Gene expression changes in the brain of a Cushing's syndrome mouse model

The Selective Glucocorticoid Receptor Modulator Cort125329 Decreases Neuroinflammation and Gliosis and Enhances Myelination in the Wobbler Model of Amyotrophic Lateral Sclerosis

The Wobbler mouse is a genetic model of familial amyotrophic lateral sclerosis. Wobblers show spinal cord neurodegeneration associated with gliosis, neuroinflammation, and demyelination. Like human neurodegenerative diseases, Wobblers show high levels of corticosterone in the blood and the nervous system. The role of glucocorticoids in neuropathology is suggested by the observation that pathological signs attenuate with treatment with glucocorticoid receptor (GR) antagonists/modulators. In the present study, we demonstrated in 5-month-old clinically afflicted Wobbler mice that the selective GR modulator CORT125329 decreased motoneuron degeneration, astro- and microgliosis, and levels of pro-inflammatory factors (HMGB1, toll-like receptor 4, tumor necrosis factor α, and its receptor). In addition, CORT125329 increased the acetylcholine-producing enzyme choline acetyltransferase, the neurotrophin brain-derived neurotrophic factor, and their cellular colocalization. Furthermore, the increased oligodendrocyte number and a healthier myelin ultrastructure are consistent with the enhanced axonal myelination after CORT125329 treatment. Finally, the high expression of immunoreactive protein and mRNA levels of aquaporin4 in Wobblers was decreased by CORT125329 treatment, implying this water channel is a glucocorticoid target involved in neuropathology. The beneficial effects of CORT125329 correlated with enhanced motor behavioral performance and trophic changes of the forelimbs. In conclusion, our results support further preclinical and clinical studies on GR modulators in sporadic amyotrophic lateral sclerosis.

Neurochemical Anatomy of Cushing's Syndrome

The neurochemical anatomy underlying Cushing's syndrome is examined for regional brain metabolism as well as neurotransmitter levels and receptor binding of biogenic amines and amino acids. Preliminary studies generally indicate that glucose uptake, blood flow, and activation on fMRI scans decreased in neocortical areas and increased in subcortical areas of patients with Cushing's syndrome or disease. Glucocorticoid-mediated increases in hippocampal metabolism occurred despite in vitro evidence of glucocorticoid-induced decreases in glucose uptake or consumption, indicating that in vivo increases are the result of indirect, compensatory, or preliminary responses. In animal studies, glucocorticoid administration decreased 5HT levels and 5HT1A receptor binding in several brain regions while adrenalectomy increased such binding. Region-specific effects were also obtained in regard to the dopaminergic system, with predominant actions of glucocorticoid-induced potentiation of reuptake blockers and releasing agents. More in-depth neuroanatomical analyses are warranted of these and amino acid-related neurotransmission.

Neuropsychiatric Adverse Effects of Synthetic Glucocorticoids: A Systematic Review and Meta-Analysis

CONTEXT

Synthetic glucocorticoids are widely used to treat patients with a broad range of diseases. While efficacious, glucocorticoids can be accompanied by neuropsychiatric adverse effects.

OBJECTIVE

This systematic review and meta-analysis assesses and quantifies the proportion of different neuropsychiatric adverse effects in patients using synthetic glucocorticoids.

METHODS

Six electronic databases were searched to identify potentially relevant studies. Randomized controlled trials, cohort studies, and cross-sectional studies assessing psychiatric side effects of glucocorticoids measured with validated questionnaires were eligible. Risk of bias was assessed with RoB 2, ROBINS-I, and AXIS appraisal tool. For proportions of neuropsychiatric outcomes, we pooled proportions, and when possible, differences in questionnaire scores between glucocorticoid users and nonusers were expressed as standardized mean differences (SMD). Data were pooled in a random-effects logistic regression model.

RESULTS

We included 49 studies with heterogeneity in study populations, type, dose, and duration of glucocorticoids. For glucocorticoid users, meta-analysis showed a proportion of 22% for depression (95% CI, 14%-33%), 11% for mania (2%-46%), 8% for anxiety (2%-25%), 16% for delirium (6%-36%), and 52% for behavioral changes (42%-61%). Questionnaire scores for depression (SMD of 0.80 [95% CI 0.35-1.26]), and mania (0.78 [0.14-1.42]) were higher than in controls, indicating more depressive and manic symptoms following glucocorticoid use.

CONCLUSION

The heterogeneity of glucocorticoid use is reflected in the available studies. Despite this heterogeneity, the proportion of neuropsychiatric adverse effects in glucocorticoid users is high. The most substantial associations with glucocorticoid use were found for depression and mania. Upon starting glucocorticoid treatment, awareness of possible psychiatric side effects is essential. More structured studies on incidence and potential pathways of neuropsychiatric side effects of prescribed glucocorticoids are clearly needed.

