Glucocorticoid feedback paradox: a homage to Mary Dallman.

As the end product of the hypothalamus-pituitary-adrenal (HPA) axis, the glucocorticoid hormones cortisol and corticosterone coordinate circadian activities, stress-coping, and adaptation to change. For this purpose, the hormone promotes energy metabolism and controls defense reactions in the body and brain. This life-sustaining action exerted by glucocorticoids occurs in concert with the autonomic nervous and immune systems, transmitters, growth factors/cytokines, and neuropeptides. The current contribution will focus on the glucocorticoid feedback paradox in the HPA-axis: the phenomenon that stress responsivity remains resilient if preceded by stress-induced secretion of glucocorticoid hormone, but not if this hormone is previously administered. Furthermore, in animal studies, the mixed progesterone/glucocorticoid antagonist RU486 or mifepristone switches to an apparent partial agonist upon repeated administration. To address these enigmas several interesting phenomena are highlighted. These include the conditional nature of the excitation/inhibition balance in feedback regulation, the role of glucose as a determinant of stress responsivity, and the potential of glucocorticoids in resetting the stress response system. The analysis of the feedback paradox provides also a golden opportunity to review the progress in understanding the role of glucocorticoid hormone in resilience and vulnerability during stress, the science that was burned deeply in Mary Dallman's emotions.

Brain mineralocorticoid and glucocorticoid receptor balance in neuroendocrine regulation and stress-related psychiatric etiopathologies.

Cortisol and corticosterone (CORT) coordinate circadian events and manage the stress response by differential activation of two complementary brain receptor systems, i.e., the mineralocorticoid receptor (MR) and the glucocorticoid receptor (GR), which mediate rapid non-genomic and slow genomic actions. Several recent discoveries are highlighted from molecular fine-tuning of the MR/GR balance by FKBP5 to CORTs role in neural network regulation underlying stress adaptation in emotional, cognitive, and social domains of behavior. The data suggest that MR mediates CORT action on risk assessment, social interaction, and response selection, while GR activation promotes memory consolidation and behavioral adaptation; there are also sex differences in CORT action. New evidence suggests that targeting the MR/GR balance resets a dysregulated stress response system and promotes resilience.

The perinatal origins of childhood anxiety disorders and the role of early-life maternal predictors.

BACKGROUND: The development of childhood anxiety disorders (CADs) is likely to depend on pathways that can be programmed by early-life risk factors. We test the hypothesis that early-life maternal factors can predict this programming effect on CAD. METHODS: Data were obtained from 198 women and children from the Mercy Pregnancy and Emotional Wellbeing Study (MPEWS), a cohort study with data collected across pregnancy, postpartum and until 4 years of age. Maternal antenatal depression was measured using the Structured Clinical Interview for DSM-IV (SCID-IV), together with antenatal hair cortisol concentrations, maternal childhood trauma and parenting stress at 6 months postpartum. CAD was assessed with the Preschool Age Psychiatric Assessment and the Child Behaviour Checklist. RESULTS: Antenatal depression, a history of maternal childhood trauma and lower gestational age at birth were each associated with anxiety disorders at 4 years of age in their children. A multivariate binary logistic model with these early predictors explained approximately 9% of variance in CAD outcome at 4 years of age; however, only maternal trauma and gestational age were significant predictors in the model. The effect of early parenting stress on CAD was found to vary by the concentration of maternal antenatal hair cortisol, whereby postpartum parenting stress was associated with CAD only when there were higher maternal antenatal cortisol levels. CONCLUSIONS: This study suggests the importance of maternal factors pre-conception, pregnancy and in the postnatal period, which predict CADs and this is consistent with a developmental programming hypothesis for CAD.

The role of glucocorticoid and mineralocorticoid receptor DNA methylation in antenatal depression and infant stress regulation.

