Reprogramming of glucocorticoid receptor function by hypoxia

Comparative Analysis of the Effects of Maternal Hypoxia and Placental Ischemia on HIF1-Dependent Metabolism and the Glucocorticoid System in the Embryonic and Newborn Rat Brain

Prenatal hypoxia, often accompanied by maternal glucocorticoid stress, can predispose offspring to neurological disorders in adulthood. If placental ischemia (PI) primarily reduces fetal oxygen supply, the maternal hypoxia (MH) model also elicits a pronounced fetal glucocorticoid exposure. Here, we compared MH and PI in rats to distinguish their unique and overlapping effects on embryonic and newborn brain development. We analyzed glucocorticoid transport into the developing brain, glucocorticoid receptor (GR) expression, and GR-dependent transcription, along with key enzymes regulating glucocorticoid metabolism in maternal (MP) and fetal placentas (FP) and in the brain. Additionally, we examined hypoxia-inducible factor 1-alpha (HIF1α) and its downstream genes, as well as glycolysis and the pentose phosphate pathway, both associated with the transport of substrates essential for glucocorticoid synthesis and degradation. Both MH and PI induced HIF1-dependent metabolic alterations, enhancing glycolysis and transiently disrupting redox homeostasis. However, only MH caused a maternal glucocorticoid surge that altered early fetal brain glucocorticoid responsiveness. Over time, these differences may lead to distinct long-term outcomes in neuronal structure and function. This work clarifies the individual contributions of hypoxic and glucocorticoid stresses to fetal brain development, suggesting that combining the MH and PI models could provide valuable insights for future investigations into the mechanisms underlying developmental brain pathologies, including non-heritable psychoneurological and neurodegenerative disorders.

The Interaction of Vasopressin with Hormones of the Hypothalamo-Pituitary-Adrenal Axis: The Significance for Therapeutic Strategies in Cardiovascular and Metabolic Diseases

A large body of evidence indicates that vasopressin (AVP) and steroid hormones are frequently secreted together and closely cooperate in the regulation of blood pressure, metabolism, water-electrolyte balance, and behavior, thereby securing survival and the comfort of life. Vasopressin cooperates with hormones of the hypothalamo-pituitary-adrenal axis (HPA) at several levels through regulation of the release of corticotropin-releasing hormone (CRH), adrenocorticotropic hormone (ACTH), and multiple steroid hormones, as well as through interactions with steroids in the target organs. These interactions are facilitated by positive and negative feedback between specific components of the HPA. Altogether, AVP and the HPA cooperate closely as a coordinated functional AVP-HPA system. It has been shown that cooperation between AVP and steroid hormones may be affected by cellular stress combined with hypoxia, and by metabolic, cardiovascular, and respiratory disorders; neurogenic stress; and inflammation. Growing evidence indicates that central and peripheral interactions between AVP and steroid hormones are reprogrammed in cardiovascular and metabolic diseases and that these rearrangements exert either beneficial or harmful effects. The present review highlights specific mechanisms of the interactions between AVP and steroids at cellular and systemic levels and analyses the consequences of the inappropriate cooperation of various components of the AVP-HPA system for the pathogenesis of cardiovascular and metabolic diseases.

[The effect of ethylmethylhydroxypyridine succinate on the parameters of chronic neuroinflammation and plastic processes in the brain of old rats during course of dexamethasone administration]

OBJECTIVE

To study was to evaluate the potential modulatory impact of succinate/SUCNR1 signaling on the non-genomic immunosuppressive and gene-mediated inflammatory-degenerative effects of glucocorticoid receptor (GR) activation in the cerebral cortex (CC) of aging rats.

MATERIAL AND METHODS

Using Western blot analysis, we assessed the expression level of pro-inflammatory (TNF-α, IL-1β), anti-inflammatory cytokines (IL-10, TGF-β1), mitochondriogenesis markers (PGC-1α, NDUFV2, SDHA, cyt c1, COX2, ATP5A), angiogenesis marker VEGF, neurotrophin BDNF, GR, succinate receptor SUCNR1 in the CC of 18-month-old rats with isolated administration of the highly specific GR ligand dexamethasone (1 mg/kg, i.p., daily, 10 days) and its combined administration with the succinate-containing drug Mexidol (100 mg/kg, i.p., daily, 10 days).

