Adolescent Stress-Induced Ventral Hippocampus Redox Dysregulation Underlies Behavioral Deficits and Excitatory/Inhibitory Imbalance Related to Schizophrenia

BACKGROUND AND HYPOTHESIS

Redox dysregulation has been proposed as a convergent point of childhood trauma and the emergence of psychiatric disorders, such as schizophrenia (SCZ). A critical region particularly vulnerable to environmental insults during adolescence is the ventral hippocampus (vHip). However, the impact of severe stress on vHip redox states and their functional consequences, including behavioral and electrophysiological changes related to SCZ, are not entirely understood.

STUDY DESIGN

After exposing adolescent animals to physical stress (postnatal day, PND31-40), we explored social and cognitive behaviors (PND47-49), the basal activity of pyramidal glutamate neurons, the number of parvalbumin (PV) interneurons, and the transcriptomic signature of the vHip (PND51). We also evaluated the impact of stress on the redox system, including mitochondrial respiratory function, reactive oxygen species (ROS) production, and glutathione (GSH) levels in the vHip and serum.

STUDY RESULTS

Adolescent-stressed animals exhibited loss of sociability, cognitive impairment, and vHip excitatory/inhibitory (E/I) imbalance. Genome-wide transcriptional profiling unveiled the impact of stress on redox system- and synaptic-related genes. Stress impacted mitochondrial respiratory function and changes in ROS levels in the vHip. GSH and glutathione disulfide (GSSG) levels were elevated in the serum of stressed animals, while GSSG was also increased in the vHip and negatively correlated with sociability. Additionally, PV interneuron deficits in the vHip caused by adolescent stress were associated with oxidative stress.

CONCLUSIONS

Our results highlight the negative impact of adolescent stress on vHip redox regulation and mitochondrial function, which are partially associated with E/I imbalance and behavioral abnormalities related to SCZ.

Prenatal substance exposure, early-life adversity, and parenting: Associations with adolescent stress response

We tested a conceptual model examining associations between prenatal substance exposure and adolescent cortisol reactivity profiles in response to an acute social evaluative stressor. We included cortisol reactivity in infancy, and direct and interactive effects of early-life adversity and parenting behaviors (sensitivity, harshness) from infancy to early school age on adolescent cortisol reactivity profiles in model testing. Participants were 216 families (51% female children; 116 cocaine-exposed) recruited at birth, oversampled for prenatal substance exposure, and assessed from infancy to early adolescence (EA). Majority of participants self-identified as Black (72% mothers, 57.2% adolescents), and caregivers were primarily from low-income families (76%), were single (86%), and had high school or below education (70%) at recruitment. Latent profile analyses identified three cortisol reactivity patterns including elevated (20.4%), moderate (63.1%), and blunted (16.5%) reactivity groups. Prenatal tobacco exposure was associated with higher likelihood of membership in the elevated reactivity compared to the moderate reactivity group. Higher caregiver sensitivity in early life was associated with lower likelihood of membership in the elevated reactivity group. Prenatal cocaine exposure was associated with higher maternal harshness. Interaction effects among early-life adversity and parenting indicated that caregiver sensitivity buffered, and harshness exacerbated, the likelihood that high early adversity would be associated with the elevated and blunted reactivity groups. Results highlight the potential importance of prenatal alcohol and tobacco exposure for cortisol reactivity and the role of parenting as exacerbating or buffering the impact of early-life adversity on adolescent stress response.

