to an immune response, highlighting the importance of further studies on downstream implications (behavior, feeding, welfare, reproduction).

Abstract

In fish, as observed in mammals, any stressful event affects the immune system to a larger or shorter extent. The neuroendocrine-immune axis is a bi-directional network of mobile compounds and their receptors that are shared between both systems (neuroendocrine and immune) and that regulate their respective responses. However, how and to what extent immunity modulates the neuroendocrine system is not yet fully elucidated. This study was carried out to understand better central gene expression response patterns in a high-valued farmed fish species to an acute peripheral inflammation, focusing on genes related to the hypothalamus-pituitary-interrenal axis and the opioid system. European seabass, Dicentrarchus labrax, were intra-peritoneally injected with either Freund’s Incomplete Adjuvant to induce a local inflammatory response or Hanks Balances Salt Solution to serve as the control. An undisturbed group was also included to take into account the effects due to handling procedures. To evaluate the outcomes of an acute immune response, fish were sampled at 4, 24, 48, and 72 h post-injection. The brain was sampled and dissected for isolation of different regions: telencephalon, optic tectum, hypothalamus, and pituitary gland. The expression of several genes related to the neuroendocrine response was measured by real-time PCR. Data were statistically analyzed by ANOVA and discriminant analyses to obtain these genes’ responsiveness for the different brain regions. Serotonergic receptors were upregulated in the telencephalon, whereas the optic tectum inhibited these transcription genes. The hypothalamus showed a somewhat delayed response in which serotonin and glucocorticoid receptors were concerned. Still, the hypothalamic corticotropin-releasing hormone played an important role in differentiating fish undergoing an inflammatory response from those not under such conditions. Opioid receptors gene expression increased in both the hypothalamus and the telencephalon, while in the optic tectum, most were downregulated. However, no changes in the pituitary gland were observed. The different brain regions under immune stimulation demonstrated clear, distinct responses regarding gene transcription rates as well as the time period needed for the effect to occur. Further, more integrative studies are required to associate functions to the evaluated genes more safely and better understand the triggering mechanisms.

Exploring the link between adolescent inhalant misuse and suicidal behaviour: a behavioural toxicology perspective

Adolescent inhalant misuse has a known association with suicidal thoughts and behaviour. This association persists even after inhalant misuse has ceased. Previous studies have hypothesised that this association may derive from socioeconomic disadvantage or vulnerability, and potentially mediated by impulsivity. This association may also be due to the central nervous system depressant effects of inhalants. This review takes a behavioural toxicology perspective, focussed particularly on the serotonergic system and the Hypothalamic-Pituitary-Adrenal (HPA) axis, as potential links between adolescent inhalant misuse and suicidal behaviour. The challenges of bridging the pre-clinical and clinical literature in this area are discussed, along with promising avenues for future research; ultimately aimed at reducing suicide risk in a vulnerable adolescent population group.

Repeated stimulation of the HPA axis alters white blood cell count without increasing oxidative stress or inflammatory cytokines in fasting elephant seal pups

The hypothalamic-pituitary-adrenal (HPA) axis controls the release of glucocorticoids, which regulate immune and inflammatory function by modulating cytokines, white blood cells and oxidative stress via glucocorticoid receptor (GR) signaling. Although the response to HPA activation is well characterized in many species, little is known about the impacts of HPA activation during extreme physiological conditions. Hence, we challenged 18 simultaneously fasting and developing elephant seal pups with daily intramuscular injections of adrenocorticotropin (ACTH), a GR antagonist (RU486), or a combination of the two (ACTH+RU486) for 4 days. We collected blood at baseline, 2 h and 4 days after the beginning of treatment. ACTH and ACTH+RU486 elevated serum aldosterone and cortisol at 2 h, with effects diminishing at 4 days. RU486 alone induced a compensatory increase in aldosterone, but not cortisol, at 4 days. ACTH decreased neutrophils at 2 h, while decreasing lymphocytes and increasing the neutrophil:lymphocyte ratio at 4 days. These effects were abolished by RU486. Despite alterations in white blood cells, there was no effect of ACTH or RU486 on transforming growth factor-β or interleukin-6 levels; however, both cytokines decreased with the 4 day fasting progression. Similarly, ACTH did not impact protein oxidation, lipid peroxidation or antioxidant enzymes, but plasma isoprostanes and catalase activity decreased while glutathione peroxidase increased with fasting progression. These data demonstrate differential acute (2 h) and chronic (4 days) modulatory effects of HPA activation on white blood cells and that the chronic effect is mediated, at least in part, by GR. These results also underscore elephant seals' extraordinary resistance to oxidative stress derived from repeated HPA activation.

Therapeutic effects of saffron extract on different memory types, anxiety, and hippocampal BDNF and TNF-α gene expressions in sub-chronically stressed rats

Objective: While stress reportedly impairs memory, saffron enhances it. This study investigated the therapeutic effects of saffron extract on different memory types, anxiety-like behavior, and expressions of BDNF and TNF-α genes in sub-chronically stressed rats.Methods: Rats were randomly assigned to control, restraint stress (6 h/day/7 days), two 7-days saffron treatments with 30 and 60 mg/kg, and two stress-saffron groups (30 and 60 mg/kg/7 post-stress days). Serum cortisol level and hippocampal BDNF and TNF-α gene expressions were measured. Open field, passive avoidance, novel object recognition, and object location tests were performed to assess anxiety-like behavior and avoidance as well as cognitive and spatial memories, respectively.Results: The low saffron dose in the sub-chronic stressed group led to a significant increase in passive avoidance latency from day 3 onward whereas this effect was observed after 7 days under the high-dose treatment that simultaneously led to a significant decline in serum cortisol level. While the low saffron dose led to a sharp drop in hippocampal TNF-α gene expression, the high dose significantly increased the hippocampal BDNF gene expression in the sub-chronic stress group. Finally, both saffron doses reduced anxiety in the stressed groups.Conclusion: Compared to the low saffron dose, the high dose had a latent but long-lasting impact. Cognitive and spatial memories remained unaffected by either stress or saffron treatment. In addition, only the high saffron dose reversed anxiety in the sub-chronically stressed group. These findings suggest that various doses of saffron act differently on different brain functions under sub-chronic stress conditions.Abbreviations: Brain derived neurotrophic factor (BDNF), tumor necrosis factor-α (TNF-α), hypothalamic-pituitary-adrenal axis (HPA), novel object recognition task (NORT), novel object location task (NOLT), open field test (OFT), passive avoidance (PA).

