Social Isolation Stress Research Articles

Effects of social isolation on the cognition and expression of 5-HT2C receptor and ADAR1 in BALB/c mice

Objective To explore the effects of social isolation on the cognition and expression of 5-HT2C receptor(5-HT2CR) and adenosine deaminase that act on RNA 1(ADAR1) in BALB/c mice. Methods The healthy BALB/c mice were isolated for 2, 4, and 8 weeks individually since postnatal 21 days respectively to set up isolation mice model, the same age mice without isolation were regarded as control group. The new object location and the new object recognition tests were used to measure the spatial and non-spatial cognitive function, and western blot was used to measure the protein expression of 5-HT2CR and ADAR1. Results The new object location test showed that the spatial discrimination index (DI) of BALB/c mice isolated for 2 weeks was decreased significantly compared with the control group(control group was (0.075±0.340), isolation group was (-0.653±0.308), P<0.05), and no obvious difference was found for the group isolated for 4 and 8 weeks. The new object recognition test showed that the non-spatial DI of BALB/c mice isolated for 2 and 4 weeks were decreased significantly compared with the control group(control 2 weeks group was (0.088±0.210), isolation 2 weeks group was (-0.945±0.194), P<0.05; control 4 weeks group was (0.105±0.267), isolation 4 weeks group was (-0.506±0.215), P<0.05), and no obvious difference was found for the group isolated for 8 weeks.Compared with the control group the expression of 5-HT2CR and ADAR1 in the hippocampus were decreased significantly for the group isolated for 2 weeks. (5-HT2CR: control group was (1.025±0.144), isolation group was (0.891±0.026), P<0.05.ADAR1: control group was (0.839±0.120), isolation group was (0.629±0.094), P<0.05). Conclusions Two week social isolation results in the decrease of spatial and non-spatial cognitive function in BALB/c mice, in the meanwhile, social isolation stress results in the obvious decrease of 5-HT2C receptor and ADAR1 protein expression in the hippocampus of BALB/c mice. Key words: Social isolation; Cognitive function; 5-HT2C receptor; Adenosine deaminase that act on RNA 1

Abstract 571: Short Term Taste Preference for Cholesterol Rich Diet in ABCA1 Null Mice

Background: Plasma HDL particle is one of the essential player for maintaining cholesterol homeostasis in mammal. Even though cholesterol can be ubiquitously biosynthesized upon requirement, cholesterol in diet is efficiently used to maintain cholesterol homeostasis which implicates existence of sensing system for cholesterol in diet. The study of taste preference on cholesterol was not well explored. In this project we examined taste preference in mice using a novel method called dual diet test (DDT) system. Methods: Chow pellets of 1.2% cholesterol or 0.02% Acesulfame potassium (AmK, calorie-free sweet molecule) were prepared based on standard mouse chow, CE-2(0.2% cholesterol, Crea Japan). The mouse chow tray was divided into three sections. Water nozzle was set in the center section. Each chow was weighed then set ether right or left section. One session was composed by 1-3 days and remaining chow was weighed to calculate consumption of each chow diet. The diet position was switched randomly at each session. The operation was performed between ZT9-ZT10 when mice were less active in a day. To avoid social isolation stress, 2-5 littermates were placed per cage. Results: C56B/6 wild type mice and LCAT null mice significantly preferred 1.2% cholesterol containing chow compared to control chow during 6 sessions by 18-28 weeks old littermates (n=16, n=8, respectively). These mice also significantly preferred AmK-chow compared to the control chow. ABCA1 null and ABCA1 heterozygote mice exhibited significance on the preference of 1.2% cholesterol in the first 3 sessions but not for the later sessions. Repeating the experiment after interval period improved their cholesterol preference in ABCA1 null mice. No gender difference was observed. Preferences to AmK-chow were significant in all trials. Conclusions: The preference in higher cholesterol or sweet in diet were detected at this novel DDT system, significantly. In ABCA1 null or heterozygote mice, long-term preferences to high cholesterol diet were abolished perhaps due to their lack of focus on cholesterol-rich chow of which less reward to these mice. In this experiment, mice synchronized in consuming higher cholesterol containing diet indicating mice are sensing cholesterol as a preferred tastant.