RESULTS

Dexamethasone caused a decrease in the content of all detectable parameters in the CC of 18-month-old rats, including anti-inflammatory IL-10, TGF-β1, PGC-1α, VEGF, BDNF, which progressed by 10 days, amounting to 40-60%, which is consistent with the literature data on transrepression by GR of key pro-inflammatory (NFkB, AP1, STAT1), anti-inflammatory (PPARγ, ERRα), pro-anabolic transcription factors (estrogen, androgen receptors). The administration of Mexidol daily an hour after the injection of dexamethasone did not affect the dexamethasone-induced suppression of pro-inflammatory cytokines, but increased the expression levels of anti-inflammatory cytokines, protein markers of mitochondrio-, angio- and synaptogenesis.

CONCLUSION

The study demonstrates for the first time the prospect and pathogenetic foundation of the combined use of dexamethasone and Mexidol in an aging body in order to minimize the activity of GC aimed at suppressing pro-anabolic programs and mechanisms for resolving inflammation.

The impact of hepatocyte-specific deletion of hypoxia-inducible factors on the development of polymicrobial sepsis with focus on GR and PPARα function

Introduction

Polymicrobial sepsis causes acute anorexia (loss of appetite), leading to lipolysis in white adipose tissue and proteolysis in muscle, and thus release of free fatty acids (FFAs), glycerol and gluconeogenic amino acids. Since hepatic peroxisome proliferator-activated receptor alpha (PPARα) and glucocorticoid receptor (GR) quickly lose function in sepsis, these metabolites accumulate (causing toxicity) and fail to yield energy-rich molecules such as ketone bodies (KBs) and glucose. The mechanism of PPARα and GR dysfunction is not known.

Methods & results

We investigated the hypothesis that hypoxia and/or activation of hypoxia inducible factors (HIFs) might play a role in these issues with PPARα and GR. After cecal ligation and puncture (CLP) in mice, leading to lethal polymicrobial sepsis, bulk liver RNA sequencing illustrated the induction of the genes encoding HIF1α and HIF2α, and an enrichment of HIF-dependent gene signatures. Therefore, we generated hepatocyte-specific knock-out mice for HIF1α, HIF2α or both, and a new HRE-luciferase reporter mouse line. After CLP, these HRE-luciferase reporter mice show signals in several tissues, including the liver. Hydrodynamic injection of an HRE-luciferase reporter plasmid also led to (liver-specific) signals in hypoxia and CLP. Despite these encouraging data, however, hepatocyte-specific HIF1α and/or HIF2α knock-out mice suggest that survival after CLP was not dependent on the hepatocyte-specific presence of HIF proteins, which was supported by measuring blood levels of glucose, FFAs, and KBs. The HIF proteins were also irrelevant in the CLP-induced glucocorticoid resistance, but we found indications that the absence of HIF1α in hepatocytes causes less inactivation of PPARα transcriptional function.

Conclusion

We conclude that HIF1α and HIF2α are activated in hepatocytes in sepsis, but their contribution to the mechanisms leading to lethality are minimal.

Dexamethasone Selectively Inhibits Detachment of Metastatic Thyroid Cancer Cells during Random Positioning

We recently reported that synthetic glucocorticoid dexamethasone (DEX) is able to suppress metastasis-like spheroid formation in a culture of follicular thyroid cancer (FTC)-133 cells cultured under random positioning. We now show that this inhibition was selective for two metastatic thyroid carcinoma cells, FTC-133 and WRO, whereas benign Nthy-ori 3-1 thyrocytes and recurrent ML-1 follicular thyroid cancer cells were not affected by DEX. We then compare Nthy-ori 3-1 and FTC-133 cells concerning their adhesion and mechanosignaling. We demonstrate that DEX disrupts random positioning-triggered p38 stress signaling in FTC-133 cells, thereby antagonizing a variety of biological functions. Thus, DEX treatment of FTC-133 cells is associated with increased adhesiveness, which is mainly caused by the restored, pronounced formation of a normal number of tight junctions. Moreover, we show that Nthy-ori 3-1 and ML-1 cells upregulate the anti-adhesion protein mucin-1 during random positioning, presumably as a protection against mechanical stress. In summary, mechanical stress seems to be an important component in this metastasis model system that is processed differently by metastatic and healthy cells. The balance between adhesion, anti-adhesion and cell–cell connections enables detachment of adherent human cells on the random positioning machine—or not, allowing selective inhibition of thyroid in vitro metastasis by DEX.