The chemical chaperon 4-phenyl butyric acid restored high-fat diet- induced hippocampal insulin content and insulin receptor level reduction along with spatial learning and memory deficits in male rats

This study assessed the effect of a chronic high-fat diet (HFD) on plasma and hippocampal insulin and corticosterone levels, the hippocampus insulin receptor amount, and spatial learning and memory with or without receiving 4-phenyl butyric acid (4-PBA) in male rats. Rats were divided into high-fat and normal diet groups, then each group was subdivided into dimethyl sulfoxide (DMSO) and 4-PBA groups. After weaning, the rats were fed with HFD for 20 weeks. Then, 4-PBA or DMSO were injected for 3 days. Subsequently, oral glucose tolerance test was done. On the following day, spatial memory tests were performed. Then the hippocampus Bip, Chop, insulin, corticosterone, and insulin receptor levels were determined. HFD increased plasma glucose, leptin and corticosterone concentrations, hippocampus Bip, Chop and corticosterone levels, food intake, abdominal fat weight and body weight along with impaired glucose tolerance. It decreased plasma insulin, and insulin content, and its receptor amount in hippocampus. HFD lengthened escape latency and shortened the duration spent in target zone. 4-PBA administration improved the HFD- induced adverse changes. Chronic HFD possibly through the induction of endoplasmic reticulum (ER) stress and subsequent changes in the levels of hippocampal corticosterone, insulin and insulin receptor along with possible leptin resistance caused spatial learning and memory deficits.

Psychosocial Crowding Stress-Induced Changes in Synaptic Transmission and Glutamate Receptor Expression in the Rat Frontal Cortex

This study demonstrates how exposure to psychosocial crowding stress (CS) for 3, 7, and 14 days affects glutamate synapse functioning and signal transduction in the frontal cortex (FC) of rats. CS effects on synaptic activity were evaluated in FC slices of the primary motor cortex (M1) by measuring field potential (FP) amplitude, paired-pulse ratio (PPR), and long-term potentiation (LTP). Protein expression of GluA1, GluN2B mGluR1a/5, VGLUT1, and VGLUT2 was assessed in FC by western blot. The body’s response to CS was evaluated by measuring body weight and the plasma level of plasma corticosterone (CORT), adrenocorticotropic hormone (ACTH), and interleukin 1 beta (IL1B). CS 3 14d increased FP and attenuated LTP in M1, while PPR was augmented in CS 14d. The expression of GluA1, GluN2B, and mGluR1a/5 was up-regulated in CS 3d and downregulated in CS 14d. VGLUTs expression tended to increase in CS 7d. The failure to blunt the effects of chronic CS on FP and LTP in M1 suggests the impairment of habituation mechanisms by psychosocial stressors. PPR augmented by chronic CS with increased VGLUTs level in the CS 7d indicates that prolonged CS exposure changed presynaptic signaling within the FC. The CS bidirectional profile of changes in glutamate receptors’ expression seems to be a common mechanism evoked by stress in the FC.

Fermented Maillard reaction products attenuate stress-induced testicular dysfunction in mice

Chronic stress can cause psychological diseases and affect male fertility and the reproductive system. Maillard reaction of milk proteins improves their functional and nutritional properties through modification of proteins. Previously, we determined that Maillard reaction product (MRP) from milk casein and MRP fermented (FMRP) with Lactobacillus rhamnosus 4B15 (4B15) had anti-anxiolytic effects in mice under chronic stress. Therefore, we aimed to investigate the effects of MRP and FMRP on chronic stress-induced testicular dysfunction in mice through quantitative real-time PCR (qRT-PCR) and in situ hybridization analysis. Mice were pretreated with MRP and FMRP for 10 wk; simultaneously, from the third week of the experimental period, they were exposed to unpredictable chronic mild stress (UCMS) for 7 wk. The expression levels of the luteinizing hormone subunit β (Lhb) and follicle-stimulating hormone subunit β (Fshb) were remarkably reduced after exposure to UCMS. However, treatment with MRP and FMRP inhibited the UCMS-induced reduction, with FMRP showing especially significant inhibition. Moreover, the expression of steroidogenesis-related genes [luteinizing hormone receptor (Lhr), follicle-stimulating hormone (Fshr), 3-β hydroxysteroid dehydrogenase 2 (Hsd3b2), and steroidogenic acute regulatory protein (StAR)] were significantly reduced in response to UCMS. In contrast, the transcript levels of these genes were highest in the MRP-treated mice. Mice pretreated with FMRP also exhibited higher levels of gene expression compared with the nonstressed mice. Moreover, UCMS significantly downregulated the expression of genes associated with testicular function [i.e., a disintegrin and metallopeptidase domain 5 (Adam5), Adam29, bone morphogenetic protein 2 (Bmp2), tektin 3 (Tekt3), and sperm adhesion molecule 1 (Spam1)]. However, the administration of MRP and FMRP prevented the UCMS-induced reduction in the expressions of above genes. The localization of Lhr, Srd5a2, Adam29, and Spam1 was confirmed by in situ hybridization analysis and the results were consistent with those of qRT-PCR. Consequently, these results indicated that MRP and FMRP, manufactured by the heat treatment of milk casein and fermentation with probiotic 4B15, have the potential to prevent chronic stress-induced testicular dysfunction.