Feasibility of combining biosensor and ecological momentary assessment to measure stress experiences among economically disadvantaged adolescents

Adolescent stress is complex and impairing. Novel measures are needed to understand stress variability within individuals over time from a physiological as well as a subjective perspective. To test the feasibility of combining ecological momentary assessment (EMA) and wearable biosensors to assess adolescent stress, using an idiographic approach with experience sampling methods. A small sample (n = 23) of predominantly African American, economically disadvantaged adolescents were asked to complete EMA surveys four times per day and wear an armband measuring Heart rate (HR) and skin response for a 2-week period. Descriptive analyses examined number of hours of armband wear, percentage of viable data, and percentage of surveys completed by gender and race. Associations between biosensor data and EMA reports within and across individuals were also examined using hierarchical linear regression. EMA survey completion was good (81%) as was adherence to biosensor protocols, although technological difficulties interfered with collection of HR variability for youth with darker skin tones. Youth reported stressful events in 12.79% of EMA surveys, although 43% reported no negative mood experiences. Convergent validity was supported for detecting between-person (EMA) and within-person (EMA and biosensors) variability in stress across time, although associations across youth were highly variable. Results suggest value for biobehavioral methods in understanding day-to-day stress in adolescents but highlight variability in stress experiences as well as technological limitations, especially for youth of colour.

Therapeutic Effects of Spirulina platensis Against Adolescent Stress-Induced Oxidative Stress, Brain-Derived Neurotrophic Factor Alterations and Morphological Remodeling in the Amygdala of Adult Female Rats

Objective

The amygdala structural and functional abnormalities have been implicated in numerous neuropsychiatric and neurodevelopmental disorders. Given the important role of the amygdala in stress responses and the susceptibility of the females to adolescent stress, the present study investigated the beneficial effects of Spirulina platensis microalgae (SP) as a neuroprotective supplement against adolescent stress-induced oxidative stress, brain-derived neurotrophic factor (BDNF) alterations, molecular and morphological remodeling in the basolateral amygdala (BLA) of adult female rats.

Methods

During the adolescent period (PNDs 30–40) rats were subjected to restraint stress (2 h/day for 10 days). Then, the animals were subjected to 15 days treatment (PNDs 41–55) with SP (200 mg/kg/day) followed by biochemical (BDNF and stress oxidative markers), molecular (BDNF and its receptor tropomyosin receptor kinase B [TrkB] mRNA expression), and morphological (dendritic length and spines) assessments in the BLA.

Results

The study revealed that adolescent stress decreased BDNF levels and reduced apical dendritic length and branch points of pyramidal neurons in the BLA. In addition, chronic stress significantly increased oxidative stress parameters and decreased BDNF and TrkB mRNA expression in the BLA. Treatment with SP alleviated both biochemical, molecular, and neuroanatomical deficits that induced by adolescent stress.

Conclusion

Our findings provide important evidence that SP as a non-pharmacological intervention during adolescent period can protect against chronic stress-induced neuroanatomical biochemical, and molecular deficits in adulthood, and thus, reduce stress-related disorders.

Protective Effects of Spirulina platensis, Voluntary Exercise and Environmental Interventions Against Adolescent Stress-Induced Anxiety and Depressive-Like Symptoms, Oxidative Stress and Alterations of BDNF and 5HT-3 Receptors of the Prefrontal Cortex in Female Rats

BACKGROUND AND PURPOSE

Ample evidence indicates that chronic adolescence stress is associated with an increased risk of developing neuropsychiatric disorders in adulthood. Given the importance of the effective therapeutic ways to overcome adolescent stress-related deficits, the present study investigated the effects of Spirulina platensis (SP), environmental enrichment (EE), and voluntary exercise (EX) and their combination on anxiety or depression-like behaviors, oxidative stress, and alterations of BDNF and 5HT-3 receptors in the prefrontal cortex (PFC) induced by adolescent stress in adult female rats.

METHODS

During the adolescent period (PNDs30-40), rats were subjected to restraint stress. Then, the animals were subjected to SP treatment (200 mg/kg/day), EX, EE, and the combined treatments (SP+EX, and SP+EE) for 15 days between PNDs41-55. Subsequently, anxiety or depression-like behaviors, BDNF levels, oxidative stress markers and mRNA expression of BDNF and 5HT₃ in the PFC were assessed.

