Glucocorticoid Receptor Response Research Articles

Expression of Glucocorticoid Receptor and Early Growth Response Gene 1 during Postnatal Development of Two Inbred Strains of Mice Exposed to Early Life Stress

Early life stress can elicit profound changes in adult gene expression and behavior. One consequence of early life stress is a decreased expression of glucocorticoid receptors (GRs) in the frontal cortex and hippocampus. However, neither the time of onset nor the mechanism(s) leading to decreased GR expression during postnatal development are known. The present study used two inbred strains of mice that differ in their behavioral responsiveness to stress (Balb/c and C57Bl/6), exposed them to an established paradigm of early life stress (infant maternal separation), and measured their expression of frontal cortical and hippocampal GRs and the putative transcriptional activator of the GR gene, early growth response gene (egr)-1, at defined stages of postnatal development. In both strains, real-time RT-PCR experiments revealed that decreased expression of GR in adolescence and adulthood is, in fact, preceded by increased GR expression during early life stress exposure. Thus, the early life stress-induced disruption of the normal stress-hyporesponsive period during infancy is accompanied by increased GR expression. Moreover, chronic treatment with the antidepressant drug fluoxetine during adolescence or adulthood reversed the effect of early life stress on adult GR mRNA expression. In contrast to the strain-independent effect of early life stress on GR expression, however, changes in egr-1 expression occurred only in Balb/c mice, and unlike the biphasic developmental changes in GR mRNA expression, egr-1 mRNA was decreased throughout postnatal development. Moreover, there was no consistent overlap of anatomic regions affected by decreased GR and egr-1 protein expression. Thus, in Balb/c mice, changes in GR and egr-1 expression can independently contribute to the phenotypes resulting from early life stress exposure. These findings illustrate that the impact of early life stress on gene expression changes is modulated by the genetic background and that the persistent changes in GR and egr-1 expression that arise early during postnatal developmental are reversible by chronic fluoxetine treatment during adolescence and adulthood.

PWE-086 Ursodeoxycholic acid modulates the glucocorticoid receptor in oesophageal cells

Introduction Hydrophobic bile acids have been identified as aetiological agents in inflammatory oesophageal diseases. Ursodeoxycholic acid (UDCA) has been shown to attenuate the inflammatory effects of hydrophobic bile acids in numerous cell lines. This has been shown to be partly mediated by UDCA activation of the glucocorticoid receptor (GR). Here, we investigate the potential role of UDCA in modulating the GR in oesophageal cell lines. Methods Western blot analysis and RT-PCR were used to characterise GR expression in oesophageal cell lines (HET1A, SKGT-4). High Content Analysis (GE In-Cell analyser 1000) was used to investigate nuclear translocation of the GR in response to UDCA stimulation. Trans-activation of glucocorticoid response elements (GRE) was determined in a transient transfection assay using a construct of the human GRE promoter ligated to a firefly luciferase reporter gene Similarly trans-repression of NFKB was determined using a construct of the human NFKB promoter ligated to a luciferase reporter gene. Results GR was found to be present in the oesophageal cell lines used at the mRNA and protein levels. No GRβ was expressed at the mRNA level suggesting that the GR present is GRα. UDCA induced translocation of the GR in a time- and concentration-dependent manner (EC50 of 298.68 μM in SKGT-4 and 320 μM in HET1A cell lines, 54% and 36% efficacy of dexamethasone 100 nM, respectively, both p Conclusion Glucocorticoids are used as anti-inflammatory agents for treating a spectrum of diseases. Their chronic use is limited due to serious side effects, primarily thought to be due to GR-mediated transactivation. Here we show that UDCA can act as a GR modulator, with the ability to differentiate between transrepression and transactivation pathways. As a result UDCA may be of benefit in treating inflammatory conditions of the oesophagus.

