Cardiac GR Mediates the Diurnal Rhythm in Ventricular Arrhythmia Susceptibility

RATIONALE

Ventricular arrhythmias (VAs) demonstrate a prominent day-night rhythm, commonly presenting in the early morning. Transcriptional rhythms in cardiac ion channels accompany this phenomenon, but their role in the morning vulnerability to VAs and the underlying mechanisms are not understood.

OBJECTIVE

The objectives are to investigate the recruitment of transcription factors to time-of-day differentially accessible chromatin that underpins day-night ion channel rhythms and to assess the significance of this for the heart's day-night rhythm in VA susceptibility.

METHODS AND RESULTS

Assay for transposase-accessible chromatin with sequencing performed in mouse ventricular myocyte nuclei at the beginning of the inactive (zeitgeber time, time of lights on, start of sleep period) and active (time of lights off, start of awake period [ZT12]) periods revealed differentially accessible chromatin sites annotating to rhythmically transcribed ion channels and transcription factor binding motifs in these regions. Notably, motif enrichment for the glucocorticoid receptor (GR; transcriptional effector of corticosteroid signaling) binding site in open chromatin profiles at ZT12 was observed, in line with the well-recognized ZT12 peak in circulating corticosteroids. Molecular, electrophysiological, and in silico biophysically detailed modeling approaches demonstrated GR-mediated transcriptional control of ion channels (including Scn5a underlying the cardiac Na+ current, Kcnh2 underlying the rapid delayed rectifier K+ current, and Gja1 responsible for electrical coupling) and their contribution to the day-night rhythm in the vulnerability to VA. Strikingly, both pharmacological block of GR and cardiomyocyte-specific genetic knockout of GR blunted or abolished ion channel expression rhythms and abolished the ZT12 susceptibility to pacing-induced VA in isolated hearts.

CONCLUSIONS

Our study registers a day-night rhythm in chromatin accessibility that accompanies diurnal cycles in ventricular myocytes. Our approaches directly implicate the cardiac GR in the myocyte excitability rhythm and mechanistically link the ZT12 surge in glucocorticoids to intrinsic VA propensity at this time.

Imbalanced glucocorticoid and mineralocorticoid stress hormone receptor function has sex-dependent and independent regulatory effects in the mouse hippocampus

Many stress-related neuropsychiatric disorders display pronounced sex differences in their frequency and clinical symptoms. Glucocorticoids are primary stress hormones that have been implicated in the development of these disorders but whether they contribute to the observed sex bias is poorly understood. Glucocorticoids signal through two closely related nuclear receptors, the glucocorticoid (GR) and mineralocorticoid receptor (MR). To elucidate the sex-specific and independent actions of glucocorticoids in the hippocampus, we developed knockout mice lacking hippocampal GR, MR, or both GR and MR. Mice deficient in hippocampal MR or both GR and MR showed an altered molecular phenotype of CA2 neurons and reduced anxiety-like behavior in both sexes, but altered stress adaptation behavior only in females and enhanced fear-motivated cue learning only in males. All three knockout mouse models displayed reduced sociability but only in male mice. Male and female mice deficient in both hippocampal GR and MR exhibited extensive neurodegeneration in the dentate gyrus. Global transcriptomic analysis revealed a marked expansion in the number of dysregulated genes in the hippocampus of female knockout mice compared to their male counterparts; however, the overall patterns of gene dysregulation were remarkably similar in both sexes. Within and across sex comparisons identified key GR and MR target genes and associated signaling pathways underlying the knockout phenotypes. These findings define major sex-dependent and independent effects of GR/MR imbalances on gene expression and functional profiles in the hippocampus and inform new strategies for treating men and women with stress-related neuropsychiatric disorders.

International Union of Basic and Clinical Pharmacology CXIII: Nuclear Receptor Superfamily-Update 2023

The NR superfamily comprises 48 transcription factors in humans that control a plethora of gene network programs involved in a wide range of physiologic processes. This review will summarize and discuss recent progress in NR biology and drug development derived from integrating various approaches, including biophysical techniques, structural studies, and translational investigation. We also highlight how defective NR signaling results in various diseases and disorders and how NRs can be targeted for therapeutic intervention via modulation via binding to synthetic lipophilic ligands. Furthermore, we also review recent studies that improved our understanding of NR structure and signaling. SIGNIFICANCE STATEMENT: Nuclear receptors (NRs) are ligand-regulated transcription factors that are critical regulators of myriad physiological processes. NRs serve as receptors for an array of drugs, and in this review, we provide an update on recent research into the roles of these drug targets.

Glucocorticoids regulate thrombopoiesis by remodeling the megakaryocyte transcriptome

BACKGROUND

Glucocorticoids are widely known for their immunomodulatory action. Their synthetic analogs are used to treat several autoimmune diseases, including immune thrombocytopenia. However, their efficacy and mechanisms of action in immune thrombocytopenia are not fully understood.

OBJECTIVES

To investigate the mechanism of glucocorticoid actions on platelet production.

METHODS

The actions of glucocorticoids on platelet production were studied combining in vivo, ex vivo and in vitro approaches.

RESULTS

Dexamethasone reduced bleeding in mice and rapidly increased circulating young platelet counts. In vitro glucocorticoid treatment stimulated proplatelet formation by megakaryocytes and platelet-like particle release. This effect was blocked by glucocorticoid receptor antagonist RU486, indicating a glucocorticoid receptor-dependent mechanism. Genome-wide analysis revealed that dexamethasone regulates the expression of >1000 genes related to numerous cellular functions, including predominant cytoplasm and cytoskeleton reorganization. Dexamethasone and other glucocorticoids induced the expression of Gda (the gene encoding guanine deaminase), which has been reported to have a role in dendrite development. Inhibition of guanine deaminase enzymatic activity blocked dexamethasone stimulation of proplatelet formation, implicating a critical role for this enzyme in glucocorticoid-mediated platelet production.

CONCLUSION

Our findings identify glucocorticoids as new regulators of thrombopoiesis.

Impaired glucocorticoid receptor function attenuates herpes simplex virus 1 production during explant-induced reactivation from latency in female mice

IMPORTANCE

A correlation exists between stress and increased episodes of human alpha-herpes virus 1 reactivation from latency. Stress increases corticosteroid levels; consequently, the glucocorticoid receptor (GR) is activated. Recent studies concluded that a GR agonist, but not an antagonist, accelerates productive infection and reactivation from latency. Furthermore, GR and certain stress-induced transcription factors cooperatively transactivate promoters that drive the expression of infected cell protein 0 (ICP0), ICP4, and VP16. This study revealed female mice expressing a GR containing a serine to alanine mutation at position 229 (GRS229A) shed significantly lower levels of infectious virus during explant-induced reactivation compared to male GRS229A or wild-type parental C57BL/6 mice. Furthermore, female GRS229A mice contained fewer VP16 + TG neurons compared to male GRS229A mice or wild-type mice during the early stages of explant-induced reactivation from latency. Collectively, these studies revealed that GR transcriptional activity has female-specific effects, whereas male mice can compensate for the loss of GR transcriptional activation.

The Concise Guide to PHARMACOLOGY 2023/24: Nuclear hormone receptors

The Concise Guide to PHARMACOLOGY 2023/24 is the sixth in this series of biennial publications. The Concise Guide provides concise overviews, mostly in tabular format, of the key properties of approximately 1800 drug targets, and nearly 6000 interactions with about 3900 ligands. There is an emphasis on selective pharmacology (where available), plus links to the open access knowledgebase source of drug targets and their ligands (https://www.guidetopharmacology.org/), which provides more detailed views of target and ligand properties. Although the Concise Guide constitutes almost 500 pages, the material presented is substantially reduced compared to information and links presented on the website. It provides a permanent, citable, point-in-time record that will survive database updates. The full contents of this section can be found at http://onlinelibrary.wiley.com/doi/10.1111/bph.16179. Nuclear hormone receptors are one of the six major pharmacological targets into which the Guide is divided, with the others being: G protein-coupled receptors, catalytic receptors, enzymes and transporters. These are presented with nomenclature guidance and summary information on the best available pharmacological tools, alongside key references and suggestions for further reading. The landscape format of the Concise Guide is designed to facilitate comparison of related targets from material contemporary to mid-2023, and supersedes data presented in the 2021/22, 2019/20, 2017/18, 2015/16 and 2013/14 Concise Guides and previous Guides to Receptors and Channels. It is produced in close conjunction with the Nomenclature and Standards Committee of the International Union of Basic and Clinical Pharmacology (NC-IUPHAR), therefore, providing official IUPHAR classification and nomenclature for human drug targets, where appropriate.

The Concise Guide to PHARMACOLOGY 2023/24: Introduction and Other Protein Targets

The Concise Guide to PHARMACOLOGY 2023/24 is the sixth in this series of biennial publications. The Concise Guide provides concise overviews, mostly in tabular format, of the key properties of approximately 1800 drug targets, and about 6000 interactions with about 3900 ligands. There is an emphasis on selective pharmacology (where available), plus links to the open access knowledgebase source of drug targets and their ligands (www.guidetopharmacology.org), which provides more detailed views of target and ligand properties. Although the Concise Guide constitutes almost 500 pages, the material presented is substantially reduced compared to information and links presented on the website. It provides a permanent, citable, point-in-time record that will survive database updates. The full contents of this section can be found at http://onlinelibrary.wiley.com/doi/10.1111/bph.16176. In addition to this overview, in which are identified 'Other protein targets' which fall outside of the subsequent categorisation, there are six areas of focus: G protein-coupled receptors, ion channels, nuclear hormone receptors, catalytic receptors, enzymes and transporters. These are presented with nomenclature guidance and summary information on the best available pharmacological tools, alongside key references and suggestions for further reading. The landscape format of the Concise Guide is designed to facilitate comparison of related targets from material contemporary to mid-2023, and supersedes data presented in the 2021/22, 2019/20, 2017/18, 2015/16 and 2013/14 Concise Guides and previous Guides to Receptors and Channels. It is produced in close conjunction with the Nomenclature and Standards Committee of the International Union of Basic and Clinical Pharmacology (NC-IUPHAR), therefore, providing official IUPHAR classification and nomenclature for human drug targets, where appropriate.