Responses to chronic corticosterone on brain glucocorticoid receptors, adrenal gland, and gut microbiota in mice lacking neuronal serotonin

Dysregulation of the stress-induced activation of the hypothalamic-pituitary-adrenocortical axis can result in disease. Bidirectional communication exists between the brain and the gut, and alterations in these interactions appear to be involved in stress regulation and in the pathogenesis of neuropsychiatric diseases, such as depression. Serotonin (5HT) plays a crucial role in the functions of these two major organs but its direct influence under stress conditions remains unclear. To investigate the role of neuronal 5HT on chronic stress responses and its influence on the gut microbiome, mice lacking the gene for tryptophan hydroxylase-2 were treated with the stress hormone corticosterone (CORT) for 21 days. The intake of fluid and food, as well as body weights were recorded daily. CORT levels, expression of glucocorticoid receptors (GR) in the brain and the size of the adrenal gland were evaluated. Caecum was used for 16S rRNA gene characterization of the gut microbiota. Results show that 5HT depletion produced an increase in food intake and a paradoxical reduction in body weight that were enhanced by CORT. Neuronal 5HT depletion impaired the feedback regulation of CORT levels but had no putative effect on the CORT-induced decrease in hippocampal GR expression and the reduction of the adrenal cortex size. Finally, the composition and structure of the gut microbiota were significantly impacted by the absence of neuronal 5HT, and these alterations were enhanced by chronic CORT treatment. Therefore, we conclude that neuronal 5HT influences the stress-related responses at different levels involving CORT levels regulation and the gut microbiome.

Stress, glucocorticoid signaling pathway, and metabolic disorders

BACKGROUND AND AIMS

Glucocorticoids and the GR serve as an essential molecular mediator of stress and different physiologic processes. This review summarizes main findings from studies on the role of the GC/GR signaling in the modulation of genes for nutrient processing by the different organs involved in metabolic diseases.

METHODS

Descriptive review of relevant papers known to the author was conducted.

RESULTS

Several high-throughput screenings in the past 15 years have identified potential GR DNA-binding regions in different cell types with genes that are annotated to be important for the control of metabolism. Transcriptional regulation of these GC-responsive genes provides links between the hypothalamic-pituitary-adrenal axis (HPA) and systemic energy homeostasis in both physiological and pathophysiological states. Future studies must reconsider the use of agonist, the utilization of animal models of stress and metabolic disorders, and validation in humans.

CONCLUSION

This review recapitulates the significant role of the GC/GR signaling in molecular metabolic control and metabolic disorders. Potential future research focus and optimizations have also been identified.

Forebrain overexpression of type 1 adenylyl cyclase promotes molecular stability and behavioral resilience to physical stress

The ability to cope with stress is essential for emotional stability and mental health. It is also hypothesized that factors promoting resilience to stress may offer treatment strategies for maladaptive disorders such as anxiety and depression. Here, we find that physical restraint reduces the expression of type 1 adenylyl cyclase (Adcy1), a neurospecific synaptic enzyme that positively regulates the cAMP signaling cascade. Conversely, an increase of forebrain Adcy1 expression in transgenic mouse (i.e., Adcy1 ^tg mouse) predisposes individuals to molecular stability and behavioral resilience. Transgenic overexpression of Adcy1 prevents the physical restraint-induced down-regulation of brain-derived neurotrophic factor (BDNF) and neuropeptide Y (NPY). Further, Adcy1 ^tg mice maintain regular locomotive activity in novelty exploration and voluntary wheel running following physical restraint. Adcy1 ^tg mice show higher corticosterone and lower basal glucocorticoid receptor (GR) expression, along with a higher MR (mineralocorticoid receptor) to GR ratio in the hippocampus. Further, Adcy1 ^tg mice show reduced immobility under acute physical stress conditions in the forced swimming test and are more sensitive to the antidepressant desipramine. Our results demonstrate a novel function of Adcy1 in stress coping and suggest Adcy1 as a potential target to antagonize stress vulnerability and promote antidepressant efficacy.

Aging increases vulnerability to stress-induced depression via upregulation of NADPH oxidase in mice

Brain aging proceeds with cellular and molecular changes in the limbic system. Aging-dependent changes might affect emotion and stress coping, yet the underlying mechanisms remain unclear. Here, we show aged (18-month-old) mice exhibit upregulation of NADPH oxidase and oxidative stress in the hippocampus, which mirrors the changes in young (2-month-old) mice subjected to chronic stress. Aged mice that lack p47phox, a key subunit of NADPH oxidase, do not show increased oxidative stress. Aged mice exhibit depression-like behavior following weak stress that does not produce depressive behavior in young mice. Aged mice have reduced expression of the epigenetic factor SUV39H1 and its upstream regulator p-AMPK, and increased expression of Ppp2ca in the hippocampus-changes that occur in young mice exposed to chronic stress. SUV39H1 mediates stress- and aging-induced sustained upregulation of p47phox and oxidative stress. These results suggest that aging increases susceptibility to stress by upregulating NADPH oxidase in the hippocampus.

LPA1 receptor and chronic stress: Effects on behaviour and the genes involved in the hippocampal excitatory/inhibitory balance

The LPA₁ receptor, one of the six characterized G protein-coupled receptors (LPA_1-6) through which lysophosphatidic acid acts, is likely involved in promoting normal emotional behaviours. Current data suggest that the LPA-LPA_1-receptor pathway may be involved in mediating the negative consequences of stress on hippocampal function. However, to date, there is no available information regarding the mechanisms whereby the LPA₁ receptor mediates this adaptation. To gain further insight into how the LPA-LPA₁ pathway may prevent the negative consequences of chronic stress, we assessed the effects of the continuous delivery of LPA on depressive-like behaviours induced by a chronic restraint stress protocol. Because a proper excitatory/inhibitory balance seems to be key for controlling the stress response system, the gene expression of molecular markers of excitatory and inhibitory neurotransmission was also determined. In addition, the hippocampal expression of mineralocorticoid receptor genes and glucocorticoid receptor genes and proteins as well as plasma corticosterone levels were determined. Contrary to our expectations, the continuous delivery of LPA in chronically stressed animals potentiated rather than inhibited some (e.g., anhedonia, reduced latency to the first immobility period), though not all, behavioural effects of stress. Furthermore, this treatment led to an alteration in the genes coding for proteins involved in the excitatory/inhibitory balance in the ventral hippocampus and to changes in corticosterone levels. In conclusion, the results of this study reinforce the assumption that LPA is involved in emotional regulation, mainly through the LPA₁ receptor, and regulates the effects of stress on hippocampal gene expression and hippocampus-dependent behaviour.