Sexually dimorphic functional alterations of rat hepatic glucocorticoid receptor in response to fluoxetine

Gender-related differences in the expression and functional properties of the hepatic glucocorticoid receptor were studied before and after antidepressant fluoxetine administration to both unstressed and rats exposed to a chronic social isolation stress. Some of the receptor's functional properties, including hormone-binding capacity ( B max), hormone-binding potency ( B max/ K D ratio) and the DNA-binding ability, were found to be sexually dimorphic. Fluoxetine treatment (5 mg/kg body mass, 21 day, intraperitoneally) induced a decrease in B max and in the amount of Hsp70 co-immunoprecipitated with the glucocorticoid receptor only in males, and stimulated the association of the receptor with Hsp90 in females. When applied during the last three weeks of the 6-week isolation, fluoxetine parallelly elevated B max and the receptor protein level in female animals, while in males diminished B max and inhibited association of the receptor with Hsp70. Binding of dexamethasone-receptor complexes both to DNA-cellulose and to isolated liver nuclei did not appear to be a target for fluoxetine action. The results point to sex-related differences in the glucocorticoid receptor functioning and in its response to fluoxetine, and suggest that these differences may contribute to well known sexual dimorphism in the sensitivity to stress, to stress-related disorders and to antidepressant treatment.

Paired Hormone Response Elements Predict Caveolin-1 as a Glucocorticoid Target Gene

Glucocorticoids act in part via glucocortocoid receptor binding to hormone response elements (HREs), but their direct target genes in vivo are still largely unknown. We developed the criterion that genomic occurrence of paired HREs at an inter-HRE distance less than 200 bp predicts hormone responsiveness, based on synergy of multiple HREs, and HRE information from known target genes. This criterion predicts a substantial number of novel responsive genes, when applied to genomic regions 10 kb upstream of genes. Multiple-tissue in situ hybridization showed that mRNA expression of 6 out of 10 selected genes was induced in a tissue-specific manner in mice treated with a single dose of corticosterone, with the spleen being the most responsive organ. Caveolin-1 was strongly responsive in several organs, and the HRE pair in its upstream region showed increased occupancy by glucocorticoid receptor in response to corticosterone. Our approach allowed for discovery of novel tissue specific glucocorticoid target genes, which may exemplify responses underlying the permissive actions of glucocorticoids.

Genomic and Nongenomic Cross Talk between the Gonadotropin-Releasing Hormone Receptor and Glucocorticoid Receptor Signaling Pathways

The GnRH receptor (GnRHR), a member of the G protein-coupled receptor family, is a central regulator of reproductive function in all vertebrates. The peptide hormone GnRH exerts its effects via binding to the GnRHR in pituitary gonadotropes. We investigated the mechanisms of regulation of transcription of the mGnRHR gene in the mouse pituitary gonadotrope L beta T2 cell line by GnRH and dexamethasone (dex). Reporter assays with transfected mGnRHR promoter show that both dex and GnRH increase transcription of the mGnRHR gene via an activating protein-1 (AP-1) site. Real-time PCR confirmed this on the endogenous mGnRHR gene, and small interfering RNA experiments revealed a requirement for the glucocorticoid receptor (GR) for both the dex and GnRH response. Chromatin immunoprecipitation (ChIP) and immunofluorescence assays provide evidence that both GnRH and dex up-regulate the GnRHR gene via nuclear translocation and interaction of the GR with the AP-1 region on the mGnRHR promoter. We show that GnRH activates the unliganded GR by rapid phosphorylation of the GR at Ser-234 in a GnRHR-dependent fashion to transactivate a GRE reporter gene in L beta T2 and COS-1 cells. Using kinase inhibitors, we established a direct link between GnRH-induced protein kinase C and MAPK activation, leading to unliganded GR phosphorylation at Ser-234 and transactivation of the glucocorticoid response element. Furthermore, we show that GnRH and dex synergistically activate the endogenous GnRHR promoter in L beta T2 cells, via a mechanism involving steroid receptor coactivator-1 recruitment to the GnRHR AP-1 region. Our results suggest a novel mechanism of rapid nongenomic cross talk between the hypothalamic-pituitary-gonadal and hypothalamic-pituitary-adrenal axes via GnRHR-dependent phosphorylation and activation of the unliganded GR in response to GnRH.