Adipocyte Glucocorticoid Receptor Inhibits Immune Regulatory Genes to Maintain Immune Cell Homeostasis in Adipose Tissue

Glucocorticoids acting via the glucocorticoid receptors (GR) are key regulators of metabolism and the stress response. However, uncontrolled or excessive GR signaling adversely affects adipose tissue, including endocrine, immune, and metabolic functions. Inflammation of the adipose tissue promotes systemic metabolic dysfunction; however, the molecular mechanisms underlying the role of adipocyte GR in regulating genes associated with adipose tissue inflammation are poorly understood. We performed in vivo studies using adipocyte-specific GR knockout mice in conjunction with in vitro studies to understand the contribution of adipocyte GR in regulating adipose tissue immune homeostasis. Our findings show that adipocyte-specific GR signaling regulates adipokines at both mRNA and plasma levels and immune regulatory (Coch, Pdcd1, Cemip, and Cxcr2) mRNA gene expression, which affects myeloid immune cell presence in white adipose tissue. We found that, in adipocytes, GR directly influences Cxcr2. This chemokine receptor promotes immune cell migration, indirectly affecting Pdcd1 and Cemip gene expression in nonadipocyte or stromal cells. Our findings suggest that GR adipocyte signaling suppresses inflammatory signals, maintaining immune homeostasis. We also found that GR signaling in adipose tissue in response to stress is sexually dimorphic. Understanding the molecular relationship between GR signaling and adipose tissue inflammation could help develop potential targets to improve local and systemic inflammation, insulin sensitivity, and metabolic health.

Glucocorticoid receptors drive breast cancer cell migration and metabolic reprograming via PDK4

Corticosteroids act on the glucocorticoid receptor (GR; NR3C1) to resolve inflammation and are routinely prescribed to breast cancer patients undergoing chemotherapy treatment to alleviate side effects. Triple negative breast cancers (TNBCs) account for 15-20% of diagnoses and lack expression of estrogen and progesterone receptors as well as amplified HER2, but often express high GR levels. GR is a mediator of TNBC progression to advanced metastatic disease, however the mechanisms underpinning this transition to more aggressive behavior remain elusive. We previously showed that tissue/cellular stress (hypoxia, chemotherapies) as well as factors in the tumor microenvironment (TGFβ, HGF) activate p38 MAPK, which phosphorylates GR on Ser134. In the absence of ligand, p-Ser134-GR further upregulates genes important for responses to cellular stress, including key components of the p38 MAPK pathway. Herein, we show that p-Ser134-GR is required for TNBC metastatic colonization to the lungs of female mice. To understand the mechanisms of p-Ser134-GR action in the presence of GR agonists, we examined glucocorticoid-driven transcriptomes in CRISPR knock-in models of TNBC cells expressing wild-type or phospho-mutant (S134A) GR. We identified dexamethasone- and p-Ser134-GR-dependent regulation of specific gene sets controlling TNBC migration (NEDD9, CSF1, RUNX3) and metabolic adaptation (PDK4, PGK1, PFKFB4). TNBC cells harboring S134A-GR displayed metabolic reprogramming that was phenocopied by PDK4 knockdown. PDK4 knockdown or chemical inhibition also blocked cancer cell migration. Our results reveal a convergence of GR agonists (i.e., host stress) with cellular stress signaling whereby pSer134-GR critically regulates TNBC metabolism, an exploitable target for the treatment of this deadly disease.

Apoptotic cell death in disease-Current understanding of the NCCD 2023

Apoptosis is a form of regulated cell death (RCD) that involves proteases of the caspase family. Pharmacological and genetic strategies that experimentally inhibit or delay apoptosis in mammalian systems have elucidated the key contribution of this process not only to (post-)embryonic development and adult tissue homeostasis, but also to the etiology of multiple human disorders. Consistent with this notion, while defects in the molecular machinery for apoptotic cell death impair organismal development and promote oncogenesis, the unwarranted activation of apoptosis promotes cell loss and tissue damage in the context of various neurological, cardiovascular, renal, hepatic, infectious, neoplastic and inflammatory conditions. Here, the Nomenclature Committee on Cell Death (NCCD) gathered to critically summarize an abundant pre-clinical literature mechanistically linking the core apoptotic apparatus to organismal homeostasis in the context of disease.

Case report: Changes in the levels of stress hormones during Takotsubo syndrome

Background

Takotsubo syndrome is an acute cardiac condition usually involving abnormal regional left ventricular wall motion and impaired left ventricular contractility. It is due mainly to hyper-stimulation of the sympathetic nerve system, inducing an excess of catecholamines, usually triggered by intense psychological or physiological stress. The relationship between Takotsubo syndrome and the circulating stress hormones cortisol and copeptin (a surrogate marker of arginine vasopressin) has not been well documented.

Case summary

Here, we describe the dynamic changes in circulating cortisol and copeptin during an entire episode of Takotsubo syndrome in a post-partum woman after spontaneous vaginal delivery. The patient was diagnosed with inverted Takotsubo syndrome accompanied by HELLP syndrome. We found qualitative and quantitative changes in cortisol: a loss of circadian rhythm and a three-fold elevation in the plasma concentration of the hormone with a peak appearing several hours before circulating cardiac biomarkers began to rise. By contrast, levels of copeptin remained normal during the entire episode.

Discussion

Our findings indicate that the levels of cortisol change during Takotsubo syndrome whereas those of copeptin do not. This association between elevated cortisol and Takotsubo syndrome suggests that aberrant levels of this stress hormone may contribute to the observed cardiac pathology. We conclude that biochemical assays of circulating cortisol and cardiac biomarkers may be a useful complement to the diagnosis of Takotsubo syndrome by non-invasive cardiac imaging.

Chronic restraint stress produces sex-specific behavioral and molecular outcomes in the dorsal and ventral rat hippocampus

Stress-related disorders display differences at multiple levels according to sex. While most studies have been conducted in male rodents, less is known about comparable outcomes in females. In this study, we found that the chronic restraint stress model (2.5 h/day for 14 days) triggers different somatic responses in male and female adult rats. Chronic restraint produced a loss in sucrose preference and novel location preference in male rats. However, chronic restraint failed to produce loss of sucrose preference in females, while it improved spatial performance. We then characterized the molecular responses associated with these behaviors in the hippocampus, comparing the dorsal and ventral poles. Notably, sex- and hippocampal pole-specific transcriptional signatures were observed, along with a significant concordance between the female ventral and male dorsal profiles. Functional enrichment analysis revealed both shared and specific terms associated with each pole and sex. By looking into signaling pathways that were associated with these terms, we found an ample array of sex differences in the dorsal and, to a lesser extent, in the ventral hippocampus. These differences were mainly present in synaptic TrkB signaling, Akt pathway, and glutamatergic receptors. Unexpectedly, the effects of stress on these pathways were rather minimal and mostly dissociated from the sex-specific behavioral outcomes. Our study suggests that female rats are resilient and males susceptible to the restraint stress exposure in the sucrose preference and object location tests, while the activity of canonical signaling pathways is primarily determined by sex rather than stress in the dorsal and ventral hippocampus.

Intestinal epithelial glucocorticoid receptor promotes chronic inflammation-associated colorectal cancer

Synthetic immunosuppressive glucocorticoids (GCs) are widely used to control inflammatory bowel disease (IBD). However, the impact of GC signaling on intestinal tumorigenesis remains controversial. Here, we report that intestinal epithelial GC receptor (GR), but not whole intestinal tissue GR, promoted chronic intestinal inflammation-associated colorectal cancer in both humans and mice. In patients with colorectal cancer, GR was enriched in intestinal epithelial cells and high epithelial cell GR levels were associated with poor prognosis. Consistently, intestinal epithelium–specific deletion of GR (GR iKO) in mice increased macrophage infiltration, improved tissue recovery, and enhanced antitumor response in a chronic inflammation–associated colorectal cancer model. Consequently, GR iKO mice developed fewer and less advanced tumors than control mice. Furthermore, oral GC administration in the early phase of tissue injury delayed recovery and accelerated the formation of aggressive colorectal cancers. Our study reveals that intestinal epithelial GR signaling repressed acute colitis but promoted chronic inflammation–associated colorectal cancer. Our study suggests that colorectal epithelial GR could serve as a predictive marker for colorectal cancer risk and prognosis. Our findings further suggest that, although synthetic GC treatment for IBD should be used with caution, there is a therapeutic window for GC therapy during colorectal cancer development in immunocompetent patients.

THE CONCISE GUIDE TO PHARMACOLOGY 2021/22: Introduction and Other Protein Targets

The Concise Guide to PHARMACOLOGY 2021/22 is the fifth in this series of biennial publications. The Concise Guide provides concise overviews, mostly in tabular format, of the key properties of nearly 1900 human drug targets with an emphasis on selective pharmacology (where available), plus links to the open access knowledgebase source of drug targets and their ligands (www.guidetopharmacology.org), which provides more detailed views of target and ligand properties. Although the Concise Guide constitutes over 500 pages, the material presented is substantially reduced compared to information and links presented on the website. It provides a permanent, citable, point‐in‐time record that will survive database updates. The full contents of this section can be found at http://onlinelibrary.wiley.com/doi/bph.15537. In addition to this overview, in which are identified ‘Other protein targets’ which fall outside of the subsequent categorisation, there are six areas of focus: G protein‐coupled receptors, ion channels, nuclear hormone receptors, catalytic receptors, enzymes and transporters. These are presented with nomenclature guidance and summary information on the best available pharmacological tools, alongside key references and suggestions for further reading. The landscape format of the Concise Guide is designed to facilitate comparison of related targets from material contemporary to mid‐2021, and supersedes data presented in the 2019/20, 2017/18, 2015/16 and 2013/14 Concise Guides and previous Guides to Receptors and Channels. It is produced in close conjunction with the Nomenclature and Standards Committee of the International Union of Basic and Clinical Pharmacology (NC‐IUPHAR), therefore, providing official IUPHAR classification and nomenclature for human drug targets, where appropriate.