Inhibition of JNK ameliorates depressive-like behaviors and reduces the activation of pro-inflammatory cytokines and the phosphorylation of glucocorticoid receptors at serine 246 induced by neuroinflammation

Depression is associated with immune dysregulation and the aberrant activity of the hypothalamic-pituitary-adrenal (HPA) axis. However, the neurobiological molecular mechanisms underlying these associations remain unclear. c-Jun amino-terminal kinase (JNK), an important modulator in inflammation and stress responses, is often critically implicated in the development of central nervous system diseases. However, whether and how JNK mediates neuroinflammation-induced depression remains largely unknown. In this study, we investigated the role of JNK in depressive-like behaviors induced by central lipopolysaccharide (LPS) infusion. The results showed that LPS infusion led to depressive-like behaviors, accompanied by increased proinflammatory cytokine expression, increased JNK activation, and upregulated glucocorticoid receptor (GR) phosphorylation at serine 246 (pGR-Ser²⁴⁶) in the habenula (Hb), amygdala (Amyg) and medial prefrontal cortex (mPFC). Treatment with SP600125, a known JNK inhibitor, prevented the LPS-induced hyper-activation of JNK and alleviated depressive-like behaviors. Moreover, LPS-induced increases in the expression levels of TNF-α, IL-1β and pGR-Ser²⁴⁶ in these brain regions were reduced when the rats were treated with SP600125. Our results show, for the first time, that JNK activities in the Hb, Amyg, and mPFC are involved in the modulation of neuroinflammation-induced depression and participate in the regulation of the expression of proinflammatory cytokines and GR phosphorylation, which are pathological factors associated with depression. Our findings provide new insights into the mechanism of neuroinflammation-associated depression and suggest that the JNK pathway may be a potential target for treating inflammation-related depression.

Protective Effect of Sphaerococcus coronopifolius Crude Extract in Combination with Bacillus Calmette-Guerin on Ligature-Induced Depression in Female Wistar Rats

OBJECTIVE

Immunomodulation is a therapeutic technique that modulates the balance of cytokines in the body. In this regard, our experiment was conducted to investigate the potential effect of S. coronopifolius crude extract in combination with low dose of Bacillus Calmette-Guerin (BCG) on depression-like behaviors in female Wistar rats.

METHODS

Sciatic nerve injury was employed to induce depression and intradermal injection of 0.02 mL of BCG per rat was administered to lead an activation of innate immune system. Daily intra-peritoneal injections of 25 mg algae extract kg-1 body weight were performed for 14 continuous days. Forced Swimming (FS) and Open Field (OF) tests were conducted to assess despairing and spontaneous behaviors. At the end of the experiment, brain was removed to determine the activities of catalase (CAT) and glutathione-S-transferase (GST), whereas spleen and adrenals were used for the histopathological study.

RESULTS

The combined treatment exhibited antidepressant-like activity in FST by reducing immobility time, without inducing any significant change in ambulatory behavior in OFT. The histological analyses of spleen and adrenal structure showed a conserved architecture.

CONCLUSION

The results suggested that algae extract produce an antidepressant-like effect in combination with low dose of BCG, which is possibly trigged by its anti-oxidant and anti-inflammatory properties.

Proteomic Analysis of Brain Tissue from a Chronic Model of Stress Using a Combined 2D Gel Electrophoresis and Mass Spectrometry Approach

Aging of the brain can result in excessive glucocorticoid secretion, potentially due to chronic stress and related situations. This can lead to dysfunction of brain areas involved in control of the hypothalamic-pituitary adrenal axis, growth, and metabolism, as well as areas associated with cognition and mood regulation. This chapter presents a protocol for two-dimensional differential in-gel electrophoresis (2D-DIGE) analysis of hypothalamus and hippocampus tissue obtained from mice following exposure to high levels of corticosterone for 14 days. The chapter also presents a method for identification of the affected proteins in these brain regions using matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry.

[Pharmacological Effects of Yokukansankachimpihange on Urinary Catecholamine in Restraint-stressed Mice]

Herbal medicines, acupuncture and moxibustion are often used for unidentified complaints. It is well known that catecholamine secreted by the sympatho-adrenal medullary system primarily functions to increase cardiac output and raise glucose levels in the blood during acute stress. In the present study, the effects of yokukansankachimpihange (YKSKCH, a Kampo medicine) on urinary catecholamine in mice that were repeatedly stressed by restraining were examined. Restraint stress (240 min/d×3 d×3 cycles, daytime: 12:00-16:00) induced a marked increase in noradrenaline (NA) and adrenaline (A) levels in the urine. Oral administration of YKSKCH (750 mg/kg of body weight) significantly inhibited the increase in urinary NA and A levels in mice after repeated restraint stress. In addition, the NA/dopamine (physical stress) and A/dopamine (mental stress) ratios were lower in the 750 mg/kg YKSKCH-treated group than in the control group. The tail suspension test was also performed and locomotor activity was investigated. Oral administration of YKSKCH at 750 mg/kg significantly reduced the immobility time, which was longer in mice after repeated restraint stress. Furthermore, oral administration of YKSKCH at 750 mg/kg increased locomotor activity, which was lower in mice after repeated restraint stress. These results suggest that YKSKCH has positive effects on mental and physical stress after repeated restraint stress, without reducing locomotor activity.

Brain-Immune Alterations and Mitochondrial Dysfunctions in a Mouse Model of Paediatric Autoimmune Disorder Associated with Streptococcus: Exacerbation by Chronic Psychosocial Stress

Adverse psychosocial experiences have been shown to modulate individual responses to immune challenges and affect mitochondrial functions. The aim of this study was to investigate inflammation and immune responses as well as mitochondrial bioenergetics in an experimental model of Paediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcus (PANDAS). Starting in adolescence (postnatal day 28), male SJL/J mice were exposed to five injections (interspaced by two weeks) with Group-A beta-haemolytic streptococcus (GAS) homogenate. Mice were exposed to chronic psychosocial stress, in the form of protracted visual exposure to an aggressive conspecific, for four weeks. Our results indicate that psychosocial stress exacerbated individual response to GAS administrations whereby mice exposed to both treatments exhibited altered cytokine and immune-related enzyme expression in the hippocampus and hypothalamus. Additionally, they showed impaired mitochondrial respiratory chain complexes IV and V, and reduced adenosine triphosphate (ATP) production by mitochondria and ATP content. These brain abnormalities, observed in GAS-Stress mice, were associated with blunted titers of plasma corticosterone. Present data support the hypothesis that challenging environmental conditions, in terms of chronic psychosocial stress, may exacerbate the long-term consequences of exposure to GAS processes through the promotion of central immunomodulatory and oxidative stress.