FoxA1 Binding Directs Chromatin Structure and the Functional Response of a Glucocorticoid Receptor-Regulated Promoter

Reconstitution of the glucocorticoid receptor (GR)-regulated mouse mammary tumor virus (MMTV) promoter in Xenopus oocytes was used to monitor the effects of different transcription factor contexts. Three constitutively binding factors, nuclear factor 1 (NF1), octamer transcription factor 1 (Oct1), and the Forkhead box A1 (FoxA1), were shown to act in concert, to direct the chromatin structure, and to enhance the GR response. FoxA1 has a dominant effect in the absence of hormone and induces a cluster of DNase I-hypersensitive sites in the segment comprising bp -400 to +25. This FoxA1-mediated chromatin remodeling does not induce MMTV transcription, as opposed to that of the GR. However, the robust FoxA1-dependent chromatin opening has the following drastic functional consequences on the hormone regulation: (i) GR-DNA binding is facilitated, as revealed by dimethyl sulfate in vivo footprinting, leading to increased hormone-induced transcription, and (ii) the GR antagonist RU486 is converted into a partial agonist in the presence of FoxA1 via ligand-independent GR activation. We conclude that FoxA1 mediates a preset chromatin structure and directs a context-specific response of a nuclear receptor. Furthermore, the alternative nucleosome arrangement induced by GR and FoxA1 implies this to be determined by constitutive binding of transcription factors rather than by the DNA sequence itself.

Gene Expression Patterns Associated with Posttraumatic Stress Disorder Following Exposure to the World Trade Center Attacks

Although genetic risk factors for posttraumatic stress disorder (PTSD) in similarly traumatized cohorts can be confounded with risk for type of exposure, the primary risk for exposure to the 9/11 attack on New York City was proximity, allowing study of PTSD risk in a sample that is not confounded by exposure-related risk. Thirty-five Caucasians (15 with PTSD, stratified for exposure, age, and gender) were selected from a population-representative sample of persons exposed to the attack from which longitudinal data had been collected in four previous waves. Whole blood gene expression and cortisol levels were obtained. Seventeen probe sets were differentially expressed in PTSD. Identified genes were generally involved in hypothalamic-pituitary-adrenal (HPA) axis, signal transduction, or brain and immune cell function. FKBP5, a modulator of glucocorticoid receptor (GR) sensitivity, showed reduced expression in PTSD, consistent with enhanced GR responsiveness. FKBP5 expression was predicted by cortisol when entered with PTSD severity in regression analysis. Quantitative polymerase chain reaction confirmed significant reductions in FKBP5. Also less expressed in PTSD were STAT5B, a direct inhibitor of GR, and major histocompatibility complex (MHC) Class II. Consistent with observations of HPA axis dysfunction in PTSD, several genes involved in glucocorticoid signaling are differentially expressed among those with current PTSD.

Discovery of selective glucocorticoid receptor modulators by multiplexed reporter screening

Glucocorticoids are widely used to suppress inflammation and treat various immune-mediated diseases. Some glucocorticoid receptor (GR)-regulated genes mediate the therapeutic response, whereas others cause debilitating side effects. To discover selective modulators of the GR response, we developed a high-throughput, multiplexed system to monitor regulation of 4 promoters simultaneously. An initial screen of 1,040 natural products and Food and Drug Administration-approved drugs identified modulators that caused GR to regulate only a subset of its target promoters. Some compounds selectively inhibited GR-mediated gene activation without altering the repression of cytokine expression by GR. This approach will facilitate identification of genes and small molecules that augment beneficial effects of GR and diminish deleterious ones. Our results have important implications for the development of GR modulators and the identification of cross-talk pathways that control selective GR gene regulation.

