Expression of glucocorticoid inducible genes is associated with reductions in cornu ammonis and dentate gyrus volumes in patients with major depressive disorder

Role of Serum/Glucocorticoid-Regulated Kinase 1 (SGK1) in Immune and Inflammatory Diseases

Serum/glucocorticoid-regulated kinase 1 (SGK1), a member of the serine/threonine protein kinase gene family, is primarily regulated by serum and glucocorticoids. SGK1 is involved in the development of tumors and fibrotic diseases. However, relatively little research has been conducted on their role in immune and inflammatory diseases. SGK1 may act as a pivotal immune regulatory gene by modulating immune cells (e.g., T cells, macrophages, dendritic cells, and neutrophils) and functions and is involved in the pathogenesis of some immune and inflammatory diseases, such as inflammatory bowel disease, multiple sclerosis, allergic diseases, sepsis, and major depressive disorder. This review aims to provide an overview of the latest research focusing on the immune and inflammatory regulatory roles of SGK1 and provide new insights into diagnostic and therapeutic approaches for immune and inflammatory diseases.

Hippocampal and amygdala volumes vary with transdiagnostic psychopathological dimensions of distress, anxious arousal, and trauma

Reduced hippocampal and/or amygdala volumes have been reported in patients with a variety of different anxiety diagnoses, suggesting that structural alterations may vary transdiagnostically across the internalizing disorders. The current study measured hippocampal and amygdala volumes in anxiety and mood disorder patients assessing differences that vary dimensionally with transdiagnostic factors of distress, anxious arousal, and trauma, based on a principal components analysis of questionnaires relating to symptomology. High-resolution structural images were collected in a sample of 165 patients, and volumes extracted from the hippocampal formation (including CA1, CA2/3, CA4/DG, subiculum, and molecular layer) and the amygdala. Transdiagnostically, increasing distress was associated with reduced hippocampal CA1 volume, increasing anxious arousal was associated with reduced hippocampal CA4/DG volume, and increasing trauma severity was associated with reduced amygdala volume in women. Taken together, the data indicate that subcortical brain volumes decrease as the severity of transdiagnostic psychopathological symptomology increases.

Psychosocial factors and hippocampal subfields: The Medea-7T study

Specific subfields within the hippocampus have shown vulnerability to chronic stress, highlighting the importance of looking regionally within the hippocampus to understand the role of psychosocial factors in the development of neurodegenerative diseases. A systematic review on psychosocial factors and hippocampal subfield volumes was performed and showed inconsistent results, highlighting the need for future studies to explore this relationship. The current study aimed to explore the association of psychosocial factors with hippocampal (subfield) volumes, using high-field 7T MRI. Data were from the Memory Depression and Aging (Medea)-7T study, which included 333 participants without dementia. Hippocampal subfields were automatically segmented from T2-weighted images using ASHS software. Generalized linear models accounting for correlated outcomes were used to assess the association between subfields (i.e., entorhinal cortex, subiculum, Cornu Ammonis [CA]1, CA2, CA3, dentate gyrus, and tail) and each psychosocial factor (i.e., depressive symptoms, anxiety symptoms, childhood maltreatment, recent stressful life events, and social support), adjusted for age, sex, and intracranial volume. Neither depression nor anxiety was associated with specific hippocampal (subfield) volumes. A trend for lower total hippocampal volume was found in those reporting childhood maltreatment, and a trend for higher total hippocampal volume was found in those who experienced a recent stressful life event. Among subfields, low social support was associated with lower volume in the CA3 (B = -0.43, 95% CI: -0.72; -0.15). This study suggests possible differential effects among hippocampal (subfield) volumes and psychosocial factors.

