Hypophysitis: Defining Histopathologic Variants and a Review of Emerging Clinical Causative Entities

Inflammatory disease of the pituitary gland is known as hypophysitis. There are multiple histological subtypes, the most common being lymphocytic, and the pathogenesis is variable and diverse. Hypophysitis can be primary and idiopathic or autoimmune related, or secondary to local lesions, systemic disease, medications, and more. Although hypophysitis was previously accepted as an exceedingly rare diagnosis, a greater understanding of the disease process and new insights into possible etiologic sources have contributed to an increased frequency of recognition. This review provides an overview of hypophysitis, its causes, and detection strategies and management.

Atypical pituitary hormone-target tissue axis

A long-held belief is that pituitary hormones bind to their cognate receptors in classical target glands to actuate their manifold functions. However, a number of studies have shown that multiple types of pituitary hormone receptors are widely expressed in non-classical target organs. Each pituitary gland-derived hormone exhibits a wide range of nonconventional biological effects in these non-classical target organs. Herein, the extra biological functions of pituitary hormones, thyroid-stimulating hormone, follicle-stimulating hormone, luteinizing hormone, adrenocorticotrophic hormone, and prolactin when they act on non-classical organs were summarized, defined by the novel concept of an "atypical pituitary hormone-target tissue axis." This novel proposal explains the pathomechanisms of abnormal glucose and lipid metabolism, obesity, hypertension, fatty liver, and atherosclerosis while offering a more comprehensive and systematic insights into the coordinated regulation of environmental factors, genetic factors, and neuroendocrine hormones on human biological functions. The continued exploration of the physiology of the "atypical pituitary hormone-target tissue axis" could enable the identification of novel therapeutic targets for metabolic diseases.

Treatment of Cushing Disease With Pituitary-Targeting Seliciclib

CONTEXT

Preclinical studies show seliciclib (R-roscovitine) suppresses neoplastic corticotroph proliferation and pituitary adrenocorticotrophic hormone (ACTH) production.

OBJECTIVE

To evaluate seliciclib as an effective pituitary-targeting treatment for patients with Cushing disease (CD).

METHODS

Two prospective, open-label, phase 2 trials, conducted at a tertiary referral pituitary center, included adult patients with de novo, persistent, or recurrent CD who received oral seliciclib 400 mg twice daily for 4 consecutive days each week for 4 weeks. The primary endpoint in the proof-of-concept single-center study was normalization of 24-hour urinary free cortisol (UFC; ≤ 50 µg/24 hours) at study end; in the pilot multicenter study, primary endpoint was UFC normalization or ≥ 50% reduction in UFC from baseline to study end.

RESULTS

Sixteen patients were consented and 9 were treated. Mean UFC decreased by 42%, from 226.4 ± 140.3 µg/24 hours at baseline to 131.3 ± 114.3 µg/24 hours by study end. Longitudinal model showed significant UFC reductions from baseline to each treatment week. Three patients achieved ≥ 50% UFC reduction (range, 55%-75%), and 2 patients exhibited 48% reduction; none achieved UFC normalization. Plasma ACTH decreased by 19% (P = 0.01) in patients who achieved ≥ 48% UFC reduction. Three patients developed grade ≤ 2 elevated liver enzymes, anemia, and/or elevated creatinine, which resolved with dose interruption/reduction. Two patients developed grade 4 liver-related serious adverse events that resolved within 4 weeks of seliciclib discontinuation.

CONCLUSION

Seliciclib may directly target pituitary corticotrophs in CD and reverse hypercortisolism. Potential liver toxicity of seliciclib resolves with treatment withdrawal. The lowest effective dose requires further determination.

Brain and pituitary-adrenal lesions of Trypanosoma brucei brucei and Trypanosoma congolense infections in the West African Dwarf rams: Is trypanotolerance overrated?