Understanding fetal programming pathways that underpin the relationship between maternal and offspring mental health necessitates an exploration of potential role of epigenetic variation in early development. Two genes involved in stress response regulation, the glucocorticoid and mineralocorticoid receptors (NR3C1 and NR3C2) have been a focus in understanding stressful exposures and mental health outcomes. Data were obtained from 236 pregnant women from the Mercy Pregnancy Emotional Wellbeing Study (MPEWS), a selected pregnancy cohort, recruited in early pregnancy. Depression was measured using the Structured Clinical Interview for DSM-IV (SCID-IV) and repeated measures of the Edinburgh Postnatal Depression Scale (EPDS). Antidepressant use, stressful events and anxiety symptoms were measured. NR3C1 and NR3C2 DNA methylation was measured in placental and infant buccal samples. Infant cortisol was measured in repeat saliva samples across a task. This study found maternal early pregnancy depressive disorder and symptoms were associated with lower DNA methylation at NR3C2 CpG_24 in placental tissue. There were no significant differences for depression or antidepressant use for DNA methylation of NR3C1. Antenatal depression was associated with lower infant cortisol reactivity at 12 months. DNA methylation in CpG_24 site in NR3C2 in placental samples suppressed the relationship between early maternal depressive symptoms and infant cortisol reactivity. These findings show a relationship between antenatal depression, NR3C2 DNA methylation and infant cortisol response providing support for a specific fetal programming pathway. Further research is required to examine the stability of this epigenetic mark across childhood and long-term mental health outcomes.

Trans-generational stress regulation: Mother-infant cortisol and maternal mental health across the perinatal period.

Understanding maternal mental health and cortisol regulation across pregnancy and the relationship to the development of the offspring's stress regulation is critical to a range of health outcomes. The aim of this study was to investigate infant and maternal cortisol in women with depression. Data were obtained from 241 pregnant women within the Mercy Pregnancy and Emotional Wellbeing Study (MPEWS), a selected pregnancy cohort study. Depression was measured using the Structured Clinical Interview for DSM-IV (SCID-IV) and repeat Edinburgh Postnatal Depression Scale (EPDS). Repeated measures of antidepressant use, stressful events, anxiety symptoms and maternal hair cortisol concentrations (HCC) and infant cortisol at 12 months postpartum in saliva and hair. Socio-emotional outcomes were measured at 12 months by maternal report on the Brief Infant and Toddler Socio-emotional Assessment (BITSEA). This study found that maternal depression was not associated with maternal HCC. Anxiety, stress and antidepressant use were not associated with maternal HCC. Independently, higher maternal 3rd trimester maternal depressive and anxiety symptoms were associated with lower infant cortisol response at 12 months of age. A higher number of postpartum stressful events was associated with lower infant cortisol response. Lower infant stress reactivity was associated with higher externalizing symptoms at 12 months of age. Future studies are required to understand implications for later mental health.

Mineralocorticoid Receptors, Neuroinflammation and Hypertensive Encephalopathy.

Worldwide, raised blood pressure is estimated to affect 35-40% of the adult population and is a main conditioning factor for cardiovascular diseases and stroke. Animal models of hypertension have provided great advances concerning the pathophysiology of human hypertension, as already shown for the deoxycorticosterone-salt treated rat, the Dahl-salt sensitive rat, the Zucker obese rat and the spontaneously hypertensive rat (SHR). SHR has been widely used to study abnormalities of the brain in chronic hypertension. This review summarises present and past evidence that in the SHR, hypertension causes hippocampal tissue damage which triggers a pro-inflammatory feedforward cascade affecting this vulnerable brain region. The cascade is driven by mineralocorticoid receptor (MR) activation responding to endogenous corticosterone rather than aldosterone. Increased MR expression is a generalised feature of the SHR which seems to support first the rise in blood pressure. Then oxidative stress caused by vasculopathy and hypoxia further increases MR activation in hippocampal neurons and glia cells, activates microglia activation and pro-inflammatory mediators, and down-regulates anti-inflammatory factors. In contrast to MR, involvement of the glucocorticoid receptor (GR) in SHR is less certain. GR showed normal expression levels and blockage with an antagonist failed to reduce blood pressure of SHR. The findings support the concept that MR:GR imbalance caused by vasculopathy causes a switch in MR function towards a proverbial "death" receptor.