Sansoninto, a traditional herbal medicine, ameliorates behavioral abnormalities and down-regulation of early growth response-1 expression in mice exposed to social isolation stress

Social isolation (SI) mice exhibit behavioral abnormalities such as impairments of sociability- and attention-like behaviors, offering an animal model of neurodevelopmental disorders such as attention-deficit/hyperactivity disorder (ADHD). This study aimed to identify the effects of Sansoninto (SST; 酸棗仁湯 suān zǎo rén tāng) on the psychiatric symptoms related to ADHD using SI mice. Four-week-old mice were socially isolated during the experimental period, and SST administration (800 or 2400 mg/kg, p.o.) was started at 2 weeks after starting SI. SST ameliorated SI-induced impairments of sociability- and attention-like behaviors in a dose-dependent manner, and tended to ameliorate contextual- and auditory-dependent fear memory deficit. Moreover, the expression level of Egr-1 was down-regulated by SI stress, and was restored by a high dose of SST. These findings suggest that SST is useful for improvement of psychiatric disorders such as ADHD.

Ovarian hormones modify anxiety behavior and glucocorticoid receptors after chronic social isolation stress

Chronic social isolation could lead to a disruption in the Hypothalamic-Pituitary-Adrenal (HPA) axis, resulting in anxiety and depressive-like behaviors but cycling estrogens could modify these behaviors. The aim of this study was to determine if changes in ovarian hormones during the normal cycle could interact with social isolation to alter anxiety and depressive-like behaviors. In parallel, we examined the expression of glucocorticoid receptor (GR) and synaptic vesicle protein synaptophysin in the hippocampus and hypothalamus of Sprague Dawley normal cycling female rats. We assigned rats to either isolated or paired housing for 8 weeks. To assess anxiety and depressive-like behaviors, we used the open field test and forced swim test, respectively. Female rats were tested at either diestrus, estrus, or proestrus stage of the estrous cycle. After behaviors, rats were perfused and brains collected. Brain sections containing hippocampus and hypothalamus were analyzed using immunohistochemistry for synaptophysin and glucocorticoid receptor (GR) levels. We found an increase in depressive-like behaviors for isolated animals compared to paired housed rats, regardless of the estrous cycle stage. Interestingly, we found a decrease in anxiety behaviors in females in the estrus stage accompanied by a decrease in GR expression in hippocampal DG and CA3. However, no changes in synaptophysin were observed in any of the areas of studied. Our results support the beneficial effects of circulating ovarian hormones in anxiety, possibly by decreasing GR expression.

Antistress effects of Kampo medicine "Yokukansan" via regulation of orexin secretion.

ObjectiveVarious stressors induce stress responses through the hypothalamic–pituitary–adrenal and the sympathetic–adrenal–medullary axes, which are regulated, in part, by orexin. For example, secretion of orexin in the hypothalamus is increased in rats exposed to the stress of social isolation for 1 week. In this study, the antistress effects of Kampo medicine Yokukansan (YKS) via the regulation of orexin secretion were investigated using a rat model.Methods and resultsThe administration of 300 mg/kg per day of YKS to rats for 1 week significantly decreased the plasma orexin levels compared with non-treated rats, whereas the administration of 1,000 mg/kg of YKS had no effect on orexin levels. Therefore, 300 mg/kg of YKS was an effective dose for controlling orexin secretion. Subsequently, rats were divided into group-housed control (Con), individually housed stress (Stress), and individually housed YKS (300 mg/kg)-treated stress (Stress + YKS) groups. After 1 week, a resident–intruder aggression test was performed, and the plasma levels of orexin and corticosterone were measured. In the Stress group, aggressive behavior and the levels of corticosterone and orexin significantly increased compared with the Con group; however, these effects were inhibited in the Stress + YKS group. Further, an orexin receptor antagonist (TCS 1102; 10 mg/kg) was intraperitoneally administered to rats exposed to isolation stress to determine whether orexin was involved in stress responses. Under these conditions, aggressive behavior and the level of corticosterone significantly decreased compared with the Stress group.ConclusionThese results suggest that orexin is involved in the control of stress response and that YKS exerts an antistress effect via the regulation of orexin secretion.