Assessing Developmental Environmental Risk Factor Exposure in Clinical High Risk for Psychosis Individuals: Preliminary Results Using the Individual and Structural Exposure to Stress in Psychosis-Risk States Scale

INTRODUCTION

Exposure to cumulative environmental risk factors across development has been linked to a host of adverse health/functional outcomes. This perspective incorporating information regarding exposure at differing developmental periods is lacking in research surrounding individuals at Clinical High Risk (CHR) for developing a psychotic disorder.

METHODS

CHR individuals (n = 35) and healthy volunteers (n = 28) completed structured clinical interviews as well as our group's newly developed Individual and Structural Exposure to Stress in Psychosis-risk-states (ISESP) interview. Lifetime cumulative scores were calculated, and severity of stress was reported for multiple developmental periods/ages. Group differences were tested, and associations with current symptom domains were examined.

RESULTS

Significant group differences were not observed for lifetime cumulative events, though CHR trended toward endorsing more events and greater stress severity. For stress severity across development, there were trending group differences for the 11-13 age range, and significant group differences for the 14-18 age range; notably, comparisons for earlier time points did not approach statistical significance. Associations between negative symptoms and cumulative severity of exposure were observed.

DISCUSSION

Results suggest exploring exposure to cumulative environmental risk factors/stressors and stress severity across developmental periods is generally informative and possibly specifically so for predictive models and diathesis-stress psychosis risk conceptualizations.

Ketamine improved depressive-like behaviors via hippocampal glucocorticoid receptor in chronic stress induced- susceptible mice

Chronic stress is an important factor for depression. Most individuals recover from stress, while some develop into depression. The pathogenesis of resilience or susceptibility remains unclear. Stress activates the hypothalamic-pituitary-adrenal (HPA) axis and releases stress hormones to regulate individual response to stress. Hence, we assessed the effects of chronic social defeat stress (CSDS) on susceptible behaviors, plasma corticosterone (CORT) concentration, glucocorticoid receptor (GR) expressions in hippocampus and medial prefrontal cortex (mPFC). Mice that plasma CORT concentration is increased 2 h after single social defeat stress developed into susceptible mice after 10 d social defeat stress. The plasma CORT concentration was still higher than that of resilient mice 48 h after the last defeat stress. Mice administered CORT via drinking water showed susceptibility. Mifepristone, a GR antagonist improved susceptibility to chronic stress. Single dose ketamine treatment improved depressive-like behaviors, decreased plasma CORT concentration, rescued GR expression and nuclear translocation in the hippocampus of susceptible mice. These results suggested that abnormal CORT concentration after stress may predict susceptibility to depression in clinic. Ketamine may exert the antidepressant effect via normalizing HPA axis response and have significance in the clinic.

Prefrontal cortical trkB, glucocorticoids, and their interactions in stress and developmental contexts

The tropomyosin/tyrosine receptor kinase B (trkB) and glucocorticoid receptor (GR) regulate neuron structure and function and the hormonal stress response. Meanwhile, disruption of trkB and GR activity (e.g., by chronic stress) can perturb neuronal morphology in cortico-limbic regions implicated in stressor-related illnesses like depression. Further, several of the short- and long-term neurobehavioral consequences of stress depend on the developmental timing and context of stressor exposure. We review how the levels and activities of trkB and GR in the prefrontal cortex (PFC) change during development, interact, are modulated by stress, and are implicated in depression. We review evidence that trkB- and GR-mediated signaling events impact the density and morphology of dendritic spines, the primary sites of excitatory synapses in the brain, highlighting effects in adolescents when possible. Finally, we review the role of neurotrophin and glucocorticoid systems in stress-related metaplasticity. We argue that better understanding the long-term effects of developmental stressors on PFC trkB, GR, and related factors may yield insights into risk for chronic, remitting depression and related neuropsychiatric illnesses.

Hypothalamic CNTF volume transmission shapes cortical noradrenergic excitability upon acute stress

Stress-induced cortical alertness is maintained by a heightened excitability of noradrenergic neurons innervating, notably, the prefrontal cortex. However, neither the signaling axis linking hypothalamic activation to delayed and lasting noradrenergic excitability nor the molecular cascade gating noradrenaline synthesis is defined. Here, we show that hypothalamic corticotropin-releasing hormone-releasing neurons innervate ependymal cells of the 3rd ventricle to induce ciliary neurotrophic factor (CNTF) release for transport through the brain's aqueductal system. CNTF binding to its cognate receptors on norepinephrinergic neurons in the locus coeruleus then initiates sequential phosphorylation of extracellular signal-regulated kinase 1 and tyrosine hydroxylase with the Ca2+-sensor secretagogin ensuring activity dependence in both rodent and human brains. Both CNTF and secretagogin ablation occlude stress-induced cortical norepinephrine synthesis, ensuing neuronal excitation and behavioral stereotypes. Cumulatively, we identify a multimodal pathway that is rate-limited by CNTF volume transmission and poised to directly convert hypothalamic activation into long-lasting cortical excitability following acute stress.

Effect of Restraint Stress on Plasma PTH Concentration and Its Molecular Targets Expressions in Wistar Rats

BACKGROUND

There are limited numbers of experimental studies related to the potential role of parathormone/parathyroid hormone (PTH) in response to psychological stress. In the current study, we aimed to cross-examine, for the first time, changes in PTH plasma concentration and the expression of its molecular targets mediated by restraint stress in rats.

METHODS

Male Wistar rats (n = 42) were separated into control and stressed groups. They were further divided into two groups that received chronic restraint stress (CRS) for 7 and 28 consecutive days (n = 7 for each group). Elevated plus maze and tail suspension test were used to determine the anxiety- and depressive-like behaviors of a different set of rats including stress and control groups (n = 7 for each group). The plasma levels of adrenocorticotropic hormone (ACTH), corticosterone, and intact parathormone (iPTH) were measured by enzyme-linked immunosorbent assay (ELISA). In addition, alterations in the expressions of glucocorticoid receptor (GR), calcium sensing receptor (CaSR), and parathormone receptor (PTHR1) of kidney and total thyroid gland tissues were estimated by Western Blotting.