Trypanosomosis of the West African Dwarf (WAD) sheep is often neglected due to emphasis on trypanotolerance. Nevertheless, significant pathological changes may occur in tissues of infected WAD sheep. The purpose of this study was to evaluate the brain, pituitary, and adrenal lesions of Trypanosoma brucei brucei (Tbb) and Trypanosoma congolense (Tc) infections in WAD rams. Fifteen WAD rams were infected intraperitoneally with Tbb or Tc (10⁶ trypanosomes/animal) or were uninfected controls (5 rams per group). Adrenocorticotrophic hormone (ACTH) and cortisol were assayed in serum by enzyme immunoassay technique. The brain, pituitary, and adrenal glands were processed for histopathology. Serum ACTH levels of infected rams were significantly (P < .05) higher than that of controls on days 14 and 70 post infection (PI). Serum cortisol levels of infected rams were significantly (P < .05) higher than that of controls only on day 14 PI. Mortality was 60% in Tbb- and 40% in Tc-infected rams. The brain of the infected groups showed chromatolysis of cortical neurons and Purkinje cells with severe encephalitis. Degenerative, necrotic, and inflammatory changes were seen in the pituitary and adrenal glands of the infected rams. Adrenal corticomedullary ratio was significantly (P < .05) higher in Tc-infected rams than controls. Based on the high mortality levels, likely due to severe encephalitis, the WAD sheep may not be regarded as trypanotolerant.

The Effects of At-Birth Adoption on Atypical Behavior and Anxiety: A Nonhuman Primate Model

OBJECTIVE

Adopted children tend to show an increased risk for a variety of psychopathological outcomes, even when adoption occurs at birth, which some suggest is a result of nonrandom assignment of adoptees and parents. This study uses a nonhuman primate model, in which adoptions were randomly assigned, to investigate the behavioral and physiological outcomes associated with at-birth adoption.

METHOD

Immediately following birth, rhesus monkey infants were randomly assigned to be reared by either their biological mother (n = 113) or by an unrelated, lactating, adoptive mother (n = 34). At 6 months of age, infant behavior and physiology were assessed during a stressful series of mother-infant separations. Four years later, stress-related behaviors were measured following confrontation by an unfamiliar intruder, an ecologically meaningful stressor.

RESULTS

When compared to infants reared by their biological mothers, adopted infants exhibited more behavioral withdrawal and higher plasma adrenocorticotropic hormone (ACTH) concentrations in response to separation. These behavioral differences persisted 4 years later during a stressful intruder challenge, with adoptees exhibiting more behavioral withdrawal, stereotypies, and impulsive approaches of the potentially aggressive intruder.

CONCLUSION

Compared to infants reared by their biological mothers, adopted infants exhibited more behavioral inhibition, impulsivity, and higher ACTH concentrations, even when subjects were randomly assigned to be adopted or to remain with their biological mother. To the extent that these findings generalize to humans, they suggest that the overall risk for psychopathology in adopted individuals persists even after random assignment to adoption conditions.

Expression of Rasd1 in mouse endocrine pituitary cells and its response to dexamethasone

Dexamethasone-induced Ras-related protein 1 (Rasd1) is a member of the Ras superfamily of monomeric G proteins that have a regulatory function in signal transduction. Rasd1, also known as Dexras1 or AGS1, is rapidly induced by dexamethasone (Dex). While prior data indicates that Rasd1 is highly expressed in the pituitary and that the gene may function in regulation of corticotroph activity, its exact cellular localization in this tissue has not been delineated. Nor has it been determined which endocrine pituitary cell type(s) are responsive to Dex-induced expression of Rasd1. We hypothesized that Rasd1 is primarily localized in corticotrophs and furthermore, that its expression in these cells would be upregulated in response to exogenous Dex administration. Rasd1 expression in each pituitary cell type both under basal conditions and 1-hour post Dex treatment were examined in adult male mice. While a proportion of all endocrine pituitary cell types expressed Rasd1, a majority of corticotrophs and thyrotrophs expressed Rasd1 under basal condition. In vehicle treated animals, approximately 50-60% of corticotrophs and thyrotrophs cells expressed Rasd1 while the gene was detected in only 15-30% of lactotrophs, somatotrophs, and gonadotrophs. In Dex treated animals, Rasd1 expression was significantly increased in corticotrophs, somatotrophs, lactotrophs, and gonadotrophs but not thyrotrophs. In Dex treated animals, Rasd1 was detected in 80-95% of gonadotrophs and corticotrophs. In contrast, Dex treatment increased Rasd1 expression to a lesser extent (55-60%) in somatotrophs and lactotrophs. Corticotrophs of the pars intermedia, which lack glucocorticoid receptors, failed to display increased Rasd1 expression in Dex treated animals. Rasd1 is highly expressed in corticotrophs under basal conditions and is further increased after Dex treatment, further supporting its role in glucocorticoid negative feedback. In addition, the presence and Dex-induced expression of Rasd1 in endocrine pituitary cell types, other than corticotrophs, may implicate Rasd1 in novel pituitary functions.

