Glucocorticoid receptor haploinsufficiency causes hypertension and attenuates hypothalamic-pituitary-adrenal axis and blood pressure adaptions to high-fat diet

Glucocorticoid hormones are critical to respond and adapt to stress. Genetic variations in the glucocorticoid receptor (GR) gene alter hypothalamic-pituitary-adrenal (HPA) axis activity and associate with hypertension and susceptibility to metabolic disease. Here we test the hypothesis that reduced GR density alters blood pressure and glucose and lipid homeostasis and limits adaption to obesogenic diet. Heterozygous GR βgeo/+ mice were generated from embryonic stem (ES) cells with a gene trap integration of a β-galactosidase-neomycin phosphotransferase (βgeo) cassette into the GR gene creating a transcriptionally inactive GR fusion protein. Although GRβgeo/+ mice have 50% less functional GR, they have normal lipid and glucose homeostasis due to compensatory HPA axis activation but are hypertensive due to activation of the renin-angiotensin- aldosterone system (RAAS). When challenged with a high-fat diet, weight gain, adiposity, and glucose intolerance were similarly increased in control and GRβgeo/+ mice, suggesting preserved control of intermediary metabolism and energy balance. However, whereas a high-fat diet caused HPA activation and increased blood pressure in control mice, these adaptions were attenuated or abolished in GRβgeo/+ mice. Thus, reduced GR density balanced by HPA activation leaves glucocorticoid functions unaffected but mineralocorticoid functions increased, causing hypertension. Importantly, reduced GR limits HPA and blood pressure adaptions to obesogenic diet.

The role of the glucocorticoids in developing resilience to stress and addiction

There is emerging evidence that individuals have the capacity to learn to be resilient by developing protective mechanisms that prevent them from the maladaptive effects of stress that can contribute to addiction.The emerging field of the neuroscience of resilience is beginning to uncover the circuits and molecules that protect against stress-related neuropsychiatric diseases, such as addiction. Glucocorticoids (GCs) are important regulators of basal and stress-related homeostasis in all higher organisms and influence a wide array of genes in almost every organ and tissue. GCs, therefore, are ideally situated to either promote or prevent adaptation to stress. In this review, we will focus on the role of GCs in the hypothalamic-pituitary adrenocortical axis and extra-hypothalamic regions in regulating basal and chronic stress responses. GCs interact with a large number of neurotransmitter and neuropeptide systems that are associated with the development of addiction. Additionally, the review will focus on the orexinergic and cholinergic pathways and highlight their role in stress and addiction. GCs play a key role in promoting the development of resilience or susceptibility and represent important pharmacotherapeutic targets that can reduce the impact of a maladapted stress system for the treatment of stress-induced addiction.

Mice behaviorally selected for high Pavlovian fear memory exhibit fear generalization, HPA-axis alterations and increased basal activity in cortico-limbic circuits

Biological factors underlying individual variability in fearfulness and anxiety have important implications for stress-related psychiatric illness including PTSD and major depression. Using an advanced intercross line (AIL) derived from C57BL/6 and DBA/2J mouse strains and behavioral selection over 3 generations, we established two lines exhibiting High or Low fear behavior after fear conditioning. Across the selection generations, the two lines showed clear differences in training and tests for contextual and conditioned fear. Before fear conditioning training, there were no differences between lines in baseline freezing to a novel context. However, after fear conditioning High line mice demonstrated pronounced freezing in a new context suggestive of poor context discrimination. Fear generalization was not restricted to contextual fear. High fear mice froze to a novel acoustic stimulus while freezing in the Low line did not increase over baseline. Enhanced fear learning and generalization are consistent with transgenic and pharmacological disruption of the hypothalamic-pituitary-adrenal axis (HPA-axis) (Brinks, 2009, Thompson, 2004, Kaouane, 2012). To determine whether there were differences in HPA-axis regulation between the lines, morning urine samples were collected to measure basal corticosterone. Levels of secreted corticosterone in the circadian trough were analyzed by corticosterone ELISA. High fear mice were found to have higher basal corticosterone levels than low line animals. Examination of hormonal stress response components by qPCR revealed increased expression of CRH mRNA and decreased mRNA for MR and CRHR1 in hypothalamus of high fear mice. These alterations may contribute to both the behavioral phenotype and higher basal corticosterone in High fear mice. To determine basal brain activity in vivo in High and Low fear mice we used manganese-enhanced magnetic resonance imaging (MEMRI). Analysis revealed a pattern of basal brain activity made up of amygdala, cortical and hippocampal circuits that was elevated in the High line. Ongoing studies also seek to determine the relative balance of excitatory and inhibitory tone in the amygdala and hippocampus and the neuronal structure of its neurons. While these heterogeneous lines are selected on fear memory expression, HPA-axis alterations and differences in hippocampal activity segregate with the behavioral phenotypes. These differences are detectable in a basal state strongly suggesting these are biological traits underlying the behavioral phenotype (Johnson et al, 2011).