Autoregulation of human relaxin-2 gene expression critically involves relaxin and glucocorticoid receptor binding to glucocorticoid response half-sites in the relaxin-2 promoter

Relaxin peptides act in brain, reproductive and cardiovascular systems, kidneys, and connective tissue through different G protein-coupled receptors. We reported that human relaxin-2 and porcine relaxin are both agonists at the human glucocorticoid receptor (GR). Here, we investigated the possible auto-regulation of relaxin-2 gene expression via recently discovered GR-binding sites in the relaxin-2 promoter. We found that porcine relaxin increased the secretion of human relaxin-like immunoreactivity in HeLa and THP-1 cells. Silencing of GR gene expression completely abolished this effect whereas transfection of wild-type GR into naturally GR-devoid HT-29 cells established relaxin sensitivity. Relaxin was shown to stimulate CAT expression driven by different deletion constructs of the 5'-flanking region of the relaxin-2 promoter. In chromatin immunoprecipitation assays, we detected both GR and relaxin binding to the relaxin-2 promoter. Gel shift assays indicated binding of relaxin-activated GR to half-GREs located between 160 and 200 bp upstream of transcription start but not to the GRE at − 900 bp. Relaxin bound to human GR and displaced established GR agonists. Immunofluorescence experiments visualized nuclear co-localization of relaxin and GR in response to relaxin. In conclusion, we have identified a positive auto-regulatory loop of human relaxin-2 expression which involves GR and relaxin/GR binding to half-GREs in the relaxin-2 promoter.

Kinetic Complexity of the Global Response to Glucocorticoid Receptor Action

We have characterized the kinetic response of gene targets throughout the murine genome to transcriptional modulation by the glucocorticoid receptor (GR). In contrast to a model in which multiple genes are either repressed or activated during the GR response, the vast majority of responsive genes are subject to complex regulation profiles, frequently with alternate activation and repression phases. We also observe that GR binding at response elements does not always correlate with the target gene response profile. Thus, the cellular response to GR stimulation involves a highly orchestrated series of regulatory actions and not simply a binary response to hormone.

Association Between BclI SNP of the Glucocorticoid Receptor (GCR) And Immune Response to Stress

Stress influences immunity through various mechanisms including immunoregulatory elements. Previous studies show associations between high stress levels and altered immune balance such as in TH1/TH2 (IFNγ, IL‐4, IL‐10) cytokine production. Such immunoregulatory imbalances are associated with altered serum cortisol levels and can be reproduced with glucocorticoids (GC) in vitro. GC act through the GCR for which several SNPs have been described. The GCR SNPs BclI and N363S are associated with hyperreactivity to GC. We examined the associations between GCR SNPs and cytokine responses. 86 normal volunteers were stratified into four groups by k‐means clustering using Perceived Stress Score (PSS) and immunologic variables. We examined numbers of CD4+CD25+FoxP3+ (Treg) and CD4+ cells producing TH1/TH2 cytokines by intracellular flow cytometry. DNA was extracted from peripheral blood and SNP determined by PCR and RFLP analysis. Clusters were categorized by PSS into high stress (HS‐19.2±3.5, n=15), low stress (LS‐8.3±4.7, n=7) and two groups of typical stress (TS‐12.6±5.0, n=37 and 12.7±6.3, n=27). The HS cluster had decreased Treg (2.0±0.6%) and TH1 (22.1±4.4%) compared to the LS cluster with higher Treg (3.5±1.1%) and TH1 (33.4±6.7). There were no cluster differences in IL‐4 and IL‐10. BclI (but not N363S) SNP showed a trend in C/C homozygosity in 66.7% (10/15) of the HS compared to 28.6% (2/7) of the the LS cluster (χ2(1)=2.79, p=0.095). These results suggest that genetic variation, such as GCR BclI SNP, may participate in regulation of immune response to stress.

Dexamethasone Induced Apoptotic Mechanisms in Myeloma Cells by Analysis of Mutant Glucocorticoid Receptors.