THE CONCISE GUIDE TO PHARMACOLOGY 2021/22: Nuclear hormone receptors

The Concise Guide to PHARMACOLOGY 2021/22 is the fifth in this series of biennial publications. The Concise Guide provides concise overviews, mostly in tabular format, of the key properties of nearly 1900 human drug targets with an emphasis on selective pharmacology (where available), plus links to the open access knowledgebase source of drug targets and their ligands (www.guidetopharmacology.org), which provides more detailed views of target and ligand properties. Although the Concise Guide constitutes over 500 pages, the material presented is substantially reduced compared to information and links presented on the website. It provides a permanent, citable, point‐in‐time record that will survive database updates. The full contents of this section can be found at http://onlinelibrary.wiley.com/doi/bph.15540. Nuclear hormone receptors are one of the six major pharmacological targets into which the Guide is divided, with the others being: G protein‐coupled receptors, catalytic receptors, enzymes and transporters. These are presented with nomenclature guidance and summary information on the best available pharmacological tools, alongside key references and suggestions for further reading. The landscape format of the Concise Guide is designed to facilitate comparison of related targets from material contemporary to mid‐2021, and supersedes data presented in the 2019/20, 2017/18, 2015/16 and 2013/14 Concise Guides and previous Guides to Receptors and Channels. It is produced in close conjunction with the Nomenclature and Standards Committee of the International Union of Basic and Clinical Pharmacology (NC‐IUPHAR), therefore, providing official IUPHAR classification and nomenclature for human drug targets, where appropriate.

Glucocorticoid Inhibition of Estrogen Regulation of the Serotonin Receptor 2B in Cardiomyocytes Exacerbates Cell Death in Hypoxia/Reoxygenation Injury

Background Stress has emerged as an important risk factor for heart disease in women. Stress levels have been shown to correlate with delayed recovery and increased mortality after a myocardial infarction. Therefore, we sought to investigate if the observed sex-specific effects of stress in myocardial infarction may be partly attributed to genomic interactions between the female sex hormones, estrogen (E2), and the primary stress hormones glucocorticoids. Methods and Results Genomewide studies show that glucocorticoids inhibit estrogen-mediated regulation of genes with established roles in cardiomyocyte homeostasis. These include 5-HT2BR (cardiac serotonin receptor 2B), the expression of which is critical to prevent cardiomyocyte death in the adult heart. Using siRNA, gene expression, and chromatin immunoprecipitation assays, we found that 5-HT2BR is a primary target of the glucocorticoid receptor and the estrogen receptor α at the level of transcription. The glucocorticoid receptor blocks the recruitment of estrogen receptor α to the promoter of the 5-HT2BR gene, which may contribute to the adverse effects of stress in the heart of premenopausal women. Using immunoblotting, TUNEL (terminal deoxynucleotidal transferase-mediated biotin-deoxyuridine triphosphate nick-end labeling), and flow cytometry, we demonstrate that estrogen decreases cardiomyocyte death by a mechanism relying on 5-HT2BR expression. In vitro and in vivo experiments show that glucocorticoids inhibit estrogen cardioprotection in response to hypoxia/reoxygenation injury and exacerbate the size of the infarct areas in myocardial infarction. Conclusions These results established a novel mechanism underlying the deleterious effects of stress on female cardiac health in the setting of ischemia/reperfusion.

Sex-Dependent Changes of miRNA Levels in the Hippocampus of Adrenalectomized Rats Following Acute Corticosterone Administration

We explored sex-biased effects of the primary stress glucocorticoid hormone corticosterone on the miRNA expression profile in the rat hippocampus. Adult adrenalectomized (ADX) female and male rats received a single corticosterone (10 mg/kg) or vehicle injection, and after 6 h, hippocampi were collected for miRNA, mRNA, and Western blot analyses. miRNA profiling microarrays showed a basal sex-biased miRNA profile in ADX rat hippocampi. Additionally, acute corticosterone administration triggered a sex-biased differential expression of miRNAs derived from genes located in several chromosomes and clusters on the X and 6 chromosomes. Putative promoter analysis unveiled that most corticosterone-responsive miRNA genes contained motifs for either direct or indirect glucocorticoid actions in both sexes. The evaluation of transcription factors indicated that almost 50% of miRNA genes sensitive to corticosterone in both sexes was under glucocorticoid receptor regulation. Transcription factor-miRNA regulatory network analyses identified several transcription factors that regulate, activate, or repress miRNA expression. Validated target mRNA analysis of corticosterone-responsive miRNAs showed a more complex miRNA-mRNA interaction network in males compared to females. Enrichment analysis revealed that several hippocampal-relevant pathways were affected in both sexes, such as neurogenesis and neurotrophin signaling. The evaluation of selected miRNA targets from these pathways displayed a strong sex difference in the hippocampus of ADX-vehicle rats. Corticosterone treatment did not change the levels of the miRNA targets and their corresponding tested proteins. Our data indicate that corticosterone exerts a sex-biased effect on hippocampal miRNA expression, which may engage in sculpting the basal sex differences observed at higher levels of hippocampal functioning.

Tristetraprolin Prevents Gastric Metaplasia in Mice by Suppressing Pathogenic Inflammation

BACKGROUND & AIMS

Aberrant immune activation is associated with numerous inflammatory and autoimmune diseases and contributes to cancer development and progression. Within the stomach, inflammation drives a well-established sequence from gastritis to metaplasia, eventually resulting in adenocarcinoma. Unfortunately, the processes that regulate gastric inflammation and prevent carcinogenesis remain unknown. Tristetraprolin (TTP) is an RNA-binding protein that promotes the turnover of numerous proinflammatory and oncogenic messenger RNAs. Here, we assess the role of TTP in regulating gastric inflammation and spasmolytic polypeptide-expressing metaplasia (SPEM) development.

METHODS

We used a TTP-overexpressing model, the TTPΔadenylate-uridylate rich element mouse, to examine whether TTP can protect the stomach from adrenalectomy (ADX)-induced gastric inflammation and SPEM.

RESULTS

We found that TTPΔadenylate-uridylate rich element mice were completely protected from ADX-induced gastric inflammation and SPEM. RNA sequencing 5 days after ADX showed that TTP overexpression suppressed the expression of genes associated with the innate immune response. Importantly, TTP overexpression did not protect from high-dose-tamoxifen-induced SPEM development, suggesting that protection in the ADX model is achieved primarily by suppressing inflammation. Finally, we show that protection from gastric inflammation was only partially due to the suppression of Tnf, a well-known TTP target.

CONCLUSIONS

Our results show that TTP exerts broad anti-inflammatory effects in the stomach and suggest that therapies that increase TTP expression may be effective treatments of proneoplastic gastric inflammation. Transcript profiling: GSE164349.

Glucocorticoids and Androgens Protect From Gastric Metaplasia by Suppressing Group 2 Innate Lymphoid Cell Activation

BACKGROUND & AIMS

The immune compartment is critical for maintaining tissue homeostasis. A weak immune response increases susceptibility to infection, but immune hyperactivation causes tissue damage, and chronic inflammation may lead to cancer development. In the stomach, inflammation damages the gastric glands and drives the development of potentially preneoplastic metaplasia. Glucocorticoids are potent anti-inflammatory steroid hormones that are required to suppress gastric inflammation and metaplasia. However, these hormones function differently in males and females. Here, we investigate the impact of sex on the regulation of gastric inflammation.

METHODS

Endogenous glucocorticoids and male sex hormones were removed from mice using adrenalectomy and castration, respectively. Mice were treated with 5α-dihydrotestosterone (DHT) to test the effects of androgens on regulating gastric inflammation. Single-cell RNA sequencing of gastric leukocytes was used to identify the leukocyte populations that were the direct targets of androgen signaling. Type 2 innate lymphoid cells (ILC2s) were depleted by treatment with CD90.2 antibodies.

RESULTS

We show that adrenalectomized female mice develop spontaneous gastric inflammation and spasmolytic polypeptide-expressing metaplasia (SPEM) but that the stomachs of adrenalectomized male mice remain quantitatively normal. Simultaneous depletion of glucocorticoids and sex hormones abolished the male-protective effects and triggered spontaneous pathogenic gastric inflammation and SPEM. Treatment of female mice with DHT prevented gastric inflammation and SPEM development when administered concurrent with adrenalectomy and also reversed the pathology when administered after disease onset. Single-cell RNAseq of gastric leukocytes revealed that ILC2s expressed abundant levels of both the glucocorticoid receptor (Gr) and androgen receptor (Ar). We demonstrated that DHT treatment potently suppressed the expression of the proinflammatory cytokines Il13 and Csf2 by ILC2s. Moreover, ILC2 depletion protected the stomach from SPEM development.

CONCLUSIONS

Here, we report a novel mechanism by which glucocorticoids and androgens exert overlapping effects to regulate gastric inflammation. Androgen signaling within ILC2s prevents their pathogenic activation by suppressing the transcription of proinflammatory cytokines. This work revealed a critical role for sex hormones in regulating gastric inflammation and metaplasia.