The relationship between stress, HPA axis functioning and brain structure in first episode psychosis over the first 12 weeks of treatment

Stress and abnormal hypothalamic-pituitary-adrenal axis functioning have been implicated in the early phase of psychosis and may partly explain reported changes in brain structure. This study used magnetic resonance imaging to investigate whether biological measures of stress were related to brain structure at baseline and to structural changes over the first 12 weeks of treatment in first episode patients (n=22) compared with matched healthy controls (n=22). At baseline, no significant group differences in biological measures of stress, cortical thickness or hippocampal volume were observed, but a significantly stronger relationship between baseline levels of cortisol and smaller white matter volumes of the cuneus and anterior cingulate was found in patients compared with controls. Over the first 12 weeks of treatment, patients showed a significant reduction in thickness of the posterior cingulate compared with controls. Patients also showed a significant positive relationship between baseline cortisol and increases in hippocampal volume over time, suggestive of brain swelling in association with psychotic exacerbation, while no such relationship was observed in controls. The current findings provide some support for the involvement of stress mechanisms in the pathophysiology of early psychosis, but the changes are subtle and warrant further investigation.

Pituitary volume in teenagers with first-presentation borderline personality disorder

This study used magnetic resonance imaging to examine pituitary gland volume (PGV) in teenage patients with a first presentation of borderline personality disorder (BPD). No difference in PGV was observed between healthy controls (n=20) and the total BPD cohort (n=20). However, within the BPD cohort, those exposed to childhood trauma (n=9) tended to have smaller pituitaries (-18%) than those with no history of childhood trauma (n=10). These preliminary findings suggest that exposure to childhood trauma, rather than BPD, per se, might be associated with reduced PGV, possibly reflecting hypothalamic-pituitary-adrenal axis dysfunction.

Pituitary volume predicts future transition to psychosis in individuals at ultra-high risk of developing psychosis

Background We examined pituitary volume before the onset of psychosis in subjects who were at ultra-high risk (UHR) for developing psychosis. Methods Pituitary volume was measured on 1.5-mm, coronal, 1.5-T magnetic resonance images in 94 UHR subjects recruited from admissions to the Personal Assessment and Crisis Evaluation Clinic in Melbourne, Australia and in 49 healthy control subjects. The UHR subjects were scanned at baseline and were followed clinically for a minimum of 1 year to detect transition to psychosis. Results Within the UHR group, a larger baseline pituitary volume was a significant predictor of future transition to psychosis. The UHR subjects who later went on to develop psychosis (UHR-P, n = 31) had a significantly larger (+12%; p = .001) baseline pituitary volume compared with UHR subjects who did not go on to develop psychosis (UHR-NP, n = 63). The survival analysis conducted by Cox regression showed that the risk of developing psychosis during the follow-up increased by 20% for every 10% increase in baseline pituitary volume (p = .002). Baseline pituitary volume of the UHR-NP subjects was smaller not only compared with UHR-P (as described above) but also compared with control subjects (−6%; p = .032). Conclusions The phase before the onset of psychosis is associated with a larger pituitary volume, suggesting activation of the HPA axis.