Physiological Correlation between Hypothalamic-Pituitary-Adrenal Axis, Leptin, UCP1 and Lipid Panel in Mares during Late Pregnancy and Early Postpartum Period

This study aimed to investigate the dynamic change of adrenocorticotrophic hormone (ACTH), cortisol, leptin, mitochondrial uncoupling protein 1 (UCP1), lipids and lipoproteins in mares during late pregnancy and the postpartum period. A total of 20 mares (10 pregnant mares, monitored from 14 ± 2 days before expected foaling until 14 days after foaling, Group A; 10 non-pregnant and non-lactating mares, Group B) were enrolled in the study. Body Condition Score (BCS) and body weight (BW) values were recorded from each animal. In Group A, blood samples were collected on days 14 ± 2 and 7 ± 2 before foaling (T_-14; T_-7), and on days 7 and 14 after foaling (T₊₇; T₊₁₄). From mares of Group B, blood samples were collected at the beginning of the study. The levels of ACTH, cortisol, leptin, UCP1, non-esterified fatty acids (NEFAs), total cholesterol, high-density lipoproteins (HDLs), low-density lipoproteins (LDLs), triglycerides and very-low-density lipoproteins (VLDLs) were investigated. While BCS showed no statistical change throughout the monitoring period (p > 0.05), all the other studied parameters displayed statistically significant variations in Group A over the peripartum period (p < 0.0001). A significant effect of pregnancy was found on all studied parameters (p < 0.001). The ACTH and cortisol levels measured in mares belonged to Group A showed a significant positive correlation with the values of leptin, LDLs, triglycerides and VLDLs, whereas they were negatively correlated with the serum UCP1 and NEFAs values. Together, the findings gathered in this study highlight a dynamic change of serum leptin, UCP1 and lipid parameters in peripartum mares and suggest an interaction of the HPA axis with lipid metabolism and mobilization in mares during the peripartum period in order to deal with metabolic and energy demand and maintain energy homeostasis.

A New Clinical Model to Estimate the Pre-Test Probability of Cushing's Syndrome: The Cushing Score

BACKGROUND

Hypercortisolism accounts for relevant morbidity and mortality and is often a diagnostic challenge for clinicians. A prompt diagnosis is necessary to treat Cushing's syndrome as early as possible.

OBJECTIVE

The aim of this study was to develop and validate a clinical model for the estimation of pre-test probability of hypercortisolism in an at-risk population.

DESIGN

We conducted a retrospective multicenter case-control study, involving five Italian referral centers for Endocrinology (Turin, Messina, Naples, Padua and Rome). One hundred and fifty patients affected by Cushing's syndrome and 300 patients in which hypercortisolism was excluded were enrolled. All patients were evaluated, according to current guidelines, for the suspicion of hypercortisolism.

RESULTS

The Cushing score was built by multivariable logistic regression, considering all main features associated with a clinical suspicion of hypercortisolism as possible predictors. A stepwise backward selection algorithm was used (final model AUC=0.873), then an internal validation was performed through ten-fold cross-validation. Final estimation of the model performance showed an average AUC=0.841, thus reassuring about a small overfitting effect. The retrieved score was structured on a 17.5-point scale: low-risk class (score value: ≤5.5, probability of disease=0.8%); intermediate-low-risk class (score value: 6-8.5, probability of disease=2.7%); intermediate-high-risk class (score value: 9-11.5, probability of disease=18.5%) and finally, high-risk class (score value: ≥12, probability of disease=72.5%).