Combinatorial actions of glucocorticoid and mineralocorticoid stress hormone receptors are required for preventing neurodegeneration of the mouse hippocampus

Chronic stress contributes to numerous human pathologies including cognition impairments and psychiatric disorders. Glucocorticoids are primary stress hormones that activate two closely related nuclear receptors, the glucocorticoid (GR) and mineralocorticoid receptor (MR), that are both highly expressed in the hippocampus. To investigate potential combinatorial actions of hippocampal GR and MR, we developed mice with conditional knockout of both GR and MR in the hippocampus and compared them to their single knockout counterparts. Mice lacking MR alone or both GR and MR in the hippocampus exhibited altered expression of multiple CA2-specific neuronal markers and enhanced cue-dependent learning in a conditioned fear test. Provocatively, in contrast to the single knockouts, mice depleted of both GR and MR showed profound neurodegeneration of the hippocampus. Neuronal death was increased and neurogenesis was reduced in the dentate gyrus of the double knockout mice. Global gene expression assays of the knockout mice revealed a synergistic increase in the number of dysregulated genes in the hippocampus lacking both GR and MR. This large cohort of genes reliant on both GR and MR for expression was strongly associated with cell death and cell proliferation pathways. GR/MR complexes were detected in CA1 and dentate gyrus neurons suggesting receptor heterodimers contribute to the joint actions of GR and MR. These findings reveal an obligate role for MR signaling in regulating the molecular phenotype of CA2 neurons and demonstrate that combinatorial actions of GR and MR are essential for preserving dentate gyrus neurons and maintaining hippocampal health.

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New mouse model with double knockout of GR and MR in the hippocampus.

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Hippocampal MR signaling required for molecular phenotype of CA2 neurons.

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Combinatorial actions of hippocampal GR and MR prevent neurodegeneration.

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Large cohort of genes reliant on both hippocampal GR and MR for expression.

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GR/MR complexes detected in situ in CA1 and dentate gyrus neurons.

Glucocorticoids as Regulators of Macrophage-Mediated Tissue Homeostasis

Our immune system has evolved as a complex network of cells and tissues tasked with maintaining host homeostasis. This is evident during the inflammatory responses elicited during a microbial infection or traumatic tissue damage. These responses seek to eliminate foreign material or restore tissue integrity. Even during periods without explicit disturbances, the immune system plays prominent roles in tissue homeostasis. Perhaps one of the most studied cells in this regard is the macrophage. Tissue-resident macrophages are a heterogenous group of sensory cells that respond to a variety of environmental cues and are essential for organ function. Endogenously produced glucocorticoid hormones connect external environmental stress signals with the function of many cell types, producing profound changes in immune cells, including macrophages. Here, we review the current literature which demonstrates specific effects of glucocorticoids in several organ systems. We propose that tissue-resident macrophages, through glucocorticoid signaling, may play an underappreciated role as regulators of organ homeostasis.

Glucocorticoid Mediated Transcriptional Activity in Human Corneal Epithelial Cells Lacking the Glucocorticoid Receptor

The cornea is the dome-shaped transparent outermost layer of the eye, forming a physical barrier to protect the internal structures of the eye. Glucocorticoids are a mainstay in the treatment of ophthalmic diseases for their anti-inflammatory and anti-angiogenic properties. However, high doses or chronic use of glucocorticoid therapy can lead to vision-impairing effects such as increase in intraocular pressure and the formation of cataracts. The exact signaling pathways responsible for these undesirable effects of glucocorticoid use is poorly understood. One of the major molecular actions of glucocorticoids is to regulate transcription through its cognate nuclear receptor, the glucocorticoid receptor. We have previously reported the effect of glucocorticoids on global gene expression and their role in wound healing and barrier function in immortalized human corneal epithelial cells (HCE-T). In the current study, we knocked down glucocorticoid receptor using siRNA (GRKD) to determine the function of the glucocorticoid receptor in HCE-T cells. Successful knockdown of glucocorticoid receptor was confirmed by RT-PCR and immunoblot experiments. Genome-wide microarray analysis was performed and an FDR adjusted p value less than 0.01 was considered the cut off to create the list of differentially expressed genes (DEGs). Comparison of GRKD cells to HCE-T cells expressing endogenous glucocorticoid receptor (referred as NTC for No Target Control siRNA) revealed that expression of 2150 genes was altered in HCE-T cells when glucocorticoid receptor was knocked down, indicating that glucocorticoid receptor in corneal epithelial cells regulates a large cohort of genes. Inhibition of matrix metalloproteases, granulocyte adhesion and diapedesis, cyclins and cell cycle regulation were the top canonical pathways predicted by Ingenuity Pathway Analysis (IPA) to be altered in GRKD cells. In a 6-hour treatment with dexamethasone (Dex), a synthetic glucocorticoid, or with vehicle as a control, NTC cells had 2039 Dex-regulated genes, while Dex was still able to regulate 1087 genes in GRKD cells. Of these 1087 genes, 895 genes were uniquely regulated by Dex in GRKD cells suggesting that glucocorticoids might be signaling through another receptor in corneal epithelial cells. The top canonical pathways predicted to be altered by Dex in GRKD cells included PI3K/ATK Signaling, ERK5 Signaling, Prostrate Cancer Signaling, Aldosterone Signaling in Epithelial Cells, and PPAR signaling. These findings suggest that Dex could regulate large cohorts of genes through other nuclear receptors in corneal epithelial cells. Given the wide use of ophthalmic Dex in forms including eyedrops, ointments, gels, and implants, it is of clinical significance to understand the molecular actions of synthetic glucocorticoids since they appear to be ligands for multiple nuclear receptors in ocular cells and tissues.

The Impact of a Single Phosphorylation Site Mutation in the Glucocorticoid Receptor on the Molecular and Cellular Development of the Cerebral Cortex

Premature birth leads to a significant increase in adverse clinical outcomes, including Respiratory Distress Syndrome, Bronchopulmonary Dysplasia, Necrotizing Enterocolitis and Intraventricular Hemorrhage. Synthetic Glucocorticoids (sGC) are administered prenatally to pregnant mothers at risk to reduce the chance of these complications. However, there is a correlation between long-term neurological defects in the infant and the clinical use of sGC prenatally. The use of the sGCs have been linked to the development of cerebral palsy and deficits in attention and concentration. To investigate the cellular basis of these abnormalities, we examined the consequences of sGC administration of the developing murine brain. Our studies demonstrated that premature exposure to sGC alters neural stem cell biology and has long term consequences for adult behavior in mice. In humans, site-specific phosphorylation of the Glucocorticoid Receptor (GR) on Serine 211 versus Serine 226 is associated with activated or repressed transcriptional states and clinical studies indicate that the ratio of S220/S226 phosphorylation is associated with increased predisposition to specific psychiatric disease states, including Major Depressive Disorder and Bipolar Disorder. To examine the role of these phosphorylation sites in the development of behavioral abnormalities, we utilized a knock-in mouse model where Serine 220 (equivalent to human Serine 211) was replaced with an alanine (S220A). In-vitro microarray analysis of neural stem cells and QPCR validation were performed to examine the expression changes in individual transcripts in critical pathways that may correlate with long-term neurologic disorders. Our results indicated that changing the phosphorylation status of GR alters the expression of 2570 genes. Ingenuity Pathway Analysis indicated that the major pathways altered include those involved in cellular proliferation, mitochondrial function, Valine degradation and G-coupled protein receptors involved in neurotransmission. Both in-vitro and in-vivo experiments indicated that the S220A mutation alters the cells response to sGC administration by impacting proliferation and differentiation. The long-term goal of these experiments was to demonstrate a role for S220 phosphorylation in the development of neuropsychiatric disorders.

Inhibition of CXCR2 by Glucocorticoids in Adipose Tissue

Obesity-induced chronic adipose tissue inflammation is a significant risk factor for metabolic and cardiovascular disease (CVD), which affects 30.3 million adults in the United States. Interaction of adipocytes with hormonal, metabolic and immune systems play an integral role in the underlying pathophysiological mechanisms that leads to development of obesity-related complications. Despite this association, the mechanisms that coordinate the inflammatory mediators in causing adipose tissue inflammation are not well understood. Glucocorticoids (GC) are well known for their potent anti-inflammatory actions; however, the mechanism by which GC coordinate the inflammatory response of adipocytes are unknown. From our genome-wide microarray data derived from adipocyte-specific glucocorticoid receptor (GR) knockout (AdipoGRKO) mice, we found that GR inactivation leads to a significant increase in pro-inflammatory gene in white adipose tissue (WAT). Additionally, WAT isolated from AdipoGRKO mice showed significant increase in immune cell infiltration, which correlates with our gene expression data. Among the top up-regulated genes, we found the C-X-C Motif Chemokine Receptor 2 (Cxcr2), which is a powerful mediator of chemotaxis to the sites of inflammation. Although studies have shown the presence of Cxcr2 in adipocytes and suggested the contribution of Cxcr2 signaling in adipocyte development, its role in integrating adipose tissue inflammatory response is unknown. This led us to hypothesize that GR is critical to repress Cxcr2 gene expression and its pro inflammatory effects in adipocytes. Our in vitro studies using 3T3-L1 cells derived adipocytes showed that treatment with the synthetic glucocorticoid, Dexamethasone (Dex) led to a significant repression of Cxcr2 mRNA and protein levels. Furthermore, these effects are mediated by GR acting directly to repress Cxcr2 gene expression. Systemic administration of corticosterone significantly altered Cxcr2 expression in adipose tissue compared to untreated mice further supporting our results. Together our findings suggest that administration of glucocorticoids could inhibit adipose tissue inflammation and alleviate the comorbidities that arise from inflamed adipose tissue.