RESULTS

Stressed rats demonstrated enhanced anxiety levels and depression-like behaviors in adulthood. Regarding the oxidative stress markers, stressed rats exhibited significantly higher levels of malondialdehyde, a lipid peroxidation product, higher activities of antioxidant enzymes (glutathione peroxidase and superoxide dismutase) and significantly lower total antioxidant reactivity capacity in the PFC. Additionally, adolescent stress significantly increased 5HT3 receptor mRNA expression and decreased BDNF content and its mRNA expression in the PFC. Treatments with SP, EX, EE, and the combined interventions alleviated these deficits.

CONCLUSION

Our findings indicate that appropriate interventions during the adolescent period can protect against adolescent stress-induced behavioral, and biochemical defects and oxidative stress damage in adulthood.

The shortened version of the Adolescent Stress Questionnaire (ASQ-S; Sweden): a validation study in United Kingdom adolescents

BACKGROUND

Stress is an important variable of consequence, particularly in adolescence, a period of intense physical and psychological change. The measurement of stress in adolescence has been widely discussed, and a number of versions of the Adolescent Stress Questionnaire (ASQ) have been developed and validated. The present study sought to examine the psychometric properties (model fit, invariance, internal consistency, and construct validity) of the ASQ-S, which was recently developed in a Swedish context.

OBJECTIVE

The study was a secondary analysis of data gathered on the full ASQ. The ASQ-S retained nine of the ten ASQ scales, and a study in Swedish adolescents suggested that the scale was psychometrically valid, gender invariant, and that scores were internally consistent. This is the first study to examine the properties of the ASQ-S in an English-speaking population. Participants were high school children in the UK (N = 610, 61.0% girls) from school year 8 through 12.

RESULTS

Confirmatory factor analysis (CFA) revealed that the nine factor solution fit the data well (χ2s-b(288) = 751.60, CFI = 0.958, TLI = 0.948, SRMR = 0.040, RMSEA = 0.051 [90% CI = 0.047, 0.056]), and that scores were gender, school type (academic versus comprehensive), and school stage (junior versus middle high school) invariant. The nine scales correlated negatively with academic, social, and emotional self-efficacy scores, and self-esteem scores, to varying degrees. Girls reported higher stress levels than boys in six of the nine scales. A regression analysis, adjusted for gender and year in school, suggested that only the stress of peer pressure (negatively) was significantly related to adolescent alcohol use.

CONCLUSIONS

Overall this study suggests that the ASQ-S could be a valid measure of adolescent stress, although concerns remain regarding the convergent validity of scale scores.

Native American adolescent narrative written stories of stress

OBJECTIVE(S)

The purpose of this paper is to report study findings related to themes of stress and coping strategies experienced by non-reservation-based Native American adolescents as expressed by their written stories.

DESIGN

A qualitative descriptive narrative approach was used to capture written stories of stress.

ANALYSIS

Key concepts and themes were identified by using the consensual qualitative research (CQR) approach from the participant's stories of stress.

RESULTS

Written stories of stress were collected and analyzed from a convenience sample of 179 Native American adolescent's ages 13-18-years old. Five major themes related to experiences of stress emerged from the stories including (a) relationships, (b) responsibilities, (c) socioeconomic status, (d) negative coping strategies, and (e) positive coping through Native-Reliance.

CONCLUSION

The findings reveal the importance of understanding the types and response to stress experienced by Native American adolescents.