Transcriptomic Profile Identifies Hippocampal Sgk1 as the Key Mediator of Ovarian Estrogenic Regulation on Spatial Learning and Memory and Aβ Accumulation

Previous studies have shown that ovarian estrogens are involved in the occurrence and pathology of Alzheimer's disease (AD) through regulation on hippocampal synaptic plasticity and spatial memory; however, the underlying mechanisms have not yet been elucidated at the genomic scale. In this study, we established the postmenopausal estrogen-deficient model by ovariectomy (OVX). Then, we used high-throughput Affymetrix Clariom transcriptomics and found 143 differentially expressed genes in the hippocampus of OVX mice with the absolute fold change ≥ 1.5 and P < 0.05. GO analysis showed that the highest enrichment was seen in long-term memory. Combined with the response to steroid hormone enrichment and GeneMANIA network prediction, the serum and glucocorticoid-regulated kinase 1 gene (Sgk1) was found to be the most potent candidate for ovarian estrogenic regulation. Sgk1 overexpression viral vectors (oSgk1) were then constructed and injected into the hippocampus of OVX mice. Morris water maze test revealed that the impaired spatial learning and memory induced by OVX was rescued by Sgk1 overexpression. Additionally, the altered expression of synaptic proteins and actin remodeling proteins and changes in CA1 spine density and synapse density induced by OVX were also significantly reversed by oSgk1. Moreover, the OVX-induced increase in Aβ-producing BACE1 and Aβ and the decrease in insulin degrading enzyme were significantly reversed by oSgk1. The above results show that multiple pathways and genes are involved in ovarian estrogenic regulation of the function of the hippocampus, among which Sgk1 may be a novel potent target against estrogen-sensitive hippocampal dysfunctions, such as Aβ-initiated AD.

Dysregulation of adult hippocampal neuroplasticity in major depression: pathogenesis and therapeutic implications

Major depressive disorder (MDD) was previously hypothesized to be a disease of monoamine deficiency in which low levels of monoamines in the synaptic cleft were believed to underlie depressive symptoms. More recently, however, there has been a paradigm shift toward a neuroplasticity hypothesis of depression in which downstream effects of antidepressants, such as increased neurogenesis, contribute to improvements in cognition and mood. This review takes a top-down approach to assess how changes in behavior and hippocampal-dependent circuits may be attributed to abnormalities at the molecular, structural, and synaptic level. We conclude with a discussion of how antidepressant treatments share a common effect in modulating neuroplasticity and consider outstanding questions and future perspectives.

Cell type specificity of glucocorticoid signaling in the adult mouse hippocampus

Glucocorticoid stress hormones are powerful modulators of brain function and can affect mood and cognitive processes. The hippocampus is a prominent glucocorticoid target and expresses both the glucocorticoid receptor (GR: Nr3c1) and the mineralocorticoid receptor (MR: Nr3c2). These nuclear steroid receptors act as ligand-dependent transcription factors. Transcriptional effects of glucocorticoids have often been deduced from bulk mRNA measurements or spatially informed individual gene expression. However, only sparse data exists allowing insights on glucocorticoid-driven gene transcription at the cell type level. Here, we used publicly available single-cell RNA sequencing data to assess the cell-type specificity of GR and MR signaling in the adult mouse hippocampus. The data confirmed that Nr3c1 and Nr3c2 expression differs across neuronal and non-neuronal cell populations. We analyzed co-expression with sex hormones receptors, transcriptional coregulators, and receptors for neurotransmitters and neuropeptides. Our results provide insights in the cellular basis of previous bulk mRNA results and allow the formulation of more defined hypotheses on the effects of glucocorticoids on hippocampal function.