One Hormone for Two Receptors: Exploring Glucocorticoid Actions Mediated by the Glucocorticoid and Mineralocorticoid Receptors

Glucocorticoids are indispensable for mediating the response to stress, energy demands, development, and limiting inflammation. Once in the cell, these hormones exert their actions by activating nuclear receptors, transcription factors that regulate gene expression. The glucocorticoid receptor (GR) is the transcription factor that predominantly mediates both physiological and pharmacological glucocorticoid effects. Yet glucocorticoids can also bind and activate the mineralocorticoid receptor (MR), a transcription factor known to bind aldosterone thus maintaining whole-body fluid homeostasis. Phylogenetically, GR and MR are closely related and share a remarkable structural similarity. Indeed, the DNA-binding domain of MR is 96% identical to that of GR; thus MR is recruited to many of the same DNA response elements that bind GR. Moreover, GR has a low affinity for glucocorticoids but is expressed in nearly every cell, whereas MR shows a higher affinity for glucocorticoids although knowledge of MR’s expression levels is somewhat limited. These characteristics suggest that, while GR and MR can compensate for each other’s actions in many tissues, there are specific glucocorticoid and mineralocorticoid-mediated responses indicating GR-MR functional diversity. To investigate the similarities and differences between GR and MR signaling in the presence of glucocorticoid hormones, we generated U-2 OS (human osteosarcoma) cell lines stably expressing GR, MR, and both GR and MR (MRGR). Immunofluorescence analysis showed that the treatment of these cell lines with 1 nM of the synthetic glucocorticoid dexamethasone (Dex) induced nuclear translocation of both GR and MR. Moreover, Proximity Ligation Assay revealed that, in the absence of ligand, GR associated with MR in the cytoplasm and, upon 1 nM Dex exposure, GR-MR complexes were detected in the nucleus of MRGR cells. To decipher the functional contribution of GR-MR complexes in the transcriptional response to Dex, we performed RNA-seq in GR, MR, and MRGR cells treated with 1 nM of Dex. Transcriptome analysis revealed that Dex-activated GR regulated the transcription of 6180 genes. Co-expression of MR resulted in a greatly blunted Dex-mediated gene response which reduced the glucocorticoid-dependent transcriptome size by 75%. This phenomenon was also observed using a higher concentration of Dex. Indeed, 40% of genes commonly regulated by Dex in GR and MRGR cells showed a reduced magnitude of regulation when MR is co-expressed. These results suggest a functional antagonism between GR and MR in which MR inhibits GR function. Understanding the molecular mechanisms governing the cross-talk between GR and MR is crucial for the development of new therapies that address the adverse effects of glucocorticoid treatment as well as for the discovery of novel glucocorticoid-based therapeutics with minimal side effects.

Androgen Receptor Highjacks ErbB-2 Nuclear Function to Induce Triple Negative Breast Cancer Growth

Triple negative breast cancer (TNBC) has poor prognosis and neither established biomarkers nor therapeutic targets. On the one hand the androgen receptor (AR), a steroid hormone receptor (SR) which is expressed in 10-53% of TNBC and proved to be critical for BC proliferation, has been proposed as a new target in TNBC. On the other hand, we and others have shown that membrane ErbB-2 migrates to the nucleus (nuclear ErbB-2, NErbB-2) where it binds DNA at HER-2 associated sequences (HAS) to regulate BC proliferation and migration. Since we have previously shown a functional interplay between growth factors and SR signaling pathways in BC, we propose the existence of an interaction between AR and ErbB-2 which is involved in NErbB-2+/AR+ BC growth. The experimental model used was the human TNBC cell line MDA-MB-453 which displays high expression levels of AR and NErbB-2. By Western Blot (WB) we found that dihydrotestosterone (DHT) treatment for short times (minutes) did not regulate ErbB-2 phosphorylation status at residues Tyr1221/1222 and 1248 which were constitutively activated. However, DHT led to an increase in ErbB-2 phosphorylation at residue Tyr877 which we have proved to be required for ErbB-2 nuclear migration. The latter effect was blocked by the AR antagonist enzalutamide (enza). Blockage of Src activity with dasatinib inhibited DHT-induced ErbB-2 phosphorylation at Tyr877. By Immunofluorescence and confocal microscopy analyses and subcellular fractionation studies we demonstrated that DHT induced ErbB-2 nuclear migration which was inhibited by enza. By chIP we found that DHT induced ErbB-2 recruitment to a HAS site in ERK5, a gene involved in BC proliferation, and to a HAS site in FKBP5, a classical AR responsive gene. By WB we demonstrated that transfection with an ErbB-2 mutant which is unable to translocate to the nucleus and functions as a dominant negative inhibitor of ErbB-2 nuclear migration (hErbB-2ΔNLS), inhibited FKBP51 up-regulation by DHT. Finally, by microarray and bioinformatics analysis we identified 315 differentially expressed genes (DEGs) in the presence of DHT and NErbB-2 eviction. Enrichment analyses showed that the DEGs belonged to the immune response and interferon pathways. Kaplan-Meier analysis revealed that the expression of 6 genes was significantly associated with overall survival in TNBC patients from the METABRIC cohort: CXCL10, TAP1, STAT1, NMI, HLA-A and NLRC5. Multivariate Cox regression analysis identified the combined expression of the 6 genes as an independent predictor of better clinical outcome in TNBC (HR: 0.56, 95% CI 0.38-0.82, P = 0.003). In conclusion, our findings evidence that DHT-activated AR induces Src-mediated ErbB-2 rapid activation and its migration to the nucleus where it binds to HAS sites in the DNA. Moreover, based on the DEGs of NErbB-2 eviction in presence of DHT we identified a gene signature associated with favorable outcome in TNBC.

Deletion of hippocampal Glucocorticoid receptors unveils sex-biased microRNA expression and neuronal morphology alterations in mice

Sex differences in the brain have prompted many researchers to investigate the underlying molecular actors, such as the glucocorticoid receptor (GR). This nuclear receptor controls gene expression, including microRNAs (miRNAs), in non-neuronal cells. Here, we investigated sex-biased effects of GR on hippocampal miRNA expression and neuronal morphology by generating a neuron-specific GR knockout mouse (Emx1-Nr3c1^−/−). The levels of 578 mature miRNAs were assessed using NanoString technology and, in contrast to males, female Emx1-Nr3c1^−/− mice showed a substantially higher number of differentially expressed miRNAs, confirming a sex-biased effect of GR ablation. Based on bioinformatic analyses we identified several transcription factors potentially involved in miRNA regulation. Functional enrichment analyses of the miRNA-mRNA interactions revealed pathways related to neuronal arborization and both spine morphology and density in both sexes. Two recognized regulators of dendritic morphology, CAMKII-α and GSK-3β, increased their protein levels by GR ablation in female mice hippocampus, without changes in males. Additionally, sex-specific effects of GR deletion were observed on CA1 neuronal arborization and dendritic spine features. For instance, a reduced density of mushroom spines in apical dendrites was evidenced only in females, while a decreased length in basal dendrites was noted only in males. However, length and arborization of apical dendrites were reduced by GR ablation irrespective of the sex. Overall, our study provides new insights into the sex-biased GR actions, especially in terms of miRNAs expression and neuronal morphology in the hippocampus.

Protein phosphatase 1 alpha enhances glucocorticoid receptor activity by a mechanism involving phosphorylation of serine-211

By acting as a ligand-dependent transcription factor the glucocorticoid receptor (GR) mediates the actions of glucocorticoids and regulates many physiological processes. An impaired regulation of glucocorticoid action has been associated with numerous disorders. Thus, the elucidation of underlying signaling pathways is essential to understand mechanisms of disrupted glucocorticoid function and contribution to diseases. This study found increased GR transcriptional activity upon overexpression of protein phosphatase 1 alpha (PP1α) in HEK-293 cells and decreased expression levels of GR-responsive genes following PP1α knockdown in the endogenous A549 cell model. Mechanistic investigations revealed reduced phosphorylation of GR-Ser211 following PP1α silencing and provided a first indication for an involvement of glycogen synthase kinase 3 (GSK-3). Thus, the present study identified PP1α as a novel post-translational activator of GR signaling, suggesting that disruption of PP1α function could lead to impaired glucocorticoid action and thereby contribute to diseases.

Ions, the Movement of Water and the Apoptotic Volume Decrease

The movement of water across the cell membrane is a natural biological process that occurs during growth, cell division, and cell death. Many cells are known to regulate changes in their cell volume through inherent compensatory regulatory mechanisms. Cells can sense an increase or decrease in their cell volume, and compensate through mechanisms known as a regulatory volume increase (RVI) or decrease (RVD) response, respectively. The transport of sodium, potassium along with other ions and osmolytes allows the movement of water in and out of the cell. These compensatory volume regulatory mechanisms maintain a cell at near constant volume. A hallmark of the physiological cell death process known as apoptosis is the loss of cell volume or cell shrinkage. This loss of cell volume is in stark contrast to what occurs during the accidental cell death process known as necrosis. During necrosis, cells swell or gain water, eventually resulting in cell lysis. Thus, whether a cell gains or loses water after injury is a defining feature of the specific mode of cell death. Cell shrinkage or the loss of cell volume during apoptosis has been termed apoptotic volume decrease or AVD. Over the years, this distinguishing feature of apoptosis has been largely ignored and thought to be a passive occurrence or simply a consequence of the cell death process. However, studies on AVD have defined an underlying movement of ions that result in not only the loss of cell volume, but also the activation and execution of the apoptotic process. This review explores the role ions play in controlling not only the movement of water, but the regulation of apoptosis. We will focus on what is known about specific ion channels and transporters identified to be involved in AVD, and how the movement of ions and water change the intracellular environment leading to stages of cell shrinkage and associated apoptotic characteristics. Finally, we will discuss these concepts as they apply to different cell types such as neurons, cardiomyocytes, and corneal epithelial cells.

After 62 years of regulating immunity, dexamethasone meets COVID-19

Six months into the COVID-19 pandemic, effective treatments have been frustratingly sparse. The RECOVERY clinical trial, however, revealed that treatment with dexamethasone, a classic synthetic glucocorticoid, enhanced survival of critically ill patients with COVID-19. In this Comment, we discuss the immunological impacts of glucocorticoid therapy for COVID-19.

The corticosteroid dexamethasome has been shown to reduce mortality in patients hospitalized with COVID-19 who require mechanical ventilation. Here, the authors describe how this immunosuppressive drug might work.