Psychometric Properties of the Perceived Stress Questionnaire (PSQ) in 15-16 Years Old Norwegian Adolescents

A better understanding about prerequisites of health and well-being in adolescents is important to prevent chronicity and comorbidities of stress and to improve health promotion in this group. For this purpose, useful instruments are required. The Perceived Stress Questionnaire (PSQ) is developed for research, with an emphasis on predictive validity. The PSQ comprises different components of stress, and the instrument might be useful in studying prerequisites and predictors of health and well-being in adolescents. However, the instrument has not been evaluated in Norwegian psychosomatic populations and in adolescents. Moreover, the factor structure of the PSQ seems to vary between populations, and invariance across gender and concurrent validity regarding mindfulness are not previously tested. The objective of this study were to evaluate the psychometric properties of the Norwegian version of the PSQ in adolescents, including evaluate the fit of previously proposed PSQ-models in females and males and test measurement invariance across gender. Concurrent validity with respect to mindfulness (Mindful Attention Awareness Scale- Adolescent [MAAS-A]) was preliminary evaluated. Confirmatory factor analysis for each previously proposed model was conducted, separately for females and males. Multi-group factor analyses were performed to test measurement invariance of the different PSQ-models across gender. The associations between the PSQ and the MAAS-A and inter-scale correlations were preliminary evaluated. Preceding the data collection and main analyses, the instruments were translated to Norwegian following standardized procedures. The participants in study were Norwegian adolescents aged 15-16 years (N = 524). The overall PSQ performance seemed to correspond to previous findings, and internal consistency was supported across gender. A four-factor model of the PSQ showed best fit to the data in both females and males and configural and metric invariance seemed supported. Full scalar invariance was not supported for the four-factor model, implying that cross-group comparisons (between females and males) on latent means may be uncertain and must be interpreted with caution. Concurrent validity with respect to mindfulness (MAAS-A) was preliminary supported. Further studies might be needed to confirm the findings from this study.

Adolescent Stress Disrupts the Maturation of Anxiety-related Behaviors and Alters the Developmental Trajectory of the Prefrontal Cortex in a Sex- and Age-specific Manner

Adolescence is a window of vulnerability to environmental factors such as chronic stress that can disrupt brain development and cause long-lasting behavioral dysfunction, as seen in disorders like depression, anxiety, and schizophrenia. There are also sex differences in the prevalence of these disorders across the lifespan. However, the mechanisms of how adolescent stress contributes to neuropsychiatric phenotypes are not well understood, nor are the mediating effects of sex. We hypothesize that adolescent stress disrupts the γ-aminobutyric acid (GABA) system in the prefrontal cortex (PFC) in a sex-specific manner, as this system matures during adolescence and plays an important role in cognitive and emotional functioning. We exposed male and female mice to unpredictable chronic mild stress (UCMS) during adolescence (post-natal day [PND] 28-42). One cohort underwent testing for PFC-related behavioral and molecular changes 24 h following the cessation of stress (late adolescence); a separate cohort was tested approximately 2.5 weeks after the end of UCMS (adulthood). We observed an age-related decline in anxiety-like behaviors in control mice, while mice stressed in adolescence showed elevated anxiety-like behaviors in both adolescence and adulthood. PFC-dependent cognitive functioning was also impaired in adult males stressed in adolescence. Adolescent stress disrupted expression patterns of parvalbumin (PV) and perineuronal nets (PNNs) in the PFC, as well as NMDA receptor subunit composition, in a sex- and age-specific manner. The findings presented here contribute to understanding how adolescent stress may lead to neuropsychiatric disorders such as anxiety by disrupting the development of the PFC and emotional behaviors.

Adolescent Isolation Interacts With DISC1 Point Mutation to Impair Adult Social Memory and Synaptic Functions in the Hippocampus