Early Social Isolation Stress and Perinatal NMDA Receptor Antagonist Treatment Induce Changes in the Structure and Neurochemistry of Inhibitory Neurons of the Adult Amygdala and Prefrontal Cortex.

The exposure to aversive experiences during early life influences brain development and leads to altered behavior. Moreover, the combination of these experiences with subtle alterations in neurodevelopment may contribute to the emergence of psychiatric disorders, such as schizophrenia. Recent hypotheses suggest that imbalances between excitatory and inhibitory (E/I) neurotransmission, especially in the prefrontal cortex and the amygdala, may underlie their etiopathology. In order to understand better the neurobiological bases of these alterations, we studied the impact of altered neurodevelopment and chronic early-life stress on these two brain regions. Transgenic mice displaying fluorescent excitatory and inhibitory neurons, received a single injection of MK801 (NMDAR antagonist) or vehicle solution at postnatal day 7 and/or were socially isolated from the age of weaning until adulthood (3 months old). We found that anxiety-related behavior, brain volume, neuronal structure, and the expression of molecules related to plasticity and E/I neurotransmission in adult mice were importantly affected by early-life stress. Interestingly, many of these effects were potentiated when the stress paradigm was applied to mice perinatally injected with MK801 ("double-hit" model). These results clearly show the impact of early-life stress on the adult brain, especially on the structure and plasticity of inhibitory networks, and highlight the double-hit model as a valuable tool to study the contribution of early-life stress in the emergence of neurodevelopmental psychiatric disorders, such as schizophrenia.

Activation of cannabinoid receptors elicits antidepressant-like effects in a mouse model of social isolation stress.

Social isolation stress (SIS) paradigm is a chronic stress procedure able to induce profound behavioral and neurochemical changes in rodents and evokes depressive and anxiety-like behaviors. Recent studies demonstrated that the cannabinoid system plays a key role in behavioral abnormalities such as depression through different pathways; however, there is no evidence showing a relation between SIS and the cannabinoid system. This study investigated the role of the cannabinoid system in depressive-like behavior and anxiety-like behavior of IC animals. For this purpose, NMRI mice were treated with WIN55, 212-2 (non-selective cannabinoid receptor agonist) and AM-251 (cannabinoid receptor type 1 antagonist) and AM-630 (cannabinoid receptor type 2 antagonist). We found that behavioral abnormality followed by SIS was mitigated after administration of WIN55, 212-2. Also, depressive-like effects induced by SIS were significantly increased following administration of AM-251 and AM-630. Co-administration of cannabinoid receptor antagonists (AM-251 and AM-630), significantly reversed the antidepressant effect of WIN55, 212-2 in IC animals. Our findings suggest that the cannabinoid system is involved in depressive-like behaviors induced by SIS. We showed that activation of cannabinoid receptors (type 1 and 2) could mitigate depression-like behavior induced by SIS in a mouse model.

Protective effects of gabapentin against the seizure susceptibility and comorbid behavioral abnormalities in the early socially isolated mice