Mifepristone in the central nucleus of the amygdala reduces yohimbine stress-induced reinstatement of ethanol-seeking

Chronic ethanol exposure leads to dysregulation of the hypothalamic-pituitary-adrenal axis, leading to changes in glucocorticoid release and function that have been proposed to maintain pathological alcohol consumption and increase vulnerability to relapse during abstinence. The objective of this study was to determine whether mifepristone, a glucocorticoid receptor antagonist, plays a role in ethanol self-administration and reinstatement. Male, Long-Evans rats were trained to self-administer either ethanol or sucrose in daily 30 min operant self-administration sessions using a fixed ratio 3 schedule of reinforcement. Following establishment of stable baseline responding, we examined the effects of mifepristone on maintained responding and yohimbine-induced increases in responding for ethanol and sucrose. Lever responding was extinguished in separate groups of rats and animals were tested for yohimbine-induced reinstatement and corticosterone release. We also investigated the effects of local mifepristone infusions into the central amygdala (CeA) on yohimbine-induced reinstatement of ethanol- and sucrose-seeking. In addition, we infused mifepristone into the basolateral amygdala (BLA) in ethanol-seeking animals as an anatomical control. We show that both systemic and intra-CeA (but not BLA) mifepristone administration suppressed yohimbine-induced reinstatement of ethanol-seeking, while only systemic injections attenuated sucrose-seeking. In contrast, baseline consumption, yohimbine-induced increases in responding, and circulating CORT levels were unaffected. The data indicate that the CeA plays an important role in the effects of mifepristone on yohimbine-induced reinstatement of ethanol-seeking. Mifepristone may be a valuable pharmacotherapeutic strategy for preventing relapse to alcohol use disorders and, as it is FDA approved, may be a candidate for clinical trials in the near future.

Antidepressants, but not antipsychotics, modulate GR function in human whole blood: An insight into molecular mechanisms

Clinical studies have demonstrated an impairment of glucocorticoid receptor (GR)-mediated negative feedback on the hypothalamic-pituitary-adrenal (HPA) axis in patients with major depression (GR resistance), and its resolution by antidepressant treatment. Recently, we showed that this impairment is indeed due to a dysfunction of GR in depressed patients (Carvalho et al., 2009), and that the ability of the antidepressant clomipramine to decrease GR function in peripheral blood cells is impaired in patients with major depression who are clinically resistant to treatment (Carvalho et al. 2008). To further investigate the effect of antidepressants on GR function in humans, we have compared the effect of the antidepressants clomipramine, amytriptiline, sertraline, paroxetine and venlafaxine, and of the antipsychotics, haloperidol and risperidone, on GR function in peripheral blood cells from healthy volunteers (n=33). GR function was measured by glucocorticoid inhibition of lypopolysaccharide (LPS)-stimulated interleukin-6 (IL-6) levels. Compared to vehicle-treated cells, all antidepressants inhibited dexamethasone (DEX, 10-100nM) inhibition of LPS-stimulated IL-6 levels (p values ranging from 0.007 to 0.1). This effect was specific to antidepressants, as antipsychotics had no effect on DEX-inhibition of LPS-stimulated IL-6 levels. The phosphodiesterase (PDE) type 4 inhibitor, rolipram, potentiated the effect of antidepressants on GR function, while the GR antagonist, RU-486, inhibited the effect of antidepressants on GR function. These findings indicate that the effect of antidepressants on GR function are specific for this class of psychotropic drugs, and involve second messenger pathways relevant to GR function and inflammation. Furthermore, it also points towards a possible mechanism by which one maybe able to overcome treatment-resistant depression. Research in this field will lead to new insights into the pathophysiology and treatment of affective disorders.

The effect of atypical antipsychotics on pituitary gland volume in patients with first-episode psychosis: A longitudinal MRI study

BACKGROUND: Pituitary volume is currently measured as a marker of hypothalamic-pituitary-adrenal hyperactivity in patients with psychosis despite suggestions of susceptibility to antipsychotics. Qualifying and quantifying the effect of atypical antipsychotics on the volume of the pituitary gland will determine whether this measure is valid as a future estimate of HPA-axis activation in psychotic populations. AIMS: To determine the qualitative and quantitative effect of atypical antipsychotic medications on pituitary gland volume in a first-episode psychosis population. METHOD: Pituitary volume was measured from T1-weighted magnetic resonance images in a group of 43 first-episode psychosis patients, the majority of whom were neuroleptic-naive, at baseline and after 3months of treatment, to determine whether change in pituitary volume was correlated with cumulative dose of atypical antipsychotic medication. RESULTS: There was no significant baseline difference in pituitary volume between subjects and controls, or between neuroleptic-naive and neuroleptic-treated subjects. Over the follow-up period there was a negative correlation between percentage change in pituitary volume and cumulative 3-month dose of atypical antipsychotic (r=-0.37), i.e. volume increases were associated with lower doses and volume decreases with higher doses. CONCLUSIONS: Atypical antipsychotic medications may reduce pituitary gland volume in a dose-dependent manner suggesting that atypical antipsychotic medication may support affected individuals to cope with stress associated with emerging psychotic disorders.