THE CONCISE GUIDE TO PHARMACOLOGY 2019/20: Nuclear hormone receptors

The Concise Guide to PHARMACOLOGY 2019/20 is the fourth in this series of biennial publications. The Concise Guide provides concise overviews of the key properties of nearly 1800 human drug targets with an emphasis on selective pharmacology (where available), plus links to the open access knowledgebase source of drug targets and their ligands (http://www.guidetopharmacology.org), which provides more detailed views of target and ligand properties. Although the Concise Guide represents approximately 400 pages, the material presented is substantially reduced compared to information and links presented on the website. It provides a permanent, citable, point‐in‐time record that will survive database updates. The full contents of this section can be found at http://onlinelibrary.wiley.com/doi/10.1111/bph.14750. Nuclear hormone receptors are one of the six major pharmacological targets into which the Guide is divided, with the others being: G protein‐coupled receptors, catalytic receptors, enzymes and transporters. These are presented with nomenclature guidance and summary information on the best available pharmacological tools, alongside key references and suggestions for further reading. The landscape format of the Concise Guide is designed to facilitate comparison of related targets from material contemporary to mid‐2019, and supersedes data presented in the 2017/18, 2015/16 and 2013/14 Concise Guides and previous Guides to Receptors and Channels. It is produced in close conjunction with the International Union of Basic and Clinical Pharmacology Committee on Receptor Nomenclature and Drug Classification (NC‐IUPHAR), therefore, providing official IUPHAR classification and nomenclature for human drug targets, where appropriate.

Coordinate expression loss of GKN1 and GKN2 in gastric cancer via impairment of a glucocorticoid-responsive enhancer

Gastrokines (GKNs) are anti-inflammatory proteins secreted by gastric epithelial (surface mucous and pit) cells, with their aberrant loss of expression causally linked to premalignant inflammation and gastric cancer (GC). Transcriptional mechanisms accounting for GKN expression loss have not been elucidated. Using human clinical cohorts, mouse transgenics, bioinformatics, and transfection/reporter assays, we report a novel mechanism of GKN gene transcriptional regulation and its impairment in GC. GKN1/GKN2 loss is highly coordinated, with both genes showing parallel downregulation during human and mouse GC development, suggesting joint transcriptional control. In BAC transgenic studies, we defined a 152-kb genomic region surrounding the human GKN1/GKN2 genes sufficient to direct their tissue- and lineage-restricted expression. A screen of the 152-kb region for candidate regulatory elements identified a DNase I hypersensitive site (CR2) located 4 kb upstream of the GKN1 gene. CR2 showed overlapping enrichment of enhancer-related histone marks (H3K27Ac), a consensus binding site (GRE) for the glucocorticoid receptor (GR), strong GR occupancy in ChIP-seq data sets and, critically, exhibited dexamethasone-sensitive enhancer activity in reporter assays. Strikingly, GR showed progressive expression loss, paralleling that of GKN1/2, in human and mouse GC, suggesting desensitized glucocorticoid signaling as a mechanism underlying GKN loss. Finally, mouse adrenalectomy studies revealed a critical role for endogenous glucocorticoids in sustaining correct expression (and anti-inflammatory restraint) of GKNs in vivo. Together, these data link the coordinate expression of GKNs to a glucocorticoid-responsive and likely shared transcriptional enhancer mechanism, with its compromised activation contributing to dual GKN loss during GC progression.NEW & NOTEWORTHY Gastrokine 2 (GKN2) is an anti-inflammatory protein produced by the gastric epithelium. GKN2 expression is progressively lost during gastric cancer (GC), which is believed to play a casual role in GC development. Here, we use bacterial artificial chromosome transgenic studies to identify a glucocorticoid-responsive enhancer element that likely governs expression of GKN1/GKN2, which, via parallel expression loss of the anti-inflammatory glucocorticoid receptor, reveals a novel mechanism to explain the loss of GKN2 during GC pathogenesis.

Murine Glucocorticoid Receptors Orchestrate B Cell Migration Selectively between Bone Marrow and Blood

Glucocorticoids promote CXCR4 expression by T cells, monocytes, macrophages, and eosinophils, but it is not known if glucocorticoids regulate CXCR4 in B cells. Considering the important contributions of CXCR4 to B cell development and function, we investigated the glucocorticoid/CXCR4 axis in mice. We demonstrate that glucocorticoids upregulate CXCR4 mRNA and protein in mouse B cells. Using a novel strain of mice lacking glucocorticoid receptors (GRs) specifically in B cells, we show that reduced CXCR4 expression associated with GR deficiency results in impaired homing of mature B cells to bone marrow, whereas migration to other lymphoid tissues is independent of B cell GRs. The exchange of mature B cells between blood and bone marrow is sensitive to small, physiologic changes in glucocorticoid activity, as evidenced by the lack of circadian rhythmicity in GR-deficient B cell counts normally associated with diurnal patterns of glucocorticoid secretion. B cell^GRKO mice mounted normal humoral responses to immunizations with T-dependent and T-independent (Type 1) Ags, but Ab responses to a multivalent T-independent (Type 2) Ag were impaired, a surprise finding considering the immunosuppressive properties commonly attributed to glucocorticoids. We propose that endogenous glucocorticoids regulate a dynamic mode of B cell migration specialized for rapid exchange between bone marrow and blood, perhaps as a means to optimize humoral immunity during diurnal periods of activity.

OR12-02 When the Glucocorticoid Receptor Meets the Mineralocorticoid Receptor in the Nucleus of Human Cells

Adrenal corticosteroids, such as glucocorticoids and mineralocorticoids, are indispensable for mediating response to stress, development, limiting inflammation, and maintaining energy and fluid homeostasis. These hormones exert their actions via binding to two closely related nuclear receptors, the glucocorticoid receptor (GR) and mineralocorticoid receptor (MR). The GR has low affinity for corticosteroids, but is expressed in nearly every cell. In contrast, the MR shows a higher affinity for corticosteroids and its expression is largely confined to those tissues where electrolyte exchange and fluid balance are required. GR and MR act as ligand-activated transcription factors which, following interaction with co-regulators and DNA responsive elements, either promote or repress gene transcription. The affinity for the same ligands, structural homology, and binding to the same DNA regions suggest GR and MR can compensate for each other’s actions. Yet, there are specific glucocorticoid and mineralocorticoid-mediated responses indicating GR-MR functional diversity. To investigate this interplay, we developed U-2 OS (human osteosarcoma) cell lines stably expressing GR, MR, and both GR and MR (GRMR). Immunofluorescence analysis showed that treatment of these cell lines with 1 nM of the synthetic glucocorticoid dexamethasone (Dex) induced nuclear traslocation of GR and MR. Conversely, treatment with 1 nM of aldosterone (Aldo) promoted nuclear translocation of the MR only. Moreover, Proximity Ligation Assay revealed that, in the absence of ligand, GR associated with MR in the cytoplasm and, upon 1 nM Dex exposure, GR-MR dimers were detected in the nucleus of GRMR cells. Surprisingly, nuclear GR-MR dimers were also detected in the presence of Aldo, suggesting that it is necessary to activate at least one receptor to induce nuclear traslocation of the heterocomplex. To decipher the functional contribution of GR-MR dimers in the transcriptional response of GR to Dex and MR to Aldo, we performed RNA-seq in GR, MR, and GRMR cells treated with 1 nM of Dex or Aldo. Transcriptome analysis revealed that Dex-activated GR regulated the transcription of 6180 genes. Co-expression of MR resulted in a blunted Dex-mediated gene response which affected only 1608 genes, suggesting a functional antagonism of MR. Aldo-activated MR regulated the transcription of 1660 genes. However, co-expression of GR expanded the Aldo-mediated gene response to 3150 genes. Strikingly, 74% of these genes were also regulated by Dex via GR, suggesting that GR-MR dimers in the presence of aldosterone are able to mimic the glucocorticod transcriptional response. Our data suggest that the role of distinct GR and MR homo- and hetero-dimers is relevant for regulating gene expression. Dissecting the mechanism and investigating the cross-talk between GR and MR may be useful to understanding these two receptors in heath and disease.

SUN-737 Induction of the Pro-Diabetic Gene DPP4 by Glucocorticoids: New Evidence of Pro-Inflammatory Effects in Macrophages

Glucocorticoids are potent endogenous anti-inflammatory molecules, with its receptor (GR) expressed in nearly all immune cells. Macrophages are heterogeneous cells having a central role in both tissue homeostasis and inflammation. Paradoxically glucocorticoids have a limited efficacy controlling these processes and inflammation resolution of macrophage-related diseases, such as type 2 diabetes, atherosclerosis and rheumatoid arthritis. To address this issue, we explored new glucocorticoid target genes in macrophages with potential clinical and therapeutic implications for these diseases. Analysis of genomic platforms identified the pro-diabetic exopeptidase dipeptidyl peptidase 4 (DPP4) as a novel glucocorticoid-responsive gene. GR directly induces its expression by binding to two glucocorticoid-responsive elements within the DPP4 promoter. Unexpectedly, DPP4 mediated the glucocorticoid-induced spontaneous macrophage migration. These actions were blocked by both GR and DPP4 siRNA knockdowns. Furthermore, two DPP4 inhibitors, Sitagliptin and Linagliptin, used clinically for the treatment of diabetes inhibited glucocorticoid-induced mobility of macrophages. DPP4 induction by glucocorticoids was also observed in murine peritoneal macrophages and pro-inflammatory M1 polarized macrophages and was associated with an increase in their migratory properties. Provocatively, DPP4 has been shown to be involved in the inflammatory macrophage profile associated with type 2 diabetes, obesity and atherosclerosis. Since macrophages require efficient cell movement for all their functions, such as sensing of Pattern Associated Molecular Patterns (PAMPs), phagocytosis and the antigen presentation, the DPP4 induction by glucocorticoids could potentiate the macrophage infiltration and their activation in chronic inflammatory tissues and diabetes.