CONCLUSIONS

We developed and internally validated a simple tool to determine pre-test probability of hypercortisolism, the Cushing score, that showed a remarkable predictive power for the discrimination between subjects with and without a final diagnosis of Cushing's syndrome.

The Mechanisms Underlying Autonomous Adrenocorticotropic Hormone Secretion in Cushing's Disease

Cushing’s disease caused due to adrenocorticotropic hormone (ACTH)-secreting pituitary adenomas (ACTHomas) leads to hypercortisolemia, resulting in increased morbidity and mortality. Autonomous ACTH secretion is attributed to the impaired glucocorticoid negative feedback (glucocorticoid resistance) response. Interestingly, other conditions, such as ectopic ACTH syndrome (EAS) and non-neoplastic hypercortisolemia (NNH, also known as pseudo-Cushing’s syndrome) also exhibit glucocorticoid resistance. Therefore, to differentiate between these conditions, several dynamic tests, including those with desmopressin (DDAVP), corticotrophin-releasing hormone (CRH), and Dex/CRH have been developed. In normal pituitary corticotrophs, ACTH synthesis and secretion are regulated mainly by CRH and glucocorticoids, which are the ACTH secretion-stimulating and -suppressing factors, respectively. These factors regulate ACTH synthesis and secretion through genomic and non-genomic mechanisms. Conversely, glucocorticoid negative feedback is impaired in ACTHomas, which could be due to the overexpression of 11β-HSD2, HSP90, or TR4, or loss of expression of CABLES1 or nuclear BRG1 proteins. Genetic analysis has indicated the involvement of several genes in the etiology of ACTHomas, including USP8, USP48, BRAF, and TP53. However, the association between glucocorticoid resistance and these genes remains unclear. Here, we review the clinical aspects and molecular mechanisms of ACTHomas and compare them to those of other related conditions.

Gamma Knife radiosurgery for the treatment of Nelson's syndrome: a multicenter, international study

OBJECTIVE

Nelson's syndrome is a rare and challenging neuroendocrine disorder, and it is associated with elevated adrenocorticotrophic hormone (ACTH) level, skin hyperpigmentation, and pituitary adenoma growth. Management options including resection and medical therapy are traditional approaches. Ionizing radiation in the form of Gamma Knife radiosurgery (GKRS) is also being utilized to treat Nelson's syndrome. In the current study the authors sought to better define the therapeutic role of stereotactic radiosurgery (SRS) in Nelson's syndrome.

METHODS

Study patients with Nelson's syndrome were treated with single-fraction GKRS (median margin dose of 25 Gy) at 6 different centers as part of an International Radiosurgery Research Foundation (IRRF) investigation. Data including neurological function, endocrine response, and radiological tumor response were collected and sent to the study-coordinating center for review. Fifty-one patients with median endocrine and radiological follow-ups of 91 and 80.5 months from GKRS, respectively, were analyzed for endocrine remission, tumor control, and neurological outcome. Statistical methods were used to identify prognostic factors for these endpoints.

RESULTS

At last follow-up, radiological tumor control was achieved in 92.15% of patients. Endocrine remission off medical management and reduction in pre-SRS ACTH level were achieved in 29.4% and 62.7% of patients, respectively. Improved remission rates were associated with a shorter time interval between resection and GKRS (p = 0.039). Hypopituitarism was seen in 21.6% and new visual deficits were demonstrated in 15.7% of patients.

CONCLUSIONS

GKRS affords a high rate of pituitary adenoma control and improvement in ACTH level for the majority of Nelson's syndrome patients. Hypopituitarism is the most common adverse effect from GKRS in Nelson's syndrome patients and warrants longitudinal follow-up for detection and endocrine replacement.