Although glucocorticoids (GC) like dexamethasone (dex) are very effective in Multiple myeloma (MM), it is still unknown how they induce MM cell apoptosis. To investigate this issue, we studied the MM1S and MM1R cell lines. The MM1S cells are sensitive to dex-mediated apoptosis, while the MM1R cells are resistant due to lack of expression of the glucocorticoid receptor (GR). The latter resistant cells were exploited by the stable lentiviral-mediated expression of wild type (wt) or mutant GRs. Initial experiments demonstrated that infection of the MM1R cells with wt GR lentiviral vector resulted in stable expression of the wt GR and GC-induced reporter expression through the GR response element (GRE). These infected cells were now sensitive to GC-mediated apoptosis, although slightly less than MM1S cells. Nevertheless, this indicated that GR expressing MM1R cells could be used as a model to study the effectors of dex mediated apoptosis. MM1R cells were also similarly infected with lentiviral vectors expressing four different mutant GRs, that are either deficient in mediating GC-induced transactivation through the GRE or deficient in the ability to transrepress NF-KB activity. A GR mutant that transactivated through the GRE but was deficient in NF-KB transrepression did not induce apoptosis indicating that GRE transactivation was not sufficient for apoptosis. Further support for this notion was found when MM1S cells were treated with a concentration of cycloheximide which prevented GRE reporter expression but did not induce apoptosis by itself. This concentration did not affect GC-induced apoptosis supporting the finding that GC-induced transactivation is not required for apoptosis. In contrast, there was a correlation between the ability of mutant GRs to transrepress NF-KB and induce apoptosis. To test if GC-induced transactivation could participate in apoptosis in the setting of NF-KB transrepression, MM1R cells expressing a mutant GR which activates through GRE but does not transrepress NF-KB and is deficient in GC-induced apoptosis was infected with an adenoviral vector expressing the IKB super repressor to inhibit NF-KB. With abrogation of NF-KB, these cells underwent apoptosis at a higher level as compared to infection with a control adenoviral vector. Also, the addition of dex to these cells expressing IKB super repressor significantly enhanced apoptosis suggesting that transactivation through GRE can participate in apoptosis if the NF-KB survival factor is paralyzed.

Dexamethasone treatment affects nuclear glucocorticoid receptor and glucocorticoid response element binding activity in liver of rats ( Rattus norvegicus) during aging

Aging is associated with marked changes in the biochemical processes of many organs. Basal and glucocorticoid induced of liver nuclear glucocorticoid receptor (GR) on the level of protein expression and DNA-binding activity were investigated at different ages (3, 6, 12, 18 and 24 months old) in two groups of rats in: untreated and dexamethasone treated. The results showed a significant decline of GR protein immunopurified from untreated rats of advanced age. In dexamethasone-treated rats, the quantity of GR protein was lower than in controls at all ages. The interactions of liver nuclear proteins with radioactively labelled synthetic oligonucleotide analogue containing consensus GRE sequence were analysed during aging. The results showed that GRE binding activity demonstrated a decrease both in untreated and in dexamethasone treated rats. However, relative to untreated rats, dexamethasone treatment resulted in a significant increase in GRE binding at all ages, except that of three months old animals. In conclusion, the observed alterations in GR protein expression and its DNA binding activity may play a role in the changes of the cell response to glucocorticoid during aging.

Long-term imipramine treatment affects rat brain and pituitary corticosteroid receptors and heat shock proteins levels in a gender-specific manner

Gender-related differences in the effects of imipramine, on the protein levels of glucocorticoid receptor (GR), and heat shock proteins Hsp90 and Hsp70, as well as on dexamethasone binding to corticosteroid receptors (CRs) in the pituitary, hypothalamus, hippocampus and brain cortex of non-depressed rats were studied. Differences between female and male animals in the GR protein level in the tissues of untreated animals were not noticed. However, imipramine led to opposite changes in the cellular level of GR protein in the brain of female and male rats, as well as to gender- and tissue-specific changes in in vitro dexamethasone binding to GR and mineralocorticoid receptor (MR) in the hippocampus and brain cortex. Gender-related differences in the expression of Hsp90 and Hsp70 were noticed mainly in the hippocampus, only after imipramine treatment. The observed changes in the response of GR to imipramine suggest that this antidepressant may affect both the level of the receptor protein and the mechanisms regulating its binding ability in a gender-related manner.