Daily maternal separations during stress hyporesponsive period decrease the thresholds of panic-like behaviors to electrical stimulation of the dorsal periaqueductal gray of the adult rat.

The present study examined whether early life maternal separation (MS), a model of childhood separation anxiety, predisposes to panic at adulthood. For this purpose, male pups were submitted to 3-h daily maternal separations along postnatal (PN) days of either the 'stress hyporesponsive period' (SHRP) from PN4 to PN14 (MS11) or throughout lactation from PN2 to PN21 (MS20). Pups were further reunited to conscious (CM) or anesthetized (AM) mothers to assess the effect of mother-pup interaction upon reunion. Controls were subjected to brief handling (15 s) once a day throughout lactation (BH20). As adults (PN60), rats were tested for the thresholds to evoke panic-like behaviors upon electrical stimulation of dorsal periaqueductal gray matter and exposed to an elevated plus-maze, an open-field, a forced swim and a sucrose preference test. A factor analysis was also performed to gain insight into the meaning of behavioral tests. MS11-CM rather than MS20-CM rats showed enhanced panic responses and reductions in both swimming and sucrose preference. Panic facilitations were less intense in mother-neglected rats. Although MS did not affect anxiety, MS11-AM showed robust reductions of defecation in an open-field. Factor analysis singled out anxiety, hedonia, exploration, coping and gut activity. Although sucrose preference and coping loaded on separate factors, appetite (adult weight) correlated with active coping in both forced swim and open-field (central area exploration). Concluding, whereas 3h-daily maternal separations during SHRP increased rat's susceptibility to experimental panic attacks, separations throughout lactation had no effects on panic and enhanced active coping.

Brain mineralocorticoid receptor function in control of salt balance and stress-adaptation.

We will highlight in honor of Randall Sakai the peculiar characteristics of the brain mineralocorticoid receptor (MR) in its response pattern to the classical mineralocorticoid aldosterone and the naturally occurring glucocorticoids corticosterone and cortisol. Neurons in the nucleus tractus solitarii (NTS) and circumventricular organs express MR, which mediate selectively the action of aldosterone on salt appetite, sympathetic outflow and volume regulation. The MR-containing NTS neurons innervate limbic-forebrain circuits enabling aldosterone to also modulate reciprocally arousal, motivation, fear and reward. MR expressed in abundance in this limbic-forebrain circuitry, is target of cortisol and corticosterone in modulation of appraisal processes, memory performance and selection of coping strategy. Complementary to this role of limbic MR is the action mediated by the lower affinity glucocorticoid receptors (GR), which promote subsequently memory storage of the experience and facilitate behavioral adaptation. Current evidence supports the hypothesis that an imbalance between MR- and GR-mediated actions compromises resilience and adaptation to stress.

Early Life Stress Effects on Glucocorticoid-BDNF Interplay in the Hippocampus.

Early life stress (ELS) is implicated in the etiology of multiple psychiatric disorders. Important biological effects of ELS are manifested in stress-susceptible regions of the hippocampus and are partially mediated by long-term effects on glucocorticoid (GC) and/or neurotrophin signaling pathways. GC-signaling mediates the regulation of stress response to maintain homeostasis, while neurotrophin signaling plays a key role in neuronal outgrowth and is crucial for axonal guidance and synaptic integrity. The neurotrophin and GC-signaling pathways co-exist throughout the central nervous system (CNS), particularly in the hippocampus, which has high expression levels of glucocorticoid-receptors (GR) and mineralocorticoid-receptors (MR) as well as brain-derived neurotrophic factor (BDNF) and its receptor, tropomyosin-related kinase receptor B (TrkB). This review addresses the effects of ELS paradigms on GC- and BDNF-dependent mechanisms and their crosstalk in the hippocampus, including potential implications for the pathogenesis of common stress-related disorders.

Immediate Effects of Maternal Deprivation on the (Re)Activity of the HPA-Axis Differ in CD1 and C57Bl/6J Mouse Pups.