Structural basis of glucocorticoid receptor signaling bias

Dissociation between the healthy and toxic effects of cortisol, a major stress-responding hormone has been a widely used strategy to develop anti-inflammatory glucocorticoids with fewer side effects. Such strategy falls short when treating brain disorders as timing and activity state within large-scale neuronal networks determine the physiological and behavioral specificity of cortisol response. Advances in structural molecular dynamics posit the bases for engineering glucocorticoids with precision bias for select downstream signaling pathways. Design of allosteric and/or cooperative control for the glucocorticoid receptor could help promote the beneficial and reduce the deleterious effects of cortisol on brain and behavior in disease conditions.

Glucocorticoids and COVID-19

Coronavirus Disease 19 (COVID-19) is associated with high morbidity and mortality rates globally, representing the greatest health and economic challenge today. Several drugs are currently approved for the treatment of COVID-19. Among these, glucocorticoids (GCs) have received particular attention due to their anti-inflammatory and immunosuppressive effects. In fact, GC are widely used in current clinical practice to treat inflammatory, allergic and autoimmune diseases. Major mechanisms of GC action include inhibition of innate and adaptive immune activity. In particular, an important role is played by the inhibition of pro-inflammatory cytokines and chemokines, and the induction of proteins with anti-inflammatory activity. Overall, as indicated by various national and international regulatory agencies, GCs are recommended for the treatment of COVID-19 in patients requiring oxygen therapy, with or without mechanical ventilation. Regarding the use of GCs for the COVID-19 treatment of non-hospitalized patients at an early stage of the disease, many controversial studies have been reported and regulatory agencies have not recommended their use. The decision to start GC therapy should be based not only on the severity of COVID-19 disease, but also on careful considerations of the benefit/risk profile in individual patients, including monitoring of adverse events. In this review we summarize the effects of GCs on the major cellular and molecular components of the inflammatory/immune system, the benefits and the adverse common reactions in the treatment of inflammatory/autoimmune diseases, as well as in the management of COVID-19.

Dimerization of the Glucocorticoid Receptor and Its Importance in (Patho)physiology: A Primer

The glucocorticoid receptor (GR) is a very versatile protein that comes in several forms, interacts with many proteins and has multiple functions. Numerous therapies are based on GRs’ actions but the occurrence of side effects and reduced responses to glucocorticoids have motivated scientists to study GRs in great detail. The notion that GRs can perform functions as a monomeric protein, but also as a homodimer has raised questions about the underlying mechanisms, structural aspects of dimerization, influencing factors and biological functions. In this review paper, we are providing an overview of the current knowledge and insights about this important aspect of GR biology.

Homeostatic Regulation of Glucocorticoid Receptor Activity by Hypoxia-Inducible Factor 1: From Physiology to Clinic

Glucocorticoids (GCs) represent a well-known class of lipophilic steroid hormones biosynthesised, with a circadian rhythm, by the adrenal glands in humans and by the inter-renal tissue in teleost fish (e.g., zebrafish). GCs play a key role in the regulation of numerous physiological processes, including inflammation, glucose, lipid, protein metabolism and stress response. This is achieved through binding to their cognate receptor, GR, which functions as a ligand-activated transcription factor. Due to their potent anti-inflammatory and immune-suppressive action, synthetic GCs are broadly used for treating pathological disorders that are very often linked to hypoxia (e.g., rheumatoid arthritis, inflammatory, allergic, infectious, and autoimmune diseases, among others) as well as to prevent graft rejections and against immune system malignancies. However, due to the presence of adverse effects and GC resistance their therapeutic benefits are limited in patients chronically treated with steroids. For this reason, understanding how to fine-tune GR activity is crucial in the search for novel therapeutic strategies aimed at reducing GC-related side effects and effectively restoring homeostasis. Recent research has uncovered novel mechanisms that inhibit GR function, thereby causing glucocorticoid resistance, and has produced some surprising new findings. In this review we analyse these mechanisms and focus on the crosstalk between GR and HIF signalling. Indeed, its comprehension may provide new routes to develop novel therapeutic targets for effectively treating immune and inflammatory response and to simultaneously facilitate the development of innovative GCs with a better benefits-risk ratio.