Developmental Programming Through Epigenetic Changes

See related article, pages 520–526 The last decade has seen an exponential number of scientific articles addressing the concept of fetal programming of adult onset diseases. Though it has long been known (as it is probably part of common knowledge in human history) that the environment and life events during the fetal period impact on the child’s development, the notion that intrauterine life can also impact on adult health and on the incidence of late onset diseases such as hypertension and type II diabetes is relatively more recent. In 1964, Rose reported the association of ischemic heart disease and infant mortality within the same families (reviewed by1). Then Forsdahl in 1977 showed that incidence of arteriosclerotic heart disease in a certain age group could be correlated with the infant mortality rate of that same population.1 Interest in these types of association rose dramatically following Professor Barker and collaborators’ extensive observations of a well documented population in England and Wales. The meticulous work of home health visitors in the early 20th century, which noted every child weight and length at birth and throughout the first year of life as well as other observations of the mother health and living milieu, generated data which clearly demonstrated an inverse relationship between birthweight and adult incidence of cardiovascular related mortality and morbidities as well as type II diabetes.1 We will focus here on hypertension and related complications. The association between birthweight and adult blood pressure was demonstrated in many parts of the world, in industrialized as well as in more developing countries, in both men and women.1 The association is first noted in early childhood (but not at birth) and seems to increase with age. Despite the significant number of studies published, which have examined to date tens …

Therapy Insight: is there an imbalanced response of mineralocorticoid and glucocorticoid receptors in depression?

In severely depressed patients, emotional arousal, cognitive abnormality and vulnerability to psychotic episodes are linked to a hyperactive hypothalamic-pituitary-adrenal (HPA) axis and high levels of circulating cortisol. The susceptibility pathways underlying these disturbed brain functions are influenced by genetic factors, early-life priming experiences and later-life events. Cortisol is an important determinant in this so-called three hit model. The action of cortisol is protective, but can become harmful if exposure of susceptibility pathways to the stress hormone is excessive and sustained or inadequate. In this article we argue that this change in role of cortisol from protective into harmful depends on the functioning of the mineralocorticoid and glucocorticoid receptors and the context in which the organism experiences the stressor. Actions mediated by the mineralocorticoid and glucocorticoid receptors are complementary and operate in different time domains of the stress response: the mineralocorticoid receptor normally prevents stress-induced disturbances, but if such disturbances occur the glucocorticoid receptor helps the recovery process. An imbalance in these receptor-mediated actions is thought to increase vulnerability to stress-related psychiatric disorders in predisposed individuals. Correction of the imbalance between the mineralocorticoid receptor and the glucocorticoid receptor can, therefore, facilitate recovery processes still present in the diseased brain, provided that the right psychological context is offered to the individual.

Regulation of hepatic steroid receptors and enzymes by the 3β-hydroxysteroid dehydrogenase inhibitor trilostane

Therapies designed to treat hypercortisolism have usually sought to reduce circulating glucocorticoid concentrations, however the local tissue endocrine environment could be an alternative target. The 3β-hydroxysteroid dehydrogenase Δ 5–4 isomerase (3β-HSD) inhibitor trilostane is of interest, since, although it is only moderately and transiently effective in reducing circulating steroid, it is remarkably effective in alleviating Cushing's symptoms in veterinary applications. To seek alternative modes of action, male Wistar rats were treated with trilostane. Although final circulating corticosteroid concentrations were unaffected, liver 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2) transcription and translation was significantly increased, whereas 3β-HSD was not affected either in liver or adrenal. Glucocorticoid receptor (GR) mRNA was down-regulated, and mineralocorticoid receptor (MR) up-regulated by trilostane treatment: no changes in 11β-HSD1 mRNA were observed. Trilostane also had no direct effect on GR response element-mediated gene transcription. The results show that the tissue endocrine environment is affected by trilostane treatment in the absence of sustained changes in circulating corticosteroid. The combination of increased 11β-HSD2 and reduced GR expression in target organs could be expected to ameliorate the effects of excess glucocorticoid, suggesting new therapeutic approaches.