Electroacupuncture regulates the stress-injury-repair chain of events after cerebral ischemia/reperfusion injury

Inflammation after stroke is the main cause of cerebral ischemia/reperfusion injury. Cascading events after injury can lead to cell death. Heat shock protein 70 and other endogenous injury-signaling molecules are released by damaged cells, which can lead to systemic stress reactions. Protecting the brain through repair begins with the stress-injury-repair signaling chain. This study aimed to verify whether acupuncture acts through this chain to facilitate effective treatment of ischemic stroke. Rat models of cerebral ischemia/reperfusion injury were established by Zea Longa's method, and injury sites were identified by assessing neurological function, 2,3,5-triphenyltetrazolium chloride staining, and hematoxylin-eosin staining. Electroacupuncture at acupoints Baihui (DU20) and Zusanli (ST36) was performed in the model rats with dilatational waves, delivered for 20 minutes a day at 2–100 Hz and an amplitude of 2 mA. We analyzed the blood serum from the rats and found that inflammatory cytokines affected the levels of adrenotrophin and heat shock protein 70, each of which followed a similar bimodal curve. Specifically, electroacupuncture lowered the peak levels of adrenocorticotrophic hormone and heat shock protein 70. Thus, electroacupuncture was able to inhibit excessive stress, reduce inflammation, and promote the repair of neurons, which facilitated healing of ischemic stroke.

Clinical experience with repository corticotropin injection in patients with multiple sclerosis experiencing mood changes with intravenous methylprednisolone: a case series

The elevated prevalence of neuropsychiatric symptoms and disorders among patients with multiple sclerosis (MS) is well recognized, as are potential neuropsychiatric side effects of treatment with corticosteroids. Both methylprednisolone (MP) and repository corticotropin injection (HP Acthar(®) gel) have demonstrated efficacy in reducing short-term disability after exacerbations of MS. Although historical data are limited, repository corticotropin injection has not generally been associated with detrimental neuropsychiatric effects. We describe six cases of patients with relapsing-remitting MS who had previously experienced detrimental mood changes with MP treatment. Some of these patients had previous histories of mood disorders or other neuropsychiatric symptoms prior to MS diagnosis. All six patients were subsequently treated with repository corticotropin injection for MS exacerbations and each demonstrated improvements in MS symptoms. This clinical experience suggests that repository corticotropin injection should be considered as an alternative for patients who do not tolerate corticosteroids or have difficulties associated with intravenous medication. Furthermore, the rate of neuropsychiatric side effects observed in these patients was low. These observations support repository corticotropin injection as a viable alternative for the treatment of acute exacerbations of MS, particularly in patients who have a history of neuropsychiatric disorders or symptoms either independently or in response to MP treatment. In reviewing both the published data and our own clinical experience regarding potential neuropsychiatric adverse events with treatment for MS exacerbations, we hope to stimulate further research into the potential efficacy and safety of repository corticotropin injection among patients with some form of neuropsychiatric complications that must be considered when establishing a treatment plan for MS.

A review of the re-emergence of adrenocorticotrophic hormone therapy in glomerular disease, more than a drug of last resort?

There has been a re-emergence of interest in adrenocorticotropic hormone (ACTH) in patients with resistant nephrotic syndrome. We describe a patient with severe nephrosis and advanced chronic kidney disease with idiopathic membranous nephropathy resistant to conventional immunosuppressive therapies that achieved lasting remission with ACTH therapy. We explore the literature showing the extra renoprotective effects which might explain the response of proteinuric renal diseases to this treatment.

The effects of sample handling and N-phenylmaleimide on concentration of adrenocorticotrophic hormone in equine plasma

REASONS FOR PERFORMING STUDY

Previous reports suggest that adrenocorticotrophic hormone (ACTH) degrades rapidly, limiting its use as a diagnostic test.

OBJECTIVES

This study quantified effects of processing delays on ACTH concentrations and investigated the addition of N-phenylmaleimide (maleimide), a protease inhibitor, as a means of reducing ACTH degradation.

STUDY DESIGN

Experimental study.

METHODS

Venous blood was collected from 8 healthy horses and 8 horses with pituitary pars intermedia dysfunction (PPID) with a range of ACTH concentrations. Baseline ACTH concentrations were established immediately using a chemiluminescent assay. Plasma samples were then: 1) centrifuged immediately, 2) centrifuged immediately with the addition of maleimide, or 3) allowed to separate by gravity followed by the addition of maleimide, before all samples were stored at 22°C and analysed at 4, 8, 24 and 48 h post collection. A linear mixed effects model and Bland-Altman analyses were performed. Significance was set at P < 0.05.