Pituitary volume and early treatment response in drug-naïve first-episode psychosis patients

BACKGROUND: An early response to antipsychotic treatment in patients with psychosis has been associated with a better course and outcome. However, factors that predict treatment response are not well understood. The onset of schizophrenia and related disorders has been associated with increased levels of stress and hyper-activation of the hypothalamic-pituitary-adrenal (HPA) axis. This study examined whether pituitary volume at the onset of psychosis may be a potential predictor of early treatment response in first-episode psychosis (FEP) patients. METHODS: We investigated the relationship between baseline pituitary volume and symptomatic treatment response over 12 weeks using mixed model analysis in a sample of 42 drug-naïve or early treated FEP patients who participated in a controlled dose-finding study of quetiapine fumarate. Logistic regression was used to examine predictors of treatment response. Pituitary volume was measured from magnetic resonance imaging scans that were obtained upon entry into the trial. RESULTS: Larger pituitary volume was associated with less improvement in overall psychotic symptoms (Brief Psychiatric Rating Scale (BPRS) P=0.031) and positive symptoms (BPRS positive symptom subscale P=0.010). Regardless of gender, patients with a pituitary volume at the 25th percentile (413 mm(3)) were approximately three times more likely to respond to treatment by week 12 than those at the 75th percentile (635 mm(3)) (odds ratio=3.07, CI: 0.90-10.48). CONCLUSION: The association of baseline pituitary volumes with early treatment response highlights the importance of the HPA axis in emerging psychosis. Potential implications for treatment strategies in early psychosis are discussed.

An MRI study of pituitary volume and parasuicidal behavior in teenagers with first-presentation borderline personality disorder

This structural magnetic resonance imaging study examined the relationship between pituitary gland volume (PGV) and lifetime number of parasuicidal behaviors in a first-presentation, teenage borderline personality disorder (BPD) sample with minimal exposure to treatment. Hierarchical regression analysis revealed that age and number of parasuicidal behaviors were significant predictors of PGV. These findings indicate that parasuicidal behavior in BPD might be associated with greater activation of the hypothalamic-pituitary-adrenal (HPA) axis. Further studies are required using direct neuroendocrine measures and exploring other parameters of self-injurious behavior, such as recency of self-injurious behavior, intent to die and medical threat.

Stress, the hippocampus and the HPA axis: Implications for the development of psychotic disorders

The experience of stress is commonly implicated in models of the onset of psychotic disorders. However, prospective studies investigating associations between biological markers of stress and the emergence of psychotic disorders are limited and inconclusive. One biological system proposed as the link between the psychological experience of stress and the development of psychosis is the Hypothalamic-Pituitary-Adrenal (HPA) axis. This paper summarizes and discusses evidence supporting a role for HPA-axis dysfunction in the early phase of schizophrenia and related disorders. METHOD A selective review of psychiatric and psychological research on stress, coping, HPA-axis, the hippocampus and psychotic disorders was performed, with a particular focus on the relationship between HPA-axis dysfunction and the onset of psychotic disorders. RESULTS Individual strands of past research have suggested that the HPA-axis is dysfunctional in at least some individuals with established psychotic disorders; that the hippocampus is an area of the brain that appears to be implicated in the onset and maintenance of psychotic disorders; and that an increase in the experience of stress precedes the onset of a psychotic episode in some individuals. Models of the onset and maintenance of psychotic disorders that link these individual strands of research and strategies for examining these models are proposed in this paper. CONCLUSIONS The current literature provides some evidence that the onset of psychotic disorders may be associated with a higher rate of stress and changes to the hippocampus. It is suggested that future research should investigate whether a relationship exists between psychological stress, HPA-axis functioning and the hippocampus in the onset of these disorders. Longitudinal assessment of these factors in young people at 'ultra' high risk of psychosis and first-episode psychosis cohorts may enhance understanding of the possible interaction between them in the early phases of illness.