The postnatal development of the mouse is characterized by a period of hypo-responsiveness of the hypothalamic-pituitary-adrenal (HPA) axis to mild stressors. Maternal deprivation (MD) during this period can disrupt the quiescence of the HPA-axis. The present study examined the influence of strain (outbred CD1 vs. inbred C57BL/6J mice) on some central and peripheral components of the HPA-axis in neonatal mice (5-day-old) in the presence of their mother or after 24 h MD (on postnatal day 4) under basal or mild stressful conditions. In the presence of the dam, adrenal corticosterone (CORT) secretion was low in both mouse strains. Compared to CD1 mice, C57BL/6J had lower CORT levels associated with higher ACTH levels and ACTH/CORT ratio (i.e., lower adrenal sensitivity to ACTH), and higher glucocorticoid receptor (GR) mRNA expression in the paraventricular nucleus. Although MD disinhibited the HPA-axis in both strains as reflected by increased basal CORT and ACTH, we found a strain-dependent pattern. MD increased CORT more in C57BL/6J compared to CD1 mice together with a lower ACTH/CORT ratio (i.e., higher adrenal sensitivity to ACTH), while GR mRNA was no longer different in the two strains. However, this increased adrenal sensitivity in maternally deprived C57BL/6J mice was not reflected in their CORT response to a subsequent novelty stressor, possibly due to an MD-induced ceiling effect in their steroidogenic capacity. In conclusion, the immediate outcome of MD depends on the genetic background of the mother-infant dyad, suggesting that maybe also the outcome in later-life cannot be generalized.

Greater resistance to inflammation at adulthood could contribute to extended life span of p66(Shc-/-) mice.

Evidence is mounting that reactive oxygen species (ROS) produced because of stressful challenges could interfere with the proper functioning of the hypothalamic-pituitary-adrenal (HPA) axis, resulting in greater vulnerability to aging and neurodegeneration. Here we tested the hypothesis that p66(Shc-/-) mice, which have been described to have an extended life span and a high resistance to oxidative stress, might be less susceptible to the effects of inflammatory insults at adulthood. Although adrenocortical reactivity in response to bacterial endotoxin (lipopolysaccharide, LPS) did not differ as a function of the genotype, a hyperdrive of the HPA axis was revealed following treatment with a synthetic glucocorticoid agonist. When measuring changes in hippocampal oxidative status following LPS, only wild-type (WT) subjects showed increased levels of F(2)-isoprostanes, an index of lipid peroxidation and free radical formation. At the same time, the neurotrophin brain-derived neurotrophic factor was selectively increased in WT subjects, while levels of prostaglandin E(2) were decreased in the mutants. Overall, the greater resilience to inflammation-induced changes in the p66(Shc-/-) mutants might underlie the better health status and the longevity characterizing these mice.

Zebrafish development and regeneration: new tools for biomedical research.

Basic research in pattern formation is concerned with the generation of phenotypes and tissues. It can therefore lead to new tools for medical research. These include phenotypic screening assays, applications in tissue engineering, as well as general advances in biomedical knowledge. Our aim here is to discuss this emerging field with special reference to tools based on zebrafish developmental biology. We describe phenotypic screening assays being developed in our own and other labs. Our assays involve: (i) systemic or local administration of a test compound or drug to zebrafish in vivo; (ii) the subsequent detection or "readout" of a defined phenotypic change. A positive readout may result from binding of the test compound to a molecular target involved in a developmental pathway. We present preliminary data on assays for compounds that modulate skeletal patterning, bone turnover, immune responses, inflammation and early-life stress. The assays use live zebrafish embryos and larvae as well as adult fish undergoing caudal fin regeneration. We describe proof-of-concept studies on the localised targeting of compounds into regeneration blastemas using microcarriers. Zebrafish are cheaper to maintain than rodents, produce large numbers of transparent eggs, and some zebrafish assays could be scaled-up into medium and high throughput screens. However, advances in automation and imaging are required. Zebrafish cannot replace mammalian models in the drug development pipeline. Nevertheless, they can provide a cost-effective bridge between cell-based assays and mammalian whole-organism models.