RESULTS

No significant effect of plasma treatment (P = 0.1) on change in ACTH concentration was identified. However, significant effects of horse health status (P < 0.001) and time (P < 0.001) on change in ACTH concentration were identified. No significant interactions were found. Significant decreases in ACTH concentration occurred in horses with PPID between 4 and 8 h after blood collection. In non-PPID horses, the decrease in ACTH concentration over time was not significant. Agreement with baseline values decreased over time and was greater for non-PPID horses than for PPID horses.

CONCLUSIONS

Clinically useful results are still obtained if ACTH concentration is measured up to 48 h after sample collection. Allowing samples to separate by gravity rather than centrifugation did not have a significant effect on ACTH concentration, and the addition of maleimide was of no benefit.

Role of paraventricular nucleus-projecting norepinephrine/epinephrine neurons in acute and chronic stress

Chronic variable stress (CVS) exposure modifies the paraventricular nucleus of the hypothalamus (PVN) in a manner consistent with enhanced central drive of the hypothalamo-pituitary-adrenocortical (HPA) axis. As previous reports suggest that post-stress enhancement of norepinephrine (NE) action contributes to chronic stress regulation at the level of the PVN, we hypothesised that PVN-projecting NE neurons were necessary for the stress facilitatory effects of CVS. Following intra-PVN injection of saporin toxin conjugated to a dopamine beta-hydroxylase (DBH) antibody (DSAP), in rats PVN DBH immunoreactivity was almost completely eliminated, but immunoreactive afferents to other key regions involved in stress integration were spared (e.g. DBH fiber densities were unaffected in the central nucleus of the amygdala). Reductions in DBH-positive fiber density were associated with reduced numbers of DBH-immunoreactive neurons in the nucleus of the solitary tract and locus coeruleus. Following 2 weeks of CVS, DSAP injection did not alter stress-induced adrenal hypertrophy or attenuation of body weight gain, indicating that PVN-projecting NE [and epinephrine (E)] neurons are not essential for these physiological effects of chronic stress. In response to acute restraint stress, PVN-targeted DSAP injection attenuated peak adrenocorticotrophic hormone (ACTH) and corticosterone in controls, but only attenuated peak ACTH in CVS animals, suggesting that enhanced adrenal sensitivity compensated for reduced excitatory drive of the PVN. Our data suggest that PVN-projecting NE/E neurons contribute to the generation of acute stress responses, and are required for HPA axis drive (ACTH release) during chronic stress. However, loss of NE/E drive at the PVN appears to be buffered by compensation at the level of the adrenal.

Psychological reactivity to laboratory stress is associated with hormonal responses in postmenopausal women

OBJECTIVE

The present study examined associations between psychological reactivity and hormonal responses to a standardized laboratory stressor (Trier Social Stress Test, TSST) in postmenopausal women.

METHODS

Postmenopausal women aged 50-74 years undertook anxiety and mood assessments prior to and following the TSST. Blood samples were drawn at multiple timepoints for assessment of cortisol, adrenocorticotrophic hormone (ACTH) and dehydroepiandrosterone (DHEA).

RESULTS

Forty postmenopausal women completed the assessments. As expected, significant increases in anxiety and negative affect and decreases in positive affect were observed after the TSST; however, the magnitude of change in anxiety and mood varied considerably across individuals. Analyses indicated that greater increases in anxiety and negative affect after the TSST were associated with higher levels of cortisol, ACTH and DHEA after controlling for race, age, body mass index and smoking status. Changes in positive affect were not associated with cortisol, ACTH or DHEA.

CONCLUSIONS

These findings suggest that enhanced reactivity to stress is associated with higher hormone levels among postmenopausal women, which could have potential implications for health.

Endogenous opiates and behavior: 2012

This paper is the thirty-fifth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2012 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration and thermoregulation (Section 16); and immunological responses (Section 17).