FreeSurfer ‐based segmentation of hippocampal subfields: A review of methods and applications, with a novel quality control procedure for ENIGMA studies and other collaborative efforts

Structural hippocampal abnormalities are common in many neurological and psychiatric disorders, and variation in hippocampal measures is related to cognitive performance and other complex phenotypes such as stress sensitivity. Hippocampal subregions are increasingly studied, as automated algorithms have become available for mapping and volume quantification. In the context of the Enhancing Neuro Imaging Genetics through Meta Analysis Consortium, several Disease Working Groups are using the FreeSurfer software to analyze hippocampal subregion (subfield) volumes in patients with neurological and psychiatric conditions along with data from matched controls. In this overview, we explain the algorithm's principles, summarize measurement reliability studies, and demonstrate two additional aspects (subfield autocorrelation and volume/reliability correlation) with illustrative data. We then explain the rationale for a standardized hippocampal subfield segmentation quality control (QC) procedure for improved pipeline harmonization. To guide researchers to make optimal use of the algorithm, we discuss how global size and age effects can be modeled, how QC steps can be incorporated and how subfields may be aggregated into composite volumes. This discussion is based on a synopsis of 162 published neuroimaging studies (01/2013–12/2019) that applied the FreeSurfer hippocampal subfield segmentation in a broad range of domains including cognition and healthy aging, brain development and neurodegeneration, affective disorders, psychosis, stress regulation, neurotoxicity, epilepsy, inflammatory disease, childhood adversity and posttraumatic stress disorder, and candidate and whole genome (epi‐)genetics. Finally, we highlight points where FreeSurfer‐based hippocampal subfield studies may be optimized.

Low Circulating Levels of GR, FKBP5, and SGK1 in Medicated Patients With Depression Are Not Altered by Electroconvulsive Therapy

OBJECTIVES

Hypothalamic-pituitary-adrenal axis dysregulation is frequently observed in patients with depression, with increased levels of the glucocorticoid (GC) cortisol commonly reported. Hypothalamic-pituitary-adrenal axis dysregulation may be a consequence of impaired feedback inhibition due to GC receptor (GR) impairments or dysfunction, termed "glucocorticoid resistance." Here, our objective was to assess mRNA levels of GC-related markers (GR, FKBP5, serum glucocorticoid kinase 1 [SGK1]) in patients with depression versus controls and in patient samples after electroconvulsive therapy (ECT). We also examined the relationship between these GC-related markers and 24-item Hamilton Depression Rating Scale (HAM-D24) scores to assess the utility of using them as biological markers for depression or the therapeutic response to ECT.

METHODS

GR, FKBP5, and SGK1 mRNA levels were examined in whole blood samples from 88 medicated patients with depression pre-/post-ECT and 63 controls using quantitative real-time polymerase chain reaction. Exploratory subgroup correlational analyses were performed to determine the relationship between GR, FKBP5, and SGK1 and 24-item Hamilton Depression Rating Scale scores.

RESULTS

GR, FKBP5, and SGK1 mRNA levels were significantly lower in medicated patients with depression compared with controls (P < 0.001, P = 0.03, P < 0.001, respectively), but ECT did not alter their levels (all P > 0.05). There was no relationship between GR, FKBP5, or SGK1 and 24-item Hamilton Depression Rating Scale scores.

CONCLUSIONS

GR, FKBP5, and SGK1 do not seem to be involved in the peripheral molecular response to ECT and do not represent useful biomarkers for predicting the therapeutic response to ECT in a real-world clinical setting.

Negative association between left prefrontal GABA concentration and BDNF serum concentration in young adults

Background

The brain's major inhibitory neurotransmitter gamma-aminobutyric acid (GABA) and the brain-derived neurotrophic factor (BDNF) play important roles in several stress-related disorders. Magnetic resonance spectroscopy (MRS) allows for non-invasive quantification of GABA concentration in the brain. We investigated the relationship between GABA concentration in the left dorsolateral prefrontal cortex (DLPFC) and BDNF concentration in the serum in a community-based sample of young subjects.

Methods

For the GABA measurement a single voxel MR spectrum was assessed in the prefrontal lobe (25 × 40 × 30 mm) using the MEGA-PRESS method in 276 subjects. BDNF serum concentrations were assessed with an ELISA kit. For 147 subjects we had both MRS and BDNF serum data, and for 79 subjects we had genotype data on the BDNF rs6265 polymorphism. Depressive psychopathology was assessed using Beck's Depression Inventory (BDI), Montgomery-Asberg Depression Rating Scale (MADRS) and Structured Clinical Interviews for Diagnostic and Statistical Manual of Mental Disorders (SCID) for DSM-IV.