Adolescence is a pivotal period of brain development during lifespan, which is sensitive to stress exposure. Early social isolation stress (SIS) is known to provoke a variety of psychiatric comorbidities as well as seizure risk. Psychiatric comorbidities present challenging dilemmas for treatment and management in people with seizure disorders. In this study, we aimed to investigate whether gabapentin (GBP) as an anti-epileptic drug is able to alleviate the seizure activity as well as comorbid behavioral abnormalities in socially isolated mice. Results showed that early SIS induced proconvulsant effects along with depressive, aggressive and anxiety-like behaviors. Whereas the administration of both acute and chronic GBP at sub-effective doses produced no alterations in the behavioral profile of socially conditioned counterparts the same treatments effectively reversed the seizure susceptibility to pentylenetetrazole and behavioral deficits in isolated mice. Results of the study indicate that 1) Early SIS could be considered as an animal model of psychosocial stress to investigate the psychiatric comorbidities in seizure disorders, 2) Chronic administration of low dose GBP prevented the shaping of behavioral abnormalities in adulthood, 3) Chronic administration of low dose GBP produced no negative behavioral effects in socially conditioned mice suggesting the safety of the drug, 4) Gabapentin at low doses may be considered as an agent for management of epilepsy in individuals with psychiatric comorbidities.

Effects of housing environment on social isolation response,weaning stress, and immune reaction in goat kids

This study investigated how environmental structuring in the growing units of goat kids influences their ability to cope with social isolation and weaning-induced stress. Two experimental groups were arranged in an enriched (E) or barren (B) environment and each of the two groups had 10 female and 10 male kids. During the social isolation, the goat kids in group E started bleating earlier (P = 0.1612) and more frequently (P = 0.0125). Goat kids also bleated earlier (P = 0.0005) and more often after the weaning period (P = 0.0006). Only the rearing behavior of the groups exhibited significant differences in social isolation. However, after the weaning, kids showed more bipedal stance behavior (P = 0.0204) and less running behavior (P = 0.0394) than before the weaning period. Cortisol, triiodothyronine (T3), and thyroxine (T4) hormone concentrations were lower at weaning than in the other periods with social isolation (P < 0.05). The T3 hormone concentrations of the groups at weaning were significantly different (P = 0.0201). The immune response to Brucella vaccination did not differ between the groups (P = 0.2753). Findings revealed that both social isolation tests created stress in the goat kids. Considering the bleating frequencies, it can be concluded that the goat kids in the enriched environment experienced more social isolation stress than the goat kids in the barren environment.

Astressin, an antagonist of CRF receptors, reduces anxiety and fobial states in rats reared in social isolation conditions

The influence of intranasal administration of astressin, a nonselective antagonist of CRF receptors, on delayed effects of chronic social isolation in the five first weeks after mother leaving on explorative and emotional behavior in rats was studied. Social exposures were applied from 21st to 93rd days of life. The rats reared in social isolation demonstrated higher level of motor activity compared with control in open field test. The assessment of both anxiety and fobial state and behavior in elevated plus maze revealed higher levels in anxiety and fear in isolated rats. Intranasal administration of astressin (1 µg/1µl, 20 µl, 10 µl in every nostrils) reduced significantly anxiety and fear levels in isolated rats. Therefore, both anxiolytic and antifobial effects of astressin, a nonselective antagonist of CRF receptors, were demonstrated in rats exposured to social isolation stress. The results support the idea taking into account the corticoliberin mechanisms in formation of social isolation syndrome and possibilities of using CRF antagonists to control the central stress mechanisms and dependence in ontogeny.

Sexually dimorphic neuronal responses to social isolation.

Many species use social networks to buffer the effects of stress. The mere absence of a social network, however, may also be stressful. We examined neuroendocrine, PVN CRH neurons and report that social isolation alters the intrinsic properties of these cells in sexually dimorphic fashion. Specifically, isolating preadolescent female mice from littermates for <24 hr increased first spike latency (FSL) and decreased excitability of CRH neurons. These changes were not evident in age-matched males. By contrast, subjecting either males (isolated or grouped) or group housed females to acute physical stress (swim), increased FSL. The increase in FSL following either social isolation or acute physical stress was blocked by the glucocorticoid synthesis inhibitor, metyrapone and mimicked by exogenous corticosterone. The increase in FSL results in a decrease in the excitability of CRH neurons. Our observations demonstrate that social isolation, but not acute physical stress has sex-specific effects on PVN CRH neurons.

