Adrenal glucocorticoid hormones are crucial for maintenance of homeostasis and adaptation to stress. They act via the mineralocorticoid receptors (MRs) and glucocorticoid receptors (GRs)—members of the family of nuclear receptors. MRs and GRs can mediate distinct, sometimes opposite, effects of glucocorticoids. Both receptor types can mediate nongenomic steroid effects, but they are best understood as ligand-activated transcription factors. MR and GR protein structure is similar; the receptors can form heterodimers on the DNA at glucocorticoid response elements (GREs), and they share a number of target genes. The transcriptional basis for opposite effects on cellular physiology remains largely unknown, in particular with respect to MR-selective gene transcription. In this review, we discuss proven and potential mechanisms of transcriptional specificity for MRs and GRs. These include unique GR binding to “negative GREs,” direct binding to other transcription factors, and binding to specific DNA sequences in conjunction with other transcription factors, as is the case for MRs and NeuroD proteins in the brain. MR- and GR-specific effects may also depend on specific interactions with transcriptional coregulators, downstream mediators of transcriptional receptor activity. Current data suggest that the relative importance of these mechanisms depends on the tissue and physiological context. Insight into these processes may not only allow a better understanding of homeostatic regulation but also the development of drugs that target specific aspects of disease.

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.

Background: Synthetic glucocorticoids like dexamethasone can cause severe neuropsychiatric effects. They preferentially bind to the glucocorticoid receptor (GR) over the mineralocorticoid receptor (MR). High dosages result in strong GR activation, but likely also lower MR activation based on GR-mediated negative feedback on cortisol levels. Therefore, reduced MR activity may contribute to dexamethasone-induced neuropsychiatric symptoms. Objective: In this single case study, we evaluate whether dexamethasone leads to reduced MR activation in the human brain. Brain tissue of an 8-year-old brain tumor patient was used, who suffered chronically from dexamethasone-induced neuropsychiatric symptoms and deceased only hours after a high dose of dexamethasone. Main outcome measures: The efficacy of dexamethasone to induce MR activity was determined in HEK293T cells using a reporter construct. Subcellular localization of GR and MR was assessed in paraffin embedded hippocampal tissue from the patient and 2 controls. In hippocampal tissue from the patient and 8 controls, mRNA of MR/GR target genes was measured. Results: In vitro, dexamethasone stimulated MR with low efficacy and low potency. Immunofluorescence showed the presence of both GR and MR in the hippocampal cell nuclei after dexamethasone exposure. The putative MR target gene JDP2 was consistently expressed at relatively low levels in the dexamethasone-treated brain samples. Gene expression showed substantial variation in MR/GR target gene expression in two different hippocampus tissue blocks from the same patient. Conclusions: Dexamethasone may induce MR nuclear translocation in human brain. Conclusions on in vivo effects on gene expression in the brain await the availability of more tissue of dexamethasone-treated patients.

IntroductionThe synthetic glucocorticoid dexamethasone can induce serious neuropsychiatric adverse effects. Dexamethasone activates the glucocorticoid receptor (GR) but, unlike endogenous cortisol, not the mineralocorticoid receptor (MR). Moreover, dexamethasone suppresses cortisol production, thereby eliminating its MR binding. Consequently, GR overactivation combined with MR underactivation may contribute to the neuropsychiatric adverse effects of dexamethasone. The DEXA-CORT trial aims to reactivate the MR using cortisol to reduce neuropsychiatric adverse effects of dexamethasone treatment.Methods and analysisThe DEXA-CORT study is a multicentre, randomised, double-blind, placebo-controlled trial in adult patients who undergo elective brain tumour resection treated perioperatively with high doses of dexamethasone to minimise cerebral oedema. 180 patients are randomised between treatment with either two times per day 10 mg hydrocortisone or placebo during dexamethasone treatment. The primary study outcome is the difference in proportion of patients scoring ≥3 points on at least one of the Brief Psychiatric Rating Scale (BPRS) questions 5 days postoperatively or earlier at discharge. Secondary outcomes are neuropsychiatric symptoms, quality of sleep, health-related quality of life and neurocognitive functioning at several time points postoperatively. Furthermore, neuropsychiatric history, serious adverse events, prescribed (psychiatric) medication and referrals or evaluations of psychiatrist/psychologist and laboratory measurements are assessed.Ethics and disseminationThe study protocol has been approved by the Medical Research Ethics Committee of the Leiden University Medical Center, and by the Dutch competent authority, and by the Institutional Review Boards of the participating sites. It is an investigator-initiated study with financial support by The Netherlands Organisation for Health Research and Development (ZonMw) and the Dutch Brain Foundation. Results of the study will be submitted for publication in a peer-reviewed journal.Trial registration numberNL6726 (Netherlands Trial Register); open for patient inclusion. EudraCT number 2017-003705-17.

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