SUN-586 CXCR2 Repression by Glucocorticoids in Adipose Tissue

Obesity-induced type 2 diabetes (T2D) is a significant risk factor of cardiovascular disease (CVD), which affects 28.1 million adults in the United States. Adipose tissue chronic inflammation is one of the main factors that drive obesity-induced insulin resistance (IR) and T2D. Despite several studies that have shown a link between obesity, adipose tissue inflammation, and IR/T2D, the mechanisms underlying this association are not well understood. Synthetic glucocorticoids are widely used for their potent anti-inflammatory actions; however, their use is hampered due to off-target side effects. Glucocorticoids exert profound effects on adipose tissue, including the regulation of adipocyte metabolism and immune functions. However, whether their effects on adipose tissue are positive or negative it is still a controversial topic. Genome-wide microarray data obtained from adipocyte-specific glucocorticoid receptor (GR) knockout (AdipoGRKO) mice showed that lack of GR leads to a significant increase in the expression of pro-inflammatory genes in white adipose tissue (WAT). Moreover, WAT isolated from adipoGRKO mice demonstrated significant increase in immune cell infiltration, which correlates with our gene expression data. Among the most up-regulated genes, we found the C-X-C Motif Chemokine Receptor 2 (CXCR2), which is a critical mediator of chemotaxis to the sites of inflammation. Although studies have shown the presence of CXCR2 in adipocytes and suggested the contribution of CXCR2 signaling in adipocyte development, its role in obesity-driven adipose tissue inflammation is unknown. This led us to hypothesize that adipocyte specific administration of glucocorticoids can reduce obesity-induced adipocyte inflammation by inhibiting CXCR2 gene transcription and signaling. Our in vitro studies using 3T3-L1 cells derived adipocytes showed that treatment with the synthetic glucocorticoid, Dexamethasone (Dex) led to a significant repression of CXCR2 mRNA and protein levels. Correlating with these results, Dex treatment significantly inhibited macrophage migration to adipocytes in a mechanism dependent on GR activation and repression of CXCR2. Furthermore, these results were recapitulated in vivo. Together our findings suggest that local delivery of glucocorticoids to adipose tissue could ameliorate inflammation and reduce the risk of developing IR and T2D.

Glucocorticoid receptors are required effectors of TGFβ1-induced p38 MAPK signaling to advanced cancer phenotypes in triple-negative breast cancer

BACKGROUND

Altered signaling pathways typify breast cancer and serve as direct inputs to steroid hormone receptor sensors. We previously reported that phospho-Ser134-GR (pS134-GR) species are elevated in triple-negative breast cancer (TNBC) and cooperate with hypoxia-inducible factors, providing a novel avenue for activation of GR in response to local or cellular stress.

METHODS

We probed GR regulation by factors (cytokines, growth factors) that are rich within the tumor microenvironment (TME). TNBC cells harboring endogenous wild-type (wt) or S134A-GR species were created by CRISPR/Cas knock-in and subjected to transwell migration, invasion, soft-agar colony formation, and tumorsphere assays. RNA-seq was employed to identify pS134-GR target genes that are regulated both basally (intrinsic) or by TGFβ1 in the absence of exogenously added GR ligands. Regulation of selected basal and TGFβ1-induced pS134-GR target genes was validated by qRT-PCR and chromatin immunoprecipitation assays. Bioinformatics tools were used to probe public data sets for expression of pS134-GR 24-gene signatures.

RESULTS

In the absence of GR ligands, GR is transcriptionally activated via p38-dependent phosphorylation of Ser134 as a mechanism of homeostatic stress-sensing and regulated upon exposure of TNBC cells to TME-derived agents. The ligand-independent pS134-GR transcriptome encompasses TGFβ1 and MAPK signaling gene sets associated with TNBC cell survival and migration/invasion. Accordingly, pS134-GR was essential for TNBC cell anchorage-independent growth in soft-agar, migration, invasion, and tumorsphere formation, an in vitro readout of cancer stemness properties. Both pS134-GR and expression of the MAPK-scaffolding molecule 14-3-3ζ were essential for a functionally intact p38 MAPK signaling pathway downstream of MAP3K5/ASK1, indicative of a feedforward signaling loop wherein self-perpetuated GR phosphorylation enables cancer cell autonomy. A 24-gene pS134-GR-dependent signature induced by TGFβ1 predicts shortened overall survival in breast cancer patients.

CONCLUSIONS

Phospho-S134-GR is a critical downstream effector of p38 MAPK signaling and TNBC migration/invasion, survival, and stemness properties. Our studies define a ligand-independent role for GR as a homeostatic "sensor" of intrinsic stimuli as well as extrinsic factors rich within the TME (TGFβ1) that enable potent activation of the p38 MAPK stress-sensing pathway and nominate pS134-GR as a therapeutic target in aggressive TNBC.

Glucocorticoids mobilize macrophages by transcriptionally up-regulating the exopeptidase DPP4

Glucocorticoids are potent endogenous anti-inflammatory molecules, and their cognate receptor, glucocorticoid receptor (GR), is expressed in nearly all immune cells. Macrophages are heterogeneous immune cells having a central role in both tissue homeostasis and inflammation and also play a role in the pathogenesis of some inflammatory diseases. Paradoxically, glucocorticoids have only a limited efficacy in controlling the resolution of these macrophage-related diseases. Here, we report that the transcriptomes of monocyte-like THP-1 cells and macrophage-like THP-1 cells (THP1-MΦ) have largely conserved gene expression patterns. In contrast, the differentiation to THP1-MΦ significantly altered the sensitivity of gene transcription to glucocorticoids. Among glucocorticoid-regulated genes, we identified the exopeptidase dipeptidyl peptidase-4 (DPP4) as a critical glucocorticoid-responsive gene in THP1-MΦ. We found that GR directly induces DPP4 gene expression by binding to two glucocorticoid-responsive elements (GREs) within the DPP4 promoter. Additionally, we show that glucocorticoid-induced DPP4 expression is blocked by the GR antagonist RU-486 and by GR siRNA transfection and that DPP4 enzyme activity is reduced by DPP4 inhibitors. Of note, glucocorticoids highly stimulated macrophage mobility; unexpectedly, DPP4 mediated the glucocorticoid-induced macrophage migration, and siRNA-mediated knockdowns of GR and DPP4 blocked dexamethasone-induced THP1-MΦ migration. Moreover, glucocorticoid-induced DPP4 activation was also observed in proinflammatory M1-polarized murine macrophages, as well as peritoneal macrophages, and was associated with increased macrophage migration. Our results indicate that glucocorticoids directly up-regulate DPP4 expression and thereby induce migration in macrophages, potentially explaining why glucocorticoid therapy is less effective in controlling macrophage-dominated inflammatory disorders.

Glucocorticoid Signaling and the Aging Heart

A decline in normal physiological functions characterizes the aging process. While some of these changes are benign, the decrease in the function of the cardiovascular system that occurs during aging leads to the activation of pathological processes associated with an increased risk for heart disease and its complications. Imbalances in endocrine function are also common occurrences during the aging process. Glucocorticoids are primary stress hormones and are critical regulators of energy metabolism, inflammation, and cardiac function. Glucocorticoids exert their actions by binding the glucocorticoid receptor (GR) and, in some instances, to the mineralocorticoid receptor (MR). GR and MR are members of the nuclear receptor family of ligand-activated transcription factors. There is strong evidence that imbalances in GR and MR signaling in the heart have a causal role in cardiac disease. The extent to which glucocorticoids play a role in the aging heart, however, remains unclear. This review will summarize the positive and negative direct and indirect effects of glucocorticoids on the heart and the latest molecular and physiological evidence on how alterations in glucocorticoid signaling lead to changes in cardiac structure and function. We also briefly discuss the effects of other hormones systems such as estrogens and GH/IGF-1 on different cardiovascular cells during aging. We will also review the link between imbalances in glucocorticoid levels and the molecular processes responsible for promoting cardiomyocyte dysfunction in aging. Finally, we will discuss the potential for selectively manipulating glucocorticoid signaling in cardiomyocytes, which may represent an improved therapeutic approach for preventing and treating age-related heart disease.

THE CONCISE GUIDE TO PHARMACOLOGY 2019/20: Introduction and Other Protein Targets

The Concise Guide to PHARMACOLOGY 2019/20 is the fourth in this series of biennial publications. The Concise Guide provides concise overviews of the key properties of nearly 1800 human drug targets with an emphasis on selective pharmacology (where available), plus links to the open access knowledgebase source of drug targets and their ligands (www.guidetopharmacology.org), which provides more detailed views of target and ligand properties. Although the Concise Guide represents approximately 400 pages, the material presented is substantially reduced compared to information and links presented on the website. It provides a permanent, citable, point-in-time record that will survive database updates. The full contents of this section can be found at http://onlinelibrary.wiley.com/doi/10.1111/bph.14747. In addition to this overview, in which are identified Other protein targets which fall outside of the subsequent categorisation, there are six areas of focus: G protein-coupled receptors, ion channels, nuclear hormone receptors, catalytic receptors, enzymes and transporters. These are presented with nomenclature guidance and summary information on the best available pharmacological tools, alongside key references and suggestions for further reading. The landscape format of the Concise Guide is designed to facilitate comparison of related targets from material contemporary to mid-2019, and supersedes data presented in the 2017/18, 2015/16 and 2013/14 Concise Guides and previous Guides to Receptors and Channels. It is produced in close conjunction with the International Union of Basic and Clinical Pharmacology Committee on Receptor Nomenclature and Drug Classification (NC-IUPHAR), therefore, providing official IUPHAR classification and nomenclature for human drug targets, where appropriate.