Restricted effects of androgens on glucocorticoid signaling in the mouse prefrontal cortex and midbrain

Glucocorticoids are key executors of the physiological response to stress. Previous studies in mice showed that the androgen receptor (AR) influenced the transcriptional outcome of glucocorticoid treatment in white and brown adipocytes and in the liver. In the brain, we observed that chronic hypercorticism induced changes in gene expression that tended to be more pronounced in male mice. In the present study, we investigated if glucocorticoid signaling in the brain could be modulated by androgen. After chronic treatment with corticosterone, dihydrotestosterone, a combination of both, and corticosterone in combination with the AR antagonist enzalutamide, we compared the expression of glucocorticoid receptor (NR3C1, also abbreviated GR) target genes in brain regions where AR and GR are co-expressed, namely: prefrontal cortex, hypothalamus, hippocampus, ventral tegmental area and substantia nigra. We observed that androgen affected glucocorticoid signaling only in the prefrontal cortex and the substantia nigra. Dihydrotestosterone and corticosterone independently and inversely regulated expression of Sgk1 and Tsc22d3 in prefrontal cortex. AR antagonism with enzalutamide attenuated corticosterone-induced expression of Fkbp5 in the prefrontal cortex and of Fkbp5 and Sgk1 in the substantia nigra. Additionally, in the substantia nigra, AR antagonism increased expression of Th and Slc18a1, two genes coding for key components of the dopaminergic system. Our data indicate that androgen influence over glucocorticoid stimulation in the brain is not a dominant phenomenon in the context of high corticosterone levels, but can occur in the prefrontal cortex and substantia nigra.

Reversibility of Impaired Large-Scale Functional Brain Networks in Cushing's Disease after Surgery Treatment: A Longitudinal Study

INTRODUCTION

Chronic exposure to excessive endogenous cortisol leads to brain changes in Cushing's disease (CD). However, it remains unclear how CD affects large-scale functional networks (FNs) and whether these effects are reversible after treatment. This study aimed to investigate functional network changes of CD patients and their reversibility in a longitudinal cohort.

METHODS

Active CD patients (N = 37) were treated by transsphenoidal pituitary surgery and reexamined 3 months later. FNs were computed from resting-state fMRI data of the CD patients and matched normal controls (NCs, N = 37). A pattern classifier was built on the FNs to distinguish active CD patients from controls and applied to FNs of the CD patients at the 3-month follow-up. Two subgroups of endocrine-remitted CD patients were identified according to their classification scores, referred to as image-based phenotypically (IBP) recovered and unrecovered CD patients, respectively. The informative FNs identified by the classification model were compared between NCs, active CD patients, and endocrine-remitted patients as well as between IBP recovered and unrecovered CD patients to explore their functional network reversibility.

RESULTS

All 37 CD patients reached endocrine remission after treatment. The classification model identified three informative FNs, including cerebellar network (CerebN), fronto-parietal network (FPN), and default mode network. Among them, CerebN and FPN partially recovered toward normal at 3 months after treatment. Moreover, the informative FNs were correlated with 24-h urinary-free cortisol and emotion scales in CD patients.

CONCLUSION

These findings suggest that CD patients have aberrant FNs that are partially reversible toward normal after treatment.

Transcriptional glucocorticoid effects in the brain: Finding the relevant target genes

Glucocorticoids are powerful modulators of brain function. They act via mineralocorticoid and glucocorticoid receptors (MR and GR). These are best understood as transcription factors. Although many glucocorticoid effects depend on the modulation of gene transcription, it is a major challenge to link gene expression to function given the large-scale, apparently pleiotropic genomic responses. The extensive sets of MR and GR target genes are highly specific per cell type, and the brain contains many different (neuronal and non-neuronal) cell types. Next to the set "trait" of cellular context, the "state" of other active signaling pathways will affect MR and GR transcriptional activity. Here, we discuss receptor specificity and contextual factors that determine the transcriptional outcome of MR/GR signaling, experimental possibilities offered by single-cell transcriptomics approaches, and reflect on how to make sense of lists of target genes in relation to understanding the functional effects of steroid receptor activation.

Animal Models of Cushing's Syndrome

Endogenous Cushing's syndrome is characterized by unique clinical features and comorbidities, and progress in the analysis of its genetic pathogenesis has been achieved. Moreover, prescribed glucocorticoids are also associated with exogenous Cushing's syndrome. Several animal models have been established to explore the pathophysiology and develop treatments for Cushing's syndrome. Here, we review recent studies reporting animal models of Cushing's syndrome with different features and complications induced by glucocorticoid excess. Exogenous corticosterone (CORT) administration in drinking water is widely utilized, and we found that CORT pellet implantation in mice successfully leads to a Cushing's phenotype. Corticotropin-releasing hormone overexpression mice and adrenal-specific Prkar1a-deficient mice have been developed, and AtT20 transplantation methods have been designed to examine the medical treatments for adrenocorticotropic hormone-producing pituitary neuroendocrine tumors. We also review recent advances in the molecular pathogenesis of glucocorticoid-induced complications using animal models.

Structural and functional brain alterations in Cushing's disease: A narrative review

Neurocognitive and psychiatric symptoms are non-negligible in Cushing's disease and are accompanied by structural and functional alterations of the brain. In this review, we have summarized multimodal neuroimaging and neurophysiological studies to highlight the current and historical understandings of the structural and functional brain alterations in Cushing's disease. Specifically, structural studies showed atrophy of the gray matter, loss of white matter integrity, and demyelination in widespread brain regions. Functional imaging studies have identified three major functional brain connectome networks influenced by hypercortisolemia: the limbic network, the default mode network, and the executive control network. After endocrinological remission, atrophy of gray matter regions and the compromised functional network activities were partially reversible, and the widespread white matter integrity alterations cannot recover in years. In conclusion, Cushing's disease patients display structural and functional brain connectomic alterations, which provides insights into the neurocognitive and psychiatric symptoms observed in this disease.