Cellular co-localization of protein phosphatase 5 and glucocorticoid receptors in rat brain

Glucocorticoid receptors are widely expressed in brain, where they are thought to play a role in controlling neurogenesis and to mediate many of the central nervous system effects of stress. In non-neuronal cells, protein phosphatase 5 (PP5) has been found in complexes with heat shock protein 90 and glucocorticoid receptors and may be a negative modulator of glucocorticoid receptor function. In the present study, we used co-immunofluorescence analysis to examine whether PP5 and glucocorticoid receptors are co-expressed at the cellular level in rat brain. In several regions containing major populations of glucocorticoid receptor expressing neurons, PP5 and glucocorticoid receptors were co-localized at the cellular level. These include pyramidal cells of the hippocampal CA1 and CA2 regions and dentate gyrus granule cells, cerebellar Purkinje neurons, cortical pyramidal neurons, neurons of the central nucleus of the amygdala and parvocellular neurons of the hypothalamic paraventricular nucleus. There are also neuronal populations that are stained strongly for glucocorticoid receptors, such as cerebellar granule cells, where PP5 is either absent or below detection limits. Likewise, numerous neuronal populations contain PP5, but not glucocorticoid receptors. Whereas glucocorticoid receptors are expressed in both neurons and glial cells throughout the brain, PP5 appears to be primarily expressed in neurons. These studies suggest that glucocorticoid receptors may be differentially regulated by phosphatase action in different populations of central nervous system cells. Co-localization of PP5 and glucocorticoid receptors in brain regions involved in feedback control of the hypothalamus–pituitary–adrenal axis suggests that PP5 may be an important modulator of glucocorticoid receptor responses in this pathway.

Glucocorticoid resistance in squirrel monkeys results from a combination of a transcriptionally incompetent glucocorticoid receptor and overexpression of the glucocorticoid receptor co-chaperone FKBP51

Squirrel monkeys have high cortisol compared to Old World primates to compensate for glucocorticoid resistance. Glucocorticoid resistance in squirrel monkeys may result from mutations in the glucocorticoid receptor (GR) that render it less transcriptionally competent, or expression of the co-chaperone FKBP51 that reduces ligand binding. The goal of this study was to reconcile the contribution of each mechanism. Responsiveness of squirrel monkey GR in COS-7 cells was reduced compared to human GR, but induction of GR activity by maximum dexamethasone concentrations was similar. Also, expression of squirrel monkey FKBP51 reduced responsiveness of both squirrel monkey and human GR in T-REx™-293 cells. The EC 50 for dexamethasone was 100-fold higher in cells expressing squirrel monkey GR and excess FKBP51 compared to cells expressing only human GR. Effects of FKBP51 expression and treatment with FK506 were also determined in squirrel monkey SQMK-FP cells that naturally express high levels of FKBP51. Overexpression of FKBP51 in SQMK-FP cells had little effect on GR responsiveness, but treatment with FK506 that blocks the effect of FKBP51 increased GR responsiveness. Thus, glucocorticoid resistance in squirrel monkey cells results from both expression of GRs that are less responsive and overexpression of FKBP51 that further reduces GR responsiveness.

Hippocampal volume in aging combat veterans with and without post-traumatic stress disorder: Relation to risk and resilience factors

Objective To examine whether there are post-traumatic stress disorder (PTSD) related differences in hippocampal volume in middle-aged and elderly veterans and to examine the relationship of neuroendocrine activity, memory performance, and measures of risk and resilience for PTSD to hippocampal volume in this cohort. Methods Seventeen veterans with chronic PTSD and 16 veterans without chronic PTSD received an MRI scan followed by neuroendocrine assessment (24-h urinary cortisol excretion and the lysozyme IC 50-DEX, a measure of glucocorticoid receptor (GR) responsiveness), and cognitive testing. Results Veterans with PTSD did not differ from those without PTSD in hippocampal volume, but they did show significantly lower urinary cortisol levels, and poorer memory performance on the Wechsler Logical Memory test and Digit Span test. Smaller left hippocampal volumes were observed in veterans who developed PTSD in response to their first reported traumatic exposure, compared to veterans who had first experienced a traumatic event to which they did not develop PTSD, prior to experiencing a subsequent event that led to PTSD. In contrast, the two neuroendocrine measures were associated with risk factors related to early trauma exposure. Conclusion Although hippocampal volume was not found to differ between subjects with and without PTSD, smaller hippocampal volumes in PTSD may be associated with specific risk and resilience factors. These may be distinct from vulnerability markers associated with increased responsiveness to glucocorticoids and/or other neuroendocrine measures that have been observed in combat-related PTSD.