RESULTS

There was no significant difference in the plasma level of iPTH while significant increases in the levels of ACTH and corticosterone were noted in the stressed-animals at day 7 and 21 (P = 0.010 and P = 0.016, respectively) of restraint stress. However, we found a negative correlation between iPTH and corticosterone levels in acute restraint stress (r = 0.771, P = 0.002). In addition, the expression of PTHR1 significantly decreased in the kidney at day 7 (P = 0.001) and in the thyroid gland at day 28 (P = 0.05) in response to CRS.

CONCLUSIONS

To sum up, CRS has a significant effect on the expression of parathormone receptor rather than the iPTH concentration. The present results add a new dimension to stress research through the negative effect of chronic stress on the PTH signaling pathway.

Neurobiology and consequences of social isolation stress in animal model-A comprehensive review

The brain is a vital organ, susceptible to alterations under genetic influences and environmental experiences. Social isolation (SI) acts as a stressor which results in alterations in reactivity to stress, social behavior, function of neurochemical and neuroendocrine system, physiological, anatomical and behavioral changes in both animal and humans. During early stages of life, acute or chronic SIS has been proposed to show signs and symptoms of psychiatric and neurological disorders such as anxiety, depression, schizophrenia, epilepsy and memory loss. Exposure to social isolation stress induces a variety of endocrinological changes including the activation of hypothalamic-pituitary-adrenal (HPA) axis, culminating in the release of glucocorticoids (GCs), release of catecholamines, activation of the sympatho-adrenomedullary system, release of Oxytocin and vasopressin. In several regions of the central nervous system (CNS), SIS alters the level of neurotransmitter such as dopamine, serotonin, gamma aminobutyric acid (GABA), glutamate, nitrergic system and adrenaline as well as leads to alteration in receptor sensitivity of N-methyl-D-aspartate (NMDA) and opioid system. A change in the function of oxidative and nitrosative stress (O&NS) mediated mitochondrial dysfunction, inflammatory factors, neurotrophins and neurotrophicfactors (NTFs), early growth response transcription factor genes (Egr) and C-Fos expression are also involved as a pathophysiological consequences of SIS which induce neurological and psychiatric disorders.

The Role of Musk in Relieving the Neurodegenerative Changes Induced After Exposure to Chronic Stress

OBJECTIVE

This study aimed to evaluate the effect induced by musk on Alzheimer's disease-such as neurodegenerative changes in mice exposed to chronic unpredictable mild stress (CUMS).

MATERIAL AND METHODS

Forty male Swiss albino mice were divided into 4 groups (n = 10); control, CUMS, CUMS + fluoxetine, CUMS + musk. At the end of the experiment, behavior of the mice was assessed. Serum corticosterone level, hippocampal protein level of the glucocorticoid receptors, and brain-derived neurotropic factor were also assessed. Hippocampus was histopathologically examined.

RESULTS

Musk improved depressive status induced after exposure to CUMS as evidenced by the forced swimming and open field tests and improved the short-term memory as evidenced by the elevated plus maze test. Musk reduced both corticosterone levels and the hippocampal neurodegenerative changes observed after exposure to CUMS. These improvements were comparable to those induced by fluoxetine.

CONCLUSION

Musk alleviated the memory impairment and neurodegenerative changes induced after exposure to the chronic stress.

The Role of Uron and Chlorobenzene Derivatives, as Potential Endocrine Disrupting Compounds, in the Secretion of ACTH and PRL

Uron herbicides polluting the environment represent a serious concern for environmental health and may be regarded as endocrine-disrupting compounds (EDCs), which influence the regulation of human homeostasis. We aimed to investigate the effect of EDC urons (phenuron: PU, monuron: MU, and diuron: DU) and chlorobenzenes on the basal release of the adrenocorticotropic hormone (ACTH), which is a part of the adenohypophysis-adrenocortical axis. Hormone secretion in the presence of EDC was studied in two cell types: normal adenohypophysis cells (AdH) and cells of prolactinomas (PRLOMA). PRLOMA was induced in female Wistar rats by subcutaneously injecting them with estrone acetate for 6 months. AdH and PRLOMA were separated from treated and untreated experimental animals, dissociated enzymatically and mechanically in order to create monolayer cell cultures, which served as an experimental in vitro model. We investigated the effects of ED agents separately and in combination on ACTH and prolactin (PRL) release through the hypophyseal-adrenal axis. Hormone determination was carried out by the luminescent immunoassay and the radioimmunoassay methods. Our results showed that (1) uron agents separately did not change ACTH and PRL release in AdH culture; (2) ACTH secretion in arginine vasopressin- (AVP-) activated AdH cells was significantly increased by EDC treatment; (3) ED agents increased the basal hormone release (ACTH, PRL) in PRLOMA cells; and (4) EDC exposure increased ACTH release in AVP-activated PRLOMA cells. We conclude that the herbicides PU, MU, and DU carry EDC effects and show human toxicity potential.

Nitric Oxide Synthase Inhibitor Attenuates the Effects of Repeated Restraint Stress on Synaptic Transmission in the Paraventricular Nucleus of the Rat Hypothalamus