Results

GABA concentration in the left DLPFC was negatively associated with BDNF serum concentration (r = -.264, p = .001). This correlation remained significant if corrected for sex (r = -.264, p = .001). BDNF serum concentration was also positively associated with volumes and surface areas of the left prefrontal cortex (p = .048, p = .005). There were no significant associations or interaction with depressive psychopathology (BDI, MADRS, SCID) or rs6265.

Conclusion

The results of this study suggest that GABA, BDNF and prefrontal brain volumes are interrelated, but do not show a strong association to depressive psychopathology, possibly due to the mild forms of psychiatric conditions present in our community-based sample.

Neurobiological mechanisms underlying sex-related differences in stress-related disorders: Effects of neuroactive steroids on the hippocampus

Men and women differ in their vulnerability to a variety of stress-related illnesses, but the underlying neurobiological mechanisms are not well understood. This is likely due to a comparative dearth of neurobiological studies that assess male and female rodents at the same time, while human neuroimaging studies often don't model sex as a variable of interest. These sex differences are often attributed to the actions of sex hormones, i.e. estrogens, progestogens and androgens. In this review, we summarize the results on sex hormone actions in the hippocampus and seek to bridge the gap between animal models and findings in humans. However, while effects of sex hormones on the hippocampus are largely consistent in animals and humans, methodological differences challenge the comparability of animal and human studies on stress effects. We summarise our current understanding of the neurobiological mechanisms that underlie sex-related differences in behavior and discuss implications for stress-related illnesses.

The Hippocampus in Depression: More Than the Sum of Its Parts? Advanced Hippocampal Substructure Segmentation in Depression

BACKGROUND

Hippocampal volume reduction is the most replicated finding in neuroimaging studies of major depressive disorder (MDD). Varying hippocampal volume definition is a well-established problem in this field. Given that hippocampal function can be mapped onto anatomically defined substructures and that detailed examination of substructure volumes is now possible, we examined different hippocampal composite measures in MDD to look for hippocampal markers of MDD.

METHODS

Magnetic resonance imaging brain scans were compared between 80 patients with a range of MDD duration and 83 healthy control subjects. High-resolution T1-weighted and T2-weighted-fluid-attenuated inversion recovery magnetic resonance images were examined using the automated hippocampal substructure module in FreeSurfer 6.0. Between-group volumetric assessments were performed at substructure and composite substructures levels.

RESULTS

Patients with MDD showed a bilateral pattern of volume reduction in principal hippocampal substructures: the cornu ammonis (CA1-CA4), dentate gyrus, and subiculum. Changes were more pronounced on the left of these structures and in recurrent depression. CA2 to CA4 were the only substructures reduced in first-presentation depression. Overall changes were most marked in the left CA1, and CA1 volume was a predictor of illness duration.

CONCLUSIONS

Hippocampal involvement in MDD is confined to principal substructures only. Differences between patients with MDD and healthy control subjects increased with progressively restricted hippocampal definitions, with the left CA1 emerging as a potential marker of MDD. Changes were more extensive in patients with recurrent, as opposed to first-presentation, MDD, suggesting a hippocampal disease process. These findings identify core hippocampal regions in the pathology of MDD, suggesting a potential marker of disease progression in MDD.