Public health after a nuclear disaster: beyond radiation risks

In the five years since Japan's triple disaster there has been a growth in media coverage and public interest in disaster recovery. An earthquake in March 2011 triggered a tsunami that hit the Fukushima Daiichi nuclear power plant, leading to loss of the plant's core cooling capacities, followed by hydrogen explosions and subsequent radiation leakage. The nuclear accident is often discussed, both within Japan and abroad, from a perspective of radiation leakage--as would be expected in the aftermath of such an accident. Yet this has led to confusion about the importance of radiation risks, due to conflicting reports and a lack of awareness of ongoing problems that are unrelated to radiation. These misunderstandings deserve attention. This paper provides a brief review on post-disaster health in Fukushima prefecture, highlighting areas in need of further recognition by medical professionals and policy-makers, including the risks faced by one vulnerable population: the elderly. The framework for understanding the health issues in post-disaster Fukushima is radiation, due to substantial amounts of radioactive material released after the nuclear accident. Although numerous studies have been published, the health risks of radiation are still not well understood, and controversy is abundant even within the realms of scientific research. No deaths or acute health effects related to radiation exposure were reported in the general public immediately after the disaster. (1) In October 2015, the results of two studies concerning the children of Fukushima were reported within two days of each other; one found no detectable internal radiation contamination, (2) while the other found an increased risk of thyroid cancer. (3) Although the study reporting an increased risk of thyroid cancer was later publically criticized by the scientific community for faulty study design, (4) this follow-up has not reached everyone and many members of the public, and even health professionals, continue to be confused by inconsistent results. This is unfortunate, in more ways than one. Controversy over radiation risk not only increases the difficulty in creating an appropriate public health response, but also diverts attention away from other post-disaster health problems that are unrelated to radiation, resulting in issues that are neglected in disaster awareness and response. Over 80 000 people in Fukushima prefecture were forced to evacuate their homes following the nuclear accident. (5) The event brought many changes to the affected region, including widespread social disruption through the breakdown of communities (due to the evacuation and the separation of families) and social stigma attached to being from Fukushima (largely due to incorrect assumptions about radiation exposure and risk). (1) These social effects of the nuclear accident have been documented, (1,6) and hold great implications for health. After the catastrophic nuclear accident in April 1986 in the city of Chernobyl in Ukraine, it was found that the increased mental health burden was the most severe of any of the post-disaster public health problems. (1) Fukushima appears to be facing a similar situation. (1) In addition to its impact on mental health, social disruption can be seen as a risk factor for physiological disease. Rapid life changes can lead to social isolation and psychosocial stress, which are known to be associated with poor health outcomes, including an increased risk of noncommunicable diseases. Unsurprisingly, an increase in noncommunicable disease risks, such as high blood glucose levels and hyperlipidaemia, have been found in Fukushima, (7,8) alongside an increased burden of psychosocial distress, a phenomenon which has been described as a physical and mental health crisis. (7) In contrast with the findings of only marginal internal radiation contamination among children and adults, (2,9) it appears that the increasing burden of noncommunicable diseases and mental health problems may outweigh the burden of disease caused directly by radiation. …

Effects of social isolation and re-socialization on cognition and ADAR1 (p110) expression in mice.

It has been reported that social isolation stress could be a key factor that leads to cognitive deficit for both humans and rodent models. However, detailed mechanisms are not yet clear. ADAR1 (Adenosine deaminase acting on RNA) is an enzyme involved in RNA editing that has a close relation to cognitive function. We have hypothesized that social isolation stress may impact the expression of ADAR1 in the brain of mice with cognitive deficit. To test our hypothesis, we evaluated the cognition ability of mice isolated for different durations (2, 4, and 8 weeks) using object recognition and object location tests; we also measured ADAR1 expression in hippocampus and cortex using immunohistochemistry and western blot. Our study showed that social isolation stress induced spatial and non-spatial cognition deficits of the tested mice. In addition, social isolation significantly increased both the immunoreactivity and protein expression of ADAR1 (p110) in the hippocampus and frontal cortex. Furthermore, re-socialization could not only recover the cognition deficits, but also bring ADAR1 (p110) immunoreactivity of hippocampus and frontal cortex, as well as ADAR1 (p110) protein expression of hippocampus back to the normal level for the isolated mice in adolescence. In conclusion, social isolation stress significantly increases ADAR1 (p110) expression in the hippocampus and frontal cortex of the mice with cognitive deficit. This finding may open a window to better understand the reasons (e.g., epigenetic change) that are responsible for social isolation-induced cognitive deficit and help the development of novel therapies for the resulted diseases.