Inhibition of miR-378a-3p by Inflammation Enhances IL-33 Levels: A Novel Mechanism of Alarmin Modulation in Ulcerative Colitis

Ulcerative colitis (UC) is an inflammatory bowel disease (IBD) characterized by mucosa damage associated with an uncontrolled inflammatory response. This immunological impairment leads to altered inflammatory mediators such as IL-33, which is shown to increase in the mucosa of active UC (aUC) patients. MicroRNAs present a distorted feature in inflamed colonic mucosa and are potential IL-33 regulating candidates in UC. Therefore, we studied the microRNA and mRNA profiles in inflamed colonic samples of UC patients, evaluating the effect of a microRNA (selected by in silico analysis and its expression in UC patients), on IL-33 under inflammatory conditions. We found that inflamed mucosa (n = 8) showed increased expression of 40 microRNAs and 2,120 mRNAs, while 49 microRNAs and 1,734 mRNAs were decreased, as determined by microarrays. In particular, IL-33 mRNA showed a 3.8-fold increase and eight members of a microRNA family (miR-378), which targets IL-33 mRNA in the 3'UTR, were decreased (-3.9 to -3.0 times). We selected three members of the miR-378 family (miR-378a-3p, miR-422a, and miR-378c) according to background information and interaction energy analysis, for further correlation analyses with IL-33 expression through qPCR and ELISA, respectively. We determined that aUC (n = 24) showed high IL-33 levels, and decreased expression of miR-378a-3p and miR-422a compared to inactive UC (n = 10) and controls (n = 6). Moreover, both microRNAs were inversely correlated with IL-33 expression, while miR-378c does not show a significant difference. To evaluate the effect of TNFα on the studied microRNAs, aUC patients with anti-TNF therapy were compared to aUC receiving other treatments. The levels of miR-378a-3p and miR-378c were higher in aUC patients with anti-TNF. Based on these findings, we selected miR-378a-3p to exploring the molecular mechanism involved by in vitro assays, showing that over-expression of miR-378a-3p decreased the levels of an IL-33 target sequence β-gal-reporter gene in HEK293 cells. Stable miR-378a-3p over-expression/inhibition inversely modulated IL-33 content and altered viability of HT-29 cells. Additionally, in an inflammatory context, TNFα decreased miR-378a-3p levels in HT-29 cells enhancing IL-33 expression. Together, our results propose a regulatory mechanism of IL-33 expression exerted by miR-378a-3p in an inflammatory environment, contributing to the understanding of UC pathogenesis.

Deletion of the Cardiomyocyte Glucocorticoid Receptor Leads to Sexually Dimorphic Changes in Cardiac Gene Expression and Progression to Heart Failure

Background

The contribution of glucocorticoids to sexual dimorphism in the heart is essentially unknown. Therefore, we sought to determine the sexually dimorphic actions of glucocorticoid signaling in cardiac function and gene expression. To accomplish this goal, we conducted studies on mice lacking glucocorticoid receptors (GR) in cardiomyocytes (cardioGRKO mouse model).

Methods and Results

Deletion of cardiomyocyte GR leads to an increase in mortality because of the development of spontaneous cardiac pathology in both male and female mice; however, females are more resistant to GR signaling inactivation in the heart. Male cardioGRKO mice had a median survival age of 6 months. In contrast, females had a median survival age of 10 months. Transthoracic echocardiography data showed phenotypic differences between male and female cardioGRKO hearts. By 3 months of age, male cardioGRKO mice exhibited left ventricular systolic dysfunction. Conversely, no significant functional deficits were observed in female cardioGRKO mice at the same time point. Functional sensitivity of male hearts to the loss of cardiomyocyte GR was reversed following gonadectomy. RNA‐Seq analysis showed that deleting GR in the male hearts leads to a more profound dysregulation in the expression of genes implicated in heart rate regulation (calcium handling). In agreement with these gene expression data, cardiomyocytes isolated from male cardioGRKO hearts displayed altered intracellular calcium responses. In contrast, female GR‐deficient cardiomyocytes presented a response comparable with controls.

Conclusions

These data suggest that GR regulates calcium responses in a sex‐biased manner, leading to sexually distinct responses to stress in male and female mice hearts, which may contribute to sex differences in heart disease, including the development of ventricular arrhythmias that contribute to heart failure and sudden death.

Estrogen Deficiency Promotes Hepatic Steatosis via a Glucocorticoid Receptor-Dependent Mechanism in Mice

Glucocorticoids (GCs) are master regulators of systemic metabolism. Intriguingly, Cushing’s syndrome, a disorder of excessive GCs, phenocopies several menopause-induced metabolic pathologies. Here, we show that the glucocorticoid receptor (GR) drives steatosis in hypogonadal female mice because hepatocyte-specific GR knockout mice are refractory to developing ovariectomy-induced steatosis. Intriguingly, transcriptional profiling revealed that ovariectomy elicits hepatic GC hypersensitivity globally. Hypogonadism-induced GC hypersensitivity results from a loss of systemic but not hepatic estrogen (E2) signaling, given that hepatocyte-specific E2 receptor deletion does not confer GC hypersensitivity. Mechanistically, enhanced chromatin recruitment and ligand-dependent hyperphosphorylation of GR underlie ovariectomy-induced glucocorticoid hypersensitivity. The dysregulated glucocorticoid-mediated signaling present in hypogonadal females is a product of increased follicle-stimulating hormone (FSH) production because FSH treatment in ovary-intact mice recapitulates glucocorticoid hypersensitivity similar to hypogonadal female mice. Our findings uncover a regulatory axis between estradiol, FSH, and hepatic glucocorticoid receptor signaling that, when disrupted, as in menopause, promotes hepatic steatosis.

β-Arrestin-1 inhibits glucocorticoid receptor turnover and alters glucocorticoid signaling

Glucocorticoids are among the most widely used drugs to treat many autoimmune and inflammatory diseases. Although much research has been focused on investigating glucocorticoid activity, it remains unclear how glucocorticoids regulate distinct processes in different cells. Glucocorticoids exert their effects through the glucocorticoid receptor (GR), which, upon glucocorticoid binding, interacts with regulatory proteins, affecting its activity and function. These protein-protein interactions are necessary for the resolution of glucocorticoid-dependent physiological and pharmacological processes. In this study, we discovered a novel protein interaction between the glucocorticoid receptor and β-arrestin-1, a scaffold protein with a well-established role in G protein-coupled receptor signaling. Using co-immunoprecipitation and in situ proximity ligation assays in A549 cells, we observed that β-arrestin-1 and unliganded GR interact in the cytoplasm and that, following glucocorticoid binding, the protein complex is found in the nucleus. We show that siRNA-mediated β-arrestin-1 knockdown alters GR protein turnover by up-regulating the E3 ubiquitin ligase Pellino-1, which catalyzes GR ubiquitination and thereby marks the receptor for proteasomal degradation. The enhanced GR turnover observed in β-arrestin-1-deficient cells limits the duration of the glucocorticoid response on GR target genes. These results demonstrate that β-arrestin-1 is a crucial player for the stability of the glucocorticoid receptor. The GR/β-arrestin-1 interaction uncovered here may help unravel mechanisms that contribute to the cell type-specific activities of glucocorticoids.

Cardiomyocyte glucocorticoid and mineralocorticoid receptors directly and antagonistically regulate heart disease in mice

Stress is increasingly associated with heart dysfunction and is linked to higher mortality rates in patients with cardiometabolic disease. Glucocorticoids are primary stress hormones that regulate homeostasis through two nuclear receptors, the glucocorticoid receptor (GR) and mineralocorticoid receptor (MR), both of which are present in cardiomyocytes. To examine the specific and coordinated roles that these receptors play in mediating the direct effects of stress on the heart, we generated mice with cardiomyocyte-specific deletion of GR (cardioGRKO), MR (cardioMRKO), or both GR and MR (cardioGRMRdKO). The cardioGRKO mice spontaneously developed cardiac hypertrophy and left ventricular systolic dysfunction and died prematurely from heart failure. In contrast, the cardioMRKO mice exhibited normal heart morphology and function. Despite the presence of myocardial stress, the cardioGRMRdKO mice were resistant to the cardiac remodeling, left ventricular dysfunction, and early death observed in the cardioGRKO mice. Gene expression analysis revealed the loss of gene changes associated with impaired Ca²⁺ handling, increased oxidative stress, and enhanced cell death and the presence of gene changes that limited the hypertrophic response and promoted cardiomyocyte survival in the double knockout hearts. Reexpression of MR in cardioGRMRdKO hearts reversed many of the cardioprotective gene changes and resulted in cardiac failure. These findings reveal a critical role for balanced cardiomyocyte GR and MR stress signaling in cardiovascular health. Therapies that shift stress signaling in the heart to favor more GR and less MR activity may provide an improved approach for treating heart disease.

Silencing of maternal hepatic glucocorticoid receptor is essential for normal fetal development in mice

Excessive or chronic stress can lead to a variety of diseases due to aberrant activation of the glucocorticoid receptor (GR), a ligand activated transcription factor. Pregnancy represents a particular window of sensitivity in which excessive stress can have adverse outcomes, particularly on the developing fetus. Here we show maternal hepatic stress hormone responsiveness is diminished via epigenetic silencing of the glucocorticoid receptor during pregnancy. Provocatively, reinstallation of GR to hepatocytes during pregnancy by adeno-associated viral transduction dysregulates genes involved in proliferation, resulting in impaired pregnancy-induced hepatomegaly. Disruption of the maternal hepatic adaptation to pregnancy results in in utero growth restriction (IUGR). These data demonstrate pregnancy antagonizes the liver-specific effects of stress hormone signaling in the maternal compartment to ultimately support the healthy development of embryos.

Endogenous glucocorticoids prevent gastric metaplasia by suppressing spontaneous inflammation

In the stomach, chronic inflammation causes metaplasia and creates a favorable environment for the evolution of gastric cancer. Glucocorticoids are steroid hormones that repress proinflammatory stimuli, but their role in the stomach is unknown. In this study, we show that endogenous glucocorticoids are required to maintain gastric homeostasis. Removal of circulating glucocorticoids in mice by adrenalectomy resulted in the rapid onset of spontaneous gastric inflammation, oxyntic atrophy, and spasmolytic polypeptide-expressing metaplasia (SPEM), a putative precursor of gastric cancer. SPEM and oxyntic atrophy occurred independently of lymphocytes. However, depletion of monocytes and macrophages by clodronate treatment or inhibition of gastric monocyte infiltration using the Cx3cr1 knockout mouse model prevented SPEM development. Our results highlight the requirement for endogenous glucocorticoid signaling within the stomach to prevent spontaneous gastric inflammation and metaplasia, and suggest that glucocorticoid deficiency may lead to gastric cancer development.