Peripheral blood GILZ mRNA levels in depression and following electroconvulsive therapy

Dysregulation of the hypothalamic-pituitary-adrenocortical (HPA)-axis is commonly observed in patients with depression. The delayed feedback system that mediates inhibition of HPA-axis activation is regulated by glucocorticoid receptors (GRs) found in stress-responsive areas of the brain. Glucocorticoid-induced leucine zipper (GILZ) is a key molecule in glucocorticoid biology and is thought to mediate the downstream anti-inflammatory effects of GRs. Previous reports suggest that GILZ levels are altered in the blood and brains of patients with, and animal models of, depression. However, no study has yet investigated the effects of antidepressant treatment on GILZ. Therefore, our aim was to examine peripheral blood GILZ mRNA levels in patients with depression (n = 88) compared to age- and sex-matched healthy controls (n = 63), and in patients with depression following treatment with a course of electroconvulsive therapy (ECT). We also assessed the relationship between GILZ and mood and clinical outcomes following ECT. GILZ mRNA levels were assessed using qRT-PCR. GILZ levels were found to be significantly lower in patients with depression compared to controls (p < 0.002), and ECT further decreased GILZ levels (p = 0.05). Both of these results survived adjustment for potential covariates. However, we found no association between GILZ and mood scores. Overall, these results suggest that GILZ is involved in the pathophysiology of depression and the peripheral molecular response to ECT.

JNK1 controls adult hippocampal neurogenesis and imposes cell-autonomous control of anxiety behaviour from the neurogenic niche

Promoting adult hippocampal neurogenesis is expected to induce neuroplastic changes that improve mood and alleviate anxiety. However, the underlying mechanisms remain largely unknown and the hypothesis itself is controversial. Here we show that mice lacking Jnk1, or c-Jun N-terminal kinase (JNK) inhibitor-treated mice, display increased neurogenesis in adult hippocampus characterized by enhanced cell proliferation and survival, and increased maturation in the ventral region. Correspondingly, anxiety behaviour is reduced in a battery of tests, except when neurogenesis is prevented by AraC treatment. Using engineered retroviruses, we show that exclusive inhibition of JNK in adult-born granule cells alleviates anxiety and reduces depressive-like behaviour. These data validate the neurogenesis hypothesis of anxiety. Moreover, they establish a causal role for JNK in the hippocampal neurogenic niche and anxiety behaviour, and advocate targeting of JNK as an avenue for novel therapies against affective disorders.

The FKBP51 Glucocorticoid Receptor Co-Chaperone: Regulation, Function, and Implications in Health and Disease

Among the chaperones and co-chaperones regulating the glucocorticoid receptor (GR), FK506 binding protein (FKBP) 51 is the most intensely investigated across different disciplines. This review provides an update on the role of the different co-chaperones of Hsp70 and Hsp90 in the regulation of GR function. The development leading to the focus on FKBP51 is outlined. Further, a survey of the vast literature on the mechanism and function of FKBP51 is provided. This includes its structure and biochemical function, its regulation on different levels—transcription, post-transcription, and post-translation—and its function in signaling pathways. The evidence portraying FKBP51 as a scaffolding protein organizing protein complexes rather than a chaperone contributing to the folding of individual proteins is collated. Finally, FKBP51’s involvement in physiology and disease is outlined, and the promising efforts in developing drugs targeting FKBP51 are discussed.

Glucocorticoid-induced leucine zipper (GILZ) is involved in glucocorticoid-induced and mineralocorticoid-induced leptin production by osteoarthritis synovial fibroblasts

Background

Glucocorticoid-induced leucine zipper (GILZ) is a mediator of the anti-inflammatory activities of glucocorticoids. However, GILZ deletion does not impair the anti-inflammatory activities of exogenous glucocorticoids in mice arthritis models and GILZ could also mediate some glucocorticoid-related adverse events. Osteoarthritis (OA) is a metabolic disorder that is partly attributed to adipokines such as leptin, and we previously observed that glucocorticoids induced leptin secretion in OA synovial fibroblasts. The purpose of this study was to position GILZ in OA through its involvement in the anti-inflammatory activities of glucocorticoids and/or in the metabolic pathway of leptin induction. The influences of mineralocorticoids on GILZ and leptin expression were also investigated.