Neurological mechanism of Xiaochaihutang's antidepressant-like effects to socially isolated adult rats.

Xiaochaihutang (XCHT) has antidepressant effects in multiple animal models of depression in our previous studies. But the antidepressant effects and exact mechanisms of XCHT in a rat model of chronic social isolation stress (CSIS) have never been studied. We therefore aimed to investigate the effects of XCHT on depressive/anxiety-related behaviours of CSIS-exposed rats and understand the neurological mechanism involving neurogenesis. We established the CSIS model and then investigated the effects of XCHT on behavioural change. HPLC-MS/MS was adopted to quantify neurotransmitter levels in the cerebrospinal fluid (CSF). Immunofluorescence technology was used to study the effects of XCHT on neurogenesis; while expressions of 5-HT1A receptor signalling pathway in the hippocampus were measured using Western blotting. Xiaochaihutang significantly alleviated depressive/anxiety-like behaviours of CSIS-exposed rats. XCHT significantly regulated levels of monoamine neurotransmitters in the CSF without affecting Glu, GABA and ACh. XCHT also significantly increased neurogenesis in CSIS-exposed rats. Additionally, XCHT reversed CSIS-induced decrease of 5-HT1A receptor expression and promoted the expression of BDNF in the hippocampus. Our results suggest that XCHT could significantly regulate the depressive/anxiety-like behaviours induced by CSIS, which are likely attributed to the promotion of hippocampal neurogenesis and neurotrophin expressions through the activation of serotonergic system.

Modulation of long interspersed nuclear element-1 in the mouse hippocampus during maturation.

Retrotransposition of long interspersed nuclear element-1 (L1-RTP) is proposed to contribute to central nervous system (CNS) plasticity by inducing mosaicism of neuronal cells. Clinical studies have identified increased L1 copy numbers in the brains of patients with psychiatric disorders. These observations implicate that L1-RTP is important for neurogenesis and that its deregulation represents a risk factor for mental disorders. However, no supportive evidence is available for understanding the importance of L1-RTP in CNS function. To explore the physiological role of L1-RTP in CNS, we examined the L1 copy number during maturation. Interestingly, the L1 copy number increased after birth in the mouse hippocampus, but not the frontal lobe, with maximal copy numbers found in 8-week-old mice. This age-dependent L1 increase was abolished by administration of a reverse-transcriptase inhibitor, stavudine (d4T), which showed no toxic effects. Notably, the age-dependent L1 increase was attenuated by post-weaning social isolation (SI) stress, a well-known intervention for inducing psychiatric disorders in mice, or deletion of the NR2A gene that encodes a subunit of the glutamate receptor. Moreover, the negative effects of SI stress on L1-RTP were partially restored by environmental enrichment with voluntary running, but not by fluoxetine, a commonly used anti-psychiatric drug. Finally, behavioral experiments revealed that learning memory was defective in d4T-treated mice, which was similarly observed in mice raised under SI stress. We detected the modulation of L1-RTP in the hippocampus during maturation of the CNS. In a recent study, we demonstrated that stimulants such as methamphetamine and cocaine were active in the induction of L1-RTP in neuronal cells, and previous studies have shown that NR2A-deficient mice are susceptible to mental abnormality. Herein, our data support the notion that the age-dependent modulation of L1-RTP is involved in genome differentiation in the hippocampus, and that modulation defects are linked to the development of psychiatric disorders.