Disrupted-in-schizophrenia 1 (DISC1) is a strong candidate susceptibility gene for a spectrum of neuropsychiatric diseases including schizophrenia, bipolar disorder and major depression, all of which are thought to result from interactions between gene mutations and environmental risk factors such as influenza, trauma and stress. Adolescence is a key period susceptible to stress and stress-related mental illnesses. In a previous study, we found that although DISC1 L100P point mutation mice shows object recognition deficits, their sociability and social memory are relatively normal. Therefore, in this article, we investigated whether the interaction between adolescent stress and DISC1 L100P point mutation affects adult social memory, and we explored the underlying mechanisms. We found that adolescent stress (isolation from 5 weeks to 8 weeks of age) specifically impaired social memory of adult DISC1 L100P mice but not that of WT littermates, which could be rescued by administration of atypical antipsychotic drug clozapine. On the other hand, it did not induce anxiety or depression in adult mice. Adolescent isolation exacerbated adult neurogenesis deficits in the hippocampus of DISC1 L100P mice, while it had no effect on WT mice. In addition, we found that adolescent isolation led to long lasting changes in synaptic transmission and plasticity in the hippocampal circuits, some of which are specific for DISC1 L100P mice. In summary, we identified here the specific interaction between genetic mutation (DISC1 L100P) and adolescence social stress that damages synaptic function and social memory in adult hippocampal circuits.

Highlights–

Adolescent isolation (from 5 weeks to 8 weeks of age) impairs adult social memory when combined with DISC1 L100P point mutation.

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Adolescent isolation exacerbates adult neurogenesis deficit in the hippocampus of L100P mice but has no similar effect on WT mice.

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Adolescent isolation causes long lasting changes in synaptic transmission and plasticity of the hippocampal network in DISC1 L100P mice.

Transgenerational inheritance of chronic adolescent stress: Effects of stress response and the amygdala transcriptome

Adolescent stress can impact health and well-being not only during adulthood of the exposed individual but even in future generations. To investigate the molecular mechanisms underlying these long-term effects, we exposed adolescent males to stress and measured anxiety behaviors and gene expression in the amygdala-a critical region in the control of emotional states-in their progeny for two generations, offspring and grandoffspring. Male C57BL/6 mice underwent chronic unpredictable stress (CUS) for 2 weeks during adolescence and were used to produce two generations of offspring. Male and female offspring and grandoffspring were tested in behavioral assays to measure affective behavior and stress reactivity. Remarkably, transgenerational inheritance of paternal stress exposure produced a protective phenotype in the male, but not the female lineage. RNA-seq analysis of the amygdala from male offspring and grandoffspring identified differentially expressed genes (DEGs) in mice derived from fathers exposed to CUS. The DEGSs clustered into numerous pathways, and the "notch signaling" pathway was the most significantly altered in male grandoffspring. Therefore, we show that paternal stress exposure impacts future generations which manifest in behavioral changes and molecular adaptations.

Stress in childhood, adolescence and early adulthood, and cortisol levels in older age

The glucocorticoid hypothesis suggests that overexposure to stress may cause permanent upregulation of cortisol. Stress in youth may therefore influence cortisol levels even in older age. Using data from the 6-Day Sample, we investigated the effects of high stress in childhood, adolescence and early adulthood - as well as individual variables contributing to these measures; parental loss, social deprivation, school and home moves, illness, divorce and job instability - upon cortisol levels at age 77 years. Waking, waking +45 min (peak) and evening salivary cortisol samples were collected from 159 participants, and the 150 who were not using steroid medications were included in this study. After correcting for multiple comparisons, the only significant association was between early-adulthood job instability and later-life peak cortisol levels. After excluding participants with dementia or possible mild cognitive impairment, early-adulthood high stress showed significant associations with lower evening and mean cortisol levels, suggesting downregulation by stress, but these results did not survive correction for multiple comparisons. Overall, our results do not provide strong evidence of a relationship between stress in youth and later-life cortisol levels, but do suggest that some more long-term stressors, such as job instability, may indeed produce lasting upregulation of cortisol, persisting into the mid-to-late seventies.