Methods

Human synovial fibroblasts were isolated from OA patients during knee replacement surgery. Then, the cells were treated with a glucocorticoid (prednisolone), a mineralocorticoid (aldosterone), a glucocorticoid receptor (GR) antagonist (mifepristone), a selective glucocorticoid receptor agonist (Compound A), mineralocorticoid receptor (MR) antagonists (eplerenone and spironolactone), TNF-α or transforming growth factor (TGF)-β. Cells were transfected with shRNA lentiviruses for the silencing of GILZ and GR. The leptin, IL-6, IL-8 and matrix metalloproteinase (MMP)-1 levels were measured by ELISA. Leptin, the leptin receptor (Ob-R), GR and GILZ expression levels were analyzed by western blotting and/or RT-qPCR.

Results

(1) The glucocorticoid prednisolone and the mineralocorticoid aldosterone induced GILZ expression dose-dependently in OA synovial fibroblasts, through GR but not MR. Similar effects on leptin and Ob-R were observed: leptin secretion and Ob-R expression were also induced by prednisolone and aldosterone through GR; (2) GILZ silencing experiments demonstrated that GILZ was involved in the glucocorticoid-induced and mineralocorticoid-induced leptin secretion and Ob-R expression in OA synovial fibroblasts; and (3) GILZ inhibition did not alter the production of pro-inflammatory cytokines by OA synovial fibroblast or the anti-inflammatory properties of glucocorticoids.

Conclusions

The absence of GILZ prevents corticoid-induced leptin and Ob-R expression without affecting the anti-inflammatory properties of glucocorticoids in OA synovial fibroblasts. Mineralocorticoids also induce leptin and Ob-R expression through GILZ.

Genetic Moderation of Stress Effects on Corticolimbic Circuitry

Stress exposure is associated with individual differences in corticolimbic structure and function that often mirror patterns observed in psychopathology. Gene x environment interaction research suggests that genetic variation moderates the impact of stress on risk for psychopathology. On the basis of these findings, imaging genetics, which attempts to link variability in DNA sequence and structure to neural phenotypes, has begun to incorporate measures of the environment. This research paradigm, known as imaging gene x environment interaction (iGxE), is beginning to contribute to our understanding of the neural mechanisms through which genetic variation and stress increase psychopathology risk. Although awaiting replication, evidence suggests that genetic variation within the canonical neuroendocrine stress hormone system, the hypothalamic-pituitary-adrenal axis, contributes to variability in stress-related corticolimbic structure and function, which, in turn, confers risk for psychopathology. For iGxE research to reach its full potential it will have to address many challenges, of which we discuss: (i) small effects, (ii) measuring the environment and neural phenotypes, (iii) the absence of detailed mechanisms, and (iv) incorporating development. By actively addressing these challenges, iGxE research is poised to help identify the neural mechanisms underlying genetic and environmental associations with psychopathology.

Peripheral telomere length and hippocampal volume in adolescents with major depressive disorder

Several studies have reported that adults with major depressive disorder have shorter telomere length and reduced hippocampal volumes. Moreover, studies of adult populations without major depressive disorder suggest a relationship between peripheral telomere length and hippocampal volume. However, the relationship of these findings in adolescents with major depressive disorder has yet to be explored. We examined whether adolescent major depressive disorder is associated with altered peripheral telomere length and hippocampal volume, and whether these measures relate to one another. In 54 unmedicated adolescents (13-18 years) with major depressive disorder and 63 well-matched healthy controls, telomere length was assessed from saliva using quantitative polymerase chain reaction methods, and bilateral hippocampal volumes were measured with magnetic resonance imaging. After adjusting for age and sex (and total brain volume in the hippocampal analysis), adolescents with major depressive disorder exhibited significantly shorter telomere length and significantly smaller right, but not left hippocampal volume. When corrected for age, sex, diagnostic group and total brain volume, telomere length was not significantly associated with left or right hippocampal volume, suggesting that these cellular and neural processes may be mechanistically distinct during adolescence. Our findings suggest that shortening of telomere length and reduction of hippocampal volume are already present in early-onset major depressive disorder and thus unlikely to be only a result of accumulated years of exposure to major depressive disorder.