Survival after pathogen exposure in group-living insects: don't forget the stress of social isolation!

A major cost of group-living is its inherent risk of pathogen infection. To limit this risk, many group-living animals have developed the capability to prophylactically boost their immune system in the presence of group members and/or to mount collective defences against pathogens. These two phenomena, called density-dependent prophylaxis and social immunity, respectively, are often used to explain why, in group-living species, individuals survive better in groups than in isolation. However, this survival difference may also reflect an alternative and often overlooked process: a cost of social isolation on individuals' capability to fight against infections. Here, we disentangled the effects of density-dependent prophylaxis, social immunity and stress of social isolation on the survival after pathogen exposure in group-living adults of the European earwig Forficula auricularia. By manipulating the presence of group members both before and after pathogen exposure, we demonstrated that the cost of being isolated after infection, but not the benefits of social immunity or density-dependent prophylaxis, explained the survival of females. Specifically, females kept constantly in groups or constantly isolated had higher survival rates than females that were first in groups and then isolated after infection. Our results also showed that this cost of social isolation was absent in males and that social isolation did not reduce the survival of noninfected individuals. Overall, this study gives a new perspective on the role of pathogens in social evolution, as it suggests that an apparently nonadaptive, personal immune process may promote the maintenance of group-living under pathogenic environments.

PT633. Involvement of astrocyte Activation in Locus Coeruleus on the Exacerbation of Neuropathic Pain by Maternal Separation and Social Isolation Stress

PT633. Involvement of astrocyte Activation in Locus Coeruleus on the Exacerbation of Neuropathic Pain by Maternal Separation and Social Isolation Stress

Lithium attenuates the proconvulsant effect of adolescent social isolation stress via involvement of the nitrergic system.

In this study, we tested whether acute administration of lithium mitigates the deleterious effect of adolescent social isolation stress (SIS) on seizure susceptibility. In comparison with socially conditioned (SC) mice, isolated conditioned (IC) mice exhibited an increase in seizure susceptibility to pentylenetetrazole. Acute administration of lithium (10mg/kg) reversed the proconvulsant effect of SIS in IC mice, but this effect was not observed in SC mice. Coadministration of subthreshold doses of lithium (3mg/kg) with nitric oxide synthase (NOS) inhibitors reversed the effect of SIS on seizure susceptibility and decreased hippocampal nitrite levels in IC animals. In addition, a subthreshold dose of a nitric oxide precursor reduced the protective effect of lithium on seizure susceptibility and increased nitrite levels in the hippocampus of IC mice. These results suggest that lithium exerts a protective influence against the proconvulsant effect of adolescent SIS via a nitrergic system that includes activation of neuronal NOS in the hippocampus.

Attenuation of oxidative and nitrosative stress in cortical area associates with antidepressant-like effects of tropisetron in male mice following social isolation stress.

Tropisetron, a 5-HT3 receptor antagonist widely used as an antiemetic, has been reported to have positive effects on mood disorders. Adolescence is a critical period during the development of brain, where exposure to chronic stress during this time is highly associated with the development of depression. In this study, we showed that 4 weeks of juvenile social isolation stress (SIS) provoked depressive-like behaviors in male mice, which was associated with disruption of mitochondrial function and nitric oxide overproduction in the cortical areas. In this study, tropisetron (5mg/kg) reversed the negative behavioral effects of SIS in male mice. We found that the effects of tropisetron were mediated through mitigating the negative activity of inducible nitric oxide synthase (iNOS) on mitochondrial activity. Administration of aminoguanidine (specific iNOS inhibitor, 20mg/kg) augmented the protective effects of tropisetron (1mg/kg) on SIS. Furthermore, l-arginine (nitric oxide precursor, 100mg/kg) abolished the positive effects of tropisetron. These results have increased our knowledge on the pivotal role of mitochondrial function in the pathophysiology of depression, and highlighted the role of 5-HT3 receptors in psychosocial stress response during adolescence. Finally, we observed that tropisetron alleviated the mitochondrial dysfunction through decreased nitrergic system activity in the cerebral cortex.