Stress and neurodevelopmental processes in the emergence of psychosis

The notion that stress plays a role in the etiology of psychotic disorders, especially schizophrenia, is longstanding. However, it is only in recent years that the potential neural mechanisms mediating this effect have come into sharper focus. The introduction of more sophisticated models of the interplay between psychosocial factors and brain function has expanded our opportunities for conceptualizing more detailed psychobiological models of stress in psychosis. Further, scientific advances in our understanding of adolescent brain development have shed light on a pivotal question that has challenged researchers; namely, why the first episode of psychosis typically occurs in late adolescence/young adulthood. In this paper, we begin by reviewing the evidence supporting associations between psychosocial stress and psychosis in diagnosed patients as well as individuals at clinical high risk for psychosis. We then discuss biological stress systems and examine changes that precede and follow psychosis onset. Next, research findings on structural and functional brain characteristics associated with psychosis are presented; these findings suggest that normal adolescent neuromaturational processes may go awry, thereby setting the stage for the emergence of psychotic syndromes. Finally, a model of neural mechanisms underlying the pathogenesis of psychosis is presented and directions for future research strategies are explored.

DAX1 regulatory networks unveil conserved and potentially new functions

DAX1 is an orphan nuclear receptor with actions in mammalian sex determination, regulation of steroidogenesis, embryonic development and neural differentiation. Conserved patterns of DAX1 gene expression from mammals to fish have been taken to suggest conserved function. In the present study, the European sea bass, Dicentrarchus labrax, DAX1 promoter was isolated and its conserved features compared to other fish and mammalian DAX1 promoters in order to derive common regulators and functional gene networks. Fish and mammalian DAX1 promoters share common sets of transcription factor frameworks which were also present in the promoter region of another 127 genes. Pathway analysis clustered these into candidate gene networks associated with the fish and mammalian DAX1. The networks identified are concordant with described functions for DAX1 in embryogenesis, regulation of transcription, endocrine development and steroid production. Novel candidate gene network partners were also identified, which implicate DAX1 in ion homeostasis and transport, lipid transport and skeletal development. Experimental evidence is provided supporting roles for DAX1 in steroid signalling and osmoregulation in fish. These results highlight the usefulness of the in silico comparative approach to analyse gene regulation for hypothesis generation. Conserved promoter architecture can be used also to predict potentially new gene functions. The approach reported can be applied to genes from model and non-model species.

Exposure to hypergravity during the preweaning but not postweaning period reduces vestibular-related stress responses in rats

Gravitational forces, including hypergravity or microgravity, induce plasticity of vestibular-related functions. These functions are not easily reversed if exposure to the gravitational forces occurs during vestibular development. In the present study, we hypothesized that vestibular-related stress responses might be suppressed in rats exposed to hypergravity during the vestibular development period. We exposed the rats to 2 g (hypergravity) during the preweaning (BW-HG; embryonic day 14 to postnatal week 3) or postweaning (AW-HG; postnatal weeks 4-6) periods. After recovery for 4 wk at 1 g, we conducted rotarod tests and then exposed the rats to 2 g for 90 min. In BW-HG rats, vestibular-related motor coordination on the rotarod test was partially, but not fully, restored to the level of AW-HG rats or rats raised at 1 g (1-G group). Loading-induced plasma adrenocorticotropic hormone and corticosterone levels were significantly suppressed in BW-HG and in rats with a vestibular lesion compared with AW-HG and 1-G rats. Arginine vasopressin and Fos expression levels in the paraventricular hypothalamic nucleus were also significantly lower in BW-HG and vestibular lesion rats than in AW-HG and 1-G rats. By contrast, there was no difference in the electrical foot shock-induced increase in plasma corticosterone among the experimental groups, suggesting that the nonvestibular-related stress response was not suppressed by exposure to 2 g during preweaning. These results indicated that exposure to hypergravity during preweaning specifically suppressed the vestibular-related stress response, and this suppression did not recover after 4 wk at 1 g.