Corticotropin-releasing hormone (CRH)-synthesizing parvocellular neuroendocrine cells (PNCs) of the hypothalamic paraventricular nucleus (PVN) play a key role in the activation of the hypothalamic-pituitary-adrenocortical (HPA) axis. Several studies have demonstrated that synaptic inputs to these cells may undergo stress-related enhancement but, on the other hand, it has been reported that exposition to the same stressor for prolonged time periods may induce a progressive reduction in the response of the HPA axis to homotypic stressors. In the present study rats were subjected to 10 min restraint sessions, repeated twice daily for 3 or 7 days. Miniature excitatory and inhibitory postsynaptic currents (mEPSCs and mIPSCs) were then recorded from PNCs in ex vivo hypothalamic slice preparations obtained 24 h after the last restraint. Restraint stress repeated over 3 days resulted in increased mean frequency and decreased rise time and decay time constant of mEPSCs, accompanied by a decrease in the excitability of PNCs, however, no such changes were evident in slices obtained from rats subjected to restraint over 7 days. There were no changes in mIPSCs after repeated restraint. Administration of the unspecific nitric oxide synthase (NOS) blocker Nω-Nitro-L-arginine (L-NNA) before each restraint, repeated over 3 days, prevented the occurrence of an increase in mEPSC frequency. However, animals receiving L-NNA and subjected to repeated restraint had similar changes in PNCs membrane excitability and mEPSC kinetics as stressed rats not receiving L-NNA. Comparison of the effects of a single 10 min restraint session followed by either an immediate or delayed (24 h) decapitation revealed an increase in the mean mEPSC frequency and a decrease in the mean mIPSC frequency in slices prepared immediately after restraint, with no apparent effects when slice preparation was delayed by 24 h. These results demonstrate that restraint, lasting 10 min and repeated twice daily for 3 days, induces a selective and long-lasting enhancement of excitatory synaptic input onto PNCs, partially by a NOS-dependent mechanism, and reduces PNC excitability, whereas prolongation of repeated stress for up to 7 days results in an adaptation.

Asian house rats may facilitate their invasive success through suppressing brown rats in chronic interaction

BACKGROUND

The Asian house rat (Rattus tanezumi) and the brown rat (Rattus norvegicus) are closely related species and are partially sympatric in southern China. Over the past 20 years, R. tanezumi has significantly expanded northward in China and partially replaced the native brown rat subspecies, R. n. humiliatus. Although invasive species are often more aggressive than native species, we did not observe interspecific physical aggression between R. tanezumi and R. n. humiliatus. Here, we focused on whether or not R. tanezumi was superior to R. n. humiliatus in terms of nonphysical competition, which is primarily mediated by chemical signals.

RESULTS

We performed two laboratory experiments to test different paradigms in domesticated R. tanezumi and R. n. humiliatus. In Experiment 1, we caged adult male rats of each species for 2 months in heterospecific or conspecific pairs, partitioned by perforated galvanized iron sheets, allowing exchange of chemical stimuli and ultrasonic vocalization. The sexual attractiveness of male urine odor showed a tendency (marginal significance) to increase in R. tanezumi caged with R. n. humiliatus, compared with those in conspecific pairs. Hippocampal glucocorticoid receptor (GR) and brain-derived nutrition factor (BDNF) mRNA were upregulated in R. n. humiliatus and R. tanezumi, respectively, when the rats were caged in heterospecific pairs. In Experiment 2, we kept juvenile male rats in individual cages in rooms with either the same or the different species for 2 months, allowing chemical interaction. The sexual attractiveness of male urine was significantly enhanced in R. tanezumi, but reduced in R. n. humiliatus by heterospecific cues and mRNA expression of hippocampal GR and BDNF were upregulated by heterospecific cues in R. n. humiliatus and R. tanezumi, respectively. Although not identical, the results from Experiments 1 and 2 were generally consistent.

CONCLUSIONS

The results of both experiments indicate that nonphysical/chronic interspecific stimuli, particularly scent signals, between R. n. humiliatus and R. tanezumi may negatively affect R. n. humiliatus and positively affect R. tanezumi. We infer that chronic interspecific interactions may have contributed to the invasion of R. tanezumi into the range of R. n. humiliatus in natural habitats.

Synaptic Plasticity, Metaplasticity and Depression

The development of a persistent depressive affective state has for some time been thought to result from persistent alterations in neurotransmitter-mediated synaptic transmission. While the identity of those transmitters has changed over the years, the literature has lacked mechanistic connections between the neurophysiological mechanisms they regulate, and how these mechanisms alter neuronal function, and, hence, affective homeostasis. This review will examine recent work that suggests that both long-term activity-dependent changes in synaptic strength (“plasticity”), and shifting set points for the ease of induction of future long-term changes (“metaplasticity”), may be critical to establishing and reversing a depressive behavioral state. Activity-dependent long-term synaptic plasticity involves both strengthening and weakening of synaptic connections associated with a dizzying array of neurochemical alterations that include synaptic insertion and removal of a number of subtypes of AMPA, NMDA and metabotropic glutamate receptors, changes in presynaptic glutamate release, and structural changes in dendritic spines. Cellular mechanisms of metaplasticity are far less well understood. Here, we will review the growing evidence that long-term synaptic changes in glutamatergic transmission, in brain regions that regulate mood, are key determinants of affective homeostasis and therapeutic targets with immense potential for drug development.

Age- and Sex-Dependent Impact of Repeated Social Stress on Intrinsic and Synaptic Excitability of the Rat Prefrontal Cortex

Stress is implicated in psychiatric illnesses that are characterized by impairments in cognitive functions that are mediated by the medial prefrontal cortex (mPFC). Because sex and age determine stress vulnerability, the effects of repeated social stress occurring during early adolescence, mid-adolescence, or adulthood on the cellular properties of male and female rat mPFC Layer V neurons in vitro were examined. Repeated resident-intruder stress produced age- and sex-specific effects on mPFC intrinsic and synaptic excitability. Mid-adolescents were particularly vulnerable to effects on intrinsic excitability. The maximum number of action potentials (APs) evoked by increasing current intensity was robustly decreased in stressed male and female mid-adolescent rats compared with age-matched controls. These effects were associated with stress-induced changes in AP half-width, amplitude, threshold, and input resistance. Social stress at all ages generally decreased synaptic excitability by decreasing the amplitude of spontaneous excitatory postsynaptic potentials. The results suggest that whereas social stress throughout life can diminish the influence of afferents driving the mPFC, social stress during mid-adolescence additionally affects intrinsic characteristics of mPFC neurons that determine excitability. The depressant effects of social stress on intrinsic and synaptic mPFC neurons may underlie its ability to affect executive functions and emotional responses, particularly during adolescence.