Towards understanding and predicting suicidality in women: biomarkers and clinical risk assessment.

Women are under-represented in research on suicidality to date. Although women have a lower rate of suicide completion than men, due in part to the less-violent methods used, they have a higher rate of suicide attempts. Our group has previously identified genomic (blood gene expression biomarkers) and clinical information (apps) predictors for suicidality in men. We now describe pilot studies in women. We used a powerful within-participant discovery approach to identify genes that change in expression between no suicidal ideation (no SI) and high suicidal ideation (high SI) states (n=12 participants out of a cohort of 51 women psychiatric participants followed longitudinally, with diagnoses of bipolar disorder, depression, schizoaffective disorder and schizophrenia). We then used a Convergent Functional Genomics (CFG) approach to prioritize the candidate biomarkers identified in the discovery step by using all the prior evidence in the field. Next, we validated for suicidal behavior the top-ranked biomarkers for SI, in a demographically matched cohort of women suicide completers from the coroner's office (n=6), by assessing which markers were stepwise changed from no SI to high SI to suicide completers. We then tested the 50 biomarkers that survived Bonferroni correction in the validation step, as well as top increased and decreased biomarkers from the discovery and prioritization steps, in a completely independent test cohort of women psychiatric disorder participants for prediction of SI (n=33) and in a future follow-up cohort of psychiatric disorder participants for prediction of psychiatric hospitalizations due to suicidality (n=24). Additionally, we examined how two clinical instruments in the form of apps, Convergent Functional Information for Suicidality (CFI-S) and Simplified Affective State Scale (SASS), previously tested in men, perform in women. The top CFI-S item distinguishing high SI from no SI states was the chronic stress of social isolation. We then showed how the clinical information apps combined with the 50 validated biomarkers into a broad predictor (UP-Suicide), our apriori primary end point, predicts suicidality in women. UP-Suicide had a receiver-operating characteristic (ROC) area under the curve (AUC) of 82% for predicting SI and an AUC of 78% for predicting future hospitalizations for suicidality. Some of the individual components of the UP-Suicide showed even better results. SASS had an AUC of 81% for predicting SI, CFI-S had an AUC of 84% and the combination of the two apps had an AUC of 87%. The top biomarker from our sequential discovery, prioritization and validation steps, BCL2, predicted future hospitalizations due to suicidality with an AUC of 89%, and the panel of 50 validated biomarkers (BioM-50) predicted future hospitalizations due to suicidality with an AUC of 94%. The best overall single blood biomarker for predictions was PIK3C3 with an AUC of 65% for SI and an AUC of 90% for future hospitalizations. Finally, we sought to understand the biology of the biomarkers. BCL2 and GSK3B, the top CFG scoring validated biomarkers, as well as PIK3C3, have anti-apoptotic and neurotrophic effects, are decreased in expression in suicidality and are known targets of the anti-suicidal mood stabilizer drug lithium, which increases their expression and/or activity. Circadian clock genes were overrepresented among the top markers. Notably, PER1, increased in expression in suicidality, had an AUC of 84% for predicting future hospitalizations, and CSNK1A1, decreased in expression, had an AUC of 96% for predicting future hospitalizations. Circadian clock abnormalities are related to mood disorder, and sleep abnormalities have been implicated in suicide. Docosahexaenoic acid signaling was one of the top biological pathways overrepresented in validated biomarkers, which is of interest given the potential therapeutic and prophylactic benefits of omega-3 fatty acids. Some of the top biomarkers from the current work in women showed co-directionality of change in expression with our previous work in men, whereas others had changes in opposite directions, underlying the issue of biological context and differences in suicidality between the two genders. With this study, we begin to shed much needed light in the area of female suicidality, identify useful objective predictors and help understand gender commonalities and differences. During the conduct of the study, one participant committed suicide. In retrospect, when the analyses were completed, her UP-Suicide risk prediction score was at the 100 percentile of all participants tested.