Inhibitory function of the dorsomedial hypothalamic nucleus on the hypothalamic-pituitary-adrenal axis response to an emotional stressor but not immune challenge

Accumulating evidence implicates the dorsomedial hypothalamic nucleus (DMH) in the regulation of autonomic and neuroendocrine stress responses. However, although projections from the DMH to the paraventricular hypothalamic nucleus (PVN), which is the critical site of the neuroendocrine stress axis, have been described, the impact of DMH neurones in the modulation of hypothalamic-pituitary-adrenal (HPA) axis activation during stress is not fully understood. The present study aimed to investigate the role of the DMH in HPA axis responses to different types of stimuli. Male Sprague-Dawley rats fitted with a chronic jugular venous catheter were exposed to either an emotional stressor (elevated platform-exposure) or immune challenge (systemic interleukin-1β administration). Bilateral electrolytic lesions of the DMH disinhibited HPA axis responses to the emotional stressor, as indicated by higher plasma adrenocorticotrophic hormone levels during and after elevated platform exposure in lesioned animals compared to sham-lesioned controls. Moreover, DMH-lesioned animals showed increased neuronal activation in the PVN, as indicated by a higher c-Fos expression after elevated-platform exposure compared to controls. By contrast, DMH-lesions had no effects on HPA axis responses to immune challenge. Taken together, our data suggest an inhibitory role of DMH neurones on stress-induced HPA axis activation that is dependent upon the nature of the stimulus being important in response to an emotional stressor but not to immune challenge.

Inhibition of maternal behaviour by central infusion of corticotrophin-releasing hormone in marmoset monkeys

Stress can inhibit maternal behaviour and increase rates of child abuse in humans and other animals; however, the neuroendocrine mechanisms are not known. To determine whether corticotrophin-releasing hormone (CRH) plays a role in stress-induced disruption of maternal behaviour in primates, we characterised the effects of acute i.c.v. infusions of CRH on maternal and abusive behaviour in common marmoset monkeys (Callithrix jacchus). Nulliparous females were implanted with indwelling i.c.v. guide cannulae before conception. Between 18 and 58 days after the birth of her first infants, each female underwent a series of i.c.v. infusions of human CRH (0, 2, 8 and 25 μg) in 8 μl of artificial cerebrospinal fluid. In the 70 min after infusion, marmosets were tested with one of their infants, first in their home cage and, subsequently, in an unfamiliar cage in which the infant was confined in a transparent box on the cage floor. In the home cage, the highest dose of CRH significantly reduced the amount of time that mothers spent carrying their infants, as compared to vehicle alone, although it did not reliably affect aggression toward the infant or other behaviours. In the confined-infant test, the highest dose of CRH significantly reduced the amount of time that mothers spent on the cage floor, increased mothers' vocalisation rates, and tended to reduce their activity levels and time spent in proximity to their infant. Twenty-five micrograms of CRH also elicited significant elevations in plasma adrenocorticotrophic hormone and cortisol concentrations compared to vehicle. These results indicate that i.c.v.-administered CRH reduces maternal behaviour in marmoset mothers, in both familiar and unfamiliar environments, but does not increase infant abuse.

Unaltered hormonal response to stress in a mouse model of fragile X syndrome

Reports in the clinical literature and studies of fmr1 knockout mice have led to the hypothesis that, in addition to mental retardation, fragile X syndrome is characterized by a dysregulation of hypothalamic-pituitary-adrenal axis function. We have systematically examined this hypothesis by studying the effects of stress on adrenocorticotrophic hormone and corticosterone levels in adult, male fmr1 knockout mice. Initially we determined the circadian rhythms of the plasma hormone levels in both wild-type and fmr1 knockout mice and established the optimal time to impose the stress. We found no genotypic differences in the circadian rhythms of either hormone. We studied two types of stressors, immobilization and spatial novelty; spatial novelty was 5min in an elevated plus-maze. We varied the duration of immobilization and followed the time course of recovery of hormones to their pre-stress levels. Despite the lower anxiety exhibited by fmr1 knockout mice in the elevated plus-maze, hormonal responses to and recovery from this spatial novelty were similar in both genotypes. Further, we found no genotypic differences in hormonal responses to immobilization stress. The results of our study indicate that, in FVB/NJ mice, the hormonal response to and recovery from acute stress is unaltered by the lack of fragile X mental retardation protein.