Role of Scoparia dulcis linn on noise-induced nitric oxide synthase (NOS) expression and neurotransmitter assessment on motor function in Wistar albino rats

Noise pollution is one of the most widespread and fast growing environmental and occupational menaces in the modern era. Exposure to noise above 100dB is not adaptable through the brain homeostatic mechanism. Yet, the detrimental effects of noise have often been ignored. Developing reliable animal models to understand the neurobiology of noise stress and advance our research in the field of medicine to impede this growing stressor is needed. In this study experimental animals were divided into four groups, (i) Control and (ii) S. dulcis extract (200mg/kgbw) treated control group. (iii) To mimic the influence of noise, animals in this group were exposed to noise stress (100dB/4h/day) for 15days and finally, (iv) Noise exposed treated with S. dulcis extract (200mg/kgbw) group. Rota-rod and narrow beam performance results showed impaired motor co-ordination in noise exposed group on both 1st and 15th day when compared to controls. This impaired motor function on exposure to noise could be attributed to the altered norepinephrine, dopamine and serotonin levels in both the striatum and cerebellum. Moreover, the motor impaired associated changes could also be attributed to upregulated nNOS and iNOS protein expression in the cerebellum resulting in increased nitric oxide radical production. This increased reactive free radicals species can initiate lipid peroxidation mediated changes in the cerebellar Purkinje cells, which is responsible for initiating inhibitory motor response and ultimately leading to impaired motor co-ordination. Treatment with S. dulcis extract (200mg/kgbw) could control motor impairment and regulate neurotransmitter level as that of control groups when compared to noise exposed group. One key aspect of therapeutic efficacy of the plant could have resulted due to attenuated lipid peroxidation mediated damages on the cerebellar Purkinje cells thereby regulating motor impairment. Thus, targeting the antioxidant and free radicals scavenging properties of the plant could serve as a potential therapeutic to combat this environmental stressor.

AMPK Mediates Glucocorticoids Stress-Induced Downregulation of the Glucocorticoid Receptor in Cultured Rat Prefrontal Cortical Astrocytes

Chronic stress induces altered energy metabolism and plays important roles in the etiology of depression, in which the glucocorticoid negative feedback is disrupted due to imbalanced glucocorticoid receptor (GR) functions. The mechanism underlying the dysregulation of GR by chronic stress remains elusive. In this study, we investigated the role of AMP-activated protein kinase (AMPK), the key enzyme regulating cellular energy metabolism, and related signaling pathways in chronic stress-induced GR dysregulation. In cultured rat cortical astrocytes, glucocorticoid treatment decreased the level, which was accompanied by the decreased expression of liver kinase B1 (LKB1) and reduced phosphorylation of AMPK. Glucocorticoid-induced effects were attenuated by glucocorticoid-inducible kinase 1 (SGK1) inhibitor GSK650394, which also inhibited glucocorticoid induced phosphorylation of Forkhead box O3a (FOXO3a). Furthermore, glucocorticoid-induced down-regulation of GR was mimicked by the inhibition of AMPK and abolished by the AMPK activators or the histone deacetylase 5 (HDAC5) inhibitors. In line with the role of AMPK in GR expression, AMPK activator metformin reversed glucocorticoid-induced reduction of AMPK phosphorylation and GR expression as well as behavioral alteration of rats. Taken together, these results suggest that chronic stress activates SGK1 and suppresses the expression of LKB1 via inhibitory phosphorylation of FOXO3a. Downregulated LKB1 contributes to reduced activation of AMPK, leading to the dephosphorylation of HDAC5 and the suppression of transcription of GR.

Maternal betaine supplementation during gestation modifies hippocampal expression of GR and its regulatory miRNAs in neonatal piglets

Methyl donor nutrients are critical for embryonic development of brain. Hippocampus is the most susceptible brain region to various factors including prenatal supply of methyl donors. Glucocorticoid receptor (GR) expressed in hippocampus is involved in the regulation of energy homeostasis and stress sensitivity. Hippocampal GR expression is highly susceptible to epigenetic regulation, yet the effect of maternal methyl donor supplementation on epigenetic regulation of GR transcription in offspring hippocampus remains unclear. In this study, we fed sows with betaine (3 g/kg) throughout the gestation and analyzed the hippocampal expression of GR mRNA and its variants, as well as the CpG methylation status of the promoter and the microRNAs predicted to target 3' UTR of porcine GR gene in neonatal piglets. Total GR mRNA (P<0.01) and its variants GR 1-4 (P<0.05) and 1-9,10 (P<0.01), were significantly higher in the hippocampus of betaine-treated piglets, while the content of GR protein was not significantly changed. The CpGs located in the -1650 ~ -1515 segment of GR gene were hypermethylated (P<0.05). The hippocampal expression of miR-130b (P<0.05), miR-181a (P<0.05) and miR-181d (P<0.01) was significantly up-regulated. The targeting efficacy of miR-130b and miR-181d was validated in vitro using dual-luciferase reporter assay system. Our results demonstrate that maternal betaine supplementation during gestation enhances GR mRNA expression in offspring hippocampus, which involves alterations in miRNAs expression.

Revisiting the health effects of psychological stress-its influence on susceptibility to ionizing radiation: a mini-review

Both psychological stress (PS) and ionizing radiation (IR) cause varied detrimental effects on humans. There has been no direct evidence so far showing PS alone could cause cancer; however, long-lasting PS may affect our overall health and ability to cope with cancer. Due to their living conditions and occupations, some people may encounter concurrent exposure to both PS and IR to a high extent. In addition to possible health effects resulting directly from exposure to IR on these people, fear of IR exposure is also a cause of PS. The question of whether PS would influence susceptibility to IR, radiocarcinogenesis in particular, is of great concern by both the academic world and the public. Recently, investigations using animal PS models demonstrated that PS could modulate susceptibility to IR, causing increased susceptibility to radiocarcinogenesis in Trp53-heterozygous mice, hematological toxicity in peripheral blood and elevated chromosome aberration (dicentrics) frequency in splenocytes of Trp53-wild-type mice. To actively reduce health risk from exposure to IR, further studies are needed to cumulate more evidence and provide insights into the mechanisms underlying the alterations in susceptibility due to PS modulation. This mini-review gives a general overview of the significance of PS effects on humans and experimental animals, with a special focus on summarizing the latest weight-of-evidence approaches to radiobiological studies on PS-induced alterations in susceptibility in experimental animal models. The susceptibility being investigated is mainly in the context of the impact of the modulatory effect of PS on radiocarcinogenesis; we seek to improve understanding of the combined effects of exposure to both PS and IR in order to facilitate, via active intervention, strategies for radiation risk reduction.