Effects of repeated adolescent stress and serotonin transporter gene partial knockout in mice on behaviors and brain structures relevant to major depression

In humans, exposure to stress during development is associated with structural and functional alterations of the prefrontal cortex (PFC), amygdala (AMY), and hippocampus (HC) and their circuits of connectivity, and with an increased risk for developing major depressive disorder particularly in carriers of the short (s) variant of the serotonin transporter (5-HTT) gene-linked polymorphic region (5-HTTLPR). Although changes in these regions are found in carriers of the s allele and/or in depressed patients, evidence for a specific genotype × developmental stress effect on brain structure and function is limited. Here, we investigated the effect of repeated stress exposure during adolescence in mice with partial knockout of the 5-HTT gene (HET) vs. wildtype (WT) on early-adulthood behavioral measures and brain structure [using magnetic resonance imaging (MRI)] relevant to human major depression. Behaviorally, adolescent stress (AS) increased anxiety and decreased activity and did so to a similar degree in HET and WT. In a probabilistic reversal learning task, HET-AS mice achieved fewer reversals than did HET-No-AS mice. 5-HTT genotype and AS were without effect on corticosterone stress response. In terms of structural brain differences, AS reduced the volume of two long-range white matter tracts, the optic tract (OT) and the cerebral peduncle (CP), in WT mice specifically. In a region-of-interest analysis, AS was associated with increased HC volume and HET genotype with a decreased frontal lobe volume. In conclusion, we found that 5-HTT and AS genotype exerted long-term effects on behavior and development of brain regions relevant to human depression.

Glucocorticoid sensitizers Bag1 and Ppid are regulated by adolescent stress in a sex-dependent manner

Early life stress precipitates dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis and this effect is most pronounced in females. The mechanisms that mediate female sensitivity to stress-induced HPA axis dysregulation are unknown. The purpose of this study was to determine whether sex moderates the effects of chronic adolescent stress on glucocorticoid receptor (GR) translocation and moderators of the GR system. Female adolescent rats with a history of chronic stress exposure demonstrated a delayed resolution of the plasma corticosterone response to an acute stressor and this delay was accompanied by attenuated GR translocation compared to control adolescent females. The chronic stress-induced phenotype in females was similar to the baseline phenotype in male adolescent rats. Conversely, the expression patterns of GR moderators/co-chaperones became more sexually dimorphic following chronic stress, suggesting divergent function of the GR system between male and female adolescent rats. Gene expression of Ppid, a positive regulator of the GR, was predicted by plasma estradiol and 34% lower in control adolescent females than males, indicating that sex steroids may play a role in the sexually dimorphic response. After chronic adolescent stress, females displayed elevated hippocampal expression of Bag1 and Ppid genes that was not observed in males. Overall, the GR output to an acute stressor, illustrated by transcription of Nr3c1 (encoding the GR), Bag1, Fkbp5, Ppid, and Src1, was significantly upregulated and differed in a sex-specific and chronic stress-dependent manner. This study provides new evidence for sex differences during development and adaptation of the glucocorticoid receptor chaperone system.

Adolescent social defeat alters markers of adult dopaminergic function

Stressful experiences during adolescence can alter the trajectory of neural development and contribute to psychiatric disorders in adulthood. We previously demonstrated that adolescent male rats exposed to repeated social defeat stress show changes in mesocorticolimbic dopamine content both at baseline and in response to amphetamine when tested in adulthood. In the present study we examined whether markers of adult dopamine function are also compromised by adolescent experience of social defeat. Given that the dopamine transporter as well as dopamine D1 receptors act as regulators of psychostimulant action, are stress sensitive and undergo changes during adolescence, quantitative autoradiography was used to measure [(3)H]-GBR12935 binding to the dopamine transporter and [(3)H]-SCH23390 binding to dopamine D1 receptors, respectively. Our results indicate that social defeat during adolescence led to higher dopamine transporter binding in the infralimbic region of the medial prefrontal cortex and higher dopamine D1 receptor binding in the caudate putamen, while other brain regions analyzed were comparable to controls. Thus it appears that social defeat during adolescence causes specific changes to the adult dopamine system, which may contribute to behavioral alterations and increased drug seeking.